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1

Irreversibility analysis of cross flow heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

In this paper, a cross flow plate type heat exchanger, operating with unmixed fluids, was analysed with balanced cross flow. For this aim, a cross flow plate type heat exchanger was developed and manufactured in the laboratory. The heat exchanger was tested with an applicable experimental set up, and temperatures, velocity of the air and the pressure losses occurring in the system were measured so that the effectiveness of the heat exchanger has been determined. The minimum entropy generation number has been taken into consideration with respect to the second law of thermodynamics for the heat exchanger in this analysis. The minimum entropy generation number depends on parameters such as optimum flow path length, dimensionless mass velocity, dimensionless heat transfer area and dimensionless heat transfer volume. The variations between the entropy generation number and these parameters were analysed for the manufactured heat exchanger and introduced with their graphics. (author)

Ogulata, R.T.; Doba, F. [Cukurova University, Adana (Turkey). Dept. of Textile Engineering; Yilmaz, T. [Cukurova University, Adana (Turkey). Dept. of Mechanical Engineering

2000-10-01

2

Stirling Engine With Radial Flow Heat Exchangers  

Science.gov (United States)

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.

Vitale, N.; Yarr, George

1993-01-01

3

Counter flow heat exchanger between two fluids  

International Nuclear Information System (INIS)

This invention concerns a counter flow heat exchanger between a primary fluid which cools down inside tubes having the general shape of an inverted J, or in any other self expanding form, a tube bundle and a secondary fluid which heats up around this tube bundle. The latter extends between a tube plate of a central area and an annular tube plate of a peripheral area. The invention described relates in particular to a steam generator in which the secondary water is heated and vaporized, and possibly superheated, by counter flow exchange with the primary fluid

1981-01-01

4

Cryogenic Heat Exchanger with Turbulent Flows  

Science.gov (United States)

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…

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

2012-01-01

5

Stokes flow heat transfer in an annular, rotating heat exchanger  

International Nuclear Information System (INIS)

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.

2011-06-01

6

Cross-flow countercurrent involute-tube heat exchangers  

International Nuclear Information System (INIS)

The value of giving an involute form to the tubes of a cross-flow countercurrent heat exchanger (tubes all identical in shape and developed length), both for heat exchange and to absorb differential expansion is demonstrated. Two applications pertaining to nuclear heat exchangers, involving steam generators, one heated by gaseous helium (superheated steam 5330C, 112 bar) and the second by liquid sodium (superheated steam 4870C, 181 bar) are discussed. The thermal power exchanged is calculated respectively for the superheater, evaporator and economizer, together with the heat transfer area, developed length of a tube, general dimensions, and pressure drop of both heat exchanger fluids

1983-01-01

7

Two-phase Flow Distribution in Heat Exchanger Manifolds  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

Vist, Sivert

2004-01-01

8

Auxiliary heat-exchanger flow-distribution test  

International Nuclear Information System (INIS)

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

1983-09-25

9

Investigation of the tube side flow distribution in heat exchangers  

International Nuclear Information System (INIS)

The tube side flow distribution in heat exchangers is being investigated through the solution of the governing equations of fluid mechanics with distributed resistances that simulate the presence of the tubes. The modeling scheme used in the analysis and the numerical methods of solving the governing equations are described. The analysis is applied to the CRBRP-Intermediate Heat Exchanger (IHX), where its tube side plenum is simulated by several models that approximate its spherical boundary. The flow field within the plenum and the distribution of the total flow rate among the tubes are determined by the analysis

1977-09-21

10

Geothermal heat exchanger with coaxial flow of fluids  

Directory of Open Access Journals (Sweden)

Full Text Available The paper deals with a heat exchanger with coaxial flow. Two coaxial pipes of the secondary part were placed directly into a geothermal boring in such a way that geothermal water flows around the outer pipe. Starting from the energy balance of the exchanger formed in this way and the assumption of a study-state operating regime, a mathematical model was formulated. On the basis of the model, the secondary circle output temperature was determined as a function of the exchanger geometry, the coefficient of heat passing through the heat exchange areas, the average mass isobaric specific heats of fluid and mass flows. The input temperature of the exchanger secondary circle and the temperature of the geothermal water at the exit of the boring were taken as known values. Also, an analysis of changes in certain factors influencing the secondary water temperature was carried out. The parameters (flow temperature of the deep boring B-4 in Sijarinska Spa, Serbia were used. The theoretical results obtained indicate the great potential of this boring and the possible application of such an exchanger.

Peji? Dragan M.

2005-01-01

11

Geothermal heat exchanger with coaxial flow of fluids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper deals with a heat exchanger with coaxial flow. Two coaxial pipes of the secondary part were placed directly into a geothermal boring in such a way that geothermal water flows around the outer pipe. Starting from the energy balance of the exchanger formed in this way and the assumption of a study-state operating regime, a mathematical model was formulated. On the basis of the model, the secondary circle output temperature was determined as a function of the exchanger geometry, the co...

Peji? Dragan M.; Stojiljkovi? Dragan T.; Stojiljkovi? Staniša T.; ?urovi?-Petrovi? Maja; Miti? Nebojša

2005-01-01

12

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2008-01-01

13

Optimization of cross flow heat exchangers for thermoelectric waste heat recovery  

International Nuclear Information System (INIS)

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

2004-06-01

14

Flow induced vibration of AGR heat exchanger tubes  

International Nuclear Information System (INIS)

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)

1979-01-01

15

Numerical optimization for thermal flow design of a parallel flow heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

There is a need to make heat exchangers for refrigeration and air conditioning systems compact in size and light in weight, because they are quite often installed into confined spaces. To meet the need, compact and light heat exchangers including the serpentine, laminated, and parallel flow type heat exchangers have been developed and used rather than the traditional tube heat exchangers. Here, thermal and flow characteristics of a parallel flow heat exchanger have been numerically examined to investigate the effects of its geometrical parameters on thermal performance. Flow nonuniformities along passages of the heat exchanger, which are believed to be dominantly influential to the thermal performance, have been observed to eventually optimize the design of the heat exchanger. The optimization has been done by minimizing the flow nonuniformity that was served as an object function when Newton's searching method was applied. The parameters include locations of separators, and the inlet and outlet of the heat exchanger. It is found that the heat transfer of the optimized model increased approximately 7.6% and the pressure drop decreased 4.7%, compared to those of the base model of the heat exchanger.

Lee, K.S.; Chung, K.; Cha, D.J.

1999-07-01

16

Segmented heat exchanger  

Science.gov (United States)

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.

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

2010-12-14

17

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

Science.gov (United States)

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

Khaled, A.-R. A.

2014-01-01

18

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

Science.gov (United States)

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

Khaled, A-R A

2014-01-01

19

The influence of some design parameters of heating tubes on the heat exchange conditions and flow resistance in heat exchangers  

International Nuclear Information System (INIS)

A simplified method of thermal and hydraulic calculations of heat exchangers has been proposed for design purposes. This method, based on some diagrams presented in the paper, enables to establish in a very short time the surface film conductance for variable geometric dimensions of flow channels, thus shortening the computing process. (author)

1979-01-01

20

Dynamics of compressible air flow in ducts with heat exchange  

Science.gov (United States)

An investigation into the effect of heat addition on subsonic flow of an air stream in a constant-area duct preceded by a convergent nozzle is carried out. A nozzle flow apparatus with a heat exchanger encasing the constant-area duct has been built for this purpose. Hot water is provided from an electric boiler where the flow rate and the in-flow hot water temperature could be controlled. It is confirmed experimentally, as predicted analytically, that heat transfer to the gas decreases its local static pressure along the duct axis, and that this decrease is associated with an increase in Mach number toward M = 1 at the exit (thermal choking). In the case of subsonic flow, the additional entropy generated by the heat interaction exceeding the amount that produces thermal choking can only be accommodated by moving to a new Rayleigh line, at a decreased flow rate which lowers the inlet Mach number. The good correlation between the experimental results and the analytical derivations illustrates that the experimental arrangement has potential for further experiments and investigations.

Abdulhadi, M.

1986-12-01

 
 
 
 
21

A simplified method of calculating heat flow through a two-phase heat exchanger  

International Nuclear Information System (INIS)

A simplified method of calculating the heat flow through a heat exchanger in which one or both heat carrying media are undergoing a phase change is proposed. It is based on enthalpies of the heat carrying media rather than their temperatures. The method enables the determination of the maximum rate of heat flow provided the thermodynamic properties of both heat-carrying media are known. There will be no requirement to separately simulate each part of the system or introduce boundaries within the heat exchanger if one or both heat-carrying media undergo a phase change. The model can be used at the pre-design stage, when the parameters of the heat exchangers may not be known, i.e., to carry out an assessment of a complex energy scheme such as a steam power plant. One such application of this model is in thermal simulation exercises within the TRNSYS modeling environment

2005-10-01

22

Numerical simulation of two phase flows in heat exchangers  

International Nuclear Information System (INIS)

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

2006-01-01

23

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

DEFF Research Database (Denmark)

The flow structure inside the inner tank and inside the mantle of a vertical mantle heat exchanger was investigated using a full-scale tank designed to facilitate flow visualisation. The flow structure and velocities in the inner tank and in the mantle were measured using a Particle Image Velocimetry (PIV) system. A Computational Fluid Dynamics (CFD) model of the vertical mantle heat exchanger was also developed for a detailed evaluation of the heat flux at the mantle wall and at the tank wall. The flow structure was evaluated for both high and low temperature incoming flows and for both initially mixed and initially stratified inner tank and mantle. The analysis of the heat transfer showed that the flow in the mantle near the inlet is mixed convection flow and that the heat transfer is dependent on the mantle inlet temperature relative to the core tank temperature at the mantle level. (C) 2004 Elsevier Ltd. All rights reserved.

Knudsen, Søren; Furbo, Simon

2005-01-01

24

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

1996-12-31

25

Investigation of heat exchange at the laminar flow of liquids in the pipe  

Directory of Open Access Journals (Sweden)

Full Text Available The results of the experimental investigation of heat exchange of various liquids at the laminar flow in pipes are presented in the paper. The design formula is received. Possibilities of heat exchange intensification are shown.

Ilyin Roman Albertovich

2011-12-01

26

CFD simulation of flow distribution in the header of plate-fin heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The flow distribution through a plate-fin heat exchanger is studied by using a computational fluid dynamics (CFD) code, FLUENT. The flow distribution through any heat exchanger affects its performance. In designing a heat exchanger, it is assumed that the fluid is uniformly distributed through the heat exchanger core. In practice, however, it is impossible to distribute fluid uniformly, because of an improper inlet configuration, imperfect design, and a complex heat transfer process. The CFD simulation of the flow distribution in the header of a conventional plate-fin heat exchanger is presented. It is found that the flow maldistribution is very serious in the y-direction of the header. A modified header is proposed and simulated using CFD. The modified header configuration has a more uniform flow distribution than the conventional header configuration. Hence, the efficiency of the modified heat exchanger is seen to be higher than that of the conventional heat exchanger. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Wasewar, K.L. [Department of Chemical Engineering, Indian Institute of Technology, Roorkee (India); Hargunani, S.; Atluri, P. [Mechanical Engineering Group, Birla Institute of Technology and Science, Rajastan (India); Naveen, K. [Chemical Engineering Group, Birla Institute of Technology and Science, Rajastan (India)

2007-10-15

27

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

International Nuclear Information System (INIS)

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

1995-01-01

28

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

29

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

International Nuclear Information System (INIS)

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.)

2009-04-01

30

Heat exchanger panel having reference indicia and improved flow distribution  

Energy Technology Data Exchange (ETDEWEB)

In a heat exchanger panel for use in a solar energy collector system, said panel comprising a plurality of spaced parallel individual tubular passageways connecting opposed headers defined by numerous island-like bonded portions connected by a plurality of tubular channels passing therebetween, the boundaries of said headers defining a generally triangular shape with at least one of said boundaries being inclined with respect to an edge of said panel, said headers including entry and exit portions to said panel, siad entry and exit portions being laterally displaced from the center of said panel to permit a heat exchange medium to flow into said panel and across said headers so that said medium flows through each of the plurality of spaced parallel indiviual tubular passageways connecting said headers; and said parallel individual tubular passageways being interconnected by further tubular interconnecting portions spaced from said headers the improvement wherein said tubular interconnecting portions are arranged across said panel at an inclination generally corresponding to the inclination of said at least one boundary.

Kleine, C.; Middleton, V.

1980-07-01

31

Simulation Studies on A Cross Flow Plate Fin Heat Exchanger  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2008-01-01

32

Woven heat exchanger  

Science.gov (United States)

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.

Piscitella, Roger R. (Idaho Falls, ID)

1987-01-01

33

Effect of flow maldistribution and axial conduction on compact microchannel heat exchanger  

Science.gov (United States)

When a compact microchannel heat exchanger is operated at cryogenic environments, it has potential problems of axial conduction and flow maldistribution. To analyze these detrimental effects, the heat exchanger model that includes both axial conduction and flow maldistribution effect is developed in consideration of the microchannel heat exchanger geometry. A dimensionless axial conduction parameter (?) is used to describe the axial conduction effect, and the coefficient of variation (CoV) is introduced to quantify the flow maldistribution condition. The effectiveness of heat exchanger is calculated according to the various values of the axial conduction parameter and the CoV. The analysis results show that the heat exchanger effectiveness is insensitive when ? is less than 0.005, and effectiveness is degraded with the large value of CoV. Three microchannel heat exchangers are fabricated with printed circuit heat exchanger (PCHE) technology for validation purpose of the heat exchanger model. The first heat exchanger is a conventional heat exchanger, the second heat exchanger has the modified cross section to eliminate axial conduction effect, and the third heat exchanger has the modified cross section and the cross link in parallel channel to mitigate flow maldistribution effect. These heat exchangers are tested in cryogenic single-phase, and two-phase environments. The third heat exchanger shows the ideal thermal characteristic, while the other two heat exchangers experience some performance degradation due to axial conduction or flow maldistribution. The impact of axial conduction and flow maldistribution effects are verified by the simulation results and compared with the experimental results.

Baek, Seungwhan; Lee, Cheonkyu; Jeong, Sangkwon

2014-03-01

34

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are ob...

Navarro, H. A.; Cabezas-go?mez, L. C.

2007-01-01

35

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

International Nuclear Information System (INIS)

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

2010-11-01

36

Flow vibrations and dynamic instability of heat exchanger tube bundles  

International Nuclear Information System (INIS)

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

1995-01-01

37

Processes of hydrodynamics and heat exchange in descending bubble flows  

International Nuclear Information System (INIS)

This paper examines the gas content, hydraulic resistance, heat transfer, and structure of descending bubble flows in the regimes of concurrent flow and of hovering of the gas phase. A comparison of the data on hydraulic resistance and on heat transfer reveals their qualitative similarity

1986-02-01

38

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

DEFF Research Database (Denmark)

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

Friis, Alan; Szabo, Peter

2002-01-01

39

Heat exchangers  

International Nuclear Information System (INIS)

This invention relates to a heat exchanger, more particularly intended, although not exclusively, for transferring the thermal power acquired by an initial fluid medium cooling the core assemblies of a nuclear reactor to another fluid medium isolated from the first, therefore having low activity and suitable them to generate steam in a separate generator. The invention applies particularly in the case where the first fluid medium or primary fluid is a liquid metal, generally sodium, used as coolant in a fast nuclear reactor, the second fluid medium or secondary fluid also being liquid sodium, flowing through tubes between two tube plates respectively to enter an intake manifold and an outlet manifold of the secondary sodium. These tubes are externally steeped in the primary sodium. The exchanger concerned comprises two tube plates fitted inside an external envelope crossed by a primary fluid. These two tube plates are joined by a bundle of tubes extending vertically over the major part of their length and through which a secondary fluid flows, these tubes being covered externally by the primary fluid exchanging heat with the secondary fluid through these tubes

1976-01-01

40

Heat exchangers  

International Nuclear Information System (INIS)

The aim of this invention is to provide improvements in the circulation of the fluids in shell type heat exchangers used in the generation of steam, especially those operating by indirect heat exchange with a fluid circulating through a nuclear reactor. It is claimed that the improvements described promote the natural circulation both in the radial and axial directions and also reduce or eliminate sludge buildup within the exchanger. Thus the possibility of tube failure in a heat exchanger is reduced and the operation and maintenance of a heat exchanger are improved such that its useful life is enhanced and its efficiency increased. (U.K.)

1976-01-01

 
 
 
 
41

Effect of heat transfer correlations of a channel sodium flow on thermal sizing of sodium-to-sodium heat exchangers  

International Nuclear Information System (INIS)

A sodium-to-sodium heat exchanger has been widely used in a sodium-cooled fast reactor as an intermediate heat exchanger (IHX) or a decay heat exchanger (DHX). It is basically a shell-and-tube type counter-current flow heat exchanger, and sodium flows along the tube bundles on the shell-side of the heat exchanger. An accurate prediction of a heat transfer performance is very important for the heat exchanger thermal sizing in a sodium-cooled fast reactor (SFR) design application. To this end, a proper heat transfer coefficient for the appropriate design conditions should be provided for a better design of sodium heat exchangers. However, the experimental correlations for a heat transfer of liquid metal are very rare in the literature and they have large uncertainties since the experiment is very expensive and difficult. The most difficult thing is that the differences among the correlations are so serious that it is difficult to decide which correlation should be used for a particular flow situation. In the present study, we surveyed the conventional heat transfer correlations for single-phase liquid metal flows in a heat exchanger design. The thermal sizing results of sodium heat exchangers with respect to the Nusselt (Nu) number correlations were quantitatively discussed

2010-10-01

42

Numerical predictions of shell-side fluid flow and heat transfer in heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

A computer algorithm was developed to simulate two- and three-dimensional fluid flow and heat transfer in the shell side of single and two phase shell and tube heat exchangers. The governing equations are solved in primitive variable form using a semi-implicit consistent formulation in which a segregated pressure correction linked algorithm is employed. Numerical predictions are obtained for isothermal, two-dimensional, axisymmetric turbulent flow in a single phase experimental disc-and-doughnut heat exchanger. The system consists of alternating and equispaced doughnut and disc baffles located in a pipe with water flowing in turbulent regions. The two equation turbulence model as proposed by Nagano and Hishida (1987) is modified to accomodate disc and doughnut baffles. The proposed model leads to considerable computer time savings and better predictive capability for fluid flow in multibaffled regions. Four different types of two-phase shell and tube heat exchangers and steam condensors were modelled, and the numerical predictions were critically assessed by comparison with data for an experimental condensor and power plant condensor, indicating good agreeement. 44 refs., 56 figs., 9 tabs.

Zhang, Chao.

1989-11-01

43

Heat transfer within the initial part of a heat exchanger with flow swirling  

International Nuclear Information System (INIS)

The local heat transfer regularities within the initial part and the part of stabilized air flow in a longitudinal Stream-lined twisted oval tube bundle are experimentally investigated. The heat exchanger models have the twisted tubes length of 500 and 750 mm, number of tubes-37 and coolant porosity 0.527-0.544. The measurement system has ensured Nu number determination with maximum error +-7% according to the following range of parameter variation: twisting pitch Ssub(K) relation to maximum size of the tube oval dsup(s)/d=6.2-34, modified Frude criterion. Frsub(m)=64-2440, Re=2x103-4x104, wall temperature. Tsub(w) relation to the flow temperature Tsub(f)Tsub(w)/Tsub(fj=1-1.73), longitudinal coordinate x calculated from the flow inlet to the tube bundle relation to the equivalent diameter dsub(f)x/dsub(f)=3.75-103. The results obtained testify to the fact that within the initial part of the bundle in a turbulent as well as transitional flow field the character of the temperature factor Tsub(s)/Tsub(p) effect on heat transfer is identical, analogous to the temperature factor effect at the stabilized flow and does not depend on the Frsub(m) number. It has been found as well that the initial part length in twisted tube bundles at the axially symmetric flow inlet constitutes x/dsub(e)=14 and is practically independent on the Frsub(M) number. The investigation results can be used for calculating local heat transfer within the initial part and the part of a stabilized flow in heat exchangers with longitudinal flow-around of twisted tubes bundles at the axially symmetric inlet of the coolant flow

1982-02-01

44

Thermal design of multi-fluid mixed-mixed cross-flow heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

A fast analytical calculation method is developed for the thermal design and rating of multi-fluid mixed-mixed cross-flow heat exchangers. Temperature dependent heat capacities and heat transfer coefficients can iteratively be taken into account. They are determined at one or two special reference temperatures. Examples are given for the application of the method to the rating of special multi-fluid multi-pass shell-and-tube heat exchangers and multi-fluid cross-flow plate-fin heat exchangers. The accuracy of the method is tested against numerical calculations with good results. (orig.)

Roetzel, W. [Helmut Schmidt University, Institute of Thermodynamics, Hamburg (Germany); Luo, X. [Helmut Schmidt University, Institute of Thermodynamics, Hamburg (Germany); University of Shanghai for Science and Technology, Institute of Thermal Engineering, Shanghai (China)

2010-11-15

45

Potable water heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This patent describes an indirectly heated potable water heater heated by boiler water providing a high output flow rate with complete safety, comprising, an outer heated boiler water tank, one or more vented metal sheet heat exchangers contained within the tank and heated by the boiler water. The one or more sheet heat exchangers are connected to vented pipes, whereby a highly efficient high flow rate potable water heater is provided.

Lauderdale, R.J.

1986-12-30

46

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

DEFF Research Database (Denmark)

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

Kragh, Jesper; Rose, Jørgen

2007-01-01

47

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

International Nuclear Information System (INIS)

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

2009-06-21

48

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2012-01-01

49

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

DEFF Research Database (Denmark)

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

Nielsen, K.K.; Engelbrecht, K.

2012-01-01

50

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

Science.gov (United States)

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.

Angelotti, A.; Alberti, L.; La Licata, I.; Antelmi, M.

2014-04-01

51

Experimental Demonstration of a Novel Heat Exchange Loop Used for Oscillating Flow Systems  

Science.gov (United States)

This paper describes a non-resonant self-circulating heat exchanger which uses a pair of check valves to transform oscillating flow into steady flow that allows the oscillating flow system's own working gas to go through a physically remote high-temperature or cold-temperature heat source. Unlike traditional heat exchangers used in thermoacoustic systems, the length of the non-resonant self-circulating heat exchanger is not limited by the peak-to-peak displacement. In addition, it is also different from the resonant self-circulating heat exchanger that needs a specific resonant length. This invention may lead to easy design and fabrication of heat exchangers for oscillating-flow refrigeration system with large capacity. To verify this idea, we have built an experimental system by incorporating such a heat exchanger loop with a mechanical pressure wave generator. Measurements of heat transfer of the heat exchanger loop under different operating conditions including mean pressure, and operating frequency, etc. have been made. Our experiments have demonstrated its feasibility and flexibility for practical applications.

Gao, B.; Wu, Z. H.; Luo, E. C.; Dai, W.

2008-03-01

52

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

International Nuclear Information System (INIS)

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

1981-01-01

53

Two-phase flow instability in a liquid nitrogen heat exchanger  

International Nuclear Information System (INIS)

Experimental results on two-phase flow instability in a liquid nitrogen heat exchanger are shown. A preliminary visual observation study reveals that two unstable regions exist at low flow rate and high flow rate conditions, and that the corresponding flow patterns are the slug flow and the annular flow, respectively. Experiments with a heat exchanger are carried out for three cases with various combinations of tube length, attitude of the heat exchanger and the secondary flow fluid. A stability map and periods of flow oscillations are obtained in each experiment. A computer code LUSH-EX is developed based on a linear analysis technique with the density wave oscillation model. With this code, experimental data are analysed, and the oscillations in these experiments are found to be those of the density wave type. (orig.)

1986-08-01

54

Heat exchanger  

International Nuclear Information System (INIS)

In the main patent, a description was given of a heat exchanger with an exchange surface in preformed sheet metal designed for the high pressure and temperature service particularly encountered in nuclear pressurized water reactors and which is characterised by the fact that it is composed of at least one exchanger bundle sealed in a containment, the said bundle or bundles being composed of numerous juxtaposed individual compartments whose exchange faces are built of preformed sheet metal. The present addendun certificate concerns shapes of bundles and their positioning methods in the exchanger containment enabling its compactness to be increased

1975-03-10

55

Heat exchanger  

International Nuclear Information System (INIS)

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)

1977-01-01

56

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

Science.gov (United States)

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

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

2011-01-01

57

Air-side flow and heat transfer for an inclined offset strip fin-tube heat exchanger with grooves  

Energy Technology Data Exchange (ETDEWEB)

A numerical study has been performed to suggest the 1-row inclined offset strip fin-tube heat exchanger with grooves which has a similar performance to the 2-row plain offset strip fin-tube heat exchanger and to predict their air-side local flow and heat transfer characteristics. The results indicated that the reversed geometry of the main slit between the front half and the rear half of the heat exchanger causes more pressure drop than the identical one. In addition, the heat transfer rate of the 1-row A-type inclined offset strip fin-tube heat exchanger with grooves reached about 96% {approx} 99% of the 2-row offset strip fin-tube heat exchanger, and the fan power representing the energy consumption rate was reduced to 90% {approx} 99%. (author). 6 refs., 9 figs., 1 tab.

Bae, J.H.; Park, M.H. [Korea Power Engineering Company (Korea, Republic of)

1998-04-01

58

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-07-15

59

Two models for the dynamics of a cross flow heat exchanger  

International Nuclear Information System (INIS)

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)

1962-01-01

60

Device of deflection and distribution of the secondary coolant flowing in a heat exchanger  

International Nuclear Information System (INIS)

The heat exchanger includes a lower chamber closed by a curved bottom and a tube bundle in which the secondary coolant flows. The secondary coolant is returned at 1800 and distributed in the tubes, inside the chamber. The deflection device includes a truncated central piece fixed by its large base on, the bottom, with its axis confused with the axis of the heat exchanger case. Around the truncated central piece, there is a truncated peripheral crown fixed by its small base on the bottom with its axis confused with the heat exchanger axis. The height of the central piece and of the peripheral crown are 25% lower than the height of the chamber of the heat exchanger. The invention can be applied to the intermediate heat exchangers of fast nuclear reactors cooled by liquid sodium

1982-01-27

 
 
 
 
61

Update heat exchanger designing principles  

International Nuclear Information System (INIS)

Update heat exchanger design principles are analysed. Different coolant pattern in a heat exchanger are considered. It is suggested to rationally organize flow rates irregularity in it. Applying on heat exchanger designing measures on using really existing temperature and flow rate irregularities will permit to improve heat exchanger efficiency. It is expedient in some cases to artificially produce irregularities. In this connection some heat exchanger design principles must be reviewed now

1985-11-01

62

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

Science.gov (United States)

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

Charvat, Pavel; Stetina, Josef; Pech, Ondrej; Klimes, Lubomir; Ostry, Milan

2014-03-01

63

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

Directory of Open Access Journals (Sweden)

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

Charvat Pavel

2014-03-01

64

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

Scientific Electronic Library Online (English)

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

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

65

Balance of mechanical energy and intensification effects of heat exchange in laminar liquid flow  

International Nuclear Information System (INIS)

The balance of mechanical energy for laminar flows of drop liquids with term-wise separation of all the constituents is presented. Numerical studies on evaluation of effects and causes of convective heat exchange intensification for the drop liquids internal flows are carried out on the basis of analysis of the mechanical energy balance

1998-01-01

66

Analysis of flow boiling of ammonia and R-114 in a matrix heat exchanger  

Science.gov (United States)

An analysis is carried out for flow boiling in a vertical matrix aluminum heat exchanger. The prediction model, developed for thin film evaporation in a previous study, is extended to include heat transfer in the slug-flow regime that exists at low mass qualities. Appropriate criteria is used to switch from slug-flow to thin-film annular-flow analysis. The two-phase-flow convective heat transfer enhancement for the slug-flow is correlated with inclusion of fluid Reynolds and Prandtl numbers in addition to commonly used Martinelli parameter. This approach reflects transient nature of heat transfer in the slug-flow regime. The thin-film annular-flow analysis developed in the previous study is refined with inclusion of a reliable two-phase friction factor correlation. The experimentally measured pressure drop is used to validate the friction factor correlation. The resulting prediction method is used to predict exit mass qualities for ammonia and R-114. The experimental analysis includes flow boiling of ammonia and R-114 in a vertical brazed-aluminum matrix heat exchanger. The test unit has straight perforated fins on the fluid side and extruded rectangular channels on the single-phase (water) heating-media side. Only two parameters are adjusted to validate the analytical prediction method, the constant in the friction factor correlation, and the constant in the slug-flow heat transfer correlation. The results show that the combination of slug-flow and thin-film annular-flow model gives better prediction of the overall performance of the matrix heat exchanger than a single model applied for the whole range of mass qualities.

Panchal, C. B.

1989-05-01

67

Heat and mass exchanger  

Science.gov (United States)

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.

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

2011-06-28

68

Microtube strip heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

During the last quarter, Doty Scientific, Inc. (DSI) continued to make progress on the microtube strip (MTS) heat exchanger. DSI completed a heat exchanger stress analysis of the ten-module heat exchanger bank; and, performed a shell-side flow inhomogeneity analysis of the three-module heat exchanger bank. The company produced 50 tubestrips using an in-house CNC milling machine and began pressing them onto tube arrays. DSI revised some of the tooling required to encapsulate a tube array and press tubestrips into the array to improve some of the prototype tooling. 2 refs., 4 figs.

Doty, F.D.

1991-07-08

69

Heat exchangers  

International Nuclear Information System (INIS)

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

1974-01-01

70

Experimental investigation of fluid flow and heat transfer in a single-phase liquid flow micro-heat exchanger  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work presents an experimental analysis of the hydrodynamic and thermal performance of micro heat exchangers. Two micro heat exchangers, characterized by microchannels of 100x100 and 200x200 µm square cross sections, were designed for that purpose. The fluid used was deionized water and there was no phase change along the fluid circuit. The fluid pressure drop along the heat exchanger and the heat transfer were measured and corrections were made to isolate the contribution of the micro c...

Garci?a-hernando, Ne?stor; Acosta-iborra, Antonio; Ruiz-rivas, Ulpiano; Izquierdo, Marcelo

2009-01-01

71

Heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

A heat exchanger assembly is described for cooling the interior of a closed cabinet containing electronic components or the like, comprising: a finned heat pipe core including: a plurality of spaced heat pipes positioned in at least one row, a plurality of spaced fins which are provided with colinear apertures through which each of the plurality of heat pipes can extend, the heat pipes being secured to the fins; affixing means for securing the finned heat pipe core to an associated cabinet; and, a pair of fans, one being operatively connected with each end of the finned heat pipe core, one of the fans, and an associated first end of the heat pipe core, being in contact with only the air inside the associated closed cabinet, the other of the fans and an associated second end of the finned heat pipe core being in contact with only the ambient air outside the associated cabinet, and wherein the fins have a spacing and a thickness which is sized to fit the performance curve of the fans wherein the fans each have a capacity of approximately 100 CFM (cubic feet per minute) and wherein the finned heat pipe core is optimized for the fans such that approximately fourteen fins are provided per inch of heat pipe length with each of the fins being approximately 0.008 inches in thickness, whereby the finned heat pipe core and the pair of fans are capable of transferring at least 200 watts of heat when the temperature inside the associated cabinet is approximately 20/sup 0/C above the ambient temperature.

Noren, D.W.

1986-07-15

72

Plate-fin heat exchanger performance reduction in special two-phase flow conditions  

Science.gov (United States)

This paper discusses the occurrence of various flow patterns of a cold, upflowing two-phase stream in an aluminium plate-fin heat exchanger (PFHE) and their impact on the overall heat exchanger performance. Various flow patterns were observed in a flow visualization rig comprising a single PFHE passage. At high gas mass fluxes both phases flow uniformly upwards. When decreasing the gas flow, a reversing slug flow becomes more and more pronounced. In this flow pattern fluid particles of significantly different temperatures can mix within the same passage. If the number of transfer units (NTU) is high, the effective temperature difference against a hot stream of the exchanger decreases. At very low gas mass fluxes a sudden static instability with liquid logging was observed. The liquid zones thus appearing can cover and thus deactivate large portions of the heating area. In PFHE design both phenomena should be taken into account, particularly for exchangers with low mean temperature differences and heated multicomponent streams with large boiling ranges.

Müller-Menzel, T.; Hecht, T.

73

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2007-01-01

74

Heat exchanger for heat production  

International Nuclear Information System (INIS)

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

1976-01-01

75

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

Energy Technology Data Exchange (ETDEWEB)

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.)

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

2012-04-15

76

Annular flow enhanced two-phase evaporative heat exchanger for space-based systems  

Science.gov (United States)

The development of multi-kilowatt space-based systems requires the transport of waste heat loads over long distances in micro-gravity conditions. In this context two-phase heat transport systems are attractive enabling a high rate of heat transport with low pump powers compared to single phase systems. In this context the design of a two-phase heat exchanger to transfer heat from a single-phase fluid (water) to a two-phase fluid (Freon 114) is discussed. Until reliable micro-gravity (less than 10-3g) test data on the heat transfer and pressure drop in a two-phase flows are available, it is deemed necessary that the design of heat exchanger's passages should promote gravity-independent flow regimes. This would make the design and test data, obtained at ground conditions, applicable in micro-gravity environments. The design concept investigated hinges on utilizing a set of helical flow passages (with small cross sectional area) to ensure a predictable flow regime, annular flow, up to high vapor qualities (greater than 0.8), in both micro-gravity and one 'g' environments. The concept was applied to the design of a 5 kW helically coiled evaporative heat exchanger for space-based systems, which was subsequently manufactured and tested. Ground tests gave results close to analytical predictions based on computer simulations of the heat transfer and pressure drops in helical flow passages. Finally design guideline for a two-phase evaporative heat exchanger for space-based systems is provided, along with conclusions and areas to be further researched.

Nikanpour, D.

77

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2009-07-01

78

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

International Nuclear Information System (INIS)

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

2009-04-23

79

Study on direct mixing type axial flow cyclone heat exchanger between gas and particles  

Energy Technology Data Exchange (ETDEWEB)

A direct mixing type axial flow cyclone heat exchanger between gas and high temperature particles is proposed and its heat exchange performance is examined experimentally by using the mock-up apparatus. The proposal was motivated by the concept of high temperature nuclear energy conversion system for which dense gas-solid suspension flow is considered as primary coolant. However, this heat exchanger will be very useful for the existing industrial processes. In this heat exchanger, the particles, after being mixed directly with gas, transfer their heat to the gas in the form of quasi-counter-flow and are effectively re-separated by centrifugal force due to swirling motion of the gas. Figure A-1 shows the exergy efficiency obtained from the experimental data. In this figure, {Gamma}{sub th}, {eta}{sub e}, G{sub g} and d{sub p} are thermal loading ratio, exergy efficiency, inlet gas flow rate and particle diameter, respectively. The following results were obtained from the experiments. (1) The dispersion of particles is saturated if the thermal loading ratio becomes unity and more. (2) The exergy efficiency has its maximum value when the thermal loading ratio is unity and less. The smaller particle diameter is obtained with the higher the exergy efficiency. (3) Though the gas flow rate does not have much effect on the exergy efficiency, its value is restricted by the re-separation efficiency. The present heat exchanger does not need any driving mechanical and huge facility. Therefore, it is anticipated that the promotion of energy-saving in the existing industrial processes by means of this heat exchanger.

Shimizu, Akihiko; Yokomine, Takehiko

1999-07-01

80

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

Directory of Open Access Journals (Sweden)

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

Yasin Ramezani

2013-05-01

 
 
 
 
81

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

International Nuclear Information System (INIS)

Tube and shell heat exchange components such as steam generators, heat exchangers and condensers are essential parts of CANDU nuclear power stations. Excessive flow-induced vibration may cause tube failures by fatigue or more likely by fretting-wear. Such failures may lead to station shutdowns that are very undesirable in terms of lost production. Hence good performance and reliability dictate a thorough flow-induced vibration analysis at the design stage. This paper presents our approach and techniques in this respect. (author)

1977-08-19

82

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

International Nuclear Information System (INIS)

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)

1986-01-01

83

Improvements in heat exchangers  

International Nuclear Information System (INIS)

The invention concerns improvements for heat exchangers for e.g. reactor-cooling systems using liquid sodium and water as primary and secondary coolants. The construction is designed so as to base the fluid flow of the sodium on natural convection where stagnation of the sodium flow and corrosion by impurities at the bottom of the heat exchanger are avoided. In addition, a fast leakage-warning system is possible in this construction

1974-08-23

84

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

International Nuclear Information System (INIS)

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

2014-05-01

85

Numerical simulation of two phase flows in heat exchangers  

International Nuclear Information System (INIS)

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

2006-01-01

86

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

Directory of Open Access Journals (Sweden)

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

H. A. Navarro

2007-12-01

87

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

Scientific Electronic Library Online (English)

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

Navarro, H. A.; Cabezas-Gómez, L. C..

88

Microscale Regenerative Heat Exchanger  

Science.gov (United States)

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

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

2006-01-01

89

Heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

A heat exchanger is described which consists of: spaced generally parallel header and tank constructions; each of the header and tank constructions having elongated, spaced, tube receiving holes in a header surface thereof; the holes in one header surface being aligned with and facing corresponding holes in the other header surface; and elongated open ended, flattened tubes extending between and into the header and tank constructions through aligned ones of the holes; the portions of each header surface between the holes including exteriorly convex domes defined by compound curves to thereby provide increased resistance to deformation as a result of force exerted by a pressurized fluid within the header and tank construction.

Saperstein, Z.P.; Awe, R.C.; Costello, N.F.; Larrabee, S.R.

1986-10-07

90

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

International Nuclear Information System (INIS)

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

2010-05-01

91

Microtube strip heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This progress report is for the September--October 1991 quarter. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

Doty, F.D.

1991-10-16

92

A review of heat exchanger tube bundle vibrations in two-phase cross-flow  

International Nuclear Information System (INIS)

Flow-induced vibration is an important concern to the designers of heat exchangers subjected to high flows of gases or liquids. Two-phase cross-flow occurs in industrial heat exchangers, such as nuclear steam generators, condensers, and boilers, etc. Under certain flow regimes and fluid velocities, the fluid forces result in tube vibration and damage due to fretting and fatigue. Prediction of these forces requires an understanding of the flow regimes found in heat exchanger tube bundles. Excessive vibrations under normal operating conditions can lead to tube failure. Relatively little information exists on two-phase vibration. This is not surprising as single-phase flow induced vibration; a simpler topic is not yet fully understood. Vibration in two-phase is much more complex because it depends upon two-phase flow regime, i.e. characteristics of two-phase mixture and involves an important consideration, which is the void fraction. The effect of characteristics of two-phase mixture on flow-induced vibration is still largely unknown. Two-phase flow experiments are much more expensive and difficult to carry out as they usually require pressurized loops with the ability to produce two-phase mixtures. Although convenient from an experimental point of view, air-water mixture if used as a simulation fluid, is quite different from high-pressure steam-water. A reasonable compromise between experimental convenience and simulation of steam-water two-phase flow is desired. This paper reviews known models and experimental research on two-phase cross-flow induced vibration in tube bundles. Despite the considerable differences in the models, there is some agreement in the general conclusions. The effect of tube bundle geometry, random turbulence excitations, hydrodynamic mass and damping ratio on tube response has also been reviewed. Fluid-structure interaction, void fraction modeling/measurements and finally Tubular Exchanger Manufacturers Association (TEMA) considerations have also been highlighted

2004-05-01

93

A review of heat exchanger tube bundle vibrations in two-phase cross-flow  

International Nuclear Information System (INIS)

Flow-induced vibration is an important concern to the designers of heat exchangers subjected to high flows of gases or liquids. Two-phase cross-flow occurs in industrial heat exchangers, such as nuclear steam generators, condensers, and boilers etc. Under certain flow regimes and fluid velocities, the fluid forces result in tube vibration and damage due to fretting and fatigue. Prediction of these forces requires an understanding of the flow regimes found in heat exchanger tube bundles. Excessive vibrations under normal operating conditions can lead to tube failure. Relatively little information exists on two-phase vibration. This is not surprising as single-phase flow induced vibration; a simpler topic is not yet fully understood. Vibration in two-phase is much more complex because it depends upon two-phase flow regime i.e., characteristics of two-phase mixture and involves an important consideration, which is the void fraction. The effect of characteristics of two-phase mixture on flow-induced vibration is still largely unknown. Two-phase flow experiments are much more expensive and difficult to carry out as they usually require pressurized loops with the ability to produce two-phase mixtures. Although convenient from an experimental point of view, air-water mixture if used as a simulation fluid, is quite different from high-pressure steam-water. A reasonable compromise between experimental convenience and simulation of steam-water two-phase flow is desired. This paper reviews known models and experimental research on two-phase cross-flow induced vibration in tube bundles. Despite the considerable differences in the models, there is some agreement in the general conclusions. The effect of tube bundle geometry, random turbulence excitations, hydrodynamic mass and damping ratio on tube response has also been reviewed. Fluid-structure interaction, void fraction modeling/measurements and finally Tubular Exchanger manufacturers Association (TEMA) considerations have also been highlighted. (author)

2003-04-20

94

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

Science.gov (United States)

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.

Mikielewicz, Jaros?aw; Mikielewicz, Dariusz

2012-08-01

95

Plate heat exchanger  

International Nuclear Information System (INIS)

A plate heat exchanger is described, comprising multiple flat parallel comportments, each one between two neighbouring plates, these compartments being separated by narrow spaces through which a high pressure fluid flows, in normal operation, exchanging calories through the plates with another low pressure fluid passing through the compartments

1977-01-01

96

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

International Nuclear Information System (INIS)

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)

1979-01-01

97

Corrosive Resistant Heat Exchanger.  

Science.gov (United States)

A corrosive and erosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot cont...

S. L. Richlen

1987-01-01

98

Numerical study of a M-cycle cross-flow heat exchanger for indirect evaporative cooling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper numerical analyses of the thermal performance of an indirect evaporative air cooler incorporating a M-cycle cross-flow heat exchanger has been carried out The numerical model was established from solving the coupled governing equations for heat and mass transfer between the product and working air using the finite-element method The model was developed using the EES (Engineering Equation Solver) environment and validated by published experimental data Correlation between the coo...

Zhan, Changhong; Zhao, Xudong; Smith, Stefan; Riffat, S. B.

2011-01-01

99

Buffeting of heat exchanger tube arrays in a cross flow  

International Nuclear Information System (INIS)

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)

1979-01-01

100

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

Directory of Open Access Journals (Sweden)

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.

Adrian Bejan

1999-12-01

 
 
 
 
101

Two-phase flow instability in a liquid nitrogen heat exchanger  

International Nuclear Information System (INIS)

Experimental results on the two-phase flow instability in a liquid nitrogen heat exchanger are shown. The experiments are carried out in four cases with various combinations of tube lengths with some bends, the attitude of the heat exchanger, the secondary fluid and the subcooler. A stability map and periods of oscillations are obtained in each experiment. In the case of a vertical heat exchanger with a 6 m pipe containing four bends, there are two unstable regions ; while there is one unstable region in the case of that with two bends. In the experiment using the horizontal heat exchanger with four bends and steam as the secondary fluid, oscillations of higher modes together with the fundamental one occurred. For the example of the same heat exchanger with a subcooler, oscillations of two modes occurred. A computer code is developed based on the linear analysis technique with the density wave oscillation model. With this code, experimental data are analyzed and it is found that the oscillations in these experiments are those of the density wave type. (author)

1986-01-01

102

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

International Nuclear Information System (INIS)

Highlights: ? Air side heat transfer and flow characteristics of mesochannel cross-flow heat exchanger are studied experimentally. ? Hot ethylene glycol–water mixture (50:50) at constant mass flow rate is used against varying air flow. ? Air side heat transfer and fluid flow key parameters such as Nusselt number, Colburn factor, friction factor are obtained. ? General correlations are proposed for air side heat transfer and fluid flow parameters. - Abstract: Air side force convective heat transfer and flow characteristics of cross-flow mesochannel heat exchanger are investigated experimentally. A series of experiments representing 36 different operating conditions have been conducted on a finned mesochannel heat exchanger through the fully automated dynamic single-phase experimental facility which is capable of handling a wide variety of working fluids in air-to-liquid cross-flow orientation. The mesochannel heat exchanger is made of 15 aluminum slabs with arrays of wavy fins between slabs; 68 one millimeter circular diameter port located at each slab, and the air side frontal area of 304-mm × 304-mm. The ethylene glycol–water mixture as the working fluid in the liquid side was forced to flow through mesochannels maintaining constant inlet temperature and flow rate at 74 °C and 0.0345 kg/s respectively whereas the inlet flowing air into the arrays of wavy fins was changed at four different temperature levels from 28 °C to 43 °C. Frontal air velocity 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.

2012-02-01

103

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

Science.gov (United States)

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 20°C 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.

Onstad, Andrew J.

104

Hydrodynamic and heat exchange features of pebbles in radial coolant flow  

International Nuclear Information System (INIS)

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

2009-01-01

105

Improvements to heat exchangers  

International Nuclear Information System (INIS)

The heat exchanger presented consists of a chamber designed so that heating fluid passes through it over tubes carrying fluid which removes heat from the heating fluid. Generally speaking the heating fluid flows in the chamber downwards to the level of lateral holes through which it leaves the chamber or upwards from the level of lateral holes through which it enters, this level corresponding in the chamber to the top of a heating fluid mass cooled by the heat removal fluid. Partition system are foreseen in the heating fluid mass, so arranged as to define a passage through which heating fluid rises by differential thermal effect from the lowest region to that of the inlet and oulet holes. This system applies especially to exchangers associated with a liquid sodium-cooled reactor

1974-08-23

106

Study of junction flows in louvered fin round tube heat exchangers using the dye injection technique  

Energy Technology Data Exchange (ETDEWEB)

Detailed studies of junction flows in heat exchangers with an interrupted fin design are rare. However, understanding these flow structures is important for design and optimization purposes, because the thermal hydraulic performance of heat exchangers is strongly related to the flow behaviour. In this study flow visualization experiments were performed in six scaled-up models of a louvered fin round tube heat exchanger. The models have three tube rows in a staggered layout and differ only in their fin spacing and louver angle. A water tunnel was designed and built and the flow visualizations were carried out using dye injection. At low Reynolds numbers the streakline follows the tube contours, while at higher Reynolds numbers a horseshoe vortex is developed ahead of the tubes. The two resulting streamwise vortex legs are destroyed by the downstream louvers (i.e. downstream the turnaround louver), especially at higher Reynolds numbers, smaller fin pitches and larger louver angles. Increasing the fin spacing results in a larger and stronger horseshoe vortex. This illustrates that a reduction of the fin spacing results in a dissipation of vortical motion by mechanical blockage and skin friction. Furthermore it was observed that the vortex strength and number of vortices in the second tube row is larger than in the first tube row. This is due to the thicker boundary layer in the second tube row, and the flow deflection, which is typical for louvered fin heat exchangers. Visualizations at the tube-louver junction showed that in the transition part between the angled louver and the flat landing a vortex is present underneath the louver surface which propagates towards the angled louver. (author)

Huisseune, H.; Willockx, A.; De Paepe, M. [Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); T' Joen, C. [Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); Department Radiation, Radionuclides and Reactors, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); De Jaeger, P. [Department of Flow, Heat and Combustion Mechanics, Ghent University, Sint-Pietersnieuwstraat 41, 9000 Gent (Belgium); NV Bekaert SA, Bekaertstraat 2, 8550 Zwevegem (Belgium)

2010-11-15

107

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

Science.gov (United States)

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

Ahn, Kyung H.; Ibrahim, Mounir B.

1991-01-01

108

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

Science.gov (United States)

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

Ahn, Kyung H.; Ibrahim, Mounir B.

1991-01-01

109

Laminar-flow Liquid-to-air Heat Exchangers - Energy-efficient Display Cabinet Applications  

Energy Technology Data Exchange (ETDEWEB)

Provisions are stored and displayed in supermarkets and grocery stores, at a temperature lower than the ambient, in display cabinets, which are responsible for a significant amount of the energy use in this sector. During the 1990s, major changes in the regulations governing the use of synthetic refrigerants took place in Sweden. This resulted in many refrigeration systems being converted to systems with indirect cooling by means of a liquid secondary refrigerant. The cooling coil is an important component in a display cabinet and traditionally, different kinds of tube-coils, with aluminium fins on expanded circular copper tubes, have been used. Many secondary heat transfer media have relatively high viscosities at low temperatures, and so the flow regime is often laminar, which may lead to poor heat transfer. However, it is possible to achieve high heat transfer coefficients even for laminar flows if an appropriate design of the heat exchanger is applied. Flat-tube heat exchangers have been used for a long time in automotive applications, where compactness is important. The display cabinet application involves low air velocities in combination with condensation of water vapour, and sometimes even frosting, and is therefore different from other applications where flat-tube heat exchangers have been used earlier. The objective of this research work has been to find a suitable, more energy efficient, heat exchanger design for indirectly cooled display cabinets. An efficiency that would mean that temperature differences would be so small that frosting could be avoided was aimed for. This research work has sandwiched experimental investigations with theoretical modelling and parameter studies. Initially, the heat transfer and pressure drop performance of conventional cooling coils operating with liquid secondary refrigerants was studied in fullscale experiments. Thereafter, the liquid-side (or tube-side) heat transfer was studied experimentally in small-scale experiments on three single multiport extruded flat tubes with different cross-sections. In both studies, the best agreement was found with predictions using the Gnielinski correlation for thermally developing laminar flows with the constant temperature boundary condition. After this, two different heat exchangers having flat tubes and plain fins on the air side were evaluated experimentally - one with continuous plate fins and one with serpentine fins. The results show that, for conditions similar to those of display cabinets, the heat transfer and pressure drop performance is affected to little or no extent by the occurrence of condensate water. Models for different types of flat-tube heat exchangers were thereafter created using the results from the experimental studies. In order to find appropriate optimising criteria for the display cabinet heat exchangers, the energy efficiency of a complete cooling system of an imagined supermarket has been studied. Finally, different designs of flat-tube heat exchangers with plain fins have been evaluated theoretically in a parameter study. The results show that considerable savings in the required electric drive power can be obtained in comparison with the traditional cooling coil. The savings can be up to 15 %. In addition, the flat-tube heat exchangers could operate with a minimum temperature difference of around 1 K. This makes frost-free operation possible for many display cabinet applications and thereby the savings potential even larger

Haglund Stignor, Caroline

2009-02-15

110

The Design of Heat Exchangers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2011-01-01

111

The Design of Heat Exchangers  

Directory of Open Access Journals (Sweden)

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

Arturo Reyes-León

2011-09-01

112

The transient, steady-state, and stability behavior of a toroidal thermosyphon with a parallel-flow heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

The transient and steady-state heat transfer, fluid flow, and stability of a toroidal thermosyphon have been studied theoretically. The thermosyphon is heated over the lower half and cooled over the upper half by an annular parallel-flow heat exchanger. Under some conditions the system becomes unstable and the interaction between the fluids in the thermosyphon and in the heat exchanger is of special interest. Indeed, two neutrally stable curves are obtained for the same heat exchanger conditions. Detailed results and discussion are presented for the stability of the system as well as for the temperature, velocity, pressure drop, and efficiency.

Mertol, A.; Giz, A.T.; Greif, R.

1983-02-01

113

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

International Nuclear Information System (INIS)

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

2013-10-01

114

Heat pipe array heat exchanger  

Science.gov (United States)

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.

Reimann, Robert C. (Lafayette, NY)

1987-08-25

115

Numerical simulation of flow field in a fin tube heat exchanger  

International Nuclear Information System (INIS)

This paper reports on the computation of the flow field and heat transfer between two plate fins of a compact cross flow heat exchanger with staggered arrangement of tubes that has been carried out in Reynolds number range of 40 to 2000. Three Nusselt number plots on the fin show deterioration of heat transfer by 50%, or more in the stagnation zone of the rear tube due to the wake of the preceding tube. The Nusselt number distributions on the tube near the juncture of the tube and the fin deviates substantially from the two dimensional prediction. The Nusselt numbers on the midplane of the first tube in stagnation area compares well available experimental results of Nusselt number distribution on a cylinder in unbounded cross flow

1990-11-25

116

Heat transfer and flow studies of the liquid droplet heat exchanger  

Science.gov (United States)

This paper describes a lightweight, highly effective liquid droplet heat exchanger (LDHX) concept for thermal management in space. Heat is transferred by direct contact between fine droplets (100 to 300 micron diameter) of a low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the microgravity environment is accomplished by configuring the LDHX as a vortex chamber. A quasi-one-dimensional, two-phase heat transfer model of the LDHX is developed and used to investigate the potential use of the LDHX for both heating and cooling the working gas in a 100-k W(e) Braytoan cycle. Experimental studies on a small scale LDHX chamber, using air and water as the two media, show excellent agreement with the theoretical model.

Bruckner, A. P.; Shariatmadar, A.

117

Heat transfer and flow studies of the liquid droplet heat exchanger  

International Nuclear Information System (INIS)

This paper describes a lightweight, highly effective liquid droplet heat exchanger (LDHX) concept for thermal management in space. Heat is transferred by direct contact between fine droplets (100 to 300 micron diameter) of a low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the microgravity environment is accomplished by configuring the LDHX as a vortex chamber. A quasi-one-dimensional, two-phase heat transfer model of the LDHX is developed and used to investigate the potential use of the LDHX for both heating and cooling the working gas in a 100-k W(e) Brayton cycle. Experimental studies on a small scale LDHX chamber, using air and water as the two media, show excellent agreement with the theoretical model. 21 references

1987-01-01

118

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 arrange...

Suneela Sardar; Shahid Raza Malik

2013-01-01

119

Microtube strip heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

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

Doty, F.D.

1992-07-09

120

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

International Nuclear Information System (INIS)

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

2005-04-21

 
 
 
 
121

Modeling Free Convection Flow of Liquid Hydrogen within a Cylindrical Heat Exchanger Cooled to 14 K  

Energy Technology Data Exchange (ETDEWEB)

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

Green, Michael A.; Oxford U.; Yang, S.W.; Green, M.A.; Lau, W.

2004-05-08

122

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

International Nuclear Information System (INIS)

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

1974-12-01

123

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

International Nuclear Information System (INIS)

Heat exchange components must be analysed at the design stage to avoid flow-induced vibration problems. This paper presents information required to formulate flow-induced vibration excitation mechanisms in liquid and two-phase cross-flow. 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)

1978-05-12

124

Effect of flow mal-distribution on effective NTU in multi-channel counter-flow heat exchanger of single body  

Science.gov (United States)

Most heat exchangers in services belong to multi-channel heat exchangers. The working fluid is distributed among the multiple channels. This kind of heat exchangers usually has a flow distribution problem. In general, the flow is not evenly distributed and, as a result, the thermal performance of the heat exchanger degrades due to it. In this paper, such flow distribution effect in a single body multi-channel heat exchanger is evaluated in an analytic way. Transverse conduction through the heat exchanger body which is caused by the mal-distributed flow is formulated and included in NTU evaluation. The NTU relationship between the well-balanced flow distribution and the ill-balanced one is obtained. According to the analysis result, the heat exchanger has the best performance in case of the well-balanced flow distribution, as is expected, and has the performance degradation in case of the ill-balanced flow. The performance degradation is very severe in the heat exchanger with poor transverse conduction.

Jung, Jeheon; Jeong, Sangkwon

2007-04-01

125

Heat exchanger restart evaluation  

International Nuclear Information System (INIS)

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

1992-01-01

126

Heat exchanger restart evaluation  

International Nuclear Information System (INIS)

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

1992-01-01

127

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

International Nuclear Information System (INIS)

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

2013-12-01

128

Heat exchanger with heater  

International Nuclear Information System (INIS)

The subject of this invention is a heat exchanger with vertical tubes and heating enabling a distinctly improved thermo-dynamic efficiency to be obtained by placing the heater at the bottom end of the vaporiser, in other words near the primary fluid outlet, the secondary fluid flowing counter-current whilst ensuring a good degree of integration of the system as a whole (vaporiser and heater)

1976-01-01

129

Tubular heat exchanger for a nuclear reactor  

International Nuclear Information System (INIS)

Heat exchanger appliance, featuring a first heat exchanger to bring the heating fluid and a heated fluid into thermal communication by flow of the fluids inside this exchanger, and a pre-cooling heat exchanger arranged in one unit inside the first heat exchanger for the purpose of bringing the heating fluid into thermal communication with the heating fluid flowing in the first heat exchanger, so that the temperature of the heating fluid is lowered before it is placed in thermal communication with the heated fluid

1978-06-22

130

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work shows the experimental study of a continuous gas-solid fluidized bed with an immersed tube where cold water is heated by fluidized solid particles presenting inlet temperature from 450 to 700°C. Experiments were carried out in order to verify the influence of solid particle flow rate and distance between baffles immersed in a shallow fluidized bed. The solid material was 254µm diameter silica sand particles, fluidized by air in a 0.90m long and 0.15m wide heat exchanger. The me...

Berna?rdez Pe?cora, Arai? A.; Maria Regina Parise

2006-01-01

131

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

International Nuclear Information System (INIS)

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

1981-08-21

132

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

Directory of Open Access Journals (Sweden)

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 200şC from combustion having 0.35 kg/s mass flow rate flows along outside surface of the heat exchanger and transfers heat to the 25şC 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.

Nuntaphan, A.

2006-05-01

133

Heat exchanger control system  

International Nuclear Information System (INIS)

Measured values for primary temperature exit, a heat transfer tube temperature and secondary exit temperature are feed-back respectively and amounts of feed-back are collected together, to calculate a set value for a secondary fluid flow rate. The secondary fluid flow rate is controlled based on the set value. Since the control deviation for the secondary fluid is increased only with the control for the first fluid, the control deviation for the secondary flow rate is also feed-back to make them compatible. In addition, since the temperature change in the heat exchanger is shown by the flow of the fluid as a temperature change at the exit, the heat transfer tube temperature at the central portion thereof is detected and the control deviation is feed-back, to control the temperature change at the inside. Then the deviation of the temperature is scarcely caused, thereby enabling to change the reactor power following the scheduled value. (N.H.)

1993-07-14

134

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

Directory of Open Access Journals (Sweden)

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

Rafal Marcin Laskowski

2011-01-01

135

Anisotroping porous structure heat exchanger  

International Nuclear Information System (INIS)

The object of this invention is a heat exchanger with an anisotropic porous structure. Specifically, this invention concerns a heat exchanger for example, between a gas and a liquid that utilises, for the flow of one of the fluids, a containment at leats partly filled with a porous structure for improving the thermal exchanges between the hot primary fluid and the second fluid to be heated

1980-01-01

136

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 r...

1999-01-01

137

Nuclear installation comprising an integrated heat exchanger with primary coolant flowing tubes  

International Nuclear Information System (INIS)

A description is given of a nuclear reactor system having the following characteristics: a pressure vessel cylindrical in shape; a nuclear reactor core located in the centre of the pressure vessels; a heat exchanger inside a pressure vessel; a multiplicity of tubes located in the heat exchanger pressure vessel; an inlet nozzle for the water that passes through the cylindrical pressure vessel and provides communication for a fluid with the existing capacity between the heat exchanger pressure vessel and the outer surface of the tubes; a steam outlet pipe enabling the steam to leave the heat exchanger pressure vessel

1975-03-31

138

3D numerical heat transfer and fluid flow analysis in plate-fin and tube heat exchangers with electrohydrodynamic enhancement  

Energy Technology Data Exchange (ETDEWEB)

Three-dimensional laminar fluid flow and heat transfer over a four-row plate-fin and tube heat exchanger with electrohydrodynamic (EHD) wire electrodes are studied numerically. The effects of different electrode arrangements (square and diagonal), tube pitch arrangements (in-line and staggered) and applied voltage (V{sub E}=0-16 kV) are investigated in detail for the Reynolds number range (based on the fin spacing and frontal velocity) ranging from 100 to 1,000. It is found that the EHD enhancement is more effective for lower Re and higher applied voltage. The case of staggered tube pitch with square wire electrode arrangement gives the best heat transfer augmentation. For V{sub E}=16 kV and Re = 100, this study identifies a maximum improvement of 218% in the average Nusselt number and a reduction in fin area of 56% as compared that without EHD enhancement. (orig.)

Lin, Chia-Wen; Jang, Jiin-Yuh [National Cheng-Kung University, Department of Mechanical Engineering, Tainan (Taiwan)

2005-05-01

139

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

International Nuclear Information System (INIS)

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

2005-06-01

140

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Piccolo, Antonio

2011-01-01

 
 
 
 
141

Heat exchanger with ceramic elements  

Science.gov (United States)

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.

Corey, John A. (North Troy, NY)

1986-01-01

142

Double barrier heat exchanger  

International Nuclear Information System (INIS)

This invention concerns a double barrier heat exchanger, between a radioactive primary fluid and a secondary fluid, enabling a possible leak of primary fluid in the exchanger to be detected in particular. As the primary fluid flows through a primary ducting and the secondary fluid through a secondary ducting, a joint matrix is placed between the primary and secondary ductings and in contact with them. The matrix includes at least on element, for example silver, able to be made radioactive when it diffuses in the primary fluid which carries it to an activation source. The application concerns sampling systems of water cooled nuclear reactors

1981-08-10

143

Part 2: Computational simulation of flow through a vertical slurry heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

An effort was made to model the slurry flow computationally through the heat exchanger in Part 1. For that aim FLOW-3D a commercially available fluid mechanics and heat transfer finite difference code was used. The code was run on the Cray Y-MP 2/216, a two-processor supercomputer with 16 megawords (128 MB) of central memory and a 32 megaword I/O subsystem. At the time the simulation model was being formulated on the FLOW-3D the authors of the code were not aware that the code had been used for a similar purpose and were interested in finding out its capabilities. The modeling approach used three simulation strategies beginning with a single fluid model using properties of water and simulating 683 particles introduced at the inlet to the heat exchanger and were tracked towards the outlet. These particles were neutrally buoyant and had zero volume and mass. These were fluid particles that were tracked through the flow geometry. A recent addition to the model was the possibility that particles have their own inertia term. Each particle has its own independent velocity and satisfies the equation of motion as well. In this second simulation the particles were given a density similar to glass of 2.5 g/cm{sup 3} and a volume of 0.00818 cm{sup 3} which is the volume of a single spherical particle 250 {micro}m in diameter. Two different viscous drag coefficients were specified as a function of the relative velocity locally between the fluid and the particle. Also a coefficient of restitution of one (specular reflections) between particles was assigned. The last method used was with the help of a drift flux model. These models usually work well if the relative velocities are not too large between the two-phases. The best options chosen for that model is the two incompressible fluid model with different densities. No diffusion coefficients were given for each fluid so that the flow code simulates two immiscible materials. In all these models a k-{var{underscore}epsilon} turbulent flow model is used because of the expected Reynolds numbers of the flow. It was found from the limited testing on these models that the particle model with different fluid and particle densities is the most realistic and can be enhanced by increasing the number of particles allowed by the code to make the simulation more realistic. This is based in part on the comparative results between the computer simulations and the results from part 1 which indicated that with increased particle density and flow rate the particle density distribution at the entrance region of the heat exchanger becomes more uniform. The drift flux model took a much longer computing time and still did not converge to a steady state solution. It is concluded then that for a slurry flow with significant different phase density variations that a two-fluid model would be more appropriate for predicting the bulk flow in 3D geometries.

Moujaes, S.F.; Francis, J.J.; Nassersharif, B.

1999-07-01

144

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

International Nuclear Information System (INIS)

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

2012-06-24

145

Microtube strip heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

During the last quarter, Doty Scientific, Inc. (DSI) continued to make progress on the microtube strip (MTS) heat exchangers. The team has begun a heat exchanger stress analysis, however they have been concentrating the bulk of their analytical energies on a CFD model to determine the location and magnitude of shell-side flow maldistribution which decreases heat exchanger effectiveness. DSI received 120 fineblanked tubestrips from Southern Fineblanking (SFB) for manufacturing process development. Both SFB and NIST provided inspection reports of the tubestrips. DSI completed the tooling required to encapsulate a tube array and press tubestrips on the array. Pressing the tubestrips on tube arrays showed design deficiencies both in the tubestrip design and the tooling design. DSI has a number of revisions in process to correct these deficiencies. The research effort has identified a more economical fusible alloy for encapsulating the tube array, and determined the parameters required to successfully encapsulate the tube array with the new alloy. A more compact MTS heat exchanger bank was designed. 1 ref., 4 figs.

Doty, F.D.

1991-04-02

146

Sodium-NaK Engineering Handbook. Volume II. Sodium flow, heat transfer, intermediate heat exchangers, and steam generators  

International Nuclear Information System (INIS)

The second volume of a five-volume series is presented. The contents are arranged under the following chapter headings: (1) Fluid Mechanics of Liquid Metals, (2) Liquid-Metal Heat Transfer, (3) Intermediate Heat Exchangers, and (4) Steam Generators

1976-01-01

147

Investigations of flow characteristics in a plate fin and tube heat exchanger model composed of single cylinder  

Energy Technology Data Exchange (ETDEWEB)

The flow structure in a plate fin and tube heat exchanger model composed of single cylinder located between two parallel plates for duct height-to-cylinder diameter ratio of 0.365 for Reynolds numbers of 4000 and 7500 is investigated experimentally. Particle image velocimetry (PIV) technique is employed to obtain instantaneous, time-averaged and phase-averaged turbulent flow characteristics in the heat exchanger flow passage. Interactions between the main flow and the secondary flow are examined in detail in the horizontal and vertical planes of the flow passage. Horseshoe vortex system formed in close region of cylinder-plate junction and convected downstream in the main flow direction and its evolution in the circumference of the cylinder is also investigated in detail.

Sahin, B. [Department of Mechanical Engineering, Cukurova University, 01330 Adana (Turkey)]. E-mail: bsahin@cu.edu.tr; Akkoca, A. [Department of Mechanical Engineering, Mersin University, 33342 Mersin (Turkey); Oztuerk, N.A. [Department of Mechanical Engineering, Cukurova University, 01330 Adana (Turkey); Akilli, H. [Department of Mechanical Engineering, Cukurova University, 01330 Adana (Turkey)

2006-06-15

148

Long tube heat exchanger: the facility and some preliminary tests on the down center/up annular flow configuration  

Energy Technology Data Exchange (ETDEWEB)

A test facility was designed and constructed to study forced flow boiling heat transfer in a closed loop long tube heat exchanger which is a two concentric-tube vertical design. The system consists of a 12 m long heat exchanger which can be operated at pressures to 689.3 kPa with pumped or natural convection flow rates from 0.0631 to 0.631 liters/second and which can be irradiated with a maximum steady heat flux rate of 50 kW/m/sup 2/ by a set of resistive heaters operable at temperatures up to 1250/sup 0/C. The facility was also designed so that other heat exchanger configurations can be tested with minimum difficulty (i.e., little or no modification of the system other than to replace the heat exchanger). The preliminary tests indicate that the system can be operated in a stable mode. This facility was motivated primarily by the magma energy research program where energy is extracted from magma by heat exchangers similar to the configuration in this report.

Lee, D.O.; Johnson, R.W.; Weatherbee, R.L.

1980-03-01

149

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

150

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

International Nuclear Information System (INIS)

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

1985-11-01

151

Direct fired heat exchanger  

Science.gov (United States)

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.

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

1986-01-01

152

Bayonet heat exchangers in heat-assisted Stirling heat pump  

Energy Technology Data Exchange (ETDEWEB)

The Multi-Temperature Heat Supply System is a research project creating a city energy system with lower environmental load. This system consists of a gas-fueled internal combustion engine and a heat-assisted Stirling heat pump utilizing shaft power and thermal power in a combination of several cylinders. The heat pump is mainly driven by engine shaft power and is partially assisted by thermal power from engine exhaust heat source. Since this heat pump is operated by proportioning the two energy sources to match the characteristics of the driving engine, the system is expected to produce cooling and heating water at high COP. This paper describes heat exchanger development in the project to develop a heat-assisted Stirling heat pump. The heat pump employs the Bayonet type heat exchangers (BHX Type I) for supplying cold and hot water and (BHX Type II) for absorbing exhaust heat from the driving engine. The heat exchanger design concepts are presented and their heat transfer and flow loss characteristics in oscillating gas flow are investigated. The main concern in the BHX Type I is an improvement of gas side heat transfer and the spirally finned tubes were applied to gas side of the heat exchanger. For the BHX Type II, internal heat transfer characteristics are the main concern. Shell-and-tube type heat exchangers are widely used in Stirling machines. However, since brazing is applied to the many tubes for their manufacturing processes, it is very difficult to change flow passages to optimize heat transfer and loss characteristics once they have been made. The challenge was to enhance heat transfer on the gas side to make a highly efficient heat exchanger with fewer parts. It is shown that the Bayonet type heat exchanger can have good performance comparable to conventional heat exchangers.

Yagyu, S.; Fukuyama, Y.; Morikawa, T.; Isshiki, N.; Satoh, I.; Corey, J.; Fellows, C.

1998-07-01

153

Experiments on vibration of heat-exchanger tube arrays in cross flow  

International Nuclear Information System (INIS)

A series of tests has been made at the Commissariat a L Energie Atomique, Saclay, France, in cooperation with General Atomic Company, San Diego, on flow-induced vibration of simulated heat exchanger tube bundles in a cross flow of air. The tests were of two types. In the first type, a tube instrumented with pressure transducers was inserted at various locations in a tube bundle. Measurements were made of pressure spectra, coherence, and lift force. It was found that the turbulence-induced pressures rise from a low value at the bundle entrance to a relatively high value within the bundle. In the second type of test, tube bundles were fabricated from flexible plastic tubes, cantilevered off a tube sheet, and the vibration induced by cross flow was observed. An investigation was made of the effect of tube-to-tube frequency difference and spacing on the onset of instability. It was found that while present theory often qualitatively predicts the correct trends, it may not be quantitatively accurate in many cases

1981-08-21

154

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

Energy Technology Data Exchange (ETDEWEB)

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.

Austegard, Anders

1997-12-31

155

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

Directory of Open Access Journals (Sweden)

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

A. Barzegar

2009-01-01

156

Direct-contact heat exchanger for swirling countercurrent flow of hot gas and finely divided solids: A parametric study  

Energy Technology Data Exchange (ETDEWEB)

A vertically oriented solid-to-gas direct-contact heat exchanger (DCHX) has been proposed for heat recovery in high-temperature plants that process finely divided solids. The flows are countercurrent, with the inlet gas flow entering on the centerline and swirling strongly. Swirling enhances heat transfer and centrifuges the solid particles from the center to the wall in order to minimize entrainment and permit gravity separation. A computer program was written to calculate particle trajectories and heat-transfer rates (and, therefore, temperature profiles) for gas and solid phases. The flow model considers interactions between the particles and the flow field of the gas. The results of the computer program showed that the introduction of swirl significantly reduced the vertical distance required to achieve a given thermal efficiency. The countercurrent flow arrangement achieves high thermal efficiency in one contacting stage, unlike existing cocurrent suspension preheater systems, which require four or five stages. The practical application of this design to the cement industry appears unlikely, because very low gas velocities and correspondingly large areas of cross-sectional flow are required to prevent elutriation of the 74-{mu}m particles required for the chemical reactions. The computer program can be modified for spray-dryer applications by the addition of mass-transfer terms and a spray-formation model. In addition, the concept of a swirling flow heat exchanger may be applicable to other processes in which larger and heavier particles are used. 17 refs., 9 figs., 4 tabs.

Bell, K.J.; Arman, B.

1991-06-01

157

Direct-contact heat exchanger for swirling countercurrent flow of hot gas and finely divided solids: A parametric study  

Science.gov (United States)

A vertically oriented solid-to-gas direct-contact heat exchanger (DCHX) has been proposed for heat recovery in high temperature plants that process finely divided solids. The flows are countercurrent, with the inlet gas flow entering on the centerline and swirling strongly. Swirling enhances heat transfer and centrifuges the solid particles from the center to the wall in order to minimize entrainment and permit gravity separation. A computer program was written to calculate particle trajectories and heat transfer rates (and, therefore, temperature profiles) for gas and solid phases. The flow model considers interactions between the particles and the flow field of the gas. The results of the computer program showed that the introduction of swirl significantly reduced the vertical distance required to achieve a given thermal efficiency. The countercurrent flow arrangement achieves high thermal efficiency in one contacting stage, unlike existing cocurrent suspension preheater systems, which require four or five stages. The practical application of this design to the cement industry appears unlikely, because very low gas velocities and correspondingly large areas of cross-sectional flow are required to prevent elutriation of the 74 micron particles required for the chemical reactions. The computer program can be modified for spray-dryer applications by the addition of mass transfer terms and a spray-formation model. In addition, the concept of a swirling flow heat exchanger may be applicable to other processes in which larger and heavier particles are used.

Bell, K. J.; Arman, B.

1991-06-01

158

Heat exchanger module test  

Energy Technology Data Exchange (ETDEWEB)

The heat exchanger module test is a cooperative field test of shell-and-tube heat exchangers to be performed with brine from Chevron Resources Company's Heber, California, field. Overall heat transfer coefficients will be measured with isobutane and a mixture of isobutane-isopentane as the working fluid in a simulated power cycle.

Fulton, R.L.

1978-06-01

159

Wound tube heat exchanger  

Science.gov (United States)

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.

Ecker, Amir L. (Duncanville, TX)

1983-01-01

160

Annular flow enhanced two-phase evaporative heat exchanger for space-based systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The development of multi-kilowatt space-based systems requires the transport of waste heat loads over long distances in micro-gravity conditions. In this context two-phase heat transport systems are attractive enabling a high rate of heat transport with low pump powers compared to single phase systems. In this context the design of a two-phase heat exchanger to transfer heat from a single-phase fluid (water) to a two-phase fluid (Freon 114) is discussed. Until relia...

Nikanpour, D.

1991-01-01

 
 
 
 
161

Damping of heat exchanger tubes  

International Nuclear Information System (INIS)

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

1985-01-01

162

Dehumidification: Prediction of Condensate Flow Rate for Plate-Fin Tube Heat Exchangers Using the Latent j Factor  

Energy Technology Data Exchange (ETDEWEB)

Condensate flow rate is an important factor in designing dehumidifiers or evaporators. In this paper, the latentj fimtor is used to analyze the dehumidification performance of two plate-fin tube heat exchangers. This latent j factor, analogous to the total j factor, is a flmction of the mass transfa coefllcient, the volumetric air flow rate, and the Schmidt number. This latent j factor did predict condensate flow rate more directly and accurately than any other sensiblej factor method. The Iatentj factor has been used in the present study because the sensible j factor correlations presented in the literature failed to predict the condensate flow rate at high Reynolds numbers. Results show that the latent j i%ctor em be simply correlated as a fhnction of the Reynolds number based on the tube outside diameter and number of rows of the heat exchanger.

Baxter, V.D.; Chen, D.T.; Conklin, J.C.

1999-03-15

163

Dehumidification: Prediction of condensate flow rate for plate-fin tube heat exchangers using the latent j factor  

Energy Technology Data Exchange (ETDEWEB)

Condensate flow rate is an important factor in designing dehumidifiers or evaporators. In this paper, the latent j factor is used to analyze the dehumidification performance of two plate-fin tube heat exchangers. This latent j factor, analogous to the total j factor, is a function of the mass transfer coefficient, the volumetric air flow rate, and the Schmidt number. This latent j factor did predict condensate flow rate more directly and accurately than any other sensible j factor method. The latent j factor has been used in the present study because the sensible j factor correlations presented in the literature failed to predict the condensate flow rate at high Reynolds numbers. Results show that the latent j factor can be simply correlated as a function of the Reynolds number based on the tube outside diameter and number of rows of the heat exchanger.

Chen, D.T.; Conklin, J.C.; Baxter, V.D.

1999-07-01

164

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

165

Radiation effects on heat transfer in heat exchangers, (2)  

International Nuclear Information System (INIS)

In a high temperature gas-cooled reactor system, in which the working fluid exchanges heat at high temperature near 1000 deg C, the heat transfer acceleration by positively utilizing the radiation heat transfer between solid surfaces should be considered. This paper reports on the results of experiment and analysis for the effects of radiant heat on the heat transfer performance at elevated temperature by applying the heat transfer-accelerating method using radiators to the heat exchanger with tube bundle composed of two channels of heating and heated sides. As the test heat exchangers, a parallel counter flow exchanger and the cross flow exchanger simulating helical tubes were employed, and the results studied on the characteristics of each heat exchanger are described. The plates placed in parallel to flow in every space of the tube bundle arranged in a matrix were used as the heat transfer accelerator. The effects of acceleration with the plates were the increase of heat transmission from 12 to 24% and 12 to 38% in the parallel flow and cross flow heat exchangers, respectively. Also, it was clarified that the theoretical analysis, in which it was assumed that the region within pitch S and two radiator plates, with a heat-transferring tube placed at the center, is the minimum domain for calculation, and that the heat exchange by radiation occurs only between the domain and the adjacent domains, can estimate the heat transfer-accelerating effect and the temperature distribution in a heat exchanger with sufficient accuracy. (Wakatsuki, Y.)

1980-01-01

166

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 performanc...

Raj Karuppa Thundil R.; Ganne Srikanth

2012-01-01

167

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

International Nuclear Information System (INIS)

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

1975-10-17

168

Cascade reactor: heat exchanger design  

International Nuclear Information System (INIS)

The authors examined four heat-exchanger concepts: fluid-bed immersed-tube, fluid-bed direct contact, gravity-flow cascade (with helium gas in the interstices), and gravity-flow cascade (with vacuum in the interstices). Heat-transfer models and correlations can be applied with reasonable confidence for the case of a moving granule bed flowing over heat exchanger surfaces that are under vacuum, or with interstitial helium gas. Fluid-bed heat-transfer correlations are also available for immersed-tube heat-exchange surfaces. The secondary fluid can be either helium or water, but for this study, they evaluated the heat exchangers for uniform secondary steam-side conditions of conventional, superheated steam turbine cycles of modern fossil-fired power plants. All concepts use double-walled tubes to minimize tritium permeation into the steam and to reduce the possibility of water leaks into the blanket. They chose granule inlet and outlet temperatures to the heat exchanger as 1200 K and 800 K. The resulting designs are summarized in a table and discussed

1985-06-01

169

Nature's Heat Exchangers.  

Science.gov (United States)

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)

Barnes, George

1991-01-01

170

Active microchannel heat exchanger  

Science.gov (United States)

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.

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

171

Modelling of Multistream LNG Heat Exchangers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Soler Fossas, Joan

2011-01-01

172

Entropy generation analysis of parallel and counter-flow three-fluid heat exchangers with three thermal communications  

Science.gov (United States)

On the basis of the first and second laws of thermodynamics, the general expression of the number of entropy generation units of three-fluid heat exchangers with three thermal communications was derived. The effect of several non-dimensional design parameters on the number of entropy generation units of three-fluid heat exchangers was thoroughly discussed. Furthermore, the detailed comparisons of results have been given for the arrangement of the parallel flow and the counter flow. It is shown that the variation tendencies of the number of entropy generation units with the ratio of the thermal resistances, ratio of the thermal capacities, and number of heat transfer units for the parallel-flow arrangement are different from those of the counter-flow arrangement. There exists an extremum of the number of entropy generation units for the counter-flow arrangement. In addition, the entropy generation for the counter flow is mostly smaller than that of the parallel flow under the same conditions.

Deng-Fang, Ruan; Xiao-Feng, Yuan; Li, You-Rong; Wu, Shuang-Ying

2011-06-01

173

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

International Nuclear Information System (INIS)

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

1995-01-01

174

Determining the heat exchanger capacity of the 6.5/10 MW reactor as a function of temperature and water coolant flow  

International Nuclear Information System (INIS)

This paper describes the possibility of increasing the thermal power of the RA reactor, since there is a possibility to increase the heat flow of the heat exchanger. It is shown that the heat flow of the heat exchanger can be represented as a function of flow and the temperature of the incoming cooling fluid: Q = f (Q',t1'). Calculated values of the heat transfer coefficient are reduced by 25% because it has been found that the measured value was 25% higher than the real value of the heat transfer coefficient. Obtained data and diagrams can be used for determining the heat exchanger operating conditions for specific reactor operation regimes. The diagram shows that the the existing heat exchanger enables reactor operation at 10 MW power under any cooling condition, and even at 15 MW power under some conditions

1964-01-01

175

Experimental and numerical study of mixed convection with flow reversal in coaxial double-duct heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Velocity vectors in a vertical coaxial double-duct heat exchanger for parallel ascending flow of water under conditions of laminar mixed convection have been determined experimentally using the particle image velocimetry technique. The measured velocity distributions for large annular flow rates, resulting in an essentially isothermal environment for the stream in the inner tube, are in very good agreement with corresponding numerical predictions. For flow rates of the same order of magnitude in the inner tube and the annulus, and corresponding temperature differences of about 20 C, experimental observations show that flow reversal occurs simultaneously in both streams over large axial distances for both heating and cooling of the flow in the inner tube. (author)

Mare, Thierry; Voicu, Ionut; Miriel, Jacques [Laboratoire de Genie Civil et de Genie Mecanique (LGCGM), INSA de Rennes, IUT Saint Malo, 35043 Rennes (France); Galanis, Nicolas [Faculte de genie, Universite de Sherbrooke, Sherbrooke, QC (Canada); Sow, Ousmane [Laboratoire d' Energie Appliquee, Ecole superieure Polytechnique, Dakar (Senegal)

2008-04-15

176

Support for heat exchangers  

International Nuclear Information System (INIS)

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

1979-01-01

177

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

International Nuclear Information System (INIS)

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

2009-02-01

178

Thin film heat exchanger  

International Nuclear Information System (INIS)

The description is given of a heat exchanger between a first 'hot' fluid and a second fluid to be heated, of the type comprising at least one heat exchange wall separating the fluids and through which heat is exchanged. The characteristic of this exchanger is that the wall which includes an upper end is a cyclindrical area of which the generating lines are vertical and the straight section is composed of a regular succession of undulations alternately marking peaks of convex waves and peaks of concave waves and that the exchanger includes facilities for introducing the second fluid in the upper end near the convex wave peaks of the face of the wall turned towards the second fluid

1976-01-01

179

Thermoelectric heat exchange element  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2007-08-14

180

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

International Nuclear Information System (INIS)

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

1987-01-01

 
 
 
 
181

Heat exchanger design handbook  

CERN Document Server

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

Thulukkanam, Kuppan

2013-01-01

182

Plate-Type Heat Exchanger  

International Science & Technology Center (ISTC)

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

183

Lightweight Long Life Heat Exchanger.  

Science.gov (United States)

A shuttle orbiter flight configuration aluminum heat exchanger was designed, fabricated, and tested. The heat exchanger utilized aluminum clad titanium composite parting sheets for protection against parting sheet pin hole corrosion. The heat exchanger, w...

E. K. Moore

1976-01-01

184

An investigation of flow and resistance characteristics of heat exchanger with the 2-D LDV system and visualization technique  

International Nuclear Information System (INIS)

An experimental study of the heat exchanger which would be used in a nuclear reactor for low temperature heat-supplying is presented. A 2-D Laser Doppler Velocimeter was used as a unique technique to measure the mean velocity and turbulence intensity distributions in different sections of the model. The relationship between the resistance coefficient and Reynolds number also obtained in terms of the total pressure rakes covered by the casings and the wall static pressure pick-up holes. The flow visualization has realized by using a piece of light source with an Argon-Ion laser. It is apparent that the polystyrene particles seeded in the flow can trace the mean flow. The results showed that the self-similar phenomenon exists in the tube bundle flow system. There are some secondary vortices in the cross sections between two passages of the model

1987-01-01

185

A corrosive resistant heat exchanger  

Science.gov (United States)

A corrosive and erosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is pumped through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium. 3 figs., 3 tabs.

Richlen, S.L.

1987-08-10

186

Air flow measurement with the hydrometric vane behind laminated pipe heat exchangers; Luftstrommessung mit dem Fluegelradanemometer hinter Lamellenrohrwaermeuebertragern  

Energy Technology Data Exchange (ETDEWEB)

For the operation and control of operational parameters, air flow measurement under stationary conditions is necessary for space hvac systems. In the scope of this investigation, laminated pipe heat exchangers as heaters for dry collers and plate heat exchangers for heat recovery from outgoing air are considered. This article describes the test configuration, the test object, as well as the measured results. (HW) [Deutsch] Zur Inbetriebnahme und Ueberwachung der Betriebsparameter ist die Luftstrommessung unter stationaeren Bedingungen bei raumlufttechnischen Anlagen erforderlich. Im Rahmen der vorliegenden Untersuchung werden Lamellenrohrwaermeuebertrager, die als Erhitzer oder trockener Kuehler eingesetzt werden, und Plattenwaermeuebertrager, die zur Waermerueckgewinnung aus Fortluft eingesetzt werden, betrachtet. Der vorliegende Beitrag beschreibt die Versuchsanordnung, das Versuchsobjekt sowie die Messergebnisse. (HW)

Presser, K.H. [Fachhochschule Rheinland-Pfalz, Abteilung Trier, Fachbereich Versorgungstechnik, Trier (Germany)

1995-01-01

187

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

International Nuclear Information System (INIS)

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

1964-01-01

188

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 temperatu...

2011-01-01

189

Proactive heat exchanger program  

International Nuclear Information System (INIS)

This paper describes the proactive heat exchanger program at Pickering Nuclear Generating Station. The objectives, methodology, benefits and costs are presented. Examples of initial results are included. 4 refs, 2 figs

1992-11-22

190

Heat exchanger cleaning  

International Nuclear Information System (INIS)

A survey covers the various types of heat-exchange equipment that is cleaned routinely in fossil-fired generating plants, the hydrocarbon-processing industry, pulp and paper mills, and other industries; the various types, sources, and adverse effects of deposits in heat-exchange equipment; some details of the actual procedures for high-pressure water jetting and chemical cleaning of some specific pieces of equipment, including nuclear steam generators. (DN)

1980-05-01

191

Tubular heat exchangers. Rohrbuendel-Waermeaustauscher  

Energy Technology Data Exchange (ETDEWEB)

Depending on the field of application or on the use of the medium, heat exchangers which work according to the principle of counterflow, parallel flow or cross-flow are used in the area of heating technology, in service water heating or cooling systems. Heat exchangers with hair pin tube bundles, as two plate device, or with electric insert, water vapor generators and tube-in-tube heat exchangers are differentiated. Structure and mode of operation of tubular heat exchangers are explained with reference to the regulations. Compared to plate heat exchanges it shows that plate heat exchangers are more compact and that due to the embossed plates high velocities and turbulances can be produced in the narrow water pipes but this has the disadvantage that they are sensitive to pressure shock and soiling. (BWI).

Laeng, H. (Markom AG, Zurich (Switzerland))

1991-03-01

192

Counterflow Regolith Heat Exchanger  

Science.gov (United States)

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.

Zubrin, Robert; Jonscher, Peter

2013-01-01

193

CROSSMIX; A mathematical model of a multi-pass cross-flow heat exchanger with primary fluid mixing  

International Nuclear Information System (INIS)

A two-dimensional model of a multi-pass cross-flow heat exchanger incorporating the interaction between primary and secondary fluids has been developed. Turbulent mixing and the cross flows due to temperature induced density gradients in the primary fluid are also included. The modelling equations are solved numerically using finite difference methods. The model is applicable to either serpentine or helical boilers and enables the effects of blanked-off tubes and other asymmetries to be predicted. An essential input to the model is the turbulent diffusivity within the relevant boiler geometry and the acquisition of these experimental data is discussed. (author)

1979-10-25

194

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2009-01-01

195

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

International Nuclear Information System (INIS)

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

2013-11-01

196

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  

Energy Technology Data Exchange (ETDEWEB)

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.

Rizzo, Enrico, E-mail: enrico.rizzo@kit.edu [Institute for Technical Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Heller, Reinhard [Institute for Technical Physics, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Richard, Laura Savoldi; Zanino, Roberto [Dipartimento Energia, Politecnico di Torino, 10129 Torino (Italy)

2013-11-15

197

Heat exchangers for district energy systems  

Energy Technology Data Exchange (ETDEWEB)

The three types of heat exchangers which are suitable for district heating applications were described. The three types which are dominating the market are: (1) the plate and frame heat exchanger, (2) the shell and coil heat exchanger, and (3) the brazed plate heat exchanger. The advantages and special features of each type were summarized. ELGE AB is a manufacturer of these heat exchangers and has sold them mainly to the Scandinavian market, but some units also to the United States and Canada. The fouling phenomenon associated with heat exchangers, and the factors affecting fouling, such as temperature, distribution, turbulence, velocity, flow, surface finish and water quality, were described. Recommendations were made as to how the life-cycle cost of the heat exchanger could be improved.

Dahlberg, M. [ELGE AB, Linkoping (Sweden)

1995-12-31

198

Thermosyphon heat exchanger  

Science.gov (United States)

Report summarizes final development, testing, and certification of pumpless, liquid-to-air heat exchanger for solar heating. System requires blower but no pump in water loop. Output is 35,000 Btu/hr when water temperature is 49 C.

Hankins, J. D.

1980-01-01

199

Heat exchange enhancement structure  

International Nuclear Information System (INIS)

A passive heat exchange enhancement structure which operates by free convection includes a flat mounting portion having a plurality of integral fins bent outwardly from one side edge thereof. The mounting portion is securable around a stovepipe, to a flat surface or the like for transferring heat from the pipe through the fins to the surrounding air by rotation-enhanced free convection

1980-01-01

200

Heat exchanger for automobiles. Waermetauscher fuer Kraftfahrzeuge  

Energy Technology Data Exchange (ETDEWEB)

A heat exchanger for automobiles with inlet and outlet openings for the heat transfer medium and cooling air passages has improved in a way that the cooling medium flows from the inlet to the outlet in a way that the covered zone is at the same time the coolest part of the heat exchange surface.

Schmehl, T.; Breuer, N.

1992-10-22

 
 
 
 
201

Duct acoustic resonances induced by flow over coiled and rectangular heat exchanger test banks, of plain and finned tubes  

International Nuclear Information System (INIS)

The generation of acoustic resonances in ducts of rectangular and circular cross-section by gas flow over straight and coiled tube heat exchanger banks contained in the ducts has been studied. It has been shown that there is a distinct difference in behaviour between shallow heat exchanger banks, ie less than 40 rows deep, and deep banks, ie greater than 50 rows deep. It has also been shown that there is a distinct difference between the behaviour of finned tubes and plain tubes which is also dependent on the method of supporting the tubes. Some of these features can be predicted from theory but other aspects cannot as yet be explained by theory. (author)

1979-01-01

202

Vibration isolation of dimple plate heat exchangers / Pieter Vergeer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dimple plate heat exchangers are a new type of welded compact plate heat exchangers. The dimple plates increase the turbulence of the fluid flowing over the plate, increasing the efficiency of the heat exchanger without increasing pressure drop over the heat exchanger. The compact design of the heat exchanger makes it possible to install the heat exchanger at the top of condenser columns, reducing the footprint area of the column by replacing standard shell and tube condense...

Vergeer, Pieter

2012-01-01

203

Vortex structure of a flow in a heat exchanger with twisted tubes  

International Nuclear Information System (INIS)

Experimental study on the intensity of longitudinal rate pulsations, autocorrelation function, spectral density and turbulence macroquantities in twisted tube beams with relative twisting pitches S/d=12.5 and 25 is carried out, therewith analogue thermoanemometric equipment, computers and digital signal analyser with tape interrecording, that allows an accurate X-ray analysis, was used. It is noticed that in the flow core an appreciable anisotropy of properties is detected that is due to presence of open channels and places of the tube contact. With high Reynolds numbers turbulent structure in this flow region yields to isotropic that may be used in designing heat mass transfer calculations in such beams

1986-01-01

204

Heat transfer and pressure drop in a compact pin-fin heat exchanger with pin orientation at 18 deg to the flow direction  

Science.gov (United States)

The heat transfer and pressure drop characteristics of a novel, compact heat exchanger in helium gas were measured at 3.5 MPa and Reynolds numbers of 450 to 12,000. The pin-fin specimen consisted of pins, 0.51 mm high and spaced 2.03 mm on centers, spanning a channel through which the helium flows; the angle of the row of pins to the flow direction was 18 deg. The specimen was radiatively heated on the top side at heat fluxes up to 74 W/sq cm and insulated on the back side. Correlations were developed for the friction factor and Nusselt number. The Nusselt number compares favorably to those of past studies of staggered pin-fins, when the measured temperatures are extrapolated to the temperature of the wall-fluid interface.

Olson, D. A.

1991-01-01

205

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

International Nuclear Information System (INIS)

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

1987-01-01

206

High temperature heat exchanger  

International Nuclear Information System (INIS)

The high temperature heat exchanger described is made up of a stack of blocks forming the body of the exchanger itself, and the end connecting blocks in which the primary and secondary ducts are drilled. Each end block has at least two surfaces inclined with respect to each other, on which the primary and secondary ducts respectively emerge. These surfaces are inter-joined and support a primary and secondary fluid separation piece

1975-01-01

207

Plate heat exchanger  

International Nuclear Information System (INIS)

The heat exchanger described is of the plate type. It includes, at least, one exchange bundle formed by a set of compartments side by side, each compartment being composed of two superimposed metal sheets, and separate inlet and outlet manifolds for the coolant circulating in that compartment. The manifolds of a given compartment substantially fill two half widths on opposite sides, at the ends of the compartment

1974-01-01

208

Microgravity condensing heat exchanger  

Science.gov (United States)

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

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

2011-01-01

209

Heat exchanger panel  

Science.gov (United States)

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

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

2005-01-01

210

Probe Measures Fouling As In Heat Exchangers  

Science.gov (United States)

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.

Marner, Wilbur J.; Macdavid, Kenton S.

1990-01-01

211

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

International Nuclear Information System (INIS)

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

1960-01-01

212

Cooling device for a heat exchange fluid  

International Nuclear Information System (INIS)

The invention refers to a system for cooling process or operation fluids, in which the local or general superheating of the coolant must be avoided. It particularly applies to the bleed fluid of a nuclear power station steam generator. This invention aims to create a heat exchange system that uses static components only and that is therefore completely reliable whilst remaining simple and relatively economical. This system includes a regeneration heat exchanger (with a primary and secondary system) and a triple flow heat exchanger with three circuits. The first and second circuits are in fluid communication with the primary and secondary circuits of the regeneration heat exchanger. The fluid communication between the regeneration heat exchanger and the triple circuit heat exchanger is such that the process fluid first goes through one of the circuits of the regeneration heat exchanger where it is cooled, then through one of the first two circuits of the triple circuit heat exchanger where it is cooled still more, then through the other of the circuits of the regeneration exchanger where it is heated and finally through the second of the first two circuits of the triple circuit heat exchanger where it is cooled again. A coolant flows through the third circuit in order to cool the process fluid concerned

1975-05-15

213

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

International Nuclear Information System (INIS)

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

2008-10-01

214

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

Energy Technology Data Exchange (ETDEWEB)

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

Zhao, X.; Riffat, S.B. [School of the Built Environment, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Li, J.M. [Department of Thermal Engineering, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084 (China)

2008-10-15

215

Cryogenic heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

A heat exchanger for vaporizing a cryogenic fluid comprises a conduit through which the fluid is passed and a heat transfer sleeve surrounding the conduit. The sleeve is comprised of two heat transfer sections, each having a central arcuate portion in close partial circumferential contact with the conduit, a plurality of radially extending heat transfer fins, and a pair of interlocking members located on the fins at a predetermined distance from the central portion for assembling the two sections together around the conduit. In the assembled state, the resiliency of the fins on which the interlocking members are located provides a continuous clamping for which permits the two central portions to maintain intimate contact with the conduit as it undergoes thermal contraction, while also facilitating assembly and disassembly of the two sections. Each heat transfer fins is also provided with a corrugated or rippled surface near its tip to increase its surface area and the rate of heat transfer and vaporization.

Lutjens, R. D.; Duron, P. P.

1984-12-11

216

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Barzegar, A.; Dehghan, A. A.

2009-01-01

217

Tubular heat exchanger  

International Nuclear Information System (INIS)

The invention concerns a heat exchanger of which the tubes, placed in a long casing, cross the casing cover in a sealed manner. These tubes are fixed to the tube plate forming this cover or to the branch tubes it comprises by means of compression joints. These joints make it possible to do away with welds that are sources of defects and to improve the operational safety of the apparatus. An advantageous form of the heat exchanger under the invention includes a manifold for each thermal exchange fluid, and one end of each tube is connected to this manifold by a pipe that is itself connected to the tube by a threaded connection. The latter provides for easy disconnection of the pipe in order to introduce a probe for inspecting the state of the tubes

1975-08-20

218

Straight tube heat exchanger for hot gases  

International Nuclear Information System (INIS)

The hot helium gas entering the heat exchanger flows through several units with the gas pipes being arranged in crosscounter flow. The second cold gas entering surrounds these units in a duct, which is in turn surrounded by a duct, in which the cooled helium gas flows back. Entry and outlet of both gases are situated at the same end of the heat exchanger, so that it can expand freely from one end to the other. (GL)

1979-01-01

219

A numerical analysis of three-dimensional turbulent fluid flow and heat transfer in plate-fin and tube heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Fluid flow and heat transfer over a multi-row (1-5 rows) plate-fin and tube heat exchanger are studied numerically. Flow is incompressible, three-dimensional and turbulent. The effects of tube arrangements and tube row numbers are investigated in detail for the Reynolds number ReH (based on the fin spacing H) ranging from 2000 to 10000. The effects of turbulence are simulated by the k-{epsilon} turbulence model. Stream and isothermal lines through the whole tube bank, local and average Nusselt number and pressure coefficient in the streamwise direction are presented. The numerical results for the average heat transfer coefficient agree well with the previously published experimental data.

Jang, Jiin-Yuh [National Cheng-Kung Univ., Tainan (Taiwan, Province of China); Chang, Wen-Jen; Lin, Min-Sheng [Feng-Chia Univ., Taichung (Taiwan, Province of China)

1996-12-31

220

Experimental evaluation of vibrations in heat exchangers  

International Nuclear Information System (INIS)

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

1997-10-27

 
 
 
 
221

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 count...

2011-01-01

222

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

International Nuclear Information System (INIS)

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

2008-11-05

223

Heat exchanger classification  

International Nuclear Information System (INIS)

The heat exchanger is the result of a combination of two half-exchangers, and hence of the combination of the conditions imposed on each of them, combination implying a specific type of construction. This reasoning led to the adoption of the type of construction as the initial criterion. According to type, the mean limit values are indicated for pressure, temperature and area, and it must be considered that these limits do not all act together. These indications enable comparisons between the possibilities of different types of exchangers. Whereas for pressure and temperature, these comparisons are immediate, insofar as area is concerned, it is necessary to account for the type of surface, tubes or plates, and its arrangement, irrespective of mechanical and maintenance conditions, for example. It must also be noted that divergencies sometimes exist between the limits guaranteed by builders and those allowed by major users

1971-06-16

224

Heat exchanger tube tool  

International Nuclear Information System (INIS)

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

1976-01-01

225

High Efficiency Flat Panel Microchannel Heat Exchanger.  

Science.gov (United States)

An apparatus providing high efficiency heat exchange between two fluids is disclosed. The apparatus most commonly comprises a flat panel with microchannels directing the flow of the two fluids, specifically: with a small hydraulic diameter in order to inc...

K. W. Kelly A. McCandless

2005-01-01

226

Heat transfer characteristics of a helical heat exchanger  

International Nuclear Information System (INIS)

Heat transfer performance of a helical heat exchanger was investigated. The heat exchanger is composed of a helical tube with rectangular cross section and two cover plates. The ?–Ntu relation of the heat exchanger was obtained using a numerical method. In the analysis, the flow in the tube (helical flow) was considered to be mixed and the flow outside the tube (radial flow) was unmixed. In the experiment, the Darcy friction factor (f) and convective heat transfer coefficient (h) of the radial flow were measured. The radial flow was air and the helical flow was water. Four different channel spacing (0.5, 0.8, 1.2 and 1.6 mm) were individually considered. The Reynolds numbers were in the range 307–2547. Two correlations, one for the Darcy friction factor and the other for the Nusselt number, were proposed. - Highlights: ? We analyze the heat transfer characteristics of a helical heat exchanger and examine the effectiveness–Ntu relation. ? Increasing number of turns of the heat exchanger would slightly increase the effectiveness. ? There is an optimum Ntu value corresponding to a maximum effectiveness. ? We measure the Darcy friction factor and Nusselt number of the radial flow and examine the correlations.

2012-06-01

227

Heat exchanger with transpired, highly porous fins  

Science.gov (United States)

The heat exchanger includes a fin and tube assembly with increased heat transfer surface area positioned within a hollow chamber of a housing to provide effective heat transfer between a gas flowing within the hollow chamber and a fluid flowing in the fin and tube assembly. A fan is included to force a gas, such as air, to flow through the hollow chamber and through the fin and tube assembly. The fin and tube assembly comprises fluid conduits to direct the fluid through the heat exchanger, to prevent mixing with the gas, and to provide a heat transfer surface or pathway between the fluid and the gas. A heat transfer element is provided in the fin and tube assembly to provide extended heat transfer surfaces for the fluid conduits. The heat transfer element is corrugated to form fins between alternating ridges and grooves that define flow channels for directing the gas flow. The fins are fabricated from a thin, heat conductive material containing numerous orifices or pores for transpiring the gas out of the flow channel. The grooves are closed or only partially open so that all or substantially all of the gas is transpired through the fins so that heat is exchanged on the front and back surfaces of the fins and also within the interior of the orifices, thereby significantly increasing the available the heat transfer surface of the heat exchanger. The transpired fins also increase heat transfer effectiveness of the heat exchanger by increasing the heat transfer coefficient by disrupting boundary layer development on the fins and by establishing other beneficial gas flow patterns, all at desirable pressure drops.

Kutscher, Charles F. (Golden, CO); Gawlik, Keith (Boulder, CO)

2002-01-01

228

Heat Exchangers Analysis  

Directory of Open Access Journals (Sweden)

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.

S.C. Pang

2013-01-01

229

Plate heat exchanger with different flow resistance for the fluids. Plattvaermevaexlare med olika stroemningsmotstaand foer medierna  

Energy Technology Data Exchange (ETDEWEB)

The depressions form thresholds in the flow channels for one fluid and will be located between the flow passages for the other fluid. Thus the flow resistances will be quite different in the channels.

Dahlgren, A.; Blomgren, R.

1987-04-21

230

Magnetic heat pump flow director  

Science.gov (United States)

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.

Howard, Frank S. (inventor)

1995-01-01

231

Liquid/liquid heat exchanger  

Science.gov (United States)

Conceptual design for heat exchanger, utilizing two immiscible liquids with dissimilar specific gravities in direct contact, is more efficient mechanism of heat transfer than conventional heat exchangers with walls or membranes. Concept could be adapted for collection of heat from solar or geothermal sources.

Miller, C. G.

1980-01-01

232

Development of high effectiveness droplet heat exchangers  

Science.gov (United States)

An experimental and analytical investigation has been carried out to assess the feasibility of developing high effectiveness, high temperature droplet heat exchangers and to identify practical applications for this type of direct contact heat exchanger. The droplet heat exchanger (DHX) concept studies uses a counterflowing gas and droplet configuration, uniformly sized droplets or particles, and a uniform dispersion of droplets in gas to achieve high heat exchanger effectiveness. Direct contact between the heat transfer media eliminates the solid heat transfer surfaces that are used in conventional heat exchangers and is expected to make very high temperature heat transfer practical. Low temperature simulation tests and analysis have been used to demonstrate that uniformly sized droplets can be generated over a wide range of fluid properties and operating conditions appropriate for high temperature droplet heat exchanger applications. One- and two-dimensional, two-phase flow and heat transfer computer models have been developed and used to characterize both individual component configurations and overall DHX heat transfer rates and effectiveness. The computer model and test data began to diverge as the operating pressure was increased, indicating a need for more general transport rate correlations and a better understanding of the two-phase flows that govern DHX operation.

Thayer, W. J., III; Sekins, K. M.; Bruckner, A. P.

1985-04-01

233

Fault-Tolerant Heat Exchanger  

Science.gov (United States)

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

Izenson, Michael G.; Crowley, Christopher J.

2005-01-01

234

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

Energy Technology Data Exchange (ETDEWEB)

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.

Culver, G.

1990-11-01

235

High heat flux single phase heat exchanger  

Science.gov (United States)

This paper presents the results obtained to date in a program to develop a high heat flux, single-phase heat exchanger for spacecraft thermal management. The intended application is a net generation interface heat exchanger to couple the crew module water thermal bus to the two-phase ammonia main thermal bus in the Space Station Freedom. The large size of the interface heat exchanger is dictated by the relatively poor water-side heat transfer characteristics. The objective of this program is to develop a single-phase heat transfer approach which can achieve heat fluxes and heat transfer coefficients comparable to those of the evaporation ammonia side. A new heat exchanger concept has been developed to meet these objecties. The main feature of this heat exchanger is that it can achieve very high heat fluxes with a pressure drop one to two orders of magnitude lower than those of previous microchannel or jet impingement high heat flux heat exchangers. This paper describes proof-of-concept experiments performed in air and water and presents analytical model of the heat exchanger.

Valenzuela, Javier A.; Izenson, Michael G.

1990-01-01

236

Cryogenic regenerative heat exchangers  

CERN Document Server

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.

Ackermann, Robert A

1997-01-01

237

Tube bundle heat exchanger  

International Nuclear Information System (INIS)

The heat exchanger described includes a combined heavy external structure composed of an outside cylindrical envelope fixed by its ends to an annular inlet head and an annular head for removing one of the fluids, an internal light structure then fitted in the heavy structure and formed by an annular bundle of tubes inserted and welded by their ends into holes drilled in the end plates and arranged in concentric layers leaving a large central passage accessible for fitting up. It can be used as steam generator in PWR and LMFBR type reactors

1974-01-01

238

Triple loop heat exchanger for an absorption refrigeration system  

Energy Technology Data Exchange (ETDEWEB)

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.

Reimann, Robert C. (Lafayette, NY)

1984-01-01

239

Optimum design of double pipe heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

Heat exchangers are used in industrial processes to recover heat between two process fluids. Although the necessary equations for heat transfer and the pressure drop in a double pipe heat exchanger are available, using these equations the optimization of the system cost is laborious. In this paper the optimal design of the exchanger has been formulated as a geometric programming with a single degree of difficulty. The solution of the problem yields the optimum values of inner pipe diameter, outer pipe diameter and utility flow rate to be used for a double pipe heat exchanger of a given length, when a specified flow rate of process stream is to be treated for a given inlet to outlet temperature. (author)

Swamee, Prabhata K. [Department of Civil Engineering, Indian Institute of Technology, Roorkee, Roorkee 247 667 (India); Aggarwal, Nitin [Department of Chemical Engineering, New Jersey Institute of Technology, NJ 07032 (United States); Aggarwal, Vijay [UOP, Unitech Trade Center, Sector 43, Block C, Sushant Lok Phase-1, Gurgaon, 122 001 Haryana (India)

2008-05-15

240

Hybrid Heat Exchangers  

Science.gov (United States)

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

Tu, Jianping Gene; Shih, Wei

2010-01-01

 
 
 
 
241

Study on the 3-dimensional flow characteristics in compact heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

In this research, three-dimensional flows in the tube banks are analized containing the wall effect by the fin. A three-dimensional Navier-Stokes Equation war, used in the curvilinear body-fitted coordinate system with standard {kappa}-{epsilon} model for better analysis of recirculation flow. By varying the distance between tubes (pitch length, L/D), tube configuration, and Reynolds number, the changes of flow properties like velocity, pressure are analized to understand the flow characteristics around the tube bank. Also the typical characteristics on the flow for the different parameters are discussed.

Baek, Je Huyn; Jeong, Han Seol; Yang, Choong Mo [Pohang Univ. of Science and Technology, Pohang, Kyungbuk (Korea, Republic of)

1996-12-31

242

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

International Nuclear Information System (INIS)

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)

1984-04-16

243

Heat exchanger for high temperatures and pressures  

International Nuclear Information System (INIS)

This invention refers to a heat exchanger for high temperatures and pressures. Specifically, the invention concerns a high temperature and high pressure heat exchanger of the type comprising, within a leaktight containment, a plurality of tubes around which flows a primary fluid and through which flows a secondary fluid, and at least one plate delimitating an outlet chamber for the secondary fluid at one of the ends of the containment. This exchanger prevents the establishment of excessive thermal gradients in the wall of this chamber, when rapid changes in the temperature of this secondary fluid occur

1977-01-01

244

Two phase heat exchanger symposium  

International Nuclear Information System (INIS)

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

1985-08-04

245

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

International Nuclear Information System (INIS)

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)

1979-01-01

246

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

Energy Technology Data Exchange (ETDEWEB)

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.

Austegard, Anders

1997-12-31

247

Improvements to heat exchangers with U tubes  

International Nuclear Information System (INIS)

The aim of this invention is to build an improved heat exchanger with return bend tubes. Under the invention, a tube with a return bend is provided that defines the flow path of a running fluid in heat exchange relation with another fluid taking a path on which the return bend tube is placed, so that one of the branches of the return bend tube has a greater temperature than the other. The tube is fitted and supported so that the stresses of its return bend are no greater than they would be were the heat exchanger entirely at ambient temperature

1976-08-06

248

Next Generation Microchannel Heat Exchangers  

CERN Document Server

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.

Ohadi, Michael; Dessiatoun, Serguei; Cetegen, Edvin

2013-01-01

249

Evaluation of heat transfer performance on drum side of orthogonal flow type Na heat exchanger. Application of inviscid vortex-free flow model to zig-zag tube arrangement system  

International Nuclear Information System (INIS)

Recently, for the purpose of heightening the economical efficiency and performance of FBRs, it has been attempted to evaluate the performance of intermediate heat exchangers and steam generators with large computation codes. If the heat transfer characteristics of individual heating tubes can be grasped with the required accuracy by numerical analysis, it is most economical and realistic. There is the possibility of being able to forecast the heat transfer coefficient using the inviscid vortex-free flow model considering only the basic features of flow fields with the practical accuracy. In this research, first, the visualization experiment on the flow orthogonally crossing the tube nest of zig-zag arrangement using water was carried out to elucidate the features. Based on the observed results, the analysis of the heat transfer coefficient of alkali metals orthogonally crossing the tube nest of zig-zag arrangement was carried out for single tube heating and whole tube heating systems, using the inviscid vortex-free flow model. The visualization experiment and the numerical analysis are reported. (K.I.)

1996-06-01

250

Mathematical Modeling of Spiral Heat Exchanger  

Directory of Open Access Journals (Sweden)

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

Probal Guha , Vaishnavi Unde

2014-04-01

251

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

2011-01-01

252

Heat exchanger with auxiliary cooling system  

International Nuclear Information System (INIS)

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

1980-01-01

253

Heat exchanger leakage problem location  

Science.gov (United States)

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.

Hej?ík, Ji?í; Jícha, Miroslav

2012-04-01

254

Heat exchanger leakage problem location  

Directory of Open Access Journals (Sweden)

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.

Jícha Miroslav

2012-04-01

255

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

International Nuclear Information System (INIS)

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

1986-01-01

256

Performance Investigation of Plate Type Heat Exchanger (A Case Study  

Directory of Open Access Journals (Sweden)

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.

Simarpreet Singh

2014-04-01

257

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

International Nuclear Information System (INIS)

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

2005-04-21

258

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

Science.gov (United States)

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

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

2002-01-01

259

Vibration in nuclear heat exchangers due to liquid and two-phase flow  

International Nuclear Information System (INIS)

The relationships discussed are based on findings derived from a comprehensive vibration testing program which included both water and simulated two-phase (air-water) flow regimes. Tube bundles of various configurations and spacings were tested in crossflow using 3/4 in (1.9 cm) and 7/8 in. (2.2 cm) o.d. tubes with 36 in. (91 cm) span lengths and as many as 40 tubes per array. Sufficient test loop capacity was provided to drive most test array configurations up to and beyond fluid-elastic instability. Parameters obtained included displacement, effective force coefficients, damping coefficients, Strouhal numbers, and instability constants for various tube array configurations in both liquid and simulated two-phase flow mediums

1981-01-01

260

Component Cooling Heat Exchanger Heat Transfer Capability Operability Monitoring  

International Nuclear Information System (INIS)

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

2010-05-16

 
 
 
 
261

High Temperature Heat Exchanger Project  

Energy Technology Data Exchange (ETDEWEB)

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

Anthony E. Hechanova, Ph.D.

2008-09-30

262

Method for removing coronene from heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

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

Kmak, W.

1980-07-29

263

Method for removing coronene from heat exchangers  

International Nuclear Information System (INIS)

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

1980-01-01

264

Thermodynamic Optimization of GSHPS Heat Exchangers  

Directory of Open Access Journals (Sweden)

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.

Ahmad Kahrobaeian

2007-09-01

265

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

Directory of Open Access Journals (Sweden)

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

Saad Farhan

2013-04-01

266

Random excitation of heat exchanger tubes by two-phase cross-flows  

International Nuclear Information System (INIS)

This paper reports the results of several experimental studies performed at CEA, which concern the random forces exerted on tube arrays subjected to two-phase cross-flows. A rather large data base was obtained in air-water at various void fractions. The data obtained in steam-water and freon refer to the high void fraction range which is typically that of PWR steam generators at nominal conditions. From this information an empirical correlation between the random forces exerted on the tubes and the homogeneous void fraction is derived which is found to hold over a large range of mass-flux. Furthermore the data referring to the distinct fluid mixtures explored here, are found to collapse reasonably well on the same correlation curve

1992-11-08

267

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

CERN Document Server

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...

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

2012-01-01

268

A heat exchanger expert system  

Energy Technology Data Exchange (ETDEWEB)

This article describes a real-time expert system for detecting and diagnosing faults in a 20-kilowatt (kW) microwave transmitter heat exchanger. Expert systems enhance operator productivity by quickly identifying problems and recommending appropriate solutions, or predicting i pending problems that have not yet occurred. The heat exchanger expert system has been tested and debugged. Applications and extensions of the expert system to heating, air-conditioning, and ventilating problems are discussed.

Bagby, D.G.; Cormier, R.A. (Jet Propulsion Lab., California Inst. of Technology, Pasadena, CA (US))

1989-01-01

269

Electroforming thin channel heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

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

Steffani, C.P.

1991-06-01

270

Microtube strip heat exchanger. Final technical report  

Energy Technology Data Exchange (ETDEWEB)

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

Doty, F.D.

1992-07-09

271

How flow dispersion affects exchanger performance  

International Nuclear Information System (INIS)

The Fluid Dynamics of the two streams in heat exchangers have not been analyzed sufficiently for studies of pressure drop. While the effect of axial dispersion of the process stream on the driving force is generally considered in the design of mass transfer operations, it is ignored for the design of the heat transmitting area. There may exist, however, large differences in heat exchanger efficiency as a result of different flow patterns, which may lie between perfect mixing and plug flow. In general, the heat transfer characteristics of different types of heat exchangers, e.g., single pass, cross flow, shell and tube, are represented by the correction factor F = Q/sub T//UA?T/sub iotan/ or the heat exchanger effectiveness E = Q/sub T//[(mc/sub p/)min (T/sub in/ - t/sub in/]. Graphical representations are generally given for plug flow and perfect mixing and are used to obtain the heat transfer, transfer area and the fluid outlet temperatures. In reality, however, neither of the extremes, plug or perfect mixing, are to be expected. The flow patterns will be of an intermediate type. In this article, graphical representations are given for this situation in terms of the factor, E, whose application is recommended when outlet temperatures are to be calculated

1987-01-01

272

Sleeving repair of heat exchanger tubes  

International Nuclear Information System (INIS)

Defective heat exchanger tubes can be repaired using techniques that do not involve the cost and schedule penalties of component replacement. FTI's years of experience repairing steam generator tubes have been successfully applied to heat exchangers. Framatome Technologies heat exchanger sleeves can bridge defective areas of the heat exchanger tubes, sleeves have been designed to repair typical heat exchanger tube defects caused by excessive tube vibration, stress corrosion cracking, pitting or erosion. By installing a sleeve, the majority of the tube's heat transfer and flow capacity is maintained and the need to replace the heat exchanger can be delayed or eliminated. Both performance and reliability are improved. FTI typically installs heat exchanger tube sleeves using either a roll expansion or hydraulic expansion process. While roll expansion of a sleeve can be accomplished very quickly, hydraulic expansion allows sleeves to be installed deep within a tube where a roll expander cannot reach. Benefits of FTI's heat exchanger tube sleeving techniques include: - Sleeves can be positioned any where along the tube length, and for precise positioning of the sleeve eddy current techniques can be employed. - Varying sleeve lengths can be used. - Both the roll and hydraulic expansion processes are rapid and both produce joints that do not require stress relief. - Because of low leak rates and speed of installations, sleeves can be used to preventatively repair likely-to-fail tubes. - Sleeves can be used for tube stiffening and to limit leakage through tube defects. - Because of installation speed, there is minimal impact on outage schedules and budgets. FTI's recently installed heat exchanger sleeving at the Kori-3 Nuclear Power Station in conjunction with Korea Plant Service and Engineering Co., Ltd. The sleeves were installed in the 3A and 3B component cooling water heat exchangers. A total of 859 tubesheet and 68 freespan sleeves were installed in the 3A heat exchanger, and 1020 tubesheet and 244 freespan sleeves were installed in the 3B heat exchanger. Hydraulically expanded sleeves were used in the freespan areas while the tubesheet sleeves were roll expanded. (author)

2000-04-18

273

Sleeving repair of heat exchanger tubes  

Energy Technology Data Exchange (ETDEWEB)

Defective heat exchanger tubes can be repaired using techniques that do not involve the cost and schedule penalties of component replacement. FTI's years of experience repairing steam generator tubes have been successfully applied to heat exchangers. Framatome Technologies heat exchanger sleeves can bridge defective areas of the heat exchanger tubes, sleeves have been designed to repair typical heat exchanger tube defects caused by excessive tube vibration, stress corrosion cracking, pitting or erosion. By installing a sleeve, the majority of the tube's heat transfer and flow capacity is maintained and the need to replace the heat exchanger can be delayed or eliminated. Both performance and reliability are improved. FTI typically installs heat exchanger tube sleeves using either a roll expansion or hydraulic expansion process. While roll expansion of a sleeve can be accomplished very quickly, hydraulic expansion allows sleeves to be installed deep within a tube where a roll expander cannot reach. Benefits of FTI's heat exchanger tube sleeving techniques include: - Sleeves can be positioned any where along the tube length, and for precise positioning of the sleeve eddy current techniques can be employed. - Varying sleeve lengths can be used. - Both the roll and hydraulic expansion processes are rapid and both produce joints that do not require stress relief. - Because of low leak rates and speed of installations, sleeves can be used to preventative repair likely-to-fail tubes. - Sleeves can be used for tube stiffening and to limit leakage through tube defects. - Because of installation speed, there is minimal impact on outage schedules and budgets. FTI's recently installed heat exchanger sleeving at the Kori-3 Nuclear Power Station in conjunction with Korea Plant Service and Engineering Co., Ltd. The sleeves were installed in the 3A and 3B component cooling water heat exchangers. A total of 859 tubesheet and 68 freespan sleeves were installed in the 3A heat exchanger, and 1020 tubesheet and 244 freespan sleeves were installed in the 3B heat exchanger. Hydraulically expanded sleeves were used in the freespan areas while the tubesheet sleeves were roll expanded. (author)

Street, Michael D.; Schafer, Bruce W. [Framatome Technologies, Inc. Virginia (United States)

2000-07-01

274

Heat pipe heat exchanger analytic design model  

Energy Technology Data Exchange (ETDEWEB)

This paper presents an analytical model to predict, as functions of operating characteristics and geometry, the overall thermal performance and pressure drops of a gas-gas heat exchanger using a closed two-phase thermosyphon. First, the thermal efficiency of a generic rank is correlated to the overall heat transfer characteristics. The correlations are then reviewed to estimate the gas pressure drops and heat transfer coefficients both outside and inside the closed two-phase thermosyphon. Finally, the gas temperatures at each rank inlet, the efficiency of the heat exchanger, and the gas pressure drops are correlated to the efficiencies of the various ranks.

Niro, A. (Politecnico di Milano, Milan (Italy). Dipt. di Energetica)

1991-09-01

275

21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.  

Science.gov (United States)

...exchanger is a device, consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood or perfusion fluid flowing through the device. (b) Classification. Class II (performance...

2010-04-01

276

Heat exchangers for HHT plants  

International Nuclear Information System (INIS)

Closed gas turbine installations are equipped with recuperator, precooler and, depending on the design concept, intercooler. If the heat source is a nuclear reactor, core auxiliary heat interchangers must be provided additionally. The report deals with the corresponding heat exchangers of the HHT reference plant (high-temperature reactor with helium turbine). (orig.)

1979-01-01

277

Direct-contact heat exchanger  

Science.gov (United States)

The working principle of direct contact heat exchanger, where heat transfer takes place between two immiscible fluids coming into direct contact, is described. Typical direct contact devices are outlined. A better understanding of the principles involved and the development of computational models for multiphase subsytems are concluded as stimulus for direct contact heat and mass transfer applications.

Bricard, A.

278

Hierarchic modeling of heat exchanger thermal hydraulics  

International Nuclear Information System (INIS)

Volume Averaging Technique (VAT) is employed in order to model the heat exchanger cross-flow as a porous media flow. As the averaging of the transport equations lead to a closure problem, separate relations are introduced to model interphase momentum and heat transfer between fluid flow and the solid structure. The hierarchic modeling is used to calculate the local drag coefficient C_d as a function of Reynolds number Re_h. 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 C_d are large, we believe that hierarchic modeling is an appropriate strategy for calculation of complex transport phenomena in heat exchanger geometries.(author)

2002-09-09

279

Explosive plugging of heat exchangers  

International Nuclear Information System (INIS)

The mechanism and development of explosive welding and particularly the application to tube-to-tubeplate welding is briefly reviewed. The need for plugging of heat exchangers in the power generating industry and the requirement for producing a high integrity weld are discussed. Details are given of the explosive plugging system developed for the reheater heat exchanger of the prototype fast reactor (PFR), including data on weld lengths and distortion of adjoining holes. Results of destructive and nondestructive tests on trial plugging of a seven hole array are given. The system described has been successfully applied to an actual heat exchanger and the procedure followed is briefly discussed

1972-09-17

280

Heat exchanger using graphite foam  

Science.gov (United States)

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.

Campagna, Michael Joseph; Callas, James John

2012-09-25

 
 
 
 
281

A heat exchanger provided with plates  

International Nuclear Information System (INIS)

The invention relates to a heat exchanger of the plate type, in which two fluids exchange calories through parallel metal plates, delimiting spaces separated from each other in which two fluids respectively flow without direct contact between them. The invention particularly applies in the case where one of the two fluids is water under pressure or else a circulating liquid metal, specially sodium, used in the system of a pressurised water or fast neutron reactor, the second fluid being water to be vaporised in the exchanger by the calories supplied by the first fluid. The arrangement is designed to give minimum bulk, particularly enabling the exchanger to be housed in the area between the core of a nuclear reactor and a casing or outer vessel, or else in an external sealed containment, with a view to recovering with the best efficiency the heat acquired by a coolant flowing through the core

1976-01-01

282

Heat exchange apparatus utilizing thermal siphon pipes  

Energy Technology Data Exchange (ETDEWEB)

A heat exchange apparatus is descirbed in which each of a plurality of thermal siphon pipes has an upper portion extending in an upper heat exchange section and a lower portion extending in a lower heat exchange section. Each pipe is closed at its ends and contains a heat transfer fluid so that when a hot fluid is passed through the lower heat exchange section, the heat is transferred from the hot fluid to the heat exchange fluid. A cool fluid is passed through the upper heat exchange section to remove the heat from the heat exchange fluid.

Daman, E.L.; Kunsagi, L.

1980-10-07

283

Investigation of Flow and Heat Transfer Characteristics of Plate Heat Exchanger Taking into Account Entrance Effects and Variation in Corrugation Height  

International Nuclear Information System (INIS)

Numerical analysis has been carried out to investigate the heat transfer characteristics of a plate heat exchanger. The multi-cell models with inlet part and outlet part are used for performing numerical simulation. The plate heat exchanger is characterized by chevron angle of 15 .deg. , corrugation pitch of 24mm and corrugation height 6?12mm. The length of the inlet-part considered in the analysis ranges from 24.8 to 124mm and Reynolds numbers range from 1,000 to 10,000. The correlations such as friction factor and Colburn factor are compared with previous experimental data. The results can be utilized for designing the plate heat exchanger

2010-11-01

284

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

Directory of Open Access Journals (Sweden)

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.

Z. Konopka

2008-07-01

285

DESIGN OF A COMPACT HEAT EXCHANGER FOR HEAT RECUPERATION FROM A HIGH TEMPERATURE ELECTROLYSIS SYSTEM  

Energy Technology Data Exchange (ETDEWEB)

Design details of a compact heat exchanger and supporting hardware for heat recuperation in a high-temperature electrolysis application are presented. The recuperative heat exchanger uses a vacuum-brazed plate-fin design and operates between 300 and 800°C. It includes corrugated inserts for enhancement of heat transfer coefficients and extended heat transfer surface area. Two recuperative heat exchangers are required per each four-stack electrolysis module. The heat exchangers are mated to a base manifold unit that distributes the inlet and outlet flows to and from the four electrolysis stacks. Results of heat exchanger design calculations and assembly details are also presented.

G. K. Housley; J.E. O' Brien; G.L. Hawkes

2008-11-01

286

Interface Heat Exchanger Heat Transfer Element Test.  

Science.gov (United States)

The Interface Heat Exchanger Coldplate, Part Number 58A831057, is a two-circuit coldplate for the Gemini B coolant system. The purpose of the test was to determine the heat transfer coefficient from the interface surface of the coldplate to the coolant fl...

1968-01-01

287

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

International Nuclear Information System (INIS)

The current interest in refurbishment, life extension and new-build activity has meant a renewed emphasis on technical specifications that will ensure improved reliability and longer life. Preventing vibration and fretting-wear problems in steam generators and heat exchangers requires design specifications that bring together specific guidelines, analysis methods, requirements and appropriate performance criteria. The specifications must be firmly based on experimental data and field inspections. In addition, the specifications must be supported by theoretical analyses and fundamental scaling correlations, to cover conditions and geometries over the wide range applicable to existing components and probable future designs. The specifications are expected to evolve to meet changing industry requirements. This paper outlines the steps required to generate and support design specifications, and relates them to typical steam-generator design features and computer modeling capabilities. It also describes current issues that are driving changes to flow-induced vibration and fretting-wear specifications that can be applied to the design process for component refurbishment, replacement or new designs. These issues include recent experimental or field evidence for new excitation mechanisms, e.g., the possibility of in-plane fluidelastic instability of U-tubes, the demand for longer reactor and component lifetimes, the need for better predictions of dynamic properties and vibration response, e.g., two-phase random-turbulence excitation, and requirements to consider system 'excursions' or abnormal scenarios, e.g., a main steam line break in the case of steam generators. The paper describes steps being taken to resolve these issues. (author)

2008-11-16

288

Advantages of brazed heat exchangers in the gas processing industry  

Energy Technology Data Exchange (ETDEWEB)

Brazed aluminum heat exchangers have superior heat transfer capabilities and can be cost effective for non-corrosive gases and liquids as compared with traditional shell-and-tube exchangers. Even so, brazed aluminum exchangers are often not considered because of complicated design equations and complex stacking arrangements. The simpler yet less efficient shell-and-tube exchangers or networks of shell-and-tubes are employed instead. Recently, the design equations for multistream brazed aluminum heat exchangers for both single and multiphase flow have been added to the Heat Exchanger Rating package of the process simulator PROSIM{reg_sign}.

Lunsford, K.M. [Bryan Research and Engineering, Bryan, TX (United States)

1996-12-31

289

High-temperature self-circulating thermoacoustic heat exchanger  

Science.gov (United States)

Thermoacoustic and Stirling engines and refrigerators use heat exchangers to transfer heat between the oscillating flow of their thermodynamic working fluids and external heat sources and sinks. An acoustically driven heat-exchange loop uses an engine's own pressure oscillations to steadily circulate its own thermodynamic working fluid through a physically remote high-temperature heat source without using moving parts, allowing for a significant reduction in the cost and complexity of thermoacoustic and Stirling heat exchangers. The simplicity and flexibility of such heat-exchanger loops will allow thermoacoustic and Stirling machines to access diverse heat sources and sinks. Measurements of the temperatures at the interface between such a heat-exchange loop and the hot end of a thermoacoustic-Stirling engine are presented. When the steady flow is too small to flush out the mixing chamber in one acoustic cycle, the heat transfer to the regenerator is excellent, with important implications for practical use.

Backhaus, S.; Swift, G. W.; Reid, R. S.

2005-07-01

290

Designing heat exchangers for process heat reactors  

International Nuclear Information System (INIS)

A brief account is given of the IAEA specialist meeting on process heat applications technology held in Julich, November 1979. The main emphasis was on high temperature heat exchange. Papers were presented covering design requirements, design construction and prefabrication testing, and selected problems. Primary discussion centered around mechanical design, materials requirements, and structural analysis methods and limits. It appears that high temperature heat exchanges design to nuclear standards, is under extensive development but will require a lengthy concerted effort before becoming a commercial reality. (author)

1980-01-01

291

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

International Nuclear Information System (INIS)

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

2011-12-01

292

Analysis of Heat Transfer Enhancement in Spiral Plate Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available In the present study, the heat transfer coefficients of benzene in a spiral plate heat exchanger are investigated. The test section consists of a Plate of width 0.3150 m, thickness 0.001 m and Mean hydraulic diameter of 0.01 m. The mass flow rate of water (Hot fluid is varying from 0.5 kg sec-1 to 0.8 kg sec-1 and the mass flow rate of benzene (cold fluid varies from 0.4 kg sec-1 to 0.7 kg sec-1. Experiments have been conducted by varying the mass flow rate, temperature and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the nusselt number which can be used for practical applications is proposed.

Kaliannan Saravanan

2009-02-01

293

Condensation and frost formation in heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

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.

Rostami, A.A.

1982-01-01

294

Condensation and frost formation in heat exchangers  

International Nuclear Information System (INIS)

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

1982-01-01

295

Vibration damping in multispan heat exchanger tubes  

International Nuclear Information System (INIS)

Heat exchanger tubes can be damaged or fail if subjected to excessive flow-induced vibration, either from fatigue or fretting-wear. Good heat exchanger design requires that the designer understands and accounts for the vibration mechanisms that might occur, such as vortex shedding, turbulent excitation or fluidelastic instability. To incorporate these phenomena into a flow-induced vibration analysis of a heat exchanger requires information about damping. Damping in multispan heat exchanger tubes largely consists of three components: viscous damping along the tube, and friction and squeeze-film damping at the supports. Unlike viscous damping, squeeze-film damping and friction damping are poorly understood and difficult to measure. In addition, the effect of temperature-dependent fluid viscosity on tube damping has not been verified. To investigate these problems, a single vertical heat exchanger tube with multiple spans was excited by random vibration. Tests were conducted in air and in water at three different temperatures (25, 60, and 90oC). At room temperature, tests were carried out at five different preloads. Frequency response spectra and resonant peak-fitted damping ratios were calculated for all tests. Energy dissipation rates at the supports and the rate of excitation energy input were also measured. Results indicate that damping does not change over the range of temperatures tested and friction damping is very dependent on preload. (author)

1998-01-01

296

Liquid droplet heat exchanger studies  

International Nuclear Information System (INIS)

Recent studies at the University of Washington (Bruckner, et al., 1982, 1984, 1985) and elsewhere (Taussig, et al., 1985) have addressed the feasibility of direct contact heat exchanger concepts, such as the liquid droplet heat exchanger (LDHX), for space power systems. In the LDHX heat is transferred by direct contact between a recirculating cloud of finely dispersed liquid droplets and a working gas. A critical design requirements of the LDHX is effective separation of the heat exchange media following heat transfer. The principle of the cyclone dust separator, in which particulate matter is separated from a swirling gas by centrifugal forces, offers an effective approach to the problem. A variety of cyclone-based LDHX geometries have been investigated, culminating in a low aspect ratio vortex chamber configuration (Bruckner, et al., 1984, 1985)

1986-01-13

297

Experimental research on heat transfer in a coupled heat exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available 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 than 35%, and the average heating efficiency increases more than 55%, compared with the ordinary air-source heat pump.

Liu Yin

2013-01-01

298

Nonstationary heat exchange in channels  

International Nuclear Information System (INIS)

Results are reported for investigations of nonstationary processes of heat transfer to a single-phase heat-transport medium in tube-type channels in the presence of various types of disturbances. Two characteristic stages are distinguished for processes with aperiodic variation in flow rate: in the first, both the flow rate and heat flux vary and in the second, only the heat flux changes. A formula for calculating the reduced coefficient of nonstationary heat transfer has been obtained on the basis of experiments carried out with constant flow rate and variable heat flux and experiments with the flow rate changing in accordance with different laws. The universality of the formula has been confirmed by a series of experiments in which the transport-medium flow rate and the channel thermal power were varied simultaneously. 12 refs

1981-01-01

299

Compact gas-gas heat exchanger IFP  

Energy Technology Data Exchange (ETDEWEB)

The European market study carried out by IFP and Creusot-Loire in the present framework has shown that a 2 millions toe/year savings can be expected from new gas-gas heat recovery systems in the present industrial context. The main constraint to be overcome is the cost of setting up in industrial plants. The compactness and modular conception of the new stacked perforated plates (SPP) gas-gas heat exchanger will undoubtedly help in getting this new equipment on to the market. The exchanger consists of a block formed by the stacking of judiciously superpositioned perforated metal plates whose apertures create the fluid flow passages. This compact gas-gas cross flow heat exchanger is easy to manufacture, with low pressure drops and easy to clean fume passages. The different plates perforations geometries, tested in laboratories on small models (exchange area: 0.35 mS) showed the possibility of attaining specific areas of 125 mS/mT and heat transfer coefficients up to 70 W/mS/K. The data obtained from these tests serve as a basis for planning industrial devices and have been used to design a prototype (exchange area: 12.5 mS) which includes cleaning devices. The tests of this prototype carried out on a 1.6 MW boiler with fume flow-rates in range of a 2000 mT/h and outlet temperatures up to 400C showed a good agreement with the laboratory tests and demonstrated that specific heat transfer in excess of 5 kW/mT.C should be achievable, an order of magnitude better than tubular radiator-type units. A comparison of the expected cost price of the SPP unit with a number of other heat exchangers indicates that the SPP unit could be very competitive on the market for energy saving devices.

Grehier, A.; Raimbault, C.; Rojey, A.; Busson, C.; Chlique, B.; Dreuilhe, J.

1984-01-01

300

Heat Exchanger for Motor Vehicle Cooling System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1997-01-01

 
 
 
 
301

Heat exchanger with immersed tubes  

International Nuclear Information System (INIS)

A heat exchanger made of plunging tubes and separating two circulating fluids (the secondary fluid generally being water) is described. This heat exchanger is of the 'once-through' type but it directly produces superheated steam. This is made possible by a new design of each tube, these tubes being arranged in such a way as to allow internal recycling. In addition, the secondary fluid can come directly from a condenser, without previous re-heating. This design also allows an easy dismantling of the various internal structures for maintenance and control during operation

1975-01-01

302

Analytical study of heat exchanger design  

Energy Technology Data Exchange (ETDEWEB)

Analytical expressions for the temperature distributions for cold as well as hot fluids for a counterflow, tube-in-tube heat exchanger have been derived in terms of known design variables, like the properties of the material of the tube, geometrical configurations, inlet temperatures etc., by applying initial boundary conditions. The effects of change in configuration of flow on temperature distribution have been discussed in detail. Expressions for efficiency of the heat exchanger have also been derived, based on known design parameters for various special cases. (author).

Prabhakant; Tiwari, G.N. (Indian Inst. of Tech., New Delhi (India). Centre of Energy Studies)

1991-01-01

303

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Wai Meng Chin; Raghavan, Vijay R.

2011-01-01

304

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

International Nuclear Information System (INIS)

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

1998-04-01

305

Fluid circulation system for heat exchangers  

International Nuclear Information System (INIS)

A fluid circulation system for heat exchangers has two groups of tubes through which primary and secondary fluids flow, the tubes of one group being interdigitated with the tubes of the other group, and a heat transfer material interposed between the two groups of tubes, whereby heat is transferred from the primary fluid through the heat transfer material to the secondary fluid. A shell forms a closure around the tubes and the heat transfer material, and the shell has tertiary fluid inlet and outlet means. Openings in the heat transfer material form passageways through which the tertiary fluid can flow from the inlet means, through the heat exchanger, to the outlet means. Piping connects the tertiary fluid outlet means to the tertiary fluid inlet means , forming a complete cycle. Installed in this piping is a heat removal system. If the secondary fluid flow is interrupted, the tertiary fluid provides a redundant means by which the heat of the primary fluid can be removed from the heat exchanger. Monitoring means can be inserted into the piping, to detect any leakages which may occur in the primary and secondary tubes. Condensers or desiccating material can be installed in the heat removal means to remove any liquids which may leak into the tertiary fluid. Additionally, if the tertiary fluid is a gas or vapor, a turbine can be inserted into the piping and the tertiary fluid's power utilized to provide energy to power the compressor or pump which is circulating the tertiary fluid. In an emergency, this turbine can be connected to an electrical generator and provide emergency power to the rest of the plant

1982-01-01

306

Heat exchanger for coal gasification process  

Science.gov (United States)

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

Blasiole, George A. (Greensburg, PA)

1984-06-19

307

Polymer-based heat exchanger desiccant systems  

Energy Technology Data Exchange (ETDEWEB)

The increasing popularity of desiccant-enhanced air conditioning systems has sparked new interest in the search for a better, more efficient desiccant material. The ultimate goal of this research was to develop a material that, when applied to an existing air-to-air heat exchanger, would achieve the necessary heat and mass transfer in a single process, thus transforming a sensible heat exchanger into a total enthalpy exchanger. This study focused on the development and determination of appropriate polymeric desiccant materials for use in different heat and mass transfer systems. The specific objectives for the study were to select an appropriate polymer desiccant, determine the necessary materials properties for this material, and develop and implement mathematical models to analyze the desiccant performance. Two systems were investigated for this study: a rotary wheel total enthalpy exchanger and a fixed plate total enthalpy exchanger. Seven different polymer materials were analyzed to determine the most suitable candidate. Although for the specific conditions studied, the commercial paper-ceramic desiccant out-performed the PVOH materials in both rotary wheel and fixed plate systems, the results suggested that two PVOH materials, PVOH open-cell foam and PVOH/silica gel/molecular sieve composite, have potential for use in total energy exchange applications. By modifying the design conditions, total efficiencies exceeding 70% were achieved for both PVOH foam and PVOH/ceramic composite in rotary wheel systems. In addition, modified the design conditions resulted in total efficiencies greater than 90% for the PVOH foam in both counter-flow and cross-flow flat plate systems. These findings indicated that with appropriate optimization of the exchanger design, these two PVOH materials could have the potential to perform as well as desiccant materials in current rotary wheel and fixed plate exchanger systems.

Staton, J.C.; Howard, J.L.; Scott, E.P.; Kander, R.G.

1999-07-01

308

Heat transfer enhancement in heat exchangers by longitudinal vortex generators  

International Nuclear Information System (INIS)

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 ? = 25 degrees heat transfer is enhanced locally by more than 300% and in the mean by 50%. These values increase further with Re and ?

1990-11-25

309

Mechanical calculation of heat exchangers  

International Nuclear Information System (INIS)

Many heat exchangers are still being dimensioned at the present time by means of the American TEMA code (Tubular Exchanger Manufacturers Association). The basic formula of this code often gives rise to significant tubular plate thicknesses which, apart from the cost of materials, involve significant machining. Some constructors have brought into use calculation methods that are more analytic so as to take into better consideration the mechanical phenomena which come into play in a heat exchanger. After a brief analysis of these methods it is shown, how the original TEMA formulations have changed to reach the present version and how this code has incorporated Gardner's results for treating exchangers with two fixed heads. A formal and numerical comparison is then made of the analytical and TEMA methods by attempting to highlight a code based on these methods or a computer calculation programme in relation to the TEMA code

1977-10-07

310

OPTIMASI KINERJA HEAT EXCHANGER TABUNG KOSENTRIS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Heat exchanger effectiveness is affected by some factors such as pipe shape, temperature, cold and hot air direction and velocity entering the heat exchanger. Research about heat exchanger has been done but the significance level of the heat exchanger effectiveness resulted is unknown. A designed experiment should be done to optimize the performance of concentric tube heat exchanger with measured significance level. From the analysis of result of previous experiment, factors that seem to affe...

Didik Wahjudi

2000-01-01

311

Three-component heat exchanger  

International Nuclear Information System (INIS)

A three-component heat exchanger is proposed in which two media are carried in separate tube systems designed as approximately vertical, concentric, cylindrical (or plane) tube walls arranged in a vessel filled with a stagnant fluid compatible with the two media in such a way that a small clearance is left between the two tube walls. Such heat exchangers can be employed in nuclear power plants equipped with circuits carrying sodium and water(vapor). If the two media have very different enthalpies, the cross section or the arrangement of the different tubes relative to each other is balanced out. A lead-bismuth eutectic is proposed as the contact medium. (UWI)

1975-01-01

312

Micro-Scale Regenerative Heat Exchanger  

Science.gov (United States)

A micro-scale regenerative heat exchanger has been designed, optimized and fabricated for use in a micro-Stirling device. Novel design and fabrication techniques enabled the minimization of axial heat conduction losses and pressure drop, while maximizing thermal regenerative performance. The fabricated prototype is comprised of ten separate assembled layers of alternating metal-dielectric composite. Each layer is offset to minimize conduction losses and maximize heat transfer by boundary layer disruption. A grating pattern of 100 micron square non-contiguous flow passages were formed with a nominal 20 micron wall thickness, and an overall assembled ten-layer thickness of 900 microns. Application of the micro heat exchanger is envisioned in the areas of micro-refrigerators/coolers, micropower devices, and micro-fluidic devices.

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

2004-01-01

313

Influence of heating conditions in continuous-flow microwave or tubular heat exchange systems on the vitamin B$_1$ and B$_2$ content of milk  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of continuous-flow microwave heating of milk on the stability of vitamins B$_1$ and B$_2$ was determined by ion-pair reverse-phase high-performance liquid chromatography. Results were compared with those obtained using a conventional process having the same heating, holding and cooling phases. When milk was heated in a continuous microwave heating system, at 90 $^\\circ$C without a holding phase, no vitamin B$_1$ and vitamin B$_2$ losses were observed. However, when the holding time...

2000-01-01

314

Exchange flow with geological heterogeneity  

Science.gov (United States)

Two aquifers can be hydraulically connected by a fault cutting across the intermediate aquitard. If the upper aquifer contains denser fluid, an exchange flow across the fault will develop. The unstable density stratification leads to fingering pattern with localized zones of upwelling and downwelling along the fault. Due to the small volume of the fault relative to the aquifers the exchange-flow will quickly approach a quasi steady state. If the permeability of the fault plane is homogeneous, the average number of the quasi-steady plume fingers, , follows a power law function of the Rayleigh number Ra (? Ra1/2) and the exchange rate measured by dimensionless convective flux, the Sherwood number Sh, is a linear function of Ra (Sh? Ra). The presence of flow barriers along the fault triggers unsteady exchange flow and subsequently controls the growth of the plume fingers. If the barriers are sufficiently wide to dominate the flow system, they creates preferential pathways for exchange flow that determines the distribution of the quasi-steady fingers, and converges to a constant value. In addition, wider barriers induce substantial lateral spreading and enhance the efficiency of structural trapping, and reduce the exchange rate that follows a power law Sh? Ran, where ndeveloped fractures in unconventional reservoirs. Better understanding of the density-driven flow in a faulted system will allow more precise estimate of the reservoir capacity as well as more efficient operation of injection or production wells.

Chang, K.; Hesse, M. A.

2013-12-01

315

Issues of predicting performance of thermosyphon heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Determination of the performance of indirect solar heating systems that use thermosyphon heat exchangers requires knowledge of how thermosyphon flow rate and heat exchanger performance vary with operating conditions. In this paper, measured performance of a two-pass, tube-in-shell, double-wall heat exchanger is presented and discussed in terms of modeling issues. The inadequacy of using a simple temperature difference to predict thermosyphon flow rate is illustrated. Accuracy of prediction of thermosyphon flow rate from a pressure balance on the water loop depends on the accuracy of assumed temperature distributions in the heat exchanger and tank. For a given collector flow rate, heat exchanger performance depends on natural convection heat transfer coefficient and temperature of the antifreeze fluid and is not uniquely determined by thermosyphon flow rate. Models based on the assumption that for a given collector flow rate, overall heat transfer coefficient-area product or effectiveness of the heat exchanger are determined by thermosyphon flow rate may produce erroneous predictions of system performance.

Davidson, J.H.; Dahl, S.D. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Mechanical Engineering

1996-12-31

316

Plate heat exchangers: review of transport phenomena and design procedures  

Energy Technology Data Exchange (ETDEWEB)

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

Focke, W.W.

1983-02-01

317

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

Directory of Open Access Journals (Sweden)

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.

Wai Meng Chin

2011-01-01

318

Heat exchanger with auxiliary cooling system  

International Nuclear Information System (INIS)

The auxiliary cooling systems of nuclear reactors have a resistance to the fluid flow although they are not normally in operation and presumably may never be used. This is why the main object of the invention is to produce a heat exchanger with a simple and reliable auxiliary cooling mechanism capable of cooling the reactor without hindering the coolant flow during normal working. The exchanger includes a vertical casing, heat transfer tubes mounted in this casing, inlets and outlets for the secondary coolant to conduct it through the heat transfer tubes and inlets and outlets to conduct the primary coolant through a primary coolant space placed peripherally inside the casing and in heat transfer position with the heat transfer tubes. An auxiliary cooling system is located in an annular chamber around the heat transfer tubes. This annular chamber communicates by the top and by the bottom with the primary coolant space to cool this primary coolant, when it is not flowing, and this gives rise to natural circulation of the primary coolant downwards through this annular chamber

1976-12-16

319

Flow visualization and void fraction measurement in liquid-metal/water direct contact heat exchange by X-ray attenuation technique  

Science.gov (United States)

One concept being considered for steam generation in particular next generation nuclear reactor designs, involves water coming into direct contact with a circulating molten metal. To optimize the design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability. With the development of high performance digital detectors, radiography using X-rays or neutrons maybe a suitable technique to obtain information about that direct-contact interaction; i.e., void volume fractions, length scales and dynamic behavior. Under the basis of previous investigations, a complete methodology of the X-ray radiography for two-phase flow measurement has been developed from the facility and imaging analysis aspects. Through this developed methodology, a high energy X-ray imaging system is optimized for the direct-contact heat exchange experiment. Beside an on-line calibration procedure which practically quantifies the imaging system's performance, the extended linear system theory and Rose's model have also been used to evaluate the imaging system's performance, respectively. The bottleneck of the current imaging system and the future of system improvement direction have been pointed out. With our real-time, large-area high energy X-ray imaging system, the two-phase flow was visualized and stored digitally. An efficient image processing strategy has also been established by combining several optimal digital image processing algorithms. The approach has been implemented into a software computational tool written in MATLAB called T-XIP. Time-dependent heat transfer related variables, such as void fraction (void volume), local heat transfer coefficient, etc., were calculated using this software tool. Finally, an error analysis associated with the void fraction measurement has been given based on two procedures.

Liu, Xin

320

Heat exchangers and methods of construction thereof  

International Nuclear Information System (INIS)

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

1982-07-16

 
 
 
 
321

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

Science.gov (United States)

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

Azad, E.

2012-07-01

322

Optimum control of heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The present paper concems the control of high-performance heat exchangers for hot water service. Some of the basic control theories and their decisively important relationships are analysed from a theoretical point of view. A newly developed control is described, putting the various elements in the design into the perspective of control theory. (orig.)

Benonysson, A. [Danfoss A/S, Nordborg (Denmark); Boysen, H. [Danfoss A/S, Nordborg (Denmark)

1996-09-01

323

Heat exchanger staybolt acceptance criteria  

International Nuclear Information System (INIS)

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

1992-01-01

324

Compact gas-gas heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

The European market study carried out by IFP and Creusot-Loire in the present framework has shown that a 2 million tOE/yr saving can be expected from new gas-gas heat recovery systems in the present industrial context. The main constraint to be overcome is the cost of setting them up in industrial plants. The compactness and modular conception of the new stacked perforated plates (SPP) gas-gas heat exchanger will undoubtedly help in getting this new equipment onto the market. The exchanger consists of a block formed by the stacking of judiciously superpositioned perforated metal plates whose apertures create the fluid flow passages. This compact gas-gas crossflow heat exchanger is easy to manufacture, with low pressure drops and easy-to-clean fumes passages. A comparison of the projected cost of the SPP unit with a number of other heat exchangers indicates that the SPP unit is superior in terms of mass, size and cost and therefore will be very competitive in the market for heat recovery systems.

Grehier, A.; Busson, C.; Chliques, B.; Dreuihles, J.; Raimbault, C.; Rojey, A.

1984-01-01

325

SP-100 Heat Source Heat Exchanger Design  

Science.gov (United States)

A conceptual design for a liquid metal to gas counterflow heat exchanger has been developed for use in the SP-100 Closed Brayton Cycle (CBC) Space Reactor Power System (SRPS). The Heat Source Heat Exchanger (HSHX) is required to transfer 80 kWt from the 1350 K lithium reactor coolant to the He/Xe working fluid of the Brayton Rotating Unit (BRU). Trade studies were performed to select a concept that best meets the performance requirements as well as the mass minimization goals and packaging requirements of the SRPS. The HSHX design is based on state-of-the-art fabrication techniques developed for use in the SP-100 Thermoelectric Converter Assembly (TCA) Heat Exchanger and a previously developed Mini-BRU space power system HSHX. The HSHX is a Nb-lZr finned flat plate assembly fabricated by the Hot Isostatic Process (HIP). The approximate size of the HSHX assembly is a 0.70 m x 0.15 m cross section over its 18 cm active length. The conceptual design meets all thermal-hydraulic and structural design requirements for a five-year mission while weighing less than 50 kg.

Fallas, T. Ted; Desepte, Andrew W.; Hill, Robert J.; Manjarrez, Georgi B.; Solorzano, Enrique R.; Salamah, Samir A.; Yahalom, Raphael

1994-07-01

326

Numerical Analysis of Tube-Fin Heat Exchanger using Fluent  

Directory of Open Access Journals (Sweden)

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.

M. V. Ghori

2012-08-01

327

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

International Nuclear Information System (INIS)

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

1983-01-01

328

Tentative analysis methods of flow-induced vibrations of heat exchanger tube bundles and design criteria for prevention of vibration problems  

International Nuclear Information System (INIS)

As viewed from design, some significant practice experience of analysis of cross-flow-induced vibrations of heat exchanger tube bundles and design criteria for prevention of vibration problems in nuclear reactor engineering abroad are presented. At first, the main vibration behavior concerning the four distinct mechanisms that should be considered in vibration analysis is described, and then, eight aspects involved in the topic are expounded and discussed one by one. Finally, the essential design criteria for prevention of vibration problems are given. It could tentatively be used for designers concerned. (author)

1985-04-01

329

Tubular heat exchanger, for nuclear installations  

International Nuclear Information System (INIS)

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

1976-07-29

330

Life extension of tube shell heat exchanger through vibration analysis  

Energy Technology Data Exchange (ETDEWEB)

Vibration performances of a large scale tube-shell heat exchanger was analyzed using a finite element method. Dynamic response of Karman turbulent flow in the shell side was calculated by superposition of the vibration modes. Software was developed for the analysis. The achieved results provide a basis for safe operation and life extension of the heat exchangers. (author)

Minshan Liu; Qiwu Dong [Zhenzhou University (China)

1998-12-31

331

Joule-Thomson heat exchanger and cryostat  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a refrigerator of the type wherein a fluid is passed through the high pressure tube of a heat exchanger and then expanded through a Joule-Thomson orifice to produce refrigeration proximate the Joule-Thomson orifice. The improvement described here comprises: fibrous material disposed in the Joule-Thomson orifice which is deformed to fix the fibrous material in place, whereby the fibrous material and deformed orifice result in an orifice with large flow impedance.

Steyert, W.A.

1987-03-31

332

Condensation in horizontal heat exchanger tubes  

Energy Technology Data Exchange (ETDEWEB)

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

Leyer, S.; Zacharias, T.; Maisberger, F.; Lamm, M. [AREVA NP GmbH, Paul-Gossen-Strasse 100, Erlangen, 91052 (Germany); Vallee, C.; Beyer, M.; Hampel, U. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Bautzner Landstrasse 400, Dresden, 01328 (Germany)

2012-07-01

333

Characterization of a tube-in-shell thermosyphon heat exchanger for solar water heating  

Energy Technology Data Exchange (ETDEWEB)

Performance of a double-wall, natural convection, two-pass, tube-in-shell heat exchanger designed for use in a solar water heating system is measured. The heat exchanger is mounted along the length of a solar water storage tank. Flow of cold water on the shell side of the heat exchanger is driven solely by buoyancy forces. Hot side fluid is pumped. Flow rate, pressure drop and temperature data needed for a semi-empirical model of the heat exchanger are obtained. Performance is measured for forced convection, hot side volumetric flow rates of 0.016, 0.032 and 0.079 l/s. Temperature difference between hot and cold fluid at the inlets is varied from 0 to 75 degC. Measured values include thermosyphon and forced flow rates, temperature differences across the beat exchanger, vertical temperature distribution in the storage tank, and pressure drop due to shear on the thermosyphon side of the heat exchanger. Heat exchanger effectiveness and overall heat transfer area product (UA) are calculated. Thermosyphon mass flow rates are on the order of 0.01 kg/s. Although the low flow rates create thermal stratification of the water storage tank, they restrict energy transfer in the heat exchanger.

Dahl, S.D.; Davidson, J.H. [Univ. of Minnesota, Minneapolis, MN (United States). Mechanical Engineering Dept.

1995-11-01

334

Boiling heat transfer in compact heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Small circular and noncircular channels are representative of flow passages in compact evaporators and condensers. This paper describes results of an experimental study on heat transfer to the flow boiling of refrigerant- 12 in a small circular tube of diameter = 2.46 mm. The objective of the study was to assess the effect of channel size on the heat transfer coefficient and to obtain additional insights relative to the heat transfer mechanisms. The flow channel was made of brass and had an overall length of 0.9 m. The channel wall was electrically heated, and temperatures were measured on the channel wall and in the bulk fluid stream. Voltage taps were located at the same axial locations as the stream thermocouples to allow testing over an exit quality range of 0.21 to 0.94 and a large range of mass flux (63 to 832 kg/m{sup 2}s) and heat flux (2.5 to 59 kW/m{sup 2}). Saturation pressure was nearly constant, averaging 0.82 MPa for most of the testing; a few test data were also taken at a constant lower pressure of 0.52 MPa. Local heat transfer coefficients were determined experimentally. Analysis provided additional support for the conclusion, arrived at from previous studies, that a nucleation mechanism dominates for flow boiling in small channels; nevertheless, a convective-dominant region was identified at very low values of wall superheat (<{approx}3{degrees}C). Previous flow boiling studies in small channels, that did not include wall superheats this low, did not encounter the convective dominant mechanism. Conversely, cryogenic studies at very low wall superheats ({approx}l{degree}C) did not encounter the nucleation dominant regime. The apparent discrepancy is explained by the results of this study.

Tran, T.N.; Wambsganss, M.W. [Argonne National Lab., IL (United States); France, D.M. [Illinois Univ., Chicago, IL (United States). Dept. of Mechanical Engineering

1994-12-31

335

Applying the temperature effectiveness method to heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Off-design variations in heat load, flow rates, and service water inlet (heat sink) temperature, such as those due to seasonal changes, have been observed to cause significant variation in temperature effectiveness. This paper examines the effect of off-design test conditions on temperature effectiveness and further presents a correction to the temperature effectiveness for off-design variation in service water inlet temperature. Temperature effectiveness is the ratio of the actual heat load to the maximum theoretical heat load. As heat exchanger thermal performance degrades, temperature effectiveness decreases. It has been discovered, however, that off-design variations in system heat load, system flows, and heat sink temperature cause false trends in the temperature effectiveness. Three heat exchange systems are used to study the temperature effectiveness method: a typical water-to-water heat exchanger, an air-to-water room cooler, and a main steam condenser.

Pesce, M.M. [Power Generation Technologies, Knoxville, TN (United States)

1994-12-31

336

Application of explosive welding to heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The subject is discussed under the headings: advantages of explosive welding; principle of explosive welding; explosive welding of tubes; metallurgy of explosive welds (micrographs; microhardness); tubular heat exchangers; plugging; sleeving; retubing; construction of new heat exchangers; thermal sleeves.

Arthur, G.

1983-10-01

337

A lumped parameter, low dimension model of heat exchanger  

International Nuclear Information System (INIS)

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.)

1980-01-01

338

Pressurized bellows flat contact heat exchanger interface  

Science.gov (United States)

Disclosed is an interdigitated plate-type heat exchanger interface. The interface includes a modular interconnect to thermally connect a pair or pairs of plate-type heat exchangers to a second single or multiple plate-type heat exchanger. The modular interconnect comprises a series of parallel, plate-type heat exchangers arranged in pairs to form a slot therebetween. The plate-type heat exchangers of the second heat exchanger insert into the slots of the modular interconnect. Bellows are provided between the pairs of fins of the modular interconnect so that when the bellows are pressurized, they drive the plate-type heat exchangers of the modular interconnect toward one another, thus closing upon the second heat exchanger plates. Each end of the bellows has a part thereof a thin, membrane diaphragm which readily conforms to the contours of the heat exchanger plates of the modular interconnect when the bellows is pressurized. This ensures an even distribution of pressure on the heat exchangers of the modular interconnect thus creating substantially planar contact between the two heat exchangers. The effect of the interface of the present invention is to provide a dry connection between two heat exchangers whereby the rate of heat transfer can be varied by varying the pressure within the bellows.

Voss, Fred E. (inventor); Howell, Harold R. (inventor); Winkler, Roger V. (inventor)

1990-01-01

339

Heat exchangers: Selection, rating, and thermal design  

Energy Technology Data Exchange (ETDEWEB)

This book takes a systematic approach to the subject, focusing on the selection, design, rating, and operational challenges of various types of heat exchangers. Written by well-known authors in the field of heat transfer, this book covers all the most commonly used types of heat exchangers, including condensers and evaporators. The text begins with the classification of the different types of heat exchangers and discusses methods for their sizing and rating. Single phase forced convection correlations in ducts and pressure drop and pumping power analysis are also covered. A chapter is devoted to the special problem of fouling. Thermal design methods and processes, including designs for condensers and evaporators, complete this thorough introduction to the subject. The appendix provides information on the thermophysical properties of fluids, including the new refrigerants. Every topic features worked examples to illustrate the methods and procedures presented, and additional problems are included at the end of each chapter, with examples to be used as a student design project. An instructor's manual is available, including complete solutions to selected problems in the text. The contents include: classification of heat exchangers; basic design methods of heat exchangers; forced convection correlations for single-phase side of heat exchangers; heat exchanger pressure drop and pumping power; fouling of heat exchangers; double-pipe heat exchangers; design correlations for condensers and evaporators; shell-and-tube heat exchangers; compact heat exchangers; gasketed-plate heat exchangers; and condensers and evaporators.

Kakac, S.; Liu, H.

1998-01-01

340

Impact of manifold design on heat exchanger efficiency  

Energy Technology Data Exchange (ETDEWEB)

The impact of manifold design on single-phase heat exchanger effectiveness is studied using the NTU-Effectiveness method. Manifolds are devices that redistribute the internal flow stream of a heat exchanger from one to several passages. Two manifold types are identified; collector box and direct split designs. A general enhancement analysis is performed which covers four different combinations of performance and objective criteria. Three cases involve increasing the heat exchanger effectiveness while constraining either the internal flow head loss, the internal mass flow rate, or their product. The other case involves reducing the required heat exchanger flow length while constraining the heat transfer rate. Familiar convection correlations are then incorporated into the enhancement analysis to predict general trends an behavior when the main tube is split into several smaller tubes. Analytical estimates are presented of improved effectiveness for three operating conditions of an actual heat exchanger which possesses a manifold. Experimental data acquired from the gas-to-gas heat exchanger is compared to numerical predictions of its performance without a manifold, (baseline design). The analytical equations developed correctly estimate an improvement in heat exchanger effectiveness.

Harris, D.K.; Goldschmidt, V.W. [Purdue Univ., Lafayette, IN (United States); Warren, D.G. [Nordyne Corp., St. Louis, MO (United States)

1996-12-31

 
 
 
 
341

Liquid metal/air heat exchanger  

International Nuclear Information System (INIS)

The aim of the invention is a liquid metal/air heat exchanger which can resist to thermal expansion of tubes for which a supporting system is provided in the present case; this supporting system does not involve excessive stresses. Such heat exchangers apply to LMFBR type reactors. They are used as emergency heat exchangers when there is a failure of the reactor cooling circuits to cool the primary liquid sodium, or as heat exchangers in test or experimental circuits of reactors

1984-05-25

342

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  

Directory of Open Access Journals (Sweden)

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

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

2011-09-01

343

Heat transfer effectiveness of three-fluid separated heat pipe exchanger  

Science.gov (United States)

A heat transfer model for three-fluid separated heat pipe exchanger was analyzed, and the temperature transfer matrix for general three-fluid separated heat exchanger working in parallel-flow or counter-flow mode was obtained. It was found that the forms of temperature transfer matrix are similar for heat pipe rows with equal or different heat transfer surface area. Furthermore, by using the temperature transfer matrix of the heat pipe exchanger, the relationship between heat transfer effectiveness ? 1, ? 2 and M, NTU, U, ?t i were derived for the exchanger operating in parallel-flow or counter-flow mode, and a simple special example was adopted to demonstrate the correctness of these relationships.

Shi, Chengming; Wang, Yang; Yang, Ying; Liao, Quan

2011-03-01

344

Probabilistic study of a porous heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

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

Agrawal, O.P.; Lin, X. [Southern Illinois Univ., Carbondale, IL (United States). Dept. of Mechanical Engineering and Energy Processes

1995-12-31

345

21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.  

Science.gov (United States)

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

2010-04-01

346

Hydraulic Validation of the LHC Cold Mass Heat Exchanger Tube  

CERN Multimedia

The knowledge of the helium mass flow vs. the fraction of the tube wetted by the liquid helium II in the heat exchanger is a crucial input parameter for the heat exchange since the heat flux is direct ly proportional to the wetted surface. In the range of liquid and gas velocities inside the heat exchanger, the liquid flow behaves like in an open channel. Looking at the flow equations for such a s ituation, the velocity depends on the fluid properties only by the friction factor which is a function of the Reynolds number. Thus it was decided to build an experiment with water in order to check t he open channel equations in the heat exchanger geometry. This paper shows the results for water and gives the extrapolation for helium.

Provenaz, P

1998-01-01

347

Exergy optimization in a steady moving bed heat exchanger  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Soria-verdugo, Antonio; Almendros-iba?n?ez, Jose? Antonio; Ruiz-rivas, Ulpiano; Santana Santana, Domingo Jose?

2007-01-01

348

Fluidized bed heat exchanger utilizing angularly extending heat exchange tubes  

Energy Technology Data Exchange (ETDEWEB)

A fluidized bed heat exchanger in which air is passed through a bed of particulate material containing fuel disposed in a housing. A steam/water natural circulation system is provided and includes a steam drum disposed adjacent the fluidized bed and a series of tubes connected at one end to the steam drum. A portion of the tubes are connected to a water drum and in the path of the air and the gaseous products of combustion exiting from the bed. Another portion of the tubes pass through the bed and extend at an angle to the upper surface of the bed.

Talmud, Fred M. (Berkeley Heights, NJ); Garcia-Mallol, Juan-Antonio (Morristown, NJ)

1980-01-01

349

Design of intermediate heat exchanger for PFBR  

International Nuclear Information System (INIS)

Prototype fast breeder reactor (PFBR) is a sodium cooled 500 MWe pool type reactor. It has three heat transfer circuits viz. primary sodium circuit, secondary sodium circuit and water- steam circuit. The main vessel contains the pool of sodium and houses all the components of the primary sodium circuit. Two numbers of primary sodium pumps and four numbers of intermediate heat exchangers (IHX) have been provided. The nuclear heat generated in the core is transferred to secondary sodium in IHX by circulation of primary sodium. There are two secondary sodium circuits. Each circuit contains one sodium pump, one surge tank and four steam generators (in parallel) and is connected to two IHXs in the reactor. The secondary sodium circuits transfer the heat to water/steam in steam generators (SG). Super heated steam produced in the SGs is used to drive the turbo-alternator set to generate power. The IHX is a very important component of the reactor because it forms the boundary between radioactive primary sodium in the reactor pool and non-radioactive secondary sodium. The IHX is a counter flow shell-and-tube heat exchanger. The IHX is designed to meet the specified design requirements and constraints. This involves thermal, hydraulic, and structural design. In this paper, the design features, design conditions and design of IHX for PFBR are described. 4 figs., 3 tabs

1996-02-01

350

SAFE gas turbine cycle primary heat exchangers  

International Nuclear Information System (INIS)

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

2002-01-14

351

Preliminary SP-100/Stirling heat exchanger designs  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1994-09-01

352

Preliminary SP-100/Stirling heat exchanger designs  

International Nuclear Information System (INIS)

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

1994-01-09

353

Heat Transport Study of the Laminar Heat Pipe Heat Exchanger  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

354

Multidimensional numerical modeling of heat exchanges  

International Nuclear Information System (INIS)

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

1982-01-01

355

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

Science.gov (United States)

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.

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

1993-01-01

356

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

Science.gov (United States)

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.

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

1993-04-01

357

CALCULATION OF DISTRIBUTION OF TEMPERATURE ALONG THE CORE AT NON-STATIONARY HEAT EXCHANGE USING THE METHOD OF LOCAL THERMAL FLOWS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Statement of the problem. Engineering practice has to deal with the problems of non-stationary heat exchange in flat elements of building structures, however, the methods of its calculation are not sufficiently developed.Results. An engineering method for calculating a non-stationary temperature field in a core heat-insulated from the sides was proposed, based on local application of physical and mathematical models of non-stationary heat exchange on the core. The expression was obtained for ...

2013-01-01

358

Transient performance of closed loop solar water heating system with heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with an analysis of a forced circulation closed loop solar water heating system; withdrawal of hot water of constant flow rate from a storage tank through a heat exchanger is considered. The effect of flow rate and heat exchanger length on the performance has also been discussed for a typical set of parameters and for a typical cold day in Delhi (26 January 1980).

Tiwari, G.N.; Sharma, B.N.; Srivastava, A.

1983-07-01

359

Heat exchange phenomena and COP evaluation in heat pump systems coupled to single borehole heat exchangers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In recent years a growing interest in Borehole Heat Exchangers (BHEs) has been shown in Europe thanks to the increase of installations in systems connected to Ground Source Heat Pumps (GSHPs) used for heating and cooling needs. Different geometries and technical solutions have been de- veloped in order to improve heat exchange with the ground, accompanied by several descriptive models. Recently, innovative technologies as optical fiber for a new Distributed Thermal Response Test (DTRT) have b...

Casellato, Francesco

2013-01-01

360

Membrane and plastic heat exchangers performance  

Directory of Open Access Journals (Sweden)

Full Text Available The performance of a membrane-based heat exchanger utilizing porous paper as the heat and moisture transfer media is presented. The measured performance is compared with a plastic film heat exchanger. This novel heat exchanger is used in ventilation energy recovery systems. The results show that the sensible effectiveness is higher than the latent effectiveness. When a similar experiment was conducted using a plastic film heat exchanger surface instead of paper, where only heat is transferred, the sensible effectiveness values were lower than the effectiveness values recorded when the paper heat exchanger is used. Furthermore, energy analysis shows that utilizing a paper surface heat exchanger in a standard air conditioning system will lead to significant energy savings.

Masud Behnia

2005-09-01

 
 
 
 
361

Rational Efficiency of a Heat Exchanger  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The authors propose a new and unique definition for the rational efficiency of a heat exchanger. This new rational efficiency is defined in terms of its sub-rational efficiencies: a heat transfer rational efficiency and a friction rational efficiency for each of the fluid systems comprising the heat exchanger. The heat transfer rational efficiency is based on the definition of a mean temperature for the heat source and a mean temperature for the heat sink and reflects the exergy supplied and ...

2011-01-01

362

Compact heat exchanger for fluids  

International Nuclear Information System (INIS)

The invention concerns a welded heat exchanger with two or more fluids which can be used counter current. The principle of the apparatus allows the use of rolled welded concentric metal strips as well as spiral rolled metal strips. The ring sheets are kept apart either by their rigidity due to the cylindrical shape or by deformations in the sheets themselves or yet again by spacers or chequered and/or perforated sheets forming for instance corrugated spacers, the end sheet being thick enough to take the pressure strain

1975-01-01

363

Heat exchanger thermal insulation system  

International Nuclear Information System (INIS)

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

1974-01-01

364

Optimization of heat exchanger for indirectly heated water heater  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Kaduchová Katarína; Lenhard Richard; Janda?ka Jozef

2012-01-01

365

Thermodynamic Optimization of GSHPS Heat Exchangers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Javad Marzbanrad; Ali Sharifzadegan; Ahmad Kahrobaeian

2007-01-01

366

Microchannel crossflow fluid heat exchanger and method for its fabrication  

Science.gov (United States)

A microchannel crossflow fluid heat exchanger and a method for its fabrication are disclosed. The heat exchanger is formed from a stack of thin metal sheets which are bonded together. The stack consists of alternating slotted and unslotted sheets. Each of the slotted sheets includes multiple parallel slots which form fluid flow channels when sandwiched between the unslotted sheets. Successive slotted sheets in the stack are rotated ninety degrees with respect to one another so as to form two sets of orthogonally extending fluid flow channels which are arranged in a crossflow configuration. The heat exchanger has a high surface to volume ratio, a small dead volume, a high heat transfer coefficient, and is suitable for use with fluids under high pressures. The heat exchanger has particular application in a Stirling engine that utilizes a liquid as the working substance.

Swift, Gregory W. (Los Alamos, NM); Migliori, Albert (Santa Fe, NM); Wheatley, John C. (Los Alamos, NM)

1985-01-01

367

Microchannel Heat Exchangers with Carbon Dioxide  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2001-09-15

368

Enhancement of heat transfer and structure of flow in a double-pipe heat exchanger with uniformly distributed perforated-plate baffles in the inner pipe  

International Nuclear Information System (INIS)

The effect of the number of baffles per meter of length on the average heat transfer coefficient and on the hydraulic drag coefficient of a 70 mm I.D. inner pipe at Re between 9 . 10"3 and 50 . 10"3 was investigated. The test data were correlated in dimensionless form. The length of the inlet stabilization zone proved to be two to three pipe diameters. The profiles of velocity and of the longitudinal component of fluctuations, and also the development of the flow through the baffles are analyzed

1986-01-01

369

NGNP Process Heat Utilization: Liquid Metal Phase Change Heat Exchanger  

Energy Technology Data Exchange (ETDEWEB)

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.

Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson

2008-09-01

370

Heat exchanger with several modules in parallel  

International Nuclear Information System (INIS)

A heat exchanger with several modules in parallel is proposed. Each module includes a bundle of tubes for circulation of a fluid to be heated, vaporised and/or superheated in them, placed between two tube plates in a casing for the flow of a heating fluid formed of an alkaline molten metal. The alkaline molten metal intake manifolds at the upper part of the modules are connected to a common supply bottle. The alkaline molten metal outlet manifolds at the bottom of the modules are also connected to a common discharge bottle. The axes of the modules are distributed with a constant angular deviation on a cylinder the axis of which is the vertical axis common to the supply and discharge bottles

1975-01-01

371

Heat Transport Study of the Laminar Heat Pipe Heat Exchanger  

Directory of Open Access Journals (Sweden)

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

Wei-Keng Lin

2012-11-01

372

Thermodynamic analysis and optimization of air-cooled heat exchangers  

Science.gov (United States)

In the present study, a thermodynamic second-law analysis was performed to investigate the effects of different geometry and flow parameters on the air-cooled heat exchanger performance. For this purpose, the entropy generation due to heat transfer and pressure loss of internal and external flows of the air-cooled heat exchanger was calculated; and it was observed that the total entropy generation has a minimum at special tube-side Reynolds number. Also, it was seen that the increasing of the tube-side Reynolds number resulted in the rise of the irreversibility of the air-cooled heat exchanger. The results also showed when air-side Reynolds number decreased, the entropy generation rate of the external flow reduced. Finally, based on the computed results, a new correlation was developed to predict the optimum Reynolds number of the tube-side fluid flow.

Salimpour, Mohammad Reza; Bahrami, Zabihollah

2011-01-01

373

A heat exchanger between forced flow helium gas at 14 to 18 K andliquid hydrogen at 20 K circulated by natural convection  

Energy Technology Data Exchange (ETDEWEB)

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

Green, M.A.; Ishimoto, S.; Lau, W.; Yang, S.

2003-09-15

374

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

International Nuclear Information System (INIS)

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

2003-09-22

375

Characteristics of a gravity-assisted heat pipe-based heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

An experimental study of the performance of an air-to-air thermosyphon-based heat exchanger utilizing R-22 as the working fluid has been carried out to investigate its behavior under different operating conditions. A test installation has been developed to model a variety of HVAC real life applications. The results reported in this article describe the influence of various parameters such as: supply and exhaust air stream mass flow rates, stream temperatures and exhaust stream moisture content on the effectiveness of the heat exchangers. Heat exchanger heat flow hysteresis has been recognized. Some optimization criteria are presented. (author).

Wadowski, T.; Akbarzadeh, A.; Johnson, P. (Royal Melbourne Inst. of Tech. (AU). Manufacturing and Process Engineering Dept.)

1991-01-01

376

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

International Nuclear Information System (INIS)

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

2001-11-01

377

Dynamics of flow exchange and heat transport in hyporheic zone due to the dam-induced river temperature fluctuations  

Science.gov (United States)

Hyporheic zone (HZ) plays a dominant role in maintaining the ecosystem equilibrium on the river catchment scale. Assessing the temperature changes occurring in the HZ is critical although it is likely to be more important than other factors. As metabolic activity within HZ may be strongly affected by the thermal regime of the stream water, and also plenty of literatures have already showed that the surface water temperature may be changed greatly by the low temperature water (LTW) discharged from the lower part of a deep reservoir; especially the elevation of water-intakes of electronic station is within the mid-lower layer of deep reservoirs. However, how and to what extent the LTW in stream will impact on the HZ temperature regime and ulteriorly, on the full range of the river ecosystem are still not understood widely. This work focuses on the temperature changes and flow rates of infiltration and seepages in the HZ as the stream water influenced by LTW. Water discharged from up reservoir usually contains less sediment and the sediments within the water need to get saturated when it is running along the downstream. Therefore, the hyporheic zone porous structure will be much different at large scale due to the scour activities. Three kinds of HZ structure conception models were built for analysis due to the sediments transport and settlement characteristics along the downstream. VS2DH simulations shows water infiltrates into HZ then laterally mixes with the groundwater, gradually causing a low temperature environment in the HZ. The extent of temperature changes varies with different particle size distribution within the riverbed but it is generally according to the temperature period of stream water. We also examine the grade of infiltration surface impacts on the heat transfer and water velocity distribution in the three different models. The heat and water transport rate increases with the infiltration surface slope angle increasing, it indicates that the local riverbed topography has an assignable on the hydrodynamics in the HZ as well as the thermal phenomenon. The sensitivity of the sediment distribution regime to the hydrodynamic conditions increases with increasing water pressure head and with the sediment permeability.

Chen, X.; Zhao, J.; Chen, L.

2011-12-01

378

Conceptualizations for cleaning OTEC heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

A critical operating aspect of Ocean Thermal Energy Conversion (OTEC) plants is the maintenance of clean surfaces on the seawater-side of the heat exchangers. The objective of this program was to assess the state of the art of biofouling control techniques and to evaluate the potential of these existing methods for solving the biofouling problems in the OTEC system. The first task of the program involved an in-depth review and discussion of various fouling control methods including water treatment, surface conditioning, and cleaning techniques. The methods considered applicable to OTEC were identified. This volume summarizes the second task of the program. The compatibility of the various cleaning and fouling control techniques with the different proposed heat exchanger designs and materials are discussed. Also provided are conceptual illustrations for adapting and incorporating the methods into an OTEC power plant. These conceptual designs suggest means for overcoming some of the shortcomings of the techniques which are considered suitable, however, detailed designs of the modified systems are beyond the scope of this report. Chlorination, chemical cleaning, Amertap recirculating sponge rubber balls, and MAN flow-driven brushes are the methods considered applicable for tubular heat exchangers with seawater inside the tubes. Water jets are suggested for the open-cycle and the ''trombone'' (Applied Physics Laboratory) heat exchanger designs. Although none of the methods are immediately applicable to OTEC in their present configuration, in several cases only minor developmental efforts should produce designs which can satisfy the stringent OTEC cleanliness requirements. Further research and development appear warranted for a number of other methods which indicate promise for long-range applicability. Specific recommendations are included.

Rice, M.S.; Hagel, D.; Conn, A.F.

1978-09-01

379

Fluid dynamical considerations on heat exchanger networks  

Scientific Electronic Library Online (English)

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

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

380

Fluid dynamical considerations on heat exchanger networks  

Directory of Open Access Journals (Sweden)

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

A. J. M. Vieira

2000-03-01

 
 
 
 
381

Heat exchanger. Also for cooling; Waermerueckgewinnungsanlagen. Auch zum Kuehlen  

Energy Technology Data Exchange (ETDEWEB)

The usefulness of conventional heat recovery systems in animal houses during heating periods tends to be restricted to times when the perceptible heat given off by the animals is not sufficient to generate a heat output that is desirable for the pens. Once the temperature in the animal house exceeds this setpoint temperature, control valves are deployed to channel the incoming / outgoing air flow past the heat exchanger via a bypass valve, thus preventing any further exchange of heat between the incoming and outgoing air. By humidifying the outgoing air prior to entry into the heat exchanger, this is cool and can escape the fresh air heat. Because of the separate streams of air (Supply and exhaust air) it affects the water content is not the stable air. Using a dynamic calculation model, the fall in temperature inside the stable can be predicted depending on the thermal efficiency of the heat exchanger, the air flow and ventilation rate and the amount of water vaporised. The report deals with the theoretical principles and the effect of heat exchangers featuring adiabatic cooling of the incoming and/or outgoing air on the climate in animal houses. On the basis of an example, the cooling effect of different variants is compared and assessed. The results presented are based on a dynamic calculation model. The technical and economic feasibility of heat recovery systems of this kind will be examined later in a pilot plant. (orig.)

Caenegem, Ludo van; Sax, Markus; Schick, Matthias [Forschungsanstalt Agroscope Reckenholz-Taenikon ART, Ettenhausen (Switzerland). Forschungsgruppe Bau, Tier und Arbeit

2012-07-01

382

Design of a liquid metals heat exchanger  

International Nuclear Information System (INIS)

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

1976-01-01

383

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2013-09-01

384

Direct contact heat exchangers for space  

Science.gov (United States)

Direct contact heat exchanger concepts have been investigated for use in space, including droplet vortex heat exchangers, coflowing droplet heat exchangers, electrostatically driven heat exchangers, and belt and disk heat exchangers. These concepts are characterized by a low heat exchanger mass per unit of heat transferred, low pressure losses, high reliability, and compactness in design. Operation in zero-G poses unique problems for those direct contact heat exchangers which require separation of two fluid media after heat transfer is completed. Other problems include maintenance of good heat transfer coefficients in the absence of buoyant forces, exposure of heat transfer media to vacuum conditions for certain applications, and materials compatibility. A preliminary systems analysis indicates the potential for substantial weight reductions in turbine Brayton cycle space power systems for output powers above several MW(e). Based on the status of current technology and the results of this analysis, recommendations are made for the most attractive applications and the R&D required to ready a direct contact heat exchanger for use in space.

Taussig, R. T.; Thayer, W. J.; Lo, V. C. H.; Sakins, K. M.; Bruckner, A. P.

1985-06-01

385

Confirmation of effectiveness of horizontal heat exchanger for PCCS  

International Nuclear Information System (INIS)

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

2005-01-01

386

Simultaneous synthesis of flexible heat exchanger network  

Energy Technology Data Exchange (ETDEWEB)

A framework is presented for generating flexible heat exchanger networks (HENs) over a specified range of variations in the flow rates and temperatures of the streams. The flexible HEN is synthesised using a combination of a multiperiod simultaneous MINLP model and search algorithms, where the total annual costs due to utility duties, exchanger areas and selection of matches are optimised. The simultaneous HEN synthesis allows the data to be distributed according to a probability distribution and it does not rely on the concept of pinch point. Both search algorithms involve a developed multiperiod NLP/LP model where utility costs are minimised. The proposed procedures are explained through an example including variations resulting in a network with variable splits and bypasses. This framework results in a HEN working under variations without losing stream temperature targets while keeping an economically optimal energy integration. (Author)

Aaltola, Juha [Helsinki Univ. of Technology,Hut (Finland)

2002-06-01

387

Supervision of the thermal performance of heat exchanger trains  

Energy Technology Data Exchange (ETDEWEB)

In oil refining, heat exchanger networks are employed to recover heat and therefore save energy of the plant. However, many heat exchangers in crude oil pre-heat trains are under high risk of fouling. Under fouling conditions, the thermal performance of heat exchangers is continuously reduced and its supervision becomes an important task. The large number of heat exchangers in pre-heat trains and the change of operation conditions and feedstock charges make the daily supervision a difficult task. This work applies an approach to follow the performance of heat exchangers [M.A.S. Jeronimo, L.F. Melo, A.S. Braga, P.J.B.F. Ferreira, C. Martins, Monitoring the thermal efficiency of fouled heat exchangers - A simplified method, Experimental Thermal and Fluid Science 14 (1997) 455-463] and extends it to monitor the whole train. The approach is based on the comparison of measured and predicted heat exchanger effectiveness. The measured value is computed from the four inlet and outlet temperatures of a heat exchanger unit. The predicted clean and dirty values of effectiveness are calculated from classical literature relations as a function of NTU and of heat capacity ratio (R). NTU and R are continuously adjusted according to mass flow rate changes. An index of fouling is defined for the whole network and the results show the performance degradation of the network with time. The work also suggests that Jeronimo's index of fouling can be used to estimate the fouling thermal resistance of heat exchangers. (author)

Negrao, C.O.R.; Tonin, P.C.; Madi, M. [Federal University of Technology Parana UTFPR, Post-graduate Program in Mechanical and Materials Engineering PPGEM, Thermal Science Laboratory LACIT, Av. Sete de Setembro, 3165, CEP 80230-901, Curitiba, Parana (Brazil)

2007-02-15

388

Design of single passage heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

The available literature has been reviewed, and information useful for heat exchanger design has been presented and compared. The available design information is presented in the form of simplified equations that are suitable for the design of heat exchangers for livestock buildings. The equations presented have been used to develop a computer program as an example of how they can be arranged to aid in designing heat exchangers. 14 refs.

Fehr, R.L.; Walton, L.R.; Parker, B.F.

1981-01-01

389

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

International Nuclear Information System (INIS)

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

1986-07-20

390

Experimental determination of correlations for average heat transfer coefficients in heat exchangers on both fluid sides  

Science.gov (United States)

This paper presents an experimental-numerical method for determining heat transfer coefficients in cross-flow heat exchangers with extended heat exchange surfaces. Coefficients in the correlations defining heat transfer on the liquid- and air-side were determined based on experimental data using a non-linear regression method. Correlation coefficients were determined from the condition that the weighted sum of squared liquid and air temperature differences at the heat exchanger outlet, obtained by measurements and those calculated, achieved minimum. Minimum of the sum of the squares was found using the Levenberg-Marquardt method. The uncertainty in estimated parameters was determined using the error propagation rule by Gauss. The outlet temperature of the liquid and air leaving the heat exchanger was calculated using an analytical model of the heat