WorldWideScience

Sample records for flow heat exchanger

  1. Cryogenic heat exchanger with turbulent flows

    International Nuclear Information System (INIS)

    An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N2 and He gases from room temperatures. We present first the experimental results of various parameters which characterize the heat exchanger (efficiency, number of transfer units, heat exchange coefficient, etc) as a function of the mass flow rate of the gas to be cooled. An analysis of the Nu-Re diagram is also presented. All experiments were conducted with N2 gas. The scope of this tool is readily extended to research purposes. (paper)

  2. Stirling Engine With Radial Flow Heat Exchangers

    Science.gov (United States)

    Vitale, N.; Yarr, George

    1993-01-01

    Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.

  3. Cryogenic Heat Exchanger with Turbulent Flows

    Science.gov (United States)

    Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard

    2012-01-01

    An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…

  4. Flow and heat transfer enhancement in tube heat exchangers

    Science.gov (United States)

    Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

    2015-08-01

    The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.

  5. Simulation Studies on A Cross Flow Plate Fin Heat Exchanger

    Directory of Open Access Journals (Sweden)

    M. Thirumarimurugan

    2008-01-01

    Full Text Available Compact heat exchangers which were initially developed for the aerospace industries in the1940s have been considerably improved in the past few years. The main reasons for the goodperformance of compact heat exchangers are their special design which includes turbulent which inturn use high heat transfer coefficient and resists fouling, and maximum temperature driving forcebetween the hot and cold fluids. Numerous types use special enhancement techniques to achieve therequired heat transfer in smaller plot areas and, in many cases, less initial investment. One such type ofcompact heat exchanger is the Plate-fin heat exchanger. The complexity of compact heat exchangerdesign equations results from the exchangers unique ability to transfer heat between multiple processstreams and a wide array of possible flow configurations. This paper presents the performanceevaluation of cross flow plate fin heat exchanger with several different Gas-Liquid systems.Experimental results such as exchanger effectiveness, overall heat transfer coefficients were calculatedfor the flow systems of Cross flow Heat Exchangers. A steady state model for the outlet temperature ofboth the cold and hot fluid and overall heat transfer coefficient of a plate-fin cross flow heat exchangerwas developed and simulated using MATLAB, which was verified with the experiments conducted.

  6. Flow and heat-transfer at the intake of a radially symmetrical longitudinal flow heat exchanger

    International Nuclear Information System (INIS)

    At the admission section of a radially symmetrical longitudinal flow heat exchanger, cross flow of the tubes occurs. The cross flow is followed by an inclined flow, which turns over to a well-balanced longitudinal flow along the tubes. At two heat exchanger models (tube pitch S? = 1.5, S? = 2.0) the velocity distribution, the pressure-drop and the heat-transfer is determined experimentally. By the variation of the boundary-conditions, the influence of the geometry, the mass flow, the tube pitch and the position of the first spacer is shown in this investigation. Finally the experimental datas are compared with results of calculations. (orig.)

  7. Thermal performance modeling of cross-flow heat exchangers

    CERN Document Server

    Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria

    2014-01-01

    This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges

  8. Liquid-fluidized-bed heat exchanger flow distribution models

    Energy Technology Data Exchange (ETDEWEB)

    Cole, L.T.; Allen, C.A.

    1979-01-01

    Allied Chemical Corporation at the Idaho National Engineering Laboratory is developing liquid-fluidized-bed shell-and-tube heat exchangers for geothermal applications. Sand fluidized by geothermal water on the shell side prevents scaling and increases heat transfer coefficients over conventional heat exchangers. Tests were conducted on two instrumented fluidized-bed heat exchanger models, constructed primarily of plexiglass, which differ in tube bundle orientation. One contains a horizontal bundle and the other a vertical tube bundle. Plexiglass construction allowed visual observation of flow patterns. The vertical model proved to have more uniform flow distribution and higher heat transfer coefficients than the horizontal model. The horizontal heat exchanger experienced piling on top of the tubes and areas of poor fluidization existed in the bed. Geometric considerations show that a horizontal design is more conducive to large flow rates than a vertical design. New design concepts for both vertical and horizontal assemblies and recommendations for further developmental work are presented.

  9. Measurement of flow field and local heat transfer distribution on a scraped heat exchanger crystalliser surface

    OpenAIRE

    Rodriguez, Marcos; Ravelet, Florent; Delfos, Rene; Witkamp, Geert-Jan

    2008-01-01

    In a cylindrical scraped heat exchanger crystallizer geometry the flow field influence on the local heat transfer distribution on an evenly cooled scraped heat exchanger surface has been studied by direct measurements of the heat exchanger surface temperature and the fluid velocity field inside the crystallizer. Liquid Crystal Thermometry revealed that the local heat transfer is higher in the middle area of the scraped surface. Stereoscopic PIV measurements demonstrated that the secondary flo...

  10. Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger

    OpenAIRE

    Pavel Neuberger; Radomír Adamovský; Michaela Še?ová

    2014-01-01

    Temperature changes and heat flows in soils that host “slinky”-type horizontal heat exchangers are complex, but need to be understood if robust quantification of the thermal energy available to a ground-source heat pump is to be achieved. Of particular interest is the capacity of the thermal energy content of the soil to regenerate when the heat exchangers are not operating. Analysis of specific heat flows and the specific thermal energy regime within the soil, including that captured by the ...

  11. Fabrication and Analysis of Counter Flow Helical Coil Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Swapnil Ahire

    2014-09-01

    Full Text Available Heat recovery is the capture of energy contained in fluids otherwise that would be lost from a facility. Heat sources may include heat pumps, chillers, steam condensate lines, hot flue gases from boiler, hot air associated with kitchen and laundry facilities, exhaust gases of the engines, power-generation equipment. Helical coil heat exchanger is one of the devices which are used for the heat recovery system. A heat exchanger is a device used to transfer heat between two or more fluids with different temperatures for various application including power plants, nuclear reactors, refrigeration & air condition system, automotive industries, heat recovery system, chemical processing and food industries. Common examples of heat exchangers in everyday use are air pre-heaters and conditioners, automobile radiators, condensers, evaporators, and coolers In present paper analysis of counter flow heat exchanger is done and then variations of various dimensionless numbers i.e. Reynolds Number, Nusselt’s Number and Dean’s number are studied.

  12. Optimization of cross flow heat exchangers for thermoelectric waste heat recovery

    International Nuclear Information System (INIS)

    Thermoelectric waste heat recovery is investigated for current thermoelectric materials with advanced heat exchangers. Numerical heat exchanger models integrated with models for Bi2Te3 thermoelectric modules are validated against experimental data from previous cross flow heat exchanger studies as well as experiments using thermoelectrics between counterflow hot water and cooling air flow channels. The models are used in optimization studies of thermoelectric waste heat recovery with air cooling in a cross flow heat exchanger. Power losses from an air fan and a fluid pump result in an optimal configuration at intermediate cooling air and hot fluid flows. Results show that heat exchangers with Bi2Te3 thermoelectrics can achieve net power densities over 40 W/l

  13. Applications of two-phase flow and heat transfer in compact heat exchangers

    OpenAIRE

    Lintern, Andrew Charles

    2008-01-01

    Three applications of two-phase flow and heat transfer in plate-fin heat exchangers have been studied. A dephlegmator is a heat exchanger in which reflux condensation of a vapour mixture occurs, and plate-fln versions have importance in cryogenic gas separation processes. Numerical calculations for different binary mixtures show that the number of transfer units can be expressed as a simple function of the inlet vapour state and flow rate, heat load, and channel geometry. Th...

  14. Segmented heat exchanger

    Science.gov (United States)

    Baldwin, Darryl Dean (Lafayette, IN); Willi, Martin Leo (Dunlap, IL); Fiveland, Scott Byron (Metamara, IL); Timmons, Kristine Ann (Chillicothe, IL)

    2010-12-14

    A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.

  15. Numerical simulation of shell-side heat transfer and flow of natural circulation heat exchanger

    International Nuclear Information System (INIS)

    In order to analyze the influence on the heat transfer and flow characteristics of the heat exchanger model of different solving models and structures, a variety of transformation to the model equivalent for the heat exchanger was studied. In this paper, Fluent software was used to simulate the temperature-field and flow-field of the equivalent model, and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distribution of temperature-field and flow-field for different models, the heat-transferring process and natural convection situation of heat exchanger were deeply understood. The results show that the temperature difference between the inside and outside of the natural circulation heat exchanger tubes is larger and the flow is more complex, so the turbulence model is the more reasonable choice. Asymmetry of tubes position makes the flow and heat transfer of the fluid on both sides to be dissymmetrical and makes the fluid interaction, and increases the role of natural convection. The complex structure of heat exchanger makes the flow and heat transfer of the fluid on both sides to be irregular to some extent when straight tubes into C-bent are transformed, and all these make the turbulence intensity increase and improve the effect of heat transfer. (authors)

  16. Effect of nanoparticles on heat transfer in mini double-pipe heat exchangers in turbulent flow

    Science.gov (United States)

    Aghayari, Reza; Maddah, Heydar; Ashori, Fatemeh; Hakiminejad, Afshin; Aghili, Mehdi

    2015-03-01

    In this work, heat transfer of a fluid containing nanoparticles of aluminum oxide with the water volume fraction (0.1-0.3) percent has been reported. Heat transfer of the fluid containing nano water aluminum oxide with a diameter of about 20 nm in a horizontal double pipe counter flow heat exchanger under turbulent flow conditions was studied. The results showed that the heat transfer of nanofluid in comparison with the heat transfer of fluid is slightly higher than 12 percent.

  17. Numerical simulation of two phase flows in heat exchangers

    International Nuclear Information System (INIS)

    The author gives an overview of his research activity since 1981. He first gives a detailed presentation of properties and equations of two-phase flows in heat exchangers, and of their mathematical and numerical investigation: semi-local equations (mass conservation, momentum conservation and energy conservation), homogenized conservation equations (mass, momentum and enthalpy conservation, boundary conditions), equation closures, discretization, resolution algorithm, computational aspects and applications. Then, he reports the works performed in the field of turbulent flows, hyperbolic methods, low Mach methods, the Neptune project, and parallel computing

  18. Laminar fluid flow and heat transfer in a fin-tube heat exchanger with vortex generators

    Energy Technology Data Exchange (ETDEWEB)

    Yanagihara, J.I.; Rodriques, R. Jr. [Polytechnic School of Univ. of Sao Paolo, Sao Paolo (Brazil). Dept. of Mechanical Engineering

    1996-12-31

    Development of heat transfer enhancement techniques for fin-tube heat exchangers has great importance in industry. In recent years, heat transfer augmentation by vortex generators has been considered for use in plate fin-tube heat exchangers. The present work describes a numerical investigation about the influence of delta winglet pairs of vortex generators on the flow structure and heat transfer of a plate fin-tube channel. The Navier-Stokes and Energy equations are solved by the finite volume method using a boundary-fitted coordinate system. The influence of vortex generators parameters such as position, angle of attack and aspect ratio were investigated. Local and global influences of vortex generators in heat transfer and flow losses were analyzed by comparison with a model using smooth fin. The results indicate great advantages of this type of geometry for application in plate fin-tube heat exchangers, in terms of large heat transfer enhancement and small pressure loss penalty. (author)

  19. Analysis of the flow structure and heat transfer in a vertical mantle heat exchanger

    DEFF Research Database (Denmark)

    Knudsen, Søren; Morrison, GL; Behnia, M; Furbo, Simon

    2005-01-01

    The flow structure inside the inner tank and inside the mantle of a vertical mantle heat exchanger was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the inner tank and in the mantle were measured using a Particle Image Velocimetry (PIV) system. A Computational Fluid Dynamics (CFD) model of the vertical mantle heat exchanger was also developed for a detailed evaluation of the heat flux at the mantle wall and at the tank wall. ...

  20. Analysis of heat flow and "channelling" in a scraped-surface heat exchanger

    OpenAIRE

    Fitt, AD; Lee, MEM; PLEASE, CP

    2007-01-01

    Scraped-surface heat exchangers (SSHEs) are widely used in industries that manufacture and thermally process fluids; in particular, the food industry makes great use of such devices. Current understanding of the heat flow and fluid dynamics in SSHEs is predominantly based on empirical evidence. In this study a theoretical approach (based on asymptotic analysis) is presented for analysing both the flow and heat transfer in an idealised SSHE (a cylindrical annulus) for Newtonian fluids. The the...

  1. Flow length effect in heat exchangers with turbulent flow at low Prandtl number

    International Nuclear Information System (INIS)

    This work brings out the effect of energy length on the mean overall heat transfer coefficient of a heat exchanger for turbulent flow with low Prandtl number. For this purpose simple heat transfer correlations are proposed in the thermal energy length region and with these correlations the correction factors are calculated for selected special cases. The effect of flow parameters and total heat exchanger length has also been investigated. Finally comments are made regarding thermal boundary conditions and in its light the commonly used design method is assessed

  2. CFD Based Evaluation Of Effectiveness Of Counter Flow Heat Exchanger

    OpenAIRE

    Gurpreet Kour

    2014-01-01

    Engineers are continually being asked to improve effectiveness of heat transfer equipments. These requests may arise as a result of the need to increase profitability or accommodate capital limitations. Processes which use heat transfer equipment i.e. heat exchanger must frequently be improved for these reasons. Artifical roughness is important technique for enhancing the effectiveness of heat exchanger. In this work effectiveness of smooth as well as roughened tube in heat ex...

  3. Modeling heat efficiency, flow and scale-up in the corotating disc scraped surface heat exchanger

    DEFF Research Database (Denmark)

    Friis, Alan; Szabo, Peter; Karlson, Torben

    2002-01-01

    A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer performance predicted by the model agrees well with experimental observations for the laboratory scale CDHE whereas the overall heat transfer in the scaled-up version was not in equally good agreement. Th...

  4. CFD Based Evaluation Of Effectiveness Of Counter Flow Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Gurpreet Kour

    2014-04-01

    Full Text Available Engineers are continually being asked to improve effectiveness of heat transfer equipments. These requests may arise as a result of the need to increase profitability or accommodate capital limitations. Processes which use heat transfer equipment i.e. heat exchanger must frequently be improved for these reasons. Artifical roughness is important technique for enhancing the effectiveness of heat exchanger. In this work effectiveness of smooth as well as roughened tube in heat exchanger is theoretically investigated by using ring type roughness geometry. The performance obtained is then compared with smooth tube. Ringed tube has a significant effect on effectiveness of heat exchanger. The effectiveness is 3.2 times as compared with plane tube was reported. The effectiveness found to be increased with increasing roughness and decreasing pitch between the rings.

  5. Study on flow-induced vibration and anti-vibration measures of nuclear heat exchanger

    International Nuclear Information System (INIS)

    Nuclear heat exchanger is the important equipment of nuclear power plant. Shell-and-tube is the ordinary style used in heat exchanger structure. Unreasonable design will make tubes vibrate and maybe lead tubes broken. Then the running safety of nuclear power plant is influenced. The flow-induced vibration mechanism is studied. Based on structure characteristic of shell-and-tube heat exchange, the failure modes of heat exchange caused by flow-induced vibration are analyzed roundly. Specific approaches are presented to prevent nuclear heat exchange from vibration. (authors)

  6. Flow/heat transfer analysis and shape optimization of a heat exchanger with internally finned tube

    International Nuclear Information System (INIS)

    Analyses of flow and heat transfer characteristics and shape optimization of internally finned circular tubes have been performed for three-dimensional periodically fully developed turbulent flow and heat transfer. CFD and mathematical optimization are coupled in order to optimize the shape of heat exchanger. The design variables such as fin widths (d1, d2) and fin height (h) are numerically optimized by minimizing the pressure loss and maximizing the heat transfer rate for limiting conditions of d1=0.2?1.5 mm, d2=0.2?1.5 mm, and h=0.2?1.5 mm. Due to the periodic boundary conditions along main flow direction, the three layers of meshes are considered. The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by means of the Sequential Quadratic Programming(SQP) method which is widely used in the constrained nonlinear optimization problem

  7. A simple and accurate numerical network flow model for bionic micro heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Pieper, M.; Klein, P. [Fraunhofer Institute (ITWM), Kaiserslautern (Germany)

    2011-05-15

    Heat exchangers are often associated with drawbacks like a large pressure drop or a non-uniform flow distribution. Recent research shows that bionic structures can provide possible improvements. We considered a set of such structures that were designed with M. Hermann's FracTherm {sup registered} algorithm. In order to optimize and compare them with conventional heat exchangers, we developed a numerical method to determine their performance. We simulated the flow in the heat exchanger applying a network model and coupled these results with a finite volume method to determine the heat distribution in the heat exchanger. (orig.)

  8. Flow boiling heat transfer of ammonia/water mixture in a plate heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Taboas, Francisco [Universidad de Cordoba, Campus de Rabanales, Edificio Leonardo da Vinci, 14014 Cordoba (Spain); Valles, Manel; Bourouis, Mahmoud; Coronas, Alberto [CREVER - Universitat Rovira i Virgili, Av. Paisos Catalans No. 26, 43007 Tarragona (Spain)

    2010-06-15

    The objective of this work is to contribute to the development of plate heat exchangers as desorbers for ammonia/water absorption refrigeration machines driven by waste heat or solar energy. In this study, saturated flow boiling heat transfer and the associated frictional pressure drop of ammonia/water mixture flowing in a vertical plate heat exchanger is experimentally investigated. Experimental data is presented to show the effects of heat flux between 20 and 50 kW m{sup -2}, mass flux between 70 and 140 kg m{sup -2} s{sup -1}, mean vapour quality from 0.0 to 0.22 and pressure between 7 and 15 bar, for ammonia concentration between 0.42 and 0.62. The results show that for the selected operating conditions, the boiling heat transfer coefficient is highly dependent on the mass flux, whereas the influence of heat flux and pressure are negligible mainly at higher vapour qualities. The pressure drop increases with increasing mass flux and quality. However, the pressure drop is independent of the imposed heat flux. (author)

  9. Microplate Heat Exchanger Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a microplate heat exchanger for cryogenic cooling systems used for continuous flow distributed cooling systems, large focal plane arrays, multiple...

  10. Numerical Analysis of Heat Transfer and Fluid Flow in Heat Exchangers with Emphasis on Pin Fin Technology

    OpenAIRE

    Nabati, Hamid

    2012-01-01

    One of the most important industrial processes is heat transfer, carried out by heat exchangers in single and multiphase flow applications. Despite the existence of well-developed theoretical models for different heat transfer mechanisms, the expanding need for industrial applications requiring the design and optimization of heat exchangers, has created a solid demand for experimental work and effort. This thesis concerns the use of numerical approaches to analyze and optimize heat transfer a...

  11. Influence of baffle configurations on flow and heat transfer characteristics of trisection helical baffle heat exchangers

    International Nuclear Information System (INIS)

    Highlights: • Nephograms with velocity-vector superimposed are proposed on special slices. • Single vortex secondary flow and shortcut leakage patterns are clearly depicted. • Local heat transfer coefficient field and average value on tubes are presented. • Circumferential overlap scheme performs best over other schemes. - Abstract: Numerical simulation of flow and heat transfer characteristics in four trisection helical baffle heat exchangers with equilateral triangle tube layouts was conducted. The heat exchangers have the same helical pitch but four different baffle shapes or connections, i.e., a circumferential overlap (CO) scheme, an end-to-end (EE) scheme, a blocked V-notches (BV) scheme, and a middle axial overlap (MO) scheme. The single vortex secondary flow in each helical cycle and the leakage flow patterns in the V-notches of the adjacent baffles of these schemes are clearly depicted on the meridian slices and unfolded hexagon slices. The results for nine tubes in a 60° sector and four tube layers reveal that the local heat transfer coefficient of the center tube is much higher than that of the other tubes for all the schemes. The results show that the CO scheme has the highest shell-side heat transfer coefficient and comprehensive indexes, the BV scheme has the highest pressure drop and the worst comprehensive indexes, and the MO scheme has the lowest values of both shell-side heat transfer coefficient and pressure drop and the second highest comprehensive indexes. The average values of comprehensive index ho/?po of CO scheme in the calculated range is respectively 16.5%, 27.3% and 13.5% higher than that of the EE, BV and MO schemes

  12. New counter flow heat exchanger designed for ventilation systems in cold climates

    DEFF Research Database (Denmark)

    Kragh, Jesper; Rose, JØrgen

    2007-01-01

    In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure drop. Preheating the inlet air (outdoor air) to a temperature above 0 degrees C before it enters the exchanger is one solution often used to solve the problem, however, this method reduces the energy saving potential significantly. To minimize the energy cost, a more efficient way to solve the freezing problem is therefore desirable. In this paper, the construction and test measurements of a new counter flow heat exchanger designed for cold climates are presented. The developed heat exchanger is capable of continuously defrosting itself without using supplementary heating. Other advantages of the developed beat exchanger are low pressure loss, cheap materials and a simple construction. The disadvantage is that the exchanger is big compared with other heat exchangers. In this paper, the new heat exchanger's efficiency is calculated theoretically and measured experimentally. The experiment shows that the heat exchanger is capable of continuously defrosting itself at outside air temperatures well below the freezing point while still maintaining a very high efficiency. Further analysis and development of a detailed simulation model of a counter flow air-to-air heat exchanger will be described in future articles.

  13. Degradation of the performance of microchannel heat exchangers due to flow maldistribution

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Engelbrecht, Kurt

    2012-01-01

    The effect of flow maldistribution on the performance of microchannel parallel plate heat exchangers is investigated using an established single blow numerical model and cyclic steady-state regenerator experiments. It is found that as the variation of the individual channel thickness in a particular stack (heat exchanger) increases the actual performance of the heat exchanger decreases significantly, deviating from the expected nominal performance. We show that this is due to both the varying fluid flow velocities in each individual channel and the thermal cross talk between the channels transverse to the direction of the flow.

  14. Pressure loss and heat transfer studies performed on axial-flow finned-tube bundle heat exchangers

    International Nuclear Information System (INIS)

    The experimental studies intend to determine the dependence on the parameters of influence state of flow, tube length, and bundle pitch of the heat transfer and pressure loss characteristic of two tube types in the bundle. By means of suitable parameters for heat flow and pressure loss a comparison will be made of the heat transfer and pressure loss power of the axial-flow furried-tube bundle systems investigated here and conventional heat exchangers. (orig.)

  15. Borehole Heat Exchangers: heat transfer simulation in the presence of a groundwater flow

    International Nuclear Information System (INIS)

    The correct design of the Borehole Heat Exchanger is crucial for the operation and the energy performance of a Ground Source Heat Pump. Most design methods and tools are based on the assumption that the ground is a solid medium where conduction is the only heat transfer mechanism. In turn in regions rich in groundwater the groundwater flow influence has to be assessed, by including the convection effects. In this paper a numerical model of a 100 m U-pipe in a saturated porous medium is presented. The model is created adopting MT3DMS coupled to MODFLOW. A Darcy flow is imposed across the medium. The typical operation of a Borehole Heat Exchanger operating both in winter and in summer is simulated for two years, under different groundwater velocities. The energy injected to and extracted from the ground is derived as a function of the Darcy velocity and compared with the purely conductive case. Temperature fields in the ground at key moments are shown and discussed. From both the energy and the aquifer temperature field points of view, the velocity ranges for respectively negligible and relevant influence of the groundwater flow are identified.

  16. Experimental and Exergy Analysis of A Double Pipe Heat Exchanger for Parallel Flow Arrangement

    Directory of Open Access Journals (Sweden)

    Parth P. Parekh

    2014-07-01

    Full Text Available This paper presents For Experimental and Exergy Analysis of a Double Pipe Heat Exchanger for Parallel- flow Arrangement. The Double pipe heat exchanger is one of the Different types of heat exchangers. double-pipe exchanger because one fluid flows inside a pipe and the other fluid flows between that pipe and another pipe that surrounds the first.In a parallel flow, both the hot and cold fluids enter the Heatexchanger at same end andmove in same direction. The present work is taken up to carry experimental work and the exergy analysis based on second law analysis of a Double-Pipe Heat Exchanger. In experimental set up hot water and cold water will be used working fluids. The inlet Hot water will be varied from 40 0C and 50 0C and cold water temperature will be varied from between 15 and 20 0C. It has been planned to find effects of the inlet condition of both working fluid flowing through the heat exchanger on the heat transfer characteristics, entropy generation, and Exergy loss. The Mathematical modelling of heat exchanger will based on the conservation equation of mass, energy and based on second law of thermodynamics to find entropy generation and exergy losses.

  17. Theoretical investigation on thermal performance of heat pipe flat plate solar collector with cross flow heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Lan; Wu, Shuang-Ying; Zhang, Qiao-Ling; Li, You-Rong [Chongqing University, Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing (China); Chongqing University, College of Power Engineering, Chongqing (China)

    2012-07-15

    Based on the heat transfer characteristics of absorber plate and the heat transfer effectiveness-number of heat transfer unit method of heat exchanger, a new theoretical method of analyzing the thermal performance of heat pipe flat plate solar collector with cross flow heat exchanger has been put forward and validated by comparisons with the experimental and numerical results in pre-existing literature. The proposed theoretical method can be used to analyze and discuss the influence of relevant parameters on the thermal performance of heat pipe flat plate solar collector. (orig.)

  18. Numerical simulation of fluid flow and heat transfer in a concentric tube heat exchanger

    International Nuclear Information System (INIS)

    In this paper, numerical simulation of a concentric tube heat exchanger is presented to determine the convective heat transfer coefficient and friction factor in a smooth tube. Increasing the convective heat transfer coefficient can increase heat transfer rate in a concentric tube heat exchanger from a given tubular surface area. This can be achieved by using heat transfer augmentation devices. This work constitutes the initial phase of the numerical simulation of heat transfer from tubes employing augmentation devices, such as twisted tapes, wire-coil inserts, for heat transfer enhancement. A computational fluid dynamics (CFD) simulation tool was developed with CFX software and the results obtained from the simulations are validated with the empirical correlations for a smooth tube heat exchanger. The difficulties associated with the simulation of a heat exchanger augmented with wire-coil inserts are discussed. (author)

  19. Investigation of the flow conditions in a high-performance heat exchanger

    Science.gov (United States)

    ?opata, Stanis?aw; Oc?oñ, Pawe?

    2010-09-01

    CFD (Computational Fluid Dynamics) computations are carried out in order to investigate the flow distribution and its influence on the heat transfer processes in the high-performance heat exchanger. The subject of this investigation is the classical model of the high-performance heat exchanger with elliptical tubes and rectangular fins. It is possible to find the flow domains where the heat transfer conditions are impaired due to the fully developed turbulent flow. Therefore, the considerable thermal loads occur that may cause the breakdown of the heat exchanger. The emphasis of this investigation is put on the zones and the locations where the tubes are not properly fed with liquid, that result in occurrence of cavitation.

  20. Heat exchanger

    International Nuclear Information System (INIS)

    A heat exchanger having primary and secondary conduits in heat-exchanging relationship is described comprising: at least one serpentine tube having parallel sections connected by reverse bends, the serpentine tube constituting one of the conduits; a group of open-ended tubes disposed adjacent to the parallel sections, the open-ended tubes constituting the other of the conduits, and forming a continuous mass of contacting tubes extending between and surrounding the serpentine tube sections; and means securing the mass of tubes together to form a predetermined cross-section of the entirety of the mass of open-ended tubes and tube sections

  1. Velocity Boundary Layer Analysis of a Flat Plate Heat Exchanger in Laminar Flow: A Case Study

    OpenAIRE

    M. Mirdrikvand; B. Roozbehani; S. I. Moqadam; A. C. Roshan; Y. Ramezani

    2012-01-01

    In this article, a behavioral analysis of velocity boundary layer in a flat plate heat exchanger in laminar flow condition through CFD simulation using FLUENT software is done. The main objective of this study is to determine the velocity vectors between the flat plates of the heat exchanger. In addition, wake occurrence, differences of velocity at different surfaces between plates, angles of velocity vectors and the effect of wake phenomenon on the shear stresses exerted on the plates are di...

  2. Heat transfer coefficient in a shallow fluidized bed heat exchanger with a continuous flow of solid particles

    Scientific Electronic Library Online (English)

    Araí A. Bernárdez, Pécora; Maria Regina, Parise.

    2006-09-01

    Full Text Available This work shows the experimental study of a continuous gas-solid fluidized bed with an immersed tube where cold water is heated by fluidized solid particles presenting inlet temperature from 450 to 700°C. Experiments were carried out in order to verify the influence of solid particle flow rate and d [...] istance between baffles immersed in a shallow fluidized bed. The solid material was 254µm diameter silica sand particles, fluidized by air in a 0.90m long and 0.15m wide heat exchanger. The measurements were taken at steady state conditions for solid mass flow rate from 10 to 100 kg/h, in a heat exchanger with the presence of 5 or 8 baffles. Bed temperature measurements along the length of the heat exchanger were experimentally obtained and heat balances for differential control volumes of the heat exchanger were made in order to obtain the axial profile of the bed-to-tube heat transfer coefficient. The results showed that heat transfer coefficient increases with the solid particle mass flow rate and with the presence of baffles, suggesting that these are important factors to be considered in the design of such heat exchanger.

  3. Non-newtonian flow and pressure drop of pineapple juice in a plate heat exchanger

    Scientific Electronic Library Online (English)

    R. A. F., Cabral; J. A. W., Gut; V. R. N., Telis; J., Telis-Romero.

    2010-12-01

    Full Text Available The study of non-Newtonian flow in plate heat exchangers (PHEs) is of great importance for the food industry. The objective of this work was to study the pressure drop of pineapple juice in a PHE with 50º chevron plates. Density and flow properties of pineapple juice were determined and correlated w [...] ith temperature (17.4

  4. Double tube heat exchanger with novel enhancement: Part I - flow development length and adiabatic friction factor

    Energy Technology Data Exchange (ETDEWEB)

    Tiruselvam, R.; Raghavan, Vijay R. [Universiti Teknologi PETRONAS, Faculty of Mechanical Engineering, Tronoh (Malaysia)

    2012-04-15

    The study is conducted to evaluate the flow characteristics in a double tube heat exchanger using two new and versatile enhancement configurations. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Correlations are proposed for flow development length and friction factor for use in predicting fluid pumping power in thermal equipment as well as in subsequent heat transfer characterization of the surface. (orig.)

  5. Air side flow analysis of fin-tube heat exchanger with vortex generator

    International Nuclear Information System (INIS)

    Fin-tube heat exchangers are widely used in refrigeration systems. To improve the performance of fin-tube heat exchangers, the shape of plain fin was developed in slit fin and louver fin. These pins have higher heat transfer performance as well as larger pressure drop. Recent studies of a Delta Winglet Vortex Generator (DWVG) show less heat transfer capacity than louver fin. However, the DWVG has very small pressure drop. This paper compares the performance for the plain fin and DWVG fin in terms of flow characteristics and heat transfer based on CFD analyses. The DWVG generates vortex and delayed flow separation and leads to a reduction of a wake region behind a tube. The results show that the DWVG produces improved heat transfer and reduced pressure drop compared to a plain fin. This result is opposite to the Reynolds analogy.

  6. Measurement of flow field and wall temperature distribution in a scraped heat exchanger crystallizer

    OpenAIRE

    Rodriguez, Marcos; Ravelet, Florent; Delfos, Rene; Witkamp, Geert-Jan

    2008-01-01

    During crystallization the control and effective distribution of heat transfer from the solution to the heat exchanger (HE) plays an important role. Inhomogeneity in temperature on the HE-surface limits the production capacity and increases the tendency of an isolating scale layer formation. To avoid scaling, scraper blades on the HE are commonly used. In a typical axi-symmetric geometry the scale layer formation was investigated. We studied the influence of the flow field on the actual heat ...

  7. Velocity Boundary Layer Analysis: A Flat Plate Heat Exchanger in Laminar Flow

    Directory of Open Access Journals (Sweden)

    Yasin Ramezani

    2013-05-01

    Full Text Available Plate heat exchangers (PHEs are among the most applicable thermal facilities in diverse industries, particularly in oil and gas operations. Due to their high thermal efficiencies, PHEs are widely used in industries.Plate heat exchangers are mainly made of thin plates that are pressed into a whole frame and shaped in a package. They are designed in various types based on which the plates might be flat or curved with different angles according to their applications. PHEs are much more sensitive to temperature and pressure than other heat exchangers. Their sensitivity is due to their structures that are mainly specified by plate perforations and gasket designs.In this article, a behavioral analysis of velocity Boundary layer in a flat plate heat exchanger in laminar flow condition through CFD simulation using software is done. The main objective of this study is to determine the velocity vectors between the flat plates of heat exchanger. In addition wake occurrence, differences of velocity at different surfaces between plates, angles of velocity vectors and effect of wake phenomenon on the shear stresses exerted on the plates are discussed in detail. The study reveals results graphically based on fluid’s behavior in co-current and counter current flows and discusses thermal indexes consisting of heat transfer coefficient, Nusslet and total heat flux in both conditions.

  8. Flow and heat transfer characteristics of indirect dry cooling system with horizontal heat exchanger A-frames at ambient winds

    International Nuclear Information System (INIS)

    Ambient winds are key issues in the operation of indirect dry cooling system in power plants, so it is of use to make clear the thermo-hydraulic performances of indirect dry cooling system at ambient winds. On the basis of two indirect dry cooling systems with horizontally arranged heat exchanger bundles in the patterns of radial and rectangular A-frames, the computational models of air-side flow and heat transfer coupled with the performances of the circulating water and exhaust steam are developed. The velocity, pressure and temperature fields of cooling air in the absence and presence of winds are presented and the average mass flow rate of cooling air, inlet air temperature as well as the heat rejection for the A-frames of each cooling sector of the air-cooled heat exchanger are calculated, by which the outlet water temperature of heat exchanger and the back pressure of turbine are obtained. The results show that the wind effects on the thermo-hydraulic performances of indirect dry cooling system differ completely from those with vertically arranged air-cooled heat exchanger outside. The velocity and temperature fields present central symmetric characteristics for the heat exchanger in the radial pattern, however, the differences are observed for the heat exchanger A-frames in the rectangular pattern. The thermo-hydraulic performances of the upwind A-frames are most deteriorated by the adverse impacts of ambient winds, but they are improved for the downwind ones, just similar to those of direct dry cooling system. As the wind speed increases, the mass flow rate and heat rejection of the downwind A-frames increase, but they are reduced for the upwind ones. The outlet water temperature of the heat exchanger and back pressure of turbine increase with increasing wind speed. The investigation of wind effects on the flow and heat transfer characteristics of indirect dry cooling system with horizontal heat exchanger A-frames is of benefit to the design and operation of air-cooled heat exchangers and cooling towers. (authors)

  9. Effectiveness-ntu computation with a mathematical model for cross-flow heat exchangers

    Scientific Electronic Library Online (English)

    H. A., Navarro; L. C., Cabezas-Gómez.

    2007-12-01

    Full Text Available Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers [...] with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are obtained by discretizing the coil along the tube fluid path. In each cross section of the element, tube-side fluid temperature is assumed to be constant because the heat capacity rate ratio C*=Cmin/Cmax tends toward zero in the element. Thus temperature is controlled by effectiveness of a local element corresponding to an evaporator or a condenser-type element. The model is validated through comparison with theoretical algebraic relations for single-pass cross-flow arrangements with one or more rows. Very small relative errors are obtained showing the accuracy of the present model. epsilon -NTU curves for several complex circuit arrangements are presented. The model developed represents a useful research tool for theoretical and experimental studies on heat exchangers performance.

  10. Coefficients of turbulent heat and pulse exchange in liquid flows with high level of turbulence

    International Nuclear Information System (INIS)

    For calculating characteristics of turbulent heat and pulse exchange the method is suggested which allows to use the measurement data of velocity pulsation in channels with complex geometry. In the method single-type characteristic of turbulent pulse exchange is used for inlet with unspecified geometry and for area with developed flow. The characteristics are necessary as closing dependences for numerical study of thermohydraulic processes in channels

  11. Numerical simulation of two phase flows in heat exchangers

    International Nuclear Information System (INIS)

    The report presents globally the works done by the author in the thermohydraulic applied to nuclear reactors flows. It presents the studies done to the numerical simulation of the two phase flows in the steam generators and a finite element method to compute these flows. (author)

  12. Dynamic model of counter flow air to air heat exchanger for comfort ventilation with condensation and frost formation

    DEFF Research Database (Denmark)

    Nielsen, Toke Rammer; Rose, JØrgen

    2009-01-01

    In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Condensation and freezing occur often in efficient heat exchangers used in cold climates. To develop efficient heat exchangers and defrosting strategies for cold climates, heat and mass transfer must be calculated under conditions with condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements on a prototype heat exchanger for cold climates.

  13. HEAT TRANSFER AND FLUID FLOW ANALYSIS IN PLATE-FIN AND TUBE HEAT EXCHANGERS WITH DIFFERENT SHAPED VORTEX GENERATORS

    Directory of Open Access Journals (Sweden)

    K.Thirumalai kannan

    2012-03-01

    Full Text Available Numerical analyses were carried out to study the heat transfer and flow in the plate-fin and tube heat exchangers with different shaped vortex generators mounted behind the tubes. The effects of different span angles a (? = 30°, 45° and 60° are investigated in detail for the Reynolds number ranging from 500 to 2500. Numerical simulation was performed by computational fluid dynamics of the heat transfer and fluid flow. The results indicated that the triangle shaped winglet is able to generate longitudinal vortices and improve the heat transfer performance in the wake regions. The case of ? = 45° provides the best heat transfer augmentation than rectangle shape winglet generator in case of inline tubes. Common flow up configuration causes significant separation delay, reduces form drag, and removes the zone of poor heat transfer from the near wake of the tubes.

  14. Thermal-hydraulic issues of flow boiling and condensation in organic Rankine cycle heat exchangers

    Science.gov (United States)

    Mikielewicz, Jaros?aw; Mikielewicz, Dariusz

    2012-08-01

    In the paper presented are the issues related to the design and operation of micro heat exchangers, where phase changes can occur, applicable to the domestic micro combined heat and power (CHP) unit. Analysed is the stability of the two-phase flow in such unit. A simple hydraulic model presented in the paper enables for the stability analysis of the system and analysis of disturbance propagation caused by a jump change of the flow rate. Equations of the system dynamics as well as properties of the working fluid are strongly non-linear. A proposed model can be applicable in designing the system of flow control in micro heat exchangers operating in the considered CHP unit.

  15. Numerical simulation of turbine cascade flow with blade-fluid heat exchange.

    Czech Academy of Sciences Publication Activity Database

    Louda, Petr; Svá?ek, P.; Fo?t, J.; Fürst, J.; Halama, J.; Kozel, Karel

    2013-01-01

    Ro?. 219, ?. 13 (2013), s. 7206-7214. ISSN 0096-3003 R&D Projects: GA ?R(CZ) GAP101/10/1329 Institutional support: RVO:61388998 Keywords : turbomachinery * heat exchange * turbulent flow * coupled problem Subject RIV: BA - General Mathematics Impact factor: 1.600, year: 2013

  16. New idea of heat exchanger for study of flow-induced vibration for tube arrays in cross-flow

    International Nuclear Information System (INIS)

    The flow-induced vibration of tube arrays is very important in heat exchanger. On the basis of the author's theory system and research experiment in the field of flow induced vibration, a new idea to study the flow induced vibration of tube bundle in heat exchanger is presented in this paper. The oscillating fluid mechanics theorem and parameter polynomial method are used to solve the flow equations. Then, the fluid force induced the bundles vibration can be obtained. The full functional analysis method is applied to predict the stability condition of fluid-elasticity. The theory of propagation characteristic of oscillating pressure is used to analyze the phenomena of flow-induced vibration including acoustic resonance. The idea indicates a new approach in the study of the flow-induced vibration in this area

  17. Theoretical and experimental investigation of wickless heat pipes flat plate solar collector with cross flow heat exchanger

    International Nuclear Information System (INIS)

    In this work, a wickless heat pipes flat plate solar collector with a cross flow heat exchanger was investigated theoretically and experimentally under the meteorological conditions of Cairo, Egypt. The author's earlier simulation program of wickless heat pipes flat plate solar water heaters was modified to be valid for the present type of wickless heat pipes solar collector by including the solution of the dimensionless governing equations of the present analysis. For verifying the modified simulation program, a wickless heat pipes flat plate solar collector with a cross flow heat exchanger was designed, constructed, and tested at different meteorological conditions and operating parameters. These parameters include different cooling water mass flow rates and different inlet cooling water temperatures. The comparison between the experimental results and their corresponding simulated ones showed considerable agreement. Under different climatic conditions, the experimental and theoretical results showed that the optimal mass flow rate is very close to the ASHRAE standard mass flow rate for testing conventional flat plate solar collectors. Also, the experimental and theoretical results indicated that the number of wickless heat pipes has a significant effect on the collector efficiency

  18. INTENSIFICATION OF HEAT TRANSFER AND FLOW IN HEAT EXCHANGER WITH SHELL AND HELICALLY COILED TUBE BY USING NANO FLUIDS

    Directory of Open Access Journals (Sweden)

    Dr. Khalid Faisal Sultan

    2015-01-01

    Full Text Available This article presents an experimental study on enhancement of heat transfer and pressure drop of nanofluids flow. In this study the method using to enhancement of heat transfer and pressure drop, by used the helically coiled tube heat exchange and the nanofluids instead of the base fluid (oil. The concentrations of nanofluid used are ranging from (5 – 30 wt%. The shell of the heat exchanger is constant wall temperature (CWT . Two types of nanoparticles used in this paper silver (Ag (30nm and Titanium Oxide (TiO2 (50nm as well as the base fluid (oil. The effect of different parameters such as flow Reynolds number, nanofluid temperature, concentration and type of nanoparticle on heat transfer coefficient and pressure drop of the flow are studied at constant wall temperature. The obtained results show an increase in heat transfer coefficient of 45.35% for Ag + oil and 32.29% for TiO2 + oil at concentration of 30 wt % compared with base fluid (oil. The heat transfer coefficient and pressure drop is increased by using nanofluids (Ag, TiO2 – oil instead of the base fluid (oil. In addition the results indicated that by using heat exchanger with shell and helically coiled tube, the heat transfer performance is improved as well as the pressure drop enhancement due to the curvature of the tube. Furthermore, a maximum increase of 34.15% (Ag + Oil and 27.23% (TiO2+ Oil in Nusselt number ratio for a range of Reynolds numbers between 20 and 200. This paper decided that the nanofluid behaviors are close to typical Newtonian fluids through the relationship between viscosity and shear rate. Moreover to performance index are used to present the corresponding flow and heat transfer technique. The type and size nanoparticles play an important role in enhancement of heat transfer rate

  19. Flow-induced vibration analysis of heat exchanger and steam generator designs

    International Nuclear Information System (INIS)

    Tube and shell heat exchange components such as steam generators, heat exchangers and condensers are essential parts of CANDU (CANadian Deuterium Uranium) nuclear power stations. A flow-induced vibration analysis is presented. In cross-flow three basic flow-induced vibration excitation mechanisms are considered, namely: fluidelastic instability, forced vibration response due to random flow turbulence and periodic wake shedding (the first two mechanisms in both liquid and two-phase cross-flow). Periodic wake shedding has not been detected in two-phase flow but is possible in liquid flow. It is only significant for upstream tube rows. Random flow turbulence is he dominant excitation in both liquid and two-phase axial flow. These vibration excitation mechanisms and the dynamics of multispan tubes are formulated in a computer model. The model predicts tube vibration response and critical velocities for fluidelastic instability. A description of the model is given. The vibration analysis of a steam generator is outlined as an example. The parameters required to formulate the vibration excitation mechanisms are discussed. Periodic wake shedding excitation is formulated in terms of a Strouhal No. and a lift coefficient which is generally less than unity. Fluidelastic instability thresholds are related to dimensionless flow velocity and dimensionless damping for both liquid and two-phase cross-flow. Some statistical parameters to describe random flow turbulence excitation are deduced from experimental data. The power spectral density of the latter is related to a power of the flow velocity. The velocity exponent is roughly two for liquid flow and near unity for two-phase flow. For a given mass flux, the random excitation reaches a maximum at a steam quality of roughly 15%. Damping in two-phase flow is found to be at least four times greater than in liquid flow

  20. Hydrodynamic and heat exchange features of pebbles in radial coolant flow

    International Nuclear Information System (INIS)

    Regarded were the features of radial gas flow in a pebbles bed. The investigation showed that the spherical elements heat emission intensity was defined by the surface vortex formation as well as by gas flux laminarization due to its accelerated flow. A rather simple expression for Nu number as a function of Re number in the range of 5x102-104 for the spherical elements diameter 7, 15 and 22 mm, which takes into consideration the geometrical parameter influence on the heat exchange was obtained

  1. Experimental investigation of air side heat transfer and fluid flow performances of multi-port serpentine cross-flow mesochannel heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Faisal A.; Dasgupta, Engr Sarbadaman [Dept. of Mechanical, Automotive, and Materials Engineering (MAME), University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4 (Canada); Fartaj, Amir, E-mail: fartaj@uwindsor.ca [Dept. of Mechanical, Automotive, and Materials Engineering (MAME), University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4 (Canada)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Air side heat transfer and flow characteristics of mesochannel cross-flow heat exchanger are studied experimentally. Black-Right-Pointing-Pointer Hot ethylene glycol-water mixture (50:50) at constant mass flow rate is used against varying air flow. Black-Right-Pointing-Pointer Air side heat transfer and fluid flow key parameters such as Nusselt number, Colburn factor, friction factor are obtained. Black-Right-Pointing-Pointer General correlations are proposed for air side heat transfer and fluid flow parameters. - Abstract: Air side force convective heat transfer and flow characteristics of cross-flow mesochannel heat exchanger are investigated experimentally. A series of experiments representing 36 different operating conditions have been conducted on a finned mesochannel heat exchanger through the fully automated dynamic single-phase experimental facility which is capable of handling a wide variety of working fluids in air-to-liquid cross-flow orientation. The mesochannel heat exchanger is made of 15 aluminum slabs with arrays of wavy fins between slabs; 68 one millimeter circular diameter port located at each slab, and the air side frontal area of 304-mm Multiplication-Sign 304-mm. The ethylene glycol-water mixture as the working fluid in the liquid side was forced to flow through mesochannels maintaining constant inlet temperature and flow rate at 74 Degree-Sign C and 0.0345 kg/s respectively whereas the inlet flowing air into the arrays of wavy fins was changed at four different temperature levels from 28 Degree-Sign C to 43 Degree-Sign C. Frontal air velocity was altered in nine steps from 3 m/s to 11 m/s at each temperature level corresponding range of Reynolds number 752 < Re{sub a} < 3165. The air side heat transfer and flow characteristics of mesochannel heat exchanger were evaluated during air heating, and heat transfer and fluid flow correlations were derived accordingly. The air side Nusselt number (Nu{sub a}) and Colburn factor (j{sub a}) were found higher in comparison with other studies.

  2. Heat transfer to an in-containment heat exchanger in natural convection flow: Validation of the AEA Technology computational fluid dynamics code CFDS-FLOW3D

    International Nuclear Information System (INIS)

    Validation is presented of an appropriate computer code for modelling heat transfer from the containment atmosphere to an in-containment heat exchanger using new data from ENEL. This work has been carried out in collaboration with ENEL, CISE and ANSALDO. The study helps to identify conditions under which natural circulation induced by the heat exchanger does initiate. The Computational Fluid Dynamics (CFD) code CFDS-FLOW3D, developed by AEA Technology, has been used, initially in a 2-dimensional mode, to simulate the natural convection flow generated within a test vessel by an internal heat exchanger operating in a steam-air gas mixture. The model incorporates a calculations of the heat exchanger condensation rate based on local conditions. Calculational parameters have identified which allow the transient timesteps to converge sufficiently but without using excessive CPU time. Results of pre-test calculations performed for 2 different geometrical configurations are presented. These calculations suggest that the heat exchanger will operate as intended and, at the design values of pressure and temperature, would exceed the planned test power by up to 28%. Post-test simulation results are presented for the first test performed. Good general agreement with major measured parameters is found and a possible explanation for the high upward velocity measured outside the heat exchanger exit is offered. The simulation underestimated the total condenser power by about 16%; this is believed to be due to unpredicting the steady state steam fraction in the vessel. CFDS-FLOW3D is found to be a suitable tool for simulating the details of complex buoyancy driven flows, including non-condensibles, in passive containment cooling applications. The code is sufficiently flexible to be able to represent correctly heat exchanger condensation effects and to be able to simulate the resultant natural convection flows in either 2-D or, if required, in 3-D. (author). 3 refs, 9 figs

  3. A 2-D oscillating flow analysis in Stirling engine heat exchangers

    Science.gov (United States)

    Ahn, Kyung H.; Ibrahim, Mounir B.

    1991-01-01

    A two-dimensional oscillating flow analysis was conducted, simulating the gas flow inside Stirling heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re(max) = 1920 (Va = 80), 10800 (Va = 272), 19300 (Va = 272), and 60800 (Va = 126). The results are compared with experimental results of previous investigators. Also, predictions of the flow regime on present oscillating flow conditions were checked by comparing velocity amplitudes and phase differences with those from laminar theory and quasi-steady profile. A high Reynolds number k-epsilon turbulence model was used for turbulent oscillating pipe flow. Finally, performance evaluation of the K-epsilon model was made to explore the applicability of quasi-steady turbulent models to unsteady oscillating flow analysis.

  4. Study of two-phase flow redistribution between two passes of a heat exchanger

    International Nuclear Information System (INIS)

    The object of the present thesis deals with the study of two-phase flow redistribution between two passes of a heat exchanger. Mass flow rate measurements of each component performed at each channel outlet of the second pass allowed us to determine the influence of mass flow, gas quality, flow direction (upward or downward) and common header geometry upon flow redistribution. Local void fraction inside common header was measured with an optical probe. A two-dimensional two-phase flow computational code was developed from a two-fluid model. Modelling of interfacial momentum transfer was used in order to take into account twp-phase flow patterns in common headers. Numerical simulation results show qualitative agreement with experimental results. Present theoretical model limitations are analysed and future improvements are proposed

  5. Numerical computations on flow and heat transfer characteristics of a helically coiled heat exchanger using different turbulence models

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wei-Cheng [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Ferng, Yuh-Ming, E-mail: ymferng@ess.nthu.edu.tw [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Chieng, Ching-Chang [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon (Hong Kong)

    2013-10-15

    Highlights: • This study investigates thermal–hydraulic behaviors of helically coiled tube HXs. • Three turbulence models are incorporated with N–S equations in simulations. • Flow and heat transfer characteristics in a helically coiled tube HX are captured. • Existing experimental data on Nu number validate the present CFD model. -- Abstract: This study investigates the thermal–hydraulic characteristics of helically coiled tube heat exchangers applied in high temperature gas reactors. In the heat exchanger, the high-temperature helium and the low-temperature water flow through the shell side and the coiled tube, respectively. Three turbulence models are incorporated with Navier–Stokes equations in the numerical simulations: realizable k–?, low-Reynolds k–? and Reynolds stress. Existing experimental data on the Nusselt (Nu) number validate the present CFD simulations using these turbulence models.

  6. Numerical computations on flow and heat transfer characteristics of a helically coiled heat exchanger using different turbulence models

    International Nuclear Information System (INIS)

    Highlights: • This study investigates thermal–hydraulic behaviors of helically coiled tube HXs. • Three turbulence models are incorporated with N–S equations in simulations. • Flow and heat transfer characteristics in a helically coiled tube HX are captured. • Existing experimental data on Nu number validate the present CFD model. -- Abstract: This study investigates the thermal–hydraulic characteristics of helically coiled tube heat exchangers applied in high temperature gas reactors. In the heat exchanger, the high-temperature helium and the low-temperature water flow through the shell side and the coiled tube, respectively. Three turbulence models are incorporated with Navier–Stokes equations in the numerical simulations: realizable k–?, low-Reynolds k–? and Reynolds stress. Existing experimental data on the Nusselt (Nu) number validate the present CFD simulations using these turbulence models

  7. Microtube strip heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Doty, F.D.

    1992-07-09

    The purpose of this contract has been to explore the limits of miniaturization of heat exchangers with the goals of (1) improving the theoretical understanding of laminar heat exchangers, (2) evaluating various manufacturing difficulties, and (3) identifying major applications for the technology. A low-cost, ultra-compact heat exchanger could have an enormous impact on industry in the areas of cryocoolers and energy conversion. Compact cryocoolers based on the reverse Brayton cycle (RBC) would become practical with the availability of compact heat exchangers. Many experts believe that hardware advances in personal computer technology will rapidly slow down in four to six years unless lowcost, portable cryocoolers suitable for the desktop supercomputer can be developed. Compact refrigeration systems would permit dramatic advances in high-performance computer work stations with conventional'' microprocessors operating at 150 K, and especially with low-cost cryocoolers below 77 K. NASA has also expressed strong interest in our MTS exchanger for space-based RBC cryocoolers for sensor cooling. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  8. Microtube strip heat exchanger

    Science.gov (United States)

    Doty, F. D.

    1992-07-01

    The purpose of this contract has been to explore the limits of miniaturization of heat exchangers with the goals of (1) improving the theoretical understanding of laminar heat exchangers, (2) evaluating various manufacturing difficulties, and (3) identifying major applications for the technology. A low-cost, ultra-compact heat exchanger could have an enormous impact on industry in the areas of cryocoolers and energy conversion. Compact cryocoolers based on the reverse Brayton cycle (RBC) would become practical with the availability of compact heat exchangers. Many experts believe that hardware advances in personal computer technology will rapidly slow down in four to six years unless lowcost, portable cryocoolers suitable for the desktop supercomputer can be developed. Compact refrigeration systems would permit dramatic advances in high-performance computer work stations with 'conventional' microprocessors operating at 150 K, and especially with low-cost cryocoolers below 77 K. NASA has also expressed strong interest in our MTS exchanger for space-based RBC cryocoolers for sensor cooling. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  9. Experiments on flow induced vibrations in a heat exchanger tube bundle

    International Nuclear Information System (INIS)

    Most structure and equipment used in nuclear power plant and process plant, such as reactor internals, fuel rod bundles, steam generator tubes and heat exchanger tubes are sub-merged in the fluid. These structures are subjected to flow-induced vibration. An experimental study has been carried out for Reynolds number (7.15 x 103 3) and reduced velocities (1 r < 19) on a research heat exchanger tube bundle to simulate the real conditions. Effect of thermal loading has also been considered. Experimental natural frequencies have been compared to existing literature. Effect of flow rate and pressure on tube drag, lift and axial forces has been analyzed. It has been shown that temperature increase results favorably with respect to stability against vibration as indicated by decrease in volumetric fretting wear loss at loose supports which is due to increase in damping with temperature (thermal damping). (authors)

  10. Velocity Boundary Layer Analysis of a Flat Plate Heat Exchanger in Laminar Flow: A Case Study

    Directory of Open Access Journals (Sweden)

    M. Mirdrikvand

    2012-01-01

    Full Text Available In this article, a behavioral analysis of velocity boundary layer in a flat plate heat exchanger in laminar flow condition through CFD simulation using FLUENT software is done. The main objective of this study is to determine the velocity vectors between the flat plates of the heat exchanger. In addition, wake occurrence, differences of velocity at different surfaces between plates, angles of velocity vectors and the effect of wake phenomenon on the shear stresses exerted on the plates are discussed in detail. The study graphically illustrates results based on fluid’s behavior by a 3D and 2D simulation with air and water as cold and hot streams that affect plate’s situation and its hydro dynamical operations. Consequently, some important design features regarding wake point occurrence and pressure loss are investigated. In addition, eddy current and reverse flows in the wake area and the angles of the velocity vectors are described.

  11. Numerical Dynamic Simulation of Optimized Cross-Flow Heat Exchanger with Various Refrigerants

    Science.gov (United States)

    Osman, Kahar; Jong, Rudiyanto P.; Shariff, M. Shahril

    2010-06-01

    Dynamic behaviors of fluid flow and interaction with the pipe material as well as the temperature are very useful in the design of heat exchangers. The information can be used to determine the effective operating condition and the limitation of the heat exchanger which will then benefited the manufacturers and consumers in terms of economy and safety. A single pass cross flow heat exchanger with conduction and forced convection heat transfer was represented by a mathematical model consist sets of partial differential equations. The equations were then transformed to non-dimensional form for the solution. A computer program was developed to solve the problem numerically. The governing equations were solved by finite difference method using implicit method. Five different types of refrigerant were used in the study; water, R-134a, R-23, R-22 and ammonia. Time response for steady state temperature then was determined and compared between the refrigerants which were then shows that ammonia has the shortest time response and water is the lowest steady state temperature. The results also showed that the tube length affects the air final temperature difference with the increase of temperature difference along with the tube length. The working fluid temperature difference was also affected by tube length with unique behaviors of the increase in temperature with respect to tube length. Finally, maximum air velocity showed the increase with working fluid velocity up to certain magnitude then the air velocity showed negligible change with the increase of working fluid velocity.

  12. Modeling free convection flow of liquid hydrogen within a cylindrical heat exchanger cooled to 14 K

    OpenAIRE

    Yang, SQ; Green, MA; Lau, W

    2005-01-01

    A liquid hydrogen in a absorber for muon cooling requires that up to 300 W be removed from 20 liters of liquid hydrogen. The wall of the container is a heat exchanger between the hydrogen and 14 K helium gas in channels within the wall. The warm liquid hydrogen is circulated down the cylindrical walls of the absorber by free convection. The flow of the hydrogen is studied using FEA methods for two cases and the heat transfer coefficient to the wall is calculated. The first case is when the wa...

  13. Microtube Strip Heat Exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Doty, F.D.

    1990-12-27

    Doty Scientific (DSI) believes their Microtube-Strip Heat Exchanger will contribute significantly to (a) the closed Brayton cycles being pursued at MIT, NASA, and elsewhere; (b) reverse Brayton cycle cryocoolers, currently being investigated by NASA for space missions, being applied to MRI superconducting magnets; and (c) high-efficiency cryogenic gas separation schemes for CO{sub 2} removal from exhaust stacks. The goal of this current study is to show the potential for substantial progress in high-effectiveness, low-cost, gas-to-gas heat exchangers for diverse applications at temperatures from below 100 K to above 1000 K. To date, the highest effectiveness measured is about 98%, and relative pressure drops below 0.1% with a specific conductance of about 45 W/kgK are reported. During the pre-award period DSI built and tested a 3-module heat exchanger bank using 103-tube microtube strip (MTS) modules. To add to their analytical capabilities, DSI has acquired computational fluid dynamics (CFD) software. This report describes the pre-award work and the status of the ten tasks of the current project, which are: analyze flow distribution and thermal stresses within individual modules; design a heat exchanger bank of ten modules with 400 microtube per module; obtain production quality tubestrip die and AISI 304 tubestrips; obtain production quality microtubing; construct revised MTS heat exchanger; construct dies and fixtures for prototype heat exchanger; construct 100 MTS modules; assemble 8-10 prototype MTS heat exchangers; test prototype MTS heat exchanger; and verify test through independent means. 7 refs., 9 figs. 1 tab. (CK)

  14. Microtube strip heat exchanger

    Science.gov (United States)

    Doty, F. D.

    1990-12-01

    Doty Scientific (DSI) believes their microtube-strip heat exchanger will contribute significantly to the following: (1) the closed Brayton cycles being pursued at MIT, NASA, and elsewhere; (2) reverse Brayton cycle cryocoolers, currently being investigated by NASA for space missions, being applied to MRI superconducting magnets; and (3) high-efficiency cryogenic gas separation schemes for CO2 removal from exhaust stacks. The goal of this current study is to show the potential for substantial progress in high-effectiveness, low-cost, gas-to-gas heat exchangers for diverse applications at temperatures from below 100 K to above 1000 K. To date, the highest effectiveness measured is about 98 percent and relative pressure drops below 0.1 percent with a specific conductance of about 45 W/kgK are reported. During the pre-award period DSI built and tested a 3-module heat exchanger bank using 103-tube microtube strip (MTS) modules. To add to their analytical capabilities, DSI has acquired computational fluid dynamics (CFD) software. This report describes the pre-award work and the status of the ten tasks of the current project, which are: analyze flow distribution and thermal stresses within individual modules; design a heat exchanger bank of ten modules with 400 microtube per module; obtain production quality tubestrip die and AISI 304 tubestrips; obtain production quality microtubing; construct revised MTS heat exchanger; construct dies and fixtures for prototype heat exchanger; construct 100 MTS modules; assemble 8 to 10 prototype MTS heat exchangers; test prototype MTS heat exchanger; and verify test through independent means.

  15. Nuclear research reactor IEA-R1 heat exchanger inlet nozzle flow - a preliminary study

    International Nuclear Information System (INIS)

    As a computational fluid mechanics training task, a preliminary model was developed. ANSYS-CFXR code was used in order to study the flow at the inlet nozzle of the heat exchanger of the primary circuit of the nuclear research reactor IEA-R1. The geometry of the inlet nozzle is basically compounded by a cylinder and two radial rings which are welded on the shell. When doing so there is an offset between the holes through the shell and the inlet nozzle. Since it is not standardized by TEMA, the inlet nozzle was chosen for a preliminary study of the flow. Results for the proposed model are presented and discussed. (author)

  16. Heat exchanger restart evaluation

    International Nuclear Information System (INIS)

    On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4A was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the identified tube. The leaking tube was removed and examined metallurgically to determine the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summarized

  17. Heat exchanger restart evaluation

    International Nuclear Information System (INIS)

    On December 24, 1991, the K-Reactor was in the shutdown mode with full AC process water flow and full cooling water flow. Safety rod testing was being performed as part of the power ascension testing program. The results of cooling water samples indicated tritium concentrations higher than allowable. Further sampling and testing confirmed a Process Water System to Cooling Water System leak in heat exchanger 4A (HX 4A). The heat exchanger was isolated and the plant shutdown. Heat exchanger 4kA was removed from the plant and moved to C-Area prior to performing examinations and diagnostic testing. This included locating and identifying the leaking tube or tubes, eddy current examination of the leaking tube and a number of adjacent tubes, visually inspecting the leaking tube from both the inside as well as the area surrounding the failure mechanism. In addition ten other tubes that either exhibited eddy current indications or would represent a baseline condition were removed from heat exchanger 4A for metallurgical examination. Additional analysis and review of heat exchanger leakage history was performed to determine if there are any patterns which can be used for predictive purposes. Compensatory actions have been taken to improve the sensitivity and response time to any future events of this type. The results of these actions are summarized herein

  18. Quasi-steady-state model of a counter flow air-to-air heat exchanger with phase change

    DEFF Research Database (Denmark)

    Rose, JØrgen; Nielsen, Toke Rammer

    2008-01-01

    Using mechanical ventilation with highly efficient heat-recovery in northern European or arctic climates is a very efficient way of reducing the energy use for heating in buildings. However, it also presents a series of problems concerning condensation and frost formation in the heat-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes into account the effects of condensation and frost formation. The model is developed as an Excel spreadsheet, and specific results are compared with laboratory measurements. As an example, the model is used to determine the most energy-efficient control strategy for a specific heat-exchanger under northern European and arctic climate conditions. (C) 2007 Elsevier Ltd. All rights reserved.

  19. Parametric study of gross flow maldistribution in a single-pass shell and tube heat exchanger in turbulent regime

    International Nuclear Information System (INIS)

    Highlights: • A potential means of reducing flow maldistribution in exchangers. • In turbulent flows, maldistribution is but only tube number. • A Gaussian function can also express flow maldistribution in the exchanger. -- Abstract: Uniform distribution of flow in tube bundle of shell and tube heat exchangers is an arbitrary assumption in conventional heat exchanger design. Nevertheless, in practice, flow maldistribution may be an inevitable occurrence which may have severe impacts on thermal and mechanical performance of heat exchangers i.e. fouling. The present models for flow maldistribution in the tube-side deal only with the maximum possible velocity deviation. Other flow maldistribution models propose and recommend the use of a probability distribution, e.g. Gaussian distribution. None of these, nevertheless, estimate quantitatively the number of tubes that suffer from flow maldistribution. This study presents a mathematical model for predicting gross flow maldistribution in the tube-side of a single-pass shell and tube heat exchanger. It can quantitatively estimate the magnitude of flow maldistribution and the number of tubes which have been affected. The validation of the resultant model has been confirmed when compared with similar study using computational fluid dynamics (CFD)

  20. Heat exchanger performance monitoring guidelines

    International Nuclear Information System (INIS)

    Fouling can occur in many heat exchanger applications in a way that impedes heat transfer and fluid flow and reduces the heat transfer or performance capability of the heat exchanger. Fouling may be significant for heat exchanger surfaces and flow paths in contact with plant service water. This report presents guidelines for performance monitoring of heat exchangers subject to fouling. Guidelines include selection of heat exchangers to monitor based on system function, safety function and system configuration. Five monitoring methods are discussed: the heat transfer, temperature monitoring, temperature effectiveness, delta P and periodic maintenance methods. Guidelines are included for selecting the appropriate monitoring methods and for implementing the selected methods. The report also includes a bibliography, example calculations, and technical notes applicable to the heat transfer method

  1. Heat exchange effectiveness and pressure drop for air flow through perforated plates with and without crosswind

    Science.gov (United States)

    Kutscher, C. F.

    1994-05-01

    Low-porosity perforated plates are being used as absorbers for heating ambient air in a new type of unglazed solar collector. This paper investigates the convective heat transfer effectiveness for low-speed air flow through thin, isothermal perforated plates with and without a crosswind on the upstream face. The objective of this work is to provide information that will allow designers to optimize hole size and spacing. In order to obtain performance data, a wind tunnel and small lamp array were designed and built. Experimental data were taken for a range of plate porosities from 0.1 to 5 percent, hole Reynolds numbers from 100 to 2000, and wind speeds from 0 to 4 m/s. Correlations were developed for heat exchange effectiveness and also for pressure drop. Infrared thermography was used to visualize the heat transfer taking place at the surface.

  2. Investigation and application of reduced-order methods for flows study in heat exchanger tube bundles

    International Nuclear Information System (INIS)

    The objective of this thesis is to study the ability of model reduction for investigations of flow-induced vibrations in heat exchangers tube bundle systems.These mechanisms are a cause of major concern because heat exchangers are key elements of nuclear power plants and on-board stoke-holds.In a first part, we give a recall on heat exchangers functioning and on vibratory problems to which they are prone. Then, complete calculations leaded with the CFD numerical code Code-Saturne are carried out, first for the flow around a single circular cylinder (fixed then elastically mounted) and then for the case of a tube bundle system submitted to cross-flow. Reduced-order method POD is applied to the flow resolution with fixed structures. The obtained results show the efficiency of this technique for such configurations, using stabilization methods for the dynamical system resolution in the tube-bundle case. Multiphase-POD, which is a method enabling the adaptation of POD to fluid-structure interactions, is applied. Large displacements of a single cylinder elastically mounted under cross-flow, corresponding to the lock-in phenomenon,are well reproduced with this reduction technique. In the same way, large displacements of a confined moving tube in a bundle are shown to be faithfully reconstructed.Finally, the use of model reduction is extended to parametric studies. First, we propose to use the method which consists in projecting Navier-Stokes equations for several values of the Reynolds number on to a unique POD basis. The results obtained confirm the fact that POD predictability is limited to a range of parameter values. Then, a basis interpolation method, constructed using Grassmann manifolds and allowing the construction of a POD basis from other pre-calculated basis, is applied to basic cases. (author)

  3. PIPO-FE: an updated computer code to evaluate heat exchanger flow-induced vibration

    International Nuclear Information System (INIS)

    PIPO-FE is the latest version of a computer code that has been developed over the past 30 years to assess the flow-induced vibration of heat exchanger and steam generator tubes due to fluidelastic instability, vortex shedding and random-turbulence excitation. The code has recently been updated to include design guidelines prepared by Chalk River Laboratories of Atomic Energy of Canada Ltd. and the Department of Mechanical Engineering of Ecole Polytechnique, Montreal, and to estimate fretting-wear damage caused by random-turbulence vibration. This paper provides a general description of PIPO-FE and its capabilities, with a focus on how it can be used to support the design and modification of power plant heat exchangers. (author)

  4. Experimental study of the flow induced vibration of multi-span heat exchanger tube bundles in liquid cross-flow

    International Nuclear Information System (INIS)

    It is well known that flow induced vibration is one of the factors which imposes limits on the design of heat exchangers and steam generators employed in the Nuclear Power Industry. The results of numerous liquid cross-flow tests conducted on single span laboratory tube bundles have already been reported by the author. These test results have been utilized to develop criterion for design purposes. It remains a fact, nevertheless, that there exists a strong need for test results acquired on multi-span bundles. Such bundles much more closely approximate real heat exchangers and steam generators. Like real heat exchangers, their resonant frequencies are clustered close together, thereby overcoming one of the principal shortcomings of single span test facilities. In this paper, the design of a new four span test facility along with the results of a series of vibration tests are discussed in detail. Using spectral analysis equipment the tube response is carefully examined for the resonant frequencies which it contains and fluidelastic instability measurements have been made. To the author's knowledge, this constitutes one of the first reports in the literature of the results of systematic laboratory vibration tests conducted on a realistic multi-span tube bundle facility subjected to liquid cross-flow. It is expected that these test results, coupled with the results of tests planned for the future, will throw significant new light on this important industrial problem. (orig.)

  5. Performance testing of cross flow heat exchanger operating in the atmosphere of flue gas particulate with vapor condensation

    Directory of Open Access Journals (Sweden)

    Nuntaphan, A.

    2006-05-01

    Full Text Available Performance testing of a cross flow heat exchanger operating under the atmosphere of flue gas particulate from combustion was carried out in this work. This heat exchanger exchanges heat between flue gas from the fuel oil combustion and cold water. The heat exchanger is composed of a spiral finned tube bank having 3 rows and 8 tubes per row with a staggered arrangement. The fin spacings considered are 2.85 and 6.10 mm. The theories of thermodynamics and heat transfer are used for analyzing the performance of this system.In this experiment, the flue gas temperature of 200ºC from combustion having 0.35 kg/s mass flow rate flows along outside surface of the heat exchanger and transfers heat to the 25ºC cooling water having 0.15 kg/s mass flow rate flowing in the tube side. Each experiment uses 750 hr for testing. During the testing, part of flue gas condenses on the heat transfer surface.From the experiment, it was found that the heat transfer rate of both heat exchangers tended to decrease with time while the airside pressure drop increased. These results come from the fouling on the heat transfer surface. Moreover, it is found that the heat exchanger having 2.85 mm fin spacing has an approximately 4 times higher fouling resistance than that of the 6.10 mm fin spacing.In this work a model for calculating the fouling resistance is also developed as a the function of time. The model is developed from that of Kern and Seaton and the mean deviation of the model is 0.789.

  6. An Empirical Study of Helical Coil Heat Exchanger Used in Liquid Evaporization and Droplet Disengagement for a Laminar Fluid Flow

    Directory of Open Access Journals (Sweden)

    Kapil Dev*1,

    2014-04-01

    Full Text Available Heat exchanger is an important component in industrial systems especially in process industries. Many commercial designs and types of heat exchangers are available in market for transfer of heat as well as for recovery of waste heat for the process plants. As helical coil have compact size and higher heat transfer coefficient they are widely used in industrial applications such as food preservation, refrigeration, process plant, power generation, etc. An attempt has been made to study the parallel flow and counter flow of inner higher temperature fluid flow and lower temperature fluid flow, which are separated by copper surface in a helical coil heat exchanger. Helical geometry allows the effective handling at higher temperatures and extreme temperature differentials without any highly induced stress or expansion of joints. These heat exchanger consists of series of stacked helical coiled tubes and the tube ends are connected by manifolds, which also acts as fluid entry and exit locations. In this paper, we focus on design parameters and heat transfer conditions of a vaporizer or generator of a simple vapour absorption refrigeration system having flow condition of refrigerant taken as laminar flow.

  7. Characteristics and flow visualization of a thermosyphon in melts inside a composite heat exchanger tube

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Y.S.; Chiou, J.; Yang, W.J.; Zhang, N. (Dept. of Mechanical Engineering and Applied Mechanics, Univ. of Michigan, Ann Arbor, MI (US)); Lee, C.P. (General Electric Co., Cincinnati, OH (US))

    1990-01-01

    The characteristics of a thermosyphon in molten aluminum inside the annulus of a composite heat exchanger tube has been studied. The physical system consists of two concentric, hollow, carbon steel cylinders press- fitted with a hollow aluminum cylinder in the annulus. It is heated by a helical electric heater wound around the outer surface and is cooled by air flowing through the inner tube. The lower half of the heater surface is insulated to create enough temperature difference to initiate thermosyphon action in the molten aluminum. The orientation of the composite structure is varied from the horizontal to an inclined, to a vertical position. The temperature-time history of the aluminum is monitored at strategic locations to determine the characteristics and mechanisms of thermosyphoning. Flow instability is manifested in the form of temperature fluctuations. The phenomenon have also been studied by means of flow visualization in a transparent composite heat transfer tube with one-half of the outer surface wound with a sheet heater. A molten paraffin wax mixed with an aluminum pigment as the tracer confined in the annulus is cooled by a water stream flowing through the inner tube.

  8. Air flow test of MK-III dump heat exchanger tube arrays for JOYO

    Energy Technology Data Exchange (ETDEWEB)

    Isozaki, Kazunori; Kawahara, Hirotaka; Tomita, Naoki [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1997-07-01

    The reactor thermal power of JOYO MK-III is to be increased from 100MWt to 140MWt due to high performance of reactor core. So, Dump Heat Exchanger(DHX) of MK-III was designed to improve its heat removal capability by changing U type heat transport tube arrays to {Sigma} type tube arrays and increasing air flow. Natural frequency between support and support of MK-III DHX`s tube arrays was about 15Hz, and Karman vortex shedding frequency of tube arrays was about 90Hz by Y.N.Chen`s report. Then, a possibility of piling up of Karman vortex shedding frequency in high frequency mode was to be considered. And, air velocity of flow tube arrays is also increased compared to the MK-II DHX. Sodium leak accident of MONJU was caused by a flow-induced vibration of thermometer well. Therefore, the air flow test to tube arrays of MK-III DHX was conducted. High cycles fatigue damage of tube arrays was evaluated. Since, peak stress is below 2kg/mm{sup 2}, it can be said that high cycles fatigue damage of tube arrays by Karman vortex shedding vibration will not be caused. (J.P.N.)

  9. Numerical simulation of vortex induced vibration and related parameters in cross flow shell and tubes heat exchanger: a review

    International Nuclear Information System (INIS)

    This paper presents a brief review of studies on cross flow induced vortices in downside of tubes which leads to vibration. Two types of vibrations have been studied for tubes in cross flow: first vibration of the tube due to vortex shedding which is important primarily in cross flow but this vibration disappears in slug flow or froth flow regions which are important in numerous heat exchangers, secondly fluid elastic excitation which is most dangerous mechanism in heat exchanger tube bundles. The paper also presents the other parameters such as temperature variation on tube, pressure effect, lift and drag generation and their influence on heat exchanger tubes, different models comparison and tube size effect of tubes for vortices. (author)

  10. Effect of non-uniformity in coolant flow distribution through the volume of heat exchangers on their efficiency

    International Nuclear Information System (INIS)

    Thermohydraulic irregularities in the BN-600 facility intermediate heat exchangers induced by lateral feed and removal of intertubular space coolant, heat-transfer tubes annular package peculiarity, tube bundle deformation, existing tolerances for heat-transfer tubes manufacturing, hole centres shifting while drilling of tube boards are considered. It is shown, that with mixed convection effect regard coolants mutual movements essentially affect efficiency, whereupon with heating coolant movement in gravity force direction heat exchanger efficiency increases and with reverse flow - decreases and modes with coolant 'flip-flop' are possible

  11. Liquid-Metal/Water Direct Contact Heat Exchange: Flow Visualization, Flow Stability, and Heat Transfer Using Real-Time X-Ray Imaging

    International Nuclear Information System (INIS)

    Advanced reactor system designs are being considered with liquid-metal cooling connected to a steam power cycle. In addition, current reactor safety systems are considering auxiliary cooling schemes that assure ex-vessel debris coolability utilizing direct water injection into molten material pools to achieve core quenching and eventual coolability. The phenomenon common in both applications is direct contact heat exchange. The current study focuses on detailed measurements of liquid-metal/water direct contact heat exchange that is directly applicable to improvements in effective heat transfer in devices that are being considered for both of these purposes.In this study, a test facility was designed at the University of Wisconsin-Madison to map the operating range of liquid-metal/water direct contact heat exchange. The test section (184-cm height, 45.75-cm width, and 10-cm depth) is a rectangular slice of a larger heat exchange device. This apparatus was used not only to provide measurements of integral thermal performance (i.e., volumetric heat transfer coefficient), but also local heat transfer coefficients in a bubbly flow regime with X-ray imaging based on measured parameters such as bubble formation time, bubble rise velocity, and bubble diameters.To determine these local heat transfer coefficients, a complete methodology of the X-ray radiography for two-phase flow measurement has been developed. With this methodology, a high-energy X-ray imaging system is optimized for our heat exchange experiments. With this real-time, large-area, high-energy X-ray imaging system, the two-phase flow was quantitatively visualized. An efficient image processing strategy was developed by combining several optimal digital image-processing algorithms into a software computational tool written in MATLAB called T-XIP. Time-dependent heat transfer-related variables such as bubble volumes and velocities, were determined. Finally, an error analysis associated with these measurements has been given based on two independent procedures. This methodology will allow one to utilize X-ray attenuation for imaging vapor bubbles with acceptable errors (bubbles ?1 to 5 cm ± 5 to 20%).Subcooled water (Tsat - Twater [approximately equal to] 10 deg. C) was brought into contact with liquid lead (or lead alloys) at an elevated temperature (Tlm = 500 deg. C and Tlm - Tmelting [approximately equal to] 200 deg. C). The study was conducted over a range of ambient pressures (1 to 10 bar) with four different water injection rates (1.5 to 8 g/s; 0.1 to 1 kg/m2.s). The results showed that the system pressure has a slight effect on volumetric heat transfer coefficient, the bubble formation time, and the bubble rise velocity. Increasing the system pressure, however, resulted in an increase in the bubble average heat transfer coefficient. Increasing the water injection rate directly had only a small effect on the bubble rise velocity or formation rate. Increasing the water injection rate resulted in a decrease in the local bubble heat transfer coefficient.Direct contact heat transfer also has some key disadvantages; e.g., flow instabilities caused by local vapor explosion is one of the issues related to direct contact heat exchange, particularly for liquid/liquid exchange with high temperature differences. In this study, the region of stable heat transfer was mapped and the effects of the liquid metal temperature, the water injection rate, and the operating pressure were investigated. The pressure required to stabilize the heat exchange process was found to be a function of the water injection rate but generally increasing the system pressure helped stabilize the system. It was also found that the larger the injection rate, the higher the pressure required to stabilize the system

  12. Tubed heat exchanger

    International Nuclear Information System (INIS)

    A tubed heat exchanger is described, which has at least one tube with transverse flow over it. The invention concerns the improvement of efficiency by avoiding thick boundary layers on the tube. It has transverse ribs set on it with special projections, which, according to the invention lie only on one side of the main plane of the ribs. Eight pictures illustrate the proposal. (RW)

  13. Heat transfer and pressure drop of supercritical carbon dioxide flowing in several printed circuit heat exchanger channel patterns

    International Nuclear Information System (INIS)

    Closed-loop Brayton cycles using supercritical carbon dioxide (SCO2) show potential for use in high-temperature power generation applications including High Temperature Gas Reactors (HTGR) and Sodium-Cooled Fast Reactors (SFR). Compared to Rankine cycles SCO2 Brayton cycles offer similar or improved efficiency and the potential for decreased capital costs due to a reduction in equipment size and complexity. Compact printed-circuit heat exchangers (PCHE) are being considered as part of several SCO2 Brayton designs to further reduce equipment size with increased energy density. Several designs plan to use a gas cooler operating near the pseudo-critical point of carbon dioxide to benefit from large variations in thermophysical properties, but further work is needed to validate correlations for heat transfer and pressure-drop characteristics of SCO2 flows in candidate PCHE channel designs for a variety of operating conditions. This paper presents work on experimental measurements of the heat transfer and pressure drop behavior of miniature channels using carbon dioxide at supercritical pressure. Results from several plate geometries tested in horizontal cooling-mode flow are presented, including a straight semi-circular channel, zigzag channel with a bend angle of 80 degrees, and a channel with a staggered array of extruded airfoil pillars modeled after a NACA 0020 airfoil with an 8.1 mm chord length facing into the flow. Heat transfer coefficients and bulk temperatures are calculated from measured local wall temperatures and local heat fluxes. The experimental results are compared to several methods for estimating the friction factor and Nusselt number of cooling-mode flows at supercritical pressures in millimeter-scale channels. (authors)

  14. Effect of corrugation angle on the hydrodynamic behaviour of power-law fluids during a flow in plate heat exchangers

    OpenAIRE

    Fernandes, Carla S.; Dias, Ricardo P.; Nóbrega, João M.; Maia, João M.

    2005-01-01

    In this study, CFD calculations were made in order to analyze the hydrodynamic behaviour of a power-law fluid in the channels of plate heat exchangers with corrugation angles of 30º and 60º during a non-isothermal flow. For the observed laminar flow, the numerical results show that a typical velocity profile in the 3D channel of the plate heat exchanger with corrugation angle 30º assumes an approximate parabolic shape and that for a corrugation angle of 60º the profile have a irregular cor...

  15. Spatial vibrations of helical heat-exchanger tubes excited by internal coolant flow

    International Nuclear Information System (INIS)

    A complete system of differential equations for vibrations of screw spiral heat-exchange tubes excited by the inner flow of a coolant as well as an analytical formulation of a set of permissible boundary conditions are obtained on the basis of the Hamilton-Ostrogradsky variation principle. Many results obtained earlier by different authors as applied to curvilinear and linear pipe-lines and spatial rods are shown to follow from the above system as particular cases. Depending on fixation conditions of the heat ecxchange tube ends the system is established to be either conservative or nonconservative one. In the first case when the flow velocity exceeds its critical value a bending form of the stability loss is possible, while in the second case - a flatter one. Particular examples of conservative and nonconservative systems are considered with boundary problems formulated for them. The obtained equations and dependences with their essen-- tial common character may be widely applied in the engineer design of power-generating equipment elements

  16. Experimental studies on pressure drop characteristics of cryogenic cross-counter flow coiled finned tube heat exchangers

    Science.gov (United States)

    Gupta, Prabhat Kumar; Kush, P. K.; Tiwari, Ashesh

    2010-04-01

    Cross-counter flow coiled finned tube heat exchangers used in medium capacity helium liquefiers/refrigerators were developed in our lab. These heat exchangers were developed using integrated low finned tubes. Experimental studies have been performed to know the pressure drop characteristics of tube side and shell side flow of these heat exchangers. All experiments were performed at room temperature in the Reynolds number range of 3000-30,000 for tube side and 25-155 for shell side. The results of present experiments indicate that available correlations for tube side can not be used for prediction of tube side pressure drop data due to complex surface formation at inner side of tube during formation of fins over the outer surface. Results also indicate that surface roughness effect becomes more pronounced as the value of di/ D m increases. New correlations based on present experimental data are proposed for predicting the friction factors for tube side and shell side.

  17. Velocity Boundary Layer Analysis: A Flat Plate Heat Exchanger in Laminar Flow

    OpenAIRE

    Yasin Ramezani; Dariush Moradi; Mojtaba Mirdrikvand

    2013-01-01

    Plate heat exchangers (PHEs) are among the most applicable thermal facilities in diverse industries, particularly in oil and gas operations. Due to their high thermal efficiencies, PHEs are widely used in industries.Plate heat exchangers are mainly made of thin plates that are pressed into a whole frame and shaped in a package. They are designed in various types based on which the plates might be flat or curved with different angles according to their applications. PHEs are much more sensitiv...

  18. New counter flow heat exchanger designed for ventilation systems in cold climates

    DEFF Research Database (Denmark)

    Kragh, Jesper; Rose, Jørgen; Nielsen, Toke Rammer; Svendsen, Svend

    2007-01-01

    In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure drop. Preheating the inlet air (outdoor air) to a temperature above 0 degrees C before it enters the exchanger is one solution often used to solve the problem, however, this method reduces the energy savi...

  19. An experimental and numerical study of a jetfire stop material and a new helical flow heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Austegard, Anders

    1997-12-31

    This thesis consists of two parts. Part 1: Experimental and numerical study of jetfire stop, and Part 2: Experimental and numerical study of a new kind of shell and tube heat exchanger with helical flow on shell side. Part 1 describes the development of the model for simulation of the temperature development through Viking jetfirestop. A simulation program is developed that calculates the temperature development through Viking jetfire stop. In the development of the model, measurements of reaction energy, pyrolysis and heat conductivity at low temperatures are made. The conductivity at higher temperatures and when pyrolysis reactions are going on is estimated experimentally and by numerical calculations. Full-scale jet fire test and small-scale xenon lamp experiments are made to test the simulation model. Part 2 contains the development of a model that simulate the fluid flow and heat transfer in a helical flow shell and tube heat exchanger. It consists of the development of a porosity model and a model for pressure drop and heat transfer as well as experiments in non-standard tube layouts. Results from the simulation program are compared with experiments on a helical flow shell and tube heat exchanger. There is a separate appendix volume. 62 refs., 152 figs., 22 tabs.

  20. Comparison of a Conventional Heat Exchangers with a New Designed Heat Exchanger Experimentally

    Directory of Open Access Journals (Sweden)

    Tansel Koyun

    2014-04-01

    Full Text Available In this study, the air-water heat exchanger designed have been experimentally compared to conventional heat exchangers with and without fin. The same parameters for the three heat exchangers (pump flow, heating power, etc... have been used. In the experiments, speed-flow adjustment has been made to supply heat transfer at an optimum. As a result, during the circulation of water in pipe of the air-water heat exchanger, the corrosion fouling factor has not been formed. In addition, the efficiency of the new designed heat exchanger has been found between fin and finless heat exchanger efficiencies. The results have been shown in the diagrams.

  1. Transient Thermal Behavior of a Vertical Solar Storage Tank with a Mantle Heat Exchanger During No-Flow Operation

    Directory of Open Access Journals (Sweden)

    A. Barzegar

    2009-01-01

    Full Text Available Transient thermal behavior of a vertical storage tank of a domestic solar heating system with a mantle heat exchanger has been investigated numerically in the charging mode. It is assumed that the tank is initially filled with uniform cold water. At an instant of time, the hot fluid from collector outlet is uniformly injected in the upper section of the mantle heat exchanger and after heat transfer with the fluid inside the tank, withdrawn from the bottom part of the heat exchanger. The conservation equations in the cylindrical coordinate and in axis-symmetric condition have been used according to the geometry under investigation. Governing equations have been discretized by employing the finite volume method and the SIMPLER algorithm has been used for coupling between momentum and pressure equations. The Low Reynolds Number (LRN k ?? model is utilized for treating turbulence in the fluid. First, the transient thermal behavior of heat storage tank and the process of formation of thermal stratification in the heat storage tank were investigated. Then, the influence of Rayleigh number in the heat storage tank, Reynolds number in the mantle heat exchanger and vertical positioning of mantle on the flow and thermal fields and the formation of the thermal stratification was investigated. It is found that for higher values of Rayleigh number, a more suitable thermal stratification is established inside the tank. Also it is noticed that increasing the incoming fluid velocity through the mantle heat exchanger causes a faster formation of the thermal stratification. A superior thermal performance was achieved when the mantle heat exchanger is positioned at the middle height of the storage tank.

  2. Damping of heat exchanger tubes

    International Nuclear Information System (INIS)

    Damping information is required for flow-induced vibration analyses of heat exchangers. There are several possible energy dissipation mechanisms that contribute to overall tube damping, including structural damping, friction damping, tube-to-fluid viscous damping and squeeze-film damping. These mechanisms and their relative contribution to overall tube damping are discussed. The approach is to identify the more important energy dissipation mechanisms and to formulate them in terms of heat exchanger tube parameters. This will give the designer a method to evaluate overall tube damping. The results of recent measurements on a simple two-span heat exchanger tube, on tube bundles in two-phase cross-flow, and on real heat exchangers in the field are disscussed

  3. Compact cryocooler heat exchangers

    International Nuclear Information System (INIS)

    Compact heat exchangers are subject to different constraints as a room temperature gas is cooled down by a cold stream returning from a JT valve (or a similar cryoprocess component). In particular, the optimization of exchangers for liquid helium systems has to cover a wide range in temperature and density of the fluid. In the present work we address the following thermodynamic questions: 1. The optimization of intermediate temperatures which optimize stage operation (a stage is assumed to have a constant cross section); 2. The optimum temperature difference available for best overall economic performance values. The results are viewed in the context of porous media concepts applied to rather low speeds of fluid flow in narrow passages. In this paper examples of fluid/solid constraints imposed in this non-classical low temperature area are presented

  4. Computational fluid dynamics and measurement of flow field and wall temperature distribution in a scraped heat exchanger crystallizer.

    OpenAIRE

    Rodriguez, Marcos; Ravelet, Florent; Delfos, Rene; Derksen, J.J.; Witkamp, Geert-Jan

    2008-01-01

    During crystallization the control and effective distribution of heat transfer from the solution to the heat exchanger (HE) plays an important role. Inhomogeneity in temperature on the HE-surface limits the production capacity and increases the tendency of an isolating scale layer formation. To avoid scaling, scraper blades on the HE are commonly used. In a typical axi-symmetric geometry the scale layer formation was investigated. In a previous paper, we studied the influence of the flow fiel...

  5. Shell side numerical analysis of a shell and tube heat exchanger considering the effects of baffle inclination angle on fluid flow using CFD

    OpenAIRE

    Raj Karuppa Thundil R.; Ganne Srikanth

    2012-01-01

    In this present study, attempts were made to investigate the impacts of various baffle inclination angles on fluid flow and the heat transfer characteristics of a shell-and-tube heat exchanger for three different baffle inclination angles namely 0°,10° and 20°. The simulation results for various shell and tube heat exchangers, one with segmental baffles perpendicular to fluid flow and two with segmental baffles inclined to the direction of fluid flow are compared for their performance. ...

  6. Optimization of Heat Exchangers

    International Nuclear Information System (INIS)

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics (pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger design.

  7. Optimization of Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Ivan Catton

    2010-10-01

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.

  8. Comparative Study of Heat Exchangers Using CFD

    OpenAIRE

    Melvinraj C R; Vishal Varghese C

    2014-01-01

    A parallel flow heat exchanger and a corresponding ribbed tube heat exchanger is modeled and numerically analysed using a commercial finite volume CFD package. Pro-E & ANSYS 14.5 softwares are used for the designing and the analysis. CFD predictions of effectiveness of the two heat exchangers are obtained and compared. After selecting the best modeling approach, the sensitivity of the results to particular flow rate is investigated. It is observed that the flow and the tempera...

  9. Heat exchangers: operation problems

    International Nuclear Information System (INIS)

    The main operation problems for heat exchangers are fouling, corrosion, vibrations and mechanical resistance. Fouling and corrosion lead to an over dimensioning, energy consumption increase, corroded pieces change, shutdown costs. Vibrations are taken in account during the dimensioning phase of the heat exchangers. Mechanical resistance problems are, for the classical ones, described in regulation texts. (A.B.). 5 figs., 4 tabs

  10. Numerical simulation of heat exchanger

    International Nuclear Information System (INIS)

    Accurate and detailed knowledge of the fluid flow field and thermal distribution inside a heat exchanger becomes invaluable as a large, efficient, and reliable unit is sought. This information is needed to provide proper evaluation of the thermal and structural performance characteristics of a heat exchanger. It is to be noted that an analytical prediction method, when properly validated, will greatly reduce the need for model testing, facilitate interpolating and extrapolating test data, aid in optimizing heat-exchanger design and performance, and provide scaling capability. Thus tremendous savings of cost and time are realized. With the advent of large digital computers and advances in the development of computational fluid mechanics, it has become possible to predict analytically, through numerical solution, the conservation equations of mass, momentum, and energy for both the shellside and tubeside fluids. The numerical modeling technique will be a valuable, cost-effective design tool for development of advanced heat exchangers

  11. Numerical simulation of heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Sha, W.T.

    1985-01-01

    Accurate and detailed knowledge of the fluid flow field and thermal distribution inside a heat exchanger becomes invaluable as a large, efficient, and reliable unit is sought. This information is needed to provide proper evaluation of the thermal and structural performance characteristics of a heat exchanger. It is to be noted that an analytical prediction method, when properly validated, will greatly reduce the need for model testing, facilitate interpolating and extrapolating test data, aid in optimizing heat-exchanger design and performance, and provide scaling capability. Thus tremendous savings of cost and time are realized. With the advent of large digital computers and advances in the development of computational fluid mechanics, it has become possible to predict analytically, through numerical solution, the conservation equations of mass, momentum, and energy for both the shellside and tubeside fluids. The numerical modeling technique will be a valuable, cost-effective design tool for development of advanced heat exchangers.

  12. Fouling analyses for heat exchangers of NPP

    International Nuclear Information System (INIS)

    Fouling of heat exchanges is generated by water-borne deposits, commonly known as foulants including particulate matter from the air, migrated corrosion produces; silt, clays, and sand suspended in water; organic contaminants; and boron based deposits in plants. This fouling is known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. In order to analyze the fouling for heat exchangers of nuclear power plant, the fouling factor is introduced based on the ASME O and M codes and TEMA standards. This paper focuses on the fouling analyses for the heat exchangers of several primary systems; the RHR heat exchanger of the residual heat removal system, the letdown heat exchanger of the chemical and volume control system, and the CCW heat exchanger of the component cooling water system, Based on the results of the fouling levels for the three heat exchangers are assumed

  13. Support for heat exchangers

    International Nuclear Information System (INIS)

    The very large heat exchangers which are typical of many nuclear power plants place great demands on their supports. The support here described is for a vertical heat exchanger. A convex Lubrit plate allows a certain amount of transverse and rotational movement of the heat exhanger relative to the foundation. Taps engaging in the support surface of the heat exchanger and between the support box and the concrete foundation ensure that relative movement is restricted to those surfaces where it is intended. A steel box structure embedded in the concrete foundation dissipates heat transferred through the support system and avoids overheating the concrete. Horizontal stays support the heat exchanger against the concrete walls. (JIW)

  14. Flow-induced vibration specifications for steam generators and liquid heat exchangers

    International Nuclear Information System (INIS)

    It is desirable to avoid vibration problems by following appropriate guidelines and specifications at the design stage. Accordingly, design specifications were developed to prevent tube failures due to vibration in nuclear steam generators and liquid heat exchangers. These specifications are outlined in this report. (author). 14 refs., 2 figs

  15. Experimental study and numerical simulation of flow and heat transfer performance on an offset plate-fin heat exchanger

    Science.gov (United States)

    Du, Juan; Qian, Zuo-Qin; Dai, Zhong-yuan

    2015-10-01

    An experimental investigation of heat transfer and pressure drop characteristics of an offset plate-fin heat exchanger for cooling of lubricant oil is conducted. The empirical correlations for j-factor and f-factor are obtained by evaluating the experimental data with a modified Wilson plot method. A numerical simulation is performed and the comparison between numerical results and experimental data are presented and discussed. The results show that the simulation results are consistent with experimental data.

  16. Plate-Type Heat Exchanger

    International Science & Technology Center (ISTC)

    Conduction of Experimental Studies of Heat Exchange Element of Plate-Type Heat Exchanger Aiming at Enhancement of its Effectiveness Owing to Design Improvement and Optimization of Used Heat Exchange Intensifiers

  17. Influence of Ionic Fluid in Counter flow in Shell and Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    N.D.Shirgire

    2014-07-01

    Full Text Available An Ionanofluids are a new and innovative class of heat transfer fluids which exhibit fascinating thermo physical properties compared to their base ionic liquids. In this paper (1-Butyl-3-methylimidazolium chloride (BmimCLionic fluid is used comparison with Distilled Water. Distilled Water is non Ionic form in nature, so, results using (BmimCLis Overall good efficient in heat transfer device, were obtained with experimental work results on thermal conductivity and heat capacity,. As compared to (BmimCL those of their base ionic liquids such as (mineral oils and ethylene glycol etc are less thermophysical properties . as coolants in heat exchanger are also used to access their feasibility and performance in heat transfer devices.

  18. Enhancement of Performance of Shell and Tube Heat Exchanger Using Pertinent Leakage Flow Between Baffle and Tube Bundles

    International Nuclear Information System (INIS)

    In this study, the effects of the leakage flow between the baffle and tube bundles on the performance of a shell and tube heat exchanger (STHE) were examined using the commercial software ANSYS FLUENT v.14. A computational fluid dynamics model was developed for a small STHE with five different cases for the ratio of the leakage cross-sectional area to the baffle cross-sectional area, ranging from 0 to 40%, in order to determine the optimum leakage flow corresponding to the maximum outlet temperature. Using fixed tube wall and inlet temperatures for the shell side of the STHE, the flow and temperature fields were calculated by increasing the Reynolds number from 4952 to 14858. The present results showed that the outlet temperature, pressure drop, and heat transfer coefficient were strongly affected by the leakage flow, as well as the Reynolds number. In contrast with a previous researchers finding that the leakage flow led to simultaneous decreases in the pressure drop and heat transfer rate, the present study found that the pertinent leakage flow provided momentum in the recirculation zone near the baffle plate and thus led to the maximum outlet temperature, a small pressure drop, and the highest heat transfer rate. The optimum leakage flow was shown in the case with a ratio of 20% among the five different cases.

  19. Heat exchanger design handbook

    CERN Document Server

    Thulukkanam, Kuppan

    2013-01-01

    Completely revised and updated to reflect current advances in heat exchanger technology, Heat Exchanger Design Handbook, Second Edition includes enhanced figures and thermal effectiveness charts, tables, new chapter, and additional topics--all while keeping the qualities that made the first edition a centerpiece of information for practicing engineers, research, engineers, academicians, designers, and manufacturers involved in heat exchange between two or more fluids.See What's New in the Second Edition: Updated information on pressure vessel codes, manufacturer's association standards A new c

  20. Identification of some cross flow heat exchanger dynamic responses by measurement with low level binary pseudo-random input signals

    International Nuclear Information System (INIS)

    An experiment was performed to assess the usefulness of the binary cross-correlation method in the context of the identification problem. An auxiliary burner was excited with a discrete interval binary code and the response to the perturbation of the input heat was observed by recording the variations of the primary inlet, primary outlet and secondary outlet temperatures. The observations were analysed to yield cross-correlation functions and frequency responses were subsequently determined between primary inlet and primary outlet temperatures and also between primary inlet and secondary outlet temperatures. The analysis verified (1) that these dynamic responses of this cross flow heat exchanger may be predicted theoretically, (2) in so far as this heat exchanger is representative of the generality of plant, that the binary cross-correlation method provides adequate identification of plant dynamics for control purposes in environments where small input variations and low signal to noise ratio are obligatory. (author)

  1. Shell side numerical analysis of a shell and tube heat exchanger considering the effects of baffle inclination angle on fluid flow using CFD

    Directory of Open Access Journals (Sweden)

    Raj Karuppa Thundil R.

    2012-01-01

    Full Text Available In this present study, attempts were made to investigate the impacts of various baffle inclination angles on fluid flow and the heat transfer characteristics of a shell-and-tube heat exchanger for three different baffle inclination angles namely 0°,10° and 20°. The simulation results for various shell and tube heat exchangers, one with segmental baffles perpendicular to fluid flow and two with segmental baffles inclined to the direction of fluid flow are compared for their performance. The shell side design has been investigated numerically by modeling a small shell-and-tube heat exchanger. The study is concerned with a single shell and single side pass parallel flow heat exchanger. The flow and temperature fields inside the shell are studied using non-commercial CFD software tool ANSYS CFX 12.1. For a given baffle cut of 36 %, the heat exchanger performance is investigated by varying mass flow rate and baffle inclination angle. From the CFD simulation results, the shell side outlet temperature, pressure drop, recirculation near the baffles, optimal mass flow rate and the optimum baffle inclination angle for the given heat exchanger geometry are determined.

  2. Performance Investigation of Plate Type Heat Exchanger (A Case Study)

    OpenAIRE

    Simarpreet Singh; Sanjeev Jakhar

    2014-01-01

    Heat exchanger is a thermodynamic system which is most commonly used in the process industry for exchanging heat energy between the fluids. flowing in the same or opposite direction. It is desired that effectiveness of heat exchanger should remain as large as possible. Heat exchanger's performance may be improved by the addition of fins or corrugations. These investigations include design of plate type heat exchanger, heat transfer enhancement, flow phenomenon and cleanliness ...

  3. Computational thermal-fluid dynamics analysis of the laminar flow regime in the meander flow geometry characterizing the heat exchanger used in high temperature superconducting current leads

    International Nuclear Information System (INIS)

    Highlights: • The laminar regime in the meander flow geometry has been analysed with a previously validated computational strategy. • Several meander flow geometries as well as flow conditions have been analysed. • A range for the Reynolds number has been defined in which the flow can be considered laminar. • Correlations for the pressure drop and the heat transfer coefficients in the laminar regime have been derived. • A comparison between the computed the experimental pressure drop of the W7-X HTS current lead prototype is presented. -- Abstract: The Karlsruhe Institute of Technology and the Politecnico di Torino have developed and validated a computational thermal-fluid dynamics (CtFD) strategy for the systematic analysis of the thermal-hydraulics inside the meander flow heat exchanger used in high-temperature superconducting current leads for fusion applications. In the recent past, the application of this CtFD technique has shown that some operating conditions occurring in these devices may not reach the turbulent regime region. With that motivation, the CtFD analysis of the helium thermal-fluid dynamics inside different meander flow geometries is extended here to the laminar flow regime. Our first aim is to clarify under which operative conditions the flow regime can be considered laminar and how the pressure drop as well as the heat transfer are related to the geometrical parameters and to the flow conditions. From the results of this analysis, correlations for the pressure drop and for the heat transfer coefficient in the meander flow geometry have been derived, which are applicable with good accuracy to the design of meander flow heat exchangers over a broad range of geometrical parameters

  4. Mathematical simulation of heat exchanger working conditions

    Science.gov (United States)

    Gavlas, Stanislav; ?ur?anský, Peter; Lenhard, Richard; Janda?ka, Jozef

    2015-05-01

    One of the When designing a new heat exchanger it is necessary to consider all the conditions imposed on the exchanger and its desired properties. Most often the investigation of heat transfer is to find heat surface. When applying exchanger for proposed hot air engine, it will be a counter-flow heat exchanger of gas - gas type. Gas, which transfers the heat will be exhaust gas from the combustion of biomass. An important step in the design and verification is to analyze exchanger designed using numerical methods, the verification of the correctness of design and verification of boundary conditions which include temperatures, flow rates and pressure drops. Due to the fact that the heat transfer in the heat exchanger is a three-dimensional plot and timeindependent, the system is described by partial differential equations that need to be solved by numerical methods.

  5. Mathematical simulation of heat exchanger working conditions

    Directory of Open Access Journals (Sweden)

    Gavlas Stanislav

    2015-01-01

    Full Text Available One of the When designing a new heat exchanger it is necessary to consider all the conditions imposed on the exchanger and its desired properties. Most often the investigation of heat transfer is to find heat surface. When applying exchanger for proposed hot air engine, it will be a counter-flow heat exchanger of gas - gas type. Gas, which transfers the heat will be exhaust gas from the combustion of biomass. An important step in the design and verification is to analyze exchanger designed using numerical methods, the verification of the correctness of design and verification of boundary conditions which include temperatures, flow rates and pressure drops. Due to the fact that the heat transfer in the heat exchanger is a three-dimensional plot and timeindependent, the system is described by partial differential equations that need to be solved by numerical methods.

  6. Testing and analysis of immersed heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Farrington, R.B.; Bingham, C.E.

    1986-08-01

    The objectives were to determine the performance of four immersed, ''supply-side'' heat exchangers used in solar domestic-hot-water systems; to examine the effects of flow rate, temperature difference, and coil configuration on performance; and to develop a simple model to predict the performance of immersed heat exchangers. We tested four immersed heat exchangers: a smooth coil, a finned spiral, a single-wall bayonet, and a double-wall bayonet. We developed two analyticl models and a simple finite difference model. We experimentally verified that the performance of these heat exchangers depends on the flow rate through them; we also showed that the temperature difference between the heat exchanger's inlet and the storage tank can strongly affect a heat exchanger's performance. We also compared the effects of the heat exchanger's configuration and correlated Nusselt and Rayleigh numbers for each heat exchanger tested. The smooth coil had a higher effectiveness than the others, while the double-wall bayonet had a very low effectiveness. We still do not know the long-term effectiveness of heat exchangers regarding scale accumulation, nor do we know the effects of very low flow rates on a heat exchanger's performance.

  7. NUMERICAL SIMULATION OF VERTICAL GROUND HEAT EXCHANGERS FOR GROUND SOURCE HEAT PUMPS

    OpenAIRE

    Jalaluddin

    2011-01-01

    Abstract: This paper presents the numerical simulation of several types of vertical ground heat exchangers. The ground heat exchangers (GHEs) such as U-tube, double-tube and multi-tube were simulated using the commercial CFD software FLUENT. Water flows through the heat exchangers and exchanges the heat to the ground. The inlet and outlet water temperatures, flow rate, and heat exchange rate are presented. The heat exchange rates in discontinuous short-time period of operation ...

  8. Fouling analyses of heat exchangers for PSR

    International Nuclear Information System (INIS)

    Fouling of heat exchangers is generated by water-borne deposits, commonly known as foulants including particulate matter from the air, migrated corrosion produces; silt, clays, and sand suspended in water; organic contaminants; and boron based deposits in plants. This fouling is known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. This paper focuses on fouling analyses for six heat exchangers of two primary systems in two nuclear power plants; the regenerative heat exchangers of the chemical and volume control system and the component cooling water heat exchangers of the component cooling water system. To analyze the fouling for heat exchangers, fouling factor was introduced based on the ASME O and M codes and TEMA standards. Based on the results of the fouling analyses, the present thermal performances and fouling levels for the six heat exchangers were predicted

  9. Monogroove liquid heat exchanger

    Science.gov (United States)

    Brown, Richard F. (Inventor); Edelstein, Fred (Inventor)

    1990-01-01

    A liquid supply control is disclosed for a heat transfer system which transports heat by liquid-vapor phase change of a working fluid. An assembly (10) of monogroove heat pipe legs (15) can be operated automatically as either heat acquisition devices or heat discharge sources. The liquid channels (27) of the heat pipe legs (15) are connected to a reservoir (35) which is filled and drained by respective filling and draining valves (30, 32). Information from liquid level sensors (50, 51) on the reservoir (35) is combined (60) with temperature information (55) from the liquid heat exchanger (12) and temperature information (56) from the assembly vapor conduit (42) to regulate filling and draining of the reservoir (35), so that the reservoir (35) in turn serves the liquid supply/drain needs of the heat pipe legs (15), on demand, by passive capillary action (20, 28).

  10. Experimental study of heat exchange coefficients, critical heat flux and charge losses, using water-steam mixtures in turbulent flow in a vertical tube

    International Nuclear Information System (INIS)

    Two stainless steel tubes were used (with diameters of 5 and 10 mm, lengths 400 and 600 mm respectively), heated electrically (50 Hz). The mixture flows from top to bottom. The work was carried out mainly on mixtures of high concentration (x > 0.1), at pressures between 50 and 60 kg/cm2, flowing as a liquid film on the walls of the tube with droplets suspended in the central current of steam. By analysis of the heat transfer laws the exchange mechanisms were established, and the conditions under which the critical heat flux may be exceeded without danger of actual burnout were determined. In this way high output concentrations (xs > 0.9) may be obtained. An attempt has been made to find out to what extent existing correlation formulae can be used to account for the phenomena observed. It is shown that those dealing with exchange coefficients can only be applied in a first approximation in cases where exchange by convection is preponderant, and only below the critical flux. The formulae proposed by WAPD and CISE do not give a satisfactory estimation of the critical heat flux, and the essential reasons for this inadequacy are explained. Lastly, the Martinelli and Nelson method may be used to an approximation of 30 per cent for the calculation of charge losses. (author)

  11. Tube boiler heat exchanger

    International Nuclear Information System (INIS)

    The tube boiler heat exchanger has been designed for use in a steam generator circuit of a sodium cooled fast breeder reactor. U-type heat exchanger tubes with legs of different lengths are suspended within the boiler. They are made of steel with 9% chrome content. Each tube is passed through an opening in the tube wall with some clearance and then tightly sealed to the tube wall by means of a sleeve. This seal is achieved by a brazed connection using Nicrobraz 135 brazing metal (nickel base alloy) applied by means of a high frequency induction technique. (GL/DG)

  12. Numerical study of a novel counter-flow heat and mass exchanger for dew point evaporative cooling

    International Nuclear Information System (INIS)

    The paper presents numerical investigation of a novel counter-flow heat and mass exchanger used in the indirect evaporative dew point cooling systems, a potential alternative to the conventional mechanical compression air conditioning systems. Numeric simulation was carried out to optimise the geometrical sizes and operating conditions of the exchanger in order to enhance the cooling (dew point and wet bulb) effectiveness of the exchanger and maximise the energy efficiency of the dew point cooling system. The results of the simulations indicated that cooling (dew point and wet bulb) effectiveness and energy efficiency are largely dependent on the dimensions of the airflow passages, air velocity and working-to-intake-air ratio, and less dependent on the temperature of the feed water. It is recommended that exchanger intake air velocity should be controlled to a value below 0.3-0.5 m/s; height of air passage (channel) should be set to 6 mm or below and the length of the passage should be 200 time the height; the working-to-intake-air ratio should be around 0.4. Under the UK summer design condition, i.e., 28 deg. C of dry bulb temperature, 20 deg. C of wet bulb temperature and 16 deg. C of dew point temperature, the exchanger can achieve wet-bulb effectiveness of up to 1.3 and dew-point effectiveness of up to 0.9

  13. Experimental evaluation of vibrations in heat exchangers

    International Nuclear Information System (INIS)

    Flow induced vibrations may produce damage of heat exchangers, condensers and steam generators tubes. To evaluate this problem a set of tests were developed to know the real support state of the tubes, which have great influence on the vibration response. This paper include a description of the tests and the results obtained applying them on a heat exchanger equipment. (author)

  14. An Empirical Study of Helical Coil Heat Exchanger Used in Liquid Evaporization and Droplet Disengagement for a Laminar Fluid Flow

    OpenAIRE

    Kapil Dev*1,

    2014-01-01

    Heat exchanger is an important component in industrial systems especially in process industries. Many commercial designs and types of heat exchangers are available in market for transfer of heat as well as for recovery of waste heat for the process plants. As helical coil have compact size and higher heat transfer coefficient they are widely used in industrial applications such as food preservation, refrigeration, process plant, power generation, etc. An attempt has been made ...

  15. Transient Thermal Behavior of a Vertical Solar Storage Tank with a Mantle Heat Exchanger During No-Flow Operation

    OpenAIRE

    A. Barzegar; A. A. Dehghan

    2009-01-01

    Transient thermal behavior of a vertical storage tank of a domestic solar heating system with a mantle heat exchanger has been investigated numerically in the charging mode. It is assumed that the tank is initially filled with uniform cold water. At an instant of time, the hot fluid from collector outlet is uniformly injected in the upper section of the mantle heat exchanger and after heat transfer with the fluid inside the tank, withdrawn from the bottom part of the heat excha...

  16. Design specifications to ensure flow-induced vibration and fretting-wear performance in CANDU steam generators and heat exchangers

    International Nuclear Information System (INIS)

    Preventing flow-induced vibration and fretting-wear problems in steam generators and heat exchangers requires design specifications that bring together specific guidelines, analysis methods, requirements and appropriate performance criteria. This paper outlines the steps required to generate and support such design specifications for CANDU nuclear steam generators and heat exchangers, and relates them to typical steam-generator design features and computer modeling capabilities. It also describes current issues that are driving changes to flow-induced vibration and fretting-wear specifications that can be applied to the design process for component refurbishment, replacement or new designs. These issues include recent experimental or field evidence for new excitation mechanisms, e.g., the possibility of in-plane fluidelastic instability of U-tubes, the demand for longer reactor and component lifetimes, the need for better predictions of dynamic properties and vibration response, e.g., two-phase random-turbulence excitation, and requirements to consider system 'excursions' or abnormal scenarios, e.g., a main steam line break in the case of steam generators. The paper describes steps being taken to resolve these issues. (author)

  17. The numerical analysis of the flow fields near fin surface of a plate fin-oval tube heat exchanger with delta wing vortex generators

    International Nuclear Information System (INIS)

    In present study, the flow field near the fin surface of plate fin - oval tube heat exchanger with delta wing vortex generator was numerically analyzed. As results, the well developed vortex behind delta wing was observed. These vortex can improve heat transfer fin surface behind delta wing vortex generators

  18. Magnetic heat pump flow director

    Science.gov (United States)

    Howard, Frank S. (inventor)

    1995-01-01

    A fluid flow director is disclosed. The director comprises a handle body and combed-teeth extending from one side of the body. The body can be formed of a clear plastic such as acrylic. The director can be used with heat exchangers such as a magnetic heat pump and can minimize the undesired mixing of fluid flows. The types of heat exchangers can encompass both heat pumps and refrigerators. The director can adjust the fluid flow of liquid or gas along desired flow directions. A method of applying the flow director within a magnetic heat pump application is also disclosed where the comb-teeth portions of the director are inserted into the fluid flow paths of the heat pump.

  19. Manufacture of heat exchangers

    International Nuclear Information System (INIS)

    A tube bundle for use in a heat exchanger has a series of spaced parallel tubes supported by tube plates and is manufactured by depositing welding material around the end of each tube, machining the deposited material to form an annular flange around the end of the tube and welding the flange into apertures in the tube plate. Preferably the tubes have a length which is slightly less than the distance between the outer surfaces of the tube plates and the deposited material is deposited so that it overlaps and protects the end surfaces of the tubes. A plug may be inserted in the bore of the tubes during the welding material deposition which, as described, is effected by manual metal arc welding. One use of heat exchangers incorporating a tube bundle manufactured as above is in apparatus for reducing the volume of, and recovering nitric acid from, radioactive effluents from a nuclear reprocessing plant. (author)

  20. Heat Exchangers Analysis

    Directory of Open Access Journals (Sweden)

    S.C. Pang

    2013-01-01

    Full Text Available Current research performs mathematics correlations between engine speed, coolant flow, vehicle speed and driving gear. A step-by-step procedure is described to obtain the engine cooling system parameters mathematically (include a CFD model. After obtaining the parameters, the thermal equilibrium of engine cooling system is studied thoroughly. The study of thermal equilibrium provides some insights on how to reduce engine cooling load and when the interference of cooling fan is required. A segmented spread sheet model is developed in order to explain the phenomenon which air flow driven by uniform ram air could dissipate higher amount of heat flow than air flow driven by cooling fan. The segmentation analysis concluded that minimum mCp fluid is switched to coolant when the air flow is concentrated at small portion of area.

  1. Comparative Study of Heat Exchangers Using CFD

    Directory of Open Access Journals (Sweden)

    Melvinraj C R

    2014-05-01

    Full Text Available A parallel flow heat exchanger and a corresponding ribbed tube heat exchanger is modeled and numerically analysed using a commercial finite volume CFD package. Pro-E & ANSYS 14.5 softwares are used for the designing and the analysis. CFD predictions of effectiveness of the two heat exchangers are obtained and compared. After selecting the best modeling approach, the sensitivity of the results to particular flow rate is investigated. It is observed that the flow and the temperature fields obtained from CFD simulations provide valuable information about the parts of the heat exchanger design that need improvement. Correlation based approaches may indicate the existence of the weakness but CFD simulations can also pin point the source and the location of it. Using CFD may speed up the design process and may improve the final design.

  2. Counterflow Regolith Heat Exchanger Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat...

  3. Power engineering, power saving and investigations on heat exchange in Russia (materials of the first Russian national conference on heat exchange)

    International Nuclear Information System (INIS)

    Review of works, presented at the 1-st Russian national conference on heat exchange and related directly to power engineering and power saving, is shown. The program of conference covered all trends in modern science on heat exchange: natural and forced convection; heat exchange by chemical transformations; boiling; boiling crisis and beyond-the-crisis heat exchange; two-phase flows; evaporation and condensation; dispersion flows and porous media; heat exchange intensification; radiation and complex heat exchange; thermal conductivity and thermal insulation

  4. Transient thermal, hydraulic, and mechanical analysis of a counter flow offset strip fin intermediate heat exchanger using an effective porous media approach

    Science.gov (United States)

    Urquiza, Eugenio

    This work presents a comprehensive thermal hydraulic analysis of a compact heat exchanger using offset strip fins. The thermal hydraulics analysis in this work is followed by a finite element analysis (FEA) to predict the mechanical stresses experienced by an intermediate heat exchanger (IHX) during steady-state operation and selected flow transients. In particular, the scenario analyzed involves a gas-to-liquid IHX operating between high pressure helium and liquid or molten salt. In order to estimate the stresses in compact heat exchangers a comprehensive thermal and hydraulic analysis is needed. Compact heat exchangers require very small flow channels and fins to achieve high heat transfer rates and thermal effectiveness. However, studying such small features computationally contributes little to the understanding of component level phenomena and requires prohibitive computational effort using computational fluid dynamics (CFD). To address this issue, the analysis developed here uses an effective porous media (EPM) approach; this greatly reduces the computation time and produces results with the appropriate resolution [1]. This EPM fluid dynamics and heat transfer computational code has been named the Compact Heat Exchanger Explicit Thermal and Hydraulics (CHEETAH) code. CHEETAH solves for the two-dimensional steady-state and transient temperature and flow distributions in the IHX including the complicating effects of temperature-dependent fluid thermo-physical properties. Temperature- and pressure-dependent fluid properties are evaluated by CHEETAH and the thermal effectiveness of the IHX is also calculated. Furthermore, the temperature distribution can then be imported into a finite element analysis (FEA) code for mechanical stress analysis using the EPM methods developed earlier by the University of California, Berkeley, for global and local stress analysis [2]. These simulation tools will also allow the heat exchanger design to be improved through an iterative design process which will lead to a design with a reduced pressure drop, increased thermal effectiveness, and improved mechanical performance as it relates to creep deformation and transient thermal stresses.

  5. The effect of plate heat exchanger’s geometry on heat transfer

    Directory of Open Access Journals (Sweden)

    Oana GIURGIU

    2014-11-01

    Full Text Available The study presents further Computational Fluid Dynamics (CFD numerical analysis for two models of plate heat exchangers. Comparatively was studied the influence of geometric characteristics of plates on the intensification process of heat exchange. For this purpose, it was examined the distribution of velocity and temperatures fields on active plate height. Heat transfer characteristics were analysed through the variation of mass flow on the primary heat agent.

  6. Appendix to the thesis an experimental and numerical study of a jetfire stop material and a new helical flow heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Austegard, Anders

    1997-12-31

    This thesis consists of two parts. Part 1: Experimental and numerical study of jetfire stop, and Part 2: Experimental and numerical study of a new kind of shell and tube heat exchanger with helical flow on shell side. Part 1 describes the development of the model for simulation of the temperature development through Viking jetfirestop. A simulation program is developed that calculates the temperature development through Viking jetfirestop. In the development of the model, measurements of reaction energy, pyrolysis and heat conductivity at low temperatures are made. The conductivity at higher temperatures and when pyrolysis reactions are going on is estimated experimentally and by numerical calculations. Full-scale jet fire test and small-scale xenon lamp experiments are made to test the simulation model. Part 2 contains the development of a model that simulate the fluid flow and heat transfer in a helical flow shell and tube heat exchanger. It consists of the development of a porosity model and a model for pressure drop and heat transfer as well as experiments in non-standard tube layouts. Results from the simulation program are compared with experiments on a helical flow shell and tube heat exchanger. This is a separate appendix volume, including computer codes and simulated results. 316 figs., 11 tabs.

  7. Fouling of a double pipe heat exchanger

    OpenAIRE

    Llinares Fontdevila, Antonio

    2004-01-01

    Every single heat exchanger in operation in modern industries is exposed to fouling to a greater or lesser extent depending on the surface temperature, surface condition, material of construction, fluid velocity, flow geometry and fluid composition. The fouling phenomenon is time dependent and will result in a decrease in thermal effectiveness of a heat exchanger. Once the thermal effectiveness decreases to a minimum acceptable level, cleaning of the equipment becomes necessary to restore its...

  8. Numerical Analysis of Tube-Fin Heat Exchanger using Fluent

    OpenAIRE

    M. V. Ghori; R. K. Kirar

    2012-01-01

    Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of two-row plain Tube and Fin heat exchanger using FLUENT software. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created and meshed by using GAMBIT software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models k-, and SST k...

  9. Analytical framework for borehole heat exchanger (BHE) simulation influenced by horizontal groundwater flow and complex top boundary conditions

    Science.gov (United States)

    Rivera, Jaime; Blum, Philipp; Bayer, Peter

    2015-04-01

    Borehole heat exchangers (BHE) are the most widely used technologies for tapping low-enthalpy energy resources in the shallow subsurface. Analysis of these systems requires a proper simulation of the relevant processes controlling the transfer of heat between the BHE and the ground. Among the available simulation approaches, analytical methods are broadly accepted, especially when low computational costs and comprehensive analyses are demanded. Moreover, these methods constitute the benchmark solutions to evaluate the performance of more complex numerical models. Within the spectrum of existing (semi-)analytical models, those based on the superposition of problem-specific Green's functions are particularly appealing. Green's functions can be derived, for instance, for nodal or line sources with constant or transient strengths. In the same manner, functional forms can be obtained for scenarios with complex top boundary conditions whose temperature may vary in space and time. Other relevant processes, such as advective heat transport, mechanical dispersion and heat transfer through the unsaturated zone could be incorporated as well. A keystone of the methodology is that individual solutions can be added up invoking the superposition principle. This leads to a flexible and robust framework for studying the interaction of multiple processes on thermal plumes of BHEs. In this contribution, we present a new analytical framework and its verification via comparison with a numerical model. It simulates a BHE as a line source, and it integrates both horizontal groundwater flow and the effect of top boundary effects due to variable land use. All these effects may be implemented as spatially and temporally variable. For validation, the analytical framework is successfully applied to study cases where highly resolved temperature data is available.

  10. Mathematical Modeling of Spiral Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Probal Guha , Vaishnavi Unde

    2014-04-01

    Full Text Available Compact Heat Exchangers (CHEs are increasingly being used on small and medium scale industries. Due to their compact size and efficient design, they facilitate more efficient heat transfer. Better heat transfer would imply lesser fuel consumption for the operations of the plant, giving improvement to overall efficiency. This reduction in consumption of fuel is a step towards sustainable development. This report exclusively deals with the study the spiral heat exchanger.The design considerations for spiral heat exchanger is that the flow within the spiral has been assumed as flow through a duct and by using Shah London empirical equation for Nusselt number design parameters are further optimized.This is accompanied by a detailed energy balance to generate a concise mathematical model

  11. Performance Investigation of Plate Type Heat Exchanger (A Case Study

    Directory of Open Access Journals (Sweden)

    Simarpreet Singh

    2014-04-01

    Full Text Available Heat exchanger is a thermodynamic system which is most commonly used in the process industry for exchanging heat energy between the fluids. flowing in the same or opposite direction. It is desired that effectiveness of heat exchanger should remain as large as possible. Heat exchanger's performance may be improved by the addition of fins or corrugations. These investigations include design of plate type heat exchanger, heat transfer enhancement, flow phenomenon and cleanliness factor. In process plants, this type of heat exchange is generally used for recovering heat content of exhaust steam. However, with the flow of fluid for a long period, fouling occurs on the plate surface. Therefore, it is required to investigate the effect of fouling, wherever the heat exchanger is installed. An extensive experimental investigation has been carried out under clean and dirty condition of the said plate type heat exchanger. Heat transfer and flow data were collected in experiment. From collected data heat transfer rate, overall heat transfer coefficient, fouling factor and cleanliness factor were evaluated. Based upon the cleanliness factor data, next date of cleanliness for plate type heat exchanger was predicted. It is felt that the outcome of the present research work may be quite useful for efficient operation of plate type heat exchanger installed in Process plants.

  12. Heat exchanger repair

    International Nuclear Information System (INIS)

    There are two ways to rapir heater tubes in tubular heat exchangers, partial replacement of tubes and a technique called sleeving. In the former case, the defective tube section is cut out, removed, and replaced by a new section butt welded to the old piece of tube which remained in place. In the sleeving technique, a tube sleeve is slid into the defective tube and, after expansion, welded to the original tube. In this case, the welding technique employed is not laser welding, as is often maintained in the literature, but TIG pulsation welding. The results of preliminary tests and the qualification of both processes are outlined in the article; an account is given also of the replacement of the tube sections when repairing condensate coolers. (orig.)

  13. A comparison between heat transfer correlations obtained from experimental data and numerical simulation of flow of stirred yoghurt during cooling in plate heat exchangers

    OpenAIRE

    Afonso, Isabel M.; Fernandes, Carla S.; Maia, João M.; Melo, Luis F.

    2004-01-01

    Thermal processing is widely used in the food industry mainly to improve quality and safety of food products. The investigation of heat transfer problems of non-Newtonian fluids during heating and cooling in heat exchangers is of major interest since the main factor limiting heat transfer is the viscous behaviour of these fluids. Therefore, the knowledge of the interface heat transfer coefficients is important in the design of food processes and processing equipment. In the present work, s...

  14. Component Cooling Heat Exchanger Heat Transfer Capability Operability Monitoring

    International Nuclear Information System (INIS)

    The ultimate heat sink (UHS) is of highest importance for nuclear power plant safe and reliable operation. The most important component in line from safety-related heat sources to the ultimate heat sink water body is a component cooling heat exchanger (CC Heat Exchanger). The Component Cooling Heat Exchanger has a safety-related function to transfer the heat from the Component Cooling (CC) water system to the Service Water (SW) system. SW systems throughout the world have been the root of many plant problems because the water source, usually river, lake, sea or cooling pond, are conductive to corrosion, erosion, biofouling, debris intrusion, silt, sediment deposits, etc. At Krsko NPP, these problems usually cumulate in the summer period from July to August, with higher Sava River (service water system) temperatures. Therefore it was necessary to continuously evaluate the CC Heat Exchanger operation and confirm that the system would perform its intended function in accordance with the plant's design basis, given as a minimum heat transfer rate in the heat exchanger design specification sheet. The Essential Service Water system at Krsko NPP is an open cycle cooling system which transfers heat from safety and non-safety-related systems and components to the ultimate heat sink the Sava River. The system is continuously in operation in all modes of plant operation, including plant shutdown and refueling. However, due to the Sava River impurities and our limited abilities of the water treatment, the system is subject to fouling, sedimentation buildup, corrosion and scale formation, which could negatively impact its performance being unable to satisfy its safety related post accident heat removal function. Low temperature difference and high fluid flows make it difficult to evaluate the CC Heat Exchanger due to its specific design. The important effects noted are measurement uncertainties, nonspecific construction, high heat transfer capacity, and operational specifics (e.g. using CC Heat Exchanger bypass valves for CC temperature control, variation of plant heat loads, pumps performance, and day-night temperature difference, with lagging effects on heat transfer dynamics). Krsko NPP is continuously monitoring the Component Cooling (CC) Heat Exchanger performance using the on-line process information system (PIS). By defining the mathematical algorithm, it is possible to continuously evaluate the CC Heat Exchanger operability by verifying if the heat transfer rate calculation is in accordance with the heat exchanger design specification sheet requirements. These calculations are limited to summer periods only when the bypass valves are neither throttled nor open.(author).

  15. Use of the Laser-Doppler-Anemometry for the measurement of velocity distributions at the intake of a longitudinal flow heat exchanger

    International Nuclear Information System (INIS)

    The Laser-Doppler-Anemometry (LDA) is an optical technic to measure flow velocities. In this report the principles of this method as well as the LDA-system components are described. Especially the signal-processing and the special conditions of use are discussed. The measurement of a two-dimensional velocity distribution at the intake of a longitudinal flow heat exchanger is shown in this investigation. (orig.)

  16. Visualization and void fraction distribution of downward gas liquid two-phase flow in a plate heat exchanger by neutron radiography

    Science.gov (United States)

    Asano, Hitoshi; Takenaka, Nobuyuki; Wakabayashi, Toshiaki; Fujii, Terushige

    2005-04-01

    Adiabatic vertically downward air-water two-phase flows in a commercial plate heat exchanger were visualized by a neutron radiography method as a non-destructive test in order to clarify the flow characteristics and the differences of the liquid distributions from those of the vertically upward flows. Flow behaviors in a single channel and a multi-channel plate heat exchanger were investigated. From the visualized results of the flows in a single channel, it was shown that water fell down without a spreading at a lower gas volumetric flux of less than about 2 m/s. In the case of a higher gas volumetric flux above 2 m/s, liquid spread around the enlarged section and the liquid distribution in the main part of the heat exchanger seemed to be homogenous. Measured average void fractions for the air-water downward flows showed almost the same tendency as those for the upward flows in spite of the difference of the flow patterns. On the other hand, liquid distributions into 18 parallel channels were evaluated from the measured results of the liquid volumetric fractions in each channel. It was shown that the liquid distribution depended on the inlet liquid flow rate. However, the effect of the gas flow rate was a little. In the case of higher liquid flow rate, the liquid fraction became higher with a deeper channel due to a larger liquid momentum. However, in the case of a lower liquid flow rate, the opposite tendency was observed, i.e., the liquid fraction in the nearest channel to the inlet was higher.

  17. Heat pipes in modern heat exchangers

    International Nuclear Information System (INIS)

    Heat pipes are very flexible systems with regard to effective thermal control. They can easily be implemented as heat exchangers inside sorption and vapour-compression heat pumps, refrigerators and other types of heat transfer devices. Their heat transfer coefficient in the evaporator and condenser zones is 103-105 W/m2 K, heat pipe thermal resistance is 0.01-0.03 K/W, therefore leading to smaller area and mass of heat exchangers. Miniature and micro heat pipes are welcomed for electronic components cooling and space two-phase thermal control systems. Loop heat pipes, pulsating heat pipes and sorption heat pipes are the novelty for modern heat exchangers. Heat pipe air preheaters are used in thermal power plants to preheat the secondary-primary air required for combustion of fuel in the boiler using the energy available in exhaust gases. Heat pipe solar collectors are promising for domestic use. This paper reviews mainly heat pipe developments in the Former Soviet Union Countries. Some new results obtained in USA and Europe are also included

  18. Expanded microchannel heat exchanger: design, fabrication and preliminary experimental test

    CERN Document Server

    Denkenberger, David C; Pearce, Joshua M; Zhai, John; 10.1177/0957650912442781

    2012-01-01

    This paper first reviews non-traditional heat exchanger geometry, laser welding, practical issues with microchannel heat exchangers, and high effectiveness heat exchangers. Existing microchannel heat exchangers have low material costs, but high manufacturing costs. This paper presents a new expanded microchannel heat exchanger design and accompanying continuous manufacturing technique for potential low-cost production. Polymer heat exchangers have the potential for high effectiveness. The paper discusses one possible joining method - a new type of laser welding named "forward conduction welding," used to fabricate the prototype. The expanded heat exchanger has the potential to have counter-flow, cross-flow, or parallel-flow configurations, be used for all types of fluids, and be made of polymers, metals, or polymer-ceramic precursors. The cost and ineffectiveness reduction may be an order of magnitude or more, saving a large fraction of primary energy. The measured effectiveness of the prototype with 28 micro...

  19. Method for removing coronene from heat exchangers

    International Nuclear Information System (INIS)

    A method for removing a coronene deposit in a reforming process is described that consists of (A) contacting a hydrocarbonacous feedstock with a catalyst in the presence of added hydrogen at reforming conditions in a reforming zone; (B) splitting the total reforming zone effluent into a first stream and a second stream; (C) passing said first stream into a first train of heat exchangers arranged in parallel with a second train of heat exchangers; (D) passing said second stream into said second train of heat exchangers, said reforming zone effluent comprising coronene, at least a portion of which deposits in said heateexchangers; (E) separating the heat exchanged total reforming zone effluent into a hydrogen-rich gaseous phase and a liquid hydrocarbon phase comprising normally liquid hydrocarbons and normally gaseous hydrocarbons, the improvement which comprises reducing the flow of said first stream in said first train of heat exchangers to produce a temperature sufficient to condense at least a portion of said reformer effluent therein such that the resulting condensate contacts said coronene deposit, and simultaneously increasing the flow of said second stream in said second train of heat exchangers

  20. High Temperature Heat Exchanger Project

    Energy Technology Data Exchange (ETDEWEB)

    Anthony E. Hechanova, Ph.D.

    2008-09-30

    The UNLV Research Foundation assembled a research consortium for high temperature heat exchanger design and materials compatibility and performance comprised of university and private industry partners under the auspices of the US DOE-NE Nuclear Hydrogen Initiative in October 2003. The objectives of the consortium were to conduct investigations of candidate materials for high temperature heat exchanger componets in hydrogen production processes and design and perform prototypical testing of heat exchangers. The initial research of the consortium focused on the intermediate heat exchanger (located between the nuclear reactor and hydrogen production plan) and the components for the hydrogen iodine decomposition process and sulfuric acid decomposition process. These heat exchanger components were deemed the most challenging from a materials performance and compatibility perspective

  1. An Experimental Study to Show the Effect of Time of Opening and Closing the Solenoid Valve on Effectiveness of Finned Cross Flow Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Saad Farhan

    2013-04-01

    Full Text Available   In this research an experimental study was carried out to show the effect of time of opening and closing the solenoid valve on the effectiveness of finned cross flow heat exchanger, which has changed the time of opening and closing the solenoid valve (2, 4, 6 sec. with change the mass flow rate of water each time and the range values between (0.027-0.0816 kg/s with constant of mass flow rate of air at (0.032 kg/s.                     The results obtained from experiment works that the decreasing in the time of opening and closing the solenoid valve from (6 sec. to (2 sec. leads to increase internal heat transfer coefficient (hi the highest increase was by (18.37% at mass flow rate of water (0.027 kg/s and increase the overall heat transfer coefficient (U and the highest percentage of increase (7.36% at mass flow rate of water (0.027 kg/s.                                   The experimental results obtained show that the increasing both the number of units transmitted (NTU and effectiveness of the finned heat exchanger when decrease the time of opening and closing the solenoid valve from (6 sec. to (2 sec. and the highest percentage of the increase occurring is (8.4% and (1.74% respectively at mass flow rate of water (0.027 kg/s.

  2. Characteristics of Vertical Mantle Heat Exchangers for Solar Water Heaters

    DEFF Research Database (Denmark)

    Shah, Louise Jivan; Morrison, G.L.; Behnia, M.

    1999-01-01

    - The flow structure in vertical mantle heat exchangers was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the mantle were measured using a particle Image Velocimetry (PIV) system. A CFD simulation model of vertical mantle heat exchangers was also developed for detailed evaluation of the heat flux distribution over the mantle surface. Both the experimental and simulation results indicate that distribution of the flow around th...

  3. Electroforming thin channel heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Steffani, C.P.

    1991-06-01

    Research at Lawrence Livermore National Laboratory has shown that thin channel heat exchangers can be produced on bimetallic mandrels by the stack and plate method. Depth to width ratios of 100 to 1 are easily produced, with other ratios dependent on heating or cooling requirements. Mass production of these plates may be possible using reel to reel'' methods. Future generations of heat exchangers may be produced via composite electroforming, chemical vapor deposition (CVD) or physical vapor deposition (PVD). 6 refs.

  4. Microtube strip heat exchanger. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Doty, F.D.

    1992-07-09

    The purpose of this contract has been to explore the limits of miniaturization of heat exchangers with the goals of (1) improving the theoretical understanding of laminar heat exchangers, (2) evaluating various manufacturing difficulties, and (3) identifying major applications for the technology. A low-cost, ultra-compact heat exchanger could have an enormous impact on industry in the areas of cryocoolers and energy conversion. Compact cryocoolers based on the reverse Brayton cycle (RBC) would become practical with the availability of compact heat exchangers. Many experts believe that hardware advances in personal computer technology will rapidly slow down in four to six years unless lowcost, portable cryocoolers suitable for the desktop supercomputer can be developed. Compact refrigeration systems would permit dramatic advances in high-performance computer work stations with ``conventional`` microprocessors operating at 150 K, and especially with low-cost cryocoolers below 77 K. NASA has also expressed strong interest in our MTS exchanger for space-based RBC cryocoolers for sensor cooling. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  5. Hierarchic modeling of heat exchanger thermal hydraulics

    International Nuclear Information System (INIS)

    Volume Averaging Technique (VAT) is employed in order to model the heat exchanger cross-flow as a porous media flow. As the averaging of the transport equations lead to a closure problem, separate relations are introduced to model interphase momentum and heat transfer between fluid flow and the solid structure. The hierarchic modeling is used to calculate the local drag coefficient Cd as a function of Reynolds number Reh. For that purpose a separate model of REV is built and DNS of flow through REV is performed. The local values of heat transfer coefficient h are obtained from available literature. The geometry of the simulation domain and boundary conditions follow the geometry of the experimental test section used at U.C.L.A. The calculated temperature fields reveal that the geometry with denser pin-fins arrangement (HX1) heats fluid flow faster. The temperature field in the HX2 exhibits the formation of thermal boundary layer between pin-fins, which has a significant role in overall thermal performance of the heat exchanger. Although presented discrepancies of the whole-section drag coefficient Cd are large, we believe that hierarchic modeling is an appropriate strategy for calculation of complex transport phenomena in heat exchanger geometries.(author)

  6. Heat exchanger using graphite foam

    Science.gov (United States)

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  7. A Numerical Procedure for Flow Distribution and Pressure Drops for U and Z Type Configurations Plate Heat Exchangers with Variable Coefficients

    International Nuclear Information System (INIS)

    In Plate Heat Exchangers it is important to determine the flow distribution and pressure drops, because they affect directly the performance of a heat exchanger. This work proposes an incompressible, one-dimensional, steady state, discrete model allowing for variable overall momentum coefficients to determine these magnitudes. The model consists on a modified version of the Bajura and Jones model for dividing and combining flow manifolds. The numerical procedure is based on the finite differences approximation approach proposed by Datta and Majumdar. A linear overall momentum coefficient distribution is used in the dividing manifold, but the model is not limited to linear distributions. Comparisons are made with experimental, numerical and analytical data, yielding good results.

  8. Thermal hydraulic simulation of moderator heat exchanger

    International Nuclear Information System (INIS)

    Pressurized heavy water reactors form the majority in the first stage of India's nuclear power programme. Heavy water is both moderator and primary coolant. The heat generated in the moderator due to neutron moderation and capture has to be removed in moderator heat exchangers. It has been desired to improve the performance characteristics of moderator heat exchangers, whereby moderator would enter the calandria vessel at a low temperature and would enable higher power of operation for the same limiting temperature of moderator in the calandria. Results of studies carried out using a three dimensional computer code for various operating options are given. Using these velocities the heat exchangers have been analysed for flow induced vibrations. 7 refs., 6 figs., 6 tabs

  9. Tube in shell heat exchangers

    International Nuclear Information System (INIS)

    An improved tube-in-shell heat exchanger to be used between liquid metal and water is described for use in the liquid metal coolant system of fast breeder reactors. It is stated that this design is less prone to failures which could result in sodium water reactions than previous exchangers. (UK)

  10. Comparative study of the performance of the M-cycle counter-flow and cross-flow heat exchangers for indirect evaporative cooling – Paving the path toward sustainable cooling of buildings

    International Nuclear Information System (INIS)

    This paper provides a comparative study of the performance of cross-flow and counter-flow M-cycle heat exchangers for dew point cooling. It is recognised that evaporative cooling systems offer a low energy alternative to conventional air conditioning units. Recently emerged dew point cooling, as the renovated evaporative cooling configuration, is claimed to have much higher cooling output over the conventional evaporative modes owing to use of the M-cycle heat exchangers. Cross-flow and counter-flow heat exchangers, as the available structures for M-cycle dew point cooling processing, were theoretically and experimentally investigated to identify the difference in cooling effectiveness of both under the parallel structural/operational conditions, optimise the geometrical sizes of the exchangers and suggest their favourite operational conditions. Through development of a dedicated computer model and case-by-case experimental testing and validation, a parametric study of the cooling performance of the counter-flow and cross-flow heat exchangers was carried out. The results showed the counter-flow exchanger offered greater (around 20% higher) cooling capacity, as well as greater (15%–23% higher) dew-point and wet-bulb effectiveness when equal in physical size and under the same operating conditions. The cross-flow system, however, had a greater (10% higher) Energy Efficiency (COP). As the increased cooling effectiveness will lead to reduced air volume flow rate, smaller system size and lower cost, whilst the size and cost are the inherent barriers for use of dew point cooling as the alternation of the conventional cooling systems, the counter-flow system is considered to offer practical advantages over the cross-flow system that would aid the uptake of this low energy cooling alternative. In line with increased global demand for energy in cooling of building, largely by economic booming of emerging developing nations and recognised global warming, the research results will be of significant importance in terms of promoting deployment of the low energy dew point cooling system, helping reduction of energy use in cooling of buildings and cut of the associated carbon emission. -- Highlights: ? Quantitatively identify benefits of the counter-flow M-cycle heat exchangers over the cross-flow parallels for dew point cooling processing. ? Seeking the way to overcome the barriers in building application of the low energy evaporative dew point cooling system. ? Reduce size/cost of the dew point evaporative cooling system by increasing its cooling effectiveness and cooling capacity. ? Enable alternation of the conventional vapour compression refrigeration system by the low energy cost dew point evaporative cooling. ? Significantly reduce fossil fuel energy use in cooling of buildings and cut the associated carbon emission.

  11. Heat Exchanger for Motor Vehicle Cooling System

    OpenAIRE

    Thuliez, Jean-Luc; Chevroulet, Tristan; Stoll, Daniel

    1997-01-01

    Heat exchanger for a motor vehicle cooling system including a sleeve-like meter hermetically mounted on, and surrounding, a hollow tubular chassis meter of the vehicle. The sleeve is provided with inlets and outlets communicating with the space between the sleeve and the chassis meter and vehicle coolant flows through the inlet and outlet. Air, flowing over the outside surface of the sleeve and the inside surface of the chassis meter, cools the vehicle coolant. SMH - MCC Smart, car concepts (...

  12. Heat exchanger and related methods

    Energy Technology Data Exchange (ETDEWEB)

    Turner, Terry D.; McKellar, Michael G.

    2015-12-22

    Heat exchangers include a housing having an inlet and an outlet and forming a portion of a transition chamber. A heating member may form another portion of the transition chamber. The heating member includes a first end having a first opening and a second end having a second opening larger than the first opening. Methods of conveying a fluid include supplying a first fluid into a transition chamber of a heat exchanger, supplying a second fluid into the transition chamber, and altering a state of a portion of the first fluid with the second fluid. Methods of sublimating solid particles include conveying a first fluid comprising a material in a solid state into a transition chamber, heating the material to a gaseous state by directing a second fluid through a heating member and mixing the first fluid and the second fluid.

  13. A computational fluid dynamics and effectiveness-NTU based co-simulation approach for flow mal-distribution analysis in microchannel heat exchanger headers

    International Nuclear Information System (INIS)

    Refrigerant flow mal-distribution is a practical challenge in most microchannel heat exchangers (MCHXs) applications. Geometry design, uneven heat transfer and pressure drop in the different microchannel tubes are three main reasons leading to the flow mal-distribution. To efficiently and accurately account for these three effects, a new MCHX co-simulation approach is proposed in this paper. The proposed approach combines a detailed header simulation based on computational fluid dynamics (CFD) and a robust effectiveness-based finite volume tube-side heat transfer and refrigerant flow modeling tool. The co-simulation concept is demonstrated on a ten-tube MCHX case study. Gravity effect and uneven airflow effect were numerically analyzed using both water and condensing R134a as the working fluids. The approach was validated against experimental data for an automotive R134a condenser. The inlet header was cut open after the experimental data had been collected. The detailed header geometry was reproduced using the proposed CFD header model. Good prediction accuracy was achieved compared to the experimental data. The presented co-simulation approach is capable of predicting detailed refrigerant flow behavior while accurately predicts the overall heat exchanger performance. - Highlights: •MCHX header flow distribution is analyzed by a co-simulation approach. •The proposed method is capable of simulating both single-phase and two-phase flow. •An actual header geometry is reproduced in the CFD header model. •The modeling work is experimentally validated with good accuracy. •Gravity effect and air side mal-distribution are accounted for

  14. Predict the temperature distribution in gas-to-gas heat pipe heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Azad, E. [Iranian Research Organization for Science and Technology, Department of Advanced Materials and Renewable Energy, Tehran (Iran, Islamic Republic of)

    2012-07-15

    A theoretical model has been developed to investigate the thermal performance of a continuous finned circular tubing of an air-to-air thermosyphon-based heat pipe heat exchanger. The model has been used to determine the heat transfer capacity, which expresses the thermal performance of heat pipe heat exchanger. The model predicts the temperature distribution in the flow direction for both evaporator and condenser sections and also the saturation temperature of the heat pipes. The approach used for the present study considers row-by-row heat-transfer in evaporator and condenser sections of the heat pipe heat exchanger. (orig.)

  15. Heat exchangers and methods of construction thereof

    International Nuclear Information System (INIS)

    A heat exchanger is described comprising a shell having first inlet means and first outlet means for the flow of a first fluid therethrough, a plurality of tubes within the shell to provide a path for flow of a second fluid in heat exchange relation to the first fluid, second inlet means and second outlet means for flow of the second fluid to and from the tubes respectively, a tubular member concentric with at least a portion of the length of one of the tubes to define a space between the tube and the tubular member, at least one radially outwardly projecting portion on the tubular member, and a plurality of tube support means spaced apart and disposed generally perpendicular to the tube axes, wherein the tubular member is fixedly attached at one end to one of the tube support means and at the other end to an adjacent one of the tube support means, the space between the tube and the tubular member is closed to flow of both the first fluid and the second fluid, and the radially outwardly projecting portion on the tubular member extends longitudinally to allow flexing of the tubular member and expanding thereof radially outwardly during construction of the heat exchanger so as to allow insertion of the tube into the tubular member, the radially outwardly projecting portion defining a gap which contributes to the space between the tube and the tubular member. 6 figs

  16. Numerical Analysis of Tube-Fin Heat Exchanger using Fluent

    Directory of Open Access Journals (Sweden)

    M. V. Ghori

    2012-08-01

    Full Text Available Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of two-row plain Tube and Fin heat exchanger using FLUENT software. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created and meshed by using GAMBIT software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models k-, and SST k-omega, with steady-state solvers to calculate pressure drop, flow, and temperature fields. Model validation is carried out by comparing the simulated value friction factor f and Colburn factor j to experimental results investigate by Wang. Reasonable agreement is found between the simulations and experimental data, and the fluent software has been sufficient for simulating the flow fields in tube-fin heat exchangers.

  17. Cardioplegia heat exchanger design modelling using computational fluid dynamics.

    Science.gov (United States)

    van Driel, M R

    2000-11-01

    A new cardioplegia heat exchanger has been developed by Sorin Biomedica. A three-dimensional computer-aided design (CAD) model was optimized using computational fluid dynamics (CFD) modelling. CFD optimization techniques have commonly been applied to velocity flow field analysis, but CFD analysis was also used in this study to predict the heat exchange performance of the design before prototype fabrication. The iterative results of the optimization and the actual heat exchange performance of the final configuration are presented in this paper. Based on the behaviour of this model, both the water and blood fluid flow paths of the heat exchanger were optimized. The simulation predicted superior heat exchange performance using an optimal amount of energy exchange surface area, reducing the total contact surface area, the device priming volume and the material costs. Experimental results confirm the empirical results predicted by the CFD analysis. PMID:11131219

  18. Heat exchanger staybolt acceptance criteria

    International Nuclear Information System (INIS)

    The structural integrity demonstration of the primary coolant piping system includes evaluating the structural capacity of each component against a large break or equivalent Double-Ended Guillotine Break. A large break at the inlet or outlet heads of the heat exchangers would occur if the restraint members of the heads become inactive. The structural integrity of the heads is demonstrated by showing the redundant capacity of the staybolts to restrain the head at design conditions and under seismic loadings. The Savannah River Site heat exchanger head is attached to the tubesheet by 84 staybolts. Access to the staybolts is limited due to a welded seal cap over the staybolts. An ultrasonic testing (UT) inspection technique to provide an in-situ examination of the staybolts has recently been developed at SRS. Examination of the staybolts will be performed to ensure their service condition and configuration is within acceptance limits. An acceptance criteria methodology has been developed to disposition flaws reported in the staybolt inspections while ensuring adequate restraint capacity of the staybolts to maintain integrity of the heat exchanger heads against collapse. The methodology includes an approach for the baseline and periodic inspections of the staybolts. The heat exchanger head is analyzed with a three-dimensional finite element model. The restraint provided by the staybolts is evaluated for several postulated cases of inactive or missing staybolts. Evaluation of specific, inactive staybolt configurations based on the UT results can be performed with the finite element model and fracture methodology in this report

  19. Noise spectra measured on the Dragon reactor primary heat exchanges

    International Nuclear Information System (INIS)

    The frequency spectra of secondary water flow and tube wall temperatures have been measured on Dragon primary heat exchangers. No indication of tube wall temperature oscillations leading to tube burnout was found from the noise spectra analysed. (author)

  20. Flat tube heat exchangers – Direct and indirect noise levels in heat pump applications

    International Nuclear Information System (INIS)

    In the outdoor unit of an air-source heat pump the fan is a major noise source. The noise level from the fan is dependent on its state of operation: high air-flow and high pressure drop often result in higher noise levels. In addition, an evaporator that obstructs an air flow is a noise source in itself, something that may contribute to the total noise level. To be able to reduce the noise level, heat exchanger designs other than the common finned round tubes were investigated in this study. Three types of heat exchanger were evaluated to detect differences in noise level and air-side heat transfer performance at varying air flow. The measured sound power level from all the heat exchangers was low in comparison to the fan sound power level (direct effect). However, the heat exchanger design was shown to have an important influence on the sound power level from the fan (indirect effect). One of the heat exchangers with flat tubes was found to have the lowest sound power level, both direct and indirect, and also the highest heat transfer rate. This type of flat tube heat exchanger has the potential to reduce the overall noise level of a heat pump while maintaining heat transfer efficiency. - Highlights: •The direct noise from a heat exchanger is negligible in heat pump applications. •The design of the heat exchanger highly influences the noise from an outdoor unit. •Flat tube heat exchangers can reduce the noise from the outdoor unit of a heat pump. •Flat tube heat exchangers can increase the energy efficiency of a heat pump

  1. Modeling and Performance Analysis of Alternative Heat Exchangers for Heavy Vehicles

    OpenAIRE

    Lin, Wamei

    2014-01-01

    Cross flow heat exchangers made from aluminum are common as radiators in vehicles. However, due to the increasing power requirement and the limited available space in vehicles, it is extremely difficult to increase the size of heat exchangers (HEXs) placed in the front of vehicles. Placing the heat exchanger on the roof or at the underbody of vehicles might offer opportunity to increase the size of the heat exchangers. A new configuration of heat exchangers has to be developed to accommodate ...

  2. Comparative thermal analysis of theoretical and experimental studies of modified indirect evaporative cooler having cross flow heat exchanger with one fluid mixed and the other unmixed

    Energy Technology Data Exchange (ETDEWEB)

    Bisoniya, Trilok Singh [Department of Mechanical Engineering, Sagar Institute of Research and Technology, Ayodhya Bypass Road, Bhopal 462041 (India); Rajput, S.P.S. [Department of Mechancical Engineering, Maulana Azad National Institute of Technology, Bhopal, 462051 (India); Kumar, Anil [Department of Energy, Maulana Azad National Institute of Technology, Bhopal, 462051 (India)

    2011-07-01

    The comparative thermal analysis of theoretical and experimental studies of modified indirect evaporative cooler having cross flow heat exchanger with one fluid mixed and the other unmixed is presented in this research paper. A heat and mass transfer mathematical model is developed to simulate the properties of indirect evaporative cooler. The theoretical result analysis was done by plotting the curves between various performance parameters. This work presents the fabrication and experiments carried out on the indirect evaporative cooler at various outdoor air conditions. The data acquired by experiment were analyzed by plotting the curves between various performance parameters. The theoretical and experimental results were compared and analyzed. The theoretical model can be used to predict the performance of modified indirect evaporative cooler.

  3. Optimization of heat exchanger for indirectly heated water heater

    Science.gov (United States)

    Kaduchová, Katarína; Lenhard, Richard; Janda?ka, Jozef

    2012-04-01

    Due to the optimization of geometrical parameters of the heat exchanger in indirect heated water heaters created a mathematical model of heating hot water, by which I have subsequently made the simulation of the device to change its geometrical parameters. Based on these results, the impacts of the geometrical parameters affect the performance of the heat exchanger. The results of the optimization to create a CFD model which watched at the behavior of optimized heat exchanger for indirect heated water heaters.

  4. Test results of a Stirling engine utilizing heat exchanger modules with an integral heat pipe

    Science.gov (United States)

    Skupinski, Robert C.; Tower, Leonard K.; Madi, Frank J.; Brusk, Kevin D.

    1993-01-01

    The Heat Pipe Stirling Engine (HP-1000), a free-piston Stirling engine incorporating three heat exchanger modules, each having a sodium filled heat pipe, has been tested at the NASA-Lewis Research Center as part of the Civil Space Technology Initiative (CSTI). The heat exchanger modules were designed to reduce the number of potential flow leak paths in the heat exchanger assembly and incorporate a heat pipe as the link between the heat source and the engine. An existing RE-1000 free-piston Stirling engine was modified to operate using the heat exchanger modules. This paper describes heat exchanger module and engine performance during baseline testing. Condenser temperature profiles, brake power, and efficiency are presented and discussed.

  5. Preliminary SP-100/Stirling heat exchanger designs

    International Nuclear Information System (INIS)

    Analytic modeling of several heat exchanger concepts to couple the SP-100 nuclear reactor primary lithium loop and the Space Stirling Power Convertor (SSPC) was performed. Four 25 kWe SSPC's are used to produce the required 100 kW of electrical power. This design work focused on the interface between a single SSPC and the primary lithium loop. Manifolding to separate and collect the four channel flow was not modeled. This work modeled two separate types of heat exchanger interfaces (conductive coupling and radiative coupling) to explore their relative advantages and disadvantages. The minimum mass design of the conductively coupled concepts was 18 kg or 0.73 kg/kWe for a single 25 kWe convertor. The minimum mass radiatively coupled concept was 41 kg or 1.64 kg/kWe. The direct conduction heat exchanger provides a lighter weight system because of its ability to operate the Stirling convertor evaporator at higher heat fluxes than those attainable by the radiatively coupled systems. Additionally the conductively coupled concepts had relatively small volumes and provide potentially simpler assembly. Their disadvantages were the tight tolerances and material joining problems associated with this refractory to superalloy interface. The advantages of the radiatively coupled designs were the minimal material interface problems

  6. Preliminary SP-100/Stirling heat exchanger designs

    International Nuclear Information System (INIS)

    Analytic modeling of several heat exchanger concepts to couple the SP-100 nuclear reactor lithium loop and the Space Stirling Power Convertor (SSPC) was performed. Four 25 kWe SSPC's are used to produce the required 100 kW of electrical power. This design work focused on the interface between a single SSPC and the primary lithium loop. Manifolding to separate and collect the four channel flow was not modeled. This work modeled two separate types of heat exchanger interfaces (conductive coupling and radiative coupling) to explore their relative advantages and disadvantages. The minimum mass design of the conductively coupled concepts was 18 kg or 0.73 kg/kWe for a single 25 kWe convertor. The minimum mass radiatively coupled concept was 41 kg or 1.64 kg/kWe. The direct conduction heat exchanger provides a lighter weight system because of its ability to operate the Stirling convertor evaporator at higher heat fluxes than those attainable by the radiatively coupled systems. Additionally the conductively coupled concepts had relatively small volumes and provide potentially simpler assembly. Their disadvantages were the tight tolerances and material joining problems associated with this refractory to superalloy interface. The advantages of the radiatively coupled designs were the minimal material interface problems

  7. Preliminary SP-100/Stirling heat exchanger designs

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, P.; Tower, L. [Sverdrup Technology, Inc., Brook Park, OH (United States). Lewis Research Center Group; Dawson, R. [Aerospace Design and Fabrication Inc., Brook Park, OH (United States); Blue, B.; Dunn, P. [National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center

    1994-09-01

    Analytic modeling of several heat exchanger concepts to couple the SP-100 nuclear reactor lithium loop and the Space Stirling Power Convertor (SSPC) was performed. Four 25 kWe SSPC`s are used to produce the required 100 kW of electrical power. This design work focused on the interface between a single SSPC and the primary lithium loop. Manifolding to separate and collect the four channel flow was not modeled. This work modeled two separate types of heat exchanger interfaces (conductive coupling and radiative coupling) to explore their relative advantages and disadvantages. The minimum mass design of the conductively coupled concepts was 18 kg or 0.73 kg/kWe for a single 25 kWe convertor. The minimum mass radiatively coupled concept was 41 kg or 1.64 kg/kWe. The direct conduction heat exchanger provides a lighter weight system because of its ability to operate the Stirling convertor evaporator at higher heat fluxes than those attainable by the radiatively coupled systems. Additionally the conductively coupled concepts had relatively small volumes and provide potentially simpler assembly. Their disadvantages were the tight tolerances and material joining problems associated with this refractory to superalloy interface. The advantages of the radiatively coupled designs were the minimal material interface problems.

  8. Heat exchanger for solar water heaters

    Science.gov (United States)

    Cash, M.; Krupnick, A. C.

    1977-01-01

    Proposed efficient double-walled heat exchanger prevents contamination of domestic water supply lines and indicates leakage automatically in solar as well as nonsolar heat sources using water as heat transfer medium.

  9. Online performance assessment of heat exchanger using artificial neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Ahilan, C.; Kumanan, S. [Department of Production Engineering, National Institute of Technology Tiruchirappalli (India); Sivakumaran, N. [Department of Instrumentation and Control Engineering, National Institute of Technology Tiruchirappalli (India)

    2011-07-01

    Heat exchanger is a device in which heat is transferred from one medium to another across a solid surface. The performance of heat exchanger deteriorates with time due to fouling on the heat transfer surface. It is necessary to assess periodically the heat exchanger performance, in order to maintain at high efficiency level. Industries follow adopted practices to monitor but it is limited to some degree. Online monitoring has an advantage to understand and improve the heat exchanger performance. In this paper, online performance monitoring system for shell and tube heat exchanger is developed using artificial neural networks (ANNs). Experiments are conducted based on full factorial design of experiments to develop a model using the parameters such as temperatures and flow rates. ANN model for overall heat transfer coefficient of a design/ clean heat exchanger system is developed using a feed forward back propagation neural network and trained. The developed model is validated and tested by comparing the results with the experimental results. This model is used to assess the performance of heat exchanger with the real/fouled system. The performance degradation is expressed using fouling factor (FF), which is derived from the overall heat transfer coefficient of design system and real system. It supports the system to improve the performance by asset utilization, energy efficient and cost reduction interms of production loss.

  10. Online performance assessment of heat exchanger using artificial neural networks

    Directory of Open Access Journals (Sweden)

    C. Ahilan, S. Kumanan, N. Sivakumaran

    2011-09-01

    Full Text Available Heat exchanger is a device in which heat is transferred from one medium to another across a solid surface. The performance of heat exchanger deteriorates with time due to fouling on the heat transfer surface. It is necessary to assess periodically the heat exchanger performance, in order to maintain at high efficiency level. Industries follow adopted practices to monitor but it is limited to some degree. Online monitoring has an advantage to understand and improve the heat exchanger performance. In this paper, online performance monitoring system for shell and tube heat exchanger is developed using artificial neural networks (ANNs. Experiments are conducted based on full factorial design of experiments to develop a model using the parameters such as temperatures and flow rates. ANN model for overall heat transfer coefficient of a design/ clean heat exchanger system is developed using a feed forward back propagation neural network and trained. The developed model is validated and tested by comparing the results with the experimental results. This model is used to assess the performance of heat exchanger with the real/fouled system. The performance degradation is expressed using fouling factor (FF, which is derived from the overall heat transfer coefficient of design system and real system. It supports the system to improve the performance by asset utilization, energy efficient and cost reduction interms of production loss.

  11. Comparative design evaluation of plate fin heat exchanger and coiled finned tube heat exchanger for helium liquefier in the temperature range of 300-80 K

    International Nuclear Information System (INIS)

    Present indigenous helium liquefaction system at RRCAT uses the cross-counter flow coiled-finned tube heat exchangers developed completely from Indian resources. These coiled-finned tube heat exchangers are mainly suitable up to medium capacity helium liquefiers. For large capacity helium liquefier, plate fin heat exchangers are more suitable options. This paper presents the comparative evaluation of the design of both types of heat exchangers in the temperature range of 300-80 K for helium liquefier. (author)

  12. Optimization of heat exchanger for indirectly heated water heater

    OpenAIRE

    Kaduchová Katarína; Lenhard Richard; Janda?ka Jozef

    2012-01-01

    Due to the optimization of geometrical parameters of the heat exchanger in indirect heated water heaters created a mathematical model of heating hot water, by which I have subsequently made the simulation of the device to change its geometrical parameters. Based on these results, the impacts of the geometrical parameters affect the performance of the heat exchanger. The results of the optimization to create a CFD model which watched at the behavior of optimized heat exchanger for indirect hea...

  13. Analytical Study on Thermal and Mechanical Design of Printed Circuit Heat Exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Su-Jong Yoon; Piyush Sabharwall; Eung-Soo Kim

    2013-09-01

    The analytical methodologies for the thermal design, mechanical design and cost estimation of printed circuit heat exchanger are presented in this study. In this study, three flow arrangements of parallel flow, countercurrent flow and crossflow are taken into account. For each flow arrangement, the analytical solution of temperature profile of heat exchanger is introduced. The size and cost of printed circuit heat exchangers for advanced small modular reactors, which employ various coolants such as sodium, molten salts, helium, and water, are also presented.

  14. CFD simulation of air to air enthalpy heat exchanger

    International Nuclear Information System (INIS)

    Highlights: • A CFD model capable of modelling conjugate heat and mass transfer processes. • A mesh independence studies and a CFD model validation have been conducted. • Effects of flow direction on the effectiveness have been examined. • Performance parameters were sensible and latent effectiveness and pressure drop. - Abstract: A CFD model which supports conjugate heat and mass transfer problem representation across the membrane of air-to-air energy recovery heat exchangers has been developed. The model consists of one flow passage for the hot stream and another for the adjacent cold stream. Only half of each flow passage volume has been modelled on each side of the membrane surface. Three dimensional, steady state and laminar flow studies have been conducted using a commercial CFD package. The volumetric species transport model has been adopted to describe the H2O and air gas mixtures. Mesh dependency has been examined and followed by validation of the CFD model against published data. Furthermore, effects of flow direction at the inlet of the heat exchanger on its thermal effectiveness have been investigated. Simulation results are presented and analysed in terms of sensible effectiveness, latent effectiveness and pressure drop across the membrane heat exchanger. Results have shown that counter-flow configuration has greater sensitivity to the mesh centre perpendicular distance from the membrane when compared to the other two flow configurations (cross-/parallel-flow). However, the lateral mesh element length has shown minimal effect on the thermal effectiveness of the enthalpy heat exchanger. For the quasi-flow heat exchanger, a perpendicular flow direction to the inlets has been found to produce a higher performance in contrast to the non-perpendicular flow

  15. Design of a liquid metals heat exchanger

    International Nuclear Information System (INIS)

    The method that has been used in this design is that of the summation of the partial resistances to the heat transference, permitting to obtain the value of the total coefficient of heat transfer which will be equal to the reciprocal of the summation of all the resistances. The obtained exchanger is of tubes and rod type shield with the primary sodium flowing through the tubes and the secondary sodium flowing in counter-current through the shield. The shield has a nominal diameter of 6 inches and the bundle of tubes is formed by 31 tubes with a nominal diameter of 1/2 inch. The shield as well as the tubes are of stainless steel. The total heat transfer area is of 7.299 square meters, and the effective length of heat transfer is of 3.519 meters. After sizing the interchanger it was proceeded to simulate its functioning through a computer program in which the effective length of heat transfer was divided in 150 points in such a way that according to the integration of the distinct parameters along these points a comparison can finally be made between the design values and those of the simulation, which show a concordance. (author)

  16. A heat exchanger between forced flow helium gas at 14 to 18 K and liquid hydrogen at 20 K circulated by natural convection

    International Nuclear Information System (INIS)

    The Muon Ionization Cooling Experiment (MICE) has three 350-mm long liquid hydrogen absorbers to reduce the momentum of 200 MeV muons in all directions. The muons are then re-accelerated in the longitudinal direction by 200 MHz RF cavities. The result is cooled muons with a reduced emittance. The energy from the muons is taken up by the liquid hydrogen in the absorber. The hydrogen in the MICE absorbers is cooled by natural convection to the walls of the absorber that are in turn cooled by helium gas that enters at 14 K. This report describes the MICE liquid hydrogen absorber and the heat exchanger between the liquid hydrogen and the helium gas that flows through passages in the absorber wall

  17. Fluid dynamical considerations on heat exchanger networks

    Scientific Electronic Library Online (English)

    A. J. M., Vieira; F. L. P., Pessoa; E. M., Queiroz.

    2000-03-01

    Full Text Available The synthesis and analysis of heat exchanger networks are issues of great industrial interest due to the possibilities of decreasing plant costs, through the reduction of the utilities consumption and/or the number of equipments, in a grassroot design or retrofitting an existent network. The present [...] paper explores a new design algorithm based on the Total Annual Cost (TAC) optimization for a thermal equipment, with mean tubeside and shellside flow velocities constraints, studying also the influence of pumping cost in the network’s final cost.

  18. Thermal behavior of a heat exchanger module for seasonal heat storage

    DEFF Research Database (Denmark)

    Fan, Jianhua; Furbo, Simon

    2012-01-01

    Experimental and theoretic investigations are carried out to study the heat transfer capacity rate of a heat exchanger module for seasonal heat storage with sodium acetate trihydrate (SAT) supercooling in a stable way. A sandwich heat storage test module has been built with the phase change material (PCM) storage box in between two plate heat exchangers. Charge of the PCM storage is investigated experimentally with solid phase SAT as initial condition. Discharge of the PCM storage with the presence of crystallization is studied experimentally. Fluid flow and heat transfer in the PCM module are theoretically investigated by Computational Fluid Dynamics (CFD) calculations. The heat transfer rates between the PCM storage and the heating fluid/cooling fluid in the plate heat exchangers are determined. The CFD calculated temperatures are compared to measured temperatures. Based on the studies, recommendations on how best to transfer heat to and from the seasonal heat storage module are given.

  19. Experimental investigation of a reticulated porous alumina heat exchanger for high temperature gas heat recovery

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, A; Chandran, RB; Davidson, JH

    2015-01-22

    The present study presents an experimental study of a prototype counter-flow heat exchanger designed to recover sensible heat from inert and reactive gases flowing through a high temperature solar reactor for splitting CO2. The tube-in-tube heat exchanger is comprised of two concentric alumina tubes, each filled with reticulated porous alumina with a nominal porosity of 80% and pore density of 5 pores per inch (ppi). The RPC provides high heat transfer surface area per unit volume (917 m(-1)) with low pressure drop. Measurements include the permeability, inertial coefficient, overall heat transfer coefficient, effectiveness and pressure drop. For laminar flow and an inlet gas temperature of 1240 K, the overall heat transfer coefficients are 36-41 W m(-2) K-1. The measured performance is in good agreement with a prior CFD model of the heat exchanger. (C) 2014 Elsevier Ltd. All rights reserved.

  20. Hydraulic and thermal design of a gas microchannel heat exchanger

    International Nuclear Information System (INIS)

    In this paper investigations on the design of a gas flow microchannel heat exchanger are described in terms of hydrodynamic and thermal aspects. The optimal choice for thermal conductivity of the solid material is discussed by analysis of its influences on the thermal performance of a micro heat exchanger. Two numerical models are built by means of a commercial CFD code (Fluent). The simulation results provide the distribution of mass flow rate, inlet pressure and pressure loss, outlet pressure and pressure loss, subjected to various feeding pressure values. Based on the thermal and hydrodynamic analysis, a micro heat exchanger made of polymer (PEEK) is designed and manufactured for flow and heat transfer measurements in air flows. Sensors are integrated into the micro heat exchanger in order to measure the local pressure and temperature in an accurate way. Finally, combined with numerical simulation, an operating range is suggested for the present micro heat exchanger in order to guarantee uniform flow distribution and best thermal and hydraulic performances.

  1. Hydraulic and thermal design of a gas microchannel heat exchanger

    Science.gov (United States)

    Yang, Yahui; Brandner, Juergen J.; Morini, Gian Luca

    2012-05-01

    In this paper investigations on the design of a gas flow microchannel heat exchanger are described in terms of hydrodynamic and thermal aspects. The optimal choice for thermal conductivity of the solid material is discussed by analysis of its influences on the thermal performance of a micro heat exchanger. Two numerical models are built by means of a commercial CFD code (Fluent). The simulation results provide the distribution of mass flow rate, inlet pressure and pressure loss, outlet pressure and pressure loss, subjected to various feeding pressure values. Based on the thermal and hydrodynamic analysis, a micro heat exchanger made of polymer (PEEK) is designed and manufactured for flow and heat transfer measurements in air flows. Sensors are integrated into the micro heat exchanger in order to measure the local pressure and temperature in an accurate way. Finally, combined with numerical simulation, an operating range is suggested for the present micro heat exchanger in order to guarantee uniform flow distribution and best thermal and hydraulic performances.

  2. A Cell Model to Describe and Optimize Heat and Mass Transfer in Contact Heat Exchangers

    OpenAIRE

    Piotr Yakimychev; Nickolay Yelin; Vadim Mizonov

    2011-01-01

    A cell model to describe and optimize heat and mass transfer in contact heat exchangers for utilization of exhaust gases heat is proposed. The model is based on the theory of Markov chains and allows calculating heat and mass transfer at local moving force of the processes in each cell. The total process is presented as two parallel chains of cells (one for water flow and one for gas flow). The corresponding cells of the chains can exchange heat and mass, and water and gas can travel along th...

  3. Double tube heat exchanger with novel enhancement: Part II - single phase convective heat transfer

    Energy Technology Data Exchange (ETDEWEB)

    Tiruselvam, R.; Chin, W.M.; Raghavan, Vijay R. [OYL Sdn. Bhd., Research and Application Department, Kuala Lumpur (Malaysia)

    2012-08-15

    The study is conducted to evaluate the heat transfer characteristics of two new and versatile enhancement configurations in a double tube heat exchanger annulus. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Heat transfer coefficients are determined by the Wilson Plot technique in laminar and turbulent flow and correlations are proposed for Nusselt numbers. Comparisons are then made between heat transfer and flow friction. (orig.)

  4. Damping of multispan heat exchanger tubes. Pt. 1: in gases

    International Nuclear Information System (INIS)

    Flow-induced vibration analyses of heat exchanger tubes require the knowledge of damping. This paper treats the question of damping on multispan heat exchanger tubes in air and gases. The different energy dissipation mechanisms that contribute to tube damping are discussed. The available experimental data are reviewed and analysed. We find that the main damping mechanism in gases is friction between tube and tube-supports. Damping is strongly related to tube-support thickness. Damping values are recommended for design purposes. This study is interesting in the nuclear industry for it often uses heat exchangers

  5. Feasibility study of improved heat exchanger

    International Nuclear Information System (INIS)

    Generally shell and tube type heat exchangers have been used widely for many years in the auxiliary cooling systems of nuclear power plants. Recently, however, in general industrial facilities and so on many plate heat exchangers excellent in heat transfer performance have been used, compared with shell and tube heat exchangers, and their heat exchanger bodies and cooling system facilities have been rationalized. We carried out confirmation tests on the plate type heat exchangers in structural strength, aseismatic strength, heat transfer performance and maintenance regarding their application to nuclear power plants. As a result, we have confirmed that they can be applied to seawater systems of actual plants. The tests further provided useful information on their actual operation. (author)

  6. Handbook for heat exchangers and tube banks design

    CERN Document Server

    Annaratone, Donatello

    2010-01-01

    The motion of fluids is never in parallel- or counter-flow in heat exchangers and tube banks, leading to complexities in the equations for calculating their transferred heat and temperatures. This review of the topic includes 70 design and verification tables.

  7. Numerical simulation of two phase flows in heat exchangers; Simulation numerique des ecoulements diphasiques dans les echangeurs

    Energy Technology Data Exchange (ETDEWEB)

    Grandotto Biettoli, M

    2006-04-15

    The report presents globally the works done by the author in the thermohydraulic applied to nuclear reactors flows. It presents the studies done to the numerical simulation of the two phase flows in the steam generators and a finite element method to compute these flows. (author)

  8. Micro tube heat exchangers for Space Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Mezzo fabricates micro tube heat exchangers for a variety of applications, including aerospace, automotive racing, Department of Defense ground vehicles,...

  9. Heat exchanger with vertical flexible tubes of the 'descending' type

    International Nuclear Information System (INIS)

    This invention concerns a heat exchanger with vertical flexible tubes of the 'descending' type, particularly intended for the evaporation of a saline solution. For the record, a vertical tube heat exchanger for heating a secondary fluid by a primary fluid is of the 'descending' type when the secondary fluid flows by gravity in thin films along the outside of the tubes in which the primary fluid is flowing. Specifically, the purpose of this invention is a heat exchanger of the above type comprising new arrangements for fixing the tubes by their upper ends and the creation on the outside of these tubes of a thin continuous descending film of secondary fluid to be heated

  10. Characteristics of cooling water fouling in a heat exchange system

    International Nuclear Information System (INIS)

    This study investigated the efficiency of the physical water treatment method in preventing and controlling fouling accumulation on heat transfer surfaces in a laboratory heat exchange system with tap and artificial water. To investigate the fouling characteristics, an experimental test facility with a plate type heat exchange system was newly built, where cooling and hot water moved in opposite directions forming a counter-flow heat exchanger. The obtained fouling resistances were used to analyze the effects of the physical water treatment on fouling mitigation. Furthermore, the surface tension and pH values of water were also measured. This study compared the fouling characteristics of cooling water in the heat exchange system with and without the mitigation methods for various inlet velocities. In the presence of the electrode devices with a velocity of 0.5m/s, the fouling resistance was reduced by 79% compared to that in the absence of electrode devices

  11. High temperature heat exchange: nuclear process heat applications

    International Nuclear Information System (INIS)

    The unique element of the HTGR system is the high-temperature operation and the need for heat exchanger equipment to transfer nuclear heat from the reactor to the process application. This paper discusses the potential applications of the HTGR in both synthetic fuel production and nuclear steel making and presents the design considerations for the high-temperature heat exchanger equipment

  12. THE STUDY OF HEAT EXCHANGE DYNAMICS OF VENTILATION EMISSIONS ON HEAT UTILIZATION WITH CONSIDERATION FOR WATER VAPOUR CONDENSATION

    Directory of Open Access Journals (Sweden)

    V. S. Ezhov

    2010-10-01

    Full Text Available Problem statement. Known corrosion-resistant air heaters made from glass tubes have not received wide acceptance because of some defects (low mechanical strength, temperature deformation, complexity and unreliability of assemblies, etc., whereas the structure of insulated glazing heat exchange devices has some advantages. The aim of present paper is to study heat exchange dynamics of venti-lation emissions in insulated glazing air heater on heat utilization with considera-tion for water vapor condensation.Results and conclusions. The study of heat exchange in channel insulated glazing heat exchanger at heat utilization of corrosion-active ventilation emissions is car-ried out with consideration for water vapour condensation on heat-exchange sur-faces. It is shown that the rate of heat exchange under longitudinal flow of vertical glass surfaces air heated and steam-and-air cooled is 15—20 % lower than the rate of heat exchange at air cooling.

  13. Thermofluidynamic study of a sodium-sodium heat exchanger

    International Nuclear Information System (INIS)

    Sodium-sodium heat exchanges are installated in the reactor coolant system of fast breeder nuclear power plant. In the traditional engineering practice the thermal-hydraulic design of such heat exchanges is based on well-known Nu-Re-Pr correlations while three-dimensional effects are generally neglected in some applications, especially for flow regime, buoyant flow and non-uniform heat sources distributions, the 3D behaviour is an important issue in determining the heat exchanger performances. Herein a fully 3D thermal-hydraulic model of a sodium-sodium heat exchanger is presented. Each one of the 268 tubes of the bundle is modeled individually and the annular shell flow and temperature field is computed with a CFD calculation using the computer code CFX-4.1. The global heat transfer parameters of the heat exchanger are computed and compared with measured data for selected operational conditions which include the effect of local tube plugging by oxidic solid material. The comparison indicates a very good agreement between code predictions and measured data. (author)

  14. Investigation into fouling factor in compact heat exchanger

    Directory of Open Access Journals (Sweden)

    Masoud Asadi

    2013-03-01

    Full Text Available Fouling problems cannot be avoided in many heat exchanger operations, and it is necessary to introduce defensive measures to minimize fouling and the cost of cleaning. The fouling control measures used during either design or operation must be subjected to a thorough economic analysis, taking into consideration all the costs of the fouling control measures and their projected benefits in reducing costs due to fouling. Under some conditions, nearly asymptotic fouling resistances can be obtained, and this suggests a somewhat different approach to the economics. Fouling is a generic term for the deposition of foreign matter on a heat transfer surface. Deposits accumulating in the small channels of a compact heat exchanger affect both heat transfer and fluid flow. Fouling deposits constricting passages in a compact heat exchanger are likely to increase the pressure drop and therefore reduce the flow rate. Reduced flow rate may be a process constraint; it reduces efficiency and increases the associated energy use and running costs. Maintenance costs will also increase. Fouling remains the area of greatest concern for those considering the installation of compact heat exchangers. The widespread installation of compact heat exchangers has been hindered by the perception that the small passages are more strongly affected by the formation of deposits. In this paper different types of fouling and treatment are presented.

  15. Optimization of heat exchanger for indirectly heated water heater

    Directory of Open Access Journals (Sweden)

    Kaduchová Katarína

    2012-04-01

    Full Text Available Due to the optimization of geometrical parameters of the heat exchanger in indirect heated water heaters created a mathematical model of heating hot water, by which I have subsequently made the simulation of the device to change its geometrical parameters. Based on these results, the impacts of the geometrical parameters affect the performance of the heat exchanger. The results of the optimization to create a CFD model which watched at the behavior of optimized heat exchanger for indirect heated water heaters.

  16. Conjugate heat and mass transfer in heat mass exchanger ducts

    CERN Document Server

    Zhang, Li-Zhi

    2013-01-01

    Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi

  17. Heat exchange apparatus for a reactor

    International Nuclear Information System (INIS)

    A heat exchange apparatus for transferring heat from a reactor gas coolant to a secondary fluid medium is described. The heat exchange apparatus comprises an elongated vertically extending hole in a concrete shield. Supported within the hole in spaced relation to the wall thereof is an elongated vertical extending tubular shroud which shroud has a gas entry at its lower end and a gas exit at its upper end. Means are provided for dividing the annular space between the shroud 16 and the wall of the hole into an upper and a lower region. Disposed in the shield is an inlet for reactor coolant which communicates with the lower region and is positioned vertically so as to be spaced above the gas entry to the shroud to thereby suppress natural convection during nonoperating standby conditions of the apparatus. An outlet for reactor coolant, which is disposed in the shield, communicates with the upper region. A plurality of vertically extending, spaced apart bayonet tube assemblies are supported within the shroud and means are provided for passing secondary fluid through these tube assemblies. A circulator is provided for causing the reactor coolant to flow in through the inlet, downward in the annular space, into the shroud through the gas entry, upward through the shroud and out through the outlet during emergency conditions of the reactor

  18. Heat transfer characteristics of a new helically coiled crimped spiral finned tube heat exchanger

    Science.gov (United States)

    Srisawad, Kwanchanok; Wongwises, Somchai

    2009-02-01

    In the present study, the heat transfer characteristics in dry surface conditions of a new type of heat exchanger, namely a helically coiled finned tube heat exchanger, is experimentally investigated. The test section, which is a helically coiled fined tube heat exchanger, consists of a shell and a helical coil unit. The helical coil unit consists of four concentric helically coiled tubes of different diameters. Each tube is constructed by bending straight copper tube into a helical coil. Aluminium crimped spiral fins with thickness of 0.5 mm and outer diameter of 28.25 mm are placed around the tube. The edge of fin at the inner diameter is corrugated. Ambient air is used as a working fluid in the shell side while hot water is used for the tube-side. The test runs are done at air mass flow rates ranging between 0.04 and 0.13 kg/s. The water mass flow rates are between 0.2 and 0.4 kg/s. The water temperatures are between 40 and 50°C. The effects of the inlet conditions of both working fluids flowing through the heat exchanger on the heat transfer coefficients are discussed. The air-side heat transfer coefficient presented in term of the Colburn J factor is proportional to inlet-water temperature and water mass flow rate. The heat exchanger effectiveness tends to increase with increasing water mass flow rate and also slightly increases with increasing inlet water temperature.

  19. Heat exchange intensification in evaporators of the ship refrigerating machinery with application of belt turbulence promoters

    Directory of Open Access Journals (Sweden)

    Proshkin Oleg Vladimirovich

    2009-10-01

    Full Text Available The search of methods of intensification of the heat exchange process at boiling in evaporators of refrigerators is made to decrease mass-dimension pa-rameters of heat exchange equipment. The heat exchange process at boiling within belt six-ray turbulence promoter, made as a six-ray star is investigated. The results of the model experiment for hydrodynamics and heat exchange of two-phase flow observation are presented.

  20. Optimization of parameters of heat exchangers vehicles

    Directory of Open Access Journals (Sweden)

    Andrei MELEKHIN

    2014-09-01

    Full Text Available The relevance of the topic due to the decision of problems of the economy of resources in heating systems of vehicles. To solve this problem we have developed an integrated method of research, which allows to solve tasks on optimization of parameters of heat exchangers vehicles. This method decides multicriteria optimization problem with the program nonlinear optimization on the basis of software with the introduction of an array of temperatures obtained using thermography. The authors have developed a mathematical model of process of heat exchange in heat exchange surfaces of apparatuses with the solution of multicriteria optimization problem and check its adequacy to the experimental stand in the visualization of thermal fields, an optimal range of managed parameters influencing the process of heat exchange with minimal metal consumption and the maximum heat output fin heat exchanger, the regularities of heat exchange process with getting generalizing dependencies distribution of temperature on the heat-release surface of the heat exchanger vehicles, defined convergence of the results of research in the calculation on the basis of theoretical dependencies and solving mathematical model.

  1. Compact interior heat exchangers for CO{sub 2} mobile heat pumping systems

    Energy Technology Data Exchange (ETDEWEB)

    Hafner, Armin

    2003-07-01

    The natural refrigerant carbon dioxide (CO{sub 2}) offers new possibilities for design of flexible, efficient and environmentally safe mobile heat pumping systems. As high-efficient car engines with less waste heat are developed, extra heating of the passenger compartment is needed in the cold season. A reversible transcritical CO{sub 2} system with gliding temperature heat rejection can give high air delivery temperature which results in rapid heating of the passenger compartment and rapid defogging or defrosting of windows. When operated in cooling mode, the efficiency of transcritical CO{sub 2} systems is higher compared to common (HFC) air conditioning systems, at most dominant operating conditions. Several issues were identified for the design of compact interior heat exchangers for automotive reversible CO{sub 2} heat pumping systems. Among theses issues are: (1) Refrigerant flow distribution, (2) Heat exchanger fluid flow circuiting, (3) Air temperature uniformity downstream of the heat exchanger, (4) Minimization of temperature approach, (5) Windshield flash fogging due to retained water inside the heat exchanger, (6) Internal beat conduction in heating mode operation, and (7) Refrigerant side pressure drop In order to provide a basis for understanding these issues, the author developed a calculation model and set up a test facility and investigated different prototype heat exchangers experimentally.

  2. Heat transfer of high thermal energy storage with heat exchanger for solar trough power plant

    International Nuclear Information System (INIS)

    High temperature thermal energy storage was studied by a lab-scale cylindrical storage tank experiment. A heat exchanger of thermal energy storage is used for separating two fluids, storage medium, and heat transfer fluid (HTF). There are two types of pipe in the heat exchanger, a vertical straight pipe and a helical coiled pipe. The experimental results were validated with the created mathematical model of nonsteady state heat exchanger. The highest storage efficiency is 0.631 at the HTF flow rate of 0.1 kg/s in a helical coiled pipe heat exchanger. The HTF and storage medium temperatures were measured for validating the model at various HTF flow rates. The agreement between model and experiment was presented with the error below 10%. This model is able to calculate the storage temperature of solar thermal power plants that performs in the liquid temperature range of selected HTF and storage medium

  3. Tube in-shell heat exchanger

    International Nuclear Information System (INIS)

    A tube-in-shell heat exchanger is described. It comprises a bundle of heat exchange tubes extending within an elongate shell. The tubes pass through a tube sheet and are connected thereto by means comprising branch pipes and compression pipe couplings

  4. The fouling in the tubular heat exchanger of Algiers refinery

    Science.gov (United States)

    Harche, Rima; Mouheb, Abdelkader; Absi, Rafik

    2015-06-01

    Crude oil fouling in refinery preheat exchangers is a chronic operational problem that compromises energy recovery in these systems. Progress is hindered by the lack of quantitative knowledge of the dynamic effects of fouling on heat exchanger transfer and pressure drops. In subject of this work is an experimental determination of the thermal fouling resistance in the tubular heat exchanger of the crude oil preheats trains installed in an Algiers refinery. By measuring the inlet and outlet temperatures and mass flows of the two fluids, the overall heat transfer coefficient has been determined. Determining the overall heat transfer coefficient for the heat exchanger with clean and fouled surfaces, the fouling resistance was calculated. The results obtained from the two cells of exchangers studies, showed that the fouling resistance increased with time presented an exponential evolution in agreement with the model suggested by Kern and Seaton, with the existence of fluctuation caused by the instability of the flow rate and the impact between the particles. The bad cleaning of the heat exchangers involved the absence of the induction period and caused consequently, high values of the fouling resistance in a relatively short period of time.

  5. Experimental study on the heat transfer characteristics in corrugated and flat plate type heat exchanger

    International Nuclear Information System (INIS)

    An experiment was performed to study heat transfer characteristics between corrugated heat exchanger and flat plate type one. While heat capacity(13.86kW) was provided constantly and the flow speed was varied from 2.8 to 17.9m/s, the temperature and the pressure drop were measured. Furthermore, heat transfer coefficient, Colburn factor and Nusselt number were calculated using them. With increase of the flow speed for both exchangers, the coefficient and the pressure drop increased, but Colburn factor decreased. The coefficient, pressure drop and Colburn factor of the corrugated type were all higher than those of the flat one, which is due to the flow interruption with recirculation and reattachment of the corrugated type. The empirical correlations of Nusselt number were suggested for the tested two heat exchangers

  6. Damping of multispan heat exchanger tubes. Pt. 2: in liquids

    International Nuclear Information System (INIS)

    Damping information is required for flow-induced vibration analyses of heat exchanger tubes. This paper treats the question of damping of multispan heat exchanger tubes in liquids. There are three important energy dissipation mechanisms that contribute to damping in liquids. These are: viscous damping between tube and liquid, squeeze-film damping in the clearance between tube and tube-support and friction damping at the tube-support. These mechanisms are discussed and formulated in terms of heat exchanger tube parameters. The available experimental data on damping in liquids are reviewed and analysed. Semi-empirical expressions have been developed to formulate damping. These expressions are recommended for design purposes. This study is interesting in the nuclear industry for it often uses heat exchangers

  7. Performance of Helical Coil Heat Recovery Exchanger using Nanofluid as Coolant

    Directory of Open Access Journals (Sweden)

    Navid Bozorgan

    2015-07-01

    Full Text Available Nanofluids are expected to be a promising coolant condidate in chemical processes for heat transfer system size reduction. This paper focuses on reducing the number of turns in a helical coil heat recovery exchanger with a given heat exchange capacity in a biomass heating plant using ?-Al2O3/n-decane nanofluid as coolant. The nanofluid flows through the tubes and the hot n-hexane flows through the shell. The numerical results show that using nanofluid as coolant in a helical coil heat exchanger can reduce the manufacturing cost of the heat exchanger and pumping power by reducing the number of turns of the coil.

  8. Experimental study of heat transfer in a heat exchanger with rectangular channels

    International Nuclear Information System (INIS)

    This paper presents the results of an experimental study related to characterisation of a mini channel heat exchanger. Such heat exchanger may be used in water cooling of electronic components. The results obtained show the efficiency of this exchanger even with very low water flow rates. Indeed, in spite of the importance of the extracted heat fluxes which can reach about 50Kw/m2, the temperature of the cooled Aluminium bloc remained always lower than the tolerated threshold of 80 degree in electronic cooling. Moreover, several thermal characteristics such as equivalent thermal resistance of the exchanger, the average internal convective heat transfer coefficient and the increase in the temperature of the cooling water have been measured. The results presented have been obtained with in quinconcerectangular mini-channel heat exchanger, with a hydraulic diameter Dh = 2mm. NOMENCLATURE h D Hydraulic diameter (mm). int

  9. Testing and plugging power plant heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Sutor, F. [Expando Seal Tools, Inc., Montgomeryville, PA (United States)

    1994-12-31

    Heat Exchanger tubes fail for any number of reasons including but certainly not limited to the cumulative effects of corrosion, erosion, thermal stress and fatigue. This presentation will attempt to identify the most common techniques for determining which tubes are leaking and then introduce the products in use to plug the leaking tubes. For the sake of time I will limit the scope of this presentation to include feedwater heaters and secondary system heat exchangers such as Hydrogen Coolers, Lube Oil Coolers, and nuclear Component Cooling Water, Emergency Cooling Water, Regenerative Heat Recovery heat exchangers.

  10. Heat exchanger device and method for heat removal or transfer

    Energy Technology Data Exchange (ETDEWEB)

    Koplow, Jeffrey P

    2015-03-24

    Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

  11. Heat exchanger device and method for heat removal or transfer

    Energy Technology Data Exchange (ETDEWEB)

    Koplow, Jeffrey P.

    2015-12-08

    Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

  12. Heat exchanger device and method for heat removal or transfer

    Science.gov (United States)

    Koplow, Jeffrey P

    2013-12-10

    Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.

  13. Heat transfer and fluid flow in minichannels and microchannels

    CERN Document Server

    Kandlikar, Satish; Li, Dongqing; Colin, Stephane; King, Michael R

    2013-01-01

    Heat exchangers with minichannel and microchannel flow passages are becoming increasingly popular due to their ability to remove large heat fluxes under single-phase and two-phase applications. Heat Transfer and Fluid Flow in Minichannels and Microchannels methodically covers gas, liquid, and electrokinetic flows, as well as flow boiling and condensation, in minichannel and microchannel applications. Examining biomedical applications as well, the book is an ideal reference for anyone involved in the design processes of microchannel flow passages in a heat exchanger. Each chapter is accompan

  14. Experimental investigation of a reticulated porous alumina heat exchanger for high temperature gas heat recovery

    International Nuclear Information System (INIS)

    The present study presents an experimental study of a prototype counter-flow heat exchanger designed to recover sensible heat from inert and reactive gases flowing through a high temperature solar reactor for splitting CO2. The tube-in-tube heat exchanger is comprised of two concentric alumina tubes, each filled with reticulated porous alumina with a nominal porosity of 80% and pore density of 5 pores per inch (ppi). The RPC provides high heat transfer surface area per unit volume (917 m?1) with low pressure drop. Measurements include the permeability, inertial coefficient, overall heat transfer coefficient, effectiveness and pressure drop. For laminar flow and an inlet gas temperature of 1240 K, the overall heat transfer coefficients are 36–41 W m?2 K?1. The measured performance is in good agreement with a prior CFD model of the heat exchanger. - Highlights: • A ceramic heat exchanger provides gas-phase heat recuperation for a solar thermochemical reactor. • Alumina reticulated porous ceramic (RPC) provides high surface area and low pressure drop. • Heat transfer and pressure drop are measured at temperatures up to 1240 K. • RPC provides a 9-fold increase in heat transfer compared to bare tubes

  15. Intermediate heat exchanger project for Super Phenix

    International Nuclear Information System (INIS)

    The Super Phenix (1200 MWe) intermediate heat exchangers are derived directly from those of Phenix (250 MWe). The intermediate exchangers are housed in the reactor vessel annulus: as this annulus must be of the smallest volume possible, these IHX are required to work at a high specific rating. The exchange surface is calculated for nominal conditions. A range is then defined, consistent with the above requirements and throughout which the ratio between bundle thickness and bundle length remains acceptable. Experimental technics and calculations were used to determine the number of tube constraint systems required to keep the vibration amplitude within permissible limits. From a knowledge of this number, the pressure drop produced by the primary flow can be calculated. The bundle geometry is determined together with the design of the corresponding tube plates and the way in which these plates should be joined to the body of the IHX. The experience (technical and financial) acquired in the construction of Phenix is then used to optimize the design of the Super Phenix project. An approximate definition of the structure of the IHX is obtained by assuming a simplified load distribution in the calculations. More sophisticated calculations (e.g. finite element method) are then used to determine the behaviour of the different points of the IHX, under nominal and transient conditions

  16. Numerical analysis of fin-tube plate heat exchanger by using CFD technique

    OpenAIRE

    Ahmed F. Khudheyer; Mahmoud Sh. Mahmoud

    2011-01-01

    Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a two-row plain fin-and-tube heat exchanger using Open FOAM, an open-source CFD code. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created, meshed, calculated, and post-processed using open source software. Fluid flow and heat transfer are simulated and results compared using ...

  17. Method of pressure pulse cleaning heat exchanger tubes, upper tube support plates and other areas in a nuclear steam generator and other tube bundle heat exchangers

    International Nuclear Information System (INIS)

    This patent describes the art of removing corrosive deposits from locations within a heat exchanger in which the heat exchanger is characterized by an enclosed tank containing heat exchanger tubes which are closely packed together and support plates arranged transverse to and sequentially spaced along the longitudinal axis of the heat exchanger tubes and forming junctions therewith, where the support plates contain a multiplicity of transverse holes extending through their entire thickness and where crevices exist between the outer surface of the heat exchanger tubes and the support plates at the site of the junctions and wherein these crevices and the holes in the support plates act as flow holes to permit liquid which is placed in the enclosed tank to rise to a multiplicity of levels within the tank. The heat exchanger also contains an outer shell and a tube support sheet at the lower extremity of the tank to provide a base support for the multiplicity of heat exchanger tubes

  18. Forced convection heat exchange inside porous sintered metals

    International Nuclear Information System (INIS)

    Methods and results of investigating heat exchange in the process of liquid flow inside porous sintered metals have been analyzed. It has been shown that experimental data available include extremely conflicting correlations between heat transfer coefficient and Reynolds number, porosity, and relative wall thickness. Scattering of the data can attain one order of magnitude. The volume coefficient of heat transfer inside pores determined in papers does not correspond to its real value in the initial equations of the inner problem of porous cooling. Calculating and experimental method of determining the heat transfer coefficient has been developed and realized on the unit of radiation heating. More accurate experimental data on intraporous heat exchange have been obtained. It has been established that relative wall thickness does not affect the intensity of heat transfer inside pores

  19. Performances of heat exchangers on HTGR application

    International Nuclear Information System (INIS)

    Rising oil price is making the high-temperature gas-cooled reactor (HTGR) an attractive alternative energy resource for high temperature process heat applications. Motivation and aspect of nuclear process applications to steam reforming and coal gasification, etc. are described. Studies on heat transfer problems are reviewed. The present status of designed high temperature heat exchangers is summarized. The performances of He-He high temperature heat exchanger tested in Japan is reported. Several problems in the future research and development of technologies for process heat application by HTGR are discussed. 29 refs

  20. Continuous cleaning of heat exchanger with recirculating fluidized bed

    International Nuclear Information System (INIS)

    Fluidized bed heat exchangers for liquids have been studied in the United States, the Netherlands, and the Federal Republic of Germany. Between 1965 and 1970, fluidized bed heat exchangers were developed in the United States as brine heaters in seawater desalination. Furthermore, their potential in the utilization of geothermal energy was tested between 1975 and 1980. In the Netherlands, fluidized bed heat exchangers have been developed since 1973 for brine heating and heat recovery in multistage flash evaporators for seawater desalination and, since about 1980, for applications in the process industry. The authors became interested in fluidized bed heat exchangers first in 1978 in connection with wastewater evaporation. The authors emphasize that the results of all these groups were in basic agreement. They can be summarized as follows: 1. The fluidized bed will in many cases maintain totally clean surfaces and neither scaling nor fouling will occur. In cases where even a fluidized bed cannot completely prevent scaling or fouling, the thickness of the layer is controlled. In these cases stable operation maintaining acceptable overall heat transfer coefficients is possible without cleaning. 2. There are always excellent heat transfer coefficients as low superficial velocities of less than ? < 0.5 m/s. 3. The pressure losses are comparable with those in normal heat exchangers since fluidized bed heat exchangers are mostly operated at low superficial velocities. 4. Feed flow may be varied between 50 and 150% or more of the design feed flow. 5. Erosion is negligible. 6. Fluidized bed particles can be manufactured from all sorts of chemically and mechanically resistant materials, such as sand, glass, ceramics, and metals

  1. On-line fouling monitor for heat exchangers

    International Nuclear Information System (INIS)

    Biological and/or chemical fouling in utility service water system heat exchangers adversely affects operation and maintenance costs, and reduced heat transfer capability can force a power deaerating or even a plant shut down. In addition, service water heat exchanger performance is a safety issue for nuclear power plants, and the issue was highlighted by NRC in Generic Letter 89-13. Heat transfer losses due to fouling are difficult to measure and, usually, quantitative assessment of the impact of fouling is impossible. Plant operators typically measure inlet and outlet water temperatures and flow rates and then perform complex calculations for heat exchanger fouling resistance or ''cleanliness''. These direct estimates are often imprecise due to inadequate instrumentation. Electric Power Research Institute developed and patented an on-line condenser fouling monitor. This monitor may be installed in any location within the condenser; does not interfere with routine plant operations, including on-line mechanical and chemical treatment methods; and provides continuous, real-time readings of the heat transfer efficiency of the instrumented tube. This instrument can be modified to perform on-line monitoring of service water heat exchangers. This paper discusses the design, construction of the new monitor, and algorithm used to calculate service water heat exchanger fouling

  2. Computational fluid modeling in a heat exchanger design

    Energy Technology Data Exchange (ETDEWEB)

    Eghlimi, A.; Fletcher, C.A.J.; Adam, Q.

    1999-07-01

    The design of efficient heat exchangers are crucial in many industrial applications including power utility boilers, water heaters, etc. However, in many engineering problems heat exchanger design has evolved a traditional experimental manner. This approach is not only costly but also involves technical difficulties in taking direct full-scale measurements. This raises up the issue of CFD (Computational Fluid Dynamic) modeling as a design tool. In the present study, CFD has been used to model complex flows in a heat exchanger. The efficient local fluid and thermal flow simulation around fins assist in the design process of heat exchangers. The steady-state Reynolds-averaged Navier-Stokes equations are discretized directly in physical space in a turbulent flow modeling. The complicated 3D fin and baffle arrangement has been studied. An exhaust flue (products of combustion) enter a steel tube with heat absorbing fins welded on the inside, and the hole tube sits inside a pressure vessel containing water. The heat transfer from the carrier fluid to the fins and then to the surrounding water has been studied computationally. For a fixed diameter flue there can be an infinite variety of fins configurations. The present work models the convection, conduction and radiation heat transfer inside the heat exchanger. It is desired to improve the efficiency of the heat exchanger and this can be achieved by accurately modeling the heat transfer from the fins to the surrounding fluid. A periodic heat transfer boundary condition has been applied to save the computational time. The transport equations have been under-relaxed to provide a stable solution procedure. A solution adoption mesh refinement technique has been used to refine the grid based on the numerical solution data. In this study, three turbulence models have been employed in conjunction with three near wall treatment approaches. The standard {kappa}-{epsilon}, RNG based {kappa}-{epsilon} and full Reynolds stress models with standard wall function, a pressure sensitized based wall function and a two layer zonal model have been employed. FLUENT CFD software has been utilized for this modeling. The study involves modeling conduction inside the fins and heat exchanger tube, convection inside the tube and radiation from the mixture gas (products of combustion) to the fins and surrounding water. The results are physically consistent and represent CFD analysis in modeling a heat exchanger.

  3. Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

    International Nuclear Information System (INIS)

    Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers

  4. Analysis of field coordination on heat exchanger shell side with different diameter tubes and holding structure

    International Nuclear Information System (INIS)

    In order to overcome the disadvantages of the rod-baffle heat exchanger, which achieves the high heat transfer efficiency only at high flow velocity, and which with non compact layout of tubes and is weak in the resistance of operation mode changes, this paper proposed two sizes of heat exchange tubes and holding and support structures to replace the traditional rod-baffle support unit, to increase the heat exchange coefficient on shell side and the heat exchange effectiveness. Three-dimensional numerical simulation was conducted on the shellside flow field and heat exchange field by the CFD software, and the calculation method was proposed for the included angle for the shellside velocity-temperature gradient fields of the vertical flow heat exchanger with complex structure. The quantitative relationship of the field coordination angle for the shellside velocity field and temperature gradient field was obtained and it is proved that the new structure is with better field coordination relation. (authors)

  5. Control Dewar Subcooler Heat Exchanger Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Rucinski, R.; /Fermilab

    1993-10-04

    The calculations done to size the control dewar subcooler were done to obtain a sufficient subcooler size based on some conservative assumptions. The final subcooler design proposed in the design report will work even better because (1) It has more tubing length, and (2) will have already subcooled liquid at the inlet due to the transfer line design. The subcooler design described in the 'Design Report of the 2 Tesla Superconducting Solenoid for the Fermilab D0 Detector Upgrade' is the final design proposed. A short description of this design follows. The subcooler is constructed of 0.50-inch OD copper tubing with 1.0-inch diameter fins. It has ten and one half spirals at a 11.375-inch centerline diameter to provide 31 feet of tubing length. The liquid helium supply for the solenoid flows through the subcooler and then is expanded through a J-T valve. The subcooler spirals are immersed in the return two phase helium process stream. The return stream is directed over the finned tubing by an annulus created by a 10-inch pipe inside a 12-inch pipe. The transfer line from the refrigerator to the control dewar is constructed such that the liquid helium supply tube is in the refrigerator return stream, thereby subcooling the liquid up to the point where the u-tubes connect the transfer line to the control dewar. The subcooler within the control dewar will remove the heat picked up in the helium supply u-tube/bayonets. The attached subcooler/heat exchanger calculations were done neglecting any subcooling in the transfer line. All heat picked up in the transfer line from the refrigerator storage dewar to the control dewar is absorbed by the supply stream. The subcooler was sized such that the two phase supply fluid is subcooled at 1.7 atm pressure and when expanded through a JT valve to 1.45 atm pressure it is at a saturated liquid state. The calculations apply during steady state operation and at a flow rate of 16 g/s. The analysis of the heat exchanger was broken into two parts relating to the heat transfer mode taking place. The first part is considered the condensing part in which the helium supply stream is changed from two phase fluid to one phase liquid. The second part is the subcooling part where the liquid temperature is lowered, i.e.. subcooled. A summary of the calculations and results appears on the next page. The raw calculations follow the summary.

  6. A Review on Heat Transfer Improvent of Plate Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Abhishek Nandan

    2015-03-01

    Full Text Available Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a lack in data and generalized equations for the calculation of different parameters in the heat exchanger. It requires more attention to find out various possible correlations and generalized solutions for the performance improvement of plate heat exchanger.

  7. Condensing Heat Exchanger with Hydrophilic Antimicrobial Coating

    Science.gov (United States)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor)

    2014-01-01

    A multi-layer antimicrobial hydrophilic coating is applied to a substrate of anodized aluminum, although other materials may form the substrate. A silver layer is sputtered onto a thoroughly clean anodized surface of the aluminum to about 400 nm thickness. A layer of crosslinked, silicon-based macromolecular structure about 10 nm thickness overlies the silver layer, and the outermost surface of the layer of crosslinked, silicon-based macromolecular structure is hydroxide terminated to produce a hydrophilic surface with a water drop contact angle of less than 10.degree.. The coated substrate may be one of multiple fins in a condensing heat exchanger for use in the microgravity of space, which has narrow channels defined between angled fins such that the surface tension of condensed water moves water by capillary flow to a central location where it is pumped to storage. The antimicrobial coating prevents obstruction of the capillary passages.

  8. Multi-channel heat exchanger-reactor using arborescent distributors: A characterization study of fluid distribution, heat exchange performance and exothermic reaction

    International Nuclear Information System (INIS)

    A multi-functional heat exchanger-reactor comprising arborescent (tree-like) distributors and collector, 16 mini-channels in parallel and T-mixers is introduced in this paper. Flow distribution property, pressure drop and heat exchange performance of proposed heat exchanger-reactor are tested and discussed. Firstly, flow distribution uniformity is characterized by CFD simulation and then qualitatively confirmed by visualization experiment. Results show that for total flowrates ranging from 5 mL s?1 to 20 mL s?1, good distribution uniformity is obtained, with maximum flowrate deviation less than 10%. Then, experiments of heat exchange between hot and cold water are carried out. High values of overall heat transfer coefficient ranging from 2000 to 5000 W m?2 °C?1 are obtained under our working conditions. The volumetric heat exchange capability (UA/V) is found to be around 200 kW m?3 °C?1, showing a high heat exchange capability with compact design. The roles of end-effect and non-established flow are discussed and are supposed to be responsible for efficient heat transfer. Finally a typical fast exothermic reaction, neutralization between acid and basic solutions, is carried out to test the thermal control capability of the studied heat exchanger-reactor. Results indicate that isothermal condition could be realized by circulating appropriate flowrate of coolant through the heat exchanger. The design of heat exchanger-reactor with arborescent distributor and collector makes possible the application of multi-channel systems. This paper introduces systematically the successful integration of heat exchanger-reactor and its performance evaluation. - Highlights: • A design of mini scale, multichannel heat exchanger-reactor is proposed. • Uniform distribution for parallel channels is obtained with arborescent structure. • High global heat exchange coefficient is found experimentally. • Thermal control capability is verified with an exothermic reaction

  9. Heat Exchanger Support Bracket Design Calculations

    Energy Technology Data Exchange (ETDEWEB)

    Rucinski, Russ; /Fermilab

    1995-01-12

    This engineering note documents the design of the heat exchanger support brackets. The heat exchanger is roughly 40 feet long, 22 inches in diameter and weighs 6750 pounds. It will be mounted on two identical support brackets that are anchored to a concrete wall. The design calculations were done for one bracket supporting the full weight of the heat exchanger, rounded up to 6800 pounds. The design follows the American Institute of Steel Construction (AISC) Manual of steel construction, Eighth edition. All calculated stresses and loads on welds were below allowables.

  10. Development and application of out-of-focus imaging in order to characterize heat and mass exchanges in two-phase flows

    International Nuclear Information System (INIS)

    The aim of this paper is to present the capacity of the out-of-focus imaging in order to measure droplets size in presence of heat and mass exchanges. It is supported with optical simulations first based on geometrical optics, and then with the Lorenz-Mie theory. Finally, this technique is applied in presence of heat and mass transfers in the TOSQAN experiment. (authors)

  11. Two-phase refrigerant distribution in a parallel flow minichannel heat exchanger having lower combining/dividing header

    Science.gov (United States)

    Byun, Ho-Won; Kim, Nae-Hyun

    2015-10-01

    R-410A distribution in a two pass evaporator with lower horizontal combining-dividing header was investigated. Tubes were heated to yield a test section outlet superheat of 5 °C with inlet quality of 0.2. The number of tubes was ten for the inlet pass and 12 or 14 for the outlet pass. For each case, mass flux was varied from 73 to 143 kg/m2 s. In the combining/dividing header, two-phase mixture out of the inlet pass is first merged and then re-distributed to the outlet pass. More liquid is forced downstream as mass flux or quality increases Effect of insertion device in the inlet header was also investigated. Efforts were made to develop correlations to predict the liquid or gas distribution in a header with limited success. Header pressure drop data are also provided.

  12. Expanded microchannel heat exchanger: design, fabrication and preliminary experimental test

    OpenAIRE

    Denkenberger, David C.; Brandemuehl, Michael J.; Pearce, Joshua M.; Zhai, John

    2012-01-01

    This paper first reviews non-traditional heat exchanger geometry, laser welding, practical issues with microchannel heat exchangers, and high effectiveness heat exchangers. Existing microchannel heat exchangers have low material costs, but high manufacturing costs. This paper presents a new expanded microchannel heat exchanger design and accompanying continuous manufacturing technique for potential low-cost production. Polymer heat exchangers have the potential for high effe...

  13. A study on the development of fouling analysis technique for shell-and-tube heat exchangers

    International Nuclear Information System (INIS)

    Fouling of heat exchangers is generated by water-borne deposits, commonly known as foulants including particulate matter from the air, migrated corrosion produces; silt, clays, and sand suspended in water; organic contaminants; and boron based deposits in plants. The fouling is known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. This paper describes the fouling analysis technique developed in this study which can analyze the thermal performance for heat exchangers and estimate the future fouling variations. To develop the fouling analysis technique for heat exchangers, fouling factor was introduced based on the ASME O and M codes and TEMA standards. For the purpose of verifying the fouling analysis technique, the fouling analyses were performed for four heat exchangers in several nuclear power plants; two residual heat removal heat exchangers of the residual heat removal system and two component cooling water heat exchangers of the component cooling water system

  14. A heat exchanger analogy of automotive paint ovens

    International Nuclear Information System (INIS)

    Computational prediction of vehicle temperatures in an automotive paint oven is essential to predict paint quality and manufacturability. The complex geometry of vehicles, varying scales in the flow, transient nature of the process, and the tightly coupled conjugate heat transfer render the numerical models computationally very expensive. Here, a novel, simplified model of the oven is developed using an analogy to a three-stream cross flow heat exchanger that transfers heat from air to a series of moving bodies and supporting carriers. The analogous heat exchanger equations are developed and solved numerically. Steady state Computational Fluid Dynamics (CFD) simulations are carried out to model the flow field and to extract the heat transfer coefficients around the body and carriers. The air temperature distribution from the CFD models is used as a boundary condition in the analogous model. Correction coefficients are used in the analogy to take care of various assumptions. These are determined from existing test data. The same corrections are used to predict air temperatures for a modified configuration of the oven and a different vehicle. The method can be used to conduct control volume analysis of ovens to determine energy efficiency, and to study new vehicle or oven designs. -- Highlights: • Analogy of an automotive paint oven as a three stream cross flow heat exchanger. • The three streams are vehicle bodies, carriers and hot air. • Convection coefficients and inlet air stream temperatures from steady CFD simulations. • Analogy useful for overall energy efficiency analysis of conveyor ovens in general

  15. Characterization of a mini-channel heat exchanger for a heat pump system

    International Nuclear Information System (INIS)

    In this paper a mini-channel aluminum heat exchanger used in a reversible heat pump is presented. Mini-channel finned heat exchangers are getting more and more interest for refrigeration systems, especially when compactness and low refrigerant charge are desired. Purpose of this paper was to characterize the mini-channel heat exchanger used as evaporator in terms of heat transfer performance and to study the refrigerant distribution in the manifold. The heat exchanger characterization was performed experimentally by means of a test rig built up for this purpose. It is composed of an air-to-air heat pump, air channels for the external and internal air circulation arranged in a closed loop, measurement sensors and an acquisition system. The overall heat transfer capacity was assessed. Moreover, in order to characterize the flow field of the refrigerant in the manifold of the heat exchanger, a numerical investigation of the fluid flow by means of CFD was performed. It was meant to evaluate the goodness of the present design and to identify possible solutions for the future improvement of the manifold design.

  16. Characterization of a mini-channel heat exchanger for a heat pump system

    Science.gov (United States)

    Arteconi, A.; Giuliani, G.; Tartuferi, M.; Polonara, F.

    2014-04-01

    In this paper a mini-channel aluminum heat exchanger used in a reversible heat pump is presented. Mini-channel finned heat exchangers are getting more and more interest for refrigeration systems, especially when compactness and low refrigerant charge are desired. Purpose of this paper was to characterize the mini-channel heat exchanger used as evaporator in terms of heat transfer performance and to study the refrigerant distribution in the manifold. The heat exchanger characterization was performed experimentally by means of a test rig built up for this purpose. It is composed of an air-to-air heat pump, air channels for the external and internal air circulation arranged in a closed loop, measurement sensors and an acquisition system. The overall heat transfer capacity was assessed. Moreover, in order to characterize the flow field of the refrigerant in the manifold of the heat exchanger, a numerical investigation of the fluid flow by means of CFD was performed. It was meant to evaluate the goodness of the present design and to identify possible solutions for the future improvement of the manifold design.

  17. Minimizing district heating flow demand by cascading building heating loads

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L.; Snoek, C.; Onno, T. [Natural Resources Canada, Ottawa, ON (Canada)

    2003-07-01

    An example of cascading heating loads in buildings was presented along with guidelines for effective cascading of building thermal loads. In order to minimize district heating flow demand, it is necessary to increase the temperature difference in the main heat exchanger between the district heating supply and the return. A high change in temperature results in lower flows, better performance and lower heat production cost. Individual houses, commercial buildings and multifunctional buildings have multiple heating loads. Cascading ensures that the maximum amount of energy is extracted from the district heated water before it is returned. This paper presents the characteristics of the following examples of district heating systems: the Sudbury YMCA building constructed in year 2000; a heat production plant that includes a combined cycle gas turbine combined heat and power plant; and, a network of supply and return pipes. The methodologies to establish the thermal loads in each case was presented. All the cascaded systems resulted in higher temperature change and lower flows compared to similar sized, parallel connected systems. 2 tabs., 8 figs.

  18. Lightweight Thermal Storage Heat Exchangers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR proposal aims to develop thermal energy storage heat exchangers that are significantly lighter and higher conductance than the present art which involves...

  19. Acoustic resonance in plate heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Rodarte, Enrique; Miller, Norman; Hrnjak, Predrag [Illinois Univ., Mechanical and Industrial Engineering Dept., Urbana, IL (United States)

    1998-12-01

    A `whistling` sound, which develops under transient conditions in some automobile air conditioning systems equipped with plate type evaporators, was identified as acoustic resonance. The `whistle` was reproduced in the laboratory under steady-state conditions. Testing of these heat exchangers was done first with R134a and then with nitrogen. Nitrogen testing proved to be much faster and easier and provided results comparable to the results obtained using R134a. The evidence presented in this work suggests the acoustic resonance in this type of heat exchanger is similar in nature to the acoustic resonance problems reported for tube array in duct type heat exchangers. This is to the authors` knowledge the first time that acoustic resonance problems have been reported in the literature for plate heat exchangers. (Author)

  20. Shape optimization of a heat exchanger with internally finned tube

    International Nuclear Information System (INIS)

    Optimization of a heat exchanger with internally finned circular tubes has been performed for three-dimensional periodically fully developed turbulent flow and heat transfer. The design variables of fin number N, fin width (d1,d2) and fin height(H) , are numerically optimized for the limiting conditions of N = 22?37, d1= 0.5?1.5 mm, d2 0.5?1.5 mm, H = 0.1?1.5. Due to the periodic boundary conditions along main flow direction, the three layers of meshes are considered. The CFD and the mathematical optimization are coupled to optimize the heat exchanger. The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by using the Sequential Quadratic Programming (SQP) method which is widely used in the constrained nonlinear optimization problem

  1. Effect of Liquid/Vapour Maldistribution on the Performance of Plate Heat Exchanger Evaporators

    DEFF Research Database (Denmark)

    Jensen, Jonas Kjær; Kærn, Martin Ryhl; Ommen, Torben Schmidt; Markussen, Wiebke Brix; Reinholdt, Lars; Elmegaard, Brian

    2015-01-01

    Plate heat exchangers are often applied as evaporators in industrial refrigeration and heat pump systems. In the design and modelling of such heat exchangers the flow and liquid/vapour distribution is often assumed to be ideal. However, maldistribution may occur and will cause each channel to behave differently due to the variation of the mass flux and vapour quality. To evaluate the effect of maldistribution on the performance of plate heat exchangers, a numerical model is developed in which th...

  2. Fouling characteristics of compact heat exchangers and enhanced tubes.

    Energy Technology Data Exchange (ETDEWEB)

    Panchal, C. B.; Rabas, T. J.

    1999-07-15

    Fouling is a complex phenomenon that (1) encompasses formation and transportation of precursors, and (2) attachment and possible removal of foulants. A basic understanding of fouling mechanisms should guide the development of effective mitigation techniques. The literature on fouling in complex flow passages of compact heat exchangers is limited; however, significant progress has been made with enhanced tubes.

  3. HEAT TRANSFER COEFFICIENT AND FRICTION FACTOR CHARACTERISTICS OF A GRAVITY ASSISTED BAFFLED SHELL AND HEAT-PIPE HEAT EXCHANGER

    Directory of Open Access Journals (Sweden)

    P. Raveendiran

    2015-06-01

    Full Text Available The heat transfer coefficients and friction factors of a baffled shell and heat pipe heat exchanger with various inclination angles were determined experimentally; using methanol as working fluid and water as heat transport fluid were reported. Heat pipe heat exchanger reported in this investigation have inclination angles varied between 15o and 60o for different mass flow rates and temperature at the shell side of the heat exchanger. All the required parameters like outlet temperature of both hot and cold side of heat exchanger and mass flow rate of fluids were measured using an appropriate instrument. Different tests were performed from which condenser side heat transfer coefficient and friction factor were calculated. In all operating conditions it has been found that the heat transfer coefficient increases by increasing the mass flow rate and angle of inclination. The reduction in friction factor occurs when the Reynolds number is increased. The overall optimum experimental effectiveness of GABSHPHE has found to be 42% in all operating conditioning at ? = 45o.

  4. PS1 satellite refrigerator heat exchanger: Failure of the LN2 heat exchanger to low pressure helium

    International Nuclear Information System (INIS)

    The PS1 heat exchanger is one of three prototype heat exchangers built by Atomic Welders before Meyer was given the contract to build the Satellite Refrigerator Heat Exchanger components. This heat exchanger was first put into operation in July 1983. In November 1991, this heat exchanger experienced a failure in the shell of heat exchanger 1 causing nitrogen to contaminate the helium in the refrigerator. The resulting contamination plugged heat exchanger 3. The break occurred at a weld that connects a 0.25 inch thick ring to heat exchanger 1. The failure appears to be a fatigue of the shell due to temperature oscillations. The flow rate through the break was measured to be 1.0 scfm for a pressure drop over the crack of 50 psi. An ANSYS analysis of the failure area indicates that the stress would be 83,000 psi if the metal did not yield. This is based on cooling down the shell to 80K from 300K with the shell side helium on the outside of the shell at 300K. This is the largest change in temperature that occurs during operation. During normal operations, the temperature swings are not nearly this large, however temperatures down to 80K are not unusual (LN2 overflowing pot). The highest temperatures are typically 260K. The analysis makes no attempt to estimate the stress concentration factor at this weld but there is no doubt that it is greater than 1. No estimate as to the number of cycles to cause failure was calculated nor any estimate as to the actual number of cycles was made

  5. CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin Inclinations

    OpenAIRE

    Subodh Bahirat,; P. V. Joshi

    2014-01-01

    ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT ...

  6. Theoretical and numerical analyses of a ceramic monolith heat exchanger

    International Nuclear Information System (INIS)

    This study assessed the performance of a ceramic monolith heat exchanger, estimating heat transfer and pressure drop by numerical computation and the ?-NTU method. A heat exchanger consists of rectangular ducts for exhaust gas, a ceramic core, and rectangular ducts for air and exhaust gases, as well as air in the cross-flow direction. The numerical computations were performed for the whole domain, including the exhaust gas, ceramic core, and air. In addition, the heat exchanger was examined using a conventional ?- NTU method with several Nusselt number correlations from the literature to characterize the flow in the rectangular duct. The results of these numerical computation analyses demonstrated that the effectiveness of the heat exchanger, as demonstrated using the ?-NTU method with Stephan's Nusselt number correlation, came closest to the results of computation with a relative error of 2%. The air-side pressure drops indicated by the results of numerical computation were 13-22% higher than those calculated using the head loss equation with the inclusion of a friction factor that was obtained from previous experiments examining heat transfer conditions

  7. Heat Pipe Blocks Return Flow

    Science.gov (United States)

    Eninger, J. E.

    1982-01-01

    Metal-foil reed valve in conventional slab-wick heat pipe limits heat flow to one direction only. With sink warmer than source, reed is forced closed and fluid returns to source side through annular transfer wick. When this occurs, wick slab on sink side of valve dries out and heat pipe ceases to conduct heat.

  8. Heat transfer from oriented heat exchange areas

    Science.gov (United States)

    Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej

    2014-03-01

    This paper deals with the transfer of heat-driven heat transfer surface area in relation to the construction of the criterion equation for "n" horizontal pipe one about another. On the bases of theoretical models have been developed for calculating the thermal performance of natural convection by Churilla and Morgan, for various pipe diameters and temperatures. These models were compared with models created in CFD-Fluent Ansys the same boundary conditions. The aim of the analyse of heat and fluxional pipe fields "n" pipes one about another at natural convection is the creation of criterion equation on the basis of which the heat output of heat transfer from pipe oriented areas one above another with given spacing could be quantified. At presence a sum of criterion equations exists for simple geometrical shapes of individual oriented geometrical areas but the criterion equation which would consider interaction of fluxional field generated by free convection from multiple oriented areas is not mentioned in standardly accessible technical literature and other magazine publications.

  9. Predicted and measured velocity distribution in a model heat exchanger

    International Nuclear Information System (INIS)

    This paper presents a comparison between numerical predictions, using the porous media concept, and measurements of the two-dimensional isothermal shell-side velocity distributions in a model heat exchanger. Computations and measurements were done with and without tubes present in the model. The effect of tube-to-baffle leakage was also investigated. The comparison was made to validate certain porous media concepts used in a computer code being developed to predict the detailed shell-side flow in a wide range of shell-and-tube heat exchanger geometries

  10. Heat exchange equipment for the Sizewell 'B' turbine generators

    International Nuclear Information System (INIS)

    The Heat Exchange Equipment associated with the Sizewell 'B' Turbine Generators embodies features specific to the wet steam cycle of the PWR. In comparison with fossil fuelled plant, steam conditions are considerably lower and so for a given electrical output, steam and feed water flows are of necessity much higher. In addition, the plant must embody measures to combat wet steam erosion and to accommodate substantial quantities of draining separated condensate. The paper describes key features of design, layout and materials selection on the Sizewell 'B' heat exchange equipment which address these problems. (author)

  11. The water-cryogen heat exchanger

    Science.gov (United States)

    Bartlit, J. R.; Boyer, K.; Williamson, K. D.

    1970-01-01

    Heat exchanger, using water as heat medium, converts liquid hydrogen to gaseous hydrogen at a very high rate. Possible applications include treatment of liquified natural gas in cities to bring the gas on-line quickly, conversion of liquid oxygen and liquid nitrogen for steel mills, and high volume inert purging.

  12. A fundamentally new approach to air-cooled heat exchangers.

    Energy Technology Data Exchange (ETDEWEB)

    Koplow, Jeffrey P.

    2010-01-01

    We describe breakthrough results obtained in a feasibility study of a fundamentally new architecture for air-cooled heat exchangers. A longstanding but largely unrealized opportunity in energy efficiency concerns the performance of air-cooled heat exchangers used in air conditioners, heat pumps, and refrigeration equipment. In the case of residential air conditioners, for example, the typical performance of the air cooled heat exchangers used for condensers and evaporators is at best marginal from the standpoint the of achieving maximum the possible coefficient of performance (COP). If by some means it were possible to reduce the thermal resistance of these heat exchangers to a negligible level, a typical energy savings of order 30% could be immediately realized. It has long been known that a several-fold increase in heat exchanger size, in conjunction with the use of much higher volumetric flow rates, provides a straight-forward path to this goal but is not practical from the standpoint of real world applications. The tension in the market place between the need for energy efficiency and logistical considerations such as equipment size, cost and operating noise has resulted in a compromise that is far from ideal. This is the reason that a typical residential air conditioner exhibits significant sensitivity to reductions in fan speed and/or fouling of the heat exchanger surface. The prevailing wisdom is that little can be done to improve this situation; the 'fan-plus-finned-heat-sink' heat exchanger architecture used throughout the energy sector represents an extremely mature technology for which there is little opportunity for further optimization. But the fact remains that conventional fan-plus-finned-heat-sink technology simply doesn't work that well. Their primary physical limitation to performance (i.e. low thermal resistance) is the boundary layer of motionless air that adheres to and envelops all surfaces of the heat exchanger. Within this boundary layer region, diffusive transport is the dominant mechanism for heat transfer. The resulting thermal bottleneck largely determines the thermal resistance of the heat exchanger. No one has yet devised a practical solution to the boundary layer problem. Another longstanding problem is inevitable fouling of the heat exchanger surface over time by particulate matter and other airborne contaminants. This problem is especially important in residential air conditioner systems where often little or no preventative maintenance is practiced. The heat sink fouling problem also remains unsolved. The third major problem (alluded to earlier) concerns inadequate airflow to heat exchanger resulting from restrictions on fan noise. The air-cooled heat exchanger described here solves all of the above three problems simultaneously. The 'Air Bearing Heat Exchanger' provides a several-fold reduction in boundary layer thickness, intrinsic immunity to heat sink fouling, and drastic reductions in noise. It is also very practical from the standpoint of cost, complexity, ruggedness, etc. Successful development of this technology is also expected to have far reaching impact in the IT sector from the standpointpoint of solving the 'Thermal Brick Wall' problem (which currently limits CPU clocks speeds to {approx}3 GHz), and increasing concern about the the electrical power consumption of our nation's information technology infrastructure.

  13. Heat transfer processes in parallel-plate heat exchangers of thermoacoustic devices – numerical and experimental approaches

    OpenAIRE

    Jaworski, Artur J.; Piccolo, Antonio

    2012-01-01

    This paper addresses the issues of heat transfer in oscillatory flow conditions, which are typically found in thermoacoustic devices. The analysis presented concerns processes taking place in the individual “channels” of the parallel-plate heat exchangers (HX), and is a mixture of experimental and numerical approaches. In the experimental part, the paper describes the design of experimental apparatus to study the thermal-fluid processes controlling heat transfer in thermoacoustic ...

  14. Borehole Heat Exchangers; Intercambiadores goetermicos verticales

    Energy Technology Data Exchange (ETDEWEB)

    Llopis Trillo, G.; Lopez Jimeno, C.

    2009-07-01

    Ground source heat pump systems are applied to air conditioning and domestic hot water in buildings for its high energetic efficiency. In urban areas of major European countries, the most commonly used are those, that include borehole heat exchangers. Their use in Spain, compared with its surrounding countries is quite small. Here it is described their functioning system, their advantages over other geothermal heat exchangers, their equipment and materials used in their construction their means of thermal transfer, and it is done a prediction about the future of their use in our country. (Author)

  15. Phase Change Material Heat Exchanger Life Test

    Science.gov (United States)

    Lillibridge, Sean; Stephan, Ryan

    2009-01-01

    Low Lunar Orbit (LLO) poses unique thermal challenges for the orbiting space craft, particularly regarding the performance of the radiators. The IR environment of the space craft varies drastically from the light side to the dark side of the moon. The result is a situation where a radiator sized for the maximal heat load in the most adverse situation is subject to freezing on the dark side of the orbit. One solution to this problem is to implement Phase Change Material (PCM) Heat Exchangers. PCM Heat Exchangers act as a "thermal capacitor," storing thermal energy when there is too much being produced by the space craft to reject to space, and then feeding that energy back into the thermal loop when conditions are more favorable. Because they do not use an expendable resource, such as the feed water used by sublimators and evaporators, PCM Heat Exchangers are ideal for long duration LLO missions. In order to validate the performance of PCM Heat Exchangers, a life test is being conducted on four n-Pentadecane, carbon filament heat exchangers. Fluid loop performance, repeatability, and measurement of performance degradation over 2500 melt-freeze cycles will be performed.

  16. Performance of a Thermoelectric Device with Integrated Heat Exchangers

    Science.gov (United States)

    Barry, Matthew M.; Agbim, Kenechi A.; Chyu, Minking K.

    2015-06-01

    Thermoelectric devices (TEDs) convert heat directly into electrical energy, making them well suited for waste heat recovery applications. An integrated thermoelectric device (iTED) is a restructured TED that allows more heat to enter the p-n junctions, thus producing a greater power output . An iTED has heat exchangers incorporated into the hot-side interconnectors with flow channels directing the working fluid through the heat exchangers. The iTED was constructed of p- and n-type bismuth-telluride semiconductors and copper interconnectors and rectangular heat exchangers. The performance of the iTED in terms of , produced voltage and current , heat input and conversion efficiency for various flow rates (), inlet temperatures (C) ) and load resistances () with a constant cold-side temperature ( = 0C) was conducted experimentally. An increase in had a greater effect on the performance than did an increase in . A 3-fold increase in resulted in a 3.2-, 3.1-, 9.7-, 3.5- and 2.8-fold increase in and respectively. For a constant of 50C, a 3-fold increase in from 3300 to 9920 resulted in 1.6-, 1.6-, 2.6-, 1.5- and 1.9-fold increases in , , , and respectively.

  17. Review of Heat Transfer Augmentation Within A Plate Heat Exchanger By Different Shapes Of Ribs

    Directory of Open Access Journals (Sweden)

    A. D. Yadav

    2013-05-01

    Full Text Available Heat transfer augmentation techniques (passive, active or a combination of passive and active methods are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air-conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger working condition (both flow and heat transfer conditions. In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. Twisted tapes, wire coils, ribs, fins, dimples, etc., are the most commonly used passive heat transfer augmentation tools. In the present paper, emphasis is given to works dealing with different shapes of ribs, and there arrangement because, according to recent studies, these are known to be economic heat transfer augmentation tools. The present review is organized in four different sections: circular ribs with staggered at 90º; circular ribs with staggered at 45º, triangular ribs with staggered at 90ºand triangular ribs with staggered at 45º.

  18. Study on numerical and experimental heat transfer characteristics of heat exchanger with helical turbulators

    International Nuclear Information System (INIS)

    Heat exchangers have been widely used devices in the industry because of supply heat transfer between two fluids that are at different temperatures and separated by a solid wall. There are two groups: active and passive methods. The active methods requires extra external power sources, for instance, mechanical aids, surface and fluid vibration, electrostatic fields, injection or suction of fluid and jet impingement. The other is the passive methods, on the contrary, without additional external power, such as a surface coating, rough surfaces, extended surfaces, displaced enhancement devices, turbulent or swirl flow devices, coiled tubes and additives for liquids and gases. Experimental study of the heat exchangers is very useful but very expensive because of the high cost of the tools. A suitable computational fluid dynamics (CFD) code is run to compare to experimental studies, provides flow field information. Experimental analysis and three-dimensional numerical simulations for the concentric-tube heat exchanger with helical turbulators having different pitches distance were performed to reveal the effects of pitches distance on the heat transfer and pressure drop characteristics. The conclusions can be summarized; the FLUENT was applied successfully for the heat transfer and pressure drop analysis in the concentric-tube heat exchanger with helical turbulator. The numerical, experimental and empirical correlation results were in a good agreement with each others. Whereas Nu number increases with increase of Re number, the friction factor reduces. The results indicated the effective enhancement of the heat transfer performance. It can be concluded that numerical calculations provided more detailed knowledge of the heat transfer and flow distribution than experimental studies. The values of the pressure drop can be negligible, when comparing with the heat transfer enhancement. The numerical and experimental results show as a validated computational technique using in this study. The obtained results for different pitch of helical turbulators can be applied to heat exchanger designs for commercial applications. (author)

  19. A heat exchanger model that includes axial conduction, parasitic heat loads, and property variations

    Energy Technology Data Exchange (ETDEWEB)

    Nellis, G.F. [University of Wisconsin, Madison, WI (United States). Cryogenic Engineering Lab.

    2003-09-01

    High performance heat exchangers are a critical component in many cryogenic systems and the performance of these devices is typically very sensitive to axial conduction, property variations, and parasitic heat losses to the environment. This paper presents a numerical model of a heat exchanger in which these effects are explicitly modeled. The governing equations are derived, nondimensionalized, discretized, and solved on an exponentially distributed grid. The resulting numerical model is simple to implement and computationally efficient and can therefore easily be integrated into complex system models. The numerical model is validated against analytical solutions in the appropriate limits and then used to investigate the effect of heat exchanger end conditions (adiabatic vs fixed temperature) and radiation parasitics. The numerical model, which explicitly considers the combined effect of several loss mechanisms as they interact, is compared to simple models that consider these effects separately. Finally, the model is applied to an example heat exchanger core under a specific set of operating conditions in order to demonstrate its utility. This numerical model may also be used to examine the effect of property variations including temperature driven changes in specific heat capacity, metal conductivity, parasitic heat load, and heat transfer coefficients and is therefore useful in the design of a variety of cryogenic system components including counter- and parallel-flow heat exchangers for gas liquefaction, mixed-gas refrigeration, and reverse Brayton systems. (author)

  20. A heat exchanger model that includes axial conduction, parasitic heat loads, and property variations

    Science.gov (United States)

    Nellis, G. F.

    2003-09-01

    High performance heat exchangers are a critical component in many cryogenic systems and the performance of these devices is typically very sensitive to axial conduction, property variations, and parasitic heat losses to the environment. This paper presents a numerical model of a heat exchanger in which these effects are explicitly modeled. The governing equations are derived, nondimensionalized, discretized, and solved on an exponentially distributed grid. The resulting numerical model is simple to implement and computationally efficient and can therefore easily be integrated into complex system models. The numerical model is validated against analytical solutions in the appropriate limits and then used to investigate the effect of heat exchanger end conditions (adiabatic vs fixed temperature) and radiation parasitics. The numerical model, which explicitly considers the combined effect of several loss mechanisms as they interact, is compared to simple models that consider these effects separately. Finally, the model is applied to an example heat exchanger core under a specific set of operating conditions in order to demonstrate its utility. This numerical model may also be used to examine the effect of property variations including temperature driven changes in specific heat capacity, metal conductivity, parasitic heat load, and heat transfer coefficients and is therefore useful in the design of a variety of cryogenic system components including counter- and parallel-flow heat exchangers for gas liquefaction, mixed-gas refrigeration, and reverse Brayton systems.

  1. Enhanced two phase flow in heat transfer systems

    Science.gov (United States)

    Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D

    2013-12-03

    A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.

  2. Liquid Salt Heat Exchanger Technology for VHTR Based Applications

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark; Sridhara, Kumar; Allen, Todd; Peterson, Per

    2012-10-11

    The objective of this research is to evaluate performance of liquid salt fluids for use as a heat carrier for transferring high-temperature process heat from the very high-temperature reactor (VHTR) to chemical process plants. Currently, helium is being considered as the heat transfer fluid; however, the tube size requirements and the power associated with pumping helium may not be economical. Recent work on liquid salts has shown tremendous potential to transport high-temperature heat efficiently at low pressures over long distances. This project has two broad objectives: To investigate the compatibility of Incoloy 617 and coated and uncoated SiC ceramic composite with MgCl2-KCl molten salt to determine component lifetimes and aid in the design of heat exchangers and piping; and, To conduct the necessary research on the development of metallic and ceramic heat exchangers, which are needed for both the helium-to-salt side and salt-to-process side, with the goal of making these heat exchangers technologically viable. The research will consist of three separate tasks. The first task deals with material compatibility issues with liquid salt and the development of techniques for on-line measurement of corrosion products, which can be used to measure material loss in heat exchangers. Researchers will examine static corrosion of candidate materials in specific high-temperature heat transfer salt systems and develop an in situ electrochemical probe to measure metallic species concentrations dissolved in the liquid salt. The second task deals with the design of both the intermediate and process side heat exchanger systems. Researchers will optimize heat exchanger design and study issues related to corrosion, fabrication, and thermal stresses using commercial and in-house codes. The third task focuses integral testing of flowing liquid salts in a heat transfer/materials loop to determine potential issues of using the salts and to capture realistic behavior of the salts in a small scale prototype system. This includes investigations of plugging issues, heat transfer, pressure drop, and the corrosion and erosion of materials in the flowing system.

  3. Comparison between conventional heat exchanger performance and an heat pipes exchanger

    International Nuclear Information System (INIS)

    The thermal performance of conventional compact heat exchanger and of exchanger with heat pipes are simulated using a digital computer, for equal volumes and the same process conditions. The comparative analysis is depicted in graphs that indicate which of the situations each equipment is more efficient. (author)

  4. Evaluating humidity recovery efficiency of currently available heat and moisture exchangers: a respiratory system model study

    Scientific Electronic Library Online (English)

    Jeanette Janaina Jaber, Lucato; Alexander Bernard, Adams; Rogério, Souza; Jamili Anbar, Torquato; Carlos Roberto Ribeiro, Carvalho; John J, Marini.

    2009-06-01

    Full Text Available OBJECTIVES: To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. INTRODUCTION: Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat [...] and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. METHODS: Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37°C), a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH) was calculated for each setting. RESULTS: Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. CONCLUSIONS: Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.

  5. Flow measurements related to gas exchange applications

    OpenAIRE

    Laurantzon, Fredrik

    2012-01-01

    This thesis deals with flow measuring techniques applied to steady and pulsating gas flows relevant to gas exchange systems for internal combustion engines. Gas flows in such environments are complex, i.e. they are inhomogeneous, three-dimensional, unsteady, non-isothermal and exhibit significant density changes. While a variety of flow metering devices are available and have been devised for such flow conditions, the performance of these flow metersis to a large extent undocumented when a st...

  6. Simulation of induction heating process with radiative heat exchange

    Directory of Open Access Journals (Sweden)

    A. Kachel

    2007-05-01

    Full Text Available Purpose: Numerical modelling of induction heating process is a complex issue. It needs analysis of coupled electromagnetic and thermal fields. Calculation models for electromagnetic field analysis as well as thermal field analysis need simplifications. In case of thermal field calculations, correct modelling of radiative heat exchange between the heated charge and inductor’s thermal insulation is essential. Most commercial calculation programs enabling coupled analysis of electromagnetic and thermal fields do not allow taking into consideration radiative heat exchange between calculation model components, which limits thermal calculations only to the charge area. The paper presents a supplementation of the program Flux 2D with radiative heat exchange procedures.Design/methodology/approach: Commercial program Flux 2D designed for coupled electromagnetic and thermal calculation (based on finite element method was supplemented with authors program for radiative heat exchange based on numerical integration of classic equations.Findings: Supplementation EM-T calculations with radiative heat exchange between charge and inductor enables to calculate thermal insulation parameters and increase precision of modelling.Research limitations/implications: Procedures for radiative heat exchange enables calculation of two surfaces (flat or cylindrical with finite dimensions. The surfaces can be displaced relative to each other (charge shorter or longer than thermal insulation of inductor. Material of surfaces is modelled as: flat, diffuse, radiant surfaces absorb energy evenly in the whole spectrum (grey bodies. The whole system is modelled as in a steady thermal state (quasi-steady.Originality/value: Authors program extends Flux 2D features with a possibility for calculating radiative heat transfer. The application of radiative process is possible between all components of the studied model, not only for the boundary conditions.

  7. Materials, Turbomachinery and Heat Exchangers for Supercritical CO2 Systems

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark; Nellis, Greg; Corradini, Michael

    2012-10-19

    The objective of this project is to produce the necessary data to evaluate the performance of the supercritical carbon dioxide cycle. The activities include a study of materials compatibility of various alloys at high temperatures, the heat transfer and pressure drop in compact heat exchanger units, and turbomachinery issues, primarily leakage rates through dynamic seals. This experimental work will serve as a test bed for model development and design calculations, and will help define further tests necessary to develop high-efficiency power conversion cycles for use on a variety of reactor designs, including the sodium fast reactor (SFR) and very high-temperature gas reactor (VHTR). The research will be broken into three separate tasks. The first task deals with the analysis of materials related to the high-temperature S-CO{sub 2} Brayton cycle. The most taxing materials issues with regard to the cycle are associated with the high temperatures in the reactor side heat exchanger and in the high-temperature turbine. The system could experience pressures as high as 20MPa and temperatures as high as 650°C. The second task deals with optimization of the heat exchangers required by the S-CO{sub 2} cycle; the S-CO{sub 2} flow passages in these heat exchangers are required whether the cycle is coupled with a VHTR or an SFR. At least three heat exchangers will be required: the pre-cooler before compression, the recuperator, and the heat exchanger that interfaces with the reactor coolant. Each of these heat exchangers is unique and must be optimized separately. The most challenging heat exchanger is likely the pre-cooler, as there is only about a 40°C temperature change but it operates close to the CO{sub 2} critical point, therefore inducing substantial changes in properties. The proposed research will focus on this most challenging component. The third task examines seal leakage through various dynamic seal designs under the conditions expected in the S-CO{sub 2} cycle, including supercritical, choked, and two-phase flow conditions.

  8. Simulation of induction heating process with radiative heat exchange

    OpenAIRE

    Kachel, A; R. Przy?ucki

    2007-01-01

    Purpose: Numerical modelling of induction heating process is a complex issue. It needs analysis of coupled electromagnetic and thermal fields. Calculation models for electromagnetic field analysis as well as thermal field analysis need simplifications. In case of thermal field calculations, correct modelling of radiative heat exchange between the heated charge and inductor’s thermal insulation is essential. Most commercial calculation programs enabling coupled analysis of electromagnetic and ...

  9. The dynamic behaviour of heat exchangers

    International Nuclear Information System (INIS)

    In order to study the dynamics of nuclear power plants, one needs mathematical models made up of ordinary differential equations. This report deals with models for heat exchangers. These models allow exact evaluations of the temperatures for any steady state. The deformation of the temperature maps during transients is taken into account. To do this, average temperatures are evaluated keeping In mind, on one hand the partial differential equations, on the other hand, the physical phenomenons which are involved. Seven ordinary differential equations at most, are necessary for one heat exchanger. Theses models were compared with mathematically exact ones and also with experimental results, that EDF was able to measure on EDF-1 heat exchangers. The results appear to be correct. (authors)

  10. Thermal conductivity of backfill materials for inground heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Shadley, J.T.; Den Braven, K.R. [Univ. of Idaho, Moscow, ID (United States). Dept. of Mechanical Engineering

    1995-11-01

    The thermal conductivity of the material immediately surrounding the heat exchangers in a vertical borehole directly affects the performance and costs of a ground-coupled heat pump (GCHP) system by regulating the flow of energy to or from the ground. Many properties of the backfill material such as moisture content, composition, specific heat and density influence the thermal conductivity. The thermal conductivities of a wide variety of pure backfill materials and mixtures were measured. All the materials examined were compared with a standard bentonite backfill. Saturated natural sandy soil was the backfill material with the highest thermal conductivity. One attractive mixture consists of a pure silica sand, acrylic latex, and graphite. This mixture forms a solid backfill around the heat exchanger. Yet, the attractiveness of any backfill material combination remains very location and application dependent, varying with the native soils at the site, and the mode in which the GCHP is to be used.

  11. A numerical analysis on the heat transfer and pressure drop characteristics of welding type plate heat exchangers

    International Nuclear Information System (INIS)

    Numerical analysis was carried out to examine the heat transfer and pressure drop characteristics of plate heat exchangers for absorption application using computational Fluid Dynamics(CFD) technique. A commercial CFD software package, FLUENT was used to predict the characteristics of heat transfer, pressure drop and flow distribution within plate heat exchangers. In this paper, a welded plate heat exchanger with the plate of chevron embossing type was numerically analyzed by controlling mass flow rate, solution concentration, and inlet temperatures. The working fluid is H2O/LiBr solution with the LiBr concentration of 50?60% in mass. The numerical simulation show reasonably good agreement with the experimental results. Also, the numerical results show that plate of the chevron shape gives better results than plate of the elliptical shape from the view points of heat transfer and pressure drop. These results provide a guideline to apply the welded PHE for the solution heat exchanger of absorption systems

  12. Magnetic Heat Pump Containing Flow Diverters

    Science.gov (United States)

    Howard, Frank S.

    1995-01-01

    Proposed magnetic heat pump contains flow diverters for suppression of undesired flows. If left unchecked, undesired flows mix substantial amounts of partially heated and partially cooled portions of working fluid, effectively causing leakage of heat from heated side to cooled side. By reducing leakage of heat, flow diverters increase energy efficiency of magnetic heat pump, potentially offering efficiency greater than compressor-driven refrigerator.

  13. Design and optimization of a downhole coaxial heat exchanger for an enhanced geothermal system (EGS)

    OpenAIRE

    Yekoladio, Peni Junior; Bello-Ochende, Tunde; Meyer, Josua P.

    2013-01-01

    The present study considers the design, performance analysis and optimization of a downhole coaxial heat exchanger for an enhanced geothermal system (EGS). The optimum mass flow rate of the geothermal fluid for minimum pumping power and maximum extracted heat energy was determined. In addition, the coaxial pipes of the downhole heat exchanger were sized based on the optimum geothermal mass flow rate and steady-state operation. Transient effect or time-dependent cooling of the E...

  14. Tube-in-shell heat exchangers

    International Nuclear Information System (INIS)

    A tube-in-shell heat exchanger has double sealing joints between the tubes and a tube plate of the heat exchanger constituted by the provision of a secondary tube plate spaced from the normal tube plate and through which each tube extends with sealing in addition to the normal tube to tube plate sealing joints, there being a bellows enveloping the tubes and sealed to both the normal and the secondary tube plates. The space between these tube plates can be monitored for leakage. (author)

  15. Experimental Study on Heat Transfer Characteristics of Shell and Tube Heat Exchanger Using Hitran Wire Matrix Turbulators As Tube Inserts.

    Directory of Open Access Journals (Sweden)

    Manoj

    2014-06-01

    Full Text Available Shell and tube heat exchangers are extensively used in boilers, oil coolers, pre-heaters, condensers etc. They are also having special importance in process application as well as refrigeration and air conditioning industries. The present paper emphasizes on heat transfer characteristics of shell and tube heat exchangers with the aid of hiTRAN wire matrix inserts is been studied. Investigations were made on effect of mass flow rate of water on heat transfer characteristics in case of plain tube without inserts. When hiTRAN wire matrix tube inserts are used, which effectively increases the turbulence of tube side flow due to the hydrodynamic and thermal agitation of boundary layer in turns increases additional pressure drop is available in the system. This results in increase in the wall shear, reduced wall temperature which enhances substantial increase in tube side heat transfer characteristics. Heat and cooling processes streams is a standard operation in many industries this operation is often performed in heat exchangers where the heated or cold fluid flows under laminar conditions inside the tubes the mechanisms of under those flow conditions are complex poorly understood since they can involve both forced and natural convection making accurate prediction for heat exchanger. Heat transfer in laminar flow regimes is low by default but can be greatly increased by the use of passive heat transfer enhancement such as tube inserts. The present analysis the hiTRAN wire matrix turbulators were used and increased heat transfer characteristics as expected outcomes.

  16. Thermodynamic performance analysis and algorithm model of multi-pressure heat recovery steam generators (HRSG) based on heat exchangers layout

    International Nuclear Information System (INIS)

    Highlights: • A general model of multi-pressure HRSG based on heat exchangers layout is built. • The minimum temperature difference is introduced to replace pinch point analysis. • Effects of layout on dual pressure HRSG thermodynamic performances are analyzed. - Abstract: Changes of heat exchangers layout in heat recovery steam generator (HRSG) will modify the amount of waste heat recovered from flue gas; this brings forward a desire for the optimization of the design of HRSG. In this paper the model of multi-pressure HRSG is built, and an instance of a dual pressure HRSG under three different layouts of Taihu Boiler Co., Ltd. is discussed, with specified values of inlet temperature, mass flow rate, composition of flue gas and water/steam parameters as temperature, pressure etc., steam mass flow rate and heat efficiency of different heat exchangers layout of HRSG are analyzed. This analysis is based on the laws of thermodynamics and incorporated into the energy balance equations for the heat exchangers. In the conclusion, the results of the steam mass flow rate, heat efficiency obtained for three heat exchangers layout of HRSGs are compared. The results show that the optimization of heat exchangers layout of HRSGs has a great significance for waste heat recovery and energy conservation

  17. Heat exchanger design for desalination plants

    International Nuclear Information System (INIS)

    The Office of Saline Water (OSW) accomplished a very large amount of significant work related to the design and performance of large heat exchanger bundles and enhanced heat transfer surfaces. This work was undertaken to provide basic technical and economic data for the design of distillation plants for the desalination of seawater, and should be of value to other industrial applications as well. The OSW work covers almost every aspect of heat exchanger design, and ranges academic research to data gathering on commercial desalting plants. Exchanger design configurations include multistage flash plant condensers, vertical tube falling film and upflow evaporators, and horizontal tube spray film evaporators. Unfortunately, the data is scattered through a large number of reports of which many are concerned primarily with factors other than heat transfer, and the quality of reporting and the quality of the data are far from consistent. This report catalogues and organizes the heat exchanger data developed by the OSW. Some analysis as to the validity of the data is made and ranges of performance that can be expected are given. Emphasis is placed on the vertical tube, falling film evaporators. A thorough analysis of the large literature file that was surveyed was not possible. No analysis was made of the quality of original data, but apparent data discrepancies are pointed out where such discrepancies happen to be found

  18. Heat Transfer Analysis of the Passive Residual Heat Removal Heat Exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wenwen; Tian, Wenxi; Su, Guanghui; Qiu, Suizheng [Jiaotong University, Shaanxi (China)

    2014-08-15

    In the present study, thermal-hydraulics characteristics of AP1000 passive residual heat removal heat exchanger (PRHR-HX) at initial operating stage were analyzed based on the porous media models. The data predicated by RELAP5 under the condition of the station blackout was employed as the inlet flow rate and temperature boundary of CFD calculation. The heat transfer from the primary side coolant to the in-containment refueling water storage tank (IRWST) side fluid was calculated in a three-dimensional geometry during iterations, and the distributed resistances were added into the C-type tube bundle regions. Three-dimensional distributions of velocity and temperature in the IRWST were calculated by the CFD code ANSYS FLUENT. The primary temperature, heat transfer coefficients of two sides and the heat transfer were obtained using the coupled heat transfer between the primary side and the IRWST side. The simulation results indicated that the water temperature rises gradually which leads to a thermal stratification phenomenon in the tank and the heat transfer capability decreases with an increase of water temperature. The present results indicated that the method containing coupled heat transfer from the primary side fluid to IRWST side fluid and porous media model is a suitable approach to study the transient thermal-hydraulics of PRHR/IRWST.

  19. Heat Transfer Analysis of the Passive Residual Heat Removal Heat Exchanger

    International Nuclear Information System (INIS)

    In the present study, thermal-hydraulics characteristics of AP1000 passive residual heat removal heat exchanger (PRHR-HX) at initial operating stage were analyzed based on the porous media models. The data predicated by RELAP5 under the condition of the station blackout was employed as the inlet flow rate and temperature boundary of CFD calculation. The heat transfer from the primary side coolant to the in-containment refueling water storage tank (IRWST) side fluid was calculated in a three-dimensional geometry during iterations, and the distributed resistances were added into the C-type tube bundle regions. Three-dimensional distributions of velocity and temperature in the IRWST were calculated by the CFD code ANSYS FLUENT. The primary temperature, heat transfer coefficients of two sides and the heat transfer were obtained using the coupled heat transfer between the primary side and the IRWST side. The simulation results indicated that the water temperature rises gradually which leads to a thermal stratification phenomenon in the tank and the heat transfer capability decreases with an increase of water temperature. The present results indicated that the method containing coupled heat transfer from the primary side fluid to IRWST side fluid and porous media model is a suitable approach to study the transient thermal-hydraulics of PRHR/IRWST

  20. Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger

    Directory of Open Access Journals (Sweden)

    S. Sathiyan

    2013-06-01

    Full Text Available This work presents new predictive correlations for heat transfer to immiscible liquid-liquid mixtures in a spiral plate heat exchanger. Liquid-liquid heat transfer studies were carried out in spiral plate heat exchangers for the water-octane, water-kerosene, and water-dodecane systems. For each composition of the mixture, the mass flow rate of the cold fluid was varied, keeping that of the hot fluid and the fluid inlet temperatures constant. Two-phase cold flow rates were in the laminar range, while the hot fluid flow was turbulent. Calculations of the LMTD (log mean temperature difference correction factor showed that the flow was countercurrent. Heat transfer coefficients of the two-phase liquids were found to be strongly dependent on the composition of the liquid mixture and exhibited abrupt transitions as a function of the compositions. Given the absence of predictive correlations in the literature that sufficiently capture this compositiondependence, new empirical correlations were developed using part of the experimental data, with the composition of the cold fluid as an explicit variable. Statistical analysis of the regression yielded satisfactory results. The correlations were tested against the rest of the experimental data and were found to predict heat transfer coefficients within ± 15%. These preliminary studies should be useful in designing compact exchangers for handling two-phase water-organics mixtures.

  1. Heat transfer to immiscible liquid mixtures in a spiral plate heat exchanger

    Scientific Electronic Library Online (English)

    S., Sathiyan; Murali, Rangarajan; S., Ramachandran.

    2013-06-01

    Full Text Available This work presents new predictive correlations for heat transfer to immiscible liquid-liquid mixtures in a spiral plate heat exchanger. Liquid-liquid heat transfer studies were carried out in spiral plate heat exchangers for the water-octane, water-kerosene, and water-dodecane systems. For each comp [...] osition of the mixture, the mass flow rate of the cold fluid was varied, keeping that of the hot fluid and the fluid inlet temperatures constant. Two-phase cold flow rates were in the laminar range, while the hot fluid flow was turbulent. Calculations of the LMTD (log mean temperature difference) correction factor showed that the flow was countercurrent. Heat transfer coefficients of the two-phase liquids were found to be strongly dependent on the composition of the liquid mixture and exhibited abrupt transitions as a function of the compositions. Given the absence of predictive correlations in the literature that sufficiently capture this compositiondependence, new empirical correlations were developed using part of the experimental data, with the composition of the cold fluid as an explicit variable. Statistical analysis of the regression yielded satisfactory results. The correlations were tested against the rest of the experimental data and were found to predict heat transfer coefficients within ± 15%. These preliminary studies should be useful in designing compact exchangers for handling two-phase water-organics mixtures.

  2. Damping in heat exchanger tube bundles. A review

    International Nuclear Information System (INIS)

    Damping is a major concern in the design and operation of tube bundles with loosely supported tubes in baffles for process shell and tube heat exchangers and steam generators which are used in nuclear, process and power generation industries. System damping has a strong influence on the amplitude of vibration. Damping depends upon the mechanical properties of the tube material, geometry of intermediate supports and the physical properties of shell-side fluid. Type of tube motion, number of supports, tube frequency, vibration amplitude, tube mass or diameter, side loads, support thickness, higher modes, shell-side temperature etc., affect damping in tube bundles. The importance of damping is further highlighted due to current trend of larger exchangers with increased shell-side velocities in modern units. Various damping mechanisms have been identified (Friction damping, Viscous damping, Squeeze film damping, Support damping. Two-Phase damping, and very recent-Thermal damping), which affect the performance of process exchangers and steam generators with respect to flow induced vibration design, including standard design guidelines. Damping in two-phase flow is very complex and highly void fraction, and flow-regime dependent. The current paper focuses on the various known damping mechanisms subjected to both single and two-phase cross-flow in process heat exchangers and steam generators and formulates the design guidelines for safer design. (author)

  3. Xenon recirculation-purification with a heat exchanger

    International Nuclear Information System (INIS)

    Liquid-xenon based particle detectors have been dramatically growing in size during the last years, and are now exceeding the one-ton scale. The required high xenon purity is usually achieved by continuous recirculation of xenon gas through a high-temperature getter. This challenges the traditional way of cooling these large detectors, since in a thermally well insulated detector, most of the cooling power is spent to compensate losses from recirculation. The phase change during recondensing requires five times more cooling power than cooling the gas from ambient temperature to -1000C (173 K). Thus, to reduce the cooling power requirements for large detectors, we propose to use the heat from the purified incoming gas to evaporate the outgoing xenon gas, by means of a heat exchanger. Generally, a heat exchanger would appear to be only of very limited use, since evaporation and liquefaction occur at zero temperature difference. However, the use of a recirculation pump reduces the pressure of the extracted liquid, forces it to evaporate, and thus cools it down. We show that this temperature difference can be used for an efficient heat exchange process. We investigate the use of a commercial parallel plate heat exchanger with a small liquid xenon detector. Although we expected to be limited by the available cooling power to flow rates of about 2 SLPM, rates in excess of 12 SLPM can easily be sustained, limited only by the pump speed and the impedance of the flow loop. The heat exchanger operates with an efficiency of (96.8±0.5)%. This opens the possibility for fast xenon gas recirculation in large-scale experiments, while minimizing thermal losses.

  4. Effective material usage in a compact heat exchanger with periodic micro-channels / Bertus George Kleynhans

    OpenAIRE

    Kleynhans, Bertus George

    2012-01-01

    All modern High Temperature Reactors (HTR) thermal cycles have one thing in common: the use of some form of heat exchanger. This heat exchanger is used to pre-heat or cool the primary loop gas, from where the secondary power generation cycle is driven. The Compact Heat Exchanger (CHE) type offers high heat loads in smaller volumes. Various studies have been done to improve the heat transfer in the flow channels of these CHEs but little focus has been placed on the thermal design of surroundin...

  5. A new waste heat district heating system with combined heat and power (CHP) based on ejector heat exchangers and absorption heat pumps

    International Nuclear Information System (INIS)

    A new waste heat district heating system with CHP based on ejector heat exchangers and absorption heat pumps (DH-EHE) is presented to decrease heating energy consumption of existing CHP systems by recovering waste heat of exhausted steam from a steam turbine, which could also increase heat transmission capacity of the primary heating network (PHN) by decreasing temperature of the return water of existing PHN. A new ejector heat exchanger based on ejector refrigeration cycle is invented to decrease temperature of the return water of PHN to 30 °C under the designed case. DH-EHE is analyzed in terms of laws of thermodynamics and economics. Compared to conventional district heating systems with CHP (CDH), DH-EHE can decrease consumption of steam extracted from a steam turbine by 41.4% and increase heat transmission capacity of the existing PHN by 66.7% without changing the flow rate of circulating water. The heating cost of DH-EHE is 8.62 ¥/GJ less than that of CDH. Compared to CDH, the recovery period of additional investment of DH-EHE is about two years. DH-EHE shows better economic and environmental benefits, which is promising for both district heating systems for long-distance heat transmission and waste heat district heating systems. - Highlights: • Heating capacity of this new heating system increases by 41% by waste heat recovery. • Temperature of return water of the primary heating network can be reduced to 30 °C. • Heating cost of new heating system is 8.62¥/GJ less than that of conventional one. • The recovery period of additional investment of new heating system is about 2 years. • This new heating system shows better economic and environmental benefits

  6. Numerical Simulations of Recovery Heat Exchangers.

    Czech Academy of Sciences Publication Activity Database

    Novotný, P.; Vít, T.; Dan?ová, Petra

    Prague : Institute of Thermomechanics AS CR, v. v. i., 2011 - (Fuis, V.), s. 439-442 ISBN 978-80-87012-33-8. [Engineering Mechanics 2011 /17./. Svratka (CZ), 09.05.2011-12.05.2011] Grant ostatní: GA TA ?R(CZ) TA01020313 Institutional research plan: CEZ:AV0Z20760514 Keywords : recovery heat exchanger s * heat recovery * numerical simulations Subject RIV: BJ - Thermodynamics

  7. A study on the formation of fouling in a heat exchanging system for river water

    International Nuclear Information System (INIS)

    When the water flowing inside of the heat transfer equipment such as heat exchangers, condensers, and boilers is heated, calcium, magnesium sulfate, and other minerals in the water are deposited and built up for scales on the heat transfer surfaces. When those scales accumulate on the heat transfer surfaces, their performance of the heat transfer become progressively reduced due to the increase of the heat transfer resistance. The mechanism of this reduced heat transfer is called fouling. This study investigated the formation of the fouling in a heat exchanger with river and tap water flowed inside of it as a coolant. In order to visualize the formation of the fouling and to measure the fouling coefficients, a lab-scale heat exchanging system was used. Based on the experimental results, it was found that the formation of fouling for river water was quite different with the formation for tap water

  8. Heat exchanger operation in the externally heated air valve engine with separated settling chambers

    International Nuclear Information System (INIS)

    The crucial role in the externally heated air valve engine is played by its heat exchangers which work in a closed cycle. These are: a heater and a cooler and they are subject to a numerical analysis in the paper. Both of them are equipped with fixed volumes that are separate settling chambers causing that heat exchangers behave as almost stationary recuperators and analysis of the stationary behaviour is the main goal of the paper. Power and efficiency of the engine must be not lower than their averaged values for the same engine working in unsteady conditions. The results of calculations confirm such a statement. The pressure drop in the exchanger is another natural phenomenon presented. It has been overcome by use of additional blowers and the use of them is an additional focus of the presented analysis. A separation of settling chambers and additional blowers is a novelty in the paper. There is also a pre-heater applied in the engine which does not differ from well-known heat exchangers met in energy generation devices. The main objective of the paper is to find the behaviour of the engine model under stationary conditions of the heat exchangers and compare it with the non-stationary ones. - Highlights: • Externally heated air engine combined with forced working gas flow (supercharging). • Separate settling chambers allow for achieving stable and constant heat exchange parameters. • Pressure drop in heat exchangers overcome by additional blowers. • Reciprocating piston air engine, cam governing system, standard lubrication for externally heated engine. • Different fuels: oil, coal, gas, biomass also solar or nuclear energy

  9. Exchange Rate Uncertainty and International Portfolio Flows

    OpenAIRE

    Caporale, Guglielmo Maria; Ali, Faek Menla; Spagnolo, Nicola

    2013-01-01

    This paper examines the impact of exchange rate uncertainty on different components of portfolio flows, namely equity and bond flows, as well as the dynamic linkages between exchange rate volatility and the variability of these two types of flows. Specifically, a bivariate GARCH-BEKK-in-mean model is estimated using bilateral data for the US vis-à-vis Australia, the UK, Japan, Canada, the euro area, and Sweden over the period 1988:01- 2011:12. The results indicate that the effect of exchange ...

  10. Solution of operational problems utilization of an EX-IRT-2000 heat exchanger

    International Nuclear Information System (INIS)

    The Bandung TRIGA Mark II Reactor has been successfully operated for 21 years, especially in low power operation or as neutron sources for various experiments. Most of the operating time, approximately 80% of routine operation, was dedicated for radio-isotope production. During routine operation for radio-isotope production, the reactor could not be operated at full power. The reactor was operated at 60% of the maximum power (1 MWth) due to the inability of the original heat exchanger to operate properly. The reason is that slack deposition was built-up on the secondary side of the heat exchanger. Therefore, it reduced the coefficient of heat transfer considerably. To solve the problems, a set of heat exchanger including the pump was installed In parallel with the original unit. The heat exchanger was an IRT-2000 Reactor Heat exchanger which was collected from the abandoned IRT-2000 Project. The heat exchanger has capacity of 1.25 MW. The new heat exchanger could reduced the outlet temperature of the primary coolant Into 42 deg. C. While the original-heat exchanger at the worst condition and at 600 kW of power reach outlet temperature 49 deg. C. The IRT Heat Exchanger is a counter flow heat exchanger. (author)

  11. Heat transfer to helium. Application to the design of heat exchangers

    International Nuclear Information System (INIS)

    The discovery of superconductivity has lead to a new technology at very low temperatures. This technology utilises liquid helium to maintain superconducting devices below their transition temperatures. These devices contain the heat exchangers for the circulation of the helium. The helium could be in two-phase flow or in single phase but near its critical point. This paper describes a study of the heat transfer and pressure drop characteristics of helium in two-phase flow and in the supercritical state. The results are compared with existing correlations. For two-phase pressure drop two methods were used: one based on slip between phases and the other based on a homogeneous model. The heat transfer data are compared with a number of existing correlations. The author proposes the best methods for calculating helium heat exchangers

  12. Exergo-ecological evaluation of heat exchanger

    Directory of Open Access Journals (Sweden)

    Stanek Wojciech

    2014-01-01

    Full Text Available Thermodynamic optimization of thermal devices requires information about the influence of operational and structural parameters on its behaviour. The interconnections among parameters can be estimated by tools such as CFD, experimental statistic of the deviceetc. Despite precise and comprehensive results obtained by CFD, the time of computations is relatively long. This disadvantage often cannot be accepted in case of optimization as well as online control of thermal devices. As opposed to CFD the neural network or regression is characterized by short computational time, but does not take into account any physical phenomena occurring in the considered process. The CFD model of heat exchanger was built using commercial package Fluent/Ansys. The empirical model of heat exchanger has been assessed by regression and neural networks based on the set of pseudo-measurements generated by the exact CFD model. In the paper, the usage of the developed empirical model of heat exchanger for the minimisation of TEC is presented. The optimisationconcerns operational parameters of heat exchanger. The TEC expresses the cumulative exergy consumption of non-renewable resources. The minimization of the TEC is based on the objective function formulated by Szargut. However, the authors extended the classical TEC by the introduction of the exergy bonus theory proposed by Valero. The TEC objective function fulfils the rules of life cycle analysis because it contains the investment expenditures (measured by the cumulative exergy consumption of non-renewable natural resources, the operation of devices and the final effects of decommissioning the installation.

  13. Heat exchanger and method for its production

    International Nuclear Information System (INIS)

    The patent refers to heat exchangers, preferably to steam generators for nuclear power stations, in which the parallel tubes are fixed to each other by welding to distancing elements. A method is described for the fabrication by a welding machine, so that the number of necessary tests can be reduced drastically. (P.K.)

  14. Heat exchanger and method for its production

    International Nuclear Information System (INIS)

    The patent refers to heat exchangers preferably steam generators for nuclear power stations with a number of parallel tubes arranged in curved planes. The fixing of the tubes to each other is accomplished by welding to distancing elements, e.g. fins of the adjacent tubes. This system eliminates the danger of fretting corrosion and vibration of the tubes. (P.K.)

  15. Shell side CFD analysis of a small shell-and-tube heat exchanger

    International Nuclear Information System (INIS)

    The shell side design of a shell-and-tube heat exchanger; in particular the baffle spacing, baffle cut and shell diameter dependencies of the heat transfer coefficient and the pressure drop are investigated by numerically modeling a small heat exchanger. The flow and temperature fields inside the shell are resolved using a commercial CFD package. A set of CFD simulations is performed for a single shell and single tube pass heat exchanger with a variable number of baffles and turbulent flow. The results are observed to be sensitive to the turbulence model selection. The best turbulence model among the ones considered is determined by comparing the CFD results of heat transfer coefficient, outlet temperature and pressure drop with the Bell-Delaware method results. For two baffle cut values, the effect of the baffle spacing to shell diameter ratio on the heat exchanger performance is investigated by varying flow rate.

  16. Tube vibration in industrial size test heat exchanger

    International Nuclear Information System (INIS)

    Tube vibration data from tests of a specially built and instrumented, industrial-type, shell-and-tube heat exchanger are reported. The heat exchanger is nominally 0.6 m (2 ft) in dia and 3.7 m (12 ft) long. Both full tube and no-tubes-in-window bundles were tested for inlet/outlet nozzles of different sizes and with the tubes supported by seven, equally-spaced, single-segmental baffles. Prior to water flow testing, natural frequencies and damping of representative tubes were measured in air and water. Flow testing was accomplished by increasing the flow rates in stepwise fashion and also by sweeping through a selected range of flow rates. The primary variables measured and reported are tube accelerations and/or displacements and pressure drop through the bundle. Tests of the full tube bundle configuration revealed tube rattling to occur at intermediate flow rates, and fluidelastic instability, with resultant tube impacting, to occur when the flow rate exceeded a threshold level; principally, the four-span tubes were involved in the regions immediately adjacent to the baffle cut. For the range of flow rates tested, fluidelastic instability was not achieved in the no-tubes-in-window bundle; in this configuration the tubes are supported by all seven baffles and are, therefore, stiffer

  17. Holding element for the tubes of a heat exchanger

    International Nuclear Information System (INIS)

    The holding element is arranged in a spacer grid having openings which receive each one a tube of the heat exchanger and which allow the coolant to flow through them around the tubes. It comprises a ring fastener on the plate defining with the tube a regular annular space for the said coolant, this ring being prolongated by at least three elastic plates symmetrically inclined to bear upon the tube and hold it in the opening axis

  18. Heat transfer and pressure loss for smoke gas in finned tube heat exchangers. Varmeovergang og tryktab for roeggas i ribberoersvarmevekslere

    Energy Technology Data Exchange (ETDEWEB)

    Krighaar, M.; Wit, J. de; Ingerslev, I.; Paulsen, O. (Energiteknologi, Dansk Teknologisk Institut (DK))

    1990-01-01

    The aim was to investigate heat transfer and pressure loss in relation to transverse flow round bunches of pipes fitted into a finned tube heat exchanger. Conditions of both condensing and non-condensing operation were dealt with. Various pipe types were examined in order to discover potentials for utilization in gas-fired boilers. Measurements were taken on ribbed pipe heat exchangers, and computer calculations were made to determine convection conditions. (AB).

  19. Exhaust bypass flow control for exhaust heat recovery

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, Michael G.

    2015-09-22

    An exhaust system for an engine comprises an exhaust heat recovery apparatus configured to receive exhaust gas from the engine and comprises a first flow passage in fluid communication with the exhaust gas and a second flow passage in fluid communication with the exhaust gas. A heat exchanger/energy recovery unit is disposed in the second flow passage and has a working fluid circulating therethrough for exchange of heat from the exhaust gas to the working fluid. A control valve is disposed downstream of the first and the second flow passages in a low temperature region of the exhaust heat recovery apparatus to direct exhaust gas through the first flow passage or the second flow passage.

  20. Maintenance experience on process heat exchangers in Dhruva reactor

    International Nuclear Information System (INIS)

    Dhruva a 100 MW (thermal) high flux research reactor has two types of heat exchangers operating in various process system i.e. shell and tube type and plate type. Annexure-1 indicates various heat exchangers in different systems of the reactor. Among the heat exchangers, those used in main coolant system, vault and shield cooling system did not warrant regular overhaul after commissioning but for periodic fastness, tightness checks in view of the high standard of purity and close chemistry control on the process fluids on both the sides of the heat exchangers. In addition, the heat transfer performance of these heat exchangers have been consistent without any degradation. Therefore shell and tube type heat exchangers in process water system and plate type heat exchangers in process water and Spent Fuel Storage Building (SFSB) bay water recirculation systems are typically chosen for highlighting the maintenance experience. Maintenance experience on process heat exchangers is given. 4 ills

  1. Temperature Profile Data in the Zone of Flow Establishment above a Model Air-cooled Heat Exchanger with 0.56 m2 Face Area Operating under Natural Convection

    Directory of Open Access Journals (Sweden)

    Chu Chi Ming

    2010-01-01

    Full Text Available The aim of this study was to analyze the temperature profile in the Zone of Flow Establishment (ZFE above a 0.56 m2 hot screen placed at different height above an electrically heated model air-cooled heat exchanger operating under natural convection. Installation of screens increased the temperature difference from 30 to 140 K with respect to ambient that resulted in the air velocity increased at the inlet of the special duct from 0.67 m sec-1 to more than 2.0 m sec-1 under different heat loads ranging from 1 to 2.5 kW. The investigation of temperature profile was done above the hot screens placed at 0.35, 0.65, 0.95 and 1.25 m height over the electrically heated model air-cooled heat exchanger. The results show that the exit air temperature near to the electric heater and above the hot screens did not differ significantly but at heights of 0.09 m and upward the temperature difference differed by 2 to 6 K depending on the height of the hot screens. Maximum temperature difference was observed for hot screen placed at 0.65 and 0.95 m. Although, the temperatures at the beginning of the zone of flow establishment were almost the same for every heat load, the radial profile of temperature turned from parabolic in shape to uniformly flat for the configuration without screen and with screen respectively. This indicates turbulence increase above the hot screens.

  2. NUMERICAL AND EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER OF ZnO/WATER NANOFLUID IN THE CONCENTRIC TUBE AND PLATE HEAT EXCHANGERS

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Talaie

    2011-01-01

    Full Text Available The plate and concentric tube heat exchangers are tested by using the water-water and nanofluid-water streams. The ZnO/Water (0.5%v/v nanofluid has been used as the hot stream. The heat transfer rate omitted of hot stream and overall heat transfer coefficients in both heat exchangers are measured as a function of hot and cold streams mass flow rates. The experimental results show that the heat transfer rate and heat transfer coefficients of the nanofluid in both of the heat exchangers is higher than that of the base liquid (i.e., water and the efficiency of plate heat exchange is higher than concentric tube heat exchanger. In the plate heat exchanger the heat transfer coefficient of nanofluid at mcold = mhot =10gr/sec is about 20% higher than base fluid and under the same conditions in the concentric heat exchanger is 14% higher than base fluid. The heat transfer rate and heat transfer coefficients increases with increase in mass flow rates of hot and cold streams. Also the CFD code is used to simulate the performance of the mentioned heat exchangers. The CFD results are compared to the experimental data and showed good agreement. It is shown that the CFD is a reliable tool for investigation of heat transfer of nanofluids in the various heat exchangers.

  3. Testing and analysis of load-side immersed heat exchangers for solar domestic hot water systems

    Energy Technology Data Exchange (ETDEWEB)

    Farrington, R.B.; Bingham, C.E.

    1987-10-01

    This report describes work to determine the performance of load-side heat exchangers for use in residential solar domestic hot water systems. We measured the performance of four heat exchangers: a smooth coil and a finned coil having heat transfer areas of 2.5 m/sup 2/ (26 ft/sup 2/) and those having areas of 1.7 m/sup 2/ (19 ft/sup 2/). A numerical model using the thermal network program MITAS was constructed, and results were compared to the experimental results. Research showed a smooth coil with only 70% of the surface area of a finned coil performed better than the finned coil. Also, load-side heat exchangers can maintain and enhance stratification in storage tanks, permitting the use of control strategies that take advantage of stratified storage tanks to increase system performance. The analytical model, which agreed reasonably well with the experimental results, was used to vary heat exchanger flow rate and area and initial tank temperature for both a smooth- and a finned-coil heat exchanger. Increasing the heat exchanger flow rate and area results in higher heat transfer rates but not necessarily optimal performance. Lower initial tank temperatures resulted in reduced tank stratification. The smooth heat exchanger outperformed the finned heat exchanger with the same outside surface area. 15 refs., 37 figs., 9 tabs.

  4. Heat transfer enhancement utilizing chaotic advection in coiled tube heat exchangers

    International Nuclear Information System (INIS)

    The present study introduced a novel chaotic coil heat exchanger utilizing chaotic advection to enhance heat transfer at low Reynolds numbers. Using Lagrangian tracing of fluid particles and their sensitivity to the initial condition and fluid element calculations, it was shown that mixing was significantly increased due to the chaotic advection. Heat transfer performance in the coil and chaotic configuration was visualized by isotherms contours of temperature in different cross-sections. In order to evaluate the hydraulic-thermal performance of heat exchangers, Nusselt numbers and friction factor were calculated and comparison was made between the two configurations. Numerical calculations revealed that the chaotic coil configuration displayed heat transfer enhancement of 4–26% relative to the fully developed Nusselt numbers in the regular coil with only 5–8% change in the pressure drop. - Highlights: • A novel chaotic coil heat exchanger is introduced in this study. • It is shown that mixing is increased significantly due to the altered chaotic advection mechanism. • By increasing the Reynolds number, results show impressive enhancement in chaotic heat exchanger performance. • Reorientation in chaotic flow leads to higher pressure loss than that in the normal helical coil

  5. Thermal hydraulic parameter studies of heat exchanger for the TRIGA MARK II research reactor

    International Nuclear Information System (INIS)

    Thermal Hydraulic studies have being conducted at PUSPATI TRIGA Mark II (RTP) Nuclear Research Reactor. The purpose of this study is to determine the heat transfer characteristic and heat exchanger performance at difference reactor power. Fundamental concept and a plate type application of heat exchanger in RTP are presented in this study. A plate type heat exchanger is a device for RTP reactor cooling system built for efficient heat transfer from one fluid to another. The study involves the observation of inlet and outlet temperature profile, flow rate and pressure at the reactor pool and heat exchanger. The observed parameters are compared to basic engineering calculation and the output of the study has been beneficial to evaluate the performance of newly-installed plate type heat exchanger. (author)

  6. Intermediate heat exchanger project for Super Phenix

    International Nuclear Information System (INIS)

    The Super Phenix (1 200 MWe) intermediate heat exchangers are derived directly from those of Phenix (250 MWe) which has been in operation at Marcoule near Avignon (Gard - France) for the last two years. The active part structure (exchange tube bundle) is very similar for both reactors and design studies have proved that this concept, based on experience gained in Phenix plan construction, was able to achieve the required operating conditions. The characteristics related to reactor pool-type design are presented. Thermal, hydraulic and mechanical considerations are then presented. (Auth.)

  7. Heat exchanger with several parallel tubes with fins attached

    International Nuclear Information System (INIS)

    The tubes of the heat exchanger convey a first fluid. They are provided with ripple shaped sheet metal fins, which are distributed over the tubes length. A second fluid flows in the remaining spaces between the fins. The corrugations on each fin are only on the outer part of which immediately surrounds the corresponding tube and extend towards the neighbouring tube in the same row. The corrugations are free from perforations. The pressure loss of the second fluid is thereby significantly reduced and maintains good heat transfer properties. 7 figs

  8. A study on the pressure drop characteristics of plate and shell heat exchangers

    International Nuclear Information System (INIS)

    Plate and Shell Heat Exchanger(P and SHE) has been applied to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. The purpose of this study is to analyze the characteristics of pressure drop in plate and shell heat exchanger. An experiment for single phase flow pressure drop in plate and shell heat exchanger was performed. Also numerical work was conducted using the FLUENT code for k-? model. The dependence of friction factor on geometrical parameters was numerically investigated. The study examines the internal flow and the pressure distribution in the channel of plate and shell heat exchanger. The results of CFD analysis compared with experimental data, and the difference of frictor factor in plate side and shell side are 10% and 12%, respectively. Therefore, the CFD analysis model is effectively predict the performance of plate and shell heat exchanger

  9. Optimization of heat exchanger networks using genetic algorithms

    International Nuclear Information System (INIS)

    Most thermal processes encountered in the power industry (chemical, metallurgical, nuclear and thermal power stations) necessitate the transfer of large amounts of heat between fluids having different thermal potentials. A common practice applied to achieve such a requirement consists of using heat exchangers. In general, each current of fluid is conveniently cooled or heated independently from each other in the power plant. When the number of heat exchangers is large enough, however, a convenient arrangement of different flow currents may allow a considerable reduction in energy consumption to be obtained (Linnhoff and Hidmarsh, 1983). In such a case the heat exchangers form a 'Heat Exchanger Network' (HEN) that can be optimized to reduce the overall energy consumption. This type of optimization problem, involves two separates calculation procedures. First, it is necessary to optimize the topology of the HEN that will permit a reduction in energy consumption to be obtained. In a second step the power distribution across the HEN should be optimized without violating the second law of thermodynamics. The numerical treatment of this kind of problem requires the use of both discrete variables (for taking into account each heat exchanger unit) and continuous variables for handling the thermal load of each unit. It is obvious that for a large number of heat exchangers, the use of conventional calculation methods, i.e., Simplexe, becomes almost impossible. Therefore, in this paper we present a 'Genetic Algorithm' (GA), that has been implemented and successfully used to treat complex HENs, containing a large number of heat exchangers. As opposed to conventional optimization techniques that require the knowledge of the derivatives of a function, GAs start the calculation process from a large population of possible solutions of a given problem (Goldberg, 1999). Each possible solution is in turns evaluated according to a 'fitness' criterion obtained from an objective equation. This equation must completely describe the optimization problem to be handled, i.e., maximization or minimization. The best solutions are then retained and Genetic operators such as crossover and mutation are then applied in order to reproduce a new population of solutions that have a better fitness than the previous ones. These processes of crossover, mutation and selection are repeated until a suitable convergence criterion is able to stop the procedure. It is important to point out that GAs handle a coded form of each possible solution (for instance binary coded solutions) that represent the individuals, i.e., chromosomes of a population, instead of handling the solution to the problem itself. In order to carry out the synthesis of HEN we have implemented two different coded populations; one population is used to code for the topology of the HEN and the second for the heat load handled by each heat exchanger (Lewin et al., 1998). Ck is a coefficient used to adjust the degree of penalty. This approach has been used to treat several HEN problems taken from the open literature. In general the results obtained with the proposed algorithm are in excellent agreement with those obtained by using conventional techniques, i.e., Simplexe. We have found that the use of GAs also permits other satisfactory solutions corresponding to different heat exchanger topologies and thermal load distributions to be obtained. Further, we were able to handle HENs containing more than 15 heat exchanges, that were impossible to solve using conventional methods. However, it is important to point out that the proposed technique is not appropriate to handle HENs that require the division of currents. (author)

  10. Heat Transfer and Pressure Drop Characteristics in Straight Microchannel of Printed Circuit Heat Exchangers

    Directory of Open Access Journals (Sweden)

    Jang-Won Seo

    2015-05-01

    Full Text Available Performance tests were carried out for a microchannel printed circuit heat exchanger (PCHE, which was fabricated with micro photo-etching and diffusion bonding technologies. The microchannel PCHE was tested for Reynolds numbers in the range of 100?850 varying the hot-side inlet temperature between 40 °C–50 °C while keeping the cold-side temperature fixed at 20 °C. It was found that the average heat transfer rate and heat transfer performance of the countercurrrent configuration were 6.8% and 10%?15% higher, respectively, than those of the parallel flow. The average heat transfer rate, heat transfer performance and pressure drop increased with increasing Reynolds number in all experiments. Increasing inlet temperature did not affect the heat transfer performance while it slightly decreased the pressure drop in the experimental range considered. Empirical correlations have been developed for the heat transfer coefficient and pressure drop factor as functions of the Reynolds number.

  11. Optimization of baffle configurations to prevent aeroacoustic instabilities in heat exchangers - preliminary experiments

    OpenAIRE

    Moreira, Miguel; Antunes, J; Debut, V.; Pina, H.

    2008-01-01

    It is well known that gas heat exchangers are prone to aeroacoustic instabilities, which often lead to severe noise levels, structural vibrations and fatigue. These are unacceptable, as they threaten the component integrity and expose the plant workers to excessive noise levels. Such phenomenon is due to a cooperative interplay between the Karman vortices generated by the cross-flow and the heat exchanger acoustical modes (mainly those transverse to the tube banks). Energy exchanges are then ...

  12. Erosion durability of steels in steam boiler heat exchanger tubes

    Energy Technology Data Exchange (ETDEWEB)

    Meuronen, V. [Lappeenranta University of Technology, Lappeenranta (Finland). Dept. of Energy Technology

    2000-05-01

    The erosion durability of three tube materials that are generally used in the heat exchangers of steam boilers was tested by having an air flow containing particles flowing through tube banks. The materials tested were St35.8, 15Mo3 and 10CrMo910. The last one was the most resistive to erosion. The material 15Mo3 had a higher resistance than St35.8, but lower than 10CrMo910. Correlations between erosion resistance and the strength, and erosion resistance and the ductility of the steels were observed. 4 refs., 4 figs., 5 tabs.

  13. Fouling of a plate heat exchanger by cheese whey solutions

    OpenAIRE

    Corcoran, Brian

    1997-01-01

    A plate heat exchanger rig was developed at Dublin City University to study fouling of plate heat exchangers using cheese whey solutions. The rig consisted of an Alfa-Laval plate heat exchanger, 316 stainless steel pipework, pressure and temperature measurement and was temperature controlled with all information logged via an Anville data acquisition system. Cheese whey solutions of various concentration were passed through the plate heat exchanger for periods of up to four hours. The eff...

  14. Materials development for HTGR heat exchangers

    International Nuclear Information System (INIS)

    High-temperature, gas-cooled reactors (HTGR's) are uranium/thorium-fueled, graphite-moderated, helium-cooled systems capable of producing high-temperature primary coolant. Several variants of this system are under active development in the United States and worldwide. In one version, the primary coolant heat is transferred to steam generators producing 5380C/16.5 MPa steam for use in electricity generation or process heat applications. The materials and design technology for steam generators in this system are well developed, relying heavily upon prior experience with fossil-fired steam generators and the steam generators of the commercial HTGR's. The major work that remains to be done is to complete qualification of the materials and to respond to evolving rules pertinent to elevatedtemperature nuclear design and construction. Other versions of the HTGR generate much higher primary coolant gas temperatures (8500 to 9500C) and exchange this heat, through intermediate heat exchangers (IHX's), to a secondary loop for higher temperature process heat applications. Although IHX's for these systems are typically pressure-balanced (low-stress) units, their design involves several challenges, including the potential interactions between structural materials and impurities present in the HTGR primary coolant. Considerable work is required to qualify materials for IHX applications, including detailed mechanical property characterization, determination of environmental influences on performance, provision of welding materials and procedures for producing joints of adequate strength and integrity, and provisions for wear protection. Some of the work currently under way addressing these issues is described

  15. Earth Air Heat Exchanger in Parallel Connection

    OpenAIRE

    ManojkumarDubey1 , Dr. J.L.Bhagoria2 , Dr. Atullanjewar

    2013-01-01

    The temperature of earth at a certain depth about 2 to 3m the temperature of ground remains nearly constant throughout the year. This constant temperature is called the undisturbed temperature of earth which remains higher than the outside temperature in winter and lower than the outside temperature in summer. When ambient air is drawn through buried pipes, the air is cooled in summer and heated in winter, before it is used for ventilation. The earth air heat exchanger can fulfil in both purp...

  16. Selection of materials for heat exchangers

    International Nuclear Information System (INIS)

    This paper provides a frame work for selecting heat exchangers materials especially those used in nuclear power plants. Typical examples of materials selection for heat exchanger tubing of nuclear power plants and condensers are presented. The paper brings out also, the importance of continued intensive R and D in materials in order to enhance the reliability and reduce cost by improving upon the existing materials by minor additions of alloying elements or new materials. The properties of Cr- Mo - alloys with minor additions of W, V, Nb and N are discussed in view of their use at elevated temperatures in the power industry. These alloys were found to provide considerable operation flexibility due to their low expansion coefficient and high thermal conductivity in comparison with the austenitic stainless steels. Also, the Ni base alloy Inconel 617. Could be selected for his excellent combination of creep and hot corrosion resistance up to a temperature of a 50 degree C. 2 figs., 7 tabs

  17. Ventilation Heat Recovery from Wood-Burning Domestic Flues. A Theoretical Analysis Based on a Triple Concentric Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Lionel Druette

    2013-01-01

    Full Text Available This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective is to predict outlet temperature for the specific geometry of the heat exchanger studied here. Thus, the governing differential equations are derived for a counter-co-current flow arrangement of the three fluids. Then analytical solutions for the steady-state temperature distribution are obtained as well as the amount of heat transferred to the outside. An expression for the effectiveness of the heat exchanger is also proposed. Based on these results, calculations are performed on a case study to predict the fluid temperature distribution along the heat exchanger. Finally, a parametric study is carried out on this case study to assess the influence of the relevant parameters on the effectiveness of the heat exchanger. In addition, computation of heat losses to the outside justifies whether insulation is needed.

  18. Horizontal Heat Exchanger Design and Analysis for Passive Heat Removal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Vierow, Karen

    2005-08-29

    This report describes a three-year project to investigate the major factors of horizontal heat exchanger performance in passive containment heat removal from a light water reactor following a design basis accident LOCA (Loss of Coolant Accident). The heat exchanger studied in this work may be used in advanced and innovative reactors, in which passive heat removal systems are adopted to improve safety and reliability The application of horizontal tube-bundle condensers to passive containment heat removal is new. In order to show the feasibility of horizontal heat exchangers for passive containment cooling, the following aspects were investigated: 1. the condensation heat transfer characteristics when the incoming fluid contains noncondensable gases 2. the effectiveness of condensate draining in the horizontal orientation 3. the conditions that may lead to unstable condenser operation or highly degraded performance 4. multi-tube behavior with the associated secondary-side effects This project consisted of two experimental investigations and analytical model development for incorporation into industry safety codes such as TRAC and RELAP. A physical understanding of the flow and heat transfer phenomena was obtained and reflected in the analysis models. Two gradute students (one funded by the program) and seven undergraduate students obtained research experience as a part of this program.

  19. Plating Patches On Heat-Exchanger Jackets

    Science.gov (United States)

    Loureiro, Henry; Kubik, Frank

    1989-01-01

    Permanent repairs made without welding. Technique used to repair nickel-alloy nozzle jacket of Space Shuttle main engine. Applicable to other metal heat-exchanger jackets with similar configurations. Does not require welding, brazing, soldering, or other operations involving high temperatures and consequent damage to surrounding areas. Portion of jacket around damaged area removed by grinding and polishing out to edges adjacent to tube/jacket braze bonds. Spaces between tubes filled with wax preventing contamination of spaces during subsequent plating.

  20. Comparative studies on micro heat exchanger optimisation.

    OpenAIRE

    Okabe, T.; Foli, K; Olhofer, M; Jin, Y; Sendhoff, B

    2003-01-01

    Although many methods for dealing with multi-objective optimisation (MOO) problems are available as stated in K. Deb (2001) and successful applications have been reported on C.A. Coello et al. (2001), the comparison between MOO methods applied to real-world problem was rarely carried out. This paper reports the comparison between MOO methods applied to a real-world problem, namely, the optimization of a micro heat exchanger (?HEX). Two MOO methods, dynamically weighted aggregation (DWA) propo...

  1. Development and application of radiotracer technique for online leak detection in high pressure heat exchangers

    International Nuclear Information System (INIS)

    A radiotracer technique for online leak detection in high-pressure heat exchanger systems have been developed and successfully applied in various process industries in India. Bromine-82 as dibromobiphenyl is used as a radiotracer for leak detection in heat exchangers involving flow of organic fluids. The radiotracer is injected into high pressure side of the heat exchanger system and monitored at strategically selected locations in low pressure side using NaI(Tl) scintillation detectors connected to a preset data acquisition system. The tracer concentration curves monitored as a function of time are analyzed to identify the leaking heat exchanger(s). A number of leak detection investigations have been carried out since year 2001 leading to high economical benefits to the industry. This paper discusses principle of leak detection in high-pressure heat exchanger systems using radiotracer technique with two specific case studies. (author)

  2. Comparison of shell-and-tube with plate heat exchangers for the use in low-temperature organic Rankine cycles

    International Nuclear Information System (INIS)

    Highlights: • Binary cycles for low-temperature heat sources are investigated. • Shell-and-tube and plate heat exchangers are modeled. • System optimization of the cycle variables and heat exchanger geometry. • ORCs with plate heat exchangers obtain in most cases higher efficiencies. - Abstract: Organic Rankine cycles (ORCs) can be used for electricity production from low-temperature heat sources. These ORCs are often designed based on experience, but this experience will not always lead to the most optimal configuration. The ultimate goal is to design ORCs by performing a system optimization. In such an optimization, the configuration of the components and the cycle parameters (temperatures, pressures, mass flow rate) are optimized together to obtain the optimal configuration of power plant and components. In this paper, the configuration of plate heat exchangers or shell-and-tube heat exchangers is optimized together with the cycle configuration. In this way every heat exchanger has the optimum allocation of heat exchanger surface, pressure drop and pinch-point-temperature difference for the given boundary conditions. ORCs with plate heat exchangers perform mostly better than ORCs with shell-and-tube heat exchangers, but one disadvantage of plate heat exchangers is that the geometry of both sides is the same, which can result in an inefficient heat exchanger. It is also shown that especially the cooling-fluid inlet temperature and mass flow have a strong influence on the performance of the power plant

  3. He4 evaporation heat exchangers for a He3/He4 dilution refrigerator

    International Nuclear Information System (INIS)

    Two types of He4 evaporation heat exchanger are described. A minimum temperature of 1.18 K was attained with a flow impedance of the order of 1011 cm-3. The orifice at the pumping line and the additional buffer volume in the exchanger were effective for stabilization of the exchanger temperature and for the short term overloads, while the temperature of the exchanger with the orifice remained relatively higher than that without orifice. (author)

  4. Acoustic pulsations and vibratory stresses in heat exchangers

    International Nuclear Information System (INIS)

    The flow of a heat-bearing fluid in a heat exchanger causes the loosening of nonstreamlined obstacles which it encounters. The effect is simultaneously to produce a mechanical excitation of these obstacles and to generate fluctuations of pressure downstream from them. The high Reynolds numbers attained in heat exchangers mean that the excitatory stresses are random, and the estimation of the mechanical stresses produced necessitates the use of statistical methods. The danger of excitation may be reduced by the use of partitions or screens. Pressure pulsations generated by obstacles are not greatly influenced by mechanical vibrations of the obstacles so long as the amplitude of such vibrations remains low. On the other hand. The proximity of partitions and coincidences with acoustic resonances sometimes impose a synchronization of pulsations and consequently an increase in amplitude. These acoustic pulsations are propagated in the flow and create mechanical vibrations on the sides of the exchanger. These vibrations may in some cases reach substantial magnitudes at points far removed from the obstacles constituting the source of excitation

  5. Role of heat exchangers in helium liquefaction cycles: Simulation studies using Collins cycle

    International Nuclear Information System (INIS)

    Highlights: ? Role of heat exchangers in basic helium liquefier analyzed to design large-scale ones. ? Heat exchangers that determine inlet temperature to expanders are more significant. ? Limiting values of nondimensional UA for each heat exchanger have been determined. ? Extra area distributed such that effectiveness of all heat exchangers increase uniformly. ? Heat exchanger performance variation have little influence on the optimum expander flow. - Abstract: Energy efficiency of large-scale helium liquefiers generally employed in fusion reactors and accelerators is determined by the performance of their constituting components. Simulation with Aspen HYSYS® V7.0, a commercial process simulator, helps to understand the effects of heat exchanger parameters on the performance of a helium liquefier. Effective UA (product of overall heat transfer coefficient U, heat transfer surface area A and deterioration factor F) has been taken as an independent parameter, which takes into account all thermal irreversibilities and configuration effects. Nondimensionalization of parameters makes the results applicable to plants of any capacity. Rate of liquefaction is found to increase linearly with the effectiveness of heat exchangers. Performance of those heat exchangers that determine the inlet temperatures to expanders have more influence on the liquid production. Variation of sizes of heat exchangers does not affect the optimum rate of flow through expanders. Increasing UA improves the rate of liquid production; however, the improvement saturates at limiting UA. Maximum benefit in liquefaction is obtained when the available heat transfer surface area is distributed in such a way that the effectiveness remains equal for all heat exchangers. Conclusions from this study may be utilized in analyzing and designing large helium plants.

  6. Development of Heat Exchangers for Air-conditioners Capable of Supplying High-temperature (80°C) Air

    Science.gov (United States)

    Itoh, Masaaki; Urata, Kazumoto; Matsushima, Hiroaki; Kunugi, Yoshifumi; Kogure, Hiroshi; Harada, Iwao

    A new kind of heat exchanger for air conditioners was studied analytically and experimentally and the following results were obtained. To supply high-temperature air, it is effective to use "Pair Heat Exchangers" where fins are separated between pipe rows and the refrigerant flows counter-crosswise to the air flow. These heat exchangers enabled air at 80°C to be supplied by HCFC-22 air-conditioners when the discharge pressure was 3.0 MPa and refrigerant temperature at the inlet of heat exchanger was 120°C. The main effect of dividing fins is to prevent heat conduction between pipe rows through the fins.

  7. Vibration in shell and tube heat exchangers - prediction versus operation (Paper No. 003)

    International Nuclear Information System (INIS)

    The continued demand for improved performance of heat exchangers under serious limitations of cost and space, has led to designs that are more compact with increased flow rates. Though these changes have undoubtedly achieved the improved thermodynamic performance intended, they have at the same time made the heat exchanger tubes susceptible to flow induced vibration. Also, there has been a trend towards higher capacity heat exchangers having increased shell side flow velocities to improve the heat transfer. As a consequence, there has been a significant increase in the incidence of tube failures due to flow induced vibrations. Problems caused by flow induced vibrations like mechanical wear, fatigue failure, acoustic noise and mixing of shell side and tube side fluids are evaluated. (author). 2 figs., 2 tables, 10 refs

  8. Design experience with liquid-to-gas heat exchanger using finned heat pipes

    International Nuclear Information System (INIS)

    Heat pipes are high capacity heat transfer devices. Therefore, many studies have been carried out on their theory and application in liquid-gas heat exchangers and radiators. In this present study, a heat exchanger composed of 18 thermosyphones ( heat pipes without wicks) arranged in two rows with staggered configuration was constructed. Heat was absorbed by lower part of the tube from hot water and removed from upper part of the tube by air stream. Analysis showed that the boiling limit is the lowest limit. Since the capacity of each thermosyphone is lower than this limit, it is assured that the designed thermosyphones operate securely at the design condition. Calculations showed that they are capable of transferring 1908 watts heat from a hot water with 80 degree centigrade temperature and 6 liters per minute flow. Experimental results approved a capacity of 1730 watts. Comparison of the two mentioned values indicates the satisfactory design and construction. Theoretical and experimental values of heat transfer coefficient of inside and outside of the condensing part of the tube are in good agreement. The inside heat transfer coefficient of the used heat pipes was 7900 w/m 2.K while this value is 230 for a similar metallic tube

  9. OXIDE DISPERSION-STRENGTHENED HEAT EXCHANGER TUBING

    Energy Technology Data Exchange (ETDEWEB)

    Harper, Mark A.

    2001-11-06

    Oxide dispersion strengthened (ODS) alloys (e.g. the INCOLOY{reg_sign} MA956 alloy) are known for their excellent high temperature properties and are prime candidate materials for the construction of very high temperature heat exchangers that will be used in Vision 21 power plants. The main limitation of these materials is their poor weldability. Commercially available ODS tubing also tends to exhibit relatively poor circumferential creep strength due to current processing practices resulting in a fine grain size in the transverse direction. Thus far, these two characteristics of the ODS tubing have restricted its use to mostly non-pressure containing applications. The objectives of this program are to develop: (a) an MA956 tube with sufficient circumferential creep strength for long term use as heat exchanger tubing for very high temperatures; (b) a welding technique(s) for producing adequate joints between an MA956 tube and an MA956 tube, and an MA956 tube and an INCONEL 601 tube; (c) the bending strain limits, below which recrystallization will not occur in a MA956 tube during normal operation; and (d) the high temperature corrosion limits for the MA956 alloy with respect to working-fluid side and fireside environments. Also, this program seeks to generate data for use by heat exchanger designers and the ASME Boiler and Pressure Vessel Code, and perform an analysis of the mechanical property, tube bending, and corrosion data in order to determine the implications on the design of a very high temperature heat exchanger (T>1093 C/2000 F). After one year, work is currently being conducted on increasing the circumferential strength of a MA956 tube, developing joining techniques for this material, determining the tube bending strain limits, and establishing the high temperature corrosion parameters for the MA956 alloy in environments expected to be present in Vision 21 power plants. Work in these areas will is continuing into the next fiscal year, with success anticipated to produce innovative developments that will allow the reliable use of ODS alloys for heat exchanger tubing, as well as a variety of applications previously not possible with metallic materials.

  10. The causes of milk deposit formation on the walls of the heat exchangers during the heat treatment of milk

    OpenAIRE

    Bojan Matijevi?; Josip ?ulig

    2006-01-01

    The results of research on finding the causes and preventing the formation of milk deposit are described in this paper.During the heat treatment of milk, an unwanted phenomenon occurs; the formation of milk deposit on heating surfaces of heat exchangers. This phenomenon causes the decrease of heat transfer coefficient as well as the pressure drop, it restricts the flow of milk, and causes additional production costs and increases production loss.The formation of milk deposit is a result of co...

  11. Numerical Investigation of Air-Side Heat Transfer and Pressure Drop in Circular Finned-Tube Heat Exchangers

    OpenAIRE

    Mon, Mi Sandar

    2009-01-01

    A three-dimensional numerical study is performed to investigate the heat transfer and pressure drop performance on the air-side of circular finned tube bundles in cross flow. New heat transfer and pressure drop correlations for the air-cooled heat exchangers have been developed with the Reynolds number ranging from 5000 to 70000. The heat transfer and pressure drop results agree well with several existing experimental correlations. In addition, the influence of the geometric parameters on the...

  12. Effect of segmental baffles on the shell-and-tube heat exchanger effectiveness

    OpenAIRE

    Vuki? Mi?a V.; Tomi? Mladen A.; Živkovi? Predrag M.; Ili? Gradimir S.

    2014-01-01

    In this paper, the results of the experimental investigations of fluid flow and heat transfer in laboratory experimental shell-and-tube heat exchanger are presented. Shell-and-tube heat exchanger is with one pass of warm water on the shell side and two passes of cool water in tube bundle. Shell-and-tube heat exchanger is with 24x2 tubes (U-tube) in triangle layout. During each experimental run, the pressure drops and the fluid temperatures on shell side, al...

  13. Technology Solutions Case Study: Foundation Heat Exchanger, Oak Ridge, Tennessee

    Energy Technology Data Exchange (ETDEWEB)

    None

    2014-03-01

    The foundation heat exchanger, developed by Oak Ridge National Laboratory, is a new concept for a cost-effective horizontal ground heat exchanger that can be connected to water-to-water or water-to-air heat pump systems for space conditioning as well as domestic water heating.

  14. CFD Analysis of Shell and Tube Heat Exchanger to Study the Effect of Baffle Cut on the Pressure Drop

    OpenAIRE

    Avinash D Jadhav; Tushar A Koli

    2014-01-01

    The shell side design of a shell and tube heat exchanger; in particular the baffle spacing, baffle cut and shell diameter dependencies of the heat transfer coefficient and the pressure drop are investigated by numerically modelling a small heat exchanger. The flow and temperature fields inside the shell are resolved using a commercial CFD package. A set of CFD simulations is performed for a single shell and single tube pass heat exchanger with a variable number of baffles and turb...

  15. Cross-flow membrane-based enthalpy exchanger balanced and unbalanced flow

    International Nuclear Information System (INIS)

    Highlights: • A resubmission is performed to be considered for publication. • The main corrections are suitably inserted in the text. • The reviewer recommendations are completely addressed and took into account. - Abstract: In order to deepen the understanding of the main phenomena governing the membrane based energy recovery ventilators performance, we present a three dimensional numerical study of the mechanisms of heat and mass transfer in a cross-flow heat exchanger with balanced and unbalanced flow. This work involves the use of a control-volume method and solves the set of Navier–Stokes equations in the air streams and as well as in the membrane core. The results are compared to literature available data and the agreement is seen to be satisfactory. The effect of operating parameters such as the Reynolds number, volume flow rates and temperature on the performance of the heat exchanger are also investigated

  16. Heat transfer characteristics and pressure drop in straight microchannel of the printed circuit heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoon Ho; Moon, Jung Eun; Lee, Kyu Jung [Korea Univ., Seoul (Korea, Republic of); Choi, Young Jong [Innowill Corp., Daejeon (Korea, Republic of)

    2008-12-15

    The performance experiments for a microchannel Printed Circuit Heat Exchanger (PCHE) of high-performance and high-efficiency on the two technologies of micro photo-etching and diffusion bonding were performed in this study. The microchannel PCHE were experimentally investigated for Reynolds number in ranges of 100 {approx} 700 under various flow conditions in the hot side and the cold side. The inlet temperatures of the hot side were conducted in range of 40 .deg. C {approx} 50 .deg. C while that of the cold-side were fixed at 20 .deg. C. In the flow pattern, the counter flow was provided 6.8% and 10 {approx} 15% higher average heat transfer rate and heat transfer performance than the parallel flow, respectively. The average heat transfer rate, heat transfer performance and pressure drop increases with increasing Reynolds number in all the experiment. The increasing of inlet temperature in the experiment range has not an effect on the heat transfer performance while the pressure drop decrease slightly with that of inlet temperature. The experimental correlations to the heat transfer coefficient and pressure drop factor as a function of the Reynolds number have been suggested for the microchannel PCHE.

  17. Heat transfer characteristics and pressure drop in straight microchannel of the printed circuit heat exchangers

    International Nuclear Information System (INIS)

    The performance experiments for a microchannel Printed Circuit Heat Exchanger (PCHE) of high-performance and high-efficiency on the two technologies of micro photo-etching and diffusion bonding were performed in this study. The microchannel PCHE were experimentally investigated for Reynolds number in ranges of 100 ? 700 under various flow conditions in the hot side and the cold side. The inlet temperatures of the hot side were conducted in range of 40 .deg. C ? 50 .deg. C while that of the cold-side were fixed at 20 .deg. C. In the flow pattern, the counter flow was provided 6.8% and 10 ? 15% higher average heat transfer rate and heat transfer performance than the parallel flow, respectively. The average heat transfer rate, heat transfer performance and pressure drop increases with increasing Reynolds number in all the experiment. The increasing of inlet temperature in the experiment range has not an effect on the heat transfer performance while the pressure drop decrease slightly with that of inlet temperature. The experimental correlations to the heat transfer coefficient and pressure drop factor as a function of the Reynolds number have been suggested for the microchannel PCHE

  18. A NUMERCIAL COMPARISON OF SINGLE-PHASE FORCED CONVECTIVE HEAT TRANSFER BETWEEN ROUND TUBE AND STRAIGHT MICROCHANNEL HEAT EXCHANGERS

    Directory of Open Access Journals (Sweden)

    P. MOHAJERI KHAMENEH,

    2010-11-01

    Full Text Available Three dimensional simulations of the single-phase laminar flow and forced convective heat transfer of water in round tube and straight microchannel heat exchangers were investigated numerically. This numerical method was developed to measure heat transfer parameters of round tube and straight microchannel tube geometries. Then, similarities and differences were compared between different geometries. The geometries and operating conditions of those indicated heat exchangers were created using a finite volume-based computational fluid dynamics technique. In this article, at each Z-location variation of dimensionless local temperature, nondimensional local heat flux variation and dimensionless local Nusselt number distribution along the tube length were compared between round tube and straight microchannel heat exchangers. Consequently, averaged computational Nusselt number was obtained for those indicated models and then validation study was performed for round tube counter flow type heat exchanger model. Finally, all of these numerical results for both kind of geometries in counter flow heat exchangers were discussed in details.

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

    Science.gov (United States)

    Erickson, Lisa R.; Ungar, Eugene K.

    2013-01-01

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

  20. Simulation of boiling flow in evaporator of separate type heat pipe with low heat flux

    International Nuclear Information System (INIS)

    Highlights: • A boiling flow model in a separate type heat pipe with 65 mm diameter tube. • Nucleate boiling is the dominant mechanism in large pipes at low mass and heat flux. • The two-phase heat transfer coefficient is less sensitive to the total mass flux. - Abstract: The separate type heat pipe heat exchanger is considered to be a potential selection for developing passive cooling spent fuel pool – for the passive pressurized water reactor. This paper simulates the boiling flow behavior in the evaporator of separate type heat pipe, consisting of a bundle of tubes of inner diameter 65 mm. It displays two-phase characteristic in the evaporation section of the heat pipe working in low heat flux. In this study, the two-phase flow model in the evaporation section of the separate type heat pipe is presented. The volume of fluid (VOF) model is used to consider the interaction between the ammonia gas and liquid. The flow patterns and flow behaviors are studied and the agitated bubbly flow, churn bubbly flow are obtained, the slug bubble is likely to break into churn slug or churn froth flow. In addition, study on the heat transfer coefficients indicates that the nucleate boiling is the dominant mechanism in large pipes at low mass and heat flux, with the heat transfer coefficient being less sensitive to the total mass flux

  1. Rényi entropy flows from quantum heat engines

    Science.gov (United States)

    Ansari, Mohammad H.; Nazarov, Yuli V.

    2015-03-01

    We evaluate Rényi entropy flows from generic quantum heat engines (QHE) to a weakly coupled probe environment kept in thermal equilibrium. We show that the flows are determined not only by heat flow but also by a quantum coherent flow that can be separately measured in experiment apart from the heat flow measurement. The same pertains to Shannon entropy flow. This appeals for a revision of the concept of entropy flows in quantum nonequlibrium thermodynamics.

  2. Heat transfer studies in a spiral plate heat exchanger for water: palm oil two phase system

    Directory of Open Access Journals (Sweden)

    S. Ramachandran

    2008-09-01

    Full Text Available Experimental studies were conducted in a spiral plate heat exchanger with hot water as the service fluid and the two-phase system of water ? palm oil in different mass fractions and flow rates as the cold process fluid. The two phase heat transfer coefficients were correlated with Reynolds numbers (Re in the form h = a Re m, adopting an approach available in literature for two phase fluid flow. The heat transfer coefficients were also related to the mass fraction of palm oil for identical Reynolds numbers. The two-phase multiplier (ratio of the heat transfer coefficient of the two phase fluid and that of the single phase fluid was correlated with the Lockhart Martinelli parameter in a polynomial form. This enables prediction of the two-phase coefficients using single-phase data. The predicted coefficients showed a spread of ± 10 % in the laminar range.

  3. Heat transfer studies in a spiral plate heat exchanger for water: palm oil two phase system

    Scientific Electronic Library Online (English)

    S., Ramachandran; P., Kalaichelvi; S., Sundaram.

    2008-09-01

    Full Text Available Experimental studies were conducted in a spiral plate heat exchanger with hot water as the service fluid and the two-phase system of water ? palm oil in different mass fractions and flow rates as the cold process fluid. The two phase heat transfer coefficients were correlated with Reynolds numbers ( [...] Re) in the form h = a Re m, adopting an approach available in literature for two phase fluid flow. The heat transfer coefficients were also related to the mass fraction of palm oil for identical Reynolds numbers. The two-phase multiplier (ratio of the heat transfer coefficient of the two phase fluid and that of the single phase fluid) was correlated with the Lockhart Martinelli parameter in a polynomial form. This enables prediction of the two-phase coefficients using single-phase data. The predicted coefficients showed a spread of ± 10 % in the laminar range.

  4. AUTOMATIC EVOLUTION OF HEAT EXCHANGER NETWORKS WITH SIMULTANEOUS HEAT EXCHANGER DESIGN

    Scientific Electronic Library Online (English)

    F.S., LIPORACE; F.L.P., PESSOA; E.M., QUEIROZ.

    1999-03-01

    Full Text Available Recently, a new software (AtHENS) that automatically synthesizes a heat exchanger network with minima consumption of utilities was developed. This work deals with the next step, which represents the evolution of the initial network. Hence, new procedures to identify and break loops are incorporated, [...] for which a new algorithm is proposed. Also, a heat exchanger design procedure which uses the available pressure drop to determine the film coefficient on the tube side and shell side is added, providing the utilization of more realistic heat exchangers in the network during its optimization. Results obtained from a case study point to the possibility of equipment design having a strong influence on the network synthesis.

  5. CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin Inclinations

    Directory of Open Access Journals (Sweden)

    Subodh Bahirat,

    2014-08-01

    Full Text Available ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT was used in the fin-tube heat exchanger. The fluid flow and heat transfer are simulated and result compared for both laminar and turbulent flow models k-epsilon and SST k-omega, with steady state solvers to calculate heat transfer, flow velocity and temperature fields of variable inclined fin angles (? = 00 ,100 , 200 , 300 , 400 ,500 . Model is validate by comparing the simulated value of velocity, temperature and colburn factor with experimental and numerical results investigated by WANG [1] and GHORI KIRAR [10]. Reasonable agreement is found between the simulations and other results, and the ANSYS Fluent software is sufficient for simulating the flow fields in tube fin heat exchanger.

  6. Numerical Study on Heat Transfer Performance of Crossflow Fin-tube Heat Exchanger Depending on Different Fan Positions

    International Nuclear Information System (INIS)

    The convective heat transfer of a crossflow fin-tube heat exchanger was studied numerically. In order to investigate the dependence of the heat transfer performance on the fan position, several cases with different blowing and suction types were selected for the fan position. A staggered tube arrangement was used for the heat exchanger, and the temperatures of the tube wall and air were 50 .deg. C and 30 .deg. C, respectively. The three-dimensional flow structures were examined based on the results. In addition, the convective heat transfer coefficient and mean temperature difference between the inlet and outlet of the heat exchanger were analyzed for the various fan positions, and the heat transfer performance was investigated.

  7. Heat Exchanger Anchors for Thermo-active Tunnels

    OpenAIRE

    Mimouni, Thomas; Dupray, Fabrice; Minon, Sophie; Laloui, Lyesse

    2013-01-01

    Shallow geothermal power represents an important energy resource for the heating and cooling of the buildings. Due to relatively low temperature levels encountered at shallow depths in the soil, between 10°C and 20°C, heat pumps are required to process the extracted heat, forming the so called ground source heat pump system. Different types of heat exchangers with the ground were developed in order to optimize the heat exchanges, from simple geothermal loops grouted in boreholes reaching dept...

  8. Unglazed selective absorber solar air collector: Heat exchange analysis

    Science.gov (United States)

    Njomo, D.

    Unglazed solar air collectors show promise for applications such as ventilation air heating or crop drying. In this paper a mathematical model is developed to analyze the heat exchanges in an unglazed non-porous selective absorber air heater. It is shown that at quasi-steady state the energy balance equations of the components of the collector cascade into a single first order differential equation. The solution of this differential equation is written down as an explicit expression of the local temperature of the fluid flowing in the collector in terms of the time dependent solar intensity. The effect of various parameters such as the inlet fluid temperature, the mass flow rate, and the depth of the air channel on the thermal performances of the unglazed selective absorber collector are also studied. These performances are comparable to those of a conventional two glass covers air collector for low wind speeds.

  9. Numerical Simulation of the Convective Heat Exchange in the Separation air and Oil Flows in a Staggered Bank of Round Tubes in a Wide Range of Change in the Reynolds Number

    Science.gov (United States)

    Isaev, S. A.; Zhukova, Yu. V.; Malyshkin, D. A.

    2015-07-01

    An analysis of the convective heat exchange in the separation air and oil flows in banks of heated round tubes and their hydraulic losses at Reynolds numbers changing in a wide range from 100 to 400 for the laminar flow and from 103 to 8·103 for the turbulent fl ow has been performed. For solving the Navier-Stokes and energy equations, multiblock computational technologies realized in the VP2/3 package and original procedures for correction of the pressure gradient in a fl ow and its mean-mass temperature were used. The Reynolds-averaged Navier-Stokes equations were closed using the Menter shear-stress transfer model modified with account for the curvature of streamlines within the framework of the Leshtsiner-Rody approach with an Isaev-Kharchenko-Usachov constant equal to 0.2. The results of numerical simulation were compared with the corresponding experimental data of A. Zhukaukas. The dependence of the local and integral characteristics of a fl ow of a heat-transfer agent in a staggered bank of round tubes on the properties of this agent was determined.

  10. Numerical analysis of fin-tube plate heat exchanger by using CFD technique

    Directory of Open Access Journals (Sweden)

    Ahmed F. Khudheyer

    2011-07-01

    Full Text Available Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a two-row plain fin-and-tube heat exchanger using Open FOAM, an open-source CFD code. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 330 to 7000. Model geometry is created, meshed, calculated, and post-processed using open source software. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-epsilon, and Menter SST k-omega, with steady-state solvers to calculate pressure drop, flow, and temperature fields. Model validation is carried out by comparing the simulated case friction factor f and Colburn factor j to experimental results from the literature. For friction factor determination, little difference is found between the flow models simulating laminar flow, while in transitional flow, the laminar flow model produced the most accurate results and the k-omega SST turbulence model was more accurate in turbulent flow regimes. The most accurate simulations for heat transfer in laminar flow are found using the laminar flow model, while heat transfer in transitional flow is best represented with the SST k-omega turbulence model, and heat transfer in turbulent flow is more accurately simulated with the k-epsilon turbulence model. Reasonable agreement is found between the simulations and experimental data, and the open-source software has been sufficient for simulating the flow fields in tube-fin heat exchangers.

  11. Second-Law based thermodynamic analysis of a novel heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    He, Y.L.; Lei, Y.G.; Tao, W.Q.; Zhang, J.F.; Chu, P.; Li, R. [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University (China)

    2009-01-15

    In the present investigation, second-law based thermodynamics analysis was applied to a new heat exchanger with helical baffles. The helical baffles are designed as quadrant ellipses and each baffle occupies one quadrant of the cross-section of the shell side. Experimental tests were carried out with cold water in the tube side with a constant flow rate, and hot oil on the shell side with flow rate range from 4-24 m{sup 3}/h. The temperatures and pressures for the inlet and outlet of both sides were measured. The heat transfer, pressure drop, entropy generation, and exergy loss of the new heat exchanger were investigated and compared with the results for a conventional shell-and-tube heat exchanger with segmental baffles. The computed results indicated that both the entropy generation number and exergy losses of the new heat exchanger design are lower than those of the heat exchanger with segmental baffles, which means that the novel heat exchanger has a higher efficiency than the heat exchanger with segmental baffles, from the second-law based thermodynamics viewpoint. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  12. Simultaneous heat and mass transfer to air from a compact heat exchanger with water spray precooling and surface deluge cooling

    International Nuclear Information System (INIS)

    Various methods are available to enhance heat exchanger performance with evaporative cooling. In this study, evaporative mist precooling, deluge cooling, and combined cooling schemes are examined experimentally and compared to model predictions. A flexible model of a compact, finned-tube heat exchanger with a wetted surface is developed by applying the governing conservation and rate equations and invoking the heat and mass transfer analogy. The model is applicable for dry, partially wet, or fully wet surface conditions and capable of predicting local heat/mass transfer, wetness condition, and pressure drop of the heat exchanger. Experimental data are obtained from wind tunnel experiments using a louver-fin flat-tube heat exchanger with single-phase tube-side flow. Total capacity, pressure drop, and water drainage behavior under various water usage rates and air face velocities are analyzed and compared to data for dry-surface conditions. A heat exchanger partitioning method for evaporative cooling is introduced to study partially wet surface conditions, as part of a consistent and general method for interpreting wet-surface performance data. The heat exchanger is partitioned into dry and wet portions by introducing a wet surface factor. For the wet part, the enthalpy potential method is used to determine the air-side sensible heat transfer coefficient. Thermal and hydraulic performance is compared to empirical correlations. Total capacity predictions from the model agree with the experimental results with an average deviation of 12.6%. The model is also exercised for four water augmentation schemes; results support operating under a combined mist precooling and deluge cooling scheme. -- Highlights: • A new spray-cooled heat exchanger model is presented and is validated with data. • Heat duty is shown to be asymptotic with spray flow rate. • Meaningful heat transfer coefficients for partially wet conditions are obtained. • Colburn jwet is lower than jdry but no significant change in f was observed. • Simulations suggest using combined precooling and deluge cooling scheme

  13. NUMERICAL AND EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER OF ZnO/WATER NANOFLUID IN THE CONCENTRIC TUBE AND PLATE HEAT EXCHANGERS

    OpenAIRE

    Mohammad Reza Talaie; Masoud Haghshenas Fard; Somaye Nasr

    2011-01-01

    The plate and concentric tube heat exchangers are tested by using the water-water and nanofluid-water streams. The ZnO/Water (0.5%v/v) nanofluid has been used as the hot stream. The heat transfer rate omitted of hot stream and overall heat transfer coefficients in both heat exchangers are measured as a function of hot and cold streams mass flow rates. The experimental results show that the heat transfer rate and heat transfer coefficients of the nanofluid in both of the heat exchangers is hig...

  14. Characterization of various losses in a cryogenic counterflow heat exchanger

    Science.gov (United States)

    Aminuddin, Mohammad; Zubair, Syed M.

    2014-11-01

    A detailed assessment of irreversibility, predominantly heat in-leak and axial wall conduction, is essential in accurately predicting the performance of high effectiveness heat exchangers employed in cryogenic applications. Integration into a refrigeration system as well requires consideration of parasitic heat loss by conduction from exchanger cold end to the adjacent components. Governing equations incorporating these effects in a counterflow exchanger are solved numerically and the model predictions evaluated for heat exchanger ineffectiveness and heat loss by conduction. The optimum performance mandates minimization of both. Although ineffectiveness decreases at higher longitudinal conduction, cold end loss increases with deterioration of the overall performance. Utilizing lower heat capacity rate hot fluid, nevertheless, reduces the cold end loss. Heat in-leak is relatively high with concurrent consideration of axial wall conduction and has adverse consequence on heat exchanger effectiveness. Analysis of the net heat transferred to lower stages of refrigeration reveals a critical NTU.

  15. Steam generator with duplex heat exchange tubes

    International Nuclear Information System (INIS)

    The invention claims a design of a steam generator for fast reactors. The advantage of the design is that it does not require additional expansion tanks for the steam generator and that the steam generator may be filled with indication liquid, e.g., sodium, after assembly work has been completed at the power plant. Another advantage is that in a vertical steam generator with duplex heat exchange tubes the configuration facilitates the detection of a failure of the walls of the duplex tubes. (J.P.)

  16. LMFBR intermediate-heat-exchanger experience

    International Nuclear Information System (INIS)

    This paper presents developmental and operating experience of large Intermediate Heat Exchangers (IHX's) in US from the Fast Flux Test Facility (FFTF) to the Clinch River Breeder Reactor Plant (CRBRP) to the Large Development Plant (LDP). Design commonalities and deviations among these IHX's are synopsized. Various developmental tests that were conducted in the areas of hydraulic, structural and mechanical design are also presented. The FFTF is currently operating. Performance data of the FFTF IHXs are reviewed, and comparisons between actual and predicted performances are made. The results are used to assess the adequacy of IHX designs

  17. LMFBR intermediate-heat-exchanger experience

    Energy Technology Data Exchange (ETDEWEB)

    Cho, S.M.; Beaver, T.R.

    1983-01-01

    This paper presents developmental and operating experience of large Intermediate Heat Exchangers (IHX's) in US from the Fast Flux Test Facility (FFTF) to the Clinch River Breeder Reactor Plant (CRBRP) to the Large Development Plant (LDP). Design commonalities and deviations among these IHX's are synopsized. Various developmental tests that were conducted in the areas of hydraulic, structural and mechanical design are also presented. The FFTF is currently operating. Performance data of the FFTF IHXs are reviewed, and comparisons between actual and predicted performances are made. The results are used to assess the adequacy of IHX designs.

  18. Fouling and corrosion of freshwater heat exchangers

    International Nuclear Information System (INIS)

    Fouling in freshwater heat exchangers (HX) costs the Canadian nuclear power industry millions of dollars annually in replacement energy and capital equipment. The main reasons are loss of heat transfer and corrosion. Underdeposit pitting is the predominant corrosion mechanism. Erosion corrosion has also been observed. Failure analyses, field studies, and laboratory research have provided us with information to help explain the reasons for reduced performance. Newly installed HX tubing immediately becomes colonized with a complex community of bacteria in a slimey organic matrix. The biofilm itself produces corrosive species and in addition it promotes the attachment of sediment particles and the deposition of calcareous material. The result is a thick, adherent deposit which creates crevices, concentrates aggressive species and alters the system's hydrodynamics

  19. Basic characteristics of heat-exchanger type steam reformer heated by high temperature helium gas, (2)

    International Nuclear Information System (INIS)

    A computer simulation model has been developed to analyze the basic characteristics of heat-exchanger type steam-methane reformer which is the key component to produce hydrogen using the nuclear process heat from high temperature gas cooled reactor. This model is based on the one-dimensional one taking account of heat transfer and reaction kinetics. In the previous report, the analytical model and the solution procedure have been described, and an example of calculation result has been shown compared with the experimental data in reference. This report describes simulation results of the dependencies of the characteristic quantities such as heat flux, reaction rates and hydrogen production rate in reformer tube on selected parameters, namely, the operating conditions (inlet gas temperatures, pressure and flow rates), the activities of the catalyst, the heat transfer rate and the dimensions of reaction tube. (author)

  20. Effect of Liquid/Vapour Maldistribution on the Performance of Plate Heat Exchanger Evaporators

    DEFF Research Database (Denmark)

    Jensen, Jonas Kjær; Kærn, Martin Ryhl

    2015-01-01

    Plate heat exchangers are often applied as evaporators in industrial refrigeration and heat pump systems. In the design and modelling of such heat exchangers the flow and liquid/vapour distribution is often assumed to be ideal. However, maldistribution may occur and will cause each channel to behave differently due to the variation of the mass flux and vapour quality. To evaluate the effect of maldistribution on the performance of plate heat exchangers, a numerical model is developed in which the mass, momentum and energy balances are applied individually to each channel, including suitable correlations for heat transfer and pressure drop. The flow distribution on both the refrigerant and secondary side is determined based on equal pressure drop while the liquid/vapour distribution is imposed to the model. Results show that maldistribution may cause up to a 25 % reduction of the overall heat transfer coefficient, compared to a lumped model with uniform distribution.

  1. New waste heat district heating system with combined heat and power based on absorption heat exchange cycle in China

    International Nuclear Information System (INIS)

    A new waste heat district heating system with combined heat and power based on absorption heat exchange cycle (DHAC) was developed to increase the heating capacity of combined heat and power (CHP) through waste heat recovery, and enhance heat transmission capacity of the existing primary side district heating network through decreasing return water temperature by new type absorption heat exchanger (AHE). The DHAC system and a conventional district heating system based on CHP (CDH) were analyzed in terms of both thermodynamics and economics. Compared to CDH, the DHAC increased heating capacity by 31% and increased heat transmission capacity of the existing primary side district heating network by 75%. The results showed that the exergetic efficiency of DHAC was 10.41% higher and the product exergy monetary cost was 36.6¥/GJ less than a CHD. DHAC is an effective way to increase thermal utilization factor of CHP, and to reduce district heating cost. - Highlights: ? Absorption heat pumps are used to recover waste heat in CHP. ? Absorption heat exchanger can reduce exergy loss in the heat transfer process. ? New waste heat heating system (DHAC) can increase heating capacity of CHP by 31%. ? DHAC can enhance heat transmission capacity of the primary pipe network by 75%. ? DHAC system has the higher exergetic efficiency and the better economic benefit.

  2. Finned heat exchanger. Ib. General and basic aspects

    International Nuclear Information System (INIS)

    This paper is a review of the main literature studies about the finned heat exchanger modelling and simulation. Finned heat exchangers are used in cryogenic industry, nuclear industry, food industry, medicine, etc.. The aspects concerning the air circulation through the heat exchanger component tubes are studied, as well as those involved in the thermal transfer from technological fluid to wall or from fin to air. A particular attention is devoted to the physical and mathematical complete models of finned heat exchangers, as well as to the criterial relationship for the calculation of the partial heat transfer to air (?2), fin efficiency (?a) and friction coefficient (f). Details are also given about the influence of the thermal contact resistance on the finned heat exchanger performance. This study is a useful tool for a correct technological sizing of this type of heat exchangers. (authors)

  3. Performance of multi tubes in tube helically coiled as a compact heat exchanger

    Science.gov (United States)

    Nada, S. A.; El Shaer, W. G.; Huzayyin, A. S.

    2014-12-01

    Multi tubes in tube helically coiled heat exchanger is proposed as a compact heat exchanger. Effects of heat exchanger geometric parameters and fluid flow parameters; namely number of inner tubes, annulus hydraulic diameter, Reynolds numbers and input heat flux, on performance of the heat exchanger are experimentally investigated. Different coils with different numbers of inner tubes, namely 1, 3, 4 and 5 tubes, were tested. Results showed that coils with 3 inner tubes have higher values of heat transfer coefficient and compactness parameter (bar{h} Ah ). Pressure drop increases with increasing both of Reynolds number and number of inner tubes. Correlations of average Nusselt number were deduced from experimental data in terms of Reynolds number, Prandtl number, Number of inner coils tubes and coil hydraulic diameter. Correlations prediction was compared with experimental data and the comparison was fair enough.

  4. Polar Heat Flow on Io

    Science.gov (United States)

    Veeder, G. J.; Matson, D. L.; Johnson, T. V.; Davies, A. G.; Blaney, D. L.

    2003-01-01

    Recently, Galileo spacecraft data have revealed Io's polar regions to be much warmer than previously expected. This unexpected development came from Photo-Polarimeter Radiometer (PPR) data which show that the minimum night temperatures are in the range of 90-95 K virtually everywhere on Io. The minimum night temperatures show no dependence upon latitude and, when away from the sunset terminator, they show no dependence upon time of night. This is indeed bizarre behavior for surface units which generally had been assumed to be passive with respect to Io's pervasive volcanism. Night temperatures of 90-95 K at high, polar latitudes are particularly hard to explain. Even assuming infinite thermal inertia, at these latitudes there is insufficient sunlight to support these warm night temperatures. Thus, through the process of elimination of other possibilities, we come to the conclusion that these surfaces are volcanically heated. Taking previously passive units and turning them into new sources of heat flow is a radical departure from previous thermophysical model paradigms. However, the geological interpretation is straight forward. We are simply seeing the effect of old, cool lava flows which cover most of the surface of Io but yet have some heat to radiate. Under these new constraints, we have taken on the challenge of formulating a physical model which quantitatively reproduces all of the observations of Io's thermal emission. In the following we introduce a new parametric model which suffices to identify a previously unrecognized polar component of Io's heat flow.

  5. Design of the Glenwood Springs downhole heat exchanger

    Science.gov (United States)

    Chiu, P.

    1982-04-01

    A heat exchanger has been designed to obtain 250,000 Btu/hr from a 20 in. diameter geothermal well at various brine temperatures. The system consists of a 10 in. diameter plastic pipe to promote convective flow in the well and a 4 in. diameter, Schedule 40 steel U-tube containing distilled water to extract the energy. Subject to the validity of the major assumptions, the required lengths of one leg of the U-tube at various brine temperatures are 34 ft (1500 F), 42 ft (1400 F), 54 ft (1300 F), and 75 ft (1200 F) for a mean working fluid temperature of 900 F.

  6. Heat transfer pipe shielding device for heat exchanger

    International Nuclear Information System (INIS)

    The front face and the rear face of a frame that surrounds the circumference of the water chamber body of a multi-tube heat exchanger are covered by a rotational shielding plate. A slit is radially formed to the shielding plate for the insertion of a probe or cleaner to the heat transfer pipe and a deflector is disposed on the side opposite to the slit. The end of the heat transfer pipe to be inspected is exposed to the outer side by way of the slit by the rotation of the shielding plate, and the probe or cleaner is inserted in the heat transfer pipe to conduct an eddy current injury monitoring test or cleaning. The inside of the water chamber and the heat transfer pipe is exhausted by a ventilation nozzle disposed to the frame. Accordingly, a shielding effect upon inspection and cleaning can be obtained and, in addition, inspection and exhaustion at the cleaning position can be conducted easily. Since the operation for attachment and detachment is easy, the effect of reducing radiation dose per unit can be obtained by the shortening of the operation time. (N.H.)

  7. Exchange flow in a shallow lake embayment.

    Science.gov (United States)

    Pálmarsson, Sveinn O; Schladow, S Geoffrey

    2008-12-01

    Convectively driven currents can arise in the littoral zones of lakes, as a result of either differential heating or differential cooling of the shallow water. The result of these flows is to produce a surface flow away from shore with a bottom return flow or a bottom flow away from shore with a surface return flow. Measurements taken in a shallow embayment of Clear Lake, California, USA, show the presence of both kinds of convectively driven flows under a large variety of summer conditions. The magnitude of these flows is sufficient to transport material a distance on the order of 0.5 km during such events. Through both advection and dispersion the net result of this process would be to reduce the accumulation of particles and particle-associated contaminants such as mercury in the littoral zone and to move them offshore where they are more prone to permanent burial or further transport. PMID:19475920

  8. Continued evaluation of compact heat exchangers for OTEC evaluation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McGowan, J.G.

    1979-10-01

    The objectives of this work investigating the applicability of compact plate heat type heat exchangers to OTEC power systems were: (1) an analytical and experimental evaluation of the performance characteristics of compact heat exchangers using ammonia as the working fluid operating under the entire range of OTEC system conditions; and (2) an evaluation of the applicable manufacturing processes, maintenance requirements, and arrangement concepts for large-scale compact OTEC heat exchangers with specific emphasis on total economics. The work was carried out to establish the applicability of compact plate type heat exchangers to OTEC power systems and to provide: (1) experimental verification of predicted performance (heat transfer and fluid flow) under OTEC operating conditions (using NH/sub 3/); (2) provide initial performance data for several desirable plate type OTEC heat exchanger panels; (3) provide test apparatus for continued experimental testing of OTEC compact heat exchanger panels; and (4) provide design information on applicable manufacturing processes maintenance requirements and arrangement concepts for plate type heat exchangers.

  9. Heat exchanger for fuel cell power plant reformer

    Science.gov (United States)

    Misage, Robert (Manchester, CT); Scheffler, Glenn W. (Tolland, CT); Setzer, Herbert J. (Ellington, CT); Margiott, Paul R. (Manchester, CT); Parenti, Jr., Edmund K. (Manchester, CT)

    1988-01-01

    A heat exchanger uses the heat from processed fuel gas from a reformer for a fuel cell to superheat steam, to preheat raw fuel prior to entering the reformer and to heat a water-steam coolant mixture from the fuel cells. The processed fuel gas temperature is thus lowered to a level useful in the fuel cell reaction. The four temperature adjustments are accomplished in a single heat exchanger with only three heat transfer cores. The heat exchanger is preheated by circulating coolant and purge steam from the power section during startup of the latter.

  10. Finned heat exchangers. Ia. General and basic aspects

    International Nuclear Information System (INIS)

    This paper is a review of the main literature studies about the finned heat exchanger modelling and simulation. Finned heat exchangers are used in cryogenic industry, nuclear industry, food industry, medicine, etc. The aspects concerning the air circulation through the heat exchanger component tubes are studied, as well as those involved in the thermal transfer from technological fluid to wall or from fin to air. A particular attention is devoted to the physical and mathematical complete models of finned heat exchangers, as well as to the criterial relationship for the calculation of the partial thermal transfer to air, ?2, fin efficiency, ?a and friction coefficient, f. Details are also given about the influence of the thermal contact resistance on the finned heat exchanger performance. This study is a useful tool for a correct technological sizing of this heat exchanger type. (authors)

  11. Performance of multiple mini-tube heat exchangers as an internal heat exchanger of a vapor-injection cycle heat pump

    Science.gov (United States)

    Jang, Jin Yong; Jeong, Ji Hwan

    2015-05-01

    A multiple mini-tube (MMT) heat exchanger was considered as an internal heat exchanger of vapor-injection cycle heat pump. Heat transfer and pressure drop in multiple mini-tube heat exchangers were numerically and experimentally investigated. Results show that the best performance of the MMT heat exchanger can be obtained when the intermediate-pressure two-phase refrigerant is supplied to the shell-side and this refrigerant reaches a saturated vapor state at the exit of the heat exchanger.

  12. Free shear layer and swirl flow heat transfer enhancement

    Science.gov (United States)

    Wirtz, R. A.; Greiner, M.; Snyder, B.

    1990-05-01

    Two wall shape induced convective heat transfer enhancement mechanisms for channel flows are investigated. The first uses transverse grooves in a channel wall to produce unstable free shear layers which cause traveling waves to be superimposed on the mean flow, thus augmenting heat transfer. The second uses streamline curvature to produce a swirling secondary flow. In this case, a serpentine channel is investigated. Flow visualization and heat transfer/pressure drop measurements with both air and water show that the expected augmentation mechanisms are operable in both the grooved and serpentine channel configurations at flow rates normally encountered in compact heat exchanger applications. When compared to other enhanced surfaces (such as offset strip fins or corrugated plate fins) on an equal pumping power basis, both the grooved and serpentine configurations of the present study produce performance curves which are comparable to, and in some cases superior to other conventional techniques.

  13. Numerical Simulation of Thermal Performance of Printed Circuit Heat Exchangers with Microchannels of Different Shapes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yeon Hwa; Lee, Kyu Jung [Korea University, Seoul (Korea, Republic of); Moon, Dong Ju [Korea Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Yoon Ho [Samgsung Electronics Company, Suwon (Korea, Republic of)

    2011-01-15

    The performance of microchannel PCHE (Printed Circuit Heat Exchanger) is superior to that of other existing commercial heat exchangers. Further, it is also more efficient than other heat exchangers. Various microchannels, whose shapes are straight (I), Wavy, Beehive, Surf, I-Wavy, I-Beehive, or I-Surf, are computationally modeled in this study. The counter-flow arrangement is used, and the flow characteristics, heat transfer, and pressure drop in the microchannels under various mass flow rate conditions are investigated. The results for I microchannel is chosen as the benchmarks and is compared with those of newly proposed microchannels. It is found that the surf-shaped microchannel is most efficient in improving the overall performance of a PCHE.

  14. Entropy flow in quantum heat engines

    Science.gov (United States)

    Ansari, Mohammad; Nazarov, Yuli

    2015-03-01

    We evaluate Shannon and Renyi entropy flows from generic quantum heat engines (QHE) to a weakly-coupled probe environment kept in thermal equilibrium. We show the flows are determined by two quantities: heat flow and fictitious dissipation that manifest the quantum coherence in the engine. Our theory leads to novel physics in quantum heat engines.

  15. Heat exchanger tube vibration: comparison between operating experiences and vibration analyses

    International Nuclear Information System (INIS)

    Tube failures due to excessive flow-induced vibration must be avoided to assure the reliable performance of heat exchangers. Such components must be thoroughly analysed for vibration at the design stage. Several flow-induced vibration mechanisms are possible. In this paper, particular attention is given to fluidelastic instability of tube bundles subjected to liquid and two-phase cross-flow. The performance of ten operating heat exchanger components is reviewed to validate our recommended vibration analysis guidelines. Both tube failure histories and satisfactory performances are considered. The results show that a fluidelastic instability constant K=3.3 is a reasonable design criterion. (auth)

  16. Numerical study on turbulent heat transfer and pressure drop of nanofluid in coiled tube-in-tube heat exchangers

    International Nuclear Information System (INIS)

    Highlights: • The performance of helically coiled tube heat exchanger using nanofluid is modeled. • The 3D turbulent flow and conjugate heat transfer of CTITHE are solved using FVM. • The effects of nanoparticle concentration and curvature ratio are investigated. • The Gnielinski correlation for Nu for turbulent flow in helical tubes can be used for water-based Al2O3 nanofluid. - Abstract: A computational fluid dynamics (CFD) study has been carried out to study the heat transfer and pressure drop characteristics of water-based Al2O3 nanofluid flowing inside coiled tube-in-tube heat exchangers. The 3D realizable k–? turbulent model with enhanced wall treatment was used. Temperature dependent thermophysical properties of nanofluid and water were used and heat exchangers were analyzed considering conjugate heat transfer from hot fluid in the inner-coiled tube to cold fluid in the annulus region. The overall performance of the tested heat exchangers was assessed based on the thermo-hydrodynamic performance index. Design parameters were in the range of; nanoparticles volume concentrations 0.5%, 1.0% and 2.0%, coil diameters 0.18, 0.24 and 0.30 m, inner tube and annulus sides flow rates from 2 to 5 LPM and 10 to 25 LPM, respectively. Nanofluid flows inside inner tube side or annular side. The results obtained showed a different behavior depending on the parameter selected for the comparison with the base fluid. Moreover, when compared at the same Re or Dn, the heat transfer coefficient increases by increasing the coil diameter and nanoparticles volume concentration. Also, the friction factor increases with the increase in curvature ratio and pressure drop penalty is negligible with increasing the nanoparticles volume concentration. Conventional correlations for predicting average heat transfer and friction factor in turbulent flow regime such as Gnielinski correlation and Mishra and Gupta correlation, respectively, for helical tubes are also valid for the tested nanofluids which suggests that nanofluids behave like a homogeneous fluid

  17. Liquid-Liquid Heat Exchanger With Zero Interpath Leakage Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Future manned spacecraft will require thermal management systems that effectively and safely control the temperature in inhabited modules. Interface heat exchangers...

  18. Study regarding the influence of the crimping angle on the performances of the heat exchangers

    Directory of Open Access Journals (Sweden)

    Opruta D.

    2013-04-01

    Full Text Available The aim of this study is to determine the geometry of a plate for heat exchanger with high heat flow and low values for pressure losses. For this, in Solid Work software, were designed three plate geometries with different crimping angles for the flow channels. Was analyzed the influence of the crimping angle ? on the fluid distribution and heat transfer. Also, were compared the data resulted from Computational Fluid Dynamics numeric simulation with the experimental ones for the plate heat exchangers with gaskets. The analysis of the vortices and temperature field distribution was achieved with the aid of simulation software Fluent. In order to validate the numerical simulation's results experimental research were carried out on a heat exchangers stand

  19. A new ejector heat exchanger based on an ejector heat pump and a water-to-water heat exchanger

    International Nuclear Information System (INIS)

    Highlights: • EHE is based on the reverse Carnot cycle and current heat transfer mechanisms. • EHE can decrease the return water temperature in the PHN to 35 °C. • EHE can increase the heating capacity of the existed PHN by approximately 43%. • The return water temperature in the PHN is much lower than that in the SHN. • EHE has a simpler structure, lower manufacture cost, and better regulation characteristics. - Abstract: As urban construction has been developing rapidly in China, urban heating load has been increasing continually. Heating capacity of the existed primary heating network (PHN) cannot meet district heating requirements of most metropolises in northern China. A new type of ejector heat exchanger (EHE) based on an ejector heat pump and a water-to-water heat exchanger (WWHE) was presented to increase the heating capacity of the existed PHN, and the EHE was also analyzed in terms of laws of thermodynamics. A new parameter, the exergy distribution ratio (EDR), is introduced, which is adopted to analyze regulation characteristics of the EHE. We find that the EHE shows better performance when EDR ranges from 44% to 63%. EHE can decrease the temperature of return water in the PHN to 35 °C, therefore, this can increase the heating capacity of existed PHN by about 43%. The return water with lower temperature in the PHN could recover more low-grade waste heat in industrial systems. Because of its smaller volume and lower investment, EHEs could be applied more appropriately in district heating systems for long-distance heating and waste heat district heating systems

  20. Thermal energy storage heat exchanger: Molten salt heat exchanger design for utility power plants

    Science.gov (United States)

    Ferarra, A.; Yenetchi, G.; Haslett, R.; Kosson, R.

    1977-01-01

    The use of thermal energy storage (TES) in the latent heat of molten salts as a means of conserving fossil fuels and lowering the cost of electric power was evaluated. Public utility systems provided electric power on demand. This demand is generally maximum during late weekday afternoons, with considerably lower overnight and weekend loads. Typically, the average demand is only 60% to 80% of peak load. As peak load increases, the present practice is to purchase power from other grid facilities or to bring older less efficient fossil-fuel plants on line which increase the cost of electric power. The widespread use of oil-fired boilers, gas turbine and diesel equipment to meet peaking loads depletes our oil-based energy resources. Heat exchangers utilizing molten salts can be used to level the energy consumption curve. The study begins with a demand analysis and the consideration of several existing modern fossil-fuel and nuclear power plants for use as models. Salts are evaluated for thermodynamic, economic, corrosive, and safety characteristics. Heat exchanger concepts are explored and heat exchanger designs are conceived. Finally, the economics of TES conversions in existing plants and new construction is analyzed. The study concluded that TES is feasible in electric power generation. Substantial data are presented for TES design, and reference material for further investigation of techniques is included.

  1. FASTEF Heat exchanger tube rupture CFD simulation

    International Nuclear Information System (INIS)

    The aim of this technical note is to present CFD simulations of a tube rupture incidental scenario in a Primary Heat eXchanger (PHX)/Primary Pump (PP) assembly for two design variants of the FAst-Spectrum Transmutation Experimental Facility FASTEF ongoing design, in the framework of the FP7 Central Design Team (CDT) European project. The simulation domain reproduces with some simplification the entire primary coolant loop. The objective is to understand whether it is necessary take some counter-measures to avoid the ingress of steam in the cold plenum. The simulation has been performed on two successive updates of the design and of the nominal operation. The simulations show a good resistance to steam ingress, under the condition that provision is made to avoid an excessive accumulation of steam at the top of the PHX/PP assembly casing.

  2. FASTEF Heat exchanger tube rupture CFD simulation

    Energy Technology Data Exchange (ETDEWEB)

    Moreau, V., E-mail: moreau@crs4.it [CRS4, Centre for Advanced Studies, Research and Development in Sardinia, Polaris, Edificio 1, 09010 Pula, CA (Italy)

    2012-11-15

    The aim of this technical note is to present CFD simulations of a tube rupture incidental scenario in a Primary Heat eXchanger (PHX)/Primary Pump (PP) assembly for two design variants of the FAst-Spectrum Transmutation Experimental Facility FASTEF ongoing design, in the framework of the FP7 Central Design Team (CDT) European project. The simulation domain reproduces with some simplification the entire primary coolant loop. The objective is to understand whether it is necessary take some counter-measures to avoid the ingress of steam in the cold plenum. The simulation has been performed on two successive updates of the design and of the nominal operation. The simulations show a good resistance to steam ingress, under the condition that provision is made to avoid an excessive accumulation of steam at the top of the PHX/PP assembly casing.

  3. Multiple utilities targeting for heat exchanger networks

    International Nuclear Information System (INIS)

    A targeting methodology is proposed to determine the optimum loads for multiple utilities considering the cost tradeoffs in energy and capital for heat exchanger networks (HENs). The method is based on a newly-developed Cheapest Utility Principle (CUP), which simply states that it is optimal to increase the load of the cheapest utility and maintain the loads of the relatively expensive utilities constant while increasing the total utility consumption. In other words, the temperature driving forces at the utility pinches once optimized do not change even when the minimum approach temperature (?Tmin) at the process pinch is varied. The CUP holds rigorously when the relationship between the exchanger area and the capital cost is linear. Even when the relationship is non-linear, it proves to be an excellent approximation that reduces the computational effort during multiple utilities targeting. By optimizing the utility pinches sequentially and recognizing that these optimized utility pinches essentially do not change with the process ?Tmin, the results can be elegantly represented through the optimum load distribution (OLD) plots introduced in this work. (author)

  4. Fluid induced structural vibrations in steam generators and heat exchangers

    International Nuclear Information System (INIS)

    Fluid-elastic instability (FEI) in tube bundle heat exchangers was studied experimentally. The motion of an array of 15 stainless steel vibrating tubes (? 25.4mm) in water cross-flow, suspended using stainless steel piano wire has been recorded with a CCD camera. The individual motion and relative motion of the tubes are reported and can be used for computational model validation. The relative displacement of the tubes allows identification of the most potentially damaging patterns of tube bundle vibration. A critical reduced velocity may be determined by specification of an allowable limit on tube motion amplitude. Measurements were made for various tube array configurations, tube natural frequencies and flow conditions. (author)

  5. CFD Simulation Studies on the Performance of Rectangular Coil Heat Exchanger

    Science.gov (United States)

    Samsudeen, N.; Anantharaman, N.; Raviraj, Pol.

    2010-10-01

    The simulation studies are made to understand the concept of heat transfer by convection in a rectangular coiled type heat exchanger. The rectangular coil heat exchanger consists of inner and outer coil arrangements with several straight portions and bends so that the exterior flow is very similar to flow within tube-bundles. The present work focuses mainly on exploring the various flow pattern and temperature distribution through the pipe. Computer simulation studies were performed for four different angle of tube bundle inclination (0°, 30°, 60°, and 90°) with two set flow arrangements (inline and staggered arrangement) in the shell side of the heat exchanger. The simulation results show that the effect of the tube bundle inclination on the fluid velocity distribution and the heat transfer performance is observed maximum for the coil with tube bundle inclination angle between 30 degrees and 60 degrees with the staggered arrangement than with the inline arrangement due to proper mixing in the shell side and the outside flow over the tube bundle helps to create turbulence without increasing the velocity in the shell side of the heat exchanger.

  6. Numerical Analysis of a Multi-Row Multi-Column Compact Heat Exchanger

    International Nuclear Information System (INIS)

    In the present study we carry out three-dimensional fluid flow and heat transfer simulations on the external side of a compact heat exchanger to analyze the interaction between the fluid and its geometry. The overall objective is to use the resulting information for the design of more compact devices. The type of heat exchanger considered here is the common plain-fin and tube, with air flowing over the tubes and water as the inner-tube fluid. Two heat exchanger configurations, in which the tube arrangement is either in-line or staggered, conform the basic geometries. The size of the heat exchanger –regardless of the type of arrangement– which serves as the baseline for the parametric analysis, is defined by fixing its length; i.e., the number of rows in the flow direction. For the two heat exchanger configurations examined here, the dimensional form of the governing equations, along with the corresponding boundary conditions, are solved under specific flow and temperature values using a finite element method to compute the velocity, pressure and temperature fields. From these, the heat transfer rate and pressure drop are then calculated. The computations are performed for a range in the values of the Reynolds number within the laminar regime. For all cases considered, results from this investigation indicate that the geometrical arrangement plays a major role in the amount of heat being exchanged and that, for a given device, the length needed to exchange 99% of the corresponding amount of energy that may be transferred by the baseline model, is confined to less than 30% of the size of the original device.

  7. The effect of external factors on the characteristics of waste heat heat exchangers of a GPA

    Energy Technology Data Exchange (ETDEWEB)

    Makar, R.M.; Ostapenko, A.N.; Patychenko, A.S.; Sereda, N.I.; Shelkovskiy, B.I.

    1983-01-01

    The effect of different factors in operational conditions is examined on the basic parameters of waste heat heat exchangers of gas pumping units with gas turbine motors. The range is shown of the regulation of the heat conductivity in heat exchangers with standard gate valve units. The obtained data make it possible to develop a VER for specific conditions.

  8. Superphenix 1 intermediate heat exchanger fabrication

    International Nuclear Information System (INIS)

    The eight Superphenix 375-MW (thermal) intermediate heat exchangers (IHXs) are similar in overall design to the Phenix components. Detailed design changes had to be made during fabrication on the following grounds: Due to seismic resistance, the support area was raised as high as possible to situate the component natural frequencies well out of the resonance peak range and remove thick plate-to-shell connections from heavy thermal load areas. Integration of lessons drawn from the Phenix incidents, due mainly to secondary sodium radial temperature disparities, resulted in the design of a more adaptable outlet header, together with a sodium mixing device, and in the reduction of temperature differences by heat insulation. To avoid circumferential temperature disparities, the iron shot biological shielding plug was replaced by stacked stainless steel plates within an outer shell, which in the new design, is not a supporting structure. The thermal-hydraulic and mechanical design of the component necessitated the elaboration of sophisticated computer codes, with validation of results on mock-ups. The detailed design studies and the actual manufacturing work had to adapt to both design developments and to inherent fabrication difficulties, mainly related to the very tight tolerances imposed for these exceptionally large components and to the welding of steel with an excessive boron content. The construction of the Creys-Malville IHXs afforded valuable industrial experience, which should provide a basis for the design of simpler and less costly IHX units for the forthcoming 1500-MW (electric) breeder

  9. Numerical studies of an eccentric tube-in-tube helically coiled heat exchanger for IHEP-ADS helium purification system

    CERN Document Server

    Zhang, Jianqin

    2014-01-01

    The tube-in-tube helically coiled (TTHC) heat exchanger is preferred in the purifier of IHEP-ADS helium purification system. The position of an internal tube is usually eccentric in a TTHC heat exchanger in practice, while most TTHC heat exchangers in the literature studied are concentric. In this paper, TTHC heat exchangers with different eccentricity ratios are numerically studied for turbulent flow and heat transfer characteristics under different flow rates. The fluid considered is helium at the pressure of 20Mpa, with temperature dependent thermo-physical properties for the inner tube and the annulus. The inner Nusselt number between the concentric and eccentric TTHC heat exchangers are compared, so is the annulus Nusselt number. The results show that with the eccentricity increasing, the annulus Nusselt number increases substantially. According to the numerical data, new empirical correlations of Nusselt number as a function of Reynolds number and eccentricity for the inner tube and the annulus are pres...

  10. A Liquid-Liquid Thermoelectric Heat Exchanger as a Heat Pump for Testing Phase Change Material Heat Exchangers

    Science.gov (United States)

    Sheth, Rubik B.; Makinen, Janice; Le, Hung V.

    2016-01-01

    The primary objective of the Phase Change HX payload on the International Space Station (ISS) is to test and demonstrate the viability and performance of Phase Change Material Heat Exchangers (PCM HX). The system was required to pump a working fluid through a PCM HX to promote the phase change material to freeze and thaw as expected on Orion's Multipurpose Crew Vehicle. Due to limitations on ISS's Internal Thermal Control System, a heat pump was needed on the Phase Change HX payload to help with reducing the working fluid's temperature to below 0degC (32degF). This paper will review the design and development of a TEC based liquid-liquid heat exchanger as a way to vary to fluid temperature for the freeze and thaw phase of the PCM HX. Specifically, the paper will review the design of custom coldplates and sizing for the required heat removal of the HX.

  11. Development of heat resistant ion exchange resin. First Report

    International Nuclear Information System (INIS)

    In nuclear power stations, as a means of maintaining the soundness of nuclear reactors, the cleaning of reactor cooling water has been carried out. But as for the ion exchange resin which is used as the cleaning agent in the filtrating and desalting facility in reactor water cleaning system, since the heat resistance is low, high temperature reactor water is cooled once and cleaned, therefore large heat loss occurs. If the cleaning can be done at higher temperature, the reduction of heat loss and compact cleaning facilities become possible. In this study, a new ion exchange resin having superior heat resistance has been developed, and the results of the test of evaluating the performance of the developed ion exchange resin are reported. The heat loss in reactor water cleaning system, the heat deterioration of conventional ion exchange resin, and the development of the anion exchange resin of alkyl spacer type are described. The outline of the performance evaluation test, the experimental method, and the results of the heat resistance, ion exchange characteristics and so on of C4 resin are reported. The with standable temperature of the developed anion exchange resin was estimated as 80 - 90degC. The ion exchange performance at 95degC of this resin did not change from that at low temperature in chloride ions and silica, and was equivalent to that of existing anion exchange resin. (K.I.)

  12. Simulation model air-to-air plate heat exchanger

    International Nuclear Information System (INIS)

    A simple simulation model of an air-to-air plate heat exchanger is presented. The model belongs to a collection of simulation models that allows the efficient computer simulation of heating, ventilation, and air-conditioning (HVAC) systems. The main emphasis of the models is to shorten computation time and to use only input data that are known in the design process of an HVAC system. The target of the models is to describe the behavior of HVAC components in the part-load operation mode, which is becoming increasingly important in energy efficient HVAC systems. The models are intended to be used for yearly energy calculations or load calculations with time steps of about 10 minutes or larger. Short- time dynamic effects, which are of interest for different aspects of control theory, are neglected. The part-load behavior is expressed in terms of the nominal condition and the dimensionless variation of the heat transfer with change of mass flow and temperature. The effectiveness- NTU relations are used to parametrize the convective heat transfer at nominal conditions and to compute the part-load condition. If the heat transfer coefficients on the two exchanger sides are not equal (i. e. due to partial bypassing of air), their ratio can be easily calculated and set as a parameter. The model is static and uses explicit equations only. The explicit model formulation ensures short computation time and numerical stability, which allows using the model with sophisticated engineering methods like automatic system optimization. This paper fully outlines the algorithm description and its simplifications. It is not tailored for any particular simulation program to ensure easy implementation in any simulation program

  13. CFD Analysis of Shell and Tube Heat Exchanger to Study the Effect of Baffle Cut on the Pressure Drop

    Directory of Open Access Journals (Sweden)

    Avinash D Jadhav

    2014-07-01

    Full Text Available The shell side design of a shell and tube heat exchanger; in particular the baffle spacing, baffle cut and shell diameter dependencies of the heat transfer coefficient and the pressure drop are investigated by numerically modelling a small heat exchanger. The flow and temperature fields inside the shell are resolved using a commercial CFD package. A set of CFD simulations is performed for a single shell and single tube pass heat exchanger with a variable number of baffles and turbulent flow. The results are observed to be sensitive to the turbulence model selection. The best turbulence model among the ones considered is determined by comparing the CFD results of heat transfer coefficient, outlet temperature and pressure drop with the Bell–Delaware method results. For two baffle cut values, the effect of the baffle spacing to shell diameter ratio on the heat exchanger performance is investigated by varying flow rate.

  14. Effective Heat Transfer Enhancement in Finned Tube Heat Exchanger with Different Fin Profiles

    Directory of Open Access Journals (Sweden)

    J.A.Livingston1 , P. Selvakumar2

    2013-04-01

    Full Text Available During cross flow in a heat exchanger, heat transfer in the front portion of the tube is more compared to back portion of the tube. This is due to less formation of vortices at the backside of the tube. For uniform heat transfer to take place throughout the tube, it is necessary to increase the vortex formation at the rear side of the tube. The aim of this study is to explore the possibilities of improving the flow structure and thereby increasing uniform heat transfer around the tubes by introducing special type of fin arrangement over the tubes. The effect of shape and orientation of the fin on vortex generation and respective heat transfers are studied numerically. It have been identified that by introducing special type of fin arrangement over the tube there is a possibility for increase the vortex formation at the rear portion of the tube, which significantly leads to creation of uniform heat transfer all around the tube.

  15. Influence of supercritical ORC parameters on plate heat exchanger design

    International Nuclear Information System (INIS)

    The applications of Organic Rankine Cycle (ORC) appear to be growing in the field of waste heat utilization. This thermodynamic cycle can be successfully used in the field of biomass combustion, geothermal systems or solar desalination systems, providing efficient systems. In the last years, a very intense investigation on the utilization of low temperature waste heat for supplying ORC systems has brought new research potential in the area of thermodynamic optimisation of this cycle. More specifically, the use of supercritical fluid parameters in the ORC processes seems to become more and more attractive leading to lower exergy destruction systems together with higher heat utilization systems. However, the investigation of the heat exchanger design and the heat exchange coefficients is of high importance for these applications as the effective heat transfer reflects on the overall process energetic and exergetic efficiency. It is important to study the relatively unknown heat transfer mechanisms around the critical point to improve both the heat exchanger surface and the design algorithms. The aim of this paper is to investigate the influence of the ORC parameters on the heat exchanger design. More specifically, the basic parameters of the design of the heat exchangers will be defined in the cases of supercritical fluid parameters and the convective coefficients as well as resulting heat transfer surface will be calculated for various fluid parameters. - Highlights: ? Optimisation of the heat exchanger partitioning. ? Comparison of proposed correlations for calculating heat transfer coefficients. ? Calculation of the heat transfer coefficients under supercritical fluid parameters. ? Calculation of the necessary heat transfer surface. ? Calculation of the heat exchanger efficiency under supercritical fluid parameters.

  16. THERMAL ANALYSIS OF EARTH AIR HEAT EXCHANGER USING CFD

    Directory of Open Access Journals (Sweden)

    Vaibhav Madane

    2015-05-01

    Full Text Available This project focuses on Earth Air Heat Exchanger which is reducing energy consumption in a building. The air is passing through the buried tubes and heat exchange takes place between air and surrounding soil. This equipment helps to reduce energy consumption of an air conditioning unit. This project analyses the thermal performance of earth air heat exchanger by using computational fluid dynamics modeling. The model is validated against experimental observations and investigations on an experimental setup in Ajmer. Simulation results are in fair agreement with experimental data. Effects of pipe materials on thermal performance of earth air heat exchangers are also studied for summer conditions in Mumbai. Results have shown that the performance of earth air heat exchanger is not significantly affected by material of buried pipes.

  17. The heat exchanger of small pellet boiler for phytomass

    Science.gov (United States)

    Mi?ieta, Jozef; Lenhard, Richard; Janda?ka, Jozef

    2014-08-01

    Combustion of pellets from plant biomass (phytomass) causes various troubles. Main problem is slagging ash because of low melting temperature of ash from phytomass. This problem is possible to solve either improving energetic properties of phytomass by additives or modification of boiler construction. A small-scale boiler for phytomass is different in construction of heat exchanger and furnace mainly. We solve major problem - slagging ash, by decreasing combustion temperature via redesign of pellet burner and boiler body. Consequence of lower combustion temperature is also lower temperature gradient of combustion gas. It means that is necessary to design larger heat exchanging surface. We plane to use underfed burner, so we would utilize circle symmetry heat exchanger. Paper deals design of heat exchanger construction with help of CFD simulation. Our purpose is to keep uniform water flux and combustion gas flux in heat exchanger without zone of local overheating and excess cooling.

  18. Theoretical and experimental investigation of a Moving Bed Heat Exchanger for Solar Central Receiver Power Plants

    Science.gov (United States)

    Baumann, T.; Zunft, S.

    2012-11-01

    A Moving Bed Heat Exchanger for heat extraction from solar heated granular materials is investigated with respect to flow behaviour. To overcome limitations of existing empirical models, a numerical CFD model is established and parametrised with the help of experiments. Parametric studies are performed to quantify the effect of inlet velocities on the velocity field. A good agreement with an empirical model is found. Also, a comparison with PIV measurements confirms its validity, making it a solid basis for future design work.

  19. Heat exchanger CFD analysis for the W7-X high temperature superconductor current lead prototype

    International Nuclear Information System (INIS)

    The Karlsruhe Institute of Technology (KIT) is responsible for the design, construction and testing of the high temperature superconductor current leads for the Wendelstein 7-X (W7-X) stellarator. Two prototypes of the W7-X current lead, using a meander-flow heat exchanger, have been tested in 2010 at KIT. Following an approach originally developed and applied to a sub-size mock-up heat exchanger, the Computational Fluid Dynamics code StarCD is used here for the 3D thermal-hydraulic analysis of the heat exchanger in the prototypes. The resulting friction and Nusselt parameters are then fed to a global 1D model of the current lead and the results compared to the measured pressure drop and temperature profiles along the heat exchanger.

  20. The thermodynamics of heat- and mass exchange in chemical engineering. Vol. 1. 2. rev. ed.

    International Nuclear Information System (INIS)

    The second and completely revised edition of the approved textbook 'The thermodynamics of heat- and mass exchange in chemical engineering' is devoted to students of technical and natural science disciplines as well as to practicians and scientists, which are confronted with thermodynamical problems of chemical engineering. Starting from the different phases and properties of matter, the first and the second law of thermodynamics are discussed together with many applications. After an introduction of the equilibrium state, the general principle of similarity for heat- and mass exchange is discussed, considering in particular the heat- and mass exchange in the counter flow between two phases. In a final chapter, the heat- and mass exchange between the vapor- and liquid phase is discussed, with special emphasis on problems as evaporation and drying. (orig./HK)

  1. Plugging margin evaluation considering the fouling of shell-and-tube heat exchanger

    International Nuclear Information System (INIS)

    As operating time of heat exchangers progresses, fouling generated by water-borne deposits increases, number of tube plugging increases, and thermal performance decreases. The fouling and plugging of tubes are known to interfere with normal flow characteristics and reduce thermal efficiencies of heat exchangers. This paper describes the plugging margin evaluation method which can reflect the current fouling level developed in this study. To develop the plugging margin evaluation methods for heat exchangers, fouling factor was introduced based on the ASME O and M codes and TEMA standards. For the purpose of verifying the plugging margin evaluation methods, the fouling and plugging margin evaluations were performed for a component cooling heat exchanger in a nuclear power plant

  2. Advanced heat exchanger development for molten salts

    International Nuclear Information System (INIS)

    Highlights: • Hastelloy N and 242, shows corrosion resistance to molten salt at nominal operating temperatures. • Both diffusion welds and sheet material in Hastelloy N were corrosion tested in at 650, 700, and 850 °C for 200, 500, and 1000 h. • Thermal gradients and galvanic couples in the molten salts enhance corrosion rates. • Corrosion rates found were typically <10 mils per year. - Abstract: This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non-nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, that show good corrosion resistance in molten salt at nominal operating temperatures up to 700 °C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet material in Hastelloy N were corrosion tested in 58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850 °C for 200, 500, and 1000 h. Corrosion rates were similar between welded and nonwelded materials, typically <100 ?m per year after 1000 h of corrosion tests. No catastrophic corrosion was observed in the diffusion welded regions. For materials of construction, nickel-based alloys and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of the type of salt impurity and alloy composition, with respect to chromium and carbon, to better define the best conditions for corrosion resistance. Also presented is the division of the nuclear reactor and high-temperature components per American Society of Mechanical Engineers (ASME) standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa

  3. Advanced heat exchanger development for molten salts

    Energy Technology Data Exchange (ETDEWEB)

    Sabharwall, Piyush, E-mail: Piyush.Sabharwall@inl.gov [Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Clark, Denis; Glazoff, Michael [Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark [University of Wisconsin, Madison (United States)

    2014-12-15

    Highlights: • Hastelloy N and 242, shows corrosion resistance to molten salt at nominal operating temperatures. • Both diffusion welds and sheet material in Hastelloy N were corrosion tested in at 650, 700, and 850 °C for 200, 500, and 1000 h. • Thermal gradients and galvanic couples in the molten salts enhance corrosion rates. • Corrosion rates found were typically <10 mils per year. - Abstract: This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non-nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, that show good corrosion resistance in molten salt at nominal operating temperatures up to 700 °C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet material in Hastelloy N were corrosion tested in 58 mol% KF and 42 mol% ZrF{sub 4} at 650, 700, and 850 °C for 200, 500, and 1000 h. Corrosion rates were similar between welded and nonwelded materials, typically <100 ?m per year after 1000 h of corrosion tests. No catastrophic corrosion was observed in the diffusion welded regions. For materials of construction, nickel-based alloys and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of the type of salt impurity and alloy composition, with respect to chromium and carbon, to better define the best conditions for corrosion resistance. Also presented is the division of the nuclear reactor and high-temperature components per American Society of Mechanical Engineers (ASME) standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.

  4. Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, B.J.; White, M.J.; Klebaner, A.; /Fermilab

    2011-06-10

    Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters. A numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger was developed and the effect of various design parameters on overall heat exchanger size was investigated. It was found that highly conductive metals should be avoided in the design of compact JT heat exchangers. For the geometry considered, the optimal conductivity is around 3.5 W/m-K and can range from 0.3-10 W/m-K without a large loss in performance. The model was implemented with an isenthalpic expansion process. Increasing the cold side inlet temperature from 2K to 2.2 K decreased the liquid fraction from 0.856 to 0.839 which corresponds to a 0.12 g/s increase in supercritical helium supply needed to maintain liquid level in the cooling bath. Lastly, it was found that the effectiveness increased when the heat load was below the design value. Therefore, the heat exchanger should be sized on the high end of the required heat load.

  5. MULTI-SCALE MODELING AND APPROXIMATION ASSISTED OPTIMIZATION OF BARE TUBE HEAT EXCHANGERS

    Energy Technology Data Exchange (ETDEWEB)

    Bacellar, Daniel [University of Maryland, College Park; Ling, Jiazhen [University of Maryland, College Park; Aute, Vikrant [University of Maryland, College Park; Radermacher, Reinhard [University of Maryland, College Park; Abdelaziz, Omar [ORNL

    2014-01-01

    Air-to-refrigerant heat exchangers are very common in air-conditioning, heat pump and refrigeration applications. In these heat exchangers, there is a great benefit in terms of size, weight, refrigerant charge and heat transfer coefficient, by moving from conventional channel sizes (~ 9mm) to smaller channel sizes (< 5mm). This work investigates new designs for air-to-refrigerant heat exchangers with tube outer diameter ranging from 0.5 to 2.0mm. The goal of this research is to develop and optimize the design of these heat exchangers and compare their performance with existing state of the art designs. The air-side performance of various tube bundle configurations are analyzed using a Parallel Parameterized CFD (PPCFD) technique. PPCFD allows for fast-parametric CFD analyses of various geometries with topology change. Approximation techniques drastically reduce the number of CFD evaluations required during optimization. Maximum Entropy Design method is used for sampling and Kriging method is used for metamodeling. Metamodels are developed for the air-side heat transfer coefficients and pressure drop as a function of tube-bundle dimensions and air velocity. The metamodels are then integrated with an air-to-refrigerant heat exchanger design code. This integration allows a multi-scale analysis of air-side performance heat exchangers including air-to-refrigerant heat transfer and phase change. Overall optimization is carried out using a multi-objective genetic algorithm. The optimal designs found can exhibit 50 percent size reduction, 75 percent decrease in air side pressure drop and doubled air heat transfer coefficients compared to a high performance compact micro channel heat exchanger with same capacity and flow rates.

  6. Heat transfer characteristics of printed circuit heat exchanger in supercritical CO2 loop

    International Nuclear Information System (INIS)

    Full text of publication follows: A supercritical carbon dioxide (S-CO2) cycle is promising for gas turbine cycle nuclear reactors since it gives 4?11% higher efficiency than a He cycle due to reduction of compressor work around the critical point. The cycle has been applied to direct cycle fast and thermal reactors; helium, sodium or lead cooled indirect cycle fast reactors by TIT, INEEL, ANL and MIT. The highest cycle efficiency is attained at a partial pre-cooling cycle instead of a usual Brayton cycle by compensating the pressure and temperature dependency of the specific heat. Present gas turbine reactors aim about 95% recuperator effectiveness in order to achieve high cycle efficiency, but dimension of such a high effective recuperator becomes huge. A Printed Circuit Heat Exchanger (PCHE) developed by HEATRIC, UK, has an advantage in down-sizing of the recuperator. PCHE has been applied to petrochemical plant so far, but has never been applied to nuclear reactors. In this study heat transfer characteristics of the PCHE is examined experimentally in the supercritical CO2 loop and analyzed numerically. Preliminary results will be presented in the 6. IIR Gustav Lorentzen Natural Working Fluids Conference in UK to be held in August/2004. More detailed results are provided in this paper. The experiments was carried out under the following conditions; pressure ranges 6.5 to 10.5 MPa for the cold side and 2.2 to 3.2 MPa for the hot side; the maximum inlet temperature is 108 deg. C for the cold side and 280 deg. C for the hot side; mass flow rate of CO2 is changed from 40 to 70 kg/h. Empirical correlations for the heat transfer coefficients, friction factors and Colburn's j factors are proposed. Heat exchanger effectiveness reaches 98% when the number of exchanger heat transfer units (Ntu) is 18. Two-dimensional thermal-hydraulic computer program were used for numerical calculations. PCHE test specimen is modeled as a double banking zigzag flow channel configuration with a counter flow and rectangular cross sections. Flow is assumed to be fully developed in the channels. The numerical calculations predict experimental results well. (authors)

  7. Model of Heat Exchangers for Waste Heat Recovery from Diesel Engine Exhaust for Thermoelectric Power Generation

    Science.gov (United States)

    Baker, Chad; Vuppuluri, Prem; Shi, Li; Hall, Matthew

    2012-06-01

    The performance and operating characteristics of a hypothetical thermoelectric generator system designed to extract waste heat from the exhaust of a medium-duty turbocharged diesel engine were modeled. The finite-difference model consisted of two integrated submodels: a heat exchanger model and a thermoelectric device model. The heat exchanger model specified a rectangular cross-sectional geometry with liquid coolant on the cold side, and accounted for the difference between the heat transfer rate from the exhaust and that to the coolant. With the spatial variation of the thermoelectric properties accounted for, the thermoelectric device model calculated the hot-side and cold-side heat flux for the temperature boundary conditions given for the thermoelectric elements, iterating until temperature and heat flux boundary conditions satisfied the convection conditions for both exhaust and coolant, and heat transfer in the thermoelectric device. A downhill simplex method was used to optimize the parameters that affected the electrical power output, including the thermoelectric leg height, thermoelectric n-type to p-type leg area ratio, thermoelectric leg area to void area ratio, load electrical resistance, exhaust duct height, coolant duct height, fin spacing in the exhaust duct, location in the engine exhaust system, and number of flow paths within the constrained package volume. The calculation results showed that the configuration with 32 straight fins was optimal across the 30-cm-wide duct for the case of a single duct with total height of 5.5 cm. In addition, three counterflow parallel ducts or flow paths were found to be an optimum number for the given size constraint of 5.5 cm total height, and parallel ducts with counterflow were a better configuration than serpentine flow. Based on the reported thermoelectric properties of MnSi1.75 and Mg2Si0.5Sn0.5, the maximum net electrical power achieved for the three parallel flow paths in a counterflow arrangement was 1.06 kW for package volume of 16.5 L and exhaust flow enthalpy flux of 122 kW.

  8. 3D numerical simulation of fluid–solid coupled heat transfer with variable property in a LBE-helium heat exchanger

    International Nuclear Information System (INIS)

    Highlights: • Heat transfer in heat exchanger can be improved by increasing helium's flow rate. • The outlet temperature of helium decreases with increasing helium's flow rate. • Balance is necessary between good heat transfer and high helium outlet temperature. - Abstract: LBE-helium experimental loop of ADS (LELA) and LBE-helium heat exchanger have been designed and constructed with the supporting of the “ADS Transmutation System” project of Chinese Academy of Sciences. In order to investigate the flow and heat transfer characteristics between LBE and helium, 3D numerical simulation of fluid–solid coupled heat transfer with variable property in the LBE-helium heat exchanger is conducted in the present study. The effects of mass-flow-rates of helium and LBE in the shell-side and tube-side on the heat transfer performance are addressed. It is found that the heat transfer performance can be significantly improved by increasing helium mass-flow-rate in the shell-side. In order to easily and quickly obtain the outlet temperatures of helium and LBE, a concept of modified effectiveness is introduced and correlated as the function of tube-side to shell-side heat capacity rate ratio. The results show that the outlet temperature of helium decreases with increasing helium mass-flow-rate. Therefore, considering the utilization of high-temperature helium in the future, for example power generation, there should be a tradeoff between good heat transfer performance and high outlet helium temperature when confirming helium mass-flow-rate

  9. Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

    International Nuclear Information System (INIS)

    OAK-B135 Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers. In the nuclear industry, steam generators are often affected by this problem. However, flow-induced vibration is not limited to nuclear power plants, but to any type of heat exchanger used in many industrial applications such as chemical processing, refrigeration and air conditioning. Specifically, shell and tube type heat exchangers experience flow-induced vibration due to the high velocity flow over the tube banks. Flow-induced vibration in these heat exchangers leads to equipment breakdown and hence expensive repair and process shutdown. The goal of this research is to provide accurate measurements that can help modelers to validate their models using the measured experimental parameters and thereby develop better design criteria for avoiding fluid-elastic instability in heat exchangers. The research is divided between two primary experimental efforts, the first conducted using water alone (single phase) and the second using a mixture of air or steam and water as the working fluid (two phase). The outline of this report is as follows: After the introduction to fluid-elastic instability, the experimental apparatus constructed to conduct the experiments is described in Chapter 2 along with the measurement procedures. Chapter 3 presents results obtained on the tube array and the flow loop, as well as techniques used in data processing. The project performance is described and evaluated in Chapter 4 followed by a discussion of publications and presentations relevant to the project in Chapter 5, while the conclusions and recommendations for future work are presented in Chapter 6

  10. Development of micro-structured heat exchangers; Developpement d'echangeurs de chaleur microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Bouzon, C.

    2004-10-01

    This study has been carried out to defend the Technological Diploma of Research, in the aim to develop micro-structured heat exchangers. Realized within the Research Group on the Heat exchangers and Energy (GREThE) of the Atomic Energy Commission (CEA) of Grenoble. The rise of micro-technologies and the optimization of heat exchangers have led to emergence from few years of new structures of fluid paths with scales lower than the millimeter, thus making it possible to produce heat exchangers ultra-compacts. The micro-structured exchangers are heat exchangers whose hydraulic diameters are lower than the millimeter but with external dimensions of several centimeters. The study is based on two patents filed by the CEA and the characterization of these two geometries. A first concept of cross flow type finds applications with Gas/Liquid heat exchanger. A second type, a countercurrent, is more adapted to Liquid/Liquid applications. An approach with simplified analytical models and by numerical simulation was employed for each concept. An experimental study on the Gas/Liquid concept was also carried out. (author)

  11. Numerical Validation of Heat Transfer Correlations for Design of the Intermediate Heat Exchanger in a Sodium Cooled Fast Reactor

    International Nuclear Information System (INIS)

    The design of the intermediate heat exchanger (IHX) in a sodium cooled fast reactor needs the heat transfer correlations for a parallel flow, a cross flow and an inclined flow. However, the experimental correlations for liquid metal such as sodium are rare since the experiment is very expensive and difficult. This fact leads us to perform CFD calculations to evaluate the previous correlations. The CFD at present is mature enough to calculate complex flows and the CFD calculation of a sodium heat transfer does not need a special treatment. In the present study the existing sodium heat transfer correlations for the design of an IHX are evaluated by the CFD results and the compared results are presented

  12. Numerical estimation of heat transfer characteristics for two-row plate-finned tube heat exchangers with experimental data

    Science.gov (United States)

    Chen, Han-Taw; Lu, Chih-Han; Huang, Yao-Sheng; Liu, Kuo-Chi

    2015-06-01

    This study applies a three-dimensional computational fluid dynamics commercial software in conjunction with various flow models to estimate the heat transfer and fluid flow characteristics of the two-row plate-finned tube heat exchanger in staggered arrangement. The effect of air speed and fin spacing on the results obtained is investigated. Temperature and velocity distributions of air between the two fins and heat transfer coefficient on the fins are determined using the laminar flow and RNG k-? turbulence models. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. Furthermore, the fin temperature measured at the selected locations also coincides with the experimental temperature data. The results obtained using the RNG k-? turbulence model are more accurate than those using the laminar flow model. An interesting finding is the number of grid points may also need to change with fin spacing and air speed.

  13. Manufacture of power station heat exchangers using modern production technology

    International Nuclear Information System (INIS)

    Heat exchangers of high quality and operational safety can only be fabricated economically if fabrication is as 'simple' as possible and can be controlled and if, through value analysis, the work flows can be mechanized and automated and the following requirements are met: use of materials that are easy to work with for the application considered, choice of product designs and wall thicknesses that offer favourable conditions for processing and non-destructive testing, placing of seams in such a way that good accessibility for welding and minimum residual welding stresses are assured, minimizing the number of welding seams, use of automatic welding machines for submerged-arc welding and electronically controlled sources of welding current - semi-automatic equipment for spatter-free interfaces (pulse technique), electronically controlled equipment for welding in rollers and pipes and CNC-controlled machining centres for drilling pipe galleries (deep-hole drilling) and baffle plates and for machining the sealing elements after welding. Continuous inspections in each phase of fabrication assures that heat exchangers are made which fully meet the requirements of nuclear power station operators. (orig.)

  14. Flow boiling heat transfer in volumetrically heated packed bed

    International Nuclear Information System (INIS)

    Highlights: • The onset of nucleate boiling in the volumetrically heated packed bed is researched. • A correlation for predicting qONB is developed. • The effects on boiling heat transfer coefficient are investigated. - Abstract: The volumetrically heated packed bed has been widely utilized in modern industry. However, due to the variability and randomness of packed bed channels, flow boiling heat transfer characteristics becomes complex, and there are no published research regarding this topic. To study flow boiling heat transfer characteristics of volumetrically heated packed beds, electromagnetic induction heating method is used to heat oxidized carbon steel balls adopted to stack the packed bed, with water as coolant in the experiment. The experimental results indicate that heat flux at onset of nucleate boiling (ONB) increases as mass flux and inlet subcooling are increased. A new correlation is developed to predict the ONB heat flux qONB in volumetrically heated packed bed, the predictions by which agree well with the experimental data, and the deviation remains less than 15%. Subcooled flow boiling heat transfer coefficient (hsub) increases with increasing mass flux, and equilibrium quality is slightly affected by heat flux. The saturated flow boiling heat transfer coefficient (hsat) increases with mass flux and equilibrium quality when equilibrium quality is lower than about 0.05, while the nucleate boiling is suppressed when the equilibrium quality exceeds a certain value

  15. CFD analysis of fin tube heat exchanger with a pair of delta winglet vortex generators

    International Nuclear Information System (INIS)

    Among tubular heat exchangers, fin tube types are the most widely used in refrigeration and air-conditioning equipment. Efforts to enhance the performance of these heat exchangers included variations in the fin shape from a plain fin to a slit and louver type. In the context of heat transfer augmentation, the performance of vortex generators has also been investigated. Delta winglet vortex generators have recently attracted research interest, partly due to experimental data showing that their addition to fin-tube heat exchangers considerably reduces pressure loss at heat transfer capacity of nearly the same level. The efficiency of the delta winglet vortex generators widely varies depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. Flow mixing due to vortices and delayed separation due to acceleration influence the overall fin performance. The fin with delta winglet vortex generators exhibited a pressure loss lower than that of a plain fin, and the heat transfer performance was enhanced at high air velocity or Reynolds number

  16. Improving a process's efficiency by exploiting heat pockets in its heat exchange network

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yufei; Feng, Xiao; Cai, Yan; Zhu, Maobin; Chu, Khim H. [Department of Chemical Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)

    2009-11-15

    On the grand composite curve of a heat exchange network, a heat pocket exists when a local heat source above the pinch point or a local heat sink below the pinch point appears. In this paper, heat recovery in the heat pocket is presented by combining the pinch technology and exergy analysis. When the heat pocket is big, hot streams in the pocket can be used to generate a higher level utility, and the cold streams in the pocket can be heated by a lower level utility. In this way, exergy loss can be reduced, and the process's efficiency can be improved. The heat exchange network of a hydrogen production process is used as a case study. The energy performance of the heat exchange network can be further improved by recovering the heat in the heat pocket, compared with the scheme based only on pinch technology. (author)

  17. Study on performance of plate fin - oval tube heat exchanger with vortex generators

    International Nuclear Information System (INIS)

    An experimental study was carried out to investigate the enhancement of heat transfer from the in-line and staggered arrays of oval tubes in the plate fin - tube heat exchanger with Delta - Wing type Vortex Generators(DWVG). Measurements of average heat(mass) - transfer coefficients on the tube surface were made using a naphthalene sublimation technique, and the flow losses were measured for Reynolds number ranging from 2000 to 3200. The influence of vortex generators parameters such as position and angle of attack was investigated. It was found that the heat transfer enhancement were increased by the existence of a vortex generators and flow losses were decreased by the oval tubes. The results indicate that performance of plate fin - tube heat exchanger can be improved simultanously by using vortex generators and oval tubes

  18. Study on performance of plate fin - oval tube heat exchanger with vortex generators

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hyeon Sik; Chun, Young Woo; Chung, In Kee [Yeungnam Univ., Gyeongsan (Korea, Republic of)

    2005-07-01

    An experimental study was carried out to investigate the enhancement of heat transfer from the in-line and staggered arrays of oval tubes in the plate fin - tube heat exchanger with Delta - Wing type Vortex Generators(DWVG). Measurements of average heat(mass) - transfer coefficients on the tube surface were made using a naphthalene sublimation technique, and the flow losses were measured for Reynolds number ranging from 2000 to 3200. The influence of vortex generators parameters such as position and angle of attack was investigated. It was found that the heat transfer enhancement were increased by the existence of a vortex generators and flow losses were decreased by the oval tubes. The results indicate that performance of plate fin - tube heat exchanger can be improved simultanously by using vortex generators and oval tubes.

  19. Investigation of Brazed Plate Heat Exchangers With Variable Chevron Angles

    Directory of Open Access Journals (Sweden)

    S. Muthuraman

    2013-08-01

    Full Text Available - Experiments to measure the condensation heat transfer coefficient and the pressure drop in brazed plate heat exchangers (BPHEs were performed with the refrigerants R410A and R22. Brazed plate heat exchangers with different chevron angles of 45°, 35°, and 20° were used. Varying the mass flux, the condensation temperature, and the vapor quality of the refrigerant, we measured the condensation heat transfer coefficient and the pressure drops. Both the heat transfer coefficient and the pressure drop increased proportionally with the mass flux and the vapor quality and inversely with the condensation temperature and the chevron angle.

  20. Improvements of U-pipe Borehole Heat Exchangers

    OpenAIRE

    Acuña, José

    2010-01-01

    The sales of Ground Source Heat Pumps in Sweden and many other countries are having a rapid growth in the last decade. Today, there are approximately 360 000 systems installed in Sweden, with a growing rate of about 30 000 installations per year. The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a Borehole Heat Exchanger (BHE), a closed loop in a vertical borehole. The fluid transports the heat from the groun...

  1. Thermal behavior of a heat exchanger module for seasonal heat storage

    DEFF Research Database (Denmark)

    Fan, Jianhua; Furbo, Simon; Andersen, Elsa; Chen, Ziqian; Perers, Bengt; Dannemand, Mark

    2012-01-01

    Experimental and theoretic investigations are carried out to study the heat transfer capacity rate of a heat exchanger module for seasonal heat storage with sodium acetate trihydrate (SAT) supercooling in a stable way. A sandwich heat storage test module has been built with the phase change material (PCM) storage box in between two plate heat exchangers. Charge of the PCM storage is investigated experimentally with solid phase SAT as initial condition. Discharge of the PCM storage with the prese...

  2. Map of Io's volcanic heat flow

    Science.gov (United States)

    Davies, Ashley Gerard; Veeder, Glenn J.; Matson, Dennis L.; Johnson, Torrence V.

    2015-12-01

    We present a map of Io's volcanic heat flow. Io's high heat flow is a result of intense tidal heating, which generates widespread volcanic activity. The surface expression of ongoing volcanic activity constrains the location and magnitude of tidal dissipation within Io. Tidal heating models place heating either at relatively shallow (aesthenosphere) levels, or deep in the mantle. It was thought that actual tidal heating could be approximated using a combination of these end-member models. Io's volcanic heat flow has now been mapped in sufficient detail to compare with the models. Our maps show that the distribution of heat flow is not matched by current models of deep nor shallow tidal heating, nor by any combination of these two models. We find relatively low heat flow at sub-jovian (0°W) and anti-jovian (180°W) longitudes, at odds with the pure aesthenospheric heating model. Furthermore, there are large swaths of Io's surface where there is poor correlation between the number of hot spots in an area and the power emitted. We have previously accounted for ?54% of Io's observed heat flow. We now show that Io's anomalously warm poles, possibly the result of heat flow from deep-mantle heating, would yield the "missing" energy (48 TW) if the polar surfaces are at temperatures of ?90 K to ?95 K and cover latitudes above ?43° to ?48° respectively. This possibility implies a ratio of deep to shallow heating of about 1:1. However, explaining regional variations in surface volcanic activity requires more detailed modeling of the location and magnitude of the internal tidal dissipation and the consequences of mantle convection and advection within Io. Future model predictions can be compared to our heat flow map.

  3. Integrated system of nuclear reactor and heat exchanger

    International Nuclear Information System (INIS)

    The invention concerns PWRs in which the heat exchanger is associated with a pressure vessel containing the core and from which it can be selectively detached. This structural configuration applies to electric power generating uses based on land or on board ships. An existing reactor of this kind is fitted with a heat exchanger in which the tubes are 'U' shaped. This particular design of heat exchangers requires that the ends of the curved tubes be solidly maintained in a tube plate of great thickness, hence difficult to handle and to fabricate and requiring unconventional fine control systems for the control rods and awkward coolant pump arrangements. These complications limit the thermal power of the system to level below 100 megawatts. On the contrary, the object of this invention is to provide a one-piece PWR reactor capable of reaching power levels of 1500 thermal megawatts at least. For this, a pressure vessel is provided in the cylindrical assembly with not only a transversal separation on a plane located between the reactor and the heat exchanger but also a cover selectively detachable which supports the fine control gear of the control rods. Removing the cover exposes a part of the heat exchanger for easy inspection and maintenance. Further, the heat exchanger can be removed totally from the pressure vessel containing the core by detaching the cylindrical part, which composes the heat exchanger section, from the part that holds the reactor core on a level with the transversal separation

  4. Experience on failed moderator heat exchangers tube leak detection at Narora Atomic Power Station

    International Nuclear Information System (INIS)

    Nuclear side various heat exchangers of the station which handle radioactive fluids are cooled by a close loop cooling water system, known as active process water system (APW). Active process water system transfers its heat to tertiary cooling water system known as active process water cooling system which in turn is cooled with the help of an induced draft cooling tower. Use of two cooling water loops provide double barrier to radioactivity release to the environment. On line sampling facility for tritium activity detection in all heat exchangers on their cooling water side provides indication of regarding failure of a particular heat exchanger. During September, 1995, NAPS Unit-1 active process water system showed gradual increase in tritium activity. Individual heat exchanger sample results could not provide confirmatory information regarding the leaky heat exchanger because of minor nature of leak. As the global tritium activity of active process water system kept on increasing, unit was shutdown to identify and repair the leaky heat exchanger. Sampling from isolated heat exchangers were done after putting fresh water to it. Sample results (tritium activity) indicated leak from moderator system HX ? 1. Detection of the leaky tube was experienced to extremely difficult task, because of size, location and nature of failure. All conventional methods of tube leak detection were applied but without success. These methods involved helium leak test from either side, vacuum drop test, pressure drop test, eddy current testing and fluorescent dye method. Having found no indication of failed tube moderator heat exchanger was reverted back to normal configuration with increase in process water flow through shell side in steps and parallel monitoring of tritium activity trend. Beyond 50% of PW flow, tritium activity level in active process water started increasing. Process water was throttled back and about 40% flow, tritium activity in process water got stabilised. Thus, it was established that the tube leakage was due to flow induced vibration from shell side. Subsequently, the moderator heat exchanger was again opened and leaky tube was identified after giving 50% flow through shell side. A single tube on the topmost row was found leaking. Eddy current testing of the defective tube and its adjacent tubes, some other tubes on random basis was done by dual frequency technique. Results indicated defects in 8 nos. of tubes in the top row at the middle baffle plate location. Rest of the tubes were healthy. The heat exchanger design was re-evaluated for hydraulic behavior. The results indicated localised velocity, at middle baffle plate location at process water entry point was above safe limit for higher gross flow rate of process water. Hence, in consultation with the supplier and designers, total 32 nos. of tubes including the 8 defective ones on the topmost row were plugged to shield the lower rows of tubes from direct impact of incoming process water flow. Also to keep local velocities within safe limit, gross flow of process water through shell side was restricted. The modification was carried out in all four moderator system heat exchangers of both the units. There has been no failure in these heat exchangers since then. (authors)

  5. Optimal design of plate-fin heat exchangers by a Bees Algorithm

    International Nuclear Information System (INIS)

    In this study, the application of Bees Algorithm (BA) in the optimum design of a cross flow plate-fin heat exchanger with offset strip fin is investigated. First, heat exchanger is optimized and designed according to the effectiveness optimization. Then, an analysis based on the second law of thermodynamics and minimizations of entropy generation units is performed. Specific heat duty, space restriction and permitted pressure drop are considered as the constraints for maximizing the effectiveness and minimizing the entropy generation units. Hot and cold flow length of the heat exchangers, number of fin layers, fin frequency, fin height, fin strip length and fin thickness are introduced as optimization variables. The effectiveness and accuracy of the suggested algorithm are compared with literature. The results have shown that BA can find optimum configuration with higher accuracy in comparison with Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Imperialist Competitive Algorithm (ICA) and preliminary design. - Highlights: •We analyzed a plate-fin heat exchanger with offset strip fins. •This is the first application of a Bees Algorithm for plate-fin heat exchanger design. •Preliminarily design and effectiveness of PFHE was improved by minimizing the entropy generation units. •The results show the superiority of this method over GA, PSO and ICA and preliminary design

  6. CFD-based thermo-hydraulic modeling of low pressure drop tungsten-foam heat exchanger

    International Nuclear Information System (INIS)

    A very low pressure drop helium-cooled heat exchanger for high heat loads (> 20 MW/m2) is design and developed here. The concept is based on open-cell tungsten foam, which is integrally bonded to the inside of a thin tungsten tube. Recently, we reported initial experimental results of a preliminary design with a verified surface heat load capability of up to 22 MW/m2. A modified concept is under development, in which the foam and flow configurations are being designed to minimize the flow-path length of coolant through the foam resulting in a low pressure drop foam-based heat exchanger. This unique approach will result in a scalable heat exchanger channel that does not entail significant additional pressure drop as a function of length. Both monolithic tungsten and tungsten alloys with greater ductility are being investigated. We report here on the thermo-hydraulic modeling analysis based on (1) the extended Darcy's law and (2) a detailed CFD analysis. The extended Darcy's law approach is based on measured pressure drop tests, while the CFD analysis uses a detailed tungsten foam structure to simulate flow through the open cell structure. To this end, a realistic solid model of the foam using micro-computer Tomography along with an analytical solid model of tungsten foam were created and meshed for CFD and thermal FEM analysis. The analytically calculated pressure drops and flow rates will be compared with the results from the detailed CFD analyses. Effective heat transfer coefficients will be estimated using Darcy's law and compared with the CFD-based results. Thermal FEM analysis based on both, the effective analytical heat transfer coefficient and the extracted CFD based heat transfer coefficients are being performed. The heat load capabilities of an all tungsten low pressure drop foam-based heat exchanger are presented. (orig.)

  7. Review of the experience obtained in the evaluation of vibrations and their effects on the structural integrity of heat exchangers

    International Nuclear Information System (INIS)

    Flow induced vibrations may produce damage of shell-tube type heat exchangers, condensers and steam generators tubes. These vibrations could be produce by changes in the equipment operational condition or by a wrong evaluation during the design procedure. The typical results are tube damage by impact or fretting wear. This paper include a review of the flow-induced vibration mechanisms that affect shell-tube heat exchangers and some practical examples that show the results obtained evaluating this equipment. (author)

  8. COMPARATIVEANALYSIS OF ADVANCED CONTROLLERS IN A HEAT EXCHANGER

    Directory of Open Access Journals (Sweden)

    Mr. P.Sivakumar

    2013-01-01

    Full Text Available Temperature control of the shell and tube heat exchanger is characteristics of nonlinear, time varying and time lag. Since the temperature control with conventional PID controller cannot meet a wide range of precision temperature control requirement, we design temperature control system of the shell and tube heat exchanger by combining fuzzy and PID control methods in this paper. The simulation and experiments are carried out; making a comparison with conventional PID control showing that fuzzy PID strategy can efficiently improve the performance of the shell and tube heat exchanger.

  9. Experiments for performance enhancement of the innovative heat exchanger

    International Nuclear Information System (INIS)

    In present study, three dimension numerical analysis of Heatric PCHE is performed and compared to existing experimental data. And according to the results, the parameters to influence on thermal-hydraulic performance of PCHE have been derived and a Parametric study for the derived parameters has been performed. Based on these results, a new shape of channel in heat exchanger has been designed. And, performing three dimensional numerical analysis of a new designed heat exchanger and existing PCBE, thermal-hydraulic performance of the new designed heat exchanger has been validated numerically. And, the loop for experiments is designed for experimental investigation

  10. The influence of heat exchanger design on the synthesis of heat exchanger networks

    Directory of Open Access Journals (Sweden)

    Liporace F.S.

    2000-01-01

    Full Text Available Heat exchanger network (HEN synthesis has been traditionally performed without accounting for a more detailed unit design, which is important since the final HEN may require unfeasible units. Recently, publications on this matter have appeared, as well as softwares that simultaneously perform synthesis and units design. However, these publications do not clearly show the influence of the new added features on the final HEN. Hence, this work aims at showing that units' design can strongly affect the final HEN. Improvements on heat transfer area and total annual cost estimations, which influence the HEN structural evolution, are the main responsible for that. It is also shown the influence of some design bounds settings, which can indicate an unfeasible unit design and, therefore, the need for a new match search or the maintenance of a loop. An example reported in the literature is used to illustrate the discussion.

  11. The influence of heat exchanger design on the synthesis of heat exchanger networks

    Scientific Electronic Library Online (English)

    F.S., Liporace; F.L.P., Pessoa; E.M., Queiroz.

    2000-12-01

    Full Text Available Heat exchanger network (HEN) synthesis has been traditionally performed without accounting for a more detailed unit design, which is important since the final HEN may require unfeasible units. Recently, publications on this matter have appeared, as well as softwares that simultaneously perform synth [...] esis and units design. However, these publications do not clearly show the influence of the new added features on the final HEN. Hence, this work aims at showing that units' design can strongly affect the final HEN. Improvements on heat transfer area and total annual cost estimations, which influence the HEN structural evolution, are the main responsible for that. It is also shown the influence of some design bounds settings, which can indicate an unfeasible unit design and, therefore, the need for a new match search or the maintenance of a loop. An example reported in the literature is used to illustrate the discussion.

  12. A minichannel aluminium tube heat exchanger - Pt. 2: Evaporator performance with propane

    Energy Technology Data Exchange (ETDEWEB)

    Fernando, Primal; Palm, Bjoern; Ameel, Tim; Lundqvist, Per; Granryd, Eric [Department of Energy Technology, Division of Applied Thermodynamics and Refrigeration, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden)

    2008-06-15

    This paper presents heat transfer data for a multiport minichannel heat exchanger vertically mounted as an evaporator in a test-rig simulating a small water-to-water heat pump. The multiport minichannel heat exchanger was designed similar to a shell-and-tube type heat exchanger, with a six-channel tube of 1.42 mm hydraulic diameter, a tube-side heat transfer area of 0.777 m{sup 2} and a shell-side heat transfer area of 0.815 m{sup 2}. Refrigerant propane with a desired vapour quality flowed upward through the tubes and exited with a desired superheat of 1-4 K. A temperature-controlled glycol solution that flowed downward on the shell-side supplied the heat for the evaporation of the propane. The heat transfer rate between the glycol solution and propane was controlled by varying the evaporation temperature and propane mass flow rate while the glycol flow rate was fixed (18.50 l min{sup -1}). Tests were conducted for a range of evaporation temperatures from -15 to +10{sup o}C, heat flux from 2000 to 9000 W m{sup -2} and mass flux from 13 to 66 kg m{sup -2} s{sup -1}. The heat transfer coefficients were compared with 14 correlations found in the literature. The experimental heat transfer coefficients were higher than those predicted by many of the correlations. A correlation which was previously developed for a very large and long tube (21 mm diameter and 10 m long) was in good agreement with the experimental data (97% of the data within {+-}30%). Several other correlations were able to predict the data within a reasonable deviation (within {+-}30%) after some adjustments to the correlations. (author)

  13. Optimal design of a NGNP heat exchanger with cost model

    International Nuclear Information System (INIS)

    With steady increase in energy consumption, the vulnerability of the fossil fuel supply, and environmental concerns, the U.S. Department of Energy (DOE) has initiated the Next Generation Nuclear Power Plants (NGNP), also known as Very High Temperature Reactor (VHTR). The VHTR is planned to be operational by 2021 with possible demonstration of a hydrogen generating plant. Various engineering design studies on both the reactor plant and energy conversion system are underway. For this and related Generation IV plants, it is the goal to not only meet safety criteria but to also be efficient, economically competitive, and environmentally friendly (proliferation resistant). Traditionally, heat exchanger (HX) design is based on two main approaches: Log-Mean Temperature Difference (LMTD) and effectiveness-NTU (?-NTU). These methods yield the dimension of the HX under anticipate condition and vice-versa. However, one is not assured that the dimension calculated give the best performing HX when economics are also considered. Here, we develop and show a specific optimization algorithm (exercise) using LMTD and simple (optimal) design theory to establish a reference case for the Printed Circuit Heat Exchanger (PCHE). Computational Fluid Dynamics (CFD) was further used as a design tool to investigate the optimal design of PCHE thermohydraulic flow. The CFD results were validated against the Blasius correlation before being subjected to optimal design analyses. Benchmark results for the pipe flow indicated that the predictive ability of SST k-? is superior to the other (standard and RNG k-? and RSM) turbulence models. The difference between CFD and the empirical expression is less than 10%. (author)

  14. Investigation of Condensation Heat Transfer Correlation of Heat Exchanger Design in Secondary Passive Cooling System

    International Nuclear Information System (INIS)

    Recently, condensation heat exchangers have been studied for applications to the passive cooling systems of nuclear plants. To design vertical-type condensation heat exchangers in secondary passive cooling systems, TSCON (Thermal Sizing of CONdenser), a thermal sizing program for a condensation heat exchanger, was developed at KAERI (Korea Atomic Energy Research Institute). In this study, the existing condensation heat transfer correlation of TSCON was evaluated using 1,157 collected experimental data points from the heat exchanger of a secondary passive cooling system for the case of pure steam condensation. The investigation showed that the Shah correlation, published in 2009, provided the most satisfactory results for the heat transfer coefficient with a mean absolute error of 34.8%. It is suggested that the Shah correlation is appropriate for designing a condensation heat exchanger in TSCON

  15. Low Cost Polymer heat Exchangers for Condensing Boilers

    Energy Technology Data Exchange (ETDEWEB)

    Butcher, Thomas [Brookhaven National Lab. (BNL), Upton, NY (United States); Trojanowski, Rebecca [Brookhaven National Lab. (BNL), Upton, NY (United States); Wei, George [Brookhaven National Lab. (BNL), Upton, NY (United States); Worek, Michael [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-09-30

    Work in this project sought to develop a suitable design for a low cost, corrosion resistant heat exchanger as part of a high efficiency condensing boiler. Based upon the design parameters and cost analysis several geometries and material options were explored. The project also quantified and demonstrated the durability of the selected polymer/filler composite under expected operating conditions. The core material idea included a polymer matrix with fillers for thermal conductivity improvement. While the work focused on conventional heating oil, this concept could also be applicable to natural gas, low sulfur heating oil, and biodiesel- although these are considered to be less challenging environments. An extruded polymer composite heat exchanger was designed, built, and tested during this project, demonstrating technical feasibility of this corrosion-resistant material approach. In such flue gas-to-air heat exchangers, the controlling resistance to heat transfer is in the gas-side convective layer and not in the tube material. For this reason, the lower thermal conductivity polymer composite heat exchanger can achieve overall heat transfer performance comparable to a metal heat exchanger. However, with the polymer composite, the surface temperature on the gas side will be higher, leading to a lower water vapor condensation rate.

  16. Development of a micro-heat exchanger with stacked plates using LTCC technology

    Directory of Open Access Journals (Sweden)

    E. Vásquez-Alvarez

    2010-09-01

    Full Text Available A green ceramic tape micro-heat exchanger was developed using Low Temperature Co-fired Ceramics technology (LTCC. The device was designed by using Computational Aided Design software and simulations were made using a Computational Fluid Dynamics package (COMSOL Multiphysics to evaluate the homogeneity of fluid distribution in the microchannels. Four geometries were proposed and simulated in two and three dimensions to show that geometric details directly affect the distribution of velocity in the micro-heat exchanger channels. The simulation results were quite useful for the design of the microfluidic device. The micro-heat exchanger was then constructed using the LTCC technology and is composed of five thermal exchange plates in cross-flow arrangement and two connecting plates, with all plates stacked to form a device with external dimensions of 26 x 26 x 6 mm³.

  17. Development of a micro-heat exchanger with stacked plates using LTCC technology

    Scientific Electronic Library Online (English)

    E., Vásquez-Alvarez; F. T., Degasperi; L. G., Morita; M. R., Gongora-Rubio; R., Giudici.

    2010-09-01

    Full Text Available A green ceramic tape micro-heat exchanger was developed using Low Temperature Co-fired Ceramics technology (LTCC). The device was designed by using Computational Aided Design software and simulations were made using a Computational Fluid Dynamics package (COMSOL Multiphysics) to evaluate the homogen [...] eity of fluid distribution in the microchannels. Four geometries were proposed and simulated in two and three dimensions to show that geometric details directly affect the distribution of velocity in the micro-heat exchanger channels. The simulation results were quite useful for the design of the microfluidic device. The micro-heat exchanger was then constructed using the LTCC technology and is composed of five thermal exchange plates in cross-flow arrangement and two connecting plates, with all plates stacked to form a device with external dimensions of 26 x 26 x 6 mm³.

  18. Application of design calculation for RSG-GAS heat-exchanger

    International Nuclear Information System (INIS)

    Objective of this paper is to apply the design calculation for the RSG-GAS heat exchanger. The principle of conventional design calculation requires repeated steps in entering the existing input data. This method can be solved easily by computer program. The method is based on the fast reaching convergence in the trial-error process. Data options of standard geometries, heat duty, flow rate, expected temperature including acceptable pressure drop limitation were applied. The main heat exchanger design is to decide the heat transfer area, geometry's and also other dimensions. Result of program as like design specification in the same manner as listed in the sheet of TEMA standard. Creating the computer program is used to design the heat exchanger of RSG-GAS. Calculation results agreed very well with verified results achieved from the reference source. Indeed, design result for the exchanger of RSG-GAS seemly shows that the heat exchanger sizing is greater than existing exchanger of RSG-GAS

  19. Comparison of heat transfer in straight and corrugated minichannels with two-phase flow

    Directory of Open Access Journals (Sweden)

    Peukert P.

    2014-03-01

    Full Text Available Measurements of heat transfer rates performed with an experimental condensation heat exchanger are reported for a corrugated minichannel tube and for a straight minichannel tube. The two cases were compared at same flow regimes. The corrugation appears advantageous for relatively low steam pressures and flow rates where much higher heat transfer rates were observed close to the steam entrance, thus allowing shortening the heat exchanger with the associated advantages of costs lowering and smaller built-up space. At high steam pressures and high flow rates both tubes performed similarly.

  20. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    International Nuclear Information System (INIS)

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm-3 (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial SiC materials are much lower due to phonon scattering by impurities (e.g., sintering aids located at the grain boundaries of these materials). The thermal conductivity of our SiC was determined using the laser flash method and it is 214 W/mK at 373 K and 64 W/mK at 1273 K. These values are very close to those of pure SiC and are much higher than those of SiC materials made by industrial processes. This SiC made by our LSI process meets the thermal properties required for use in high temperature heat exchanger. Cellulose and phenolic resin carbons lack the well-defined atomic structures associated with common carbon allotropes. Atomic-scale structure was studied using high resolution transmission electron microscopy (HRTEM), nitrogen gas adsorption and helium gas pycnometry. These studies revealed that cellulose carbon exhibits a very high degree of atomic disorder and angstrom-scale porosity. It has a density of only 93% of that of pure graphite, with primarily sp2 bonding character and a low concentration of graphene clusters. Phenolic resin carbon shows more structural order and substantially less angstrom-scale porosity. Its density is 98% of that of pure graphite, and Fourier transform analysis of its TEM micrographs has revealed high concentrations of sp3 diamond and sp2 graphene nano-clusters. This is the first time that diamond nano-clusters have been observed in carbons produced from phenolic resin. AC and DC electrical measurements were made to follow the thermal conversion of microcrystalline cellulose to carbon. This study identifies five regions of electrical conductivity that can be directly correlated to the chemical decomposition and microstructural evolution during carbonization. In Region I, a decrease in overall AC conductivity occurs due to the initial loss of the polar groups from cellulose molecules. In Region II, the AC conductivity starts to increase with heat treatment temperature due to the formation and growth of conducting carbon clusters. In Region III, a further increase of AC conductivity with increasing heat treatment temperature is observed.

  1. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    Energy Technology Data Exchange (ETDEWEB)

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm{sup -3} (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial SiC materials are much lower due to phonon scattering by impurities (e.g., sintering aids located at the grain boundaries of these materials). The thermal conductivity of our SiC was determined using the laser flash method and it is 214 W/mK at 373 K and 64 W/mK at 1273 K. These values are very close to those of pure SiC and are much higher than those of SiC materials made by industrial processes. This SiC made by our LSI process meets the thermal properties required for use in high temperature heat exchanger. Cellulose and phenolic resin carbons lack the well-defined atomic structures associated with common carbon allotropes. Atomic-scale structure was studied using high resolution transmission electron microscopy (HRTEM), nitrogen gas adsorption and helium gas pycnometry. These studies revealed that cellulose carbon exhibits a very high degree of atomic disorder and angstrom-scale porosity. It has a density of only 93% of that of pure graphite, with primarily sp2 bonding character and a low concentration of graphene clusters. Phenolic resin carbon shows more structural order and substantially less angstrom-scale porosity. Its density is 98% of that of pure graphite, and Fourier transform analysis of its TEM micrographs has revealed high concentrations of sp3 diamond and sp2 graphene nano-clusters. This is the first time that diamond nano-clusters have been observed in carbons produced from phenolic resin. AC and DC electrical measurements were made to follow the thermal conversion of microcrystalline cellulose to carbon. This study identifies five regions of electrical conductivity that can be directly correlated to the chemical decomposition and microstructural evolution during carbonization. In Region I, a decrease in overall AC conductivity occurs due to the initial loss of the polar groups from cellulose molecules. In Region II, the AC conductivity starts to increase with heat treatment temperature due to the formation and growth of conducting carbon clusters. In Region III, a further increase of AC conductivity with increasing heat treatment temperature is obs

  2. Current status and development of heat exchangers for boiling water reactor nuclear power plant

    International Nuclear Information System (INIS)

    More efficient and reliable operation is required for BWR heat exchangers because of nuclear plant safety and other reasons. Heat exchangers are classified into two categories of systems, the system for normal operation and the system for emergency operation. The present state and future improvement of heat exchangers are described in view of heat transfer performance, material selection, structural design, vibration, and so on. When noncondensing gas exists in vapour, heat transfer performance deteriorates, so that the heat transfer characteristics should be corrected by the adaption of venting the non condensing gas from the system. Heat transfer tubes should have high corrosion resistance to working fluid as well as high thermal conductivity, strength and economy. From that point of view, 30% cupro-nickel tubes will be replaced with 10% cupro-nickel tubes or titanium tubes though some technical development is necessary. These heat exchangers are now designed according to the MITI criteria for the technology concerning nuclear and thermal power generation, ASME Boiler and Pressure Vessel Code Sec. III and some other criteria. Most of heat transfer tube failures are caused from the tube vibration induced by working fluid flow, so that the vibration test and analysis were performed on U-tube elements. Some correction was obtained for design and fabrication techniques. (Iwase, T.)

  3. Application of transient analysis methodology to heat exchanger performance monitoring

    International Nuclear Information System (INIS)

    A transient testing technique is developed to evaluate the thermal performance of industrial scale heat exchangers. A Galerkin-based numerical method with a choice of spectral basis elements to account for spatial temperature variations in heat exchangers is developed to solve the transient heat exchanger model equations. Testing a heat exchanger in the transient state may be the only viable alternative where conventional steady state testing procedures are impossible or infeasible. For example, this methodology is particularly suited to the determination of fouling levels in component cooling water system heat exchangers in nuclear power plants. The heat load on these so-called component coolers under steady state conditions is too small to permit meaningful testing. An adequate heat load develops immediately after a reactor shutdown when the exchanger inlet temperatures are highly time-dependent. The application of the analysis methodology is illustrated herein with reference to an in-situ transient testing carried out at a nuclear power plant. The method, however, is applicable to any transient testing application

  4. Evaluation of fluid bed heat exchanger optimization parameters. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1980-03-01

    Uncertainty in the relationship of specific bed material properties to gas-side heat transfer in fluidized beds has inhibited the search for optimum bed materials and has led to over-conservative assumptions in the design of fluid bed heat exchangers. An experimental program was carried out to isolate the effects of particle density, thermal conductivity, and heat capacitance upon fluid bed heat transfer. A total of 31 tests were run with 18 different bed material loads on 12 material types; particle size variations were tested on several material types. The conceptual design of a fluidized bed evaporator unit was completed for a diesel exhaust heat recovery system. The evaporator heat transfer surface area was substantially reduced while the physical dimensions of the unit increased. Despite the overall increase in unit size, the overall cost was reduced. A study of relative economics associated with bed material selection was conducted. For the fluidized bed evaporator, it was found that zircon sand was the best choice among materials tested in this program, and that the selection of bed material substantially influences the overall system costs. The optimized fluid bed heat exchanger has an estimated cost 19% below a fin augmented tubular heat exchanger; 31% below a commercial design fluid bed heat exchanger; and 50% below a conventional plain tube heat exchanger. The comparisons being made for a 9.6 x 10/sup 6/ Btu/h waste heat boiler. The fluidized bed approach potentially has other advantages such as resistance to fouling. It is recommended that a study be conducted to develop a systematic selection of bed materials for fluidized bed heat exchanger applications, based upon findings of the study reported herein.

  5. Procedimiento para el cálculo de circuitos en el modelado del flujo en intercambiadores de calor de aletas y tubos / Procedure for Calculating Circuits in the Modeling of Flow in fin-and-tube Heat Exchangers

    Scientific Electronic Library Online (English)

    Edwin, Córdoba-Tuta; David, Fuentes-Díaz.

    2015-01-01

    Full Text Available En este trabajo se presenta un procedimiento general para la simulación del comportamiento del flujo en los intercambiadores de tubos y aletas con una gran flexibilidad en el manejo de la información. Este procedimiento está basado en el uso de Programación Orientada a Objetos y específicamente al u [...] so de C++, esto debido a todas las ventajas de este tipo de programación. La entrada de datos se lleva a cabo por medio de archivos, de forma que programas de terceros puedan generar la configuración del intercambiador y permitir calcular el intercambiador en forma paramétrica. Los resultados para el análisis se presentan en tres formatos diferentes: valores separados por comas (CSV), texto plano estructurado y autodocumentado (XML) y un formato para la visualización gráfica de resultados (VTK). Abstract in english This paper presents a general method for simulating the flow behavior in the fin-and-tube heat exchangers with high flexibility in handling the information. This procedure is based on the use of Object-Oriented Programming and specifically using C++, this because of all the advantages of this type o [...] f programming. Data entry is carried out by files, so that third-party programs can generate configuration and permit calculation in parametric form. The results for the analysis are presented in three different formats: comma separated value (CSV), structured plain text and self-documenting (XML) and a graphical display of results (VTK).

  6. Heat Flow Measurements on LHC Components

    CERN Document Server

    Camacho, D; Ferlin, G; Pangallo, M; Policella, C; Rieubland, Jean Michel; Simon, L; Vandoni, Giovanna

    1999-01-01

    The refrigeration and liquefaction capacity necessary to operate at 1.9 K the 27 km long string of superconducting magnets of the LHC has been determined on the basis of heat load estimates, including static heat inleaks from ambient temperature, resistive heating and dynamic beam-induced heat loads. At all temperature levels, the static heat inleaks determine at least one third of the total heat loads in nominal operating conditions of the machine. Design validation of individual cryocomponents therefore requires a correct estimate of the heat inleaks they induce at all temperature levels, in order not to exceed the allocated heat budget. This paper illustrates the measurements of heat inleaks for several cold components of the future machine, including insulating supports, radiation shields, multi-layer insulation, instrumentation current leads. Distinct methods to determine the heat flow are chosen, depending on the expected heat loads, the temperature range spanned by the heat intercepts, and the working ...

  7. Simulasi Performansi Heat Exchanger Type Shell And Tube Dengan Double Segmental Baffle Terhadap Helical Baffle

    Directory of Open Access Journals (Sweden)

    Anggareza Adhitiya

    2013-12-01

    Full Text Available Pada heat exchanger type shell and tube, selain pengunaan baffle yang bertujuan untuk mengarahkan aliran pada sisi shell juga bertujuan untuk meningkatkan laju perpindahan panas yang terjadi antara fluida kerja dengan cara menimbulkan olakan aliran di sisi shell. Olakan –olakan ini nantinya yang akan mempengaruhi besarnya perpindahan panas dalam sisi shell. Pada kondisi standart baffle yang digunakan pada tugas akhir ini adalah jenis double segmental. Double segmental baffle mempunyai tingkat pressure drop yang cukup besar. sehingga perlu di ganti dengan baffle jenis helical yang mempunyai pressure drop yang lebih kecil. Untuk mengetahui performansi heat exchanger maka perlu adanya penelitian lebih lanjut simulasi numerik pada baffle heat exchanger type shell and tube. agar didapat pengaruh jenis baffle yang di gunakan terhadap karakteristik aliran dan perpindahan panas dari suatu heat exchanger type shell and tube. Tugas Akhir ini menggunakan program GAMBIT 2.4.6 untuk penggambaran geometri secara tiga dimensi dan program FLUENT 6.3.26 untuk mensimulasi aliran yang terjadi di dalam shell and tube heat exchanger. Pada software FLUENT 6.3.26 digunakan permodelan 3D Steady Flow dengan  memilih k – Epsilon RNG sebagai turbulence modeling serta mengaktifkan persamaan energy. Penelitian dilakukan dengan menggunakan dua variasi heat exchanger dengan jenis baffle yang berbeda .Heat exchanger type shell and tube dengan jenis double segmental baffle mempunyai nilai koefisien konveksi rata-rata = 218.408 w/m2.K. Sedangkan untuk helical baffle sebesar = 171.122 w/m2.K. Temperature outflow pada heat exchanger type shell and tube dengan jenis double segmental baffle = 306.7450K. Di ikuti dengan pressure drop sebesar = 2100 pascal Sedangkan untuk helical baffle mempunyai temperatur outflow sebesar = 307.0220K dengan pressure drop sebesar = 500 pascal.

  8. The entropy matrix generated exergy model for a photovoltaic heat exchanger under critical operating conditions

    Energy Technology Data Exchange (ETDEWEB)

    Dehra, H. [American Institute Industry Forum on Energy, Montreal, PQ (Canada)

    2006-07-01

    This paper used an entropy generation framework to analyze the collection and transport of solar exergy of a photovoltaic (PV) heat exchanger under buoyancy induced hybrid airflow. Investigations were conducted on a vertically-inclined PV heat exchanger composed of 2 adjacent PV modules and a back panel with buoyancy-induced air movement through the inlet damper system. Measurements of the exchanger were used to create an entropy matrix. Measured mass flow rate was used to calculate entropy transport due to steady heat flux. Non-linearity of temperature dependent boundary conditions was eliminated through the use of a 1-D heat balance model. The effect of radiative transport of entropy exchange between surface nodes of the PV module and back panel were considered using the radiosity-irradiation method. Radiation exchange factors were used to calculate radiative transport of entropies. Convective heat transfer coefficients were then calculated using temperatures obtained from the heat balance model. The inverse of entropy matrix was multiplied with the heat source element matrix to obtain temperatures at 30 different nodes. The temperature matrix obtained at the nodes was then used to obtain entropy generation due to energy conversion. Results indicated that air temperature was higher at the outlet of the exchanger. Surface temperature of the PV module was also higher than ambient air temperature. The back panel was heated by long wave radiation entropy exchange from the PV module and its temperature was marginally higher than ambient air temperature. Considerable variation in the surface temperature along the exchanger's height was observed. It was concluded that the proposed model predicted the results obtained from the experimental apparatus. 7 refs., 5 figs.

  9. Continuation of Studies on Development of ODS Heat Exchanger Tubing

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Brown; David Workman; Bimal Kad; Gaylord Smith; Archie Robertson; Ian Wright

    2008-04-15

    The Department of Energy (DOE), National Energy Technology Center (NETL), has initiated a strategic plan for the development of advanced technologies needed to design and build fossil fuel plants with very high efficiency and environmental performance. These plants, referred to as 'Vision 21' and FutureGen programs by DOE, will produce electricity, chemicals, fuels, or a combination of these products, and possibly secondary products such as steam/heat for industrial use. MA956 is a prime candidate material being considered for a high temperature heat exchanger in the 'Vision 21' and FutureGen programs. This material is an oxide dispersion strengthened (ODS) alloy; however, there are some gaps in the data required to commit to the use of these alloys in a full-size plant. To fill the technology gaps for commercial production and use of the material for 'Advanced Power Generation Systems' this project has performed development activity to significant increase in circumferential strength of MA956 as compared to currently available material, investigated bonding technologies for bonding tube-to-tube joints through joining development, and performed tensile, creep and fire-side corrosion tests to validate the use and fabrication processes of MA956 to heat exchanger tubing applications. Development activities within this projected has demonstrated increased circumferential strength of MA956 tubes through flow form processing. Of the six fabrication technologies for bonding tube-to-tube joints, inertia friction welding (IFW) and flash butt welding (FBW) were identified as processes for joining MA956 tubes. Tensile, creep, and fire-side corrosion test data were generated for both base metal and weld joints. The data can be used for design of future systems employing MA956. Based upon the positive development activities, two test probes were designed and fabricated for field exposure testing at 1204 C ({approx}2200 F) flue gas. The probes contained tube portions with FBW and IFW welded MA956. Field testing of the probes and remaining heat exchanger design activity will be performed by Oak Ridge National Laboratory under DOE Contract DE-AC05-00OR22725.

  10. Exchange Rate Misalignment, Volatility and Import Flows in Malaysia

    OpenAIRE

    Naseem, N.A.M; Tan, Hui-Boon; Hamizah, M.S

    2008-01-01

    This paper investigates the effect of real exchange rate misalignment and volatility on Malaysian import flows during 1991:Q1 to 2003:Q4. A measure of the quantitative proxy of the real exchange rate misalignment is constructed using the Natural Real Exchange Rate (NATREX) equilibrium model, whereas the volatility of real exchange rate is generated from the GARCH model. This paper differs from existing literature as the effects of exchange rate misalignment significantly hastened the level of...

  11. Process Heat Exchanger Options for Fluoride Salt High Temperature Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Piyush Sabharwall; Eung Soo Kim; Michael McKellar; Nolan Anderson

    2011-04-01

    The work reported herein is a significant intermediate step in reaching the final goal of commercial-scale deployment and usage of molten salt as the heat transport medium for process heat applications. The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production and process heat application, which would support large-scale deployment.

  12. Process Heat Exchanger Options for the Advanced High Temperature Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Piyush Sabharwall; Eung Soo Kim; Michael McKellar; Nolan Anderson

    2011-06-01

    The work reported herein is a significant intermediate step in reaching the final goal of commercial-scale deployment and usage of molten salt as the heat transport medium for process heat applications. The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production and process heat application, which would support large-scale deployment.

  13. Heat Pipe Heat Exchangers with Double Isolation Layers for Prevention of Interpath Leakage Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Current manned spacecraft heat rejection systems use two heat exchangers and an intermediate fluid loop to provide isolation between the crew compartment air and...

  14. Heat Pipe Heat Exchangers with Double Isolation Layers for Prevention of Interpath Leakage Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Cooling Technologies, Inc. (ACT), supported by Hamilton Sundstrand, proposes to develop a heat pipe heat exchanger that is low mass and provides two levels...

  15. Testing the SPOT heat exchanger at the OKB Gidropress stand

    International Nuclear Information System (INIS)

    The work is aimed at describing the SPOT heat exchanger test (the system for the passive heat removal), intended for the prolonged heat removal from the reactor core by the NPP de-energizing with the loss of all the emergency electric supply sources. The descriptions of the testing stand, the heat exchanger model, the purposes and methodology of the tests are presented. The test results by the customer program are discussed. The obtained data are applied for substantiating the full-scale SPOT efficiency

  16. Thermal performance analysis of heat exchanger for closed wet cooling tower using heat and mass transfer analogy

    International Nuclear Information System (INIS)

    In closed wet cooling towers, the heat transfer between the air and external tube surfaces can be composed of the sensible heat transfer and the latent heat transfer. The heat transfer coefficient can be obtained from the equation for external heat transfer of tube banks. According to experimental data, the mass transfer coefficient was affected by the air velocity and spray water flow rate. This study provides the correlation equation for mass transfer coefficient based on the analogy of the heat and mass transfer and the experimental data. The results from this correlation equation showed fairly good agreement with experimental data. The cooling capacity and thermal efficiency of the closed wet cooling tower were calculated from the correlation equation to analyze the performance of heat exchanger for the tower

  17. High Effectiveness Heat Exchanger for Cryogenic Refrigerators Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose an innovative high performance cryogenic heat exchanger manufactured of titanium by photo-etching and diffusion bonding. This is a parallel plate design...

  18. Various methods to improve heat transfer in exchangers

    Science.gov (United States)

    Pavel, Zitek; Vaclav, Valenta

    2015-05-01

    The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.

  19. Phase Change Material (PCM) Heat Exchanger Development Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Project has identified two PCM HX concepts that will be designed, developed and demonstrated on-board the International Space Station (ISS):The first heat exchanger...

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

    CERN Document Server

    Lee, H S

    2010-01-01

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

  1. A minichannel aluminium tube heat exchanger - Pt. 3: Condenser performance with propane

    Energy Technology Data Exchange (ETDEWEB)

    Fernando, Primal; Palm, Bjoern; Ameel, Tim; Lundqvist, Per; Granryd, Eric [Department of Energy Technology, Division of Applied Thermodynamics and Refrigeration, Royal Institute of Technology (KTH), Stockholm (Sweden)

    2008-06-15

    This paper reports heat transfer results obtained during condensation of refrigerant propane inside a minichannel aluminium heat exchanger vertically mounted in an experimental setup simulating a water-to-water heat pump. The condenser was constructed of multiport minichannel aluminium tubes assembled as a shell-and-tube heat exchanger. Propane vapour entered the condenser tubes via the top end and exited sub-cooled from the bottom. Coolant water flowed upward on the shell-side. The heat transfer areas of the tube-side and the shell-side of the condenser were 0.941 m{sup 2} and 0.985 m{sup 2}, respectively. The heat transfer rate between the two fluids was controlled by varying the evaporation temperature while the condensation temperature was fixed. The applied heat transfer rate was within 3900-9500 W for all tests. Experiments were performed at constant condensing temperatures of 30{sup o}C, 40{sup o}C and 50{sup o}C, respectively. The cooling water flow rate was maintained at 11.90 l min{sup -1} for all tests. De-superheating length, two-phase length, sub-cooling length, local heat transfer coefficients and average heat transfer coefficients of the condenser were calculated. The experimental heat transfer coefficients were compared with predictions from correlations found in the literature. The experimental heat transfer coefficients in the different regions were higher than those predicted by the available correlations. (author)

  2. Morse homology for the heat flow

    OpenAIRE

    Weber, Joa

    2010-01-01

    We use the heat flow on the loop space of a closed Riemannian manifold to construct an algebraic chain complex. The chain groups are generated by perturbed closed geodesics. The boundary operator is defined in the spirit of Floer theory by counting, modulo time shift, heat flow trajectories that converge asymptotically to nondegenerate closed geodesics of Morse index difference one.

  3. Computer aided heat transfer analysis in a laboratory scaled heat exchanger unit

    International Nuclear Information System (INIS)

    In this study. an explanation of a laboratory scaled heat exchanger unit and a software which is developed to analyze heat transfer. especially to use it in heat transfer courses, are represented. Analyses carried out in the software through sample values measured in the heat exchanger are: (l) Determination of heat transfer rate, logarithmic mean temperature difference and overall heat transfer coefficient; (2)Determination of convection heat transfer coefficient inside and outside the tube and the effect of fluid velocity on these; (3)Investigation of the relationship between Nusselt Number. Reynolds Number and Prandtl Number by using multiple non-linear regression analysis. Results are displayed on the screen graphically

  4. Radiative properties effects on unsteady natural convection inside a saturated porous medium. Application for porous heat exchangers

    International Nuclear Information System (INIS)

    The present article deals with a numerical study of coupled fluid flow and heat transfer by transient natural convection and thermal radiation in a porous bed confined between two-vertical hot plates and saturated by a homogeneous and isotropic fluid phase. The main objective is to study the effects of radiative properties on fluid flow and heat transfer behavior inside the porous material. The numerical results show that the temperature, the axial velocity, the volumetric flow rate and the convective heat flux exchanged at the channel's exit are found to be increased when the particle emissivity (?) and/or the absorption coefficient (?) increase or when the scattering coefficient (?s) and/or the single scattering albedo (?) decrease. Furthermore, the amount of heat (Qc) transferred to fluid and the energetic efficiency Ec are found to be increased when there is a raise in the particle emissivity values. In order to improve the performance of heat exchanger, we proposed the model of a porous heat exchanger which includes a porous bed of large spherical particles with high emissivity as a practical application of the current study. - Highlights: • The temperature increases with the particle emissivity ?. • The volumetric flow rate and the convective heat flux exchanged increase with the particle emissivity ?. • The amount of heat transferred to fluid and the energetic efficiency increase with the particle emissivity ?. • A heat exchanger including a porous bed of spherical particles with high emissivity is proposed like a practical application

  5. Simulation of stirred yoghurt processing in plate heat exchangers

    OpenAIRE

    Fernandes, Carla S.; Dias, Ricardo P.; Nóbrega, João M.; Afonso, Isabel A.; Melo, Luis F.; Maia, João M.

    2005-01-01

    In the present work, simulations of stirred yoghurt processing in a plate heat exchanger were performed using computational fluid dynamics (CFD) calculations and the results compared with experimental data, showing a very good agreement. A Herschel–Bulkley model for the viscosity and an Arrhenius-type term for the temperature dependence were used to model the thermo-rheological behaviour of yoghurt. The heat exchanger used in this study operates in a parallel arrangement, thus simplifyi...

  6. Surface interactions and deposit growth in fouling of heat exchangers

    OpenAIRE

    Oliveira, Ros??rio; L. F. Melo; Pinheiro, Maria Manuela; Vieira, M. J.

    1993-01-01

    Fouling of heat exchangers is a costly problem in industJ)'. There is a need for a better understanding of the phenomena involved in the build up of deposits on surfaces. The paper reviews the basic mechanisms of fouling, emphasizing their rdle in determining the overall fouling rate. Mass transfer, adhesion, chemical or biological reactions can be the rate limiting processes depending on the design and operating conditions of the heat exchanger. Reference is made to the most c...

  7. Experimental performance investigation of a shell and tube heat exchanger by exergy based sensitivity analysis

    Science.gov (United States)

    Mert, Suha Orçun; Reis, Alper

    2015-07-01

    Heat exchangers are used extensively in many industrial branches, primarily so in chemical and energy sectors. They also have important household usage as they are used in central and local heating systems. Any betterment on heat exchangers will serve greatly in preserving our already dwindling and costly energy resources. Strong approach of exergy analysis -which helps find out where the first steps should be taken in determining sources of inefficiencies and how to remedy them- will be used as a means to this end. The maximum useful work that can be harnessed from systems relationships with its environment is defined as exergy. In this study, the inlet and outlet flow rate values of fluids and temperature of hot stream both on shell and tube parts of a shell-tube heat exchange system have been inspected and their effects on the exergy efficiency of this thermal system have been analyzed. It is seen that the combination of high tube side inlet temperature, low shell side flow rate and high tube side flow rate are found to be the optimum for this experimental system with reaching 75, 65, and 32 % efficiencies respectively. Selecting operating conditions suitable to this behavior will help to increase the overall efficiency of shell-tube heat exchange systems and cause an increment in energy conservation.

  8. Hydraulic transmissivity and heat exchange efficiency of open fractures: a model based on lowpass filtered apertures

    CERN Document Server

    Neuville, Amélie; Schmittbuhl, Jean; 10.1111/j.1365-246X.2011.05126.x

    2011-01-01

    Natural open joints in rocks commonly present multi-scale self-affine apertures. This geometrical complexity affects fluid transport and heat exchange between the flow- ing fluid and the surrounding rock. In particular, long range correlations of self-affine apertures induce strong channeling of the flow which influences both mass and heat advection. A key question is to find a geometrical model of the complex aperture that describes at best the macroscopic properties (hydraulic conductivity, heat exchange) with the smallest number of parameters. Solving numerically the Stokes and heat equa- tions with a lubrication approximation, we show that a low pass filtering of the aperture geometry provides efficient estimates of the effective hydraulic and thermal properties (apertures). A detailed study of the influence of the bandwidth of the lowpass filtering on these transport properties is also performed. For instance, keeping the information of amplitude only of the largest Fourier length scales allows us to rea...

  9. Advanced microchannel heat exchanger with S-shaped fins

    International Nuclear Information System (INIS)

    Fin shape effects on thermal-hydraulic characteristics were studied for a Microchannel Heat Exchanger (MCHE) with S-shaped fins using 3D-CFD and changing the fin parameters: fin angle, overlapping length, fin width, fin length, and edge roundness. The fin angle effect on the pressure drop is consistent with the equation obtained experimentally by Weisbach for a circular bent tube: the pressure drop in the S-shaped fin configuration results from bent flow. The overlap of fins with those located immediately downstream at the offset position provides a guide wing effect that reduces the pressure drop remarkably. The overlap was changed by changing the fin radial position and arc length. The pressure drop was minimized when the downstream fins are placed in the middle of the bent flow channels formed by the fins upstream, which differs from Ito's configuration obtained from experiments with a single bent duct. Regarding arc length, the pressure drop is minimized at the standard overlapping length, which was formed to have the longest arc without a change in channel width. Shorter arc lengths from the optimum value by 30 and 50%, respectively, give 2.4 and 4.6% decreases in the heat transfer rate and 17 and 13% increases in the pressure drop. Thinner fins show better thermal-hydraulic performance for fin widths of 0.2-0.8 mm. However, the pressure drop reduced by the longer fin and heat transfer rate was also reduced. Rounded fins with 0.1 mm radius increased the pressure drop by about 30% compared with that of the fin designed with no roundness. (author)

  10. Three-dimensional performance analysis of plain fin tube heat exchangers in transitional regime

    International Nuclear Information System (INIS)

    Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a four-row plain fin-and-tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS CFX 12.0. Heat transfer and pressure drop characteristics of the heat exchanger are investigated for Reynolds numbers ranging from 400 to 2000. Fluid flow and heat transfer are simulated and results compared using both laminar and turbulent flow models (k-?) with steady and incompressible fluid flow. Model validation is carried out by comparing the simulated case friction factor (f) and Colburn factor (j) with the experimental data of Wang et al.. Reasonable agreement is found between the simulations and experimental data. In this study the effect of geometrical parameters such as fin pitch, longitudinal pitch and transverse pitch of tube spacing are studied. Results are presented in the form of friction factor (f) and Colburn factor (j). For both laminar and transitional flow conditions heat transfer and friction factor decrease with the increase of longitudinal and transverse pitches of tube spacing whereas they increase with fin pitches for both in-line and staggered configurations. Efficiency index increases with the increase of longitudinal and transverse pitches of tube spacing but decreases with increase of fin pitches. For a particular Reynolds number, the efficiency index is higher in in-line arrangement than the staggered case. - Highlights: ? 3D CFD simulations for plain-fin-and-tube heat exchanger. ? Validated with experimental data. ? Parametric study for the effects of fluid flow and heat transfer.

  11. Quantum, cyclic and 'particle exchange' heat engines

    CERN Document Server

    Humphrey, T E

    2004-01-01

    We show that a range of 'non-cyclic' heat engines, including thermionic and thermoelectric devices, the three-level amplifier (thermally pumped laser), solar cells and LEDs and some Brownian heat engines all share a common thermodynamic mechanism for achieving reversibility and finite power, which is quite different from that utilized in cyclic heat engines such as the Carnot, Otto or Brayton cycles.

  12. Heat transfer and pressure drop during hydrocarbon refrigerant condensation inside a brazed plate heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Longo, Giovanni A. [University of Padova, Department of Management and Engineering, Str.lla S.Nicola 3, I-36100 Vicenza (Italy)

    2010-08-15

    This paper presents the heat transfer coefficients and pressure drop measured during HC-600a, HC-290 and HC-1270 saturated vapour condensation inside a brazed plate heat exchanger: the effects of refrigerant mass flux, saturation temperature (pressure) and fluid properties are investigated. The heat transfer coefficients show weak sensitivity to saturation temperature (pressure) and great sensitivity to refrigerant mass flux and fluid properties. A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 15-18 kg m{sup -2} s{sup -1}. In the forced convection condensation region the heat transfer coefficients show a 35-40% enhancement for a 60% increase of the refrigerant mass flux. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. HC-1270 shows heat transfer coefficients 5% higher than HC-600a and 10-15% higher than HC-290, together with frictional pressure drop 20-25% lower than HC-290 and 50-66% lower than HC-600a. (author)

  13. Liquid-metal-gas heat exchanger for HTGR type reactors

    International Nuclear Information System (INIS)

    The aim of this study is to investigate the heat transfer characteristics of a liquid metal heat exchanger (HE) for a helium-cooled high temperature reactor. A tube-type heat exchanger is considered as well as two direct exchangers: a bubble-type heat exchanger and a heat exchanger according to the spray principle. Experiments are made in order to determine the gas content of bubble-type heat exchangers, the dependence of the droplet diameter on the nozzle diameter, the falling speed of the droplets, the velocity of the liquid jet, and the temperature variation of liquid jets. The computer codes developed for HE calculation are structured so that they may be used for gas/liquid HE, too. Each type of HE that is dealt with is designed by accousting for a technical and an economic assessment. The liquid-lead jet spray is preferred to all other types because of its small space occupied and its simple design. It shall be used in near future in the HTR by the name of lead/helium HE. (GL)

  14. Heat flow of the Norwegian continental shelf

    Science.gov (United States)

    Pascal, Christophe

    2015-04-01

    Terrestrial heat flow influences a large collection of geological processes. Its determination is a requirement to assess the economic potential of deep sedimentary basins. Published heat flow calculations from e.g. major oil provinces are however seldom. Robust heat flow determinations in drillholes require logging of undisturbed temperatures and intensive sampling of core material for petrophysical measurements. Temperature logging in exploration drillholes is traditionally conducted during drill breaks or shortly after drilling, resulting in temperatures severely disturbed by mud circulation and coring is restricted to selected intervals. Alternatively, test temperatures, information from electric logs and lithological descriptions of drill cuttings can be used to overcome these limitations. The present contribution introduces new heat flow determinations based on 63 exploration drillholes from the Norwegian North Sea, the Mid Norway Margin and the Barents Shelf. Our analyses are based on released DST temperatures, precise lithological descriptions of drill cuttings, previously measured rock matrix thermal conductivities and established porosity laws. Our results suggest median heat flow values of 64 mW/m2, 65 mW/m2 and 72 mW/m2 for the North Sea, the Mid Norway Margin (mainly the Trøndelag Platform) and the SW Barents Shelf respectively. The Barents Shelf shows significantly high heat flow, suggesting lateral transfer of heat from the mantle of the adjacent young ocean. In detail, heat flow increases by ~ 10 mW/m2 from the southern Norwegian North Sea towards the Mid Norway Margin. This result appears to be in very good agreement with seismic tomographic studies suggesting northward thinning of the underlying mantle lithosphere. Our results together with published marine heat flow data from the Mid Norway Margin suggest a gradual decrease in heat flow levels from both the North Sea and the Trøndelag Platform towards the centres of the deep Møre and Vøring basins. This latter effect is attributed to reduced heat input from crustal sources caused by the extreme attenuation of the crystalline basement below these two basins.

  15. The consideration of dynamics and control in the design of heat exchanger networks

    International Nuclear Information System (INIS)

    The heat exchanger network method is a way of abstracting the enthalpy and heat flows from the blueprints of a planned or existing processing plant. It enables a systematic design of a plant-wide heat recovery system which is optimal with regard to energy costs, capital costs and operational requirements. A heat exchanger network is a representation of all heat transfer relations between hot process streams and cold process streams within a plant. During the past ten years, the optimal design of heat exchanger networks (i.e. the optimal arrangement of heat transfer relations within a plant) has developed into a field of research of its own. Both, static methods ('interaction analysis') and dynamic methods ('process reaction curve analysis') from control theory have been used to explore the new field of heat exchanger network dynamics. As a major tool, an interactive, portable computer program for network simulation and controllability assessment has been developed (it is available as a design tool within the frame of the International Energy Agency). Based on the well-understood global parameters: effectiveness and NTU, which follow from the network design, some straightforward methods covering the following topics are presented: - 'paths' for control and disturbance signal transfer across the network, - locations of control bypasses around heat exchangers, and their capacity of emitting control signals or absorbing disturbances, - influence of the equipment besides the heat exchangers (which can be regarded as 'surrounding' the network, thus forming an 'associated' network). It has been found that networks which are designed according to the 'pinch-based' method have a potential for good controllability. It is shown how, using the freedoms given in the 'pinch-based' design and the above-mentioned methods, that potential is put into effect. (author)

  16. Heat-transfer analysis of double-pipe heat exchangers for indirect-cycle SCW NPP

    Science.gov (United States)

    Thind, Harwinder

    SuperCritical-Water-cooled Reactors (SCWRs) are being developed as one of the Generation-IV nuclear-reactor concepts. SuperCritical Water (SCW) Nuclear Power Plants (NPPs) are expected to have much higher operating parameters compared to current NPPs, i.e., pressure of about 25 MPa and outlet temperature up to 625 °C. This study presents the heat transfer analysis of an intermediate Heat exchanger (HX) design for indirect-cycle concepts of Pressure-Tube (PT) and Pressure-Vessel (PV) SCWRs. Thermodynamic configurations with an intermediate HX gives a possibility to have a single-reheat option for PT and PV SCWRs without introducing steam-reheat channels into a reactor. Similar to the current CANDU and Pressurized Water Reactor (PWR) NPPs, steam generators separate the primary loop from the secondary loop. In this way, the primary loop can be completely enclosed in a reactor containment building. This study analyzes the heat transfer from a SCW primary (reactor) loop to a SCW and Super-Heated Steam (SHS) secondary (turbine) loop using a double-pipe intermediate HX. The numerical model is developed with MATLAB and NIST REFPROP software. Water from the primary loop flows through the inner pipe, and water from the secondary loop flows through the annulus in the counter direction of the double-pipe HX. The analysis on the double-pipe HX shows temperature and profiles of thermophysical properties along the heated length of the HX. It was found that the pseudocritical region has a significant effect on the temperature profiles and heat-transfer area of the HX. An analysis shows the effect of variation in pressure, temperature, mass flow rate, and pipe size on the pseudocritical region and the heat-transfer area of the HX. The results from the numerical model can be used to optimize the heat-transfer area of the HX. The higher pressure difference on the hot side and higher temperature difference between the hot and cold sides reduces the pseudocritical-region length, thus decreases the heat-transfer surface area of the HX.

  17. Statistical properties of the energy exchanged between two heat baths coupled by thermal fluctuations

    DEFF Research Database (Denmark)

    Ciliberto, S.; Imparato, A.; Naert, A.; Tanase, M.

    2013-01-01

    We study both experimentally and theoretically the statistical properties of the energy exchanged between two electrical conductors, kept at different temperatures by two different heat reservoirs, and coupled by the electrical thermal noise. Such a system is ruled by the same equations as two Brownian particles kept at different temperatures and coupled by an elastic force. We measure the heat flowing between the two reservoirs and the thermodynamic work done by one part of the system on the ot...

  18. An investigation of a compact heat exchanger unit using CFD with experimental support

    Directory of Open Access Journals (Sweden)

    Peukert Pavel

    2015-01-01

    Full Text Available The paper contains a comparison of a numerical simulation with a real experiment. In the measured and simulated device is located a heat exchanger with a centrifugal fan. Due to the fan and the geometrical arrangement the flow is relative uneven and so the heat transfer hard to predict. The simulation should be time and cost affordable, so a standard k-? turbulence model and a relative simple mesh was used for the computations.

  19. An investigation of a compact heat exchanger unit using CFD with experimental support

    Science.gov (United States)

    Peukert, Pavel; Kolá?, Jan; Adámek, Karel

    2015-05-01

    The paper contains a comparison of a numerical simulation with a real experiment. In the measured and simulated device is located a heat exchanger with a centrifugal fan. Due to the fan and the geometrical arrangement the flow is relative uneven and so the heat transfer hard to predict. The simulation should be time and cost affordable, so a standard k-? turbulence model and a relative simple mesh was used for the computations.

  20. Analysis of Condensation Phenomena in PAFS (Passive Auxiliary Feedwater System) Horizontal Heat Exchanger of APR+

    International Nuclear Information System (INIS)

    APR+ (Advanced Power Reactor Plus) is the next generation nuclear power plant in Korea. It adopts PAFS (Passive Auxiliary Feedwater System) on the secondary system. It can replace the conventional active system for auxiliary feedwater injection to the steam generator, and it enable to supply the coolant by a passive system. It cools down the secondary system by heat transfer at a horizontal U-tube in PCCT (Passive Condensate Cooling Tank). High pressure steam flow from the steam generator is condensed in the horizontal heat exchanger. The water in PCCT is maintained at an atmospheric pressure, so that boiling heat transfer at the outside wall of heat exchanger and natural convection occur in PCCT pool. The heat exchanger and PCCT is higher than steam generator, so condensate can be drained and injected to feedwater system without any active system. This study aims at design of the horizontal heat exchanger in PAFS. It should remove the heat generated in the steam generator. To satisfy this requirement, a system code analysis is conducted. The amount of condensation heat transfer is investigated by MARS (Multi-dimensional Analysis for Reactor Safety) code analysis