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Sample records for flow heat exchanger

  1. Radial flow heat exchanger

    Science.gov (United States)

    Valenzuela, Javier (Hanover, NH)

    2001-01-01

    A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.

  2. Heat exchanger with oscillating flow

    Science.gov (United States)

    Scotti, Stephen J. (inventor); Blosser, Max L. (inventor); Camarda, Charles J. (inventor)

    1993-01-01

    Various heat exchange apparatuses are described in which an oscillating flow of primary coolant is used to dissipate an incident heat flux. The oscillating flow may be imparted by a reciprocating piston, a double action twin reciprocating piston, fluidic oscillators or electromagnetic pumps. The oscillating fluid flows through at least one conduit in either an open loop or a closed loop. A secondary flow of coolant may be used to flow over the outer walls of at least one conduit to remove heat transferred from the primary coolant to the walls of the conduit.

  3. Heat exchange method using natural flow of heat exchange medium

    International Nuclear Information System (INIS)

    Heat exchange is effected in a simple and economical manner by allowing natural flow, i.e., without mechanical compressors, pumps, etc., of a heat exchange fluid such as a conventional refrigerant liquid between two heat exchangers which are exposed to air at different temperatures. The two heat exchangers, which may conveniently take the form of fin-tube heat exchangers, for example, are arranged with one end at a higher elevation than the other, the upper ends of the two exchangers being connected in direct communication and the lower ends being likewise connected. As the refrigerant liquid absorbs heat and evaporates in the heat exchanger exposed to the warmer air the vapor travels through the upper connecting line to the other heat exchanger, where it rejects heat and is condensed, the liquid flows through the lower connecting line back to the first heat exchanger, and so on, with heat exchange between the two air streams or masses occurring during the natural, continuous flow of the refrigerant in gaseous and liquid form

  4. 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)

  5. 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.

  6. 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…

  7. 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.

  8. Characteristics of heat flow in recuperative heat exchangers

    Directory of Open Access Journals (Sweden)

    Lalovi? Milisav

    2005-01-01

    Full Text Available A simplified model of heat flow in cross-flow tube recuperative heat exchangers (recuperators was presented in this paper. One of the purposes of this investigation was to analyze changes in the values of some parameters of heat transfer in recuperators during combustion air preheating. The logarithmic mean temperature (Atm and overall heat transfer coefficient (U, are two basic parameters of heat flow, while the total heated area surface (A is assumed to be constant. The results, presented as graphs and in the form of mathematical expressions, were obtained by analytical methods and using experimental data. The conditions of gaseous fuel combustions were defined by the heat value of gaseous fuel Qd = 9263.894 J.m-3, excess air ratio ?= 1.10, content of oxygen in combustion air ?(O2 = 26%Vol, the preheating temperature of combustion air (cold fluid outlet temperature tco = 100-500°C, the inlet temperature of combustion products (hot fluid inlet temperature thi = 600-1100°C.

  9. Auxiliary heat-exchanger flow-distribution test

    International Nuclear Information System (INIS)

    The Auxiliary Heat Exchanger Flow Distribution Test was the first part of a test program to develop a water-cooled (tube-side), compact heat exchanger for removing heat from the circulating gas in a High-Temperature Gas-Cooled Reactor (HTGR). The function of this heat exchanger is to provide emergency cooldown for the HTGR. It is designed to operate over a wide range of helium or helium mixture conditions from depressurized to pressurized reactor operations

  10. 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.)

  11. 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

  12. 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 ...

  13. 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.

  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. Flow-induced vibration of component cooling water heat exchangers

    International Nuclear Information System (INIS)

    This paper presents an evaluation of flow-induced vibration problems of component cooling water heat exchangers in one of Taipower's nuclear power stations. Specifically, it describes flow-induced vibration phenomena, tests to identify the excitation mechanisms, measurement of response characteristics, analyses to predict tube response and wear, various design alterations, and modifications of the original design. Several unique features associated with the heat exchangers are demonstrated, including energy-trapping modes, existence of tube-support-plate (TSP)-inactive modes, and fluidelastic instability of TSP-active and -inactive modes. On the basis of this evaluation, the difficulties and future research needs for the evaluation of heat exchangers are identified. 11 refs., 19 figs., 3 tabs

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

    Directory of Open Access Journals (Sweden)

    Pavel Neuberger

    2014-02-01

    Full Text Available 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 heat-exchangers, has been characterised by meticulous measurements. These reveal that high concentrations of antifreeze mix in the heat-transfer fluid of the heat exchanger have an adverse impact on heat flows discharged into the soil.

  17. 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...

  18. A novel compact heat exchanger using gap flow mechanism

    Science.gov (United States)

    Liang, J. S.; Zhang, Y.; Wang, D. Z.; Luo, T. P.; Ren, T. Q.

    2015-02-01

    A novel, compact gap-flow heat exchanger (GFHE) using heat-transfer fluid (HTF) was developed in this paper. The detail design of the GFHE coaxial structure which forms the annular gap passage for HTF is presented. Computational fluid dynamics simulations were introduced into the design to determine the impacts of the gap width and the HTF flow rate on the GFHE performance. A comparative study on the GFHE heating rate, with the gap widths ranged from 0.1 to 1.0 mm and the HTF flow rates ranged from 100 to 500 ml/min, was carried out. Results show that a narrower gap passage and a higher HTF flow rate can yield a higher average heating rate in GFHE. However, considering the compromise between the GFHE heating rate and the HTF pressure drop along the gap, a 0.4 mm gap width is preferred. A testing loop was also set up to experimentally evaluate the GFHE capability. The testing results show that, by using 0.4 mm gap width and 500 ml/min HTF flow rate, the maximum heating rate in the working chamber of the as-made GFHE can reach 18 °C/min, and the average temperature change rates in the heating and cooling processes of the thermal cycle test were recorded as 6.5 and 5.4 °C/min, respectively. These temperature change rates can well satisfy the standard of IEC 60068-2-14:2009 and show that the GFHE developed in this work has sufficient heat exchange capacity and can be used as an ideal compact heat exchanger in small volume desktop thermal fatigue test apparatus.

  19. Analysis of heat transfers inside counterflow plate heat exchanger augmented by an auxiliary fluid flow.

    Science.gov (United States)

    Khaled, A-R A

    2014-01-01

    Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost. PMID:24719572

  20. 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.

  1. Characteristics of fluid flow and heat transfer in a fluidized heat exchanger with circulating solid particles

    International Nuclear Information System (INIS)

    The commercial viability of heat exchanger is mainly dependent on its long-term fouling characteristic because the fouling increase the pressure loss and degrades the thermal performance of a heat exchanger. An experimental study was performed to investigate the characteristics of fluid flow and heat transfer in a fluidized bed heat exchanger with circulating various solid particles. The present work showed that the higher densities of particles had higher drag force coefficients, and the increases in heat transfer were in the order of sand, copper, steel, aluminum, and glass below Reynolds number of 5,000

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

    DEFF Research Database (Denmark)

    Knudsen, SØren; Morrison, GL

    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. The flow structure was evaluated for both high and low temperature incoming flows and for both initially mixed and initially stratified inner tank and mantle. The analysis of the heat transfer showed that the flow in the mantle near the inlet is mixed convection flow and that the heat transfer is dependent on the mantle inlet temperature relative to the core tank temperature at the mantle level. (C) 2004 Elsevier Ltd. All rights reserved.

  3. Analysis of flow induced vibration in heat exchangers

    International Nuclear Information System (INIS)

    A description will be given of three different types of heat exchangers developed by the Dutch Nuclear Industry Group ''Neratoom'' in cooperation with TNO for the sodium-cooled fast breeder reactor SNR-300 at Kalkar. Moreover, the research related with flow induced vibrations carried out by TNO (Organization for Applied Scientific Research) will be presented. The flow induced forces on the tubes of the straight-tube steam generators were measured at the inlet and outlet section where partial crossflow occurs. With the measured flow induced forces the response of a tube was calculated as a function of the tube-to-supportbush clearances taking into account the non-linear damping effects from the sodium. The theoretical results showed that for this particular design no tube impact damage is to be expected which was confirmed later by a full scale experiment. Special attention will be devoted to the steam generator with helical-coil tube-bundles, where the sodium flows in a counter cross-flow over the tube-bundle. Extensive measurements of the power spectra of the flow induced forces were carried out since no information could be found in the literature. The vibration analysis will be presented and vibration modes of the entire bundle will be compared with experimentally obtained results. Finally a description of the vibration tests to be carried out on the intermediate heat exchanger (IHX) will be presented. (author)

  4. Thermal induced flow oscillations in heat exchangers for supercritical fluids

    Science.gov (United States)

    Friedly, J. C.; Manganaro, J. L.; Krueger, P. G.

    1972-01-01

    Analytical model has been developed to predict possible unstable behavior in supercritical heat exchangers. From complete model, greatly simplified stability criterion is derived. As result of this criterion, stability of heat exchanger system can be predicted in advance.

  5. 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)

  6. 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

  7. Analysis of Heat Transfers inside Counterflow Plate Heat Exchanger Augmented by an Auxiliary Fluid Flow

    OpenAIRE

    A.-R. A. Khaled

    2014-01-01

    Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conduct...

  8. Experimental study on the cross flow air cooled plate heat exchanger using fin with electric pump.

    Directory of Open Access Journals (Sweden)

    Pankaj kumar mishra

    2013-03-01

    Full Text Available Experimental study on the cross flow air cooled plate heat exchanger using fin with electric pump was performed. Two prototype plate heat exchanger were manufactured in a stack of single wave plates and double plates in parallel. Cooling air flows through the plate heat exchanger in across wise direction against internal cooling water. In this study prototype heat exchanger were tested in a laboratoryscale experiments. From test double wave plates heatexchanger shows approximately 52.50 % enhanced heat transfer performance compare to single wave plates heat exchanger . However double wave heat exchanger costs 30%additional pressure drop .

  9. 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...

  10. Experimental study on the cross flow air cooled plate heat exchanger using fin with electric pump.

    OpenAIRE

    Pankaj kumar mishra

    2013-01-01

    Experimental study on the cross flow air cooled plate heat exchanger using fin with electric pump was performed. Two prototype plate heat exchanger were manufactured in a stack of single wave plates and double plates in parallel. Cooling air flows through the plate heat exchanger in across wise direction against internal cooling water. In this study prototype heat exchanger were tested in a laboratoryscale experiments. From test double wave plates heatexchanger shows approximately 52.50 % enh...

  11. Ribbed tubed heat exchanger with multiple flow through it

    International Nuclear Information System (INIS)

    This exchanger is designed to give a reduction of the previously very high cost of manufacture and monitoring in operation. For this purpose the usual large number of small bore tubes is reduced to only 2 tubes. Three long coaxial cylindrical bodies of different diameters form an inner and an outer annular space with the media flowing through them, by their spacing. Four long bars installed on a horizontal diametral plane divide these annular spaces into an upper and a lower half each over the whole length. For example, oil enters at the left hand of the heat exchanger into the upper half of the outer annular space, passes into a reversing area at the right hand end and leaves the lower half at the left hand end. Fuel flows from the right hand end of the upper half of the inner annular space, reverses its flow direction in the second reversing area at the left hand end and leaves the lower half at the right hand end. Many radial rubs inside the annular spaces forster heat transfer. (RW)

  12. Woven heat exchanger

    Science.gov (United States)

    Piscitella, Roger R. (Idaho Falls, ID)

    1987-01-01

    In a woven ceramic heat exchanger using the basic tube-in-shell design, each heat exchanger consisting of tube sheets and tube, is woven separately. Individual heat exchangers are assembled in cross-flow configuration. Each heat exchanger is woven from high temperature ceramic fiber, the warp is continuous from tube to tube sheet providing a smooth transition and unitized construction.

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

    OpenAIRE

    Thirumarimurugan, M.; Kannadasan, T.; Ramasamy, E.

    2008-01-01

    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...

  14. The black box model of a double-tube counter-flow heat exchanger

    Science.gov (United States)

    Laskowski, Rafa?

    2014-12-01

    Variable working conditions of a double-tube counter-flow heat exchanger were analysed. During operation of the heat exchanger, the parameters (temperatures and mass flow rates) of both fluids at its inlet change, which leads to a change in its performance. Heat transfer effectiveness is commonly used to assess the heat exchanger performance, defined as the ratio of the actual to the maximum heat flow rate. In the present paper, the heat exchanger was considered to be a `black box', and the aim was to investigate how the inlet parameters (temperatures and mass flow rates of both fluids) affect the outlet ones (temperatures of both fluids), and thus to attempt to introduce a new relation for the heat transfer effectiveness of a counter-flow heat exchanger as a function of only inlet parameters. Following the analysis, a relation for the heat transfer effectiveness as a function of inlet parameters with five constant coefficients was obtained. These coefficients depend on the heat exchanger geometry and on the properties of the heat transfer fluids; they are not general-purpose, but specific to a counter-flow heat exchanger. The form of the proposed relation for the heat transfer effectiveness of a counter-flow heat exchanger is not satisfactory as it involves five constant coefficients; therefore, a new approach was chosen, consisting in analysing a parameter defined as the ratio of the minimum to the actual arithmetic mean temperature difference. Using the parameter defined in this way, the relation for the heat transfer effectiveness of a counter-flow heat exchanger was obtained as a function of two parameters: the ratio of the heat capacity rates of both fluids, and NTU, with no constant coefficients. The proposed relations were verified against the data produced by a simulator of a double-tube counter-flow heat exchanger.

  15. 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.

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

    OpenAIRE

    Parekh, Parth P.; Chavda, Dr Neeraj K.

    2014-01-01

    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...

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

    DEFF Research Database (Denmark)

    Friis, Alan; Szabo, Peter

    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. The lack of the model to predict the heat transfer performance in scale-up leads us to identify the key dimensionless parameters relevant for scale-up.

  18. THEORETICAL AND EXPERIMENTAL ANALYSIS OF A CROSS-FLOW HEAT EXCHANGER

    Directory of Open Access Journals (Sweden)

    R. Tu?rul O?ULATA

    1996-03-01

    Full Text Available In this study, cross-flow plate type heat exchanger has been investigated because of its effective use in waste heat recovery systems. For this purpose, a heat regain system has been investigated and manufactured in laboratory conditions. Manufactured heat exchanger has been tested with an applicable experimental set up and temperatures, velocity of the air and the pressure losses occuring in the system have been measured and the efficiency of the system has been determined. The irreversibility of heat exchanger has been taken into consideration while the design of heat exchanger is being performed. So minimum entropy generation number has been analysied with respect to second law of thermodynamics in cross-flow heat exchanger. The minimum entropy generation number depends on parameters called optimum flow path length, dimensionless mass velocity and dimensionless heat transfer area. Variations of entropy generation number with these parameters have been analysied and introduced their graphics with their comments.

  19. A REVIEW ON EFFECT OF VORTEX GENERATORS ON FLOW CHARACTERISTICS AND HEAT TRANSFER IN HEAT EXCHANGERS

    Directory of Open Access Journals (Sweden)

    S.A.Wani

    2015-02-01

    Full Text Available The development of high-performance thermal systems has increased interest in heat transfer enhancement techniques. The high thermal performance enhancement of heat exchanger systems is needed to use energy source efficiently due to the sky-rocketing prices of petroleum and coal fuels. Heat exchangers are widely used in industry both for cooling and heating. Insertion of turbulator in the flow passage is one of the favorable passive heat transfer augmentation techniques due to their advantages of easy fabrication, operation as well as low maintenance. The purpose of this experiment is to find the efficient shape and size of the vortex generator by using and comparing various types of Winglet pairs.

  20. Modeling of turbulent heat transfer and thermal dispersion for flows in flat plate heat exchangers

    International Nuclear Information System (INIS)

    In this paper, heat transfer and dispersion for both laminar and turbulent regimes in heat exchangers and nuclear cores are considered. Such hydraulic systems might be seen as spatially periodic porous media. The existence of a turbulent flow within a porous medium structure suggests the use of a spatial average operator, combined to a statistical average operator. Previous works [M.H.J. Pedras, M.J.S. De Lemos, Macroscopic turbulence modeling for incompressible flow through un-deformable porous media, Int. J. Heat Mass Transfer 44 (2001) 1081-1093; F. Kuwahara, A. Nakayama, H. Koyama, A numerical study of thermal dispersion in porous medium, J. Heat Transfer 118 (1996) 756-761] have applied a double average procedure to the thermal balance equation, which led to a macroscopic turbulent transport and a subsequent macro-scale equation featuring dynamic dispersion. Considering the heat flux at the solid surfaces as a boundary condition for the fluid energy balance, the model proposed in this paper allows one to take into account this dispersion as the sum of two contributions. The first one is the classical dispersion due to velocity heterogeneities [G. Taylor, Dispersion of solute matter in solvent flowing slowly through a tube, Proc. Roy. Soc. Lond. A 219 (1953) 186-203] and the second one is due to wall heat transfer. Applying Whitaker up-scaling method [S. Whitaker, Theory and. applications of transport in porous media: the method of volume averaging, Kluwer Academimethod of volume averaging, Kluwer Academic Publishers, 1999], a 'closure problem' is then derived for a representative elementary volume, using the so-called Boussinesq approximation to account for small scale turbulence. The model is used to compute macro-scale heat transfer properties for turbulent flows inside a flat plate heat exchanger. It is shown that, for such flows, both dispersive fluxes strongly predominate over the macroscopic turbulent. heat flux. (authors)

  1. Microplate Heat Exchanger Project

    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...

  2. Sizing problem for a cross flow heat exchanger with wing-type vortex generator

    Science.gov (United States)

    Kotcioglu, Isak; Caliskan, Sinan; Ozdemir, Veysel; Baskaya, Senol

    2009-08-01

    In the present study, sizing of a single pass cross flow heat exchanger with unmixed fluid streams has been investigated. The heat exchanger is a cross flow heat exchanger. It has overall dimensions of 20 × 20 × 20 cm. Two the most common heat exchanger design problems are the rating and sizing problem. Sizing problems deal with designing an exchanger and determining its physical size to meet the specified heat duty, pressure drops and other considerations. It means the determination of the exchanger construction type, flow arrangement, heat transfer surface geometries and materials, and the physical sizes of an exchanger to meet specified heat transfer and pressure drop. In this study, the physical size (length, width, height, mass flow rates of both fluids and surface areas on each side of the exchanger) are determined. Inputs to the sizing problem are surface geometries, fluid mass flow rates, inlet and outlet fluid temperatures and pressure drop on each side. Dimensions of L a , L b , and L c for the selected surfaces were investigated such that the design meets the heat duty and pressure drops on both sides exactly.

  3. 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.

  4. Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed

    International Nuclear Information System (INIS)

    Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.

  5. Characteristics of fluid flow in a solid particle circulating fluidized heat exchanger

    International Nuclear Information System (INIS)

    The commercial viability of heat exchanger is mainly dependent on their long-term fouling characteristics because the fouling increases the pressure loss and degrades the thermal performance of a heat exchanger. An experimental study was performed to investigate the characteristics of fluid flow in a fluidized bed heat exchanger with circulating various solid particles. The present work showed that the drag force coefficients of particles in the internal flow were higher than in the external flow, in addition, they were lower with the shapes of particles being closer to the spherical geometries

  6. 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.

  7. 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.)

  8. Analysis of a double pipe heat exchanger performance by use of porous baffles and pulsating flow

    International Nuclear Information System (INIS)

    Highlights: • A double pipe heat exchanger performance is numerically studied. • Use of porous baffles and pulsating flow to enhance heat exchanger efficiency. • The governing equations are solved by the control volume method. • The efficiency increases with the amplitude and frequency of pulsation. • The highest values of are obtained when only hot fluid is pulsating (Case3). - Abstract: A numerical investigation is carried out to analyze the effect of porous baffles and flow pulsation on a double pipe heat exchanger performance. The hot fluid flows in the inner cylinder, whereas the cold fluid circulates in the annular gap. The Darcy–Brinkman–Forchheimer model is adopted to describe the flow in the porous regions and the finite volume method is used to solve the governing equations with the appropriate boundary conditions. The effects of the amplitude and frequency of pulsation, as well as the porous baffles permeability on the flow structure and the heat exchanger efficiency are analyzed. The results reveal that the addition of an oscillating component to the mean flow affects the flow structure, and enhances the heat transfer in comparison to the steady non pulsating flow. The highest heat exchanger performance is obtained when only the flow of the hot fluid is pulsating

  9. Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

    Directory of Open Access Journals (Sweden)

    Teng Tun-Chien

    2011-01-01

    Full Text Available Abstract This study analyzes the characteristics of alumina (Al2O3/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%. The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C, and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration.

  10. Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow.

    Science.gov (United States)

    Teng, Tun-Ping; Hung, Yi-Hsuan; Teng, Tun-Chien; Chen, Jyun-Hong

    2011-01-01

    This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration. PMID:21827644

  11. Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

    Science.gov (United States)

    Teng, Tun-Ping; Hung, Yi-Hsuan; Teng, Tun-Chien; Chen, Jyun-Hong

    2011-08-01

    This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration.

  12. Forced convective and subcooled flow boiling heat transfer to pure water and n-heptane in an annular heat exchanger

    International Nuclear Information System (INIS)

    Highlights: ? The cooling performance of water and n-heptane is compared during subcooled flow boiling. ? Although n-heptane leaves the heat exchanger warmer it has a lower heat transfer coefficient. ? Flow rate, heat flux and degree of subcooling have direct effect on heat transfer coefficient. ? The predictions of some correlations are evaluated against experimental data. - Abstract: In this research, subcooled flow boiling heat transfer coefficients of pure n-heptane and distilled water at different operating conditions have been experimentally measured and compared. The heat exchanger consisted of vertical annulus which is heated from the inner cylindrical heater with variable heat flux (less than 140 kW/m2). Heat flux is varied so that two different flow regimes from single phase forced convection to nucleate boiling condition are created. Meanwhile, liquid flow rate is changed in the range of 2.5 × 10?5–5.8 × 10?5 m3/s to create laminar up to transition flow regimes. Three subcooling levels including 10, 20 and 30 °C are also considered. Experimental results demonstrated that subcooled flow boiling heat transfer coefficient increases when higher heat flux, higher liquid flow rate and greater subcooling level are applied. Furthermore, influence of the operating conditions on the bubbles generation on the heat transfer surface is also discussed. It is also shown that water is better cooling fluid in comparison with n-heptane

  13. 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

  14. Heat exchanger

    International Nuclear Information System (INIS)

    A heat exchanger is proposed for the application in liquid-metal cooled fast breeder nuclear reactors, in which one may do without a liquid-metal intermediate loop. According to the invention, both tube bundles of the heat exchanger are surrounded by particles housing a particle size of 50 ?m to 1,000 ?m. A fluidized bed is produced by a fluidizing gas (e.g. helium), a cyclone separator retains the particles in the waste gas. The tube bundles are kept advantageously in separated sections. (UWI)

  15. Heat and mass exchanger

    Science.gov (United States)

    Lowenstein, Andrew (Princeton, NJ); Sibilia, Marc J. (Princeton, NJ); Miller, Jeffrey A. (Hopewell, NJ); Tonon, Thomas (Princeton, NJ)

    2011-06-28

    A mass and heat exchanger includes at least one first substrate with a surface for supporting a continuous flow of a liquid thereon that either absorbs, desorbs, evaporates or condenses one or more gaseous species from or to a surrounding gas; and at least one second substrate operatively associated with the first substrate. The second substrate includes a surface for supporting the continuous flow of the liquid thereon and is adapted to carry a heat exchange fluid therethrough, wherein heat transfer occurs between the liquid and the heat exchange fluid.

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

    OpenAIRE

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

    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...

  17. 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.

  18. Heat exchanger for heat production

    International Nuclear Information System (INIS)

    The description is given of a heat exchanger of the kind in which a primary fluid, flowing in a bundle of parallel tubes which are connected, at least at their lower end, to a tube plate, exchanges its heat with a secondary fluid flowing around the tubes inside an outer casing. Each tube has, at least in the middle part of the exchanger, the shape of a portion of a circle with a central angle less than or equal to 900, and the bottom tube plate which is substantially normal at the lower ends of the tubes has an angle of not less than 450 with the horizontal

  19. Experimental investigation of stabilization of flowing water temperature with a water-PCM heat exchanger

    Directory of Open Access Journals (Sweden)

    Charvat Pavel

    2014-03-01

    Full Text Available Experiments have been carried out in order to investigate the stabilization of water temperature with a water-PCM heat exchanger. The water-PCM heat exchanger was of a rather simple design. It was a round tube, through which the water flowed, surrounded with an annular layer of PCM. The heat exchanger was divided into one meter long segments (modules and the water temperature was monitored at the outlet of each of the segments. A paraffin-based PCM with the melting temperature of 42 °C was used in the experiments. The experimental set-up consisted of two water reservoirs kept at different temperatures, the water-PCM heat exchanger, PC controlled valves and a data acquisition system. As the first step a response to a step change in the water temperature at the inlet of the heat exchanger was investigated. Subsequently, a series of experiments with a square wave change of temperature at the inlet of the exchanger were carried out. The square wave temperature profile was achieved by periodic switching between the two water reservoirs. Several amplitudes and periods of temperature square wave were used. The results of experiments show that a water-PCM heat exchanger can effectively be used to stabilize the flowing water temperature when the inlet temperature changes are around the melting range of the PCM.

  20. Heat exchangers

    International Nuclear Information System (INIS)

    Description is given of a heat exchanger with exchange surfaces of preformed metal-sheets constituting at least one exchange bundle. A bundle comprises juxtaposed independent compartments, each of which comprising two superimposed preformed sheets and its respective manifolds for the inlet and outlet of a coolant. Substantially in parallel relationship to one surface of the respective compartment, said manifolds are mounted at the ends and on the opposed surfaces of the compartment, thus giving it, in cross-section, the shape of a Z with truncated arms. Since the sheets forming each compartments are of rectangular shape, the various juxtaposed independent compartments constitute an exchange-bundle of generally parallelepipedic shape, the manifolds being arranged in stepped fashion and defining those two sides of the parallelepiped inclined with respect to the axis of the latter. The heat-exchanger according to the invention can be used in particular in nuclear power stations, either mobile or not, e.g. of the PWR-type, and also in small-size installations

  1. 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

  2. Heat exchanger

    International Nuclear Information System (INIS)

    A heat exchanger such as forms, for example, part of a power steam boiler is made up of a number of tubes that may be arranged in many different ways, and it is necessary that the tubes be properly supported. The means by which the tubes are secured must be as simple as possible so as to facilitate construction and must be able to continue to function effectively under the varying operating conditions to which the heat exchanger is subject. The arrangement described is designed to meet these requirements, in an improved way. The tubes are secured to a member extending past several tubes and abutment means are provided. At least some of the abutment means comprise two abutment pieces and a wedge secured to the supporting member, that acts on these pieces to maintain the engagement. (U.K.)

  3. 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.)

  4. Numerical analysis of non-isothermal Newtonian flows in plate heat exchangers

    OpenAIRE

    Fernandes, Carla S.; Dias, Ricardo P.; No?brega, Joa?o M.; Maia, Joa?o M.; Wadekar, Vishwas V.

    2005-01-01

    Numerical analysis of non-isothermal Newtonian flows in plate heat exchanger passages is carried out in the laminar flow region. The results of this analysis are compared with information available in the literature. Some interesting trends are observed for both heat transfer and pressure drop with varying chevron angle. Areas of further work are delineated and it is emphasised that practical ranges of inter-plate distance, corrugation pitch and the development ratio need to be studied to ful...

  5. Microscale Regenerative Heat Exchanger

    Science.gov (United States)

    Moran, Matthew E.; Stelter, Stephan; Stelter, Manfred

    2006-01-01

    The device described herein is designed primarily for use as a regenerative heat exchanger in a miniature Stirling engine or Stirling-cycle heat pump. A regenerative heat exchanger (sometimes called, simply, a "regenerator" in the Stirling-engine art) is basically a thermal capacitor: Its role in the Stirling cycle is to alternately accept heat from, then deliver heat to, an oscillating flow of a working fluid between compression and expansion volumes, without introducing an excessive pressure drop. These volumes are at different temperatures, and conduction of heat between these volumes is undesirable because it reduces the energy-conversion efficiency of the Stirling cycle.

  6. 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.

  7. 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 nuclear power stations. Excessive flow-induced vibration may cause tube failures by fatigue or more likely by fretting-wear. Such failures may lead to station shutdowns that are very undesirable in terms of lost production. Hence good performance and reliability dictate a thorough flow-induced vibration analysis at the design stage. This paper presents our approach and techniques in this respect. (author)

  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. The effect of groundwater flow on the thermal front created by borehole heat exchangers

    OpenAIRE

    Tolooiyan, Ali; Hemmingway, Phil

    2012-01-01

    This paper presents an analysis performed using a coupled TEMP/W-SEEP/W finite element model to consider both the conducive and convective effects of groundwater flow on the thermal regime created by a ground source energy system. The change in the development of the sub-surface thermal regime created by ground source energy borehole heat exchangers caused by a groundwater flow across a site, relative to a scenario where groundwater flow does not exist is examined. Analys...

  10. 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.

  11. Analysis of loss-of-flow transients in the intermediate heat exchanger using the COMMIX code

    International Nuclear Information System (INIS)

    The intermediate heat exchanger (IHX) is an important component of the liquid-metal fast breeder reactor (LMFBR). It plays a very important role in the safe and reliable operation of a nuclear plant. Evaluation of thermal-hydraulic conditions are important in the design and development of a reliable and economical heat exchanger. These evaluations would provide complete maps of the temperature field of both the working fluids and the heat transfer tube. The maps are used for a large range of operating conditions, including nominal as well as off-nominal. Knowledge of temperature and flow distribution in both the shell and the tube side will ensure that the unit will meet its thermal performance requirements. Moreover, information is needed to provide proper evaluation of the thermal performance characteristics of a heat exchanger under the natural circulation conditions that result from a loss of coolant. The flow pattern and the thermal map of a shell-and-tube heat exchanger may be obtained either through actual testing of a scale model or by using analytical methods. To provide these evaluations multidimensional thermal-hydraulic codes are assessed for heat exchanger applications. The purpose of this paper is to present the thermal performance evaluation of the IHX of the Fast Flux Test Facility (FFTF) during a loss-of-coolant transient using the COMMIX-1B code and to compare the results with experimental data

  12. Heat exchanger

    Science.gov (United States)

    Brackenbury, P.J.

    1983-12-08

    A heat exchanger comparising a shell attached at its open end to one side of a tube sheet and a detachable head connected to the other side of said tube sheet. The head is divided into a first and second chamber in fluid communication with a nozzle inlet and nozzle outlet, respectively, formed in said tube sheet. A tube bundle is mounted within said shell and is provided with inlets and outlets formed in said tube sheet in communication with said first and second chambers, respectively.

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

    DEFF Research Database (Denmark)

    Nielsen, Toke Ramme; 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.

  14. Algebraic solution of capillary tube flows. Part II: Capillary tube suction line heat exchangers

    International Nuclear Information System (INIS)

    Capillary tube suction line heat exchangers have been modeled using both numerical and analytical approaches. The former requires a reasonable understanding of the governing heat and fluid flow equations, thermodynamic relations, numerical methods, and computer programming, and therefore are not suitable for most refrigeration and air-conditioning practitioners. Alternatively, empirical algebraic formulations for diabatic capillary tube flows have been proposed in the literature, in spite of their lack of generality and accuracy. This paper introduces a physically consistent, unconditionally convergent, easy-to-implement semi-empirical algebraic model for capillary tube suction line heat exchangers, with the same level of accuracy as found with more sophisticated first-principles models. The methodology treats the refrigerant flow and the heat transfer as independent phenomena, thus allowing the derivation of explicit algebraic expressions for the refrigerant mass flow rate and the heat exchanger effectiveness. The thermal and hydraulic models are then conflated through the so-called Buckingham-? theorem using in-house experimental data collected for diabatic capillary tube flows of refrigerants HFC-134a and HC-600a. Comparisons between the model predictions and the experimental data revealed that more than 90% and nearly 100% of all data can be predicted within ±10% and ±15% error bands, respectively.

  15. 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)

  16. 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.

  17. 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.

  18. 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

  19. Vibration damping of heat exchanger tube bundles in two-phase flow

    International Nuclear Information System (INIS)

    Two-phase flow exists in many shell-and-tube heat exchangers such as condensers, evaporators and nuclear steam generators. To avoid flow-induced vibration problems, it is necessary to have some information on tube damping mechanisms. This report pertains to the development of a model to formulate damping in two-phase cross-flow. This formulation is based on information available in the literature and particularly on the results of a recently completed experimental program. The compilation of a data base, the development of a semi-empirical model and the formulation of design guidelines are discussed in this report. The calculation of heat exchanger tube damping in two-phase cross-flow is illustrated by an example

  20. 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

  1. 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

  2. Numerical investigation of a high-temperature counter-flow compact heat exchanger

    International Nuclear Information System (INIS)

    Very High Temperature Reactors (VHTRs) require high temperature, high integrity, and highly effective heat exchangers during normal and off-normal conditions. A class of compact plate-type heat exchanger, Printed Circuit Heat Exchangers (PCHEs) is being considered for use in VHTRs. In the current study, simplified and full-size PCHE models are investigated numerically using FluentTM software. The geometry considered in the study replicate the PCHEs that were fabricated using Alloy 617 plates for use in a high-temperature helium test facility at The Ohio State University. The cases considered are based upon the design conditions of the high-temperature test facility: operating pressure of 3 MPa, hot side inlet temperature of 1,173 K, cold side inlet temperature of 813 K, and mass flow rates ranging from 10 to 80 kg/h. The ranges of mass flow rates and temperatures correspond to laminar and laminar-to-turbulent transition flows in the PCHE flow passages. Heat transfer and pressure drop are evaluated in both models to provide preliminary performance data for the laboratory scale PCHEs to be operated at temperatures similar to those of the VHTRs. Local convective heat transfer coefficients are calculated for channels on the hot and cold sides and compared to published experimental results for the laminar flow cases and the Gnielinski correlation for the transition flow cases. The overall heat transfer coefficient ranges from 563-1,697 W/m2-K. The max from 563-1,697 W/m2-K. The maximum pressure drop in this particular PCHE is found to be approximately 1.5% of the system operating pressure. The calculated convective heat transfer coefficients and pressure drop compare well with the models in the literature. (author)

  3. The Design of Heat Exchangers

    OpenAIRE

    Arturo Reyes-León; Miguel Toledo Velázquez; Pedro Quinto-Diez; Florencio Sánchez-Silva; Juan Abugaber-Francis; Celerino Reséndiz-Rosas

    2011-01-01

    A relation between heat transferred and energy loss, for turbulent flow. In different tube arrangements, is made. The conditions are determined which decide the dimensions and velocities for a heat exchanger. Also, a reference to the economic dimensioning of heat exchangers is presented. In this study, the conditions which a heat exchanger must satisfy represent the best balance between the amounts of material employed. The investigation is restricted to the case of turbulent flow.

  4. The Design of Heat Exchangers

    Directory of Open Access Journals (Sweden)

    Arturo Reyes-León

    2011-09-01

    Full Text Available A relation between heat transferred and energy loss, for turbulent flow. In different tube arrangements, is made. The conditions are determined which decide the dimensions and velocities for a heat exchanger. Also, a reference to the economic dimensioning of heat exchangers is presented. In this study, the conditions which a heat exchanger must satisfy represent the best balance between the amounts of material employed. The investigation is restricted to the case of turbulent flow.

  5. Shell-side single-phase flows and heat transfer in shell-and-tube heat exchangers, 2

    International Nuclear Information System (INIS)

    Attention is focused on flows and heat transfer around a tube bundle located near the inlet nozzle in segmentally baffled tubular heat exchangers. A finite-difference analysis is performed to determine flow patterns, local heat ransfer coefficients, and pressure drops across a tube bundle. They are found to agree within a reasonable accuracy with experimental data. Particular attention is directed to the effects of the diameter of an inlet nozzle on flow patterns and local heat transfer coefficients. A noteworthy finding is that, with the use of a relatively large inlet nozzle whose diameter is roughly half of the shell diameter, the variation of local heat transfer coefficient in a tube bundle is contained in a tolerable range of 30 per cent. (author)

  6. Heat pipe array heat exchanger

    Science.gov (United States)

    Reimann, Robert C. (Lafayette, NY)

    1987-08-25

    A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

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

    International Nuclear Information System (INIS)

    Highlights: ? Air side heat transfer and flow characteristics of mesochannel cross-flow heat exchanger are studied experimentally. ? Hot ethylene glycol–water mixture (50:50) at constant mass flow rate is used against varying air flow. ? Air side heat transfer and fluid flow key parameters such as Nusselt number, Colburn factor, friction factor are obtained. ? 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 × 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 °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 °C to 43 °C. Frontal air velocity waC. 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 a a) and Colburn factor (ja) were found higher in comparison with other studies.

  8. Modeling pressure drop of inclined flow through a heat exchanger for aero-engine applications

    International Nuclear Information System (INIS)

    In the present work further numerical predictions for the flow field through a specific type of a heat exchanger, which is planned to be used in the exhaust nozzle of aircraft engines. In order to model the flow field through the heat exchanger, a porous medium model is used based on a simple quadratic relation, which connects the pressure drop with the inlet air velocity in the external part of the heat exchanger. The aim of this work is to check the applicability of the quadratic law in a variety of velocity inlet conditions configured by different angles of attack. The check is performed with CFD and the results are compared with new available experimental data for these inlet conditions. A detailed qualitative analysis shows that although the quadratic law has been derived for a zero angle of attack, it performs very well for alternative non-zero angles. These observations are very helpful since this simple pressure drop law can be used for advanced computations where the whole system of the exhaust nozzle together with the heat exchangers can be modeled within a holistic approach

  9. Modeling pressure drop of inclined flow through a heat exchanger for aero-engine applications

    Energy Technology Data Exchange (ETDEWEB)

    Missirlis, D. [Laboratory of Fluid Mechanics and Turbomachinery, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54 124 (Greece); Yakinthos, K. [Laboratory of Fluid Mechanics and Turbomachinery, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54 124 (Greece)]. E-mail: kyros@eng.auth.gr; Storm, P. [MTU Aero Engines GmbH, Dachauerstrasse 665, 80995 Muenchen (Germany); Goulas, A. [Laboratory of Fluid Mechanics and Turbomachinery, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54 124 (Greece)

    2007-06-15

    In the present work further numerical predictions for the flow field through a specific type of a heat exchanger, which is planned to be used in the exhaust nozzle of aircraft engines. In order to model the flow field through the heat exchanger, a porous medium model is used based on a simple quadratic relation, which connects the pressure drop with the inlet air velocity in the external part of the heat exchanger. The aim of this work is to check the applicability of the quadratic law in a variety of velocity inlet conditions configured by different angles of attack. The check is performed with CFD and the results are compared with new available experimental data for these inlet conditions. A detailed qualitative analysis shows that although the quadratic law has been derived for a zero angle of attack, it performs very well for alternative non-zero angles. These observations are very helpful since this simple pressure drop law can be used for advanced computations where the whole system of the exhaust nozzle together with the heat exchangers can be modeled within a holistic approach.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. Hydraulic nonuniformities and ''secondary flows'' in a model of tube-casing heat exchanger

    International Nuclear Information System (INIS)

    The aerodynamic experiment is carried out on the model of an intermediate heat exchanger of a fast reactor NPP. The feature of such heat exchanger is lateral inflow and outflow of coolant of the intertube space. The tube bundle spread over the concentric circles. The testing has been carried out at Re being (16-32)x103, the inlet of air into the model has been performed from the damping chamber. A considerable hydraulic nonuniformity of the gas flow distribution over the apparatus cross section is observed. The following reasons of nonuniformities are shown: the difference in form factors in friction laws for various channels peripheral and central bundle channels, the display of ''secondary flow'' in the complex cross section box, loosely filled by the tube bundle

  16. Influence of the Flow from an Axial Fan on the Performance of a Heat Exchanger

    OpenAIRE

    Moore, J.; Grimes, R.; Walsh, E.

    2012-01-01

    Limited water supplies in arid regions that have abundant solar resources eliminates the use of water as a feasible means of cooling condensers in a Concentrated Solar Power (CSP) plant condenser. This has triggered the need to optimise existing air-cooled condenser technology, which is currently extremely inefficient. This paper aims to investigate the influence of various fan parameters on the performance of a cross-flow heat exchanger. The study first focuses on the effect of varying the d...

  17. Simulation of Cross Flow Heat Exchanger for Multi Tubes Using FLUENT 6.3.26

    OpenAIRE

    Suneela Sardar; Shahid Raza Malik

    2013-01-01

    In chemical engineering a lot of work is done to improve the results of the equipment to make its widespread applications be possible. Simulation is extensively used as the power of the computer is well known nowadays. Simulation is frequently used to study both real and virtual behavior. In this paper experimentation, simulation and development of mathematical models are performed. Practical experiments are made on a cross flow heat exchanger for a multi tube layout with staggered arrangemen...

  18. Visualization of fluidized-bed heat exchanger in upward/downward flow condition by neutron radiography

    International Nuclear Information System (INIS)

    Heat transfer characteristics of a fluidized-bed heat exchanger are dominated by the characteristics of bed-material movement, especially, in the neighboring region of the heat transfer tube. In the present experiment, a simulated fluidized-bed heat exchanger model was partitioned into two channels to form an upward and downward flow simultaneously in the same fluidized-bed model. Then the total amount of circulating material was kept at the same value even at the different void fractions between two channels. The flow pattern of bed material was visualized by neutron radiography with introducing tracers into the fluidized bed. The simulated fluidized bed consisted of aluminum plates, and the bed materials were sands of 96% SiO2 (mean particle diameter: 0.154-0.321 mm, density: 2550 kg/m3). Bed materials were almost transparent for neutrons. On the contrary, tracer particles of about 1 mm diameter made of B4C with clay were opaque. Thus, the tracer particles were detected clear enough for PTV (Particle Tracking Velocimetry). The fluidized-bed behavior was then discussed in relation to the heat transfer characteristics around the heated tubes submerged in the bed

  19. 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.

  20. 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

  1. Modeling of flow-induced vibrations in heat exchangers and nuclear reactors

    International Nuclear Information System (INIS)

    Appropriate scaling factors for the modeling of the fluid-mechanical interaction of complex structures are discussed. The possible mechanisms of flow-excited vibration are described, and scaling parameters are derived from considerations of the mechanical and fluid systems. Emphasis is placed on flow-induced vibrations of banks of cylinders in single phase, high Reynolds number, turbulent, cross flow, as occur for example in light water nuclear reactors and heat exchangers. It is concluded that the modeling of the tube banks in light water nuclear reactors will involve a mismatch of Reynolds number, but that the major phenomena of fluid-solid interaction in the single-phase flow region will probably be closely replicated if the Reynolds number is high enough so that the entering flow is turbulent and if the scaling ratio is not too large. (auth)

  2. 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.

  3. 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)

  4. 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)

  5. 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.

  6. 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)

  7. 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)

  8. Experimental and numerical investigation of the flow field through a heat exchanger for aero-engine applications

    International Nuclear Information System (INIS)

    An experimental and computational study for the flow development through a heat exchanger for aero-engine applications is presented. The heat exchanger consists of elliptic tubes in a U formation, the ends of which are attached to the collector pipe, which has a cylindrical cross section. In this way, two identical packages (named as matrices) are formed and located at a certain distance between them. The elliptic tubes are placed in a staggered arrangement. Detailed flow measurements using a 3-hole pitot-static probe were carried out on a 1:1 scale model of the heat exchanger in order to measure the pressure drop through the heat exchanger and the velocity distribution behind it. The flow through the heat exchanger was modeled with a computational fluid dynamics approach. The heat exchanger matrices were modeled using a porous medium assumption. The pressure drop through each element of the porous medium was linked to an effective local velocity. In order to check the validity of the computational modeling, the results were compared to the measured flow parameters such as pressure and velocity distributions. Two sets of modeling were performed assuming a laminar and a turbulent flow. The results showed that the laminar approach gave better results and this is supported by the corresponding Reynolds numbers, which indicated that the global flow field is transitional

  9. The concept of a new approximate relation for heat transfer effectiveness for a cross-flow heat exchanger with unmixed fluids

    Directory of Open Access Journals (Sweden)

    Rafal Marcin Laskowski

    2011-01-01

    Full Text Available This paper presents an approximate relation for the heat transfer effectiveness for a counter-flow heat exchanger, which was compared with the exact solution. Based on the obtained approximate relation for a counter-flow heat exchanger the approximate heat transfer effectiveness for a cross-flow heat exchanger in which both fluids do not mix is proposed. This approximate heat transfer effectiveness was compared with the exact solution proposed by Mason, the most well-known relation. A comparison between the most frequently used approximate formula and the exact solution proposed by Mason was made, too. The heat transfer effectiveness was analyzed for the ratio of the heat capacity of fluids C in the range from 0 to 1 and the number of transfer units NTU from the most common range 0 – 5.

  10. 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.

  11. Optimization of zigzag flow channels of a printed circuit heat exchanger for nuclear power plant application

    International Nuclear Information System (INIS)

    Printed circuit heat exchanger (PCHE) is recently considered as a recuperator for the high-temperature gas cooled reactor. In this study, shape optimization of zigzag flow channels in a PCHE has been performed to enhance heat transfer performance and reduce the friction loss based on three-dimensional Reynolds-averaged Navier-Stokes analysis with the Shear Stress Transport Turbulence model. A multi-objective genetic algorithm is used for the multi-objective optimization. Two non-dimensional objective functions related to heat transfer performance and friction loss are employed. The shape of a flow channel is defined by two geometric design variables, viz. the cold channel angle and the ellipse aspect ratio of the cold channel. The experimental points within the design space are selected using Latin hypercube sampling as the design of the experiment. The response surface approximation model is used to approximate the Pareto-optimal front. Five optimal designs on the Pareto-optimal front have been selected using k-means clustering. The flow and heat transfer characteristics, as well as the objective function values, of these designs have been compared with those of the reference design. (author)

  12. Assessment of flow induced vibration in a sodium-sodium heat exchanger

    International Nuclear Information System (INIS)

    The 500 MWe Prototype Fast Breeder Reactor (PFBR) is under construction at Kalpakkam. It is a liquid metal sodium cooled pool type fast reactor with all primary components located inside a sodium pool. The heat produced due to fission in the core is transported by primary sodium to the secondary sodium in a sodium to sodium Intermediate Heat Exchanger (IHX), which in turn is transferred to water in the steam generator. PFBR IHX is a shell and tube type heat exchanger with primary sodium on shell side and secondary sodium in the tube side. Since IHX is one of the critical components placed inside the radioactive primary sodium, trouble-free operation of the IHX is very much essential for power plant availability. To validate the design and the adequacy of the support system provided for the IHX, flow induced vibration (FIV) experiments were carried out in a water test loop on a 60 deg. sector model. This paper discusses the flow induced vibration measurements carried out in 60 deg. sector model of IHX, the modeling criteria, the results and conclusion

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

    International Nuclear Information System (INIS)

    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 ? 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/mm2, it can be said that high cycles fatigue damage of tube arrays by Karman vortex shedding vibration will not be caused. (J.P.N.)

  14. 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)

  15. Flow pattern and void fraction distribution of gas-liquid two-phase flow in a plate heat exchanger measured by neutron radiography

    International Nuclear Information System (INIS)

    In order to clarify the flow behavior of gas-liquid two-phase flow in plate heat exchanger used in air-conditioning system, flow behavior of adiabatic and boiling two-phase flows were visualized by a neutron radiography method. In the experiments under adiabatic condition, the air-water two-phase flows in an aluminum plate heat exchanger consisted of a single passage with grooves cut at an angle to the flow direction were visualized. In the boiling two-phase flow experiments, chlorofluorocarbon R141b was used as the working fluid. From the visualized images the two-dimensional distributions of void fraction were measured by some image processing techniques. As a result, it was shown that the liquid phase tended to flow straight and the phase distributions were strongly affected by the configuration at the inlet of heat exchanger. (author)

  16. Numerical computation for parallel plate thermoacoustic heat exchangers in standing wave oscillatory flow

    OpenAIRE

    Piccolo, Antonio

    2011-01-01

    A simplified computational method for studying the heat transfer characteristics of parallel plate thermoacoustic heat exchangers is presented. The model integrates the thermoacoustic equations of the standard linear theory into an energy balance-based numerical calculus scheme. Details of the time-averaged temperature and heat flux density distributions within a representative domain of the heat exchangers and adjoining stack are given. The effect of operation conditions and geometrical p...

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

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, M. [Univ. of Wisconsin - Madison, 839 Engineering Research Building, 1500 Engineering Drive, Madison, WI 53706 (United States); Kruizenga, A. [Sandia National Laboratory (United States); Anderson, M.; Corradini, M. [Univ. of Wisconsin - Madison, 839 Engineering Research Building, 1500 Engineering Drive, Madison, WI 53706 (United States)

    2012-07-01

    Closed-loop Brayton cycles using supercritical carbon dioxide (SCO{sub 2}) 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 SCO{sub 2} 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 SCO{sub 2} 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 SCO{sub 2} 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)

  18. A computational study of flow mal-distribution on the thermal hydraulic performance of an intermediate heat exchanger in LMFBR

    International Nuclear Information System (INIS)

    The flow and thermal non-uniformities occurring in the intermediate heat exchanger (IHX) of a liquid metal-cooled fast breeder reactor have been characterized through numerical simulations. For modeling the primary and secondary sodium flow through the IHX, an equivalent anisotropic porous medium approach has been used. The pressure drop in the equivalent porous medium is accounted through the inclusion of additional pressure drop terms in the Navier–Stokes equations, with the help of standard correlations for cross flow or parallel flow over tubes. For secondary sodium flow, the effects of a flow distributor device with orifices and baffles at the inlet have also been included, in addition to axial flow through the tubes. The heat exchange between primary and secondary streams is incorporated in the form of a volumetric heat source or sink term, which is corrected iteratively. The resulting flow distributions are in reasonable agreement with available experimental results. The study shows that the temperature of the secondary sodium flow at the exit can be made more uniform by exchanging less heat near the inner wall of IHX, as compared to the region close to the outer wall, using suitable flow distribution devices. (author)

  19. Heat transfer in turbulent flow

    International Nuclear Information System (INIS)

    This book reports on heat transfer and turbulent flow. The topics covered include fundamental research on turbulence in heat transfer processes, boundary layer flows, temperature turbulence spectrum, turbulence modeling, and applications to heat exchangers, gas turbines, and other engineering problems

  20. Numerical simulation of a three-layered radiant porous heat exchanger including lattice Boltzmann simulation of fluid flow

    International Nuclear Information System (INIS)

    This paper deals with the hydrodynamic and thermal analysis of a new type of porous heat exchanger. This system operates based on energy conversion between gas enthalpy and thermal radiation. The proposed porous heat exchanger has one high temperature and two heat recovery (HR1 and HR2) sections. In high temperature section, the enthalpy of flowing high temperature gas that is converted to thermal radiation emitted towards the two heat recovery sections where the reverse energy conversion from thermal radiation to gas enthalpy takes place. In each section, a 2-D rectangular porous segment which is assumed to be absorbing, emitting and scattering is present. For theoretical analysis of the porous heat exchanger, the gas and solid are considered in non-local thermal equilibrium and separate energy equations are used for the two phases. Besides, in the gas flow simulation, the lattice Boltzmann method is applied to obtain the velocity distribution through the porous segments. For the purpose of thermal analysis of the proposed porous heat exchanger, volume-averaged velocities through the porous matrix obtained by lattice Boltzmann method are used in the gas energy equation, and then the coupled energy equations for gas and porous medium of each section are numerically solved using finite difference method. The radiative transfer equation is solved by discrete ordinates method to calculate the distribution of radiative heat flux in the porous medium. radiative heat flux in the porous medium. The numerical results consist of the gas and porous media temperature distributions. The variation of radiative heat flux are also presented. Furthermore, the effects of scattering albedo, optical thickness and inlet gas temperature on the efficiency of the proposed porous heat exchanger are investigated. It is revealed that this type of heat exchanger has high efficiency in comparison to conventional one. Also, the present numerical results for a porous radiant burner are compared with theoretical finding by the other investigator and good agreement is found.

  1. 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.; No?brega, Joa?o M.; Maia, Joa?o 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...

  2. Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers.

    Science.gov (United States)

    Emad Dehkordi, S; Schincariol, Robert A; Olofsson, Bo

    2014-09-16

    The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10(-7) m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings. PMID:25227154

  3. 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.

  4. 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

  5. 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...

  6. 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.

  7. Plate heat exchanger

    International Nuclear Information System (INIS)

    The plate exchanger described includes a series of individual modules joined together, communicating in pairs to delimit two flow circuits separated by two fluids mutually exchanging calories. Each module includes at least one flat frame around a central cavity, at least two apertures made in the frame respectively for the inlet and oulet of the fluids crossing the cavity and at least one opening in the frame for the fluids to pass to a neighbouring module. The frames of the modules form a stack plane upon plane and are isolated by a thin leak-tight sheet parallel to the plane of the frames and separating the fluid substances in two superimposed frames. The heat transfer between these fluids occurs through this thin sheet from one module to the next in the stack

  8. 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.

  9. 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.

  10. 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...

  11. Analytical Entropy Analysis of Recuperative Heat Exchangers

    OpenAIRE

    Marija Zivic; Zdravko Virag; Antun Galovic

    2003-01-01

    Abstract: The analytical solutions for the temperature variation of two streams in parallel flow, counter flow and cross-flow heat exchangers and related entropy generation due to heat exchange between the streams are presented. The analysis of limiting cases for the relative entropy generation is performed, and corresponding analytical expressions are given. The obtained results may be included in a more general procedure concerning optimal heat exchanger design.

  12. Modelling of Multistream LNG Heat Exchangers

    OpenAIRE

    Soler Fossas, Joan

    2011-01-01

    The main goal of this thesis is to find out if a liquefied natural gas multistream heat exchanger numerical model is achievable. This should include several features usually neglected in nowadays available heat exchanger models, such as flow maldistribution, changes in fluid properties and heat exchanger dynamic behaviour. In order to accomplish that objective a simpler case is modelled. Efforts are put in achieving numerical stability.A counter flow natural gas and mixed refrigerant heat exc...

  13. Nature's Heat Exchangers.

    Science.gov (United States)

    Barnes, George

    1991-01-01

    Discusses the heat-transfer systems of different animals. Systems include heat conduction into the ground, heat transferred by convection, heat exchange in lizards, fish and polar animals, the carotid rete system, electromagnetic radiation from animals and people, and plant and animal fiber optics. (MDH)

  14. Flow-loss, efficiency, and change-of-state calculations for fluid-flow engines and heat exchangers

    Science.gov (United States)

    Bitterlich, W.; Kestner, D.; Patil, M. D.

    A theoretical analysis of the energy losses in devices transfused by fluids is presented, with a focus on the phase-change processes affecting the fluid medium inside the device. Flow losses are shown to be equivalent to the dissipative work due to friction stresses, using their relationship to heat transfer or mechanical work in order to derive equations of flow efficiency for specific types of devices (turbopump, turbocompressor, turbine, and heat exchanger). A polytropic (P) approximation of phase transformation inside the device is employed to arrive at constant P relations, dissipated-P-work values, and P efficiencies for both ideal and real fluids with actual and P efficiencies found to be almost equal for most of the devices. Standard-value ranges are given for each type of device, and sample calculations for simple and supercritical-evaporation steam-turbine and closed gas-turbine systems are presented. The applicability of mean efficiency and P-transformation calculations to discontinuous devices is demonstrated.

  15. Numerical flow simulation of stainless steel lamella heat exchangers; Numerische Stroemungssimulation an Edelstahl-Lamellenwaermeaustauschern

    Energy Technology Data Exchange (ETDEWEB)

    Perencevic, Stanislav [Guenther AG und Co.KG, Fuerstenfeldbruck (Germany). F und E

    2011-07-01

    During the development of new fin systems for air heat exchangers, significant differences were found between the measured and theoretical performance. In the calculations, it is absolutely necessary to know the real heat transfer coefficient {alpha}{sub R} and the fin efficiency {eta}{sub R}. One common method forr calculating {alpha}{sub R} and {eta}{sub R} was developed by Th. E. Schmidt; it is described in many textbooks and also in the VDI Waermeatlas. The publication analyzes fluid flow and heat transfer on a noble steel fin using CFD simulations. It is found that in case of fins with low thermal conductivity and unfavourable fin geometries, calculations according to Th. E. Schmidt im Fall will provide results that deviate strongly from the measurements. The reasons for this are explained. [German] Im Rahmen der Entwicklung neuer Lamellensysteme fuer luftbeaufschlagte Waermeaustauscher haben Untersuchungen an Waermeaustauschern mit Edelstahllamellen ergeben, dass es signifikante Diskrepanzen zwischen gemessener und theoretisch ermittelter Leistung gibt. Bei der Leistungsberechnung eines Waermeaustauschers ist die Kenntnis vom realen Waermeuebergangskoeffizienten {alpha}{sub R} und des Lamellenwirkungsgrades {eta}{sub R} grundlegend. Eine oft verwendete Methode zur Berechnung von {alpha}{sub R} und {eta}{sub R} stammt von Th. E. Schmidt und wird in vielen Lehrbuechern und auch im VDI Waermeatlas beschrieben. In dieser Arbeit werden anhand von CFD-Simulationen (CFD: computational fluid dynamics) die Stroemungsvorgaenge und der Waermetransport an einer Edelstahllamelle analysiert. Es wird gezeigt, dass die Berechnungsmethode nach Th. E. Schmidt im Fall von Lamellen mit niedriger Waermeleitungszahl und bei unguenstigen Lamellengeometrien stark abweichende Ergebnisse im Vergleich zu Messungen liefert. Die Gruende hierfuer werden erlaeutert.

  16. Biofouling and cleaning tests of OTEC external flow heat exchanger tubes

    Energy Technology Data Exchange (ETDEWEB)

    Hill, F.K.

    1979-11-01

    Heat transfer measurements before and after ultrasonic cleaning were done on sections of 3-in.-O.D., Alclad aluminum tubing (alloy 3004 clad with 7072) that had been biofouled by ocean surface water at a NOAA data bouy 170 nautical miles west of Tampa, Florida, in the Gulf of Mexico. The tubes were sealed inside and exposed to seawater flow at 2.5 ft/sec on the outside. They were arranged in a water box in the geometry of the folded-tube, Ocean Thermal Energy Conversion (OTEC) heat exchangers being developed by the Applied Physics Laboratory (APL). The biofouling exposure periods varied from 3-1/2 to 13 weeks. The heat transfer measurements on some of the fouled tubes were at sea, but some had to be done (due to program limitations) 3 to 6 weeks after their removal from the data buoy, and some of those were exposed to air due to seal failures of the plastic shipping bags. Thus, the thickness and character of the fouling on the tubes varied considerably, but no barnacles were seen on any of them. For the specimens not exposed to air no appreciable corrosion or scale was seen; when scale and/or corrosion were present, much longer ultrasonic cleaning times (using a tank with bottom-mounted tranducers generating 0.7 W/cm/sup 2/) were required. The test results indicated that a building of fouling resistance coefficient R/sub f/ of about 0.00005 Btu/sup -1/hr-ft/sup 2/-/sup 0/F per week occurred. After four weeks, and R/sub f/ approx. = 0.0002, a 25- to 30-sec exposure to ultrasonic radiation at an intensity of 0.7 W/cm/sup 2/ reduced R/sub f/ to the visually judged cleaned condition, where only a slight discoloration of the surface remained.

  17. Experimental Research on Gas-Solid Flow in an External Heat Exchanger with Double Outlets

    Science.gov (United States)

    Liu, H. Z.; Lu, X. F.

    A new type scaling-up scheme of CFB boiler that takes separator as center and furnaces are laid around was put forward in this paper. In the recycle system, a new type heat exchanger device with double outlets was designed for this disposal scheme. As we know, the external heat exchanger is very important for the CFB, which be able no only to adjust the steam temperature, but also to adjust the bed temperature. In this paper, through the adjustment of air speed in different room of the heat exchanger, the adjusting performance of the new type heat exchanger was analyzed. Moreover, the test of the pressure in the whole recycle system was analyzed. The pressure balance system of the circulating circuit with this new arrangement scheme was realized. Through this test research, the main conclusions were got as follows: The external heat exchanger, which has two recycled solid outlets, could run flexibly and stably and could successfully discharge the materials from the standpipe into either of the furnaces. This test device has a good pressure and material balance system.

  18. The effect of unbalance flow on the performance of compact heat exchanger for HTGR-GT system

    International Nuclear Information System (INIS)

    As for the design of the compact heat exchanger (recuperator) of HTGR-GT system by the helium gas turbine, heat exchanger effectiveness (HEE) is set to the goal in 92% of very high values. A recuperator is consisted of multi-layer core element with the combination of ultra fine offset fins (fin height x pitch x offset x thickness, 1.1-1.5 mm x 1.1-1.5 mm x 3 mm x 0.15 mm), separator, header with ultra fine straight fins (fin height x pitch x thickness, 1.1-1.5 mm x 3 mm x 0.15 mm) and ducts. By the concept design of this recuperator, it got the prospect that 95% of HEE can be achieved by making this ultra-fine offset fin-type core element with the flow channel width x height x length, 890 mm x 6,800 mm x 940 mm. However, there is possibility that the flow unbalance occurs to the cold flow, which is supplied to the direction of the core element height from the header when the recuperator size becomes large-sized in this way and as results, that the performance of the recuperator declines. Therefore, by implementing the three-dimensional heat transfer flow analysis of the recuperator, it evaluated a performance about the heat transfer of the recuperator when the virtual flow unbalance occurs to the direction of the height of the duct of the side of cold flow. As a result, the following conclusion was derived; (1) Helium flow unbalance in the cold flow header is caused by the maximum, -20% to 14% to all the helium flow rate. (2) When the flow unbalance which is identicalWhen the flow unbalance which is identical with cold flow along the header occurs on the hot flow header, it declines by about 0.5% to HEE per recuperator 1 unit when the flow unbalance does not occur on the cold flow. (3)When the symmetrical flow unbalance in cold flow header occur on the hot flow header, the rate with the declining heat transfer performance of the recuperator is the biggest. It declines by about 1.3% to the HEE per recuperator 1 unit when the flow unbalance does not occur on the cold flow header of the case. When above result, the assumed flow unbalance occurred, the thing about which it is possible to design the recuperator which meets a design request specification was concluded. (author)

  19. 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

  20. Overview of numerical methods for predicting flow-induced vibration and wear of heat-exchanger tubes

    International Nuclear Information System (INIS)

    Practical interest in performing predictive analysis of vibration and wear risks of industrial tube bundles, e.g. in nuclear reactor heat exchangers, subjected to cross flow is broadly recognized. A predictive analysis of an heat-exchanger design against severe vibration and wear has to cope with experimental data on FIV and fretting wear, together with the use of analytical and numerical methods for predicting linear and nonlinear tube response. This paper describes a general approcah of the problem currently under development at C.E.A. Attention is especially paid to some key aspects of the numerical techniques, namely, the modelisation of flow-induced forcing functions and the modelisation of impact and sliding at tube-support gaps. These topics are exemplified by numerical results related to some typical situations including the case of random vibration induced by flow turbulence and fluid-elastic vibration

  1. An experimental analysis of the flow pattern in heat exchangers with an egg carton configuration (parallel, convergent and divergent cases)

    International Nuclear Information System (INIS)

    An experimental analysis about the flow patterns that appear in the channel formed between two corrugated plates with an egg carton configuration is reported. The types of flow instabilities caused by the corrugated plates are identified and described by means of flow visualization experiments, and photographic sequences illustrate the flow features present for each case. The influence on flow instabilities of Reynolds number, phase angle, convergence/divergence angle and spacing between corrugated plates is investigated. The corrugated plates are set divergent and convergent in order to investigate if recirculations are broken by chaotic advection. The improvement of heat transfer in the laminar regime has become an essential task in many applications and therefore the experiments are conducted in this regime. The corrugated plates geometry provides two main advantages over the conventional plane plates: the recirculation zones observed in the longitudinal direction and the three-dimensionality of the flow, i.e. the recirculations reduce the thermal resistances while the three-dimensionality of flow generates a better mixing and a more uniform temperature distribution. This experimental study contributes to the general knowledge on the subject being the first that addresses the analysis of convergent and divergent egg carton plates. It is expected that the results presented here will shed some light as to advantageously use these geometries in the near-future heat exhese geometries in the near-future heat exchangers. (Because of the improve chaotic mixing in divergent corrugated plates, this configuration may be a good option to improve heat exchangers performance, because a better mixing is always related to the presence of core fluid near exchange surfaces, and consequently an increase in temperature gradients and heat transfer.)

  2. Model tests on fluid-elastic vibrations in heat exchangers with tubes in cross-flow

    International Nuclear Information System (INIS)

    The excitation of high amplitude vibrations in heat exchanger models has been investigated with the aim of finding rules which can be used to ensure that fluid-elastic vibrations can be avoided in power plants. It has been found that unstable pressure distribution around the tubes is the reason for the excitation of the vibrations. By changing the damping and natural frequency of the tubes, the influence of the tube material was detected. Theoretical considerations and experimental results yield a rule which enables engineers to find a criterion for the safe layout of full-size heat exchangers. (author)

  3. 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

  4. 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

  5. Wet surface heat transfer and pressure drop of aluminum parallel flow heat exchangers at different inclination angles

    International Nuclear Information System (INIS)

    The effect of inclination angle on the heat transfer and pressure drop characteristics of brazed aluminum heat exchangers was experimentally investigated under wet conditions. Three samples having different fin pitches (1.25, 1.5 and 2.0 mm) were tested. Results show that heat transfer coefficients are not affected by the inclination angle. However, friction factors increase as the inclination angle increases with negligible difference between the forward and backward inclination. The effect of fin pitch on the heat transfer coefficient and on the pressure drop is also discussed. Comparison of the dry and wet surface heat transfer coefficients reveals that dry surface heat transfer coefficients are significantly larger than wet surface heat transfer coefficients. Possible explanation is provided by considering the condensate drainage pattern. The data are also compared with the existing correlation

  6. 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

  7. Method of relative comparison of the thermohydraulic efficiency of heat exchange intensification in channels of heat-exchange surfaces

    International Nuclear Information System (INIS)

    One introduces a technique to compare relatively thermohydraulic efficiency of heat transfer intensification in channels of heat exchange surfaces of any design types. It is shown that one should compare thermohydraulic efficiency of heat exchange intensification as to the thermal power of heat exchangers and pressure losses in channels with turbulators and in polished channels of heat exchange surfaces on the basis of dimensions of heat exchangers, their heat exchange surfaces and at similar (as to Re numbers) modes of coolant flow

  8. Calculation of heat exchange and friction in grooves, transversal to turbulent flow

    International Nuclear Information System (INIS)

    Paper presents a model of flow and the appropriate simple methods of the effective design calculation of heat emission and friction in grooves characterized by transverse cross section diverse shape at working surfaces of power equipment flowed around by liquid or gas turbulent flow. One introduces a model ensuring both calculation of heat emission and of friction in a groove based on the certain value of resistance coefficient for abrupt expansion in a channel. The calculation results are compared with the experimental study data

  9. 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 ...

  10. 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.

  11. 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)

  12. Counterflow Regolith Heat Exchanger

    Science.gov (United States)

    Zubrin, Robert; Jonscher, Peter

    2013-01-01

    A problem exists in reducing the total heating power required to extract oxygen from lunar regolith. All such processes require heating a great deal of soil, and the heat energy is wasted if it cannot be recycled from processed material back into new material. 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 exchanger with internal and external augers attached to the inner rotating tube to move the regolith. Hot regolith in the outer tube is moved in one direction by a right-hand - ed auger, and the cool regolith in the inner tube is moved in the opposite direction by a left-handed auger attached to the inside of the rotating tube. In this counterflow arrangement, a large fraction of the heat from the expended regolith is transferred to the new regolith. The spent regolith leaves the heat exchanger close to the temperature of the cold new regolith, and the new regolith is pre-heated close to the initial temperature of the spent regolith. Using the CoRHE can reduce the heating requirement of a lunar ISRU system by 80%, reducing the total power consumption by a factor of two. The unique feature of this system is that it allows for counterflow heat exchange to occur between solids, instead of liquids or gases, as is commonly done. In addition, in variants of this concept, the hydrogen reduction can be made to occur within the counterflow heat exchanger itself, enabling a simplified lunar ISRU (in situ resource utilization) system with excellent energy economy and continuous nonbatch mode operation.

  13. 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.

  14. 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 ...

  15. Corrosion protected reversing heat exchanger

    International Nuclear Information System (INIS)

    A reversing heat exchanger of the plate and fin type having multiple aluminum parting sheets in a stacked arrangement with corrugated fins separating the sheets to form multiple flow paths, means for closing the ends of the sheets, an input manifold arrangement of headers for the warm end of of the exchanger and an output manifold arrangement for the cold end of the exchanger with the input air feed stream header and the waste gas exhaust header having an alloy of zinc and aluminum coated on the inside surface for providing corrosion protection to the stack

  16. Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

    OpenAIRE

    Teng Tun-Chien; Teng Tun-Ping; Hung Yi-Hsuan; Chen Jyun-Hong

    2011-01-01

    Abstract This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample ...

  17. 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

  18. Chapter 11. Heat Exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Rafferty, Kevin D.; Culver, Gene

    1998-01-01

    Most geothermal fluids, because of their elevated temperature, contain a variety of dissolved chemicals. These chemicals are frequently corrosive toward standard materials of construction. As a result, it is advisable in most cases to isolate the geothermal fluid from the process to which heat is being transferred. The task of heat transfer from the geothermal fluid to a closed process loop is most often handled by a plate heat exchanger. The two most common types used in geothermal applications are: bolted and brazed. For smaller systems, in geothermal resource areas of a specific character, downhole heat exchangers (DHEs) provide a unique means of heat extraction. These devices eliminate the requirement for physical removal of fluid from the well. For this reason, DHE-based systems avoid entirely the environmental and practical problems associated with fluid disposal. Shell and tube heat exchangers play only a minor role in low-temperature, direct-use systems. These units have been in common use in industrial applications for many years and, as a result, are well understood. For these reasons, shell and tube heat exchangers will not be covered in this chapter.

  19. PIPO-FE: an updated computer code to evaluate heat exchanger and steam generator 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, random-turbulence excitation and vortex shedding. 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 the updated code and includes examples to illustrate how the code can be used to support the design and modification of power plant heat exchangers and related research activities. (author)

  20. Microgravity condensing heat exchanger

    Science.gov (United States)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

    2011-01-01

    A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

  1. Visualization and void fraction measurement of gas-liquid two-phase flow in plate heat exchanger

    International Nuclear Information System (INIS)

    Adiabatic and boiling gas-liquid two-phase flows in a simulated plate heat exchanger with a single-ribbed channel were visualized by a thermal neutron radiography method. In the experiments under adiabatic condition, the air-water two-phase flows in an aluminum test section were visualized. In the boiling two-phase flow experiments, chlorofluorocarbon R141b was used as the working fluid. Two-dimensional distributions of void fraction were measured from visualized images via some image processing techniques. As a result, it was shown that both the phases tended to flow straight in the ribbed channel, and mixing of gas and liquid phases was weak. Moreover, when working fluids flew into the test section as a gas-liquid mixture, the phase distributions were strongly affected by a liquid pool at the test section inlet

  2. Heat exchanger panel

    Science.gov (United States)

    Warburton, Robert E. (Inventor); Cuva, William J. (Inventor)

    2005-01-01

    The present invention relates to a heat exchanger panel which has broad utility in high temperature environments. The heat exchanger panel has a first panel, a second panel, and at least one fluid containment device positioned intermediate the first and second panels. At least one of the first panel and the second panel have at least one feature on an interior surface to accommodate the at least one fluid containment device. In a preferred embodiment, each of the first and second panels is formed from a high conductivity, high temperature composite material. Also, in a preferred embodiment, the first and second panels are joined together by one or more composite fasteners.

  3. Shell-side single-phase flows and heat transfer in shell-and-tube heat exchangers, 3

    International Nuclear Information System (INIS)

    An experimental investigation is performed to find the axial and circumferential distribution of local heat transfer coefficients around a tube bundle in segmentally turbular heat exchangers. The variation in the axial distribution of the heat transfer coefficient is found to be negligible compared with that of circumferential distribution or that within the tube bundle. Local heat transfer coefficients are sensitive to the ratio of the inlet nozzle diameter to the shell diameter in the inlet nozzle region of the tube bundle, while they remain invariant in the center region. No remarkable decrease of local heat transfer coefficients in the window zone is observed, so it is considered that there isn't any effective recirculation zones at the edge there. The normalization of the circumferential heat transfer coefficient using its averaged value keeps the distribution pattern unchanged with the Reynolds number, the ratio of inlet nozzle diameter to shell diameter and location of the tube within the bundle. These normalized values are assumed to agree with those of a tube bank of two dimensional array, with reasonable accuracy. (author)

  4. 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)

  5. High Temperature Composite Heat Exchangers

    Science.gov (United States)

    Eckel, Andrew J.; Jaskowiak, Martha H.

    2002-01-01

    High temperature composite heat exchangers are an enabling technology for a number of aeropropulsion applications. They offer the potential for mass reductions of greater than fifty percent over traditional metallics designs and enable vehicle and engine designs. Since they offer the ability to operate at significantly higher operating temperatures, they facilitate operation at reduced coolant flows and make possible temporary uncooled operation in temperature regimes, such as experienced during vehicle reentry, where traditional heat exchangers require coolant flow. This reduction in coolant requirements can translate into enhanced range or system payload. A brief review of the approaches and challengers to exploiting this important technology are presented, along with a status of recent government-funded projects.

  6. On the influence of state-to-state distributions on exchange reaction rates in shock heated air flows

    Science.gov (United States)

    Kunova, O.; Nagnibeda, E.

    2015-04-01

    In this Letter, non-equilibrium rates of Zeldovich reactions N2(i) + O ? NO + N, O2(i) + N ? NO + O in shock heated air flows are studied on the basis of state-to-state vibrational distributions. The comparison of reaction rate coefficients computed using state-to-state and thermally equilibrium vibrational distributions behind shock waves and different state-specific models for exchange reactions is presented. Reaction rates are calculated for various conditions before a shock front including a particular case of vibrationally excited free stream molecules. An essential influence of initial vibrational excitation of reactants on reaction rates behind a shock wave is shown.

  7. 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...

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

    OpenAIRE

    Kapil Dev

    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 ...

  9. 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)

  10. CHARACTERIZATION OF HEAT TRANSFER AND EVAPORATIVE COOLING OF HEAT EXCHANGERS FOR SORPTION BASED SOLAR COOLING APPLICATIONS

    OpenAIRE

    Gonza?lez Morales, Ce?sar Augusto

    2013-01-01

    The content of this Master thesis is the characterization of three different cross unmixed flow heat exchangers. All of the heat exchangers have different inner geometries and dimensions. In order to perform the characterization of these heat exchangers, measurements of heat transfer were done under different conditions: five different temperatures at the inlet of the sorption side, different mass flow for both inlet sides of the heat exchangers.The heat transfer measurements were done with a...

  11. Numerical Simulation of Passive Residual Heat Removal Heat Exchanger

    International Nuclear Information System (INIS)

    FLUENT software was employed to simulate the temperature-field and flow-field of AP1000 passive residual heat removal heat exchanger (PRHR HX), and investigate its heat-transferring and flow characteristics. Through comparative analysis of the distributions of temperature-field and flow-field in different locations at the same time, and the variations of temperature-field and flow-field in the same location at different time, heat-transferring process and natural convection situation of PRHR HX were understood deeply. It contributes to analyze the natural circulation capacity of PRHR HX, and provides some references for the effective operation of passive residual heat removal system. (authors)

  12. Triple loop heat exchanger for an absorption refrigeration system

    Science.gov (United States)

    Reimann, Robert C. (Lafayette, NY)

    1984-01-01

    A triple loop heat exchanger for an absorption refrigeration system is disclosed. The triple loop heat exchanger comprises portions of a strong solution line for conducting relatively hot, strong solution from a generator to a solution heat exchanger of the absorption refrigeration system, conduit means for conducting relatively cool, weak solution from the solution heat exchanger to the generator, and a bypass system for conducting strong solution from the generator around the strong solution line and around the solution heat exchanger to an absorber of the refrigeration system when strong solution builds up in the generator to an undesirable level. The strong solution line and the conduit means are in heat exchange relationship with each other in the triple loop heat exchanger so that, during normal operation of the refrigeration system, heat is exchanged between the relatively hot, strong solution flowing through the strong solution line and the relatively cool, weak solution flowing through the conduit means. Also, the strong solution line and the bypass system are in heat exchange relationship in the triple loop heat exchanger so that if the normal flow path of relatively hot, strong solution flowing from the generator to an absorber is blocked, then this relatively, hot strong solution which will then be flowing through the bypass system in the triple loop heat exchanger, is brought into heat exchange relationship with any strong solution which may have solidified in the strong solution line in the triple loop heat exchanger to thereby aid in desolidifying any such solidified strong solution.

  13. The effect of flow-hole structure and water chemistry on scale adhesion at the leading edge of a flow hole in a heat exchanger

    International Nuclear Information System (INIS)

    In the heat exchangers of power plants, scale deposition may occur, especially at the leading edge of contraction. The growth of scale can lead to an increase in pressure and cause oscillation of the water level. In our previous study, the dependence of flow on contraction geometry was analyzed numerically and empirically. It was shown that the contraction ratio of hydraulic diameter of the flow path contributed greatly to the difference in pressure drop and turbulent kinetic energy at the leading edge of the flow path. In this study, the effect of contraction geometry and flow rate on scale adhesion was studied in AVT chemistry at 270degC using a high-velocity scale-adhesion test loop. The differential pressure and the amount of scale deposited due to scale adhesion at the leading edge of the flow path increased more in a quatrefoil-type flow path than in drill-type flow path. The differential pressure and the amount of scale deposited also increased with increasing flow rate. Based on the results of the previous study, the flow behavior around the two different contractions under the above test conditions was also analyzed numerically. The test and analysis results indicated that the increase in scale adhesion at the leading edge of a quatrefoil-type flow path might be correlated with the localized increase in turbulent kinetic energy and pressure drop at the contraction inlet. (author)

  14. 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.

  15. Simulation of the heat exchange between the supersonic flow and the stationary body in a gas centrifuge

    Science.gov (United States)

    Zvonarev, K. V.; Seleznev, V. D.; Tokmantsev, V. I.; Abramov, Yu. V.

    2012-11-01

    We have made comparative calculations of the heat exchange in the subpersonic flow of gaseous UF6 around the stationary cylindrical body inside the rotating rotor of the gas centrifuge. It has been revealed that the integral heat flux from the gas to the body calculated with the use of the ANSYS-CFX program complex from the viewpoint of the continuum model is much smaller than the heat flow calculated by the Monte Carlo method of direct statistical simulation. Estimates show that under the conditions being considered the boundary layer on the surface of the body has no time to be formed and has a thickness of the order of the mean free path of the gas molecules and, therefore, the use of the methods of continuum mechanics in this region is incorrect. On the contrary, the method of direct statistical simulation permits taking into account the interaction of gas molecules directly with the surface of the streamline body and obtaining more correct results.

  16. 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.

  17. Fault-Tolerant Heat Exchanger

    Science.gov (United States)

    Izenson, Michael G.; Crowley, Christopher J.

    2005-01-01

    A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing. The reason this heat exchanger can tolerate a single-point leak is that the heat-transfer fluids are everywhere separated by a vented volume and at least two seals. The combination of fault tolerance, compactness, and light weight is implemented in a unique heat-exchanger core configuration: Each fluid passage is entirely surrounded by a vented region bridged by solid structures through which heat is conducted between the fluids. Precise, proprietary fabrication techniques make it possible to manufacture the vented regions and heat-conducting structures with very small dimensions to obtain a very large coefficient of heat transfer between the two fluids. A large heat-transfer coefficient favors compact design by making it possible to use a relatively small core for a given heat-transfer rate. Calculations and experiments have shown that in most respects, the fault-tolerant heat exchanger can be expected to equal or exceed the performance of the non-fault-tolerant heat exchanger that it is intended to supplant (see table). The only significant disadvantages are a slight weight penalty and a small decrease in the mass-specific heat transfer.

  18. DHE (downhole heat exchangers). [Downhole Heat Exchangers (DHE)

    Energy Technology Data Exchange (ETDEWEB)

    Culver, G.

    1990-11-01

    The use of downhole heat exchangers (DHE) for residential or commercial space and domestic water heating and other applications has several desirable features. Systems are nearly or completely passive -- that is, no or very little geothermal water or steam is produced from the well either reducing or completely eliminating surface environmental concerns and the need for disposal systems or injection wells. Initial cost of pumps and installation are eliminated or reduced along with pumping power costs and maintenance costs associated with pumping often corrosive geothermal fluids. Many residential and small commercial systems do not require circulating pumps because the density difference in the incoming and outgoing sides of the loop are sufficient to overcome circulating friction losses in the entire system. The major disadvantage of DHEs is their dependence on natural heat flow. In areas where geological conditions provide high permeability and a natural hydraulic gradient, DHEs can provide a substantial quantity of heat. A single 500-ft (152 m) well in Klamath Falls, Oregon, supplies over one megawatt thermal and output is apparently limited by the surface area of pipe that can be installed in the well bore. In contrast, DHEs used in conjunction with heat pumps may supply less than 8 KW from a well of similar depth. Here output is limited by conductive heat flow with perhaps a small contribution from convection near the well bore. The highest capacity DHE reported to date, in Turkey, supplies 6 MW thermal from an 820-ft (250 m) well. There were two main goals for this project. The first was to gather, disseminate and exchange internationally information on DHES. The second was to perform experiments that would provide insight into well bore/aquifer interaction and thereby provide more information on which to base DHE designs. 27 refs., 31 figs., 3 tabs.

  19. Experimental study of flow resistance for inclined tube bundles in the intermediate heat exchange of liquid metal reactor

    International Nuclear Information System (INIS)

    An experimental study of measurement of pressure drop in an inclined tube bundle located in a rectangular duct is performed. The main emphasis of present study is placed on the derivation of pressure drop correlation applicable to the design of the intermediate heat exchanger in a liquid metal reactor as well as the general exchanger. An experimental facility that can measure the pressure drop in a tube bundle is designed, manufactured and installed, and the pressure drop is measured varying the flow rate and the test sections that have different inclined angles. Measurements are made for pressure drop in a triangular tube array of P/d=1.6 and inclination angles of 30, 45, 60 and 90 degrees. The Reynolds number based on the inlet free stream velocity and tube diameter ranges from 900 and 6.5 x 104. The experimental data show that the magnitude of dimensionless flow resistance increases with the increase of inclined tube angle. The measured data are compared with six previous correlations available in the literatures. The agreement with previous correlations is generally good except some discrepancies in a certain region. It is found that the experimental data obtained from present study can be applied to the evaluation and modification of previous correlations

  20. Hybrid Heat Exchangers

    Science.gov (United States)

    Tu, Jianping Gene; Shih, Wei

    2010-01-01

    A hybrid light-weight heat exchanger concept has been developed that uses high-conductivity carbon-carbon (C-C) composites as the heat-transfer fins and uses conventional high-temperature metals, such as Inconel, nickel, and titanium as the parting sheets to meet leakage and structural requirements. In order to maximize thermal conductivity, the majority of carbon fiber is aligned in the fin direction resulting in 300 W/m.K or higher conductivity in the fin directions. As a result of this fiber orientation, the coefficient of thermal expansion (CTE) of the C-C composite in both non-fiber directions matches well with the CTE of various high-temperature metal alloys. This allows the joining of fins and parting sheets by using high-temperature braze alloys.

  1. Two phase heat exchanger symposium

    International Nuclear Information System (INIS)

    This book compiles the papers presented at the conference on the subject of heat transfer mechanics and instrumentation. Theoretical and experimental data are provided in each paper. The topics covered are: temperature effects of steel; optimization of design of two-phase heat exchanges; thermosyphon system and low grade waste heat recovery; condensation heat transfer in plate heat exchangers; forced convective boiling; and performance analysis of full bundle submerged boilers

  2. Design study of plastic film heat exchanger

    Science.gov (United States)

    Guyer, E. C.; Brownell, D. L.

    1986-02-01

    This report presents the results of an effort to develop and design a unique thermoplastic film heat exchanger for use in an industrial heat pump evaporator system and other energy recovery applications. The concept for the exchanger is that of individual heat exchange elements formed by two adjoining and freely hanging plastic films. Liquid flows downward in a regulated fashion between the films due to the balance of hydrostatic and frictional forces. The fluid stream on the outside of film may be a free-falling liquid film, a condensing gas, or a noncondensing gas. The flow and structural principles are similar to those embodied in an earlier heat exchange system developed for use in waste water treatment systems (Sanderson). The design allows for high heat transfer rates while working within the thermal and structural limitations of thermoplastic materials. The potential of this new heat exchanger design lies in the relatively low cost of plastic film and the high inherent corrosion and fouling resistance. This report addresses the selection of materials, the potential heat transf er performance, the mechanical design and operation of a unit applied in a low pressure steam recovery system, and the expected selling price in comparison to conventional metallic shell and tube heat exchangers.

  3. Next Generation Microchannel Heat Exchangers

    CERN Document Server

    Ohadi, Michael; Dessiatoun, Serguei; Cetegen, Edvin

    2013-01-01

    In Next Generation Microchannel Heat Exchangers, the authors’ focus on the new generation highly efficient heat exchangers and presentation of novel data and technical expertise not available in the open literature.  Next generation micro channels offer record high heat transfer coefficients with pressure drops much less than conventional micro channel heat exchangers. These inherent features promise fast penetration into many mew markets, including high heat flux cooling of electronics, waste heat recovery and energy efficiency enhancement applications, alternative energy systems, as well as applications in mass exchangers and chemical reactor systems. The combination of up to the minute research findings and technical know-how make this book very timely as the search for high performance heat and mass exchangers that can cut costs in materials consumption intensifies.

  4. Heat exchanger with auxiliary cooling system

    International Nuclear Information System (INIS)

    A heat exchanger with an auxiliary cooling system is described which is capable of cooling a nuclear reactor should the normal cooling mechanism become inoperable. A cooling coil is disposed around vertical heat transfer tubes that carry secondary coolant therethrough and is located in a downward flow of primary coolant that passes in heat transfer relationship with both the cooling coil and the vertical heat transfer tubes. A third coolant is pumped through the cooling coil which absorbs heat from the primary coolant which increases the downward flow of the primary coolant thereby increasing the natural circulation of the primary coolant through the nuclear reactor

  5. 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.

  6. Experimental research on heat transfer in a coupled heat exchanger

    OpenAIRE

    Liu Yin; Ma Jing; Zhou Guang-Hui; Guan Ren-Bo

    2013-01-01

    The heat exchanger is a devise used for transferring thermal energy between two or more different temperatures. The widespreadly used heat exchanger can only achieve heat exchange between two substances. In this paper, a coupled heat exchanger is proposed, which includes a finned heat exchanger and a double pipe heat exchanger, for multiple heat exchange simultaneously. An experiment is conducted, showing that the average heating capacity increases more tha...

  7. Tube bundle heat exchanger

    International Nuclear Information System (INIS)

    The heat exchanger consists of tube bundles mounted in parallel. Each bundle consists of a jacket in which tubes for a first coolant are mounted. Straight tubes are connected with their open ends to tube plates which, in turn, are connected to the jacket provided with the inlet and outlet for a second coolant. This passes between the outer surfaces of straight tubes and the inner jacket surface. Spacers are inserted between the tube bundles, this along the whole length of the bundles. The second coolant enters one tube plate through the open ends of inlet tubes. It leaves through the other tube plate of the respective bundle, through the open ends of the outlet tubes. The other open ends of the inlet and/or outlet tubes are inserted in auxiliary tube plates mounted in the jacket on both sides of the tube bundles. (H.S.)

  8. 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.)

  9. 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).

  10. Heat exchanger leakage problem location

    Directory of Open Access Journals (Sweden)

    Jícha Miroslav

    2012-04-01

    Full Text Available Recent compact heat exchangers are very often assembled from numerous parts joined together to separate heat transfer fluids and to form the required heat exchanger arrangement. Therefore, the leak tightness is very important property of the compact heat exchangers. Although, the compact heat exchangers have been produced for many years, there are still technological problems associated with manufacturing of the ideal connection between the individual parts, mainly encountered with special purpose heat exchangers, e.g. gas turbine recuperators. This paper describes a procedure used to identify the leakage location inside the prime surface gas turbine recuperator. For this purpose, an analytical model of the leaky gas turbine recuperator was created to assess its performance. The results obtained are compared with the experimental data which were acquired during the recuperator thermal performance analysis. The differences between these two data sets are used to indicate possible leakage areas.

  11. 40 CFR 63.11499 - What are the standards and compliance requirements for heat exchange systems?

    Science.gov (United States)

    2010-07-01

    ...standards and compliance requirements for heat exchange systems? (a) If the cooling water flow rate in your heat exchange system is equal to or...reactor as the surrogate indicator of heat exchanger system leaks when complying...

  12. 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.

  13. 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...

  14. Thermodynamic Optimization of GSHPS Heat Exchangers

    Directory of Open Access Journals (Sweden)

    Ahmad Kahrobaeian

    2007-09-01

    Full Text Available

    In this paper, a new method for determining the optimized dimensions of a ground source heat pump system (GSHPS heat exchanger is presented. Using the GSHPS is one of the ways for utilization of infinite, clean and renewable energies in the environment. In recent years, due to limitation of physical space for installing the heat exchangers and avoiding the environmental effects on heat exchanger operation, vertical GSHP systems are used more than the other ones. Determination of optimum heat exchanger size is one of the most important parameters in the optimization of the heat exchanger design. In this study, optimum length and diameter for the heat exchanger is determined for different mass flows by using the second law of thermodynamics. The optimal length and diameter minimize entropy generation and therefore result in increased efficiency of the heat pump.

    • An initial version of this pa per was published in May of 2004 in the proceedings of Second International Applied Thermodynamics Conference, Istanbul, Turkey.

  15. Computation of two-dimensional isothermal flow in shell-and-tube heat exchangers

    International Nuclear Information System (INIS)

    A computational procedure is outlined whereby two-dimensional isothermal shell-side flow distributions can be calculated for tube bundles having arbitrary boundaries and flow blocking devices, such as sealing strips, defined in arbitrary locations. The procedure is described in some detail and several computed results are presented to illustrate the robustness and generality of the method

  16. Heat transfer analysis of flat and louvered fin-and-tube heat exchangers using CFD

    OpenAIRE

    Carija, Z.; Frankovic, B.

    2008-01-01

    This paper analyzes the fluid flow and heat exchange on the air side of a multi-row fin-and-tube heat exchanger. A comparison is given between fin-and-tube heat exchanger characteristics with flat and louvered fins in a wider range of operating conditions defined by Reynolds number (based on fin spacing and air frontal velocities). The detailed representation of calculated data for the louvered heat exchanger shows significantly better heat transfer characteristics and a ...

  17. Rotor bore and turbine rotor wheel/spacer heat exchange flow circuit

    Science.gov (United States)

    Caruso, Philip M. (Selkirk, NY); Eldrid, Sacheverel Quentin (Saratoga Springs, NY); Ladhani, Azad A. (Niskayuna, NY); DeMania, Alan Richard (Niskayuna, NY); Palmer, Gene David (Clifton Park, NY); Wilson, Ian David (Clifton Park, NY); Rathbun, Lisa Shirley (Scotia, NY); Akin, Robert Craig (Schenectady, NY)

    2002-01-01

    In a turbine having closed-circuit steam-cooling passages about the rim of the rotor during steady-state operation, compressor discharge air is supplied to the rotor bore for passage radially outwardly into the wheel space cavities between the wheels and spacers. Communicating slots and channels in the spacers and wheels at circumferentially spaced positions enable egress of the compressor discharge air into the hot gas flow path. At turbine startup, cooling air flows through the closed-circuit steam passages to cool the outer rim of the rotor while compressor discharge air pre-warms the wheels and spacers. At steady-state, cooling steam is supplied in the closed-circuit steam-cooling passages and compressor discharge air is supplied through the bore and into the wheel space cavities to cool the rotor.

  18. 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.

  19. Milk fouling in heat exchangers.

    OpenAIRE

    Jeurnink, Th.J.M.

    1996-01-01

    The mechanisms of fouling of heat exchangers by milk were studied. Two major fouling mechanisms were indentified during the heat treatment of milk: (i) the formation and the subsequent deposition of activated serum protein molecules as a result of the heat denaturation; (ii) the precipitation of calcium phosphate as a result of the decreased solubility of this salt upon heating. Both foulants are formed in the bulk of the solution and are transported to the surface, where they can be deposite...

  20. The dry heat exchanger calorimeter system

    International Nuclear Information System (INIS)

    A radiometric isothermal heat flow calorimeter and preconditioner system that uses air instead of water as the heat exchange medium has been developed at Mound. The dry heat exchanger calorimeter is 42 inches high by 18 inches in diameter and the preconditioner is a 22 inch cube, making it extremely compact compared to existing units. The new system is ideally suited for transportable, stand-alone, or glovebox applications. Preliminary tests of the system have produced sample measurements with standard deviations less than 0.25% and sample errors less than 0.50%. These tests have shown that the dry heat exchanger system will yield acceptance data with an accuracy comparable to those of Mound water bath systems now in use. 4 figs., 1 tab

  1. The dry heat exchanger calorimeter system

    International Nuclear Information System (INIS)

    This paper reports on a radiometric isothermal heat flow calorimeter and preconditioner system that uses air instead of water as the heat exchange medium which has been developed for use with nuclear material. The dry heat exchanger calorimeter is 42 in. high by 18 in. in diameter and the preconditioner is a 22 in. cube, making it extremely compact compared to existing units. The new system is ideally suited for transportable, stand-alone, or glovebox applications. Preliminary tests of the system have produced sample measurements with standard deviations less than 0.25% and sample errors less than 0.50%. These tests have shown that the dry heat exchanger system will yield acceptable data with an accuracy comparable to those of Mound water bath systems now in use

  2. Influence of SiC particles on the heat exchange at the metal-mould interface during composite flow along the mould channel

    Directory of Open Access Journals (Sweden)

    Z. Konopka

    2008-07-01

    Full Text Available Calculation results concerning the heat transfer coefficient at the metal-mould interface during flow of the AlMg10 alloy matrix composites containing various fractions of solid SiC particles and, for the purpose of comparison, of the pure AlMg10 alloy in the channel-like cavity of the spiral castability test mould have been presented. Cooling curves and flow velocities have been determined on the basis of metal temperature measured during flow. These experimental data have been used for calculation of the heat transfer coefficient values at given points of a metal stream along the mould channel. Comparison of obtained values and the analysis of the influence of SiC particles on the heat exchange have been presented.

  3. Multidimensional numerical modeling of heat exchangers

    International Nuclear Information System (INIS)

    A comprehensive, multidimensional, thermal-hydraulic model is developed for the analysis of shell-and-tube heat exchangers for liquid-metal services. For the shellside fluid, the conservation equations of mass, momentum, and energy for continuum fluids are modified using the concept of porosity, surface permeability and distributed resistance to account for the blockage effects due to the presence of heat-transfer tubes, flow baffles/shrouds, the support plates, etc. On the tubeside, the heat-transfer tubes are connected in parallel between the inlet and outlet plenums, and tubeside flow distribution is calculated based on the plenum-to-plenum pressure difference being equal for all tubes. It is assumed that the fluid remains single-phase on the shell side and may undergo phase-change on the tube side, thereby simulating the conditions of Liquid Metal Fast Breeder Reactor (LMFBR) intermediate heat exchangers (IHX) and steam generators (SG)

  4. 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 (...

  5. 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.

  6. Flow-induced vibration and fretting-wear specifications to ensure steam-generator and heat exchanger lifetime performance

    International Nuclear Information System (INIS)

    The current interest in refurbishment, life extension and new-build activity has meant a renewed emphasis on technical specifications that will ensure improved reliability and longer life. Preventing 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. The specifications must be firmly based on experimental data and field inspections. In addition, the specifications must be supported by theoretical analyses and fundamental scaling correlations, to cover conditions and geometries over the wide range applicable to existing components and probable future designs. The specifications are expected to evolve to meet changing industry requirements. This paper outlines the steps required to generate and support design specifications, 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)

  7. Heat exchanger for coal gasification process

    Science.gov (United States)

    Blasiole, George A. (Greensburg, PA)

    1984-06-19

    This invention provides a heat exchanger, particularly useful for systems requiring cooling of hot particulate solids, such as the separated fines from the product gas of a carbonaceous material gasification system. The invention allows effective cooling of a hot particulate in a particle stream (made up of hot particulate and a gas), using gravity as the motive source of the hot particulate. In a preferred form, the invention substitutes a tube structure for the single wall tube of a heat exchanger. The tube structure comprises a tube with a core disposed within, forming a cavity between the tube and the core, and vanes in the cavity which form a flow path through which the hot particulate falls. The outside of the tube is in contact with the cooling fluid of the heat exchanger.

  8. Effect of the Moments of Probability Density Function for Non-uniform Air Flow Distribution on the Hydraulic Performance of a Fin-tube Heat Exchanger

    OpenAIRE

    Wai Meng Chin; Vijay R. Raghavan

    2011-01-01

    The work presented in this paper examines the effect of a non-uniform airflow velocity distribution on the air pressure drop through the fin passages of a single row fin-tube heat exchanger. Water flow rate through the tubes and its temperature are taken as constant. Maldistribution of the airflow increases the average pressure drop with respect to that of a uniform flow. As a result of this, the pumping power required by the fan or blower will also increase. The increase of the pumping power...

  9. Calculation of heat-mass exchange and friction in near-wall flows based on the two-scale four-parametric model of turbulence

    International Nuclear Information System (INIS)

    The calculational results on heat-mass exchange and friction in near-wall flows by injection through a gap and porous surface of homogeneous or extraneous gases in the main flow are presented. The above results are obtained on the basis of the turbulence model, including two expressions for the turbulence scale and four transfer equations for the second order velocity fields, enthalpy and concentration. The agreement of the calculational results with the known experimental data made it possible to prove more substantially satisfactory compliance of the calculations with the published experimental data by injection of extraneous gas into super-sound area of the Laval's nozzle

  10. Plate heat exchangers: review of transport phenomena and design procedures

    Energy Technology Data Exchange (ETDEWEB)

    Focke, W.W.

    1983-02-01

    The Chilton-Colburn analogy for momentum and heat transfer is not valid for plate heat exchangers. However, for the turbulent regime a correlation exists between heat transfer and energy dissipation. Turbulence models based on an energy dissipation analogy may, therefore, provide a good basis for predicting the flow and heat transfer in plate heat exchangers. Flow distribution to plates is a critical aspect of plate heat exchanger performance, particularly where cooling of highly viscous and non-Newtonian fluids are involved and give rise to laminar flow. For this flow regime very little information is available. Design flexibility is obtained by using chevron plates of different corrugation angles in one exchanger. The existence of optimal angles has been identified.

  11. Turbulence Model Comparison for Compact Plate Heat Exchanger Design Application.

    OpenAIRE

    Vitillo, F.; Cachon, L.; Millan, P; Reulet, P.; Laroche, E.

    2014-01-01

    In the framework of the Gas-Power Conversion System for the Advanced Sodium Technological Reactor for Industrial Demonstration (ASTRID) project design, works done at CEA are focused on the design of the sodium-gas heat exchanger. Compact plate heat exchangers are indicated as the most suitable technology for such applications. An innovative compact heat exchanger geometry is proposed in this paper: its innovationconsists increatinga 3D mixing flow. The proposed geometry has also very good mec...

  12. 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

  13. AP600 passive residual heat removal heat exchanger test

    International Nuclear Information System (INIS)

    The AP600 reactor is a pressurized water reactor being designed to utilize a passive residual heat removal (PRHR) heat exchanger as the safety grade means for residual heat removal. The PRHR heat exchanger is utilized during many design basis events and is especially important in mitigating non-loss-of-coolant accidents such as loss of normal feedwater and feedwater line break. The PRHR system transfers decay heat from the reactor coolant system to the containment by heating and boiling the water in the in-containment refueling water storage tank (IRWST). The steam produced transfers heat to the atmosphere by condensing on the inside of the containment shell. The condensate is collected by gutters on the containment shell and is returned to the IRWST, which provides a heat sink for an indefinite amount of time. The PRHR test facility is a prototypical representation of the PRHR heat exchanger with respect to tube material, diameter, pitch, and tube length, such that the gravity-induced flow characteristics in the pool are representative of the design. The main scaling parameter for the pool is the pool volume per tube, which preserves the buoyancy and pool mixing effects. A generalized PRHR boiling correlation was developed using the approach given by Rohsenow such that pressure effects can be induced

  14. Carbon nanotube heat-exchange systems

    Science.gov (United States)

    Hendricks, Terry Joseph (Arvada, CO); Heben, Michael J. (Denver, CO)

    2008-11-11

    A carbon nanotube heat-exchange system (10) and method for producing the same. One embodiment of the carbon nanotube heat-exchange system (10) comprises a microchannel structure (24) having an inlet end (30) and an outlet end (32), the inlet end (30) providing a cooling fluid into the microchannel structure (24) and the outlet end (32) discharging the cooling fluid from the microchannel structure (24). At least one flow path (28) is defined in the microchannel structure (24), fluidically connecting the inlet end (30) to the outlet end (32) of the microchannel structure (24). A carbon nanotube structure (26) is provided in thermal contact with the microchannel structure (24), the carbon nanotube structure (26) receiving heat from the cooling fluid in the microchannel structure (24) and dissipating the heat into an external medium (19).

  15. Tube-in-shell heat exchangers

    International Nuclear Information System (INIS)

    Tube-in-shell heat exchangers normally comprise a bundle of parallel tubes within a shell container, with a fluid arranged to flow through the tubes in heat exchange with a second fluid flowing through the shell. The tubes are usually end supported by the tube plates that separate the two fluids, and in use the tube attachments to the tube plates and the tube plates can be subject to severe stress by thermal shock and frequent inspection and servicing are required. Where the heat exchangers are immersed in a coolant such as liquid Na such inspection is difficult. In the arrangement described a longitudinally extending central tube is provided incorporating axially spaced cylindrical tube plates to which the opposite ends of the tubes are attached. Within this tube there is a tubular baffle that slidably seals against the wall of the tube between the cylindrical tube plates to define two co-axial flow ducts. These ducts are interconnected at the closed end of the tube by the heat exchange tubes and the baffle comprises inner and outer spaced walls with the interspace containing Ar. The baffle is easily removable and can be withdrawn to enable insertion of equipment for inspecting the wall of the tube and tube attachments and to facilitate plugging of defective tubes. Cylindrical tube plates are believed to be superior for carrying pressure loads and resisting the effects of thermal shock. Some protection against thermal shock can be effected by arranging that the secondary heat exchange fluid is on the tube side, and by providing a thermal baffle to prevent direct impingement of hot primary fluid on to the cylindrical tube plates. The inner wall of the tubular baffle may have flexible expansible region. Some nuclear reactor constructions incorporating such an arrangement are described, including liquid metal reactors. (U.K.)

  16. Circulating heat exchangers for oscillating wave engines and refrigerators

    Science.gov (United States)

    Swift, Gregory W.; Backhaus, Scott N.

    2003-10-28

    An oscillating-wave engine or refrigerator having a regenerator or a stack in which oscillating flow of a working gas occurs in a direction defined by an axis of a trunk of the engine or refrigerator, incorporates an improved heat exchanger. First and second connections branch from the trunk at locations along the axis in selected proximity to one end of the regenerator or stack, where the trunk extends in two directions from the locations of the connections. A circulating heat exchanger loop is connected to the first and second connections. At least one fluidic diode within the circulating heat exchanger loop produces a superimposed steady flow component and oscillating flow component of the working gas within the circulating heat exchanger loop. A local process fluid is in thermal contact with an outside portion of the circulating heat exchanger loop.

  17. Fabrication and testing of microchannel heat exchangers

    Science.gov (United States)

    Cuta, Judith M.; Bennett, Wendy D.; McDonald, Carolyn E.; Ravigururajan, T. S.

    1995-09-01

    Micro-channel heat-exchanger test articles were fabricated and performance tested. The heat exchangers are being developed for innovative applications, and have been shown to be capable of handling heat loads of up to 100 W/cm2. The test articles were fabricated to represent two different designs for the micro-channel portion of the heat exchanger. One design consists of 166 micro-channels etched in silicon substrate, and a second design consists of 54 micro-channels machined in copper substrate. The devices were tested in an experimental loop designed for performance testing in single- and two-phase flow with water and R124. Pressure and liquid subcooling can be regulated over the range of interest, and a secondary heat removal loop provides stable loop performance for steady-state tests. The selected operating pressures are approximately 0.344 MPa for distilled water and 0.689 MPa for R124. The temperature ranges are 15.5 to 138 C for distilled water and 15.5 to 46 C for R-124. The mass flow range 7.6 X 10-8 to 7.6 X 10MIN5 kg/min for both distilled water and R124.

  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. The influence of radiative heat exchange on the character of gasdynamic flows under conditions of pulsed discharge in high-pressure cesium vapor

    Science.gov (United States)

    Baksht, F. G.; Lapshin, V. F.

    2015-01-01

    The gasdynamics of pulse-periodic radiative discharge in high-pressure cesium vapor has been studied in the framework of a two-temperature multifluid model. It is established that, at a limited volume of the gas-discharge tube, the character of gasdynamic flows depends on the conditions of radiative heat exchange in discharge plasma. In cases in which the main contribution to radiative energy losses is related to a spectral region with optical thickness ? R (?) ˜ 1, there is nonlocal radiative heat exchange in discharge plasma, which is uniformly heated over the entire tube volume and moves from the discharge axis to tube walls during the entire pulse of discharge current. Under the conditions of radiative losses determined by the spectral region where ? R (?) ? 1, the reabsorption of radiation is absent and discharge plasma is nonuniformly heated by the current pulse. This leads to the appearance of reverse motions, so that the heated plasma is partly pushed toward the tube walls and partly returned to the discharge axis.

  20. Effect of the Moments of Probability Density Function for Non-uniform Air Flow Distribution on the Hydraulic Performance of a Fin-tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Wai Meng Chin

    2011-01-01

    Full Text Available The work presented in this paper examines the effect of a non-uniform airflow velocity distribution on the air pressure drop through the fin passages of a single row fin-tube heat exchanger. Water flow rate through the tubes and its temperature are taken as constant. Maldistribution of the airflow increases the average pressure drop with respect to that of a uniform flow. As a result of this, the pumping power required by the fan or blower will also increase. The increase of the pumping power is calculated by means of a discretization technique and it is analyzed with respect to the non-uniform distribution statistical moments of probability density function, i.e., the mean, standard deviation, skew and kurtosis. The analysis reveals that the increase of pumping power is dependent on the exchanger NTU, standard deviation and skew of the velocity distribution. Kurtosis has no effect on the pressure drop. Correlations have been developed to predict this increase of pumping power from known statistical moments and resulting air temperatures. These can then be used as design tools to optimize the sizing of the heat exchanger within the air-conditioning unit, hence giving the best energy efficiency performance.

  1. Experimental investigation of passive residual heat removal system with air cooled heat exchanger

    International Nuclear Information System (INIS)

    The objective of this work is to obtain the Performance test data for the passive residual heat removal (RHR) heat exchanger in the advanced PWR. The RHR heat exchanger is designed to remove the decay heat with combined effects of the natural circulation of water by means of the thermosyphon at the inside and the natural convection of the air at the outside. Two test models were made to simulate the RHR heat exchanger. The one is the single bundle test model which consisted of a finned tubular heat exchanger unit. The other is the multi-bundle test model which has the finned tubular heat exchanger consisting of ten bundles of tubular units. The Maximum heat removal capabilities of each model were investigated. The cooling water flow rates by the thermosyphon were measured and were in good agreement with the theoretical predictions. The effects of chimney and elevation between the heater and the heat exchanger were investigated

  2. Ceramic heat exchanger

    Science.gov (United States)

    LaHaye, P.G.; Rahman, F.H.; Lebeau, T.P.; Severin, B.K.

    1998-06-16

    A tube containment system is disclosed. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture. 6 figs.

  3. Heat exchanger for reactor coolant cleanup system

    International Nuclear Information System (INIS)

    A reactor coolant cleanup system of a BWR reactor comprises a regeneration heat exchangers, non-regenerative heat exchangers and a filtration desalter. Main pipelines connected to an inlet and an exit of each of the regenerative heat exchangers are connected with primary and secondary bypass lines bypassing each of the regenerative heat exchangers. Upon inspection of the regenerative heat exchangers, operation of one regenerative heat exchanger among a plurality of regenerative heat exchangers is stopped while the operation is continued using other regenerative heat exchangers. That is, opening/closing valves on the side of the inlet and the exit of one regeneration heat exchanger are closed and opening/closing valves of the bypass pipelines are opened. With such procedures, water from the reactor is not supplied to the inspected regenerative heat exchanger but supplied to other regeneration heat exchangers by way of the bypass lines. Accordingly, one regenerative heat exchanger can be inspected without stopping operation of all regenerative heat exchangers. (I.N.)

  4. Entropy resistance minimization: An alternative method for heat exchanger analyses

    International Nuclear Information System (INIS)

    In this paper, the concept of entropy resistance is proposed based on the entropy generation analyses of heat transfer processes. It is shown that smaller entropy resistance leads to larger heat transfer rate with fixed thermodynamic force difference and smaller thermodynamic force difference with fixed heat transfer rate, respectively. For the discussed two-stream heat exchangers in which the heat transfer rates are not given and the three-stream heat exchanger with prescribed heat capacity flow rates and inlet temperatures of the streams, smaller entropy resistance leads to larger heat transfer rate. For the two-stream heat exchangers with fixed heat transfer rate, smaller entropy resistance leads to larger effectiveness. Furthermore, it is shown that smaller values of the concepts of entropy generation numbers and modified entropy generation number do not always correspond to better performance of the discussed heat exchangers. - Highlights: • The concept of entropy resistance is defined for heat exchangers. • The concepts based on entropy generation are used to analyze heat exchangers. • Smaller entropy resistance leads to better performance of heat exchangers. • The applicability of entropy generation minimization is conditional

  5. Analysis of flow-induced vibration of heat exchanger and steam generator tube bundles using the AECL computer code PIPEAU-2

    International Nuclear Information System (INIS)

    PIPEAU-2 is a computer code developed at the Chalk River Nuclear Laboratories for the flow-induced vibration analysis of heat exchanger and steam generator tube bundles. It can perform this analysis for straight and 'U' tubes. All the theoretical work underlying the code is analytical rather than numerical in nature. Highly accurate evaluation of the free vibration frequencies and mode shapes is therefore obtained. Using the latest experimentally determined parameters available, the free vibration analysis is followed by a forced vibration analysis. Tube response due to fluid turbulence and vortex shedding is determined, as well as critical fluid velocity associated with fluid-elastic instability

  6. Oscillating side-branch enhancements of thermoacoustic heat exchangers

    Science.gov (United States)

    Swift, Gregory W.

    2003-05-13

    A regenerator-based engine or refrigerator has a regenerator with two ends at two different temperatures, through which a gas oscillates at a first oscillating volumetric flow rate in the direction between the two ends and in which the pressure of the gas oscillates, and first and second heat exchangers, each of which is at one of the two different temperatures. A dead-end side branch into which the gas oscillates has compliance and is connected adjacent to one of the ends of the regenerator to form a second oscillating gas flow rate additive with the first oscillating volumetric flow rate, the compliance having a volume effective to provide a selected total oscillating gas volumetric flow rate through the first heat exchanger. This configuration enables the first heat exchanger to be configured and located to better enhance the performance of the heat exchanger rather than being confined to the location and configuration of the regenerator.

  7. 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)

  8. 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

  9. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    Science.gov (United States)

    2010-04-01

    ...false Cardiopulmonary bypass heat exchanger. 870.4240 Section 870...4240 Cardiopulmonary bypass heat exchanger. (a) Identification. A cardiopulmonary bypass heat exchanger is a device, consisting...

  10. Heat exchanger bypass test procedure

    International Nuclear Information System (INIS)

    The HC-21C Muffle Furnace Process has been experiencing problems with corrosion of the off-gas piping system. During the processing cycle, condensation is forming and corroding the off-gas piping. The corrosion products build up in the rotameters and cause them to be dysfunctional. The condensation is suspected to be occurring in the heat exchanger, so the test will bypass the heat exchanger to verify this. This process test will help to establish a temperature profile for the off-gas system near the rotameter. Also, this information will be used to help determine the location and cause of water condensation that is occurring in the off-gas equipment. The process test will include operating one of the two furnaces in Room 230A to stabilize Pu bearing material. During the test run, various temperature readings will be taken and visual inspections done

  11. Study of transient behavior of finned coil heat exchangers

    Science.gov (United States)

    Rooke, S. P.; Elissa, M. G.

    1993-01-01

    The status of research on the transient behavior of finned coil cross-flow heat exchangers using single phase fluids is reviewed. Applications with available analytical or numerical solutions are discussed. Investigation of water-to-air type cross-flow finned tube heat exchangers is examined through the use of simplified governing equations and an up-wind finite difference scheme. The degenerate case of zero air-side capacitance rate is compared with available exact solution. Generalization of the numerical model is discussed for application to multi-row multi-circuit heat exchangers.

  12. 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.

  13. 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.

    1993-04-01

    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.

  14. SAFE gas turbine cycle primary heat exchangers

    Science.gov (United States)

    Reid, Robert S.; Kapernick, Richard J.

    2002-01-01

    Los Alamos National Laboratory and Marshall Space Flight Center are jointly developing two modular heat pipe heat exchangers, collectively named FIGMENT (Fission Inert Gas Metal Exchanger for Non-nuclear Testing). The FIGMENT heat exchangers are designed to transfer power from the SAFE nuclear reactor cores to gas turbine energy converters. A stainless steel prototype heat exchanger will be built during 2002 in preparation for the construction of a larger refractory metal version. Two promising FIGMENT stainless steel heat exchanger concepts are reviewed here. .

  15. 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

  16. Heat Transport Study of the Laminar Heat Pipe Heat Exchanger

    OpenAIRE

    Wei-Keng Lin; Ke Chine Liaw; Min-Zen Tsai; Min-Gung Chu

    2012-01-01

    The purpose of this experiment is to analyze the performance of the Laminar Heat Pipe Heat Exchanger. The test samples were divided two groups, one is the metal corrugated sheet with heat pipe, and the other is the metal corrugated sheet only. By dipping these two group samples into hot water and to see the thermal image by Infrared thermal imager. The results shown the temperature risen of the sheet with heat pipe was faster than that of the sheet without heat pipe. In addition, the bigger o...

  17. NGNP Process Heat Utilization: Liquid Metal Phase Change Heat Exchanger

    International Nuclear Information System (INIS)

    One key long-standing issue that must be overcome to fully realize the successful growth of nuclear power is to determine other benefits of nuclear energy apart from meeting the electricity demands. The Next Generation Nuclear Plant (NGNP) will most likely be producing electricity and heat for the production of hydrogen and/or oil retrieval from oil sands and oil shale to help in our national pursuit of energy independence. For nuclear process heat to be utilized, intermediate heat exchange is required to transfer heat from the NGNP to the hydrogen plant or oil recovery field in the most efficient way possible. Development of nuclear reactor--process heat technology has intensified the interest in liquid metals as heat transfer media because of their ideal transport properties. Liquid metal heat exchangers are not new in practical applications. An important rational for considering liquid metals is the potential convective heat transfer is among the highest known. Thus explains the interest in liquid metals as coolant for intermediate heat exchange from NGNP. For process heat it is desired that, intermediate heat exchangers (IHX) transfer heat from the NGNP in the most efficient way possible. The production of electric power at higher efficiency via the Brayton Cycle, and hydrogen production, requires both heat at higher temperatures and high effectiveness compact heat exchangers to transfer heat to either the power or process cycle. Compact heat exchangers maximize t cycle. Compact heat exchangers maximize the heat transfer surface area per volume of heat exchanger; this has the benefit of reducing heat exchanger size and heat losses. High temperature IHX design requirements are governed in part by the allowable temperature drop between the outlet and inlet of the NGNP. In order to improve the characteristics of heat transfer, liquid metal phase change heat exchangers may be more effective and efficient. This paper explores the overall heat transfer characteristics and pressure drop of the phase change heat exchanger with Na as the heat exchanger coolant. In order to design a very efficient and effective heat exchanger one must optimize the design such that we have a high heat transfer and a lower pressure drop, but there is always a trade-off between them. Based on NGNP operational parameters, a heat exchanger analysis with the sodium phase change will be presented to show that the heat exchanger has the potential for highly effective heat transfer, within a small volume at reasonable cost

  18. 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.

  19. 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.

  20. Investigation of effect of oblique ridges on heat transfer in plate heat exchangers

    OpenAIRE

    Novosád Jan; Dvo?ák Václav

    2014-01-01

    This article deals with numerical investigation of flow in plate heat exchangers. These are counterflow heat exchangers formed by plates. These plates are shaped by the ridges to intensify heat transfer. The objective of the work is the investigation of effect of straight oblique triangular ridges for increasing of heat transfer and pressure losses. The ridges on adjacent plates intersect and thus form a channel of complex shape. The research includes various types of ridges with different fi...

  1. Thermodynamic Optimization of GSHPS Heat Exchangers

    OpenAIRE

    Ahmad Kahrobaeian; Ali Sharifzadegan; Javad Marzbanrad

    2007-01-01

    In this paper, a new method for determining the optimized dimensions of a ground source heat pump system (GSHPS) heat exchanger is presented. Using the GSHPS is one of the ways for utilization of infinite, clean and renewable energies in the environment. In recent years, due to limitation of physical space for installing the heat exchangers and avoiding the environmental effects on heat exchanger operation, vertical GSHP systems are used more than the other ones. Determination of opt...

  2. Microchannel Heat Exchangers with Carbon Dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Y.; Ohadi, M.M.; Radermacher, R.

    2001-09-15

    The objective of the present study was to determine the performance of CO{sub 2} microchannel evaporators and gas coolers in operational conditions representing those of residential heat pumps. A set of breadboard prototype microchannel evaporators and gas coolers was developed and tested. The refrigerant in the heat exchangers followed a counter cross-flow path with respect to the airflow direction. The test conditions corresponded to the typical operating conditions of residential heat pumps. In addition, a second set of commercial microchannel evaporators and gas coolers was tested for a less comprehensive range of operating conditions. The test results were reduced and a comprehensive data analysis, including comparison with the previous studies in this field, was performed. Capacity and pressure drop of the evaporator and gas cooler for the range of parameters studied were analyzed and are documented in this report. A gas cooler performance prediction model based on non-dimensional parameters was also developed and results are discussed as well. In addition, in the present study, experiments were conducted to evaluate capacities and pressure drops for sub-critical CO{sub 2} flow boiling and transcritical CO{sub 2} gas cooling in microchannel heat exchangers. An extensive review of the literature failed to indicate any previous systematic study in this area, suggesting a lack of fundamental understanding of the phenomena and a lack of comprehensive data that would quantify the performance potential of CO{sub 2} microchannel heat exchangers for the application at hand. All experimental tests were successfully conducted with an energy balance within {+-}3%. The only exceptions to this were experiments at very low saturation temperatures (-23 C), where energy balances were as high as 10%. In the case of evaporators, it was found that a lower saturation temperature (especially when moisture condensation occurs) improves the overall heat transfer coefficient significantly. However, under such conditions, air side pressure drop also increases when moisture condensation occurs. An increase in airflow rate also increases the overall heat transfer coefficient. Air side pressure drop mainly depends on airflow rate. For the gas cooler, a significant portion of the heat transfer occurred in the first heat exchanger module on the refrigerant inlet side. The temperature and pressure of CO{sub 2} significantly affect the heat transfer and fluid flow characteristics due to some important properties (such as specific heat, density, and viscosity). In the transcritical region, performance of CO{sub 2} strongly depends on the operating temperature and pressure. Semi-empirical models were developed for predictions of CO{sub 2} evaporator and gas cooler system capacities. The evaporator model introduced two new factors to account for the effects of air-side moisture condensate and refrigerant outlet superheat. The model agreed with the experimental results within {+-}13%. The gas cooler model, based on non-dimensional parameters, successfully predicted the experimental results within {+-}20%. Recommendations for future work on this project include redesigning headers and/or introducing flow mixers to avoid flow mal-distribution problems, devising new defrosting techniques, and improving numerical models. These recommendations are described in more detail at the end of this report.

  3. 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.

  4. Heat Transport Study of the Laminar Heat Pipe Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Wei-Keng Lin

    2012-11-01

    Full Text Available The purpose of this experiment is to analyze the performance of the Laminar Heat Pipe Heat Exchanger. The test samples were divided two groups, one is the metal corrugated sheet with heat pipe, and the other is the metal corrugated sheet only. By dipping these two group samples into hot water and to see the thermal image by Infrared thermal imager. The results shown the temperature risen of the sheet with heat pipe was faster than that of the sheet without heat pipe. In addition, the bigger of the temperature difference between hot water temperature and ambient temperature, the quicker of the temperature risen for the metal corrugated sheet, and the temperature of the metal corrugated sheet were homogenous as well. For example, when the water temperature is 30?, ambient temperature is 20?, the metal corrugated sheet with heat pipe rise rapidly to 26? within 1 minute, while the metal corrugated sheet without heat pipe rise to 22? only, this temperature difference would be more obvious with the increasing of the hot water temperature. When the hot water temperature is up to 40?, the metal corrugated sheet with heat pipe rise rapidly to 31? within 1 minute, while the metal corrugated sheet without het pipe is still rise up to 22? only. When the hot water temperature is up to 50?, The metal corrugated sheet with heat pipe rise rapidly to 33? within 1 minute, while the sheet without heat pipe still keep at 22?, the results shown the heat pipe affect the temperature rising speed is obvious, and it also implying heat pipe is a very important parameter for the heat transfer rate of the Laminar Heat Pipe Heat Exchanger.

  5. 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

  6. Condensation in horizontal heat exchanger tubes

    International Nuclear Information System (INIS)

    Many innovative reactor concepts for Generation III nuclear power plants use passive safety equipment for residual heat removal. These systems use two phase natural circulation. Heat transfer to the coolant results in a density difference providing the driving head for the required mass flow. By balancing the pressure drop the system finds its operational mode. Therefore the systems depend on a strong link between heat transfer and pressure drop determining the mass flow through the system. In order to be able to analyze these kind of systems with the help of state of the art computer codes the implemented numerical models for heat transfer, pressure drop or two phase flow structure must be able to predict the system performance in a wide parameter range. Goal of the program is to optimize the numerical models and therefore the performance of computer codes analyzing passive systems. Within the project the heat transfer capacity of a heat exchanger tube will be investigated. Therefore the tube will be equipped with detectors, both temperature and pressure, in several directions perpendicular to the tube axis to be able to resolve the angular heat transfer. In parallel the flow structure of a two phase flow inside and along the tube will be detected with the help of x-ray tomography. The water cooling outside of the tube will be realized by forced convection. It will be possible to combine the flow structure measurement with an angular resolved heat transfer for a wide angular resolved heat transfer for a wide parameter range. The test rig is set up at the TOPLFOW facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), so that it will be possible to vary the pressure between 5 and 70 bar. The steam mass content will be varied between 0 and 100 percent. The results will be compared to the large scaled Emergency Condenser Tests performed at the INKA test facility in Karlstein (Germany). The paper will explain the test setup and the status of the project will be presented. (authors)

  7. 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.

  8. 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)

  9. 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.

  10. Heat exchanger for nuclear reactors

    International Nuclear Information System (INIS)

    In a pressure vessel of a nuclear reactor heat exchangers are arranged in an annulus around the central reactor core. The heat exchangers consist of three tube banks with tube plates, the planes of the tube plates of the exterior banks running rectangular to those of the inner bank. The inlet and outlet pipes of the tube plates lead through construction openings. Their diameter is slightly larger than the diagonal of a tube bank. The pipes of the outer banks are running through the construction opening on both sides of a central passage. This passage contains exlusively the pipes of the middle plate of the central tube bank. The pipes of the exterior tube banks additionally leave alloys in which those pipes of the other plates of the central bank are running that are arranged sideways of the center. Furthermore, the pipes of one exterior tube bank are displaced against those of the other exterior bank. In this way the construction openings in the prestressed-concrete pressure vessel can be limited to a minimum. (TK)

  11. Improved ceramic heat exchange material

    Science.gov (United States)

    Mccollister, H. L.

    1977-01-01

    Improved corrosion resistant ceramic materials that are suitable for use as regenerative heat exchangers for vehicular gas turbines is reported. Two glass-ceramic materials, C-144 and C-145, have superior durability towards sulfuric acid and sodium sulfate compared to lithium aluminosilicate (LAS) Corning heat exchange material 9455. Material C-144 is a leached LAS material whose major crystalline phase is silica keatite plus mullite, and C-145 is a LAS keatite solid solution (S.S.) material. In comparison to material 9455, material C-144 is two orders of magnitude better in dimensional stability to sulfuric acid at 300 C, and one order of magnitude better in stability to sodium sulfate at 1000 C. Material C-145 is initially two times better in stability to sulfuric acid, and about one order of magnitude better in stability to sodium sulfate. Both C-144 and C-145 have less than 300 ppm delta L/L thermal expansion from ambient to 1000 C, and good dimensional stability of less than approximately 100 ppm delta L/L after exposure to 1000 C for 100 hours. The glass-ceramic fabrication process produced a hexagonal honeycomb matrix having an 85% open frontal area, 50 micrometer wall thickness, and less than 5% porosity.

  12. Heat exchanger for cooling a liquid metal by air

    International Nuclear Information System (INIS)

    According to the invention, the heat exchanger has an array of vertical tubes arranged along one or, preferentially, several cylindrical and coaxial rows and two toroidal collectors; the tubes are extending between the upper and the lower toroidal collectors. A deflector and a casing enveloping the tubes allow the cooling air to flow in contact with the tubes between a vertical inlet conduit and a vertical outlet conduit. The invention applies, more particularly, to heat exchangers used for cooling the secondary liquid sodium coming from a sodium-sodium heat exchanger immerged in the vessel of a fast neutron reactor

  13. 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.)

  14. Spacecraft Radiator Freeze Protection Using a Regenerative Heat Exchanger

    Science.gov (United States)

    Ungar, Eugene K.; Schunk, Richard G.

    2011-01-01

    An active thermal control system architecture has been modified to include a regenerative heat exchanger (regenerator) inboard of the radiator. Rather than using a radiator bypass valve a regenerative heat exchanger is placed inboard of the radiators. A regenerator cold side bypass valve is used to set the return temperature. During operation, the regenerator bypass flow is varied, mixing cold radiator return fluid and warm regenerator outlet fluid to maintain the system setpoint. At the lowest heat load for stable operation, the bypass flow is closed off, sending all of the flow through the regenerator. This lowers the radiator inlet temperature well below the system set-point while maintaining full flow through the radiators. By using a regenerator bypass flow control to maintain system setpoint, the required minimum heat load to avoid radiator freezing can be reduced by more than half compared to a radiator bypass system.

  15. 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

  16. Passive restriction of blood flow and counter-current heat exchange via lingual retia in the tongue of a neonatal gray whale Eschrichtius robustus (Cetacea, Mysticeti).

    Science.gov (United States)

    Ekdale, Eric G; Kienle, Sarah S

    2015-04-01

    Retia mirabilia play broad roles in cetacean physiology, including thermoregulation during feeding and pressure regulations during diving. Vascular bundles of lingual retia are described within the base of the tongue of a neonatal female gray whale (Eschrichtius robustus). Each rete consists of a central artery surrounded by four to six smaller veins. The retia and constituent vessels decrease in diameter as they extend anteriorly within the hyoglossus muscle from a position anterior to the basihyal cartilage toward the apex of the tongue. The position of the retia embedded in the hyoglossus and the anterior constriction of the vessels differs from reports of similar vascular bundles that were previously identified in gray whales. The retia likely serve as a counter-current heat exchange system to control body temperature during feeding. Cold blood flowing toward the body center within the periarterial veins would accept heat from warm blood in the central artery flowing toward the anterior end of the tongue. Although thermoregulatory systems have been identified within the mouths of a few mysticete species, the distribution of such vascular structures likely is more widespread among baleen whales than has previously been described. PMID:25737382

  17. 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.

  18. 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

  19. Micro tube heat exchangers for Space Project

    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,...

  20. Slotting Fins of Heat Exchangers to Provide Thermal Breaks

    Science.gov (United States)

    Scull, Timothy D.

    2003-01-01

    Heat exchangers that include slotted fins (in contradistinction to continuous fins) have been invented. The slotting of the fins provides thermal breaks that reduce thermal conduction along flow paths (longitudinal thermal conduction), which reduces heat-transfer efficiency. By increasing the ratio between transverse thermal conduction (the desired heat-transfer conduction) and longitudinal thermal conduction, slotting of the fins can be exploited to (1) increase heat-transfer efficiency (thereby reducing operating cost) for a given heat-exchanger length or to (2) reduce the length (thereby reducing the weight and/or cost) of the heat exchanger needed to obtain a given heat transfer efficiency. By reducing the length of a heat exchanger, one can reduce the pressure drop associated with the flow through it. In a case in which slotting enables the use of fins with thermal conductivity greater than could otherwise be tolerated on the basis of longitudinal thermal conduction, one can exploit the conductivity to make the fins longer (in the transverse direction) than they otherwise could be, thereby making it possible to make a heat exchanger that contains fewer channels and therefore, that weighs less, contains fewer potential leak paths, and can be constructed from fewer parts and, hence, reduced cost.

  1. 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.

  2. 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

  3. Design of heat exchangers by numerical methods

    International Nuclear Information System (INIS)

    Differential equations describing the heat tranfer in shell - and tube heat exchangers are derived and solved numerically. The method of ?T sub(lm) is compared with the proposed method in cases where the specific heat at constant pressure, Cp and the overall heat transfer coefficient, U, vary with temperature. The error of the method of ?T sub (lm) for the computation of the exchanger lenght is less than + 10%. However, the numerical method, being more accurate and at the same time easy to use and economical, is recommended for the design of shell-and-tube heat exchangers. (Author)

  4. Advanced intermediate heat exchanger for FBR

    International Nuclear Information System (INIS)

    A proposal was made to replace secondary sodium loop with an advanced intermediate heat exchanger (AIHX) that contains primary sodium tubing, tertiary water/steam tubing, and thermally connecting secondary heat transfer medium. With using a medium such as Gallium and Pb-Bi this heat exchanger could realize sodium FBR with effectively no possibility of sodium water reaction in the case of SG rupture. The present paper reports the design estimation of this heat exchanger and Pb-Bi experimental test facility to obtain heat transfer performances. (author)

  5. Plate heat exchangers design, applications and performance

    CERN Document Server

    Wang, L; Manglik, R M

    2007-01-01

    Heat exchangers are important, and used frequently in the processing, heat and power, air-conditioning and refrigeration, heat recovery, transportation and manufacturing industries. Such equipment is also important in electronics cooling and for environmental issues like thermal pollution, waste disposal and sustainable development.The present book concerns plate heat exchangers (PHEs), which are one of the most common types in practice. The overall objectives are to present comprehensive descriptions of such heat exchangers and their advantages and limitations, to provide in-depth thermal and

  6. 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

  7. Simultaneous synthesis of flexible heat exchanger networks

    OpenAIRE

    Aaltola, Juha

    2003-01-01

    In industry there is still lot of potential to make an energy system more efficient and thereby reduce the waste heat available. On the other hand there is an option to export the waste heat to another industry or to society. When the use of a heat exchanger network is considered for these tasks the optimization framework developed in this work can be implemented to calculate the cost of optimal investments. This thesis presents a framework for generating flexible heat exchanger networks ...

  8. Heat exchanger for nuclear reactor

    Energy Technology Data Exchange (ETDEWEB)

    Artaud, R.; Aubert, M.; Elbeze, R.; Renaux, C.

    1983-01-04

    Heat exchanger for a nuclear reactor of the type in which the main vessel is sealed by an upper slab, comprises a plurality of substantially straight exchange tubes mounted between on the one hand an upper annular tube plate associated with a secondary fluid discharge chamber and on the other a lower annular tube plate associated with a supply chamber, a ferrule surrounding the said tubes and provided with a discharge orifice for the primary fluid, a central shaft which communicates with the supply chamber , and a supply manifold and a discharge manifold for the secondary fluid, wherein it comprises a supporting ferrule fixed to the periphery of the upper tube plate and sealed at its upper end by a dome, said ferrule having on its outer periphery a supporting flange by the said slab, the manifolds being superimposed in the supporting ferrule and fixed to a horizontal plate, which is itself fixed to the supporting ferrule, the supply manifold being connected by at least one pipe to the upper end of the shaft, the discharge manifold being connected to the discharge chamber also by means of a pipe, whereby the pipes are positioned in the supporting ferrule.

  9. Heat exchanger network retrofit optimization involving heat transfer enhancement

    International Nuclear Information System (INIS)

    Heat exchanger network retrofit plays an important role in energy saving in process industry. Many design methods for the retrofit of heat exchanger networks have been proposed during the last three decades. Conventional retrofit methods rely heavily on topology modifications which often result in a long retrofit duration and high initial costs. Moreover, the addition of extra surface area to the heat exchanger can prove difficult due to topology, safety and downtime constraints. Both of these problems can be avoided through the use of heat transfer enhancement in heat exchanger network retrofit. This paper presents a novel design approach to solve heat exchanger network retrofit problems based on heat transfer enhancement. An optimisation method based on simulated annealing has been developed to find the appropriate heat exchangers to be enhanced and to calculate the level of enhancement required. The physical insight of enhanced exchangers is also analysed. The new methodology allows several possible retrofit strategies using different retrofit methods be determined. Comparison of these retrofit strategies demonstrates that retrofit modification duration and payback time are reduced when heat transfer enhancement is utilised. Heat transfer enhancement can be also used as a substitute for increased heat exchanger network surface area to reduce retrofit investment costs.

  10. Bank of heat exchangers intended for liquid cooling or heating

    International Nuclear Information System (INIS)

    The invention concerns the heat exchangers cooling a significant volume of water, by straight natural air draught, such as the towers or the draught ducts of dry type air coolers. In a compact form, they enable water cooling problems to be solved in certain industrial installations such as isotope separation plants. The design of this bank of exchangers is also such that its cost is considerably diminished in relation to that of conventional banks. To this effect, this bank is composed of one or several rows of thin flexible plastic pockets forming as many water or other liquid sheets, connected to intake and discharge collectors and arranged one after the other and separated by air flow gaps. These pockets are suspended from one of their ends to hangers fixed to the assembly frame whilst restrictors prevent the pockets from swelling so avoiding any contact between them in order to maintain the air circulation gaps between them

  11. 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.

  12. 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)

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

    OpenAIRE

    Sathiyan, S.; Murali Rangarajan; S.Ramachandran

    2013-01-01

    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...

  14. 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.

  15. Experimental investigation on heat transfer analysis of conical coil heat exchanger with 90° cone angle

    Science.gov (United States)

    Purandare, Pramod S.; Lele, Mandar M.; Gupta, Raj Kumar

    2015-03-01

    In the present study, an experimental investigation on thermal performance of the conical coil heat exchanger with 90° conical coil heat exchanger is reported. Three different conical coil heat exchangers of same mean coil diameter (Dm = 200 mm) with different tube diameters ( di = 8, 10, 12.5 mm) are analyzed under steady state condition. The analysis is carried out for the tube side hot fluid flow range of 10-100 lph ( Re = 500-5,000), while the shell side flow range of 30-90 lph. The data available from experimentation leads to evaluate heat transfer coefficients for inside and outside the tube of the conical coil heat exchanger by Wilsons plot method. The calculations are further extended to estimate Nusselt Number ( Nu) and effectiveness. The empirical correlations are proposed for predicting Nu and the outlet temperatures of hot and cold fluids. The predicted empirical correlations show reasonable agreement with the experimental results within the given range of parameters.

  16. A method for locating steam leakage in a heat exchanger with flow tubes dipped in liquid sodium, and a device for carrying out said method

    International Nuclear Information System (INIS)

    The present invention is a second certificate of addition to the method of locating a steam leakage in a heat exchanger. The improvement is characterized in that it comprises the steps of using the exchanger normal working fluid (e.g. water) as the tracing hydrogenated fluid, injecting a sodium inert gas into sets of tubes comprising at least one tube, and observing the readings of the fluid-sensing device (said device being based on the dosing of hydrogen, in particular in sodium) until an absence of hydrogen-leakage detection by said device identifies the leaky tube. This can be applied to rapid leakage detection in heat exchangers

  17. 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

  18. 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

  19. COMPARATIVE THERMAL ANALYSIS OF HELIXCHANGER WITH SEGMENTAL HEAT EXCHANGER USING BELL-DELAWARE METHOD

    OpenAIRE

    S. Pavithran; P. V. Hadgekar; S.S. Shinde

    2012-01-01

    Heat exchangers are important heat transfer apparatus in oil refining, chemical engineering, environmental protection, electric power generation etc. The present work modifies the existing Bell-Delaware method used for conventional heat exchanger, taking into consideration the helical geometry of Helixchanger. Thermal analysis was carried out to study the impacts of various baffle inclination angles on fluid flow and heat transfer of heat exchangers with helical baffles. The analysis was con...

  20. 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.

  1. High temperature alloys and ceramic heat exchanger

    International Nuclear Information System (INIS)

    From the standpoint of energy saving, the future operating temperatures of process heat and gas turbine plants will become higher. For this purpose, ceramics is the most promissing candidate material in strength for application to high-temperature heat exchangers. This report deals with a servey of characteristics of several high-temperature metallic materials and ceramics as temperature-resistant materials; including a servey of the state-of-the-art of ceramic heat exchanger technologies developed outside of Japan, and a study of their application to the intermediate heat exchanger of VHTR (a very-high-temperature gas-cooled reactor). (author)

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

    OpenAIRE

    Zhang, Jianqin; Li, Shaopeng

    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 co...

  3. 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.

  4. 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.

  5. 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

  6. Improved ceramic heat exchanger materials

    Science.gov (United States)

    Rauch, H. W.

    1980-01-01

    The development and evaluation of materials for potential application as heat exchanger structures in automotive gas turbine engines is discussed. Test specimens in the form of small monolithic bars were evaluated for thermal expansion and dimensional stability before and after exposure to sea salt and sulfuric acid, followed by short and long term cycling at temperatures up to 1200 C. The material finally selected, GE-7808, consists of the oxides, ZrO2-MgO-Al2O3-S1O2, and is described generically as ZrMAS. The original version was based on a commercially available cordierite (MAS) frit. However, a clay/talc mixture was demonstrated to be a satisfactory very low cost source of the cordierite (MAS) phase. Several full size honeycomb regenerator cores, about 10.2 cm thick and 55 cm diameter were fabricated from both the frit and mineral versions of GE-7808. The honeycomb cells in these cores had rectangular dimensions of about 0.5 mm x 2.5 mm and a wall thickness of approximately 0.2 mm. The test data show that GE-7808 is significantly more stable at 1100 C in the presence of sodium than the aluminosilicate reference materials. In addition, thermal exposure up to 1100 C, with and without sodium present, results in essentially no change in thermal expansion of GE-7808.

  7. 14 CFR 23.1125 - Exhaust heat exchangers.

    Science.gov (United States)

    2010-01-01

    ...2010-01-01 false Exhaust heat exchangers. 23.1125 Section 23...System § 23.1125 Exhaust heat exchangers. For reciprocating engine...apply: (a) Each exhaust heat exchanger must be constructed and...

  8. 14 CFR 29.1125 - Exhaust heat exchangers.

    Science.gov (United States)

    2010-01-01

    ...2010-01-01 false Exhaust heat exchangers. 29.1125 Section 29...System § 29.1125 Exhaust heat exchangers. For reciprocating engine...apply: (a) Each exhaust heat exchanger must be constructed and...

  9. 14 CFR 25.1125 - Exhaust heat exchangers.

    Science.gov (United States)

    2010-01-01

    ...2010-01-01 false Exhaust heat exchangers. 25.1125 Section 25...System § 25.1125 Exhaust heat exchangers. For reciprocating engine...apply: (a) Each exhaust heat exchanger must be constructed and...

  10. 40 CFR 63.1435 - Heat exchanger provisions.

    Science.gov (United States)

    2010-07-01

    ...2010-07-01 2010-07-01 true Heat exchanger provisions. 63.1435 Section...Polyols Production § 63.1435 Heat exchanger provisions. (a) The owner...requirements of § 63.104 for heat exchange systems, with the...

  11. 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)

  12. 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

  13. Heat exchanger, head and shell acceptance criteria

    Energy Technology Data Exchange (ETDEWEB)

    Lam, P.S.; Sindelar, R.L.

    1992-09-01

    Instability of postulated flaws in the head component of the heat exchanger could not produce a large break, equivalent to a DEGB in the PWS piping, due to the configuration of the head and restraint provided by the staybolts. Rather, leakage from throughwall flaws in the head would increase with flaw length with finite leakage areas that are bounded by a post-instability flaw configuration. Postulated flaws at instability in the shell of the heat exchanger or in the cooling water nozzles could produce a large break in the Cooling Water System (CWS) pressure boundary. An initial analysis of flaw stability for postulated flaws in the heat exchanger head was performed in January 1992. This present report updates that analysis and, additionally, provides acceptable flaw configurations to maintain defined structural or safety margins against flaw instability of the external pressure boundary components of the heat exchanger, namely the head, shell, and cooling water nozzles. Structural and flaw stability analyses of the heat exchanger tubes, the internal pressure boundary of the heat exchangers or interface boundary between the PWS and CWS, were previously completed in February 1992 as part of the heat exchanger restart evaluation and are not covered in this report.

  14. Heat exchanger, head and shell acceptance criteria

    International Nuclear Information System (INIS)

    Instability of postulated flaws in the head component of the heat exchanger could not produce a large break, equivalent to a DEGB in the PWS piping, due to the configuration of the head and restraint provided by the staybolts. Rather, leakage from throughwall flaws in the head would increase with flaw length with finite leakage areas that are bounded by a post-instability flaw configuration. Postulated flaws at instability in the shell of the heat exchanger or in the cooling water nozzles could produce a large break in the Cooling Water System (CWS) pressure boundary. An initial analysis of flaw stability for postulated flaws in the heat exchanger head was performed in January 1992. This present report updates that analysis and, additionally, provides acceptable flaw configurations to maintain defined structural or safety margins against flaw instability of the external pressure boundary components of the heat exchanger, namely the head, shell, and cooling water nozzles. Structural and flaw stability analyses of the heat exchanger tubes, the internal pressure boundary of the heat exchangers or interface boundary between the PWS and CWS, were previously completed in February 1992 as part of the heat exchanger restart evaluation and are not covered in this report

  15. Analysis of a Flooded Heat Exchanger

    Science.gov (United States)

    Fink, Aaron H.; Luyben, William L.

    2015-01-01

    Flooded heat exchangers are often used in industry to reduce the required heat-transfer area and the size of utility control valves. These units involve a condensing vapor on the hot side that accumulates as a liquid phase in the lower part of the vessel. The heat transfer occurs mostly in the vapor space, but the condensate becomes somewhat…

  16. 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

  17. 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

  18. 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...

  19. The LUX prototype detector: Heat exchanger development

    International Nuclear Information System (INIS)

    The LUX (large underground xenon) detector is a two-phase xenon time projection chamber (TPC) designed to search for WIMP–nucleon dark matter interactions. As with all noble element detectors, continuous purification of the detector medium is essential to produce a large (>1ms) electron lifetime; this is necessary for efficient measurement of the electron signal which in turn is essential for achieving robust discrimination of signal from background events. In this paper, we describe the development of a novel purification system deployed in a prototype detector. The results from the operation of this prototype indicated heat exchange with an efficiency above 94% up to a flow rate of 42 slpm, allowing for an electron drift length greater than 1 m to be achieved in approximately 2 days and sustained for the duration of the testing period

  20. The LUX prototype detector: Heat exchanger development

    Energy Technology Data Exchange (ETDEWEB)

    Akerib, D.S. [Department of Physics, Case Western Reserve University, Cleveland, OH 44106 (United States); Bai, X. [South Dakota School of Mines and Technology, 501 East St Joseph St., Rapid City, SD 57701 (United States); Bedikian, S. [Yale University, Department of Physics, 217 Prospect St., New Haven, CT 06511 (United States); Bernstein, A. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94551 (United States); Bolozdynya, A. [National Research Nuclear University MEPHI, Faculty of the Experimental and Theoretical Physics, Kashirskoe Sh., 31, Moscow 115409 (Russian Federation); Bradley, A. [Department of Physics, Case Western Reserve University, Cleveland, OH 44106 (United States); Cahn, S.B. [Yale University, Department of Physics, 217 Prospect St., New Haven, CT 06511 (United States); Carr, D. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94551 (United States); Chapman, J.J. [Brown University, Department of Physics, 182 Hope St., Providence, RI 02912 (United States); Clark, K., E-mail: kjc20@psu.edu [Department of Physics, Case Western Reserve University, Cleveland, OH 44106 (United States); Classen, T. [University of California Davis, Department of Physics, One Shields Ave., Davis, CA 95616 (United States); Curioni, A. [Yale University, Department of Physics, 217 Prospect St., New Haven, CT 06511 (United States); Dahl, C.E. [Department of Physics, Case Western Reserve University, Cleveland, OH 44106 (United States); Dazeley, S. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94551 (United States); Viveiros, L. de [Brown University, Department of Physics, 182 Hope St., Providence, RI 02912 (United States); Dragowsky, M. [Department of Physics, Case Western Reserve University, Cleveland, OH 44106 (United States); Druszkiewicz, E. [University of Rochester, Department of Physics and Astronomy, Rochester, NY 14627 (United States); and others

    2013-05-01

    The LUX (large underground xenon) detector is a two-phase xenon time projection chamber (TPC) designed to search for WIMP–nucleon dark matter interactions. As with all noble element detectors, continuous purification of the detector medium is essential to produce a large (>1ms) electron lifetime; this is necessary for efficient measurement of the electron signal which in turn is essential for achieving robust discrimination of signal from background events. In this paper, we describe the development of a novel purification system deployed in a prototype detector. The results from the operation of this prototype indicated heat exchange with an efficiency above 94% up to a flow rate of 42 slpm, allowing for an electron drift length greater than 1 m to be achieved in approximately 2 days and sustained for the duration of the testing period.

  1. 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.

  2. SAFE Reactor Brayton Cycle Primary Heat Exchangers

    International Nuclear Information System (INIS)

    Gas cooling of power-dense nuclear reactor cores can produce large thermal and stress gradients through sensible temperature changes in the coolant. In-core heat pipes remove heat isothermally and reduce the severity of these gradients. The modular SAFE reactor concept consists of numerous heat pipes that permit core re-assembly during test and preflight integration. The redundancy inherent in the modular heat pipe-based design enhances reactor reliability. The SAFE reactor is designed to operate for extended periods near full power even if several fuel pins or modules fail. Los Alamos National Laboratory and Marshall Space Flight Center are jointly developing two modular heat pipe heat exchangers, collectively named FIGMENT (Fission Inert Gas Metal Exchanger for Non-nuclear Testing). The FIGMENT heat exchangers are designed to transfer power from the SAFE nuclear reactor cores to gas turbine energy converters. A stainless steel prototype heat exchanger will be built in preparation for the construction of a larger refractory metal version. Several promising FIGMENT stainless steel heat exchanger concepts are reviewed here. (authors)

  3. Performance evaluation criteria for use of enhanced heat transfer surfaces in heat exchanger design

    International Nuclear Information System (INIS)

    Previous work of Bergles and Webb is extended to establish a broad range of Performance Evaluation Criteria (PEC) applicable to single phase flow in tubes. The equations include the effects of shell-side enhancement and fouling and are applicable to roughness and internally finned tubes. Detailed procedures are outlined to calculate the performance improvement and to select the 'optimum' surface geometry. PEC are presented for four design cases: (1) reduced heat exchanger material; (2) increased heat duty- (3) reduced log-mean temperature difference- and (4) reduced pumping power. The 11 cases discussed include fixed flow area and variable flow area. Appropriate PEC for two-phase exchangers are also discussed. (author)

  4. 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

  5. Enceladus' enigmatic heat flow

    Science.gov (United States)

    Howett, Carly; Spencer, John; Verbiscer, Anne

    2014-11-01

    Enceladus’ heat flow provides a fundamental constraint on its tidal dissipation mechanisms, orbital evolution, and the physical processes that generate the plumes. An initial estimate of this value, 5.8±1.3 GW, was made by Spencer et al. (2006) using Cassini Composite Infrared Spectrometer (CIRS) 600 to 1100 cm-1 observations. This number was refined using 10 to 600 cm-1 CIRS observations to 15.8±3.1 GW by Howett et al. (2011). However, recent reanalysis of high-spatial resolution 10 to 1100 cm-1 CIRS observations of Enceladus’ active south polar region conducted by Spencer and Howett gives a heat flow of 4.64±0.23 GW. Whilst all of these heat flow estimates are much larger than those expected in a steady state, 1.1 GW (Meyer and Wisdom, 2007), their obvious discrepancy is a puzzle. Was the passive emission component simply underestimated in the 15.8 GW determination, or is there significant between-stripe endogenic emission that is excluded in the most recent estimate, or is something else going on?

  6. Inverse heat transfer problem in digital temperature control in plate fin and tube heat exchangers

    Science.gov (United States)

    Taler, Dawid; Sury, Adam

    2011-12-01

    The aim of the paper is a steady-state inverse heat transfer problem for plate-fin and tube heat exchangers. The objective of the process control is to adjust the number of fan revolutions per minute so that the water temperature at the heat exchanger outlet is equal to a preset value. Two control techniques were developed. The first is based on the presented mathematical model of the heat exchanger while the second is a digital proportional-integral-derivative (PID) control. The first procedure is very stable. The digital PID controller becomes unstable if the water volumetric flow rate changes significantly. The developed techniques were implemented in digital control system of the water exit temperature in a plate fin and tube heat exchanger. The measured exit temperature of the water was very close to the set value of the temperature if the first method was used. The experiments showed that the PID controller works also well but becomes frequently unstable.

  7. Acceptance criteria for heat exchanger head staybolts

    Energy Technology Data Exchange (ETDEWEB)

    Sindelar, R.L.; Lam, P.S.; Barnes, D.M.; Placr, A.; Morrison, J.M.

    1991-01-01

    Each of the six primary coolant loop systems of the Savannah River Site production reactors contains two parallel single-pass heat exchangers to transfer heat from the primary coolant (D{sub 2}O) to the secondary cooling water (H{sub 2}O). The configuration of the heat exchangers includes a plenary space defined by the heat exchanger tubesheet and the heat exchanger head at both the heat exchanger inlet and outlet to the primary piping. The primary restraint of the heat exchanger head (Type 304 stainless steel) is provided by 84 staybolts (Type 303 stainless steel) which attach to the tubesheet. The staybolts were cap seal-welded in the mid-1960's and are immersed in moderator. Access to inspect the staybolts is limited to a recently-developed ultrasonic technique shooting a beam through the staybolt assembly. Acceptance Criteria to allow disposition of flaws detected by UT inspection have been developed. The structural adequacy to protect against collapse loading of the head is demonstrated by finite element analysis of the head assembly and fracture analysis of flaw postulates in the staybolts. Both normal operation and normal operation plus seismic loading conditions were considered. Several bounding cases containing various configurations of nonactive (exceeding critical flaw size) staybolts were analyzed. The model of the head assembly can be applied to evaluate any active staybolt configurations based on the results from future inspections. 9 refs.

  8. Acceptance criteria for heat exchanger head staybolts

    Energy Technology Data Exchange (ETDEWEB)

    Sindelar, R.L.; Lam, P.S.; Barnes, D.M.; Placr, A.; Morrison, J.M.

    1991-12-31

    Each of the six primary coolant loop systems of the Savannah River Site production reactors contains two parallel single-pass heat exchangers to transfer heat from the primary coolant (D{sub 2}O) to the secondary cooling water (H{sub 2}O). The configuration of the heat exchangers includes a plenary space defined by the heat exchanger tubesheet and the heat exchanger head at both the heat exchanger inlet and outlet to the primary piping. The primary restraint of the heat exchanger head (Type 304 stainless steel) is provided by 84 staybolts (Type 303 stainless steel) which attach to the tubesheet. The staybolts were cap seal-welded in the mid-1960`s and are immersed in moderator. Access to inspect the staybolts is limited to a recently-developed ultrasonic technique shooting a beam through the staybolt assembly. Acceptance Criteria to allow disposition of flaws detected by UT inspection have been developed. The structural adequacy to protect against collapse loading of the head is demonstrated by finite element analysis of the head assembly and fracture analysis of flaw postulates in the staybolts. Both normal operation and normal operation plus seismic loading conditions were considered. Several bounding cases containing various configurations of nonactive (exceeding critical flaw size) staybolts were analyzed. The model of the head assembly can be applied to evaluate any active staybolt configurations based on the results from future inspections. 9 refs.

  9. Exergy optimization in a steady moving bed heat exchanger.

    Science.gov (United States)

    Soria-Verdugo, A; Almendros-Ibáñez, J A; Ruiz-Rivas, U; Santana, D

    2009-04-01

    This work provides an energy and exergy optimization analysis of a moving bed heat exchanger (MBHE). The exchanger is studied as a cross-flow heat exchanger where one of the phases is a moving granular medium. The optimal MBHE dimensions and the optimal particle diameter are obtained for a range of incoming fluid flow rates. The analyses are carried out over operation data of the exchanger obtained in two ways: a numerical simulation of the steady-state problem and an analytical solution of the simplified equations, neglecting the conduction terms. The numerical simulation considers, for the solid, the convection heat transfer to the fluid and the diffusion term in both directions, and for the fluid only the convection heat transfer to the solid. The results are compared with a well-known analytical solution (neglecting conduction effects) for the temperature distribution in the exchanger. Next, the analytical solution is used to derive an expression for the exergy destruction. The optimal length of the MBHE depends mainly on the flow rate and does not depend on particle diameter unless they become very small (thus increasing sharply the pressure drop). The exergy optimal length is always smaller than the thermal one, although the difference is itself small. PMID:19426351

  10. Mathematical Modeling of Spiral Heat Exchanger

    OpenAIRE

    Probal Guha , Vaishnavi Unde

    2014-01-01

    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 ...

  11. Practical thermodynamic tools for heat exchanger design engineers

    International Nuclear Information System (INIS)

    This book provides an approach to the design of heat exchanger equipment as is used throughout the mechanical and chemical industries, offering practical information that goes beyond the present state of this applied art. It introduces a number of guidelines to be satisfied by physical laws in thermal engineering, treating thermodynamics, fluid mechanics, and heat transfer as a unified body of knowledge. This is followed by a discussion of the Bernouli theorem and friction factor, with a comparison of the many equations proposed. There is coverage of the complexities of two-phase flow, illustrated by equipment in the refrigeration industry. Contains detailed examples of a variety of heat exchangers, and introduces reduced properties for boiling and condensation. Text concludes with a discussion of departure from ideal analytical conditions in heat exchangers

  12. Heat transfer from oriented heat exchange areas

    OpenAIRE

    Vantuch Martin; Huzvar Jozef; Kapjor Andrej

    2014-01-01

    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 a...

  13. Influence of corrugation angle in the stirred yoghurt processing in plate heat exchangers

    OpenAIRE

    Fernandes, Carla S.; Afonso, Isabel M.; Melo, Luis F.; Maia, Joa?o M.

    2004-01-01

    Research on heat transfer of non-Newtonian fluids during thermal processing is very useful for optimise heat exchanger design, as well as to define quality levels of the final product. In the present study non-isothermal, non-Newtonian flow in plate heat exchangers were simulated numerically, in order to evaluate the influence of corrugation angles on the thermal and hydrodynamics characteristics of yoghurt cooling in a plate heat exchanger. Simulations were carried out using the commercia...

  14. IMPROVED PERFORMANCE OF HELIXCHANGER OVER SEGMENTAL BAFFLE HEAT EXCHANGER USING KERN’S METHOD

    OpenAIRE

    S. Pavithran; MustansirHatim Pancha; Sunil Kumar Shinde

    2012-01-01

    Heat exchangers being one of the most important heat & mass transfer apparatus in industries like oil refining, chemical engineering, electric power generation etc. are designed with preciseness for optimum performance and long service life. This paper analyses the conventional segmental baffle heat exchanger using the Kern method with varied shell side flow rates. This is a proven method used in design of Heat Exchangers with a baffle cut of 25%. The paper also consists of the thermal analys...

  15. Heat exchanger fouling: Prediction, measurement, and mitigation

    Science.gov (United States)

    The US Department of Energy (DOE), Office of Industrial Programs (OIP) sponsors the development of innovative heat exchange systems. Fouling is a major and persistent cost associated with most industrial heat exchangers and nationally wastes an estimated 2.9 Quads per year. To predict and control fouling, three OIP projects are currently exploring heat exchanger fouling in specific industrial applications. A fouling probe has been developed to determine empirically the fouling potential of an industrial gas stream and to derive the fouling thermal resistance. The probe is a hollow metal cylinder capable of measuring the average heat flux along the length of the tube. The local heat flux is also measured by a heat flux meter embedded in the probe wall. The fouling probe has been successfully tested in the laboratory at flue gas temperatures up to 2200 F and a local heat flux up to 41,000 BTU/hr sq ft. The probe has been field tested at a coal-fired boiler plant. Future tests at a municipal waste incinerator are planned. Two other projects study enhanced heat exchanger tubes, specifically the effect of enhanced surface geometries on the tube bundle performance. Both projects include fouling in a liquid heat transfer fluid. Identifying and quantifying the factors affecting fouling in these enhanced heat transfer tubes will lead to techniques to mitigate fouling.

  16. Earth Air Heat Exchanger in Parallel Connection

    Directory of Open Access Journals (Sweden)

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

    2013-06-01

    Full Text Available 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 purpose heating in winter and cooling in summer. This paper investigates the experimental studies on earth air heat exchanger system in parallel connection in the summer climate.

  17. 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)

  18. Lightweight Thermal Storage Heat Exchangers Project

    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. Ageing management of heavy water heat exchangers

    International Nuclear Information System (INIS)

    In all the nuclear power stations, it is mandatory to monitor the health of all heavy water heat exchangers - such as shutdown cooling heat exchangers, bleed coolers, moderator heat exchangers, pre-cooling heat exchangers etc in order to avoid any tube failure resulting in release of radioactivity to secondary side. Hence, these equipment are subjected to regulatory inspections. Even though very stringent requirements at design stage and fabrication stage are followed. In-service inspection of the tubing by eddy current is the most powerful method to assess the health of the tubes. This paper describes eddy current method followed for in-service inspection of tubes and how the defect level is assessed. The basis for plugging of the tubes based on the criteria given in the American Society of Mechanical Engineers (ASME) section XI and US Nuclear Regulatory Guides are also discussed. (author)

  20. Fatigue Testing of Heat-Exchanger Tubes

    Science.gov (United States)

    Ackerman, P.

    1984-01-01

    Acclerated fatigue-life testing of heat-exchanger tubes simplified by technique that substitutes mechanical side load for thermally-generated axisymmetric stress. Load amplitudes adjusted to produce strains equivalent to those produced by anticipated thermal stress.

  1. Design concept for vessels and heat exchangers

    International Nuclear Information System (INIS)

    A design concept for vessels and heat exchangers against internal and external loads resulting from normal operation and accident is shown. A definition and explanation of the operating conditions and stress levels are given. A description of the type of analysis (stress, fatigue, deformation, stability, earthquake and vibration) is presented in detail, also including technical guidelines which are used for the vessels and heat exchangers and their individual structure parts. (Author)

  2. 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

    2015-02-01

    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.

  3. Development of thermal-hydraulic model for condensation heat exchanger in APR+ (I)

    International Nuclear Information System (INIS)

    In the present study, pervious researches for the design of condensation heat exchangers was collected and the characteristics of them was analyzed according to orientation, the flow regime map, which can be applied for the primary system of condensation heat exchanger, was proposed. the heat transfer models of boiling and condensation were developed

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

    OpenAIRE

    Subodh Bahirat,; Joshi, P. V.

    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 ...

  5. 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

  6. Device for supporting flat heat exchange packets for recuperative heat exchange

    International Nuclear Information System (INIS)

    A honeycombed structure of the supporting framework allows to place very closely a great number of adjacent tube-shaped cases which contain the heat exchanger sets connected in parallel. Thus individual components of the heat exchangers are easily accessible fact which is of great advantage for heat exchangers operating in HTRs being subject to high dynamic loads which are due to pressure- and temperature variations. (GL)

  7. Confirmation of effectiveness of horizontal heat exchanger for PCCS

    International Nuclear Information System (INIS)

    Two kinds of experiments were performed to confirm the effectiveness of a horizontal heat exchanger for Passive Containment Cooling System (PCCS) to prevent containment break due to overpressurization during a severe accident in a next generation BWR. Analysis tools were prepared based on the experiments to predict system responses including the thermal-hydraulic behavior in the heat exchanger. Fundamental thermal-hydraulic experiment was performed first using a single condenser tube to confirm the capability of a horizontal condenser tube of the heat exchanger. It was confirmed that steam is condensed completely with small degradation by non-condensable gas and small pressure loss across the condenser tube without any instability. New condensation and degradation models were proposed and installed into the codes to predict the thermal-hydraulic behavior accurately in the primary side of the horizontal heat exchanger. Large-scale experiment was performed next using a tube bundle experimental facility to confirm the total performance of the horizontal heat exchanger and to prepare analysis codes. Flow regime in the secondary side was found to change from bubbly to churn-like flows with elevation in the tube bundle. Effects of such flow regime transition, however, were little on the heat removal distribution among the tubes. No instability was induced in the primary flows, either. One-dimensional RELAP5 code was thermally coupled with a multi-dimensional ACE-3D code to d with a multi-dimensional ACE-3D code to predict the multi-channel primary-side flows and multi-dimensional secondary-side flows simultaneously. System analysis was performed using RELAP5 and MELCORE codes being validated using the results of both experiments. The PCCS using the horizontal heat exchanger succeeded to prevent the containment break for more than one day during a typical severe accident scenario TQUV, while the containment may break without the PCCS. According to the experiment and analysis results, the effectiveness of the horizontal heat exchanger for PCCS was confirmed. (authors)

  8. Comparative study of rotating regenerators and heat-pipe heat exchangers

    Science.gov (United States)

    MacMichael, D. B. A.; Reay, D. A.; Foster, E. L.

    1980-07-01

    A heat wheel was purchased and installed for air to air heat recovery on a Terylene fiber drying and setting oven at ICI Wilton. At the same time a heat pipe heat exchanger was prepared at IRD and tested under controlled conditions. The heat wheel was then replaced by the heat pipe unit. During this procedure measurements were made regularly to monitor the performance of the oven and the heat exchangers. Neither of the heat exchangers attained their rated conditions. It was concluded that recuperative energy conservation is technically and economically feasible, provided that attention is paid to the problems of air flow control and minimizing installation costs. It was also realized that a good saving could be made by paying attention to stray leaks from the oven and by reducing the exhaust air flow from the setting sections. On the question of comparative performance of the two heat exchangers it is not possible to propose that one type is preferable to the other, although the heat wheel created more problems in respect of maintaining airflow.

  9. A design of compact and enhanced heat exchanger used in integrated nuclear reactor

    International Nuclear Information System (INIS)

    Thermal-hydraulic characteristics and design methods of a compact and enhanced heat exchanger are presented in this paper. The heat exchanger was designed with concentric double-pipe of double-side heat transfer and annular flow channel, which possesses more than 2 times as much density of heat transfer surface as that of ordinary tubular heat exchangers and lower pressure drop in primary side. This type of heat exchanger is especially suitable for application in the integrated nuclear reactor with natural circulation in primary circuit. (authors)

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

    CERN Document Server

    Hansen, B J; Klebaner, A; 10.1063/1.4706971

    2012-01-01

    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 ...

  11. Heat transfer and rheology of stirred yoghurt during cooling in plate heat exchangers

    OpenAIRE

    Afonso, I. M.; Hes, Lubos; Maia, J. M.; Melo, L. F.

    2003-01-01

    In the present work an experimental investigation was conducted to obtain a correlation for the determination of convective heat transfer coefficients of stirred yoghurt in a plate heat exchanger. A rheological study was carried out in order to characterise the stirred yoghurt flow behaviour, evaluating its dependency both on shear rate and temperature. A shift in the temperature dependency was evidenced at 25 ºC. It is also shown that the material shows a complex flow behaviour, changing ...

  12. Comparative Study and Analysis between Helical Coil and Straight Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    N. D. Shirgire

    2014-08-01

    Full Text Available The purpose of this study is to determine the relative advantage of using a helically coiled heat exchanger against a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is higher as compared to Straight tube due to their shape. Helical coils offer advantageous over straight tubes due to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or helix angle influences the torsion to which the fluid is subjected to the centrifugal force results in the development of secondary flow. Due to the curvature effect, the fluid streams in the outer side of the pipe moves faster than the fluid streams in the inner side of the pipe. In current work the fluid to fluid heat exchange is taken into consideration. Most of the investigations on heat transfer coefficients are for constant wall temperature or constant heat flux. The effectiveness, overall heat transfer coefficient, effect of cold water flow rate on effectiveness of heat exchanger when hot water mass flow rate is kept constant and effect of hot water flow rate on effectiveness when cold water flow rate kept constant studied and compared for parallel flow, counter flow arrangement of Helical coil and Straight tube heat exchangers. All readings were taken at steady state condition of heat exchanger. The result shows that the heat transfer coefficient is affected by the geometry of the heat exchanger. Helical coil heat exchanger are superior in all aspect studied here.

  13. Design of common heat exchanger network for batch processes

    International Nuclear Information System (INIS)

    Heat integration of energy streams is very important for the efficient energy recovery in production systems. Pinch technology is a very useful tool for heat integration and maximizing energy efficiency. Creating of heat exchangers network as a common solution for systems in batch mode that will be applicable in all existing time slices is very difficult. This paper suggests a new methodology for design of common heat exchanger network for batch processes. Heat exchanger network designs were created for all determined repeatable and non-repeatable time periods – time slices. They are the basis for creating the common heat exchanger network. The common heat exchanger network as solution, satisfies all heat-transfer needs for each time period and for every existing combination of selected streams in the production process. This methodology use split of some heat exchangers into two or more heat exchange units or heat exchange zones. The reason for that is the multipurpose use of heat exchangers between different pairs of streams in different time periods. Splitting of large heat exchangers would maximize the total heat transfer usage of heat exchange units. Final solution contains heat exchangers with the minimum heat load as well as the minimum need of heat transfer area. The solution is applicable for all determined time periods and all existing stream combinations. - Highlights: •Methodology for design of energy efficient systems in batch processes. •Common Heat Exchanger Network solution based on designs with Pinch technology. •Multipurpose use of heat exchangers in batch processes

  14. Mechanical design of heat exchangers and pressure vessel components

    International Nuclear Information System (INIS)

    The twenty-two chapters in this book are prefaced by brief descriptions of the computer codes referenced or listed within the pages that follow. The first chapter, which contains an outline of the more accepted heat-exchanger types and basic design considerations, is followed by another outlining various design-stress criteria. The next twenty chapters contain considerable detailed information concerning the design and operation of heat exchangers. The authors devote 121 pages to one of the most important design considerations, flow-induced vibration. Another chapter is dedicated to methods of seismic analysis. The remaining chapters address mechanical and thermal design as well as manufacturing

  15. Research of heat exchange rate of the pulsating heat pipe

    Directory of Open Access Journals (Sweden)

    Kravets V. Yu.

    2010-02-01

    Full Text Available Given article presents experimental research of heat transfer characteristics of the pulsating heat pipe (PHP which consists of seven coils with 1 mm inner diameter. Water was used as the heat carrier. PHP construction, measuring circuit and research technique are presented. It is shown that under PHP functioning there are two characteristic modes of operation, which can be distinguished by values of thermal resistance. PHP heat exchange features are disclosed.

  16. 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.

  17. Effect of the axial scraping velocity on enhanced heat exchangers

    International Nuclear Information System (INIS)

    Highlights: • The flow pattern has been obtained by means of PIV in an enhanced heat exchanger. • The effects of the Reynolds number and the scraping velocity have been analysed. • The turbulence level of the flow has been related to the scraping velocity. • A numerical RNG k–? turbulent model has been validated with the experimental data. -- Abstract: The flow pattern within an enhanced tubular heat exchanger equipped with a reciprocating scraping device is experimentally analysed. The insert device, specially designed to avoid fouling and to enhance heat transfer, has also been used to produce ice slurry. It consists of several circular perforated scraping discs mounted on a coaxial shaft. The whole is moved alternatively along the axial direction by a hydraulic cylinder. The phase-averaged velocity fields of the turbulent flow have been obtained with PIV technique for both scraping semi-cycles. Special attention has been paid to the effect of the non-dimensional scraping velocity and the Reynolds number in the flow field. CFD simulations provide support for the identification of the flow patterns and the parameter assessment extension. The results show how the scraping parameters affect the turbulence level produced in the flow and therefore the desired heat transfer enhancement

  18. 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 thermoacous...

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

    OpenAIRE

    J.A.Livingston; Selvakumar, P

    2013-01-01

    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 int...

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

    OpenAIRE

    Livingston, J. A.; Selvakumar, P.

    2013-01-01

    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...

  1. 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.

  2. Heat Exchanger With Internal Pin Elements

    Science.gov (United States)

    Gerstmann, Joseph (Framingham, MA); Hannon, Charles L. (Arlington, MA)

    2004-01-13

    A heat exchanger/heater comprising a tubular member having a fluid inlet end, a fluid outlet end and plurality of pins secured to the interior wall of the tube. Various embodiments additionally comprise a blocking member disposed concentrically inside the pins, such as a core plug or a baffle array. Also disclosed is a vapor generator employing an internally pinned tube, and a fluid-heater/heat-exchanger utilizing an outer jacket tube and fluid-side baffle elements, as well as methods for heating a fluid using an internally pinned tube.

  3. 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.

  4. Dynamic responses of heat exchanger tube banks

    International Nuclear Information System (INIS)

    Understanding and modeling fluid/structure interaction in cylinder bundles is a basic requirement in the development of analytical methods and guidelines for designing LMFBR heat exchanger and reactor fuel assemblies that are free from component vibration problems. As a step toward satisfying this requirement, an analytical and experimental study of tube banks vibrating in liquids is presented. A general method of analysis is presented for free and forced vibrations of tube banks including tube/fluid interaction, and numerical results are given for tube banks subjected to various types of excitations. Two cantilevered tubes were tested in a water tank, and the natural frequencies and forced responses of coupled motion were measured. Experimental data and analytical results are in reasonably good agreement. The analytical method presented is currently being extended to account for the flowing fluid in tube banks and will be used in the development of the mathematical models for crossflow- and parallel-flow-induced vibrations of tube bundles. Those models will be useful in predicting the response of tube bundles and in design to avoid detrimental vibration

  5. 40 CFR 63.1409 - Heat exchange system provisions.

    Science.gov (United States)

    2010-07-01

    ...where the cooling water enters and exits each heat exchanger or any combination of heat exchangers. (i) For samples taken at the entrance...samples taken at the entrance and exit of each heat exchanger or any combination of heat exchangers,...

  6. 40 CFR 63.104 - Heat exchange system requirements.

    Science.gov (United States)

    2010-07-01

    ...where the cooling water enters and exits each heat exchanger or any combination of heat exchangers. (i) For samples taken at the entrance...samples taken at the entrance and exit of each heat exchanger or any combination of heat exchangers in...

  7. Decontamination of Primary Heat Exchanger Heat Transfer Plate in HANARO

    International Nuclear Information System (INIS)

    In HANARO, a multi-purpose research reactor, a 30 MWth open-tank-in-pool type, a plate type primary heat exchanger transfers the reactor core residual heat absorbed by a primary coolant to a secondary coolant. There was a leakage in the gasket of the no. one heat exchanger after about five years of normal operation. The leaking heat transfer plate pack was replaced with a new one and decontaminated. This paper describes the method of decontaminating the radioactivity of the no. 1 heat exchanger used plate pack and the results. A chemical treatment method was applied to the decontamination. This treatment method consists of cleaning the used plate with a hydro jet after properly depositing it in a scale agent

  8. Heat transfer and pressure drop characteristics of nanofluids in a plate heat exchanger.

    Science.gov (United States)

    Kwon, Y H; Kim, D; Li, C G; Lee, J K; Hong, D S; Lee, J G; Lee, S H; Cho, Y H; Kim, S H

    2011-07-01

    In this paper, the heat transfer characteristics and pressure drop of the ZnO and Al2O3 nanofluids in a plate heat exchanger were studied. The experimental conditions were 100-500 Reynolds number and the respective volumetric flow rates. The working temperature of the heat exchanger was within 20-40 degrees C. The measured thermophysical properties, such as thermal conductivity and kinematic viscosity, were applied to the calculation of the convective heat transfer coefficient of the plate heat exchanger employing the ZnO and Al2O3 nanofluids made through a two-step method. According to the Reynolds number, the overall heat transfer coefficient for 6 vol% Al2O3 increased to 30% because at the given viscosity and density of the nanofluids, they did not have the same flow rates. At a given volumetric flow rate, however, the performance did not improve. After the nanofluids were placed in the plate heat exchanger, the experimental results pertaining to nanofluid efficiency seemed inauspicious. PMID:22121605

  9. RECITAL SCRUTINY ON TUBE-INTUBE COMPACT HEAT EXCHANGERS

    OpenAIRE

    V.NATARAJAN,; Senthil Kumar, Dr P.

    2011-01-01

    This paper focused on the investigational cram of the recital characteristics of tube-in-tube compact heat exchangers. Experiments are conducted in the compact heat exchangers with R-134a and liquefiedpetroleum gas. The effectiveness of the heat exchangers was calculated using the experiment data and it was found that the effectiveness of heat exchanger-1 is above 75 and heat exchanger-2 is above 84% for R-134a.The effectiveness of heat exchanger-1 is about 60% and heat exchanger-2 is about 8...

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

    OpenAIRE

    P. MOHAJERI KHAMENEH,; I. MIRZAIE,; Pourmahmoud, N.; Rahimi Eosboee, M.; Majidyfar, S.; Mansoor, M.

    2010-01-01

    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 ...

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

    Directory of Open Access Journals (Sweden)

    Jeanette Janaina Jaber Lucato

    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.

  12. 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.

  13. 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.

  14. Compact heat exchanger technologies for the HTRs recuperator application

    International Nuclear Information System (INIS)

    Modern HTR nuclear power plants which are now under development (projects GT-MHR, PBMR) are based on the direct cycle concept. This concept leads to a more important efficiency compared to the steam cycle but requires the use of high performance components such as an helium/helium heat exchanger called recuperator to guarantee the cycle efficiency. Using this concept, a net plant efficiency of around 50% can be achieved in the case of an electricity generating plant. As geometric constraints are particularly important for such a gas reactor to limit the size of the primary vessels, compact heat exchangers operating at high pressure and high temperature are attractive potential solutions for the recuperator application. In this frame, Framatome and CEA have reviewed the various technologies of compact heat exchangers used in industry. The first part of the paper will give a short description of the heat exchangers technologies and their ranges of application. In a second part, a selection of potential compact heat exchangers technologies are proposed for the recuperator application. This selection will be based upon their capabilities to cope with the operating conditions parameters (pressure, temperature, flow rate) and with other parameters such as fouling, corrosion, compactness, weight, maintenance and reliability. (author)

  15. Negative Joule Heating in Ion-Exchange Membranes

    CERN Document Server

    Biesheuvel, P M; Hamelers, H V M

    2014-01-01

    In ion-exchange membrane processes, ions and water flow under the influence of gradients in hydrostatic pressure, ion chemical potential, and electrical potential (voltage), leading to solvent flow, ionic fluxes and ionic current. At the outer surfaces of the membranes, electrical double layers (EDLs) are formed (Donnan layers). When a current flows through the membrane, we argue that besides the positive Joule heating in the bulk of the membrane and in the electrolyte outside the membrane, there is also negative Joule heating in one of the EDLs. We define Joule heating as the inner product of the two vectors current and field strength. Also when fluid flows through a charged membrane, at one side of the membrane there is pressure-related cooling, due to the osmotic and hydrostatic pressure differences across the EDLs.

  16. 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.

  17. Intensification of heat and mass transfer by ultrasound: Application to heat exchangers and membrane separation processes.

    Science.gov (United States)

    Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E

    2015-07-01

    This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions. PMID:25216897

  18. 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.

  19. 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.

  20. A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.

    Science.gov (United States)

    de Jong, J A; Wijnant, Y H; de Boer, A

    2014-03-01

    A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer. PMID:24606258

  1. Performance Evaluation of Plate-Fin-And Tube Heat Exchanger with Wavy Fins- A Review

    Directory of Open Access Journals (Sweden)

    Sandip S. Kale

    2014-09-01

    Full Text Available The plate fin-and-tube heat exchangers are widely used in variety of industrial applications, particularly in the heating, air-conditioning and refrigeration, HVAC industries. In most cases the working fluid is liquid on the tube side exchanging heat with a gas, usually air. It is seen that the performance of heat exchangers can be greatly increased with the use of unconventionally shaped flow passages such as plain, perforated offset strip, louvered, wavy, vortex generator and pin. The current study is focused on wavy-fin. The wavy surface can lengthen the path of airflow and cause better airflow mixing. In order to design better heat exchangers and come up with efficient designs, a thorough understanding of the flow of air in these channels is required. Hence this study focuses on the heat transfer and friction characteristics of the air side for wavy fin and tube heat exchanger.

  2. 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.

  3. Modeling particle deposition on HVAC heat exchangers

    International Nuclear Information System (INIS)

    Fouling of fin-and-tube heat exchangers by particle deposition leads to diminished effectiveness in supplying ventilation and air conditioning. This paper explores mechanisms that cause particle deposition on heat exchanger surfaces. We present a model that accounts for impaction, diffusion, gravitational settling, and turbulence. Simulation results suggest that some submicron particles deposit in the heat exchanger core, but do not cause significant performance impacts. Particles between 1 and 10(micro)m deposit with probabilities ranging from 1-20% with fin edge impaction representing the dominant mechanism. Particles larger than 10(micro)m deposit by impaction on refrigerant tubes, gravitational settling on fin corrugations, and mechanisms associated with turbulent airflow. The model results agree reasonably well with experimental data, but the deposition of larger particles at high velocities is underpredicted. Geometric factors, such as discontinuities in the fins, are hypothesized to be responsible for the discrepancy

  4. Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger

    Science.gov (United States)

    Grabenstein, V.; Kabelac, S.

    2012-11-01

    Plate heat exchanger (PHE) are today widely used in industrial heat transfer applications due to their good thermal performance, modest space requirement, easy accessibility to all areas and their lower capital and operating costs as compared to shell-and-tube heat exchangers. Although authoritative models for the design of PHE used as condensers are missing, the number of applications where a PHE is operating as a condenser increases. On the way to a reliable model based on physical approaches for the prediction of heat transfer and pressure drop during the condensation process inside a PHE, the flow and heat interactions as well as their dependence on the geometrical parameters of the corrugated plates and the operating conditions must be studied in detail. In this work the stepwise procedure for the fundamental construction of such a model is described. An experimental setup was built to analyze the characteristics of the two-phase-flow in PHE. A single gap, consisting of two transparent corrugated plates, was tested with a two-phase flow of air/water and also with boiling refrigerant R365mfc. Flow pattern maps were constructed for plates with corrugation angles of 27 and 63 degrees relative to the direction of flow. Investigations of the local heat transfer coefficients and the pressure drop were done with the same plates. The measurement of the local heat transfer coefficients was carried out by the use of the "Temperature Oscillation InfraRed Thermography" (TOIRT) method. Based on these results three main flow patterns are defined: film flow, bubbly flow and slug flow. For each of the three flow patterns an own model for the heat transfer and pressure drop mechanism are developed and the heat transfer coefficient and the friction factor is calculated with different equations depending on the actual steam quality, mass flow and geometrical parameters by means of a flow pattern map. The theory of the flow pattern based prediction models is proved with own experimental data. The measurements were carried out with an experimental setup in a technical scale. The refrigerant cycle works with R134a as refrigerant and involves two PHEs, used as condenser and evaporator, and a 55 kWel compressor for the compression of the vapor phase. The setup allows the measurement of quasi-local heat transfer coefficients inside the PHEs. Additional heat exchangers assure saturated vapor at the inlet and saturated liquid at the outlet of the condenser.

  5. Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger

    International Nuclear Information System (INIS)

    Plate heat exchanger (PHE) are today widely used in industrial heat transfer applications due to their good thermal performance, modest space requirement, easy accessibility to all areas and their lower capital and operating costs as compared to shell-and-tube heat exchangers. Although authoritative models for the design of PHE used as condensers are missing, the number of applications where a PHE is operating as a condenser increases. On the way to a reliable model based on physical approaches for the prediction of heat transfer and pressure drop during the condensation process inside a PHE, the flow and heat interactions as well as their dependence on the geometrical parameters of the corrugated plates and the operating conditions must be studied in detail. In this work the stepwise procedure for the fundamental construction of such a model is described. An experimental setup was built to analyze the characteristics of the two-phase-flow in PHE. A single gap, consisting of two transparent corrugated plates, was tested with a two-phase flow of air/water and also with boiling refrigerant R365mfc. Flow pattern maps were constructed for plates with corrugation angles of 27 and 63 degrees relative to the direction of flow. Investigations of the local heat transfer coefficients and the pressure drop were done with the same plates. The measurement of the local heat transfer coefficients was carried out by the use of the 'Temperature Oscillation InfraRed Thermography' (TOIRe Oscillation InfraRed Thermography' (TOIRT) method. Based on these results three main flow patterns are defined: film flow, bubbly flow and slug flow. For each of the three flow patterns an own model for the heat transfer and pressure drop mechanism are developed and the heat transfer coefficient and the friction factor is calculated with different equations depending on the actual steam quality, mass flow and geometrical parameters by means of a flow pattern map. The theory of the flow pattern based prediction models is proved with own experimental data. The measurements were carried out with an experimental setup in a technical scale. The refrigerant cycle works with R134a as refrigerant and involves two PHEs, used as condenser and evaporator, and a 55 kWel compressor for the compression of the vapor phase. The setup allows the measurement of quasi-local heat transfer coefficients inside the PHEs. Additional heat exchangers assure saturated vapor at the inlet and saturated liquid at the outlet of the condenser.

  6. Heat exchanger containing a component capable of discontinuous movement

    Science.gov (United States)

    Wilson, David Gordon (Winchester, MA)

    2002-01-01

    Regenerative heat exchangers are described for transferring heat between hot and cold fluids. The heat exchangers have seal-leakage rates significantly less than those of conventional regenerative heat exchangers because the matrix is discontinuously moved and is releasably sealed while in a stationary position. Both rotary and modular heat exchangers are described. Also described are methods for transferring heat between a hot and cold fluid using the discontinuous movement of matrices.

  7. 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...

  8. Heat transfer in heat exchangers of sodium cooled fast reactor systems

    International Nuclear Information System (INIS)

    The present paper describes the heat transfer in heat exchangers of sodium cooled fast reactors. Practical empirical correlations regarding heat transfer coefficients for intermediate heat exchangers (IHXs) and air coolers (ACs) were derived using test data obtained at the fast reactor 'Monju' and 'Joyo' and also at the 50 MW steam generator facility (50 MW SG). The correlation proposed by Seban and Shimazaki was applicable to estimate the heat transfer coefficients in both flows of IHX, i.e., primary and secondary flows, when the Peclet number was larger than 30. When the Peclet number for shell-side was small, the Nusselt number decreased as a function of the Peclet number. It was clarified that this characteristic was not caused by the heat conduction in flow direction. The heat conduction effect can be neglected even in the natural circulation conditions of the Monju plant. As for the heat transfer coefficient of AC provided in the secondary heat transport system of the fast breeder reactor, data in the above mentioned three facilities were evaluated. As a result, empirical correlations were derived for the average heat transfer coefficients of a large capacity finned air cooler made of stainless steel. These correlations could contribute to analyze the plant dynamics with better accuracy than before

  9. 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...

  10. Hydrodynamics, heat transfer and flow boiling instabilities in microchannels

    OpenAIRE

    Barber, Jacqueline Claire

    2010-01-01

    Boiling in microchannels is a very efficient mode of heat transfer with high heat and mass transfer coefficients achieved. Less pumping power is required for two-phase flows than for single-phase liquid flows to achieve a given heat removal. Applications include electronics cooling such as cooling microchips in laptop computers, and process intensification with compact evaporators and heat exchangers. Evaporation of the liquid meniscus is the main contributor to the high hea...

  11. 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

  12. COMPARATIVE THERMAL ANALYSIS OF HELIXCHANGER WITH SEGMENTAL HEAT EXCHANGER USING BELL-DELAWARE METHOD

    Directory of Open Access Journals (Sweden)

    S. Pavithran

    2012-05-01

    Full Text Available Heat exchangers are important heat transfer apparatus in oil refining, chemical engineering, environmental protection, electric power generation etc. The present work modifies the existing Bell-Delaware method used for conventional heat exchanger, taking into consideration the helical geometry of Helixchanger. Thermal analysis was carried out to study the impacts of various baffle inclination angles on fluid flow and heat transfer of heat exchangers with helical baffles. The analysis was conducted for conventional shell and tube heat Exchanger and Helixchanger for five baffle inclination angles. Analysis results indicate that continual helical baffles can reduce or even eliminate dead regions in the shell side of shell-and-tube heat exchangers. The pressure drop varies drastically with baffle inclination angle and shell-side Reynolds number. The variation of the pressure drop is relatively large for small inclination angle. However, for ?>350, the effect of ? on pressure drop is very small. Compared to the segmental heat exchangers, the heat exchangers with continual helical baffles have higher heat transfer coefficients to the same pressure drop. The detailed knowledge on the heat transfer and pressure drop across the shell side will provide further basis flow for further optimization of shell-and-tube heat exchangers.

  13. An Experimental Investigation of Two Phase Natural Circulation Loop (NCL) with End Heat Exchangers

    OpenAIRE

    Ummid I Shaikh, R. R. Kulkarni

    2014-01-01

    Abstract: The steady state behaviour of two-phase natural circulation loop with heat exchangers at the hot and cold ends is studied experimentally. A vertical rectangular and uniform cross section Natural Circulation Loop (NCL) with end heat exchangers is designed and fabricated. Steam is used as hot fluid and tap water as cold fluid. The experimentation is carried out for various hot fluid flow rates. Four flow patterns are identified viz. Small bubbly flow, b...

  14. 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

  15. 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.

  16. 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.

  17. 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 flohe 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.

  18. Heat transfer in liquid metal heat exchangers at mixed convection in an intertube space

    International Nuclear Information System (INIS)

    Results of complex calculation-theoretical and experimental study of heat transfer in fast liquid metal reactor heat exchangers are presented. Formulas to calculate coefficients of effective heat conductivity in three-component media and heat transfer to liquid metal and gaseous coolants, when they flow around a tube bundle at an angle, are obtained. The main complex criteria for similarity of temperature fields in model and full-scale heat exchangers during on-coming and following convections are clarified. Heat transfer coefficients on a stabilized section for corridor and staggered arrangement of tubes is a bundle are obtained experimentally. The boundary of recirculation modes and degree of capacity decrease during mixed convection are established mixed convection are established

  19. Comparative analysis of compact heat exchangers for application as the intermediate heat exchanger for advanced nuclear reactors

    Energy Technology Data Exchange (ETDEWEB)

    N. Bartel; M. Chen; V.P. Utgikar; X. Sun; I.H. Kim; R. Christensen; P. Sabharwall

    2015-04-01

    A comparative evaluation of alternative compact heat exchanger designs for use as the intermediate heat exchanger in advanced nuclear reactor systems is presented in this article. Candidate heat exchangers investigated included the Printed circuit heat exchanger (PCHE) and offset strip-fin heat exchanger (OSFHE). Both these heat exchangers offer high surface area to volume ratio (a measure of compactness [m2/m3]), high thermal effectiveness, and overall low pressure drop. Helium–helium heat exchanger designs for different heat exchanger types were developed for a 600 MW thermal advanced nuclear reactor. The wavy channel PCHE with a 15° pitch angle was found to offer optimum combination of heat transfer coefficient, compactness and pressure drop as compared to other alternatives. The principles of the comparative analysis presented here will be useful for heat exchanger evaluations in other applications as well.

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

    OpenAIRE

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

    2008-01-01

    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 identic...

  1. 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

  2. Modelling Heat Exchangers for Domestic Boilers

    OpenAIRE

    Teixeira, S. F. C. F.; Teixeira, J. C. F.

    2000-01-01

    In the present paper the thermal behaviour of fin-tube heat exchangers is modeled. Particular attention has been given to the plate fins. The heat fluxes in the fins are described using a finite volume technique to discretize the energy equation. The thermal interactions with the water in the tubes and the surrounding air are treated as external boundaries, using appropriate relationships for forced convection in pipes and flat plates. The numerical results are presented in terms of dimension...

  3. 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

  4. 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)

  5. Experimental analysis of an air–water heat pump with micro-channel heat exchanger

    International Nuclear Information System (INIS)

    A multi-port extruded (MPE) aluminium flat tube air heat exchanger was compared to a round tube finned coil (FC). The MPE heat exchanger has parallel flow vertical tube configuration with headers in horizontal position and conventional folded louvred fins. The two heat exchangers were mounted on a 10 kW cooling capacity R410A packaged air heat pump. They were sized to approximately obtain the same cooling and heating capacities in chiller and heating mode, respectively. Climatic room steady state tests without frosting phenomena occurring during heat pump operation, demonstrated that the round tube and the flat tube heat exchanger performance are comparable. The MPE heat exchanger was tested with different refrigerant inlet distributor/outlet tubes configurations to investigate the effect of liquid refrigerant distribution. Cycling frosting/defrosting operations were tested with two equivalent machines placed in parallel outdoor and working at full load condition, one of the units was equipped with the MPE heat exchanger while the other mounted a standard finned coil. Penalization factors were analytically introduced to evaluate frosting associated heating energy and energy efficiency degradation. Test results indicate that both the heat pumps are penalized by frost formation but both the penalization factors are higher for the MPE-unit than the FC-unit one in the ?6 to 4 °C air dry bulb temperature range. For the two units, a roughly linear dependence of the heati roughly linear dependence of the heating energy penalization factor and of the energy efficiency factor from the difference between outdoor air and saturated air at the evaporation temperature humidity ratio can be pointed out. - Highlights: ? A multi-port aluminium flat tube heat exchanger was compared to a round tube finned one in a heat pump application. ? In steady state tests without frosting the round and the flat tube heat exchanger are comparable. ? Different inlet distributor/outlet tubes configurations were tested to investigate liquid distribution. ? Cycling frosting/defrosting operations were compared with two machines placed in parallel outdoor.

  6. A Laboratory Exercise Using a Physical Model for Demonstrating Countercurrent Heat Exchange

    Science.gov (United States)

    Loudon, Catherine; Davis-Berg, Elizabeth C.; Botz, Jason T.

    2012-01-01

    A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of…

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

    Energy Technology Data Exchange (ETDEWEB)

    Ozden, Ender [Department of Mechanical Engineering, Middle East Technical University, 06531 Ankara (Turkey); Tari, Ilker, E-mail: itari@metu.edu.t [Department of Mechanical Engineering, Middle East Technical University, 06531 Ankara (Turkey)

    2010-05-15

    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.

  8. 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.

  9. 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.)

  10. Tube-in-shell heat exchangers

    International Nuclear Information System (INIS)

    A method is described for repairing a defective tube weld in a heat exchanger. A sleeve is inserted within the tube to bridge the defect, one end of the sleeve being brazed to the tube and the other end bonded to the tube sheet by explosive welding. (author)

  11. 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.

  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. New plates for different types of plate heat exchangers

    OpenAIRE

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

    2008-01-01

    The first patent for a plate heat exchanger was granted in 1878 to Albretch Dracke, a German inventor. The commercial embodiment of these equipments has become available in 1923. However, the plate heat exchanger development race began in the 1930’s and these gasketed plate and frame heat exchangers were mainly used as pasteurizers (e.g. for milk and beer). Industrial plate heat exchangers were introduced in the 1950’s and initially they were converted dairy models. Brazed plate heat exch...

  14. Numerical investigation of the influence of heat exchanger U-bends on temperature profile and heat transfer of secondary working fluids

    OpenAIRE

    Clarke, R.; Finn, Donal

    2008-01-01

    In this paper, numerical investigations, conducted using computational fluid dynamics, on the enhancement of internal convection heat transfer following a heat exchanger U-bend under laminar flow conditions in secondary working fluids are described. Under laminar flow conditions enhanced mixing within the heat exchanger U-bends is known to occur due to the development of secondary flows, known as Dean vortices. Numerical investigations indicated that within the U-bend, secondary flows partial...

  15. Heat-metric method of thermal energy estimation in ship heat-exchange systems

    Directory of Open Access Journals (Sweden)

    Krasnov Vladislav Alekseevich

    2010-04-01

    Full Text Available A thermal energy estimation method is described in the paper. It may be taken as the base for creation special thermal energy audit devices in ship heat-exchange systems. The analysis of errors in thermal energy estimation, measuring circuit, installation diagram for calibration of heat flow density converters are given in the article. The considered method is direct in spite of the enthalpy method applied nowadays.

  16. Numerical study of 2D heat transfer in a scraped surface heat exchanger

    OpenAIRE

    Sun, KH; Pyle, DL; Fitt, AD; Please, CP; Baines, MJ; Hall-Taylor, N

    2004-01-01

    A numerical study of fluid mechanics and heat transfer in a scraped surface heat exchanger with non-Newtonian power law fluids is undertaken. Numerical results are generated for 2D steady-state conditions using finite element methods. The effect of blade design and material properties, and especially the independent effects of shear thinning and heat thinning on the flow and heat transfer, are studied. The results show that the gaps at the root of the blades, where the blades are connected to...

  17. IMPROVED PERFORMANCE OF HELIXCHANGER OVER SEGMENTAL BAFFLE HEAT EXCHANGER USING KERN’S METHOD

    Directory of Open Access Journals (Sweden)

    S. Pavithran

    2012-11-01

    Full Text Available Heat exchangers being one of the most important heat & mass transfer apparatus in industries like oil refining, chemical engineering, electric power generation etc. are designed with preciseness for optimum performance and long service life. This paper analyses the conventional segmental baffle heat exchanger using the Kern method with varied shell side flow rates. This is a proven method used in design of Heat Exchangers with a baffle cut of 25%. The paper also consists of the thermal analysis of a helixchanger (Continuous Helical baffled Heat Exchanger using the Kern method, modified to estimate the results for different flow rates at a fixed helical angle of 25?.The results obtained in this paper show us that the desired properties from a Heat exchanger i.e High Heat Transfer Co-efficient and lower pressure drop are more effectively obtained in a Helixchanger. The shell side zigzag flow induced by the Segmental baffle arrangement is completely eliminated in a Helixchanger. The flow pattern in the shell side of the continuous helical baffle heat exchanger is rotational & helical due to the geometry of continuous helical baffles. This flow pattern, at a certain fixed helical angle, results in significant increase in the heat transfer coefficient, however at the cost of lower pressure drop.

  18. Materials development for HTGR heat exchangers

    International Nuclear Information System (INIS)

    Some versions of the HTGR generate high 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

  19. Heat exchangers with several heat exchanger matrices mounted in a common casing for separately conducted media

    International Nuclear Information System (INIS)

    The heat exchanger is suited for plants with a closed gas cycle such as, e. g., HTR with a helium turbine or drive units for vehicles. It contains heat exchanger matrices running parallel to each other and formed by the folds of a uniformly folded band and by walls covering the saddles of the folds. Two neighbouring matrices each are combined to form a heat exchanger unit and supported between supporting walls. The heat exchanger unit is not firmly connected with these supporting walls and therefore can easily to be inserted or dismounted. For sealing purposes, the fold saddles are contacting the supporting walls because of the high pressure of the meUWIdium, Ior the remaining seals between hp and lp-compartments labyrinth boxes being provided. (UWI)

  20. 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 expanderm 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.

  1. Heat and mass transfer characteristics of organic sorbent coated on heat transfer surface of a heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Inaba, Hideo [Okayama University, Tsushima, Okayama (Japan); Komatsu, Fujio; Horibe, Akihiko; Haruki, Naoto [Okayama University, Graduate School of Natural Science and Technology, Tsushima, Okayama (Japan); Machida, Akito [Advanced Tech.Lab., Mayekawa Mfg. Co., Ltd., Moriya, Ibaraki (Japan)

    2008-09-15

    This paper describes heat and mass transfer characteristics of organic sorbent coated on heat transfer surface of a fin-tube heat exchanger. The experiments in which the moist air was passed into the heat exchanger coated with sorption material were conducted under various conditions of air flow rate (0.5-1.0 m/s) and the temperature of brine (14-20 C) that was the heat transfer fluid to cool the air flow in the dehumidifying process. It is found that the sorption rate of vapor is affected by the air flow rate and the brine temperature. Meanwhile, the attempt of clarifying the sorption mechanism is also conducted. Finally the average mass transfer coefficient of the organic sorbent coated on heat transfer surface of a fin-tube heat exchanger is non-dimensionalized as a function of Reynolds number and non-dimensional temperature, and it is found that the effect of non-dimensional temperature on them is larger than Reynolds number. (orig.)

  2. Heat-exchanger concepts for neutral-beam calorimeters

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, C.C.; Polk, D.H.; McFarlin, D.J.; Stone, R.

    1981-10-05

    Advanced cooling concepts that permit the design of water cooled heat exchangers for use as calorimeters and beam dumps for advanced neutral beam injection systems were evaluated. Water cooling techniques ranging from pool boiling to high pressure, high velocity swirl flow were considered. Preliminary performance tests were carried out with copper, inconel and molybdenum tubes ranging in size from 0.19 to 0.50 in. diameter. Coolant flow configurations included (1) smooth tube/straight flow, (2) smooth tube with swirl flow created by tangential injection of the coolant, and (3) axial flow in internally finned tubes. Additionally, the effect of tube L/D was evaluated. A CO/sub 2/ laser was employed to irradiate a sector of the tube exterior wall; the laser power was incrementally increased until burnout (as evidenced by a coolant leak) occurred. Absorbed heat fluxes were calculated by dividing the measured coolant heat load by the area of the burn spot on the tube surface. Two six element thermopiles were used to accurately determine the coolant temperature rise. A maximum burnout heat flux near 14 kW/cm/sup 2/ was obtained for the molybdenum tube swirl flow configuration.

  3. Heat-exchanger concepts for neutral-beam calorimeters

    International Nuclear Information System (INIS)

    Advanced cooling concepts that permit the design of water cooled heat exchangers for use as calorimeters and beam dumps for advanced neutral beam injection systems were evaluated. Water cooling techniques ranging from pool boiling to high pressure, high velocity swirl flow were considered. Preliminary performance tests were carried out with copper, inconel and molybdenum tubes ranging in size from 0.19 to 0.50 in. diameter. Coolant flow configurations included (1) smooth tube/straight flow, (2) smooth tube with swirl flow created by tangential injection of the coolant, and (3) axial flow in internally finned tubes. Additionally, the effect of tube L/D was evaluated. A CO2 laser was employed to irradiate a sector of the tube exterior wall; the laser power was incrementally increased until burnout (as evidenced by a coolant leak) occurred. Absorbed heat fluxes were calculated by dividing the measured coolant heat load by the area of the burn spot on the tube surface. Two six element thermopiles were used to accurately determine the coolant temperature rise. A maximum burnout heat flux near 14 kW/cm2 was obtained for the molybdenum tube swirl flow configuration

  4. 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)

  5. The heat flow of Europa

    OpenAIRE

    Ruiz Pérez, Javier

    2007-01-01

    The heat flow from Europa has profound implications for ice shell thickness and structure, as well as for the existence of an internal ocean, which is strongly suggested by magnetic data. The brittle–ductile transition depth and the effective elastic thickness of the lithosphere are here used to perform heat flow estimations for Europa. Results give preferred heat flow values (for a typical geological strain rate of 10?15 s?1) of 70–110 mWm?2 for a brittle–ductile transit...

  6. 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.

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

    OpenAIRE

    Opruta D.; Bode F.; Irimie O.

    2013-01-01

    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 e...

  8. A screening method for the optimal selection of plate heat exchanger configurations

    OpenAIRE

    Pinto, J. M.; J.A.W. Gut

    2002-01-01

    An optimization method for determining the best configuration(s) of gasketed plate heat exchangers is presented. The objective is to select the configuration(s) with the minimum heat transfer area that still satisfies constraints on the number of channels, the pressure drop of both fluids, the channel flow velocities and the exchanger thermal effectiveness. The configuration of the exchanger is defined by six parameters, which are as follows: the number of channels, the numbers of passes on e...

  9. Impact of exchange flows on wetland flushing

    OpenAIRE

    Nepf, Heidi; Andradottir, Hrund O.

    2001-01-01

    The flushing of littoral regions is governed by barotropic river flows, QR, and baroclinic exchange flows, ?Q. This note presents field observations of two different flushing regimes in a shallow wetland that borders a lake. In spring, when river flows are high, the wetland circulation is river- or jet-dominated, ?Q/QR < 1, and the river short- circuits through the wetland in a much shorter time than the nominal residence time. During summer low flows, however, the wetland circulation is do...

  10. 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 thicomes 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)

  11. A probabilistic model of a porous heat exchanger

    Science.gov (United States)

    Agrawal, O. P.; Lin, X. A.

    1995-01-01

    This paper presents a probabilistic one-dimensional finite element model for heat transfer processes in porous heat exchangers. The Galerkin approach is used to develop the finite element matrices. Some of the submatrices are asymmetric due to the presence of the flow term. The Neumann expansion is used to write the temperature distribution as a series of random variables, and the expectation operator is applied to obtain the mean and deviation statistics. To demonstrate the feasibility of the formulation, a one-dimensional model of heat transfer phenomenon in superfluid flow through a porous media is considered. Results of this formulation agree well with the Monte-Carlo simulations and the analytical solutions. Although the numerical experiments are confined to parametric random variables, a formulation is presented to account for the random spatial variations.

  12. 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.

  13. Preliminary thermal sizing of intermediate heat exchanger for NHDD system

    International Nuclear Information System (INIS)

    Nuclear Hydrogen Development and Demonstration (NHDD) system is a Very High Temperature gascooled Reactor (VHTR) coupled with hydrogen production systems. Intermediate heat exchanger transfers heat from the nuclear reactor to the hydrogen production system. This study presented the sensitivity analysis on a preliminary thermal sizing of the intermediate heat exchanger. Printed Circuit Heat Exchanger (PCHE) was selected for the thermal sizing because the printed circuit heat exchanger has the largest compactness among the heat exchanger types. The analysis was performed to estimate the effect of key parameters including the operating condition of the intermediate system, the geometrical factors of the PCHE, and the working fluid of the intermediate system.

  14. Heat transfer and pressure drop characteristics of smooth horizontal tubes in the transitional flow regime

    OpenAIRE

    Meyer, Josua P.; Olivier, Jonathan A.

    2014-01-01

    The operating conditions of many heat exchangers are in, or close to, the transitional flow regime. However, in this regime, not a lot of design information is available and some design books even recommend to not design heat exchangers to operate in the transitional flow regime. Furthermore, it is known that the type of inlet of heat exchangers influences the transition characteristics. It was therefore the purpose of this study to measure heat transfer and pressure drop characteris...

  15. An Experimental Investigation of Heat Transfer Coefficients for Spiral Plate Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Kaliannan Saravanan

    2009-02-01

    Full Text Available Spiral plate heat exchangers play a vital role in cooling high density and high viscous fluids. This paper presents an experimental investigation of convective heat transfer co-efficient for electrolytes using spiral plate heat exchanger. The test section consists of a Plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot fluid is varying from 0.4 kg sec-1 to 0.8 kg sec-1 and the mass flow rate of cold fluid varies from 0.3 kg sec-1 to 0.8 kg sec-1. Experiments have been conducted by varying the mass flow rate, temperature and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the nusselt number that can be used for practical applications is proposed.

  16. Corrosion of materials for heat exchangers and the countermeasures

    International Nuclear Information System (INIS)

    When the materials for heat exchangers are selected, the heat transfer performance, mechanical strength, workability, cost, corrosion resistance and so on are taken in consideration. Most of the failure of heat exchangers is due to corrosion, and the corrosion failure on cooling water side occurs frequently, to which attention is not paid much usually. The rate of occurrence of corrosion failure is overwhelmingly high in heating tubes, and the failure owing to cooling water exceeds that owing to process fluid. The material of heating tubes is mostly aluminum brass, and local failure such as pitting corrosion or stress corrosion cracking holds a majority. The cause of corrosion failure due to cooling water is mostly the poor water quality. The mechanism of corrosion of metals can be explained by the electrochemical reaction between the metals and solutions. As for the factors affecting corrosion, dissolved oxygen, pH, Cl- ions, temperature, flow velocity, and foreign matters are enumerated. Copper alloys are sensitive to the effect of polluted sea water. Erosion corrosion is caused by eddies and bubbles owing to high flow velocity, and impingement attack is caused by scratching foreign matters. The quality of fresh water affects corrosion more than sea water in case of copper alloys. The preliminary examination of water quality is essential. (Kako, I.)

  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. Mean heat transfer coefficients during the evaporation of 1,1,1,2-tetrafluoroethane (R-134a) in a plate heat exchanger

    OpenAIRE

    EMILA DJORDJEVIC; STEPHAN KABELAC; SLOBODAN SERBANOVIC

    2007-01-01

    In this study the transfer coefficient of evaporation heat of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a) in a vertical plate heat exchanger was experimentally investigated. The results are presented as the dependancy of the mean heat transfer coefficient for the whole heat exchanger on the mean vapor quality. The influences of mass flux, heat flux and flow configuration on the heat transfer coefficient were also taken into account and a comparison with previously published experimenta...

  19. Heat transfer in a PEMFC flow channel

    International Nuclear Information System (INIS)

    A numerical method was applied to the heat transfer performance in the flow channel for a proton exchange membrane fuel cell (PEMFC) using the finite element method (FEM). The heat transfer enhancement has been analyzed by transversely installing a baffle plate and a rectangular cylinder to manage flow pattern in the flow channel of the fuel cell. Case studies include baffle plates (gap ratios from 00.05 to 0.2) and the rectangular cylinder (width-to-height ratios from 0.66 to 1.66 with a constant gap ratio of 0.2; various gap ratios from 0.05 to 0.3 with a constant width-to-height ratio 1.0) at constant Reynolds number. The results show that the transverse installation of a baffle plate and a rectangular cylinder in the flow channel can effectively enhance the local heat transfer performance of a PEMFC. The installation of a rectangular cylinder has a better effective heat transfer performance than a baffle plate; the larger the width of the cylinder is the better effective heat transfer performance becomes.

  20. Local description of the energy transfer process in a packed bed heat exchanger

    International Nuclear Information System (INIS)

    The energy transfer process in a packed-bed heat exchanger, in counter0flow arrangement is considered. The phenomenon is described through a Continuum Theory of Mixtures approach, in which fluid and solid (porous matrix) are regarded as continuous constituents possessing, each one, its own temperature and velocity fields. The heat 'exchangers consists of two channels, separated by an impermeable wall without thermal resistence, in which there exists a saturated flow. Some particular cases are simulated. (author)

  1. Experimental evaluation of water surface heat exchange

    International Nuclear Information System (INIS)

    An investigation was conducted at Indian Point Power Station to determine the heat exchange rate between a water surface and the atmosphere. Experimental data were obtained using two sets of evaporation pans. One set of pans was located on the Hudson River near the power plant intake structure, to simulate the natural environment, including normal wave action. The other set of pans was placed on shore. The experimental heat transfer values obtained with the on-river pans were found to be considerably higher than values predicted from certain semiempirical formulae and than those obtained with the on-shore testing pans. 5 refs

  2. 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

  3. Gentilly-2 moderator heat exchanger repair

    International Nuclear Information System (INIS)

    At the time of an unscheduled outage for a problem with the fuelling machine, an operator noted a sound coming from the inlet moderator heat exchanger 3211-HX1. The noise was reported as a loose object knocking around between the tubesheet and the inlet piping. Upon separating the tubesheet from the Heat Exchanger, the tubesheet overlay and tubes extensions were found severely damaged. The repair work would be required to be performed insitu in a highly contaminated environment during end of the year where obtaining manpower resources were difficult. The team work between Hydro-Quebec and Babcock and Wilcox Canada Nuclear Services and use of non-conventional tooling was a big part of the success for this project. The repair started on December 21st, 2007 and the vessel was turned over to HQ on January 24, 2008. (author)

  4. A Mass Computation Model for Lightweight Brayton Cycle Regenerator Heat Exchangers

    Science.gov (United States)

    Juhasz, Albert J.

    2010-01-01

    Based on a theoretical analysis of convective heat transfer across large internal surface areas, this paper discusses the design implications for generating lightweight gas-gas heat exchanger designs by packaging such areas into compact three-dimensional shapes. Allowances are made for hot and cold inlet and outlet headers for assembly of completed regenerator (or recuperator) heat exchanger units into closed cycle gas turbine flow ducting. Surface area and resulting volume and mass requirements are computed for a range of heat exchanger effectiveness values and internal heat transfer coefficients. Benefit cost curves show the effect of increasing heat exchanger effectiveness on Brayton cycle thermodynamic efficiency on the plus side, while also illustrating the cost in heat exchanger required surface area, volume, and mass requirements as effectiveness is increased. The equations derived for counterflow and crossflow configurations show that as effectiveness values approach unity, or 100 percent, the required surface area, and hence heat exchanger volume and mass tend toward infinity, since the implication is that heat is transferred at a zero temperature difference. To verify the dimensional accuracy of the regenerator mass computational procedure, calculation of a regenerator specific mass, that is, heat exchanger weight per unit working fluid mass flow, is performed in both English and SI units. Identical numerical values for the specific mass parameter, whether expressed in lb/(lb/sec) or kg/ (kg/sec), show the dimensional consistency of overall results.

  5. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Rijo Jacob, E-mail: rijojthomas@gmail.com [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur 721302 (India); Ghosh, Parthasarathi; Chowdhury, Kanchan [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur 721302 (India)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Role of heat exchangers in basic helium liquefier analyzed to design large-scale ones. Black-Right-Pointing-Pointer Heat exchangers that determine inlet temperature to expanders are more significant. Black-Right-Pointing-Pointer Limiting values of nondimensional UA for each heat exchanger have been determined. Black-Right-Pointing-Pointer Extra area distributed such that effectiveness of all heat exchangers increase uniformly. Black-Right-Pointing-Pointer 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{sup Registered-Sign} 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.

  7. 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.

  8. Optimal Operation of Parallel Heat Exchanger Networks

    OpenAIRE

    Aaltvedt, Stian

    2013-01-01

    Optimal operation of parallel heat exchanger networks is desirable for many processesaiming to achieve increased supply and potentially higher profit. The aimis to control the final outlet temperature within a certain range, which in manycases includes a trade off between maximum outlet temperature and minimumoperating costs.The goal with this study has been to investigate the performance of the selfoptimizingJäschke temperature control variable, proposed by post doctor JohannesJäsc...

  9. Cleaning and Heat Transfer in Heat Exchanger with Circulating Fluidized Beds

    Science.gov (United States)

    Kang, Ho Keun; Ahn, Soo Whan; Choi, Jong Woong; Lee, Byung Chang

    2010-06-01

    Fluidized bed type heat exchangers are known to increase the heat transfer and prevent the fouling. For proper design of circulating fluidized bed heat exchanger it is important to know the effect of design and operating parameters on the bed to the wall heat transfer coefficient. The present experimental and numerical study was conducted to investigate the effects of circulating solid particles on the characteristics of fluid flow, heat transfer and cleaning effect in the fluidized bed vertical shell and tube type heat exchanger with counterflow, at which a variety of solid particles such as glass (3 mmF), aluminum (2˜3 mmF), steel (2˜2.5 mmF), copper (2.5 mmF) and sand (2˜4 mmF) were used in the fluidized bed with a smooth tube. Seven different solid particles have the same volume, and the effects of various parameters such as water flow rates, particle diameter, materials and geometry were investigated. The present experimental and numerical results showed that the flow velocity range for collision of particles to the tube wall was higher with heavier density solid particles, and the increase in heat transfer was in the order of sand, copper, steel, aluminum, and glass. This behaviour might be attributed to the parameters such as surface roughness or particle heat capacity. Fouling examination using 25,500 ppm of ferric oxide (Fe2O3) revealed that the tube inside wall is cleaned by a mild and continuous scouring action of fluidized solid particles. The fluidized solid particles not only keep the surface clean, but they also break up the boundary layer improving the heat transfer coefficient even at low fluid velocities.

  10. Maintenance experience with shell and tube type heat exchangers of Cirus

    International Nuclear Information System (INIS)

    Cirus is a 40 MWt research reactor. The reactor utilizes metallic natural uranium fuel cladded in aluminium, demineralized light water as primary coolant and heavy water as moderator. The primary coolant (PCW) and moderator (HW) both recirculate in two different closed loops and cooled by sea water (ultimate heat sink) flowing through shell and tube heat exchangers. There are six numbers of primary coolant/sea water (PCW/SW) and three numbers of heavy water/sea water (HW/SW) heat exchangers connected in parallel in two different loops. One heat exchanger remains stand-by in both systems to provide necessary redundancy for routine servicing and maintenance. The heat exchangers have rendered over 35 years of service. This paper describes maintenance experience with the above said heat exchangers, various problems encountered, ageing studies and various innovative changes/modifications incorporated to reduce the down time and maintenance efforts. 1 fig

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

    OpenAIRE

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

    2009-01-01

    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 outc...

  12. Performance of overall heat transfer in multi-channel heat exchanger by alumina nanofluid

    International Nuclear Information System (INIS)

    This study employs a direct synthesis method to prepare alumina/water (Al2O3/water) nanofluid working fluid for a multi-channel heat exchanger (MCHE) experiment, and then simulates its application to electronic chip cooling system to evaluate the practicability of its actual performance. The experimental variables included nanofluids of different weight concentrations (0, 0.5, and 1.0 wt.%) and the inlet water temperature at different flow values. Results show that the overall heat transfer coefficient ratio was higher at higher nanoparticle concentrations. In other words, the overall heat transfer coefficient ratio was higher when the probability of collision between nanoparticles and the wall of the heat exchanger was increased under higher concentration, confirming that nanofluids have considerable potential for use in electronic chip cooling systems.

  13. Pressure drop characteristics of cryogenic mixed refrigerant at macro and micro channel heat exchangers

    Science.gov (United States)

    Baek, Seungwhan; Jeong, Sangkwon; Hwang, Gyuwan

    2012-12-01

    Mixed Refrigerant-Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. The temperature glide effect is one of the major features of using mixed refrigerants since a recuperative heat exchanger in a MR-JT refrigerator is utilized for mostly two-phase flow. Although a pressure drop estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in MR-JT refrigerator heat exchanger designs, it has been rarely discussed so far. In this paper, macro heat exchangers and micro heat exchangers are compared in order to investigate the pressure drop characteristics in the experimental MR-JT refrigerator operation. The tube in tube heat exchanger (TTHE) is a well-known macro-channel heat exchanger in MR-JT refrigeration. Printed Circuit Heat Exchangers (PCHEs) have been developed as a compact heat exchanger with micro size channels. Several two-phase pressure drop correlations are examined to discuss the experimental pressure measurement results. The result of this paper shows that cryogenic mixed refrigerant pressure drop can be estimated with conventional two-phase pressure drop correlations if an appropriate flow pattern is identified.

  14. Heat transfer enhancement with laminar liquid-gas slug flows

    OpenAIRE

    Howard, JA; Walsh, PA; Walsh, EJ; Muzychka, YS

    2010-01-01

    This paper investigates a two-phase non-boiling slug flow regime for the purposes of enhancing heat transfer in microchannel heat sinks or compact heat exchangers. The primary focus is upon understanding the mechanisms leading to enhanced heat transfer and also the effect of utilizing different Prandtl number fluids. Experiments were conducted using Infrared thermography and results presented in terms of Nusselt number versus inverse Graetz parameter. These results spanned both the thermal en...

  15. Design of a ceramic heat exchanger for sulfuric acid decomposition

    International Nuclear Information System (INIS)

    It has been proposed that compact ceramic heat exchangers can be used for high temperature, corrosive applications. This paper discusses the development and optimization of a microchannel heat exchanger for the decomposition of sulfuric acid as part of the hydrogen producing sulfur iodine thermo-chemical cycle. The optimization process combines thermalhydraulic and structural modelling (UNLV) with empirical corrosion, performance and validation testing (Ceramatec, Inc.). The optimization process included an investigation of various materials of construction based on material, mechanical and corrosion properties. Within the designs investigated, micro-channel features were varied to adjust the cross-sectional profiles and the 'tortuosity' of the serpentine flow paths to increase the thermal performance while maintaining low pressure drops and thermo-mechanical stresses within system. The results of these coupled optimization efforts and the associated overall performance improvement will be reported. (author)

  16. Assessment of thermoelectric module with nanofluid heat exchanger

    International Nuclear Information System (INIS)

    For applications such as cooling of electronic devices, it is a common practice to sandwich the thermoelectric module between an integrated chip and a heat exchanger, with the cold-side of the module attached to the chip. This configuration results thermal contact resistances in series between the chip, module, and heat exchanger. In this paper, an appraisal of thermal augmentation of thermoelectric module using nanofluid-based heat exchanger is presented. The system under consideration uses commercially available thermoelectric module, 27 nm Al2O3-H2O nanofluid, and a heat source to replicate the chip. The volume fraction of nanofluid is varied between 0% and 2%. At optimum input current conditions, experimental simulations were performed to measure the transient and steady-state thermal response of the module to imposed isoflux conditions. Data collected from the nanofluid-based exchanger is compared with that of deionized water. Results show that there exist a lag-time in thermal response between the module and the heat exchanger. This is attributed to thermal contact resistance between the two components. A comparison of nanofluid and deionized water data reveals that the temperature difference between the hot- and cold-side, ?T = Th - Tc ? 0, is almost zero for nanofluid whereas ?T > 0 for water. When ?T ? 0, the contribution of Fourier effect to the overall heating is approximately zero hence enhancins approximately zero hence enhancing the module cooling capacity. Experimental evidence further shows that temperature gradient across the thermal paste that bonds the chip and heat exchanger is much lower for the nanofluid than for deionized water. Low temperature gradient results in low resistance to the flow of heat across the thermal paste. The average thermal contact resistance, R = ?T/Q, is 0.18 and 0.12 deg. C/W, respectively for the deionized water and nanofluid. For the range of optimum current, 1.2 ? current ? 4.1 A, considered in this study, the COP ranges between 1.96 and 0.68

  17. 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...

  18. Fabrication experiments for large helix heat exchangers

    International Nuclear Information System (INIS)

    The helical tube has gained increasing attention as a heat transfer element for various kinds of heat exchangers over the last decade. Regardless of reactor type and heat transport medium, nuclear steam generators of the helix type are now in operation, installlation, fabrication or in the project phase. As a rule, projects are based on the extrapolation of existing technologies. In the particlular case of steam generators for HTGR power stations, however, existing experience is with steam generators of up to about 2 m diameter whereas several projects involve units more than twice as large. For this reason it was felt that a fabrication experiment was necessary in order to verify the feasibility of modern steam generator designs. A test rig was erected in the SULZER steam generator shops at Mantes, France, and skilled personnel and conventional production tools were employed in conducting experiments relating to the coiling, handling and threading of large helices. (Auth.)

  19. 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.

  20. Heat Exchanger Design for Solar Gas-Turbine Power Plant

    OpenAIRE

    Yakah, Noah

    2012-01-01

    The aim of this project is to select appropriate heat exchangers out of available gas-gas heat exchangers for used in a proposed power plant. The heat exchangers are to be used in the power plant for the purposes of waste heat recovery, recuperation and intercooling.In selecting an optimum heat exchanger for use, the PCHE was identified as the best candidate for waste heat recovery and recuperation. In order to ascertain the viability of this assertion the PCHE was designed and a 1D modeling ...

  1. Microchannel heat exchanger for two-phase Mixed Refrigerant Joule Thomson process

    Science.gov (United States)

    Baek, Seungwhan; Lee, Jisung; Lee, Cheonkyu; Jeong, Sangkwon

    2014-01-01

    Mixed Refrigerant Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. Printed Circuit Heat Exchanger (PCHE) is one of the promising cryogenic compact recuperators for MR-JT refrigerators due to its compactness, high NTU and robustness. However, PCHE composed with microchannel bundles can cause flow mal-distribution, and it can cause the degradation of thermal performance of the system. To mitigate the flow mal-distribution problem, the cross link (or intra-layer bypass) can be adapted to parallel microchannels. Two heat exchangers are fabricated in this study; one has straight channels, and the other one has intra-layer bypass structure between channels to enhance the flow distribution. The MR-JT refrigerators are operated with these two heat exchanger and the no-load temperatures are compared. The lower no load temperature achieved with the intra-layer bypass structured heat exchanger. The results indicate that the flow mal-distribution in the microchannel heat exchanger can be mitigated with intra-layer bypass structure, and relaxation of flow mal-distribution in the heat exchanger guarantee the MR-JT refrigerator's performance.

  2. Heat exchange model in absorption chamber of water-direct-absorption-typed laser energy meter

    Science.gov (United States)

    Feng Wei, Ji; Qun Sun, Li; Zhang, Kai; Hu, XiaoYang; Zhou, Shan

    2015-04-01

    The interaction between laser and water flow is very complicated in the absorption chamber of a high energy laser (HEL) energy meter which directly uses water as an absorbing medium. Therefore, the heat exchange model cannot be studied through traditional methods, but it is the most important factor to improve heat exchange efficiency in the absorption chamber. After the exchanges of heat and mass were deeply analyzed, experimental study and numerical fitting were brought out. The original testing data of laser power and water flow temperature at one moment were utilized to calculate those at the next moment, and then the calculated temperature curve was compared with the measured one. If the two curves matched well, the corresponding coefficient was obtained. Meanwhile, numerous experiments were performed to study the effects of laser power, duration, focal spot scale, and water flow rate on heat exchange coefficient. In addition, the relationship between water phase change and heat exchange was analyzed. The heat exchange coefficient was increased by optimizing the construction of the absorption chamber or increasing water flow rate. The results provide the reference for design of water-direct-absorption-typed HEL energy meters, as well as for analysis of the interaction between other similar lasers and water flow.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. PENGARUH TEBAL ISOLASI TERMAL TERHADAP EFEKTIVITAS PLATE HEAT EXCHANGER

    Directory of Open Access Journals (Sweden)

    Ekadewi Anggraini Handoyo

    2000-01-01

    Full Text Available In a heat exchanger, there is heat transferred either from the surrounding or to the surrounding, which is not expected. A thermal insulator is used to reduce this heat transfer. The effectiveness of a heat exchanger will increase if the heat loss to surrounding can be reduced. Theoretically, the thicker the insulator the smaller the heat loss in a plate heat exchanger. A research is carried on to study the effect of an insulator thickness on heat exchanger effectiveness. The insulators used are glasswool and rockwool. It turns out that the effectiveness is increasing until a maximum point, and then decreasing when the thickness of the insulator is increasing. Abstract in Bahasa Indonesia : Dalam suatu heat exchanger selalu terjadi perpindahan panas ke atau dari lingkungan yang tidak diharapkan. Untuk mengurangi perpindahan panas ini digunakan isolator termal. Efektivitas heat exchanger akan meningkat jika panas yang hilang ke atau dari lingkungan dapat dikurangi. Secara teoritis untuk heat exchanger berbentuk kotak semakin tebal isolator termal yang digunakan semakin kecil panas mengalir ke atau dari lingkungan. Dalam penelitian ini dicari pengaruh ketebalan isolator termal terhadap efektivitas suatu plate heat exchanger. Percobaan dilakukan untuk 2 jenis isolator, yaitu glasswool dan rockwool. Hasil yang didapat adalah efektivitas akan meningkat sampai harga tertentu dan kemudian akan berkurang dengan penambahan ketebalan isolator termal. Kata kunci: isolator termal, efektivitas, plate heat exchanger.

  8. 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...

  9. Prototype Vent Gas Heat Exchanger for Exploration EVA - Performance and Manufacturing Characteristics

    Science.gov (United States)

    Quinn, Gregory J.; Strange, Jeremy; Jennings, Mallory

    2013-01-01

    NASA is developing new portable life support system (PLSS) technologies, which it is demonstrating in an unmanned ground based prototype unit called PLSS 2.0. One set of technologies within the PLSS provides suitable ventilation to an astronaut while on an EVA. A new component within the ventilation gas loop is a liquid-to-gas heat exchanger to transfer excess heat from the gas to the thermal control system s liquid coolant loop. A unique bench top prototype heat exchanger was built and tested for use in PLSS 2.0. The heat exchanger was designed as a counter-flow, compact plate fin type using stainless steel. Its design was based on previous compact heat exchangers manufactured by United Technologies Aerospace Systems (UTAS), but was half the size of any previous heat exchanger model and one third the size of previous liquid-to-gas heat exchangers. The prototype heat exchanger was less than 40 cubic inches and weighed 2.57 lb. Performance of the heat exchanger met the requirements and the model predictions. The water side and gas side pressure drops were less 0.8 psid and 0.5 inches of water, respectively, and an effectiveness of 94% was measured at the nominal air side pressure of 4.1 psia.

  10. Thermal Analysis of Fin and Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Ms N. B. Rairker

    2014-06-01

    Full Text Available This paper studied experimentally the effect of heat transfer of fin and tube type heat exchanger for different mass flow rate of fluid. The thermal stresses induced on fin and tube is also studied by ansys software at steady state condition by changing the width of fin and diameter of tube. Readings were taken experimentally by changing mass flow rate of fluid at respective temperatures. Comparison was done on theoretically and experimentally obtained results. It is observed that as the width of fin increases thermal stresses on fin also increases. Likewise for tube, by varying diameter of tube different values of stress are obtained. It is also observed at full valve position maximum thermal stresses are induced on fin as well as tube.

  11. 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.

  12. Characteristics of Multiple-Pass Heat Exchanger with Melting of Falling Snow

    Science.gov (United States)

    Ishikawa, Nobuyuki; Aoki, Kazuo; Hattori, Masaru; Kobayashi, Yoshiharu

    The structure of a multiple-pass heat exchanger composed of pipes and plate fins is similar to that of heat exchangers used for melting snow. In this study, we investigated the characteristics of a multiple-pass heat exchanger having two types, a regular pitch type and an irregular one, focusing on the brine pipe pitch of the multiple-pass heat exchanger. The perfect melting condition and the melting efficiency were related to the dimensionless parameters of the heat exchanger and its operating conditions. The calculated results for the perfect melting condition and the melting efficiency agreed with the results obtained from field tests on melting of falling snow. Applying the irregular pitch extends the critical condition for perfect melting when the flow rate of brine is low or the area for melting of falling snow is large. Also, the melting efficiency of the irregular pitch is higher than that of the regular pitch.

  13. Experimental investigation of heat transfer coefficient of CuO/Water nanofluid in double pipe heat exchanger with or without electric field

    OpenAIRE

    S.Senthilraja; KCK.Vijayakumar; R.Gangadevi

    2014-01-01

    This article reports an experimental study of heat transfer coefficient of CuO/Water nanofluid flowing in a horizontal double pipe counter flow heat exchanger in the presence and absence of electric field. The CuO nanoparticles of about 27nm diameter were used in this study. The heat exchange takes place between a CuO/water nanofluid circulating inner tube and a hot air stream flowing through the outer tube. The electric field was supplied on the air side of the heat exchanger and its volt...

  14. 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...

  15. A Numerical Method for Rating Thermal Performance in Spiral Heat Exchangers

    OpenAIRE

    Martin Martinez Garcia; Miguel Angel Moreles

    2012-01-01

    The steady state heat transfer equations associated to two fluids in counter flow, hot and cold, in a spiral heat exchanger are considered in this study. A numerical method for solution was proposed to approximate the temperature distribution and overall heat transfer coefficients using the flow rates and the temperatures at inlets and outlets. In particular the effectiveness and correction factor were computed as performance parameters and develop a tool for design. The method is tested and ...

  16. 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

  17. 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.

  18. Aerodynamics of heat exchangers for high-altitude aircraft

    Science.gov (United States)

    Drela, Mark

    1996-01-01

    Reduction of convective beat transfer with altitude dictates unusually large beat exchangers for piston- engined high-altitude aircraft The relatively large aircraft drag fraction associated with cooling at high altitudes makes the efficient design of the entire heat exchanger installation an essential part of the aircraft's aerodynamic design. The parameters that directly influence cooling drag are developed in the context of high-altitude flight Candidate wing airfoils that incorporate heat exchangers are examined. Such integrated wing-airfoil/heat-exchanger installations appear to be attractive alternatives to isolated heat.exchanger installations. Examples are drawn from integrated installations on existing or planned high-altitude aircraft.

  19. Heat exchange tube acoustic excitation response analysis

    International Nuclear Information System (INIS)

    In the present paper, heat exchange tube resistance to an acoustic field, is studied particularly in the case where the tubes are to be located either at the suction or discharge end of a compressor or upstream from a sonic relief valve or even mounted between these two elements. The aim is to estimate the stress levels involved with a view to arriving at a tube lifetime assessment, from which could be derived a preliminary design calculation method to be used by the design engineering teams at preliminary project stage

  20. Heat exchanger bypass system for an absorption refrigeration system

    Science.gov (United States)

    Reimann, Robert C. (Lafayette, NY)

    1984-01-01

    A heat exchanger bypass system for an absorption refrigeration system is disclosed. The bypass system operates to pass strong solution from the generator around the heat exchanger to the absorber of the absorption refrigeration system when strong solution builds up in the generator above a selected level indicative of solidification of strong solution in the heat exchanger or other such blockage. The bypass system includes a bypass line with a gooseneck located in the generator for controlling flow of strong solution into the bypass line and for preventing refrigerant vapor in the generator from entering the bypass line during normal operation of the refrigeration system. Also, the bypass line includes a trap section filled with liquid for providing a barrier to maintain the normal pressure difference between the generator and the absorber even when the gooseneck of the bypass line is exposed to refrigerant vapor in the generator. Strong solution, which may accumulate in the trap section of the bypass line, is diluted, to prevent solidification, by supplying weak solution to the trap section from a purge system for the absorption refrigeration system.

  1. 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)

  2. 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.

  3. 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)

  4. 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

  5. Heat flow of standard depth

    International Nuclear Information System (INIS)

    Secular and long-term periodic changes in surface temperature cause perturbations to the geothermal gradient which may be significant to depths of at least 1000 m, and major corrections are required to determine absolute values of heat flow from the Earth's interior. However, detailed climatic models remain contentious and estimates of error in geothermal gradients differ widely. Consequently, regions of anomalous heat flow which could contain geothermal resources may be more easily resolved by measuring relative values at a standard depth (e.g. 100 m) so that all data are subject to similar corrections. (orig./ME)

  6. 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.

  7. Unity Mach number axial dispersion model for heat exchanger design

    International Nuclear Information System (INIS)

    Recently a new axial dispersion model for the thermal design of heat exchangers with deviations from plug flow has been developed by considering the limiting case of unity dispersive Mach number of the hyperbolic dispersion model. The main advantage of the new dispersion model is that known and proved design charts and formulae for plug flow can further be applied. Only the numbers of transfer units have to be corrected. The corrections are simple functions of the dispersive Peclet numbers of the hot and the cold flow stream. In this paper a method for the determination of the dispersive Peclet numbers by transient tracer experiments is presented. The experimental inlet signals and outlet responses are evaluated in the frequency domain using Laplace transforms. Together with the analytical solution of the model equations the dispersive Peclet numbers are obtained. For comparison the evaluation procedure in the frequency domain is also applied to the parabolic dispersion model and the model of stirred tanks in series.

  8. Investigation of Brazed Plate Heat Exchangers With Variable Chevron Angles

    OpenAIRE

    Muthuraman, S.

    2013-01-01

    - 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 pres...

  9. Cleaning of the heat exchanger, Task 3.08/04-01

    International Nuclear Information System (INIS)

    A problem of decreased cooling appeared after longer operation of the reactor at nominal power of 6.5 MW. The reason of increased coolant temperature in the primary coolant loop and lower temperatures in the secondary coolant loop indicated problems to be related to heat exchangers. Deposits of sand and sludge in the secondary coolant pipes caused decrease of he flow, i.e. decrease of the effective surface for heat exchange. Cleaning of the heat exchanger pipes demanded detailed radiation protection plan to avoid higher exposure of the 74 staff members involved in the operation

  10. Optimal assignment of multiple utilities in heat exchange networks

    International Nuclear Information System (INIS)

    Existing numerical geometry-based techniques, developed by [A.I.A. Salama, Numerical techniques for determining heat energy targets in pinch analysis, Computers and Chemical Engineering 29 (2005) 1861-1866; A.I.A. Salama, Determination of the optimal heat energy targets in heat pinch analysis using a geometry-based approach, Computers and Chemical Engineering 30 (2006) 758-764], have been extended to optimally assign multiple utilities in heat exchange network (HEN). These techniques utilize the horizontal shift between the cold composite curve (CC) and the stationary hot CC to determine the HEN optimal energy targets, grand composite curve (GCC), and the complement grand composite curve (CGCC). The proposed numerical technique developed in this paper is direct and simultaneously determines the optimal heat-energy targets and optimally assigns multiple utilities as compared with an existing technique based on sequential assignment of multiple utilities. The technique starts by arranging in an ascending order the HEN stream and target temperatures, and the resulting set is labelled T. Furthermore, the temperature sets where multiple utilities are introduced are arranged in an ascending order and are labelled Tic and Tih for the cold and hot sides, respectively. The graphical presentation of the results is facilitated by the insertion at each multiple-utility temperature a perturbed temperature equals the insertion temperature minus a small perturbnsertion temperature minus a small perturbation. Furthermore, using the heat exchanger network (HEN) minimum temperature-differential approach (?Tmin) and stream heat-capacity flow rates, the presentation is facilitated by using the conventional temperature shift of the HEN CCs. The set of temperature-shifted stream and target temperatures and perturbed temperatures in the overlap range between the CCs is labelled Tol. Using Tol, a simple formula employing enthalpy-flow differences between the hot composite curve CCh and the cold composite curve CCc is used to determine the horizontal shift (bias) B between the CCs. In the overlap range, the Bs are determined at all temperatures in set Tol to generate the bias set B. The maximum value of B's in set B , B*, is used in an optimization scheme to determine the optimal assignment of multiple utilities, optimal heat- energy targets, grand composite curve (GCC), and the complement grand composite curve (CGCC) (Salama, 2009), if needed. It should be pointed out that the optimal heat-energy targets and optimal multiple utilities are needed in heat-pinch analysis. The motivations for the present work is to complement the work of Shenoy [U.V. Shenoy, A. Sinha, S. Bandyopadhyay, Multiple utilities targeting for heat exchanger networks, Trans Institution of Chemical Engineers Part A, 76 (1998) 259-272], by approaching the multiple-utility targeting not sequential but rather in a direct manner. Furthermore, the proposed technique builds on the strengths of the numerical techniques developed by Salama [A.I.A. Salama, Numerical techniques for determining heat energy targets in pinch analysis, Computers and Chemical Engineering 29 (2005)1861-1866; A.I.A. Salama, Determination of the optimal heat energy targets in heat pinch analysis using a geometry-based approach, Computers and Chemical Engineering 30 (2006) 758-764], which are different from the conventional one that starts with the problem table algorithm (PTA). The proposed technique starts with the determination of the optimally positioned CCs and then proceeds to determine the optimal heat energy targets, heat pinch-point location, grand composite curve (GCC), complement grand composite curve (CGCC) [A.I.A. Salama, Numerical construction of HEN composite curves and their attributes, Computers and Chemical Engineering, 33 (2009) 181-190], and optimal assignment of multiple utilities. Moreover, the proposed numerical technique can handle both quasi-linear CCs and CCs exhibiting discontinuities (assuming the critical lower bound on ?Tmin,?Tminc, is known) hence, it is more robust and versat

  11. 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)

  12. Buoyant pulsating exchanging flow through a vent

    International Nuclear Information System (INIS)

    Buoyancy-driven bidirectional pulsating exchange flow through a vent in a horizontal partition is studied experimentally using a brine/water system. The associated transient and pulsating exchange flows were studied by densimetric measurements, flow visualization, and laser Doppler velocimetry (LDV) measurements for three different vent length-to-diameter ratios: 0.106, 0.0376, and 0.008. A time scale, based on the rate of decay of the density difference between the two compartments, is developed that collapses all experimental data regarding the decay of density in the top compartment into one curve. Flow visualization was used to understand the flow features contributing to the pulsating flow and to provide a quantitative measure of the major pulsation frequency. Interfacial instability between brine and water at the vent was found to contribute to the pulsation. The pulsation frequencies and their decay were determined from the power spectrum of LDV measurements. For the small length-to-diameter ratios (0.008 and 0.0376) there are two different frequencies that decay at different rates, suggesting multiple flow processes that contribute to flow pulsations. 17 refs., 7 figs., 2 tabs

  13. 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.

  14. Polymer spiral film gas-liquid heat exchanger for waste heat recovery in exhaust gases

    OpenAIRE

    Breton, Antoine

    2012-01-01

    In this master thesis report the development of an innovative spiral heat exchanger based on polymer materials is described. Building prototypes, erection of a test bench and firsts tests of the heat exchanger are presented. The heat exchanger prototype survived all tests especially several days in contact with aggressive gases. A facility integrating a Diesel exhaust gases production has been developed to test this heat exchanger design. Performance results obtained during the tes...

  15. Heat transfer entropy resistance for the analyses of two-stream heat exchangers and two-stream heat exchanger networks

    International Nuclear Information System (INIS)

    The entropy generation minimization method is often used to analyze heat transfer processes from the thermodynamic viewpoint. In this paper, we analyze common heat transfer processes with the concept of entropy generation, and propose the concept of heat transfer entropy resistance. It is found that smaller heat transfer entropy resistance leads to smaller equivalent thermodynamic force difference with prescribed heat transfer rate and larger heat transfer rate with prescribed equivalent thermodynamic force difference. With the concept of heat transfer entropy resistance, the performance of two-stream heat exchangers (THEs) and two-stream heat exchanger networks (THENs) is analyzed. For the cases discussed in this paper, it is found that smaller heat transfer entropy resistance always leads to better heat transfer performance for THEs and THENs, while smaller values of the entropy generation, entropy generation numbers and revised entropy generation number do not always. -- Highlights: • The concept of entropy resistance is defined. • The minimum entropy resistance principle is developed. • Smaller entropy resistance leads to better heat transfer

  16. 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 tthe 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.

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

    OpenAIRE

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

    2012-01-01

    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 opti...

  18. Analysis of supercritical carbon dioxide heat exchangers in cooling process

    OpenAIRE

    Chen, Yang; Lundqvist, Per

    2006-01-01

    Carbon dioxide transcritical cycles have become more and more investigated during the last decade. For all systems operating with such a cycle, there will be at least one heat exchanger to either heat or cool the supercritical carbon dioxide. Unlike in the sub-critical region, the supercritical carbon dioxide’s thermophysical properties will have sharp variations in the region close to its critical point. This variation has a significant influence on the shape of the heat exchanger’s temp...

  19. Thermohydraulic design of heat exchangers for direct-cycle integrated gas turbine plants

    International Nuclear Information System (INIS)

    Closed gas turbine plants coupled directly to a gas-cooled nuclear reactor consist of two kinds of main heat exchangers. The heat leaving the process at its low-temperature end is transferred from the gas to an intermediate water circuit by coolers. Heat transfer at an intermediate temperature range from the low-pressure to the high-pressure gas takes place in the recuperator. Integration of the gas turbine cycle in a single prestressed concrete pressure vessel requires compact design and special arrangement of all components including the heat exchangers. In this paper some general correlations for the dimensions of heat exchangers with longitudinal flow are given and discussed with respect to optimum design of recuperator and cooler. The dimensions considered are flow cross-section, length and heat transfer area of the apparatus. Minimizing the pod diameter in the concrete pressure vessel is important, and gives an advantage to longitudinal flow heat exchangers as compared to cross-flow types. Different types of heat transfer surfaces such as smooth, rough and finned walls are compared and criteria for the determination of optimum surface extension are given. The experimental results available indicate that a reduction of length can be achieved by the use of finned or rough surfaces. (author)

  20. Air-side thermal hydraulic performance of an integrated fin and micro-channel heat exchanger

    International Nuclear Information System (INIS)

    An integrated fin and micro-channel heat exchanger has been proposed. For 11 heat exchanger samples with different flow depth, fin height, fin pitch and fin thickness, a series of tests were conducted to determine their effect on the air-side thermal hydraulic performance. The heat transfer coefficient and pressure drop for heat exchangers with different geometrical configurations were reported in terms of Colburn factor j and Fanning friction factor f, as functions of Reynolds number. The general correlations for j and f factors were derived and can predict 96% and 92% of the experimental data, within rms errors of ±10% and ±12%, respectively. The air-side heat transfer and flow characteristics of the integrated fin were compared with that of the multi-louver fin and the wavy fin.

  1. Heat exchanger development at Reaction Engines Ltd.

    Science.gov (United States)

    Varvill, Richard

    2010-05-01

    The SABRE engine for SKYLON has a sophisticated thermodynamic cycle with heat transfer between the fluid streams. The intake airflow is cooled in an efficient counterflow precooler, consisting of many thousand small bore thin wall tubes. Precooler manufacturing technology has been under investigation at REL for a number of years with the result that flightweight matrix modules can now be produced. A major difficulty with cooling the airflow to sub-zero temperatures at low altitude is the problem of frost formation. Frost control technology has been developed which enables steady state operation. The helium loop requires a top cycle heat exchanger (HX3) to deliver a constant inlet temperature to the main turbine. This is constructed in silicon carbide and the feasibility of manufacturing various matrix geometries has been investigated along with suitable joining techniques. A demonstration precooler will be made to run in front of a Viper jet engine at REL's B9 test facility in 2011. This precooler will incorporate full frost control and be built from full size SABRE engine modules. The facility will incorporate a high pressure helium loop that rejects the absorbed heat to a bath of liquid nitrogen.

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

    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...

  3. 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

  4. Evaluation of a Passive Heat Exchanger Based Cooling System for Fuel Cell Applications

    Science.gov (United States)

    Colozza, Anthony J.; Burke, Kenneth A.

    2011-01-01

    Fuel cell cooling is conventionally performed with an actively controlled, dedicated coolant loop that exchanges heat with a separate external cooling loop. To simplify this system the concept of directly cooling a fuel cell utilizing a coolant loop with a regenerative heat exchanger to preheat the coolant entering the fuel cell with the coolant exiting the fuel cell was analyzed. The preheating is necessary to minimize the temperature difference across the fuel cell stack. This type of coolant system would minimize the controls needed on the coolant loop and provide a mostly passive means of cooling the fuel cell. The results indicate that an operating temperature of near or greater than 70 C is achievable with a heat exchanger effectiveness of around 90 percent. Of the heat exchanger types evaluated with the same type of fluid on the hot and cold side, a counter flow type heat exchanger would be required which has the possibility of achieving the required effectiveness. The number of heat transfer units required by the heat exchanger would be around 9 or greater. Although the analysis indicates the concept is feasible, the heat exchanger design would need to be developed and optimized for a specific fuel cell operation in order to achieve the high effectiveness value required.

  5. Heat exchangers for cardioplegia systems: in vitro study of four different concepts.

    Science.gov (United States)

    Drummond, Mário; Novello, Waldyr Parorali; de Arruda, Antonio Celso Fonseca; Braile, Domingo Marcolino

    2003-05-01

    The aim of this work is the evaluation of four different heat exchangers used for myocardium during cardioplegic system in cardiac surgeries. Four types of shell and tube heat exchangers made of different exchange elements were constructed, as follows: stainless steel tubes, aluminium tubes, polypropylene hollow fiber, and bellows type. The evaluation was performed by in vitro tests of parameters such as heat transfer, pressure drop, and hemolysis tendency. The result has shown that all four systems tested were able to achieve the heat performance, and to offer low resistance to flow, and safety, as well as have low tendency to hemolysis. However, we can emphasize that the bellows type heat exchanger has a significant difference with regard to the other three types. PMID:12752210

  6. High efficient configuration design and simulation of platelet heat exchanger in solar thermal thruster

    Science.gov (United States)

    Xing, BaoYu; Liu, Kun; Huang, MinChao; Cheng, MouSen

    2014-06-01

    Solar thermal propulsion system includes solar thermal propulsion and nuclear thermal propulsion, and it is a significant issue to improve the heat transfer efficiency of the solar thermal thruster. This paper proposes a platelet configuration to be used in the heat exchanger core, which is the most important component of solar thermal system. The platelet passage can enhance the heat transfer between the propellant and the hot core heated by the concentrated sunlight. Based on fluid-solid coupled heat transfer, the paper utilized the platelet heat transfer characteristic to simulate the heat transfer and flow field of the platelet passage. A coupled system includes the coupled flow and heat transfer between the fluid region and solid region. The simulation result shows that the propellant can be heated to the design temperature of 2300K in platelet passage of the thermal propulsion system, and the fluid-solid coupled method can solve the heat transfer in the platelet structure more precisely.

  7. Sensitivity Analysis for DHRS Heat Exchanger Performance Tests of PGSFR

    International Nuclear Information System (INIS)

    The STELLA-1 facility has been constructed and separate effect tests of heat exchangers for DHRS are going to be conducted. Two kinds of heat exchangers including DHX (shell-and-tube sodium-to-sodium heat exchanger) and AHX (helical-tube sodium-to-air heat exchanger) will be tested for design codes V and V. Main test points are a design point and a plant normal operation point of each heat exchanger. Additionally, some plant transient conditions are taken into account for establishing a test condition set. To choose the plant transient test conditions, a sensitivity analysis has been conducted using the design codes for each heat exchanger. The sensitivity of the PGSFR DHRS heat exchanger tests (the DHX and AHX in the STELLA-1 facility) has been analyzed through a parametric study using the design codes SHXSA and AHXSA at the design point and the plant normal operation point. The DHX heat transfer performance was sensitive to the change in the inlet temperature of the shell-side and the AHX heat transfer performance was sensitive to the change in the inlet temperature of the tube side. The results of this work will contribute to an improvement of the test matrix for the separate effect test of each heat exchanger

  8. Analysis of fabrication process for AP1000 passive residual heat removal heat exchanger

    International Nuclear Information System (INIS)

    This paper introduces the design parameters of the passive residual heat removal heat exchanger for American advanced passive pressurized water reactor (AP1000), describes the fabrication process for the head, tubesheet, heat exchange tube, corrugated plate and support frame assembly of the heat exchanger, mainly in terms of material, forging, welding, and heat treatment, and also analyzes the crucial steps for the support frame assembling, tubesheet plate welding, tube penetration welding of C tube bundle, closure/head welding, heat treatment, hydraulic (pressure) test, and etc. in the process of heat exchanger assembling. (author)

  9. Experimental study of passive residual heat removal system with air cooled heat exchanger

    International Nuclear Information System (INIS)

    The objective of this work is to investigate the heat removal capability of the passive Residual heat removal(RHR) heat exchanger in the advanced PWR system. Two test models were made to simulate the RHR heat exchanger. The one is the single bundle test model which consisted of a finned tubular heat exchanger unit. The other is the multi-bundle test model which has the finned tubular heat exchanger consisting of ten bundles of tubular units. The maximum heat removal capabilities of each model were investigated. The effects of chimney and elevation were observed

  10. 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

  11. Potential of geothermal heat exchangers for office building climatisation

    Energy Technology Data Exchange (ETDEWEB)

    Eicker, Ursula; Vorschulze, Christoph [Centre of Applied Research Sustainable Energy Technologies zafh.net, University of Applied Sciences Stuttgart, Schellingstrasse 24, 70174 Stuttgart (Germany)

    2009-04-15

    Low depth geothermal heat exchangers can be efficiently used as a heat sink for building energy produced during summer. If annual average ambient temperatures are low enough, direct cooling of a building is possible. Alternatively the heat exchangers can replace cooling towers in combination with active cooling systems. In the current work, the performance of vertical and horizontal geothermal heat exchangers implemented in two office building climatisation projects is evaluated. A main result of the performance analysis is that the ground coupled heat exchangers have good coefficients of performance ranging from 13 to 20 as average annual ratios of cold produced to electricity used. Best performance is reached, if the ground cooling system is used to cool down high temperature ambient air. The maximum heat dissipation per meter of ground heat exchanger measured was lower than planned and varied between 8 W m{sup -1} for the low depth horizontal heat exchangers up to 25 W m{sup -1} for the vertical heat exchangers. The experimental results were used to validate a numerical simulation model, which was then used to study the influence of soil parameters and inlet temperatures to the ground heat exchangers. The power dissipation varies by {+-}30% depending on the soil conductivity. The heat conductivity of vertical tube filling material influences performance by another {+-}30% for different materials. Depending on the inlet temperature level to the ground heat exchanger, the dissipated power increases from 2 W m{sup -1} for direct cooling applications at 20 C up to 52 W m{sup -1} for cooling tower substitutions at 40 C. This directly influences the cooling costs, which vary between 0.12 and 2.8EUR kW h{sup -1}. As a result of the work, planning and operation recommendations for the optimal choice of ground coupled heat exchangers for office building cooling can be given. (author)

  12. Radiant heat exchange measurements for Tore Supra

    International Nuclear Information System (INIS)

    In order to minimize the energy consumption of the low temperature cryogenic system connected to the superconducting magnet of TORE-SUPRA, heat exchange from thermal radiation between the vacuum vessels and the thermal shields has been studied. Accordingly large scale cold and hot walls of T.S. have been simulated in a model with reduced dimensions. In this model, the experiment consists in the measurement of the thermal radiated power between two concentric cylindrical surfaces of stainless steel under vacuum conditions. The temperature of the external cylinder was kept constant at 80 K. The internal cylinder was bakeable up to 2500C. Various surface treatments were applied on the two cylinders (mechanical polishing and metal deposition of Al, Ag, Ni)

  13. 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)

  14. Heat Recovery Ventilation for Housing: Air-to-Air Heat Exchangers.

    Science.gov (United States)

    Corbett, Robert J.; Miller, Barbara

    The air-to-air heat exchanger (a fan powered ventilation device that recovers heat from stale outgoing air) is explained in this six-part publication. Topic areas addressed are: (1) the nature of air-to-air heat exchangers and how they work; (2) choosing and sizing the system; (3) installation, control, and maintenance of the system; (4) heat

  15. 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...

  16. Combined Steady-State and Dynamic Heat Exchanger Experiment

    Science.gov (United States)

    Luyben, William L.; Tuzla, Kemal; Bader, Paul N.

    2009-01-01

    This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…

  17. The influence of heat exchanger design on the synthesis of heat exchanger networks

    OpenAIRE

    Liporace F.S.; Pessoa F. L. P.; Queiroz E. M.

    2000-01-01

    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 aff...

  18. 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

  19. 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: 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.

  20. Ceramic heat exchangers for gas turbines or turbojets

    Science.gov (United States)

    Boudigues, S.; Fabri, J.

    The required performance goals and several proposed designs for SiC heat exchangers for aerospace turbines are presented. Ceramic materials are explored as a means for achieving higher operating temperatures while controlling the weight and cost of the heat exchangers. Thermodynamic analyses and model tests by ONERA have demonstrated the efficacy of introducing a recooling cycle and placing the heat exchangers between stages of the turbine. Sample applications are discussed for small general aviation aircraft and subsonic missiles equipped with single-flux exchangers. A double-flux exchanger is considered for an aircraft capable of Mach 0.8 speed and at least 11 km altitude for cruise. Finally, the results of initial attempts to manufacture SiC honeycomb heat exchangers are detailed.