WorldWideScience

Sample records for vaporizing heat sink

  1. Modeling of a heat sink and high heat flux vapor chamber

    Science.gov (United States)

    Vadnjal, Aleksander

    An increasing demand for a higher heat flux removal capability within a smaller volume for high power electronics led us to focus on a novel cold plate design. A high heat flux evaporator and micro channel heat sink are the main components of a cold plate which is capable of removing couple of 100 W/cm2. In order to describe performance of such porous media device a proper modeling has to be addressed. A universal approach based on the volume average theory (VAT) to transport phenomena in porous media is shown. An approach on how to treat the closure for momentum and energy equations is addressed and a proper definition for friction factors and heat transfer coefficients are discussed. A numerical scheme using a solution to Navier-Stokes equations over a representative elementary volume (REV) and the use of VAT is developed to show how to compute friction factors and heat transfer coefficients. The calculation show good agreement with the experimental data. For the heat transfer coefficient closure, a proper average for both fluid and solid is investigated. Different types of heating are also investigated in order to determine how it influences the heat transfer coefficient. A higher heat fluxes in small area condensers led us to the micro channels in contrast to the classical heat fin design. A micro channel can have various shapes to enhance heat transfer, but the shape that will lead to a higher heat flux removal with a moderate pumping power needs to be determined. The standard micro-channel terminology is usually used for channels with a simple cross section, e.g. square, round, triangle, etc., but here the micro channel cross section is going to be expanded to describe more complicated and interconnected micro scale channel cross sections. The micro channel geometries explored are pin fins (in-line and staggered) and sintered porous micro channels. The problem solved here is a conjugate problem involving two heat transfer mechanisms; (1) porous media

  2. Investigation of internally finned LED heat sinks

    Science.gov (United States)

    Li, Bin; Xiong, Lun; Lai, Chuan; Tang, Yumei

    2018-03-01

    A novel heat sink is proposed, which is composed of a perforated cylinder and internally arranged fins. Numerical studies are performed on the natural convection heat transfer from internally finned heat sinks; experimental studies are carried out to validate the numerical results. To compare the thermal performances of internally finned heat sinks and externally finned heat sinks, the effects of the overall diameter, overall height, and installation direction on maximum temperature, air flow and heat transfer coefficient are investigated. The results demonstrate that internally finned heat sinks show better thermal performance than externally finned heat sinks; the maximum temperature of internally finned heat sinks decreases by up to 20% compared with the externally finned heat sinks. The existence of a perforated cylinder and the installation direction of the heat sink affect the thermal performance significantly; it is shown that the heat transfer coefficient of the heat sink with the perforated cylinder is improved greater than that with the imperforated cylinder by up to 34%, while reducing the mass of the heat sink by up to 13%. Project supported by the Scientific Research Fund of Sichuan Provincial Education Department (No. 18ZB0516) and the Sichuan University of Arts and Science (No. 2016KZ009Y).

  3. UHS, Ultimate Heat Sink Cooling Pond Analysis

    International Nuclear Information System (INIS)

    Codell, R.; Nuttle, W.K.

    1998-01-01

    1 - Description of program or function: Three programs model performance of an ultimate heat sink cooling pond. National Weather Service data is read and analyzed to predict periods of lowest cooling performance and highest evaporative loss. The data is compared to local site data for significant differences. Then the maximum pond temperature is predicted. Five programs model performance of an ultimate heat sink spray pond. The cooling performance, evaporative water loss, and drift water loss as a function of wind speed are estimated for a spray field. These estimates are used in conjunction with National Weather Service data to predict periods of lowest cooling performance and highest evaporative loss. This data is compared to local site data for significant differences. Then the maximum pond temperature is predicted. 2 - Method of solution: The transfer of heat and water vapor is modeled using an equilibrium temperature procedure for an UHS cooling pond. The UHS spray pond model considers heat, mass, and momentum transfer from a single water drop with the surrounding air, and modification of the surrounding air resulting from the heat, mass, and momentum transfer from many drops in different parts of a spray field. 3 - Restrictions on the complexity of the problem: The program SPRCO uses RANF, a uniform random number generator which is an intrinsic function on the CDC. All programs except COMET use the NAMELIST statement, which is non standard. Otherwise these programs conform to the ANSI Fortran 77 standard. The meteorological data scanning procedure requires tens of years of recorded data to be effective. The models and methods, provided as useful tool for UHS analyses of cooling ponds and spray ponds, are intended as guidelines only. Use of these methods does not automatically assure NRC approval, nor are they required procedures for nuclear-power-plant licensing

  4. Topology Optimization of Thermal Heat Sinks

    DEFF Research Database (Denmark)

    Klaas Haertel, Jan Hendrik; Engelbrecht, Kurt; Lazarov, Boyan Stefanov

    2015-01-01

    In this paper, topology optimization is applied to optimize the cooling performance of thermal heat sinks. The coupled two-dimensional thermofluid model of a heat sink cooled with forced convection and a density-based topology optimization including density filtering and projection are implemented...... in COMSOL Multiphysics. The optimization objective is to minimize the heat sink’s temperature for a prescribed pressure drop and fixed heat generation. To conduct the optimization, COMSOL’s Optimization Module with GCMMA as the optimization method is used. The implementation of this topology optimization...... approach in COMSOL Multiphysics is described in this paper and results for optimized two-dimensional heat sinks are presented. Furthermore, parameter studies regarding the effect of the prescribed pressure drop of the system on Reynolds number and realized heat sink temperature are presented and discussed....

  5. Heat of vaporization spectrometer

    International Nuclear Information System (INIS)

    Edwards, D. Jr.

    1978-01-01

    Multilayer desorption measurements of various substances adsorbed on a stainless steel substrate are found to exhibit desorption profiles consistent with a zeroth order desorption model. The singleness of the desorption transients together with their narrow peak widths makes the technique ideally suited for a heat of vaporization spectrometer for either substance analysis or identification

  6. Sources and sinks of stratospheric water vapor

    International Nuclear Information System (INIS)

    Ellsaesser, H.W.

    1979-11-01

    A tutorial review of the understanding of stratospheric H 2 O and the processes controlling it is presented. Paradoxes posed by currently available observational data are cited and suggestions made as to how they might be resolved. Such resolution appears to require: that the bulk of our current data provides unrepresentative and misleading vertical and latitudinal H 2 O gradients immediately downstream from the tropical tropopause; and, that there exists within the troposphere a mechanism different from or in addition to the tropical tropopause cold trap for drying air to the mixing ratios found in the lower stratosphere. Satisfaction of these requirements will reconcile much heretofore puzzling observational data and will obviate the necessity for a stratospheric sink for H 2 O

  7. Novel Natural Convection Heat Sink Design Concepts From First Principles

    Science.gov (United States)

    2016-06-01

    CONVECTION HEAT SINK DESIGN CONCEPTS FROM FIRST PRINCIPLES by Derek E. Fletcher June 2016 Thesis Advisor: Garth Hobson Second Reader...COVERED Master’s Thesis 4. TITLE AND SUBTITLE NOVEL NATURAL CONVECTION HEAT SINK DESIGN CONCEPTS FROM FIRST PRINCIPLES 5. FUNDING NUMBERS 6...CONVECTION HEAT SINK DESIGN CONCEPTS FROM FIRST PRINCIPLES Derek E. Fletcher Lieutenant Commander, United States Navy B.S., Southwestern

  8. Investigation of Heat Sink Efficiency for Electronic Component Cooling Applications

    DEFF Research Database (Denmark)

    Staliulionis, Ž.; Zhang, Zhe; Pittini, Riccardo

    2014-01-01

    Research and optimisation of cooling of electronic components using heat sinks becomes increasingly important in modern industry. Numerical methods with experimental real-world verification are the main tools to evaluate efficiency of heat sinks or heat sink systems. Here the investigation...... of relatively simple heat sink application is performed using modeling based on finite element method, and also the potential of such analysis was demonstrated by real-world measurements and comparing obtained results. Thermal modeling was accomplished using finite element analysis software COMSOL and thermo...

  9. Development and testing of aluminum micro channel heat sink

    Science.gov (United States)

    Kumaraguruparan, G.; Sornakumar, T.

    2010-06-01

    Microchannel heat sinks constitute an innovative cooling technology for the removal of a large amount of heat from a small area and are suitable for electronics cooling. In the present work, Tool Steel D2 grade milling slitting saw type plain milling cutter is fabricated The microchannels are machined in aluminum work pieces to form the microchannel heat sink using the fabricated milling cutter in an horizontal milling machine. A new experimental set-up is fabricated to conduct the tests on the microchannel heat sink. The heat carried by the water increases with mass flow rate and heat input. The heat transfer coefficient and Nusselt number increases with mass flow rate and increased heat input. The pressure drop increases with Reynolds number and decreases with input heat. The friction factor decreases with Reynolds number and decreases with input heat. The thermal resistance decreases with pumping power and decreases with input heat.

  10. Genetic Algorithm Design of a 3D Printed Heat Sink

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Tong [ORNL; Ozpineci, Burak [ORNL; Ayers, Curtis William [ORNL

    2016-01-01

    In this paper, a genetic algorithm- (GA-) based approach is discussed for designing heat sinks based on total heat generation and dissipation for a pre-specified size andshape. This approach combines random iteration processesand genetic algorithms with finite element analysis (FEA) to design the optimized heat sink. With an approach that prefers survival of the fittest , a more powerful heat sink can bedesigned which can cool power electronics more efficiently. Some of the resulting designs can only be 3D printed due totheir complexity. In addition to describing the methodology, this paper also includes comparisons of different cases to evaluate the performance of the newly designed heat sinkcompared to commercially available heat sinks.

  11. Heat sink management during CANDU low level operation

    International Nuclear Information System (INIS)

    Wang Liansheng

    2008-01-01

    This paper introduces the practice of low-level operation with opening on the main heat transport system during an outage for a Candu-6 nuclear power plant, analyses the risks of losing heat sink during this condition, and points out the safety measures and management requirement for controlling such risks. This paper can be used as a reference for improving and optimizing the heat sink management for the coming outages. (author)

  12. Design consideration for a diversity of heat sink

    Energy Technology Data Exchange (ETDEWEB)

    Rueckbrodt, Karin; Meischak, Stefan [AREVA NP GmbH, Erlangen (Germany)

    2013-07-01

    The defense in depth approach requires in all cases to prevent and mitigate accidents that could release radioactive materials. To assure the physical design barriers (preserve fuel integrity, reactor coolant pressure boundary integrity, and containment integrity) the decay heat has to be removed. External and internal events have to be taken in consideration for the robustness of all the involved cooling systems. To ensure the cooling function in all conceivable and all unlikely events an analysis for the necessity of a diversified heat sink is essential. The diversified concepts analyses the type of the primary heat sink and use contrary sources for the heat sink, air instead of water, well instead of a river. A complete diversity is realized if also for the heat transfer diversified systems are implemented. The described solutions are mainly applied for BWR plants, but can be partly transferred analogously to PWR plants. (orig.)

  13. Phase Change Material Heat Sink for an ISS Flight Experiment

    Science.gov (United States)

    Quinn, Gregory; Stieber, Jesse; Sheth, Rubik; Ahlstrom, Thomas

    2015-01-01

    A flight experiment is being constructed to utilize the persistent microgravity environment of the International Space Station (ISS) to prove out operation of a microgravity compatible phase change material (PCM) heat sink. A PCM heat sink can help to reduce the overall mass and volume of future exploration spacecraft thermal control systems (TCS). The program is characterizing a new PCM heat sink that incorporates a novel phase management approach to prevent high pressures and structural deformation that often occur with PCM heat sinks undergoing cyclic operation in microgravity. The PCM unit was made using brazed aluminum construction with paraffin wax as the fusible material. It is designed to be installed into a propylene glycol and water cooling loop, with scaling consistent with the conceptual designs for the Orion Multipurpose Crew Vehicle. This paper reports on the construction of the PCM heat sink and on initial ground test results conducted at UTC Aerospace Systems prior to delivery to NASA. The prototype will be tested later on the ground and in orbit via a self-contained experiment package developed by NASA Johnson Space Center to operate in an ISS EXPRESS rack.

  14. Optimization of triangular microchannel heat sinks using constructible theory

    International Nuclear Information System (INIS)

    Mardani, Moloud; Salimpour, Mohammad Reza

    2016-01-01

    The present paper examines the optimization of triangular microchannel heat sinks. The impact of volume fraction of solid material and pressure drop on the maximum temperature of the microchannel heat sinks are investigated and their optimum operating conditions are compared. From the results, it is seen that increasing the side angle of the triangular microchannel, improves its performance. Furthermore, there is an appropriate agreement between the analytical and numerical results. Finally, the effect of degrees of freedom on the performance of microchannels is investigated. To accomplish this end, the triangular microchannels with the side angle of 60 degree have been chosen as it has the best performance compared to other microchannels. It is observed that the minimized maximum temperatures of optimized microchannel heat sinks with three degrees of freedom are 10% lower than the ones with two degrees of freedom

  15. Characterization of Single Phase and Two Phase Heat and Momentum Transport in a Spiraling Radial Inow Microchannel Heat Sink

    Science.gov (United States)

    Ruiz, Maritza

    Thermal management of systems under high heat fluxes on the order of hundreds of W/cm2 is important for the safety, performance and lifetime of devices, with innovative cooling technologies leading to improved performance of electronics or concentrating solar photovoltaics. A novel, spiraling radial inflow microchannel heat sink for high flux cooling applications, using a single phase or vaporizing coolant, has demonstrated enhanced heat transfer capabilities. The design of the heat sink provides an inward swirl flow between parallel, coaxial disks that form a microchannel of 1 cm radius and 300 micron channel height with a single inlet and a single outlet. The channel is heated on one side through a conducting copper surface, and is essentially adiabatic on the opposite side to simulate a heat sink scenario for electronics or concentrated photovoltaics cooling. Experimental results on the heat transfer and pressure drop characteristics in the heat sink, using single phase water as a working fluid, revealed heat transfer enhancements due to flow acceleration and induced secondary flows when compared to unidirectional laminar fully developed flow between parallel plates. Additionally, thermal gradients on the surface are small relative to the bulk fluid temperature gain, a beneficial feature for high heat flux cooling applications. Heat flux levels of 113 W/cm2 at a surface temperature of 77 deg C were reached with a ratio of pumping power to heat rate of 0.03%. Analytical models on single phase flow are used to explore the parametric trends of the flow rate and passage geometry on the streamlines and pressure drop through the device. Flow boiling heat transfer and pressure drop characteristics were obtained for this heat sink using water at near atmospheric pressure as the working fluid for inlet subcooling levels ranging from 20 to 80 deg C and mean mass flux levels ranging from 184-716 kg/m. 2s. Flow enhancements similar to singlephase flow were expected, as well

  16. Enhanced heat sink with geometry induced wall-jet

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, Md. Mahamudul, E-mail: sohel0991@gmail.com; Tikadar, Amitav; Bari, Fazlul; Morshed, A. K. M. M. [Department of Mechanical Engineering Bangladesh University of Engineering and Technology, Dhaka-1000. Bangladesh (Bangladesh)

    2016-07-12

    Mini-channels embedded in solid matrix have already proven to be a very efficient way of electronic cooling. Traditional mini-channel heat sinks consist of single layer of parallel channels. Although mini-channel heat sink can achieve very high heat flux, its pumping requirement for circulating liquid through the channel increase very sharply as the flow velocity increases. The pumping requirements of the heat sink can be reduced by increasing its performance. In this paper a novel approach to increase the thermal performance of the mini-channel heat sink is proposed through geometry induced wall jet which is a passive technique. Geometric irregularities along the channel length causes abrupt pressure change between the channels which causes cross flow through the interconnections thus one channel faces suction and other channel jet action. This suction and jet action disrupts boundary layer causing enhanced heat transfer performance. A CFD model has been developed using commercially available software package FLUENT to evaluate the technique. A parametric study of the velocities and the effect of the position of the wall-jets have been performed. Significant reduction in thermal resistance has been observed for wall-jets, it is also observed that this reduction in thermal resistance is dependent on the position and shape of the wall jet.

  17. Analysis of ultimate-heat-sink spray ponds. Technical report

    International Nuclear Information System (INIS)

    Codell, R.

    1981-08-01

    This report develops models which can be utilized in the design of certain types of spray ponds used in ultimate heat sinks at nuclear power plants, and ways in which the models may be employed to determine the design basis required by U.S. Nuclear Regulatory Commission Regulatory Guide 1.27

  18. VAPOR PRESSURES AND HEATS OF VAPORIZATION OF PRIMARY COAL TARS

    Energy Technology Data Exchange (ETDEWEB)

    Eric M. Suuberg; Vahur Oja

    1997-07-01

    This project had as its main focus the determination of vapor pressures of coal pyrolysis tars. It involved performing measurements of these vapor pressures and from them, developing vapor pressure correlations suitable for use in advanced pyrolysis models (those models which explicitly account for mass transport limitations). This report is divided into five main chapters. Each chapter is a relatively stand-alone section. Chapter A reviews the general nature of coal tars and gives a summary of existing vapor pressure correlations for coal tars and model compounds. Chapter B summarizes the main experimental approaches for coal tar preparation and characterization which have been used throughout the project. Chapter C is concerned with the selection of the model compounds for coal pyrolysis tars and reviews the data available to us on the vapor pressures of high boiling point aromatic compounds. This chapter also deals with the question of identifying factors that govern the vapor pressures of coal tar model materials and their mixtures. Chapter D covers the vapor pressures and heats of vaporization of primary cellulose tars. Chapter E discusses the results of the main focus of this study. In summary, this work provides improved understanding of the volatility of coal and cellulose pyrolysis tars. It has resulted in new experimentally verified vapor pressure correlations for use in pyrolysis models. Further research on this topic should aim at developing general vapor pressure correlations for all coal tars, based on their molecular weight together with certain specific chemical characteristics i.e. hydroxyl group content.

  19. Field Test of a Steam Condenser Heat Sink Concept

    Science.gov (United States)

    1974-01-01

    stored underground for a specified time. A functional and economical heat rejection system is an important design consideration for such...per- mits the use of tunnels for other than just heat sink purposes. If existing tunnels can be used, the concept becomes economically attractive...that the water meter readings aie a valid indication of the mpu ! and that condensate was lost bv seepage thionuli the lock and or ballast into the

  20. Diamond Microchannel Heat Sink Designs For High Heat Flux Thermal Control

    National Research Council Canada - National Science Library

    Corbin, Michael

    2002-01-01

    .... Many investigators have suggested the use of diamond heat spreaders to reduce flux levels at or near to its source, and some have suggested that diamond microchannel heat sinks ultimately may play...

  1. A novel high performance, ultra thin heat sink for electronics

    International Nuclear Information System (INIS)

    Escher, W.; Michel, B.; Poulikakos, D.

    2010-01-01

    We present an ultra thin heat sink for electronics, combining optimized impinging slot-jets, micro-channels and manifolds for efficient cooling. We first introduce a three-dimensional numerical model of the heat transfer structure, to investigate its hydrodynamic and thermal performance and its sensitivity to geometric parameters. In a second step we propose a three-dimensional hydrodynamic numerical model representing the complete system. Based on this model we design a novel manifold providing uniform fluid distribution. In order to save computational time a simpler semi-empirical model is proposed and validated. The semi-empirical model allows a robust optimization of the heat sink geometric parameters. The design is optimized for a 2 x 2 cm 2 chip and provides a total thermal resistance of 0.087 cm 2 K/W for flow rates 2 for a temperature difference between fluid inlet and chip of 65 K.

  2. Pin fin compliant heat sink with enhanced flexibility

    Science.gov (United States)

    Schultz, Mark D.

    2018-04-10

    Heat sinks and methods of using the same include a top and bottom plate, at least one of which has a plurality of pin contacts flexibly connected to one another, where the plurality of pin contacts have vertical and lateral flexibility with respect to one another; and pin slice layers, each having multiple pin slices, arranged vertically between the top and bottom plates such that the plurality of pin slices form substantially vertical pins connecting the top and bottom plates.

  3. Analytical analysis and experimental verification of interleaved parallelogram heat sink

    International Nuclear Information System (INIS)

    Chen, Hong-Long; Wang, Chi-Chuan

    2017-01-01

    Highlights: • A novel air-cooled heat sink profile (IPFM) is proposed to compete with the typical design. • It features two different perimeters with odd fin being rectangular and the rest being parallelogram. • A new modified dimensionless parameter characterized the flow length in triangular region is proposed. • The analytical predictions are in line with the experiments for both conventional and IPFM design. • IPFM design shows a much lower pressure drop and a superior performance especially for dense fins. - Abstract: In this study, a novel air-cooled heat sink profile is proposed to compete with the conventional design. The new design is termed as IPFM (Interleaved Parallelogram Fin Module) which features two different geometrical perimeter shapes of fins. This new design not only gains the advantage of lower pressure drop for power saving; but also gains a material saving for less fin surface area. An assessment of flow impedance and performance between the conventional and IPFM heat sink is analytically investigated and experimentally verified. A new modified dimensionless friction factor for triangular region is proposed. The analytical predictions agree with experimental measurements for both conventional and IPFM design. In electronic cooling design, especially for cloud server air-cooled heat sink design, the flow pattern is usually laminar with Reynolds number being operated less than 2000. In this regime, the IPFM design shows 8–12% less of surface than conventional design when the flow rate is less than 10 CFM; yet the thermal performance is slightly inferior to the conventional design when the flowrate is raised towards 25 CFM. Yet in the test range of 5–25 CFM, a 10–15% lower flow impedance is observed. The smaller fin spacing, the more conspicuous reduction of flow impedance is observed. The optimization of cutting angle is around 35° for 10 CFM, and it is reduced to 15° at a larger flowrate of 20 CFM.

  4. Thermal design heat sinks, thermoelectrics, heat pipes, compact heat exchangers, and solar cells

    CERN Document Server

    Lee, H S

    2010-01-01

    The proposed is written as a senior undergraduate or the first-year graduate textbook,covering modern thermal devices such as heat sinks, thermoelectric generators and coolers, heat pipes, and heat exchangers as design components in larger systems. These devices are becoming increasingly important and fundamental in thermal design across such diverse areas as microelectronic cooling, green or thermal energy conversion, and thermal control and management in space, etc. However, there is no textbook available covering this range of topics. The proposed book may be used as a capstone design cours

  5. An analytical model for annular flow boiling heat transfer in microchannel heat sinks

    International Nuclear Information System (INIS)

    Megahed, A.; Hassan, I.

    2009-01-01

    An analytical model has been developed to predict flow boiling heat transfer coefficient in microchannel heat sinks. The new analytical model is proposed to predict the two-phase heat transfer coefficient during annular flow regime based on the separated model. Opposing to the majority of annular flow heat transfer models, the model is based on fundamental conservation principles. The model considers the characteristics of microchannel heat sink during annular flow and eliminates using any empirical closure relations. Comparison with limited experimental data was found to validate the usefulness of this analytical model. The model predicts the experimental data with a mean absolute error 8%. (author)

  6. Two-phase pressure drop and flow visualization of FC-72 in a silicon microchannel heat sink

    International Nuclear Information System (INIS)

    Megahed, Ayman; Hassan, Ibrahim

    2009-01-01

    The rapid development of two-phase microfluidic devices has triggered the demand for a detailed understanding of the flow characteristics inside microchannel heat sinks to advance the cooling process of micro-electronics. The present study focuses on the experimental investigation of pressure drop characteristics and flow visualization of a two-phase flow in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 276 μm, width of 225 μm, and a length of 16 mm. Experiments are carried out for mass fluxes ranging from 341 to 531 kg/m 2 s and heat fluxes from 60.4 to 130.6 kW/m 2 using FC-72 as the working fluid. Bubble growth and flow regimes are observed using high speed visualization. Three major flow regimes are identified: bubbly, slug, and annular. The frictional two-phase pressure drop increases with exit quality for a constant mass flux. An assessment of various pressure drop correlations reported in the literature is conducted for validation. A new general correlation is developed to predict the two-phase pressure drop in microchannel heat sinks for five different refrigerants. The experimental pressure drops for laminar-liquid laminar-vapor and laminar-liquid turbulent-vapor flow conditions are predicted by the new correlation with mean absolute errors of 10.4% and 14.5%, respectively.

  7. The use of segregated heat sink structures to achieve enhanced passive cooling for outdoor wireless devices

    International Nuclear Information System (INIS)

    O'Flaherty, K; Punch, J

    2014-01-01

    Environmental standards which govern outdoor wireless equipment can stipulate stringent conditions: high solar loads (up to 1 kW/m 2 ), ambient temperatures as high as 55°C and negligible wind speeds (0 m/s). These challenges result in restrictions on power dissipation within a given envelope, due to the limited heat transfer rates achievable with passive cooling. This paper addresses an outdoor wireless device which features two segregated heat sink structures arranged vertically within a shielded chimney structure: a primary sink to cool temperature-sensitive components; and a secondary sink for high power devices. Enhanced convective cooling of the primary sink is achieved due to the increased mass flow within the chimney generated by the secondary sink. An unshielded heat sink was examined numerically, theoretically and experimentally, to verify the applicability of the methods employed. Nusselt numbers were compared for three cases: an unshielded heat sink; a sink located at the inlet of a shield; and a primary heat sink in a segregated structure. The heat sink, when placed at the inlet of a shield three times the length of the sink, augmented the Nusselt number by an average of 64% compared to the unshielded case. The Nusselt number of the primary was found to increase proportionally with the temperature of the secondary sink, and the optimum vertical spacing between the primary and secondary sinks was found to be close to zero, provided that conductive transfer between the sinks was suppressed.

  8. Performance of a polymeric heat sink with circular microchannels

    Energy Technology Data Exchange (ETDEWEB)

    Barba, Alessandro; Musi, Barbara; Spiga, Marco [Department of Industrial Engineering, University of Parma, Parco Area delle Scienze 181, 43100 Parma (Italy)

    2006-06-15

    The object of this work is the thermal investigation of a polymeric microchannel heat sink designed for the active cooling of small flat surfaces. Its performance, pressure drop, temperature distribution, and thermal resistance are evaluated. A three-dimensional procedure is developed and applied to a geometrical configuration consisting of a circular microduct (with a gas running through it), embedded in a solid substrate with rectangular cross-section. The conjugate heat transfer problem is solved assuming fully developed laminar flow in forced convection. The bottom side of the heat sink receives a uniform heat flux, while the top side is adiabatic. Considering a gas flow with low Prandtl and Reynolds numbers, the temperature distribution is given by the sum of a linear function (in the stream direction) and a numerical solution obtained in 2-D coordinates resorting to a finite element software, based on the Rayleigh-Ritz-Galerkin method, with user-defined error tolerance. Rarefaction, compressibility and viscous dissipation are neglected, i.e., the Knudsen, Mach and Brinkman numbers are low. The theoretical results are shown in some graphs and compared with experimental data concerning helium and nitrogen flows in Nylon circular microducts. The agreement is quite satisfactory. [Author].

  9. Heat Transfer Enhancement by Finned Heat Sinks with Micro-structured Roughness

    Science.gov (United States)

    Ventola, L.; Chiavazzo, E.; Calignano, F.; Manfredi, D.; Asinari, P.

    2014-04-01

    We investigated the benefits of micro-structured roughness on heat transfer performance of heat sinks, cooled by forced air. Heat sinks in aluminum alloy by direct metal laser sintering (DMLS) manufacturing technique were fabricated; values of the average surface roughness Ra from 1 to 25 microns (standard milling leads to roughness around 1 micron) under turbulent regimes (Reynolds number based on heating edge from 3000 to 17000) have been explored. An enhancement of 50% in thermal performances with regards to standard manufacturing was observed. This may open the way for huge boost in the technology of electronic cooling by DMLS.

  10. Heat transfer enhancement by finned heat sinks with micro-structured roughness

    International Nuclear Information System (INIS)

    Ventola, L; Chiavazzo, E; Asinari, P; Calignano, F; Manfredi, D

    2014-01-01

    We investigated the benefits of micro-structured roughness on heat transfer performance of heat sinks, cooled by forced air. Heat sinks in aluminum alloy by direct metal laser sintering (DMLS) manufacturing technique were fabricated; values of the average surface roughness R a from 1 to 25 microns (standard milling leads to roughness around 1 micron) under turbulent regimes (Reynolds number based on heating edge from 3000 to 17000) have been explored. An enhancement of 50% in thermal performances with regards to standard manufacturing was observed. This may open the way for huge boost in the technology of electronic cooling by DMLS.

  11. Thermal performance measurements on ultimate heat sinks--cooling ponds

    International Nuclear Information System (INIS)

    Hadlock, R.K.; Abbey, O.B.

    1977-12-01

    The primary objective of the studies described is to obtain the requisite data, with respect to modeling requirements, to characterize thermal performance of heat sinks for nuclear facilities existing at elevated water temperatures in result of experiencing a genuinely large heat load and responding to meteorological influence. The data should reflect thermal performance for combinations leading to worst-case meteorological influence. A geothermal water retention basin has been chosen as the site for the first measurement program and data have been obtained in the first of several experiments scheduled to be performed there. These data illustrate the thermal and water budgets during episodes of cooling from an initially high pond water bulk temperature. Monitoring proceeded while the pond experienced only meteorological and seepage influence. The data are discussed and are presented as a data volume which may be used for calculation purposes. Suggestions for future measurement programs are stated with the intent to maintain and improve relevance to nuclear ultimate heat sinks while continuing to examine the performance of the analog geothermal pond. It is further suggested that the geothermal pond, with some modification, may be a suitable site for spray pond measurements

  12. Experimental investigation of heat transfer performance for a novel microchannel heat sink

    International Nuclear Information System (INIS)

    Wang, Y; Ding, G-F

    2008-01-01

    We demonstrated a novel microchannel heat sink with a high local heat transfer efficiency contributed by a complicated microchannel system, which comprises parallel longitudinal microchannels etched in a silicon substrate and transverse microchannels electroplated on a copper heat spreader. The thermal boundary layer develops in transverse microchannels. Meanwhile, the heat transfer area is increased compared with the conventional microchannel heat sink only having parallel longitudinal microchannels. Both benefits yield high local heat transfer efficiency and enhance the overall heat transfer, which is attractive for the cooling of high heat flux electronic devices. Infrared tests show the temperature distribution in the test objects. The effects of flow rate and heat flux levels on heat transfer characteristics are presented. A uniform temperature distribution is obtained through the heating area. The reference temperatures decrease with the increasing flow rate from 0.64 ml min −1 to 6.79 ml min −1 for a constant heat flux of 10.4 W cm −2 . A heat flux of 18.9 W cm −2 is attained at a flow rate of 6.79 ml min −1 for assuring the maximum temperature of the microchannel heat sink less than the maximum working temperature of electronic devices

  13. New Configurations of Micro Plate-Fin Heat Sink to Reduce Coolant Pumping Power

    Science.gov (United States)

    Rezania, A.; Rosendahl, L. A.

    2012-06-01

    The thermal resistance of heat exchangers has a strong influence on the electric power produced by a thermoelectric generator (TEG). In this work, a real TEG device is applied to three configurations of micro plate-fin heat sink. The distance between certain microchannels is varied to find the optimum heat sink configuration. The particular focus of this study is to reduce the coolant mass flow rate by considering the thermal resistances of the heat sinks and, thereby, to reduce the coolant pumping power in the system. The three-dimensional governing equations for the fluid flow and the heat transfer are solved using the finite-volume method for a wide range of pressure drop laminar flows along the heat sink. The temperature and the mass flow rate distribution in the heat sink are discussed. The results, which are in good agreement with previous computational studies, show that using suggested heat sink configurations reduces the coolant pumping power in the system.

  14. New Configurations of Micro Plate-Fin Heat Sink to Reduce Coolant Pumping Power

    DEFF Research Database (Denmark)

    Kolaei, Alireza Rezania; Rosendahl, Lasse

    2012-01-01

    the optimum heat sink configuration. The particular focus of this study is to reduce the coolant mass flow rate by considering the thermal resistances of the heat sinks and, thereby, to reduce the coolant pumping power in the system. The threedimensional governing equations for the fluid flow and the heat......The thermal resistance of heat exchangers has a strong influence on the electric power produced by a thermoelectric generator (TEG). In this work, a real TEG device is applied to three configurations of micro plate-fin heat sink. The distance between certain microchannels is varied to find...... heat sink configurations reduces the coolant pumping power in the system....

  15. A highly stable microchannel heat sink for convective boiling

    International Nuclear Information System (INIS)

    Lu, Chun Ting; Pan Chin

    2009-01-01

    To develop a highly stable two-phase microchannel heat sink, we experimented with convective boiling in diverging, parallel microchannels with different distributions of laser-etched artificial nucleation sites. Each microchannel had a mean hydraulic diameter of 120 µm. The two-phase flow visualization and the magnitudes of pressure drop and inlet temperature oscillations under boiling conditions demonstrated clearly the merits of using artificial nucleation sites to further stabilize the flow boiling in diverging, parallel microchannels. The stability map showed the plane of subcooling number versus phase change number. It illustrated that diverging, parallel microchannels with artificial nucleation cavities have a much wider stable region than parallel microchannels with uniform cross-sections or diverging, parallel microchannels without artificial nucleation cavities. In addition, the results revealed that the design with cavities distributed uniformly along the downstream half of the channel presented the best stability performance among the three distributions of nucleation sites. This particular design can be regarded as a highly stable microchannel heat sink for convective boiling

  16. OPG's approach of crediting natural circulation in outage heat sinks

    International Nuclear Information System (INIS)

    Fung, K.K.; Mackinnon, J.C.

    2001-01-01

    A review of crediting natural circulation as a backup means of removing the reactor core decay heat during an outage in Ontario Power Generation's nuclear stations was completed in 2000. The objective was to define the configurations and conditions under which natural circulation can be confidently credited as an effective heat transport mechanism for use in shutdown heat sink management. The project was an interdisciplinary program, and involved analyses in the areas of heat transport system thermalhydaulics, fuel and fuel channel thermal and mechanical behaviour, radiation physics, and probabilistic risks. The assessment shows that it is economically acceptable to credit natural circulation as a backup means of removing the core decay heat whenever the no fuel failure criteria are met. The economic risks associated with such a potential use decrease with time after shutdown. The waiting times after shutdown when there would be various levels of risks of damaging the pressure tubes and fuel bundles were derived for use in planning maintenance activities so as to minimize the economic risks. (author)

  17. Effects of Symmetrically Arranged Heat Sources on the Heat Release Performance of Extruded-Type Heat Sinks

    Energy Technology Data Exchange (ETDEWEB)

    Ku, Min Ye [Chonbuk National Univ., Chonju (Korea, Republic of)

    2016-02-15

    In this study we investigated the effects of symmetrically arranged heat sources on the heat release performances of extruded-type heat sinks through experiments and thermal fluid simulations. Also, based on the results we suggested a high-efficiency and cost-effective heat sink for a solar inverter cooling system. In this parametric study, the temperatures between heaters on the base plate and the heat release rates were investigated with respect to the arrangements of heat sources and amounts of heat input. Based on the results we believe that the use of both sides of the heat sink is the preferred method for releasing the heat from the heat source to the ambient environment rather than the use of a single side of the heat sink. Also from the results, it is believed that the symmetric arrangement of the heat sources is recommended to achieve a higher rate of heat transfer. From the results of the thermal fluid simulation, it was possible to confirm the qualitative agreement with the experimental results. Finally, quantitative comparison with respect to mass flow rates, heat inputs, and arrangements of the heat source was also performed.

  18. Novel two-phase jet impingement heat sink for active cooling of electronic devices

    International Nuclear Information System (INIS)

    Oliveira, Pablo A. de; Barbosa, Jader R.

    2017-01-01

    Highlights: • Novel jet-based heat sink integrates the evaporator and the expansion device. • The system was tested with a small-scale oil-free R-134a compressor. • The thermodynamic performance of the cooling system was evaluated experimentally. • The single-jet maximum cooling capacity was 160 W, with a COP of 2.3 and a η 2nd of 8%. • Maximum heat transfer coefficient of 15 kW m −2 K −1 and surface temperature of 30 °C. - Abstract: This work presents a compact vapor compression cooling system equipped with a small-scale oil-free R-134a compressor and a jet-impingement-based heat sink that integrates the evaporator and the expansion device into a single unit. At the present stage of the development, a single orifice was used to generate the high-speed two-phase impinging jet on the heated surface. The effects of the compressor piston stroke, applied thermal load and orifice diameter on the system performance were quantified. The thermodynamic performance of the system was evaluated in terms of the temperature of the heated surface, impinging jet heat transfer coefficient, several system thermal resistances, coefficient of performance, second-law efficiency and second-law ratio. The coefficient of performance of the new refrigeration system increased with the cooling capacity, justifying its application in the removal of large thermal loads. The maximum system cooling capacity with a single jet was approximately 160 W, which was achieved with an orifice diameter of 500 μm and operation at a full compressor piston stroke. This condition corresponded to a COP of 2.3, a second-law efficiency of 8.0%, a jet impingement heat transfer coefficient above 15 kW m −2 K −1 and a heater surface temperature of approximately 30 °C.

  19. Indirect heating of natural gas using vapor chambers; Aquecimento indireto de gas natural com uso de camaras de vapor

    Energy Technology Data Exchange (ETDEWEB)

    Milanez, Fernando H; Mantellil, Marcia H.B.; Borges, Thomaz P.F. [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica; Landa, Henrique G. de [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas

    2005-07-01

    Operation safety and reliability are major guidelines in the design of city-gate units. Conventional natural gas heaters operate by a indirect mechanism, where liquid water is used to transfer heat by natural convection between the combustion chamber and the natural gas coil. In this work, the concept of vapor chamber is evaluated as an indirect gas heater. In a vapor chamber, liquid water is in contact with the heat source, and vaporizes. The vapor condenses in contact with the heat sink. A reduced scale model was built and tested in order to compare these two heating concepts where the combustion chamber was replaced by electrical cartridge heaters. This engineering model can operate either as a conventional heater or as a vapor chamber. The comparison between the concepts was done by inducing a controlled power to the cartridges and by measuring the resulting temperature distributions. In the novel design, the heat exchanger efficiency increases, and the thermal inertia decreases, compared to the conventional system. The new sealed concept of the chamber prevents water evaporation losses. (author)

  20. Development of a discharge model for the Bopp and Reuther Degasser/Condenser relief valves for heat sink assessment

    International Nuclear Information System (INIS)

    Hasnaoui, C. . chiheb@hasnaoui.net; Huynh, M.

    2004-01-01

    A total loss of all sustained engineering heat sinks is considered as a severe accident with low probability of occurrence. Following a total loss of all sustained engineering heat sinks, the Degasser/Condenser relief valves (3332-RV11 and RV21) would then become the sole means available for the depressurization of the primary heat transport system. Accurate estimation of the discharge through these valves is required to assess the impact of this kind of accident on fuel cooling and the primary circuit integrity. This paper describes a model used to estimate the Degasser/Condenser relief valve discharge capacity. This model is used to predict the flow discharge under a range of conditions upstream of the relief valves; from sub-cooled to saturated liquid and up to vapor conditions. The defined model is then used to estimate the relief valve discharge rates under various hypothetical conditions of the PHTS using the Cathena code. (author)

  1. Enhancement of heat dissipation of LED module with cupric-oxide composite coating on aluminum-alloy heat sink

    International Nuclear Information System (INIS)

    Kim, Donghyun; Lee, Junghoon; Kim, Junho; Choi, Chang-Hwan; Chung, Wonsub

    2015-01-01

    Highlights: • We fabricate the CuO/resin composite coating layer on aluminum alloy heat sink. • CuO/resin coating considerably improved the surface emissivity. • The LED junction temperature was reduced by CuO/resin coated heat sink. • The thermal resistance of heat sink was decreased by CuO/resin composite coating at 200 μm thickness. - Abstract: A composite coating composed of cupric oxide (CuO) and silicon-based resin was applied to an aluminum-alloy heat sink for a light emitting diode (LED) module. The purpose of the composite coating is to improve the heat dissipation performance of heat sink by enhancing thermal radiation emission. The heat dissipation performance was investigated in terms of LED junction temperature and thermal resistance using a thermal transient method. The CuO and silicon-based resin composite coating showed higher emissivity, and the lower junction temperature and thermal resistance of the heat sink was achieved. In addition, a continuous operation test of the LED chip with the heat sink revealed that the surface treated with the CuO composite coating stably dissipated heat without degradation. In conclusion, the composite coating proposed here showed a significant improvement of the heat dissipation performance of the aluminum-alloy heat sink due to the enhanced thermal radiation property.

  2. Characterization of Radial Curved Fin Heat Sink under Natural and Forced Convection

    Science.gov (United States)

    Khadke, Rishikesh; Bhole, Kiran

    2018-02-01

    Heat exchangers are important structures widely used in power plants, food industries, refrigeration, and air conditioners and now widely used in computing systems. Finned type of heat sink is widely used in computing systems. The main aim of the design of the heat sink is to maintain the optimum temperature level. To achieve this goal so many geometrical configurations are implemented. This paper presents a characterization of radially curved fin heat sink under natural and forced convection. Forced convection is studied for the optimization of temperature for better efficiency. The different alternatives in geometry are considered in characterization are heat intensity, the height of the fin and speed of the fan. By recognizing these alternatives the heat sink is characterized by the heat flux usually generated in high-end PCs. The temperature drop characteristics across height and radial direction are presented for the constant heat input and air flow in the heat sink. The effect of dimensionless elevation height (0 ≤ Z* ≤ 1) and Elenbaas Number (0.4 ≤ El ≤ 2.8) of the heat sink were investigated for study of the Nusselt number. Based on experimental characterization, process plan has been developed for the selection of the similar heat sinks for desired output (heat dissipation and temperature distribution).

  3. Surface hardening of titanium alloys with melting depth controlled by heat sink

    Science.gov (United States)

    Oden, Laurance L.; Turner, Paul C.

    1995-01-01

    A process for forming a hard surface coating on titanium alloys includes providing a piece of material containing titanium having at least a portion of one surface to be hardened. The piece having a portion of a surface to be hardened is contacted on the backside by a suitable heat sink such that the melting depth of said surface to be hardened may be controlled. A hardening material is then deposited as a slurry. Alternate methods of deposition include flame, arc, or plasma spraying, electrodeposition, vapor deposition, or any other deposition method known by those skilled in the art. The surface to be hardened is then selectively melted to the desired depth, dependent on the desired coating thickness, such that a molten pool is formed of the piece surface and the deposited hardening material. Upon cooling a hardened surface is formed.

  4. Entropy generation of nanofluid flow in a microchannel heat sink

    Science.gov (United States)

    Manay, Eyuphan; Akyürek, Eda Feyza; Sahin, Bayram

    2018-06-01

    Present study aims to investigate the effects of the presence of nano sized TiO2 particles in the base fluid on entropy generation rate in a microchannel heat sink. Pure water was chosen as base fluid, and TiO2 particles were suspended into the pure water in five different particle volume fractions of 0.25%, 0.5%, 1.0%, 1.5% and 2.0%. Under laminar, steady state flow and constant heat flux boundary conditions, thermal, frictional, total entropy generation rates and entropy generation number ratios of nanofluids were experimentally analyzed in microchannel flow for different channel heights of 200 μm, 300 μm, 400 μm and 500 μm. It was observed that frictional and total entropy generation rates increased as thermal entropy generation rate were decreasing with an increase in particle volume fraction. In microchannel flows, thermal entropy generation could be neglected due to its too low rate smaller than 1.10e-07 in total entropy generation. Higher channel heights caused higher thermal entropy generation rates, and increasing channel height yielded an increase from 30% to 52% in thermal entropy generation. When channel height decreased, an increase of 66%-98% in frictional entropy generation was obtained. Adding TiO2 nanoparticles into the base fluid caused thermal entropy generation to decrease about 1.8%-32.4%, frictional entropy generation to increase about 3.3%-21.6%.

  5. Heat transfer and flow structure evaluation of a synthetic jet emanating from a planar heat sink

    International Nuclear Information System (INIS)

    Manning, Paul; Persoons, Tim; Murray, Darina

    2014-01-01

    Direct impinging synthetic jets are a proven method for heat transfer enhancement, and have been subject to extensive research. However, despite the vast amount of research into direct synthetic jet impingement, there has been little research investigating the effects of a synthetic jet emanating from a heated surface, this forms the basis of the current research investigation. Both single and multiple orifices are integrated into a planar heat sink forming a synthetic jet, thus allowing the heat transfer enhancement and flow structures to be assessed. The heat transfer analysis highlighted that the multiple orifice synthetic jet resulted in the greatest heat transfer enhancements. The flow structures responsible for these enhancements were identified using a combination of flow visualisation, thermal imaging and thermal boundary layer analysis. The flow structure analysis identified that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process. Flow visualisation revealed entrainment of local air adjacent to the heated surface; this occurred from vortex roll-up at the surface of the heat sink and from the highly sheared jet flow. Furthermore, a secondary entrainment was identified which created a surface impingement effect. It is proposed that all three flow features enhance the heat transfer characteristics of the system.

  6. 78 FR 55117 - Ultimate Heat Sink for Nuclear Power Plants; Draft Regulatory Guide

    Science.gov (United States)

    2013-09-09

    ... NUCLEAR REGULATORY COMMISSION [NRC-2013-0203] Ultimate Heat Sink for Nuclear Power Plants; Draft... (DG), DG-1275, ``Ultimate Heat Sink for Nuclear Power Plants.'' This regulatory guide (RG) describes methods and procedures acceptable to the NRC staff that nuclear power plant facility licensees and...

  7. Micro-structured rough surfaces by laser etching for heat transfer enhancement on flush mounted heat sinks

    International Nuclear Information System (INIS)

    Ventola, L; Scaltrito, L; Ferrero, S; Chiavazzo, E; Asinari, P; Maccioni, G

    2014-01-01

    The aim of this work is to improve heat transfer performances of flush mounted heat sinks used in electronic cooling. To do this we patterned 1.23 cm 2 heat sinks surfaces by microstructured roughnesses built by laser etching manufacturing technique, and experimentally measured the convective heat transfer enhancements due to different patterns. Each roughness differs from the others with regards to the number and the size of the micro-fins (e.g. the micro- fin length ranges from 200 to 1100 μm). Experimental tests were carried out in forced air cooling regime. In particular fully turbulent flows (heating edge based Reynolds number ranging from 3000 to 17000) were explored. Convective heat transfer coefficient of the best micro-structured heat sink is found to be roughly two times compared to the smooth heat sinks one. In addition, surface area roughly doubles with regard to smooth heat sinks, due to the presence of micro-fins. Consequently, patterned heat sinks thermal transmittance [W/K] is found to be roughly four times the smooth heat sinks one. We hope this work may open the way for huge boost in the technology of electronic cooling by innovative manufacturing techniques.

  8. Thermal effect of a thermoelectric generator on parallel microchannel heat sink

    DEFF Research Database (Denmark)

    Kolaei, Alireza Rezania; Rosendahl, Lasse

    2012-01-01

    Thermoelectric generators (TEG) convert heat energy to electrical power by means of semiconductor charge carriers serving as working fluid. In this work, a TEG is applied to a parallel microchannel heat sink. The effect of the inlet plenum arrangement on the laminar flow distribution...... in the channels is considered at a wide range of the pressure drop along the heat sink. The particular focus of this study is geometrical effect of the TEG on the heat transfer characteristics in the micro-heat sink. The hydraulic diameter of the microchannels is 270 μm, and three heat fluxes are applied...... on the hot surface of the TEG. By considering the maximum temperature limitation for Bi_2 Te_3 material and using the microchannel heat sink for cooling down the TEG system, an optimum pumping power is achieved. The results are in a good agreement with the previous experimental and theoretical studies....

  9. Thermal performance analysis of optimized hexagonal finned heat sinks in impinging air jet

    Energy Technology Data Exchange (ETDEWEB)

    Yakut, Kenan, E-mail: kyakut@atauni.edu.tr [Department of Mechanical Engineering, Faculty of Engineering, Atatürk University, 25100, Erzurum (Turkey); Yeşildal, Faruk, E-mail: fayesildal@agri.edu.tr [Department of Mechanical Engineering, Faculty of Patnos Sultan Alparslan Natural Sciences and Engineering, Ağrı İbrahim Çeçen University, 04100, Ağrı (Turkey); Karabey, Altuğ, E-mail: akarabey@yyu.edu.tr [Department of Machinery and Metal Technology, Erciş Vocational High School, Yüzüncü Yıl University, 65400, Van (Turkey); Yakut, Rıdvan, E-mail: ryakut@kafkas.edu.tr [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Kafkas University, 36100, Kars (Turkey)

    2016-04-18

    In this study, thermal performance analysis of hexagonal finned heat sinks which optimized according to the experimental design and optimization method of Taguchi were investigated. Experiments of air jet impingement on heated hexagonal finned heat sinks were carried out adhering to the L{sub 18}(2{sup 1*}3{sup 6}) orthogonal array test plan. Optimum geometries were determined and named OH-1, OH-2. Enhancement efficiency with the first law of thermodynamics was analyzed for optimized heat sinks with 100, 150, 200 mm heights of hexagonal fin. Nusselt correlations were found out and variations of enhancement efficiency with Reynolds number presented in η–Re graphics.

  10. Heat sink design considerations in medium power electronic applications with long power cycles

    CERN Document Server

    AUTHOR|(SzGeCERN)744611; Papastergiou, Konstantinos; Thiringer, Torbjörn; Bongiorno, Massimo

    2015-01-01

    The aim of this work is to investigate the impact of the heat sink thickness and material, as well as, of the convection coefficient of the water cooling system on the power-electronics module thermal stressing. The heat extraction capability of different thicknesses is tested. It is concluded that the thickest heat sink results in marginally lower temperature variation at the junction level compared to the second thickest one. In the thickest heat sink case, the linear dependence of the thermal resistance on the thickness counteracts the benefit of the increased thermal capacitance. The increase in the cooling medium flow rate, which corresponds to an increase in the convection coefficient between the heat sink bottom surface and the water, can be avoided by increasing the thickness of the heat sink. In this way, the energy consumption of the cooling system is reduced. The increase in the flow rate drastically reduces the thermal stressing in the thinnest heat sink case. The increase of the heat sink thickne...

  11. Enhancing heat transfer in microchannel heat sinks using converging flow passages

    International Nuclear Information System (INIS)

    Dehghan, Maziar; Daneshipour, Mahdi; Valipour, Mohammad Sadegh; Rafee, Roohollah; Saedodin, Seyfolah

    2015-01-01

    Highlights: • The fluid flow and conjugate heat transfer in microchannel heat sinks are studied. • The Poiseuille and Nusselt numbers are presented for width-tapered MCHS. • Converging walls are found to enhance the thermal performance of MCHS. • The optimum performance of MCHS for fixed inlet and outlet pressures is discussed. • For the optimum configuration, the pumping power is reduced up to 75%. - Abstract: Constrained fluid flow and conjugate heat transfer in microchannel heat sinks (MCHS) with converging channels are investigated using the finite volume method (FVM) in the laminar regime. The maximum pressure of the MCHS loop is assumed to be limited due to constructional or operational conditions. Results show that the Poiseuille number increases with increased tapering, while the required pumping power decreases. Meanwhile, the Nusselt number increases with tapering as well as the convection heat transfer coefficient. The MCHS having the optimum heat transfer performance is found to have a width-tapered ratio equal to 0.5. For this tapering configuration and at the maximum pressure constraint of 3000 Pa, the pumping power reduces by a factor of 4 while the overall heat removal rate is kept fixed in comparison with a straight channel

  12. Topology optimization of a pseudo 3D thermofluid heat sink model

    DEFF Research Database (Denmark)

    Haertel, Jan H. K.; Engelbrecht, Kurt; Lazarov, Boyan S.

    2018-01-01

    sink and a fixed heat production rate in the base plate. Optimized designs are presented and the resulting fin geometry is discussed from a thermal engineering point of view and compared to fin shapes resulting from a pressure drop minimization objective. Parametric studies are conducted to analyze......This paper investigates the application of density-based topology optimization to the design of air-cooled forced convection heat sinks. To reduce the computational burden that is associated with a full 3D optimization, a pseudo 3D optimization model comprising a 2D modeled conducting metal base...... layer and a thermally coupled 2D modeled thermofluid design layer is used. Symmetry conditions perpendicular to the flow direction are applied to generate periodic heat sink designs. The optimization objective is to minimize the heat sink heat transfer resistance for a fixed pressure drop over the heat...

  13. Transient cooling of electronics using phase change material (PCM)-based heat sinks

    International Nuclear Information System (INIS)

    Kandasamy, Ravi; Wang Xiangqi; Mujumdar, Arun S.

    2008-01-01

    Use of a phase change material (PCM)-based heat sink in transient thermal management of plastic quad flat package (QFP) electronic devices was investigated experimentally and numerically. Results show that increased power inputs enhance the melting rate as well as the thermal performance of the PCM-based heat sinks until the PCM is fully melted. A three-dimensional computational fluid dynamics model was proposed to simulate the problem and demonstrated good agreement with experimental data. Results indicate the potential for PCM-based heat sinks for use in intermittent-use devices

  14. Residual stresses and their mechanisms of production at circumferential weld by heat-sink welding

    International Nuclear Information System (INIS)

    Ueda, Yukio; Nakacho, Keiji; Ohkubo, Katsumi; Shimizu, Tsubasa.

    1983-01-01

    In the previous report, the authors showed effectiveness of the heat-sink welding (water cooling) to accomplish this end by conducting theoretical analysis and an experiment on residual stresses in the 4B pipe of SUS 304 by the conventional welding and the heat-sink welding at a certain standard heat-input condition. In this research, different pipe sizes and varied heat-input are applied. The welding residual stresses by the conventional welding and the heat-sink welding are obtained by the theoretical analysis and their production mechanisms are clarified. Hence the influence of the above changes of conditions on effectiveness of the heat-sink welding is investigated. The main results are summarized as follow. (1) In case of this pipes such as 2B and 4B pipes, it is important to minimize heat-input per one pass (especially for latter half passes) in order to improve the effectiveness of the heat-sink welding. The effectiveness can be predicted either by theoretical analysis of the temperature distribution history with consideration of the characteristic of heat transfer under spray-watering or by experimental measurement. (2) In case of 24B pipes, thick pipes, it is desirable to minimize heat-input for the first half passes, by which the heat-sink welding becomes more effective. In addition, no matter whether the conventional welding or the heat-sink welding, it is important to prevent angular distorsion which produces tensile axial stresses on the inner surface of the pipe in the weld zone. Possible measures to meet these requirements are to apply restraining jigs, to minimize the section area of the groove (ex. application of the narrow gap arc welding), and to change continuous welding to skip one. (J.P.N.)

  15. A review on heat sink for thermo-electric power generation: Classifications and parameters affecting performance

    International Nuclear Information System (INIS)

    Elghool, Ali; Basrawi, Firdaus; Ibrahim, Thamir Khalil; Habib, Khairul; Ibrahim, Hassan; Idris, Daing Mohamad Nafiz Daing

    2017-01-01

    Highlights: • Coupling a thermoelectric power generation (TEG) to a heat sink is presented. • Review the classifications and parameters affecting performance of the TEG with heat sink. • Discuss different mathematical models of the heat sinks. • The passive heat sinks are most appropriate because of the inherent efficiency of TEG. • Medium temperature range below 300 °C is found to be most suitable for HPHS. - Abstract: In recent years, there have been growing interests in key areas related to global warming resulting from environmental emissions, and the diminishing sources of fossil fuel. The increased interest has led to significant research efforts towards finding novel technologies in clean energy production. Consequently, the merits of a thermo-electric generator (TEG) have promised a revival of alternative means of producing green energy. It is, however, impractical to account for the cost of thermal energy input to the TEG which is in the form of final waste heat. This is because the technology presents critical limitations in determining its cost efficiency nor its economic disadvantages. This paper reviews the principles of thermo-electric power production, as well the materials use, performance achieved, and application areas. The paper also takes a particular deliberation on TEG heat sinks geometries and categories. The review emphasizes more on the TEG performance while considering a number of heat sink parameters related to its performance.

  16. CTE-Matched, Liquid-Cooled, High Thermal Conductivity Heat Sink, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose the development of a CTE-matched, liquid-cooled, high thermal conductivity heat sink for use in spacecraft thermal management applications. The material...

  17. Linking potential heat source and sink to urban heat island: Heterogeneous effects of landscape pattern on land surface temperature.

    Science.gov (United States)

    Li, Weifeng; Cao, Qiwen; Lang, Kun; Wu, Jiansheng

    2017-05-15

    Rapid urbanization has significantly contributed to the development of urban heat island (UHI). Regulating landscape composition and configuration would help mitigate the UHI in megacities. Taking Shenzhen, China, as a case study area, we defined heat source and heat sink and identified strong and weak sources as well as strong and weak sinks according to the natural and socioeconomic factors influencing land surface temperature (LST). Thus, the potential thermal contributions of heat source and heat sink patches were differentiated. Then, the heterogeneous effects of landscape pattern on LST were examined by using semiparametric geographically weighted regression (SGWR) models. The results showed that landscape composition has more significant effects on thermal environment than configuration. For a strong source, the percentage of patches has a positive impact on LST. Additionally, when mosaicked with some heat sink, even a small improvement in the degree of dispersion of a strong source helps to alleviate UHI. For a weak source, the percentage and density of patches have positive impacts on LST. For a strong sink, the percentage, density, and degree of aggregation of patches have negative impacts on LST. The effects of edge density and patch shape complexity vary spatially with the fragmentation of a strong sink. Similarly, the impacts of a weak sink are mainly exerted via the characteristics of percent, density, and shape complexity of patches. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Analysis of the transient compressible vapor flow in heat pipes

    Science.gov (United States)

    Jang, J. H.; Faghri, A.; Chang, W. S.

    1989-01-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.

  19. Analysis of the transient compressible vapor flow in heat pipe

    International Nuclear Information System (INIS)

    Jang, J.H.; Faghri, A.; Chang, W.S.

    1989-07-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures

  20. The influence of heat sink temperature on the seasonal efficiency of shallow geothermal heat pumps

    Science.gov (United States)

    Pełka, Grzegorz; Luboń, Wojciech; Sowiżdżał, Anna; Malik, Daniel

    2017-11-01

    Geothermal heat pumps, also known as ground source heat pumps (GSHP), are the most efficient heating and cooling technology utilized nowadays. In the AGH-UST Educational and Research Laboratory of Renewable Energy Sources and Energy Saving in Miękinia, shallow geothermal heat is utilized for heating. In the article, the seasonal efficiency of two geothermal heat pump systems are described during the 2014/2015 heating season, defined as the period between 1st October 2014 and 30th April 2015. The first system has 10.9 kW heating capacity (according to European Standard EN 14511 B0W35) and extracts heat from three vertical geothermal loops at a depth of 80m each. During the heating season, tests warmed up the buffer to 40°C. The second system has a 17.03 kW heating capacity and extracts heat from three vertical geothermal loops at a depth of 100 m each, and the temperature of the buffer was 50°C. During the entire heating season, the water temperatures of the buffers was constant. Seasonal performance factors were calculated, defined as the quotient of heat delivered by a heat pump to the system and the sum of electricity consumed by the compressor, source pump, sink pump and controller of heat pumps. The measurements and calculations give the following results: - The first system was supplied with 13 857 kWh/a of heat and consumed 3 388 kWh/a electricity. The SPF was 4.09 and the average temperature of outlet water from heat pump was 40.8°C, and the average temperature of brine flows into the evaporator was 3.7 °C; - The second system was supplied with 12 545 kWh/a of heat and consumed 3 874 kWh/a electricity. The SPF was 3.24 and the average temperature of outlet water from heat pump was 51.6°C, and the average temperature of brine flows into the evaporator was 5.3°C. To summarize, the data shown above presents the real SPF of the two systems. It will be significant in helping to predict the SPF of objects which will be equipped with ground source heat pumps.

  1. Study of ultimate heat sink to Angra-1,2 and 3 Nuclear Power Plants

    International Nuclear Information System (INIS)

    Moreira, R.M.; Pinto, A.M.F.

    1985-03-01

    This report presents the premises, results and conclusion of study done to ultimate heat sink of Angra 1,2 and 3 units, with base in postulated accidents that generate transient heat discharges to environment. It's explicitily presumed the eventuality of discharging heat water recirculation. (C.M.) [pt

  2. Thermal management of electronics using phase change material based pin fin heat sinks

    International Nuclear Information System (INIS)

    Baby, R; Balaji, C

    2012-01-01

    This paper reports the results of an experimental study carried out to explore the thermal characteristics of phase change material based heat sinks for electronic equipment cooling. The phase change material (PCM) used in this study is n – eicosane. All heat sinks used in the present study are made of aluminium with dimensions of 80 × 62 mm 2 base with a height of 25 mm. Pin fins acts as the thermal conductivity enhancer (TCE) to improve the distribution of heat more uniformly as the thermal conductivity of the PCM is very low. A total of three different pin fin heat sink geometries with 33, 72 and 120 pin fins filled with phase change materials giving rise to 4%, 9% and 15% volume fractions of the TCE respectively were experimentally investigated. Baseline comparisons are done with a heat sink filled with PCM, without any fin. Studies are conducted for heat sinks on which a uniform heat load is applied at the bottom for the finned and unfinned cases. The effect of pin fins of different volume fractions with power levels ranging from 4 to 8 W corresponding to a heat flux range of 1. 59 to 3.17 kW/m 2 , was explored in this paper. The volume fraction of the PCM (PCM volume / (Total volume – fin volume)) is also varied as 0. 3, 0.6 and 1 to determine the effect of PCM volume on the overall performance of the electronic equipment.

  3. Development of Thermal Design Program for an Electronic Telecommunication System Using Heat Sink

    International Nuclear Information System (INIS)

    Lee, Jung Hwan; Kim, Jong Man; Chun, Ji Hwan; Bae, Chul Ho; Suh, Myung Won

    2007-01-01

    The purpose of this study is to investigate the cooling performance of heat sinks for an electronic telecommunication system by adequate natural convection. Heat generation rates of electronic components and the temperature distributions of heat sinks and surrounding air are analyzed experimentally and numerically. In order to perform the heat transfer analysis for the thermal design of telecommunication system, a program is developed. The program used the graphic user interface environment to determine the arrangement of heat sources, interior fan capacity, and heat sink configuration. The simulation results showed that the heat sinks were able to achieve a cooling capacity of up to 230W at the maximum temperature difference of 19 .deg. C. To verify the results from the numerical simulation, an experiment was conducted under the same condition as the numerical simulation, and their results were compared. The design program gave good prediction of the effects of various parameters involved in the design of a heat sinks for an electronic telecommunication system

  4. Fluid-cooled heat sink for use in cooling various devices

    Science.gov (United States)

    Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth; Narumanchi, Sreekant

    2017-09-12

    The disclosure provides a fluid-cooled heat sink having a heat transfer base, a shroud, and a plurality of heat transfer fins in thermal communication with the heat transfer base and the shroud, where the heat transfer base, heat transfer fins, and the shroud form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop of the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.

  5. Performance evaluation of a wavy-fin heat sink for power electronics

    International Nuclear Information System (INIS)

    Lorenzini, Marco; Fabbri, Giampietro; Salvigni, Sandro

    2007-01-01

    The almost daily increase in dissipated power per unit area of electronic components sets higher and higher demands on the performance of the heat sinks. These must not only be able to dissipate high heat fluxes, but must also keep costs to a minimum and exhibit a reliable behaviour. In this paper a novel, modular heat sink consisting of elements with wavy fin profile which can be pressed together to construct the component is presented. Its performance under steady-state conditions are assessed for the case of forced convection in terms of velocity distribution in the channels and global thermal resistance. Configurations with uniform and non-uniform heat flux are studied and some considerations are made as to the influence of the spacers between fan and heat sink proper

  6. Assessment of hypervapotron heat sink performance using CFD under DEMO relevant first wall conditions

    Energy Technology Data Exchange (ETDEWEB)

    Domalapally, Phani, E-mail: p_kumar.domalapally@cvrez.cz

    2016-11-01

    Highlights: • Performance of Hypervapotron heat sink was tested for First wall limiter application. • Two different materials were tested Eurofer 97 and CuCrZr at PWR conditions. • Simulations were performed to see the effect of the different inlet conditions and materials on the maximum temperature. • It was found that CuCrZr heat sink performance is far better than Eurofer heat sink at the same operating conditions. - Abstract: Among the proposed First Wall (FW) cooling concepts for European Demonstration Fusion Power Plant (DEMO), water cooled FW is one of the options. The heat flux load distribution on the FW of the DEMO reactor is not yet precisely defined. But if the heat loads on the FW are extrapolated from ITER conditions, the numbers are quite high and have to be handled none the less. The design of the FW itself is challenging as the thermal conductivity ratio of heat sink materials in ITER (CuCrZr) and in DEMO (Eurofer 97) is ∼10–12 and the operating conditions are of Pressurized Water Reactor (PWR) in DEMO instead of 70 °C and 4 MPa as in ITER. This paper analyzes the performance of Hypervapotron (HV) heat sink for FW limiter application under DEMO conditions. Where different materials, temperatures, heat fluxes and velocities are considered to predict the performance of the HV, to establish its limits in handling the heat loads before reaching the upper limits from temperature point of view. In order to assess the performance, numerical simulations are performed using commercial CFD code, which was previously validated in predicting the thermal hydraulic performance of HV geometry. Based on the results the potential usage of HV heat sink for DEMO will be assessed.

  7. Analysis of the transient compressible vapor flow in heat pipe

    Science.gov (United States)

    Jang, Jong Hoon; Faghri, Amir; Chang, Won Soon

    1989-01-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.

  8. Numerical study of metal foam heat sinks under uniform impinging flow

    International Nuclear Information System (INIS)

    Andreozzi, A; Bianco, N; Iasiello, M; Naso, V

    2017-01-01

    The ever-increasing demand for performance improvement and miniaturization of electronics has led to a significant generation of waste heat that must be dissipated to ensure a reliable device operation. The miniaturization of the components complicates this task. In fact, reducing the heat transfer area, at the same required heat rate, it is necessary to increase the heat flux, so that the materials operate in a temperature range suitable to its proper functioning. Traditional heat sinks are no longer capable of dissipating the generated heat and innovative approaches are needed to address the emerging thermal management challenges. Recently, heat transfer in open-cell metal foams under an impinging jet has received attention due to the considerable heat transfer potential of combining two cooling technologies: impinging jet and porous medium. This paper presents a numerical study on Finned Metal Foam (FMF) and Metal Foam (MF) heat sinks under impinging air jet cooling. The analysis is carried out by means of the commercial software COMSOL Multiphysics®. The purpose is to analyze the thermal performance of the metal foam heat sink, finned or not, varying its geometric parameters. Results are presented in terms of predicted dissipated heat rate, convective heat transfer coefficient and pressure losses. (paper)

  9. Thermodynamic analysis and optimization of an ammonia-water power system with LNG (liquefied natural gas) as its heat sink

    International Nuclear Information System (INIS)

    Wang, Jiangfeng; Yan, Zhequan; Wang, Man; Dai, Yiping

    2013-01-01

    Due to a good behavior of ammonia-water during the two-phase heat addition process and the liquefied natural gas with great cold energy, an ammonia-water power system with LNG as its heat sink is proposed to utilize the low grade waste heat. Based on the thermodynamic mathematical models, the effects of key thermodynamic design parameters, including turbine inlet pressure, turbine inlet temperature, ammonia mass fraction, pinch temperature difference and approach temperature difference in the heat recovery vapor generator, on the system performance are examined from the view of both thermodynamics and economics. To obtain the optimum performance, multi-objective optimization is conducted to find the best thermodynamic design parameters from both thermodynamic and economic aspects using NSGA-II (Non-dominated sorting genetic algorithm-II). The exergy efficiency, total heat transfer capability and turbine size parameter are selected as three objective functions to maximize the exergy efficiency, and minimize the total heat transfer capability and turbine size parameter under the given waste heat conditions. The results show that turbine inlet pressure, turbine inlet temperature, ammonia mass fraction, pinch temperature difference and approach temperature difference have significant effects on the system performance. By multi-objective optimization, the Pareto frontier solution for the ammonia-water power system is obtained. - Highlights: ► An ammonia-water power system with LNG as its heat sink is proposed. ► The effects of key parameters on the system performance are examined. ► Multi-objective optimization is conducted to obtain optimum system performance

  10. Treatment of the loss of ultimate heat sink initiating events in the IRSN level 1 PSA

    International Nuclear Information System (INIS)

    Dupuy, Patricia; Georgescu, Gabriel; Corenwinder, Francois

    2014-01-01

    The total loss of the ultimate heat sink is an initiating event which, even it is mainly of external origin, has been considered in the frame of internal events Level 1 PSA by IRSN. The on-going actions on the development of external hazards PSA and the recent incident of loss of the heat sink induced by the ingress of vegetable matter that occurred in France in 2009 have pointed out the need to improve the modeling of the loss of the heat sink initiating event and sequences to better take into account the fact that this loss may be induced by external hazards and thus affect all the site units. The paper presents the historical steps of the modeling of the total loss of the heat sink, the safety stakes of this modeling, the main assumptions used by IRSN in the associated PSA for the 900 MWe reactors and the results obtained. The total loss of the heat sink was not initially addressed in the safety demonstration of French NPPs. On the basis of the insights of the first probabilistic assessments performed in the 80's, the risks associated to this 'multiple failure situation' turned out to be very significant and design and organisational improvements were implemented on the plants. Reviews of the characterization of external hazards and of their consequences on the installations and French operating feedback have revealed that extreme hazards may induce a total loss of the heat sink. Moreover, the accident that occurred at Fukushima in 2011 has pointed out the risk of such a loss of long duration at all site units in case of extreme hazards. In this context, it seems relevant to further improve the modelling of the total loss of the heat sink by considering the external hazards that may cause this loss. In a first step, IRSN has improved the assumptions and data used in the loss of the heat sink PSA model, in particular by considering that such a loss may affect all the site units. The next challenge will be the deeper analysis of the impact of external hazards on

  11. A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium.

    Science.gov (United States)

    McCarron, Daniel J; Hughes, Ifan G; Tierney, Patrick; Cornish, Simon L

    2007-09-01

    The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D(2) transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude.

  12. A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium

    International Nuclear Information System (INIS)

    McCarron, Daniel J.; Hughes, Ifan G.; Tierney, Patrick; Cornish, Simon L.

    2007-01-01

    The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D 2 transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude

  13. Effect of heat sink layer on ultrafast magnetization recovery of FeCo films

    International Nuclear Information System (INIS)

    Ren, Y; Zhao, J Q; Zhang, Z Z; Jin, Q Y; Hu, H N; Zhou, S M

    2008-01-01

    For FeCo alloy thin films with Ag, Cu, Pt, Ta and Cr as heat sink layers, ultrafast demagnetization and recovery processes of transient magnetization have been studied by the time-resolved magneto-optical Kerr effect. For all samples, the ultrafast demagnetization process is accomplished within almost the same time interval of 500 fs, which is independent of the heat sink layer material and the pump fluence. The recovery rate of the FeCo film grown on the Si(1 0 0) substrate is enhanced with a heat sink layer. In addition, the recovery rate is found to be independent of the heat sink layer thickness; it decreases with increasing pump fluence. Among all heat sink layers, the sample with the Cr layer achieves the highest recovery rate because it has the same bcc structure as that of the FeCo layer and the small lattice mismatch. The sample with the Ta layer, has the largest damage threshold of pump fluence because of the highest melting point

  14. Development and numerical investigation of novel gradient-porous heat sinks

    International Nuclear Information System (INIS)

    Wang, Baicun; Hong, Yifeng; Wang, Liang; Fang, Xudong; Wang, Pengfei; Xu, Zhongbin

    2015-01-01

    Highlights: • A novel design of gradient-porous heat sink (GPHS) was proposed in this work. • A 3D model was constructed to study the hydraulic and thermal performances of GPHS. • GPHS is capable of improving the hydraulic and thermal performances simultaneously. • GPHS with decreasing dp by Y can effectively suppress the bottom wall temperature. - Abstract: A novel design of gradient-porous heat sink (GPHS) was proposed and numerically studied in this work. Computational simulation was carried out to analyze the effects of gradient porous material (GPM) configuration on the hydraulic and thermal performances of heat sinks in comparison of homogeneous-porous heat sink (HPHS) serving as the control. Both gradient pore-size (dp) in the flow direction and the direction normal to flow direction were studied. It was found that, compared with conventional HPHS, GPHS can effectively improve the hydraulic and thermal performances simultaneously. Both the friction factor and overall thermal resistance of heat sinks with GPM configurations are considerably lowered. The Nusselt numbers of GPHS with gradient in flow direction are larger than those of homogeneous porous material (HPM) configurations. GPHS is also featured with the capabilities of effectively suppressing the bottom wall temperature and enhancing the convection performance.

  15. A heated vapor cell unit for DAVLL in atomic rubidium

    OpenAIRE

    McCarron, Daniel J.; Hughes, Ifan G.; Tierney, Patrick; Cornish, Simon L.

    2007-01-01

    The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D2 transitions in atomic rubidium is described. A 5 cm-long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field...

  16. Experimental investigation of inserts configurations and PCM type on the thermal performance of PCM based heat sinks

    International Nuclear Information System (INIS)

    Mahmoud, Saad; Tang, Aaron; Toh, Chin; AL-Dadah, Raya; Soo, Sein Leung

    2013-01-01

    Highlights: • Inclusion of PCM can reduce heating rate and peak temperatures of the heat sinks. • Increasing the number of fins can enhance heat transfer to PCM. • Honeycomb inserts can replace machined fin structures in PCM based heat sinks. • PCMs with lower melting points produced lower heat sink operating temperatures. - Abstract: Efficient thermal management in portable electronic devices is necessary to ensure sufficiently low operating temperatures for reliability, increased installed functions, and user comfort. Using Phase Change Materials (PCMs) based heat sinks offers potential in these applications. However, PCMs generally suffer from low thermal conductivities; therefore it is important to enhance their thermal conductivity and improve cooling performance. This study presents experimental investigation of the effects of PCM material, heat sink designs and power levels on PCM based heat sinks performance for cooling electronic devices. Six PCMs were used including paraffin wax (as reference material), two materials based on mixture of inorganic hydrated salts, two materials based on mixture of organic substances and one material based on a mixture of both organic and inorganic materials. Also, six heat sink designs were tested: one with single cavity, two with parallel fin arrangement, two with cross fin arrangement, and one with honeycomb insert inside the single cavity. Heat sinks thermal performance was investigated using paraffin wax type PCM with power inputs ranging from 3 W to 5 W. Results showed that the inclusion of PCM can reduce heating rates and peak temperatures of heat sinks with increasing the number of fins can enhance heat distribution to PCM leading to lower heat sinks peak temperatures. Also, the use of honeycomb inserts to replace machined finned structures has shown comparable thermal performance. Regarding the PCM type, the material with the lowest melting temperature has shown the best performance in terms of lowest

  17. Enhancing ultra-high CPV passive cooling using least-material finned heat sinks

    Energy Technology Data Exchange (ETDEWEB)

    Micheli, Leonardo, E-mail: lm409@exeter.ac.uk; Mallick, Tapas K., E-mail: T.K.Mallick@exeter.ac.uk [Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall TR10 9FE (United Kingdom); Fernandez, Eduardo F., E-mail: E.Fernandez-Fernandez2@exeter.ac.uk [Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall TR10 9FE (United Kingdom); Centre of Advanced Studies in Energy and Environment, University of Jaen, Jaen 23071 (Spain); Almonacid, Florencia, E-mail: facruz@ujaen.es [Centre of Advanced Studies in Energy and Environment, University of Jaen, Jaen 23071 (Spain); Reddy, K. S., E-mail: ksreddy@iitm.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai, 600036 (India)

    2015-09-28

    Ultra-high concentrating photovoltaic (CPV) systems aim to increase the cost-competiveness of CPV by increasing the concentrations over 2000 suns. In this work, the design of a heat sink for ultra-high concentrating photovoltaic (CPV) applications is presented. For the first time, the least-material approach, widely used in electronics to maximize the thermal dissipation while minimizing the weight of the heat sink, has been applied in CPV. This method has the potential to further decrease the cost of this technology and to keep the multijunction cell within the operative temperature range. The designing procedure is described in the paper and the results of a thermal simulation are shown to prove the reliability of the solution. A prediction of the costs is also reported: a cost of 0.151$/W{sub p} is expected for a passive least-material heat sink developed for 4000x applications.

  18. A numerical method for PCM-based pin fin heat sinks optimization

    International Nuclear Information System (INIS)

    Pakrouh, R.; Hosseini, M.J.; Ranjbar, A.A.; Bahrampoury, R.

    2015-01-01

    Highlights: • Optimization of PCM-based heat sink by using the Taguchi method. • Derivation of optimal PCM percentage to reach the maximum critical time. • Optimization is performed for four different critical temperatures. • Effective design factors are fins’ height and fins’ number. • The optimum configuration depends on geometric properties and the critical temperature. - Abstract: This paper presents a numerical investigation on geometric optimization of PCM-based pin fin heat sinks. Paraffin RT44HC is used as PCM while the fins and heat sink base is made of aluminum. The fins act as thermal conductivity enhancers (TCEs). The main goal of the study is to obtain the configurations that maximize the heat sink operational time. An approach witch couples Taguchi method with numerical simulations is utilized for this purpose. Number of fins, fins height, fins thickness and the base thickness are parameters which are studied for optimization. In this study natural convection and PCM volume variation during melting process are considered in the simulations. Optimization is performed for different critical temperatures of 50 °C, 60 °C, 70 °C and 80 °C. Results show that a complex relation exists between PCM and TCE volume percentages. The optimal case strongly depends on the fins’ number, fins’ height and thickness and also the critical temperature. The optimum PCM percentages are found to be 60.61% (corresponds to 100 pin fin heat sink with 4 mm thick fins) for critical temperature of 50 °C and 82.65% (corresponds to 100 pin fin heat sink with 2 mm thick fins) for other critical temperatures

  19. Pitch-based carbon foam heat sink with phase change material

    Science.gov (United States)

    Klett, James W.; Burchell, Timothy D.

    2004-08-24

    A process for producing a carbon foam heat sink is disclosed which obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications. The foam is encased and filled with a phase change material to provide a very efficient heat sink device.

  20. Experimental investigation of thermoelectric power generation versus coolant pumping power in a microchannel heat sink

    DEFF Research Database (Denmark)

    Kolaei, Alireza Rezania; Rosendahl, Lasse; Andreasen, Søren Juhl

    2012-01-01

    The coolant heat sinks in thermoelectric generators (TEG) play an important role in order to power generation in the energy systems. This paper explores the effective pumping power required for the TEGs cooling at five temperature difference of the hot and cold sides of the TEG. In addition......, the temperature distribution and the pressure drop in sample microchannels are considered at four sample coolant flow rates. The heat sink contains twenty plate-fin microchannels with hydraulic diameter equal to 0.93 mm. The experimental results show that there is a unique flow rate that gives maximum net-power...

  1. High Efficiency Microchannel Diamond Heat Sinks, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — While absolute power levels in microelectronic devices are relatively modest (a few tens to a few hundred watts), heat fluxes can be significant (~50 W/cm2 in...

  2. The effect of substrate conduction on boiling data on pin-fin heat sinks

    International Nuclear Information System (INIS)

    McNeil, D.A.; Raeisi, A.H.; Kew, P.A.; Hamed, R.S.

    2015-01-01

    Heat-transfer experiments for a copper heat sink containing pin-fins with a cross section of 1 mm by 1 mm and a height of 1 mm have been reported previously. The pin-fins were manufactured on a 5 mm thick, 50 mm square base plate in a square, in-line arrangement with a pitch of 2 mm. Data were produced while boiling R113 and water at atmospheric pressure. The heat sink was heated from below through a 5 mm thick aluminium wall by an electrical heating method that is normally associated with the uniform heat flux boundary condition. However, variations in the heat-transfer coefficient and the liquid subcooling interacted with the high thermal conductivity of the aluminium and copper materials to produce a near isothermal wall boundary condition. Thus, heat conduction effects had to be taken into account when determining the heat-flux distribution required in the analysis of the data. Many experiments like these have used the uniform heat-flux assumption to analyse the data. The discrepancies produced from this approach are explored. Single-phase flows across a pin-fin surface produce a reasonably uniform distribution of heat-transfer coefficient. However, the liquid temperature increases as it moves across the heat sink. This produces a non-uniform heat flux distribution at the solid–fluid interface. The uniform heat-flux assumption is shown to lead to errors of ±17% in the estimation of the heat-transfer coefficient. The original boiling flow experiments found that the water data were confined and that the majority of the R113 data were not. The confined and unconfined data are processed with the thermal conduction in the walls taken into account and by assuming a uniform heat flux at the solid–fluid interface. The uniform heat-flux distribution analysis for unconfined flows shows errors in the heat-transfer coefficient to be typically ±17%. Confined flows produce smaller errors, typically ±12%, close to the onset of nucleation. However, these damp out

  3. Copper matrix composites as heat sink materials for water-cooled divertor target

    Directory of Open Access Journals (Sweden)

    Jeong-Ha You

    2015-12-01

    Full Text Available According to the recent high heat flux (HHF qualification tests of ITER divertor target mock-ups and the preliminary design studies of DEMO divertor target, the performance of CuCrZr alloy, the baseline heat sink material for DEMO divertor, seems to only marginally cover the envisaged operation regime. The structural integrity of the CuCrZr heat sink was shown to be affected by plastic fatigue at 20 MW/m². The relatively high neutron irradiation dose expected for the DEMO divertor target is another serious concern, as it would cause significant embrittlement below 250 °C or irradiation creep above 350 °C. Hence, an advanced design concept of the divertor target needs to be devised for DEMO in order to enhance the HHF performance so that the structural design criteria are fulfilled for full operation scenarios including slow transients. The biggest potential lies in copper-matrix composite materials for the heat sink. In this article, three promising Cu-matrix composite materials are reviewed in terms of thermal, mechanical and HHF performance as structural heat sink materials. The considered candidates are W particle-reinforced, W wire-reinforced and SiC fiber-reinforced Cu matrix composites. The comprehensive results of recent studies on fabrication technology, design concepts, materials properties and the HHF performance of mock-ups are presented. Limitations and challenges are discussed.

  4. Thermal conductivity from hierarchical heat sinks using carbon nanotubes and graphene nanosheets.

    Science.gov (United States)

    Hsieh, Chien-Te; Lee, Cheng-En; Chen, Yu-Fu; Chang, Jeng-Kuei; Teng, Hsi-sheng

    2015-11-28

    The in-plane (kip) and through-plane (ktp) thermal conductivities of heat sinks using carbon nanotubes (CNTs), graphene nanosheets (GNs), and CNT/GN composites are extracted from two experimental setups within the 323-373 K temperature range. Hierarchical three-dimensional CNT/GN frameworks display higher kip and ktp values, as compared to the CNT- and GN-based heat sinks. The kip and ktp values of the CNT/GN-based heat sink reach as high as 1991 and 76 W m(-1) K(-1) at 323 K, respectively. This improved thermal conductivity is attributed to the fact that the hierarchical heat sink offers a stereo thermal conductive network that combines point, line, and plane contact, leading to better heat transport. Furthermore, the compression treatment provided an efficient route to increase both kip and ktp values. This result reveals that the hierarchical carbon structures become denser, inducing more thermal conductive area and less thermal resistivity, i.e., a reduced possibility of phonon-boundary scattering. The correlation between thermal and electrical conductivity (ε) can be well described by two empirical equations: kip = 567 ln(ε) + 1120 and ktp = 20.6 ln(ε) + 36.1. The experimental results are obtained within the temperature range of 323-373 K, suitably complementing the thermal management of chips for consumer electronics.

  5. Optimal geometric structure for nanofluid-cooled microchannel heat sink under various constraint conditions

    International Nuclear Information System (INIS)

    Wang Xiaodong; Bin An; Xu Jinliang

    2013-01-01

    Highlights: ► An inverse geometry optimization method is used to optimize heat sink structure. ► Nanofluid is used as coolant of heat sink. ► Three parameters are simultaneously optimized at various constraint conditions. ► The optimal designs of nanofluid-cooled heat sink are obtained. - Abstract: A numerical model is developed to analyze the flow and heat transfer in nanofluid-cooled microchannel heat sink (MCHS). In the MCHS model, temperature-dependent thermophysical properties are taken into account due to large temperature differences in the MCHS and strong temperature-dependent characteristics of nanofluids, the model is validated by experimental data with good agreement. The simplified conjugate-gradient method is coupled with MCHS model as optimization tool. Three geometric parameters, including channel number, channel aspect ratio, and width ratio of channel to pitch, are simultaneously optimized at fixed inlet volume flow rate, fixed pumping power, and fixed pressure drop as constraint condition, respectively. The optimal designs of MCHS are obtained for various constraint conditions and the effects of inlet volume flow rate, pumping power, and pressure drop on the optimal geometric parameters are discussed.

  6. Evaluation of heat sink materials for thermal management of lithium batteries

    Science.gov (United States)

    Dimpault-Darcy, E. C.; Miller, K.

    Aluminum, neopentyl glycol (NPG), and resins FT and KT are evaluated theoretically and experimentally as heat sink materials for lithium battery packs. The thermal performances of the two resins are compared in a thermal vacuum experiment. As solutions to the sublimation property were not immediately apparent, a theoretical comparison of the thermal performance of NPG versus KT, Al, and no material, is presented.

  7. Evaluation of heat sink materials for thermal management of lithium batteries

    Science.gov (United States)

    Dimpault-Darcy, E. C.; Miller, K.

    1988-01-01

    Aluminum, neopentyl glycol (NPG), and resins FT and KT are evaluated theoretically and experimentally as heat sink materials for lithium battery packs. The thermal performances of the two resins are compared in a thermal vacuum experiment. As solutions to the sublimation property were not immediately apparent, a theoretical comparison of the thermal performance of NPG versus KT, Al, and no material, is presented.

  8. Minimum success criteria at SGTR combined with loss of secondary heat sink

    International Nuclear Information System (INIS)

    Parzer, I.; Petelin, S.

    1993-01-01

    A parametric analysis has been performed investigating minimum success criteria for the hypothetical Steam Generator Tube Rupture (SGTR) accident in a Pressurized Water Reactor (PWR) Nuclear Power Plant, combined with the total loss of secondary heat sink. The analyses have been performed by RELAP5/MOD2 and MOD3 computer codes using Krsko NPP input deck. The Krsko NPP is a 2-loop Westinghouse PWR, 640 MWe, located in Slovenia and operating from 1981. Two break sizes have been chosen for the SGTR event: 2 and 5 double-ended broken tubes have been assumed. Total loss of secondary heat sink has been assumed from the beginning of the calculation. The ways of cooling down the plant after the postulated accident have been investigated, including Bleed ampersand Feed through the primary system. The NPP Krsko Emergency Operating Procedures (EOP) have been verified for this case. Some suggestions have been made, how to improve FR-H.1 procedure (Loss of Secondary Heat Sink), to include some steps, which take into account also SGTR when it is combined with loss of secondary heat sink. Possible misinterpretations of E-0 procedure (Reactor Trip or Safety Injection) have been studied

  9. Numerical study on the heat transfer performance of non-Newtonian fluid flow in a manifold microchannel heat sink

    International Nuclear Information System (INIS)

    Li, Si-Ning; Zhang, Hong-Na; Li, Xiao-Bin; Li, Qian; Li, Feng-Chen; Qian, Shizhi; Joo, Sang Woo

    2017-01-01

    Highlights: • Heat transfer performance of non-Newtonian fluid flow in a MHS is studied. • Pseudo-plastic fluid flow can clearly promote the heat transfer efficiency in MMC. • Heat transfer enhancement is attributed to the emergence of secondary flow. • The heat transfer uniformity can also be improved by pseudo-plastic fluid flow. - Abstract: As the miniaturization and integration become the leading trend of the micro-electro-mechanical systems, it is of great significance to improve the microscaled heat transfer performance. This paper presents a three-dimensional (3D) numerical simulation on the flow characteristics and heat transfer performance of non-Newtonian fluid flow in a manifold microchannel (MMC) heat sink and traditional microchannel (TMC) heat sink. The non-Newtonian fluid was described by the power-law model. The analyses concentrated on the non-Newtonian fluid effect on the heat transfer performance, including the heat transfer efficiency and uniformity of temperature distribution, as well as the influence of inlet/outlet configurations on fluid flow and heat transfer. Comparing with Newtonian fluid flow, pseudo-plastic fluid could reduce the drag resistance in both MMC and TMC, while the dilatant fluid brought in quite larger drag resistance. For the heat transfer performance, the introduction of pseudo-plastic fluid flow greatly improved the heat transfer efficiency owing to the generation of secondary flow due to the shear-thinning property. Besides, the temperature distribution in MMC was more uniform by using pseudo-plastic fluid. Moreover, the inlet/outlet configuration was also important for the design and arrangement of microchannel heat sinks, since the present work showed that the maximum temperature was prone to locating in the corners near the inlet and outlet. This work provides guidance for optimal design of small-scale heat transfer devices in many cooling applications, such as biomedical chips, electronic systems, and

  10. Viscoelastic Fluid over a Stretching Sheet with Electromagnetic Effects and Nonuniform Heat Source/Sink

    Directory of Open Access Journals (Sweden)

    Kai-Long Hsiao

    2010-01-01

    Full Text Available A magnetic hydrodynamic (MHD of an incompressible viscoelastic fluid over a stretching sheet with electric and magnetic dissipation and nonuniform heat source/sink has been studied. The buoyant effect and the electric number E1 couple with magnetic parameter M to represent the dominance of the electric and magnetic effects, and adding the specific item of nonuniform heat source/sink is presented in governing equations which are the main contribution of this study. The similarity transformation, the finite-difference method, Newton method, and Gauss elimination method have been used to analyze the present problem. The numerical solutions of the flow velocity distributions, temperature profiles, and the important wall unknown values of f''(0 and θ'(0 have been carried out. The parameter Pr, E1, or Ec can increase the heat transfer effects, but the parameter M or A* may decrease the heat transfer effects.

  11. Fabrication and evaluation of chemically vapor deposited tungsten heat pipe.

    Science.gov (United States)

    Bacigalupi, R. J.

    1972-01-01

    A network of lithium-filled tungsten heat pipes is being considered as a method of heat extraction from high temperature nuclear reactors. The need for material purity and shape versatility in these applications dictates the use of chemically vapor deposited (CVD) tungsten. Adaptability of CVD tungsten to complex heat pipe designs is shown. Deposition and welding techniques are described. Operation of two lithium-filled CVD tungsten heat pipes above 1800 K is discussed.

  12. Minimal vascular flows cause strong heat sink effects in hepatic radiofrequency ablation ex vivo.

    Science.gov (United States)

    Lehmann, Kai S; Poch, Franz G M; Rieder, Christian; Schenk, Andrea; Stroux, Andrea; Frericks, Bernd B; Gemeinhardt, Ole; Holmer, Christoph; Kreis, Martin E; Ritz, Jörg P; Zurbuchen, Urte

    2016-08-01

    The present paper aims to assess the lower threshold of vascular flow rate on the heat sink effect in bipolar radiofrequency ablation (RFA) ex vivo. Glass tubes (vessels) of 3.4 mm inner diameter were introduced in parallel to bipolar RFA applicators into porcine liver ex vivo. Vessels were perfused with flow rates of 0 to 1,500 ml/min. RFA (30 W power, 15 kJ energy input) was carried out at room temperature and 37°C. Heat sink effects were assessed in RFA cross sections by the decrease in ablation radius, area and by a high-resolution sector planimetry. Flow rates of 1 ml/min already caused a significant cooling effect (P ≤ 0.001). The heat sink effect reached a maximum at 10 ml/min (18.4 mm/s) and remained stable for flow rates up to 1,500 ml/min. Minimal vascular flows of ≥1 ml/min cause a significant heat sink effect in hepatic RFA ex vivo. A lower limit for volumetric flow rate was not found. The maximum of the heat sink effect was reached at a flow rate of 10 ml/min and remained stable for flow rates up to 1,500 ml/min. Hepatic inflow occlusion should be considered in RFA close to hepatic vessels. © 2016 Japanese Society of Hepato-Biliary-Pancreatic Surgery.

  13. Development of the heat sink structure of a beam dump for the proton accelerator

    International Nuclear Information System (INIS)

    Maeng, W. Y.; Gil, C. S.; Kim, J. H.; Kim, D. H.

    2007-01-01

    The beam dump is the essential component for the good beam quality and the reliable performance of the proton accelerator. The beam dump for a 20 MeV and 20 mA proton accelerator was designed and manufactured in this study. The high heats deposited, and the large amount of radioactivity produced in beam dump should be reduced by the proper heat sink structure. The heat source by the proton beam of 20 MeV and 20 mA was calculated. The radioactivity assessments of the beam dump were carried out for the economic shielding design with safety. The radioactivity by the protons and secondary neutrons in designed beam dump were calculated in this sturdy. The effective engineering design for the beam dump cooling was performed, considering the mitigation methods of the deposited heats with small angle, the power densities with the stopping ranges in the materials and the heat distributions in the beam dump. The heat sink structure of the beam dump was designed to meet the accelerator characteristics by placing two plates of 30 cm by 60 cm at an angle of 12 degree. The highest temperatures of the graphite, copper, and copper faced by cooling water were designed to be 223 degree, 146 degree, and 85 degree, respectively when the velocity of cooling water was 3 m/s. The heat sink structure was manufactured by the brazing graphite tiles to a copper plate with the filler alloy of Ti-Cu-Ag. The brazing procedure was developed. The tensile stress of the graphite was less than 75% of a maximum tensile stress during the accelerator operation based on the analysis. The safety analyses for the commissioning of the accelerator operation were also performed. The specimens from the brazed parts of beam dump structure were made to identify manufacturing problems. The soundness of the heat sink structure of the beam dump was confirmed by the fatigue tests of the brazed specimens of the graphite-copper tile components with the repetitive heating and cooling. The heat sink structure developed

  14. Experimental comparison between different configurations of PCM based heat sinks for cooling electronic components

    International Nuclear Information System (INIS)

    Gharbi, Salma; Harmand, Souad; Jabrallah, Sadok Ben

    2015-01-01

    The thermal control of electronic components is aimed at ensuring their use in a temperature range compatible with their performances. This paper presents an experimental study of the behavior of phase change materials (PCMs) as the cooling system for electronic devices. Four configurations are used to control the increase in the system temperature: pure PCM, PCM in a silicone matrix, PCM in a graphite matrix and pure PCM in a system of fins. Thermo-physical properties of different PCMs are determined and found to be desirable for application in this study. Solid liquid interface visualization and temperature evolution are employed to understand the mechanism of heat transfer during the different stages. Results indicated that the inclusion of PCM can lower component increase temperature and extends twice the critical time of the heat sink. The use of Graphite matrix filled by PCM showed more improvement on system thermal performance than silicon matrix. Also, for the same fraction of copper, it was found that incorporating long copper fins with suitable spacing into PCM, can enhance heat distribution into PCM leading to longer remain component temperature below the critical limit. This work therefore shows that the combination of PCM and long, well-spaced fins presents an effective means for thermal control of electronic devices. - Highlights: • Study on thermal performance of different PCM based heat sink in electronic cooling. • Examination of heat transfer mechanism into heat sink for different conditions. • Graphite matrix shows more efficiency than silicon. • Inclusion PCM can reduce temperature increasing. • Heat sink with longer well spaced fins can extend longer the critical time

  15. Modeling and simulation of loss of the ultimate heat sink in a typical material testing reactor

    International Nuclear Information System (INIS)

    El-Khatib, Hisham; El-Morshedy, Salah El-Din; Higazy, Maher G.; El-Shazly, Karam

    2013-01-01

    Highlights: ► A thermal–hydraulic model has been developed to simulate loss of the ultimate heat sink in MTR. ► The model involves three coupled sub-models for core, heat exchanger and cooling tower. ► The model is validated against PARET for steady-state and verified by operation data for transients. ► The model is used to simulate the behavior of the reactor under a loss of the ultimate heat sink. ► The model results are analyzed and discussed. -- Abstract: A thermal–hydraulic model has been developed to simulate loss of the ultimate heat sink in a typical material testing reactor (MTR). The model involves three interactively coupled sub-models for reactor core, heat exchanger and cooling tower. The model is validated against PARET code for steady-state operation and verified by the reactor operation records for transients. Then, the model is used to simulate the thermal–hydraulic behavior of the reactor under a loss of the ultimate heat sink event. The simulation is performed for two operation regimes: regime I representing 11 MW power and three cooling tower cells operated, and regime II representing 22 MW power and six cooling tower cells operated. In regime I, the simulation is performed for 1, 2 and 3 cooling tower cells failed while in regime II, it is performed for 1, 2, 3, 4, 5 and 6 cooling tower cells failed. The simulation is performed under protected conditions where the safety action called power reduction is triggered by reactor protection system to decrease the reactor power by 20% when the coolant inlet temperature to the core reaches 43 °C and scram is triggered if the core inlet temperature reaches 44 °C. The model results are analyzed and discussed.

  16. Heat Sinking, Cross Talk, and Temperature Stability for Large, Close-Packed Arrays of Microcalorimeters

    Science.gov (United States)

    Imoto, Naoko; Bandler, SImon; Brekosky, Regis; Chervenak, James; Figueroa-Felicano, Enectali; Finkbeiner, Frederick; Kelley, Richard; Kilbourne, Caroline; Porter, Frederick; Sadleir, Jack; hide

    2007-01-01

    We are developing large, close-packed arrays of x-ray transition-edge sensor (TES) microcalorimeters. In such a device, sufficient heat sinking is important to to minimize thermal cross talk between pixels and to stabilize the bath temperature for all pixels. We have measured cross talk on out 8 x 8 arrays and studied the shape and amount of thermal crosstalk as a function of pixel location and efficiency of electrothermal feedback. In this presentation, we will compare measurements made on arrays with and without a backside, heat-sinking copper layer, as well as results of devices on silicon-nitride membranes and on solid substrates, and we will discuss the implications for energy resolution and maximum count rate. We will also discuss the dependence of pulse height upon bath temperature, and the measured and required stability of the bath temperature.

  17. Monitoring the risk of loss of heat sink during plant shutdowns at Bruce Generating Station 'A'

    International Nuclear Information System (INIS)

    Krishnan, K.S.; Mancuso, F.; Vecchiarelli, D.

    1996-01-01

    A relatively simple loss of shutdown heat sink fault tree model has been developed and used during unit outages at Bruce Nuclear Generation Station 'A' to assess, from a risk and reliability perspective, alternative heat sink strategies and to aid in decisions on allowable outage configurations. The model is adjusted to reflect the various unit configurations planned during a specific outage, and identifies events and event combinations leading to loss of fuel cooling. The calculated failure frequencies are compared to the limits consistent with corporate and international public safety goals. The importance measures generated by the interrogation of the fault tree model for each outage configuration are also used to reschedule configurations with high fuel damage frequency later into the outage and to control the configurations with relatively high probability of fuel damage to short intervals at the most appropriate time into the outage. (author)

  18. Thermal Management of Transient Power Spikes in Electronics - Phase Change Energy Storage or Copper Heat Sinks?

    OpenAIRE

    Krishnan, S.; Garimella, S V

    2004-01-01

    A transient thermal analysis is performed to investigate thermal control of power semiconductors using phase change materials, and to compare the performance of this approach to that of copper heat sinks. Both the melting of the phase change material under a transient power spike input, as well as the resolidification process, are considered. Phase change materials of different kinds (paraffin waxes and metallic alloys) are considered, with and without the use of thermal conductivity enhancer...

  19. Performance evaluation of RANS-based turbulence models in simulating a honeycomb heat sink

    Science.gov (United States)

    Subasi, Abdussamet; Ozsipahi, Mustafa; Sahin, Bayram; Gunes, Hasan

    2017-07-01

    As well-known, there is not a universal turbulence model that can be used to model all engineering problems. There are specific applications for each turbulence model that make it appropriate to use, and it is vital to select an appropriate model and wall function combination that matches the physics of the problem considered. Therefore, in this study, performance of six well-known Reynolds-Averaged Navier-Stokes ( RANS) based turbulence models which are the Standard k {{-}} ɛ, the Renormalized Group k- ɛ, the Realizable k- ɛ, the Reynolds Stress Model, the k- ω and the Shear Stress Transport k- ω and accompanying wall functions which are the standard, the non-equilibrium and the enhanced are evaluated via 3D simulation of a honeycomb heat sink. The CutCell method is used to generate grid for the part including heat sink called test section while a hexahedral mesh is employed to discretize to inlet and outlet sections. A grid convergence study is conducted for verification process while experimental data and well-known correlations are used to validate the numerical results. Prediction of pressure drop along the test section, mean base plate temperature of the heat sink and temperature at the test section outlet are regarded as a measure of the performance of employed models and wall functions. The results indicate that selection of turbulence models and wall functions has a great influence on the results and, therefore, need to be selected carefully. Hydraulic and thermal characteristics of the honeycomb heat sink can be determined in a reasonable accuracy using RANS- based turbulence models provided that a suitable turbulence model and wall function combination is selected.

  20. A comparison of micro-structured flat-plate and cross-cut heat sinks for thermoelectric generation application

    DEFF Research Database (Denmark)

    Rezania, Alireza; Rosendahl, L. A.

    2015-01-01

    . In this study, a micro-structured plate-fin heat sink is compared to a modified design of cross-cut heat sink applied to TEGs over a range of temperatures and thermal conductivities. The particular focus of this study is to explore the net power output from the TEG module. The three-dimensional governing...... equations for the flow and heat transfer are solved using computational fluid dynamics (CFD) in conjunction with the thermoelectric characteristics of the TEG over a wide range of flow inlet velocities. The results show that at small flow inlet velocity, the maximum net power output in TEG with plate......Heat sink configuration has strong impact on net power output from thermoelectric generators (TEGs). A weak cooling strategy can even cause negative net power output from the thermoelectric device. However, the net power output can be significantly improved by optimal design of the heat sink...

  1. Two-phase flow instabilities in a silicon microchannels heat sink

    International Nuclear Information System (INIS)

    Bogojevic, D.; Sefiane, K.; Walton, A.J.; Lin, H.; Cummins, G.

    2009-01-01

    Two-phase flow instabilities are highly undesirable in microchannels-based heat sinks as they can lead to temperature oscillations with high amplitudes, premature critical heat flux and mechanical vibrations. This work is an experimental study of boiling instabilities in a microchannel silicon heat sink with 40 parallel rectangular microchannels, having a length of 15 mm and a hydraulic diameter of 194 μm. A series of experiments have been carried out to investigate pressure and temperature oscillations during the flow boiling instabilities under uniform heating, using water as a cooling liquid. Thin nickel film thermometers, integrated on the back side of a heat sink with microchannels, were used in order to obtain a better insight related to temperature fluctuations caused by two-phase flow instabilities. Flow regime maps are presented for two inlet water temperatures, showing stable and unstable flow regimes. It was observed that boiling leads to asymmetrical flow distribution within microchannels that result in high temperature non-uniformity and the simultaneously existence of different flow regimes along the transverse direction. Two types of two-phase flow instabilities with appreciable pressure and temperature fluctuations were observed, that depended on the heat to mass flux ratio and inlet water temperature. These were high amplitude/low frequency and low amplitude/high frequency instabilities. High speed camera imaging, performed simultaneously with pressure and temperature measurements, showed that inlet/outlet pressure and the temperature fluctuations existed due to alternation between liquid/two-phase/vapour flows. It was also determined that the inlet water subcooling condition affects the magnitudes of the temperature oscillations in two-phase flow instabilities and flow distribution within the microchannels.

  2. Convective heat transfer enhancement by diamond shaped micro-protruded patterns for heat sinks: Thermal fluid dynamic investigation and novel optimization methodology

    International Nuclear Information System (INIS)

    Ventola, Luigi; Dialameh, Masoud; Fasano, Matteo; Chiavazzo, Eliodoro; Asinari, Pietro

    2016-01-01

    Highlights: • A novel methodology for optimal design of patterned heat sink surfaces is proposed. • Heat transfer enhancement by patterned surfaces is measured experimentally. • Role of fluid dynamics and geometrical scales on heat transfer is clarified. - Abstract: In the present work, micro-protruded patterns on flush mounted heat sinks for convective heat transfer enhancement are investigated and a novel methodology for thermal optimization is proposed. Patterned heat sinks are experimentally characterized in fully turbulent regime, and the role played by geometrical parameters and fluid dynamic scales is discussed. A methodology specifically suited for micro-protruded pattern optimization is designed, leading to 73% enhancement in thermal performance respect to commercially available heat sinks, at fixed costs. This work is expected to introduce a new methodological approach for a more systematic and efficient development of solutions for electronics cooling.

  3. Enthalpy model for heating, melting, and vaporization in laser ablation

    OpenAIRE

    Vasilios Alexiades; David Autrique

    2010-01-01

    Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu) target in a helium (He) background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model th...

  4. Rectified heat transfer into translating and pulsating vapor bubbles

    NARCIS (Netherlands)

    Hao, Y.; Prosperetti, Andrea

    2002-01-01

    It is well known that, when a stationary vapor bubble is subject to a sufficiently intense acoustic field, it will grow by rectified heat transfer even in a subcooled liquid. The object of this paper is to study how translation, and the ensuing convective effects, influence this process. It is shown

  5. Importance of thermal radiation from heat sink in cooling of three phase PWM inverter kept inside an evacuated chamber

    Directory of Open Access Journals (Sweden)

    Anjan Sarkar

    2017-04-01

    Full Text Available The paper describes a thermal analysis of a three-phase inverter operated under a Sinusoidal Pulse Width Modulation (SPWM technique which used three sine waves displaced in 120° phase difference as reference signals. The IGBT unit is assumed to be placed with a heat sink inside an evacuated chamber and the entire heat has to be transferred by conduction and radiation. The main heat sources present here are the set of IGBTs and diodes which generates heat on a pulse basing on their switching frequencies. Melcosim (a well-known tool developed by Mitsubishi Electric Corporation has been used to generate the power pulse from one set of IGBT and diode connected to a phase. A Scilab code is written to study the conduction and thermal radiation of heat sink and their combined effect on transient growth of the junction temperature of IGBT unit against complex switching pulses. The results mainly show that how thermal radiation from heat sink plays a crucial role in maintaining the junction temperature of IGBT within a threshold limit by adjusting various heat sink parameters. As the IGBT heat generation rate becomes higher, radiative heat transfer of the heat sink increases sharply which enhances overall cooling performance of the system.

  6. On the thermal analysis of a plate-fin heat sink considering the thermal-entry length effect

    International Nuclear Information System (INIS)

    Bassiouny, Ramadan; Maher, Hisham; Hegazy, Adel A.

    2016-01-01

    Highlights: • Dissipated convective heat strongly depends on convection coefficient. Two correlations were developed for so and validated. • A clear error in air temperature distribution along the heat sink was seen if coefficient were not properly selected. • The error decreases when thermal-entry length effect is considered, as for thermal flow through short conduits as Pr <1. - Abstract: Cooling electric and electronic components is very imperative to keep these components functioning properly. The heat sink is a device used to dissipate generated heat and accordingly cool these components. Airflow through heat sinks experiences velocity and thermal boundary layer variation that significantly affects the heat transfer process and heat sink performance as a result. The present study aims at developing an analytical model that compares the effect of adopting fully-developed or thermally-developing flow on convective heat transfer coefficient and accordingly longitudinal predicted air temperature distribution. Experiments on plate-fin heat sinks were carried out to validate the developed model. The results quantitatively showed a noticeable overprediction in the air temperature distribution when the heat transfer coefficient was estimated based on a fully-developed assumption. On the other hand, a close agreement between predicted and measured values was noticed when the thermal-entry length effect was considered.

  7. CFD study of liquid-cooled heat sinks with microchannel flow field configurations for electronics, fuel cells, and concentrated solar cells

    International Nuclear Information System (INIS)

    Ramos-Alvarado, Bladimir; Li Peiwen; Liu Hong; Hernandez-Guerrero, Abel

    2011-01-01

    A study of the heat transfer performance of liquid-cooled heat sinks with conventional and novel micro-channel flow field configurations for application in electronic devices, fuel cells, and concentrated solar cells is presented in this paper. The analyses were based on computations using the CFD software ANSYS FLUENT. The flow regime in heat sinks is constrained to laminar flow in the study. Details of the heat transfer performance, particularly, the uniformity of temperature distribution on the heating surface, as well as the pressure losses and pumping power in the operation of the studied heat sinks were obtained. Comparisons of the flow distribution uniformity in multiple flow channels, temperature uniformity on heating surfaces, and pumping power consumption of heat sinks with novel flow field configurations and conventional flow field configurations were conducted. It was concluded that the novel flow field configurations studied in this work exhibit appreciable benefits for application in heat sinks. - Highlights: → We present novel designs of flow channel configurations in liquid cooled heat sinks. → The flow and heat transfer in heat sinks were simulated using CFD tool. → The temperature and pressure loss in novel and conventional heat sinks were studied. → Figure of merit of heat sinks in different flow channel configurations was presented. → The heat sinks having our novel design of flow channel configurations are excellent.

  8. IAEA ICSP on HWR moderator subcooling requirements to demonstrate backup heat sink

    International Nuclear Information System (INIS)

    Choi, J.; Nitheanandan, T.

    2013-01-01

    The IAEA launched a new International Collaborative Standard Problem (ICSP) on 'HWR Moderator Subcooling Requirements to Demonstrate Backup Heat Sink Capabilities of Moderator during Accidents'. The purpose of the ICSP is to benchmark analysis computer codes in simulating contact boiling experimental data to assess the subcooling requirements for an overheated pressure tube, plastically deforming into contact with the calandria tube during a postulated large break loss of coolant accident. The experimental data obtained for the ICSP blind simulation can be used to assess safety analysis computer codes simulating thermal radiation heat transfer to the pressure tube, pressure tube deformation or failure, pressure tube to calandria tube heat transfer, calandria tube to moderator heat transfer, and calandria tube deformation or failure. (author)

  9. Influence of sinusoidal flow on the thermal and hydraulic performance of microchannel heat sink

    International Nuclear Information System (INIS)

    Om, N I; Gunnasegaran, P; Rajasegaran, S

    2013-01-01

    In this paper, the effect of sinusoidal flow on the thermal and hydraulic performance of microchannel heat sink (MCHS) is numerically investigated. This investigation covers Reynolds number in the range of 100 ≤ Re ≤ 1000 and pure water is used as a working fluid. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using finite volume method (FVM). The water flow field and heat transfer performance inside the sinusoidal microchannels is simulated and the results are compared with the straight microchannels. The effect of using sinusoidal microchannels on temperature distribution, Nusselt number, friction factor and thermal resistance is presented in this paper. It is found that with same rectangular cross-section, sinusoidal microchannels have a better heat transfer performance compared to the straight microchannels.

  10. A Quick Overview of Compact Air-Cooled Heat Sinks Applicable for Electronic Cooling—Recent Progress

    Directory of Open Access Journals (Sweden)

    Chi-Chuan Wang

    2017-02-01

    Full Text Available This study provides an overview regarding enhancement of an air-cooled heat sink applicable for electronic cooling subject to cross-flow forced convection. Some novel designs and associated problems in air-cooled heat sinks are discussed, including the drawback of adding surfaces, utilization of porous surfaces such as metal foam or carbon foam, problems and suitable applicable range of highly interrupted surfaces (louver or slit and longitudinal vortex generator. Though the metal foam may accommodate significant surface area, it is comparatively ineffective for air-cooling application due to its much lower fin efficiency, and this shortcoming can be improved by integrating with solid fin. For highly dense fin spacing (e.g., <1.0 mm, cannelure or grooved surface may be a better choice, and fin structure with periodic contraction and expansion may not be suitable for it introduces additional pressure drop penalty. The partial bypass concept, which manipulates a larger temperature difference at the trailing part of heat sink, can be implemented to significantly reduce the pressure drop. Through some certain niche operation, t the thermal resistance of the partial bypass heat sink may be superior to the conventional heat sink. The trapezoid fin surface featuring easier manufacturing and a smaller weight is shown to have competitive performance against traditional rectangular fin geometry. The IPFM (Interleaved Parallelogram Fin Module design which combines two different geometrical fins with the odd number fins being rectangular shape, and parallelogram shape in even fin numbers, shows 8%–12% less surface than conventional design but still offers a lower thermal resistance than the conventional rectangular heat sink in lower flowrate operation. The cross-cut design shows appreciable improvements as compared to the conventional plate fin design especially in high velocity regime and the single cross-cut heat sinks are superior to multiple cross

  11. Vapor-Compression Heat Pumps for Operation Aboard Spacecraft

    Science.gov (United States)

    Ruemmele, Warren; Ungar, Eugene; Cornwell, John

    2006-01-01

    Vapor-compression heat pumps (including both refrigerators and heat pumps) of a proposed type would be capable of operating in microgravity and would be safe to use in enclosed environments like those of spacecraft. The designs of these pumps would incorporate modifications of, and additions to, vapor-compression cycles of heat pumps now used in normal Earth gravitation, in order to ensure efficiency and reliability during all phases of operation, including startup, shutdown, nominal continuous operation, and peak operation. Features of such a design might include any or all of the following: (1) Configuring the compressor, condenser, evaporator, valves, capillary tubes (if any), and controls to function in microgravitation; (2) Selection of a working fluid that satisfies thermodynamic requirements and is safe to use in a closed crew compartment; (3) Incorporation of a solenoid valve and/or a check valve to prevent influx of liquid to the compressor upon startup (such influx could damage the compressor); (4) Use of a diode heat pipe between the cold volume and the evaporator to limit the influx of liquid to the compressor upon startup; and (5) Use of a heated block to vaporize any liquid that arrives at the compressor inlet.

  12. Experimental Study of Single Phase Flow in a Closed-Loop Cooling System with Integrated Mini-Channel Heat Sink

    Directory of Open Access Journals (Sweden)

    Lei Ma

    2016-06-01

    Full Text Available The flow and heat transfer characteristics of a closed-loop cooling system with a mini-channel heat sink for thermal management of electronics is studied experimentally. The heat sink is designed with corrugated fins to improve its heat dissipation capability. The experiments are performed using variable coolant volumetric flow rates and input heating powers. The experimental results show a high and reliable thermal performance using the heat sink with corrugated fins. The heat transfer capability is improved up to 30 W/cm2 when the base temperature is kept at a stable and acceptable level. Besides the heat transfer capability enhancement, the capability of the system to transfer heat for a long distance is also studied and a fast thermal response time to reach steady state is observed once the input heating power or the volume flow rate are varied. Under different input heat source powers and volumetric flow rates, our results suggest potential applications of the designed mini-channel heat sink in cooling microelectronics.

  13. A passive emergency heat sink for water-cooled reactors with particular application to CANDU reactors

    International Nuclear Information System (INIS)

    Spinks, N.J.

    1996-01-01

    Water in an overhead pool can serve as a general-purpose passive emergency heat sink for water-cooled reactors. It can be used for containment cooling, for emergency depressurization of the heat transport-system, or to receive any other emergency heat, such as that from the CANDU moderator. The passive emergency water system provides in-containment depressurization of steam generators and no other provision is needed for supply of low-pressure emergency water to the steam generators. For containment cooling, the pool supplies water to the tube side of elevated tube banks inside containment. The elevation with respect to the reactor heat source maximizes heat transport, by natural convection, of hot containment gases. This effective heat transport combines with the large heat-transfer coefficients of tube banks, to reduce containment overpressure during accidents. Cooled air from the tube banks is directed past the break in the heat-transport system, to facilitate removal of hydrogen using passive catalytic recombiners. (author)

  14. Cappuccino and Specific Heat Versus Heat of Vaporization

    Science.gov (United States)

    Hidden, Frits; Boomsma, Jorn; Schins, Anton; van den Berg, Ed

    2012-02-01

    A cappuccino is prepared by adding about 50 mL frothing, foaming milk to a cup of espresso. Whole milk is best for foaming and the ideal milk temperature when adding it to the espresso is 65 °C. The espresso itself may be warmer than that. During the heating the milk should not burn, as that would spoil the taste. The best way is to heat the milk slowly while stirring to froth the milk and create foam. But modern cappuccino machines in restaurants do not have time for slow heating. Could we heat the milk by just adding hot water?

  15. STEAM GENERATOR TUBE INTEGRITY ANALYSIS OF A TOTAL LOSS OF ALL HEAT SINKS ACCIDENT FOR WOLSONG NPP UNIT 1

    Directory of Open Access Journals (Sweden)

    HEOK-SOON LIM

    2014-02-01

    Full Text Available A total loss of all heat sinks is considered a severe accident with a low probability of occurrence. Following a total loss of all heat sinks, the degasser/condenser relief valves (DCRV become the sole means available for the depressurization of the primary heat transport system. If a nuclear power plant has a total loss of heat sinks accident, high-temperature steam and differential pressure between the primary heat transport system (PHTS and the steam generator (SG secondary side can cause a SG tube creep rupture. To protect the PHTS during a total loss of all heat sinks accident, a sufficient depressurization capability of the degasser/condenser relief valve and the SG tube integrity is very important. Therefore, an accurate estimation of the discharge through these valves is necessary to assess the impact of the PHTS overprotection and the SG tube integrity of the primary circuit. This paper describes the analysis of DCRV discharge capacity and the SG tube integrity under a total loss of all heat sink using the CATHENA code. It was found that the DCRV's discharge capacity is enough to protect the overpressure in the PHTS, and the SG tube integrity is maintained in a total loss of all heat accident.

  16. Steam Generator Tube Integrity Analysis of A Total Loss of all Heat Sinks Accident for Wolsong NPP Unit 1

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Heoksoon; Song, Taeyoung; Chi, Moongoo [Korea Htydro and Nuclear Power Co., Ltd., Daejeon (Korea, Republic of); Kim, Seoungrae [Nuclear Engineering Service and Solution, Daejeon (Korea, Republic of)

    2014-02-15

    A total loss of all heat sinks is considered a severe accident with a low probability of occurrence. Following a total loss of all heat sinks, the degasser/condenser relief valves (DCRV) become the sole means available for the depressurization of the primary heat transport system. If a nuclear power plant has a total loss of heat sinks accident, high-temperature steam and differential pressure between the primary heat transport system (PHTS) and the steam generator (SG) secondary side can cause a SG tube creep rupture. To protect the PHTS during a total loss of all heat sinks accident, a sufficient depressurization capability of the degasser/condenser relief valve and the SG tube integrity is very important. Therefore, an accurate estimation of the discharge through these valves is necessary to assess the impact of the PHTS overprotection and the SG tube integrity of the primary circuit. This paper describes the analysis of DCRV discharge capacity and the SG tube integrity under a total loss of all heat sink using the CATHENA code. It was found that the DCRV's discharge capacity is enough to protect the overpressure in the PHTS, and the SG tube integrity is maintained in a total loss of all heat accident.

  17. Steam Generator Tube Integrity Analysis of A Total Loss of all Heat Sinks Accident for Wolsong NPP Unit 1

    International Nuclear Information System (INIS)

    Lim, Heoksoon; Song, Taeyoung; Chi, Moongoo; Kim, Seoungrae

    2014-01-01

    A total loss of all heat sinks is considered a severe accident with a low probability of occurrence. Following a total loss of all heat sinks, the degasser/condenser relief valves (DCRV) become the sole means available for the depressurization of the primary heat transport system. If a nuclear power plant has a total loss of heat sinks accident, high-temperature steam and differential pressure between the primary heat transport system (PHTS) and the steam generator (SG) secondary side can cause a SG tube creep rupture. To protect the PHTS during a total loss of all heat sinks accident, a sufficient depressurization capability of the degasser/condenser relief valve and the SG tube integrity is very important. Therefore, an accurate estimation of the discharge through these valves is necessary to assess the impact of the PHTS overprotection and the SG tube integrity of the primary circuit. This paper describes the analysis of DCRV discharge capacity and the SG tube integrity under a total loss of all heat sink using the CATHENA code. It was found that the DCRV's discharge capacity is enough to protect the overpressure in the PHTS, and the SG tube integrity is maintained in a total loss of all heat accident

  18. Comparison between field data and ultimate heat-sink cooling-pond and spray-pond models

    International Nuclear Information System (INIS)

    Codell, R.

    1982-09-01

    Two previously published reports, NUREG-0693 and NUREG-0733, presented models and methods by which ultimate heat sink cooling ponds and spray ponds used for safety-related water supplies in nuclear power plants could be analyzed for design-basis conditions of heat load and meteorology. These models were only partially verified with field data. The present report compares the NRC models to data collected for NRC by Battelle Pacific Northwest Laboratories on the performance of small geothermally heated ponds and spray ponds. These comparisons generally support the conclusion that the NRC models are useful tools in predicting ultimate heat sink performance

  19. Waste Tyres as Heat Sink to Reduce the Driveway Surface Temperatures in Malaysia

    Directory of Open Access Journals (Sweden)

    Aniza Abdul Aziz

    2013-12-01

    Full Text Available The development of roads and driveways are on the rise as automobiles are now a necessity to all. This excessive development with its requirements increased the urban heat temperature and the generation of waste tyres. Waste tyre management has therefore been taken seriously by developed countries and since the European directive to ban used tyre products and whole tire disposal from landfill in 2003 and 2006 respectively, many researchers have looked for alternative ways to use the waste tyre. In Malaysia, The Smart and Cool Home Developer attempted to develop an eco-house by utilising waste tyre as the foundation for the driveway and claimed that the buried tyres act as a heat sink for the concrete and reduce the surface temperature of the driveway. Hence investigations were conducted on two sample houses to investigate this phenomenon. Findings from this pilot study show that waste tyres do act as a heat sink to the concrete driveways which affect the ambient temperature and relative humidity of the immediate surroundings.

  20. Quasi-static Cycle Performance Analysis of Micro Modular Reactor for Heat Sink Temperature Variation

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seong Kuk; Lee, Jekyoung; Ahn, Yoonhan; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Cha, Jae Eun [KAERI, Daejeon (Korea, Republic of)

    2015-10-15

    A Supercritical CO{sub 2} (S-CO{sub 2}) cycle has potential for high thermal efficiency in the moderate turbine inlet temperature (450 - 750 .deg. C) and achieving compact system size because of small specific volume and simple cycle layouts. Owing to small specific volume of S-CO{sub 2} and the development of heat exchanger technology, it can accomplish complete modularization of the system. The previous works focused on the cycle performance analysis for the design point only. However, the heat sink temperature can be changed depending on the ambient atmosphere condition, i.e. weather, seasonal change. This can influence the compressor inlet temperature, which alters the cycle operating condition overall. To reflect the heat sink temperature variation, a quasi-static analysis code for a simple recuperated S-CO{sub 2} Brayton cycle has been developed by the KAIST research team. Thus, cycle performance analysis is carried out with a compressor inlet temperature variation in this research. In the case of dry air-cooling system, the ambient temperature of the local surrounding can affect the compressor inlet temperature. As the compressor inlet temperature increases, thermal efficiency and generated electricity decrease. As further works, the experiment of S-CO{sub 2} integral test loop will be performed to validate in-house codes, such as KAIST{sub T}MD and the quasi-static code.

  1. Effect of pipe insulation losses on a loss-of-heat sink accident for an LMR

    International Nuclear Information System (INIS)

    Horak, W.C.; Guppy, J.G.; Wood, P.M.

    1985-01-01

    The efficacy of pipe radiation losses as a heat sink during LOHS in a loop-type LMR plant is investigated. The Super System Code (SSC), which was modified to include pipe radiation losses, was used to simulate such an LOHS in an LMR plant. In order to enhance these losses, the pipes were assumed to be insulated by rock wool, a material whose thermal conductivity increases with increasing temperature. A transient was simulated for a total of eight days, during which the coolant temperatures peaked well below saturation conditions and then declined steadily. The coolant flow rate in the loop remained positive throughout the transient

  2. Fluid-cooled heat sink with improved fin areas and efficiencies for use in cooling various devices

    Science.gov (United States)

    Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth; Narumanchi, Sreekant

    2015-04-21

    The disclosure provides a fluid-cooled heat sink having a heat transfer base and a plurality of heat transfer fins in thermal communication with the heat transfer base, where the heat transfer base and the heat transfer fins form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop of the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.

  3. Optimum thermal design of microchannel heat sink with triangular reentrant cavities

    International Nuclear Information System (INIS)

    Xia Guodong; Chai Lei; Wang Haiyan; Zhou Mingzheng; Cui Zhenzhen

    2011-01-01

    The effect of geometric parameters on water flow and heat transfer characteristics in microchannel heat sink with triangular reentrant cavities is numerically investigated. A three-dimensional laminar flow model, consisting of Navier-Stokes equations and energy conservation equation, with the conjugate heat transfer between the silicon base and water taken into consideration is solved numerically. In order to find the optimum geometric parameters, four variables, representing the distance and geometry of the triangular reentrant cavity, are designed. It is found that the vortices in the triangular reentrant cavities lead to chaotic advection and can greatly enhance the convective fluid mixing. The thermal and hydraulic boundary layers are interrupted and the repeated developing flow enhances heat transfer in the constant cross-section segment. Furthermore, the effects of the four design variables on heat transfer augmentation and pressure drop penalty are investigated depending on different Reynolds numbers by using the simulated annealing method. Based on the thermal enhancement factor performance maps, the optimal geometric parameters are obtained in principle. - Research highlights: → The microchannels with different triangular reentrant cavities are numerically investigated. → The heat transfer enhancement attributes to fluid mixing and redeveloped thermal boundary layers. → The optimal distance and geometry of the triangular reentrant cavity are obtained in principle.

  4. Numerical analysis of high-power broad-area laser diode with improved heat sinking structure using epitaxial liftoff technique

    Science.gov (United States)

    Kim, Younghyun; Sung, Yunsu; Yang, Jung-Tack; Choi, Woo-Young

    2018-02-01

    The characteristics of high-power broad-area laser diodes with the improved heat sinking structure are numerically analyzed by a technology computer-aided design based self-consistent electro-thermal-optical simulation. The high-power laser diodes consist of a separate confinement heterostructure of a compressively strained InGaAsP quantum well and GaInP optical cavity layers, and a 100-μm-wide rib and a 2000-μm long cavity. In order to overcome the performance deteriorations of high-power laser diodes caused by self-heating such as thermal rollover and thermal blooming, we propose the high-power broad-area laser diode with improved heat-sinking structure, which another effective heat-sinking path toward the substrate side is added by removing a bulk substrate. It is possible to obtain by removing a 400-μm-thick GaAs substrate with an AlAs sacrificial layer utilizing well-known epitaxial liftoff techniques. In this study, we present the performance improvement of the high-power laser diode with the heat-sinking structure by suppressing thermal effects. It is found that the lateral far-field angle as well as quantum well temperature is expected to be improved by the proposed heat-sinking structure which is required for high beam quality and optical output power, respectively.

  5. Enthalpy model for heating, melting, and vaporization in laser ablation

    Directory of Open Access Journals (Sweden)

    Vasilios Alexiades

    2010-09-01

    Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.

  6. Application of risk-informed design methods to select the PSACS ultimate heat sink

    International Nuclear Information System (INIS)

    Elliott, Michael A.; Apostolakis, George E.

    2009-01-01

    In the early phases of advanced system design, information is scarce. The technologies, components and processes to be used have not been specified adequately or are not well understood and uncertainties are very large. Yet, it is during these early phases that design teams and other stakeholders are required to make critical decisions to guide the development of the system. To aid in this decision making, a formal process is proposed based on the Analytic-Deliberative Decision-Making Process (ADP) that allows stakeholders to synthesize rationally their knowledge and experience and facilitate learning and sharing of best practices. The ADP identifies and prioritizes attributes relevant to a decision problem and supports the formulation of metrics to measure the performance of different design options. This paper reports on an application of the ADP to the selection of an ultimate heat sink for the Flexible Conversion Ratio (FCR) reactor's Passive Secondary Auxiliary Cooling System (PSACS). Two ultimate heat sink options are identified and evaluated, air and water.

  7. ATHENA simulations of divertor pump trip and loss of heat sink transients for the GSSR

    Energy Technology Data Exchange (ETDEWEB)

    Sjoeberg, A

    2001-04-01

    The ITER-FEAT Generic Site Safety Report includes evaluations of the consequences of various types of conceivable transients that may occur during operation. The transients that have to be considered in this respect are specified in the Accident Analysis Specifications document of the safety report. For the divertor primary heat transport system the ranges of transients include amongst others a trip of the main circulation pump in the divertor cooling loop as well as a loss of heat sink, both initiated at full fusion power operation. The thermal-hydraulic consequences related to the coolability of the divertor primary heat transport system components for these two transients have been evaluated and summarized in the safety report and in the current report an overview of those efforts and associated outcome is provided. The analyses have been made with the ATHENA thermal-hydraulic code using a separately developed ATHENA model of the ITER-FEAT divertor cooling system. The results from the analyses indicate that for the pump trip transient the margin against overheating of critical highly loaded parts of the divertor cassette is small but seems sufficient. In case of the loss of heat sink transient the conservative analysis reveals that the pressurizer safety valve will be opened for an extended period of time and the long term transient development indicates a risk of completely filling up the pressurizer vessel. Thus the margins against jeopardizing the integrity of the divertor cooling system with the current design are for this case small but can for a long term operation at associate conditions pose a problem.

  8. Design of an additional heat sink based on natural circulation in pressurized water reactors

    International Nuclear Information System (INIS)

    Frischengruber, Kurt; Solanilla, Roberto; Fernandez, Ricardo; Blumenkrantz, Arnaldo; Castano, Jorge

    1989-01-01

    Residual heat removal through the steam generators in Nuclear Power Plant with pressurized water reactors (PWR) or pressurized heavy water reactors (PHWR in pressured vessel or pressured tube types) requires the maintenance of the steam generator inventory and the availability of and appropriate heat sink, which are based on the operability of the steam generators feedwater system. This paper describes the conceptual design of an assured heat removal system which includes only passive elements and is based on natural circulation. The system can supplement the original systems of the plant. The new system includes a condenser/boiler heat exchanger to condense the steam produced in the steam generator, transferring the heat to the water of an open pool at atmospheric pressure. The condensed steam flows back to the steam generators by natural circulation effects. The performance of an Atucha type PHWR nuclear power station with and without the proposed system is calculated in an emergency power case for the first 5000 seconds after the incident. The analysis shows that the proposed system offers the possibility to cool-down the plant to a low energy state during several hours and avoids the repeated actuation of the primary and secondary system safety valves. (Author) [es

  9. Thermal management of a multiple mini-channel heat sink by the integration of a thermal responsive shape memory material

    International Nuclear Information System (INIS)

    Di Maio, E.; Mastrullo, R.; Mauro, A.W.; Toto, D.

    2014-01-01

    In this paper, a novel application of a thermo-responsive shape memory polymer (SMP) is proposed to smart-control the forced flow of water in a multi mini-channel heat sink. In particular, it is reported that millimeter-sized cylinders made of SMP could be used to smartly obstruct the fluid flow by adapting the flow cross section to the heat load to be removed. By integrating the sensing, the control and the actuation functions within a unique, millimeter-sized device, these micro-valves, unlike the traditional actuators normally used for flow control, could be easily embedded into small heat sinks, with significant space and energy saving, useful, in particular, in systems where several miniaturized components have to be cooled concurrently, such as the modern mainframes or the concentrated photovoltaic solar cells. Two possible configurations for the SMP were considered in this study: an “open” configuration, without any obstruction of the water flow free and an “obstructed” configuration, with the millimeter-sized cylinder partially occupying the mini-channel. A numerical, steady state analysis was carried out with water in single-phase forced convection, to determine the effect of these two states on the internal fluid flow characteristics under different conditions of heat flux and pressure drop and to evaluate the overall thermal behavior of the smart-controlled multiple mini-channel heat sink in terms of ability to control the temperature of the system and to reduce the energy consumption. -- Highlights: • A novel application of a SMP material is investigated for the thermal management of a heat sink. • Numerical simulations to find the matching of the heat sink and material system after regulation were carried out. • The investigated system is able to control the heat sink temperature. • Further analysis for system stability are required

  10. Vapor Compression and Thermoelectric Heat Pump Heat Exchangers for a Condensate Distillation System: Design and Experiment

    Science.gov (United States)

    Erickson, Lisa R.; Ungar, Eugene K.

    2013-01-01

    Maximizing the reuse of wastewater while minimizing the use of consumables is critical in long duration space exploration. One of the more promising methods of reclaiming urine is the distillation/condensation process used in the cascade distillation system (CDS). This system accepts a mixture of urine and toxic stabilizing agents, heats it to vaporize the water and condenses and cools the resulting water vapor. The CDS wastewater flow requires heating and its condensate flow requires cooling. Performing the heating and cooling processes separately requires two separate units, each of which would require large amounts of electrical power. By heating the wastewater and cooling the condensate in a single heat pump unit, mass, volume, and power efficiencies can be obtained. The present work describes and compares two competing heat pump methodologies that meet the needs of the CDS: 1) a series of mini compressor vapor compression cycles and 2) a thermoelectric heat exchanger. In the paper, the system level requirements are outlined, the designs of the two heat pumps are described in detail, and the results of heat pump performance tests are provided. A summary is provided of the heat pump mass, volume and power trades and a selection recommendation is made.

  11. Cernavoda NPP Unit 1: Ensuring heat sink at very low Danube river levels

    International Nuclear Information System (INIS)

    Urjan, D.

    2005-01-01

    Full text: On August 24, 2003 the summer heat wave has caused the Danube River to drop to its lowest level in more than a century, forcing a government commission of experts and a team of technical specialists from Cernavoda NPP to close Romania's unique nuclear reactor in operation at Cernavoda. The paper presents some of the required actions needed for plant shutdown and ensuring adequate fuel cooling at very low suction bay levels, due to the Danube River level drop (Danube waters cools the reactor). The water level in the Danube River at Cernavoda village, where the reactor is located, fell to a depth of less than three meters (10 feet) on Saturday, down from its usual level of almost seven meters (23 feet). Consequently, the Unit 1 nuclear power plant was shut down Sunday due to this record drought, which left insufficient water to cool down the reactor. Operating Instruction procedures were elaborated in order to provide a logical sequence of actions when the bay level decreases under 2.25 m, or the estimated level after 3 days will be lower than 1.8 m. When Raw Service Water (RSW) is lost, Recirculated Cooling Water (RCW) will remain in service only for Moderator, ESC, HT Pumps, HT Purification, D/C Cooler, LAC's, and D 2 O Feed Pump. Alternate water sources, like potable water and water from the fire protection system were taken in consideration in order to ensure heat sink to the RCW loads. At the same time, in case of total loss of Class III and Class IV Power, and Stand-By Diesel Generators unavailable because of the loss of heat sink provided by the RSW, Emergency Power System (EPS) was configured to supply directly the Class III Power 6 kV bus (BUG bus). Economical Impact According to a report, closing the nuclear plant costs Romania $500,000 a day. The total cost includes also losses due to a 40 percent reduction in hydroelectric power generation due to reduced river flow. The country had to cease power exports until the reactor comes back on line

  12. Manufacturing and characterisation of SiC-fibre-reinforced copper in heat sink applications

    International Nuclear Information System (INIS)

    Kimmig, Stefan

    2013-01-01

    The wall materials in future fusion reactors will be operating under extreme thermal and mechanical load conditions. The divertor region of such a device is the most severely loaded component. This part is exposed to heat fluxes of up to 15 MW m 2 due to the impinging plasma particle flux. Tungsten is currently considered as the best choice for the plasmafacing-materials (PFM) in the divertor region. An efficient heat sink material is required underneath the PFM for sufficient heat transfer to the cooling channels. In the research reactor ITER a copper alloy (CuCrZr) is foreseen as heat sink material, which is able to withstand temperatures of up to 350 C, corresponding to a water coolant temperature of 150 C. For the commercial use of fusion energy an increase of the thermal efficiency is necessary by increasing the coolant temperature to over 300 C. This will cause higher stresses in the connection area between PFM and the heat sink due to different coefficients of thermal expansion combined with higher temperatures. The mechanical properties of CuCrZr are insufficient for these conditions and fibre reinforced copper metal matrix composites (CuMMC) are considered as an alternative material to strengthen the critical connection area between the heat sink and the PFM. The composite should combine the high heat conductivity of a copper matrix with the high stiffness and mechanical strength of silicon-carbide fibres (SiC-fibres). During this investigation SiC-fibres of two different production principles were studied regarding their usage for the manufacturing of a CuMMC. The main goals for the CuMMC are a tensile strength of 300 MPa combined with a heat conductivity of more than 200 W m -1 K -1 . Both of these parameters are affected by the single fibre tensile strength and by the bonding between the fibres and the copper matrix. The achievable heat conductivity in the CuMMC depends on the fibre volume ratio within the composite. Higher fibre strength reduces the

  13. Thermodynamic analysis of the effect of channel geometry on heat transfer in double-layered microchannel heat sinks

    International Nuclear Information System (INIS)

    Zhai, Yuling; Li, Zhouhang; Wang, Hua; Xu, Jianxin

    2017-01-01

    Highlights: • A novel geometry with rectangular and complex channels in each layer is presented. • It shows lower pressure drop and more uniform temperature distribution. • The essence of enhanced heat transfer is analyzed from thermodynamics. - Abstract: Novel double-layered microchannel heat sinks with different channel geometries in each layer (Structure 2 for short) are designed to reduce pressure drop and maintain good heat transfer performance, which is compared with structure 1 (the same of complex channel geometry in each layer). The effect of parallel flow, counter flow and different channel geometries on heat transfer is studied numerically. Moreover, the essence of heat transfer enhancement is analyzed by thermodynamics. On one hand, the synergy relationship between flow field and temperature field is analyzed by field synergy principle. On the other hand, the irreversibility of heat transfer is studied by transport efficiency of thermal energy. The results show that the temperature distribution of counter flow is more uniform than that of parallel flow. Furthermore, heat dissipation and pressure drop of structure 2 are both better and lower than that of structure 1. Form the viewpoint of temperature distribution, structure C2 (i.e., counter flow with rectangular channels in upper layer and complex channels in bottom layer) presents the most uniform bottom temperature for microelectronic cooling. However, comprehensive heat transfer performance of structure P2 (i.e., parallel flow with rectangular channels in upper layer and complex channels in bottom layer) shows the best from the viewpoint of thermodynamics. The reasons can be ascribed to the channel geometry of structure P2 can obviously improve the synergy relationship between temperature and velocity fields, reduce fluid temperature gradient and heat transfer irreversibility.

  14. Atmospheric solar heating rate in the water vapor bands

    Science.gov (United States)

    Chou, Ming-Dah

    1986-01-01

    The total absorption of solar radiation by water vapor in clear atmospheres is parameterized as a simple function of the scaled water vapor amount. For applications to cloudy and hazy atmospheres, the flux-weighted k-distribution functions are computed for individual absorption bands and for the total near-infrared region. The parameterization is based upon monochromatic calculations and follows essentially the scaling approximation of Chou and Arking, but the effect of temperature variation with height is taken into account in order to enhance the accuracy. Furthermore, the spectral range is extended to cover the two weak bands centered at 0.72 and 0.82 micron. Comparisons with monochromatic calculations show that the atmospheric heating rate and the surface radiation can be accurately computed from the parameterization. Comparisons are also made with other parameterizations. It is found that the absorption of solar radiation can be computed reasonably well using the Goody band model and the Curtis-Godson approximation.

  15. Review and evaluation of information on the thermal performance of ultimate heat sinks: spray ponds and cooling ponds

    International Nuclear Information System (INIS)

    Drake, R.L.

    1975-09-01

    A report is presented which identifies and evaluates available information and data useful in validating and improving existing models for the thermal performance of ultimate heat sinks. Included are discussions of the thermal elements of cooling ponds and spray ponds, the available information and data pertinent to the problem, and the requirements and needs for further research and performance data. An outline is presented of the necessary elements required for a performance test of an ultimate heat sink before the system is thermally approved. (auth)

  16. Comparative Performance of Surrogate-Assisted MOEAs for Geometrical Design of Pin-Fin Heat Sinks

    Directory of Open Access Journals (Sweden)

    Siwadol Kanyakam

    2012-01-01

    Full Text Available This paper presents the comparative performance of several surrogate-assisted multiobjective evolutionary algorithms (MOEAs for geometrical design of a pin-fin heat sink (PFHS. The surrogate-assisted MOEAs are achieved by integrating multiobjective population-based incremental learning (PBIL with a quadratic response surface model (QRS, a radial-basis function (RBF interpolation technique, and a Kriging (KRG or Gaussian process model. The mixed integer/continuous multiobjective design problem of PFHS with the objective to minimise junction temperature and fan pumping power simultaneously is posed. The optimum results obtained from using the original multiobjective PBIL and the three versions of hybrid PBIL are compared. It is shown that the hybrid PBIL using KRG is the best performer. The hybrid PBILs require less number of function evaluations to surpass the original PBIL.

  17. Passive afterheat removal in the HTGR with the liner cooling system as a heat sink

    International Nuclear Information System (INIS)

    Rehm, W.; Jahn, W.; Verfondern, K.

    1984-09-01

    The report deals with the transients of temperature and system pressure and the fission product behaviour in the primary circuit of an HTGR during passive afterheat removal, where the liner cooling system of the PCRV serves as a heat sink. The analysis has been made for the PNP-500-reactor representing nuclear plants with medium thermal power. The investigations show that the liner cooling system is able to control a core heatup. High temperature loads are encountered in the upper core region. In the case of a reactor under pressure the fuel elements and the primary circuit remain intact as the first and second barriers for fission products. In the case of a depressurized primary circuit the liner cooling system also keeps the PCRV at normal operating temperatures. The effects of a core heatup on component damage and release of fission products are thus limited. (orig.) [de

  18. Thermal analysis of a multi-layer microchannel heat sink for cooling concentrator photovoltaic (CPV) cells

    Science.gov (United States)

    Siyabi, Idris Al; Shanks, Katie; Mallick, Tapas; Sundaram, Senthilarasu

    2017-09-01

    Concentrator Photovoltaic (CPV) technology is increasingly being considered as an alternative option for solar electricity generation. However, increasing the light concentration ratio could decrease the system output power due to the increase in the temperature of the cells. The performance of a multi-layer microchannel heat sink configuration was evaluated using numerical analysis. In this analysis, three dimensional incompressible laminar steady flow model was solved numerically. An electrical and thermal solar cell model was coupled for solar cell temperature and efficiency calculations. Thermal resistance, solar cell temperature and pumping power were used for the system efficiency evaluation. An increase in the number of microchannel layers exhibited the best overall performance in terms of the thermal resistance, solar cell temperature uniformity and pressure drop. The channel height and width has no effect on the solar cell maximum temperature. However, increasing channel height leads to a reduction in the pressure drop and hence less fluid pumping power.

  19. A assessment of loss-of-heat-sink accident with scram in the LMFBR

    International Nuclear Information System (INIS)

    Bari, R.A.; Ludewig, H.; Pratt, W.T.; Sun, Y.H.

    1978-01-01

    A description of a slow core meltdown in a liquid metal fast breeder reactor is presented for conditions of loss-of-heat-sink following neutronic shutdown. Simple models are developed for the prediction of phase changes and/or relocation of the core materials including fuel, clad, ducts, control rod absorber material (B 4 C), and plenum gases. The sequence of events is accounted for and the accident progression is described up to the point of recriticality. The neutronic behavior of the disrupted core is analyzed in R-Z geometry with a static transport theory code. For most scenarios assessed, the reactor is expected to become recritical although large ramp rates are not anticipated. (author)

  20. Assessment of the loss-of-heat-sink accident with scram in the LMFBR

    International Nuclear Information System (INIS)

    Bari, R.A.; Ludewig, H.; Pratt, W.T.; Sun, Y.H.

    1978-01-01

    A description of a slow core meltdown in a liquid metal fast breeder reactor is presented for the conditions of loss-of-heat-sink following neutronic shutdown. Simple models are developed for the prediction of phase changes and/or relocation of the core materials including fuel, clad, ducts, control rod absorber material (B 4 C), and plenum gases. The sequence of events is accounted for and the accident progression is described up to the point of recriticality. The neutronic behavior of the disrupted core is analyzed in R-Z geometry with a static transport theory code. For most scenarios assessed, the reactor is expected to become recritical although large ramp rates are not anticipated

  1. Thermosyphon Phenomenon as an alternate heat sink of Shutdown Cooling System for the CANDU reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jonghyun [GNEST, Seoul (Korea, Republic of); Lee, Kwangho; Oh, Haechol; Jun, Hwangyong [KEPRI, Taejon (Korea, Republic of)

    2006-07-01

    During the outage(overhaul) of the CANDU plant, there is a period when the coolant is partially drained to the reactor header level and the coolant is cooled and depressurized by Shutdown Cooling System(SDCS) other than PHTS pump. In the postulated accident of the loss of SDCS-the PHTS pump failure, the primary coolant system should be cooled by the alternate heat sink using the thermosyphon pheonomenon(TS) through the steam generator(SG) This study was aimed at verification and analyzing the core cooling ability of the TS. And the sensitivity analysis was done for the number of SGs used in the TS. As an analysis tool, RELAP5/CANDU was used.

  2. Prediction of vapor pressure and heats of vaporization of edible oil/fat compounds by group contribution

    DEFF Research Database (Denmark)

    Ceriani, Roberta; Gani, Rafiqul; Liu, Y.A.

    2013-01-01

    In the present work, a group contribution method is proposed for the estimation of vapor pressures and heats of vaporization of organic liquids found in edible fat/oil and biofuel industries as a function of temperature. The regression of group contribution parameters was based on an extensive...

  3. Experimental investigation of a PCM-HP heat sink on its thermal performance and anti-thermal-shock capacity for high-power LEDs

    International Nuclear Information System (INIS)

    Wu, Yuxuan; Tang, Yong; Li, Zongtao; Ding, Xinrui; Yuan, Wei; Zhao, Xuezhi; Yu, Binhai

    2016-01-01

    Highlights: • A phase-change material (PCM) base heat pipe heat sink (PCM-HP heat sink) is designed. • The PCM-HP heat sink can significantly lower the LED heating rate and temperature. • The PCM-HP heat sink achieves a best anti-thermal-shock capacity in LED cyclic working modes. - Abstract: High-power LEDs demonstrate a number of benefits compared with conventional incandescent lamps and fluorescent lamps, including a longer lifetime, higher brightness and lower power consumption. However, owing to their severe high heat flux, it is difficult to develop effective thermal management of high-power LEDs, especially under cyclic working modes, which cause serious periodic thermal stress and limit further development. Focusing on the above problem, this paper designed a phase-change material (PCM) base heat pipe heat sink (PCM-HP heat sink) that consists of a PCM base, adapter plate, heat pipe and finned radiator. Different parameters, such as three types of interior materials to fill the heat sink, three LED power inputs and eight LED cyclic working modes, were separately studied to investigate the thermal performance and anti-thermal-shock capacity of the PCM-HP heat sink. The results show that the PCM-HP heat sink possesses remarkable thermal performance owing to the reduction of the LED heating rate and peak temperature. More importantly, an excellent anti-thermal-shock capacity of the PCM-HP heat sink is also demonstrated when applied in LED cyclic working modes, and this capacity demonstrates the best range.

  4. ATHENA simulations of divertor loss of heat sink transient for the GSSR - Final report with updates

    Energy Technology Data Exchange (ETDEWEB)

    Sponton, L.L

    2001-05-01

    The ITER-FEAT Generic Site Safety Report includes evaluations of the consequences of various types of conceivable transients that can occur during operation. The transients that have to be considered in this respect are specified in the Accident Analysis Specifications document of the safety report. For the divertor primary heat transport system the ranges of transients include amongst others a loss of heat sink at full fusion power operation. The thermal-hydraulic consequences related to the coolability of the divertor primary heat transport system components for this transient have been evaluated and summarised in the safety report and in the current report an overview of those efforts and associated outcome is provided. The analyses have been made with the ATHENA thermal-hydraulic code using a separately developed ATHENA model of the ITER-FEAT divertor cooling system. In the current report results from calculations with an updated pressurizer model and pressurizer control system are outlined. The results show that the pressurizer safety valve does not open, that the pressurizer level increase is moderate and that no temperature increases jeopardize the structure integrity.

  5. A new approach to the modeling of ultimate heat sink cooling ponds

    International Nuclear Information System (INIS)

    Policastro, A.J.; Wastag, M.; Paul, J.; Carhart, R.A.

    1996-01-01

    Ultimate heat sink (UHS) cooling pond thermal performance is analyzed by a new method in which zero, one, and three-dimensional models are used in combination. A typical UHS pond has an irregular shape covering 20 hectares at an average depth of 4 m with a heavy thermal load of 40 MWt (megawatts thermal) per hectare. The resulting flow field can be one, two or three dimensional. A three-dimensional numerical model (Paul 1983) is modified and used to determine the effective dimensionality of the pond under accident conditions. The model's surface heat transfer formulas and its predictions of thermal hydraulics are verified using laboratory and field data. The Paul model shows that, unlike normal cooling ponds, a typical UHS pond is vertically-mixed with only a longitudinal temperature variation. Buoyancy-driven circulations, strong discharge-to-intake flow, and rapid surface heat removal break down the usual vertical stratification. Predictions of the one-dimensional MITEMP model are shown to agree with Paul model predictions for a typical UHS pond at the Catawba Nuclear Power Plant

  6. ATHENA simulations of divertor loss of heat sink transient for the GSSR - Final report with updates

    International Nuclear Information System (INIS)

    Sponton, L.L.

    2001-05-01

    The ITER-FEAT Generic Site Safety Report includes evaluations of the consequences of various types of conceivable transients that can occur during operation. The transients that have to be considered in this respect are specified in the Accident Analysis Specifications document of the safety report. For the divertor primary heat transport system the ranges of transients include amongst others a loss of heat sink at full fusion power operation. The thermal-hydraulic consequences related to the coolability of the divertor primary heat transport system components for this transient have been evaluated and summarised in the safety report and in the current report an overview of those efforts and associated outcome is provided. The analyses have been made with the ATHENA thermal-hydraulic code using a separately developed ATHENA model of the ITER-FEAT divertor cooling system. In the current report results from calculations with an updated pressurizer model and pressurizer control system are outlined. The results show that the pressurizer safety valve does not open, that the pressurizer level increase is moderate and that no temperature increases jeopardize the structure integrity

  7. Using AlN-Coated Heat Sink to Improve the Heat Dissipation of LED Packages

    Directory of Open Access Journals (Sweden)

    Jean Ming-Der

    2016-01-01

    Full Text Available This study optimizes aluminum nitride (AlN ceramics, in order to enhance the thermal performance of light-emitting diode (LED packages. AlN coatings are grown on copper/ aluminum substrates as a heat interface material, using an electrostatic spraying process. The effect of the deposition parameters on the coatings is determined. The thermal performance of AlN coated Cu/Al substrates is evaluated in terms of the heat dissipated and compared by measuring the LED case temperature. The structure and properties of the coating are also examined a scanning electron microscopy (SEM. In sum, the thermal performance of the LED is increased and good heat resistance characteristics are obtained. The results show that using AlN ceramic coating on a copper/aluminum substrate increases the thermal performance.

  8. Fluid flow and heat transfer of nanofluids in microchannel heat sink with V-type inlet/outlet arrangement

    Directory of Open Access Journals (Sweden)

    Ayoub Abdollahi

    2017-03-01

    Full Text Available The fluid flow and heat transfer characteristics of laminar nanofluid flow in microchannel heat sink (MCHS with V-Type inlet/outlet arrangement are numerically studied. A constant heat flux boundary condition is applied on the base plate of MCHS and all the other surfaces of MCHS are insulated. Four different kinds of nanofluids are utilized as working fluids which are SiO2, Al2O3, ZnO and CuO dispersed in pure water as a base fluid. Three different volume fractions of 1%, 1.5% and 2% and three distinctive nanoparticle diameters of 30 nm, 40 nm and 60 nm were employed. The results specify that the SiO2 nanofluid has the uppermost heat transfer rate compared to other tested nanofluids. Increasing the nanoparticles volume fraction together with decreasing the nanoparticles diameter enhances the Nusselt number value. The pressure drop coefficient did not change significantly by using nanofluid with various volume fractions and varied nanoparticle diameters. Moreover, the results indicate that nanofluid can enhance the performance of MCHS with V-shaped inlet/outlet arrangement.

  9. Assessment of cooling tower (ultimate heat sink) performance in the Byron individual plant examination

    International Nuclear Information System (INIS)

    Campbell, H.D.; Hawley, J.T.; Klopp, G.T.; Thelen, W.A.

    2004-01-01

    A time-dependent model of the Byron Nuclear Generation Station safety-related cooling towers has been developed for use with the Byron PRA (IPE). The model can either be run in a stand-alone program with externally supplied heat loads, or can be directly coupled into MAAP (Modular Accident Analysis Program). The primary feature of the model is a careful tracking of the basin temperature through the progression of different severe accidents. Heat removal rates from containment, both from containment fan-coolers and the residual heat removal system, are determined by the feed-back of this time-varying return temperature. Also, the inventory of the basin is tracked in time, and this is controlled by make-up, evaporative losses due to the heat load supplied to the towers, and the possibility of unsecured blowdown. The model has been used to determine the overall capabilities and vulnerabilities of the Byron Ultimate Heat Sink (UHS). It was determined that the UHS is very reliable with respect to maintaining acceptably low basin temperatures, requiring only at most two of eight operating cooling tower fans. Further, when the two units have their Essential Service Water (ESW) systems cross-tied, one of four ESW operating pumps is sufficient to handle the loads from the accident unit with the other unit proceeding to an orderly shutdown. The major vulnerability of the Byron UHS is shown to be the ability to maintain inventory, although the time-scales for basin dry-out are relatively long, being eight to twenty-one hours, depending upon when blowdown is secured. (author)

  10. Effects of thermal property variations on the liquid flow and heat transfer in microchannel heat sinks

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhigang [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Huai, Xiulan; Tao, Yujia; Chen, Huanzhuo [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080 (China)

    2007-12-15

    Three-dimensional conjugate numerical simulations using the inlet, average and variable thermal properties respectively were performed for the laminar water flow and heat transfer in rectangular microchannels with D{sub h} of 0.333 mm at Re of 101-1775. Both average and variable properties are adopted in data reduction. The calculated local and average characteristics of flow and heat transfer are compared among different methods, and with the experiments, correlations and simplified theoretical solution data from published literatures. Compared with the inlet property method, both average and variable property methods have significantly lower f{sub app}, but higher convective heat transfer coefficient h{sub z} and Nu{sub z}. Compared with the average property method, the variable property method has higher f{sub app}Re{sub ave} and lower h{sub z} at the beginning, but lower f{sub app}Re{sub ave} and higher h{sub z} at the later section of the channel. The calculated Nu{sub ave} agree well with the Sieder-Tate correlation and the recently reported experiment, validating the traditional macroscale theory in predicting the flow and heat transfer characteristics in the dimension and Re range of the present work. (author)

  11. Condensation heat transfer correlation for water-ethanol vapor mixture flowing through a plate heat exchanger

    Science.gov (United States)

    Zhou, Weiqing; Hu, Shenhua; Ma, Xiangrong; Zhou, Feng

    2018-04-01

    Condensation heat transfer coefficient (HTC) as a function of outlet vapor quality was investigated using water-ethanol vapor mixture of different ethanol vapor concentrations (0%, 1%, 2%, 5%, 10%, 20%) under three different system pressures (31 kPa, 47 kPa, 83 kPa). A heat transfer coefficient was developed by applying multiple linear regression method to experimental data, taking into account the dimensionless numbers which represents the Marangoni condensation effects, such as Re, Pr, Ja, Ma and Sh. The developed correlation can predict the condensation performance within a deviation range from -22% to 32%. Taking PHE's characteristic into consideration and bringing in Ma number and Sh number, a new correlation was developed, which showed a much more accurate prediction, within a deviation from -3.2% to 7.9%.

  12. Characteristics of entropy generation and heat transfer in double-layered micro heat sinks with complex structure

    International Nuclear Information System (INIS)

    Zhai, Y.L.; Xia, G.D.; Liu, X.F.; Wang, J.

    2015-01-01

    Highlights: • A novel DL-MCHS with complex structure is presented. • A model of entropy generation rate of DL-MCHSs is derived from the first and second laws of thermodynamics. • DL-MCHSs show better thermodynamic advantage and thermal performance under large volumetric flow rate. - Abstract: A new type of double-layered micro heat sink (DL-MCHS) with complex structure is designed and investigated numerically. Moreover, a model of entropy generation rate of DL-MCHSs is also derived from the first and second laws of thermodynamics. Results for the relationship of entropy generation rate between the first and second layer of DL-MCHSs, total entropy generation rate, the average temperature on the bottom wall, thermal resistance and pressure drop are investigated in detail, respectively. The results indicate that the effect of entropy generation rate of the first layer on total entropy generation rate is dominant. The thermal characteristic of DL-MCHSs with complex structure is better than that of all DL-MCHSs and single-layered micro heat sinks (SL-MCHSs) with simple structure under the same volumetric flow rate. However, DL-MCHSs only show better thermodynamic advantage and thermal performance than SL-MCHSs with complex structure when the volumetric flow rate larger than a certain value. It is not reasonable to use DL-MCHSs for cooling microelectronic equipments under small volumetric flow rate due to the larger irreversibility. Finally, the pressure drop of DL-MHCSs can be reduced by properly changing the channel height under various volumetric flow rates. Due to the less irreversibility and more uniform temperature distribution on the bottom wall, DL-MCHSs can effectively eliminate the internal thermal stresses in microelectronic equipments. Therefore, DL-MCHSs are an alternative method for the electronic cooling. Moreover, the thermodynamic analysis provides references for the actual application design

  13. Numerical simulation of the thermal hydraulic performance of a plate pin fin heat sink

    International Nuclear Information System (INIS)

    Yuan Wuhan; Zhao Jiyun; Tso, C.P.; Wu Tianhua; Liu Wei; Ming Tingzhen

    2012-01-01

    The computational fluid dynamic software FLUENT is used in assessing the electronics cooling potential of a plate pin fin heat sink (PPFHS), including the conjugate effect. The simulation results are validated with reported experimental data. The simulation shows that pin height and air velocity have significant influences on the thermal hydraulic performances of PPFHS while the influences of in-line/staggered array and neighbor pin flow-directional center distance (NPFDCD) of the PPFHS are less notable. In applying the present design to the cooling of a desktop PC CPU at a heat flux of 2.20 W/cm 2 , the temperature can be kept at less than 358 K with an air velocity over 6.5 m/s. - Highlights: ► Pin height and air velocity significantly influence thermal performance of PPFHS. ► Less influence by in-line or staggered array. ► Less influence by neighbor pin flow-directional center distance. ► Design with >6.5 m/s air can cool to 2 flux.

  14. Thermal performance experiments on ultimate heat sinks, spray ponds, and cooling ponds

    International Nuclear Information System (INIS)

    Hadlock, R.K.

    1976-12-01

    A program of measurement on a Battelle-Northwest (BNW) spray pond has been completed to prove an integrated instrumentation system for application in future field experiments. The measurement programs in the field will produce data of relevance to the design and understanding of performance for ultimate heat sinks as components of emergency core cooling systems. In the absence of active emergency cooling systems, the data will be obtained on analog systems--prime candidates among these are the naturally-occurring hot ponds at Yellowstone National Park and man-made hot cooling ponds at Savannah River National Laboratory as well as spray ponds at various industrial facilities. The proof experiment has provided data that not only illustrate the effectiveness of the instrumentation system but also display interesting site-specific heat transfer processes. The data to be obtained in the field will also be site specific but must be of generic applicability in modeling for design and performance purposes. The integrated instrumentation system will evolve, through modest modifications and substantial supplementation, to provide the requisite data for the more demanding situation of work in and about hot water

  15. Analysis and Optimization of Trapezoidal Grooved Microchannel Heat Sink Using Nanofluids in a Micro Solar Cell

    Directory of Open Access Journals (Sweden)

    Ruijin Wang

    2017-12-01

    Full Text Available It is necessary to control the temperature of solar cells for enhancing efficiency with increasing concentrations of multiple photovoltaic systems. A heterogeneous two-phase model was established after considering the interacting between temperature, viscosity, the flow of nanofluid, and the motion of nanoparticles in the nanofluid, in order to study the microchannel heat sink (MCHS using Al2O3-water nanofluid as coolant in the photovoltaic system. Numerical simulations were carried out to investigate the thermal performance of MCHS with a series of trapezoidal grooves. The numerical results showed us that, (1 better thermal performance of MCSH using nanofluid can be achieved from a heterogeneous two-phase model than that from single-phase model; (2 The effects of flow field, volume fraction, nanoparticle size on the heat transfer enhancement in MCHS were interpreted by a non-dimensional parameter NBT (i.e., ratio of Brownian diffusion and thermophoretic diffusion. In addition, the geometrical parameters of MCHS and the physical parameters of the nanofluid were optimized. This can provide a sound foundation for the design of MCHS.

  16. Nonlinear radiative heat flux and heat source/sink on entropy generation minimization rate

    Science.gov (United States)

    Hayat, T.; Khan, M. Waleed Ahmed; Khan, M. Ijaz; Alsaedi, A.

    2018-06-01

    Entropy generation minimization in nonlinear radiative mixed convective flow towards a variable thicked surface is addressed. Entropy generation for momentum and temperature is carried out. The source for this flow analysis is stretching velocity of sheet. Transformations are used to reduce system of partial differential equations into ordinary ones. Total entropy generation rate is determined. Series solutions for the zeroth and mth order deformation systems are computed. Domain of convergence for obtained solutions is identified. Velocity, temperature and concentration fields are plotted and interpreted. Entropy equation is studied through nonlinear mixed convection and radiative heat flux. Velocity and temperature gradients are discussed through graphs. Meaningful results are concluded in the final remarks.

  17. Effect of the inter-block spacing on the thermal performance of a PCM based heat sink

    Energy Technology Data Exchange (ETDEWEB)

    Faraji, M.; El Qarnia, H. [Cadi Ayyad Univ., Marrakech (Morocco). Faculte des sciences Semlalia, Dept. de physique, Laboratoire de mecanique des fluides et d' energetique; El Khadir, L. [Cadi Ayyad Univ., Marrakech (Morocco). Faculte des sciences Semlalia, Dept. de physique, Laboratoire d' tomatique de l' Environnement et Procedes de Transferts

    2010-07-01

    Advanced electronic devices require efficient thermal control systems. Heat transfer analysis of such systems is challenging because of constraints regarding space limitations, power consumption and noise level. This study considered the problem of melting and natural convection in a rectangular enclosure heated with 3 heat sources with a constant and uniform volumetric heat generation. The heat sources were protruding and mounted on a vertical conducting plate. Conjugate conduction in a plate and heat sources coupled with natural convection and melting process were examined in an effort to determine the effects of the inter-blocks spacing ratio on the thermal performance of the cooling PCM-heat sink. The percentage contribution of substrate heat conduction on the total removed heat from heat sources was also investigated. Correlations were derived for the non- dimensional secured working time and the corresponding melt fraction. In order to investigate the thermal behaviour of the proposed heat sink, a mathematical model was developed based on the mass, momentum and energy conservation equations. The results revealed that for lower inter-blocks spacing, the dimensionless secured working time needed by the chips to reach the critical temperature was maximized. The highest inter-blocks spacing ratio provoked a sudden rise in chip temperatures and thus reduced the dimensionless secured working time. It was concluded that this approach can be used in the design of PCM-based cooling systems. 9 refs., 2 tabs., 4 figs.

  18. In-vessel natural circulation during a hypothetical loss-of-heat-sink accident in the Fast Flux Test Facility

    International Nuclear Information System (INIS)

    Perkins, K.R.; Bari, R.A.; Pratt, W.T.

    1979-05-01

    The capability to remove decay heat from the FFTF core via in-vessel natural circulation has been analyzed for the preboiling phase using a lumped parameter model. The results indicate that boiling will occur in the average fuel assembly for a wide spectrum of initial conditions which appear to be representative of the hypothetical loss-of-heat-sink accident. Two-phase pressure drop calculations indicate that, once the saturation temperature is reached, coolability can only be assured for decay heat levels which are less than 0.5% of the operating power. A review of the limited sodium boiling data indicates that boiling-induced natural circulation may support up to 4% of the operating power, but geometric atypicalities and a large degree of inlet subcooling for the existing data limit the applicability to the loss-of-heat-sink accident in FFTF

  19. Behavior of tungsten coatings on CuCrZr heat sink with the different interlayers under high heat flux

    International Nuclear Information System (INIS)

    Chong, F.L.; Chen, J.L.; Li, J.G.; Zheng, X.B.; Hu, D.Y.; Ding, C.X.

    2007-01-01

    In recent years, tungsten coated CuCrZr by means of vacuum plasma spraying technology was studied at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). Plasma spraying technology is a good integration way of armor material and heat sink, which overcomes the disadvantage of heavy weight and poor workability of tungsten, and offers the ability to coat large area, even complex shapes and in situ repair of damaged parts. But tungsten coated CuCrZr is a challenge due to the larger mismatch of their thermal expansion coefficients (CTE), which will induce the stress concentration on the joint interface of plasma facing component. In order to enhance the adhesion of W coating on CuCrZr substrate and avoid the thermal stress concentration, it is necessary to use a compliant interlayer. At present, titanium (Ti), nickel-chromium-aluminum (NiCrAl) alloys and W/Cu mixtures were chosen as the compliant layers to insert between W coating and CuCrZr substrate. The adhesion strength was performed at RT. The behaviors of W/Cu mock up under high heat flux were carried out by means of the electron beam facility with actively cooling. The results indicated that the mock-ups with the interlayer architectures can withstand the higher heat flux compared to that with the sharp interface, which exhibited the effect of interlayers on reducing the maximum stress and enhancing the properties of resistant heat flux load, though the maximum surface temperature increased due to inserting the interlayers. Among three interlayers, W/Cu interlayer was much better due to its good heat removal capability and flexible W/Cu ratios. Meanwhile, the behaviors of W/Cu mock-ups with the different interlayers were analyzed and optimized by ANSYS finite element code. (authors)

  20. Some conclusions obtained from the thermo-hydraulic behavior analysis of the nuclear power plant Atucha I, in case of loss of coolant accident with second heat sink

    International Nuclear Information System (INIS)

    Ventura, Mirta A.

    2003-01-01

    This paper is based on the recompilation, analysis and elaboration of the results of the operator (NA-SA), in the framework of the Atucha I Second Heat Sink project. The results have been compared with those obtained for the same power plant without second heat sink. The conclusions of the work permit the establishment of the operation rules of the plant. (author)

  1. Impact of heat source/sink on radiative heat transfer to Maxwell nanofluid subject to revised mass flux condition

    Science.gov (United States)

    Khan, M.; Irfan, M.; Khan, W. A.

    2018-06-01

    Nanofluids retain noteworthy structure that have absorbed attentions of numerous investigators because of their exploration in nanotechnology and nanoscience. In this scrutiny a mathematical computation of 2D flows of Maxwell nanoliquid influenced by a stretched cylinder has been established. The heat transfer structure is conceded out in the manifestation of thermal radiation and heat source/sink. Moreover, the nanoparticles mass flux condition is engaged in this exploration. This newly endorsed tactic is more realistic where the conjecture is made that the nanoparticle flux is zero and nanoparticle fraction regulates itself on the restrictions consequently. By utilizing apposite conversion the governing PDEs are transformed into ODEs and then tackled analytically via HAM. The attained outcomes are plotted and deliberated in aspect for somatic parameters. It is remarked that with an intensification in the Deborah number β diminish the liquid temperature while it boosts for radiation parameter Rd . Furthermore, the concentration of Maxwell liquid has conflicting impact for Brownian motion Nb and thermophoresis parameters Nt .

  2. High Thermal Dissipation of Al Heat Sink When Inserting Ceramic Powders by Ultrasonic Mechanical Coating and Armoring.

    Science.gov (United States)

    Tsai, Wei-Yu; Huang, Guan-Rong; Wang, Kuang-Kuo; Chen, Chin-Fu; Huang, J C

    2017-04-26

    Aluminum alloys, which serve as heat sink in light-emitting diode (LED) lighting, are often inherent with a high thermal conductivity, but poor thermal total emissivity. Thus, high emissive coatings on the Al substrate can enhance the thermal dissipation efficiency of radiation. In this study, the ultrasonic mechanical coating and armoring (UMCA) technique was used to insert various ceramic combinations, such as Al₂O₃, SiO₂, or graphite, to enhance thermal dissipation. Analytic models have been established to couple the thermal radiation and convection on the sample surface through heat flow equations. A promising match has been reached between the theoretical predictions and experimental measurements. With the adequate insertion of ceramic powders, the temperature of the Al heat sinks can be lowered by 5-11 °C, which is highly favorable for applications requiring cooling components.

  3. COOLING MICROELECTRONIC DEVICES USING OPTIMAL MICROCHANNEL HEAT SINKS: UNA COMPARACIÓN DE DOS ALGORITMOS DE OPTIMIZACIÓN GLOBAL

    Directory of Open Access Journals (Sweden)

    Jorge Mario Cruz Duarte

    Full Text Available This article deals with the design of optimum microchannel heat sinks through Unified Particle Swarm Optimisation (UPSO and Harmony Search (HS. These heat sinks are used for the thermal management of electronic devices, and we analyse the performance of UPSO and HS in their design, both, systematically and thoroughly. The objective function was created using the entropy generation minimisation criterion. In this study, we fixed the geometry of the microchannel, the amount of heat to be removed, and the properties of the cooling fluid. Moreover, we calculated the entropy generation rate, the volume flow rate of air, the channel width, the channel height, and the Knudsen number. The results of several simulation optimizations indicate that both global optimisation strategies yielded similar results, about 0.032 W/K, and that HS required five times more iterations than UPSO, but only about a nineteenth of its computation time. In addition, HS revealed a greater chance (about three times of finding a better solution than UPSO, but with a higher dispersion rate (about five times. Nonetheless, both algorithms successfully optimised the design for different scenarios, even when varying the material of the heat sink, and for different heat transfer rates.

  4. Experimental and Numerical Investigation of Forced Convection Heat Transfer in Heat Sink with Rectangular Plates at Varying Inclinations on Vertical Base

    Science.gov (United States)

    Patil, Harshal Bhauso; Dingare, Sunil Vishnu

    2018-03-01

    Heat exchange upgrade is a vital territory of research area. Utilization of reasonable systems can bring about noteworthy specialized points of interest coming about reserve funds of cost. Rectangular plates are viewed as best balance arrangement utilized for heat exchange improvement. This gives an enlargement strategy to heat exchange with beginning of limit layer and vortex development. To assess and look at the rate of heat exchange enhancement by rectangular plate fins with differing inclinations (0°-30°-60°), shifting Re and heat supply under forced convection are the principle destinations of this study. The study is done by fluctuating introductions of fins with various inclinations, input heat supply and Re under forced convection. The coefficient of heat transfer increments observed with the expansion in air speed for all the examined designs. The coefficient of the heat transfer is discovered higher at the edge of introduction of fins at 30° for inline arrangement and 0° for staggered arrangement. Looking at both the arrangements, it is discovered that the heat transfer coefficient in 0° fin staggered arrangement is about 17% higher than 30° inline arrangement and 76% higher than the vertical plate fin. For plate fin heat sink, boundary layer formation and growth results in decrease of the coefficient of heat transfer in forced convection. This issue is overcome by accommodating some rectangular fins on the plate fin. It brings about increment of heat transfer coefficient of the RPFHS under the states of trial factors. As indicated by past research, it is discovered that examination of the plate fin heat sink with various sorts of fins for horizontal orientation is done yet but this investigation expects to discover the upgrade of transfer coefficient of plate fin heat sink for its vertical position with rectangular plates at different inclinations under the shifting scopes of heat input supply, fin arrangements and Reynolds number (Re).

  5. Effect of heat radiation in a Walter’s liquid B fluid over a stretching sheet with non-uniform heat source/sink and elastic deformation

    Directory of Open Access Journals (Sweden)

    A.K. Abdul Hakeem

    2014-07-01

    Full Text Available In this present article heat transfer in a Walter’s liquid B fluid over an impermeable stretching sheet with non-uniform heat source/sink, elastic deformation and radiation are reported. The basic boundary layer equations for momentum and heat transfer, which are non-linear partial differential equations, are converted into non-linear ordinary differential equations by means of similarity transformation. The dimensionless governing equations for this investigation are solved analytically using hyper geometric functions. The results are carried out for prescribed surface temperature (PST and prescribed power law surface heat flux (PHF. The effects of viscous dissipation, Prandtl number, Eckert number, heat source/sink parameter with elastic deformation and radiation are shown in the several plots and addressed.

  6. Braze Development of Graphite Fiber for Use in Phase Change Material Heat Sinks

    Science.gov (United States)

    Quinn, Gregory; Beringer, Woody; Gleason, Brian; Stephan, Ryan

    2011-01-01

    Hamilton Sundstrand (HS), together with NASA Johnson Space Center, developed methods to metallurgically join graphite fiber to aluminum. The goal of the effort was to demonstrate improved thermal conductance, tensile strength and manufacturability compared to existing epoxy bonded techniques. These improvements have the potential to increase the performance and robustness of phase change material heat sinks that use graphite fibers as an interstitial material. Initial work focused on evaluating joining techniques from four suppliers, each consisting of a metallization step followed by brazing or soldering of one inch square blocks of Fibercore graphite fiber material to aluminum end sheets. Results matched the strength and thermal conductance of the epoxy bonded control samples, so two suppliers were down-selected for a second round of braze development. The second round of braze samples had up to a 300% increase in strength and up to a 132% increase in thermal conductance over the bonded samples. However, scalability and repeatability proved to be significant hurdles with the metallization approach. An alternative approach was pursued which used a nickel braze allow to prepare the carbon fibers for joining with aluminum. Initial results on sample blocks indicate that this approach should be repeatable and scalable with good strength and thermal conductance when compared with epoxy bonding.

  7. Analysis of unscrammed loss of flow and heat sink for PRISM with GEM

    International Nuclear Information System (INIS)

    Slovik, G.C.; Van Tuyle, G.J.; Kennett, R.J.

    1991-01-01

    The US Department of Energy is sponsoring an advanced liquid-metal reactor design by General Electric Company (GE) called PRISM. The intent is to design a reactor with passively safe responses to many operational and severe accidents. PRISM is under review at the US Nuclear Regulatory Commission for licensability with Brookhaven National Laboratory providing technical assistance. Recently, the PRISM design has been modified to include three gas expansion modules (GEMs) on its core periphery. The GEMs were added to quickly reduce the power (by inserting negative reactivity) during loss-of-flow events to curtail peak fuel and clad temperatures predicted in the previous design. The GEM prototypes have been tested at the Fast Flux Test Facility. The significance of the GEMs in PRISM is discussed in this paper through the evaluation of the unprotected loss of flow (ULOF) and loss of heat sink using the SSC code. It has been demonstrated in the past that SSC predicts results similar to GE and other liquid-metal reactor codes

  8. Production of Cu/diamond composites for first-wall heat sinks

    International Nuclear Information System (INIS)

    Nunes, D.; Correia, J.B.; Carvalho, P.A.; Shohoji, N.; Fernandes, H.; Silva, C.; Alves, L.C.; Hanada, K.; Osawa, E.

    2011-01-01

    Due to their suitable thermal conductivity and strength, copper-based materials have been considered appropriate heat sinks for first wall panels in nuclear fusion devices. However, increased thermal conductivity and mechanical strength are demanded and the concept of property tailoring involved in the design of metal matrix composites advocates for the potential of nanodiamond dispersions in copper. Copper-nanodiamond composite materials can be produced by mechanical alloying followed by a consolidation operation. Yet, this powder metallurgy route poses several challenges: nanodiamond presents intrinsically difficult bonding with copper; contamination by milling media must be closely monitored; and full densification and microstructural homogeneity should be obtained with consolidation. The present line of work is aimed at an optimization of the processing conditions of Cu-nanodiamond composites. The challenges mentioned above have been addressed, respectively, by incorporating chromium in the matrix to form a stable carbide interlayer binding the two components; by assessing the contamination originating from the milling operation through particle-induced X-ray emission spectroscopy; and by comparing the densification obtained by spark plasma sintering with hot-extrusion data from previous studies.

  9. Demonstration of Super Cooled Ice as a Phase Change Material Heat Sink for Portable Life Support Systems

    Science.gov (United States)

    Leimkuehler, Thomas O.; Bue, Grant C.

    2009-01-01

    A phase change material (PCM) heat sink using super cooled ice as a nontoxic, nonflammable PCM is being developed. The latent heat of fusion for water is approximately 70% larger than most paraffin waxes, which can provide significant mass savings. Further mass reduction is accomplished by super cooling the ice significantly below its freezing temperature for additional sensible heat storage. Expansion and contraction of the water as it freezes and melts is accommodated with the use of flexible bag and foam materials. A demonstrator unit has been designed, built, and tested to demonstrate proof of concept. Both testing and modeling results are presented along with recommendations for further development of this technology.

  10. Analysis on the Role of RSG-GAS Pool Cooling System during Partial Loss of Heat Sink Accident

    Science.gov (United States)

    Susyadi; Endiah, P. H.; Sukmanto, D.; Andi, S. E.; Syaiful, B.; Hendro, T.; Geni, R. S.

    2018-02-01

    RSG-GAS is a 30 MW reactor that is mostly used for radioisotope production and experimental activities. Recently, it is regularly operated at half of its capacity for efficiency reason. During an accident, especially loss of heat sink, the role of its pool cooling system is very important to dump decay heat. An analysis using single failure approach and partial modeling of RELAP5 performed by S. Dibyo, 2010 shows that there is no significant increase in the coolant temperature if this system is properly functioned. However lessons learned from the Fukushima accident revealed that an accident can happen due to multiple failures. Considering ageing of the reactor, in this research the role of pool cooling system is to be investigated for a partial loss of heat sink accident which is at the same time the protection system fails to scram the reactor when being operated at 15 MW. The purpose is to clarify the transient characteristics and the final state of the coolant temperature. The method used is by simulating the system in RELAP5 code. Calculation results shows the pool cooling systems reduce coolant temperature for about 1 K as compared without activating them. The result alsoreveals that when the reactor is being operated at half of its rated power, it is still in safe condition for a partial loss of heat sink accident without scram.

  11. Performance Estimation of Supercritical CO2 Cycle for the PG-SFR application with Heat Sink Temperature Variation

    International Nuclear Information System (INIS)

    Ahn, Yoonhan; Cho, Seong Kuk; Lee, Jeong Ik

    2015-01-01

    The heat sink temperature conditions are referred from the annual database of sea water temperature in East sea. When the heat sink temperature increases, the compressor inlet temperature can be influenced and the sudden power decrease can happen due to the large water pumping power. When designing the water pump, the pumping margin should be considered as well. As a part of Prototype Generation IV Sodium-cooled Fast Reactor (PG-SFR) development, the Supercritical CO 2 cycle (S-CO 2 ) is considered as one of the promising candidate that can potentially replace the steam Rankine cycle. S-CO 2 cycle can achieve distinctively high efficiency compared to other Brayton cycles and even competitive performance to the steam Rankine cycle under the mild turbine inlet temperature region. Previous studies explored the optimum size of the S-CO 2 cycle considering component designs including turbomachinery, heat exchangers and pipes. Based on the preliminary design, the thermal efficiency is 31.5% when CO 2 is sufficiently cooled to the design temperature. However, the S-CO 2 compressor performance is highly influenced by the inlet temperature and the compressor inlet temperature can be changed when the heat sink temperature, in this case sea water temperature varies. To estimate the S-CO 2 cycle performance of PG-SFR in the various regions, a Quasi-static system analysis code for S-CO 2 cycle is developed by the KAIST research team. A S-CO 2 cycle for PG-SFR is designed and assessed for off-design performance with the heat sink temperature variation

  12. Numerical investigation of thermal performance of a water-cooled mini-channel heat sink for different chip arrangement

    Energy Technology Data Exchange (ETDEWEB)

    Tikadar, Amitav, E-mail: amitav453@gmail.com; Hossain, Md. Mahamudul; Morshed, A. K. M. M. [Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka, 1000 (Bangladesh)

    2016-07-12

    Heat transfer from electronic chip is always challenging and very crucial for electronic industry. Electronic chips are assembled in various manners according to the design conditions and limitationsand thus the influence of chip assembly on the overall thermal performance needs to be understand for the efficient design of electronic cooling system. Due to shrinkage of the dimension of channel and continuous increment of thermal load, conventional heat extraction techniques sometimes become inadequate. Due to high surface area to volume ratio, mini-channel have the natural advantage to enhance convective heat transfer and thus to play a vital role in the advanced heat transfer devices with limited surface area and high heat flux. In this paper, a water cooled mini-channel heat sink was considered for electronic chip cooling and five different chip arrangements were designed and studied, namely: the diagonal arrangement, parallel arrangement, stacked arrangement, longitudinal arrangement and sandwiched arrangement. Temperature distribution on the chip surfaces was presented and the thermal performance of the heat sink in terms of overall thermal resistance was also compared. It is found that the sandwiched arrangement of chip provides better thermal performance compared to conventional in line chip arrangement.

  13. AN EXPERIMENTAL STUDY ON A VAPOR COMPRESSION REFRIGERATION CYCLE BY ADDING INTERNAL HEAT EXCHANGER

    Directory of Open Access Journals (Sweden)

    Muhammad Asmail Eleiwi

    2013-05-01

    Full Text Available Thispaper presents practical study to improve the indication COP of a vaporcompression refrigeration cycle in instrumented automobile air conditioner bydesigning internal heat exchanger and installing it in the vapor compressionrefrigeration cycle.  Two cases of  vapor compression refrigeration cycle were takenin this paper:  the first case is thatthe vapor compression refrigeration cycle without internal heat exchanger andin  the second case the vapor compressionrefrigeration cycle with heat exchanger ; in these two cases, the temperatureat each point of  a vapor compressionrefrigeration cycle, the low and the high pressure ,the indoor temperature andthe outdoor temperature were measured at each time at compressor speed 1450 rpmand 2900 rpm for each blower speed 1, blower speed 2 and blower speed 3.Therefrigerant fluid was used in the vapor compression refrigeration cycle withoutIHE and with IHE is R134a..

  14. Transient performance of a thermal energy storage-based heat sink using a liquid metal as the phase change material

    International Nuclear Information System (INIS)

    Fan, Li-Wu; Wu, Yu-Yue; Xiao, Yu-Qi; Zeng, Yi; Zhang, Yi-Ling; Yu, Zi-Tao

    2016-01-01

    Highlights: • A liquid metal is adopted as the PCM in a thermal energy storage-based heat sink. • Transient performance of the heat sink is tested in comparison to an organic PCM. • The liquid metal has a similar volumetric latent heat of fusion to the organic PCM. • Outperformance of the liquid metal is found due to its higher thermal conductivity. • Liquid metals are preferred when the system weight is less important than volume. - Abstract: In this Technical Note, the use of a liquid metal, i.e., a low melting point Pb–Sn–In–Bi alloy, as the phase change material (PCM) in thermal energy storage-based heat sinks is tested in comparison to an organic PCM (1-octadecanol) having a similar melting point of ∼60 °C. The thermophysical properties of the two types of PCM are characterized, revealing that the liquid metal is much more conductive while both have nearly identical volumetric latent heat of fusion (∼215 MJ/m"3). By using at the same volume of 80 mL, i.e., the same energy storage capacity, the liquid metal is shown to outperform significantly over the organic PCM under the various heating powers up to 105.3 W/cm"2. During the heating period, the use of the liquid metal leads to a remarkable extension of the effective protection time to nearly twice longer as well as a reduction of the highest overheating temperature by up to 50 °C. The cool-down period can also be shortened significantly by taking advantage of the much higher thermal conductivity of the liquid metal. These findings suggest that liquid metals could serve as a promising PCM candidate for particular applications where the volume limit is very rigorous and the penalty in weight increment is acceptable.

  15. INTENSIFICATION OF HEAT TRANSFER FROM THE IC CHIP TO THE HEAT SINK THROUGH THE USE OF NANOFILM THERMOELECTRIC HEAT PUMP

    Directory of Open Access Journals (Sweden)

    T. A. Ismailov

    2014-01-01

    Full Text Available The article considers the to enhance the efficiency the thermoelectric heat pump by making the branches of semiconductor p- and n-type as nanofilms and creating conditions for the emergence of additional thermoeffect between the hot and cold junctions of dissimilar metals that will create a more efficient heat pumps with small dimensions.

  16. Cumulative effects of using pin fin heat sink and porous metal foam on thermal management of lithium-ion batteries

    International Nuclear Information System (INIS)

    Mohammadian, Shahabeddin K.; Zhang, Yuwen

    2017-01-01

    Highlights: • 3D transient thermal analysis of a pouch Li-ion cell has been carried out. • Using pin fin heat sink improves the temperature reduction at low pumping powers. • Using pin fin heat sink enhances the temperature uniformity at low air flow rates. • Porous aluminum foam insertion with pin fins improves temperature reduction. • Porous aluminum foam insertion with pin fins enhances temperature uniformity. - Abstract: Three-dimensional transient thermal analysis of an air-cooled module was carried out to investigate cumulative effects of using pin fin heat sink and porous metal foam on thermal management of a Li-ion (lithium-ion) battery pack. Five different cases were designed as Case 1: flow channel without any pin fin or porous metal foam insertion, Case 2: flow channel with aluminum pin fins, Case 3: flow channel with porous aluminum foam pin fins, Case 4: fully inserted flow channel with porous aluminum foam, and Case 5: fully inserted flow channel with porous aluminum foam and aluminum pin fins. The effects of porous aluminum insertions, pin fin types, air flow inlet temperature, and air flow inlet velocity on the temperature uniformity and maximum temperature inside the battery pack were systematically investigated. The results showed that using pin fin heat sink (Case 2) is appropriate only for low air flow velocities. In addition, the use of porous aluminum pin fins or embedding porous aluminum foam inside the air flow channel (Cases 3 and 4) are not beneficial for thermal management improvement. The combination of aluminum pin fins and porous aluminum foam insertion inside the air flow channel (Case 5) is a proper option that improves both temperature reduction and temperature uniformity inside the battery cell.

  17. Analysis of the one-dimensional transient compressible vapor flow in heat pipes

    Science.gov (United States)

    Jang, Jong H.; Faghri, Amir; Chang, Won S.

    1991-01-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds as well as high mass flow rates are successfully predicted.

  18. Experimental Results For Hydrocarbon Refrigerant Vaporization In Brazed Plate Heat Exchangers at High Pressure

    OpenAIRE

    Desideri, Adriano; Schmidt Ommen, Torben; Wronski, Jorrit; Quoilin, Sylvain; Lemort, Vincent; Haglind, Fredrik

    2016-01-01

    In this contribution, the experimental heat transfer coefficient  and the pressure drop measured during HFC refrigerants vaporization inside small brazed plate heat exchanger (PHE) at typical evaporation temperature for organic Rankine cycle systems for low thermal energy quality applications are presented. Scientific work focusing on the heat transfer in PHEs has been carried out since the late 19th century. More recent publications have been focusing on vaporization and condensation of ref...

  19. Fabrication of mock-up with Be armour tiles diffusion bonded to the CuCrZr heat sink

    International Nuclear Information System (INIS)

    Moreschi, L.F.; Pizzuto, A.; Alessandrini, I.; Agostini, M.; Visca, E.; Merola, M.

    2001-01-01

    The aim of this work is the manufacture of high heat flux mock-ups with Be armour tiles on a CuCrZr heat sink for fabricating the beryllium section of the divertor vertical target (DVT) in the ITER reactor. Diffusion bonding between the CuCrZr bar and the beryllium tiles was obtained by inserting an aluminium interlayer to accommodate surface irregularities as well as to provide a compliant layer for accommodating thermal mismatches during both manufacturing and operation and cycles

  20. A heat transfer correlation for transient vapor uptake of powdered adsorbent embedded onto the fins of heat exchangers

    KAUST Repository

    Li, Ang; Thu, Kyaw; Ismail, Azhar Bin; Ng, Kim Choon

    2015-01-01

    significant application potential in the adsorption desalination plants and chillers but seldom addressed in the literature. An experiment is designed to measure the heat transfer for several adsorption temperatures under a single vapor component environment

  1. Numerical Simulation of Vapor Bubble Growth and Heat Transfer in a Thin Liquid Film

    International Nuclear Information System (INIS)

    Yu-Jia, Tao; Xiu-Lan, Huai; Zhi-Gang, Li

    2009-01-01

    A mathematical model is developed to investigate the dynamics of vapor bubble growth in a thin liquid film, movement of the interface between two fluids and the surface heat transfer characteristics. The model takes into account the effects of phase change between the vapor and liquid, gravity, surface tension and viscosity. The details of the multiphase now and heat transfer are discussed for two cases: (1) when a water micro-droplet impacts a thin liquid film with a vapor bubble growing and (2) when the vapor bubble grows and merges with the vapor layer above the liquid film without the droplet impacting. The development trend of the interface between the vapor and liquid is coincident qualitatively with the available literature, mostly at the first stage. We also provide an important method to better understand the mechanism of nucleate spray cooling. (fundamental areas of phenomenology (including applications))

  2. A non-equilibrium model for soil heating and moisture transport during extreme surface heating: The soil (heat-moisture-vapor) HMV-Model Version

    Science.gov (United States)

    William Massman

    2015-01-01

    Increased use of prescribed fire by land managers and the increasing likelihood of wildfires due to climate change require an improved modeling capability of extreme heating of soils during fires. This issue is addressed here by developing and testing the soil (heat-moisture-vapor) HMVmodel, a 1-D (one-dimensional) non-equilibrium (liquid- vapor phase change)...

  3. 3-Dimensional numerical study of cooling performance of a heat sink with air-water flow through mini-channel

    Science.gov (United States)

    Majumder, Sambit; Majumder, Abhik; Bhaumik, Swapan

    2016-07-01

    The present microelectronics market demands devices with high power dissipation capabilities having enhanced cooling per unit area. The drive for miniaturizing the devices to even micro level dimensions is shooting up the applied heat flux on such devices, resulting in complexity in heat transfer and cooling management. In this paper, a method of CPU processor cooling is introduced where active and passive cooling techniques are incorporated simultaneously. A heat sink consisting of fins is designed, where water flows internally through the mini-channel fins and air flows externally. Three dimensional numerical simulations are performed for large set of Reynolds number in laminar region using finite volume method for both developing flows. The dimensions of mini-channel fins are varied for several aspect ratios such as 1, 1.33, 2 and 4. Constant temperature (T) boundary condition is applied at heat sink base. Channel fluid temperature, pressure drop are analyzed to obtain best cooling option in the present study. It has been observed that as the aspect ratio of the channel decreases Nusselt number decreases while pressure drop increases. However, Nusselt number increases with increase in Reynolds number.

  4. Vapor pressure, heat capacities, and phase transitions of tetrakis(tert-butoxy)hafnium

    Czech Academy of Sciences Publication Activity Database

    Fulem, Michal; Růžička, K.

    2011-01-01

    Roč. 311, Dec. (2011), s. 25-29 ISSN 0378-3812 Institutional research plan: CEZ:AV0Z10100521 Keywords : tetrakis(tert-butoxy)hafnium * MO precursor * vapor pressure * heat capacity * vaporization enthalpy * enthalpy of fusion Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.139, year: 2011

  5. Resistive heating enhanced soil vapor extraction of chlorinated solvents from trichloroethylene contaminated silty, low permeable soil

    NARCIS (Netherlands)

    Zutphen, M. van; Heron, G.; Enfield, C.G.; Christensen, T.H.

    1998-01-01

    A 2D-laboratory box experiment (12 x 56 x 116 cm) was conducted to simulate the enhancement of soil vapor extraction by the application of low frequency electrical heating Uoule heating) for the remediation of a low permeable, silty soil contaminated with trichloroethylene. Joule heating enlarged

  6. Evaluation of thermal-hydraulic performance of hydrocarbon refrigerants during flow boiling in a microchannels array heat sink

    International Nuclear Information System (INIS)

    Chávez, Cristian A.; Leão, Hugo L.S.L.; Ribatski, Gherhardt

    2017-01-01

    Highlights: • Evaluation of refrigerants R600a, R290 and R1270 during flow boiling in a microchannels array. • Comparison of data for hydrocarbons with previous data for R134a. • Parametric analysis of heat transfer coefficient, pressure drop, ONB and exergy behaviors. • Comparison of the experimental data and prediction methods from literature. • In general, refrigerant R290 presents the best performance. - Abstract: The present study concerns an experimental evaluation of the performance of hydrocarbon refrigerants during flow boiling in a microchannels array heat sink. The heat sink is composed of fifty channels with cross sectional areas of 123 × 494 μm"2 and length of 15 mm manufactured in a copper block. Heat transfer coefficient and pressure drop data were obtained for refrigerants R600a, R290 and R1270, mass velocities from 165 to 823 kg/m"2 s, heat fluxes up to 400 kW/m"2, liquid subcooling at the inlet of the test section of 5, 10 and 15 °C and saturation temperature of 25 °C. The data were compared with experimental results obtained in a previous study for R134a and predictions by methods from literature. In general, R290 presented the best performance, providing the highest average heat transfer coefficient and a pressure drop only slightly higher than R1270 that was the fluid presenting the lowest pressure drop. An exergy analysis also revealed the refrigerant R290 as the one presenting the best performance. However, R290 needed the highest excess of superheating to trigger the boiling process (ONB). The methods from literature evaluated in the present study poorly predicted the experimental data for two-phase pressure drop. On the other hand, the method of Kanizawa et al. (2016) was quite accurate in predicting the heat transfer results.

  7. A passive emergency heat sink for water cooled reactors with particular application to CANDU reg-sign reactors

    International Nuclear Information System (INIS)

    Spinks, N.J.

    1996-01-01

    Water in an overhead pool can serve as a general-purpose passive emergency heat sink for water-cooled reactors. It can be used for containment cooling, for emergency depressurization of the heat transport-system, or to receive any other emergency heat, such as that from the CANDU reg-sign moderator. The passive emergency water system provides in-containment depressurization of steam generators and no other provision is needed for supply of low-pressure emergency water to the steam generators. For containment cooling, the pool supplies water to the tube side of elevated tube banks inside containment. The elevation with respect to the reactor heat source maximizes heat transport, by natural convection, of hot containment gases. This effective heat transport combines with the large heat-transfer coefficients of tube banks, to reduce containment overpressure during accidents. Cooled air from the tube banks is directed past the break in the heat-transport system, to facilitate removal of hydrogen using passive catalytic recombiners

  8. Comparative Effectiveness of Different Phase Change Materials to Improve Cooling Performance of Heat Sinks for Electronic Devices

    Directory of Open Access Journals (Sweden)

    Ahmad Hasan

    2016-08-01

    Full Text Available This paper thermo-physically characterizes salt hydrate, paraffin wax and milk fat as phase change materials (PCMs. The three PCMs are compared in terms of improving heat sink (HS performance for cooling electronic packaging. An experimental study is carried out on commercially available finned HS with and without PCM under natural ventilation (NV and forced ventilation (FV at different heat loads (4 W to 10 W. The results indicate that integration of all of the PCMs into the HS improves its cooling performance; however, milk fat lags behind the other two PCMs in terms of cooling produced. A three-dimensional pressure-based conjugate heat transfer model has been developed and validated with experimental results. The model predicts the parametric influence of PCM melting range, thermal conductivity and density on HS thermal management performance. The HS cooling performance improves with increased density and conductivity while it deteriorates with the wider melting range of the PCMs.

  9. Use of an integrated containment and ultimate heat sink (UHS) response approach to evaluate nuclear power plant modifications

    International Nuclear Information System (INIS)

    Wetzel, M.C.; Vieira, A.T.; Patton, D.C.

    1994-01-01

    Detailed containment and Ultimate Heat Sink (UHS) performance evaluations often are required to support major plant modifications, such as power up-rates and steam generator replacements. These UHS and containment pressure and temperature response evaluations are interrelated. Not only is the containment heat load to the UHS a factor in these evaluations, but other heat loads, such as those from the spent fuel pool, may change as a result of the plant modification and impact containment or UHS response. Our experience is that if an integrated containment/UHS response model is developed prior to the feasibility evaluations for such plant modifications, significant savings in engineering hours can be achieved. This paper presents an overview of such a front-end engineering tool that has been developed and used to support engineering evaluations. 3 refs., 2 figs

  10. Efficient on-chip hotspot removal combined solution of thermoelectric cooler and mini-channel heat sink

    International Nuclear Information System (INIS)

    Hao, Xiaohong; Peng, Bei; Xie, Gongnan; Chen, Yi

    2016-01-01

    Highlights: • A combined solution of thermoelectric cooler (TEC) and mini-channel heat sink to remove the hotspot of the chip has been proposed. • The TEC's mathematical model is established to assess its work performance. • A comparative study on the proposed efficient On-Chip Hotspot Removal Combined Solution. - Abstract: Hotspot will significantly degrade the reliability and performance of the electronic equipment. The efficient removal of hotspot can make the temperature distribution uniform, and ensure the reliable operation of the electronic equipment. This study proposes a combined solution of thermoelectric cooler (TEC) and mini-channel heat sink to remove the hotspot of the chip in the electronic equipment. Firstly, The TEC's mathematical model is established to assess its work performance under different boundary conditions. Then, the hotspot removal capability of the TEC is discussed for different cooling conditions, which has shown that the combined equipment has better hotspot removal capability compared with others. Finally, A TEC is employed to investigate the hotspot removal capacity of the combined solution, and the results have indicated that it can effectively remove hotspot in the diameter of 0.5 mm, the power density of 600W/cm 2 when its working current is 3A and heat transfer thermal resistance is 0 K/W.

  11. Swimming pools as heat sinks for air conditioners: Model design and experimental validation for natural thermal behavior of the pool

    Energy Technology Data Exchange (ETDEWEB)

    Woolley, Jonathan; Harrington, Curtis; Modera, Mark [University of California Davis, Western Cooling Efficiency Center, 1450 Drew Avenue, Suite 100, Davis, CA 95618 (United States)

    2011-01-15

    Swimming pools as thermal sinks for air conditioners could save approximately 40% on peak cooling power and 30% of overall cooling energy, compared to standard residential air conditioning. Heat dissipation from pools in semi-arid climates with large diurnal temperature shifts is such that pool heating and space cooling may occur concurrently; in which case heat rejected from cooling equipment could directly displace pool heating energy, while also improving space cooling efficiency. The performance of such a system relies on the natural temperature regulation of swimming pools governed by evaporative and convective heat exchange with the air, radiative heat exchange with the sky, and conductive heat exchange with the ground. This paper describes and validates a model that uses meteorological data to accurately predict the hourly temperature of a swimming pool to within 1.1 C maximum error over the period of observation. A thorough review of literature guided our choice of the most appropriate set of equations to describe the natural mass and energy exchange between a swimming pool and the environment. Monitoring of a pool in Davis, CA, was used to confirm the resulting simulations. Comparison of predicted and observed pool temperature for all hours over a 56 day experimental period shows an R-squared relatedness of 0.967. (author)

  12. Temperature control at DBS electrodes using a heat sink: experimentally validated FEM model of DBS lead architecture

    Science.gov (United States)

    Elwassif, Maged M.; Datta, Abhishek; Rahman, Asif; Bikson, Marom

    2012-08-01

    There is a growing interest in the use of deep brain stimulation (DBS) for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. The extent of temperature increases around DBS electrodes during normal operation (joule heating and increased metabolic activity) or coupling with an external source (e.g. magnetic resonance imaging) remains poorly understood and methods to mitigate temperature increases are being actively investigated. We developed a heat transfer finite element method (FEM) simulation of DBS incorporating the realistic architecture of Medtronic 3389 leads. The temperature changes were analyzed considering different electrode configurations, stimulation protocols and tissue properties. The heat-transfer model results were then validated using micro-thermocouple measurements during DBS lead stimulation in a saline bath. FEM results indicate that lead design (materials and geometry) may have a central role in controlling temperature rise by conducting heat. We show how modifying lead design can effectively control temperature increases. The robustness of this heat-sink approach over complimentary heat-mitigation technologies follows from several features: (1) it is insensitive to the mechanisms of heating (e.g. nature of magnetic coupling); (2) it does not interfere with device efficacy; and (3) can be practically implemented in a broad range of implanted devices without modifying the normal device operations or the implant procedure.

  13. Estimation of the vaporization heat of organic liquids. Pt. 3

    International Nuclear Information System (INIS)

    Ducros, M.; Sannier, H.

    1982-01-01

    In our previous publications it has been shown that the method of Benson's group permits the estimation of the enthalpies of vaporization of organic compounds. In the present paper we have applied this method for unsaturated hydrocarbons, thus completing our previous work on acyclic alkenes. For the alkylbenzenes we have changed the values of the groups C-(Csub(b))(C)(H) 2 and C-(Csub(b))(C) 2 (H) previously determined. A more accurate value for the enthalpies of vaporization of the alkylbenzenes of higher molecular weight is obtained. (orig.)

  14. Impact of Improved Heat Sinking of an X-Ray Calorimeter Array on Crosstalk, Noise, and Background Events

    Science.gov (United States)

    Kilbourne, C. A.; Adams, J. S.; Brekosky, R. P.; Chervenak, J. A.; Chiao, M. P.; Kelley, R. L.; Kelly, D. P.; Porter, F. S.

    2011-01-01

    The x-ray calorimeter array of the Soft X-ray Spectrometer (SXS) of the Astro-H satellite will incorporate a silicon thermistor array produced during the development of the X-Ray Spectrometer (XRS) of the Suzaku satellite. On XRS, inadequate heat sinking of the array led to several non-ideal effects. The thermal crosstalk, while too small to be confused with x-ray signals, nonetheless contributed a noise term that could be seen as a degradation in energy resolution at high flux. When energy was deposited in the silicon frame around the active elements of the array, such as by a cosmic ray, the resulting pulse in the temperature of the frame resulted in coincident signal pulses on most of the pixels. In orbit, the resolution was found to depend on the particle background rate. In order to minimize these effects on SXS, heat-sinking gold was applied to areas on the front and back of the array die, which was thermally anchored to the gold of its fanout board via gold wire bonds. The thermal conductance from the silicon chip to the fanout board was improved over that of XRS by an order of magnitude. This change was sufficient for essentially eliminating frame events and allowing high-resolution to be attained at much higher counting rates. We will present the improved performance, the measured crosstalk, and the results of the thermal characterization of such arrays.

  15. MHD effects on heat transfer over stretching sheet embedded in porous medium with variable viscosity, viscous dissipation and heat source/sink

    Directory of Open Access Journals (Sweden)

    Hunegnaw Dessie

    2014-09-01

    Full Text Available In this analysis, MHD boundary layer flow and heat transfer of a fluid with variable viscosity through a porous medium towards a stretching sheet by taking in to the effects of viscous dissipation in presence of heat source/sink is considered. The symmetry groups admitted by the corresponding boundary value problem are obtained by using Lie’s scaling group of transformations. These transformations are used to convert the partial differential equations of the governing equations into self-similar non-linear ordinary differential equations. Numerical solutions of these equations are obtained by Runge-Kutta fourth order with shooting method. Numerical results obtained for different parameters such as viscosity variation parameter A, permeability parameter k1, heat source/sink parameter λ, magnetic field parameter M, Prandtl number Pr, and Eckert number Ec are drawn graphically and effects of different flow parameters on velocity and temperature profiles are discussed. The skin-friction coefficient -f″(0 and heat transfer coefficient −θ′(0 are presented in tables.

  16. Analysis of combined heat and mass transfer of water- Vapor in a ...

    African Journals Online (AJOL)

    In this paper, the combined heat and mass transfer of water-vapor into a cylindrical zeolite adsorber has been numerically simulated The twodimensional heat and mass transfer equations are numerically solved using gPROMS program - a general Process Modeling System {lJ program, inserting the proper initial and ...

  17. Analysis of combined heat and mass transfer of water-vapor in a ...

    African Journals Online (AJOL)

    Jn this paper, the combined heat and mass transfer of water-vapor into a cylindrical zeolite adsorber has been numerically simulated The twodimensional heat and mass transfer equations are numerically solved using gPROMS program - a general Process Modeling System [J] program, inserting the proper initial and ...

  18. Convective boiling in a parallel microchannel heat sink with a diverging cross-section design and artificial nucleation sites

    International Nuclear Information System (INIS)

    Lu, Chun Ting; Pan, Chin

    2009-01-01

    To develop a highly stable boiling heat transfer microchannel heat sink, the three types of diverging microchannels, namely Type-1, Type-2 and Type-3, were designed to explore experimentally the effect of different distribution of artificial nucleation sites on enhancing boiling heat transfer in 10 parallel diverging microchannels with a mean hydraulic diameter of 120 μm. The Type-1 system is with no cavities, Type-2 is with cavities distributed uniformly along the downstream half of the channel, while Type-3 is with cavities distributed uniformly along the whole channel. The artificial nucleation sites are laser-etched pits on the channel bottom wall with a mouth diameter of about 20-22 μm based on the heterogeneous nucleation theory. The results of the present study reveal the presence of the artificial nucleation sites for flow boiling in parallel diverging microchannel significantly reduces the wall superheat and enhances the boiling heat transfer performance. Additionally, the Type-3 design demonstrates the best boiling heat transfer performance. (author)

  19. Vapor Compression and Thermoelectric Heat Pumps for a Cascade Distillation Subsystem: Design and Experiment

    Science.gov (United States)

    Erickson, Lisa R.; Ungar, Eugene K.

    2012-01-01

    Humans on a spacecraft require significant amounts of water for drinking, food, hydration, and hygiene. Maximizing the reuse of wastewater while minimizing the use of consumables is critical for long duration space exploration. One of the more promising consumable-free methods of reclaiming wastewater is the distillation/condensation process used in the Cascade Distillation Subsystem (CDS). The CDS heats wastewater to the point of vaporization then condenses and cools the resulting water vapor. The CDS wastewater flow requires heating for evaporation and the product water flow requires cooling for condensation. Performing the heating and cooling processes separately would require two separate units, each of which would demand large amounts of electrical power. Mass, volume, and power efficiencies can be obtained by heating the wastewater and cooling the condensate in a single heat pump unit. The present work describes and compares two competing heat pump methodologies that meet the needs of the CDS: 1) a series of mini compressor vapor compression cycles and 2) a thermoelectric heat exchanger. In the paper, the CDS system level requirements are outlined, the designs of the two heat pumps are described in detail, and the results of heat pump analysis and performance tests are provided. The mass, volume, and power requirement for each heat pump option is compared and the advantages and disadvantages of each system are listed.

  20. Detailed kinetic and heat transport model for the hydrolysis of lignocellulose by anhydrous hydrogen fluoride vapor

    Energy Technology Data Exchange (ETDEWEB)

    Rorrer, G.L.; Mohring, W.R.; Lamport, D.T.A.; Hawley, M.C.

    1988-01-01

    Anhydrous Hydrogen Fluoride (HF) vapor at ambient conditions efficiently and rapidly hydrolyzed lignocellulose to glucose and lignin. The unsteady-state reaction of HF vapor with a single lignocellulose chip was mathematically modeled under conditions where external and internal mass-transfer resistances were minimized. The model incorporated physical adsorption of HF vapor onto the lignocellulosic matrix and solvolysis of cellulose to glucosyl fluoride by adsorbed HF into the differential material and energy balance expressions. Model predictions for the temperature distribution and global glucose yield in the HF-reacting lignocellulose chip as a function of reaction time and HF vapor stream temperature agreed reasonably with the complimentary experimental data. The model correctly predicted that even when mass-transfer resistances for the reaction of HF vapor with a single lignocellulose chip are minimized, external and internal heat-transfer resistances are still significant.

  1. Radiation Effects in Dual Heat Sinks for Cooling of Concentrated Photovoltaics

    Science.gov (United States)

    2016-06-01

    heat transfer out of a module is by radiation [7]. 1. Previous work Previous work in field has been focused on improving convection transfer via...LEFT BLANK 35 VII. CONCLUSION AND RECOMMENDATION A. CONCLUSION This thesis examined means to improve heat transfer out of a CPV module by... heat transfer by radiation to lower the operating temperature of the CPV system, and therefore increase the power output. Experimental and

  2. Unsteady MHD flow of a dusty nanofluid past a vertical stretching surface with non-uniform heat source/sink

    Directory of Open Access Journals (Sweden)

    C. Sulochana

    2016-02-01

    Full Text Available We analyzed the momentum and heat transfer characteristics of unsteady MHD flow of a dusty nanofluid over a vertical stretching surface in presence of volume fraction of dust and nano particles with non uniform heat source/sink. We considered two types of nanofluids namely Ag-water and Cu-water embedded with conducting dust particles. The governing equations are transformed in to nonlinear ordinary differential equations by using similarity transformation and solved numerically using Shooting technique. The effects of non-dimensional governing parameters on velocity and temperature profiles for fluid and dust phases are discussed and presented through graphs. Also, the skin friction coefficient and Nusselt number are discussed and presented for two dusty nanofluids separately in tabular form. Results indicate that an increase in the volume fraction of dust particles enhances the heat transfer in Cu-water nanofluid compared with Ag-water nanofluid and a raise in the volume fraction of nano particles shows uniform heat transfer in both Cu-water and Ag-water nanofluids.

  3. An analysis of the vapor flow and the heat conduction through the liquid-wick and pipe wall in a heat pipe with single or multiple heat sources

    Science.gov (United States)

    Chen, Ming-Ming; Faghri, Amir

    1990-01-01

    A numerical analysis is presented for the overall performance of heat pipes with single or multiple heat sources. The analysis includes the heat conduction in the wall and liquid-wick regions as well as the compressibility effect of the vapor inside the heat pipe. The two-dimensional elliptic governing equations in conjunction with the thermodynamic equilibrium relation and appropriate boundary conditions are solved numerically. The solutions are in agreement with existing experimental data for the vapor and wall temperatures at both low and high operating temperatures.

  4. Heat Sink Effect on Tumor Ablation Characteristics as Observed in Monopolar Radiofrequency, Bipolar Radiofrequency, and Microwave, Using Ex Vivo Calf Liver Model

    Science.gov (United States)

    Pillai, Krishna; Akhter, Javid; Chua, Terence C.; Shehata, Mena; Alzahrani, Nayef; Al-Alem, Issan; Morris, David L.

    2015-01-01

    Abstract Thermal ablation of liver tumors near large blood vessels is affected by the cooling effect of blood flow, leading to incomplete ablation. Hence, we conducted a comparative investigation of heat sink effect in monopolar (MP) and bipolar (BP) radiofrequency ablation (RFA), and microwave (MW) ablation devices. With a perfused calf liver, the ablative performances (volume, mass, density, dimensions), with and without heat sink, were measured. Heat sink was present when the ablative tip of the probes were 8.0 mm close to a major hepatic vein and absent when >30 mm away. Temperatures (T1 and T2) on either side of the hepatic vein near the tip of the probes, heating probe temperature (T3), outlet perfusate temperature (T4), and ablation time were monitored. With or without heat sink, BP radiofrequency ablated a larger volume and mass, compared with MP RFA or MW ablation, with latter device producing the highest density of tissue ablated. MW ablation produced an ellipsoidal shape while radiofrequency devices produced spheres. Percentage heat sink effect in Bipolar radiofrequency : Mono-polar radiofrequency : Microwave was (Volume) 33:41:22; (mass) 23:56:34; (density) 9.0:26:18; and (relative elipscity) 5.8:12.9:1.3, indicating that BP and MW devices were less affected. Percentage heat sink effect on time (minutes) to reach maximum temperature (W) = 13.28:9.2:29.8; time at maximum temperature (X) is 87:66:16.66; temperature difference (Y) between the thermal probes (T3) and the temperature (T1 + T2)/2 on either side of the hepatic vessel was 100:87:20; and temperature difference between the (T1 + T2)/2 and temperature of outlet circulating solution (T4), Z was 20.33:30.23:37.5. MW and BP radiofrequencies were less affected by heat sink while MP RFA was the most affected. With a single ablation, BP radiofrequency ablated a larger volume and mass regardless of heat sink. PMID:25738477

  5. Amelioration of irradiation injury to Florida grapefruit by pretreatment with vapor heat or fungicides

    International Nuclear Information System (INIS)

    Miller, W.R.; McDonald, R.E.

    1998-01-01

    Grapefruit shipped to certain markets must be certified free of Caribbean fruit fly (Anastrepha suspensa Loew) (CFF) infestation. Low-dose irradiation is effective for the control of CFF by sterilization. This treatment is expected to be approved for industry usage in the near future. 'Marsh' grapefruit (Citrus paradisi Macf.) was treated with vapor heat (2 hours at 38 degrees C), and fungicidal treatments of thiabendazole (TBZ) (4 gm.L-1) and TBZ (1 gm.L-1) plus imazalil (1 gm.L-1) prior to irradiation at 0.5 or 1.0 kGy. Vapor heat reduced the severity and incidence of peel injury by approximately 50% without adversely affecting other quality attributes. The fungicide did not reduce peel injury. The use of vapor heat before low-dose irradiation quarantine treatment of grapefruit may ameliorate or eliminate peel injury caused by irradiation

  6. Thermal Fluid Analysis of the Heat Sink and Chip Carrier Assembly for a US Army Research Laboratory Liquid-Fueled Thermophotovoltaic Power Source Demonstrator

    Science.gov (United States)

    2016-09-01

    temperatures above 500 °C.1 Figure 1 describes the primary components of a TPV system : a heat source, an emitter, and a photovoltaic converter. The heat...carrier surface not covered by the photovoltaic cell. 4. Mesh The mesh was set to level 3 with the minimum gap size manually set to 0.01 inch. A...heat sink to control the temperature of the photovoltaic cell while exposed to radiation from the emitter. 15. SUBJECT TERMS TPV

  7. The mechanical design of a vapor compressor for a heat pump to be used in space

    Science.gov (United States)

    Berner, F.; Oesch, H.; Goetz, K.; Savage, C. J.

    1982-01-01

    A heat pump developed for use in Spacelab as a stand-alone refrigeration unit as well as within a fluid loop system is discussed. It will provide an active thermal control for payloads. Specifications for the heat pump were established: (1) heat removal rates at the source; (2) heat source temperatures from room temperature; (3) heat-sink fluid temperatures at condenser inlet; and (4) minimum power consumption. A reversed Carnot cycle heat pump using Freon 12 as working fluid incorporating a one-cylinder reciprocating compressor was selected. The maximum crankshaft speed was fixed relatively high at 100 rpm. The specified cooling rates then made it necessary to select a cylinder volume of 10 cu cm, which was obtained with a bore of 40 mm and a stroke of 8 mm.

  8. Safety assessment for the ultimate heat sink (UHS) system with non-injection concept in nuclear power plants (NPPs)

    International Nuclear Information System (INIS)

    Kim, Yun Il; Woo, Tae Ho

    2017-01-01

    Following the Fukushima accident, it is proposed to find a better safety system, which has a pool-type cooling system without coolant injections. Since the conventional piping-based injection systems have failed in treating the three major severe accidents, the artificial pool could be constructed to cover the failed reactor core systems in which the pool-like structure is constructed. Regarding this study, there were some previous studies about the ultimate heat sink (UHS). In this study, the system dynamics (SD) modeling is performed in the case of Fukushima Unit 1 accident. The basic events are obtained by the Boolean values as 0 and 1. The quantifications are obtained by the SD algorithm incorporated with the Vensim software. In the simulations work, there is a plateau region between the 25th and 45th years in the interested period. The nonlinear algorithm is applied for the UHS analysis which was not installed for the commercial use yet. (author)

  9. Optimization of Dimples in Microchannel Heat Sink with Impinging Jets — Part A: Mathematical Model and the Influence of Dimple Radius

    Science.gov (United States)

    Ming, Tingzhen; Cai, Cunjin; Yang, Wei; Shen, Wenqing; Gan, Ting

    2018-06-01

    With increasing heat fluxes caused by electronic components, dimples have attracted wide attention by researchers and have been applied to microchannel heat sink in modern advanced cooling technologies. In this work, the combination of dimples, impinging jets and microchannel heat sink was proposed to improve the heat transfer performance on a cooling surface with a constant heat flux 500 W/cm2. A mathematical model was advanced for numerically analyzing the fluid flow and heat transfer characteristics of a microchannel heat sink with impinging jets and dimples (MHSIJD), and the velocity distribution, pressure drop, and thermal performance of MHSIJD were analyzed by varying the radii of dimples. The results showed that the combination of dimples and MHSIJ can achieve excellent heat transfer performance; for the MHSIJD model in this work, the maximum and average temperatures can be as low as 320 K and 305 K, respectively when mass flow rate is 30 g/s; when dimple radius is larger than 0.195 mm, both the heat transfer coefficient and the overall performance h/ΔP of MHSIJD are higher than those of MHSIJ.

  10. Thermosyphon analysis of a repository: A simplified model for vapor flow and heat transfer

    International Nuclear Information System (INIS)

    Manteufel, R.D.; Powell, M.W.

    1994-01-01

    A simplified model is developed for thermally-driven buoyant gas flow in an unsaturated repository such as that anticipated at Yucca Mountain. Based on a simplified thermosyphon model, the strength of buoyant gas flow is related to key thermal-hydraulic parameters (e.g., bulk permeability and maximum repository temperature). The effects of buoyant gas flow on vapor flow and heat transport near the repository horizon are assessed, namely: (i) the strength of buoyant flow through the repository, (ii) the effect of buoyant flow on vapor transfer, and (iii) the effect of buoyant flow on heat transfer

  11. Dual-pressure vaporization Kalina cycle for cascade reclaiming heat resource for power generation

    International Nuclear Information System (INIS)

    Guo, Zhanwei; Zhang, Zhi; Chen, Yaping; Wu, Jiafeng; Dong, Cong

    2015-01-01

    Graphical abstract: Schematic of the dual-pressure evaporation Kalina cycle. - Highlights: • Dual-pressure vaporization Kalina cycle for high-grade heat resource is investigated. • It is designed with 2nd evaporation branch for cascade utilization of heat resource. • Work and basic concentrations, dew point temperature of evaporation are optimized. • Power recovery efficiency of proposed cycle is 17% higher than that of Kalina cycle. • Dual-p vaporization Kalina cycle fits reclaiming heat resource higher than 350 °C. - Abstract: To further improve the cycle efficiency with the heat transfer curves between higher than 350 °C heat resource and the evaporating working medium of the Kalina cycle and to reduce the exhaust temperature of heat resource, the dual-pressure vaporization Kalina cycle for cascade utilization of high-to-mid grade heat resource is proposed. The optimization was conducted for parameters in this modified Kalina cycle such as concentrations of work solution and basic solution, evaporation dew point temperature. Under the conditions of inlet temperatures of heat resource and cooling water of respectively 400 °C and 25 °C and the constraints of proper heat transfer pinch point temperature differences, the maximum evaporation pressure not exceeds 20 MPa, the vapour quality at the turbine outlet is greater than 0.85 and the exhaust temperature of heat resource is not lower than 90 °C, the optimum parameters are obtained that the work and basic concentrations are 0.45 and 0.272 respectively, the dew point temperature of evaporation is 300 °C, and the corresponding power recovery efficiency of the dual-pressure vaporization Kalina cycle reaches 27%, which is 17% higher than that of the Kalina cycle with optimum parameters.

  12. Thermal characteristics of high-temperature R718 heat pumps with turbo compressor thermal vapor recompression

    International Nuclear Information System (INIS)

    Šarevski, Milan N.; Šarevski, Vasko N.

    2017-01-01

    Highlights: • High pressure ratio, high speed, transonic R718 centrifugal compressors. • High efficient industrial evaporators/concentrators with turbo thermal vapor recompression. • Utilization of waste heat from industrial thermal and processing systems. • R718 is an ideal refrigerant for the novel high-temperature industrial heat pumps. • Application of single-stage R718 centrifugal compressors. - Abstract: Characteristics of R718 centrifugal compressors are analyzed and range of their applications in industrial high-temperature heat pumps, district heating systems and geothermal green house heating systems are estimated. Implementation of turbo compressor thermal vapor recompression in industrial evaporating/concentrating plants for waste heat utilization results in a high energy efficiency and in other technical, economical and environmental benefits. A novel concept of turbo compression R718 heat pumps is proposed and an assessment of their thermal characteristics is presented for utilization of waste heat from industrial thermal plants and systems (boilers, furnaces, various technological and metallurgical cooling processes, etc.), and for applications in district heating and geothermal green house heating systems. R718 is an ideal refrigerant for the novel high-temperature turbo compression industrial heat pumps. Direct evaporation and condensation are advantages of the proposed system which lead to higher COP, and to simplification of the plant and lower cost.

  13. The response of leaves to heat stress in tomato plants with source-sink modulated by growth regulators

    Directory of Open Access Journals (Sweden)

    Zofia Starck

    2014-01-01

    Full Text Available The response to heat stress was investigated in heat-sensitive, Roma V. F. and heat-tolerant, Robin, cultivars whose fruit growth was stimulated by NOA + GA3 , or NOA + GA3 + zeatin. The treated plants were compared with untreated control plant. In each of these series half of the plants were subjected to one or three cycles of heat stress. A single cycle of 38°/25°C day and night did not significantly affect either the respiration rate or chlorophyll content. In PGR-untreated intact cv. Roma, heat stress inhibited starch formation during the day and strongly depressed night export from the blades. High temperature depressed the night transport less in plants having a higher sink demand of fruits in plant treated with PGR. In this case the amount of substances available for export was much higher and both sugars and starch were more intensively remobilized at night. In intact Robin plants, PGR and heat stress much less affected sugar and starch content. High temperature diminished noctural starch remobilization only in the NOA + GA3 series. Leaf disc growth was evaluated as a measure of response to heat stress after elimination of the direct effect of fruit demands. One cycle of high temperature did not negatively affect the growth of leaf discs; it even caused thermal low growth activation in both cultivars. Three cycles of heat stress depressed leaf disc growth after short-term stimulation, especially in Roma plants. Immediately after 3-day heat stress, there was no response of discs to GA3 or zeatin added to the solution on which the discs were floated. Leaf disc growth of Robin control and NOA + GA3 series was very similar in plants from optimal temperature conditions. High temperature inhibited only disc growth of the NOA + GA3 series owing to depression of starch break-down, diminishing the pool of sugars. In contrast, leaf discs of Roma cv. excided from NOA + GA3 treated plants from the optimal temperature series, grew more intensively

  14. Macroscopic modeling for heat and water vapor transfer in dry snow by homogenization.

    Science.gov (United States)

    Calonne, Neige; Geindreau, Christian; Flin, Frédéric

    2014-11-26

    Dry snow metamorphism, involved in several topics related to cryospheric sciences, is mainly linked to heat and water vapor transfers through snow including sublimation and deposition at the ice-pore interface. In this paper, the macroscopic equivalent modeling of heat and water vapor transfers through a snow layer was derived from the physics at the pore scale using the homogenization of multiple scale expansions. The microscopic phenomena under consideration are heat conduction, vapor diffusion, sublimation, and deposition. The obtained macroscopic equivalent model is described by two coupled transient diffusion equations including a source term arising from phase change at the pore scale. By dimensional analysis, it was shown that the influence of such source terms on the overall transfers can generally not be neglected, except typically under small temperature gradients. The precision and the robustness of the proposed macroscopic modeling were illustrated through 2D numerical simulations. Finally, the effective vapor diffusion tensor arising in the macroscopic modeling was computed on 3D images of snow. The self-consistent formula offers a good estimate of the effective diffusion coefficient with respect to the snow density, within an average relative error of 10%. Our results confirm recent work that the effective vapor diffusion is not enhanced in snow.

  15. Geothermal as a heat sink application for raising air conditioning efficency

    Science.gov (United States)

    Ibrahim, Hesham Safwat Osman Mohamed

    2016-04-01

    Objective: Geothermal applications in heating, ventilation, air-conditioning is a US technology for more than 30 years old ,which saves more than 30% average energy cost than the traditional air-conditioning systems systems. Applying this technology in Middle East and African countries would be very feasible specially in Egypt specially as it suffers Electric crisis --The temperature of the condensers and the heat rejecting equipment is much higher than the Egyptian land at different depth which is a great advantages, and must be measured, recorded, and studied accurately -The Far goal of the proposal is to construct from soil analysis a temperature gradient map for Egypt and , African countries on different depth till 100 m which is still unclear nowadays and must be measured and recorded in databases through researches - The main model of the research is to study the heat transfer gradient through the ground earth borehole,grout,high density polyethylene pipes , and water inlet temperature which affect the electric efficiency of the ground source heat pump air conditioning unit Impact on the Region: Such research result will contribute widely in Energy saving sector specially the air conditioning sector in Egypt and the African countries which consumes more than 30% of the electric consumption of the total consumption . and encouraging Green systems such Geothermal to be applied

  16. Finalize field testing of cold climate heat pump (CCHP) based on tandem vapor injection compressors

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Bo [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Baxter, Van D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Abdelaziz, Omar [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Rice, C. Keith [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-03-01

    This report describes the system diagram and control algorithm of a prototype air-source cold climate heat pump (CCHP) using tandem vapor injection (VI) compressors. The prototype was installed in Fairbanks, Alaska and underwent field testing starting in 09/2016. The field testing results of the past six months, including compressor run time fractions, measured COPs and heating capacities, etc., are presented as a function of the ambient temperature. Two lessons learned are also reported.

  17. Low flow velocity, fine-screen heat exchangers and vapor-cooled cryogenic current leads

    International Nuclear Information System (INIS)

    Steyert, W.A.; Stone, N.J.

    1978-09-01

    The design, construction, and testing of three compact, low temperature heat exchangers are reported. A method is given for the construction of a small (approximately = 20-cm 3 volume) exchanger that can handle 6 g/s helium flow with low pressure drops (ΔP/P = 10 percent) and adequate heat transfer (N/sub tu/ = 3). The use of screen for simple, vapor-cooled current leads into cryogenic systems is also discussed

  18. A heat transfer correlation for transient vapor uptake of powdered adsorbent embedded onto the fins of heat exchangers

    KAUST Repository

    Li, Ang

    2015-10-23

    We present a detailed study on the transient heat transfer phenomena of powdered-adsorbent mixed with an organic binder for adherence to the fins of a heat exchangers. The transient performance of such an adsorbent-heat exchanger configuration has significant application potential in the adsorption desalination plants and chillers but seldom addressed in the literature. An experiment is designed to measure the heat transfer for several adsorption temperatures under a single vapor component environment. Analysis on the experimental data indicates that the adsorbent-adsorbate interactions contribute about 75% of the total thermal resistances throughout the uptake processes. It is found that the initial local adsorption heat transfer coefficients are significantly higher than the average values due primarily to the thermal mass effect of the adsorbent–adsorbate interaction layers. From these experiments, a correlation for the transient local adsorption heat transfer coefficients is presented at the sub-atmospheric pressures and assorted application temperatures.

  19. What Is the Boiling Point and Heat of Vaporization of Sulfuric Acid?

    Science.gov (United States)

    Myers, R. Thomas

    1983-01-01

    Discusses the values presented in various handbooks for the boiling point and heat of vaporization of sulfuric acid, noting discrepencies. Analyzes various approaches to data presentation, discussing the data on sulfuric acid in light of the Trouton constant. Points out the need for a more critical use of tables. (JM)

  20. Waste Tyres as Heat Sink to Reduce the Driveway Surface Temperatures in Malaysia

    OpenAIRE

    Aniza Abdul Aziz; Sreenivasaiah Purushothama Rao; Elias Salleh

    2013-01-01

    The development of roads and driveways are on the rise as automobiles are now a necessity to all. This excessive development with its requirements increased the urban heat temperature and the generation of waste tyres. Waste tyre management has therefore been taken seriously by developed countries and since the European directive to ban used tyre products and whole tire disposal from landfill in 2003 and 2006 respectively, many researchers have looked for alternative ways to use the waste tyr...

  1. A Thermal Management System Using Ammonium Carbamate as an Endothermic Heat Sink (POSTPRINT)

    Science.gov (United States)

    2017-04-01

    Condenser Evaporator TES Separator XV HGBV Refrigerant Loop (R134a) Transfer Loop (Water) Coolant Supply TES Recharge Loop (Water) Inline...environment or thermal capacitances: _Wcomp qHEX;Tx qEvap;Tx ð11Þ where qEvap;Tx is the heat transferred into the evaporator from the coolant loop (or TES... transfer capability) of a VCS is a complex function of the operating conditions for each system component ( evaporator , compressor, condenser , and

  2. Uncertainty in unprotected loss-of-heat-sink, loss-of-flow, and transient-overpower accidents.

    Energy Technology Data Exchange (ETDEWEB)

    Morris, E. E.; Nuclear Engineering Division

    2007-10-08

    The sensitivities of various output parameters to selected input parameters in unprotected combined loss of heat-sink and loss-of-flow (ULOHS), loss-of-flow (ULOF), and transient-overpower (UTOP) accidents are explored in this report. This line of investigation was suggested by R. A. Wigeland. For an initial examination of potential sensitivities, the MATWS computer program has been compiled as part of a dynamic link library (DLL) so that uncertain input parameters can be sampled from their probability distributions using the GoldSim simulation software. The MATWS program combines the point-kinetics module from the SAS4A/SASSYS computer code with a simplified representation of the reactor heat removal system. Coupling with the GoldSim software by means of a DLL not only provides a convenient mechanism for sampling the stochastic input parameters but also allows the use of various tools that are available in GoldSim for analyzing the dependence of various MATWS outputs on these parameters. Should a decision be made to continue this investigation, the techniques used to couple MATWS and GoldSim could also be applied to couple the SAS4A/SASSYS computer code with GoldSim. The work described here illustrates the type of results that can be obtained from the stochastic analysis.

  3. A study on emergency response guideline during the loss of steam generator secondary heat sink in pressurizer water reactor

    International Nuclear Information System (INIS)

    Yoon, D. J.; Lee, J. Y.; Song, D. S.

    1999-01-01

    A loss of secondary heat sink can occur as a result of several different initiating events, which are a loss of main feedwater during power operation, a loss of off-site power, or any other scenario for which main feedwater is isolated or lost. At this point the opening and closing of the PORV or safety valves will result in a loss of RCS inventory similar in nature to a small break loss of coolant accident. If operator action is not taken, the pressurizer PORV or safety valves will continue to cycle open and closed at the valve setpoint pressure removing RCS inventory and a limited amount of core decay heat until eventually enough inventory will be lost to result in core uncovery. We conclude that a requirement to successfully initiate bleed and feed on steam generator dryout, without any significant core uncovery expected to occur, is that the PORV flow to power ratio must exceed 140 (lbm/hr)/Mwt. For all plants whose PORV capacity is less than 140 (lbm/hr)/Mwt, since symptoms of SG dryout cannot be used to initiate bleed and feed, increasing RCS pressure and temperature or pressure greater than 2335 psig cannot be used. The only alternative symptom available is SG narrow range level. Since Kori 1,2,3 and 4' PORV capacity is more than the criteria, the bleed and feed operation can be initiated at steam generator dryout

  4. Uncertainty in unprotected loss-of-heat-sink, loss-of-flow, and transient-overpower accidents

    International Nuclear Information System (INIS)

    Morris, E.E.

    2007-01-01

    The sensitivities of various output parameters to selected input parameters in unprotected combined loss of heat-sink and loss-of-flow (ULOHS), loss-of-flow (ULOF), and transient-overpower (UTOP) accidents are explored in this report. This line of investigation was suggested by R. A. Wigeland. For an initial examination of potential sensitivities, the MATWS computer program has been compiled as part of a dynamic link library (DLL) so that uncertain input parameters can be sampled from their probability distributions using the GoldSim simulation software. The MATWS program combines the point-kinetics module from the SAS4A/SASSYS computer code with a simplified representation of the reactor heat removal system. Coupling with the GoldSim software by means of a DLL not only provides a convenient mechanism for sampling the stochastic input parameters but also allows the use of various tools that are available in GoldSim for analyzing the dependence of various MATWS outputs on these parameters. Should a decision be made to continue this investigation, the techniques used to couple MATWS and GoldSim could also be applied to couple the SAS4A/SASSYS computer code with GoldSim. The work described here illustrates the type of results that can be obtained from the stochastic analysis

  5. Effect of Using Extra Fins on the Pin Fin Classic Geometry for Enhancement Heat Sink Performance using EGM Method

    Directory of Open Access Journals (Sweden)

    Kadhum Audaa Jehhef

    2018-04-01

    Full Text Available In the present study, the effect of new cross-section fin geometries on overall thermal/fluid performance had been investigated. The cross-section included the base original geometry of (triangular, square, circular, and elliptical pin fins by adding exterior extra fins along the sides of the origin fins. The present extra fins include rectangular extra fin of 2 mm (height and 4 mm (width and triangular extra fin of 2 mm (base 4 mm (height. The use of entropy generation minimization method (EGM allows the combined effect of thermal resistance and pressure drop to be assessed through the simultaneous interaction with the heat sink. A general dimensionless expression for the entropy generation rate is obtained by considering a control volume around the pin fin including a base plate and applying the conservations equations of mass and energy with the entropy balance. The dimensionless numbers used includes the aspect ratio (ε, Reynolds number (Re, Nusselt number (Nu, and the drag coefficients (CD. Fourteen different cross-section fin geometries are examined for the heat transfer, fluid friction, and the minimum entropy generation rate. The results showed that the Nusselt number increases with increasing the Reynolds number for all employed models. The ellipse models (ET and ER-models give the highest value in the Nusselt number as compared with the classical pin fins. The fin of the square geometry with four rectangular extra fins (SR-models gives an agreement in Nusselt number as compared with the previous study.

  6. Feasibility study of a dedicate nuclear desalination system: Low-pressure inherent heat sink nuclear desalination plant (LIND)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ho Sik; No, Hee Cheon; Jo, Yu Gwan; Wivisono, Andhika Feri; Park, Byung Ha; Choi, Jin Young; Lee, Jeong Ik; Jeong, Yong Hoon; Cho, Nam Zin [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2015-04-15

    In this paper, we suggest the conceptual design of a water-cooled reactor system for a low-pressure inherent heat sink nuclear desalination plant (LIND) that applies the safety-related design concepts of high temperature gas-cooled reactors to a water-cooled reactor for inherent and passive safety features. Through a scoping analysis, we found that the current LIND design satisfied several essential thermal-hydraulic and neutronic design requirements. In a thermal-hydraulic analysis using an analytical method based on the Wooton-Epstein correlation, we checked the possibility of safely removing decay heat through the steel containment even if all the active safety systems failed. In a neutronic analysis using the Monte Carlo N-particle transport code, we estimated a cycle length of approximately 6 years under 200 MW{sub th} and 4.5% enrichment. The very long cycle length and simple safety features minimize the burdens from the operation, maintenance, and spent-fuel management, with a positive impact on the economic feasibility. Finally, because a nuclear reactor should not be directly coupled to a desalination system to prevent the leakage of radioactive material into the desalinated water, three types of intermediate systems were studied: a steam producing system, a hot water system, and an organic Rankine cycle system.

  7. Feasibility study of a dedicated nuclear desalination system: Low-pressure Inherent heat sink Nuclear Desalination plant (LIND

    Directory of Open Access Journals (Sweden)

    Ho Sik Kim

    2015-04-01

    Full Text Available In this paper, we suggest the conceptual design of a water-cooled reactor system for a low-pressure inherent heat sink nuclear desalination plant (LIND that applies the safety-related design concepts of high temperature gas-cooled reactors to a water-cooled reactor for inherent and passive safety features. Through a scoping analysis, we found that the current LIND design satisfied several essential thermal–hydraulic and neutronic design requirements. In a thermal–hydraulic analysis using an analytical method based on the Wooton–Epstein correlation, we checked the possibility of safely removing decay heat through the steel containment even if all the active safety systems failed. In a neutronic analysis using the Monte Carlo N-particle transport code, we estimated a cycle length of approximately 6 years under 200 MWth and 4.5% enrichment. The very long cycle length and simple safety features minimize the burdens from the operation, maintenance, and spent-fuel management, with a positive impact on the economic feasibility. Finally, because a nuclear reactor should not be directly coupled to a desalination system to prevent the leakage of radioactive material into the desalinated water, three types of intermediate systems were studied: a steam producing system, a hot water system, and an organic Rankine cycle system.

  8. Effects on heat transfer of multiphase magnetic fluid due to circular magnetic field over a stretching surface with heat source/sink and thermal radiation

    Directory of Open Access Journals (Sweden)

    A. Zeeshan

    Full Text Available The purpose of the current article is to explore the boundary layer heat transport flow of multiphase magnetic fluid with solid impurities suspended homogeneously past a stretching sheet under the impact of circular magnetic field. Thermal radiation effects are also taken in account. The equations describing the flow of dust particles in fluid along with point dipole are modelled by employing conservation laws of mass, momentum and energy, which are then converted into non-linear coupled differential equations by mean of similarity approach. The transformed ODE’s are tackled numerically with the help of efficient Runga-Kutta method. The influence of ferromagnetic interaction parameter, viscous dissipation, fluid-particle interaction parameter, Eckert number, Prandtl number, thermal radiation parameter and number of dust particles, heat production or absorption parameter with the two thermal process namely, prescribed heat flux (PHF or prescribed surface temperature (PST are observed on temperature and velocity profiles. The value of skin-friction coefficient and Nusselt number are calculated for numerous physical parameters. Present results are correlated with available for a limited case and an excellent agreement is found. Keywords: Ferromagnetic interaction parameter, Dusty magnetic fluid, stretching sheet, Magnetic dipole, Heat source/sink, Thermal radiation

  9. Reducing cell-to-cell spacing for large-format lithium ion battery modules with aluminum or PCM heat sinks under failure conditions

    International Nuclear Information System (INIS)

    Coleman, Brittany; Ostanek, Jason; Heinzel, John

    2016-01-01

    Highlights: • Finite element analysis to evaluate heat sinks for large format li-ion batteries. • Solid metal heat sink and composite heat sink (metal filler and wax). • Transient simulations show response from rest to steady-state with normal load. • Transient simulations of two different failure modes were considered. • Significance of spacing, material properties, interface quality, and phase change. - Abstract: Thermal management is critical for large-scale, shipboard energy storage systems utilizing lithium-ion batteries. In recent years, there has been growing research in thermal management of lithium-ion battery modules. However, there is little information available on the minimum cell-to-cell spacing limits for indirect, liquid cooled modules when considering heat release during a single cell failure. For this purpose, a generic four-cell module was modeled using finite element analysis to determine the sensitivity of module temperatures to cell spacing. Additionally, the effects of different heat sink materials and interface qualities were investigated. Two materials were considered, a solid aluminum block and a metal/wax composite block. Simulations were run for three different transient load profiles. The first profile simulates sustained high rate operation where the system begins at rest and generates heat continuously until it reaches steady state. And, two failure mode simulations were conducted to investigate block performance during a slow and a fast exothermic reaction, respectively. Results indicate that composite materials can perform well under normal operation and provide some protection against single cell failure; although, for very compact designs, the amount of wax available to absorb heat is reduced and the effectiveness of the phase change material is diminished. The aluminum block design performed well under all conditions, and showed that heat generated during a failure is quickly dissipated to the coolant, even under the

  10. Large scale three-dimensional topology optimisation of heat sinks cooled by natural convection

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Sigmund, Ole; Aage, Niels

    2016-01-01

    the Bousinessq approximation. The fully coupled non-linear multiphysics system is solved using stabilised trilinear equal-order finite elements in a parallel framework allowing for the optimisation of large scale problems with order of 20-330 million state degrees of freedom. The flow is assumed to be laminar...... topologies verify prior conclusions regarding fin length/thickness ratios and Biot numbers, but also indicate that carefully tailored and complex geometries may improve cooling behaviour considerably compared to simple heat fin geometries. (C) 2016 Elsevier Ltd. All rights reserved....

  11. Thermodynamic analysis of vapor compression heat pump cycle for tap water heating and development of CO_2 heat pump water heater for residential use

    International Nuclear Information System (INIS)

    Saikawa, Michiyuki; Koyama, Shigeru

    2016-01-01

    Highlights: • The ideal vapor compression cycle for tap water heating and its COP were defined. • It was verified theoretically that CO_2 achieves the highest COP for tap water heating. • The prototype of CO_2 heat pump water heater for residential use was developed. • Further COP improvement of CO_2 heat pump water heater was estimated. - Abstract: The ideal vapor compression cycle for tap water heating and its coefficient of performance (COP) have been studied theoretically at first. The ideal cycle is defined as the cycle whose high temperature heat source varies temperature with constant specific heat and other processes are same as the reverse Carnot cycle. The COP upper limit of single stage compression heat pump cycle for tap water heating with various refrigerants such as fluorocarbons and natural refrigerants was calculated. The refrigerant which achieves the highest COP for supplying hot water is CO_2. Next, the prototype of CO_2 heat pump water heater for residential use has been developed. Its outline and experimental results are described. Finally its further possibility of COP improvement has been studied. The COP considered a limit from a technical point of view was estimated about 6.0 at the Japanese shoulder season (spring and autumn) test condition of heating water from 17 °C to 65 °C at 16 °C heat source air temperature (dry bulb)/12 °C (wet bulb).

  12. Evaluation of the Safety Issue Concerning the Potential for Loss of Decay Heat Removal Function due to Crude Oil Spill in the Ultimate Heat Sink of Nuclear Reactors

    International Nuclear Information System (INIS)

    Jo, Jong Chull; Roh, Kyung Wan; Yune, Young Gill; Kang, Dong Gu; Kim, Hho Jhung

    2008-01-01

    A barge crashed into a moored oil tanker at about 7:15 a.m., Dec. 12, 2007, dumping around 10,500 tons of crude oil into the sea in Korea. The incident took place about 15 kilometers northwest of Manripo beach in South Chungcheong where is Korea's west coast in the Yellow Sea. In a few days, the oil slicks spread to the northern and southern tips of the Taean Peninsula by strong winds and tides. As time went the spilled oil floating on the surface of sea water was volatilized to become tar-balls and lumps and drifted far away in the southern direction. 13 days after the incident, some of oil slicks and tar lumps were observed to flow in the service water intake at the Younggwang nuclear power plants (NPPs) operating 6 reactors, which are over 150 km away from the incident spot in the southeastern direction. According to the report by the Younggwang NPPs, a total weight 83 kg of tar lumps was removed for about 3 days. Oil spills in the sea can happen in any country or anytime due to human errors or mistakes, wars, terrors, intentional dumping of waste oils, and natural disasters like typhoon and tsunami. In fact, there have been 7 major oil spills over 10,000 tons that have occurred around the world since 1983. As such serious oil spill incidents may happen near the operating power plants using the sea water as ultimate heat sink. To ensure the safe operation of nuclear reactors it is required to evaluate the potential for loss of decay heat removal function of nuclear reactors due to the spilled oils flowing in the service water intake, from which the service water is pumped. Thus, Korea Institute of Nuclear Safety identified this problem as one of the important safety. When an incident of crude oil spill from an oil carrier occurs in the sea near the nuclear power plants, the spilled oil can be transported to the intake pit, where all service water pumps locate, by sea current and wind drift (induced) current. The essential service water pumps take the service

  13. Evaluation of the Safety Issue Concerning the Potential for Loss of Decay Heat Removal Function due to Crude Oil Spill in the Ultimate Heat Sink of Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Jong Chull; Roh, Kyung Wan; Yune, Young Gill; Kang, Dong Gu; Kim, Hho Jhung [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2008-05-15

    A barge crashed into a moored oil tanker at about 7:15 a.m., Dec. 12, 2007, dumping around 10,500 tons of crude oil into the sea in Korea. The incident took place about 15 kilometers northwest of Manripo beach in South Chungcheong where is Korea's west coast in the Yellow Sea. In a few days, the oil slicks spread to the northern and southern tips of the Taean Peninsula by strong winds and tides. As time went the spilled oil floating on the surface of sea water was volatilized to become tar-balls and lumps and drifted far away in the southern direction. 13 days after the incident, some of oil slicks and tar lumps were observed to flow in the service water intake at the Younggwang nuclear power plants (NPPs) operating 6 reactors, which are over 150 km away from the incident spot in the southeastern direction. According to the report by the Younggwang NPPs, a total weight 83 kg of tar lumps was removed for about 3 days. Oil spills in the sea can happen in any country or anytime due to human errors or mistakes, wars, terrors, intentional dumping of waste oils, and natural disasters like typhoon and tsunami. In fact, there have been 7 major oil spills over 10,000 tons that have occurred around the world since 1983. As such serious oil spill incidents may happen near the operating power plants using the sea water as ultimate heat sink. To ensure the safe operation of nuclear reactors it is required to evaluate the potential for loss of decay heat removal function of nuclear reactors due to the spilled oils flowing in the service water intake, from which the service water is pumped. Thus, Korea Institute of Nuclear Safety identified this problem as one of the important safety. When an incident of crude oil spill from an oil carrier occurs in the sea near the nuclear power plants, the spilled oil can be transported to the intake pit, where all service water pumps locate, by sea current and wind drift (induced) current. The essential service water pumps take the

  14. Evaporation and vapor shielding of CFC targets exposed to plasma heat fluxes relevant to ITER ELMs

    International Nuclear Information System (INIS)

    Safronov, V.M.; Arkhipov, N.I.; Landman, I.S.; Pestchanyi, S.E.; Toporkov, D.A.; Zhitlukhin, A.M.

    2009-01-01

    Carbon fibre composite NB31 was tested at plasma gun facility MK-200UG by plasma heat fluxes relevant to Edge Localised Modes in ITER. The paper reports the results obtained on the evaporation threshold of carbon fibre composite, the velocity of carbon vapor motion along and across the magnetic field lines, and the parameters of carbon plasma such as temperature, density and ionization state. First experimental results on investigation of the vapor shield onset conditions are presented also. The obtained experimental data are compared with the results of numerical modeling.

  15. Three-dimensional transient cooling simulations of a portable electronic device using PCM (phase change materials) in multi-fin heat sink

    International Nuclear Information System (INIS)

    Wang, Yi-Hsien; Yang, Yue-Tzu

    2011-01-01

    Transient three-dimensional heat transfer numerical simulations were conducted to investigate a hybrid PCM (phase change materials) based multi-fin heat sink. Numerical computation was conducted with different amounts of fins (0 fin, 3 fins and 6 fins), various heating power level (2 W, 3 W and 4 W), different orientation tests (vertical/horizontal/slanted), and charge and discharge modes. Calculating time step (0.03 s, 0.05 s, and 0.07 s) size was discussed for transient accuracy as well. The theoretical model developed is validated by comparing numerical predictions with the available experimental data in the literature. The results showed that the transient surface temperatures are predicted with a maximum discrepancy within 10.2%. The operation temperature can be controlled well by the attendance of phase change material and the longer melting time can be conducted by using a multi-fin hybrid heat sink respectively. -- Highlights: → Electronic device cooling use phase change materials. → N-eicosane is adapted as phase change materials. → Present surface transient temperatures prediction error is within 10.2%. → Hybrid PCM-heat sink system provides stable operation temperature. → Orientation effects show independent on the phase change performance.

  16. Numerical Study of Thermal and Flow Characteristics of Plate-Fin Heat Sink with Longitudinal Vortex Generator Installed on the Ground

    Directory of Open Access Journals (Sweden)

    Yen-Tso Chang

    2014-01-01

    Full Text Available This study applied the commercial software ANSYS CFD (FLUENT, for simulating the transient flow field and investigating the influence of each parameter of longitudinal vortex generators (LVGs on the thermal flux of a plate-fin heat sink. Vortex generator was set in front of plate-fin heat sink and under the channel, which was in common-flow-down (CFD and common-flow-up (CFU conditions, which have the result of vortex generator of delta winglet pair (DWP. In this study the parameters were varied, such as the minimum transverse distance between winglet pair, the attack angle of the vortex generator, fins number, the fin height, and the distance between the vortex generator and plate-fin. The coolant fluid flew into the fin-to-fin channel and pushed the vortex from different geometry toward the bottom. This phenomenon took off the heat from the plate to enhance the heat transfer. The numerical results indicated that the LVGs located close to the plate-fin heat sink are zero with the attack angle being 30°, presenting optimal overall conditions.

  17. Enhancing the moderator effectiveness as a heat sink during loss-of-coolant accidents in CANDU-PHW reactors using glass-peened surfaces

    International Nuclear Information System (INIS)

    Nitheanandan, T.; Tiede, R.W.; Sanderson, D.B.; Fong, R.W.L.; Coleman, C.E.

    1998-08-01

    The horizontal fuel channel concept is a distinguishing feature of the CANDU-PHW reactor. Each fuel channel consists of a Zr-2.5Nb pressure tube and a Zircaloy-2 calandria tube, separated by a gas filled annulus. The calandria tube is surrounded by heavy-water moderator that also provides a backup heat sink for the reactor core. This heat sink (about 10 mm away from the hot pressure tube) ensures adequate cooling of fuel in the unlikely event of a loss-of-coolant accident (LOCA). One of the ways of enhancing the use of the moderator as a heat sink is to improve the heat-transfer characteristics between the calandria tube and the moderator. This enhancement can be achieved through surface modifications to the calandria tube which have been shown to increase the tube's critical heat flux (CHF) value. An increase in CHIF could be used to reduce moderator subcooling requirements for CANDU fuel channels or increase the margin to dryout. A series of experiments was conducted to assess the benefits provided by glass-peening the outside surface of calandria tubes for postulated LOCA conditions. In particular, the ability to increase the tube's CHF, and thereby reduce moderator subcooling requirements was assessed. Results from the experiments confirm that glass-peening the outer surface of a tube increases its CHF value in pool boiling. This increase in CHF could be used to reduce moderator subcooling requirements for CANDU fuel channels by at least 5 degrees C. (author)

  18. Thermal ionization and plasma state of high temperature vapor of UO2, Cs, and Na: Effect on the heat and radiation transport properties of the vapor phase

    International Nuclear Information System (INIS)

    Karow, H.U.

    1979-01-01

    The paper deals with the question how far the thermophysical state and the convective and radiative heat transport properties of vaporized reactor core materials are affected by the thermal ionization existing in the actual vapor state. The materials under consideration here are: nuclear oxide fuel (UO 2 ), Na (as the LMFBR coolant material), and Cs (alkaline fission product, partly retained in the fuel of the core zone). (orig./RW) [de

  19. Transient local heat fluxes during the entire vapor bubble life time

    Energy Technology Data Exchange (ETDEWEB)

    Stephan, P.; Fuchs, T; Wagner, E.; Schweizer, N. [Technische Universitaet Darmstadt (Germany). Technical Thermodynamics], e-mail: pstephan@ttd.tu-darmstadt.de

    2009-07-01

    Recent experimental and numerical investigations of the nucleate boiling heat transfer process at a single active nucleation site are presented and used for an evaluation of the local heat fluxes during the entire life time of a vapor bubble from its nucleation to the rise through the thermal boundary layer. In a special boiling cell, vapor bubbles are generated at a single nucleation site on a 20 {mu}m thin stainless steel heating foil. An infrared camera captures the temperature distribution at the wall with high temporal and spatial resolution. The bubble shape is recorded with a high-speed camera. Measurements were conducted with the pure fluids FC-84 and FC-3284 and with its binary mixtures. For pure fluids, up to 50-60% of the latent heat flows through the three-phase-contact line region. For mixtures, this ratio is clearly reduced. These observations are in agreement with the numerical model of the author's group. The fully transient model contains a multi scale approach ranging from the nanometer to the millimeter scale for the detailed description of the relevant local and global phenomena. It describes the transient heat and fluid flow during the entire periodic cycle of a growing, detaching and rising bubble including the waiting time between two successive bubbles from a single nucleation site. The detailed analysis of the computed transient temperature profiles in wall and fluid give accurate information about the heat supply, temporal energy storage and local evaporation rates. (author)

  20. Transient local heat fluxes during the entire vapor bubble life time

    International Nuclear Information System (INIS)

    Stephan, P.; Fuchs, T; Wagner, E.; Schweizer, N.

    2009-01-01

    Recent experimental and numerical investigations of the nucleate boiling heat transfer process at a single active nucleation site are presented and used for an evaluation of the local heat fluxes during the entire life time of a vapor bubble from its nucleation to the rise through the thermal boundary layer. In a special boiling cell, vapor bubbles are generated at a single nucleation site on a 20 μm thin stainless steel heating foil. An infrared camera captures the temperature distribution at the wall with high temporal and spatial resolution. The bubble shape is recorded with a high-speed camera. Measurements were conducted with the pure fluids FC-84 and FC-3284 and with its binary mixtures. For pure fluids, up to 50-60% of the latent heat flows through the three-phase-contact line region. For mixtures, this ratio is clearly reduced. These observations are in agreement with the numerical model of the author's group. The fully transient model contains a multi scale approach ranging from the nanometer to the millimeter scale for the detailed description of the relevant local and global phenomena. It describes the transient heat and fluid flow during the entire periodic cycle of a growing, detaching and rising bubble including the waiting time between two successive bubbles from a single nucleation site. The detailed analysis of the computed transient temperature profiles in wall and fluid give accurate information about the heat supply, temporal energy storage and local evaporation rates. (author)

  1. Theoretical analysis of the dynamic interactions of vapor compression heat pumps

    Energy Technology Data Exchange (ETDEWEB)

    MacArthur, J W

    1984-01-01

    A detailed mathematical model of vapor compression heat pumps is described. Model derivations of the various heat pump components are given. The component models include the condenser, evaporator, accumulator, expansion device, and compressor. Details of the modeling techniques are presented, as is the solution methodology. Preliminary simulation results are also illustrated. The model developed predicts the spatial values of temperature and enthalpy as functions of time for the two heat exchangers. The temperatures and enthalpies in the accumulator, compressor and expansion device are modeled in lumped-parameter fashion. Pressure responses are determined by using continuity satisfying models for both the condenser and evaporator. The discussion of the solution methodology describes the combined implicit/explicit integration formulation that is used to solve the governing equations. The summary provides a list of future work anticipated in the area of dynamic heat pump modeling.

  2. Autoignition characteristics of laminar lifted jet flames of pre-vaporized iso-octane in heated coflow air

    KAUST Repository

    Al-Noman, Saeed M.; Choi, Sang Kyu; Chung, Suk-Ho

    2015-01-01

    The stabilization characteristics of laminar non-premixed jet flames of pre-vaporized iso-octane, one of the primary reference fuels for octane rating, have been studied experimentally in heated coflow air. Non-autoignited and autoignited lifted

  3. Experimental investigation on fluid flow and heat transfer characteristics of a submerged combustion vaporizer

    International Nuclear Information System (INIS)

    Han, Chang-Liang; Ren, Jing-Jie; Wang, Yan-Qing; Dong, Wen-Ping; Bi, Ming-Shu

    2017-01-01

    Highlights: • Thermal performance analysis of submerged combustion vaporizer (SCV) was performed experimentally. • Visualization study of shell-side flow field for SCV was carried out. • The effects of various operational parameters on the overall system performance were discussed. • Two new non-dimensional Nusselt correlations were proposed to predict the heat transfer performance of SCV. - Abstract: Submerged combustion vaporizer (SCV) occupies a decisive position in liquefied natural gas (LNG) industrial chain. In this paper, a visual experimental apparatus was established to have a comprehensive knowledge about fluid flow and heat transfer performance of SCV. Trans-critical liquid nitrogen (LN_2) was selected as alternative fluid to substitute LNG because of safety reason. Some unique experimental phenomena inside the SCV (local water bath freezes on the external surface of tube bundle) were revealed. Meanwhile the influences of static water height, superficial flue gas velocity, heat load, tube-side inlet pressure and tube-side mass flux on the system performance were systematically discussed. Finally, based on the obtained experimental results, two new empirical Nusselt number correlations were regressed to predict the shell-side and tube-side heat transfer characteristics of SCV. The maximum errors between predicted results and experimental data were respectively ±25% and ±20%. The outcomes of this paper were critical to the optimum design and economical operation of SCV.

  4. An axial heat transfer analytical model for capillary-pumped loop vapor line temperature distributions

    International Nuclear Information System (INIS)

    Lin, H.-W.; Lin, W.-K.

    2007-01-01

    This paper aims to study the capillary-pumped loop (CPL) vapor line temperature distributions. A simple axial heat transfer method is developed to predict the vapor line temperature from evaporator outlet to condenser inlet. CPL is a high efficiency two-phase heat transfer device. Since it does not need any other mechanical force such as pump, furthermore, it might be used to do the thermal management of high power electronic component such as spacecraft, notebook and computer servers. It is a cyclic circulation pumped by capillary force, and this force is generated from the fine porous structure in evaporator. A novel semi-arc porous evaporator to CPL in 1U server is designed on the ground with a horizontal position and scale down the whole device to the miniature size. From the experimental results, the CPL could remove heat 90 W in steady-state and keep the heat source temperature about 70 deg. C. Finally, a good agreement between the simulation and experimental values has been achieved. Comparing with experiment and simulation results, the deviation values of the distributions of the condenser inlet temperature are less than 8%

  5. Reducing deuterium-tritium ice roughness by electrical heating of the saturated vapor

    International Nuclear Information System (INIS)

    Mapoles, E.R.; Sater, J.D.; Monsler, E.; Pipes, J.

    1996-01-01

    High gain targets for inertial confinement fusion (ICF) contain a layer of deuterium-tritium (DT) ice which surrounds a volume of DT gas in thermal equilibrium with the solid. The roughness of the cryogenic fuel layer inside of ICF targets is one of the sources of imperfections which cause implosions to deviate from perfect one dimensional performance. Experiments at Lawrence Livermore National Laboratory have shown that applying a heat flux across the inner surface of a hydrogen layer such as that inside an ICF target reduces the intrinsic roughness of the surface. We have developed a technique to generate this heat flux by applying and electric field to the DT vapor in the center of these shells. This vapor has a small but significant conductivity due to ionization caused by beta decay of tritium in the vapor and the solid. We describe here experiments using a 1.15 GHz cavity to apply an electric field to frozen DT inside of a sapphire test cell. The cell and cavity geometry allows visual observation of the frozen layers

  6. Modeling of fuel vapor jet eruption induced by local droplet heating

    KAUST Repository

    Sim, Jaeheon

    2014-01-10

    The evaporation of a droplet by non-uniform heating is numerically investigated in order to understand the mechanism of the fuel-vapor jet eruption observed in the flame spread of a droplet array under microgravity condition. The phenomenon was believed to be mainly responsible for the enhanced flame spread rate through a droplet cloud at microgravity conditions. A modified Eulerian-Lagrangian method with a local phase change model is utilized to describe the interfacial dynamics between liquid droplet and surrounding air. It is found that the localized heating creates a temperature gradient along the droplet surface, induces the corresponding surface tension gradient, and thus develops an inner flow circulation commonly referred to as the Marangoni convection. Furthermore, the effect also produces a strong shear flow around the droplet surface, thereby pushing the fuel vapor toward the wake region of the droplet to form a vapor jet eruption. A parametric study clearly demonstrated that at realistic droplet combustion conditions the Marangoni effect is indeed responsible for the observed phenomena, in contrast to the results based on constant surface tension approximation

  7. Effect of melt surface depression on the vaporization rate of a metal heated by an electron beam

    International Nuclear Information System (INIS)

    Guilbaud, D.

    1995-01-01

    In order to produce high density vapor, a metal confined in a water cooled crucible is heated by an electron beam (eb). The energy transfer to the metal causes partial melting, forming a pool where the flow is driven by temperature induced buoyancy and capillary forces. Furthermore, when the vaporization rate is high, the free surface is depressed by the thrust of the vapor. The main objective of this paper is to analyse the combined effects of liquid flow and vapor condensation back on the liquid surface. This is done with TRIO-EF, a general purpose fluid mechanics finite element code. A suitable iterative scheme is used to calculate the free surface flow and the temperature field. The numerical simulation gives an insight about the influence of the free surface in heat transfer. The depression of the free surface induces strong effects on both liquid and vapor. As liquid is concerned, buoyancy convection in the pool is enhanced, the energy flux from electron beam is spread and constriction of heat flux under the eb spot is weakened. It results that heat transfer towards the crucible is reinforced. As vapor is concerned, its fraction that condenses back on the liquid surface is increased. These phenomena lead to a saturation of the net vaporization rate as the eb spot radius is reduced, at constant eb power. (author). 8 refs., 13 figs., 2 tabs

  8. Micro-channel heat sink with slurry of water with micro-encapsulated phase change material: 3D-numerical study

    International Nuclear Information System (INIS)

    Sabbah, Rami; Farid, Mohammad M.; Al-Hallaj, Said

    2009-01-01

    This study investigates the influence of using micro-encapsulated phase change material (MEPCM) on the thermal and hydraulic performance of micro-channel heat sinks used for heat dissipation of high power electronic devices. A three-dimensional, one-phase, laminar flow model of a rectangular channel using water slurry of MEPCM with temperature dependent physical properties was developed. The results showed a significant increase in the heat transfer coefficient under certain conditions for heat flux rates of 100 W/cm 2 and 500 W/cm 2 that is mainly dependant on the channel inlet and outlet temperatures and the selected MEPCM melting temperature. Lower and more uniform temperatures across the electronic device can be achieved at less pumping power compared to using water only as the cooling fluid

  9. Operational Performance Characterization of a Heat Pump System Utilizing Recycled Water as Heat Sink and Heat Source in a Cool and Dry Climate

    Directory of Open Access Journals (Sweden)

    Piljae Im

    2018-01-01

    Full Text Available The wastewater leaving from homes and businesses contains abundant low-grade energy, which can be utilized through heat pump technology to heat and cool buildings. Although the energy in the wastewater has been successfully utilized to condition buildings in other countries, it is barely utilized in the United States, until recently. In 2013, the Denver Museum of Nature & Science at Denver, the United States implemented a unique heat pump system that utilizes recycled wastewater from a municipal water system to cool and heat its 13,000 m2 new addition. This recycled water heat pump (RWHP system uses seven 105 kW (cooling capacity modular water-to-water heat pumps (WWHPs. Each WWHP uses R-410A refrigerant, has two compressors, and can independently provide either 52 °C hot water (HW or 7 °C chilled water (CHW to the building. This paper presents performance characterization results of this RWHP system based on the measured data from December 2014 through August 2015. The annual energy consumption of the RWHP system was also calculated and compared with that of a baseline Heating, Ventilation, and Air Conditioning (HVAC system which meets the minimum energy efficiencies that are allowed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 90.1-2013. The performance analysis results indicate that recycled water temperatures were favorable for effective operation of heat pumps. As a result, on an annual basis, the RWHP system avoided 50% of source energy consumption (resulting from reduction in natural gas consumption although electricity consumption was increased slightly, reduced CO2 emissions by 41%, and saved 34% in energy costs as compared with the baseline system.

  10. Two-Phase Flow in High-Heat-Flux Micro-Channel Heat Sink for Refrigeration Cooling Applications. Part 1: Micro-Channel Heat Sink for Direct Refrigeration Cooling

    Science.gov (United States)

    2008-09-01

    the two-phase mixture exiting the condenser. Throttling from high to low pressure was achieved by a manual metering valve situated upstream of the micro...channel et al. htp N4hsP) correlation (2002) kh sp = Nu kf dh’ Nuta, = const (Refer to Eqs. (1.4.6) and (1.4.7)), = 0.023Re" Prf4 f f E=1.0+6Bol6 +f(Bo)x...12.26% (318 data points) 0Id" +30%OND A ~’AAK - -30%",A- / A’ A* 10 " , , , htp ,&xp [W/M 2 K] Figure 1.4.8 Comparison of heat transfer coefficient

  11. Numerical and Experimental Study of an Ambient Air Vaporizer Coupled with a Compact Heat Exchanger

    Science.gov (United States)

    Kimura, Randon

    The University of Washington was tasked with designing a "21st century engine" that will make use of the thermal energy available in cryogenic gasses due to their coldness. There are currently large quantities of cryogenic gases stored throughout the U.S. at industrial facilities whereupon the regasification process, the potential for the fluid to do work is wasted. The engine proposed by the University of Washington will try to capture some of that wasted energy. One technical challenge that must be overcome during the regasification process is providing frost free operation. This thesis presents the numerical analysis and experimental testing of a passive heat exchange system that uses ambient vaporizers coupled with compact heat exchangers to provide frost free operation while minimizing pressure drop.

  12. Influence of vapor-mass flux on simultaneous heat and moisture transfer in unsaturated porous media

    International Nuclear Information System (INIS)

    Hartley, J.G.; Boo, J.H.

    1987-01-01

    This paper evaluates the validity of neglecting vapor transport by moisture content gradients (VMG) and liquid transport by temperature gradients (LTG) in coupled heat and moisture transfer in moist porous media. A review of previous work reveals discrepancies between model predictions and experimental data. The results presented here show that these discrepancies result from neglecting VMG. The governing equations which describe the coupled heat and moisture transfer are solved numerically for an infinite slab of an unsaturated porous medium, and existing experimental and empirical data for a moist sandy silt soil are used. Predicted moisture content distributions during dry-out and drying rates are found to be significantly affected by VMG. Accurate results can be obtained when VMG is neglected in the energy equation provided that it is retained in the mass conservation equation

  13. Prediction of heat capacities and heats of vaporization of organic liquids by group contribution methods

    DEFF Research Database (Denmark)

    Ceriani, Roberta; Gani, Rafiqul; Meirelles, A.J.A.

    2009-01-01

    In the present work a group contribution method is proposed for the estimation of the heat capacity of organic liquids as a function of temperature for fatty compounds found in edible oil and biofuels industries. The data bank used for regression of the group contribution parameters (1395 values...

  14. Dual solutions for unsteady mixed convection flow of MHD micropolar fluid over a stretching/shrinking sheet with non-uniform heat source/sink

    Directory of Open Access Journals (Sweden)

    N. Sandeep

    2015-12-01

    Full Text Available The aim of the present study is to investigate the influence of non-uniform heat source/sink, mass transfer and chemical reaction on an unsteady mixed convection boundary layer flow of a magneto-micropolar fluid past a stretching/shrinking sheet in the presence of viscous dissipation and suction/injection. The governing equations of the flow, heat and mass transfer are transformed into system of nonlinear ordinary differential equations by using similarity transformation and then solved numerically using Shooting technique with Matlab Package. The influence of non-dimensional governing parameters on velocity, microrotation, temperature and concentration profiles are discussed and presented with the help of their graphical representations. Also, friction factor, heat and mass transfer rates have been computed and presented through tables. Under some special conditions, present results are compared with the existed results to check the accuracy and validity of the present study. An excellent agreement is observed with the existed results.

  15. Evaporation and Vapor Shielding of CFC Targets Exposed to Plasma Heat Fluxes Relevant to ITER ELMs

    International Nuclear Information System (INIS)

    Safronov, V.; Arkhipov, N.I.; Toporkov, D.A.; Zhitlukhin, A.M.; Landman, I.

    2007-01-01

    Full text of publication follows: Carbon-fibre composite (CFC) is foreseen presently as armour material for the divertor target in ITER. During the transient processes such as instabilities of Edge Localized Modes (ELMs) the target as anticipated will be exposed to the plasma heat loads of a few MJ/m 2 on the time scale of a fraction of ms, which causes an intense evaporation at the target surface and contaminates tokamak plasma by evaporated carbon. The ITER transient loads are not achievable at existing tokamaks therefore for testing divertor armour materials other facilities, in particular plasma guns are employed. In the present work the CFC targets have been tested for ITER at the plasma gun facility MK- 200 UG in Troitsk by ELM relevant heat fluxes. The targets in the applied magnetic field up to 2 T were irradiated by hydrogen plasma streams of diameter 6 - 8 cm, impact ion energy 2 - 3 keV, pulse duration 0.05 ms and energy density varying in the range 0.05 - 1 MJ/m 2 . Primary attention has been focused on the measurement of evaporation threshold and investigation of carbon vapor properties. Fast infrared pyrometer, optical and VUV spectrometers, framing cameras and plasma calorimeters were applied as diagnostics. The paper reports the results obtained on the evaporation threshold of CFC, the evaporation rate of the carbon fibers oriented parallel and perpendicular to the exposed target surface, the velocity of carbon vapor motion along and across the magnetic field lines, and the parameters of carbon plasma such as temperature, density and ionization state measured up to the distance 15 cm at varying plasma load. First experimental results on investigation of the vapor shield onset conditions are presented also. (authors)

  16. Pressure intelligent control strategy of Waste heat recovery system of converter vapors

    Science.gov (United States)

    Feng, Xugang; Wu, Zhiwei; Zhang, Jiayan; Qian, Hong

    2013-01-01

    The converter gas evaporative cooling system is mainly used for absorbing heat in the high temperature exhaust gas which produced by the oxygen blowing reaction. Vaporization cooling steam pressure control system of converter is a nonlinear, time-varying, lagging behind, close coupling of multivariable control object. This article based on the analysis of converter operation characteristics of evaporation cooling system, of vaporization in a production run of pipe pressure variation and disturbance factors.For the dynamic characteristics of the controlled objects,we have improved the conventional PID control scheme.In Oxygen blowing process, we make intelligent control by using fuzzy-PID cascade control method and adjusting the Lance,that it can realize the optimization of the boiler steam pressure control.By design simulation, results show that the design has a good control not only ensures drum steam pressure in the context of security, enabling efficient conversion of waste heat.And the converter of 1800 flue gas through pipes and cool and dust removal also can be cooled to about 800. Therefore the converter haze evaporative cooling system has achieved to the converter haze temperature decrease effect and enhanced to the coal gas returns-ratio.

  17. Potential ability of zeolite to generate high-temperature vapor using waste heat

    Science.gov (United States)

    Fukai, Jun; Wijayanta, Agung Tri

    2018-02-01

    In various material product industries, a large amount of high temperature steam as heat sources are produced from fossil fuel, then thermal energy retained by condensed water at lower than 100°C are wasted. Thermal energies retained by exhaust gases at lower than 200°C are also wasted. Effective utilization of waste heat is believed to be one of important issues to solve global problems of energy and environment. Zeolite/water adsorption systems are introduced to recover such low-temperature waste heats in this study. Firstly, an adsorption steam recovery system was developed to generate high temperature steam from unused hot waste heat. The system used a new principle that adsorption heat of zeolite/water contact was efficiently extracted. A bench-scaled system was constructed, demonstrating contentious generation of saturated steam nearly 150°C from hot water at 80°C. Energy conservation is expected by returning the generated steam to steam lines in the product processes. Secondly, it was demonstrated that superheated steam/vapor at higher than 200°C could be generated from those at nearly 120°C using a laboratory-scaled setup. The maximum temperature and the time variation of output temperature were successfully estimated using macroscopic heat balances. Lastly, the maximum temperatures were estimated whose saturate air at the relative humidity 20-80% were heated by the present system. Theoretically, air at higher than 200°C was generated from saturate air at higher than 70°C. Consequently, zeolite/water adsorption systems have potential ability to regenerate thermal energy of waste water and exhaust gases.

  18. Assessment of Coping Capability of KORI Unit 1 under Extended Loss AC Power and Loss of Ultimate Heat Sink Initiated by Beyond Design Natural Disaster

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Hyun; Ha, Sang Jun [KHNP CRI, Daejeon (Korea, Republic of); Han, Kee Soo [Nuclear Engineering Service and Solution (NESS) Co. Ltd., Deajeon (Korea, Republic of); Park, Chan Eok [KEPCO Engineering and Constructd., Deajeon (Korea, Republic of)

    2016-10-15

    In Korea, the government and industry performed comprehensive safety inspection on all domestic nuclear power plants against beyond design basis external events and fifty action items have been issued. In addition to post- Fukushima action items, the stress tests for all domestic nuclear power plants are on the way to enhance the safety of domestic nuclear power plants through finding the vulnerabilities in intentional stress conditions initiated by beyond design natural disaster. This paper presents assessment results of coping capability of KORI Unit 1 under the simultaneous Extended Loss of AC Power (ELAP) and Loss of Ultimate Heat Sink (LUHS) which is a representative plant condition initiated by beyond design natural disaster. The assessment of the coping capability of KORI Unit 1 has been performed under simultaneous the extended loss of AC power and loss of ultimate heat sink initiated by beyond design natural disaster. It is concluded that KORI Unit 1 has the capability, in the event of loss of safety functions by beyond design natural disaster, to sufficiently cool down the reactor core without fuel damage, to keep pressure boundaries of the reactor coolant system in transient condition and to control containment and temperature to maintain the integrity of the containment buildings.

  19. Assessment of Coping Capability of KORI Unit 1 under Extended Loss AC Power and Loss of Ultimate Heat Sink Initiated by Beyond Design Natural Disaster

    International Nuclear Information System (INIS)

    Kim, Chang Hyun; Ha, Sang Jun; Han, Kee Soo; Park, Chan Eok

    2016-01-01

    In Korea, the government and industry performed comprehensive safety inspection on all domestic nuclear power plants against beyond design basis external events and fifty action items have been issued. In addition to post- Fukushima action items, the stress tests for all domestic nuclear power plants are on the way to enhance the safety of domestic nuclear power plants through finding the vulnerabilities in intentional stress conditions initiated by beyond design natural disaster. This paper presents assessment results of coping capability of KORI Unit 1 under the simultaneous Extended Loss of AC Power (ELAP) and Loss of Ultimate Heat Sink (LUHS) which is a representative plant condition initiated by beyond design natural disaster. The assessment of the coping capability of KORI Unit 1 has been performed under simultaneous the extended loss of AC power and loss of ultimate heat sink initiated by beyond design natural disaster. It is concluded that KORI Unit 1 has the capability, in the event of loss of safety functions by beyond design natural disaster, to sufficiently cool down the reactor core without fuel damage, to keep pressure boundaries of the reactor coolant system in transient condition and to control containment and temperature to maintain the integrity of the containment buildings

  20. CANDU heat sinks improvements as a follow up to Fukushima Daiichi accident ''the regulator perspective''

    Energy Technology Data Exchange (ETDEWEB)

    Mesmous, Noreddine; Harwood, Chris [Canadian Nuclear Safety Commission, Ottawa, ON (Canada)

    2015-06-15

    The purpose of this paper is to provide a summary of the Canadian Nuclear Safety Commission (CNSC) recommendations related to improving the heat sink strategy as a follow up to the Fukushima Daiichi Accident (FDA). As a follow up to FDA, CNSC staff tasked the Nuclear Power Plant (NPP) licensees to review the lessons learned from the FDA and re-examine the NPP safety cases. The reviews have examined the CANDU defence-in-depth strategy and considered events more severe than those that have historically been regarded as credible, and evaluated their impact on the NPPs safety. Availability of emergency equipment was shown to be crucial during the FDA and its availability could have arrested the accident progression early enough to minimize any radioactive release to the environment. As a result, licensees presented appropriate evaluations of the means to provide coolant make-up to the primary Heat Transport System (HTS), boilers, moderator, calandria vault, and irradiated fuel pools.

  1. Radiation effects on the mixed convection flow induced by an inclined stretching cylinder with non-uniform heat source/sink.

    Science.gov (United States)

    Hayat, Tasawar; Qayyum, Sajid; Alsaedi, Ahmed; Asghar, Saleem

    2017-01-01

    This study investigates the mixed convection flow of Jeffrey liquid by an impermeable inclined stretching cylinder. Thermal radiation and non-uniform heat source/sink are considered. The convective boundary conditions at surface are imposed. Nonlinear expressions of momentum, energy and concentration are transformed into dimensionless systems. Convergent homotopic solutions of the governing systems are worked out by employing homotopic procedure. Impact of physical variables on the velocity, temperature and concentration distributions are sketched and discussed. Numerical computations for skin friction coefficient, local Nusselt and Sherwood numbers are carried out. It is concluded that velocity field enhances for Deborah number while reverse situation is observed regarding ratio of relaxation to retardation times. Temperature and heat transfer rate are enhanced via larger thermal Biot number. Effect of Schmidt number on the concentration and local Sherwood number is quite reverse.

  2. Application of a novel biological nanofluid in a liquid block heat sink for cooling of an electronic processor: Thermal performance and irreversibility considerations

    International Nuclear Information System (INIS)

    Bahiraei, Mehdi; Heshmatian, Saeed

    2017-01-01

    Highlights: • Cooling of an electronic processor is performed by means of a biological nanofluid. • Heat transfer coefficient rises by raising either Reynolds number or concentration. • By increasing Reynolds number and concentration, temperature becomes more uniform. • Surface temperature reduces by augmenting either Reynolds number or concentration. • Irreversibility in heat sink reduces by raising concentration and Reynolds number. - Abstract: Hydrothermal characteristics and entropy generation of a biological nanofluid containing silver nanoparticles are evaluated in a liquid block heat sink for cooling of an electronic processor. The liquid block under study has 20 channels, and its bottom surface is placed on the processor. Nanoparticles synthesized through plant extract technique from green tea leaves are employed. The degree of improvement in cooling, pumping power, thermal performance and irreversibilities are examined for case of using the nanofluid instead of water. By increasing Reynolds number and particle concentration, temperature distribution becomes more uniform in processor surface and heat transfer coefficient also increases. Furthermore, the surface temperature decreases with increasing concentration and Reynolds number, such that it reduces by 2.21 °C in case of using the nanofluid with concentration of 1% instead of water at Reynolds number of 500. Moreover, maximum temperature of the processor surface decreases by increasing Reynolds number and concentration and therefore, the possibility of hot spot formation diminishes. Results show that at a constant work consumption, the nanofluid also presents better cooling compared to water. Entropy generation analysis reveals that irreversibility in the whole liquid block decreases with increasing either concentration or Reynolds number, which is a positive result based on second law of thermodynamics.

  3. Suppressed beta relaxations and reduced heat capacity in ultrastable organic glasses prepared by physical vapor deposition

    Science.gov (United States)

    Ediger, Mark

    Glasses play an important role in technology as a result of their macroscopic homogeneity (e.g., the clarity of window glass) and our ability to tune properties through composition changes. A problem with liquid-cooled glasses is that they exhibit marginal kinetic stability and slowly evolve towards lower energy glasses and crystalline states. In contrast, we have shown that physical vapor deposition can prepare glasses with very high kinetic stability. These materials have properties expected for ``million-year-old'' glasses, including high density, low enthalpy, and high mechanical moduli. We have used nanocalorimetry to show that these high stability glasses have lower heat capacities than liquid-cooled glasses for a number of molecular systems. Dielectric relaxation has been used to show that the beta relaxation can be suppressed by nearly a factor of four in vapor-deposited toluene glasses, indicating a very tight packing environment. Consistent with this view, computer simulations of high stability glasses indicate reduced Debye-Waller factors. These high stability materials raise interesting questions about the limiting properties of amorphous packing arrangements.

  4. System Model of Heat and Mass Transfer Process for Mobile Solvent Vapor Phase Drying Equipment

    Directory of Open Access Journals (Sweden)

    Shiwei Zhang

    2014-01-01

    Full Text Available The solvent vapor phase drying process is one of the most important processes during the production and maintenance for large oil-immersed power transformer. In this paper, the working principle, system composition, and technological process of mobile solvent vapor phase drying (MVPD equipment for transformer are introduced in detail. On the basis of necessary simplification and assumption for MVPD equipment and process, a heat and mass transfer mathematical model including 40 mathematical equations is established, which represents completely thermodynamics laws of phase change and transport process of solvent, water, and air in MVPD technological processes and describes in detail the quantitative relationship among important physical quantities such as temperature, pressure, and flux in key equipment units and process. Taking a practical field drying process of 500 KV/750 MVA power transformer as an example, the simulation calculation of a complete technological process is carried out by programming with MATLAB software and some relation curves of key process parameters changing with time are obtained such as body temperature, tank pressure, and water yield. The change trend of theoretical simulation results is very consistent with the actual production record data which verifies the correctness of mathematical model established.

  5. A computational study of droplet evaporation with fuel vapor jet ejection induced by localized heat sources

    KAUST Repository

    Sim, Jaeheon

    2015-05-12

    Droplet evaporation by a localized heat source under microgravity conditions was numerically investigated in an attempt to understand the mechanism of the fuel vapor jet ejection, which was observed experimentally during the flame spread through a droplet array. An Eulerian-Lagrangian method was implemented with a temperature-dependent surface tension model and a local phase change model in order to effectively capture the interfacial dynamics between liquid droplet and surrounding air. It was found that the surface tension gradient caused by the temperature variation within the droplet creates a thermo-capillary effect, known as the Marangoni effect, creating an internal flow circulation and outer shear flow which drives the fuel vapor into a tail jet. A parametric study demonstrated that the Marangoni effect is indeed significant at realistic droplet combustion conditions, resulting in a higher evaporation constant. A modified Marangoni number was derived in order to represent the surface force characteristics. The results at different pressure conditions indicated that the nonmonotonic response of the evaporation rate to pressure may also be attributed to the Marangoni effect.

  6. Modeling water vapor and heat transfer in the normal and the intubated airways.

    Science.gov (United States)

    Tawhai, Merryn H; Hunter, Peter J

    2004-04-01

    Intubation of the artificially ventilated patient with an endotracheal tube bypasses the usual conditioning regions of the nose and mouth. In this situation any deficit in heat or moisture in the air is compensated for by evaporation and thermal transfer from the pulmonary airway walls. To study the dynamics of heat and water transport in the intubated airway, a coupled system of nonlinear equations is solved in airway models with symmetric geometry and anatomically based geometry. Radial distribution of heat, water vapor, and velocity in the airway are described by power-law equations. Solution of the time-dependent system of equations yields dynamic airstream and mucosal temperatures and air humidity. Comparison of model results with two independent experimental studies in the normal and intubated airway shows a close correlation over a wide range of minute ventilation. Using the anatomically based model a range of spatially distributed temperature paths is demonstrated, which highlights the model's ability to predict thermal behavior in airway regions currently inaccessible to measurement. Accurate representation of conducting airway geometry is shown to be necessary for simulating mouth-breathing at rates between 15 and 100 l x min(-1), but symmetric geometry is adequate for the low minute ventilation and warm inspired air conditions that are generally supplied to the intubated patient.

  7. Containment condensing heat transfer

    International Nuclear Information System (INIS)

    Gido, R.G.; Koestel, A.

    1983-01-01

    This report presents a mechanistic heat-transfer model that is valid for large scale containment heat sinks. The model development is based on the determination that the condensation is controlled by mass diffusion through the vapor-air boundary layer, and the application of the classic Reynolds' analogy to formulate expressions for the transfer of heat and mass based on hydrodynamic measurements of the momentum transfer. As a result, the analysis depends on the quantification of the shear stress (momentum transfer) at the interface between the condensate film and the vapor-air boundary layer. In addition, the currently used Tagami and Uchida test observations and their range of applicability are explained

  8. DETERMINATION OF HEAT TRANSFER COEFFICIENTS FOR FRENCH PLASTIC SEMEN STRAW SUSPENDED IN STATIC NITROGEN VAPOR OVER LIQUID NITROGEN.

    Science.gov (United States)

    Santo, M V; Sansinena, M; Chirife, J; Zaritzky, N

    2015-01-01

    The use of mathematical models describing heat transfer during the freezing process is useful for the improvement of cryopreservation protocols. A widespread practice for cryopreservation of spermatozoa of domestic animal species consists of suspending plastic straws in nitrogen vapor before plunging into liquid nitrogen. Knowledge of surface heat transfer coefficient (h) is mandatory for computational modelling; however, h values for nitrogen vapor are not available. In the present study, surface heat transfer coefficients for plastic French straws immersed in nitrogen vapor over liquid nitrogen was determined; vertical and horizontal positions were considered. Heat transfer coefficients were determined from the measurement of time-temperature curves and from numerical solution of heat transfer partial differential equation under transient conditions using finite elements. The h values experimentally obtained for horizontal and vertically placed straws were compared to those calculated using correlations based on the Nusselt number for natural convection. For horizontal straws the average obtained value was h=12.5 ± 1.2 W m(2) K and in the case of vertical straws h=16 ± 2.48 W m(2) K. The numerical simulation validated against experimental measurements, combined with accurate h values provides a reliable tool for the prediction of freezing curves of semen-filled straws immersed in nitrogen vapor. The present study contributes to the understanding of the cryopreservation techniques for sperm freezing based on engineering concepts, improving the cooling protocols and the manipulation of the straws.

  9. Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance

    Energy Technology Data Exchange (ETDEWEB)

    Ratcliff, Matthew A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Burton, Jonathan L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sindler, Petr [National Renewable Energy Laboratory (NREL), Golden, CO (United States); McCormick, Robert L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Christensen, Earl D [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Fouts, Lisa A [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2018-04-03

    Knock-limited loads for a set of surrogate gasolines all having nominal 100 research octane number (RON), approximately 11 octane sensitivity (S), and a heat of vaporization (HOV) range of 390 to 595 kJ/kg at 25 degrees C were investigated. A single-cylinder spark-ignition engine derived from a General Motors Ecotec direct injection (DI) engine was used to perform load sweeps at a fixed intake air temperature (IAT) of 50 degrees C, as well as knock-limited load measurements across a range of IATs up to 90 degrees C. Both DI and pre-vaporized fuel (supplied by a fuel injector mounted far upstream of the intake valves and heated intake runner walls) experiments were performed to separate the chemical and thermal effects of the fuels' knock resistance. The DI load sweeps at 50 degrees C intake air temperature showed no effect of HOV on the knock-limited performance. The data suggest that HOV acts as a thermal contributor to S under the conditions studied. Measurement of knock-limited loads from the IAT sweeps for DI at late combustion phasing showed that a 40 vol% ethanol (E40) blend provided additional knock resistance at the highest temperatures, compared to a 20 vol% ethanol blend and hydrocarbon fuel with similar RON and S. Using the pre-vaporized fuel system, all the high S fuels produced nearly identical knock-limited loads at each temperature across the range of IATs studied. For these fuels RON ranged from 99.2 to 101.1 and S ranged from 9.4 to 12.2, with E40 having the lowest RON and highest S. The higher knock-limited loads for E40 at the highest IATs examined were consistent with the slightly higher S for this fuel, and the lower engine operating condition K values arising from use of this fuel. The study highlights how fuel HOV can affect the temperature at intake valve closing, and consequently the pressure-temperature history of the end gas leading to more negative values of K, thereby enhancing the effect of S on knock resistance.

  10. Preliminary analysis of NAPL behavior in soil-heated vapor extraction for in-situ environmental restoration

    International Nuclear Information System (INIS)

    Webb, S.W.; Phelan, J.M.

    1995-01-01

    Simulations of soil-heated vapor extraction have been performed to evaluate the NAPL removal performance as a function of borehole vacuum. The possibility of loss of NAPL containment, or NAPL migration into the unheated soil, is also evaluated in the simulations. A practical warning sign indicating migration of NAPL into the unheated zone is discussed

  11. Numerical investigation of vessel heating using a copper vapor laser and a pulsed dye laser in treating vascular skin lesions

    Science.gov (United States)

    Pushkareva, A. E.; Ponomarev, I. V.; Isaev, A. A.; Klyuchareva, S. V.

    2018-02-01

    A computer simulation technique was employed to study the selective heating of a tissue vessel using emission from a pulsed copper vapor laser and a pulsed dye laser. The depth and size of vessels that could be selectively and safely removed were determined for the lasers under examination.

  12. Roughness Length of Water Vapor over Land Surfaces and Its Influence on Latent Heat Flux

    Directory of Open Access Journals (Sweden)

    Sang-Jong Park

    2010-01-01

    Full Text Available Latent heat flux at the surface is largely dependent on the roughness length for water vapor (z0q. The determination of z0q is still uncertain because of its multifaceted characteristics of surface properties, atmospheric conditions and insufficient observations. In this study, observed values from the Fluxes Over Snow Surface II field experiment (FLOSS-II from November 2002 to March 2003 were utilized to estimate z0q over various land surfaces: bare soil, snow, and senescent grass. The present results indicate that the estimated z0q over bare soil is much smaller than the roughness length of momentum (z0m; thus, the ratio z0m/z0q is larger than those of previous studies by a factor of 20 - 150 for the available flow regime of the roughness Reynolds number, Re* > 0.1. On the snow surface, the ratio is comparable to a previous estimation for the rough flow (Re* > 1, but smaller by a factor of 10 - 50 as the flow became smooth (Re* < 1. Using the estimated ratio, an optimal regression equation of z0m/z0q is determined as a function of Re* for each surface type. The present parameterization of the ratio is found to greatly reduce biases of latent heat flux estimation compared with that estimated by the conventional method, suggesting the usefulness of current parameterization for numerical modeling.

  13. Generalized correlation of latent heats of vaporization of coal liquid model compounds between their freezing points and critical points

    Energy Technology Data Exchange (ETDEWEB)

    Sivaraman, A.; Kobuyashi, R.; Mayee, J.W.

    1984-02-01

    Based on Pitzer's three-parameter corresponding states principle, the authors have developed a correlation of the latent heat of vaporization of aromatic coal liquid model compounds for a temperature range from the freezing point to the critical point. An expansion of the form L = L/sub 0/ + ..omega..L /sub 1/ is used for the dimensionless latent heat of vaporization. This model utilizes a nonanalytic functional form based on results derived from renormalization group theory of fluids in the vicinity of the critical point. A simple expression for the latent heat of vaporization L = D/sub 1/epsilon /SUP 0.3333/ + D/sub 2/epsilon /SUP 0.8333/ + D/sub 4/epsilon /SUP 1.2083/ + E/sub 1/epsilon + E/sub 2/epsilon/sup 2/ + E/sub 3/epsilon/sup 3/ is cast in a corresponding states principle correlation for coal liquid compounds. Benzene, the basic constituent of the functional groups of the multi-ring coal liquid compounds, is used as the reference compound in the present correlation. This model works very well at both low and high reduced temperatures approaching the critical point (0.02 < epsilon = (T /SUB c/ - T)/(T /SUB c/- 0.69)). About 16 compounds, including single, two, and three-ring compounds, have been tested and the percent root-mean-square deviations in latent heat of vaporization reported and estimated through the model are 0.42 to 5.27%. Tables of the coefficients of L/sub 0/ and L/sub 1/ are presented. The contributing terms of the latent heat of vaporization function are also presented in a table for small increments of epsilon.

  14. Effect of Vapor Heat Treatment on the Mortality of Bactrocera dorsalis (Diptera: Tephritidae and the Quality of Mango cv. Arumanis

    Directory of Open Access Journals (Sweden)

    Tri Wulan Widya Lestari

    2017-07-01

    Full Text Available Arumanis is a superior export variety mango from Indonesia. One inhibiting factor on the production of this fruit variety is the infestation of Bactrocera dorsalis (Diptera: Tephritidae fruit fly. Vapor heat treatment was recommended by ISPM No. 28 of 2007 as an effective treatment in eradicating fruit flies. This research was aimed to find out the optimum temperature and the duration of vapor heat treatment on the mortality of egg and larvae of B. dorsalis. The experiment was conducted in the Laboratory of Vapor Heat Treatment, BBPOPT, Jatisari, from October 2016 to January 2017. The observed parameters were temperature, duration of treatment, mortality of egg and larvae of fruit fly, and fruit quality. The results showed that vapor heat treatment at 47°C for 40 minutes (min was effective to reduce the number of eggs and larvae of B. dorsalis and had no negative impact on the fruit quality.   Intisari Buah mangga varietas Arumanis merupakan varietas mangga ekspor unggulan Indonesia. Salah satu faktor pembatas produksi buah mangga varietas Arumanis adalah lalat buah B. dorsalis (Diptera: Tephritidae. Perlakuan uap panas direkomendasikan oleh ISPM Nomor 28 tahun 2007 sebagai tindakan perlakuan yang efektif dalam mengeradikasi lalat buah. Penelitian ini bertujuan untuk mengetahui suhu dan waktu optimum perlakuan uap panas terhadap mortalitas telur dan larva B. dorsalis pada buah mangga varietas Arumanis tanpa merusak kualitas buah. Penelitian dilaksanakan di Laboratorium Vapor Heat Treatment, BBPOPT, Jatisari, pada Oktober 2016 sampai dengan Januari 2017. Parameter yang diamati adalah suhu, lamanya waktu perlakuan, mortalitas telur dan larva lalat buah, dan kualitas buah. Hasil penelitian menunjukkan bahwa perlakuan uap panas pada suhu 47°C selama 40 menit terbukti efektif membunuh telur dan larva B. dorsalis dan tidak berdampak negatif terhadap kualitas buah.

  15. Vapor bubble behavior in subcooled flow boiling in annuli heated by water

    International Nuclear Information System (INIS)

    Licheng Sun; Zhongning Sun; Changqi Yan

    2005-01-01

    Full text of publication follows: This paper describes experimental and theoretical work conducted on vapor bubble behavior in subcooled flow boiling at atmospheric pressure. The test section is mainly consisted of two concentrically installed circular tubes, the outside tube is made of quartz and therefore all test courses can be visualized. Water is forced to flow through annuli with gap sizes of 3 mm and 5 mm, and is heated by high temperature water in the inner tube. The main objective is to visually study the bubble behavior of subcooled flow boiling water in the condition of surface heated by water. The results show that bubbles depart from wall directly or slide a certain distance before departure, this is same as that heated by electricity. There exists a bubble layer near the wall, most bubbles move and disappear in the layer after departure, the bubble sliding behavior is not very obvious in 5 mm annulus, however, we found that most bubbles in 3 mm annulus will slide a long distance before departure and their growth courses are different from usual experimental results. The bubbles are not always growing, but shrinking a little quickly after growing for some time, and then the course will repeat for some times till they depart from wall or disappeared, the collision and coalescence of bubbles is very common and makes the bubbles depart from wall more easily in 3 mm annulus. At last, the forces on bubbles growing and detaching in flow along the wall are analyzed to comprehend these phenomena more accurately. (authors)

  16. High-temperature quadrupole mass spectrometer for studying vaporization from materials heated by a CO2 laser

    International Nuclear Information System (INIS)

    Fredin, L.; Hansen, G.P.; Sampson, M.P.; Margrave, J.L.; Behrens, R.G.

    1986-09-01

    To evaluate the effectiveness of mass spectrometry techniques in studying vaporization from selected materials, we designed a mass spectrometer than can be used either with a continuous wave or pulsed laser heating system or with a conventional furnace heating system. Our experimental apparatus, the components of which are described in detail, consisted of a quadrupole mass spectrometer positioned in a crossed-beam configuration, controlling electronics, a data acquisition system, a vacuum system, a cryogenic collimation system, and a laser heating system. Results of mass spectral scans taken during laser pyrolysis of polymeric materials and laser vaporization of graphite were compatible with data reported in other studies. Results of mass spectral studies of laser-induced combustion in the Ti + C system are also presented

  17. Heat sink considerations during SLAR defuelling activities of the 1995 maintenance outage at the Point Lepreau G.S

    International Nuclear Information System (INIS)

    Richard, R.A.; Edgar, D.J.; Gibb, R.A.

    1996-01-01

    In order to conduct the Spacer Locate and Reposition (SLAR) activities, individual fuel channels were de-fuelled using the SLAR tool itself. The presence of the tool in the channel containing fuel caused concerns over channel flow interruption. A methodology was devised to assess the limited fuel heat up during de-fuelling and during possible prolonged periods of complete flow interruption. Once established, the approach could be used to assess the effect of varying parameters which could effect channel heat-up. Costly delays in SLAR maintenance activities were avoided by ensuring the sequence of channel visits was such that the individual channel powers decayed sufficiently to prevent channel heat up beyond acceptable temperature limits. (author)

  18. Numerical analysis of unsteady 3D flow of Carreau nanofluid with variable thermal conductivity and heat source/sink

    Science.gov (United States)

    Irfan, M.; Khan, M.; Khan, W. A.

    Inspired by modern deeds of nanotechnology and nanoscience and their abundant applications in the field of science and engineering, we establish a mathematical relation for unsteady 3D forced convective flow of Carreau nanofluid over a bidirectional stretched surface. Heat transfer phenomena of Carreau nanofluid is inspected through the variable thermal conductivity and heat generation/absorption impact. Furthermore, this research paper presents a more convincing approach for heat and mass transfer phenomenon of nanoliquid by utilizing new mass flux condition. Practically, zero mass flux condition is more adequate because in this approach we assume nanoparticle amends itself accordingly on the boundaries. Now the features of Buongiorno's relation for Carreau nanofluid can be applied in a more efficient way. An appropriate transformation is vacant to alter the PDEs into ODEs and then tackled numerically by employing bvp4c scheme. The numerous consequence of scheming parameters on the Carreau nanoliquid velocity components, temperature and concentration fields are portrayed graphically and deliberated in detail. The numerical outcomes for local skin friction and the wall temperature gradient for nanoliquid are intended and vacant through tables. The outcomes conveyed here manifest that impact of Brownian motion parameter Nb on the rate of heat transfer for nanoliquids becomes negligible for the recently recommended revised relation. Addationally, for authentication of the present relation, the achieved results are distinguished with earlier research works in specific cases and marvelous agreement has been noted.

  19. Study of SI engine fueled with methanol vapor and dissociation gas based on exhaust heat dissociating methanol

    International Nuclear Information System (INIS)

    Fu, Jianqin; Deng, Banglin; Liu, Jingping; Wang, Linjun; Xu, Zhengxin; Yang, Jing; Shu, Gequn

    2014-01-01

    Highlights: • The full load power decreases successively from gasoline engine, methanol vapor engine to dissociated methanol engine. • Both power and thermal efficiency of dissociated methanol engine can be improved by boosting pressure. • The conversion efficiency of recovered exhaust gas energy is largely influenced by the BMEP. • At the same BMEP, dissociated methanol engine has higher thermal efficiency than methanol vapor engine and gasoline engine. - Abstract: To improve the fuel efficiency of internal combustion (IC) engine and also achieve the goal of direct usage of methanol fuel on IC engine, an approach of exhaust heat dissociating methanol was investigated, which is a kind of method for IC engine exhaust heat recovery (EHR). A bottom cycle system is coupled with the IC engine exhaust system, which uses the exhaust heat to evaporate and dissociate methanol in its catalytic cracker. The methanol dissociation gas (including methanol vapor) is used as the fuel for IC engine. This approach was applied to both naturally aspirated (NA) engine and turbocharged engine, and the engine performance parameters were predicted by the software GT-power under various kinds of operating conditions. The improvement to IC engine performance and the conversion efficiency of recovered exhaust gas energy can be evaluated by comparing the performances of IC engine fueled with various kinds of fuels (or their compositions). Results show that, from gasoline engine, methanol vapor engine to dissociated methanol engine, the full load power decreases successively in the entire speed area due to the declining of volumetric efficiency, while it is contrary in the thermal efficiency at the same brake mean effective pressure (BMEP) level because of the improving of fuel heating value. With the increase of BMEP, the conversion efficiency of recovered exhaust gas energy is promoted. All those results indicate that the approach of exhaust heat dissociating methanol has large

  20. Manufacturing W fibre-reinforced Cu composite pipes for application as heat sink in divertor targets of future nuclear fusion reactors

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Alexander v.; You, Jeong-Ha [Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany); Ewert, Dagmar [Institut fuer Textil- und Verfahrenstechnik Denkendorf, 73770 Denkendorf (Germany); Siefken, Udo [Louis Renner GmbH, 85221 Dachau (Germany)

    2016-07-01

    An important plasma-facing component (PFC) in future nuclear fusion reactors is the so-called divertor which allows power exhaust and removal of impurities from the main plasma. The most highly loaded parts of a divertor are the target plates which have to withstand intense particle bombardment. This intense particle bombardment leads to high heat fluxes onto the target plates which in turn lead to severe thermomechanical loads. With regard to future nuclear fusion reactors, an improvement of the performance of divertor targets is desirable in order to ensure reliable long term operation of such PFCs. The performance of a divertor target is most closely linked to the properties of the materials that are used for its design. W fibre-reinforced Cu (Wf/Cu) composites are regarded as promising heat sink materials in this respect. These materials do not only feature adequate thermophysical and mechanical properties, they do also offer metallurgical flexibility as their microstructure and hence their macroscopic properties can be tailored. The contribution will point out how Wf/Cu composites can be used to realise an advanced design of a divertor target and how these materials can be fabricated by means of liquid Cu infiltration.

  1. Anisotropy in thermal conductivity of graphite flakes–SiC_p/matrix composites: Implications in heat sinking design for thermal management applications

    International Nuclear Information System (INIS)

    Molina, J.M.; Louis, E.

    2015-01-01

    Within the frame of heat dissipation for electronics, a very interesting family of anisotropic composite materials, fabricated by liquid infiltration of a matrix into preforms of oriented graphite flakes and SiC particles, has been recently proposed. Aiming to investigate the implications of the inherent anisotropy of these composites on their thermal conductivity, and hence on their potential applications, materials with matrices of Al–12 wt.% Si alloy and epoxy polymer have been fabricated. Samples have been cut at a variable angle with respect to the flakes plane and thermal conductivity has been measured by means of two standard techniques, namely, steady state technique and laser flash method. Experimental results are presented and discussed in terms of current models, from which important technological implications for heat sinking design can be derived. - Highlights: • Anisotropy in thermal conductivity of graphite flakes-based composites is evaluated. • Samples are cut in a direction forming a variable angle with the oriented flakes. • For angles 0° and 90°, thermal conductivity does not depend on sample geometry. • For intermediate angles, thermal conductivity strongly depends on sample geometry. • “Thin” samples must be thicker than 600 μm, “thick” samples must be encapsulated.

  2. Anisotropy in thermal conductivity of graphite flakes–SiC{sub p}/matrix composites: Implications in heat sinking design for thermal management applications

    Energy Technology Data Exchange (ETDEWEB)

    Molina, J.M., E-mail: jmmj@ua.es [Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Ap. 99, E-03080 Alicante (Spain); Departamento de Física Aplicada, Universidad de Alicante, Ap. 99, E-03080 Alicante (Spain); Departamento de Química Inorgánica, Universidad de Alicante, Ap. 99, | E-03080 Alicante (Spain); Louis, E. [Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Ap. 99, E-03080 Alicante (Spain); Departamento de Física Aplicada, Universidad de Alicante, Ap. 99, E-03080 Alicante (Spain); Unidad Asociada del Consejo Superior de Investigaciones Científicas, Universidad de Alicante, Ap. 99, | E-03080 Alicante (Spain)

    2015-11-15

    Within the frame of heat dissipation for electronics, a very interesting family of anisotropic composite materials, fabricated by liquid infiltration of a matrix into preforms of oriented graphite flakes and SiC particles, has been recently proposed. Aiming to investigate the implications of the inherent anisotropy of these composites on their thermal conductivity, and hence on their potential applications, materials with matrices of Al–12 wt.% Si alloy and epoxy polymer have been fabricated. Samples have been cut at a variable angle with respect to the flakes plane and thermal conductivity has been measured by means of two standard techniques, namely, steady state technique and laser flash method. Experimental results are presented and discussed in terms of current models, from which important technological implications for heat sinking design can be derived. - Highlights: • Anisotropy in thermal conductivity of graphite flakes-based composites is evaluated. • Samples are cut in a direction forming a variable angle with the oriented flakes. • For angles 0° and 90°, thermal conductivity does not depend on sample geometry. • For intermediate angles, thermal conductivity strongly depends on sample geometry. • “Thin” samples must be thicker than 600 μm, “thick” samples must be encapsulated.

  3. The thermo-mechanical behaviour of W-Cu metal matrix composites for fusion heat sink applications: The influence of the Cu content

    Science.gov (United States)

    Tejado, E.; Müller, A. v.; You, J.-H.; Pastor, J. Y.

    2018-01-01

    Copper and its alloys are used as heat sink materials for next generation fusion devices and will be joined to tungsten as an armour material. However, the joint of W and Cu experiences high thermal stresses when exposed to high heat loads so an interlayer material could effectively ensure the lifetime of the component by reducing the thermal mismatch. Many researchers have published results on the production of W-Cu composites aiming attention at its thermal conductivity; nevertheless, the mechanical performance of these composites remains poor. This paper reports the characterization of the thermo-mechanical behaviour of W-Cu composites produced via a liquid Cu melt infiltration of porous W preform. This technique was applied to produce composites with 15, 30 and 40 wt% Cu. The microstructure, thermal properties, and mechanical performance were investigated and measured from RT to 800 °C. The results demonstrated that high densification and superior mechanical properties can indeed be achieved via this manufacturing route. The mechanical properties (elastic modulus, fracture toughness, and strength) of the composites show a certain dependency on the Cu content; fracture mode shifts from the dominantly brittle fracture of W particles with constrained deformation of the Cu phase at low Cu content to the predominance of the ductile fracture of Cu when its ratio is higher. Though strong degradation is observed at 800 °C, the mechanical properties at operational temperatures, i.e. below 350 °C, remain rather high-even better than W/Cu materials reported previously. In addition, we demonstrated that the elastic modulus, and therefore the coefficient of thermal expansion, can be tailored via control of the W skeleton's porosity. As a result, the W-Cu composites presented here would successfully drive away heat produced in the fusion chamber avoiding the mismatch between materials while contributing to the structural support of the system.

  4. Does Artificial Ascites Induce the Heat-Sink Phenomenon during Percutaneous Radiofrequency Ablation of the Hepatic Subcapsular Area?: an in vivo Experimental Study Using a Rabbit Model

    International Nuclear Information System (INIS)

    Kim, Young Sun; Rhim, Hyun Chul; Choi, Dong Il; Lim, Hyo K.

    2009-01-01

    To evaluate the effect of the heat-sink phenomenon induced by artificial ascites on the size of the ablation zone during percutaneous radiofrequency (RF) ablation of the hepatic subcapsular area in an in vivo rabbit model. A total of 21 percutaneous rabbit liver RF ablations were performed with and without artificial ascites (5% dextrose aqueous solution). The rabbits were divided into three groups: a) control group (C, n = 7); b) room temperature ascites group (R, n = 7); and c) warmed ascites group (W, n = 7). The tip of a 1 cm, internally cooled electrode was placed on the subcapsular region of the hepatic dome via ultrasound guidance, and ablation was continued for 6 min. Changes in temperature of the ascites were monitored during the ablation. The size of the ablation zones of the excised livers and immediate complications rates were compared statistically between the groups (Mann-Whitney U test, Kruskal-Wallis test, linear-by-linear association, p = 0.05). One rabbit from the 'W' group expired during the procedure. In all groups, the ascites temperatures approached their respective body temperatures as the ablations continued; however, a significant difference in ascites temperature was found between groups 'W' and 'R' throughout the procedures (39.2± 0.4 .deg. C in group W and 33.4±4.3 .deg. C in group R at 6 min, p = 0.003). No significant difference was found between the size of the ablation zones (782.4±237.3 mL in group C, 1,172.0±468.9 mL in group R, and 1,030.6±665.1 mL in group W, p = 0.170) for the excised liver specimens. Diaphragmatic injury was identified in three of seven cases (42.9%) upon visual inspection of group 'C' rabbits (p = 0.030). Artificial ascites are not likely to cause a significant heat-sink phenomenon in the percutaneous RF ablation of the hepatic subcapsular region

  5. Does artificial ascites induce the heat-sink phenomenon during percutaneous radiofrequency ablation of the hepatic subcapsular area?: an in vivo experimental study using a rabbit model.

    Science.gov (United States)

    Kim, Young Sun; Rhim, Hyunchul; Choi, Dongil; Lim, Hyo K

    2009-01-01

    To evaluate the effect of the heat-sink phenomenon induced by artificial ascites on the size of the ablation zone during percutaneous radiofrequency (RF) ablation of the hepatic subcapsular area in an in vivo rabbit model. A total of 21 percutaneous rabbit liver RF ablations were performed with and without artificial ascites (5% dextrose aqueous solution). The rabbits were divided into three groups: a) control group (C, n = 7); b) room temperature ascites group (R, n = 7); and c) warmed ascites group (W, n = 7). The tip of a 1 cm, internally cooled electrode was placed on the subcapsular region of the hepatic dome via ultrasound guidance, and ablation was continued for 6 min. Changes in temperature of the ascites were monitored during the ablation. The size of the ablation zones of the excised livers and immediate complications rates were compared statistically between the groups (Mann-Whitney U test, Kruskal-Wallis test, linear-by-linear association, p = 0.05). One rabbit from the "W" group expired during the procedure. In all groups, the ascites temperatures approached their respective body temperatures as the ablations continued; however, a significant difference in ascites temperature was found between groups "W" and "R" throughout the procedures (39.2+/-0.4 degrees C in group W and 33.4+/-4.3 degrees C in group R at 6 min, p = 0.003). No significant difference was found between the size of the ablation zones (782.4+/-237.3 mL in group C, 1,172.0+/-468.9 mL in group R, and 1,030.6+/-665.1 mL in group W, p = 0.170) for the excised liver specimens. Diaphragmatic injury was identified in three of seven cases (42.9%) upon visual inspection of group "C" rabbits (p = 0.030). Artificial ascites are not likely to cause a significant heat-sink phenomenon in the percutaneous RF ablation of the hepatic subcapsular region.

  6. Numerical analyses of the effect of a biphasic thermosyphon vapor channel sizes on the heat transfer intensity when heat removing from a power transformer of combined heat and power station

    Directory of Open Access Journals (Sweden)

    Nurpeiis Atlant

    2017-01-01

    Full Text Available Numerical analyses of the effect of a biphasic thermosyphon vapor channel sizes on the heat transfer intensity was conducted when heat removing from an oil tank of a power transformer of combined heat and power station (CHP. The power transformer cooling system by the closed biphasic thermosyphon was proposed. The mathematical modeling of heat transfer and phase transitions of coolant in the thermosyphon was performed. The problem of heat transfer is formulated in dimensionless variables “velocity vorticity vector – current function – temperature” and solved by finite difference method. As a result of numerical simulation it is found that an increase in the vapor channel length from 0.15m to 1m leads to increasing the temperature difference by 3.5 K.

  7. Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k

    OpenAIRE

    K. L. Shivabasappa; P. Nirguna Babu; Y. Jagannadha Rao

    2008-01-01

    The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data o...

  8. Vapor pressure of heat transfer fluids of absorption refrigeration machines and heat pumps: Binary solutions of lithium nitrate with methanol

    International Nuclear Information System (INIS)

    Safarov, Javid T.

    2005-01-01

    Vapor pressure p of LiNO 3 + CH 3 OH solutions at T = (298.15 to 323.15) K was reported, osmotic φ and activity coefficients γ; and activity of solvent a s have been evaluated. The experiments were carried out in molality range m = (0.18032 to 5.2369) mol . kg -1 . The Antoine equation was used for the empiric description of experimental vapor pressure results. The Pitzer-Mayorga model with inclusion of Archer's ionic strength dependence of the third virial coefficient was used for the description of calculated osmotic coefficients. The parameters of Archer extended Pitzer model were used for evaluation of activity coefficients

  9. Dynamics and controls of urban heat sink and island phenomena in a desert city: Development of a local climate zone scheme using remotely-sensed inputs

    Science.gov (United States)

    Nassar, Ahmed K.; Blackburn, G. Alan; Whyatt, J. Duncan

    2016-09-01

    This study aims to determine the dynamics and controls of Surface Urban Heat Sinks (SUHS) and Surface Urban Heat Islands (SUHI) in desert cities, using Dubai as a case study. A Local Climate Zone (LCZ) schema was developed to subdivide the city into different zones based on similarities in land cover and urban geometry. Proximity to the Gulf Coast was also determined for each LCZ. The LCZs were then used to sample seasonal and daily imagery from the MODIS thermal sensor to determine Land Surface Temperature (LST) variations relative to desert sand. Canonical correlation techniques were then applied to determine which factors explained the variability between urban and desert LST. Our results indicate that the daytime SUHS effect is greatest during the summer months (typically ∼3.0 °C) with the strongest cooling effects in open high-rise zones of the city. In contrast, the night-time SUHI effect is greatest during the winter months (typically ∼3.5 °C) with the strongest warming effects in compact mid-rise zones of the city. Proximity to the Arabian Gulf had the largest influence on both SUHS and SUHI phenomena, promoting daytime cooling in the summer months and night-time warming in the winter months. However, other parameters associated with the urban environment such as building height had an influence on daytime cooling, with larger buildings promoting shade and variations in airflow. Likewise, other parameters such as sky view factor contributed to night-time warming, with higher temperatures associated with limited views of the sky.

  10. Relation between heat of vaporization, ion transport, molar volume, and cation-anion binding energy for ionic liquids.

    Science.gov (United States)

    Borodin, Oleg

    2009-09-10

    A number of correlations between heat of vaporization (H(vap)), cation-anion binding energy (E(+/-)), molar volume (V(m)), self-diffusion coefficient (D), and ionic conductivity for 29 ionic liquids have been investigated using molecular dynamics (MD) simulations that employed accurate and validated many-body polarizable force fields. A significant correlation between D and H(vap) has been found, while the best correlation was found for -log(DV(m)) vs H(vap) + 0.28E(+/-). A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids. A deviation of some ILs from the reported master curve is explained based upon ion packing and proposed diffusion pathways. No general correlations were found between the ion diffusion coefficient and molecular volume or the diffusion coefficient and cation/anion binding energy.

  11. Modelación y simulación de disipadores de calor para procesadores de computadora en COMSOL Multiphysics Modeling and simulation of heat sinks for computer processors in COMSOL Multiphysics

    Directory of Open Access Journals (Sweden)

    Sulin Garro Acón

    2012-11-01

    Full Text Available En este estudio se analizó la transferencia de calor en tres disipadores de calor utilizados para enfriar los procesadores de computadoras de escritorio. El objetivo de estos disipadores es evitar el sobrecalentamiento de la unidad de procesamiento y la consecuente reducción de la vida útil del computador. Los disipadores de calor se modelaron usando COMSOL Multiphysics con las dimensiones reales de los dispositivos y la generación de calor se modeló con una fuente puntual. Luego se modificaron los diseños de los disipadores para lograr una temperatura más baja en la zona más caliente del procesador. El resultado fue una reducción en la temperatura en el rango de 5-78 grados Kelvin, al rediseñarse el disipador de calor con variaciones feasibles como la reducción del grosor de las placas de intercambio de calor y el aumento de su número. Esto demuestra la posibilidad de desarrollar diseños optimizados para disipadores de calor que no requieran más materiales sino una mejor ingeniería. El trabajo se inició como parte del curso CM-4101 Modelización y Simulación.In this study, the heat transfer of three desktop- computer heat sinks was analyzed. The objective of using these heat sinks is to avoid overheating of the computer’s processing unit and in turn reduce the corresponding loss in the unit’s service time. The heat sinks were modeled using COMSOL Multiphysics with the actual dimensions of the devices, and heat generation was modeled with a point source. In the next step, the heat sink designs were modified to achieve a lower temperature in the higher temperature location on the heat sink. The results were temperature reductions in the range of 5-78 degrees Kelvin, by making feasible variations in design such as reducing the thickness of the heat exchanger fins and increasing their number. This paper demonstrates that there is room to develop improved designs that do not require more materials but rather a better engineering

  12. Exergoeconomic analysis and multi objective optimization of performance of a Carbon dioxide power cycle driven by geothermal energy with liquefied natural gas as its heat sink

    International Nuclear Information System (INIS)

    Ahmadi, Mohammad H.; Mehrpooya, Mehdi; Pourfayaz, Fathollah

    2016-01-01

    Highlights: • A small scale transcritical Carbon dioxide cycle is investigated. • Exergoeconomic analysis of a CO_2 power cycle driven by geothermal energy with LNG as its heat sink. • Three decision-making methods are employed to select final answers. - Abstract: In this study a transcritical Carbon dioxide power cycle has been coupled to a liquefied natural gas to work either as the cold source and to further enhance to generate electricity. The detailed thermodynamic analysis is performed in order to investigate the effect of key parameters on the cycle performance. Also, heat exchangers are measured to find the heat transfer surface area for economic evaluation. To investigate the aforementioned cycle and for optimization purposes, an exergoeconomic analysis is done to know the important components with respect to exergoeconomic criterion. The exergoeconomic analysis reveals that Carbon dioxide turbine and condenser have the highest rate of sum cost rate associated with capital investment and the cost of exergy destruction and special attention should be paid to these components. The parametric analysis shows that there is an optimum turbine inlet pressure which brings about the highest exergy efficiency and lowest product cost rate. Moreover, the condensate pressure has the highest effect on system exergy efficiency compared to others. With the help of multi-objective optimization, the cumulative effects of these variables are investigated on the system to maximize the exergetic efficiency and to minimize the product cost rate of the system. Results show that the system is capable of producing power with exergy efficiency and product cost rate equal to 20.5% and 263592.15 $/year, respectively, according to technique for order of preference by similarity to ideal solution decision making technique. Also, the system exergy efficiency of 22.1% and 295001.26 $/year product cost rate is achieved through linear programming techniques for multidimensional

  13. Vapor pressure of heat transfer fluids of absorption refrigeration machines and heat pumps: Binary solutions of lithium nitrate with methanol

    Energy Technology Data Exchange (ETDEWEB)

    Safarov, Javid T. [Heat and Refrigeration Techniques, Azerbaijan Technical University, Huseyn Javid Avn. 25, AZ1073 Baku (Azerbaijan)]. E-mail: javids@azdata.net

    2005-12-15

    Vapor pressure p of LiNO{sub 3} + CH{sub 3}OH solutions at T = (298.15 to 323.15) K was reported, osmotic {phi} and activity coefficients {gamma}; and activity of solvent a {sub s} have been evaluated. The experiments were carried out in molality range m = (0.18032 to 5.2369) mol . kg{sup -1}. The Antoine equation was used for the empiric description of experimental vapor pressure results. The Pitzer-Mayorga model with inclusion of Archer's ionic strength dependence of the third virial coefficient was used for the description of calculated osmotic coefficients. The parameters of Archer extended Pitzer model were used for evaluation of activity coefficients.

  14. Operation characteristic of a heat pump of mechanical vapor recompression propelled by fans and its performance analysis applied to waste-water treatment

    Science.gov (United States)

    Weike, Pang; Wenju, Lin; Qilin, Pan; Wenye, Lin; Qunte, Dai; Luwei, Yang; Zhentao, Zhang

    2014-01-01

    In this paper, a set of heat pump (called as Mechanical Vapor Recompression, MVR) propelled by a centrifugal fan is tested and it shows some special characteristic when it works together with a falling film evaporator. Firstly, an analysis of the fan's suction and discharge parameters at stable state, such as its pressure and temperature, indicates that a phenomenon of wet compression is probably to appear during vapor compression. As a result, superheat after saturated vapor is compressed is eliminated, which reduces discharge temperature of the system. It is because drops boil away and absorb the super heat into their latent heat during vapor compression. Meanwhile, drops in the suction vapor add to the compressed vapor, which increase the given heat of the MVR heat pump. Next, assistant electric heat could adjust and keep steady of the operating pressure and temperature of an MVR heat pump. With the evaporation temperature up to be high, heat balance is broken and supplement heat needs to increase. Thirdly, the performance of an MVR heat pump is affect by the balance of falling film and evaporation that has an effect on heat transfer. Then, two parameters standing for the performance are measured as it runs in practical condition. The two important parameters are consumptive electricity power and productive water capacity. According to theoretical work in ideal condition by calculation and fan's input power by measure as running, adiabatic efficiency (ηad) of a centrifugal fan is calculated when it is applied in a heat pump of MVR. Following, based on ηad, practical SMER and COP of an MVR heat pump are discovered to be correlative with it. Finally, in dependence on productive water in theory and in practice, displacement efficiency (ηv) of centrifugal fans is obtained when compressing vapor, and so provide some references of matching a fan for an MVR heat pump. On the other hand, it is helpful to research and develop MVR heat pumps, and also to check

  15. Enthalpy of mixing and heat of vaporization of ethyl acetate with benzene and toluene at 298.15 k and 308.15 k

    Directory of Open Access Journals (Sweden)

    K. L. Shivabasappa

    2008-03-01

    Full Text Available The present work was carried out in two phases. First, enthalpy of mixing was measured and then the heat of vaporization for the same mixtures was obtained. The data are useful in the design of separation equipments. From the various designs available for the experimental determination of enthalpy of mixing, and heat of vaporization, the apparatus was selected, modified and constructed. The apparatus of enthalpy of mixing was tested with a known system Benzene - i-Butyl Alcohol and the data obtained was in very good agreement with literature values. Experiments were then conducted for mixtures of Ethyl Acetate with Benzene and Toluene. The experimental data was fitted to the standard correlations and the constants were evaluated. Heat of vaporization data were obtained from a static apparatus and tested for accuracy by conducting experiments with a known system Benzene - n-Hexane and the data obtained were found to be in agreement with literature values. Experiments were then conducted to measure heat of vaporization for the mixtures of Ethyl Acetate with Benzene and Toluene. Using experimental data of enthalpy of mixing from the first phase, and heat capacity data, the heat of vaporization were calculated.

  16. Use of process steam in vapor absorption refrigeration system for cooling and heating applications: An exergy analysis

    Directory of Open Access Journals (Sweden)

    S. Anand

    2016-12-01

    Full Text Available The exponential increase in cost of conventional fuels shifts the interest toward the use of alternative as well waste energy sources for the operation of refrigeration and air-conditioning units. The present study therefore analyzes the performance of a process steam-operated vapor absorption system for cooling and heating applications using ammonia and water as working fluids based on first and second laws of thermodynamics. A mathematical model has been developed based on exergy analysis to investigate the performance of the system. The different performance parameters such as coefficient of performance (COP and exergetic efficiency of absorption system for cooling and heating applications are also calculated under different operating conditions. The results obtained show that cooling and heating COP along with second law efficiency (exergy efficiency increases with the heat source temperature at constant evaporator, condenser, and absorber temperature. Also, COP as well as exergy efficiency increases with an increase in the evaporator temperature at constant generator, condenser, and absorber temperature. The effect of ambient temperature on the exergetic efficiency for cooling and heating applications is also studied. The results obtained from the simulation studies can be used to optimize different components of the system so that the performance can be improved significantly.

  17. Simulation and experimental study of solar-absorption heat transformer integrating with two-stage high temperature vapor compression heat pump

    Directory of Open Access Journals (Sweden)

    Nattaporn Chaiyat

    2014-11-01

    Full Text Available In this study, simulation and experiment studies of a 10 kW solar H2O–LiBr absorption heat transformer (AHT integrating with a two-stage vapor compression heat pump (VCHP were carried out. The whole system was named as compression/absorption heat transformer (CAHT. The VCHP was used to recover rejected heat at the AHT condenser which was transferred back to the AHT evaporator at a higher temperature. The AHT unit took solar heat from a set of flat-plate solar collectors in parallel connection. R-134a and R-123 were refrigerants in the VCHP cycle. From the simulation, the total cycle coefficient (COP of the solar-CAHT was 0.71 compared with 0.49 of the normal solar-AHT. From the experiment, the total cycle COPs of the solar-CAHT and the solar-AHT were 0.62 and 0.39, respectively. The experimental results were lower than those of the simulated models due to the oversize of the experimental compressor. The annual expense of the solar-CAHT was found to be 5113 USD which was lower than 5418 USD of the solar-AHT. So it could be concluded that the modified unit was beneficial than the normal unit in terms of energy efficiency and economic expense.

  18. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps.

    Science.gov (United States)

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg 2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N 2 sorption, 27 Al/ 29 Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2 nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H 2 O and N 2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.

  19. Measuring and predicting the dynamic effects of a confined thin metal plate pulse heated into the liquid-vapor regime

    International Nuclear Information System (INIS)

    Baxter, R.C.

    1977-01-01

    The dynamic response of a confined thin layer of lead heated rapidly and uniformly to a supercritical state was investigated. Lead targets 0.025 mm and 0.05 mm thick were contained between a thin titanium tamping layer and a thick layer of fused quartz with several different gap widths between the lead and the confining surfaces. After being heated by an electron beam for about 50 ns, lead specimens expanded to a state of approximately half liquid and half vapor. Measurements of the stress in the quartz and the velocity of the tamper produced by the expanding lead were compared with one dimensional hydrodynamic computer program predictions. Measured and predicted peak stresses in the quartz for no gaps were approximately 12 kilobars and agreed within one kilobar. Peak stresses decreased rapidly with gap size to values, at 0.02 mm gaps, of about one kilobar for the 0.025 mm lead targets and five kilobars for the 0.05 mm targets. These values were confirmed by measurements. Predictions and measurements of tamper velocity (momentum) were within 10% only when the lead and confining walls were in close contact. The observed velocities for even very small gaps were substantially below predictions. These differences are attributed primarily to separation of the liquid and vapor phases during the expansion

  20. Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

    Science.gov (United States)

    Frazier, D. O.; Hung, R. J.; Paley, M. S.; Penn, B. G.; Long, Y. T.

    1996-01-01

    A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is

  1. Experimental results for hydrocarbon refrigerant vaporization in brazed plate heat exchangers at high pressure

    OpenAIRE

    Desideri, Adriano; Rhyl Kaern, Martin; Ommen Schmidt, Torben; Wronski, Jorrit; Quoilin, Sylvain; Lemort, Vincent; Haglind, Fredrik

    2016-01-01

    In recent years the interest in small capacity organic Rankine cycle (ORC) power systems for harvesting low quality waste thermal energy from industrial processes has been steadily growing. Micro ORC systems are normally equipped with brazed plate heat exchangers which allows for efficient heat transfer with a compact design. An accurate prediction of the heat transfer process characterizing these devices is required from the design phase to the development of model- based control strategies....

  2. Thermodynamic state, specific heat, and enthalpy function of saturated UO2 vapor between 3,000 K and 5,000 K

    International Nuclear Information System (INIS)

    Karow, H.U.

    1977-02-01

    The properties have been determined by means of statistical mechanics. The discussion of the thermodynamic state includes the evaluation of the plasma state and its contribution to the caloric variables-of-state of saturated oxide fuel vapor. Because of the extremely high ion and electron density due to thermal ionization, the ionized component of the fuel vapor does no more represent a perfect kinetic plasma. At temperatures around 5,000 K, UO 2 vapor reaches the collective plasma state and becomes increasingly 'metallic'. - Moreover, the nonuniform molecular equilibrium composition of UO 2 vapor has been taken into account in calculating its caloric functions-of-state. The contribution to specific heat and enthalpy of thermally excited electronic states of the vapor molecules has been derived by means of a Rydberg orbital model of the UO 2 molecule. The resulting enthalpy functions and specific heats for saturated UO 2 vapor of equilibrium composition and that for pure UO 2 gas are compared with the enthalpy and specific heat data of gaseous UO 2 at lower temperatures known from literature. (orig./HP) [de

  3. Vapor compression heat pump system field tests at the tech complex

    Science.gov (United States)

    Baxter, Van D.

    1985-11-01

    The Tennessee Energy Conservation In Housing (TECH) complex has been utilized since 1977 as a field test site for several novel and conventional heat pump systems for space conditioning and water heating. Systems tested include the Annual Cycle Energy System (ACES), solar assisted heat pumps (SAHP) both parallel and series, two conventional air-to-air heat pumps, an air-to-air heat pump with desuperheater water heater, and horizontal coil and multiple shallow vertical coil ground-coupled heat pumps (GCHP). A direct comparison of the measured annual performance of the test systems was not possible. However, a cursory examination revealed that the ACES had the best performance, however, its high cost makes it unlikely that it will achieve wide-spread use. Costs for the SAHP systems are similar to those of the ACES but their performance is not as good. Integration of water heating and space conditioning functions with a desuperheater yielded significant efficiency improvement at modest cost. The GCHP systems performed much better for heating than for cooling and may well be the most efficient alternative for residences in cold climates.

  4. Heat flow in vapor dominated areas of the Yellowstone Plateau volcanic field: implications for the thermal budget of the Yellowstone Caldera

    Science.gov (United States)

    Hurwitz, Shaul; Harris, Robert; Werner, Cynthia Anne; Murphy, Fred

    2012-01-01

    Characterizing the vigor of magmatic activity in Yellowstone requires knowledge of the mechanisms and rates of heat transport between magma and the ground surface. We present results from a heat flow study in two vapor dominated, acid-sulfate thermal areas in the Yellowstone Caldera, the 0.11 km2 Obsidian Pool Thermal Area (OPTA) and the 0.25 km2 Solfatara Plateau Thermal Area (SPTA). Conductive heat flux through a low permeability layer capping large vapor reservoirs is calculated from soil temperature measurements at >600 locations and from laboratory measurements of soil properties. The conductive heat output is 3.6 ± 0.4 MW and 7.5 ± 0.4 MW from the OPTA and the SPTA, respectively. The advective heat output from soils is 1.3 ± 0.3 MW and 1.2 ± 0.3 MW from the OPTA and the SPTA, respectively and the heat output from thermal pools in the OPTA is 6.8 ± 1.4 MW. These estimates result in a total heat output of 11.8 ± 1.4 MW and 8.8 ± 0.4 MW from OPTA and SPTA, respectively. Focused zones of high heat flux in both thermal areas are roughly aligned with regional faults suggesting that faults in both areas serve as conduits for the rising acid vapor. Extrapolation of the average heat flux from the OPTA (103 ± 2 W·m−2) and SPTA (35 ± 3 W·m−2) to the ~35 km2 of vapor dominated areas in Yellowstone yields 3.6 and 1.2 GW, respectively, which is less than the total heat output transported by steam from the Yellowstone Caldera as estimated by the chloride inventory method (4.0 to 8.0 GW).

  5. Assessing Near-surface Heat, Water Vapor and Carbon Dioxide Exchange Over a Coastal Salt-marsh

    Science.gov (United States)

    Bogoev, I.; O'Halloran, T. L.; LeMoine, J.

    2017-12-01

    Coastal ecosystems play an important role in mitigating the effects of climate change by storing significant quantities of carbon. A growing number of studies suggest that vegetated estuarine habitats, specifically salt marshes, have high long-term rates of carbon sequestration, perhaps even higher than mature tropical and temperate forests. Large amounts of carbon, accumulated over thousands of years, are stored in the plant materials and sediment. Improved understanding of the factors that control energy and carbon exchange is needed to better guide restoration and conservation management practices. To that end, we recently established an observation system to study marsh-atmosphere interactions within the North Inlet-Winyah Bay National Estuarine Research Reserve. Near-surface fluxes of heat, water vapor (H2O) and carbon dioxide (CO2) were measured by an eddy-covariance system consisting of an aerodynamic open-path H2O / CO2 gas analyzer with a spatially integrated 3D sonic anemometer/thermometer (IRGASON). The IRGASON instrument provides co-located and highly synchronized, fast response H2O, CO2 and air- temperature measurements, which eliminates the need for spectral corrections associated with the separation between the sonic anemometer and the gas analyzer. This facilitates calculating the instantaneous CO2 molar mixing ratio relative to dry air. Fluxes computed from CO2 and H2O mixing ratios, which are conserved quantities, do not require post-processing corrections for air-density changes associated with temperature and water vapor fluctuations. These corrections are particularly important for CO2, because they could be even larger than the measured flux. Here we present the normalized frequency spectra of air temperature, water vapor and CO2, as well as their co-spectra with the co-located vertical wind. We also show mean daily cycles of sensible, latent and CO2 fluxes and analyze correlations with air/water temperature, wind speed and light availability.

  6. Capillary pumped loop body heat exchanger

    Science.gov (United States)

    Swanson, Theodore D. (Inventor); Wren, deceased, Paul (Inventor)

    1998-01-01

    A capillary pumped loop for transferring heat from one body part to another body part, the capillary pumped loop comprising a capillary evaporator for vaporizing a liquid refrigerant by absorbing heat from a warm body part, a condenser for turning a vaporized refrigerant into a liquid by transferring heat from the vaporized liquid to a cool body part, a first tube section connecting an output port of the capillary evaporator to an input of the condenser, and a second tube section connecting an output of the condenser to an input port of the capillary evaporator. A wick may be provided within the condenser. A pump may be provided between the second tube section and the input port of the capillary evaporator. Additionally, an esternal heat source or heat sink may be utilized.

  7. Water injection into vapor- and liquid-dominated reservoirs: Modeling of heat transfer and mass transport

    Energy Technology Data Exchange (ETDEWEB)

    Pruess, K.; Oldenburg, C.; Moridis, G.; Finsterle, S. [Lawrence Berkeley National Lab., CA (United States)

    1997-12-31

    This paper summarizes recent advances in methods for simulating water and tracer injection, and presents illustrative applications to liquid- and vapor-dominated geothermal reservoirs. High-resolution simulations of water injection into heterogeneous, vertical fractures in superheated vapor zones were performed. Injected water was found to move in dendritic patterns, and to experience stronger lateral flow effects than predicted from homogeneous medium models. Higher-order differencing methods were applied to modeling water and tracer injection into liquid-dominated systems. Conventional upstream weighting techniques were shown to be adequate for predicting the migration of thermal fronts, while higher-order methods give far better accuracy for tracer transport. A new fluid property module for the TOUGH2 simulator is described which allows a more accurate description of geofluids, and includes mineral dissolution and precipitation effects with associated porosity and permeability change. Comparisons between numerical simulation predictions and data for laboratory and field injection experiments are summarized. Enhanced simulation capabilities include a new linear solver package for TOUGH2, and inverse modeling techniques for automatic history matching and optimization.

  8. Water desalting schemes when using heat gas-vapor mixture in front of contact condenser

    OpenAIRE

    Kuznetsova, Svitlana A.

    2016-01-01

    Ukraine is a country with low quality of fresh water; there are regions with its deficiency. One of the possible solutions to this problem is the desalination of the brackish water from surface and groundwater sources by using heat of the mixture before the contact condenser in gas-steam turbine plants. The plants produce electricity and heat energy for the needs of the industrial, agricultural complexes and the population of Kherson, Nikolaev and Odessa regions. The studies were carried out ...

  9. The influence of chemical composition of LNG on the supercritical heat transfer in an intermediate fluid vaporizer

    Science.gov (United States)

    Xu, Shuangqing; Chen, Xuedong; Fan, Zhichao; Chen, Yongdong; Nie, Defu; Wu, Qiaoguo

    2018-04-01

    A three-dimensional transient computational fluid dynamics (CFD) model has been established for the simulations of supercritical heat transfer of real liquefied natural gas (LNG) mixture in a single tube and a tube bundle of an intermediate fluid vaporizer (IFV). The influence of chemical composition of LNG on the thermal performance has been analyzed. The results have also been compared with those obtained from the one-dimensional steady-state calculations using the distributed parameter model (DPM). It is found that the current DPM approach can give reasonable prediction accuracy for the thermal performance in the tube bundle but unsatisfactory prediction accuracy for that in a single tube as compared with the corresponding CFD data. As benchmarked against pure methane, the vaporization of an LNG containing about 90% (mole fraction) of methane would lead to an absolute deviation of 5.5 K in the outlet NG temperature and a maximum relative deviation of 11.4% in the tube side HTC in a bundle of about 816 U tubes at the inlet pressure of 12 MPa and mass flux of 200 kg·m-2·s-1. It is concluded that the influence of LNG composition on the thermal performance should be taken into consideration in order to obtain an economic and reliable design of an IFV.

  10. Application of Evaporative Cooling for the Condensation of Water Vapors from a Flue Gas Waste Heat Boilers CCP

    Directory of Open Access Journals (Sweden)

    Galashov Nikolay

    2016-01-01

    Full Text Available The object of the study are boilers that burn organic fuel and the recovery boilers (RB of the combined cycle plant (CCP, which are al-so working on the products of the combustion of hydrocarbon fuels. The purpose of research is to find technologies that increase efficiency of the thermal power plant (TPP and technologies that reduce the environmental impact on the environment by burning fossil fuels. The paper deals with the technology of the boilers burning hydrocarbon fuel with condensation of water vapor from the exhaust flue gases. Considered the problems caused by using of this technology. Research shows that the main problem of this technology in the boilers is the lack of reliable methods of calculation of heat exchangers, condensers. Particular attention is paid to the application of this technology in the recovery boilers combined-cycle plants, which are currently gaining increasing use in the generation of electricity from the combustion of gas in power plants. It is shown that the application of technology of condensation of water vapor in RB CCP, the temperature decreases of exhaust gases from 100 to 40 °С, allows increasing the effi-ciency of the RB with 86.2 % to 99.5 %, i.e. at 12.3 %, and increase the ef-ficiency of the CCP at 2.8 %.

  11. Relationship between 578-nm (copper vapor) laser beam geometry and heat distribution within biological tissues

    Science.gov (United States)

    Ilyasov, Ildar K.; Prikhodko, Constantin V.; Nevorotin, Alexey J.

    1995-01-01

    Monte Carlo (MC) simulation model and the thermoindicative tissue phantom were applied for evaluation of a depth of tissue necrosis (DTN) as a result of quasi-cw copper vapor laser (578 nm) irradiation. It has been shown that incident light focusing angle is essential for DTN. In particular, there was a significant rise in DTN parallel to elevation of this angle up to +20 degree(s)C and +5 degree(s)C for both the MC simulation and tissue phantom models, respectively, with no further increase in the necrosis depth above these angles. It is to be noted that the relationship between focusing angles and DTN values was apparently stronger for the real target compared to the MC-derived hypothetical one. To what extent these date are applicable for medical practice can be evaluated in animal models which would simulate laser-assisted therapy for PWS or related dermatologic lesions with converged 578 nm laser beams.

  12. Determination of heat transfer coefficient with vapor condensation inside the tubes diesel’s radiator sections

    Directory of Open Access Journals (Sweden)

    Y.K.Sklifus

    2012-12-01

    Full Text Available The article presents the calculation of heat transfer coefficient during condensation of steam, the mathematical model of temperature distribution in the gas and liquid phases of the coolant and the model of the formation of the condensate film on the walls of the tubes.

  13. Angular distributions of atomic vapor stream produced by electron beam heating

    Energy Technology Data Exchange (ETDEWEB)

    Ohba, Hironori; Amekawa, Kazuhiro; Shibata, Takemasa [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-03-01

    The angular distributions were measured as a function of deposition rate for aluminium, copper, gadolinium and cerium vapor stream produced by an electron beam gun with water-cooled copper crucible. The distributions were recorded on the mounted on a semicircular (120mm in radius) mask over the evaporation source. The measured distributions were able to be described by a simple cosine law, that is cos{sup n} {theta}, except for the case of extremely high evaporation rate with a porous material, where n is a rate-dependent beaming exponent, {theta} is the angle from the vertical. For many kinds of evaporants, it was confirmed that the beaming exponents increase continuously from unity to 3 or 4 with increasing deposition rate and are approximately proportional to R{sup 0.25} where R is the deposition rate. Moreover, it was found that the beaming exponents n are able to be expressed as n = {alpha} Kn{sub 0}{sup -0.25}, where Kn{sub 0}{sup -1} is the inverse of Knudsen number, which is defined by the mean free path of evaporated atoms and the evaporation spot size, and {alpha} is the constant. (author)

  14. Angular distributions of atomic vapor stream produced by electron beam heating

    International Nuclear Information System (INIS)

    Ohba, Hironori; Amekawa, Kazuhiro; Shibata, Takemasa

    1997-03-01

    The angular distributions were measured as a function of deposition rate for aluminium, copper, gadolinium and cerium vapor stream produced by an electron beam gun with water-cooled copper crucible. The distributions were recorded on the mounted on a semicircular (120mm in radius) mask over the evaporation source. The measured distributions were able to be described by a simple cosine law, that is cos n θ, except for the case of extremely high evaporation rate with a porous material, where n is a rate-dependent beaming exponent, θ is the angle from the vertical. For many kinds of evaporants, it was confirmed that the beaming exponents increase continuously from unity to 3 or 4 with increasing deposition rate and are approximately proportional to R 0.25 where R is the deposition rate. Moreover, it was found that the beaming exponents n are able to be expressed as n = α Kn 0 -0.25 , where Kn 0 -1 is the inverse of Knudsen number, which is defined by the mean free path of evaporated atoms and the evaporation spot size, and α is the constant. (author)

  15. What's Up with Sinking?

    Science.gov (United States)

    Blintz, William

    2005-01-01

    In Hamlet, Shakespeare invites readers to ponder a famous philosophical question: To be or not to be? That is the question. In this issue, two trade books invite students to explore the question: To sink or not to sink? That is the experiment. Though both books are targeted for younger children, teachers can use these books with elementary…

  16. A numerical investigation of the sCO2 recompression cycle off-design behaviour, coupled to a sodium cooled fast reactor, for seasonal variation in the heat sink temperature

    International Nuclear Information System (INIS)

    Floyd, J.; Alpy, N.; Moisseytsev, A.; Haubensack, D.; Rodriguez, G.; Sienicki, J.; Avakian, G.

    2013-01-01

    Highlights: • Year-round behaviour of the supercritical CO 2 recompression cycle is simulated. • Behaviour of the system was uncertain due to large changes in the fluid properties. • Cycle thermodynamic optimisation and component preliminary designs were performed. • No off design cycle stability issues, compressors operate away from surge region. • Independent speed control of compressors maintains power and cycle efficiency. -- Abstract: Supercritical CO 2 cycles are particularly attractive for Generation IV Sodium-Cooled Fast Reactors (SFRs) as they can be simple and compact, but still offer steam-cycle equivalent efficiency while also removing potential for Na/H 2 O reactions. However, CO 2 thermophysical properties are very sensitive close to the critical point which raises, in particular, questions about the compressor and so cycle off-design behaviour when subject to inevitable temperature increases that result from seasonal variations in the heat sink temperature. This publication reports the numerical investigation of such an issue that has been performed using the Plant Dynamics Code (ANL, USA), the cycle being optimised for the next French SFR, ASTRID (1500 MW th ), as a test-case. On design, the net plant efficiency is 42.2% for a high pressure (25 MPa) turbine with an inlet temperature of 515 °C and considering a cycle low temperature of 35 °C. The off-design cycle behaviour is studied based on preliminary designs for the main components and assuming the use of a fixed heat sink flow rate. First results obtained using a common fixed shaft speed for all turbomachines, without any other active control, show no stability issues and roughly constant density (and volumetric flow rate) at the main compressor inlet for the range of heat sink temperature considered (21–40 °C). This occurs because the new stationary states are found without requiring a significant shift of mass to the higher pressure level, meaning the compressor inlet pressure

  17. Experimental results for hydrocarbon refrigerant vaporization inside brazed plate heat exchangers at high pressure

    DEFF Research Database (Denmark)

    Desideri, Adriano; Ommen, Torben Schmidt; Wronski, Jorrit

    2016-01-01

    fluids at typical working conditions of ORC systems for low temperature waste heat recovery (WHR) applications. Based on these premises, a novel testrig has been recently designed and built at the Technical University of Denmark to simulate the evaporating condition occurring in a small capacity ORC...... power unit. In this contribution the preliminary experimental results obtained from the first experimental campaign carried out on the rig are reported. HFC-134a was selected as working fluid. The experiments were carried out at saturation temperature of 60, 70 and 80 °C and inlet and outlet qualities...

  18. Experimental observations of the microlayer in vapor bubble growth on a heated solid

    International Nuclear Information System (INIS)

    Koffman, L.D.; Plesset, M.S.

    1983-01-01

    Experimental measurements of microlayer formation and of the time history of microlayer thickness change have been obtained for nucleate boiling of water and ethanol. These detailed measurements were obtained using laser interometry combined with high-speed cinematography. The measurement technique is discussed in detail with emphasis on the difficulties encountered in interpretation of the fringe patterns. The measurements for water can be reasonably applied to the data of Gunther and Kreith, in which case it is concluded that microlayer evaporate alone cannot account for the increased heat transfer rates observed in highly subcooled nucleate boiling. It appears that microconvection must play at least an equal role

  19. Flooding and sinking of nuclear merchant ships

    International Nuclear Information System (INIS)

    Lettnin, H.K.J.; Wehowsky, P.

    1978-01-01

    In contrast to land-based power plants for ship reactors the marine environment brings up the peril of sinking. But this peril is low for nuclear ships with its high safety standard. An evaluation of casualties from 1964 - 1974 for ships>8000 GRT allows to estimate a very low sink probability for nuclear ships in the range of 10 -7 to 10 -8 p.a. In spite of this low probability a sinking cannot be excluded absolutely. Therefore passive means must be provided for sinking in deep waters: to maintain the integrity of at least one enclosure as activity barrier; to supply seawater into the safety containment for decay heat removal. For sinking in shallow waters and flooding at least one of the redundant decay heat removal systems including power supply stays operable. A mathematical tool is available for the design of flood openings of sufficient cross sections to flood the containment and to reach a pressure balance in case of postulated sinking in deep waters of any depth

  20. Autoignition characteristics of laminar lifted jet flames of pre-vaporized iso-octane in heated coflow air

    KAUST Repository

    Alnoman, Saeed

    2015-12-01

    The stabilization characteristics of laminar non-premixed jet flames of pre-vaporized iso-octane, one of the primary reference fuels for octane rating, have been studied experimentally in heated coflow air. Non-autoignited and autoignited lifted flames were analyzed. With the coflow air at relatively low initial temperatures below 940 K, an external ignition source was required to stabilize the flame. These lifted flames had tribrachial edge structures and their liftoff heights correlated well with the jet velocity scaled by stoichiometric laminar burning velocity, indicating the importance of the edge propagation speed on flame stabilization. At high initial temperatures over 940 K, the autoignited flames were stabilized without requiring an external ignition source. These autoignited lifted flames exhibited either tribrachial edge structures or mild combustion behaviors depending on the level of fuel dilution. Two distinct transition behaviors were observed in the autoignition regime from a nozzle-attached flame to a lifted tribrachial-edge flame and then to lifted mild combustion as the jet velocity increased at a certain fuel dilution level. The liftoff data of the autoignited flames with tribrachial edges were analyzed based on calculated ignition delay times. Analysis of the experimental data suggested that ignition delay time may be much less sensitive to initial temperature under atmospheric pressure conditions as compared with predictions. © 2015 Elsevier Ltd. All rights reserved.

  1. Force Field Benchmark of the TraPPE_UA for Polar Liquids: Density, Heat of Vaporization, Dielectric Constant, Surface Tension, Volumetric Expansion Coefficient, and Isothermal Compressibility.

    Science.gov (United States)

    Núñez-Rojas, Edgar; Aguilar-Pineda, Jorge Alberto; Pérez de la Luz, Alexander; de Jesús González, Edith Nadir; Alejandre, José

    2018-02-08

    The transferable potential for a phase equilibria force field in its united-atom version, TraPPE_UA, is evaluated for 41 polar liquids that include alcohols, thiols, ethers, sulfides, aldehydes, ketones, and esters to determine its ability to reproduce experimental properties that were not included in the parametrization procedure. The intermolecular force field parameters for pure components were fit to reproduce experimental boiling temperature, vapor-liquid coexisting densities, and critical point (temperature, density, and pressure) using Monte Carlo simulations in different ensembles. The properties calculated in this work are liquid density, heat of vaporization, dielectric constant, surface tension, volumetric expansion coefficient, and isothermal compressibility. Molecular dynamics simulations were performed in the gas and liquid phases, and also at the liquid-vapor interface. We found that relative error between calculated and experimental data is 1.2% for density, 6% for heat of vaporization, and 6.2% for surface tension, in good agreement with the experimental data. The dielectric constant is systematically underestimated, and the relative error is 37%. Evaluating the performance of the force field to reproduce the volumetric expansion coefficient and isothermal compressibility requires more experimental data.

  2. Evaporation of Droplets in Plasma Spray-Physical Vapor Deposition Based on Energy Compensation Between Self-Cooling and Plasma Heat Transfer

    Science.gov (United States)

    Liu, Mei-Jun; Zhang, Meng; Zhang, Qiang; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2017-10-01

    In the plasma spray-physical vapor deposition process (PS-PVD), there is no obvious heating to the feedstock powders due to the free molecular flow condition of the open plasma jet. However, this is in contrast to recent experiments in which the molten droplets are transformed into vapor atoms in the open plasma jet. In this work, to better understand the heating process of feedstock powders in the open plasma jet of PS-PVD, an evaporation model of molten ZrO2 is established by examining the heat and mass transfer process of molten ZrO2. The results reveal that the heat flux in PS-PVD open plasma jet (about 106 W/m2) is smaller than that in the plasma torch nozzle (about 108 W/m2). However, the flying distance of molten ZrO2 in the open plasma jet is much longer than that in the plasma torch nozzle, so the heating in the open plasma jet cannot be ignored. The results of the evaporation model show that the molten ZrO2 can be partly evaporated by self-cooling, whereas the molten ZrO2 with a diameter <0.28 μm and an initial temperature of 3247 K can be completely evaporated within the axial distance of 450 mm by heat transfer.

  3. Predicting the heat of vaporization of iron at high temperatures using time-resolved laser-induced incandescence and Bayesian model selection

    Science.gov (United States)

    Sipkens, Timothy A.; Hadwin, Paul J.; Grauer, Samuel J.; Daun, Kyle J.

    2018-03-01

    Competing theories have been proposed to account for how the latent heat of vaporization of liquid iron varies with temperature, but experimental confirmation remains elusive, particularly at high temperatures. We propose time-resolved laser-induced incandescence measurements on iron nanoparticles combined with Bayesian model plausibility, as a novel method for evaluating these relationships. Our approach scores the explanatory power of candidate models, accounting for parameter uncertainty, model complexity, measurement noise, and goodness-of-fit. The approach is first validated with simulated data and then applied to experimental data for iron nanoparticles in argon. Our results justify the use of Román's equation to account for the temperature dependence of the latent heat of vaporization of liquid iron.

  4. Irradiation of 'carabao' (Manila 'super') mangoes II. Comparison of the effects of gamma radiation and the vapor heat treatment on fruit quality

    International Nuclear Information System (INIS)

    Lizada, M.C.C.; Esguerra, E.B.; Brena, S.R.; Fuentes, R.A.

    1990-01-01

    'Carabao' mango fruits subjected to gamma radiation at 100, 150 or 250 Gy resulted in fruits of an acceptable quality. In contrast to the vapor heat treatment, no internal breakdown was observed even in fruits irradiated at 350 Gy. At this dose a low but significant incidence of pulp discoloration was found, albeit in only one trial. Both the vapor heat treatment and gamma radiation need to be supplemented with hot water treatment for effective and more consistent disease control. Although irradiation appears to delay ripening, its effect seems to be largely on peel color development. The results of this study indicate that irradiation might be an appropriate quarantine treatment for the 'Carabao' mango. (Auth.). 7 tabs., 3 figs

  5. The effect of water vapor in the reactor cavity in a MHTGR [Modular High Temperature Gas Cooled Reactor] on the radiation heat transfer

    International Nuclear Information System (INIS)

    Cappiello, M.W.

    1991-01-01

    Analyses have been completed to determine the effect of the presence of water vapor in the reactor cavity in a modular high temperature gas cooled reactor on the predicted radiation heat transfer from the vessel wall to the reactor cavity cooling system. The analysis involves the radiation heat transfer between two parallel plates with an absorbing and emitting medium present. Because the absorption in the water vapor is spectrally dependent, the solution is difficult even for simple geometries. A computer code was written to solve the problem using the Monte Carlo method. The code was validated against closed form solutions, and shows excellent agreement. In the analysis of the reactor problem, the results show that the reduction in heat transfer, and the consequent increase in the vessel wall temperature, can be significant. This effect can be cast in terms of a reduction in the wall surface emissivities from 0.8 to 0.59. Because of the insulating effect of the water vapor, increasing the gap distance between the vessel wall and the cooling system will cause the vessel wall temperature to increase further. Care should be taken in the design of the facility to minimize the gap distance and keep temperature increase within allowable limits. 3 refs., 6 figs., 4 tabs

  6. The free-piston Vuilleumier machine: a new refrigerating sink from heat loss recovery?; La machine de Vuilleumier a pistons libres: une nouvelle source de froid par recuperation?

    Energy Technology Data Exchange (ETDEWEB)

    Rochelle, P. [Laboratoire de Mecanique Physique, UP6, 78 - Saint Cyr l' Ecole (France); Rochelle, P.; Grosu, L. [Laboratoire d' Energetique et d' Economie de l' Energie, UP10, 92 - Ville d' Avray (France)

    2002-07-01

    The Vuilleumier machine combines two Stirling cycles: a prime mover and a refrigerating cycle. lt could produce cold and heat at low temperature levels from heat loss recovered at the exhaust of heat generating processes (industrial transforming processes, thermal engines,...). Here, these regenerating dual cycle machines and their potential applications, particularly those concerning transportation vehicles, are examined. Towards this purpose, the Vuilleumier machine principles are briefly described along with a more in-depth look at the free-piston configuration type. In principle, these machines are simple to build, but specific starting and continuous running conditions must be met, and here they are established. Then, we discuss the applicability of these systems to vehicles, and the usable geometrical configurations are shortly examined with, as an application, the pre-design calculus of a 'pancake' machine. (authors)

  7. Analytical solutions for hydromagnetic natural convection flow of a particulate suspension through isoflux-isothermal channels in the presence of a heat source or sink

    International Nuclear Information System (INIS)

    Chamkha, Ali J.; Al-Rashidi, Seham S.

    2010-01-01

    This work considers the problem of steady natural convection hydromagnetic flow of a particulate suspension through an infinitely long channel in the presence of heat generation or absorption effects. The channel walls are maintained at isoflux-isothermal condition. That is, the thermal boundary conditions are such that one of the channel walls is maintained at constant heat flux while the other is maintained at a constant temperature. Various closed-form solutions of the governing equations for different special cases are obtained. A parametric study of the physical parameters involved in the problem is done to illustrate the influence of these parameters on the velocity and temperature profiles of both phases.

  8. Large-scale fabrication of linear low density polyethylene/layered double hydroxides composite films with enhanced heat retention, thermal, mechanical, optical and water vapor barrier properties

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Jiazhuo; Zhang, Kun; Zhao, Qinghua [College of Chemistry and Material Science, Shandong Agricultural University, 61 Daizong Street, Tai' an 271018 (China); Wang, Qingguo, E-mail: wqgyyy@126.com [College of Food Science and Engineering, Shandong Agricultural University, 61 Daizong Street, Tai' an 271018 (China); Xu, Jing, E-mail: jiaxu@sdau.edu.cn [College of Chemistry and Material Science, Shandong Agricultural University, 61 Daizong Street, Tai' an 271018 (China)

    2016-11-15

    Novel LDH intercalated with organic aliphatic long-chain anion was large-scale synthesized innovatively by high-energy ball milling in one pot. The linear low density polyethylene (LLDPE)/layered double hydroxides (LDH) composite films with enhanced heat retention, thermal, mechanical, optical and water vapor barrier properties were fabricated by melt blending and blowing process. FT IR, XRD, SEM results show that LDH particles were dispersed uniformly in the LLDPE composite films. Particularly, LLDPE composite film with 1% LDH exhibited the optimal performance among all the composite films with a 60.36% enhancement in the water vapor barrier property and a 45.73 °C increase in the temperature of maximum mass loss rate compared with pure LLDPE film. Furthermore, the improved infrared absorbance (1180–914 cm{sup −1}) of LLDPE/LDH films revealed the significant enhancement of heat retention. Therefore, this study prompts the application of LLDPE/LDH films as agricultural films with superior heat retention. - Graphical abstract: The fabrication process of LLDPE/LDH composite films. - Highlights: • LDH with basal spacing of 4.07 nm was synthesized by high-energy ball milling. • LLDPE composite films with homogeneous LDH dispersion were fabricated. • The properties of LLDPE/LDH composite films were improved. • LLDPE/LDH composite films show superior heat retention property.

  9. Large-scale fabrication of linear low density polyethylene/layered double hydroxides composite films with enhanced heat retention, thermal, mechanical, optical and water vapor barrier properties

    International Nuclear Information System (INIS)

    Xie, Jiazhuo; Zhang, Kun; Zhao, Qinghua; Wang, Qingguo; Xu, Jing

    2016-01-01

    Novel LDH intercalated with organic aliphatic long-chain anion was large-scale synthesized innovatively by high-energy ball milling in one pot. The linear low density polyethylene (LLDPE)/layered double hydroxides (LDH) composite films with enhanced heat retention, thermal, mechanical, optical and water vapor barrier properties were fabricated by melt blending and blowing process. FT IR, XRD, SEM results show that LDH particles were dispersed uniformly in the LLDPE composite films. Particularly, LLDPE composite film with 1% LDH exhibited the optimal performance among all the composite films with a 60.36% enhancement in the water vapor barrier property and a 45.73 °C increase in the temperature of maximum mass loss rate compared with pure LLDPE film. Furthermore, the improved infrared absorbance (1180–914 cm −1 ) of LLDPE/LDH films revealed the significant enhancement of heat retention. Therefore, this study prompts the application of LLDPE/LDH films as agricultural films with superior heat retention. - Graphical abstract: The fabrication process of LLDPE/LDH composite films. - Highlights: • LDH with basal spacing of 4.07 nm was synthesized by high-energy ball milling. • LLDPE composite films with homogeneous LDH dispersion were fabricated. • The properties of LLDPE/LDH composite films were improved. • LLDPE/LDH composite films show superior heat retention property.

  10. Physical model for vaporization

    OpenAIRE

    Garai, Jozsef

    2006-01-01

    Based on two assumptions, the surface layer is flexible, and the internal energy of the latent heat of vaporization is completely utilized by the atoms for overcoming on the surface resistance of the liquid, the enthalpy of vaporization was calculated for 45 elements. The theoretical values were tested against experiments with positive result.

  11. A Comparative Cycle and Refrigerant Simulation Procedure Applied on Air-Water Heat Pumps

    DEFF Research Database (Denmark)

    Mader, Gunda; Palm, Björn; Elmegaard, Brian

    2012-01-01

    A vapor compression heat pump absorbs heat from the environment at a low temperature level and rejects heat at a high temperature level. The bigger the difference between the two temperature levels the more challenging is it to gain high energy efficiency with a basic cycle layout as found in most...... small capacity heat pump applications today. Many of the applicable refrigerants also reach their technical limits regarding low vapor pressure for very low source temperatures and high discharge temperatures for high sink temperatures. These issues are especially manifest for air-water heat pumps. Many...... alternative cycle setups and refrigerants are known to improve the energy efficiency of a vapor compression cycle and reduce discharge temperatures. However not all of them are feasible for small capacity heat pumps from a cost and complexity point of view. This paper presents a novel numerical approach...

  12. Carbothermic Reduction Kinetics of Phosphorous Vaporization from Tri-calcium Phosphate (TCP) Under Microwave Rapid Heating With/Without the Presence of Fe3O4

    Science.gov (United States)

    Yoshikawa, Noboru; Sunako, Manami; Kawahira, Keita; Suzuki, Koki; Miyamoto, Kazunori; Taniguchi, Shoji

    2018-03-01

    The kinetics of vapor phase dephosphorization from tri-calcium phosphate (TCP) by carbothermic reduction was studied with and without the presence of Fe3O4. Microwave heating was utilized to obtain large variations in the heating rate (HR). In the reduction of TCP alone, the phosphorous removal fraction (RF; equal to ΔP2O5/P2O5 0 , where ΔP2O5 is the weight change and P2O5 0is the P2O5 weight before heating) decreased as the HR increased. In other words, a shorter residence time at a high temperature resulted in a smaller reduction fraction of TCP. An apparently third-order reaction was postulated to account for the kinetics using a fitting simulation based on the additive law of the reaction progress. On the other hand, the phosphorous removal (dephosphorization) rate (RR; equal to ΔP2O3/t MW, where tMW is the microwave heating time period) increased as the HR increased above 1200 °C. The reduction ratio of Fe3O4 above 1100 °C is higher than 97 pct regardless of the heating rate. The reduction of TCP in the presence of Fe3O4 showed that RF increased slightly with increasing HR despite a shorter residence time at a high temperature. The RR also increased with the HR even though RF decreased to half of the values observed in the cases without Fe3O4 for temperatures above 1200 °C. The practicality and optimal operation conditions of phosphorus vapor removal were discussed.

  13. Carbothermic Reduction Kinetics of Phosphorous Vaporization from Tri-calcium Phosphate (TCP) Under Microwave Rapid Heating With/Without the Presence of Fe3O4

    Science.gov (United States)

    Yoshikawa, Noboru; Sunako, Manami; Kawahira, Keita; Suzuki, Koki; Miyamoto, Kazunori; Taniguchi, Shoji

    2018-06-01

    The kinetics of vapor phase dephosphorization from tri-calcium phosphate (TCP) by carbothermic reduction was studied with and without the presence of Fe3O4. Microwave heating was utilized to obtain large variations in the heating rate (HR). In the reduction of TCP alone, the phosphorous removal fraction (RF; equal to ΔP2O5/P2O 5 0 , where ΔP2O5 is the weight change and P2O 5 0 is the P2O5 weight before heating) decreased as the HR increased. In other words, a shorter residence time at a high temperature resulted in a smaller reduction fraction of TCP. An apparently third-order reaction was postulated to account for the kinetics using a fitting simulation based on the additive law of the reaction progress. On the other hand, the phosphorous removal (dephosphorization) rate (RR; equal to ΔP2O3/ t MW, where tMW is the microwave heating time period) increased as the HR increased above 1200 °C. The reduction ratio of Fe3O4 above 1100 °C is higher than 97 pct regardless of the heating rate. The reduction of TCP in the presence of Fe3O4 showed that RF increased slightly with increasing HR despite a shorter residence time at a high temperature. The RR also increased with the HR even though RF decreased to half of the values observed in the cases without Fe3O4 for temperatures above 1200 °C. The practicality and optimal operation conditions of phosphorus vapor removal were discussed.

  14. Vapor pressure and evaporation rate of certain heat-resistant compounds in a vacuum at high temperatures

    Science.gov (United States)

    Bolgar, A. S.; Verkhoglyadova, T. S.; Samsonov, G. V.

    1985-01-01

    The vapor pressure and evaporation rate of borides of titanium, zirconium, and chrome; and of strontium and carbides of titanium, zirconium, and chrome, molybdenum silicide; and nitrides of titanium, niobium, and tantalum in a vacuum were studied. It is concluded that all subject compounds evaporate by molecular structures except AlB sub 12' which dissociates, losing the aluminum.

  15. Energies and carbon sinks

    International Nuclear Information System (INIS)

    Riedacker, A.

    2002-01-01

    The Kyoto Protocol puts a lot of emphasis on carbon sinks. This emphasis almost obliterates the other potential contributions of biomass in the fight against climatic changes and toward sustainable development. Biomass represents an infinite supply of renewable energy sources which do not increase the levels of carbon in the atmosphere, contribute to energy savings resulting from the use of wood rather than other materials, the sustainable management of soils, the fight against drought, agroforestry from which the production of foods depends, the mitigating of certain extreme climatic occurrences and the protection of dams from increased silting. The industrial revolution contributed to the increase in greenhouse gas emissions. When discussing some of the finer points of the Kyoto Protocol, the focus was placed on carbon sinks. The author indicates that the biomass cycle had to be considered, both in situ and ex situ. Details to this effect are provided, and a section dealing with greenhouse gases other than carbon must be taken into account. The rural environment must be considered globally. The author indicates that in the future, the emissions resulting from the transportation of agricultural products will have to be considered. Within the realm of the policies on sustainable development, the fight against climatic change represents only one aspect. In arid and semi-arid regions, one must take into account meeting the energy needs of the populations, the fight against drought and the preservation of biodiversity. The planting of trees offers multiple advantages apart from being a carbon sink: roughage, wood for burning, protection of soils, etc. A few examples are provided. 8 refs., 3 figs

  16. Sinking a Granular Raft

    Science.gov (United States)

    Protière, Suzie; Josserand, Christophe; Aristoff, Jeffrey M.; Stone, Howard A.; Abkarian, Manouk

    2017-03-01

    We report experiments that yield new insights on the behavior of granular rafts at an oil-water interface. We show that these particle aggregates can float or sink depending on dimensionless parameters taking into account the particle densities and size and the densities of the two fluids. We characterize the raft shape and stability and propose a model to predict its shape and maximum length to remain afloat. Finally we find that wrinkles and folds appear along the raft due to compression by its own weight, which can trigger destabilization. These features are characteristics of an elastic instability, which we discuss, including the limitations of our model.

  17. 水和丙酮工质的金属纤维毡蒸气腔热管的传热性能%Thermal performance of vapor chamber heat pipe with metal felt wick of water or acetone working fluid

    Institute of Scientific and Technical Information of China (English)

    徐鹏程; 陶汉中; 张红

    2015-01-01

    通过实验研究了金属纤维毡吸液芯蒸气腔热管的传热特性,测试了在单一热源下,不同热通量、风速以及工质种类时蒸气腔热管的启动性能与均温特性,并使用红外热像仪对蒸气腔热管冷凝端拍摄。实验中蒸气腔热管使用的工质分别为水与丙酮。实验结果表明:金属纤维毡蒸气腔热管的启动时间基本在3000 s左右;蒸气腔热管的蒸发端与冷凝端的等温性能良好,其中水工质的冷热端最小温差为1.35℃,因此使用金属纤维毡吸液芯蒸气腔热管可以避免电子器件的局部高温。%The heat transfer characteristics of the vapor chamber heat pipe with metal fiber felt wick were studied by experiments. Under different conditions, the isothermal characteristics and startup performance of the vapor chamber heat pipe using a single heat source were tested. The variables were heat flux, cooling wind speed and working fluid. The condenser section of the vapor chamber heat pipe was filmed by infrared thermography. The working fluid used in the vapor chamber heat pipe was water or acetone. The vapor chamber heat pipe could startup smoothly from ambient temperature at different heating powers, and startup time was about 3000 s. Both evaporator and condenser sections of the vapor chamber heat pipe had good isothermal performance, and the minimum temperature difference of the heat pipe using water as working fluid was 1.35℃. So electronic devices could avoid local high temperature by using the vapor chamber heat pipe with metal fiber felt wick.

  18. Hydrodynamics of vapor-liquid annular dispersed flows in channels with heated rod clusters under unsteady conditions

    International Nuclear Information System (INIS)

    Kroshilin, A.E.; Kroshilin, V.E.; Nigmatulin, B.I.

    1984-01-01

    A one-dimensional unsteady hydrodynamic model of vapour-liquid disperse-annular flows in channels with heated fuel rod clusters has been constructed. Regularities in the appearance of critical heat transfer due to the dryout of a near-wall liquid film on rod surfaces in such channels are investigated. The model developed takes into account the main flow regularities in the channels with heated rod clusters. The calculations made have shown that the time before crisis appearance agrees satisfactorily with the experimental data

  19. Hard X-ray photoelectron spectroscopy study for transport behavior of CsI in heating test simulating a BWR severe accident condition: Chemical effects of boron vapors

    Energy Technology Data Exchange (ETDEWEB)

    Okane, T., E-mail: okanet@spring8.or.jp [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Kobata, M. [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Sato, I. [Oarai Research and Development Center, Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Ibaraki, 311-1393 (Japan); Kobayashi, K. [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Osaka, M. [Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 4002 Narita-cho, Oarai-machi, Ibaraki, 311-1393 (Japan); Yamagami, H. [Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Kouto, Sayo-cho, Hyogo, 679-5148 (Japan); Faculty of Science, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8555 (Japan)

    2016-02-15

    Highlights: • We have clarified the temperature-dependent chemical forms of Cs/I products. • We have examined the CsI-decomposing effects of B{sub 2}O{sub 3} vapor. • The possibility of Cs re-evaporation from CsI-deposited surface is suggested. • We have demonstrated the usefulness of HAXPES on FP chemistry. - Abstract: Transport behavior of CsI in the heating test, which simulated a BWR severe accident, was investigated by hard X-ray photoelectron spectroscopy (HAXPES) with an emphasis on the chemical effect of boron vapors. CsI deposited on metal tube at temperatures ranging from 150 °C to 750 °C was reacted with vapor/aerosol B{sub 2}O{sub 3}, and the chemical form of reaction products on the sample surface was examined from the HAXPES spectra of core levels, e.g., Ni 2p, Cs 3d and I 3d levels, and valence band. For the samples at ∼300 °C, while the chemical form of major product on the sample surface without an exposure to B{sub 2}O{sub 3} was suggested to be CsI from the HAXPES spectra, an intensity ratio of Cs/I was dramatically reduced at the sample surface after the reaction with B{sub 2}O{sub 3}. The results suggest the possibility of significant decomposition of deposited CsI induced by the chemical reaction with B{sub 2}O{sub 3} at specific temperatures.

  20. Experimental study of the structure of vapor phase during boiling of R134a on heat exchange surfaces of heat pump

    Science.gov (United States)

    Ustinov, D. A.; Sukhikh, A. A.; Sidenkov, D. V.; Ustinov, V. A.

    2017-10-01

    The heat supply by means of heat pumps is considered now as a rational method of local heating which can lead to economy of primary fuel. At use of low-potential heat, for example, the heat of a ground (5 … 18 °C) or ground waters (8 … 10°C) only small depressing of temperature of these sources (on 3 … 5°C) is possible that demands application of heat exchangers with intensified heatmass transfer surfaces. In thermal laboratory of TOT department the 200 W experimental installation has been developed for research of process of boiling of freon R134a. The principle of action of the installation consists in realisation of reverse thermodynamic cycle and consecutive natural measurement of characteristics of elements of surfaces of heat exchangers of real installations at boiling points of freon from-10°C to +10°C and condensing temperatures from 15°C to 50 °C. The evaporator casing has optical windows for control of process of boiling of freon on ribbed on technology of distorting cut tubes. Temperature measurement in characteristic points of a cycle is provided by copper-constantan thermocouples which by means of ADT are connected to the computer that allows treat results of measurements in a real time mode. The structure of a two-phase flow investigated by means of the optical procedure based on laser technique.

  1. Trace metal analysis in arctic aerosols by an inductively coupled plasma-time of flight-mass spectrometer combined with an inductively heated vaporizer

    International Nuclear Information System (INIS)

    Luedke, Christian; Skole, Jochen; Taubner, Kerstin; Kriews, Michael

    2005-01-01

    Two newly developed instruments were combined to analyze the trace metal content in size separated arctic aerosols during the measurement campaign ASTAR 2004 (Arctic Study of Tropospheric Aerosols, Clouds and Radiation 2004) at Spitsbergen in May-June 2004. The aim of this extensive aerosol measurement campaign was to obtain a database for model-calculations of arctic aerosol, which play an important role in the global climate change. The ASTAR project was centered on two aircraft measurement campaigns, scheduled from 2004 to 2005, addressing both aerosol and cloud measurements, combined with ground-based and satellite observations. In the present paper one example for the analysis of ground-based aerosol particles is described. The sampling of aerosol particles was performed in a well-known manner by impaction of the particles on cleaned graphite targets. By means of a cascade impactor eight size classes between 0.35 and 16.6 μm aerodynamic diameters were separated. To analyze the metal content in the aerosol particles the targets were rapidly heated up to 2700 deg. C in an inductively heated vaporizer system (IHVS). An argon flow transports the vaporized sample material into the inductively coupled plasma (ICP) used as ionization source for the time of flight-mass spectrometer (TOF-MS). The simultaneous extraction of the ions from the plasma, as realized in the TOF instrument, allows to obtain the full mass spectrum of the sample during the vaporization pulse without any limitation in the number of elements detected. With optimized experimental parameters the element content in arctic aerosol particles was determined in a mass range between 7 Li and 209 Bi. Comparing the size distribution of the elemental content of the aerosol particles, two different meteorological situations were verified. For calibration acidified reference solutions were placed on the cleaned target inside the IHVS. The limits of detection (LOD) for the element mass on the target range

  2. Heat Removal Performance of Hybrid Control Rod for Passive In-Core Cooling System

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Mo; Jeong, Yeong Shin; Kim, In Guk; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of)

    2015-10-15

    The two-phase closed heat transfer device can be divided by thermosyphon heat pipe and capillary wicked heat pipe which uses gravitational force or capillary pumping pressure as a driving force of the convection of working fluid. If there is a temperature difference between reactor core and ultimate heat sink, the decay heat removal and reactor shutdown is possible at any accident conditions without external power sources. To apply the hybrid control rod to the commercial nuclear power plants, its modelling about various parameters is the most important work. Also, its unique geometry is coexistence of neutron absorber material and working fluid in a cladding material having annular vapor path. Although thermosyphon heat pipe (THP) or wicked heat pipe (WHP) shows high heat transfer coefficients for limited space, the maximum heat removal capacity is restricted by several phenomena due to their unique heat transfer mechanism. Validation of the existing correlations on the annular vapor path thermosyphon (ATHP) which has different wetted perimeter and heated diameter must be conducted. The effect of inner structure, and fill ratio of the working fluid on the thermal performance of heat pipe has not been investigated. As a first step of the development of hybrid heat pipe, the ATHP which contains neutron absorber in the concentric thermosyphon (CTHP) was prepared and the thermal performance of the annular thermosyphon was experimentally studied. The heat transfer characteristics and flooding limit of the annular vapor path thermosyphon was studied experimentally to model the performance of hybrid control rod. The following results were obtained: (1) The annular vapor path thermosyphon showed better evaporation heat transfer due to the enhanced convection between adiabatic and condenser section. (2) Effect of fill ratio on the heat transfer characteristics was negligible. (3) Existing correlations about flooding limit of thermosyphon could not reflect the annular vapor

  3. Effects of heat treatment on the microstructure of amorphous boron carbide coating deposited on graphite substrates by chemical vapor deposition

    International Nuclear Information System (INIS)

    Li Siwei; Zeng Bin; Feng Zude; Liu Yongsheng; Yang Wenbin; Cheng Laifei; Zhang Litong

    2010-01-01

    A two-layer boron carbide coating is deposited on a graphite substrate by chemical vapor deposition from a CH 4 /BCl 3 /H 2 precursor mixture at a low temperature of 950 o C and a reduced pressure of 10 KPa. Coated substrates are annealed at 1600 o C, 1700 o C, 1800 o C, 1900 o C and 2000 o C in high purity argon for 2 h, respectively. Structural evolution of the coatings is explored by electron microscopy and spectroscopy. Results demonstrate that the as-deposited coating is composed of pyrolytic carbon and amorphous boron carbide. A composition gradient of B and C is induced in each deposition. After annealing, B 4 C crystallites precipitate out of the amorphous boron carbide and grow to several hundreds nanometers by receiving B and C from boron-doped pyrolytic carbon. Energy-dispersive spectroscopy proves that the crystallization is controlled by element diffusion activated by high temperature annealing, after that a larger concentration gradient of B and C is induced in the coating. Quantified Raman spectrum identifies a graphitization enhancement of pyrolytic carbon. Transmission electron microscopy exhibits an epitaxial growth of B 4 C at layer/layer interface of the annealed coatings. Mechanism concerning the structural evolution on the basis of the experimental results is proposed.

  4. The influence of vapor superheating on the level of heat regeneration in a subcritical ORC coupled with gas power plant

    Science.gov (United States)

    Wiśniewski, Sławomir; Borsukiewicz-Gozdur, Aleksandra

    2010-09-01

    The authors presented problems related to utilization of exhaust gases of the gas turbine unit for production of electricity in an Organic Rankine Cycle (ORC) power plant. The study shows that the thermal coupling of ORC cycle with a gas turbine unit improves the efficiency of the system. The undertaken analysis concerned four the so called "dry" organic fluids: benzene, cyclohexane, decane and toluene. The paper also presents the way how to improve thermal efficiency of Clausius-Rankine cycle in ORC power plant. This method depends on applying heat regeneration in ORC cycle, which involves pre-heating the organic fluid via vapour leaving the ORC turbine. As calculations showed this solution allows to considerably raise the thermal efficiency of Clausius-Rankine cycle.

  5. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant.

    Science.gov (United States)

    Caleman, Carl; van Maaren, Paul J; Hong, Minyan; Hub, Jochen S; Costa, Luciano T; van der Spoel, David

    2012-01-10

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  6. Epitaxial growth of Si1−xGex alloys and Ge on Si(100) by electron-cyclotron-resonance Ar plasma chemical vapor deposition without substrate heating

    International Nuclear Information System (INIS)

    Ueno, Naofumi; Sakuraba, Masao; Murota, Junichi; Sato, Shigeo

    2014-01-01

    By using electron-cyclotron-resonance (ECR) Ar-plasma chemical vapor deposition (CVD) without substrate heating, the epitaxial growth process of Si 1−x Ge x alloy and Ge films deposited directly on dilute-HF-treated Si(100) was investigated. From the reflection high energy electron diffraction patterns of the deposited Si 1−x Ge x alloy (x = 0.50, 0.75) and Ge films on Si(100), it is confirmed that epitaxial growth can be realized without substrate heating, and that crystallinity degradation at larger film thickness is observed. The X-ray diffraction peak of the epitaxial films reveals the existence of large compressive strain, which is induced by lattice matching with the Si(100) substrate at smaller film thicknesses, as well as strain relaxation behavior at larger film thicknesses. The Ge fraction of Si 1−x Ge x thin film is in good agreement with the normalized GeH 4 partial pressure. The Si 1−x Ge x deposition rate increases with an increase of GeH 4 partial pressure. The GeH 4 partial pressure dependence of partial deposition rates [(Si or Ge fraction) × (Si 1−x Ge x thickness) / (deposition time)] shows that the Si partial deposition rate is slightly enhanced by the existence of Ge. From these results, it is proposed that the ECR-plasma CVD process can be utilized for Ge fraction control in highly-strained heterostructure formation of group IV semiconductors. - Highlights: • Si 1−x Ge x alloy and Ge were epitaxially grown on Si(100) without substrate heating. • Large strain and its relaxation behavior can be observed by X-ray diffraction. • Ge fraction of Si 1−x Ge x is equal to normalized GeH 4 partial pressure. • Si partial deposition rate is slightly enhanced by existence of Ge

  7. Development of producing equipment of mixed butane-air with low dew point. Energy saving dewatering apparatus and 6A-Gas producing apparatus utilizing vaporization latent heat of butane and potential heat of air

    Energy Technology Data Exchange (ETDEWEB)

    Komine, Jin; Okada, Hiroto; Taniue, Nobuo; Tanoue, Keiju; Yamada, Tatsuhiko; Maekawa, Hisami; Murakami, Keiji

    1988-02-10

    A producing equipment of mixed butane-air with low dew point was developed. The dewatering was made during the period from the middle of May to the middle of October with high atmospheric humidity. The production capacity of the mixed gas is 3000 Nm/sup 3/ of 22% of butane and 78% of air per hour. The designed dew point is 18/sup 0/C or less under the pressure of 0.7 kg/cm/sup 2/G. The saturation temperature is 7.5/sup 0/C after the liquid butane is evacuated by a regulating valve. The air introduced into the dehumidifier through finned tubes is cooled to dewater based on those data. The partially vaporized butane is completely gasified by hot water in a vaporizer and mixed with the dewatered air by a venture mixer to produce the mixed butane-air. When the dewatering is incomplete, the spray nozzle must be just exchanged. The dew point of the produced gas was sufficiently below the designed value. The investment cost is low. The total operating cost is reduced by the remarkably decreased fuel cost though the power cost is increased. The noise level is low and the heat control is easy. (11 figs, 4 tabs, 1 photo)

  8. The role of plantation sinks

    International Nuclear Information System (INIS)

    Read, Peter

    2001-01-01

    In this paper it is argued that in the long term biofuel should play a significant role in global climate policy. Recent technological developments, as well as sustainable development criteria, would favour growing biofuel in community- scale plantations in developing countries. It is also pointed out that the lead times involved in growing biofuels are so great that the inclusion of biofuel plantation sinks in the CDM for the first commitment period would be desirable. It is suggested that to meet opposition to the inclusion of plantation sinks in the first commitment period plantation, sinks should be linked to biofuels technology development and production, and a biofuels obligation for plantation sink projects in the CDM should be established. (Author)

  9. Tubing For Sampling Hydrazine Vapor

    Science.gov (United States)

    Travis, Josh; Taffe, Patricia S.; Rose-Pehrsson, Susan L.; Wyatt, Jeffrey R.

    1993-01-01

    Report evaluates flexible tubing used for transporting such hypergolic vapors as those of hydrazines for quantitative analysis. Describes experiments in which variety of tubing materials, chosen for their known compatibility with hydrazine, flexibility, and resistance to heat.

  10. Vapor pressures and thermophysical properties of selected hexenols and recommended vapor pressure for hexan-1-ol

    Czech Academy of Sciences Publication Activity Database

    Štejfa, V.; Fulem, Michal; Růžička, K.; Matějka, P.

    2015-01-01

    Roč. 402, Sep (2015), 18-29 ISSN 0378-3812 Institutional support: RVO:68378271 Keywords : alcohols * vapor pressure * heat capacity * ideal - gas thermodynamic properties * vaporization enthalpy Subject RIV: BJ - Thermodynamics Impact factor: 1.846, year: 2015

  11. Islands sinking; Land unter

    Energy Technology Data Exchange (ETDEWEB)

    Zimmermann, Joerg-Rainer

    2013-04-15

    The urbanization is a global trend. Today, 22 of the 30megacities, each with more than 10 million inhabitants, are located in developing countries and emerging countries. These megacities consume the most electricity: About two-thirds of the global consumption of electricity and heat are consumed in megacities. At the same time, the prosperity is concentrated in monopolies: In the last 50 years, the per capita income of the urban population has increased by about 150 %. The productivity of urban areas increases. Thus, cities are of central importance to our culture. If global warming is not stopped, climate change hits them with full force.

  12. Continuous condensation device for vapors in the atmosphere

    International Nuclear Information System (INIS)

    Tricot, M.

    1983-01-01

    The continuous condensation device for vapors from the atmosphere is such those in which this atmosphere circulates in contact with a cold source involving the condensation of these vapors. It includes a thermoelectric module using the Peltier effect; the hot side is bonded to a heat sink and the cold side is in contact with an insulated condensation chamber in which flows the atmosphere charged with vapors to be condensated. The condensation chamber has a metallic structure through which a low voltage direct current is passed; this structure has small blades with holes, through which the condensate flows under gravity in the lower part of the chamber which have a hole to evacuate this liquid. The thermoelectric module comprises an assembly of thermocouples made of an array of alloy plates. The temperature inside the condensation chamber is maintained at just above 0 0 C. This device is used for the sampling of atmosphere water especially in the determination of tritium content of the atmosphere around nuclear installations [fr

  13. Perlakuan Uap Panas (Vapor Heat Treatment untuk Disinfestasi Lalat Buah dan Mempertahankan Mutu Buah Belimbing (Averrhoa carambola L.

    Directory of Open Access Journals (Sweden)

    Eti Rohaeti

    2010-04-01

    Full Text Available The objectives of this research were to study mortality of carambola fruit fly (B. carambolae D & H and to study responses of VHT on quality of carambola (A. carambola L. Fruit fly mortality due to heat has been investigated by immersing fruit fly eggs into hot water at temperatures of 40, 43, 46 dan 49oC for 30 minutes and then at temperature of 46.5oC for 0, 5, 10, 15, 20, 25, 30 minutes. Star fruit were treated at temperature of 46.5oC for 5, 15, 30 minutes and then stored in temperatures of 5, 15oC and room temperature (28-30 oC. The result show that mortality has been achieved 100% at temperature more than 43.0oC for 30 minutes and at temperature 46.0oC for more than 15 minutes. VHT had significant influences to decrease the fruit respiration rates, chilling injury, antraknose, to increase the weight loss, color, and soluble solid content. However, there were no significant change in the hardness, water content, vitamin C and organoleptic test. VHT at temperature 46.5oC for 20 up to 30 minutes were effective to kill fruit flies inside carambola and VHT combined by storing in temperature of 15oC were able to maintain carambola quality during storage.

  14. Comparison of the Organic Flash Cycle (OFC) to other advanced vapor cycles for intermediate and high temperature waste heat reclamation and solar thermal energy

    International Nuclear Information System (INIS)

    Ho, Tony; Mao, Samuel S.; Greif, Ralph

    2012-01-01

    The Organic Flash Cycle (OFC) is proposed as a vapor power cycle that could potentially improve the efficiency with which high and intermediate temperature finite thermal sources are utilized. The OFC's aim is to improve temperature matching and reduce exergy losses during heat addition. A theoretical investigation is conducted using high accuracy equations of state such as BACKONE, Span–Wagner, and REFPROP in a detailed thermodynamic and exergetic analysis. The study examines 10 different aromatic hydrocarbons and siloxanes as potential working fluids. Comparisons are drawn between the OFC and an optimized basic Organic Rankine Cycle (ORC), a zeotropic Rankine cycle using a binary ammonia-water mixture, and a transcritical CO 2 cycle. Results showed aromatic hydrocarbons to be the better suited working fluid for the ORC and OFC due to higher power output and less complex turbine designs. Results also showed that the single flash OFC achieves comparable utilization efficiencies to the optimized basic ORC. Although the OFC improved heat addition exergetic efficiency, this advantage was negated by irreversibilities introduced during flash evaporation. A number of potentially significant improvements to the OFC are possible though which includes using a secondary flash stage or replacing the throttling valve with a two-phase expander. -- Highlights: ► The Organic Flash Cycle (OFC) is proposed to improve temperature matching. ► Ten aromatic hydrocarbon and siloxane working fluids are considered. ► Accurate equations of state explicit in Helmholtz energy are used in the analysis. ► The OFC is compared to basic ORCs, zeotropic, and transcritical cycles. ► The OFC achieves comparable power output to the optimized basic ORC.

  15. Determining Adequate Averaging Periods and Reference Coordinates for Eddy Covariance Measurements of Surface Heat and Water Vapor Fluxes over Mountainous Terrain

    Directory of Open Access Journals (Sweden)

    Yi-Ying Chen Ming-Hsu Li

    2012-01-01

    Full Text Available Two coordinate rotation approaches (double and planar-fit rotations and no rotation, in association with averaging periods of 15 - 480 min, were applied to compute surface heat and water vapor fluxes using the eddy covariance approach. Measurements were conducted in an experimental watershed, the Lien-Hua-Chih (LHC watershed, located in central Taiwan. For no rotation and double rotation approaches, an adequate averaging period of 15 or 30 min was suggested for better energy closure and small variations on energy closure fractions. For the planar-fit rotation approach, an adequate averaging period of 60 or 120 min was recommended, and a typical averaging period of 30 min is not superior to that of 60 or 120 min in terms of better energy closure and small variations on energy closure fractions. The Ogive function analysis revealed that the energy closure was improved with the increase of averaging time by capturing sensible heat fluxes at low-frequency ranges during certain midday hours at LHC site. Seasonal variations of daily energy closure fractions, high in dry season and low in wet season, were found to be associated with the surface dryness and strength of turbulent development. The mismatching of flux footprint areas among flux sensors was suggested as the cause of larger CF variations during the dry seasons as that indicated by the footprint analysis showing scattered source areas. During the wet season, the underestimation of turbulent fluxes by EC observations at the LHC site was attributed to weak turbulence developments as the source area identified by the footprint analysis was closer to the flux tower than those scattered in dry season.

  16. [Review of lime carbon sink.

    Science.gov (United States)

    Liu, Li Li; Ling, Jiang Hua; Tie, Li; Wang, Jiao Yue; Bing, Long Fei; Xi, Feng Ming

    2018-01-01

    Under the background of "missing carbon sink" mystery and carbon capture and storage (CCS) technology development, this paper summarized the lime material flow process carbon sink from the lime carbonation principles, impact factors, and lime utilization categories in chemical industry, metallurgy industry, construction industry, and lime kiln ash treatment. The results showed that the lime carbonation rate coefficients were mainly impacted by materials and ambient conditions; the lime carbon sink was mainly in chemical, metallurgy, and construction industries; and current researches focused on the mechanisms and impact factors for carbonation, but their carbon sequestration calculation methods had not been proposed. Therefore, future research should focus on following aspects: to establish a complete system of lime carbon sequestration accounting method in view of material flow; to calculate lime carbon sequestration in both China and the world and explain their offset proportion of CO 2 emission from lime industrial process; to analyze the contribution of lime carbon sequestration to missing carbon sink for clarifying part of missing carbon sinks; to promote the development of carbon capture and storage technology and provide some scientific bases for China's international negotiations on climate change.

  17. Cumulus convection and the terrestrial water-vapor distribution

    Science.gov (United States)

    Donner, Leo J.

    1988-01-01

    Cumulus convection plays a significant role in determining the structure of the terrestrial water vapor field. Cumulus convection acts directly on the moisture field by condensing and precipitating water vapor and by redistributing water vapor through cumulus induced eddy circulations. The mechanisms by which cumulus convection influences the terrestrial water vapor distribution is outlined. Calculations using a theory due to Kuo is used to illustrate the mechanisms by which cumulus convection works. Understanding of these processes greatly aids the ability of researchers to interpret the seasonal and spatial distribution of atmospheric water vapor by providing information on the nature of sources and sinks and the global circulation.

  18. Sinking bubbles in stout beers

    Science.gov (United States)

    Lee, W. T.; Kaar, S.; O'Brien, S. B. G.

    2018-04-01

    A surprising phenomenon witnessed by many is the sinking bubbles seen in a settling pint of stout beer. Bubbles are less dense than the surrounding fluid so how does this happen? Previous work has shown that the explanation lies in a circulation of fluid promoted by the tilted sides of the glass. However, this work has relied heavily on computational fluid dynamics (CFD) simulations. Here, we show that the phenomenon of sinking bubbles can be predicted using a simple analytic model. To make the model analytically tractable, we work in the limit of small bubbles and consider a simplified geometry. The model confirms both the existence of sinking bubbles and the previously proposed mechanism.

  19. Suppression of Frost Nucleation Achieved Using the Nanoengineered Integral Humidity Sink Effect.

    Science.gov (United States)

    Sun, Xiaoda; Rykaczewski, Konrad

    2017-01-24

    Inhibition of frost formation is important for increasing efficiency of refrigeration systems and heat exchangers, as well as for preventing the rapid icing over of water-repellant coatings that are designed to prevent accumulation of rime and glaze. From a thermodynamic point of view, this task can be achieved by either increasing hydrophobicity of the surface or decreasing the concentration of water vapor above it. The first approach has been studied in depth, but so far has not yielded a robust solution to the problem of frost formation. In this work, we systematically explore how frost growth can be inhibited by controlling water vapor concentration using bilayer coatings with a porous exterior covering a hygroscopic liquid-infused layer. We lay the theoretical foundation and provide experimental validation of the mass transport mechanism that governs the integral humidity sink effect based on this coating platform as well as reveal intriguing sizing effects about this system. We show that the concentration profile above periodically spaced pores is governed by the sink and source concentrations and two geometrical parameters: the nondimensional pore size and the ratio of the pore spacing to the boundary layer thickness. We demonstrate that when the ratio of the pore spacing to the boundary layer thickness vanishes, as for the nanoporous bilayer coatings, the entire surface concentration becomes uniform and equal to the concentration set by the hygroscopic liquid. In other words, the surface concentration becomes completely independent of the nanopore size. We identified the threshold geometrical parameters for this condition and show that it can lead to a 65 K decrease in the nucleation onset surface temperature below the dew point. With this fundamental insight, we use bilayer coatings to nanoengineer the integral humidity sink effect to provide extreme antifrosting performance with up to a 2 h delay in nucleation onset at 263 K. The nanoporous bilayer

  20. The lithium vapor box divertor

    International Nuclear Information System (INIS)

    Goldston, R J; Schwartz, J; Myers, R

    2016-01-01

    It has long been recognized that volumetric dissipation of the plasma heat flux from a fusion power system is preferable to its localized impingement on a material surface. Volumetric dissipation mitigates both the anticipated very high heat flux and intense particle-induced damage due to sputtering. Recent projections to a tokamak demonstration power plant suggest an immense upstream parallel heat flux, of order 20 GW m −2 , implying that fully detached operation may be a requirement for the success of fusion power. Building on pioneering work on the use of lithium by Nagayama et al and by Ono et al as well as earlier work on the gas box divertor by Watkins and Rebut, we present here a concept for a lithium vapor box divertor, in which lithium vapor extracts momentum and energy from a fusion-power-plant divertor plasma, using fully volumetric processes. At the high powers and pressures that are projected this requires a high density of lithium vapor, which must be isolated from the main plasma in order to avoid lithium build-up on the chamber walls or in the plasma. Isolation is achieved through a powerful multi-box differential pumping scheme available only for condensable vapors. The preliminary box-wise calculations are encouraging, but much more work is required to demonstrate the practical viability of this scheme, taking into account at least 2D plasma and vapor flows within and between the vapor boxes and out of the vapor boxes to the main plasma. (paper)

  1. Vapor generation methods for explosives detection research

    Energy Technology Data Exchange (ETDEWEB)

    Grate, Jay W.; Ewing, Robert G.; Atkinson, David A.

    2012-12-01

    The generation of calibrated vapor samples of explosives compounds remains a challenge due to the low vapor pressures of the explosives, adsorption of explosives on container and tubing walls, and the requirement to manage (typically) multiple temperature zones as the vapor is generated, diluted, and delivered. Methods that have been described to generate vapors can be classified as continuous or pulsed flow vapor generators. Vapor sources for continuous flow generators are typically explosives compounds supported on a solid support, or compounds contained in a permeation or diffusion device. Sources are held at elevated isothermal temperatures. Similar sources can be used for pulsed vapor generators; however, pulsed systems may also use injection of solutions onto heated surfaces with generation of both solvent and explosives vapors, transient peaks from a gas chromatograph, or vapors generated by s programmed thermal desorption. This article reviews vapor generator approaches with emphasis on the method of generating the vapors and on practical aspects of vapor dilution and handling. In addition, a gas chromatographic system with two ovens that is configurable with up to four heating ropes is proposed that could serve as a single integrated platform for explosives vapor generation and device testing. Issues related to standards, calibration, and safety are also discussed.

  2. How Low Can You Sink?

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 2; Issue 2. How Low Can You Sink? In Search of Global Minima. Vivek S Borkar. General Article Volume 2 ... Author Affiliations. Vivek S Borkar1. Department of Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India ...

  3. Laminar nanofluid flow in microheat-sinks

    Energy Technology Data Exchange (ETDEWEB)

    Koo, J.; Kleinstreuer, C. [North Carolina State University, Raleigh, NC (United States). Dept. of Mechanical and Aerospace Engineering

    2005-06-01

    In response to the ever increasing demand for smaller and lighter high-performance cooling devices, steady laminar liquid nanofluid flow in microchannels is simulated and analyzed. Considering two types of nanofluids, i.e., copper-oxide nanospheres at low volume concentrations in water or ethylene glycol, the conjugated heat transfer problem for microheat-sinks has been numerically solved. Employing new models for the effective thermal conductivity and dynamic viscosity of nanofluids, the impact of nanoparticle concentrations in these two mixture flows on the microchannel pressure gradients, temperature profiles and Nusselt numbers are computed, in light of aspect ratio, viscous dissipation, and enhanced temperature effects. Based on these results, the following can be recommended for microheat-sink performance improvements: Use of large high-Prandtl number carrier fluids, nanoparticles at high volume concentrations of about 4% with elevated thermal conductivities and dielectric constants very close to that of the carrier fluid, microchannels with high aspect ratios, and treated channel walls to avoid nanoparticle accumulation. (Author)

  4. Control system pre-feedbacked for the super heated steam temperature in heat recovering units; Sistema de control pre-retroalimentado para la temperatura de vapor sobrecalentado en recuperadores de calor

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Alvarez, Hilario; Madrigal Espinosa, Guadalupe [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1996-12-31

    The study that is presented corresponds to the analysis, design and development of a pre-feedbacked control system for the superheated steam temperature regulation in the heat recovery units of a combined cycle thermoelectric power plant. The designs of the feedback controller and the pre-feedback control system were implemented based in a linear model of the tempering zone. This linear model was obtained through the application of parametric identification techniques to the non-linear mathematical model of a combined cycle power plant. [Espanol] El estudio que se presenta corresponde al analisis, diseno y desarrollo de un sistema de control pre-retroalimentado para regular la temperatura de vapor sobrecalentado en los recuperadores de calor de una central termoelectrica de ciclo combinado. Los disenos del controlador retroalimentado y del sistema de control prealimentado se realizaron con base en un modelo lineal de la zona de atemperacion. Este modelo lineal se obtuvo aplicando tecnicas de identificacion parametrica al modelo matematico no-lineal de una central de ciclo combinado.

  5. Control system pre-feedbacked for the super heated steam temperature in heat recovering units; Sistema de control pre-retroalimentado para la temperatura de vapor sobrecalentado en recuperadores de calor

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Alvarez, Hilario; Madrigal Espinosa, Guadalupe [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1997-12-31

    The study that is presented corresponds to the analysis, design and development of a pre-feedbacked control system for the superheated steam temperature regulation in the heat recovery units of a combined cycle thermoelectric power plant. The designs of the feedback controller and the pre-feedback control system were implemented based in a linear model of the tempering zone. This linear model was obtained through the application of parametric identification techniques to the non-linear mathematical model of a combined cycle power plant. [Espanol] El estudio que se presenta corresponde al analisis, diseno y desarrollo de un sistema de control pre-retroalimentado para regular la temperatura de vapor sobrecalentado en los recuperadores de calor de una central termoelectrica de ciclo combinado. Los disenos del controlador retroalimentado y del sistema de control prealimentado se realizaron con base en un modelo lineal de la zona de atemperacion. Este modelo lineal se obtuvo aplicando tecnicas de identificacion parametrica al modelo matematico no-lineal de una central de ciclo combinado.

  6. Experimental Investigation of Heat Pipe Startup Under Reflux Mode

    Science.gov (United States)

    Ku, Jentung

    2018-01-01

    In the absence of body forces such as gravity, a heat pipe will start as soon as its evaporator temperature reaches the saturation temperature. If the heat pipe operates under a reflux mode in ground testing, the liquid puddle will fill the entire cross sectional area of the evaporator. Under this condition, the heat pipe may not start when the evaporator temperature reaches the saturation temperature. Instead, a superheat is required in order for the liquid to vaporize through nucleate boiling. The amount of superheat depends on several factors such as the roughness of the heat pipe internal surface and the gravity head. This paper describes an experimental investigation of the effect of gravity pressure head on the startup of a heat pipe under reflux mode. In this study, a heat pipe with internal axial grooves was placed in a vertical position with different tilt angles relative to the horizontal plane. Heat was applied to the evaporator at the bottom and cooling was provided to the condenser at the top. The liquid-flooded evaporator was divided into seven segments along the axial direction, and an electrical heater was attached to each evaporator segment. Heat was applied to individual heaters in various combinations and sequences. Other test variables included the condenser sink temperature and tilt angle. Test results show that as long as an individual evaporator segment was flooded with liquid initially, a superheat was required to vaporize the liquid in that segment. The amount of superheat required for liquid vaporization was a function of gravity pressure head imposed on that evaporator segment and the initial temperature of the heat pipe. The most efficient and effective way to start the heat pipe was to apply a heat load with a high heat flux to the lowest segment of the evaporator.

  7. A study of hear sink performance in air and soil for use in a thermoelectric energy harvesting device

    Science.gov (United States)

    Snyder, J.; Lawrence, E. E.

    2002-01-01

    A suggested application of a thermoelectric generator is to exploit the natural temperature difference between the air and the soil to generate small amounts of electrical energy. Since the conversion efficiency of even the best thermoelectric generators available is very low, the performance of the heat sinks providing the heat flow is critical. By providing a constant heat input to various heat sinks, field tests of their thermal conductances in soil and in air were performed. Aprototype device without a thermoelectric generator was constructed, buried, and monitored to experimentally measure the heat flow achievable in such a system. Theoretical considerations for design and selection of improved heat sinks are also presented. In particular, the method of shape factoranalysis is used to give rough estimates and upper bounds for the thermal conductance of a passive heat sink buried in soil.

  8. Tropical Wetlands as Carbon Sinks

    Science.gov (United States)

    Jones, M. B.; Saunders, M.

    2007-12-01

    This presentation focuses on the tropical wetlands of sub-Saharan Africa. These are an understudied ecosystem in which large emergent grasses and sedges normally dominate and which have the potential to sequester significant amounts of carbon. Measurements of Net Primary Production of these wetlands show that they are some of the highest values recorded for any ecosystem. We have used eddy covariance to measure Net Ecosystem Exchange of pristine and disturbed wetlands and show that pristine systems can have sink strengths as strong as tropical forests while disturbed systems that have been reclaimed for agricultural purposes have a very much reduced carbon sink activity and may be net carbon sources. The management issues surrounding the use of these wetlands illustrate a direct conflict between the production of food crops for the local population and the maintenance of carbon sequestration as an ecosystem service.

  9. Sinking offshore platform. Nedsenkbar fralandsplatform

    Energy Technology Data Exchange (ETDEWEB)

    Einstabland, T.B.; Olsen, O.

    1988-12-19

    The invention deals with a sinking offshore platform of the gravitational type designed for being installed on the sea bed on great depths. The platform consists of at least three inclining pillars placed on a foundation unit. The pillars are at the upper end connected to a tower structure by means of a rigid construction. The tower supports the platform deck. The rigid construction comprises a centre-positioned cylinder connected to the foundation. 11 figs.

  10. Condensation of vapor bubble in subcooled pool

    Science.gov (United States)

    Horiuchi, K.; Koiwa, Y.; Kaneko, T.; Ueno, I.

    2017-02-01

    We focus on condensation process of vapor bubble exposed to a pooled liquid of subcooled conditions. Two different geometries are employed in the present research; one is the evaporation on the heated surface, that is, subcooled pool boiling, and the other the injection of vapor into the subcooled pool. The test fluid is water, and all series of the experiments are conducted under the atmospheric pressure condition. The degree of subcooling is ranged from 10 to 40 K. Through the boiling experiment, unique phenomenon known as microbubble emission boiling (MEB) is introduced; this phenomenon realizes heat flux about 10 times higher than the critical heat flux. Condensation of the vapor bubble is the key phenomenon to supply ambient cold liquid to the heated surface. In order to understand the condensing process in the MEB, we prepare vapor in the vapor generator instead of the evaporation on the heated surface, and inject the vapor to expose the vapor bubble to the subcooled liquid. Special attention is paid to the dynamics of the vapor bubble detected by the high-speed video camera, and on the enhancement of the heat transfer due to the variation of interface area driven by the condensation.

  11. Verification of Carbon Sink Assessment. Can We Exclude Natural Sinks?

    International Nuclear Information System (INIS)

    Alexandrov, G.; Yamagata, Y

    2004-01-01

    Any human-induced terrestrial sink is susceptible to the effects of elevated atmospheric CO2 concentration, nitrogen deposition, climate variability and other natural or indirect human-induced factors. It has been suggested in climate negotiations that the effects of these factors should be excluded from estimates of carbon sequestration used to meet the emission reduction commitments under the Kyoto Protocol. This paper focuses on the methodologies for factoring out the effects of atmospheric and climate variability/change. We estimate the relative magnitude of the non-human induced effects by using two biosphere models and discuss possibilities for narrowing estimate uncertainty

  12. Trends and regional distributions of land and ocean carbon sinks

    Directory of Open Access Journals (Sweden)

    J. L. Sarmiento

    2010-08-01

    Full Text Available We show here an updated estimate of the net land carbon sink (NLS as a function of time from 1960 to 2007 calculated from the difference between fossil fuel emissions, the observed atmospheric growth rate, and the ocean uptake obtained by recent ocean model simulations forced with reanalysis wind stress and heat and water fluxes. Except for interannual variability, the net land carbon sink appears to have been relatively constant at a mean value of −0.27 Pg C yr−1 between 1960 and 1988, at which time it increased abruptly by −0.88 (−0.77 to −1.04 Pg C yr−1 to a new relatively constant mean of −1.15 Pg C yr−1 between 1989 and 2003/7 (the sign convention is negative out of the atmosphere. This result is detectable at the 99% level using a t-test. The land use source (LU is relatively constant over this entire time interval. While the LU estimate is highly uncertain, this does imply that most of the change in the net land carbon sink must be due to an abrupt increase in the land sink, LS = NLS – LU, in response to some as yet unknown combination of biogeochemical and climate forcing. A regional synthesis and assessment of the land carbon sources and sinks over the post 1988/1989 period reveals broad agreement that the Northern Hemisphere land is a major sink of atmospheric CO2, but there remain major discrepancies with regard to the sign and magnitude of the net flux to and from tropical land.

  13. A Lithium Vapor Box Divertor Similarity Experiment

    Science.gov (United States)

    Cohen, Robert A.; Emdee, Eric D.; Goldston, Robert J.; Jaworski, Michael A.; Schwartz, Jacob A.

    2017-10-01

    A lithium vapor box divertor offers an alternate means of managing the extreme power density of divertor plasmas by leveraging gaseous lithium to volumetrically extract power. The vapor box divertor is a baffled slot with liquid lithium coated walls held at temperatures which increase toward the divertor floor. The resulting vapor pressure differential drives gaseous lithium from hotter chambers into cooler ones, where the lithium condenses and returns. A similarity experiment was devised to investigate the advantages offered by a vapor box divertor design. We discuss the design, construction, and early findings of the vapor box divertor experiment including vapor can construction, power transfer calculations, joint integrity tests, and thermocouple data logging. Heat redistribution of an incident plasma-based heat flux from a typical linear plasma device is also presented. This work supported by DOE Contract No. DE-AC02-09CH11466 and The Princeton Environmental Institute.

  14. Constrained Vapor Bubble Experiment

    Science.gov (United States)

    Gokhale, Shripad; Plawsky, Joel; Wayner, Peter C., Jr.; Zheng, Ling; Wang, Ying-Xi

    2002-11-01

    Microgravity experiments on the Constrained Vapor Bubble Heat Exchanger, CVB, are being developed for the International Space Station. In particular, we present results of a precursory experimental and theoretical study of the vertical Constrained Vapor Bubble in the Earth's environment. A novel non-isothermal experimental setup was designed and built to study the transport processes in an ethanol/quartz vertical CVB system. Temperature profiles were measured using an in situ PC (personal computer)-based LabView data acquisition system via thermocouples. Film thickness profiles were measured using interferometry. A theoretical model was developed to predict the curvature profile of the stable film in the evaporator. The concept of the total amount of evaporation, which can be obtained directly by integrating the experimental temperature profile, was introduced. Experimentally measured curvature profiles are in good agreement with modeling results. For microgravity conditions, an analytical expression, which reveals an inherent relation between temperature and curvature profiles, was derived.

  15. Heating systems for heating subsurface formations

    Science.gov (United States)

    Nguyen, Scott Vinh [Houston, TX; Vinegar, Harold J [Bellaire, TX

    2011-04-26

    Methods and systems for heating a subsurface formation are described herein. A heating system for a subsurface formation includes a sealed conduit positioned in an opening in the formation and a heat source. The sealed conduit includes a heat transfer fluid. The heat source provides heat to a portion of the sealed conduit to change phase of the heat transfer fluid from a liquid to a vapor. The vapor in the sealed conduit rises in the sealed conduit, condenses to transfer heat to the formation and returns to the conduit portion as a liquid.

  16. Sink-to-Sink Coordination Framework Using RPL: Routing Protocol for Low Power and Lossy Networks

    Directory of Open Access Journals (Sweden)

    Meer M. Khan

    2016-01-01

    Full Text Available RPL (Routing Protocol for low power and Lossy networks is recommended by Internet Engineering Task Force (IETF for IPv6-based LLNs (Low Power and Lossy Networks. RPL uses a proactive routing approach and each node always maintains an active path to the sink node. Sink-to-sink coordination defines syntax and semantics for the exchange of any network defined parameters among sink nodes like network size, traffic load, mobility of a sink, and so forth. The coordination allows sink to learn about the network condition of neighboring sinks. As a result, sinks can make coordinated decision to increase/decrease their network size for optimizing over all network performance in terms of load sharing, increasing network lifetime, and lowering end-to-end latency of communication. Currently, RPL does not provide any coordination framework that can define message exchange between different sink nodes for enhancing the network performance. In this paper, a sink-to-sink coordination framework is proposed which utilizes the periodic route maintenance messages issued by RPL to exchange network status observed at a sink with its neighboring sinks. The proposed framework distributes network load among sink nodes for achieving higher throughputs and longer network’s life time.

  17. Mobile vapor recovery and vapor scavenging unit

    International Nuclear Information System (INIS)

    Stokes, C.A.; Steppe, D.E.

    1991-01-01

    This patent describes a mobile anti- pollution apparatus, for the recovery of hydrocarbon emissions. It comprises a mobile platform upon which is mounted a vapor recovery unit for recovering vapors including light hydrocarbons, the vapor recovery unit having an inlet and an outlet end, the inlet end adapted for coupling to an external source of hydrocarbon vapor emissions to recover a portion of the vapors including light hydrocarbons emitted therefrom, and the outlet end adapted for connection to a means for conveying unrecovered vapors to a vapor scavenging unit, the vapor scavenging unit comprising an internal combustion engine adapted for utilizing light hydrocarbon in the unrecovered vapors exiting from the vapor recovery unit as supplemental fuel

  18. Heat transfer system

    Science.gov (United States)

    Not Available

    1980-03-07

    A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

  19. Fracture as a material sink

    Science.gov (United States)

    Volokh, K. Y.

    2017-12-01

    Cracks are created by massive breakage of molecular or atomic bonds. The latter, in its turn, leads to the highly localized loss of material, which is the reason why even closed cracks are visible by a naked eye. Thus, fracture can be interpreted as the local material sink. Mass conservation is violated locally in the area of material failure. We consider a theoretical formulation of the coupled mass and momenta balance equations for a description of fracture. Our focus is on brittle fracture and we propose a finite strain hyperelastic thermodynamic framework for the coupled mass-flow-elastic boundary value problem. The attractiveness of the proposed framework as compared to the traditional continuum damage theories is that no internal parameters (like damage variables, phase fields, etc.) are used while the regularization of the failure localization is provided by the physically sound law of mass balance.

  20. Influence of boron vapor on transport behavior of deposited CsI during heating test simulating a BWR severe accident condition

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Isamu, E-mail: sato.isamu@jaea.go.jp; Onishi, Takashi; Tanaka, Kosuke; Iwasaki, Maho; Koyama, Shin-ichi

    2015-06-15

    In order to evaluate influence of B on the release and transport of Cs and I during severe accidents, basic experiments have been performed on the interaction between deposited Cs/I compounds and vapor/aerosol B compounds. CsI and B{sub 2}O{sub 3} were utilized as a Cs/I compound and a B compound, respectively. Deposited CsI on the thermal gradient tube (TGT) at temperatures ranging from 423 K to 1023 K was reacted with vapor/aerosol B{sub 2}O{sub 3}, and then observed how it changed Cs/I deposition profiles. As a result, vapor/aerosol B{sub 2}O{sub 3} stripped a portion of deposited CsI within a temperature range from 830 K to 920 K to make gaseous CsBO{sub 2} and I{sub 2}. In addition, gaseous I{sub 2} was re-deposited at a temperature range from 530 K to 740 K, while CsBO{sub 2} travelled through the sampling tubes and filters without deposition. It is evident that B enables Cs compounds such as CsBO{sub 2} to transport Cs to the colder regions.

  1. Vapor condensation device

    International Nuclear Information System (INIS)

    Sakurai, Manabu; Hirayama, Fumio; Kurosawa, Setsumi; Yoshikawa, Jun; Hosaka, Seiichi.

    1992-01-01

    The present invention enables to separate and remove 14 C as CO 3 - ions without condensation in a vapor condensation can of a nuclear facility. That is, the vapor condensation device of the nuclear facility comprises (1) a spray pipe for spraying an acidic aqueous solution to the evaporation surface of an evaporation section, (2) a spray pump for sending the acidic aqueous solution to the spray pipe, (3) a tank for storing the acidic aqueous solution, (4) a pH sensor for detecting pH of the evaporation section, (5) a pH control section for controlling the spray pump, depending on the result of the detection of the pH sensor. With such a constitution, the pH of liquid wastes on the vaporization surface is controlled to 7 by spraying an aqueous solution of dilute sulfuric acid to the evaporation surface, thereby enabling to increase the transfer rate of 14 C to condensates to 60 to 70%. If 14 C is separated and removed as a CO 2 gas from the evaporation surface, the pH of the liquid wastes returns to the alkaline range of 9 to 10 and the liquid wastes are returned to a heating section. The amount of spraying the aqueous solution of dilute sulfuric acid can be controlled till the pH is reduced to 5. (I.S.)

  2. Causes of sinks near Tucson, Arizona, USA

    Science.gov (United States)

    Hoffmann, J.P.; Pool, D.R.; Konieczki, A.D.; Carpenter, M.C.

    1998-01-01

    Land subsidence in the form of sinks has occurred on and near farmlands near Tucson, Pima County, Arizona, USA. The sinks occur in alluvial deposits along the flood plain of the Santa Cruz River, and have made farmlands dangerous and unsuitable for farming. More than 1700 sinks are confined to the flood plain of the Santa Cruz River and are grouped along two north-northwestward-trending bands that are approximately parallel to the river and other flood-plain drainages. An estimated 17,000 m3 of sediment have been removed in the formation of the sinks. Thirteen trenches were dug to depths of 4-6 m to characterize near-surface sediments in sink and nonsink areas. Sediments below about 2 m included a large percentage of dispersive clays in sink areas. Sediments in nonsink areas contain a large component of medium- to coarse-grained, moderately to well sorted sand that probably fills a paleochannel. Electromagnetic surveys support the association of silts and clays in sink areas that are highly electrically conductive relative to sand in nonsink areas. Sinks probably are caused by the near-surface process of subsurface erosion of dispersive sediments along pre-existing cracks in predominantly silt and clay sediments. The pre-existing cracks probably result from desiccation or tension that developed during periods of water-table decline and channel incision during the past 100 years or in earlier periods.

  3. Forest carbon sinks in the Northern Hemisphere

    Science.gov (United States)

    Christine L. Goodale; Michael J. Apps; Richard A. Birdsey; Christopher B. Field; Linda S. Heath; Richard A. Houghton; Jennifer C. Jenkins; Gundolf H. Kohlmaier; Werner Kurz; Shirong Liu; Gert-Jan Nabuurs; Sten Nilsson; Anatoly Z. Shvidenko

    2002-01-01

    There is general agreement that terrestrial systems in the Northern Hemisphere provide a significant sink for atmospheric CO2; however, estimates of the magnitude and distribution of this sink vary greatly. National forest inventories provide strong, measurement-based constraints on the magnitude of net forest carbon uptake. We brought together...

  4. Recommended vapor pressures for thiophene, sulfolane, and dimethyl sulfoxide

    Czech Academy of Sciences Publication Activity Database

    Fulem, Michal; Růžička, K.; Růžička, M.

    2011-01-01

    Roč. 303, č. 2 (2011), s. 205-216 ISSN 0378-3812 Institutional research plan: CEZ:AV0Z10100521 Keywords : thiophene sulfolane * dimethyl sulfoxide * vapor pressure * heat capacity * vaporization enthalpy * recommended vapor pressure equation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.139, year: 2011

  5. Petroleum Vapor Intrusion

    Science.gov (United States)

    One type of vapor intrusion is PVI, in which vapors from petroleum hydrocarbons such as gasoline, diesel, or jet fuel enter a building. Intrusion of contaminant vapors into indoor spaces is of concern.

  6. Experimental Study on Compression/Absorption High-Temperature Hybrid Heat Pump with Natural Refrigerant Mixture

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji Young; Park, Seong Ryong; Baik, Young Jin; Chang, Ki Chang; Ra, Ho Sang; Kim, Min Sung [Korea Institute of Energy Research, Daejeon (Korea, Republic of); Kim, Yong Chan [Korea University, Seoul (Korea, Republic of)

    2011-12-15

    This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than 90 .deg. C when the heat source and sink temperatures were 50 .deg. C. Experiments with various NH{sub 3}/H{sub 2}O mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific NH{sub 3} concentration.

  7. Energy Efficiency Evaluation and Economic Feasibility Analysis of a Geothermal Heating and Cooling System with a Vapor-Compression Chiller System

    Directory of Open Access Journals (Sweden)

    Muharrem Imal

    2015-09-01

    Full Text Available Increasing attention has been given to energy utilization in Turkey. In this report, we present an energy efficiency evaluation and economic feasibility analysis of a geothermal heating and cooling system (GSHP and a mechanical compression water chiller system (ACHP to improve the energy utilization efficiency and reduce the primary energy demand for industrial use. Analyses of a mechanical water chiller unit, GSW 180, and geothermal heating and cooling system, EAR 431 SK, were conducted in experimental working areas of the office buildings in a cigarette factory in Mersin, Turkey. The heating and cooling loads of the cigarette factory building were calculated, and actual thermal data were collected and analyzed. To calculate these loads, the cooling load temperature difference method was used. It was concluded that the geothermal heating and cooling system was more useful and productive and provides substantial economic benefits.

  8. Energy Efficiency Evaluation and Economic Feasibility Analysis of a Geothermal Heating and Cooling System with a Vapor-Compression Chiller System

    OpenAIRE

    Imal, Muharrem; Yılmaz, Koray; Pınarbaşı, Ahmet

    2015-01-01

    Increasing attention has been given to energy utilization in Turkey. In this report, we present an energy efficiency evaluation and economic feasibility analysis of a geothermal heating and cooling system (GSHP) and a mechanical compression water chiller system (ACHP) to improve the energy utilization efficiency and reduce the primary energy demand for industrial use. Analyses of a mechanical water chiller unit, GSW 180, and geothermal heating and cooling system, EAR 431 SK, were conducted in ...

  9. Ocean carbon sinks and international climate policy

    International Nuclear Information System (INIS)

    Rehdanz, Katrin; Tol, Richard S.J.; Wetzel, Patrick

    2006-01-01

    Terrestrial vegetation sinks have entered the Kyoto Protocol as offsets for anthropogenic greenhouse gas emissions, but ocean sinks have escaped attention. Ocean sinks are as unexplored and uncertain as were the terrestrial sinks at the time of negotiation of the Kyoto Protocol. It is not unlikely that certain countries will advocate the inclusion of ocean carbon sinks to reduce their emission reduction obligations in post-2012 negotiations. We use a simple model of the international market for carbon dioxide emissions to evaluate who would gain or loose from allowing for ocean carbon sinks. Our analysis is restricted to information on anthropogenic carbon sequestration within the exclusive economic zone of a country. We use information on the actual carbon flux and derive the human-induced uptake for the period from 1990 onwards. Like the carbon sequestration of business as usual forest management activities, natural ocean carbon sequestration applies at zero costs. The total amount of anthropogenic ocean carbon sequestration is large, also in the exclusive economic zones. As a consequence, it substantially alters the costs of emission reduction for most countries. Countries such as Australia, Denmark, France, Iceland, New Zealand, Norway and Portugal would gain substantially, and a large number of countries would benefit too. Current net exporters of carbon permits, particularly Russia, would gain less and oppose the inclusion of ocean carbon sinks

  10. Oil vaporizer

    Energy Technology Data Exchange (ETDEWEB)

    Dumontier, F

    1904-03-31

    An oil burner particularly applicable to heavy oils, composed essentially of one or more gasification chambers, heated by the flame from the burners, to which the combustible gases are fed by the collectors suitably fixed on the chambers, all parts of the apparatus and especially the gasification chambers being easily demountable to permit cleaning, and all arranged in such a manner as to avoid fouling by reducing or localizing the deposition of solid deposits in the coking chamber.

  11. Nonazeotropic Heat Pump

    Science.gov (United States)

    Ealker, David H.; Deming, Glenn

    1991-01-01

    Heat pump collects heat from water circulating in heat-rejection loop, raises temperature of collected heat, and transfers collected heat to water in separate pipe. Includes sealed motor/compressor with cooling coils, evaporator, and condenser, all mounted in outer housing. Gradients of temperature in evaporator and condenser increase heat-transfer efficiency of vapor-compression cycle. Intended to recover relatively-low-temperature waste heat and use it to make hot water.

  12. Prediction of critical heat flux for water in uniformly heated vertical ...

    African Journals Online (AJOL)

    Keywords: CHF - Heat transfer - Water vapor - Porous coated tubes. Auteur correspondant ... electrical and mechanical characteristics were well validated. Figure. 1 shows ... resistance to vapor filtration from the heating wall to the liquid bulk.

  13. A Possible Sink for Methane on Mars

    NARCIS (Netherlands)

    Nørnberg, P.; Jensen, S. J. K.; Skibsted, J.; Jakobsen, H. J.; ten Kate, I. L.; Gunnlaugsson, H. P.; Merrison, J. P.; Finster, K.; Bak, E.; Iversen, J. J.; Kondrup, J. C.

    2014-01-01

    Mechanical simulated wind activation of mineral surfaces act as a trap for Methane through formation of covalent Si-C bonds stable up to temperatures above 250 C. This mechanism is proposed as a Methane sink on Mars.

  14. Energy, exergy, economic (3E) analyses and multi-objective optimization of vapor absorption heat transformer using NSGA-II technique

    International Nuclear Information System (INIS)

    Jain, Vaibhav; Sachdeva, Gulshan

    2017-01-01

    Highlights: • Study includes energy, exergy and economic analyses of absorption heat transformer. • It addresses multi-objective optimization study using NSGA-II technique. • Total annual cost and total exergy destruction are simultaneously optimized. • Results with multi-objective optimized design are more acceptable than other. - Abstract: Present paper addresses the energy, exergy and economic (3E) analyses of absorption heat transformer (AHT) working with LiBr-H 2 O fluid pair. The heat exchangers namely absorber, condenser, evaporator, generator and solution heat exchanger are designed for the size and cost estimation of AHT. Later, the effect of operating variables is examined on the system performance, size and cost. Simulation studies showed a conflict between thermodynamic and economic performance of the system. The heat exchangers with lower investment cost showed high irreversible losses and vice versa. Thus, the operating variables of systems are determined economically as well as thermodynamically by implementing non-dominated sort genetic algorithm-II (NSGA-II) technique of multi-objective optimization. In present work, if the cost based optimized design is chosen, total exergy destruction is 2.4% higher than its minimum possible value; whereas, if total exergy based optimized design is chosen, total annual cost is 6.1% higher than its minimum possible value. On the other hands, total annual cost and total exergy destruction are only 1.0% and 0.8%, respectively more from their minimum possible values with multi-objective optimized design. Thus, the multi-objective optimized design of the AHT is best outcome than any other single-objective optimized designs.

  15. Temperature Oscillations in Loop Heat Pipes - A Revisit

    Science.gov (United States)

    Ku, Jentung

    2018-01-01

    Three types of temperature oscillation have been observed in the loop heat pipes. The first type is an ultra-high frequency temperature oscillation with a period on the order of seconds or less. This type of temperature oscillation is of little significance in spacecraft thermal control because the amplitude is in the noise level. The second type is a high frequency, low amplitude temperature oscillation with a period on the order of seconds to minutes and an amplitude on the order of one Kelvin. It is caused by the back-and-forth movement of the vapor front near the inlet or outlet of the condenser. The third type is a low frequency, high amplitude oscillation with a period on the order of hours and an amplitude on the order of tens of Kelvin. It is caused by the modulation of the net heat load into the evaporator by the attached large thermal mass which absorbs and releases energy alternately. Several papers on LHP temperature oscillation have been published. This paper presents a further study on the underlying physical processes during the LHP temperature oscillation, with an emphasis on the third type of temperature oscillation. Specifically, equations governing the thermal and hydraulic behaviors of LHP operation will be used to describe interactions among LHP components, heat source, and heat sink. The following sequence of events and their interrelationship will also be explored: 1) maxima and minima of reservoir and thermal mass temperatures; 2) the range of the vapor front movement inside the condenser; 3) rates of change of the reservoir and thermal mass temperatures; 4) the rate of heat absorption and heat release by the thermal mass and the rate of vapor front movement; and 5) inflection points of the reservoir and thermal mass temperatures.

  16. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    Directory of Open Access Journals (Sweden)

    Tamil Many K Thandavan

    Full Text Available Vapor phase transport (VPT assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn was used to prepare un-doped and Al-doped zinc oxide (ZnO nanostructures (NSs. The structure and morphology were characterized by field emission scanning electron microscopy (FESEM and x-ray diffraction (XRD. Photoluminescence (PL properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni, oxygen interstitials (Oi, zinc vacancy (Vzn, singly charged zinc vacancy (VZn-, oxygen vacancy (Vo, singly charged oxygen vacancy (Vo+ and oxygen anti-site defects (OZn in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs.

  17. Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

    Science.gov (United States)

    Thandavan, Tamil Many K; Gani, Siti Meriam Abdul; San Wong, Chiow; Md Nor, Roslan

    2015-01-01

    Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs.

  18. Experimental study on heat transfer with condensation of vapors of pure nitrogen tetroxide with nitrogen oxide additions on a bundle of horizontal tubes

    International Nuclear Information System (INIS)

    Batishcheva, T.M.; Derov, B.T.; Kolykhan, L.I.; Pulyaev, V.F.

    1977-01-01

    The results of an experimental investigation of heat transfer during condensation of pure N 2 O 4 vapours and with NO admixtures on the outside surface of a bundle of horizontal tubes are considered. The tests with pure N 2 O 4 have been performed at pressures between 0.3-1.0 MPa in the range of thermal loads 22-121 kW/m 2 , temperature heads of 5-33 grades with complete condensation and evaporation. The content of admixtures boiling at high temperatures do not exceed 0.8%. A concentration of noncondensing nitrogen oxide in a gas phase have changed in the range of 3-27%. It is shown, that a concentration of noncondensible NO doesn't result in a considerable decrease of the heat transfer intensity as well as in the case of condensation of vapour-liquid mixtures. The generalized criterion relations are presented

  19. Numerical and experimental analysis of heat pipes with application in concentrated solar power systems

    Science.gov (United States)

    Mahdavi, Mahboobe

    Thermal energy storage systems as an integral part of concentrated solar power plants improve the performance of the system by mitigating the mismatch between the energy supply and the energy demand. Using a phase change material (PCM) to store energy increases the energy density, hence, reduces the size and cost of the system. However, the performance is limited by the low thermal conductivity of the PCM, which decreases the heat transfer rate between the heat source and PCM, which therefore prolongs the melting, or solidification process, and results in overheating the interface wall. To address this issue, heat pipes are embedded in the PCM to enhance the heat transfer from the receiver to the PCM, and from the PCM to the heat sink during charging and discharging processes, respectively. In the current study, the thermal-fluid phenomenon inside a heat pipe was investigated. The heat pipe network is specifically configured to be implemented in a thermal energy storage unit for a concentrated solar power system. The configuration allows for simultaneous power generation and energy storage for later use. The network is composed of a main heat pipe and an array of secondary heat pipes. The primary heat pipe has a disk-shaped evaporator and a disk-shaped condenser, which are connected via an adiabatic section. The secondary heat pipes are attached to the condenser of the primary heat pipe and they are surrounded by PCM. The other side of the condenser is connected to a heat engine and serves as its heat acceptor. The applied thermal energy to the disk-shaped evaporator changes the phase of working fluid in the wick structure from liquid to vapor. The vapor pressure drives it through the adiabatic section to the condenser where the vapor condenses and releases its heat to a heat engine. It should be noted that the condensed working fluid is returned to the evaporator by the capillary forces of the wick. The extra heat is then delivered to the phase change material

  20. A Feasibility Study on District Heating and Cooling Business Using Urban Waste Heat

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Joon; Choi, Byoung Youn; Lee, Kyoung Ho; Lee, Jae Bong [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Yoo, Jae In; Yoon, Jae Ho; Oh, Myung Do; Park, Moon Su; Kang, Han Kee; Yoo, Kyeoung Hoon; Bak, Jong Heon; Kim, Sun Chang; Park, Heong Kee; Bae, Tae Sik [Korea Academy of Industrial Technology, Seoul (Korea, Republic of)

    1996-12-31

    Investigation of papers related to waste heat utilization using heat pump. Estimate of various kinds of urban waste heat in korea. Investigation and study on optimal control of district heating and cooling system. Prediction of energy saving and environmental benefits when the urban waste heat will be used as heat source and sink of heat pump for district heating and cooling. Estimation of economic feasibility on district heating and cooling project utilizing urban waste heat. (author). 51 refs., figs

  1. Sink Potential of Canadian Agricultural Soils

    International Nuclear Information System (INIS)

    Boehm, M.; Junkins, B.; Desjardins, R.; Lindwall, W.; Kulshreshtha, S.

    2004-01-01

    Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO2-Eq yr-1 in 1990 to 52 Tg CO2-Eq yr-1 in 2008. Adoption of the sink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO2-Eq yr-1 (L), 42 Tg CO2-Eq yr-1 (M) or 36 Tg CO2-Eq yr-1 (H). Among the sink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH4 and N2O emissions from enteric fermentation and manure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992)

  2. A Comparative Study of Three Different Chemical Vapor Deposition Techniques of Carbon Nanotube Growth on Diamond Films

    Directory of Open Access Journals (Sweden)

    Betty T. Quinton

    2013-01-01

    Full Text Available This paper compares between the methods of growing carbon nanotubes (CNTs on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD techniques for growing CNTs on diamond: thermal CVD (T-CVD, microwave plasma-enhanced CVD (MPE-CVD, and floating catalyst thermal CVD (FCT-CVD. Scanning electron microscopy (SEM and high-resolution transmission electron microscopy (TEM were used to analyze the morphology and topology of the CNTs. Raman spectroscopy was used to assess the quality of the CNTs by determining the ID/IG peak intensity ratios. Additionally, the CNT/diamond samples were sonicated for qualitative comparisons of the durability of the CNT forests. T-CVD provided the largest diameter tubes, with catalysts residing mainly at the CNT/diamond interface. The MPE-CVD process yielded non uniform defective CNTs, and FCT-CVD resulted in the smallest diameter CNTs with catalyst particles imbedded throughout the length of the nanotubes.

  3. Technical and Economic Working Domains of Industrial Heat Pumps: Part 1 - Vapour Compression Heat Pumps

    DEFF Research Database (Denmark)

    Ommen, Torben Schmidt; Jensen, Jonas Kjær; Markussen, Wiebke Brix

    2014-01-01

    A large amount of operational and economic constraints limit the applicability of heat pumps operated with natural working fluids. The limitations are highly dependent on the integration of heat source and sink streams. An evaluation of feasible operating conditions is carried out considering...... the constraints of available refrigeration equipment and a requirement of a positive Net Present Value of the investment. The considered sink outlet temperature range is from 40 °C to 140 °C, but for the heat pumps considered in this paper, the upper limit is 100 °C. Five heat pumps are studied. For each set...... of heat sink and source temperatures the optimal solution is determined. At low sink temperature glide R717 heat pumps show best performance, while at higher sink glide transcritical R744 may become important. In a second paper, the results of the VCHP are compared to a similar study considering...

  4. The non-Newtonian heat and mass transport of He 2 in porous media used for vapor-liquid phase separation. Ph.D. Thesis

    Science.gov (United States)

    Yuan, S. W. K.

    1985-01-01

    This investigation of vapor-liquid phase separation (VLPS) of He 2 is related to long-term storage of cryogenic liquid. The VLPS system utilizes porous plugs in order to generate thermomechanical (thermo-osmotic) force which in turn prevents liquid from flowing out of the cryo-vessel (e.g., Infrared Astronomical Satellite). An apparatus was built and VLPS data were collected for a 2 and a 10 micrometer sintered stainless steel plug and a 5 to 15 micrometer sintered bronze plug. The VLPS data obtained at high temperature were in the nonlinear turbulent regime. At low temperature, the Stokes regime was approached. A turbulent flow model was developed, which provides a phenomenological description of the VLPS data. According to the model, most of the phase separation data are in the turbulent regime. The model is based on concepts of the Gorter-Mellink transport involving the mutual friction known from the zero net mass flow (ZNMF) studies. The latter had to be modified to obtain agreement with the present experimental VLPS evidence. In contrast to the well-known ZNMF mode, the VLPS results require a geometry dependent constant (Gorter-Mellink constant). A theoretical interpretation of the phenomenological equation for the VLPS data obtained, is based on modelling of the dynamics of quantized vortices proposed by Vinen. In extending Vinen's model to the VLPS transport of He 2 in porous media, a correlation between the K*(GM) and K(p) was obtained which permits an interpretation of the present findings. As K(p) is crucial, various methods were introduced to measure the permeability of the porous media at low temperatures. Good agreement was found between the room temperature and the low temperature K(p)-value of the plugs.

  5. Analysis regarding steam generator furnace's incident heat, temperature and composition of combustion gases; Analisis de calor incidente, temperatura y composicion de gases de combustion en hornos de generadores de vapor

    Energy Technology Data Exchange (ETDEWEB)

    Diego Marin, Antonio [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2006-07-01

    In order to obtain more precise evaluations of the combustion process in the furnace of a steam generator a suction pyrometer has been integrated to measure the temperature of the combustion gases; an ellipsoidal radiometer to measure the incident heat by thermal radiation in the water walls; a water cooled probe to determine the particle concentration, as well as a water cooled probe to determine the composition of the combustion gases present. This document clarifies the form of use of these instruments and their engineering specifications, simultaneously presenting an analysis that considers, unlike others, the internal conditions of the furnace to obtain a more precise evaluation of the efficiency that the combustion process presents and bases for the taking of preventive actions in specific zones of the furnace. Thus, the present work exhibits instruments and techniques of analysis to study the phenomena occurring within a steam generator. [Spanish] Con el fin de obtener evaluaciones mas precisas del proceso de combustion en el horno de un generador de vapor, se ha integrado un pirometro de succion para medir la temperatura de los gases de combustion; un radiometro elipsoidal para medir el calor incidente por radiacion termica en las paredes del agua; una sonda enfriada con agua para determinar la concentracion de particulas, asi como una sonda refrigerada con agua para determinar la composicion de los gases de combustion presentes. Este documento aclara la forma de uso de estos instrumentos y sus especificaciones tecnicas, a la vez que presenta un analisis que considera, a diferencia de otros, las condiciones internas del horno para obtener una evaluacion mas precisa sobre la eficiencia del proceso de combustion y bases para la toma de acciones preventivas en zonas especificas del horno. Asi, el presente trabajo exhibe instrumentos y tecnicas de analisis para estudiar los fenomenos que ocurren dentro de un generador de vapor.

  6. Landfills as sinks for (hazardous) substances.

    Science.gov (United States)

    Scharff, Heijo

    2012-12-01

    The primary goal of waste regulations is to protect human health and the environment. This requires the removal from the material cycle of those materials that cannot be processed without harm. Policies to promote recycling hold a risk that pollutants are dispersed. Materials have an environmental impact during their entire life cycle from extraction through production, consumption and recycling to disposal. Essentially there are only two routes for pollutants that cannot be rendered harmless: storage in sinks or dispersion into the environment. Many sinks do not contain substances absolutely, but result in slow dispersion. Dispersion leads to exposure and impact to human health and the environment. It is therefore important to assess the impact of the release to the environment. Based on various sources this paper discusses important material flows and their potential impact. This is compared with the intentions and achievements of European environmental and resource policy. The polluter pays principle is being implemented in Europe, but lags behind implementation of waste management regulations. As long as producers are allowed to add hazardous substances to their products and don't take their products back, it is in society's best interest to carefully consider whether recycling or storage in a sink is the better solution. This requires further development of life-cycle assessment tools and harmonization of regulations. In many cases the sink is unavoidable. Landfills as sinks will be needed in the future. Fail-safe design and construction as well as sustainable management of landfills must be further developed.

  7. Inyección de aire secundario caliente en calderas de vapor bagaceras y su influencia en el rendimiento térmico Injection of heated secondary air in steam bagasse boilers and its influence on thermal efficiency

    Directory of Open Access Journals (Sweden)

    Marcos A. Golato

    2005-12-01

    Full Text Available Como alternativa para aumentar la eficiencia térmica de calderas bagaceras productoras de vapor, se evalúa la inyección de aire secundario al hogar, previamente calentado. Además, se reúne información sobre la combustión y los factores que influyen en dicho fenómeno. Se calculó el rendimiento térmico en una caldera bagacera con inyección de aire secundario frío, mediante el empleo de balances de masa y energía con datos de ensayos experimentales. Se planteó luego un modelo teórico para el caso de calentar todo este aire secundario, y se determinó el nuevo rendimiento térmico. Finalmente se realizó un análisis técnico-económico para evaluar la rentabilidad del uso de esta tecnología, teniendo en cuenta el ahorro de bagazo y su equivalente en gas natural. Para el caso analizado, los resultados mostraron: aumento del rendimiento térmico de la caldera (1,62 puntos; mejora del índice de generación de vapor (2,27%; reducción del consumo de bagazo (2,45%; aceptable periodo de repago de la inversión (114 días de zafra.Previously heated secondary air injection is evaluated as an alternative to increase thermal efficiency of bagasse steam boilers. Aspects regarding the combustion process and the factors affecting it are also described. Tests were made in a bagasse boiler of a sugar mill. Thermal efficiency of the bagasse boiler with cold secondary air injection was determined by solving mass and energy balances. A new thermal efficiency for the case in which all secondary air is pre-heated with hot gases was determined afterwards. Finally, a technical-economic analysis was made to evaluate the yield of this technology, taking into account bagasse saving and its equivalent in natural gas. For the analyzed case, the results showed: an increase in the thermal efficiency of the boiler (1,62 points; a higher steam production index (2,27%; a reduction in bagasse consumption (2,45%; an acceptable payback period of the investment (114

  8. Numerical study of natural melt convection in cylindrical cavity with hot walls and cold bottom sink

    Directory of Open Access Journals (Sweden)

    Ahmanache Abdennacer

    2013-01-01

    Full Text Available Numerical study of natural convection heat transfer and fluid flow in cylindrical cavity with hot walls and cold sink is conducted. Calculations are performed in terms of the cavity aspect ratio, the heat exchanger length and the thermo physical properties expressed via the Prandtl number and the Rayleigh number. Results are presented in the form of isotherms, streamlines, average Nusselt number and average bulk temperature for a range of Rayleigh number up to 106. It is observed that Rayleigh number and heat exchanger length influences fluid flow and heat transfer, whereas the cavity aspect ratio has no significant effects.

  9. Sources, sinks, trends, and opportunities

    International Nuclear Information System (INIS)

    Ciborowski, P.

    1989-01-01

    Each year the emission of greenhouse gases commits the earth to a warming of 0.02 to 0.06 degrees C. Many of these gases are released as by-products of fossil fuel combustion. The remainder are produced as a result of forest clearing in the tropics or agriculture or industrial activities. Carbon dioxide (CO 2 ) is the most important greenhouse gas, contributing about half of global heating. In addition, there are what are known as the non-CO 2 greenhouse gases: methane (CH 4 ), nitrous oxide (N 2 O), freon CFC-12 (CF 2 Cl 2 ), freon CFC-11 (CF 3 Cl), and tropospheric ozone (O 3 ). Carbon monoxide and the nitrogen gases, increase the amount of methane and ozone in the troposphere. There are also about 15 or 20 other greenhouse gases of lesser importance. This paper reviews the sources of some of these greenhouse gases, analyzes trends in their emissions, and suggests means through which greenhouse gas emissions can be limited

  10. Heat sinking of highly integrated photonic and electronic circuits

    NARCIS (Netherlands)

    van Rijn, M.B.J.; Smit, M.K.

    2017-01-01

    Dense integration of photonic and electronic circuits poses high requirements on thermal management. In this paper we present analysis of temperature distributions in PICs in InP membranes on top of a BiCMOS chip, which contain hot spots in both the photonic and the electronic layer (lasers, optical

  11. Cost Estimates Of Concentrated Photovoltaic Heat Sink Production

    Science.gov (United States)

    2016-06-01

    PV), return on investment (ROI) 15. NUMBER OF PAGES 59 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18. SECURITY...improvements increase overall system returns on investment and 11 provide pathways for further reduction in system costs (Phillips et al., 2015). Phillips...generation. As the CPV market has matured, production costs have come down to near flat-panel photovoltaic (PV) production costs. CPV units

  12. Capillary-Condenser-Pumped Heat-Transfer Loop

    Science.gov (United States)

    Silverstein, Calvin C.

    1989-01-01

    Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.

  13. Collapsing criteria for vapor film around solid spheres as a fundamental stage leading to vapor explosion

    International Nuclear Information System (INIS)

    Freud, Roy; Harari, Ronen; Sher, Eran

    2009-01-01

    Following a partial fuel-melting accident, a Fuel-Coolant Interaction (FCI) can result with the fragmentation of the melt into tiny droplets. A vapor film is then formed between the melt fragments and the coolant, while preventing a contact between them. Triggering, propagation and expansion typically follow the premixing stage. In the triggering stage, vapor film collapse around one or several of the fragments occurs. This collapse can be the result of fragments cooling, a sort of mechanical force, or by any other means. When the vapor film collapses and the coolant re-establishes contact with the dry surface of the hot melt, it may lead to a very rapid and rather violent boiling. In the propagation stage the shock wave front leads to stripping of the films surrounding adjacent droplets which enhance the fragmentation and the process escalates. During this process a large quantity of liquid vaporizes and its expansion can result in destructive mechanical damage to the surrounding structures. This multiphase thermal detonation in which high pressure shock wave is formed is regarded as 'vapor explosion'. The film boiling and its possible collapse is a fundamental stage leading to vapor explosion. If the interaction of the melt and the coolant does not result in a film boiling, no explosion occurs. Many studies have been devoted to determine the minimum temperature and heat flux that is required to maintain a film boiling. The present experimental study examines the minimum temperature that is required to maintain a film boiling around metal spheres immersed into a liquid (subcooled distilled water) reservoir. In order to simulate fuel fragments that are small in dimension and has mirror-like surface, small spheres coated with anti-oxidation layer were used. The heat flux from the spheres was calculated from the sphere's temperature profiles and the sphere's properties. The vapor film collapse was associated with a sharp rise of the heat flux during the cooling

  14. Pumped two-phase heat transfer loop

    Science.gov (United States)

    Edelstein, Fred

    1988-01-01

    A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

  15. Measurement and analysis of transient vaporization in oxide fuel materials

    International Nuclear Information System (INIS)

    Benson, D.A.; Bergeron, E.G.

    1979-01-01

    This paper describes a series of experiments in which samples are heated to produce high vapor pressure states in times of 10 -6 to 10 -3 seconds. Experimental measurements of vapor pressures over fresh UO 2 from the pulsed electron beam and pulsed reactor heating tests are presented and compared with other high temperature data. The interpretation of the vapor pressure measured in the tests is discussed in detail. Effects of original sample stoichiometry, chemical interactions with the container and non-equilibrium evaporation due to induced temperature gradients are discussed. Special attention is given to dynamic behavior in rapid heating and vaporization of the oxide due to chemical non-equilibrium. Finally, similar projected reactor experiments on irradiated fuel are described and vapor pressure predictions made using available equilibrium models. A discussion of information accessible from such future tests and its importance is presented. (orig.) [de

  16. Measurement and analysis of transient vaporization in oxide fuel materials

    International Nuclear Information System (INIS)

    Gorham-Bergeron, E.; Benson, D.A.

    1978-01-01

    A series of experiments is described in which samples are heated to produce high vapor pressure states in times of 10 -6 to 10 -3 seconds. Experimental measurements of vapor pressures over fresh UO 2 from the pulsed electron beam and pulsed reactor heating tests are presented and compared with other high temperature data. The interpretation of the vapor pressures measured in the tests is discussed in detail. Effects of original sample stoichiometry, chemical interactions with the container and non-equilibrium evaporation due to induced temperature gradients are discussed. Special attention is given to dynamic behavior in rapid heating and vaporization of the oxide due to chemical nonequilibrium. Finally, similar projected reactor experiments on irradiated fuel are described and vapor pressure predictions made using available equilibrium models. A discussion of information accessible from such future tests and its importance is presented

  17. Development and Validation of Water Vapor Tracers as Diagnostics for the Atmospheric Hydrologic Cycle

    Science.gov (United States)

    Bosilovich, Michael G.; Schubert, Siegfried D.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    Understanding of the local and remote sources of water vapor can be a valuable diagnostic in understanding the regional atmospheric hydrologic cycle. In the present study, we have implemented passive tracers as prognostic variables to follow water vapor evaporated in predetermined regions until the water tracer precipitates. The formulation of the sources and sinks of tracer water is generally proportional to the prognostic water vapor variable. Because all water has been accounted for in tracers, the water vapor variable provides the validation of the tracer water and the formulation of the sources and sinks. The tracers have been implemented in a GEOS General Circulation Model (GCM) simulation consisting of several summer periods to determine the source regions of precipitation for the United States and India. The recycling of water and interannual variability of the sources of water will be examined. Potential uses in GCM sensitivity studies, predictability studies and data assimilation will be discussed.

  18. Patterns of Seasonal Heat Uptake and Release Over the Arctic Ocean Between 1979-2016

    Science.gov (United States)

    Helmberger, M. N.; Serreze, M. C.

    2017-12-01

    As the Arctic Ocean loses its sea ice cover, there is a stronger oceanic heat gain from the surface fluxes throughout the spring and summer; ultimately meaning that there is more energy to transfer out of the ocean to the atmosphere and outer space in the autumn and winter. Recent work has shown that the increased oceanic heat content at the end of summer in turn delays autumn ice growth, with implications for marine shipping and other economic activities. Some of the autumn and winter heat loss to the atmosphere is represented by evaporation, which increases the atmospheric water vapor content, and there is growing evidence that this is contributing to increases in regional precipitation. However, depending on patterns of seasonal sea ice retreat and weather conditions, the spring-summer heat uptake and autumn-winter heat loss can be highly variable from year to year and regionally. Here, we examine how the seasonality in upper ocean heat uptake and release has evolved over the past 37 years and the relationships between this seasonal heat gain and loss and the evolution of sea ice cover. We determine which regions have seen the largest increases in total seasonal heat uptake and how variable this uptake can be. Has the timing at which the Arctic Ocean (either as a whole or by region) transitions from an atmospheric energy sink to an atmospheric energy source (or from a source to a sink) appreciably changed? What changes have been observed in the seasonal rates of seasonal heat uptake and release? To begin answering these questions, use is made of surface fluxes from the ERA-Interim reanalysis and satellite-derived sea ice extent spanning the period 1979 through the present. Results from ERA-Interim will be compared to those from other reanalyses and satellite-derived flux estimates.

  19. Thermal Analysis of Hybrid Thermal Control System and Experimental Investigation of Flow Boiling in Micro-channel Heat Exchangers

    Science.gov (United States)

    Lee, Seunghyun

    Future manned space endeavors will require a new class of vehicles, capable of conducting different types of missions and enduring varying gravitational and temperature environments. Thermal management will play a vital role in these new vehicles, and is complicated by the need to tackle both low and high heat sink temperatures. The present study assesses the feasibility of hybrid thermal control system by thermodynamic analysis and investigates the heat transfer mechanisms in two large micro-channel heat exchangers in vapor compression mode and two-phase mode. Unlike prior published two-phase micro-channel studies that concern mostly miniature heat sinks, this study addresses transport characteristics of a heat sink containing large length-to-diameter ratio, up to 609.6 to 1,micro-channels. In the thermodynamic analysis, four different operational modes are considered: single-phase, two-phase, basic heat pump and heat pump with liquid-side, suction-side heat exchanger. A thermodynamic trade study is conducted for six different working fluids to assess important performance parameters including mass flow rate of the working fluid, maximum pressure, radiator area, compressor/pump work, and coefficient of performance (COP). R134a is determined to be most suitable based on its ability to provide a balanced compromise between reducing flow rate and maintaining low system pressure, and a moderate coefficient of performance (COP); this fluid is also both nontoxic and nonflammable, and features zero ozone depletion potential (ODP) and low global warming potential (GWP). It is shown how specific mission stages dictate which mode of operation is most suitable, and this information is used to size the radiator for the H-TCS. The experimental flow boiling investigation consists of exploring the steady-state and the transient two-phase heat transfer characteristics of two large micro-channel heat exchangers that serve as evaporators in the vapor compression loop using R134a as

  20. Is there a decrease in the sink of atmospheric CO2 in the Nordic seas?

    International Nuclear Information System (INIS)

    Olsen, Are; Anderson, Leif G.

    2002-01-01

    It is well known that the seas off Norway sink a lot of carbon dioxide from the atmosphere, mainly because of the large heat loss from the sea in the area, which makes CO 2 more soluble in the water. Whether this sink has increased after the industrial revolution and thereby contributes to slowing down the increase of atmospheric CO 2 is uncertain. That is, it is uncertain whether there is a sink of anthropogenic CO 2 . There are indications that the opposite is true, that the sink of CO 2 in this area has slowed down along with the rise in the concentration of atmospheric CO 2 . Storing of anthropogenic CO 2 , however, takes place at higher latitudes where deep-water formation occurs, such as in the Nordic seas, where water that is saturated with anthropogenic CO 2 is transported down in the deep sea and becomes shielded from the atmosphere. Model calculations show that increased CO 2 in the atmosphere will reduce the sink of this gas in the Nordic seas. This conclusion is supported by observations from the Barents Sea

  1. Regulation of assimilate import into sink organs: Update on molecular drivers of sink strength

    Directory of Open Access Journals (Sweden)

    Saadia eBihmidine

    2013-06-01

    Full Text Available Recent developments have altered our view of molecular mechanisms that determine sink strength, defined here as the capacity of non-photosynthetic structures to compete for import of photoassimilates. We review new findings from diverse systems, including stems, seeds, flowers, and fruits. An important advance has been the identification of new transporters and facilitators with major roles in the accumulation and equilibration of sugars at a cellular level. Exactly where each exerts its effect varies among systems. Sugarcane and sweet sorghum stems, for example, both accumulate high levels of sucrose, but may do so via different paths. The distinction is central to strategies for targeted manipulation of sink strength using transporter genes, and shows the importance of system-specific analyses. Another major advance has been the identification of deep hypoxia as a feature of normal grain development. This means that molecular drivers of sink strength in endosperm operate in very low oxygen levels, and under metabolic conditions quite different than previously assumed. Successful enhancement of sink strength has nonetheless been achieved in grains by up-regulating genes for starch biosynthesis. Additionally, our understanding of sink strength is enhanced by awareness of the dual roles played by invertases (INV, not only in sucrose metabolism, but also in production of the hexose sugar signals that regulate cell-cycle and cell-division programs. These contributions of INV to cell expansion and division prove to be vital for establishment of young sinks ranging from flowers to fruit. Since INV genes are themselves sugar-responsive feast genes, they can mediate a feed-forward enhancement of sink strength when assimilates are abundant. Greater overall productivity and yield have thus been attained in key instances, indicating that even broader enhancements may be achievable as we discover the detailed molecular mechanisms that drive sink strength

  2. Computed Heats of Formation

    National Research Council Canada - National Science Library

    Politzer, Peter

    1998-01-01

    ..., the heats of vaporization and sublimation. The latter are determined by means of relationships that we have developed involving the computed electrostatic potential on the molecular surface 2,3...

  3. Vapor pressures and thermophysical properties of selected monoterpenoids

    Czech Academy of Sciences Publication Activity Database

    Štejfa, V.; Dergal, F.; Mokbel, I.; Fulem, Michal; Jose, J.; Růžička, K.

    2015-01-01

    Roč. 406, Nov (2015), 124-133 ISSN 0378-3812 Institutional support: RVO:68378271 Keywords : monoterpenoids * vapor pressure * heat capacity * ideal - gas thermodynamic properties * vaporization and sublimation enthalpy Subject RIV: BJ - Thermodynamics Impact factor: 1.846, year: 2015

  4. Recommended vapor pressure and thermophysical data for ferrocene

    Czech Academy of Sciences Publication Activity Database

    Fulem, Michal; Růžička, K.; Červinka, C.; Rocha, M.A.A.; Santos, L.M.N.B.F.; Berg, R.F.

    2013-01-01

    Roč. 57, FEB (2013), 530-540 ISSN 0021-9614 Institutional support: RVO:68378271 Keywords : ferrocene * vapor pressure * heat capacity * ideal gas thermodynamic properties * sublimation enthalpy * recommended vapor pressure equation Subject RIV: BJ - Thermodynamics Impact factor: 2.423, year: 2013

  5. Vapor generation rate model for dispersed drop flow

    International Nuclear Information System (INIS)

    Unal, C.; Tuzla, K.; Cokmez-Tuzla, A.F.; Chen, J.C.

    1991-01-01

    A comparison of predictions of existing nonequilibrium post-CHF heat transfer models with the recently obtained rod bundle data has been performed. The models used the experimental conditions and wall temperatures to predict the heat flux and vapor temperatures at the location of interest. No existing model was able to reasonably predict the vapor superheat and the wall heat flux simultaneously. Most of the models, except Chen-Sundaram-Ozkaynak, failed to predict the wall heat flux, while all of the models could not predict the vapor superheat data or trends. A recently developed two-region heat transfer model, the Webb-Chen two-region model, did not give a reasonable prediction of the vapor generation rate in the far field of the CHF point. A new correlation was formulated to predict the vapor generation rate in convective dispersed droplet flow in terms of thermal-hydraulic parameters and thermodynamic properties. A comparison of predictions of the two-region heat transfer model, with the use of a presently developed correlation, with all the existing post-CHF data, including single-tube and rod bundle, showed significant improvements in predicting the vapor superheat and tube wall heat flux trends. (orig.)

  6. Minimization of sink mark defects in injection molding process ...

    African Journals Online (AJOL)

    user

    3Institute of Remote Sensing, Anna University, Chennai-600025, INDIA .... Most of the Taguchi based studies used sink mark index or sink index as the parameter. It is an .... Maintaining higher pack pressure requires additional power and cost.

  7. Overview of chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M.; Stinton, D.P.; Lowden, R.A.

    1993-06-01

    Chemical vapor infiltration (CVI) is developing into a commercially important method for the fabrication of continuous filament ceramic composites. Current efforts are focused on the development of an improved understanding of the various processes in CVI and its modeling. New approaches to CVI are being explored, including pressure pulse infiltration and microwave heating. Material development is also proceeding with emphasis on improving the oxidation resistance of the interfacial layer between the fiber and matrix. This paper briefly reviews these subjects, indicating the current state of the science and technology.

  8. Numerical routine for magnetic heat pump cascading

    DEFF Research Database (Denmark)

    Filonenko, Konstantin; Lei, Tian; Engelbrecht, Kurt

    Heat pumps use low-temperature heat absorbed from the energy source to create temperature gradient (TG) across the energy sink. Magnetic heat pumps (MHP) can perform this function through operating active magnetic regeneration (AMR) cycle. For building heating, TGs of up to a few K might...

  9. Source and sink nodes in absence seizures.

    Science.gov (United States)

    Rodrigues, Abner C; Machado, Birajara S; Caboclo, Luis Otavio S F; Fujita, Andre; Baccala, Luiz A; Sameshima, Koichi

    2016-08-01

    As opposed to focal epilepsy, absence seizures do not exhibit a clear seizure onset zone or focus since its ictal activity rapidly engages both brain hemispheres. Yet recent graph theoretical analysis applied to absence seizures EEG suggests the cortical focal presence, an unexpected feature for this type of epilepsy. In this study, we explore the characteristics of absence seizure by classifying the nodes as to their source/sink natures via weighted directed graph analysis based on connectivity direction and strength estimation using information partial directed coherence (iPDC). By segmenting the EEG signals into relatively short 5-sec-long time windows we studied the evolution of coupling strengths from both sink and source nodes, and the network dynamics of absence seizures in eight patients.

  10. Experimental study of vapor bubble dynamics

    International Nuclear Information System (INIS)

    Pasquini, Maria-Elena

    2015-01-01

    The object of this thesis is an experimental study of vapor bubble dynamics in sub-cooled nucleate boiling. The test section is locally heated by focusing a laser beam: heat fluxes from 1 e4 to 1.5 e6 W/m 2 and water temperature between 100 and 88 C have been considered. Three boiling regimes have been observed. Under saturated conditions and with low heat fluxes a developed nucleate boiling regime has been observed. Under higher sub-cooling and still with low heat fluxes an equilibrium regime has been observed in which the liquid flowrate evaporating at the bubble base is compensated by the vapor condensing flowrate at bubble top. A third regime have been observed at high heat fluxes for all water conditions: it is characterized by the formation of a large dry spot on the heated surface that keeps the nucleation site dry after bubble detachment. The condensation phase starts after bubble detachment. Bubble equivalent radius at detachment varies between 1 and 2.5 mm. Bubble properties have been measured and non-dimensional groups have been used to characterize bubble dynamics. Capillary waves have been observed on the bubble surface thanks to high-speed images acquisition. Two main phenomena have been proposed to explain capillary waves effects on bubble condensation: increasing of the phases interface area and decreasing of vapor bubble translation velocity, because of the increased drag force on the deformed bubble. (author) [fr

  11. Fuel vapor pressure (FVAPRS)

    International Nuclear Information System (INIS)

    Mason, R.E.

    1979-04-01

    A subcode (FVAPRS) is described which calculates fuel vapor pressure. This subcode was developed as part of the fuel rod behavior modeling task performed at EG and G Idaho, Inc. The fuel vapor pressure subcode (FVAPRS), is presented and a discussion of literature data, steady state and transient fuel vapor pressure equations and estimates of the standard error of estimate to be expected with the FVAPRS subcode are included

  12. Vapor pumps and gas-driven machines

    International Nuclear Information System (INIS)

    Guillet, R.

    1991-01-01

    The vapor pump, patented in 1979 by Gaz de France, is an additional mass and heat exchanger which uses the combustion air of fuel-burning machines as an additional cold source. This cold source is preheated and, above all, humidified before reaching the burner, by means of the residual sensible and latent heat in the combustion products of the fuel-burning process. This final exchanger thus makes it possible, in many cases, to recover all the gross calorific value of natural gas, even when the combustion products leave the process at a wet temperature greater than 60 0 C, the maximum dew point of the products of normal combustion. Another significant advantage of the vapor pump being worth highlighting is the selective recycling of water vapor by the vapor pump which reduces the adiabatic combustion temperature and the oxygen concentration in the combustion air, two factors which lead to considerable reductions in nitrogen oxides formation, hence limiting atmospheric pollution. Alongside a wide range of configurations which make advantageous use of the vapor pump in association with gas-driven machines and processes, including gas turbines, a number of boiler plant installations are also presented [fr

  13. The maximum power condition of the brayton cycle with heat exchange processes

    International Nuclear Information System (INIS)

    Jung, Pyung Suk; Cha, Jin Girl; Ro, Sung Tack

    1985-01-01

    The ideal brayton cycle has been analyzed with the heat exchange processes between the working fluid and the heat source and the sink while their heat capacity rates are constant. The power of the cycle can be expressed in terms of a temperature of the cycle and the heat capacity rate of the working fluid. There exists an optimum power condition where the heat capacity rate of the working fluid has a value between those of the heat source and the heat sink, and the cycle efficiency is determined by the inlet temperatures of the heat source and the sink. (Author)

  14. Pressure Profiles in a Loop Heat Pipe under Gravity Influence

    Science.gov (United States)

    Ku, Jentung

    2015-01-01

    During the operation of a loop heat pipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity-neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed.

  15. Vapor generator steam drum spray heat

    International Nuclear Information System (INIS)

    Fasnacht, F.A. Jr.

    1978-01-01

    A typical embodiment of the invention provides a combination feedwater and cooldown water spray head that is centrally disposed in the lower portion of a nuclear power plant steam drum. This structure not only discharges the feedwater in the hottest part of the steam drum, but also increases the time required for the feedwater to reach the steam drum shell, thereby further increasing the feedwater temperature before it contacts the shell surface, thus reducing thermal shock to the steam drum structure

  16. PWFA plasma source - interferometric diagnostics for Li vapor density measurements

    International Nuclear Information System (INIS)

    Sivakumaran, V.; Mohandas, K.K.; Singh, Sneha; Ravi Kumar, A.V.

    2015-01-01

    A prototype (40 cm long) plasma source based on Li heat pipe oven has been developed for the Plasma Wakefield Acceleration (PWFA) experiments at IPR (IPR), Gujarat as a part of the ongoing Accelerator Programme. Li vapor in the oven is produced by heating solid Li in helium buffer gas. A uniform column of Li plasma is generated by UV photo ionization (193 nm) of the Li vapor in the heat pipe oven. In these experiments, an accurate measurement of Li vapor density is important as it has got a direct consequence on the plasma electron density. In the present experiment, the vapor density is measured optically by using Hook method (spectrally resolved white light interferometry). The hook like structure formed near the vicinity of the Li 670.8 nm resonance line was recorded with a white light Mach Zehnder interferometer crossed with an imaging spectrograph to estimate the Li vapor density. The vapor density measurements have been carried out as a function of external oven temperature and the He buffer gas pressure. This technique has the advantage of being insensitive to line broadening and line shape, and its high dynamic range even with optically thick absorption line. Here, we present the line integrated Lithium vapor density measurement using Hook method and also compare the same with other optical diagnostic techniques (White light absorption and UV absorption) for Li vapor density measurements. (author)

  17. Effect of impact angle on vaporization

    Science.gov (United States)

    Schultz, Peter H.

    1996-09-01

    Impacts into easily vaporized targets such as dry ice and carbonates generate a rapidly expanding vapor cloud. Laboratory experiments performed in a tenuous atmosphere allow deriving the internal energy of this cloud through well-established and tested theoretical descriptions. A second set of experiments under near-vacuum conditions provides a second measure of energy as the internal energy converts to kinetic energy of expansion. The resulting data allow deriving the vaporized mass as a function of impact angle and velocity. Although peak shock pressures decrease with decreasing impact angle (referenced to horizontal), the amount of impact-generated vapor is found to increase and is derived from the upper surface. Moreover, the temperature of the vapor cloud appears to decrease with decreasing angle. These unexpected results are proposed to reflect the increasing roles of shear heating and downrange hypervelocity ricochet impacts created during oblique impacts. The shallow provenance, low temperature, and trajectory of such vapor have implications for larger-scale events, including enhancement of atmospheric and biospheric stress by oblique terrestrial impacts and impact recycling of the early atmosphere of Mars.

  18. Technical and economic working domains of industrial heat pumps: Part 1 - single stage vapour compression heat pumps

    DEFF Research Database (Denmark)

    Ommen, Torben Schmidt; Jensen, Jonas Kjær; Markussen, Wiebke Brix

    2015-01-01

    A large amount of operational and economic constraints limit the applicability of heat pumps operated with natural working fluids. The limitations are highly dependent on the integration of heat source and sink streams. An evaluation of feasible operating conditions was carried out considering......, the transcritical R744 expands the working domain for low sink outlet temperatures....

  19. Petroleum Vapor - Field Technical

    Science.gov (United States)

    The screening approach being developed by EPA OUST to evaluate petroleum vapor intrusion (PVI) requires information that has not be routinely collected in the past at vapor intrusion sites. What is the best way to collect this data? What are the relevant data quality issues and ...

  20. Boundary vapor contentsin an annular channel

    International Nuclear Information System (INIS)

    Remizov, O.V.; Shurkin, N.G.; Podgornyj, K.K.; Gal'chenko, Eh.F.; Bukhteev, I.S.

    1978-01-01

    The work is aimed at the experimental investigation of the worsening of the heat transfer in an annular channel. The experiments have been carried out on the annular channel 32x28x3000 mm with the even distribution of the heat flux along the length at pressures of 6.9-19.6 MPa, flow rate of 350-1000 kg/m 2 s, and specific heat fluxes from 0.18 up to 0.6 MW/m 2 . Heating is external, oneside. Water monodistillate of the following composition has been used as a coolant: pH 9; dry residue - 0.8-1.2 mg/kg, oxygen -10-15 mg/kg. It is found out that the change character of the temperature field of the heating surface of the annular channel at the regime with the worsen of heat emission depends on the ratio of regime parameters. At pressures of 6.9-13.7 MPa and flow rate of 350-500 kg/m 2 s the channel wall temperature rises monotoneously, never reaching its maximum. With pressure rise > 13.7 MPa and mass velocity > 500 kg/m 2 s the temperature of the heat emitting surface reaches its maximum, and then slowly falls. At pressures of 6.9-11.8 MPa the boundary vapor content value within the whole range of mass velocities does not depend on the specific heat flux q. At pressures higher than 13.7 MPa and mass velocities of 350-1000 kg/m 2 s the boundary vapor content depends on q. The heating of the external or internal surface of the annular channel affects the value of the boundary vapor content within the whole range of regime parameters' change under investigation

  1. On the meaning of sink capture efficiency and sink strength for point defects

    International Nuclear Information System (INIS)

    Mansur, L.K.; Wolfer, W.G.

    1982-01-01

    The concepts of sink capture efficiency and sink strength for point defects are central to the theory of point defect reactions in materials undergoing irradiation. Two fundamentally different definitions of the capture efficiency are in current use. The essential difference can be stated simply. The conventional meaning denotes a measure of the loss rate of point defects to sinks per unit mean point defect concentration. A second definition of capture efficiency, introduced recently, gives a measure of the point defect loss rate without normalization to the mean point defect concentration. The relationship between the two capture efficiencies is here derived. By stating the relationship we hope to eliminate confusion caused by comparisons of the two types of capture efficiencies at face value and to provide a method of obtaining one from the other. Internally consistent usage of either of the capture efficiencies leads to the same results for the calculation of measuable quantities, as is required physically. (orig.)

  2. Subsurface Thermal Energy Storage for Improved Heating and Air Conditioning Efficiency

    Science.gov (United States)

    2016-11-21

    through water evaporation , although some cooling also occurs due to sensible heat transfer . Cooling towers are very effective heat transfer devices... evaporator coil connected to the building heating , ventilation, and air conditioning (HVAC) system. The refrigerant evaporates in the coil, removing...vapor is directed to a condensing coil, where the refrigerant vapor condenses back into a liquid, releasing its heat of vaporization. During

  3. DSMC simulations of vapor transport toward development of the lithium vapor box divertor concept

    Science.gov (United States)

    Jagoe, Christopher; Schwartz, Jacob; Goldston, Robert

    2016-10-01

    The lithium vapor divertor box concept attempts to achieve volumetric dissipation of the high heat efflux from a fusion power system. The vapor extracts the heat of the incoming plasma by ionization and radiation, while remaining localized in the vapor box due to differential pumping based on rapid condensation. Preliminary calculations with lithium vapor at densities appropriate for an NSTX-U-scale machine give Knudsen numbers between 0.01 and 1, outside both the range of continuum fluid dynamics and of collisionless Monte Carlo. The direct-simulation Monte Carlo (DSMC) method, however, can simulate rarefied gas flows in this regime. Using the solver contained in the OpenFOAM package, pressure-driven flows of water vapor will be analyzed. The use of water vapor in the relevant range of Knudsen number allows for a flexible similarity experiment to verify the reliability of the code before moving to tests with lithium. The simulation geometry consists of chains of boxes on a temperature gradient, connected by slots with widths that are a representative fraction of the dimensions of the box. We expect choked flow, sonic shocks, and order-of-magnitude pressure and density drops from box to box, but this expectation will be tested in the simulation and then experiment. This work is supported by the Princeton Environmental Institute.

  4. Laser vapor phase deposition of semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Karlov, N.V.; Luk' ianchuk, B.S.; Sisakian, E.V.; Shafeev, G.A.

    1987-06-01

    The pyrolytic effect of IR laser radiation is investigated with reference to the initiation and control of the vapor phase deposition of semiconductor films. By selecting the gas mixture composition and laser emission parameters, it is possible to control the deposition and crystal formation processes on the surface of semiconductors, with the main control action achieved due to the nonadiabatic kinetics of reactions in the gas phase and high temperatures in the laser heating zone. This control mechanism is demonstrated experimentally during the laser vapor deposition of germanium and silicon films from tetrachlorides on single-crystal Si and Ge substrates. 5 references.

  5. Drag Reduction by Leidenfrost Vapor Layers

    KAUST Repository

    Vakarelski, Ivan Uriev

    2011-05-23

    We demonstrate and quantify a highly effective drag reduction technique that exploits the Leidenfrost effect to create a continuous and robust lubricating vapor layer on the surface of a heated solid sphere moving in a liquid. Using high-speed video, we show that such vapor layers can reduce the hydrodynamic drag by over 85%. These results appear to approach the ultimate limit of drag reduction possible by different methods based on gas-layer lubrication and can stimulate the development of related energy saving technologies.

  6. Method for the generation of variable density metal vapors which bypasses the liquidus phase

    Science.gov (United States)

    Kunnmann, Walter; Larese, John Z.

    2001-01-01

    The present invention provides a method for producing a metal vapor that includes the steps of combining a metal and graphite in a vessel to form a mixture; heating the mixture to a first temperature in an argon gas atmosphere to form a metal carbide; maintaining the first temperature for a period of time; heating the metal carbide to a second temperature to form a metal vapor; withdrawing the metal vapor and the argon gas from the vessel; and separating the metal vapor from the argon gas. Metal vapors made using this method can be used to produce uniform powders of the metal oxide that have narrow size distribution and high purity.

  7. Eddy transport of water vapor in the Martian atmosphere

    Science.gov (United States)

    Murphy, J. R.; Haberle, Robert M.

    1993-01-01

    Viking orbiter measurements of the Martian atmosphere suggest that the residual north polar water-ice cap is the primary source of atmospheric water vapor, which appears at successively lower northern latitudes as the summer season progresses. Zonally symmetric studies of water vapor transport indicate that the zonal mean meridional circulation is incapable of transporting from north polar regions to low latitudes the quantity of water vapor observed. This result has been interpreted as implying the presence of nonpolar sources of water. Another possibility is the ability of atmospheric wave motions, which are not accounted for in a zonally symmetric framework, to efficiently accomplish the transport from a north polar source to the entirety of the Northern Hemisphere. The ability or inability of the full range of atmospheric motions to accomplish this transport has important implications regarding the questions of water sources and sinks on Mars: if the full spectrum of atmospheric motions proves to be incapable of accomplishing the transport, it strengthens arguments in favor of additional water sources. Preliminary results from a three dimensional atmospheric dynamical/water vapor transport numerical model are presented. The model accounts for the physics of a subliming water-ice cap, but does not yet incorporate recondensation of this sublimed water. Transport of vapor away from this water-ice cap in this three dimensional framework is compared with previously obtained zonally symmetric (two dimensional) results to quantify effects of water vapor transport by atmospheric eddies.

  8. The steady-state modeling and optimization of a refrigeration system for high heat flux removal

    International Nuclear Information System (INIS)

    Zhou Rongliang; Zhang Tiejun; Catano, Juan; Wen, John T.; Michna, Gregory J.; Peles, Yoav; Jensen, Michael K.

    2010-01-01

    Steady-state modeling and optimization of a refrigeration system for high heat flux removal, such as electronics cooling, is studied. The refrigeration cycle proposed consists of multiple evaporators, liquid accumulator, compressor, condenser and expansion valves. To obtain more efficient heat transfer and higher critical heat flux (CHF), the evaporators operate with two-phase flow only. This unique operating condition necessitates the inclusion of a liquid accumulator with integrated heater for the safe operation of the compressor. Due to the projected incorporation of microchannels into the system to enhance the heat transfer in heat sinks, the momentum balance equation, rarely seen in previous vapor compression cycle heat exchangers modeling efforts, is utilized in addition to the mass and energy balance equations to capture the expected significant microchannel pressure drop witnessed in previous experimental investigations. Using the steady-state model developed, a parametric study is performed to study the effect of various external inputs on the system performance. The Pareto optimization is applied to find the optimal system operating conditions for given heat loads such that the system coefficient of performance (COP) is optimized while satisfying the CHF and other system operation constraints. Initial validation efforts show the good agreement between the experimental data and model predictions.

  9. Thermal Design of Vapor Cooling of Flight Vehicle Structures Using LH2 Boil-Off

    Science.gov (United States)

    Wang, Xiao-Yen; Zoeckler, Joseph

    2015-01-01

    Using hydrogen boil-off vapor to cool the structure of a flight vehicle cryogenic upper stage can reduce heat loads to the stage and increase the usable propellant in the stage or extend the life of the stage. The hydrogen vapor can be used to absorb incoming heat as it increases in temperature before being vented overboard. In theory, the amount of heat leaking into the hydrogen tank from the structure will be reduced if the structure is cooled using the propellant boil-off vapor. However, the amount of boil-off vapor available to be used for cooling and the reduction in heat leak to the propellant tank are dependent to each other. The amount of heat leak reduction to the LH2 tank also depends on the total heat load on the stage and the vapor cooling configurations.

  10. The vapor pressure and enthalpy of vaporization of M-xylene

    Energy Technology Data Exchange (ETDEWEB)

    Rothenberg, S J; Seiler, F A; Bechtold, W E; Eidson, A F

    1988-12-01

    We measured the vapor pressure of m-xylene over the temperature range 273 to 293 deg K with a single-sided capacitance manometer. The enthalpy of vaporization was 42.2 {+-} 0.1 (SE) kj/ g{center_dot}mol. Combining our own data with previously published data, we recommend using the values 42.0, 40.6, and 39.1 ({+-} 0.1) (SE) kjg{center_dot}mol for the enthalpy of vaporization of m-xylene at 300, 340, and 380 deg. K, respectively, and a value for the change in heat capacity on vaporization ({delta}Cpdeg.) of 35 {+-} 3 (SE) J/g{center_dot}mol{center_dot}K over the temperature range studied. (author)

  11. The vapor pressure and enthalpy of vaporization of M-xylene

    International Nuclear Information System (INIS)

    Rothenberg, S.J.; Seiler, F.A.; Bechtold, W.E.; Eidson, A.F.

    1988-01-01

    We measured the vapor pressure of m-xylene over the temperature range 273 to 293 deg K with a single-sided capacitance manometer. The enthalpy of vaporization was 42.2 ± 0.1 (SE) kj/ g·mol. Combining our own data with previously published data, we recommend using the values 42.0, 40.6, and 39.1 (± 0.1) (SE) kjg·mol for the enthalpy of vaporization of m-xylene at 300, 340, and 380 deg. K, respectively, and a value for the change in heat capacity on vaporization (ΔCpdeg.) of 35 ± 3 (SE) J/g·mol·K over the temperature range studied. (author)

  12. Piezoelectric trace vapor calibrator

    International Nuclear Information System (INIS)

    Verkouteren, R. Michael; Gillen, Greg; Taylor, David W.

    2006-01-01

    The design and performance of a vapor generator for calibration and testing of trace chemical sensors are described. The device utilizes piezoelectric ink-jet nozzles to dispense and vaporize precisely known amounts of analyte solutions as monodisperse droplets onto a hot ceramic surface, where the generated vapors are mixed with air before exiting the device. Injected droplets are monitored by microscope with strobed illumination, and the reproducibility of droplet volumes is optimized by adjustment of piezoelectric wave form parameters. Complete vaporization of the droplets occurs only across a 10 deg. C window within the transition boiling regime of the solvent, and the minimum and maximum rates of trace analyte that may be injected and evaporated are determined by thermodynamic principles and empirical observations of droplet formation and stability. By varying solution concentrations, droplet injection rates, air flow, and the number of active nozzles, the system is designed to deliver--on demand--continuous vapor concentrations across more than six orders of magnitude (nominally 290 fg/l to 1.05 μg/l). Vapor pulses containing femtogram to microgram quantities of analyte may also be generated. Calibrated ranges of three explosive vapors at ng/l levels were generated by the device and directly measured by ion mobility spectrometry (IMS). These data demonstrate expected linear trends within the limited working range of the IMS detector and also exhibit subtle nonlinear behavior from the IMS measurement process

  13. Source-sink relationships in radish plant

    Directory of Open Access Journals (Sweden)

    Z. Starck

    2015-01-01

    Full Text Available The problem of source-sink relationships in di- and tetraploidal radish plants grown in. hydroponic cultures was investigated in two stages of their development: with intensively growing swollen hypocotyl and in the period of actively accumulating nutrients in the storage organ. It was found, that the proportion, between the mass of organs, their RGR and NAR was very similar in di- and tetraploidal populations, probably owing to a similar rate of photosynthesis and pattern of assimilates distribution. The high variability of swollen hypocotyls size is slightly correlated with the size of the whole aerial part and is not correlated with the rate of photosynthesis in leaves. Partial defoliation of radish plants did not affect the rate of photosynthesis of the remaining leaves. Only in the cotyledones the oldest donors of 14C-assimilates, a slight compensation of photosynthesis was reported. It may suggest, that the rate of photosynthesis in radish plants is not under the control of sink activity. The size of the storage organ have determined in some extent its attractive force and influenced the amount of 14C-assimilates exported from their donors. Translocation of photosynthates from the young, still growing leaves was conditioned mainly by their retention power. Therefore, in young radish plants cotyledons were the main donor of 14C-assimilates.

  14. Causes of sinks near Tucson, Arizona, USA

    Science.gov (United States)

    Hoffmann, John P.; Pool, Donald R.; Konieczki, A. D.; Carpenter, Michael C.

    Land subsidence in the form of sinks has occurred on and near farmlands near Tucson, Pima County, Arizona, USA. The sinks occur in alluvial deposits along the flood plain of the Santa Cruz River, and have made farmlands dangerous and unsuitable for farming. More than 1700 sinks are confined to the flood plain of the Santa Cruz River and are grouped along two north-northwestward-trending bands that are approximately parallel to the river and other flood-plain drainages. An estimated 17,000m3 of sediment have been removed in the formation of the sinks. Thirteen trenches were dug to depths of 4-6m to characterize near-surface sediments in sink and nonsink areas. Sediments below about 2m included a large percentage of dispersive clays in sink areas. Sediments in nonsink areas contain a large component of medium- to coarse-grained, moderately to well sorted sand that probably fills a paleochannel. Electromagnetic surveys support the association of silts and clays in sink areas that are highly electrically conductive relative to sand in nonsink areas. Sinks probably are caused by the near-surface process of subsurface erosion of dispersive sediments along pre-existing cracks in predominantly silt and clay sediments. The pre-existing cracks probably result from desiccation or tension that developed during periods of water-table decline and channel incision during the past 100 years or in earlier periods. Résumé Des effondrements en forme d'entonnoir se sont produits sur et près d'exploitations agricoles de Pima (Arizona). Ces entonnoirs apparaissent dans les alluvions le long de la plaine d'inondation de la rivière Santa Cruz ; ils ont rendu ces terrains dangereux et inexploitables pour l'agriculture. Plus de 1700 entonnoirs existent dans la plaine d'inondation de la rivière Santa Cruz et sont groupés en deux bandes orientées nord-nord-ouest, approximativement parallèles à la rivière et aux autres chenaux de la plaine d'inondation. Un volume de sédiments estim

  15. Improvements to vapor generators

    International Nuclear Information System (INIS)

    Keller, Arthur; Monroe, Neil.

    1976-01-01

    A supporting system is proposed for vapor generators of the 'supported' type. Said supporting system is intended to compensate the disparities of thermal expansion due to the differences in the vertical dimensions of the tubes in the walls of the combustion chamber and their collectors compared to that of the balloon tanks and the connecting tube clusters of vaporization, the first one being longer than the second ones. Said system makes it possible to build said combustion chamber higher than the balloon tanks and the tube clusters of vaporization. The capacity of steam production is thus enhanced [fr

  16. The effect of external boundary conditions on condensation heat transfer in rotating heat pipes

    Science.gov (United States)

    Daniels, T. C.; Williams, R. J.

    1979-01-01

    Experimental evidence shows the importance of external boundary conditions on the overall performance of a rotating heat pipe condenser. Data are presented for the boundary conditions of constant heat flux and constant wall temperature for rotating heat pipes containing either pure vapor or a mixture of vapor and noncondensable gas as working fluid.

  17. High heat flux device of thermonuclear device

    International Nuclear Information System (INIS)

    Tachikawa, Nobuo.

    1994-01-01

    The present invention provides an equipments for high heat flux device (divertor) of a thermonuclear device, which absorbs thermal deformation during operation, has a high installation accuracy, and sufficiently withstands for thermal stresses. Namely, a heat sink member is joined to a structural base. Armour tiles are joined on the heat sink member. Cooling pipes are disposed between the heat sink member and the armour tiles. With such a constitution, the heat sink member using a highly heat conductive material having ductility, such as oxygen free copper, the cooling pipes using a material having excellent high temperature resistance and excellent elongation, such as aluminum-dispersed reinforced copper, and the armour tiles are completely joined on the structural base. Therefore, when thermal deformation tends to cause in the high heat flux device such as a divertor, cooling pipes cause no plastic deformation because of their high temperature resistance, but the heat sink member such as a oxygen free copper causes plastic deformation to absorb thermal deformation. As a result, the high heat flux device such as a divertor causes no deformation. (I.S.)

  18. [Clothing and heat disorder].

    Science.gov (United States)

    Satsumoto, Yayoi

    2012-06-01

    The influence of the clothing material properties(like water absorbency and rapid dryness, water vapor absorption, water vapor permeability and air permeability) and the design factor of the clothing(like opening condition and fitting of clothing), which contributed to prevent heat disorder, was outlined. WBGT(wet-bulb globe temperature) is used to show a guideline for environmental limitation of activities to prevent heat disorder. As the safety function is more important than thermal comfort for some sportswear and protective clothing with high cover area, clothing itself increases the risk of heat disorder. WBGT is corrected by CAF (clothing adjustment factor) in wearing such kind of protective clothing.

  19. Sink-oriented Dynamic Location Service Protocol for Mobile Sinks with an Energy Efficient Grid-Based Approach

    Directory of Open Access Journals (Sweden)

    Hyunseung Choo

    2009-03-01

    Full Text Available Sensor nodes transmit the sensed information to the sink through wireless sensor networks (WSNs. They have limited power, computational capacities and memory. Portable wireless devices are increasing in popularity. Mechanisms that allow information to be efficiently obtained through mobile WSNs are of significant interest. However, a mobile sink introduces many challenges to data dissemination in large WSNs. For example, it is important to efficiently identify the locations of mobile sinks and disseminate information from multi-source nodes to the multi-mobile sinks. In particular, a stationary dissemination path may no longer be effective in mobile sink applications, due to sink mobility. In this paper, we propose a Sink-oriented Dynamic Location Service (SDLS approach to handle sink mobility. In SDLS, we propose an Eight-Direction Anchor (EDA system that acts as a location service server. EDA prevents intensive energy consumption at the border sensor nodes and thus provides energy balancing to all the sensor nodes. Then we propose a Location-based Shortest Relay (LSR that efficiently forwards (or relays data from a source node to a sink with minimal delay path. Our results demonstrate that SDLS not only provides an efficient and scalable location service, but also reduces the average data communication overhead in scenarios with multiple and moving sinks and sources.

  20. Sink-oriented Dynamic Location Service Protocol for Mobile Sinks with an Energy Efficient Grid-Based Approach.

    Science.gov (United States)

    Jeon, Hyeonjae; Park, Kwangjin; Hwang, Dae-Joon; Choo, Hyunseung

    2009-01-01

    Sensor nodes transmit the sensed information to the sink through wireless sensor networks (WSNs). They have limited power, computational capacities and memory. Portable wireless devices are increasing in popularity. Mechanisms that allow information to be efficiently obtained through mobile WSNs are of significant interest. However, a mobile sink introduces many challenges to data dissemination in large WSNs. For example, it is important to efficiently identify the locations of mobile sinks and disseminate information from multi-source nodes to the multi-mobile sinks. In particular, a stationary dissemination path may no longer be effective in mobile sink applications, due to sink mobility. In this paper, we propose a Sink-oriented Dynamic Location Service (SDLS) approach to handle sink mobility. In SDLS, we propose an Eight-Direction Anchor (EDA) system that acts as a location service server. EDA prevents intensive energy consumption at the border sensor nodes and thus provides energy balancing to all the sensor nodes. Then we propose a Location-based Shortest Relay (LSR) that efficiently forwards (or relays) data from a source node to a sink with minimal delay path. Our results demonstrate that SDLS not only provides an efficient and scalable location service, but also reduces the average data communication overhead in scenarios with multiple and moving sinks and sources.

  1. Gasoline Reid Vapor Pressure

    Science.gov (United States)

    EPA regulates the vapor pressure of gasoline sold at retail stations during the summer ozone season to reduce evaporative emissions from gasoline that contribute to ground-level ozone and diminish the effects of ozone-related health problems.

  2. Influence of Orientation and Radiative Heat Transfer on Aluminum Foams in Buoyancy-Induced Convection

    Science.gov (United States)

    Billiet, Marijn; De Schampheleire, Sven; Huisseune, Henk; De Paepe, Michel

    2015-01-01

    Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was made by investment casting of a polyurethane preform and has a porosity of 0.946 and a pore density of 10 pores per linear inch. The second foam is manufactured by casting over a solvable core and has a porosity of 0.85 and a pore density of 2.5 pores per linear inch. The effects of orientation and radiative heat transfer are experimentally investigated. The heat sinks are tested in a vertical and horizontal orientation. The effect of radiative heat transfer is investigated by comparing a painted/anodized heat sink with an untreated one. The heat flux through the heat sink for a certain temperature difference between the environment and the heat sink’s base plate is used as the performance indicator. For temperature differences larger than 30 ∘C, the finned heat sink outperforms the in-house-made aluminum foam heat sink on average by 17%. Furthermore, the in-house-made aluminum foam dissipates on average 12% less heat than the other aluminum foam for a temperature difference larger than 40 ∘C. By painting/anodizing the heat sinks, the heat transfer rate increased on average by 10% to 50%. Finally, the thermal performance of the horizontal in-house-made aluminum foam heat sink is up to 18% larger than the one of the vertical aluminum foam heat sink. PMID:28793601

  3. Influence of Orientation and Radiative Heat Transfer on Aluminum Foams in Buoyancy-Induced Convection

    Directory of Open Access Journals (Sweden)

    Marijn Billiet

    2015-10-01

    Full Text Available Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was made by investment casting of a polyurethane preform and has a porosity of 0.946 and a pore density of 10 pores per linear inch. The second foam is manufactured by casting over a solvable core and has a porosity of 0.85 and a pore density of 2.5 pores per linear inch. The effects of orientation and radiative heat transfer are experimentally investigated. The heat sinks are tested in a vertical and horizontal orientation. The effect of radiative heat transfer is investigated by comparing a painted/anodized heat sink with an untreated one. The heat flux through the heat sink for a certain temperature difference between the environment and the heat sink’s base plate is used as the performance indicator. For temperature differences larger than 30 °C, the finned heat sink outperforms the in-house-made aluminum foam heat sink on average by 17%. Furthermore, the in-house-made aluminum foam dissipates on average 12% less heat than the other aluminum foam for a temperature difference larger than 40 °C. By painting/anodizing the heat sinks, the heat transfer rate increased on average by 10% to 50%. Finally, the thermal performance of the horizontal in-house-made aluminum foam heat sink is up to 18% larger than the one of the vertical aluminum foam heat sink.

  4. Mobile heat accumulators for lorry or train transport?; Mobile Waermespeicher fuer den LKW- oder Zugtransport?

    Energy Technology Data Exchange (ETDEWEB)

    Goldenberg, Philipp

    2013-07-01

    Where heat grids cannot be laid for geographic reasons, mobile heat accumulators may be appropriate. The mobile heat accumulators are transported by lorry or train between the heat source and the heat sink. The waste heat can be decoupled from biogas plants, waste incineration plants or industrial sites. Existing road or rail networks can be used for transportation. Decisive factors to achieve low heat production costs are: free waste heat, large and continuous heat quantities as well as a short distance between the heat source and the heat sink. (orig.)

  5. R-22 vapor explosions

    International Nuclear Information System (INIS)

    Anderson, R.P.; Armstrong, D.R.

    1977-01-01

    Previous experimental and theoretical studies of R-22 vapor explosions are reviewed. Results from two experimental investigations of vapor explosions in a medium scale R-22/water system are reported. Measurements following the drop of an unrestrained mass of R-22 into a water tank demonstrated the existence of two types of interaction behavior. Release of a constrained mass of R-22 beneath the surface of a water tank improved the visual resolution of the system thus allowing identification of two interaction mechansims: at low water temperatures, R-22/water contact would produce immediate violent boiling; at high water temperatures a vapor film formed around its R-22 as it was released, explosions were generated by a surface wave which initiated at a single location and propagated along the vapor film as a shock wave. A new vapor explosion model is proposed, it suggests explosions are the result of a sequence of three independent steps: an initial mixing phase, a trigger and growth phase, and a mature phase where a propagating shock wave accelerates the two liquids into a collapsing vapor layer causing a high velocity impact which finely fragments and intermixes the two liquids

  6. Effects of biofouling on the sinking behavior of microplastics

    Science.gov (United States)

    Kaiser, David; Kowalski, Nicole; Waniek, Joanna J.

    2017-12-01

    Although plastic is ubiquitous in marine systems, our current knowledge of transport mechanisms is limited. Much of the plastic entering the ocean sinks; this is intuitively obvious for polymers such as polystyrene (PS), which have a greater density than seawater, but lower density polymers like polyethylene (PE) also occur in sediments. Biofouling can cause large plastic objects to sink, but this phenomenon has not been described for microplastics microplastic particles in estuarine and coastal waters to determine how biofouling changes their sinking behavior. Sinking velocities of PS increased by 16% in estuarine water (salinity 9.8) and 81% in marine water (salinity 36) after 6 weeks of incubation. Thereafter sinking velocities decreased due to lower water temperatures and reduced light availability. Biofouling did not cause PE to sink during the 14 weeks of incubation in estuarine water, but PE started to sink after six weeks in coastal water when sufficiently colonized by blue mussels Mytilus edulis, and its velocity continued to increase until the end of the incubation period. Sinking velocities of these PE pellets were similar irrespective of salinity (10 vs. 36). Biofilm composition differed between estuarine and coastal stations, presumably accounting for differences in sinking behavior. We demonstrate that biofouling enhances microplastic deposition to marine sediments, and our findings should improve microplastic transport models.

  7. The potential contribution of sinks to meeting Kyoto Protocol commitments

    DEFF Research Database (Denmark)

    Missfeldt, F.; Haites, E.

    2001-01-01

    scenario, at least some of the sinks have costs lower than the market price, so the larger the eligible sinks, the lower the compliance costs for industrialised countries. Greater use of sinks also reduces the net income received by the economies in transition and developing countries. Increased use......, a range of average costs is used with the lowest cost allowing maximum use of sinks. The effects considered are the impacts on compliance costs for OECD countries, economies in transition, and developing countries and the mix of actions used by industrialised countries to achieve compliance. In every...

  8. Multicomponent droplet vaporization in a convecting environment

    International Nuclear Information System (INIS)

    Megaridis, C.M.; Sirignano, W.A.

    1990-01-01

    In this paper a parametric study of the fundamental exchange processes for energy, mass and momentum between the liquid and gas phases of multicomponent liquid vaporizing droplets is presented. The model, which examines an isolated, vaporizing, multicomponent droplet in an axisymmetric, convecting environment, considers the different volatilities of the liquid components, the alteration of the liquid-phase properties due to the spatial/temporal variations of the species concentrations and also the effects of multicomponent diffusion. In addition, the model accounts for variable thermophysical properties, surface blowing and droplet surface regression due to vaporization, transient droplet heating with internal liquid circulation, and finally droplet deceleration with respect to the free flow due to drag. The numerical calculation employs finite-difference techniques and an iterative solution procedure that provides time-varying spatially-resolved data for both phases. The effects of initial droplet composition, ambient temperature, initial Reynolds number (based on droplet diameter), and volatility differential between the two liquid components are investigated for a liquid droplet consisting of two components with very different volatilities. It is found that mixtures with higher concentration of the less volatile substance actually vaporize faster on account of intrinsically higher liquid heating rates

  9. Omnivory in birds is a macroevolutionary sink.

    Science.gov (United States)

    Burin, Gustavo; Kissling, W Daniel; Guimarães, Paulo R; Şekercioğlu, Çağan H; Quental, Tiago B

    2016-04-07

    Diet is commonly assumed to affect the evolution of species, but few studies have directly tested its effect at macroevolutionary scales. Here we use Bayesian models of trait-dependent diversification and a comprehensive dietary database of all birds worldwide to assess speciation and extinction dynamics of avian dietary guilds (carnivores, frugivores, granivores, herbivores, insectivores, nectarivores, omnivores and piscivores). Our results suggest that omnivory is associated with higher extinction rates and lower speciation rates than other guilds, and that overall net diversification is negative. Trait-dependent models, dietary similarity and network analyses show that transitions into omnivory occur at higher rates than into any other guild. We suggest that omnivory acts as macroevolutionary sink, where its ephemeral nature is retrieved through transitions from other guilds rather than from omnivore speciation. We propose that these dynamics result from competition within and among dietary guilds, influenced by the deep-time availability and predictability of food resources.

  10. Metal hydride heat pump engineering demonstration and evaluation model

    Science.gov (United States)

    Lynch, Franklin E.

    1993-01-01

    Future generations of portable life support systems (PLSS's) for space suites (extravehicular mobility units or EMU's) may require regenerable nonventing thermal sinks (RNTS's). For purposes of mobility, a PLSS must be as light and compact as possible. Previous venting PLSS's have employed water sublimators to reject metabolic and equipment heat from EMU's. It is desirable for long-duration future space missions to minimize the use of water and other consumables that need to be periodically resupplied. The emission of water vapor also interferes with some types of instrumentation that might be used in future space exploration. The test article is a type of RNTS based on a metal hydride heat pump (MHHP). The task of reservicing EMU's after use must be made less demanding in terms of time, procedures, and equipment. The capability for quick turnaround post-EVA servicing (30 minutes) is a challenging requirement for many of the RNTS options. The MHHP is a very simple option that can be regenerated in the airlock within the 30 minute limit by the application of a heating source and a cooling sink. In addition, advanced PLSS's must provide a greater degree of automatic control, relieving astronauts of the need to manually adjust temperatures in their liquid cooled ventilation garments (LCVG's). The MHHP includes automatic coolant controls with the ability to follow thermal load swings from minimum to maximum in seconds. The MHHP includes a coolant loop subsystem with pump and controls, regeneration equipment for post-EVA servicing, and a PC-based data acquisition and control system (DACS).

  11. The tracking of interfaces in an electron-beam vaporizer

    International Nuclear Information System (INIS)

    Westerberg, K.W.; McClelland, M.A.; Finlayson, B.A.

    1993-03-01

    A numerical analysis is made of the material and energy flow in an electron beam vaporizer. In this system the energy from an electron beam heats metal confined in a water-cooled crucible. Metal is vaporized from a liquid pool circulating in a shell of its own solid. A modified Galerkin finite element method is used to calculate the flow and temperature fields along with the interface locations. The mesh is parameterized with spines which stretch and pivot as the phase boundaries move. The discretized equations are arranged in an ''arrow'' matrix and solved using the Newton-Raphson method. Results are given for an experimental aluminum vaporizer. The effects of buoyancy and capillary driven flow are included along with the surface contributions of vapor thrust, latent heat, thermal radiation, and crucible contact resistance

  12. Thermodynamic and transport properties of sodium liquid and vapor

    International Nuclear Information System (INIS)

    Fink, J.K.; Leibowitz, L.

    1995-01-01

    Data have been reviewed to obtain thermodynamically consistent equations for thermodynamic and transport properties of saturated sodium liquid and vapor. Recently published Russian recommendations and results of equation of state calculations on thermophysical properties of sodium have been included in this critical assessment. Thermodynamic properties of sodium liquid and vapor that have been assessed include: enthalpy, heat capacity at constant pressure, heat capacity at constant volume, vapor pressure, boiling point, enthalpy of vaporization, density, thermal expansion, adiabatic and isothermal compressibility, speed of sound, critical parameters, and surface tension. Transport properties of liquid sodium that have been assessed include: viscosity and thermal conductivity. For each property, recommended values and their uncertainties are graphed and tabulated as functions of temperature. Detailed discussions of the analyses and determinations of the recommended equations include comparisons with recommendations given in other assessments and explanations of consistency requirements. The rationale and methods used in determining the uncertainties in the recommended values are also discussed

  13. Production of gaseous or vaporous fuels from solid carbonaceous materials

    Energy Technology Data Exchange (ETDEWEB)

    1951-05-16

    A process for the production of gaseous or vaporous fuels from solid carbonaceous materials consists of subjecting the materials in separate zones to at least three successive thermal treatments at least two of which are carried out at different temperature levels. The materials being maintained in zones in the form of beds of finely divided particles fluidized by the passage of gases or vapors upwardly there-through, and recovering product vapors or gases overhead. The total hot gaseous or vaporous effluent and entrained solids from one of the zones is passed directly without separation to another of the zones situated closely adjacent to and vertically above the first named zone in the same vessel, and the heat required in at least one of the thermal treatment zones is supplied at least in part as the sensible heat of residual solids transferred from a thermal treatment zone operated at a higher temperature.

  14. Copepods use chemical trails to find sinking marine snow aggregates

    DEFF Research Database (Denmark)

    Lombard, Fabien; Koski, Marja; Kiørboe, Thomas

    2013-01-01

    Copepods are major consumers of sinking marine particles and hence reduce the efficiency of the biological carbon pump. Their high abundance on marine snow suggests that they can detect sinking particles remotely. By means of laboratory observations, we show that the copepod Temora longicornis ca...

  15. Characterizing source-sink dynamics with genetic parentage assignments

    NARCIS (Netherlands)

    Peery, M. Zachariah; Beissinger, Steven R.; House, Roger F.; Berube, Martine; Hall, Laurie A.; Sellas, Anna; Palsboll, Per J.

    2008-01-01

    Source-sink dynamics have been suggested to characterize the population structure of many species, but the prevalence of source-sink systems in nature is uncertain because of inherent challenges in estimating migration rates among populations. Migration rates are often difficult to estimate directly

  16. Vapor pressures and enthalpies of vaporization of azides

    International Nuclear Information System (INIS)

    Verevkin, Sergey P.; Emel'yanenko, Vladimir N.; Algarra, Manuel; Manuel Lopez-Romero, J.; Aguiar, Fabio; Enrique Rodriguez-Borges, J.; Esteves da Silva, Joaquim C.G.

    2011-01-01

    Highlights: → We prepared and measured vapor pressures and vaporization enthalpies of 7 azides. → We examined consistency of new and available in the literature data. → Data for geminal azides and azido-alkanes selected for thermochemical calculations. - Abstract: Vapor pressures of some azides have been determined by the transpiration method. The molar enthalpies of vaporization Δ l g H m of these compounds were derived from the temperature dependencies of vapor pressures. The measured data sets were successfully checked for internal consistency by comparison with vaporization enthalpies of similarly structured compounds.

  17. Collapsing criteria for vapor film around solid spheres as a fundamental stage leading to vapor explosion

    Energy Technology Data Exchange (ETDEWEB)

    Freud, Roy [Nuclear Research Center - Negev, Beer-Sheva (Israel)], E-mail: freud@bgu.ac.il; Harari, Ronen [Nuclear Research Center - Negev, Beer-Sheva (Israel); Sher, Eran [Pearlstone Center for Aeronautical Studies, Department of Mechanical Engineering, Ben-Gurion University, Beer-Sheva (Israel)

    2009-04-15

    Following a partial fuel-melting accident, a Fuel-Coolant Interaction (FCI) can result with the fragmentation of the melt into tiny droplets. A vapor film is then formed between the melt fragments and the coolant, while preventing a contact between them. Triggering, propagation and expansion typically follow the premixing stage. In the triggering stage, vapor film collapse around one or several of the fragments occurs. This collapse can be the result of fragments cooling, a sort of mechanical force, or by any other means. When the vapor film collapses and the coolant re-establishes contact with the dry surface of the hot melt, it may lead to a very rapid and rather violent boiling. In the propagation stage the shock wave front leads to stripping of the films surrounding adjacent droplets which enhance the fragmentation and the process escalates. During this process a large quantity of liquid vaporizes and its expansion can result in destructive mechanical damage to the surrounding structures. This multiphase thermal detonation in which high pressure shock wave is formed is regarded as 'vapor explosion'. The film boiling and its possible collapse is a fundamental stage leading to vapor explosion. If the interaction of the melt and the coolant does not result in a film boiling, no explosion occurs. Many studies have been devoted to determine the minimum temperature and heat flux that is required to maintain a film boiling. The present experimental study examines the minimum temperature that is required to maintain a film boiling around metal spheres immersed into a liquid (subcooled distilled water) reservoir. In order to simulate fuel fragments that are small in dimension and has mirror-like surface, small spheres coated with anti-oxidation layer were used. The heat flux from the spheres was calculated from the sphere's temperature profiles and the sphere's properties. The vapor film collapse was associated with a sharp rise of the heat flux

  18. Sinking towards destiny: High throughput measurement of phytoplankton sinking rates through time-resolved fluorescence plate spectroscopy.

    Science.gov (United States)

    Bannon, Catherine C; Campbell, Douglas A

    2017-01-01

    Diatoms are marine primary producers that sink in part due to the density of their silica frustules. Sinking of these phytoplankters is crucial for both the biological pump that sequesters carbon to the deep ocean and for the life strategy of the organism. Sinking rates have been previously measured through settling columns, or with fluorimeters or video microscopy arranged perpendicularly to the direction of sinking. These side-view techniques require large volumes of culture, specialized equipment and are difficult to scale up to multiple simultaneous measures for screening. We established a method for parallel, large scale analysis of multiple phytoplankton sinking rates through top-view monitoring of chlorophyll a fluorescence in microtitre well plates. We verified the method through experimental analysis of known factors that influence sinking rates, including exponential versus stationary growth phase in species of different cell sizes; Thalassiosira pseudonana CCMP1335, chain-forming Skeletonema marinoi RO5A and Coscinodiscus radiatus CCMP312. We fit decay curves to an algebraic transform of the decrease in fluorescence signal as cells sank away from the fluorometer detector, and then used minimal mechanistic assumptions to extract a sinking rate (m d-1) using an RStudio script, SinkWORX. We thereby detected significant differences in sinking rates as larger diatom cells sank faster than smaller cells, and cultures in stationary phase sank faster than those in exponential phase. Our sinking rate estimates accord well with literature values from previously established methods. This well plate-based method can operate as a high throughput integrative phenotypic screen for factors that influence sinking rates including macromolecular allocations, nutrient availability or uptake rates, chain-length or cell size, degree of silification and progression through growth stages. Alternately the approach can be used to phenomically screen libraries of mutants.

  19. Phase change heat transfer device for process heat applications

    International Nuclear Information System (INIS)

    Sabharwall, Piyush; Patterson, Mike; Utgikar, Vivek; Gunnerson, Fred

    2010-01-01

    The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up to ∼1300 K) and industrial scale power transport (≥50 MW), but also due to a potentially large separation distance between the nuclear and industrial plants (100+ m) dictated by safety and licensing mandates. The work reported here is the preliminary analysis of two-phase thermosyphon heat transfer performance with alkali metals. A thermosyphon is a thermal device for transporting heat from one point to another with quite extraordinary properties. In contrast to single-phased forced convective heat transfer via 'pumping a fluid', a thermosyphon (also called a wickless heat pipe) transfers heat through the vaporization/condensing process. The condensate is further returned to the hot source by gravity, i.e., without any requirement of pumps or compressors. With this mode of heat transfer, the thermosyphon has the capability to transport heat at high rates over appreciable distances, virtually isothermally and without any requirement for external pumping devices. Two-phase heat transfer by a thermosyphon has the advantage of high enthalpy transport that includes the sensible heat of the liquid, the latent heat of vaporization, and vapor superheat. In contrast, single-phase forced convection transports only the sensible heat of the fluid. Additionally, vapor-phase velocities within a thermosyphon are much greater than single-phase liquid velocities within a forced convective loop. Thermosyphon performance can be limited by the sonic limit (choking) of vapor flow and/or by condensate entrainment. Proper thermosyphon requires analysis of both.

  20. Optimum design of vaporizer fin with liquefied natural gas by numerical analysis

    International Nuclear Information System (INIS)

    Jeong, Hyo Min; Chung, Han Shik; Lee, Sang Chul; Kong, Tae Woo; Yi, Chung Seub

    2006-01-01

    Generally, the temperature drop under 0 .deg. C on vaporizer surface creates frozen dews. This problem seems to increase as the time progress and humidity rises. In addition, the frozen dews create frost deposition. Consequently, heat transfer on vaporizer decreases because frost deposition causes adiabatic condition. Therefore, it is very important to solve this problem. This paper aims to study of the optimum design of used vaporizer at local LNG station. In this paper, experimental results were compared with numerical results. Geometries of numerical and experimental vaporizers were identical. Studied parameters of vaporizer are angle between two fins (Φ) and fin thickness (TH F ). Numerical analysis results were presented through the correlations between the ice layer thickness (TH ICE ) on the vaporizer surface to the temperature distribution of inside vaporizer (T IN ), fin thickness (TH F ), and angle between two fins (Φ). Numerical result shows good agreement with experimental outcome. Finally, the correlations for optimum design of vaporizer are proposed on this paper

  1. Microscale interfacial behavior at vapor film collapse on high-temperature particle surface

    International Nuclear Information System (INIS)

    Abe, Yutaka; Tochio, Daisuke

    2009-01-01

    It has been pointed out that vapor film on a premixed high-temperature droplet surface should be collapsed to trigger vapor explosion. Thus, it is important to clarify the micromechanism of vapor film collapse behavior for the occurrence of vapor explosion. In the present study, microscale vapor-liquid interface behavior upon vapor film collapse caused by an external pressure pulse is experimentally observed and qualitatively analyzed. In the analytical investigation, interfacial temperature and interface movement were estimated with heat conduction analysis and visual data processing technique. Results show that condensation can possibly occur at the vapor-liquid interface when the pressure pulse arrived. That is, this result indicates that the vapor film collapse behavior is dominated not by fluid motion but by phase change. (author)

  2. Non-equilibrium phenomena near vapor-liquid interfaces

    CERN Document Server

    Kryukov, Alexei; Puzina, Yulia

    2013-01-01

    This book presents information on the development of a non-equilibrium approach to the study of heat and mass transfer problems using vapor-liquid interfaces, and demonstrates its application to a broad range of problems. In the process, the following peculiarities become apparent: 1. At vapor condensation on the interface from gas-vapor mixture, non-condensable components can lock up the interface surface and condensation stops completely. 2. At the evolution of vapor film on the heater in superfluid helium (He-II), the boiling mass flux density from the vapor-liquid interface is effectively zero at the macroscopic scale. 3. In problems concerning the motion of He-II bridges inside capillaries filled by vapor, in the presence of axial heat flux the He-II bridge cannot move from the heater as would a traditional liquid, but in the opposite direction instead. Thus the heater attracts the superfluid helium bridge. 4. The shape of liquid-vapor interface at film boiling on the axis-symmetric heaters immersed in l...

  3. Sinks as integrative elements of the anthropogenic metabolism

    Science.gov (United States)

    Kral, Ulrich; Brunner, Paul H.

    2015-04-01

    The anthropogenic metabolism is an open system requiring exchange of materials and energy between the anthroposphere and the environment. Material and energy flows are taken from nature and become utilized by men. After utilization, the materials either remain in the anthroposphere as recycling products, or they leave the anthroposphere as waste and emission flows. To accommodate these materials without jeopardizing human and environmental health, limited natural sinks are available; thus, man-made sinks have to be provided where natural sinks are missing or overloaded. The oral presentation (1) suggests a coherent definition of the term "sink", encompassing natural and man-made processes, (2) presents a framework to analyse and evaluate anthropogenic material flows to sinks, based on the tool substance flow analysis and impact assessment methodology, and (3) applies the framework in a case study approach for selected substances such as Copper and Lead in Vienna and Perfluorooctane sulfonate in Switzerland. Finally, the numeric results are aggregated in terms of a new indicator that specifies on a regional scale which fractions of anthropogenic material flows to sinks are acceptable. The following results are obtained: In Vienna, 99% of Cu flows to natural and man-made sinks are in accordance with accepted standards. However, the 0.7% of Cu entering urban soils and the 0.3% entering receiving waters surpass the acceptable level. In the case of Pb, 92% of all flows into sinks prove to be acceptable, but 8% are disposed of in local landfills with limited capacity. For PFOS, 96% of all flows into sinks are acceptable. 4% cannot be evaluated due to a lack of normative criteria, despite posing a risk for human health and the environment. The case studies corroborate the need and constraints of sinks to accommodate inevitable anthropogenic material flows.

  4. Characterization of industrial process waste heat and input heat streams

    Energy Technology Data Exchange (ETDEWEB)

    Wilfert, G.L.; Huber, H.B.; Dodge, R.E.; Garrett-Price, B.A.; Fassbender, L.L.; Griffin, E.A.; Brown, D.R.; Moore, N.L.

    1984-05-01

    The nature and extent of industrial waste heat associated with the manufacturing sector of the US economy are identified. Industry energy information is reviewed and the energy content in waste heat streams emanating from 108 energy-intensive industrial processes is estimated. Generic types of process equipment are identified and the energy content in gaseous, liquid, and steam waste streams emanating from this equipment is evaluated. Matchups between the energy content of waste heat streams and candidate uses are identified. The resultant matrix identifies 256 source/sink (waste heat/candidate input heat) temperature combinations. (MHR)

  5. Secondhand Exposure to Vapors From Electronic Cigarettes

    Science.gov (United States)

    Czogala, Jan; Fidelus, Bartlomiej; Zielinska-Danch, Wioleta; Travers, Mark J.; Sobczak, Andrzej

    2014-01-01

    Introduction: Electronic cigarettes (e-cigarettes) are designed to generate inhalable nicotine aerosol (vapor). When an e-cigarette user takes a puff, the nicotine solution is heated and the vapor is taken into lungs. Although no sidestream vapor is generated between puffs, some of the mainstream vapor is exhaled by e-cigarette user. The aim of this study was to evaluate the secondhand exposure to nicotine and other tobacco-related toxicants from e-cigarettes. Materials and Methods: We measured selected airborne markers of secondhand exposure: nicotine, aerosol particles (PM2.5), carbon monoxide, and volatile organic compounds (VOCs) in an exposure chamber. We generated e-cigarette vapor from 3 various brands of e-cigarette using a smoking machine and controlled exposure conditions. We also compared secondhand exposure with e-cigarette vapor and tobacco smoke generated by 5 dual users. Results: The study showed that e-cigarettes are a source of secondhand exposure to nicotine but not to combustion toxicants. The air concentrations of nicotine emitted by various brands of e-cigarettes ranged from 0.82 to 6.23 µg/m3. The average concentration of nicotine resulting from smoking tobacco cigarettes was 10 times higher than from e-cigarettes (31.60±6.91 vs. 3.32±2.49 µg/m3, respectively; p = .0081). Conclusions: Using an e-cigarette in indoor environments may involuntarily expose nonusers to nicotine but not to toxic tobacco-specific combustion products. More research is needed to evaluate health consequences of secondhand exposure to nicotine, especially among vulnerable populations, including children, pregnant women, and people with cardiovascular conditions. PMID:24336346

  6. Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

    Science.gov (United States)

    Koplow, Jeffrey P.

    2016-02-16

    Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.

  7. Fire ants perpetually rebuild sinking towers

    Science.gov (United States)

    Phonekeo, Sulisay; Mlot, Nathan; Monaenkova, Daria; Hu, David L.; Tovey, Craig

    2017-07-01

    In the aftermath of a flood, fire ants, Solenopsis invicta, cluster into temporary encampments. The encampments can contain hundreds of thousands of ants and reach over 30 ants high. How do ants build such tall structures without being crushed? In this combined experimental and theoretical study, we investigate the shape and rate of construction of ant towers around a central support. The towers are bell shaped, consistent with towers of constant strength such as the Eiffel tower, where each element bears an equal load. However, unlike the Eiffel tower, the ant tower is built through a process of trial and error, whereby failed portions avalanche until the final shape emerges. High-speed and novel X-ray videography reveal that the tower constantly sinks and is rebuilt, reminiscent of large multicellular systems such as human skin. We combine the behavioural rules that produce rafts on water with measurements of adhesion and attachment strength to model the rate of growth of the tower. The model correctly predicts that the growth rate decreases as the support diameter increases. This work may inspire the design of synthetic swarms capable of building in vertical layers.

  8. Study on the effect of subcooling on vapor film collapse on high temperature particle surface

    International Nuclear Information System (INIS)

    Abe, Yutaka; Tochio, Daisuke; Yanagida, Hiroshi

    2000-01-01

    Thermal detonation model is proposed to describe vapor explosion. According to this model, vapor film on pre-mixed high temperature droplet surface is needed to be collapsed for the trigger of the vapor explosion. It is pointed out that the vapor film collapse behavior is significantly affected by the subcooling of low temperature liquid. However, the effect of subcooling on micro-mechanism of vapor film collapse behavior is not experimentally well identified. The objective of the present research is to experimentally investigate the effect of subcooling on micro-mechanism of film boiling collapse behavior. As the results, it is experimentally clarified that the vapor film collapse behavior in low subcooling condition is qualitatively different from the vapor film collapse behavior in high subcooling condition. In case of vapor film collapse by pressure pulse, homogeneous vapor generation occurred all over the surface of steel particle in low subcooling condition. On the other hand, heterogeneous vapor generation was observed for higher subcooling condition. In case of vapor film collapse spontaneously, fluctuation of the gas-liquid interface after quenching propagated from bottom to top of the steel particle heterogeneously in low subcooling condition. On the other hand, simultaneous vapor generation occurred for higher subcooling condition. And the time transient of pressure, particle surface temperature, water temperature and visual information were simultaneously measured in the vapor film collapse experiment by external pressure pulse. Film thickness was estimated by visual data processing technique with the pictures taken by the high-speed video camera. Temperature and heat flux at the vapor-liquid interface were estimated by solving the heat condition equation with the measured pressure, liquid temperature and vapor film thickness as boundary conditions. Movement of the vapor-liquid interface were estimated with the PIV technique with the visual observation

  9. Recoverying device for sodium vapor in inert gas

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, Tamotsu; Nagashima, Ikuo

    1992-11-06

    A multi-pipe type heat exchanger for cooling an inert gas and a mist trap connected to the inert gas exit of the heat exchanger are disposed. A mist filter having bottomed pipes made of an inert gas-permeable sintered metal is disposed in the mist trap, and an inert gas discharge port is disposed at the upper side wall. With such a constitution, a high temperature inert gas containing sodium vapors can be cooled efficiently by the multi-pipe type heat exchanger capable of easy temperature control, thereby converting sodium vapors into mists, and the inert gas containing sodium mists can be flown into the mist trap. Sodium mists are collected by the mist filter and sodium mists flown down are discharged from the discharge port. With such procedures, a great amount of the inert gas containing sodium vapors can be processed continuously. (T.M.).

  10. Configuration of dishwasher to improve energy efficiency of water heating

    Science.gov (United States)

    Gluesenkamp, Kyle R.

    2018-04-24

    A washing machine includes a sealed tub for accepting articles to be washed. A liquid circulation circuit sprays a pressurized liquid (e.g. water, detergent, solvent) around the articles to clean them. The liquid circulation circuit is in thermal contact with a hot side of a thermoelectric device. A heat sink is in thermal contact with both a cold side of the thermoelectric device and a heat sink charging circuit. A liquid is successively directed one or more times through the liquid circulation circuit with the thermoelectric device powered on, and then directed one or more times through the heat sink charging circuit with the thermoelectric device powered off. Finally, the liquid is discharged from the tub after having its temperature lowered by heat exchange to the heat sink.

  11. Improvements in or relating to devices for conducting excess heat away from heat sources

    International Nuclear Information System (INIS)

    Cooke-Yarborough, E.H.

    1976-01-01

    Reference is made to radioisotope powered heat engines. Should such an engine stop working for any reason the radioisotope heat source will continue to generate heat, and this may cause overheating and possible damage to the engine as well as the heat source. A device is described for conducting excess heat from the heat source to a heat sink but which in normal operation of the engine will impede heat conduction and so reduce thermal losses. The device may be used to support and/or locate the heat source. Constructional and operational details are given. (U.K.)

  12. Vaporization of irradiated droplets

    International Nuclear Information System (INIS)

    Armstrong, R.L.; O'Rourke, P.J.; Zardecki, A.

    1986-01-01

    The vaporization of a spherically symmetric liquid droplet subject to a high-intensity laser flux is investigated on the basis of a hydrodynamic description of the system composed of the vapor and ambient gas. In the limit of the convective vaporization, the boundary conditions at the fluid--gas interface are formulated by using the notion of a Knudsen layer in which translational equilibrium is established. This leads to approximate jump conditions at the interface. For homogeneous energy deposition, the hydrodynamic equations are solved numerically with the aid of the CON1D computer code (''CON1D: A computer program for calculating spherically symmetric droplet combustion,'' Los Alamos National Laboratory Report No. LA-10269-MS, December, 1984), based on the implict continuous--fluid Eulerian (ICE) [J. Comput. Phys. 8, 197 (1971)] and arbitrary Lagrangian--Eulerian (ALE) [J. Comput. Phys. 14, 1227 (1974)] numerical mehtods. The solutions exhibit the existence of two shock waves propagating in opposite directions with respect to the contact discontinuity surface that separates the ambient gas and vapor

  13. Vapor liquid fraction determination

    International Nuclear Information System (INIS)

    1980-01-01

    This invention describes a method of measuring liquid and vapor fractions in a non-homogeneous fluid flowing through an elongate conduit, such as may be required with boiling water, non-boiling turbulent flows, fluidized bed experiments, water-gas mixing analysis, and nuclear plant cooling. (UK)

  14. Enthalpy of Vaporization and Vapor Pressures: An Inexpensive Apparatus

    Science.gov (United States)

    Battino, Rubin; Dolson, David A.; Hall, Michael A.; Letcher, Trevor M.

    2007-01-01

    A simple and inexpensive method to determine the enthalpy of vaporization of liquids by measuring vapor pressure as a function of temperature is described. The vapor pressures measured with the stopcock cell were higher than the literature values and those measured with the sidearm rubber septum cell were both higher and lower than literature…

  15. Maximizing Lifetime of Wireless Sensor Networks with Mobile Sink Nodes

    Directory of Open Access Journals (Sweden)

    Yourong Chen

    2014-01-01

    Full Text Available In order to maximize network lifetime and balance energy consumption when sink nodes can move, maximizing lifetime of wireless sensor networks with mobile sink nodes (MLMS is researched. The movement path selection method of sink nodes is proposed. Modified subtractive clustering method, k-means method, and nearest neighbor interpolation method are used to obtain the movement paths. The lifetime optimization model is established under flow constraint, energy consumption constraint, link transmission constraint, and other constraints. The model is solved from the perspective of static and mobile data gathering of sink nodes. Subgradient method is used to solve the lifetime optimization model when one sink node stays at one anchor location. Geometric method is used to evaluate the amount of gathering data when sink nodes are moving. Finally, all sensor nodes transmit data according to the optimal data transmission scheme. Sink nodes gather the data along the shortest movement paths. Simulation results show that MLMS can prolong network lifetime, balance node energy consumption, and reduce data gathering latency under appropriate parameters. Under certain conditions, it outperforms Ratio_w, TPGF, RCC, and GRND.

  16. Effect of fluid-to-structure heat transfer on the structural damage potential to a liquid-metal fast breeder reactor

    International Nuclear Information System (INIS)

    Hakim, S.J.; Abramson, P.B.

    1979-01-01

    Deterministic calculations simulating a hypothetical accident in a liquid-metal fast breeder reactor that leads to a hydrodynamic disassembly of the core have been carried out to estimate the system's damage potential due to the vapor-pressure-driven expansion of molten core material and its dependency on the heat transfer to the remaining structure. These calculations ignored the effect on the work potential of sodium left in the core during the disassembly. Results indicate that steel cladding in the upper axial blankets and fission gas plenum acts as a thermodynamic energy sink that could reduce the total thermodynamic work energy by between one and two orders of magnitude, provided little or no sodium is present in the core at the time of interaction. These results have been found to be insensitive to the rate of heat transferred from the molten fuel to the molten steel that comprises the molten core material

  17. Graphite Foam Heat Exchangers for Thermal Management

    Energy Technology Data Exchange (ETDEWEB)

    Klett, J.W.

    2004-06-07

    Improved thermal management is needed to increase the power density of electronic and more effectively cool electronic enclosures that are envisioned in future aircraft, spacecraft and surface ships. Typically, heat exchanger cores must increase in size to more effectively dissipate increased heat loads, this would be impossible in many cases, thus improved heat exchanger cores will be required. In this Phase I investigation, MRi aimed to demonstrate improved thermal management using graphite foam (Gr-foam) core heat exchangers. The proposed design was to combine Gr-foams from POCO with MRi's innovative low temperature, active metal joining process (S-Bond{trademark}) to bond Gr-foam to aluminum, copper and aluminum/SiC composite faceplates. The results were very favorable, so a Phase II SBIR with the MDA was initiated. This had primarily 5 tasks: (1) bonding, (2) thermal modeling, (3) cooling chip scale packages, (4) evaporative cooling techniques and (5) IGBT cold plate development. The bonding tests showed that the ''reflow'' technique with S-Bond{reg_sign}-220 resulted in the best and most consistent bond. Then, thermal modeling was used to design different chip scale packages and IGBT cold plates. These designs were used to fabricate many finned graphite foam heat sinks specifically for two standard type IC packages, the 423 and 478 pin chips. These results demonstrated several advantages with the foam. First, the heat sinks with the foam were lighter than the copper/aluminum sinks used as standards. The sinks for the 423 design made from foam were not as good as the standard sinks. However, the sinks made from foam for the 478 pin chips were better than the standard heat sinks used today. However, this improvement was marginal (in the 10-20% better regime). However, another important note was that the epoxy bonding technique resulted in heat sinks with similar results as that with the S-bond{reg_sign}, slightly worse than the S

  18. Heat receiving plates in thermonuclear device

    International Nuclear Information System (INIS)

    Kitamura, Kazunori.

    1988-01-01

    Purpose: To obtain a heat receiving plate structure capable of withstanding sputtering wear and retaining the thermal deformation and residual stress low upon junction and available at a reduced cost. Constitution: Junction structures between heat sinks and armours are the same as usual, whereas high melting armour (for example, made of tungsten) are used at the portion on a heat receiving plate where the thermal load and particle load are higher while materials having a heat expansion coefficient similar to that of the heat sink (stainless steel) are used at the portion where the thermal load and particle load are lower on a heat receiving plate depending on the thermal load and particle load distribution. This can reduce the thermal deformation for the entire divertor heat receiving plate to obtain a heat receiving plate of a good surface dimensional accuracy. (Takahashi, M.)

  19. Temperature effects on sinking velocity of different Emiliania huxleyi strains.

    Science.gov (United States)

    Rosas-Navarro, Anaid; Langer, Gerald; Ziveri, Patrizia

    2018-01-01

    The sinking properties of three strains of Emiliania huxleyi in response to temperature changes were examined. We used a recently proposed approach to calculate sinking velocities from coccosphere architecture, which has the advantage to be applicable not only to culture samples, but also to field samples including fossil material. Our data show that temperature in the sub-optimal range impacts sinking velocity of E. huxleyi. This response is widespread among strains isolated in different locations and moreover comparatively predictable, as indicated by the similar slopes of the linear regressions. Sinking velocity was positively correlated to temperature as well as individual cell PIC/POC over the sub-optimum to optimum temperature range in all strains. In the context of climate change our data point to an important influence of global warming on sinking velocities. It has recently been shown that seawater acidification has no effect on sinking velocity of a Mediterranean E. huxleyi strain, while nutrient limitation seems to have a small negative effect on sinking velocity. Given that warming, acidification, and lowered nutrient availability will occur simultaneously under climate change scenarios, the question is what the net effect of different influential factors will be. For example, will the effects of warming and nutrient limitation cancel? This question cannot be answered conclusively but analyses of field samples in addition to laboratory culture studies will improve predictions because in field samples multi-factor influences and even evolutionary changes are not excluded. As mentioned above, the approach of determining sinking rate followed here is applicable to field samples. Future studies could use it to analyse not only seasonal and geographic patterns but also changes in sinking velocity over geological time scales.

  20. Biological control of the terrestrial carbon sink

    Science.gov (United States)

    Schulze, E.-D.

    2006-03-01

    different reasons depending on the region of the world: anthropogenic nitrogen deposition is the controlling factor in Europe, increasing global temperatures is the main factor in Siberia, and maybe rising CO2 the factor controlling the carbon fluxes in Amazonia. However, this has not lead to increases in net biome productivity, due to associated losses. Also important is the interaction between biodiversity and biogeochemical processes. It is shown that net primary productivity increases with plant species diversity (50% species loss equals 20% loss in productivity). However, in this extrapolation the action of soil biota is poorly understood although soils contribute the largest number of species and of taxonomic groups to an ecosystem. The global terrestrial carbon budget strongly depends on areas with pristine old growth forests which are carbon sinks. The management options are very limited, mostly short term, and usually associated with high uncertainty. Unmanaged grasslands appear to be a carbon sink of similar magnitude as forest, but generally these ecosystems lost their C with grazing and agricultural use. Extrapolation to the future of Earth climate shows that the biota will not be able to balance fossil fuel emissions, and that it will be essential to develop a carbon free energy system in order to maintain the living conditions on earth.