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Sample records for fin heat exchanger

  1. Heat exchanger with transpired, highly porous fins

    DOEpatents

    Kutscher, Charles F.; Gawlik, Keith

    2002-01-01

    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.

  2. Airside performances of finned eight-tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Li, Cheng; Li, Junming

    2016-11-01

    For applications in the relatively low temperature refrigeration systems with large constant temperature bath, the present work performed the experimental studies on the airside performances of the staggered finned eight-tube heat exchangers with large fin pitches. The airside heat transfer coefficients and pressure drops for three fin types and two fin pitches are obtained and analyzed. The heat transfer enhancement with louver fins is 11-16 % higher than the flat fins and that with sinusoidal corrugated fins is 1.1-3.4 % higher than the flat fins. Higher Re brings larger enhancement for various fins. Fin pitches show weak influence on heat transfer for eight tube rows. However, effects of fin pitch on heat transfer for both the sinusoidal corrugation and the louvered fin are larger than the flat fins and they are different from those for N ≤ 6. Airside Colburn j factor are compared with previous and it could be concluded that the airside j factor is almost constant for finned tube heat exchangers with eight tubes and large fin pitches, when Re is from 250 to 2500. The results are different from previous studies for fewer tube rows.

  3. Finned Tube With Vortex Generators For A Heat Exchanger.

    DOEpatents

    Sohal, Manohar S.; O'Brien, James E.

    2005-12-20

    A system for and method of manufacturing a finned tube for a heat exchanger is disclosed herein. A continuous fin strip is provided with at one pair of vortex generators. A tube is rotated and linearly displaced while the continuous fin strip with vortex generators is spirally wrapped around the tube.

  4. Finned Tube With Vortex Generators For A Heat Exchanger.

    DOEpatents

    Sohal, Monohar S.; O'Brien, James E.

    2004-09-14

    A system for and method of manufacturing a finned tube for a heat exchanger is disclosed herein. A continuous fin strip is provided with at least one pair of vortex generators. A tube is rotated and linearly displaced while the continuous fin strip with vortex generators is spirally wrapped around the tube.

  5. Slotting Fins of Heat Exchangers to Provide Thermal Breaks

    NASA Technical Reports Server (NTRS)

    Scull, Timothy D.

    2003-01-01

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

  6. Study of transient behavior of finned coil heat exchangers

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  7. Brazed aluminum, Plate-fin heat exchangers for OTEC

    SciTech Connect

    Foust, H.D.

    1980-12-01

    Brazed aluminum plate-fin heat exchangers have been available for special applications for over thirty years. The performance, compactness, versatility, and low cost of these heat exchangers has been unequaled by other heat exchanger configuration. The application of brazed aluminum has been highly limited because of necessary restrictions for clean non-corrosive atmospheres. Air and gas separation have provided ideal conditions for accepting brazed aluminum and in turn have benefited by the salient features of these plate-fin heat exchangers. In fact, brazed aluminum and cryogenic gas and air separation have become nearly synonymous. Brazed aluminum in its historic form could not be considered for a seawater atmosphere. However, technology presents a new look of significant importance to OTEC in terms of compactness and cost. The significant technological variation made was to include one-piece hollow extensions for the seawater passages. Crevice corrosion sites are thereby entirely eliminated and pitting corrosion attack will be controlled by an integral and sacrificial layer of a zinc-aluminum alloy. This paper on brazed aluminum plate-fin heat exchangers for OTEC will aquaint the reader with the state-of-art and variations suggested to qualify this form of aluminum for seawater use. In order to verify the desirable cost potential for OTEC, Trane teamed with Westinghouse to perform an OTEC system analysis with this heat exchanger. These results are very promising and reported in detail elsewhere.

  8. Performance Prediction of Cross-finned Tube Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Kondou, Chieko; Senshu, Takao; Matsumura, Kenji; Oguni, Kensaku

    An important issue in heat pumps is increasing their efficiency, in order to achieve a significant optimization for heat exchangers. Techniques to simulate the flow length averaged heat transfer coefficient and static pressure drop through the flow passage are presented in this paper. In addition, an analytical evaluation of the cost reduction for a cross-fined tube heat exchanger of outdoor heat pump units is instantiated. The dimensionless factors, Colburn's factor j and Fanning's friction factor f, express the heat transfer performance and frictional characteristics, as a function of Reynolds number. These depend on slit possession, an original parameter used in this study. Further, this paper describes an approximate expression of the fin efficiency, which can be used for to survey the fin parameters. The above three concepts were necessary to forecast the performance on the airside. In the results, the cost minimum point was obtained with a comparable performance.

  9. Experimental and numerical investigation on air-side performance of fin-and-tube heat exchangers with various fin patterns

    SciTech Connect

    Tang, L.H.; Zeng, M.; Wang, Q.W.

    2009-07-15

    Air-side heat transfer and friction characteristics of five kinds of fin-and-tube heat exchangers, with the number of tube rows (N = 12) and the diameter of tubes (D{sub o} = 18 mm), have been experimentally investigated. The test samples consist of five types of fin configurations: crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators (VGs) and mixed fin with front 6-row vortex-generator fin and rear 6-row slit fin. The heat transfer and friction factor correlations for different types of heat exchangers were obtained with the Reynolds numbers ranging from 4000 to 10000. It was found that crimped spiral fin provides higher heat transfer and pressure drop than the other four fins. The air-side performance of heat exchangers with the above five fins has been evaluated under three sets of criteria and it was shown that the heat exchanger with mixed fin (front vortex-generator fin and rear slit fin) has better performance than that with fin with delta-wing vortex generators, and the slit fin offers best heat transfer performance at high Reynolds numbers. Based on the correlations of numerical data, Genetic Algorithm optimization was carried out, and the optimization results indicated that the increase of VG attack angle or length, or decrease of VG height may enhance the performance of vortex-generator fin. The heat transfer performances for optimized vortex-generator fin and slit fin at hand have been compared with numerical method. (author)

  10. Plate-fin panel heat exchanger and panel components thereof

    SciTech Connect

    Heronemus, W.E.

    1985-02-05

    A plate-fin panel for a heat exchanger may be either formed as an aluminum extrusion or fabricated from a corrugated metal sheet sandwiched between two flat metal sheets. The extruded aluminum version may be clad with protective sheet metal jackets made of, or coated with, a corrosion resistant Cu-Ni alloy. Individual panel sections can be joined together by tongue and groove engagement to obtain a total desired panel width if available extrusion press or rolling mill capacity is insufficient. The plate-fin panels are assembled into slotted headering plates, and a layer of synthetic plastics potting compound seals dissimilar metal joints against electrolytic corrosion as well as leakage and provides sufficient adhesive strength to reduce or eliminate the need for welding the panels to the headers. Mechanical brush or hydraulic jet apparatus is capable of continuously or intermittently cleaning slime or encrustations from all panel surfaces exposed to seawater.

  11. Measurement of frost characteristics on heat exchanger fins. Part 2: Data and analysis

    SciTech Connect

    Chen, H.; Thomas, L.; Besant, R.W.

    1999-07-01

    Part 1 of this paper described the frost growth test facility and instrumentation. In Part 2, results are presented for typical operating conditions with frost growth on heat exchanger fins. Typical data are presented for frost height distributions on fins, increase in pressure loss for airflow through a finned test section, frost mass accumulation on fins, and heat rate. Special attention is given to the uncertainty in each of these measurements and calculations.

  12. Boiling heat transfer of refrigerant R-21 in upward flow in plate-fin heat exchanger

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. V.; Shamirzaev, A. S.

    2015-11-01

    The article presents the results of experimental investigation of boiling heat transfer of refrigerant R-21 in upward flow in a vertical plate-fin heat exchanger with transverse size of the channels that is smaller than the capillary constant. The heat transfer coefficients obtained in ranges of small mass velocities and low heat fluxes, which are typical of the industry, have been poorly studied yet. The characteristic patterns of the upward liquid-vapor flow in the heat exchanger channels and the regions of their existence are detected. The obtained data show a weak dependence of heat transfer coefficient on equilibrium vapor quality, mass flow rate, and heat flux density and do not correspond to calculations by the known heat transfer models. A possible reason for this behavior is a decisive influence of evaporation of thin liquid films on the heat transfer at low heat flux.

  13. Effects of slitted fins on the heat transfer and pressure drop characteristics of a compact heat exchanger

    SciTech Connect

    Kim, C.H.; Yun, J.Y.

    1996-12-31

    A compact heat exchanger which consists of air-cooled aluminum fins and copper tubes circulating refrigerant has been used in a cooling system for a long time. There are two key parameters to be seriously considered for a design of the heat exchanger and its performance improvement. These are the heat transfer rate and pressure drop coefficient which varies with the change of the tube size, its arrangement and the fin configuration. In here, a numerical study was carried to understand the effect of the fin configuration on the heat transfer and pressure drop of the heat exchanger. The diameter and the arrangement of tubes were fixed but three different types of the fin configuration were used to see its effect on the heat transfer capacity and the static pressure drop. The calculation results were compared with that of a flat plate fin. From the comparison, it was found that the slitted fins have higher pressure drop; however, they have higher heat transfer rate. It means that the simpler of the fin configuration, the lower pressure drop and heat transfer coefficients are obtained. It is mainly due to the discretisation of the thermal boundary layer on the fin surface to maximize the heat transfer to air. The slitted sides of fins act like obstacles in the airflow path. From the experimental result, it was found that the same trend in the variation of the heat transfer rate and the pressure drop with the change of the fin configuration was obtained.

  14. Dry/wet performance of a plate-fin air-cooled heat exchanger with continuous corrugated fins

    SciTech Connect

    Hauser, S.G.; Kreid, D.K.; Johnson, B.M.

    1981-01-01

    The performance and operating characteristics of a plate-fin heat exchanger in dry/wet or deluge operations was experimentally determined. Development of the deluge heat/mass transfer model continued. The experiments were conducted in a specially-designed wind tunnel at the PNL. Air that was first heated and humidified to specified conditions was circulated at a controlled rate through a 2 ft x 6 ft heat exchanger module. The heat exchanger used in the tests was a wavy surface, plate fin on tube configuration. Hot water was circulated through the tubes at high flow rates to maintain an essentially isothermal condition on the tube side. Deionized water sprayed on the top of the vertically oriented plate fins was collected at the bottom of the core and recirculated. Instrumentation was provided for measurement of flow rates and thermodynamic conditions in the air, in the core circulation water, and in the deluge water. Measurements of the air side pressure drop and heat rejection rate were made as a function of air flow rate, air inlet temperature and humidity, deluge water flow rate, and the core inclination from the vertical. An overall heat transfer coefficient and an effective deluge film convective coefficient was determined. The deluge model, for predicting heat transfer from a wet finned heat exchanger was further developed and refined, and a major extension of the model was formulated that permits simultaneous calculation of both the heat transfer and evaporation rates from the wetted surface. The experiments showed an increase in the heat rejection rate due to wetting, accompanied by a proportional increase in the air side pressure drop. For operation at the same air side pressure drop, the enhancement ratio Q/sub w//Q/sub d/ varied between 2 and 5 for the conditions tested. Thus, the potential enhancement of heat transfer due to wetting can be substantial.

  15. Experimental investigation of plastic finned-tube heat exchangers, with emphasis on material thermal conductivity

    SciTech Connect

    Chen, Lin; Li, Zhen; Guo, Zeng-Yuan

    2009-07-15

    In this paper, two modified types of polypropylene (PP) with high thermal conductivity up to 2.3 W/m K and 16.5 W/m K are used to manufacture the finned-tube heat exchangers, which are prospected to be used in liquid desiccant air conditioning, heat recovery, water source heat pump, sea water desalination, etc. A third plastic heat exchanger is also manufactured with ordinary PP for validation and comparison. Experiments are carried out to determine the thermal performance of the plastic heat exchangers. It is found that the plastic finned-tube heat exchanger with thermal conductivity of 16.5 W/m K can achieve overall heat transfer coefficient of 34 W/m{sup 2} K. The experimental results are compared with calculation and they agree well with each other. Finally, the effect of material thermal conductivity on heat exchanger thermal performance is studied in detail. The results show that there is a threshold value of material thermal conductivity. Below this value improving thermal conductivity can considerably improve the heat exchanger performance while over this value improving thermal conductivity contributes very little to performance enhancement. For the finned-tube heat exchanger designed in this paper, when the plastic thermal conductivity can reach over 15 W/m K, it can achieve more than 95% of the titanium heat exchanger performance and 84% of the aluminum or copper heat exchanger performance with the same dimension. (author)

  16. Development of colburn ` j' factor and fanning friction factor ` f' correlations for compact heat exchanger plain fins by using CFD

    NASA Astrophysics Data System (ADS)

    Bala Sundar Rao, R.; Ranganath, G.; Ranganayakulu, C.

    2013-07-01

    A numerical model has been developed for plain fin of plate fin heat exchanger. Plain fin performance has been analyzed with the help of CFD by changing the various parameters of the fin, Colburn ` j' and fanning friction ` f' factors are calculated. These values compared with the standard values. The correlations have been developed between Reynolds number Re, fin height h, fin thickness t, fin spacing s, Colburn factor ` j' and friction factor ` f'.

  17. Local Heat Transfer for Finned-Tube Heat Exchangers using Oval Tubes

    SciTech Connect

    O'Brien, James Edward; Sohal, Manohar Singh

    2000-08-01

    This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with either a circular tube or an elliptical tube in crossflow. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.56 x 10-3 to 15.6 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 630 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. The elliptical tube had an aspect ratio of 3:1 and a/H equal to 4.33. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of circular and oval tubes and their relationship to the complex horseshoe vortex system that forms in the flow stagnation region. Fin surface stagnation-region Nusselt numbers are shown to be proportional to the square-root of Reynolds number.

  18. SIMULATION OF BOILING HEAT TRANSFER AROUND MICRO PIN-FIN HEAT EXCHANGER: PROGRESS AND CHALLENGES

    SciTech Connect

    Tyagi, M.; Maha, A.; Singh, K. V.; Li, G.; and Pang, S.S.

    2006-07-01

    Boiling at microscales is a challenging problem for the computational models as well as the resources. During boiling, the formation and departure of vapor bubbles from the heated surface involves the physics from nano/micro level to the macro level. Therefore, a hierarchical methodology is needed to incorporate the nano/microscale physics with the macroscale system performance. Using micro-fabrication techniques, microstructures (micropin-fins) can be fabricated around the tubes in the heat exchanger of Pressurized Water Reactors (PWRs) to increase the heat-exchanging efficiency and reduce the overall size of the heat-exchanger for the given heat transfer rates. Combined with high fidelity simulations of the thermal transport in the entire system, optimal design of microstructure patterns and layouts can be worked out pragmatically. Properly patterned microstructures on the pipe in the steam generation zone should create more nuclei for bubble to form and result in a reduced average bubble size and shorter retention time, i.e. the time for the vapor phase sticking on the pipe surface. The smaller average steam bubble size and shorter bubble retention time will enhance the overall thermal efficiency. As a preliminary step, a periodic arrangement of micropin-fins containing four in-line cylindrical fins was modeled. The governing equations for the mass, momentum and energy transport were solved in the fluid in a conjugate heat transfer mode. In the future, several studies will be conducted to simulate different geometric arrangements, different fin cross-sections, and realistic operating conditions including phase-change with boiling by adding complexities in simple steps.

  19. Heat Transfer Enhancement for Finned-tube Heat Exchangers with Winglets

    SciTech Connect

    O'Brien, James Edward; Sohal, Manohar Singh

    2000-11-01

    This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51 x 10-3 to 14.0 x 10-3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 670 – 6300 with a duct height of 1.106 cm and a duct width-toheight ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean finsurface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal air-cooled condensers), the enhancement level is nearly a factor of two. At higher Reynolds numbers, the enhancement level is close to 50%.

  20. Heat transfer in thin, compact heat exchangers with circular, rectangular, or pin-fin flow passages

    NASA Technical Reports Server (NTRS)

    Olson, D. A.

    1992-01-01

    Heat transfer and pressure drop have been measured of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up to 77 W/sq cm. Correlations were developed for the isothermal friction factor as a function of Reynolds number, and for the Nusselt number as a function of Reynolds number and the ratio of wall temperature to fluid temperature. The specimen with the pin fin internal geometry had significantly better heat transfer than the other specimens, but it also had higher pressure drop. For certain conditions of helium flow and heating, the temperature more than doubled from the inlet to the outlet of the specimens, producing large changes in gas velocity, density, viscosity, and thermal conductivity. These changes in properties did not affect the correlations for friction factor and Nusselt number in turbulent flow.

  1. Study on Fins' Effect of Boiling Flow in Millimeter Channel Heat Exchanger

    NASA Astrophysics Data System (ADS)

    Watanabe, Satoshi

    2005-11-01

    Recently, a lot of researches about compact heat exchangers with mini-channels have been carried out with the hope of obtaining a high-efficiency heat transfer, due to the higher ratio of surface area than existing heat exchangers. However, there are many uncertain phenomena in fields such as boiling flow in mini-channels. Thus, in order to understand the boiling flow in mini-channels to design high-efficiency heat exchangers, this work focused on the visualization measurement of boiling flow in a millimeter channel. A transparent acrylic channel (heat exchanger form), high-speed camera (2000 fps at 1024 x 1024 pixels), and halogen lamp (backup light) were used as the visualization system. The channel's depth is 2 mm, width is 30 mm, and length is 400 mm. In preparation for commercial use, two types of channels were experimented on: a fins type and a normal slit type (without fins). The fins are circular cylindrical obstacles (diameter is 5 mm) to promote heat transfer, set in a triangular array (distance between each center point is 10 mm). Especially in this work, boiling flow and heat transfer promotion in the millimeter channel heat exchanger with fins was evaluated using a high-speed camera.

  2. Heat Transfer Enhancement for Finned-Tube Heat Exchangers with Vortex Generators: Experimental and Numerical Results

    SciTech Connect

    O'Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert

    2002-08-01

    A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numerical modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  5. Experimental Investigation of Gas-Side Performance of a Compact Finned-Tube Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Gedeon, Louis

    1959-01-01

    Heat-transfer and pressure-drop data were obtained experimentally for the gas side of a liquid-metal to air, compact finned-tube heat exchanger. The heat exchanger was fabricated from 0.185-inch Inconel tubing in an inline array. The fins were made of 310 stainless-steel- clad copper with a total thickness of 0.010 inch, and the fin pitch was 15.3 fins per inch. The liquid used as the heating medium was sodium. The heat-exchanger inlet gas temperature was varied from 5100 to 1260 R by burning JP fuel for airflow rates of 0.4 to 10.5 pounds per second corresponding to an approximate Reynolds number range of 300 to 9000. The sodium inlet temperature was held at 1400 R with the exception of a few runs taken at 1700 and 1960 R. The maximum ratio of surface temperature to air bulk temperature was 1.45. Friction-factor data with heat transfer were best represented by a single line when the density and viscosity of Reynolds number were evaluated at the average film temperature. At the lower Reynolds numbers reported, the friction data with heat transfer plotted slightly above the friction data without heat transfer. The density of the friction factor was calculated at the average bulk temperature. Heat-transfer results of this investigation were correlated by evaluating the physical properties of air (specific heat, viscosity, and thermal conductivity) at the film temperature.

  6. Numerical study of a round tube heat exchanger with louvered fins and delta winglets

    NASA Astrophysics Data System (ADS)

    Huisseune, H.; T'Joen, C.; De Jaeger, P.; Ameel, B.; De Paepe, M.

    2012-11-01

    Louvered fin and round tube heat exchangers are widely used in air conditioning devices and heat pumps. In this study the effect of punching delta winglet vortex generators in the louvered fin surface is studied numerically. The delta winglets are located in a common-flow-down orientation behind each tube of the staggered tube layout. It is shown that the generated vortices significantly reduce the size of the tube wakes. Three important heat transfer enhancement mechanisms can be distinguished: a better flow mixing, boundary layer thinning and a delay in flow separation from the tube surface. The compound heat exchanger has a better thermal hydraulic performance then when only louvers or only delta winglets are used. Comparison to other enhanced fin designs clearly shows its potential, especially for low Reynolds number applications.

  7. Measurement of frost characteristics on heat exchanger fins. Part 1: Test facility and instrumentation

    SciTech Connect

    Thomas, L.; Chen, H.; Besant, R.W.

    1999-07-01

    A special test facility was developed to characterize frost growing on heat exchanger fins where the cold surfaces and the air supply conditions were similar to those experienced in freezers, i.e., cold surface temperatures ranging from {minus}35 C to {minus}40 C, air supply temperatures from {minus}10 C to {minus}20 C, and 80% to 100% relative humidity (RH). This test facility included a test section with removable fins to measure the frost height and mass concentration. Frost height on heat exchanger fins was measured using a new automated laser scanning system to measure the height of frost and its distribution on selected fins. The increase in air pressure loss resulting from frost growth on the fins was measured directly in the test loop. The frost mass accumulation distribution was measured for each test using special pre-etched fins that could be easily subdivided and weighed. The total heat rate was measured using a heat flux meter. These frost-measuring instruments were calibrated and the uncertainty of each is stated.

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

    SciTech Connect

    Huisseune, H.; Willockx, A.; De Paepe, M.; T'Joen, C.; De Jaeger, P.

    2010-11-15

    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)

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

    SciTech Connect

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

    2011-06-10

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

  10. The combined effects of wall longitudinal heat conduction and inlet fluid flow maldistribution in crossflow plate-fin heat exchangers

    NASA Astrophysics Data System (ADS)

    Ranganayakulu, Ch.; Seetharamu, K. N.

    An analysis of a crossflow plate-fin compact heat exchanger, accounting for the combined effect of two-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow distribution on both hot and cold fluid sides is carried out using a finite element method. Using the fluid flow maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of wall longitudinal heat conduction and inlet fluid flow nonuniformity on crossflow plate-fin heat exchanger.

  11. Fluid-structure interaction numerical simulation of thermal performance and mechanical property on plate-fins heat exchanger

    NASA Astrophysics Data System (ADS)

    Zhang, Lingjie; Qian, Zuoqin; Deng, Jun; Yin, Yuting

    2015-09-01

    A numerical simulation and experimental study of heat transfer, fluid flow and fins mechanical property on plate-fin heat exchanger has been presented in this paper. The methods used in this study are experiment, CFD analysis, fluid-structure interaction and finite element method. An air-oil wind tunnel is established for this experiment. The temperature difference, pressure drop, streamlines are obtained in overall model, and the heat transfer coefficient, j/ f factor, temperature and stress distribution of plate-fin body are obtained in different fin thickness and fin offset. The prediction from the CFD simulation shows reasonably good agreement with the experimental results.

  12. A computer program for designing fin-and-tube heat exchanger for EGR cooler application

    NASA Astrophysics Data System (ADS)

    Syaiful, Marwan, M. A.; Tandian, N. P.; Bae, M.

    2016-03-01

    EGR (exhaust gas recirculation) cooler is a kind of heat exchanger that is used to cool exhaust gas recirculation prior to be mixed with fresh air in an intake manifold of vehicle in order to obtain good reduction of NOxemissions. A fin-and-tube heat exchanger is more preferred as an EGR cooler than a shell-and-tube heat exchanger in this study due to its compactness. Manually designing many configurations of fin-and-tube heat exchanger for EGR cooler application consumes a lot of time and is high cost. Therefore, a computer aided design process of EGR cooler is required to overcome this problem. The EGR cooler design process was started by arranging the sequences of calculation algorithm in a computer program. A cooling media for this EGR cooler is air. The design is based on the effectiveness-number transfer unit (NTU) method. The EGR cooler design gives the geometry, heat transfer surface area, heat transfer coefficient and pressure drop of the EGR cooler. Comparison of the EGR cooler Nusselt number obtained in this study and that reported in literature shows less than 6.2% discrepancy.

  13. Numerical estimation of heat transfer characteristics for two-row plate-finned tube heat exchangers with experimental data

    NASA Astrophysics Data System (ADS)

    Chen, Han-Taw; Lu, Chih-Han; Huang, Yao-Sheng; Liu, Kuo-Chi

    2016-05-01

    This study applies a three-dimensional computational fluid dynamics commercial software in conjunction with various flow models to estimate the heat transfer and fluid flow characteristics of the two-row plate-finned tube heat exchanger in staggered arrangement. The effect of air speed and fin spacing on the results obtained is investigated. Temperature and velocity distributions of air between the two fins and heat transfer coefficient on the fins are determined using the laminar flow and RNG k-ɛ turbulence models. More accurate results can be obtained, if the heat transfer coefficient obtained is close to the inverse results and matches existing correlations. Furthermore, the fin temperature measured at the selected locations also coincides with the experimental temperature data. The results obtained using the RNG k-ɛ turbulence model are more accurate than those using the laminar flow model. An interesting finding is the number of grid points may also need to change with fin spacing and air speed.

  14. The Experimental Study of Atmospheric Stirling Engines Using Pin-Fin Arrays' Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Isshiki, Seita; Sato, Hidekazu; Konno, Shoji; Shiraishi, Hiroaki; Isshiki, Naotsugu; Fujii, Iwane; Mizui, Hiroyuki

    This paper reports experimental results on two kinds of atmospheric Stirling engines that were designed and manufactured using a pin-fin array heat exchanger for the heater and cooler (abbreviated to “pin-fin Stirling engine” hereafter). The first one is a large β type pin-fin Stirling engine with a 1.7-liter displacement volume and power piston volume. The heater consists of an aluminum circular disk with a diameter of 270mm and with large-scale pin-fin arrays carved into the surface. The maximum output reached 91W at a temperature difference of 330K, which is 36% of the scheduled value and 68% of the Kolin's cubic power law. The maximum thermal efficiency was estimated 4.2%. The second engine is an α type pin-fin Stirling engine. Glass syringes were used for the piston-cylinder system and the Ross-yoke mechanism was used for the crank mechanism. By changing temperature difference, the characteristic of output torque in the large range was measured with a precision torque detector.

  15. Compound heat transfer enhancement for shell side of double-pipe heat exchanger by helical fins and vortex generators

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Guo, Hongmei; Wu, Jianhua; Du, Wenjuan

    2012-07-01

    To improve heat transfer performance of shell side of double-pipe heat exchanger with helical fins on its inner tube, some vortex generators (VGs) were installed along the centerline of the helical channel. Heat transfer performance and pressure drop characteristic of the enhanced heat exchangers were investigated using air as the working fluid and steam as the heating medium. The helical fins were in the annulus and span its full width at different helical pitch. Wing-type VGs (delta or rectangular wing) and winglet-type VGs (delta or rectangular winglet pair) were used to combine with helical fins. The friction factor and Nusselt number can be well correlated by power-law correlations in the Reynolds number range studied. In order to evaluate the thermal performance of the shell side enhanced over the shell side without enhancement, comparisons were made under three constraints: (1) identical mass flow rate, IMF; (2) identical pressure drop, IPD and (3) identical pumping power, IPP. The results show the shell side enhanced by the compound heat transfer enhancement has better performance than the shell side only enhanced by helical fins at shorter helical pitch under the three constraints.

  16. 3D Numerical heat transfer and fluid flow analysis in plate-fin and tube heat exchangers with electrohydrodynamic enhancement

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Wen; Jang, Jiin-Yuh

    2005-05-01

    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 (VE=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 VE=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.

  17. Thermal performance of plate-fin heat exchanger using passive techniques: vortex-generator and nanofluid

    NASA Astrophysics Data System (ADS)

    Khoshvaght-Aliabadi, Morteza

    2016-04-01

    This experimental study investigates the effects of vortex-generator (VG) and Cu/water nanofluid flow on performance of plate-fin heat exchangers. The Cu/water nanofluids are produced by using a one-step method, namely electro-exploded wire technique, with four nanoparticles weight fractions (i.e. 0.1, 0.2, 0.3, and 0.4 %). Required properties of nanofluids are systematically measured, and empirical correlations are developed. A highly precise test loop is fabricated to obtain accurate results of the heat transfer and pressure drop characteristics. Experiments are conducted for nanofluids flow inside the plain and VG channels. Based on the experimental results, utilizing the VG channel instead of the plain channel enhances the heat transfer rate, remarkably. Also, the results show that the VG channel is more effective than the nanofluid on the performance of plate-fin heat exchangers. It is observed that the combination of the two heat transfer enhancement techniques has a noticeably high thermal-hydraulic performance, about 1.67. Finally, correlations are developed to predict Nusselt number and friction factor of nanofluids flow inside the VG channel.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  19. New application of plate-fin heat exchanger with regenerative cryocoolers

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung; Gwak, Kyung Hyun

    2015-09-01

    A design idea is newly proposed and investigated for the application of plate-fin heat exchanger (PFHX) with regenerative cryocoolers. The role of this heat exchanger is to effectively absorb heat from the stream of coolant and deliver it to the cold-head of a cryocooler. While various types of tubular HX's have been developed so far, a small PFHX could be more useful for this purpose by taking advantage of compactness and design flexibility. In order to confirm the feasibility and effectiveness, a prototype of aluminum-brazed PFHX is designed, fabricated, and tested with a single-stage GM cryocooler in experiments for subcooling liquid nitrogen from 78 K to 65-70 K. The results show that the PFHX is 30-50% more effective in cooling rate than the tubular HX's. Several potential applications of PFHX are presented and discussed with specific design concepts.

  20. Condensation heat transfer and pressure drop of R-134a saturated vapour inside a brazed compact plate fin heat exchanger with serrated fin

    NASA Astrophysics Data System (ADS)

    Ramana Murthy, K. V.; Ranganayakulu, C.; Ashok Babu, T. P.

    2016-05-01

    This paper presents the experimental heat transfer coefficient and pressure drop measured during R-134a saturated vapour condensation inside a small brazed compact plate fin heat exchanger with serrated fin surface. The effects of saturation temperature (pressure), refrigerant mass flux, refrigerant heat flux, effect of fin surface characteristics and fluid properties are investigated. The average condensation heat transfer coefficients and frictional pressure drops were determined experimentally for refrigerant R-134a at five different saturated temperatures (34, 38, 40, 42 and 44 °C). A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 22 kg/m2s. In the forced convection condensation region, the heat transfer coefficients show a three times increase and 1.5 times increase in frictional pressure drop for a doubling of the refrigerant mass flux. The heat transfer coefficients show weak sensitivity to saturation temperature (Pressure) and great sensitivity to refrigerant mass flux and fluid properties. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow. Correlations are provided for the measured heat transfer coefficients and frictional pressure drops.

  1. Augmentation of heat transfer by longitudinal vortices in plate-fin heat exchangers with two rows of tubes

    SciTech Connect

    Rodrigues, R. Jr.; Yanagihara, J.I.

    1999-07-01

    The thermal performance of fin-tube compact heat exchangers is highly affected by the thermal resistance occurring on the air side, which is much higher than the thermal resistance inside the tubes. Since this kind of heat exchanger is widely used in these days, with applications on air-conditioning, refrigeration, automobilistic industry and many other areas, the development of more efficient and cheaper heat exchangers is highly attractive, because it will permit the manufacturing of more competitive equipments. This work presents results of numerical simulations for fin-tube compact heat exchangers using smooth fins and longitudinal vortex generators. The computational model has two rows of round tubes in staggered arrangement. Built-in delta winglet vortex generators were used, and its geometric dimensions were chosen according to the best results of literature. The steady-state numerical simulations were carried out at Re = 300, with a code based on the finite volume method. The typical configuration, where the vortex generators of both tube rows have identical parameters set, was compared with new ones where the vortex generators of the second row have different attack angles and positions. The global and local influence of vortex generators on heat transfer and flow losses are analyzed by comparison with a smooth fin model without vortex generators. The results show that a best heat transfer performance can be obtained by positioning the vortex generators of the second row at a particular position and angle of attack, when the increasing of the flow losses was smaller than the heat transfer enhancement achieved.

  2. Net Shape Fins for Compact Heat Exchanger Produced by Cold Spray

    NASA Astrophysics Data System (ADS)

    Cormier, Yannick; Dupuis, Philippe; Jodoin, Bertrand; Corbeil, Antoine

    2013-10-01

    This work explores the manufacturability of pyramidal fin arrays produced using the cold spray process. Near-net shaped pyramidal fin arrays of various sizes and fin densities were manufactured using masks made of commercially available steel wire mesh. The feedstock powders used to produce the fins are characterized using scanning electron microscopy. Obstruction of the masks was investigated. The standoff distances between the substrate, mesh, and nozzle were empirically determined. Fin array characterization was performed using digital microscopy. The fin arrays' heat transfer performance was assessed experimentally for a range of Reynolds number relevant to the application sought. The fins produced using the cold spray process outperform traditional straight (rectangular) fins at the same fin density and it is hypothesized that this is due to increased fluid mixing and turbulence.

  3. The optimization of fin-tube heat exchanger with longitudinal vortex generators using response surface approximation and genetic algorithm

    NASA Astrophysics Data System (ADS)

    Wu, Xuehong; Liu, DanDan; Zhao, Min; Lu, YanLi; Song, Xiaoyong

    2016-09-01

    Delta winglet works better than other vortex generators in improving the performance of fin-tube heat exchangers. In this paper, Response Surface Approximation is used to study the effects of the fin pitch, the ratio of the longitudinal tube pitch to transverse tube pitch, the ratio of both sides V 1 , V h of delta winglets and the attack angle of delta winglets on the performance of fin-tube heat exchanger. Firstly, Twenty-nine numerical group experiments including five times repeated experiments at the central point are conducted. Then, the analyses of variable (ANOVA) and regression are performed to verify the accuracy of the polynomial coefficients. Finally, the optimization of the fin-tube heat exchanger using the Genetic Algorithm is conducted and the best performance of j/f (1/3) is found to be 0.07945, which is consistent with the numerical result.

  4. Large-eddy simulation of turbulent flows around a fin-tube heat exchanger enclosed by a compartment

    NASA Astrophysics Data System (ADS)

    Son, Changkeun; Song, Simon; Lee, Jeesoo; Kang, Seongwon

    2014-11-01

    The main objective of the present study is to analyze heat transfer and flow characteristics of a heat exchanger in an industrial application using high-fidelity simulation techniques. Large-eddy simulations (LES) were performed to investigate the turbulent flows around a fin-tube heat exchanger enclosed by a compartment. The complex geometry of the compartment poses a difficulty in a simulation as the local Re number is about two orders of different magnitude, and generates various scales of the 3-D vortices and complex flow patterns. Careful tests with both grid resolution and turbulent inflow boundary condition were performed in order to compare our results to the measured data from a MRV experiment as well as the results from RANS simulations. From interaction of the flow structures such as the 3-D vortices, a few interesting flow phenomena were observed which are different from a plain fin-tube heat exchanger, such as helical flows and a jet stream observed behind the fin-tube region. Also, performance of the heat exchanger was analyzed using the data from plain fin-tube heat exchangers. Based on this analysis, a numerical technique for heat exchanger was devised and tested to show a possibility of reducing the computational cost significantly, using a porous media model.

  5. Numerical Analysis on Optimization of a Fin and Tube Type Adsorber/Desorber Heat Exchanger using ACF/C2H5OH Pair

    NASA Astrophysics Data System (ADS)

    Kariya, Keishi; Kuwahara, Ken; Koyama, Shigeru

    This study deals with a two dimensional numerical analysis of the fin and tube type adsorber/desorber heat exchanger design such as fin height, fin pitch, fin thickness and tube diameter effect on the performance of closed adsorption cooling system with activated carbon fiber (ACF) of type A-20, which has relatively higher surface area, and ethanol pair. The simulation results show that the fin tube diameter is effective on the performance of the heat exchanger. It is also found that the cycle COP can be optimized in the condition of fin pitch 4.5mm and fin height 20mm, respectively when other parameters are fixed.

  6. Parametric study of graphite foam fins and application in heat exchangers

    NASA Astrophysics Data System (ADS)

    Collins, Michael

    This thesis focuses on the simulation and experimental studies of finned graphite foam extended surfaces to test their heat transfer characteristics and potential applications in condensers. Different fin designs were developed to conduct a parametric study on the thermal effectiveness with respect to thickness, spacing and fin offset angle. Each fin design was computationally simulated to estimate the heat transfer under specific conditions. The simulations showed that this optimal fin configuration could conduct more than 297% the amount of thermal energy as compared to straight aluminum fins. Graphite foam fins were then implemented into a simulation of the condenser system. The condenser was simulated with six different orientations of baffles to examine the incoming vapor and resulting two-phase flow patterns. The simulations showed that using both horizontal and vertical baffling provided the configuration with the highest heat transfer and minimized the bypass regions where the vapor would circumvent the graphite foam. This baffle configuration increased the amount of vapor flow through the inner graphite fins and cold water pipes, which gave this configuration the highest heat transfer. The results from experimental tests using the condenser system confirmed that using three baffles will increase performance consistent with the simulation results. The experimental data showed that the condenser using graphite foam had five times the heat transfer compared to the condenser using only aluminum fins. Incorporating baffles into the condenser using graphite foam enabled this system to conduct nearly ten times more heat transfer than the condenser system which only had aluminum fins without baffles. The results from this research indicate that graphite foam is a far superior material heat transfer enhancement material for heat transfer compared to aluminum used as an extended surface. The longitudinal and horizontal baffles incorporated into the condenser system

  7. Modeling the dynamic operation of a small fin plate heat exchanger - parametric analysis

    NASA Astrophysics Data System (ADS)

    Motyliński, Konrad; Kupecki, Jakub

    2015-09-01

    Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC) offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP) units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700-900 °C) is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the cold sides

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

    NASA Astrophysics Data System (ADS)

    Onstad, Andrew J.

    Compact heat exchangers have been designed following the same basic methodology for over fifty years. However, with the present emphasis on energy efficiency and light weight of prime movers there is increasing demand for completely new heat exchangers. Moreover, new materials and mesoscale fabrication technologies offer the possibility of significantly improving heat exchanger performance over conventional designs. This work involves fundamental flow and heat transfer experimentation to explore two new heat exchange systems: in Part I, large arrays of impinging jets with local extraction and in Part II, metal foams used as fins. Jet impingement cooling is widely used in applications ranging from paper manufacturing to the cooling of gas turbine blades because of the very high local heat transfer coefficients that are possible. While the use of single jet impingement results in non-uniform cooling, increased and more uniform mean heat transfer coefficients may be attained by dividing the total cooling flow among an array of smaller jets. Unfortunately, when the spent fluid from the array's central jets interact with the outer jets, the overall mean heat transfer coefficient is reduced. This problem can be alleviated by locally extracting the spent fluid before it is able to interact with the surrounding jets. An experimental investigation was carried out on a compact impingement array (Xn/Djet = 2.34) utilizing local extraction of the spent fluid (Aspent/Ajet = 2.23) from the jet exit plane. Spatially resolved measurements of the mean velocity field within the array were carried out at jet Reynolds numbers of 2300 and 5300 by magnetic resonance velocimetry, MRV. The geometry provided for a smooth transition from the jet to the target surface and out through the extraction holes without obvious flow recirculation. Mean Nusselt number measurements were also carried out for a Reynolds number range of 2000 to 10,000. The Nusselt number was found to increase with the

  9. Study of plate-fin heat exchanger and cold plate for the active thermal control system of Space Station

    NASA Technical Reports Server (NTRS)

    Chyu, MING-C.

    1992-01-01

    Plate-fin heat exchangers will be employed in the Active Thermal Control System of Space Station Freedom. During ground testing of prototypic heat exchangers, certain anomalous behaviors have been observed. Diagnosis has been conducted to determine the cause of the observed behaviors, including a scrutiny of temperature, pressure, and flow rate test data, and verification calculations based on such data and more data collected during the ambient and thermal/vacuum tests participated by the author. The test data of a plate-fin cold plate have been also analyzed. Recommendation was made with regard to further tests providing more useful information of the cold plate performance.

  10. Optimization of Fin Distribution to Improve the Temperature Uniformity of a Heat Exchanger in a Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Wu, Cheng; Tang, Zebo; Yang, Xue; Deng, Yadong; Su, Chuqi

    2015-06-01

    Thermoelectric generators (TEGs) are currently a topic of interest for energy recovery in vehicles. By applying TEGs to the outside surface of the exhaust tailpipe, a small amount of electrical power can be generated because of the temperature difference between the hot exhaust gases and the automobile coolant. The amount of power is anticipated to be a few hundred watts based on the expected temperature difference and the properties of the thermoelectric materials used in TEGs. It is well know that, for thermoelectric exhaust energy recovery, the temperature uniformity of the heat exchangers has a strong influence on the electric power generation. In the current research, the temperature uniformity of a heat exchanger was improved by optimizing the fin distribution to maximize the electric power generated for a given vehicle TEG. A computational fluid dynamics (CFD) model of the heat exchanger was constructed to assess the influence of different fin distributions on the temperature uniformity and the pressure drop in the exhaust system. For the fin distributions, four factors were considered: the length of, spacing between, angle of, and thickness of the fins. Based on these four factors, a design of experiments study using the orthogonal experimental method was conducted to analyze the sensitivity to the design variables and build a database to set up a surrogate model using the Kriging response surface method. A multi-island genetic algorithm was used to optimize the fin distribution based on this surrogate model. To validate the accuracy of the CFD model, a generic heat exchanger module was manufactured and a related testbed constructed, then the temperature distribution on the surface of the exchanger was measured to compare with the results obtained by CFD.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  12. Effects of PM fouling on the heat exchange effectiveness of wave fin type EGR cooler for diesel engine use

    NASA Astrophysics Data System (ADS)

    Jang, Sang-Hoon; Hwang, Se-Joon; Park, Sang-Ki; Choi, Kap-Seung; Kim, Hyung-Man

    2012-06-01

    Developing an effective method of reducing nitrogen oxide emissions is an important goal in diesel engine research. The use of cooled exhaust gas recirculation has been considered one of the most effective techniques of reducing nitrogen oxide. However, since the combustion characteristics in a diesel engine involves high temperature and load, the amount of particulate matter emission tends to increase, and there is a trade-off between the amount of nitrogen oxide and particulate matter emissions. In the present study, engine dynamometer experiments are performed to investigate the effects of particulate matter fouling on the heat exchange characteristics of wave fin type exhaust gas recirculation coolers that have four cases of two wave pitch and three fin pitch lengths. To optimize the fin and wave pitches of the EGR cooler, the exhaust gas temperature, pressure drop and heat exchange effectiveness are compared. The experimental results show that the exhaust gas recirculation cooler with a fin pitch of 3.6 mm and a wave pitch of 8.8 mm exhibits better heat exchange characteristics and smaller particulate matter fouling effect than the other coolers.

  13. UNIQUE METHOD FOR LIQUID NITROGEN PRECOOLING OF A PLATE FIN HEAT EXCHANGER IN A HELIUM REFRIGERATION CYCLE.

    SciTech Connect

    Weber, T

    2004-06-02

    Precooling of helium by means of liquid nitrogen is one the oldest and most common process features used in helium refrigerators. The principal tasks are to permit a rapid cool down to 80 K of the plant, to increase the cooling power of the plant in low temperature operation and to increase the rate of pure liquid production. The advent of aluminum plate fin heat exchangers in the design of helium refrigerators has made this task more complicated because of the potential damage to these heat exchangers.

  14. Influence of PM fouling on effectiveness of heat exchanges in a diesel engine with fin-type EGR coolers of different sizes

    NASA Astrophysics Data System (ADS)

    Park, Sangki; Choi, Kapseung; Kim, Hyungman; Lee, Kihyung

    2010-12-01

    The particulate matter (PM) fouling in exhaust gas recirculation (EGR) coolers degrades the heat transfer performance considerably, which in turn has a significant influence on the design of the EGR cooler. To investigate the effects of PM fouling on the heat exchange effectiveness in the fin-type EGR coolers of six different sizes, engine dynamometer experiments were performed. The experimental results show that the heat exchange effectiveness varies with the size of the fin-type EGR cooler.

  15. Statistical analysis of entropy generation in longitudinally finned tube heat exchanger with shell side nanofluid by a single phase approach

    NASA Astrophysics Data System (ADS)

    Konchada, Pavan Kumar; Pv, Vinay; Bhemuni, Varaprasad

    2016-06-01

    The presence of nanoparticles in heat exchangers ascertained increment in heat transfer. The present work focuses on heat transfer in a longitudinal finned tube heat exchanger. Experimentation is done on longitudinal finned tube heat exchanger with pure water as working fluid and the outcome is compared numerically using computational fluid dynamics (CFD) package based on finite volume method for different flow rates. Further 0.8% volume fraction of aluminum oxide (Al2O3) nanofluid is considered on shell side. The simulated nanofluid analysis has been carried out using single phase approach in CFD by updating the user-defined functions and expressions with thermophysical properties of the selected nanofluid. These results are thereafter compared against the results obtained for pure water as shell side fluid. Entropy generated due to heat transfer and fluid flow is calculated for the nanofluid. Analysis of entropy generation is carried out using the Taguchi technique. Analysis of variance (ANOVA) results show that the inlet temperature on shell side has more pronounced effect on entropy generation.

  16. Heat transfer characteristics of the metal hydride vessel based on the plate-fin type heat exchanger

    NASA Astrophysics Data System (ADS)

    Oi, Tsutomu; Maki, Kohei; Sakaki, Yoshinori

    Heat transfer characteristics of the metal hydride vessel based on the plate-fin type heat exchanger were investigated. Metal hydride beds were filled with AB 2 type hydrogen-storage alloy's particles, Ti 0.42Zr 0.58Cr 0.78Fe 0.57Ni 0.2Mn 0.39Cu 0.03, with a storage capacity of 0.92 wt.%. Heat transfer model in the metal hydride bed based on the heat transfer mechanism for packed bed proposed by Kunii and co-workers is presented. The time-dependent hydrogen absorption/desorption rate and pressure in the metal hydride vessel calculated by the model were compared with the experimental results. During the hydriding, calculated hydrogen absorption rates agreed with measured ones. Calculated thermal equilibrium hydrogen pressures were slightly lower than the measured hydrogen pressures at the inlet of metal hydride vessel. Taking account of the pressure gradient between the inlet of metal hydride vessel and the metal hydride bed, it is considered that this discrepancy is reasonable. During the dehydriding, there were big differences between the calculated hydrogen desorption rates and measured ones. As calculated hydrogen desorption rates were lower than measured ones, there were big differences between the calculated thermal equilibrium hydrogen pressures and the measured hydrogen pressures at the inlet of metal hydride vessel. It is considered that those differences are due to the differences of the heat transfer characteristics such as thermal conductivity of metal hydride particles and porosity between the assumed and actual ones. It is important to obtain the heat transfer characteristics such as thermal conductivity of metal hydride particles and porosity both during the hydriding and dehydriding to design a metal hydride vessel.

  17. Conjugate Heat Transfer Computation for Evaluation of Single-Blow Method for Compact Fin-Tube Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Song, Gil-Dal; Nishino, Koichi

    Computations have been carried out to evaluate heat transfer coefficients given by the single-blow method that is characterized by a transient and conjugate heat transfer problem between the fluid and the solid. Both heat conduction and convection equations are solved numerically to obtain the transient fluid and fin temperature distributions. Finite volume solutions indicate that the fin temperature distribution of the single-blow method varies with time and position and that the fluid temperature distribution of the single-blow method is close to that observed in the steady-state computation specified with the constant wall temperature condition. It is found that the local heat transfer coefficient resulting from the single-blow method is almost identical to that from the steady-state constant wall temperature computation and is nearly time-independent.

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

    SciTech Connect

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

    1999-03-15

    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.

  19. A complementary experimental and numerical study of the flow and heat transfer in offset strip-fin heat exchangers

    SciTech Connect

    DeJong, N.C.; Zhang, L.W.; Jacobi, A.M.; Balachandar, S.; Tafti, D.K.

    1998-08-01

    A detailed analysis of experimental and numerical results for flow and heat transfer in similar offset strip-fin geometries is presented. Surface-average heat transfer and pressure drop, local Nusselt numbers and skin friction coefficients on the fin surface, instantaneous flow structures, and local time-averaged velocity profiles are contrasted for a range of Reynolds numbers using both prior and new experimental and numerical results. This contrast verifies that a two-dimensional unsteady numerical simulation captures the important features of the flow and heat transfer for a range of conditions. However, flow three-dimensionality appears to become important for Reynolds numbers greater than about 1,300, and thermal boundary conditions are important for Reynolds numbers below 1,000. The results indicate that boundary layer development, flow separation and reattachment, wake formation, and vortex shedding are all important in this complex geometry.

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

    NASA Technical Reports Server (NTRS)

    Olson, D. A.

    1991-01-01

    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.

  1. Indoor Solar Thermal Energy Saving Time with Phase Change Material in a Horizontal Shell and Finned-Tube Heat Exchanger

    PubMed Central

    Paria, S.; Sarhan, A. A. D.; Goodarzi, M. S.; Baradaran, S.; Rahmanian, B.; Yarmand, H.; Alavi, M. A.; Kazi, S. N.; Metselaar, H. S. C.

    2015-01-01

    An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM) in a shell around a finned-tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned-tube where distilled water was employed as the heat transfer fluid (HTF). The focus of this study was on the behavior of PCM for storage (charging or melting) and removal (discharging or solidification), as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises. PMID:25879052

  2. Indoor solar thermal energy saving time with phase change material in a horizontal shell and finned-tube heat exchanger.

    PubMed

    Paria, S; Sarhan, A A D; Goodarzi, M S; Baradaran, S; Rahmanian, B; Yarmand, H; Alavi, M A; Kazi, S N; Metselaar, H S C

    2015-01-01

    An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM) in a shell around a finned-tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned-tube where distilled water was employed as the heat transfer fluid (HTF). The focus of this study was on the behavior of PCM for storage (charging or melting) and removal (discharging or solidification), as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises. PMID:25879052

  3. Indoor solar thermal energy saving time with phase change material in a horizontal shell and finned-tube heat exchanger.

    PubMed

    Paria, S; Sarhan, A A D; Goodarzi, M S; Baradaran, S; Rahmanian, B; Yarmand, H; Alavi, M A; Kazi, S N; Metselaar, H S C

    2015-01-01

    An experimental as well as numerical investigation was conducted on the melting/solidification processes of a stationary phase change material (PCM) in a shell around a finned-tube heat exchanger system. The PCM was stored in the horizontal annular space between a shell and finned-tube where distilled water was employed as the heat transfer fluid (HTF). The focus of this study was on the behavior of PCM for storage (charging or melting) and removal (discharging or solidification), as well as the effect of flow rate on the charged and discharged solar thermal energy. The impact of the Reynolds number was determined and the results were compared with each other to reveal the changes in amount of stored thermal energy with the variation of heat transfer fluid flow rates. The results showed that, by increasing the Reynolds number from 1000 to 2000, the total melting time decreases by 58%. The process of solidification also will speed up with increasing Reynolds number in the discharging process. The results also indicated that the fluctuation of gradient temperature decreased and became smooth with increasing Reynolds number. As a result, by increasing the Reynolds number in the charging process, the theoretical efficiency rises.

  4. The Effect of Circuiting Arrangement on the Thermal Performance of Refrigeration Mixtures in Tube-and-Fin Condensing Heat Exchangers

    SciTech Connect

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

    1999-03-15

    For the pure or azeotropic refrigerants typically used in present air conditioning and refrigeration applications, the refrigerant changes phase at a constant temperature. Thus, the refrigerant circuiting arrangement such as crossfiow, counterfiow, or cross-counterflow, has no effect on the thermal performance. For zeotropic refrigerant mixtures, however, the phase-change occurs over a temperature range, or "glide", and the refrigerant circuiting arrangement, or flow path through the heat exchanger, can affect the thermal performance of both the heat exchangers as well as the overall efficiency of the vapor compression cooling cycle. The effects of tsvo diflerent circuiting arrangements on the thermal performance of a zeotropic retligerant mixture and an almost azeotropic refrigerant mixture in a four-row cross-countertlow heat exchanger arrangement are reported here. The two condensers differ only in the manner of circuiting the refrigerant tubes, where one has refrigerant always flowing downward in the active heat transfer region ("identical order") and the other has refrigerant alternating flow direction in the active heat transfer region ("inverted order"). All other geometric parameters, such as bce are% fin louver geometry, refrigerant tube size and enhancement etc., are the same for both heat exchangers. One refrigerant mixture (R-41OA) un&rgoes a small temperature change ("low glide") during phase change, and the other retligerant mixture (a multi- component proprietary mixture) has a substantial temperature change ("high glide") of approximately 10"C during the phase change process. The overall thermal conductance, two-phase conductance, and pressure drop are presented. For the flow conditions of these tests, which are representative of resi&ntial cooling conditions, inverted order circuiting is more desirable than identical order. The potential thermal advantages of the i&ntical order arrangement for high-glide zeotropic refrigerant mixtures are negated

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

    SciTech Connect

    Jang, Jiin-Yuh; Chang, Wen-Jen; Lin, Min-Sheng

    1996-12-31

    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.

  6. Influence of Alumina Addition to Aluminum Fins for Compact Heat Exchangers Produced by Cold Spray Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Farjam, Aslan; Cormier, Yannick; Dupuis, Philippe; Jodoin, Bertrand; Corbeil, Antoine

    2015-10-01

    In this work, aluminum and aluminum-alumina powder mixtures were used to produce pyramidal fin arrays on aluminum substrates using cold spray as an additive manufacturing process. Using aluminum-alumina mixtures instead of pure aluminum powder could be seen as a cost-effective measure, preventing nozzle clogging or the need to use expensive polymer nozzles that wear out rapidly during cold spray. The fin geometries that were produced were observed using a 3D digital microscope to determine the flow passages width and fins' geometric details. Heat transfer and pressure drop tests were carried out using different ranges of appropriate Reynolds numbers for the sought commercial application to compare each fin array and determine the effect of alumina content. It was found that the presence of alumina reduces the fins' performance when compared to pure aluminum fins but that they were still outperforming traditional fins. Numerical simulations were performed to model the fin arrays and were used to predict the pressure loss in the fin array and compare these results with experimental values. The numerical model opens up new avenues in predicting different applicable operating conditions and other possible fin shapes using the same fin composition, instead of performing costly and time-consuming experiments.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  9. Plate-fin Heat-exchangers for a 10 kW Brayton Cryocooler and a 1 km HTS Cable

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung; Gwak, Kyung Hyun; Jung, Seyong; Yang, Hyung Suk; Hwang, Si-Dole

    Plate-fin heat exchangers (PFHX) are designed and fabricated for a cryogenic cooling system, serving for a 10 kW Brayton cryocooler and a 1 km HTS transmission cable under development in Korea. To achieve compactness and thermal efficiency at the same time, a recuperative HX for Brayton cycle and a sub-cooling HX of liquid nitrogen for HTS cable are designed as integrated parts. A key design feature is focused on the coldest part of sub-cooling HX, where the streams of liquid nitrogen and refrigerant (helium gas) are arranged as two-pass cross-flow so that the risk of freeze-out of liquid nitrogen can be reduced. Details of hardware PFHX design are presented and discussed towards its immediate application to the HTS cable system.

  10. Microgravity condensing heat exchanger

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  11. Heat exchange apparatus

    DOEpatents

    Degtiarenko, Pavel V.

    2003-08-12

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

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

    NASA Astrophysics Data System (ADS)

    Urquiza, Eugenio

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

  13. Honeycomb-Fin Heat Sink

    NASA Technical Reports Server (NTRS)

    Rippel, Wally E.

    1989-01-01

    Improved finned heat sink for electronic components more lightweight, inexpensive, and efficient. Designed for use with forced air, easily scaled up to dissipate power up to few hundred watts. Fins are internal walls of aluminum honeycomb structure. Cell structure gives strength to thin aluminum foil. Length of channels chosen for thermodynamic efficency; columns of cells combined in any reasonable number because flowing air distributed to all. Heat sink cools nearly as effectively at ends as near its center, no matter how many columns of cells combined.

  14. Hybrid Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Tu, Jianping Gene; Shih, Wei

    2010-01-01

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

  15. Compact heat and mass exchangers of the plate fin type in thermal sorption systems: Application in an absorption heat pump with the working pair CH3OH-LiBr/ZnBr2

    NASA Astrophysics Data System (ADS)

    Becker, Harry

    The possible application of Compact Heat and Mass Exchangers (CHME) in a gas fired Absorption Heat Pump (AHP) for domestic heating is studied. The above mentioned heat and mass exchangers are of the plate type. The space between the parallel and plain plates is filled up with corrugated plates of a certain height. The plain and finned plates are stacked and welded together. This gives a heat and mass exchanger which is very compact, expressed by a high area density (m2/m3). This leads to heat and mass transfer processes with small temperature and concentration differences. For testing purposes a pilot plant was built using the above type of components in order to test their heat and/or mass transfer performance. Only the generator is of the Shell And Tube (SAT) type. As the working pair, CH3OH - LiBr/ ZnBr2 was chosen, with the alcohol as the solvent and the salt mixture as the absorbent. This leads to sub atmospheric working pressures with only solvent in the vapor phase. Three series of experiments have been carried out, during which the input parameters were varied over a certain range. It is concluded that the plate fin CHMES are very suitable for application in an AHP for domestic heating purposes.

  16. Heat exchanger

    DOEpatents

    Daman, Ernest L.; McCallister, Robert A.

    1979-01-01

    A heat exchanger is provided having first and second fluid chambers for passing primary and secondary fluids. The chambers are spaced apart and have heat pipes extending from inside one chamber to inside the other chamber. A third chamber is provided for passing a purge fluid, and the heat pipe portion between the first and second chambers lies within the third chamber.

  17. Heat transfer and pressure drop performance of a finned-tube heat exchanger proposed for use in the NASA Lewis Altitude Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Vanfossen, G. J.

    1985-01-01

    A segment of the heat exchanger proposed for use in the NASA Lewis Altitude Wind Tunnel (AWT) facility has been tested under dry and icing conditions. The heat exchanger has the largest pressure drop of any component in the AWT loop. It is therefore critical that its performance be known at all conditions before the final design of the AWT is complete. The heat exchanger segment is tested in the NASA Lewis Icing Research Tunnel (IRT) in order to provide an icing cloud environment similar to what will be encountered in the AWT. Dry heat transfer and pressure drop data are obtained and compared to correlations available in the literature. The effects of icing sprays on heat transfer and pressure drop are also investigated.

  18. HEAT EXCHANGER

    DOEpatents

    Fox, T.H. III; Richey, T. Jr.; Winders, G.R.

    1962-10-23

    A heat exchanger is designed for use in the transfer of heat between a radioactive fiuid and a non-radioactive fiuid. The exchanger employs a removable section containing the non-hazardous fluid extending into the section designed to contain the radioactive fluid. The removable section is provided with a construction to cancel out thermal stresses. The stationary section is pressurized to prevent leakage of the radioactive fiuid and to maintain a safe, desirable level for this fiuid. (AEC)

  19. Heat exchanger

    SciTech Connect

    Drury, C.R.

    1988-02-02

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

  20. The combined effects of inlet fluid flow and temperature nonuniformity in cross flow plate-fin compact heat exchanger using finite element method

    NASA Astrophysics Data System (ADS)

    Ranganayakulu, C.; Seetharamu, K. N.

    An analysis of a crossflow plate-fin heat exchanger accouning for the combined effects of inlet fluid flow nonuniformity and temperature nonuniformity on both hot and cold fluid sides is carried out using a Finite Element Model. A mathematical equation is developed to generate different types of fluid flow/temperature maldistribution models considering the possible deviations in inlet fluid flow. Using these fluid flow maldistribution models, the exchanger effectiveness and its deteriorations due to flow/temperature nonuniformity are calculated for entire range of design and operating conditions. It was found that the performance deteriorations are quite significant in some typical applications due to inlet fluid flow/temperature nonuniformity. Zusammenfassung Mit Hilfe der Finitelement-Methode wird der zusammenwirkende Einfluß ungleichförmiger Strömungs- und Temperaturverteilungen am Eintritt des kalten, wie des warmen Fluids eines kreuzstrombetriebenen, berippten Kompakt-Plattenwärmetauschers untersucht. Über eine mathematische Beziehung lassen sich verschiedene Arten ungleichmäßiger Strömungs bzw. Temperaturverteilungen in den Eintrittsquerschnitten generieren. Unter Verwendung dieser Fehlverteilungsmodelle wird deren Einfluß auf den Austauscher-Gütegrad im gesamten Auslegungs- und Betriebsbereich ermittelt. Es zeigte sich, daß diese Auswirkungen bei typischen Ungleichförmigkeiten der Strömungs- bzw. Temperaturfelder in den Eintrittsquerschnitten erheblich sein können.

  1. Numerical study of heat transfer enhancement of finned flat tube bank fin with vortex generators mounted on both surfaces of the fin

    NASA Astrophysics Data System (ADS)

    Song, Ke-Wei; Wang, Liang-Bi; Fan, Ju-Fang; Zhang, Yong-Heng; Liu, Song

    2008-06-01

    Tube bank fin heat exchanger is one of the most compact heat exchangers, and it is widely used in industry equipments. The flat tube bank fin heat exchangers with vortex generators (VGs) have significant good heat transfer performance, and are used as radiators of locomotive. Here, we study heat transfer enhancement of a new fin where VGs are mounted on both surfaces of the fin. The heat transfer performance of this pattern is evaluated by a numerical method, and the results are compared with those obtained, under identical mass flow rate, when the VGs are mounted only on one surface of the fin. The results reveal that using this new pattern the height of VGs can be reduced and still obtain satisfactory heat transfer enhancement, while the pressure drop is reduced. The results also reveal that if VGs on one surface of the fin is determined, the locations where VGs are mounted on other surface of the same fin are very important, with configurations studied in this paper, depending on the value of Reynolds number, there exists an optimum location with which best heat transfer performance can be obtained.

  2. Heat exchanger

    DOEpatents

    Wolowodiuk, Walter

    1976-01-06

    A heat exchanger of the straight tube type in which different rates of thermal expansion between the straight tubes and the supply pipes furnishing fluid to those tubes do not result in tube failures. The supply pipes each contain a section which is of helical configuration.

  3. Corrosive resistant heat exchanger

    DOEpatents

    Richlen, Scott L.

    1989-01-01

    A corrosive and errosive 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 conveyed 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.

  4. Effects of the arrangement of triangle-winglet-pair vortex generators on heat transfer performance of the shell side of a double-pipe heat exchanger enhanced by helical fins

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Shang, Bojun; Meng, Huibo; Li, Yaxia; Wang, Cuihua; Gong, Bin; Wu, Jianhua

    2016-04-01

    To improve heat transfer performance of the shell side of a double-pipe heat exchanger enhanced by helical fins, triangle-winglet-pair vortex generators (VG) were installed along the centerline of the helical channel with rectangular cross section. The effects of the arrangement of the triangle-winglet-pair VG, such as the geometry, the angle of attack and the quantity on heat transfer performance and pressure drop characteristics have been investigated experimentally to find out the optimal design of the VG. Air was used as working fluid within the range of Re from 680 to 16,000. The results show that, the heat exchange effectiveness of the shell side with VG is 16.6 % higher than that without VG. The vortices and the unsteadiness of the flow introduced by the VG make a great contribution to the increase. Under identical pressure drop condition, the angle of attack of 30° is the best choice compared with 45° and 60°. Under the three constraints, i.e., identical mass flow rate, identical pressure drop and identical pumping power, the largest VG size can achieve the best enhancement effect. Installation of three pairs of VG within one pitch is an optimal design for the shell side used in the present experiments. The enhancement effect of isosceles right triangle is better than that of right triangle in which one acute angle is 30°.

  5. Segmented heat exchanger

    DOEpatents

    Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann

    2010-12-14

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

  6. Heat pipe array heat exchanger

    DOEpatents

    Reimann, Robert C.

    1987-08-25

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

  7. Woven heat exchanger

    DOEpatents

    Piscitella, R.R.

    1984-07-16

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

  8. Numerical investigation for finding the appropriate design parameters of a fin-and-tube heat exchanger with delta-winglet vortex generators

    NASA Astrophysics Data System (ADS)

    Behfard, M.; Sohankar, A.

    2016-01-01

    A numerical simulation is performed to investigate the heat transfer and pressure drop characteristics of three-row inline tube bundles as a part of a heat exchanger (Re = 1000, Pr = 4.29). To enhance heat transfer, two pairs of delta winglet-type vortex generators (VGs) installed beside the first row and between the first and second rows of the tube bundles. The diameter of the second row of the tubes is chosen smaller than those of the first and third. A comprehensive study on the effects of various geometrical parameters such as transverse and longitudinal positions of VGs, length and height of VGs and angle of attack of the delta winglets is performed to augment heat transfer. Based on this study the best values of these design parameters are determined. The results showed that the best model increases the convective heat transfer ratio and thermal performance factor about 59 and 43 %, respectively, in compare with the geometry without VG.

  9. Flow and heat transfer enhancement in tube heat exchangers

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  10. Solving nonlinear heat transfer constant area fin problems

    NASA Technical Reports Server (NTRS)

    1968-01-01

    Tables and graphs were compiled for solving nonlinear heat transfer constant area fin problems. The differential equation describing one-dimensional steady-state temperature distribution and heat flow under three modes of heat transfer with heat generation was investigated.

  11. Woven heat exchanger

    DOEpatents

    Piscitella, Roger R.

    1987-01-01

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

  12. Woven heat exchanger

    DOEpatents

    Piscitella, Roger R.

    1987-05-05

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

  13. Brayton-cycle heat exchanger technology program

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  14. Evaluation of a Fin and Tube Type Adsorber/Desorber Heat Exchanger using =ACF/C2H5OH Pair

    NASA Astrophysics Data System (ADS)

    Kariya, Keishi; Makimoto, Naoya; Kuwahara, Ken; Koyama, Shigeru

    This study deals with the experiment to clarify the characteristics of adsorption refrigeration system employing activated carbon fiber (ACF) and ethanol pair and to evaluate the performance of adsorber/desorber heat exchanger defined by two kind of index to the system performance. The experiments are carried out by varying system running parameters such as regeneration temperature for adsorber, ethanol temperature in the evaporator, pre-heating/cooling cycle time, adsorption/desorption cycle time. Regeneration temperature for adsorber is from 60 to 90 °C and ethanol temperature is from 0 to 20 °C and pre-heating/cooling cycle time is 60 and 120 second and adsorption/desorption cycle time is from 120 to 300 second. Results show that the system can be operated with regeneration temperature of 60 °C and the system performance improves with increase of ethanol temperature. It is also found that the system performance is affected by regeneration temperature for adsorber and the pre-heating/cooling cycle time and adsorption/desorption cycle time.

  15. Mixed convection laminar flow and heat transfer of liquids in horizontal internally finned tubes

    SciTech Connect

    Shome, B.

    1998-01-01

    Energy and material savings, as well as economic incentives, have led to concentrated efforts over the past several decades in the field of heat transfer enhancement to produce more efficient and compact heat exchangers. Internally finned tubes are widely used for heat transfer enhancement, particularly in chemical process and petroleum industries. A finned tube heat exchanger with optimum geometry could offer 35--40% increase in heat duty for equal pumping power and size over a smooth tube heat exchanger or a comparable decrease in the heat exchanger size for a given heat duty. Developing mixed convection flow in internally finned tubes with variable viscosity was numerically investigated for a fin geometry range of 8 {le} N {le} 24, 0.1 {le} H {le} 0.3 and an operating condition range of 50 {le} Pr{sub in} {le} 1,250, 0 {le} Ra{sub in} {le} 10{sup 7}, and 0 {le} q{sub w}d/k{sub in} {le} 2,000. The numerical model was validated by comparison with existing numerical and experimental data. Internal finning was found to produce a complex two-cell, buoyancy-induced vortex structure. The results show that coring (retarded velocity in the interfin region) leads to poor heat transfer performance of tubes with large numbers of fins or with tall fins. The overall results indicated that large enhancement in the heat transfer can be obtained in the entrance region. Furthermore, variable viscosity effects are seen to have a pronounced effect on the friction factor and Nusselt number predictions.

  16. Pressurized bellows flat contact heat exchanger interface

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  17. Direct fired heat exchanger

    DOEpatents

    Reimann, Robert C.; Root, Richard A.

    1986-01-01

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

  18. Wound tube heat exchanger

    DOEpatents

    Ecker, Amir L.

    1983-01-01

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

  19. Heat exchange device

    SciTech Connect

    Callison, G.

    1984-01-17

    A heat exchange device is adapted to recover heat from the fire box of a wood burning stove or the like for heating ambient air in a room or other enclosed space. The heat exchange device is adapted to mount in a recess in a stove top in place of a lid which is normally supplied with the stove. The device according to the invention includes heat exchange means which extend into the fire box of the stove below the top surface thereof. The heat from the heat exchange device is transmitted into a main cavity of the device where the heat is transferred to air forced through the main cavity by a blower mounted to an outside surface of the device. Air exit means are provided on a surface opposite to the surface on which the blower is mounted to provide a passage for heated air into the room or other enclosed space to be heated. The device may also include a top mounted isolated handle for ease in handling the device such as for moving from one area to another. In a second embodiment of the device, a high temperature heat exchange glass plate is mounted on the surface of the device which is in contact with the fire box. Heat is transmitted by heat exchange plate to the main cavity of the device where the air is heated and blown into the room as above.

  20. Optimization of Heat Exchangers

    SciTech Connect

    Ivan Catton

    2010-10-01

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

  1. Nature's Heat Exchangers.

    ERIC Educational Resources Information Center

    Barnes, George

    1991-01-01

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

  2. Testing and analysis of immersed heat exchangers

    SciTech Connect

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

    1986-08-01

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

  3. Active microchannel heat exchanger

    DOEpatents

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

    2001-01-01

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

  4. Microscale Regenerative Heat Exchanger

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  5. Rate of Heat Transfer from Finned Metal Surfaces

    NASA Technical Reports Server (NTRS)

    Taylor, G Fayette; Rehbock, A

    1930-01-01

    The object was to evaluate the factors which control the rate of heat transfer to a moving current of air from finned metal surfaces similar to those used on aircraft engine cylinders. The object was to establish data which will enable the finning of cooling surfaces to be designed to suit the particular needs of any specific application. Most of the work was done on flat copper specimens 6 inches square, upon which were mounted copper fins with spacings varying from 1/2 inch to 1/12 inch. All fins were 1 inch deep, 6 inches long, and .020 inch thick. The results of the investigation are given in the form of curves included here. In general, it was found that for specimens of this kind, the effectiveness of a given fin does not decrease very rapidly until its distance from adjacent fins has been reduced to 1/9 or 1/10 of an inch. A formula for the heat transfer from a flat surface without fins was developed, and an approximate formula for the finned specimens is suggested.

  6. Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater.

    PubMed

    Chabane, Foued; Moummi, Noureddine; Benramache, Said

    2014-03-01

    The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s(-1). Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s(-1) with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency.

  7. Experimental study of heat transfer and thermal performance with longitudinal fins of solar air heater

    PubMed Central

    Chabane, Foued; Moummi, Noureddine; Benramache, Said

    2013-01-01

    The thermal performance of a single pass solar air heater with five fins attached was investigated experimentally. Longitudinal fins were used inferior the absorber plate to increase the heat exchange and render the flow fluid in the channel uniform. The effect of mass flow rate of air on the outlet temperature, the heat transfer in the thickness of the solar collector, and the thermal efficiency were studied. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg s−1. Moreover, the maximum efficiency values obtained for the 0.012 and 0.016 kg s−1 with and without fins were 40.02%, 51.50% and 34.92%, 43.94%, respectively. A comparison of the results of the mass flow rates by solar collector with and without fins shows a substantial enhancement in the thermal efficiency. PMID:25685486

  8. Heat and mass exchanger

    DOEpatents

    Lowenstein, Andrew; Sibilia, Marc J.; Miller, Jeffrey A.; Tonon, Thomas

    2007-09-18

    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.

  9. Enhancement of natural-convection heat transfer from a horizontal heated plate using grid fins

    SciTech Connect

    Kitamura, Kenzo; Nagae, Naoyuki; Kimura, Fumiyoshi

    1996-01-01

    An enhancement technique was developed for natural-convection heat transfer from a horizontal heated plate. In order to enhance the heat transfer, grid fins made of copper plates were soldered to the copper base plate. These grid fins function not only as an extended surface but also as a heat-transfer promoter. The apparent heat-transfer coefficient of the above enhanced plate were measured and compared with those of a nontreated, smooth plate and a conventional plate with vertical straight fins. It was found that the highest performance is achieved by the present plate. By adopting grid fins with appropriate size and height, the heat-transfer coefficient at the central portion of the present plate is increased by 35% compared to that of the conventional finned plate with the same fin area of fin height.

  10. Thermoelectric heat exchange element

    DOEpatents

    Callas, James J.; Taher, Mahmoud A.

    2007-08-14

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

  11. Vacuum powered heat exchanger

    SciTech Connect

    Ruffolo, R.F.

    1986-06-24

    In an internal combustion engine including an oil lubrication system, a liquid cooling system, and an improved air intake system is described. The improved air intake system comprises: a housing including a first opening in one end, which opening is open to the atmosphere and a second opening comprising an air outlet opening in the other end open to the air intake manifold of the engine, a heat exchanger positioned in the first opening. The heat exchanger consists of a series of coils positioned in the flow path of the atmospheric air as it enters the housing, the heat exchanger being fluidly connected to either the engine lubrication system or the cooling system to provide a warm heat source for the incoming air to the housing, acceleration means positioned in the housing downstream of the heat exchanger, the acceleration means comprising a honeycomb structure positioned across the air intake flow path. The honey-comb structure includes a multitude of honey combed mini-venturi cells through which the heated air flows in an accelerated mode, a removable air filter positioned between the heat exchanger and the acceleration means and a single opening provided in the housing through which the air filter can be passed and removed, and additional openings in the housing positioned downstream of the heat exchanger and upstream of the air filter, the additional openings including removable flaps for opening and closing the openings to control the temperature of the air flowing through the housing.

  12. A corrosive resistant heat exchanger

    DOEpatents

    Richlen, S.L.

    1987-08-10

    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.

  13. Greywater heat exchanger

    SciTech Connect

    Holmberg, D.

    1983-11-21

    A kilowatt meter and water meter were installed to monitor pregreywater usage. The design considerations, the heat exchanger construction and installation, and the monitoring of usage levels are described.

  14. Microtube Strip Heat Exchanger

    SciTech Connect

    Doty, F.D.

    1990-12-27

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

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

    SciTech Connect

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

    2015-04-04

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

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

    DOE PAGES

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

    2015-04-04

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

  17. Radial flow heat exchanger

    DOEpatents

    Valenzuela, Javier

    2001-01-01

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

  18. Counterflow Regolith Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Zubrin, Robert; Jonscher, Peter

    2013-01-01

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

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

    SciTech Connect

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

    2008-11-01

    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.

  20. Monogroove liquid heat exchanger

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  1. Heat exchanger restart evaluation

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-03-18

    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.

  2. Heat exchanger restart evaluation

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-02-28

    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.

  3. Heat exchanger restart evaluation

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-03-18

    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 summary herein.

  4. Downhole heat exchangers

    SciTech Connect

    Culver, G.; Lund, J.W.

    1999-09-01

    The downhole heat exchanger (DHE) eliminates the problem of disposal of geothermal fluid, since only heat is taken from the well. The exchanger consists of a system of pipes or tubes suspended in the well through which clean secondary water is pumped or allowed to circulate by natural convection. These systems offer substantial economic savings over surface heat exchangers where a single-well system is adequate (typically less than 0.8 MWt, with well depths up to about 500 ft) and may be economical under certain conditions at well depths to 1500 ft. Several designs have proven successful; but, the most popular are a simple hairpin loop or multiple loops of iron pipe (similar to the tubes in a U-tube and shell exchanger) extending to near the well bottom. An experimental design consisting of multiple small tubes with headers at each end suspended just below the water surface appears to offer economic and heating capacity advantages. The paper describes design and construction details and New Zealand`s experience with downhole heat exchangers.

  5. Chimney heat exchanger

    SciTech Connect

    Whiteley, I.C.

    1981-09-01

    A heat exchanger for installation on the top of a chimney of a building includes a housing having a lower end receiving the top of the chimney and an upper end with openings permitting the escape of effluent from the chimney and a heat exchanger assembly disposed in the housing including a central chamber and a spirally arranged duct network defining an effluent spiral path between the top of the chimney and the central chamber and a fresh air spiral path between an inlet disposed at the lower end of the housing and the central chamber, the effluent and fresh air spiral paths being in heat exchange relationship such that air passing through the fresh air spiral path is heated by hot effluent gases passing upward through the chimney and the effluent spiral path for use in heating the building. A pollution trap can be disposed in the central chamber of the heat exchanger assembly for removing pollutants from the effluent, the pollution trap including a rotating cage carrying pumice stones for absorbing pollutants from the effluent with the surface of the pumice gradually ground off to reveal fresh stone as the cage rotates.

  6. Modular heat exchanger

    DOEpatents

    Culver, Donald W.

    1978-01-01

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

  7. Heat exchanger panel

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  8. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1991-10-16

    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.

  9. Method for making heat exchange tubes

    SciTech Connect

    Cunningham, J.L.; Campbell, B.J.

    1987-09-15

    This patent describes a method of making a heat exchange tube from difficult to work materials such as titanium and stainless steel in a single finning pass. It consists of inserting a mandrel having at least a first larger diameter portion and a second smaller diameter portion inside a plain tube. Then move the axes of a rotating disc carrying finning arbors toward the tube so that first and second sets of discs on the arbors, which are separated from each other by a spacer member, will sequentially force portions of the tube toward the first and second portions of the mandrel. The first set of discs serve to initially form the fins on the tube to at least approximately their final outside diameter and the second set of discs, whose discs are axially spaced so as to have a greater pitch than the discs of the first set, serve to reduce the root diameter of the fins previously formed by the first set of discs without substantially changing the outer diameter of the fins formed by the first set of discs. The greater pitch of the second set of discs causes an elongation of the tube and reduces its tendency to twist during finning.

  10. Heat transfer coefficients for staggered arrays of short pin fins

    NASA Astrophysics Data System (ADS)

    Vanfossen, G. J.

    Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

  11. Heat transfer coefficients for staggered arrays of short pin fins

    NASA Astrophysics Data System (ADS)

    Vanfossen, G. J.

    1981-03-01

    Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

  12. Finned Carbon-Carbon Heat Pipe with Potassium Working Fluid

    NASA Technical Reports Server (NTRS)

    Juhasz, Albert J.

    2010-01-01

    This elemental space radiator heat pipe is designed to operate in the 700 to 875 K temperature range. It consists of a C-C (carbon-carbon) shell made from poly-acrylonitride fibers that are woven in an angle interlock pattern and densified with pitch at high process temperature with integrally woven fins. The fins are 2.5 cm long and 1 mm thick, and provide an extended radiating surface at the colder condenser section of the heat pipe. The weave pattern features a continuous fiber bath from the inner tube surface to the outside edges of the fins to maximize the thermal conductance, and to thus minimize the temperature drop at the condenser end. The heat pipe and radiator element together are less than one-third the mass of conventional heat pipes of the same heat rejection surface area. To prevent the molten potassium working fluid from eroding the C C heat pipe wall, the shell is lined with a thin-walled, metallic tube liner (Nb-1 wt.% Zr), which is an integral part of a hermetic metal subassembly which is furnace-brazed to the inner surface of the C-C tube. The hermetic metal liner subassembly includes end caps and fill tubes fabricated from the same Nb-1Zr alloy. A combination of laser and electron beam methods is used to weld the end caps and fill tubes. A tungsten/inert gas weld seals the fill tubes after cleaning and charging the heat pipes with potassium. The external section of this liner, which was formed by a "Uniscan" rolling process, transitions to a larger wall thickness. This section, which protrudes beyond the C-C shell, constitutes the "evaporator" part of the heat pipe, while the section inside the shell constitutes the condenser of the heat pipe (see figure).

  13. New Configurations of Micro Plate-Fin Heat Sink to Reduce Coolant Pumping Power

    NASA Astrophysics Data System (ADS)

    Rezania, A.; Rosendahl, L. A.

    2012-06-01

    The thermal resistance of heat exchangers has a strong influence on the electric power produced by a thermoelectric generator (TEG). In this work, a real TEG device is applied to three configurations of micro plate-fin heat sink. The distance between certain microchannels is varied to find the optimum heat sink configuration. The particular focus of this study is to reduce the coolant mass flow rate by considering the thermal resistances of the heat sinks and, thereby, to reduce the coolant pumping power in the system. The three-dimensional governing equations for the fluid flow and the heat transfer are solved using the finite-volume method for a wide range of pressure drop laminar flows along the heat sink. The temperature and the mass flow rate distribution in the heat sink are discussed. The results, which are in good agreement with previous computational studies, show that using suggested heat sink configurations reduces the coolant pumping power in the system.

  14. Boundary element method applied to a gas-fired pin-fin-enhanced heat pipe

    SciTech Connect

    Andraka, C.E.; Knorovsky, G.A.; Drewien, C.A.

    1998-02-01

    The thermal conduction of a portion of an enhanced surface heat exchanger for a gas fired heat pipe solar receiver was modeled using the boundary element and finite element methods (BEM and FEM) to determine the effect of weld fillet size on performance of a stud welded pin fin. A process that could be utilized by others for designing the surface mesh on an object of interest, performing a conversion from the mesh into the input format utilized by the BEM code, obtaining output on the surface of the object, and displaying visual results was developed. It was determined that the weld fillet on the pin fin significantly enhanced the heat performance, improving the operating margin of the heat exchanger. The performance of the BEM program on the pin fin was measured (as computational time) and used as a performance comparison with the FEM model. Given similar surface element densities, the BEM method took longer to get a solution than the FEM method. The FEM method creates a sparse matrix that scales in storage and computation as the number of nodes (N), whereas the BEM method scales as N{sup 2} in storage and N{sup 3} in computation.

  15. Heat exchanger-accumulator

    DOEpatents

    Ecker, Amir L.

    1980-01-01

    What is disclosed is a heat exchanger-accumulator for vaporizing a refrigerant or the like, characterized by an upright pressure vessel having a top, bottom and side walls; an inlet conduit eccentrically and sealingly penetrating through the top; a tubular overflow chamber disposed within the vessel and sealingly connected with the bottom so as to define an annular outer volumetric chamber for receiving refrigerant; a heat transfer coil disposed in the outer volumetric chamber for vaporizing the liquid refrigerant that accumulates there; the heat transfer coil defining a passageway for circulating an externally supplied heat exchange fluid; transferring heat efficiently from the fluid; and freely allowing vaporized refrigerant to escape upwardly from the liquid refrigerant; and a refrigerant discharge conduit penetrating sealingly through the top and traversing substantially the length of the pressurized vessel downwardly and upwardly such that its inlet is near the top of the pressurized vessel so as to provide a means for transporting refrigerant vapor from the vessel. The refrigerant discharge conduit has metering orifices, or passageways, penetrating laterally through its walls near the bottom, communicating respectively interiorly and exteriorly of the overflow chamber for controllably carrying small amounts of liquid refrigerant and oil to the effluent stream of refrigerant gas.

  16. Heat exchanger tube mounts

    DOEpatents

    Wolowodiuk, W.; Anelli, J.; Dawson, B.E.

    1974-01-01

    A heat exchanger in which tubes are secured to a tube sheet by internal bore welding is described. The tubes may be moved into place in preparation for welding with comparatively little trouble. A number of segmented tube support plates are provided which allow a considerable portion of each of the tubes to be moved laterally after the end thereof has been positioned in preparation for internal bore welding to the tube sheet. (auth)

  17. High flux heat exchanger

    NASA Astrophysics Data System (ADS)

    Flynn, Edward M.; Mackowski, Michael J.

    1993-01-01

    This interim report documents the results of the first two phases of a four-phase program to develop a high flux heat exchanger for cooling future high performance aircraft electronics. Phase 1 defines future needs for high flux heat removal in advanced military electronics systems. The results are sorted by broad application categories: (1) commercial digital systems, (2) military data processors, (3) power processors, and (4) radar and optical systems. For applications expected to be fielded in five to ten years, the outlook is for steady state flux levels of 30-50 W/sq cm for digital processors and several hundred W/sq cm for power control applications. In Phase 1, a trade study was conducted on emerging cooling technologies which could remove a steady state chip heat flux of 100 W/sq cm while holding chip junction temperature to 90 C. Constraints imposed on heat exchanger design, in order to reflect operation in a fighter aircraft environment, included a practical lower limit on coolant supply temperature, the preference for a nontoxic, nonflammable, and nonfreezing coolant, the need to minimize weight and volume, and operation in an accelerating environment. The trade study recommended the Compact High Intensity Cooler (CHIC) for design, fabrication, and test in the final two phases of this program.

  18. Liquid/liquid heat exchanger

    NASA Technical Reports Server (NTRS)

    Miller, C. G.

    1980-01-01

    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.

  19. Fault-Tolerant Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Izenson, Michael G.; Crowley, Christopher J.

    2005-01-01

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

  20. Heat exchanger analysis on a Microvax II/GPX

    NASA Astrophysics Data System (ADS)

    Haught, Alan F.

    1988-12-01

    The finite element code FIDAP was used to examine the fluid flow path within a flat plate tube/fin heat exchanger and the resulting heat transfer from the fins and tube walls. The mathematical formulation, mesh development and analysis procedure are presented, and the results obtained are compared with experimental observations of the fluid flow and measurements of the fluid heating. This problem illustrates the capabilities of finite element techniques for analyzing complex three-dimensional convection-dominated heat transfer, and demonstrates the scope of problems which can be addressed on a Micro VAX II/GPX workstation.

  1. Experimental study on thermal performance of micro pin fin heat sinks with various shapes

    NASA Astrophysics Data System (ADS)

    Hua, Junye; Li, Gui; Zhao, Xiaobao; Li, Qihe

    2016-07-01

    This paper presents a visualization experimental study on the heat transfer characteristics of various shapes of micro pin fins, including the circular, ellipse, diamond, square and triangle shape micro pin fin arrays with various equivalent diameters and pin fin density. The influences study of different sizes and shapes of pin fin on Nusselt number and heat transfer coefficient have been conducted. The results show that with the increase of the flow rate, the temperature of the bottom of the experimental section decreases. And the Nusselt number of different shapes of micro pin fins increases with the increase of Re. In which, the heat transfer performance of the ellipse shape pin fin appears better among the other shapes of pin fins. However, the higher pin fin of the ellipse shape density leads to a weaker flow performance. Besides, the micro-scale heat transfer correlation between the Nusselt number and the Reynolds number is fitted based on the experimental data.

  2. The heat pipe exchanger with controllable heat exchanging area

    NASA Astrophysics Data System (ADS)

    Oshiro, M.; Takasu, S.; Kurihara, M.; Taneda, K.; Nakamoto, T.; Nakayama, H.

    1984-03-01

    The heat transfer rate through the heat exchanger in an industrial boiler that burns heavy oils must be controlled so as not to decrease the exhaust gas temperature below the dew point of sulfuric acid. Two systems of heat pipe exchangers are examined: one controls the heat exchange area of the condenser section of the heat pipes and the other uses the variable conductance heat pipes. The characteristics of these two systems are described. The temperatures at various points and the gas quantity are plotted against the boiler loads. The maintainability and operational reliability of both systems are demonstrated.

  3. Heat exchange assembly

    DOEpatents

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

    2004-06-08

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

  4. Two phase heat exchanger symposium

    SciTech Connect

    Pearson, J.T.; Kitto, J.B.

    1985-01-01

    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.

  5. Condensing Heat Exchanger with Hydrophilic Antimicrobial Coating

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  6. Theoretical determination of design parameters for an arrayed heat sink with vertical plate fins

    NASA Astrophysics Data System (ADS)

    Lin, Shiang-Jiun; Chen, Yi-Jin

    2016-05-01

    This paper employs theoretical approach to determine the adequate design parameters of an arrayed plate-fins heat sink based on maximizing heat flow. According to analyzed results, increasing the dimensions of configurative parameters does not always yield the significant increase in the heat flow. As the fin length and fin space increases until a critical value, the heat flow will significantly reduce the increment or decay, respectively.

  7. Heat exchanger bypass test report

    SciTech Connect

    De Vries, M.L.

    1995-01-26

    This test report documents the results that were obtained while conducting the test procedure which bypassed the heat exchangers in the HC-21C sludge stabilization process. The test was performed on November 15, 1994 using WHC-SD-CP-TC-031, ``Heat Exchanger Bypass Test Procedure.`` The primary objective of the test procedure was to determine if the heat exchangers were contributing to condensation of moisture in the off-gas line. This condensation was observed in the rotameters. Also, a secondary objective was to determine if temperatures at the rotameters would be too high and damage them or make them inaccurate without the heat exchangers in place.

  8. Experimental Study of Heat Transfer of Parallel Louvered Fins through Laser Holographic Interferometry

    NASA Astrophysics Data System (ADS)

    Kurosaki, Yasuo; Kashiwagi, Takao; Kobayashi, Hiroki; Uzuhashi, Hideo; Tang, Xue-Zhong

    The objectives of this paper are experimentally to study the detail of heat transfer in louver-array and to propose the preferable geometrical arrangement of louver from the point of view of improving the performance of heat exchanger. Our approach toward that goal was made via the following steps. The first step in the present study is optically to visualize the temperature field around louvers by employing the primitive heated flat louver model consisting of thin bakelite plate and thin Nichrome foil as a heater, and to measure the heat transfer coefficients of the louvers. Our experiment achieved to visualize the isotherms through the Laser holographic interferometry. The clear isotherms for various louver arrangements were successfully obtained. The thermal boundary layer and wake generated by an upstream louver were clearly observed to extend toward downstream ones ; the heat transfer coefficients obtained by the experiment were virtually affected by those boundary layers and wakes. The second step is to examine the plausible arrangement of louver for enhancing heat transfer. The slight position shift of downstream louvers toward the direction avoiding the influence of heated air wake was proposed from both the observation of isotherms and the measurement of heat transfer coefficients in staggered louver array ; its effectiveness was varified by the experiment. The improvement of the performance of heat exchanger is expected by applying the proposed minor rearrangement of louver array for enhanced fins.

  9. Quasi-stationary phase change heat transfer on a fin

    NASA Astrophysics Data System (ADS)

    Orzechowski, Tadeusz; Stokowiec, Katarzyna

    2016-03-01

    The paper presents heat transfer research basing on a long fin with a circular cross-section. Its basis is welded to the pipe where the hot liquid paraffin, having a temperature of 70°C at the inflow, is pumped. The analyzed element is a recurrent part of a refrigeration's condenser, which is immersed in a paraffin. The temperature of the inflowing liquid is higher than the temperature of the melting process for paraffin, which allows the paraffin to liquify. The temperature at the basis of the rib changes and it is assumed that the heat transfer is quasi-stationary. On this basis the estimation of the mean value of heat transfer coefficient was conducted. The unsteady thermal field of the investigated system was registered with an infrared camera V50 produced by a Polish company Vigo System. This device is equipped with a microbolometric detector with 384 × 288 elements and the single pixel size 25 × 25 μm. Their thermal resolution is lower than 70 mK at a temperature of 30 °C. The camera operates at 7,5 ÷ 14 μm long-wave infrared radiation range. For a typical lens 35 mm the special resolution is 0.7 mrad. The result of the calculations is mean heat transfer coefficient for the considered time series. It is equal to 50 W m -2 K-1 and 47 W m -2 K-1 on the left and right side of the fin, respectively. The distance between the experimental data and the curve approximating the temperature distribution was assessed with the standard deviation, Sd = 0.04 K.

  10. Heat exchanger leakage problem location

    NASA Astrophysics Data System (ADS)

    Hejčík, Jiří; Jícha, Miroslav

    2012-04-01

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

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

    SciTech Connect

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

    1987-10-01

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

  12. Graphite Foam Heat Exchangers for Thermal Management

    SciTech Connect

    Klett, J.W.

    2004-06-07

    Improved thermal management is needed to increase the power density of electronic and more effectively cool electronic enclosures that are envisioned in future aircraft, spacecraft and surface ships. Typically, heat exchanger cores must increase in size to more effectively dissipate increased heat loads, this would be impossible in many cases, thus improved heat exchanger cores will be required. In this Phase I investigation, MRi aimed to demonstrate improved thermal management using graphite foam (Gr-foam) core heat exchangers. The proposed design was to combine Gr-foams from POCO with MRi's innovative low temperature, active metal joining process (S-Bond{trademark}) to bond Gr-foam to aluminum, copper and aluminum/SiC composite faceplates. The results were very favorable, so a Phase II SBIR with the MDA was initiated. This had primarily 5 tasks: (1) bonding, (2) thermal modeling, (3) cooling chip scale packages, (4) evaporative cooling techniques and (5) IGBT cold plate development. The bonding tests showed that the ''reflow'' technique with S-Bond{reg_sign}-220 resulted in the best and most consistent bond. Then, thermal modeling was used to design different chip scale packages and IGBT cold plates. These designs were used to fabricate many finned graphite foam heat sinks specifically for two standard type IC packages, the 423 and 478 pin chips. These results demonstrated several advantages with the foam. First, the heat sinks with the foam were lighter than the copper/aluminum sinks used as standards. The sinks for the 423 design made from foam were not as good as the standard sinks. However, the sinks made from foam for the 478 pin chips were better than the standard heat sinks used today. However, this improvement was marginal (in the 10-20% better regime). However, another important note was that the epoxy bonding technique resulted in heat sinks with similar results as that with the S-bond{reg_sign}, slightly worse than the S-bond{reg_sign}, but still

  13. Numerical simulation of turbulent heat transfer from perforated plate-fin heat sinks

    NASA Astrophysics Data System (ADS)

    Ismail, Md. Farhad; Hasan, Muhammad Noman; Ali, Mohammad

    2014-04-01

    Excessive heat from microelectronic components is essential to remove to increase the reliability of the system. In this paper, various types of perforations in the form of small channels such as square, circular, triangular and hexagonal cross sections are introduced and thermal performances are compared to improve the cooling performance of heat sink. The governing equations are solved by adopting a control volume based finite element method with an unstructured non-uniform grid system. Flow and heat transfer characteristics are presented for Reynolds numbers from 2 × 104 to 4 × 104 based on the fin length and Prandtl number is taken as Pr = 0.71. RANS based k-ɛ turbulence model is used to predict the turbulent flow parameters. The predicted results are validated by the previously published experimental data and in reasonable agreement with the experiment. Results show that fins having circular perforations have better thermal and fluid dynamic performances than the other types of fins considered here.

  14. High Temperature Heat Exchanger Project

    SciTech Connect

    Anthony E. Hechanova, Ph.D.

    2008-09-30

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

  15. Modular heat exchanger

    DOEpatents

    Giardina, Angelo R. [Marple Township, Delaware County, PA

    1981-03-03

    A shell and tube heat exchanger having a plurality of individually removable tube bundle modules. A lattice of structural steel forming rectangular openings therein is placed at each end of a cylindrical shell. Longitudinal structural members are placed in the shell between corners of the rectangular openings situated on opposite ends of the shell. Intermediate support members interconnect the longitudinal supports so as to increase the longitudinal supports rigidity. Rectangular parallelpiped tube bundle moldules occupy the space defined by the longitudinal supports and end supports and each include a rectangular tube sheet situated on each end of a plurality of tubes extending therethrough, a plurality of rectangular tube supports located between the tube sheets, and a tube bundle module stiffening structure disposed about the bundle's periphery and being attached to the tube sheets and tube supports. The corners of each tube bundle module have longitudinal framework members which are mateable with and supported by the longitudinal support members. Intermediate support members constitute several lattice, each of which is situate d in a plane between the end support members. The intermediate support members constituting the several lattice extend horizontally and vertically between longitudinal supports of adjacent tube module voids. An alternative embodiment for intermediate support members constitute a series of structural plates situated at the corners of the module voids and having recesses therein for receiving the respective longitudinal support members adjacent thereto, protrusions separating the recesses, and a plurality of struts situated between protrusions of adjacent structural plates.

  16. Modular heat exchanger

    DOEpatents

    Giardina, A.R.

    1981-03-03

    A shell and tube heat exchanger is described having a plurality of individually removable tube bundle modules. A lattice of structural steel forming rectangular openings therein is placed at each end of a cylindrical shell. Longitudinal structural members are placed in the shell between corners of the rectangular openings situated on opposite ends of the shell. Intermediate support members interconnect the longitudinal supports so as to increase the longitudinal supports rigidity. Rectangular parallelepiped tube bundle modules occupy the space defined by the longitudinal supports and end supports and each include a rectangular tube sheet situated on each end of a plurality of tubes extending there through, a plurality of rectangular tube supports located between the tube sheets, and a tube bundle module stiffening structure disposed about the bundle's periphery and being attached to the tube sheets and tube supports. The corners of each tube bundle module have longitudinal framework members which are mateable with and supported by the longitudinal support members. Intermediate support members constitute several lattices, each of which is situated in a plane between the end support members. The intermediate support members constituting the several lattices extend horizontally and vertically between longitudinal supports of adjacent tube module voids. An alternative embodiment for intermediate support members constitute a series of structural plates situated at the corners of the module voids and having recesses therein for receiving the respective longitudinal support members adjacent thereto, protrusions separating the recesses, and a plurality of struts situated between protrusions of adjacent structural plates. 12 figs.

  17. Direct-contact heat exchanger

    NASA Astrophysics Data System (ADS)

    Bricard, A.

    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.

  18. Liquid droplet heat exchanger studies

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Hedges, D. E.; Yungster, S.

    1987-01-01

    Recent analytical and experimental investigations of the liquid droplet heat exchanger (LDHX) concept for space power applications are described. The performance of the LDHX is compared to that of a conventional heat exchanger for heat rejection applications in a Brayton cycle, using the mass-specific heat exchanger effectiveness as a figure of merit. It is shown that the LDHX has an order of magnitude advantage over the conventional heat exchanger. Furthermore, significant improvement in cycle efficiency and power to mass ratio is possible. Two-phase flow experiments in a laboratory scale LDHX, using air and water as the two media, show very good agreement with the quasi-one-dimensional model used in the parametric studies.

  19. Efficient heat-transfer surfaces assembled from partially finned flat-oval tubes

    NASA Astrophysics Data System (ADS)

    Pis'mennyi, E. N.

    2011-04-01

    The state of finned convective heat-transfer surfaces and prospects for using them in power engineering and industry are briefly reviewed. The characteristics of a heat-recovery economizer made of partially finned flat-oval tubes are presented by way of comparing them with design versions employing known types of finned tubes, and the results gained from its operation downstream of a PTVM-30M boiler are given.

  20. Heat exchanger with ceramic elements

    DOEpatents

    Corey, John A.

    1986-01-01

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

  1. Heat exchanger using graphite foam

    DOEpatents

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

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

  2. Numerical study of finned heat pipe-assisted latent heat thermal energy storage system

    NASA Astrophysics Data System (ADS)

    Tiari, Saeed; Qiu, Songgang; Mahdavi, Mahboobe

    2014-11-01

    In the present study the thermal characteristics of a finned heat pipe-assisted latent heat thermal energy storage system are investigated numerically. A transient two dimensional finite volume based model employing enthalpy-porosity technique is implemented to analyze the performance of a thermal energy storage unit with square container and high melting temperature phase change material. The effects of heat pipe spacing, fin length and numbers as well as the influence of natural convection on the thermal response of the thermal energy storage unit have been studied. The obtained results reveal that the natural convection has considerable effect on the melting process of the phase change material. Increasing the number of heat pipes leads to the increase of melting rate and the decrease of base wall temperature. Also, the increase of fin length results in the decrease of temperature difference within the phase change material in the container, providing more uniform temperature distribution. Furthermore, it is showed that the number of fins does not affect the performance of the system considerably.

  3. Fluid flow and heat transfer of a power-law fluid in an internally finned tube with different fin lengths

    NASA Astrophysics Data System (ADS)

    Grabski, Jakub Krzysztof; Kołodziej, Jan Adam

    2016-06-01

    In the paper an analysis of fluid flow and heat transfer of a power-law fluid in an internally finned tube with different fin length is conducted. Nonlinear momentum equation of a power-law fluid flow and nonlinear energy equation are solved using the Picard iteration method. Then on each iteration step the solution of inhomogeneous equation consists of two parts: the general solution and the particular solution. Firstly the particular solution is obtained by interpolation of the inhomogeneous term by means of the radial basis functions and monomials. Then the general solution is obtained using the method of fundamental solutions and by fulfilling boundary conditions.

  4. Heat exchange apparatus utilizing thermal siphon pipes

    SciTech Connect

    Daman, E.L.; Kunsagi, L.

    1980-10-07

    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.

  5. Phase Change Material Heat Exchangers

    NASA Video Gallery

    NASA’s Game Changing Development is taking on a technologydevelopment and demonstration effort to design, build, and test the next generation of Phase Change Material Heat Exchangers (PCM HXs) on ...

  6. Numerical simulation of heat exchanger

    SciTech Connect

    Sha, W.T.

    1985-01-01

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

  7. Plate heat exchanger design theory

    NASA Astrophysics Data System (ADS)

    Shah, R. K.; Wanniarachchi, A. S.

    Plate heat exchangers are commonly used in hygienic applications as well as in chemical processing and other industrial applications. Pertinent information on plate exchangers from a designer's point of view is summarized to provide a basic insight into performance behavior of chevron plates. Basic design methods are presented and a method of coupling between heat transfer and pressure drop is introduced. A step by step design procedure for rating and sizing problems is outlined.

  8. Heat transfer, erosion and acid condensation characteristics for novel H-type finned oval tube

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Zhao, X.; Tang, G.

    2015-09-01

    Low efficiency of heat transfer, acid corrosion and erosion of economizers affect the economy and security in coal-fired power plants significantly. The H-type finned oval tube is proposed to alleviate these problems. Based on the H-type finned oval tube, we investigated three novel types of fins, including bleeding dimples, longitudinal vortex generators (LVGs), and compound dimple-LVG. We considered the three aspects together, and obtained the heat transfer, acid condensation rate and erosion loss. The results show that the tube bank with the new structured fins can improve the performance on the three aspects, and the compound dimple-LVG performs the highest comprehensive effect.

  9. Thermal performance analysis of optimized hexagonal finned heat sinks in impinging air jet

    NASA Astrophysics Data System (ADS)

    Yakut, Kenan; Yeşildal, Faruk; Karabey, Altuǧ; Yakut, Rıdvan

    2016-04-01

    In this study, thermal performance analysis of hexagonal finned heat sinks which optimized according to the experimental design and optimization method of Taguchi were investigated. Experiments of air jet impingement on heated hexagonal finned heat sinks were carried out adhering to the L18(21*36) orthogonal array test plan. Optimum geometries were determined and named OH-1, OH-2. Enhancement efficiency with the first law of thermodynamics was analyzed for optimized heat sinks with 100, 150, 200 mm heights of hexagonal fin. Nusselt correlations were found out and variations of enhancement efficiency with Reynolds number presented in η-Re graphics.

  10. Heat exchanger and related methods

    SciTech Connect

    Turner, Terry D.; McKellar, Michael G.

    2015-12-22

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

  11. Experimental Study on Cooling Heat Transfer of Supercritical Carbon Dioxide Inside Horizontal Micro-Fin Tubes

    NASA Astrophysics Data System (ADS)

    Kuwahara, Ken; Higashiiu, Shinya; Ito, Daisuke; Koyama, Shigeru

    This paper deals with the experimental study on cooling heat transfer of supercritical carbon dioxide inside micro-fin tubes. The geometrical parameters in micro-fin tubes used in the present study are 6.02 mm in outer diameter, 4.76 mm to 5.11 mm in average inner diameter, 0.15 mm to 0.24 mm in fin height, 5 to 25 in helix angle, 46 to 52 in number of fins and 1.4 to 2.3 in area expansion ratio. Heat transfer coefficients were measured at 8-10 MPa in pressure, 360-690 kg/(m2•s) in mass velocity and 20-75 °C in CO2 temperature. The measured heat transfer coefficients of micro-fin tubes were 1.4 to 2 times higher than those of the smooth tube having 4.42 in inner diameter. The predicted heat transfer coefficients using the correlation equation, which was developed for single-phase turbulent fluid flow inside micro-fin-tubes, showed large deviations to the measured values. The new correlation to predict cooling heat transfer coefficient of supercritical carbon dioxide inside micro-fin tubes was developed taking into account the shape of fins based on experimental data empirically. This correlation equation agreed within ±20% of almost all of the experimental data.

  12. Earth-air heat exchanger

    SciTech Connect

    Kammel, D.W.

    1985-01-01

    Optimizing the thermal environment of a livestock building is beneficial to the growth and production of the animal. Minimizing temperature extremes of inlet ventilation air to the livestock building by passing the air through underground ducts would accomplish this goal. Providing this optimum environment by reducing heating and cooling loads would reduce energy costs and increase profits for the producer. The heat transfer in an earth-air heat exchanger was studied in two phases to develop design criteria for these systems. The experimental phase consisted of an earth-air exchanger installation from which data were collected during hot weather (cooling effect), cold weather (heating effect), and mild weather performances. The analytical phase developed a finite element program for simulating the earth-air heat exchanger and studying the effects of important parameters on the heat transfer rate and the air temperature. Results of the first phase were used to verify the computer model. Design criteria for the earth-air heat exchanger were determined based on the information obtained in the two phases of this study.

  13. Mathematical equations for heat conduction in the fins of air-cooled engines

    NASA Technical Reports Server (NTRS)

    Harper, R R; Brown, W B

    1923-01-01

    The problem considered in this report is that of reducing actual geometrical area of fin-cooling surface, which is, of course, not uniform in temperature, to equivalent cooling area at one definite temperature, namely, that prevailing on the cylinder wall at the point of attachment of the fin. This makes it possible to treat all the cooling surface as if it were part of the cylinder wall and 100 per cent effective. The quantities involved in the equations are the geometrical dimensions of the fin, thermal conductivity of the material composing it, and the coefficient of surface heat dissipation between the fin and the air streams.

  14. Heat transfer simulation of motorcycle fins under varying velocity using CFD method

    NASA Astrophysics Data System (ADS)

    Shahril, K.; Mohd Kasim, Nurhayati Binti; Sabri, M.

    2013-12-01

    Motorcycle engine releases heat to the atmosphere through the mode of force convection. To solve this, fins are provided on the outer of the cylinder. The heat transfer rate is defined depending on the velocity of vehicle, fin geometry and the ambient temperature. Increasing the temperature difference between the object and the environment, increasing the convection heat transfer coefficient, or increasing the surface area of the object increases the heat transfer. Many experimental methods are available in literature to analyze the effect of these factors on the heat transfer rate. However, CFD analysis will be use to simulate the heat transfer of the engine block. ANSYS software is selected to run the simulation.

  15. FEM simulation for cold press forging forming of the round-fin heat sink

    NASA Astrophysics Data System (ADS)

    Wang, Kesheng; Han, Yu; Zhang, Haiyan; Zhang, Lihan

    2013-05-01

    In this paper, the finite element method is used to investigate the forming process of cold press forging for the round-fin heat sink in the automotive lighting. A series of simulations on the round-fin heat sink forming using the program DEFORM were carried out. The blank thickness and friction coefficient on the formation of round-fin were studied, and the tooling structure with counterpressure on the heat sink formation was also investigated. The results show that the blank thickness is very good for the round-fin formation, and the thicker the blank is, the better the round-fin can be formed; and also When both the punch-blank interface and the die-blank interface have the same value of friction factor, the larger value of friction factor is in favor of round-fin forming, the further investigation reveals that the friction at the punch-blank interface has more significant effect on preventing the initiation of flow-through compared with the friction at the die-blank interface, which implies that the punch-blank interface has more significant effect on the material flow in the formation of round-fin. Meanwhile, The tooling structure with counterpressure is helpful to the formation of round-fin heat sink, which not only ensures the height of each round-fin on the heat sink is uniform but also retards the initiation of flow-through on the reverse side of round-fin. In addition, the experiments of press forging process were conducted to validate the finite element analysis, and the simulation results are in good agreement with the experimental data.

  16. A novel trapezoid fin pattern applicable for air-cooled heat sink

    NASA Astrophysics Data System (ADS)

    Chen, Chien-Hung; Wang, Chi-Chuan

    2015-11-01

    The present study proposed a novel step or trapezoid surface design applicable to air-cooled heat sink under cross flow condition. A total of five heat sinks were made and tested, and the corresponding fin patterns are (a) plate fin; (b) step fin (step 1/3, 3 steps); (c) 2-step fin (step 1/2, 2 steps); (d) trapezoid fin (trap 1/3, cutting 1/3 length from the rear end) and (e) trapezoid fin (trap 1/2, cutting 1/2 length from the rear end). The design is based on the heat transfer augmentation via (1) longer perimeter of entrance region and (2) larger effective temperature difference at the rear part of the heat sink. From the test results, it is found that either step or trapezoid design can provide a higher heat transfer conductance and a lower pressure drop at a specified frontal velocity. The effective conductance of trap 1/3 design exceeds that of plate surface by approximately 38 % at a frontal velocity of 5 m s-1 while retains a lower pressure drop of 20 % with its surface area being reduced by 20.6 %. For comparisons exploiting the overall thermal resistance versus pumping power, the resultant thermal resistance of the proposed trapezoid design 1/3, still reveals a 10 % lower thermal resistance than the plate fin surface at a specified pumping power.

  17. Ceramic heat exchanger

    DOEpatents

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

    1998-06-16

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

  18. Ceramic heat exchanger

    DOEpatents

    LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

    1998-01-01

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

  19. Condensate removal device for heat exchanger

    NASA Technical Reports Server (NTRS)

    Trusch, R. B.; Oconnor, E. W. (Inventor)

    1975-01-01

    A set of perforated tubes disposed at the gas output side of a heat exchanger, in a position not to affect the rate of flow of the air or other gas is described. The tubes are connected to a common manifold which is connected to a sucking device. Where it is necessary to conserve and recirculate the air sucked through the tubes, the output of the manifold is run through a separator to remove the condensate from the gas. The perforations in the slurper tubes are small, lying in the range of 0.010 inch to 0.100 inch. The tubes are disposed in contact with the surfaces of the heat exchanger on which the condensate is precipitated, whether fins or plates, so that the water may be directed to the tube openings by means of surface effects, together with the assistance of the air flow. Only about 5 percent of the air output need be thus diverted, and it effectively removes virtually all of the condensate.

  20. Lightweight long life heat exchanger

    NASA Technical Reports Server (NTRS)

    Moore, E. K.

    1975-01-01

    The design, fabrication, and evaluation of a full scale shuttle-type condensing heat exchanger constructed of aluminum and utilizing aluminum clad titanium parting sheets is described. A long term salt spray test of candidate parting sheet specimens is described. The results of an investigation into an alternate method of making composite sheet material are discussed.

  1. Deposition of biological aerosols on HVAC heat exchangers

    SciTech Connect

    Siegel, Jeffrey; Walker, Ian

    2001-09-01

    Many biologically active materials are transported as bioaerosols 1-10 {micro}m in diameter. These particles can deposit on cooling and heating coils and lead to serious indoor air quality problems. This paper investigates several of the mechanisms that lead to aerosol deposition on fin and tube heat exchangers. A model has been developed that incorporates the effects of several deposition mechanisms, including impaction, Brownian and turbulent diffusion, turbophoresis, thermophoresis, diffusiophoresis, and gravitational settling. The model is applied to a typical range of air velocities that are found in commercial and residential HVAC systems 1 - 6 m/s (200 - 1200 ft/min), particle diameters from 1 - 8 {micro}m, and fin spacings from 3.2 - 7.9 fins/cm (8 - 16 fins/inch or FPI). The results from the model are compared to results from an experimental apparatus that directly measures deposition on a 4.7 fins/cm (12 FPI) coil. The model agrees reasonably well with this measured data and suggests that cooling coils are an important sink for biological aerosols and consequently a potential source of indoor air quality problems.

  2. Optimization of the Heat Exchangers of a Thermoelectric Generation System

    NASA Astrophysics Data System (ADS)

    Martínez, A.; Vián, J. G.; Astrain, D.; Rodríguez, A.; Berrio, I.

    2010-09-01

    The thermal resistances of the heat exchangers have a strong influence on the electric power produced by a thermoelectric generator. In this work, the heat exchangers of a thermoelectric generator have been optimized in order to maximize the electric power generated. This thermoelectric generator harnesses heat from the exhaust gas of a domestic gas boiler. Statistical design of experiments was used to assess the influence of five factors on both the electric power generated and the pressure drop in the chimney: height of the generator, number of modules per meter of generator height, length of the fins of the hot-side heat exchanger (HSHE), length of the gap between fins of the HSHE, and base thickness of the HSHE. The electric power has been calculated using a computational model, whereas Fluent computational fluid dynamics (CFD) has been used to obtain the thermal resistances of the heat exchangers and the pressure drop. Finally, the thermoelectric generator has been optimized, taking into account the restrictions on the pressure drop.

  3. Heat exchanger with oscillating flow

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  4. Heat exchanger with oscillating flow

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  5. Light bulb heat exchanger for magnetohydrodynamic generator applications - Preliminary evaluation

    NASA Technical Reports Server (NTRS)

    Smith, J. M.; Hwang, C. C.; Seikel, G. R.

    1974-01-01

    The light-bulb heat-exchanger concept is investigated as a possible means of using a combustion heat source to supply energy to an inert gas MHD power generator system. In this concept, combustion gases flow through a central passage which consists of a duct with transparent walls through which heat is transferred by radiation to a radiation receiver which in turn heats the inert gas by convection. The effects of combustion-gas emissivity, transparent-wall-transmissivity, radiation-receiver emissivity, and the use of fins in the inert gas coolant passage are studied. The results indicate that inert gas outlet temperatures of 2500 K are possible for combustion temperatures of 3200 K and that sufficient energy can be transferred from the combustion gas to reduce its temperature to approximately 2000 K. At this temperature more conventional heat exchangers can be used.

  6. Oxidizer heat exchanger component test

    NASA Technical Reports Server (NTRS)

    Kanic, P. G.

    1988-01-01

    The RL10-IIB engine, is capable of multimode thrust operation. The engine operates at two low-thrust levels: tank head idle (THI), approximately 1 to 2 percent of full thrust; and pumped idle, 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient thermal conditioning; PI operation provides vehicle tank prepressurization and maneuver thrust for low-g deployment. Stable combustion of the RL10-IIB engine during the low-thrust operating modes can be accomplished by using a heat exchanger to supply gaseous oxygen to the propellant injector. The oxidized heat exchanger (OHE) vaporizes the liquid oxygen using hydrogen as the energy source. This report summarizes the test activity and post-test data analysis for two possible heat exchangers, each of which employs a completely different design philosophy. One design makes use of a low-heat transfer (PHT) approach in combination with a volume to attenuate pressure and flow oscillations. The test data showed that the LHT unit satisfied the oxygen exit quality of 0.95 or greater in both the THI and PI modes while maintaining stability. The HHT unit fulfilled all PI requirements; data for THI satisfactory operation is implied from experimental data that straddle the exact THI operating point.

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

    SciTech Connect

    Culver, G.

    1990-11-01

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

  8. Heat exchangers: Selection, rating, and thermal design

    SciTech Connect

    Kakac, S.; Liu, H.

    1998-01-01

    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.

  9. Heat exchanger expert system logic

    NASA Technical Reports Server (NTRS)

    Cormier, R.

    1988-01-01

    The reduction is described of the operation and fault diagnostics of a Deep Space Network heat exchanger to a rule base by the application of propositional calculus to a set of logic statements. The value of this approach lies in the ease of converting the logic and subsequently implementing it on a computer as an expert system. The rule base was written in Process Intelligent Control software.

  10. Computation of conjugate natural convection heat transfer from a rectangular fin on a partially heated horizontal base

    NASA Astrophysics Data System (ADS)

    Mobedi, M.; Saidi, A.; Sunden, B.

    In this study, a numerical investigation has been carried out to reveal the mechanism of fluid flow and heat transfer from a vertical rectangular fin attached to a partially heated horizontal base. The problem is a conjugate conduction-convection heat transfer problem with open boundaries. The governing equations for the problem are the conservation of mass, momentum and energy equations for the fluid and the heat conduction equation for the fin. The control volume technique based on the SIMPLEC algorithm with a nonstaggerred grid arrangement is employed to solve the governing equations. The effect of the heated base, on the mechanism of the fluid flow and heat transfer, is numerically investigated. Temperature distribution and flow patterns around the fin are plotted to support the discussion. Results are obtained for air at laminar and steady flow.

  11. Evaluation of fluid bed heat exchanger optimization parameters. Final report

    SciTech Connect

    Not Available

    1980-03-01

    Uncertainty in the relationship of specific bed material properties to gas-side heat transfer in fluidized beds has inhibited the search for optimum bed materials and has led to over-conservative assumptions in the design of fluid bed heat exchangers. An experimental program was carried out to isolate the effects of particle density, thermal conductivity, and heat capacitance upon fluid bed heat transfer. A total of 31 tests were run with 18 different bed material loads on 12 material types; particle size variations were tested on several material types. The conceptual design of a fluidized bed evaporator unit was completed for a diesel exhaust heat recovery system. The evaporator heat transfer surface area was substantially reduced while the physical dimensions of the unit increased. Despite the overall increase in unit size, the overall cost was reduced. A study of relative economics associated with bed material selection was conducted. For the fluidized bed evaporator, it was found that zircon sand was the best choice among materials tested in this program, and that the selection of bed material substantially influences the overall system costs. The optimized fluid bed heat exchanger has an estimated cost 19% below a fin augmented tubular heat exchanger; 31% below a commercial design fluid bed heat exchanger; and 50% below a conventional plain tube heat exchanger. The comparisons being made for a 9.6 x 10/sup 6/ Btu/h waste heat boiler. The fluidized bed approach potentially has other advantages such as resistance to fouling. It is recommended that a study be conducted to develop a systematic selection of bed materials for fluidized bed heat exchanger applications, based upon findings of the study reported herein.

  12. Cryogenic Heat Exchanger with Turbulent Flows

    ERIC Educational Resources Information Center

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

    2012-01-01

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

  13. Length to diameter ratio and row number effects in short pin fin heat transfer

    NASA Technical Reports Server (NTRS)

    Brigham, B. A.; Vanfossen, G. J.

    1984-01-01

    The relative effects of pin length to diameter ratio and of pin row geometry on the heat transfer from pin fins, was determined. Array averaged heat transfer coefficients on pin and endwall surfaces were measured for two configurations of staggered arrays of short pin fins (length to diameter ratio of 4). One configuration contained eight streamwise rows of pins, while the other contained only four rows. Results showed that both the 8-row and the 4-row configurations for an L sub p/D of 4, exhibit higher heat transfer than in similar tests on shorter pin fins (L sub p/D of 1/2 and 2). It was also found that for this L sub p/D ratio, the array averaged heat transfer was slightly higher with eight rows of staggered pins than with only four rows. Previously announced in STAR as N83-14431

  14. The Effect of Baffles on the Temperature Distribution and Heat-transfer Coefficients of Finned Cylinders

    NASA Technical Reports Server (NTRS)

    Schey, Oscar W; Rollin, Vern G

    1936-01-01

    This report presents the results of an investigation to determine the effect of baffles on the temperature distribution and the heat-transfer coefficient of finned cylinders. The tests were conducted in a 30-inch wind tunnel on electrically heated cylinders with fins of 0.25 and 0.31 inch pitch. The results of these tests showed that the use of integral baffles gave a reduction of 31.9 percent in the rear wall temperatures and an increase of 54.2 percent in the heat transfer coefficient as compared with a cylinder without baffles.

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

    SciTech Connect

    Koplow, Jeffrey P.

    2010-01-01

    We describe breakthrough results obtained in a feasibility study of a fundamentally new architecture for air-cooled heat exchangers. A longstanding but largely unrealized opportunity in energy efficiency concerns the performance of air-cooled heat exchangers used in air conditioners, heat pumps, and refrigeration equipment. In the case of residential air conditioners, for example, the typical performance of the air cooled heat exchangers used for condensers and evaporators is at best marginal from the standpoint the of achieving maximum the possible coefficient of performance (COP). If by some means it were possible to reduce the thermal resistance of these heat exchangers to a negligible level, a typical energy savings of order 30% could be immediately realized. It has long been known that a several-fold increase in heat exchanger size, in conjunction with the use of much higher volumetric flow rates, provides a straight-forward path to this goal but is not practical from the standpoint of real world applications. The tension in the market place between the need for energy efficiency and logistical considerations such as equipment size, cost and operating noise has resulted in a compromise that is far from ideal. This is the reason that a typical residential air conditioner exhibits significant sensitivity to reductions in fan speed and/or fouling of the heat exchanger surface. The prevailing wisdom is that little can be done to improve this situation; the 'fan-plus-finned-heat-sink' heat exchanger architecture used throughout the energy sector represents an extremely mature technology for which there is little opportunity for further optimization. But the fact remains that conventional fan-plus-finned-heat-sink technology simply doesn't work that well. Their primary physical limitation to performance (i.e. low thermal resistance) is the boundary layer of motionless air that adheres to and envelops all surfaces of the heat exchanger. Within this boundary layer

  16. Fluidized bed heat exchanger utilizing angularly extending heat exchange tubes

    DOEpatents

    Talmud, Fred M.; Garcia-Mallol, Juan-Antonio

    1980-01-01

    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.

  17. Finned double-tube PCM system as a waste heat storage

    NASA Astrophysics Data System (ADS)

    Alhamdo, M. H.; Theeb, M. A.; Golam, A. S.

    2015-11-01

    In this work, focus is taken on developing a waste heat recovery system for capturing potential of exhaust heat from an air conditioner unit to be reused later. This system has the ability to store heat in phase change material (PCM) and then release it to a discharge water system when required. To achieve this goal, a system of Finned, Water-PCM, Double tube (FWD) has been developed and tested. Different profiles of fins attached to the (FWD) system have been investigated for increasing the thermal conductivity of the PCM. These include using Circular Finned, Water-PCM, Double tube (CFWD) system; Longitudinal Finned, Water-PCM, Double tube (LFWD) system; Spiral Finned, Water-PCM, Double tube (SFWD) system; as well as; Without Fins, Water-PCM, Double tube (WFWD) system. An experimental test rig that attached to an air-conditioner unit has been built to include 32- tubes of the FWD systems for both vertical and horizontal layouts during charging and water discharging processes. Results show a significant performance improvement when using spiral and circular fins during charging process at vertical position. However, longitudinal and without fins showed better performance in horizontal position. Overall, the developed SFWD system in vertical position has been found to exhibit the most effective type due to the fastest PCM melting and solidification. As compared to the WFWD system, the FWD systems have been found to increase the PCM temperature gain of about 15.3% for SFWD system; 8.2% for CFWD; and 4.3% for LFWD system.

  18. Heat Exchange, Additive Manufacturing, and Neutron Imaging

    SciTech Connect

    Geoghegan, Patrick

    2015-02-23

    Researchers at the Oak Ridge National Laboratory have captured undistorted snapshots of refrigerants flowing through small heat exchangers, helping them to better understand heat transfer in heating, cooling and ventilation systems.

  19. Heat exchanger for solar water heaters

    NASA Technical Reports Server (NTRS)

    Cash, M.; Krupnick, A. C.

    1977-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  1. Application of nanofluids in heat transfer enhancement of compact heat exchanger

    NASA Astrophysics Data System (ADS)

    Gunnasegaran, P.; Shuaib, N. H.; Jalal, M. F. Abdul; Sandhita, E.

    2012-11-01

    In this paper, numerical investigation using ethylene glycol (EG) as a base fluid with diamond and SiO2 as the coolants with nanoparticle volume fractions (φ) ranged from 0.1 % to 2 % on automobile flat tube plain fin compact heat exchanger (CHE) is conducted. The convective heat transfer coefficient in the developing regions along the flat tubes with the nanofluid flow showed marked improvement over the base fluid (0 %). Quantitative results of the heat transfer enhancement of CHE with increasing volumetric concentrations of nanofluids at various Reynolds numbers are presented.

  2. Energy recovery heat exchanger installation

    SciTech Connect

    Bradshaw, N.F.

    1983-08-16

    An installation is disclosed for energy recovery heat exchangers arranged to transfer heat into or out of air exhausted from an air handling system for paint spray booths. The system includes a collection chamber about which the intakes of a series of exhaust fans are arranged to draw exhaust air into an exhaust stack. Pairs of inclined wetted surface coil sets are mounted in the walls of the enclosures, each in communication with the intake of an exhaust fan so as to receive airflow of each exhaust fan. Each of the enclosures is provided with an access door to enable cleaning and other maintenance chores to be carried out on the coil sets and pivotally mounted blocking panels may be positioned to close off air flow across the coils and bypassing of the exhaust flow through the access doors in the event excessive overspray solids are present in the exhaust flow.

  3. Brush/Fin Thermal Interfaces

    NASA Technical Reports Server (NTRS)

    Knowles, Timothy R.; Seaman, Christopher L.; Ellman, Brett M.

    2004-01-01

    Brush/fin thermal interfaces are being developed to increase heat-transfer efficiency and thereby enhance the thermal management of orbital replaceable units (ORUs) of electronic and other equipment aboard the International Space Station. Brush/fin thermal interfaces could also be used to increase heat-transfer efficiency in terrestrial electronic and power systems. In a typical application according to conventional practice, a replaceable heat-generating unit includes a mounting surface with black-anodized metal fins that mesh with the matching fins of a heat sink or radiator on which the unit is mounted. The fins do not contact each other, but transfer heat via radiation exchange. A brush/fin interface also includes intermeshing fins, the difference being that the gaps between the fins are filled with brushes made of carbon or other fibers. The fibers span the gap between intermeshed fins, allowing heat transfer by conduction through the fibers. The fibers are attached to the metal surfaces as velvet-like coats in the manner of the carbon fiber brush heat exchangers described in the preceding article. The fiber brushes provide both mechanical compliance and thermal contact, thereby ensuring low contact thermal resistance. A certain amount of force is required to intermesh the fins due to sliding friction of the brush s fiber tips against the fins. This force increases linearly with penetration distance, reaching 1 psi (6.9 kPa) for full 2-in. (5.1 cm) penetration for the conventional radiant fin interface. Removal forces can be greater due to fiber buckling upon reversing the sliding direction. This buckling force can be greatly reduced by biasing the fibers at an angle perpendicularly to the sliding direction. Means of containing potentially harmful carbon fiber debris, which is electrically conductive, have been developed. Small prototype brush/fin thermal interfaces have been tested and found to exhibit temperature drops about onesixth of that of conventional

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

    SciTech Connect

    Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson

    2008-09-01

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

  5. High-temperature ceramic heat exchanger element for a solar thermal receiver

    NASA Technical Reports Server (NTRS)

    Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

    1982-01-01

    A study has been completed on the development of a high-temperature ceramic heat exchanger element to be integrated into a solar reciver producing heated air. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The ceramic shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is fabricated by an innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. Fabrication of a one-half scale demonstrator ceramic receiver has been completed.

  6. Study on turbulent flow and heat transfer performance of tubes with internal fins in EGR cooler

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Ling, Xiang; Peng, Hao

    2015-01-01

    In this paper, flow and heat transfer performances of the tubes with internal longitudinal fins in Exhaust Gas Recirculation (EGR ) cooler were investigated by three-dimension computation and experiment . Each test tube was a single-pipe structure, without inner tube. Three-dimension computation was performed to determine the thermal characteristics difference between the two kinds of tubes, that is, the tube with an inner solid staff as a blocked structure and the tube without the blocked structure. The effects of fin width and fin height on heat transfer and flow are examined. For proving the validity of numerical method, the calculated results were compared with corresponding experimental data. The tube-side friction factor and heat transfer coefficient were examined. As a result, the maximum deviations between the numerical results and the experimental data are approximately 5.4 % for friction factor and 8.6 % for heat transfer coefficient, respectively. It is found that two types of internally finned tubes enhance significantly heat transfer. The heat transfer of the tube with blocked structure is better, while the pressure drop of the tube without blocked structure is lower. The comprehensive performance of the unblocked tube is better to applied in EGR cooler.

  7. Improved ceramic heat exchange material

    NASA Technical Reports Server (NTRS)

    Mccollister, H. L.

    1977-01-01

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

  8. Improvements in Heat Transfer for Anti-Icing of Gas-Heated Airfoils with Internal Fins and Partitions

    NASA Technical Reports Server (NTRS)

    Gray, Vernon H.

    1950-01-01

    The effect of modifying the gas passage of hollow metal airfoils by the additIon of internal fins and partitions was experimentally investigated and comparisons were made among a basic unfinned airfoil section and two airfoil designs having metal fins attached at the leading edge of the internal gas passage. An analysis considering the effects of heat conduction in the airfoil metal was made to determine the internal modification effectiveness that may be obtained in gas-heated components, such as turbojet-inlet guide vanes, support struts, hollow propeller blades, arid. thin wings. Over a wide range of heated-gas flow and tunnel-air velocity, the increase In surface-heating rates with internal finning was marked (up to 3.5 times), with the greatest increase occurring at the leading edge where anti-icing heat requirements are most critical. Variations in the amount and the location of internal finning and. partitioning provided. control over the local rates of surface heat transfer and permitted efficient anti-icing utilization of the gas-stream heat content.

  9. Direct contact heat exchangers for space

    NASA Astrophysics Data System (ADS)

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

    1985-06-01

    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.

  10. Fluid-cooled heat sink with improved fin areas and efficiencies for use in cooling various devices

    DOEpatents

    Bharathan, Desikan; Bennion, Kevin; Kelly, Kenneth; Narumanchi, Sreekant

    2015-04-21

    The disclosure provides a fluid-cooled heat sink having a heat transfer base and a plurality of heat transfer fins in thermal communication with the heat transfer base, where the heat transfer base and the heat transfer fins form a central fluid channel through which a forced or free cooling fluid may flow. The heat transfer pins are arranged around the central fluid channel with a flow space provided between adjacent pins, allowing for some portion of the central fluid channel flow to divert through the flow space. The arrangement reduces the pressure drop of the flow through the fins, optimizes average heat transfer coefficients, reduces contact and fin-pin resistances, and reduces the physical footprint of the heat sink in an operating environment.

  11. Heat/mass transfer and flow characteristics of pin fin cooling channels in turbine blades

    NASA Astrophysics Data System (ADS)

    Lau, S. C.; Saxena, A.

    Experiments studied the local heat/mass transfer distributions and pressure drops in pin fin channels that modeled internal cooling passages in gas turbine blades. Heat/mass transfer distributions were determined for a straight flow through a pin fin channel (H/D = 1.0, X/D = S/D = 2.5) and a flow through the pin fin channel with trailing edge flow ejection. The overall friction factor and local pressure drop results were obtained for various configurations and lengths of the trailing edge ejection holes. The results show that, when there is trailing edge flow ejection, the main flow stream turns toward the trailing edge ejection holes. The wake regions downstream of the pins and the regions affected by secondary flow shift toward the ejection holes. The local channel wall heat/mass transfer is generally high immediately upstream of a pin, in the wake region downstream of a pin, and in the regions affected by secondary flow. In the case with trailing edge flow ejection, the heat/mass transfer generally decreases in the radial direction as a result of the reducing radial mass flow rate. The overall friction is higher when the trailing edge ejection holes are longer and when they are configured such that more flow is forced further downstream in the pin fin channel before exiting through the ejection holes.

  12. Design of single passage heat exchangers

    SciTech Connect

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

    1981-01-01

    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.

  13. Boiling heat transfer on fins - experimental and numerical procedure

    NASA Astrophysics Data System (ADS)

    Orzechowski, T.; Tyburczyk, A.

    2014-03-01

    The paper presents the research methodology, the test facility and the results of investigations into non-isothermal surfaces in water boiling at atmospheric pressure, together with a discussion of errors. The investigations were conducted for two aluminium samples with technically smooth surfaces and thickness of 4 mm and 10 mm, respectively. For the sample of lower thickness, on the basis of the surface temperature distribution measured with an infrared camera, the local heat flux and the heat transfer coefficient were determined and shown in the form of a boiling curve. For the thicker sample, for which 1-D model cannot be used, numerical calculations were conducted. They resulted in obtaining the values of the local heat flux on the surface the invisible to the infrared, camera i.e. on the side on which the boiling of the medium proceeds.

  14. Length to diameter ratio and row number effects in short pin fin heat transfer

    NASA Technical Reports Server (NTRS)

    Brigham, B. A.; Vanfossen, G. J.

    1982-01-01

    The relative effects of pin length to diameter ratio and of pin row geometry on the heat transfer from pin fins, was determined. Array averaged heat transfer coefficients on pin and endwall surfaces were measured for two configurations of staggered arrays of short pin fins (length to diameter ratio of 4). One configuration contained eight streamwise rows of pins, while the other contained only four rows. Results showed that both the 8-row and the 4-row configurations for an L sub p/D of 4, exhibit higher heat transfer than in similar tests on shorter pin fns (L sub p/D of 1/2 and 2). It was also found that for this L sub p/D ratio, the array averaged heat transfer was slightly higher with eight rows of staggered pins than with only four rows.

  15. High temperature heat exchange: nuclear process heat applications

    SciTech Connect

    Vrable, D.L.

    1980-09-01

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

  16. The effect of channel convergence on heat transfer in a passage with short pin fins

    NASA Technical Reports Server (NTRS)

    Brigham, B. A.

    1984-01-01

    Array averaged heat transfer coefficients were obtained for two configurations of short pin fins in a converging channel and for two flat plate configurations in a converging channel. The effect of flow acceleration due to channel convergence and the effect of varying pin length on the heat transfer was determined. Results are presented in the form of Nusselt number versus Reynolds number for the four geometries tested.

  17. Experimental investigation of a manifold heat-pipe heat exchanger

    SciTech Connect

    Konev, S.V.; Wang Tszin` Lyan`; D`yakov, I.I.

    1995-12-01

    Results of experimental investigations of a heat exchanger on a manifold water heat pipe are given. An analysis is made of the temperature distribution along the heat-transfer agent path as a function of the transferred heat power. The influence of the degree of filling with the heat transfer agent on the operating characteristics of the construction is considered.

  18. Probe Measures Fouling As In Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Marner, Wilbur J.; Macdavid, Kenton S.

    1990-01-01

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

  19. Heat transfer enhancement by a multilobe vortex generator in internally finned tubes

    SciTech Connect

    Tsui, Y.Y.; Leu, S.W.

    1999-04-01

    A three-dimensional computational method is employed to study the flow and heat transfer in internally finned tubes with a multilobe vortex generator inserted. Governing equations are discretized using the finite volume method. The irregular lobe geometry is treated using curvilinear nonstaggered grids. The linear interpolation method is adopted to calculate face velocities. The results show that secondary flows induced by the lobes are transformed to become axial vortices downstream of the vortex generator. As a consequence of the transport by the vortex flow, the core flow is moved to the fins and the tube wall, while the wall flow moves to the core. In this way, both heat transfer and flow mixing are enhanced. When the fin height is increased, the axial vortex is more restricted in the centerline region, and the strength of the vortex flow, represented by circulation, is decreased. In turn, the total pressure loss is also decreased. However, the heat transfer increases with fin height. Consequently, efficiency is greatly promoted.

  20. Solar water heating system and heat exchanger therefor

    SciTech Connect

    Koskela, M.O.

    1982-04-27

    In a solar water system including a solar collector prevention of damage to the collector during freezing conditions is achieved by providing a relatively small independent heat exchanger between the solar collector and the water heater and a vacuum breaking system whereby the water in the solar collector is drained into the heat exchanger. The heat exchanger is connected to a thermal siphon arrangement with the water heater.

  1. Heat Exchanger With Reservoir And Controls

    NASA Technical Reports Server (NTRS)

    Brown, Richard F.; Edelstein, Fred

    1989-01-01

    Heat-pipe assembly operates as evaporator or as condenser. New heat exchanger incorporates important improvements over previous designs. By adding reservoir to primary loop, locating ultrasonic liquid-level sensors on reservoir rather than directly on one of heat pipes, and revising control logic, uneven distribution of flow among heat pipes and erroneous behavior of valves eliminated.

  2. Fabrication of Wire Mesh Heat Exchangers for Waste Heat Recovery Using Wire-Arc Spraying

    NASA Astrophysics Data System (ADS)

    Rezaey, R.; Salavati, S.; Pershin, L.; Coyle, T.; Chandra, S.; Mostaghimi, J.

    2014-04-01

    Waste heat can be recovered from hot combustion gases using water-cooled heat exchangers. Adding fins to the external surfaces of the water pipes inserted into the hot gases increases their surface area and enhances heat transfer, increasing the efficiency of heat recovery. A method of increasing the heat transfer surface area has been developed using a twin wire-arc thermal spray system to generate a dense, high-strength coating that bonds wire mesh to the outside surfaces of stainless steel pipes through which water passes. At the optimum spray distance of 150 mm, the oxide content, coating porosity, and the adhesion strength of the coating were measured to be 7%, 2%, and 24 MPa, respectively. Experiments were done in which heat exchangers were placed inside a high-temperature oven with temperature varying from 300 to 900 °C. Several different heat exchanger designs were tested to estimate the total heat transfer in each case. The efficiency of heat transfer was found to depend strongly on the quality of the bond between the wire meshes and pipes and the size of openings in the wire mesh.

  3. Subcooled freon-11 flow boiling in top-heated finned coolant channels with and without a twisted tape

    NASA Technical Reports Server (NTRS)

    Smith, Alvin; Boyd, Ronald D., Sr.

    1989-01-01

    An experimental study was conducted in top-heated finned horizontal tubes to study the effect of enhancement devices on flow boiling heat transfer in coolant channels. The objectives are to examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for circular coolant channels with spiral finned walls and/or spiral fins with a twisted tape, and improve the data reduction technique of a previous investigator. The working fluid is freon-11 with an inlet temperature of 22.2 C (approximately 21 C subcooling). The coolant channel's exit pressure and mass velocity are 0.19 M Pa (absolute) and 0.21 Mg/sq. ms, respectively. Two tube configurations were examined; i.e., tubes had either 6.52 (small pitch) or 4.0 (large pitch) fins/cm of the circumferential length (26 and 16 fins, respectively). The large pitch fins were also examined with a twisted tape insert. The inside nominal diameter of the copper channels at the root of the fins was 1.0 cm. The results show that by adding enhancement devices, boiling occurs almost simultaneously at all axial locations. The case of spiral fins with large pitch resulted in larger mean (circumferentially averaged) heat transfer coefficients, h sub m, at all axial locations. Finally, when twisted tape is added to the tube with large-pitched fins, the power required for the onset of boiling is reduced at all axial and circumferential locations.

  4. Influence of a pulsating flow on the transfer of heat from cylinders and finned tubes

    NASA Astrophysics Data System (ADS)

    Perwaiz, J.; Base, T. E.

    The effect of pulsations in the flow on forced convective heat transfer coefficients around a circular cylinder and a finned tube is studied. Convection measurement experiments were performed to determine the rate of heat transfer (average Nusselt numbers) from a circular cylinder and a finned tube in a pulsating crossflow. The experiments were performed using the unsteady flow inducer wind tunnel, which had facility for generating time-dependent flow. The forced convective heat transfer in steady crossflows was checked for both the circular cylinder and the finned tube to validate the experimental techniques and apparatus. The findings indicate the dependence of heat transfer on the dimensionless frequency of the crossflow. Specifically, at higher mean flows there is considerable discrepancy between the Nusselt number for steady flows and the Nusselt number for unsteady flows with the same mean flow value. The effects on the variation in the heat transfer must be carefully taken into account in the design and analysis of thermal systems exposed to pulsating flows.

  5. Heat Exchanger Lab for Chemical Engineering Undergraduates

    ERIC Educational Resources Information Center

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

    2015-01-01

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

  6. Heat exchanger with a removable tube section

    DOEpatents

    Wolowodiuk, W.; Anelli, J.

    1975-07-29

    A heat exchanger is described in which the tube sheet is secured against primary liquid pressure, but which allows for easy removal of the tube section. The tube section is supported by a flange which is secured by a number of shear blocks, each of which extends into a slot which is immovable with respect to the outer shell of the heat exchanger. (auth)

  7. Condensing heat exchangers for maximum boiler efficiency

    SciTech Connect

    Johnson, D.W.; DiVitto, J.G.; Rakocy, M.E.

    1994-12-31

    Until now, boiler efficiency has been limited due to the minimum temperature allowed at the stack. Heat lost up the stack was in exchange for keeping the flue gas temperature above the water vapor dew point. If water vapor was allowed to condense out, rapid deterioration, due to acid corrosion, of the outlet duct and stack would result. With the development of the condensing heat exchanger, boiler efficiency can now exceed 90%. Approximately 1% gain in boiler efficiency can be expected for every 40 F (4.5 C) reduction in flue gas stack temperature. In the CHX{reg_sign} condensing heat exchanger, all gas wetted surfaces are covered with DuPont Teflon{reg_sign}. The Teflon covered heat exchanger surfaces are impervious to all acids normally resulting from the combustion of fossil fuels. This allows the flue gas to be cooled to below the water vapor dew point with no subsequent corrosion of the heat exchanger surfaces.

  8. Fuel delivery system including heat exchanger means

    NASA Technical Reports Server (NTRS)

    Coffinberry, G. A. (Inventor)

    1978-01-01

    A fuel delivery system is presented wherein first and second heat exchanger means are each adapted to provide the transfer of heat between the fuel and a second fluid such as lubricating oil associated with the gas turbine engine. Valve means are included which are operative in a first mode to provide for flow of the second fluid through both first and second heat exchange means and further operative in a second mode for bypassing the second fluid around the second heat exchanger means.

  9. Testing and plugging power plant heat exchangers

    SciTech Connect

    Sutor, F.

    1994-12-31

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

  10. Improved ceramic heat exchanger materials

    NASA Technical Reports Server (NTRS)

    Rauch, H. W.

    1980-01-01

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

  11. Thermographic analysis of flow distribution in compact heat exchangers for a Formula 1 car

    NASA Astrophysics Data System (ADS)

    Caffagni, E.; Levoni, P.; Piraccini, M.; Muscio, A.; Corticelli, M. A.; Barozzi, G. S.

    2007-01-01

    A non-intrusive approach is investigated to calculate the internal flow distribution in heat exchangers. In particular, the liquid flow rate can be determined in each tube of an air-liquid finned-tube heat exchanger. A purposely designed test bench impresses a sudden change of temperature of the liquid flowing through the heat exchanger. The thermal transient that follows is monitored by a thermographic camera. This measures the rise of surface temperature along each tube. The temperature evolution pattern is then correlated to the flow rate in the tube by simple mathematical processing. The heat exchanger is tested in still air. Modification is not required. The approach is tested on heat exchangers for a F1 race car, with encouraging results.

  12. Development, Fabrication, and Testing of a Liquid/Liquid Microchannel Heat Exchanger for Constellation Spacecrafts

    NASA Technical Reports Server (NTRS)

    Hawkins-Reynolds, Ebony; Le, Hung; Stephan, Ryan

    2010-01-01

    Microchannel technology can be incorporated into heat exchanger designs to decrease the mass and volume of space hardware. The National Aeronautics and Space Administration at the Johnson Space Center (NASA JSC) partnered with Pacific Northwest National Laboratories (PNNL) to develop a liquid/liquid microchannel heat exchanger that has significant mass and volume savings without sacrificing thermal and pressure drop performance. PNNL designed the microchannel heat exchanger to the same performance design requirements of a conventional plate and fin liquid/liquid heat exchanger; 3 kW duty with inlet temperatures of 26 C and 4 C. Both heat exchangers were tested using the same test parameters on a test apparatus and performance data compared.

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

    SciTech Connect

    Koplow, Jeffrey P

    2015-03-24

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

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

    SciTech Connect

    Koplow, Jeffrey P.

    2015-12-08

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

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

    SciTech Connect

    Koplow, Jeffrey P

    2013-12-10

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

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

    DOEpatents

    Koplow, Jeffrey P.

    2012-07-24

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

  17. Phase Change Material Heat Exchanger Life Test

    NASA Technical Reports Server (NTRS)

    Lillibridge, Sean; Stephan, Ryan; Lee, Steve; He, Hung

    2008-01-01

    Low Lunar Orbit (LLO) poses unique thermal challenges for the orbiting space craft, particularly regarding the performance of the radiators. The emitted infrared (IR) heat flux from the lunar surface varies drastically from the light side to the dark side of the moon. Due to the extremely high incident IR flux, especially at low beta angles, a radiator is oftentimes unable to reject the vehicle heat load throughout the entire lunar orbit. One solution to this problem is to implement Phase Change Material (PCM) Heat Exchangers. PCM Heat Exchangers act as a "thermal capacitor," storing thermal energy when the radiator is unable to reject the required heat load. The stored energy is then removed from the PCM heat exchanger when the environment is more benign. Because they do not use an expendable resource, such as the feed water used by sublimators and evaporators, PCM Heat Exchangers are ideal for long duration Low Lunar Orbit missions. The Advanced Thermal Control project at JSC is completing a PCM heat exchanger life test to determine whether further technology development is warranted. The life test is being conducted on four nPentadecane, carbon filament heat exchangers. Fluid loop performance, repeatability, and measurement of performance degradation over 2500 melt-freeze cycles will be performed and reported in the current document.

  18. Numerical simulations of flow and heat transfer past a circular cylinder with a periodic array of fins

    NASA Astrophysics Data System (ADS)

    Lee, Dong Hyuk; Ha, Man Yeong; Balachandar, S.; Lee, Sangsan

    2004-05-01

    Three-dimensional, time-dependent solutions of flow and heat transfer past a circular cylinder with a periodic array of circular fins is obtained using an accurate and efficient spectral multidomain methodology. A Fourier expansion with a corresponding uniform grid is used along the circumferential direction. A spectral multidomain method with Chebyshev collocation is used along the r-z plane to handle the periodic array of circular fins attached to the surface of the cylinder. At a Reynolds number of 300 based on the cylinder diameter, results for the finned cylinder are compared with those of a smooth cylinder in order to see the effects of the presence of the fin array on flow and heat transfer. Detailed structure of fluid flow and temperature fields are obtained as a function of time to investigate how the fin array changes heat transfer mechanism related to the vortical structure in the wake region.

  19. High effectiveness liquid droplet/gas heat exchanger for space power applications

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Mattick, A. T.

    1983-01-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approx. 100 to 300 micron diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9 to 0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Bryaton cycle is discussed to illustrate the performance and operational characteristics of this heat exchanger concept.

  20. High effectiveness liquid droplet/gas heat exchanger for space power applications

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Mattick, A. T.

    1983-01-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approximately 100-300 microns in diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber.The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9-0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Brayton cycle is discussed to illustrate the performance and operational characteristics of this new heat exchanger concept.

  1. Heat exchanger, head and shell acceptance criteria

    SciTech Connect

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

    1992-09-01

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

  2. Analysis of a Flooded Heat Exchanger

    ERIC Educational Resources Information Center

    Fink, Aaron H.; Luyben, William L.

    2015-01-01

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

  3. Use of the exergy concept for design improvement of heat exchangers and heat exchanger networks

    SciTech Connect

    Ranasinghe, J.

    1989-01-01

    The second law of thermodynamics, through the exergy concept, allows us to quantify and rationally coat the consumption of exergy (irreversibility) used to drive the heat exchange process and the effluent losses of exergy in a heat exchanger. For systems with a network of heat exchangers, the exergy concept recognizes that properly integrated heat pumps reduce the heat transfer irreversibility; this results in reduced utility consumption. Heat engines properly integrated in heat exchanger networks also recover a fraction of the thermodynamic potential destroyed during the heat transfer process and generate power at very high efficiencies. Heat exchanger design conditions are characterized and potential trade-off options discussed. A modification to the irreversibility minimization method is proposed next, and the proposed method gives more realistic guide posts for heat exchangers, compared to the corresponding guide posts obtained from present methods. This thesis also proposes a method to obtain the irreversibility cost coefficients for heat exchangers residing in complex systems. The application of the modified irreversibility method proposed here, and the thermoeconomic method, are illustrated by optimizing an emerging technology ceramic heat exchanger residing in a complex power plant. A method based on the exergy concept is developed to recognize the potential for improvement of processes with process integrated heat pumps and heat engines. Once potential processes have been identified, economically optimum load and level of integration have to be determined. The method of formulating the economic optimization problem is presented, and bounds for some design variables are finally developed.

  4. Spray Cooling Trajectory Angle Impact Upon Heat Flux Using a Straight Finned Enhanced Surface

    NASA Technical Reports Server (NTRS)

    Silk, Eric A.; Kim, Jungho; Kiger, Ken

    2005-01-01

    Experiments were conducted to study the effects of spray trajectory angles upon heat flux for flat and enhanced surface spray cooling. The surface enhancement consisted of straight fins machined on the top surface of a copper heater block. Spray cooling curves were obtained with the straight fin surface aligned both parallel (axial) and perpendicular (transverse) to the spray axis. Measurements were also obtained on a flat surface heater block for comparison purposes. Each copper block had a cross-sectional area of 2.0 sq cm. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) conditions. Results show that the maximum CHF in all cases was attained for a trajectory angle of 30' from the surface normal. Furthermore, trajectory angles applied to straight finned surfaces can have a critical heat flux (CHF) enhancement as much as 75% (heat flux value of 140 W/sq cm) relative to the vertical spray orientation for the analogous flat surface case under nominally degassed conditions.

  5. Heat Exchanger Support Bracket Design Calculations

    SciTech Connect

    Rucinski, Russ; /Fermilab

    1995-01-12

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

  6. Conservation laws and associated Lie point symmetries admitted by the transient heat conduction problem for heat transfer in straight fins

    NASA Astrophysics Data System (ADS)

    Ndlovu, Partner; Moitsheki, Rasselo

    2013-08-01

    Some new conservation laws for the transient heat conduction problem for heat transfer in a straight fin are constructed. The thermal conductivity is given by a power law in one case and by a linear function of temperature in the other. Conservation laws are derived using the direct method when thermal conductivity is given by the power law and the multiplier method when thermal conductivity is given as a linear function of temperature. The heat transfer coefficient is assumed to be given by the power law function of temperature. Furthermore, we determine the Lie point symmetries associated with the conserved vectors for the model with power law thermal conductivity.

  7. Heat transfer enhancement in a parabolic trough solar receiver using longitudinal fins and nanofluids

    NASA Astrophysics Data System (ADS)

    Amina, Benabderrahmane; Miloud, Aminallah; Samir, Laouedj; Abdelylah, Benazza; Solano, J. P.

    2016-10-01

    In this paper, we present a three dimensional numerical investigation of heat transfer in a parabolic trough collector receiver with longitudinal fins using different kinds of nanofluid, with an operational temperature of 573 K and nanoparticle concentration of 1% in volume. The outer surface of the absorber receives a non-uniform heat flux, which is obtained by using the Monte Carlo ray tracing technique. The numerical results are contrasted with empirical results available in the open literature. A significant improvement of heat transfer is derived when the Reynolds number varies in the range 2.57×104 ≤ Re ≤ 2.57×105, the tube-side Nusselt number increases from 1.3 to 1.8 times, also the metallic nanoparticles improve heat transfer greatly than other nanoparticles, combining both mechanisms provides better heat transfer and higher thermo-hydraulic performance.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  9. Stirling Engine With Radial Flow Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Vitale, N.; Yarr, George

    1993-01-01

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

  10. Joule-Thomson expander and heat exchanger

    NASA Technical Reports Server (NTRS)

    Norman, R. H.

    1976-01-01

    The Joule-Thomson Expander and Heat Exchanger Program was initiated to develop an assembly (JTX) which consists of an inlet filter, counterflow heat exchanger, Joule-Thomson expansion device, and a low pressure jacket. The program objective was to develop a JTX which, when coupled to an open cycle supercritical helium refrigerating system (storage vessel), would supply superfluid helium (He II) at 2 K or less for cooling infrared detectors.

  11. Measuring Heat-Exchanger Water Leakage

    NASA Technical Reports Server (NTRS)

    Zampiceni, J.

    1986-01-01

    Water leakage in heat exchanger measured directly with help of electroytic hygrometer. In new technique, flow of nitrogen gas set up in one loop of heat exchanger. Other loop filled with water under pressure. Water concentration produced by leakage of water into nitrogen flow measured by hygrometer. New measurement method determines water concentrations up to 2,000 parts per million with accuracy of +/- 5 percent.

  12. Ceramic heat exchangers: Manufacturing techniques and performance

    NASA Astrophysics Data System (ADS)

    Merrigan, M. A.; Sandstrom, D. J.

    1981-05-01

    The objective of the ceramic heat pipe program being conducted at Los Alamos is demonstration of the practical feasibility of this technology for the solution of severe high temperature recuperation functions. Ceramic heat pipe recuperators were theoretically shown to offer distinct advantages over conventional ceramic heat exchangers from the standpoint of efficiency of heat recuperation and economics. The main stumbling block to their widespread utilization is related to the problems of materials for construction and the details of fabrication and assembly. The performance objectives of ceramic heat pipes and some aspects of the materials technology program aimed at solving the problem of economic ceramic heat pipe fabrication are described.

  13. Proceedings of the DOE/Advanced Heat Exchangers Program Review

    NASA Astrophysics Data System (ADS)

    1992-02-01

    Semiannual review meetings of the USDOE's Advanced Heat Exchanger Program with the objective of reviewing ongoing and recently completed project activities. Personnel from industrial contractors and National Laboratories present technical aspects of their projects. The projects deal with high temperature heat exchangers for waste heat recuperation and process heat exchange and other areas such as materials performance and heat transfer enhancement. Topics presented are high pressure heat exchangers, ceramic heat exchangers, enhanced tubes, and materials studies to include silicon carbide whiskers and alumina.

  14. Heat transfer from oriented heat exchange areas

    NASA Astrophysics Data System (ADS)

    Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej

    2014-03-01

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

  15. A 2D inverse problem of predicting boiling heat transfer in a long fin

    NASA Astrophysics Data System (ADS)

    Orzechowski, Tadeusz

    2016-10-01

    A method for the determination of local values of the heat transfer coefficient on non-isothermal surfaces was analyzed on the example of a long smooth-surfaced fin made of aluminium. On the basis of the experimental data, two cases were taken into consideration: one-dimensional model for Bi < 0.1 and two-dimensional model for thicker elements. In the case when the drop in temperature over the thickness could be omitted, the rejected local values of heat fluxes were calculated from the integral of the equation describing temperature distribution on the fin. The corresponding boiling curve was plotted on the basis of temperature gradient distribution as a function of superheat. For thicker specimens, where Bi > 0.1, the problem was modelled using a 2-D heat conduction equation, for which the boundary conditions were posed on the surface observed with a thermovision camera. The ill-conditioned inverse problem was solved using a method of heat polynomials, which required validation.

  16. Impact of Cubic Pin Finned Surface Structure Geometry upon Spray Cooling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Silk, Eric A.; Kim, Jungho; Kiger, Ken

    2005-01-01

    Experiments were conducted to study the effects of enhanced surface structures on heat flux using spray cooling. The surface enhancements consisted of cubic pin fins machined on the top surface of copper heater blocks. The structure height, pitch, and width were parametrically vaned. Each copper block had a projected cross-sectional area of 2.0 sq cm. Measurements were also obtained on a heater block with a flat surface for baseline comparison purposes. A 2 x 2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data were obtained under nominally degassed (chamber pressure of 41.4 kPa) and gassy conditions (chamber with N2 gas at 100.7 kPa) with a bulk fluid temperature of 20.5 C. Results for both the degassed and gassy cases show that structure width and separation distance have a dominant effect upon the heat transfer for the size ranges used. Cubic pin fin height had little impact upon heat flux. The maximum critical heat flux (CHF) attained for any of the surfaces was 121 W/sq cm, giving an enhancement of 51% relative to the flat surface case under nominally degassed conditions. The gassy case had a maximum CHF of 149 W/sq cm, giving an enhancement of 38% relative to the flat surface case.

  17. Sorption Characteristics of Sorption Material Coated on Heat Transfer surface of a Heat Exchanger

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Komatsu, Fujio; Horibe, Akihiko; Haruki, Naoto; Machida, Akito

    This paper describes sorption characteristics of organic sorbent coated on heat transfer surface of a plate-fin-tube heat exchanger. The organic sorbent is a bridged complex of soldium polyacrylate. This bridged complex containing the carboxyl group as water vapor adsorption site has a larger adsorption abilities as compared with silica gel. The experiments in which the moist air was passed into the heat exchanger coated with sorption material were conducted under various conditions of air flow rate and the temperature of brine that was the heat transfer fluid to cool the air flow in the dehumidifying process. It is found that the sorption rate of vapor is affected by the air flow rate and the brine temperature. Meanwhile, the attempt of clarifying the sorption mechanism is also conducted. Finally the average mass transfer coefficient of the organic sorbent was non-dimensionalized as a function of Reynolds number and non-dimensional temperature. In addition, it was observed that the factor which affects the sorption rate in the water vapor sorption process of the organic sorbent coated on the heat exchanger shifts from the “adsorption step” to the “sorption step”.

  18. Heat Exchanger With Internal Pin Elements

    DOEpatents

    Gerstmann, Joseph; Hannon, Charles L.

    2004-01-13

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

  19. High effectiveness contour matching contact heat exchanger

    NASA Technical Reports Server (NTRS)

    Blakely, Robert L. (Inventor); Roebelen, George J., Jr. (Inventor); Davenport, Arthur K. (Inventor)

    1988-01-01

    There is a need in the art for a heat exchanger design having a flexible core providing contour matching capabilities, which compensates for manufacturing tolerance and distortion buildups, and which accordingly furnishes a relatively uniform thermal contact conductance between the core and external heat sources under essentially all operating conditions. The core of the heat exchanger comprises a top plate and a bottom plate, each having alternate rows of pins attached. Each of the pins fits into corresponding tight-fitting recesses in the opposite plate.

  20. Observer-based monitoring of heat exchangers.

    PubMed

    Astorga-Zaragoza, Carlos-Manuel; Alvarado-Martínez, Víctor-Manuel; Zavala-Río, Arturo; Méndez-Ocaña, Rafael-Maxim; Guerrero-Ramírez, Gerardo-Vicente

    2008-01-01

    The goal of this work is to provide a method for monitoring performance degradation in counter-flow double-pipe heat exchangers. The overall heat transfer coefficient is estimated by an adaptive observer and monitored in order to infer when the heat exchanger needs preventive or corrective maintenance. A simplified mathematical model is used to synthesize the adaptive observer and a more complex model is used for simulation. The reliability of the proposed method was demonstrated via numerical simulations and laboratory experiments with a bench-scale pilot plant. PMID:17706652

  1. Phase Change Material Heat Exchanger Life Test

    NASA Technical Reports Server (NTRS)

    Lillibridge, Sean; Stephan, Ryan

    2009-01-01

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

  2. Heat exchanger with auxiliary cooling system

    DOEpatents

    Coleman, John H.

    1980-01-01

    A heat exchanger with an auxiliary cooling system 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.

  3. Pressurized-Flat-Interface Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Voss, F. E.; Howell, H. R.; Winkler, R. V.

    1990-01-01

    High thermal conductance obtained without leakage between loops. Heat-exchanger interface enables efficient transfer of heat between two working fluids without allowing fluids to intermingle. Interface thin, flat, and easy to integrate into thermal system. Possible application in chemical or pharmaceutical manufacturing when even trace contamination of process stream with water or other coolant ruins product. Reduces costs when highly corrosive fluids must be cooled or heated.

  4. Solution of mixed convection heat transfer from isothermal in-line fins

    NASA Astrophysics Data System (ADS)

    Khalilollahi, Amir

    1993-11-01

    Transient and steady state combined natural and forced convective flows over two in-line finite thickness fins (louvers) in a vertical channel are numerically solved using two methods. The first method of solution is based on the 'Simple Arbitrary Lagrangian Eulerian' (SALE) technique which incorporates mainly two computational phases: (1) a Lagrangian phase in which the velocity field is updated by the effects of all forces, and (2) an Eulerian phase that executes all advective fluxes of mass, momentum and energy. The second method of solution uses the finite element code entitled FIDAP. In the first part, comparison of the results by FIDAP, SALE, and available experimental work were done and discussed for steady state forced convection over louvered fins. Good agreements were deduced between the three sets of results especially for the flow over a single fin. In the second part and in the absence of experimental literature, the numerical predictions were extended to the transient transports and to the opposing flow where pressure drop is reversed. Results are presented and discussed for heat transfer and pressure drop in assisting and opposing mixed convection flows.

  5. Solution of mixed convection heat transfer from isothermal in-line fins

    NASA Technical Reports Server (NTRS)

    Khalilollahi, Amir

    1993-01-01

    Transient and steady state combined natural and forced convective flows over two in-line finite thickness fins (louvers) in a vertical channel are numerically solved using two methods. The first method of solution is based on the 'Simple Arbitrary Lagrangian Eulerian' (SALE) technique which incorporates mainly two computational phases: (1) a Lagrangian phase in which the velocity field is updated by the effects of all forces, and (2) an Eulerian phase that executes all advective fluxes of mass, momentum and energy. The second method of solution uses the finite element code entitled FIDAP. In the first part, comparison of the results by FIDAP, SALE, and available experimental work were done and discussed for steady state forced convection over louvered fins. Good agreements were deduced between the three sets of results especially for the flow over a single fin. In the second part and in the absence of experimental literature, the numerical predictions were extended to the transient transports and to the opposing flow where pressure drop is reversed. Results are presented and discussed for heat transfer and pressure drop in assisting and opposing mixed convection flows.

  6. Radiator Heat Pipes with Carbon-Carbon Fins and Armor for Space Nuclear Reactor Power Systems

    NASA Astrophysics Data System (ADS)

    Tournier, Jean-Michel; El-Genk, Mohamed

    2005-02-01

    Technologies for Space Reactor Power Systems are being developed to enable future NASA's missions early next decade to explore the farthest planets in the solar system. The choices of the energy conversion technology for these power systems require radiator temperatures that span a wide range, from 350 K to 800 K. Heat pipes with carbon-carbon fins and armor are the preferred choice for these radiators because of inherent redundancy and efficient spreading and rejection of waste heat into space at a relatively small mass penalty. The performance results and specific masses of radiator heat pipes with cesium, rubidium, and potassium working fluids are presented and compared in this paper. The heat pipes operate at 40% of the prevailing operation limit (a design margin of 60%), typically the sonic and/or capillary limit. The thickness of the carbon-carbon fins is 0.5 mm but the width is varied, and the evaporator and condenser sections are 0.15 and 1.35 m long, respectively. The 400-mesh wick and the heat pipe thin metal wall are titanium, and the carbon-carbon armor (~ 2 mm-thick) provides both structural strength and protection against meteoroids impacts. The cross-section area of the D-shaped radiator heat pipes is optimized for minimum mass. Because of the low vapor pressure of potassium and its very high Figure-Of-Merit (FOM), radiator potassium heat pipes are the best performers at temperatures above 800 K, where the sonic limit is no longer an issue. On the other hand, rubidium heat pipes are limited by the sonic limit below 762 K and by the capillary limit at higher temperature. The transition temperature between these two limits for the cesium heat pipes occurs at a lower temperature of 724 K, since cesium has lower FOM than rubidium. The present results show that with a design margin of 60%, the cesium heat pipes radiator is best at 680-720 K, the rubidium heat pipes radiator is best at 720-800 K, while the potassium heat pipes radiator is the best

  7. Radiator Heat Pipes with Carbon-Carbon Fins and Armor for Space Nuclear Reactor Power Systems

    SciTech Connect

    Tournier, Jean-Michel; El-Genk, Mohamed

    2005-02-06

    Technologies for Space Reactor Power Systems are being developed to enable future NASA's missions early next decade to explore the farthest planets in the solar system. The choices of the energy conversion technology for these power systems require radiator temperatures that span a wide range, from 350 K to 800 K. Heat pipes with carbon-carbon fins and armor are the preferred choice for these radiators because of inherent redundancy and efficient spreading and rejection of waste heat into space at a relatively small mass penalty. The performance results and specific masses of radiator heat pipes with cesium, rubidium, and potassium working fluids are presented and compared in this paper. The heat pipes operate at 40% of the prevailing operation limit (a design margin of 60%), typically the sonic and/or capillary limit. The thickness of the carbon-carbon fins is 0.5 mm but the width is varied, and the evaporator and condenser sections are 0.15 and 1.35 m long, respectively. The 400-mesh wick and the heat pipe thin metal wall are titanium, and the carbon-carbon armor ({approx} 2 mm-thick) provides both structural strength and protection against meteoroids impacts. The cross-section area of the D-shaped radiator heat pipes is optimized for minimum mass. Because of the low vapor pressure of potassium and its very high Figure-Of-Merit (FOM), radiator potassium heat pipes are the best performers at temperatures above 800 K, where the sonic limit is no longer an issue. On the other hand, rubidium heat pipes are limited by the sonic limit below 762 K and by the capillary limit at higher temperature. The transition temperature between these two limits for the cesium heat pipes occurs at a lower temperature of 724 K, since cesium has lower FOM than rubidium. The present results show that with a design margin of 60%, the cesium heat pipes radiator is best at 680-720 K, the rubidium heat pipes radiator is best at 720-800 K, while the potassium heat pipes radiator is the best

  8. Heat exchanger restart evaluation. Revision 1

    SciTech Connect

    Morrison, J.M.; Hirst, C.W.; Lentz, T.F.

    1992-03-18

    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 summary herein.

  9. ETR HEAT EXCHANGER BUILDING, TRA644. WORKERS ARE INSTALLING HEAT EXCHANGER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    ETR HEAT EXCHANGER BUILDING, TRA-644. WORKERS ARE INSTALLING HEAT EXCHANGER PIPING. INL NEGATIVE NO. 56-3122. Jack L. Anderson, Photographer, 9/21/1956 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  10. Heat transfer from a horizontal finned tube bundle in bubbling fluidized beds of small and large particles

    SciTech Connect

    Devaru, C.B.; Kolar, A.K.

    1995-12-31

    Steady state average heat transfer coefficient measurements were made by the local thermal simulation technique in a cold, square, bubbling air-fluidized bed (0.305 m x 0.305 m) with immersed horizontal finned tube bundles (in-line and staggered) with integral 60{degree} V-thread. Studies were conducted using beds of small (average particle diameter less than 1 mm) sand particles and of large (average particle diameter greater thin 1 mm) particles (raagi, mustard, millet and coriander). The fin pitch varied from 0.8 to 5.0 mm and the fin height varied from 0.69 to 4.4 mm. The tube pitch ratios used were 1.75 and 3.5. The influence of bed particle diameter, fluidizing velocity, fin pitch, and tube pitch ratio on average heat transfer coefficient was studied. Fin pitch and bed particle diameter are the most significant parameters affecting heat transfer coefficient within the range of experimental conditions. Bed pressure drop depends only on static bed height. New direct correlations, incorporating easily measurable quantities, for average heat transfer coefficient for finned tube bundles (in-line and staggered) are proposed.

  11. Energy absorber for sodium-heated heat exchanger

    DOEpatents

    Essebaggers, J.

    1975-12-01

    A heat exchanger is described in which water-carrying tubes are heated by liquid sodium and in which the results of accidental contact between the water and the sodium caused by failure of one or more of the water tubes is minimized. An energy absorbing chamber contains a compressible gas and is connected to the body of flowing sodium by a channel so that, in the event of a sodium-water reaction, products of the reaction will partially fill the energy absorbing chamber to attenuate the rise in pressure within the heat exchanger.

  12. Heat exchanger for coal gasification process

    DOEpatents

    Blasiole, George A.

    1984-06-19

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

  13. Effects of Pin Detached Space on Heat Transfer and Pin-Fin Arrays

    SciTech Connect

    Siw, Sin C.; Chyu, Minking K.; Shih, Tom I-P.; Alvin, Mary Anne

    2012-08-01

    Heat transfer and pressure characteristics in a rectangular channel with pin-fin arrays of partial detachment from one of the endwalls have been experimentally studied. The overall channel geometry (W = 76.2 mm, E = 25.4 mm) simulates an internal cooling passage of wide aspect ratio (3:1) in a gas turbine airfoil. With a given pin diameter, D = 6.35 mm = ¼E, three different pin-fin height-to-diameter ratios, H/D = 4, 3, and 2, were examined. Each of these three cases corresponds to a specific pin array geometry of detachment spacing (C) between the pin tip and one of the endwalls, i.e., C/D = 0, 1, 2, respectively. The Reynolds number, based on the hydraulic diameter of the unobstructed cross-section and the mean bulk velocity, ranges from 10,000 to 25,000. The experiment employs a hybrid technique based on transient liquid crystal imaging to obtain the distributions of the local heat transfer coefficient over all of the participating surfaces, including the endwalls and all the pin elements. Experimental results reveal that the presence of a detached space between the pin tip and the endwall has a significant effect on the convective heat transfer and pressure loss in the channel. The presence of pin-to-endwall spacing promotes wall-flow interaction, generates additional separated shear layers, and augments turbulent transport. In general, an increase in detached spacing, or C/D, leads to lower heat transfer enhancement and pressure drop. However, C/D = 1, i.e., H/D = 3, of a staggered array configuration exhibits the highest heat transfer enhancement, followed by the cases of C/D = 0 and C/D = 2, i.e., H/D = 4 or 2, respectively.

  14. Conjugate heat transfer of a finned tube. Part B: Heat transfer augmentation and avoidance of heat transfer reversal by longitudinal vortex generators

    SciTech Connect

    Fiebig, M.; Chen, Y.; Grosse-Gorgemann, A.; Mitra, N.K.

    1995-08-01

    Numerical investigations of three-dimensional flow and heat transfer in a finned tube with punched longitudinal vortex generators (LVG`s) are carried out for Reynolds number of 250 and 300. Air with a Prandtl number of 0.7 is used as the fluid. The flow is both thermally and hydrodynamically developing. The LVG is a delta winglet pair (DWP) punched out of the fin and is located directly behind the tube, symmetrically separated by one tube diameter. The DWP generates longitudinal vortices in the wake of the tube, defers flow separation on the tube, deflects the main stream into the tube wake, and strong reduces the ``dead water zone.`` Heat transfer reversal is avoided by the DWP. Comparison of the span-averaged Nusselt numbers for the fin with and without DWP shows significant local heat transfer enhancement of several hundred percent in the tube wake. For Re = 300 and Fi = 200 the global heat transfer augmentation by a DWP, which amounts to only 2.5% of the fin area, is 31%.

  15. Micro-Scale Regenerative Heat Exchanger

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  16. Carbon nanotube heat-exchange systems

    DOEpatents

    Hendricks, Terry Joseph; Heben, Michael J.

    2008-11-11

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

  17. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, D.G.

    1993-11-09

    Regenerative heat exchangers are described for transferring heat between hot and cold fluids. The heat exchangers have seal-leakage rates significantly less than those of conventional regenerative heat exchangers because the matrix is discontinuously moved and is releasably sealed while in a stationary position. Both rotary and modular heat exchangers are described. Also described are methods for transferring heat between a hot and cold fluid using the discontinuous movement of matrices. 11 figures.

  18. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, David G.

    1993-01-01

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

  19. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, David Gordon

    2001-04-17

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

  20. Heat exchanger containing a component capable of discontinuous movement

    DOEpatents

    Wilson, David Gordon

    2002-01-01

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

  1. Fluid Analysis and Improved Structure of an ATEG Heat Exchanger Based on Computational Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Tang, Z. B.; Deng, Y. D.; Su, C. Q.; Yuan, X. H.

    2015-06-01

    In this study, a numerical model has been employed to analyze the internal flow field distribution in a heat exchanger applied for an automotive thermoelectric generator based on computational fluid dynamics. The model simulates the influence of factors relevant to the heat exchanger, including the automotive waste heat mass flow velocity, temperature, internal fins, and back pressure. The result is in good agreement with experimental test data. Sensitivity analysis of the inlet parameters shows that increase of the exhaust velocity, compared with the inlet temperature, makes little contribution (0.1 versus 0.19) to the heat transfer but results in a detrimental back pressure increase (0.69 versus 0.21). A configuration equipped with internal fins is proved to offer better thermal performance compared with that without fins. Finally, based on an attempt to improve the internal flow field, a more rational structure is obtained, offering a more homogeneous temperature distribution, higher average heat transfer coefficient, and lower back pressure.

  2. The Role of Filtration in Maintaining Clean Heat Exchanger Coils

    SciTech Connect

    Li Yang; James E. Braun; Eckhard A. Groll

    2004-06-30

    The main purpose of the study was to investigate the role of filtration in maintaining clean heat exchanger coils and overall performance. Combinations of 6 different levels of filtration (MERV 14, 11, 8, 6, 4, and no filter) and 4 different coils (an eight-row lanced-fin coil, HX8L), (an eight-row wavy-fin coil, HX8W), (a four-row lanced-fin coil, HX4L) and (a two-row lanced-fin coil, HX2L) were tested at 4 different air velocities (1.52, 2.03, 2.54,3.05 m/s (300, 400, 500, 600 ft/min)). The fouled conditions were obtained after injection of 600 grams of ASHRAE standard dust upstream of the filter/coil combination. This magnitude of dust is representative of a year of normal operation for an air conditioning system. The air-side pressure drops of the coils and filters and air-side heat transfer coefficients of the coils were determined from the measurements under the clean and fouled conditions. Depending upon the filter and coil test, the coil pressure drops increased in the range of 6%-30% for an air velocity at 2.54 m/s (500 ft/min). The impact was significantly greater for tests performed without a filter. The largest relative effect of fouling on pressure drop occurs for coils with fewer rows and having lanced fins. Coils with a greater number of rows can hold more dust so that a fixed amount of dust has a relatively smaller impact. The impact of fouling on air-side heat transfer coefficients was found to be relatively small. In some cases, heat transfer was actually enhanced due to additional turbulence caused by the presence of dust. The experimental results for pressure drops and heat transfer coefficients were correlated and the correlations were implemented within computer models of prototypical rooftop air conditioners and used to evaluate the impact of fouling on cooling capacity and EER. The equipment cooling capacity is reduced with fouling primarily because of a decrease in air flow due to the increase pressure drop rather than due to changes in h

  3. 14 CFR 29.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... secondary heat exchanger between the primary exhaust gas heat exchanger and the ventilating air system; or... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Exhaust System § 29.1125 Exhaust heat... inspecting the critical parts of each exchanger; (3) Each exchanger must have cooling provisions wherever...

  4. 14 CFR 29.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... secondary heat exchanger between the primary exhaust gas heat exchanger and the ventilating air system; or... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Exhaust System § 29.1125 Exhaust heat... inspecting the critical parts of each exchanger; (3) Each exchanger must have cooling provisions wherever...

  5. Experimental and numerical study on laminar natural convection in a cavity heated from bottom due to an inclined fin

    NASA Astrophysics Data System (ADS)

    Varol, Yasin; Öztop, Hakan F.; Özgen, Filiz; Koca, Ahmet

    2012-01-01

    Natural convection heat transfer in an inclined fin attached square enclosure is studied both experimentally and numerically. Bottom wall of enclosure has higher temperature than that of top wall while vertical walls are adiabatic. Inclined fin has also adiabatic boundary conditions. Numerical solutions have been done by writing a computer code in Fortran platform and results are compared with Fluent commercial code and experimental method. Governing parameters are Rayleigh numbers (8.105 ≤ Ra ≤ 4 × 106) and inclination angle (30° ≤ and ≤ 120°). The temperature measurements are done by using thermocouples distributed uniformly at the wall of the enclosure. Remarkably good agreement is obtained between the predicted results and experimental data. A correlation is also developed including all effective parameters on heat transfer and fluid flow. It was observed that heat transfer can be controlled by attaching an inclined fin onto wall.

  6. Low heat transfer oxidizer heat exchanger design and analysis

    NASA Technical Reports Server (NTRS)

    Kanic, P. G.; Kmiec, T. D.; Peckham, R. J.

    1987-01-01

    The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487.

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

    NASA Technical Reports Server (NTRS)

    Jennings, Mallory; Quinn, Gregory; Strange, Jeremy

    2012-01-01

    NASA is developing new portable life support system (PLSS) technologies, which it is demonstrating in an unmanned ground based prototype unit called PLSS 2.0. One set of technologies within the PLSS provides suitable ventilation to an astronaut while on an EVA. A new component within the ventilation gas loop is a liquid-to-gas heat exchanger to transfer excess heat from the gas to the thermal control system's liquid coolant loop. A unique bench top prototype heat exchanger was built and tested for use in PLSS 2.0. The heat exchanger was designed as a counter-flow, compact plate fin type using stainless steel. Its design was based on previous compact heat exchangers manufactured by United Technologies Aerospace Systems, but was half the size of any previous heat exchanger model and one third the size of previous liquid-to-gas heat exchangers. The prototype heat exchanger was less than 40 cubic inches and weighed 2.6 lb. The water side and gas side pressure drops were 0.8 psid and 0.5 inches of water, respectively. Performance of the heat exchanger at the nominal pressure of 4.1 psia was measured at 94%, while a gas inlet pressure of 25 psia resulted in an effectiveness of 84%. These results compared well with the model, which was scaled for the small size. Modeling of certain phenomena that affect performance, such as flow distribution in the headers was particularly difficult due to the small size of the heat exchanger. Data from the tests has confirmed the correction factors that were used in these parts of the model.

  8. Optimization of Borehole Heat Exchanger Arrays

    NASA Astrophysics Data System (ADS)

    Schulte, Daniel; Rühaak, Wolfram; Welsch, Bastian; Oladyshkin, Sergey; Sass, Ingo

    2016-04-01

    Arrays of borehole heat exchangers are an increasingly popular source for renewable energy. Furthermore, they can serve as borehole thermal energy storages for seasonally fluctuating heat sources like solar thermal energy or district heating grids. However, the uncertainty of geological parameters and the nonlinear behavior of the complex system make it difficult to simulate and predict the required design of borehole heat exchanger arrays. As a result, the arrays easily turn out to be over or undersized, which compromises the economic feasibility of these systems. Here, we present a novel optimization strategy for the design of borehole thermal energy storages. The arbitrary polynomial chaos expansion method is used to build a proxy model from a set of numerical training simulations, which allows for the consideration of parameter uncertainties. Thus, the resulting proxy model bypasses the problem of excessive computation time for the numerous function calls required for a mathematical optimization. Additionally, we iteratively refine the proxy model during the optimization procedure using additional numerical simulation runs. With the presented solution, many aspects of borehole heat exchanger arrays can be optimized under geological uncertainty.

  9. Heat transfer in counterflow heat exchangers with helical turbulators

    NASA Astrophysics Data System (ADS)

    Zamankhan, Piroz

    2010-10-01

    A 3D mathematical model has been developed to investigate the heat transfer augmentation in a circular tube with a helical turbulator. Glycol-water blends of various concentrations were used in the inner tube, and pure water was used in the outer tube. Changes in fluid physical properties with temperature were taken into account, and k- ε, k - ω , and large eddy simulations were developed for turbulence modeling. The simulation results showed a nonlinear variation in Reynolds and Prandtl numbers for a long model of a heat exchanger even in the absence of a turbulator. The presence of the turbulator was found to increase the heat transfer, sometimes without inducing turbulence, but also increased the pressure drop. The results demonstrate that the model could be used as a useful tool for optimization of heat exchanger performance in the presence of a turbulator. Comparisons with experimental data showed reasonably agreement with large eddy simulation results.

  10. Brayton heat exchange unit development program

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  11. High Performance Woven Mesh Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Wirtz, Richard A.; Li, Chen; Park, Ji-Wook; Xu, Jun

    2002-07-01

    Simple-to-fabricate woven mesh structures, consisting of bonded laminates of two-dimensional plain-weave conductive screens, or three-dimensional orthogonal weaves are described. Geometric equations show that these porous matrices can be fabricated to have a wide range of porosity and a highly anisotropic thermal conductivity vector. A mathematical model of the thermal performance of such a mesh, deployed as a heat exchange surface, is developed. Measurements of pressure drop and overall heat transfer rate are reported and used with the performance model to develop correlation equations of mesh friction factor and Colburn j-factor as a function of coolant properties, mesh characteristics and flow rate through the mesh. A heat exchanger performance analysis delineates conditions where the two mesh technologies offer superior performance.

  12. Application of Collocation Spectral Method for Irregular Convective-Radiative Fins with Temperature-Dependent Internal Heat Generation and Thermal Properties

    NASA Astrophysics Data System (ADS)

    Sun, Ya-Song; Ma, Jing; Li, Ben-Wen

    2015-11-01

    A collocation spectral method (CSM) is developed to solve the fin heat transfer in triangular, trapezoidal, exponential, concave parabolic, and convex geometries. In the thermal process of fin heat transfer, fin dissipates heat to environment by convection and radiation; internal heat generation, thermal conductivity, heat transfer coefficient, and surface emissivity are functions of temperature; ambient fluid temperature and radiative sink temperature are considered to be nonzero. The temperature in the fin is approximated by Chebyshev polynomials and spectral collocation points. Thus, the differential form of energy equation is transformed into the matrix form of algebraic equation. In order to test efficiency and accuracy of the developed method, five types of convective-radiative fins are examined. Results obtained by the CSM are assessed by comparing available results in references. These comparisons indicate that the CSM can be recommended as a good option to simulate and predict thermal performance of the convective-radiative fins.

  13. A high temperature ceramic heat exchanger element for a solar thermal receiver

    NASA Technical Reports Server (NTRS)

    Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

    1982-01-01

    The development of a high-temperature ceramic heat exchanger element to be integrated into a solar receiver producing heated air was studied. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is to be fabricated by a innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. The unit is sized to produce 2150 F air at 2.7 atm pressure, with a pressure drop of about 2 percent of the inlet pressure. This size is compatible with a solar collector providing a receiver input of 85 kw(th). Fabrication of a one-half scale demonstrator ceramic receiver was completed.

  14. High-temperature ceramic heat exchanger element for a solar thermal receiver

    NASA Technical Reports Server (NTRS)

    Strumpf, H. J.; Kotchick, D. M.; Coombs, M. G.

    1982-01-01

    A study was performed by AiResearch Manufacturing Company, a division of The Garrett Corporation, on the development a high-temperature ceramic heat exchanger element to be integrated into a solar receiver producing heated air. A number of conceptual designs were developed for heat exchanger elements of differing configuration. These were evaluated with respect to thermal performance, pressure drop, structural integrity, and fabricability. The final design selection identified a finned ceramic shell as the most favorable concept. The shell is surrounded by a larger metallic shell. The flanges of the two shells are sealed to provide a leak-tight pressure vessel. The ceramic shell is to be fabricated by an innovative combination of slip casting the receiver walls and precision casting the heat transfer finned plates. The fins are bonded to the shell during firing. The unit is sized to produce 2150 F ar at 2.7 atm pressure, with a pressure drop of about 2 percent of the inlet pressure. This size is compatible with a solar collector providing a receiver input of 85 kw(th). Fabrication of a one-half scale demonstrator ceramic receiver has been completed.

  15. The Influence of a Dispersion Cone on the Temperature Distribution in the Heat Exchanger of a Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    MusiaŁ, M.; Borcuch, M.; Wojciechowski, K.

    2016-03-01

    This paper presents the results of a numerical simulation of heat distribution in the heat exchanger of a prototype thermoelectric generator constructed and examined in the Thermoelectric Research Laboratory in AGH University, Cracow, Poland. The area of interest was to prepare a numerical model and determine the influence of a dispersion cone on the temperature distribution along the heat exchanger. The role of a dispersion element is to mix the air stream to improve the flow between the internal heat exchanger's fins in order to enhance heat exchange. The estimation of power output parameters and exchanger efficiency has been performed in order to assess the cone impact for three selected air inlet temperatures. The results show that the presence of the cone increases the efficiency of the thermoelectric generator by at least 25%.

  16. Preliminary SP-100/Stirling heat exchanger designs

    NASA Technical Reports Server (NTRS)

    Schmitz, Paul; Tower, Leonard; Dawson, Ronald; Blue, Brian; Dunn, Pat

    1993-01-01

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

  17. Triple loop heat exchanger for an absorption refrigeration system

    DOEpatents

    Reimann, Robert C.

    1984-01-01

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

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

    PubMed

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

    2014-01-01

    This paper investigates the enhancement of heat transfer coefficient and Nusselt number of a nanofluid containing nanoparticles (γ-AL2O3) with a particle size of 20 nm and volume fraction of 0.1%-0.3% (V/V). Effects of temperature and concentration of nanoparticles on Nusselt number changes and heat transfer coefficient in a double pipe heat exchanger with counter turbulent flow are investigated. Comparison of experimental results with valid theoretical data based on semiempirical equations shows an acceptable agreement. Experimental results show a considerable increase in heat transfer coefficient and Nusselt number up to 19%-24%, respectively. Also, it has been observed that the heat transfer coefficient increases with the operating temperature and concentration of nanoparticles.

  19. 1-MWe heat exchangers for OTEC. Final acceptance document

    SciTech Connect

    Snyder, J.E.

    1980-06-19

    Acceptance documents for major units of 1 MWe OTEC heat exchangers, including condensers and evaporators, are provided. Included are a transportation plan for the heat exchangers and design specifications for the phase separator. (LEW)

  20. Multi-Purpose Logistics Module (MPLM) Cargo Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Zampiceni, John J.; Harper, Lon T.

    2002-01-01

    This paper describes the New Shuttle Orbiter's Multi- Purpose Logistics Modulo (MPLM) Cargo Heat Exchanger (HX) and associated MPLM cooling system. This paper presents Heat Exchanger (HX) design and performance characteristics of the system.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  2. Optimizing PT Arun LNG main heat exchanger

    SciTech Connect

    Irawan, B.

    1995-12-01

    The capacity of a LNG liquefaction unit has been increased by upgrading the refrigeration system, without making changes to the main heat exchanger (MHE). It is interesting, that after all modifications were completed, a higher refrigerant circulation alone could not increase LNG production. However, by optimizing the refrigerant component ratio, the UA of the MHE increased and LNG production improved. This technical evaluation will provide recommendations and show how the evaluation of the internal temperature profile helped optimize the MHE operating conditions.

  3. Model of Heat Exchangers for Waste Heat Recovery from Diesel Engine Exhaust for Thermoelectric Power Generation

    NASA Astrophysics Data System (ADS)

    Baker, Chad; Vuppuluri, Prem; Shi, Li; Hall, Matthew

    2012-06-01

    The performance and operating characteristics of a hypothetical thermoelectric generator system designed to extract waste heat from the exhaust of a medium-duty turbocharged diesel engine were modeled. The finite-difference model consisted of two integrated submodels: a heat exchanger model and a thermoelectric device model. The heat exchanger model specified a rectangular cross-sectional geometry with liquid coolant on the cold side, and accounted for the difference between the heat transfer rate from the exhaust and that to the coolant. With the spatial variation of the thermoelectric properties accounted for, the thermoelectric device model calculated the hot-side and cold-side heat flux for the temperature boundary conditions given for the thermoelectric elements, iterating until temperature and heat flux boundary conditions satisfied the convection conditions for both exhaust and coolant, and heat transfer in the thermoelectric device. A downhill simplex method was used to optimize the parameters that affected the electrical power output, including the thermoelectric leg height, thermoelectric n-type to p-type leg area ratio, thermoelectric leg area to void area ratio, load electrical resistance, exhaust duct height, coolant duct height, fin spacing in the exhaust duct, location in the engine exhaust system, and number of flow paths within the constrained package volume. The calculation results showed that the configuration with 32 straight fins was optimal across the 30-cm-wide duct for the case of a single duct with total height of 5.5 cm. In addition, three counterflow parallel ducts or flow paths were found to be an optimum number for the given size constraint of 5.5 cm total height, and parallel ducts with counterflow were a better configuration than serpentine flow. Based on the reported thermoelectric properties of MnSi1.75 and Mg2Si0.5Sn0.5, the maximum net electrical power achieved for the three parallel flow paths in a counterflow arrangement was 1

  4. 14 CFR 23.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Exhaust heat exchangers. 23.1125 Section 23... § 23.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes the following apply: (a) Each exhaust heat exchanger must be constructed and installed to withstand the vibration, inertia,...

  5. 40 CFR 63.1409 - Heat exchange system provisions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 12 2014-07-01 2014-07-01 false Heat exchange system provisions. 63... § 63.1409 Heat exchange system provisions. (a) Unless one or more of the conditions specified in... subpart shall monitor each heat exchange system used to cool process equipment in an affected...

  6. 40 CFR 63.1328 - Heat exchange systems provisions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 12 2012-07-01 2011-07-01 true Heat exchange systems provisions. 63... Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins § 63.1328 Heat exchange... of this subpart. (h) The compliance date for heat exchange systems subject to the provisions of...

  7. 14 CFR 23.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Exhaust heat exchangers. 23.1125 Section 23... § 23.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes the following apply: (a) Each exhaust heat exchanger must be constructed and installed to withstand the vibration, inertia,...

  8. 40 CFR 63.1328 - Heat exchange systems provisions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 12 2014-07-01 2014-07-01 false Heat exchange systems provisions. 63... Heat exchange systems provisions. (a) Except as specified in paragraph (b) of this section, each owner... § 63.1335(e)(6), for the purposes of this subpart. (h) The compliance date for heat exchange...

  9. 40 CFR 63.1328 - Heat exchange systems provisions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 11 2010-07-01 2010-07-01 true Heat exchange systems provisions. 63... Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins § 63.1328 Heat exchange... of this subpart. (h) The compliance date for heat exchange systems subject to the provisions of...

  10. 14 CFR 23.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Exhaust heat exchangers. 23.1125 Section 23... § 23.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes the following apply: (a) Each exhaust heat exchanger must be constructed and installed to withstand the vibration, inertia,...

  11. 14 CFR 23.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Exhaust heat exchangers. 23.1125 Section 23... § 23.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes the following apply: (a) Each exhaust heat exchanger must be constructed and installed to withstand the vibration, inertia,...

  12. 14 CFR 23.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Exhaust heat exchangers. 23.1125 Section 23... § 23.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes the following apply: (a) Each exhaust heat exchanger must be constructed and installed to withstand the vibration, inertia,...

  13. 40 CFR 63.1328 - Heat exchange systems provisions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 11 2011-07-01 2011-07-01 false Heat exchange systems provisions. 63... Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and Resins § 63.1328 Heat exchange... of this subpart. (h) The compliance date for heat exchange systems subject to the provisions of...

  14. Heat exchanger support apparatus in a fluidized bed

    DOEpatents

    Lawton, Carl W.

    1982-01-01

    A heat exchanger is mounted in the upper portion of a fluidized combusting bed for the control of the temperature of the bed. A support, made up of tubes, is extended from the perforated plate of the fluidized bed up to the heat exchanger. The tubular support framework for the heat exchanger has liquid circulated therethrough to prevent deterioration of the support.

  15. 40 CFR 63.1409 - Heat exchange system provisions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... normal range. (5) The recirculating heat exchange system is used to cool process fluids that contain less...-through heat exchange system is used to cool process fluids that contain less than 5 percent by weight of... 40 Protection of Environment 12 2013-07-01 2013-07-01 false Heat exchange system provisions....

  16. OXIDE DISPERSION-STRENGTHENED HEAT EXCHANGER TUBING

    SciTech Connect

    Harper, Mark A.

    2001-11-06

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

  17. Heat-Transfer and Friction Measurements with Variable Properties for Airflow Normal to Finned and Unfinned Tube Banks

    NASA Technical Reports Server (NTRS)

    Ragsdale, Robert G.

    1958-01-01

    A single-line correlation of both the heat-transfer and pressure- drop data for electrically heated unfinned tubes is obtained by evaluating the density in the Reynolds number, specific heat, thermal conductivity, and viscosity at the film temperature, and the density in the friction coefficient at the bulk temperature. The heat-transfer data for finned tubes also exhibit an effect of physical-property variation which is removed by evaluating all properties, including density, at the primary surface temperature, and using k* = 0.015 square root of T/530 for the thermal conductivity of air where T is the absolute temperature. The pressure drop for finned tubes is correlated by the use of bulk density in both the Reynolds number and friction coefficient. The data reported are for Reynolds numbers from 2000 to 35,000, surface temperatures from 600 to 1400 R, and an air inlet temperature of 530 R.

  18. Analysis of the heat transfer in double and triple concentric tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Rădulescu, S.; Negoiţă, L. I.; Onuţu, I.

    2016-08-01

    The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.

  19. A heat transfer model of a horizontal ground heat exchanger

    NASA Astrophysics Data System (ADS)

    Mironov, R. E.; Shtern, Yu. I.; Shtern, M. Yu.; Rogachev, M. S.

    2016-04-01

    Ground-source heat pumps are gaining popularity in Eastern Europe, especially those which are using the horizontal ground heat exchanger (GHX). Due to the difficulty of accessing GHX after the installation, materials and the quality of the installation must satisfy the very high requirements. An inaccurate calculation of GHX can be the reason of a scarcity of heat power in a crucial moment. So far, there isn't any appropriate mathematical description of the horizontal GHX which takes into account the mutual influence of GHX pipes on each other. To solve this problem we used the temperature wave approach. As a result, a mathematical model which describes the dependence of the heat transfer rate per unit length of the horizontal GHX pipe on the thermal properties of soil, operating time of GHX and the distance between pipes was obtained. Using this model, heat transfer rates per unit length of a horizontal GHX were plotted as functions of the distance between pipes and operating time. The modeling shows that heat transfer rates decreases rapidly with the distance between pipes lower then 2 meters. After the launch of heat pump, heat power of GHX is reduced during the first 20 - 30 days and get steady after that. The obtained results correlate with experimental data. Therefore the proposed mathematical model can be used to design a horizontal GHX with the optimal characteristics, and predict its capability during operation.

  20. The Conduction of Heat through Cryogenic Regenerative Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Superczynski, W. F.; Green, G. F.

    2006-04-01

    The need for improved regenerative cryocooler efficiency may require the replacement of conventional matrices with ducts. The ducts can not be continuous in the direction of temperature gradient when using conventional materials to prevent unacceptable conduction losses. However, this discontinuity creates a complex geometry to model and determine conduction losses. Chesapeake Cryogenics, Inc. has designed, fabricated and tested an apparatus for measuring the heat conduction through regenerative heat exchangers implementing different matrices. Data is presented for stainless steel photo etched disk, phophorus-bronze embossed ribbon coils and screens made of both stainless steel and phosphorus-bronze. The heat conduction was measured with the regenerators evacuated and pressurized with helium gas. In this test apparatus, helium gas presence increased the heat leak significantly. A description of the test apparatus, instrumentation, experimental methods and data analysis are presented.

  1. Preliminary design package for maxi-therm heat exchanger module

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Heat exchangers were developed for use in a solar heating and cooling system installed in a single family dwelling. Each of the three exchangers consisted of a heating and cooling module and a submersed electric water heating element. Information necessary to evaluate the preliminary design of the heat exchanger is presented in terms of the development and verification plans, performance specifications, installation and maintenance, and hazard analysis.

  2. Theoretical and experimental studies of rectangular duct heat exchangers to be used in a high-altitude subsonic aircraft

    NASA Astrophysics Data System (ADS)

    Mathias, James Allen

    A unique need exists for heat exchangers that operate efficiently at an altitude of 85,000 feet. The application involves transferring heat to the low pressure ambient air at a low velocity that is in the laminar flow regime. Because it is desired that low pressure ambient air experience a small decrease in pressure, heat exchangers were examined with relatively short flowlengths and the boundary layers of the ambient air may be developing for a significant portion of the flowlength. These unique requirements of heat exchangers prompted an experimental study of compact heat exchangers made with relatively short rectangular fins that formed rectangular ducts. Compact heat exchangers made with rectangular fins were experimentally tested to determine the pressure drop of the air across the heat exchanger and the heat transfer to the air; the experiments were performed with air at Reynolds numbers between 100 and 1000. By placing the experimental apparatus in a chamber that was partially evacuated, experiments were also performed with air at a Reynolds number of approximately 250 at simulated elevated altitudes up to 83,000 feet. The results of the experiments performed at sea level and elevated altitudes compared very well. The results of the experiments that measured the pressure drop of the air determined the additional pressure drop caused by the developing boundary layers. An equation obtained from the data of the pressure drop measurements predicted the entrance length of the developing boundary layers. The Nusselt number of the air was calculated from the data of the heat transfer experiments. The Nusselt number significantly increased of the experiments performed with the boundary layers of the air developing for a significant portion of the rectangular duct. An equation was obtained that predicted the Nusselt number for compact heat exchangers with short flowlengths and with air at low Reynolds numbers. The equation that predicted the Nusselt number and the

  3. Reynolds number effects on pressure loss and turbulence characteristics of four tube-bundle heat exchangers

    NASA Technical Reports Server (NTRS)

    Gentry, L., Jr.; Gentry, C. L., Jr.

    1983-01-01

    The aerodynamic characteristics of pressure loss and turbulence on four tube-bundle configurations representing heat-exchanger geometries with nominally the same heat capacity were measured as a function of Reynolds numbers from about 4000 to 400,000 based on tube hydraulic diameter. Two configurations had elliptical tubes, the other two had round tubes, and all four had plate fins. The elliptical-tube configurations had lower pressure loss and turbulence characteristics than the round-tube configurations over the entire Reynolds number range.

  4. Development of a compact laminar flow heat exchanger with stainless steel micro-tubes

    NASA Astrophysics Data System (ADS)

    Saji, N.; Nagai, S.; Tsuchiya, K.; Asakura, H.; Obata, M.

    2001-05-01

    The present paper describes the design concept and manufacturing of a new compact laminar flow heat exchanger with stainless-steel micro-tubes for helium refrigerators. In the temperature range of less than 20 K, aluminum plate fin type heat exchangers exhibit a remarkable fall of performance characteristics as a compact heat exchanger. We presented in a previous paper that some compact heat exchangers with good performance in the temperature range of less than 4 K are required for a subcooled He II refrigerator cycle to be worked with 3He turbo-compressors (F. Doty, et al., A new look at the closed brayton cycle, Proceedings, IECEC-90 Reno, NV, 1991, p. 116). For this requirement, we developed a micro-tube strip counter flow type heat exchanger, which consists of 12 elements with a total of 4800 stainless steel micro-tubes. Each element is formed with 400 tubes and a newly developed vacuum brazing method was applied for the bonding to the side plate. Each tube has an inner diameter of 0.5 mm, an outer diameter of 0.7 mm and is 310 mm long. We developed a cladding plate with two layers of gold brazing sheet sandwiched inside. In aerodynamic and thermal design of the element, the laminar flow conditions were adopted for the flows of inner and outer tubes to keep a high heat transfer rate and a low pressure loss.

  5. Microchannel Heat Exchangers with Carbon Dioxide

    SciTech Connect

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

    2001-09-15

    The objective of the present study was to determine the performance of CO{sub 2} microchannel evaporators and gas coolers in operational conditions representing those of residential heat pumps. A set of breadboard prototype microchannel evaporators and gas coolers was developed and tested. The refrigerant in the heat exchangers followed a counter cross-flow path with respect to the airflow direction. The test conditions corresponded to the typical operating conditions of residential heat pumps. In addition, a second set of commercial microchannel evaporators and gas coolers was tested for a less comprehensive range of operating conditions. The test results were reduced and a comprehensive data analysis, including comparison with the previous studies in this field, was performed. Capacity and pressure drop of the evaporator and gas cooler for the range of parameters studied were analyzed and are documented in this report. A gas cooler performance prediction model based on non-dimensional parameters was also developed and results are discussed as well. In addition, in the present study, experiments were conducted to evaluate capacities and pressure drops for sub-critical CO{sub 2} flow boiling and transcritical CO{sub 2} gas cooling in microchannel heat exchangers. An extensive review of the literature failed to indicate any previous systematic study in this area, suggesting a lack of fundamental understanding of the phenomena and a lack of comprehensive data that would quantify the performance potential of CO{sub 2} microchannel heat exchangers for the application at hand. All experimental tests were successfully conducted with an energy balance within {+-}3%. The only exceptions to this were experiments at very low saturation temperatures (-23 C), where energy balances were as high as 10%. In the case of evaporators, it was found that a lower saturation temperature (especially when moisture condensation occurs) improves the overall heat transfer coefficient

  6. Thermal control of a lidar laser system using a non-conventional ram air heat exchanger

    NASA Technical Reports Server (NTRS)

    Killough, Brian D.; Alexander, William, Jr.; Swofford, Doyle P.

    1990-01-01

    This paper describes the analysis and performance testing of a uniquely designed external heat exchanger. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. Estimates showed insufficient cooling capacity with a conventional staggered tube array in the limited space available. Thus, a non-conventional design wes developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and liquid flight conditions for the non-conventional parallel bank arrangement and the conventional staggered tube arrangement. Performance comparisons of each of the two designs are presented. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile. These analyses predict significantly improved performance over the conventional design and show adequate thermal control margins.

  7. Thermal control of a lidar laser system using a non-conventional ram air heat exchanger

    NASA Astrophysics Data System (ADS)

    Killough, Brian D.; Alexander, William, Jr.; Swofford, Doyle P.

    1990-10-01

    This paper describes the analysis and performance testing of a uniquely designed external heat exchanger. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. Estimates showed insufficient cooling capacity with a conventional staggered tube array in the limited space available. Thus, a non-conventional design wes developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and liquid flight conditions for the non-conventional parallel bank arrangement and the conventional staggered tube arrangement. Performance comparisons of each of the two designs are presented. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile. These analyses predict significantly improved performance over the conventional design and show adequate thermal control margins.

  8. Heat exchanger life extension via in-situ reconditioning

    DOEpatents

    Holcomb, David E.; Muralidharan, Govindarajan

    2016-06-28

    A method of in-situ reconditioning a heat exchanger includes the steps of: providing an in-service heat exchanger comprising a precipitate-strengthened alloy wherein at least one mechanical property of the heat exchanger is degraded by coarsening of the precipitate, the in-service heat exchanger containing a molten salt working heat exchange fluid; deactivating the heat exchanger from service in-situ; in a solution-annealing step, in-situ heating the heat exchanger and molten salt working heat exchange fluid contained therein to a temperature and for a time period sufficient to dissolve the coarsened precipitate; in a quenching step, flowing the molten salt working heat-exchange fluid through the heat exchanger in-situ to cool the alloy and retain a supersaturated solid solution while preventing formation of large precipitates; and in an aging step, further varying the temperature of the flowing molten salt working heat-exchange fluid to re-precipitate the dissolved precipitate.

  9. Bubble Behavior and Heat Transfer of Nucleate Pool Boiling on Micro-Pin-Finned Surface in Microgravity

    NASA Astrophysics Data System (ADS)

    Wei, Jin-Jia; Xue, Yan-Fang; Zhao, Jian-Fu; Li, Jing

    2011-01-01

    Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic components with high heat flux in microgravity, and was verified by experiments performed utilizing the drop tower Beijing. Micro-pin-fins with the dimensions of 50 × 60 μm2 (thickness × height) and the space of 50 μm were fabricated on the chip surface by the dry etching technique. FC-72 was used as the working fluid. Nucleate pool boiling of FC-72 on a smooth surface was also tested for comparison. Unlike much obvious deterioration of heat transfer of nucleate pool boiling on the smooth surface in microgravity, constant heater surface temperature of nucleate pool boiling for the micro-pin-finned surface was observed, even though a large coalesced bubble completely covered the surface under microgravity condition. The performance of high efficient heat transfer on micro-pin-finned surface is independent of the gravity, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary forces.

  10. OPTIMIZATION OF INTERNAL HEAT EXCHANGERS FOR HYDROGEN STORAGE TANKS UTILIZING METAL HYDRIDES

    SciTech Connect

    Garrison, S.; Tamburello, D.; Hardy, B.; Anton, D.; Gorbounov, M.; Cognale, C.; van Hassel, B.; Mosher, D.

    2011-07-14

    Two detailed, unit-cell models, a transverse fin design and a longitudinal fin design, of a combined hydride bed and heat exchanger are developed in COMSOL{reg_sign} Multiphysics incorporating and accounting for heat transfer and reaction kinetic limitations. MatLab{reg_sign} scripts for autonomous model generation are developed and incorporated into (1) a grid-based and (2) a systematic optimization routine based on the Nelder-Mead downhill simplex method to determine the geometrical parameters that lead to the optimal structure for each fin design that maximizes the hydrogen stored within the hydride. The optimal designs for both the transverse and longitudinal fin designs point toward closely-spaced, small cooling fluid tubes. Under the hydrogen feed conditions studied (50 bar), a 25 times improvement or better in the hydrogen storage kinetics will be required to simultaneously meet the Department of Energy technical targets for gravimetric capacity and fill time. These models and methodology can be rapidly applied to other hydrogen storage materials, such as other metal hydrides or to cryoadsorbents, in future work.

  11. Performance of Wire Springs as Extended Heat Transfer Surface for Compact Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Iwai, Hiroshi; Kawakami, Soushi; Suzuki, Kenjiro; Tsujii, Junichi; Abiko, Tetsuo

    Use of thin metal wire structures as a new type of extended heat transfer surface is proposed. As one of the most basic shapes of such wire structures, heat transfer performance of spring shaped fins is experimentally investigated under relatively low Reynolds number conditions. The averaged heat transfer coefficient is evaluated by a single-blow method while the pressure drop is measured at a steady state flow condition. The effects of the geometric parameters such as the wire diameter, the spring pitch and the pitch ratio were systematically examined and the obtained data were compared with that of a conventional offset fin, which is commercially available. It was found that the geometric parameters of the spring fins and the arrangement of spring fins in the test section affect their heat transfer performance. Some types of spring fins showed better heat transfer performance than a conventional offset fin, when they are evaluated in terms of the total heat transfer at a constant pumping power.

  12. Condensation in horizontal heat exchanger tubes

    SciTech Connect

    Leyer, S.; Zacharias, T.; Maisberger, F.; Lamm, M.; Vallee, C.; Beyer, M.; Hampel, U.

    2012-07-01

    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)

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

    SciTech Connect

    2014-03-01

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

  14. Reliability analysis on a shell and tube heat exchanger

    NASA Astrophysics Data System (ADS)

    Lingeswara, S.; Omar, R.; Mohd Ghazi, T. I.

    2016-06-01

    A shell and tube heat exchanger reliability was done in this study using past history data from a carbon black manufacturing plant. The heat exchanger reliability study is vital in all related industries as inappropriate maintenance and operation of the heat exchanger will lead to major Process Safety Events (PSE) and loss of production. The overall heat exchanger coefficient/effectiveness (Uo) and Mean Time between Failures (MTBF) were analyzed and calculated. The Aspen and down time data was taken from a typical carbon black shell and tube heat exchanger manufacturing plant. As a result of the Uo calculated and analyzed, it was observed that the Uo declined over a period caused by severe fouling and heat exchanger limitation. This limitation also requires further burn out period which leads to loss of production. The MTBF calculated is 649.35 hours which is very low compared to the standard 6000 hours for the good operation of shell and tube heat exchanger. The guidelines on heat exchanger repair, preventive and predictive maintenance was identified and highlighted for better heat exchanger inspection and repair in the future. The fouling of heat exchanger and the production loss will be continuous if proper heat exchanger operation and repair using standard operating procedure is not followed.

  15. High-temperature self-circulating thermoacoustic heat exchanger

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

    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.

  16. Turbulent heat exchanger {Delta}T and {Delta}P

    SciTech Connect

    Steinmeyer, D.

    1996-12-31

    Optimum pressure drop ({Delta}P) and temperature difference ({Delta}T) in turbulent flow heat exchangers are presented in three frameworks: as quantitatively defined by fluid properties, the value of energy and the cost of heat exchange surface (with a little help from a relationship between [power/mass] and heat transfer); as the energy cost for heat recovery (with the {Delta}T cost being about equal to the heat exchanger cost and the {Delta}P cost being about 1/3 as great); and as the second law lost work inherent in heat exchange (with the {Delta}T loss being {approximately}3 times the {Delta}T loss).

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

    NASA Astrophysics Data System (ADS)

    Motamedi, Ashkan; Pacheco-Vega, Arturo; Rafael Pacheco, J.

    2012-11-01

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

  18. Acoustic resonance in heat exchanger tube bundles

    SciTech Connect

    Blevins, R.D. )

    1994-02-01

    A series of experiments has been made on aeroacoustic tones produced by flow over tubes in a duct. The sound is characterized by the onset of a loud and persistent acoustic resonance. The acoustic resonance occurs at the frequency of the acoustic modes. The magnitude and extent of the resonance are functions of tube pattern and tube pitch. The sound levels increase in proportion with Mach number, dynamic head and pressure drop. A design procedure for predicting the magnitude of the sound within the tube array is presented. Methods of resonance avoidance are illustrated. An example is made for a large petrochemical heat exchanger.

  19. Heat exchanger for a Stirling engine

    SciTech Connect

    Fujiwara, M.; Nomaguchi, T.; Kazumoto, Y.; Tsuchino, K.; Kawajiri, K.; Hisamori, Y.

    1987-05-05

    A heat exchanger is described for a Stirling engine comprising: a domed cylinder having a domed portion and a cylindrical portion. The domed cylinder serves as a high-temperature cylinder and a regenerator housing of the Stirling engine; a cylindrical inner liner which is coaxially disposed inside the domed cylinder and which divides the inside of the domed cylinder into an expansion space inside of the inner liner and a regenerator space between the outer surface of the inner liner and the inner surface of the cylindrical portion of the domed cylinder.

  20. Experimental study of single-phase pressure drop and heat transfer in a micro-fin tube

    SciTech Connect

    Li, Xiao-Wei; Meng, Ji-An; Li, Zhi-Xin

    2007-11-15

    The single-phase pressure drop and heat transfer in a micro-fin tube were measured using oil and water as the working fluids. The Prandtl number varied from 3.2 to 220 and the Reynolds number ranged from 2500 to 90,000. The results show that there is a critical Reynolds number, Re{sub cr}, for heat transfer enhancement. For Reheat transfer in the micro-fin tube is the same as that in a smooth tube, but for Reynolds numbers higher than Re{sub cr}, the heat transfer in the micro-fin tube is gradually enhanced compared with a smooth tube. It reaches more than twice that in a smooth tube for Reynolds numbers greater than 30,000 with water as the working fluid. The Nusselt number is proportional to Pr {sup 0.56} in the enhanced region and is proportional to Pr {sup 0.3} in the non-enhanced region. For the high Prandtl number working fluid (oil, 80< Pr <220), the critical Reynolds number for heat transfer enhancement is about 6000, while for the low Prandtl number working fluid (water, 3.2< Pr <5.8), the critical Reynolds number for heat transfer enhancement is about 10,000. The friction factors in the micro-fin tube are almost the same as for a smooth tube for Reynolds numbers below 10,000. For Reynolds numbers higher than 30,000, the friction factor is about 40-50% higher than for a smooth tube. (author)

  1. Radiant heat exchange calculations in radiantly heated and cooled enclosures

    SciTech Connect

    Chapman, K.S.; Zhang, P.

    1995-08-01

    This paper presents the development of a three-dimensional mathematical model to compute the radiant heat exchange between surfaces separated by a transparent and/or opaque medium. The model formulation accommodates arbitrary arrangements of the interior surfaces, as well as arbitrary placement of obstacles within the enclosure. The discrete ordinates radiation model is applied and has the capability to analyze the effect of irregular geometries and diverse surface temperatures and radiative properties. The model is verified by comparing calculated heat transfer rates to heat transfer rates determined from the exact radiosity method for four different enclosures. The four enclosures were selected to provide a wide range of verification. This three-dimensional model based on the discrete ordinates method can be applied to a building to assist the design engineer in sizing a radiant heating system. By coupling this model with a convective and conductive heat transfer model and a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater location. In addition, objects such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the performance of the radiant heating system.

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

    NASA Astrophysics Data System (ADS)

    Aminuddin, Mohammad; Zubair, Syed M.

    2014-11-01

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

  3. Detailed temporally resolved 2-D Velocity Measurements in a Novel Heat Exchanger Surface

    NASA Astrophysics Data System (ADS)

    Guezennec, Yann G.; Ko, Jang-Hyok; Choi, Woong-Chul

    1998-11-01

    Using flow visualization as a primary tool, a novel, high-performance heat transfer surface for compact heat exchangers was designed, specifically for low Reynolds number applications. This geometry was specifically created to enhance or generate strong three-dimensional transport even at low Reynolds number. It consists of a staggered array of "pin" mounted normal to the fins. A 15:1 model of this heat exchanger surface core was built out of Plexiglas to provide optical access and this model was placed in a 1'x1' water channel. The flow speed was adjusted to match the Reynolds based on the hydraulic diameter based on the fin pitch. The flow was seeded with small polystyrene particles and illuminated by a laser sheet from an Argon Ion laser. The fluid motion was recorded using a CCD camera and an S-VHS video recorder. In post-processing, the video records were automatically digitized and processed using a cinematographic PIV technique. The temporal evolution of the 2-D flow field (side view) clearly shows the presence of unsteady, shed vortical regions behind the pins, modulated by the spatially-periodic acceleration/deceleration and meandering of the mean flow between the periodic array of staggered pins. In the perpendicular view (top view), the results show the presence of two strong cross-stream transport mechanisms, mainly the horse-shoe vortex near the pin-fin junctions and the very strong spanwise transport in the separated wake region of the pins. This transport is most likely associated with the strong interaction of the longitudinal vortices (emanating form the horseshoe) and the spanwise vortices from the pin wake. This vortex interaction sets up a strong spanwise pressure gradient inducing large cross-stream transport from the fin to the core flow. Animation of the results illustrating these effects will be presented.

  4. Aerodynamics of heat exchangers for high-altitude aircraft

    NASA Technical Reports Server (NTRS)

    Drela, Mark

    1996-01-01

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

  5. Numerical modeling of a 2K J-T heat exchanger used in Fermilab Vertical Test Stand VTS-1

    SciTech Connect

    Gupta, Prabhat Kumar; Rabehl, Roger

    2014-07-01

    Fermilab Vertical Test Stand-1 (VTS-1) is in operation since 2007 for testing the superconducting RF cavities at 2 K. This test stand has single layer coiled finned tubes heat exchanger before J-T valve. A finite difference based thermal model has been developed in Engineering Equation Solver (EES) to study its thermal performance during filling and refilling to maintain the constant liquid level of test stand. The model is also useful to predict its performance under other various operating conditions and will be useful to design the similar kind of heat exchanger for future needs. Present paper discusses the different operational modes of this heat exchanger and its thermal characteristics under these operational modes. Results of this model have also been compared with the experimental data gathered from the VTS-1 heat exchanger and they are in good agreement with the present model.

  6. Heat transfer, pressure drop, and mass flow rate in pin fin channels with long and short trailing edge ejection holes

    NASA Astrophysics Data System (ADS)

    Lau, S. C.; Han, J. C.; Batten, T.

    1988-06-01

    The turbulent heat transfer and friction characteristics in the pin fin channels with small trailing edge ejection holes found in internally-cooled turbine airfoils have been experimentally investigated. It is found that the overall heat transfer increases when the length of the trailing edge ejection holes is increased and when the trailing edge ejection holes are configured such that much of the cooling air is forced to flow further downstream in the radial flow direction prior to exiting. The increase in the overall heat transfer is shown to be accompanied by an increase in the overall pressure drop.

  7. BASIMO - Borehole Heat Exchanger Array Simulation and Optimization Tool

    NASA Astrophysics Data System (ADS)

    Schulte, Daniel; Rühaak, Wolfram; Welsch, Bastian; Bär, Kristian; Sass, Ingo

    2016-04-01

    Borehole heat exchangers represent a well-established technology, which pushes for new fields of applications and novel modifications. Current simulation tools cannot - or only to some extent - describe features like inclined or partly insulated boreholes unless they run fully discretized models of the borehole heat exchangers. However, fully discretized models often come at a high computational cost, especially for large arrays of borehole heat exchangers. We present a tool, which uses one dimensional thermal resistance and capacity models for the borehole heat exchangers coupled with a numerical finite element model for the subsurface heat transport. An unstructured tetrahedral mesh bypasses the limitations of structured grids for borehole path geometries, while the thermal resistance and capacity model is improved to account for borehole heat exchanger properties changing with depth. The presented tool benefits from the fast analytical solution of the thermal interactions within the boreholes while still allowing for a detailed consideration of the borehole heat exchanger properties.

  8. 14 CFR 25.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Exhaust heat exchangers. 25.1125 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Exhaust System § 25.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes, the following apply: (a) Each exhaust heat...

  9. 40 CFR 63.654 - Heat exchange systems.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 11 2014-07-01 2014-07-01 false Heat exchange systems. 63.654 Section... Emission Standards for Hazardous Air Pollutants From Petroleum Refineries § 63.654 Heat exchange systems. (a) Except as specified in paragraph (b) of this section, the owner or operator of a heat...

  10. 14 CFR 25.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Exhaust heat exchangers. 25.1125 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Exhaust System § 25.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes, the following apply: (a) Each exhaust heat...

  11. 14 CFR 29.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Exhaust heat exchangers. 29.1125 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Exhaust System § 29.1125 Exhaust heat exchangers. For reciprocating engine powered rotorcraft the following apply: (a) Each exhaust heat...

  12. 14 CFR 29.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Exhaust heat exchangers. 29.1125 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Exhaust System § 29.1125 Exhaust heat exchangers. For reciprocating engine powered rotorcraft the following apply: (a) Each exhaust heat...

  13. 14 CFR 29.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Exhaust heat exchangers. 29.1125 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant Exhaust System § 29.1125 Exhaust heat exchangers. For reciprocating engine powered rotorcraft the following apply: (a) Each exhaust heat...

  14. 40 CFR 63.654 - Heat exchange systems.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 11 2012-07-01 2012-07-01 false Heat exchange systems. 63.654 Section... Emission Standards for Hazardous Air Pollutants From Petroleum Refineries § 63.654 Heat exchange systems. (a) Except as specified in paragraph (b) of this section, the owner or operator of a heat...

  15. 14 CFR 25.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Exhaust heat exchangers. 25.1125 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Exhaust System § 25.1125 Exhaust heat exchangers. For reciprocating engine powered airplanes, the following apply: (a) Each exhaust heat...

  16. 40 CFR 63.1409 - Heat exchange system provisions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 12 2012-07-01 2011-07-01 true Heat exchange system provisions. 63... Standards for Hazardous Air Pollutant Emissions: Manufacture of Amino/Phenolic Resins § 63.1409 Heat... each heat exchange system used to cool process equipment in an affected source, according to...

  17. A Project to Design and Build Compact Heat Exchangers

    ERIC Educational Resources Information Center

    Davis, Richard A.

    2005-01-01

    Students designed and manufactured compact, shell-and-tube heat exchangers in a project-based learning exercise integrated with our heat transfer course. The heat exchangers were constructed from common building materials available at home improvement centers. The cost of materials for a device was less than $20. The project gave students…

  18. 40 CFR 63.654 - Heat exchange systems.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 11 2013-07-01 2013-07-01 false Heat exchange systems. 63.654 Section... Emission Standards for Hazardous Air Pollutants From Petroleum Refineries § 63.654 Heat exchange systems. (a) Except as specified in paragraph (b) of this section, the owner or operator of a heat...

  19. Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

    NASA Astrophysics Data System (ADS)

    Kılıç, Bayram; İpek, Osman

    2016-06-01

    In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

  20. Heat exchanger for fuel cell power plant reformer

    DOEpatents

    Misage, Robert; Scheffler, Glenn W.; Setzer, Herbert J.; Margiott, Paul R.; Parenti, Jr., Edmund K.

    1988-01-01

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

  1. Circulatory heat sources for canine respiratory heat exchange.

    PubMed Central

    Solway, J; Leff, A R; Dreshaj, I; Munoz, N M; Ingenito, E P; Michaels, D; Ingram, R H; Drazen, J M

    1986-01-01

    We assessed the roles of the pulmonary and bronchial circulations as potential heat sources to the pulmonary airways during respiratory heat loss, by observing the changes in airstream temperature that accompanied temporary occlusion of the pulmonary or bronchial circulations. Baseline end-expiratory and end-inspiratory airstream temperatures were 35.4 +/- 0.2 degrees C (SEM) and 30.9 +/- 0.3 degrees C, respectively, among all trials. With occlusion of the lower lobe pulmonary arteries for 3 min ipsilateral end-expiratory and end-inspiratory airstream temperatures fell by 2.8 +/- 0.2 and 1.1 +/- 0.2 degrees C, respectively, during hyperpnea with room temperature air, and by 3.5 +/- 0.5 and 1.8 +/- 0.2 degrees C, respectively, during hyperpnea with frigid air. In marked contrast, interruption of the bronchial circulation for 3 min had no effect on airstream temperatures. These data indicate that under these conditions, the pulmonary circulation, but not the bronchial circulation, serves as an important local heat source for respiratory heat exchange within the pulmonary airways. Images PMID:3760181

  2. High temperature heat exchanger studies for applications to gas turbines

    NASA Astrophysics Data System (ADS)

    Min, June Kee; Jeong, Ji Hwan; Ha, Man Yeong; Kim, Kui Soon

    2009-12-01

    Growing demand for environmentally friendly aero gas-turbine engines with lower emissions and improved specific fuel consumption can be met by incorporating heat exchangers into gas turbines. Relevant researches in such areas as the design of a heat exchanger matrix, materials selection, manufacturing technology, and optimization by a variety of researchers have been reviewed in this paper. Based on results reported in previous studies, potential heat exchanger designs for an aero gas turbine recuperator, intercooler, and cooling-air cooler are suggested.

  3. Heat exchanger and water tank arrangement for passive cooling system

    SciTech Connect

    Gillett, James E.; Johnson, F. Thomas; Orr, Richard S.; Schulz, Terry L.

    1993-01-01

    A water storage tank in the coolant water loop of a nuclear reactor contains a tubular heat exchanger. The heat exchanger has tubesheets mounted to the tank connections so that the tubesheets and tubes may be readily inspected and repaired. Preferably, the tubes extend from the tubesheets on a square pitch and then on a rectangular pitch therebetween. Also, the heat exchanger is supported by a frame so that the tank wall is not required to support all of its weight.

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

    NASA Astrophysics Data System (ADS)

    Jang, Jin Yong; Jeong, Ji Hwan

    2016-04-01

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

  5. Review of Current Experience on Intermediate Heat Exchanger (IHX) and A Recommended Code Approach

    SciTech Connect

    Duane Spencer; Kevin McCoy

    2010-02-02

    The purpose of the ASME/DOE Gen IV Task 7 Part I is to review the current experience on various high temperature reactor intermediate heat exchanger (IHX) concepts. There are several different IHX concepts that could be envisioned for HTR/VHTR applications in a range of temperature from 850C to 950C. The concepts that will be primarily discussed herein are: (1) Tubular Helical Coil Heat Exchanger (THCHE); (2) Plate-Stamped Heat Exchanger (PSHE); (3) Plate-Fin Heat Exchanger (PFHE); and (4) Plate-Machined Heat Exchanger (PMHE). The primary coolant of the NGNP is potentially subject to radioactive contamination by the core as well as contamination from the secondary loop fluid. To isolate the radioactivity to minimize radiation doses to personnel, and protect the primary circuit from contamination, intermediate heat exchangers (IHXs) have been proposed as a means for separating the primary circuit of the NGNP (Next Generation Nuclear Plant) or other process heat application from the remainder of the plant. This task will first review the different concepts of IHX that could be envisioned for HTR/VHTR applications in a range of temperature from 850 to 950 C. This will cover shell-and-tube and compact designs (including the platefin concept). The review will then discuss the maturity of the concepts in terms of design, fabricability and component testing (or feedback from experience when applicable). Particular attention will be paid to the feasibility of developing the IHX concepts for the NGNP with operation expected in 2018-2021. This report will also discuss material candidates for IHX applications and will discuss specific issues that will have to be addressed in the context of the HTR design (thermal aging, corrosion, creep, creep-fatigue, etc). Particular attention will be paid to specific issues associated with operation at the upper end of the creep regime.

  6. Global optimization algorithm for heat exchanger networks

    SciTech Connect

    Quesada, I.; Grossmann, I.E. )

    1993-03-01

    This paper deals with the global optimization of heat exchanger networks with fixed topology. It is shown that if linear area cost functions are assumed, as well as arithmetic mean driving force temperature differences in networks with isothermal mixing, the corresponding nonlinear programming (NLP) optimization problem involves linear constraints and a sum of linear fractional functions in the objective which are nonconvex. A rigorous algorithm is proposed that is based on a convex NLP underestimator that involves linear and nonlinear estimators for fractional and bilinear terms which provide a tight lower bound to the global optimum. This NLP problem is used within a spatial branch and bound method for which branching rules are given. Basic properties of the proposed method are presented, and its application is illustrated with several example problems. The results show that the proposed method only requires few nodes in the branch and bound search.

  7. Direct contact droplet heat exchangers for thermal management in space

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Hertzberg, A.

    1982-01-01

    A liquid droplet heat exchanger for space applications is described which transfers heat between a gas and a liquid metal dispersed into droplets. The ability of the droplet heat exchanger to transfer heat between two media in direct contact over a wide temperature range circumvents many of the material limitations of conventional tube-type heat exchangers and does away with complicated plumbing systems and their tendency toward single point failure. Droplet heat exchangers offer large surface to volume ratios in a compact geometry, very low gas pressure drop, and high effectiveness. The application of the droplet heat exchanger in a high temperature Brayton cycle is discussed to illustrate its performance and operational characteristics.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  9. Advanced heat exchanger development for molten salts

    DOE PAGES

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark

    2014-12-01

    This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, which show corrosion resistance to molten salt at nominal operating temperatures up to 700°C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet materialmore » in Hastelloy N were corrosion tested in?58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850°C for 200, 500, and 1,000 hours. Corrosion rates found were similar between welded and nonwelded materials, typically <10 mils per year. For materials of construction, nickel and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of contaminant type and alloy composition with respect to chromium and carbon to better define the optimal chromium and carbon composition, independent of galvanic or differential solubility effects. Also presented is the division of the nuclear reactor and high temperature components per ASME standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.« less

  10. Advanced heat exchanger development for molten salts

    SciTech Connect

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark

    2014-12-01

    This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, which show corrosion resistance to molten salt at nominal operating temperatures up to 700°C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet material in Hastelloy N were corrosion tested in?58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850°C for 200, 500, and 1,000 hours. Corrosion rates found were similar between welded and nonwelded materials, typically <10 mils per year. For materials of construction, nickel and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of contaminant type and alloy composition with respect to chromium and carbon to better define the optimal chromium and carbon composition, independent of galvanic or differential solubility effects. Also presented is the division of the nuclear reactor and high temperature components per ASME standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.

  11. Thermal Propulsion Capture System Heat Exchanger Design

    NASA Technical Reports Server (NTRS)

    Richard, Evan M.

    2016-01-01

    One of the biggest challenges of manned spaceflight beyond low earth orbit and the moon is harmful radiation that astronauts would be exposed to on their long journey to Mars and further destinations. Using nuclear energy has the potential to be a more effective means of propulsion compared to traditional chemical engines (higher specific impulse). An upper stage nuclear engine would allow astronauts to reach their destination faster and more fuel efficiently. Testing these engines poses engineering challenges due to the need to totally capture the engine exhaust. The Thermal Propulsion Capture System is a concept for cost effectively and safely testing Nuclear Thermal Engines. Nominally, hydrogen exhausted from the engine is not radioactive, but is treated as such in case of fuel element failure. The Thermal Propulsion Capture System involves injecting liquid oxygen to convert the hydrogen exhaust into steam. The steam is then cooled and condensed into liquid water to allow for storage. The Thermal Propulsion Capture System concept for ground testing of a nuclear powered engine involves capturing the engine exhaust to be cooled and condensed before being stored. The hydrogen exhaust is injected with liquid oxygen and burned to form steam. That steam must be cooled to saturation temperatures before being condensed into liquid water. A crossflow heat exchanger using water as a working fluid will be designed to accomplish this goal. Design a cross flow heat exchanger for the Thermal Propulsion Capture System testing which: Eliminates the need for water injection cooling, Cools steam from 5800 F to saturation temperature, and Is efficient and minimizes water requirement.

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

    DOEpatents

    Koplow, Jeffrey P.

    2016-02-16

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

  13. Effect of Channel Configurations for Tritium Transfer in Printed Circuit Heat Exchangers

    SciTech Connect

    Chang Oh; Eung Kim; Robert Shrake; Mike Patterson

    2009-05-01

    The Next Generation Nuclear Plant (NGNP), a very High temperature Gas-Cooled Reactor (VHTR) concept, will provide the first demonstration of a closed-loop Brayton cycle at a commercial scale of a few hundred megawatts electric and hydrogen production. The power conversion system (PCS) for the NGNP will take advantage of the significantly higher reactor outlet temperatures of the VHTR to provide higher efficiencies than can be achieved in the current generation of light water reactors. Besides demonstrating a system design that can be used directly for subsequent commercial deployment, the NGNP will demonstrate key technology elements that can be used in subsequent advanced power conversion systems for other Generation IV reactors. In anticipation of the design, development and procurement of an advanced power conversion system for the NGNP, the system integration of the NGNP and hydrogen plant was initiated to identify the important design and technology options that must be considered in evaluating the performance of the proposed NGNP. In the VHTR system, an intermediate heat exchanger (IHX), which transfers heat from the reactor core to the electricity or hydrogen production system is one key component, and its effectiveness is directly related to the system overall efficiency. In the VHTRs, the gas fluids used for coolant generally have poor heat transfer capability, so it requires very large surface area for a given condition. For this reason, a compact heat exchanger (CHE), which is widely used in industry especially for gasto-gas or gas-to-liquid heat exchange is considered as a potential candidate for an IHX replacing the classical shell and tube type heat exchanger. A compact heat exchanger is arbitrary referred to be a heat exchanger having a surface area density greater than 700 m2/m3. The compactness is usually achieved by fins and micro-channels, and leads to the enormous heat transfer enhancement and size reduction. The surface area density is the

  14. Thermal and economic analysis of plastic heat exchangers for solar water heating

    SciTech Connect

    Liu, W.; Davidson, J.; Raman, R.; Mantell, S.

    1999-07-01

    The feasibility of polymer heat exchangers for solar water heaters is examined in terms of thermal performance and cost of tube-in-shell and immersed designs. High temperature nylon and cross-linked polyethylene were identified as suitable polymers for this application. These materials can meet the high temperature and pressure requirements of a domestic potable hot water system. The heat exchanger designs are compared for heat transfer area required to provide 3,000 and 6,000 W. A nylon tube-in-shell heat exchanger, sized for a 3,000 W load, is approximately 80% of the cost of a copper tube-in-shell heat exchanger. For an immersed heat exchanger, a high temperature nylon tube bank design has the lowest cost. The nylon tube bank heat exchanger, sized for a 3,000 W load, is approximately 80% the cost of an immersed coiled copper tube heat exchanger.

  15. Matrix heat exchanger including a liquid, thermal couplant

    DOEpatents

    Fewell, Thomas E.; Ward, Charles T.

    1976-01-01

    A tube-to-tube heat exchanger is disclosed with a thermally conductive matrix between and around the tubes to define annuli between the tubes and matrix. The annuli are filled to a level with a molten metal or alloy to provide a conductive heat transfer path from one tube through the matrix to the second tube. A matrix heat exchanger of this type is particularly useful for heat transfer between fluids which would react should one leak into the second.

  16. Numerical Analysis for Optimal Design of Fin and Tube Type Adsorber

    NASA Astrophysics Data System (ADS)

    Kariya, Keishi; Kuwahara, Ken; Shigeru, Koyama

    Adsorption cooling systems driven by low temperature waste heat (below 100°C) or renewable energy sources have gained considerable attention as one of the solutions for both energy and environment related problems. In this study, a two dimensional numerical analysis is carried out to evaluate the adsorption characteristics and to determine the performance of a fin and tube type adsorber/desorber heat exchanger; activated carbon fiber (ACF) of type A-20, which has relatively higher surface area, and ethanol are used as adsorbent/refrigerant pair. The effects of heat exchanger design configurations such as fin height, fin thickness, fin pitch, tube diameter and apparent density of ACF bed on the performance are examined numerically. The simulation results show that the cooling capacity can be optimized in the condition of fin height 15mm and fin pitch 5.5mm when other parameters are fixed.

  17. Analytical and experimental study of fluid friction and heat transfer in low Reynolds number flow heat exchangers

    NASA Astrophysics Data System (ADS)

    Muzychka, Yuri Stephan

    1999-11-01

    Analysis of fluid friction and heat transfer in low Reynolds number flow heat exchangers is undertaken. Three configurations typically utilized in compact heat exchangers are examined. These are: the plain non- circular duct of constant cross-sectional area, the offset or interrupted strip fin, and the turbulator strip. Analytical models for each of these geometries are developed by combining asymptotic solutions using simple non-linear superposition. Models for predicting the friction factor-Reynolds number product, f Re, and Nusselt number, Nu, in non-circular ducts for hydrodynamically fully developed flow (HFDF), hydrodynamically developing flow (HDF), thermally fully developed flow (TFDF), thermally developing flow (TDF), and simultaneously developing flow (SDF) are developed. Thermal and hydrodynamic entrance models are developed by combining the asymptotic solutions for small and large values of the dimensionless duct length. Through the use of a novel characteristic length, the square root of the cross-sectional flow area, scatter in the dimensionless data for fully developed laminar flows is considerably reduced. Most numerical and analytical data are predicted within +/-10% for HFDF and TFDF, +/-12% for HDF and TDF, and +/-15% for SDF for most non-circular ducts. Simple analytic models for predicting the Fanning friction factor, f, and Colburn j factor of two common enhancement devices, the offset strip fin and the turbulator strip are developed from fundamental solutions of fluid dynamics and heat transfer. Models for the offset strip fin are valid over the full range of Reynolds numbers for rectangular and other non-circular sub-channel cross- sections. Model predictions for the offset strip fin agree with published experimental data within +/-20%. Models for the turbulator strip are valid over the full Reynolds number range for both straight and curved turbulator profiles. Model predictions for the turbulator strip agree with new experimental data to

  18. Combined Steady-State and Dynamic Heat Exchanger Experiment

    ERIC Educational Resources Information Center

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

    2009-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  20. An experimental investigation on liquid methane heat transfer enhancement through the use of longitudinal fins in cooling channels

    NASA Astrophysics Data System (ADS)

    Galvan, Manuel de Jesus

    In the past years, hydrocarbon fuels have been the focus of attention as the interest in developing reusable, high-performing liquid rocket engines has grown. Liquid methane (LCH4) has been of particular interest because of the cost, handling, and storage advantages that it presents when compared to currently used propellants. Deep space exploration requires thrusters that can operate reliably during long-duration missions. One of the challenges in the development of a reliable engine has been providing adequate combustion chamber cooling to prevent engine failure. Regenerative (regen) cooling has presented itself as an appealing option because it provides improved cooling and engine efficiency over other types of cooling, such as film or dump cooling. Due to limited availability of experimental sub-critical liquid methane cooling data for pressure-fed regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through smooth sub-scale cooling channels. In addition to investigating smooth channels, the cSETR has conducted experiments to investigate the effects of internal longitudinal fins on the heat transfer of methane. To conduct the experiments, the cSETR developed a conduction-based thermal concentrator known as the High Heat Flux Test Facility (HHFTF) in which the channels are heated. In this study, a smooth channel and three channels with longitudinal fins all with cross sectional geometries of 3.2 mm x 3.2 mm were tested. The Nusselt numbers ranged from 70 and 510, and Reynolds numbers were between 50,000 and 128,000. Sub-cooled film-boiling phenomena were discovered in the data pertaining to the smooth and two finned channels. Sub-cooled film-boiling was not

  1. Parametric study on heat transfer enhancement and pressure drop of an internal blade tip-wall with pin-fin arrays

    NASA Astrophysics Data System (ADS)

    Xie, Gongnan; Sundén, Bengt; Wang, Lieke; Utriainen, Esa

    2011-01-01

    One way to cool gas turbine tips is to design serpentine passages with 180° turns inside the blades to fully utilize the coolant potential. It is therefore a desire to improve the cooling of the blade tips to ensure a long durability and safe operation. In the present work, a two-pass channel with a 180° turn and various arrays of pin-fins mounted internally on the tip-cap is considered. The effects of pin-fin height, diameter and pitches on the heat transfer enhancement and pressure drop are investigated numerically. The nominal ratio of height to diameter (H/D) of the pin-fins is 2, and the ratio of tip clearance to pin-fin height is about 10. The inlet Reynolds numbers based on hydraulic diameter are ranging from 100,000 to 600,000. Details of the three dimensional fluid flow and heat transfer over the pin-finned tips are presented. The overall performances of various tips are compared. It is found that due to the combination of turning, impingement and pin-fin crossflow, the heat transfer coefficient of the pin-finned tips is up to a factor of 2.1 higher than that of the smooth tip. This augmentation is achieved at the expense of a penalty of pressure drop around 30%. Results show that the magnitude of the heat transfer enhancement depends upon pin-fin configuration and arrangement. It is suggested that pin-fins are suitable to enhance the blade tip heat transfer and thus to improve the tip cooling.

  2. Study on the effect of punched holes on flow structure and heat transfer of the plain fin with multi-row delta winglets

    NASA Astrophysics Data System (ADS)

    Tian, Liting; Liu, Bin; Min, Chunhua; Wang, Jin; He, Yaling

    2015-11-01

    Three dimensional numerical simulations are performed to investigate the flow and heat transfer characteristics of the plain fin with multi-row delta winglets punched out from the fin. The Reynolds number based on the tube outside diameter varies from 360 to 1440. The effects of punched holes and their orientations on flow structure and heat transfer are numerically studied. Results show that a down-wash flow is formed through the hole punched at the windward side, which has little influence on the longitudinal vortices in the main flow, and a longitudinal main vortex is formed behind each delta winglet. An up-wash flow is formed through the hole punched at the leeward side, the up-wash flow impinges the longitudinal vortices generated by the delta winglet, and then a counter-rotating pair of main vortices is generated behind each delta winglet. The windward punched holes have little effect on the flow friction and heat transfer of the plain fin with delta winglets, while the leeward punched holes deteriorate the heat transfer and decrease the flow friction of the fin channel, the Nusselt number decreases by 3.5-5.0 % with a corresponding decrease of 3.9-4.8 % in the friction factor. The effect of the punched holes on the heat transfer of the fin can be well explained by the field synergy principle. The overall analysis of the thermal performance is performed for all fin configurations, including the slit fins and the wavy fins with one-row delta winglets, the plain fin with the windward punched delta winglets shows the better thermal performance than one with the leeward punched delta winglets.

  3. Universal Monitor (UM) for OTEC compact heat exchangers

    SciTech Connect

    Kuzay, T.M.

    1981-09-01

    Universal Monitor (UM), is a device-independent concept to measure, with precision, the initiation and progression of fouling in any given OTEC Compact Heat Exchanger model with or without the application of countermeasures. Design description and supporting analyses for the Universal Monitor for OTEC Compact Heat Exchangers are presented.

  4. Investigation on the cooling performance of a compact heat exchanger using nanofluids

    NASA Astrophysics Data System (ADS)

    Abdul Jalal, M. F.; Shuaib, N. H.; Gunnasegaran, P.; Sandhita, E.

    2012-11-01

    In this paper, analysis of ethylene glycol (EG) as a base fluid with aluminum dioxide (Al2O3), diamond (DM), silicon dioxide (SiO2) and titanium dioxide (TiO2) as the coolants on compact heat exchangers (CHEs) with flattened tube plate fin is performed. By using ɛ-NTU rating method the cooling performance under cross flow arrangement of the CHEs with unmixed air and nanofluid as coolant will be investigated. The nanoparticles volume fraction φ is varied from 0 % to 4 %. The mathematical formulation, nanofluid properties and relevant input data are extracted from literatures. The CHE performance with respect to heat transfer coefficient, pressure drop and pumping power by means of MATLAB SIMULINK is investigated. The result shows that with the increase of nanoparticles volume fraction and nanofluid Reynold number, the CHE exhibits enhancement in term of heat transfer coefficient with the penalty of increase in pressure drop as well as pumping power.

  5. Cyclic high temperature heat storage using borehole heat exchangers

    NASA Astrophysics Data System (ADS)

    Boockmeyer, Anke; Delfs, Jens-Olaf; Bauer, Sebastian

    2016-04-01

    The transition of the German energy supply towards mainly renewable energy sources like wind or solar power, termed "Energiewende", makes energy storage a requirement in order to compensate their fluctuating production and to ensure a reliable energy and power supply. One option is to store heat in the subsurface using borehole heat exchangers (BHEs). Efficiency of thermal storage is increasing with increasing temperatures, as heat at high temperatures is more easily injected and extracted than at temperatures at ambient levels. This work aims at quantifying achievable storage capacities, storage cycle times, injection and extraction rates as well as thermal and hydraulic effects induced in the subsurface for a BHE storage site in the shallow subsurface. To achieve these aims, simulation of these highly dynamic storage sites is performed. A detailed, high-resolution numerical simulation model was developed, that accounts for all BHE components in geometrical detail and incorporates the governing processes. This model was verified using high quality experimental data and is shown to achieve accurate simulation results with excellent fit to the available experimental data, but also leads to large computational times due to the large numerical meshes required for discretizing the highly transient effects. An approximate numerical model for each type of BHE (single U, double U and coaxial) that reduces the number of elements and the simulation time significantly was therefore developed for use in larger scale simulations. The approximate numerical model still includes all BHE components and represents the temporal and spatial temperature distribution with a deviation of less than 2% from the fully discretized model. Simulation times are reduced by a factor of ~10 for single U-tube BHEs, ~20 for double U-tube BHEs and ~150 for coaxial BHEs. This model is then used to investigate achievable storage capacity, injection and extraction rates as well as induced effects for

  6. Circulating heat exchangers for oscillating wave engines and refrigerators

    DOEpatents

    Swift, Gregory W.; Backhaus, Scott N.

    2003-10-28

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

  7. Reactor safety research section probability of heat exchanger leaks

    SciTech Connect

    Cramer, D.S.; Shine, E.P.; Copeland, W.J.

    1992-02-01

    Three heat exchangers (HXs) were changed out after the December 1991 leak of Process Water to the Savannah River. This leaves 6 of the original 304 stainless steel heat exchangers which will remain in K-Reactor for restart. This report discusses SRS site specific data which were used to estimate the probability of a leak within a one-year period as a function of leak rate and root cause in these six heat exchangers in conjunction with six new heat exchangers presently in service in K-Reactor. Based on several assumptions and statistical models, SRS data indicate that the total probability of a leak occurring during a one-year period in K-Reactor with 6 original (304 stainless steel) and 6 new (316-L or SEA-CURE) heat exchangers, with a leak rate greater than 20, 40 or 90 pounds/hr, is 0.013, 0.004 or 0.0005, respectively.

  8. Self-defrosting recuperative air-to-air heat exchanger

    DOEpatents

    Drake, Richard L.

    1993-01-01

    A heat exchanger includes a stationary spirally or concentrically wound heat exchanger core with rotating baffles on upper and lower ends thereof. The rotating baffles include rotating inlets and outlets which are in communication with respective fixed inlets and outlets via annuli. The rotation of the baffles causes a concurrent rotation of the temperature distribution within the stationary exchanger core, thereby preventing frost build-up in some applications and preventing the formation of hot spots in other applications.

  9. Heat transfer coefficients and pressure drops for R-134a and an ester lubricant mixture in a smooth tube and a micro-fin tube

    SciTech Connect

    Eckels, S.J.; Doerr, T.M.; Pate, M.B.

    1998-10-01

    This paper reports average heat transfer coefficients and pressure drops during the evaporation and condensation of mixtures of R-134a and a 150 SUS penta erythritol ester branched-acid lubricant. The smooth tube and micro-fin tube tested in this study had outer diameters of 9.52 mm (3/8 in.). The micro-fin tube had 60 fins, a fin height of 0.2 mm (0.008 in), and a spiral angle of 18{degree}. The objective of this study is to evaluate the effectiveness of the micro-fin tube with R-134a and to determine the effect of circulating lubricant. The experimental results show that the micro-fin tube has distinct performance advantages over the smooth tube. For example, the average heat transfer coefficients during evaporation and condensation in the micro-fin tube were 50--200% higher than those for the smooth tube, while the average pressure drops were on average only 10--50% higher. The experimental results indicate that the presence of a lubricant degrades the average heat transfer coefficients during both evaporation and condensation at high lubricant concentrations. Pressure drops during evaporation increased with the addition of a lubricant in both tubes. For condensation, pressure drops were unaffected by the addition of a lubricant.

  10. On effectiveness and entropy generation in heat exchanger

    NASA Astrophysics Data System (ADS)

    Xiong, Daxi; Li, Zhixin; Guo, Zengyuan

    1996-12-01

    Some conceptual problems were discussed in the present paper. Firstly, according to the physical meaning of effectiveness, a new expression of effectiveness was developed by using an ideal heat exchanger model and temperature histogram method, in which the non-uniform inlet temperature profile was considered. Secondly, the relation of entropy generation number to effectiveness was studied, it was pointed out that both of them could express the perfect degree of a heat exchanger to the second thermodynamic law. Finally, to describe both quantity and quality of heat transferred in a heat exchanger, a criterion named as comprehensive thermal performance coefficient (CTPE) was presented.

  11. Ceramic heat-exchanger applications study

    SciTech Connect

    McFarlin, D.J.; Sgamboti, C.T.; Lessard, R.D.

    1982-10-01

    To put the potential benefits of ceramic heat exchangers (CHX) applications into quantitative perspective, several industrial cogeneration and electric utiity power generation systems were surveyed and evaluated. This study was focused on coal-based fuel fired applications, for which system performance and economic assessments were made. Seven CHX applications in the industrial cogeneration sector were selected for evaluation. These include (1) Gasified Coal-Fired Gas Turbine, (2) Pressurized Fluidized Bed Combustor (PFBC)-Gas Turbine, (3) Atmospheric Fluidized Bed Combustor (AFBC)-Gas Turbine, (4 and 5) AFBC Combined Cycle with and without reheat and (6 and 7) Indirect Coal-Fired Gas Turbine and Combined Cycle. The performance and economics of these cogeneration systems were evaluated and compared with other competing systems (both advanced and State-of-the-Art). For the electric utility power generation sector five applications utilizing a CHX were selected and evaluated; their performance and cost factors were compared to those of a reference pulverized coal-fired steam plant with flue gas desulfurization. These five applications included (1) PFBC-Combined Cycle, (2) AFBC-Combined Cycle, (3) Industrial Coal Gasifier-Combined Cycle, (4) Indirect Coal-Fired Combined Cycle, and (5) Indirect Coal-Fired Simple Cycle. Of the five CHX applications evaluated in the power generation sector, only the AFBC system showed a clear gain over the reference pulverized coal system.

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

    SciTech Connect

    Skupinski, R.C.; Tower, L.K.; Madi, F.J.; Brusk, K.D.

    1993-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  14. Optimized heat exchanger unit in a thermoacoustic refrigerator

    NASA Astrophysics Data System (ADS)

    El-Fawal, Mawahib Hassan; Mohd-Ghazali, Normah

    2012-06-01

    Due to concern over the environmental impact caused by hazardous refrigerants, the last ten years or so has seen increasing research into thermoacoustic refrigeration. A thermoacoustic refrigerator is a device which uses acoustic power to pump heat. It holds the merits of simple mechanical design, absence of harmful refrigerants and having no or few moving parts. However, the performance of the thermoacoustic refrigerator, particularly the standing wave types, is currently not competitive compared to its counterpart conventional vapor-compression refrigerator. Thermoacoustic refrigeration prototypes, built up-to-date, achieved 0.1-0.2 relative coefficient of performance (COPR) compared with that of 0.33-0.5 for the conventional vapor-compression refrigerators. The poor heat exchanger design is one of the reasons for this poor efficiency. This paper discussed the influence of the thermoacoustic refrigerator heat exchanger's parameters on its design and the optimization of the performance of the system using the Lagrange multiplier method. The results showed that, the dissipated power is less than the published value by about 49% in the cold heat exchanger and about 38.5% in the hot heat exchanger. Furthermore, the increase of the cold heat exchanger effectiveness is found to be 3%. Thus, the decrease in the dissipated power in both heat exchangers with effective cold heat exchanger increases the performance of the thermoacoustic refrigerator.

  15. An apparatus for the testing of small cryogenic heat exchangers

    NASA Astrophysics Data System (ADS)

    Venkatarathnam, G.; Sarangi, Sunil

    1996-02-01

    Most cryogenic processes demand high effectiveness heat exchangers. The performance of these exchangers is determined not only by convective heat transfer resistance, but also by other irreversibilities such as axial conduction, flow maldistribution, heat transfer with surroundings, and finite number of lateral heat transfer paths. While determination of heat transfer correlations for exchanger cores is sufficient in most conventional applications, high-Ntu cryogenic exchangers must be tested under true operating conditions. As a part of our matrix heat exchanger development program, an apparatus has been constructed for testing small, compact heat exchangers at low temperature. The apparatus, enclosed in a vacuum vessel, provides a variable cold end temperature and means for direct measurement of ineffectiveness. Temperature approaches at both ends and pressure drop in both channels are also measured. The construction of the apparatus as well as the instrumentation and data acquisition methods are discussed. The results of a test on a small matrix heat exchanger using the test apparatus are also presented.

  16. Heat exchanger and method of making. [rocket lining

    NASA Technical Reports Server (NTRS)

    Fortini, A.; Kazaroff, J. M. (Inventor)

    1980-01-01

    A heat exchange of increased effectiveness is disclosed. A porous metal matrix is disposed in a metal chamber or between walls through which a heat-transfer fluid is directed. The porous metal matrix has internal bonds and is bonded to the chamber in order to remove all thermal contact resistance within the composite structure. Utilization of the invention in a rocket chamber is disclosed as a specific use. Also disclosed is a method of constructing the heat exchanger.

  17. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    SciTech Connect

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm{sup -3} (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial Si

  18. Direct-contact closed-loop heat exchanger

    DOEpatents

    Berry, Gregory F.; Minkov, Vladimir; Petrick, Michael

    1984-01-01

    A high temperature heat exchanger with a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

  19. Computer model studies of a solar cooker: A finned pot

    SciTech Connect

    Pejack, E.R.

    1992-12-31

    A mathematical model of a box-type solar cooker, accounting for the solar energy input and internal heat exchange among the pot, walls, top cover and air has been developed and reported earlier. The model considers the variable sun angle and intensity, box and reflector orientation, heat losses, cooking time, wind, and other variables. In the present application of the model, an extended surface, or fin, is attached to the pot. The fin acts to increase the direct solar radiation to the pot-fin system as well as add surface area for convection from the air in the box. Results for specific geometries of fins with variable length and thickness show that the food temperatures can be appreciably increased with the finned pot.

  20. Thermal management optimization of an air-cooled Li-ion battery module using pin-fin heat sinks for hybrid electric vehicles

    NASA Astrophysics Data System (ADS)

    Mohammadian, Shahabeddin K.; Zhang, Yuwen

    2015-01-01

    Three dimensional transient thermal analysis of an air-cooled module that contains prismatic Li-ion cells next to a special kind of aluminum pin fin heat sink whose heights of pin fins increase linearly through the width of the channel in air flow direction was studied for thermal management of Lithium-ion battery pack. The effects of pin fins arrangements, discharge rates, inlet air flow velocities, and inlet air temperatures on the battery were investigated. The results showed that despite of heat sinks with uniform pin fin heights that increase the standard deviation of the temperature field, using this kind of pin fin heat sink compare to the heat sink without pin fins not only decreases the bulk temperature inside the battery, but also decreases the standard deviation of the temperature field inside the battery as well. Increasing the inlet air temperature leads to decreasing the standard deviation of the temperature field while increases the maximum temperature of the battery. Furthermore, increasing the inlet air velocity first increases the standard deviation of the temperature field till reaches to the maximum point, and after that decreases. Also, increasing the inlet air velocity leads to decrease in the maximum temperature of the battery.

  1. Fin-efficiency calculation for condensation in the presence of noncondensable gases

    NASA Astrophysics Data System (ADS)

    Panchal, C. B.

    Plate-fin heat exchangers are being considered for many condenser applications. They are commonly used for the gas-separation process because they can provide a high thermal performance to obtain a low mean-temperature difference, essential for the gas-separation process. Plate-fin heat exchangers are also considered for the heat-pump system using nonazeotropic refrigerant mixtures. The brazed plate-fin condenser was considered to be a leading candidate for the Ocean Thermal Energy Conversion (OTEC) system, where high-performance heat exchangers are essential for maintaining a low mean-temperature difference. Calculation of the fin efficiency is difficult for condensation in the presence of noncondensable gases due to the spatial variation of the interfacial temperature. An analysis was carried out to develop a simplified method to calculate the fin efficiency for condensation of a vapor in the presence of noncondensable gases. The analysis includes the variation in the interfacial temperature along the fin surface. Appropriate assumptions are made to simplify the coupled heat-conduction equation in the fin and the heat/mass fluxes at the interface. The resulting expression for the fin efficiency includes mass-flux parameters, and it is similar to the common expression used for single-phase flow.

  2. Temperature distribution in internally heated walls of heat exchangers composed of nonnuclear flow passages

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Low, George M

    1951-01-01

    In the walls of heat exchangers composed of noncircular passages, the temperature varies in the circumferential direction because of local variations of the heat-transfer coefficients. A prediction of the magnitude of this variation is necessary in order to determine the region of highest temperature and in order to determine the admissible operating temperatures. A method for the determination of these temperature distributions and of the heat-transfer characteristics of a special type of heat exchanger is developed. The heat exchanger is composed of polygonal flow passages and the passage walls are uniformly heated by internal heat sources. The coolant flow within the passages is assumed to be turbulent. The circumferential variation of the local heat-transfer coefficients is estimated from flow measurements made by Nikuradse, postulating similarity between velocity and temperature fields. Calculations of temperature distributions based on these heat-transfer coefficients are carried out and results for heat exchangers with triangular and rectangular passages are presented.

  3. Comparison of natural convection heat exchangers for solar water heating systems

    SciTech Connect

    Davidson, J.; Liu, W.

    1998-09-15

    Thermosyphon heat exchangers are used in indirect solar water heating systems to avoid using a pump to circulate water from the storage tank to the heat exchanger. In this study, the authors consider the effect of heat exchanger design on system performance. They also compare performance of a system with thermosyphon flow to the same system with a 40W pump in the water loop. In the first part of the study, the authors consider the impact of heat exchanger design on the thermal performance of both one- and two-collector solar water heaters. The comparison is based on Solar Rating and Certification Corporation (SRCC) OG300 simulations. The thermosyphon heat exchangers considered are (1) a one-pass, double wall, 0.22 m{sup 2}, four tube-in-shell heat exchanger manufactured by AAA Service and Supply, Inc., (the Quad-Rod); (2) a two-pass, double wall, 0.2 m{sup 2}, tube-in-shell made by Heliodyne, Inc., but not intended for commercial development; (3) a one-pass, single wall, 0.28 m{sup 2}, 31 tube-in-shell heat exchanger from Young Radiator Company, and (4) a one-pass single-wall, 0.61 m{sup 2}, four coil-in-shell heat exchanger made by ThermoDynamics Ltd. The authors compare performance of the systems with thermosyphon heat exchangers to a system with a 40 W pump used with the Quad-Rod heat exchanger. In the second part of the study, the effects of reducing frictional losses through the heat exchanger and/or the pipes connecting the heat exchanger to the storage tank, and increasing heat transfer area are evaluated in terms of OG300 ratings.

  4. Exergy Transfer Characteristics on Low Temperature Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Wu, S. Y.; Yuan, X. F.; Li, Y. R.; Peng, L.

    By analyzing exergy transfer process of the low temperature heat exchangers operating below the surrounding temperature, the concept of exergy transfer coefficient is put forward and the expressions which involving relevant variables for the exergy transfer coefficient, the heat transfer units number and the ratio of cold to hot fluids heat capacity rate, etc. are derived. Taking the parallel flow, counter flow and cross flow low temperature heat exchangers as examples, the numerical results of exergy transfer coefficient are given and the comparison of exergy transfer coefficient with heat transfer coefficient is analyzed.

  5. Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump

    DOEpatents

    Phillips, Benjamin A.; Zawacki, Thomas S.; Marsala, Joseph

    1994-11-29

    Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium.

  6. Physical explosion analysis in heat exchanger network design

    NASA Astrophysics Data System (ADS)

    Pasha, M.; Zaini, D.; Shariff, A. M.

    2016-06-01

    The failure of shell and tube heat exchangers is being extensively experienced by the chemical process industries. This failure can create a loss of production for long time duration. Moreover, loss of containment through heat exchanger could potentially lead to a credible event such as fire, explosion and toxic release. There is a need to analyse the possible worst case effect originated from the loss of containment of the heat exchanger at the early design stage. Physical explosion analysis during the heat exchanger network design is presented in this work. Baker and Prugh explosion models are deployed for assessing the explosion effect. Microsoft Excel integrated with process design simulator through object linking and embedded (OLE) automation for this analysis. Aspen HYSYS V (8.0) used as a simulation platform in this work. A typical heat exchanger network of steam reforming and shift conversion process was presented as a case study. It is investigated from this analysis that overpressure generated from the physical explosion of each heat exchanger can be estimated in a more precise manner by using Prugh model. The present work could potentially assist the design engineer to identify the critical heat exchanger in the network at the preliminary design stage.

  7. Tube vibration in industrial-size test heat exchanger (90/sup 0/ square layout)

    SciTech Connect

    Halle, H.; Wambsganss, M.W.

    1983-02-01

    Tube vibrations in heat exchangers are being systematically investigated in a series of tests performed with an industrial-size test exchanger. Results from waterflow tests of eleven different tube bundles, in six- and eight-crosspass configurations on a 90/sup 0/ square layout with a pitch-to-diameter ratio of 1.25 are reported. The test cases include full tube bundles, no-tubes-in-window bundles, finned tube bundles, and proposed field and design fixes. The testing focused on identification of the lowest critical flowrate to initiate fluidelastic instability (large amplitude tube motion) and the location within the bundle of the tubes which first experience instability. The test results are tabulated to permit comparison with results obtained from previous tests with a 30/sup 0/ triangular layout tube bundle. Instability criteria are evaluated preliminarily. Pressure drop data are also generated and reported.

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

    ERIC Educational Resources Information Center

    Corbett, Robert J.; Miller, Barbara

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

  9. On boundary condition in heat-exchange processes

    NASA Astrophysics Data System (ADS)

    Stolyarov, E. P.

    2016-10-01

    This paper describes the numerical study of heat-exchange of solid body with high-temperature external flow. As follows from the Newton's boundary condition, connecting a heat-flux density with temperature difference between the flow and a body, the heat-exchange coefficient is physically equivalent to the body-surface-normal component of the entropy flux from external flow at equilibrium flow regime. The method of determination of the heat-exchange characteristics using the time-history temperature measurements by a thin-film thermocouple sensor is described. As it is shown from the numerical analysis, the asymptotic value of the heat-exchange coefficient that corresponded to equilibrium regime of external flow exists. Implementation time of this value, i.e. relaxation time, may be of some characteristic time scales of the sensor measuring layer.

  10. The predictive protective control of the heat exchanger

    NASA Astrophysics Data System (ADS)

    Nevriva, Pavel; Filipova, Blanka; Vilimec, Ladislav

    2016-06-01

    The paper deals with the predictive control applied to flexible cogeneration energy system FES. FES was designed and developed by the VITKOVICE POWER ENGINEERING joint-stock company and represents a new solution of decentralized cogeneration energy sources. In FES, the heating medium is flue gas generated by combustion of a solid fuel. The heated medium is power gas, which is a gas mixture of air and water steam. Power gas is superheated in the main heat exchanger and led to gas turbines. To protect the main heat exchanger against damage by overheating, the novel predictive protective control based on the mathematical model of exchanger was developed. The paper describes the principle, the design and the simulation of the predictive protective method applied to main heat exchanger of FES.

  11. Microchannel crossflow fluid heat exchanger and method for its fabrication

    DOEpatents

    Swift, G.W.; Migliori, A.; Wheatley, J.C.

    1982-08-31

    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.

  12. Microchannel crossflow fluid heat exchanger and method for its fabrication

    DOEpatents

    Swift, Gregory W.; Migliori, Albert; Wheatley, John C.

    1985-01-01

    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.

  13. Microchannel crossflow fluid heat exchanger and method for its fabrication

    DOEpatents

    Swift, G.W.; Migliori, A.; Wheatley, J.C.

    1985-05-14

    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. 9 figs.

  14. Acoustically enhanced heat exchange and drying apparatus

    DOEpatents

    Bramlette, T.T.; Keller, J.O.

    1987-07-10

    A heat transfer drying apparatus includes an acoustically augmented heat transfer chamber for receiving material to be dried. The chamber includes a first heat transfer gas inlet, a second heat transfer gas inlet, a material inlet, and a gas outlet which also serves as a dried material and gas outlet. A non-pulsing first heat transfer gas source provides a first drying gas to the acoustically augmented heat transfer chamber through the first heat transfer gas inlet. A valveless, continuous second heat transfer gas source provides a second drying gas to the acoustically augmented heat transfer chamber through the second heat transfer gas inlet. The second drying gas also generates acoustic waves which bring about acoustical coupling with the gases in the acoustically augmented heat transfer chamber. The second drying gas itself oscillates at an acoustic frequency of approximately 180 Hz due to fluid mechanical motion in the gas. The oscillations of the second heat transfer gas coupled to the first heat transfer gas in the acoustically augmented heat transfer chamber enhance heat and mass transfer by convection within the chamber. 3 figs.

  15. Chromate/silicate aluminum surface treatment for heat exchangers

    SciTech Connect

    Patel, B.B.; Ramo, S.J. Jr.

    1993-08-10

    A process is described for surface treating an aluminum heat exchanger by successively immersing the heat exchanger within a series of chemical solutions to provided the heat exchanger with a corrosive-resistent hydrophilic coating; the process comprising the steps of: providing a cleaning mixture including 40 to 60 weight percent of nitric acid and 1 to 5 weight percent of sodium fluoride, adding water to the cleaning mixture to form an aqueous cleaning solution having a total concentration of cleaning mixture between 2.0 to 5.0 weight percent; providing a chromate mixture including 10 weight percent of chromium trioxide, 25 weight percent of nitric acid and between 10 to 11 weight percent of hydrofluoric acid, providing a chromate activator comprising less than 25 weight percent of molybdic acid and disodium salt, adding water and the chromate activator to the chromate mixture to form an aqueous chromate solution; providing a silicate mixture comprising 90 to 100 weight percent of silicate of soda and 0 to 10 weight percent of potassium hydroxide, adding water to the silicate mixture to form an aqueous silicate solution; immersing the heat exchanger within an aqueous cleaning solution, and removing the heat exchanger from the cleaning solution; immersing the cleansed heat exchanger in the aqueous chromate solution, and removing the heat exchanger from the chromate solution; immersing the chromed heat exchanger in the aqueous silicate solution, and subsequently removing the heat exchanger from the silicate solution; and characterized by maintaining the total concentration of chromate mixture within the aqueous chromate solution at 0.9 to 1.5 weight percent ([plus minus] 0.1%) and the total concentration of chromate activator within the aqueous chromate solution at 1.1 weight percent ([plus minus] 0.1 %) thereby providing the necessary chemical concentration for producing a corrosion-resistent hydrophilic coating which is substantially free from musty odor emission.

  16. Study on the Heat-Flow Controllable Heat Exchanger-3rd report

    NASA Astrophysics Data System (ADS)

    Ishikawa, Osamu; Hamano, Masayoshi; Yanadori, Michio

    The heat-flow controllable heat exchanger for the purpose of heat recovery through the waste hot water at the bathroom and the washing room has been developed. The system is especially available at the house of cold area and the recovery heat is used to warm the suction air conducted from ventilation device. As the result of field test, it is clarified that the heat recovery rate by the system is very large. Also, the exchanger is possible to control the amount of recorery heat. Therefore, it is considered that the exchanger is applicable in the ventilation systems used the waste hot water.

  17. Wire-packed heat exchangers for dilution refrigerators.

    PubMed

    Polturak, E; Rappaport, M; Rosenbaum, R

    1978-03-01

    Very simple wire-packed step heat exchangers for dilution refrigerators are described. No sintering is used in fabrication. Flow impedances and thermal resistance between the liquid and the copper wires are low. A refrigerator with five wire-packed heat exchangers in addition to a countercurrent heat exchanger attains a temperature of 11.4 mK with a single mixing chamber and 6.1 mK with two mixing chambers. High cooling power is achieved at modest (3)He circulation rates. PMID:18699084

  18. Control strategies in a thermal oil - Molten salt heat exchanger

    NASA Astrophysics Data System (ADS)

    Roca, Lidia; Bonilla, Javier; Rodríguez-García, Margarita M.; Palenzuela, Patricia; de la Calle, Alberto; Valenzuela, Loreto

    2016-05-01

    This paper presents a preliminary control scheme for a molten salt - thermal oil heat exchanger. This controller regulates the molten salt mass flow rate to reach and maintain the desired thermal oil temperature at the outlet of the heat exchanger. The controller architecture has been tested using an object-oriented heat exchanger model that has been validated with data from a molten salt testing facility located at CIEMAT-PSA. Different simulations are presented with three different goals: i) to analyze the controller response in the presence of disturbances, ii) to demonstrate the benefits of designing a setpoint generator and iii) to show the controller potential against electricity price variations.

  19. Heat exchanger and water tank arrangement for passive cooling system

    DOEpatents

    Gillett, J.E.; Johnson, F.T.; Orr, R.S.; Schulz, T.L.

    1993-11-30

    A water storage tank in the coolant water loop of a nuclear reactor contains a tubular heat exchanger. The heat exchanger has tube sheets mounted to the tank connections so that the tube sheets and tubes may be readily inspected and repaired. Preferably, the tubes extend from the tube sheets on a square pitch and then on a rectangular pitch there between. Also, the heat exchanger is supported by a frame so that the tank wall is not required to support all of its weight. 6 figures.

  20. Antioxidant and Antiproliferative Activities of Heated Sterilized Pepsin Hydrolysate Derived from Half-Fin Anchovy (Setipinna taty)

    PubMed Central

    Song, Ru; Wei, Rongbian; Zhang, Bin; Yang, Zuisu; Wang, Dongfeng

    2011-01-01

    In this paper we studied the antioxidant and antiproliferative activities of the heated pepsin hydrolysate from a marine fish half-fin anchovy (HAHp-H). Furthermore, we compared the chemical profiles including the amino acid composition, the browning intensity, the IR and UV-visible spectra, and the molecular weight distribution between the half-fin anchovy pepsin hydrolysate (HAHp) and HAHp-H. Results showed that heat sterilization on HAHp improved the 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical-scavenging activity and reducing power. In addition, the antiproliferative activities were all increased for HAHp-H on DU-145 human prostate cancer cell line, 1299 human lung cancer cell line and 109 human esophagus cancer cell line. The contents of free amino acid and reducing sugar of HAHp-H were decreased (P < 0.05). However, hydrophobic amino acid residues and the browning intensity of HAHp-H were increased. FT-IR spectroscopy indicated that amide I and amide III bands of HAHp-H were slightly modified, whereas band intensity of amide II was reduced dramatically. Thermal sterilization resulted in the increased fractions of HAHp-H with molecular weight of 3000–5000 Da and below 500 Da. The enhanced antioxidant and antiproliferative activities of HAHp-H might be attributed to the Maillard reaction. PMID:21747752

  1. Low Cost Polymer heat Exchangers for Condensing Boilers

    SciTech Connect

    Butcher, Thomas; Trojanowski, Rebecca; Wei, George; Worek, Michael

    2015-09-30

    Work in this project sought to develop a suitable design for a low cost, corrosion resistant heat exchanger as part of a high efficiency condensing boiler. Based upon the design parameters and cost analysis several geometries and material options were explored. The project also quantified and demonstrated the durability of the selected polymer/filler composite under expected operating conditions. The core material idea included a polymer matrix with fillers for thermal conductivity improvement. While the work focused on conventional heating oil, this concept could also be applicable to natural gas, low sulfur heating oil, and biodiesel- although these are considered to be less challenging environments. An extruded polymer composite heat exchanger was designed, built, and tested during this project, demonstrating technical feasibility of this corrosion-resistant material approach. In such flue gas-to-air heat exchangers, the controlling resistance to heat transfer is in the gas-side convective layer and not in the tube material. For this reason, the lower thermal conductivity polymer composite heat exchanger can achieve overall heat transfer performance comparable to a metal heat exchanger. However, with the polymer composite, the surface temperature on the gas side will be higher, leading to a lower water vapor condensation rate.

  2. Heat exchanger for reactor core and the like

    DOEpatents

    Kaufman, Jay S.; Kissinger, John A.

    1986-01-01

    A compact bayonet tube type heat exchanger which finds particular application as an auxiliary heat exchanger for transfer of heat from a reactor gas coolant to a secondary fluid medium. The heat exchanger is supported within a vertical cavity in a reactor vessel intersected by a reactor coolant passage at its upper end and having a reactor coolant return duct spaced below the inlet passage. The heat exchanger includes a plurality of relatively short length bayonet type heat exchange tube assemblies adapted to pass a secondary fluid medium therethrough and supported by primary and secondary tube sheets which are releasibly supported in a manner to facilitate removal and inspection of the bayonet tube assemblies from an access area below the heat exchanger. Inner and outer shrouds extend circumferentially of the tube assemblies and cause the reactor coolant to flow downwardly internally of the shrouds over the tube bundle and exit through the lower end of the inner shroud for passage to the return duct in the reactor vessel.

  3. AN ASSESSMENT OF THE STATE OF THE ART, AND POTENTIAL DESIGN IMPROVEMENTS, FOR FLAT-TUBE HEAT EXCHANGERS IN AIR CONDITIONING AND REFRIGERATION APPLICATIONS - PHASE I

    SciTech Connect

    Jacobi, A.M.; Park, Y.; Tafti, D.; Zhang, X.

    2001-09-30

    Project objective is to evaluate the air-side heat transfer and pressure-drop performance of serpentine-fin, flat-tube heat exchangers. This assessment is conducted for smooth, corrugated, and interrupted fins, over a wide range of geometric and operating parameters, spanning HVAC and R applications. The performance of serpentine-fin, flat-tube exchangers is compared to that of conventional round-tube designs, which are considered the technology baseline. The research includes a literature review, a preliminary comparison of flat-tube to round-tube performance, a computational fluid dynamic study of flow through the heat exchangers, and complementary modeling to predict the performance of flat-tube designs over a wide range of conditions. Recommendations are provided for a new experimental study to provide performance data for dry, wet, and frosted-surface conditions. Specific flow visualization and naphthalene sublimation experiments are recommended to understand the flow and heat transfer interactions in the flat-tube geometry. These data could be used to evaluate condensate retention and frost-formation effects on flat-tube heat exchanger performance, and to compare this behavior to that of the conventional round-tube geometry. These findings will be highly valuable to design and development engineers as they work toward the next generation of highly compact, energy efficient HVAC and R systems.

  4. Process Heat Exchanger Options for the Advanced High Temperature Reactor

    SciTech Connect

    Piyush Sabharwall; Eung Soo Kim; Michael McKellar; Nolan Anderson

    2011-06-01

    The work reported herein is a significant intermediate step in reaching the final goal of commercial-scale deployment and usage of molten salt as the heat transport medium for process heat applications. The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production and process heat application, which would support large-scale deployment.

  5. Process Heat Exchanger Options for Fluoride Salt High Temperature Reactor

    SciTech Connect

    Piyush Sabharwall; Eung Soo Kim; Michael McKellar; Nolan Anderson

    2011-04-01

    The work reported herein is a significant intermediate step in reaching the final goal of commercial-scale deployment and usage of molten salt as the heat transport medium for process heat applications. The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production and process heat application, which would support large-scale deployment.

  6. Acoustically enhanced heat exchange and drying apparatus

    DOEpatents

    Bramlette, T. Tazwell; Keller, Jay O.

    1989-01-01

    A heat transfer apparatus includes a first chamber having a first heat transfer gas inlet, a second heat transfer gas inlet, and an outlet. A first heat transfer gas source provides a first gas flow to the first chamber through the first heat transfer gas inlet. A second gas flow through a second chamber connected to the side of the first chamber, generates acoustic waves which bring about acoustical coupling of the first and second gases in the acoustically augmented first chamber. The first chamber may also include a material inlet for receiving material to be dried, in which case the gas outlet serves as a dried material and gas outlet.

  7. Proceedings: Fifth EPRI Balance-of-Plant Heat Exchanger NDE Symposium

    SciTech Connect

    1998-10-01

    This publication is a compilation of the agenda and material presented at the Fifth EPRI Steam Balance-of-Plant Heat Exchanger NDE Symposium which was held on June 15-17, 1997 at Lake Tahoe, Nevada. Along with the proceedings of the symposium, an attendance list is included in this document. The topics that are presented in the symposium are included in this publication in a Plenary Session and Sessions 1, 2, 3 and 4. An overview of the American Society for Nondestructive Testing (ASNT) Central Certification Program is presented in the Plenary Session. The following is a sampling of titles presented in the other sessions: An Engineer's Guide to Eddy Current Testing; ID Pit Sizing in a Carbon Steel Tubed Fuel Oil Storage Transfer Heater; Pilgrim Feedwater Heater Tube Repair; Through the Tube Plugging Application for Once Through Heat Exchangers; PFEC Inspection Method for Detection and Sizing of Uniform Wall Thinning; Some Characteristics of Pulsed Eddy Current Technique in Ferromagnetic Heat Exchanger Tubing; Utility Perspective on PC Based Database Management and Analysis Software; and NDE Demonstration and Inspection of Ginna Power Plant Moisture Separator Finned Tubing.

  8. Oscillating side-branch enhancements of thermoacoustic heat exchangers

    DOEpatents

    Swift, Gregory W.

    2003-05-13

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

  9. 1-MWE heat exchangers for OTEC. Final design report

    SciTech Connect

    Sprouse, A.M.

    1980-06-19

    The design of a 1 MWe OTEC heat exchanger is documented, including the designs of the evaporator and associated systems, condenser, instrumentation, and materials for corrosion/erosion control and fabrication processes. (LEW)

  10. Various methods to improve heat transfer in exchangers

    NASA Astrophysics Data System (ADS)

    Pavel, Zitek; Vaclav, Valenta

    2015-05-01

    The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.

  11. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Surgical Devices § 870.4240 Cardiopulmonary..., consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood...

  12. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Surgical Devices § 870.4240 Cardiopulmonary..., consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood...

  13. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Surgical Devices § 870.4240 Cardiopulmonary..., consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood...

  14. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Surgical Devices § 870.4240 Cardiopulmonary..., consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood...

  15. 21 CFR 870.4240 - Cardiopulmonary bypass heat exchanger.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (CONTINUED) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Surgical Devices § 870.4240 Cardiopulmonary..., consisting of a heat exchange system used in extracorporeal circulation to warm or cool the blood...

  16. 40 CFR 63.654 - Heat exchange systems.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 63.654 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FOR SOURCE CATEGORIES (CONTINUED) National Emission Standards for Hazardous Air Pollutants From Petroleum Refineries § 63.654 Heat exchange...

  17. Heat exchanger identification by using iterative fuzzy observers

    NASA Astrophysics Data System (ADS)

    Lalot, Sylvain; Guðmundsson, Oddgeir; Pálsson, Halldór; Pálsson, Ólafur Pétur

    2016-05-01

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

  18. Fouling of carbon steel heat exchanger caused by iron bacteria

    SciTech Connect

    Starosvetsky, J.; Armon, R.; Starosvetsky, D. ); Groysman, A.

    1999-01-01

    A carbon steel heat exchanger installed in a reverse osmosis unit failed after 1 1/2 years from start-up as a result of tubes, lids, tube sheets, and connection pipes clogging from rust deposits. Chemical analysis of cooling water and scraped precipitates, as well laboratory screening of the deposits for bacteria, revealed that activity of iron-oxidizing bacteria present in cooling water could lead to heat exchanger blockage.

  19. A simplified model of heat transfer in heat exchangers and stack plates of thermoacoustic refrigerators

    NASA Astrophysics Data System (ADS)

    Herman, Cila; Chen, Yuwen

    2006-08-01

    A simplified model of heat transfer was developed to investigate the thermal behavior of heat exchangers and stack plates of thermoacoustic devices. The model took advantage of previous results describing the thermal behavior of the thermoacoustic core and heat transfer in oscillating flow to study the performance of heat exchangers attached to the core. The configuration considered is a flat tube (with a working fluid flowing in the tube) of the thickness of the stack plate attached to both ends of the stack plate. Geometrical and operational parameters as well as thermophysical properties of the heat exchangers, transport fluids in the heat exchangers, stack plate and the thermoacoustic working fluid were organized into dimensionless groups that allowed accounting for their impact on the performance of the heat exchangers. Two types of thermal boundary conditions were considered: constant temperature and constant heat flux along the heat exchanger tubes. Numerical simulations were carried out with the model introduced in the paper. The temperature distributions and heat fluxes near the edge of the stack plate were found to be nonlinear. The influence of system parameters on the thermal performance of the heat exchangers was analyzed.

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

    NASA Astrophysics Data System (ADS)

    Harche, Rima; Mouheb, Abdelkader; Absi, Rafik

    2016-05-01

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

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

    SciTech Connect

    Dahl, S.D.; Davidson, J.H.

    1995-11-01

    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.

  2. Selection and costing of heat exchangers. Air-cooled type

    NASA Astrophysics Data System (ADS)

    1994-12-01

    ESDU 94043 extends the information in ESDU 92013 which, when an air-cooled exchanger is found appropriate and is costed, provides the results for a datum design 40 ft (12.2 m) long with G-fins and 1 in (25 mm) diameter tube operating at a noise level of 85 dBa. It provides factors derived from an analysis of manufacturer's data to be applied to the cost results from ESDU 92013 to account for variations in those parameters and features. Additional guidance on the configuration and use of air-cooled exchangers is given. The data are incorporated in ESDUpac A9213 which is a Fortran program that implements the selection and costing method of ESDU 92013. It is provided on disc in the software volume compiled to run under DOS with a user-friendly interface that prompts on screen for input data.

  3. Investigations of heat transfer, entropy generation and pressure build up for upward flow in a vertical channel equipped with a fin array

    NASA Astrophysics Data System (ADS)

    Nemitallah, Medhat A.; Zohir, Alaa E.

    2016-09-01

    The optimal thermal systems design criteria by maximizing the amount of heat transfer per pressure losses is a very important topic. In this work, flow and convection and radiation heat transfer characteristics are studied numerically for a flow in a vertical channel equipped with transverse fin array. The influences of fin height on heat transfer characteristics and fluid flow is investigated. Large number of fins is used (40 fins) in order to reach the fully developed conditions after few fins from the entrance. Based on the calculated data of temperature and velocity, the local entropy generation is calculated through the whole channel by solving the entropy generation equation. The results are validated against the available data in the literature and both results are in a good agreement. Optimizations for flow conditions and channel geometry are performed in order to obtain maximum heat transfer per pumping power losses. The results showed that the highest values of total heat transfer per pumping power losses are obtained at fin height to the gap width values of 0.1 and 0.3. The effect of heat transfer by radiation on entropy generation is examined and, the effect of the ratio, Gr/Re2, on the pressure field is also investigated. It was found that a positive pressure gradient appears downstream in the channel when the value of Gr/Re2 exceeds a certain limit. For Gr/Re2 values between 0 and 9, the pressure gradient is negative; however, when the value Gr/Re2 exceeds 9, the pressure starts to build up through the channel axis.

  4. Fast reactor power plant design having heat pipe heat exchanger

    DOEpatents

    Huebotter, P.R.; McLennan, G.A.

    1984-08-30

    The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

  5. Fast reactor power plant design having heat pipe heat exchanger

    DOEpatents

    Huebotter, Paul R.; McLennan, George A.

    1985-01-01

    The invention relates to a pool-type fission reactor power plant design having a reactor vessel containing a primary coolant (such as liquid sodium), and a steam expansion device powered by a pressurized water/steam coolant system. Heat pipe means are disposed between the primary and water coolants to complete the heat transfer therebetween. The heat pipes are vertically oriented, penetrating the reactor deck and being directly submerged in the primary coolant. A U-tube or line passes through each heat pipe, extended over most of the length of the heat pipe and having its walls spaced from but closely proximate to and generally facing the surrounding walls of the heat pipe. The water/steam coolant loop includes each U-tube and the steam expansion device. A heat transfer medium (such as mercury) fills each of the heat pipes. The thermal energy from the primary coolant is transferred to the water coolant by isothermal evaporation-condensation of the heat transfer medium between the heat pipe and U-tube walls, the heat transfer medium moving within the heat pipe primarily transversely between these walls.

  6. Capillary pumped loop body heat exchanger

    NASA Technical Reports Server (NTRS)

    Swanson, Theodore D. (Inventor); Wren, deceased, Paul (Inventor)

    1998-01-01

    A capillary pumped loop for transferring heat from one body part to another body part, the capillary pumped loop comprising a capillary evaporator for vaporizing a liquid refrigerant by absorbing heat from a warm body part, a condenser for turning a vaporized refrigerant into a liquid by transferring heat from the vaporized liquid to a cool body part, a first tube section connecting an output port of the capillary evaporator to an input of the condenser, and a second tube section connecting an output of the condenser to an input port of the capillary evaporator. A wick may be provided within the condenser. A pump may be provided between the second tube section and the input port of the capillary evaporator. Additionally, an esternal heat source or heat sink may be utilized.

  7. Self-defrosting recuperative air-to-air heat exchanger

    DOEpatents

    Drake, R.L.

    1993-12-28

    A heat exchanger is described which includes a stationary spirally or concentrically wound heat exchanger core with rotating baffles on upper and lower ends thereof. The rotating baffles include rotating inlets and outlets which are in communication with respective fixed inlets and outlets via annuli. The rotation of the baffles causes a concurrent rotation of the temperature distribution within the stationary exchanger core, thereby preventing frost build-up in some applications and preventing the formation of hot spots in other applications. 3 figures.

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

    SciTech Connect

    Squires, B.

    1992-11-01

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

  9. Advanced heat-pipe heat exchanger and microprocessor-based modulating burner controls development

    NASA Astrophysics Data System (ADS)

    Lowenstein, A.; Cohen, B.; Feldman, S.; Spatz, M.; Smith, E.

    1986-03-01

    The development of a novel condensing heat exchanger, a modulating gas burner, and a zone-controlled residential warm-air heating system is described. The condensing heat exchanger uses ten thermosyphons which are manifolded at both the condenser and evaporator ends to achieve a compact low-cost design. Initial tests have demonstrated a + 92 percent steady-state efficiency for a conventional clamshell furnace operating with the thermosyphon heat exchanger located outside the furnace cabinet. A 100,000 -Btu/hr modulating burner has also been developed. Comprehensive study of the burner's operating characteristics has produced guidelines for the design and application of the device. Finally, the modulating burner has been incorporated into a zone-controlled heating system. In parallel with the development of the preceding heating system components, the performance of thermosyphons over a wide range of operating conditions is being explored with the objective of improving design procedures for incorporating these devices into heat exchangers.

  10. Technology Development Roadmap for the Advanced High Temperature Reactor Secondary Heat Exchanger

    SciTech Connect

    P. Sabharwall; M. McCllar; A. Siahpush; D. Clark; M. Patterson; J. Collins

    2012-09-01

    This Technology Development Roadmap (TDRM) presents the path forward for deploying large-scale molten salt secondary heat exchangers (MS-SHX) and recognizing the benefits of using molten salt as the heat transport medium for advanced high temperature reactors (AHTR). This TDRM will aid in the development and selection of the required heat exchanger for: power production (the first anticipated process heat application), hydrogen production, steam methane reforming, methanol to gasoline production, or ammonia production. This TDRM (a) establishes the current state of molten salt SHX technology readiness, (b) defines a path forward that systematically and effectively tests this technology to overcome areas of uncertainty, (c) demonstrates the achievement of an appropriate level of maturity prior to construction and plant operation, and (d) identifies issues and prioritizes future work for maturing the state of SHX technology. This study discusses the results of a preliminary design analysis of the SHX and explains the evaluation and selection methodology. An important engineering challenge will be to prevent the molten salt from freezing during normal and off-normal operations because of its high melting temperature (390°C for KF ZrF4). The efficient transfer of energy for industrial applications depends on the ability to incorporate cost-effective heat exchangers between the nuclear heat transport system and industrial process heat transport system. The need for efficiency, compactness, and safety challenge the capabilities of existing heat exchanger technology. The description of potential heat exchanger configurations or designs (such as printed circuit, spiral or helical coiled, ceramic, plate and fin, and plate type) were covered in an earlier report (Sabharwall et al. 2011). Significant future work, much of which is suggested in this report, is needed before the benefits and full potential of the AHTR can be realized. The execution of this TDRM will focuses

  11. A Freezable Heat Exchanger for Space Suit Radiator Systems

    NASA Technical Reports Server (NTRS)

    Nabity, James A.; Mason, Georgia R.; Copeland, Robert J.; Trevino, Luis a.

    2008-01-01

    During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut s metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to space, thus becoming the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the astronaut during an EVA can reduce the amount of expendable water consumed in the sublimator. Radiators have no moving parts and are thus highly reliable. Past freezable radiators have been too heavy, but the weight can be greatly reduced by placing a small and freeze tolerant heat exchanger between the astronaut and radiator, instead of making the very large radiator freeze tolerant. Therefore, the key technological innovation to improve space suit radiator performance was the development of a lightweight and freezable heat exchanger that accommodates the variable heat load generated by the astronaut. Herein, we present the heat transfer performance of a newly designed heat exchanger that endured several freeze / thaw cycles without any apparent damage. The heat exchanger was also able to continuously turn down or turn up the heat rejection to follow the variable load.

  12. Temperature control system for a J-module heat exchanger

    DOEpatents

    Basdekas, Demetrios L.; Macrae, George; Walsh, Joseph M.

    1978-01-01

    The level of primary fluid is controlled to change the effective heat transfer area of a heat exchanger utilized in a liquid metal nuclear power plant to eliminate the need for liquid metal control valves to regulate the flow of primary fluid and the temperature of the effluent secondary fluid.

  13. 14 CFR 25.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... carrying flammable fluids. (b) If an exhaust heat exchanger is used for heating ventilating air— (1) There... air system; or (2) Other means must be used to preclude the harmful contamination of the ventilating... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Exhaust System § 25.1125 Exhaust...

  14. 14 CFR 25.1125 - Exhaust heat exchangers.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... carrying flammable fluids. (b) If an exhaust heat exchanger is used for heating ventilating air— (1) There... air system; or (2) Other means must be used to preclude the harmful contamination of the ventilating... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Exhaust System § 25.1125 Exhaust...

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  16. Study on the heat-flow controllable heat exchanger (2nd report): Dehumidification in the greenhouse by the ventilation type dehumidifier with heat-flow controllable heat exchanger

    SciTech Connect

    Yanadori, Michio; Hamano, Masayoshi )

    1994-07-01

    A novel ventilation type dehumidifier with heat-flow controllable heat exchanger was installed on the wall of a greenhouse. Dehumidification and heat recovery experiments were conducted. The construction of the novel dehumidifier is simpler than that of the conventional dehumidifier with a compressor. It was found that the required input for the ventilation type dehumidifier was less than that of a conventional dehumidifier with compressor.

  17. Carbon-Fiber Brush Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Knowles, Timothy R.

    2004-01-01

    Velvetlike and brushlike pads of carbon fibers have been proposed for use as mechanically compliant, highly thermally conductive interfaces for transferring heat. A pad of this type would be formed by attaching short carbon fibers to either or both of two objects that one desires to place in thermal contact with each other. The purpose of using a thermal-contact pad of this or any other type is to reduce the thermal resistance of an interface between a heat source and a heat sink.

  18. Analysis of thermosyphon heat exchangers for use in solar domestic hot water heating systems

    NASA Astrophysics Data System (ADS)

    Dahl, Scott David

    1998-11-01

    A recent innovation in the solar industry is the use of thermosyphon heat exchangers. Determining the performance of these systems requires knowledge of how thermosyphon flow rate and heat exchanger performance vary with operating conditions. This study demonstrates that several thermosyphon heat exchanger designs operate in the laminar mixed convection regime. Empirical heat transfer and pressure drop correlations are obtained for three tube-in-shell heat exchangers (four, seven, and nine tube). Thermosyphon flow is on the shell side. Correlations are obtained with uniform heat flux on the tube walls and with a mixture of glycol and water circulating inside the tubes. Ranges of Reynolds, Prandtl, and Grashof numbers are 50 to 1800, 2.5 and 6.0, and 4×105 to 1×108, respectively. Nusselt number correlations are presented in a form that combines the contributions of forced and natural convection, Nu4Mixed=Nu4Forced+Nu4Natural. The Nusselt number is influenced by natural convection when the term Raq0.25/(Re0.5Pr0.33) is greater than unity. Pressure drop through these three designs is not significantly affected by mixed convection because most pressure drop losses are at the heat exchanger inlet and outlet. A comparison and discussion of the performance of several other heat exchanger designs (tube-in-shell and coil-in- shell designs) are presented. Generally, the coil-in- shell heat exchangers perform better than the tube-in- shell heat exchangers. Data from all heat exchanger designs is used to develop a new one-dimensional model for thermosyphon heat exchangers in solar water heating systems. The model requires two empirically determined relationships, pressure drop as a function of water mass flow rate and the overall heat transfer coefficient-area product (UA) as a function of Reynolds, Prandtl, and Grashof number. A testing protocol is presented that describes the procedure to obtain the data for the correlations. Two new TRNSYS component models are presented

  19. Air Circulation and Heat Exchange Under Reduced Pressures

    NASA Technical Reports Server (NTRS)

    Rygalov, V.; Wheeler, R.; Dixon, M.; Fowler, P.; Hillhouse, L.

    2010-01-01

    Heat exchange rates decrease non-linearly with reductions in atmospheric pressure. This decrease creates risk of thermal stress (elevated leaf temperatures) for plants under reduced pressures. Forced convection (fans) significantly increases heat exchange rate under almost all pressures except below 10 kPa. Plant cultivation techniques under reduced pressures will require forced convection. The cooling curve technique is a reliable means of assessing the influence of environmental variables like pressure and gravity on gas exchange of plant. These results represent the extremes of gas exchange conditions for simple systems under variable pressures. In reality, dense plant canopies will exhibit responses in between these extremes. More research is needed to understand the dependence of forced convection on atmospheric pressure. The overall thermal balance model should include latent and radiative exchange components.

  20. Renormalized anisotropic exchange for representing heat assisted magnetic recording media

    SciTech Connect

    Jiao, Yipeng; Liu, Zengyuan; Victora, R. H.

    2015-05-07

    Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.

  1. Direct-contact closed-loop heat exchanger

    DOEpatents

    Berry, G.F.; Minkov, V.; Petrick, M.

    1981-11-02

    A high temperature heat exchanger is disclosed which has a closed loop and a heat transfer liquid within the loop, the closed loop having a first horizontal channel with inlet and outlet means for providing direct contact of a first fluid at a first temperature with the heat transfer liquid, a second horizontal channel with inlet and outlet means for providing direct contact of a second fluid at a second temperature with the heat transfer liquid, and means for circulating the heat transfer liquid.

  2. Wall mounted heat exchanger characterization. [cryogenic propellant tanks

    NASA Technical Reports Server (NTRS)

    Bullard, B. R.

    1975-01-01

    Analytical models are presented for describing the heat and mass transfer and the energy distribution in the contents of a cryogenic propellant tank, under varying gravity levels. These models are used to analytically evaluate the effectiveness of a wall heat exchanger as a means of controlling the pressure in the tank during flight and during fill operations. Pressure and temperature histories are presented for tanks varying in size from 4 to 22.5 feet in diameter and gravity levels from 0-1. Results from the subscale test program, utilizing both non-cryogenic and cryogenic fluid, designed to evaluate a tank wall heat exchanger are described and compared with the analytical models. Both the model and test results indicate that a passive tank wall heat exchanger can effectively control tank pressure. However, the weight of such a system is considerably higher than that of an active mixer system.

  3. The design and fabrication of a Stirling engine heat exchanger module with an integral heat pipe

    NASA Technical Reports Server (NTRS)

    Schreiber, Jeffrey G.

    1988-01-01

    The conceptual design of a free-piston Stirling Space Engine (SSE) intended for space power applications has been generated. The engine was designed to produce 25 kW of electric power with heat supplied by a nuclear reactor. A novel heat exchanger module was designed to reduce the number of critical joints in the heat exchanger assembly while also incorporating a heat pipe as the link between the engine and the heat source. Two inexpensive verification tests are proposed. The SSE heat exchanger module is described and the operating conditions for the module are outlined. The design process of the heat exchanger modules, including the sodium heat pipe, is briefly described. Similarities between the proposed SSE heat exchanger modules and the LeRC test modules for two test engines are presented. The benefits and weaknesses of using a sodium heat pipe to transport heat to a Stirling engine are discussed. Similarly, the problems encountered when using a true heat pipe, as opposed to a more simple reflux boiler, are described. The instruments incorporated into the modules and the test program are also outlined.

  4. Special heat transfer monitor (HTM) for the Trane Company OTEC heat exchanger

    SciTech Connect

    Kuzay, T.M.; Panchal, C.B.; Gavin, A.P.

    1981-02-01

    A Heat Transfer Monitor (HTM) is a sensitive device which quantifies development of biofouling in the OTEC heat exchanger surfaces in terms of degrading heat transfer coefficient as biofouling progresses. The Carnegie-Mellon University (CMU) type HTM has been successfully utilized to date for plain circular OTEC heat exchanger tubes. With the development of compact heat exchangers for OTEC with non-circular and/or complex tube geometries, a device independent HTM (Universal Monitor) concept is being sought. For the meantime, however, novel methods have been developed to extend the principles of the CMU type HTM to noncircular tube geometries. The theory, formulation, analytical solutions and laboratory test results are presented for the novel use of the CMU HTM concept with such a special tube for the Trane Company heat exchanger for OTEC.

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

    PubMed

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

    2015-07-01

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

  6. Heat treatment of exchangers to remove coke

    SciTech Connect

    Turner, J.D.

    1990-02-20

    This patent describes a process for preparing furfural coke for removal from metallic surfaces. It comprises: heating the furfural coke without causing an evolution of heat capable of undesirably altering metallurgical properties of the surfaces in the presence of a gas containing molecular oxygen at a sufficient temperature below 800{degrees}F (427{degrees}C) for a sufficient time to change the crush strength of the coke so as to permit removal with a water jet at a pressure of five thousand pounds per square inch.

  7. Conceptual Design of a Condensing Heat Exchanger for Space Systems Using Porous Media

    NASA Technical Reports Server (NTRS)

    Hasan, Mohammad M.; Khan, Lutful I.; Nayagam, Vedha; Balasubramaniam, Ramaswamy

    2006-01-01

    Condensing heat exchangers are used in many space applications in the thermal and humidity control systems. In the International Space Station (ISS), humidity control is achieved by using a water cooled fin surface over which the moist air condenses, followed by "slurper bars" that take in both the condensate and air into a rotary separator and separates the water from air. The use of a cooled porous substrate as the condensing surface provides and attractive alternative that combines both heat removal as well as liquid/gas separation into a single unit. By selecting the pore sizes of the porous substrate a gravity independent operation may also be possible with this concept. Condensation of vapor into and on the porous surface from the flowing air and the removal of condensate from the porous substrate are the critical processes involved in the proposed concept. This paper describes some preliminary results of the proposed condensate withdrawal process and discusses the on-going design and development work of a porous media based condensing heat exchanger at the NASA Glenn Research Center in collaboration with NASA Johnson Space Center.

  8. Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump

    DOEpatents

    Phillips, Benjamin A.; Zawacki, Thomas S.

    1996-12-03

    Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium.

  9. Progress Report for Diffusion Welding of the NGNP Process Application Heat Exchangers

    SciTech Connect

    R.E. Mizia; D.E. Clark; M.V. Glazoff; T.E. Lister; T.L. Trowbridge

    2011-04-01

    The NGNP Project is currently investigating the use of metallic, diffusion welded, compact heat exchangers to transfer heat from the primary (reactor side) heat transport system to the secondary heat transport system. The intermediate heat exchanger will transfer this heat to downstream applications such as hydrogen production, process heat, and electricity generation. The channeled plates that make up the heat transfer surfaces of the intermediate heat exchanger will have to be assembled into an array by diffusion welding.

  10. Assessment of next generation nuclear plant intermediate heat exchanger design.

    SciTech Connect

    Majumdar, S.; Moisseytsev, A.; Natesan, K.; Nuclear Engineering Division

    2008-10-17

    The Next Generation Nuclear Plant (NGNP), which is an advanced high temperature gas reactor (HTGR) concept with emphasis on production of both electricity and hydrogen, involves helium as the coolant and a closed-cycle gas turbine for power generation with a core outlet/gas turbine inlet temperature of 900-1000 C. In the indirect cycle system, an intermediate heat exchanger is used to transfer the heat from primary helium from the core to the secondary fluid, which can be helium, nitrogen/helium mixture, or a molten salt. The system concept for the vary high temperature reactor (VHTR) can be a reactor based on the prismatic block of the GT-MHR developed by a consortium led by General Atomics in the U.S. or based on the PBMR design developed by ESKOM of South Africa and British Nuclear Fuels of U.K. This report has made an assessment on the issues pertaining to the intermediate heat exchanger (IHX) for the NGNP. A detailed thermal hydraulic analysis, using models developed at ANL, was performed to calculate heat transfer, temperature distribution, and pressure drop. Two IHX designs namely, shell and straight tube and compact heat exchangers were considered in an earlier assessment. Helical coil heat exchangers were analyzed in the current report and the results were compared with the performance features of designs from industry. In addition, a comparative analysis is presented between the shell and straight tube, helical, and printed circuit heat exchangers from the standpoint of heat exchanger volume, primary and secondary sides pressure drop, and number of tubes. The IHX being a high temperature component, probably needs to be designed using ASME Code Section III, Subsection NH, assuming that the IHX will be classified as a class 1 component. With input from thermal hydraulic calculations performed at ANL, thermal conduction and stress analyses were performed for the helical heat exchanger design and the results were compared with earlier-developed results on

  11. 40 CFR Table 6 to Subpart Hhhhh of... - Requirements for Heat Exchange Systems

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 13 2011-07-01 2011-07-01 false Requirements for Heat Exchange Systems... Manufacturing Pt. 63, Subpt. HHHHH, Table 6 Table 6 to Subpart HHHHH of Part 63—Requirements for Heat Exchange... your heat exchange systems. For each . . . You must . . . Heat exchange system, as defined in §...

  12. 40 CFR Table 6 to Subpart Hhhhh of... - Requirements for Heat Exchange Systems

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 14 2013-07-01 2013-07-01 false Requirements for Heat Exchange Systems... Manufacturing Pt. 63, Subpt. HHHHH, Table 6 Table 6 to Subpart HHHHH of Part 63—Requirements for Heat Exchange... your heat exchange systems. For each . . . You must . . . Heat exchange system, as defined in §...

  13. 40 CFR Table 6 to Subpart Hhhhh of... - Requirements for Heat Exchange Systems

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 14 2014-07-01 2014-07-01 false Requirements for Heat Exchange Systems... Manufacturing Pt. 63, Subpt. HHHHH, Table 6 Table 6 to Subpart HHHHH of Part 63—Requirements for Heat Exchange... your heat exchange systems. For each . . . You must . . . Heat exchange system, as defined in §...

  14. 40 CFR Table 6 to Subpart Hhhhh of... - Requirements for Heat Exchange Systems

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 13 2010-07-01 2010-07-01 false Requirements for Heat Exchange Systems... Manufacturing Pt. 63, Subpt. HHHHH, Table 6 Table 6 to Subpart HHHHH of Part 63—Requirements for Heat Exchange... your heat exchange systems. For each . . . You must . . . Heat exchange system, as defined in §...

  15. 40 CFR Table 6 to Subpart Hhhhh of... - Requirements for Heat Exchange Systems

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 14 2012-07-01 2011-07-01 true Requirements for Heat Exchange Systems... Manufacturing Pt. 63, Subpt. HHHHH, Table 6 Table 6 to Subpart HHHHH of Part 63—Requirements for Heat Exchange... your heat exchange systems. For each . . . You must . . . Heat exchange system, as defined in §...

  16. Development, Fabrication, and Testing of a Liquid/Liquid Microchannel Heat Exchanger for Constellation Spacecrafts

    NASA Technical Reports Server (NTRS)

    Hawkins-Reynolds, Ebony; Le,Hung; Stephans, Ryan A.

    2009-01-01

    Minimizing mass and volume is critically important for space hardware. Microchannel technology can be used to decrease both of these parameters for heat exchangers. Working in concert with NASA, Pacific Northwest National Laboratories (PNNL) has developed a microchannel liquid/liquid heat exchanger that has resulted in significant mass and volume savings. The microchannel heat exchanger delivers these improvements without sacrificing thermal and pressure drop performance. A conventional heat exchanger has been tested and the performance of it recorded to compare it to the microchannel heat exchanger that PNNL has fabricated. The microchannel heat exchanger was designed to meet all of the requirements of the baseline heat exchanger, while reducing the heat exchanger mass and volume. The baseline heat exchanger was designed to have an transfer approximately 3.1 kW for a specific set of inlet conditions. The baseline heat exchanger mass was 2.7 kg while the microchannel mass was only 2.0 kg. More impressive, however, was the volumetric savings associated with the microchannel heat exchanger. The microchannel heat exchanger was an order of magnitude smaller than the baseline heat exchanger (2180cm3 vs. 311 cm3). This paper will describe the test apparatus designed to complete performance tests for both heat exchangers. Also described in this paper will be the performance specifications for the microchannel heat exchanger and how they compare to the baseline heat exchanger.

  17. Supercritical heat exchanger field test (SHEFT), I. Field performance data on shell-and-tube heat exchangers in geothermal service

    SciTech Connect

    Silvester, L.F.; Beaulaurier, L.O.; Mirk, K.F.; Fulton, R.L.

    1981-06-01

    Field performance data on shell-and-tube heat exchangers in geothermal service are presented. The test data were taken for geothermal brine on the tube side and hydrocarbon on the shell side in counterflow for six primary heat exchangers, and for hydrocarbon on the shell side and cooling water on the tube side for the condenser. Test data were for heating isobutane, 1 90/10 isobutane/isopentane mixture, and a 80/20 isobutane/isopentane mixture at supercritical conditions in the vicinity of their critical pressure and temperature, and for condensing the same fluids. The test data were used in a preliminary data analysis to determine the reported heat exchanger performance parameters.

  18. Liquid Salt Heat Exchanger Technology for VHTR Based Applications

    SciTech Connect

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

    2012-10-11

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

  19. Heat exchanger module for stirling engines

    SciTech Connect

    Darche, M. J. P.; Carlquist, S.

    1985-02-12

    The invention relates to Stirling engines and provides a modular assembly composed of a cylinder head, a heater, a regenerator, a cooler and a cold duct, and making it possible by mounting a plurality of identical modules on an engine assembly to construct a multi-cylinder double acting Stirling engine of the indirect heating type.

  20. CFD analysis of the plate heat exchanger - Mathematical modelling of mass and heat transfer in serial connection with tubular heat exchanger

    NASA Astrophysics Data System (ADS)

    Bojko, Marian; Kocich, Radim

    2016-06-01

    Application of numerical simulations based on the CFD calculation when the mass and heat transfer between the fluid flows is essential component of thermal calculation. In this article the mathematical model of the heat exchanger is defined, which is subsequently applied to the plate heat exchanger, which is connected in series with the other heat exchanger (tubular heat exchanger). The present contribution deals with the possibility to use the waste heat of the flue gas produced by small micro turbine. Inlet boundary conditions to the mathematical model of the plate heat exchanger are obtained from the results of numerical simulation of the tubular heat exchanger. Required parameters such for example inlet temperature was evaluated from temperature field, which was subsequently imported to the inlet boundary condition to the simulation of plate heat exchanger. From the results of 3D numerical simulations are evaluated basic flow variables including the evaluation of dimensionless parameters such as Colburn j-factor and friction ft factor. Numerical simulation is realized by software ANSYS Fluent15.0.

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

    SciTech Connect

    Banerjee, A; Chandran, RB; Davidson, JH

    2015-01-22

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

  2. Effect of Heat Exchanger Material and Fouling on Thermoelectric Exhaust Heat Recovery

    SciTech Connect

    Love, Norman; Szybist, James P; Sluder, Scott

    2011-01-01

    This study is conducted in an effort to better understand and improve the performance of thermoelectric heat recovery systems for automotive use. For this purpose an experimental investigation of thermoelectrics in contact with clean and fouled heat exchangers of different materials is performed. The thermoelectric devices are tested on a bench-scale thermoelectric heat recovery apparatus that simulates automotive exhaust. The thermoelectric apparatus consists of a series of thermoelectric generators contacting a hot-side and a cold-side heat exchanger. The thermoelectric devices are tested with two different hot-side heat exchanger materials, stainless steel and aluminum, and at a range of simulated exhaust gas flowrates (40 to 150 slpm), exhaust gas temperatures (240 C and 280 C), and coolant-side temperatures (40 C and 80 C). It is observed that for higher exhaust gas flowrates, thermoelectric power output increases while overall system efficiency decreases. Degradation of the effectiveness of the EGR-type heat exchangers over a period of driving is also simulated by exposing the heat exchangers to diesel engine exhaust under thermophoretic conditions to form a deposit layer. For the fouled EGR-type heat exchangers, power output and system efficiency is observed to be significantly lower for all conditions tested. The study found, however, that heat exchanger material is the dominant factor in the ability of the system to convert heat to electricity with thermoelectric generators. This finding is thought to be unique to the heat exchangers used for this study, and not a universal trend for all system configurations.

  3. Performance Expectations of Closed-Brayton-Cycle Heat Exchangers in 100-kWe Nuclear Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.

    2003-01-01

    Performance expectations of closed-Brayton-cycle heat exchangers to be used in 100-kWe nuclear space power systems were forecast. Proposed cycle state points for a system supporting a mission to three of Jupiter s moons required effectiveness values for the heat-source exchanger, recuperator and rejection exchanger (gas cooler) of 0.98,0.95 and 0.97, respectively. Performance parameters such as number of thermal units (Nm), equivalent thermal conductance (UA), and entropy generation numbers (Ns) varied from 11 to 19,23 to 39 kWK, and 0.019 to 0.023 for some standard heat exchanger configurations. Pressure-loss contributions to entropy generation were significant; the largest frictional contribution was 114% of the heat-transfer irreversibility. Using conventional recuperator designs, the 0.95 effectiveness proved difficult to achieve without exceeding other performance targets; a metallic, plate-fin counterflow solution called for 15% more mass and 33% higher pressure-loss than the target values. Two types of gas-coolers showed promise. Single-pass counterflow and multipass cross-counterflow arrangements both met the 0.97 effectiveness requirement. Potential reliability-related advantages of the cross-countefflow design were noted. Cycle modifications, enhanced heat transfer techniques and incorporation of advanced materials were suggested options to reduce system development risk. Carbon-carbon sheeting or foam proved an attractive option to improve overall performance.

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

    SciTech Connect

    Anderson, Mark; Nellis, Greg; Corradini, Michael

    2012-10-19

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

  5. A prototype heat pipe heat exchanger for the capillary pumped loop flight experiment

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Yun, Seokgeun; Kroliczek, Edward J.

    1992-01-01

    A Capillary Pumped Two-Phase Heat Transport Loop (CAPL) Flight Experiment, currently planned for 1993, will provide microgravity verification of the prototype capillary pumped loop (CPL) thermal control system for EOS. CAPL employs a heat pipe heat exchanger (HPHX) to couple the condenser section of the CPL to the radiator assembly. A prototype HPHX consisting of a heat exchanger (HX), a header heat pipe (HHP), a spreader heat pipe (SHP), and a flow regulator has been designed and tested. The HX transmits heat from the CPL condenser to the HHP, while the HHP and SHP transport heat to the radiator assembly. The flow regulator controls flow distribution among multiple parallel HPHX's. Test results indicated that the prototype HPHX could transport up to 800 watts with an overall heat transfer coefficient of more than 6000 watts/sq m-deg C. Flow regulation among parallel HPHX's was also demonstrated.

  6. Near-Term Laser Launch Capability: The Heat Exchanger Thruster

    NASA Astrophysics Data System (ADS)

    Kare, Jordin T.

    2003-05-01

    The heat exchanger (HX) thruster concept uses a lightweight (up to 1 MW/kg) flat-plate heat exchanger to couple laser energy into flowing hydrogen. Hot gas is exhausted via a conventional nozzle to generate thrust. The HX thruster has several advantages over ablative thrusters, including high efficiency, design flexibility, and operation with any type of laser. Operating the heat exchanger at a modest exhaust temperature, nominally 1000 C, allows it to be fabricated cheaply, while providing sufficient specific impulse (~600 seconds) for a single-stage vehicle to reach orbit with a useful payload; a nominal vehicle design is described. The HX thruster is also comparatively easy to develop and test, and offers an extremely promising route to near-term demonstration of laser launch.

  7. Mill Scale Corrosion and Prevention in Carbon Steel Heat Exchanger

    NASA Astrophysics Data System (ADS)

    Sharma, Pankaj; Roy, Himadri

    2015-10-01

    The cause of material degradation of an ASTM A-124 grade carbon steel tube belonging to a heat exchanger has been investigated. Visual examination, followed by an in-depth microstructural characterization using optical microscopy, energy dispersive X-ray, and scanning electron microscopy, was carried out for understanding the primary cause of material degradation. Based on the results of an extensive examination as well as the background information provided on the heat exchanger, it was determined that the steel tubes were predominantly damaged by the mechanism of crevice corrosion facilitated by the presence of mill scale. It is concluded that the heat exchanger tubes were not properly investigated for defects after their fabrication. Based on the situation, the proper cleaning method was selected for preventing further corrosion in the system. A chemical cleaning process was designed using acid pickling along with an inhibitor and a surfactant.

  8. Diffusion Welding of Compact Heat Exchangers for Nuclear Applications

    SciTech Connect

    Denis Clark; Ron Mizia; Dr. Michael V. Glazoff; Mr. Michael W. Patterson

    2012-06-01

    The next-­-generation nuclear plant (NGNP) is designed to be a flexible source of energy, producing various mixes of electrical energy and process heat (for example, for hydrogen generation) on demand. Compact heat exchangers provide an attractive way to move energy from the helium primary reactor coolant to process heat uses. For process heat efficiency, reactor outlet temperatures of 750-­-900°C are desirable. There are minor but deleterious components in the primary coolant; the number of alloys that can handle this environment is small. The present work concentrates on Alloys 800H and 617.

  9. Enhancing ultra-high CPV passive cooling using least-material finned heat sinks

    NASA Astrophysics Data System (ADS)

    Micheli, Leonardo; Fernandez, Eduardo F.; Almonacid, Florencia; Reddy, K. S.; Mallick, Tapas K.

    2015-09-01

    Ultra-high concentrating photovoltaic (CPV) systems aim to increase the cost-competiveness of CPV by increasing the concentrations over 2000 suns. In this work, the design of a heat sink for ultra-high concentrating photovoltaic (CPV) applications is presented. For the first time, the least-material approach, widely used in electronics to maximize the thermal dissipation while minimizing the weight of the heat sink, has been applied in CPV. This method has the potential to further decrease the cost of this technology and to keep the multijunction cell within the operative temperature range. The designing procedure is described in the paper and the results of a thermal simulation are shown to prove the reliability of the solution. A prediction of the costs is also reported: a cost of 0.151/Wp is expected for a passive least-material heat sink developed for 4000x applications.

  10. Enhancing ultra-high CPV passive cooling using least-material finned heat sinks

    SciTech Connect

    Micheli, Leonardo Mallick, Tapas K.; Fernandez, Eduardo F.; Almonacid, Florencia; Reddy, K. S.

    2015-09-28

    Ultra-high concentrating photovoltaic (CPV) systems aim to increase the cost-competiveness of CPV by increasing the concentrations over 2000 suns. In this work, the design of a heat sink for ultra-high concentrating photovoltaic (CPV) applications is presented. For the first time, the least-material approach, widely used in electronics to maximize the thermal dissipation while minimizing the weight of the heat sink, has been applied in CPV. This method has the potential to further decrease the cost of this technology and to keep the multijunction cell within the operative temperature range. The designing procedure is described in the paper and the results of a thermal simulation are shown to prove the reliability of the solution. A prediction of the costs is also reported: a cost of 0.151$/W{sub p} is expected for a passive least-material heat sink developed for 4000x applications.

  11. Prefabricated heat-exchanging fireplace. Final technical report

    SciTech Connect

    Schleper, M.A.

    1981-06-15

    A heat-exchanging fireplace was installed in a 2000 square foot home and the standard air distribution equipment was ducted directly to the forced-air heating system of the home. The standard air distribution equipment for the fireplace included two squirrel-cage blowers which were connected to a thermostat, allowing a choice of temperature ranges; and a snap disc thermostat was used to disconnect the blowers in order to avoid blowing cold air after the fire died out. Arranged in this manner, one is able to set the regular home thermostat a few degrees lower than the fireplace thermostat, and this will allow the regular heating system to turn on after the fire has gone out in the fireplace. Energy consumption in both the fireplace and the conventional heating system was monitored throughout a heating season and then compared with past heating seasons when only a conventional heating system was used.

  12. Performance of a Thermoelectric Device with Integrated Heat Exchangers

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  13. A modular phase change heat exchanger for a solar oven

    SciTech Connect

    Bushnell, D.L.; Sohi, M. )

    1992-10-01

    A modular energy storing heat exchanger designed to use pentaerythritol for thermal storage (solid-solid phase change at 182 C) is tested in an oven by circulating heat transfer oil which is electrically heated in a manner to simulate a concentrating solar collector. Three efficiencies for heating the system under controlled and measured power input are determined - the heat exchanger efficiency, the efficiency of the heater with distribution lines, and the total system efficiency. Thermal energy retention times and cooking extraction times are determined, and along with the efficiencies, are compared with the results previously reported for a nonmodular heat exchanger. The modular configuration provides a highly improved extraction rate for cooking due to its wrap-around character and its increased surface-to-volume ratio. A full scale glass model of the copper tubing of the system is described and flow observations reported demonstrating how uniformly the parallel pumping branches perform and how trapped air pockets affect pumping power. A technique for measuring pumping power is described and its application to the system is quantified to show that less than 1 watt is required to circulate the heat transfer oil even when the system includes the solar collector and its longer connecting tubes.

  14. Internal dust recirculation system for a fluidized bed heat exchanger

    DOEpatents

    Gamble, Robert L.; Garcia-Mallol, Juan A.

    1981-01-01

    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 in a heat exchange relation to the bed and includes a steam drum disposed adjacent the bed and a tube bank extending between the steam drum and a water drum. The tube bank is located in the path of the effluent gases exiting from the bed and a baffle system is provided to separate the solid particulate matter from the effluent gases. The particulate matter is collected and injected back into the fluidized bed.

  15. Fuel type impact at heat exchanger performance

    NASA Astrophysics Data System (ADS)

    Durčanský, Peter; Patsch, Marek; Jandačka, Jozef

    2016-06-01

    Possible solution to the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration in combination with increasing energy effectiveness. The use of renewable sources, such as biomass, represents an important contribution to possible solution of this problem. When designing a new heat source it is required to follow a number of technical regulations and recommendations. The proposed combustion furnace is intended for combustion of biomass, either piece, or in the form of wood biomass. But the combustion is not only affected by design of furnace, but also by fuel and its properties.

  16. FinEx-Fin Experiment On HIFIRE-5

    NASA Astrophysics Data System (ADS)

    Bohrk, H.; Lohle, S.; Fuchs, U.; Elsaber, H.; Weihs, H.

    2011-05-01

    A set of four ceramic fins will fly as a passenger experiment onboard the american- australian hypersonic vehicle HIFiRE-5. The paper describes their lay-out and design. They consist of C/C-SiC and are mounted to the rocket by aluminum fin shoes. With a total of eight implanted thermocouples, the fins serve to determine three-dimensional heat flux to the CMC fins on the basis of a non-integer system identification approach. Both, the approach and the calibration procedure are described. It is, moreover, demonstrated that the fins are ready for flight.

  17. Ground Source Heat Pump Sub-Slab Heat Exchange Loop Performance in a Cold Climate

    SciTech Connect

    Mittereder, N.; Poerschke, A.

    2013-11-01

    This report presents a cold-climate project that examines an alternative approach to ground source heat pump (GSHP) ground loop design. The innovative ground loop design is an attempt to reduce the installed cost of the ground loop heat exchange portion of the system by containing the entire ground loop within the excavated location beneath the basement slab. Prior to the installation and operation of the sub-slab heat exchanger, energy modeling using TRNSYS software and concurrent design efforts were performed to determine the size and orientation of the system. One key parameter in the design is the installation of the GSHP in a low-load home, which considerably reduces the needed capacity of the ground loop heat exchanger. This report analyzes data from two cooling seasons and one heating season. Upon completion of the monitoring phase, measurements revealed that the initial TRNSYS simulated horizontal sub-slab ground loop heat exchanger fluid temperatures and heat transfer rates differed from the measured values. To determine the cause of this discrepancy, an updated model was developed utilizing a new TRNSYS subroutine for simulating sub-slab heat exchangers. Measurements of fluid temperature, soil temperature, and heat transfer were used to validate the updated model.

  18. Heat exchanger selection and design analyses for metal hydride heat pump systems

    SciTech Connect

    Mazzucco, Andrea; Voskuilen, Tyler G.; Waters, Essene L.; Pourpoint, Timothee L.; Rokni, Masoud

    2016-01-01

    This paper presents a design analysis for the development of highly efficient heat exchangers within stationary metal hydride heat pumps. The design constraints and selected performance criteria are applied to three representative heat exchangers. The proposed thermal model can be applied to select the most efficient heat exchanger design and provides outcomes generally valid in a pre-design stage. Heat transfer effectiveness is the principal performance parameter guiding the selection analysis, the results of which appear to be mildly (up to 13%) affected by the specific Nusselt correlation used. The thermo-physical properties of the heat transfer medium and geometrical parameters are varied in the sensitivity analysis, suggesting that the length of independent tubes is the physical parameter that influences the performance of the heat exchangers the most. The practical operative regions for each heat exchanger are identified by finding the conditions over which the heat removal from the solid bed enables a complete and continuous hydriding reaction. The most efficient solution is a design example that achieves the target effectiveness of 95%.

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

    NASA Astrophysics Data System (ADS)

    Morel, Sławomir

    2015-09-01

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

  20. Heat exchanger selection and design analyses for metal hydride heat pump systems

    DOE PAGES

    Mazzucco, Andrea; Voskuilen, Tyler G.; Waters, Essene L.; Pourpoint, Timothee L.; Rokni, Masoud

    2016-01-01

    This paper presents a design analysis for the development of highly efficient heat exchangers within stationary metal hydride heat pumps. The design constraints and selected performance criteria are applied to three representative heat exchangers. The proposed thermal model can be applied to select the most efficient heat exchanger design and provides outcomes generally valid in a pre-design stage. Heat transfer effectiveness is the principal performance parameter guiding the selection analysis, the results of which appear to be mildly (up to 13%) affected by the specific Nusselt correlation used. The thermo-physical properties of the heat transfer medium and geometrical parameters aremore » varied in the sensitivity analysis, suggesting that the length of independent tubes is the physical parameter that influences the performance of the heat exchangers the most. The practical operative regions for each heat exchanger are identified by finding the conditions over which the heat removal from the solid bed enables a complete and continuous hydriding reaction. The most efficient solution is a design example that achieves the target effectiveness of 95%.« less