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Sample records for convectively cooled structures

  1. Convective cooling of photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, E.; Gibbons, C. [Energy Engineering Group, Mechanical Engineering Department, Cork Institute of Technology, Bishopstown, Cork (Ireland)

    2004-07-01

    Most solar cells presently on the market are based on silicon wafers, the so-called first generation technology. As this technology has matured costs have become increasingly dominated by material costs. In the last ten years, continuous work has brought the efficiency of standard cells to the 25% region. A switch to second generation or thin film technology cells now seems imminent. Thin film technology eliminates the silicon wafer and offer the prospect of reducing material and manufacturing costs, but they exhibit lower efficiencies of around 10% for a commercial device. Third generation or tandem cells are currently at a 'proof of concept' research level, with a theoretical conversion rate of 86.8% being asserted Whatever the material construction and manufacturing method of cells, the thermal effect of overheating will prevail in the semiconductor and it is accepted that a lowered temperature will bring about an increase in conversion efficiency. The aim of this project is to improve the efficiency of PV electrical output, by convectively cooling the cells through perforations in them. As the cells heat up they lose efficiency. As the panel heats up a loss in efficiency of 0.5% per C increase in temperature has been recorded. (orig.)

  2. Evaluation of finite element formulations for transient conduction forced-convection analysis. [of heat transfer for active cooling of hypersonic airframe and engine structures

    Science.gov (United States)

    Thornton, E. A.; Wieting, A. R.

    1979-01-01

    Conventional versus upwind convective finite elements, and lumped versus consistent formulations for practical conduction/forced convection analysis are evaluated on the basis of numerical studies, with finite element and finite difference lumped-parameter temperatures compared to closed-form analytical solutions for convection problems. Attention is given to two practical combined conduction and forced convection applications, stressing that the finite element method, showing superior accuracy, is competitive with the finite difference lumped-parameter method. Also considered are the computational time savings offered by the zero capacitance nodes procedure and comparative finite element and finite difference lumped-parameter computer times. The present study has reference to the design of actively cooled engine and airframe structures for hypersonic flight.

  3. Convection-Dominated Accretion Flows with Radiative Cooling

    Institute of Scientific and Technical Information of China (English)

    LI Shuang-Liang; XUE Li; LU Ju-Fu

    2007-01-01

    @@ By numerically solving the set of basic equations describing black hole accretion flows with low accretion rates,we show that although the dynamical structure of these flows is essentially unaffected by radiative processes in comparison with the case in which the radiation is not considered, the radiative cooling can be more important than the advective cooling in the flow's convection-dominated zone, and this result may have implications to distinguish observationally convection-dominated accretion flows from advection-dominated accretion flows.

  4. Convective cores in galactic cooling flows

    CERN Document Server

    Kritsuk, A G; Müller, E

    2000-01-01

    We use hydrodynamic simulations with adaptive grid refinement to study the dependence of hot gas flows in X-ray luminous giant elliptical galaxies on the efficiency of heat supply to the gas. We consider a number of potential heating mechanisms including Type Ia supernovae and sporadic nuclear activity of a central supermassive black hole. As a starting point for this research we use an equilibrium hydrostatic recycling model (Kritsuk 1996). We show that a compact cooling inflow develops, if the heating is slightly insufficient to counterbalance radiative cooling of the hot gas in the central few kiloparsecs. An excessive heating in the centre, instead, drives a convectively unstable outflow. We model the onset of the instability and a quasi-steady convective regime in the core of the galaxy in two-dimensions assuming axial symmetry. Provided the power of net energy supply in the core is not too high, the convection remains subsonic. The convective pattern is dominated by buoyancy driven large-scale mushroom-...

  5. Optimal convection cooling flows in general geometries

    CERN Document Server

    Alben, Silas

    2016-01-01

    We generalize a recent method for computing optimal 2D convection cooling flows in a horizontal layer to a wide range of geometries, including those relevant for technological applications. We write the problem in a conformal pair of coordinates which are the pure conduction temperature and its harmonic conjugate. We find optimal flows for cooling a cylinder in an annular domain, a hot plate embedded in a cold surface, and a channel with hot interior and cold exterior. With a constraint of fixed kinetic energy, the optimal flows are all essentially the same in the conformal coordinates. In the physical coordinates, they consist of vortices ranging in size from the length of the hot surface to a small cutoff length at the interface of the hot and cold surfaces. With the constraint of fixed enstrophy (or fixed rate of viscous dissipation), a geometry-dependent metric factor appears in the equations. The conformal coordinates are useful here because they map the problems to a rectangular domain, facilitating num...

  6. Fundamental Research on Convective Heat Transfer in Electronic Cooling Technology

    Institute of Scientific and Technical Information of China (English)

    C.F.Ma; Y.P.Gan; 等

    1992-01-01

    During the past six years comprehensive research programs have been conducted at the Beijing Polytechnic University to provide a better understanding of heat transfer characteristics of existing and condidate cooling techniques for electronic and microelestanding of heat transfer characteristics of existing and condidate cooling techniques for electronic and microleectronic devices.This paper provides a review and summary of the programs with emphasis on direct liquid cooling.Included in this review are the heat transfer investigations related to the following cooling modes:liquid free,mixed and forced convection.liquid jet impingement,flowing liquid film cooling,pool boiling,spray cooling,foreign gas jet impingement in liquid pool,and forced convection air-cooling.

  7. Study of Natural Convection Passive Cooling System for Nuclear Reactors

    Science.gov (United States)

    Abdillah, Habibi; Saputra, Geby; Novitrian; Permana, Sidik

    2017-07-01

    Fukushima nuclear reactor accident occurred due to the reactor cooling pumps and followed by all emergencies cooling systems could not work. Therefore, the system which has a passive safety system that rely on natural laws such as natural convection passive cooling system. In natural convection, the cooling material can flow due to the different density of the material due to the temperature difference. To analyze such investigation, a simple apparatus was set up and explains the study of natural convection in a vertical closed-loop system. It was set up that, in the closed loop, there is a heater at the bottom which is representing heat source system from the reactor core and cooler at the top which is showing the cooling system performance in room temperature to make a temperature difference for convection process. The study aims to find some loop configurations and some natural convection performances that can produce an optimum flow of cooling process. The study was done and focused on experimental approach and simulation. The obtained results are showing and analyzing in temperature profile data and the speed of coolant flow at some point on the closed-loop system.

  8. Thermal computations for electronics conductive, radiative, and convective air cooling

    CERN Document Server

    Ellison, Gordon

    2010-01-01

    IntroductionPrimary mechanisms of heat flowConductionApplication example: Silicon chip resistance calculationConvectionApplication example: Chassis panel cooled by natural convectionRadiationApplication example: Chassis panel cooled only by radiation 7Illustrative example: Simple thermal network model for a heat sinked power transistorIllustrative example: Thermal network circuit for a printed circuit boardCompact component modelsIllustrative example: Pressure and thermal circuits for a forced air cooled enclosureIllustrative example: A single chip package on a printed circuit board-the proble

  9. Multicloud convective parametrizations with crude vertical structure

    Energy Technology Data Exchange (ETDEWEB)

    Khouider, Boualem [University of Victoria, Mathematics and Statistics, PO BOX 3045 STN CSC, Victoria, BC (Canada); Majda, Andrew J. [New York University, Department of Mathematics and Center for Atmosphere/Ocean Sciences, Courant Institute, New York, NY (United States)

    2006-11-15

    Recent observational analysis reveals the central role of three multi-cloud types, congestus, stratiform, and deep convective cumulus clouds, in the dynamics of large scale convectively coupled Kelvin waves, westward propagating two-day waves, and the Madden-Julian oscillation. The authors have recently developed a systematic model convective parametrization highlighting the dynamic role of the three cloud types through two baroclinic modes of vertical structure: a deep convective heating mode and a second mode with low level heating and cooling corresponding respectively to congestus and stratiform clouds. The model includes a systematic moisture equation where the lower troposphere moisture increases through detrainment of shallow cumulus clouds, evaporation of stratiform rain, and moisture convergence and decreases through deep convective precipitation and a nonlinear switch which favors either deep or congestus convection depending on whether the troposphere is moist or dry. Here several new facets of these multi-cloud models are discussed including all the relevant time scales in the models and the links with simpler parametrizations involving only a single baroclinic mode in various limiting regimes. One of the new phenomena in the multi-cloud models is the existence of suitable unstable radiative convective equilibria (RCE) involving a larger fraction of congestus clouds and a smaller fraction of deep convective clouds. Novel aspects of the linear and nonlinear stability of such unstable RCE's are studied here. They include new modes of linear instability including mesoscale second baroclinic moist gravity waves, slow moving mesoscale modes resembling squall lines, and large scale standing modes. The nonlinear instability of unstable RCE's to homogeneous perturbations is studied with three different types of nonlinear dynamics occurring which involve adjustment to a steady deep convective RCE, periodic oscillation, and even heteroclinic chaos in

  10. Cooling Augmentation with Microchanneled Structures

    Institute of Scientific and Technical Information of China (English)

    X.F.Peng; B.X.Wang

    1993-01-01

    Experiments were conducted to investigate the heat transfer characteristics and cooling performance of subcooled liquid,water,flowing through rectangular cross-section microchanneled structures machined on a stainless steel plate.Heat transfer or flow mode stransition was observed when the heating rate or wall temperature was increased.This transition was found to be suggestively induced by the variation in liquid thermophysical properties due to the significant rise of liquid temperature in the microstructures.The influence of such parameters as liquid velocity,subcooling,property variation,and microchannel geometric configuration on the heat transfer behavior,cooling performance and the heat transfer and liquid flow mode transition were also investigated.The experiments indicated that both single-phase forced convection and flow boiling characteristics were quite different from those in normal-sized tubes and the heat transfer was obviously intensified.

  11. Temporal response of laser power standards with natural convective cooling.

    Science.gov (United States)

    Xu, Tao; Gan, Haiyong; Yu, Jing; Zang, Erjun

    2016-01-25

    Laser power detectors with natural convective cooling are convenient to use and hence widely applicable in a power range below 150 W. However, the temporal response characteristics of the laser power detectors need to be studied in detail for accurate measurement. The temporal response based on the absolute laser power standards with natural convective cooling is studied through theoretical analysis, numerical simulations, and experimental verifications. Our results show that the response deviates from a single exponential function and that an ultimate response balance is difficult to achieve because the temperature rise of the heat sink leads to continuous increase of the response. To determine the measurement values, an equal time reading method is proposed and validated by the laser power calibrations.

  12. The convection cooling system of the Yakutsk permafrost seed repository

    Institute of Scientific and Technical Information of China (English)

    Vladimir N.Panin; Georgii P.Kuzmin

    2014-01-01

    Temperature is critical to maintaining seed viability under long term storage conditions. It has been common practice to use refrigeration systems to maintain required storage temperatures. A seed repository constructed in permafrost in Ya kutsk, Russia is the first seed storage facility that relies solely on natural cold. This paper describes the design and per formance of the cooling system of the repository. An innovative aspect of the cooling system is that it utilizes the patterns of temperature wave propagation in permafrost. Predicted and measured ground temperatures for the first year of operation are presented and analyzed. Results indicate that convection air cooling systems can be used to control the temperature regime in underground facilities in permafrost.

  13. Numerical study on film cooling and convective heat transfer characteristics in the cutback region of turbine blade trailing edge

    Directory of Open Access Journals (Sweden)

    Xie Yong-Hui

    2016-01-01

    Full Text Available Gas turbine blade trailing edge is easy to burn out under the exposure of high-temperature gas due to its thin shape. The cooling of this area is an important task in gas turbine blade design. The structure design and analysis of trailing edge is critical because of the complexity of geometry, arrangement of cooling channels, design requirement of strength, and the working condition of high heat flux. In the present paper, a 3-D model of the trailing edge cooling channel is constructed and both structures with and without land are numerically investigated at different blowing ratio. The distributions of film cooling effectiveness and convective heat transfer coefficient on cutback and land surface are analyzed, respectively. According to the results, it is obtained that the distributions of film cooling effectiveness and convective heat transfer coefficient both show the symmetrical characteristics as a result of the periodic structure of the trailing edge. The increase of blowing ratio significantly improves the film cooling effectiveness and convective heat transfer coefficient on the cutback surface, which is beneficial to the cooling of trailing edge. It is also found that the land structure is advantageous for enhancing the streamwise film cooling effectiveness of the trailing edge surface while the film cooling effectiveness on the land surface remains at a low level. Convective heat transfer coefficient exhibits a strong dependency with the blowing ratio, which suggests that film cooling effectiveness and convective heat transfer coefficient must be both considered and analyzed in the design of trailing edge cooling structure.

  14. Cooling by convection vs cooling by conduction for treatment of fever in critically ill adults.

    Science.gov (United States)

    Creechan, T; Vollman, K; Kravutske, M E

    2001-01-01

    Cooling with water-flow blankets, which are difficult to manipulate and interfere with patients' care, may be ineffective in controlling fever. To compare the effectiveness of cooling via convective airflow blankets with cooling via conductive water-flow blankets for treatment of fever in critically ill adults. A 2-group experimental design was used to compare cooling via convection (n = 20) with cooling via conduction (n = 17) in critically ill adults with an infection-related fever of 38.5 degrees C or greater. Esophageal temperature was measured every 15 minutes until a temperature of 38.0 degrees C was reached or 8 hours had elapsed. Alternative cooling measures were withheld unless the temperature increased to more than 40.0 degrees C. Data on nurses' satisfaction were collected, and complications related to each cooling method were examined. Temperatures decreased more rapidly in the airflow group (mean decrease, 0.377 degree C/h) than in the water-flow group (mean decrease, 0.163 degree C/h). A temperature of 38.0 degrees C was achieved more often in the airflow group (75% vs 47.1%). Fever (temperature > 38.5 degrees C) recurred sooner in the water-flow group (6.6 hours) than in the airflow group (22.2 hours). Both methods were easy to use. Compared with the water-flow blanket, the airflow blanket was recommended for future use twice as often and interfered less with patients' care. In critically ill adults with an infection or a suspected infection, cooling with an airflow blanket is more effective and more preferred for cooling than is cooling with a water-flow blanket.

  15. Turbulence convective heat transfer for cooling the photovoltaic cells

    Science.gov (United States)

    Arianmehr, Iman

    Solar PV (photovoltaic) is a rapidly advancing renewable energy technology which converts sunlight directly into electricity. One of the outstanding challenges of the current PV technology is the reduction in its conversion efficiency with increasing PV panel temperature, which is closely associated with the increase in solar intensity and the ambient temperature surrounding the PV panels. To more effectively capture the available energy when the sun is most intense, significant efforts have been invested in active and passive cooling research over the last few years. While integrated cooling systems can lead to the highest total efficiencies, they are usually neither the most feasible nor the most cost effective solutions. This work examines some simple passive means of manipulating the prevailing wind turbulence to enhance convective heat transfer over a heated plate in a wind tunnel.

  16. Experimental StudyHigh Altitude Forced Convective Cooling of Electromechanical Actuation Systems

    Science.gov (United States)

    2016-01-01

    within industry, so as to keep its applicability to what might be used to cool EMAS. Therefore, a parallel plate sink was chosen. This type of heat ...cooling 3 Approved for public release; distribution unlimited. o Convection, liquid to air heat exchanger o Convection, air cooling with fan...surface or heat exchanger to remove the thermal energy away from critical components and convect it to an airstream. The most common source of the air

  17. Latent cooling and microphysics effects in deep convection

    Science.gov (United States)

    Fernández-González, S.; Wang, P. K.; Gascón, E.; Valero, F.; Sánchez, J. L.

    2016-11-01

    Water phase changes within a storm are responsible for the enhancement of convection and therefore the elongation of its lifespan. Specifically, latent cooling absorbed during evaporation, melting and sublimation is considered the main cause of the intensification of downdrafts. In order to know more accurately the consequences of latent cooling caused by each of these processes (together with microphysical effects that they induce), four simulations were developed with the Wisconsin Dynamical and Microphysical Model (WISCDYMM): one with all the microphysical processes; other without sublimation; melting was suppressed in the third simulation; and evaporation was disabled in the fourth. The results show that sublimation cooling is not essential to maintain the vertical currents of the storm. This is demonstrated by the fact that in the simulation without sublimation, maximum updrafts are in the same range as in the control simulation, and the storm lifespan is similar or even longer. However, melting was of vital importance. The storm in the simulation without melting dissipated prematurely, demonstrating that melting is indispensable to the enhancement of downdrafts below the freezing level and for avoiding the collapse of low level updrafts. Perhaps the most important finding is the crucial influence of evaporative cooling above the freezing level that maintains and enhances mid-level downdrafts in the storm. It is believed that this latent cooling comes from the evaporation of supercooled liquid water connected with the Bergeron-Findeisen process. Therefore, besides its influence at low levels (which was already well known), this evaporative cooling is essential to strengthen mid-level downdrafts and ultimately achieve a quasi-steady state.

  18. Natural Convection and Boiling for Cooling SRP Reactors During Loss of Circulation Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Buckner, M.R.

    2001-06-26

    This study investigated natural convection and boiling as a means of cooling SRP reactors in the event of a loss of circulation accident. These studies show that single phase natural convection cooling of SRP reactors in shutdown conditions with the present piping geometry is probably not feasible.

  19. Convective cooling in a pool-type research reactor

    Science.gov (United States)

    Sipaun, Susan; Usman, Shoaib

    2016-01-01

    A reactor produces heat arising from fission reactions in the nuclear core. In the Missouri University of Science and Technology research reactor (MSTR), this heat is removed by natural convection where the coolant/moderator is demineralised water. Heat energy is transferred from the core into the coolant, and the heated water eventually evaporates from the open pool surface. A secondary cooling system was installed to actively remove excess heat arising from prolonged reactor operations. The nuclear core consists of uranium silicide aluminium dispersion fuel (U3Si2Al) in the form of rectangular plates. Gaps between the plates allow coolant to pass through and carry away heat. A study was carried out to map out heat flow as well as to predict the system's performance via STAR-CCM+ simulation. The core was approximated as porous media with porosity of 0.7027. The reactor is rated 200kW and total heat density is approximately 1.07+E7 Wm-3. An MSTR model consisting of 20% of MSTR's nuclear core in a third of the reactor pool was developed. At 35% pump capacity, the simulation results for the MSTR model showed that water is drawn out of the pool at a rate 1.28 kg s-1 from the 4" pipe, and predicted pool surface temperature not exceeding 30°C.

  20. Convective cooling in a pool-type research reactor

    Energy Technology Data Exchange (ETDEWEB)

    Sipaun, Susan, E-mail: susan@nm.gov.my [Malaysian Nuclear Agency, Industrial Technology Division, Blok 29T, Bangi 43200, Selangor (Malaysia); Usman, Shoaib, E-mail: usmans@mst.edu [Missouri University of Science and Technology, Nuclear Engineering, 222 Fulton Hall 301 W.14th St., Rolla 64509 MO (United States)

    2016-01-22

    A reactor produces heat arising from fission reactions in the nuclear core. In the Missouri University of Science and Technology research reactor (MSTR), this heat is removed by natural convection where the coolant/moderator is demineralised water. Heat energy is transferred from the core into the coolant, and the heated water eventually evaporates from the open pool surface. A secondary cooling system was installed to actively remove excess heat arising from prolonged reactor operations. The nuclear core consists of uranium silicide aluminium dispersion fuel (U{sub 3}Si{sub 2}Al) in the form of rectangular plates. Gaps between the plates allow coolant to pass through and carry away heat. A study was carried out to map out heat flow as well as to predict the system’s performance via STAR-CCM+ simulation. The core was approximated as porous media with porosity of 0.7027. The reactor is rated 200kW and total heat density is approximately 1.07+E7 Wm{sup −3}. An MSTR model consisting of 20% of MSTR’s nuclear core in a third of the reactor pool was developed. At 35% pump capacity, the simulation results for the MSTR model showed that water is drawn out of the pool at a rate 1.28 kg s{sup −1} from the 4” pipe, and predicted pool surface temperature not exceeding 30°C.

  1. Use of local convective and radiant cooling at warm environment

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Krejcirikova, Barbora; Kaczmarczyk, Jan

    2012-01-01

    with one panel equipped with small fans. A reference condition without cooling was tested as well. The response of the subjects to the exposed conditions was collected by computerized questionnaires. The cooling devices significantly (p.... The acceptability of the thermal environment was similar for all cooling devices. The acceptability of air movement and PAQ increased when the local cooling methods were used. The best results were achieved with personalized ventilation and cooling fan. The minimal improvement in PAQ was reported when the radiant...

  2. Cooling of Water in a Flask: Convection Currents in a Fluid with a Density Maximum

    Science.gov (United States)

    Velasco, S.; White, J. A.; Roman, F. L.

    2010-01-01

    The effect of density inversion on the convective flow of water in a spherical glass flask cooled with the help of an ice-water bath is shown. The experiment was carried out by temperature measurements (cooling curves) taken at three different heights along the vertical diameter of the flask. Flows inside the flask are visualized by seeding the…

  3. Cooling of Water in a Flask: Convection Currents in a Fluid with a Density Maximum

    Science.gov (United States)

    Velasco, S.; White, J. A.; Roman, F. L.

    2010-01-01

    The effect of density inversion on the convective flow of water in a spherical glass flask cooled with the help of an ice-water bath is shown. The experiment was carried out by temperature measurements (cooling curves) taken at three different heights along the vertical diameter of the flask. Flows inside the flask are visualized by seeding the…

  4. Experimental characterization of self-sensing SMA actuators under controlled convective cooling

    Science.gov (United States)

    Lewis, N.; York, A.; Seelecke, S.

    2013-09-01

    Shape memory alloy (SMA) wires are attractive for actuation systems due to their high energy density, light weight and silent operation. In addition, they feature self-sensing capabilities by relating electrical resistance measurements to strain changes. In real world applications SMAs typically operate in non-ambient air and it is imperative to understand an actuator’s behavior under varying convective cooling conditions, especially for smaller diameter wires, where convective effects are amplified. This paper shows that the multi-functionality of SMA actuators can be further extended by related heating power to convective air speed. It investigates the relationship between the normalized excess power needed and corresponding airspeed under controlled, laminar airflow patterns in a small-scale wind tunnel. For each experiment, airflow through the wind tunnel, strain in the SMA wire, and power supplied to the SMA wire were controlled, while the stress and resistance of the wire were measured. The ability to understand and predict an SMA wire’s behavior under various external airflows will aid in the design and understanding of future SMA actuated structures, such as micro-air vehicles, and shows that SMAs can function as self-sensing actuators and airspeed sensors.

  5. Fingering convection and cloudless models for cool brown dwarf atmospheres

    CERN Document Server

    Tremblin, P; Mourier, P; Baraffe, I; Chabrier, G; Drummond, B; Homeier, D; Venot, O

    2015-01-01

    This work aims to improve the current understanding of the atmospheres of brown dwarfs, especially cold ones with spectral type T and Y, whose modeling is a current challenge. Silicate and iron clouds are believed to disappear at the photosphere at the L/T transition, but cloudless models fail to reproduce correctly the spectra of T dwarfs, advocating for the addition of more physics, e.g. other types of clouds or internal energy transport mechanisms. We use a one-dimensional (1D) radiative/convective equilibrium code ATMO to investigate this issue. This code includes both equilibrium and out-of-equilibrium chemistry and solves consistently the PT structure. Included opacity sources are H2-H2, H2-He, H2O, CO, CO2, CH4, NH3, K, Na, and TiO, VO if they are present in the atmosphere. We show that the spectra of Y dwarfs can be accurately reproduced with a cloudless model if vertical mixing and NH3 quenching are taken into account. T dwarf spectra still have some reddening in e.g. J - H compared to cloudless mode...

  6. Convection versus conduction cooling for induction of mild hypothermia during neurovascular procedures in adults.

    Science.gov (United States)

    Théard, M A; Tempelhoff, R; Crowder, C M; Cheng, M A; Todorov, A; Dacey, R G

    1997-07-01

    Hypothermia for cerebral protection is usually achieved by administration of intravenous fluids at room temperature, cooling ambient air, ice packs, and a temperature-adjustable circulating water mattress. We compared cooling by conduction by using a water mattress to cool by convection by using a forced-air cooling device. Twenty patients were prospectively randomized to two groups: 10 patients cooled by convection (CC) and 10 patients cooled by traditional methods (TC). Two patients in the CC group were withdrawn from the study and excluded from the analysis; one patient for failure to cool despite the use of both techniques, and the other for the abrupt onset of arrhythmias and myocardial depression during hypothermia. Temperature was measured at the tympanic membrane, pulmonary artery, and esophageal probe sites and recorded every 15 min. The time required to reach the target temperature range of 33-34 degrees C was recorded. We found no differences in the temperatures measured at the three sites during cooling and rewarming. Baseline temperatures recorded from the pulmonary artery catheter before beginning "active cooling" were similar in both groups (TC, 35.0 +/- 0.2 degrees C vs. CC, 35.3 +/- 0.1 degrees C). We found no difference in the time to target temperature between TC and CC (TC, 178 +/- 25 min vs. CC, 142 +/- 21 min). One patient had some arrhythmias on cooling in the convective group, but her preoperative condition may have been responsible. In conclusion, cooling by convection appears to be a safe alternative to conduction cooling.

  7. Experimental Investigation of Convective Heat Transfer during Night Cooling with Different Ventilation Systems and Surface Emissivities

    DEFF Research Database (Denmark)

    Le Dreau, Jerome; Heiselberg, Per; Jensen, Rasmus Lund

    2013-01-01

    Night-time ventilation is a promising approach to reduce the energy needed for cooling buildings without reducing thermal comfort. Nevertheless actual building simulation tools have showed their limits in predicting accurately the efficiency of night-time ventilation, mainly due to inappropriate...... air and the room, and floor emissivities. This extensive experimental study enabled a detailed analysis of the convective and radiative flow at the different surfaces of the room. The experimentally derived convective heat transfer coefficients (CHTC) have been compared to existing correlations...... ventilation, the convective heat transfer was well predicted by existing correlations. Nevertheless the change of floor emissivity influenced the CHTC at the surface of interest....

  8. Complex Convective Thermal Fluxes and Vorticity Structure

    Science.gov (United States)

    Redondo, Jose M.; Tellez, Jackson; Sotillos, Laura; Lopez Gonzalez-Nieto, Pilar; Sanchez, Jesus M.; Furmanek, Petr; Diez, Margarita

    2015-04-01

    Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux [2]. The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces [6]and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied

  9. MR-6 type fuel elements cooling in natural convection conditions after the reactor shut down

    Energy Technology Data Exchange (ETDEWEB)

    Pytel, K.; Bykowski, W.; Moldysz, A. [Institute of Atomic Energy, Otwock Swierk (Poland)

    2002-07-01

    Natural cooling conditions of the nuclear fuel in the channel type reactor after its shut down are commonly determined with relatively high uncertainty. This is not only to he lack of adequate measurements of thermal parameters i.e. the residual power generation, the coolant flow and temperatures, but also due to indeterminate model of convection mechanism. The numerical simulation of natural convection in multitube fuel assembly in the fuel channel leads to various convection modes including evidently chaotic behaviour. To determine the real cooling conditions in the MARIA research reactor a series of experiments has been performed with fuel assembly equipped with a set of thermocouples. After some forced cooling period (the shortest was half an hour after the reactor shut down) the reactor was left with the only natural convection. Two completely different cooling modes have been observed. The MARIA core consists of series of individual fuel channel and so called bypasses, maintaining the hydraulic properties of the fuel channel, connected in parallel. Initially, the convection cells were established trough few so-called bypasses providing a very effective mode of cooling. In this mode the flow charts were identical to those existing in forced cooling mode. After certain period the system switched on the second cooling mode with natural circulation within the individual fuel cells. Higher temperatures and temperature fluctuations were characteristic for this mode approaching 30 deg in amplitude. In almost all the cases the system was switching few times between modes, but eventually remained in the second mode. The switching times were not regular and the process has a chaotic behaviour. (author)

  10. Thermal Conditions in a Simulated Office Environment with Convective and Radiant Cooling Systems

    DEFF Research Database (Denmark)

    Mustakallio, Panu; Bolashikov, Zhecho Dimitrov; Kostov, Kalin

    2013-01-01

    ventilation (MVRC). CB was based on convection cooling while the remaining three systems (CBR, CCMV and MVRC) on combined radiant and convective cooling. Measurements were performed in design (64 W/m2) and usual (38 W/m2) cooling conditions. Air temperature, operative temperature, radiant asymmetry, air......The thermal conditions in a two person office room were measured with four air conditioning systems: chilled beam (CB), chilled beam with radiant panel (CBR), chilled ceiling with ceiling installed mixing ventilation (CCMV) and four desk partition mounted local radiant cooling panels with mixing...... velocity and turbulent intensity were measured and draft rate levels calculated in the room. Manikin-based equivalent temperature (MBET) was determined by two thermal manikins to identify the impact of the local thermal conditions generated by the studied systems on occupants’ thermal comfort. The results...

  11. Study on forced air convection cooling for electronic assemblies

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The slotted fin concept was employed to improve the air cooling performance of plate-fin in heat sinks.Numerical simulations of laminar heat transfer and flow pressure drop were conducted for the integral plate fin,discrete plate fin and discrete slotted fin heat sinks.It is found that the performance of the discrete plate fin is better than that of the integral continuum plate fin and the performance of slotted fin is better than that of the discrete plate fin at the same pumping power of the fan.A new type of heat sink characterized by discrete and slotted fin surfaces with thinner fins and smaller spaces between fins is then proposed.Preliminary computation shows that this type of heat sink may be useful for the next generation of higher thermal load CPUs.The limit of cooling capacity for air-cooling techniques was also addressed.

  12. Three dimensional free convection couette flow with transpiration cooling

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Free convection flow between two vertical parallel plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion has been analyzed. Due to this type of injection velocity, the flow becomes three-dimensional. Analytical expressions for the velocity, temperature, skin friction and rate of heat transfer were obtained. The important characteristics of the problem, namely the skin friction and the rate of heat transfer are discussed in detail with the help of graphs.

  13. Operating temperatures for a convectively cooled recessed incandescent light fixture

    Energy Technology Data Exchange (ETDEWEB)

    Yarbrough, D.W.; Toor, I.

    1980-12-01

    Test results are given for the operation of a recessed incandescent light fixture intended for residential use. The fixture is labeled for use in direct contact with attic thermal insulation. Temperature control of the powered fixture is provided by convective heat transfer from the ceiling side of the fixture. The fixture was operated at power levels up to two times the rated power of 75 watts and under thermal insulations up to R-40. In all operating configurations tested the fixture surface in contact with attic insulation was found to be less than 175/sup 0/C. The observed surface temperatures are judged to be safe for operation in contact with loose-fill or batt-type insulations. It was observed that the power leads inside one fixture configuration are exposed to temperatures as high as 168/sup 0/C. The electrical insulation could, therefore, have a limited life. The properties of the internal fixture wiring were not, however, studied in detail.

  14. Evaluation of immersion coil designs for natural convection-driven batch cooling or heating in tanks

    Energy Technology Data Exchange (ETDEWEB)

    Joye, Donald D.; Smith, Michael A.

    2000-09-01

    Various designs of immersion coils for batch cooling or heating of liquids in tanks were investigated to determine which design was most efficient. This equipment has direct utility in chemical batch processing operations and, particularly, wort cooling - a critical step in small-scale batch brewing of beer. This operation does not use a stirrer or agitation for a variety of reasons, hence it is dependent on natural-convection mechanisms for heat transfer, yet quick cooling is desired. Four basic coil designs with several permutations were evaluated. The results fell into four groups - best, good, mediocre, and worst performers. We found that coil placement and shape were design parameters that had a critical effect on the rate of cooling. Coil spacing also had a significant effect on the cooling rate when it was less than about 2 diameters. (Author)

  15. Modeling of steady-state convective cooling of cylindrical Li-ion cells

    Science.gov (United States)

    Shah, K.; Drake, S. J.; Wetz, D. A.; Ostanek, J. K.; Miller, S. P.; Heinzel, J. M.; Jain, A.

    2014-07-01

    While Lithium-ion batteries have the potential to serve as an excellent means of energy storage, they suffer from several operational safety concerns. Temperature excursion beyond a specified limit for a Lithium-ion battery triggers a sequence of decomposition and release, which can preclude thermal runaway events and catastrophic failure. To optimize liquid or air-based convective cooling approaches, it is important to accurately model the thermal response of Lithium-ion cells to convective cooling, particularly in high-rate discharge applications where significant heat generation is expected. This paper presents closed-form analytical solutions for the steady-state temperature profile in a convectively cooled cylindrical Lithium-ion cell. These models account for the strongly anisotropic thermal conductivity of cylindrical Lithium-ion batteries due to the spirally wound electrode assembly. Model results are in excellent agreement with experimentally measured temperature rise in a thermal test cell. Results indicate that improvements in radial thermal conductivity and axial convective heat transfer coefficient may result in significant peak temperature reduction. Battery sizing optimization using the analytical model is discussed, indicating the dependence of thermal performance of the cell on its size and aspect ratio. Results presented in this paper may aid in accurate thermal design and thermal management of Lithium-ion batteries.

  16. Analytical model of transient thermal effect on convectional cooled end-pumped laser rod

    Indian Academy of Sciences (India)

    Khalid S Shibib; Mohammad A Munshid; Kadim A Hubiter

    2013-10-01

    The transient analytical solutions of temperature distribution, stress, strain and optical path difference in convectional cooled end-pumped laser rod are derived. The results are compared with other works and good agreements are found. The effects of increasing the edge cooling and face cooling are studied. It is found that an increase in the edge cooling has significant effect on reducing the maximum temperature that can be reached in the laser rod but it has no effect on the value of optical path difference. It is also found that increasing this type of cooling significantly reduces the time required to reach the thermal equilibrium with a slight increase in the max. tensile hoop stress that can be reached as the cooling increases. On the other hand, increase in face cooling reduces the response time, optical path difference and the maximum temperature that can be reached in the laser rod but a significant increase in the max. tensile hoop stress is observed. A matching between the advantages of these two type of cooling may be useful for a designer.

  17. 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

    This work presents the application of density-based topology optimisation to the design of three-dimensional heat sinks cooled by natural convection. The governing equations are the steady-state incompressible Navier-Stokes equations coupled to the thermal convection-diffusion equation through...... and several optimised designs are presented for Grashof numbers between 103 and 106. Interestingly, it is observed that the number of branches in the optimised design increases with increasing Grashof numbers, which is opposite to two-dimensional topology optimised designs. Furthermore, the obtained...... 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....

  18. Natural air convection for cooling of particle accelerator electromagnets: case studies at CERN

    CERN Document Server

    Moreira, Mariana

    Cooling by natural convection is investigated on two air-cooled corrector magnets at CERN. The heat transfer coefficient (HTC) for each magnet is estimated analytically using established empirical correlations for certain geometries. The HTC is also estimated numerically with three-dimensional steady-state finite element simulations. Air convection around the respective coils as well as heat conduction inside the coils are modelled. Different formulas for the HTC are tested in the post-processing of the simulation results. The HTC for each magnet is then determined experimentally by measuring surface temperatures on the coils through time at constant currents. A method to extract the HTC from these temperature curves is developed, in which the curves are fitted to a function that is derived from a thermodynamical analysis of the heating process. Some plausible ranges for the HTC for each magnet for different currents are obtained. The results of the different estimation methods are compared with the experimen...

  19. Core flows and heat transfer induced by inhomogeneous cooling with sub- and supercritical convection

    CERN Document Server

    Dietrich, Wieland; Wicht, Johannes

    2016-01-01

    The amount and spatial pattern of heat extracted from cores of terrestrial planets is ultimately controlled by the thermal structure of the lower rocky mantle. Using the most common model to tackle this problem, a rapidly rotating and differentially cooled spherical shell containing an incompressible and viscous liquid is numerically investigated. To gain the physical basics, we consider a simple, equatorial symmetric perturbation of the CMB heat flux shaped as a spherical harmonic $Y_{11}$. The thermodynamic properties of the induced flows mainly depend on the degree of nonlinearity parametrised by a horizontal Rayleigh number $Ra_h=q^\\ast Ra$, where $q^\\ast$ is the relative CMB heat flux anomaly amplitude and $Ra$ is the Rayleigh number which controls radial buoyancy-driven convection. Depending on $Ra_h$ we characterise three flow regimes through their spatial patterns, heat transport and flow speed scalings: in the linear conductive regime the radial inward flow is found to be phase shifted $90^\\circ$ eas...

  20. Hydrothermal convection and mordenite precipitation in the cooling Bishop Tuff, California, USA

    Science.gov (United States)

    Randolph-Flagg, N. G.; Breen, S. J.; Hernandez, A.; Self, S.; Manga, M.

    2014-12-01

    We present field observations of erosional columns in the Bishop Tuff and then use laboratory results and numerical models to argue that these columns are evidence of relict convection in a cooling ignimbrite. Many square kilometers of the Bishop Tuff have evenly-spaced, vertical to semi-vertical erosional columns, a result of hydrothermal alteration. These altered regions are more competent than the surrounding tuff, are 0.1-0.7 m in diameter, are separated by ~ 1 m, and in some cases are more than 8 m in height. JE Bailey (U. of Hawaii, dissertation, 2005) suggested that similar columns in the Bandelier Tuff were formed when slumping allowed water to pool at the surface of the still-cooling ignimbrite. As water percolated downward it boiled generating evenly spaced convection cells similar to heat pipes. We quantify this conceptual model and apply it the Bishop Tuff to understand the physics within ignimbrite-borne hydrothermal systems. We use thin sections to measure changing porosity and use scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses to show that pore spaces in the columns are cemented by the mineral mordenite, a low temperature zeolite that precipitates between 120-200 oC (Bish et al., 1982), also found in the Bandelier Tuff example. We then use scaling to show 1) that water percolating into the cooling Bishop Tuff would convect and 2) that the geometry and spacing of the columns is predicted by the ignimbrite temperature and permeability. We use the computer program HYDROTHERM (Hayba and Ingebritsen, 1994; Kipp et al., 2008) to model 2-phase convection in the Bishop Tuff. By systematically changing permeability, initial temperature, and topography we can identify the pattern of flows that develop when the ignimbrite is cooled by water from above. Hydrothermally altered columns in ignimbrite are the natural product of coupled heat, mass, and chemical transport and have similarities to other geothermal systems, economic ore deposits

  1. Use of local convective and radiant cooling at warm environment: effect on thermal comfort and perceived air quality

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Duszyk, Marcin; Krejcirikova, Barbora

    2012-01-01

    The effect of four local cooling devices (convective, radiant and combined) on thermal comfort and perceived air quality reported by 24 subjects at 28 ˚C and 50% RH was studied. The devices studied were: (1) desk cooling fan, (2) personalized ventilation providing clean air, (3) two radiant panels...

  2. Experimental and theoretical analysis of a hybrid solar thermoelectric generator with forced convection cooling

    Science.gov (United States)

    Sundarraj, Pradeepkumar; Taylor, Robert A.; Banerjee, Debosmita; Maity, Dipak; Sinha Roy, Susanta

    2017-01-01

    Hybrid solar thermoelectric generators (HSTEGs) have garnered significant research attention recently due to their potential ability to cogenerate heat and electricity. In this paper, theoretical and experimental investigations of the electrical and thermal performance of a HSTEG system are reported. In order to validate the theoretical model, a laboratory scale HSTEG system (based on forced convection cooling) is developed. The HSTEG consists of six thermoelectric generator modules, an electrical heater, and a stainless steel cooling block. Our experimental analysis shows that the HSTEG is capable of producing a maximum electrical power output of 4.7 W, an electrical efficiency of 1.2% and thermal efficiency of 61% for an average temperature difference of 92 °C across the TEG modules with a heater power input of 382 W. These experimental results of the HSTEG system are found to be in good agreement with the theoretical prediction. This experimental/theoretical analysis can also serve as a guide for evaluating the performance of the HSTEG system with forced convection cooling.

  3. Viscoelastic Effects on the Entropy Production in Oscillatory Flow between Parallel Plates with Convective Cooling

    Directory of Open Access Journals (Sweden)

    Federico Vázquez

    2008-12-01

    Full Text Available The heat transfer problem of a zero-mean oscillatory flow of a Maxwell fluid between infinite parallel plates with boundary conditions of the third kind is considered. With these conditions, the amount of heat entering or leaving the system depends on the external temperature as well as on the convective heat transfer coefficient. The local and global time-averaged entropy production are computed, and the consequences of convective cooling of the plates are also assessed. It is found that the global entropy production is a minimum for certain suitable combination of the physical parameters. For a discrete set of values of the oscillatory Reynolds number, the extracted heat from one of the plates shows maxima.

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

    CERN Document Server

    Alexandersen, Joe; Aage, Niels

    2015-01-01

    This work presents the application of density-based topology optimisation to the design of three-dimensional heat sinks cooled by natural convection. The governing equations are the steady-state incompressible Navier-Stokes equations coupled to the thermal convection-diffusion equation through 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 40-330 million state degrees of freedom. The flow is assumed to be laminar and several optimised designs are presented for Grashof numbers between $10^3$ and $10^6$. Interestingly, it is observed that the number of branches in the optimised design increases with increasing Grashof numbers, which is opposite to two-dimensional optimised designs.

  5. Core cooling by subsolidus mantle convection. [thermal evolution model of earth

    Science.gov (United States)

    Schubert, G.; Cassen, P.; Young, R. E.

    1979-01-01

    Although vigorous mantle convection early in the thermal history of the earth is shown to be capable of removing several times the latent heat content of the core, a thermal evolution model of the earth in which the core does not solidify can be constructed. The large amount of energy removed from the model earth's core by mantle convection is supplied by the internal energy of the core which is assumed to cool from an initial high temperature given by the silicate melting temperature at the core-mantle boundary. For the smaller terrestrial planets, the iron and silicate melting temperatures at the core-mantle boundaries are more comparable than for the earth; the models incorporate temperature-dependent mantle viscosity and radiogenic heat sources in the mantle. The earth models are constrained by the present surface heat flux and mantle viscosity and internal heat sources produce only about 55% of the earth model's present surface heat flow.

  6. Natural Convective Heat and Mass Transfer of Water with Corrosion Products at Super—Critical Pressures under Cooling COnditions

    Institute of Scientific and Technical Information of China (English)

    Pei-XueJiang; Ze-PeiRen; 等

    1993-01-01

    A numerical study is reported of laminar natural convective heat and mass transfer on a vertical cooled plate for water containing metal corrosion products at super-critical pressures.The influence of variable properties at super-critical pressures on natural convertion has been analyzed.The difference between heat and mass transfer under cooling or heating conditions is also discussed and some correlations for heat and mass transfer under cooling conditions are recommended.

  7. Numerical investigation into entropy generation in a transient generalized Couette flow of nanofluids with convective cooling

    Indian Academy of Sciences (India)

    M H Mkwizu; O D Makinde; Yaw Nkansah-Gyekye

    2015-10-01

    This work investigates the effects of convective cooling on entropy generation in a transient generalized Couette flow of water-based nanofluids containing Copper (Cu) and Alumina (Al2O3) as nanoparticles. Both First and Second Laws of thermodynamics are utilised to analyse the problem. The model partial differential equations for momentum and energy balance are tackled numerically using a semidiscretization finite difference method together with Runge–Kutta Fehlberg integration scheme. Graphical results on the effects of parameter variation on velocity, temperature, skin friction, Nusselt number, entropy generation rate, irreversibility ratio and Bejan number are presented and discussed.

  8. Forced Convective Air Cooling from Electronic Component Arrays in a Parallel Plate Channel

    Institute of Scientific and Technical Information of China (English)

    D.Y.Cai; Y.P.Gan; 等

    1994-01-01

    This paper discusses air forced convection heat transfer from inline protruding elements arranged in eight rows.The streamwise and spanwise spacings between elements were varied using a splitter plate that can be positioned at three different modular configurations.A set of empirical formulas was presented to correlate the experimental data for the design of air cooling systems.Arrays of componets with one odd-size module have been tested also.Experimental results show that blocks near the entrance and behind the odd-size module have improved performance compared with uniform arrangements.Accordingly,temperature sensitive components are suggested to be arranged in these locations.

  9. Sensitivity analysis of the thermal performance of radiant and convective terminals for cooling buildings

    DEFF Research Database (Denmark)

    Le Dréau, J.; Heiselberg, P.

    2014-01-01

    on both radiation and convection. In order to characterise the advantages and drawbacks of the different terminals, steady-state simulations of a typical office room have been performed using four types of terminals (active chilled beam, radiant floor, wall and ceiling). A sensitivity analysis has been...... conducted to determine the parameters influencing their thermal performance the most. The air change rate, the outdoor temperature and the air temperature stratification have the largest effect on the cooling need (maintaining a constant operative temperature). For air change rates higher than 0.5 ACH...

  10. Modelling the Effect of Variable Viscosity on Unsteady Couette Flow of Nanofluids with Convective Cooling

    Directory of Open Access Journals (Sweden)

    Ahmada Omar Ali

    2015-01-01

    Full Text Available This paper investigates numerically the effects of variable viscosity on unsteady generalized Couette flow of a water base nanofluid with convective cooling at the moving surface. The Buongiorno model utilized for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The nonlinear governing equations of continuity, momentum, energy and nanoparticles concentration are tackled numerically using a semi discretization finite difference method together with Runge-Kutta Fehlberg integration scheme. Numerical results for velocity, temperature, and nanoparticles concentration profiles together with skin friction and Nusselt number are obtained graphically and discussed quantitatively.

  11. The Tropical Convective Spectrum. 1; Archetypal Vertical Structures

    Science.gov (United States)

    Boccippio, Dennis J.; Petersen, Walter A.; Cecil, Daniel J.

    2004-01-01

    A taxonomy of tropical convective vertical structures is constructed through cluster analysis of three years of Tropical Rainfall Measuring Mission [TRMM] Precipitation Radar [PR] vertical profiles, their surface rainfall and associated radar-based classifiers (convective/stratiform and bright band existence). archetypal profile types are identified. These include nine convective types, divided into warm, "just cold", midlevel, deep and deep/wet-growth categories, seven stratiform types, divided into warm, "just cold", midlevel and deep categories, three "mixed" types (deep profiles with low reflectivity aloft), and six fragment types (non-precipitating anvils and sheared deep convective profiles). The taxonomy allows for description of any storm or local Convective spectrum by the nine primary convective and stratiform types, a significant reduction over full three-dimensional radar data which nonetheless retains vertical structure information. The analysis provides a quasi-independent corroboration of the TRMM 2A23 convective/stratiform classification. The global frequency of occurrence and contribution to rainfall for the profile types is presented, demonstrating primary rainfall contribution by midlevel glaciated convection and similar depth decaying/stratiform stages. Close correspondence is found between deep convective profile frequency and annualized lightning production. Passive microwave and lightning properties associated with the profiles are reported, and cases presented illustrating known nonuniqueness problems with 85 and 37 GHz brightness temperature pairs (the same pairs corresponding to both convective and stratiform profiles), and how supplementary lightning information might be used to mitigate these problems.

  12. Numerical investigation of transient heat transfer to hydromagnetic channel flow with radiative heat and convective cooling

    Science.gov (United States)

    Makinde, O. D.; Chinyoka, T.

    2010-12-01

    This present study consists of a numerical investigation of transient heat transfer in channel flow of an electrically conducting variable viscosity Boussinesq fluid in the presence of a magnetic field and thermal radiation. The temperature dependent nature of viscosity is assumed to follow an exponentially model and the system exchanges heat with the ambient following Newton's law of cooling. The governing nonlinear equations of momentum and energy transport are solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, fluid temperature, skin friction and heat transfer rate for various parametric values. Our results reveal that combined effect of thermal radiation, magnetic field, viscosity variation and convective cooling have significant impact in controlling the rate of heat transfer in the boundary layer region.

  13. Computational Modelling of Couette Flow of Nanofluids with Viscous Heating and Convective Cooling

    Directory of Open Access Journals (Sweden)

    Oluwole Daniel Makinde

    2014-01-01

    Full Text Available The combined effect of viscous heating and convective cooling on Couette flow and heat transfer characteristics of water base nanofluids containing Copper Oxide (CuO and Alumina (Al2O3 as nanoparticles is investigated. It is assumed that the nanofluid flows in a channel between two parallel plates with the channel’s upper plate accelerating and exchange heat with the ambient surrounding following the Newton’s law of cooling, while the lower plate is stationary and maintained at a constant temperature. Using appropriate similarity transformation, the governing Navier-Stokes and the energy equations are reduced to a set of nonlinear ordinary differential equations. These equations are solved analytically by regular perturbation method with series improvement technique and numerically by an efficient Runge-Kutta-Fehlberg integration technique coupled with shooting method. The effects of the governing parameters on the dimensionless velocity, temperature, skin friction, pressure drop and Nusselt number are presented graphically, and discussed quantitatively.

  14. Enhancement of Natural Convection by Carbon Nanotube Films Covered Microchannel-Surface for Passive Electronic Cooling Devices.

    Science.gov (United States)

    Zhang, Guang; Jiang, Shaohui; Yao, Wei; Liu, Changhong

    2016-11-16

    Owing to the outstanding properties of thermal conduction, lightweight, and chemical durability, carbon nanotubes (CNTs) have revealed promising applications in thermal management materials. Meanwhile, the increasingly popular portable electronics and the rapid development of space technology need lighter weight, smaller size, and more effective thermal management devices. Here, a novel kind of heat dissipation devices based on the superaligned CNT films and underlying microchannels is proposed, and the heat dissipation properties are measured at the natural condition. Distinctive from previous studies, by combining the advantages of microchannels and CNTs, such a novel heat dissipation device enables superior natural convection heat transfer properties. Our findings prove that the novel CNT-based devices could show an 86.6% larger total natural heat dissipation properties than bare copper plate. Further calculations of the radiation and natural convection heat transfer properties demonstrate that the excellent passive cooling properties of these CNT-based devices are primarily caused by the reinforcement of the natural convection heat transfer properties. Furthermore, the heat dissipation mechanisms are briefly discussed, and we propose that the very high heat transfer coefficients and the porous structures of superaligned CNT films play critical roles in reinforcing the natural convection. The novel CNT-based heat dissipation devices also have advantages of energy-saving, free-noise, and without additional accessories. So we believe that the CNT-based heat dissipation devices would replace the traditional metal-finned heat dissipation devices and have promising applications in electronic devices, such as photovoltaic devices, portable electronic devices, and electronic displays.

  15. Convective Heat and Mass Transfer in Water at Super—Critical Pressures under Heating or Cooling Conditions in Vertical Tubes

    Institute of Scientific and Technical Information of China (English)

    Pei-XueJiang; Ze-PeiRen; 等

    1995-01-01

    Forced and mixed convection heat and mass transfer are studied numerically for water containing metallic corrosion products in a heated or cooled vertical tube with variable thermophysical properties at super-citical pressures.the fouling mechanisms and fouling models are presented.The influence of variable properties at super-critical pressures on forced or mixed convection has been analyzed.The differences between heat and mass transfer under heating and cooling conditions are discussed.It is found that variable properties,especially buoyancy,greatly influence the fluid flow and heat mass fransfer.

  16. Buoyancy Effects on Unsteady MHD Flow of a Reactive Third-Grade Fluid with Asymmetric Convective Cooling

    Directory of Open Access Journals (Sweden)

    Tirivanhu Chinyoka

    2015-01-01

    Full Text Available This article examines the combined effects of buoyancy force and asymmetrical convective cooling on unsteady MHD channel flow and heat transfer characteristics of an incompressible, reactive, variable viscosity and electrically conducting third grade fluid. The chemical kinetics in the flow system is exothermic and the asymmetric convective heat transfers at the channel walls follow the Newton’s law of cooling. The coupled nonlinear partial differential equations governing the problem are derived and solved numerically using a semi-implicit finite difference scheme. Graphical results are presented and physical aspects of the problem are discussed with respect to various parameters embedded in the system.

  17. Analysis of sublimation-cooled coated mirrors in convective and radiative environments.

    Science.gov (United States)

    Howe, J. T.; Green, M. J.

    1973-01-01

    Analytical solutions were obtained for the thermal response of a transpiration- or sublimation-cooled spherical mirror coating exposed to convective and radiative heating. The solutions allow unlimited spectral detail to be accounted for. Results indicate that transpiration-cooled thick coatings (1 cm) may withstand up to 10 kW/sq cm on a steady basis without excessive temperature rise for quartzlike materials with an internal absorption coefficient of 0.01 per cm. On a transient basis, fluxes up to 20 kW/sq cm can be accommodated for a second (cW laser exposure time), 4 kW/sq cm for 5 sec (planetary entry heating time), and of the order of MW/sq cm for millisecond times (short-duration laser bursts) without transpiration cooling for a material with an absorption coefficient of 0.1 per cm. Proportionately higher fluxes can be accommodated with lower absorption coefficients. Thermal stresses produced by the heat pulse are found to be high but within the strength of the materials. The regime in which meaningful solutions may be obtained is mapped in detail.

  18. MHD simulations of near-surface convection in cool main-sequence stars

    CERN Document Server

    Beeck, Benjamin; Reiners, Ansgar

    2014-01-01

    The solar photospheric magnetic field is highly structured owing to its interaction with the convective flows. Its local structure has a strong influence on the profiles of spectral lines not only by virtue of the Zeeman effect, but also through the modification of the thermodynamical structure (e.g. line weakening in hot small-scale magnetic structures). Many stars harbor surface magnetic fields comparable to or larger than the Sun at solar maximum. Therefore, a strong influence of the field on the surface convection and on spectral line profiles can be expected. We carried out 3D local-box MHD simulations of unipolar magnetized regions (average fields of 20, 100, and 500G) with parameters corresponding to six main-sequence stars (spectral types F3V to M2V). The influence of the magnetic field on the convection and the local thermodynamical structure were analyzed in detail. For three spectral lines, we determined the impact of the magnetic field on the disc-integrated Stokes-I profiles. Line weakening has i...

  19. An experimental investigation of liquid methane convection and boiling in rocket engine cooling channels

    Science.gov (United States)

    Trujillo, Abraham Gerardo

    In the past decades, interest in developing hydrocarbon-fueled rocket engines for deep spaceflight missions has continued to grow. In particular, liquid methane (LCH4) has been of interest due to the weight efficiency, storage, and handling advantages it offers over several currently used propellants. Deep space exploration requires reusable, long life rocket engines. Due to the high temperatures reached during combustion, the life of an engine is significantly impacted by the cooling system's efficiency. Regenerative (regen) cooling is presented as a viable alternative to common cooling methods such as film and dump cooling since it provides improved engine efficiency. Due to limited availability of experimental sub-critical liquid methane cooling data for regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through sub-scale cooling channels. To conduct the experiments, the csETR developed a High Heat Flux Test Facility (HHFTF) where all the channels are heated using a conduction-based thermal concentrator. In this study, two smooth channels with cross sectional geometries of 1.8 mm x 4.1 mm and 3.2 mm x 3.2 mm were tested. In addition, three roughened channels all with a 3.2 mm x 3.2 mm square cross section were also tested. For the rectangular smooth channel, Reynolds numbers ranged between 68,000 and 131,000, while the Nusselt numbers were between 40 and 325. For the rough channels, Reynolds numbers ranged from 82,000 to 131,000, and Nusselt numbers were between 65 and 810. Sub-cooled film-boiling phenomena were confirmed for all the channels presented in this work. Film-boiling onset at Critical Heat Flux (CHF) was correlated to a Boiling Number (Bo) of

  20. Convected transient analysis for large space structures maneuver and deployment

    Science.gov (United States)

    Housner, J.

    1984-01-01

    Convected-transient analysis techniques in the finite-element method are used to investigate the deployment and maneuver of large spacecraft structures with multiple-member flexible trusses and frames. Numerical results are presented for several sample problems.

  1. MHD simulations reveal crucial differences between solar and very-cool star magnetic structures

    CERN Document Server

    Beeck, Benjamin; Reiners, Ansgar

    2011-01-01

    We carried out 3D radiative magnetohydrodynamic simulations of the convective and magnetic structure in the surface layers (uppermost part of the convection zone and photosphere) of main-sequence stars of spectral types F3 to M2. The simulation results were analyzed in terms of sizes and properties of the convection cells (granules) and magnetic flux concentrations as well as velocity, pressure, density, and temperature profiles. Our numerical simulations show for the first time a qualitative difference in the magneto-convection between solar-like stars and M dwarfs. Owing to higher surface gravity, lower opacity (resulting in higher density at optical depth unity), and more stable downflows, small-scale magnetic structures concentrate into pore-like configurations of reduced intensity. This implies that in very cool stars magnetic surface structures like plage regions and starspots significantly differ from the solar example. Such a difference would have major impact on the interpretation of Doppler imaging ...

  2. Peristaltic flow of a reactive viscous fluid through a porous saturated channel and convective cooling conditions

    Science.gov (United States)

    Asghar, S.; Hussain, Q.; Hayat, T.; Alsaedi, A.

    2015-07-01

    This article addresses the heat transfer in a peristaltic flow of a reactive combustible viscous fluid through a porous saturated medium. The flow here is induced because of travelling waves along the channel walls. It is assumed that exothermic chemical reactions take place within the channel under the Arrhenius kinetics and the convective heat exchange with the ambient medium at the surfaces of the channel walls follows Newton's law of cooling. The analysis is carried out in the presence of viscous dissipation and without consumption of the material. The governing equations are formulated by employing the long-wavelength approximation. Closed-form solutions for the stream function, axial velocity, and axial pressure gradient are obtained. It is found that the temperature decreases at high Biot numbers, and the Nusselt number increases with increasing reaction parameter. The Biot number and reaction parameter produce the opposite effects on the Nusselt number.

  3. Experimental investigation of the influence of the air jet trajectory on convective heat transfer in buildings equipped with air-based and radiant cooling systems

    DEFF Research Database (Denmark)

    Le Dreau, Jerome; Heiselberg, Per; Jensen, Rasmus Lund

    2015-01-01

    The complexity and diversity of airflow in buildings make the accurate definition of convective heat transfer coefficients (CHTCs) difficult. In a full-scale test facility, the convective heat transfer of two cooling systems (active chilled beam and radiant wall) has been investigated under steady......-state and dynamic conditions. With the air-based cooling system, a dependency of the convective heat transfer on the air jet trajectory has been observed. New correlations have been developed, introducing a modified Archimedes number to account for the air flow pattern. The accuracy of the new correlations has been...... evaluated to±15%. Besides the study with an air-based cooling system, the convective heat transfer with a radiant cooling system has also been investigated. The convective flow at the activated surface is mainly driven by natural convection. For other surfaces, the complexity of the flow and the large...

  4. Numerical comparison of convective heat transfer augmentation devices used in cooling channels of hypersonic vehicles

    Science.gov (United States)

    Maldonado, Jaime J.

    1994-01-01

    Hypersonic vehicles are exposed to extreme thermal conditions compared to subsonic aircraft; therefore, some level of thermal management is required to protect the materials used. Normally, hypersonic vehicles experience the highest temperatures in the nozzle throat, and aircraft and propulsion system leading edges. Convective heat transfer augmentation techniques can be used in the thermal management system to increase heat transfer of the cooling channels in those areas. The techniques studied in this report are pin-fin, offset-fin, ribbed and straight roughened channel. A smooth straight channel is used as the baseline for comparing the techniques. SINDA '85, a lumped parameter finite difference thermal analyzer, is used to model the channels. Subroutines are added to model the fluid flow assuming steady one dimensional compressible flow with heat addition and friction. Correlations for convective heat transfer and friction are used in conjunction with the fluid flow analysis mentioned. As expected, the pin-fin arrangement has the highest heat transfer coefficient and the largest pressure drop. All the other devices fall in between the pin-fin and smooth straight channel. The selection of the best heat augmentation method depends on the design requirements. A good approach may be a channel using a combination of the techniques. For instance, several rows of pin-fins may be located at the region of highest heat flux, surrounded by some of the other techniques. Thus, the heat transfer coefficient is maximized at the region of highest heat flux while the pressure drop is not excessive.

  5. Experimental study of an upward sub-cooled forced convection in a rectangular channel

    Science.gov (United States)

    Kouidri, A.; Madani, B.; Roubi, B.; Hamadouche, A.

    2016-07-01

    The upward sub-cooled forced convection in a rectangular channel is investigated experimentally. The aim of the present work is the studying of the local heat transfer phenomena. Concerning the experimentation: the n-pentane is used as a working fluid, the independent variables are: the velocity in the range from 0.04 to 0.086 m/s and heat flux density with values between 1.8 and 7.36 W/cm2. The results show that the local Nusselt number distribution is not uniform along the channel; however, uniformity is observed in the mean Nusselt number for Reynolds under 1600. On the other hand, a new correlation to predict the local fluid temperature is established as a function of local wall temperature. The wall's heat is dissipated under the common effect of the sub-cooled regime; therefore, the local heat transfer coefficient is increased. The study of the thermal equilibrium showed that for Reynolds less than 1500; almost all of the heat flux generated by the heater cartridges is absorbed by the fluid.

  6. The Tropical Convective Spectrum. Part 1; Archetypal Vertical Structures

    Science.gov (United States)

    Boccippio, Dennis J.; Petersen, Walter A.; Cecil, Daniel J.

    2005-01-01

    A taxonomy of tropical convective and stratiform vertical structures is constructed through cluster analysis of 3 yr of Tropical Rainfall Measuring Mission (TRMM) "warm-season" (surface temperature greater than 10 C) precipitation radar (PR) vertical profiles, their surface rainfall, and associated radar-based classifiers (convective/ stratiform and brightband existence). Twenty-five archetypal profile types are identified, including nine convective types, eight stratiform types, two mixed types, and six anvil/fragment types (nonprecipitating anvils and sheared deep convective profiles). These profile types are then hierarchically clustered into 10 similar families, which can be further combined, providing an objective and physical reduction of the highly multivariate PR data space that retains vertical structure information. The taxonomy allows for description of any storm or local convective spectrum by the profile types or families. The analysis provides a quasi-independent corroboration of the TRMM 2A23 convective/ stratiform classification. The global frequency of occurrence and contribution to rainfall for the profile types are presented, demonstrating primary rainfall contribution by midlevel glaciated convection (27%) and similar depth decaying/stratiform stages (28%-31%). Profiles of these types exhibit similar 37- and 85-GHz passive microwave brightness temperatures but differ greatly in their frequency of occurrence and mean rain rates, underscoring the importance to passive microwave rain retrieval of convective/stratiform discrimination by other means, such as polarization or texture techniques, or incorporation of lightning observations. Close correspondence is found between deep convective profile frequency and annualized lightning production, and pixel-level lightning occurrence likelihood directly tracks the estimated mean ice water path within profile types.

  7. The development of convective structures in the solar photosphere

    Science.gov (United States)

    Baran, O.; Stodilka, M.

    2016-12-01

    We study the development of convective structures in the solar photosphere on the basis of the photospheric convection models obtained using data from VTT by the solving of the inverse nonequilibrium radiative transfer problem. Temporal changes of the variations of vertical velocity and temperature within granular cells are analyzed. Features of the appearance and the disappearance of granules according to their size, the formation of "trees" of fragmenting granules are investigated.

  8. The development of convective structures in the solar photosphere

    Science.gov (United States)

    Baran, O.; Stodilka, M.

    2016-12-01

    We study the development of convective structures in the solar photosphere on the basis of the photospheric convection models obtained using data from VTT by the solving of the inverse nonequilibrium radiative transfer problem. Temporal changes of the variations of vertical velocity and temperature within granular cells are analyzed. Features of the appearance and the disappearance of granules according to their size, the formation of "trees" of fragmenting granules are investigated.

  9. Effects of variable thermal diffusivity on the structure of convection

    CERN Document Server

    Shcheritsa, O V; Mazhorova, O S

    2016-01-01

    The multiscale flow structure in the solar convection zone - the coexistence of such features as the granules, mesogranules, supergranules and giant cells - has not yet been properly understood. Here, the possible role of one physical factor - variations in the thermal diffusivity - in the formation of a multiscale convection structure is investigated. Thermal convection in a plane horizontal fluid layer is numerically simulated. The temperature dependence of thermal diffusivity is chosen so as to produce a sharp kink in the static temperature profile near the upper layer boundary. As a result, the magnitude of the (negative) static temperature gradient dTs/dz, being small over the most part of the layer thickness, reaches large values in a thin boundary sublayer. To identify the structures on different scales, we apply a smoothing procedure, computational-homology techniques and spectral processing to the temperature field. The flow is found to be a superposition of three cellular structures with three diffe...

  10. Experimental study of convective heat transfer during cooling with low air velocity in a stack of objects

    Energy Technology Data Exchange (ETDEWEB)

    Ben Amara, Sami; Laguerre, Onrawee [Cemagref - Refrigeration Processes Engineering Research Unit, parc de Tourvoie, BP 44, 92163 cedex, Antony (France); Flick, Denis [National Agronomic Institute - INAPG, 16 rue Claude Bernard, 75231 cedex 05, Paris (France)

    2004-12-01

    During cooling with low air velocity (u{<=}0.2 m.s{sup -1}) of a stack of foodstuffs (a few centimeters dimension), the radiation and conduction between products can be of the same order of magnitude as convection. A method was developed to quantify these various transfer modes. The experiment was carried out using an in-line spherical arrangement; however, the same methodology can be applied to other product shapes. The results confirm that the heat transfers by radiation and conduction cannot be neglected. In addition, the convective heat transfer coefficient varies not only with air velocity but also with the product position in the stack. (authors)

  11. Improved lumped models for transient combined convective and radiative cooling of a two-layer spherical fuel element

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Alice Cunha da; Su, Jian, E-mail: alicecs@poli.ufrj.br, E-mail: sujian@nuclear.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil)

    2013-07-01

    The High Temperature Gas cooled Reactor (HTGR) is a fourth generation thermal nuclear reactor, graphite-moderated and helium cooled. The HTGRs have important characteristics making essential the study of these reactors, as well as its fuel element. Examples of these are: high thermal efficiency,low operating costs and construction, passive safety attributes that allow implication of the respective plants. The Pebble Bed Modular Reactor (PBMR) is a HTGR with spherical fuel elements that named the reactor. This fuel element is composed by a particulate region with spherical inclusions, the fuel UO2 particles, dispersed in a graphite matrix and a convective heat transfer by Helium happens on the outer surface of the fuel element. In this work, the transient heat conduction in a spherical fuel element of a pebble-bed high temperature reactor was studied in a transient situation of combined convective and radiative cooling. Improved lumped parameter model was developed for the transient heat conduction in the two-layer composite sphere subjected to combined convective and radiative cooling. The improved lumped model was obtained through two-point Hermite approximations for integrals. Transient combined convective and radiative cooling of the two-layer spherical fuel element was analyzed to illustrate the applicability of the proposed lumped model, with respect to die rent values of the Biot number, the radiation-conduction parameter, the dimensionless thermal contact resistance, the dimensionless inner diameter and coating thickness, and the dimensionless thermal conductivity. It was shown by comparison with numerical solution of the original distributed parameter model that the improved lumped model, with H2,1/H1,1/H0,0 approximation yielded significant improvement of average temperature prediction over the classical lumped model. (author)

  12. Structures, profile consistency, and transport scaling in electrostatic convection

    DEFF Research Database (Denmark)

    Bian, N.H.; Garcia, O.E.

    2005-01-01

    that for interchange modes, profile consistency is in fact due to mixing by persistent large-scale convective cells. This mechanism is not a turbulent diffusion, cannot occur in collisionless systems, and is the analog of the well-known laminar "magnetic flux expulsion" in magneiohydrodynamics. This expulsion process...... involves a "pinch" across closed streamlines and further results in the formation of pressure fingers along the-separatrix of the convective cells. By nature, these coherent structures are dissipative because the mixing process that leads to their formation relies on a finite amount of collisional...... diffusion. Numerical simulations of two-dimensional interchange modes confirm the role of laminar expulsion by convective cells, for profile consistency and structure formation. They also show that the fingerlike pressure structures ultimately control the rate of heat transport across the plasma layer...

  13. Study of natural convection cooling of a nanofluid subjected to a magnetic field

    Science.gov (United States)

    Mahmoudi, Ahmed; Mejri, Imen; Omri, Ahmed

    2016-06-01

    This paper presents a numerical study of natural convection cooling of water-Al2O3 nanofluid by two heat sinks vertically attached to the horizontal walls of a cavity subjected to a magnetic field. The left wall is hot, the right wall is cold, while the horizontal walls are insulated. Lattice Boltzmann method (LBM) is applied to solve the coupled equations of flow and temperature fields. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number of the base fluid, Ra =103 to 105, Hartmann number varied from Ha = 0 to 60 and the solid volume fraction of nanoparticles between ϕ = 0 and 6%. In order to investigate the effect of heat sinks location, three different configurations of heat sinks are considered. The effects of Rayleigh numbers, Hartmann number and heat sinks location on the streamlines, isotherms, Nusselt number are investigated. Results show that the heat transfer rate decreases with the increase of Hartmann number and increases with the rise of Rayleigh number. In addition it is observed that the average Nusselt number increases linearly with the increase of the nanoparticles solid volume fraction. Also, results show that the heat sinks positions greatly influence the heat transfer rate depending on the Hartmann number, Rayleigh number and nanoparticle solid volume fraction.

  14. Improved Lumped Models for Transient Combined Convective and Radiative Cooling of Multilayer Spherical Media

    Directory of Open Access Journals (Sweden)

    Chen An

    2017-01-01

    Full Text Available In this work, we studied the transient combined convection and radiation of multilayer spherical media with volumetric heat generation, extending the previous work on the particular case of a spherical body subjected to radiative cooling. The proposed lumped models were obtained through two-point Hermite approximations for the average temperature and heat flux in each layer. For the average temperature, the plain trapezoidal rule (H0,0 approximation was employed in all layers, except for the innermost layer, where the second-order two-side corrected trapezoidal rule (H2,1 approximation was utilized. For the heat flux, the plain trapezoidal rule (H0,0 approximation was employed for all the layers. The transient heat conduction in a TRISO-coated fuel particle being composed of five layers (namely, fuel kernel, buffer of porous carbon, inner pyrocarbon, silicon carbide, and outer pyrocarbon was analyzed using the proposed lumped models, the results of which were verified by comparison with the finite difference solution of the original distributed parameter model. Parametric studies were conducted to examine the effects of the dimensionless heat generation rate, the radiation-conduction parameter, and the Biot number on the temporal variations of the average temperatures.

  15. Convective Heat Transfer with and without Film Cooling in High Temperature, Fuel Rich and Lean Environments

    Science.gov (United States)

    2014-09-01

    the test section, a metal sleeve was placed around the entire ceramic transition as seen at the bottom left of Fig. 3.4. Despite the structural...Wade, W. R. Measurements of Total Hemispherical Emissivity of Several Stably Oxidized Metals and Some Refractory Oxide Coatings. Technical report...materials. Ceramics are capable of withstanding the high Taw condition but crack after repeated heating and cooling cycles. Thus, ceramics not viable in

  16. The structure of convective rain cells at mid-latitudes

    Directory of Open Access Journals (Sweden)

    N. Rebora

    2006-01-01

    Full Text Available Rain cells are structures which represent an important component of convective precipitation and a study of their properties represents a necessary step both towards improved stochastic models of small-scale precipitation and for the verification of deterministic high resolution local-area models. The case of intense convective precipitation in the tropics has been analysed in a recent study (von Hardenberg et al., 2003. Here we extend the analysis to mid-latitudes and we present results on the structure of convective rain cells observed by radar measurements in Italy. In particular we consider the average shape of precipitation cells and its dependence on radar resolution and the distributions of ellipticities.

  17. Average Natural Convective Heat Transfer of Air-cooled Condensing Heat Exchanger of Emergency Cooldown Tank - Effect of Tube Banks

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Seon Jeong; Lee, Hee Joon [Kookmin University, Seoul (Korea, Republic of); Kim, Myoung Jun; Moon, Joo Hyung; Bae, Youngmin; Kim, Young-In [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Recently emergency cooldown tank(ECT) is a great concern of passive cooling system for the safety of nuclear reactor. After the operation of a conventional passive cooling system for an extended period, however, the water level falls as a result of the evaporation from the ECT, as steam is emitted from the open top of the tank. In this study, the effect of heat transfer area at the air cooled condensing heat exchanger was investigated by changing 5×5 tube banks into 4×4 and 3×3. Moreover, each of air-side natural convective heat transfer coefficient of tube banks was compared to existing correlations. This study presents the effect of heat transfer area at air-cooled condensing heat exchanger. As heat transfer area decreased, the temperature of outlet increased. In other words, the cooling performance got lower with the decrease of heat transfer area. In addition, the average natural convective heat transfer coefficient was 15.3 W/m{sup 2}/K from the 4×4 tube banks, and 4.92 W/m{sup 2}/K from the 3×3 tube banks, which had quite a large error more than 46% especially with the value of 4×4 tube banks compared to the value from correlation equation. Therefore, according to this result, it is needed to measure the local heat transfer coefficient of vertical cylinder more elaborately in further study.

  18. Blade-to-coolant heat-transfer results and operating data from a natural-convection water-cooled single-stage turbine

    Science.gov (United States)

    Diaguila, Anthony J; Freche, John C

    1951-01-01

    Blade-to-coolant heat-transfer data and operating data were obtained with a natural-convection water-cooled turbine over range of turbine speeds and inlet-gas temperatures. The convective coefficients were correlated by the general relation for natural-convection heat transfer. The turbine data were displaced from a theoretical equation for natural convection heat transfer in the turbulent region and from natural-convection data obtained with vertical cylinders and plates; possible disruption of natural convection circulation within the blade coolant passages was thus indicated. Comparison of non dimensional temperature-ratio parameters for the blade leading edge, midchord, and trailing edge indicated that the blade cooling effectiveness is greatest at the midchord and least at the trailing edge.

  19. Structure functions in rotating Rayleigh–Bénard convection

    NARCIS (Netherlands)

    Kunnen, R.P.J.; Clercx, H.J.H.; Geurts, Bernardus J.

    2011-01-01

    A combined numerical–experimental investigation on the scaling of velocity structure functions in turbulent rotating Rayleigh–B´enard convection is carried out. Direct numerical simulations in a cylindrical domain and a horizontally periodic domain are compared with experiments using a cylindrical t

  20. THE SPATIO-TEMPORAL STRUCTURE OF BINARY FLUID CONVECTION WITH HORIZONTAL FLOW

    Institute of Scientific and Technical Information of China (English)

    NING Li-zhong; YOSHIFUMI Harada; HIDEO Yahata; LI Jian-zhong

    2004-01-01

    The convection structure in a rectangular channel with a horizontal flow forΓ= 12 was studied. The simulations were preformed by solving the hydrodynamic equations using the SIMPLE method. The convective behavior in an absolutely and convectively unstable regime was studied. The results show that the two types of convection patterns in this system appear depending on the convection intensity and horizontal flow. A periodically localized traveling wave state was found in this system.

  1. Convection generated by a small heat source in a box with a cooled upper contour at constant temperature

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, L P; Marino, B M [Facultad de Ciencias Exactas, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, B 7000 GHG Tandil (Argentina); Tovar, R; Castillo, J A, E-mail: lthomas@exa.unicen.edu.ar [Centro de Investigacion en EnergIa, Universidad Nacional Autonoma de Mexico Priv. Xochicalco s/n, Col. Centro, Temixco, Morelos (Mexico)

    2011-05-01

    The flow generated by a linear heat source inside a thermally insulated box with the upper boundary maintained at constant temperature is analyzed by means of a series of experiments. The attention is focused on the steady state during which the heat provided by the source is absorbed by the upper boundary giving place to a particular convective process in two well defined zones. One of them occupies most part of the box from the lower boundary and is characterized by a turbulent convective flow; the other is the thermal boundary layer developed below the cooled top contour where strong fluctuations are detected. Special interest is found in the analogies with the results obtained employing a configuration similar to that used to research the Rayleigh-Benard convection with lower and upper boundaries at constant temperatures but without internal sources. This study has particular relevance to understanding and predicting the use of the cooled-ceiling systems in buildings as a passive solution to enhance the comfort of its inhabitants during hot days with the consequential energy savings.

  2. Convection and Easterly Wave Structure Observed in the Eastern Pacific Warm-Pool during EPIC-2001

    Science.gov (United States)

    Peterson, Walter A.; Cifelli, R.; Boccippio, D.; Rutledge, S. A.; Fairall, C. W.; Arnold, James E. (Technical Monitor)

    2002-01-01

    During September-October 2001, the East Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System (EPIC-2001) ITCZ field campaign focused on studies of deep convection in the warm-pool region of the East Pacific. In addition to the TAO mooring array, observational platforms deployed during the field phase included the NOAA ship RN Ronald H. Brown, the NSF ship RN Horizon, and the NOAA P-3 and NCAR C-130 aircraft. This study combines C-band Doppler radar, rawinsonde, and surface heat flux data collected aboard the RN Brown to describe ITCZ convective structure and rainfall statistics in the eastern Pacific as a function of 3-5 day easterly wave phase. Three distinct easterly wave passages occurred during EPIC-2001. Wind and thermodynamic data reveal that the wave trough axes exhibited positively correlated U and V winds and a slight westward phase tilt with height. A relatively strong (weak) northeasterly deep tropospheric shear followed the trough (ridge) axis. Temperature and humidity perturbations exhibited mid-to upper level cooling (warming) and drying (moistening) in the northerly (trough and southerly) phase. At low levels warming (cooling) occurred in the northerly (southerly) phase with little change in the relative humidity, though mixed layer mixing ratios were larger during the northerly phase. When composited, radar, sounding, lightning and surface heat flux observations suggest the following systematic behavior as a function of wave phase: approximately zero to one quarter wavelength ahead of (behind) the wave trough in northerly (southerly) flow, larger (smaller) CAPE, lower (higher) CIN, weaker (stronger) tropospheric shear, higher (lower) conditional mean rain rates, higher (lower) lightning flash densities, and more (less) robust convective vertical structure occurred. Latent and sensible heat fluxes reached a minimum in the northerly phase and then increased through the trough, reaching a peak during the ridge phase

  3. Convectively Aggregated Structures Across a Hierarchy of Models

    Science.gov (United States)

    Silvers, Levi; Dipankar, Anurag; Hohenegger, Cathy

    2015-04-01

    Convective clouds are among the most interesting and poorest understood atmospheric phenomena. This study explores the interaction between deep convection and the lower troposphere with a focus on the coupling of deep convection to the lower tropospheric clouds, water vapor, and relative humidity. We are particularly interested in the controlling factors of the cloud amount and cloud size at cloud base across various model set-ups. In particular we seek to determine how the generation of large convective structures depends on the characteristics of the lower troposphere and parameterization choices. Our experiments are analyzed by comparing the mean state, the probability distribution functions of particular quantities, and snapshots in time of the spatial distribution of cloud related fields. It is shown that the formation of aggregated convective structures depends on the different model setups. Experiments performed using an NWP model (ICON-NWP) and two cloud-resolving models (ICON-LES and UCLA-LES) are compared. The ICOsahedral Nonhydrostatic (ICON) model is used to provide a unified modeling framework in which both the NWP and CRM versions use the same dynamical core but different physics packages. This allows for a fair comparison between the GCM and CRM and leads to a better understanding of both. To check the robustness of the CRM results we also compare the ICON experiments with the UCLA-LES model. The initial analysis looks at the ICON-NWP and both CRM experiments with a uniform domain size of (1800 km)2 and doubly periodic boundary conditions to determine some of the fundamental differences between the models. The NWP experiment has an effective resolution of 13.5 km while the CRM's have resolutions in the range of 5 km. We run the NWP experiments with the full suit of physics parameterizations as well as with the convection turned off. Further sensitivity studies are then made to isolate some of the key characteristics of the convection in each model

  4. Heat and mass transfer during cooling and storage of agricultural products as influenced by natural convection

    OpenAIRE

    Beukema, K.J.

    1980-01-01

    Three different models of bulk-stored agricultural products with air flow through the bulk, predicting the temperature profiles or the velocity of natural convection, are developed. The temperature distribution in a cylindrical container with insulated walls and open top and bottom, filled with heat-generating model material is studied experimentally, used to calculate the velocity of natural convection and compared with model predictions. A two-dimensional two-phase model of temper...

  5. Boundary layer structure in turbulent Rayleigh-Benard convection

    CERN Document Server

    Shi, Nan; Schumacher, Joerg

    2012-01-01

    The structure of the boundary layers in turbulent Rayleigh-Benard convection is studied by means of three-dimensional direct numerical simulations. We consider convection in a cylindrical cell at an aspect ratio one for Rayleigh numbers of Ra=3e+9 and 3e+10 at fixed Prandtl number Pr=0.7. Similar to the experimental results in the same setup and for the same Prandtl number, the structure of the laminar boundary layers of the velocity and temperature fields is found to deviate from the prediction of the Prandtl-Blasius-Pohlhausen theory. Deviations decrease when a dynamical rescaling of the data with an instantaneously defined boundary layer thickness is performed and the analysis plane is aligned with the instantaneous direction of the large-scale circulation in the closed cell. Our numerical results demonstrate that important assumptions which enter existing classical laminar boundary layer theories for forced and natural convection are violated, such as the strict two-dimensionality of the dynamics or the s...

  6. Analysis of Heat Transfer in Berman Flow of Nanofluids with Navier Slip, Viscous Dissipation, and Convective Cooling

    Directory of Open Access Journals (Sweden)

    O. D. Makinde

    2014-01-01

    Full Text Available Heat transfer characteristics of a Berman flow of water based nanofluids containing copper (Cu and alumina (Al2O3 as nanoparticles in a porous channel with Navier slip, viscous dissipation, and convective cooling are investigated. It is assumed that the exchange of heat with the ambient surrounding takes place at the channel walls following Newton’s law of cooling. The governing partial differential equations and boundary conditions are converted into a set of nonlinear ordinary differential equations using appropriate similarity transformations. These equations are solved analytically by regular perturbation methods with series improvement technique and numerically using an efficient Runge-Kutta Fehlberg integration technique coupled with shooting scheme. The effects of the governing parameters on the dimensionless velocity, temperature, skin friction, pressure drop, and Nusselt numbers are presented graphically and discussed quantitatively.

  7. Topical report: Natural convection shutdown heat removal test facility (NSTF) evaluation for generating additional reactor cavity cooling system (RCCS) data.

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, M. T.; Kilsdonk, D. J.; Tzanos, C.P.; Lomperski, S.; Aeschlimann, R.W.; Pointer, D.; Nuclear Engineering Division

    2005-09-01

    As part of the Department of Energy (DOE) Generation IV roadmapping activity, the Very High Temperature gas cooled Reactor (VHTR) has been selected as the principal concept for hydrogen production and other process-heat applications such as district heating and potable water production. On this basis, the DOE has selected the VHTR for additional R&D with the ultimate goal of demonstrating emission-free electricity and hydrogen production with this advanced reactor concept. One of the key passive safety features of the VHTR is the potential for decay heat removal by natural circulation of air in a Reactor Cavity Cooling System (RCCS). The air-cooled RCCS concept is notably similar to the Reactor Vessel Auxiliary Cooling System (RVACS) that was developed for the General Electric PRISM sodium-cooled fast reactor. As part of the DOE R&D program that supported the development of this fast reactor concept, the Natural Convection Shutdown Heat Removal Test Facility (NSTF) was developed at ANL to provide proof-of-concept data for the RVACS under prototypic natural convection flow, temperature, and heat flux conditions. Due to the similarity between RVACS and the RCCS, current VHTR R&D plans call for the utilization of the NSTF to provide RCCS model development and validation data, in addition to supporting design validation and optimization activities. Both air-cooled and water-cooled RCCS designs are to be included. In support of this effort, ANL has been tasked with the development of an engineering plan for mechanical and instrumentation modifications to NSTF to ensure that sufficiently detailed temperature, heat flux, velocity and turbulence profiles are obtained to adequately qualify the codes under the expected range of air-cooled RCCS flow conditions. Next year, similar work will be carried out for the alternative option of a water-cooled RCCS design. Analysis activities carried out in support of this experiment planning task have shown that: (a) in the RCCS, strong

  8. Precise convective cooling simulation of electronic equipment under various g-conditions

    Science.gov (United States)

    Adam, Johannes; Stuempel, Dieter; Rath, Michael

    1991-12-01

    Using the thermohydraulic code 'THEBES' a three dimensional flow analysis of a Spacelab rack under forced convection and a combined convective, conductive and radiative analysis of a closed electronic box under various g conditions are presented. The capabilities and features of THEBES are described. The motivation to extend the thermal analysis cycle for better treatment of fluid flow and solid to air heat transfer is discussed. It is proposed to include THEBES in a thermal analysis toolsat and present a concept for integration of THEBES with ESABASE.

  9. Critical heat flux in natural convection cooled TRIGA reactors with hexagonal bundle

    Energy Technology Data Exchange (ETDEWEB)

    Yang, J.; Avery, M.; De Angelis, M.; Anderson, M.; Corradini, M. [Univ. of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Feldman, E. E.; Dunn, F. E.; Matos, J. E. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States)

    2012-07-01

    A three-rod bundle Critical Heat Flux (CHF) study at low flow, low pressure, and natural convection condition has been conducted, simulating TRIGA reactors with the hexagonally configured core. The test section is a custom-made trefoil shape tube with three identical fuel pin heater rods located symmetrically inside. The full scale fuel rod is electrically heated with a chopped-cosine axial power profile. CHF experiments were carried out with the following conditions: inlet water subcooling from 30 K to 95 K; pressure from 110 kPa to 230 kPa; mass flux up to 150 kg/m{sup 2}s. About 50 CHF data points were collected and compared with a few existing CHF correlations whose application ranges are close to the testing conditions. Some tests were performed with the forced convection to identify the potential difference between the CHF under the natural convection and forced convection. The relevance of the CHF to test parameters is investigated. (authors)

  10. Heat and mass transfer during cooling and storage of agricultural products as influenced by natural convection

    NARCIS (Netherlands)

    Beukema, K.J.

    1980-01-01

    Three different models of bulk-stored agricultural products with air flow through the bulk, predicting the temperature profiles or the velocity of natural convection, are developed. The temperature distribution in a cylindrical container with insulated walls and open top and bottom, filled

  11. Determination of blade-to-coolant heat-transfer coefficients on a forced-convection, water-cooled, single-stage turbine

    Science.gov (United States)

    Freche, John C; Schum, Eugene F

    1951-01-01

    Blade-to-coolant convective heat-transfer coefficients were obtained on a forced-convection water-cooled single-stage turbine over a large laminar flow range and over a portion of the transition range between laminar and turbulent flow. The convective coefficients were correlated by the general relation for forced-convection heat transfer with laminar flow. Natural-convection heat transfer was negligible for this turbine over the Grashof number range investigated. Comparison of turbine data with stationary tube data for the laminar flow of heated liquids showed good agreement. Calculated average midspan blade temperatures using theoretical gas-to-blade coefficients and blade-to-coolant coefficients from stationary-tube data resulted in close agreement with experimental data.

  12. Human response to local convective and radiant cooling in a warm environment

    DEFF Research Database (Denmark)

    Melikov, Arsen Krikor; Krejcirikova, Barbora; Kaczmarczyk, Jan

    2013-01-01

    thermal comfort compared to the condition without cooling. The acceptability of the thermal environment was similar for all cooling devices. The acceptability of air movement and perceived air quality increased when local cooling methods were used. The best results were...... quality. The intensity of the reported sick building syndrome symptoms increased during the exposure time, with or without cooling devices in operation. Air movement had very little effect on sick building syndrome symptoms, but they increased when the pollution level was high. The lowest prevalence...... of symptoms was reported with personalized ventilation and with the radiant panel with attached fans, which also caused subjects to report less fatigue. Sick building syndrome symptoms increased most when the tabletop fan, generating movement of polluted room air, was in operation. The temperature...

  13. The influence of nanoparticle migration on forced convective heat transfer of nanofluid under heating and cooling regimes.

    Science.gov (United States)

    Kozlova, Sofya V; Ryzhkov, Ilya I

    2014-09-01

    In this paper, laminar convective heat transfer of water-alumina nanofluid in a circular tube with uniform heat flux at the tube wall is investigated. The investigation is performed numerically on the basis of two-component model, which takes into account nanoparticle transport by diffusion and thermophoresis. Two thermal regimes at the tube wall, heating and cooling, are considered and the influence of nanoparticle migration on the heat transfer is analyzed comparatively. The intensity of thermophoresis is characterized by a new empirical model for thermophoretic mobility. It is shown that the nanoparticle volume fraction decreases (increases) in the boundary layer near the wall under heating (cooling) due to thermophoresis. The corresponding variations of nanofluid properties and flow characteristics are presented and discussed. The intensity of heat transfer for the model with thermophoresis in comparison to the model without thermophoresis is studied by plotting the dependence of the heat transfer coefficient on the Peclet number. The effectiveness of water-alumina nanofluid is analyzed by plotting the average heat transfer coefficient against the required pumping power. The analysis of the results reveals that the water-alumina nanofluid shows better performance in the heating regime than in the cooling regime due to thermophoretic effect.

  14. The onset of nonpenetrative convection in a suddenly cooled layer of fluid

    Energy Technology Data Exchange (ETDEWEB)

    Ihle, Christian F. [Program in Fluid Dynamics, Facultad de Ciencias Fisicas y Matematicas, Universidad de Chile, Blanco Encalada 2002 Of. 327, Santiago (Chile); Nino, Yarko [Departamento de Ingenieria Civil, Division de Recursos Hidricos y Medio Ambiente, Universidad de Chile, Av. Blanco Encalada 2002, Santiago (Chile)

    2006-04-15

    Conditions for the onset of nonpenetrative convection in a horizontal Boussinesq fluid layer subject to a step change in temperature are studied using propagation theory. A wide range of Prandtl numbers and two different kinematic boundary conditions are considered. It is shown that for high Rayleigh numbers, critical conditions for the onset of convective motion reproduce exactly those for the unsteady Rayleigh-Benard instability. Present results extend those of previous research and show a tendency of the rigid-rigid and free-rigid critical curves to converge for low Prandtl numbers. Comparison between present and previously reported results on critical conditions for the onset of instabilities and onset time using different methods yields good agreement on a middle to high Prandtl number range. A ratio of 10 between experimentally measured and theoretically predicted onset times is suggested for stress-free bounded systems. (author)

  15. Thermo-Elastic Analysis of Internally Cooled Structures Using a Higher Order Theory

    Science.gov (United States)

    Arnold, Steven M.; Bednarcyk, Brett A.; Aboudi, Jacob

    2001-01-01

    This paper presents the results of a study on the thermomechanical behavior of internally cooled silicon nitride structures. Silicon nitride is under consideration for elevated temperature aerospace engine applications. and techniques for lowering the operating temperature of structures composed of this material are under development. Lowering the operating temperature provides a large payoff in terms of fatigue life and may be accomplished through the use of thermal barrier coatings (TBC's) and the novel concept of included cooling channels. Herein, an in-depth study is performed on the behavior of a flame-impinged silicon nitride plate with a TBC and internal channels cooled by forced air. The analysis is performed using the higher order theory for functionally graded materials (HOTFGM), which has been developed through NASA Glenn Research Center funding over the past several years. HOTFGM was chosen over the traditional finite element approach as a prelude to an examination of functionally graded silicon nitride structures for which HOTFGM is ideally suited. To accommodate the analysis requirement% of the internally cooled plate problem, two crucial enhancements were made to the two-dimensional Cartesian-based version of HOTFGM. namely, incorporation of internal boundary capabilities and incorporation of convective boundary conditions. Results indicate the viability and large benefits of cooling the plate via forced air through cooling channels. Furthermore, cooling can positively impact the stress and displacement fields present in the plate, yielding an additional payoff in terms of fatigue life. Finally, a spin-off capability resulted from inclusion of internal boundaries within HOTFGM; the ability to simulate the thermo-elastic response of structures with curved surfaces. This new capability is demonstrated, and through comparison with an analytical solution, shown to be viable and accurate.

  16. Flow structure in turbulent rotating Rayleigh-Bénard convection

    Science.gov (United States)

    Kunnen, Rudie; Corre, Yoann; Clercx, Herman

    2012-11-01

    Turbulent Rayleigh-Bénard convection is usually studied in an upright cylinder. The addition of axial rotation has profound effects on the flow structuring. The well-known large-scale circulation (LSC) of the non-rotating case is still found at low rotation rates but is replaced by an irregular array of vertically aligned vortical plumes at higher rotation rates. We report PIV measurements of turbulent rotating convection in a cylindrical cell of diameter-to-height aspect ratio Γ = 1 / 2 at Rayleigh number Ra = 4 . 5 ×109 and at many rotation rates covering both the LSC and the vortical-plume regime. We focus on: (i) the azimuthal precession of the LSC, (ii) collective motions of the vortical plumes, and (iii) the sidewall boundary layers. With these results we can clarify remarkable differences between the Γ = 1 and Γ = 1 / 2 cases reported recently in the literature. Traineeship project carried out in Eindhoven as part of Master's Degree at Université Paris-Sud, France.

  17. Convection heat transfer from discrete heat sources in a liquid cooled rectangular channel

    Energy Technology Data Exchange (ETDEWEB)

    Bhowmik, H. [Department of Mechanical Engineering, Dhaka University of Engineering and Technology, Gazipur 1700 (Bangladesh); Tso, C.P. [Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, 75450 Melaka (Malaysia); Tou, K.W.; Tan, F.L. [School of Mechanical and Production Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2005-11-01

    Steady-state experiments are performed to study general convective heat transfer from an in-line four simulated electronic chips in a vertical rectangular channel using water as the working fluid. The experimental data covers a wide range for laminar flow under natural, mixed and forced convection conditions with Reynolds number based on channel hydraulic diameter ranging from 40 to 2220 and Reynolds number based on heat source length ranging from 50 to 2775, respectively. The heat flux ranges from 0.1W/cm{sup 2} to 0.6W/cm{sup 2}. The inlet water temperature is at 24{sup o}C. The effect of heat fluxes, flow rates and geometrical parameters such as chip number are investigated. The experimental results indicate that the heat transfer coefficient is strongly affected by Reynolds number and fully-developed values of heat transfer coefficient are reached before the first chip. Empirical correlations are developed for relations using Nusselt number, Reynolds number and Grashof number, based on channel hydraulic diameter. (author)

  18. Thermal environment in a simulated double office room with convective and radiant cooling systems

    DEFF Research Database (Denmark)

    Mustakallio, Panu; Bolashikov, Zhecho Dimitrov; Rezgals, Lauris

    2017-01-01

    The thermal environment in a double office room obtained with chilled beam (CB), chilled beam with radiant panel (CBR), chilled ceiling with ceiling installed mixing ventilation (CCMV) and overhead mixing total volume ventilation (MTVV) under summer (cooling) condition was compared. Design (peak......) and usual (average) heat load from solar radiation, office equipment, lighting and occupants was simulated, respectively at 62 W/m2 and 38 W/m2 under four different workstation layouts. Air temperature, globe (operative) temperature, radiant asymmetry, air velocity and turbulent intensity were measured...... CCMV especially in the design heat load cases. With CBR, the thermal environment was found to be between CB and CCMV. MTVV generated high draught level under the tested design heat load cases. All cooling systems generated similar thermal environment in the usual heat load cases. It would...

  19. Thermal transfer structures coupling electronics card(s) to coolant-cooled structure(s)

    Science.gov (United States)

    David, Milnes P; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Parida, Pritish R; Schmidt, Roger R

    2014-12-16

    Cooling apparatuses and coolant-cooled electronic systems are provided which include thermal transfer structures configured to engage with a spring force one or more electronics cards with docking of the electronics card(s) within a respective socket(s) of the electronic system. A thermal transfer structure of the cooling apparatus includes a thermal spreader having a first thermal conduction surface, and a thermally conductive spring assembly coupled to the conduction surface of the thermal spreader and positioned and configured to reside between and physically couple a first surface of an electronics card to the first surface of the thermal spreader with docking of the electronics card within a socket of the electronic system. The thermal transfer structure is, in one embodiment, metallurgically bonded to a coolant-cooled structure and facilitates transfer of heat from the electronics card to coolant flowing through the coolant-cooled structure.

  20. The effect of ultrasound irradiation on the convective heat transfer rate during immersion cooling of a stationary sphere.

    Science.gov (United States)

    Kiani, Hossein; Sun, Da-Wen; Zhang, Zhihang

    2012-11-01

    were the main cause of heating effect. The results showed that closer distances to the transducer surface showed higher cooling rates. On the other hand, despite having a bigger distance from the transducer, when the sphere was located close to the gas-liquid interface the enhancement factor of heat transfer was higher. Ultrasound irradiation showed promising effect for the enhancement of convective heat transfer rate during immersion cooling. More investigations are required to demonstrate the behavior of ultrasound assisted heat transfer and resolve the proper way of the application of ultrasound to assist the cooling and/or freezing processes. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. Comparison of radiant and convective cooling of office room: effect of workstation layout

    DEFF Research Database (Denmark)

    Bolashikov, Zhecho Dimitrov; Melikov, Arsen Krikor; Rezgals, Lauris;

    2014-01-01

    The impact of heat source location (room layout) on the thermal environment generated in a double office room with four cooling ventilation systems - overhead ventilation, chilled ceiling with overhead ventilation, active chilled beam and active chilled beam with radiant panels was measured...... and compared. The room was furnished with two workstations, two laptops and two thermal manikins resembling occupants. Two heat load levels, design (65 W/m2) and usual (39 W/m2), were generated by adding heat from warm panels simulating solar radiation. Two set-ups were studied: occupants sitting...

  2. Evaluation by Rocket Combustor of C/C Composite Cooled Structure Using Metallic Cooling Tubes

    Science.gov (United States)

    Takegoshi, Masao; Ono, Fumiei; Ueda, Shuichi; Saito, Toshihito; Hayasaka, Osamu

    In this study, the cooling performance of a C/C composite material structure with metallic cooling tubes fixed by elastic force without chemical bonding was evaluated experimentally using combustion gas in a rocket combustor. The C/C composite chamber was covered by a stainless steel outer shell to maintain its airtightness. Gaseous hydrogen as a fuel and gaseous oxygen as an oxidizer were used for the heating test. The surface of these C/C composites was maintained below 1500 K when the combustion gas temperature was about 2800 K and the heat flux to the combustion chamber wall was about 9 MW/m2. No thermal damage was observed on the stainless steel tubes that were in contact with the C/C composite materials. The results of the heating test showed that such a metallic tube-cooled C/C composite structure is able to control the surface temperature as a cooling structure (also as a heat exchanger) as well as indicated the possibility of reducing the amount of coolant even if the thermal load to the engine is high. Thus, application of this metallic tube-cooled C/C composite structure to reusable engines such as a rocket-ramjet combined-cycle engine is expected.

  3. Impacts of Vertical Structure of Convection on Tropical Circulation in a Warmer Climate

    Science.gov (United States)

    Chen, C. A.; Chou, C.

    2014-12-01

    The atmosphere becomes warmer and more humid under global warming, while changes in precipitation show a large discrepancy on a regional scale. Changes in regional precipitation are usually associated with changes in tropical circulation. Stronger (weaker) upward motion enhances (reduces) precipitation amount and intensity, in addition to the effect of enhanced water vapor. In a more detailed analysis, however, changes in atmospheric vertical motion can be either strengthened or weakened, even within convective areas with positive rainfall anomalies. To understand the diverse responses of changes in tropical circulation in a warmer climate as well as the associated mechanism, atmospheric stability and the impact of the vertical structure of convection on tropical circulation are investigated in 32 coupled global climate models from CMIP3 and CMIP5. The study regions are convective areas with positive precipitation anomalies. Under global warming, an upward shift structure of vertical velocity is observed in all model simulations, which implies a deepening of convection and a more stable atmosphere. Areas with enhanced (weakened) ascending motion, the climatological bottom-heavy (top-heavy) structure of vertical velocity tends to import more (less) moist static energy to counteract the stabilization due to the effect of deepened convection, and then the ascending motion is strengthened (weakened). The bottom-heavy-like structure is dominated by shallow convection, while the top-heavy-like structure is usually associated with deep convection. In other words, shallow convection tends to strengthen tropical circulation and enhance upward motion in future climate.

  4. Coupled calculation of external heat transfer and material temperatures of convection-cooled turbine blades. Final report; Gekoppelte Berechnung des aeusseren Waermeuebergangs und der Materialtemperaturen konvektionsgekuehlter Turbinenschaufeln. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Heselhaus, A.

    1997-05-01

    In this work a hybrid program system consisting of a 3D finite-volume Navier-Stokes flow solver and a 3D finite-element heat conduction solver has been developed. It enables the coupled calculation of structure temperatures in diabatic solid/fluid configurations. The grids of both the finite element and the finite volume computational domain may be completely independent. The coupled program fully resolves the thermal interaction between heat transfer and the resulting material temperatures. The developed coupling algorithm is numerically stable, conservative and works without the need to define ambient temperatures in the flowfield. This allows for the simulation of any solid/fluid configuration. When simulating combined blade/endwall cooling or filmcooling, only a coupled procedure is capable to completely account for the interaction between all relevant thermal parameters. It is found that the coupled calculation of convective cooling in a realistic guide vane leads locally to 45 K higher and 107 K lower blade temperatures than the uncoupled calculation. This shows that accounting for the thermal interaction between the flow and the structure offers both potential to save cooling air and a lower margin of safety when designing cooling systems close to the thermal limits of the blade material. (orig.) [Deutsch] Im Rahmen der vorliegenden Arbeit wurde ein Verfahren zur Berechnung der Temperaturverteilung in diabat umstroemten Koerpern entwickelt, bei dem ein 3D-Finite Volumen Navier-Stokes Stroemungsloeser und ein 3D-Finite Elemente Waermeleitungsloeser zu einem hybriden Programmsystem gekoppelt werden. Dabei besteht die Moeglichkeit, voellig unabhaengige Rechennetze fuer Stroemung und Struktur zu verwenden. Mit dem gekoppelten Verfahren kann die Wechselwirkung zwischen resultierenden Materialtemperaturen und dem davon rueck-beeinflussten Waermeuebergang beruecksichtigt werden. Weiterhin ist der hier entwickelte, stabile und konservative Kopplungsalgorithmus nicht

  5. Convection of Paramagnetic Fluid in a Cube Heated and Cooled from Side Walls and Placed below a Superconducting Magnet

    Science.gov (United States)

    Bednarz, Tomasz; Fornalik, Elzbieta; Tagawa, Toshio; Ozoe, Hiroyuki; Szmyd, Janusz S.

    The magnetic convection of paramagnetic fluid is studied in a strong magnetic field. The fluid in a cubic enclosure is heated from one vertical wall and cooled from the opposite one. The fluid is the 80% mass aqueous solution of glycerol with 0.8 mol/kg concentration of gadolinium nitrate hexahydrate to make the working fluid paramagnetic. The small amount of liquid crystal slurry is added to the fluid in order to visualize the temperature profiles in a vertical cross-section. This system is placed directly below the solenoid of the superconducting magnet which is oriented vertically. The temperature of cold wall is constantly controlled by the water flowing from a thermostating bath. On the other hand, the hot wall is heated by a nichrome wire from a DC power supply. In the numerical computations, the configuration of the system is modeled to be as close as possible to the real system. The physical properties of the working fluid are used to compute dimensionless parameters in the numerical model and the computations are carried out for corresponding cases. Later, the numerical and experimental results are compared with each other.

  6. Structural Assembly for Cold Plate Cooling

    Science.gov (United States)

    Zaffetti, Mark A. (Inventor); Taddey, Edmund P. (Inventor)

    2014-01-01

    A device including a structural member having a heat spreader and an electronic device mounted directly to a first surface of the heat spreader of the structural member. The device also includes a cold plate mounted directly to the first surface of the heat spreader of the structural member.

  7. The influence of local effects on thermal sensation under non-uniform environmental conditions — Gender differences in thermophysiology, thermal comfort and productivity during convective and radiant cooling

    DEFF Research Database (Denmark)

    Schellen, L.; Loomans, M.G.L.C.; de Wit, M.H.;

    2012-01-01

    , thermal comfort and productivity in response to thermal non-uniform environmental conditions. Twenty healthy subjects (10 males and 10 females, age 20–29years) were exposed to two different experimental conditions: a convective cooling situation (CC) and a radiant cooling situation (RC). During...... the experiments physiological responses, thermal comfort and productivity were measured. The results show that under both experimental conditions the actual mean thermal sensation votes significantly differ from the PMV-index; the subjects are feeling colder than predicted. Furthermore, the females are more...

  8. Temperature-controlled radiofrequency ablation of cardiac tissue: an in vitro study of the impact of electrode orientation, electrode tissue contact pressure and external convective cooling

    DEFF Research Database (Denmark)

    Petersen, H H; Chen, X; Pietersen, A

    1999-01-01

    A variety of basic factors such as electrode tip pressure, flow around the electrode and electrode orientation influence lesion size during radiofrequency ablation, but importantly is dependent on the chosen mode of ablation. However, only little information is available for the frequently used t...... temperature-controlled mode. The purpose of the present experimental study was to evaluate the impact during temperature-controlled radiofrequency ablation of three basic factors regarding electrode-tissue contact and convective cooling on lesion size....

  9. Effects of Melt Convection and Solid Transport on Macrosegregation and Grain Structure in Equiaxed Al-Cu Alloys

    Science.gov (United States)

    Rerko, Rodney S.; deGroh, Henry C., III; Beckermann, Christoph

    2000-01-01

    Macrosegregation in metal casting can be caused by thermal and solutal melt convection, and the transport of unattached solid crystals resulting from nucleation in the bulk liquid or dendrite fragmentation. To develop a comprehensive numerical model for the casting of alloys, an experimental study has been conducted to generate benchmark data with which such a solidification model could be tested. The objectives were: (1) experimentally study the effects of solid transport and thermosolutal convection on macrosegregation and grain size; and (2) provide a complete set of boundary conditions temperature data, segregation data, and grain size data - to validate numerical models. Through the control of end cooling and side wall heating, radial temperature gradients in the sample and furnace were minimized. Thus the vertical crucible wall was adiabatic. Samples at room temperature were 24 cc and 95 mm long. The alloys used were Al-1 wt. pct. Cu, and Al- 10 wt. pct. Cu; the starting point for solidification was isothermal at 710 and 685 C respectively. To induce an equiaxed structure various amounts of the grain refiner TiB2 were added. Samples were either cooled from the top, or the bottom. Several trends in the data stand out. In attempting to model these experiments, concentrating on these trends or differences may be beneficial.

  10. Spiral plume structures in turbulent natural convection between two vertical walls

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By means of direct numerical simulation, coherent structures are investigated in turbulent natural convection between two vertical differentially heated walls. It is observed that large-scale spanwise vortices and spiral plume structures exist together in the flow. Spiral plume structures appear at the positions with relatively large helicity, large normal vorticity and high fluctuating temperature. In this note, the shape, the characteristics and formation of the spiral structures are studied and compared with those in Rayleigh-Bénard convection. The conditional sampling analysis indicates the main properties of the spiral structures.

  11. The atmospheric structure during episodes of open cellular convection observed in KonTur 1981

    Energy Technology Data Exchange (ETDEWEB)

    Kruspe, G.; Bakan, S. (Max-Planck-Inst. fuer Meteorologie, Hamburg (West Germany))

    1990-02-20

    The KonTur (Konvektion and Turbulenz) 1981 experiment was primarily dedicated to the study of organized boundary layer convection. While two research aircraft were used for detailed boundary layer measurements, an aerological network of four stations in the North Sea yielded information on the mean atmospheric structure in organized convective situations. During the second experiment phase in October 1981, cold air advection caused intense convective activity. Four periods of well-organized open convection cells could be determined from NOAA satellite images. The present paper contains the results from the aerological data set, which allowed the derivation of mean profiles of the dynamic and thermodynamic quantities. Finally, the evolution of the most pronounced cellular episode is presented in a case study. Cellular episodes appeared during rather cold and dry periods in which potential temperature, specific humidity, and equivalent potential temperature in the convection layer reached a relative minimum. However, none of the mean atmospheric profiles differ considerably from those found under convective conditions without cellular organization. During the cellular episodes, horizontal gradients show generally small values throughout the convection layer.

  12. The atmospheric structure during episodes of open cellular convection observed in KonTur 1981

    Science.gov (United States)

    Kruspe, G.; Bakan, S.

    1990-02-01

    The KonTur (Konvektion und Turbulenz) 1981 experiment was primarily dedicated to the study of organized boundary layer convection. While two research aircraft were used for detailed boundary layer measurements, an aerological network of four stations in the North Sea yielded information on the mean atmospheric structure in organized convective situations. During the second experiment phase in October 1981, cold air advection caused intense convective activity. Four periods of well-organized open convection cells could be determined from NOAA satellite images. The present paper contains the results from the aerological data set, which allowed the derivation of mean profiles of the dynamic and thermodynamic quantities with acceptable accuracy, but also of the horizontal gradients of thermodynamic quantities. Finally, the evolution of the most pronounced cellular episode is presented in a case study. Cellular episodes appeared during rather cold and dry periods in which potential temperature, specific humidity, and equivalent potential temperature in the convection layer reached a relative minimum. However, none of the mean atmospheric profiles differ considerably from those found under convective conditions without cellular organization. During the cellular episodes, horizontal gradients show generally small values throughout the convection layer.

  13. Turbulent Compressible Convection with Rotation. Part 1; Flow Structure and Evolution

    Science.gov (United States)

    Brummell, Nicholas H.; Hurlburt, Neal E.; Toomre, Juri

    1996-01-01

    The effects of Coriolis forces on compressible convection are studied using three-dimensional numerical simulations carried out within a local modified f-plane model. The physics is simplified by considering a perfect gas occupying a rectilinear domain placed tangentially to a rotating sphere at various latitudes, through which a destabilizing heat flux is driven. The resulting convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers, evaluating conditions where the influence of rotation is both weak and strong. Given the computational demands of these high-resolution simulations, the parameter space is explored sparsely to ascertain the differences between laminar and turbulent rotating convection. The first paper in this series examines the effects of rotation on the flow structure within the convection, its evolution, and some consequences for mixing. Subsequent papers consider the large-scale mean shear flows that are generated by the convection, and the effects of rotation on the convective energetics and transport properties. It is found here that the structure of rotating turbulent convection is similar to earlier nonrotating studies, with a laminar, cellular surface network disguising a fully turbulent interior punctuated by vertically coherent structures. However, the temporal signature of the surface flows is modified by inertial motions to yield new cellular evolution patterns and an overall increase in the mobility of the network. The turbulent convection contains vortex tubes of many scales, including large-scale coherent structures spanning the full vertical extent of the domain involving multiple density scale heights. Remarkably, such structures align with the rotation vector via the influence of Coriolis forces on turbulent motions, in contrast with the zonal tilting of streamlines found in laminar flows. Such novel turbulent mechanisms alter the correlations which drive mean shearing flows and affect the

  14. Spontaneous Formation of Surface Magnetic Structure from Large-scale Dynamo in Strongly-stratified Convection

    CERN Document Server

    Masada, Youhei

    2016-01-01

    We report the first successful simulation of spontaneous formation of surface magnetic structures from a large-scale dynamo by strongly-stratified thermal convection in Cartesian geometry. The large-scale dynamo observed in our strongly-stratified model has physical properties similar to those in earlier weakly-stratified convective dynamo simulations, indicating that the $\\alpha^2$-type mechanism is responsible for it. Additionally to the large-scale dynamo, we find that large-scale structures of the vertical magnetic field are spontaneously formed in the convection zone surface only for the case of strongly-stratified atmosphere. The organization of the vertical magnetic field proceeds in the upper convection zone within tens of convective turn-over time and band-like bipolar structures are recurrently-appeared in the dynamo-saturated stage. We examine possibilities of several candidates as the origin of the surface magnetic structure formation, and then suggest the existence of an as-yet-unknown mechanism ...

  15. Solid state lighting devices and methods with rotary cooling structures

    Energy Technology Data Exchange (ETDEWEB)

    Koplow, Jeffrey P.

    2017-03-21

    Solid state lighting devices and methods for heat dissipation with rotary cooling structures are described. An example solid state lighting device includes a solid state light source, a rotating heat transfer structure in thermal contact with the solid state light source, and a mounting assembly having a stationary portion. The mounting assembly may be rotatably coupled to the heat transfer structure such that at least a portion of the mounting assembly remains stationary while the heat transfer structure is rotating. Examples of methods for dissipating heat from electrical devices, such as solid state lighting sources are also described. Heat dissipation methods may include providing electrical power to a solid state light source mounted to and in thermal contact with a heat transfer structure, and rotating the heat transfer structure through a surrounding medium.

  16. Upper Troposphere Lower Stratosphere structure during convective systems using GPS radio occultations

    DEFF Research Database (Denmark)

    Biondi, Riccardo

    The deep convective systems play a fundamental role in atmospheric circulation and climate. Thunderstorms and meso-scale convective systems produce fast vertical transport, redistributing water vapor and trace gases and influencing the thermal structure of the upper troposphere and lower...... stratosphere (UTLS) contributing to the troposphere-stratosphere transport and affecting the Earth global circulation and the climate changes. The Global Positioning System (GPS) Radio Occultation (RO) technique enables measurement of atmospheric density structure in any meteorological condition...... to the analysis of tropical storms for the future mission ACES will also be evaluated. Using data from the past and ongoing GPS RO missions we have defined an algorithm to detect the clouds top of the convective systems and their thermal structure. Other satellite and in-situ measurements co-located with GPS ROs...

  17. Aircraft Measurements of Convective System Vertical Structure and Coldpools during the DYNAMO Project

    Science.gov (United States)

    Guy, N.; Jorgensen, D. P.; Chen, S. S.; Wang, Q.

    2012-12-01

    The DYNAMO (Dynamics of the Madden-Julian Oscillation) field experiment employed a large number of measurement platforms with which to study environmental and convective cloud system characteristics of the MJO initiation region in the Indian Ocean. One such platform, the NOAA P-3 instrumented aircraft, provided mobility to sample convective cloud systems along with the surrounding environment. The tail-mounted, X-band Doppler radar allowed a pseudo-dual-Doppler analysis technique to study system kinematics and derive vertical wind motion. GPS dropwindsondes provided a robust means for thermodynamic characterization both in and around the sampled convective cloud systems. This presentation will focus on the relationships between coldpool strength and depth (along with other environmental characteristics) and the vertical structure of convective systems. In addition, a comparison of the DYNAMO observations to previous results in the region (e.g. TOGA COARE) will be presented. Differences in organizational aspects of convective clouds into mesoscale convective systems between the studies will provide a context of regional differences, which may serve as a basis for future model simulations.

  18. Three-dimensional simulations of near-surface convection in main-sequence stars. III. The structure of small-scale magnetic flux concentrations

    CERN Document Server

    Beeck, Benjamin; Cameron, Robert H; Reiners, Ansgar

    2015-01-01

    The convective envelopes of cool main-sequence stars harbour magnetic fields with a complex global and local structure. These fields affect the near-surface convection and the outer stellar atmospheres in many ways and are responsible for the observable magnetic activity of stars. Our aim is to understand the local structure in unipolar regions with moderate average magnetic flux density. These correspond to plage regions covering a substantial fraction of the surface of the Sun (and likely also the surface of other Sun-like stars) during periods of high magnetic activity. We analyse the results of 18 local-box magnetohydrodynamics simulations covering the upper layers of the convection zones and the photospheres of cool main-sequence stars of spectral types F to early M. The average vertical field in these simulations ranges from 20 to 500G. We find a substantial variation of the properties of the surface magnetoconvection between main-sequence stars of different spectral types. As a consequence of a reduced...

  19. Cooling of the Building Structure by Night-time Ventilation

    DEFF Research Database (Denmark)

    Artmann, Nikolai

    , architects and engineers are still hesitant to apply passive cooling techniques. The basic concept of night-time ventilation involves cooling the building structure overnight in order to provide a heat sink during the occupancy period. As this requires a sufficiently high temperature difference between...... a building energy simulation program (HELIOS), and the effect of different parameters such as building construction, heat gains, air change rates, heat transfer coefficients and climatic conditions on the number of overheating degree hours (operative room temperature >26 °C) was evaluated. Besides climatic...... air flow rates and the possibility of a cold air jet flowing along the ceiling, but the magnitude of these effects is hard to predict. Heat transfer during night-time ventilation in case of mixing and displacement ventilation has been investigated in a full scale test room. The performance of night...

  20. Structured Red Giant Winds with Magnetized Hot Bubbles and the Corona/Cool Wind Dividing Line

    CERN Document Server

    Suzuki, T K

    2006-01-01

    (Abridged) By performing magnetohydrodynamical (MHD) simulations, we investigate mass loss of intermediate- and low-mass stars from main sequence to red giant branch phases. Alfven waves, which are excited by the photospheric perturbations due to the surface convections, travel outwardly and dissipate by nonlinear processes to accelerate and heat stellar winds. We dynamically treat these processes in open magnetic field regions from the photospheres to 25 stellar radii. When the star evolves to slightly blueward of the dividing line (Linsky & Haisch), the steady hot corona with temperature, T ~ 10^6 K, suddenly disappears. Instead, many hot (~ 10^6 K) and warm (>~ 10^5 K) bubbles are formed in cool (T <~ 2 x 10^4 K) chromospheric winds because of thermal instability; the RGB star wind is not a steady stream but structured outflow. The densities of the bubbles which are supported by the magnetic pressure can be kept low to reduce the radiative cooling so that the bubbles survive long time. Even in the s...

  1. Benchmarking of thermal hydraulic loop models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES), phase-I: Isothermal steady state forced convection

    Science.gov (United States)

    Cho, Jae Hyun; Batta, A.; Casamassima, V.; Cheng, X.; Choi, Yong Joon; Hwang, Il Soon; Lim, Jun; Meloni, P.; Nitti, F. S.; Dedul, V.; Kuznetsov, V.; Komlev, O.; Jaeger, W.; Sedov, A.; Kim, Ji Hak; Puspitarini, D.

    2011-08-01

    As highly promising coolant for new generation nuclear reactors, liquid Lead-Bismuth Eutectic has been extensively worldwide investigated. With high expectation about this advanced coolant, a multi-national systematic study on LBE was proposed in 2007, which covers benchmarking of thermal hydraulic prediction models for Lead-Alloy Cooled Advanced Nuclear Energy System (LACANES). This international collaboration has been organized by OECD/NEA, and nine organizations - ENEA, ERSE, GIDROPRESS, IAEA, IPPE, KIT/IKET, KIT/INR, NUTRECK, and RRC KI - contribute their efforts to LACANES benchmarking. To produce experimental data for LACANES benchmarking, thermal-hydraulic tests were conducted by using a 12-m tall LBE integral test facility, named as Heavy Eutectic liquid metal loop for integral test of Operability and Safety of PEACER (HELIOS) which has been constructed in 2005 at the Seoul National University in the Republic of Korea. LACANES benchmark campaigns consist of a forced convection (phase-I) and a natural circulation (phase-II). In the forced convection case, the predictions of pressure losses based on handbook correlations and that obtained by Computational Fluid Dynamics code simulation were compared with the measured data for various components of the HELIOS test facility. Based on comparative analyses of the predictions and the measured data, recommendations for the prediction methods of a pressure loss in LACANES were obtained. In this paper, results for the forced convection case (phase-I) of LACANES benchmarking are described.

  2. Conceptual Design of Structural Components of a Dual Cooled Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyung-Kyu; Lee, Young-Ho; Lee, Kang-Hee; Kim, Jae-Yong; Yoon, Kyung-Ho

    2008-01-15

    A dual cooled fuel, featured by an internal as well as an external coolant flow passage of a fuel rod, was suggested to enable a large-scaled power-uprate of PWR plant and launched as one of the National Nuclear R and D Projects in 2007. It is necessary to make the dual cooled fuel be compatible with an OPR-1000 system to maximize the economy. Also, the structural components of the dual cooled fuel should be designed to realize their features. To this end, a conceptual design of a spacer grid, outer and center guide tubes, and top and bottom end pieces has been carried out in the project 'Development of Design Technology for Dual Cooled Fuel Structure'. For the spacer grids, it is suggested that springs and dimples are located at or near the cross points of the straps due to a considerably narrowed rod-to-rod gap. Candidate shapes of the grids were also developed and applied for domestic patents. For the outer and center guide tubes, a dual tube like a fuel rod was suggested to make the subchannel areas around the guide tubes be similar to those around the fuel rods of enlarged diameter. It was applied for the domestic patent as well. For the top and bottom end pieces, the shape and pattern have been changed from the conventional ones reflecting the fuel rods' changes. Technical issues and method of resolution for each components were listed up for a basic design works in the following years.

  3. Flightweight radiantly and actively cooled panel: Thermal and structural performance

    Science.gov (United States)

    Shore, C. P.; Nowak, R. J.; Kelly, H. N.

    1982-01-01

    A 2- by 4-ft flightweight panel was subjected to thermal/structural tests representative of design flight conditions for a Mach 6.7 transport and to off-design conditions simulating flight maneuvers and cooling system failures. The panel utilized Rene 41 heat shields backed by a thin layer of insulation to radiate away most of the 12 Btu/ft2-sec incident heating. A solution of ethylene glycol in water circulating through tubes in an aluminum-honeycomb-sandwich panel absorbed the remainder of the incident heating (0.8 Btu/sq ft-sec). The panel successfully withstood (1) 46.7 hr of radiant heating which included 53 thermal cycles and 5000 cycles of uniaxial inplane loading of + or - 1200 lfb/in; (2) simulated 2g-maneuver heating conditions and simulated cooling system failures without excessive temperatures on the structural panel; and (3) the extensive thermal/structural tests and the aerothermal tests reported in NASA TP-1595 without significant damage to the structural panel, coolant leaks, or hot-gas ingress to the structural panel.

  4. Influence of aerodynamics on the heat absorption of convection cooled turbine blades. Final report; Einfluss der Aerodynamik auf die Waermeaufnahme konvektionsgekuehlter Turbinenschaufeln. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, S.; Schiele, R.; Sieger, K.; Schulz, A.

    1995-12-31

    The objective of this project is the integration of aerodynamic and thermal design in the example of convection cooled turbine blades. For this purpose, in a first section of this project, a boundary-layer numerical method is to be further developed to permit the calculation of heat transfer and fluidic losses of convection cooled cascades. Using this improved calculation method, a prototype aerothermic design of a turbine stator is to be conducted in a second section of the project. Finally, the aerodynamic losses and the heat transfer behavior of the new cascade are to be experimentally investigated to make a design assessment. Due to its decisive importance to aerodynamics and heat transfer in gas-turbine blades, special interest is focused on the process of laminar-turbulent transition. (orig.) [Deutsch] Ziel des Vorhabens ist daher die Zusammenfuehrung der aerodynamischen und thermischen Auslegung am Beispiel konvektionsgekuehlter Turbinenschaufeln. Dazu soll in einem ersten Teil des Vorhabens ein Grenzschichtrechenverfahren weiterentwickelt werden, das die Berechnung des Waermeuebergangs und der stroemungsmechanischen Verluste konvektionsgekuehlter Schaufelgitter ermoeglicht. Mit Hilfe dieses verbesserten Berechnungsverfahrens soll in einem zweiten Teil des Vorhabens eine prototypische aerothermische Auslegung eines Turbinenleitrades durchgefuehrt werden. Schliesslich sollen die aerodynamischen Verluste und das Waermeuebergangsverhalten des neuen Schaufelgitters experimentell untersucht und somit die Auslegung bewertet werden. Aufgrund seiner entscheidenden Bedeutung fuer Aerodynamik und Waermeuebergang an Gasturbinenschaufeln gilt dem Vorgang des laminar-turbulenten Umschlags dabei besonderes Interesse. (orig.)

  5. Design Report for the ½ Scale Air-Cooled RCCS Tests in the Natural convection Shutdown heat removal Test Facility (NSTF)

    Energy Technology Data Exchange (ETDEWEB)

    Lisowski, D. D. [Argonne National Lab. (ANL), Argonne, IL (United States); Farmer, M. T. [Argonne National Lab. (ANL), Argonne, IL (United States); Lomperski, S. [Argonne National Lab. (ANL), Argonne, IL (United States); Kilsdonk, D. J. [Argonne National Lab. (ANL), Argonne, IL (United States); Bremer, N. [Argonne National Lab. (ANL), Argonne, IL (United States); Aeschlimann, R. W. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2014-06-01

    The Natural convection Shutdown heat removal Test Facility (NSTF) is a large scale thermal hydraulics test facility that has been built at Argonne National Laboratory (ANL). The facility was constructed in order to carry out highly instrumented experiments that can be used to validate the performance of passive safety systems for advanced reactor designs. The facility has principally been designed for testing of Reactor Cavity Cooling System (RCCS) concepts that rely on natural convection cooling for either air or water-based systems. Standing 25-m in height, the facility is able to supply up to 220 kW at 21 kW/m2 to accurately simulate the heat fluxes at the walls of a reactor pressure vessel. A suite of nearly 400 data acquisition channels, including a sophisticated fiber optic system for high density temperature measurements, guides test operations and provides data to support scaling analysis and modeling efforts. Measurements of system mass flow rate, air and surface temperatures, heat flux, humidity, and pressure differentials, among others; are part of this total generated data set. The following report provides an introduction to the top level-objectives of the program related to passively safe decay heat removal, a detailed description of the engineering specifications, design features, and dimensions of the test facility at Argonne. Specifications of the sensors and their placement on the test facility will be provided, along with a complete channel listing of the data acquisition system.

  6. Cooling-induced structure formation and evolution in collapsars

    CERN Document Server

    Batta, Aldo

    2013-01-01

    The collapse of massive rotating stellar cores and the associated accretion onto the newborn compact object is thought to power long gamma ray bursts (GRBs). The physical scale and dynamics of the accretion disk are initially set by the angular momentum distribution in the progenitor, and the physical conditions make neutrino emission the main cooling agent in the flow. The formation and evolution of structure in these disks is potentially very relevant for the energy release and its time variability, which ultimately imprint on the observed GRB properties. To begin to characterize these, taking into account the three dimensional nature of the problem, we have carried out an initial set of calculations of the collapse of rotating polytropic cores in three dimensions, making use of a pseudo-relativistic potential and a simplified cooling prescription. We focus on the effects of self gravity and cooling on the overall morphology and evolution of the flow for a given rotation rate in the context of the collapsar...

  7. Modern structural steels with improved properties through accelerated cooling

    Energy Technology Data Exchange (ETDEWEB)

    Tschersich, H.J.; Schriever, U.; Bobbert, J.; Kuntze, C. [Thyssen Stahl AG, Duisburg (Germany)

    1995-12-31

    The last decade has seen an enormous increase in the stringency of the demands placed on steels. The main characteristics involved are higher strength and toughness, better suitability for welding and, in certain cases, corrosion resistance. The reason for these heightened demands resides in the higher strains to which the material is exposed in structural applications and in a greater need for safety. In many areas, the steel industry has succeeded in offering appropriate solutions through improved metallurgical and rolling techniques. Accelerated cooled steel grades are one example.

  8. The role of viscosity contrast on plume structure in laboratory modeling of mantle convection

    CERN Document Server

    Prakash, Vivek N; Arakeri, Jaywant H

    2016-01-01

    We have conducted laboratory experiments to model important aspects of plumes in mantle convection. We focus on the role of the viscosity ratio U (between the ambient fluid and the plume fluid) in determining the plume structure and dynamics. In our experiments, we are able to capture geophysical convection regimes relevant to mantle convection both for hot spots (when U > 1) and plate-subduction (when U < 1) regimes. The planar laser induced fluorescence (PLIF) technique is used for flow visualization and characterizing the plume structures. The convection is driven by compositional buoyancy generated by the perfusion of lighter fluid across a permeable mesh and the viscosity ratio U is systematically varied over a range from 1/300 to 2500. The planform, near the bottom boundary for U=1, exhibits a well-known dendritic line plume structure. As the value of U is increased, a progressive morphological transition is observed from the dendritic-plume structure to discrete spherical plumes, accompanied with th...

  9. Thermal structure of intense convective clouds derived from GPS radio occultations

    DEFF Research Database (Denmark)

    Biondi, Riccardo; Randel, W. J.; Ho, S. -P.

    2012-01-01

    Thermal structure associated with deep convective clouds is investigated using Global Positioning System (GPS) radio occultation measurements. GPS data are insensitive to the presence of clouds, and provide high vertical resolution and high accuracy measurements to identify associated temperature...... occultations with CALIPSO profiles over deep convection. Results show a sharp spike in GPS bending angle highly correlated to the top of the clouds, corresponding to anomalously cold temperatures within the clouds. Above the clouds the temperatures return to background conditions, and there is a strong...

  10. Thermal structure of intense convective clouds derived from GPS radio occultations

    DEFF Research Database (Denmark)

    Biondi, Riccardo; Randel, W. J.; Ho, S.-P.

    2011-01-01

    Thermal structure associated with deep convective clouds is investigated using Global Positioning System (GPS) radio occultation measurements. GPS data are insensitive to the presence of clouds, and provide high vertical resolution and high accuracy measurements to identify associated temperature...... occultations with CALIPSO profiles over deep convection. Results show a sharp spike in GPS bending angle highly correlated to the top of the clouds, corresponding to anomalously cold temperatures within the clouds. Above the clouds the temperatures return to background conditions, and there is a strong...

  11. Mathematical modeling of the thermal and hydrodynamic structure of the cooling reservoir

    Science.gov (United States)

    Saminskiy, G.; Debolskaya, E.

    2012-04-01

    Hydrothermal conditions of the cooling reservoir is determined by the heat and mass transfer from the water surface to the atmosphere and the processes of heat transfer directly in the water mass of the reservoir. As the capacity of power plants, the corresponding increase in the volume of heated water and the use of deep lakes and reservoirs as coolers there is a need to develop new, more accurate, and the application of existing methods for the numerical simulation. In calculating the hydrothermal regime it must take into account the effect of wind, density (buoyancy) forces, and other data of the cooling reservoir. In addition to solving practical problems it is important to know not only the magnitude of the average temperature, but also its area and depth distribution. A successful solution can be achieved through mathematical modeling of general systems of equations of transport processes and the correct formulation of the problem, based on appropriate initial data. The purpose of the work is application of software package GETM for simulating the hydrothermal regime of cooling reservoir with an estimate of three-dimensional structure of transfer processes, the effects of wind, the friction of the water surface. Three-dimensional models are rarely applied, especially for far-field problems. If such models are required, experts in the field must develop and apply them. Primary physical processes included are surface heat transfer, short-wave and long-wave radiation and penetration, convective mixing, wind and flow induced mixing, entrainment of ambient water by pumped-storage inflows, inflow density stratification as impacted by temperature and dissolved and suspended solids. The model forcing data consists of the system bathymetry developed into the model grid; the boundary condition flow and temperature; the tributary and flow and temperature; and the system meteorology. Ivankovskoe reservoir belongs to the reservoirs of valley type (Tver region, Russia). It

  12. BioTRIZ Suggests Radiative Cooling of Buildings Can Be Done Passively by Changing the Structure of Roof Insulation to Let Longwave Infrared Pass

    Institute of Scientific and Technical Information of China (English)

    Salmaan Craig; David Harrison; Andrew Cripps; Daniel Knott

    2008-01-01

    This paper demonstrates the application of a design tool called Bio TRIZ. Its developers claim that it can be used to access biological strategies for solving engineering problems. Our aim is to design a roof for hot climates that gets free cooling through radiant coupling with the sky. The insulation in a standard roof stops the sun and convection from warming the thermal mass.But it also restricts the mass's longwave view of the cool sky. Different solutions to this conflict are offered by BioTRIZ. The chosen solution is to replace the standard insulation component with an open cell honeycomb. The vertical cells would allow longwave radiation to pass, while arresting convection. The solutions offered by BioTRIZ's technological counterpart include no such changes in structure. It is estimated that the thermal mass in the biomimetic roof would remain on average 4.5℃ cooler than in a standard roof over a year in Riyadh, Saudi Arabia.

  13. Analysis of the electrolyte convection inside the concentration boundary layer during structured electrodeposition of copper in high magnetic gradient fields.

    Science.gov (United States)

    König, Jörg; Tschulik, Kristina; Büttner, Lars; Uhlemann, Margitta; Czarske, Jürgen

    2013-03-19

    To experimentally reveal the correlation between electrodeposited structure and electrolyte convection induced inside the concentration boundary layer, a highly inhomogeneous magnetic field, generated by a magnetized Fe-wire, has been applied to an electrochemical system. The influence of Lorentz and magnetic field gradient force to the local transport phenomena of copper ions has been studied using a novel two-component laser Doppler velocity profile sensor. With this sensor, the electrolyte convection within 500 μm of a horizontally aligned cathode is presented. The electrode-normal two-component velocity profiles below the electrodeposited structure show that electrolyte convection is induced and directed toward the rim of the Fe-wire. The measured deposited structure directly correlates to the observed boundary layer flow. As the local concentration of Cu(2+) ions is enhanced due to the induced convection, maximum deposit thicknesses can be found at the rim of the Fe-wire. Furthermore, a complex boundary layer flow structure was determined, indicating that electrolyte convection of second order is induced. Moreover, the Lorentz force-driven convection rapidly vanishes, while the electrolyte convection induced by the magnetic field gradient force is preserved much longer. The progress for research is the first direct experimental proof of the electrolyte convection inside the concentration boundary layer that correlates to the deposited structure and reveals that the magnetic field gradient force is responsible for the observed structuring effect.

  14. Luminaries-level structure improvement of LEDs for heat dissipation enhancement under natural convection

    Indian Academy of Sciences (India)

    Ke Wu; Le Wang; Yi-Bo Yu; Zhi-Yi Huang; Pei Liang

    2013-12-01

    Heat dissipation enhancement of LED luminaries is of great significance to the large-scale application of LED. Luminaries-level structure improvement by the method of boring through-hole is adopted to intensify heat dissipation. Furthermore, the natural convection heat transfer process of LED luminaries is simulated by computational fluid dynamics (CFD) model before and after the structural modification. As shown by computational results, boring through-hole is beneficial to develop bottomto-top natural convection, eliminate local circumfluence, and finally form better flow pattern. Analysis based on field synergy principle shows that boring through-hole across LED luminaries improves the synergy between flow field and temperature field, and effectively decreases the thermal resistance of luminaries-level heat dissipation structure. Under the same computational conditions, by luminaries-level structure improvement the highest temperature of heat sink is decreased by about 8° C and the average heat transfer coefficient is increased by 45.8%.

  15. A brief review on mixed convection heat transfer in channel flow with vortex generator for electronic chip cooling

    Directory of Open Access Journals (Sweden)

    S K Mandal

    2016-06-01

    Full Text Available In an effort to increase processor speeds, 3D IC architecture is being aggressively pursued by researchers and chip manufacturers. This architecture allows extremely high level of integration with enhanced electrical performance and expanded functionality, and facilitates realization of VLSI and ULSI technologies. However, utilizing the third dimension to provide additional device layers poses thermal challenges due to the increased heat dissipation and complex electrical interconnects among different layers. The conflicting needs of the cooling system requiring larger flow passage dimensions to limit the pressure drop, and the IC architecture necessitating short interconnect distances to reduce signal latency warrant paradigm shifts in both of their design approach. Additional considerations include the effects due to temperature non-uniformity, localized hot spots, complex fluidic connections, and mechanical design. This paper reviews the advances in electronic chip cooling in the last decade and provides a vision for code signing integrated cooling systems. For various heat fluxes on each side of a chip acting as discrete heat source, the current single-phase cooling technology is projected to provide adequate cooling, albeit with high pressure drops. Effectively mitigating the high temperatures surrounding local hot spots remains a challenging issue. Various forms of tabulators above the chips, different geometric arrangements of the chips positioned top and bottom wall of the duct serves very well in the heat augmentation technique with better performance

  16. Air-cooled volcanoes ? New insights on convective airflow process within Miyakejima and Piton de la Fournaise volcanoes

    Science.gov (United States)

    Antoine, R.; Geshi, N.; Kurita, K.; Aoki, Y.; Ichihara, M.; Staudacher, T.; Bachelery, P.

    2012-04-01

    Subsurface airflow in the unsaturated zone of the soil has been extensively investigated in a variety of disciplines such as mining, nuclear waste or agriculture science. In volcanology, the recent discovery of subsurface airflow close to the terminal cone of Piton de La Fournaise volcano (La Réunion Island, France) provides for the first time insights into the convective behavior of air within the unsaturated layer [1]. The characteristics of the aerothermal system, its occurrence in other volcanoes, its ability to transport heat during quiescent periods and the perturbation of this system before eruptions are the key questions we want to address following this discovery. In this study, we present observations of subsurface convective airflow within opened fractures located at the summit of Miyakejima and Piton de la Fournaise volcanoes from anemometric and temperature data. Two anemometers and thermocouples were placed at the surface and at the center of the fracture at two-meter depth during a diurnal cycle. Six thermocouples also measured the temperature at 1 meter-depth, on a profile set perpendicularly to the fracture. Finally, a thermal camera was used to make punctual measurements of the surface temperature of the fracture. At Miyakejima, two surveys were realized in winter 2010 and summer 2011. During the winter, mild air exit was detected from the fracture with a central vertical velocity of 20 to 50 cm/s. The temperature of the site was constant during the diurnal cycle (~ 22°C), leading to a maximum temperature contrast of 15°C between the fracture and the atmosphere just before sunrise. During summer, a different hydrodynamic behavior was observed: Air inflow was detected during the whole diurnal cycle with a mean velocity of 20 cm/s. The temperature of the fracture followed the temperature of the atmosphere at 2 meters-depth. In the case of Piton de la Fournaise volcano, the same convective behavior was observed at two different fractures during

  17. RF ACCELERATING STRUCTURE FOR THE MUON COOLING EXPERIMENT.

    Energy Technology Data Exchange (ETDEWEB)

    CORLETT,J.; GREEN,M.; LI,D.; HOLTKAMP,N.; MORETTI,A.; KIRK,H.G.; PALMER,R.B.; ZHAO,Y.; SUMMERS,D.

    1999-03-29

    The ionization cooling of muons requires longitudinal acceleration of the muons after scattering in a hydrogen target. In order to maximize the accelerating voltage, we propose using linear accelerating structures with cells bounded by thin beryllium metal foils. This produces an on-axis field equivalent to the maximum surface field, whereas with beam-pipes the accelerating field is approximately half that of the peak surface field in the cavity. The muons interact only weakly with the thin foils. A {pi}/2 interleaved cavity structure has been chosen, with alternate cells coupled together externally, and the two groups of cells fed in quadrature. At present they are considering an operating temperature of 77K to gain a factor of at least two in Q-value over room temperature. The authors describe the design of the {pi}/2 interleaved cavity structure, design of an alternative {pi}-mode open structure, preliminary experimental results from a low-power test cavity, and plans for high-power testing.

  18. Numerical investigation of double diffusive buoyancy forces induced natural convection in a cavity partially heated and cooled from sidewalls

    Directory of Open Access Journals (Sweden)

    Rasoul Nikbakhti

    2016-03-01

    Full Text Available This paper deals with a numerical investigation of double-diffusive natural convective heat and mass transfer in a cavity filled with Newtonian fluid. The active parts of two vertical walls of the cavity are maintained at fixed but different temperatures and concentrations, while the other two walls, as well as inactive areas of the sidewalls, are considered to be adiabatic and impermeable to mass transfer. The length of the thermally active part equals half of the height. The non-dimensional forms of governing transport equations that describe double-diffusive natural convection for two-dimensional incompressible flow are functions of temperature or energy, concentration, vorticity, and stream-function. The coupled differential equations are discretized via FDM (Finite Difference Method. The Successive-Over-Relaxation (SOR method is used in the solution of the stream function equation. The analysis has been done for an enclosure with different aspect ratios ranging from 0.5 to 11 for three different combinations of partially active sections. The results are presented graphically in terms of streamlines, isotherms and isoconcentrations. In addition, the heat and mass transfer rate in the cavity is measured in terms of the average Nusselt and Sherwood numbers for various parameters including thermal Grashof number, Lewis number, buoyancy ratio and aspect ratio. It is revealed that the placement order of partially thermally active walls and the buoyancy ratio influence significantly the flow pattern and the corresponding heat and mass transfer performance in the cavity.

  19. An analysis on Free Convection Cooling of a 3×3 Heater Array in Rectangular Enclosure using Cu-EG-Water Nanofluid

    Directory of Open Access Journals (Sweden)

    Abimanyu Purusothaman

    2016-01-01

    Full Text Available This paper deals with the study of natural convection cooling of a discrete heater array in Cu-EG-water nanofluid filled rectangular enclosure. A 3 × 3 array of non-protruding heat sources is embedded on one of the vertical walls of the enclosure while the top horizontal and opposite vertical walls are assumed to be isothermally cold. The remaining portions in which the heaters are mounted and all other walls are insulated. The above setup is modeled into a system of partial differential equations which are solved numerically using finite volume method based on the Semi-Implicit Method for Pressure Linked Equation (SIMPLE algorithm and power law scheme. The wide range of parameters for computation are the aspect ratio of the enclosure, the mixture proportion of Ethylene glycol-water, the solid volume fraction of the nanoparticle along with two different thermal conductivity models. It is observed that the proper choice of the computation parameters and thermal conductivity models could be able to maximize the heat transfer rate from the heater array. Also, the results obtained in this study will provide new guidelines in the field of electronic equipment cooling.

  20. Peculiarities of convection and oil maturation in 3D porous medium structure.

    Science.gov (United States)

    Yurie Khachay, Professor; Mindubaev, Mansur

    2017-04-01

    An important estimation of oil source thickness productivity is to study the thermal influences of magmatic intrusions on the maturation of the organic matter. The heterogeneity of permeability distribution of the reservoir rock and respectively the convection structure provide temperature heterogeneity and different degree of maturity for the oil source material. A numerical algorithm for solving the problem of developed convection in two-dimensional and three-dimensional models of the porous medium, which consists of a system of Darcy equations, heat conduction with convection term and the continuity equation, is developed. Because of the effective values of the coefficients of thermal conductivity, heat capacity, viscosity and permeability of the medium depend from the temperature; the system of equations is nonlinear. For solution we used the dimensionless system of coordinates. For numerical solution we used the longitudinal cross-implicit scheme. The coordinates step for the 3D model had been used constant and equal to H/20, where H=1- dimensionless thickness of porous medium layer. As it is shown from the variants of numerical solution, by the stationary regime of developed convection because of the temperature heterogeneous distribution in the sedimentary reservoir the formation of oil source matter different degree of maturity is possible. That result is very significant for estimation of reservoirs oil-bearing The work was fulfilled by supporting of the Fund of UB RAS, project 1518532. Reference 1. Yurie Khachay and Mansur Mindubaev, 2016, Effect of convective transport in porous media on the conductions of organic matter maturation and generation of hydrocarbons in trap rocks complexes, Energy Procedia. 74 pp.79-83.

  1. Identification of dominant flow structures in rapidly rotating convection of liquid metals using Dynamic Mode Decomposition

    Science.gov (United States)

    Horn, S.; Schmid, P. J.; Aurnou, J. M.

    2016-12-01

    The Earth's metal core acts as a dynamo whose efficiency in generating and maintaining the magnetic field is essentially determined by the rotation rate and the convective motions occurring in its outer liquid part. For the description of the primary physics in the outer core the idealized system of rotating Rayleigh-Bénard convection is often invoked, with the majority of studies considering only working fluids with Prandtl numbers of Pr ≳ 1. However, liquid metals are characterized by distinctly smaller Prandtl numbers which in turn result in an inherently different type of convection. Here, we will present results from direct numerical simulations of rapidly rotating convection in a fluid with Pr ≈ 0.025 in cylindrical containers and Ekman numbers as low as 5 × 10-6. In this system, the Coriolis force is the source of two types of inertial modes, the so-called wall modes, that also exist at moderate Prandtl numbers, and cylinder-filling oscillatory modes, that are a unique feature of small Prandtl number convection. The obtained flow fields were analyzed using the Dynamic Mode Decomposition (DMD). This technique allows to extract and identify the structures that govern the dynamics of the system as well as their corresponding frequencies. We have investigated both the regime where the flow is purely oscillatory and the regime where wall modes and oscillatory modes co-exist. In the purely oscillatory regime, high and low frequency oscillatory modes characterize the flow. When both types of modes are present, the DMD reveals that the wall-attached modes dominate the flow dynamics. They precess with a relatively low frequency in retrograde direction. Nonetheless, also in this case, high frequency oscillations have a significant contribution.

  2. Effects of rotation on natural convection cooling from three rows of heat sources in a rectangular cavity

    Energy Technology Data Exchange (ETDEWEB)

    Jin, L.F.; Tou, K.W. [Nanyang Technological Univ., Singapore (Singapore). School of Mechanical and Production Engineering; Tso, C.P. [Multimedia Univ., Melaka (Malaysia). Faculty of Engineering and Technology

    2005-09-01

    Two-dimensional unsteady numerical studies are made on an air-filled enclosure rotated about its horizontal axis with an array of three rows of heat sources on one of the walls, revealing three physically realizable phenomena, namely, uni-periodic oscillation, multi-periodic oscillation and chaotic oscillation. The evolutionary process of flow field and natural convection characteristics from stationary to rotating situation is studied. Rotation results in an imbalance between clockwise and counter-clockwise circulations, increases heat transfer in the worst scenario, reduces the oscillation of Nusselt number, and improves or reduces mean performance in each cycle. The optimal distribution of heaters in rotating fluid is close to the results in the stationary situation if they have same dominated circulation direction. (author)

  3. Structural evolution in the crystallization of rapid cooling silver melt

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Z.A., E-mail: ze.tian@gmail.com [School of Physics and Electronics, Hunan University, Changsha 410082 (China); Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Dong, K.J.; Yu, A.B. [Laboratory for Simulation and Modelling of Particulate Systems School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)

    2015-03-15

    The structural evolution in a rapid cooling process of silver melt has been investigated at different scales by adopting several analysis methods. The results testify Ostwald’s rule of stages and Frank conjecture upon icosahedron with many specific details. In particular, the cluster-scale analysis by a recent developed method called LSCA (the Largest Standard Cluster Analysis) clarified the complex structural evolution occurred in crystallization: different kinds of local clusters (such as ico-like (ico is the abbreviation of icosahedron), ico-bcc like (bcc, body-centred cubic), bcc, bcc-like structures) in turn have their maximal numbers as temperature decreases. And in a rather wide temperature range the icosahedral short-range order (ISRO) demonstrates a saturated stage (where the amount of ico-like structures keeps stable) that breeds metastable bcc clusters. As the precursor of crystallization, after reaching the maximal number bcc clusters finally decrease, resulting in the final solid being a mixture mainly composed of fcc/hcp (face-centred cubic and hexagonal-closed packed) clusters and to a less degree, bcc clusters. This detailed geometric picture for crystallization of liquid metal is believed to be useful to improve the fundamental understanding of liquid–solid phase transition. - Highlights: • A comprehensive structural analysis is conducted focusing on crystallization. • The involved atoms in our analysis are more than 90% for all samples concerned. • A series of distinct intermediate states are found in crystallization of silver melt. • A novelty icosahedron-saturated state breeds the metastable bcc state.

  4. Radiative cooling for thermophotovoltaic systems

    Science.gov (United States)

    Zhou, Zhiguang; Sun, Xingshu; Bermel, Peter

    2016-09-01

    Radiative cooling has recently garnered a great deal of attention for its potential as an alternative method for photovoltaic thermal management. Here, we will consider the limits of radiative cooling for thermal management of electronics broadly, as well as a specific application to thermal power generation. We show that radiative cooling power can increase rapidly with temperature, and is particularly beneficial in systems lacking standard convective cooling. This finding indicates that systems previously operating at elevated temperatures (e.g., 80°C) can be passively cooled close to ambient under appropriate conditions with a reasonable cooling area. To examine these general principles for a previously unexplored application, we consider the problem of thermophotovoltaic (TPV) conversion of heat to electricity via thermal radiation illuminating a photovoltaic diode. Since TPV systems generally operate in vacuum, convective cooling is sharply limited, but radiative cooling can be implemented with proper choice of materials and structures. In this work, realistic simulations of system performance are performed using the rigorous coupled wave analysis (RCWA) techniques to capture thermal emitter radiation, PV diode absorption, and radiative cooling. We subsequently optimize the structural geometry within realistic design constraints to find the best configurations to minimize operating temperature. It is found that low-iron soda-lime glass can potentially cool the PV diode by a substantial amount, even to below ambient temperatures. The cooling effect can be further improved by adding 2D-periodic photonic crystal structures. We find that the improvement of efficiency can be as much as an 18% relative increase, relative to the non-radiatively cooled baseline, as well as a potentially significant improvement in PV diode lifetime.

  5. Effects of Slotted Structures on Nonlinear Characteristics of Natural Convection in a Cylinder with an Internal Concentric Slotted Annulus

    CERN Document Server

    Shen, Chunyun; Zhang, Yuwen; Li, Zheng

    2016-01-01

    Natural convection in a cylinder with an internally slotted annulus was solved by SIMPLE algorithm, and the effects of different slotted structures on nonlinear characteristics of natural convection were investigated. The results show that the equivalent thermal conductivity Keq increases with Rayleigh number, and reaches the maximum in the vertical orientation. Nonlinear results were obtained by simulating the fluid flow at different conditions. With increasing Rayleigh number, heat transfer is intensified and the state of heat transfer changes from the steady to unsteady. We investigated different slotted structures effects on natural convection, and analyze the corresponding nonlinear characteristics.

  6. Heat pipe and surface mass transfer cooling of hypersonic vehicle structures

    Science.gov (United States)

    Colwell, Gene T.; Modlin, James M.

    1992-01-01

    The problem of determining the feasibility of cooling hypersonic vehicle leading-edge structures exposed to severe aerodynamic surface heating using heat pipe and mass transfer cooling techniques is addressed. A description is presented of a numerical finite-difference-based hypersonic leading-edge cooling model incorporating poststartup liquid metal heat pipe cooling with surface transpiration and film cooling to predict the transient structural temperature distributions and maximum surface temperatures of hypersonic vehicle leading edge. An application of this model to the transient cooling of a typical aerospace plane wing leading-edge section. The results of this application indicated that liquid metal heat pipe cooling alone is insufficient to maintain surface temperatures below an assumed maximum level of 1800 K for about one-third of a typical aerospace plane ascent trajectory through the earth's atmosphere.

  7. RCCS Experiments and Validation for High Temperature Gas-Cooled Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Chang Oh; Cliff Davis; Goon C. Park

    2007-09-01

    A reactor cavity cooling system (RCCS), an air-cooled helical coil RCCS unit immersed in the water pool, was proposed to overcome the disadvantages of the weak cooling ability of air-cooled RCCS and the complex structure of water-cooled RCCS for the high temperature gas-cooled reactor (HTGR). An experimental apparatus was constructed to investigate the various heat transfer phenomena in the water pool type RCCS, such as the natural convection of air inside the cavity, radiation in the cavity, the natural convection of water in the water pool and the forced convection of air in the cooling pipe. The RCCS experimental results were compared with published correlations. The CFX code was validated using data from the air-cooled portion of the RCCS. The RELAP5 code was validated using measured temperatures from the reactor vessel and cavity walls.

  8. Convectively Forced Gravity Waves and their Sensitivity to Heating Profile and Atmospheric Structure

    Science.gov (United States)

    Halliday, Oliver; Parker, Douglas; Griffiths, Stephen; Vosper, Simon; Stirling, Alison

    2016-04-01

    It has been known for some time that convective heating is communicated to its environment by gravity waves. Despite this, the radiation of gravity waves in macro-scale models, which are typically forced at the grid-scale by meso-scale parameterization schemes, is not well understood. We present here theoretical work directed toward improving our fundamental understanding of convectively forced gravity wave effects at the meso-scale, in order to begin to address this problem. Starting with the hydrostatic, non-rotating, 2D, Boussinesq equations in a slab geometry, we find a radiating, analytical solution to prescribed sensible heat forcing for both the vertical velocity and potential temperature response. Both Steady and pulsed heating with adjustable horizontal structure is considered. From these solutions we construct a simple model capable of interrogating the spatial and temporal sensitivity to chosen heating functions of the remote forced response in particular. By varying the assumed buoyancy frequency, the influence of the model stratosphere on the upward radiation of gravity waves, and in turn, on the tropospheric response can be understood. Further, we find that the macro-scale response to convection is highly dependent on the radiation characteristics of gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and upper boundary condition of the domain.

  9. A review on the thermal hydraulic characteristics of the air-cooled heat exchangers in forced convection

    Indian Academy of Sciences (India)

    Ankur Kumar; Jyeshtharaj B Joshi; Arun K Nayak; Pallippattu K Vijayan

    2015-05-01

    In this paper, a review is presented on the experimental investigations and the numerical simulations performed to analyze the thermal-hydraulic performance of the air-cooled heat exchangers. The air-cooled heat exchangers mostly consist of the finned-tube bundles. The primary role of the extended surfaces (fins) is to provide more heat transfer area to enhance the rate of heat transfer on the air side. The secondary role of the fins is to generate vortices, which help in enhancing the mixing and the heat transfer coefficient. In this study, the annular and plate fins are considered, the annular fins are further divided into four categories: (1) plane annular fins, (2) serrated fins, (3) crimped spiral fins, (4) perforated fins, and similarly for the plate fins, the fin types are: (1) plain plate fins, (2) wavy plate fins, (3) plate fins with DWP, and (4) slit and strip fins. In Section 4, the performance of the various types of fins is presented with respect to the parameters: (1) Reynolds number, (2) fin pitch, (3) fin height, (4) fin thickness, (5) tube diameter, (6) tube pitch, (7) tube type, (8) number of tube rows, and (9) effect of dehumidifying conditions. In Section 5, the conclusions and the recommendations for the future work have been given.

  10. A study on the structure of the convective atmosphere over the Bay of Bengal during BOBMEX-99

    Indian Academy of Sciences (India)

    U C Mohanty; N V Sam; S Das; A N V Satyanarayana

    2003-06-01

    Convective activity is one of the major processes in the atmosphere influencing the local and large scale weather in the tropics. The latent heat released by the cumulus cloud is known to drive monsoon circulation, which on the other hand supplies the moisture that maintains the cumulus clouds. An investigation is carried out on the convective structure of the atmosphere during active and suppressed periods of convection using data sets obtained from the Bay of Bengal and Monsoon Experiment (BOBMEX). The cumulus convection though being a small-scale phenomenon, still influences its embedding environment by interaction through various scales. This study shows the variation in the kinematic and convective parameters during the transition from suppressed to active periods of convection. Convergence in the lower levels and strong upward vertical velocity, significant during active convection are associated with the formation of monsoon depressions. The apparent heat source due to latent heat release and the vertical transport of the eddy heat by cumulus convection, and the apparent moisture sink due to net condensation and vertical divergence of the eddy transport of moisture, are estimated through residuals of the thermodynamic equation and examined in relation to monsoon activity during BOBMEX.

  11. The Influence of Knitting Structure on Heating and Cooling Dynamic

    Directory of Open Access Journals (Sweden)

    Daiva MIKUČIONIENĖ

    2013-05-01

    Full Text Available The comfort provided by clothing depends on several factors, one of them being thermal comfort. Human thermal comfort depends on a combination of clothing, climate, and physical activity. It is known, the fibre type, yarn properties, fabric structure, finishing are the main factors affecting thermo-physiological comfort. The thermal property of knitted fabric is very important not only for its thermal comfort but also for protection against cross weather conditions. Most of the studies carried out have been devoted to measure static thermal properties. But it is very important not only amount of the heat released to the environment but also the dynamics of the heat transmission. The main goal of this work was to investigate the dynamic of the heat and cool transfer through the fabrics with different knitting pattern and different type of the yarns. Three different types of knitted fabrics were developed for this experimental work.DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4434

  12. The Influence of Knitting Structure on Heating and Cooling Dynamic

    Directory of Open Access Journals (Sweden)

    Daiva MIKUČIONIENĖ

    2013-05-01

    Full Text Available The comfort provided by clothing depends on several factors, one of them being thermal comfort. Human thermal comfort depends on a combination of clothing, climate, and physical activity. It is known, the fibre type, yarn properties, fabric structure, finishing are the main factors affecting thermo-physiological comfort. The thermal property of knitted fabric is very important not only for its thermal comfort but also for protection against cross weather conditions. Most of the studies carried out have been devoted to measure static thermal properties. But it is very important not only amount of the heat released to the environment but also the dynamics of the heat transmission. The main goal of this work was to investigate the dynamic of the heat and cool transfer through the fabrics with different knitting pattern and different type of the yarns. Three different types of knitted fabrics were developed for this experimental work.DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4434

  13. Porous medium convection at large Rayleigh number: Studies of coherent structure, transport, and reduced dynamics

    Science.gov (United States)

    Wen, Baole

    Buoyancy-driven convection in fluid-saturated porous media is a key environmental and technological process, with applications ranging from carbon dioxide storage in terrestrial aquifers to the design of compact heat exchangers. Porous medium convection is also a paradigm for forced-dissipative infinite-dimensional dynamical systems, exhibiting spatiotemporally chaotic dynamics if not "true" turbulence. The objective of this dissertation research is to quantitatively characterize the dynamics and heat transport in two-dimensional horizontal and inclined porous medium convection between isothermal plane parallel boundaries at asymptotically large values of the Rayleigh number Ra by investigating the emergent, quasi-coherent flow. This investigation employs a complement of direct numerical simulations (DNS), secondary stability and dynamical systems theory, and variational analysis. The DNS confirm the remarkable tendency for the interior flow to self-organize into closely-spaced columnar plumes at sufficiently large Ra (up to Ra ≃ 105), with more complex spatiotemporal features being confined to boundary layers near the heated and cooled walls. The relatively simple form of the interior flow motivates investigation of unstable steady and time-periodic convective states at large Ra as a function of the domain aspect ratio L. To gain insight into the development of spatiotemporally chaotic convection, the (secondary) stability of these fully nonlinear states to small-amplitude disturbances is investigated using a spatial Floquet analysis. The results indicate that there exist two distinct modes of instability at large Ra: a bulk instability mode and a wall instability mode. The former usually is excited by long-wavelength disturbances and is generally much weaker than the latter. DNS, strategically initialized to investigate the fully nonlinear evolution of the most dangerous secondary instability modes, suggest that the (long time) mean inter-plume spacing in

  14. EFFECT OF COOLED BOUNDARY ON THE TURBULENT STRUCTURE

    Institute of Scientific and Technical Information of China (English)

    Li Guo-xiang; Mao Hua-yong; Li Na

    2003-01-01

    The flow field in the cooled channel of a heat exchanger was measured using the X-type film probes of Hot Wire/Firm Anemotheter, and the turbulent mechanism was discussed. It is concluded that the airflow is cooled in the flow process, the distribution of the turbulent intensity is relatively convergent near the centerline and the boundary, the constriction action produced due to heat release at the foot of the fins causes u to decrease and w to increase near the root downstream. It is concluded that the turbulent flow with cooled boundary results from the balance of production, dissipation and intermittency caused by constriction action.

  15. Formation of Large-Scale Semi-Organized Structures in Turbulent Convection

    CERN Document Server

    Elperin, T; Rogachevskii, I; Zilitinkevich, S

    2002-01-01

    A new mean-field theory of turbulent convection is developed. This theory predicts the convective wind instability in a shear-free turbulent convection which causes formation of large-scale semi-organized fluid motions in the form of cells or rolls. Spatial characteristics of these motions, such as the minimum size of the growing perturbations and the size of perturbations with the maximum growth rate, are determined. This study predicts also the existence of the convective shear instability in a sheared turbulent convection which results in generation of convective shear waves with a nonzero hydrodynamic helicity. Increase of shear promotes excitation of the convective shear instability. Applications of the obtained results to the atmospheric turbulent convection and the laboratory experiments on turbulent convection are discussed. This theory can be applied also for the describing a mesogranular turbulent convection in astrophysics.

  16. Discussion on Structure of Some Convection Furnaces%浅谈几种常见对流炉的结构

    Institute of Scientific and Technical Information of China (English)

    韩秀奎

    2009-01-01

    Convection heating is a popular means for tempering furnace . In this article structures of some convection furnaces were described and merits and drawbacks of each furnace were also compared.%对流加热是目前钢化炉常见的一种加热方式,文章介绍了玻璃对流加热的几种常见结构,并对优缺点进行比较.

  17. Metal Cooling in Simulations of Cosmic Structure Formation

    CERN Document Server

    Smith, Britton D; Abel, Tom

    2007-01-01

    The addition of metals to any gas can significantly alter its evolution by increasing the rate of radiative cooling. In star-forming environments, enhanced cooling can potentially lead to fragmentation and the formation of low-mass stars, where metal-free gas-clouds have been shown not to fragment. Adding metal cooling to numerical simulations has traditionally required a choice between speed and accuracy. We introduce a method that uses the sophisticated chemical network of the photoionization software, CLOUDY, to include radiative cooling from a complete set of metals up to atomic number 30 (Zn) that can be used with large-scale three-dimensional hydrodynamic simulations. Our method is valid over an extremely large temperature range (50 K 10^-4 Zsun, regions of density and temperature exist where gas is both thermally unstable and has a cooling time less than its dynamical time. We identify these doubly unstable regions as the most inducive to fragmentation. At high redshifts, the cosmic microwave backgrou...

  18. Finite-Element Analysis of Forced Convection and Conduction

    Science.gov (United States)

    Wieting, A. R.

    1982-01-01

    TAP2 thermal-analysis program was developed as part of research on finite element methodology for thermal analysis of convectively cooled structures, such as scramjet engines and hypersonic aircraft. Program simplifies computations when both structural and thermal analyses are required and is suited for thermal analysis of nuclear reactors and solar-panel heating systems.

  19. Self-organization of local magnetoplasma structures in the upper layers of the solar convection zone

    Energy Technology Data Exchange (ETDEWEB)

    Chumak, O. V., E-mail: chuo@yandex.ru [Moscow State University, Sternberg Astronomical Institute (Russian Federation)

    2013-08-15

    Self-organization and evolution of magnetoplasma structures in the upper layers of the solar convection zone are discussed as a process of diffuse aggregation of magnetic flux tubes. Equations describing the tube motion under the action of magnetic interaction forces, hydrodynamic forces, and random forces are written explicitly. The process of aggregation of magnetic flux tubes into magnetic flux clusters of different shapes and dimensions is simulated numerically. The obtained structures are compared with the observed morphological types of sunspot groups. The quantitative comparison with the observational data was performed by comparing the fractal dimensions of the photospheric magnetic structures observed in solar active regions with those of structures obtained in the numerical experiment. The model has the following free parameters: the numbers of magnetic flux tubes with opposite polarities on the considered area element (Nn and Ns), the average radius of the cross section of the magnetic flux tube (a), its effective length (l), the twist factor of the tube field (k), and the absolute value of the average velocity of chaotic tube displacements (d). Variations in these parameters in physically reasonable limits leads to the formation of structures (tube clusters of different morphological types) having different fractal dimensions. Using the NOAA 10488 active region, which appeared and developed into a complicated configuration near the central meridian, as an example, it is shown that good quantitative agreement between the fractal dimensions is achieved at the following parameters of the model: Nn = Ns = 250 ± 50; a = 150 ± 50 km; l ∼ 5000 km, and d = 80 ± 10 m/s. These results do not contradict the observational data and theoretical estimates obtained in the framework of the Parker “spaghetti” model and provide new information on the physical processes resulting in the origin and evolution of local magnetic plasma structures in the near

  20. Convectively coupled Kelvin waves in aquachannel simulations: 1. Propagation speeds, composite structures, and comparison with aquaplanets

    Science.gov (United States)

    Blanco, Joaquín. E.; Nolan, David S.; Tulich, Stefan N.

    2016-10-01

    Convectively coupled Kelvin waves (CCKWs) represent a significant contribution to the total variability of the Intertropical Convergence Zone (ITCZ). This study analyzes the structure and propagation of CCKWs simulated by the Weather Research and Forecasting (WRF) model using two types of idealized domains. These are the "aquachannel," a flat rectangle on a beta plane with zonally periodic boundary conditions and length equal to the Earth's circumference at the equator, and the "aquapatch," a square domain with zonal extent equal to one third of the aquachannel's length. A series of simulations are performed, including a doubly nested aquapatch, in which convection is solved explicitly along the equator. The model intercomparison is carried out throughout the use of several techniques such as power spectra, filtering, wave tracking, and compositing, and it is extended to some simulations from the Aquaplanet Experiment (APE). Results show that despite the equatorial superrotation bias produced by the WRF simulations, the CCKWs simulated with this model propagate with similar phase speeds (relative to the low-level mean flow) as the corresponding waves from the APE simulations. Horizontal and vertical structures of the CCKWs simulated with aquachannels are also in overall good agreement with those from aquaplanet simulations and observations, although there is a distortion of the zonal extent of anomalies when the shorter aquapatch is used.

  1. On the correspondence between flow structures and convective heat transfer augmentation for multiple jet impingement

    Science.gov (United States)

    Terzis, Alexandros

    2016-09-01

    The correspondence between local fluid flow structures and convective heat transfer is a fundamental aspect that is not yet fully understood for multiple jet impingement. Therefore, flow field and heat transfer experiments are separately performed investigating mutual-jet interactions exposed in a self-gained crossflow. The measurements are taken in two narrow impingement channels with different cross-sectional areas and a single exit design. Hence, a gradually increased crossflow momentum is developed from the spent air of the upstream jets. Particle image velocimetry (PIV) and liquid crystal thermography (LCT) are used in order to investigate the aerothermal characteristics of the channel with high spatial resolution. The PIV measurements are taken at planes normal to the target wall and along the centreline of the jets, providing quantitative flow visualisation of jet and crossflow interactions. Spatially resolved heat transfer coefficient distributions on the target plate are evaluated with transient techniques and a multi-layer of thermochromic liquid crystals. The results are analysed aiming to provide a better understanding about the impact of near-wall flow structures on the convective heat transfer augmentation for these complex flow phenomena.

  2. Deep Structures and Initiation of Plate Tectonics in Thermochemical Mantle Convection Models

    Science.gov (United States)

    Hansen, U.; Stein, C.

    2015-12-01

    Recently deep thermochemical structures have been studied intensively. The observed large anomalies with reduced seismic velocities (LLSVPs) beneath Africa and the Pacific are obtained in numerical models as an initial dense layer at the core-mantle boundary (CMB) is pushed up to piles by the convective flow (e.g., McNamara et al., EPSL 229, 1-9, 2010). Adding a dense CMB layer to a model featuring active plate tectonics, Trim et al. (EPSL 405, 1-14, 2014) find that surface mobility is strongly hindered by the dense material and can even vanish completely for a CMB layer that has a too high density or too large a volume.In a further study we employed a fully rheological model in which oceanic plates form self-consistently. We observe that an initial dense CMB layer strongly affects the formation of plates and therefore the onset time of plate tectonics. We present a systematic 2D parameter study exploring the time of plate initiation and discuss the resulting deep thermal and thermochemical structures in a self-consistent thermochemical mantle convection system.

  3. Alternative Room Cooling System

    Directory of Open Access Journals (Sweden)

    Md. Fazle Rabbi

    2015-06-01

    Full Text Available The rapidly growing population results in an increasing demand for much more residential and commercial buildings, which leads to vertical growth of the buildings and needs proper ventilation of those buildings. Natural air ventilation system is not sufficient for conventional building structures. Hence fans and air-conditioners are must to meet the requirement of proper ventilation as well as space conditioning. Globally building sector consumes largest energy in heating, cooling, ventilation and space conditioning. This load can be minimized by the application of solar chimney and modification in building structure for heating, cooling, ventilation and space conditioning. Passive solar cooling is a subject of interest to provide cooling by using the sun, a powerful energy source. This is done for ensuring human comfort in hot climates. ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers defines Comfort as ‘that state of mind which expresses satisfaction with the thermal environment.’ The present paper describes the development of a solar passive cooling system, which can provide thermal cooling throughout the summer season in hot and humid climates. The constructed passive system works on natural convection mode of air. Such system reduces the inside temperature of up to 5°C from the atmospheric temperature. Temperature can further be reduced by the judicious use of night ventilation.

  4. The Impact of Microphysics on Intensity and Structure of Hurricanes and Mesoscale Convective Systems

    Science.gov (United States)

    Tao, Wei-Kuo; Shi, Jainn J.; Jou, Ben Jong-Dao; Lee, Wen-Chau; Lin, Pay-Liam; Chang, Mei-Yu

    2007-01-01

    During the past decade, both research and operational numerical weather prediction models, e.g. Weather Research and Forecast (WRF) model, have started using more complex microphysical schemes originally developed for high-resolution cloud resolving models (CRMs) with a 1-2 km or less horizontal resolutions. WRF is a next-generation mesoscale forecast model and assimilation system that has incorporated modern software framework, advanced dynamics, numeric and data assimilation techniques, a multiple moveable nesting capability, and improved physical packages. WRF model can be used for a wide range of applications, from idealized research to operational forecasting, with an emphasis on horizontal grid sizes in the range of 1-10 km. The current WRF includes several different microphysics options such as Purdue Lin et al. (1983), WSM 6-class and Thompson microphysics schemes. We have recently implemented three sophisticated cloud microphysics schemes into WRF. The cloud microphysics schemes have been extensively tested and applied for different mesoscale systems in different geographical locations. The performances of these schemes have been compared to those from other WRF microphysics options. We are performing sensitivity tests in using WRF to examine the impact of six different cloud microphysical schemes on precipitation processes associated hurricanes and mesoscale convective systems developed at different geographic locations [Oklahoma (IHOP), Louisiana (Hurricane Katrina), Canada (C3VP - snow events), Washington (fire storm), India (Monsoon), Taiwan (TiMREX - terrain)]. We will determine the microphysical schemes for good simulated convective systems in these geographic locations. We are also performing the inline tracer calculation to comprehend the physical processes (i.e., boundary layer and each quadrant in the boundary layer) related to the development and structure of hurricanes and mesoscale convective systems.

  5. Directly connected heat exchanger tube section and coolant-cooled structure

    Energy Technology Data Exchange (ETDEWEB)

    Chainer, Timothy J.; Coico, Patrick A.; Graybill, David P.; Iyengar, Madhusudan K.; Kamath, Vinod; Kochuparambil, Bejoy J.; Schmidt, Roger R.; Steinke, Mark E.

    2015-09-15

    A method is provided for fabricating a cooling apparatus for cooling an electronics rack, which includes an air-to-liquid heat exchanger, one or more coolant-cooled structures, and a tube. The heat exchanger is associated with the electronics rack and disposed to cool air passing through the rack, includes a plurality of coolant-carrying tube sections, each tube section having a coolant inlet and outlet, one of which is coupled in fluid communication with a coolant loop to facilitate flow of coolant through the tube section. The coolant-cooled structure(s) is in thermal contact with an electronic component(s) of the rack, and facilitates transfer of heat from the component(s) to the coolant. The tube connects in fluid communication one coolant-cooled structure and the other of the coolant inlet or outlet of the one tube section, and facilitates flow of coolant directly between that coolant-carrying tube section of the heat exchanger and the coolant-cooled structure.

  6. Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet

    Energy Technology Data Exchange (ETDEWEB)

    In, Se Hwan; Hong, Yong Jun; Yeom, Han Kil; Ko, Hyo Bong; Park, Seong Je [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

    2016-03-15

    The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

  7. Optimization of convective heat transfer coefficient in water jet cooled mirror%射流式水冷镜对流换热系数的优化

    Institute of Scientific and Technical Information of China (English)

    李斌; 焦路光; 刘亮; 李兰; 周琼; 袁圣付; 刘文广

    2011-01-01

    介绍了射流水冷技术并将其应用到高能激光器反射镜的冷却中,设计了射流式水冷镜.采用计算流体力学的方法,利用通用有限元软件ANSYS的流体分析模块FLOTRAN对单孔内射流进行了数值模拟,详细讨论了各孔参数对换热性能的影响.实现了孔参数的优化.结果表明:在水冷镜中采用射流技术可以获得很好的对流换热效果,换热系数可达100 KW/(m·K)以上,且具有结构简单、可控性强等特点.%The jet cooling technology was introduced and used in the cooling of high power laser mirror, then the water jet cooled mirror was designed.Computational fluid dynamics method was adopted to simulate the jet in a hole by the fluid analysis module FLOTRAN of the finite element analysis software ANSYS, then the influence on the capability of heat transfer of the parameters of the hole was discussed and optimization of the parameters was achieved.The results show that great capability of heat transfer can be achieved by using the jet cooling technology, with simple structure and good controllability, and the heat transfer coefficient can be higher than 100 kW/(m2 · K).

  8. Utilizing of inner porous structure in injection moulds for application of special cooling method

    Science.gov (United States)

    Seidl, M.; Bobek, J.; Šafka, J.; Habr, J.; Nováková, I.; Běhálek, L.

    2016-04-01

    The article is focused on impact evaluation of controlled inner structure of production tools and new cooling method on regulation of thermal processes for injection moulding technology. The mould inserts with porous structure were cooled by means of liquid CO2 which is very progressive cooling method and enables very fast and intensive heat transfer among the plastic product, the production tool and cooling medium. The inserts were created using rapid prototype technology (DLSM) and they had a bi-component structure consisting of thin compact surface layer and defined porous inner structure of open cell character where liquid CO2 was flowing through. This analyse includes the evaluation of cooling efficiency for different inner structures and different time profiles for dosing of liquid CO2 into the porous structure. The thermal processes were monitored using thermocouples and IR thermal analyse of product surface and experimental device. Intensive heat removal influenced also the final structure and the shape and dimensional accuracy of the moulded parts that were made of semi-crystalline polymer. The range of final impacts of using intensive cooling method on the plastic parts was defined by DSC and dimensional analyses.

  9. Convection Destroys the Core/Mantle Structure in Hybrid C/O/Ne White Dwarfs

    CERN Document Server

    Brooks, Jared; Bildsten, Lars; Quataert, Eliot; Paxton, Bill

    2016-01-01

    A hybrid C/O/Ne white dwarf (WD) -- an unburned C/O core surrounded by an O/Ne/Na mantle -- can be formed if the carbon flame is quenched in a super-AGB (SAGB) star or white dwarf merger remnant. We show that this segregated hybrid structure becomes unstable to rapid mixing within 2,000 years of the onset of WD cooling. Carbon burning includes a weak reaction that removes electrons, resulting in a lower electron-to-baryon ratio ($Y_{\\rm e}$) in the regions processed by carbon burning compared to the unburned C/O core, making the O/Ne mantle denser than the C/O core as the WD cools. This is unstable to efficient mixing. We use the results of $\\texttt{MESA}$ models with different size C/O cores to quantify the rate at which the cores mix with the mantle as they cool. In all cases, we find that the WDs undergo significant core/mantle mixing on timescales shorter than the time available to grow the WD to the Chandrasekhar mass ($M_{\\rm Ch}$) by accretion. As a result, hybrid WDs that reach $M_{\\rm Ch}$ due to lat...

  10. Vibrational branching ratios and hyperfine structure of BH and its suitability for laser cooling

    Science.gov (United States)

    Hendricks, Richard; Holland, Darren; Truppe, Stefan; Sauer, Ben; Tarbutt, Michael

    2014-08-01

    The simple structure of the BH molecule makes it an excellent candidate for direct laser cooling. We measure the branching ratios for the decay of the A^{1}Pi (v'=0) state to vibrational levels of the ground state, X^{1}Sigma^{+}, and find that they are exceedingly favourable for laser cooling. We verify that the branching ratio for the spin-forbidden transition to the intermediate a^{3}Pi state is inconsequentially small. We measure the frequency of the lowest rotational transition of the X state, and the hyperfine structure in the relevant levels of both the X and A states, and determine the nuclear electric quadrupole and magnetic dipole coupling constants. Our results show that, with a relatively simple laser cooling scheme, a Zeeman slower and magneto-optical trap can be used to cool, slow and trap BH molecules.

  11. Vibrational branching ratios and hyperfine structure of $^{11}$BH and its suitability for laser cooling

    CERN Document Server

    Hendricks, R J; Truppe, S; Sauer, B E; Tarbutt, M R

    2014-01-01

    The simple structure of the BH molecule makes it an excellent candidate for direct laser cooling. We measure the branching ratios for the decay of the ${\\rm A}^{1}\\Pi (v'=0)$ state to vibrational levels of the ground state, ${\\rm X}^{1}\\Sigma^{+}$, and find that they are exceedingly favourable for laser cooling. We verify that the branching ratio for the spin-forbidden transition to the intermediate ${\\rm a}^{3}\\Pi$ state is inconsequentially small. We measure the frequency of the lowest rotational transition of the X state, and the hyperfine structure in the relevant levels of both the X and A states, and determine the nuclear electric quadrupole and magnetic dipole coupling constants. Our results show that, with a relatively simple laser cooling scheme, a Zeeman slower and magneto-optical trap can be used to cool, slow and trap BH molecules.

  12. Vibrational branching ratios and hyperfine structure of BH and its suitability for laser cooling

    Directory of Open Access Journals (Sweden)

    Richard eHendricks

    2014-08-01

    Full Text Available The simple structure of the BH molecule makes it an excellent candidate for direct laser cooling. We measure the branching ratios for the decay of the A^{1}Pi (v'=0 state to vibrational levels of the ground state, X^{1}Sigma^{+}, and find that they are exceedingly favourable for laser cooling. We verify that the branching ratio for the spin-forbidden transition to the intermediate a^{3}Pi state is inconsequentially small. We measure the frequency of the lowest rotational transition of the X state, and the hyperfine structure in the relevant levels of both the X and A states, and determine the nuclear electric quadrupole and magnetic dipole coupling constants. Our results show that, with a relatively simple laser cooling scheme, a Zeeman slower and magneto-optical trap can be used to cool, slow and trap BH molecules.

  13. Wavelike Structures in the Turbulent Layer During the Morning Development of Convection at Dome C, Antarctica

    Science.gov (United States)

    Petenko, Igor; Argentini, Stefania; Casasanta, Giampietro; Kallistratova, Margarita; Sozzi, Roberto; Viola, Angelo

    2016-11-01

    In the period January-February 2014, observations were made at the Concordia station, Dome C, Antarctica to study atmospheric turbulence in the boundary layer using a high-resolution sodar. The turbulence structure was observed beginning from the lowest height of about 2 m, with a vertical resolution of less than 2 m. Typical patterns of the diurnal evolution of the spatio-temporal structure of turbulence detected by the sodar are analyzed. Here, we focus on the wavelike processes observed within the transition period from stable to unstable stratification occurring in the morning hours. Thanks to the high-resolution sodar measurements during the development of the convection near the surface, clear undulations were detected in the overlying turbulent layer for a significant part of the time. The wavelike pattern exhibits a regular braid structure, with undulations associated with internal gravity waves attributed to Kelvin-Helmholtz shear instability. The main spatial and temporal scales of the wavelike structures were determined, with predominant periodicity of the observed wavy patterns estimated to be 40-50 s. The horizontal scales roughly estimated using Taylor's frozen turbulence hypothesis are about 250-350 m.

  14. Atomic and electronic structure transformations of silver nanoparticles under rapid cooling conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lobato, I; Rojas, J [Instituto Peruano de EnergIa Nuclear, Avenida Canada 1470, Lima 41 (Peru); Landauro, C V; Torres, J [Facultad de Ciencias Fisicas, Universidad Nacional Mayor de San Marcos, P.O. box 14-0149, Lima 14 (Peru)], E-mail: jrojast@unmsm.edu.pe

    2009-02-04

    The structural evolution and dynamics of silver nanodrops Ag{sub 2869} (4.4 nm in diameter) under rapid cooling conditions have been studied by means of molecular dynamics simulations and electronic density of state calculations. The interaction of silver atoms is modelled by a tight-binding semiempirical interatomic potential proposed by Cleri and Rosato. The pair correlation functions and the pair analysis technique are used to reveal the structural transition in the process of solidification. It is shown that Ag nanoparticles evolve into different nanostructures under different cooling processes. At a cooling rate of 1.5625 x 10{sup 13} K s{sup -1} the nanoparticles preserve an amorphous-like structure containing a large amount of 1551 and 1541 pairs which correspond to icosahedral symmetry. For a lower cooling rate (1.5625 x 10{sup 12} K s{sup -1}), the nanoparticles transform into a crystal-like structure consisting mainly of 1421 and 1422 pairs which correspond to the face centred cubic and hexagonal close packed structures, respectively. The variations of the electronic density of states for the differently cooled nanoparticles are small, but in correspondence with the structural changes.

  15. Atomic and electronic structure transformations of silver nanoparticles under rapid cooling conditions

    Science.gov (United States)

    Lobato, I.; Rojas, J.; Landauro, C. V.; Torres, J.

    2009-02-01

    The structural evolution and dynamics of silver nanodrops Ag2869 (4.4 nm in diameter) under rapid cooling conditions have been studied by means of molecular dynamics simulations and electronic density of state calculations. The interaction of silver atoms is modelled by a tight-binding semiempirical interatomic potential proposed by Cleri and Rosato. The pair correlation functions and the pair analysis technique are used to reveal the structural transition in the process of solidification. It is shown that Ag nanoparticles evolve into different nanostructures under different cooling processes. At a cooling rate of 1.5625 × 1013 K s-1 the nanoparticles preserve an amorphous-like structure containing a large amount of 1551 and 1541 pairs which correspond to icosahedral symmetry. For a lower cooling rate (1.5625 × 1012 K s-1), the nanoparticles transform into a crystal-like structure consisting mainly of 1421 and 1422 pairs which correspond to the face centred cubic and hexagonal close packed structures, respectively. The variations of the electronic density of states for the differently cooled nanoparticles are small, but in correspondence with the structural changes.

  16. A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

    Energy Technology Data Exchange (ETDEWEB)

    Riihimaki, Laura D.; Comstock, Jennifer M.; Luke, Edward; Thorsen, Tyler J.; Fu, Qiang

    2017-07-28

    To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement (ARM) site are used to classify cloud phase within a deep convective cloud in a shallow to deep convection transitional case. The cloud cannot be fully observed by a lidar due to signal attenuation. Thus we develop an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka band cloud radar. This approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid, indicating complexity to how ice growth and diabatic heating occurs in the vertical structure of the cloud.

  17. Design and fabrication of a skin stringer discrete tube actively cooled structural panel

    Science.gov (United States)

    Anthony, F. M.

    1978-01-01

    The design optimization and practical implementation of actively cooled structural panel concepts was investigated. The desired actively cooled structural panel consisted of the cooled skin and a substructure. The primary load carrying components were fabricated from 2024-T3 aliminum alloy. The 3003-H14 coolant passage tubing was chosen because of its excellent corrosion resistance, workability needed to obtain the desired cross sectional shape, and strength. The Epon 951 adhesive was selected for its excellent structural properties and is the thinnest of available films, 0.064 mm. The Eccobond 58C silver filled epoxy was chosen because of its high thermal conductivity, and the alumina filled Epon 828 was chosen for structural and expansion characteristics.

  18. Radiation Pressure-supported Accretion Disks: Vertical Structure, Energy Advection, and Convective Stability

    CERN Document Server

    Gu, Wei-Min

    2012-01-01

    By taking into account the local energy balance per unit volume between the viscous heating and the advective cooling plus the radiative cooling, we investigate the vertical structure of radiation pressure-supported accretion disks in spherical coordinates. Our solutions show that the photosphere of the disk is close to the polar axis and therefore the disk seems to be extremely thick. However, the profile of density implies that most of the accreted matter exists in a moderate range around the equatorial plane. We show that the well-known polytropic relation between the pressure and the density is unsuitable for describing the vertical structure of radiation pressure-supported disks. More importantly, we find that the energy advection is significant even for slightly sub-Eddington accretion disks. We argue that the non-negligible advection may help to understand why the standard thin disk model is likely to be inaccurate above \\sim 0.3 Eddington luminosity, which was found by some works on the black hole spi...

  19. Engineering review of the core support structure of the Gas Cooled Fast Breeder Reactor

    Energy Technology Data Exchange (ETDEWEB)

    None

    1978-09-01

    The review of the core support structure of the gas cooled fast breeder reactor (GCFR) covered such areas as the design criteria, the design and analysis of the concepts, the development plan, and the projected manufacturing costs. Recommendations are provided to establish a basis for future work on the GCFR core support structure.

  20. High-resolution calculations of the solar global convection with the reduced speed of sound technique: I. The structure of the convection and the magnetic field without the rotation

    CERN Document Server

    Hotta, H; Yokoyama, T

    2014-01-01

    We carry out non-rotating high-resolution calculations of the solar global convection, which resolve convective scales of less than 10 Mm. To cope with the low Mach number conditions in the lower convection zone, we use the reduced speed of sound technique (RSST), which is simple to implement and requires only local communication in the parallel computation. In addition, the RSST allows us to expand the computational domain upward to about $0.99 R_{\\odot}$ as it can also handle compressible flows. Using this approach, we study the solar convection zone on the global scale, including small-scale near-surface convection. In particular, we investigate the influence of the top boundary condition on the convective structure throughout the convection zone as well as on small-scale dynamo action. Our main conclusions are: 1. The small-scale downflows generated in the near-surface layer penetrate into deeper layers to some extent and excite small-scale turbulence in the region $>0.9R_\\odot$, where $R_\\odot$ is the so...

  1. Investigation of structure of superconducting power transmission cables with LN2 counter-flow cooling

    Science.gov (United States)

    Furuse, Mitsuho; Fuchino, Shuichiro; Higuchi, Noboru

    2003-04-01

    Establishment of long-distance cooling techniques and design of a compact cross section are required for development of HTC superconducting underground power cables. To save space of return coolant, a counter-flow cooling system appears promising. However, it is difficult to cool down long cables because of heat exchange between counter-flows due to high thermal conductivity of dielectric materials which separate both flows in range of liquid nitrogen temperature. We estimated temperature distributions analytically along model HTS power cables with counter-flow. Results of calculation showed that when liquid-nitrogen-impregnated polypropylene laminated paper was chosen for a dielectric material, great thickness was required to reduce heat exchange between counter-flows. We investigated various cable structures to optimize the counter-flow cooling system and cable size.

  2. Structures, Branching Ratios and Laser Cooling Scheme for 138BaF Molecule

    CERN Document Server

    Chen, Tao; Yan, Bo

    2016-01-01

    For laser cooling considerations, we have theoretically investigated the electronic, rovibrational and hypefine structures of BaF molecule. The highly diagonal Franck-Condon factors and the branching ratios for all possible transitions within the lowest-lying four electronic states have also been calculated. Meanwhile, the mixing between metastable A'2{\\Delta} and A2{\\Pi} states and further the lifetime of the {\\Delta} state have been estimated since the loss procedure via {\\Delta} state would like fatally destroy the main quasi-cycling {\\Sigma}-{\\Pi} transition for cooling and trapping. The resultant hyperfine splittings of each rovibrational states in X2{\\Sigma}+ state provide benchmarksfor sideband modulations of cooling and repumping lasers and remixing microwaves to address all necessary levels. The calculated Zeeman shift and g-factors for both X and A states serve as benchmarks for selections of the trapping laser polarizations. Our study paves the way for future laser cooling and magneto-optical trapp...

  3. Cooling rate dependence of simulated Cu64.5Zr35.5 metallic glass structure

    Science.gov (United States)

    Ryltsev, R. E.; Klumov, B. A.; Chtchelkatchev, N. M.; Shunyaev, K. Yu.

    2016-07-01

    Using molecular dynamics simulations with embedded atom model potential, we study structural evolution of Cu64.5Zr35.5 alloy during the cooling in a wide range of cooling rates γ ∈ (1.5 ṡ 109, 1013) K/s. Investigating short- and medium-range orders, we show that the structure of Cu64.5Zr35.5 metallic glass essentially depends on cooling rate. In particular, a decrease of the cooling rate leads to an increase of abundances of both the icosahedral-like clusters and Frank-Kasper Z16 polyhedra. The amounts of these clusters in the glassy state drastically increase at the γmin = 1.5 ṡ 109 K/s. Analysing the structure of the glass at γmin, we observe the formation of nano-sized crystalline grain of Cu2Zr intermetallic compound with the structure of Cu2Mg Laves phase. The structure of this compound is isomorphous with that for Cu5Zr intermetallic compound. Both crystal lattices consist of two types of clusters: Cu-centered 13-atom icosahedral-like cluster and Zr-centered 17-atom Frank-Kasper polyhedron Z16. That suggests the same structural motifs for the metallic glass and intermetallic compounds of Cu-Zr system and explains the drastic increase of the abundances of these clusters observed at γmin.

  4. Structural and Microhardness Changes After Turning of the AISI 1045 Steel for Minimum Quantity Cooling Lubrication

    Science.gov (United States)

    Maruda, Radoslaw W.; Krolczyk, Grzegorz M.; Michalski, Mariusz; Nieslony, Piotr; Wojciechowski, Szymon

    2017-01-01

    This work presents the cooling effect under minimum quantity cooling lubrication and dry cutting on structural changes and microhardness of the ferritic-pearlitic AISI 1045 steel after turning. Due to the fact that the AISI 1045 steel has a two-phase structure, microhardness tests using the Vickers method were conducted with a load of 0.05 HV separately for ferrite and pearlite grains. The tests showed that cooling of the cutting zone under minimum quantity cooling lubrication (MQCL) condition decreased the depth of the hardened layer compared to dry cutting by approximately 40% for both pearlite and ferrite. Scanning electron microscopy analysis revealed that applying MQCL limits the formation of plastic deformations, among others, by reducing the surface crumple zone by approximately 50% compared to dry cutting. As a result of cooling being applied to the cutting zone using the MQCL method, the average diameter of ferrite grains has been decreased in the entire surface area compared to dry cutting. When using dry cutting, clear structural changes of the surface layer were also observed. This may be the result of sulfide inclusions which have formed, causing microcracks on the edge of the hardened layer and surface deformation visible as notches.

  5. Structural engineering developments in power plant cooling tower construction. 100 years of natural draught cooling towers - from tower cooler to cooling tower. Bautechnische Entwicklungen im Kraftwerkskuehlturmbau. 100 Jahre Naturzugkuehltuerme - vom Kaminkuehler zum Kuehlkamin

    Energy Technology Data Exchange (ETDEWEB)

    Damjakob, H.; Depe, T.; Vrangos, V. (Balcke-Duerr AG, Ratingen (Germany))

    1992-06-01

    Almost exactly 100 years ago, tower-type structures were first used for the production of artificial ventilation for cooling purposes. The shell of these so-called tower coolers, today known as 'natural draught cooling towers', was, from the outset, the subject of multiple structural engineering develepments in respect of design, material, construction and statistical calculation. These developments have been stimulated especially by the spasmodic increase in dimensions in the application of power plant cooling towers and, more recently, in connection with ecological requirements. (orig.).

  6. Simulation of quasi-linear mesoscale convective systems in northern China: Lightning activities and storm structure

    Science.gov (United States)

    Li, Wanli; Qie, Xiushu; Fu, Shenming; Su, Debin; Shen, Yonghai

    2016-01-01

    Two intense quasi-linear mesoscale convective systems (QLMCSs) in northern China were simulated using the WRF (Weather Research and Forecasting) model and the 3D-Var (three-dimensional variational) analysis system of the ARPS (Advanced Regional Prediction System) model. A new method in which the lightning density is calculated using both the precipitation and non-precipitation ice mass was developed to reveal the relationship between the lightning activities and QLMCS structures. Results indicate that, compared with calculating the results using two previous methods, the lightning density calculated using the new method presented in this study is in better accordance with observations. Based on the calculated lightning densities using the new method, it was found that most lightning activity was initiated on the right side and at the front of the QLMCSs, where the surface wind field converged intensely. The CAPE was much stronger ahead of the southeastward progressing QLMCS than to the back it, and their lightning events mainly occurred in regions with a large gradient of CAPE. Comparisons between lightning and non-lightning regions indicated that lightning regions featured more intense ascending motion than non-lightning regions; the vertical ranges of maximum reflectivity between lightning and non-lightning regions were very different; and the ice mixing ratio featured no significant differences between the lightning and non-lightning regions.

  7. The Structure of Cool Flame Fronts of Pentane,Iso—Pentane and Their Mixture

    Institute of Scientific and Technical Information of China (English)

    Z.A.Mansurov; Ch.K.Westbrook; 等

    2000-01-01

    An experimental study of the combustion of two isomers of n-pentane and iso-pertane in laminar cool flames has been carried out.Thrree flames were studied,one with n-pentane,the second with iso-pentane,and the third with an equimolar mixture of the two isomers.Particular attention has been given to the low temperature region ahead of the hot region of the flame and the cool flame chemistry occurring there.A unique experimental facility has been used to provide access to this cool flame region.Comparison are made of the structures of the three flames,with particular attention on the different intermediate species produced and the correlations between the fuel molecule structure and the specific intermediates produced.

  8. Structure of Cool Flame Fronts of Pentane, Iso-Pentane and Their Mixture

    Energy Technology Data Exchange (ETDEWEB)

    Mansurov, Z A; Mironenko, A A; Bodykov, D U; Rakhimetkaliev, K N; Westbrook, C K

    2000-01-11

    An experimental study of the combustion of two isomers of pentane, n-pentane and iso-pentane, in laminar cool flames has been carried out. Three flames were studied, one with n-pentane, the second with iso-pentane, and the third with an equimolar mixture of the two isomers. Particular attention has been given to the low temperature region ahead of the hot region of the flame and the cool flame chemistry occurring there. A unique experimental facility has been used to provide access to this cool flame region. Comparisons are made of the structures of the three flames, with particular attention on the different intermediate species produced and the correlations between the fuel molecule structure and the specific intermediates produced.

  9. Improvement of thermal comfort by cooling clothing in warm climate

    DEFF Research Database (Denmark)

    Sakoi, Tomonori; Melikov, Arsen Krikor; Kolencíková, Sona;

    2014-01-01

    comfort compared to convective cooling alone. The supply of a small amount of water allowed the cooling clothing to provide a continuous cooling effect, whereas the effect of convective cooling alone decreased as sweat dried. However, the controllability of the cooling clothing needs to be improved....

  10. Vertical structure of cumulonimbus towers and intense convective clouds over the South Asian region during the summer monsoon season

    Science.gov (United States)

    Bhat, G. S.; Kumar, Shailendra

    2015-03-01

    The vertical structure of radar reflectivity factor in active convective clouds that form during the South Asian monsoon season is reported using the 2A25 version 6 data product derived from the precipitation radar measurements on board the Tropical Rainfall Measuring Mission satellite. We define two types of convective cells, namely, cumulonimbus towers (CbTs) and intense convective cells (ICCs). CbT is defined referring to a reflectivity threshold of 20 dBZ at 12 km altitude and is at least 9 km thick. ICCs are constructed referring to reflectivity thresholds at 8 km and 3 km altitudes. Cloud properties reported here are based on 10 year climatology. It is observed that the frequency of occurrence of CbTs is highest over the foothills of Himalayas, plains of northern India and Bangladesh, and minimum over the Arabian Sea and equatorial Indian Ocean west of 90°E. The regional differences depend on the reference height selected, namely, small in the case of CbTs and prominent in 6-13 km height range for ICCs. Land cells are more intense than the oceanic ones for convective cells defined using the reflectivity threshold at 3 km, whereas land versus ocean contrasts are not observed in the case of CbTs. Compared to cumulonimbus clouds elsewhere in the tropics, the South Asian counterparts have higher reflectivity values above 11 km altitude.

  11. Analyzing the structure of the optical path difference of the supersonic film cooling

    Science.gov (United States)

    Ding, Haolin; Yi, Shihe; Fu, Jia; He, Lin

    2016-10-01

    While high-speed aircraft are flying in the atmosphere, its optical-hood is subjected to severe aerodynamic heating. Supersonic film cooling method can effectively isolate external heating, but the flow structures formed by the supersonic film cooling can cause the beam degradation and affect the imaging quality. To research the aero-optics of supersonic film cooling, an experimental model was adopted in this paper, its mainstream Mach number 3.4, designed jet Mach number 2.5, measured jet Mach number 2.45. High-resolution images of flow were acquired by the nano-based planar laser scattering (NPLS) technique, by reconstructing the density field of supersonic film cooling, and then, the optical path difference (OPD) were acquired by the ray-tracing method. Depending on the comparison between K-H vortex and OPD distribution, the valleys of OPD correspond to the vortex `rollers' and the peaks to the `braids'. However, the corresponding relationship becomes quite irregular for the flow field with developed vortices, and cannot be summarized in this manner. And then, the OPD were analyzed by correlation function and structure function, show that, there is a relationship between the shape of OPD correlation function and the vortex structure, the correlation function type changed with the development of the vortex. The correctness that the mixing layer makes a main contribution to the aero-optics of supersonic film cooling was verified, and the structure function of aero-optical distortion has a power relationship that is similar to that of atmospheric optics. At last, the power spectrum corresponding to the typical region of supersonic film cooling were acquired by improved periodgram.

  12. Numerical Simulation of the Dynamics, Cloud Microphysics and Radar Echo Structures of Tropical and Mid-Latitude Convection.

    Science.gov (United States)

    Cheng, Chee Pong

    forms at high levels but melts well before reaching the surface. When a mid-latitude hailstorm sounding (also lifted) is used as input to the convective model, the radar reflectivity occurs aloft and is associated with hail. The stronger updraft of the hailstorm cell allows raindrops to accumulate aloft. Since the drops are suspended high enough and for a sufficiently long time above the 0(DEGREES)C level the raindrops are converted to hail. This result confirms quantitatively the hypothesis of Zipser and Le Mone that the strong vertical velocity in the hailstorm accounts for its different radar echo structure compared to tropical cells. The model further reveals the microphysical-dynamical chain of events involved, especially the effectiveness of the ice-phase processes in the hailstorm case and its relative ineffectiveness in the tropical cells. When the microphysical equations are coupled with tropical anvil cloud air motions, a stratiform radar echo is produced and the precipitation particle growth, melting and evaporation in the model confirm anvil-cloud processes inferred and hypothesized by Leary and Houze. Output from model runs for tropical cells of different sizes are used to estimate mass and heat fluxes by an ensemble of tropical convective cells. The model cells cannot by themselves match the heat flux profiles derived from large -scale heat-budget studies, unless mesoscale anvil vertical motions are invoked to supplement the convective motions.

  13. Volume-imaging lidar observations of the convective structure surrounding the flight path of a flux-measuring aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Eloranta, E.W.; Forrest, D.K. (Univ. of Wisconsin, Madison (United States))

    1992-11-30

    This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. Here the authors report on convective structure measurements in the atmospheric boundary layer (ABL) made from instrumented aircraft flights. To compensate for the limited spatial resolution of the aircraft flight path the data is correlated with simultaneous LIDAR measurements which provide a much larger scale picture of the atmosphere. Together these two diagnostics provide a much more informative picture of the ABL, especially in the vicinity of particular convective eddy structures. It becomes clear from this work that stable results require longer flight paths than the 15km legs in this sample area. Horizontal wind speeds from the two instruments agree very well.

  14. Vertical Structures of Anvil Clouds of Tropical Mesoscale Convective Systems Observed by CloudSat

    Science.gov (United States)

    Yuan, J.; Houze, R. A., Jr.; Heymsfield, A.

    2011-01-01

    A global study of the vertical structures of the clouds of tropical mesoscale convective systems (MCSs) has been carried out with data from the CloudSat Cloud Profiling Radar. Tropical MCSs are found to be dominated by cloud-top heights greater than 10 km. Secondary cloud layers sometimes occur in MCSs, but outside their primary raining cores. The secondary layers have tops at 6--8 and 1--3 km. High-topped clouds extend outward from raining cores of MCSs to form anvil clouds. Closest to the raining cores, the anvils tend to have broader distributions of reflectivity at all levels, with the modal values at higher reflectivity in their lower levels. Portions of anvil clouds far away from the raining core are thin and have narrow frequency distributions of reflectivity at all levels with overall weaker values. This difference likely reflects ice particle fallout and therefore cloud age. Reflectivity histograms of MCS anvil clouds vary little across the tropics, except that (i) in continental MCS anvils, broader distributions of reflectivity occur at the uppermost levels in the portions closest to active raining areas; (ii) the frequency of occurrence of stronger reflectivity in the upper part of anvils decreases faster with increasing distance in continental MCSs; and (iii) narrower-peaked ridges are prominent in reflectivity histograms of thick anvil clouds close to the raining areas of connected MCSs (superclusters). These global results are consistent with observations at ground sites and aircraft data. They present a comprehensive test dataset for models aiming to simulate process-based upper-level cloud structure around the tropics.

  15. Experimental Study on the Impact of External Geometrical Shape on Free and Forced Convection Time Dependent Average Heat Transfer Coefficient during Cooling Process

    Directory of Open Access Journals (Sweden)

    Sundus Hussein Abd

    2012-01-01

    Full Text Available In this research, an experimental study was conducted to high light the impact of the exterior shape of a cylindrical body on the forced and free convection heat transfer coefficients when the body is hold in the entrance of an air duct. The impact of changing the body location within the air duct and the air speed are also demonstrated. The cylinders were manufactured with circular, triangular and square sections of copper for its high thermal conductivity with appropriate dimensions, while maintaining the surface area of all shapes to be the same. Each cylinder was heated to a certain temperature and put inside the duct at certain locations. The temperature of the cylinder was then monitored. The heat transfer coefficient were then calculated for forced convection for several Reynolds number (4555-18222.The study covered free convection impact for values of Rayleigh number ranging between (1069-3321. Imperical relationships were obtained for all cases of forced and free convection and compared with equations of circular cylindrical shapes found in literature. These imperical equations were found to be in good comparison with that of other sources.

  16. Strong winter cooling over the Irminger Sea in winter 2014–2015, exceptional deep convection, and the emergence of anomalously low SST

    NARCIS (Netherlands)

    de Jong, M.F.; de Steur, L.

    2016-01-01

    Deep convection is presumed to be vital for the North Atlantic Meridional Overturning Circulation,even though observational evidence for the link remains inconclusive. Modeling studies have suggested thatconvection will weaken as a result of enhanced freshwater input. The emergence of anomalously lo

  17. Measurement of the convective heat-transfer coefficient

    CERN Document Server

    Conti, Rosaria; Fiordilino, Emilio

    2014-01-01

    We propose an experiment for investigating how objects cool down toward the thermal equilibrium with its surrounding through convection. We describe the time dependence of the temperature difference of the cooling object and the environment with an exponential decay function. By measuring the thermal constant tau, we determine the convective heat-transfer coefficient, which is a characteristic constant of the convection system.

  18. Effect of Melt Convection and Solid Transport on Macrosegregation and Grain Structure in Equiaxed Al-Cu Alloys

    Science.gov (United States)

    Rerko, Rodney S.; deGroh, Henry C., III; Beckermann, Christoph; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Macrosegregation in metal casting can be caused by thermal and solutal melt convection, and the transport of unattached solid crystals. These free grains can be a result of, for example, nucleation in the bulk liquid or dendrite fragmentation. In an effort to develop a comprehensive numerical model for the casting of alloys, an experimental study has been conducted to generate benchmark data with which such a solidification model could be tested. The specific goal of the experiments was to examine equiaxed solidification in situations where sinking of grains is (and is not) expected. The objectives were: 1) experimentally study the effects of solid transport and thermosolutal convection on macrosegregation and grain size distribution patterns; and 2) provide a complete set of controlled thermal boundary conditions, temperature data, segregation data, and grain size data, to validate numerical codes. The alloys used were Al-1 wt. pct. Cu, and Al-10 wt. pct. Cu with various amounts of the grain refiner TiB2 added. Cylindrical samples were either cooled from the top, or the bottom. Several trends in the data stand out. In attempting to model these experiments, concentrating on experiments that show clear trends or differences is recommended.

  19. Formation of the structures from dusty clusters in neon dc discharge under cooling

    Science.gov (United States)

    Polyakov, D. N.; Shumova, V. V.; Vasilyak, L. M.

    2016-11-01

    The formation of structures consisted of dusty clusters in plasma at the discharge tube cooling to a temperature of liquid nitrogen was discovered. The dependence of the reduced electric field in the positive column of a discharge on gas temperature was experimentally measured. Depending on the pressure of neon were observed the different structural transitions in the regions of growing current-voltage characteristics at low discharge currents ≤ 1 mA. It was found that the regions of existence of structured clusters and the regions of structural transitions were characterized by the higher values of the reduced electric field than the regions of destruction of ordered structures.

  20. Physical and Structural Studies on the Cryo-cooling of Insulin Crystals

    Science.gov (United States)

    Lovelace, J.; Bellamy, H.; Snell, E. H.; Borgstahl, G.

    2003-01-01

    Reflection profiles were analyzed from microgravity-(mg) and earth-grown insulin crystals to measure mosaicity (h) and to reveal mosaic domain structure and composition. The effects of cryocooling on single and multi-domain crystals were compared. The effects of cryocooling on insulin structure were also re-examined. Microgravity crystals were larger, more homogeneous, and more perfect than earth crystals. Several mg crystals contained primarily a single mosaic domain with havg of 0.005deg. The earth crystals varied in quality and all contained multiple domains with havg of 0.031deg. Cryocooling caused a 43-fold increase in h for mg crystals (havg=0.217deg) and an %fold increase for earth crystals (havg=0.246deg). These results indicate that very well-ordered crystals are not completely protected from the stresses associated with cryocooling, especially when structural perturbations occur. However, there were differences in the reflection profiles. For multi-mosaic domain crystals, each domain individually broadened and separated from the other domains upon cryo-cooling. Cryo-cooling did not cause an increase in the number of domains. A crystal composed of a single domain retained this domain structure and the reflection profiles simply broadened. Therefore, an improved signal-to-noise ratio for each reflection was measured from cryo-cooled single domain crystals relative to cryo-cooled multi-domain crystals. This improved signal, along with the increase in crystal size, facilitated the measurement of the weaker high- resolution reflections. The observed broadening of reflection profiles indicates increased variation in unit cell dimensions which may be linked to cryo-cooling-associated structural changes and disorder.

  1. Processing-structure-mechanical property relationship in Ti-Nb microalloyed steel: Continuous cooling versus interrupted cooling

    Energy Technology Data Exchange (ETDEWEB)

    Natarajan, V.V. [Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Liu, S. [Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); School of Materials Science and Engineering, University of Science and Technology, Beijing (China); Challa, V.S.A. [Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Misra, R.D.K., E-mail: dmisra2@utep.edu [Laboratory for Excellence in Advanced Steel Research, Materials Science and Engineering Program, Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968 (United States); Sidorenko, D.M.; Mulholland, M.D.; Manohar, M.; Hartmann, J.E. [ArcelorMittal Global R& D Center, 3001 East Columbus Drive, East Chicago, IN 46312 (United States)

    2016-08-01

    The process parameters associated with thermo-mechanical controlled processing (TMCP) of steels play an important role in influencing the ultimate mechanical properties. The study of TMCP parameters have not received the required attention. In this regard, we elucidate here the impact of finish cooling temperature on interrupted cooling and compare with continuous cooling on microstructural evolution and precipitation behavior and associated mechanical properties in Ti-Nb microalloyed steels. The microstructural evolution was studied via transmission electron microscopy and electron back scattered diffraction (EBSD). The microstructure of continuously cooled and interrupted cooled steels with different finish exit temperatures consisted of polygonal ferrite, bainite and martensite/austenite constituent. However, the fraction of different microstructural constituents was different in each of the experimental steels. Similarly, there were differences in the distribution and average size of (Nb, Ti)C precipitates. The aforementioned differences in the microstructure and precipitation introduced differences in tensile properties. Furthermore, electron back scattered diffraction studies indicated distinct variation in average grain area and high angle boundaries between continuously cooled and interrupted cooled steels.

  2. Stochastic Convection Parameterizations

    Science.gov (United States)

    Teixeira, Joao; Reynolds, Carolyn; Suselj, Kay; Matheou, Georgios

    2012-01-01

    computational fluid dynamics, radiation, clouds, turbulence, convection, gravity waves, surface interaction, radiation interaction, cloud and aerosol microphysics, complexity (vegetation, biogeochemistry, radiation versus turbulence/convection stochastic approach, non-linearities, Monte Carlo, high resolutions, large-Eddy Simulations, cloud structure, plumes, saturation in tropics, forecasting, parameterizations, stochastic, radiation-clod interaction, hurricane forecasts

  3. Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade

    Science.gov (United States)

    Szwaba, Ryszard; Kaczynski, Piotr; Doerffer, Piotr; Telega, Janusz

    2016-08-01

    This paper presents the study of the flow structure and heat transfer, and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade. The investigations focus on heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillet, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.

  4. Correlation of thermophoretically-modified small particle diffusional deposition rates in forced convection systems with variable properties, transpiration cooling and/or viscous dissipation

    Science.gov (United States)

    Gokoglu, S. A.; Rosner, D. E.

    1984-01-01

    A cooled object (heat exchanger tube or turbine blade) is considered to be immersed in a hot fluid stream containing trace amounts of suspended vapors and/or small particles. Numerical prediction calculations were done for self-similar laminar boundary layers and law-of-the-wall turbulent boundary layers. Correlations are presented for the effect of thermophoresis in the absence of transpiration cooling and viscous dissipation; the effect of real suction and blowing in the absence of thermophoresis; the effect of viscous dissipation on thermophoresis in the absence of transpiration cooling; and the combined effect of viscous dissipation and transpiration cooling on thermophoresis. The final correlation, St/St-sub-zero, is insensitive to particle properties, Euler number, and local mainstream temperature.

  5. Thermal and structural finite element analysis of water cooled silicon monochromator for synchrotron radiation comparison of two different cooling schemes

    CERN Document Server

    Artemiev, A I; Busetto, E; Hrdy, J; Mrazek, D; Plesek, I; Savoia, A

    2001-01-01

    The article describes the results of Finite Element Analysis (FEA) of the first Si monochromator crystal distortions due to Synchrotron Radiation (SR) heat load and consequent analysis of the influence of the distortions on a double crystal monochromator performance. Efficiencies of two different cooling schemes are compared. A thin plate of Si crystal is lying on copper cooling support in both cases. There are microchannels inside the cooling support. In the first model the direction of the microchannels is parallel to the diffraction plane. In the second model the direction of the microchannels is perpendicular to the diffraction plane or in other words, it is a conventional cooling scheme. It is shown that the temperature field along the crystal volume is more uniform and more symmetrical in the first model than in the second (conventional) one.

  6. Effect of cooling rate on structural and electromagnetic properties of high-carbon ferrochrome powders

    Science.gov (United States)

    Yang, Jian-ping; Chen, Jin; Hao, Jiu-jiu; Guo, Li-na; Liu, Jin-ying

    2016-03-01

    The structural and electromagnetic properties of high-carbon ferrochrome powders (HCFCP) obtained at different cooling rates were respectively investigated by means of optical microscope, X-ray diffractometer, electron probe as well as the vector network analyzer in the frequency range of 1-18 GHz. The results show that the cell structure of main phase, (Cr,Fe)7C3, transforms from hexagonal to orthogonal with the improvement of cooling rate. Meanwhile the mass ratio of Cr to Fe in (Cr,Fe)7C3 gradually declines, while that for CrFe goes up. Both the real part and the imaginary part of relative complex permittivity of HCFCP are in an increasing order with cooling rate rising in most frequencies. For comparison, the relative complex permeability presents an opposite changing tendency. The peaks of the imaginary part of relative complex permeability appearing in low and high frequencies are attributed to nature resonance. The reflection loss of HCFCP gradually decreases as cooling rate reduces and frequency enhances. At 2.45 GHz, the algebraic sum of dielectric loss factor and magnetic loss factor increases first and then decreases in the temperature extent from 298 K to 1273 K.

  7. Optimization of Heat-Sink Cooling Structure in EAST with Hydraulic Expansion Technique%Optimization of Heat-Sink Cooling Structure in EAST with Hydraulic Expansion Technique

    Institute of Scientific and Technical Information of China (English)

    许铁军; 黄生洪; 谢韩; 宋云涛; 张平; 戢翔; 高大明

    2011-01-01

    Considering utilization of the original chromium-bronze material, two processing techniques including hydraulic expansion and high temperature vacuum welding were proposed for the optimization of heat-sink structure in EAST. The heat transfer performance of heat-sink with or without cooling tube was calculated and different types of connection between tube and heat-sink were compared by conducting a special test. It is shown from numerical analysis that the diameter of heat-sink channel can be reduced from 12 mm to 10 mm. Compared with the original sample, the thermal contact resistance between tube and heat-sink for welding sample can reduce the heat transfer performance by 10%, while by 20% for the hydraulic expansion sample. However, the welding technique is more complicated and expensive than hydraulic expansion technique. Both the processing technique and the heat transfer performance of heat-sink prototype should be further considered for the optimization of heat-sink structure in EAST.

  8. Squall and Cloud Lines as Structural Components of an Arabian Sea Convective Cloud Cluster.

    Science.gov (United States)

    1985-01-01

    and M. Garstang, 1982: Suboloud layer energetics of precipitating convection. =. 12L. laX.., 11, 102-117. Betta , A. K., 1976: The thermodynamic...tur- bulence data. Ph.D. dissertation, Department of Earth and Atmospheric Sciences, Saint Louis University, 199 Pp. Miller, M. J., and A. K. Betta

  9. QUANTITATIVE RESEARCH ON THE STRENGTH AND MICROSTRUCTURE IN TRACE-Ti-BEARING STRUCTURE STEEL WITH DIFFERENT COOLING TECHNIQUES

    Institute of Scientific and Technical Information of China (English)

    LIU Ji-xiong; ZHONG Ding-zhong; LI Ping-he; JI Yu; ZHANG Min

    2002-01-01

    Aim: To study the strength and microstructure of trace-Ti-bearing stracture steel.Materials and Methods: The strength and microstructure of the trace Ti bearing structure steel were studied by two kinds of controlled cooling simulation testing results in the first stage cooling and the last stage cooling after hot press deformation in the trace-Ti-bearing structure steel. Results: It showed that the ferrite grain size, the relative contribution of the involved strength and the mechanical strength were influenced more or less by different cooling rates. Both the refinement of ferrite grain and the increase of mechanical strength could be obtained by the proper decrease of water cooling interruption temperature (WTI) and coiling temperature (CT) in the first stage cooling or the proper increase of water cooling beginning temperature (WTB) and proper decrease of coiling temperature (CT) in the last stage cooling. Conclusion: The strength, the ferrite grain refinement and the yield tensile ratio in the first stage cooling process are much better than those in the last stage cooling process.

  10. Using a multiwavelength suite of microwave instruments to investigate the microphysical structure of deep convective cores

    Science.gov (United States)

    Battaglia, A.; Mroz, K.; Lang, Tim; Tridon, F.; Tanelli, S.; Tian, Lin; Heymsfield, Gerald M.

    2016-08-01

    Due to the large natural variability of its microphysical properties, the characterization of solid precipitation is a longstanding problem. Since in situ observations are unavailable in severe convective systems, innovative remote sensing retrievals are needed to extend our understanding of such systems. This study presents a novel technique able to retrieve the density, mass, and effective diameter of graupel and hail in severe convection through the combination of airborne microwave remote sensing instruments. The retrieval is applied to measure solid precipitation properties within two convective cells observed on 23-24 May 2014 over North Carolina during the IPHEx campaign by the NASA ER-2 instrument suite. Between 30 and 40 degrees of freedom of signal are associated with the measurements, which is insufficient to provide full microphysics profiling. The measurements have the largest impact on the retrieval of ice particle sizes, followed by ice water contents. Ice densities are mainly driven by a priori assumptions, though low relative errors in ice densities suggest that in extensive regions of the convective system, only particles with densities larger than 0.4 g/cm3 are compatible with the observations. This is in agreement with reports of large hail on the ground and with hydrometeor classification derived from ground-based polarimetric radars observations. This work confirms that multiple scattering generated by large ice hydrometeors in deep convection is relevant for airborne radar systems already at Ku band. A fortiori, multiple scattering will play a pivotal role in such conditions also for Ku band spaceborne radars (e.g., the GPM Dual Precipitation Radar).

  11. Evaluation of a large capacity heat pump concept for active cooling of hypersonic aircraft structure

    Science.gov (United States)

    Pagel, L. L.; Herring, R. L.

    1978-01-01

    Results of engineering analyses assessing the conceptual feasibility of a large capacity heat pump for enhancing active cooling of hypersonic aircraft structure are presented. A unique heat pump arrangement which permits cooling the structure of a Mach 6 transport to aluminum temperatures without the aid of thermal shielding is described. The selected concept is compatible with the use of conventional refrigerants, with Freon R-11 selected as the preferred refrigerant. Condenser temperatures were limited to levels compatible with the use of conventional refrigerants by incorporating a unique multipass condenser design, which extracts mechanical energy from the hydrogen fuel, prior to each subsequent pass through the condenser. Results show that it is technically feasible to use a large capacity heat pump in lieu of external shielding. Additional analyses are required to optimally apply this concept.

  12. Structure, branching ratios, and a laser-cooling scheme for the 138BaF molecule

    Science.gov (United States)

    Chen, Tao; Bu, Wenhao; Yan, Bo

    2016-12-01

    For laser-cooling considerations, we have theoretically investigated the electronic, rovibrational, and hyperfine structures of the BaF molecule. The highly diagonal Franck-Condon factors and the branching ratios for all possible transitions within the lowest-lying four electronic states have also been calculated. Meanwhile, the mixing between the metastable A'2Δ and A2Π states and, further, the lifetime of the Δ state have been estimated since the loss procedure via the Δ state might fatally break the main quasicycling Σ -Π transition for cooling and trapping. The resultant hyperfine splittings of each rovibrational state in the X2Σ+ state provide benchmarks for sideband modulations of the cooling and repumping lasers and the remixing microwaves to address all necessary levels. The calculated Zeeman shift and g factors for both X and A states serve as benchmarks for selection of the trapping laser polarizations. Our study paves the way for future laser cooling and magneto-optical trapping of the BaF molecule.

  13. Structural Changes of α Phase in Furnace Cooled Eutectoid Zn-Al Based Alloy

    Institute of Scientific and Technical Information of China (English)

    Y.H. Zhu; K.C. Chan; G.K.H. Pang; T.M. Yue; W.B. Lee

    2007-01-01

    Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnace cooled eutectoid Zn-Al based alloy was studied by transmission electron microscopy. Two kinds of precipitates in the α phase were detected in the FCZA22 alloy during ageing at 170℃. One was the hcp transitional α"m phase which appears as directional rods and the round precipitates. The other was the fcc α'm phase.It was found that the transitional phase α'm grew in three preferential directions of , and . The orientation relationship between the α phase and transitional phase α'm was determined as (02-2)α'm(fcc)//(02-2)α(fcc), [-111]α'm(fcc)//[-233]α(fcc). The non-equilibrium phase decomposition of the α phase is discussed in correlation with the equilibrium phase relationships.

  14. Three-dimensional numerical analysis of convection and conduction cooling of spherical biocrystals with localized heating from synchrotron X-ray beams.

    Science.gov (United States)

    Mhaisekar, Ashutosh; Kazmierczak, Michael J; Banerjee, Rupak

    2005-05-01

    The differential momentum and thermal energy equations for fluid flow and convective heat-transfer around the sample biocrystal, with coupled internal heat conduction, are solved using advanced computational fluid dynamics techniques. Average \\bar{h} as well as local h(theta) values of the convective heat-transfer coefficients are obtained from the fundamental equations. The results of these numerical solutions show the three-dimensional fluid flow field around the sample in conjunction with the detailed internal temperature distribution inside the crystal. The external temperature rise and maximum internal temperature increase are reported for various cases. The effect of the important system parameters, such as gas velocity and properties, crystal size and thermal conductivity and incident beam conditions (intensity and beam size), are all illustrated with comparative examples. For the reference case, an external temperature rise of 7 K and internal temperature increase of 0.5 K are calculated for a 200 microm-diameter cryocooled spherical biocrystal subjected to a 13 keV X-ray beam of 4 x 10(14) photons s(-1) mm(-2) flux density striking half the sample. For all the cases investigated, numerical analysis shows that the controlling thermal resistance is the rate of convective heat-transfer and not internal conduction. Thermal diffusion results in efficient thermal spreading of the deposited energy and this results in almost uniform internal crystal temperatures (DeltaT(internal) approximately 0.5 K), in spite of the non-uniform h(theta) with no more than 1.3 K internal temperature difference for the worst case of localized and focused beam heating. Rather, the major temperature variation occurs between the outer surface of the crystal/loop system and the gas stream, T(s) - T(gas), which itself is only about DeltaT(external) approximately 5-10 K, and depends on the thermal loading imposed by the X-ray beam, the rate of convection and the size of the loop

  15. Development of Wind Operated Passive Evaporative Cooling Structures for Storage of Tomatoes

    Directory of Open Access Journals (Sweden)

    M. O. Sunmonu

    2016-08-01

    Full Text Available A Wind operated passive evaporative cooler was developed. Two cooling chambers were made with clay container (cylindrical and square shapes. These two containers were separately inserted inside bigger clay pot inter- spaced with clay soil of 7 cm (to form pot-in-pot and wall-in wall with the outside structure wrapped with jute sack. The soil and the jute sacks were wetted with salt solution. Five blades were constructed inside the cooling chambers with aluminium material which were connected with a shaft to a vane located on a wooden cover outside the cooling chamber. The vanes (made of aluminium were to be powered by the wind which in turn rotates the blades inside the cooling chamber. The total volume of 40500cm3 and storage capacity of 31500cm3 were recorded for the square structures while total volume of 31792.5cm3 and storage capacity of 24727.5cm3 were recorded for the cylindrical structures. During the test period, the average temperatures of 27.07oC, 27.09oC and 33.6oC were obtained for the pot-in-pot (cylindrical, wall-in-wall (square and the ambient respectively. The average relative humidity of 92.27%, 91.99% and 69.41% were obtained for the pot-in-pot (cylindrical, wall-in-wall (square and the ambient respectively. The average minimum and maximum wind speed recorded for the month of October was 2.5m/s and 2.6m/s respectively

  16. Thermal analysis and cooling structure design of the primary collimator in CSNS/RCS

    CERN Document Server

    Zou, Yi-Qing; Kang, Ling; Qu, Hua-Min; He, Zhe-Xi; Yu, Jie-Bing; 10.1088/1674-1137/37/5/057004

    2013-01-01

    The rapid cycling synchrotron (RCS) of the China Spallation Neutron Source (CSNS) is a high intensity proton ring with beam power of 100 kW. In order to control the residual activation to meet the requirements of hands-on maintenance, a two-stage collimation system has been designed for the RCS. The collimation system consists of one primary collimator made of thin metal to scatter the beam and four secondary collimators as absorbers. Thermal analysis is an important aspect in evaluating the reliability of the collimation system. The calculation of the temperature distribution and thermal stress of the primary collimator with different materials is carried out by using ANSYS code. In order to control the temperature rise and thermal stress of the primary collimator to a reasonable level, an air cooling structure is intended to be used. The mechanical design of the cooling structure is presented, and the cooling effciency with different chin numbers and wind velocity is also analyzed. Finally, the fatigue life...

  17. Volume and structural analysis of super-cooled water under high pressure

    Science.gov (United States)

    Duki, Solomon F.; Tsige, Mesfin

    2012-02-01

    Motivated by recent experimental study of super-cooled water at high pressure [1], we performed atomistic molecular dynamic simulations study on bulk water molecules at isothermal-isobaric ensemble. These simulations are performed at temperatures that range from 40 K to 380 K using two different cooling rates, 10K/ns and 10K/5ns, and pressure that ranges from 1atm to 10000 atm. Our analysis for the variation of the volume of the bulk sample against temperature indicates a downward concave shape for pressures above certain values, as reported in [1]. The same downward concave behavior is observed at high pressure on the mean-squared-displacements (MSD) of the water molecules when the MSD is plotted against time. To get further insight on the effect of the pressure on the sample we have also performed a structural analysis of the sample.[4pt] [1] O. Mishima, J. Chem. Phys. 133, 144503 (2010);

  18. Convection in stellar envelopes a changing paradigm

    CERN Document Server

    Spruit, H C

    1996-01-01

    Progress in the theory of stellar convection over the past decade is reviewed. The similarities and differences between convection in stellar envelopes and laboratory convection at high Rayleigh numbers are discussed. Direct numerical simulation of the solar surface layers, with no other input than atomic physics, the equations of hydrodynamics and radiative transfer is now capable of reproducing the observed heat flux, convection velocities, granulation patterns and line profiles with remarkably accuracy. These results show that convection in stellar envelopes is an essentially non-local process, being driven by cooling at the surface. This differs distinctly from the traditional view of stellar convection in terms of local concepts such as cascades of eddies in a mean superadiabatic gradient. The consequences this has for our physical picture of processes in the convective envelope are illustrated with the problems of sunspot heat flux blocking, the eruption of magnetic flux from the base of the convection ...

  19. Pulsation driving and convection

    Science.gov (United States)

    Antoci, Victoria

    2015-08-01

    Convection in stellar envelopes affects not only the stellar structure, but has a strong impact on different astrophysical processes, such as dynamo-generated magnetic fields, stellar activity and transport of angular momentum. Solar and stellar observations from ground and space have shown that the turbulent convective motion can also drive global oscillations in many type of stars, allowing to study stellar interiors at different evolutionary stages. In this talk I will concentrate on the influence of convection on the driving of stochastic and coherent pulsations across the Hertzsprung-Russell diagram and give an overview of recent studies.

  20. The Structure and Life-Cycle of Midlatitude Mesoscale Convective Complexes.

    Science.gov (United States)

    Maddox, Robert Alan

    Enhanced infrared satellite imagery has been used to document the existence and frequent occurrence, over middle latitudes of the United States, of large, convectively driven weather systems. These systems, named Mesoscale Convective Complexes (MCCs), have not been heretofore recognized or documented in the scientific literature. It is shown that these systems frequently produce a variety of severe convective weather phenomena (such as tornadoes, hailstorms and flash floods) that significantly impact human activities. A preliminary climatology of MCCs, based on satellite data from two warm seasons, indicates that these systems frequently affect United States agricultural regions and it is hypothesized that MCCs produce a highly significant portion of the growing season precipitation over these areas. Objective analyses of composited meteorological conditions attending ten MCC weather systems have revealed a number of distinctive characteristics and interactions with their larger scale environment. These analyses are used to develop a physically realistic model of the life -cycle of the typical midlatitude Mesoscale Convective Complex. The systems develop within a relatively weak and stagnant large -scale setting and are usually closely linked to the eastward progression of a weak middle tropospheric short-wave trough. Initial thunderstorms develop within a region of mesoscale convergence and lifting that is primarily forced by low-level warm advection. The MCC system rapidly grows and takes on a mesoscale organization while it moves slowly eastward ahead of the short-wave trough. Diabatic heating eventually produces a system that is warm core in the middle troposphere and cold core in lower and upper levels. The mature MCC, although it occurs within a considerably different large -scale setting, exhibits many similarities to tropical convective systems. Strong inflow within the lower half of the toposphere forces an intense mesoscale updraft that maintains a region

  1. Activities relating to understanding the initiation, organization and structure of moist convection in the Southeast environment

    Science.gov (United States)

    Mcnider, Richard T.

    1992-01-01

    In the spring and summer of 1986, NASA/Marshall Space Flight Center (MSFC) will sponsor the Satellite Precipitation And Cloud Experiment (SPACE) to be conducted in the Central Tennessee, Northern Alabama, and Northeastern Mississippi area. The field program will incorporate high altitude flight experiments associated with meteorological remote sensor development for future space flight, and an investigation of precipitation processes associated with mesoscale and small convective systems. In addition to SPACE, the MIcroburst and Severe Thunderstorm (MIST) program, sponsored by the National Science Foundation (NSF), and the FAA-Lincoln Laboratory Operational Weather Study (FLOWS), sponsored by the Federal Aviation Administration (FAA), will take place concurrently within the SPACE experiment area. All three programs (under the joint acronym COHMEX (COoperative Huntsville Meteorological EXperiment)) will provide a data base for detailed analysis of mesoscale convective systems while providing ground truth comparisons for remote sensor evaluation. The purpose of this document is to outline the experiment design criteria for SPACE, and describe the special observing facilities and data sets that will be available under the COHMEX joint program. In addition to the planning of SPACE-COHMEX, this document covers three other parts of the program. The field program observations' main activity was the operation of an upper air rawinsonde network to provide ground truth for aircraft and spacecraft observations. Another part of the COHMEX program involved using boundary layer mesoscale models to study and simulate the initiation and organization of moist convection due to mesoscale thermal and mechanical circulations. The last part of the program was the collection, archival and distribution of the resulting COHMEX-SPACE data sets.

  2. Identification of Structural Motifs of Imidazolium Based Ionic Liquids from Jet-Cooled Infrared Spectroscopy.

    Science.gov (United States)

    Young, Justin W.; Booth, Ryan S.; Annesley, Christopher; Stearns, Jaime A.

    2016-06-01

    Highly variable and potentially revolutionary, ionic liquids (IL) are a class of molecules with potential for numerous Air Force applications such as satellite propulsion, but the complex nature of IL structure and intermolecular interactions makes it difficult to adequately predict structure-property relationships in order to make new IL-based technology a reality. For example, methylation of imidazolium ionic liquids leads to a substantial increase in viscosity but the underlying physical mechanism is not understood. In addition the role of hydrogen bonding in ILs, especially its relationship to macroscopic properties, is a matter of ongoing research. Here, structural motifs are identified from jet-cooled infrared spectra of different imidazolium based ionic liquids, such as 1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide. Measurements of the C-H stretches indicate three structural families present in the gas phase.

  3. Spectral characteristics of heterocyclic compounds with a chain structure, cooled in an ultrasonic jet

    Science.gov (United States)

    Povedailo, V. A.; Yakovlev, D. L.

    2006-11-01

    We have recorded the fluorescence excitation spectra of three heterocyclic compounds with a chain structure [BPO (2-phenyl-5-(4-diphenylyl)oxazole), POPOP (1,4-di[2-(5-phenyloxazolyl)]benzene, and TOPOT (1,4-di[2-(5-n-tolyloxazolyl)]benzene] and the fluorescence spectra of POPOP, under conditions where the molecules were cooled in an ultrasonic helium jet. A line structure is observed in the spectra of POPOP and TOPOT; for the BPO molecules, whose configuration changes considerably during electronic excitation, vibrational structure is apparent only in the low-frequency region of the excitation spectrum, and a diffuse spectrum is recorded starting from ν 0 0 + 200 cm-1. For all the compounds, in the spectra we recorded vibrations with frequencies up to 100 cm-1, arising due to the flexibility of the molecular structure. The rotational contours of the lines for the electronic and vibronic transitions of the POPOP molecules (Trot = 10.5 K) and TOPOT molecules (Trot = 15 K) are structureless and bell-shaped. The degree of polarization of the fluorescence Pfl for the jet-cooled POPOP molecules for excitation of vibrations along the absorption band up to 2000 cm-1 above ν 0 0 is practically constant (˜8.4%) and matches Pfl for high-temperature vapors.

  4. Scaling laws and flow structures of double diffusive convection in the finger regime

    CERN Document Server

    Yang, Yantao; Lohse, Detlef

    2016-01-01

    Direct numerical simulations are conducted for double diffusive convection (DDC) bounded by two parallel plates, with fluid properties similar to the values of seawater. The DDC flow is driven by an unstable salinity difference and stabilized at the same time by a temperature difference. For these conditions the flow can be in the finger regime. We develop scaling laws for three key response parameters of the system: The non-dimensional salinity flux $Nu_S$ mainly depends on the salinity Rayleigh number $Ra_S$, which measures the strength of the salinity difference, and exhibits a very weak dependence on the density ratio $\\Lambda$, which is the ratio of the buoyancy forces induced by two scalar differences. The non-dimensional flow velocity $Re$ and the non-dimensional heat flux $Nu_T$ are dependent on both $Ra_S$ and $\\Lambda$. However, the rescaled Reynolds number $Re\\Lambda^{\\alpha^{\\rm eff}_u}$ and the rescaled convective heat flux $(Nu_T-1)\\Lambda^{\\alpha^{\\rm eff}_T}$ depend only on $Ra_S$. The two exp...

  5. Multifractal properties of embedded convective structures in orographic precipitation: toward subgrid-scale predictability

    Science.gov (United States)

    Nogueira, M.; Barros, A. P.; Miranda, P. M. A.

    2013-09-01

    Rain and cloud fields produced by fully nonlinear idealized cloud resolving numerical simulations of orographic convective precipitation display statistical multiscaling behavior, implying that multifractal diagnostics should provide a physically robust basis for the downscaling and sub-grid scale parameterizations of moist processes. Our results show that the horizontal scaling exponent function (and respective multiscaling parameters) of the simulated rainfall and cloud fields varies with atmospheric and terrain properties, particularly small-scale terrain spectra, atmospheric stability, and advective timescale. This implies that multifractal diagnostics of moist processes for these simulations are fundamentally transient, exhibiting complex nonlinear behavior depending on atmospheric conditions and terrain forcing at each location. A particularly robust behavior found here is the transition of the multifractal parameters between stable and unstable cases, which has a clear physical correspondence to the transition from stratiform to organized (banded and cellular) convective regime. This result is reinforced by a similar behavior in the horizontal spectral exponent. Finally, our results indicate that although nonlinearly coupled fields (such as rain and clouds) have different scaling exponent functions, there are robust relationships with physical underpinnings between the scaling parameters that can be explored for hybrid dynamical-statistical downscaling.

  6. Aeroacoustic Noise Analysis of a Locomotive Cooling System Ducts and Structure Optimization

    Directory of Open Access Journals (Sweden)

    Shanshan Li

    2015-07-01

    Full Text Available Aero acoustic noise of a locomotive cab cooling system ducts was analyzed by method of Computational Fluid Dynamics (CFD and Computational Aero acoustic (CAA approach. Flow characteristic of the ducts was analyzed by CFD software, then near-field and far-field aero acoustic noise was forecasted with BNS model and FW-H model respectively. Duct structure was optimized according to the analysis of flow field and sound field. Results indicated that noise characteristic of sensitive frequency band at the position of human ear with the optimized duct has a significant improvement.

  7. The cooling effect of crushed rock structures on permafrost under an embankment

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide an extensive cooling effect, which produces a rising permafrost table and decreasing soil temperatures. The rise of the permafrost table under the embankment ranges from an increase of 1.08 m to 1.67 m, with an average of 1.27 m from 2004 to 2007. Mean annual soil temperatures under the crushed rock layer embankment decreased significantly from 2005 to 2007, with average decreases of ?1.03 °C at the depth of 0.5 m, ?1.14 °C at the depth of 1.5 m, and ?0.5 °C at the depth of 5 m. During this period, mean annual soil temperatures under the crushed rock cover embankment showed a slight decrease at shallow depths, with an average decrease of ?0.2 °C at the depth of 0.5 m and 1.5 m, but a slight rise at the depth of 5 m. After the crushed rock structures were closed or crammed with sand, the cooling effect of the crushed rock layer embankment was greatly reduced and that of the crushed rock cover embankment was just slightly reduced.

  8. Free convection of a nanofluid in a square cavity with a heat source on the bottom wall and partially cooled from sides

    Directory of Open Access Journals (Sweden)

    Mahmoodi Mostafa

    2014-01-01

    Full Text Available The problem of free convection fluid flow and heat transfer in a square cavity with a flush mounted heat source on its bottom wall and two heat sinks on its vertical side walls has been investigated numerically. Via changing the location of the heat sinks, six different arrangements have been generated. The cavity was filled with Cu-water nanofluid. The governing equations were discretized using the finite volume method and SIMPLER algorithm. Using the developed code, a parametric study was undertaken, and effects of Rayleigh number, arrangements of the heat sinks and volume fraction of the nanoparticles on fluid flow and heat transfer inside the cavity were investigated. Also for the middle-middle heat sinks arrangement, capability of five different water based nanofluids on enhancement of the rate of heat transfer was examined and compared. From the obtained results it was found that the average Nusselt number, for all six different arrangements of the heat sinks, was an increasing function of the Rayleigh number and the volume fraction of the nanoparticles. Also it was found that at high Rayleigh numbers, maximum and minimum average Nusselt number occurred for middle-middle and top-bottom arrangement, respectively. Moreover it was found that for the middle-middle arrangement, at high Rayleigh numbers, maximum and minimum rate of heat transfer was obtained by Cu-water and TiO2-water nanofluids respectively.

  9. Thermo-fluid analysis of water cooled research reactors in natural convection; Analise termofluidodinamica de reatores nucleares de pesquisa refrigerados a agua em regime de conveccao natural

    Energy Technology Data Exchange (ETDEWEB)

    Veloso, Maria Auxiliadora Fortini

    2004-07-01

    The STHIRP-1 computer program, which fundamentals are described in this work, uses the principles of the subchannels analysis and has the capacity to simulate, under steady state and transient conditions, the thermal and hydraulic phenomena which occur inside the core of a water-refrigerated research reactor under a natural convection regime. The models and empirical correlations necessary to describe the flow phenomena which can not be described by theoretical relations were selected according to the characteristics of the reactor operation. Although the primary objective is the calculation of research reactors, the formulation used to describe the fluid flow and the thermal conduction in the heater elements is sufficiently generalized to extend the use of the program for applications in power reactors and other thermal systems with the same features represented by the program formulations. To demonstrate the analytical capacity of STHIRP-l, there were made comparisons between the results calculated and measured in the research reactor TRIGA IPR-R1 of CDTN/CNEN. The comparisons indicate that the program reproduces the experimental data with good precision. Nevertheless, in the future there must be used more consistent experimental data to corroborate the validation of the program. (author)

  10. Thermochemical and phase structure of the D"-Region constrained by 3-D spherical mantle convection and seismic tomography

    Science.gov (United States)

    Wu, B.; Olson, P.

    2011-12-01

    Results of time-dependent 3-D spherical mantle convection simulations with Newtonian rheology, solid-state phase transitions, and multiple composition as well as imposed plate motion back to 120 Ma are compared with observed lower mantle seismic heterogeneity to interpret structure in the D"-region. Synthetic seismic tomography images are created from the simulated temperature, composition, and phase change heterogeneity, which are then compared to the global seismic tomography models in terms of pattern and statistical properties. Several models are found that match the seismic tomography in terms of their RMS variation, Gaussian-like frequency distribution, and spherical harmonic degree-2 pattern for global-scale low velocity and high velocity regions. For these best-fitting models the heat flow at the CMB and the mantle heat flow at the surface are about 13.1 ~ 14.7 TW and 31 TW, respectively, and the Urey ratio is in range of 0.36 ~ 0.58. 3-D mantle convection constrained by plate motion history explains the statistics and the global pattern of lower mantle seismic heterogeneity provided that thermal, chemical and phase change heterogeneity is included in the mantle D"-region, and predicts large temporal and spatial variations in heat transport across the CMB.

  11. Ceramics and healthy heating and cooling systems: thermal ceramic panels in buildings. Conditions of comfort and energy demand versus convective systems

    Directory of Open Access Journals (Sweden)

    V. Echarri Iribarren

    2016-12-01

    Full Text Available Porcelain stoneware is a widely used building material. In recent years, its range of uses has expanded to encompass a new spectrum of innovative and inventive applications in architecture. In this research, we analysed the patented Thermal Ceramic Panel. This consists of a thin porcelain stoneware panel that incorporates a capillary system of polypropylene tubes measuring 3.5 mm in diameter embedded in a conductive ceramic interface. The system works with hot or cold water, producing healthy heating and cooling by means of radiant surfaces. Following an initial prototype test in which panels were placed on the walls of an office, we conducted simulations at the University of Alicante Museum using wall, ceiling and baffle panels, having previously monitored the state of the building. Thermal behaviour parameters were analysed and compared with those of other standard finishing materials, obtaining results for thermal comfort and energy savings in comparison with all-air systems.

  12. Global Variability of Mesoscale Convective System Anvil Structure from A-Train Satellite Data

    Science.gov (United States)

    Yuan, Jian; Houze, Robert A.

    2010-01-01

    Mesoscale convective systems (MCSs) in the tropics produce extensive anvil clouds, which significantly affect the transfer of radiation. This study develops an objective method to identify MCSs and their anvils by combining data from three A-train satellite instruments: Moderate Resolution Imaging Spectroradiometer (MODIS) for cloud-top size and coldness, Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) for rain area size and intensity, and CloudSat for horizontal and vertical dimensions of anvils. The authors distinguish three types of MCSs: small and large separated MCSs and connected MCSs. The latter are MCSs sharing a contiguous rain area. Mapping of the objectively identified MCSs shows patterns of MCSs that are consistent with previous studies of tropical convection, with separated MCSs dominant over Africa and the Amazon regions and connected MCSs favored over the warm pool of the Indian and west Pacific Oceans. By separating the anvil from the raining regions of MCSs, this study leads to quantitative global maps of anvil coverage. These maps are consistent with the MCS analysis, and they lay the foundation for estimating the global radiative effects of anvil clouds. CloudSat radar data show that the modal thickness of MCS anvils is about 4-5 km. Anvils are mostly confined to within 1.5-2 times the equivalent radii of the primary rain areas of the MCSs. Over the warm pool, they may extend out to about 5 times the rain area radii. The warm ocean MCSs tend to have thicker non-raining and lightly raining anvils near the edges

  13. Global Variability of Mesoscale Convective System Anvil Structure from A-Train Satellite Data

    Science.gov (United States)

    Yuan, Jian; Houze, Robert A.

    2010-01-01

    Mesoscale convective systems (MCSs) in the tropics produce extensive anvil clouds, which significantly affect the transfer of radiation. This study develops an objective method to identify MCSs and their anvils by combining data from three A-train satellite instruments: Moderate Resolution Imaging Spectroradiometer (MODIS) for cloud-top size and coldness, Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) for rain area size and intensity, and CloudSat for horizontal and vertical dimensions of anvils. The authors distinguish three types of MCSs: small and large separated MCSs and connected MCSs. The latter are MCSs sharing a contiguous rain area. Mapping of the objectively identified MCSs shows patterns of MCSs that are consistent with previous studies of tropical convection, with separated MCSs dominant over Africa and the Amazon regions and connected MCSs favored over the warm pool of the Indian and west Pacific Oceans. By separating the anvil from the raining regions of MCSs, this study leads to quantitative global maps of anvil coverage. These maps are consistent with the MCS analysis, and they lay the foundation for estimating the global radiative effects of anvil clouds. CloudSat radar data show that the modal thickness of MCS anvils is about 4-5 km. Anvils are mostly confined to within 1.5-2 times the equivalent radii of the primary rain areas of the MCSs. Over the warm pool, they may extend out to about 5 times the rain area radii. The warm ocean MCSs tend to have thicker non-raining and lightly raining anvils near the edges

  14. Asymmetric structures of field-aligned currents and convection of ionospheric plasma controlled by the IMF azimuthal component and season of year

    DEFF Research Database (Denmark)

    Lukianova, R. Yu.; Kozlovsky, A.; Christiansen, Freddy

    2010-01-01

    We present the results of using the statistical model of field-aligned currents (FACs) based on satellite data and the numerical model of the electric potential distribution in order to detect the asymmetric part in FAC structures and ionospheric plasma convection controlled by the IMF azimuthal (B...... y ) component at different seasons of the year. These structures can be identified by plotting diagrams, which represent differences in corresponding maps for opposite signs of IMF B y . Circular near-pole current symmetric about the noon meridian and corresponding convection vortices around...

  15. Numerical analysis of the cooling structure of side-pumped solid laser%侧面泵浦固体激光器冷却结构数值分析

    Institute of Scientific and Technical Information of China (English)

    吕坤鹏; 唐晓军; 刘磊; 刘洋

    2016-01-01

    针对侧面泵浦固体激光器的强制对流冷却结构,利用CFD软件Ansys Fluent数值分析了在冷却结构中添加分流隔板对流动状况的影响,计算了特定流量时冷却结构的压降,并在该冷却条件下得到增益介质自身的温度分布。计算结果表明:分流隔板对冷却结构整个阻力的影响可以忽略,但对通道内水流状况具有明显的影响,由于板条两侧水流的不对称性以及同一侧水流的不均匀性,导致增益介质自身的温度分布也存在较大的不一致。%For forced convection cooling structure in side-pumped solid-state laser,the influence of orifice plates in the cooling structure on the flow state was analyzed by the commercial CFD software Ansys Fluent. The pressure drop of the cooling structure was computed under specific flow,and temperature distribution of Nd ∶YAG was obtained under the cooling condition. The results show that orifice plates have no effect on flow resistance of the cooling structure,but they have a prominent influence on the flow state. The asymmetric flow at both sides of Nd ∶YAG and the uneven flow at one side of Nd ∶YAG will lead to different temperature distributions of Nd ∶YAG.

  16. Vibration test on KMRR reactor structure and primary cooling system piping

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Seung Hoh; Kim, Tae Ryong; Park, Jin Hoh; Park, Jin Suk; Ryoo, Jung Soo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1994-10-01

    Most equipments, piping systems and reactor structures in nuclear power plants are subjected to flow induced vibration due to high temperature and high pressure coolant flowing inside or outside of the equipments, systems and structures. Because the flow induced vibration sometimes causes significant damage to reactor structures and piping systems, it is important and necessary to evaluate the vibration effect on them and to prove their structural integrity. Korea Multipurpose Research Reactor (KMRR) being constructed by KAERI is 30 MWt pool type research reactor. Since its main structures and piping systems were designed and manufactured in accordance with the standards and guidelines for commercial nuclear power plant, it was decided to evaluate their vibratory response in accordance with the standards and guidelines for commercial NPP. The objective of this vibration test is the assessment of vibration levels of KMRR reactor structure and primary cooling piping system for their structural integrity under the steady-state or transient operating condition. 38 figs, 14 tabs, 2 refs. (Author).

  17. Extended Subadiabatic Layer in Simulations of Overshooting Convection

    Science.gov (United States)

    Käpylä, Petri J.; Rheinhardt, Matthias; Brandenburg, Axel; Arlt, Rainer; Käpylä, Maarit J.; Lagg, Andreas; Olspert, Nigul; Warnecke, Jörn

    2017-08-01

    We present numerical simulations of hydrodynamic overshooting convection in local Cartesian domains. We find that a substantial fraction of the lower part of the convection zone (CZ) is stably stratified according to the Schwarzschild criterion while the enthalpy flux is outward directed. This occurs when the heat conduction profile at the bottom of the CZ is smoothly varying, based either on a Kramers-like opacity prescription as a function of temperature and density or a static profile of a similar shape. We show that the subadiabatic layer arises due to nonlocal energy transport by buoyantly driven downflows in the upper parts of the CZ. Analysis of the force balance of the upflows and downflows confirms that convection is driven by cooling at the surface. We find that the commonly used prescription for the convective enthalpy flux being proportional to the negative entropy gradient does not hold in the stably stratified layers where the flux is positive. We demonstrate the existence of a non-gradient contribution to the enthalpy flux, which is estimated to be important throughout the convective layer. A quantitative analysis of downflows indicates a transition from a tree-like structure where smaller downdrafts merge into larger ones in the upper parts to a structure in the deeper parts where a height-independent number of strong downdrafts persist. This change of flow topology occurs when a substantial subadiabatic layer is present in the lower part of the CZ.

  18. Corrosion mechanisms of candidate structural materials for supercritical water-cooled reactor

    Institute of Scientific and Technical Information of China (English)

    Lefu ZHANG; Fawen ZHU; Rui TANG

    2009-01-01

    Nickel-based alloys, austenitic stainless steel, ferritic/martensitic heat-resistant steels, and oxide dispersion strengthened steel are presently considered to be the candidate structural or fuel-cladding materials for supercritical water-cooled reactor (SCWR), one of the promising generation IV reactor for large-scale electric power production. However, corrosion and stress corrosion cracking of these candidate alloys still remain to be a major problem in the selection of nuclear fuel cladding and other structural materials, such as water rod. Survey of literature and experimental results reveal that the general corrosion mechanism of those candidate materials exhibits quite complicated mechanism in high-temperature and high-pressure supercritical water. Formation of a stable protective oxide film is the key to the best corrosion-resistant alloys. This paper focuses on the mechanism of corrosion oxide film breakdown for SCWR candidate materials.

  19. Interaction of Mesoscale Convection and Frontogenesis

    Institute of Scientific and Technical Information of China (English)

    彭加毅; 方娟; 伍荣生

    2004-01-01

    On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using the thermodynamical equation and frontogenetical function. The results show that the outbreak of the severe storm is closely related to the local frontogenesis. In fact, the interaction between the shearing instability of the low-level jet (LLJ) and the topographic forcing generates an gravity-inertia wave as well as local frontogenesis (the first front), which consequently induce the onset of the severe storm. From then on, owing to the horizontal and vertical advection of the potential temperature, the new frontogenesis (the second front) is formed to the northeast side of the severe storm, which initiates the second rain belt.Meanwhile, a two-front structure emerges over the southeastern part of Hubei province. Accompanied with the further intensification of the convection, the rain droplets evaporation cooling strengthens the first front and weakens the second front, resulting in single front structure over the southeastern part of Hubei province in the period of the strong convection.

  20. High-gradient normal-conducting RF structures for muon cooling channels

    Energy Technology Data Exchange (ETDEWEB)

    Corlett, J.N.; Green, M.A.; Hartman, N.; Ladran, A.; Li, D.; MacGill, R.; Rimmer, R.; Moretti, A.; Jurgens, T.; Holtkamp, N.; Black, E.; Summers, D.; Booke, M.

    2001-06-12

    We present a status report on the research and development of high-gradient normal-conducting RF structures for the ionization cooling of muons in a neutrino factory or muon collider. High-gradient RF structures are required in regions enclosed in strong focusing solenoidal magnets, precluding the application of superconducting RF technology [1]. We propose using linear accelerating structures, with individual cells electromagnetically isolated, to achieve the required gradients of over 15 MV/m at 201 MHz and 30 MV/m at 805 MHz. Each cell will be powered independently, and cell length and drive phase adjusted to optimize shunt impedance of the assembled structure. This efficient design allows for relatively small field enhancement on the structure walls, and an accelerating field approximately 1.7 times greater than the peak surface field. The electromagnetic boundary of each cell may be provided by a thin Be sheet, or an assembly of thin-walled metal tubes. Use of thin, low-Z materials will allow passage of the muon beams without significant deterioration in beam quality due to scattering. R and D in design and analysis of robust structures that will operate under large electric and magnetic fields and RF current heating are discussed, including the experimental program based in a high-power test laboratory developed for this purpose.

  1. Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    electrons and isotropic ion precipitation (AO is mapped to the dawn periphery of the Central Plasma Sheet (CPS; the soft small scale structured precipitation (SSSL is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL. In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA, are observed. The ion energies decrease with increasing latitude. The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM. In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1 and flow out at the AO or DAZ latitudes (Region 2. In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2. In the SSSL, there is anti-sunward convection; in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By . It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996, for the nightside sector of the auroral oval to the dawn sector.

    Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; plasma convection

  2. Modelling of phenomena in solid state for the steel casting cooled by liquid

    Directory of Open Access Journals (Sweden)

    A. Kulawik

    2011-04-01

    Full Text Available In this paper a mathematical model of cooling process for steel castings is presented. Effect of convective motion of the coolant onmaterial structure after cooling process is investigated. Mathematical and numerical model based on Generalized Difference Method for axysimmertric elements is used. To solve the Navier-Stokes equation the characteristic based split scheme (CBS has been applied. The solution of the heat transport equation with the convective term has been obtained by a stabilized meshless method. To determine of the phase transformation the macroscopic model built on the basis of Time Temperature Transformation diagrams for continuous cooling of medium-carbon steel has been used. The temporary temperature fields, the phase transformation, thermal and structural strains for the cooled element and the fields of temperature and velocity for the coolant have been determined.

  3. Thermal-structural analysis of the platelet heat-pipe-cooled leading edge of hypersonic vehicle

    Science.gov (United States)

    Hongpeng, Liu; Weiqiang, Liu

    2016-10-01

    One of the main challenges for the hypersonic vehicle is its thermal protection, more specifically, the cooling of its leading edge. To investigate the feasibility of a platelet heat-pipe-cooled leading edge structure, thermal/stress distributions for steady-state flight conditions are calculated numerically. Studies are carried on for IN718/Na, C-103/Na and T-111/Li compatible material combinations of heat pipe under nominal operations and a central heat pipe failure cases, and the influence of wall thickness on the design robustness is also investigated. And the heat transfer limits (the sonic limit, the capillary limit and the boiling limit) are also computed to check the operation of platelet heat pipes. The results indicate that, with a 15 mm leading edge radius and a wall thickness of 0.5 mm, C-103/Na and T-111/Li combinations of heat pipe is capable of withstanding both nominal and failure conditions for Mach 8 and Mach 10 flight respectively.

  4. Structure and Dynamics of Cool Flare Loops Observed by the Interface Region Imaging Spectrograph

    Science.gov (United States)

    Mikuła, K.; Heinzel, P.; Liu, W.; Berlicki, A.

    2017-08-01

    Flare loops were well observed with the Interface Region Imaging Spectrograph (IRIS) during the gradual phase of two solar flares on 2014 March 29 and 2015 June 22. Cool flare loops are visible in various spectral lines formed at chromospheric and transition-region temperatures and exhibit large downflows which correspond to the standard scenario. The principal aim of this work is to analyze the structure and dynamics of cool flare loops observed in Mg ii lines. Synthetic profiles of the Mg ii h line are computed using the classical cloud model and assuming a uniform background intensity. In this paper, we study novel IRIS NUV observations of such loops in Mg ii h and k lines and also show the behavior of hotter lines detected in the FUV channel. We obtained the spatial evolution of the velocities: near the loop top, the flow velocities are small and they are increasing toward the loop legs. Moreover, from slit-jaw image (SJI) movies, we observe some plasma upflows into the loops, which are also detectable in Mg ii spectra. The brightness of the loops systematically decreases with increasing flow velocity, and we ascribe this to the effect of Doppler dimming, which works for Mg ii lines. Emission profiles of Mg ii were found to be extremely broad, and we explain this through the large unresolved non-thermal motions.

  5. Structure and superconducting transition in splat-cooled U–T alloys (T = Mo, Pd, Pt)

    Energy Technology Data Exchange (ETDEWEB)

    Kim-Ngan, N.-T.H., E-mail: tarnawsk@up.krakow.pl [Institute of Physics, Pedagogical University, Podchorazych 2, 30-084 Krakow (Poland); Paukov, M. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic); Sowa, S.; Krupska, M. [Institute of Physics, Pedagogical University, Podchorazych 2, 30-084 Krakow (Poland); Tkach, I.; Havela, L. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic)

    2015-10-05

    Highlights: • Splat-cooled U–6 at.% Mo, U–5 at.% Pd, U–5 at.% Pt alloys become superconducting below 1 K. • U–5 at.% Pd and U–5 at.% Pt reveal only one resistivity jump at T{sub c}. • Two distinguishable resistivity drops were observed for U–6 at.% Mo. • A broad maximum was observed at T{sub c} in the specific heat. • Those splats consist of two phases having orthorhombic α- and cubic γ-U structure. - Abstract: U–T (T = Mo, Pd, Pt) alloys were prepared by splat cooling technique and characterized by X-ray diffraction. The resistivity and specific heat measurements were performed down to 0.3 K to study their superconductivity. The superconducting transition in the alloy with 6 at.% Mo (U–6%Mo) revealed by a smooth decrease below 1.5 K and a sharp drop at 0.6 K in the resistivity, while a single sharp drop was revealed at T{sub c} ≈ 0.8 K for those with 5 at.% Pd and Pt doping (U–5%Pd and U–5%Pt). With applying magnetic fields, the resistivity drops move to lower temperatures. The superconductivity transitions were revealed by only one broad peak at T{sub c} in the C(T) curves.

  6. Structural evolution of Ti50Cu50 on rapid cooling by molecular dynamics simulation

    Science.gov (United States)

    Pang, J. J.; Tan, M. J.; Liew, K. M.

    2012-03-01

    The structural evolution and atomic structure of the Ti50Cu50 compound have been investigated by means of molecular dynamics simulation using the generalized embedded-atom model (GEAM) potential. Gibbs free energy calculation manifests the large driving force of undercooled Ti50Cu50 for crystallization and thus the poor glass-forming ability. Radial distribution functions (RDFs) within the temperature range from 2000 K to 300 K are analyzed and reveal the increasing degree of short-range order and reducing periodic length between peaks on cooling. Atomic arrangement is characterized by the Voronoi tessellation method, showing that the frequency of icosahedral configurations is most sensitive to temperature and grows upon quenching while that of the others remains relatively stable. The thermal behavior of the structure factors follows the Debye model up to the supercooled liquid temperature. The structural investigation of amorphous Ti50Cu50 demonstrates that there exist a variety of polyhedral configurations in Ti50Cu50 amorphous alloy, where icosahedral and bcc clusters are the major types. Due to the existence of bcc clusters and the other distorted polyhedra other than full icosahedra, the structural analysis reconfirms the inference from the Gibbs free energy calculation.

  7. Convection roll-driven generation of supra-wavelength periodic surface structures on dielectrics upon irradiation with femtosecond pulsed lasers

    Science.gov (United States)

    Tsibidis, George D.; Skoulas, Evangelos; Papadopoulos, Antonis; Stratakis, Emmanuel

    2016-08-01

    The significance of the magnitude of the Prandtl number of a fluid in the propagation direction of induced convection rolls is elucidated. Specifically, we report on the physical mechanism to account for the formation and orientation of previously unexplored supra-wavelength periodic surface structures in dielectrics, following melting and subsequent capillary effects induced upon irradiation with ultrashort laser pulses. Counterintuitively, it is found that such structures exhibit periodicities, which are markedly, even multiple times, higher than the laser excitation wavelength. It turns out that the extent to which the hydrothermal waves relax depends upon the laser beam energy, produced electron densities upon excitation with femtosecond pulsed lasers, the magnitude of the induced initial local roll disturbances, and the magnitude of the Prandtl number with direct consequences on the orientation and size of the induced structures. It is envisaged that this elucidation may be useful for the interpretation of similar, albeit large-scale periodic or quasiperiodic structures formed in other natural systems due to thermal gradients, while it can also be of great importance for potential applications in biomimetics.

  8. Structure and Evolution of Nearby Stars with Planets II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog

    CERN Document Server

    Takeda, G; Sills, A; Rasio, F A; Fischer, D A; Valenti, J A; Takeda, Genya; Ford, Eric B.; Sills, Alison; Rasio, Frederic A.; Fischer, Debra A.; Valenti, Jeff A.

    2006-01-01

    We derive detailed theoretical models for 1074 nearby stars from the SPOCS (Spectroscopic Properties of Cool Stars) Catalog. The California and Carnegie Planet Search has obtained high-quality echelle spectra of over 1000 nearby stars taken with the Hamilton spectrograph at Lick Observatory, the HIRES spectrograph at Keck, and UCLES at the Anglo Australian Observatory. A uniform analysis of the high-resolution spectra has yielded precise stellar parameters, enabling systematic error analyses and accurate theoretical stellar modeling. We have created a large database of theoretical stellar evolution tracks using the Yale Stellar Evolution Code (YREC) to match the observed parameters of the SPOCS stars. Our very dense grids of evolutionary tracks eliminate the need for interpolation between stellar evolutionary tracks and allow precise determinations of physical stellar parameters (mass, age, radius, size and mass of the convective zone, etc.). Combining our stellar models with the observed stellar atmospheric ...

  9. Cooling technique

    Energy Technology Data Exchange (ETDEWEB)

    Salamon, Todd R; Vyas, Brijesh; Kota, Krishna; Simon, Elina

    2017-01-31

    An apparatus and a method are provided. Use is made of a wick structure configured to receive a liquid and generate vapor in when such wick structure is heated by heat transferred from heat sources to be cooled off. A vapor channel is provided configured to receive the vapor generated and direct said vapor away from the wick structure. In some embodiments, heat conductors are used to transfer the heat from the heat sources to the liquid in the wick structure.

  10. Design and simulation of a novel high-efficiency cooling heat-sink structure using fluid-thermodynamics

    Science.gov (United States)

    Hongqi, Jing; Li, Zhong; Yuxi, Ni; Junjie, Zhang; Suping, Liu; Xiaoyu, Ma

    2015-10-01

    A novel high-efficiency cooling mini-channel heat-sink structure has been designed to meet the package technology demands of high power density laser diode array stacks. Thermal and water flowing characteristics have been simulated using the Ansys-Fluent software. Owing to the increased effective cooling area, this mini-channel heat-sink structure has a better cooling effect when compared with the traditional macro-channel heat-sinks. Owing to the lower flow velocity in this novel high efficient cooling structure, the chillers' water-pressure requirement is reduced. Meanwhile, the machining process of this high-efficiency cooling mini-channel heat-sink structure is simple and the cost is relatively low, it also has advantages in terms of high durability and long lifetime. This heat-sink is an ideal choice for the package of high power density laser diode array stacks. Project supported by the Defense Industrial Technology Development Program (No. B1320133033).

  11. Heat-stop structure design with high cooling efficiency for large ground-based solar telescope.

    Science.gov (United States)

    Liu, Yangyi; Gu, Naiting; Rao, Changhui; Li, Cheng

    2015-07-20

    A heat-stop is one of the most important thermal control devices for a large ground-based solar telescope. For controlling the internal seeing effect, the temperature difference between the heat-stop and the ambient environment needs to be reduced, and a heat-stop with high cooling efficiency is required. In this paper, a novel design concept for the heat-stop, in which a multichannel loop cooling system is utilized to obtain higher cooling efficiency, is proposed. To validate the design, we analyze and compare the cooling efficiency for the multichannel and existing single-channel loop cooling system under the same conditions. Comparative results show that the new design obviously enhances the cooling efficiency of the heat-stop, and the novel design based on the multichannel loop cooling system is obviously better than the existing design by increasing the thermal transfer coefficient.

  12. Influence of reheating and cooling conditions on structure and mechanical properties of C-Mn-Si steel

    Directory of Open Access Journals (Sweden)

    T. Kvačkaj

    2008-07-01

    Full Text Available The paper deals with structure and properties development of AHSS (advance high-strength steel and UHSS (ultra high-strength steel steel grades for various groups of automotive parts. C-Mn-Si type steel properties are evaluated based on the results of laboratory controlled rolling and cooling. The important influence on mechanical and plastic properties, amount of residual austenite (RA and final structural type has, except for cooling rate, also starting temperature of intensive cooling (TIC which follows after hot plastic deformations. If TIC is from interval of 620-760°C the final structure predominantly consists of ferrite with RA. Mostly acicular ferrite with RA, as well as bainite with RA was obtained when TIC was kept in the range of 760-850°C.

  13. Convection Fingerprints on the Vertical Profiles of Q1 and Q2

    Science.gov (United States)

    Chang, C.; Lin, H.; Chou, C.

    2013-12-01

    Different types of tropical convection left their fingerprints on vertical structures of apparent heat source (Q1) and apparent moisture sink (Q2). Profile of deep convection on condensation heating and drying has been well-documented, yet direct assessment of shallow convection remains to be explored. Shallow convection prevails over subtropical ocean, where large-scale subsidence is primarily balanced by radiative cooling and moistening due to surface evaporation instead of moist convection. In this study a united framework is designed to investigate the vertical structures of tropical marine convections in three reanalysis data, including ERA-Interim, MERRA, and CFSR. It starts by sorting and binning data from the lightest to the heaviest rain. Then the differences between two neighboring bins are used to examine the direct effects for precipitation change, in light of the fact that non-convective processes would change slowly from bin to bin. It is shown that all three reanalyses reveal the shallow convective processes in light rain bins, featured by re-evaporating and detraining at the top of boundary layer and lower free troposphere. For heavy rain bins, three reanalyses mainly differ in their numbers and altitudes of heating and drying peaks, implying no universal agreement has been reached on partitioning of cloud populations. Coherent variations in temperature, moisture, and vertical motion are also discussed. This approach permits a systematical survey and comparison of tropical convection in GCM-type models, and preliminary studies of three reanalyses suggest certain degree of inconsistency in simulated convective feedback to large-scale heat and moisture budgets.

  14. Equatorial cloud level convection on Venus

    Science.gov (United States)

    Lee, Yeon Joo; Imamura, Takeshi; Sugiyama, Koichiro; Sato, Takao M.; Maejima, Yasumitsu

    2016-10-01

    In the equatorial region on Venus, a clear cloud top morphology difference depending on solar local time has been observed through UV images. Laminar flow shaped clouds are shown on the morning side, and convective-like cells on the afternoon side (Titov et al. 2012). Baker et al. (1998) suggested that deep convective motions in the low-to-middle cloud layers at the 40–60 km range can explain cellular shapes. Imamura et al. (2014), however argued that this cannot be a reason, as convection in the low-to-middle cloud layers can be suppressed near sub solar regions due to a stabilizing effect by strong solar heating. We suggest that the observed feature may be related to strong solar heating at local noon time (Lee et al. 2015). Horizontal uneven distribution of an unknown UV absorber and/or cloud top structure may trigger horizontal convection (Toigo et al. 1994). In order to examine these possibilities, we processed 1-D radiative transfer model calculations from surface to 100 km altitude (SHDOM, Evans 1998), which includes clouds at 48-71 km altitudes (Crisp et al. 1986). The results on the equatorial thermal cooling and solar heating profiles were employed in a 2D fluid dynamic model calculation (CReSS, Tsuboki and Sakakibara 2007). The calculation covered an altitude range of 40-80 km and a 100-km horizontal distance. We compared three conditions; an 'effective' global circulation condition that cancels out unbalanced net radiative energy at equator, a condition without such global circulation effect, and the last condition assumed horizontally inhomogeneous unknown UV absorber distribution. Our results show that the local time dependence of lower level cloud convection is consistent with Imamura et al.'s result, and suggest a possible cloud top level convection caused by locally unbalanced net energy and/or horizontally uneven solar heating. This may be related to the observed cloud morphology in UV images. The effective global circulation condition, however

  15. Convection in complex shaped vessel; Convection dans des enceintes de forme complexe

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    The 8 november 2000, the SFT (Societe Francaise de Thermique) organized a technical day on the convection in complex shaped vessels. Nine papers have been presented in the domains of the heat transfers, the natural convection, the fluid distribution, the thermosyphon effect, the steam flow in a sterilization cycle and the transformers cooling. Eight papers are analyzed in ETDE and one paper dealing with the natural convection in spent fuels depository is analyzed in INIS. (A.L.B.)

  16. Numerical study on the thermal and flow characteristics of periodically formed inner wavy structures in a cooling channel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ju Chul; Park, Sang Hu; Son, Chang Min; Min, June Kee; Ha, Man Yeong [Pusan National University, Busan (Korea, Republic of); Cho, Jong Rae [Korea Maritime University, Busan (Korea, Republic of)

    2015-09-15

    In industrial fields of machine and aerospace, cooling systems consisting of channels are widely used to increase energy efficiency and prevent system overheat. In cooling channels, a reduced pressure drop, an enhanced heat transfer, and a short channel length are considered key design requirements for optimizing the total volume and weight of a system. In this work, we improved heat transfer efficiency by using milli-scale wavy structures inside the channel. By optimizing the inner structures through computational fluid dynamics analysis and Taguchi method, the Nusselt number increased by approximately 11.7% with a similar pressure drop compared with that of a normal channel for a Reynolds number of 1000.

  17. Mechanism and scaling for convection of isolated structures in nonuniformly magnetized plasmas

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Naulin, V.

    2005-01-01

    Large-scale radial advection of isolated structures in nonuniformly magnetized plasmas is investigated. The underlying mechanism considered is due to the nonlinear evolution of interchange motions, without any presumption of plasma sheaths. Theoretical arguments supported by numerical simulations...... of the structures, compares favorably with recent experimental measurements of radially propagating blob structures in the scrape-off layer of magnetically confined plasmas. (C) 2005 American Institute of Physics....

  18. Design of a water cooled monoblock divertor for DEMO using Eurofer as structural material

    Energy Technology Data Exchange (ETDEWEB)

    Richou, Marianne, E-mail: marianne.richou@cea.fr [CEA, IRFM, F-13108 Saint Paul Lez Durance (France); Li-Puma, Antonella [CEA, DEN, Saclay, DM2S, SERMA, F-91191 Gif-sur-Yvette (France); Visca, Eliseo [Associazione EURATOM-ENEA sulla Fusione, C.R. Frascati, IT-00044 Frascati (Italy)

    2014-10-15

    The performed investigation focus on a monoblock type design for a water cooled DEMO divertor using Eurofer as structural material. In 2013, a study case of such a concept was presented. It was shown that basic concepts using Eurofer as structural material are limited to an incident heat flux of 8 MW m{sup −2}. Since, the EFDA agency issued new specifications. In this study, the conceptual design is reassessed with regard to specifications. Then, steady state thermal analyses and thermo-mechanical elastic analyses have been performed to define an upgrade of the geometry taking into account new specifications, design criteria and the maximum heat flux requirement of 10 MW m{sup −2}. An analysis of the influence of each adjustable geometrical parameter on thermo-mechanical design criteria was performed. As a consequence, geometrical parameters were set in order to fit to materials requirements. For defined hydraulic conditions taken in the most favourable configuration, the limit of this design is estimated to an incident heat flux of 10 MW m{sup −2}. Margin to critical heat flux and rules against progressive deformation/ratcheting in structural material limit the design.

  19. Effect of Internal Heat Recovery in Ammonia-Water Absorption Cooling Cycles: Exergy and Structural Analysis

    Directory of Open Access Journals (Sweden)

    Miquel Nogués

    2009-03-01

    Full Text Available First and second law analysis have been conducted for three low temperature driven ammonia-water absorption cooling cycles with increasing internal heat recovery. Based on the results of exergy analysis the structural analysis has been achieved. The obtained Coefficients of Structural Bonds (CSB consider how the irreversibility of the whole cycle is affected by a change in the irreversibility related to an efficiency improvement of a single component. Trends for the different configurations are similar, while quantitative differences among the main heat exchangers are considerable. The highest values of the CSB are found for the refrigerant heat exchanger. Also the evaporator, the condenser, the generator and the absorber show values higher than unity. The lowest CSB’s are obtained in the solution heat exchanger. In general, CSB’s decrease with increasing efficiency. That means that for very efficient heat exchangers, a further improvement looks less attractive. The dephlegmator is an exception as it shows a singularity of the CSB value due to its complex interactions with the other components. Once the CSB’s are obtained for the main components, they can be used in the structural method of the thermoeconomic optimisation. This method enables us to find the optimum design of a component in a straightforward calculation.

  20. Workshop 4 Converter cooling & recuperation

    Science.gov (United States)

    Iles, Peter; Hindman, Don

    1995-01-01

    Cooling the PV converter increases the overall TPV system efficiency, and more than offsets the losses incurred in providing cooling systems. Convective air flow methods may be sufficient, and several standard water cooling systems, including thermo-syphon radiators, capillary pumps or microchannel plates, are available. Recuperation is used to increase system efficiency, rather than to increase the emitter temperature. Recuperators operating at comparable high temperatures, such as in high temperature turbines have worked effectively.

  1. Electrical conductivity of old oceanic mantle in the northwestern Pacific I: 1-D profiles suggesting differences in thermal structure not predictable from a plate cooling model

    Science.gov (United States)

    Baba, Kiyoshi; Tada, Noriko; Matsuno, Tetsuo; Liang, Pengfei; Li, Ruibai; Zhang, Luolei; Shimizu, Hisayoshi; Abe, Natsue; Hirano, Naoto; Ichiki, Masahiro; Utada, Hisashi

    2017-08-01

    Seafloor magnetotelluric (MT) experiments were recently conducted in two areas of the northwestern Pacific to investigate the nature of the old oceanic upper mantle. The areas are far from any tectonic activity, and "normal" mantle structure is therefore expected. The data were carefully analyzed to reduce the effects of coastlines and seafloor topographic changes, which are significant boundaries in electrical conductivity and thus distort seafloor MT data. An isotropic, one-dimensional electrical conductivity profile was estimated for each area. The profiles were compared with those obtained from two previous study areas in the northwestern Pacific. Between the four profiles, significant differences were observed in the thickness of the resistive layer beyond expectations based on cooling of homogeneous oceanic lithosphere over time. This surprising feature is now further clarified from what was suggested in a previous study. To explain the observed spatial variation, dynamic processes must be introduced, such as influence of the plume associated with the formation of the Shatsky Rise, or spatially non-uniform, small-scale convection in the asthenosphere. There is significant room of further investigation to determine a reasonable and comprehensive interpretation of the lithosphere-asthenosphere system beneath the northwestern Pacific. The present results demonstrate that electrical conductivity provides key information for such investigation.[Figure not available: see fulltext.

  2. Intermittent convective transport carried by propagating electromagnetic filamentary structures in nonuniformly magnetized plasma

    DEFF Research Database (Denmark)

    Xu, G.S.; Naulin, Volker; Fundamenski, W.

    2010-01-01

    Drift-Alfvén vortex filaments associated with electromagnetic turbulence were recently identified in reversed field pinch devices. Similar propagating filamentary structures were observed in the Earth magnetosheath, magnetospheric cusp and Saturn’s magnetosheath by spacecrafts. The characteristic......, heat, and momentum in the fusion plasmas can be interpreted in terms of the ballistic motion of these solitary electromagnetic filamentary structures....

  3. Cooling rate dependence of simulated ${\\rm Cu_{64.5}Zr_{35.5}}$ metallic glass structure

    CERN Document Server

    Ryltsev, R E; Chtchelkatchev, N M

    2016-01-01

    Using molecular dynamics simulations with embedded atom model potential, we study structural evolution of ${\\rm Cu_{64.5}Zr_{35.5}}$ alloy during the cooling in a wide range of cooling rates $\\gamma\\in(1.5\\cdot 10^{9},10^{13})$ K/s. Investigating short- and medium-range order, we show that structure of ${\\rm Cu_{64.5}Zr_{35.5}}$ metallic glass essentially depends on cooling rate. In particular, a decrease of the cooling rate leads to a increase of abundances of both the icosahedral-like clusters and Frank-Kasper Z16 polyhedra. The amounts of these clusters in the glassy state drastically increase at the $\\gamma_{\\rm min}=1.5\\cdot 10^{9}$ K/s. Analysing the structure of the glass at $\\gamma_{\\rm min}$, we observe the formation of nano-sized crystalline grain of ${\\rm Cu_2Zr}$ intermetallic compound with the structure of ${\\rm Cu_2Mg}$ Laves phase. The structure of this compound is isomorphous with that for ${\\rm Cu_5Zr}$ intermetallic compound. Both crystal lattices consist of two type of clusters: Cu-centered...

  4. Performance Evaluation of PBL Schemes of ARW Model in Simulating Thermo-Dynamical Structure of Pre-Monsoon Convective Episodes over Kharagpur Using STORM Data Sets

    Science.gov (United States)

    Madala, Srikanth; Satyanarayana, A. N. V.; Srinivas, C. V.; Tyagi, Bhishma

    2016-05-01

    In the present study, advanced research WRF (ARW) model is employed to simulate convective thunderstorm episodes over Kharagpur (22°30'N, 87°20'E) region of Gangetic West Bengal, India. High-resolution simulations are conducted using 1 × 1 degree NCEP final analysis meteorological fields for initial and boundary conditions for events. The performance of two non-local [Yonsei University (YSU), Asymmetric Convective Model version 2 (ACM2)] and two local turbulence kinetic energy closures [Mellor-Yamada-Janjic (MYJ), Bougeault-Lacarrere (BouLac)] are evaluated in simulating planetary boundary layer (PBL) parameters and thermodynamic structure of the atmosphere. The model-simulated parameters are validated with available in situ meteorological observations obtained from micro-meteorological tower as well has high-resolution DigiCORA radiosonde ascents during STORM-2007 field experiment at the study location and Doppler Weather Radar (DWR) imageries. It has been found that the PBL structure simulated with the TKE closures MYJ and BouLac are in better agreement with observations than the non-local closures. The model simulations with these schemes also captured the reflectivity, surface pressure patterns such as wake-low, meso-high, pre-squall low and the convective updrafts and downdrafts reasonably well. Qualitative and quantitative comparisons reveal that the MYJ followed by BouLac schemes better simulated various features of the thunderstorm events over Kharagpur region. The better performance of MYJ followed by BouLac is evident in the lesser mean bias, mean absolute error, root mean square error and good correlation coefficient for various surface meteorological variables as well as thermo-dynamical structure of the atmosphere relative to other PBL schemes. The better performance of the TKE closures may be attributed to their higher mixing efficiency, larger convective energy and better simulation of humidity promoting moist convection relative to non

  5. Investigation of the Cooling and Thermal-Measuring System of a Compound-Structure Permanent-Magnet Synchronous Machine

    Directory of Open Access Journals (Sweden)

    Jingang Bai

    2014-03-01

    Full Text Available The compound-structure permanent-magnet synchronous machine (CS-PMSM is a power-split device which can enable the internal combustion engine (ICE to operate at optimum efficiency during all driving conditions by controlling its torque and speed. However, the CS-PMSM has more serious temperature rise and heat dissipation problems than conventional permanent-magnet (PM machines, especially when the CS-PMSM is running at low speed and under full load conditions. As the thermal resistance of double-layer air gaps is quite big, the hot spot proves to be in the inner winding rotor. To ensure the safe operation of the CS-PMSM, the use of forced-air and water cooling in the inner winding rotor are investigated. The study shows that the water cooling can provide a better cooling effect, but require a complicated mechanical structure. Considering the complexity of the high efficiency cooling system, a real-time temperature monitoring method is proposed and a temperature measuring system which can accurately measure the real-time temperature of multiple key points in the machine is developed to promptly adjust the operating and cooling conditions based on the measured temperature results. Finally, the temperature rise experiment of the CS-PMSM prototype is done and the simulation results are partly validated by the experimental data.

  6. X-ray observations of complex temperature structure in the cool-core cluster A85

    Energy Technology Data Exchange (ETDEWEB)

    Schenck, David E.; Datta, Abhirup; Burns, Jack O. [Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Science, University of Colorado, Boulder, CO 80309 (United States); Skillman, Sam [Kavli Fellow, Kavli Institute for Particle Astrophysics and Cosmology, SLAC, CA 94025 (United States)

    2014-07-01

    X-ray observations were used to examine the complex temperature structure of A85, a cool-core galaxy cluster. Temperature features can provide evidence of merging events which shock heat the intracluster gas. Temperature maps were made from both Chandra and XMM-Newton observations. The combination of a new, long-exposure XMM observation and an improved temperature map binning technique produced the highest fidelity temperature maps of A85 to date. Hot regions were detected near the subclusters to the south and southwest in both the Chandra and XMM temperature maps. The presence of these structures implies A85 is not relaxed. The hot regions may indicate the presence of shocks. The Mach numbers were estimated to be ∼1.9 at the locations of the hot spots. Observational effects will tend to systematically reduce temperature jumps, so the measured Mach numbers are likely underestimated. Neither temperature map showed evidence for a shock in the vicinity of the presumed radio relic near the southwest subcluster. However, the presence of a weak shock cannot be ruled out. There was tension between the temperatures measured by the two instruments.

  7. X-ray Observations of Complex Temperature Structure in the Cool-core cluster Abell 85

    CERN Document Server

    Schenck, David; Burns, Jack; Skillman, Sam

    2014-01-01

    X-ray observations were used to examine the complex temperature structure of Abell 85, a cool-core galaxy cluster. Temperature features can provide evidence of merging events which shock heat the intracluster gas. Temperature maps were made from both \\textit{Chandra} and \\textit{XMM-Newton} obervations. The combination of a new, long-exposure \\textit{XMM} observation and an improved temperature map binning technique produced the highest fidelity temperature maps of A85 to date. Hot regions were detected near the subclusters to the South and Southwest in both the \\textit{Chandra} and \\textit{XMM} temperature maps. The presence of these structures implies A85 is not relaxed. The hot regions may indicate the presence of shocks. The Mach numbers were estimated to be $\\sim$1.9 at the locations of the hot spots. Observational effects will tend to systematically reduce temperature jumps, so the measured Mach numbers are likely underestimated. Neither temperature map showed evidence for a shock in the vicinity of the...

  8. Structural relaxation time and cooling rate of a melt in the glass transition region

    Science.gov (United States)

    Sanditov, D. S.; Sydykov, B. S.

    2015-03-01

    The nature of the parameter involved in the Bartenev equation qτg = C relating the cooling rate of a glass-forming melt to its structural relaxation time in the glass transition region is discussed on the basis of the Volkenshtein-Ptitsyn theory using a number of known relationships. It is established that parameter C for amorphous substances with the same fragility is linearly temperature dependent. This parameter is shown to equal the narrow temperature range δ T g characterizing the liquid-glass transition region (by Nemilov); i.e., C = δ T g. It is concluded that δ T g for most glassy systems is only ˜0.7% of the glass transition temperature T g. The narrowness of temperature range δ T g is explained by the small fluctuation volume fraction f g "frozen" at the glass transition temperature. The concept of a close relationship between constant C and the structural order at T g (i.e., the characteristic of the inner state of a nonequilibrium "frozen" amorphous system) is developed.

  9. Anomalously Weak Solar Convection

    Science.gov (United States)

    Hanasoge, Shravan M.; Duvall, Thomas L.; Sreenivasan, Katepalli R.

    2012-01-01

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical- harmonic degree l..Within the wavenumber band l convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers l convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.

  10. Combination of NMR and MRI quantitation of moisture and structure changes for convection cooking of fresh chicken meat.

    Science.gov (United States)

    Shaarani, Sharifudin Md; Nott, Kevin P; Hall, Laurance D

    2006-03-01

    This study demonstrates that a combination of bulk NMR and magnetic resonance imaging measurements of the T(2)-values of water protons can be used to determine the heat-induced changes in the structure and moisture content of fresh chicken meat which had been cooked in a convection oven at 200°C for a range of times. The gravimetric moisture content was also determined for both the raw and cooked meat. Multi-exponential fitting of the bulk NMR T(2) relaxation time data demonstrated three distinct water populations T(21) (39-43ms), T(22) (82-99ms) and T(23) (2-3ms) for raw meat which changed to 18-31ms (T(21)), 61-208ms (T(22)) and 3-7ms (T(23)) after the meat had been cooked. The T(1) and T(2) values obtained by MRI for cooked meat decreased progressively with increased heating time. There are highly significant correlations between the T(2) values from MRI and the T(21) values from bulk NMR measurements of cooked meat (r=0.986; p<0.01), and also between the normalised M(0) values from MRI and the gravimetric moisture content (r=0.953; p<0.01).

  11. An experimental study of hypervapotron structure in external reactor vessel cooling

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yufeng; Zhang, Ming [State Nuclear Power Technology R& D Center (Beijing), Beijing (China); Hou, Fangxin [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing (China); Gao, Tianfang [State Nuclear Power Technology R& D Center (Beijing), Beijing (China); Chen, Peipei, E-mail: chenpeipei@snptc.com.cn [State Power Investment Group Corporation, Beijing (China)

    2016-07-15

    Highlights: • Experiments are performed to study the application of hypervapotron in ERVC design. • CHF experiments on two surfaces are conducted under different flow conditions. • Hypervapotron improves CHF performance by 40–60% compared with smooth surface. • Visualization shows fin structure removes vapor mushroom for better liquid supply. - Abstract: In vessel retention (IVR) is one of the key strategies for many advanced LWR designs to mitigate postulated severe accidents. The success of IVR substantially relies on external reactor vessel cooling (ERVC) by which the decay heat is removed from the melt core in the reactor vessel lower head. The main challenge of IVR is to provide an adequate safety margin of ERVC against critical heat flux (CHF) of subcooled flow boiling in the reactor lower head flow channel. Due to uncertainties in corium melt pool configuration, large CHF margin of ERVC is usually required by regulatory authorities to demonstrate reliability of severe accident mitigation methods. Various CHF enhancement designs have been proposed and studied in literature. In this paper, an experimental study of hypervapotron structure as a novel design to improve CHF performance of ERVC is conducted. Hypervapotron is chosen as one of the potential engineering options for International Thermonuclear Experimental Reactor (ITER) program as a divertor structure to remove highly intense heat from fusion chamber. This study is to conduct CHF experiments at typical PWR ERVC working conditions. The CHF experiments are performed in a 30 mm by 61 mm rectangular flow channel with a 200 mm long heated surface along the flow direction. Both smooth and hypervapotron surface are tested at various inclination angles of the test section to simulate various positions of the reactor lower head. The hypervapotron is found to have a 40–60% CHF improvement compared with the smooth surface. The high speed visualization indicates that hypervapotron is able to

  12. Actively convected liquid metal divertor

    Science.gov (United States)

    Shimada, Michiya; Hirooka, Yoshi

    2014-12-01

    The use of actively convected liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the convected liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem.

  13. Structural and phase transformations in iron-based alloy obtained in conditions of high cooling rate crystallization

    Science.gov (United States)

    Kovalevskaya, Zh. G.; Khimich, M. A.

    2016-11-01

    The production of parts by selective electron beam melting (SEBM) is accompanied by the formation of nonequilibrium structures. This is caused by the crystallization of alloys with high cooling rates. To evaluate the influence of cooling rate on the process of structural and phase transformations in the Fe-8Si-5Al-2C alloy, the electron beam melting of plasma coating was carried out. The dendritic structure was formed in the molten pool. The distance between dendritic branches of the second order was 2-5 µm. This corresponds to the cooling rate of about 103 K/s. The electron microscopy has shown that dendrites were formed by α-phase, while γ-phase was localized between α-phase crystals in form of intercalations. The secondary phases (intermetallic, aluminum and iron carbosilicides, aluminates and iron carboaluminates) are of sub-micron size and located in the α- and γ-phase boundary intersections or within the grains of the main phase. The microhardness of the alloy increases twofold. This suggests that complex hardening by solid-solution and dispersed hardening by the secondary phase particles occurs during crystallization with the above-mentioned cooling rate.

  14. Effect of composition and cooling rate on structures and properties of quenched or cast Al-V-Fe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shek, C.H.; He, G.; Bian, Z.; Chen, G.L.; Lai, J.K.L

    2003-09-25

    Rapidly solidified Al-V-Fe alloys are promising structural materials because of the high tensile strength of up to 1400 MPa combined with the light weight. In this investigation, the authors prepared Al-V-Fe alloys of various V and Fe contents by melt-spinning and water-cooled copper mould casting. The alloy samples were characterized with X-ray diffraction (XRD), SEM, TEM, nanoindention, and tensile test. It was shown that the V and Fe contents strongly affect the microstructure and hence the mechanical properties. Increasing V and Fe content causes an increase of the volume fraction of the quasicrystalline phase which gives rise to the strengthening of the alloy. The amount of quasicrystals depends also on the cooling rate during solidification. At very high cooling rate, dispersions of quasicrystals and amorphous nanoscale clusters are favored while at low cooling rate, a stable Al{sub 10}V crystalline phase form instead in the {alpha}-Al matrix. A gradual transition between these two extremes is observed at intermediate cooling rates.

  15. Fabrication of TBMs cooling structures demonstrators using additive manufacturing (AM) technology and HIP

    Energy Technology Data Exchange (ETDEWEB)

    Ordás, Nerea, E-mail: nordas@ceit.es [CEIT-IK4 and Tecnun (University of Navarra), Donostia-San Sebastián (Spain); Ardila, Luis Carlos [IK4-LORTEK Joining Research Institute, Ordizia (Spain); Iturriza, Iñigo [CEIT-IK4 and Tecnun (University of Navarra), Donostia-San Sebastián (Spain); Garcianda, Fermín; Álvarez, Pedro [IK4-LORTEK Joining Research Institute, Ordizia (Spain); García-Rosales, Carmen [CEIT-IK4 and Tecnun (University of Navarra), Donostia-San Sebastián (Spain)

    2015-10-15

    Highlights: • TBM geometrically relevant component components were obtained by addtive manufacturing. • P91, a ferritic–martensitic steel metallurgically similar to EUROFER was used. • Dense core walls were obtained by SLM, though contour of cooling channel walls are slightly porous. • HIP after SLM is effective in removing the porosity and homogenizing the microstructure. • After HIP + normalizing + tempering mechanical behavior is similar to P91 as received. - Abstract: Several mock-ups, each of them consisting of six rectangular channels with dimensions according to the EU Test Blanket Modules (TBMs) specifications, were manufactured by selective laser melting (SLM) technology using P91, a ferritic–martensitic 9%Cr–1%Mo–V steel with a metallurgical behavior similar to EUROFER, the reference structural material for DEMO blanket concepts. SLM parameters led to an as-built density of 99.35% Theoretical Density (TD) that increased up to 99.74% after hot isostatic pressing (HIP). Dimensional control showed that the differences between the original design and the component are below 100 μm. By the appropriate selection of normalization and tempering parameters it was possible to obtain a material fulfilling P91 specification. The microstructure was investigated after SLM, HIP and normalizing and tempering treatments. In all cases, it consisted of thin martensitic laths. Subsize tensile samples were extracted from the mock-ups to measure the mechanical tensile properties after each step of the manufacturing process. The effect of thermal treatments on hardness was also evaluated.

  16. Parameterizing convective organization

    Directory of Open Access Journals (Sweden)

    Brian Earle Mapes

    2011-06-01

    Full Text Available Lateral mixing parameters in buoyancy-driven deep convection schemes are among the most sensitive and important unknowns in atmosphere models. Unfortunately, there is not a true optimum value for plume mixing rate, but rather a dilemma or tradeoff: Excessive dilution of updrafts leads to unstable stratification bias in the mean state, while inadequate dilution allows deep convection to occur too easily, causing poor space and time distributions and variability. In this too-small parameter space, compromises are made based on competing metrics of model performance. We attempt to escape this “entrainment dilemma” by making bulk plume parameters (chiefly entrainment rate depend on a new prognostic variable (“organization,” org meant to reflect the rectified effects of subgrid-scale structure in meteorological fields. We test an org scheme in the Community Atmosphere Model (CAM5 with a new unified shallow-deep convection scheme (UW-ens, a 2-plume version of the University of Washington scheme. Since buoyant ascent involves natural selection, subgrid structure makes convection systematically deeper and stronger than the pure unorganized case: plumes of average (or randomly sampled air rising in the average environment. To reflect this, org is nonnegative, but we leave it dimensionless. A time scale characterizes its behavior (here ∼3 h for a 2o model. Currently its source is rain evaporation, but other sources can be added easily. We also let org be horizontally transported by advection, as a mass-weighted mean over the convecting layer. Linear coefficients link org to a plume ensemble, which it assists via: 1 plume base warmth above the mean temperature 2 plume radius enhancement (reduced mixing, and 3 increased probability of overlap in a multi-plume scheme, where interactions benefit later generations (this part has only been implemented in an offline toy column model. Since rain evaporation is a source for org, it functions as a time

  17. Experimental characterization of the ITER TF structure cooling in HELIOS test facility

    Science.gov (United States)

    Hoa, C.; Rousset, B.; Lacroix, B.; Nicollet, S.; Vallcorba, R.; Bessette, D.; Vostner, A.; Gauthier, F.

    2015-12-01

    During ITER plasma operation, large thermal loads are generated in the stainless steel Toroidal Field (TF) coil casing. To minimize the impact on the temperature of the TF Cable in Conduit Conductor (CICC), these heat loads are intercepted by case cooling channels which are implemented at the interface to the winding pack. One of the design options for the case cooling channels consists of a stainless steel pipe inserted in a rectangular groove which is machined in the casing and filled by a charged resin of high thermal conductivity. A higher number of cooling pipes is arranged at the plasma facing wall of the case, thus providing a better shielding to the TF conductor at high field. To assess the efficiency of the cooling pipes and their thermal coupling with the charged resin, experimental characterizations have been performed. First of all, the thermal resistance vs temperature of some of the individual components of a TF coil has been measured on representative samples in a cryogenic bench. Further characterizations have been performed on an integrated mock-up of the TF cooling scheme at cryogenic temperature in HELIOS test facility at CEA Grenoble. The mock-up consists of a piece of TF casing that can be heated uniformly on its surface, one cooling channel implemented in the groove which is filled with the charged resin, the filler, the ground insulation, the radial plate and one insulated CICC. The cooling pipe and the CICC are cooled by supercritical helium at 4.4 K and 5 bar; the instrumentation consists of temperature, pressure and mass flow sensors. Both stationary and transient operating modes have been investigated to assess the thermal efficiency of the case cooling design. The experimental tests are presented and the first results are discussed and analyzed in this document.

  18. Study of heat exchange in cooling systems of heat-stressed structures

    Science.gov (United States)

    Vikulin, A. V.; Yaroslavtsev, N. L.; Zemlyanaya, V. A.

    2017-01-01

    Increasing working parameters of the cycle of gas-turbine engines, complicating design of gas-turbine plants, as well as growing aerodynamic, thermal, static, and dynamic loads, necessitate the development of promising cooling systems for heat-stressed structures. This work is devoted to an experimental study of heat exchange in ducts equipped with systems of inclined and cross walls (fins). It has been found that an increase in the Reynolds number Re from 3000 to 20000 leads to a decrease in the heat exchange, which is characterized by the relative Nusselt number overline{Nu}, by 19-30% at the angle of inclination of the walls φ = 0, 40°, 50°, and 90° if the length of the walls x w is comparable to the spacing b s and by 12-15% at φ = 30° and 90° if x w ≫ b s. If cross walls are used in cooling ducts, the length of the walls x w plays the governing role; an increase in this characteristic from 1.22 × 10-3 to 3.14 × 10-3 m leads to an increase in the intensity of heat exchange by 30-40% and to a decrease in the capacity of the entire system of the walls. It has been shown that, on surfaces with wavy fins, the intensity of heat exchange is closest to that determined in the models under study. For example, values of the Colborne criterion StPr2/3 for ducts equipped with wavy fins and for the models under study differ only slightly (by 2-20% depending on the value of the angle φ). However, the difference for surfaces with short plate fins and ducts equipped with inclined walls is high (30-40%). This is due to the design features of these surfaces and to the severe effect of the inlet portion on heat exchange, since the surfaces are characterized by a higher ratio of the duct length to the hydraulic diameter L/d h at small fin thicknesses ((0.1-0.15) × 10-3 m). The experimental results can be used in developing designs of nozzle and rotor blades of high-temperature gas turbines in gas-turbine engines and plants.

  19. Numerical simulation heat transfer by natural convection in liquid metal with a sinusoidal temperature

    Directory of Open Access Journals (Sweden)

    Missoum Abdelkrim

    2016-01-01

    Full Text Available This study focuses on the numerical simulation of heat transfer by natural convection in a rectangular enclosure, filled with a liquid metal (low Prandtl number partially heated from below with a sinusoidal temperature. The value of the study lies in its involvement in the crystal growth for the manufacture of semiconductors and electronics cooling. Indeed, the occurrence of convection during crystal growth can lead to in homogeneities that lead to striations and defects that affect the quality of the crystals obtained by the Bridgman techniques or Chochrawlski. Temperature of the oscillations, due to the instabilities of the convective flow in the liquid metal, also induces non-uniform cooling in the solidification front. Convection is then studied in order to reduce it. A modelling of the problem in two dimensions was conducted using Comsol computer code that is based on the finite element method, by varying the configuration of the control parameters, namely, the Rayleigh number, the nature of fluid (Prandtl number and amplitude of temperature on heat transfer rate (Nusselt number on convective structures that appear.

  20. Effect of the cooling rate on the phase composition and structure of copper matte converting slags

    Science.gov (United States)

    Selivanov, E. N.; Gulyaeva, R. I.; Udoeva, L. Yu.; Belyaev, V. V.; Pankratov, A. A.

    2009-08-01

    The effect of the cooling rate on the phase composition and microstructure of copper matte converting slags is studied by X-ray diffraction, combined thermogravimetry and calorimetry, mineragraphy, and electron-probe microanalysis. The compositions of oxide and sulfide phases are determined, and the forms of nonferrous metals in slags cooled at a rate of 0.3 and 900°C/s are revealed. At high cooling rates of the slags, iron silicate glass is shown to form apart from sulfide phases. Repeated heating of the slags leads to the development of devitrification, “cold” crystallization, and melting. A decrease in the cooling rate favors an increase in the grain sizes in oxides (magnetite, iron silicates) and sulfides (bornite-, sphalerite, and galena-based solid solutions).

  1. Noninvasive thermal coagulation of deep subsurface tissue structures using a laser probe with integrated contact cooling.

    Science.gov (United States)

    Cilip, Christopher M; Scott, Nicholas J; Trammell, Susan R; Fried, Nathaniel M

    2008-01-01

    Cooling methods are used during cosmetic laser surgery to preserve a superficial layer of the skin surface. This study investigates contact cooling for sparing a deeper layer of the tissue surface during laser irradiation of subsurface tissues, with the goal of developing noninvasive laser therapy applications beyond cosmetic surgery. A laser probe was designed and tested for simultaneous laser irradiation and contact cooling of liver tissue, ex vivo. Gross and histologic examination was used to quantify thermal lesion dimensions. Liver lesions of 5.8-mm-diameter were created, while preserving the tissue surface to a depth of 1.5 mm. In vivo animal studies are planned to optimize the laser and cooling parameters for potential clinical applications.

  2. Stress memory effect in viscoelastic stagnant lid convection

    Science.gov (United States)

    Patočka, V.; Čadek, O.; Tackley, P. J.; Čížková, H.

    2017-06-01

    Present thermochemical convection models of planetary evolution often assume a purely viscous or viscoplastic rheology. Ignoring elasticity in the cold, outer boundary layer is, however, questionable since elastic effects may play an important role there and affect surface topography as well as the stress distribution within the stiff cold lithosphere. Here we present a modelling study focused on the combined effects of Maxwell viscoelastic rheology and a free surface in the stagnant lid planetary convection. We implemented viscoelastic rheology in the StagYY code using a tracer-based stress advection scheme that suppresses subgrid oscillations. We apply this code to perform thermal convection models of the cooling planetary mantles and we demonstrate that while the global characteristics of the mantle flow do not change significantly when including viscoelasticity, the stress state of the cold lithosphere may be substantially different. Transient cooling of an initially thin upper thermal boundary layer results in a complex layered stress structure due to the memory effects of viscoelastic rheology. The stress state of the lid may thus contain a record of the planetary thermal evolution.

  3. Preliminary thermal/structural analysis of a carbon-carbon/refractory-metal heat-pipe-cooled wing leading edge

    Science.gov (United States)

    Glass, David E.; Camarda, Charles J.

    1990-01-01

    This study presents preliminary thermal/structural analyses of a carbon-carbon/refractory-metal heat-pipe-cooled wing leading edge concept designed for an air breathing single-stage-to-orbit hypersonic vehicle. The concept features chordwise (i.e., normal to the leading edge) and spanwise (i.e., parallel to the leading edge) refractory-metal heat pipes which are completely embedded within a carbon-carbon primary structure. Studies of the leading edge were performed using nonlinear thermal and linear structural three-dimensional finite element analyses. The concept was shown to be thermally feasible within the limits of the assumptions made in the analyses when internal radiative cooling is present during ascent, and a three-dimensional carbon-carbon architecture is used. In addition, internal radiative cooling was found not to be necessary during descent. The linear stress analysis indicated excessively large thermal stresses in the rafractory metal walls of the heat pipes even though a soft layer of carbon was included between the heat pipe and the carbon-carbon structure in an attempt to reduce the thermal stresses. A nonlinear structural analysis may be necessary to properly model the response of the refractory-metal heat pipes.

  4. Analysis of Turbine Blade Relative Cooling Flow Factor Used in the Subroutine Coolit Based on Film Cooling Correlations

    Science.gov (United States)

    Schneider, Steven J.

    2015-01-01

    Heat transfer correlations of data on flat plates are used to explore the parameters in the Coolit program used for calculating the quantity of cooling air for controlling turbine blade temperature. Correlations for both convection and film cooling are explored for their relevance to predicting blade temperature as a function of a total cooling flow which is split between external film and internal convection flows. Similar trends to those in Coolit are predicted as a function of the percent of the total cooling flow that is in the film. The exceptions are that no film or 100 percent convection is predicted to not be able to control blade temperature, while leaving less than 25 percent of the cooling flow in the convection path results in nearing a limit on convection cooling as predicted by a thermal effectiveness parameter not presently used in Coolit.

  5. Uncertainties in H2 and HD Chemistry and Cooling and their Role in Early Structure Formation

    CERN Document Server

    Glover, S C O

    2008-01-01

    At low temperatures, the main coolant in primordial gas is molecular hydrogen, H2. Recent work has shown that primordial gas that is not collapsing gravitationally but is cooling from an initially ionized state forms hydrogen deuteride, HD, in sufficient amounts to cool the gas to the temperature of the cosmic microwave background. This extra cooling can reduce the characteristic mass for gravitational fragmentation and may cause a shift in the characteristic masses of population III stars. Motivated by the importance of the atomic and molecular data for the cosmological question, we assess several chemical and radiative processes that have hitherto been neglected: the sensitivity of the low temperature H2 cooling rate to the ratio of ortho-H2 to para-H2, the uncertainty in the low temperature cooling rate of H2 excited by collisions with H, the effects of cooling from H2 excited by collisions with H+ and e-, and the large uncertainties in the rates of several of the reactions responsible for determining the ...

  6. HANARO cooling features: design and experience

    Energy Technology Data Exchange (ETDEWEB)

    Park, Cheol; Chae, Hee-Taek; Han, Gee-Yang; Jun, Byung-Jin; Ahn, Guk-Hoon [HANARO Operating Team, Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-08-01

    In order to achieve the safe core cooling during normal operation and upset conditions, HANARO adopted an upward forced convection cooling system with dual containment arrangements instead of the forced downward flow system popularly used in the majority of forced convection cooling research reactors. This kind of upward flow system was selected by comparing the relative merits of upward and downward flow systems from various points of view such as safety, performance, maintenance. However, several operational matters which were not regarded as serious at design come out during operation. In this paper are presented the design and operational experiences on the unique cooling features of HANARO. (author)

  7. Crystallization and Cooling of a Deep Silicate Magma Ocean

    Science.gov (United States)

    Bower, Dan; Wolf, Aaron

    2016-04-01

    Impact and accretion simulations of terrestrial planet formation suggest that giant impacts are both common and expected to produce extensive melting. The moon-forming impact, for example, likely melted the majority of Earth's mantle to produce a global magma ocean that subsequently cooled and crystallised. Understanding the cooling process is critical to determining magma ocean lifetimes and recognising possible remnant signatures of the magma ocean in present-day mantle heterogeneities. Modelling this evolution is challenging, however, due to the vastly different timescales and lengthscales associated with turbulent convection (magma ocean) and viscous creep (present-day mantle), in addition to uncertainties in material properties and chemical partitioning. We consider a simplified spherically-symmetric (1-D) magma ocean to investigate both its evolving structure and cooling timescale. Extending the work of Abe (1993), mixing-length theory is employed to determine convective heat transport, producing a high resolution model that parameterises the ultra-thin boundary layer (few cms) at the surface of the magma ocean. The thermodynamics of mantle melting are represented using a pseudo-one-component model, which retains the simplicity of a standard one-component model while introducing a finite temperature interval for melting. This model is used to determine the cooling timescale for a variety of plausible thermodynamic models, with special emphasis on comparing the center-outwards vs bottom-up cooling scenarios that arise from the assumed EOS.

  8. Mixed time integration schemes for transient conduction forced-convection analysis

    Science.gov (United States)

    Liu, W. K.; Lin, J. I.

    1983-01-01

    A partition procedure for forced-convection conduction transient problems is presented. Mixed time partitions are defined wherein coupled conduction force-matrix equations are discretized using an implicit integration method, followed by derivation of a mixed time integration technique. Explicit-implicit and explicit-explicit partitions are performed for a stability analysis for transient conditions, e.g., those found in an actively air-cooled engine and airframe structure.

  9. Microtextured Surfaces for Turbine Blade Impingement Cooling

    Science.gov (United States)

    Fryer, Jack

    2014-01-01

    Gas turbine engine technology is constantly challenged to operate at higher combustor outlet temperatures. In a modern gas turbine engine, these temperatures can exceed the blade and disk material limits by 600 F or more, necessitating both internal and film cooling schemes in addition to the use of thermal barrier coatings. Internal convective cooling is inadequate in many blade locations, and both internal and film cooling approaches can lead to significant performance penalties in the engine. Micro Cooling Concepts, Inc., has developed a turbine blade cooling concept that provides enhanced internal impingement cooling effectiveness via the use of microstructured impingement surfaces. These surfaces significantly increase the cooling capability of the impinging flow, as compared to a conventional untextured surface. This approach can be combined with microchannel cooling and external film cooling to tailor the cooling capability per the external heating profile. The cooling system then can be optimized to minimize impact on engine performance.

  10. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe

    This thesis deals with topology optimisation for coupled convection problems. The aim is to extend and apply topology optimisation to steady-state conjugate heat transfer problems, where the heat conduction equation governs the heat transfer in a solid and is coupled to thermal transport...... in a surrounding uid, governed by a convection-diffusion equation, where the convective velocity field is found from solving the isothermal incompressible steady-state Navier-Stokes equations. Topology optimisation is also applied to steady-state natural convection problems. The modelling is done using stabilised...... finite elements, the formulation and implementation of which was done partly during a special course as prepatory work for this thesis. The formulation is extended with a Brinkman friction term in order to facilitate the topology optimisation of fluid flow and convective cooling problems. The derived...

  11. Effect of Temperature, Fractional Deformation, and Cooling Rate on the Structure and Properties of Steel 09GNB

    Science.gov (United States)

    Kodzhaspirov, G. E.; Sulyagin, R. V.

    2005-01-01

    The effect of temperature, divisibility of deformation, and cooling rate in high-temperature thermomechanical treatment (HTTMT) on the structure and mechanical properties of low-alloy steel 09GNB is studied. The steel is used as a high-strength material for the production of offshore structures, strips, and other welded articles. The study is performed using the method of experimental design where the parameters are fractional deformation (number of passes in rolling), final temperature of the deformation, and rate of post-deformation cooling. The results of the experiments are used to construct regression equations describing the qualitative and quantitative effect of the parameters of HTTMT on the mechanical properties of the steel. Microstructure and fracture surfaces of the steel are analyzed.

  12. Simulation of cooling and solidification of three-dimensional bulk borosilicate glass: effect of structural relaxations

    Science.gov (United States)

    Barth, N.; George, D.; Ahzi, S.; Rémond, Y.; Joulaee, N.; Khaleel, M. A.; Bouyer, F.

    2014-02-01

    The modeling of the viscoelastic stress evolution and specific volume relaxation of a bulky glass cast is presented in this article and is applied to the experimental cooling process of an inactive nuclear waste vitrification process. The concerned borosilicate glass is solidified and cooled down to ambient temperature in a stainless steel canister, and the thermomechanical response of the package is simulated. There exists a deviant compression of the liquid core due to the large glass package compared to standard tempered glass plates. The stress load development of the glass cast is finally studied for different thermal load scenarios, where the cooling process parameters or the final cooldown rates were changed, and we found a great influence of the studied cooldown rates on the maximum stress build-up at ambient temperature.

  13. Direct numerical simulation and statistical analysis of turbulent convection in lead-bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Otic, I.; Grotzbach, G. [Forschungszentrum Karlsruhe GmbH, Institut fuer Kern-und Energietechnik (Germany)

    2003-07-01

    Improved turbulent heat flux models are required to develop and analyze the reactor concept of an lead-bismuth cooled Accelerator-Driven-System. Because of specific properties of many liquid metals we have still no sensors for accurate measurements of the high frequency velocity fluctuations. So, the development of the turbulent heat transfer models which are required in our CFD (computational fluid dynamics) tools needs also data from direct numerical simulations of turbulent flows. We use new simulation results for the model problem of Rayleigh-Benard convection to show some peculiarities of the turbulent natural convection in lead-bismuth (Pr = 0.025). Simulations for this flow at sufficiently large turbulence levels became only recently feasible because this flow requires the resolution of very small velocity scales with the need for recording long-wave structures for the slow changes in the convective temperature field. The results are analyzed regarding the principle convection and heat transfer features. They are also used to perform statistical analysis to show that the currently available modeling is indeed not adequate for these fluids. Basing on the knowledge of the details of the statistical features of turbulence in this convection type and using the two-point correlation technique, a proposal for an improved statistical turbulence model is developed which is expected to account better for the peculiarities of the heat transfer in the turbulent convection in low Prandtl number fluids. (authors)

  14. Large–eddy simulations of wall heat transfer and coherent structures in mixed convection over a wavy wall

    NARCIS (Netherlands)

    Kuhn, S.; Kenjeres, S.; Von Rohr, P.R.

    2009-01-01

    In this numerical study the mixed convective flow of water over a heated wavy surface over a range of Reynolds and Richardson numbers, including transitional and turbulent flow regimes (20 ≤ Re ≤ 2000 and 0.5 ≤ Ri ≤ 5000) is investigated. A dynamic Large Eddy Simulation (LES) approach is applied whe

  15. Long-term unsteadiness and large-scale structures in Rayleigh-Bénard convection with and without electromagnetic forcing

    NARCIS (Netherlands)

    Verdoold, J.

    2010-01-01

    This dissertation focuses on turbulent thermal convection, which occurs in a wide range of (geo)physical situations, like in the atmosphere, the oceans, the interior of stars or planets, and engineering applications, like metal casting or crystal growth processes. In this work, a special type of th

  16. Convection heat transfer

    CERN Document Server

    Bejan, Adrian

    2013-01-01

    Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.

  17. National Convective Weather Diagnostic

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current convective hazards identified by the National Convective Weather Detection algorithm. The National Convective Weather Diagnostic (NCWD) is an automatically...

  18. Development of wind operated passive evaporative cooling structures for storage of tomatoes

    Science.gov (United States)

    A wind operated passive evaporative cooler was developed. Two cooling chambers were made with clay containers (cylindrical and square shapes). These two containers were separately inserted inside bigger clay pot inter- spaced with clay soil of 7 cm (to form pot-in-pot and wall-in wall) with the outs...

  19. Influence of cooling rate on structural and magnetic properties of (Fe78Nb8B141-xTbx alloys

    Directory of Open Access Journals (Sweden)

    G. Ziółkowski

    2017-05-01

    Full Text Available In the presented work we are focused on the influence of cooling rate on structural and magnetic properties of (Fe78Nb8B141-xTbx (x = 0.08, 0.1, 0.12 nanocrystalline bulk alloys. The samples were fabricated using the vacuum suction technique with different cooling rates controlled by different sample diameters (from 0.5 to 1.5 mm. The increased Nb content leads to the formation of specific microstructure and allows obtaining ultra-high coercive alloys just after casting without any additional treatment. The coercivity exceeds 8.6 T at the room temperature in case of optimal chemical and preparation conditions (x = 0.12, d = 0.5 mm and 5.6 T for x = 0.1. The impact of Tb content as well as the cooling rate on magnetic and structural (XRD, SEM, MFM properties is widely discussed in the context of reduction of rare earths in the RE-based permanent magnets.

  20. On laminar convection in solar type stars

    CERN Document Server

    Bruevich, E A

    2010-01-01

    We present a new model of large-scale multilayer convection in solar type stars. This model allows us to understand such self-similar structures observed at solar surface as granulation, supergranulation and giant cells. We study the slow-rotated hydrogen star without magnetic field with the spherically-symmetric convective zone. The photon's flux comes to the convective zone from the central thermonuclear zone of the star. The interaction of these photons with the fully ionized hydrogen plasma with $T>10^5K$ is carried out by the Tomson scattering of photon flux on protons and electrons. Under these conditions plasma is optically thick relative to the Tomson scattering. This fact is the fundamental one for the multilayer convection formation. We find the stationary solution of the convective zone structure. This solution describes the convective layers responsible to the formation of the structures on the star's surface.

  1. Ultra-light and stable composite structure to support and cool the ATLAS pixel detector barrel electronics modules

    CERN Document Server

    Olcese, M; Castiglioni, G; Cereseto, R; Cuneo, S; Dameri, M; Gemme, C; Glitza, K W; Lenzen, G; Mora, F; Netchaeva, P; Ockenfels, W; Piano, E; Pizzorno, C; Puppo, R; Rebora, A; Rossi, L; Thadome, J; Vernocchi, F; Vigeolas, E; Vinci, A

    2004-01-01

    The design of an ultra light structure, the so-called "stave", to support and cool the sensitive elements of the Barrel Pixel detector, the innermost part of the ATLAS detector to be installed on the new Large Hadron Collider at CERN (Geneva), is presented. Very high- dimensional stability, minimization of the material and ability of operating 10 years in a high radiation environment are the key design requirements. The proposed solution consists of a combination of different carbon-based materials (impregnated carbon-carbon, ultra high modulus carbon fibre composites) coupled to a thin aluminum tube to form a very light support with an integrated cooling channel. Our design has proven to successfully fulfil the requirements. The extensive prototyping and testing program to fully qualify the design and release the production are discussed.

  2. Replication of nanopits and nanopillars by roll-to-roll extrusion coating using a structured cooling roll

    DEFF Research Database (Denmark)

    Murthy, Swathi; Pranov, Henrik; Pedersen, Henrik Chresten

    2016-01-01

    This paper investigates a novel, very high throughput, roll-to-roll (R2R) process for nanostructuring of polymer foils, called R2R extrusion coating. It has the potential to accelerate the integration of nanostructured materials in consumer products for a variety of applications, including optical......, technical, and functional surfaces and devices. In roll-to-roll extrusion coating, a molten polymer film is extruded through a flat die forming a melt curtain, and then laminated onto a carrier foil. The lamination occurs as the melt curtain is pressed between a cooling roller and a counter roller....... By mounting a nanostructured metal shim on the surface of the cooling roller, the relief structure from the shim can be replicated onto a thermoplastic foil. Among the benefits of P oil, the process are availability of a wide range of commercial extruders, off-the-shelf extrusion grade polymers, functional...

  3. Role of upper-level wind shear on the structure and maintenance of derecho-producing convective systems

    Science.gov (United States)

    Coniglio, Michael Charles

    Common large-scale environments associated with the development of derecho-producing convective systems from a large number of events are identified using statistical clustering of the 500-mb geopotential heights as guidance. The majority of the events (72%) fall into three main patterns that include a well-defined upstream trough (40%), a ridge (20%), and a zonal, low-amplitude flow (12%), which is defined as an additional warm-season pattern that is not identified in past studies of derecho environments. Through an analysis of proximity soundings, discrepancies are found in both low-level and deep-tropospheric shear parameters between observations and the shear profiles considered favorable for strong, long-lived convective systems in idealized simulations. To explore the role of upper-level shear in derecho environments, a set of two-dimensional simulations of density currents within a dry, neutrally stable environment are used to examine the ability of a cold pool to lift environmental air within a vertically sheared flow. The results confirm that the addition of upper-level shear to a wind profile with weak to moderate low-level shear increases the vertical displacement of low-level parcels despite a decrease in the vertical velocity along the cold pool interface, as suggested by previous studies. Parcels that are elevated above the surface (1-2 km) overturn and are responsible for the deep lifting in the deep-shear environments. This deep overturning caused by the upper-level shear helps to maintain the tilt of the convective systems in more complex two-dimensional and three dimensional simulations. The overturning also is shown to greatly increase the size of the convective systems in the three-dimensional simulations by facilitating the initiation and maintenance of convective cells along the cold pool. When combined with estimates of the cold pool motion and the storm-relative hodograph, these results may best be used for the prediction of the demise of

  4. Transition to geostrophic convection: the role of the boundary conditions

    NARCIS (Netherlands)

    Kunnen, R.P.J.; Ostilla-Monico, Rodolfo; Poel, van der E.P.; Verzicco, R.; Lohse, D.

    2016-01-01

    Rotating Rayleigh–Bénard convection, the flow in a rotating fluid layer heated from below and cooled from above, is used to analyse the transition to the geostrophic regime of thermal convection. In the geostrophic regime, which is of direct relevance to most geo- and astrophysical flows, the system

  5. Chaotic asymmetric convection in the Bridgman-Stockbarger technique

    Science.gov (United States)

    Potts, H.; Wilcox, W. R.

    1986-01-01

    Convection was observed in naphthalene in a vertical Bridgman-Stockbarger arrangement. Differing from the assumptions of the theorists, the flow was neither steady nor axi-symmetric because of the heating and cooling conditions employed. It is suggested that such irregular convection may be common and cause compositional striations and azimuthal composition variations.

  6. A case study of microphysical structures and hydrometeor phase in convection using radar Doppler spectra at Darwin, Australia

    Science.gov (United States)

    Riihimaki, L. D.; Comstock, J. M.; Luke, E.; Thorsen, T. J.; Fu, Q.

    2017-07-01

    To understand the microphysical processes that impact diabatic heating and cloud lifetimes in convection, we need to characterize the spatial distribution of supercooled liquid water. To address this observational challenge, ground-based vertically pointing active sensors at the Darwin Atmospheric Radiation Measurement site are used to classify cloud phase within a deep convective cloud. The cloud cannot be fully observed by a lidar due to signal attenuation. Therefore, we developed an objective method for identifying hydrometeor classes, including mixed-phase conditions, using k-means clustering on parameters that describe the shape of the Doppler spectra from vertically pointing Ka-band cloud radar. This approach shows that multiple, overlapping mixed-phase layers exist within the cloud, rather than a single region of supercooled liquid. Diffusional growth calculations show that the conditions for the Wegener-Bergeron-Findeisen process exist within one of these mixed-phase microstructures.

  7. Structure of Water Mist Stream and its Impact on Cooling Efficiency of Casting Die

    Directory of Open Access Journals (Sweden)

    R. Władysiak

    2012-04-01

    Full Text Available The work is a continuation of research on the use water mist cooling in order to increase efficiency of die-casting aluminum alloys. The paper presents results of research and analysis process, spraying water and generated a stream of water mist, the effect of the type of nozzle, the nozzle size and shape of the emitting of the water mist on the wall surface of casting die on the microstructure and geometry of water mist stream and cooling efficiency. Tests were used to perform high-speed camera to record video in the visible and infrared camera. Results were used to develop a computerized image analysis and statistical analysis. The study showed that there are statistical relationships between water and air flow and geometry of the nozzle and nozzle emitting a stream of microstructure parameters of water mist and heat the incoming stream. These relationships are described mathematical models that allow you to control the generating of adequate stream of water mist and a further consequence, the cooling efficiency of casting die.

  8. RESONANCE CONTROL FOR THE COUPLED CAVITY LINAC AND DRIFT TUBE LINAC STRUCTURES OF THE SPALLATION NEUTRON SOURCE LINAC USING A CLOSED-LOOP WATER COOLING SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Bernardin, J. D. (John D.); Brown, R. L. (Richard L.); Brown, S. K. (Stanley K.); Bustos, G. R. (Gerald R.); Crow, M.L. (Martin L.); Gregory, W. S.; Hood, M. E. (Michael E.); Jurney, J. D. (James D.); Medalen, I. (Ivan); Owen, A. C. (Albert C.); Weiss, Robert E.

    2001-01-01

    The Spallation Neutron Source (SNS) is a facility being designed for scientific and industrial research and development. SNS will generate and use neutrons as a diagnostic tool for medical purposes, material science, etc. The neutrons will be produced by bombarding a heavy metal target with a high-energy beam of protons, generated and accelerated with a linear particle accelerator, or linac. The low energy end of the linac consists of two room temperature copper structures, the drift tube linac (DTL), and the coupled cavity linac (CCL). Both of these accelerating structures use large amounts of electrical energy to accelerate the protons to an energy of 185 MeV. Approximately 60-80% of the electrical energy is dissipated in the copper structure and must be removed. This is done using specifically designed water cooling passages within the linac's copper structure. Cooling water is supplied to these cooling passages by specially designed resonance control and water cooling systems.

  9. Deciphering Core Collapse Supernovae Is Convection the Key?; 1, prompt convection

    CERN Document Server

    Mezzacappa, A; Bruenn, S W; Blondin, J M; Guidry, M W; Strayer, M R; Umar, A S

    1996-01-01

    We couple two-dimensional hydrodynamics to detailed one-dimensional multigroup flux-limited diffusion neutrino transport to investigate prompt convection in core collapse supernovae. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-dimensional simulations that implement multigroup flux-limited diffusion neutrino transport and one-dimensional hydrodynamics. The development and evolution of prompt convection and its ramifications for the shock dynamics are investigated for both 15 and 25 solar mass models, representative of the two classes of stars with compact and extended iron cores, respectively. In the absence of neutrino transport, prompt convection develops and dissipates on a time scale $\\sim$15 ms for both models. Prompt convection seeds convection behind the shock, which causes distortions in the shock's sphericity, but on the average, the shock radius is not boosted significan...

  10. Heat Transfer Characteristics of Different Heat Transfer Structures in Gasification Convective Syngas Cooler%煤粉加压气化炉膜式螺旋管和蛇形管对流传热特性研究

    Institute of Scientific and Technical Information of China (English)

    赵振兴; 杨震; 刘宏; 常勇强; 曹子栋

    2011-01-01

    对煤粉加压气化炉对流段的不同换热结构进行了换热特性的实验研究,其中换热结构包括膜式螺旋管环形通道换热器和膜式蛇形管平行通道换热器,实验气体为单质气体N、He及其混合气,实验压力为0.5~3.5 MPa.为此,针对不同冲刷形式、不同气体和压力提出了换热器换热系数及其扩展的计算方法,同时给出了典型冲刷形式的对流换热的关联式和适用条件.实验研究表明:冲刷形式对换热系数有很大影响,单通道和多通道换热系数与换热面积之间呈加权平均的关系;在相同换热条件下,膜式螺旋管环形通道换热器的换热系数高于膜式蛇形管平行通道换热器.%An experiment was conducted to study the heat transfer characteristics for a convection cooling section with the different heat transfer structures at high temperature and pressure in a coal pressurized gasifier. The heat transfer structures included an annular channel heat exchanger with membrane spiral tubes and a parallel channel heat exchanger with membrane serpentine tubes. In this study, the high pressure single gas (He or N2) and mixture gas (He+N2) were used to replace the high pressure syngas, and the test pressure for each gas was from 0.5 MPa to 3MPa. The heat transfer coefficients and extension method under different working pressure, gas composition and flow forms were presented. The correlations of the typical flow forms and their applicable condition were obtained. The results show that flow form greatly influenced the heat transfer coefficient of the high pressure gas convection. The heat transfer coefficients of the single annular channel heat exchanger and multi-annular channel heat exchanger displayed the areaweighted average relation. In addition, the heat transfer capacity of the annular channel heat exchanger with membrane spiral tubes was higher than that of the parallel channel under the same heat transfer conditions.

  11. Impact of land convection on temperature diurnal variation in the tropical lower stratosphere inferred from COSMIC GPS radio occultations

    Directory of Open Access Journals (Sweden)

    S. M. Khaykin

    2013-07-01

    Full Text Available Following recent studies evidencing the influence of deep convection on the chemical composition and thermal structure of the tropical lower stratosphere, we explore its impact on the temperature diurnal variation in the upper troposphere and lower stratosphere using the high-resolution COSMIC GPS radio-occultation temperature measurements spanning from 2006 through 2011. The temperature in the lowermost stratosphere over land during summer displays a marked diurnal cycle characterized by an afternoon cooling. This diurnal cycle is shown collocated with most intense land convective areas observed by the Tropical Rainfall Measurement Mission (TRMM precipitation radar and in phase with the maximum overshooting occurrence frequency in late afternoon. Two processes potentially responsible for that are identified: (i non-migrating tides, whose physical nature is internal gravity waves, and (ii local cross-tropopause mass transport of adiabatically cooled air by overshooting turrets. Although both processes can contribute, only the lofting of adiabatically cooled air is well captured by models, making it difficult to characterize the contribution of non-migrating tides. The impact of deep convection on the temperature diurnal cycle is found larger in the southern tropics, suggesting more vigorous convection over clean rain forest continents than desert areas and polluted continents in the northern tropics.

  12. Fast cooling techniques for gravitational wave antennas

    CERN Document Server

    Furtado, S R

    2002-01-01

    The resonant-mass technique for the detection of gravitational waves may involve, in the near future, the cooling of very large masses (about 100 tons) from room temperature (300 K) to extreme cryogenic temperatures (20 mK). To cool these detectors to cryogenic temperatures an exchange gas (helium) is used, and the heat is removed from the antenna to the cold reservoir by thermal conduction and natural convection. With the current technique, cooling times of about 1 month can be obtained for cylindrical bar antennas of 2.5 tons. Should this same technique be used to cool a 100 ton spherical antenna the cooling time would be about 10 months, making the operation of these antennas impracticable. In this paper, we study the above-mentioned cooling technique and others, such as thermal switching and forced convection from room temperature to liquid nitrogen temperature (77 K) using an aluminium truncated icosahedron of 19 kg weight and 25 cm diameter.

  13. Electron cooling

    Science.gov (United States)

    Meshkov, I.; Sidorin, A.

    2004-10-01

    The brief review of the most significant and interesting achievements in electron cooling method, which took place during last two years, is presented. The description of the electron cooling facilities-storage rings and traps being in operation or under development-is given. The applications of the electron cooling method are considered. The following modern fields of the method development are discussed: crystalline beam formation, expansion into middle and high energy electron cooling (the Fermilab Recycler Electron Cooler, the BNL cooler-recuperator, cooling with circulating electron beam, the GSI project), electron cooling in traps, antihydrogen generation, electron cooling of positrons (the LEPTA project).

  14. Stochastic Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Blaskiewicz, M.

    2011-01-01

    Stochastic Cooling was invented by Simon van der Meer and was demonstrated at the CERN ISR and ICE (Initial Cooling Experiment). Operational systems were developed at Fermilab and CERN. A complete theory of cooling of unbunched beams was developed, and was applied at CERN and Fermilab. Several new and existing rings employ coasting beam cooling. Bunched beam cooling was demonstrated in ICE and has been observed in several rings designed for coasting beam cooling. High energy bunched beams have proven more difficult. Signal suppression was achieved in the Tevatron, though operational cooling was not pursued at Fermilab. Longitudinal cooling was achieved in the RHIC collider. More recently a vertical cooling system in RHIC cooled both transverse dimensions via betatron coupling.

  15. Topology optimisation for natural convection problems

    CERN Document Server

    Alexandersen, Joe; Andreasen, Casper Schousboe; Sigmund, Ole

    2014-01-01

    This paper demonstrates the application of the density-based topology optimisation approach for the design of heat sinks and micropumps based on natural convection effects. The problems are modelled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equations coupled to the convection-diffusion equation through the Boussinesq approximation. In order to facilitate topology optimisation, the Brinkman approach is taken to penalise velocities inside the solid domain and the effective thermal conductivity is interpolated in order to accommodate differences in thermal conductivity of the solid and fluid phases. The governing equations are discretised using stabilised finite elements and topology optimisation is performed for two different problems using discrete adjoint sensitivity analysis. The study shows that topology optimisation is a viable approach for designing heat sink geometries cooled by natural convection and micropumps powered by natural convection.

  16. Extra lightweight mechanical support structures with the integrated cooling system for a new generation of vertex detectors

    CERN Document Server

    Zherebchevsky, V I; Krymov, E B; Maltsev, N A; Makarov, N A; Feofilov, G A

    2014-01-01

    The performance of new extra lightweight mechanical support structures with the integrated liquid cooling system for monolithic silicon pixel detectors has been investigated. These detectors will be used to upgrade the inner tracking system in the ALICE experiment at the CERN Large Hadron Collider. The extra lightweight mechanical support structures, together with the novel pixel detectors, provide a record-breaking total radiation length of 0.3% X 0 per layer, which will make it possible to considerably extend the physical program of investigations of the quark-gluon plasma in ultra-relativistic heavy-ion collisions at the Large Hadron Collider. This is particularly important in measuring the yields of heavy-flavor hadrons and low-mass dileptons with low transverse momenta. The experimental results of the thermal tests and the comparative analysis of five samples of extra lightweight mechanical support structures for monolithic silicon pixel detectors are presented. The high efficiency of heat drain using th...

  17. CALIBRATION OF THE MIXING-LENGTH THEORY FOR CONVECTIVE WHITE DWARF ENVELOPES

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, P.-E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Ludwig, H.-G. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg (Germany); Freytag, B. [Department of Physics and Astronomy at Uppsala University, Regementsvägen 1, Box 516, SE-75120 Uppsala (Sweden); Fontaine, G.; Brassard, P. [Département de Physique, Université de Montréal, C. P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7 (Canada); Steffen, M., E-mail: tremblay@stsci.edu [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany)

    2015-02-01

    A calibration of the mixing-length parameter in the local mixing-length theory (MLT) is presented for the lower part of the convection zone in pure-hydrogen-atmosphere white dwarfs. The parameterization is performed from a comparison of three-dimensional (3D) CO5BOLD simulations with a grid of one-dimensional (1D) envelopes with a varying mixing-length parameter. In many instances, the 3D simulations are restricted to the upper part of the convection zone. The hydrodynamical calculations suggest, in those cases, that the entropy of the upflows does not change significantly from the bottom of the convection zone to regions immediately below the photosphere. We rely on this asymptotic entropy value, characteristic of the deep and adiabatically stratified layers, to calibrate 1D envelopes. The calibration encompasses the convective hydrogen-line (DA) white dwarfs in the effective temperature range 6000 ≤ T {sub eff} (K) ≤15, 000 and the surface gravity range 7.0 ≤ log g ≤ 9.0. It is established that the local MLT is unable to reproduce simultaneously the thermodynamical, flux, and dynamical properties of the 3D simulations. We therefore propose three different parameterizations for these quantities. The resulting calibration can be applied to structure and envelope calculations, in particular for pulsation, chemical diffusion, and convective mixing studies. On the other hand, convection has no effect on the white dwarf cooling rates until there is a convective coupling with the degenerate core below T {sub eff} ∼ 5000 K. In this regime, the 1D structures are insensitive to the MLT parameterization and converge to the mean 3D results, hence they remain fully appropriate for age determinations.

  18. Peltier Junction heats and cools car seat

    Energy Technology Data Exchange (ETDEWEB)

    Gottschalk, M.A.

    1994-10-10

    Electrically heated seats may soon become heated and cooled seats. The design called the CCS module exploits the heat-pump capability of a class of semiconductor thermoelectric devices (TEDs) known as Peltier Junction. Every CCS module contain two TEDs. Heating and cooling occurs through convection and conduction. The heart of the system is the thermoelectric heat pump. This is originally conceived as the sole heating/cooling options for a prototype electric vehicle.

  19. Natural convection in superposed fluid-porous layers

    CERN Document Server

    Bagchi, Aniruddha

    2013-01-01

    Natural Convection in Composite Fluid-Porous Domains provides a timely overview of the current state of understanding on the phenomenon of convection in composite fluid-porous layers. Natural convection in horizontal fluid-porous layers has received renewed attention because of engineering problems such as post-accident cooling of nuclear reactors, contaminant transport in groundwater, and convection in fibrous insulation systems. Because applications of the problem span many scientific domains, the book serves as a valuable resource for a wide audience.

  20. Measurement of the Convective Heat-Transfer Coefficient

    Science.gov (United States)

    Conti, Rosaria; Gallitto, Aurelio Agliolo; Fiordilino, Emilio

    2014-01-01

    We propose an experiment for investigating how objects cool down toward the thermal equilibrium with their surroundings. We describe the time dependence of the temperature difference of the cooling objects and the environment with an exponential decay function. By measuring the thermal constant t, we determine the convective heat-transfer…

  1. Preliminary structural design and thermo-mechanical analysis of helium cooled solid breeder blanket for Chinese Fusion Engineering Test Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Li, Min; Chen, Hongli, E-mail: hlchen1@ustc.edu.cn; Zhou, Guangming; Liu, Qianwen; Wang, Shuai; Lv, Zhongliang; Ye, Minyou

    2015-02-15

    Highlights: • A helium cooled solid breeder blanket module was designed for CFETR. • Multilayer U-shaped pebble beds were adopted in the blanket module. • Thermal and thermo-mechanical analyses were carried out under normal operating conditions. • The analysis results were found to be acceptable. - Abstract: With the aim to bridge the R&D gap between ITER and fusion power plant, the Chinese Fusion Engineering Test Reactor (CFETR) was proposed to be built in China. The mission of CFETR is to address the essential R&D issues for achieving practical fusion energy. Its blanket is required to be tritium self-sufficient. In this paper, a helium cooled solid breeder blanket adopting multilayer U-shaped pebble beds was designed and analyzed. Thermo-mechanical analysis of the first wall and side wall combined with breeder unit was carried out for normal operating steady state conditions. The results showed that the maximum temperatures of the structural material, neutron multiplier and tritium breeder pebble beds are 523 °C, 558 °C and 787 °C, respectively, which are below the corresponding limits of 550 °C, 650 °C and 920 °C. The maximum equivalent stress of the structure is under the allowable value with a margin about 14.5%.

  2. Bidispersive-inclined convection

    Science.gov (United States)

    Mulone, Giuseppe; Straughan, Brian

    2016-01-01

    A model is presented for thermal convection in an inclined layer of porous material when the medium has a bidispersive structure. Thus, there are the usual macropores which are full of a fluid, but there are also a system of micropores full of the same fluid. The model we employ is a modification of the one proposed by Nield & Kuznetsov (2006 Int. J. Heat Mass Transf. 49, 3068–3074. (doi:10.1016/j.ijheatmasstransfer.2006.02.008)), although we consider a single temperature field only. PMID:27616934

  3. The Impact on Simulated Storm Structure and Intensity of Variations in the Lifted Condensation Level and the Level of Free Convection

    Science.gov (United States)

    McCaul, Eugene W., Jr.; Cohen, Charles; Arnold, James E. (Technical Monitor)

    2001-01-01

    The sensitivities of convective storm structure and intensity to changes in the altitudes of the prestorm environmental lifted condensation level and level of free convection axe studied using a full-physics three-dimensional cloud model. Matrices of simulations are conducted for a range of LCL=LFC altitudes, using a single moderately-sheared curved hodograph trace in conjunction with 1 convective available potential energy values of either 800 or 2000 J/kg, with the matrices consisting of all four combinations of two distinct choices of buoyancy and shear profile shape. For each value of CAPE, the LCL=LFC altitudes are also allowed to vary in a series of simulations based on the most highly compressed buoyancy and shear profiles for that CAPE, with the environmental buoyancy profile shape, subcloud equivalent potential temperature, subcloud lapse rates of temperature and moisture, and wind profile held fixed. For each CAPE, one final simulation is conducted using a near optimal LFC, but a lowered LCL, with a neutrally buoyant environmental thermal profile specified in between. Results show that, for the buoyancy-starved small-CAPE environments, the simulated storms are supercells and are generally largest and most intense when LCL=LFC altitudes lie in the approximate range 1.5-2.5 km above the surface. The simulations show similar trends for the shear-starved large-CAPE environments, except that conversion from supercell to multicell morphology frequently occurs when the LCL is high. For choices of LCL=LFC height within the optimal 1.5-2.5 km range, peak storm updraft overturning efficiency may approaches unity relative to parcel theory, while for lower LCL=LFC heights, overturning efficiency is reduced significantly. The enhancements of overturning efficiency and updraft diameter with increasing LFC height are shown to be the result of systematic increases in the mean equivalent potential temperature of the updraft at cloud base. For the shear

  4. Observation of deep convection initiation from shallow convection environment

    Science.gov (United States)

    Lothon, Marie; Couvreux, Fleur; Guichard, Françoise; Campistron, Bernard; Chong, Michel; Rio, Catherine; Williams, Earle

    2010-05-01

    In the afternoon of 10 July 2006, deep convective cells initiated right in the field of view of the Massachusetts Institute Technology (MIT) C-band Doppler radar. This radar, with its 3D exploration at 10 min temporal resolution and 250 m radial resolution, allows us to track the deep convective cells and also provides clear air observations of the boundary layer structure prior to deep convection initiation. Several other observational platforms were operating then which allow us to thoroughly analyse this case: Vertically pointing aerosol lidar, W-band radar and ceilometer from the ARM Mobile Facility, along with radiosoundings and surface measurements enable us to describe the environment, from before their initiation to after the propagation of of one propagating cell that generated a circular gust front very nicely caught by the MIT radar. The systems considered here differ from the mesoscale convective systems which are often associated with African Easterly Waves, increasing CAPE and decreasing CIN. The former have smaller size, and initiate more locally, but there are numerous and still play a large role in the atmospheric circulation and scalar transport. Though, they remain a challenge to model. (See the presentation by Guichard et al. in the same session, for a model set up based on the same case, with joint single-column model and Large Eddy Simulation, which aims at better understanding and improving the parametrisation of deep convection initiation.) Based on the analysis of the observations mentioned above, we consider here the possible sources of deep convection initiation that day, which showed a typical boundary-layer growth in semi-arid environment, with isolated deep convective events.

  5. THE INFLUENCE OF THE INGOT MOLD COOLING ON THE STRUCTURE OF SILUMINA CASTINGS AK15M3 AT VERTICAL CENTRIFUGAL CASTING

    Directory of Open Access Journals (Sweden)

    V. Yu. Stecenko

    2013-01-01

    Full Text Available Influence of ways of the mold cooling on structure of castings with diameter of 135 mm from AK15M3 silumin at vertical centrifugal casting is investigated. It is established that for production of castings with diameter 135 mm from AK15M3 silumin with high mechanical and tribotechnical properties it is necessary to apply a shaped mould with water-spray cooling at expense of cooler of 0,42 m3/h.

  6. Modelling of large-scale structures arising under developed turbulent convection in a horizontal fluid layer (with application to the problem of tropical cyclone origination

    Directory of Open Access Journals (Sweden)

    G. V. Levina

    2000-01-01

    Full Text Available The work is concerned with the results of theoretical and laboratory modelling the processes of the large-scale structure generation under turbulent convection in the rotating-plane horizontal layer of an incompressible fluid with unstable stratification. The theoretical model describes three alternative ways of creating unstable stratification: a layer heating from below, a volumetric heating of a fluid with internal heat sources and combination of both factors. The analysis of the model equations show that under conditions of high intensity of the small-scale convection and low level of heat loss through the horizontal layer boundaries a long wave instability may arise. The condition for the existence of an instability and criterion identifying the threshold of its initiation have been determined. The principle of action of the discovered instability mechanism has been described. Theoretical predictions have been verified by a series of experiments on a laboratory model. The horizontal dimensions of the experimentally-obtained long-lived vortices are 4÷6 times larger than the thickness of the fluid layer. This work presents a description of the laboratory setup and experimental procedure. From the geophysical viewpoint the examined mechanism of the long wave instability is supposed to be adequate to allow a description of the initial step in the evolution of such large-scale vortices as tropical cyclones - a transition form the small-scale cumulus clouds to the state of the atmosphere involving cloud clusters (the stage of initial tropical perturbation.

  7. Simulation and Optimization of Air-Cooled PEMFC Stack for Lightweight Hybrid Vehicle Application

    Directory of Open Access Journals (Sweden)

    Jingming Liang

    2015-01-01

    Full Text Available A model of 2 kW air-cooled proton exchange membrane fuel cell (PEMFC stack has been built based upon the application of lightweight hybrid vehicle after analyzing the characteristics of heat transfer of the air-cooled stack. Different dissipating models of the air-cooled stack have been simulated and an optimal simulation model for air-cooled stack called convection heat transfer (CHT model has been figured out by applying the computational fluid dynamics (CFD software, based on which, the structure of the air-cooled stack has been optimized by adding irregular cooling fins at the end of the stack. According to the simulation result, the temperature of the stack has been equally distributed, reducing the cooling density and saving energy. Finally, the 2 kW hydrogen-air air-cooled PEMFC stack is manufactured and tested by comparing the simulation data which is to find out its operating regulations in order to further optimize its structure.

  8. Research on Cooling Effectiveness in Stepped Slot Film Cooling Vane

    Institute of Scientific and Technical Information of China (English)

    LI Yulong; WU Hong; ZHOU Feng; RONG Chengjun

    2016-01-01

    As one of the most important developments in air cooling technology for hot parts of the aero-engine,film cooling technology has been widely used.Film cooling hole structure exists mainly in areas that have high temperature,uneven cooling effectiveness issues when in actual use.The first stage turbine vanes of the aero-engine consume the largest portion of cooling air,thereby the research on reducing the amount of cooling air has the greatest potential.A new stepped slot film cooling vane with a high cooling effectiveness and a high cooling uniformity was researched initially.Through numerical methods,the affecting factors of the cooling effectiveness of a vane with the stepped slot film cooling structure were researched.This paper focuses on the cooling effectiveness and the pressure loss in different blowing ratio conditions,then the most reasonable and scientific structure parameter can be obtained by analyzing the results.The results show that 1.0 mm is the optimum slot width and 10.0 is the most reasonable blowing ratio.Under this condition,the vane achieved the best cooling result and the highest cooling effectiveness,and also retained a low pressure loss.

  9. Compactness result for periodic structures and its application to the homogenization of a diffusion-convection equation

    Directory of Open Access Journals (Sweden)

    Anvarbek M. Meirmanov

    2011-09-01

    Full Text Available We prove the strong compactness of the sequence ${c^{varepsilon}(mathbf{x},t}$ in $L_2(Omega_T$, $Omega_T={(mathbf{x},t:mathbf{x}inOmega subset mathbb{R}^3, tin(0,T}$, bounded in $W^{1,0}_2(Omega_T$ with the sequence of time derivative ${partial/partial tig(chi(mathbf{x}/varepsilon c^{varepsilon}ig}$ bounded in the space $L_2ig((0,T; W^{-1}_2(Omegaig$. As an application we consider the homogenization of a diffusion-convection equation with a sequence of divergence-free velocities ${mathbf{v}^{varepsilon}(mathbf{x},t}$ weakly convergent in $L_2(Omega_T$.

  10. Mechanisms Responsible for the Observed Thermodynamic Structure in a Convective Boundary Layer Over the Hudson Valley of New York State

    Science.gov (United States)

    Freedman, Jeffrey M.; Fitzjarrald, David R.

    2017-02-01

    We examine cases of a regional elevated mixed layer (EML) observed during the Hudson Valley Ambient Meteorology Study (HVAMS) conducted in New York State, USA in 2003. Previously observed EMLs referred to topographic domains on scales of 105 -106 km2 . Here, we present observational evidence of the mechanisms responsible for the development and maintenance of regional EMLs overlying a valley-based convective boundary layer (CBL) on much smaller spatial scales (deployed during the HVAMS, we show that cross-valley horizontal advection, along-valley channelling, and fog-induced cold-air pooling are responsible for the formation and maintenance of the EML and valley-CBL coupling over New York State's Hudson Valley. The upper layer stability of the overlying EML constrains growth of the valley CBL, and this has important implications for air dispersion, aviation interests, and fog forecasting.

  11. Application of formal optimization techniques in thermal/structural design of a heat-pipe-cooled panel for a hypersonic vehicle

    Science.gov (United States)

    Camarda, Charles J.; Riley, Michael F.

    1987-01-01

    Nonlinear mathematical programming methods are used to design a radiantly cooled and heat-pipe-cooled panel for a Mach 6.7 transport. The cooled portion of the panel is a hybrid heat-pipe/actively cooled design which uses heat pipes to transport the absorbed heat to the ends of the panel where it is removed by active cooling. The panels are optimized for minimum mass and to satisfy a set of heat-pipe, structural, geometric, and minimum-gage constraints. Two panel concepts are investigated: cylindrical heat pipes embedded in a honeycomb core and an integrated design which uses a web-core heat-pipe sandwich concept. The latter was lighter and resulted in a design which was less than 10 percent heavier than an all actively cooled concept. The heat-pipe concept, however, is redundant and can sustain a single-point failure, whereas the actively cooled concept cannot. An additional study was performed to determine the optimum number of coolant manifolds per panel for a minimum-mass design.

  12. Supernova-regulated ISM: the effects of radiative cooling and thermal conductivity on the multi-phase structure

    CERN Document Server

    Gent, Frederick; Shukurov, Anvar; Fletcher, Andrew; Sarson, Graeme R

    2010-01-01

    The hydrodynamic state of the interstellar medium (ISM) heated and randomly stirred by supernovae (SNe) is investigated. We use a three-dimensional non-ideal hydrodynamic ISM model in a domain extending 0.5 x 0.5 kpc horizontally and 2 kpc vertically to explore the relative importance of various physical and numerical effects on the multi-phase, turbulent ISM. We include both Type I and II SNe, the latter occurring only in dense regions. First we investigate the role of the thermal instability in the temperature range 300-6100 K, comparing results obtained for two different cooling functions, one susceptible to the instability, the other stable. The presence of thermal instability in the system is mainly visible as the tendency of the gas to avoid the relevant temperature range, as it quickly evolves towards either colder or warmer phases. Nevertheless, the formation of dense structures for both cooling functions appears to be dominated by expanding and colliding supernova remnants, rather than by the thermal...

  13. Enhancement of Nucleate Boiling Heat Flux on Macro/Micro-Structured Surfaces Cooled by Multiple Impinging Jets

    Science.gov (United States)

    Kugler, Scott Lee

    1997-01-01

    An experimental investigation of nucleate boiling heat transfer from modified surfaces cooled by multiple in-line impinging circular jets is reported and found to agree with single jet results. A copper block is heated from the back by two electrical arcs, and cooled on the opposite side by three identical liquid jets of distilled water at subcoolings of 25 C 50 C and 77 C and Freon 113 at 24 C subcooling. Liquid flow rates are held constant at 5, 10, and 15 GPH for each of the three jets with jet velocities ranging from 1.4 m/s to 1 1.2 m/s and jet diameters from 0.95 mm to 2.2 mm. To increase the maximum heat flux (CHF) and heat removal rate, the boiling surface was modified by both macro and micro enhancements. Macro modification consists of machined radial grooves in the boiling surface arranged in an optimally designed pattern to allow better liquid distribution along the surface. These grooves also reduce splashing of liquid droplets, and provide 'channels' to sweep away bubbles. Micro modification was achieved by flame spraying metal powder on the boiling surface, creating a porous, sintered surface. With the addition of both micro and macro structured enhancements, maximum heat flux and nucleate boiling can be enhanced by more than 200%. Examination of each surface modification separately and together indicates that at lower superheats, the micro structure provides the enhanced heat transfer by providing more nucleation sites, while for higher superheats the macro structure allows better liquid distribution and bubble removal. A correlation is presented to account for liquid subcoolings and surface enhancements, in addition to the geometrical and fluid properties previously reported in the literature.

  14. National Convective Weather Forecast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NCWF is an automatically generated depiction of: (1) current convection and (2) extrapolated signficant current convection. It is a supplement to, but does NOT...

  15. Zoned mantle convection.

    Science.gov (United States)

    Albarède, Francis; Van Der Hilst, Rob D

    2002-11-15

    We review the present state of our understanding of mantle convection with respect to geochemical and geophysical evidence and we suggest a model for mantle convection and its evolution over the Earth's history that can reconcile this evidence. Whole-mantle convection, even with material segregated within the D" region just above the core-mantle boundary, is incompatible with the budget of argon and helium and with the inventory of heat sources required by the thermal evolution of the Earth. We show that the deep-mantle composition in lithophilic incompatible elements is inconsistent with the storage of old plates of ordinary oceanic lithosphere, i.e. with the concept of a plate graveyard. Isotopic inventories indicate that the deep-mantle composition is not correctly accounted for by continental debris, primitive material or subducted slabs containing normal oceanic crust. Seismological observations have begun to hint at compositional heterogeneity in the bottom 1000 km or so of the mantle, but there is no compelling evidence in support of an interface between deep and shallow mantle at mid-depth. We suggest that in a system of thermochemical convection, lithospheric plates subduct to a depth that depends - in a complicated fashion - on their composition and thermal structure. The thermal structure of the sinking plates is primarily determined by the direction and rate of convergence, the age of the lithosphere at the trench, the sinking rate and the variation of these parameters over time (i.e. plate-tectonic history) and is not the same for all subduction systems. The sinking rate in the mantle is determined by a combination of thermal (negative) and compositional buoyancy and as regards the latter we consider in particular the effect of the loading of plates with basaltic plateaux produced by plume heads. Barren oceanic plates are relatively buoyant and may be recycled preferentially in the shallow mantle. Oceanic plateau-laden plates have a more pronounced

  16. Organised convection embedded in a large-scale flow

    Science.gov (United States)

    Naumann, Ann Kristin; Stevens, Bjorn; Hohenegger, Cathy

    2017-04-01

    In idealised simulations of radiative convective equilibrium, convection aggregates spontaneously from randomly distributed convective cells into organized mesoscale convection despite homogeneous boundary conditions. Although these simulations apply very idealised setups, the process of self-aggregation is thought to be relevant for the development of tropical convective systems. One feature that idealised simulations usually neglect is the occurrence of a large-scale background flow. In the tropics, organised convection is embedded in a large-scale circulation system, which advects convection in along-wind direction and alters near surface convergence in the convective areas. A large-scale flow also modifies the surface fluxes, which are expected to be enhanced upwind of the convective area if a large-scale flow is applied. Convective clusters that are embedded in a large-scale flow therefore experience an asymmetric component of the surface fluxes, which influences the development and the pathway of a convective cluster. In this study, we use numerical simulations with explicit convection and add a large-scale flow to the established setup of radiative convective equilibrium. We then analyse how aggregated convection evolves when being exposed to wind forcing. The simulations suggest that convective line structures are more prevalent if a large-scale flow is present and that convective clusters move considerably slower than advection by the large-scale flow would suggest. We also study the asymmetric component of convective aggregation due to enhanced surface fluxes, and discuss the pathway and speed of convective clusters as a function of the large-scale wind speed.

  17. Homogenization of the internal structures of a reactor with the cooling fluid

    Energy Technology Data Exchange (ETDEWEB)

    Robbe, M.F. [CEA Saclay, SEMT, 91 - Gif sur Yvette (France); Bliard, F. [Socotec Industrie, Service AME, 78 - Montigny le Bretonneux (France)

    2001-07-01

    To take into account the influence of a structure net among a fluid flow, without modelling exactly the structure shape, a concept of ''equivalent porosity method'' was developed. The structures are considered as solid pores inside the fluid. The structure presence is represented by three parameters: a porosity, a shape coefficient and a pressure loss coefficient. The method was studied for an Hypothetical Core Disruptive Accident in a Liquid Metal Fast Breeder Reactor, but it can be applied to any problem involving fluid flow getting through a solid net. The model was implemented in the computer code CASTEM-PLEXUS and validated on an analytical shock tube test, simulating an horizontal slice of a schematic LMFBR in case of a HCDA (bubble at high pressure, liquid sodium and internal structures of the reactor). A short parametric study shows the influence of the porosity and the structure shape on the pressure wave impacting the shock tube bottom. These results were used to simulate numerically the HCDA mechanical effects in a small scale reactor mock-up. (author)

  18. Cooling Technology for Electronic Computers

    Science.gov (United States)

    Nakayama, Wataru

    The rapid growth of data processing speed in computers has been sustained by the advances in cooling technology. This article first presents a review of the published data of heat loads in recent Japanese large-scale computers. The survey indicates that, since around 1980, the high-level integration of microelectronic circuits has brought about almost four fold increase in the power dissipation from logic chips. The integration also has invited the evolutions of multichip modules and new schemes of electronic interconnections. Forced convection air-cooling and liquid cooling coupled with thermal connectors are discussed with reference to the designs employed in actual computers. More advanced cooling schemes are also discussed. Finally, the importance of thermal environmental control of computer rooms is emphasized.

  19. A Study of Structure and Mechanism of a Meso-beta-scale Convective Vortex and Associated Heavy Rainfall in the Dabie Mountain Area Part Ⅰ: Diagnostic Analysis of the Structure

    Institute of Scientific and Technical Information of China (English)

    XU Wenhui; NI Yunqi; WANG Xiaokang; QIU Xuexing; BAO Xinghua; JIN Wenyan

    2011-01-01

    An analysis was conducted on the evolutional process of a mesoscale convective vortex (MCV) and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in different stages,by using the mesoscale reanalysis data with 3 km and 1 h resolution generated by the Local Analysis and Prediction System (LAPS) in the Southern China Heavy Rainfall Experiment.The results showed that the latent heat released by convection in the midtroposphere was the main energy source for the development of a low-level vortex.There was a positive feedback interaction between the convection and the vortex,and the evolution of the MCV was closely related to the strength of the positive interaction.The most typical characteristics of the thermal structure in different stages were that,there was a relatively thin diabatic heating layer in the midtroposphere in the formative stage; the thickness of diabatic heating layer significantly increased in the mature stage; and it almost disappeared in the decay stage.The characteristics of the dynamic structure were that,in the formative stage,there was no anticyclonic circulation at the high level; in the mature stage,an anticyclonic circulation with strong divergence was formed at the high level; in the decay stage,the anticyclonic circulation was damaged and the high-level atmosphere was in a disordered state of turbulence.Finally,the structural schematics of the MCV in the formative and mature stage were established respectively.

  20. 76 FR 43230 - National Pollutant Discharge Elimination System-Cooling Water Intake Structures at Existing...

    Science.gov (United States)

    2011-07-20

    ... Water Intake Structures at Existing Facilities and Phase I Facilities AGENCY: Environmental Protection... the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due.... Certain other material, such as copyrighted material, will be publicly available only in hard copy...

  1. An Observational Investigation of Penetrative Convection

    DEFF Research Database (Denmark)

    Jensen, Niels Otto; Lenschow, D. H.

    1978-01-01

    Data taken during the Air Mass Transformation Experiment (AMTEX) by the NCAR Electra aircraft have proven useful for investigating the structure of thermals penetrating into the turbulent inversion layer which caps the convective mixed layer. Variances, covariances, spectra and cospectra...

  2. Excited-state structure, vibrations, and nonradiative relaxation of jet-cooled 5-fluorocytosine.

    Science.gov (United States)

    Lobsiger, Simon; Trachsel, Maria A; Den, Takuya; Leutwyler, Samuel

    2014-03-20

    The S0 → S1 vibronic spectrum and S1 state nonradiative relaxation of jet-cooled keto-amino 5-fluorocytosine (5FCyt) are investigated by two-color resonant two-photon ionization spectroscopy at 0.3 and 0.05 cm(–1) resolution. The 0(0)(0) rotational band contour is polarized in-plane, implying that the electronic transition is (1)ππ*. The electronic transition dipole moment orientation and the changes of rotational constants agree closely with the SCS-CC2 calculated values for the (1)ππ* (S1) transition of 5FCyt. The spectral region from 0 to 300 cm(–1) is dominated by overtone and combination bands of the out-of-plane ν1′ (boat), ν2′ (butterfly), and ν3′ (HN–C6H twist) vibrations, implying that the pyrimidinone frame is distorted out-of-plane by the (1)ππ* excitation, in agreement with SCS-CC2 calculations. The number of vibronic bands rises strongly around +350 cm(–1); this is attributed to the (1)ππ* state barrier to planarity that corresponds to the central maximum of the double-minimum out-of-plane vibrational potentials along the ν1′, ν2′, and ν3′ coordinates, which gives rise to a high density of vibronic excitations. At +1200 cm(–1), rapid nonradiative relaxation (k(nr) ≥ 10(12) s(–1)) sets in, which we interpret as the height of the (1)ππ* state barrier in front of the lowest S1/S0 conical intersection. This barrier in 5FCyt is 3 times higher than that in cytosine. The lifetimes of the ν′ = 0, 2ν1′, 2ν2′, 2ν1′ + 2ν2′, 4ν2′, and 2ν1′ + 4ν2′ levels are determined from Lorentzian widths fitted to the rotational band contours and are τ ≥ 75 ps for ν′ = 0, decreasing to τ ≥ 55 ps at the 2ν1′ + 4ν2′ level at +234 cm(–1). These gas-phase lifetimes are twice those of S1 state cytosine and 10–100 times those of the other canonical nucleobases in the gas phase. On the other hand, the 5FCyt gas-phase lifetime is close to the 73 ps lifetime in room-temperature solvents. This lack of

  3. The excited-state structure, vibrations, lifetimes, and nonradiative dynamics of jet-cooled 1-methylcytosine

    Science.gov (United States)

    Trachsel, Maria A.; Wiedmer, Timo; Blaser, Susan; Frey, Hans-Martin; Li, Quansong; Ruiz-Barragan, Sergi; Blancafort, Lluís; Leutwyler, Samuel

    2016-10-01

    We have investigated the S0 → S1 UV vibronic spectrum and time-resolved S1 state dynamics of jet-cooled amino-keto 1-methylcytosine (1MCyt) using two-color resonant two-photon ionization, UV/UV holeburning and depletion spectroscopies, as well as nanosecond and picosecond time-resolved pump/delayed ionization measurements. The experimental study is complemented with spin-component-scaled second-order coupled-cluster and multistate complete active space second order perturbation ab initio calculations. Above the weak electronic origin of 1MCyt at 31 852 cm-1 about 20 intense vibronic bands are observed. These are interpreted as methyl group torsional transitions coupled to out-of-plane ring vibrations, in agreement with the methyl group rotation and out-of-plane distortions upon 1ππ∗ excitation predicted by the calculations. The methyl torsion and ν1 ' (butterfly) vibrations are strongly coupled, in the S1 state. The S0 → S1 vibronic spectrum breaks off at a vibrational excess energy Eexc ˜ 500 cm-1, indicating that a barrier in front of the ethylene-type S1⇝S0 conical intersection is exceeded, which is calculated to lie at Eexc = 366 cm-1. The S1⇝S0 internal conversion rate constant increases from kIC = 2 ṡ 109 s-1 near the S1(v = 0) level to 1 ṡ 1011 s-1 at Eexc = 516 cm-1. The 1ππ∗ state of 1MCyt also relaxes into the lower-lying triplet T1 (3ππ∗) state by intersystem crossing (ISC); the calculated spin-orbit coupling (SOC) value is 2.4 cm-1. The ISC rate constant is 10-100 times lower than kIC; it increases from kISC = 2 ṡ 108 s-1 near S1(v = 0) to kISC = 2 ṡ 109 s-1 at Eexc = 516 cm-1. The T1 state energy is determined from the onset of the time-delayed photoionization efficiency curve as 25 600 ± 500 cm-1. The T2 (3nπ∗) state lies >1500 cm-1 above S1(v = 0), so S1⇝T2 ISC cannot occur, despite the large SOC parameter of 10.6 cm-1. An upper limit to the adiabatic ionization energy of 1MCyt is determined as 8.41 ± 0.02 e

  4. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Andreasen, Casper Schousboe; Aage, Niels

    conduction governs in the solid parts of the design domain and couples to convection-dominated heat transfer to a surrounding fluid. Both loosely coupled and tightly coupled problems are considered. The loosely coupled problems are convection-diffusion problems, based on an advective velocity field from......The work focuses on applying topology optimisation to forced and natural convection problems in fluid dynamics and conjugate (fluid-structure) heat transfer. To the authors' knowledge, topology optimisation has not yet been applied to natural convection flow problems in the published literature...... and the current work is thus seen as contributing new results to the field. In the literature, most works on the topology optimisation of weakly coupled convection-diffusion problems focus on the temperature distribution of the fluid, but a selection of notable exceptions also focusing on the temperature...

  5. Convective scale structure and evolution of a squall line observed by C-band dual Doppler radar in an arid region of northwestern China

    Science.gov (United States)

    Liu, Liping; Zhuang, Wei; Zhang, Pengfei; Mu, Rong

    2010-09-01

    A long-lived and loosely organized squall line moved rapidly across Ürümqi, the capital city of Xinjiang Uygur Autonomous Region of China on 26 June 2005, generating hail and strong winds. The squall line was observed by a dual Doppler radar system in a field experiment conducted in 2004 and 2005 by the Chinese Academy of Meteorological Sciences and the local meteorological bureau in northwestern China. The 3D wind fields within the squall line were retrieved through dual Doppler analyses and a variational Doppler radar analysis system (VDRAS). The formation and structure of the squall line as well as the genesis and evolution of embedded convective cells were investigated. During its life period, the squall line consisted of six storm cells extending about 100 km in length, and produced hail of about 25 mm in diameter and strong surface winds up to 11 m s-1. Radar observations revealed a broad region of stratiform rain in a meso- β cyclone, with the squall line located to the west of this. Two meso- γ scale vortices were found within the squall line. Compared to typical squall lines in moist regions, such as Guangdong Province and Shanghai, which tend to be around 300-400 km in length, have echo tops of 17-19 km, and produce maximum surface winds of about 25 m s-1 and temperature variations of about 8°C this squall line system had weaker maximum reflectivity (55 dB Z), a lower echo top (13 km) and smaller extension (about 100 km), relatively little stratiform rainfall preceding the convective line, and a similar moving speed and temperature variation at the surface.

  6. Simulation of Impinging Cooling Performance with Pin Fins and Mist Cooling Adopted in a Simplified Gas Turbine Transition Piece

    Directory of Open Access Journals (Sweden)

    Tao Xu

    2014-01-01

    Full Text Available The gas turbine transition piece was simplified to a one-four cylinder double chamber model with a single row of impinging holes in the outer wall. Heat transfer augmentation in the coolant chamber was achieved through the use of pin fin structure and mist cooling, which could increase the turbulence and heat transfer efficiency. The present research is focused on heat transfer and pressure characteristics of the impinging cooling in the coolant chamber using FLUENT software. With the given diameter of impinging hole, pin fin diameter ratios D/d have been numerically studied in ranges from 1 to 2. Three different detached L were simulated. The impinging cooling performance in all cases was compared between single-phase and two-phase (imported appropriate mist flow in the coolant chamber. All the simulation results reveal that the factors of L and D/d have significant effects on the convective heat transfer. After the pin fin structure was taken, the resulting temperature decrease of 38.77 K at most compared with the result of structure without pin fins. And with the mist injecting into the cooling chamber, the area weighted average temperature got a lower value without excess pressure loss, which could satisfy the more stringent requirements in engineering.

  7. Basics of lava-lamp convection

    Science.gov (United States)

    Gyüre, Balázs; Jánosi, Imre M.

    2009-10-01

    Laboratory experiments are reported in an immiscible two-fluid system, where thermal convection is initiated by heating at the bottom and cooling at the top. The lava-lamp regime is characterized by a robust periodic exchange process where warm blobs rise from the bottom, attach to the top surface for a while, then cold blobs sink down again. Immiscibility allows to reach real steady (dynamical equilibrium) states which can be sustained for several days. Two modes of lava-lamp convection could be identified by recording and evaluating temperature time series at the bottom and at the top of the container: a “slow” mode is determined by an effective heat transport speed at a given temperature gradient, while a second mode of constant periodicity is viscosity limited. Contrasting of laboratory and geophysical observations yields the conclusion that the frequently suggested lava-lamp analogy fails for the accepted models of mantle convection.

  8. On the convective overstability in protoplanetary discs

    CERN Document Server

    Latter, Henrik

    2015-01-01

    This paper explores the driving of low-level hydrodynamical activity in protoplanetary-disc dead zones. A small adverse radial entropy gradient, ordinarily stabilised by rotation, excites oscillatory convection (`convective overstability') when thermal diffusion, or cooling, is neither too strong nor too weak. I revisit the linear theory of the instability, discuss its prevalence in protoplanetary discs, and show that unstable modes are exact nonlinear solutions in the local Boussinesq limit. Overstable modes cannot grow indefinitely, however, as they are subject to a secondary parametric instability that limits their amplitudes to relatively low levels. If parasites set the saturation level of the ensuing turbulence then the convective overstability is probably too weak to drive significant angular momentum transport or to generate vortices. But I also discuss an alternative, and far more vigorous, saturation route that generates radial `layers' or `zonal flows' (witnessed also in semiconvection). Numerical ...

  9. Convection pump and method of operation

    Energy Technology Data Exchange (ETDEWEB)

    Steinhour, Leif Alexi

    2017-07-11

    This disclosure provides systems, methods, and apparatus related to a convection pump. In one aspect, an apparatus includes a chamber, the chamber having an inlet at a first end of the chamber and an outlet at a second end of the chamber. The chamber further has a first surface and a second surface, the first surface being opposite to the second surface. A baffle having a substantially helical shape is disposed inside the chamber. A heating device is configured to heat the first surface of the chamber. A cooling device is configured to cool the second surface of the chamber.

  10. Transient heat transfer behavior of water spray evaporative cooling on a stainless steel cylinder with structured surface for safety design application in high temperature scenario

    Science.gov (United States)

    Aamir, Muhammad; Liao, Qiang; Hong, Wang; Xun, Zhu; Song, Sihong; Sajid, Muhammad

    2017-02-01

    High heat transfer performance of spray cooling on structured surface might be an additional measure to increase the safety of an installation against any threat caused by rapid increase in the temperature. The purpose of present experimental study is to explore heat transfer performance of structured surface under different spray conditions and surface temperatures. Two cylindrical stainless steel samples were used, one with pyramid pins structured surface and other with smooth surface. Surface heat flux of 3.60, 3.46, 3.93 and 4.91 MW/m2 are estimated for sample initial average temperature of 600, 700, 800 and 900 °C, respectively for an inlet pressure of 1.0 MPa. A maximum cooling rate of 507 °C/s was estimated for an inlet pressure of 0.7 MPa at 900 °C for structured surface while for smooth surface maximum cooling rate of 356 °C/s was attained at 1.0 MPa for 700 °C. Structured surface performed better to exchange heat during spray cooling at initial sample temperature of 900 °C with a relative increase in surface heat flux by factor of 1.9, 1.56, 1.66 and 1.74 relative to smooth surface, for inlet pressure of 0.4, 0.7, 1.0 and 1.3 MPa, respectively. For smooth surface, a decreasing trend in estimated heat flux is observed, when initial sample temperature was increased from 600 to 900 °C. Temperature-based function specification method was utilized to estimate surface heat flux and surface temperature. Limited published work is available about the application of structured surface spray cooling techniques for safety of stainless steel structures at very high temperature scenario such as nuclear safety vessel and liquid natural gas storage tanks.

  11. Transient heat transfer behavior of water spray evaporative cooling on a stainless steel cylinder with structured surface for safety design application in high temperature scenario

    Science.gov (United States)

    Aamir, Muhammad; Liao, Qiang; Hong, Wang; Xun, Zhu; Song, Sihong; Sajid, Muhammad

    2016-05-01

    High heat transfer performance of spray cooling on structured surface might be an additional measure to increase the safety of an installation against any threat caused by rapid increase in the temperature. The purpose of present experimental study is to explore heat transfer performance of structured surface under different spray conditions and surface temperatures. Two cylindrical stainless steel samples were used, one with pyramid pins structured surface and other with smooth surface. Surface heat flux of 3.60, 3.46, 3.93 and 4.91 MW/m2 are estimated for sample initial average temperature of 600, 700, 800 and 900 °C, respectively for an inlet pressure of 1.0 MPa. A maximum cooling rate of 507 °C/s was estimated for an inlet pressure of 0.7 MPa at 900 °C for structured surface while for smooth surface maximum cooling rate of 356 °C/s was attained at 1.0 MPa for 700 °C. Structured surface performed better to exchange heat during spray cooling at initial sample temperature of 900 °C with a relative increase in surface heat flux by factor of 1.9, 1.56, 1.66 and 1.74 relative to smooth surface, for inlet pressure of 0.4, 0.7, 1.0 and 1.3 MPa, respectively. For smooth surface, a decreasing trend in estimated heat flux is observed, when initial sample temperature was increased from 600 to 900 °C. Temperature-based function specification method was utilized to estimate surface heat flux and surface temperature. Limited published work is available about the application of structured surface spray cooling techniques for safety of stainless steel structures at very high temperature scenario such as nuclear safety vessel and liquid natural gas storage tanks.

  12. Theoretical electronic structure of the molecule SrCl for the feasibility of laser cooling

    Science.gov (United States)

    Rafei, B.; Younes, G.; Korek, M.

    2017-07-01

    Electronic structure of the molecule SrCl has been investigated by employing the ab initio methods CASSCF/MRCI+Q with Davidson correction in the representation 2s+1Λ±, neglecting spin-orbit effects, and using the computational program Molpro. The potential energy curves of the low-lying doublet and quartet electronic states have been investigated. The harmonic vibrational wave number ωe, the relative electronic energy Te, referred to the ground state, the rotational constant Be and the equilibrium internuclear distance Re, have been calculated for the investigated electronic states. Moreover, the static dipolar moments have been determined in term of the internuclear distance Re.

  13. Natural convective heat transfer from square cylinder

    Science.gov (United States)

    Novomestský, Marcel; Smatanová, Helena; Kapjor, Andrej

    2016-06-01

    This article is concerned with natural convective heat transfer from square cylinder mounted on a plane adiabatic base, the cylinders having an exposed cylinder surface according to different horizontal angle. The cylinder receives heat from a radiating heater which results in a buoyant flow. There are many industrial applications, including refrigeration, ventilation and the cooling of electrical components, for which the present study may be applicable

  14. Improved solar models constructed with a formulation of convection for stellar structure and evolution calculations without the mixing-length theory approximations

    Science.gov (United States)

    Lydon, Thomas J.; Fox, Peter A.; Sofia, Sabatino

    1993-01-01

    We have updated a previous attempt to incorporate within a solar model a treatment of convection based upon numerical simulations of convection rather than mixing-length theory (MLT). We have modified our formulation of convection for a better treatment of the kinetic energy flux. Our solar model has been updated to include a complete range of OPAL opacities, the Debye-Hueckel correction to the equation of state, helium diffusion due to gravitational settling, and atmospheres by Kurucz. We construct a series of models using both MLT and our revised formulation of convection and the compared results to measurements of the solar radius, the solar luminosity, and the depth of the solar convection zone as inferred from helioseismology. We find X(solar) = 0.702 +/- 0.005, Y(solar) = 0.278 +/- 0.005, and Z(solar) = 0.0193 +/- 0.0005.

  15. Convective Regimes in Crystallizing Basaltic Magma Chambers

    Science.gov (United States)

    Gilbert, A. J.; Neufeld, J. A.; Holness, M. B.

    2015-12-01

    Cooling through the chamber walls drives crystallisation in crustal magma chambers, resulting in a cumulate pile on the floor and mushy regions at the walls and roof. The liquid in many magma chambers, either the bulk magma or the interstitial liquid in the mushy regions, may convect, driven either thermally, due to cooling, or compositionally, due to fractional crystallization. We have constructed a regime diagram of the possible convective modes in a system containing a basal mushy layer. These modes depend on the large-scale buoyancy forcing characterised by a global Rayleigh number and the proportion of the chamber height constituting the basal mushy region. We have tested this regime diagram using an analogue experimental system composed of a fluid layer overlying a pile of almost neutrally buoyant inert particles. Convection in this system is driven thermally, simulating magma convection above and within a porous cumulate pile. We observe a range of possible convective regimes, enabling us to produce a regime diagram. In addition to modes characterised by convection of the bulk and interstitial fluid, we also observe a series of regimes where the crystal pile is mobilised by fluid motions. These regimes feature saltation and scouring of the crystal pile by convection in the bulk fluid at moderate Rayleigh numbers, and large crystal-rich fountains at high Rayleigh numbers. For even larger Rayleigh numbers the entire crystal pile is mobilised in what we call the snowglobe regime. The observed mobilisation regimes may be applicable to basaltic magma chambers. Plagioclase in basal cumulates crystallised from a dense magma may be a result of crystal mobilisation from a plagioclase-rich roof mush. Compositional convection within such a mush could result in disaggregation, enabling the buoyant plagioclase to be entrained in relatively dense descending liquid plumes and brought to the floor. The phenocryst load in porphyritic lavas is often interpreted as a

  16. Finite element methodology for transient conduction/forced-convection thermal analysis

    Science.gov (United States)

    Thornton, E. A.; Wieting, A. R.

    1979-01-01

    Finite element methodology for steady state thermal analysis of convectively cooled structures has been extended for transient analysis. The finite elements are based on representing the fluid passages by fluid bulk-temperature nodes and fluid-solid interface nodes. The formulation of the finite element equations for a typical flow passage is based on the weighted residual method with upwind weighting functions. Computer implementation of the convective finite element methodology using explicit and implicit time integration algorithms is described. Accuracy and efficiency of the methodology is evaluated by comparisons with analytical solutions and finite-difference lumped-parameter analyses. The comparative analyses demonstrate that finite element conduction/conduction methodology may be used to predict transient temperatures with an accuracy equal or superior to the lumped-parameter finite-difference method.

  17. Lithospheric cooling as a basin forming mechanism within accretionary crust.

    Science.gov (United States)

    Holt, P. J.; Allen, M.; van Hunen, J.; Björnseth, H. M.

    2009-04-01

    Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, lithospheric stretching, lithospheric cooling following rifting and, possibly, dynamic topography. In this work forward models have been used to investigate lithospheric growth due to cooling beneath accretionary crust, as a new basin forming mechanism. Accretionary crust is formed from collision of island arcs, accretionary complexes and fragments of reworked older crust at subduction zones, and therefore has thin lithosphere due to melting and increased convection. This is modeled using a 1D infinite half space cooling model similar to lithospheric cooling models for the oceans. The crustal composition and structure used in the models has been varied around average values of accretionary crust to represent the heterogeneity of accretionary crust. The initial mantle lithosphere thickness used in the model was 20 km. The model then allows the lithosphere to thicken as it cools and calculates the subsidence isostatically. The model produces sediment loaded basins of 2-7 km for the various crustal structures over 250 Myrs. Water-loaded tectonic subsidence curves from the forward models were compared to tectonic subsidence curves produced from backstripping wells from the Kufrah and Ghadames basins, located on the accretionary crust of North Africa. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. This shows that lithospheric cooling provides a good method for producing large basins with prolonged subsidence in accretionary crust without the need for initial extension.

  18. Simulation and performance enhancement of the air cooling system in a DC/AC power converter station

    Energy Technology Data Exchange (ETDEWEB)

    Lozowy, R.; El-Shaboury, A.; Soliman, H.; Ormiston, S. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Mechanical and Manufacturing Engineering

    2010-07-01

    This study analyzed the flow structure and heat transfer in a large 3-dimensional domain with turbulence, mixed convection, an impinging jet, and flow over heated blocks. The objective was to better understand turbulent mixed-convection cooling of heat-generating bodies in 3-dimensional enclosures, which is important to industry. The cooling of 2 thyristor valve halls was simulated. Each valve hall housed 3 towers that contained electronics used in DC/AC power conversion. The simulation results included the magnitudes of the net air flows for all the inter-block gaps and the maximum temperature in each gap. A parametric study was also performed to investigate the effects of the air inlet location, size and aspect ratio. The effects of the air injection angle on cooling effectiveness was also examined. The study showed that for fixed inlet mass flow rate, significant improvement in the cooling effectiveness can be obtained by changing the injection angle of the inlet air jet, the location of the inlet grill, or the size of the inlet grill. It was concluded that these study results may be relevant to other applications, such as the design of power transformers, the design of cooling systems for spent nuclear fuel and computer server cooling racks. 13 refs., 12 figs.

  19. Passive low energy cooling of buildings

    CERN Document Server

    Givoni, Baruch

    1994-01-01

    A practical sourcebook for building designers, providing comprehensive discussion of the impact of basic architectural choices on cooling efficiency, including the layout and orientation of the structure, window size and shading, exterior color, and even the use of plantings around the site. All major varieties of passive cooling systems are presented, with extensive analysis of performance in different types of buildings and in different climates: ventilation; radiant cooling; evaporative cooling; soil cooling; and cooling of outdoor spaces.

  20. Danish Cool

    DEFF Research Database (Denmark)

    Toft, Anne Elisabeth

    2016-01-01

    Danish Cool. Keld Helmer-Petersen, Photography and the Photobook Handout exhibition text in English and Chinese by Anne Elisabeth Toft, Curator The exhibition Danish Cool. Keld Helmer-Petersen, Photography and the Photobook presents the ground-breaking work of late Danish photographer Keld Helmer...

  1. 核电循环泵轴承冷却风扇结构及其流场分析%Structure and Flow Field Analysis of Bearing Cooling Fans of the Circulating Cooling Water Pump in a Nuclear Power Plant

    Institute of Scientific and Technical Information of China (English)

    吴明哲; 王晓冬; 孙德臣

    2016-01-01

    The circulating cooling water pump in a nuclear power plant operates in a high temperature environment,and the pump bearing receives a large amount of heat load,so the work reliability is of great importance.To reduce the bearing’s working temperature and ensure its safe operation,a cooling device should be installed in the pump system.The structure of the bearing’s axial flow cooling fan in the pump was proposed,and the optimum design method of the bearing’s axial flow cooling fan in the pump was established.For the fan blades,the optimized calculation using BFGS algorithm was proceeded.A simulation verification of the system was proposed by using FLUENT,whose results showed that the design method is suitable for the bearing’s axial flow cooling fan design in circulating cooling water pumps in a nuclear power plant.%核电站冷却水循环泵在高温环境下工作,泵轴承受到很大的热负载,其工作可靠性至关重要。为降低轴承工作温度、保证轴承安全工作,在泵轴系统上设置了冷却装置。提出了泵轴承冷却用轴流式风扇的结构,建立了风扇结构的 BFGS 优化计算方法,采用计算流体力学软件 FLUENT 对风扇流场进行了数值分析。数值模拟结果表明,基于 BFGS 设计方法得到的冷却风扇性能有较好的设计计算精度,能够满足核电站冷却水循环泵轴承冷却的要求,该计算方法方便可行。

  2. Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets

    Directory of Open Access Journals (Sweden)

    C. E. Valladares

    Full Text Available We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two different types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The first event consisted of the passage of traveling convection vortices (TCV. The other event occurred in association with the development of large plasma jets (LPJ embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also confirmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O+ recombination due to an elevated Ti, which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km longitudinal extension and were 200-300 km in width. They were seen principally with the Sondrestrom, and SuperDARN radars. Enhanced ion temperature (Ti was also observed by the Sondrestrom and EISCAT radars. These channels of high Ti were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma flow is important to define the

  3. Active Cooling Of A Mobile Phone Handset

    OpenAIRE

    Grimes, Ronan; WALSH, EDMOND; Walsh, Pat

    2010-01-01

    Abstract Power dissipation levels in mobile phones continue to increase due to gaming, higher power applications, and increased functionality associated with the internet. The current cooling methodologies of natural convection and radiation limit the power dissipation within a mobile phone to between 1-2 W depending on size. As power dissipation levels increase, products such as mobile phones will require active cooling to ensure that the devices operate within an acceptable tempe...

  4. Using Jupiter's gravitational field to probe the Jovian convective dynamo.

    Science.gov (United States)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2016-03-23

    Convective motion in the deep metallic hydrogen region of Jupiter is believed to generate its magnetic field, the strongest in the solar system. The amplitude, structure and depth of the convective motion are unknown. A promising way of probing the Jovian convective dynamo is to measure its effect on the external gravitational field, a task to be soon undertaken by the Juno spacecraft. We calculate the gravitational signature of non-axisymmetric convective motion in the Jovian metallic hydrogen region and show that with sufficiently accurate measurements it can reveal the nature of the deep convection.

  5. Scaling and universality in turbulent convection.

    Science.gov (United States)

    Celani, Antonio; Matsumoto, Takeshi; Mazzino, Andrea; Vergassola, Massimo

    2002-02-01

    Anomalous correlation functions of the temperature field in two-dimensional turbulent convection are shown to be universal with respect to the choice of external sources. Moreover, they are equal to the anomalous correlations of the concentration field of a passive tracer advected by the convective flow itself. The statistics of velocity differences is found to be universal, self-similar, and close to Gaussian. These results point to the conclusion that temperature intermittency in two-dimensional turbulent convection may be traced back to the existence of statistically preserved structures, as it is in passive scalar turbulence.

  6. Impact of cooling condition on the crystal structure and surface quality of preferred c-axis-oriented AIN films for SAW devices

    Institute of Scientific and Technical Information of China (English)

    ZHANG Geng-yu; YANG Bao-he; ZHAO Jian; LI Cui-ping; LI Ming-ji

    2011-01-01

    AIN films with preferred c-axis orientation are deposited on Si substrates using the radio frequency (RF) magnetron sputtering method. The post-processing is carried out under the cooling conditions including high vacuum, low vacuum under deposition gas ambient and low vacuum under dynamic N2 ambient. Structures and morphologies of the films are analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM). The hardness and Young's modulus are investigated by the nanoindenter. The experimental results indicate that the (100) and (110) peak intensities decrease in the XRD spectra and the root-mean-square of roughness (Rrms) of the film decreases gradually with the increase of the cooling rate. The maximum values of the hardness and Young's modulus are obtained by cooling in low vacuum under deposition gas ambient. The reason for orientation variation of the films is explained from the perspective of the Al-N bond formation.

  7. Thermal study of the structure of an internal combustion engine and assessment of cooling system efficiency by a numerical tridimensional simulation

    Energy Technology Data Exchange (ETDEWEB)

    Lagasse, J.P.; Rossi, F.N. (Regie Nationale des Usines Renault 92 - Boulogne (FR))

    1989-01-01

    This paper proposes a calculation tool to evaluate the thermal field of the structure of an internal combustion engine. For this purpose a calculation procedure has been devised to take into account the thermal exchanges with the cooling fluid, the gases taking part to the combustion, the exchanges with the environment under the hood, the lubrificating liquid. The particularity of our study is to model with precision the action of the cooling fluid by solving the tridimensional thermo-hydraulic problem. This enables to evaluate quantitatively the efficiency of the cooling system and the influence of some geometrical modifications. We discuss the case of the housing of a car diesel-engine in using simultaneously an industrial thermo-hydraulic finite elements software (developed by C.E.A.) and a combustion specific one-dimensional software.

  8. Discussion on Calculation of Structure Stability of Super Large Cooling Tower%超大型冷却塔结构稳定性计算的探讨

    Institute of Scientific and Technical Information of China (English)

    董胜宪; 戴永志

    2014-01-01

    Hyperbolic natural draft cooling tower is an important project in construction of electricity, with power construction in China's booming, stand-alone power plants installed capacity increased, cooling tower of power plant have gone from cooling tower of large and medium to very large cooling towers. Very large cooling tower structure stability already mentioned work on our agenda, should be a matter of attention.%双曲线自然通风冷却塔是电力建设中的一项重要工程,随着我国电力建设事业的蓬勃发展,发电厂单机装机容量的增大,电厂内的冷却塔已从过去的大中型冷却塔转为超大型冷却塔。超大型冷却塔结构稳定性工作已提到我们的议事日程上,应该引起各方面的重视。

  9. Simulation study on the formation and transition properties of cluster structures in liquid metals during rapid cooling processes

    Institute of Scientific and Technical Information of China (English)

    郑采星; 刘让苏; 董科军; 彭平; 刘海蓉; 徐仲榆; 卢小勇

    2002-01-01

    For the first time, a molecular dynamics simulation study has been performed for a liquid metal system consisting of 50000 atoms to deeply investigate the transitions of microstructure configurations dudng the rapid cooling processes. Especially, the cluster-type index method has been adopted to analyze the transforming and evolving processes of clusters and cluster configurations from liquid metal atoms. It has been found that the bigger cluster configurations in the system are formed by means of connecting some small clusters (they are combined by several smaller clusters), and not taken on the multi-shells configuration accumulated with an atom as the center and the surrounding atoms arranged according to some fixed pattern. With the decrease in temperature, the probability of repetitive appearance for clusters increases largely, which reveals that clusters are indeed possessing a certain relative stability and continuity (namely hereditary effect). These results will give us an important enlightenment to understand not only the forming mechanisms and microscopic processes of the short-order sections and disorder sparse sections in amorphous structures but also the freezing processes of liquid metals.``

  10. Steel Structure Installation Construction of Air Cooling Platform%空冷平台钢结构安装施工

    Institute of Scientific and Technical Information of China (English)

    王俊杰

    2011-01-01

    China Power Investment Sinkiang Wusu Thermal Power Plant Stage I(2×300MW)Unit Project # I Air Cooling Platform adopts steel truss structure .Steel truss has the characteristics of great span, high section height, big weight and the like.Integral installation technique of long span steel truss ,construction process,lifting order,quality and safety control measures are introduced aiming at difficulties for the project constuction.The project schedule,quality and safety are ensured due to appropriate measure and reasonable organization.%中电投新疆乌苏热电厂一期(2×300MW)机组工程#1空冷平台采用钢桁架结构.铜桁架具有跨度大、截面高度高、重量大等特点.针对工程施工难点,介绍大跨度钢桁架整片安装技术、施工工艺流程、吊装顺序、质量和安全控制措施.由于措施得当,组织合理,保证了工程进度,质量和安全.

  11. Irreversible structure change of the as prepared FeMnP{sub 1−x}Si{sub x}-structure on the initial cooling through the curie temperature

    Energy Technology Data Exchange (ETDEWEB)

    Höglin, Viktor, E-mail: viktor.hoglin@kemi.uu.se [Department of Chemistry – Ångström Laboratory, Box 538, 751 21 Uppsala (Sweden); Cedervall, Johan [Department of Chemistry – Ångström Laboratory, Box 538, 751 21 Uppsala (Sweden); Andersson, Mikael Svante; Sarkar, Tapati; Nordblad, Per [Department of Engineering Sciences, Solid State Physics, Box 534, 751 21 Uppsala (Sweden); Sahlberg, Martin [Department of Chemistry – Ångström Laboratory, Box 538, 751 21 Uppsala (Sweden)

    2015-01-15

    FeMnP{sub 0.75}Si{sub 0.25} experiences a first order para- to ferromagnetic transition at about 200 K. In common with some other alloy compositions crystallizing in the Fe{sub 2}P structure, the magnetic transition of the as prepared alloy occurs at a lower temperature than on subsequent cooling events. This virgin effect is found to be accompanied by a magnetostrictively induced irreversible structure change that persists on succeeding cooling heating cycles. These findings provide means to understand and control the thermal hysteresis of the (Fe{sub 1−x}Mn{sub x}){sub 2}P{sub 1−y}Si{sub y} alloy system which is a promising material class for use in magnetocaloric refrigerators. - Highlights: • FeMnP{sub 1−x}Si{sub x} exhibits a first order phase transition at the Curie temperature (T{sub c}). • The lattice parameters exhibit a discontinuous change at the transition. • The structure is permanently altered by the initial cooling through T{sub c}. • The transition temperature on cooling is enhanced by initial cooling. • Subsequent cooling/heating does not cause further changes of T{sub c}.

  12. Experimental investigations on active cooling thermal protection structure of hydrocarbon-fueled scramjet combustor in arc heated facility

    Science.gov (United States)

    Jianqiang, Tu; Jinlong, Peng; Xianning, Yang; Lianzhong, Chen

    2016-10-01

    The active cooling thermal protection technology is the efficient method to resolve the long-duration work and reusable problems of hydrocarbon-fueled scramjet combustor, where worst thermo-mechanical loads occur. The fuel is passed through coolant channels adjacent to the heated surfaces to absorb heat from the heating exchanger panels, prior to injection into the combustor. The heating exchanger both cooled down the wall temperature of the combustor wall and heats and cracks the hydrocarbon fuel inside the panel to permit an easier combustion and satisfying combustion efficiency. The subscale active cooling metallic panels, with dimensions of 100×100 mm and different coolant channel sizes, have been tested under typical combustion thermal environment produced by arc heated Turbulent Flow Duct (TFD). The heat exchange ability of different coolant channel sizes has been obtained. The big-scale active cooling metallic panel, with dimensions of 100 × 750 mm and the coolant channel sizes of better heating exchange performance, has been made and tested in the big-scale arc heated TFD facility. The test results show that the local superheated ablation is easy to happen for the cooling fuel assigned asymmetrically in the bigscale active cooling metallic panel, and the cooling fuel rate can reduce 8%˜10% after spraying the Thermal Barrier Coating (TBC) in the heating surface.

  13. Primary Issues of Mixed Convection Heat Transfer Phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Chae, Myeong-Seon; Chung, Bum-Jin [Kyung Hee University, Yongin (Korea, Republic of)

    2015-10-15

    The computer code analyzing the system operating and transient behavior must distinguish flow conditions involved with convective heat transfer flow regimes. And the proper correlations must be supplied to those flow regimes. However the existing safety analysis codes are focused on the Light Water Reactor and they are skeptical to be applied to the GCRs (Gas Cooled Reactors). One of the technical issues raise by the development of the VHTR is the mixed convection, which occur when the driving forces of both forced and natural convection are of comparable magnitudes. It can be encountered as in channel of the stacked with fuel elements and a decay heat removal system and in VHTR. The mixed convection is not intermediate phenomena with natural convection and forced convection but independent complicated phenomena. Therefore, many researchers have been studied and some primary issues were propounded for phenomena mixed convection. This paper is to discuss some problems identified through reviewing the papers for mixed convection phenomena. And primary issues of mixed convection heat transfer were proposed respect to thermal hydraulic problems for VHTR. The VHTR thermal hydraulic study requires an indepth study of the mixed convection phenomena. In this study we reviewed the classical flow regime map of Metais and Eckert and derived further issues to be considered. The following issues were raised: (1) Buoyancy aided an opposed flows were not differentiated and plotted in a map. (2) Experimental results for UWT and UHF condition were also plotted in the same map without differentiation. (3) The buoyancy coefficient was not generalized for correlating with buoyancy coefficient. (4) The phenomenon analysis for laminarization and returbulization as buoyancy effects in turbulent mixed convection was not established. (5) The defining to transition in mixed convection regime was difficult.

  14. Structure formation in sugar containing pectin gels - influence of tartaric acid content (pH) and cooling rate on the gelation of high-methoxylated pectin.

    Science.gov (United States)

    Kastner, H; Kern, K; Wilde, R; Berthold, A; Einhorn-Stoll, U; Drusch, S

    2014-02-01

    The aim of the study was the application of a recently published method, using structuring parameters calculated from dG'/dt, for the characterisation of the pectin sugar acid gelation process. The influence of cooling rate and pH on structure formation of HM pectin gels containing 65 wt.% sucrose were investigated. The results show that the structure formation process as well as the properties of the final gels strongly depended on both parameters. With increasing cooling rates from 0.5 to 1.0 K/min the initial structuring temperature slightly decreased and the maximum structuring velocity increased. The lower the cooling rates, the firmer and more elastic were the final gels. With increasing acid content (decreasing pH from 2.5-2.0) the initial structuring temperatures were nearly constant. The final gel properties varied visibly but not systematically. Gels with the lowest and highest pH were less elastic and weaker compared to those with medium acid concentrations. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Simulation of Thermomagnetic Convection in a Cavity Using the Lattice Boltzmann Model

    Directory of Open Access Journals (Sweden)

    Mahshid Hadavand

    2011-01-01

    Full Text Available Thermomagnetic convection in a differentially heated square cavity with an infinitely long third dimension is numerically simulated using the single relaxation time lattice Boltzmann method (LBM. This problem is of considerable interest when dealing with cooling of microelectronic devices, in situations where natural convection does not meet the cooling requirements, and forced convection is not viable due to the difficulties associated with pumping a ferrofluid. Therefore, circulation is achieved by imposing a magnetic field, which is created and controlled by placing a dipole at the bottom of the enclosure. The magnitude of the magnetic force is controlled by changing the electrical current through the dipole. In this study, the effects of combined natural convection and magnetic convection, which is commonly known as “thermomagnetic convection,” are analysed in terms of the flow modes and heat transfer characteristics of a magnetic fluid.

  16. Convection and oscillations

    CERN Document Server

    Houdek, G

    2010-01-01

    In this short review on stellar convection dynamics I address the following, currently very topical, issues: (1) the surface effects of the Reynolds stresses and nonadiabaticity on solar-like pulsation frequencies, and (2) oscillation mode lifetimes of stochastically excited oscillations in red giants computed with different time-dependent convection formulations.

  17. The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS08 field experiment – Part 2: Observations of the convective environment

    Directory of Open Access Journals (Sweden)

    R. K. Smith

    2012-05-01

    Full Text Available Analyses of thermodynamic data gathered from airborne dropwindsondes during the Tropical Cyclone Structure (2008 experiment are presented for the disturbance that became Typhoon Nuri. Although previous work has suggested that Nuri formed within the protective recirculating "pouch" region of a westward propagating wave-like disturbance and implicated rotating deep convective clouds in driving the inflow to spin up the tangential circulation of the system-scale flow, the nature of the thermodynamic environment that supported the genesis remains a topic of debate. During the genesis phase, vertical profiles of virtual potential temperature show little variability between soundings on a particular day and the system-average soundings likewise show a negligible change. There is a tendency also for the lower and middle troposphere to moisten. However, the data show that, on the scale of the recirculating region of the disturbance, there was no noticeable reduction of virtual temperature in the lower troposphere, but a small warming (less than 1 K in the upper troposphere. Vertical profiles of pseudo-equivalent potential temperature, θe, during the genesis show a modestly decreasing deficit of θe in the vertical between the surface and the height of minimum θe (between 3 and 4 km, from 17.5 K to 15.2 K. The findings reported here are consistent with those found for developing disturbances observed in the Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT experiment in 2010. Some implications of the findings are discussed.

  18. Coupled Heat and Fluid Flow Modeling of the Earth's Largest Zinc Ore Deposit at Red Dog, Alaska: Implications for Structurally-Focused, Free Convection in Submarine Sedimentary Basins

    Science.gov (United States)

    Garven, G.; Dumoulin, J. A.; Bradley, D. A.; Young, L. E.; Kelley, K. D.; Leach, D. L.

    2002-12-01

    Crustal heat flow can provide a strong mechanism for driving groundwater flow, particularly in submarine basins where other mechanisms for driving pore fluid flow such as topography, compaction and crustal deformation are too weak or too slow to have a significant effect on disturbing conductive heat flow. Fault zones appear to play a crucial role in focusing fluid migration in basins, as inferred in ancient rocks by many examples of hydrothermal deposits of sediment-hosted ores worldwide. Many rift-hosted deposits of lead, zinc, and barite ore appear to have formed at or near the seafloor by focused venting of hot basinal fluids and modified seawater, although the geophysical nature of these systems is not so well known. For example, the upper Kuna Formation, a finely laminated, black, organic-rich siliceous mudstone and shale in the Western Brooks Range of northwest Alaska, is host to the largest resources of zinc yet discovered in the Earth's crust, containing ore reserves in excess of 175 Mt averaging about 16% Zn and 5% Pb. Although situated today in a highly-deformed series of structural allocthonous plates thrusted during the Jurassic to Cretaceous Brookian Orogeny, the stratiform ores are thought to have formed much earlier in the anoxic, mud-rich Carboniferous-age Kuna Basin when adjacent carbonate platforms were drowned by rifting and tectonic subsidence. Fluid inclusion studies of ore-stage sphalerite and gangue minerals indicate sub-seafloor mineralization temperatures less than 200oC and most likely between 120 to 150 oC, during a period of sediment diagenesis and extensional faulting. We have constructed fully-coupled numerical models of heat and fluid flow to test hydrologic theories for free convection, submarine venting and subsequent ore formation, as constrained by paleoheat flow and petrologic observations. A finite element grid was designed and adapted for a cross section of the Kuna Basin, geologically restored to latest Mississippian time

  19. Numerical Investigations of Mixed Convection of Incompressible Viscous Fluid in LNG Storage with a Various Locations of Input and Output Mass

    Directory of Open Access Journals (Sweden)

    Sklyarenko Kristina A.

    2015-01-01

    Full Text Available The article shows the results of mathematical simulation of mixed convection in the low-temperature storage of liquefied natural gas with a regenerative cooling. The regimes of mixed convection in a closed area with the different arrangement of the input and output sections of the masses are investigated. Two-dimensional nonstationary problem in the model of the Navier-Stokes in dimensionless variables “vorticity - stream function - temperature” was examined. Are obtained distributions of the hydrodynamic parameters and temperatures, characteristic basic laws governing the processes being investigated. Detailed circulating currents and carried out analysis of the mechanism of vortices formation and the temperature distribution in the solution for mixed convection mode with low Reynolds and Grashof numbers (Gr = 106, 100 structure of liquid flow and temperature in the low temperature LNG storage tanks.

  20. Structural Changes and Convective Processes in Tropical Cyclones as Seen in Infrared and Water Vapor Satellite Data

    Science.gov (United States)

    2013-05-10

    structural changes, respectively, in tropical cyclones ( Willoughby et al. 1982). Figure 1. A vertical cross-section of a typical tropical cyclone...of typhoons. J. Meteor., 5, 247-265. Shapiro, L. J., and H. E. Willoughby , 1982: The response of balanced hurricanes to local sources of heat and...Statistical Methods in the Atmospheric Sciences. Elsevier Inc, 648 pp. Willoughby , H. E., J. A. Clos, and M. G. Shoreibah, 1982: Concentric eyewalls

  1. Turbulent convection model in the overshooting region: II. Theoretical analysis

    CERN Document Server

    Zhang, S Q

    2012-01-01

    Turbulent convection models are thought to be good tools to deal with the convective overshooting in the stellar interior. However, they are too complex to be applied in calculations of stellar structure and evolution. In order to understand the physical processes of the convective overshooting and to simplify the application of turbulent convection models, a semi-analytic solution is necessary. We obtain the approximate solution and asymptotic solution of the turbulent convection model in the overshooting region, and find some important properties of the convective overshooting: I. The overshooting region can be partitioned into three parts: a thin region just outside the convective boundary with high efficiency of turbulent heat transfer, a power law dissipation region of turbulent kinetic energy in the middle, and a thermal dissipation area with rapidly decreasing turbulent kinetic energy. The decaying indices of the turbulent correlations $k$, $\\bar{u_{r}'T'}$, and $\\bar{T'T'}$ are only determined by the ...

  2. High Rayleigh number convection numerical experiments

    Science.gov (United States)

    Verzicco, Roberto

    2002-03-01

    Numerical experiments on the flow developing in a cylindrical cell of aspect ratio Γ = 1/2 heated from below and cooled from above, are conducted for Rayleigh numbers (Ra) ranging from 2 x 10^6 up to 2 x 10^11. The aim of the present study is to numerically replicate the experiments by Roche et al. (2001) and Niemela et al. (2000) performed using gaseous helium close to the critical point as working fluid (Pr = 0.7). The numerical simulation permitted us to generate a large data base which was validated by the experimental results and, on the other hand, provided physical insights which are missed by the experimental approaches usually limited to pointwise temperature and global heat exchange measurements. Attention is focussed on the presence of large-scale structures whose characterization is important owing to the introduction of constant `winds' sweeping the plates and generating viscous and thermal boundary layers. The analysis of instantaneous snapshots clearly indicates that the topology of the recirculating large scale structures is quite different with respect to what is commonly observed in Γ = 1 cells where a unique large scale recirculation structure completely fills the fluid volume (e.g. Verzicco & Camussi, 1999). It is shown that a transition occurs at about Ra = 10^9; at lower Ra the flow is characterized by the presence of two counter-rotating toroidal rings attached to the horizontal plates. At larger Ra, in contrast, the most intense structure consists of two counter-rotating rolls of unitary aspect ratio. The two types of flow, which co-exists in the range 10^9 < Ra < 10^10, determine different properties of both the thermal and the viscous boundary layers. Indeed, even if the limited range of Ra analyzed in the present simulation does not allow the presence of a transition to be clearly observed in the Nu vs Ra diagram, the proposed scenario is confirmed by the direct analysis of the boundary layer thicknesses and of the kinetic energy and

  3. Convection Heat Transfer and Flow Calculations Suitable for Electric Machines Thermal Models

    OpenAIRE

    Cavagnino, Andrea

    2008-01-01

    This paper deals with the formulations used to predict convection cooling and flow in electric machines. Empirical dimensionless analysis formulations are used to calculate convection heat transfer. The particular formulation used is selected to match the geometry of the surface under consideration and the cooling type used. Flow network analysis, which is used to study the ventilation inside the machine, is also presented. In order to focus the discussion using examples, a commercial softwar...

  4. Influence of cooling rate on the structure and mechanical properties of G17CrMoV5 – 10 cast steel

    Directory of Open Access Journals (Sweden)

    G. Golański

    2009-07-01

    Full Text Available The paper presents results of research on the influence of cooling rate on the structure and properties of G17CrMoV5 – 10 (L17HMF cast steel. The material for research was a section taken out from an outer cylinder of a steam turbine body after about 250 000 hours of operation at the temperature of 535°C and pressure 9 MPa. The investigated cast steel was subjected to heat treatment which consisted in cooling at the rates corresponding to the processes, such as: bainitic hardening, normalizing and full annealing. Tempering after the process of cooling from austenitizing temperature was carried out at the temperatures of: 700, 720 and 740°C. Performed research has proved that structures obtained after bainitic hardening and normalizing are characterized by a large strength margin which allows to apply high temperatures of tempering. It has been shown that the cast steel of bainitic structure, with similar mechanical properties as the cast steel of bainitic – ferritic structure, is characterized by almost twice as high impact energy. Full annealing and tempering of the examined cast steel ensures only the required impact strength, with mechanical properties comparable to those after service.

  5. Convective Radio Occultations Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Biondi, R. [Atmospheric Radiation Measurement, Washington, DC (United States)

    2016-03-01

    Deep convective systems are destructive weather phenomena that annually cause many deaths and injuries as well as much damage, thereby accounting for major economic losses in several countries. The number and intensity of such phenomena have increased over the last decades in some areas of the globe. Damage is mostly caused by strong winds and heavy rain parameters that are strongly connected to the structure of the particular storm. Convection over land is usually stronger and deeper than over the ocean and some convective systems, known as supercells, also develop tornadoes through processes that remain mostly unclear. The intensity forecast and monitoring of convective systems is one of the major challenges for meteorology because in situ measurements during extreme events are too sparse or unreliable and most ongoing satellite missions do not provide suitable time/space coverage.

  6. Explore the Water-cooled Slag Cooler Drum Master Cylinder Structure%滚筒水冷式冷渣机主筒结构探讨

    Institute of Scientific and Technical Information of China (English)

    吴浪

    2014-01-01

    在锅炉系统中,冷渣机对高温炉渣的冷却起着重要的作用,而滚筒水冷式冷渣机因其自身所具有的一些优点得到了较为广泛的应用。在滚筒水冷式冷渣机中,其主筒结构对其性能和工作效率等都会产生直接的影响。针对生产的实际需求,对滚筒水冷式冷渣机进行改进和完善时,要充分考虑主筒结构设计和所要改善的问题,从而使其能够更好地发挥冷却作用。%In the boiler system, slag cooler for cooling high-temperature slag plays an important role, and the cold cylinder water-cooled slag machine has its own advantages has been more widely used. In the cylinder water-cooled slag cooler in the main tube structures have a direct impact on their performance and work efficiency will be. When the actual demand for the production of cylinder water-cooled slag cooler to improve and perfect, to fully consider the master cylinder and the structural design issues to be improved, making it better able to exert a cooling effect.

  7. Calculation of vibrational branching ratios and hyperfine structure of 24Mg19F and its suitability for laser cooling and magneto-optical trapping

    Science.gov (United States)

    Xu, Liang; Yin, Yanning; Wei, Bin; Xia, Yong; Yin, Jianping

    2016-01-01

    More recently, laser cooling of the diatomic radical magnesium monofluoride (24Mg19F ) is being experimentally preformed [Appl. Phys. Express 8, 092701 (2015), 10.7567/APEX.8.092701 and Opt. Express 22, 28645 (2014), 10.1364/OE.22.028645] and was also studied theoretically [Phys. Rev. A 91, 042511 (2015), 10.1103/PhysRevA.91.042511]. However, some important problems still remain unsolved, so, in our paper, we perform further theoretical study for the feasibility of laser cooling and trapping the 24Mg19F molecule. At first, the highly diagonal Franck-Condon factors of the main transitions are verified by the closed-form approximation, Morse approximation, and Rydberg-Klein-Rees inversion methods, respectively. Afterwards, we investigate the lower X 2Σ1/2 + hyperfine manifolds using a quantum effective Hamiltonian approach and obtain the zero-field hyperfine spectrum with an accuracy of less than 30 kHz ˜5 μ K compared with the experimental results, and then find out that one cooling beam and one or two repumping beams with their first-order sidebands are enough to implement an efficient laser slowing and cooling of 24Mg19F . Meanwhile, we also calculate the accurate hyperfine structure magnetic g factors of the rotational state (X 2Σ1/2 +,N =1 ) and briefly discuss the influence of the external fields on the hyperfine structure of 24Mg19F as well as its possibility of preparing three-dimensional magneto-optical trapping. Finally we give an explanation for the difference between the Stark and Zeeman effects from the perspective of parity and time reversal symmetry. Our study shows that, besides appropriate excitation wavelengths, the short lifetime for the first excited state A 2Π1 /2 , and lighter mass, the 24Mg19F radical could be a good candidate molecule amenable to laser cooling and magneto-optical trapping.

  8. Evidence of convective heat transfer enhancement induced by spinodal decomposition.

    Science.gov (United States)

    Poesio, P; Lezzi, A M; Beretta, G P

    2007-06-01

    Spinodal decomposition can be driven by either diffusion or self-induced convection; the importance of convection relative to diffusion depends on the Péclet number, defined as the ratio between convective and diffusive mass fluxes. Diffusion is the dominating mechanism of phase segregation when the Péclet number is small - i.e., when viscosity and diffusivity are large - or when the domain characteristic size is small. For low-viscosity mixtures, convection is the dominating process and the segregation is very rapid as it takes a few seconds compared to the hours needed in the case of pure diffusion. In such cases, strong convective motion of the phase segregating domains is generated even in small-size systems and is almost independent of the temperature difference as long as it is below the transition value. We study experimentally the enhancement of heat transfer in a 1-mm -thick cell. A water-acetonitrile-toulene mixture is quenched into a two-phase region so as to induce convection-driven spinodal decomposition. The heat transfer rate is measured and compared to that obtained in the absence of convective motion. A substantial reduction in the cooling time obtains in the case of spinodal decomposition. The heat transfer enhancement induced by this self-induced, disordered but effectively convective effect may be exploited in the cooling or heating of small-scale systems whereby forced convection cannot be achieved because of the small sizes involved. A scaling analysis of the data based on the diffuse interface H model for a symmetric mixture near the equilibrium point yields very encouraging agreement and insights.

  9. Observing Convective Aggregation

    Science.gov (United States)

    Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita

    2017-06-01

    Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

  10. Automatic remote sensing detection of the convective boundary layer structure over flat and complex terrain using the novel PathfinderTURB algorithm

    Science.gov (United States)

    Poltera, Yann; Martucci, Giovanni; Hervo, Maxime; Haefele, Alexander; Emmenegger, Lukas; Brunner, Dominik; Henne, stephan

    2016-04-01

    We have developed, applied and validated a novel algorithm called PathfinderTURB for the automatic and real-time detection of the vertical structure of the planetary boundary layer. The algorithm has been applied to a year of data measured by the automatic LIDAR CHM15K at two sites in Switzerland: the rural site of Payerne (MeteoSwiss station, 491 m, asl), and the alpine site of Kleine Scheidegg (KSE, 2061 m, asl). PathfinderTURB is a gradient-based layer detection algorithm, which in addition makes use of the atmospheric variability to detect the turbulent transition zone that separates two low-turbulence regions, one characterized by homogeneous mixing (convective layer) and one above characterized by free tropospheric conditions. The PathfinderTURB retrieval of the vertical structure of the Local (5-10 km, horizontal scale) Convective Boundary Layer (LCBL) has been validated at Payerne using two established reference methods. The first reference consists of four independent human-expert manual detections of the LCBL height over the year 2014. The second reference consists of the values of LCBL height calculated using the bulk Richardson number method based on co-located radio sounding data for the same year 2014. Based on the excellent agreement with the two reference methods at Payerne, we decided to apply PathfinderTURB to the complex-terrain conditions at KSE during 2014. The LCBL height retrievals are obtained by tilting the CHM15K at an angle of 19 degrees with respect to the horizontal and aiming directly at the Sphinx Observatory (3580 m, asl) on the Jungfraujoch. This setup of the CHM15K and the processing of the data done by the PathfinderTURB allows to disentangle the long-transport from the local origin of gases and particles measured by the in-situ instrumentation at the Sphinx Observatory. The KSE measurements showed that the relation amongst the LCBL height, the aerosol layers above the LCBL top and the gas + particle concentration is all but

  11. Regeneratively Cooled Porous Media Jacket

    Science.gov (United States)

    Mungas, Greg (Inventor); Fisher, David J. (Inventor); London, Adam Pollok (Inventor); Fryer, Jack Merrill (Inventor)

    2013-01-01

    The fluid and heat transfer theory for regenerative cooling of a rocket combustion chamber with a porous media coolant jacket is presented. This model is used to design a regeneratively cooled rocket or other high temperature engine cooling jacket. Cooling jackets comprising impermeable inner and outer walls, and porous media channels are disclosed. Also disclosed are porous media coolant jackets with additional structures designed to transfer heat directly from the inner wall to the outer wall, and structures designed to direct movement of the coolant fluid from the inner wall to the outer wall. Methods of making such jackets are also disclosed.

  12. Cooling rate correction and Detection of mineralogical evolution during Thellier-Thellier's experiments on baked clays. Applications to French protohistoric structures

    Science.gov (United States)

    Lanos, P.; Hervé, G.; Chauvin, A.; Perron d'Arc, M.

    2011-12-01

    Archaeointensity protocols have been considerably improved since the last years to better detect multidomain (MD) grains effects or mineralogical evolutions during Thellier's experiments. Current published data respect more strict criteria and take into account the anisotropy of thermoremanent magnetization (TRM). However the effect of the cooling rate on the intensity of the TRM acquired during cooling, which depends on the type of the ferromagnetic grains, remains difficult to precisely quantify. The main problem is to estimate the true cooling rate of the archeological structures and usually a 24 hours cooling is assumed. An experimental study of 35 small bricks baked in two kilns during summer 2007 and 2008 (in Sallèles d'Aude, southern France) gives new elements about the cooling rate correction. The used kilns are of two different sizes, similar to classical archaeological structures. Intensity of the geomagnetic field (43 μT) in the kilns and the temperature decrease during the cooling (around 12 hours for the small kiln and 70 hours for the other one) were measured. Discrepancies between the TRM intensity after fast (1.5 hour in the laboratory) and low cooling of 24 hours are over a very wide range between -5 and +30%. The use of the true cooling rate of the kilns (respectively 12 and 72 hours) gives mean archaeointensities (43.8±1.8 μT and 42.7±2.2 μT) corresponding to the intensity of the field measured within them. By applying the usual cooling of 24 hours, the intensity of the field is underestimated by 3 μT in the small kiln and is overestimated by 3 μT in the bigger kiln. Consequently, a wrong cooling rate correction may explain the dispersion between archaeointensities. The second aspect of the presentation corresponds to the detection of mineralogical evolution during successive heatings of the Thellier-Thellier's protocol. This problem is particularly important for the millennia BC in Europe, as very well heated structures are less common

  13. The development and design of cooling structure in lead-carbon batteries%铅炭电池壳体散热结构的开发设计

    Institute of Scientific and Technical Information of China (English)

    马换玉; 周燕; 刘松

    2014-01-01

    介绍了一种铅炭电池用电池壳体开发设计。实验结果表明,具有散热结构的槽体使铅炭电池大电流充放电过程中产生的热量能够快速的散出,降温效果明显,减少电池失水,通过计算得出在散热结构的槽体上贴附高导热的石墨散热膜,可以进一步加强散热效果。%The development and design of the battery tank for lead-carbon battery was introduced in this paper.The results showed that the tank with a cooling structure made the heat,which generated in the process of large-current charging and discharging,dissipated quickly,reduced the water loss.And the heat dissipation and cooling effect was enhanced when the graphite cool-ing film with high thermal conductivity adhered to the tank.

  14. Experimental investigation of cooling performance of a novel HVAC system combining natural ventilation with diffuse ceiling inlet and TABS

    DEFF Research Database (Denmark)

    Yu, Tao; Heiselberg, Per Kvols; Lei, Bo;

    2015-01-01

    Highlights •An experimental investigation of cooling performance of a combined HVAC system is carried out. •Cooling performance of TABS with and without the influence of diffuse ceiling is analyzed. •Radiant and convective heat transfer coefficients of TABS cooling are studied. •Cooling components...

  15. Dynamic model of a micro-tubular solid oxide fuel cell stack including an integrated cooling system

    Science.gov (United States)

    Hering, Martin; Brouwer, Jacob; Winkler, Wolfgang

    2017-02-01

    A novel dynamic micro-tubular solid oxide fuel cell (MT-SOFC) and stack model including an integrated cooling system is developed using a quasi three-dimensional, spatially resolved, transient thermodynamic, physical and electrochemical model that accounts for the complex geometrical relations between the cells and cooling-tubes. The modeling approach includes a simplified tubular geometry and stack design including an integrated cooling structure, detailed pressure drop and gas property calculations, the electrical and physical constraints of the stack design that determine the current, as well as control strategies for the temperature. Moreover, an advanced heat transfer balance with detailed radiative heat transfer between the cells and the integrated cooling-tubes, convective heat transfer between the gas flows and the surrounding structures and conductive heat transfer between the solid structures inside of the stack, is included. The detailed model can be used as a design basis for the novel MT-SOFC stack assembly including an integrated cooling system, as well as for the development of a dynamic system control strategy. The evaluated best-case design achieves very high electrical efficiency between around 75 and 55% in the entire power density range between 50 and 550 mW /cm2 due to the novel stack design comprising an integrated cooling structure.

  16. Coupling between lower-tropospheric convective mixing and low-level clouds: Physical mechanisms and dependence on convection scheme.

    Science.gov (United States)

    Vial, Jessica; Bony, Sandrine; Dufresne, Jean-Louis; Roehrig, Romain

    2016-12-01

    Several studies have pointed out the dependence of low-cloud feedbacks on the strength of the lower-tropospheric convective mixing. By analyzing a series of single-column model experiments run by a climate model using two different convective parametrizations, this study elucidates the physical mechanisms through which marine boundary-layer clouds depend on this mixing in the present-day climate and under surface warming. An increased lower-tropospheric convective mixing leads to a reduction of low-cloud fraction. However, the rate of decrease strongly depends on how the surface latent heat flux couples to the convective mixing and to boundary-layer cloud radiative effects: (i) on the one hand, the latent heat flux is enhanced by the lower-tropospheric drying induced by the convective mixing, which damps the reduction of the low-cloud fraction, (ii) on the other hand, the latent heat flux is reduced as the lower troposphere stabilizes under the effect of reduced low-cloud radiative cooling, which enhances the reduction of the low-cloud fraction. The relative importance of these two different processes depends on the closure of the convective parameterization. The convective scheme that favors the coupling between latent heat flux and low-cloud radiative cooling exhibits a stronger sensitivity of low-clouds to convective mixing in the present-day climate, and a stronger low-cloud feedback in response to surface warming. In this model, the low-cloud feedback is stronger when the present-day convective mixing is weaker and when present-day clouds are shallower and more radiatively active. The implications of these insights for constraining the strength of low-cloud feedbacks observationally is discussed.

  17. Multisensor Observations of the Lifecycles of Propagating Tropical Convective Systems: Horizontal and Vertical Structure, Diabatic Heating and Moistening, and Relationship to Environmental Parameters

    Science.gov (United States)

    Elsaesser, G.; Li, Y.; Kummerow, C. D.; Carbone, R. E.

    2013-12-01

    Tropical oceanic convective systems are identified and tracked through use of the CMORPH high-resolution rainfall product. The composite areal coverage of rainfall (provided by TRMM PR and CMORPH), convective/stratiform ratio (from TRMM PR), vertical extent of the raining system (TRMM PR) and the diabatic heating and moistening tendencies (Q1-QR, Q2 from the Spectral Latent Heating Algorithm product) are all quantified, as a function of both system lifecycle stage and system longevity. System longevity is shown to have strong relationships with environmental shear and humidity. The composite changes in total precipitable water (TPW) and SST (from the GHRSST product) along the paths of the systems are discussed, both as a function of system stage and longevity. Unlike the composite convective events, individual systems undergo both systematic and random variations in terms of convective organization, surface rainfall characteristics, and propagation direction as their lifecycle proceeds. These variations are investigated as a function of varying environmental shear along the path of system (provided from NCEP re-analysis), the distribution of water vapor surrounding the system (from AIRS Version-6 0.25-degree product), and newly derived QuikSCAT-based 'triggering energy' (often associated with convergence zones at the edges of large cold pools) that is a function of both the system in question as well as near-vicinity convection.

  18. Heat Transfer and Cooling Techniques at Low Temperature

    CERN Document Server

    Baudouy, B

    2014-07-17

    The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.

  19. Sensitivity of Tropical Cyclones to Parameterized Convection in the NASA GEOS5 Model

    Science.gov (United States)

    Lim, Young-Kwon; Schubert, Siegfried D.; Reale, Oreste; Lee, Myong-In; Molod, Andrea M.; Suarez, Max J.

    2014-01-01

    The sensitivity of tropical cyclones (TCs) to changes in parameterized convection is investigated to improve the simulation of TCs in the North Atlantic. Specifically, the impact of reducing the influence of the Relaxed Arakawa-Schubert (RAS) scheme-based parameterized convection is explored using the Goddard Earth Observing System version5 (GEOS5) model at 0.25 horizontal resolution. The years 2005 and 2006 characterized by very active and inactive hurricane seasons, respectively, are selected for simulation. A reduction in parameterized deep convection results in an increase in TC activity (e.g., TC number and longer life cycle) to more realistic levels compared to the baseline control configuration. The vertical and horizontal structure of the strongest simulated hurricane shows the maximum lower-level (850-950hPa) wind speed greater than 60 ms and the minimum sea level pressure reaching 940mb, corresponding to a category 4 hurricane - a category never achieved by the control configuration. The radius of the maximum wind of 50km, the location of the warm core exceeding 10 C, and the horizontal compactness of the hurricane center are all quite realistic without any negatively affecting the atmospheric mean state. This study reveals that an increase in the threshold of minimum entrainment suppresses parameterized deep convection by entraining more dry air into the typical plume. This leads to cooling and drying at the mid- to upper-troposphere, along with the positive latent heat flux and moistening in the lower-troposphere. The resulting increase in conditional instability provides an environment that is more conducive to TC vortex development and upward moisture flux convergence by dynamically resolved moist convection, thereby increasing TC activity.

  20. Tangent linear superparameterization of convection in a 10 layer global atmosphere with calibrated climatology

    Science.gov (United States)

    Kelly, Patrick; Mapes, Brian; Hu, I.-Kuan; Song, Siwon; Kuang, Zhiming

    2017-06-01

    This paper describes a new intermediate global atmosphere model in which synoptic and planetary dynamics including the advection of water vapor are explicit in 10 layers, the time-mean flow is centered near a realistic state through the use of carefully calibrated time-independent 3-D forcings, and temporal anomalies of convective tendencies of heat and moisture in each column are represented as a linear matrix acting on the anomalous temperature and moisture profiles. Currently, this matrix is Kuang's [] linear response function (LRF) of a cyclic convection-permitting model (CCPM) in equilibrium with specified atmospheric cooling (i.e., without radiation or WISHE interactions, so it conserves column moist static energy exactly). The goal of this effort is to cleanly test the role of convection's free-tropospheric moisture sensitivity in tropical waves, without incurring large changes of mean climate that confuse the interpretation of experiments with entrainment parameters in the convection schemes of full-physics GCMs. When the sensitivity to free-tropospheric moisture is multiplied by a factor ranging from 0 to 2, the model's variability ranges from: (1) moderately strong convectively coupled Kelvin waves with speeds near 20 m s-1; to (0) similar but much weaker waves; to (2) similar but stronger and slightly faster waves as the water vapor field plays an increasingly important role. Longitudinal structure in the model's time-mean tropical flow is not fully realistic, and does change significantly with matrix-coupled variability, but further work on editing the anomaly physics matrix and calibrating the mean state could improve this class of models.

  1. Enhancing the efectiveness of film cooling

    Institute of Scientific and Technical Information of China (English)

    Tom I-P.Shih; Sangkwon Na

    2007-01-01

    Advanced gas turbine stages are designed to operate at increasingly higher inlet temperatures to increase thermal efficiency and specific power output.To maintain durability and reasonable life,film cooling is needed in addition to internal cooling,especially for the first stage.Film cooling lowers material temperature by forced convection inside film-cooling holes and by forming a layer of coolant about component surfaces to insulate them from the hot gases.Unfortunately,each cooling jet forms a pair of counter-rotating vortices that entrains hot gas and causes the film-cooling jet to lift off from the surface that it is intended to protect.This paper gives an overview of efforts to enhance the effectiveness of film-cooling.This paper also describes two new design concepts.One design concept seeks to minimize the entrainment of hot gases underneath of film-cooling jets by using flow-aligned blockers.The other design concept shifts the interaction between the approaching hot gas and the cooling jet to occur further above the surface by using an upstream ramp.For both design concepts,computational fluid dynamics results are presented to examine their usefulness in enhancing film-cooling effectiveness.

  2. Ventilative Cooling

    DEFF Research Database (Denmark)

    Heiselberg, Per Kvols; Kolokotroni, Maria

    This report, by venticool, summarises the outcome of the work of the initial working phase of IEA ECB Annex 62 Ventilative Cooling and is based on the findings in the participating countries. It presents a summary of the first official Annex 62 report that describes the state-of-the-art of ventil......This report, by venticool, summarises the outcome of the work of the initial working phase of IEA ECB Annex 62 Ventilative Cooling and is based on the findings in the participating countries. It presents a summary of the first official Annex 62 report that describes the state...

  3. Convective heat transfer

    CERN Document Server

    Kakac, Sadik; Pramuanjaroenkij, Anchasa

    2014-01-01

    Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....

  4. The three stages of magma ocean cooling

    Science.gov (United States)

    Warren, Paul H.

    1992-12-01

    Models of magma ocean (MO) cooling and crystallization can provide important constraints on MO plausibility for a given planet, on the origin of long term, stable crusts, and even on the origin of the solar system. Assuming the MO is initially extensive enough to have a mostly molten surface, its first stage of cooling is an era of radiative heat loss from the surface, with extremely rapid convection below, and no conductive layer in between. The development of the chill crust starts the second stage of MO cooling. Heat loss is now limited by conduction through the crust. The third stage of cooling starts when the near surface MO evolves compositionally to the point of saturation with feldspar. At this point, the cooling rate again precipitously diminishes, the rate of crustal thickness growth as a function of temperature suddenly increases. More work on incorporating chemical constraints into the evolving physical models of MO solidification would be worthwhile.

  5. Transparent electric convection heater

    OpenAIRE

    Khalid, A.; Luck, J.L.

    2001-01-01

    An optically transparent electrically heated convection heater for use as a space heater in homes, offices, shops. Typically, said convection heater consists of a transparent layer 1 upon which is deposited a layer of a transparent electrically conductive material 2 such as indium-tin-oxide, electrodes 3 and 3a are formed on opposite edges of the transparent electrically conductive layer 2 and electrical wires 4 and 4a are connected to the electrodes. The transparent electrically conductive l...

  6. Patterns of fish assemblage structure and dynamics in waters of the Savannah River Plant. Comprehensive Cooling Water Study final report

    Energy Technology Data Exchange (ETDEWEB)

    Aho, J.M.; Anderson, C.S.; Floyd, K.B.; Negus, M.T.; Meador, M.R.

    1986-06-01

    Research conducted as part of the Comprehensive Cooling Water Study (CCWS) has elucidated many factors that are important to fish population and community dynamics in a variety of habitats on the Savannah River Plant (SRP). Information gained from these studies is useful in predicting fish responses to SRP operations. The overall objective of the CCWS was (1) to determine the environmental effects of SRP cooling water withdrawals and discharges and (2) to determine the significance of the cooling water impacts on the environment. The purpose of this study was to: (1) examine the effects of thermal plumes on anadromous and resident fishes, including overwintering effects, in the SRP swamp and associated tributary streams; (2) assess fish spawning and locate nursery grounds on the SRP; (3) examine the level of use of the SRP by spawning fish from the Savannah River, this objective was shared with the Savannah River Laboratory, E.I. du Pont de Nemours and Company; and (4) determine impacts of cooling-water discharges on fish population and community attributes. Five studies were designed to address the above topics. The specific objectives and a summary of the findings of each study are presented.

  7. Cool snacks

    DEFF Research Database (Denmark)

    Grunert, Klaus G; Brock, Steen; Brunsø, Karen

    2016-01-01

    such a product requires an interdisciplinary effort where researchers with backgrounds in psychology, anthropology, media science, philosophy, sensory science and food science join forces. We present the COOL SNACKS project, where such a blend of competences was used first to obtain thorough insight into young...

  8. Enhancement of laminar convective heat transfer using microparticle suspensions

    Science.gov (United States)

    Zhu, Jiu Yang; Tang, Shiyang; Yi, Pyshar; Baum, Thomas; Khoshmanesh, Khashayar; Ghorbani, Kamran

    2016-04-01

    This paper investigates the enhancement of convective heat transfer within a sub-millimetre diameter copper tube using Al2O3, Co3O4 and CuO microparticle suspensions. Experiments are conducted at different particle concentrations of 1.0, 2.0 and 5.0 wt% and at various flow rates ranging from 250 to 1000 µl/min. Both experimental measurements and numerical analyses are employed to obtain the convective heat transfer coefficient. The results indicate a significant enhancement in convective heat transfer coefficient due to the implementation of microparticle suspensions. For the case of Al2O3 microparticle suspension with 5.0 wt% concentration, a 20.3 % enhancement in convective heat transfer coefficient is obtained over deionised water. This is comparable to the case of Al2O3 nanofluid at the same concentration. Hence, there is a potential for the microparticle suspensions to be used for cooling of compact integrated systems.

  9. Enhancement of laminar convective heat transfer using microparticle suspensions

    Science.gov (United States)

    Zhu, Jiu Yang; Tang, Shiyang; Yi, Pyshar; Baum, Thomas; Khoshmanesh, Khashayar; Ghorbani, Kamran

    2017-01-01

    This paper investigates the enhancement of convective heat transfer within a sub-millimetre diameter copper tube using Al2O3, Co3O4 and CuO microparticle suspensions. Experiments are conducted at different particle concentrations of 1.0, 2.0 and 5.0 wt% and at various flow rates ranging from 250 to 1000 µl/min. Both experimental measurements and numerical analyses are employed to obtain the convective heat transfer coefficient. The results indicate a significant enhancement in convective heat transfer coefficient due to the implementation of microparticle suspensions. For the case of Al2O3 microparticle suspension with 5.0 wt% concentration, a 20.3 % enhancement in convective heat transfer coefficient is obtained over deionised water. This is comparable to the case of Al2O3 nanofluid at the same concentration. Hence, there is a potential for the microparticle suspensions to be used for cooling of compact integrated systems.

  10. Stochastic cooling

    Energy Technology Data Exchange (ETDEWEB)

    Bisognano, J.; Leemann, C.

    1982-03-01

    Stochastic cooling is the damping of betatron oscillations and momentum spread of a particle beam by a feedback system. In its simplest form, a pickup electrode detects the transverse positions or momenta of particles in a storage ring, and the signal produced is amplified and applied downstream to a kicker. The time delay of the cable and electronics is designed to match the transit time of particles along the arc of the storage ring between the pickup and kicker so that an individual particle receives the amplified version of the signal it produced at the pick-up. If there were only a single particle in the ring, it is obvious that betatron oscillations and momentum offset could be damped. However, in addition to its own signal, a particle receives signals from other beam particles. In the limit of an infinite number of particles, no damping could be achieved; we have Liouville's theorem with constant density of the phase space fluid. For a finite, albeit large number of particles, there remains a residue of the single particle damping which is of practical use in accumulating low phase space density beams of particles such as antiprotons. It was the realization of this fact that led to the invention of stochastic cooling by S. van der Meer in 1968. Since its conception, stochastic cooling has been the subject of much theoretical and experimental work. The earliest experiments were performed at the ISR in 1974, with the subsequent ICE studies firmly establishing the stochastic cooling technique. This work directly led to the design and construction of the Antiproton Accumulator at CERN and the beginnings of p anti p colliding beam physics at the SPS. Experiments in stochastic cooling have been performed at Fermilab in collaboration with LBL, and a design is currently under development for a anti p accumulator for the Tevatron.

  11. Primary volcanic structures from a type section of Deccan Trap flows around Narsingpur–Harrai–Amarwara, central India: Implications for cooling history

    Indian Academy of Sciences (India)

    Piyali Sengupta; Arijit Ray

    2006-12-01

    Field investigations of the Deccan Trap lava sequence along a 70 km traverse in the Narsingpur–Harrai–Amarwara area of central India indicate twenty lava flows comprising a total thickness of around 480m. Primary volcanic structures like vesicles and cooling joints are conspicuous in this volcanic succession and are used to divide individual flows into three well-defined zones namely the lower colonnade zone, entablature zone, and the upper colonnade zone. The variable nature of these structural zones is used for identification and correlation of lava flows in the field. For twenty lava flows, the thicknesses of upper colonnade zones of eight flows are ∼5m while those of eight other flows are ∼8m each. The thicknesses of upper colonnade zones of remaining four flows could not be measured in the field. Using the thicknesses of these upper colonnade zones and standard temperature-flow thickness-cooling time profiles for lava pile, the total cooling time of these sixteen Deccan Trap lava flows has been estimated at 12 to 15 years.

  12. 水冷变频高速电动机的结构设计%Structure Design of Water-Cooled Inverter Duty High Speed Electric Motor

    Institute of Scientific and Technical Information of China (English)

    林治新

    2014-01-01

    Based on the structrue design of the standard three-phase electric motor, this article discussed in detail the heat-dissipation function and structure of the water-cooled motors. The water-cooled, inverter-drived and high speed motors for dragging rock wool machine were developed to meet the market demand.%以普通三相电动机结构设计为基础,详细论述了水冷电机的散热能力及结构,开发出适用于拖动岩棉机械的水冷、变频、高速电动机,满足了市场需求。

  13. Regulation of the climate in coupled convection-permitting simulations

    Science.gov (United States)

    Hohenegger, Cathy; Stevens, Bjorn

    2017-04-01

    The question of the regulation of the climate, in particular the existence of a stable climatic state and its basic characteristics, is investigated in this study. In contrast to previous studies, we use a convection-permitting simulation with an explicit representation of convection and of cloud cover. The grid spacing amounts to 3 km. The simulation is coupled to a slab ocean and is integrated in an idealized set-up of radiative convective equilibrium without rotation, without continent and with spatially uniform insolation. It is found that the system equilibrates at a sea surface temperature near the one of the present-day tropics. The equilibration results from the self-aggregation of convection that generates the dry and clear subtropics needed to radiate the excess heat from the system. When artificially preventing the self-aggregation, the existence of a runaway greenhouse cannot be ruled out. This is very different from what happens when performing a similar simulation at low resolution (T63) with a General Circulation Model (GCM) and parameterized cloud and convective processes. In that case, the atmosphere cools through an increase in planetary albedo arising from clouds. The total cloud radiative effect is 2.5 times larger than in the convection-permitting simulation. Perturbing the system by increasing the solar insolation also reveals a different behavior of the two simulations, with a larger warming in the convection-permitting simulation than in the GCM due to their distinct cloud feedbacks.

  14. High Temperature Sodium Thermal Convection Test Loop

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A project for the evaluation of compatibility characteristic of structural materials used in China experimental fast reactor(CEFR) has been in operation. The conditions which these structural materials contact with liquid sodium in reactor can be simulated by the tests in high temperature sodium thermal convection test loop. The main aims of designing and constructing the thermal convection test loop is for the corrosion test of CEFR materials, and the objective is to obtain the corrosion data of domestic materials.The main features of the test loop are shown in Fig.1. The primary components of the loop

  15. A very cool cooling system

    CERN Multimedia

    Antonella Del Rosso

    2015-01-01

    The NA62 Gigatracker is a jewel of technology: its sensor, which delivers the time of the crossing particles with a precision of less than 200 picoseconds (better than similar LHC detectors), has a cooling system that might become the precursor to a completely new detector technique.   The 115 metre long vacuum tank of the NA62 experiment. The NA62 Gigatracker (GTK) is composed of a set of three innovative silicon pixel detectors, whose job is to measure the arrival time and the position of the incoming beam particles. Installed in the heart of the NA62 detector, the silicon sensors are cooled down (to about -20 degrees Celsius) by a microfluidic silicon device. “The cooling system is needed to remove the heat produced by the readout chips the silicon sensor is bonded to,” explains Alessandro Mapelli, microsystems engineer working in the Physics department. “For the NA62 Gigatracker we have designed a cooling plate on top of which both the silicon sensor and the...

  16. 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.

  17. Feasibility analysis of modified AL-6XN steel for structure component application in supercritical water-cooled reactor

    Institute of Scientific and Technical Information of China (English)

    Xinggang LI; Qingzhi YAN; Rong MA; Haoqiang WANG; Changchun GE

    2009-01-01

    Modified AL-6XN austenite steel was patterned after AL-6XN superaustenitic stainless steel by introducing microalloy elements such as zirconium and titanium in order to adapt to recrystallizing thermo-mechanical treatment and further improve crevice corrosion resistance. Modified AL-6XN exhibited comparable tensile strength, and superior plasticity and impact toughness to commercial AL-6XN steel. The effects of aging behavior on corrosion resistance and impact toughness were measured to evaluate the qualification of modified AL-6XN steel as an in-core component and cladding material in a supercritical water-cooled reactor. Attention should be paid to degradation in corrosion resistance and impact toughness after aging for 50 hours when modified AL-6XN steel is considered as one of the candidate materials for in-core components and cladding tubes in supercritical water-cooled reactors.

  18. Thermohaline convection in main sequence stars

    Science.gov (United States)

    Vauclair, S.

    2009-07-01

    Thermohaline convection is a well-known process in oceanography, which has long been put aside in stellar physics. In the ocean, it occurs when warm salted layers sit on top of cool and less salted ones. Then the salted water rapidly diffuses downwards even in the presence of stabilizing temperature gradients, due to double diffusion between the falling blobs and their surroundings. A similar process may occur in stars in case of inverse μ-gradients in a thermally stabilized medium. This process has important consequences in stellar physics.

  19. Provisioning cooling elements for chillerless data centers

    Energy Technology Data Exchange (ETDEWEB)

    Chainer, Timothy J.; Parida, Pritish R.

    2016-12-13

    Systems and methods for cooling include one or more computing structure, an inter-structure liquid cooling system that includes valves configured to selectively provide liquid coolant to the one or more computing structures; a heat rejection system that includes one or more heat rejection units configured to cool liquid coolant; and one or more liquid-to-liquid heat exchangers that include valves configured to selectively transfer heat from liquid coolant in the inter-structure liquid cooling system to liquid coolant in the heat rejection system. Each computing structure further includes one or more liquid-cooled servers; and an intra-structure liquid cooling system that has valves configured to selectively provide liquid coolant to the one or more liquid-cooled servers.

  20. Waterways structural optimum design of electric car radiator

    Institute of Scientific and Technical Information of China (English)

    FAN Bailin; CHEN hua; ZHANG Pei; DOU Jinping

    2012-01-01

    Thermal resistance was composed by thermal resistance of Aluminum substrate, thermal resistance of convective heat transfer and the thermal resistance of the cooling liquid. The change rule was studied through the calculation on Aluminum plate thermal resistance, thermal resistance of convective heat transfer and the thermal resistance of the cooling liquid. Its change regular- ity was simulated by toolbox In the MATLAB, and it was found that thermal resistance of convective heat transfer effect on the effi- ciency was most obvious in a certain amount of the heat and flow for thermal resistance of the Pin-fin radiator under the premise. The structural parameters of radiator were related to the size of thermal resistance.

  1. Irradiated stars with convective envelopes

    CERN Document Server

    Lucy, L B

    2016-01-01

    The structure of low-mass stars irradiated by a close companion is considered. Irradiation modifies the surface boundary conditions and thereby also the adiabatic constants of their outer convection zones. This then changes the models' radii and luminosities. For short-period M dwarf binaries with components of similar mass, the radius inflation due to their mutual irradiation is found to be < 0.4%. This is an order of magnitude too small to explain the anomalous radii found for such binaries. Although stronger irradiation of an M dwarf results in a monotonically increasing radius, a saturation effect limits the inflation to < 5%.

  2. Convective self-aggregation feedbacks in near-global cloud-resolving simulations of an aquaplanet

    Science.gov (United States)

    Bretherton, Christopher S.; Khairoutdinov, Marat F.

    2015-12-01

    Positive feedbacks between precipitable water, reduced radiative cooling and enhanced surface fluxes promote convective self-aggregation in limited-area cloud-resolving model (CRM) simulations over uniform sea-surface temperature (SST). Near-global aquaplanet simulations with 4 km horizontal grid spacing and no cumulus or boundary layer parameterization are used to test the importance of these feedbacks to realistically organized tropical convection. A 20,480 × 10,240 km equatorially centered channel with latitudinally varying SST is used. Realistic midlatitude and tropical cloud structures develop. The natural zonal variability of humidity and convection are studied in a 30 day control simulation. The temporal growth of a small white-noise humidity perturbation and intrinsic predictability implications are explored. Atmospheric column budgets of moist-static energy (MSE) quantify its covariation with precipitation, surface heat flux, and radiative energy loss. Zonal Fourier analysis partitions these budgets by length scale. Radiative feedbacks on MSE natural variability and perturbation growth are found to be positive, broadly similar across scales, and comparable to limited-area CRMs, capable of e-folding a column MSE perturbation in 6-14 days. Surface fluxes are highest in synoptic-scale dry intrusions, inhibiting aggregation by damping tropical MSE perturbations. Sub-4-day MSE variations are due mainly to advection. Both tropics and midlatitudes have large-scale intrinsic predictability horizons of 15-30 days. An identical simulation but with 20 km grid spacing has more mesoscale variability and low cloud.

  3. Starspots due to large-scale vortices in rotating turbulent convection

    CERN Document Server

    Käpylä, P J; Hackman, T

    2011-01-01

    We study the generation of large-scale vortices in rotating turbulent convection by means of Cartesian direct numerical simulations. We find that for sufficiently rapid rotation, cyclonic structures on a scale large in comparison to that of the convective eddies, emerge, provided that the fluid Reynolds number exceeds a critical value. For slower rotation, cold cyclonic vortices are preferred, whereas for rapid rotation, warm anti-cyclonic vortices are favoured. In some runs in the intermediate regime both types of cyclones co-exist for thousands of convective turnover times. The temperature contrast between the vortices and the surrounding atmosphere is of the order of five per cent. We relate the simulation results to observations of rapidly rotating late-type stars that are known to exhibit large high-latitude spots from Doppler imaging. In many cases, cool spots are accompanied with spotted regions with temperatures higher than the average. In this paper, we investigate a scenario according to which the s...

  4. Convection and Mixing in Giant Planet Evolution

    CERN Document Server

    Vazan, Allona; Kovetz, Attay; Podolak, Morris

    2015-01-01

    The primordial internal structures of gas giant planets are unknown. Often giant planets are modeled under the assumption that they are adiabatic, convective, and homogeneously mixed, but this is not necessarily correct. In this work, we present the first self-consistent calculation of convective transport of both heat and material as the planets evolve. We examine how planetary evolution depends on the initial composition and its distribution, whether the internal structure changes with time, and if so, how it affects the evolution. We consider various primordial distributions, different compositions, and different mixing efficiencies and follow the distribution of heavy elements in a Jupiter-mass planet as it evolves. We show that a heavy-element core cannot be eroded by convection if there is a sharp compositional change at the core-envelope boundary. If the heavy elements are initially distributed within the planet according to some compositional gradient, mixing occurs in the outer regions resulting in a...

  5. Simulating deep convection with a shallow convection scheme

    Directory of Open Access Journals (Sweden)

    C. Hohenegger

    2011-10-01

    Full Text Available Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM. Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle.

    Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

  6. Improvement of heat pipe performance through integration of a coral biomaterial wick structure into the heat pipe of a CPU cooling system

    Science.gov (United States)

    Putra, Nandy; Septiadi, Wayan Nata

    2016-08-01

    The very high heat flux dissipated by a Central Processing Unit (CPU) can no longer be handled by a conventional, single-phased cooling system. Thermal management of a CPU is now moving towards two-phase systems to maintain CPUs below their maximum temperature. A heat pipe is one of the emerging cooling systems to address this issue because of its superior efficiency and energy input independence. The goal of this research is to improve the performance of a heat pipe by integrating a biomaterial as the wick structure. In this work, the heat pipe was made from copper pipe and the biomaterial wick structure was made from tabulate coral with a mean pore diameter of 52.95 μm. For comparison purposes, the wick structure was fabricated from sintered Cu-powder with a mean pore diameter of 58.57 µm. The working fluid for this experiment was water. The experiment was conducted using a processor as the heat source and a plate simulator to measure the heat flux. The utilization of coral as the wick structure can improve the performance of a heat pipe and can decrease the temperature of a simulator plate by as much as 38.6 % at the maximum heat load compared to a conventional copper heat sink. This method also decreased the temperature of the simulator plate by as much as 44.25 °C compared to a heat pipe composed of a sintered Cu-powder wick.

  7. Improvement of heat pipe performance through integration of a coral biomaterial wick structure into the heat pipe of a CPU cooling system

    Science.gov (United States)

    Putra, Nandy; Septiadi, Wayan Nata

    2017-04-01

    The very high heat flux dissipated by a Central Processing Unit (CPU) can no longer be handled by a conventional, single-phased cooling system. Thermal management of a CPU is now moving towards two-phase systems to maintain CPUs below their maximum temperature. A heat pipe is one of the emerging cooling systems to address this issue because of its superior efficiency and energy input independence. The goal of this research is to improve the performance of a heat pipe by integrating a biomaterial as the wick structure. In this work, the heat pipe was made from copper pipe and the biomaterial wick structure was made from tabulate coral with a mean pore diameter of 52.95 μm. For comparison purposes, the wick structure was fabricated from sintered Cu-powder with a mean pore diameter of 58.57 µm. The working fluid for this experiment was water. The experiment was conducted using a processor as the heat source and a plate simulator to measure the heat flux. The utilization of coral as the wick structure can improve the performance of a heat pipe and can decrease the temperature of a simulator plate by as much as 38.6 % at the maximum heat load compared to a conventional copper heat sink. This method also decreased the temperature of the simulator plate by as much as 44.25 °C compared to a heat pipe composed of a sintered Cu-powder wick.

  8. Thermal behaviour of cooling ceilings; Thermisches Verhalten von Kuehldecken

    Energy Technology Data Exchange (ETDEWEB)

    Beck, C.

    2002-07-01

    The thermal behaviour of cooling ceilings is so far described by characteristic equations in the form of q=C x {delta}{theta}{sup n}. In special cases these equations are extended by terms which take into account the radiation exchange between heat sink and space user (operational ambient temperature). This is insufficient. Therefore a model is presented, which describes more exactly the individual processes (radiation, convection) at the cooled surface. As a first step the ceiling area is divided into three ranges in which different phenomena are affecting the heat transfer considerably: 1. Range under the influence of free convection in the space. 2. Range with forced convection caused by a plume along the window. 3. Range with forced convection caused by air flow through supply air outlets. For each of these ranges the fundamentals of heat transfer are applied using the substantial variables. The results of these models are then compared in a second step with results from laboratory tests. This model is developed first for steady-state conditions. It is extended by a second model to describe the dynamic processes (storage). Finally, both steady-state and unsteady conditions are investigated systematically. Results are presented for the cooling rate effected by the temperature of cooling ceiling, ambient conditions, supply air flow rate, supply air temperature and type of the air outlet. The results computed indicate that the maximum total cooling rate is always gained by a combination of a cooling ceiling and a supply air with minimum permissible temperature. In these cases the cooling rate of the ceiling is lower than that without ventilation of the space. However, the additional cooling rate of the ventilation compensates this effect in all cases investigated. This is an important finding, since cooling ceilings usually must be combined with an HVAC system for reasons of dehumidifying. Dried, cooled supply air can thus be supplied to the space without

  9. Convective heat transfer and infrared thermography.

    Science.gov (United States)

    Carlomagno, Giovanni M; Astarita, Tommaso; Cardone, Gennaro

    2002-10-01

    Infrared (IR) thermography, because of its two-dimensional and non-intrusive nature, can be exploited in industrial applications as well as in research. This paper deals with measurement of convective heat transfer coefficients (h) in three complex fluid flow configurations that concern the main aspects of both internal and external cooling of turbine engine components: (1) flow in ribbed, or smooth, channels connected by a 180 degrees sharp turn, (2) a jet in cross-flow, and (3) a jet impinging on a wall. The aim of this study was to acquire detailed measurements of h distribution in complex flow configurations related to both internal and external cooling of turbine components. The heated thin foil technique, which involves the detection of surface temperature by means of an IR scanning radiometer, was exploited to measure h. Particle image velocimetry was also used in one of the configurations to precisely determine the velocity field.

  10. Active control of convection

    Energy Technology Data Exchange (ETDEWEB)

    Bau, H.H. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  11. From convection rolls to finger convection in double-diffusive turbulence

    CERN Document Server

    Yang, Yantao; Lohse, Detlef

    2015-01-01

    Double diffusive convection (DDC), which is the buoyancy driven flow with fluid density depending on two scalar components, is ubiquitous in many natural and engineering enviroments. Of great interests are scalers transfer rate and flow structures. Here we systematically investigate DDC flow between two horizontal plates, driven by an unstable salinity gradient and stabilized by a temperature gradient. Counterintuitively, when increasing the stabilizing temperature gradient, the salinity flux first increases, even though the velocity monotonically decreases, before it finally breaks down to the purely diffusive value. The enhanced salinity transport is traced back to a transition in the overall flow pattern, namely from large scale convection rolls to well-organised vertically-oriented salt fingers. We also show and explain that the unifying theory of thermal convection originally developed by Grossmann and Lohse for Rayleigh-B\\'{e}nard convection can be directly applied to DDC flow for a wide range of contro...

  12. Experimental Progress in Fast Cooling in the ESR

    CERN Document Server

    Steck, Markus; Beller, Peter; Franzke, Bernhard; Nolden, Fritz

    2005-01-01

    The ESR storage ring at GSI is operated with highly charged heavy ions. Due to the high electric charge the ions interact much stronger with electromagnetic fields. Therefore both cooling methods which are applied to stored ions in the ESR, stochastic cooling and electron cooling, are more powerful than for singly charged particles. The experimental results exhibit cooling times for stochastic cooling of a few seconds. For cold ion beams, electron cooling provides cooling times which are one to two orders of magnitude smaller. The beams are cooled to beam parameters which are limited by intrabeam scattering. At small ion numbers, however, intrabeam scattering is suppressed by electron cooling, clear evidence was found that the ion beam forms a one-dimensional ordered structure, a linear chain of ions. The strengths of stochastic cooling and electron cooling are complementary and can be combined favorably. Stochastic cooling is employed for pre-cooling of hot secondary beams followed by electron cooling to pro...

  13. Mathematical models of convection

    CERN Document Server

    Andreev, Victor K; Goncharova, Olga N; Pukhnachev, Vladislav V

    2012-01-01

    Phenomena of convection are abundant in nature as well as in industry. This volume addresses the subject of convection from the point of view of both, theory and application. While the first three chapters provide a refresher on fluid dynamics and heat transfer theory, the rest of the book describes the modern developments in theory. Thus it brings the reader to the ""front"" of the modern research. This monograph provides the theoretical foundation on a topic relevant to metallurgy, ecology, meteorology, geo-and astrophysics, aerospace industry, chemistry, crystal physics, and many other fiel

  14. A New And Fundamental View Of Organized Tropical Convection

    Science.gov (United States)

    Webster, P. J.; Toma, V. E.

    2012-12-01

    During the last decade, a paradigm has emerged to explain the existence of tropical organized convection. Based on the projection of spatial and temporal patterns of observed convection onto dispersion relationships of equatorially trapped very shallow modes (h=10-30 m, where h is the equivalent depth of a shallow fluid) the convectively coupled equatorial mode (CCEM) theory has developed. However, there is an incompleteness and some inconsistencies in the theory that need to be addressed. Whereas the horizontal structure of these shallow modes appears similar to that observed, the vertical structure consistent with small h requires a high vertical wave number. This is not observed. Second, basic scaling of the tropics, as initially undertaken by Charney in the 1960s suggests an extremely stable vertical structure, far more stable than equivalent scales at higher latitudes. In fact, at the scales of observed organized convection in the tropics (about 106m) the atmosphere is essentially barotropic to high approximation resulting in almost complete lack of communication between the upper and lower troposphere. The CCEM theory suggests that the observed modes are consistent with existing convection but there is no explanation of how the convection forms and organizes in this very stable tropical environment. It is also noted that there are discrete genesis regions of organized convection formation within the tropics and that organized convection does not occur indiscriminately. Based on these factors we propose that organized convection occurs through regional instabilities of the basic state in which vortex tube stretching overcomes the inherent stability restriction. The instabilities determine the spatial and temporal scales of the convective phenomena. We provide examples of instabilities. Further, in certain regions, influences from higher latitudes may be important. In the end, CCEMs appears as a result and not an explanation or a cause of organized convection.

  15. A thermosyphon heat pipe cooler for high power LEDs cooling

    Science.gov (United States)

    Li, Ji; Tian, Wenkai; Lv, Lucang

    2016-08-01

    Light emitting diode (LED) cooling is facing the challenge of high heat flux more seriously with the increase of input power and diode density. The proposed unique thermosyphon heat pipe heat sink is particularly suitable for cooling of high power density LED chips and other electronics, which has a heat dissipation potential of up to 280 W within an area of 20 mm × 22 mm (>60 W/cm2) under natural air convection. Meanwhile, a thorough visualization investigation was carried out to explore the two phase flow characteristics in the proposed thermosyphon heat pipe. Implementing this novel thermosyphon heat pipe heat sink in the cooling of a commercial 100 W LED integrated chip, a very low apparent thermal resistance of 0.34 K/W was obtained under natural air convection with the aid of the enhanced boiling heat transfer at the evaporation side and the enhanced natural air convection at the condensation side.

  16. A new back-and-forth iterative method for time-reversed convection modeling: Implications for the Cenozoic evolution of 3-D structure and dynamics of the mantle

    Science.gov (United States)

    Glišović, Petar; Forte, Alessandro M.

    2016-06-01

    The 3-D distribution of buoyancy in the convecting mantle drives a suite of convection-related manifestations. Although seismic tomography is providing increasingly resolved images of the present-day mantle heterogeneity, the distribution of mantle density variations in the geological past is unknown, and, by implication, this is true for the convection-related observables. The one major exception is tectonic plate motions, since geologic data are available to estimate their history and they currently provide the only available constraints on the evolution of 3-D mantle buoyancy in the past. We developed a new back-and-forth iterative method for time-reversed convection modeling with a procedure for matching plate velocity data at different instants in the past. The crucial aspect of this reconstruction methodology is to ensure that at all times plates are driven by buoyancy forces in the mantle and not vice versa. Employing tomography-based retrodictions over the Cenozoic, we estimate the global amplitude of the following observables: dynamic surface topography, the core-mantle boundary ellipticity, the free-air gravity anomalies, and the global divergence rates of tectonic plates. One of the major benefits of the new data assimilation method is the stable recovery of much shorter wavelength changes in heterogeneity than was possible in our previous work. We now resolve what appears to be two-stage subduction of the Farallon plate under the western U.S. and a deeply rooted East African Plume that is active under the Ethiopian volcanic fields during the Early Eocene.

  17. Raman spectroscopic studies on the structural changes of poly(3-methylthiophene)during heating and cooling processes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Poly(3-methylthiophene) (PMeT) electrosynthesized by direct oxidation of 3-methylthiophene in boron trifluoride diethyl etherate (BFEE) has been studied by Raman spectroscopy in the temperature scale of 123-458 K. Experimental results demonstrate that the thermal stability of PMeT in the oxidized state is much lower than that of the polymer in the neutral state. Furthermore, during the cooling process, the conformation of neutral species changes from a coil-like state into a rod-like state, while the conformation of the oxidized species does not change.

  18. Convection flow study within a horizontal fluid layer under the action of gas flow

    Directory of Open Access Journals (Sweden)

    Kreta Aleksei

    2016-01-01

    Full Text Available Experimental investigation of convective processes within horizontal evaporating liquid layer under shear–stress of gas flow is presented. It is found the structures of the convection, which move in opposite direction relative to each other. First convective structure moves in reverse direction with the flow of gas, and the second convective structure moves towards the gas flow. Convection flow within the liquid layer is registered with help of PIV technique. Average evaporation flow rate of Ethanol liquid layer under Air gas flow is measured. Influence of the gas velocity, at a constant temperature of 20 °C, on the evaporation flow rate has been studied.

  19. Experimental study on convective boiling heat transfer in narrow-gap annulus tubes

    Institute of Scientific and Technical Information of China (English)

    LI Bin; ZHAO Jian-Fu; ZHOU Fang-De; TANG Ze-Mei; HU Wen-Rui

    2004-01-01

    Since convective boiling or highly subcooled single-phase forced convection in micro-channels is an effective cooling mechanism with a wide range of applications, more experimental and theoretical studies are required to explain and verify the forced convection heat transfer phenomenon in narrow channels. In this experimental study, we model the convective boiling behavior of water with low latent heat substance Freon 113 (R-113), with the purpose of saving power consumption and visualizing experiments. Both heat transfer and pressure drop characteristics were measured in subcooled and saturated concentric narrow gap forced convection boiling. Data were obtained to qualitatively identify the effects of gap size, pressure, flow rate and wall superheat on boiling regimes and the transition between various regimes. Some significant differences from unconfined forced convection boiling were found,and also, the flow patterns in narrow vertical annulus tubes have been studied quantitatively.

  20. Some Properties of the Kinetic Energy Flux and Dissipation in Turbulent Stellar Convection Zones

    CERN Document Server

    Meakin, Casey

    2010-01-01

    We investigate simulated turbulent flow within thermally driven stellar convection zones. Different driving sources are studied, including cooling at the top of the convectively unstable region, as occurs in surface convection zones; and heating at the base by nuclear burning. The transport of enthalpy and kinetic energy, and the distribution of turbulent kinetic energy dissipation are studied. We emphasize the importance of global constraints on shaping the quasi-steady flow characteristics, and present an analysis of turbulent convection which is posed as a boundary value problem that can be easily incorporated into standard stellar evolution codes for deep, efficient convection. Direct comparison is made between the theoretical analysis and the simulated flow and very good agreement is found. Some common assumptions traditionally used to treat quasi-steady turbulent flow in stellar models are briefly discussed. The importance and proper treatment of convective boundaries are indicated.

  1. Evaluation of advanced cooling therapy's esophageal cooling device for core temperature control.

    Science.gov (United States)

    Naiman, Melissa; Shanley, Patrick; Garrett, Frank; Kulstad, Erik

    2016-05-01

    Managing core temperature is critical to patient outcomes in a wide range of clinical scenarios. Previous devices designed to perform temperature management required a trade-off between invasiveness and temperature modulation efficiency. The Esophageal Cooling Device, made by Advanced Cooling Therapy (Chicago, IL), was developed to optimize warming and cooling efficiency through an easy and low risk procedure that leverages heat transfer through convection and conduction. Clinical data from cardiac arrest, fever, and critical burn patients indicate that the Esophageal Cooling Device performs very well both in terms of temperature modulation (cooling rates of approximately 1.3°C/hour, warming of up to 0.5°C/hour) and maintaining temperature stability (variation around goal temperature ± 0.3°C). Physicians have reported that device performance is comparable to the performance of intravascular temperature management techniques and superior to the performance of surface devices, while avoiding the downsides associated with both.

  2. CDM Convective Forecast Planning guidance

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The CDM Convective Forecast Planning (CCFP) guidance product provides a foreast of en-route aviation convective hazards. The forecasts are updated every 2 hours and...

  3. ATLAS - Liquid Cooling Systems

    CERN Multimedia

    Bonneau, P.

    1998-01-01

    Photo 1 - Cooling Unit - Side View Photo 2 - Cooling Unit - Detail Manifolds Photo 3 - Cooling Unit - Rear View Photo 4 - Cooling Unit - Detail Pump, Heater and Exchanger Photo 5 - Cooling Unit - Detail Pump and Fridge Photo 6 - Cooling Unit - Front View

  4. Gas turbine heat transfer and cooling technology

    CERN Document Server

    Han, Je-Chin; Ekkad, Srinath

    2012-01-01

    FundamentalsNeed for Turbine Blade CoolingTurbine-Cooling TechnologyTurbine Heat Transfer and Cooling IssuesStructure of the BookReview Articles and Book Chapters on Turbine Cooling and Heat TransferNew Information from 2000 to 2010ReferencesTurbine Heat TransferIntroductionTurbine-Stage Heat TransferCascade Vane Heat-Transfer ExperimentsCascade Blade Heat TransferAirfoil Endwall Heat TransferTurbine Rotor Blade Tip Heat TransferLeading-Edge Region Heat TransferFlat-Surface Heat TransferNew Information from 2000 to 20102.10 ClosureReferencesTurbine Film CoolingIntroductionFilm Cooling on Rotat

  5. Internal Wave Generation by Convection

    OpenAIRE

    Lecoanet, Daniel

    2016-01-01

    In nature, it is not unusual to find stably stratified fluid adjacent to convectively unstable fluid. This can occur in the Earth's atmosphere, where the troposphere is convective and the stratosphere is stably stratified; in lakes, where surface solar heating can drive convection above stably stratified fresh water; in the oceans, where geothermal heating can drive convection near the ocean floor, but the water above is stably stratified due to salinity gradients; possible in the Earth's liq...

  6. Convection and segregation in a flat rotating sandbox

    Science.gov (United States)

    Rietz, Frank; Stannarius, Ralf

    2012-01-01

    A flat box, almost completely filled with a mixture of granulate, is rotated slowly about its horizontal central axis. In this experiment, a regular vortex flow of the granular material is observed in the cell plane. These vortex structures have a superficial analogy to convection rolls in dissipative structures of ordinary liquids. Whereas in the latter, the origin of the convection can often be attributed to gradients e.g. of densities or surface tensions, there is no trivial explanation at present for the convection of the granulate in the rotating container. Despite the simplicity of the experiment, the underlying mechanisms for convection and segregation are difficult to extract. Here, we present a comprehensive experimental study of the patterns under various experimental conditions and propose a mechanism for the convection.

  7. The Cool Surge Following Flux Emergence in a Radiation-MHD Experiment

    Science.gov (United States)

    Nóbrega-Siverio, D.; Moreno-Insertis, F.; Martínez-Sykora, J.

    2016-05-01

    Cool and dense ejections, typically Hα surges, often appear alongside EUV or X-ray coronal jets as a result of the emergence of magnetized plasma from the solar interior. Idealized numerical experiments explain those ejections as being indirectly associated with the magnetic reconnection taking place between the emerging and preexisting systems. However, those experiments miss basic elements that can importantly affect the surge phenomenon. In this paper we study the cool surges using a realistic treatment of the radiation transfer and material plasma properties. To that end, the Bifrost code is used, which has advanced modules for the equation of state of the plasma, photospheric and chromospheric radiation transfer, heat conduction, and optically thin radiative cooling. We carry out a 2.5D experiment of the emergence of magnetized plasma through (meso) granular convection cells and the low atmosphere to the corona. Through detailed Lagrange tracing we study the formation and evolution of the cool ejection and, in particular, the role of the entropy sources; this allows us to discern families of evolutionary patterns for the plasma elements. In the launch phase, many elements suffer accelerations well in excess of gravity; when nearing the apex of their individual trajectories, instead, the plasma elements follow quasi-parabolic trajectories with accelerations close to {g}⊙ . We show how the formation of the cool ejection is mediated by a wedge-like structure composed of two shocks, one of which leads to the detachment of the surge from the original emerged plasma dome.

  8. Properties of convective motions in facular regions

    Science.gov (United States)

    Kostik, R.; Khomenko, E. V.

    2012-09-01

    Aims: We study the properties of solar granulation in a facular region from the photosphere up to the lower chromosphere. Our aim is to investigate the dependence of granular structure on magnetic field strength. Methods: We used observations obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two different instruments: the Triple Etalon SOlar Spectrometer (TESOS) to measure velocity and intensity variations along the photosphere in the Ba ii 4554 Å line; and, simultaneously, the Tenerife Infrared Polarimeter (TIP-II) to the measure Stokes parameters and the magnetic field strength at the lower photosphere in the Fe i 1.56 μm lines. Results: We find that the convective velocities of granules in the facular area decrease with magnetic field while the convective velocities of intergranular lanes increase with the field strength. Similar to the quiet areas, there is a contrast and velocity sign reversal taking place in the middle photosphere. The reversal heights depend on the magnetic field strength and are, on average, about 100 km higher than in the quiet regions. The correlation between convective velocity and intensity decreases with magnetic field at the bottom photosphere, but increases in the upper photosphere. The contrast of intergranular lanes observed close to the disk center is almost independent of the magnetic field strength. Conclusions: The strong magnetic field of the facular area seems to stabilize the convection and to promote more effective energy transfer in the upper layers of the solar atmosphere, since the convective elements reach greater heights.

  9. Solar convection and oscillations in magnetic regions

    CERN Document Server

    Jacoutot, L; Wray, A; Mansour, N N

    2008-01-01

    The goal of this research is to investigate how magnetic field affects the dynamics of granular convection and excitation of solar oscillations by means of realistic numerical simulations. We have used a 3D, compressible, non-linear radiative magnetohydrodynamics code developed at the NASA Ames Research Center. This code takes into account several physical phenomena: compressible fluid flow in a highly stratified medium, sub-grid scale turbulence models, radiative energy transfer between the fluid elements, and a real-gas equation of state. We have studied the influence of the magnetic field of various strength on the convective cells and on the excitation mechanisms of the acoustic oscillations by calculating spectral properties of the convective motions and oscillations. The results reveal substantial changes of the granulation structure with increased magnetic field, and a frequency-dependent reduction in the oscillation power in a good agreement with solar observations. These simulations suggest that the ...

  10. Single phase forced convection cooling of high power leds

    NARCIS (Netherlands)

    Ozdemir, M.Z.; Chestakov, D.; Frijns, A.J.H.

    2011-01-01

    LEDs are strong candidates for future illumination applications dueto their much lower consumption of energy compared to conventional lighting options. One of key problems in development of LEDs is successful thermal management during illumination. Therefore, current research ongoing related to high

  11. Forced-Convection, Liquid-Cooled, Microchannel Heat Sinks

    Science.gov (United States)

    1988-01-07

    as electrical insulator) Flip chip over Clean chip (T,A,M,W/S,W,M,I) and dry Mount chip with beeswax to a glass slide (be sure wax coats the entire...resistor side of chip) Soak in BHF for 3 min Wash with Dl water and dry Demount chip from glass slide Mount chip with beeswax to a polishing...T,A,M,W/S,W,M,I) and dry Pre-etch the surface with full-strength potassium ferricyanide for 5 min (do not use solvents after this step to insure

  12. An Analysis of Thermally-Related Surface Rainfall Budgets Associated with Convective and Stratiform Rainfall

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yushu; Xiaofan LI

    2011-01-01

    Both water vapor and heat processes play key roles in producing surface rainfall.While the water vapor effects of sea surface temperature and cloud radiative and microphysical processes on surface rainfall have been investigated in previous studies,the thermal effects on rainfall are analyzed in this study using a series of two-dimensional equilibrium cloud-resolving model experiments forced by zonally-uniform,constant,large-scale zonal wind and zero large-scale vertical velocity.The analysis of thermally-related surface rainfall budget reveals that the model domain mean surface rain rate is primarily associated with the mean infrared cooling rate.Convective rainfall and transport of hydrometeor concentration from convective regions to raining stratiform regions corresponds to the heat divergence over convective regions,whereas stratiform rainfall corresponds to the transport of hydrometeor concentration from convective regions and heat divergence over raining stratiform regions.The heat divergence over convective regions is mainly balanced by the heat convergence over rainfall-free regions,which is,in turn,offset by the radiative cooling over rainfall-free regions.The sensitivity experiments of rainfall to the effects of sea surface temperature and cloud radiative and microphysical processes show that the sea surface temperature and cloud processes affect convective rainfall through the changes in infrared cooling rate over rainfall-free regions and transport rate of heat from convective regions to rainfall-free regions.

  13. The role of radiation in organizing convection in weak temperature gradient simulations

    Science.gov (United States)

    Sessions, Sharon L.; Sentić, Stipo; Herman, Michael J.

    2016-03-01

    Using a cloud system resolving model with the large scale parameterized by the weak temperature gradient approximation, we investigated the influence of interactive versus noninteractive radiation on the characteristics of convection and convective organization. The characteristics of convecting environments are insensitive to whether radiation is interactive compared to when it is not. This is not the case for nonconvecting environments; interactive radiative cooling profiles show strong cooling at the top of the boundary layer which induces a boundary layer circulation that ultimately exports moist entropy (or analogously moist static energy) from dry domains. This upgradient transport is associated with a negative gross moist stability, and it is analogous to boundary layer circulations in radiative convective equilibrium simulations of convective self-aggregation. This only occurs when radiation cools interactively. Whether radiation is static or interactive also affects the existence of multiple equilibria-steady states which either support precipitating convection or which remain completely dry depending on the initial moisture profile. Interactive radiation drastically increases the range of parameters which permit multiple equilibria compared to static radiation; this is consistent with the observation that self-aggregation in radiative-convective equilibrium simulations is more readily attained with interactive radiation. However, the existence of multiple equilibria in absence of interactive radiation suggests that other mechanisms may result in organization.

  14. Natural convection heat transfer within horizontal spent nuclear fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Canaan, R.E.

    1995-12-01

    Natural convection heat transfer is experimentally investigated in an enclosed horizontal rod bundle, which characterizes a spent nuclear fuel assembly during dry storage and/or transport conditions. The basic test section consists of a square array of sixty-four stainless steel tubular heaters enclosed within a water-cooled rectangular copper heat exchanger. The heaters are supplied with a uniform power generation per unit length while the surrounding enclosure is maintained at a uniform temperature. The test section resides within a vacuum/pressure chamber in order to subject the assembly to a range of pressure statepoints and various backfill gases. The objective of this experimental study is to obtain convection correlations which can be used in order to easily incorporate convective effects into analytical models of horizontal spent fuel systems, and also to investigate the physical nature of natural convection in enclosed horizontal rod bundles in general. The resulting data consist of: (1) measured temperatures within the assembly as a function of power, pressure, and backfill gas; (2) the relative radiative contribution for the range of observed temperatures; (3) correlations of convective Nusselt number and Rayleigh number for the rod bundle as a whole; and (4) correlations of convective Nusselt number as a function of Rayleigh number for individual rods within the array.

  15. Climatology of convective showers dynamics in a convection-permitting model

    Science.gov (United States)

    Brisson, Erwan; Brendel, Christoph; Ahrens, Bodo

    2017-04-01

    Convection-permitting simulations have proven their usefulness in improving both the representation of convective rain and the uncertainty range of climate projections. However, most studies have focused on temporal scales greater or equal to convection cell lifetime. A large knowledge gap remains on the model's performance in representing the temporal dynamic of convective showers and how could this temporal dynamic be altered in a warmer climate. In this study, we proposed to fill this gap by analyzing 5-minute convection-permitting model (CPM) outputs. In total, more than 1200 one-day cases are simulated at the resolution of 0.01° using the regional climate model COSMO-CLM over central Europe. The analysis follows a Lagrangian approach and consists of tracking showers characterized by five-minute intensities greater than 20 mm/hour. The different features of these showers (e.g., temporal evolution, horizontal speed, lifetime) are investigated. These features as modeled by an ERA-Interim forced simulation are evaluated using a radar dataset for the period 2004-2010. The model shows good performance in representing most features observed in the radar dataset. Besides, the observed relation between the temporal evolution of precipitation and temperature are well reproduced by the CPM. In a second modeling experiment, the impact of climate change on convective cell features are analyzed based on an EC-Earth RCP8.5 forced simulation for the period 2071-2100. First results show only minor changes in the temporal structure and size of showers. The increase in convective precipitation found in previous studies seems to be mainly due to an increase in the number of convective cells.

  16. Cool visitors

    CERN Multimedia

    2006-01-01

    Pictured, from left to right: Tim Izo (saxophone, flute, guitar), Bobby Grant (tour manager), George Pajon (guitar). What do the LHC and a world-famous hip-hop group have in common? They are cool! On Saturday, 1st July, before their appearance at the Montreux Jazz Festival, three members of the 'Black Eyed Peas' came on a surprise visit to CERN, inspired by Dan Brown's Angels and Demons. At short notice, Connie Potter (Head of the ATLAS secretariat) organized a guided tour of ATLAS and the AD 'antimatter factory'. Still curious, lead vocalist Will.I.Am met CERN physicist Rolf Landua after the concert to ask many more questions on particles, CERN, and the origin of the Universe.

  17. Examining the Impact of Prandtl Number and Surface Convection Models on Deep Solar Convection

    Science.gov (United States)

    O'Mara, B. D.; Augustson, K.; Featherstone, N. A.; Miesch, M. S.

    2015-12-01

    Turbulent motions within the solar convection zone play a central role in the generation and maintenance of the Sun's magnetic field. This magnetic field reverses its polarity every 11 years and serves as the source of powerful space weather events, such as solar flares and coronal mass ejections, which can affect artificial satellites and power grids. The structure and inductive properties are linked to the amplitude (i.e. speed) of convective motion. Using the NASA Pleiades supercomputer, a 3D fluids code simulates these processes by evolving the Navier-Stokes equations in time and under an anelastic constraint. This code simulates the fluxes describing heat transport in the sun in a global spherical-shell geometry. Such global models can explicitly capture the large-scale motions in the deep convection zone but heat transport from unresolved small-scale convection in the surface layers must be parameterized. Here we consider two models for heat transport by surface convection, including a conventional turbulent thermal diffusion as well as an imposed flux that carries heat through the surface in a manner that is independent of the deep convection and the entropy stratification it establishes. For both models, we investigate the scaling of convective amplitude with decreasing diffusion (increasing Rayleigh number). If the Prandtl number is fixed, we find that the amplitude of convective motions increases with decreasing diffusion, possibly reaching an asymptotic value in the low diffusion limit. However, if only the thermal diffusion is decreased (keeping the viscosity fixed), we find that the amplitude of convection decreases with decreasing diffusion. Such a high-Prandtl-number, high-Peclet-number limit may be relevant for the Sun if magnetic fields mix momentum, effectively acting as an enhanced viscosity. In this case, our results suggest that the amplitude of large-scale convection in the Sun may be substantially less than in current models that employ an

  18. Cooling of Neutron Stars

    Directory of Open Access Journals (Sweden)

    Grigorian H.

    2010-10-01

    Full Text Available We introduce the theoretical basis for modeling the cooling evolution of compact stars starting from Boltzmann equations in curved space-time. We open a discussion on observational verification of different neutron star models by consistent statistics. Particular interest has the question of existence of quark matter deep inside of compact object, which has to have a specific influence on the cooling history of the star. Besides of consideration of several constraints and features of cooling evolution, which are susceptible of being critical for internal structure of hot compact stars we have introduced a method of extraction of the mass distribution of the neutron stars from temperature and age data. The resulting mass distribution has been compared with the one suggested by supernove simulations. This method can be considered as an additional checking tool for the consistency of theoretical modeling of neutron stars. We conclude that the cooling data allowed existence of neutron stars with quark cores even with one-flavor quark matter.

  19. 3D thermal analysis of a permanent magnet motor with cooling fans

    Institute of Scientific and Technical Information of China (English)

    Zheng TAN; Xue-guan SONG; Bing JI; Zheng LIU; Ji-en MA; Wen-ping CAO

    2015-01-01

    Overheating of permanent magnet (PM) machines has become a major technical challenge as it gives rise to magnet demagnetization, degradation of insulation materials, and loss of motor efficiency. This paper proposes a state-of-the-art cooling system for an axial flux permanent magnet (AFPM) machine with the focus on its structural optimization. A computational fluid dynamics (CFD) simulation with thermal consideration has been shown to be an efficient approach in the literature and is thus employed in this work. Meanwhile, a simplified numerical approach to the AFPM machine with complex configuration in 3D consisting of conduction, forced convection, and conjugate heat transfer is taken as a case study. Different simplification meth-ods (including configuration and working conditions) and two optimized fans for forced convection cooling are designed and installed on the AFPM machine and compared to a natural convection cooling system. The results show that the proposed ap-proach is effective for analyzing the thermal performance of a complex AFPM machine and strikes a balance between reasona-ble simplification, accuracy, and computational resource.%目的:提出一种适合永磁电机的冷却系统设计方案,降低电机本体温度。  创新点:提出一种适合永磁电机热分析的CFD仿真模型。  方法:采用计算流体动力学方法对包含冷却风扇的永磁电机进行空间三维热力学分析和优化设计。  结论:本文提出并优化后的冷却风扇可有效降低永磁电机的最高和平均温度。

  20. Intensive probing of a clear air convective field by radar and instrumental drone aircraft.

    Science.gov (United States)

    Rowland, J. R.

    1973-01-01

    An instrumented drone aircraft was used in conjunction with ultrasensitive radar to study the development of a convective field in the clear air. Radar data are presented which show an initial constant growth rate in the height of the convective field of 3.8 m/min, followed by a short period marked by condensation and rapid growth at a rate in excess of 6.1 m/min. Drone aircraft soundings show general features of a convective field including progressive lifting of the inversion at the top of the convection and a cooling of the air at the top of the field. Calculations of vertical heat flux as a function of time and altitude during the early stages of convection show a linear decrease in heat flux with altitude to near the top of the convective field and a negative heat flux at the top. Evidence is presented which supports previous observations that convective cells overshoot their neutral buoyancy level into a region where they are cool and moist compared to their surroundings. Furthermore, only that portion of the convective cell that has overshot its neutral buoyancy level is generally visible to the radar.

  1. Intensive probing of a clear air convective field by radar and instrumental drone aircraft.

    Science.gov (United States)

    Rowland, J. R.

    1973-01-01

    An instrumented drone aircraft was used in conjunction with ultrasensitive radar to study the development of a convective field in the clear air. Radar data are presented which show an initial constant growth rate in the height of the convective field of 3.8 m/min, followed by a short period marked by condensation and rapid growth at a rate in excess of 6.1 m/min. Drone aircraft soundings show general features of a convective field including progressive lifting of the inversion at the top of the convection and a cooling of the air at the top of the field. Calculations of vertical heat flux as a function of time and altitude during the early stages of convection show a linear decrease in heat flux with altitude to near the top of the convective field and a negative heat flux at the top. Evidence is presented which supports previous observations that convective cells overshoot their neutral buoyancy level into a region where they are cool and moist compared to their surroundings. Furthermore, only that portion of the convective cell that has overshot its neutral buoyancy level is generally visible to the radar.

  2. Latent heating and aerosol-precipitation interactions within mesoscale convective systems

    Science.gov (United States)

    Marinescu, Peter James

    Two studies are presented in this thesis that focus on understanding cloud processes within simulations of two mesoscale convective system (MCS) events that occurred during the Midlatitude Continental Convective Clouds Experiment (MC3E). Simulations are conducted with the Regional Atmospheric Modeling System (RAMS) and are compared with a suite of observations obtained during MC3E. It is concluded that the simulations reasonably reproduce the two MCS events of interest. Both studies provide information that can assist in the advancement of cloud process parameterizations in atmospheric models. The first study details the microphysical process contributions to latent heating profiles within MCS convective and stratiform regions and the evolution of these profiles throughout the MCS lifetime. Properly representing the distinctions between the latent heating profiles of MCS convective and stratiform regions has significant implications for the atmospheric responses to latent heating on various scales. The simulations show that throughout the MCSs, condensation and deposition are the primary contributors to latent warming, as compared to riming and nucleation processes. In terms of latent cooling, sublimation, melting, and evaporation all play significant roles. Furthermore, it is evident that throughout the MCS lifecycle, convective regions demonstrate an approximately linear decrease in the magnitudes of latent heating rates, while the evolution of latent heating within stratiform regions is associated with transitions between MCS flow regimes. The second study addresses the relative roles of middle-tropospheric and lower-tropospheric aerosol particles on MCS precipitation during the mature stage. A suite of sensitivity simulations for each MCS event is conducted, where the simulations are initialized with different aerosol profiles that vary in the vertical location of the peak aerosol particle number concentrations. Importantly, the total integrated aerosol mass

  3. An Expanded Analysis of Nitrogen Ice Convection in Sputnik Planum

    Science.gov (United States)

    Umurhan, Orkan M.; Lyra, Wladimir; Wong, Teresa; McKinnon, William B.; Nimmo, Francis; Howard, Alan D.; Moore, Jeffrey M.; Binzel, Richard; White, Oliver; Stern, S. Alan; Ennico, Kimberly; Olkin, Catherine B.; Weaver, Harold A.; Young, Leslie; New Horizons Geology and Geophysics Science Team

    2016-10-01

    The New Horizons close-encounter flyby of Pluto revealed 20-35 km scale ovoid patterns on the informally named Sputnik Planum. These features have been recently interpreted and shown to arise from the action of solid-state convection of (predominantly) nitrogen ice driven by Pluto's geothermal gradient. One of the major uncertainties in the convection physics centers on the temperature and grain-size dependency of nitrogen ice rheology, which has strong implications for the overturn times of the convecting ice. Assuming nitrogen ice in Sputnik Planum rests on a passive water ice bedrock that conducts Pluto's interior heat flux, and, given the uncertainty of the grain-size distribution of the nitrogen ice in Sputnik Planum, we examine a suite of two-dimensional convection models that take into account the thermal contact between the nitrogen ice layer and the conducting water-ice bedrock for a given emergent geothermal flux. We find for nitrogen ice layers several km deep, the emerging convection efficiently cools the nitrogen-ice water-ice bedrock interface resulting in temperature differences across the convecting layer of 10-20 K (at most) regardless of layer depth. For grain sizes ranging from 0.01 mm to 5 mm the resulting horizontal size to depth ratios of the emerging convection patterns go from 4:1 up to 6:1, suggesting that the nitrogen ice layer in Sputnik Planum may be anywhere between 3.5 and 8 km deep. Such depths are consistent with Sputnik Planum being a large impact basin (in a relative sense) analogous to Hellas on Mars. In this grain-size range we also find, (i) the calculated cell overturn times are anywhere from 1e4 to 5e5 yrs and, (ii) there is a distinct transition from steady state to time dependent convection.

  4. Vertical Motions in Convective Clouds Over Darwin, Australia

    Science.gov (United States)

    Mallinson, H.; Schumacher, C.; Ahmed, F.

    2015-12-01

    Vertical motions are essential in parameterizing convection in large-scale models. Yet in tropical systems vertical motions are difficult to obtain, especially in areas of active convection. This study uses three months of profiler data from Darwin, Australia to directly compare vertical velocity and spectrum width with reflectivity at a height of 1 km (a near-surface rain proxy) for shallow, mid-level, and deep convective clouds. Vertical velocities for all convective clouds were also compared to echo-top heights of varying reflectivities to better understand convective cloud dynamics in relation to their vertical structure. In shallow convective clouds (tops 40 dBz). These regimes could represent different stages in the convective cloud life cycle with strong updrafts and moderate reflectivity occurring in the growing phase and strong downdrafts and large reflectivity occurring in the mature phase. The weak up-and downdraft couplet and low reflectivities suggest a dissipating phase. Mid-level convective clouds (tops 4-8 km) also show three distinct regimes: moderate updrafts at low reflectivities (possible growing phase), a weak up-and downdraft couplet at moderate reflectivities (possible dissipating phase), and strong up-and downdrafts at large reflectivities (mature phase). Deep convective clouds (tops >8 km) show strong updrafts above 4 km for all reflectivities with the strongest downdrafts occurring at large reflectivities. While maximum updrafts vary in height and occur at different reflectivities among cloud types, mean downdraft depth never exceeds 3 km and is always strongest at large reflectivities, which may allow better characterization of cold pool properties. Throughout all convective cloud types, spectrum width has the highest values at lower heights than where the strongest up-and downdrafts occur while also showing a maximum value core around the transition height. In addition, maximum vertical motions occur at or just beneath the 30-dBz echo

  5. Mechanisms initiating deep convection over complex terrain during COPS

    Directory of Open Access Journals (Sweden)

    Christoph Kottmeier

    2008-12-01

    Full Text Available Precipitating convection in a mountain region of moderate topography is investigated, with particular emphasis on its initiation in response to boundary-layer and mid- and upper-tropospheric forcing mechanisms. The data used in the study are from COPS (Convective and Orographically-induced Precipitation Study that took place in southwestern Germany and eastern France in the summer of 2007. It is found that the initiation of precipitating convection can be roughly classified as being due to either: (i surface heating and low-level flow convergence; (ii surface heating and moisture supply overcoming convective inhibition during latent and/or potential instability; or (iii mid-tropospheric dynamical processes due to mesoscale convergence lines and forced mean vertical motion. These phenomena have to be adequately represented in models in order to improve quantitative precipitation forecast. Selected COPS cases are analysed and classified into these initiation categories. Although only a subset of COPS data (mainly radiosondes, surface weather stations, radar and satellite data are used here, it is shown that convective systems are captured in considerable detail by sensor synergy. Convergence lines were observed by Doppler radar in the location where deep convection is triggered several hours later. The results suggest that in many situations, observations of the location and timing of convergence lines will facilitate the nowcasting of convection. Further on, forecasting of the initiation of convection is significantly complicated if advection of potentially convective air masses over changing terrain features plays a major role. The passage of a frontal structure over the Vosges - Rhine valley - Black Forest orography was accompanied by an intermediate suppression of convection over the wide Rhine valley. Further downstream, an intensification of convection was observed over the Black Forest due to differential surface heating, a convergence line

  6. Mixing properties of thermal convection in the earth's mantle

    NARCIS (Netherlands)

    Schmalzl, J.T.

    1996-01-01

    The structure of mantle convection will greatly influence the generation and the survival of compositional heterogeneities. Conversely, geochemical observations can be used to obtain information about heterogeneities in the mantle and then, with certain model assumptions, information about the patte

  7. Large-scale vortices in rapidly rotating Rayleigh-B\\'enard convection

    CERN Document Server

    Guervilly, Céline; Jones, Chris A

    2014-01-01

    Using numerical simulations of rapidly rotating Boussinesq convection in a Cartesian box, we study the formation of long-lived, large-scale, depth-invariant coherent structures. These structures, which consist of concentrated cyclones, grow to the horizontal size of the box, with velocities significantly larger than the convective motions. We vary the rotation rate, the thermal driving and the aspect ratio in order to determine the domain of existence of these large-scale vortices (LSV). We find that two conditions are required for their formation. First, the Rayleigh number, a meaure of the thermal driving, must be several times its value at the linear onset of convection; this corresponds to Reynolds numbers, based on the convective velocity and the box depth, $\\gtrsim 100$. Second, the rotational constraint on the convection structures must be strong. This requires that the local Rossby number, based on the convective velocity and the horizontal convective scale, $\\lesssim 0.15$. Simulations in which certa...

  8. Finding the patterns in mantle convection

    Science.gov (United States)

    Atkins, Suzanne; Rozel, Antoine; Valentine, Andrew; Tackley, Paul; Trampert, Jeannot

    2016-04-01

    Inverting mantle flow for past configurations is one of the great outstanding problems in geodynamics. We demonstrate a new method for probabilistic inversion of present-day Earth observations for mantle properties and history. Convection is a non-linear and chaotic, thwarting most standard inversion methods. Because of its chaotic and unpredictable nature, small errors in initial conditions, parameter selection, and computational precision can all significantly change the results produced by mantle convection simulations. However, some patterns and statistics of convection contain the signature of the parameters used in the simulations over long time-scales. Geodynamical studies often vary these parameters to investigate their effects on the patterns produced. We show that with a large enough set of simulations, we can investigate the relationship between input parameters and convection patterns in a more rigorous way. Probabilistic inversion is the only way to approach highly non-linear problems. We use neural networks to represent the probability density function linking convection simulation input parameters and the patterns they produce. This allows us to find input parameters, whilst taking into account all of the uncertainties that are inherent in the inversion of any Earth system: how well do we understand the physics of the process; what do we already know about the input parameters; and how certain are our observations? We show that the mantle structures produced by 4.5 Gyr of convection simulations contain enough information on yield stress, viscosity coefficients, mantle heating rate, and the initial state of primordial material that we can infer them directly without requiring any other information, such as plate velocity.

  9. Turbulent convection in the Sun: modeling in unstructured meshes

    CERN Document Server

    Olshevsky, Vyacheslav; Ham, Frank

    2014-01-01

    We adopted an unstructured hydrodynamical solver CharLES to the problem of global convection in the Sun. With the aim to investigate the properties of solar turbulent convection and reproduce differential rotation pattern. We performed simulations in two spherical shells, with 1.3 and 10 million cells. In the first, coarse mesh, the solution does not reproduce realistic convection, and is dominated by numerical effects. In the second mesh, thermal conduction leads to cooling of bottom layers, that could not be compensated by solar irradiance. More simulations in the 10M cells mesh should be performed to investigate the influence of transport coefficients and numerical effects. Our estimate of the code performance suggests, that realistic simulations in even finer grids could be performed for reasonable computational cost.

  10. Boiling incipience and convective boiling of neon and nitrogen

    Science.gov (United States)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. This design precludes nucleate boiling in the flow channels as they are too small to handle vapor flow. Consequently, it was necessary to determine boiling incipience under the operating conditions of the magnet system. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of plus or minus 15 percent

  11. Rayleigh-Bénard convection in a vertical annular container near the convection threshold.

    Science.gov (United States)

    Wang, Bo-Fu; Wan, Zhen-Hua; Ma, Dong-Jun; Sun, De-Jun

    2014-04-01

    The instabilities and transitions of flow in an annular container with a heated bottom, a cooled top, and insulated sidewalls are studied numerically. The instabilities of the static diffusive state and of axisymmetric flows are investigated by linear stability analysis. The onset of convection is independent of the Prandtl number but determined by the geometry of the annulus, i.e., the aspect ratio Γ (outer radius to height) and radius ratio δ (inner radius to outer radius). The stability curves for onset of convection are presented for 0.001≤δ≤0.8 at six fixed aspect ratios: Γ=1, 1.2, 1.6, 1.75, 2.5, and 3.2. The instability of convective flow (secondary instability), which depends on both the annular geometry and the Prandtl number, is studied for axisymmetric convection. Two pairs of geometric control parameters are chosen to perform the secondary instability analysis-Γ=1.2, δ=0.08 and Γ=1.6, δ=0.2-and the Prandtl number ranges from 0.02 to 6.7. The secondary instability exhibits some similarities to that for convection in a cylinder. A hysteresis stability loop is found for Γ=1.2, δ=0.08 and frequent changes of critical mode with Prandtl number are found for Γ=1.6, δ=0.2. The three-dimensional flows beyond the axisymmetry-breaking bifurcations are obtained by direct numerical simulation for Γ=1.2, δ=0.08.

  12. Numerical study of reservoir cooling by means of peltier effect

    OpenAIRE

    Farias, Rodrigo Martins; Santos, Elizaldo Domingues dos; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira

    2008-01-01

    The present work studies numerically and experimentally the water cooling process by means of natural convection inside a closed reservoir. The cooling process is performed by Peltier or Thermoelectric effect. The purpose here is to obtain the thermal gradient inside the reservoir and to search for the best point where the coldest water can be extracted from the reservoir, which can be considered a geometric optimization of the device thermal design. The analyzed flow is incompressible, lamin...

  13. The Solar Convection Spectrum

    Science.gov (United States)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  14. Thermal Vibrational Convection

    Science.gov (United States)

    Gershuni, G. Z.; Lyubimov, D. V.

    1998-08-01

    Recent increasing awareness of the ways in which vibrational effects can affect low-gravity experiments have renewed interest in the study of thermal vibrational convection across a wide range of fields. For example, in applications where vibrational effects are used to provide active control of heat and mass transfer, such as in heat exchangers, stirrers, mineral separators and crystal growth, a sound understanding of the fundamental theory is required. In Thermal Vibrational Convection, the authors present the theory of vibrational effects caused by a static gravity field, and of fluid flows which appear under vibration in fluid-filled cavities. The first part of the book discusses fluid-filled cavities where the fluid motion only appears in the presence of temperature non-uniformities, while the second considers those situations where the vibrational effects are caused by a non-uniform field. Throughout, the authors concentrate on consideration of high frequency vibrations, where averaging methods can be successfully applied in the study of the phenomena. Written by two of the pioneers in this field, Thermal Vibrational Convection will be of great interest to scientists and engineers working in the many areas that are concerned with vibration, and its effect on heat and mass transfer. These include hydrodynamics, hydro-mechanics, low gravity physics and mechanics, and geophysics. The rigorous approach adopted in presenting the theory of this fascinating and highly topical area will facilitate a greater understanding of the phenomena involved, and will lead to the development of more and better-designed experiments.

  15. The Gaia-ESO Survey: Extracting diffuse interstellar bands from cool star spectra, DIB-based interstellar medium line-of-sight structures at the kpc scale

    CERN Document Server

    Puspitarini, L; Babusiaux, C; Chen, H-C; Bonifacio, P; Sbordone, L; Caffau, E; Duffau, S; Hill, V; Monreal-Ibero, A; Royer, F; Arenou, F; R.,; Peralta, A; Drew, J E; Bonito, R; Lopez-Santiago, J; Alfaro, E; Bensby, T; Bragaglia, A; Flaccomio, E; Lanzafame, A; Pancino, E; Recio-Blanco, A; Smiljanic, R; Costado, M T; Lardo, C; de Laverny, P; Zwitter, T

    2014-01-01

    We study how diffuse interstellar bands (DIBs) measured toward distance-distributed target stars can be used to locate dense interstellar (IS) clouds in the Galaxy and probe a line-of-sight (LOS) kinematical structure, a potential useful tool when gaseous absorption lines are saturated or not available in the spectral range. Cool target stars are numerous enough for this purpose. We have devised automated DIB fitting methods appropriate to cool star spectra and multiple IS components. The data is fitted with a combination of a synthetic stellar spectrum, a synthetic telluric transmission, and empirical DIB profiles. In parallel, stellar distances and extinctions are estimated self-consistently by means of a 2D Bayesian method, from spectroscopically-derived stellar parameters and photometric data. We have analyzed Gaia-ESO Survey (GES) and previously recorded spectra that probe between $\\sim$ 2 and 10 kpc long LOS in five different regions of the Milky Way. Depending on the observed spectral intervals, we ext...

  16. Heat transfer through a horizontal annular layer of magnetic fluid during the cooling of cylindrical current conductors

    Energy Technology Data Exchange (ETDEWEB)

    Polevikov, V.K.; Fertman, V.E.

    1977-01-01

    The results of a numerical study are presented for stationary natural convection in an annular magnetic fluid layer which cools a horizontal cylindrical current conductor. The system of two-dimensional hydrodynamics equations was solved in a non-inductive approximation by the finite differences method. A monotonic conservative differential system of second order accuracy was used. The studies were made in the ranges: 10 < or = to Pr < or = to 10/sup 4/, 0 < or = to Ra < or = to 10/sup 6/, 0 < or = to Ra/sub m/ < or = to 10/sup 8/, 1.5 < or = to r/sub 2//r/sub 1/ < or = to 5 (Pr--Prandtl number; Ra--Rayleigh number; Ra/sub m/--parameter of magnetic convection mechanism; r/sub 2//r/sub 1/--radius ratio of coaxial cylinders). The developmental characteristics of thermoconvective structures, local and integral thermal currents in an annular layer during a change in specific parameters are discussed. Critical formulae are constructed which describe convective heat transfer when Ra/sub m/ much greater than Ra and Ra/sub m/ much less than Ra in which case a good agreement is obtained with known experimental data. The results of the study may be used in devising cooling systems for electrical cables. 5 illustrations, 11 references.

  17. Natural convection between a vertical cylinder and a surrounding array

    Energy Technology Data Exchange (ETDEWEB)

    McEligot, D.M.; O`Brien, J.E.; Stoots, C.M.; Larson, T.K.; Christenson, W.A.; Mecham, D.C.; Lussie, W.G.

    1992-09-01

    The generic situation considered is natural convection between a single heated, vertical cylinder and a surrounding array of cooler vertical cylinders in a triangular pattern. The ratio of the test section temperature to the cooling tube temperature was varied up to 2.6 by adjusting the electrical power. The Rayleigh number, based on test section diameter and air properties evaluated at cooling tube temperature, ranged from 2.9 x 10{sup 4} to 4.6 x 10{sup 5}. Results indicate that the convective heat transfer data could be approximated as Nu{sub D} (T{sub ts}/T{sub ct}){sup 0.14} = 0.156 Ra{sub D}{sup 1/3} in the apparent turbulent region for Ra{sub L} > 1.2 x 10{sup 11.}

  18. Natural convection between a vertical cylinder and a surrounding array

    Energy Technology Data Exchange (ETDEWEB)

    McEligot, D.M.; O' Brien, J.E.; Stoots, C.M.; Larson, T.K.; Christenson, W.A.; Mecham, D.C.; Lussie, W.G.

    1992-01-01

    The generic situation considered is natural convection between a single heated, vertical cylinder and a surrounding array of cooler vertical cylinders in a triangular pattern. The ratio of the test section temperature to the cooling tube temperature was varied up to 2.6 by adjusting the electrical power. The Rayleigh number, based on test section diameter and air properties evaluated at cooling tube temperature, ranged from 2.9 x 10{sup 4} to 4.6 x 10{sup 5}. Results indicate that the convective heat transfer data could be approximated as Nu{sub D} (T{sub ts}/T{sub ct}){sup 0.14} = 0.156 Ra{sub D}{sup 1/3} in the apparent turbulent region for Ra{sub L} > 1.2 x 10{sup 11.}

  19. Thermal/structural analyses of several hydrogen-cooled leading-edge concepts for hypersonic flight vehicles

    Science.gov (United States)

    Gladden, Herbert J.; Melis, Matthew E.; Mockler, Theodore T.; Tong, Mike

    1990-01-01

    The aerodynamic heating at high flight Mach numbers, when shock interference heating is included, can be extremely high and can exceed the capability of most conventional metallic and potential ceramic materials available. Numerical analyses of the heat transfer and thermal stresses are performed on three actively cooled leading-edge geometries (models) made of three different materials to address the issue of survivability in a hostile environment. These analyses show a mixture of results from one configuration to the next. Results for each configuration are presented and discussed. Combinations of enhanced internal film coefficients and high material thermal conductivity of copper and tungsten are predicted to maintain the maximum wall temperature for each concept within acceptable operating limits. The exception is the TD nickel material which is predicted to melt for most cases. The wide range of internal impingement film coefficients (based on correlations) for these conditions can lead to a significant uncertainty in expected leading-edge wall temperatures. The equivalent plastic strain, inherent in each configuration which results from the high thermal gradients, indicates a need for further cyclic analysis to determine component life.

  20. Application of a structure with a diode thermal effect for solar heating and cooling of a building; Application d'une structure a effet de diode thermique au chauffage et a la climatisation solaire d'un local

    Energy Technology Data Exchange (ETDEWEB)

    Boukadida, N. [Faculte des Sciences de Monastir (Tunisia); Vullierme, J.J. [Ecole Nationale Superieure de Mecanique et d' Aerotechnique (ENSMA), Lab. d' Etudes Thermiques, 86 - Poitiers (France)

    2002-07-01

    The aim of this study is to present the effect of a structure with a diode thermal effect on the building thermal behavior. Numerical simulations allowed us to compare the thermal behavior of a building equipped with this structure on its east, south and west frontages to that of standing or conventional building with large or low inertia. Results showed that the structure has a diode thermal effect mainly for the heating application. The revetment nature of the interior structure sides has an effect on the total coefficient of heat transfer The efficiency of this structure is sensible for cases where we can allow a low temperature inside the building during the winter season for a heating application and a high temperature during the summer season for a cooling application. (authors)

  1. Low mass integrated cooling

    CERN Document Server

    Mapelli, Alessandro

    2014-01-01

    Low mass on - detec tor cooling systems are being developed and stud ied by the Detector Technology group (PH - DT) in the CERN Physics Department in close collaboration with LHC and non - LHC experiments . Two approaches are currently being investigated. The first approach, for barrel configurations, consists in integrating the cooli ng apparatus in light mechanical structures support ing the detectors. In this case , the thermal management can be achieved either with light cooling pipes and thin plates or with a network of microchannels embedded in thin strips of silicon or polyimide . Both configuratio ns are being investigated in the context of the 2018 upgrade program of the ALICE Inner Tracking System (ITS). Moreover, it is also possible to use a s ilicon microchannel cooling device itself as structural support for the detectors and electronics. Such a configur ation has been adopted by the NA62 collaboration for the ir GigaTracKer (GTK) as well as by the LHCb collaboration for the 2018 major upgrade of...

  2. In-Vessel Storage Cooling Analysis in PGSFR

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jung; Lee, Tae Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    The IVS is the place where store the spent fuel temporarily. It is located in the annular space of the reactor core outside, and the spent fuel is stored for two cycles in IVS to reduce the decay heat and radioactivity. A total of 60 spent fuel can be stored in IVS, the minimum distance between spent fuels is more than 20 mm. The spent fuel is fixed in such a way that the nose piece is mounted on the receptacle, which is the same way as the core. Since the spent fuel stored in IVS generates the decay heat continuously, it is necessary to cool the spent fuel during the storage period. However, it is not possible to cool the spent fuel by using cold sodium in the inlet plenum because the orifice hole in the receptacle is blocked. In this study, the cooling performance of spent fuels in IVS by the natural convection due to the temperature difference between hot pool and IVS inside using CFD is assessed. The IVS cooling performance analysis using natural convection due to the temperature difference between the IVS and hot pool is evaluated by CFD. The analyses in various geometry and boundary condition are performed. For all cases, the temperature at the active bundle outlet is higher than 590 .deg. C. Therefore, the spent fuel cooling in IVS using natural convection is difficult to expect the cooling effect.

  3. Spherical-shell boundaries for two-dimensional compressible convection in a star

    Science.gov (United States)

    Pratt, J.; Baraffe, I.; Goffrey, T.; Geroux, C.; Viallet, M.; Folini, D.; Constantino, T.; Popov, M.; Walder, R.

    2016-10-01

    -called 321D link. We find that the inclusion in the spherical shell of the boundary between the radiative and convection zones decreases the amplitude of convective velocities in the convection zone. The inclusion of near-surface layers in the spherical shell can increase the amplitude of convective velocities, although the radial structure of the velocity profile established by deep convection is unchanged. The impact of including the near-surface layers depends on the speed and structure of small-scale convection in the near-surface layers. Larger convective velocities in the convection zone result in a commensurate increase in the overshooting layer width and a decrease in the convective turnover time. These results provide support for non-local aspects of convection.

  4. Numerical simulation of natural convection in a differentially heated tall enclosure using a spectral element method

    OpenAIRE

    Pitz, DB; Chew, JW

    2015-01-01

    Natural convection in differentially heated enclosures is a benchmark problem used to investigate the physics of buoyant flows and to validate numerical methods. Such configurations are also of interest in engineering applications such as cooling of electronic components and air flow around buildings. In this work a spectral element method is used to carry out direct numerical simulations of natural convection in a tall enclosure of aspect ratio 4 with isothermal vertical walls and adiabatic ...

  5. Rapid PCR thermocycling using microscale thermal convection.

    Science.gov (United States)

    Muddu, Radha; Hassan, Yassin A; Ugaz, Victor M

    2011-03-05

    Many molecular biology assays depend in some way on the polymerase chain reaction (PCR) to amplify an initially dilute target DNA sample to a detectable concentration level. But the design of conventional PCR thermocycling hardware, predominantly based on massive metal heating blocks whose temperature is regulated by thermoelectric heaters, severely limits the achievable reaction speed(1). Considerable electrical power is also required to repeatedly heat and cool the reagent mixture, limiting the ability to deploy these instruments in a portable format. Thermal convection has emerged as a promising alternative thermocycling approach that has the potential to overcome these limitations(2-9). Convective flows are an everyday occurrence in a diverse array of settings ranging from the Earth's atmosphere, oceans, and interior, to decorative and colorful lava lamps. Fluid motion is initiated in the same way in each case: a buoyancy driven instability arises when a confined volume of fluid is subjected to a spatial temperature gradient. These same phenomena offer an attractive way to perform PCR thermocycling. By applying a static temperature gradient across an appropriately designed reactor geometry, a continuous circulatory flow can be established that will repeatedly transport PCR reagents through temperature zones associated with the denaturing, annealing, and extension stages of the reaction (Figure 1). Thermocycling can therefore be actuated in a pseudo-isothermal manner by simply holding two opposing surfaces at fixed temperatures, completely eliminating the need to repeatedly heat and cool the instrument. One of the main challenges facing design of convective thermocyclers is the need to precisely control the spatial velocity and temperature distributions within the reactor to ensure that the reagents sequentially occupy the correct temperature zones for a sufficient period of time(10,11). Here we describe results of our efforts to probe the full 3-D velocity and

  6. Study of the circulation theory of the cooling system in vertical evaporative cooling generator

    Institute of Scientific and Technical Information of China (English)

    YU; Shunzhou; CAI; Jing; GUO; Chaohong

    2006-01-01

    The article briefly states the current development of evaporative cooling generator and its advantages comparing with generators of traditional cooling. Vertical evaporative cooling generator, which adopts Close-Loop-Self-Cycle with no-pump and free convection boil in the hollow stator bar, is one of the great developments in generator design. This article emphasizes the importance of cooling system in generator; expatiates the circulation theory in two aspects, energy and flow; and analyzes the essential reason,motivity and stability of Close-Loop-Self-Cycle. The article points out that the motivity of the circulation is the heat absorbed by coolant. After absorbing heat the coolant will have the ability of doing work because of the phase change. In another words, it is the buoyancy causing by density difference leads to the Close-Loop-Self-Cycle. This conclusion is validated by experimental data.

  7. Assessment of Alphamagnetic Spectrometer (AMS) Upper Experiment Structural Configuration Shielding Effectiveness Associated with Change from Cryo-Cooled Magnet to Permanent Magnet

    Science.gov (United States)

    Scully, Robert

    2012-01-01

    In the spring of 2010, the Alpha Magnetic Spectrometer 2 (AMS-02) underwent a series of system level electromagnetic interference control measurements, followed by thermal vacuum testing. Shortly after completion of the thermal vacuum testing, the project decided to remove the cryogenically cooled superconducting magnet, and replace it with the original permanent magnet design employed in the earlier AMS- 01 assembly. Doing so necessitated several structural changes, as well as removal or modification of numerous electronic and thermal control devices and systems. At this stage, the project was rapidly approaching key milestone dates for hardware completion and delivery for launch, and had little time for additional testing or assessment of any impact to the electromagnetic signature of the AMS-02. Therefore, an analytical assessment of the radiated emissions behavioural changes associated with the system changes was requested.

  8. Tropical convection and climate sensitivity

    Science.gov (United States)

    Williams, Ian Nobuo

    Surface temperature has become a popular measure of climate change, but it does not provide the most critical test of climate models. This thesis presents new methods to evaluate climate models based on processes determining the climate sensitivity to radiative forcing from atmospheric greenhouse gases. Cloud radiative feedbacks depend on temperature and relative humidity profiles in addition to surface temperature, through the dependence of cloud type on boundary layer buoyancy. Buoyancy provides a reference to which the onset of deep convection is invariant, and gives a compact description of sea surface temperature changes and cloud feedbacks suitable for diagnostics and as a basis for simplified climate models. This thesis also addresses uncertainties in climate sensitivity involving terrestrial ecosystem responses to global warming. Different diagnostics support different conclusions about atmospheric transport model errors that could imply either stronger or weaker northern terrestrial carbon sinks. Equilibrium boundary layer concepts were previously used in idealized tropical climate models, and are extended here to develop a diagnostic of boundary layer trace gas transport and mixing. Hypotheses linking surface temperature to climate and precipitation sensitivity were tested in this thesis using comprehensive and idealized climate model simulations, and observational datasets. The results do not support the thermostat hypothesis that predicts deep cloud cover will increase with radiative forcing and limit sea surface temperatures to the maximum present-day warm pool temperature. Warm pool temperatures increased along with or even faster than the tropical average over the past several decades, while diagnosed deep cloud cover has not significantly increased, in agreement with global warming simulations. Precipitation sensitivity also depends on more than surface temperature alone, including thermodynamic profiles and air-sea temperature differences. The

  9. Mathematical modelling of convective processes in a weld pool under electric arc surfacing

    Science.gov (United States)

    Sarychev, V. D.; Granovskii, A. Yu; Nevskii, S. A.; Konovalov, S. V.

    2017-01-01

    The authors develop the mathematical model of convective processes in a molten pool under electric arc surfacing with flux-cored wire. The model is based on the ideas of how convective flows appear due to temperature gradient and action of electromagnetic forces. Influence of alloying elements in the molten metal was modeled as a non-linear dependence of surface tension upon temperature. Surface tension and its temperature coefficient were calculated according to the electron density functional method with consideration to asymmetric electron distribution at the interface “molten metal / shielding gas”. Simultaneous solution of Navier-Stokes and Maxwell equations according to finite elements method with consideration to the moving heat source at the interface showed that there is a multi-vortex structure in the molten metal. This structure gives rise to a downward heat flux which, at the stage of heating, moves from the centre of the pool and stirs it full width. At the cooling stage this flux moves towards the centre of the pool and a single vortex is formed near the symmetry centre. This flux penetration is ∼ 10 mm. Formation of the downward heat flux is determined by sign reversal of the temperature coefficient of surface tension due to the presence of alloying elements.

  10. Generating buoyant magnetic flux ropes in solar-like convective dynamos

    CERN Document Server

    Nelson, Nicholas J

    2014-01-01

    Our Sun exhibits strong convective dynamo action which results in magnetic flux bundles emerging through the stellar surface as magnetic spots. Global-scale dynamo action is believed to generate large-scale magnetic structures in the deep solar interior through the interplay of convection, rotation, and shear. Portions of these large-scale magnetic structures are then believed to rise through the convective layer, forming magnetic loops which then pierce the photosphere as sunspot pairs. Previous global simulations of 3D MHD convection in rotating spherical shells have demonstrated mechanisms whereby large-scale magnetic wreaths can be generated in the bulk of the convection zone. Our recent simulations have achieved sufficiently high levels of turbulence to permit portions of these wreaths to become magnetically buoyant and rise through the simulated convective layer through a combination of magnetic buoyancy and advection by convective giant cells. These buoyant magnetic loops are created in the bulk of the...

  11. Mixed convection around calandria tubes in a ¼ scale CANDU-6 moderator circulation tank

    Energy Technology Data Exchange (ETDEWEB)

    Atkins, M.D.; Rossouw, D.J.; Boer, M. [Nuclear Science Division, School of Mechanical and Aeronautical Engineering, University of the Witwatersrand, Johannesburg (South Africa); Kim, T., E-mail: tong.kim@wits.ac.za [Nuclear Science Division, School of Mechanical and Aeronautical Engineering, University of the Witwatersrand, Johannesburg (South Africa); Rhee, B.W.; Kim, H.T. [Severe Accident and PHWR Safety Research Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-05-15

    Highlights: • A secondary jet is formed at a stagnation region and is directed towards the center of the MCT. • The secondary jet undergoes the significant dissipation and mixing due to calandria tubes (CTs). • Its cooling effectiveness is reduced on the CTs in the bottom of the MCT. • With forced convection dominance, peak heat transfer is on the upper CT surface. • With natural convection dominance, peak heat transfer is on the lower CT surface. - Abstract: This study experimentally characterizes mixed convection around calandria tubes (CTs) in a ¼ scale CANDU-6 moderator circulation tank (MCT) that uses air as the working fluid. In a full scale CANDU-6 reactor that undergoes a postulated dual failure with a loss-of-coolant accident without the emergency core cooling system available, mixed convection heat transfer occurs around the CTs. The cooling effectiveness of the moderator is diminished as an emergency heat sink if overheating eventually leads to film boiling. To prevent the onset of film boiling, local sub-cooling margins of the moderator needs to be maintained or else the critical heat flux should be increased. Circulating the moderator which interacts with the overheated CTs increases the heat transfer into the moderator which may suppress film boiling. The present experimental results demonstrate that the cooling effectiveness of the circulating moderator, in particular the secondary jet, is attenuated substantially as it is convected away from the inner wall towards the center of the MCT. The momentum of the secondary jet is diffused through the CTs. At a low jet Reynolds number, the secondary jet becomes ineffective so that some overheated CTs positioned in the other half of the MCT are cooled only by natural convection.

  12. Numerical investigation of Rayleigh–Bénard convection in a cylinder of unit aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bo-Fu; Jiang, Jin [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); Zhou, Lin [Institute of Structural Mechanics, Chinese Academy of Engineering Physics, Mianyang, 621900 (China); Sun, De-Jun, E-mail: jinjiang@whu.edu.cn [Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China)

    2016-02-15

    Thermal convection in a vertical cylindrical cavity with a heated bottom, cooled top and insulated sidewall is investigated numerically. The radius to height ratio (Γ = height/radius) is fixed to unity and the Prandtl number is varied from 0.04 to 1. Rayleigh numbers up to 16 000 are considered in this study. Ten different kinds of flow regime have been identified, including both steady and unsteady patterns. The transition from steady to oscillatory flow occurs at a much lower Rayleigh number for small Prandtl number flow than for large Prandtl number flow. A bifurcation analysis shows the coexistence of two flow patterns in a certain parameter regime. The effect of flow structure on heat transfer is studied for a Prandtl number of unity. (paper)

  13. Analysis of the Magnetic Field Effect on Entropy Generation at Thermosolutal Convection in a Square Cavity

    Directory of Open Access Journals (Sweden)

    Ammar Ben Brahim

    2011-05-01

    Full Text Available Thermosolutal convection in a square cavity filled with air and submitted to an inclined magnetic field is investigated numerically. The cavity is heated and cooled along the active walls with a mass gradient whereas the two other walls of the cavity are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined in transient state for laminar flow by solving numerically the continuity, momentum energy and mass balance equations, using a Control Volume Finite—Element Method. The structure of the studied flows depends on four dimensionless parameters which are the Grashof number, the buoyancy ratio, the Hartman number and the inclination angle. The results show that the magnetic field parameter has a retarding effect on the flow in the cavity and this lead to a decrease of entropy generation, Temperature and concentration decrease with increasing value of the magnetic field parameter.

  14. Convective mixing in homogeneous porous media flow

    Science.gov (United States)

    Ching, Jia-Hau; Chen, Peilong; Tsai, Peichun Amy

    2017-01-01

    Inspired by the flow processes in the technology of carbon dioxide (CO2) storage in saline formations, we modeled a homogeneous porous media flow in a Hele-Shaw cell to investigate density-driven convection due to dissolution. We used an analogy of the fluid system to mimic the diffusion and subsequent convection when CO2 dissolves in brine, which generates a heavier solution. By varying the permeability, we examined the onset of convection, the falling dynamics, the wavelengths of fingers, and the rate of dissolution, for the Rayleigh number Ra (a dimensionless forcing term which is the ratio of buoyancy to diffusivity) in the range of 2.0 ×104≤Ra≤8.26 ×105 . Our results reveal that the effect of permeability influences significantly the initial convective speed, as well as the later coarsening dynamics of the heavier fingering plumes. However, the total dissolved mass, characterized by a nondimensional Nusselt number Nu, has an insignificant dependence on Ra. This implies that the total dissolution rate of CO2 is nearly constant in high Ra geological porous structures.

  15. Theory and simulations of rotating convection

    CERN Document Server

    Barker, Adrian J; Lithwick, Yoram

    2014-01-01

    We study thermal convection in a rotating fluid, with the ultimate goal of explaining the structure of convection zones in rotating stars and planets. We first derive mixing-length theory for rapidly-rotating convection, arriving at the results of Stevenson (1979) via simple physical arguments. The theory predicts the properties of convection as a function of the imposed heat flux and rotation rate, independent of microscopic diffusivities. In particular, it predicts the mean temperature gradient; the rms velocity and temperature fluctuations; and the size of the eddies that dominate heat transport. We test all of these predictions with high resolution three-dimensional hydrodynamical simulations. The results agree remarkably well with the theory across more than two orders of magnitude in rotation rate. For example, the temperature gradient is predicted to scale as the rotation rate to the 4/5th power at fixed flux, and the simulations yield $0.75\\pm 0.06$. We conclude that the mixing length theory is a soli...

  16. Extensional basin evolution in the presence of small-scale convection

    DEFF Research Database (Denmark)

    Petersen, Kenni Dinesen; Nielsen, S.B.; Clausen, O.R.

    2011-01-01

    . This is formulated by assuming that the temperature at a fixed depth (the asymptotic thickness of the lithosphere) is constant. It is implicitly assumed, that this temperature is maintained by sub-lithospheric, small-scale convection, but the dynamics, controlling this process, are not considered. Here, we apply...... a two-dimensional, numerical, thermo-mechanical model of the lithosphere and upper mantle to asses the effects of small-scale convection. Given a particular mantle rheology, our model features such convection, and, over time, the horizontally averaged geotherm converges towards a self-consistent, quasi......-steady-state. Extension of the convecting equilibrium model causes the formation of rifts or continental margins which, posterior to extension, cools and subsides as predicted by the plate model. However, in contrast to the plate model, the ascended asthenosphere is not instantaneously decoupled from the convecting upper...

  17. Titan Balloon Convection Model Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This innovative research effort is directed at determining, quantitatively, the convective heat transfer coefficients applicable to a Montgolfiere balloon operating...

  18. Numerical Simulation of Multiplicity and Stability of Mixed Convection in Rotating Curved Ducts

    Directory of Open Access Journals (Sweden)

    Wang Liqiu

    2005-01-01

    Full Text Available A numerical study is made on the fully developed bifurcation structure and stability of the mixed convection in rotating curved ducts of square cross-section with the emphasis on the effect of buoyancy force. The rotation can be positive or negative. The fluid can be heated or cooled. The study reveals the rich solution and flow structures and complicated stability features. One symmetric and two symmetric/asymmetric solution branches are found with seventy five limit points and fourteen bifurcation points. The flows on these branches can be symmetric, asymmetric, 2-cell, and up to 14-cell structures. Dynamic responses of the multiple solutions to finite random disturbances are examined by the direct transient computation. It is found that possible physically realizable fully developed flows evolve, as the variation of buoyancy force, from a stable steady multicell state at a large buoyancy force of cooling to the coexistence of three stable steady multicell states, a temporal periodic oscillation state, the coexistence of periodic oscillation and chaotic oscillation, a chaotic temporal oscillation, a subharmonic-bifurcation-driven asymmetric oscillating state, and a stable steady 2-cell state at large buoyancy force of heating.

  19. 2-D traveling-wave patterns in binary fluid convection

    Energy Technology Data Exchange (ETDEWEB)

    Surko, C.M.; Porta, A.L. [Univ. of California, La Jolla, CA (United States)

    1996-12-31

    An overview is presented of recent experiments designed to study two-dimensional traveling-wave convection in binary fluid convection in a large aspect ratio container. Disordered patterns are observed when convection is initiated. As time proceeds, they evolve to more ordered patterns, consisting of several domains of traveling-waves separated by well-defined domain boundaries. The detailed character of the patterns depends sensitively on the Rayleigh number. Numerical techniques are described which were developed to provide a quantitative characterization of the traveling-wave patterns. Applications of complex demodulation techniques are also described, which make a detailed study of the structure and dynamics of the domain boundaries possible.

  20. The Texas horned lizard as model for robust capillary structures for passive directional transport of cooling lubricants

    Science.gov (United States)

    Comanns, Philipp; Winands, Kai; Pothen, Mario; Bott, Raya A.; Wagner, Hermann; Baumgartner, Werner

    2016-04-01

    Moisture-harvesting lizards, such as the Texas horned lizard Phrynosoma cornutum, have remarkable adaptations for inhabiting arid regions. Special skin structures, in particular capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and to transport it to the snout for ingestion. This fluid transport is passive and directional towards the lizard's snout. The directionality is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen. Following a biomimetic approach, these principles were transferred to technical prototype design and manufacturing. Capillary structures, 50 μm to 300 μm wide and approx. 70 μm deep, were realized by use of a pulsed picosecond laser in hot working tool steel, hardened to 52 HRC. In order to achieve highest functionality, strategies were developed to minimize potential structural inaccuracies, which can occur at the bottom of the capillary structures caused by the laser process. Such inaccuracies are in the range of 10 μm to 15 μm and form sub-capillary structures with greater capillary forces than the main channels. Hence, an Acceleration Compensation Algorithm was developed for the laser process to minimize or even avoid these inaccuracies. The capillary design was also identified to have substantial influence; by a hexagonal capillary network of non-parallel capillaries potential influences of sub-capillaries on the functionality were reduced to realize a robust passive directional capillary transport. Such smart surface structures can lead to improvements of technical systems by decreasing energy consumption and increasing the resource efficiency.