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Sample records for flow heat exchanger

  1. Radial flow heat exchanger

    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

    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. A laminar-flow heat exchanger

    Doty, F. D.; Hosford, G.; Jones, J. D.; Spitzmesser, J. B.

    The advantages of designing heat exchangers in the laminar flow regime are discussed from a theoretical standpoint. It is argued that laminar flow designs have the advantages of reducing thermodynamic and hydrodynamic irreversibilities and hence increasing system efficiency. More concretely, laminar flow heat exchangers are free from the turbulence-induced vibration common in conventional heat exchangers and can thus offer longer life and greater reliability. The problems of manufacturing heat exchangers suited to laminar flow are discussed. A method of manufacture which allows compact, modular design is outlined. Experience with this method of manufacture is described, and experimental results are presented. The problems of fouling and flow maldistribution are briefly discussed, and some possible applications are mentioned.

  4. Stirling Engine With Radial Flow Heat Exchangers

    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.

  5. Stokes Flow Heat Transfer In An Annular, Rotating Heat Exchanger

    Saatdjian, E.; Rodrigo, A.J.S.; Mota, J.P.B.

    2011-01-01

    Abstract The heat transfer rate into highly viscous, low thermal-conductivity fluids can be enhanced significantly by chaotic advection in three-dimensional flows dominated by viscous forces. The physical effect of chaotic advection is to render the cross-sectional temperature field uniform, thus increasing both the wall temperature gradient and the heat flux into the fluid. A method of analysis for one such flow?the flow in the eccentric, annular, rotating heat exchanger?and a pro...

  6. Cryogenic Heat Exchanger with Turbulent Flows

    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. Stokes flow heat transfer in an annular, rotating heat exchanger

    The heat transfer rate into highly viscous, low thermal-conductivity fluids can be enhanced significantly by chaotic advection in three-dimensional flows dominated by viscous forces. The physical effect of chaotic advection is to render the cross-sectional temperature field uniform, thus increasing both the wall temperature gradient and the heat flux into the fluid. A method of analysis for one such flow-the flow in the eccentric, annular, rotating heat exchanger-and a procedure to determine the best heat transfer conditions, namely the optimal values of the eccentricity ratio and time-periodic rotating protocol, are discussed. It is shown that in continuous flows, such as the one under consideration, there exists an optimum frequency of the rotation protocol for which the heat transfer rate is a maximum. - Highlights: → The eccentric, annular, rotating heat exchanger is studied for periodic Stokes flow. → Counter-rotating the inner tube with a periodic velocity enhances the heat transfer. → The heat-transfer enhancement under such conditions is due to chaotic advection. → For a given axial flow rate there is a frequency that maximizes the heat transfer. → There is also an optimum value of the eccentricity ratio.

  8. Flow and heat transfer enhancement in tube heat exchangers

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

    2015-11-01

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

  9. Axial flow heat exchanger devices and methods for heat transfer using axial flow devices

    Koplow, Jeffrey P.

    2016-02-16

    Systems and methods described herein are directed to rotary heat exchangers configured to transfer heat to a heat transfer medium flowing in substantially axial direction within the heat exchangers. Exemplary heat exchangers include a heat conducting structure which is configured to be in thermal contact with a thermal load or a thermal sink, and a heat transfer structure rotatably coupled to the heat conducting structure to form a gap region between the heat conducting structure and the heat transfer structure, the heat transfer structure being configured to rotate during operation of the device. In example devices heat may be transferred across the gap region from a heated axial flow of the heat transfer medium to a cool stationary heat conducting structure, or from a heated stationary conducting structure to a cool axial flow of the heat transfer medium.

  10. Characteristics of heat flow in recuperative heat exchangers

    Lalović 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 λ= 1.10, content of oxygen in combustion air ν(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.

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

    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.

  12. Two-phase Flow Distribution in Heat Exchanger Manifolds

    Vist, Sivert

    2004-01-01

    The current study has investigated two-phase refrigerant flow distribution in heat exchange manifolds. Experimental data have been acquired in a heat exchanger test rig specially made for measurement of mass flow rate and gas and liquid distribution in the manifolds of compact heat exchangers. Twelve different manifold designs were used in the experiments, and CO2 and HFC-134a were used as refrigerants.

  13. Thermal performance modeling of cross-flow heat exchangers

    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

  14. Flow-induced vibration of component cooling water heat exchangers

    This paper presents an evaluation of flow- induced vibration problems of component cooling water heat exchangers. 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 fluid-elastic 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

  15. Flow and vibration analysis to upgrade a CANDU heat exchanger

    This paper presents an example to illustrate the use of two-dimensional flow calculations to optimize the location of sealing strips and rods in a shell-and-tube heat exchanger. This is done to minimize flow maldistribution and potential flow-induced vibration damage without significantly de-rating the unit. The calculations are carried out for an existing design

  16. Liquid-gas direct heat exchangers. Part 1: Fluid Flow

    The annular liquid-gas flow in vertical ducts is studied in order to know the possibilities of these devices as direct heat exchangers. The liquid-gas flow rate in liquid lifting and the friction losses are correlated with the Froude number of the mixture. (author) 17 refs

  17. On turbulence modelling of industrial heat exchanger flows

    The present research is focussed on the prediction of shell-side flow in shell-and-tube heat exchangers. In order to simplify the analysis, the flow field is divided into three regions: (a) the tube-free region, away from the shell, baffles and tubes, (b) the tube-filled region, and (c) the near-wall region. The flow within each region is modelled separately, but the solutions within consecutive regions must be matched near the corresponding boundaries. (author)

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

    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.

  19. Flow-induced vibration of component cooling water heat exchangers

    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

  20. Flow induced vibration of AGR heat exchanger tubes

    This paper describes the development work carried out to estimate the flow induced vibrating forces and response of a bank of low finned A.G.R. heat exchanger tubes assembled in a staggered formation, where XL = 2.77, XT = 1.6. Tests carried out on two rigs are described, the first, an atmospheric rig was designed to simulate a section of a full size heat exchanger complete with tubes, supports and return bends. The second was a smaller rig representing a section of tubes between supports. It was fitted in a pressurised wind tunnel and used to investigate vibrations at high Reynolds numbers. (author)

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

    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.

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

    Wani, S A; S.R.Patil

    2015-01-01

    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 the...

  3. Segmented heat exchanger

    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.

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

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

  5. Flow induced vibration in shell and tube heat exchangers

    Assessing heat exchanger designs, from the standpoint of flow induced vibration, is becoming increasingly important as shell side flow velocities are increased in a quest for better thermal performance. This paper reviews the state of the art concerning the main sources of vibration excitation, i.e. vortex shedding resonance, turbulent buffeting, fluidelastic instability and acoustic resonance, as well as the structural dynamics of the tubes. It is concluded that there are many areas which require further investigation but there are sufficient data available at present to design, with reasonable confidence, units that will be free from flow induced vibration. Topics which are considered to be key areas for further work are listed

  6. Analysis of flow induced vibration in heat exchangers

    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)

  7. Liquid metal heat transfer in heat exchangers under low flow rate conditions

    The present paper describes the liquid metal heat transfer in heat exchangers under low flow rate conditions. Measured data from some experiments indicate that heat transfer coefficients of liquid metals at very low Péclet number are much lower than what are predicted by the well-known empirical relations. The cause of this phenomenon was not fully understood for many years. In the present study, one countercurrent-type heat exchanger is analyzed using three, separated countercurrent heat exchanger models: one is a heat exchanger model in the tube bank region, while the upper and lower plena are modeled as two heat exchangers with a single heat transfer tube. In all three heat exchangers, the same empirical correlation is used in the heat transfer calculation on the tube and the shell sides. The Nusselt number, as a function of the Péclet number, calculated from measured temperature and flow rate data in a 50 MW experimental facility was correctly reproduced by the calculation result, when the calculated result is processed in the same way as the experiment. Finally, it is clarified that the deviation is a superficial phenomenon which is caused by the heat transfer in the plena of the heat exchanger. (author)

  8. Numerical simulation of two phase flows in heat exchangers

    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

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

    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

  10. Heat transfer enhancement in cross-flow heat exchanger using vortex generator

    Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator

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

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

    2005-01-01

    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......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...

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

    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)

  13. Turbulence and heat exchange in condensing vapor-liquid flow

    Lakehal, Djamel; Fulgosi, Marco; Banerjee, Sanjoy; Yadigaroglu, George

    2008-06-01

    Turbulence and heat exchange during condensation of a vapor stream countercurrently flowing to a subcooled liquid stream in a slightly inclined channel has been investigated by direct numerical simulation (DNS). Condensation rates and imposed pressure gradients have been varied, and capillary-gravity waves have been allowed to develop at the (deformable) vapor-liquid interface. These simulations extend our previous DNS of turbulence and scalar exchange in stratified gas-liquid flows without condensation. The previous studies indicated that for conditions in which the gas-liquid interface remained continuous, i.e., did not "break," scalar exchange rates on both the gas and liquid sides were largely determined by sweeps which brought high momentum fluid from the bulk flow to the interface. As sweep frequencies were found to scale with interfacial friction velocities, scalar exchange coefficients could be parametrized with a surface renewal theory. The issue addressed in the current work is how these findings are altered by condensation which acts somewhat like suction through a wall on the vapor side and injection through a wall on the liquid side. Both suction and injection have been found to affect shear stresses, turbulence characteristics, and scalar exchange rates, and hence similar effects might be expected during condensation. The present simulations indicate that the turbulence characteristics in both phases are affected, with turbulence intensities and Reynolds stresses being enhanced on the vapor side and attenuated on the liquid side. For a given imposed pressure gradient, the interfacial shear stress decreases as a result of the interfacial momentum exchange due to condensation. Interfacial waves are also found to be damped by condensation and the streamwise vortical structures on the liquid side are attenuated. The frequencies of sweeps and ejections, however, do scale with the interfacial friction velocity, reduced due to condensation, as does the liquid-side heat transfer coefficient. The simulations indicate that the scaling relationship between the interfacial friction velocity and the liquid-side heat transfer coefficient is similar to that in the absence of condensation, although the interfacial friction velocity itself is different, being dependent on condensation rates. As condensation rates depend in turn on the liquid-side heat transfer, their prediction becomes a coupled problem. A procedure for determining condensation rates as a function of imposed pressure gradient and liquid subcooling is derived from the simulations.

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

    Gurpreet Kour

    2014-01-01

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

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

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

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

    Thirumarimurugan, M.; T Kannadasan; E. Ramasamy

    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...

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

    Friis, Alan; Szabo, Peter; Karlson, Torben

    2002-01-01

    A comparison of two different scale corotating disc scraped surface heat exchangers (CDHE) was performed experimentally. The findings were compared to predictions from a finite element model. We find that the model predicts well the flow pattern of the two CDHE's investigated. The heat transfer p...

  18. Plate heat exchanger - inertia flywheel performance in loss of flow transient

    Abou-El-Maaty, Talal; Abd-El-Hady, Amr [Atomic Energy Authority, Cairo (Egypt). Reactors Dept.

    2009-04-15

    One of the most versatile types of heat exchangers used is the plate heat exchanger. It has principal advantages over other heat exchangers in that plates can be added and/or removed easily in order to change the area available for heat transfer and therefore its overall performance. The cooling systems of Egypt's second research reactor (ETRR 2) use this type of heat exchanger for cooling purposes in its primary core cooling and pool cooling systems. In addition to the change in the number of heat exchanger cooling channels, the effect of changing the amount of mass flow rate on the heat exchanger performance is an important issues in this study. The inertia flywheel mounted on the primary core cooling system pump with the plate heat exchanger plays an important role in the case of loss of flow transients. The PARET code is used to simulate the effect of loss of flow transients on the reactor core. Hence, the core outlet temperature with the pump-flywheel flow coast down is fed into the plate heat exchanger model developed to estimate the total energy transferred to the cooling tower, the primary side heat exchanger temperature variation, the transmitted heat exchanger power, and the heat exchanger effectiveness. In addition, the pressure drop in both, the primary side and secondary side of the plate heat exchanger is calculated in all simulated transients because their values have limits beyond which the heat exchanger is useless. (orig.)

  19. Heat transfer in tube bundles of heat exchangers with flow baffles induced forced mixing

    Thermal analysis of shell-and-tube heat exchangers is being investigated through geometric modeling of the unit configuration in addition to considering the heat transfer processes taking place within the tube bundle. The governing equations that characterize the heat transfer from the shell side fluid to the tube side fluid across the heat transfer tubewalls are indicated. The equations account for the heat transfer due to molecular conduction, turbulent thermal diffusion, and forced fluid mixing among various shell side fluid channels. The analysis, though general in principle, is being applied to the Clinch River Breeder Reactor Plant-Intermediate Heat Exchanger, which utilizes flow baffles appropriately designed for induced forced fluid mixing in the tube bundle. The results of the analysis are presented in terms of the fluid and tube wall temperature distributions of a non-baffled and baffled tube bundle geometry. The former case yields axial flow in the main bundle region while the latter is associated with axial/cross flow in the bundle. The radial components of the axial/cross flow yield the necessary fluid mixing that results in reducing the thermal unbalance among the heat transfer to the allowable limits. The effect of flow maldistribution, present on the tube or shell sides of the heat exchangers, in altering the temperature field of tube bundles is also noted

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

    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.

  1. Heat exchanger

    Thurley, J.

    1975-11-06

    This heat exchanger, which heats and evaporates a working fluid with the combustion gases of a burner by a heat exchange fluid, is meant to improve the efficiency considerably by including the container containing the heat exchange fluid, as the radiated heat of the burner, which is otherwise lost, is used in this way. As the hottest parts of the burner and the adjacent distribution channel for the combustion gas are cooled by the heat exchange fluid, the cladding of the burner in fire-resisting material becomes unnecessary. The weight and cost are reduced, and the life of the burner and the accesibility of all parts are improved. A horizontal square outer container contains a similar inner container open at the top of half the length and width of the outer container. The two communicating containers are filled to half their height with the primary medium. An upper and lower chamber, both fed axially with fuel, form the burner together with a connected coaxial turbulence chamber. The greater part (of the burner) and the connected horizontal distribution channel are below the level of the cooling primary. The pipe bundle has the combustion gases, rising from the lower distribution channel and the primary fluid heated by these gases flowing through it and is heated by them, where the secondary medium evaporates. The waste gases rising from the primary medium leave the outer container by two chimney openings at the top of the outer container. The maximum heat emitted per hour is stated to be about 100 million KJoules - compared to about 72 million KJoules according to the previous state of technology. The 180kw approx. of blower power previously required to produce the second output is reduced to about 110kw.

  2. Parallel tube heat exchanger

    An improved heat exchanger for use in liquid metal cooled nuclear reactors, is described, which consists of a bundle of spaced, parallel tube assemblies for immersion in a primary heat exchange fluid. Each assembly defines flow and counterflow paths for a secondary heat exchange fluid in successive passes. Insulation reduces heat transfer between the flows of successive passes. (U.K.)

  3. Flow field predictions in a model heat exchanger

    Theodossiou, V. M.; Sousa, A. C. M.; Carlucci, L. N.

    1988-09-01

    A numerical study of the two-dimensional isothermal steady flow distribution of an incompressible fluid in the shell side of an experimental heat exchanger is described. Computations are performed with and without tubes present in the model, for Reynolds numbers up to 10,000. Baffles and tube bundles are modelled by incorporating the “porous medium” concept into the governing equations. The resulting equations described in primitive variables are solved using a semi-implicit predictor-corrector type scheme. A Multi-Grid technique is employed to solve the linearized pressure correction equation which links momentum and continuity equations. Predictions with the proposed scheme indicate good qualitative agreement when compared with experimental measurements.

  4. Woven heat exchanger

    Piscitella, R.R.

    1984-07-16

    This invention relates to a heat exchanger for waste heat recovery from high temperature industrial exhaust streams. 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.

  5. Numerical simulation of flow field in shellside of heat exchanger in nuclear power plant

    Heat exchanger is the important equipment of nuclear power plant. Numerical simulation can give the detail information inside the heat exchange, and has been an effective research method. The geometric structure of shell-and-tube heat exchanger is very complex and it is difficult to simulate the whole flow field presently. According to the structure characteristics of the heat exchanger, a periodic whole-section calculation model was presented. The numerical simulation of flow field in shellside of heat exchange of a nuclear power plant was done by using this model. The results of simulation show that heat transfer in the periodic section of the heat exchange is uniform, the heat transfer is enhanced by using baffles in heat exchange, and frictional resistance is primary from the effect of segmental baffles. (authors)

  6. Flow vibrations and dynamic instability of heat exchanger tube bundles

    This paper presents a review of external-flow-induced vibration of heat exchanger tube bundles. Attention is focused on a dynamic instability, known as ''fluidelastic instability'', which can develop when flow is transverse to the tube axis. The main physical models proposed in the literature are successively reviewed in a critical way. As a consequence, some concepts are clarified, some a priori plausible misinterpretations are rejected and finally, certain basic mechanisms, induced by the flow-structure interaction and responsible for the ultimate onset of fluidelastic instability, are elucidated. Design tools and methods for predictive analysis of industrial cases are then presented. The usual design tool is the ''stability map'', i.e. an empirical correlation which must be interpreted in a conservative way. Of course, when using this approach, the designer must also consider reasonable safety margins. In the area of predictive analysis, the ''unsteady semi-analytical models'' seem to be a promising and efficient methodology. A modern implementation of these ideas mix an original experimental approach for taking fluid dynamic forces into account, together with non-classical numerical methods of mechanical vibration. (authors). 20 refs., 9 figs

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

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

  8. Heat transfer enhancement in cross-flow heat exchangers using oval tubes and multiple delta winglets

    Tiwari, S.; Maurya, D.; Biswas, G.; Eswaran, V. [Indian Institute of Technology, Kanpur (India). Dept. of Mechanical Engineering

    2003-07-01

    A three-dimensional study of laminar flow and heat transfer in a channel with built-in oval tube and delta winglets is carried out through the solution of the complete Navier-Stokes and energy equations using a body-fitted grid and a finite-volume method. The geometrical configuration represents an element of a gas-liquid fin-tube cross-flow heat exchanger. The size of such heat exchangers can be reduced through enhancement of transport coefficients on the air (gas) side, which are usually small compared to the liquid side. In a suggested strategy, oval tubes are used in place of circular tubes, and delta-winglet type vortex generators in various configuration's are mounted on the fin-surface. An evaluation of the strategy is attempted in this investigation. The investigation is carried out for different angles of attack of the winglets to the incoming flow for the case of two winglet pairs. The variation of axial location of the winglets is also considered for one pair of winglets mounted in common-flow-down configuration. The structures of the velocity field and the heat transfer characteristics have been presented. The results indicate that vortex generators in conjunction with the oval tube show definite promise for the improvement of fin-tube heat exchangers. (author)

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

    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.

  10. Bifurcation of vortex turbulent flow and heat exchange intensification in a dimple

    The aim of the paper is to study the vortex intensification of heat exchange based on the turbulent modes of flowing out the dimples of asymmetrical form. The problem is solved by the computer simulation method. Effect of dimple parameter variation on the heat exchange value is analysed. It is noted that in the case of the vortex flow bifurcation essential decrease of heat exchange takes place

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

    Parth P. Parekh; Dr.Neeraj K. Chavda

    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...

  12. Enhancement of heat exchanges on a condenser using an air flow containing water droplets

    Boulet, P.; Tissot, J.; Trinquet, F.; Fournaison, L

    2013-01-01

    A study has been carried out on the enhancement of the heat exchanged on a tube and fin exchanger using an air flow containing water droplets. An experimental setup has been used, which consists of a channel where an air flow with droplets is crossing a heat exchanger fed with water. A model representing the heat transfer has been presented and validated using the experimental data. The heat exchange improvement obtained thanks to the injection of droplets in the air upstream to the heat exch...

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

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

    2011-05-15

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

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

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

    2010-06-15

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

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

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

    2007-01-01

    In cold climates, mechanical ventilation systems with highly efficient heat recovery will experience problems with condensing water from the extracted humid indoor air. If the condensed water changes to ice in the heat exchanger, the airflow rate will quickly fall due to the increasing pressure...... 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...

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

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

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

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

  18. 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...

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

    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

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

    Parth P. Parekh

    2014-07-01

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

  1. Heat exchanger

    Heat exchangers for use in uranium enrichment plant are subject to particularly stringent safety requirements and should be capable of being repaired and maintained quickly. It is proposed to improve a heat exchanger which has a roller type of design consisting of heat exchanger tubes arranged around a core tube, which are connected together in tube floors. According to the invention the tube floors are connected solidly to the outer jacket (possibly via intermadiate pieces), while the heat exchanger tubes end at the side near the inside of the jacket in the tube floors. Manufacture can be further simplified if core tube, roller and outer jacket which are solidly connected form a compact unit. (UWI)

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

    Dr. Khalid Faisal Sultan

    2015-01-01

    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...

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

    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 DarcyBrinkmanForchheimer 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

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

    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 (20-60C, 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.

  5. Methodological aspects of numerical simulation of vortical structure dynamics and heat exchange in viscous turbulent flows

    The article presents methods for simulating non-stationary flows and heat exchange in spatial curved regions. In non-stationary turbulent flows heat and mass exchange is to a great exchange conditioned by effects of non-linear interaction of organized (coherent) vortical structures. Numeric simulation of turbulent flows within the framework of solution of complete non-stationary equations of Navier-Stokes and Reynolds closed by a differential turbulence model, allows one to investigate mechanisms and regularities in the development and interaction of vortical structures. 3 refs., 5 figs

  6. An experimental observation of the effect of flow direction for evaporation heat transfer in plate heat exchanger

    This study provides an Infrared Thermal Image observation on the evaporation heat transfer of refrigerant R-410A in plate heat exchanger with various flow arrangement and exit superheat conditions. An experimental method was derived for estimating the superheat region area of two-phase refrigerant evaporation in plate heat exchanger. The experimental results show that the superheat region area for parallel flow is much larger than that for counter flow as that estimated by Yang et al. [9]. There is an early superheated region at the central part of the plate heat exchanger for parallel flow arrangement. This effect is not significant for counter flow arrangement. The Yang et al. [9] method under estimated the superheat area approximately 40%–53% at various flow rates and degree of exit superheat. Even though the flow inside a plate heat exchanger is extremely turbulent because of the chevron flow passages, the assumption of uniform temperature distribution in the cross section normal to the bulk flow direction will cause significant uncertainties for estimating the superheat area for refrigerant evaporating in a plate heat exchanger

  7. Two models for the dynamics of a cross flow heat exchanger

    Two models of a cross flow heat exchanger, a concentric tube counter flow model and a cross flow model, are studied theoretically. Differential equations describing the behaviour of the models are derived and from them equations for the steady state temperatures and the temperature transfer functions are obtained. (author)

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

    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

  9. Turbulent flow heat transfer and pressure loss in a double pipe heat exchanger with triangular fins

    Vinous M. Hameed, Bashar Muslem Essa

    2016-01-01

    Full Text Available Experimental investigation of heat transfer and friction factor characteristics in a double pipe heat exchanger with triangular fins was studied. The working fluids were air, flowing in the annular pipe, and water through the inner circular tube. The test section is consisting of two parts. The first part is an insulated tube which has been manufactured from Perspex material of (54mm inner diameter, (2000mm length and (3mm thickness. The second part is an internal copper tube without or with triangular copper fins. The smooth copper tube has (2250mm long and (20mm, 22mm inner and outer diameter respectively. The triangular fins were made of the copper with thickness of 0.3mm and 10mm height. They were installed on the straight copper tube section in three different cases (32, 27, and 22 mm distance between each two successive fins and (15mm pitch between each two of fins. Air at various mass flow rates (0.001875 to 0.003133 kg/sec flows through annuli and water at Reynold's numbers ranging from (10376.9 to 23348.03 flows through the inner tube. The inlet cold air and hot water temperatures are 30oC and 70oC, respectively. The experimental results showed an increase in convective heat transfer coefficient by decreasing in distance between two fins and by increasing Reynold's number. This is due to increase in surface area. It was found that (Space=22mm gives good heat transfer enhancement.

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

    Rafal Marcin Laskowski

    2011-01-01

    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 compari...

  11. Experimental study of two phase adiabatic flow distribution in small channel heat exchanger

    Poggi, F.; Macchi Tejeda, H.; Leducq, D.; Bontems, A.

    2007-01-01

    Small-channel heat exchangers are widely used for car air-conditioning. However information about their behaviour remains scarce. An experimental device was achieved to characterize the distribution of single and two-phase adiabatic flows in a small channels heat exchanger, and to measure its singular and regular pressure losses. A transparent polycarbonate test section comprised a 16 mm diameter header connected to 8 flat tubes with 7 small channels (Dh = 0.889 mm). Both were studied with ho...

  12. Flow-induced vibration test and analysis of heat exchanger in NPP

    A method of comparing the results of calculation with test is used to verify the reliability and adequacy of the program in order to evaluate the flow-induced vibration of heat-exchanger tubes, so the program can be applied to design of safety related heat-exchanger in NPP. The shell side flow velocity and tube vibration are measured. The results of measurement show that there is a margin of safety in general for the results of calculated by program TASC and PIPO 1, but it should be noted that the flow velocities may be higher at a few points of the shell side. (7 refs., 10 figs., 4 tabs.)

  13. On the heat exchange crisis while surface cooling with a two-phase flow

    Heat exchange crisis by surface cooling with two-phase flow is analytically considered. Dependence describing critical value of flow-around rate is obtained. This formula makes it possible to express effective cross section of droplet capture by flow-around bodies and distribution of captured droplet flow on their surface in form of function from liquid physical parameters and its steam, droplet radius as well as roughness height and surface overheat

  14. Heat and mass exchanger

    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.

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

    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.)

  16. Heat Exchanger

    A liquid metal heated tube and shell heat exchanger where straight tubes extend between upper and lower tube sheets. In order to prevent thermal stress problems, one tube sheet is fixed to the shell, and the other tube sheet is sealed to the shell by means of a flexible bellows. In the event of a catastrophic bellows failure, a housing that utilizes a packing gland sliding seal is used to enclose and back-up the bellows. Also, a key and slot arrangement is provided for preventing relative rotation between the shell and tube sheet which could damage the bellows and cause failure thereof. This exchanger is seen to be of use in sodium cooled reactors between the liquid sodium circuit on the steam generator

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

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

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

    Hwang, Seong Won; Jeong, Ji Hwan [Pusan National University, Busan (Korea, Republic of)

    2009-07-01

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

  19. Heat transfer in borehole heat exchangers and the contribution of groundwater flow

    Liuzzo Scorpo, Alberto

    2014-01-01

    The exploitation of geothermal heat by ground source heat pumps is presently growing throughout Europe and the world. In Italy, at the end of 2010, borehole heat exchangers covered most of the 30% of the total energy used for space conditioning, showing an increase of 50%compared to 2005. The forecasts for 2015 suggest a further increase in the direct uses of the geothermal heat exceeding 50% compared to 2010 and a corresponding increase in the geothermal energy consumption. The possibilit...

  20. Flow model test development of CRBRP intermediate heat exchanger

    The details of these tests, flow data achieved, finalized design configurations of the flow distribution devices, and final interpretation of the results are given in this paper. The tests consist of the: Primary Inlet Plenum Flow Model Test which has the objective of finalizing the design of the primary flow inlet plenum configuration that results in a circumferentially uniform flow entering the tube bundle; Tube Bundle Flow Model Test which has the objective of achieving optimum design configurations for the flow baffles in the bundle, which is based on the baffles capability to create the necessary forced fluid mixing of the shell side flow within the pressure drop limitation imposed on the unit's design; and Intermediate Flow Model Test with its objective of confirming the design of the intermediate flow inlet plenum, which has a hemispherical shape with a ring baffle attached, in distributing the flow evenly among the tubes. The paper includes details of the flow fields within various test models in a wide range of operating flow rates. 2 refs

  1. Numerical simulation of two phase flows in heat exchangers

    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)

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

    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)

  3. Numerical Study of the Inertia Effect on Flow Distribution in Micro-gap Plate Heat Exchanger

    This paper presents numerical study on flow and heat transfer characteristics in micro-gap plate heat exchanger. In particular, we investigate the effect of flow inertia on the flow distribution from single main channel to multiple parallel micro-gaps. The flow regime of the main channel is varied from laminar regime (Reynolds number of 100) to turbulent regime (Reynolds number of 10000) by changing the flow rate, and non-uniformity of the flow distribution and temperature field is evaluated quantitatively based on the standard deviation. The flow distribution is found to be significantly affected by not only the header design but also the flow rate of the main channel. It is also observed that the non-uniformity of the temperature field has its maximum at the intermediate flow regime

  4. Intermediate heat exchanger tube vibration induced by cross and parallel mixed flow

    The characteristics of pool type LMFBR intermediate heat exchanger (IHX) tube vibrations induced by cross and parallel mixed flow were basically investigated. Secondary coolant in IHX tube bundle is mixed flow of parallel jit flow along the tube axis through flow holes in baffle plates and cross flow. By changing these two flow rate, flow distributions vary in the tube bundle. Mixed flow also induces vibrations which cause fretting wear and fatigue of tube. It is therefore very important to evaluate the tube vibration characteristics for estimating the tube integrity. The results show that the relationships between tube vibrations and flow distributions in the tube bundle were cleared, and mixed flow induced tube vibration could be evaluated on the base of the characteristics of both parallel and cross flow induced vibration. From these investigations it could be concluded that the characteristics of tube vibration for various flow distributions can be systematically evaluated. (author)

  5. Flow distribution analysis in nuclear heat exchangers with application to CRBRP-IHX

    The shell side flow distribution of a shell-and-tube heat exchanger, in which the shell side fluid moves downwards in an axial/cross flow combination dictated by the design of the flow baffles, is examined. Depending on the degree of overlapping and perforation of the baffles, the magnitude of the cross flow component can be controlled in a manner compatible with the unit design. Axial/cross flow field would yield a relatively small pressure drop on the shell side, and in the meantime it creates sufficient fluid mixing to minimize any thermal unbalance among the heat transfer tubes. Such requirements are essential in the design of nuclear heat exchangers similar to the CRBRP-IHX. The present flow distribution analysis utilizes two models: The lumped model and the detailed model. The lumped model employs an overall flow distribution and pressure drop approach to determine the magnitudes of the axial and cross flow components as a function of the baffle overlapping and baffle perforation. The detailed model utilizes more of a fundamental approach in solving the governing equations for the conservation of mass and momentum of a turbulent flowing fluid in a nodal mesh. The mesh incorporates distributed resistances resulting from the presence of the heat transfer tubes and the flow baffles in the tube bundle. The model employs a modified version of the computer code VARR II tailored specifically to the analysis of the shell side flow of heat exchangers. The results of both models are indicated and compared with emphasis on demonstrating the influence of the baffle overlapping and baffle perforation on the flow field and the pressure distribution

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

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

  7. Oscillating-flow loss test results in rectangular heat exchanger passages

    Wood, J. Gary

    1991-09-01

    Test results of oscillating flow losses in rectangular heat exchanger passages of various aspect ratios are given. This work was performed in support of the design of a free-piston Stirling engine (FPSE) for a dynamic space power conversion system. Oscillating flow loss testing was performed using an oscillating flow rig, which was based on a variable stroke and variable frequency linear drive motor. Tests were run over a range of oscillating flow parameters encompassing the flow regimes of the proposed engine design. Test results are presented in both tabular and graphical form and are compared against analytical predictions.

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

    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.

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

    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 (α = 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 α = 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.

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

    Louda, Petr; Sváček, P.; Fořt, J.; Fürst, J.; Halama, J.; Kozel, Karel

    2013-01-01

    Roč. 219, č. 13 (2013), s. 7206-7214. ISSN 0096-3003 R&D Projects: GA ČR(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

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

    Nielsen, Kaspar Kirstein; Engelbrecht, Kurt; Christensen, Dennis; Jensen, Jesper Buch; Smith, Anders; Bahl, Christian

    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...

  12. Buffeting of heat exchanger tube arrays in a cross flow

    A model for turbulence-induced vibration of tube arrays in a cross flow is presented and compared with experimental data. The model is based on random vibration theory. The model is found to provide reasonable agreement with experimental data for tube arrays not subject to instability. (author)

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

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

  14. Granular flow and thermal performance of Moving Bed Heat Exchangers: Comparison of the Euler-Euler model with experimental results

    Baumann, Torsten

    2014-01-01

    A moving bed heat exchanger (MBHX) is a promising technology option for efficient heat recovery from hot particles and can be used as steam generator for concentrating solar power plants with particle-based thermal energy storage. A moving bed heat exchanger is a tube bundle heat exchanger, in which a granular bulk flows downwards gravity driven while passing the heat exchanger tubes. In the tubes, a heat transfer fluid is heated up, e.g. evaporating water. For the solar specific device in...

  15. Criteria for the cross-flow-induced tube vibrations in tube bank heat exchangers

    Properties of the various excitation sources of cross-flow-induced vibrations in tube bank heat exchangers, such as Karman vortex shedding, wake swing, jet switch, jet instability and fluid-elastic whirling are shown. The working charts are examined using the experimental results obtained on a heat exchanger with mixed cross-parallel flow. It is shown for the present case that only the coupled second bending mode of the entire tube can be excited by the flow due to its S-shaped pattern. The hydrodynamic added mass is then discussed. The investigation shows that the added mass of a tube in a cross flow is far less than that in a stationary fluid. It is therefore recommended that great care be taken when transferring data from stationary fluid tests to prototypes working with dense fluid across tubes. (author)

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

    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

  17. Heat Transfer & Periodic Flow Analysis of Heat Exchanger by CFD with Nano Fluids

    Mr.V.V.Ramakrishna

    2016-01-01

    Many heat transfer applications such as steam generators in a boiler or air cooling coil of an air conditioner, can be modelled in a bank of tubes containing a fluid flowing at one temperature that is immersed in a second fluid in a cross flow at different temperature. CFD simulations are a useful tool for understanding flow and heat transfer principles as well as for modelling these types of geometries. Both the fluids considered in the present study are CUO Nano fluids, and flow...

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

    K.Thirumalai kannan; B Senthil Kumar

    2012-01-01

    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 (α = 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...

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

    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

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

    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 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)

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

    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)

  2. Entropy Generation Minimization in a Ram-Air Cross-Flow Heat Exchanger

    Adrian Bejan

    1999-12-01

    Full Text Available This paper presents the constrained thermodynamic optimization of a crossflow heat exchanger with ram air on the cold side. The ram-air stream passes through a diffuser before entering the heat exchanger, and exits through a nozzle. This configuration is used in the environmental control systems of aircraft. In the first part of the study the heat exchanger is optimized alone, subject to fixed total volume and volume fraction occupied by solid walls. Optimized geometric features such as the ratio of channel spacings and flow lengths are reported. It is found that the optimized features are relatively insensitive to changes in other physical parameters of the installation. In the second part of the study the entropy generation rate also accounts for the irreversibility due to discharging the ram-air stream into the atmosphere. The optimized geometric features are relatively insensitive to this additional effect, emphasizing the robustness of the thermodynamic optimum.

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

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

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

    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 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.

  5. Additions to compact heat exchanger technology: Jet impingement cooling & flow & heat transfer in metal foam-fins

    Onstad, Andrew J.

    Compact heat exchangers have been designed following the same basic methodology for over fifty years. However, with the present emphasis on energy efficiency and light weight of prime movers there is increasing demand for completely new heat exchangers. Moreover, new materials and mesoscale fabrication technologies offer the possibility of significantly improving heat exchanger performance over conventional designs. This work involves fundamental flow and heat transfer experimentation to explore two new heat exchange systems: in Part I, large arrays of impinging jets with local extraction and in Part II, metal foams used as fins. Jet impingement cooling is widely used in applications ranging from paper manufacturing to the cooling of gas turbine blades because of the very high local heat transfer coefficients that are possible. While the use of single jet impingement results in non-uniform cooling, increased and more uniform mean heat transfer coefficients may be attained by dividing the total cooling flow among an array of smaller jets. Unfortunately, when the spent fluid from the array's central jets interact with the outer jets, the overall mean heat transfer coefficient is reduced. This problem can be alleviated by locally extracting the spent fluid before it is able to interact with the surrounding jets. An experimental investigation was carried out on a compact impingement array (Xn/Djet = 2.34) utilizing local extraction of the spent fluid (Aspent/Ajet = 2.23) from the jet exit plane. Spatially resolved measurements of the mean velocity field within the array were carried out at jet Reynolds numbers of 2300 and 5300 by magnetic resonance velocimetry, MRV. The geometry provided for a smooth transition from the jet to the target surface and out through the extraction holes without obvious flow recirculation. Mean Nusselt number measurements were also carried out for a Reynolds number range of 2000 to 10,000. The Nusselt number was found to increase with the Reynolds number to the 0.6 power with peak Nusselt numbers near 75 at a Reynolds number of 10,000. Open-celled metallic foams offer three important characteristics which enable them to perform well in heat exchange applications. They contain a very large surface area to volume ratio, a highly complex flow passage through the foam, and in many cases, significant thermal conductivity in the solid phase. Unfortunately, difficulty arises when metal foams are implemented in heat exchanger designs. The performance of the foam has not been characterized in a way which is conducive to analytical design of high performance heat exchangers. The second part of this work provides both flow and heat transfer measurements for metal foam geometries. Full-field velocity measurements through a foam sample were acquired using MRV. The measurements show transverse velocities on the order of 25-30% of the Darcy velocity, UD, which produce enhanced thermal dispersion within the foam matrix. A mechanical dispersion coefficient, DM, was formed which demonstrates the transverse dispersion to be 13 times the kinematic viscosity and 9 times the thermal diffusivity of air at 20C and 1 atm. To describe the heat transfer performance of the foam as a fin, we have developed a new method that utilizes a well documented, periodic heat exchanger core test and a new one heated wall (OHW) test which when used in conjunction are shown to determine the convective performance (hmAc), the conductive performance (ksAc), and the effective bond resistance associated to attaching metal foams to primary heat transfer surfaces (RBond). Small pore diameter foams, d ? 1 mm, where found to perform approximately a factor of 2 greater per unit volume than a comparable fine-fin heat exchanger surface at the same pumping power which points to the fact the foam as a system is conduction limited not convection limited.

  6. Heat Transfer & Periodic Flow Analysis of Heat Exchanger by CFD with Nano Fluids

    Mr.V.V.Ramakrishna

    2016-01-01

    Full Text Available Many heat transfer applications such as steam generators in a boiler or air cooling coil of an air conditioner, can be modelled in a bank of tubes containing a fluid flowing at one temperature that is immersed in a second fluid in a cross flow at different temperature. CFD simulations are a useful tool for understanding flow and heat transfer principles as well as for modelling these types of geometries. Both the fluids considered in the present study are CUO Nano fluids, and flow is classified as laminar and steady with Reynolds number between 100- 600.The mass flow rate of the cross flow and diameter has been varied (such as 0.05, 0.1, 0.15, 0.20, 0.25, 0.30 kg/sec and 0.8, 1.0.1.2 &1.4cm and the models are used to predict the flow and temperature fields that result from convective heat transfer. Due to symmetry of the tube bank and the periodicity of the flow inherent in the tube bank geometry, only a portion of the geometry will be modelled and with symmetry applied to the outer boundaries. The inflow boundary will be redefined as a periodic zone and the outflow boundary is defined as the shadow. The various static pressures, velocities, and temperatures obtained are reported. In this present project tubes of different diameters and different mass flow rates are considered to examine the optimal flow distribution. Further the problem has been subjected to effect of materials used for tubes manufacturing on heat transfer rate. Materials considered are copper and Nickle Chromium alloys. Results emphasize the utilization of alloys in place of copper as tube material serves better heat transfer with most economical way.

  7. Flow and conjugate heat exchange in a rotating cavity with an axially supplied working medium

    Volkov, K. N.

    2011-03-01

    Numerical modeling of the turbulent flow and conjugate heat exchange in a cavity bounded by a rotor and a stator is carried out. Coupled thermal calculations are based on the unsteady heat-conduction equation describing the temperature distribution within a solid and Reynolds-averaged Navier-Stokes equations closed using the k-ɛ turbulence model, which allow calculation of the velocity, pressure, and temperature distributions in the fluid-filled region. The space-time distributions of the temperature and the heat flux on the metal-fluid interface are obtained in two- and three-dimensional formulations of the problem on a structured and an unstructured grid.

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

    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. Heat pipe array heat exchanger

    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.

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

    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

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

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

  12. Flow measurement and characterization in shallow geothermal systems used for downhole heat exchanger applications

    Churchill, D.; Culver, G.G.; Reistad, G.M.

    1977-01-01

    In the largest non-electrical application of geothermal energy presently occurring in the United States, over 400 relatively shallow wells are being used for extraction of energy with downhole heat exchangers. Despite this large amount of application, the exact nature of the flows in the wells has not before been characterized. Knowledge to date on the nature of flows in the systems is summarized, and an ongoing experimental program for making appropriate downhole measurements to determine flows is described in detail. Flow characterization was a principal object of this study. Horizontal cross-flows of geothermal fluid may occur at upper and/or lower levels in the well where perforations in the well casing are situated. In addition, natural convection may induce vertical flows within the well casing which would be influenced by the presence or absence of a heat exchanger. Three main aspects of the experimental program are reported on: (i) a review of potentially applicable methods for measuring vertical and horizontal flows in wells, (ii) the limitations and preliminary results of using a vane anemometer for measuring vertical flows, and (iii) the description of the selected hot-film probe, its associated pressurized calibration facility, and means of making well measurements.

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

    Tube and shell heat exchange components such as steam generators, heat exchangers and condensers are essential parts of CANDU (CANadian Deuterium Uranium) nuclear power stations. Excessive flow-induced vibration may cause tube failures by fatigue or more lkiely by fretting-wear. Such failures may lead to station shutdowns that are very undersirable 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. The vibration excitation mechanisms and the dynamics of multispan tubes are formulated in a computer model. The model predicts tube vibration response and critical velocities for fluidelastic instability. A description of the model is given. The vibration analysis of a steam generator is outlined as an example. (Auth.)

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

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

  15. Vibration of heat exchange components in liquid and two-phase cross-flow

    Heat exchange components must be analysed at the design stage to avoid flow-induced vibration problems. Information required to formulate flow-induced vibration excitation mechanisms in liquid and two-phase cross-flow is presented. Three basic excitation mechanisms are considered, namely: 1) fluidelastic instability 2) periodic wake shedding and 3) response to random flow turbulence. The vibration excitation information is deduced from vibration response data for various types of tube bundles. Sources of information are: 1) fundamental studies on tube bundles, 2) model testing 3) field measurements and 4) operating experiences. Fluidelastic instability is formulated in terms of dimensionless flow velocity and dimensionless damping; periodic wake shedding in terms of Strouhal number and lift coefficient; and random turbulence excitation in terms of statistical parameters of random forces. Guidelines are recommended for design purposes. (author)

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

    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)

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

    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)

  18. CFD analysis of the two-phase bubbly flow characteristics in helically coiled rectangular and circular tube heat exchangers

    Hussain, Alamin; Fsadni, Andrew M.

    2016-03-01

    Due to their ease of manufacture, high heat transfer efficiency and compact design, helically coiled heat exchangers are increasingly being adopted in a number of industries. The higher heat transfer efficiency over straight pipes is due to the secondary flow that develops as a result of the centrifugal force. In spite of the widespread use of helically coiled heat exchangers, and the presence of bubbly two-phase flow in a number of systems, very few studies have investigated the resultant flow characteristics. This paper will therefore present the results of CFD simulations for the two-phase bubbly flow in helically coiled heat exchangers as a function of the volumetric void fraction and the tube cross-section design. The CFD results are compared to the scarce flow visualisation experimental results available in the open literature.

  19. Effect of nonuniform inlet air flow on air-cooled heat-exchanger performance

    Blowers used to propel air across tube bundles generate a non-uniform flow field due to their construction details. A formalism to evaluate heat transfer degradation due to non-uniform airflow has been developed. Certain symmetry relations for cross flowheat exchangers, heretofore unavailable in the open literature, have been derived. The solution presented here was developed to model a 4 tube pass air blast heat exchanger for the Clinch River Breeder Reactor Plant Project. This case is utilized to show how this method can be used as a design tool to select the most suitable blower construction for a particular application. A numerical example is used to illustrate the salient points of the solution

  20. Heat exchanger restart evaluation

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

  1. Heat exchanger restart evaluation

    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

  2. Two-phase flow phenomena assessment in minichannels for compact heat exchangers using image analysis methods

    Highlights: • Analysis of the two-phase flow structure in minichannel. • Innovative use of stereology methods and hi-speed photography. • Application of stereological parameters to flow monitoring. - Abstract: The paper describes a method of two-phase flow structure evaluation for minichannels. The two-phase flow structure appears in gas–liquid mixture. The research is based on innovative approach, with the use of stereology methods. Evaluation of the flow structure is made by image analysis. The images are obtained with high-speed visualization technique. The applied stereological analysis is based on the linear methods – the random secants method and directed secants method. Development of mini heat exchangers requires knowledge of the two-phase flow phenomena. The major result of conducted research is that for each flow structure there is a set of stereological parameters, enabling the quantitative estimation of the two-phase flow. It has been found that the interrelation of stereological parameters, during the change of the flow structure, can be used for controlling the operating conditions. The basic conclusion is that the knowledge about the character of the changes taking place in the flow structure may be used for constant process adjustment for various two-phase gas–liquid or gas–solid systems

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

    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)

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

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

  5. Shellside flow-induced tube vibration in typical heat exchanger configurations: Overview of a research program

    Halle, H.; Chenoweth, J. M.; Wambsganss, M. W.

    A comprehensive research program is being conducted to develop the necessary criteria to assist designers and operators of shell-and-tube heat exchangers to avoid detrimental flow-induced tube vibration. This paper presents an overview of the insights gained from shellside water-flow testing on a horizontal, industrial-sized test exchanger that can be configured in many ways using interchangeable tube bundles and replaceable nozzles. Nearly 50 different configurations have been tested representing various combinations of triangular, square, rotated-triangular, and rotated-square tubefield layouts; odd and even numbers of crosspasses; and both single- and double-segmental baffles with different cut sizes and orientations. The results are generally consistent with analytical relationships that predict tube vibration response by the combined reinforcing effect of the vibration mode shape and flow velocity distribution. An understanding of the vibration and instability performance is facilitated by recognizing that the excitation is induced by three separate, though sometimes interacting, flow conditions. These are the crossflows that generate classic fluidelastic instabilities in the interior of the tube bundle, the entrance and exit bundle flow from and into the shell nozzles, and the localized high velocity bypass and leakage stream flows. The implications to design and/or possible field remedies to avoid vibration problems are discussed.

  6. Heat exchanger performance monitoring guidelines

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

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

    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

  8. Heat exchanger vibration

    The heat exchangers of various types are common items of plant in the generation and transmission of electricity. The amount of attention given to the flow-induced vibrations of heat exchangers by designers is usually related to the operational history of similar items of plant. Consequently, if a particular design procedure yields items of plant which behave in a satisfactory manner during their operational life, there is little incentive to improve or refine the design procedure. On the other hand, failures of heat exchangers clearly indicate deficiencies in the design procedures or in the data available to the designer. When such failures are attributable to flow-induced vibrations, the identification of the mechanisms involved is a prime importance. Ideally, basic research work provides the background understanding and the techniques necessary to be able to identify the important mechanisms. In practice, the investigation of a flow-induced vibration problem may identify the presence of mechanisms but may not be able to quantify their effects adequately. In these circumstances the need for additional work is established and the objectives of the research programme emerge. The purpose of this paper is to outline the background to the current research programme at C.E.R.L. on heat exchanger vibration

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

    Nuntaphan, A.

    2006-05-01

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

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

    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)

  11. Experimental Study of Inlet/Outlet Flow Characteristics in Tube-side of Shell and Tube Heat Exchanger

    The inlet/outlet flow in the tube-side of the shell and tube heat exchanger was experimentally measured to investigate the effect of the porous baffle on uniform flow distribution. A 1/3rd scale-downed model of a heat exchanger was used and particle image velocimetry was applied for measuring the instantaneous velocity vector fields. The absolute errors in the flow rate were calculated and compared for the tube-side with and without the porous baffle, by varying the flow rate from 60 to 90 LPM. The results revealed that the porous baffle can improve flow uniformity and reduce the absolute error in the flow rate of the model with the baffle by about 74%, compared to that without the baffle. This result can be used for improving the performance and design of the shell and tube heat exchanger

  12. Experimental Study of Inlet/Outlet Flow Characteristics in Tube-side of Shell and Tube Heat Exchanger

    Tu, Xin Cheng; Wang, Kai; Kim, Hyoung-Bum [Gyeongsang National University, Jinju (Korea, Republic of); Park, Seung-Ha [Donghwa Entec Co. Ltd., Busan (Korea, Republic of)

    2014-07-15

    The inlet/outlet flow in the tube-side of the shell and tube heat exchanger was experimentally measured to investigate the effect of the porous baffle on uniform flow distribution. A 1/3rd scale-downed model of a heat exchanger was used and particle image velocimetry was applied for measuring the instantaneous velocity vector fields. The absolute errors in the flow rate were calculated and compared for the tube-side with and without the porous baffle, by varying the flow rate from 60 to 90 LPM. The results revealed that the porous baffle can improve flow uniformity and reduce the absolute error in the flow rate of the model with the baffle by about 74%, compared to that without the baffle. This result can be used for improving the performance and design of the shell and tube heat exchanger.

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

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

    1997-07-01

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

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

    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 Σ 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.)

  15. Heat exchanger with packing element between flow shield and the wall of the housing

    The heat exchanger comprises a housing with a supply duct and an outlet duct for a first medium, a pipe bundle installed in the housing, the pipes being in connection with the supply duct, and an exit duct for a second medium, and round the pipe bundle over a greater part of the length thereof is placed a flow shield with a smaller spacing on the outer side than on the inner side of the housing, also one or more spacing elements between the flow shield and the inner wall of the inner shield of the housing, which elements substantially restrict the passage of the first medium through the space between the flow shield on the inner wall of the housing characterised in that the spacing element(s) is (are) composed of parts made of different metals, which metals have different expansion coefficients. (G.C.)

  16. Hydrodynamics and heat exchange during electro-conducting liquid flow in a round tube in a transversal magnetic field

    The review of existing experimental data on hydrodynamics and heat exchange, as well as on experimental studies on heat exchange during liquid metal flow in a horizontal tube in a transversal magnetic field is presented. The comparison of available data on flows in a round tube and a plane channel is carried out. The formula for calculation of the heat transfer coefficient, average by perimeter, by turbulent flow of electro-conducting liquids in a round tube in a transversal magnetic field is obtained

  17. Heat exchange effects on the performance of a clearance-sealed piston prover for gas flow measurements

    Kutin, J.; Bobovnik, G.; Bajsić, I.

    2015-12-01

    This paper deals with heat exchange effects in a compact, high-speed, clearance-sealed version of a piston prover for gas flow measurements that has the temperature measurements limited to the time-averaged temperature of the gas flow. A lumped-element mathematical model is used to study the physical background of the heat exchange effects. Experimental testing is performed to validate the theoretical results, estimate the required temperature homogeneity in the piston prover and propose a modified measurement model that considers the heat exchange effects. These effects are almost linearly related to the temperature difference between the gas flow into the piston prover and the cylinder wall, with the sensitivity coefficient being dependent on the measured flow rate. The piston-prover configuration with the gas temperature sensor in the mixed inlet /outlet flow is found to be advantageous in comparison to a measurement of the inlet temperature.

  18. Experimental investigation of heat exchange development along the tube length during liquid metal flow in transverse magnetic field under conditions of uniform heating

    Paper presents the results of the experimental study of heat exchange at a liquid-metal coolant flow along the horizontally heated tube at thermal flow constant density at the wall in a transverse magnetic field. One measured three-dimensional fields of the averaged temperature and calculated coefficients of heat transfer along the tube length within the Reynolds and the Hartmann number wide range for various values of thermal flow density

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

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

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

    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)

  1. Numerical simulation of fluid flow and heat transfer over crossflow tube bank heat exchangers in power utility boilers

    Zdravistch, Franz

    This research work consists of the development of the gas flow simulation capabilities in Design Software for Power Utility Boilers, a specialized Computational Fluid Dynamics code that has been developed to be used as a design and modification tool for power utility boilers and tube bank heat exchangers. Appropriate boundary conditions and a two-layer wall function have been implemented to accurately simulate the detailed fluid flow and heat transfer over tube bank configurations. The predictions have been validated against a large number of experimental data for different configurations and over a wide range of Reynolds numbers. Original validations have been obtained for local heat transfer in the turbulent regime. Also, results for three-dimensional tube banks and boilers show that the complex structure of the flow and temperature fields is accurately captured by the simulations. To enhance numerical efficiency, an innovative Additive Correction Multigrid-SIMPLEC algorithm combined with Dynamic Relaxation has been developed and implemented. A velocity potential-SIMPLEC algorithm was used for the velocity-pressure coupling on the fine grid, while the corrections from the velocity potential equation were introduced into the momentum correction equations as a source term, keeping the iterative structure of the algorithm on the coarse grid. Results show that the method is effective not only for highly elliptic flows like in square wall driven cavity cases but also for highly hyperbolic flows in curvilinear stretched grids. A momentum and energy sources formulation has been developed to simulate the global influence on the flow and temperature fields created by the tube banks in the boiler. In this formulation, the resistance to the flow and the temperature loss across the tube banks was modelled as sources (sinks) of momentum and energy. The intensity of the sources is a function of the tube bank geometry and operating conditions and of the drag and heat transfer coefficients. The values of the drag and heat transfer coefficients were calibrated using empirical relations, including convective and radiative heat transfer effects. Results for pressure and temperature drop agree well with experimental data, including real scale boiler measurements.

  2. Heat exchanger with ceramic elements

    Corey, John A. (North Troy, NY)

    1986-01-01

    An annular heat exchanger assembly includes a plurality of low thermal growth ceramic heat exchange members with inlet and exit flow ports on distinct faces. A mounting member locates each ceramic member in a near-annular array and seals the flow ports on the distinct faces into the separate flow paths of the heat exchanger. The mounting member adjusts for the temperature gradient in the assembly and the different coefficients of thermal expansion of the members of the assembly during all operating temperatures.

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

    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 NavierStokes 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)

  4. Thermal analysis of shell-side flow of shell-and tube heat exchanger using experimental and theoretical methods

    In this paper the thermal behavior of the shell-side flow of a shell-and-tu fe heat exchanger has been studied using theoretical and experimental methods. The experimental method Provided the effect of the major parameters of the shell-side flow on thermal energy exchange. In the numerical method, besides the effect of the major parameters, the effect of different geometric parameters and Re on thermal energy exchange in shell-side flow has been considered. Numerical analysis for six baffle spacings namely 0.20, 0.25, 0.33, 0.50, 0.66, and 1.0 of inside diameter of the shell and five baffle cuts namely 16%, 20%, 25%, 34%, and 46% of baffle diameter, have been carried out. In earlier numerical analyses, the repetition of an identical geometrical module of exchanger as a calculation domain has been studied. While in this work, as a new approach in current numerical analysis, the entire geometry of shell-and-tube heat exchanger including entrance and exit regions as a calculation domain has been chosen. The results show that the flow and heat profiles vary alternatively between baffles. A shell-and-tube heat exchanger of gas-liquid chemical reactor system has been used in the experimental method. Comparison of the numerical results show good agreement with experimental results of this research and other published experimental results over a wide rang of Reynolds numbers (1,000-1,000,000)

  5. Thermal modeling of a greenhouse integrated to an aquifer coupled cavity flow heat exchanger system

    Sethi, V.P. [Department of Mechanical Engineering, Punjab Agricultural University, Ludhiana 141 008, Punjab (India); Sharma, S.K. [Energy Research Centre, Panjab University, Chandigarh 160 017, Punjab (India)

    2007-06-15

    A thermal model is developed for heating and cooling of an agricultural greenhouse integrated with an aquifer coupled cavity flow heat exchanger system (ACCFHES). The ACCFHES works on the principal of utilizing deep aquifer water available at the ground surface through an irrigation tube well already installed in every agricultural field at constant year-round temperature of 24 C. The analysis is based on the energy balance equations for different components of the greenhouse. Using the derived analytical expressions, a computer program is developed in C{sup ++} for computing the hourly greenhouse plant and room air temperature for various design and climatic parameters. Experimental validation of the developed model is carried out using the measured plant and room air temperature data of the greenhouse (in which capsicum is grown) for the winter and summer conditions of the year 2004-2005 at Chandigarh (31 N and 78 E), Punjab, India. It is observed that the predicted and measured values are in close agreement. Greenhouse room air and plant temperature is maintained 6-7 K and 5-6 K below ambient, respectively for an extreme summer day and 7-8 K and 5-6 K above ambient, respectively for an extreme winter night. Finally, parametric studies are conducted to observe the effect of various operating parameters such as mass of the plant, area of the plant, mass flow rate of the circulating air and area of the ACCFHES on the greenhouse room air and plant temperature. (author)

  6. A relaxation-projection method for compressible flows. Part II: Artificial heat exchanges for multiphase shocks

    The relaxation-projection method developed in Saurel et al. [R. Saurel, E. Franquet, E. Daniel, O. Le Metayer, A relaxation-projection method for compressible flows. Part I: The numerical equation of state for the Euler equations, J. Comput. Phys. (2007) 822-845] is extended to the non-conservative hyperbolic multiphase flow model of Kapila et al. [A.K. Kapila, Menikoff, J.B. Bdzil, S.F. Son, D.S. Stewart, Two-phase modeling of deflagration to detonation transition in granular materials: reduced equations, Physics of Fluids 13(10) (2001) 3002-3024]. This model has the ability to treat multi-temperatures mixtures evolving with a single pressure and velocity and is particularly interesting for the computation of interface problems with compressible materials as well as wave propagation in heterogeneous mixtures. The non-conservative character of this model poses however computational challenges in the presence of shocks. The first issue is related to the Riemann problem resolution that necessitates shock jump conditions. Thanks to the Rankine-Hugoniot relations proposed and validated in Saurel et al. [R. Saurel, O. Le Metayer, J. Massoni, S. Gavrilyuk, Shock jump conditions for multiphase mixtures with stiff mechanical relaxation, Shock Waves 16 (3) (2007) 209-232] exact and approximate 2-shocks Riemann solvers are derived. However, the Riemann solver is only a part of a numerical scheme and non-conservative variables pose extra difficulties for the projection or cell average of the solution. It is shown that conventional Godunov schemes are unable to converge to the exact solution for strong multiphase shocks. This is due to the incorrect partition of the energies or entropies in the cell averaged mixture. To circumvent this difficulty a specific Lagrangian scheme is developed. The correct partition of the energies is achieved by using an artificial heat exchange in the shock layer. With the help of an asymptotic analysis this heat exchange takes a similar form as the 'pseudoviscosity' introduced by Von Neumann and Richtmyer [J. Von Neumann, R.D. Richtmyer, A method for the numerical calculation of hydrodynamic shocks, J. Appl. Phys. 21 (1950) 232-237]. The present Lagrangian numerical scheme thus combines Riemann solvers and artificial heat exchanges. An Eulerian variant is then obtained by using the relaxation-projection method developed earlier by the authors for the Euler equations. The method is validated against exact solutions based on the multiphase shock relations as well as exact solutions of the Euler equations in the context of interface problems. The method is able to solve interfaces separating pure fluids or heterogeneous mixtures with very large density ratio and with very strong shocks

  7. Direct fired heat exchanger

    Reimann, Robert C. (Lafayette, NY); Root, Richard A. (Spokane, WA)

    1986-01-01

    A gas-to-liquid heat exchanger system which transfers heat from a gas, generally the combustion gas of a direct-fired generator of an absorption machine, to a liquid, generally an absorbent solution. The heat exchanger system is in a counterflow fluid arrangement which creates a more efficient heat transfer.

  8. Adaptive predictive control of laboratory heat exchanger

    Bobl, Vladimr; Kubal?k, Marek; Dostl, Petr; Novk, Jakub

    2014-01-01

    Heat exchange belongs to the class of basic thermal processes which occur in a range of industrial technologies, particularly in the energetic, chemical, polymer and rubber industry. The process of heat exchange is often implemented by through-flow heat exchangers. It is apparent that for an exact theoretical description of dynamics of heat exchange processes it is necessary to use partial differential equations. Heat exchange is namely a process with distributed parameters. It is also necess...

  9. Flow induced vibration mock-up test for heat exchanger tubes of PWR steam generator

    It is one of the most important subjects to estimate the flow-related stability of the heat exchanger tubes. A large scale model steam generator has been developed to verify the stability of the tubes in the Japanese PWR steam generators for the two-phase flow-induced vibration and to accumulate related technical data of thermal-hydraulic and flow-induced vibration of U-bend tube bundle. The model steam generator has 230 U-bend tubes of 46 different radius and 5 columns for each of practical diameter and material, and the anti vibration bars are inserted into each spacing between tube arrays. The freon R123 has been used as the secondary side fluid in stead of water-steam two-phase. In the test, void fraction and interfacial velocities in U-bend and straight tube-bundle are measured with bi-optical probes, and vibration responses of some selected tubes are measured with strain gauges and accelerators. It is verified that the U-bend tubes are stable when they are supported as the design requires under normal and some over power no operating condition. The thermal hydraulic code FIT-III has been well verified with measured thermal and hydraulic data. (author)

  10. Numerical investigation of forced convection of nano fluid flow in horizontal U-longitudinal finned tube heat exchanger

    Qasim, S. M.; Sahar, A. F. A.; Firas, A. A.

    2015-11-01

    A numerical study has been carried out to investigate the heat transfer by laminar forced convection of nanofluid taking Titania (TiO2) and Alumina (Al2O3) as nanoparticles and the water as based fluid in a three dimensional plain and U-longitudinal finned tube heat exchanger. A Solid WORKS PREMIUM 2012 is used to draw the geometries of plain tube heat exchanger or U-longitudinal copper finned tube heat exchanger. Four U-longitudinal copper fins have 100 cm long, 3.8cm height and 1mm thickness are attached to a straight copper tube of 100 cm length, 2.2 cm inner diameter and 2.39 cm outer diameter. The governing equations which used as continuity, momentum and energy equations under assumptions are utilized to predict the flow field, temperature distribution, and heat transfer of the heat exchanger. The finite volume approach is used to obtain all the computational results using commercial ANSYS Fluent copy package 14.0 with assist of solid works and Gambit software program. The effect of various parameters on the performance of heat exchanger are investigated numerically such as Reynolds' number (ranging from 270 to 1900), volume consternation of nanoparticles (0.2%, 0.4%, 0.6%, 0.8%), type of nanoparticles, and mass flow rate of nanofluid in the hot region of heat exchanger. For 0.8% consternation of nanoparticles, heat transfer has significant enhancement in both nanofluids. It can be found about 7.3% for TiO2 and about 7.5% for Al2O3 compared with the water only as a working fluid.

  11. Influence of outlet flow temperature at EX07 heat exchangers of ALBA synchrotron cooling system

    Escaler Puigoriol, Francesc Xavier

    2014-01-01

    The ALBA synchrotron cooling system relies in two heat exchangers (EX07 A and B) that transfer heat from the system hot water to cold water coming from a cogeneration plant. As a result, the water temperature can be reduced to a given set point. This temperature set point is currently fixed at 21° C.

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

    Suneela Sardar

    2013-10-01

    Full Text Available 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 arrangement to study the rate of heat transfer. Simulation is carried out when experimental results are obtained. For designing and meshing of plate geometries GAMBIT 2.3.16 is used and then solution and analysis are accomplished on FLUENT 6.3.26. By comparing experimental and simulated results, it is found that both validate each other with minor differences. Empirical relationships have been also developed. Re and Nu relationships are developed mathematically and compared to the models found in literature concerned. The developed models are found in good agreement with theoretically available models. The future research in this regard can be done by using viscous fluids and an advanced version of the software like Cubit for designing and meshing the plate geometry.DOI: http://dx.doi.org/10.5755/j01.erem.65.3.4453

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

    Austegard, Anders

    1997-12-31

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

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

    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 −ω 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.

  15. Wound tube heat exchanger

    Ecker, Amir L. (Duncanville, TX)

    1983-01-01

    What is disclosed is a wound tube heat exchanger in which a plurality of tubes having flattened areas are held contiguous adjacent flattened areas of tubes by a plurality of windings to give a double walled heat exchanger. The plurality of windings serve as a plurality of effective force vectors holding the conduits contiguous heat conducting walls of another conduit and result in highly efficient heat transfer. The resulting heat exchange bundle is economical and can be coiled into the desired shape. Also disclosed are specific embodiments such as the one in which the tubes are expanded against their windings after being coiled to insure highly efficient heat transfer.

  16. Analysis of transient and hysteresis behavior of cross-flow heat exchangers under variable fluid mass flow rate for data center cooling applications

    Effective thermal management of data centers is an important aspect of reducing the energy required for the reliable operation of data processing and communications equipment. Liquid and hybrid (air/liquid) cooling approaches are becoming more widely used in today's large and complex data center facilities. Examples of these approaches include rear door heat exchangers, in-row and overhead coolers and direct liquid cooled servers. Heat exchangers are primary components of liquid and hybrid cooling systems, and the effectiveness of a heat exchanger strongly influences the thermal performance of a cooling system. Characterizing and modeling the dynamic behavior of heat exchangers is important for the design of cooling systems, especially for control strategies to improve energy efficiency. In this study, a dynamic thermal model is solved numerically in order to predict the transient response of an unmixed–unmixed crossflow heat exchanger, of the type that is widely used in data center cooling equipment. The transient response to step and ramp changes in the mass flow rate of both the hot and cold fluid is investigated. Five model parameters are varied over specific ranges to characterize the transient performance. The parameter range investigated is based on available heat exchanger data. The thermal response to the magnitude, time period and initial and final conditions of the transient input functions is studied in detail. Also, the hysteresis associated with the fluid mass flow rate variation is investigated. The modeling results and performance data are used to analyze specific dynamic performance of heat exchangers used in practical data center cooling applications. - Highlights: • The transient performance of a crossflow heat exchanger was modeled and studied. • This study provides design information for data center thermal management. • The time constant metric was used to study the impacts of many variable inputs. • The hysteresis behavior associated with heat exchanger dynamic response is studied. • Specific discussions for practical data center cooling applications are performed

  17. Damping of heat exchanger tubes

    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

  18. Second law analysis and heat transfer in a cross-flow heat exchanger with a new winglet-type vortex generator

    Kotcioglu, Isak [Department of Mechanical Engineering, Faculty of Engineering, University of Atatuerk, 25240 Erzurum (Turkey); Caliskan, Sinan [Department of Mechanical Engineering, Faculty of Engineering, University of Hitit, 19030 Corum (Turkey); Cansiz, Ahmet [Department of Electrical-Electronics Engineering, Faculty of Engineering, University of Atatuerk, 25240 Erzurum (Turkey); Baskaya, Senol [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Gazi University, Maltepe 06570, Ankara (Turkey)

    2010-09-15

    In this paper a second law analysis of a cross-flow heat exchanger (HX) is studied in the presence of a balance between the entropy generation due to heat transfer and fluid friction. The entropy generation in a cross-flow HX with a new winglet-type convergent-divergent longitudinal vortex generator (CDLVG) is investigated. Optimization of HX channel geometry and effect of design parameters regarding the overall system performance are presented. For the HX flow lengths and CDLVGs the optimization model was developed on the basis of the entropy generation minimization (EGM). It was found that increasing the cross-flow fluid velocity enhances the heat transfer rate and reduces the heat transfer irreversibility. The test results demonstrate that the CDLVGs are potential candidate procedure to improve the disorderly mixing in channel flows of the cross-flow type HX for large values of the Reynolds number. (author)

  19. Optimization of Heat Exchangers

    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.

  20. Optimization of Heat Exchangers

    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.

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

    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.

  2. Nature's Heat Exchangers.

    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)

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

    Raj Karuppa Thundil R.; Ganne Srikanth

    2012-01-01

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

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

    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 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)

  5. Active microchannel heat exchanger

    Tonkovich, Anna Lee Y. (Pasco, WA) [Pasco, WA; Roberts, Gary L. (West Richland, WA) [West Richland, WA; Call, Charles J. (Pasco, WA) [Pasco, WA; Wegeng, Robert S. (Richland, WA) [Richland, WA; Wang, Yong (Richland, WA) [Richland, WA

    2001-01-01

    The present invention is an active microchannel heat exchanger with an active heat source and with microchannel architecture. The microchannel heat exchanger has (a) an exothermic reaction chamber; (b) an exhaust chamber; and (c) a heat exchanger chamber in thermal contact with the exhaust chamber, wherein (d) heat from the exothermic reaction chamber is convected by an exothermic reaction exhaust through the exhaust chamber and by conduction through a containment wall to the working fluid in the heat exchanger chamber thereby raising a temperature of the working fluid. The invention is particularly useful as a liquid fuel vaporizer and/or a steam generator for fuel cell power systems, and as a heat source for sustaining endothermic chemical reactions and initiating exothermic reactions.

  6. Distribution of air-water R134a in a header of a parallel flow heat exchanger

    Flow distribution in a header of a parallel flow heat exchanger was experimentally investigated using R-134a. Both downward and upward flow configuration were tested with tubes protruded to the center of the header. For the test range, the flow pattern at the inlet of the header was identified as stratified flow. It was observed that, for the downward flow, most of the liquid was extracted from the frontal part of the header. For the upward flow, however, most of the liquid was extracted from the rear part of the header. For the downward configuration, better distribution was obtained at a low mass flux and at a low quality. For the upward configuration, however, the mass flux or quality had minor influence on the flow distribution

  7. Nuclear heat exchangers

    This paper presents general design features and characteristics of nuclear heat exchangers including nuclear steam generators. In particular, the heat exchangers in the pressurized light or heavy water reactor and the liquid metal fast breeder reactor plants, and their thermal and hydraulic characteristics are discussed in detail

  8. Heat exchangers: operation problems

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

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

    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

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

    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

  11. Ventilators controlled depending on demand. Energy-saving control of cross-flow heat exchangers with change-over operation

    Wiening, W.; Hoffmann, U.; Rake, H.; Probst, J.

    1986-02-01

    The energy requirement of ventilating and airconditioning plants for the ventilation and airconditioning of rooms and buildings is determined by the heating and refrigeration energy required for the processing of the air mass flow. The adaptation of the air mass flow to the respective demands of the rooms to be ventilated is one method to save energy. Under certain circumstances, this may lead to an operation of the plant with a heavily fluctuating air flow, or to the necessity to shift the air flow between different values. The majority of temperature control devices usually applied is not suitable for this kind of operation. By example of a cross-flow heat exchanger which is frequently used in ventilating plants, the problems and a first attempt to regulate the system by variable air mass flow have been investigated. The result is a hierarchical control system operated digitally for control and surveillance of intermittent operation of cross-flow heat exchangers, the capacity of which has been established by experimental research. (orig.).

  12. Numerical simulation of non-stationary separated gas flow with account for heat exchange

    Investigations of separated gas flow and heat transfer of a cylinder under cross flow were conducted. Calculations were conducted on the basis of numerical integration of the Mavier-Stokes equation by the arbitrary Lagrangian-Eulerian method. 3 refs.; 4 figs

  13. Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement

    Bimal Kad

    2007-09-30

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program were to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. The research program outlined was iterative and intended to systematically (i) examine and identify post-extrusion forming methodologies to create hoop strengthened tubes, to be (ii) evaluated at 'in-service' loads at service temperatures and environments. Our report outlines the significant hoop creep enhancements possible via secondary cross-rolling and/or flow-forming operations. Each of the secondary processes i.e. hot rotary forming and ambient-temperature flow forming exhibited improvement over the base-line hoop-creep performance. The flow formed MA956 tubes exhibited performance superior to all other rolling/forming variants. At the conclusion of this program 2ksi creep-test exposure for flow formed materials exceeded 7300 hours, 7694 hours and 4200 hours for creep tests operating at 950 C, 975 C and 1000 C respectively. The Larsen-Miller parameter for these improvised flow-formed tubes now exceeds 54.14, i.e., better than ever recorded previously. The creep performance enhancement in cross-rolled MA956 material samples versus the base creep property is elucidated. At least 2-3 orders of magnitude of improvement in creep rates/day and concomitant increases in creeplife are demonstrated for the flow formed tubes versus the base reference tests.

  14. Support for heat exchangers

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

  15. Analytical Entropy Analysis of Recuperative Heat Exchangers

    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.

  16. Heat exchange assembly

    Lowenstein, Andrew; Sibilia, Marc; Miller, Jeffrey; Tonon, Thomas S.

    2004-06-08

    A heat exchange assembly comprises a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane, a plurality of first end-piece members equaling the number of plates and a plurality of second end-piece members also equaling the number of plates, each of the first and second end-piece members including a recessed region adapted to fluidly connect and couple with the first and second ends of the plate, respectively, and further adapted to be affixed to respective adjacent first and second end-piece members in a stacked formation, and each of the first and second end-piece members further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180.degree. turning of the fluid within the plate to create a serpentine-like fluid flow path between points of entry and exit of the fluid, and at least two fluid conduits extending through the stacked plurality of first and second end-piece members for providing first fluid connections between the parallel fluid entry points of adjacent plates and a fluid supply inlet, and second fluid connections between the parallel fluid exit points of adjacent plates and a fluid discharge outlet so that the heat transfer fluid travels in parallel paths through each respective plate.

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

    N.D.Shirgire

    2014-07-01

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

  18. The Effect of Reynolds Number on the Thermal and Hydrodynamic Characteristics of Turbulence Flow of the Nanofluid in the Heat Exchanger

    VAH?D?N?A, F.; M?R?, M.

    2015-01-01

    Abstract. Reynolds number is one of the most important parameters in investigation of heat transfer in double tube heat exchangers. In this paper, the effect of this parameter has been investigated on the convective heat transfer coefficient and surface friction coefficient of the wall. Turbulent forced convection heat transfer of nanofluid flow of Al2O3 /water in a double tube heat exchanger with rough tubes in the annular portion was numerically studied. The finite volume method and the sec...

  19. Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement

    Bimal K. Kad

    2006-09-30

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. The research program outlined here is iterative in nature and is intended to systematically (a) examine and identify post-extrusion forming methodologies to create hoop strengthened tubes, which will be (b) evaluated at ''in-service'' loads at service temperatures and environments. In this 12th quarter of performance, program activities are concluded for Task 2 and continuing for Tasks 3, 4 and reported herein. Two sets of MA956 tubes rotary cross-rolled at rolling angles of {Beta}=2{sup o} and 8{sup o} and two sets of flow formed and recrystallized tubes are being evaluated under hoop creep conditions in air. While, the rotary cross-rolled samples exhibit improvement over the baseline performance, it is he flow formed tubes that exhibit superior performance. Current test exposure for flow formed materials exceeds 6000 hours for a creep test operating at 950 C at 2Ksi stress. The Larsen-Miller parameter for these improvised flow-formed tubes now exceeds 52.4, i.e., better than ever recorded previously. These samples are at various stages of creep testing and evaluation in Task 4. The creep performance enhancement in cross-rolled MA956 material samples versus the base creep property is elucidated. At least 2-3 orders of magnitude of improvement in creep rates/day and concomitant increases in creep-life are demonstrated for the flow formed tubes versus the base reference tests.

  20. Thermoelectric heat exchange element

    Callas, James J. (Peoria, IL); Taher, Mahmoud A. (Peoria, IL)

    2007-08-14

    A thermoelectric heat exchange module includes a first substrate including a heat receptive side and a heat donative side and a series of undulatory pleats. The module may also include a thermoelectric material layer having a ZT value of 1.0 or more disposed on at least one of the heat receptive side and the heat donative side, and an electrical contact may be in electrical communication with the thermoelectric material layer.

  1. Characteristics of heat exchange in the region of injection into a supersonic high-temperature flow

    Bakirov, F. G.; Shaykhutdinov, Z. G.

    1985-01-01

    An experimental investigation of the local heat transfer coefficient distribution during gas injection into the supersonic-flow portion of a Laval nozzle is discussed. The controlling dimensionless parameters of the investigated process are presented in terms of a generalized relation for the maximum value of the heat transfer coefficient in the nozzle cross section behind the injection hole. Data on the heat transfer coefficient variation along the nozzle length as a function of gas injection rate are also presented, along with the heat transfer coefficient distribution over a cross section of the nozzle.

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

    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 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.)

  3. Design evaluation of flow-induced vibrations for a large shell and tube type nuclear heat exchanger

    Increased flow requirements for a large sized shell and tube type nuclear heat exchanger during advanced stage of manufacturing required re-evaluation of the Design to withstand flow-induced vibrations and suggest suitable Design alternatives within the constraints imposed at this advanced stage of manufacturing. Detailed flow-induced vibration analysis was done and two design alternatives offered. The first one consisted in attaching a wire-netted grid mounted alongside the baffle supports and the second considered removal of tubes from the vibration prone double span window region, which was counter-checked for heat-transfer adequacy requirement. Of the two alternatives, the second one was accepted due to its easy application at the advanced manufacturing stage. While the application of the wire-netted grid was not considered in the specific case, this might find application wherever the vibration prone double span tubes cannot be removed due to heat transfer requirements of Design

  4. Determination of optimum aspect ratio for laminar flow heat transfer of dilute viscoelastic solutions in flattened tube heat exchangers

    Ismail, Z. [Universiti Malaya, Civil Engineering Department, Kuala Lumpur (Malaysia); Karim, R. [TTDI, Kuala Lumpur (Malaysia)

    2012-08-15

    Heat transfer of viscoelastic liquids in five flattened tubes with aspect ratios ranging from 1.4 to 5.7 were presented. Water was used as the heating medium; and solutions of polyacrylamide were used as the viscoelastic solutions. Heat transfer increase from flattening was 101% higher while secondary flow contributed a maximum increase of 65% for the 250 ppm solution and about 85% for the 500 ppm solutions at an aspect ratio of 1.6. (orig.)

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

    Hap, Nguyen Van; Lee, Geun Sik [Ulsan University, Ulsan (Korea, Republic of)

    2015-03-15

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

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

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

  7. Fouling analyses for heat exchangers of NPP

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

  8. Heat exchanger design handbook

    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

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

    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 ...

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

    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)

  11. Two-phase flow on the shell-side of a segmentally baffled shell-and-tube heat exchanger

    This paper reviews work carried out at the National Engineering Laboratory, UK., related to pressure drop flow patterns and phase distribution on the shell-side of segmentally baffled shell-and-tube heat exchangers. The experimental work reported was carried out using air/water mixtures in model exchangers of rectangular cross section with tube nests containing approximately 40 tubes. Data were obtained on crossflow pressure drop and on the pressure drop attributable to the windows. In certain configurations the void fraction and flow pattern maps were obtained. The geometric conditions examined related to configurations appropriate to operation as condensers and boilers. Correlations for pressure drop and void fraction were developed and flow pattern maps obtained

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

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

    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...

  13. Counterflow Regolith Heat Exchanger

    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.

  14. 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

    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

  15. Experimental and numerical study of the distribution of a single-phase flow in a small channel heat exchanger

    Poggi, F.; Bontemps, A.; Macchi Tejeda, H.; Marechal, C.; Leducq, D.

    2009-01-01

    This study focuses on the distribution of a single-phase flow in a small channel heat exchanger. A test section consisting of a cylindrical header connected to 8 multiport flat tubes of 7 parallel small channels (Dh = 0.889 mm) enables the measurement of singular and regular local pressure losses all along the header and the small channels, as well as the flow distribution in each small channel tube. The flat tubes are inserted up to the half of the manifold, i-e with an insertion height of 8...

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

    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.

  17. Heat exchanger for a nuclear reactor with gaseous primary medium flowing around it

    The helium cooling gas enters the helical bundle of pipes from below in the heat exchanger. The helical bundle of pipes is surrounded by an outer and inner jacket. There are practically no different expansions from the support pipe in the area of the upper edge of the pipe bundle. By connecting the upper live steam part of the pipe to the outer pipe via a thermal expansion compensator, a gradual transition is created from the live steam temperature to the feedwater temperature. (DG)

  18. Chapter 11. Heat Exchangers

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

    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)

  20. Mathematical Model for Fluid Flow and Heat Transfer Processes in Plate Exchanger

    Cvete B. Dimitrieska

    2015-11-01

    Full Text Available Within the analytical solution of the system of equations which solve fluid flow and heat transfer processes, the elliptical and parabolic differential equations based on initial and boundary conditions is usually unfamiliar in a closed form. Numerical solution of equation system is necessarily obtained by discretization of equations. When system of equations relate to estimation of two dimensional stationary problems, the applicable method for estimation in basic two – dimensional form is recommended.

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

    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 ...

  2. Modular heat exchanger

    A heat exchanger for use in nuclear reactors is disclosed which includes a heat exchange tube bundle formed from similiar modules each having a hexagonal shroud containing a large number of thermally conductive tubes which are connected with inlet and outlet headers at opposite ends of each module, the respective headers being adapted for interconnection with suitable inlet and outlet manifold means. In order to adapt the heat exchanger for operation in a high temperature and high pressure environment and to provide access to all tube ports at opposite ends of the tube bundle, a spherical tube sheet is arranged in sealed relation across the chamber with an elongated duct extending outwardly therefrom to provide manifold means for interconnection with the opposite end of the tube bundle

  3. Fouling analyses of heat exchangers for PSR

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

  4. Preliminary Studies of S-CO2 Critical Flow for Leak Modeling in Sodium-CO2 Heat Exchanger

    The amount of chemical reaction between sodium and CO2 will vary depending on several factors; the crack or rupture size, the interfacial area between sodium and CO2, the amount of released CO2, and so on. These factors are as influential as the reaction temperature of Na-CO2 interaction. To specify these factors, it is important to predict the CO2 leak mechanism during the CO2 leakage. However, only limited number of studies has been performed for understanding the CO2 leak mechanism. sodium to supercritical CO2 heat exchanger, an isentropic critical flow model was developed. Based on a simple flow model a preliminary numerical study was carried out by including simplified Na-CO2 reaction. However, friction between CO2 and crack wall should be considered to simulate more realistic CO2 critical flow, which represents more realistic situation. Thus, the Fanno flow, which considers friction in a compressible flow, will replace the isentropic flow model for better predictability. If this model can reasonably simulate the transient response of the CO2 leak scenario, several physical models will be added to the current analysis; real gas model, Na-CO2 interaction, two-phase model for liquid sodium and gaseous CO2, heat transport in the sodium tank, and so on

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

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

  6. Heat exchange apparatus

    Degtiarenko, Pavel V.

    2003-08-12

    A heat exchange apparatus comprising a coolant conduit or heat sink having attached to its surface a first radial array of spaced-apart parallel plate fins or needles and a second radial array of spaced-apart parallel plate fins or needles thermally coupled to a body to be cooled and meshed with, but not contacting the first radial array of spaced-apart parallel plate fins or needles.

  7. Probe Measures Fouling As In Heat Exchangers

    Marner, Wilbur J.; Macdavid, Kenton S.

    1990-01-01

    Combustion deposits reduce transfer of heat. Instrument measures fouling like that on gas side of heat exchanger in direct-fired boiler or heat-recovery system. Heat-flux probe includes tube with embedded meter in outer shell. Combustion gases flow over probe, and fouling accumulates on it, just as fouling would on heat exchanger. Embedded heat-flow meter is sandwich structure in which thin Chromel layers and middle alloy form thermopile. Users determine when fouling approaches unacceptable levels so they schedule cleaning and avoid decreased transfer of heat and increased drop in pressure fouling causes. Avoids cost of premature, unnecessary maintenance.

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

    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 ...

  9. Detection of flow mixing processes using transmission methods in high-duty heat exchanging apparatus

    The COBRA-IIIC program modified by MIT has been further improved for verifying the experimental studies described in the thesis. This work has been accompanied by a review and modification of the relevant analytical equations. A mathematical relationship has been set up for the cross-mixing phenomenon of shearing flow in narrowest cross-section between two heating rods, the relationship being taken into account in the sub-channel analysis. Despite the very complex and superposing processes of the problem studied, the results obtained by the improved sub-channel analysis program using the nearly derived cross-mixing approach are quantitatively well confirmed by comparison with experimental data. Applying the improved sub-channel analysis program to describing the author's two-phase flow experiments (air-water and water-steam) with rod bundle geometries to be found in the literature, the cross-mixing approach presented in the thesis is shown to be reliable (orig./GL)

  10. Three-dimensional numerical simulation of fluid flow and heat transfer in fin-and-tube heat exchangers at different flow regimes

    Paniagua Sánchez, Leslye

    2014-01-01

    This thesis aims at unifying two distinct branches of work within the Heat Transfer Technological Center (CTTC). On one side, extensive experimental work has been done during the past years by the researchers of the laboratory. This experimental work has been complemented with numerical models for the calculation of fin and tube heat exchangers thermal and fluid dynamic behavior. Such numerical models can be referred to as fast numerical tool which can be used for industrial rating and design...

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

    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)

  12. Experimental evaluation of vibrations in heat exchangers

    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)

  13. Heat exchanger with removable orifice

    A nuclear reactor steam generator heat exchanger is described which has orifices in the entrance openings of the heat exchange tubes which, although securely fastened to the tubes, can be easily removed by remote handling equipment. (U.K.)

  14. Heat exchanger tube tool

    Certain types of heat-exchangers have tubes opening through a tube sheet to a manifold having an access opening offset from alignment with the tube ends. A tool for inserting a device, such as for inspection or repair, is provided for use in such instances. The tool is formed by a flexible guide tube insertable through the access opening and having an inner end provided with a connector for connection with the opening of the tube in which the device is to be inserted, and an outer end which remains outside of the chamber, the guide tube having adequate length for this arrangement. A flexible transport hose for internally transporting the device slides inside of the guide tube. This hose is long enough to slide through the guide tube, into the heat-exchanger tube, and through the latter to the extent required for the use of the device. The guide tube must be bent to reach the end of the heat-exchanger tube and the latter may be constructed with a bend, the hose carrying anit-friction elements at interspaced locations along its length to make it possible for the hose to negotiate such bends while sliding to the location where the use of the device is required

  15. An improved method for analysis of time dependent one-dimensional heat exchange between a river flow and atmosphere

    In this work an improvement of the methodology for analysis of time dependent one-dimensional heat exchange between a river flow and atmosphere at additional discharge of condenser heated water from thermal power plant, published at the XXI Yugoslav Conference of ETAN, is performed. In comparison with the already published methodology this work comprises the following improvements: The dispersive member along the river flow is taken into account, so that the basic second order partial differential equation is to be solved. With this improvement the mentioned methodology becomes applicable for analysis of rivers with high and low velocities. The assumption for stationarity is dropped out for at least three consequent days, in a manner that the conditions for equality of temperature and derivative at the beginning and at the end of the day is replaced with assumption that the river flow reaches minimal and maximal ambient temperature at sunrise and sunset. It is possible to conclude that the main characteristics of the developed methodology is the minimal number of hydro meteorological data are needed, that is only two temperature measurements of the water and two measurements of the wind velocity for the whole day - night time period. This conclusion is especially important when statistical analyses of data for longer past period of time are made, i.e. when it is not possible to obtain additional information. (author)

  16. Magnetic heat pump flow director

    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.

  17. Heat Exchangers Analysis

    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.

  18. Flow visualization of annular and delta winglet vortex generators in fin-and-tube heat exchanger application

    Wang, C.-C.; Wei, C.-S. [Energy and Resources Labs., Hsinchu (Taiwan); Lo, J.; Lin, Y.-T. [Yuan Ze Univ., Taiwan (Taiwan). Dept. of Mechanical Engineering

    2002-08-01

    This study presents flow visualization and frictional results of enlarged fin-and-tube heat exchangers with and without the presence of vortex generators. Two types of vortex generators and a plain fin geometry were examined in this study. For plain fin geometry at Re=500, the horseshoe vortex generated by the tube row is not so pronounced, and the horseshoe vortex separates into two streams as it flows across the second row and consequently loses its vortical strength. This phenomenon may support the ''maximum phenomenon'' in low Reynolds number region reported by previous studies. With the presence of annular vortex generator, the presence of a pair of longitudinal vortices formed behind the tube is seen. The strength of the counter-rotating vortices increases with the annular height and the strength of the longitudinal vortices is so strong that may swirl with the horseshoe vortices and other flow stream. For the same winglet height, the delta winglet shows more intensely vortical motion and flow unsteadiness than those of annular winglet. This eventually leads to a better mixing phenomenon. However, it is interesting to know that the corresponding pressure drops of the delta winglet are lower than those of annular winglet. Compared to the plain fin geometry, the penalty of additional pressure drops of the proposed vortex generators is relatively insensitive to change of Reynolds number. (author)

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

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

    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. D...

  20. Surface Chemical Composition Effect on Internal Gas Flow and Molecular Heat Exchange in a Gas-Solids System

    Ukhov, Alexander; Borisov, Sergey; Porodnov, Boris

    2011-05-01

    On the basis of classical knowledge about movement of atoms and lattice theory of F. Goodman and G. Wachman the program modeling helium atom interaction with a three-dimensional crystal tungsten lattice taking into account partial surface covering by chemisorbed oxygen atoms is developed. An efficiency of molecular heat exchange of helium for pure and partially chemisorbed tungsten surface is calculated for different temperatures. Similar model of the surface and procedure of calculations have been applied for description of free-molecular gas flow in long cylindrical channel with clean and fully chemisorbed metal surface. Within the limits of the developed approach the results of calculations for both problems agree well with available experiments with surface contamination control.

  1. Counterflow Regolith Heat Exchanger Project

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

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

    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.

  3. Cryogenic regenerative heat exchangers

    Ackermann, Robert A

    1997-01-01

    An in-depth survey of regenerative heat exchangers, this book chronicles the development and recent commercialization of regenerative devices for cryogenic applications. Chapters cover historical background, concepts, practical applications, design data, and numerical solutions, providing the latest information for engineers to develop advanced cryogenic machines. The discussions include insights into the operation of a regenerator; descriptions of the cyclic and fluid temperature distributions in a regenerator; data for various matrix geometries and materials, including coarse and fine bronze, stainless steel-woven wire mesh screens, and lead spheres; and unique operating features of cryocoolers that produce deviations from ideal regenerator theory.

  4. The effect of inlet and outlet shell-side flow and heat transfer on the performance of HTGR straight tube heat exchangers

    Since the mid-1970s, various high temperature gas-cooled reactor (HTGR) steam generator, auxiliary heat exchanger (AHE), recuperator, and intermediate heat exchanger (IHX) designs have been proposed that use straight tube configurations. Each of these designs requires 90-deg turns in the helium gas flow at the inlet and/or outlet of the tube bundle. The design of the steam generator for the HTGR steam cycle/cogeneration lead plant includes a straight tube superheater (STSH) which incorporates both a 90-deg inlet and outlet turn across the tube bundle. The AHE includes a 90-deg outlet turn across the tube bundle. Previous GA Technologies Inc. (GA) recuperator and IHX designs for gas turbine and process heat HTGRs have also considered straight tube designs with 90-deg bends at the inlet and outlet. To evaluate the effect of these turns on the tube bundle performance, two model air flow tests have been performed, and a third is being planned. Fluid flow and heat transfer computer models have also been used to try to determine the effect of these 90-deg turns on the tube bundle performance. As a result of these studies, the following conclusions can be made: 1. For all of the designs investigated, the 90-deg turns reduced the bundle performance. 2. In designs where the tube pitch-to-diameter ratio is small (less than 1.3), the 90-deg turns can have a critical effect on the performance. However, use of design concepts such a flow baffles or small modular bundle designs can greatly reduce or eliminate these problems. 3. The inlet turns are more critical to the design than the outlet turns. 4. The non-uniform temperature profiles resulting from poor inlet design can result in high thermal stresses in the tubes. 5. Testing to correlate the shell-side heat transfer in the region of a 90-deg bend across a tube bundle is required to more fully understand the characteristics of this problem. 6. Although the 90-deg turns are not desirable, they are frequently necessary in realistic plant and component designs. However, with the proper analysis and testing, the designs can be developed so as to minimize their adverse effects on tube bundle performance and thermal stress. (author)

  5. Triple loop heat exchanger for an absorption refrigeration system

    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.

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

    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

  7. Process for producing flow in devices for material and heat exchange

    Chekhov, O.S.; Schavoronkov, N.M.; Nikolaikin, N.J.

    1979-11-22

    The gas flow in the washing device for removing dust from the air in granulation towers in the manufacture of ammonium nitrate is divided into several paths. The thin film floor in the scrubbing tower works hydraulically. By dividing the gas flow, the use of washing liquid is reduced to about one-third.

  8. Fluid-elastic vibrations in heat exchangers with tubes in cross-flow

    Tube vibrations in tube banks with tubes in cross-flow have been studied. Special interest has been devoted to fluid-elastic vibrations. A simple mathematical model to describe the coupling between the instationary flow and the vibrating tubes is given. Finally a method to suppress high amplitude vibrations is discussed. (author)

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

    Rivera, Jaime; Blum, Philipp; Bayer, Peter

    2015-04-01

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

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

    Austegard, Anders

    1997-12-31

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

  11. Heat exchanger repair

    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.)

  12. Next Generation Microchannel Heat Exchangers

    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.

  13. Design study of plastic film heat exchanger

    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.

  14. Heat exchanger effectiveness in unsteady state

    Mai, T. H.; Chitou, N.; Padet, J.

    1999-10-01

    A method is proposed to determine the thermal effectiveness of heat exchangers in situ, when one of the fluids is submitted to any kind of flow rate variations. It leads to the definition of the average effectiveness in unsteady state, which forms an extension of the classical effectiveness used in steady state. It requires an unsophisticated equipment of measurement and should lead to an easy and continuous control of the fouling of heat exchangers.

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

    Trilok Singh Bisoniya, S.P.S. Rajput, Anil Kumar

    2011-01-01

    The comparative thermal analysis of theoretical and experimental studies of modified indirect evaporative cooler having cross flow heat exchanger with one fluid mixed and the other unmixed is presented in this research paper. A heat and mass transfer mathematical model is developed to simulate the properties of indirect evaporative cooler. The theoretical result analysis was done by plotting the curves between various performance parameters. This work presents the fabrication and experiments ...

  16. Investigations on fluid borne forces in heat exchangers with tubes in cross flow

    An experimental device is described with which steady and unsteady flow forces acting on a tube and the mechanical response of the tube to these forces can be measured. At first a single tube in cross flow was investigated to prove the reliability of the test procedure. After that experiments with four in-line tube banks with pitches ranging from 1.15 to 2.88 tube diameters were performed. The aerodynamic forces and the tube vibrations were registered simultaneously. The measurements show that four kinds of exciting mechanisms exist. Tube vibrations are caused either by vortices, buffeting, galloping or fluid elastic coupling. The tests were performed in an atmospheric wind tunnel in a range of Reynolds number 104 5 (author)

  17. Fluid-elastic instability of heat exchanger tube arrays in potential cross-flow

    In order to study the fluid-elastic instability effects of tube arrays in a uniform cross-flow, Van der Hoogt and Van Campen (1984) adopted a two-dimensional complex velocity potential approach and calculations were performed on two tubes out of a tube array. A potential flow approach was used, because, for closely packed staggered tube arrays, the wakes behind the tubes are considerably suppressed and the flow distribution around the tubes shows a 'potential-like' character. In the present paper the model is extended to account for more complex configurations, followed by an examination of their dynamical features. For a specific staggered configuration the results of the critical flow velocities will be compared with Paidoussis (1984) data, who dealt with a comparable approach. In order to account for the influence of a phase lagging effect between the motions of the tubes and the fluid forces, a modification of the model was performed by introducing a phase lag angle η. Dynamical (flutter) instability was found to occur for specific configurations of tubes whenever a non-zero phase lagging effect was incorporated in the calculations. For a specific configuration critical velocities were compared with the results obtained by Paidoussis et al. (1984), dealing with a similar approach. Although agreement was found for the critical buckling velocities using η = 00, discrepancies occurred for the critical flutter velocities, using η = 100 and η = 300 possibly due to the different way of incorporating the phase lag effect in the equations of motion. Although the present model predicts that the reduced critical velocity depends on the square root of the mass-damping parameter mδ/ρD2 in a similar way as found by Connors, the actual values are larger than the experimental values from literature. (orig./GL)

  18. Heat exchanger leakage problem location

    Hej?k, Ji?; Jcha, Miroslav

    2012-04-01

    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.

  19. Heat exchanger leakage problem location

    Jcha 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.

  20. Mathematical Modeling of Spiral Heat Exchanger

    Probal Guha , Vaishnavi Unde

    2014-04-01

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

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

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

  2. Heat pipes in modern heat exchangers

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

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

    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...

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

    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.

  5. High Temperature Heat Exchanger Project

    Anthony E. Hechanova, Ph.D.

    2008-09-30

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

  6. Fluid-elastic instability of heat exchanger tube arrays in potential cross-flow

    Possibly occurring instabilities may be classified into buckling instability (divergence) and dynamical instability (flutter). Calculations revealed only instabilities of the divergence type, whenever a phase lagging angle equal to zero between the tube and fluid motion was used. The associated critical flow velocity appeared to be strongly dependent on the system geometry, thus on the number of tubes and their mutual distance. In order to account for the influence of a phase lagging effect between the motions of the tubes and the fluid sources, a modification of the model was performed by introducing a phase lag angle eta. Dynamical (flutter) instability was found to occur for specific configurations of tubes whenever a non-zero phase lagging effect was incorporated in the calculations. For a specific configuration critical velocities were compared with the results obtained by Paidoussis, dealing with a similar approach. Although agreement was found for the critical buckling velocities using eta = 0/sup o/, discrepancies occurred for the critical futter velocities, using eta = 10/sup o/ and eta = 30/sup o/ possibly due to the different way of incorporating the phase lag effect in the equations of motion. Although the present model predicts that the reduced critical velocity depends on the square root of the mass-damping parameter mδrhoD2 in a similar way as found by Connors, the actual values are larger than the experimental values from literature

  7. Thermal hydraulic design of intermediate heat exchanger

    Intermediate heat exchanger (IHX) is a very important component of Fast Breeder Reactor because it forms the boundary between radioactive primary sodium and non-radioactive secondary sodium. IHX of the 500 MWe Prototype Fast Breeder Reactor is a shell and tube heat exchanger with primary sodium flowing on the shell side. Cross flow heat transfer at the primary sodium entrance demands unequal secondary flow distribution in various tubes to ensure good safety margin in structural design. This paper brings out details of thermal hydraulic studies to arrive at a suitable secondary flow distribution and choice of a suitable flow distribution device to achieve the same. Application of two-dimensional analysis with computer code THYC-2D has been brought out. (author). 5 refs., 14 figs., 2 tabs

  8. Thermodynamic Optimization of GSHPS Heat Exchangers

    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.

  9. Air-sand heat exchanger

    Baumann, Torsten; Zunft, Stefan [German Aerospace Center (DLR), Stuttgart (Germany); Boura, Cristiano; Eckstein, Julian; Felinks, Jan; Goettsche, Joachim; Hoffschmidt, Bernhard; Schmitz, Stefan [FH Aachen, Juelich (Germany). Solar-Inst. Juelich

    2011-07-01

    This paper summarizes research activities that analyse the thermodynamic behaviour of an Air / Sand Heat Exchanger, developed by Solar-Institut Juelich (SIJ) and the German Aerospace Centre (DLR). A numerical 3-D model, new results and a model validation of this particular cross-flow heat exchanger are presented. Simulation results were obtained for sand with 1-2 mm grain size. The simulation was validated with operational results of a new 15 kW prototype unit. Ansys, including Ansys-CFX, is used as modelling and simulation platform. The bulk material is modelled by a porous solid medium without structural dynamic interaction between fluid and solid phase. For pressure drop calculations, Ergun's model for bulk material is used. The model parameters were validated and fitted with measured values of a separate pressure drop test rig. The validation was done with quartz sand. To determine the suitability of available granular products for this application, tests have been conducted regarding the thermomechanical properties as well as their attrition behaviour and abrasion on various wall materials.

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

    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...

  11. Investigation Status of Heat Exchange while Boiling Hydrocarbon Fuel

    D. S. Obukhov

    2014-06-01

    Full Text Available The paper contains analysis of heat exchange investigations while boiling hydrocarbon fuel. The obtained data are within the limits of the S.S. Kutateladze dependence proposed in 1939. Heat exchange at non-stationary heat release has not been investigated. The data for hydrocarbon fuel with respect to critical density of heat flow are not available even for stationary conditions.

  12. Heat exchanger using graphite foam

    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.

  13. Hierarchic modeling of heat exchanger thermal hydraulics

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

  14. Heat Transfer of Nanofluid in a Double Pipe Heat Exchanger

    Aghayari, Reza; Maddah, Heydar; Zarei, Malihe; Dehghani, Mehdi; Kaskari Mahalle, Sahar Ghanbari

    2014-01-01

    This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (?-AL2O3) with a particle size of 20?nm and volume fraction of 0.1%0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations s...

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

    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.

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

    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)

  17. Heat exchanger fouling and corrosion

    Fouling of heat transfer surfaces introduces perhaps the major uncertainty into the design and operation of heat exchange equipment. After a brief description of the various types of fouling the chapter goes on to review the current theories of fouling including the turbulent burst theory. Fouling in equipment involving boiling and evaporation is often more severe than in single phase heat exchangers and moreover, in aqueous systems, is frequently associated with corrosion. The reasons for this are identified and illustrated by reference to corrosion in nuclear power plant steam generators. Finally the modification of heat transfer and pressure drop characteristics by fouling layers is briefly reviewed

  18. Heat exchanger with auxiliary cooling system

    The object is to provide a heat exchanger with a reliable simple auxiliary cooling mechanism capable of cooling a nuclear reactor without impeding the flow of the reactor coolant during normal operation. Diagrams and full operating details are given. The invention is of a heat exchanger comprising a vertical cylindrical housing with heat transfer tubes mounted in the housing, a secondary coolant inlet and outlet means for conducting a secondary coolant at one temperature through the heat transfer tubes and primary coolant inlet and outlet means for conducting a primary coolant at another temperature through a primary coolant space in the enclosure around and in heat transfer relationship with the heat transfer tubes. There is auxiliary cooling in an annular chamber formed around, and partly defined by, the housing which has openings at the top and bottom of the annular chamber to allow cooling of the primary coolant space by convection during breakdown or shutdown of the primary coolant circulation. (UK)

  19. Approximate Model of Viscous and Squeeze-film Damping Ratios of Heat Exchanger Tubes Subjected to Two-Phase Cross-Flow

    Sim, Woo Gun [Hannam University, Daejeon (Korea, Republic of)

    2015-01-15

    An analytical model was developed to estimate the viscous and squeeze-film damping ratios of heat exchanger tubes subjected to a two-phase cross-flow. Damping information is required to analyze the flow-induced vibration problem for heat exchange tubes. In heat exchange tubes, the most important energy dissipation mechanisms are related to the dynamic interaction between structures such as the tube and support and the liquid. The present model was formulated considering the added mass coefficient, based on an approximate model by Sim (1997). An approximate analytical method was developed to estimate the hydrodynamic forces acting on an oscillating inner cylinder with a concentric annulus. The forces, including the damping force, were calculated using two models developed for relatively high and low oscillatory Reynolds numbers, respectively. The equivalent diameters for the tube bundles and tube support, and the penetration depth, are important parameters to calculate the viscous damping force acting on tube bundles and the squeeze-film damping forces on the tube support, respectively. To calculate the void fraction of a two-phase flow, a homogeneous model was used. To verify the present model, the analytical results were compared to the results given by existing theories. It was found that the present model was applicable to estimate the viscous damping ratio and squeeze-film damping ratio.

  20. Approximate Model of Viscous and Squeeze-film Damping Ratios of Heat Exchanger Tubes Subjected to Two-Phase Cross-Flow

    An analytical model was developed to estimate the viscous and squeeze-film damping ratios of heat exchanger tubes subjected to a two-phase cross-flow. Damping information is required to analyze the flow-induced vibration problem for heat exchange tubes. In heat exchange tubes, the most important energy dissipation mechanisms are related to the dynamic interaction between structures such as the tube and support and the liquid. The present model was formulated considering the added mass coefficient, based on an approximate model by Sim (1997). An approximate analytical method was developed to estimate the hydrodynamic forces acting on an oscillating inner cylinder with a concentric annulus. The forces, including the damping force, were calculated using two models developed for relatively high and low oscillatory Reynolds numbers, respectively. The equivalent diameters for the tube bundles and tube support, and the penetration depth, are important parameters to calculate the viscous damping force acting on tube bundles and the squeeze-film damping forces on the tube support, respectively. To calculate the void fraction of a two-phase flow, a homogeneous model was used. To verify the present model, the analytical results were compared to the results given by existing theories. It was found that the present model was applicable to estimate the viscous damping ratio and squeeze-film damping ratio

  1. A heat exchanger computational procedure for temperature-dependent fouling

    Chiappetta, L. M.; Szetela, E. J.

    1981-01-01

    A novel heat exchanger computational procedure is described which provides a means of rapidly calculating the distributions of fluid and wall temperatures, deposit formation, and pressure loss at various points in a heat exchanger. The procedure is unique in that it is capable of treating wide variations in heat exchanger geometry without recourse to restrictive assumptions concerning heat exchanger type (e.g., co-flow, counterflow, cross flow devices, etc.). The analysis has been used extensively to predict the performance of cross-counterflow heat exchangers in which one fluid behaves as a perfect gas (e.g., air) while the other fluid is assumed to be a distillate fuel. The model has been extended to include the effects on heat exchanger performance of time varying inflow conditions. Heat exchanger performance degradation due to deposit formation with time can be simulated, making this procedure useful in predicting the effects of temperature-dependent fouling.

  2. The dry heat exchanger calorimeter system

    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

  3. Thermal hydraulic simulation of moderator heat exchanger

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

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

    P. Raveendiran; SIVARAMAN B

    2015-01-01

    The heat transfer coefficients and friction factors of a baffled shell and heat pipe heat exchanger with various inclination angles were determined experimentally; using methanol as working fluid and water as heat transport fluid were reported. Heat pipe heat exchanger reported in this investigation have inclination angles varied between 15o and 60o for different mass flow rates and temperature at the shell side of the heat exchanger. All the required parameters like outlet temperature of bot...

  5. Condensation and frost formation in heat exchangers

    The occurence of condensation and of frost formation are considered for air to heat exchangers with emphasis on how such occurrences would affect the performance of such heat exchangers when they are used in ventilating applications. The formulations which predict performance are developed for parallel, counter flow and cross flow with either formation or condensation, and for condensation the consequences for evaporation of condensate and of the effect of longitudinal conduction in the walls of the exchanger are also considered. For the prediction of the exchanger performance with frost formation there must be specified the growth of the frost layer with time and existing theories for this growth are examined, a new method of calculation of the growth is presented and this is shown to give results for the growth that are in accord with available experimental evidence. This new theory for the growth of a frost layer is used to predict the performance of a parallel flow exchanger under conditions in which frost formation occurs, by successively applying the steady state performance calculation for time increments over which the frost layer build-up is calculated for these time increments. The calculation of counter flow exchanger performance by this method, while feasible, is so time consuming that only the general aspects of the calculation are considered

  6. Multidimensional numerical modeling of heat exchangers

    Sha, W. T.; Yang, C. I.; Kao, T. T.; Cho, S. M.

    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).

  7. Multidimensional numerical modeling of heat exchangers

    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)

  8. Fluidised bed heat exchangers

    Problems that have arisen during the initial stages of development of fluidised bed boilers in which heat transfer surfaces are immersed in fluidised solids are discussed. The very high heat transfer coefficients that are obtained under these conditions can be exploited to reduce the total heat transfer surface to a fraction of that in normal boilers. However, with the high heat flux levels involved, tube stressing becomes more important and it is advantageous to use smaller diameter tubes. One of the initial problems was that the pumping power absorbed by the fluidised bed appeared to be high. The relative influence of the fluidising velocity (and the corresponding bed area), tube diameter, tube spacing, heat transfer coefficient and bed temperature on pumping power and overall cost was determined. This showed the importance of close tube packing and research was undertaken to see if this would adversely affect the heat transfer coefficient. Pressure operation also reduces the pumping power. Fouling and corrosion tests in beds burning coal suggest that higher temperatures could be reached reliably and cost studies show that, provided the better refractory metals are used, the cost of achieving higher temperatures is not unduly high. It now remains to demonstrate at large scale that the proposed systems are viable and that the methods incorporated to overcome start up and part lead running problems are satisfactory. The promising role of these heat transfer techniques in other applications is briefly discussed

  9. Numerical modeling of the aerodynamics, heat exchange, and combustion of a polydisperse ensemble of coke-ash particles in ascending axisymmetric two-phase flow

    B.B. Rokhman [National Academy of Sciences of Ukraine, Kiev (Ukraine). Institute of Coal Power Technologies

    2009-07-15

    A two-dimensional stationary model of motion, heat and mass exchange, and chemical reaction of polydisperse coke and ash particles in ascending gas-suspension flow has been constructed with allowance for the turbulent and pseudo turbulent mechanisms of transfer in the dispersed phase. The system of equations that describes motion and heat transfer in the solid phase has been closed at the level of the equations for the second moments of velocity and temperature pulsations, whereas the momentum equations of the carrying medium have been closed using the equation for turbulent gas energy, which allows for the influence of the particles and heterogeneous reactions.

  10. Heat exchanger and related methods

    Turner, Terry D.; McKellar, Michael G.

    2015-12-22

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

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

    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

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

    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. Heat transfer enhancement in heat exchangers by longitudinal vortex generators

    In this paper heat transfer enhancement and flow losses are computed for the interaction of a laminar channel flow with a pair of counterrotating longitudinal vortices generated by a pair of delta-winglets punched out of the channel wall. The geometry simulates an element of a fin-plate or fin-tube heat exchanger. The structure of the vortex flow and temperature distribution, the local heat transfer coefficients and the local flow losses are discussed for a sample case. For a Reynolds number of Red = 1000 and a vortex generator angle of attack of β = 25 degrees heat transfer is enhanced locally by more than 300% and in the mean by 50%. These values increase further with Re and β

  14. Heat Transfer Enhancement of Shell and Tube Heat Exchanger Using Conical Tapes.

    Dhanraj S.Pimple; Shreeshail.B.H; Amar Kulkarni

    2014-01-01

    This paper provides heat transfer and friction factor data for single -phase flow in a shell and tube heat exchanger fitted with a helical tape insert. In the double concentric tube heat exchanger, hot air was passed through the inner tube while the cold water was flowed through the annulus. The influences of the helical insert on heat transfer rate and friction factor were studied for counter flow, and Nusselt numbers and friction factor obtained were compared with previous data ...

  15. Thermal hydraulic analysis for the design of intermediate heat exchanger

    Prototype Fast Breeder Reactor (PFBR) is a sodium cooled reactor with 500MWe(1210MWt) capacity. Nuclear heat generated in the core is transferred to primary sodium flowing through the subassemblies. The hot primary sodium exchanges heat with secondary sodium through intermediate heat exchangers. A two dimensional analysis of the intermediate heat exchanger has clearly brought out the high values of radial temperature drop of primary and secondary sodium streams when the secondary flow is uniform. A solution of unequal secondary flow has proved to be an effective method to reduce the temperature drops leading to a safer design. (author). 7 refs., 5 figs

  16. Heat exchanger including an auxiliary cooling system

    It comprises a vertical envelope, heat transfer tubes mainted in this envelope, inlet and outlet windows for a primary coolant flowing between the tubes and inlet and outlet collectors to make the secondary coolant circulate inside the tubes, and an auxiliary cooling system situated in the inlet window, inside a shell. This shell is opened at its upper part and connected to the heat exchanger envelope at its lower part. This system cools the primary coolant when it is not in forced circulation, what creates a natural circulation of this primary coolant to the bottom. The invention can be applied to fast nuclear reactors cooled by sodium. This heat exchanger extracts the heat produced by the core operating normally, and besides, the residual power in case of pump shutdown reactor accident

  17. Carbon nanotube heat-exchange systems

    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).

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

    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.

  19. Tube-in-shell heat exchangers

    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.)

  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

    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. Preliminary Studies of S-CO{sub 2} Critical Flow for Leak Modeling in Sodium-CO{sub 2} Heat Exchanger

    Jung, Hwa-Young; Go, A-Reum; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Wi, Myung-Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    The amount of chemical reaction between sodium and CO{sub 2} will vary depending on several factors; the crack or rupture size, the interfacial area between sodium and CO{sub 2}, the amount of released CO{sub 2}, and so on. These factors are as influential as the reaction temperature of Na-CO{sub 2} interaction. To specify these factors, it is important to predict the CO{sub 2} leak mechanism during the CO{sub 2} leakage. However, only limited number of studies has been performed for understanding the CO{sub 2} leak mechanism. sodium to supercritical CO{sub 2} heat exchanger, an isentropic critical flow model was developed. Based on a simple flow model a preliminary numerical study was carried out by including simplified Na-CO{sub 2} reaction. However, friction between CO{sub 2} and crack wall should be considered to simulate more realistic CO{sub 2} critical flow, which represents more realistic situation. Thus, the Fanno flow, which considers friction in a compressible flow, will replace the isentropic flow model for better predictability. If this model can reasonably simulate the transient response of the CO{sub 2} leak scenario, several physical models will be added to the current analysis; real gas model, Na-CO{sub 2} interaction, two-phase model for liquid sodium and gaseous CO{sub 2}, heat transport in the sodium tank, and so on.

  2. Heat exchanger staybolt acceptance criteria

    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

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

    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...

  4. Rotationally symmetrical ceramic heat exchanger with axial direct flow for application in high-temperature processes. Rotationssymmetrischer axial durchstroembarer keramischer Waermetauscher zum Einsatz in Hochtemperaturprozessen

    Bittner, H.G. (Heimsoth Keramische Oefen GmbH, Hildesheim (Germany). Abt. Forschung und Entwicklung Wistra Thermoprozesstechnik, Duesseldorf (Germany)); Weber, H.; Berroth, K.; Binder, O.

    1993-10-01

    In this paper, a newly developed, finely structured, rotationally symmetrical ceramic heat exchanger ring made of SiSiC with a large specific heat exchanger surface is presented - it is produced by means of a new ceramic slip-casting process derived from the precision casting process for metals. With its very good corrosion resistance even at high temperatures, its oxidation and erosion resistance as well as excellent thermal conductivity, the heat exchanger ring is suitable for applications in corrosive atmospheres involving liquid/liquid, liquid/gas and gas/gas heat exchangers as well as high-temperature process applications. The advantage of such heat exchangers is their direct installation in pipes. Temperature measurements of a heat exchanger system made of such heat exchanger rings are compared with simplified calculations. These heat exchanger rings are particularly applicable to use in fully ceramic recuperator burners and as heat exchanger in pipes. Preheating of air up to 1000 C at waste gas temperatures of 1220 C is possible with a heat exchanger system made up of such rings, whereby a relative fuel savings of approximately 42% can be achieved in comparison to an operation mode without preheating of air. (orig.)

  5. Heat exchangers and methods of construction thereof

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

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

    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

  7. Tubular heat exchanger, for nuclear installations

    The description is given of a heat exchanger comprising an elongated heat exchanger module suitable for group mounting with other similar modules. The module includes a long casing having a hexagonal cross section configuration to make it easy to group together a set of modules in an appreciably continuous set. A set of thermally conducting tubes is arranged in the casing and extends through its entire length. An intake collector is fitted to one end of the casing and communicates with one end of the tubes and an outlet collector is fitted to the other end of the casing and communicates with the other end of the tubes, a fluid passage being made inside the casing for the flow of primary fluid through it around the thermally conducting tubes. The intake and outlet collectors are each fitted for their respective coupling to an intake manifold and an outlet manifold for the flow of a primary fluid through the tubes in the casing

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

    M. V. Ghori

    2012-08-01

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

  9. A study on the heat transfer development of heat exchanger with vortex generator

    A numerical analysis using FLUENT code was carried out to investigate flow characteristics and heat transfer development of heat exchangers. The analysis results for both cases of the fin-circular tube and the fin-flat tube heat exchanger with the vortex generator show relatively higher heat transfer coefficient than that for both cases of the fin-circular tube and the fin-flat tube heat exchangers without the vortex generator. Also, the analysis result for the fin-circular tube heat exchanger with the vortex generator has relatively higher heat transfer coefficient and higher pressure loss than those for the fin-flat tube heat exchanger with the vortex generator. The results of this study can be used to design the heat exchanger with relatively low pressure loss and maximum heat transfer coefficient. 28 figs., 15 refs. (Author) .new

  10. Heat and fluid flow characteristics of an oval fin-and-tube heat exchanger with large diameters for textile machine dryer

    Bae, Kyung Jin; Cha, Dong An; Kwon, Oh Kyung

    2016-01-01

    The objectives of this paper are to develop correlations between heat transfer and pressure drop for oval finned-tube heat exchanger with large diameters (larger than 20 mm) used in a textile machine dryer. Numerical tests using ANSYS CFX are performed for four different parameters; tube size, fin pitch, transverse tube pitch and longitudinal tube pitch. The numerical results showed that the Nusselt number and the friction factor are in a range of -16.2 ~ +3.1 to -7.7 ~ +3.9 %, respectively, compared with experimental results. It was found that the Nusselt number linearly increased with increasing Reynolds number, but the friction factor slightly decreased with increasing Reynolds number. It was also found that the variation of longitudinal tube pitch has little effect on the Nusselt number and friction factor than other parameters (below 2.0 and 2.5 %, respectively). This study proposed a new Nusselt number and friction factor correlation of the oval finned-tube heat exchanger with large diameters for textile machine dryer.

  11. Heat flow of Oregon

    Blackwell, D.D.; Hull, D.A.; Bowen, R.G.; Steele, J.L.

    1978-01-01

    An extensive new heat flow and geothermal gradient data set for the State of Oregon is presented on a contour map of heat flow at a scale of 1:1,000,000 and is summarized in several figures and tables. The 1:1,000,000 scale heat flow map is contoured at 20 mW/m/sup 2/ (0.5 HFU) intervals. Also presented are maps of heat flow and temperature at a depth of 1 km averaged for 1/sup 0/ x 1/sup 0/ intervals. Histograms and averages of geothermal gradient and heat flow for the State of Oregon and for the various physiographic provinces within Oregon are also included. The unweighted mean flow for Oregon is 81.3 +- 2.7 mW/m/sup 2/ (1.94 +- 0.06 HFU). The average unweighted geothermal gradient is 65.3 +- 2.5/sup 0/C/km. The average heat flow value weighted on the basis of geographic area is 68 +- 5 mW/m/sup 2/ (1.63 +- 0.12 HFU) and the average weighted geothermal gradient is 55.0 +- 5/sup 0/C/km.

  12. Oil Circulation Effects on Evaporation Heat Transfer in Brazed Plate Heat Exchanger using R134A

    Jang, Jaekyoo; Chang, Youngsoo; Kang, Byungha

    2012-01-01

    Experimental study was performed for oil circulation effects on evaporation heat transfer in the brazed type plate heat exchangers using R134A. In this study, distribution device was installed to ensure uniform flow distribution in the refrigerant flow passage, which enhances heat transfer performance of plate type heat exchanger. Tests were conducted for three evaporation temperature; 33℃, 37℃, and 41℃ and several oil circulation conditions. The nominal conditions of refrigerant are as follo...

  13. Heat exchanges in coarsening systems

    This paper is a contribution to the understanding of the thermal properties of ageing systems where statistically independent degrees of freedom with greatly separated time scales are expected to coexist. Focusing on the prototypical case of quenched ferromagnets, where fast and slow modes can be respectively associated with fluctuations in the bulk of the coarsening domains and in their interfaces, we perform a set of numerical experiments specifically designed to compute the heat exchanges between different degrees of freedom. Our studies promote a scenario with fast modes acting as an equilibrium reservoir to which interfaces may release heat through a mechanism that allows fast and slow degrees to maintain their statistical properties independently

  14. Fluidelastic instability in heat exchanger tube arrays and a Galerkin-free model reduction of multiphysics systems

    Shinde, Vilas

    2015-01-01

    Heat exchangers are widely used in the power generation industries. The cross-flow type of heat exchangers are more common. The rate of heat transfer is enhanced by operating the heat exchangers at higher flow rates by means of the increased flow turbulence. Although, the high flow rate operations are favoured, there are side effects in terms of the flow-induced vibrations. In the last few decades, the topic (flow induced vibrations in heat exchanger tube bundles) is studied extensively, espe...

  15. Soil Heat Flow Model

    Varas, E.; Nunez, C.; Meza, F. J.

    2008-12-01

    The Penman-Monteith method for estimating evapotranspiration (ET) has been recommended by FAO. This method requires measures of temperature, wind speed, relative humidity and heat flow in the soil. This last variable is rarely available. Soil heat flow is generally small compared to the net radiation, and many times is ignored in the energy balance. Nevertheless, the addition or subtraction of this amount in the energy balance equation should be considered for evapo-transpiration calculation. Penman-Monteith method suggests approximate estimates of soil heat flows as the difference between the maxima and minimum daily temperatures multiplied by a convenient coefficient. However, such approach ignores important variations in this parameter occurring during the day, and could influence the accuracy of the result. This work proposes to estimate soil heat flows by means of a mathematical model that includes the estimate of soil temperatures profiles and heat flows as a function of thermal properties of the soil, such as difussivity and conductivity coefficients. The model calculates soil heat flows in three stages. The first estimates hourly air temperature based on the average daily temperature and Fourier series coefficients. The obtained hourly air temperature constitutes an input variable for the second stage of the model. Surface soil temperature is assumed to be equal to air temperature. The second stage, applies heat transfer principles, using the thermal properties of the soil in order to obtain the soil temperature profile in a one meter depth soil stratum. Finally, the results of the second stage are used to calculate the hourly heat flow in the soil and compare this estimate with other methods and with measured values. Calculated hourly temperatures reproduced observed values closely. Correlation coefficients between observed and calculated values for the three summer months are 0.98, 0.96 and 0.97. Hourly soil heat fluxes are also closely estimated, showing clear diurnal variations. Correlation coefficient for the entire study period between observed and estimated values is 0.96.

  16. A lumped parameter, low dimension model of heat exchanger

    This paper reports on the results of investigation of the distributed parameter model, the difference model, and the model of the method of weighted residuals for heat exchangers. By the method of weighted residuals (MWR), the opposite flow heat exchanger system is approximated by low dimension, lumped parameter model. By assuming constant specific heat, constant density, the same form of tube cross-section, the same form of the surface of heat exchange, uniform flow velocity, the linear relation of heat transfer to flow velocity, liquid heat carrier, and the thermal insulation of liquid from outside, fundamental equations are obtained. The experimental apparatus was made of acrylic resin. The response of the temperature at the exit of first liquid to the variation of the flow rate of second liquid was measured and compared with the models. The MWR model shows good approximation for the low frequency region, and as the number of division increases, good approximation spreads to higher frequency region. (Kato, T.)

  17. 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

    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.

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

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

    1999-01-01

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

  19. Performance of heat pumps with direct expansion in vertical ground heat exchangers in heating mode

    Highlights: • The work focuses on direct expansion ground source heat pumps in heating mode. • The evaporating process of the refrigerant fluid into boreholes is analyzed. • A method to design the direct expansion borehole heat exchangers is presented. • Direct expansion and the common secondary loop heat pumps are compared. • The comparison is carried out in terms of both borehole length and performance. - Abstract: Ground source heat pump systems represent an interesting example of renewable energy technology for heating and cooling of buildings. The connection with the ground is usually done by means of a closed loop where a heat-carrier fluid (pure water or a solution of antifreeze and water) flows and, in heating mode, moves heat from ground to refrigerant fluid of heat pump. A new solution is the direct expansion heat pump. In this case, the heat-carrier fluid inside the ground loop is the same refrigerant fluid of heat pump. This paper focuses on the energy performance of direct expansion ground source heat pump with borehole heat exchangers in heating mode, looking at residential building installations. For this purpose, the evaporating process of the refrigerant fluid inside vertical tubes is investigated in order to analyze the influence of the convective heat transfer coefficient on the global heat transfer with the surrounding ground. Then, an analytical model reported in literature for the design of common borehole heat exchangers has been modified for direct expansion systems. Finally, the direct expansion and common ground source heat pumps have been compared in terms of both total borehole length and thermal performance. Results indicate that the direct expansion system has higher energy performance and requires lower total borehole length compared to the common system. However, when the two systems are compared with the same mean fluid evaporating temperature, the overall length of the ground heat exchanger of the direct expansion heat pump is greater than that of the common system

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

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

  1. Predicting particle deposition on HVAC heat exchangers

    Siegel, Jeffrey A.; Nazaroff, William W.

    Particles in indoor environments may deposit on the surfaces of heat exchangers that are used in heating, ventilation and air conditioning (HVAC) systems. Such deposits can lead to performance degradation and indoor air quality problems. We present a model of fin-and-tube heat-exchanger fouling that deterministically simulates particle impaction, gravitational settling, and Brownian diffusion and uses a Monte Carlo simulation to account for impaction due to air turbulence. The model predicts that heat exchangers with air flows and fin spacings that are typical of HVAC systems. For supermicron particles, deposition increases with particle size. The dominant deposition mechanism for 1-10 μm particles is impaction on fin edges. Gravitational settling, impaction, and air turbulence contribute to deposition for particles larger than 10 μm. Gravitational settling is the dominant deposition mechanism for lower air velocities, and impaction on refrigerant tubes is dominant for higher velocities. We measured deposition fractions for 1-16 μm particles at three characteristic air velocities. On average, the measured results show more deposition than the model predicts for an air speed of 1.5 m s -1. The amount that the model underpredicts the measured data increases at higher velocities and especially for larger particles, although the model shows good qualitative agreement with the measured deposition fractions. Discontinuities in the heat-exchanger fins are hypothesized to be responsible for the increase in measured deposition. The model and experiments reported here are for isothermal conditions and do not address the potentially important effects of heat transfer and water phase change on deposition.

  2. The Experimental Study on Heat Transfer Characteristics of The External Heat Exchanger

    Ji, X. Y.; Lu, X. F.; Yang, L.; Liu, H. Z.

    Using the external heat exchanger in large-scale CFB boilers can control combustion and heat transfer separately, make the adjustments of bed temperature and steam temperature convenient. The state of gas-solid two phase flow in the external heat exchanger is bubbling fluidized bed, but differs from the regular one as there is a directional flow in it. Consequently, the temperature distribution changes along the flow direction. In order to study the heat transfer characteristics of the water cooled tubes in the bubbling fluidized bed and ensure the uniformity of heat transfer in the external heat exchanger, a physical model was set up according to the similarity principle and at the geometric ratio of 1?28 to an external heat exchanger of a 300MW CFB boiler. The model was connected with an electrically heated CFB test-bed which provides the circulating particles. The influencing factors and the distribution rule of the particles' heat transfer coefficient in the external heat exchanger were assessed by measuring the temperature changes of the water in the tubes and different parts of particles flow along the flow direction. At the end, an empirical correlation of particles' heat transfer coefficient in external heat exchanger was given by modifying the Veedendery empirical correlation.

  3. Preliminary SP-100/Stirling heat exchanger designs

    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

  4. Multidimensional numerical modeling of heat exchanges

    A comprehensive, multidimensional, thermal-hydraulic model is developed for the analysis of shell-and-tube heat exchanges 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 premeability 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, 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-phased on the shell side and may undergo phase-change in the tube side, thereby simulating the conditions of Liquid Metal Fast Breeder Reaction (LMFBR) intermediate heat exchanges (IHX) and steam generators (SG). The analytical model predictions are compared with three sets of test data (one for IHX and two for SG) and favorable results are obtained, thus providing a limited validation of the model

  5. ANALYSIS OF HELICAL BAFFLE HEAT EXCHANGER FOR OPTIMUM HELIX ANGLE THROUGH NUMERICAL SIMULATIONS

    Roktutpal Borah; R.K Chitharthan

    2015-01-01

    Heat exchangers are very important heat & mass exchange apparatus in many industries like electric power generation, chemical industries, oil refining, etc. The most common heat exchangers used are shell-&-tube heat exchangers (STHXs). Among different kinds of baffles used in STHX, segmental baffles are most commonly used in conventional STHXs to support tubes & change fluid flow direction. But, conventional heat exchangers with segmental baffles in shell-side have some drawbacks ...

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

    Lin, Wamei

    2014-01-01

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

  7. Exergy optimization in a steady moving bed heat exchanger

    Soria-Verdugo, Antonio; Almendros-Ibáñez, José Antonio; Ruiz-Rivas, Ulpiano; Santana Santana, Domingo José

    2007-01-01

    This work provides an exergy analysis of a moving bed heat exchanger to obtain for a range of incoming fluid flow rates the operational optimum and the incidence on it of the relevant parameters such as the dimensions of the exchanger, the particle diameter and the flow rate of the fluid. The MBHE proposed can be analyzed as a cross flow heat exchanger where one of the phases is a moving granular medium. In the present work the exergy analysis of the MBHE is carried out o...

  8. HEAT EXCHANGE IN SLOT-HOLE RECUPERATORS

    Rovin, L. E.; L. N. Rusaja

    2015-01-01

    At calculation of slot heat exchangers it is necessary to take into account the additional stream of heat transferred by emission from internal wall to an external one and further distributed between heated air and environment.

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

    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.

  10. Heat exchanger thermal insulation system

    The heat exchanger insulation system described includes an outer ring, a bundle of circulation tubes connected at their ends to a tube plate and comprising a coaxial cylindrical sleeve around each tube with play along a part of its length near the ends connected to the tube plate. The sleeves are suspended by their upper ends to a perforated plate with holes into which the sleeves fit, the perforated plate being fixed to a ring fitted by its base to the tube plate by means of tie rods between the tube plate and the perforated plate. This system has been particularly designed for liquid sodium cooled reactors

  11. Optimum geometry of MEMS heat exchanger for heat transfer enhancement

    Nusrat J. Chhanda; Muhannad Mustafa; Maglub Al Nur

    2010-01-01

    The study is based on an analysis of MEMS heat exchanger of three different geometries: wavy, triangular and rectangular using water as test fluid. The problem is solved using finite element method. The aim of this analysis is to evaluate the performance of MEMS heat exchanger for different geometry and to obtain an optimum design for better heat enhancement. It is apparent from this work that rectangular surface heat exchanger shows the best performance for heat enhancement technique in comp...

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

    Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson

    2008-09-01

    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 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.

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

    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 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

  14. Microchannel Heat Exchangers with Carbon Dioxide

    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.

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

    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.

  16. Improved ceramic heat exchange material

    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.

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

    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)

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

    Novosd Jan; Dvo?k Vclav

    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...

  19. Fluidelastic instability of heat exchanger tube bundles

    This paper reports that fluidelastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to cross-flow. Most of the available data on this topic have been reviewed from the perspective of the designer. Uniform definitions of critical flow velocity for instability, damping, natural frequency and hydrodynamic mass were used. Nearly 300 data points were assembled. The authors found that only data from experiments where all tubes are free to vibrate are valid form a design point of view. In liquids, fluid damping is important and should be considered in the formulation of fluidelastic instability. From a practical design point of view, we conclude that fluidelastic instability may be expressed simply in term of dimensionless flow velocity and dimensionless mass-damping. There is no advantage in considering more sophisticated models at this time. Practical design guidelines are discussed

  20. Design of a liquid metals heat exchanger

    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)

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

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

  2. Heat exchanger device; Anordning ved varmevekslere

    Christiansen, P.E.; Borgaas, B.

    1997-04-16

    The invention relates to a heat exchanger device comprising a first heat exchanger for evaporation of liquid natural gas (LNG), and a second heat exchanger for superheating of gaseous natural gas (NG). The heat exchangers are arranged for heating these fluids by means of a heating medium and have an outlet which is connected to a mixing device for mixing the heat fluids with the corresponding unheated fluids. According to the invention, the heat exchangers comprise a common housing, in which there are provided separate passages for the fluids. The mixing device constitutes a unit together with the housing and has a single mixing chamber with one single fluid outlet. In separate passages, there are provided valves and respectively for the supply of LNG or NG in the housing and the mixing chamber. 1 fig.

  3. Hydrothermic behaviour of intermediate heat exchangers in a pool-type fast breeder reactor

    Flow distribution (primary and secondary sodium flows) and heat transfer calculations (tube side convection, cross and parallel primary flow). Analysis and design of heat exchanger bundles configuration in relation with the experimental results and computation calculations. Application of computations to the Phenix intermediate heat exchanger

  4. CFD simulation of air to air enthalpy heat exchanger

    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

  5. Performance of a shell-and-tube heat exchanger with spiral baffle plates

    In a conventional shell-and-tube heat exchanger, fluid contacts with tubes flowing up and down in a shell, therefore there is a defect in the heat transfer with tubes due to the stagnation portions. Fins are attached to the tubes in order to increase heat transfer efficiency, but there exists a limit. Therefore, it is necessary to improve heat exchanger performance by changing the fluid flow in the shell. In this study, a highly efficient shell-and-tube heat exchanger with spiral baffle plates is simulated three-dimensionally using a commercial thermal-fluid analysis code, CFX4.2. In this type of heat exchanger, fluid contacts with tubes flowing rotationally in the shell. It could improve heat exchanger performance considerably because stagnation portions in the shell could be removed. It is proved that the shell-and-tube heat exchanger with spiral baffle plates is superior to the conventional heat exchanger in terms of heat transfer

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

    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.

  7. Heat exchangers in regenerative gas turbine cycles

    Nina, M. N. R.; Aguas, M. P. N.

    1985-09-01

    Advances in compact heat exchanger design and fabrication together with fuel cost rises continuously improve the attractability of regenerative gas turbine helicopter engines. In this study cycle parameters aiming at reduced specific fuel consumption and increased payload or mission range, have been optimized together with heat exchanger type and size. The discussion is based on a typical mission for an attack helicopter in the 900 kw power class. A range of heat exchangers is studied to define the most favorable geometry in terms of lower fuel consumption and minimum engine plus fuel weight. Heat exchanger volume, frontal area ratio and pressure drop effect on cycle efficiency are considered.

  8. 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,...

  9. Heat exchangers in heavy water reactor systems

    Important features of some major heat exchange components of pressurized heavy water reactors and DHRUVA research reactor are presented. Design considerations and nuclear service classifications are discussed

  10. The role of sealing strips in tubular heat exchangers

    Tubular-type heat exchangers contain both baffle plates and sealing strips. The baffles force the flow to pass normal to the axes of the tubes and they serve to support the tubes. In order to facilitate assembly of the heat exchanger, a space exists between the tube bundle and the retaining shell. This space offers a hydraulic short circuit to the fluid, thus reducing the effectiveness of the device to exchange heat. Sealing strips, which are metal strips mounted on the shell and running parallel to the tubes, are introduced to partially block this leakage flow, thereby increasing the effectiveness of the device. The objectives of the research reported here are to experimentally determine the effectiveness of sealing strips, and to investigate the effects of their shape and location. Such results not only supply design information, but they serve to establish the accuracy of computer codes which have been developed for such heat exchangers. (author)

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

    Piotr Yakimychev; Nickolay Yelin; Vadim Mizonov

    2011-01-01

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

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

    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.)

  13. Process for repairing a cryogenic heat exchanger

    The patent describes a method for repairing leakage-causing cracks and fissures in a cryogenic heat exchanger. It comprises: reducing the interior pressure of the heat exchanger to a level which does not exceed the external pressure upon the hear exchanger while maintaining the temperature of the heat exchanger at a low level relative to the ambient external temperature; applying a curable liquid filler composition to the surface of the heat exchanger proximal the leakage site for seepage into the cracks and fissures located at the leakage. The composition upon a relatively short period of cure at low temperature forming a solid material which fills the cracks and fissures; curing the filler composition; and, applying a sealant composition to the surface of the heat exchanger at the filled leakage site. The sealant composition having long-term sealing performance under cyrogenic conditions

  14. RIBBED DOUBLE PIPE HEAT EXCHANGER: ANALYTICAL ANALYSIS

    HUSSAIN H. AL-KAYIEM

    2011-02-01

    Full Text Available This paper presents the findings obtained by modeling a Double Pipe Heat Exchanger (DPHE equipped with repeated ribs from the inside for artificial roughing. An analytical procedure was developed to analyze the thermal and hydraulic performance of the DPHE with and without ribbing. The procedure was verified by comparing with experimental reported results and they are in good agreement. Several parameters were investigated in this study including the effect of ribs pitch to height ratios, P/e= 5, 10, 15, and 20, and ribs to hydraulic diameter ratios, e/Dh= 0.0595, 0.0765, and 0.107. These parameters were studied at various operating Reynolds number ranging from 2500 to 150000. Different installation configurations were investigated, too. An enhan-cement of 4 times in the heat transfer in terms of Stanton number was achieved at the expense of 38 times increase of pressure drop across the flow in terms of friction facto values.

  15. Microbial fouling control in heat exchangers

    Biofilm formation in turbulent flow has been studied a great deal during the last 15 years. Such studies have provided the basis for further experiments designed to test the efficacy of industrial antimicrobials against biofilms in laboratory models and in actual real-world industrial water-treatment programs. Biofilm microbiology is relevant from the industrial perspective because adherent populations of microorganisms often cause an economic impact on industrial processes. For example, it is the adherent population of microorganisms in cooling-water systems that can eventually contribute to significant heat transfer and fluid frictional resistances. The microbiology of biofilms in heat exchangers can be related to the performance of industrial antimicrobials. The development of fouling biofilms and methods to quantitatively observe the effect of biofouling control agents are discussed in this paper

  16. Studies on a heat exchanger producting subcooled liquid helium

    A heat exchanger for cooling the TRISTAN final focusing superconducting quadrupole magnet was studied. This heat exchanger could produce subcooled liquid helium of 20 g/s and 0. 16 MPa below 4.4 K with saturated liquid helium at 0.11 MPa. For the heat transfer of single phase flow in the heat exchanger, the calculations with the Dittus-Boelter and Kutateladze equations agreed well with the measurements. For the heat transfer during the condensation process, the Shah equation including vapor quality was applied. The calculated heat transfer energy was twice as large as the measured value and the vapor effect on the heat transfer coefficient was not as large as that calculated by the Shah equation

  17. An assessment of in-tube flow boiling correlations for ammonia-water mixtures and their influence on heat exchanger size

    Kærn, Martin Ryhl; Modi, Anish; Jensen, Jonas Kjær; Andreasen, Jesper Graa; Haglind, Fredrik

    2016-01-01

    Heat transfer correlations for pool and flow boiling are indispensable for boiler design. The correlations for predicting in-tube flow boiling heat transfer ofammonia-water mixtures are not well established in the open literature and there is a lack of experimental measurements for the full range...

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

    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

  19. Design of heat exchangers by numerical methods

    Differential equations describing the heat tranfer in shell - and tube heat exchangers are derived and solved numerically. The method of ΔT 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 ΔT 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)

  20. Handbook for heat exchangers and tube banks design

    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.

  1. Heat exchanger network retrofit optimization involving heat transfer enhancement

    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.

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

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

  3. Optimization of parameters of heat exchangers vehicles

    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.

  4. Internal heat transfer and pressure drop measurements in a variously baffled shell and tube heat exchanger

    Galindo, P.

    1984-06-01

    Heat transfer coefficients, pressure distributions, and fluid flow patterns on the shell side of shell and tube heat exchangers are discussed. The main focus was to quantify the effect of the size of the baffle window on the heat transfer coefficient, which was measured at each tube in the bundle and at three Reynolds numbers. Pressure drops were obtained by measuring detailed pressure distributions within the exchangers. The flow visualizations provided fluid flow patterns adjacent to the shell wall, to the baffle plates, and at each tube of the array. Performance comparisons among the exchangers were carried out holding the heat transfer surface area fixed together with either the pumping power, the mass flow rate, or the pressure drop. Numerical evaluations of commonly employed design procedures are presented using the present data as a means for rank ordering their validity. Tinker's design method provided the best predictions of the present heat transfer and pressure drop results, which are unaffected by leakage and bypass.

  5. The Development of an INL Capability for High Temperature Flow, Heat Transfer, and Thermal Energy Storage with Applications in Advanced Small Modular Reactors, High Temperature Heat Exchangers, Hybrid Energy Systems, and Dynamic Grid Energy Storage C

    Sun, Xiaodong [The Ohio State Univ., Columbus, OH (United States); Zhang, Xiaoqin [The Ohio State Univ., Columbus, OH (United States); Kim, Inhun [The Ohio State Univ., Columbus, OH (United States); O' Brien, James [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sabharwall, Piyush [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-10-01

    The overall goal of this project is to support Idaho National Laboratory in developing a new advanced high temperature multi fluid multi loop test facility that is aimed at investigating fluid flow and heat transfer, material corrosion, heat exchanger characteristics and instrumentation performance, among others, for nuclear applications. Specifically, preliminary research has been performed at The Ohio State University in the following areas: 1. A review of fluoride molten salts’ characteristics in thermal, corrosive, and compatibility performances. A recommendation for a salt selection is provided. Material candidates for both molten salt and helium flow loop have been identified. 2. A conceptual facility design that satisfies the multi loop (two coolant loops [i.e., fluoride molten salts and helium]) multi purpose (two operation modes [i.e., forced and natural circulation]) requirements. Schematic models are presented. The thermal hydraulic performances in a preliminary printed circuit heat exchanger (PCHE) design have been estimated. 3. An introduction of computational methods and models for pipe heat loss analysis and cases studies. Recommendations on insulation material selection have been provided. 4. An analysis of pipe pressure rating and sizing. Preliminary recommendations on pipe size selection have been provided. 5. A review of molten fluoride salt preparation and chemistry control. An introduction to the experience from the Molten Salt Reactor Experiment at Oak Ridge National Laboratory has been provided. 6. A review of some instruments and components to be used in the facility. Flowmeters and Grayloc connectors have been included. This report primarily presents the conclusions drawn from the extensive review of literatures in material selections and the facility design progress at the current stage. It provides some useful guidelines in insulation material and pipe size selection, as well as an introductory review of facility process and components.

  6. The Development of an INL Capability for High Temperature Flow, Heat Transfer, and Thermal Energy Storage with Applications in Advanced Small Modular Reactors, High Temperature Heat Exchangers, Hybrid Energy Systems, and Dynamic Grid Energy Storage C

    The overall goal of this project is to support Idaho National Laboratory in developing a new advanced high temperature multi fluid multi loop test facility that is aimed at investigating fluid flow and heat transfer, material corrosion, heat exchanger characteristics and instrumentation performance, among others, for nuclear applications. Specifically, preliminary research has been performed at The Ohio State University in the following areas: 1. A review of fluoride molten salts' characteristics in thermal, corrosive, and compatibility performances. A recommendation for a salt selection is provided. Material candidates for both molten salt and helium flow loop have been identified. 2. A conceptual facility design that satisfies the multi loop (two coolant loops [i.e., fluoride molten salts and helium]) multi purpose (two operation modes [i.e., forced and natural circulation]) requirements. Schematic models are presented. The thermal hydraulic performances in a preliminary printed circuit heat exchanger (PCHE) design have been estimated. 3. An introduction of computational methods and models for pipe heat loss analysis and cases studies. Recommendations on insulation material selection have been provided. 4. An analysis of pipe pressure rating and sizing. Preliminary recommendations on pipe size selection have been provided. 5. A review of molten fluoride salt preparation and chemistry control. An introduction to the experience from the Molten Salt Reactor Experiment at Oak Ridge National Laboratory has been provided. 6. A review of some instruments and components to be used in the facility. Flowmeters and Grayloc connectors have been included. This report primarily presents the conclusions drawn from the extensive review of literatures in material selections and the facility design progress at the current stage. It provides some useful guidelines in insulation material and pipe size selection, as well as an introductory review of facility process and components.

  7. Graphite Foam Heat Exchangers for Thermal Management

    Klett, J.W.

    2004-06-07

    Improved thermal management is needed to increase the power density of electronic and more effectively cool electronic enclosures that are envisioned in future aircraft, spacecraft and surface ships. Typically, heat exchanger cores must increase in size to more effectively dissipate increased heat loads, this would be impossible in many cases, thus improved heat exchanger cores will be required. In this Phase I investigation, MRi aimed to demonstrate improved thermal management using graphite foam (Gr-foam) core heat exchangers. The proposed design was to combine Gr-foams from POCO with MRi's innovative low temperature, active metal joining process (S-Bond{trademark}) to bond Gr-foam to aluminum, copper and aluminum/SiC composite faceplates. The results were very favorable, so a Phase II SBIR with the MDA was initiated. This had primarily 5 tasks: (1) bonding, (2) thermal modeling, (3) cooling chip scale packages, (4) evaporative cooling techniques and (5) IGBT cold plate development. The bonding tests showed that the ''reflow'' technique with S-Bond{reg_sign}-220 resulted in the best and most consistent bond. Then, thermal modeling was used to design different chip scale packages and IGBT cold plates. These designs were used to fabricate many finned graphite foam heat sinks specifically for two standard type IC packages, the 423 and 478 pin chips. These results demonstrated several advantages with the foam. First, the heat sinks with the foam were lighter than the copper/aluminum sinks used as standards. The sinks for the 423 design made from foam were not as good as the standard sinks. However, the sinks made from foam for the 478 pin chips were better than the standard heat sinks used today. However, this improvement was marginal (in the 10-20% better regime). However, another important note was that the epoxy bonding technique resulted in heat sinks with similar results as that with the S-bond{reg_sign}, slightly worse than the S-bond{reg_sign}, but still better than the standard heat sinks. Next, work with evaporative cooling techniques, such as heat pipes, demonstrated some unique behavior with the foam that is not seen with standard wick materials. This was that as the thickness of the foam increased, the performance got better, where with standard wick materials, as the thickness increases, the performance decreases. This is yet to be completely explained. Last, the designs from the thermal model were used to fabricate a series of cold plates with the graphite foam and compare them to similar designs using high performance folded fin aluminum sinks (considered standard in the industry). It was shown that by corrugating the foam parallel to fluid flow, the pressure drop can be reduced significantly while maintaining the same heat transfer as that in the folded fin heat sink. In fact, the results show that the graphite foam heat sink can utilized 5% the pumping power as that required with the folded fin aluminum heat sink, yet remove the same amount of heat.

  8. Radiation effects on heat transfer in the reactor core and heat exchangers of an HTGR

    A general and fundamental study of the effect of radiation between duct walls on the heat transfer performance of duct flows of nonradiating gas such as helium is made by an approximate analysis and numerical calculations. Laminar and turbulent flows in a duct simulating a coolant passage in an HTGR and flows in counterflow and parallel-flow heat exchangers in an HTGR heat transfer system are investigated. An approximate analytical solution, based on the assumption that radiation from a point of duct wall produces an effect only on the narrow region opposite the point, agrees well with numerical results. The increase of radiative heat transfer causes a decrease of temperature difference between the duct walls and improves the heat transfer performance. For heat exchangers the heat transfer effectiveness is shown to depend on three nondimensional parameters and can be improved by the increase of these parameters

  9. Heat exchange fluids and techniques. [US patents

    Ranney, M.W.

    1979-01-01

    The detailed, descriptive information presented is based on US patents, issued since January 1975, that deal with heat exchange fluids and techniques, and their potential for energy saving. This book serves a double purpose in that it supplies detailed technical information and can be used as a guide to the US patent literature in this field. By indicating all the information that is significant, and eliminating legal jargon and juristic phraseology, an advanced, technically oriented review of heat exchange fluids and techniques is presented. Information is included on the design and construction of heat exchangers; heat transfer fluids; low temperature processes; heat storage; heat transfer control in buildings; solar and geothermal energy processes; and industrial, medical, and residential uses of heat exchangers. (LCL)

  10. Investigation into fouling factor in compact heat exchanger

    Masoud Asadi

    2013-03-01

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

  11. Experimental study on R-134a evaporation heat transfer characteristics in plate and shell heat exchanger

    An experiment was carried out to investigate the characteristics of the evaporation heat transfer for refrigerant R-134a flowing in a plate and shell heat exchanger. The data are useful in designing more compact and effective evaporators for various refrigeration and air conditioning systems. Two vertical counterflow channels were formed in the exchanger. The R-134a flows up in one channel exchanging heat with the hot water flowing down in the other channel. The effects of the average heat flux, mass flux, saturation temperature and vapor quality were examined in detail. The present data show that the evaporation heat transfer coefficient increases with the vapor quality. A rise in the refrigerant mass flux causes an increase in the hr value. A rise in the average imposed heat flux causes an increase in the hr value at the low quality. Finally, at a higher refrigerant saturation temperature the hr value is found to be lower

  12. Performance studies on high temperature sodium to air heat exchangers

    It has been observed that design of high temperature sodium to air heat exchanger has some uncertainties which have led to poor heat transfer performance in the past. The study of such heat exchangers is important to avoid excessive temperature build up in the reactor as decay heat removal exchangers for the prototype fast breeder reactor are to be of this design. A computer program has been developed for design of transverse finned U tube cross flow type of heat exchanger with two or more passes on the tube side. The paper deals with the features of construction of a typical sodium to air heat exchanger, types of finned tubes commonly used with comparison of different types of connection of fins to tubes. The improvements carried out during the design of second sodium to air heat exchanger to improve heat transfer performance have been highlighted. The effect of variation of few important parameters on the heat transfer performance and pressure drop has been elucidated. 7 refs., 2 tabs., 3 figs

  13. Heat Exchanger Lab for Chemical Engineering Undergraduates

    Rajala, Jonathan W.; Evans, Edward A.; Chase, George G.

    2015-01-01

    Third year chemical engineering undergraduate students at The University of Akron designed and fabricated a heat exchanger for a stirred tank as part of a Chemical Engineering Laboratory course. The heat exchanger portion of this course was three weeks of the fifteen week long semester. Students applied concepts of scale-up and dimensional…

  14. Tube in-shell heat exchanger

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

  15. Heat Exchanger Lab for Chemical Engineering Undergraduates

    Rajala, Jonathan W.; Evans, Edward A.; Chase, George G.

    2015-01-01

    Third year chemical engineering undergraduate students at The University of Akron designed and fabricated a heat exchanger for a stirred tank as part of a Chemical Engineering Laboratory course. The heat exchanger portion of this course was three weeks of the fifteen week long semester. Students applied concepts of scale-up and dimensional

  16. Cleaning Schedule Optimization of Heat Exchanger Networks Using Particle Swarm Optimization

    Biyanto, Totok R.; Suganda, Sumitra Wira; Matraji; Susatio, Yerry; Justiono, Heri; Sarwono

    2015-01-01

    Oil refinery is one of industries that require huge energy consumption. The today technology advance requires energy saving. Heat integration is a method used to minimize the energy comsumption though the implementation of Heat Exchanger Network (HEN). CPT is one of types of Heat Exchanger Network (HEN) that functions to recover the heat in the flow of product or waste. HEN comprises a number of heat exchangers (HEs) that are serially connected. However, the presence of fouling in the heat ex...

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

    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 1520 % lower than the rate of heat exchange at air cooling.

  18. Improved ceramic heat exchanger materials

    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.

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

    Abhishek Nandan; Gurpreet Singh Sokhal

    2015-01-01

    Plate heat exchanger has found a wide range of application in various industries like food industries, chemical industries, power plants etc. It reduces the wastage of energy and improves the overall efficiency of the system. Hence, it must be designed to obtain the maximum heat transfer possible. This paper is presented in order to study the various theories and results given over the improvement of heat transfer performance in a plate heat exchanger. However, there is still a la...

  20. Heat exchanger identification by using iterative fuzzy observers

    Lalot, Sylvain; Gumundsson, Oddgeir; Plsson, Halldr; Plsson, lafur Ptur

    2015-06-01

    The principle of fuzzy observers is first illustrated on a general example: the determination of the two parameters of second order systems using a step response. The set of equations describing the system are presented and it is shown that accurate results are obtained, even for a high level of noise. The heat exchanger model is then introduced. It is based on a spatial division of a counter flow heat exchanger into multiple sections. The governing equations are rewritten as a state space representation. The number of sections needed to get accurate results is determined by comparing estimated values to experimental data. Based on the mean value of the root mean squared errors, it is shown that 80 sections is an appropriate value for this heat exchanger. It is then shown that the iterative fuzzy observers can be used to determine the main parameters of the counter flow heat exchanger, i.e. the convection heat transfer coefficients, when in transient state. The final values of these parameters are <3.5 % apart from the values determined by a time consuming trial and error procedure. Finally a sensitivity study is carried out, showing that a 1.5 % variation of the actual value of the overall heat transfer coefficient corresponds to a 0.5 % variation of the estimated overall heat transfer coefficient. This study also shows that the fuzzy observers are equally efficient when the heat exchanger is in steady state.

  1. High temperature alloys and ceramic heat exchanger

    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. Testing and plugging power plant heat exchangers

    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.

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

    Fan, Jianhua; Furbo, Simon; Andersen, Elsa; Chen, Ziqian; Perers, Bengt; Dannemand, Mark

    2012-01-01

    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......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...

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

    Byun, Ho-Won; Kim, Nae-Hyun

    2015-10-01

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

  5. Heat transfer analysis of short helical borehole heat exchangers

    Highlights: ► Vertical ground heat exchanger with a helical shaped pipe is analyzed. ► The model considers the interaction between the ground and the environment. ► The results of the model are in good agreement with the experimental values. ► The weather conditions considerably affect the fluid heat carrier temperature. ► The pitch between the turns does not affect the behaviour of the heat exchanger. -- Abstract: In this paper a numerical model to analyze the thermal behaviour of vertical ground heat exchangers with a helical shaped pipe is presented. This type of configuration can be a suitable alternative to conventional ground heat exchangers, especially when the heating and cooling loads of the building are very low. The model describes the heat transfer problem by means of a network of interconnected thermal resistances and capacitances. Moreover, as the investigated ground heat exchanger is usually installed in shallow depth, the model takes into account the interaction between the ground and the ambient environment which affects the fluid heat carrier temperature into the heat exchanger and, as a consequence, the energy efficiency of the heat pump. After a sensitivity analysis on the mesh parameters, the presented model is compared with experimental data and the simulation results show good agreement with the measurements. Finally, analyses to investigate the influence of the weather conditions, of the axial heat transfer and of the pitch between the turns of the helical pipe for two types of ground are carried out.

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

    Koplow, Jeffrey P.

    2015-12-08

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

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

    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.

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

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

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

    Harche, Rima; Mouheb, Abdelkader; Absi, Rafik

    2016-05-01

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

  10. Numerical and Experimental Investigation for Heat Transfer Enhancement by Dimpled Surface Heat Exchanger in Thermoelectric Generator

    Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi

    2016-03-01

    For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.

  11. Numerical and Experimental Investigation for Heat Transfer Enhancement by Dimpled Surface Heat Exchanger in Thermoelectric Generator

    Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi

    2015-11-01

    For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio (h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.

  12. Intermediate heat exchanger project for Super Phenix

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

  13. Heat Transfer Enhancement of Shell and Tube Heat Exchanger Using Conical Tapes.

    Dhanraj S.Pimple

    2014-12-01

    Full Text Available This paper provides heat transfer and friction factor data for single -phase flow in a shell and tube heat exchanger fitted with a helical tape insert. In the double concentric tube heat exchanger, hot air was passed through the inner tube while the cold water was flowed through the annulus. The influences of the helical insert on heat transfer rate and friction factor were studied for counter flow, and Nusselt numbers and friction factor obtained were compared with previous data (Dittus 1930, Petukhov 1970, Moody 1944 for axial flows in the plain tube. The flow considered is in a low Reynolds number range between 2300 and 8800. A maximum percentage gain of 165% in heat transfer rate is obtained for using the helical insert in comparison with the plain tube.

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

    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

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

    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)

  16. Heat exchanger, head and shell acceptance criteria

    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

  17. Heat transfer and fluid flow in minichannels and microchannels

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

    The present study presents an experimental study of a prototype counter-flow heat exchanger designed to recover sensible heat from inert and reactive gases flowing through a high temperature solar reactor for splitting CO2. The tube-in-tube heat exchanger is comprised of two concentric alumina tubes, each filled with reticulated porous alumina with a nominal porosity of 80% and pore density of 5 pores per inch (ppi). The RPC provides high heat transfer surface area per unit volume (917m?1) with low pressure drop. Measurements include the permeability, inertial coefficient, overall heat transfer coefficient, effectiveness and pressure drop. For laminar flow and an inlet gas temperature of 1240K, the overall heat transfer coefficients are 3641Wm?2K?1. The measured performance is in good agreement with a prior CFD model of the heat exchanger. - Highlights: A ceramic heat exchanger provides gas-phase heat recuperation for a solar thermochemical reactor. Alumina reticulated porous ceramic (RPC) provides high surface area and low pressure drop. Heat transfer and pressure drop are measured at temperatures up to 1240K. RPC provides a 9-fold increase in heat transfer compared to bare tubes

  19. Influence of the yaw angle on heat transfer and pressure drop of helical type heat exchangers

    The influence of the flow angle φ between the tube axis and the flow direction on heat transfer and pressure drop has been studied at 15 deg. ≤ φ ≤ 90 deg. (cross flow). The Reynolds number was varied in the range 2.103 ≤ Re ≤ 105. Experimental data are given for a number of tube banks of straight tubes as well as a helical type heat exchanger with a large thread pitch of the tubes. (author)

  20. Numerical modeling of fin and tube heat exchanger for waste heat recovery

    Singh, Shobhana; Srensen, Kim; Condra, Thomas Joseph

    In the present work, multiphysics numerical modeling is carried out to predict the performance of a liquid-gas fin and tube heat exchanger design. Three-dimensional (3D) steady-state numerical model using commercial software COMSOL based on finite element method (FEM) is developed. The study...... associates conjugate heat transfer phenomenon with the turbulent flow to describe the variable temperature and velocity profile. The performance of heat exchanger design is investigated in terms of overall heat transfer coefficient, Nusselt number, Colburn j-factor, flow resistance factor, and efficiency...... between fin and tube. The present numerical model predicts the performance of the heat exchanger design, therefore, can be applied to existing waste heat recovery systems to improve the overall performance with optimized design and process-dependent parameters....

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

    Abhishek Nandan

    2015-03-01

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

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

    Navid Bozorgan

    2015-07-01

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

  3. The LUX prototype detector: Heat exchanger development

    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

  4. Condensing Heat Exchanger with Hydrophilic Antimicrobial Coating

    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.

  5. Heat Exchanger Support Bracket Design Calculations

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

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

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

    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...

  7. Continuous cleaning of heat exchanger with recirculating fluidized bed

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

  8. On-line fouling monitor for heat exchangers

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

  9. Heat exchanger module for secondary circuit of nuclear heating plant

    The heat exchanger placed in the reactor vessel consists of a bundle of heat exchange tubes, two tube plates, their lids, and inlet and outlet tubes. The heat exchange tubes of the exchanger of the secondary coolant circuit are attached by their upper ends to the upper tube plate and by their bottom ends to the bottom tube plate. The heat exchange elements are placed around the inlet tube of the secondary coolant circuit passing tightly through the upper tube plate. The outlet tube of the secondary coolant circuit passes tightly through the reactor vessel and by its upper end is attached to the inlet tube and by its bottom end to the lid of the upper tube plate. The inlet tube is tightly connected to the bottom tube plate via the expansion pressurizer. (B.S.)

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

    Ahmed F. Khudheyer; Mahmoud Sh. Mahmoud

    2011-01-01

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

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

    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.

  12. A heat exchanger with dual tubes

    The invention relates to a heat exchanger provided with dual tubes arranged in two bundles within a casing. That heat exchanger is characterized in that the tubes penetrate into the casing from the opposite ends thereof, said tubes being imbricated in such a way of the second bundle, a heat-conducting medium being contained in said casing for transferring heat from the fluid of one of said bundles to the other bundle fluid. The invention can be applied in particular to liquid-metal steam generators and also extended to PWR reactors

  13. 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...

  14. Heat exchangers: an energy viewpoint approach

    This paper, at first, presents a brief discussion of the concept of exergy. The second part studies the exchange of heat by conduction, convection and radiation as well as the irreversibilities due to the required temperature gradient. It shows the importance of the temperature level on the heat flux and the exergy lost. This analysis results also in conclusions on the fins and the thermal insulation. The third part studies the heat exchangers, in general. The loss of exergy due to the thermal exchange permits a comparison of the thermal value of these apparatus and, as well, shows the influence of the isothermal change of state of a fluid, i.e. in vaporization. Finally, based on the conclusions reached above, different types of heat exchangers used in industrial applications are analysed

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

    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 considered is helium...

  16. Heat Pipe Blocks Return Flow

    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. Tube-in-shell heat exchangers

    A tube-in-shell heat exchanger is described for use in liquid metal cooled fast breeder reactor constructions. The system consists of a bundle of heat exchange tubes with a central spine extending longitudinally through the shell and a series of longitudinally spaced transverse grids resiliently mounted on the central spine within the shell to provide transverse support for bracing the tubes apart. (U.K.)

  18. The use of helical heat exchanger for heat recovery domestic water-cooled air-conditioners

    An experimental study on the performance of a domestic water-cooled air-conditioner (WAC) using tube-in-tube helical heat exchanger for preheating of domestic hot water was carried out. The main aims are to identify the comprehensive energy performance (space cooling and hot water preheating) of the WAC and the optimum design of the helical heat exchanger taking into account the variation in tap water flow rate. A split-type WAC was set up for experimental study at different indoor and outdoor conditions. The cooling output, the amount of recovered heat, and the power consumption for different hot water flow rates were measured. The experimental results showed that the cooling coefficient of performance (COP) of the WAC improves with the inclusion of the heat recovery option by a minimum of 12.3%. This can be further improved to 20.6% by an increase in tap water flow rate. Same result was observed for the comprehensive COP of the WAC. The maximum achievable comprehensive COP was 4.92 when the tap water flow rate was set at 7.7 L/min. The overall heat transfer coefficient of the helical heat exchanger under various operating conditions were determined by Wilson plot. A mathematical model relating the over all heat transfer coefficient to the outer pipe diameter was established which provides a convenient way of optimising the design of the helical heat exchanger

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

    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

  20. A heat exchanger analogy of automotive paint ovens

    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

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

    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)

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

    Uvan Catton; Vijay K. Dhir; Deepanjan Mitra; Omar Alquaddoomi; Pierangelo Adinolfi

    2004-04-06

    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.

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

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

  4. Brayton-cycle heat exchanger technology program

    Killackey, J. J.; Coombs, M. G.; Graves, R. F.; Morse, C. J.

    1976-01-01

    The following five tasks designed to advance this development of heat exchanger systems for close loop Brayton cycle power systems are presented: (1) heat transfer and pressure drop data for a finned tubular heat transfer matrix. The tubes are arranged in a triangular array with copper stainless steel laminate strips helically wound on the tubes to form a disk fin geometry; (2) the development of a modularized waste heat exchanger. Means to provide verified double containment are described; (3) the design, fabrication, and test of compact plate fin heat exchangers representative of full scale Brayton cycle recuperators; (4) the analysis and design of bellows suitable for operation at 1600 F and 200 psia for 1,000 cycles and 50,000 hours creep life; and (5) screening tests used to select a low cost braze alloy with the desirable attributes of a gold base alloy. A total of 22 different alloys were investigated; the final selection was Nicrobraz 30.

  5. The influence of a radiated heat exchanger surface on heat transfer

    Morel S?awomir

    2015-09-01

    Full Text Available The experiment leads to establish the influence of radiated surface development heat exchangers on the values of heat flux transferred with water flowing through the exchangers and placed in electric furnace chamber. The values of emissivity coefficients are given for the investigated metal and ceramic coatings. Analytical calculations have been made for the effect of the heating medium (flame uncoated wall and then heating medium (flame coated wall reciprocal emissivity coefficients. Analysis of the values of exchanged heat flux were also realized. Based on the measurement results for the base coating properties, these most suitable for spraying the walls of furnaces and heat exchangers were selected, and determined by the intensification of heat exchange effect. These coatings were used to spray the walls of a laboratory waste-heat boiler, and then measurements of fluxes of heat absorbed by the cooling water flowing through the boiler tubes covered with different type coatings were made. Laboratory tests and calculations were also confirmed by the results of full-scale operation on the metallurgical equipment.

  6. The influence of a radiated heat exchanger surface on heat transfer

    Morel, Sławomir

    2015-09-01

    The experiment leads to establish the influence of radiated surface development heat exchangers on the values of heat flux transferred with water flowing through the exchangers and placed in electric furnace chamber. The values of emissivity coefficients are given for the investigated metal and ceramic coatings. Analytical calculations have been made for the effect of the heating medium (flame) - uncoated wall and then heating medium (flame) - coated wall reciprocal emissivity coefficients. Analysis of the values of exchanged heat flux were also realized. Based on the measurement results for the base coating properties, these most suitable for spraying the walls of furnaces and heat exchangers were selected, and determined by the intensification of heat exchange effect. These coatings were used to spray the walls of a laboratory waste-heat boiler, and then measurements of fluxes of heat absorbed by the cooling water flowing through the boiler tubes covered with different type coatings were made. Laboratory tests and calculations were also confirmed by the results of full-scale operation on the metallurgical equipment.

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

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

    2014-04-01

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

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

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

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

    Soria-Verdugo, A; Almendros-Ibez, 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. Balance-of-plant heat exchanger condition assessment guidelines

    In nuclear power plants, service water system heat exchanger integrity and thermal performance are receiving close scrutiny to ensure that they perform their functions in an emergency condition. Many safety-related service water systems are called upon to function only in emergency conditions and are therefore difficult to monitor on a regular basis to ensure functionality. For some heat exchangers it is difficult to measure and extrapolate their thermal performance data since performance testing is often conducted at flows, temperatures, and heat loads which are different from design conditions. Tube fouling and plugged tubes may also contribute to this difficulty. Performance testing and analysis of heat exchanger alone does not provide information relative to structural integrity of remaining tubes. This document is provided to complement the existing performance testing with a periodic inservice inspection program

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

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

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

    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.

  13. Reducing thermophoretic deposition in heat exchangers using wavy walled channels

    Mills, Zachary; Alexeev, Alexander

    2014-11-01

    Using computational simulations, we examined the effect of wavy walled geometries on the fouling of heat exchangers. Our model combines a lattice Boltzmann model for simulating the fluid flow, a finite difference temperature model and a Brownian dynamics model used to model the transport and deposition of aerosol particles. In our previous studies, we investigated how the geometry influences the structure of the flow within the channel. Specifically, we determined the critical pressure gradients at which the flow transitions between different flow regimes for various wave amplitudes and periods. We observed three separate flow regimes including steady flow with and without circulation and unsteady time-periodic flow. We have extended this investigation to examine the effects of these different geometries and flow regimes on heat and mass transport within the channel. In our simulations we investigated particle deposition resulting from convection and thermophoresis. From the results of our investigations we will be able to determine the geometries which reduce the rate of fouling in heat exchangers while increasing heat transport. This work is supported by General Motors Corporation.

  14. Exchange flow through a rectangular channel

    This study deals with the exchange flow of two different gases (air to He or Ar or SF6) through a rectangular channel which has 50 mm height, 200 mm length and 5 mm depth and is attached to a bottom tank filled with helium or argon or SF6. Net in-flow mass rate was measured by an electric mass balance, and velocity distribution by a laser-Doppler anemometer. Flow patterns of exchange flow were visualized with a tracer method. Discussed was the relationship between the basic features of the exchange flow and channel angle, gas density and diffusion coefficient. (author)

  15. NUMERICAL SIMULATION OF HEAT TRANSFER AND PRESSURE DROP IN PLATE HEAT EXCHANGERS USING FLUENT AS CFD TOOL

    EGEREGOR, DAFE

    2008-01-01

    Corrugated walls are commonly used as passive devices for heat and mass transfer enhancement, being most effective in applications operated at transitional and turbulent Reynolds numbers. The plate heat exchanger (PHE) is an example of this application. In this thesis work, numerical simulation is used to investigate the heat transfer and pressure drop in plate heat exchangers, with the intention of determining the effect of channel geometry and flow conditions on the heat transfer of the exc...

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

    P. Raveendiran

    2015-06-01

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

  17. Dynamic responses of heat exchanger tube banks

    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

  18. Near Field Investigation of Borehole Heat Exchangers

    Erol, Selcuk

    2015-01-01

    As an alternative and renewable energy source, the shallow geothermal energy evolving as one of the most popular energy source due to its easy accessibility and availability worldwide, and the ground source heat pump (GSHP) systems are the most frequent applications for extracting the energy from the shallow subsurface. As the heat extraction capacity of the GSHP system applications arises, the design of the borehole heat exchangers (BHE), which is the connected part of the system in the grou...

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

    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

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

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

    2015-01-01

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

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

    Sandip S. Kale; V.W.Bhatkar

    2014-01-01

    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 an...

  2. Terrestrial heat flow in Cuba

    Čermák, V.; Krešl, M.; Šafanda, J.; Bodri, L.; Nápoles-Pruna, M.; Tenreyro-Perez, R.

    The results of two joint expeditions to Cuba to measure terrestrial heat flow in 1983 and 1986 are summarized. Twenty-three new values are presented, which confirm the low heat flow in practically all of the island. The mean and standard deviation (44.7 ± 13.4 mW m -2) agree well with previous observations.

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

    Isabel M. Afonso; Maia, Joo M.; Luis F. Melo; Lubos Hes

    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 fr...

  4. Large scale experiments with a 5 MW sodium/air heat exchanger for decay heat removal

    Sodium experiments in the large scale test facility ILONA were performed to demonstrate proper operation of a passive decay heat removal system for LMFBRs based on pure natural convection flow. Temperature and flow distributions on the sodium and the air side of a 5 MW sodium/air heat exchanger in a natural draught stack were measured during steady state and transient operation in good agreement with calculations using a two dimensional computer code ATTICA/DIANA. (orig.)

  5. Design of common heat exchanger network for batch processes

    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

  6. New developments in compact plate-fin heat exchangers

    The extension of compact plate-fin heat exchanger capabilities in order to accommodate the performance requirements of regeneratively cooled hypersonic ramjet engines, laser weapons, aircraft engine infrared suppressors, and large high-efficiency gas turbine cycles is described. Attention is given to cooling fluid flow path geometry and heat exchanger fabrication techniques, such novel materials as alumina and silicon carbide, and space and weight constraints imposed on designs by airborne application. It is shown that operating temperatures, pressures and area densities have been significantly increased

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

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

  8. Predicted and measured velocity distributions in a model heat exchanger

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

  9. Mechanical design of heat exchangers and pressure vessel components

    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

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

    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.

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

    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–ε 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

  12. Research of characteristics slot-hole heat exchanger with the developed surface of heat exchange

    Malkin E. C.

    2010-03-01

    Full Text Available Thermal characteristics of multichannel slot-hole heat exchanger with the developed surface of heat exchange inside the opened-cycle water cooling system are experimentally investigated. Graphic dependences of average value of temperature of the simulator of a heat current and temperatures of the heat exchanger base are presented on tapped-off power. Dependences of tapped-off power and hydraulic losses on the of water consumption are given. It is shown, that use of developed slot-hole heat exchanger provides higher values of tapped-off power as compared to well-known two-channel slot-hole heat exchanger: at the temperature of heat-generating component simulator of +60°С the tapped-off power increases with 307 up to 750 W. Recommendations on increase of adaptability of slot-hole heat exchanger manufacturing are given. Heat exchanger is suitable for application in microprocessors and others heat-generating components and electronic equipment units cooling.

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

    Subodh Bahirat,; P. V. Joshi

    2014-01-01

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

  14. 40 CFR 63.11499 - What are the standards and compliance requirements for heat exchange systems?

    2010-07-01

    ... requirements for heat exchange systems? 63.11499 Section 63.11499 Protection of Environment ENVIRONMENTAL... and compliance requirements for heat exchange systems? (a) If the cooling water flow rate in your heat... subpart. (b) For equipment that meets Current Good Manufacturing Practice (CGMP) requirements of 21...

  15. Flow measurements related to gas exchange applications

    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...

  16. Exergy destruction analysis of a vortices generator in a gas liquid finned tube heat exchanger: an experimental study

    Ghazikhani, M.; Khazaee, I.; Monazzam, S. M. S.; Takdehghan, H.

    2016-01-01

    In the present work, the effect of using different shapes of vortices generator (VG) on a gas liquid finned heat exchanger is investigated experimentally with irreversibility analysis. In this project the ambient air with mass flow rates of 0.047-0.072 kg/s is forced across the finned tube heat exchanger. Hot water with constant flow rate of 240 L/h is circulated inside heat exchanger tubes with inlet temperature range of 45-73 °C. The tests are carried out on the flat finned heat exchanger and then repeated on the VG finned heat exchanger. The results show that using the vortex generator can decrease the ratio of air side irreversibility to heat transfer (ASIHR) of the heat exchanger. Also the results show that the IASIHR is >1.05 for all air mass flow rates, which means that ASIHR for the initial heat exchanger is higher than 5 % greater than that of improved heat exchanger.

  17. Performance of a Thermoelectric Device with Integrated Heat Exchangers

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

    2015-06-01

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

  18. Heat Transfer Study in a Coaxial Heat Exchanger Using Nanofluids

    Luciu, Răzvan-Silviu; Mateescu, Theodor

    2010-01-01

    The heat transfer of nanofluids in a coaxial heat exchanger is studied numerically using a Computational Fluid Dynamics (CFD) approach. The present study indicates an increase of the thermal performances with 50% of nanofluids compared to water. The nanofluid is composed of aluminum oxide (Al2O3) particles dispersed in water for various concentrations ranging (1, 3 and 5%).

  19. Simulation of induction heating process with radiative heat exchange

    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.

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

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

  1. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    2010-04-01

    ... bypass heat exchanger. (a) Identification. A cardiopulmonary bypass heat exchanger is a device, consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood or... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cardiopulmonary bypass heat exchanger....

  2. Use of a fluidized bed heat exchanger to improve the performance of a heat pump

    Sarubbi, R. G.; Chen, J. C.

    1981-09-01

    The outdoor evaporator heat exchanger of a 60,000 Btu heat pump in the heating mode was replaced with a fluidized bed heat exchanger. Air temperature control was achieved by recirculating the conditioned air from both the evaporator and condenser heat exchangers through a chambered plenum. Candidate particles and distributor plates for the design of the bed were tested separately. A particle size of 245 microns (glass spheres) at a static bed depth of 1-1/2 in. and a fluidizing air flow of 2.3 fps gave a heat transfer coefficient of 550 W/sq m OC and the best heat transfer to pressure drop ratio. The overall design heat transfer coefficient was 43 Btu/h-sq ft OF, which is about 5 times that of the conventional heat pump heat transfer coefficient. The heat exchanger consisted of two 20 sq ft shallow beds with a static bed 1-1/2 in. high. Particles used were sand, predominantly 300 microns in dia.

  3. Potential polymer concrete heat exchanger tubes for corrosive environments

    Fontana, J.J.; Reams, W.; Cheng, H.C.

    1986-11-01

    It has long been known that carbon steel exposed to some geothermal brines is aggressively attacked, and large corrosion allowances must be made in the design of piping used in such environments. In addition, scaling of the pipes reduces the flow through within a short period of time. Several high temperature polymer concretes have been developed which can be used as non-corrosive liner materials. In addition, polymer concretes with high thermal conductivities have been developed which may be used as heat exchanger tubes for geothermal brines. Studies have indicated that polymer concretes will not scale as rapidly as carbon steel does, thus making them attractive alternatives for heat exchanger tubes. Thin walled, thermally conductive polymer concrete tubes have been made that can withstand pressures >4.1 MPa at 150/sup 0/C without leaking. Continuing studies are being made to characterize these materials and evaluate them for heat exchanger applications.

  4. Multi-way tube-type heat exchanger

    In the cylindrical casing, U shaped heat exchange tubes are firmly anchored in the tube plate. The inner space of the casing is divided with a transverse plate normal to the plane of the tubes and with at least one partition wall parallel to the tube plane. The casing is provided with a cover whose inner space is divided with a partition and with at least one cross wall into an inlet area, an outlet area and a turning chamber. The inlet area of the cover adjoins the outlet channel of the casing and the outlet area of the cover adjoins the inlet channel of the casing via the tube plate. This configuration of the heat exchanger makes it possible to maintain the counter current flow throughout the entire heat exchange area. (E.S.)

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

    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.

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

    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

  7. Enhanced two phase flow in heat transfer systems

    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.

  8. Intermediate heat exchanger for HTR process heat application

    In the French study on the nuclear gasification of coal, the following options were recommended: Coal hydrogenation, the hydrogen being derived from CH4 reforming under the effects of HTR heat; the use of an intermediate helium circuit between the nuclear plant and the reforming plant. The purpose of the present paper is to describe the heat exchanger designed to transfer heat from the primary to the intermediate circuit

  9. Simulation of induction heating process with radiative heat exchange

    Kachel, A; Przy?ucki, R.

    2007-01-01

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

  10. Stead-state characteristic study of heat exchanger in water-cooled passive heat removal system for molten salt reactor

    Background: In the water-cooled passive heat removal system for molten salt reactor, the decay heat generated in molten salt can finally be transferred to the heat exchanger placed in water tank by natural circulation. Purpose: Based on the principles of high safety and simplification, there is a need to transfer the decay heat passively without using external power. Methods: The heat exchanger consists of a set of bundles submerged into the water tank with a tube header at each side. Based on the flow process, corresponding numerical model was constructed in the code of C++. Then the total heat exchange coefficient is got and the heat transfer area is calculated. Continually iterate the heat transfer area until the iteration stopping criterion is met, after that the dimensions of water tank are figured out. Results: While the decay power is 100 kW in the initial of the operation, the power of heat exchanger reaches the maximum value of 130 kW due to the low-temperature water in water tank. Then it drops quickly for the decrease of heat exchanger pressure and the rise of water temperature in water tank. When the heat exchanger pressure begins to rise, the heat exchanger power drops slower than before. The heat transfer ability begins to decrease quickly as the temperature difference between inside and outside of heat exchanger tubes lowers. Then it drops gradually as a result of the slowly changed pressure. During early operation, the heat exchanger pressure decreases because the steam generation rate is lower than the steam condensation rate. Then the condition varies as the heat exchanger power declines gradually. When boiling happens inside the water tank, the steam condensation rate raises due to the increasing heat transfer ability which makes the pressure of heat exchanger drops quickly. Afterwards, the heat exchanger pressure changes very slowly as the steam generation rate is approximate to the steam condensation rate. The mass of water in water tank remains unchanged essentially until the water begins to boil, then it starts to evaporate as the heat is transferred. The variation trend of the mass flow of condensate is similar to the heat exchange power of condenser. It decreases first and rises when the water reaches saturation. Then it lowers as the condenser pressure declines. Conclusions: The parameters of heat exchanger are calculated and the result shows that it can meet the requirements for heat exchange and has the self-regulation to some extent. The water tank can transfer the heat for a long time. Meanwhile the power can be adjusted by changing the water level in water tank. (authors)

  11. The dynamic behaviour of heat exchangers

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

  12. Modeling particle deposition on HVAC heat exchangers

    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

  13. Natural convection heat exchangers for solar water heating systems. Technical progress report, February 1, 1996--March 31, 1996

    Davidson, J.H.

    1998-06-01

    This progress report describes the thermodynamic testing and modeling of a thermosyphon heat exchanger used in solar water heating systems. Testing of a four tube-in-shell thermosyphon heat exchanger was performed in two parts. The first portion of the test increased the collector fluid while the storage tank remained isothermal. After the collector fluid temperature was raised to 95 C, the second part of the test allowed the storage tank to gain heat. The test was performed for two collector flow rates. Measured values included collector side forced flow rate, temperature differences across the heat exchanger, vertical temperature distribution in the storage tank, vertical water temperature profile in the heat exchanger, and pressure drop on the thermosyphon side of the heat exchanger. The overall heat transfer coefficient-area product (UA) values obtained confirmed that models which assume UA depends solely on thermosyphon flow rate do not adequately characterize thermosyphon heat exchangers. This is because heat transfer in thermosyphon exchangers occurs in the mixed convection, rather than forced flow, regime. A linear regression equation was developed to better predict UA using the Prandtl, Reynolds, and Grashof numbers and dimensionless parameters based on fluid properties calculated for the average hot and cold leg temperatures. 9 figs.

  14. Liquid Salt Heat Exchanger Technology for VHTR Based Applications

    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.

  15. Compact heat exchanger technologies for the HTRs recuperator application

    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)

  16. Negative Joule Heating in Ion-Exchange Membranes

    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.

  17. Feasibility study of helically coiled tube condensation heat exchanger for a passive auxiliary feedwater system

    The Passive Auxiliary Feedwater System (PAFS) with nearly-horizontal heat exchangers is one of passive safety features of APR+ (Advanced Power Reactor Plus) which provides the auxiliary feedwater by means of natural circulation with condensation. It is feasible to increase the heat transfer capacity of the PAFS by employing a helically coiled heat exchanger due to additional secondary flow effect by centrifugal force. In addition, a compact and flexible design can be achieved in a fixed volume by using the helically coiled heat exchanger, which is one of the most important merits of implementing this heat exchanger. In this paper, the helically coiled heat exchanger has been employed for the PAFS instead of nearly-horizontal heat exchanger. In order to evaluate the heat transfer performance of the helically coiled heat exchanger, an in-tube condensation heat transfer correlation by Wongwises has been introduced into the system analysis code, MARS-KS. A comparative numerical study was conducted for both heat exchangers. The result shows that helically coiled heat exchanger has 20% higher heat transfer efficiency than existing nearly-horizontal heat exchanger. (author)

  18. Magnetic Heat Pump Containing Flow Diverters

    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.

  19. Intensification of heat and mass transfer by ultrasound: application to heat exchangers and membrane separation processes.

    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

  20. NRC Information No. 90-26: Inadequate flow of essential service water to room coolers and heat exchangers for engineered safety-feature systems

    On March 9, 1990, the reactor at the Clinton Power Station was in cold shutdown, and the licensee was taking action to implement the recommendations contained in Generic Letter 89-13, ''Service Water System Problems Affecting Safety-Related Equipment.'' The licensee discovered that the flow of essential service water being supplied to several room coolers serving safety-related equipment was approximately half of the design flow. The safety-related equipment included components in the high-pressure and low-pressure core spray systems, the low-pressure injection system, the residual heat removal system, the standby gas treatment system, the combustible gas control system, and the nuclear protection system. After discovering the problem, the licensee declared these systems to be inoperable. The room coolers were supplied to the Clinton Power Station by American Air Filter, a subsidiary of Snyder General Corporation. Before initial operation of the Clinton Power Station, the licensee obtained the relationship of the flow and pressure drop on the water side of the room coolers from the supplier. On March 9, 1990, the licensee discovered that the relationship between flow and pressure drop for the room coolers was wrong and that flows of essential service water to the room coolers were too low. To balance the flow of essential service water through the system, plant personnel measured the flow using qualified instrumentation and adjusted flows to the room coolers according to these measurements. In some instances, the adjusted flows to specific components were somewhat less than design flows. However, the licensee is performing analyses to determine whether these flows are acceptable

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

    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.

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

    Manoj; A.M.Mulla

    2014-01-01

    Shell and tube heat exchangers are extensively used in boilers, oil coolers, pre-heaters, condensers etc. They are also having special importance in process application as well as refrigeration and air conditioning industries. The present paper emphasizes on heat transfer characteristics of shell and tube heat exchangers with the aid of hiTRAN wire matrix inserts is been studied. Investigations were made on effect of mass flow rate of water on heat transfer characteristics in ...

  3. Understanding and mitigating heat exchanger fouling in bauxite refineries

    Müller-Steinhagen, H.; Jamialahmadi, M.; Robson, B.

    1994-11-01

    Laboratory and plant measurements have been performed to evaluate possibilities of reducing the formation of desilication product (DSP) scale in the heat exchangers of the low-temperature Bayer process. It was found that the rate of scale formation is independent of the flow velocity, proportional to the square of the silica super saturation, and it increases exponentially with heat-transfer surface temperature. Because of the restricted operation conditions, variation of operating conditions may not reduce DSP formation sufficiently. Installation of turbulence promoters in the heat exchanger pipes had no beneficial aspects. Laboratory and plant measurements with a fluidized bed test heater indicated a strong potential of this technology to increase the operation times between chemical washes. Deposition of DSP could almost be eliminated if the process was modified such that developed subcooled boiling occurred at the heat-transfer surface.

  4. Fouling corrosion in aluminum heat exchangers

    Su Jingxin; Ma Minyu; Wang Tianjing; Guo Xiaomei; Hou Liguo; Wang Zhiping

    2015-01-01

    Fouling deposits on aluminum heat exchanger reduce the heat transfer efficiency and cause corrosion to the apparatus. This study focuses on the corrosive behavior of aluminum coupons covered with a layer of artificial fouling in a humid atmosphere by their weight loss, Tafel plots, electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) observations. The results reveal that chloride is one of the major elements found in the fouling which damages the passive film a...

  5. Fouling of heat exchanger surfaces: General principles

    1986-12-01

    This Data Item ESDU 86038 is an addition to the Heat Transfer Sub-series. The importance of various parameters that affect fouling are discussed. Appropriate methods for dealing with fouling in all stages from design through to operation of heat exchanger equipment are indicated. Methods of suppressing fouling by additives, or of cleaning equipment chemically or mechanically, are considered. A brief outline of the physical process of fouling including some mathematical models is given.

  6. Heat exchanger containing a component capable of discontinuous movement

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

    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.

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

    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.

  9. Heat exchanger, specifically a steam generator heated with liquid sodium

    The invention concerns a heat exchanger, specifically a liquid sodium heated steam generator. This exchanger comprises a vertical long casing, a distributor for feeding the internal capacity of the casing with a first liquid coolant (liquid sodium), at least one bundle of tubes fitted inside the casing for the circulation of a second coolant (water), in indirect heat exchange relation with the first coolant, and facilities for maintaining in the casing a free given level of liquid topped by an inert gas atmosphere (argon). The upper ends of the tubes are fitted with thermal sleeves connecting them to the side wall of the casing for crossing it under the free liquid level and the distributor is placed in the casing above the bundle of tubes

  10. Multi scale thermo-hydraulic modeling of cryogenic heat exchangers

    Pacio, Julio Cesar

    2012-07-01

    The cryogenic industry has experienced a continuous growth in the last decades, partially sustained by the worldwide development of Liquefaction of Natural Gas (LNG) projects. LNG technology provides an economically feasible way of transporting natural gas over long distances, and currently accounts for nearly 30% of the international trade of this resource. The economic feasibility of these projects, in terms of both capital and operating costs, is to a large extent controlled by the performance of the main cryogenic two-phase flow heat exchanger. This industrial scenario provides then the motivation for a detailed study of the heat exchanger from a design perspective. On the one hand, it is widely accepted that a highly detailed analysis is required at a micro scale to properly take account of the two phase heat transfer process. On the other hand, a process-level description corresponds to larger time and space scales. In general, determining the proper methodology for considering these scales and their interaction remains a challenging problem. For this reason, current techniques focus in only one particular scale. The main objective of this project is then to develop a multi scale model applicable for two-phase flow heat exchangers. In this context, a three-scale framework is postulated. This thesis was divided into macro, meso (medium) and micro scale analysis. First, a macroscopic analysis provides a broad description in terms of overall heat transfer and pressure drop, using simple models without taking into account the details of physical phenomena at lower scales. Second, at mesoscale level, flow in parallel channels is considered following a homogenization approach, thus including the effects of flow mal distribution and partial mixing. Third, the microscopic description conceives a phenomenological representation of boiling flows, following multi fluid formulations, for two specific flow patterns: annular-mist and post-dryout regimes. Finally, a multi scale design algorithm is proposed. (au)

  11. Visualization of exchange flow and numerical simulation

    The exchange flow may occur following the opening of a window for ventilation, as well as when a pipe ruptures in a high temperature gas-cooled nuclear reactor, i.e., HTGR. The exchange flows in density different gases were investigated through inclined a narrow tube. The experiments were carried out in a test chamber filled with helium and the flow behavior was visualized using the smoke methods and recorded by the high-speed camera. The image of the flow was transferred to digital data, and then the slow flow velocity was measured by PIV software. Numerical analysis was carried out by the 3D code of moving particle with Lagrange method. As the result, the fluctuated 3D exchange flow behavior was clarified. (author)

  12. Suction-liquid heat exchanger having accumulator and receiver

    A suction-liquid heat exchanger for a heat pump is provided by utilizing an inner vessel as a suction line accumulator together with a surrounding high pressure outer vessel which is utilized as a receiver in the liquid line. Heat from the liquid refrigerant in the outer vessel is transferred to the cooler liquid accumulated in the inner vessel to vaporize it, preventing slugs of liquid refrigerant from entering the compressor. The exit and entry ports of the outer vessel are at different levels. This causes a greater amount of liquid refrigerant to remain in the outer vessel on heating mode operation than on reverse flow for cooling, thereby increasing the heat transfer to the accumulator as required for the greater volume of liquid in the suction line gas and compensating for the decreased quantity of refrigerant needed for heating

  13. Laboratory simulation of heat exchange for liquids with Pr > 1: Heat transfer

    Belyaev, I. A.; Zakharova, O. D.; Krasnoshchekova, T. E.; Sviridov, V. G.; Sukomel, L. A.

    2016-02-01

    Liquid metals are promising heat transfer agents in new-generation nuclear power plants, such as fast-neutron reactors and hybrid tokamaks—fusion neutron sources (FNSs). We have been investigating hydrodynamics and heat exchange of liquid metals for many years, trying to reproduce the conditions close to those in fast reactors and fusion neutron sources. In the latter case, the liquid metal flow takes place in a strong magnetic field and strong thermal loads resulting in development of thermogravitational convection in the flow. In this case, quite dangerous regimes of magnetohydrodynamic (MHD) heat exchange not known earlier may occur that, in combination with other long-known regimes, for example, the growth of hydraulic drag in a strong magnetic field, make the possibility of creating a reliable FNS cooling system with a liquid metal heat carrier problematic. There exists a reasonable alternative to liquid metals in FNS, molten salts, namely, the melt of lithium and beryllium fluorides (Flibe) and the melt of fluorides of alkali metals (Flinak). Molten salts, however, are poorly studied media, and their application requires detailed scientific substantiation. We analyze the modern state of the art of studies in this field. Our contribution is to answer the following question: whether above-mentioned extremely dangerous regimes of MHD heat exchange detected in liquid metals can exist in molten salts. Experiments and numerical simulation were performed in order to answer this question. The experimental test facility represents a water circuit, since water (or water with additions for increasing its electrical conduction) is a convenient medium for laboratory simulation of salt heat exchange in FNS conditions. Local heat transfer coefficients along the heated tube, three-dimensional (along the length and in the cross section, including the viscous sublayer) fields of averaged temperature and temperature pulsations are studied. The probe method for measurements in a flow is described in detail. Experimental data are designated for verification of codes simulating heat exchange of molten salts.

  14. Trends in the development of heat exchangers

    Paikert, P.

    1988-03-01

    Without referring to all of the developments observed, the paper focuses on typical, important, and possibly trendsetting heat exchanger innovations and improvements of 1986/87. In spite of an intended objective description and presentation of the trends observed the report is not completely free from subjective statements and interpretations due to personal experiences.

  15. Heat exchanger for a contaminated fluid

    A heat exchanger, in particular for a contaminated fluid in the nuclear industry. The tubes forming the tube core are welded and crimped across the whole width of the tubular plate which defines the floating head together with the sealing cover, and said tubular plate is also welded and crimped to the calandria along the whole of its periphery. (author)

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

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

  17. Damping in heat exchanger tube bundles. A review

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

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

    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.

  19. Heat exchange process, particularly to cool fission gases and heat exchanger to perform the method

    Heat exchangers developed for nuclear power plants could also be used for cooling fission gases from the hydropyrolysis of heavy hydrocarbons, particularly heat exchangers with an intermediate carrier filling of liquid metal (e.g. heavy metal alloy). As the heat exchanger surfaces have to be decoked from time to time when used for cooling fission gases, where high temperatures occur, it is proposed to change the level of the fill of the intermediate carrier fill by adding or removing intermediate carrier material. It is then possible to decoke without having to remove the cooling water. (UWI)

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

    S. Sathiyan

    2013-06-01

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

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

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

    Manoj

    2014-06-01

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

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

    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 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.

  4. Brayton heat exchange unit development program

    Morse, C. J.; Richard, C. E.; Duncan, J. D.

    1971-01-01

    A Brayton Heat Exchanger Unit (BHXU), consisting of a recuperator, a heat sink heat exchanger and a gas ducting system, was designed, fabricated, and tested. The design was formulated to provide a high performance unit suitable for use in a long-life Brayton-cycle powerplant. A parametric analysis and design study was performed to establish the optimum component configurations to achieve low weight and size and high reliability, while meeting the requirements of high effectiveness and low pressure drop. Layout studies and detailed mechanical and structural design were performed to obtain a flight-type packaging arrangement. Evaluation testing was conducted from which it is estimated that near-design performance can be expected with the use of He-Xe as the working fluid.

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

    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

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

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

  7. Compact/micro heat exchangers – Their role in heat pumping equipment

    Kew, PA; Reay, DA; 2nd Micro and Nano Flows Conference (MNF2009)

    2009-01-01

    This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.

  8. Heat exchanger with concentric U tubes with intermediate neutral gas and fast neutron nuclear reactor including this type of exchanger

    The heat exchanger comprises a double-wall U tube bundle which is in a heating coolant such as liquid sodium. A neutral gas such as helium flows through the inter-tube space, under a pressure slightly above the pressure under which water flows through the inner tubes. Each vertical branch of the tube bundle is surrounded by a shell through which the sodium flows from the top to the bottom, between inlet openings and the opened lower ends of the shells. The heated coolants, helium and water, flow down through a branch and up through the other branch of the U tube bundle. The inlet and outlet zones of these heated coolants are separately situated at the upper part of the exchanger. This exchanger can be used as steam generator and integrated directly in the main vessel of an integrated fast-neutron nuclear reactor or in a vessel separated from the reactor

  9. 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

    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.

  10. Tube vibration in industrial size test heat exchanger

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

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

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

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

    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.

  13. High-heat-flux testing of helium-cooled heat exchangers for fusion applications

    High-heat-flux experiments on three types of helium-cooled divertor mock-ups were performed on the 30-kW electron beam test system and its associated helium flow loop at Sandia National Laboratories. A dispersion-strengthened copper alloy (DSCu) was used in the manufacture of all the mock-ups. The first heat exchanger provides for enhanced heat transfer at relatively low flow rates and much reduced pumping requirements. The Creare sample was tested to a maximum absorbed heat flux of 5.8 MW/m2. The second used low pressure drops and high mass flow rates to achieve good heat removal. The GA specimen was tested to a maximum absorbed heat flux of 9 MW/m2 while maintaining a surface temperature below 400 degree C. A second experiment resulted in a maximum absorbed heat flux of 34 MW/m2 and surface temperatures near 533 degree C. The third specimen was a DSCu, axial flow, helium-cooled divertor mock-up filled with a porous metal wick which effectively increases the available heat transfer area. Low mass flow and high pressure drop operation at 4.0 MPa were characteristic of this divertor module. It survived a maximum absorbed heat flux of 16 MW/m2 and reached a surface temperature of 740 degree C. Thermacore also manufactured a follow-on, dual channel porous metal-type heat exchanger, which survived a maximum absorbed heat flux of 14 MW/m2 and reached a maximum surface temperature of 690 degree C. 11refs., 20 figs., 3 tabs

  14. Subsurface environment database for application of ground heat exchanger system

    Hamamoto, H.; Hachinohe, S.; Shiraishi, H.; Takashi, I.; Sasaka, K.; Miyakoshi, A.; Goto, S.

    2010-12-01

    Ground heat exchanger system is economical and environmentally friendly technology and widely used in Europe and North America, while it is rarely used in Japan. One of the causes is relatively complex topography and geological structure in Japan in comparison with those in Europe and North America. Complex structures produce regional differences in subsurface thermal properties and temperature structure, leading to regional variation in efficiency of heat exchanger system. It is thus important to evaluate available subsurface heat energy through thermal response tests and/or numerical simulation and to design appropriate systems (depth and number of boreholes for heat exchange). Information on subsurface environment in target areas is necessary for evaluation of potential subsurface heat energy, but little information has been published. Center for Environmental Science in Saitama is a research institute established by a local government, Saitama prefecture, which is located on the north of Tokyo and has a population of over seven million. We have been collecting various subsurface environmental data in Saitama (e.g., lithological column data on over 10,000 boreholes). We have compiled the accumulated data and obtained new data (geological information, subsurface temperature distribution, and hydrogeological properties) to construct a database for application of ground heat exchanger systems in Saitama. It is important to estimate demand for heat energy in the target areas as well as available subsurface heat energy. We therefore compile meteorological data (air temperature and solar radiation) necessary for estimation for the demand and investigate regional variation in meteorological condition. We intend to disclose the database and research products using web GIS (geographic information system) in the future. It will assist spread of ground heat exchanger systems in the target areas. Investigation methods of subsurface environment survey and database construction can be applied to other areas. We present results of numerical simulation of ground heat exchanger system operation based on the database. The amount of available heat energy and influence on subsurface thermal environment vary by up to about 20 % within the study area depending on geological and meteorological conditions. Map of temperature measurement stations and numerical simulation considering with groundwater flow

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

    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

  16. Experimental investigations of the sodium/air heat exchanger with natural draught chimney for the EFR

    In a first series of experiments in the new large sodium experimental plant ILONA, the post-shutdown heat removal system for the European Fast Breeder Reactor EFR developed by Interatom and working by natural convection was tested. The air-side flow in the heat exchanger and chimney was optimized in extensive model experiments and the results were taken into account in the construction of the Na/air heat exchanger in the ILONA. A considerable increase in output was achieved, compared to the design, based on the flow model experiments for the ILONA heat exchanger. (orig.)

  17. Exhaust bypass flow control for exhaust heat recovery

    Reynolds, Michael G.

    2015-09-22

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

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

    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.

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

    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.

  20. Heat exchange intensification in air coolers of the ship refrigerating units with application four-channel belt turbulators

    Merkulov Evgeniy Igorevich

    2011-04-01

    Full Text Available Search of methods of intensification of the heat exchange process at boil-ing in air coolers of ship refrigerating units is made to decrease mass parameters of heat exchange equipment. The process of heat exchange at boiling with appli-cation of four-channel belt turbulator, made as a four-ray star is examined. The results of model experiment for research of hydrodynamics and heat exchange of two-phase flow are presented.