WorldWideScience

Sample records for gravity heat pipe

  1. Gravity-assist heat pipes for thermal control systems

    International Nuclear Information System (INIS)

    Deverall, J.E.; Keddy, E.S.; Kemme, J.E.; Phillips, J.R.

    1975-06-01

    Sodium heat pipes, operating in the gravity-assist mode, have been incorporated into irradiation capsules to provide a means for establishing and controlling a desired specimen temperature. Investigations were made of new wick structures for potassium heat pipes to operate at lower temperatures and higher heat transfer rates, and a helical trough wick structure was developed with an improved heat transfer capability in the temperature range of interest. Test results of these heat pipes led to the study of a new heat pipe limit which had not previously been considered. (12 references) (U.S.)

  2. Temperature control with high performance gravity-assist heat pipes

    International Nuclear Information System (INIS)

    Kemme, J.E.; Deverall, J.E.; Keddy, E.S.; Phillips, J.R.; Ranken, W.A.

    1975-01-01

    The development of high performance heat pipes for controlling the temperature of irradiation experiments in the Experimental Breeder Reactor (EBR-II) is described. Because this application involves vertical operation in a gravity-assist mode with the evaporator down, several tests were made with sodium and potassium heat pipes in this position to establish their performance limits as a function of operating temperature. Best performance was achieved with a new wick structure consisting of a fine porous liner next to the heat-pipe wall and four helical channels next to the vapor passage. Also, a new modification of heat-pipe theory was discovered for determining performance limits for this type of wick. In its most rudimentary form, this modification says that the dynamic pressure gradient in the vapor stream cannot exceed the gravity gradient causing return of liquid. Once this modification was expressed in the form of a limiting equation, and a term was added to account for the slight capillary force developed in the channels, good agreement was obtained between calculated limits and those measured in several tests with both sodium and potassium. These tests showed rather conclusively that only half of the liquid head in the evaporator section was causing return of condensate, whereas existing theory predicts that the full head of liquid in the heat pipe is available for condensate return. (U.S.)

  3. Pressure Profiles in a Loop Heat Pipe under Gravity Influence

    Science.gov (United States)

    Ku, Jentung

    2015-01-01

    During the operation of a loop heat pipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity-neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed.

  4. An optical method for measuring the thickness of a falling condensate in gravity assisted heat pipe

    Directory of Open Access Journals (Sweden)

    Kasanický Martin

    2015-01-01

    Full Text Available A large number of variables is the main problem of designing systems which uses heat pipes, whether it is a traditional - gravity, or advanced - capillary, pulsating, advanced heat pipes. This article is a methodology for measuring the thickness of the falling condensate in gravitational heat pipes, with using the optical triangulation method, and the evaluation of risks associated with this method.

  5. Low-gravity experiments of lightweight flexible heat pipe panels with self-rewetting fluids.

    Science.gov (United States)

    Tanaka, Kotaro; Abe, Yoshiyuki; Nakagawa, Masayuki; Piccolo, Chiara; Savino, Raffaele

    2009-04-01

    Fluids with a unique surface tension behavior, the so-called "self-rewetting fluids," are considered to be promising working fluids not only in reduced-gravity environments but also in terrestrial applications. Ultralightweight polyimide-based wickless heat pipe panels with flexible, inflatable, and deployable functions were fabricated using self-rewetting fluids. Fundamental operation tests of these panels were conducted under conditions of reduced gravity during parabolic flight. We obtained promising experimental results on the thermal performance of the panels in reduced gravity, although the experimental conditions were not entirely satisfactory.

  6. Heat pipes

    CERN Document Server

    Dunn, Peter D

    1994-01-01

    It is approximately 10 years since the Third Edition of Heat Pipes was published and the text is now established as the standard work on the subject. This new edition has been extensively updated, with revisions to most chapters. The introduction of new working fluids and extended life test data have been taken into account in chapter 3. A number of new types of heat pipes have become popular, and others have proved less effective. This is reflected in the contents of chapter 5. Heat pipes are employed in a wide range of applications, including electronics cooling, diecasting and injection mo

  7. Heat pipes

    CERN Document Server

    Dunn, Peter D

    1982-01-01

    A comprehensive, up-to-date coverage of the theory, design and manufacture of heat pipes and their applications. This latest edition has been thoroughly revised, up-dated and expanded to give an in-depth coverage of the new developments in the field. Significant new material has been added to all the chapters and the applications section has been totally rewritten to ensure that topical and important applications are appropriately emphasised. The bibliography has been considerably enlarged to incorporate much valuable new information. Thus readers of the previous edition, which has established

  8. Experimental Study on the Thermal Start-Up Performance of the Graphene/Water Nanofluid-Enhanced Solar Gravity Heat Pipe.

    Science.gov (United States)

    Zhao, Shanguo; Xu, Guoying; Wang, Ning; Zhang, Xiaosong

    2018-01-28

    The solar gravity heat pipe has been widely used for solar thermal water heating because of its high efficient heat transfer and thermal diode characteristics. Operated on fluctuant and low intensity solar radiation conditions, a solar gravity heat pipe may frequently start up. This severely affects its solar collection performance. To enhance the thermal performance of the solar gravity heat pipe, this study proposes using graphene/water nanofluid as the working fluid instead of deionized water. The stability of the prepared graphene/water nanofluid added with PVP was firstly investigated to obtain the optimum mass ratios of the added dispersant. Thermophysical properties-including the thermal conductivity and viscosity-of nanofluid with various graphene nanoplatelets (GNPs) concentrations were measured at different temperatures for further analysis. Furthermore, based on the operational evaluation on a single heat pipe's start-up process, the performance of nanofluid-enhanced solar gravity heat pipes using different concentrations of GNPs were compared by using water heating experiments. Results indicated that the use of 0.05 wt % graphene/water nanofluid instead of water could achieve a 15.1% and 10.7% reduction in start-up time under 30 and 60 W input heating conditions, respectively. Consequently, a higher thermal efficiency for solar collection could be expected.

  9. Experimental Study on the Thermal Start-Up Performance of the Graphene/Water Nanofluid-Enhanced Solar Gravity Heat Pipe

    Directory of Open Access Journals (Sweden)

    Shanguo Zhao

    2018-01-01

    Full Text Available The solar gravity heat pipe has been widely used for solar thermal water heating because of its high efficient heat transfer and thermal diode characteristics. Operated on fluctuant and low intensity solar radiation conditions, a solar gravity heat pipe may frequently start up. This severely affects its solar collection performance. To enhance the thermal performance of the solar gravity heat pipe, this study proposes using graphene/water nanofluid as the working fluid instead of deionized water. The stability of the prepared graphene/water nanofluid added with PVP was firstly investigated to obtain the optimum mass ratios of the added dispersant. Thermophysical properties—including the thermal conductivity and viscosity—of nanofluid with various graphene nanoplatelets (GNPs concentrations were measured at different temperatures for further analysis. Furthermore, based on the operational evaluation on a single heat pipe’s start-up process, the performance of nanofluid-enhanced solar gravity heat pipes using different concentrations of GNPs were compared by using water heating experiments. Results indicated that the use of 0.05 wt % graphene/water nanofluid instead of water could achieve a 15.1% and 10.7% reduction in start-up time under 30 and 60 W input heating conditions, respectively. Consequently, a higher thermal efficiency for solar collection could be expected.

  10. Experimental Study on the Thermal Start-Up Performance of the Graphene/Water Nanofluid-Enhanced Solar Gravity Heat Pipe

    Science.gov (United States)

    Zhao, Shanguo; Xu, Guoying; Wang, Ning; Zhang, Xiaosong

    2018-01-01

    The solar gravity heat pipe has been widely used for solar thermal water heating because of its high efficient heat transfer and thermal diode characteristics. Operated on fluctuant and low intensity solar radiation conditions, a solar gravity heat pipe may frequently start up. This severely affects its solar collection performance. To enhance the thermal performance of the solar gravity heat pipe, this study proposes using graphene/water nanofluid as the working fluid instead of deionized water. The stability of the prepared graphene/water nanofluid added with PVP was firstly investigated to obtain the optimum mass ratios of the added dispersant. Thermophysical properties—including the thermal conductivity and viscosity—of nanofluid with various graphene nanoplatelets (GNPs) concentrations were measured at different temperatures for further analysis. Furthermore, based on the operational evaluation on a single heat pipe’s start-up process, the performance of nanofluid-enhanced solar gravity heat pipes using different concentrations of GNPs were compared by using water heating experiments. Results indicated that the use of 0.05 wt % graphene/water nanofluid instead of water could achieve a 15.1% and 10.7% reduction in start-up time under 30 and 60 W input heating conditions, respectively. Consequently, a higher thermal efficiency for solar collection could be expected. PMID:29382094

  11. Oscillating heat pipes

    CERN Document Server

    Ma, Hongbin

    2015-01-01

    This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation,  theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary  factors affecting oscillating motions and heat transfer,  neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes.  The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, gradua...

  12. Introduction to Heat Pipes

    Science.gov (United States)

    Ku, Jentung

    2015-01-01

    This is the presentation file for the short course Introduction to Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. NCTS 21070-15. Course Description: This course will present operating principles of the heat pipe with emphases on the underlying physical processes and requirements of pressure and energy balance. Performance characterizations and design considerations of the heat pipe will be highlighted. Guidelines for thermal engineers in the selection of heat pipes as part of the spacecraft thermal control system, testing methodology, and analytical modeling will also be discussed.

  13. Heat Pipe Systems

    Science.gov (United States)

    1993-01-01

    The heat pipe was developed to alternately cool and heat without using energy or any moving parts. It enables non-rotating spacecraft to maintain a constant temperature when the surface exposed to the Sun is excessively hot and the non Sun-facing side is very cold. Several organizations, such as Tropic-Kool Engineering Corporation, joined NASA in a subsequent program to refine and commercialize the technology. Heat pipes have been installed in fast food restaurants in areas where humid conditions cause materials to deteriorate quickly. Moisture removal was increased by 30 percent in a Clearwater, FL Burger King after heat pipes were installed. Relative humidity and power consumption were also reduced significantly. Similar results were recorded by Taco Bell, which now specifies heat pipe systems in new restaurants in the Southeast.

  14. Improved Thin, Flexible Heat Pipes

    Science.gov (United States)

    Rosenfeld, John H.; Gernert, Nelson J.; Sarraf, David B.; Wollen, Peter J.; Surina, Frank C.; Fale, John E.

    2004-01-01

    Flexible heat pipes of an improved type are fabricated as layers of different materials laminated together into vacuum- tight sheets or tapes. In comparison with prior flexible heat pipes, these flexible heat pipes are less susceptible to leakage. Other advantages of these flexible heat pipes, relative to prior flexible heat pipes, include high reliability and greater ease and lower cost of fabrication. Because these heat pipes are very thin, they are highly flexible. When coated on outside surfaces with adhesives, these flexible heat pipes can be applied, like common adhesive tapes, to the surfaces of heat sinks and objects to be cooled, even if those surfaces are curved.

  15. Heat pipes and use of heat pipes in furnace exhaust

    Science.gov (United States)

    Polcyn, Adam D.

    2010-12-28

    An array of a plurality of heat pipe are mounted in spaced relationship to one another with the hot end of the heat pipes in a heated environment, e.g. the exhaust flue of a furnace, and the cold end outside the furnace. Heat conversion equipment is connected to the cold end of the heat pipes.

  16. Flexible Heat Pipe

    Science.gov (United States)

    Bienert, W. B.; Wolf, D. A.

    1985-01-01

    Narrow Tube carries 10 watts or more to moving parts. Heat pipe 12 inches long and diameter of 0.312 inch (7.92mm). Bent to minimum radius of 2.5 blocks. Flexible section made of 321 stainless steel tubing (Cajon Flexible Tubing or equivalent). Evaporator and condenser made of oxygen free copper. Working fluid methanol.

  17. Heat pipe applications workshop report

    International Nuclear Information System (INIS)

    Ranken, W.A.

    1978-04-01

    The proceedings of the Heat Pipe Applications Workshop, held at the Los Alamos Scientific Laboratory October 20-21, 1977, are reported. This workshop, which brought together representatives of the Department of Energy and of a dozen industrial organizations actively engaged in the development and marketing of heat pipe equipment, was convened for the purpose of defining ways of accelerating the development and application of heat pipe technology. Recommendations from the three study groups formed by the participants are presented. These deal with such subjects as: (1) the problem encountered in obtaining support for the development of broadly applicable technologies, (2) the need for applications studies, (3) the establishment of a heat pipe technology center of excellence, (4) the role the Department of Energy might take with regard to heat pipe development and application, and (5) coordination of heat pipe industry efforts to raise the general level of understanding and acceptance of heat pipe solutions to heat control and transfer problems

  18. Heat-Exchanger/Heat-Pipe Interface

    Science.gov (United States)

    Snyder, H. J.; Van Hagan, T. H.

    1987-01-01

    Monolithic assembly reliable and light in weight. Heat exchanger and evaporator ends of heat pipes integrated in monolithic halves welded together. Interface assembly connects heat exchanger of furnace, reactor, or other power source with heat pipes carrying heat to radiator or power-consuming system. One of several concepts proposed for nuclear power supplies aboard spacecraft, interface useful on Earth in solar thermal power systems, heat engines, and lightweight cooling systems.

  19. Solar chemical heat pipe

    International Nuclear Information System (INIS)

    Levy, M.; Levitan, R.; Rosin, H.; Rubin, R.

    1991-08-01

    The performance of a solar chemical heat pipe was studied using CO 2 reforming of methane as a vehicle for storage and transport of solar energy. The endothermic reforming reaction was carried out in an Inconel reactor, packed with a Rh catalyst. The reactor was suspended in an insulated box receiver which was placed in the focal plane of the Schaeffer Solar Furnace of the Weizman Institute of Science. The exothermic methanation reaction was run in a 6-stage adiabatic reactor filled with the same Rh catalyst. Conversions of over 80% were achieved for both reactions. In the closed loop mode the products from the reformer and from the metanator were compressed into separate storage tanks. The two reactions were run either separately or 'on-line'. The complete process was repeated for over 60 cycles. The overall performance of the closed loop was quite satisfactory and scale-up work is in progress in the Solar Tower. (authors). 35 refs., 2 figs

  20. Visual observation of a heat pipe working characteristics

    International Nuclear Information System (INIS)

    Tsuyuzaki, Noriyoshi; Saito, Takashi; Ishigami, Shinya; Kawada, Michitaka; Konno, Masanobu; Kaminaga, Fumito; Okamoto, Yoshizo.

    1988-10-01

    When the heat pipe is used in a nuclear engineering field, it is indispensable to understand transient characteristics of an accident condition as well as in a steady state at a normal operation. However there have been few informations about the transient characteristics of a heat pipe in case of rapid temperature or heat load change in an evaporator section. The purpose of this study is to examine transient and steady state characteristics of a gravity assisted heat pipe and variable conductance heat pipe(VCHP) which will be used in a neutron irradiation capsule. This report presents results of visual observation of boiling and condensation patterns on steady state or transient condition in a visible heat pipe made of a glass. The response time of the heat pipe is on the order of a few seconds when the temperature of the evaporator part is kept above the operating temperature. (author)

  1. Heat pipe and method of production of a heat pipe

    International Nuclear Information System (INIS)

    Kemp, R.S.

    1975-01-01

    The heat pipe consists of a copper pipe in which a capillary network or wick of heat-conducting material is arranged in direct contact with the pipe along its whole length. Furthermore, the interior space of the tube contains an evaporable liquid for pipe transfer. If water is used, the capillary network consists of, e.g., a phosphorus band network. To avoid contamination of the interior of the heat pipe during sealing, its ends are closed by mechanical deformation so that an arched or plane surface is obtained which is in direct contact with the network. After evacuation of the interior space, the remaining opening is closed with a tapered pin. The ratio wall thickness/tube diameter is between 0.01 and 0.6. (TK/AK) [de

  2. Neutron Imaging of Alkali Metal Heat Pipes

    Science.gov (United States)

    Kihm, K.; Kirchoff, E.; Golden, M.; Rosenfeld, J.; Rawal, S.; Pratt, D.; Swanson, A.; Bilheux, H.; Walker, L.; Voisin, S.; Hussey, D. S.; Jacobson, D. L.

    High-temperature heat pipes are two-phase, capillary driven heat transfer devices capable of passively providing high thermal fluxes. Such a device using a liquid-metal coolant can be used as a solution for successful thermal management on hypersonic flight vehicles. Imaging of the liquid-metal coolant inside will provide valuable information in characterizing the detailed heat and mass transport. Neutron imaging possesses an inherent advantage from the fact that neutrons penetrate the heat pipe metal walls with very little attenuation, but are significantly attenuated by the liquid metal contained inside. Using the BT-2 beam line at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, preliminary efforts have been conducted on a nickel-sodium heat pipe. The contrast between the attenuated beam and the background is calculated to be approximately 3%. This low contrast requires sacrifice in spatial or temporal resolution so efforts have since been concentrated on lithium (Li) which has a substantially larger neutron attenuation cross section. Using the CG-1D beam line at the High Flux Isotope Reactor (HFIR) of Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, the first neutron images of high-temperature molybdenum (Mo)-Li heat pipes have been achieved. The relatively high neutron cross section of Li allows for the visualization of the Li working fluid inside the heat pipes. The evaporator region of a gravity assisted cylindrical heat pipe prototype 25 cm long was imaged from start-up to steady state operation up to approximately 900 °C. In each corner of the square bore inside, the capillary action raises the Li meniscus above the bulk Li pool in the evaporator region. As the operational temperature changes, the meniscus shapes and the bulk meniscus height also changes. Furthermore, a three-dimensional tomographic image is also reconstructed from the total of 128 projection images taken 1.4o apart in which the Li had

  3. Pulsating Heat Pipes, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Large radiator panels, based upon state of the art conventional heat pipes with attached fins for thermal load distribution and dissipation is the current baseline...

  4. NEP heat pipe radiators. [Nuclear Electric Propulsion

    Science.gov (United States)

    Ernst, D. M.

    1979-01-01

    This paper covers improvements of heat pipe radiators for the thermionic NEP design. Liquid metal heat pipes are suitable as spacecraft radiator elements because of high thermal conductance, low mass and reliability, but the NEP thermionic system design was too large and difficult to fabricate. The current integral collector-radiator design consisting of several layers of thermionic converters, the annular-tangential collector heat pipe, the radiator heat pipe, and the transition zone designed to minimize the temperature difference between the collector heat pipe and radiator heat pipe are described. Finally, the design of micrometeoroid armor protection and the fabrication of the stainless steel annular heat pipe with a tangential arm are discussed, and it is concluded that the heat rejection system for the thermionic NEP system is well advanced, but the collector-radiator heat pipe transition and the 8 to 10 m radiator heat pipe with two bends require evaluation.

  5. High performance flexible heat pipes

    Science.gov (United States)

    Shaubach, R. M.; Gernert, N. J.

    1985-01-01

    A Phase I SBIR NASA program for developing and demonstrating high-performance flexible heat pipes for use in the thermal management of spacecraft is examined. The program combines several technologies such as flexible screen arteries and high-performance circumferential distribution wicks within an envelope which is flexible in the adiabatic heat transport zone. The first six months of work during which the Phase I contract goal were met, are described. Consideration is given to the heat-pipe performance requirements. A preliminary evaluation shows that the power requirement for Phase II of the program is 30.5 kilowatt meters at an operating temperature from 0 to 100 C.

  6. Hybrid Heat Pipes for High Heat Flux Spacecraft Thermal Control, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Grooved aluminum/ammonia Constant Conductance Heat Pipes (CCHPs) are the standard for thermal control in zero-gravity. Unfortunately, they are limited in terms of...

  7. Heat pipes. Design and industrial applications

    International Nuclear Information System (INIS)

    Semeria, R.

    1974-01-01

    Heat pipes are thermosiphons with vaporization where we can distinguish a boiler, a condenser, and eventually an adiabatic zone. To insure the returning liquid flow from the condenser to the boiler, surface tension forces, associated with the gravity forces, if need be, are used. For this, the condensing liquid is sucked by a capillary structure, generally situated against the inner wall. The review of the design methods, and particularly the prediction of the maximal performances shows the advantages and limitations of such devices. The main difficulties are technological for the heat pipes with high temperature liquid metals. The thermohydrodynamical limitations are: the maximum power which can be calculated by a balance between the friction forces and the active ones, the maximum heat flux leading to the dry-out of the evaporator, the critical conditions for the start up associated with the sonic conditions in the vapour phase. The description of heat pipes designed for some industrial applications (mainly for space) is given [fr

  8. Heat-pipe thermionic reactor concept

    DEFF Research Database (Denmark)

    Storm Pedersen, E.

    1967-01-01

    Main components are reactor core, heat pipe, thermionic converter, secondary cooling system, and waste heat radiator; thermal power generated in reactor core is transported by heat pipes to thermionic converters located outside reactor core behind radiation shield; thermionic emitters are in direct...... contact with outside envelope of heat pipes and collectors are in contact with liquid metal secondary cooling system that transfers waste heat to radiator....

  9. Poisoning of Heat Pipes

    Science.gov (United States)

    Gillies, Donald; Lehoczky, Sandor; Palosz, Witold; Carpenter, Paul; Salvail, Pat

    2007-01-01

    Thermal management is critical to space exploration efforts. In particular, efficient transfer and control of heat flow is essential when operating high energy sources such as nuclear reactors. Thermal energy must be transferred to various energy conversion devices, and to radiators for safe and efficient rejection of excess thermal energy. Applications for space power demand exceptionally long periods of time with equipment that is accessible for limited maintenance only. Equally critical is the hostile and alien environment which includes high radiation from the reactor and from space (galactic) radiation. In space or lunar applications high vacuum is an issue, while in Martian operations the systems will encounter a CO2 atmosphere. The effect of contact at high temperature with local soil (regolith) in surface operations on the moon or other terrestrial bodies (Mars, asteroids) must be considered.

  10. Space qualification of high capacity grooved heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Dubois, M.; Mullender, B.; Druart, J. [SABCA, Societe Anomyme Belgel de Construction Aeronautique (Belgium); Supper, W.; Beddows, A. [ESTEC-The (Netherlands)

    1996-12-31

    Based on the thermal requirements of the future telecommunication satellites, the development of a High Capacity Grooved Heat Pipe (HPG), was contracted by ESA to SABCA leading to an aluminium extruded heat pipe (outer diameter of 25 mm) based on a multi re-entrant grooves design. After an intensive acceptance test campaign whose results showed a good confidence in the design and the fulfillment of the required specifications of heat transport and on tilt capability (experimental maximum heat transport capability of 1500 Watt metres for a vapour temperature of 20 deg C), similar heat pipes have been developed with various outer diameters (11 mm, 15 mm and 20 mm) and with various shapes (circular outer shapes, integrated saddles). Several of these heat pipes were tested during two parabolic flight campaigns, by varying the heat loads during the micro-gravity periods. This HGP heat pipe family is now being submitted to a space qualification program according to ESA standards (ESA PSS-49), both in straight and bent configuration. Within this qualification, the heat pipes are submitted to an extended test campaign including environmental (random/sinus vibration, constant acceleration) and thermal tests (thermal performance, thermal cycle, thermal soak, ageing). (authors) 9 refs.

  11. The effect of reduced gravity on cryogenic nitrogen boiling and pipe chilldown

    Science.gov (United States)

    Darr, Samuel; Dong, Jun; Glikin, Neil; Hartwig, Jason; Majumdar, Alok; Leclair, Andre; Chung, Jacob

    2016-01-01

    Manned deep space exploration will require cryogenic in-space propulsion. Yet, accurate prediction of cryogenic pipe flow boiling heat transfer is lacking, due to the absence of a cohesive reduced gravity data set covering the expected flow and thermodynamic parameter ranges needed to validate cryogenic two-phase heat transfer models. This work provides a wide range of cryogenic chilldown data aboard an aircraft flying parabolic trajectories to simulate reduced gravity. Liquid nitrogen is used to quench a 1.27 cm diameter tube from room temperature. The pressure, temperature, flow rate, and inlet conditions are reported from 10 tests covering liquid Reynolds number from 2,000 to 80,000 and pressures from 80 to 810 kPa. Corresponding terrestrial gravity tests were performed in upward, downward, and horizontal flow configurations to identify gravity and flow direction effects on chilldown. Film boiling heat transfer was lessened by up to 25% in reduced gravity, resulting in longer time and more liquid to quench the pipe to liquid temperatures. Heat transfer was enhanced by increasing the flow rate, and differences between reduced and terrestrial gravity diminished at high flow rates. The new data set will enable the development of accurate and robust heat transfer models of cryogenic pipe chilldown in reduced gravity. PMID:28725740

  12. Lightweight Heat Pipes Made from Magnesium

    Science.gov (United States)

    Rosenfeld, John N.; Zarembo, Sergei N.; Eastman, G. Yale

    2010-01-01

    Magnesium has shown promise as a lighter-weight alternative to the aluminum alloys now used to make the main structural components of axially grooved heat pipes that contain ammonia as the working fluid. Magnesium heat-pipe structures can be fabricated by conventional processes that include extrusion, machining, welding, and bending. The thermal performances of magnesium heat pipes are the same as those of equal-sized aluminum heat pipes. However, by virtue of the lower mass density of magnesium, the magnesium heat pipes weigh 35 percent less. Conceived for use aboard spacecraft, magnesium heat pipes could also be attractive as heat-transfer devices in terrestrial applications in which minimization of weight is sought: examples include radio-communication equipment and laptop computers.

  13. Heat Pipe with Axial Wick

    Science.gov (United States)

    Ambrose, Jay H. (Inventor); Holmes, Rolland (Inventor)

    2016-01-01

    A heat pipe has an evaporator portion, a condenser portion, and at least one flexible portion that is sealingly coupled between the evaporator portion and the condenser portion. The flexible portion has a flexible tube and a flexible separator plate held in place within the flexible tube so as to divide the flexible tube into a gas-phase passage and a liquid-phase artery. The separator plate and flexible tube are configured such that the flexible portion is flexible in a plane that is perpendicular to the separator plate.

  14. Intermediate Temperature Fluids for Heat Pipes and Loop Heat Pipes, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will develop heat pipe and loop heat pipe (LHP) working fluids for what is known as the intermediate...

  15. Contribution to the study of heat pipes

    International Nuclear Information System (INIS)

    Schmidt, Eberhard

    1968-01-01

    This research thesis reports the study of heat pipes. A heat pipe is a vacuum tube closed at its both ends and containing few grams of a liquid. The evaporation of the liquid at one end and its condensation at the other end perform the heat transfer without significant drop of temperature. In this research, the author studied the thermal-hydrodynamic behaviour of heat pipes built in stainless steel and containing highly pure sodium as heat transfer metal. He more particularly studied the operation of heat pipes, including their start up, and the influence of the geometry of the capillary network on the thermal power limiting the heat pipe operation. He first proposes an analytical model to compute the threshold heat power with respect to physical properties of the heat transfer metal and to the heat pipe and capillary network geometries. He also presents an experimental device, reports experimental results and their interpretation. Analytical and experimental results are then compared, and some noticed divergences are discussed. Remaining problems for a better understanding of heat pipe operation are finally indicated [fr

  16. Experimental analytical study on heat pipes

    International Nuclear Information System (INIS)

    Ismail, K.A.R.; Liu, C.Y.; Murcia, N.

    1981-01-01

    An analytical model is developed for optimizing the thickness distribution of the porous material in heat pipes. The method was used to calculate, design and construct heat pipes with internal geometrical changes. Ordinary pipes are also constructed and tested together with the modified ones. The results showed that modified tubes are superior in performance and that the analytical model can predict their performance to within 1.5% precision. (Author) [pt

  17. Hybrid Heat Pipes for Lunar and Martian Surface and High Heat Flux Space Applications

    Science.gov (United States)

    Ababneh, Mohammed T.; Tarau, Calin; Anderson, William G.; Farmer, Jeffery T.; Alvarez-Hernandez, Angel R.

    2016-01-01

    Novel hybrid wick heat pipes are developed to operate against gravity on planetary surfaces, operate in space carrying power over long distances and act as thermosyphons on the planetary surface for Lunar and Martian landers and rovers. These hybrid heat pipes will be capable of operating at the higher heat flux requirements expected in NASA's future spacecraft and on the next generation of polar rovers and equatorial landers. In addition, the sintered evaporator wicks mitigate the start-up problems in vertical gravity aided heat pipes because of large number of nucleation sites in wicks which will allow easy boiling initiation. ACT, NASA Marshall Space Flight Center, and NASA Johnson Space Center, are working together on the Advanced Passive Thermal experiment (APTx) to test and validate the operation of a hybrid wick VCHP with warm reservoir and HiK"TM" plates in microgravity environment on the ISS.

  18. Literature review and experimental investigation of heat pipes

    Science.gov (United States)

    Barsch, W. O.; Schoenhals, R. J.; Viskanta, R.; Winter, E. R. F.

    1971-01-01

    Tests on heat pipes determine operational limits, external boundary conditions, noncondensable gas effects, startup behavior, and geometric configurations. Experiment consists of design, construction, and testing of an apparatus for measuring wick properties, conventional heat pipes and coplanar heat pipes.

  19. Niobium 1 percent zirconium/potassium and titanium/potassium life-test heat pipe design and testing

    Science.gov (United States)

    Sena, J. Tom; Merrigan, Michael A.

    Experimental lifetime performance studies currently in progress use Niobium 1 percent Zirconium (Nb-1Zr) and Titanium (Ti) heat pipes with potassium (K) as the working fluid. A heat pipe life test matrix was developed for testing the heat pipes. Because the corrosion rates in alkali metal heat pipes are affected by temperature and working fluid evaporation flux, the variable parameters of the experimental matrix are established as steady operating temperature and input heat flux density. Total impurity inventory is a factor in corrosion rate so impurity levels are being evaluated in the heat pipe materials before and after testing. Eight Nb-1Zr/K heat pipes were designed, fabricated, and tested. Two of the heat pipes have completed testing whereas the other six are currently in test. These are gravity assist heat pipes operating in a reflux mode. The heat pipes are tested by sets, one set of two and two sets of three heat pipes. Three Ti/K heat pipes are also in life test. These heat pipes are tested as a set in a horizontal position in a capillary pumped annular flow mode. Each of the heat pipes is encapsulated in a quartz vacuum container with a water calorimeter over the vacuum container for power throughput measurements. Thermocouples are attached to the heat pipes for measuring temperature. Heat input to the heat pipes is via an RF coil. The heat pipes are operating at between 800 and 900 K, with heat input fluxes of 13.8 to 30 W/sq cm. Of the Nb-1Zr/K heat pipes, two of the heat pipes have been in operation for 14,000 hours, three over 10,000 hours, and three over 7,000 hours. The Ti/K heat pipes have been in operation for 1,266 hours.

  20. Heat pipes theory, design and applications

    CERN Document Server

    Reay, David; Kew, Peter

    2013-01-01

    Heat Pipes, 6th Edition, takes a highly practical approach to the design and selection of heat pipes, making it an essential guide for practicing engineers and an ideal text for postgraduate students. This new edition has been revised to include new information on the underlying theory of heat pipes and heat transfer, and features fully updated applications, new data sections, and updated chapters on design and electronics cooling. The book is a useful reference for those with experience and an accessible introduction for those approaching the topic for the first time. Contains all informat

  1. Heat flux experiments on heat pipes for plasma facing applications

    Energy Technology Data Exchange (ETDEWEB)

    Bolt, H. [Forschungszentrum Juelich GmbH (Germany); Kohlhaas, W. [Forschungszentrum Juelich GmbH (Germany); Duwe, R. [Forschungszentrum Juelich GmbH (Germany); Gervash, A. [D.V. Efremov Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation); Linke, J. [Forschungszentrum Juelich GmbH (Germany); Mazul, I. [D.V. Efremov Inst. of Electrophysical Apparatus, St. Petersburg (Russian Federation)

    1995-12-31

    The heat removal from the leading edge of limiter blades is a critical issue for the technical feasibility of the pump limiter concept. The aim of the present work was to investigate the capability of heat pipes to remove concentrated local heat fluxes. Tubular and flat heat pipes were subjected to local surface heat loads in the JUDITH electron beam facility. The heat pipes were tested until failure or until the operational limit of the component was reached. The absorbed heat fluxes at this point were of the order of several hundred W/cm{sup 2}. (orig.).

  2. Experimental investigation on an integrated thermal management system with heat pipe heat exchanger for electric vehicle

    International Nuclear Information System (INIS)

    Zou, Huiming; Wang, Wei; Zhang, Guiying; Qin, Fei; Tian, Changqing; Yan, Yuying

    2016-01-01

    Highlights: • An integrated thermal management system is proposed for electric vehicle. • The parallel branch of battery chiller can supply additional cooling capacity. • Heat pipe performance on preheating mode is better than that on cooling mode. • Heat pipe heat exchanger is a feasible choice for battery thermal management. - Abstract: An integrated thermal management system combining a heat pipe battery cooling/preheating system with the heat pump air conditioning system is presented to fulfill the comprehensive energy utilization for electric vehicles. A test bench with battery heat pipe heat exchanger and heat pump air conditioning for a regular five-chair electric car is set up to research the performance of this integrated system under different working conditions. The investigation results show that as the system is designed to meet the basic cabinet cooling demand, the additional parallel branch of battery chiller is a good way to solve the battery group cooling problem, which can supply about 20% additional cooling capacity without input power increase. Its coefficient of performance for cabinet heating is around 1.34 at −20 °C out-car temperature and 20 °C in-car temperature. The specific heat of the battery group is tested about 1.24 kJ/kg °C. There exists a necessary temperature condition for the heat pipe heat exchanger to start action. The heat pipe heat transfer performance is around 0.87 W/°C on cooling mode and 1.11 W/°C on preheating mode. The gravity role makes the heat transfer performance of the heat pipe on preheating mode better than that on cooling mode.

  3. Flexible heat pipes with integrated bioinspired design

    Directory of Open Access Journals (Sweden)

    Chao Yang

    2015-02-01

    Full Text Available In this work we report the facile fabrication and performance evaluation of flexible heat pipes that have integrated bioinspired wick structures and flexible polyurethane polymer connector design between the copper condenser and evaporator. Inside the heat pipe, a bioinspired superhydrophilic strong-base-oxidized copper mesh with multi-scale micro/nano-structures was used as the wicking material and deionized water was selected as working fluid. Thermal resistances of the fabricated flexible heat pipes charged with different filling ratios were measured under thermal power inputs ranging from 2 W to 12 W while the device was bent at different angles. The fabricated heat pipes with a 30% filling ratio demonstrated a low thermal resistance less than 0.01 K/W. Compared with the vertically oriented straight heat pipes, bending from 30° up to 120° has negligible influence on the heat-transfer performance. Furthermore, repeated heating tests indicated that the fabricated flexible heat pipes have consistent and reliable heat-transfer performance, thus would have important applications for advanced thermal management in three dimensional and flexible electronic devices.

  4. Gas lensing in a heated spinning pipe

    CSIR Research Space (South Africa)

    Mafusire, C

    2006-07-01

    Full Text Available When a heated pipe is rotated, the dynamics of the gas inside exhibit properties reminiscent of a solid-state positive lens. The properties are a result of a parabolic distribution of refractive index in the pipe which is caused by mixing of hot...

  5. Modeling of pulsating heat pipes.

    Energy Technology Data Exchange (ETDEWEB)

    Givler, Richard C.; Martinez, Mario J.

    2009-08-01

    This report summarizes the results of a computer model that describes the behavior of pulsating heat pipes (PHP). The purpose of the project was to develop a highly efficient (as compared to the heat transfer capability of solid copper) thermal groundplane (TGP) using silicon carbide (SiC) as the substrate material and water as the working fluid. The objective of this project is to develop a multi-physics model for this complex phenomenon to assist with an understanding of how PHPs operate and to be able to understand how various parameters (geometry, fill ratio, materials, working fluid, etc.) affect its performance. The physical processes describing a PHP are highly coupled. Understanding its operation is further complicated by the non-equilibrium nature of the interplay between evaporation/condensation, bubble growth and collapse or coalescence, and the coupled response of the multiphase fluid dynamics among the different channels. A comprehensive theory of operation and design tools for PHPs is still an unrealized task. In the following we first analyze, in some detail, a simple model that has been proposed to describe PHP behavior. Although it includes fundamental features of a PHP, it also makes some assumptions to keep the model tractable. In an effort to improve on current modeling practice, we constructed a model for a PHP using some unique features available in FLOW-3D, version 9.2-3 (Flow Science, 2007). We believe that this flow modeling software retains more of the salient features of a PHP and thus, provides a closer representation of its behavior.

  6. Design and performance optimization of miniature heat pipes in LTCC

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Peter Z; Chua, K M; Wong, Stephen C K; Tan, Y M [Singapore Institute of Manufacturing Technology 71 Nanyang Drive, Singapore 638075 (Singapore)

    2006-04-01

    In this paper, performance evaluation of miniature heat pipes in LTCC was made by numerical analysis, and the optimum miniature heat pipe design was defined. The effect of the groove depth, width and vapor space on the heat transfer capacity of miniature heat pipes was analyzed. Prototypes of the miniature heat pipes in LTCC were fabricated. Preliminary charging, sealing and thermal measurement of the miniature heat pipes were performed, and the challenges were discussed.

  7. Titanium Heat Pipe Thermal Plane, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Thermacore Inc. proposes an innovative titanium heat pipe thermal plane for passive thermal control of individual cells within a fuel cell stack. The proposed...

  8. Titanium Heat Pipe Thermal Plane, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the Phase II program is to complete the development of the titanium heat pipe thermal plane and establish all necessary steps for production of this...

  9. Flexible heat pipes with integrated bioinspired design

    OpenAIRE

    Chao Yang; Chengyi Song; Wen Shang; Peng Tao; Tao Deng

    2015-01-01

    In this work we report the facile fabrication and performance evaluation of flexible heat pipes that have integrated bioinspired wick structures and flexible polyurethane polymer connector design between the copper condenser and evaporator. Inside the heat pipe, a bioinspired superhydrophilic strong-base-oxidized copper mesh with multi-scale micro/nano-structures was used as the wicking material and deionized water was selected as working fluid. Thermal resistances of the fabricated flexible ...

  10. Modelling and performance of heat pipes with long evaporator sections

    NARCIS (Netherlands)

    Wits, Wessel W.; te Riele, Gert Jan

    2017-01-01

    This paper presents a planar cooling strategy for advanced electronic applications using heat pipe technology. The principle idea is to use an array of relatively long heat pipes, whereby heat is disposed to a long section of the pipes. The proposed design uses 1 m long heat pipes and top cooling

  11. Performance testing of a hydrogen heat pipe

    International Nuclear Information System (INIS)

    Alario, J.; Kosson, R.

    1980-01-01

    Test results are presented for a reentrant groove heat pipe with hydrogen working fluid. The heat pipe became operational between 20 and 30 K after a cooldown from 77 K without any difficulty. Steady-state performance data taken over a 19 to 23 K temperature range indicated the following: (1) maximum heat transport capacity 5.4 W-m (2) static wicking height 1.42 cm and (3) overall heat pipe conductance 1.7 W/C. These data agreed remarkably well with extrapolations made from comparable ammonia test results. The maximum heat transport capacity is 9.5% larger than the extrapolated value, but the static wicking height is the same. The overall conductance is 29% of the ammonia value, which is close to the ratio of liquid thermal conductivities (24%). Also, recovery from a completely frozen condition was accomplished within 5 min by simply applying an evaporater heat load of 1.8 W

  12. Influence of gravity on flutter of cantilevered pipes conveying fluid

    Science.gov (United States)

    Rivero, Javier; Perez-Saborid, Miguel

    2012-11-01

    We have considered the dynamics of the nonlinear interaction between a flexible pipe and the conveyed fluid in the presence of gravity. The stability of the system (fllutter and buckling) depends on parameters such as the dimensionless fluid flow rate, the gravity to bending stiffness ratio and the fluid to pipe mass ratio and it has been studied in detail both numerically and experimentally. It has also been found that the stabilizing or destabilizing effects of fluid flow depends crucially on the direction of gravity respect to the undeformed midline of the pipe. We have also computed the post-critical behavior of the system by solving the full nonlinear equations of the problem and analyzed the transfer of energy within the system in the nonlinear regime. We have formulated the problem in terms of the angles of the midline of the pipe instead of its transverse displacements, so that we can deal with large deflections without recurring to the quasi-linear approximations concerning the pipe curvature usually made in the literature. Supported by the Ministerio de Educación, Cultura y Deportes of Spain under grant DPI 2010-20450 C03-02.

  13. Heat pipe with PCM for electronic cooling

    International Nuclear Information System (INIS)

    Weng, Ying-Che; Cho, Hung-Pin; Chang, Chih-Chung; Chen, Sih-Li

    2011-01-01

    This article experimentally investigates the thermal performances of a heat pipe with phase change material for electronic cooling. The adiabatic section of heat pipe is covered by a storage container with phase change material (PCM), which can store and release thermal energy depending upon the heating powers of evaporator and fan speeds of condenser. Experimental investigations are conducted to obtain the system temperature distributions from the charge, discharge and simultaneous charge/discharge performance tests. The parameters in this study include three kinds of PCMs, different filling PCM volumes, fan speeds, and heating powers in the PCM cooling module. The cooling module with tricosane as PCM can save 46% of the fan power consumption compared with the traditional heat pipe.

  14. Machined Titanium Heat-Pipe Wick Structure

    Science.gov (United States)

    Rosenfeld, John H.; Minnerly, Kenneth G.; Gernert, Nelson J.

    2009-01-01

    Wick structures fabricated by machining of titanium porous material are essential components of lightweight titanium/ water heat pipes of a type now being developed for operation at temperatures up to 530 K in high-radiation environments. In the fabrication of some prior heat pipes, wicks have been made by extruding axial grooves into aluminum unfortunately, titanium cannot be extruded. In the fabrication of some other prior heat pipes, wicks have been made by in-situ sintering of metal powders shaped by the use of forming mandrels that are subsequently removed, but in the specific application that gave rise to the present fabrication method, the required dimensions and shapes of the heat-pipe structures would make it very difficult if not impossible to remove the mandrels due to the length and the small diameter. In the present method, a wick is made from one or more sections that are fabricated separately and assembled outside the tube that constitutes the outer heat pipe wall. The starting wick material is a slab of porous titanium material. This material is machined in its original flat configuration to form axial grooves. In addition, interlocking features are machined at the mating ends of short wick sections that are to be assembled to make a full-length continuous wick structure. Once the sections have been thus assembled, the resulting full-length flat wick structure is rolled into a cylindrical shape and inserted in the heatpipe tube (see figure). This wick-structure fabrication method is not limited to titanium/water heat pipes: It could be extended to other heat pipe materials and working fluids in which the wicks could be made from materials that could be pre-formed into porous slabs.

  15. Novel Wick Structures for Improved Heat Pipe Performance Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Heat pipes are commonly used for transporting heat over relatively long distances with very low temperature drop. One of the limitations of heat pipes is the...

  16. Pulsating Heat Pipes, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — An advanced heat transport technology is presented that can enable space nuclear power systems to transfer reactor heat, convert heat into electricity, reject waste...

  17. Turbulent Heat Transfer in Ribbed Pipe Flow

    Science.gov (United States)

    Kang, Changwoo; Yang, Kyung-Soo

    2012-11-01

    From the view point of heat transfer control, surface roughness is one of the popular ways adopted for enhancing heat transfer in turbulent pipe flow. Such a surface roughness is often modeled with a rib. In the current investigation, Large Eddy Simulation has been performed for turbulent flow in a pipe with periodically-mounted ribs at Reτ=700, Pr=0.71, and p / k =2, 4, and 8. Here, p and k represent the pitch and rib height, respectively. The rib height is fixed as one tenth of the pipe radius. The profiles of mean velocity components, mean temperature, root-mean-squares (rms) of temperature fluctuation are presented at the selected streamwise locations. In comparison with the smooth-pipe case at the same Re and Pr, the effects of the ribs are clearly identified, leading to overall enhancement of turbulent heat transfer in terms of Nu. The budget of temperature variance is presented in the form of contours. The results of an Octant analysis are also given to elucidate the dominant events. Our LES results shed light on a complete understanding of the heat-transfer mechanisms in turbulent ribbed-pipe flow which has numerous applications in engineering. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2012013019).

  18. Casing free district heating pipes; Mantelfria fjaerrvaermeroer

    Energy Technology Data Exchange (ETDEWEB)

    Saellberg, Sven-Erik; Nilsson, Stefan [Swedish National Testing and Research Inst., Goeteborg (Sweden)

    2005-07-01

    Previous studies have shown that polyurethane insulation (PUR foam) on district heating pipes acts as protection against water if it is of good quality, i.e. free from cracks, cavities and other defects. On the other hand water vapour easily diffuses through PUR foam. However this is not a problem as long as the steel pipe is warmer than the surface layer, since the high temperature will prevent the vapour from condensating. What will happen with the insulation of a casing free district heating pipe where the ground water level occasionally reaches above the pipe has not been studied in detail. The current project has studied to what extent moisture enters the PUR foam insulation of two approximately one meter long district heating pipes without casing which have been in the ground for four years. Occasionally, the ground-water has entirely covered the pipes. In addition, the foam has been studied with respect to damage from the surrounding backfill material. Test specimens were taken out of the casing free pipes and were analysed with respect to moisture content. Additional measurements were done with a moisture indicator, and the electric resistance between the steel pipes and the four surveillance wires in each pipe was measured. The results from the various measurement techniques were the compared. The results show that the PUR foam remains dry as long as the service pipe is hot if no defects, such as crack and cavities, are present. Close to the service pipe, the foam actually dries out over time. The moisture content of the middle layer remains more or less constant. Only the colder parts on the outside exhibit an increase in moisture content. It was also seen that defects may lead to water ingress with subsequent humidification of the foam. However, the damaged foam area is limited. This is not the case for a regular pipe with a vapour tight casing, where experience show that moisture tend to spread along the pipe. The pipes were buried in sand and no

  19. Experimental investigations on an axial grooved cryogenic heat pipe

    Directory of Open Access Journals (Sweden)

    Senthil Kumar Muniappan

    2012-01-01

    Full Text Available This paper deals with development and studies of a trapezoidal axial grooved nitrogen heat pipe. A special liquid nitrogen cryostat has been designed and developed for evaluating the performance of heat pipe where the condenser portion is connected to the cold sink externally. Experiments have been performed on the heat pipe as well as on an equivalent diameter copper rod at different heat loads. The steady state performance of the heat pipe is compared with that of copper rod.

  20. Modeling of heat transfer into a heat pipe for a localized heat input zone

    International Nuclear Information System (INIS)

    Rosenfeld, J.H.

    1987-01-01

    A general model is presented for heat transfer into a heat pipe using a localized heat input. Conduction in the wall of the heat pipe and boiling in the interior structure are treated simultaneously. The model is derived from circumferential heat transfer in a cylindrical heat pipe evaporator and for radial heat transfer in a circular disk with boiling from the interior surface. A comparison is made with data for a localized heat input zone. Agreement between the theory and the model is good. This model can be used for design purposes if a boiling correlation is available. The model can be extended to provide improved predictions of heat pipe performance

  1. Flexible Cryogenic Heat Pipe Development Program

    Science.gov (United States)

    1976-01-01

    A heat pipe was designed for operation in the 100 - 200 K temperature range with maximum heat transport as a primary design goal; another designed for operation in the 15 - 100 K temperature range with maximum flexibility as a design goal. Optimum geometry and materials for the container and wicking systems were determined. The high power (100 - 200 K) heat pipe was tested with methane at 100 - 140 K, and test data indicated only partial priming with a performance limit of less than 50 percent of theoretical. A series of tests were conducted with ammonia at approximately 280 K to determine the performance under varying fluid charge and test conditions. The low temperature heat pipe was tested with oxygen at 85 - 95 K and with methanol at 295 - 315 K. Performance of the low temperature heat pipe was below theoretical predictions. Results of the completed testing are presented and possible performance limitation mechanisms are discussed. The lower-than-expected performance was felt to be due to small traces of non-condensible gases which prevented the composite wick from priming.

  2. Sodium Variable Conductance Heat Pipe for Radioisotope Stirling Systems

    Science.gov (United States)

    Tarau, Calin; Anderson, William G.; Walker, Kara

    2009-01-01

    In a Stirling radioisotope system, heat must continually be removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. Normally, the Stirling convertor provides this cooling. If the converter stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, and also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) has been designed to allow multiple stops and restarts of the Stirling convertor in an Advanced Stirling Radioisotope Generator (ASRG). When the Stirling convertor is turned off, the VCHP will activate when the temperatures rises 30 C above the setpoint temperature. A prototype VCHP with sodium as the working fluid was fabricated and tested in both gravity aided and against gravity conditions for a nominal heater head temperature of 790 C. The results show very good agreement with the predictions and validate the model. The gas front was located at the exit of the reservoir when heater head temperature was 790 C while cooling was ON, simulating an operating Advanced Stirling Converter (ASC). When cooling stopped, the temperature increased by 30 C, allowing the gas front to move past the radiator, which transferred the heat to the case. After resuming the cooling flow, the front returned at the initial location turning OFF the VCHP. The against gravity working conditions showed a colder reservoir and faster transients.

  3. Design of a cavity heat pipe receiver experiment

    Science.gov (United States)

    Schneider, Michael G.; Brege, Mark H.; Greenlee, William J.

    1992-01-01

    A cavity heat pipe experiment has been designed to test the critical issues involved with incorporating thermal energy storage canisters into a heat pipe. The experiment is a replication of the operation of a heat receiver for a Brayton solar dynamic power cycle. The heat receiver is composed of a cylindrical receptor surface and an annular heat pipe with thermal energy storage canisters and gaseous working fluid heat exchanger tubes surrounding it. Hardware for the cavity heat pipe experiment will consist of a sector of the heat pipe, complete with gas tube and thermal energy storage canisters. Thermal cycling tests will be performed on the heat pipe sector to simulate the normal energy charge/discharge cycle of the receiver in a spacecraft application.

  4. Computational model of miniature pulsating heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Mario J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Givler, Richard C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2013-01-01

    The modeling work described herein represents Sandia National Laboratories (SNL) portion of a collaborative three-year project with Northrop Grumman Electronic Systems (NGES) and the University of Missouri to develop an advanced, thermal ground-plane (TGP), which is a device, of planar configuration, that delivers heat from a source to an ambient environment with high efficiency. Work at all three institutions was funded by DARPA/MTO; Sandia was funded under DARPA/MTO project number 015070924. This is the final report on this project for SNL. This report presents a numerical model of a pulsating heat pipe, a device employing a two phase (liquid and its vapor) working fluid confined in a closed loop channel etched/milled into a serpentine configuration in a solid metal plate. The device delivers heat from an evaporator (hot zone) to a condenser (cold zone). This new model includes key physical processes important to the operation of flat plate pulsating heat pipes (e.g. dynamic bubble nucleation, evaporation and condensation), together with conjugate heat transfer with the solid portion of the device. The model qualitatively and quantitatively predicts performance characteristics and metrics, which was demonstrated by favorable comparisons with experimental results on similar configurations. Application of the model also corroborated many previous performance observations with respect to key parameters such as heat load, fill ratio and orientation.

  5. Heat pipes with variable thermal conductance property for space applications

    Energy Technology Data Exchange (ETDEWEB)

    Kravets, V.; Alekseik, Ye.; Alekseik, O.; Khairnasov, S. [National Technical University of Ukraine, Kyiv (Ukraine); Baturkin, V.; Ho, T. [Explorationssysteme RY-ES, Bremen (Germany); Celotti, L. [Active Space Technologies GmbH, Berlin (Germany)

    2017-06-15

    The activities presented in this paper demonstrate a new approach to provide passive thermal control using heat pipes, as demonstrated on the electronic unit of DLR’s MASCOT lander, which embarked on the NEA sample return mission Hayabusa 2 (JAXA). The focus is on the development and testing of heat pipes with variable thermal conductance in a predetermined temperature range. These heat pipes act as thermal switches. Unlike standard gasloaded heat pipes and thermal-diode heat pipes construction of presented heat pipes does not include any additional elements. Copper heat pipes with metal fibrous wicks were chosen as baseline design. We obtained positive results by choosing the heat carrier and structural parameters of the wick (i.e., pore diameter, porosity, and permeability). The increase in the thermal conductivity of the heat pipes from 0.04 W/K to 2.1 W/K was observed in the temperature range between −20 °C and +55 °C. Moreover, the heat pipes transferred the predetermined power of not less than 10 W within the same temperature range. The heat pipes have been in flight since December 2014, and the supporting telemetry data were obtained in September 2015. The data showed the nominal operation of the thermal control system.

  6. Experimental investigation on Heat Transfer Performance of Annular Flow Path Heat Pipe

    International Nuclear Information System (INIS)

    Kim, In Guk; Kim, Kyung Mo; Jeong, Yeong Shin; Bang, In Cheol

    2015-01-01

    Mochizuki et al. was suggested the passive cooling system to spent nuclear fuel pool. Detail analysis of various heat pipe design cases was studied to determine the heat pipes cooling performance. Wang et al. suggested the concept PRHRS of MSR using sodium heat pipes, and the transient performance of high temperature sodium heat pipe was numerically simulated in the case of MSR accident. The meltdown at the Fukushima Daiichi nuclear power plants alarmed to the dangers of station blackout (SBO) accident. After the SBO accident, passive decay heat removal systems have been investigated to prevent the severe accidents. Mochizuki et al. suggested the heat pipes cooling system using loop heat pipes for decay heat removal cooling and analysis of heat pipe thermal resistance for boiling water reactor (BWR). The decay heat removal systems for pressurized water reactor (PWR) were suggested using natural convection mechanisms and modification of PWR design. Our group suggested the concept of a hybrid heat pipe with control rod as Passive IN-core Cooling System (PINCs) for decay heat removal for advanced nuclear power plant. Hybrid heat pipe is the combination of the heat pipe and control rod. In the present research, the main objective is to investigate the effect of the inner structure to the heat transfer performance of heat pipe containing neutron absorber material, B 4 C. The main objective is to investigate the effect of the inner structure in heat pipe to the heat transfer performance with annular flow path. ABS pellet was used instead of B 4 C pellet as cylindrical structures. The thermal performances of each heat pipes were measured experimentally. Among them, concentric heat pipe showed the best performance compared with others. 1. Annular evaporation section heat pipe and annular flow path heat pipe showed heat transfer degradation. 2. AHP also had annular vapor space and contact cooling surface per unit volume of vapor was increased. Heat transfer coefficient of

  7. Safety review package for University of Central Florida flat-plate heat pipe experiment

    Science.gov (United States)

    Chow, Louis C.

    1998-01-01

    A flat-plate heat pipe (FPHP) experiment has been set up for micro-gravity tests on a NASA supplied aircraft. This report presents an analysis on various components of the experimental setup to certify that it will satisfy the flight safety and operation requirements.

  8. Fabrication and evaluation of chemically vapor deposited tungsten heat pipe.

    Science.gov (United States)

    Bacigalupi, R. J.

    1972-01-01

    A network of lithium-filled tungsten heat pipes is being considered as a method of heat extraction from high temperature nuclear reactors. The need for material purity and shape versatility in these applications dictates the use of chemically vapor deposited (CVD) tungsten. Adaptability of CVD tungsten to complex heat pipe designs is shown. Deposition and welding techniques are described. Operation of two lithium-filled CVD tungsten heat pipes above 1800 K is discussed.

  9. Experimental study of Large-scale cryogenic Pulsating Heat Pipe

    Science.gov (United States)

    Barba, Maria; Bruce, Romain; Bonelli, Antoine; Baudouy, Bertrand

    2017-12-01

    Pulsating Heat Pipes (PHP) are passive two-phase heat transfer devices consisting of a long capillary tube bent into many U-turns connecting the condenser part to the evaporator part. They are thermally driven by an oscillatory flow of liquid slugs and vapor plugs coming from phase changes and pressure differences along the tube. The coupling of hydrodynamic and thermodynamic effects allows high heat transfer performances. Three closed-loop pulsating heat pipes have been developed by the DACM (Department of Accelerators, Cryogenics and Magnetism) of CEA Paris-Saclay, France. Each PHP measures 3.7 meters long (0.35 m for the condenser and the evaporator and 3 m for the adiabatic part), being almost 20 times longer than the longest cryogenic PHP tested. These PHPs have 36, 22 and 12 parallel channels. Numerous tests have been performed in horizontal position (the closest configuration to non-gravity) using nitrogen as working fluid, operating between 75 and 90 K. The inner and outer diameters of the stainless steel capillary tubes are 1.5 and 2 mm respectively. The PHPs were operated at different filling ratios (20 to 90 %), heat input powers (3 to 20 W) and evaporator and condenser temperatures (75 to 90 K). As a result, the PHP with 36 parallel channels achieves a certain level of stability during more than thirty minutes with an effective thermal conductivity up to 200 kW/m.K at 10 W heat load and during forty minutes with an effective thermal conductivity close to 300 kW/m.K at 5 W heat load.

  10. Experimental investigation for the optimization of heat pipe performance in latent heat thermal storage

    Energy Technology Data Exchange (ETDEWEB)

    Ladekar, Chandrakishor; Choudhary, S. K. [RTM Nagpur University, Wardha (India); Khandare, S. S. [B. D. College of Engineering, Wardha (India)

    2017-06-15

    We investigated the optimum performance of heat pipe in Latent heat thermal energy storage (LHTES), and compared it with copper pipe. Classical plan of experimentation was used to optimize the parameters of heat pipe. Heat pipe fill ratio, evaporator section length to condenser section length ratio i.e., Heat pipe length ratio (HPLR) and heat pipe diameter, was the parameter used for optimization, as result of parametric analysis. Experiment with flow rate of 10 lit./min. was conducted for different fill ratio, HPLR and different diameter. Fill ratio of 80 %, HPLR of 0.9 and heat pipe with diameter of 18 mm showed better trend in charging and discharging. Comparison between the storage tank with optimized heat pipe and copper pipe showed almost 186 % improvement in charging and discharging time compared with the copper pipe embedded thermal storage. Heat transfer between Heat transferring fluid (HTF) and Phase change material (PCM) increased with increase in area of heat transferring media, but storage density of storage tank decreased. Storage tank with heat pipe embedded in place of copper pipe is a better option in terms of charging and discharging time as well heat storage capacity due to less heat lost. This justifies the better efficiency and effectiveness of storage tank with embedded optimized heat pipe.

  11. Heat pipes as perspective base elements of heat recovery in heat supply and ventilating systems

    Directory of Open Access Journals (Sweden)

    Matveev Andrey

    2017-01-01

    Full Text Available Thermotechnical characteristics of heat pipes are considered as high-efficient heat-transfer devices, which can provide energy-saving technologies for heat supply and ventilating systems and for different branches of industry. Thermotechnical and working (”performance capability” characteristics of heat pipes are investigated. By ”performance capability” of heat pipes and heat-transfer devices on heat pipes we mean the system state, where it can perform set functions and keep parameter values (thermal power, conductivity, thermal resistance, heat-transfer coefficient, temperature level and differential, etc. within the regulations of standardized specifications. The article presents theoretical and experimental methods of «gaslock» length determination on noncondensable gases during long-lasting tests of ammonia heat pipes made of aluminum shape АS – КRА 7.5 – R1 (alloy АD – 31. The paper gives results of research of thermotechnical characteristics of heat pipes in horizontal and vertical states (separate and as a set part while using different systems of thermal insulation. The obtained results of thermotechnical and resource tests show the advantages of ammonia heat pipes as basic elements for heat exchanger design in heating and ventilation systems.

  12. Solid0Core Heat-Pipe Nuclear Batterly Type Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ehud Greenspan

    2008-09-30

    This project was devoted to a preliminary assessment of the feasibility of designing an Encapsulated Nuclear Heat Source (ENHS) reactor to have a solid core from which heat is removed by liquid-metal heat pipes (HP).

  13. Thermal analysis of double-pipe heat exchanger in thermodynamic vent system

    International Nuclear Information System (INIS)

    Liu, Zhan; Li, Yanzhong; Zhou, Ke

    2016-01-01

    Highlights: • The thermodynamic analysis of TVS heat exchanger is investigated. • One quasi-steady state model is established to investigate the thermal performance of double-pipe heat exchanger. • The external natural convection, inner forced convection and the annular two-phase boiling are coupled. • The effect of the external natural convection should be given enough attention in the ground condition. • The influence of the pipe size is studied. - Abstract: Full use and effective management of cold capacity are significant for improving the performance of heat exchanger in the thermodynamic vent system (TVS). To understand the operation principle of TVS easily, the thermodynamic analysis, based on the ideal gas state equation and energy conservation equation, is detailed introduced. Some key operation parameters are optimized and suggested. As the low mass flow rate and low heat fluxes are involved in flow boiling of the annular pipe fluid, the Kandlikar’s boiling heat transfer correlation is selected to predict the flow boiling process, after validated with the related experimental results. One quasi-steady state model is established to investigate the heat transfer performance of double-pipe heat exchanger in normal gravity, with the bulk fluid natural convection, annular pipe two-phase boiling and inner pipe forced convection coupled from outside to inside. Determined by the local pressure and temperature, the fluid thermophysical properties are variable with the pipe length and time. With the variable fluid thermophysical properties, both the static analysis and the transient thermal performance of TVS heat exchanger are investigated respectively. Meanwhile, effects of the external natural convection and the pipe sizes on the thermal and flow performance of heat exchanger are detailed researched and analyzed. Some valuable conclusions are obtained and significant to optimize the TVS heat exchanger design.

  14. Review of liquid metal heat pipe work at Los Alamos

    International Nuclear Information System (INIS)

    Reid, R.S.; Merrigan, M.A.; Sena, J.T.

    1990-01-01

    A survey of space-power related liquid metal heat pipe work at Los Alamos National Laboratory is presented. Heat pipe development at Los Alamos has been on-going since 1963. Heat pipes were initially developed for thermionic nuclear-electrical power production in space. Since then Los Alamos has developed liquid metal heat pipes for numerous applications related to high temperature systems in both the space and terrestrial environments. Some of these applications include thermionic electrical generators, thermoelectric energy conversion (both in-core and direct radiation), thermal energy storage, hypersonic vehicle leading edge cooling, and heat pipe vapor laser cells. Some of the work performed at Los Alamos has been documented in internal reports that are often little-known. A representative description and summary of progress in space-related liquid metal heat pipe technology is provided followed by a reference section citing sources where these works may be found. 53 refs

  15. Pressure Controlled Heat Pipe for Precise Temperature Control, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research project will develop Pressure Controlled Heat Pipes (PCHPs) for precise temperature control (milli-Kelvin level). Several...

  16. Heat-pipe heat transport system for Stirling space power converter

    Science.gov (United States)

    Alger, Donald L.

    Life issues relating to a sodium-heat-pipe heat transport system are discussed. The heat-pipe system provides heat, at a temperature of 1050 K, to a 50-kWe Stirling engine/linear alternator power converter called the Stirling space power converter. Because corrosion of heat-pipe materials in contact with sodium can affect the life of the heat pipe, a literature review of sodium corrosion processes was performed. It was found that impurity reactions, primarily oxygen, and dissolution of alloy elements were the two corrosion processes likely to be operative in the heat pipe. Approaches that are being taken to minmize these corrosion processes are discussed.

  17. Mathematical Modeling of Loop Heat Pipes

    Science.gov (United States)

    Kaya, Tarik; Ku, Jentung; Hoang, Triem T.; Cheung, Mark L.

    1998-01-01

    The primary focus of this study is to model steady-state performance of a Loop Heat Pipe (LHP). The mathematical model is based on the steady-state energy balance equations at each component of the LHP. The heat exchange between each LHP component and the surrounding is taken into account. Both convection and radiation environments are modeled. The loop operating temperature is calculated as a function of the applied power at a given loop condition. Experimental validation of the model is attempted by using two different LHP designs. The mathematical model is tested at different sink temperatures and at different elevations of the loop. Tbc comparison of the calculations and experimental results showed very good agreement (within 3%). This method proved to be a useful tool in studying steady-state LHP performance characteristics.

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

    Science.gov (United States)

    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. Oscillating heat pipe simulation considering dryout phenomena

    Science.gov (United States)

    Senjaya, Raffles; Inoue, Takayoshi

    2014-10-01

    In heat transport devices such as oscillating heat pipe (OHP), dryout phenomena is very important and avoided in order to give the optimum performance. However, from the previous studies (including our studies), the dryout phenomena in OHP and its mechanism are still unclear. In our studies of OHP (Senjaya and Inoue in Appl Thermal Eng 60:251-255, 2013; Int J Heat Mass Transfer 60:816-824, 2013; Int J Heat Mass Transfer 60:825-835, 2013), we introduced the importance and roles of liquid film in the operating principle of OHP. In our previous simulation, the thickness of liquid film was assumed to be uniform along a vapor plug. Then, dryout never occurred because there was the liquid transfer from the liquid film in the cooling section to that in the heating section. In this research, the liquid film is not treated uniformly but it is meshed similarly with the vapor plugs and liquid slugs. All governing equations are also solved in each control volume of liquid film. The simulation results show that dryout occurs in the simulation without bubble generation and growth. Dryout is started in the middle of vapor plug, because the liquid supply from the left and right liquid slugs cannot reach until the liquid film in the middle of vapor plug, and propagates to the left and right sides of a vapor plug. By inserting the bubble generation and growth phenomena, dryout does not occur because the wall of heating section is always wetted during the bubble growth and the thickness of liquid film is almost constant. The effects of meshing size of liquid film and wall temperature of heating section are also investigated. The results show that the smaller meshing size, the smaller liquid transfer rate and the faster of dryout propagation. In the OHP with higher wall temperature of heating section, dryout and its propagation also occur faster.

  20. Numerical and Experimental Investigations of a Rotating Heat Pipe

    Energy Technology Data Exchange (ETDEWEB)

    Jankowski, Todd A. [Univ. of New Mexico, Albuquerque, NM (United States)

    2007-05-01

    Rotating and revolving heat pipes have been used in a variety of applications including heat pipe heat exchangers, cooling of rotating electrical machines, and heat removal in high speed cutting operations. The use of heat pipes in rotating environments has prompted many analytical, numerical, and experimental investigations of the heat transfer characteristics of these devices. Past investigations, however, have been restricted to the study of straight heat pipes. In this work, a curved rotating heat pipe is studied numerically and experimentally. In certain types of rotating machines, heat generating components, which must be cooled during normal operation, are located at some radial distance from the axis of rotation. The bent heat pipe studied here is shown to have advantages when compared to the conventional straight heat pipes in these off-axis cooling scenarios. The heat pipe studied here is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is concentric with the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. Furthermore, the heat pipe uses an annular gap wick structure. Incorporating an annular gap wick structure into the heat pipe allows for operation in a non-rotating environment. A numerical model of this rotating heat pipe is developed. The analysis is based on a two-dimensional finite-difference model of the liquid flow coupled to a one-dimensional model of the vapor flow. Although the numerical model incorporates many significant aspects of the fluid flow, the flow in the actual heat pipe is expected to be threedimensional. The rotating heat pipe with the S-shaped curve is also studied experimentally to determine how well the numerical model captures the key

  1. Heats pipes for temperature homogenization: A literature review

    International Nuclear Information System (INIS)

    Blet, Nicolas; Lips, Stéphane; Sartre, Valérie

    2017-01-01

    Highlights: • This paper is a review based on more than sixty references. • The review is sorted into various application fields. • Quantitative values of thermal gradients are compared with and without heat pipes. • Specificities of mentioned heat pipes are compared to other functions of heat pipes. - Abstract: Heat pipes offer high effective heat transfer in a purely passive way. Other specific properties of heat pipes, like temperature homogenization, can be also reached. In this paper, a literature review is carried out in order to investigate the existing heat pipe systems mainly aiming the reduction of temperature gradients. The review gathering more than sixty references is sorted into various application fields, like thermal management of electronics, of storage vessels or of satellites, for which the management of the temperature uniformity differs by the isothermal surface area, temperature ranges or the targeted precision of the temperature flattening. A summary of heat pipe characteristics for this function of temperature homogenization is then performed to identify their specificities, compared to other applications of heat pipes.

  2. A parametric study of porous wick in heat pipe

    International Nuclear Information System (INIS)

    Park, Yong Jin; Jun, Sang Ook; Jung, Ji Hun; Kim, Jeong Hwa; Lee, Dong Ho

    2008-01-01

    A Heat pipe which acquires a power by a capillary force has been used to mainly cool heat sources in satellites for long times. Among types of heat pipes, Loop Heat Pipe, Capillary Pumped Loop have usually used porous wicks such as sintered powder and fine wick to circulate a working fluid. These porous wicks have many design variables which affect thermal phenomena such as a capillary driven force, disjoining pressure, drying limitation, boiling limitation, etc. Additionally, Fins connecting an evaporator surface with a porous wick also after thermal characteristics of heat pipe. Especially, a vapor blanket thickness being main variables to decide a wick thickness has to do with fin sizes. Accordingly, understanding design variables' characteristics of porous wicks and fins is important to execute design optimization of heat pipe. In this paper, analytical methods and results will be discussed in terms of parametric study

  3. Analysis of the transient compressible vapor flow in heat pipe

    International Nuclear Information System (INIS)

    Jang, J.H.; Faghri, A.; Chang, W.S.

    1989-07-01

    The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual vapor flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures

  4. Multiphase numerical analysis of heat pipe with different working fluids for solar applications

    Science.gov (United States)

    Aswath, S.; Netaji Naidu, V. H.; Padmanathan, P.; Raja Sekhar, Y.

    2017-11-01

    Energy crisis is a prognosis predicted in many cases with the indiscriminate encroachment of conventional energy sources for applications on a massive scale. This prediction, further emboldened by the marked surge in global average temperatures, attributed to climate change and global warming, the necessity to conserve the environment and explore alternate sources of energy is at an all-time high. Despite being among the lead candidates for such sources, solar energy is utilized far from its vast potential possibilities due to predominant economic constraints. Even while there is a growing need for solar panels at more affordable rates, the other options to harness better out of sun’s energy is to optimize and improvise existing technology. One such technology is the heat pipe used in Evacuated Tube Collectors (ETC). The applications of heat pipe have been gaining momentum in various fields since its inception and substantial volumes of research have explored optimizing and improving the technology which is proving effective in heat recovery and heat transfer better than conventional systems. This paper carries out a computational analysis on a comparative simulation between two working fluids within heat pipe of same geometry. It further endeavors to study the multiphase transitions within the heat pipe. The work is carried out using ANSYS Fluent with inputs taken from solar data for the location of Vellore, Tamil Nadu. A wickless, gravity-assisted heat pipe (GAHP) is taken for the simulation. Water and ammonia are used as the working fluids for comparative multiphase analysis to arrive at the difference in heat transfer at the condenser section. It is demonstrated that a heat pipe ETC with ammonia as working fluid showed higher heat exchange (temperature difference) as against that of water as working fluid. The multiphase model taken aided in study of phase transitions within both cases and supported the result of ammonia as fluid being a better candidate.

  5. Heat transfer characteristics and limitations analysis of heat-pipe-cooled thermal protection structure

    International Nuclear Information System (INIS)

    Guangming, Xiao; Yanxia, Du; Yewei, Gui; Lei, Liu; Xiaofeng, Yang; Dong, Wei

    2014-01-01

    The theories of heat transfer, thermodynamics and fluid dynamics are employed to develop the coupled heat transfer analytical methods for the heat-pipe-cooled thermal protection structure (HPC TPS), and a three-dimensional numerical method considering the sonic limit of heat pipe is proposed. To verify the calculation correctness, computations are carried out for a typical heat pipe and the results agree well with experimental data. Then, the heat transfer characteristics and limitations of HPC TPS are mainly studied. The studies indicate that the use of heat pipe can reduce the temperature at high heat flux region of structure efficiently. However, there is a frozen startup period before the heat pipe reaching a steady operating state, and the sonic limit will be a restriction on the heat transfer capability. Thus, the effects of frozen startup must be considered for the design of HPC TPS. The simulation model and numerical method proposed in this paper can predict the heat transfer characteristics of HPC TPS quickly and exactly, and the results will provide important references for the design or performance evaluation of HPC TPS. - Highlights: • Numerical methods for the heat-pipe-cooled thermal protection structure are studied. • Three-dimensional simulation model considering sonic limit of heat pipe is proposed. • The frozen startup process of the embedded heat pipe can be predicted exactly. • Heat transfer characteristics of TPS and limitations of heat pipe are discussed

  6. Low Cost High Performance Generator Technology Program. Volume 5. Heat pipe topical, appendices

    International Nuclear Information System (INIS)

    1975-07-01

    Work performed by Dynatherm Corporation for Teledyne Isotopes during a program entitled ''Heat Pipe Fabrication, Associated Technical Support and Reporting'' is reported. The program was initiated on November 29, 1972; the main objectives were accomplished with the delivery of the heat pipes for the HPG. Life testing of selected heat pipe specimens is continuing to and beyond the present date. The program consisted of the following tasks: Heat Pipe Development of Process Definition; Prototype Heat Pipes for Fin Segment Test; HPG Heat Pipe Fabrication and Testing; Controlled Heat Pipe Life Test; and Heat Pipe Film Coefficient Determination

  7. Low Cost High Performance Generator Technology Program. Volume 5. Heat pipe topical, appendices

    Energy Technology Data Exchange (ETDEWEB)

    1975-07-01

    Work performed by Dynatherm Corporation for Teledyne Isotopes during a program entitled ''Heat Pipe Fabrication, Associated Technical Support and Reporting'' is reported. The program was initiated on November 29, 1972; the main objectives were accomplished with the delivery of the heat pipes for the HPG. Life testing of selected heat pipe specimens is continuing to and beyond the present date. The program consisted of the following tasks: Heat Pipe Development of Process Definition; Prototype Heat Pipes for Fin Segment Test; HPG Heat Pipe Fabrication and Testing; Controlled Heat Pipe Life Test; and Heat Pipe Film Coefficient Determination. (TFD)

  8. Heat losses through pipe connections in hot water stores

    DEFF Research Database (Denmark)

    Andersen, Elsa; Fan, Jianhua; Furbo, Simon

    2007-01-01

    The heat loss from pipe connections at the top of hot water storage tanks with and without a heat trap is investigated theoretically and compared to similar experimental investigations. Computational Fluid Dynamics (CFD) is used for the theoretical analysis. The investigations show that the heat...... loss from an ideally insulated pipe connected to the top of a hot water tank is mainly due to a natural convection flow in the pipe, that the heat loss coefficient of pipes connected to the top of a hot water tank is high, and that a heat trap can reduce the heat loss coefficient significantly. Further......, calculations show that the yearly thermal performance of solar domestic hot water systems is strongly reduced if the hot water tank has a thermal bridge located at the top of the tank....

  9. Commercial high efficiency dehumidification systems using heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    1993-09-01

    An improved heat pipe design using separately connected two-section one-way flow heat pipes with internal microgrooves instead of wicks is described. This design is now commercially available for use to increase the dehumidification capacity of air conditioning systems. The design also includes a method of introducing fresh air into buildings while recovering heat and controlling the humidity of the incoming air. Included are applications and case studies, load calculations and technical data, and installation, operation, and maintenance information.

  10. Heat pipes and solid sorption transformations fundamentals and practical applications

    CERN Document Server

    Vasiliev, LL

    2013-01-01

    Developing clean energy and utilizing waste energy has become increasingly vital. Research targeting the advancement of thermally powered adsorption cooling technologies has progressed in the past few decades, and the awareness of fuel cells and thermally activated (heat pipe heat exchangers) adsorption systems using natural refrigerants and/or alternatives to hydrofluorocarbon-based refrigerants is becoming ever more important. Heat Pipes and Solid Sorption Transformations: Fundamentals and Practical Applications concentrates on state-of-the-art adsorption research and technologies for releva

  11. Design and manufacture of ceramic heat pipes for high temperature applications

    International Nuclear Information System (INIS)

    Meisel, Peter; Jobst, Matthias; Lippmann, Wolfgang; Hurtado, Antonio

    2015-01-01

    Heat exchangers based on ceramic heat pipes were designed for use under highly abrasive and corrosive atmospheres at temperatures in the range of 800–1200 °C for high-temperature power-engineering applications. The presented heat pipes are gravity assisted and based on a multi-layer concept comprising a ceramic cladding and an inner metal tube that contains sodium as the working fluid. Hermetical encapsulation of the working fluid was achieved by electron-beam welding of the inner metal tube. Subsequently, closure of the surrounding ceramic tube was performed by laser brazing technology using a glass solder. Temperature resistance and functionality of the manufactured ceramic thermosyphons could be confirmed experimentally in a hot combustion gas atmosphere at temperatures up to 1100 °C. The ceramic tubes used had an outer diameter of 22 mm and a total length of 770 mm. The measured axial heat transfer of the ceramic gravity assisted heat pipes at the stationary operating point with cold/hot gas temperature of 100 °C/900 °C was 400 W. The result of the calculation using the created mathematical model amounted to 459 W. - Highlights: • Heat-pipe design consists of a ceramic shell and an inner metallic tube. • Laser brazing technology is suitable to seal ceramic heat-pipes. • Thermal characteristic of double wall thermosyphon was modelled using FEM code. • Experimental investigations demonstrated functionality of double wall thermosyphons

  12. Survey of heat-pipe application under nuclear environment

    International Nuclear Information System (INIS)

    Tsuyuzaki, Noriyoshi; Saito, Takashi; Okamoto, Yoshizo; Hishida, Makoto; Negishi, Kanji.

    1986-11-01

    Heat pipes today are employed in a wide variety of special heat transfer applications including nuclear reactor. In this nuclear technology area in Japan, A headway speed of the heat pipe application technique is not so high because of safety confirmation and investigation under each developing step. Especially, the outline of space craft is a tendency to increase the size. Therefore, the power supply is also tendency to increase the outlet power and keep the long life. Under SP-100 project, the development of nuclear power supply system which power is 1400 - 1600 KW thermal and 100 KW electric power is steadily in progress. Many heat pipes are adopted for thermionic conversion and coolant system in order to construct more safety and light weight system for the project. This paper describes the survey of the heat pipe applications under the present and future condition for nuclear environment. (author)

  13. Impact of Microgroove Shape on Flat Miniature Heat Pipe Efficiency

    Directory of Open Access Journals (Sweden)

    François Ternet

    2018-01-01

    Full Text Available Miniature heat pipes are considered to be an innovative solution able to dissipate high heat with low working fluid fill charge, provide automatic temperature control, and operate with minimum energy consumption and low noise levels. A theoretical analysis on heat pipe thermal performance using Deionized water or n-pentane as the working fluid has been carried out. Analysis on the maximum heat and capillary limitation is conducted for three microgroove cross sections: rectangular, triangular, and trapezoidal. The effect of microgroove height and width, effective length, trapezoidal microgroove inclination angle, and microgroove shape on heat pipe performance is analysed. Theoretical and experimental investigations of the heat pipes’ heat transport limitations and thermal resistances are conducted.

  14. Methodology for Life Testing of Refractory Metal / Sodium Heat Pipes

    International Nuclear Information System (INIS)

    Martin, James J.; Reid, Robert S.

    2006-01-01

    This work establishes an approach to generate carefully controlled data to find heat pipe operating life with material-fluid combinations capable of extended operation. To accomplish this goal acceleration is required to compress 10 years of operational life into 3 years of laboratory testing through a combination of increased temperature and mass fluence. Specific test series have been identified, based on American Society for Testing and Materials (ASTM) specifications, to investigate long-term corrosion rates. The refractory metal selected for demonstration purposes is a molybdenum-44.5% rhenium alloy formed by powder metallurgy. The heat pipes each have an annular crescent wick formed by hot isostatic pressing of molybdenum-rhenium wire mesh. The heat pipes are filled by vacuum distillation with purity sampling of the completed assembly. Round-the-clock heat pipe tests with 6-month destructive and non-destructive inspection intervals are conducted to identify the onset and level of corrosion. Non-contact techniques are employed to provide power to the evaporator (radio frequency induction heating at 1 to 5 kW per heat pipe) and calorimetry at the condenser (static gas gap coupled water cooled calorimeter). The planned operating temperature range extends from 1123 to 1323 K. Accomplishments before project cancellation included successful development of the heat pipe wick fabrication technique, establishment of all engineering designs, baseline operational test requirements, and procurement/assembly of supporting test hardware systems. (authors)

  15. Micro-Channel Embedded Pulsating Heat Pipes, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating Heat Pipes (ME-PHPs) represents a sophisticated and enabling...

  16. Micro-Channel Embedded Pulsating Heat Pipes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — As the need for thermal control technology becomes more demanding Micro-Channel Embedded Pulsating Heat Pipes (ME-PHPs) represents a sophisticated and enabling...

  17. Titanium Loop Heat Pipes for Space Nuclear Radiators, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project will develop titanium Loop Heat Pipes (LHPs) that can be used in low-mass space nuclear radiators, such as...

  18. Startup analysis for a high temperature gas loaded heat pipe

    Science.gov (United States)

    Sockol, P. M.

    1973-01-01

    A model for the rapid startup of a high-temperature gas-loaded heat pipe is presented. A two-dimensional diffusion analysis is used to determine the rate of energy transport by the vapor between the hot and cold zones of the pipe. The vapor transport rate is then incorporated in a simple thermal model of the startup of a radiation-cooled heat pipe. Numerical results for an argon-lithium system show that radial diffusion to the cold wall can produce large vapor flow rates during a rapid startup. The results also show that startup is not initiated until the vapor pressure p sub v in the hot zone reaches a precise value proportional to the initial gas pressure p sub i. Through proper choice of p sub i, startup can be delayed until p sub v is large enough to support a heat-transfer rate sufficient to overcome a thermal load on the heat pipe.

  19. Variable Conductance Heat Pipes for Radioisotope Stirling Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall program objective is to develop a high temperature variable conductance heat pipe (VCHP) backup radiator, and integrate it into a Stirling radioisotope...

  20. Additive Manufacturing of Heat Pipe Wicks, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Wick properties are often the limiting factor in a heat pipe design. Current technology uses conventional sintering of metal powders, screen wick, or grooves to...

  1. Pulsating Heat Pipe for Cryogenic Fluid Management, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A passive Pulsating Heat Pipe (PHP) system is proposed to distribute cooling over broad areas with low additional system mass. The PHP technology takes advantage of...

  2. Laser application of heat pipe technology in energy related programs

    International Nuclear Information System (INIS)

    Carbone, R.J.

    1975-01-01

    The design and operating parameters for a heat pipe laser utilizing metal vapors are proposed. The laser would be applied to laser induced fusion, laser induced chemistry, laser isotope separation, and power transport using optical beams. (U.S.)

  3. Heat-Pipe-Associated Localized Thermoelectric Power Generation System

    Science.gov (United States)

    Kim, Pan-Jo; Rhi, Seok-Ho; Lee, Kye-Bock; Hwang, Hyun-Chang; Lee, Ji-Su; Jang, Ju-Chan; Lee, Wook-Hyun; Lee, Ki-Woo

    2014-06-01

    The present study focused on how to improve the maximum power output of a thermoelectric generator (TEG) system and move heat to any suitable space using a TEG associated with a loop thermosyphon (loop-type heat pipe). An experimental study was carried out to investigate the power output, the temperature difference of the thermoelectric module (TEM), and the heat transfer performance associated with the characteristic of the researched heat pipe. Currently, internal combustion engines lose more than 35% of their fuel energy as recyclable heat in the exhaust gas, but it is not easy to recycle waste heat using TEGs because of the limited space in vehicles. There are various advantages to use of TEGs over other power sources, such as the absence of moving parts, a long lifetime, and a compact system configuration. The present study presents a novel TEG concept to transfer heat from the heat source to the sink. This technology can transfer waste heat to any location. This simple and novel design for a TEG can be applied to future hybrid cars. The present TEG system with a heat pipe can transfer heat and generate power of around 1.8 V with T TEM = 58°C. The heat transfer performance of a loop-type heat pipe with various working fluids was investigated, with water at high heat flux (90 W) and 0.05% TiO2 nanofluid at low heat flux (30 W to 70 W) showing the best performance in terms of power generation. The heat pipe can transfer the heat to any location where the TEM is installed.

  4. Heat pipe cooling system for underground, radioactive waste storage tanks

    International Nuclear Information System (INIS)

    Cooper, K.C.; Prenger, F.C.

    1980-02-01

    An array of 37 heat pipes inserted through the central hole at the top of a radioactive waste storage tank will remove 100,000 Btu/h with a heat sink of 70 0 F atmospheric air. Heat transfer inside the tank to the heat pipe is by natural convection. Heat rejection to outside air utilizes a blower to force air past the heat pipe condenser. The heat pipe evaporator section is axially finned, and is constructed of stainless steel. The working fluid is ammonia. The finned pipes are individually shrouded and extend 35 ft down into the tank air space. The hot tank air enters the shroud at the top of the tank and flows downward as it is cooled, with the resulting increased density furnishing the pressure difference for circulation. The cooled air discharges at the center of the tank above the sludge surface, flows radially outward, and picks up heat from the radioactive sludge. At the tank wall the heated air rises and then flows inward to comple the cycle

  5. Heat pipe thermal control of slender optics probes

    International Nuclear Information System (INIS)

    Prenger, F.C.

    1979-01-01

    The thermal design for a stereographic viewing system is presented. The design incorporates an annular heat pipe and thermal isolation techniques. Test results are compared with design predictions for a prototype configuration. Test data obtained during heat pipe startup showing temperature gradients along the evaporator wall are presented. Correlations relating maximum wall temperature differences to a liquid Reynolds number were obtained at low power levels. These results are compared with Nusselt's Falling Film theory

  6. Optimum length of finned pipe for waste heat recovery

    International Nuclear Information System (INIS)

    Soeylemez, M.S.

    2008-01-01

    A thermoeconomic feasibility analysis is presented yielding a simple algebraic optimization formula for estimating the optimum length of a finned pipe that is used for waste heat recovery. A simple economic optimization method is used in the present study by combining it with an integrated overall heat balance method based on fin effectiveness for calculating the maximum savings from a waste heat recovery system

  7. The effect of external boundary conditions on condensation heat transfer in rotating heat pipes

    Science.gov (United States)

    Daniels, T. C.; Williams, R. J.

    1979-01-01

    Experimental evidence shows the importance of external boundary conditions on the overall performance of a rotating heat pipe condenser. Data are presented for the boundary conditions of constant heat flux and constant wall temperature for rotating heat pipes containing either pure vapor or a mixture of vapor and noncondensable gas as working fluid.

  8. A study on the heat transfer characteristics of a self-oscillating heat pipe

    International Nuclear Information System (INIS)

    Yoon, Seok Hun; Oh, Cheol; Choi, Jae Hyuk

    2002-01-01

    In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe

  9. Residual stress improvement for pipe weld by means of induction heating pre-flawed pipe

    International Nuclear Information System (INIS)

    Umemoto, T.; Yoshida, K.; Okamoto, A.

    1980-01-01

    The intergranular stress corrosion cracking (IGSCC) has been found in type 304 stainless steel piping of several BWR plants. It is already well known that IGSCC is most likely to occur when three essential factors, material sensitization, high tensile stress and corrosive environment, are present. If the welding residual stress is sufficiently high (200 to approximately 400 MPa) in the inside piping surface near the welded joint, then it may be one of the biggest contributors to IGSCC. If the residual stress is reduced or reversed by some way, the IGSCC will be effectively mitigated. In this paper a method to improve the residual stress named IHSI (Induction Heating Stress Improvement) is explained. IHSI aims to improve the condition of residual stress in the inside pipe surface using the thermal stress induced by the temperature difference in pipe wall, that is produced when the pipe is heated from the outside surface by an induction heating coil and cooled on the inside surface by water simultaneously. This method becomes more attractive when it can be successfully applied to in-service piping which might have some pre-flaw. In order to verify the validity of IHSI for such piping, some experiments and calculations using finite element method were conducted. These results are mainly discussed in this paper from the view-points of residual stress, flaw behaviour during IHSI and material deterioration. (author)

  10. Heat pipe heat transport system for the Stirling Space Power Converter (SSPC)

    Science.gov (United States)

    Alger, Donald L.

    1992-08-01

    Life issues relating to a sodium heat pipe heat transport system are described. The heat pipe system provides heat, at a temperature of 1050 K, to a 50 kWe Stirling engine/linear alternator power converter called the Stirling Space Power Converter (SSPC). The converter is being developed under a National Aeronautics and Space Administration program. Since corrosion of heat pipe materials in contact with sodium can impact the life of the heat pipe, a literature review of sodium corrosion processes was performed. It was found that the impurity reactions, primarily oxygen, and dissolution of alloy elements were the two corrosion process likely to be operative in the heat pipe. Approaches that are being taken to minimize these corrosion processes are discussed.

  11. Evaluation of piping heat transfer, piping flow regimes, and steam generator heat transfer for the Semiscale Mod-1 isothermal tests

    International Nuclear Information System (INIS)

    French, R.T.

    1975-08-01

    Selected experimental data pertinent to piping heat transfer, transient fluid flow regimes, and steam generator heat transfer obtained during the Semiscale Mod-1 isothermal blowdown test series (Test Series 1) are analyzed. The tests in this first test series were designed to provide counterparts to the LOFT nonnuclear experiments. The data from the Semiscale Mod-1 intact and broken loop piping are evaluated to determine the surface heat flux and average heat transfer coefficients effective during the blowdown transient and compared with well known heat transfer correlations used in the RELAP4 computer program. Flow regimes in horizontal pipe sections are calculated and compared with data obtained from horizontal and vertical densitometers and with an existing steady state flow map. Effects of steam generator heat transfer are evaluated quantitatively and qualitatively. The Semiscale Mod-1 data and the analysis presented in this report are valuable for evaluating the adequacy and improving the predictive capability of analytical models developed to predict system response to piping heat transfer, piping flow regimes, and steam generator heat transfer during a postulated loss-of-coolant accident (LOCA) in a pressurized water reactor (PWR). 16 references. (auth)

  12. Heat pipe effects in nuclear waste isolation: a review

    International Nuclear Information System (INIS)

    Doughty, C.; Pruess, K.

    1985-12-01

    The existence of fractures favors heat pipe development in a geologic repository as does a partially saturated medium. A number of geologic media are being considered as potential repository sites. Tuff is partially saturated and fractured, basalt and granite are saturated and fractured, salt is unfractured and saturated. Thus the most likely conditions for heat pipe formation occur in tuff while the least likely occur in salt. The relative permeability and capillary pressure dependences on saturation are of critical importance for predicting thermohydraulic behavior around a repository. Mineral redistribution in heat pipe systems near high-level waste packages emplaced in partially saturated formations may significantly affect fluid flow and heat transfer processes, and the chemical environment of the packages. We believe that a combined laboratory, field, and theoretical effort will be needed to identify the relevant physical and chemical processes, and the specific parameters applicable to a particular site. 25 refs., 1 fig

  13. Loop heat pipes - highly efficient heat-transfer devices for systems of sun heat supply

    Energy Technology Data Exchange (ETDEWEB)

    Maydanik, Yu. [Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Thermophysics

    2004-07-01

    Loop heat pipes (LHPs) are hermetic heat-transfer devices operating on a closed evaporation-condensation cycle with the use of capillary pressure for pumping the working fluid [1]. In accordance with this, they possess all the main advantages of conventional heat pipes, but, as distinct from the latter, have a considerably higher heat-transfer capacity, especially when operating in the ''antigravity'' regime, when heat is transferred from above downwards. Besides, LHPs possess a higher functional versatility, are adaptable to different operating conditions and provide great scope for various design embodiments. This is achieved at the expense of both the original design of the device and the properties of the wick - a special capillary structure used for the creation of capillary pressure. The LHP schematic diagram is given in Fig. 1. The device contains an evaporator and a condenser - heat exchanger connected by means of smooth-walled pipe-lines with a relatively small diameter intended for separate motion of vapor and liquid. At present loop heat pipes are most extensively employed in thermoregulation systems of spacecrafts. Miniature LHPs are used for cooling electronics and computers. At the same time there exists a considerable potential of using these devices for the recovery of low-grade (waste) heat from different sources, and also in systems of sun heat supply. In the latter case LHPs may serve as an efficient heat-transfer link between a sun collector and a heat accumulator, which has a low thermal resistance and does not consume any additional energy for pumping the working fluid between them. (orig.)

  14. Heat Rejection System for Thermal Management in Space Utilizing a Planar Variable-Conductance Heat Pipe

    Data.gov (United States)

    National Aeronautics and Space Administration — The integral planar variable conductance heat pipe (VCHP) technology represents a novel, low-TRL heat rejection technology which should operate efficiently and...

  15. Heat Pipe Heat Exchangers with Double Isolation Layers for Prevention of Interpath Leakage, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Cooling Technologies, Inc. (ACT), supported by Hamilton Sundstrand, proposes to develop a heat pipe heat exchanger that is low mass and provides two levels...

  16. Heat pipe heat exchanger and its potential to energy recovery in the tropics

    Directory of Open Access Journals (Sweden)

    Yau Yat H.

    2015-01-01

    Full Text Available The heat recovery by the heat pipe heat exchangers was studied in the tropics. Heat pipe heat exchangers with two, four, six, and eight numbers of rows were examined for this purpose. The coil face velocity was set at 2 m/s and the temperature of return air was kept at 24°C in this study. The performance of the heat pipe heat exchangers was recorded during the one week of operation (168 hours to examine the performance data. Then, the collected data from the one week of operation were used to estimate the amount of energy recovered by the heat pipe heat exchangers annually. The effect of the inside design temperature and the coil face velocity on the energy recovery for a typical heat pipe heat exchanger was also investigated. In addition, heat pipe heat exchangers were simulated based on the effectiveness-NTU method, and their theoretical values for the thermal performance were compared with the experimental results.

  17. Aerodynamic heating of ballistic missile including the effects of gravity

    Indian Academy of Sciences (India)

    The aerodynamic heating of a ballistic missile due to only convection is analysed taking into consideration the effects of gravity. The amount of heat transferred to the wetted area and to the nose region has been separately determined, unlike A Miele's treatise without consideration of gravity. The peak heating ratesto the ...

  18. Aerodynamic heating of ballistic missile including the effects of gravity

    Indian Academy of Sciences (India)

    Abstract. The aerodynamic heating of a ballistic missile due to only convection is analysed taking into consideration the effects of gravity. The amount of heat transferred to the wetted area and to the nose region has been separately determined, unlike A Miele's treatise without consideration of gravity. The peak heating rates ...

  19. Aerodynamic heating of ballistic missile including the effects of gravity

    Indian Academy of Sciences (India)

    http://www.ias.ac.in/article/fulltext/sadh/025/05/0463-0473. Keywords. Aerodynamic heating; ballistic missile; gravity; flat-earth. Abstract. The aerodynamic heating of a ballistic missile due to only convection is analysed taking into consideration the effects of gravity. The amount of heat transferred to the wetted area and to the ...

  20. Analysis of the Technological Parameters of the Heat Exchanger in the Heating Pipe

    Directory of Open Access Journals (Sweden)

    Knyazev Vladimir

    2017-01-01

    Full Text Available The main purpose of this article is to analyze the selecting of technological parameters for the heat exchanger to improve the heat transfer and reduce the noise during operation in the heating pipe, which is used in the different systems of the planes and helicopters. In result of this study, the best technical parameters are found, considering different variations of deformation cutting heat exchanger pipes.

  1. Comprehensive optimization of a heat pipe radiator assembly filled with ammonia or acetone

    Energy Technology Data Exchange (ETDEWEB)

    Vlassov, Valeri V.; De Sousa, Fabiano L.; Takahashi, Walter K. [National Institute for Space Research (INPE/DMC), Av. dos Astronautas, 1758. S.J.Campos, SP, 12227-010 (Brazil)

    2006-11-15

    Optimal mass characteristics for a heat pipe radiator assembly for space application are investigated. The assembly consists of the heat pipe itself, an evaporator saddle and a radiator. The internal HP geometry and the dimensions of the saddle and radiator panel are the variables to be optimized. Operational and structural constraints are considered and the assembly is optimized for different operational modes in 0g and 1g gravity conditions. A new global search metaheuristic, called generalized extremal optimization, was used as the optimization tool. The results show that under certain combinations of input parameters the assembly with acetone HP can be more weight effective than the one with ammonia, in spite of the liquid transport factor criterion indicates an opposite trend. (author)

  2. Felt-metal-wick heat-pipe solar receiver

    Energy Technology Data Exchange (ETDEWEB)

    Andraka, C.E.; Adkins, D.R.; Moss, T.A. [Sandia National Labs., Albuquerque, NM (United States); Cole, H.M. [Porous Metal Products, Jacksboro, TX (United States); Andreas, N.H. [Bekaert Corp., Marietta, GA (United States)

    1994-12-31

    Reflux heat-pipe receivers have been identified as a desirable interface to couple a Stirling-cycle engine with a parabolic dish solar concentrator. The reflux receiver provides power nearly isothermally to the engine heater heads while decoupling the heater head design from the solar absorber surface design. The independent design of the receiver and engine heater head leads to higher system efficiency. Heat pipe reflux receivers have been demonstrated at approximately 65 kW{sub t} power throughput. Several 25 to 30-kW{sub e} Stirling-cycle engines are under development, and will soon be incorporated in commercial dish-Stirling systems. These engines will require reflux receivers with power throughput limits reaching 90-kW{sub t}. The extension of heat pipe technology from 60 kW{sub t} to 100 kW{sub t} is not trivial. Current heat pipe wick technology is pushed to its limits. It is necessary to develop and test advanced wick structure technologies to perform this task. Sandia has developed and begun testing a Bekaert Corporation felt metal wick structure fabricated by Porous Metal Products Inc. This wick is about 95% porous, and has liquid permeability a factor of 2 to 8 times higher than conventional technologies for a given maximum pore radius. The wick has been successfully demonstrated in a bench-scale heat pipe, and a full-scale on-sun receiver has been fabricated. This report details the wick design, characterization and installation into a heat pipe receiver, and the results of the bench-scale tests are presented. The wick performance is modeled, and the model results are compared to test results.

  3. Water pipe network as a heat source for heat pump integrated into a district heating

    Science.gov (United States)

    Jadwiszczak, Piotr; Niemierka, Elżbieta

    2017-11-01

    The paper will present a technical analysis of the performance of the Heat Pumps (HP) installed in the domestic water pipe network for a big city scale. The HP integration scheme predicts the domestic water flow as a heat source and the district heating as a heat sink. The technical factors which influence on the estimated thermal power and performance of HP unit will be identified. Additionally, the pros and cons of HP operation in water intake will be determined. The analysis will be based on long-term measurement data from Głogów city.

  4. Experimental study on heat pipe heat removal capacity for passive cooling of spent fuel pool

    International Nuclear Information System (INIS)

    Xiong, Zhenqin; Wang, Minglu; Gu, Hanyang; Ye, Cheng

    2015-01-01

    Highlights: • A passively cooling SFP heat pipe with an 8.2 m high evaporator was tested. • Heat removed by the heat pipe is in the range of 3.1–16.8 kW. • The heat transfer coefficient of the evaporator is 214–414 W/m 2 /K. • The heat pipe performance is sensitive to the hot water temperature. - Abstract: A loop-type heat pipe system uses natural flow with no electrically driven components. Therefore, such a system was proposed to passively cool spent fuel pools during accidents to improve nuclear power station safety especially for station blackouts such as those in Fukushima. The heat pipe used for a spent fuel pool is large due to the spent fuel pool size. An experimental heat pipe test loop was developed to estimate its heat removal capacity from the spent fuel pool during an accident. The 7.6 m high evaporator is heated by hot water flowing vertically down in an assistant tube with a 207-mm inner diameter. R134a was used as the potential heat pipe working fluid. The liquid R134a level was 3.6 m. The tests were performed for water velocities from 0.7 to 2.1 × 10 −2 m/s with water temperatures from 50 to 90 °C and air velocities from 0.5 m/s to 2.5 m/s. The results indicate significant heat is removed by the heat pipe under conditions that may occur in the spent fuel pool

  5. Radiant heating tests of several liquid metal heat-pipe sandwich panels

    Science.gov (United States)

    Camarda, C. J.; Basiulis, A.

    1983-01-01

    Integral heat pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat load levels. The heat pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low distortion large area structures (e.g., space antennas) and laser mirrors.

  6. Numerical study on heat transfer characteristics of thermosyphon heat pipes using nanofluids

    International Nuclear Information System (INIS)

    Huminic, Gabriela; Huminic, Angel

    2013-01-01

    Highlights: • Numerical study of nanofluid heat transfer in thermosyphon heat pipes is performed. • Effect of nanoparticle concentration and operating temperature are studied. • Fe 2 O 3 –water nanofluid with 5.3% volume concentration shows the best performance. • Results show the improvement the thermal performances of thermosyphon heat pipe with nanofluids. - Abstract: In this work, a three-dimensional analysis is used to investigate the heat transfer of thermosyphon heat pipe using water and nanofluids as the working fluid. The study focused mainly on the effects of volume concentrations of nanoparticles and the operating temperature on the heat transfer performance of the thermosyphon heat pipe using the nanofluids. The analysis was performed for water and γ-Fe 2 O 3 nanoparticles, three volume concentrations of nanoparticles (0 vol.%, 2 vol.% and 5.3 vol.%) and four operating temperatures (60, 70, 80 and 90 °C). The numerical results show that the volume concentration of nanoparticles had a significant effect in reducing the temperature difference between the evaporator and condenser. Experimental and numerical results show qualitatively that the thermosyphon heat pipe using the nanofluid has better heat transfer characteristics than the thermosyphon heat pipe using water

  7. Heat Rejection Systems Utilizing Composites and Heat Pipes: Design and Performance Testing

    Science.gov (United States)

    Jaworske, Donald A.; Beach, Duane E.; Sanzi, James L.

    2007-01-01

    Polymer matrix composites offer the promise of reducing the mass and increasing the performance of future heat rejection systems. With lifetimes for heat rejection systems reaching a decade or more in a micrometeoroid environment, use of multiple heat pipes for fault tolerant design is compelling. The combination of polymer matrix composites and heat pipes is of particular interest for heat rejection systems operating on the lunar surface. A technology development effort is under way to study the performance of two radiator demonstration units manufactured with different polymer matrix composite face sheet resin and bonding adhesives, along with different titanium-water heat pipe designs. Common to the two radiator demonstration units is the use of high thermal conductivity fibers in the face sheets and high thermal conductivity graphite saddles within a light weight aluminum honeycomb core. Testing of the radiator demonstration units included thermal vacuum exposure and thermal vacuum exposure with a simulated heat pipe failure. Steady state performance data were obtained at different operating temperatures to identify heat transfer and thermal resistance characteristics. Heat pipe failure was simulated by removing the input power from an individual heat pipe in order to identify the diminished performance characteristics of the entire panel after a micrometeoroid strike. Freeze-thaw performance was also of interest. This paper presents a summary of the two radiator demonstration units manufactured to support this technology development effort along with the thermal performance characteristics obtained to date. Future work will also be discussed.

  8. Heat pipes. (Latest citations from the US Patent Bibliographic file with exemplary claims). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-01-01

    The bibliography contains citations of selected patents concerning the design, manufacture, and applications of heat pipes. The use of heat pipes in heat exchange systems for heat storage, heat transfer, and heat utilization is discussed. Applications include semiconductor cooling, use in engine components, and building cooling and heating. (Contains 250 citations and includes a subject term index and title list.)

  9. Progress of cryogenic pulsating heat pipes at UW-Madison

    Science.gov (United States)

    Diego Fonseca, Luis; Mok, Mason; Pfotenhauer, John; Miller, Franklin

    2017-12-01

    Space agencies continuously require innovative cooling systems that are lightweight, low powered, physically flexible, easily manufactured and, most importantly, exhibit high heat transfer rates. Therefore, Pulsating Heat Pipes (PHPs) are being investigated to provide these requirements. This paper summarizes the current development of cryogenic Pulsating Heat Pipes with single and multiple evaporator sections built and successfully tested at UW-Madison. Recently, a helium based Pulsating Heat Pipe with three evaporator and three condenser sections has been operated at fill ratios between 20 % and 80 % operating temperature range of 2.9 K to 5.19 K, resulting in a maximum effective thermal conductivity up to 50,000 W/m-K. In addition, a nitrogen Pulsating Heat Pipe has been built with three evaporator sections and one condenser section. This PHP achieved a thermal performance between 32,000 W/m-K and 96,000 W/m-K at fill ratio ranging from 50 % to 80 %. Split evaporator sections are very important in order to spread cooling throughout an object of interest with an irregular temperature distribution or where multiple cooling locations are required. Hence this type of configurations is a proof of concept which hasn’t been attempted before and if matured could be applied to cryo-propellant tanks, superconducting magnets and photon detectors.

  10. An analysis of electro-osmotic and magnetohydrodynamic heat pipes

    International Nuclear Information System (INIS)

    Harrison, M.A.

    1988-01-01

    Mechanically simple methods of improving heat transport in heat pipes are investigated. These methods are electro-osmotic and magnetohydrodynamic augmentation. For the electro-osmotic case, a detailed electrokinetic model is used. The electrokinetic model used includes the effects of pore surface curvature and multiple ion diffusivities. The electrokinetic model is extended to approximate the effects of elevated temperature. When the electro-osmotic model is combined with a suitable heat-pipe model, it is found that the electro-osmotic pump should be a thin membrane. Arguments are provided that support the use of a volatile electrolyte. For the magnetohydrodynamic case, a brief investigation is provided. A quasi-one-dimensional hydromagnetic duct flow model is used. This hydromagnetic model is extended to approximate flow effects unique to heat pipes. When combined with a suitable heat pipe model, it is found that there is no performance gain for the case considered. In fact, there are serious pressure-distribution problems that have not been previously recognized. Potential solutions to these pressure-distribution problems are suggested

  11. Transient thermal performance analysis of micro heat pipes

    International Nuclear Information System (INIS)

    Liu, Xiangdong; Chen, Yongping

    2013-01-01

    A theoretical analysis of transient fluid flow and heat transfer in a triangular micro heat pipes (MHP) has been conducted to study the thermal response characteristics. By introducing the system identification theory, the quantitative evaluation of the MHP's transient thermal performance is realized. The results indicate that the evaporation and condensation processes are both extended into the adiabatic section. During the start-up process, the capillary radius along axial direction of MHP decreases drastically while the liquid velocity increases quickly at the early transient stage and an approximately linear decrease in wall temperature arises along the axial direction. The MHP behaves as a first-order LTI control system with the constant input power as the 'step input' and the evaporator wall temperature as the 'output'. Two corresponding evaluation criteria derived from the control theory, time constant and temperature constant, are able to quantitatively evaluate the thermal response speed and temperature level of MHP under start-up, which show that a larger triangular groove's hydraulic diameter within 0.18–0.42 mm is able to accelerate the start-up and decrease the start-up temperature level of MHP. Additionally, the MHP starts up fastest using the fluid of ethanol and most slowly using the working fluid of methanol, and the start-up temperature reaches maximum level for acetone and minimum level for the methanol. -- Highlights: • Transient thermal response of micro heat pipe is simulated by an improved model. • Control theory is introduced to quantify the thermal response of micro heat pipe. • Evaluation criteria are proposed to represent thermal response of micro heat pipe. • Effects of groove dimensions and working fluids on start-up of micro heat pipe are evaluated

  12. Three-dimensional numerical analysis of heat and mass transfer in heat pipes

    Science.gov (United States)

    Kaya, Tarik; Goldak, John

    2007-06-01

    A three-dimensional finite-element numerical model is presented for simulation of the steady-state performance characteristics of heat pipes. The mass, momentum and energy conservation equations are solved for the liquid and vapor flow in the entire heat pipe domain. The calculated outer wall temperature profiles are in good agreement with the experimental data. The estimations of the liquid and vapor pressure distributions and velocity profiles are also presented and discussed. It is shown that the vapor flow field remains nearly symmetrical about the heat pipe centerline, even under a non-uniform heat load. The analytical method used to predict the heat pipe capillary limit is found to be conservative.

  13. Experimental investigation on a pulsating heat pipe with hydrogen

    International Nuclear Information System (INIS)

    Deng, H R; Liu, Y M; Ma, R F; Han, D Y; Gan, Z H; Pfotenhauer, J M

    2015-01-01

    The pulsating heat pipe (PHP) has been increasingly studied in cryogenic application, for its high transfer coefficient and quick response. Compared with Nb 3 Sn and NbTi, MgB 2 whose critical transformation temperature is 39 K, is expected to replace some high-temperature superconducting materials at 25 K. In order to cool MgB 2 , this paper designs a Hydrogen Pulsating Heat Pipe, which allows a study of applied heat, filling ratio, turn number, inclination angle and length of adiabatic section on the thermal performance of the PHP. The thermal performance of the hydrogen PHP is investigated for filling ratios of 35%, 51%, 70% at different heat inputs, and provides information regarding the starting process is received at three filling ratios. (paper)

  14. Kovar Micro Heat Pipe Substrates for Microelectronic Cooling

    Energy Technology Data Exchange (ETDEWEB)

    Benson, David A.; Burchett, Steven N.; Kravitz, Stanley H.; Robino, Charles V.; Schmidt, Carrie; Tigges, Chris P.

    1999-04-01

    We describe the development of a new technology for cooling microelectronics. This report documents the design, fabrication, and prototype testing of micro scale heat pipes embedded in a flat plate substrate or heat spreader. A thermal model tuned to the test results enables us to describe heat transfer in the prototype, as well as evaluate the use of this technology in other applications. The substrate walls are Kovar alloy, which has a coefficient of thermal expansion close to that of microelectronic die. The prototype designs integrating micro heat pipes with Kovar enhance thermal conductivity by more than a factor of two over that of Kovar alone, thus improving the cooling of micro-electronic die.

  15. Novel Thermal Control Concepts Using Micro Heat Pipes - Spacecraft Thermal Control

    National Research Council Canada - National Science Library

    Peterson, G

    2001-01-01

    ...; Flexible polymer heat pipes have been fabricated and modeled; Theses polymer heat pipes offer a greater degree of flexibility and a potentially higher effective thermal conductivity than any previously developed...

  16. Design of megawatt power level heat pipe reactors

    Energy Technology Data Exchange (ETDEWEB)

    Mcclure, Patrick Ray [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Poston, David Irvin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dasari, Venkateswara Rao [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reid, Robert Stowers [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-11-12

    An important niche for nuclear energy is the need for power at remote locations removed from a reliable electrical grid. Nuclear energy has potential applications at strategic defense locations, theaters of battle, remote communities, and emergency locations. With proper safeguards, a 1 to 10-MWe (megawatt electric) mobile reactor system could provide robust, self-contained, and long-term power in any environment. Heat pipe-cooled fast-spectrum nuclear reactors have been identified as a candidate for these applications. Heat pipe reactors, using alkali metal heat pipes, are perfectly suited for mobile applications because their nature is inherently simpler, smaller, and more reliable than “traditional” reactors. The goal of this project was to develop a scalable conceptual design for a compact reactor and to identify scaling issues for compact heat pipe cooled reactors in general. Toward this goal two detailed concepts were developed, the first concept with more conventional materials and a power of about 2 MWe and a the second concept with less conventional materials and a power level of about 5 MWe. A series of more qualitative advanced designs were developed (with less detail) that show power levels can be pushed to approximately 30 MWe.

  17. Ductile fracture behaviour of primary heat transport piping material ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    1. Introduction. The design of primary heat transport piping (PHT) of nuclear reactors has to ensure that uncontrolled failure does not occur under normal, faulted or accidental service conditions. One of the most severe failure scenarios traditionally envisaged is instantaneous double-ended guillotine break (DEGB), which ...

  18. Thermal design heat sinks, thermoelectrics, heat pipes, compact heat exchangers, and solar cells

    CERN Document Server

    Lee, H S

    2010-01-01

    The proposed is written as a senior undergraduate or the first-year graduate textbook,covering modern thermal devices such as heat sinks, thermoelectric generators and coolers, heat pipes, and heat exchangers as design components in larger systems. These devices are becoming increasingly important and fundamental in thermal design across such diverse areas as microelectronic cooling, green or thermal energy conversion, and thermal control and management in space, etc. However, there is no textbook available covering this range of topics. The proposed book may be used as a capstone design cours

  19. Electrically heated pipe in pipe system for hydrate prevention on the Campos Basin

    Energy Technology Data Exchange (ETDEWEB)

    Euphemio, Mauro; Montesanti, Jose Ricardo; Braganca, Elton Jorge; Almeida, Murilo Mesquita de; Coelho, Eduardo; Maia, Alexandre Rodrigues; Peres, Marcelo Borges [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2004-07-01

    This paper will refer briefly to some key aspects considered for the design of an Electrically Heated Pipe-in-Pipe- EHPIP system integrated to an Electric Submersible Pump-ESP, to be located at 1800 m water depth in the Campos Basin. In this system, under normal operation the well will be producing through the ESP and in case of long well shut in and during well restart up, a percentage of the electrical power will be delivered to heat the PIP system. The electrical system will have a common sub sea power cable and an Electrical Switch Module, to switch power alternatively to the heating system or to the pump. The systems will not operate simultaneously. (author)

  20. Design and demonstration of heat pipe cooling for NASP and evaluation of heating methods at high heating rates

    Energy Technology Data Exchange (ETDEWEB)

    Merrigan, M.A.; Sena, J.T.

    1989-01-01

    An evaluation of two heating methods for demonstration of NASP leading edge heat pipe technology was conducted. The heating methods were and rf induction heated plasma jet and direct rf induction. Tests were conducted to determine coupling from the argon plasma jet on a surface physically similar to a heat pipe. A molybdenum tipped calorimeter was fabricated and installed in an rf induction heated plasma jet for the test. The calorimetric measurements indicated a maximum power coupling of approximately 500 W/cm{sup 2} with the rf plasma jet. The effect of change in gas composition on the heating rate was investigated using helium. An alternative to the plasma heating of a heat pipe tip, an rf concentrator was evaluated for coupling to the hemispherical tip of a heat pipe. A refractory metal heat pipe was designed, fabricated, and tested for the evaluation. The heat pipe was designed for operation at 1400 to 1900 K with power input to 1000 W/cm{sup 2} over a hemispherical nose tip. Power input of 800 W/cm{sup 2} was demonstrated using the rf concentrator. 2 refs., 13 figs.

  1. Energy and exergy evaluation of an integrated solar heat pipe wall ...

    Indian Academy of Sciences (India)

    The rate of increasing in temperature of air becomes negligible after 30 heat pipes and the trend of the thermal efficiency is descending with increasing heat pipes. The results also indicate that at a cold winter day of January, the proposed system with a 20 heat pipe collector shows maximum energy and exergy efficiency of ...

  2. Design and Fabrication of a Novel Hybrid-Structure Heat Pipe for a Concentrator Photovoltaic

    Directory of Open Access Journals (Sweden)

    Heiu-Jou Shaw

    2012-10-01

    Full Text Available This study presents a design method to fabricate a novel hybrid-structure flat plate heat pipe (NHSP heat pipe for a concentrator photovoltaic. The NHSP heat pipe is composed of a flattened copper pipe and a sintered wick structure, and a coronary-stent-like rhombic copper mesh supports the structure. The coronary-stent-like supporting structure enhances the mechanical strength and shortens the reflux path of the working fluid. Experiments demonstrate that the sintered capillary heat pipe reduces the thermal resistance by approximately 72%, compared to a traditional copper mesh-screen heat pipe. Furthermore, it can reduce thermal resistance by 65% after a supporting structure is added to the heat pipe. The results show that the NHSP heat pipe provided the best performance for the concentrator photovoltaic, which can increase photoelectric conversion efficiency by approximately 3.1%, compared to an aluminum substrate.

  3. Thermal Characteristics of Grooved Heat pipe with Hybrid Nanofluids

    Directory of Open Access Journals (Sweden)

    W S Han

    2011-01-01

    Full Text Available In the present study, the specially designed grooved heat pipe charged with nanofluids was investigated in terms of various parameters such as heat transfer rate(50∼300W with 50 W interval, volume concentration(0.005%, 0.05%, 0.1%, and hybrid combinations, inclination(5°, 45°, 90°, cooling water temperature (1℃, 10℃, and 20℃, surface state, transient state and so on. Hybrid nanofluids with different volume concentration ratios with Ag-H2O and Al2O3-H2O were used as working fluids on a grooved heat pipe(GHP. Comparing with the pure water system, nanofluidic and hybrid nanofluidic system shows greater overall thermal resistance with increasing nano-particle concentration. Also hybrid nanofluids make the system deteriorate in terms of thermal resistance. The post nanofluid experimental data regarding GHP show that the heat transfer performance is similar to the results of nanofluid system. The thermal performance of a grooved heat pipe with nanofluids and hybrid nanofluids were varied with driving parameters but they led to worse system performance.

  4. Electrically heated pipe in pipe combined with electrical submersible pumps for deepwater development

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Sidnei Guerreiro da; Euphemio, Mauro Luiz Lopes [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The general trend of deep water and ultra deep water field development is the requirement of highly insulated flow lines, as flow assurance has become one of the major considerations in designing and operating the sub sea system. If not adequately considered in the design phase, it can have significant and unexpected effects to the operational costs, increasing production lost time, decreasing efficiency. In this scenario, the use of pipe in pipe flow lines, with high passive insulation and/ or active heating (called the Electrically Heated Pipe in Pipe - EHPIP), emerges as an attractive method to prevent deposition, especially of waxes and hydrates, by actively maintaining or leading the temperature of the flow line above a critical limit. Besides, the recent heavy oil discoveries in Brazil have encouraged PETROBRAS to move a step forward in the artificial lift design and operation, by the use of Electrical Submersible Pumps (ESP) installed in deep water wells. The combination of EHPIP and ESP are particularly suitable for deep water, high viscosity and long tie back systems, but also can improve oil recovery and production efficiency by allowing the operator to drop down production losses associated Flow Assurance problems. (author)

  5. Periodic inspection for safety of CANDU heat transport piping systems

    International Nuclear Information System (INIS)

    Ellyin, F.

    1979-10-01

    Periodic inspection of heat transport and emergency core cooling piping systems is intended to maintain an adequate level of safety throughout the life of the plant, and to protect plant personnel and the public from the consequences of a failure and release of fission products. This report outlines a rational approach to the periodic inspection based on a fully probabilistic model. It demonstrates the methodology based on theoretical treatment and experimental data whereby the strength of a pressurized pipe or vessel containing a defect could be evaluated. It also shows how the extension of the defect at various lifetimes could be predicted. These relationships are prerequisite for the probabilistic formulation and analysis for the periodic inspection of piping systems

  6. A heat pipe solar collector system for winter heating in Zhengzhou city, China

    Directory of Open Access Journals (Sweden)

    Zheng Hui-Fan

    2017-01-01

    Full Text Available A heat pipe solar collector system for winter heating is investigated both experimentally and theoretically. The hourly heat collecting capacity, water temperature and contribution rate of solar collector system based on Zhengzhou city typical sunshine are calculated. The study reveals that the heat collecting capacity and water temperature increases initially and then decreases, and the solar collector system can provide from 40% to 78% heating load for a 200 m2 villa with in Zhengzhou city from November to March.

  7. Gravity and Heater Size Effects on Pool Boiling Heat Transfer

    Science.gov (United States)

    Kim, Jungho; Raj, Rishi

    2014-01-01

    The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.

  8. Studies on split heat pipe type adsorption ice-making test unit for fishing boats: Choice of heat pipe medium and experiments under unsteady heating sources

    International Nuclear Information System (INIS)

    Wang, L.W.; Wang, R.Z.; Lu, Z.S.; Chen, C.J.

    2006-01-01

    The split heat pipe type compound adsorption ice maker for fishing boats not only has the advantage of large volume cooling density but also has the advantage of less power consumption and high heat transfer performance. The available heat pipe media for the split heat pipe type compound adsorption ice maker, which are methanol, acetone and water are studied and compared in this paper, and the heat pipe medium of water shows the better performance for the reason of its stable heating and cooling process and high heat transfer performance. Considering the waste heat recovered from the diesel engine on fishing boats varies when the velocity of the fishing boat changes, the refrigeration performances at the condition of different values of heating power are studied while water is used as the heat pipe medium. Results show that the cooling power, as while as COP and SCP decrease when the heating power decreases. The highest COP and SCP are 0.41 and 731 W/kg, respectively, at the highest heating power of 4.2 kW, and the values decrease by 22% and 33%, respectively, when the heating power decreases by 15%. The values decrease by 32% and 51%, respectively, when the heating power decreases by 30%. The performance of the adsorption ice maker for the fishing boat with the 6160A type diesel engine is estimated, and the results show that the cooling power and ice productivity are as high as 5.44 kW and 1032 kg ice per day, respectively, even if the recovered waste heat decreases by 30% compared with the normal value. It can satisfy the ice requirements of such a fishing boat

  9. NASA Lewis Steady-State Heat Pipe Code Architecture

    Science.gov (United States)

    Mi, Ye; Tower, Leonard K.

    2013-01-01

    NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heat pipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given

  10. Ductile fracture behaviour of primary heat transport piping material ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Heat transport piping material of nuclear reactors. 169. Table 1. Chemical composition of. SA333, Grade 6 steel in wt%. C. Mn. Si. S. P. 0·18 0·90 0·25 0·02 0·02 room temperature. The tensile flow curve of the steel exhibited prominent yield-point effect accompanied by non-hardening strain propagation (Lüders strain) of ...

  11. Status of high-temperature heat-pipe technology

    International Nuclear Information System (INIS)

    Ranken, W.A.

    1982-01-01

    This paper discusses the application of heat pipes to nuclear reactor space power systems. Characteristics of the device that favor such an application are described and recent results of current technology development programs are presented. Research areas that will need to be addressed in demonstrating that adequate lifetimes can be achieved with evaporation/condensation cycles operating at high temperatures in a reactor environment are also discussed

  12. Experimental study of a photovoltaic solar-assisted heat-pump/heat-pipe system

    International Nuclear Information System (INIS)

    Fu, H.D.; Pei, G.; Ji, J.; Long, H.; Zhang, T.; Chow, T.T.

    2012-01-01

    A practical design for a heat pump with heat-pipe photovoltaic/thermal (PV/T) collectors is presented. The hybrid system is called the photovoltaic solar-assisted heat-pump/heat-pipe (PV-SAHP/HP) system. To focus on both actual demand and energy savings, the PV-SAHP/HP system was designed to be capable of operating in three different modes, namely, the heat-pipe, solar-assisted heat pump, and air-source heat-pump modes. Based on solar radiation, the system operates in an optimal mode. A series of experiments were conducted in Hong Kong to study the performance of the system when operating in the heat-pipe and the solar-assisted heat-pump modes. Moreover, energy and exergy analyses were used to investigate the total PV/T performance of the system. - Highlights: ► A novel PV-SAHP/HP system with three different operating modes was proposed. ► Performance of the PV-SAHP/HP system was studied experimentally. ► A optimal operating mode of the PV-SAHP/HP system was suggested in this paper.

  13. Titanium based flat heat pipes for computer chip cooling

    Science.gov (United States)

    Soni, Gaurav; Ding, Changsong; Sigurdson, Marin; Bozorgi, Payam; Piorek, Brian; MacDonald, Noel; Meinhart, Carl

    2008-11-01

    We are developing a highly conductive flat heat pipe (called Thermal Ground Plane or TGP) for cooling computer chips. Conventional heat pipes have circular cross sections and thus can't make good contact with chip surface. The flatness of our TGP will enable conformal contact with the chip surface and thus enhance cooling efficiency. Another limiting factor in conventional heat pipes is the capillary flow of the working fluid through a wick structure. In order to overcome this limitation we have created a highly porous wick structure on a flat titanium substrate by using micro fabrication technology. We first etch titanium to create very tall micro pillars with a diameter of 5 μm, a height of 40 μm and a pitch of 10 μm. We then grow a very fine nano structured titania (NST) hairs on all surfaces of the pillars by oxidation in H202. In this way we achieve a wick structure which utilizes multiple length scales to yield high performance wicking of water. It's capable of wicking water at an average velocity of 1 cm/s over a distance of several cm. A titanium cavity is laser-welded onto the wicking substrate and a small quantity of water is hermetically sealed inside the cavity to achieve a TGP. The thermal conductivity of our preliminary TGP was measured to be 350 W/m-K, but has the potential to be several orders of magnitude higher.

  14. Sensitivity study of the monogroove with screen heat pipe design

    Science.gov (United States)

    Evans, Austin L.; Joyce, Martin

    1988-01-01

    The present sensitivity study of design variable effects on the performance of a monogroove-with-screen heat pipe obtains performance curves for maximum heat-transfer rates vs. operating temperatures by means of a computer code; performance projections for both 1-g and zero-g conditions are obtainable. The variables in question were liquid and vapor channel design, wall groove design, and the number of feed lines in the evaporator and condenser. The effect on performance of three different working fluids, namely ammonia, methanol, and water, were also determined. Greatest sensitivity was to changes in liquid and vapor channel diameters.

  15. Steady-state heat losses in pipes for low-energy district heating

    DEFF Research Database (Denmark)

    Dalla Rosa, Alessandro; Li, Hongwei; Svendsen, Svend

    2010-01-01

    of low-energy DH systems. Various design concepts are considered in this paper: flexible pre-insulated twin pipes with symmetrical or asymmetrical insulation, double pipes, triple pipes. These technologies are potentially energyefficient and cost-effective solutions for DH networks in low-heat density...... areas. We start with a review of theories and methods for steady-state heat loss calculation. Next, the article shows how detailed calculations with 2D-modeling of pipes can be carried out by means of computer software based on the finite element method (FEM). The model was validated by comparison...... with analytical results and data from the literature. We took into account the influence of the temperature-dependent conductivity coefficient of polyurethane (PUR) insulation foam, which enabled to achieve a high degree of detail. We also illustrated the influence of the soil temperature throughout the year...

  16. Unsteady heat transfer performance of heat pipe with axially swallow-tailed microgrooves

    Science.gov (United States)

    Zhang, R. P.

    2017-04-01

    A mathematical model is developed for predicting the transient heat transfer and fluid flow of heat pipe with axially swallow-tailed microgrooves. The effects of liquid convective heat transfer in the microgrooves, liquid-vapor interfacial phase-change heat transfer and liquid-vapor interfacial shear stress are accounted for in the present model. The coupled non-linear control equations are solved numerically. Mass flow rate at the interface is obtained from the application of kinetic theory. Time variation of wall temperature is studied from the initial startup to steady state. The numerical results are verified by experiments. Time constants for startup and shutdown operation are defined to determine how fast a heat pipe responds to an applied input heat flux, which slightly decreases with increasing heat load.

  17. Hybrid Heat Pipes for High Heat Flux Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The thermal transport requirements for future spacecraft missions continue to increase, approaching several kilowatts. At the same time the heat acquisition areas...

  18. Hybrid Heat Pipes for High Heat Flux Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The thermal transport requirements for future spacecraft missions continue to increase, approaching several kilowatts. At the same time the heat acquisition areas...

  19. Heat pipes. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The bibliography contains citations of selected patents concerning the design, manufacture, and applications of heat pipes. The use of heat pipes in heat exchange systems for heat storage, heat transfer, and heat utilization is discussed. Applications include semiconductor cooling, use in engine components, and building cooling and heating. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  20. Heat pipes. (Latest citations from the US Patent Bibliographic file with exemplary claims). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-01

    The bibliography contains citations of selected patents concerning the design, manufacture, and applications of heat pipes. The use of heat pipes in heat exchange systems for heat storage, heat transfer, and heat utilization is discussed. Applications include semiconductor cooling, use in engine components, and building cooling and heating. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  1. Variable Conductance Heat Pipe Radiators for Lunar and Martian Environments

    Science.gov (United States)

    Anderson, William G.; Ellis, Michael C.; Walker, Kara L.

    2009-03-01

    Long-term Lunar and Martian surface systems present challenges to thermal system design, including changes in thermal load, and large changes in the thermal environment between Lunar (or Martian) day and night. For example, the heat sink temperature at the Lunar equator can vary from 210 to 315 K. The radiator must be sized to reject the design power at the maximum temperature, but must also be able to accommodate both the changing heat sink temperature, as well as changes in power. Variable Conductance Heat Pipe (VCHP) radiators were examined for the main reactor of a fission surface power system, as well as the cavity cooling radiator. A VCHP radiator was designed for Lunar Equator that is capable of maintaining a 16 K temperature drop with a 4% addition to overall mass. Without the VCHP the radiator would experience a 43 K drop in temperature. This design is also capable of handling turndown on the power without an effect to the outlet temperature. At Shackleton Crater, the temperature drop for a conventional heat pipe radiator is small enough that a VCHP is not beneficial at constant power. However, a VCHP will allow turndown ratios of 5:1 or more. A conventional radiator can not be turned down more than 2:1, without valves to bypass part of the radiator. VCHPs are also easier to start than conventional radiators, since the gas-loading prevents sublimation from the evaporator when the condenser is frozen.

  2. Variable Heat Rejection Loop Heat Pipe radiator, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Thermal control systems are sized for the maximum heat load in the warmest continuous environment. This design process results in a larger radiator surface area than...

  3. Heat-pipe development for the SPAR space-power system

    International Nuclear Information System (INIS)

    Ranken, W.A.

    1981-01-01

    The SPAR space power system design is based on a high temperature fast spectrum nuclear reactor that furnishes heat to a thermoelectric conversion system to generate an electrical power output of 100 kW/sub (e)/. An important feature of this design is the use of alkali metal heat pipes to provide redundant, reliable, and low-loss heat transfer at high temperature. Three sets of heat pipes are used in the system. These include sodium/molybdenum heat pipes to transfer heat from the reactor core to the conversion system, potassium/niobium heat pipes to couple the conversion system to the radiator in a redundant manner, and potassium/titanium heat pipes to distribute rejected heat throughout the radiator surface. The designs of these units are discussed and fabrication methods and testing results are described. 12 figures

  4. A dynamic film model of the pulsating heat pipe

    International Nuclear Information System (INIS)

    Nikolayev, Vadim S.

    2011-01-01

    This article deals with the numerical modeling of the pulsating heat pipe (PHP) and is based on the film evaporation/condensation model recently applied to the single-bubble PHP (Das et al., 2010, 'Thermally Induced Two-Phase Oscillating Flow Inside a Capillary Tube', Int. J. Heat Mass Transfer, 53(19-20), pp. 3905-3913). The described numerical code can treat the PHP of an arbitrary number of bubbles and branches. Several phenomena that occur inside the PHP are taken into account: coalescence of liquid plugs, film junction or rupture, etc. The model reproduces some of the experimentally observed regimes of functioning of the PHP such as chaotic or intermittent oscillations of large amplitudes. Some results on the PHP heat transfer are discussed. (author)

  5. Numerical investigation on pulsating heat pipes with nitrogen or hydrogen

    Science.gov (United States)

    Y Han, D.; Sun, X.; Gan, Z. H.; Y Luo, R.; Pfotenhauer, J. M.; Jiao, B.

    2017-12-01

    With flexible structure and excellent performance, pulsating heat pipes (PHP) are regarded as a great solution to distribute cooling power for cryocoolers. The experiments on PHPs with cryogenic fluids have been carried out, indicating their efficient performances in cryogenics. There are large differences in physical properties between the fluids at room and cryogenic temperature, resulting in their different heat transfer and oscillation characteristics. Up to now, the numerical investigations on cryogenic fluids have rarely been carried out. In this paper, the model of the closed-loop PHP with multiple liquid slugs and vapor plugs is performed with nitrogen and hydrogen as working fluids, respectively. The effects of heating wall temperature on the performance of close-looped PHPs are investigated and compared with that of water PHP.

  6. Porous Foam Based Wick Structures for Loop Heat Pipes

    Science.gov (United States)

    Silk, Eric A.

    2012-01-01

    As part of an effort to identify cost efficient fabrication techniques for Loop Heat Pipe (LHP) construction, NASA Goddard Space Flight Center's Cryogenics and Fluids Branch collaborated with the U.S. Naval Academy s Aerospace Engineering Department in Spring 2012 to investigate the viability of carbon foam as a wick material within LHPs. The carbon foam was manufactured by ERG Aerospace and machined to geometric specifications at the U.S. Naval Academy s Materials, Mechanics and Structures Machine Shop. NASA GSFC s Fractal Loop Heat Pipe (developed under SBIR contract #NAS5-02112) was used as the validation LHP platform. In a horizontal orientation, the FLHP system demonstrated a heat flux of 75 Watts per square centimeter with deionized water as the working fluid. Also, no failed start-ups occurred during the 6 week performance testing period. The success of this study validated that foam can be used as a wick structure. Furthermore, given the COTS status of foam materials this study is one more step towards development of a low cost LHP.

  7. Characterization of a solar photovoltaic/loop-heat-pipe heat pump water heating system

    International Nuclear Information System (INIS)

    Zhang, Xingxing; Zhao, Xudong; Xu, Jihuan; Yu, Xiaotong

    2013-01-01

    Highlights: ► Describing concept and operating principle of the PV/LHP heat pump water heating system. ► Developing a numerical model to evaluate the performance of the system. ► Experimental testing of the prototype system. ► Characterizing the system performance using parallel comparison between the modelling and experimental results. ► Investigating the impact of the operating conditions to the system’s performance. -- Abstract: This paper introduced the concept, potential application and benefits relating to a novel solar photovoltaic/loop-heat-pipe (PV/LHP) heat pump system for hot water generation. On this basis, the paper reported the process and results of characterizing the performance of such a system, which was undertaken through dedicated thermo-fluid and energy balance analyses, computer model development and operation, and experimental verification and modification. The fundamental heat transfer, fluid flow and photovoltaic governing equations were applied to characterize the energy conversion and transfer processes occurring in each part and whole system layout; while the energy balance approach was utilized to enable inter-connection and resolution of the grouped equations. As a result, a dedicated computer model was developed and used to calculate the operational parameters, optimise the geometrical configurations and sizes, and recommend the appropriate operational condition relating to the system. Further, an experimental rig was constructed and utilized to acquire the relevant measurement data that thus enabled the parallel comparison between the simulation and experiment. It is concluded that the testing and modelling results are in good agreement, indicating that the model has the reasonable accuracy in predicting the system’s performance. Under the given experimental conditions, the electrical, thermal and overall efficiency of the PV/LHP module were around 10%, 40% and 50% respectively; whilst the system’s overall performance

  8. Applications of heat pipes for HVAC dehumidification at Walt Disney World

    International Nuclear Information System (INIS)

    Allen, P.J.; Dinh, K.

    1993-01-01

    This paper presents the theory and application of heat pipes for HVAC dehumidification purposes. In HVAC applications, a heat pipe is used as a heat exchanger that transfers heat from the return air directly to the supply air. The air is pre-cooled entering the cooling coil and reheated using the same heat removed from the return air. While consuming no energy, the heat pipe lets the evaporator coil operate at a lower temperature, increasing the moisture removal capabilities of the HVAC system by 50% to 100%. WALT DISNEY WORLD is currently testing several heat pipe applications ranging from 1 to 240 tons. The applications include (1) water attractions (2) museums/artifacts areas (3) resort guest rooms and (4) locker rooms. Actual energy usage and relative humidity reductions are shown to determine the effectiveness of the heat pipe as an energy efficient method of humidity control

  9. Experimental investigation of the effect of graphene nanofluids on heat pipe thermal performance

    DEFF Research Database (Denmark)

    Sadeghinezhad, Emad; Mehrali, Mohammad; Rosen, Marc A.

    2016-01-01

    An experimental investigation has been carried out to examine the thermal, performance of a sintered wick heat pipe using aqueous graphene nanoplatelets (GNP) nanofluids. The study focuses on changes in the effects of GNP concentration, heat pipe inclination angle and input heating power. The max...

  10. Performance predictions and measurements for space-power-system heat pipes

    International Nuclear Information System (INIS)

    Prenger, F.C. Jr.

    1981-01-01

    High temperature liquid metal heat pipes designed for space power systems have been analyzed and tested. Three wick designs are discussed and a design rationale for the heat pipe is provided. Test results on a molybdenum, annular wick heat pipe are presented. Performance limitations due to boiling and capillary limits are presented. There is evidence that the vapor flow in the adiabatic section is turbulent and that the transition Reynolds number is 4000

  11. Cooling of high-density and power electronics by means of heat pipes

    International Nuclear Information System (INIS)

    Hubbeling, L.

    1980-06-01

    This report describes how heat pipes can be used for cooling modern electronic equipment, with numerous advantages over air-cooled systems. A brief review of heat-pipe properties is given, with a detailed description of a functioning prototype. This is a single-width CAMAC unit containing high-density electronic circuits cooled by three heat pipes, and allowing a dissipation of over 120 W instead of the normal maximum of 20 W. (orig.)

  12. Thermal performance of different working fluids in a dual diameter circular heat pipe

    Directory of Open Access Journals (Sweden)

    S.M. Peyghambarzadeh

    2013-12-01

    Full Text Available In this paper, heat transfer performance of a 40 cm-length circular heat pipe with screen mesh wick is experimentally investigated. This heat pipe is made of copper with two diameters; larger in the evaporator and smaller in the adiabatic and condenser. Three different liquids including water, methanol, and ethanol are separately filled within the heat pipe. Low heat fluxes are applied (up to 2500 W/m2 in the evaporator and constant temperature water bath is used at three levels including 15, 25, and 35 °C in the condenser. Results demonstrate that higher heat transfer coefficients are obtained for water and ethanol in comparison with methanol. Furthermore, increasing heat flux increases the evaporator heat transfer coefficient. For the case of methanol, some degradation in heat transfer coefficient is occurred at high heat fluxes which can be due to the surface dryout effect. Increasing the inclination angle decreases the heat pipe thermal resistance.

  13. Application study of the heat pipe to the passive decay heat removal system of the modular HTR

    International Nuclear Information System (INIS)

    Ohashi, K.; Okamoto, F.; Hayakawa, H.; Hayashi, T.

    2001-01-01

    To investigate the applicability of the heat pipe to the decay hat removal (DHR) system of the modular HTRs, preliminary study of the Heat Pipe DHR System was performed. The results show that the Heat Pipe DHR System is applicable to the modular HTRs and its heat removal capability is sufficient. Especially by applying the variable conductance heat pipe, the possibility of a fully passive DHR system with lower heat loss during normal operation is suggested. The experiments to obtain the fundamental characteristics data of the variable conductance heat pipe were carried out. The experimental results show very clear features of self-control characteristics. The experimental results and the experimental analysis results are also shown. (author)

  14. High-Speed Visual Analysis of Fluid Flow and Heat Transfer in Oscillating Heat Pipes with Different Diameters

    Directory of Open Access Journals (Sweden)

    Xiangdong Liu

    2016-10-01

    Full Text Available The oscillating heat pipe (OHP is a new member in the family of heat pipes, and it has great potential applications in energy conservation. However, the fluid flow and heat transfer in the OHP as well as the fundamental effects of inner diameter on them have not been fully understood, which are essential to the design and optimization of the OHP in real applications. Therefore, by combining the high-speed visualization method and infrared thermal imaging technique, the fluid flow and thermal performance in the OHPs with inner diameters of 1, 2 and 3 mm are presented and analyzed. The results indicate that three fluid flow motions, including small oscillation, bulk oscillation and circulation, coexist or, respectively, exist alone with the increasing heating load under different inner diameters, with three flow patterns occurring in the OHPs, viz. bubbly flow, slug flow and annular flow. These fluid flow motions are closely correlated with the heat and mass transfer performance in the OHPs, which can be reflected by the characteristics of infrared thermal images of condensers. The decrease in the inner diameter increases the frictional flow resistance and capillary instability while restricting the nucleate boiling in OHPs, which leads to a smaller proportion of bubbly flow, a larger proportion of short slug flow, a poorer thermal performance, and easier dry-out of working fluid. In addition, when compared with the 2 mm OHP, the increasing role of gravity induces the thermosyphon effect and weakens the ‘bubble pumping’ action, which results in a little smaller and bigger thermal resistances of 3 mm OHP under small and bulk oscillation of working fluid, respectively.

  15. A New Wick Structure to Significantly Improve Heat Pipe Performance, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Increasing thermal requirements for space-based thermal control systems are straining the capabilities of conventional heat pipes. Mainstream has experimentally...

  16. Two-Pipe Chilled Beam System for Both Cooling and Heating of Office Buildings

    DEFF Research Database (Denmark)

    Afshari, Alireza; Gordnorouzi, Rouzbeh; Hultmark, Göran

    2013-01-01

    Simulations were performed to compare a conventional 4-pipe chilled beam system and a 2-pipe chilled beam system. The objective was to establish requirements, possibilities and limitations for a well-functioning 2-pipe chilled beam system for both cooling and heating of office buildings. The buil...

  17. Simulation of Hybrid Photovoltaic Solar Assisted Loop Heat Pipe/Heat Pump System

    Directory of Open Access Journals (Sweden)

    Nannan Dai

    2017-02-01

    Full Text Available A hybrid photovoltaic solar assisted loop heat pipe/heat pump (PV-SALHP/HP water heater system has been developed and numerically studied. The system is the combination of loop heat pipe (LHP mode and heat pump (HP mode, and the two modes can be run separately or compositely according to the weather conditions. The performances of independent heat pump (HP mode and hybrid loop heat pipe/heat pump (LHP/HP mode were simulated and compared. Simulation results showed that on typical sunny days in spring or autumn, using LHP/HP mode could save 40.6% power consumption than HP mode. In addition, the optimal switchover from LHP mode to HP mode was analyzed in different weather conditions for energy saving and the all-year round operating performances of the system were also simulated. The simulation results showed that hybrid LHP/HP mode should be utilized to save electricity on sunny days from March to November and the system can rely on LHP mode alone without any power consumption in July and August. When solar radiation and ambient temperature are low in winter, HP mode should be used

  18. Numerical Simulation of Different Models of Heat Pipe Heat Exchanger Using AcuSolve

    Directory of Open Access Journals (Sweden)

    Zainal Nurul Amira

    2017-01-01

    Full Text Available In this paper, a numerical simulation of heat pipe heat exchanger (HPHE is computed by using CFD solver program i.e. AcuSolve. Two idealized model of HPHE are created with different variant of entry’s dimension set to be case 1 and case 2. The geometry of HPHE is designed in SolidWorks and imported to AcuSolve to simulate the fluid flow numerically. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in industry.

  19. A modeling approach for district heating systems with focus on transient heat transfer in pipe networks

    DEFF Research Database (Denmark)

    Mohammadi, Soma; Bojesen, Carsten

    2015-01-01

    Increasing the building energy efficiency in recent years results in noticeably reduction in their heating demand. Combined with the current trend for utilizing low temperature heat sources, it raises the necessity of introducing a new generation of district heating [DH] systems with lowered...... km pipelines (supply and return pipes). At the first stage, the Studstrup DH system is developed in TERMIS, which is commercial software for district heating system simulation, and then the developed model is validated and compared with the results obtained from TERMIS and measurements. The TERMIS...

  20. Study of PTFE wick structure applied to loop heat pipe

    International Nuclear Information System (INIS)

    Wu, Shen-Chun; Gu, Tzu-Wei; Wang, Dawn; Chen, Yau-Ming

    2015-01-01

    This study investigated the use of sintered PTFE (polytetrafluoroethylene) particles as the wick material of loop heat pipe (LHP), taking advantage of PTFE's low thermal conductivity to reduce the heat leakage problem during LHP's operation. Different PTFE particle sizes were tried to find the one that resulted in the best wick; LHP performance tests were then conducted, and PTFE's potential for application to LHP was examined. Using PTFE particles ranging from 300–500 μm in size, the best wick properties were effective pore radius of 1.7 μm, porosity of 50%, and permeability of 6.2 × 10 −12  m 2 . LHP performance tests showed that, under typical electronic devices' operating temperature of 85 °C, the heat load reached 450 W, the thermal resistance was 0.145 °C/W, and the critical heat load (dryout heat load) reached 600 W. Compared to LHP with a nickel wick, LHP with a PTFE wick had a significantly lower operating temperature, indicating reduced heat leakage during operation, while having comparable performance; also, during the manufacturing process, a PTFE wick required lower sintering temperature, needed shorter sintering time, and had no need for hydrogen gas during sintering. The results of this study showed that, for high heat transfer capacity cooling devices, PTFE wicks possess great potential for applications to LHPs. - Highlights: • The performances of PTFE and nickel wicks in LHP are comparable for the first time. • PTFE wick allows for lower operating temperature and thus pressure in LHP system. • A wick requiring lower temperature and manufacturing cost and less time was made. • PTFE wick has potential to replace metal wick and enhance performance of LHP

  1. Thermal performance of a flat polymer heat pipe heat spreader under high acceleration

    Science.gov (United States)

    Oshman, Christopher; Li, Qian; Liew, Li-Anne; Yang, Ronggui; Lee, Y. C.; Bright, Victor M.; Sharar, Darin J.; Jankowski, Nicholas R.; Morgan, Brian C.

    2012-04-01

    This paper presents the fabrication and application of a micro-scale hybrid wicking structure in a flat polymer-based heat pipe heat spreader, which improves the heat transfer performance under high adverse acceleration. The hybrid wicking structure which enhances evaporation and condensation heat transfer under adverse acceleration consists of 100 µm high, 200 µm wide square electroplated copper micro-pillars with 31 µm wide grooves for liquid flow and a woven copper mesh with 51 µm diameter wires and 76 µm spacing. The interior vapor chamber of the heat pipe heat spreader was 30×30×1.0 mm3. The casing of the heat spreader is a 100 µm thick liquid crystal polymer which contains a two-dimensional array of copper-filled vias to reduce the overall thermal resistance. The device performance was assessed under 0-10 g acceleration with 20, 30 and 40 W power input on an evaporator area of 8×8 mm2. The effective thermal conductivity of the device was determined to range from 1653 W (m K)-1 at 0 g to 541 W (m K)-1 at 10 g using finite element analysis in conjunction with a copper reference sample. In all cases, the effective thermal conductivity remained higher than that of the copper reference sample. This work illustrates the possibility of fabricating flexible, polymer-based heat pipe heat spreaders compatible with standardized printed circuit board technologies that are capable of efficiently extracting heat at relatively high dynamic acceleration levels.

  2. Augmented of turbulent heat transfer in an annular pipe with abrupt expansion

    Directory of Open Access Journals (Sweden)

    Togun Hussein

    2016-01-01

    Full Text Available This paper presents a study of heat transfer to turbulent air flow in the abrupt axisymmetric expansion of an annular pipe. The experimental investigations were performed in the Reynolds number range from 5000 to 30000, the heat flux varied from 1000 to 4000 W/m2, and the expansion ratio was maintained at D/d=1, 1.25, 1.67 and 2. The sudden expansion was created by changing the inner diameter of the entrance pipe to an annular passage. The outer diameter of the inner pipe and the inner diameter of the outer pipe are 2.5 and 10 cm, respectively, where both of the pipes are subjected to uniform heat flux. The distribution of the surface temperature of the test pipe and the local Nusselt number are presented in this investigation. Due to sudden expansion in the cross section of the annular pipe, a separation flow was created, which enhanced the heat transfer. The reduction of the surface temperature on the outer and inner pipes increased with the increase of the expansion ratio and the Reynolds number, and increased with the decrease of the heat flux to the annular pipe. The peak of the local Nusselt number was between 1.64 and 1.7 of the outer and inner pipes for Reynolds numbers varied from 5000 to 30000, and the increase of the local Nusselt number represented the augmentation of the heat transfer rate in the sudden expansion of the annular pipe. This research also showed a maximum heat transfer enhancement of 63-78% for the outer and inner pipes at an expansion ratio of D/d=2 at a Re=30000 and a heat flux of 4000W/m2.

  3. A Designer Fluid For Aluminum Phase Change Devices. Performance Enhancement in Copper Heat Pipes Performance Enhancement in Copper Heat Pipes. Volume 3

    Science.gov (United States)

    2016-11-17

    and the curvature varies with the height of the liquid meniscus. In the present work, the corner flow existed over a very short length. 93 Approved...to gradual changes in meniscus height whereas a pinned meniscus in an open groove varies curvature with contact angle. 114 Approved for public...region was calculated to be less than 2% of the total length for Wick #2. Flow Regions in a Grooved Heat Pipe The liquid flow in the heat pipe varies

  4. Thermal performance of different working fluids in a dual diameter circular heat pipe

    OpenAIRE

    S.M. Peyghambarzadeh; S. Shahpouri; N. Aslanzadeh; M. Rahimnejad

    2013-01-01

    In this paper, heat transfer performance of a 40 cm-length circular heat pipe with screen mesh wick is experimentally investigated. This heat pipe is made of copper with two diameters; larger in the evaporator and smaller in the adiabatic and condenser. Three different liquids including water, methanol, and ethanol are separately filled within the heat pipe. Low heat fluxes are applied (up to 2500 W/m2) in the evaporator and constant temperature water bath is used at three levels including 15...

  5. Heat transfer and pressure drop in a heat exchanger with a helical pipe containing inside springs

    Energy Technology Data Exchange (ETDEWEB)

    Yildiz, C.; Bicer, Y.; Pehlivan, D. [Firat University, Elazig (Turkey). Engineering Faculty

    1997-12-31

    In this study, a heat exchanger which is constructed by placing spring-shaped wires with varying pitch within a helical pipe was considered. The pressure drop and the overall heat transfer rates were measured for the case of air flow at various Reynolds numbers inside and constant water flow outside. The results show that the Nusselt number increases with decreasing pitch/wire diameter ratio, as much as five times with respect to an empty pipe for the same Dean number, and for this relationship, a tentative empirical formula is suggested. Although a rise up to 10 times in the inlet/outlet pressure drop values with respect to the conventional empty helical case is observed, the increase in Nusselt number, naturally, reflects an increase of about 30% in the effectiveness of the helical heat exchanger. (Author)

  6. The study of the heat-engineering characteristics of a solar heat collector based on aluminum heat pipes

    International Nuclear Information System (INIS)

    Khairnasov, S.M.; Zaripov, V.K.; Passamakin, B.M. et al.

    2013-01-01

    This paper presents the results of studies into the heat-engineering characteristics of a flat heat solar collector based on aluminum heat pipes that is designed to be used in building facades. The principle of work and the structure of the solar collector are considered; the results of its comparison with a traditional flat solar collector are presented. The studies were performed at a heat carrier temperature range of +10 - +30 degree C and at a solar heat flow density of 400 - 1000 W/m 2 . The obtained experimental heat-engineering characteristics of the collector based on heat pipes show that they are at a level of traditional flow solar collectors; for example, its efficiency is 0.65 - 0.73. Meanwhile, the hydraulic resistance of the structure with heat pipes is by a factor of 2 - 2.4 smaller and ensures a high level of scalability, reliability, and maintainability, which is important when using it as an element of facade constructions of solar heat systems. (author)

  7. A Novel Heat Pipe Plate for Passive Thermal Control of Fuel Cells, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR project aims to develop a lightweight, highly thermally and electrically conductive heat pipe plate for passive removal of the heat from the individual...

  8. Miniature Loop Heat Pipe with Multiple Evaporators and Multiple Condensers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Loop Heat Pipe (LHP) is a high performance heat transport device using capillary forces to circulate the working fluid in a closed loop. Conventional LHPs usually...

  9. Thermal Management Research Studies. Volume 1: High Performance Miniature Heat Pipes

    National Research Council Canada - National Science Library

    Ponnappan, Rengasamy

    2001-01-01

    High performance miniature heat pipes are developed for the cooling of high heat flux electronics using new capillary structures which rely on the use of a folded copper sheet fin and a folded copper screen...

  10. 46 CFR 61.15-10 - Liquefied-petroleum-gas piping for heating and cooking.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Liquefied-petroleum-gas piping for heating and cooking. 61.15-10 Section 61.15-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE... piping for heating and cooking. (a) Leak tests as described in paragraph (b) of this section shall be...

  11. Heat pipe technology. a bibliography with abstracts. Quarterly update, 31 March 1975

    International Nuclear Information System (INIS)

    1975-01-01

    Heat Pipe Technology is a continuing bibliographic summary of research on the subject of the heat pipe. The first volume was published in 1971. The 1972, 1973, and 1974 Annual Supplements have been published and distributed. This update cites additional references for 1975

  12. Impact of the amount of working fluid in loop heat pipe to remove waste heat from electronic component

    Directory of Open Access Journals (Sweden)

    Smitka Martin

    2014-03-01

    Full Text Available One of the options on how to remove waste heat from electronic components is using loop heat pipe. The loop heat pipe (LHP is a two-phase device with high effective thermal conductivity that utilizes change phase to transport heat. It was invented in Russia in the early 1980’s. The main parts of LHP are an evaporator, a condenser, a compensation chamber and a vapor and liquid lines. Only the evaporator and part of the compensation chamber are equipped with a wick structure. Inside loop heat pipe is working fluid. As a working fluid can be used distilled water, acetone, ammonia, methanol etc. Amount of filling is important for the operation and performance of LHP. This work deals with the design of loop heat pipe and impact of filling ratio of working fluid to remove waste heat from insulated gate bipolar transistor (IGBT.

  13. Temperature Oscillations in Loop Heat Pipes - A Revisit

    Science.gov (United States)

    Ku, Jentung

    2018-01-01

    Three types of temperature oscillation have been observed in the loop heat pipes. The first type is an ultra-high frequency temperature oscillation with a period on the order of seconds or less. This type of temperature oscillation is of little significance in spacecraft thermal control because the amplitude is in the noise level. The second type is a high frequency, low amplitude temperature oscillation with a period on the order of seconds to minutes and an amplitude on the order of one Kelvin. It is caused by the back-and-forth movement of the vapor front near the inlet or outlet of the condenser. The third type is a low frequency, high amplitude oscillation with a period on the order of hours and an amplitude on the order of tens of Kelvin. It is caused by the modulation of the net heat load into the evaporator by the attached large thermal mass which absorbs and releases energy alternately. Several papers on LHP temperature oscillation have been published. This paper presents a further study on the underlying physical processes during the LHP temperature oscillation, with an emphasis on the third type of temperature oscillation. Specifically, equations governing the thermal and hydraulic behaviors of LHP operation will be used to describe interactions among LHP components, heat source, and heat sink. The following sequence of events and their interrelationship will also be explored: 1) maxima and minima of reservoir and thermal mass temperatures; 2) the range of the vapor front movement inside the condenser; 3) rates of change of the reservoir and thermal mass temperatures; 4) the rate of heat absorption and heat release by the thermal mass and the rate of vapor front movement; and 5) inflection points of the reservoir and thermal mass temperatures.

  14. Post-Test Analysis of a 10-Year Sodium Heat Pipe Life Test

    Science.gov (United States)

    Rosenfeld, John H.; Locci, Ivan E.; Sanzi, James L.; Hull, David R.; Geng, Steven M.

    2011-01-01

    High-temperature heat pipes are being evaluated for use in energy conversion applications such as fuel cells, gas turbine re-combustors, Stirling cycle heat sources; and with the resurgence of space nuclear power both as reactor heat removal elements and as radiator elements. Long operating life and reliable performance are critical requirements for these applications. Accordingly, long-term materials compatibility is being evaluated through the use of high-temperature life test heat pipes. Thermacore, Inc., has carried out a sodium heat pipe 10-year life test to establish long-term operating reliability. Sodium heat pipes have demonstrated favorable materials compatibility and heat transport characteristics at high operating temperatures in air over long time periods. A representative one-tenth segment Stirling Space Power Converter heat pipe with an Inconel 718 envelope and a stainless steel screen wick has operated for over 87,000 hr (10 years) at nearly 700 C. These life test results have demonstrated the potential for high-temperature heat pipes to serve as reliable energy conversion system components for power applications that require long operating lifetime with high reliability. Detailed design specifications, operating history, and post-test analysis of the heat pipe and sodium working fluid are described. Lessons learned and future life test plans are also discussed.

  15. Heat-transfer analysis of double-pipe heat exchangers for indirect-cycle SCW NPP

    Science.gov (United States)

    Thind, Harwinder

    SuperCritical-Water-cooled Reactors (SCWRs) are being developed as one of the Generation-IV nuclear-reactor concepts. SuperCritical Water (SCW) Nuclear Power Plants (NPPs) are expected to have much higher operating parameters compared to current NPPs, i.e., pressure of about 25 MPa and outlet temperature up to 625 °C. This study presents the heat transfer analysis of an intermediate Heat exchanger (HX) design for indirect-cycle concepts of Pressure-Tube (PT) and Pressure-Vessel (PV) SCWRs. Thermodynamic configurations with an intermediate HX gives a possibility to have a single-reheat option for PT and PV SCWRs without introducing steam-reheat channels into a reactor. Similar to the current CANDU and Pressurized Water Reactor (PWR) NPPs, steam generators separate the primary loop from the secondary loop. In this way, the primary loop can be completely enclosed in a reactor containment building. This study analyzes the heat transfer from a SCW primary (reactor) loop to a SCW and Super-Heated Steam (SHS) secondary (turbine) loop using a double-pipe intermediate HX. The numerical model is developed with MATLAB and NIST REFPROP software. Water from the primary loop flows through the inner pipe, and water from the secondary loop flows through the annulus in the counter direction of the double-pipe HX. The analysis on the double-pipe HX shows temperature and profiles of thermophysical properties along the heated length of the HX. It was found that the pseudocritical region has a significant effect on the temperature profiles and heat-transfer area of the HX. An analysis shows the effect of variation in pressure, temperature, mass flow rate, and pipe size on the pseudocritical region and the heat-transfer area of the HX. The results from the numerical model can be used to optimize the heat-transfer area of the HX. The higher pressure difference on the hot side and higher temperature difference between the hot and cold sides reduces the pseudocritical-region length, thus

  16. Development, manufacturing and testing of a gas-loaded variable conductance methanol heat pipe

    Science.gov (United States)

    Vanbuggenum, R. I. J.; Daniels, D. H. W.

    1987-02-01

    The experimental technology required to measure the performance of moderate temperature heat pipes is presented. The heat pipe manufacturing process is described. The hydrodynamic characteristics of the porous structure inside the heat pipe envelope were examined using a specially developed test rig, based upon a steady-state evaporation test. A fully automated test facility was developed and validated by testing constant conductance and variable conductance heat pipes (VCHP). Theoretical performance predictions are illustrated in terms of pressure, depicted in 3D-plots, and compared with the test results of the heat pipe performance tests. The design of the VCHP was directed towards the verification of the VCHP mathematical model. The VCHP design is validated and ready for the final testing and model verification.

  17. On the performance of air conditioner with heat pipe for cooling air in the condenser

    International Nuclear Information System (INIS)

    Naphon, Paisarn

    2010-01-01

    Improvement of the air conditioning system performance by using the heat pipe for cooling air before entering the condenser is presented. In the experiment, the heat pipe is fabricated from the straight copper tube with the diameter and length of 10, 600 mm, respectively. The arrangements of the heat pipe sets are arranged in the staggered layout with the tube rows of 1, 2, 3. R134a refrigerant is used as working fluid in the heat pipe set for this present study. By comparing with a conventional air conditioning system, the air conditioning system with three rows of heat pipe gives the highest COP and EER with increasing of 6.4%, 17.5%, respectively. On the global warming and environment problems, the results of this study are expected to lead to guidelines that will allow the improved performance of the air conditioning systems which reduce its energy consumption.

  18. Choice of insulation standard for pipe networks in 4th generation district heating systems

    DEFF Research Database (Denmark)

    Lund, Rasmus Søgaard; Mohammadi, Soma

    2016-01-01

    and smart gas grids. Improving DH pipes by improving the insulation standard results in decreasing the heat and temperature losses from the pipe networks. When reducing heat losses from DH pipes, there is a trade-off between the increasing cost of pipe insulation and the associated savings in the heat...... by implementing different pipe insulation standards. In the second step, the specific grid losses found in the first step are analysed in an integrated energy systems model where all main energy sectors and their interrelations are included. The outcome of the study can provide decision support when planning...... investments in DH systems today and in the future. The results from the case of Denmark shows that pipes with higher insulation standard (series 3) is generally preferable, but the highest insulation standard available today (series 4) might be preferable in the future if fuel prices or increase or investment...

  19. Performance study of heat-pipe solar photovoltaic/thermal heat pump system

    International Nuclear Information System (INIS)

    Chen, Hongbing; Zhang, Lei; Jie, Pengfei; Xiong, Yaxuan; Xu, Peng; Zhai, Huixing

    2017-01-01

    Highlights: • The testing device of HPS PV/T heat pump system was established by a finished product of PV panel. • A detailed mathematical model of heat pump was established to investigate the performance of each component. • The dynamic and static method was combined to solve the mathematical model of HPS PV/T heat pump system. • The HPS PV/T heat pump system was optimized by the mathematical model. • The influence of six factors on the performance of HPS PV/T heat pump system was analyzed. - Abstract: A heat-pipe solar (HPS) photovoltaic/thermal (PV/T) heat pump system, combining HPS PV/T collector with heat pump, is proposed in this paper. The HPS PV/T collector integrates heat pipes with PV panel, which can simultaneously generate electricity and thermal energy. The extracted heat from HPS PV/T collector can be used by heat pump, and then the photoelectric conversion efficiency is substantially improved because of the low temperature of PV cells. A mathematical model of the system is established in this paper. The model consists of a dynamic distributed parameter model of the HPS PV/T collection system and a quasi-steady state distributed parameter model of the heat pump. The mathematical model is validated by testing data, and the dynamic performance of the HPS PV/T heat pump system is discussed based on the validated model. Using the mathematical model, a reasonable accuracy in predicting the system’s dynamic performance with a relative error within ±15.0% can be obtained. The capacity of heat pump and the number of HPS collectors are optimized to improve the system performance based on the mathematical model. Six working modes are proposed and discussed to investigate the effect of solar radiation, ambient temperature, supply water temperature in condenser, PV packing factor, heat pipe pitch and PV backboard absorptivity on system performance by the validated model. It is found that the increase of solar radiation, ambient temperature and PV

  20. Theoretical and experimental investigation of plate screen mesh heat pipe solar collector

    International Nuclear Information System (INIS)

    Brahim, Taoufik; Dhaou, Mohammed Houcine; Jemni, Abdelmajid

    2014-01-01

    Highlights: • Experimental and computer simulation are performed for wicked heat pipe solar collectors. • Outdoor tests are conducted to compare its performance at different period of the year. • Modest improvement of the collector is achievement by adding fins to the condenser region. • Mesh number of heat pipe porous structure is an important factor in collector design. • Water slightly outperform methanol for such design and operating conditions. - Abstract: Heat pipes are efficient heat transfer devices for solar hot water heating systems. However, the effective downward transfer of solar energy in an integrated heat pipe system provides increased design and implementation options. There is a lack of literature about flat plate wicked assisted heat pipe solar collector, especially with the presence of finned water-cooled condenser wicked heat pipes for solar energy applications. In this paper the consequence of incorporating fins arrays into the condenser region of screen mesh heat pipe solar collector is investigated. An experimental and a transient theoretical model are conducted to compare the performances of solar heating system at different period of the year. A good agreement is shown between the model and the experiment. Two working fluids are investigated (water and methanol) and results reveal that water slightly outperforms methanol with a collector instantaneous efficiency of nearly 60%. That modest improvement is achieved by adding fins to the condenser region of the heat pipes. Results show that the collector efficiency increase as the number of fins increases (upon certain number) and reveal that the mesh number is an important factor which affect the overall collector efficiency. An optimal heat pipe mesh number of 100 meshes/in. with two layers appears to be favorable in such collectors for their design and operating conditions

  1. Transient Response to Rapid Cooling of a Stainless Steel Sodium Heat Pipe

    Science.gov (United States)

    Mireles, Omar R.; Houts, Michael G.

    2011-01-01

    Compact fission power systems are under consideration for use in long duration space exploration missions. Power demands on the order of 500 W, to 5 kW, will be required for up to 15 years of continuous service. One such small reactor design consists of a fast spectrum reactor cooled with an array of in-core alkali metal heat pipes coupled to thermoelectric or Stirling power conversion systems. Heat pipes advantageous attributes include a simplistic design, lack of moving parts, and well understood behavior. Concerns over reactor transients induced by heat pipe instability as a function of extreme thermal transients require experimental investigations. One particular concern is rapid cooling of the heat pipe condenser that would propagate to cool the evaporator. Rapid cooling of the reactor core beyond acceptable design limits could possibly induce unintended reactor control issues. This paper discusses a series of experimental demonstrations where a heat pipe operating at near prototypic conditions experienced rapid cooling of the condenser. The condenser section of a stainless steel sodium heat pipe was enclosed within a heat exchanger. The heat pipe - heat exchanger assembly was housed within a vacuum chamber held at a pressure of 50 Torr of helium. The heat pipe was brought to steady state operating conditions using graphite resistance heaters then cooled by a high flow of gaseous nitrogen through the heat exchanger. Subsequent thermal transient behavior was characterized by performing an energy balance using temperature, pressure and flow rate data obtained throughout the tests. Results indicate the degree of temperature change that results from a rapid cooling scenario will not significantly influence thermal stability of an operating heat pipe, even under extreme condenser cooling conditions.

  2. Combination study of operation characteristics and heat transfer mechanism for pulsating heat pipe

    International Nuclear Information System (INIS)

    Cui, Xiaoyu; Zhu, Yue; Li, Zhihua; Shun, Shende

    2014-01-01

    Pulsating heat pipe (PHP) is becoming a promising heat transfer device for the application like electronics cooling. However, due to its complicated operation mechanism, the heat transfer properties of the PHP still have not been fully understood. This study experimentally investigated on a closed-loop PHP charged with four types of working fluids, deionized water, methanol, ethanol and acetone. Combined with the visualization experimental results from the open literature, the operation characteristics and the corresponding heat transfer mechanisms for different heat inputs (5 W up to 100 W) and different filling ratios (20% up to 95%) have been presented and elaborated. The results show that heat-transfer mechanism changed with the transition of operation patterns; before valid oscillation started, the thermal resistance was not like that described in the open literature where it decreased almost linearly, but would rather slowdown descending or even change into rise first before further decreasing (i.e. an inflection point existed); when the heat input further increased to certain level, e.g. 65 W or above, there presented a limit of heat-transfer performance which was independent of the types of working fluids and the filling ratios, but may be related to the structure, the material, the size and the inclination of the PHP. - Highlights: •The thermal mechanisms altered accordingly with the operation features in the PHP. •Unlike conventional heat pipes, continuous temperature soaring would not happen in the PHP. •Before the oscillation start-up, there existed a heat-transfer limit for the relatively stagnated flow in the PHP. •A limit of thermal performance existed in the PHP at relatively high heat inputs

  3. Design considerations for CRBRP heat transport system piping operating at elevated temperatures

    International Nuclear Information System (INIS)

    Pollono, L.P.; Mello, R.M.

    1979-01-01

    The heat transport system sodium piping for the Clinch River Breeder Reactor Plant (CRBRP) within the reactor containment building must withstand high temperatures for long periods of time. Each phase of the mechanical design process of the piping system is influenced by elevated temperature considerations which include material thermal creep effects, ratchetting caused by rapid temperature transients and stress relaxation, and material degradation effects. The structural design philosophy taken to design the CRBRP piping operating in a high temperature environment is described. The resulting design of the heat transport system piping is presented along with a discussion of special features that resulted from the elevated temperature considerations

  4. Evaporator Development for an Evaporative Heat Pipe System

    Science.gov (United States)

    Peters, Leigh C.

    2004-01-01

    As fossil fuel resources continue to deplete, research for alternate power sources continues to develop. One of these alternate technologies is fuel cells. They are a practical fuel source able to provide significant amounts of power for applications from laptops to automobiles and their only byproduct is water. However, although this technology is over a century old and NASA has been working with it since the early 1960 s there is still room for improvement. The research I am involved in at NASA's Glenn Research Center is focusing on what is called a regenerative fuel cell system. The unique characteristic of this type of system is that it used an outside power source to create electrolysis of the water it produces and it then reuses the hydrogen and oxygen to continue producing power. The advantage of this type of system is that, for example, on space missions it can use solar power to recharge its gas supplies between periods when the object being orbited blocks out the sun. This particular system however is far from completion. This is because of the many components that are required to make up a fuel cell that need to be tested individually. The specific part of the system that is being worked on this summer of 2004 is the cooling system. The fuel cell stack, that is the part that actually creates the power, also produces a lot of heat. When not properly cooled, it has been known to cause fires which, needless to say are not conducive to the type of power that is trying to be created. In order to cool the fuel cell stack in this system we are developing a heat pipe cooling system. One of the main components of a heat pipe cooling system is what is known as the evaporator, and that is what happens to be the part of the system we are developing this summer. In most heat pipe systems the evaporator is a tube in which the working fluid is cooled and then re-circulated through the system to absorb more heat energy from the fuel cell stack. For this system, instead

  5. Establishing low-power operating limits for liquid metal heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Secary, J. [Phillips Lab., Kirtland AFB, NM (United States); Merrigan, M.A.; Keddy, M.D. [Los Alamos National Lab., NM (United States)

    1992-05-01

    Liquid metal heat pipes operated at power throughputs well below their design point for long durations may fail as a result of the working fluid migrating to a cold region within the pipe, freezing there, and hot returning to the evaporator section. Eventually sufficient working fluid inventory may be lost to the cold region to cause a local dry-out condition in the evaporator. A joint experimental and analytical effort between the Air Force Phillips Laboratory and Los Alamos National Laboratory is underway to investigate the phenomena. Experiments include both high temperature liquid metal and low temperature organic heat pipes. To date, a low temperature working fluid has been selected and its performance in a heat pipe validated. Additionally, a low-temperature heat pipe has been fabricated and is presently being tested.

  6. Particle shape effect on heat transfer performance in an oscillating heat pipe

    Directory of Open Access Journals (Sweden)

    Chen Hsiu-hung

    2011-01-01

    Full Text Available Abstract The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP was investigated experimentally. A binary mixture of ethylene glycol (EG and deionized water (50/50 by volume was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP.

  7. Numerical and experimental analysis of heat pipes with application in concentrated solar power systems

    Science.gov (United States)

    Mahdavi, Mahboobe

    Thermal energy storage systems as an integral part of concentrated solar power plants improve the performance of the system by mitigating the mismatch between the energy supply and the energy demand. Using a phase change material (PCM) to store energy increases the energy density, hence, reduces the size and cost of the system. However, the performance is limited by the low thermal conductivity of the PCM, which decreases the heat transfer rate between the heat source and PCM, which therefore prolongs the melting, or solidification process, and results in overheating the interface wall. To address this issue, heat pipes are embedded in the PCM to enhance the heat transfer from the receiver to the PCM, and from the PCM to the heat sink during charging and discharging processes, respectively. In the current study, the thermal-fluid phenomenon inside a heat pipe was investigated. The heat pipe network is specifically configured to be implemented in a thermal energy storage unit for a concentrated solar power system. The configuration allows for simultaneous power generation and energy storage for later use. The network is composed of a main heat pipe and an array of secondary heat pipes. The primary heat pipe has a disk-shaped evaporator and a disk-shaped condenser, which are connected via an adiabatic section. The secondary heat pipes are attached to the condenser of the primary heat pipe and they are surrounded by PCM. The other side of the condenser is connected to a heat engine and serves as its heat acceptor. The applied thermal energy to the disk-shaped evaporator changes the phase of working fluid in the wick structure from liquid to vapor. The vapor pressure drives it through the adiabatic section to the condenser where the vapor condenses and releases its heat to a heat engine. It should be noted that the condensed working fluid is returned to the evaporator by the capillary forces of the wick. The extra heat is then delivered to the phase change material

  8. Using of Multiwall Carbon Nanotube Based Nanofluid in the Heat Pipe to Get Better Thermal Performance

    Directory of Open Access Journals (Sweden)

    Y. Bakhshan

    2014-09-01

    Full Text Available Thermal performance of a cylindrical heat pipe is investigated numerically. Three different types of water based nanofluids, namely, Al2O3 + Water, Diamond + Water, and Multi-Wall Carbon Nano tube (MWCNT + Water, have been used. The influence of using the simple nanofluids and MWCNT nanofluid on the heat pipe characteristics such as liquid velocity, pressure profile, temperature profile, thermal resistance, and heat transfer coefficient of heat pipe has been studied. A new correlation developed by Bakhshan and Saljooghi (2014 for viscosity of nanofluids has been implemented. The results show, a good agreement with the available analytical and experimental data. Also the results show, that the MWCNT based nanofluid has lower thermal resistance, higher heat transfer coefficient, and lower temperature difference between evaporator and condenser sections, so it has good thermal specifications as a working fluid for use in heat pipes. The prepared code has capability for parametric studies also.

  9. Study of Ground Heat Exchangers in the Form of Parallel Horizontal Pipes Embedded in the Ground

    Directory of Open Access Journals (Sweden)

    Krzysztof Neupauer

    2018-02-01

    Full Text Available In order to predict long-term changes in the temperature of the ground in which a horizontal ground heat exchanger has been installed, it is beneficial to implement simplified mathematical models of heat transfer. The possibility of using a one-dimensional equation of heat conduction while modelling heat transfer in a ground heat exchanger with horizontal pipes has been demonstrated in the work. A theoretical analysis based on the linear heat source model as well as experimental research works have been carried out. It has been concluded that the temperature profiles of the ground in which parallel pipes of the heat exchanger are placed do not significantly differ from the profiles for the heat exchanger in the form of a plate; in particular, this refers to large distances from the level in which the pipes are positioned, small distances between pipes axes and the long duration of the process. Discrepancies between the calculated temperature increases for pipe and plate exchangers varied significantly in the individual time intervals, and were approx. 20–30%. The conducted experiments have demonstrated that the temperature field around parallel pipes of the heat exchanger may be described by the linear heat source model. The compatibility of temperature maps that were determined theoretically and experimentally was satisfactory with a good degree of accuracy.

  10. Sintered Nickel Powder Wicks for Flat Vertical Heat Pipes

    Directory of Open Access Journals (Sweden)

    Geir Hansen

    2015-03-01

    Full Text Available The fabrication and performance of wicks for flat heat pipe applications produced by sintering a filamentary nickel powder has been investigated. Tape casting was used as an intermediate step in the wick production process. Thermogravimetric analysis was used to study the burn-off of the organic binder used and to study the oxidation and reduction processes of the nickel. The wicks produced were flat, rectangular and intended for liquid transport in the upwards vertical direction. Rate-of-rise experiments using heptane were used to test the flow characteristics of the wicks. The wick porosities were measured using isopropanol. The heat transfer limitation constituted by the vapour static pressure and the capillary pressure was discussed. The influence on wick performance by using pore former in the manufacturing was studied. When Pcap/Psat > 1, the use of a pore former to increase the wick permeability will always improve the wick performance. When Pcap/Psat < 1, it was shown that if the effective pore radius and the permeability increase with an equal percentage the overall influence on the wick capacity is negative. A criterion for a successful pore former introduction is proposed and the concept of a pore former evaluation plot is presented.

  11. Long Duration Exposure Facility (LDEF) low-temperature Heat Pipe Experiment Package (HEPP) flight results

    Science.gov (United States)

    Mcintosh, Roy; Mccreight, Craig; Brennan, Patrick J.

    1992-01-01

    The Low Temperature Heat Pipe Flight Experiment (HEPP) is a fairly complicated thermal control experiment that was designed to evaluate the performance of two different low temperature ethane heat pipes and a n-Heptane Phase Change Material (PCM) canister. A total of 388 days of continuous operation with an axially grooved aluminum fixed conductance heat pipe of axially grooved stainless steel heat pipe diode was demonstrated before the EDS batteries lost power. The inability of the HEPP's radiator to cool below 190 K in flight prevented freezing of the PCM and the opportunity to conduct transport tests with the heat pipes. Post flight tests showed that the heat pipes and the PCM are still functioning. This paper presents a summary of the flight data analysis for the HEPP and its related support systems. Pre and post-flight thermal vacuum tests results are presented for the HEPP thermal control system along with individual heat pipe performance and PCM behavior. Appropriate SIG related systems data will also be included along with a 'lessons learned' summary.

  12. Heat pipes. (Latest citations from the NTIS bibliographic database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-10-01

    The bibliography contains citations concerning the theory, design, fabrication, testing, and operation of heat pipes. Applications include heat rejection devices in spacecraft, use in passive solar heating systems and warm air furnaces, and electronic circuit cooling. Heat recovery operations, and materials considerations are also discussed.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  13. Study on heat pipe assisted thermoelectric power generation system from exhaust gas

    Science.gov (United States)

    Chi, Ri-Guang; Park, Jong-Chan; Rhi, Seok-Ho; Lee, Kye-Bock

    2017-11-01

    Currently, most fuel consumed by vehicles is released to the environment as thermal energy through the exhaust pipe. Environmentally friendly vehicle technology needs new methods to increase the recycling efficiency of waste exhaust thermal energy. The present study investigated how to improve the maximum power output of a TEG (Thermoelectric generator) system assisted with a heat pipe. Conventionally, the driving energy efficiency of an internal combustion engine is approximately less than 35%. TEG with Seebeck elements is a new idea for recycling waste exhaust heat energy. The TEG system can efficiently utilize low temperature waste heat, such as industrial waste heat and solar energy. In addition, the heat pipe can transfer heat from the automobile's exhaust gas to a TEG. To improve the efficiency of the thermal power generation system with a heat pipe, effects of various parameters, such as inclination angle, charged amount of the heat pipe, condenser temperature, and size of the TEM (thermoelectric element), were investigated. Experimental studies, CFD simulation, and the theoretical approach to thermoelectric modules were carried out, and the TEG system with heat pipe (15-20% charged, 20°-30° inclined configuration) showed the best performance.

  14. Electricity eliminates rust from district heat pipes. The new deoxidation method works on radiators

    Energy Technology Data Exchange (ETDEWEB)

    Sonninen, R.; Leisio, C.

    1996-11-01

    Oxygen dissolving in district heating water through district heat pipes and pipe joints made of plastic corrodes many small and medium-size district heating systems, resulting in heat cuts in the buildings connected to these systems. IN some cases, corrosion products have even circulated back to district heating power plants, thus hampering heat generation in the worst of cases. People residing in blocks of flats where some radiator components are made of plastic also face a similar problem, though on a smaller scale. A small and efficient electrochemical deoxidation cell has now been invented to eliminate this nuisance, which occurs particularly in cold winter weather. (orig.)

  15. High Temperature Variable Conductance Heat Pipes for Radioisotope Stirling Systems

    International Nuclear Information System (INIS)

    Tarau, Calin; Walker, Kara L.; Anderson, William G.

    2009-01-01

    In a Stirling radioisotope system, heat must continually be removed from the GPHS modules, to maintain the GPHS modules and surrounding insulation at acceptable temperatures. Normally, the Stirling converter provides this cooling. If the Stirling engine stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS, but also ending the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) is under development to allow multiple stops and restarts of the Stirling engine. The status of the ongoing effort in developing this technology is presented in this paper. An earlier, preliminary design had a radiator outside the Advanced Stirling Radioisotope Generator (ASRG) casing, used NaK as the working fluid, and had the reservoir located on the cold side adapter flange. The revised design has an internal radiator inside the casing, with the reservoir embedded inside the insulation. A large set of advantages are offered by this new design. In addition to reducing the overall size and mass of the VCHP, simplicity, compactness and easiness in assembling the VCHP with the ASRG are significantly enhanced. Also, the permanently elevated temperatures of the entire VCHP allows the change of the working fluid from a binary compound (NaK) to single compound (Na). The latter, by its properties, allows higher performance and further mass reduction of the system. Preliminary design and analysis shows an acceptable peak temperature of the ASRG case of 140 deg. C while the heat losses caused by the addition of the VCHP are 1.8 W.

  16. Thermal Vacuum Testing of a Helium Loop Heat Pipe for Large Area Cryocooling

    Science.gov (United States)

    Ku, Jentung; Robinson, Franklin

    2016-01-01

    A loop heat pipe must start successfully before it can commence its service. The startup transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe startup behaviors. Topics include the four startup scenarios, the initial fluid distribution between the evaporator and reservoir that determines the startup scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power startup, and methods to enhance the startup success. Also addressed are the pressure spike and pressure surge during the startup transient, and repeated cycles of loop startup and shutdown under certain conditions.

  17. Analysis of fluid flow and heat transfer in a double pipe heat exchanger with porous structures

    International Nuclear Information System (INIS)

    Targui, N.; Kahalerras, H.

    2008-01-01

    A numerical study of flow and heat transfer characteristics is made in a double pipe heat exchanger with porous structures inserted in the annular gap in two configurations: on the inner cylinder (A) and on both the cylinders in a staggered fashion (B). The flow field in the porous regions is modelled by the Darcy-Brinkman-Forchheimer model and the finite volume method is used to solve the governing equations. The effects of several parameters such as Darcy number, porous structures thickness and spacing and thermal conductivity ratio are considered in order to look for the most appropriate properties of the porous structures that allow optimal heat transfer enhancement. It is found that the highest heat transfer rates are obtained when the porous structures are attached in configuration B especially at small spacing and high thicknesses

  18. Experiments on heat pipes submitted to strong accelerations; Experimentation de caloducs soumis a de fortes accelerations

    Energy Technology Data Exchange (ETDEWEB)

    Labuthe, A. [Dassault Aviation, 92 - Saint Cloud (France)

    1996-12-31

    In order to evaluate the possibility to use heat pipes as efficient heat transfer devices in aircrafts, a study of their behaviour during strong accelerations is necessary. This study has been jointly carried out by the Laboratory of Thermal Studies of Poitiers (France) and Dassault Aviation company. It is based on a series of tests performed with an experimental apparatus that uses the centrifugal effect to simulate the acceleration fields submitted to the heat pipe. Un-priming - priming cycles have been performed under different power and acceleration levels and at various functioning temperatures in order to explore the behaviour of heat pipes: rate of un-priming and re-priming, functioning in blocked mode etc.. This preliminary study demonstrates the rapid re-priming of the tested heat pipes when submitted to favourable acceleration situations and the possibility to use them under thermosyphon conditions despite the brief unfavourable acceleration periods encountered. (J.S.)

  19. Long Duration Exposure Facility (LDEF) low temperature Heat Pipe Experiment Package (HEPP) flight results

    Science.gov (United States)

    Mcintosh, Roy; Mccreight, Craig; Brennan, Patrick J.

    1993-01-01

    The Low Temperature Heat Pipe Flight Experiment (HEPP) is a fairly complicated thermal control experiment that was designed to evaluate the performance of two different low temperature ethane heat pipes and a low-temperature (182 K) phase change material. A total of 390 days of continuous operation with an axially grooved aluminum fixed conductance heat pipe and an axially grooved stainless steel heat pipe diode was demonstrated before the data acquisition system's batteries lost power. Each heat pipe had approximately 1 watt applied throughout this period. The HEPP was not able to cool below 188.6 K during the mission. As a result, the preprogrammed transport test sequence which initiates when the PCM temperature drops below 180 K was never exercised, and transport tests with both pipes and the diode reverse mode test could not be run in flight. Also, because the melt temperature of the n-heptane PCM is 182 K, its freeze/thaw behavior could not be tested. Post-flight thermal vacuum tests and thermal analyses have indicated that there was an apparent error in the original thermal analyses that led to this unfortunate result. Post-flight tests have demonstrated that the performance of both heat pipes and the PCM has not changed since being fabricated more than 14 years ago. A summary of HEPP's flight data and post-flight test results are presented.

  20. Theoretical and bibliographic synthesis on micro-heat pipes; Synthese theorique et bibliographique sur les microcaloducs

    Energy Technology Data Exchange (ETDEWEB)

    Sartre, V.; Lallemand, M. [Institut National des Sciences Appliquees (INSA), 69 - Villeurbanne (France)

    1996-12-31

    The technology, dimensioning and performances of heat pipes are well known since several years. Micro-heat pipes occurred more recently with the miniaturization of systems to be cooled and the increase of surface heat fluxes to be dissipated. Publications concerning this topic are not much older than the 90`s. Using these papers, a bibliographic synthesis on micro-heat pipe performances, functioning and dimensioning is presented. Experimental studies demonstrate the efficiency of such systems but also their high sensitivity with respect to the capillary limit which leads to a progressive drying of the evaporator and a reduction of its thermal conductance. Theoretical studies are based on the same equations than heat pipes. More or less complex models have been proposed in the literature and a relatively simple model is presented in this paper. These studies have permitted to show the great influence of some parameters on micro-heat pipes functioning like: the pipe geometry, the fluid-wall contact angle, the level of pipes filling, and the bonding zone of the liquid film on the wall. (J.S.) 15 refs.

  1. An analysis of the temperature distribution in the pipe bending using high frequency induction heating

    International Nuclear Information System (INIS)

    Fukue, Hisayoshi; Mochizuki, Yoji; Nakamura, Harushige; Kobo, Hiroshi; Nitta, Tetsuo; Kawakami, Kiyoshi

    1986-01-01

    A pipe bending apparatus has recently been developed by applying high frequency induction heating. However, the smaller the radius of pipe bending, the greater becomes the reduction in wall thickness and the ovality of the pipe form. This makes it impossible to manufacture pipe bending which will meet the nuclear pipe design code. In order to solve this problem it is crucial to obtain a temperature distributions in a pipe which is moving. It is calculated by giving the following boundary conditions : distribution of the heat generation rate, and that of heat transfer of cooling water. In the process of analyzing these distributions, the following results were obtained. (1) The distribution of the heat generation rate is determined by the sink of energy flux of Poynting vectors. The coil efficiency thus calculated was sixty percent. This figure accords with the test data. (2) The distribution of heat transfer coefficient of cooling water is mainly determined by the rate of liquid film heat transfer, but departure from nucleate boiling and dryout has to be taken into consideration. (3) TRUMP CODE is modified so that the temperature distribution in moving pipes can be calculated by taking the boundary conditions into account. The calculated results were in accordance with the test data. (author)

  2. Experimental and numerical study of latent heat thermal energy storage systems assisted by heat pipes for concentrated solar power application

    Science.gov (United States)

    Tiari, Saeed

    A desirable feature of concentrated solar power (CSP) with integrated thermal energy storage (TES) unit is to provide electricity in a dispatchable manner during cloud transient and non-daylight hours. Latent heat thermal energy storage (LHTES) offers many advantages such as higher energy storage density, wider range of operating temperature and nearly isothermal heat transfer relative to sensible heat thermal energy storage (SHTES), which is the current standard for trough and tower CSP systems. Despite the advantages mentioned above, LHTES systems performance is often limited by low thermal conductivity of commonly used, low cost phase change materials (PCMs). Research and development of passive heat transfer devices, such as heat pipes (HPs) to enhance the heat transfer in the PCM has received considerable attention. Due to its high effective thermal conductivity, heat pipe can transport large amounts of heat with relatively small temperature difference. The objective of this research is to study the charging and discharging processes of heat pipe-assisted LHTES systems using computational fluid dynamics (CFD) and experimental testing to develop a method for more efficient energy storage system design. The results revealed that the heat pipe network configurations and the quantities of heat pipes integrated in a thermal energy storage system have a profound effect on the thermal response of the system. The optimal placement of heat pipes in the system can significantly enhance the thermal performance. It was also found that the inclusion of natural convection heat transfer in the CFD simulation of the system is necessary to have a realistic prediction of a latent heat thermal storage system performance. In addition, the effects of geometrical features and quantity of fins attached to the HPs have been studied.

  3. Preliminary feasibility study of the heat - pipe ENHS reactor

    International Nuclear Information System (INIS)

    Fratoni, M.; Kim, L.; Mattafirri, S.; Petroski, R.; Greenspan, E.

    2007-01-01

    This preliminary study assesses the feasibility of designing an Encapsulated Nuclear Heat Source (ENHS) reactor [1] to have a solid core from which heat is removed by liquid-metal heat pipes (HP). Like the SAFE space nuclear reactor core [2], the HP-ENHS core is comprised of fuel rods and HPs embedded in a solid structure arranged in a hexagonal lattice in a 3:1 ratio. The HPs extend beyond the core length and transfer heat to a secondary coolant that flows by natural circulation. The HP-ENHS reactor is designed to preserve many features of the ENHS reactor including 20-year operation without refueling, very small excess reactivity throughout life, natural circulation cooling, walk-away passive safety, and robust proliferation resistance. The target power level and specific power of the HP-ENHS reactor are those of the reference ENHS reactor [1]. Compared to previous ENHS reactor designs utilizing a lead or lead-bismuth alloy natural circulation cooling system, the HP-ENHS reactor offers a number of possible advantageous features including: (1) significantly enhanced decay heat removal capability; (2) no positive void reactivity coefficients; (3) no direct contact between the fuel clad and coolant, hence, relatively lower wet corrosion of the clad; (4) a core that is more robust for transportation; (5) higher temperature potentially offering higher efficiency and hydrogen production capability. The study focuses on four areas: material compatibility analysis, HP performance analysis, neutronic analysis and thermal-hydraulic analysis. Of four high-temperature structural materials evaluated, Mo TZM alloy is the preferred choice; its upper estimated feasible operating temperature is 1350 K. HP performance is evaluated as a function of working fluid type, operating temperature, wick design and HP diameter and length. Sodium is the preferred working fluid and the HP working temperature is 1300 K. The neutronic analysis found that it is possible to achieve criticality

  4. Hydrogen permeation resistant heat pipe for bi-modal reactors. Final report, October 1, 1994--September 30, 1995

    International Nuclear Information System (INIS)

    North, M.T.; Anderson, W.G.

    1995-01-01

    The principal objective of this program was to demonstrate technology that will make a sodium heat pipe tolerant of hydrogen permeation for a bimodal space reactor application. Special focus was placed on techniques which enhance the permeation of hydrogen out of the heat pipe. Specific objectives include: define the detailed requirements for the bimodal reactor application; design and fabricate a prototype heat pipe tolerant of hydrogen permeation; and test the prototype heat pipe and demonstrate that hydrogen which permeates into the heat pipe is removed or reduced to acceptable levels. The results of the program were fully successful. Analyses were performed on two different heat pipe designs and an experimental heat pipe was fabricated and tested. A model of the experimental heat pipe was developed to predict the enhancement in the hydrogen permeation rate out of the heat pipe. A significant improvement in the rate at which hydrogen permeates out of a heat pipe was predicted for the use of the special condenser geometry developed here. Agreement between the model and the experimental results was qualitatively good. Inclusion of the additional effects of fluid flow in the heat pipe are recommended for future work

  5. Heat removal from bipolar transistor by loop heat pipe with nickel and copper porous structures.

    Science.gov (United States)

    Nemec, Patrik; Smitka, Martin; Malcho, Milan

    2014-01-01

    Loop heat pipes (LHPs) are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements' influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT) have been made.

  6. Heat Removal from Bipolar Transistor by Loop Heat Pipe with Nickel and Copper Porous Structures

    Directory of Open Access Journals (Sweden)

    Patrik Nemec

    2014-01-01

    Full Text Available Loop heat pipes (LHPs are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements’ influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT have been made.

  7. Solid-Core Heat-Pipe Nuclear Batterly Type Reactor

    International Nuclear Information System (INIS)

    Ehud Greenspan

    2008-01-01

    This project was devoted to a preliminary assessment of the feasibility of designing an Encapsulated Nuclear Heat Source (ENHS) reactor to have a solid core from which heat is removed by liquid-metal heat pipes (HP). Like the SAFE 400 space nuclear reactor core, the HPENHS core is comprised of fuel rods and HPs embedded in a solid structure arranged in a hexagonal lattice in a 3:1 ratio. The core is oriented horizontally and has a square rather cylindrical cross section for effective heat transfer. The HPs extend from the two axial reflectors in which the fission gas plena are embedded and transfer heat to an intermediate coolant that flows by natural-circulation. The HP-ENHS is designed to preserve many features of the ENHS including 20-year operation without refueling, very small excess reactivity throughout life, natural circulation cooling, walkaway passive safety, and robust proliferation resistance. The target power level and specific power of the HP-ENHS reactor are those of the reference ENHS reactor. Compared to previous ENHS reactor designs utilizing a lead or lead-bismuth alloy natural circulation cooling system, the HP-ENHS reactor offers a number of advantageous features including: (1) significantly enhanced passive decay heat removal capability; (2) no positive void reactivity coefficients; (3) relatively lower corrosion of the cladding (4) a core that is more robust for transportation; (5) higher temperature potentially offering higher efficiency and hydrogen production capability. This preliminary study focuses on five areas: material compatibility analysis, HP performance analysis, neutronic analysis, thermal-hydraulic analysis and safety analysis. Of the four high-temperature structural materials evaluated, Mo TZM alloy is the preferred choice; its upper estimated feasible operating temperature is 1350 K. HP performance is evaluated as a function of working fluid type, operating temperature, wick design and HP diameter and length. Sodium is the

  8. Method for optimal design of pipes for low-energy district heating, with focus on heat losses

    DEFF Research Database (Denmark)

    Dalla Rosa, Alessandro; Li, Hongwei; Svendsen, Svend

    2011-01-01

    factors in the optimal design of low-energy DH systems. Various pipe configurations are considered in this paper: flexible pre-insulated twin pipes with symmetrical or asymmetrical insulation, double pipes, and triple pipes. These technologies represent potential energy-efficient and cost......-effective solutions for DH networks in low-heat density areas. We start with a review of theories and methods for steady-state heat loss calculation. Next, the article shows how detailed calculations with 2D-modeling of pipes can be carried out by means of computer software based on the finite-element method (FEM......). The model was validated by comparison with experimental measurements, analytical formulas, and data from the literature. We took into account the influence of the temperature-dependent conductivity coefficient of polyurethane insulation foam, which enabled us to achieve a high degree of accuracy. We also...

  9. Discussion on the solar concentrating thermoelectric generation using micro-channel heat pipe array

    Science.gov (United States)

    Li, Guiqiang; Feng, Wei; Jin, Yi; Chen, Xiao; Ji, Jie

    2017-11-01

    Heat pipe is a high efficient tool in solar energy applications. In this paper, a novel solar concentrating thermoelectric generation using micro-channel heat pipe array (STEG-MCHP) was presented. The flat-plate micro-channel heat pipe array not only has a higher heat transfer performance than the common heat pipe, but also can be placed on the surface of TEG closely, which can further reduce the thermal resistance between the heat pipe and the TEG. A preliminary comparison experiment was also conducted to indicate the advantages of the STEG-MCHP. The optimization based on the model verified by the experiment was demonstrated, and the concentration ratio and selective absorbing coating area were also discussed. In addition, the cost analysis was also performed to compare between the STEG-MCHP and the common solar concentrating TEGs in series. The outcome showed that the solar concentrating thermoelectric generation using micro-channel heat pipe array has the higher electrical efficiency and lower cost, which may provide a suitable way for solar TEG applications.

  10. Loop Heat Pipe Manufacturing via DMLS for CubeSAT Applications, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Cooling Technologies, Inc. (ACT) proposes to develop a low-cost Loop Heat Pipe (LHP) evaporator using a technique known as Direct Metal Laser Sintering...

  11. Loop Heat Pipe Manufacturing via DMLS for CubeSAT Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced Cooling Technologies, Inc. (ACT) proposes to develop a low-cost Loop Heat Pipe (LHP) evaporator using a technique known as Direct Metal Laser Sintering...

  12. Loop Heat Pipe with Thermal Control Valve for Passive Variable Thermal Link, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Loop heat pipes (LHPs) can provide variable thermal conductance needed to maintain electronics and batteries on Lunar/Martian rovers/landers within desired...

  13. Refractory Metal Heat Pipe Life Test - Test Plan and Standard Operating Procedures

    Science.gov (United States)

    Martin, J. J.; Reid, R. S.

    2010-01-01

    Refractory metal heat pipes developed during this project shall be subjected to various operating conditions to evaluate life-limiting corrosion factors. To accomplish this objective, various parameters shall be investigated, including the effect of temperature and mass fluence on long-term corrosion rate. The test series will begin with a performance test of one module to evaluate its performance and to establish the temperature and power settings for the remaining modules. The performance test will be followed by round-the-clock testing of 16 heat pipes. All heat pipes shall be nondestructively inspected at 6-month intervals. At longer intervals, specific modules will be destructively evaluated. Both the nondestructive and destructive evaluations shall be coordinated with Los Alamos National Laboratory. During the processing, setup, and testing of the heat pipes, standard operating procedures shall be developed. Initial procedures are listed here and, as hardware is developed, will be updated, incorporating findings and lessons learned.

  14. Titanium-Water Heat Pipe Radiator for Spacecraft Fission Power Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed program will develop titanium/water heat pipes suitable for Spacecraft Fission Power. NASA is examining small fission power reactors for future space...

  15. Titanium-Water Heat Pipe Radiator for Spacecraft Fission Power, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR Phase II program Advanced Cooling Technologies, Inc. (ACT) proposes to develop titanium/water heat pipes suitable for Spacecraft Fission Power...

  16. Assessment of existing and prospective piping technology for district-heating applications

    Energy Technology Data Exchange (ETDEWEB)

    Oliker, I.

    1979-09-01

    Data on design features and operational experience of 40 hot water and steam district-heating networks with an overall heat capacity of 18,000 MWt have been collected, systematized, and analyzed. Piping networks located in Canada, Denmark, Finland, France, Italy, Japan, Netherlands, Sweden, USA, USSR, and West Germany have been analyzed and the data assembled. The data bank and analysis of the operational experience design features of hot water and steam district-heating networks are provided in Sections 2 and 3. In Section 4 the piping installation design is optimized in order to reduce costs wherever possible, without jeopardizing overall system efficiency, reliability or service life, and employing a mixture of typical US and European district-heating practices. The status of prospective non-metallic piping materials is presented in Section 5. The following materials have been investigated: fiberglass reinforced plastic, cross-linked polyethylene, polybutylene, prestressed concrete, polymer concrete, and asbestos-cement piping. (MCW)

  17. Critical evaluation of molybdenum and its alloys for use in space reactor core heat pipes

    International Nuclear Information System (INIS)

    Lundberg, L.B.

    1981-01-01

    The choice of pure molybdenum as the prime candidate material for space reactor core heat pipes is examined, and the advantages and disadvantages of this material are brought into focus. Even though pure molybdenum heat pipes have been built and tested, this metal's high ductile-brittle transition temperature and modest creep strength place significant design restrictions on a core heat pipe made from it. Molybdenum alloys are examined with regard to their promise as potential replacements for pure molybdenum. The properties of TZM and molybdenum-rhenium alloys are examined, and it appears that Mo-Re alloys with 10 to 15 wt % rhenium offer the most advantage as an alternative to pure molybdenum in space reactor core heat pipes

  18. Heat Pipe Solar Receiver for Oxygen Production of Lunar Regolith, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovative Research project by Advanced Cooling Technologies, Inc. (ACT) will develop an advanced high temperature heat pipe solar receiver that...

  19. Experimental investigation on the thermal performance and optimization of heat sink with U-shape heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Tian Shen [Faculty of Engineering and Technology, Multimedia University, 75450 Melaka (Malaysia); Hung, Yew Mun [School of Engineering, Monash University, 46150 Bandar Sunway (Malaysia)

    2010-11-15

    Experimental investigation is carried out to study the thermal performance of a heat sink with finned U-shape heat pipes which is a contemporary central processing unit (CPU) cooler compatible for a wide range of high-frequency microprocessors. The optimum range of operating heat load based on thermal resistance analysis of the heat sink is characterized. The convection heat transfer coefficient between the fins and the ambient air is estimated by using Bessel's modified equation in conjunction with the results obtained through the experimental investigation. The thermal optimization of the heat sink involves the determination of the optimized L-ratio (ratio of the evaporator section length to the condenser section length) of the U-shape heat pipe, by evaluating the minima of the thermal resistance function, in which case the empirical convection heat transfer coefficient is applied in the calculation. In conjunction with this, the optimal L-ratio of a U-shape heat pipe is found to be dependent on other geometrical parameters such as the heat pipe diameter and the fin spacing, which are of practical engineering importance in the optimum design of the heat sink. (author)

  20. An experimental study of naturally driven heated air flow in a vertical pipe

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Mostafa; Bayat, Mohammad Mehdi [Department of Mechanical Engineering, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of)

    2011-01-15

    Specifications of warm air flow within a vertical pipe which is induced by the buoyancy effect were investigated in this study. Air from surroundings was directed into a heating chamber connected to a vertical pipe to establish a flow within the pipe. The temperature and the velocity were measured at different points within the stable flow and the mean values of these parameters were computed. Mass flow rate of air was evaluated using ideal gas assumption. In order to investigate the effect of the thermal boundary condition of the pipe, two tests were conducted; once for the pipe exposed to the surroundings and then for the pipe with a thermal insulation. A model for predicting the induced flow rate of warm air was developed and the predictions of the model were compared with the experimental data over the tested range of the parameters. (author)

  1. Theoretical investigation of the performance of a novel loop heat pipe solar water heating system for use in Beijing, China

    International Nuclear Information System (INIS)

    Zhao Xudong; Wang Zhangyuan; Tang Qi

    2010-01-01

    A novel loop heat pipe (LHP) solar water heating system for typical apartment buildings in Beijing was designed to enable effective collection of solar heat, distance transport, and efficient conversion of solar heat into hot water. Taking consideration of the heat balances occurring in various parts of the loop, such as the solar absorber, heat pipe loop, heat exchanger and storage tank, a computer model was developed to investigate the thermal performance of the system. With the specified system structure, the efficiency of the solar system was found to be a function of its operational characteristics - working temperature of the loop heat pipe, water flow rate across the heat exchanger, and external parameters, including ambient temperature, temperature of water across the exchanger and solar radiation. The relationship between the efficiency of the system and these parameters was established, analysed and discussed in detail. The study suggested that the loop heat pipe should be operated at around 72 deg. C and the water across the heat exchanger should be maintained at 5.1 l/min. Any variation in system structure, i.e., glazing cover and height difference between the absorber and heat exchanger, would lead to different system performance. The glazing covers could be made using either borosilicate or polycarbonate, but borosilicate is to be preferred as it performs better and achieves higher efficiency at higher temperature operation. The height difference between the absorber and heat exchanger in the design was 1.9 m which is an adequate distance causing no constraint to heat pipe heat transfer. These simulation results were validated with the primary testing results.

  2. Fan cycling strategies and heat pipe heat exchangers provide energy efficient dehumidification

    Energy Technology Data Exchange (ETDEWEB)

    Shirey, D.B. III [Florida Solar Energy Center, Cape Canaveral, FL (United States)

    1995-03-01

    This article describes two methods to reduce energy consumption and peak demand in buildings that require humidity control that were demonstrated at the Salvador Dali Museum in St. Petersburg, Florida. The first method centered on alternative indoor fan cycling strategies and the second method involved the use of heat pipe heat exchangers. Both approaches increased the dehumidification performance of the existing air-conditioning systems and provided substantial savings. Simple, low cost alternative fan cycling strategies were used. When possible, auto fan control replaced constant fan operation to avoid excess fan energy consumption, ventilation load and compressor operation. The alternative fan control strategies reduced indoor humidity fluctuations in all zones, and significantly reduced overall humidity levels in the museum lobby and storage area. An HPHX was installed within one of the two gallery RTUs to improve the unit`s dehumidification performance. The passive HPHX significantly reduced electric reheat and compressor operation while maintaining the precise temperature and humidity requirements within the gallery. The second gallery RTU now operates primarily as a back-up unit to the heat pipe-assisted air-conditioning unit.

  3. Multiobjective optimization for design of multifunctional sandwich panel heat pipes with micro-architected truss cores

    International Nuclear Information System (INIS)

    Roper, Christopher S.

    2011-01-01

    A micro-architected multifunctional structure, a sandwich panel heat pipe with a micro-scale truss core and arterial wick, is modeled and optimized. To characterize multiple functionalities, objective equations are formulated for density, compressive modulus, compressive strength, and maximum heat flux. Multiobjective optimization is used to determine the Pareto-optimal design surfaces, which consist of hundreds of individually optimized designs. The Pareto-optimal surfaces for different working fluids (water, ethanol, and perfluoro(methylcyclohexane)) as well as different micro-scale truss core materials (metal, ceramic, and polymer) are determined and compared. Examination of the Pareto fronts allows comparison of the trade-offs between density, compressive stiffness, compressive strength, and maximum heat flux in the design of multifunctional sandwich panel heat pipes with micro-scale truss cores. Heat fluxes up to 3.0 MW/m 2 are predicted for silicon carbide truss core heat pipes with water as the working fluid.

  4. Dynamic thermal characteristics of heat pipe via segmented thermal resistance model for electric vehicle battery cooling

    Science.gov (United States)

    Liu, Feifei; Lan, Fengchong; Chen, Jiqing

    2016-07-01

    Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a ;segmented; thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed ;segmented; model shows more precise than the ;non-segmented; model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the ;segmented; model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

  5. Experimental Investigation of Concrete Runway Snow Melting Utilizing Heat Pipe Technology

    Directory of Open Access Journals (Sweden)

    Fengchen Chen

    2018-01-01

    Full Text Available A full scale snow melting system with heat pipe technology is built in this work, which avoids the negative effects on concrete structure and environment caused by traditional deicing chemicals. The snow melting, ice-freezing performance and temperature distribution characteristics of heat pipe concrete runway were discussed by the outdoor experiments. The results show that the temperature of the concrete pavement is greatly improved with the heat pipe system. The environment temperature and embedded depth of heat pipe play a dominant role among the decision variables of the snow melting system. Heat pipe snow melting pavement melts the snow completely and avoids freezing at any time when the environment temperature is below freezing point, which is secure enough for planes take-off and landing. Besides, the exportation and recovery of geothermal energy indicate that this system can run for a long time. This paper will be useful for the design and application of the heat pipe used in the runway snow melting.

  6. Effects of heat pipe cooling on permanent mold castings of aluminum alloys

    International Nuclear Information System (INIS)

    Zhang, C.; Mucciardi, F.; Gruzleski, J.E.

    2002-01-01

    The temperature distribution within molds is a critical parameter in determining the ultimate casting quality in permanent mold casting processes, so there is a considerable incentive to develop a more effective method of mold cooling. Based on this consideration, a novel, effective and controllable heat pipe has been successfully developed and used as a new method of permanent mold cooling. Symmetric step casting of A356 alloy have been produced in an experimental permanent mold made of H13 tool steel, which is cooled by such heat pipes. The experimental results show that heat pipes can provide extremely high cooling rates in permanent mold castings of aluminum. The dendrite arm spacing of A356 alloy is refined considerably, and porosity and shrinkage of the castings are redistributed by the heat pipe cooling. Moreover, the heat pipe can be used to determine the time when the air gap forms at the interface between the mold and the casting. The effect of heat pipe cooling on solidification time of castings of A356 alloy with different coating types is also discussed in this paper. (author)

  7. Development of heat pipe technology for permanent mold casting of magnesium alloys

    International Nuclear Information System (INIS)

    Elalem, K.; Mucciardi, F.; Gruzleski, J.E.; Carbonneau, Y.

    2002-01-01

    One of the key techniques for producing sound permanent mold castings is to use controlled mold cooling such as air cooling, water cooling and heat pipe cooling. Air-cooling has limited applications in permanent mold casting due to its low cooling capability and high cost. Water-cooling is widely used in permanent mold casting, but has some disadvantages such as safety issues and the facilities required. The early applications of heat pipes in permanent mold casting have shown tremendous results due to their high cooling rates, low cost and safety. In this work, a permanent mold for magnesium casting has been designed with the intention of producing shrinkage defects in the castings. Novel heat pipes that can generate high cooling rates have been constructed and used to direct the solidification in order to reduce the shrinkage. In this paper, the design of the mold and that of the heat pipes are presented. The results of some of the computer simulations that were conducted to determine casting conditions along with the potential of using heat pipes to direct the solidification are also presented. Moreover, a preliminary evaluation of the performance of heat pipes in the permanent mold casting of magnesium will also be discussed. (author)

  8. Boiling heat transfer during impingement of two or three pipe laminar jets onto moving steel sheet

    OpenAIRE

    Fujimoto, Hitoshi; Hayashi, Naoya; Nakahara, Junya; Morisawa, Kenta; Hama, Takayuki; Takuda, Hirohiko

    2016-01-01

    The impingement of pipe laminar jets is commonly used in run-out-table cooling in hot rolling mills. In this process, a moving hot steel sheet is cooled by pipe laminar array jets. When the spacing between two neighbor jets is small in the sheet width direction, flow interaction of cooling water on the sheet is inevitable, resulting in complex heat transfer phenomena. In the present study, the boiling heat transfer during the impingement of two or three pipe laminar jets onto a moving steel s...

  9. Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

    Science.gov (United States)

    Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

    2015-01-01

    Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

  10. Experimental investigation of combined heat recovery and power generation using a heat pipe assisted thermoelectric generator system

    International Nuclear Information System (INIS)

    Remeli, Muhammad Fairuz; Date, Abhijit; Orr, Bradley; Ding, Lai Chet; Singh, Baljit; Affandi, Nor Dalila Nor; Akbarzadeh, Aliakbar

    2016-01-01

    Highlights: • A new passive combined heat recovery and power generation system was tested. • Heat pipes and thermoelectrics were used for recovering industrial waste heat. • The system could recover approximately 1079 W of heat and produce approximately 7 W of electric power. - Abstract: This paper explores a new method of recovering industrial waste heat and conversion to electricity using a Thermo-Electric Generator (TEG). For this purpose, a lab scale bench-top prototype of waste heat recovery and electricity conversion system was designed and fabricated. This bench top system consists of Bismuth Telluride (Bi 2 Te 3 ) based TEG sandwiched between two heat pipes. The first heat pipe was connected to the hot side of the TEG and the second to the cold side of TEG. The waste heat was simulated by using a 2 kW electric heater for heating the air in the system. Experiments were conducted to evaluate the system performance in terms of the heat transfer rate, heat exchanger effectiveness, and maximum output power. It was found that the highest heat exchanger effectiveness of 41% was achieved when the airspeed was set at 1.1 m/s. The system could recover around 1079 W of heat and produce around 7 W of electric power. This equated to 0.7% of thermal-to-electric conversion efficiency. The theoretical predictions showed good agreement compared to the experimental results.

  11. Research on thermal characteristics of heat pipes for led lightning devices

    Directory of Open Access Journals (Sweden)

    Lozovoi M. A.

    2014-12-01

    Full Text Available New energy-saving technologies for lighting is a promising trend in lighting technology. To this end, during the recent decade, have been actively developed and implemented lighting units based on LED modules. Reliability of such devices is largely dependent on the ensuring of cooling of the LEDs. Heat pipes are being used with ever increasing frequency for increasing an efficiency of cooling of powerful LEDs within a lightening device. Results of experimental modeling of thermal characteristics of two aluminum heat pipes with grooved capillary structure and ammonia used as a heat transfer agent, designed for application as a heat transfer elements in designs of powerful LED lightening device with forced air cooling are presented in this paper. It is shown that for the heat flux range of 50 to 100 W and for incident flow speed in the range of 0.8 to 2.1 m/s the temperature in the heating zone of the heat pipe falls into the range of 31.0 to 52.5 °C. In this case the temperature difference along the heat pipe is between 0.9…1.7 °C, when a minimal value of the fed heat flux is 50 W, and 1.7…3.1°C, when a maximum value of the heat flux is 100 W. The value of heat transfer resistance of the heat pipes was in the range of 0.012 to 0.044 °C/W. The key factors influencing the thermal characteristics of the heat pipes are: the value of the fed heat flux, the speed of cooling air flux, heat pipe inclination angle with respect to the horizon. By using five such heat pipes within the powerful LED lightning device it is possible to achieve an elimination of the total heat flux from LED modules up to 500 W. At an efficiency factor of LEDs of about 75% this is equivalent to intake power 665 W. Taking into account that luminous efficiency of modern LEDs is about 10 times as high as those of incandescent lamps, proposed lightning device will produce a luminous flux which is equivalent to the luminous flux of a lightening device with incandescent lamps

  12. Experimental investigation on the feasibility of heat pipe cooling for HEV/EV lithium-ion battery

    International Nuclear Information System (INIS)

    Tran, Thanh-Ha; Harmand, Souad; Desmet, Bernard; Filangi, Sebastien

    2014-01-01

    In this paper, the use of flat heat pipe as an effective and low-energy device to mitigate the temperature of a battery module designed for a HEV application was investigated. For this purpose, nominal heat flux generated by a battery module was reproduced and applied to a flat heat pipe cooling system. The thermal performance of the flat heat pipe cooling system was compared with that of a conventional heat sink under various cooling conditions and under several inclined positions. The results show that adding heat pipe reduced the thermal resistance of a common heat sink of 30% under natural convection and 20% under low air velocity cooling. Consequently, the cell temperature was kept below 50 °C, which cannot be achieved using heat sink. According to the space allocated for the battery pack in the vehicle, flat heat pipe can be used in vertical or horizontal position. Furthermore, flat heat pipe works efficiently under different grade road conditions. The transient behaviour of the flat heat pipe was also studied under high frequency and large amplitude variable input power. The flat heat pipe was found to handle more efficiently instant increases of the heat flux than the conventional heat sink. -- Highlights: • Constant heat flux was applied to a flat heat pipe cooling system. • Its thermal performance was compared with that of a heat sink under several cooling conditions. • The influence of the inclination was evaluated. • The heat pipe transient behaviour was also studied under variable input power. • Heat pipe was found to be an effective and low-energy solution for HEV/EV battery cooling

  13. Experimental investigation of pulsating heat pipe performance with regard to fuel cell cooling application

    International Nuclear Information System (INIS)

    Clement, Jason; Wang Xia

    2013-01-01

    A pulsating heat pipe (PHP) is a closed loop, passive heat transfer device. Its operation depends on the phase change of a working fluid within the loop. Design and performance testing of a pulsating heat pipe was conducted under conditions to simulate heat dissipation requirements of a proton exchange membrane (PEM) fuel cell stack. Integration of pulsating heat pipes within bipolar plates of the stack would eliminate the need for ancillary cooling equipment, thus also reducing parasitic losses and increasing energy output. The PHP under investigation, having dimensions of 46.80 cm long and 14.70 cm wide, was constructed from 0.3175 cm copper tube. Heat pipes effectiveness was found to be dependent upon several factors such as energy input, types of working fluid and its filling ratio. Power inputs to the evaporator side of the pulsating heat pipe varied from 80 to 180 W. Working fluids tested included acetone, methanol, and deionized water. Filling ratios between 30 and 70 percent of the total working volume were also examined. Methanol outperformed other fluids tested; with a 45 percent fluid fill ratio and a 120 W power input, the apparatus took the shortest time to reach steady state and had one of the smallest steady state temperature differences. The various conditions studied were chosen to assess the heat pipe's potential as cooling media for PEM fuel cells. - Highlights: ► Methanol as a working fluid outperformed both acetone and water in a pulsating heat pipe. ► Performance for the PHP peaked with methanol and a fill ratio of 45 percent fluid to total volume. ► A smaller resistance was associated with a higher power input to the system.

  14. Near-surface gravity actuated pipe (GAP{sup TM}) system for Brazilian deepwater fluid transfer

    Energy Technology Data Exchange (ETDEWEB)

    Fromage, Lionel; Brown, Paul A. [SBM Offshore (Monaco)

    2009-12-19

    The recent discovery of new deep water and ultra-deep water oil and gas fields offshore Brazil, including pre-salt reservoirs, has become a focal point for field development Operators and Contractors. The aggressive nature of fluids (sour, high density) in combination with deeper waters implies potential flow assurance issues. These issues challenge riser and pipeline technology to find cost effective solutions for hydrocarbon fluid transfer in field development scenarios involving phased tied-back. The near-surface GAP{sup TM}, system (Gravity Actuated Pipe{sup TM}), which has been in operation for more than two years on the Kikeh field offshore Malaysia in 1325 m of water between a Dry Tree Unit (SPAR) and a turret-moored FPSO, is considered to meet these challenges since such a product is quasi independent of water depth and takes advantage of being near surface to optimize flow assurance. Furthermore the GAP{sup TM} has undergone technical upgrades when compared to the Kikeh project in order to make it suitable for the more hostile met ocean conditions offshore Brazil. This paper presents the design features, the construction and assembly plans in Brazil and the offshore installation of a GAP fluid transfer system for operation in Brazilian deep waters. (author)

  15. The TX-model - a quantitative heat loss analysis of district heating pipes by means of IR surface temperature measurements

    Energy Technology Data Exchange (ETDEWEB)

    Zinki, Heimo [ZW Energiteknik, Nykoeping (Sweden)

    1996-11-01

    The aim of this study was to investigate the possibility of analysing the temperature profile at the ground surface above buried district heating pipes in such a way that would enable the quantitative determination of heat loss from the pair of pipes. In practical applications, it is supposed that this temperature profile is generated by means of advanced IR-thermography. For this purpose, the principle of the TX - model has been developed, based on the fact that the heat losses from pipes buried in the ground have a temperature signature on the ground surface. Qualitative analysis of this temperature signature is very well known and in practical use for detecting leaks from pipes. These techniques primarily make use of relative changes of the temperature pattern along the pipe. In the quantitative heat loss analysis, however, it is presumed that the temperature profile across the pipes is related to the pipe heat loss per unit length. The basic idea is that the integral of the temperature profile perpendicular to the pipe, called TX, is a function of the heat loss, but is also affected by other parameters such as burial depth, heat diffusivity, wind, precipitation and so on. In order to analyse the parameters influencing the TX- factor, a simulation model for the energy balance at the ground surface has been developed. This model includes the heat flow from the pipe to the surface and the heat exchange at the surface with the environment due to convection, latent heat change, solar and long wave radiation. The simulation gives the surprising result that the TX factor is by and large unaffected during the course of a day even when the sun is shining, as long as other climate conditions are relatively stable (low wind, no rain, no shadows). The results from the simulations were verified at different sites in Denmark, Finland, Sweden and USA through a co-operative research program organised and partially financed by the IEA District Heating Programme, Task III, and

  16. Heat transfer performance of a pulsating heat pipe charged with acetone-based mixtures

    Science.gov (United States)

    Wang, Wenqing; Cui, Xiaoyu; Zhu, Yue

    2017-06-01

    Pulsating heat pipes (PHPs) are used as high efficiency heat exchangers, and the selection of working fluids in PHPs has a great impact on the heat transfer performance. This study investigates the thermal resistance characteristics of the PHP charged with acetone-based binary mixtures, where deionized water, methanol and ethanol were added to and mixed with acetone, respectively. The volume mixing ratios were 2:1, 4:1 and 7:1, and the heating power ranged from 10 to 100 W with filling ratios of 45, 55, 62 and 70%. At a low filling ratio (45%), the zeotropic characteristics of the binary mixtures have an influence on the heat transfer performance of the PHP. Adding water, which has a substantially different boiling point compared with that of acetone, can significantly improve the anti-dry-out ability inside the PHP. At a medium filling ratio (55%), the heat transfer performance of the PHP is affected by both phase transition characteristics and physical properties of working fluids. At high heating power, the thermal resistance of the PHP with acetone-water mixture is between that with pure acetone and pure water, whereas the thermal resistance of the PHP with acetone-methanol and acetone-ethanol mixtures at mixing ratios of 2:1 and 4:1 is less than that with the corresponding pure fluids. At high filling ratios (62 and 70%), the heat transfer performance of the PHP is mainly determined by the properties of working fluids that affects the flow resistance. Thus, the PHP with acetone-methanol and acetone-ethanol mixtures that have a lower flow resistance shows better heat transfer performance than that with acetone-water mixture.

  17. Techniques associated with thermal-vacuum testing of the OAO-C heat pipes

    Science.gov (United States)

    Marshburn, J. P.

    1972-01-01

    The mechanical problems associated with testing the two high-heat load pipes are discussed. One of these pipes was tested three times before being accepted. The first test resulted in the discovery of non-condensable hydrogen gas, which prevented the pipe from functioning properly. The second test was a repeat of the first, to see if all the gas had been removed. The third test was to see if any changes had occurred to the pipe as a result of saddle modifications. Saddle modifications were necessary because the epoxy binding agent between the saddles and the pipe had decomposed during the testing. The test problems discussed deal with the specially designed heat-removal devices, the mobile tilt table, the table position indicator, and the heat input mechanisms, all of which were necessary to conduct a high-heat load, thermal-vacuum test. The final results showed that the techniques used were adequate for thermal-vacuum testing of heat pipes.

  18. IEEE recommended practice for the design and installation of electric pipe heating systems for nuclear power generating stations

    International Nuclear Information System (INIS)

    Anon.

    1979-01-01

    The realization that electric pipe heating systems play an important role in the normal operation of both nuclear and non-nuclear processes in nuclear power generating stations is now coming of age. This is apparent by the increased amount of space being devoted to electric pipe heating in station technical specifications, system descriptions, and operating criteria. Such electric pipe heating systems are applied on borated water systems and on water treatment systems such as caustic. Since boric acid and caustics in water will crystalize or precipitate out of the solution, depending on their concentrations at temperatures above ambient, and since such crystallization can make the piping system inoperable for normal operation, electric pipe heating systems are required to keep the solutions and piping systems in a state to perform their intended functions. Electric pipe heating systems may also be applied on piping located outdoors at nuclear generating stations for the purpose of preventing the piping systems from freezing. It should be noted that each and all of these piping systems can include valves, pumps, strainers, tanks, and instrumentation components that can be rendered inoperable due to solutions crystalizing or freezing. Therefore, a definite need exists within the nuclear power industry for recommendations that provide a uniform method for the design and installation of electric pipe heating systems that meet the requirements for rendering reliable operation of the piping system. Without such recommendations, station reliability may be jeopardized

  19. Performance Study of Solar Heat Pipe with Different Working Fluids and Fill Ratios

    Science.gov (United States)

    Harikrishnan, S. S.; Kotebavi, Vinod

    2016-09-01

    This paper elaborates on the testing of solar heat pipes using different working fluids, fill ratios and tilt angles. Methanol, Acetone and water are used as working fluids, with fill ratios 25%, 50%, 75% and 100%. Experiments were carried out at 600 and 350 inclinations. Heat pipe condenser section is placed inside a water basin containing 200ml of water. The evaporator section is exposed to sunlight where the working fluid gets heated and it becomes vapour and moves towards the condenser section. In the condenser section the heat is given to the water in the basin and the vapour becomes liquid and comes back to the evaporator section due to gravitational force. Two modes of experiments are carried out: 1) using a parabolic collector and 2) using heat pipe with evacuated tubes. On comparative study, optimum fill ratio is been found to be 25% in every case and acetone exhibited slightly more efficiency than methanol and water. As far as the heat pipe orientation is concerned, 600 inclination of the heat pipe showed better performance than 350

  20. Electrical heating tapes for hot water piping and frost protection; Elektrische Heizbaender fuer Warmwasserleitungen und Frostschutz

    Energy Technology Data Exchange (ETDEWEB)

    Nipkow, J.

    2003-07-01

    This leaflet issued by the Swiss Federal Office of Energy and professional plumbing and installation associations presents information and recommendations on the use of electrical heating tapes in sanitary installations and rainwater piping. The considerable amount of electrical power needed for the operation of these heating tapes is discussed and methods of reducing consumption by the use efficient controllers are described. It is further mentioned that the correct design and planning of sanitary installations can help reduce the necessity for the use of heating tapes. Cost comparisons are made between heat-tape and circulation-based solutions for different heat sources. Tips are provided on installation details. Frost protection for piping in unheated rooms and for rainwater down-pipes is also discussed.

  1. Advanced thermal energy management: A thermal test bed and heat pipe simulation

    Science.gov (United States)

    Barile, Ronald G.

    1986-01-01

    Work initiated on a common-module thermal test simulation was continued, and a second project on heat pipe simulation was begun. The test bed, constructed from surplus Skylab equipment, was modeled and solved for various thermal load and flow conditions. Low thermal load caused the radiator fluid, Coolanol 25, to thicken due to its temperature avoided by using a regenerator-heat-exchanger. Other possible solutions modeled include a radiator heater and shunting heat from the central thermal bus to the radiator. Also, module air temperature can become excessive with high avionics load. A second preoject concerning advanced heat pipe concepts was initiated. A program was written which calculates fluid physical properties, liquid and vapor pressure in the evaporator and condenser, fluid flow rates, and thermal flux. The program is directed to evaluating newer heat pipe wicks and geometries, especially water in an artery surrounded by six vapor channels. Effects of temperature, groove and slot dimensions, and wick properties are reported.

  2. Combined forced and natural convection heat transfer for upward flow in a uniformly heated vertical pipe

    International Nuclear Information System (INIS)

    Tanaka, Hiroaki; Hatano, Shunichi; Maruyama, Shigeo.

    1986-01-01

    For predicting the fully developed upward flow in a uniformly heated vertical pipe by taking account of the buoyancy force, the k-ε models of turbulence for low Reynolds number flows were adopted. The regime map for forced, mixed and natural convections as well as for laminar and turbulent flows was plotted from the numerical calculations. At the same time, an experiment was carried out at Reynolds numbers of 3000 and 5000 with the Grashof number varied over a wide range by using pressurized nitrogen gas as a test fluid. In agreement with the prediction, buoyancy-induced impairment of heat transfer was measured right in the mixed convection region. Further, from hot-wire measurement, complete laminarization was demonstrated in the mixed convection region at a Reynolds number of 3000. (author)

  3. Characteristics on the heat storage and recovery by the underground spiral heat exchange pipe; Chichu maisetsu spiral kan ni yoru chikunetsu shunetsu tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Imai, I. [Kure National College of Technology, Hiroshima (Japan); Taga, M. [Kinki University, Osaka (Japan)

    1996-10-27

    The consistency between the experimental value of a soil temperature and the calculation value of a soil temperature given by a non-steady heat conduction equation was confirmed. The experimental value is obtained by laying a spiral heat exchange pipe in the heat-insulated soil box and circulating hot water forcibly in the pipe. The temperature conductivity in soil significantly influences the heat transfer in soil. The storage performance is improved when the temperature conductivity increases because of the contained moisture. As the difference between the initial soil temperature and circulating water temperature becomes greater, the heat storage and recovery values increase. A thermal core heat transfer is done in the spiral pipe. Therefore, the diameter of the pipe little influences the heat storage performance, and the pitch influences largely. About 50 hours after heat is stored, the storage performance is almost the same as for a straight pipe that uses the spiral diameter as a pipe diameter. To obtain the same heat storage value, the spiral pipe is made of fewer materials than the straight pipe and low in price. The spiral pipe is more advantageous than the straight pipe in the necessary motive power and supply heat of a pump. 1 ref., 11 figs., 1 tab.

  4. Heat transfer capacity of heat pipes: An application in coalfield wildfire in China

    Science.gov (United States)

    Li, Bei; Deng, Jun; Xiao, Yang; Zhai, Xiaowei; Shu, Chi-Min; Gao, Wei

    2018-01-01

    Coalfield wildfires are serious catastrophes associated with mining activities. Generally, the coal wildfire areas have tremendous heat accumulation regions. Eliminating the internal heat is an effective method for coal wildfire control. In this study, high thermal conductivity component of a heat pipe (HP) was used for enhancing the heat dissipation efficiency and impeding heat accumulation. An experimental system was set up to analyze the thermal resistance network of the coal-HP system. A coal-HP heat removal model was also established for studying the heat transfer performance of HP on the coal pile. The HP exhibited outstanding cooling performance in the initial period, resulting in the highest temperature difference between the coal pile and ambient temperature. However, the effect of the HP on the distribution temperature of coal piles decreased with increasing distance. The largest decline in the coal temperature occurred in a 20-mm radius of the HP; the temperature decreased from 84.3 to 50.9 °C, a decline of 39.6%. The amount of energy transfer by the HP after 80 h was 1.0865, 2.1680, and 3.3649 MJ under the initial heat source temperatures of 100, 150, and 200 °C, respectively. The coal was governed below 80 °C with the HP under the experimental conditions. It revealed that the HP had a substantial effect on thermal removal and inhibited spontaneous coal combustion. In addition, this paper puts forward the technological path of HP to control typical coalfield wildfire.

  5. Modeling of the transient behavior of heat pipes with room-temperature working fluids

    Science.gov (United States)

    Brocheny, Pascal O.

    2006-07-01

    The heat pipe is a capillary-driven and two-phase flow device, capable of transporting and converting large amounts of energy with minimal losses. As a means of thermal management, uses of heat pipe technology not only include thermal control of satellites and spacecrafts in aerospace applications, but also the cooling of electronic components for ground applications. Recently, there has been a flourishing interest in exploring the use of heat pipe technology in the automotive field. However, in many thermal control applications, heat pipes using room-temperature working fluids, such as water or ammonia, with operating temperatures between 200 K (-73ºC) and 550 K (277ºC), can hardly operate at steady state conditions. The study of transient heat pipe phenomena becomes a significant area of research interests including not only startup and shutdown phases, but also heat redistribution, changes of thermal loading and heat removal. The transient performance is affected by thermal capacity and conductance of the heat pipe, capillary pumping forces, heating and cooling conditions. In the present study, the transient operations of different conventional room-temperature heat pipes were investigated analytically, including the capillary dryout and rewetting behaviors occurring at the evaporator section during startups. The physical model is based on the displacement of a leading-edge front of a thin liquid layer flowing on finite groove uniformly heated with a constant heat flux. A one-dimensional transient heat conduction model along the evaporator wall is coupled with the movement of the fluid layer during startup. Numerical solutions were obtained by a fully implicit Finite Difference Method, accounting for the movement of the liquid and a known time-variable temperature boundary condition at the liquid front. The velocity and position of the liquid front were found to vary with the applied heat flux, the initial conditions, and the thermophysical properties of the

  6. Accelerated life tests of specimen heat pipe from Communication Technology Satellite (CTS) project

    Science.gov (United States)

    Tower, L. K.; Kaufman, W. B.

    1977-01-01

    A gas-loaded variable conductance heat pipe of stainless steel with methanol working fluid identical to one now on the CTS satellite was life tested in the laboratory at accelerated conditions for 14 200 hours, equivalent to about 70 000 hours at flight conditions. The noncondensible gas inventory increased about 20 percent over the original charge. The observed gas increase is estimated to increase operating temperature by about 2.2 C, insufficient to harm the electronic gear cooled by the heat pipes in the satellite. Tests of maximum heat input against evaporator elevation agree well with the manufacturer's predictions.

  7. Experimental investigation of heat transfer to supercritical pressure carbon dioxide in a horizontal pipe

    International Nuclear Information System (INIS)

    Adebiyi, G.A.; Hall, W.B.

    1976-01-01

    Results obtained in an experimental investigation of heat transfer to supercritical and subcritical pressure CO 2 flowing through a uniformly heated 22.14 mm I.D. horizontal pipe are presented. The experimental work covers a flow inlet Reynolds number range of about 2 x 10 4 to 2 x 10 5 . Marked peripheral temperature variations are obtained which represent the influence of buoyancy. Comparison with buoyancy free data shows that heat transfer at the bottom of the pipe in enhanced and at the top is reduced by buoyancy. Criteria proposed by Jackson and Petukhov indicate that buoyancy effects would be expected under the conditions of all the experiments. (autho)

  8. Using a heat pipe (TPTC for dissipating energy generated by an electronic circuit

    Directory of Open Access Journals (Sweden)

    Rodrigo Correa

    2010-01-01

    Full Text Available This paper presents an experimental investigation aimed at estimating the thermal efficiency of a heat pipe compared to the most common elements for removing heat from a circuit (i.e., an electric fan and a fin - extended surface. The input voltage frequency for a standard power circuit was changed for the experiments, whilst all the other parameters were kept constant. An experimental statistical design was used as an analytical tool. Unexpectedly, the heat pipe showed the lowest thermal efficiency for all the experiments, although it had the advantage of being a passive element having low volume and no mobile parts.

  9. Dynamic performance of a novel solar photovoltaic/loop-heat-pipe heat pump system

    International Nuclear Information System (INIS)

    Zhang, Xingxing; Zhao, Xudong; Shen, Jingchun; Xu, Jihuan; Yu, Xiaotong

    2014-01-01

    Highlights: • A transient model was developed to predict dynamic performance of new PV/LHP system. • The model accuracy was validated by experiment giving less than 9% in error. • The new system had basic and advanced performance coefficients of 5.51 and 8.71. • The new system had a COP 1.5–4 times that for conventional heat pump systems. • The new system had higher exergetic efficiency than PV and solar collector systems. - Abstract: Objective of the paper is to present an investigation into the dynamic performance of a novel solar photovoltaic/loop-heat-pipe (PV/LHP) heat pump system for potential use in space heating or hot water generation. The methods used include theoretical computer simulation, experimental verification, analysis and comparison. The fundamental equations governing the transient processes of solar transmission, heat transfer, fluid flow and photovoltaic (PV) power generation were appropriately integrated to address the energy balances occurring in different parts of the system, e.g., glazing cover, PV cells, fin sheet, loop heat pipe, heat pump cycle and water tank. A dedicated computer model was developed to resolve the above grouping equations and consequently predict the system’s dynamic performance. An experimental rig was constructed and operated under the real weather conditions for over one week in Shanghai to evaluate the system living performance, which was undertaken by measurement of various operational parameters, e.g., solar radiation, photovoltaic power generation, temperatures and heat pump compressor consumption. On the basis of the first- (energetic) and second- (exergetic) thermodynamic laws, an overall evaluation approach was proposed and applied to conduct both quantitative and qualitative analysis of the PV/LHP module’s efficiency, which involved use of the basic thermal performance coefficient (COP th ) and the advanced performance coefficient (COP PV/T ) of such a system. Moreover, a simple comparison

  10. Numerical Analysis of Heat transfer Enhancement in a double pipe heat exchanger with a holed twisted tape

    Directory of Open Access Journals (Sweden)

    Kumar Akarsh

    2018-01-01

    Full Text Available In the present study numerical analysis of enhancement in heat transfer characteristics in a double pipe heat exchanger is studied using a holed twisted tape.The twisted tape with a constant twist ratio is inserted in a double pipe heat exchanger. Holes of diameter 1mm, 3 mm and 5 mm were drilled at regular pitch throughout the length of the tape. Numerical modeling of a double pipe heat exchanger with the holed twisted tape was constructed considering hot fluid flowing in the inner pipe and cold fluid through the annulus.Simulation was done for varied mass flow rates of hot fluid in the turbulent condition keeping the mass flow rate of cold fluid being constant. Thermal properties like Outlet temperatures, Nusselt number, overall heat transfer coefficient, heat transfer rate and pressure drop were determined for all the cases. Results indicated that normaltwisted tape without holes performed better than the bare tube. In the tested range of mass flow rates the average Nusselt number and heat transfer rate were increased by 85% and 34% respectively. Performance of Twisted tape with holes was slightly reduced than the normal twisted tape and it deteriorated further for higher values hole diameter. Pressure drop was found to be higher for the holed twisted tape than the normal tape.

  11. An experimental investigation and optimization of screen mesh heat pipes for low-mid temperature applications

    NARCIS (Netherlands)

    Jafari, Davoud; Shamsi, Hamidereza; Filippeschi, Sauro; Di Marco, Paolo; Franco, Alessandro

    2017-01-01

    The perspectives of utilization of a screen mesh heat pipe (HP) for low to medium operating temperature applications are studied in this study. A two-dimensional mathematical model for heat and mass transfer of HPs is presented to define its performances under steady state operations. The model

  12. Numerical Investigation of Heat Transfer Enhancement in a Rectangular Heated Pipe for Turbulent Nanofluid

    Directory of Open Access Journals (Sweden)

    Hooman Yarmand

    2014-01-01

    Full Text Available Thermal characteristics of turbulent nanofluid flow in a rectangular pipe have been investigated numerically. The continuity, momentum, and energy equations were solved by means of a finite volume method (FVM. The symmetrical rectangular channel is heated at the top and bottom at a constant heat flux while the sides walls are insulated. Four different types of nanoparticles Al2O3, ZnO, CuO, and SiO2 at different volume fractions of nanofluids in the range of 1% to 5% are considered in the present investigation. In this paper, effect of different Reynolds numbers in the range of 5000 < Re < 25000 on heat transfer characteristics of nanofluids flowing through the channel is investigated. The numerical results indicate that SiO2-water has the highest Nusselt number compared to other nanofluids while it has the lowest heat transfer coefficient due to low thermal conductivity. The Nusselt number increases with the increase of the Reynolds number and the volume fraction of nanoparticles. The results of simulation show a good agreement with the existing experimental correlations.

  13. Numerical simulation of turbulent unsteady compressible pipe flow with heat transfer in the entrance region

    Science.gov (United States)

    Ziaei-Rad, Masoud; Nouri-Broujerdi, Ali

    2008-12-01

    In this paper, the compressible gas flow through a pipe subjected to wall heat flux in unsteady condition in the entrance region is investigated numerically. The coupled conservation equations governing turbulent compressible viscous flow in the developing region of a pipe are solved numerically under different thermal boundary conditions. The numerical procedure is a finite-volume-based finite-element method applied to unstructured grids. The convection terms are discretized by the well-defined Roe method, whereas the diffusion terms are discretized by a Galerkin finite-element formulation. The temporal terms are evaluated based on an explicit fourth-order Runge-Kutta scheme. The effect of different thermal conditions on the pressure loss of unsteady flow is investigated. The results show that increase in the inflow temperature or pipe-wall heat flux increases the pressure drop or decreases the mass flow rate in the pipe.

  14. Mini-channel evaporator/heat pipe assembly for a chip cooling vapor compression refrigeration system

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Guilherme B.; Barbosa, Jader R. Jr.; Prata, Alvaro T. [Polo - Research Laboratories for Emerging Technologies in Cooling and Thermophysics, Department of Mechanical Engineering, Campus Universitario, Trindade, Federal University of Santa Catarina, Florianopolis, SC 88040900 (Brazil)

    2010-11-15

    We investigate a novel evaporator design for a small-scale refrigeration system whose function is to assist the existing heat pipe technology currently used in chip cooling of portable computers. A heat transfer model for the evaporator/heat pipe assembly was devised specifically for sizing the evaporator in order to keep the chip surface temperature below a certain value. A prototype was tested with R-600a at saturation temperatures of 45 and 55 C, mass flow rates between 0.5 and 1.5 kg h{sup -1} and heat transfer rates between 30 and 60 W. The experimental results demonstrated that the average refrigerant-side heat transfer coefficient is more sensitive to a change in the refrigerant mass flux than to changes in the saturation temperature and heat transfer rate. The agreement between the calculated heat transfer coefficient and the data was within {+-}10% for the conditions evaluated. (author)

  15. Analytical Investigation of the Heat-Transfer Limits of a Novel Solar Loop-Heat Pipe Employing a Mini-Channel Evaporator

    OpenAIRE

    Thierno M. O. Diallo; Min Yu; Jinzhi Zhou; Xudong Zhao; Jie Ji; David Hardy

    2018-01-01

    This paper presents an analytical investigation of heat-transfer limits of a novel solar loop-heat pipe developed for space heating and domestic hot water use. In the loop-heat pipe, the condensate liquid returns to the evaporator via small specially designed holes, using a mini-channel evaporator. The study considered the commonly known heat-transfer limits of loop-heat pipes, namely, the viscous, sonic, entrainment, boiling and heat-transfer limits due to the two-phase pressure drop in the ...

  16. Heat flow in functionally graded pipes with isothermal boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Dryden, John [University of Western Ontario, Department of Mechanical and Materials Engineering, London, ON (Canada)

    2009-06-15

    The steady state two-dimensional temperature field within a functionally graded pipe having isothermal inner and outer surfaces is calculated. The analysis is based upon the theory of complex variables. An expression, which depends upon the spatial variation of the conductivity, is suggested for the equivalent homogeneous thermal conductivity. (orig.)

  17. Modelling and simulation of heat pipes with TAIThermIR (Conference Presentation)

    Science.gov (United States)

    Winkelmann, Max E.

    2016-10-01

    Regarding thermal camouflage usually one has to reduce the surface temperature of an object. All vehicles and installations having a combustion engine usually produce a lot of heat with results on hot spots on the surface which are highly conspicuous. Using heat pipes to transfer this heat to another place on the surface more efficiently might be a way to reduce those hotspots and the overall conspicuity. In a first approach, a model for the Software TAIThermIR was developed to test which parameters of the heat pipes are relevant and what effects can be achieved. It will be shown, that the thermal resistivity of contact zones are quite relevant and the thermal coupling of the engine (source of heat) defines if the alteration of the thermal signature is large or not. Furthermore the impact of the use of heat pipes in relation to surface material is discussed. The influence of different weather scenarios on the change of signatures due to the use of heat pipes is of minor relevance and depends on the choice of the surface material. Finally application issues for real systems are discussed.

  18. Studies on cycle characteristics and application of split heat pipe adsorption ice maker

    International Nuclear Information System (INIS)

    Chen, C.J.; Wang, R.Z.; Wang, L.W.; Lu, Z.S.

    2007-01-01

    A split heat pipe adsorption ice maker, which uses a solidified compound adsorbent (calcium chloride and activated carbon)-ammonia as working pair, is studied. The application of split heat pipe technology in this system (ice maker for fishing boat powered by waste heat of exhaust gases from diesel engine) solves the corrosion problem caused by using seawater to cool the adsorber directly. Therefore, the adsorbers can be cooled or heated by the working substance of the heat pipe in the adsorption or desorption state, respectively. There are two adsorbers in the adsorption ice maker, and each adsorber contains 2.35 kg compound adsorbent in which the mass of calcium chloride is 1.88 kg. The mass transfer performance and volume cooling density of the chemical adsorbent are greatly improved by the use of the compound adsorbent. Water is chosen as the working substance of the heat pipe due to its high cooling power in comparison with the experiments performed using acetone as working substance. When the cycle time is 70 min, the average SCP of ice making is about 329.8-712.8 W/kg calcium chloride with heat and mass recovery, which is approximately 1.6-3.5 times that of the best results of a conventional chemical adsorption ice maker

  19. Investigation on the performance of a prototype of thermo-electric generation with heat pipe-heat sink

    Directory of Open Access Journals (Sweden)

    Elghool Ali

    2017-01-01

    Full Text Available A significant problem in thermo-electric generators is the thermal design of the heat sink because it affects the performance of thermo-electric modules. As compared to conventional cooling systems, heat pipe heat sink have numerous advantages. Some of these advantages are: high heat-transfer rates; absence of moving parts and lack of auxiliary consumption (passive system. This paper presents the analysis of power generation using the combination of heat pipes and thermo-electric generators. The aim is to improve power output by an appropriate design of the heat sink. The average geometrical parameters of heat sink (fin height, fin space and fin thickness were obtained from data collected from previous studies closely similar to this prototype. The prototype was tested and the temperature, voltage and current data were collected. All data were recorded by using a temperature data recorder, power meter and multimeter. It was found that the highest maximum power output was 1.925 watts at a temperature difference of 85°C. However, the prototype did not achieve the maximum output expected. This was a result of limitation of TEG model (where only one TEG was used and the limitation of the performance of the prototype. The prototype successfully generated enough power to charge a cell phone and laptop when connected to two or three TEGs. Moreover the heat pipe heat sink needs optimization to meet the design output from the manufacturer of the TEG at hot side temperature and cold side temperature

  20. Measurements of gravity and gravity-capillary waves in horizontal gas-liquid pipe flow using PIV in both phases

    NARCIS (Netherlands)

    Birvalski, M.; Tummers, M.J.; Henkes, R.A.W.M.

    2016-01-01

    An experimental study was performed in stratified wavy flow of air and water through a horizontal pipe. The velocity fields in both phases were measured simultaneously using PIV and the interfacial shape was resolved using a profile capturing technique. The objective of the study was to

  1. Numerical study of finned heat pipe-assisted thermal energy storage system with high temperature phase change material

    International Nuclear Information System (INIS)

    Tiari, Saeed; Qiu, Songgang; Mahdavi, Mahboobe

    2015-01-01

    Highlights: • A finned heat pipe-assisted latent heat thermal energy storage system is studied. • The effects of heat pipes spacing and fins geometrical features are investigated. • Smaller heat pipes spacing and longer fins improve the melting rate. • The optimal heat pipe and fin arrangements are determined. - Abstract: 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 and 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 (decreasing the heat pipe spacing) 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. It was also shown that number of the fins does not have a significant effect on the performance of the system

  2. Development and test of two flexible cryogenic heat pipes. [for spaceborne instrument cooling

    Science.gov (United States)

    Wright, J. P.; Brennan, P. J.; Mccreight, C. R.

    1976-01-01

    Results are presented for a comprehensive test program directed toward determining the physical and thermal performance of two flexible cryogenic heat pipes that can provide a highly efficient thermal link between a detector and a space radiator or other cooling system in spacecraft applications. A 100-200 K high-power heat pipe is tested with methane at 100-140 K while a 15-100 K low-temperature pipe is designed for operation with nitrogen and oxygen and is optimized for oxygen in the range 75-90 K. Parametric performance and design tradeoff studies are carried out to determine the optimum geometry and materials for the container and wicking systems. A spiral multiwrap wick in conjunction with braided bellows appears to be a workable solution to the problem of developing highly flexible heat transport devices for cryogenic applications.

  3. Performance evaluation of citric ion-stabilized magnetic fluid heat pipe

    Energy Technology Data Exchange (ETDEWEB)

    Jeyadevan, B. [Graduate School of Environmental Studies, Department of Geoscience and Technology, Tohoku University, Aramaki, Aoba 01, Aoba-ku, Sendai 980-7589 (Japan)]. E-mail: jeya@mail.kankyo.tohoku.ac.jp; Koganezawa, H. [Graduate School of Environmental Studies, Department of Geoscience and Technology, Tohoku University, Aramaki, Aoba 01, Aoba-ku, Sendai 980-7589 (Japan); Nakatsuka, K. [Graduate School of Environmental Studies, Department of Geoscience and Technology, Tohoku University, Aramaki, Aoba 01, Aoba-ku, Sendai 980-7589 (Japan)

    2005-03-15

    The performance of heat pipe (HP) using citric ion-stabilized magnetic fluid (CMF) as working fluid (WF) was evaluated. The heat transferred was influenced by the application of magnetic field and was enhanced by a maximum of 30% compared to the field-free case. Furthermore, under the optimum magnetic field configuration, the heat transferred by CMF HP was 10% higher than that with water as WF.

  4. Plant-mimetic Heat Pipes for Operation with Large Inertial and Gravitational Stresses

    Science.gov (United States)

    2015-08-07

    Engineering, Cornell University Co-P.I.: N. Michelle Holbrook, Organismic and Evolutionary Biology , Harvard University Contract #: FA9550-12-1-0227...and completed a mathematical model of steady state operation of such superheated loop heat pipes (SHLHP). We have also developed a transport theories ...and biophysics of heat transfer and flow control in plant tissues. We have developed a successful theory of coupled heat and mass transfer within

  5. An experimental study on the heat transfer characteristics of a heat pipe heat exchanger with latent heat storage. Part II: Simultaneous charging/discharging modes

    International Nuclear Information System (INIS)

    Liu Zhongliang; Wang Zengyi; Ma Chongfang

    2006-01-01

    In this part of the paper, the performance of the simultaneous charging/discharging operation modes of the heat pipe heat exchanger with latent heat storage is experimentally studied. The experimental results show that the device may operate under either the fluid to fluid heat transfer with charging heat to the phase change material (PCM) or the fluid to fluid heat transfer with discharging heat from the PCM modes according to the initial temperature of the PCM. The melting/solidification curves, the performances of the heat pipes and the device, the influences of the inlet temperature and the mass flow rate of the cold water on the operation performance are investigated by extensive experiments. The experimental results also disclose that under the simultaneous charging/discharging operation mode, although the heat transfer from the hot water directly to the cold water may vary, it always takes up a major part of the total heat recovered by the cold water due to the very small thermal resistance compared with the thermal resistance of the PCM side. The melting/solidification processes taking place in the simultaneous charging/discharging operation are compared with those in the charging only and discharging only processes. By applying a simplified thermal resistance analysis, a criterion for predicting the exact operation modes was derived and used to explain the observed experimental phenomena

  6. A Numerical Study on the Heat Transfer Characteristics of a Solar Thermal Receiver with High-temperature Heat Pipes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Young Hark; Jung, Eui Guk; Boo, Joon Hong [Korea Aerospace Univ., Goyang (Korea, Republic of)

    2007-07-01

    A numerical analysis was conducted to predict the heat transfer characteristics of a solar receiver which is subject to very high heat fluxes and temperatures for solar thermal applications. The concentration ratio of the solar receiver ranges from 200 to 1000 and the concentrated heat is required to be transported to a certain distance for specific applications. The study deals with a solar receiver incorporating high-temperature sodium heat pipe as well as typical one that employs a molten-salt circulation loop. The isothermal characteristics in the receiver section is of major concern. The diameter of the solar thermal receiver was 120 mm and the length was 400 mm. For the molten-salt circulation type receiver, 48 axial channels of the same dimensions were attached to the outer wall of the receiver with even spacing in the circumferential direction. The molten salt fed through the channels by forced convection using a special pump. For the heat pipe receiver, the channels are changed to high-temperature sodium heat pipes. Commercial softwares were employed to deal with the radiative heat transfer inside the receiver cavity and the convection heat transfer along the channels. The numerical results are compared and analyzed from the view point of high-temperature solar receiver.

  7. Design, development and test of a capillary pump loop heat pipe

    Science.gov (United States)

    Kroliczek, E. J.; Ku, J.; Ollendorf, S.

    1984-06-01

    The development of a capillary pump loop (CPL) heat pipe, including computer modeling and breadboard testing, is presented. The computer model is a SINDA-type thermal analyzer, combined with a pressure analyzer, which predicts the transients of the CPL heat pipe during operation. The breadboard is an aluminum/ammonia transport system which contains multiple parallel evaporator and condenser zones within a single loop. Test results have demonstrated the practicality and reliability of such a design, including heat load sharing among evaporators, liquid inventory/temperature control feature, and priming under load. Transport capability for this system is 65 KW-M with individual evaporator pumps managing up to 1.7 KW at a heat flux of 15 W/sq cm. The prediction of the computer model for heat transport capabilities is in good agreement with experimental results.

  8. Application experience of gas-thermal aluminum coatings to protect the pipes for underground construction and repair of heat networks

    Science.gov (United States)

    Kolpakov, A. S.

    2013-11-01

    Questions of sacrificial protection for pipes of underground heat networks with aluminum against the external corrosion are considered. The description of pilot production of pipes with a plasma aluminum coating and the deposition of a sacrificial gas-plasma aluminum coating on weld joints of pipelines and the zone of their thermal influence during assemblage is presented. Examples of repairing the segments of distribution heat networks by the pipes with the tread protection are presented.

  9. Methodology for Life Testing of Refractory Metal/Sodium Heat Pipes

    Science.gov (United States)

    Martin, James J.; Reid, Robert S.

    2006-01-01

    The focus of this work was to establish an approach to generate carefully controlled data that can conclusively establish heat pipe operating life with material-fluid combinations capable of extended operation. To accomplish this goal acceleration is required to compress 10 years of operational life into 3 years of laboratory testing through a combination of increased temperature and mass fluence. Specific test series have been identi3ed, based on American Society for Testing and Materials (ASTM) specifications, to investigate long term corrosion rates. The refractory metal selected for demonstration purposes is a Molybdenum-44.5%Rhenium alloy formed by powder metallurgy. The heat pipe makes use of an annular crescent wick design formed by hot isostatic pressing of Molybdenum-Rhenium wire mesh. The heat pipes are filled using vacuum distillation and purity sampling is considered. Testing of these units is round-the-clock with 6-month destructive and non-destructive inspection intervals to identify the onset and level of corrosion. Non-contact techniques are employed for providing power to the evaporator (radio frequency induction heating at I to 5 kW per unit) and calorimetry at the condenser (static gas gap coupled water cooled calorimeter). The planned operating temperature range would extend from 1123 to 1323 K. Accomplishments prior to project cancellation included successful demonstration of the heat pipe wick fabrication technique, establishment of all engineering designs, baselined operational test requirements and procurement/assembly of supporting test hardware systems.

  10. 2D numerical analysis of energy harvesting in oscillating heat pipe using piezoelectric transducers

    Science.gov (United States)

    Vaidya, Sajiree; Myers, Oliver; Thompson, Scott; Shamsaei, Nima; Monroe, John G.

    2017-04-01

    Energy Harvesting is a powerful process that deals with exploring different possible ways of converting energy dispersed in the environment into more useful form of energy, essentially electrical energy. Piezoelectric materials are known for their ability of transferring mechanical energy into electrical energy or vice versa. Our work takes advantage of piezoelectric material's properties to covert thermal energy into electrical energy in an oscillating heat pipe. Specific interest in an oscillating heat pipe has relevance to energy harvesting for low power generation suitable for remote electronics operation as well as low-power heat reclamation for electronic packaging. The aim of this paper is develop a 2D multi-physics design analysis model that aids in predicting electrical power generation inherent to an oscillating heat pipe. The experimental design shows a piezoelectric patch with fixed configuration, attached inside an oscillating heat pipe and its behavior when subjected to the oscillating fluid pressure was observed. Numerical analysis of the model depicting the similar behavior was done using a multiphysics FEA software. The numerical model consists of a threeway physics interaction that takes into account fluid flow, solid mechanics, and electrical response of the harvester circuit.

  11. U-PHOS Project: Development of a Large Diameter Pulsating Heat Pipe Experiment on board REXUS 22

    International Nuclear Information System (INIS)

    Nannipieri, P; Anichini, M; Barsocchi, L; Becatti, G; Buoni, L; Celi, F; Catarsi, A; Di Giorgio, P; Fattibene, P; Ferrato, E; Guardati, P; Mancini, E; Meoni, G; Nesti, F; Piacquadio, S; Pratelli, E; Quadrelli, L; Viglione, A S; Zanaboni, F; Mameli, M

    2017-01-01

    U-PHOS Project aims at analysing and characterising the behaviour of a large diameter Pulsating Heat Pipe (PHP) on board REXUS 22 sounding rocket. A PHP is a passive thermal control device where the heat is efficiently transported by means of the self-sustained oscillatory fluid motion driven by the phase change phenomena. Since, in milli-gravity conditions, buoyancy forces become less intense, the PHP diameter may be increased still maintaining the slug/plug typical flow pattern. Consequently, the PHP heat power capability may be increased too. U-PHOS aims at proving that a large diameter PHP effectively works in milli-g conditions by characterizing its thermal response during a sounding rocket flight. The actual PHP tube is made of aluminum (3 mm inner diameter, filled with FC-72), heated at the evaporator by a compact electrical resistance, cooled at the condenser by a Phase Change Material (PCM) embedded in a metallic foam. The tube wall temperatures are recorded by means of Fibre Bragg Grating (FBG) sensors; the local fluid pressure is acquired by means of a pressure transducer. The present work intends to report the actual status of the project, focusing in particular on the experiment improvements with respect to the previous campaign. (paper)

  12. Effect of nitrogen-doped graphene nanofluid on the thermal performance of the grooved copper heat pipe

    DEFF Research Database (Denmark)

    Mehrali, Mohammad; Sadeghinezhad, Emad; Azizian, Reza

    2016-01-01

    Thermal performance of a grooved heat pipe using aqueous nitrogen-doped graphene (NDG) nanofluids was analysed. This study in particular focused on the effect of varying NDG nanosheets concentrations, heat pipe inclination angles and input heating powers. The results indicated that the inclination...... angle had a major influence on the heat transfer performance of heat pipes and the inclination angle (θ) of 90° was corresponded to the best thermal performance. The maximum thermal resistance reduction of 58.6% and 99% enhancement in the evaporator heat transfer coefficient of the heat pipe were...... observed for NDG nanofluid with concentration of 0.06wt%, inclination angle of θ=90° and a heating power of 120W in comparison to DI-water under the exact same condition. Additionally, the surface temperature distribution was decreased by employing NDG nanosheets, which can in return increase the thermal...

  13. A numerical study on the heat transfer characteristics of a hydrogen storage material with inserted heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Park, Young Hark; Boo, Joon Hong [Korea Aerospace Univ., Goyang (Korea, Republic of)

    2008-07-01

    A numerical analysis was conducted to predict the effect of inserted heat pipes on the heat transfer characteristics of Metal Hydride(MH), which inherently has extremely low thermal conductivity. In order to increase the effective conductivity of MH material the most efficient insert configuration is to be identified. Less than two hours of transient time is of concern when decreasing or increasing the temperature for absorption and discharge of hydrogen gas. Commercial softwares were employed to predict the transient as well as steady-state temperature distribution of the MH material with inserted heat transfer enhancing tube or heat pipes. The numerical results were compared and analyzed from the view point of temperature uniformity and transient period.

  14. Heat pipes and two-phase loops with capillary pumping; Caloducs et boucles diphasiques a pompage capillaire

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    This workshop on heat pipes and two-phase capillary pumping loops was organized by the French society of thermal engineers. The 11 papers presented during this workshop deal with the study of thermal performances of heat pipes and on their applications in power electronics (cooling of components), and their use in satellites, aircrafts and trains. (J.S.)

  15. Metallurgical investigation of cracking of the isolation valve downstream piping of regenerative heat exchanger at beaver valley unit 1 station

    International Nuclear Information System (INIS)

    Rao, G.V.

    1998-01-01

    A metallurgical investigation was conducted to establish the mechanism and cause of cracking in the regenerative heat exchanger piping at Beaver Valley Unit 1 PWR station in the USA. The investigation, which was centered on an eight inch long pipe section containing the cracking included surface examinations, metallographic and fractographic examinations, and chemistry evaluations. The results of the examinations showed that there were two types of pipe degradation mechanisms that affected the type 304 stainless schedule 40 piping. These consisted of localized corrosive attack on the OD surface due to the presence of chlorides, sulphates and phosphates, and transgranular stress corrosion cracking in the pipe wall due to the presence of chloride contaminants. The overall results of the investigation showed that the introduction of contaminants from external sources other than pipe insulation was the cause of heat exchanger pipe cracking. (author)

  16. Self-rewetting carbon nanofluid as working fluid for space and terrestrial heat pipes

    Science.gov (United States)

    Di Paola, R.; Savino, R.; Mirabile Gattia, D.; Marazzi, R.; Vittori Antisari, M.

    2011-11-01

    Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary heat transfer fluids with peculiar surface tension properties and in particular to that of "self-rewetting fluids", i.e., liquids with a surface tension increasing with temperature and concentration. Since in the course of liquid/vapor-phase change, self-rewetting fluids behavior induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, this fluids have been proposed and investigated as new heat transfer fluids for advanced heat transfer devices, e.g., heat pipes or heat spreaders for terrestrial and space applications (Savino et al. in Space Technol 25(1):59-61, 2009). The present work is dedicated to the study of the thermophysical properties of a new class of heat transfer fluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesized by a homemade apparatus with an AC arc discharge in open air (Mirabile Gattia et al. in Nanotechnology 18:255604, 2007). SWNHs are cone-shaped nanoparticles with diameters between 1 and 5 nm and lengths in the range of 20-100 nm. SWNHs could be found in the form of quite-spherical aggregates with diameters ranging from 20 to 100 nm. The paper also discusses the results of these investigations and laboratory characterization tests of different heat pipes, including reference ordinary heat pipes and innovative pipes filled with self-rewetting fluids and self-rewetting nanofluids. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

  17. Self-rewetting carbon nanofluid as working fluid for space and terrestrial heat pipes

    International Nuclear Information System (INIS)

    Di Paola, R.; Savino, R.; Mirabile Gattia, D.; Marazzi, R.; Vittori Antisari, M.

    2011-01-01

    Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary heat transfer fluids with peculiar surface tension properties and in particular to that of “self-rewetting fluids”, i.e., liquids with a surface tension increasing with temperature and concentration. Since in the course of liquid/vapor-phase change, self-rewetting fluids behavior induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, this fluids have been proposed and investigated as new heat transfer fluids for advanced heat transfer devices, e.g., heat pipes or heat spreaders for terrestrial and space applications (Savino et al. in Space Technol 25(1):59–61, 2009). The present work is dedicated to the study of the thermophysical properties of a new class of heat transfer fluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesized by a homemade apparatus with an AC arc discharge in open air (Mirabile Gattia et al. in Nanotechnology 18:255604, 2007). SWNHs are cone-shaped nanoparticles with diameters between 1 and 5 nm and lengths in the range of 20–100 nm. SWNHs could be found in the form of quite-spherical aggregates with diameters ranging from 20 to 100 nm. The paper also discusses the results of these investigations and laboratory characterization tests of different heat pipes, including reference ordinary heat pipes and innovative pipes filled with self-rewetting fluids and self-rewetting nanofluids. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

  18. Sandwich Core Heat-Pipe Radiator for Power and Propulsion Systems

    Science.gov (United States)

    Gibson, Marc; Sanzi, James; Locci, Ivan

    2013-01-01

    Next-generation heat-pipe radiator technologies are being developed at the NASA Glenn Research Center to provide advancements in heat-rejection systems for space power and propulsion systems. All spacecraft power and propulsion systems require their waste heat to be rejected to space in order to function at their desired design conditions. The thermal efficiency of these heat-rejection systems, balanced with structural requirements, directly affect the total mass of the system. Terrestrially, this technology could be used for thermal control of structural systems. One potential use is radiant heating systems for residential and commercial applications. The thin cross section and efficient heat transportability could easily be applied to flooring and wall structures that could evenly heat large surface areas. Using this heat-pipe technology, the evaporator of the radiators could be heated using any household heat source (electric, gas, etc.), which would vaporize the internal working fluid and carry the heat to the condenser sections (walls and/or floors). The temperature could be easily controlled, providing a comfortable and affordable living environment. Investigating the appropriate materials and working fluids is needed to determine this application's potential success and usage.

  19. A comparative analysis of loop heat pipe based thermal architectures for spacecraft thermal control

    Science.gov (United States)

    Pauken, Mike; Birur, Gaj

    2004-01-01

    Loop Heat Pipes (LHP) have gained acceptance as a viable means of heat transport in many spacecraft in recent years. However, applications using LHP technology tend to only remove waste heat from a single component to an external radiator. Removing heat from multiple components has been done by using multiple LHPs. This paper discusses the development and implementation of a Loop Heat Pipe based thermal architecture for spacecraft. In this architecture, a Loop Heat Pipe with multiple evaporators and condensers is described in which heat load sharing and thermal control of multiple components can be achieved. A key element in using a LHP thermal architecture is defining the need for such an architecture early in the spacecraft design process. This paper describes an example in which a LHP based thermal architecture can be used and how such a system can have advantages in weight, cost and reliability over other kinds of distributed thermal control systems. The example used in this paper focuses on a Mars Rover Thermal Architecture. However, the principles described here are applicable to Earth orbiting spacecraft as well.

  20. A Retrospective Evaluation of Cured-in-Place Pipe (CIPP) Used in Municipal Gravity Sewers

    Science.gov (United States)

    Pipe rehabilitation and trenchless replacement technologies have seen a steadily increasing use and represent an increasing proportion of the annual expenditure on operations and maintenance of the nation’s water and wastewater infrastructure. Despite public investment in use of...

  1. Small Externally-fueled Heat Pipe Thermionic Reactor (SEHPTR) for dual mode applications

    Science.gov (United States)

    Malloy, John; Jacox, Michael; Zubrin, Robert

    1992-07-01

    The Small Externally Fueled Heat-Pipe Thermionic Reactor (SEHPTR) is described in the context of applications as a dual-mode nuclear power source for satellites. The SEHPTR is a thermionic power system based on a reactor with modular fuel elements around cylindrical thermionic heat-pipe modules with diodes for heat rejection. The SEHPTR concept is theorized to be suitable for directly heating hydrogen gas in the core to increase propulsion and reduce orbit-transfer times. The advantages of dual-mode operation of the SEHPTR are listed including enhanced mission safety and performance at relatively low costs. The SEHPTR could provide direct thermal thrust and an integrated stage that symbiotically utilizes electric power, direct thrust, and hydrogen arcjets. The system is argued to be more effective than a nuclear power system designed solely for electrical power production.

  2. A novel approach of manufacturing Nickel Wicks for loop heat pipes ...

    Indian Academy of Sciences (India)

    e-mail: prosenjit.sct.cmeri@gmail.com. MS received 12 October 2011; revised 1 June 2012; accepted 13 September 2012. Abstract. Sintered nickel powder is proposed to be used as porous wicks in loop heat pipes used for space applications such as satellites and space crafts. In this work, the manufacturing procedure for ...

  3. Evaluation of conjugate, radial heat transfer in an internally insulated composite pipe

    NARCIS (Netherlands)

    Reurings, C.; Koussios, S.; Bergsma, O.K.; Vergote, K.

    2015-01-01

    In order to compete with steel, a fibre-reinforced composite exhaust wall with a general-purpose resin system requires an effective but lightweight insulation layer. However a lack of experimental methods for heat transfer from turbulent gas flow to pipe walls lined with a porous insulation layer

  4. A novel approach of manufacturing Nickel Wicks for loop heat pipes ...

    Indian Academy of Sciences (India)

    size is a matter of concern for these bi-modal wicks as the authors reported that the pore size in the sintered ... powder cannot be injected alone because of very high viscosity binder is mixed with powder to decrease the ..... Huang X and Franchi G 2008 Design and fabrication of hybrid bi-modal wick structure for heat pipe.

  5. Characterization of a high performance ultra-thin heat pipe cooling module for mobile hand held electronic devices

    Science.gov (United States)

    Ahamed, Mohammad Shahed; Saito, Yuji; Mashiko, Koichi; Mochizuki, Masataka

    2017-11-01

    In recent years, heat pipes have been widely used in various hand held mobile electronic devices such as smart phones, tablet PCs, digital cameras. With the development of technology these devices have different user friendly features and applications; which require very high clock speeds of the processor. In general, a high clock speed generates a lot of heat, which needs to be spreaded or removed to eliminate the hot spot on the processor surface. However, it is a challenging task to achieve proper cooling of such electronic devices mentioned above because of their confined spaces and concentrated heat sources. Regarding this challenge, we introduced an ultra-thin heat pipe; this heat pipe consists of a special fiber wick structure named as "Center Fiber Wick" which can provide sufficient vapor space on the both sides of the wick structure. We also developed a cooling module that uses this kind of ultra-thin heat pipe to eliminate the hot spot issue. This cooling module consists of an ultra-thin heat pipe and a metal plate. By changing the width, the flattened thickness and the effective length of the ultra-thin heat pipe, several experiments have been conducted to characterize the thermal properties of the developed cooling module. In addition, other experiments were also conducted to determine the effects of changes in the number of heat pipes in a single module. Characterization and comparison of the module have also been conducted both experimentally and theoretically.

  6. Effect of heat treatment on the grooving corrosion resistance of ERW pipes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Kwon; Lee, Jae Young; Lim, Soo Hyun; Park, Ji Hwan; Seo, Bo Min; Kim, Seon Hwa [Soonchunhyang University, Asan (Korea, Republic of)

    2002-06-15

    The v-sharp grooving corrosion of ERW(electrical resistance welding) steel pipes limited their wide application in the industry in spite of their high productivity and efficiency. The grooving corrosion is caused mainly by the different microstructures between the matrix and weld that is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. Even though the diminishing of sulfur content is most effective to decrease the susceptibility of grooving corrosion, it requires costly process. In this study, improvement of grooving corrosion resistance was pursuited by post weld heat treatment in the temperature range between 650 .deg. C and 950 .deg. C. Also, the effect of heat input in the welding was investigated. By employing chromnoamperometry and potentiodynamic experiment, the corrosion rate and grooving corrosion index({alpha}) were obtained. It was found that heat treatment could improve the grooving corrosion resistance. Among them, the heat treated at 900 .deg. C and 950 .deg. C had excellent grooving corrosion resistance. The index of heat treated specimen at 900 .deg. C and 950 .deg. C were 1.0, 1.2, respectively, which are almost immune to the grooving corrosion. Potential difference after the heat treatment, between base and weld metal was decreased considerably. While the as-received one measured 61{approx}71 mV, that of the 900 .deg. C heat treated steel pipe measured only 10mV. The results were explained and discussed

  7. Development and testing of passive autocatalytic recombiners cooled by heat pipes

    International Nuclear Information System (INIS)

    Granzow, Christoph

    2012-01-01

    A severe accident in a nuclear power plant (NPP) can lead to core damage in conjunction with the release of large amounts of hydrogen. As hydrogen mitigation measure, passive autocatalytic recombiners (PARs) are used in today's pressurized water reactors. PARs recombine hydrogen and oxygen contained in the air to steam. The heat from this exothermic reaction causes the catalyst and its surroundings to heat up. If parts of the PAR heat up above the ignition temperature of the gas mixture, a spontaneous deflagration or detonation can occur. The aim of this work is the prevention of such high temperatures by means of passive cooling of the catalyst with heat pipes. Heat pipes are completely passive heat exchanger with a very high effective thermal conductivity. For a deeper understanding of the reaction kinetics at lower temperatures, single catalytic coated heat pipes are studied in a flow reactor. The development of a modular small-scale PAR model is then based on a test series with cooled catalyst sheets. Finally, the PAR model is tested inside a pressure vessel under boundary conditions similar to a real NPP. The experiments show, that the temperatures of the cooled catalytic sheets stay significantly below the temperature of the uncooled sheets and below the ignition temperature of the gas mixture under any set boundary conditions, although no significant reduction of the conversion efficiency can be observed. As a last point, a mathematical model of the reaction kinetics of the recombination process as well as a model of the fluid dynamic and thermohydraulic processes in a heat pipe are developed with the data obtained from the experiments.

  8. Influence of wall conduction on mixed convection heat transfer in externally finned pipes

    Energy Technology Data Exchange (ETDEWEB)

    Moukalled, F.; Darwish, M. [American Univ. of Beirut (Lebanon). Mechanical Engineering Dept.; Acharya, S. [Louisiana State Univ., Baton Rouge, LA (United States). Mechanical Engineering Dept.

    1995-08-01

    The influence of wall heat conduction on laminar mixed convection in externally finned vertical pipes are investigated numerically. Buoyancy in both aiding and opposed modes is considered. Results are presented in terms of the streamwise variation of the fluid bulk temperature and tube-side. Nusselt number, axially averaged and periodically fully developed Nusselt number values, and axial velocity and temperature profiles. For opposed flows, buoyancy forces decrease the overall heat transferred to the fluid, while for buoyancy-aided flows, buoyancy causes an enhancement in the overall heat transferred to the fluid. Including of longitudinal wall conduction increases the heat transfer to the fluid and enhances the effects of buoyancy.

  9. Design and Operation of a Cryogenic Nitrogen Pulsating Heat Pipe

    International Nuclear Information System (INIS)

    Fonseca, Luis Diego; Miller, Franklin; Pfotenhauer, John

    2015-01-01

    We report the design, experimental setup and successful test results using an innovative passive cooling system called a “Pulsating Heat Pipe” (PHP) operating at temperatures ranging from 77 K to 80 K and using nitrogen as the working fluid. PHPs, which transfer heat by two phase flow mechanisms through a closed loop tubing have the advantage that no electrical pumps are needed to drive the fluid flow. In addition, PHPs have an advantage over copper straps and thermal conductors since they are lighter in weight, exhibit lower temperature gradients and have higher heat transfer rates. PHPs consist of an evaporator section, thermally anchored to a solid, where heat is received at the saturation temperature where the liquid portion of the two-phase flow evaporates, and a condenser where heat is rejected at the saturation temperature where the vapor is condensed. The condenser section in our experiment has been thermally interfaced to a CT cryocooler from SunPower that has a cooling capacity of 10 W at 77 K. Alternating regions of liquid slugs and small vapor plugs fill the capillary tubing, with the vapor regions contracting in the condenser section and expanding in the evaporator section due to an electric heater that will generate heat loads up to 10 W. This volumetric expansion and contraction provides the oscillatory flow of the fluid throughout the capillary tubing thereby transferring heat from one end to the other. The thermal performance and temperature characteristics of the PHP will be correlated as a function of average condenser temperature, PHP fill liquid ratio, and evaporator heat load. The experimental data show that the heat transfer between the evaporator and condenser sections can produce an effective thermal conductivity up to 35000 W/m-K at a 3.5 W heat load. (paper)

  10. Reducing time for construction of district heating pipe systems; Foerkorta Byggtider foer Fjaerrvaermebyggnation

    Energy Technology Data Exchange (ETDEWEB)

    Gille, Hans [AaF Energi och Miljoe AB, Stockholm (Sweden)

    2004-07-01

    To enable shorter time of disturbance during construction of pipes for district heating there are several things that can be done. You have foremost to concentrate on the works taking place in and around the trenches for the pipes, from the first grip with the excavator until the refilling is done. There are also possibilities to reduce time for the welding works by looking over methods used for welding and, above all, when you change from welding with gas to welding with electricity. Welding with gas can be applied to larger pipe dimensions than what is common today. It takes half the time to weld with gas compared to weld with electricity, meaning that cost for welding works can be reduced. The right planning, right organisation on the site and right management of the works are the keys to success. Many of the district heating projects taking place are characterized by long open trenches and the installation of the pipes take place in as long stages as possible for pressure testing. If you can find a possible way to use less covering of the pipes and make the trenches as shallow as possible it will give possibilities to reduce time for interruption and also reduce time for construction works. To be able to reduce the length of and also the time for open trenches there is a possibility to use the same method as when you construct pipes for water and sewage systems. Work and organisation of the site must be planned on the basis of this. The question is it reasonable with such long time of disturbance for a few hundreds meter piping? There are several possibilities and measures which together make it possible to reduce time for open trenches considerably.

  11. Investigation of Counter-Flow in a Heat Pipe-Thermoelectric Generator (HPTEG)

    Science.gov (United States)

    Remeli, Muhammad Fairuz; Singh, Baljit; Affandi, Nor Dalila Nor; Ding, Lai Chet; Date, Abhijit; Akbarzadeh, Aliakbar

    2017-05-01

    This study explores a method of generating electricity while recovering waste heat through the integration of heat pipes and thermoelectric generators (i.e. HPTEG system). The simultaneous waste heat recovery and power generation processes are achieved without the use of any moving parts. The HPTEG system consists of bismuth telluride thermoelectric generators (TEG), which are sandwiched between two finned pipes to achieve a temperature gradient across the TEG for electricity generation. A counter-flow heat exchanger was built using two separate air ducts. The air ducts were thermally coupled using the HPTEG modules. The evaporator section of the heat pipe absorbed the waste heat in a hot air duct. The heat was then transferred across the TEG surfaces. The condenser section of the HPTEG collected the excess heat from the TEG cold side before releasing it to the cold air duct. A 2-kW electrical heater was installed in the hot air duct to simulate the exhaust gas. An air blower was installed at the inlet of each duct to direct the flow of air into the ducts. A theoretical model was developed for predicting the performance of the HPTEG system using the effectiveness-number of transfer units method. The developed model was able to predict the thermal and electrical output of the HPTEG, along with the rate of heat transfer. The results showed that by increasing the cold air velocity, the effectiveness of the heat exchanger was able to be increased from approximately 52% to 58%. As a consequence of the improved heat transfer, maximum power output of 4.3 W was obtained.

  12. In-Flight Performance of the TES Loop Heat Pipe Rejection System: Seven Years in Space

    Science.gov (United States)

    Rodriguez, Jose I.; Na-Nakornpanom, Arthur

    2012-01-01

    The Tropospheric Emission Spectrometer (TES) instrument heat rejection system has been operating in space for nearly 8 years since launched on NASA's EOS Aura Spacecraft. The instrument is an infrared imaging fourier transform spectrometer with spectral coverage of 3.2 to 15.4 microns. The loop heat pipe (LHP) based heat rejection system manages all of the instrument components waste heat including the two mechanical cryocoolers and their drive electronics. Five propylene LHPs collect and transport the instrument waste heat to the near room temperature nadir viewing radiators. During the early months of the mission, ice contamination of the cryogenic surfaces including the focal planes led to increased cryocooler loads and the need for periodic decontamination cycles. Focal plane decontamination cycles require power cycling both cryocoolers which also requires the two cryocooler LHPs to turn off and on during each cycle. To date, the cryocooler LHPs have undergone 24 start-ups in orbit successfully. This paper reports on the TES cryocooler loop heat pipe based heat rejection system performance. After a brief overview of the instrument thermal design, the paper presents detailed data on the highly successful space operation of the loop heat pipes since instrument turn-on in 2004. The data shows that the steady-state and transient operation of the LHPs has not changed since 2004 and shows consistent and predictable performance. The LHP based heat rejection system has provided a nearly constant heat rejection heat sink for all of its equipment which has led to exceptional overall instrument performance with world class science.

  13. Study of a Two-Pipe Chilled Beam System for both Cooling and Heating of Office Buildings

    DEFF Research Database (Denmark)

    Gordnorouzi, Rouzbeh; Hultmark, Göran; Afshari, Alireza

    Active chilled beam systems are used to provide heating and cooling in order to achieve comfortable thermal indoor climate. For heating and cooling applications, an active chilled beam has two water circuits comprising four pipes that supply warm and cold water respectively to the beam coil...... according to the space demand. Lindab Comfort A/S has introduced an active chilled beam system which has just one water circuit (two pipes) that is used for both heating and cooling. The concept is based on high temperature cooling and low temperature heating. In this study the energy saving potential...... of the new two-pipe active chilled beam system is investigated....

  14. Visualization and comparative investigations of pulsating ferro-fluid heat pipe

    International Nuclear Information System (INIS)

    Gandomkar, A.; Saidi, M.H.; Shafii, M.B.; Vandadi, M.; Kalan, K.

    2017-01-01

    Highlights: • Nanofluid was unstable and also agglomerated and deposited in the copper pipe; whereas, it was stable in the Pyrex pipe. • For the Pyrex heat pipe, applying the magnetic field caused weaker performance. • For Pyrex PHP, increasing the concentration improved the performance. • For the copper PHP, applying the magnetic field had the best performance. • For copper PHP, concentration of the nanofluid in each case of the magnet and input power has an optimum value. - Abstract: Pulsating heat pipes (PHPs) are among the best solutions for the electronics cooling due to their low cost, effectiveness and being passive. Experiments to study the effective factors on heat transfer performance have been designed and as a result, improvement of ferrofluid PHP performance has been achieved. Two different heat pipes made of copper and glass were prepared to investigate the behavior of magnetic nanofluids. In order to find the best condition for heat transfer performance, different concentrations of nanofluid with a filling ratio of 50% were tested in 3 different cases of magnetic field. The results indicated that the ferrofluid is more stable in the glass PHP. It also shows that the presence of magnetic field in the copper PHP has the best outcome while in the glass PHP, the absence of magnetic field results better. It was detected that using a more concentrated ferrofluid causes a better performance in the copper PHP only when the magnetic field is applied, while in the glass PHP, increasing the concentration of ferrofluid improves the performance of the PHP in all conditions of applying the magnetic field.

  15. Variable Conductance Heat Pipe Cooling of Stirling Convertor and General Purpose Heat Source

    Science.gov (United States)

    Tarau, Calin; Schwendeman, Carl; Anderson, William G.; Cornell, Peggy A.; Schifer, Nicholas A.

    2013-01-01

    In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal Variable Conductance Heat Pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor. In a previous NASA SBIR Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for Stirling RPS. The operation of these VCHPs was demonstrated using Stirling heater head simulators and GPHS simulators. In the most recent effort, a sodium VCHP with a stainless steel envelope was designed, fabricated and tested at NASA Glenn Research Center (GRC) with a Stirling convertor for two concepts; one for the Advanced Stirling Radioisotope Generator (ASRG) back up cooling system and one for the Long-lived Venus Lander thermal management system. The VCHP is designed to activate and remove heat from the stopped convertor at a 19 degC temperature increase from the nominal vapor temperature. The 19 degC temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the Multi-Layer Insulation (MLI). In addition, the same backup cooling system can be applied to the Stirling convertor used for the refrigeration system of the Long-lived Venus Lander. The VCHP will allow the refrigeration system to: 1) rest during transit at a lower temperature than nominal; 2) pre-cool the modules to an even lower temperature before the entry in Venus atmosphere; 3) work at nominal temperature on Venus surface; 4) briefly stop multiple times on the Venus surface to allow scientific measurements. This paper presents the experimental

  16. Thermal Characteristics of an Oscillating Heat Pipe Cooling System for Electric Vehicle Li-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Ri-Guang Chi

    2018-03-01

    Full Text Available The heat generation of lithium ion batteries in electric vehicles (EVs leads to a degradation of energy capacity and lifetime. To solve this problem, a new cooling concept using an oscillating heat pipe (OHP is proposed. In the present study, an OHP has been adopted for Li-ion battery cooling. Due to the limited space in EVs, the cooling channel is installed on the bottom of the battery module. In the bottom cooling method with an OHP, generated heat can be dissipated easily and conveniently. However, most studies on heat pipes have used bottom heating and top or side cooling methods, so we investigate the various effects of parameters with a top heating/bottom cooling mode with the OHP, i.e., the inclination angle of the system, amount of working fluid charged, the heating amount, and the cold plate temperature with ethanol as a working fluid. The experimental results show that the thermal resistance (0.6 °C/W and uneven pulsating features influence the heat transfer performance. A heater used as a simulated battery was sustained under 60 °C under 10 W and 14 W heating conditions. This indicates that the proposed cooling system with the bottom cooling is feasible for use as an EV’s battery cooling system.

  17. Thermal Analysis of the Divertor Primary Heat Transfer System Piping During the Gas Baking Process

    Energy Technology Data Exchange (ETDEWEB)

    Yoder Jr, Graydon L [ORNL; Harvey, Karen [ORNL; Ferrada, Juan J [ORNL

    2011-02-01

    A preliminary analysis has been performed examining the temperature distribution in the Divertor Primary Heat Transfer System (PHTS) piping and the divertor itself during the gas baking process. During gas baking, it is required that the divertor reach a temperature of 350 C. Thermal losses in the piping and from the divertor itself require that the gas supply temperature be maintained above that temperature in order to ensure that all of the divertor components reach the required temperature. The analysis described in this report was conducted in order to estimate the required supply temperature from the gas heater.

  18. Thermal performance analysis of a flat heat pipe working with carbon nanotube-water nanofluid for cooling of a high heat flux heater

    Science.gov (United States)

    Arya, A.; Sarafraz, M. M.; Shahmiri, S.; Madani, S. A. H.; Nikkhah, V.; Nakhjavani, S. M.

    2018-04-01

    Experimental investigation on the thermal performance of a flat heat pipe working with carbon nanotube nanofluid is conducted. It is used for cooling a heater working at high heat flux conditions up to 190 kW/m2. The heat pipe is fabricated from aluminium and is equipped with rectangular fin for efficient cooling of condenser section. Inside the heat pipe, a screen mesh was inserted as a wick structure to facilitate the capillary action of working fluid. Influence of different operating parameters such as heat flux, mass concentration of carbon nanotubes and filling ratio of working fluid on thermal performance of heat pipe and its thermal resistance are investigated. Results showed that with an increase in heat flux, the heat transfer coefficient in evaporator section of the heat pipe increases. For filling ratio, however, there is an optimum value, which was 0.8 for the test heat pipe. In addition, CNT/water enhanced the heat transfer coefficient up to 40% over the deionized water. Carbon nanotubes intensified the thermal performance of wick structure by creating a fouling layer on screen mesh structure, which changes the contact angle of liquid with the surface, intensifying the capillary forces.

  19. Thermal performance analysis of a flat heat pipe working with carbon nanotube-water nanofluid for cooling of a high heat flux heater

    Science.gov (United States)

    Arya, A.; Sarafraz, M. M.; Shahmiri, S.; Madani, S. A. H.; Nikkhah, V.; Nakhjavani, S. M.

    2017-10-01

    Experimental investigation on the thermal performance of a flat heat pipe working with carbon nanotube nanofluid is conducted. It is used for cooling a heater working at high heat flux conditions up to 190 kW/m2. The heat pipe is fabricated from aluminium and is equipped with rectangular fin for efficient cooling of condenser section. Inside the heat pipe, a screen mesh was inserted as a wick structure to facilitate the capillary action of working fluid. Influence of different operating parameters such as heat flux, mass concentration of carbon nanotubes and filling ratio of working fluid on thermal performance of heat pipe and its thermal resistance are investigated. Results showed that with an increase in heat flux, the heat transfer coefficient in evaporator section of the heat pipe increases. For filling ratio, however, there is an optimum value, which was 0.8 for the test heat pipe. In addition, CNT/water enhanced the heat transfer coefficient up to 40% over the deionized water. Carbon nanotubes intensified the thermal performance of wick structure by creating a fouling layer on screen mesh structure, which changes the contact angle of liquid with the surface, intensifying the capillary forces.

  20. 5 kWe scale-down of the SPAR/SP-100 Heat Pipe Reactor

    International Nuclear Information System (INIS)

    Adrian, J.M.; Benke, S.M.

    1987-01-01

    The SPAR/SP-100 Heat Pipe Reactor was designed to operate at 100 kWe. This report presents work done on a 5 kWe scaled-down of the SPAR/SP-100 design. This scale-down was done in order to compare the performance of a small Heat Pipe Reactor to Radioisotope Thermoelectric Generators (RTGs). The work on this design is broken into the following categories: reactor core modeling, control drum modeling, heat rejection modeling, and shadow shield modeling. The reactor core modeling will be completed using the already available computer programs FEMP2D and ORIGEN. FEMP2D will be used to complete the neutronics survey through the core and control drums and it will also be used to ensure the core will be sub-critical in case of a water abort

  1. Thermal performance of a PCB embedded pulsating heat pipe for power electronics applications

    International Nuclear Information System (INIS)

    Kearney, Daniel J.; Suleman, Omar; Griffin, Justin; Mavrakis, Georgios

    2016-01-01

    Highlights: • Planar, compact PCB embedded pulsating heat pipe for heat spreading applications. • Embedded heat pipe operates at sub-ambient pressure with environmentally. • Compatible fluids. • Range of optimum operating conditions, orientations and fill ratios identified. - Abstract: Low voltage power electronics applications (<1.2 kV) are pushing the design envelope towards increased functionality, better reliability, low profile and reduced cost. One packaging method to enable these constraints is the integration of active power electronic devices into the printed circuit board improving electrical and thermal performance. This development requires a reliable passive thermal management solution to mitigate hot spots due to the increased heat flux density. To this end, a 44 channel open looped pulsating heat pipe (OL-PHP) is experimentally investigated for two independent dielectric working fluids – Novec TM 649 and Novec TM 774 – due to their lower pressure operation and low global warming potential compared to traditional two-phase coolants. The OL-PHP is investigated in vertical (90°) orientation with fill ratios ranging from 0.30 to 0.70. The results highlight the steady state operating conditions for each working fluid with instantaneous plots of pressure, temperature, and thermal resistance; the minimum potential bulk thermal resistance for each fill ratio and the effective thermal conductivity achievable for the OL-PHP.

  2. Numerical study of heat and mass transfer in inertial suspensions in pipes.

    Science.gov (United States)

    Niazi Ardekani, Mehdi; Brandt, Luca

    2017-11-01

    Controlling heat and mass transfer in particulate suspensions has many important applications such as packed and fluidized bed reactors and industrial dryers. In this work, we study the heat and mass transfer within a suspension of spherical particles in a laminar pipe flow, using the immersed boundary method (IBM) to account for the solid fluid interactions and a volume of fluid (VoF) method to resolve temperature equation both inside and outside of the particles. Tracers that follow the fluid streamlines are considered to investigate mass transfer within the suspension. Different particle volume fractions 5, 15, 30 and 40% are simulated for different pipe to particle diameter ratios: 5, 10 and 15. The preliminary results quantify the heat and mass transfer enhancement with respect to a single-phase laminar pipe flow. We show in particular that the heat transfer from the wall saturates for volume fractions more than 30%, however at high particle Reynolds numbers (small diameter ratios) the heat transfer continues to increase. Regarding the dispersion of tracer particles we show that the diffusivity of tracers increases with volume fraction in radial and stream-wise directions however it goes through a peak at 15% in the azimuthal direction. European Research Council, Grant No. ERC-2013-CoG- 616186, TRITOS; SNIC (the Swedish National Infrastructure for Computing).

  3. Experimental study of heat transfer enhancement due to the surface vibrations in a flexible double pipe heat exchanger

    Science.gov (United States)

    Hosseinian, A.; Meghdadi Isfahani, A. H.

    2017-11-01

    In this study, the heat transfer enhancement due to the surface vibration for a double pipe heat exchanger, made of PVDF, is investigated. In order to create forced vibrations (3-9 m/s2, 100 Hz) on the outer surface of the heat exchanger electro-dynamic vibrators are used. Experiments were performed at inner Reynolds numbers ranging from 2533 to 9960. The effects of volume flow rate and temperature on heat transfer performance are evaluated. Results demonstrated that heat transfer coefficient increases by increasing vibration level and mass flow rate. The most increase in heat transfer coefficient is 97% which is obtained for the highest vibration level (9 m/s2) in the experiment range.

  4. Experimental study of heat transfer enhancement due to the surface vibrations in a flexible double pipe heat exchanger

    Science.gov (United States)

    Hosseinian, A.; Meghdadi Isfahani, A. H.

    2018-04-01

    In this study, the heat transfer enhancement due to the surface vibration for a double pipe heat exchanger, made of PVDF, is investigated. In order to create forced vibrations (3-9 m/s2, 100 Hz) on the outer surface of the heat exchanger electro-dynamic vibrators are used. Experiments were performed at inner Reynolds numbers ranging from 2533 to 9960. The effects of volume flow rate and temperature on heat transfer performance are evaluated. Results demonstrated that heat transfer coefficient increases by increasing vibration level and mass flow rate. The most increase in heat transfer coefficient is 97% which is obtained for the highest vibration level (9 m/s2) in the experiment range.

  5. Performance Comparison of Single-Phase Forced-Oscillating-Flow Heat-Pipes

    Science.gov (United States)

    Nishio, Shigefumi; Tanaka, Hisashi

    In the present work, for both a COSMOS-HP (Counter-Stream-Mode Oscillating-Flow Heat Pipe) and a dream pipe, the optimum conditions yielding the highest effective thermal conductivity and/or the highest operating coefficient are analyzed for oscillating flows of a given amplitude S. The parameters used in the optimization are the thermophysical properties of the operating liquid, the channel size and the frequency of oscillating flow. Based on the analytical results of the optimum conditions, both the optimum liquid and the optimum oscillating flow conditions are discussed. The highest effective thermal conductivity of COSMOS-HP is compared with that of a dream pipe, and it is found that the former is much higher than the latter.

  6. Transport phenomena in capillary-porous structures and heat pipes

    CERN Document Server

    Smirnov, Henry

    2009-01-01

    With emphasis on the processes involved, this text explores the experimental efforts in two-phase thermal control technology research and development. This work evaluates and compares different theoretical approaches, experimental results, and models, such as semi-empirical models for critical boiling heat fluxes.

  7. Direct high-temperature ohmic heating of metals as liquid pipes.

    Science.gov (United States)

    Grosse, A V; Cahill, J A; Liddell, W L; Murphy, W J; Stokes, C S

    1968-05-03

    When a sufficiently high electric current is passed through a liquid metal, the electromagnetic pressure pinches off the liquid metal and interrupts the flow of current. For the first time the pinch effect has been overcome by use of centrifugal acceleration. By rotation of a pipe of liquid metal, tin or bismuth or their alloys, at sufficiently high speed, it can be heated electrically without intermission of the electric current. One may now heat liquid metallic substances, by resistive (ohmic) heating, to 5000 degrees K and perhaps higher temperatures.

  8. An experimental study on heat transfer characteristics of heat pipe heat exchanger with latent heat storage. Part I: Charging only and discharging only modes

    International Nuclear Information System (INIS)

    Liu Zhongliang; Wang Zengyi; Ma Chongfang

    2006-01-01

    A new thermal storage system, a heat pipe heat exchanger with latent heat storage, is reported. The new system may operate in three basic different operation modes, the charging only, the discharging only and the simultaneous charging/discharging modes, which makes the system suitable for various time and/or weather dependent energy systems. In this part of the paper, the basic structure, the working principle and the design concept are briefly introduced. Extensive experimental results are presented of the charging only and discharging only operations, and the effects of the inlet temperature and the flow rate of the cold/hot water were also investigated. The results show that the heat exchanger performs the designed functions very well and can both store and release the thermal energy efficiently

  9. CORTES, Steady-State and Transient Heat Flow and Stress Analysis in Pipe Joints

    International Nuclear Information System (INIS)

    Gantayat, A. N.; Powell, G. H.; Textor, R. E.; Bass, B. R.; Bryson, J. W.; Moore, S. E.

    1996-01-01

    1 - Description of problem or function: CORTES is a package consisting of five finite element programs developed for the stress analysis of ANSI Bl6.9 tee joints. The five programs are: SA, the stress analysis program which analyzes pipe joints for the effects of internal pressure and arbitrary combinations of bending moment, torsional moment, axial force, and sheer force on the ends of the branch and run pipes. A limited temperature stress analysis capability is provided. EP, the elasto-plastic stress analysis program which analyzes pipe joints for the effects of internal pressure and arbitrary combinations of forces (including moments) and displacements including rotations imposed on the ends of the run and branch pipes. THFA, the transient heat flow analysis program which determines the time history of temperature variations in the pipe joints. The joint is assumed initially to be at a uniform temperature. Temperature changes are then specified at the inner surface, and a heat flow analysis is performed assuming a perfectly insulated outer surface. SHFA, the steady-state heat flow analysis program which determines the steady-state temperature distribution in pipe joints. Temperatures are specified on given cross-sections of the branch and run portions of the tee joint, and the temperature distribution throughout the remainder of the joint is calculated assuming the inner and outer surfaces are perfectly insulated. TSA, accepts as input, the output data from THFA or SHFA and performs the thermal stress analysis on the pipe joints. 2 - Method of solution: The joint is idealized as a system of 8-node hexahedral finite elements. A modified Zienkiewicz-Irons iso-parametric element which has superior bending properties compared with the unmodified iso-parametric element is used. The transient heat flow (THFA) problem is solved by a step-by-step integration procedure assuming linear variation of temperature with time within a step. 3 - Restrictions on the complexity of

  10. Annual analysis of heat pipe PV/T systems for domestic hot water and electricity production

    International Nuclear Information System (INIS)

    Pei Gang; Fu Huide; Ji Jie; Chow Tintai; Zhang Tao

    2012-01-01

    Highlights: ► A novel heat pipe photovoltaic/thermal system with freeze protection was proposed. ► A detailed annual simulation model for the HP-PV/T system was presented. ► Annual performance of HP-PV/T was predicted and analyzed under different condition. - Abstract: Heat-pipe photovoltaic/thermal (HP-PV/T) systems can simultaneously provide electrical and thermal energy. Compared with traditional water-type photovoltaic/thermal systems, HP-PV/T systems can be used in cold regions without being frozen with the aid of a carefully selected heat-pipe working fluid. The current research presents a detailed simulation model of the HP-PV/T system. Using this model, the annual electrical and thermal behavior of the HP-PV/T system used in three typical climate areas of China, namely, Hong Kong, Lhasa, and Beijing, are predicted and analyzed. Two HP-PV/T systems, with and without auxiliary heating equipment, are studied annually under four different kinds of hot-water load per unit collecting area (64.5, 77.4, 90.3, and 103.2 kg/m 2 ).

  11. Parametrical analysis of the design and performance of a solar heat pipe thermoelectric generator unit

    International Nuclear Information System (INIS)

    He, Wei; Su, Yuehong; Riffat, S.B.; Hou, JinXin; Ji, Jie

    2011-01-01

    Highlights: → An analytical model of SHP-TEG unit for the condition of constant solar irradiation. → Simulation of maximum power output and conversion efficiency of SHP-TEG. → Design optimization of SHP-TEG. -- Abstract: This paper describes a solar heat pipe thermoelectric generator (SHP-TEG) unit comprising an evacuated double-skin glass tube, a finned heat pipe and a TEG module. The system takes the advantage of heat pipe to convert the absorbed solar irradiation to a high heat flux to meet the TEG operating requirement. An analytical model of the SHP-TEG unit is presented for the condition of constant solar irradiation, which may lead to different performance characteristics and optimal design parameters compared with the condition of constant temperature difference usually dealt with in other studies. The analytical model presents the complex influence of basic parameters such as solar irradiation, cooling water temperature, thermoelement length and cross-section area and number of thermoelements, etc. on the maximum power output and conversion efficiency of the SHP-TEG. Simulation based on the analytical model has been carried out to study the performance and design optimization of the SHP-TEG.

  12. Thermal distillation system utilizing biomass energy burned in stove by means of heat pipe

    Directory of Open Access Journals (Sweden)

    Hiroshi Tanaka

    2016-09-01

    Full Text Available A thermal distillation system utilizing a part of the thermal energy of biomass burned in a stove during cooking is proposed. The thermal energy is transported from the stove to the distiller by means of a heat pipe. The distiller is a vertical multiple-effect diffusion distiller, in which a number of parallel partitions in contact with saline-soaked wicks are set vertically with narrow gaps of air. A pilot experimental apparatus was constructed and tested with a single-effect and multiple-effect distillers to investigate primarily whether a heat pipe can transport thermal energy adequately from the stove to the distiller. It was found that the temperatures of the heated plate and the first partition of the distiller reached to about 100 °C and 90 °C, respectively, at steady state, showing that the heat pipe works sufficiently. The distilled water obtained was about 0.75 and 1.35 kg during the first 2 h of burning from a single-effect and multiple-effect distillers, respectively.

  13. Optimized Design of Thermoelectric Energy Harvesting Systems for Waste Heat Recovery from Exhaust Pipes

    Directory of Open Access Journals (Sweden)

    Marco Nesarajah

    2017-06-01

    Full Text Available With the increasing interest in energy efficiency and resource protection, waste heat recovery processes have gained importance. Thereby, one possibility is the conversion of the heat energy into electrical energy by thermoelectric generators. Here, a thermoelectric energy harvesting system is developed to convert the waste heat from exhaust pipes, which are very often used to transport the heat, e.g., in automobiles, in industrial facilities or in heating systems. That is why a mockup of a heating is built-up, and the developed energy harvesting system is attached. To build-up this system, a model-based development process is used. The setup of the developed energy harvesting system is very flexible to test different variants and an optimized system can be found in order to increase the energy yield for concrete application examples. A corresponding simulation model is also presented, based on previously developed libraries in Modelica®/Dymola®. In the end, it can be shown—with measurement and simulation results—that a thermoelectric energy harvesting system on the exhaust pipe of a heating system delivers extra energy and thus delivers a contribution for a more efficient usage of the inserted primary energy carrier.

  14. L- and U-shaped heat pipes thermal modules with twin fans for cooling of electronic system under variable heat source areas

    Science.gov (United States)

    Wang, Jung-Chang

    2014-04-01

    This study utilizes a versatile superposition method with thermal resistance network analysis to design and experiment on a thermal module with embedded six L-shaped or two U-shaped heat pipes and plate fins under different fan speeds and heat source areas. This type of heat pipes-heat sink module successively transfer heat capacity from a heat source to the heat pipes, the heat sink and their surroundings, and are suitable for cooling electronic systems via forced convection mechanism. The thermal resistances contain all major components from the thermal interface through the heat pipes and fins. Thermal performance testing shows that the lowest thermal resistances of the representative L- and U-shaped heat pipes-heat sink thermal modules are respectively 0.25 and 0.17 °C/W under twin fans of 3,000 RPM and 30 × 30 mm2 heat sources. The result of this work is a useful thermal management method to facilitate rapid analysis.

  15. Studies on the Startup Transients and Performance of a Gas Loaded Sodium Heat Pipe

    Science.gov (United States)

    1989-06-01

    calculated using Eq. (88). 0cal " P p Alcoolant (88) Coolant flow rate, V - 2.3 liters/minute; specific gravity, p 1.0; and specific heat, C = 4.2 J...Steady State Calorimetric Test Data 151 mmmma 0mmr mmmmm mm ----- Eq. (88), QCal = 161.07 ( Alcoolant ) watts. 1here was good agreement between Qi (power

  16. Concept Design of a Gravity Core Cooling Tank as a Passive Residual Heat Removal System for a Research Reactor

    International Nuclear Information System (INIS)

    Lee, Kwonyeong; Chi, Daeyoung; Kim, Seong Hoon; Seo, Kyoungwoo; Yoon, Juhyeon

    2014-01-01

    A core downward flow is considered to use a plate type fuel because it is benefit to install the fuel in the core. If a flow inversion from a downward to upward flow in the core by a natural circulation is introduced within a high heat flux region of residual heat, the fuel fails instantly due to zero flow. Therefore, the core downward flow should be sufficiently maintained until the residual heat is in a low heat flux region. In a small power research reactor, inertia generated by a flywheel of the PCP can maintain a downward flow shortly and resolve the problem of a flow inversion. However, a high power research reactor more than 10 MW should have an additional method to have a longer downward flow until a low heat flux. Usually, other research reactors have selected an active residual heat removal system as a safety class. But, an active safety system is difficult to design and expensive to construct. A Gravity Core Cooling Tank (GCCT) beside the reactor pool with a Residual Heat Removal Pipe connecting two pools was developed and designed preliminarily as a passive residual heat removal system for an open-pool type research reactor. It is very simple to design and cheap to construct. Additionally, a non-safety, but active residual heat removal system is applied with the GCCT. It is a Pool Water Cooling and Purification System. It can improve the usability of the research reactor by removing the thermal waves, and purify the reactor pool, the Primary Cooling System, and the GCCT. Moreover, it can reduce the pool top radiation level

  17. Performance Evaluation of the Concept of Hybrid Heat Pipe as Passive In-core Cooling Systems for Advanced Nuclear Power Plant

    International Nuclear Information System (INIS)

    Jeong, Yeong Shin; Kim, Kyung Mo; Kim, In Guk; Bang, In Cheol

    2015-01-01

    As an arising issue for inherent safety of nuclear power plant, the concept of hybrid heat pipe as passive in-core cooling systems was introduced. Hybrid heat pipe has unique features that it is inserted in core directly to remove decay heat from nuclear fuel without any changes of structures of existing facilities of nuclear power plant, substituting conventional control rod. Hybrid heat pipe consists of metal cladding, working fluid, wick structure, and neutron absorber. Same with working principle of the heat pipe, heat is transported by phase change of working fluid inside metal cask. Figure 1 shows the systematic design of the hybrid heat pipe cooling system. In this study, the concept of a hybrid heat pipe was introduced as a Passive IN-core Cooling Systems (PINCs) and demonstrated for internal design features of heat pipe containing neutron absorber. Using a commercial CFD code, single hybrid heat pipe model was analyzed to evaluate thermal performance in designated operating condition. Also, 1-dimensional reactor transient analysis was done by calculating temperature change of the coolant inside reactor pressure vessel using MATLAB. As a passive decay heat removal device, hybrid heat pipe was suggested with a concept of combination of heat pipe and control rod. Hybrid heat pipe has distinct feature that it can be a unique solution to cool the reactor when depressurization process is impossible so that refueling water cannot be injected into RPV by conventional ECCS. It contains neutron absorber material inside heat pipe, so it can stop the reactor and at the same time, remove decay heat in core. For evaluating the concept of hybrid heat pipe, its thermal performance was analyzed using CFD and one-dimensional transient analysis. From single hybrid heat pipe simulation, the hybrid heat pipe can transport heat from the core inside to outside about 18.20 kW, and total thermal resistance of hybrid heat pipe is 0.015 .deg. C/W. Due to unique features of long heat

  18. Bypass line assisted start-up of a loop heat pipe with a flat evaporator

    International Nuclear Information System (INIS)

    Boo, Joon Hong; Jung, Eui Guk

    2009-01-01

    Loop heat pipes often experience start-up problems especially under low thermal loads. A bypass line was installed between the evaporator and the liquid reservoir to alleviate the difficulties associated with start-up of a loop heat pipe with flat evaporator. The evaporator and condenser had dimensions of 40 mm (W) by 50 mm (L). The wall and tube materials were stainless steel and the working fluid was methanol. Axial grooves were provided in the flat evaporator to serve as vapor passages. The inner diameters of liquid and vapor transport lines were 2 mm and 4 mm, respectively, and the length of the two lines was 0.5 m each. The thermal load range was up to 130 W for horizontal alignment with the condenser temperature of 10 .deg. C. The experimental results showed that the minimum thermal load for start-up was lowered by 37% when the bypass line was employed

  19. Analytical Investigation of the Heat-Transfer Limits of a Novel Solar Loop-Heat Pipe Employing a Mini-Channel Evaporator

    Directory of Open Access Journals (Sweden)

    Thierno M. O. Diallo

    2018-01-01

    Full Text Available This paper presents an analytical investigation of heat-transfer limits of a novel solar loop-heat pipe developed for space heating and domestic hot water use. In the loop-heat pipe, the condensate liquid returns to the evaporator via small specially designed holes, using a mini-channel evaporator. The study considered the commonly known heat-transfer limits of loop-heat pipes, namely, the viscous, sonic, entrainment, boiling and heat-transfer limits due to the two-phase pressure drop in the loop. The analysis considered the main factors that affect the limits in the mini-channel evaporator: the operating temperature, mini-channel aspect ratio, evaporator length, evaporator inclination angle, evaporator-to-condenser height difference and the dimension of the holes. It was found that the entrainment is the main governing limit of the system operation. With the specified loop design and operational conditions, the solar loop-heat pipe can achieve a heat-transport capacity of 725 W. The analytical model presented in this study can be used to optimise the heat-transfer capacity of the novel solar loop-heat pipe.

  20. Sodium leak detection on large pipes. Heat insulating shells made of silico-aluminate

    International Nuclear Information System (INIS)

    Antonakas, D.; Blanc, R.; Casselman, C.; Malet, J.C.

    1986-05-01

    This report presents an equipment installed on the large secondary pipes of fast reactors, ensuring several functions: support and equilibrium of static and dynamic loads, heat insulator, preheating, and the detection of possible sodium leaks. The research programs associated to the development of the shells are briefly evoked; then, the report deals no longer with the studies on silico-aluminate aging and the detection performance [fr

  1. Heat pipes et two-phase loops for spacecraft applications. ESA programmes

    Energy Technology Data Exchange (ETDEWEB)

    Supper, W. [European Space Agency / ESTEC. Thermal control and life support division (France)

    1996-12-31

    This document is a series of transparencies presenting the current and future applications of heat pipes in spacecraft and the activities in the field of capillary pumped two-phase loops: thermal tests, high-efficiency low pressure drop condensers, theoretical understanding of evaporator function, optimization of liquid and vapor flows, trade-off between low and high conductivity wicks, development of high capillary capacity wicks etc.. (J.S.)

  2. Simulation and Experimental Investigation of Thermal Performance of a Miniature Flat Plate Heat Pipe

    Directory of Open Access Journals (Sweden)

    R. Boukhanouf

    2013-01-01

    Full Text Available This paper presents the results of a CFD analysis and experimental tests of two identical miniature flat plate heat pipes (FPHP using sintered and screen mesh wicks and a comparative analysis and measurement of two solid copper base plates 1 mm and 3 mm thick. It was shown that the design of the miniature FPHP with sintered wick would achieve the specific temperature gradients threshold for heat dissipation rates of up to 80 W. The experimental results also revealed that for localised heat sources of up to 40 W, a solid copper base plate 3 mm thick would have comparable heat transfer performances to that of the sintered wick FPHP. In addition, a marginal effect on the thermal performance of the sintered wick FPHP was recorded when its orientation was held at 0°, 90°, and 180° and for heat dissipation rates ranging from 0 to 100 W.

  3. Modeling Transient Heat Transfer in Small-Size Twin Pipes for End-User Connections to Low-Energy District Heating Networks

    DEFF Research Database (Denmark)

    Dalla Rosa, Alessandro; Li, Hongwei; Svendsen, Svend

    2013-01-01

    The low-energy district heating concept has the potential of increasing the energy and exergy efficiencies of heat supply systems and of exploiting renewable energy, provided technical solutions for its wide application can be developed and implemented. This paper investigates the dynamic behaviour...... of district heating branch pipes in low-temperature operation (supply temperature 50-55°C and return temperature 20-25°C). We looked at state-of-the-art district heating branch pipes, suitable for the connection of a typical single-family house to a substation equipped with a heat exchanger for domestic hot...

  4. Preferential flow paths and heat pipes: Results from laboratory experiments on heat-driven flow in natural and artificial rock fractures

    International Nuclear Information System (INIS)

    Kneafsey, T.J.; Pruess, K.

    1997-06-01

    Water flow in fractures under the conditions of partial saturation and thermal drive may lead to fast flow along preferential localized pathways and heat pipe conditions. Water flowing in fast pathways may ultimately contact waste packages at Yucca Mountain and transport radionuclides to the accessible environment. Sixteen experiments were conducted to visualize liquid flow in glass fracture models, a transparent epoxy fracture replica, and a rock/replica fracture assembly. Spatially resolved thermal monitoring was performed in seven of these experiments to evaluate heat-pipe formation. Depending on the fracture apertures and flow conditions, various flow regimes were observed including continuous rivulet flow for high flow rates, intermittent rivulet flow and drop flow for intermediate flow rates, and film flow for low flow rates and wide apertures. These flow regimes were present in both fracture models and in the replica of a natural fracture. Heat-pipe conditions indicated by low thermal gradients were observed in five experiments. Conditions conducive to heat-pipe formation include an evaporation zone, condensation zone, adequate space for vapor and liquid to travel, and appropriate fluid driving forces. In one of the two experiments where heat pipe conditions were not observed, adequate space for liquid-vapor counterflow was not provided. Heat pipe conditions were not established in the other, because liquid flow was inadequate to compensate for imbibition and the quantity of heat contained within the rock

  5. A lead-before-break strategy for primary heat transport piping of 500 MWe Indian PHWR

    International Nuclear Information System (INIS)

    Chattopadhyay, J.; Dutta, B.K.; Kushwaha, H.S.

    1997-01-01

    Leak-Before-Break (LBB) is being used to design the primary heat transport piping system of 500 MWe Indian Pressurized Heavy Water Reactors (IPHWR). The work is categorized in three directions to demonstrate three levels of safety against sudden catastrophic break. Level 1 is inherent in the design procedure of piping system as per ASME Sec.III with a well defined factor of safety. Level 2 consists of fatigue crack growth study of a postulated part-through flaw at the inside surface of pipes. Level 3 is stability analysis of a postulated leakage size flaw under the maximum credible loading condition. Developmental work related to demonstration of level 2 and level 3 confidence is described in this paper. In a case study on fatigue crack growth on PHT straight pipes for level 2, negligible crack growth is predicted for the life of the reactor. For level 3 analysis, the R6 method has been adopted. A database to evaluate SIF of elbows with throughwall flaws under combined internal pressure and bending moment has been generated to provide one of the inputs for R6 method. The methodology of safety assessment of elbow using R6 method has been demonstrated for a typical pump discharge elbow. In this analysis, limit load of the cracked elbow has been determined by carrying out elasto-plastic finite element analysis. The limit load results compared well with those given by Miller. However, it requires further study to give a general form of limit load solution. On the experimental front, a set of small diameter pipe fracture experiments have been carried out at room temperature and 300 degrees C. Two important observations of the experiments are - appreciable drop in maximum load at 300 degrees C in case of SS pipes and out-of-plane crack growth in case of CS pipes. Experimental load deflection curves are finally compared with five J-estimation schemes predictions. A material database of PHT piping materials is also being generated for use in LBB analysis

  6. A lead-before-break strategy for primary heat transport piping of 500 MWe Indian PHWR

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, J.; Dutta, B.K.; Kushwaha, H.S. [Bhabha Atomic Research Centre, Bombay (India)] [and others

    1997-04-01

    Leak-Before-Break (LBB) is being used to design the primary heat transport piping system of 500 MWe Indian Pressurized Heavy Water Reactors (IPHWR). The work is categorized in three directions to demonstrate three levels of safety against sudden catastrophic break. Level 1 is inherent in the design procedure of piping system as per ASME Sec.III with a well defined factor of safety. Level 2 consists of fatigue crack growth study of a postulated part-through flaw at the inside surface of pipes. Level 3 is stability analysis of a postulated leakage size flaw under the maximum credible loading condition. Developmental work related to demonstration of level 2 and level 3 confidence is described in this paper. In a case study on fatigue crack growth on PHT straight pipes for level 2, negligible crack growth is predicted for the life of the reactor. For level 3 analysis, the R6 method has been adopted. A database to evaluate SIF of elbows with throughwall flaws under combined internal pressure and bending moment has been generated to provide one of the inputs for R6 method. The methodology of safety assessment of elbow using R6 method has been demonstrated for a typical pump discharge elbow. In this analysis, limit load of the cracked elbow has been determined by carrying out elasto-plastic finite element analysis. The limit load results compared well with those given by Miller. However, it requires further study to give a general form of limit load solution. On the experimental front, a set of small diameter pipe fracture experiments have been carried out at room temperature and 300{degrees}C. Two important observations of the experiments are - appreciable drop in maximum load at 300{degrees}C in case of SS pipes and out-of-plane crack growth in case of CS pipes. Experimental load deflection curves are finally compared with five J-estimation schemes predictions. A material database of PHT piping materials is also being generated for use in LBB analysis.

  7. Fractal Loop Heat Pipe Performance Comparisons of a Soda Lime Glass and Compressed Carbon Foam Wick

    Science.gov (United States)

    Myre, David; Silk, Eric A.

    2014-01-01

    This study compares heat flux performance of a Loop Heat Pipe (LHP) wick structure fabricated from compressed carbon foam with that of a wick structure fabricated from sintered soda lime glass. Each wick was used in an LHP containing a fractal based evaporator. The Fractal Loop Heat Pipe (FLHP) was designed and manufactured by Mikros Manufacturing Inc. The compressed carbon foam wick structure was manufactured by ERG Aerospace Inc., and machined to specifications comparable to that of the initial soda lime glass wick structure. Machining of the compressed foam as well as performance testing was conducted at the United States Naval Academy. Performance testing with the sintered soda lime glass wick structures was conducted at NASA Goddard Space Flight Center. Heat input for both wick structures was supplied via cartridge heaters mounted in a copper block. The copper heater block was placed in contact with the FLHP evaporator which had a circular cross-sectional area of 0.88 cm(sup 2). Twice distilled, deionized water was used as the working fluid in both sets of experiments. Thermal performance data was obtained for three different Condenser/Subcooler temperatures under degassed conditions. Both wicks demonstrated comparable heat flux performance with a maximum of 75 W/cm observed for the soda lime glass wick and 70 W /cm(sup 2) for the compressed carbon foam wick.

  8. Theoretical research of helium pulsating heat pipe under steady state conditions

    International Nuclear Information System (INIS)

    Xu, D; Liu, H M; Li, L F; Huang, R J; Wang, W

    2015-01-01

    As a new-type heat pipe, pulsating heat pipe (PHP) has several outstanding features, such as great heat transport ability, strong adjustability, small size and simple construction. PHP is a complex two-phase flow system associated with many physical subjects and parameters, which utilizes the pressure and temperature changes in volume expansion and contraction during phase changes to excite the pulsation motion of liquid plugs and vapor bubbles in the capillary tube between the evaporator and the condenser. At present time, some experimental investigation of helium PHP have been done. However, theoretical research of helium PHP is rare. In this paper, the physical and mathematical models of operating mechanism for helium PHP under steady state are established based on the conservation of mass, momentum, and energy. Several important parameters are correlated and solved, including the liquid filling ratio, flow velocity, heat power, temperature, etc. Based on the results, the operational driving force and flow resistances of helium PHP are analysed, and the flow and heat transfer is further studied. (paper)

  9. Experimental study on the supercritical startup and heat transport capability of a neon-charged cryogenic loop heat pipe

    International Nuclear Information System (INIS)

    Guo, Yuandong; Lin, Guiping; He, Jiang; Bai, Lizhan; Zhang, Hongxing; Miao, Jianyin

    2017-01-01

    Highlights: • A neon-charged CLHP integrated with a G-M cryocooler was designed and investigated. • The CLHP can realize the supercritical startup with an auxiliary heat load of 1.5 W. • Maximum heat transport capability of the CLHP was 4.5 W over a distance of 0.6 m. • There existed an optimum auxiliary heat load to expedite the supercritical startup. • There existed an optimum charged pressure to reach the largest heat transfer limit. - Abstract: Neon-charged cryogenic loop heat pipe (CLHP) can realize efficient cryogenic heat transport in the temperature range of 30–40 K, and promises great application potential in the thermal control of future space infrared exploration system. In this work, extensive experimental studies on the supercritical startup and heat transport capability of a neon-charged CLHP integrated with a G-M cryocooler were carried out, where the effects of the auxiliary heat load applied to the secondary evaporator and charged pressure of the working fluid were investigated. Experimental results showed that the CLHP could successfully realize the supercritical startup with an auxiliary heat load of 1.5 W, and there existed an optimum auxiliary heat load and charged pressure of the working fluid respectively, to achieve the maximum temperature drop rate of the primary evaporator during the supercritical startup. The CLHP could reach a maximum heat transport capability of 4.5 W over a distance of 0.6 m corresponding to the optimum charged pressure of the working fluid; however, the heat transport capability decreased with the increase of the auxiliary heat load. Furthermore, the inherent mechanisms responsible for the phenomena observed in the experiments were analyzed and discussed, to provide a better understanding from the theoretical view.

  10. Experimental investigation of a pulsating heat pipe for hybrid vehicle applications

    International Nuclear Information System (INIS)

    Burban, G.; Ayel, V.; Alexandre, A.; Lagonotte, P.; Bertin, Y.; Romestant, C.

    2013-01-01

    This paper deals with the experimental results of an unlooped pulsating heat pipe (PHP) developed and tested in an electronic thermal management field with hybrid vehicle applications in mind. The 2.5 mm inner tube diameter device was cooled by an air heat exchanger to replicate the environment of a vehicle. In order to characterize this pulsating heat pipe, four working fluids have been tested. They are acetone, methanol, water, and n-pentane, with applied thermal power ranging from 25 W to 550 W, air temperature ranging from 10 °C to 60 °C and air velocity ranging from 0.25 m s −1 to 2 m s −1 . Three inclinations have also been tested according to their horizontal positions: +45° (condenser above the evaporator), 0° and −45° (condenser below the evaporator). Among the different results, some of the most revelatory were obtained with regard to unfavourable inclination (−45°), for which the performances were very interesting considering a terrestrial application. On the other hand, one also observed low temperature limitations for water as a working fluid and degradation of performances for n-pentane tested at 60 °C air temperature. On an overall basis, however, it should be noted that the PHP functioned with high reliability and reproducibility and without any failure during the start-up or working stage. - Highlights: ► An unlooped pulsating heat pipe (PHP) has been tested varying heat power, air velocity and temperature, inclination and fluid. ► Four working fluids have been tested and classified into two groups according to the performances of the PHP. ► Interesting water phenomena have been highlighted in this study. ► The PHP worked with a good reliability and reproducibility.

  11. Experimental investigation and CFD simulation of multi-pipe earth-to-air heat exchangers (EAHEs flow performance

    Directory of Open Access Journals (Sweden)

    Amanowicz Łukasz

    2017-01-01

    Full Text Available In this paper the experimentally obtained flow characteristics of multi-pipe earth-to-air heat exchangers (EAHEs were used to validate the EAHE flow performance numerical model prepared by means of CFD software Ansys Fluent. The cut-cell meshing and the k-ε realizable turbulence model with default coefficients values and enhanced wall treatment was used. The total pressure losses and airflow in each pipe of multi-pipe exchangers was investigated both experimentally and numerically. The results show that airflow in each pipe of multi-pipe EAHE structures is not equal. The validated numerical model can be used for a proper designing of multi-pipe EAHEs from the flow characteristics point of view. The influence of EAHEs geometrical parameters on the total pressure losses and airflow division between the exchanger pipes can be also analysed. Usage of CFD for designing the EAHEs can be helpful for HVAC engineers (Heating Ventilation and Air Conditioning for optimizing the geometrical structure of multi-pipe EAHEs in order to save the energy and decrease operational costs of low-energy buildings.

  12. Experimental investigation and CFD simulation of multi-pipe earth-to-air heat exchangers (EAHEs) flow performance

    Science.gov (United States)

    Amanowicz, Łukasz; Wojtkowiak, Janusz

    2017-11-01

    In this paper the experimentally obtained flow characteristics of multi-pipe earth-to-air heat exchangers (EAHEs) were used to validate the EAHE flow performance numerical model prepared by means of CFD software Ansys Fluent. The cut-cell meshing and the k-ɛ realizable turbulence model with default coefficients values and enhanced wall treatment was used. The total pressure losses and airflow in each pipe of multi-pipe exchangers was investigated both experimentally and numerically. The results show that airflow in each pipe of multi-pipe EAHE structures is not equal. The validated numerical model can be used for a proper designing of multi-pipe EAHEs from the flow characteristics point of view. The influence of EAHEs geometrical parameters on the total pressure losses and airflow division between the exchanger pipes can be also analysed. Usage of CFD for designing the EAHEs can be helpful for HVAC engineers (Heating Ventilation and Air Conditioning) for optimizing the geometrical structure of multi-pipe EAHEs in order to save the energy and decrease operational costs of low-energy buildings.

  13. Parabolic solar cooker: Cooking with heat pipe vs direct spiral copper tubes

    Science.gov (United States)

    Craig, Omotoyosi O.; Dobson, Robert T.

    2016-05-01

    Cooking with solar energy has been seen by many researchers as a solution to the challenges of poverty and hunger in the world. This is no exception in Africa, as solar coking is viewed as an avenue to eliminate the problem of food insecurity, insufficient energy supply for household and industrial cooking. There are several types of solar cookers that have been manufactured and highlighted in literature. The parabolic types of solar cookers are known to reach higher temperatures and therefore cook faster. These cookers are currently being developed for indoor cooking. This technology has however suffered low cooking efficiency and thus leads to underutilization of the high heat energy captured from the sun in the cooking. This has made parabolic solar cookers unable to compete with other conventional types of cookers. Several methods to maximize heat from the sun for indirect cooking has been developed, and the need to improve on them of utmost urgency. This paper investigates how to optimize the heat collected from the concentrating types of cookers by proposing and comparing two types of cooking sections: the spiral hot plate copper tube and the heat pipe plate. The system uses the concentrating solar parabolic dish technology to focus the sun on a conical cavity of copper tubes and the heat is stored inside an insulated tank which acts both as storage and cooking plate. The use of heat pipes to transfer heat between the oil storage and the cooking pot was compared to the use of a direct natural syphon principle which is achieved using copper tubes in spiral form like electric stove. An accurate theoretical analysis for the heat pipe cooker was achieved by solving the boiling and vaporization in the evaporator side and then balancing it with the condensation and liquid-vapour interaction in the condenser part while correct heat transfer, pressure and height balancing was calculated in the second experiment. The results show and compare the cooking time, boiling

  14. A thermoelectric generator using loop heat pipe and design match for maximum-power generation

    KAUST Repository

    Huang, Bin-Juine

    2015-09-05

    The present study focuses on the thermoelectric generator (TEG) using loop heat pipe (LHP) and design match for maximum-power generation. The TEG uses loop heat pipe, a passive cooling device, to dissipate heat without consuming power and free of noise. The experiments for a TEG with 4W rated power show that the LHP performs very well with overall thermal resistance 0.35 K W-1, from the cold side of TEG module to the ambient. The LHP is able to dissipate heat up to 110W and is maintenance free. The TEG design match for maximum-power generation, called “near maximum-power point operation (nMPPO)”, is studied to eliminate the MPPT (maximum-power point tracking controller). nMPPO is simply a system design which properly matches the output voltage of TEG with the battery. It is experimentally shown that TEG using design match for maximum-power generation (nMPPO) performs better than TEG with MPPT.

  15. FEM-DBEM approach to analyse crack scenarios in a baffle cooling pipe undergoing heat flux from the plasma

    Directory of Open Access Journals (Sweden)

    R. Citarella

    2017-02-01

    Full Text Available Wendelstein 7-X is the world’s largest nuclear fusion experiment of stellarator type, in which a hydrogen plasma is confined by a magnet field generated with external superconducting coils, allowing the plasma to be heated up to the fusion temperature. The water-cooled Plasma Facing Components (PFC protect the Plasma Vessel (PV against radiative and convective heat from the plasma. After the assembly process of heat shields and baffles, several cracks were found in the braze and cooling pipes. Due to heat load cycles occurring during each Operational Phase (OP, thermal stresses are generated in the heat sinks, braze root and cooling pipes, capable to drive fatigue crack-growth and, possibly, a water leak through the pipe thickness. The aim of this study is to assess the most dangerous initial crack configurations in one of the most critical baffles by using numerical models based on a FEM-DBEM approach.

  16. The effects of linear accelerations on the maximum heat transfer capacity of micro pipes with triangular grooves

    International Nuclear Information System (INIS)

    Shokouhmand, H.; Kahrobaian, A.; Tabandeh, N.; Jalilvand, A.

    2002-01-01

    Micro heat pipes are widely used for the thermal control of spacecraft and their electronic components. In this paper the influence of linear accelerations in micro grooves has been studied. A mathematical model for predicating the minimum meniscus radius and the maximum heat transport in triangular groove under the influence of linear acceleration is presented and method for determining the theoretical minimum meniscus radius is developed. It is shown that both, the direction and the magnitude of the acceleration have a great effect upon heat transfer capability of micro heat pipes. The analysis presented here provides a mechanism where by the groove geometry can be optimized with respect to the length of the heat pipe and direction and magnitude of linear acceleration

  17. Experimental Study of Thermal Energy Storage Characteristics using Heat Pipe with Nano-Enhanced Phase Change Materials

    Science.gov (United States)

    Krishna, Jogi; Kishore, P. S.; Brusly Solomon, A.

    2017-08-01

    The paper presents experimental investigations to evaluate thermal performance of heat pipe using Nano Enhanced Phase Change Material (NEPCM) as an energy storage material (ESM) for electronic cooling applications. Water, Tricosane and nano enhanced Tricosane are used as energy storage materials, operating at different heating powers (13W, 18W and 23W) and fan speeds (3.4V and 5V) in the PCM cooling module. Three different volume percentages (0.5%, 1% and 2%) of Nano particles (Al2O3) are mixed with Tricosane which is the primary PCM. This experiment is conducted to study the temperature distributions of evaporator, condenser and PCM during the heating as well as cooling. The cooling module with heat pipe and nano enhanced Tricosane as energy storage material found to save higher fan power consumption compared to the cooling module that utilities only a heat pipe.

  18. Effect of Twisted-Tape Turbulators and Nanofluid on Heat Transfer in a Double Pipe Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Heydar Maddah

    2014-01-01

    Full Text Available Heat transfer and overall heat transfer in a double pipe heat exchanger fitted with twisted-tape elements and titanium dioxide nanofluid were studied experimentally. The inner and outer diameters of the inner tube were 8 and 16 mm, respectively, and cold and hot water were used as working fluids in shell side and tube side. The twisted tapes were made from aluminum sheet with tape thickness (d of 1 mm, width (W of 5 mm, and length of 120 cm. Titanium dioxide nanoparticles with a diameter of 30 nm and a volume concentration of 0.01% (v/v were prepared. The effects of temperature, mass flow rate, and concentration of nanoparticles on the overall heat transfer coefficient, heat transfer changes in the turbulent flow regime Re≥2300, and counter current flow were investigated. When using twisted tape and nanofluid, heat transfer coefficient was about 10 to 25 percent higher than when they were not used. It was also observed that the heat transfer coefficient increases with operating temperature and mass flow rate. The experimental results also showed that 0.01% TiO2/water nanofluid with twisted tape has slightly higher friction factor and pressure drop when compared to 0.01% TiO2/water nanofluid without twisted tape. The empirical correlations proposed for friction factor are in good agreement with the experimental data.

  19. Heat Transfer Modeling of an Annular On-Line Spray Water Cooling Process for Electric-Resistance-Welded Steel Pipe.

    Science.gov (United States)

    Chen, Zejun; Han, Huiquan; Ren, Wei; Huang, Guangjie

    2015-01-01

    On-line spray water cooling (OSWC) of electric-resistance-welded (ERW) steel pipes can replace the conventional off-line heat treatment process and become an important and critical procedure. The OSWC process improves production efficiency, decreases costs, and enhances the mechanical properties of ERW steel pipe, especially the impact properties of the weld joint. In this paper, an annular OSWC process is investigated based on an experimental simulation platform that can obtain precise real-time measurements of the temperature of the pipe, the water pressure and flux, etc. The effects of the modes of annular spray water cooling and related cooling parameters on the mechanical properties of the pipe are investigated. The temperature evolutions of the inner and outer walls of the pipe are measured during the spray water cooling process, and the uniformity of mechanical properties along the circumferential and longitudinal directions is investigated. A heat transfer coefficient model of spray water cooling is developed based on measured temperature data in conjunction with simulation using the finite element method. Industrial tests prove the validity of the heat transfer model of a steel pipe undergoing spray water cooling. The research results can provide a basis for the industrial application of the OSWC process in the production of ERW steel pipes.

  20. Application of NARX neural networks in thermal dynamics identification of a pulsating heat pipe

    International Nuclear Information System (INIS)

    Lee Yawei; Chang Tienli

    2009-01-01

    The pulsating heat pipe (PHP) receiving much attention in industries is a novel type of cooling device. The distinguishing feature of PHPs is the unsteady flow oscillations formed by the passing non-uniform distributions of vapour plugs and liquid slugs. This study introduces a methodology of a non-linear auto-regressive with exogenous (NARX) neural network to analyze the thermal dynamics of a PHP in both the time and frequency domains. Three heating powers: 30, 70, and 110 W are tested, and all the predicted results are presented in quite good agreement with the measured results. Herein, the harmonic analysis of the non-linear structure can be equivalently conducted with generalized frequency response functions (GFRFs). Based on the non-linear coupling between the various input spectral components, the interpretations of the higher order GFRFs have been extensively presented for demonstrating the non-linear effects on the heat transfer of a PHP at different operating conditions

  1. Effect of External Pressure Drop on Loop Heat Pipe Operating Temperature

    Science.gov (United States)

    Jentung, Ku; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Obenschain, Arthur F. (Technical Monitor)

    2002-01-01

    This paper discusses the effect of the pressure drop on the operating temperature in a loop heat pipe (LHP). Because the evaporator and the compensation chamber (CC) both contain two-phase fluid, a thermodynamic constraint exists between the temperature difference and the pressure drop for these two components. As the pressure drop increases, so will the temperature difference. The temperature difference in turn causes an increase of the heat leak from the evaporator to the CC, resulting in a higher CC temperature. Furthermore, the heat leak strongly depends on the vapor void fraction inside the evaporator core. Tests were conducted by installing a valve on the vapor line so as to vary the pressure drop, and by charging the LHP with various amounts of fluid. Test results verify that the LHP operating temperature increases with an increasing differential pressure, and the temperature increase is a strong function of the fluid inventory in the loop.

  2. Using Solar Hot Water to Address Piping Heat Losses in Multifamily Buildings

    Energy Technology Data Exchange (ETDEWEB)

    Springer, David [Alliance for Residential Building Innovation, Davis, CA (United States); Seitzler, Matt [Alliance for Residential Building Innovation, Davis, CA (United States); Backman, Christine [Alliance for Residential Building Innovation, Davis, CA (United States); Weitzel, Elizabeth [Alliance for Residential Building Innovation, Davis, CA (United States)

    2015-10-01

    Solar thermal water heating is most cost effective when applied to multifamily buildings and some states offer incentives or other inducements to install them. However, typical solar water heating designs do not allow the solar generated heat to be applied to recirculation losses, only to reduce the amount of gas or electric energy needed for hot water that is delivered to the fixtures. For good reasons, hot water that is recirculated through the building is returned to the water heater, not to the solar storage tank. The project described in this report investigated the effectiveness of using automatic valves to divert water that is normally returned through the recirculation piping to the gas or electric water heater instead to the solar storage tank. The valves can be controlled so that the flow is only diverted when the returning water is cooler than the water in the solar storage tank.

  3. Thermodynamic and experimental study on heat transfer mechanism of miniature loop heat pipe with water-copper nanofluid

    Science.gov (United States)

    Wang, Xiao-wu; Wan, Zhen-ping; Tang, Yong

    2018-02-01

    A miniature loop heat pipe (mLHP) is a promising device for heat dissipation of electronic products. Experimental study of heat transfer performance of an mLHP employing Cu-water nanofluid as working fluid was conducted. It is found that, when input power is above 25 W, the temperature differences between the evaporator wall and vapor of nanofluid, Te - Tv, and the total heat resistance of mLHP using nanofluid are always lower than those of mLHP using de-ionized water. The values of Te - Tv and total heat resistance of mLHP using nanofluid with concentration 1.5 wt. % are the lowest, while when the input power is 25 W, the values of Te - Tv and total heat resistance of mLHP using de-ionized water are even lower than those of mLHP using nanofluid with concentration 2.0 wt. %. At larger input power, the dominant interaction is collision between small bubbles and nanoparticles which can facilitate heat transfer. While at lower input power, nanoparticles adhere to the surface of large bubble. This does not benefit boiling heat transfer. For mLHP using nanofluid with larger concentration, for example 2.0%, the heat transfer may even be worse compared with using de-ionized water at lower input power. The special structure of the mLHP in this study, two separated chambers in the evaporator, produces an extra pressure difference and contributes to the heat transfer performance of the mLHP.

  4. Evaporation thermal anslysis of Swallow-tailed Axial-grooved Heat Pipe

    Science.gov (United States)

    Zhang, Renping

    2018-03-01

    A detailed mathematical model that describes evaporating characteristics through thin liquid film at the evaporator section of swallow-tailed axial-grooved heat pipe was developed. The numerical simulation results about thin film profile, liquid-vapour interface temperature, evaporating rate and heat flux at the evaporating thin film region were given by the current investigation and the effect of superheat on the liquid-vapour interface temperature, evaporating mass rate and heat flux was discussed. Meanwhile, thermal model of the meniscus region at the evaporating section was developed to calculate the rate of heat transfer. The ratio of the heat conduction in the evaporating thin liquid film region and total heat rate were also discussed. It is indicated that the thickness of thin liquid film rises in a nearly linear fashion. The disjoining pressure can be neglected with increasing the liquid film thickness, tends to be negligibly small. The heat transfer rate at the intrinsic meniscus cannot be compared with that of the evaporating liquid film region.

  5. MATHEMATICAL MODELING OF HEAT EXCHANGE IN DIRECT FLAT CHANNELS AND DIRECT ROUND PIPES WITH ROUGH WALLS UNDER THE SYMMETRIC HEAT SUPPLY

    Directory of Open Access Journals (Sweden)

    I E. Lobanov

    2017-01-01

    Full Text Available Objectives. The aim of present work was to carry out mathematical modelling of heat transfer with symmetrical heating in flat channels and round pipes with rough walls.Methods. The calculation was carried out using the L'Hôpital-Bernoulli's method. The solution of the problem of intensified heat transfer in a round tube with rough walls was obtained using the Lyon's integral.Results. Different from existing theories, a methodology of theoretical computational heat transfer determination for flat rough channels and round pipes with rough walls is developed on the basis of the principle of full viscosity superposition in a turbulent boundary layer. The analysis of the calculated heat transfer and hydroresistivity values for flat rough channels and round rough pipes shows that the increase in heat transfer is always less than the corresponding increase in hydraulic resistance, which is a disadvantage as compared to channels with turbulators, with all else being equal. The results of calculating the heat transfer for channels with rough walls in an extended range of determinant parameters, which differ significantly from the corresponding data for the channels with turbulators, determine the level of heat exchange intensification.Conclusion. An increase in the calculated values of the relative average heat transfer Nu/NuGL for flat rough channels and rough pipes with very high values of the relative roughness is significantly contributed by both an increase in the relative roughness height and an increase in the Reynolds number Re. In comparison with empirical dependencies, the main advantage of solutions for averaged heat transfer in rough flat channels and round pipes under symmetrical thermal load obtained according to the developed theory is that they allow the calculation of heat exchange in rough pipes to be made in the case of large and very large relative heights of roughness protrusions, including large Reynolds numbers, typical for pipes

  6. Multiple-effect diffusion solar still coupled with a vacuum-tube collector and heat pipe

    KAUST Repository

    Chong, Tze-Ling

    2014-08-01

    The present study develops a multiple-effect diffusion solar still (MEDS) with a bended-plate design in multiple-effect diffusion unit (MDU) to solve the peel-off problem of wick material. The MDU is coupled with a vacuum-tube solar collector to produce a high temperature gradient for high productivity. A heat pipe is used to transfer the solar heat to the MDU. A prototype MEDS-1L was built and tested outdoors. Four performance indexes are proposed for the performance evaluation of MEDS, including daily pure water production per unit area of glass cover, solar absorber, and evaporating surface (Mcov, Msol, Mevp, respectively), and solar distillation efficiency Rcov. The outdoor test results of MEDS-1L show that the solar collector supply temperature Th reaches 100°C at solar radiation 800Wm-2. The highest Mcov is 23.9kgm-2d-1 which is about 29% higher than the basin-type MEDS [11]. The highest value is 25.9kgm-2d-1 for Msol and 2.79kgm-2d-1 for Mevp. The measured Rcov is 1.5-2.44, higher than the basin-type MEDS (1.45-1.88). The Mcov, Msol, Mevp and Rcov of MEDS-1L are all higher than the theoretical calculation of a MEDS with a flat-plate solar collector coupled with a heat pipe (MEDS-FHP) [17].© 2014 Elsevier B.V.

  7. Generation of cross section data of heat pipe working fluids for compact nuclear reactors

    Energy Technology Data Exchange (ETDEWEB)

    Slewinski, Anderson; Ribeiro, Guilherme B. [Instituto Tecnológico de Aeronáutica (ITA), São José dos Campos, SP (Brazil); Caldeira, Alexandre D., E-mail: anderson_sle@live.com, E-mail: alexdc@ieav.cta.br, E-mail: gbribeiro@ieav.cta.br [Instituto de Estudos Avançados (IEAv), São José dos Campos, SP (Brazil). Divisão de Energia Nuclear

    2017-07-01

    For compact nuclear power plants, such as the nuclear space propulsion proposed by the TERRA project, aspects like mass, size and efficiency are essential drivers that must be managed during the project development. Moreover, for high temperature reactors, the use of liquid metal heat pipes as the heat removal mechanism provides some important advantages as simplicity and reliability. Considering these aforementioned aspects, this paper aims the development of the procedure necessary to calculate the microscopic absorption cross section data of several liquid metal to be used as working fluids with heat pipes; which will be later compared with the given data from JEF Report ⧣14. The information necessary to calculate the cross section data will be obtained from the latest ENDF library version. The NJOY system will be employed with the following modules: RECONR, BROADR, UNRESR and GROUPR, using the same specifications used to calculate the cross section data encountered in the JEF Report ⧣14. This methodology allows a comparison with published values, verifying the procedure developed to calculate the microscopic absorption cross section for selected isotopes using the TERRA reactor spectrum. Liquid metals isotopes of Sodium (Na), Lithium (Li), Thallium (TI) and Mercury (Hg) are part of this study. (author)

  8. Design, manufacturing and testing of a portable vaccine carrier box employing thermoelectric module and heat pipe.

    Science.gov (United States)

    Putra, N

    2009-01-01

    Vaccination is a highly effective method and a cheap tool for preventing certain infectious diseases. Routine immunization programs protect most of the world's children from diseases that claim millions of lives each year. There are many practical problems impeding vaccine delivery, especially to maintain the cold chain system, which is the means for storing and transporting vaccines in a potent state from the manufacturer to the person being immunized at a temperature of 2-8 degrees C. The development of the solid state thermoelectric cooling system has permitted newly developed packages that are capable of meeting many requirements and applications where environmental concern, size, weight, performance and noise are an issue. This paper describes the development of a vaccine carrier box. A combination of a thermoelectric module and a heat pipe is used for the cooling system. The position of the heat pipe as a heat sink on the hot side of the thermoelectric module will enhance the thermoelectric performance. The minimum temperature in the cabin of the vaccine carrier box reached -10 degrees C, which indicates that the design of the vaccine carrier box can maintain the vaccine at desired temperatures.

  9. Analysis of heat transfer and stress in the pipe with hot fluid flowing through

    International Nuclear Information System (INIS)

    Charoensri, Apisara; Pichestapong, Pipat; Rodthongkom, Chouvana

    2003-10-01

    At incomplete mixing area of high temperature and low temperature liquid near the surface of structures, temperature fluctuation of liquid gives thermal fatigue damage to wall structure. This phenomenon is called thermal striping. For designing of piping system, it is important to know thermal stresses of structure due to heat convection. In this study, authors proposed a simplified evaluation method to predict thermal stress from temperature fluctuation, for rational design against thermal striping. It is required to estimate structural responses to temperature fluctuation of fluid. The attenuation process is a thermal coupling problem between fluids and structures and has a sensitive characteristics to frequencies of temperature fluctuations were analyzed by FINAS, which is a computer program based on the finite element method by comparisons of theoretical method. When the inner surface of the pipe is due to heat convection of contained fluid with sinusoidal temperature fluctuation and the outer surface is kept insulated, temperature distribution of structure is analyzed by solving the equation of transient heat conduction. From these temperature distributions, induced thermal stresses in the structure are calculated by thermal elastic analysis. Frequency response characteristics of structures and its mechanism were investigated by both numerical and theoretical methods. Based on above investigation, a structural response diagram was derived, which can predict stress amplitude of structures from temperature amplitude and frequency of fluids

  10. Influence of void ratio on thermal performance of heat pipe receiver

    International Nuclear Information System (INIS)

    Gui Xiaohong; Tang Dawei; Liang Shiqiang; Lin Bin; Yuan Xiugan

    2012-01-01

    Highlights: ► The temperature gradient increases significantly and the utility ratio of PCM decreases obviously as void ratio increases. ► Void cavity influences the process of phase change greatly. ► PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. ► The temperature gradient of PCM zone is very significant with the effect of void cavity. - Abstract: In this paper, influence of void ratio on thermal performance of heat pipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. Numerical method is offered. The temperature field of Phase Change Material (PCM) canister is shown. Numerical results are compared with numerical ones of National Aeronautics and Space Administration (NASA). Numerical results show that the temperature gradient increases significantly and the utility ratio of PCM decreases obviously as void ratio increases. Void cavity influences the process of phase change greatly. PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. The thermal resistance of void cavity is much bigger than that of PCM canister wall. Void cavity prevents the heat transfer between PCM zone and canister wall. The temperature gradient of PCM zone is very significant with the effect of void cavity. So the thermal stress of heat pipe receiver may increase, and the lifetime may decrease as void ratio increases.

  11. Heat Pipe Heat Exchangers with Double Isolation Layers for Prevention of Interpath Leakage Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Current manned spacecraft heat rejection systems use two heat exchangers and an intermediate fluid loop to provide isolation between the crew compartment air and the...

  12. Optimization of a heat-pipe-cooled space radiator for use with a reactor-powered Stirling engine

    International Nuclear Information System (INIS)

    Moriarty, M.P.; French, E.P.

    1987-01-01

    The design optimization of a reactor-Stirling heat-pipe-cooled radiator is presented. The radiator is a self-deploying concept that uses individual finned heat pipe petals to reject waste heat from a Stirling engine. Radiator optimization methodology is presented, and the results of a parametric analysis of the radiator design variables for a 100-kW(e) system are given. The additional steps of optiminzing the radiator resulted in a net system mass savings of 3 percent. 5 references

  13. Optimum interior area thermal resistance model to analyze the heat transfer characteristics of an insulated pipe with arbitrary shape

    International Nuclear Information System (INIS)

    Chou, H.-M.

    2003-01-01

    The heat transfer characteristics for an insulated regular polygonal (or circular) pipe are investigated by using a wedge thermal resistance model as well as the interior area thermal resistance model R th =t/K s /[(1-α)A 2 +αA 3 ] with a surface area weighting factor α. The errors of the results generated by an interior area model can be obtained by comparing with the exact results generated by a wedge model. Accurate heat transfer rates can be obtained without error at the optimum α opt with the related t/R 2 . The relation between α opt and t/R 2 is α opt =1/ln(1+t/R 2 )-1/(t/R 2 ). The value of α opt is greater than zero and less than 0.5 and is independent of pipe size R 2 /R cr but strongly dependent on the insulation thickness t/R 2 . The interior area model using the optimum value α opt with the related t/R 2 should also be applied to an insulated pipe with arbitrary shape within a very small amount of error for the results of heat transfer rates. The parameter R 2 conservatively corresponds to the outside radius of the maximum inside tangent circular pipe within the arbitrary shaped pipes. The approximate dimensionless critical thickness t cr /R 2 and neutral thickness t e /R 2 of an insulated pipe with arbitrary shape are also obtained. The accuracies of the value of t cr /R 2 as well as t e /R 2 are strongly dependent on the shape of the insulated small pipe. The closer the shape of an insulated pipe is to a regular polygonal or circular pipe, the more reliable will the values of t cr /R 2 as well as t e /R 2 be

  14. METHOD OF ESTIMATION FREQUENCY PROPERTIES OF THE PREINSULATED PIPES FOR MONITORING THE STATUS OF HEATING NETWORKS

    Directory of Open Access Journals (Sweden)

    E. N. Taletskiy

    2014-01-01

    Full Text Available Proposed approximate method for the preliminary assessment of the frequency properties unadapted guiding system for monitoring the status of the organization of preinsulated pipes. Guide system elements  formed  tubes  placed  in  a  lossy  medium  (soil.  A  theoretical  analysis  shows  the  frequency dependence of the propagation constant components: the damping coefficient and the phase coefficient, take advantage of these characteristics of the system for monitoring the status heating networks.

  15. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

    A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

  16. Study of the technology of heat pipe on prevention wildfire of coal gangue hill

    Science.gov (United States)

    Deng, Jun; Li, Bei; Ding, Ximei; Ma, Li

    2017-04-01

    Self-ignitable coal gangue hill (CGH) is one kind of special combustion system, which has the characteristics of low self-ignite point, large heat storage, and easy reignition. The currently industrial fire extinguishing methods, such as inhibiting tendency of coal self-ignition, loessial overburden, and cement grouting, had unsatisfied effects for dispersing the heat out in time. Correspondingly, the CGH will lead reignition more frequently with the passage of time. The high underground temperature of CGH threatens the process of ecological and vegetation construction. Therefore, the elimination of high temperature is a vital issue to be solved urgently for habitat restoration. To achieve the ultimately ecological management goal of self-ignitable CGH - extinguishing the fire completely and never reignited, it is crucial to break the heat accumulation. Heat-pipe (HP) has a character of high efficient heat transfer capacity for eliminating the continuously high temperature in CGH. An experimental system was designed to test the heat transfer performance of HP for preventing and extinguishing the spontaneous combustion of coal gangue. Based on the heat transfer theory, the resistance network of the coal-HP heat removal system was analyzed for studying the cooling effect of HP. The experimental results show that the HP can accelerate the heat release in coal gangue pile. The coal temperature could be controlled at 59.6 ˚ C with HP in 7 h and the highest cooling value is 39.4 % with HP in 150 h, which can effectively cool the temperatures of high temperature zones. As a powerful heat transfer components, as soon as HPs were inserted into the CGH with a reasonable distance, it can completely play a vital role in inhibiting the coal self-ignition process.

  17. Aerodynamic heating of ballistic missile including the effects of gravity

    Indian Academy of Sciences (India)

    R D Neumann and J R Hayes (Summerfield 1986) carried out a sort of aerodynamic heating analysis for high velocity missiles by applying the knowledge of both inviscid and viscous flow fields over the vehicle, as the heating rate at any point of the vehicle is a function of many test-specific properties such as fluid flow field ...

  18. Loop Heat Pipe Operation Using Heat Source Temperature for Set Point Control

    Science.gov (United States)

    Ku, Jentung; Paiva, Kleber; Mantelli, Marcia

    2011-01-01

    The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly accomplished by cold biasing the reservoir and using electrical heaters to provide the required control power. Using this method, the loop operating temperature can be controlled within +/- 0.5K. However, because of the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP has been carried out to investigate the effects on the LHP operation when the control temperature sensor is placed on the heat source instead of the reservoir. In these tests, the LHP reservoir is cold-biased and is heated by a control heater. Tests results show that it is feasible to use the heat source temperature for feedback control of the LHP operation. Using this method, the heat source temperature can be maintained within a tight range for moderate and high powers. At low powers, however, temperature oscillations may occur due to interactions among the reservoir control heater power, the heat source mass, and the heat output from the heat source. In addition, the heat source temperature could temporarily deviate from its set point during fast thermal transients. The implication is that more sophisticated feedback control algorithms need to be implemented for LHP transient operation when the heat source temperature is used for feedback control.

  19. Experimental investigation on the thermal performance of a closed oscillating heat pipe in thermal management

    Science.gov (United States)

    Rao, Zhonghao; Wang, Qingchao; Zhao, Jiateng; Huang, Congliang

    2017-10-01

    To investigate the thermal performance of the closed oscillating heat pipe (OHP) as a passive heat transfer device in thermal management system, the gravitation force, surface tension, cooling section position and inclination angle were discussed with applied heating power ranging from 5 to 65 W. The deionized water was chosen as the working fluid and liquid-filling ratio was 50 ± 5%. The operation of the OHP mainly depends on the phase change of the working fluid. The working fluid within the OHP was constantly evaporated and cooled. The results show that the movement of the working fluid was similar to the forced damped mechanical vibration, it has to overcome the capillary resistance force and the stable oscillation should be that the OHP could successful startup. The oscillation frequency slowed and oscillation amplitude decreased when the inclination angle of the OHP increased. However, the thermal resistance increased. With the increment of the heating power, the average temperature of the evaporation and condensation section would be close. If the heating power was further increased, dry-out phenomenon within the OHP would appeared. With the decrement of the L, the start-up heating power also decreased and stable oscillation would be formed.

  20. Gravity

    CERN Document Server

    Rivera, Andrea

    2017-01-01

    Gravity is all around us. Learn how it is used in art, technology, and engineering. Five easy-to-read chapters explain the science behind gravity, as well as its real-world applications. Vibrant, full-color photos, bolded glossary words, and a key stats section let readers zoom in even deeper. Aligned to Common Core Standards and correlated to state standards. Abdo Zoom is a division of ABDO.

  1. Analysis of a double-pipe heat exchanger performance using heat structure coupling of MARS and CUPID

    International Nuclear Information System (INIS)

    Amidua, M.; Kim, H.; Cho, H. K.

    2015-01-01

    Thermal hydraulic phenomena in the inner tube of the double-pipe heat exchanger are expected to be reproducible by one-dimensional system analysis codes (MARS) if a proper condensation heat transfer coefficient is applied. Jeon et al (2013) and Cho et al (2013) conducted comprehensive reviews of the predictive capability of the condensation heat transfer models for the steam-water stratified flow. On the contrary, in the outer tube, a multidimensional analysis tool is required to incorporate the influence of azimuthal angle on the heat transfer rate from the inner tube outer wall to the outer tube fluid. Therefore, a coupled calculation between one dimensional system analysis code and a multidimensional computational fluid dynamics code is an attainable way to predict this effect with a reliable accuracy. CUPID is a three-dimensional computational multiphase fluid dynamics code developed by KAERI (Korea Atomic Energy Research Institute). According to Jeong et al (2010), the objective of the development is to support a resolution for the thermal hydraulic issues regarding the transient multi-dimensional twophase phenomena which can arise in an advanced light water reactor. It uses two-fluid model for the governing equations, which uses two sets of Navier-Stokes' equations for two phases. It can be used as either a typical CFD code or a component code (porous CFD code) depending on the length scale of the phenomena that need to be resolved. On the other hand, MARS is a best estimate thermalhydraulic system code and it was developed at KAERI by consolidating and restructuring the RELAP5/MOD3.2 code and COBRA-TF code (Cho et al., 2014). The MARS code has the capability to analyze best-estimated thermal hydraulic system. In this study, the coupled CUPID-MARS code was used for the simulation of a double-pipe heat exchanger. This paper presents the description of the heat exchanger, the coupling method, and the simulation results using the coupled code. The coupling

  2. In situ neutron diffraction measurement of residual stress relaxation in a welded steel pipe during heat treatment

    International Nuclear Information System (INIS)

    Chen, B.; Skouras, A.; Wang, Y.Q.; Kelleher, J.F.; Zhang, S.Y.; Smith, D.J.; Flewitt, P.E.J.; Pavier, M.J.

    2014-01-01

    Many previous studies have presented results on the relaxation of residual stress in a welded component as a result of postweld heat treatment. Techniques such as neutron diffraction and deep hole drilling have been used to measure the residual stress after the heat treatment and compare this with the residual stress for the component in the as-welded condition. The work described in this paper is novel: neutron diffraction is used to measure the relaxation of residual stress continuously as the heat treatment is being carried out. Residual stresses are measured in a butt-welded ferritic steel pipe as the pipe is heat treated to 650 °C and then cooled to room temperature. The results identify those parts of the heat treatment that lead to significant stress relaxation and the mechanisms responsible for this relaxation. The techniques developed during this work allow future heat treatments to be optimised to achieve the low levels of residual stress in welded components

  3. An examination of metal felt wicks for heat-pipe applications

    Science.gov (United States)

    Adkins, Douglas R.; Moss, Timothy A.; Andraka, Charles E.; Andreas, Nicos H.; Cole, Howard M.

    Precision metal felts are made of filaments of microndiameter wires that are chopped and layered onto a flat surface to form a wool-like material. Metal felts are commonly used as filters for micron-sized particles. The small diameters of the wires and the relatively open structure of these non-woven materials provide porosities on the order of 90% and greater. The high porosities of metal felts make them interesting candidate materials for heat pipe applications. Property measurements on selected samples of metal felts have demonstrated that typical effective pore radii range from 40 to 120 micrometers and the respective Darcy permeabilities range from 30 to 300 micrometers(exp 2). Through careful compaction of these materials, it is possible to tailor the flow characteristics of the materials to specific applications. Recently, a series of tests have been conducted at Sandia to measure the flow characteristics and pore structures of these materials as a function of compaction. Results from these tests and a discussion of the current applications of these materials in liquid-metal heat pipes for solar power conversion systems are presented.

  4. An examination of metal felt wicks for heat-pipe applications

    Energy Technology Data Exchange (ETDEWEB)

    Adkins, D.R.; Moss, T.A.; Andraka, C.E. [Sandia National Labs., Albuquerque, NM (United States); Andreas, N.H. [Bekaert Fibre Technologies, Marietta, GA (United States); Cole, H.M. [Porous Metal Products, Jacksboro, TX (United States)

    1994-11-01

    Precision metal felts are made of filaments of microndiameter wires that are chopped and layered onto a flat surface to form a wool-like material. Metal felts are commonly used as filters for micron-sized particles. The small diameters of the wires and the relatively open structure of these non-woven materials provide porosities on the order of 90% and greater. The high porosities of metal felts make them interesting candidate materials for heat pipe applications. Property measurements on selected samples of metal felts have demonstrated that typical effective pore radii range from 40 to 120 {mu}m and the respective Darcy permeabilities range from 30 to 300 {mu}m{sup 2}. Through careful compaction of these materials, it is possible to tailor the flow characteristics of the materials to specific applications. Recently, a series of tests have been conducted at Sandia to measure the flow characteristics and pore structures of these materials as a function of compaction. Results from these tests and a discussion of the current applications of these materials in liquid-metal heat pipes for solar power conversion systems are presented in this paper.

  5. Evacuated tubular collector utilizing a heat pipe. Progress report, May 1 1975--August 31, 1975

    Energy Technology Data Exchange (ETDEWEB)

    Ortabasi, U.; Fehlner, F.P.

    1975-01-01

    Research and development activities performed by the Corning Glass Works solar group during the period from May 1, 1975 to August 31, 1975 are reported. The analytical studies encompassed optical modeling of a modified cusp reflector, fresnel losses from tubular enclosures as a function of orientation, preliminary work on a digital Monte-Carlo Ray Tracing Computer Code and the determination of U/sub L/ losses as a function of vacuum level and temperature of the absorber. Compatible enclosure materials, wicks and working fluids were selected to assemble heat pipes for use as solar collector absorbers. Cusp reflectors with good accuracy were fabricated from various commercial bright aluminum sheet and their optical properties determined. Evacuation techniques were developed and special bake-out procedures were worked out to assemble the evacuated tubular collectors. The work on selective coatings narrowed down the field of potential absorber films to ''black chrome'' which has good stability in vacuum and the necessary ..cap alpha../epsilon value. Six different heat pipes and one flow-through absorber were fabricated and were partially characterized for thermal performance. Indoor and outdoor test facilities were completed and calibrated within proposed NBS standards. They are now available for parametric as well as true-life experiments with solar radiation.

  6. Thermal radiators with embedded pulsating heat pipes: Infra-red thermography and simulations

    International Nuclear Information System (INIS)

    Hemadri, Vadiraj A.; Gupta, Ashish; Khandekar, Sameer

    2011-01-01

    With the aim of exploring potential applications of Pulsating Heat Pipes (PHP), for space/terrestrial sectors, experimental study of embedded PHP thermal radiators, having two different effective Biot numbers respectively, and subjected to conjugate heat transfer conditions on their surface, i.e., natural convection and radiation, has been carried out under different thermo-mechanical boundary conditions. High resolution infrared camera is used to obtain spatial temperature profiles of the radiators. To complement the experimental study, detailed 3D computational heat transfer simulation has also been undertaken. By embedding PHP structures, it was possible to make the net thermal resistance of the mild steel radiator plate equivalent to the aluminum radiator plate, in spite of the large difference in their respective thermal conductivities (k Al ∼ 4k MS ). The study reveals that embedded PHP structures can be beneficial only under certain boundary conditions. The degree of isothermalization achieved in these structures strongly depends on its effective Biot number. The relative advantage of embedded PHP is appreciably higher if the thermal conductivity of the radiator plate material itself is low. The study indicates that the effective thermal conductivity of embedded PHP structure is of the order of 400 W/mK to 2300 W/mK, depending on the operating conditions. - Research highlights: → Study of radiator plates with embedded Pulsating Heat Pipe by infrared thermography. → Radiator is subjected to natural convection and radiation boundary conditions. → Experimental study is supported by 3D simulation. → Effective thermal conductivity of PHPs of the order of 2000 W/mK is obtained. → Efficacy of embedded PHPs depends on the effective Biot number of the system.

  7. AN INVESTMENT SUPPORT STRATEGY FOR HEAT SUPPLY, WATER-SUPPLY AND OVERFLOW-PIPE ENTERPRISES IN UKRAINE

    Directory of Open Access Journals (Sweden)

    L. Blinova

    2013-05-01

    Full Text Available The investment necessities of heat-supply, water-supply and overflow-pipe enterprises are considered in the article. Priority measures for the search of financial sources to satisfy the investment necessities are determined. The most prior and effective financial sources for satisfaction of investment necessities of heat-supply, water-supply and overflow-pipe enterprises are analyzed. The analysis shows that the creation of regional investment funds of functioning and development of housing and public utilities as independent, non-departmental establishments is one of perspective directions in forming of additional profits for providing the concrete prior necessities of enterprises taking into account regional peculiarities. Disparity of housing services, that are supplied by heat-supply, water-supply and overflow-pipe enterprises , to modern world standards predetermine considerable wear of the fixed assets of industry

  8. Effect of Material Property Variations at Near Critical Thermodynamic Conditions on Pipe Flow Heat Transfer

    Science.gov (United States)

    Barney, Rebecca; Nourgaliev, Robert; Delplanque, Jean-Pierre; McCallen, Rose

    2017-11-01

    Heat transfer is quantified and contrasted for the Poiseuille flow of a fluid at both subcritical and supercritical thermodynamic conditions in a circular pipe subject to a uniform wall heat flux. The conditions considered are relevant to Supercritical Water Reactor (SCWR) applications. In the supercritical thermodynamic regime, a fluid can exhibit large density variations of density, thermal conductivity, and viscosity, which will affect flow and heat transfer characteristics significantly. An advanced equation of state for supercritical water was implemented in a 2D and 3D Arbitrary Lagrangian-Eurlerian multi-physics simulation tool called ALE3D developed at Lawrence Livermore National Laboratory. A newly developed, robust, high-order in space and time, fully implicit reconstructed discontinuous Galerkin (rDG) method is used to enable the numerical simulation of convective heat transfer with supercritical water. Results demonstrate the capability of this approach to accurately capture the non-linear behavior and enhanced heat transfer with supercritical water. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Information management release number LLNL-ABS-736004. Work is supported by the Integrated University Program Graduate Fellowship. Opinions, findings, conclusions or recommendations expressed are of the authors and do not necessarily reflect the views of DOE office of NE.

  9. Startup of a frozen heat pipe in one-g and micro-g environments - A proposed shuttle flight experiment

    Science.gov (United States)

    Ochterbeck, J. M.; Peterson, G. P.

    1991-01-01

    An attempt is made to determine how a heat pipe freezes under various low load and/or no load conditions in both one-g and micro-g environments. Also of interest are the mechanisms that can be used to restart the heat pipe after freezing has occurred. Particular attention is given to step function power reductions and the resulting distribution of the working fluid after freezing has occurred and the effect of noncondensible gases on the frozen configuration and the restart characteristics.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Experimental Studies on Grooved Double Pipe Heat Exchanger with Different Groove Space

    Science.gov (United States)

    Sunu, P. W.; Arsawan, I. M.; Anakottapary, D. S.; Santosa, I. D. M. C.; Yasa, I. K. A.

    2018-01-01

    Experimental studies were performed on grooved double pipe heat exchanger (DPHE) with different groove space. The objective of this work is to determine optimal heat transfer parameter especially logarithmic mean temperature difference (LMTD). The document in this paper also provides the total heat observed by the cold fluid. The rectangular grooves were incised on outer surface of tube side with circumferential pattern and two different grooves space, namely 1 mm and 2 mm. The distance between grooves and the grooves high were kept constant, 8 mm and 0.3 mm respectively. The tube diameter is 20 mm and its made of aluminium. The shell is made of acrylic which has 28 mm in diameter. Water is used as the working fluid. Using counter flow scheme, the cold fluid flows in the annulus room of DPHE. The volume flowrate of hot fluid remains constant at 15 lpm. The volume flowrate of cold fluid were varied from 11 lpm to 15 lpm. Based on logarithmic mean temperature difference analysis, the LMTD of 1 mm grooves space was higher compared to that of 2 mm grooves space. The smaller grooves space has more advantage since the recirculating region are increased which essentially cause larger heat transfer enhancement.

  12. Closed loop chemical systems for energy storage and transmission (chemical heat pipe). Final report

    Energy Technology Data Exchange (ETDEWEB)

    Vakil, H.B.; Flock, J.W.

    1978-02-01

    The work documents the anlaysis of closed loop chemical systems for energy storage and transmission, commonly referred to as the Chemical Heat Pipe (CHP). Among the various chemical reaction systems and sources investigated, the two best systems were determined to be the high temperature methane/steam reforming reaction (HTCHP) coupled to a Very High Temperature Gas Cooled Reactor (VHTR) and the lower temperature, cyclohexane dehydrogenation reaction (LTCHP) coupled to existing sources such as coal or light water reactors. Solar and other developing technologies can best be coupled to the LTCHP. The preliminary economic and technical analyses show that both systems could transport heat at an incremental cost of approximately $1.50/GJ/160 km (in excess of the primary heat cost of $2.50/GJ), at system efficiencies above 80%. Solar heat can be transported at an incremental cost of $3/GJ/160 km. The use of the mixed feed evaporator concept developed in this work contributes significantly to reducing the transportation cost and increasing the efficiency of the system. The LTCHP shows the most promise of the two systems if the technical feasibility of the cyclic closed loop chemical reaction system can be established. An experimental program for establishing this feasibility is recommended. Since the VHTR is several years away from commercial demonstration and the HTCHP chemical technology is well developed, future HTCHP programs should be aimed at VHTR and interface problems.

  13. Numerical simulations and analyses of temperature control loop heat pipe for space CCD camera

    Science.gov (United States)

    Meng, Qingliang; Yang, Tao; Li, Chunlin

    2016-10-01

    As one of the key units of space CCD camera, the temperature range and stability of CCD components affect the image's indexes. Reasonable thermal design and robust thermal control devices are needed. One kind of temperature control loop heat pipe (TCLHP) is designed, which highly meets the thermal control requirements of CCD components. In order to study the dynamic behaviors of heat and mass transfer of TCLHP, particularly in the orbital flight case, a transient numerical model is developed by using the well-established empirical correlations for flow models within three dimensional thermal modeling. The temperature control principle and details of mathematical model are presented. The model is used to study operating state, flow and heat characteristics based upon the analyses of variations of temperature, pressure and quality under different operating modes and external heat flux variations. The results indicate that TCLHP can satisfy the thermal control requirements of CCD components well, and always ensure good temperature stability and uniformity. By comparison between flight data and simulated results, it is found that the model is to be accurate to within 1°C. The model can be better used for predicting and understanding the transient performance of TCLHP.

  14. gravity

    Indian Academy of Sciences (India)

    We study the cosmological dynamics for R p exp( λ R ) gravity theory in the metric formalism, using dynamical systems approach. Considering higher-dimensional FRW geometries in case of an imperfect fluid which has two different scale factors in the normal and extra dimensions, we find the exact solutions, and study its ...

  15. Numerical analysis of unsteady conjugate heat transfer for initial evolution of thermal stratification in a curved pipe

    International Nuclear Information System (INIS)

    Jo, Jong Chull; Kim, Wee Kyung; Kim, Yun Il; Cho, Sang Jin; Choi, Seok Ki

    2000-01-01

    A detailed numerical analysis of initial evolution of thermal stratification in a curved pipe with a finite wall thickness is performed. A primary emphasis of the present study is placed on the investigation of the effect of existence of pipe wall thickness on the evolution of thermal stratification. A simple and convenient numerical method of treating the unsteady conjugate heat transfer in Cartesian as well as non-orthogonal coordinate systems is presented. The proposed unsteady conjugate heat transfer analysis method is implemented in a finite volume thermal-hydraulic computer code based on a cell-centered, non-staggered grid arrangement, the SIMPLEC algorithm and a higher-order bounded convection scheme. Calculations are performed for initial evolution of thermal stratification with high Richardson number in a curved pipe. The predicted results show that the thermally stratified flow and transient conjugate heat transfer in a curved pipe with a specified wall thickness can be satisfactorily analyzed by using the numerical method presented in this paper. As the result, the present analysis method is considered to be effective for the determination of transient temperature distributions in the wall of curved piping system subjected to internally thermal stratification. In addition, the method can be extended to be applicable for the simulation of turbulent flow of thermally stratified fluid

  16. One-heater flow-through polymerase chain reaction device by heat pipes cooling.

    Science.gov (United States)

    Chen, Jyh Jian; Liao, Ming Huei; Li, Kun Tze; Shen, Chia Ming

    2015-01-01

    This study describes a novel microfluidic reactor capable of flow-through polymerase chain reactions (PCR). For one-heater PCR devices in previous studies, comprehensive simulations and experiments for the chip geometry and the heater arrangement were usually needed before the fabrication of the device. In order to improve the flexibility of the one-heater PCR device, two heat pipes with one fan are used to create the requisite temperature regions in our device. With the integration of one heater onto the chip, the high temperature required for the denaturation stage can be generated at the chip center. By arranging the heat pipes on the opposite sides of the chip, the low temperature needed for the annealing stage is easy to regulate. Numerical calculations and thermal measurements have shown that the temperature distribution in the five-temperature-region PCR chip would be suitable for DNA amplification. In order to ensure temperature uniformity at specific reaction regions, the Re of the sample flow is less than 1. When the microchannel width increases and then decreases gradually between the denaturation and annealing regions, the extension region located in the enlarged part of the channel can be observed numerically and experimentally. From the simulations, the residence time at the extension region with the enlarged channel is 4.25 times longer than that without an enlarged channel at a flow rate of 2 μl/min. The treated surfaces of the flow-through microchannel are characterized using the water contact angle, while the effects of the hydrophilicity of the treated polydimethylsiloxane (PDMS) microchannels on PCR efficiency are determined using gel electrophoresis. By increasing the hydrophilicity of the channel surface after immersing the PDMS substrates into Tween 20 (20%) or BSA (1 mg/ml) solutions, efficient amplifications of DNA segments were proved to occur in our chip device. To our knowledge, our group is the first to introduce heat pipes into

  17. Heat Transfer in a Loop Heat Pipe Using Fe2NiO4-H2O Nanofluid

    Directory of Open Access Journals (Sweden)

    Gunnasegaran Prem

    2017-01-01

    Full Text Available Nanofluids are stable suspensions of nano fibers and particles in fluids. Recent investigations show that thermal behavior of these fluids, such as improved thermal conductivity and convection coefficients are superior to those of pure fluid or fluid suspension containing larger size particles. The use of enhanced thermal properties of nanofluids in a loop heat pipe (LHP for the cooling of computer microchips is the main aim of this study. Thus, the Fe2NiO4-H2O served as the working fluid with nanoparticle mass concentrations ranged from 0 to 3 % in LHP for the heat input range from 20W to 60W was employed. Experimental apparatus and procedures were designed and implemented for measurements of the surface temperature of LHP. Then, a commercial liquid cooling kit of LHP system similar as used in experimental study was installed in real desktop PC CPU cooling system. The test results of the proposed system indicate that the average decrease of 5.75oC (14% was achieved in core temperatures of desktop PC CPU charged with Fe2NiO4-H2O as compared with pure water under the same operating conditions. The results from this study should find it’s used in many industrial processes in which the knowledge on the heat transfer behavior in nanofluids charged LHP is of uttermost importance.

  18. Detailed study of grooved heat pipes for a system functioning study; Etude fine des caloducs rainures en vue d`une etude systeme

    Energy Technology Data Exchange (ETDEWEB)

    Alexandre, A. [Ecole Nationale Superieure de Mecanique et d`Aerotechnique (ENSMA), 86 - Poitiers (France)

    1996-12-31

    The functioning of a heat pipe is complex. In this paper, a methodology for a detailed analysis of the functioning of a grooved heat pipe is developed in order to obtain the information required for a general analysis of such systems. (J.S.) 3 refs.

  19. Oscillating heat pipe cooler for heat-generating elements of electronics

    Directory of Open Access Journals (Sweden)

    Alekseik E. S.

    2013-02-01

    Full Text Available The article presents a newly-developed compact heat removal system (HRS with water used for coolant, operable in any position in space. In conditions of forced convection at output power of 120 Wt (160 Wt input power thermal resistance of the HRS is 0.1 K/Wt and the system provides the average temperature of the cooled object over the range of 58 to 60°C. Heat transfer characteristics of the HRS can be improved, as there is potential for its modification.

  20. Heat transfer characteristics in a sudden expansion pipe equipped with swirl generators

    International Nuclear Information System (INIS)

    Zohir, A.E.; Abdel Aziz, A.A.; Habib, M.A.

    2011-01-01

    This investigation is aimed at studying the heat transfer characteristics and pressure drop for turbulent airflow in a sudden expansion pipe equipped with propeller type swirl generator or spiral spring with several pitch ratios. The investigation is performed for the Reynolds number ranging from 7500 to 18,500 under a uniform heat flux condition. The experiments are also undertaken for three locations for the propeller fan (N = 15 blades and blade angle of 65 o ) and three pitch ratios for the spiral spring (P/D = 10, 15 and 20). The influences of using the propeller rotating freely and inserted spiral spring on heat transfer enhancement and pressure drop are reported. In the experiments, the swirl generator and spiral spring are used to create a swirl in the tube flow. Mean and relative mean Nusselt numbers are determined and compared with those obtained from other similar cases. The experimental results indicate that the tube with the propeller inserts provides considerable improvement of the heat transfer rate over the plain tube around 1.69 times for X/H = 5. While for the tube with the spiral spring inserts, an improvement of the heat transfer rate over the plain tube around 1.37 times for P/d = 20. Thus, because of strong swirl or rotating flow, the propeller location and the spiral spring pitch become influential on the heat transfer enhancement. The increase in pressure drop using the propeller is found to be three times and for spiral spring 1.5 times over the plain tube. Correlations for mean Nusselt number, fan location and spiral spring pitch are provided.

  1. Thermal behavior of a cryogenic loop heat pipe for space application

    Science.gov (United States)

    Gully, Philippe; Mo, Qing; Yan, Tao; Seyfert, Peter; Guillemet, Laurent; Thibault, Pierre; Liang, Jingtao

    2011-08-01

    This paper discusses a prototype of cryogenic loop heat pipe (CLHP) working around 80 K with nitrogen as the coolant, developed at CEA-SBT in collaboration with the CAS/TIPC and tested in laboratory conditions. In addition to the main loop it features a pressure reduction reservoir and a secondary circuit which allow cooling down the loop from the room temperature conditions to the nitrogen liquid temperature and transferring the evaporator heat leaks and radiation heat loads towards the condenser. The general design, the instrumentation and the experimental results of the thermal response of the CLHP are presented, analyzed and discussed both in the transient phase of cooling from room temperature (i) and in stationary conditions (ii). During phase (i), even in a severe radiation environment, the secondary circuit helped to condense the fluid and was very efficient to chill the primary evaporator. During phase (ii), we studied the effects of transferred power, filling pressure and radiation heat load for two basic configurations of cold reservoir of the secondary circuit. A maximum cold power of 19 W with a corresponding limited temperature difference of 5 K was achieved across a 0.5 m distance. We evidenced the importance of the filling pressure to optimize the thermal response. A small heating power (0.1 W) applied on the shunted cold reservoir allows to maintain a constant subcooling (1 K). The CLHP behaves as a capillary pumped loop (CPL) in such a configuration, with the cold reservoir being the compensation chamber of the thermal link. The radiation heat loads may affect significantly the thermal response of the system due to boiling process of liquid and large mass transfer towards the pressure reduction reservoir.

  2. Micro-Columnated Loop Heat Pipe: The Future of Electronic Substrates

    Science.gov (United States)

    Dhillon, Navdeep Singh

    The modern world is run by semiconductor-based electronic systems. Due to continuous improvements in semiconductor device fabrication, there is a clear trend in the market towards the development of electronic devices and components that not only deliver enhanced computing power, but are also more compact. Thermal management has emerged as the primary challenge in this scenario where heat flux dissipation of electronic chips is increasing exponentially, but conventional cooling solutions such as conduction and convection are no longer feasible. To keep device junction temperatures within the safe operating limit, there is an urgent requirement for ultra-high-conductivity thermal substrates that not only absorb and transport large heat fluxes, but can also provide localized cooling to thermal hotspots. This dissertation describes the design, modeling, and fabrication of a phase change-based, planar, ultra-thin, passive thermal transport system that is inspired by the concept of loop heat pipes and capillary pumped loops. Fabricated on silicon and Pyrex wafers using microfabrication techniques, the micro-columnated loop heat pipe (muCLHP) can be integrated directly with densely packed or multiply-stacked electronic substrates, to provide localized high-heat-flux thermal management. The muCLHP employs a dual-scale coherent porous silicon(CPS)-based micro-columnated wicking structure, where the primary CPS wick provides large capillary forces for fluid transport, while a secondary surface-wick maximizes the rate of thin-film evaporation. To overcome the wick thickness limitation encountered in conventional loop heat pipes, strategies based on MEMS surface micromachining techniques were developed to reduce parasitic heat flow from the evaporator to the compensation chamber of the device. Finite element analysis was used to confirm this reduction in a planar evaporator design, thus enabling the generation of a large motive temperature head for continuous device operation

  3. Ten Year Operating Test Results and Post-Test Analysis of a 1/10 Segment Stirling Sodium Heat Pipe, Phase III

    Science.gov (United States)

    Rosenfeld, John, H; Minnerly, Kenneth, G; Dyson, Christopher, M.

    2012-01-01

    High-temperature heat pipes are being evaluated for use in energy conversion applications such as fuel cells, gas turbine re-combustors, Stirling cycle heat sources; and with the resurgence of space nuclear power both as reactor heat removal elements and as radiator elements. Long operating life and reliable performance are critical requirements for these applications. Accordingly, long-term materials compatibility is being evaluated through the use of high-temperature life test heat pipes. Thermacore, Inc., has carried out a sodium heat pipe 10-year life test to establish long-term operating reliability. Sodium heat pipes have demonstrated favorable materials compatibility and heat transport characteristics at high operating temperatures in air over long time periods. A representative one-tenth segment Stirling Space Power Converter heat pipe with an Inconel 718 envelope and a stainless steel screen wick has operated for over 87,000 hr (10 yr) at nearly 700 C. These life test results have demonstrated the potential for high-temperature heat pipes to serve as reliable energy conversion system components for power applications that require long operating lifetime with high reliability. Detailed design specifications, operating history, and post-test analysis of the heat pipe and sodium working fluid are described.

  4. INVESTIGATIONS ON DESIGN OF HEAT STORAGE PIPE CONNECTIONS FOR SOLAR COMBISYSTEMS

    DEFF Research Database (Denmark)

    Thür, Alexander; Furbo, Simon

    2005-01-01

    This paper describes how different designed pipe connections on a tank for solar combisystems were evaluated based on experimental tests and theoretical investigations with the simulation tool TRNSYS. Measurement results from laboratory measurements were used to calibrate a TRNSYS model....... In general the results showed only very little differences between external connection and internal PEX pipes, if the internal PEX pipes have thick walls. Typically used PEX pipes with only 2 mm wall thickness lead to reduced system performance compared to PEX pipes with 6 mm wall thickness and external pipe...... for simulations with parameter analysis. The possibility to connect pipes at the bottom and use internal PEX pipes to reach the inlet/outlet level in the tank was compared with the possibility to connect the pipe at the side of the tank and pass to the bottom level of the tank inside the tank insulation...

  5. Numerical Simulation of Heat and Flow Behaviors in Butt-fusion Welding Process of HDPE Pipes with Curved Fusion Surface

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jae Hyun; Ahn, Kyung Hyun [Seoul National University, Seoul (Korea, Republic of); Choi, Sunwoong; Oh, Ju Seok [Hannam University, Daejeon (Korea, Republic of)

    2017-08-15

    Butt-fusion welding process is used to join the polymeric pipes. Recently, some researchers suggest the curved surface to enhance a welding quality. We investigated how curved welding surface affects heat and flow behaviors of polymer melt during the process in 2D axisymmetric domain with finite element method, and discussed the effect to the welding quality. In this study, we considered HDPE pipes. In heat soak stage, curved phase interface between the melt and solid is shown along the shape of welding surface. In jointing stage, squeezing flow is generated between curved welding surface and phase interface. The low shear rate in fusion domain reduces the alignment of polymer to the perpendicular direction of pipes, and then this phenomenon is expected to help to enhance the welding quality.

  6. Improvement on thermal performance of a disk-shaped miniature heat pipe with nanofluid.

    KAUST Repository

    Tsai, Tsung-Han

    2011-11-14

    The present study aims to investigate the effect of suspended nanoparticles in base fluids, namely nanofluids, on the thermal resistance of a disk-shaped miniature heat pipe [DMHP]. In this study, two types of nanoparticles, gold and carbon, in aqueous solution are used respectively. An experimental system was set up to measure the thermal resistance of the DMHP with both nanofluids and deionized [DI] water as the working medium. The measured results show that the thermal resistance of DMHP varies with the charge volume and the type of working medium. At the same charge volume, a significant reduction in thermal resistance of DMHP can be found if nanofluid is used instead of DI water.

  7. Balance-of-plant options for the Heat-Pipe Power System

    International Nuclear Information System (INIS)

    Berte, M.; Capell, B.

    1997-09-01

    The Heat-Pipe Power System (HPS) is a near-term, low-cost space fission power system with the potential for utilizing various option for balance-of-plant options. The following options have been studied: a low-power thermoelectric design (14-kWe output), a small Brayton cycle system (60--75 kWe), and a large Brayton cycle system (250 kWe). These systems were analyzed on a preliminary basis, including mass, volume, and structure calculations. These analyses have shown that the HPS system can provide power outputs from 10--250 kWe with specific powers of ∼ 14 W/kg for a 14-kWe model to ∼ 100 W/kg for a 250-kWe model. The system designs considered in this study utilize a common component base to permit easy expansion and development

  8. Characterization of cooling systems based on heat pipe principle to control operation temperature of high-tech electronic components

    International Nuclear Information System (INIS)

    Dobre, Tanase; Parvulescu, Oana Cristina; Stoica, Anicuta; Iavorschi, Gustav

    2010-01-01

    The use of cooling systems based on heat pipe principle to control operation temperature of electronic components is very efficient. They have an excellent miniaturizing capacity and this fact creates adaptability for more practical situations. Starting from the observation that these cooling systems are not precisely characterized from the thermal efficiency point of view, the present paper proposes a methodology of data acquisition for their thermal characterization. An experimental set-up and a data processing algorithm are shown to describe the cooling of a heat generating electronic device using heat pipes. A Thermalright SI-97 PC cooling system is employed as a case-study to determine the heat transfer characteristics of a fins cooler.

  9. Open Loop Heat Pipe Radiator Having a Free-Piston for Wiping Condensed Working Fluid

    Science.gov (United States)

    Weinstein, Leonard M. (Inventor)

    2015-01-01

    An open loop heat pipe radiator comprises a radiator tube and a free-piston. The radiator tube has a first end, a second end, and a tube wall, and the tube wall has an inner surface and an outer surface. The free-piston is enclosed within the radiator tube and is capable of movement within the radiator tube between the first and second ends. The free-piston defines a first space between the free-piston, the first end, and the tube wall, and further defines a second space between the free-piston, the second end, and the tube wall. A gaseous-state working fluid, which was evaporated to remove waste heat, alternately enters the first and second spaces, and the free-piston wipes condensed working fluid from the inner surface of the tube wall as the free-piston alternately moves between the first and second ends. The condensed working fluid is then pumped back to the heat source.

  10. Experimental study on high-power LEDs integrated with micro heat pipe

    Science.gov (United States)

    LI, Cong-ming; Zhou, Chuan-peng; Luo, Yi; Hamidnia, Mohammad; Wang, Xiao-dong; You, Bo

    2016-01-01

    Micro heat pipe (MHP) is applied to implement the efficient heat transfer of light emitting diode (LED) device. The fabrication of MHP is based on micro-electro-mechanical-system (MEMS) technique, 15 micro grooves were etched on one side of silicon (Si) substrate, which was then packaged with aluminum heat sink to form an MHP. On the other side of Si substrate, three LED chips were fixed by die bonding. Then experiments were performed to study the thermal performance of this LED device. The results show that the LED device with higher filling ratio is better when the input power is 1.0 W; with the increase of input power, the optimum filling ratio changes from 30% to 48%, and the time reaching stable state is reduced; when the input power is equal to 2.5 W, only the LED device with filling ratio of 48% can work normally. So integrating MHP into high-power LED device can implement the effective control of junction temperature.

  11. Thermo-hydrodynamics of closed loop pulsating heat pipe: an experimental study

    International Nuclear Information System (INIS)

    Pachghare, Pramod R.; Mahalle, Ashish

    2014-01-01

    The experimental result on the thermal performance of closed loop pulsating heat pipe (CLPHP) is presented. The CLPHP is made of copper capillary tubes, having inner and outer diameters of 2.0 mm and 3.6 mm respectively. The working fluids employed are water, ethanol, methanol and acetone also binary mixture (1:1 by volume) of water-ethanol, water-methanol and water-acetone. For all experimentations, filling ratio (FR) 50%, two-turns and vertical bottom heat mode position was maintained. The lengths of evaporator, condenser and adiabatic section are selected as 42 mm, 50 mm and 170 mm, respectively. The transparent adiabatic section is partially made of glass tube having length 80 mm, for flow visualization. The CFD analysis by VOF model in Star CCM+ simulation is carried out to validate the experimental results. The result shows that the thermal resistance decreases smoothly up to 40W heat input, thereafter reasonably steady. In comparison with all working fluids, water-acetone binary working fluid has shown the best thermal performance over other working fluids used in CLPHPs.

  12. Design and testing of a heat pipe gas combustion system for the STM4-120 Stirling engine

    Science.gov (United States)

    Khalili, K.; Godett, T. M.; Meijer, R. J.; Verhey, R. P.

    Evaporators of a novel geometry, designed to have a more compact size yet the same output as larger, conventional heat pipes, have been fabricated and tested. A technique was developed to calculate capillary pressure required inside the heat pipe. Several quarter- and full-scale evaporators were designed and successfully tested. The burner, film-cooled combustion chamber, and preheater were designed and tested separately. A complete heat pipe gas combustion system (HPGC) was tested, showing an efficiency of 89 percent was measured at 20 kWth. A film-cooled combustion chamber was tested with flame temperatures of 2200 C and wall temperatures below 1000 C using preheated air for film cooling. Also, a full-scale HPGC was tested at an excess of 95 kWth, showing efficiency in the range of 85 to 90 percent under steady-state conditions. Results of transient and startup tests, carried out to evaluate the performance of the heat pipe, all also reported.

  13. Fabrication of an improved tube-to-pipe header heat exchanger for the Fuel Failure Mockup (FFM) Facility

    International Nuclear Information System (INIS)

    Prislinger, J.J.; Jones, R.H.

    1977-05-01

    The procedure used in fabricating an improved tube-to-pipe header heat exchanger for the Fuel Failure Mockup (FFM) Facility is described. Superior performance is accomplished at reduced cost with adherence to the ASME Boiler and Pressure Vessel Code. The techniques used and the method of fabrication are described in detail

  14. Thermal Performance of a Multi-Evaporator Loop Heat Pipe with Thermal Masses and Thermoelectric Coolers

    Science.gov (United States)

    Ku, Jen-Tung; Ottenstein, Laura; Birur, Gajanana

    2004-01-01

    This paper describes thermal performance of a loop heat pipe (LHP) with two evaporators and two condensers in ambient testing. Each evaporator has an outer diameter of 15mm and a length of 76mm, and has an integral compensation chamber (CC). An aluminum mass of 500 grams is attached to each evaporator to simulate the instrument mass. A thermoelectric cooler (TEC) is installed on each CC to provide heating as well as cooling for CC temperature control. A flow regulator is installed in the condenser section to prevent vapor from going back to the evaporators in the event that one of the condensers is fully utilized. Ammonia was used as the working fluid. Tests conducted included start-up, power cycle, heat load sharing, sink temperature cycle, operating temperature control with TECs, and capillary limit tests. Experimental data showed that the loop could start with a heat load of less than 10W even with added thermal masses. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. The operating temperature could be controlled within +/- 0.5K of the set point temperature using either or both TECs, and the required TEC control heater power was less than 2W under most test conditions. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of 120W to 140W, and could recover from a dry-out when the heat load was reduced. The 500-gram aluminum mass on each evaporator had a negligible effect on the loop operation. Existing LHPs servicing orbiting spacecraft have a single evaporator with an outer diameter of about 25mm. Important performance characteristics demonstrated by this LHP included: 1) Operation of an LHP with 15mm diameter evaporators; 2) Robustness and reliability of an LHP with multiple evaporators and multiple condensers under various test conditions; 3) Heat load sharing among LHP evaporators; 4) Effectiveness of TECs in controlling

  15. Heat recovery optimization in a steam-assisted gravity drainage (SAGD) plant

    International Nuclear Information System (INIS)

    Ashrafi, Omid; Navarri, Philippe; Hughes, Robin; Lu, Dennis

    2016-01-01

    Pinch Analysis was used to improve the energy performance of a typical steam-assisted gravity drainage (SAGD) process. The objective of this work was to reduce the amount of natural gas used for steam generation in the plant and the associated greenhouse gas emissions. The INTEGRATION software was used to analyze how heat is being used in the existing design and identify inefficient heat exchanges causing excessive use of energy. Several modifications to improve the base case heat exchanger network (HEN) were identified. The proposed retrofit projects reduced the process heating demands by improving the existing heat recovery system and by recovering waste heat and decreased natural gas consumption in the steam production unit by approximately 40 MW, representing approximately 8% of total consumption. As a result, the amount of glycol used to transfer energy across the facility was also reduced, as well as the electricity consumption related to glycol pumping. It was shown that the proposed heat recovery projects reduced natural gas costs by C$3.8 million/y and greenhouse gas emissions by 61,700 t/y of CO 2 . - Highlights: • A heat integration study using Pinch analysis was performed in a SAGD process. • Several modifications are suggested to improve the existing heat recovery system. • Heat recovery projects increased boiler feed water and combustion air temperatures. • The proposed modifications reduced natural gas use for steam generation. • Heat recovery significantly reduced operating costs and greenhouse gas emissions.

  16. A Pilot Study for Retrospective Evaluation of Cured-in-Place Pipe (CIPP) Rehabilitation of Municipal Gravity Sewers

    Science.gov (United States)

    Pipe rehabilitation and trenchless pipe replacement technologies have seen a steadily increasing use over the past 30 to 40 years. Despite the massive public investment in the rehabilitation of the US water and wastewater infrastructure, there has been little formal and quantita...

  17. Numerical Investigation of the effect of adiabatic section location on thermal performance of a heat pipe network with the application in thermal energy storage systems

    Science.gov (United States)

    Mahdavi, Mahboobe; Tiari, Saeed; Qiu, Songgang

    2015-11-01

    Latent heat thermal energy storage systems benefits from high energy density and isothermal storing process. However, the low thermal conductivity of the phase change material leads to prolong the melting or solidification time. Using a passive device such as heat pipes is required to enhance the heat transfer and to improve the efficiency of the system. In the present work, the performance of a heat pipe network specifically designed for a thermal energy storage system is studied numerically. The network includes a primary heat pipe, which transfers heat received from solar receiver to the heat engine. The excess heat is simultaneously delivered to charge the phase change material via secondary heat pipes. The primary heat pipe composed of a disk shape evaporator, an adiabatic section and a disk shape condenser. The adiabatic section can be either located at the center or positioned outward to the surrounding of the container. Here, the effect of adiabatic section position on thermal performance of the system is investigated. It was concluded that displacing the adiabatic section outwards dramatically increases the average temperatures of the condensers and reduces the thermal resistance of heat pipes.

  18. Experimental performance and parametric analysis of heat pipe heat exchanger for air conditioning application integrated with evaporative cooling

    Science.gov (United States)

    Jadhav, Tushar S.; Lele, Mandar M.

    2017-11-01

    The experimental performance of different heat pipe heat exchanger (HPHX) configurations using distilled water as the working fluid is reported in the present study. The three HPHX configurations in the present investigation include HPHX with single wick structure (HPHX 1), HPHX with composite wick structure (HPHX 2) and hybrid HPHX (HPHX 3) which is the combination of HPHX 1 and HPHX 2. The parameters considered for the parametric analysis of HPHX in all the three configurations are outdoor air dry bulb temperature entering the evaporator section of HPHX (OADBT), return air dry bulb temperature entering the condenser section of HPHX (RADBT), outdoor air velocity (Ve) and return air velocity (Vc). The OADBT is varied between 40 and 24 °C and the outdoor & return air velocities between 0.6 and 2.4 m/s. The parametric analysis of HPHX without evaporative cooling is studied for RADBT = 24 °C whereas RADBT is maintained at 20 °C for the parametric analysis of HPHX integrated with evaporative cooling. In comparison with HPHX without evaporative cooling, the performance of HPHX with evaporative cooling is enhanced by 17% for single wick structure (HPHX 1), 47% for composite wick structure (HPHX 2) and 59% for hybrid HPHX (HPHX 3) for OADBT = 40 °C and at Ve = Vc of 0.6 m/s. The results of the experimental analysis highlights the benefits of HPHX integrated with evaporative cooling for achieving significant energy savings in air conditioning application.

  19. Optimized Heat Pipe Backup Cooling System Tested with a Stirling Convertor

    Science.gov (United States)

    Schwendeman, Carl L.; Tarau, Calin; Schifer, Nicholas A.; Anderson, William G.; Garner, Scott

    2016-01-01

    In a Stirling Radioisotope Power System (RPS), heat must be continuously removed from the General Purpose Heat Source (GPHS) modules to maintain the modules and surrounding insulation at acceptable temperatures. The Stirling convertor normally provides this cooling. If the Stirling convertor stops in the current system, the insulation is designed to spoil, preventing damage to the GPHS at the cost of an early termination of the mission. An alkali-metal variable conductance heat pipe (VCHP) can be used to passively allow multiple stops and restarts of the Stirling convertor by bypassing the heat during stops. In a previous NASA Small Business Innovation Research (SBIR) Program, Advanced Cooling Technologies, Inc. (ACT) developed a series of sodium VCHPs as backup cooling systems for the Stirling RPS. In 2012, one of these VCHPs was successfully tested at NASA Glenn Research Center with a Stirling convertor as an Advanced Stirling Radioisotope Generator (ASRG) backup cooling system. The prototype; however, was not optimized and did not reflect the final heat rejection path. ACT through further funding has developed a semioptimized prototype with the finalized heat path for testing at Glenn with a Stirling convertor. The semioptimized system features a two-phase radiator and is significantly smaller and lighter than the prior prototype to reflect a higher level of flight readiness. The VCHP is designed to activate and remove heat from the GPHS during stoppage with a small temperature increase from the nominal vapor temperature. This small temperature increase from nominal is low enough to avoid risking standard ASRG operation and spoiling of the multilayer insulation (MLI). The VCHP passively allows the Stirling convertor to be turned off multiple times during a mission with potentially unlimited off durations. Having the ability to turn the Stirling off allows for the Stirling to be reset and reduces vibrations on the platform during sensitive measurements or

  20. Experimental study of a novel photovoltaic solar-assisted heat pump/loop heat-pipe (PV-SAHP/LHP) system

    Science.gov (United States)

    Zhang, Tao; Pei, Gang; Zhu, Qunzhi; Ji, Jie

    2017-01-01

    A prototype of a photovoltaic solar-assisted heat-pump/loop heat-pipe system (PV-SAHP/LHP) was constructed in this paper. The system was a combination of photovoltaic solar-assisted heat pump system (PV-SAHP) and loop heat pipe photovoltaic/thermal (LHP-PV/T) system. The combined system can carry out with two modes but using the same working fluid, and the two modes can switch operation freely. R600a was employed as the working fluid, and system performance under different working mode was presented in this paper. The results show that the day average photothermal efficiency & photovoltaic efficiency can reach to 43.6% & 11.3% under LHP-PV/T working mode compared with that of 57.5% & 12.1% under PV-SAHP working mode: Besides that, a day average COP of 3.66 was obtained under PV-SAHP working mode.

  1. Interface engineering to enhance thermal contact conductance of evaporators in miniature loop heat pipe systems

    International Nuclear Information System (INIS)

    Choi, Jeehoon; Sung, Byungho; Kim, Chulju; Borca-Tasciuc, Diana-Andra

    2013-01-01

    While miniature loop heat pipes (mLHP) have significant potential for electronic cooling, they are only used in a narrow niche of applications, such as space or military. Complicated fabrication and system integration leading to high cost devices are the main culprit. To this end, this paper explores a low-cost sintering method for fabricating evaporators for mLHP that have increased heat transfer performance. Through this method, the porous wick of the evaporator is fabricated to partially fill the vapor collection channels embedded in the base plate of the evaporator. The sintering method employs an organic material used to define the vapor collection channels, which is sublimated at the end of the sintering process. Interpenetrating these two, otherwise distinctive, parts of the evaporator results in an increased contact area and thermal conductance. The heat transfer performance of an mLHP employing the new evaporator is compared to that of a system using a standard evaporator configuration, where the porous wick is rested against a flat base plate. It is found that the thermal contact conductance increases about 25%, depending on the applied heat load, while the total thermal resistance of the mLHP with the new evaporator decreases approximately by a factor of two. -- Highlights: • The mLHPs have received attention from academic and industrial communities. • But the complicated fabrication and system integration lead to high cost devices. • Thus these have stunted the advent of commercialization. • We introduce a novel low-cost sintering method for fabricating evaporators. • The mLHP with new evaporator can provide overall cooling at a lower temperature

  2. Thermoelectric Converter for Loop Heat Pipe Temperature Control: Experience and Lessons Learned

    Science.gov (United States)

    Ku, Jentung; Ottenstein, Laura

    2010-01-01

    This paper describes the theoretical background and implementation methodology of using a thermoelectric converter (TEC) for operating temperature control of a loop heat pipe (LHP). In particular, experimental results from ambient and thermal vacuum tests of an LHP are presented for illustrations. The most commonly used state-of-the-art method to control the LHP operating temperature is to cold bias its compensation chamber (CC) and use an electrical heater to maintain the CC at the desired set point temperature. Although effective, this approach has its shortcomings in that the electrical heater can only provide heating to the CC, and the required power can be large under certain conditions. An alternative method is to use a TEC, which is capable of providing both heating and cooling to the CC. In this method, one side of the TEC is attached to the CC, and the other side is connected to the evaporator via a thermal strap. Using a bipolar power supply and a control algorithm, a TEC can function as a heater or a cooler, depending on the direction of the current flow. Extensive ground tests of several LHPs have demonstrated that a TEC can provide very tight temperature control for the CC. It also offers several additional advantages: (1) The LHP can operate at temperatures below its natural operating temperature at low heat loads; (2) The required heater power for a TEC is much less than that for an electrical heater; and (3) It enhances the LHP start-up success. Although the concept of using a TEC for LHP temperature control is simple, there are many factors to be considered in its implementation for space applications because the TEC is susceptible to the shear stress and yet has to sustain the dynamic load under the spacecraft launch environment. The added features that help the TEC to withstand the dynamic load will inevitably affect the TEC thermal performance. Some experiences and lessons learned are addressed in this paper.

  3. Explicit solutions of a gravity-induced film flow along a convectively heated vertical wall.

    Science.gov (United States)

    Raees, Ammarah; Xu, Hang

    2013-01-01

    The gravity-driven film flow has been analyzed along a vertical wall subjected to a convective boundary condition. The Boussinesq approximation is applied to simplify the buoyancy term, and similarity transformations are used on the mathematical model of the problem under consideration, to obtain a set of coupled ordinary differential equations. Then the reduced equations are solved explicitly by using homotopy analysis method (HAM). The resulting solutions are investigated for heat transfer effects on velocity and temperature profiles.

  4. The Impact of Reduced Gravity on Free Convective Heat Transfer from a Finite, Flat, Vertical Plate

    Science.gov (United States)

    Lotto, Michael A.; Johnson, Kirstyn M.; Nie, Christopher W.; Klaus, David M.

    2017-10-01

    Convective heat transfer is governed by a number of factors including various fluid properties, the presence of a thermal gradient, geometric configuration, flow condition, and gravity. Empirically-derived analytical relationships can be used to estimate convection as a function of these governing parameters. Although it is relatively straightforward to experimentally quantify the contributions of the majority of these variables, it is logistically difficult to assess the influence of reduced-gravity due to practical limitations of establishing this environment. Therefore, in order to explore this regime, a series of tests was conducted to evaluate convection under reduced-gravity conditions averaging 0.45 m/sec2 (0.05 g) achieved aboard a parabolic aircraft. The results showed a reduction in net heat transfer of approximately 61% in flight relative to a 1 g terrestrial baseline using the same setup. The average experimental Nusselt Number of 19.05 ± 1.41 statistically correlated with the predicted value of 18.90 ± 0.63 (N = 13), estimated using the Churchill-Chu correlation for free convective heat transfer from a finite, flat, vertical plate. Extrapolating this to similar performance in true microgravity (10-6 g) indicates that these conditions should yield a Nusselt Number of 1.27, which is 2.6% the magnitude of free convection at 1 g, or a reduction of 97.4%. With advection essentially eliminated, heat transfer becomes limited to diffusion and radiation, which are gravity-independent and nearly equivalent in magnitude in this case. These results offer a general guideline for integrating components that utilize natural (free) convective gas cooling in a spacecraft habitat and properly sizing the thermal control system.

  5. Temperature Control with Two Parallel Small Loop Heat Pipes for GLM Program

    Science.gov (United States)

    Khrustalev, Dmitry; Stouffer, Chuck; Ku, Jentung; Hamilton, Jon; Anderson, Mark

    2014-01-01

    The concept of temperature control of an electronic component using a single Loop Heat Pipe (LHP) is well established for Aerospace applications. Using two LHPs is often desirable for redundancy/reliability reasons or for increasing the overall heat source-sink thermal conductance. This effort elaborates on temperature controlling operation of a thermal system that includes two small ammonia LHPs thermally coupled together at the evaporator end as well as at the condenser end and operating "in parallel". A transient model of the LHP system was developed on the Thermal Desktop (TradeMark) platform to understand some fundamental details of such parallel operation of the two LHPs. Extensive thermal-vacuum testing was conducted with two thermally coupled LHPs operating simultaneously as well as with only one LHP operating at a time. This paper outlines the temperature control procedures for two LHPs operating simultaneously with widely varying sink temperatures. The test data obtained during the thermal-vacuum testing, with both LHPs running simultaneously in comparison with only one LHP operating at a time, are presented with detailed explanations.

  6. Thermal performance of a small-scale loop heat pipe for terrestrial application

    International Nuclear Information System (INIS)

    Chung, Won Bok; Boo, Joon Hong

    2004-01-01

    A small-scale loop heat pipe with polypropylene wick was fabricated and tested for its thermal performance. The container and tubing of the system was made of stainless steel and several working fluids were used to see the difference in performance including methanol, ethanol, acetone, R134a, and water. The heating area was 35 mm x 35 mm and there were nine axial grooves in the evaporator to provide a vapor passage. The pore size of the polypropylene wick inside the evaporator was varied from 0.5 m to 25 m. The size of condenser was 40 mm (W) x 50 mm (L) in which ten coolant paths were provided. The inner diameter of liquid and vapor transport lines were 2.0 mm and 4.0 mm, respectively and the length of which were 0.5 m. The PP wick LHP was operated with methanol, acetone, and ethanol normally. R134a was not compatible with PP wick and water was unsuitable within operating limit of 100 .deg. C. The minimum thermal load of 10 W (0.8 W/cm 2 ) and maximum thermal load of 80 W (6.5 W/cm 2 ) were achieved using methanol as working fluid with the condenser temperature of 20 .deg. C with horizontal position

  7. New encapsulation method using low-melting-point alloy for sealing micro heat pipes

    International Nuclear Information System (INIS)

    Li, Congming; Wang, Xiaodong; Zhou, Chuanpeng; Luo, Yi; Li, Zhixin; Li, Sidi

    2017-01-01

    This study proposed a method using Low-melting-point alloy (LMPA) to seal Micro heat pipes (MHPs), which were made of Si substrates and glass covers. Corresponding MHP structures with charging and sealing channels were designed. Three different auxiliary structures were investigated to study the sealability of MHPs with LMPA. One structure is rectangular and the others are triangular with corner angles of 30° and 45°, respectively. Each auxiliary channel for LMPA is 0.5 mm wide and 135 μm deep. LMPA was heated to molten state, injected to channels, and then cooled to room temperature. According to the material characteristic of LMPA, the alloy should swell in the following 12 hours to form strong interaction force between LMPA and Si walls. Experimental results show that the flow speed of liquid LMPA in channels plays an important role in sealing MHPs, and the sealing performance of triangular structures is always better than that of rectangular structure. Therefore, triangular structures are more suitable in sealing MHPs than rectangular ones. LMPA sealing is a plane packaging method that can be applied in the thermal management of high-power IC device and LEDs. Meanwhile, implanting in commercialized fabrication of MHP is easy.

  8. New encapsulation method using low-melting-point alloy for sealing micro heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Congming; Wang, Xiaodong; Zhou, Chuanpeng; Luo, Yi; Li, Zhixin; Li, Sidi [Dalian University of Technology, Dalian (China)

    2017-06-15

    This study proposed a method using Low-melting-point alloy (LMPA) to seal Micro heat pipes (MHPs), which were made of Si substrates and glass covers. Corresponding MHP structures with charging and sealing channels were designed. Three different auxiliary structures were investigated to study the sealability of MHPs with LMPA. One structure is rectangular and the others are triangular with corner angles of 30° and 45°, respectively. Each auxiliary channel for LMPA is 0.5 mm wide and 135 μm deep. LMPA was heated to molten state, injected to channels, and then cooled to room temperature. According to the material characteristic of LMPA, the alloy should swell in the following 12 hours to form strong interaction force between LMPA and Si walls. Experimental results show that the flow speed of liquid LMPA in channels plays an important role in sealing MHPs, and the sealing performance of triangular structures is always better than that of rectangular structure. Therefore, triangular structures are more suitable in sealing MHPs than rectangular ones. LMPA sealing is a plane packaging method that can be applied in the thermal management of high-power IC device and LEDs. Meanwhile, implanting in commercialized fabrication of MHP is easy.

  9. Analytical and experimental stiffness estimation of heat pipe supporter for nuclear power plant through a homogenization process

    Directory of Open Access Journals (Sweden)

    Sang-Young Kim

    2015-07-01

    Full Text Available This article aims to study the in-plane stiffness estimation of heat pipe supporter (a large lattice structure using experimental and numerical methods. The in-plane stiffness of heat pipe supporter for nuclear power plant is very important because of the safety against natural disasters, such as seismic load or tsunami, and has to be evaluated because it greatly affects the durability of the heat exchanger. However, the modeling process of the whole lattice structure for finite element analysis increases resources needed caused by too many nodes and elements. In this study, the mechanical properties of large lattice structures are determined by a unit cell finite element analysis. The mechanical behavior of a large lattice structure has been estimated by finite element analysis through a homogenization process for reducing analysis time and efforts. The finite element analysis results have been verified and show a good agreement with the experimental results.

  10. Analytical study of the liquid phase transient behavior of a high temperature heat pipe. M.S. Thesis

    Science.gov (United States)

    Roche, Gregory Lawrence

    1988-01-01

    The transient operation of the liquid phase of a high temperature heat pipe is studied. The study was conducted in support of advanced heat pipe applications that require reliable transport of high temperature drops and significant distances under a broad spectrum of operating conditions. The heat pipe configuration studied consists of a sealed cylindrical enclosure containing a capillary wick structure and sodium working fluid. The wick is an annular flow channel configuration formed between the enclosure interior wall and a concentric cylindrical tube of fine pore screen. The study approach is analytical through the solution of the governing equations. The energy equation is solved over the pipe wall and liquid region using the finite difference Peaceman-Rachford alternating direction implicit numerical method. The continuity and momentum equations are solved over the liquid region by the integral method. The energy equation and liquid dynamics equation are tightly coupled due to the phase change process at the liquid-vapor interface. A kinetic theory model is used to define the phase change process in terms of the temperature jump between the liquid-vapor surface and the bulk vapor. Extensive auxiliary relations, including sodium properties as functions of temperature, are used to close the analytical system. The solution procedure is implemented in a FORTRAN algorithm with some optimization features to take advantage of the IBM System/370 Model 3090 vectorization facility. The code was intended for coupling to a vapor phase algorithm so that the entire heat pipe problem could be solved. As a test of code capabilities, the vapor phase was approximated in a simple manner.

  11. Flow patterns and heat transfer characteristics of flat plate pulsating heat pipes with various asymmetric and aspect ratios of the channels

    International Nuclear Information System (INIS)

    Jang, Dong Soo; Lee, Joo Seong; Ahn, Jae Hwan; Kim, Dongwoo; Kim, Yongchan

    2017-01-01

    Highlights: • Flat plate pulsating heat pipes with asymmetric and aspect ratios were tested. • Flow patterns were investigated according to channel geometry and flow condition. • Heat transfer characteristics were analyzed with various heat inputs. • Optimum asymmetric and aspect ratios were suggested for maximum thermal performance. - Abstract: The thermal performance of flat plate pulsating heat pipes (PHPs) in compact electronic devices can be improved by adopting asymmetric channels with increased pressure differences and an unbalanced driving force. The objective of this study is to investigate the heat transfer characteristics of flat plate PHPs with various asymmetric ratios and aspect ratios in the channels. The thermal performance and flow pattern of the flat plate PHPs were measured by varying the asymmetric ratio from 1.0 to 4.0, aspect ratio from 2.5 to 5.0, and heat input from 2 to 28 W. The effects of the asymmetric ratio and aspect ratio on the thermal resistance were analyzed with the measured evaporator temperature and flow patterns at various heat inputs. With heat inputs of 6 W and 12 W, the optimum asymmetric ratio and aspect ratio for the flat plate PHPs were determined to be 4.0 and 2.5, respectively. With the heat input of 18 W, the optimum asymmetric ratio and aspect ratio were determined to be 1.5 and 2.5, respectively.

  12. An experimental investigation of the interfacial condensation heat transfer in steam/water countercurrent stratified flow in a horizontal pipe

    Energy Technology Data Exchange (ETDEWEB)

    Chu, In Cheol; Yu, Seon Oh; Chun, Moon Hyun [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of); Kim, Byong Sup; Kim, Yang Seok; Kim, In Hwan; Lee, Sang Won [Korea Electric Power Research Institute, Taejon (Korea, Republic of)

    1998-12-31

    An interfacial condensation heat transfer phenomenon in a steam/water countercurrent stratified flow in a nearly horizontal pipe has been experimentally investigated. The present study has been focused on the measurement of the temperature and velocity distributions within the water layer. In particular, the water layer thickness used in the present work is large enough so that the turbulent mixing is limited and the thermal stratification is established. As a result, the thermal resistance of the water layer to the condensation heat transfer is increased significantly. An empirical correlation of the interfacial condensation heat transfer has been developed. The present correlation agrees with the data within {+-} 15%. 5 refs., 6 figs. (Author)

  13. Development and characterization of high collapse boron alloys heat treated pipes for oil wells; Tubos de aco TiB para aplicacao em revestimento de pocos de petroleo

    Energy Technology Data Exchange (ETDEWEB)

    Moreira, Fabio A.; Silva, Ronaldo; Chad, Luis [Tenaris Confab, Pindamonhangaba SP (Brazil); Fritz, Marcelo C. [Tenaris Confab, Pindamonhangaba SP (Brazil). Dept. de Engenharia do Produto

    2008-07-01

    The utilization of OCTG (Oil Country Tubular Goods) pipes will increase with the discovery of new oil wells in ultra deep waters. This study aims to evaluate the mechanical and microstructural performance of welded and heat treated pipes through quenching and tempering using a steel project based in titanium/boron for casing pipes. The objective of this development is to present a set of techniques used during the manufacturing of heated treated ERW pipes boron allowing, discussing mechanical and metallurgical aspects of the steel project, coil conformation, heat treatment and test procedures. The results are within the limits set by the API 5CT standard. It was found that the pipes obtained good geometry and uniformity of mechanical properties, showing that this product can be applied safely and reliability as wells' casing. (author)

  14. On the spectrum of vertically propagating gravity waves generated by a transient heat source

    Directory of Open Access Journals (Sweden)

    M. J. Alexander

    2004-01-01

    Full Text Available It is commonly believed that cumulus convection preferentially generates gravity waves with tropospheric vertical wavelengths approximately twice the depth of the convective heating. Individual cumulonimbus, however, act as short term transient heat sources (duration 10 to 30min. Gravity waves generated by such sources have broad frequency spectra and a wide range of vertical scales. The high-frequency components tend to have vertical wavelengths much greater than twice the depth of the heating. Such waves have large vertical group velocities, and are only observed for a short duration and at short horizontal distances from the convective source. At longer times and longer distances from the source the dominant wave components have short vertical wavelengths and much slower group velocities, and thus are more likely to be observed even though their contribution to the momentum flux in the upper stratosphere and mesosphere may be less than that of the high frequency waves. These properties of convectively generated waves are illustrated by a linear numerical model for the wave response to a specified transient heat source. The wave characteristics are documented through Fourier and Wavelet analysis, and implications for observing systems are discussed.

  15. A study on heat transfer through the fin-wick structure mounted in the evaporator for a plate loop heat pipe system

    International Nuclear Information System (INIS)

    Nguyen, Xuan Hung; Sung, Byung Ho; Choi, Jee Hoon; Kim, Chul Ju; Yoo, Jung Hyung; Seo, Min Whan

    2008-01-01

    This paper investigates the plate loop heat pipe system with an evaporator mounted with fin-wick structure to dissipate effectively the heat generated by the electronic components. The heat transfer formulation is modeled and predicted through thermal resistance analysis of the fin-wick structure in the evaporator. The experimental approach measures the thermal resistances and the operating characteristics. These results gathered in this investigation have been used to the objective of the information to improve the LHP system design so as to apply as the future cooling devices of the electronic components

  16. Effects of design variables predicted by a steady - state thermal performance analysis model of a loop heat pipe

    International Nuclear Information System (INIS)

    Jung, Eui Guk; Boo, Joon Hong

    2008-01-01

    This study deals with a mathematical modeling for the steady-state temperature characteristics of an entire loop heat pipe. The lumped layer model was applied to each node for temperature analysis. The flat type evaporator and condenser in the model had planar dimensions of 40 mm (W) x 50 mm (L). The wick material was a sintered metal and the working fluid was methanol. The molecular kinetic theory was employed to model the phase change phenomena in the evaporator and the condenser. Liquid-vapor interface configuration was expressed by the thin film theories available in the literature. Effects of design factors of loop heat pipe on the thermal performance were investigated by the modeling proposed in this study

  17. Numerical analysis of pulsating heat pipe based on separated flow model

    International Nuclear Information System (INIS)

    Kim, Jong Soo; Im, Yong Bin; Bui, Ngoc Hung

    2005-01-01

    The examination on the operating mechanism of a Pulsating Heat Pipe (PHP) using visualization revealed that the working fluid in the PHP oscillated to the axial direction by the contraction and expansion of vapor plugs. This contraction and expansion is due to the formation and extinction of bubbles in the evaporating and condensing section, respectively. In this paper, a theoretical model of PHP was presented. The theoretical model was based on the separated flow model with two liquid slugs and three vapor plugs. The results show that the diameter, surface tension and charge ratio of working fluid have significant effects on the performance of the PHP. The following conclusions were obtained. The periodic oscillations of liquid slugs and vapor plugs were obtained under specified parameters. When the hydraulic diameter of the PHP was increased to d=3 mm, the frequency of oscillation decreased. By increasing the charging ratio from 40 to 60 by volume ratio, the pressure difference between the evaporating section and condensing section increased, the amplitude of oscillation reduced, and the oscillation frequency decreased. The working fluid with higher surface tension resulted in an increase in the amplitude and frequency of oscillation. Also the average temperature of vapor plugs decreased

  18. Thermal behavior of heat-pipe-assisted alkali-metal thermoelectric converters

    Science.gov (United States)

    Lee, Ji-Su; Lee, Wook-Hyun; Chi, Ri-Guang; Chung, Won-Sik; Lee, Kye-Bock; Rhi, Seok-Ho; Jeong, Seon-Yong; Park, Jong-Chan

    2017-11-01

    The alkali-metal thermal-to-electric converter (AMTEC) changes thermal energy directly into electrical energy using alkali metals, such as sodium and potassium, as the working fluid. The AMTEC system primarily consists of beta-alumina solid electrolyte (BASE) tubes, low and high-pressure chambers, an evaporator, and a condenser and work through continuous sodium circulation, similar to conventional heat pipes. When the sodium ions pass through the BASE tubes with ion conductivity, this ion transfer generates electricity. The efficiency of the AMTEC directly depends on the temperature difference between the top and bottom of the system. The optimum design of components of the AMTEC, including the condenser, evaporator, BASE tubes, and artery wick, can improve power output and efficiency. Here, a radiation shield was installed in the low-pressure chamber of the AMTEC and was investigated experimentally and numerically to determine an optimum design for preventing radiation heat loss through the condenser and the wall of AMTEC container. A computational fluid dynamics (CFD) simulation was carried out to decide the optimum size of the low-pressure chamber. The most suitable height and diameter of the chamber were 270 mm and 180 mm, respectively, with eight BASE tubes, which were 150 mm high, 25 mm in diameter, and 105 mm in concentric diameter. Increasing the temperature ratio ( T Cond /T B ) led to high power output. The minimum dimensionless value (0.4611) for temperature ( T Cond /T B ) appeared when the radiation shield was made of 500-mesh nickel. Simulation results for the best position and shape for the radiation shield, revealed that maximum power was generated when a stainless steel shield was installed in between the BASE tubes and condenser.

  19. NASA Glenn Steady-State Heat Pipe Code GLENHP: Compilation for 64- and 32-Bit Windows Platforms

    Science.gov (United States)

    Tower, Leonard K.; Geng, Steven M.

    2016-01-01

    A new version of the NASA Glenn Steady State Heat Pipe Code, designated "GLENHP," is introduced here. This represents an update to the disk operating system (DOS) version LERCHP reported in NASA/TM-2000-209807. The new code operates on 32- and 64-bit Windows-based platforms from within the 32-bit command prompt window. An additional evaporator boundary condition and other features are provided.

  20. A new method for the determination of thermal properties of the insulation material used in district heating pipes; Ny metod foer att bestaemma fjaerrvaermeroers isoleringsfoermaaga

    Energy Technology Data Exchange (ETDEWEB)

    Adl-Zarrabi, Bijan [SP Swedish National Testing and Research Inst., Boraas (Sweden)

    2005-07-01

    Thermal resistance of district heat pipes declines during its lifetime and this leads to increased thermal losses. To be able to change the insufficient pipes in right time has a large economical impact. The conventional measurement techniques for determinations of thermal properties of insulation of the pipe are abusive and expensive. In the present project the 'Transient Plan Source' TPS-method has been studied as an alternative method. TPS-method can be used in the field and measurements are not time demanding. Thermal conductivity of district heating pipe (polyurethane foam) is measured at 20 deg C and 50 deg C with Transient Plane Source (TPS) method. Three different setups were investigated. In one of the setups the TPS sensor is embedded in the insulation of district heating pipe. Comparison between measured results and the reference value showed that the measured results by TPS method were higher than reference values. It may depend on a number of different parameters, for example TPS method measure bulk properties and the reference value is an apparent value. Relative change of thermal conductivity per Celsius degree of temperature was in the same level as reference value. It is possible to embed the TPS sensor in the insulation of the district heating pipes. The measured relative change of conductivity was in the same range as the reference value. Thus, TPS method can be used for control measurements concerning the insulation properties of district heating pipes in the field and in service.

  1. Fabrication of silicon micro heat pipes for cooling electronics; Realisation de microcaloducs en silicium pour le refroidissement de l'electronique

    Energy Technology Data Exchange (ETDEWEB)

    Launay, St.; Sartre, V.; Lallemand, M. [Institut National des Sciences Appliquees (INSA), Centre Thermique de Lyon (UMR CNRS 5008), 69 - Lyon (France); Le Berre, M.; Barbier, D. [Institut National des Sciences Appliquees (INSA), Lab. de Physique de la Matiere, 69 - Villeurbanne (France); Morfouli, P.; Boussey, J. [Institut National Polytechnique, Lab. de Microelectronique, Electromagnetisme et Photonique (UMR 5130) 38 - Grenoble (France)

    2003-07-01

    In this study, micro heat pipe arrays etched into silicon wafers were investigated, for electronic cooling purposes. Micro heat pipes of triangular cross-section (230 {mu}m width) and with liquid arteries were fabricated by wet anisotropic etching in a KOH solution. The microchannels were closed by molecular bonding of a plain wafer with the grooved one. Two test benches were developed for the micro heat pipe filling and thermal characterisation. The temperature profile at the silicon surface was deduced from experimental measurements and a 3D numerical simulation. The results have shown that with the artery micro heat pipe array, the effective thermal conductivity of the silicon wafer was improved by 330 %. (authors)

  2. Gravity crustal models and heat flow measurements for the Eurasia Basin, Arctic Ocean

    Science.gov (United States)

    Urlaub, Morelia; Schmidt-Aursch, Mechita C.; Jokat, Wilfried; Kaul, Norbert

    2009-12-01

    The Gakkel Ridge in the Arctic Ocean with its adjacent Nansen and Amundsen Basins is a key region for the study of mantle melting and crustal generation at ultraslow spreading rates. We use free-air gravity anomalies in combination with seismic reflection and wide-angle data to compute 2-D crustal models for the Nansen and Amundsen Basins in the Arctic Ocean. Despite the permanent pack-ice cover two geophysical transects cross both entire basins. This means that the complete basin geometry of the world’s slowest spreading system can be analysed in detail for the first time. Applying standard densities for the sediments and oceanic crystalline crust, the gravity models reveal an unexpected heterogeneous mantle with densities of 3.30 × 103, 3.20 × 103 and 3.10 × 103 kg/m3 near the Gakkel Ridge. We interpret that the upper mantle heterogeneity mainly results from serpentinisation and thermal effects. The thickness of the oceanic crust is highly variable throughout both transects. Crustal thickness of less than 1 km dominates in the oldest parts of both basins, increasing to a maximum value of 6 km near the Gakkel Ridge. Along-axis heat flow is highly variable and heat flow amplitudes resemble those observed at fast or intermediate spreading ridges. Unexpectedly, high heat flow along the Amundsen transect exceeds predicted values from global cooling curves by more than 100%.

  3. Follow-up investigations of GPHS motion during heat pulse intervals of reentries from gravity-assist trajectories

    International Nuclear Information System (INIS)

    Sharbaugh, R.C.

    1992-01-01

    Motion studies of the General Purpose Heat Source Module, GPHS, which were conducted in the heat pulse intervals associated with entries from earth gravity assist trajectories. The APL six-degree-of-freedom reentry program designated TMAGRA6C was used. The objectives of the studies were to (1) determine whether the GPHS module entering the earth's atmosphere from an earth-gravity-assist trajectory has a preferred orientation during the heat pulse of reentry, (2) determine the effect of magnus force on the roll rate and angle of attack of the GPHS during an EGA entry, (3) determine the effect of the magnitude of pitch and roll damping on the GPHS motion

  4. Experimental validation of an analytical model for predicting the thermal and hydrodynamic capabilities of flat micro heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Revellin, Remi; Rulliere, Romuald [Centre de Thermique de Lyon (CETHIL), UMR5008, CNRS-INSA-Univ. Lyon 1, Bat. Sadi Carnot, INSA-Lyon, F-69621 Villeurbanne Cedex (France); Lefevre, Frederic [Centre de Thermique de Lyon (CETHIL), UMR5008, CNRS-INSA-Univ. Lyon 1, Bat. Sadi Carnot, INSA-Lyon, F-69621 Villeurbanne Cedex (France)], E-mail: frederic.lefevre@insa-lyon.fr; Bonjour, Jocelyn [Centre de Thermique de Lyon (CETHIL), UMR5008, CNRS-INSA-Univ. Lyon 1, Bat. Sadi Carnot, INSA-Lyon, F-69621 Villeurbanne Cedex (France)

    2009-04-15

    An analytical model by Lefevre and Lallemand [F. Lefevre, M. Lallemand, Coupled thermal and hydrodynamic models of flat micro heat pipes for the cooling of multiple electronic components, Int. J. Heat Mass Transfer 49 (2006) 1375-1383] that couples a 2D hydrodynamic model for both the liquid and the vapor phases inside a flat micro heat pipe (FMHP) and a 3D thermal model of heat conduction inside the FMHP wall has been modified. It consists of superposing two independent solutions in order to take into account the impact of evaporation or condensation on the equivalent thermal conductivity of the capillary structure. The temperature, pressure and velocity fields can be determined using Fourier solutions. The model has been experimentally validated based on literature data from a grooved FMHP. Two new correlations for the equivalent thermal conductivities during evaporation and condensation inside rectangular micro-grooves have been proposed based on a numerical database. The influence of the saturation temperature and geometry on the maximum heat flux transferred by the system is presented.

  5. Experience of measuring wall thicknesses of district heating pipes in use with free-floating salamanders (pigs)

    International Nuclear Information System (INIS)

    Barbian, O.A.; Goedecke, H.; Krieg, W.

    1992-01-01

    A test system for district heating pipes (laid above ground or in the ground or in the offshore field) is introduced, a so-called 'intelligent' test 'pig' which, like in a pneumatic tube, floats through the pipe with the medium during operation and finds out any corrosion damage. The equipment works on the principle of ultrasonic wall thickness testing in immersed technique, and is equipped with a large number of test heads in order to scan the pipe surface completely in one run-through. The data processing in the pig with the aid of microprocessors and the type of data collection in mass memories is briefly described. The test results are clearly shown by coloured graphics, which makes efficient assessment and evaluation of the faults possible. The ability of the system to supply information (data collection, data storage, assessment and evaluation) is demonstrated by a series of typical faults, which were found worldwide in oil and gas pipes. (orig./HP) [de

  6. Development and Evaluation of Active Thermal Management System for Lithium-Ion Batteries using Solid-State Thermoelectric Heat Pump and Heat Pipes with Electric Vehicular Applications

    Science.gov (United States)

    Parekh, Bhaumik Kamlesh

    Lithium-Ion batteries have become a popular choice for use in energy storage systems in electric vehicles (EV) and Hybrid electric vehicles (HEV) because of high power and high energy density. But the use of EV and HEV in all climates demands for a battery thermal management system (BTMS) since temperature effects their performance, cycle life and, safety. Hence the BTMS plays a crucial role in the performance of EV and HEV. In this paper, three thermal management systems are studied: (a) simple aluminum as heat spreader material, (b) heat pipes as heat spreader, and (c) advanced combined solid state thermoelectric heat pump (TE) and heat pipe system; these will be subsequently referred to as Design A, B and C, respectively. A detailed description of the designs and the experimental setup is presented. The experimental procedure is divided into two broad categories: Cooling mode and Warming-up mode. Cooling mode covers the conditions when a BTMS is responsible to cool the battery pack through heat dissipation and Warming-up mode covers the conditions when the BTMS is responsible to warm the battery pack in a low temperature ambient condition, maintaining a safe operating temperature of the battery pack in both modes. The experimental procedure analyzes the thermal management system by evaluating the effect of each variable like heat sink area, battery heat generation rate, cooling air temperature, air flow rate and TE power on parameters like maximum temperature of the battery pack (T max), maximum temperature difference (DeltaT) and, heat transfer through heat sink/cooling power of TE (Q c). The results show that Design C outperforms Design A and Design B in spite of design issues which reduce its efficiency, but can still be improved to achieve better performance.

  7. Developing a theoretical model to investigate thermal performance of a thin membrane heat-pipe solar collector

    International Nuclear Information System (INIS)

    Riffat, S.B.; Zhao, X.; Doherty, P.S.

    2005-01-01

    A thin membrane heat-pipe solar collector was designed and constructed to allow heat from solar radiation to be collected at a relatively high efficiency while keeping the capital cost low. A theoretical model incorporating a set of heat balance equations was developed to analyse heat transfer processes occurring in separate regions of the collector, i.e., the top cover, absorber and condenser/manifold areas, and examine their relationship. The thermal performance of the collector was investigated using the theoretical model. The modelling predictions were validated using the experimental data from a referred source. The test efficiency was found to be in the range 40-70%, which is a bitter lower than the values predicted by modelling. The factors influencing these results were investigated

  8. Effect of various refining processes for Kenaf Bast non-wood pulp fibers suspensions on heat transfer coefficient in circular pipe heat exchanger

    Science.gov (United States)

    Ahmed, Syed Muzamil; Kazi, S. N.; Khan, Ghulamullah; Sadri, Rad; Dahari, Mahidzal; Zubir, M. N. M.; Sayuti, M.; Ahmad, Pervaiz; Ibrahim, Rushdan

    2018-03-01

    Heat transfer coefficients were obtained for a range of non-wood kenaf bast pulp fiber suspensions flowing through a circular pipe heat exchanger test loop. The data were produced over a selected temperature and range of flow rates from the flow loop. It was found that the magnitude of the heat transfer coefficient of a fiber suspension is dependent on characteristics, concentration and pulping method of fiber. It was observed that at low concentration and high flow rates, the heat transfer coefficient values of suspensions were observed higher than that of the heat transfer coefficient values of water, on the other hand the heat transfer coefficient values of suspensions decreases at low flow rates and with the increase of their concentration. The heat transfer were affected by varying fiber characteristics, such as fiber length, fiber flexibility, fiber chemical and mechanical treatment as well as different pulping methods used to liberate the fibers. Heat transfer coefficient was decreased with the increase of fiber flexibility which was also observed by previous researchers. In the present work, the characteristics of fibers are correlated with the heat transfer coefficient of suspensions of the fibers. Deviations in fiber properties can be monitored from the flowing fiber suspensions by measuring heat transfer coefficient to adjust the degree of fiber refining treatment so that papers made from those fibers will be more uniform, consistent, within the product specification and retard the paper production loss.

  9. Development of a sodium heat pipe solar receiver with hybrid drive for dish/Stirling systems for decentralised electricity supply. Final report; Entwicklung eines hybridbetriebenen Natrium-Heat Pipe Solarreceivers fuer Dish/Stirling-Systeme zur dezentralen Stromversorgung. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Laing, D.

    1997-03-01

    After detailed concept studies, a hybrid heat pipe receiver was developed, in which the heat is transferred both on the gas and the solar side only via a heat pipe. The concentrated solar radiation is absorbed on the inner cylinder of a coaxial heat pipe. A diffusion gas blower burner (a modification of the SPS burner originally used for the gas operation of the V160 Stirling engine) is situated axially behind the heat pipe. The exhaust gases flow axially over the finned outer cylinder of the heat pipe, which is simultaneously the heat exchanger for the heat pipe. An impact plate divides the receiver hollow space from the combustion chamber. The receiver is designed for a transfer power of 35 KW{sub th} at an operating temperature of 700 to 850 degrees C. The design of the capillary structure was done by the (German) Research Institute for Nuclear Technology and Energy Conversion (KE). The receiver was manufactured in collaboration with KE. The superimposition of the Stirling heater tube with the heat exchanger fins proved to be very difficult. The receiver was successfully tested in DISCOS for about 60 hours. The working behaviour of the receiver was very good. Neither the switching in the burner in solar operation nor the focussing or re-introduction of the solar radiation after passing clouds; during burner operation, represented a problem for the receiver. The heat pipe functioned without problems in every operating mode. Peak nett system efficiencies of 20% were obtained in purely gas operation and a combustion efficiency of 92% and a receiver efficiency of 83% were obtained. [Deutsch] Nach ausfuehrlichen Konzeptstudien wurde ein hybrider Heat Pipe Receiver entwickelt, bei dem die Waerme sowohl gas- als auch solarseitig ueber nur ein Waermerohr uebertragen wird. Die konzentrierte Solarstrahlung wird auf dem inneren Zylinder des koaxialen Waermerohrs absorbiert. Ein Diffusions-Gasgeblaesebrenner (eine Modifikation des urspruenglich fuer den Gasbetrieb des V160

  10. Three-dimensional analysis for liquid hydrogen in a cryogenic storage tank with heat pipe pump system

    Science.gov (United States)

    Ho, Son H.; Rahman, Muhammad M.

    2008-01-01

    This paper presents a study on fluid flow and heat transfer of liquid hydrogen in a zero boil-off cryogenic storage tank in a microgravity environment. The storage tank is equipped with an active cooling system consisting of a heat pipe and a pump-nozzle unit. The pump collects cryogen at its inlet and discharges it through its nozzle onto the evaporator section of the heat pipe in order to prevent the cryogen from boiling off due to the heat leaking through the tank wall from the surroundings. A three-dimensional (3-D) finite element model is employed in a set of numerical simulations to solve for velocity and temperature fields of liquid hydrogen in steady state. Complex structures of 3-D velocity and temperature distributions determined from the model are presented. Simulations with an axisymmetric model were also performed for comparison. Parametric study results from both models predict that as the speed of the cryogenic fluid discharged from the nozzle increases, the mean or bulk cryogenic fluid speed increases linearly and the maximum temperature within the cryogenic fluid decreases.

  11. Calculation of critical heat transfer in horizontal evaporator pipes in cooling systems of high-rise buildings

    Science.gov (United States)

    Aksenov, Andrey; Malysheva, Anna

    2018-03-01

    An exact calculation of the heat exchange of evaporative surfaces is possible only if the physical processes of hydrodynamics of two-phase flows are considered in detail. Especially this task is relevant for the design of refrigeration supply systems for high-rise buildings, where powerful refrigeration equipment and branched networks of refrigerants are used. On the basis of experimental studies and developed mathematical model of asymmetric dispersed-annular flow of steam-water flow in horizontal steam-generating pipes, a calculation formula has been obtained for determining the boundaries of the zone of improved heat transfer and the critical value of the heat flux density. A new theoretical approach to the solution of the problem of the flow structure of a two-phase flow is proposed. The applied method of dissipative characteristics of a two-phase flow in pipes and the principle of a minimum rate of entropy increase in stabilized flows made it possible to obtain formulas that directly reflect the influence of the viscous characteristics of the gas and liquid media on their distribution in the flow. The study showed a significant effect of gravitational forces on the nature of the phase distribution in the cross section of the evaporative tubes. At a mass velocity of a two-phase flow less than 700 kg / m2s, the volume content of the liquid phase near the upper outer generating lines of the tube is almost an order of magnitude lower than the lower one. The calculation of the heat transfer crisis in horizontal evaporative tubes is obtained. The calculated dependence is in good agreement with the experimental data of the author and a number of foreign researchers. The formula generalizes the experimental data for pipes with the diameter of 6-40 mm in the pressure of 2-7 MPa.

  12. The sizes of Flat Plate and Evacuated Tube Collectors with Heat Pipe area as a function of the share of solar system in the heat demand

    Directory of Open Access Journals (Sweden)

    Olek Małgorzata

    2016-01-01

    Full Text Available The popularity of solar collectors in Poland is still increasing. The correct location of the collectors and a relatively high density of solar radiation allow delivering heat even in spite of relatively low ambient temperature. Moreover, solar systems used for heating domestic heat water (DHW in summer allow nearly complete elimination of conventional energy sources (e.g. gas, coal. That is why more and more house owners in Poland decide to install solar system installations. In Poland the most common types of solar collectors are flat plate collectors (FPC and evacuated tube collectors with heat pipe (ETCHP; both were selected for the analysis. The heat demand related to the preparation of hot water, connected with the size of solar collectors’ area, has been determined. The analysis includes FPC and ETCHP and heat demand of less than 10 000 kWh/year. Simulations were performed with the Matlab software and using data from a typical meteorological year (TMY. In addition, a 126–year period of measurements of insolation for Krakow has been taken into account. The HDKR model (Hay, Davis, Klucher, Reindl was used for the calculation of solar radiation on the absorber surface. The monthly medium temperature of the absorber depends on the amount of solar system heat and on the heat demand. All the previously mentioned data were used to determine solar efficiency. Due to the fact that solar efficiency and solar system heat are connected, the calculations were made with the use of an iterative method. Additionally, the upper limit for monthly useful solar system heat is resulted from the heat demand and thus the authors prepared a model of statistical solar system heat deviations based on the Monte Carlo method. It has been found that an increase in the useful solar system heat in reference to the heat demand is associated with more than proportional increase in the sizes of the analyzed surfaces of solar collector types.

  13. Time-dependent mixed convection heat transfer from a sphere in a micro-gravity environment

    Science.gov (United States)

    Hommel, Mark J.

    1986-01-01

    A fundamental problem of interest for crystal growth in micro-gravity applications involves the mixed convection heat transfer from a sphere in a uniform flow of fluid at a differing temperature. Under the combined influence of the imposed free stream as well as an induced buoyancy force due to thermal expansion of the fluid, the heat transfer from the sphere will be different from that of either the pure forced convection flow or the pure free convection flow. For the present study, the method of matched asymptotic expansions is applied to the laminar flow problem of an impulsively heated, impulsively started sphere in an originally quiescent fluid. Time series expansions are developed for the dependent variables by acknowledging the existence of two distinct regions: one, an inner region, near the sphere, in which viscous effects are significant; and two, an outer region in which the fluid may be treated as inviscid. The time series expansions are developed in terms of the Reynolds number and Richardson number (Buoyancy Parameter), and the relevant heat transfer and drag coefficients are calculated and plotted.

  14. Time-dependent mixed convection heat transfer from a sphere in a micro-gravity environment

    International Nuclear Information System (INIS)

    Hommel, M.J.

    1987-01-01

    A fundamental problem of interest for crystal growth in micro-gravity applications involves the mixed convection heat transfer from a sphere in a uniform flow of fluid at a differing temperature. Under the combined influence of the imposed free stream as well as an induced buoyancy force due to thermal expansion of the fluid, the heat transfer from the sphere will be different from that of either the pure forced convection flow or the pure free convection flow. For the present study, the method of matched asymptotic expansions is applied to the laminar flow problem of an impulsively heated, impulsively started sphere in an originally quiescent fluid. Time series expansions are developed for the dependent variables by acknowledging the existence of two district regions: one, an inner region, near the sphere, in which viscous effects are significant; and two, an outer region in which the fluid may be treated as inviscid. The time series expansions are developed in terms of the Reynolds number and Richardson number (Buoyancy Parameter), and the relevant heat transfer and drag coefficients are calculated and plotted

  15. Quantum Einstein gravity. Advancements of heat kernel-based renormalization group studies

    International Nuclear Information System (INIS)

    Groh, Kai

    2012-10-01

    The asymptotic safety scenario allows to define a consistent theory of quantized gravity within the framework of quantum field theory. The central conjecture of this scenario is the existence of a non-Gaussian fixed point of the theory's renormalization group flow, that allows to formulate renormalization conditions that render the theory fully predictive. Investigations of this possibility use an exact functional renormalization group equation as a primary non-perturbative tool. This equation implements Wilsonian renormalization group transformations, and is demonstrated to represent a reformulation of the functional integral approach to quantum field theory. As its main result, this thesis develops an algebraic algorithm which allows to systematically construct the renormalization group flow of gauge theories as well as gravity in arbitrary expansion schemes. In particular, it uses off-diagonal heat kernel techniques to efficiently handle the non-minimal differential operators which appear due to gauge symmetries. The central virtue of the algorithm is that no additional simplifications need to be employed, opening the possibility for more systematic investigations of the emergence of non-perturbative phenomena. As a by-product several novel results on the heat kernel expansion of the Laplace operator acting on general gauge bundles are obtained. The constructed algorithm is used to re-derive the renormalization group flow of gravity in the Einstein-Hilbert truncation, showing the manifest background independence of the results. The well-studied Einstein-Hilbert case is further advanced by taking the effect of a running ghost field renormalization on the gravitational coupling constants into account. A detailed numerical analysis reveals a further stabilization of the found non-Gaussian fixed point. Finally, the proposed algorithm is applied to the case of higher derivative gravity including all curvature squared interactions. This establishes an improvement of

  16. Quantum Einstein gravity. Advancements of heat kernel-based renormalization group studies

    Energy Technology Data Exchange (ETDEWEB)

    Groh, Kai

    2012-10-15

    The asymptotic safety scenario allows to define a consistent theory of quantized gravity within the framework of quantum field theory. The central conjecture of this scenario is the existence of a non-Gaussian fixed point of the theory's renormalization group flow, that allows to formulate renormalization conditions that render the theory fully predictive. Investigations of this possibility use an exact functional renormalization group equation as a primary non-perturbative tool. This equation implements Wilsonian renormalization group transformations, and is demonstrated to represent a reformulation of the functional integral approach to quantum field theory. As its main result, this thesis develops an algebraic algorithm which allows to systematically construct the renormalization group flow of gauge theories as well as gravity in arbitrary expansion schemes. In particular, it uses off-diagonal heat kernel techniques to efficiently handle the non-minimal differential operators which appear due to gauge symmetries. The central virtue of the algorithm is that no additional simplifications need to be employed, opening the possibility for more systematic investigations of the emergence of non-perturbative phenomena. As a by-product several novel results on the heat kernel expansion of the Laplace operator acting on general gauge bundles are obtained. The constructed algorithm is used to re-derive the renormalization group flow of gravity in the Einstein-Hilbert truncation, showing the manifest background independence of the results. The well-studied Einstein-Hilbert case is further advanced by taking the effect of a running ghost field renormalization on the gravitational coupling constants into account. A detailed numerical analysis reveals a further stabilization of the found non-Gaussian fixed point. Finally, the proposed algorithm is applied to the case of higher derivative gravity including all curvature squared interactions. This establishes an improvement

  17. GPHS motion studies for heat pulse intervals of reentries from gravity-assist trajectories

    International Nuclear Information System (INIS)

    Lucero, E.F.; Sharbaugh, R.C.

    1990-03-01

    Motion studies of the General Purpose Heat Source Module, GPHS, were conducted in the heat pulse interval associated with entries from earth gravity assist trajectories. The APL six-degree-of-freedom reentry program designated TMAGRA6C was used. The objectives of the studies were to (1) determine the effect of ablation on GPHS motion, and (2) determine whether the GPHS module entering the earth's atmosphere from an earth-gravity-assist trajectory has a preferred orientation during the heat pulse phase of reentry. The results are given in summary form for easy visualization of the initial conditions investigated and to provide a quick-look of the resulting motion. Detail of the motion is also given for the parameters of interest for each case studied. Selected values of initial pitch rate, roll rate, and combinations of these within the range 0 degree to 1000 degrees/sec were investigated for initial reentry angles of -7 degrees (shallow) and -90 degrees (steep) and initial angles of attack of 0 degree (broadface to the wind) and 90 degrees. Although the studies are not exhaustive, a sufficient number of reentry conditions (initial altitude, reentry angle, angle of attack, rotational motion) have been investigated to deduce certain trends. The results also provide information on additional reentry conditions that need to be investigated. The present results show four GPHS orientations that predominate - all with some pitch oscillations and rolling motion. These are: angles of attack, α R of 0 degree, 30 degrees, 90 degrees and tumbling. It should be assumed that all these orientations are equally probable because only combinations of two initial reentry angles, γ 0 , and two values of α R . have been investigated. Further the probability for any given initial rate on orientation is not known

  18. Numerical performance study of paraffin wax dispersed with alumina in a concentric pipe latent heat storage system

    Directory of Open Access Journals (Sweden)

    Valan Arasu Amirtham

    2013-01-01

    Full Text Available Latent heat energy storage systems using paraffin wax could have lower heat transfer rates during melting/freezing processes due to its inherent low thermal conductivity. The thermal conductivity of paraffin wax can be enhanced by employing high conductivity materials such as alumina (Al2O3. A numerical analysis has been carried out to study the performance enhancement of paraffin wax with nanoalumina (Al2O3 particles in comparison with simple paraffin wax in a concentric double pipe heat exchanger. Numerical analysis indicates that the charge-discharge rates of thermal energy can be greatly enhanced using paraffin wax with alumina as compared with a simple paraffin wax as PCM.

  19. The Cryogenic Test Bed experiments: Cryogenic heat pipe flight experiment CRYOHP (STS-53). Cryogenic two phase flight experiment CRYOTP (STS-62). Cryogenic flexible diode flight experiment CRYOFD

    Science.gov (United States)

    Thienel, Lee; Stouffer, Chuck

    1995-01-01

    This paper presents an overview of the Cryogenic Test Bed (CTB) experiments including experiment results, integration techniques used, and lessons learned during integration, test and flight phases of the Cryogenic Heat Pipe Flight Experiment (STS-53) and the Cryogenic Two Phase Flight Experiment (OAST-2, STS-62). We will also discuss the Cryogenic Flexible Diode Heat Pipe (CRYOFD) experiment which will fly in the 1996/97 time frame and the fourth flight of the CTB which will fly in the 1997/98 time frame. The two missions tested two oxygen axially grooved heat pipes, a nitrogen fibrous wick heat pipe and a 2-methylpentane phase change material thermal storage unit. Techniques were found for solving problems with vibration from the cryo-collers transmitted through the compressors and the cold heads, and mounting the heat pipe without introducing parasitic heat leaks. A thermally conductive interface material was selected that would meet the requirements and perform over the temperature range of 55 to 300 K. Problems are discussed with the bi-metallic thermostats used for heater circuit protection and the S-Glass suspension straps originally used to secure the BETSU PCM in the CRYOTP mission. Flight results will be compared to 1-g test results and differences will be discussed.

  20. Numerical investigation of heat pipe-based photovoltaic–thermoelectric generator (HP-PV/TEG) hybrid system

    International Nuclear Information System (INIS)

    Makki, Adham; Omer, Siddig; Su, Yuehong; Sabir, Hisham

    2016-01-01

    Highlights: • Integration of TE generators with a heat pipe-based PV module as a hybrid system is proposed. • Numerical transient modeling based on the energy balance equations of the system was performed. • Integration of TE generators with PV module aid operating the solar cells at a steady level in harsh conditions. - Abstract: Photovoltaic (PV) cells are able to absorb about 80% of the solar spectral irradiance, however, certain percentage accounts for electricity conversion depending on the cell technology employed. The remainder energy however, can elevate the silicon junction temperature in the PV encapsulation perilously, resulting in deteriorated performance. Temperature rise at the PV cell level is addressed as one of the most critical issues that can seriously degrade and shortens the life-time of the PV cells, hence thermal management of the PV module during operation is considered essential. Hybrid PV designs which are able to simultaneously generate electrical energy and utilize the waste heat have been proven to be the most promising solution. In this study, theoretical investigation of a hybrid system comprising of thermoelectric generator integration with a heat pipe-based Photovoltaic/Thermal (PV/T) absorber is proposed and evaluated. The system presented incorporates a PV panel for direct electricity generation, a heat pipe for excessive heat absorption from the PV cells and a thermoelectric generator (TEG) performing direct heat-to-electricity conversion. A mathematical model based on the energy balance within the system is developed to evaluate the performance of the hybrid integration and the improvements associated with the thermal management of PV cells. Results are presented in terms of the overall system efficiency compared to a conventional PV panel under identical operating conditions. The integration of TEG modules with PV cells in such way aid improving the performance of the PV cells in addition to utilizing the waste-heat

  1. Indoor Heating Drives Water Bacterial Growth and Community Metabolic Profile Changes in Building Tap Pipes during the Winter Season.

    Science.gov (United States)

    Zhang, Hai-Han; Chen, Sheng-Nan; Huang, Ting-Lin; Shang, Pan-Lu; Yang, Xiao; Ma, Wei-Xing

    2015-10-27

    The growth of the bacterial community harbored in indoor drinking water taps is regulated by external environmental factors, such as indoor temperature. However, the effect of indoor heating on bacterial regrowth associated with indoor drinking water taps is poorly understood. In the present work, flow cytometry and community-level sole-carbon-source utilization techniques were combined to explore the effects of indoor heating on water bacterial cell concentrations and community carbon metabolic profiles in building tap pipes during the winter season. The results showed that the temperature of water stagnated overnight ("before") in the indoor water pipes was 15-17 °C, and the water temperature decreased to 4-6 °C after flushing for 10 min ("flushed"). The highest bacterial cell number was observed in water stagnated overnight, and was 5-11 times higher than that of flushed water. Meanwhile, a significantly higher bacterial community metabolic activity (AWCD590nm) was also found in overnight stagnation water samples. The significant "flushed" and "taps" values indicated that the AWCD590nm, and bacterial cell number varied among the taps within the flushed group (p heating periods.

  2. Efficiently-cooled plasmonic amorphous silicon solar cells integrated with a nano-coated heat-pipe plate

    Science.gov (United States)

    Zhang, Yinan; Du, Yanping; Shum, Clifford; Cai, Boyuan; Le, Nam Cao Hoai; Chen, Xi; Duck, Benjamin; Fell, Christopher; Zhu, Yonggang; Gu, Min

    2016-04-01

    Solar photovoltaics (PV) are emerging as a major alternative energy source. The cost of PV electricity depends on the efficiency of conversion of light to electricity. Despite of steady growth in the efficiency for several decades, little has been achieved to reduce the impact of real-world operating temperatures on this efficiency. Here we demonstrate a highly efficient cooling solution to the recently emerging high performance plasmonic solar cell technology by integrating an advanced nano-coated heat-pipe plate. This thermal cooling technology, efficient for both summer and winter time, demonstrates the heat transportation capability up to ten times higher than those of the metal plate and the conventional wickless heat-pipe plates. The reduction in temperature rise of the plasmonic solar cells operating under one sun condition can be as high as 46%, leading to an approximate 56% recovery in efficiency, which dramatically increases the energy yield of the plasmonic solar cells. This newly-developed, thermally-managed plasmonic solar cell device significantly extends the application scope of PV for highly efficient solar energy conversion.

  3. Indoor Heating Drives Water Bacterial Growth and Community Metabolic Profile Changes in Building Tap Pipes during the Winter Season

    Directory of Open Access Journals (Sweden)

    Hai-Han Zhang

    2015-10-01

    Full Text Available The growth of the bacterial community harbored in indoor drinking water taps is regulated by external environmental factors, such as indoor temperature. However, the effect of indoor heating on bacterial regrowth associated with indoor drinking water taps is poorly understood. In the present work, flow cytometry and community-level sole-carbon-source utilization techniques were combined to explore the effects of indoor heating on water bacterial cell concentrations and community carbon metabolic profiles in building tap pipes during the winter season. The results showed that the temperature of water stagnated overnight (“before” in the indoor water pipes was 15–17 °C, and the water temperature decreased to 4–6 °C after flushing for 10 min (“flushed”. The highest bacterial cell number was observed in water stagnated overnight, and was 5–11 times higher than that of flushed water. Meanwhile, a significantly higher bacterial community metabolic activity (AWCD590nm was also found in overnight stagnation water samples. The significant “flushed” and “taps” values indicated that the AWCD590nm, and bacterial cell number varied among the taps within the flushed group (p < 0.01. Heatmap fingerprints and principle component analyses (PCA revealed a significant discrimination bacterial community functional metabolic profiles in the water stagnated overnight and flushed water. Serine, threonine, glucose-phosphate, ketobutyric acid, phenylethylamine, glycerol, putrescine were significantly used by “before” water samples. The results suggested that water stagnated at higher temperature should be treated before drinking because of bacterial regrowth. The data from this work provides useful information on reasonable utilization of drinking water after stagnation in indoor pipes during indoor heating periods.

  4. Improving the Dimensioning of Piping Networks and Network Layouts in Low-Energy District Heating Systems Connected to Low-Energy Buildings: A Case Study in Roskilde, Denmark

    DEFF Research Database (Denmark)

    Tol, Hakan; Svendsen, Svend

    2011-01-01

    The paper presents a method for the design of a low-energy district heating (DH) system, concerning the studies of different pipe-dimensioning methods, substation types and network layouts. Computations were carried out separately on each of the pipe segments of which the DH network consisted...... dimensions were investigated for substations of different types containing buffer tanks and heat exchangers and for booster pumps installed at the DH network. Two types of network layouts were compared in terms of satisfaction of customers concerning the supply temperatures and heat loss within the DH...

  5. UQ and V&V techniques applied to experiments and simulations of heated pipes pressurized to failure

    Energy Technology Data Exchange (ETDEWEB)

    Romero, Vicente Jose [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Dempsey, J. Franklin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Antoun, Bonnie R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-05-01

    This report demonstrates versatile and practical model validation and uncertainty quantification techniques applied to the accuracy assessment of a computational model of heated steel pipes pressurized to failure. The Real Space validation methodology segregates aleatory and epistemic uncertainties to form straightforward model validation metrics especially suited for assessing models to be used in the analysis of performance and safety margins. The methodology handles difficulties associated with representing and propagating interval and/or probabilistic uncertainties from multiple correlated and uncorrelated sources in the experiments and simulations including: material variability characterized by non-parametric random functions (discrete temperature dependent stress-strain curves); very limited (sparse) experimental data at the coupon testing level for material characterization and at the pipe-test validation level; boundary condition reconstruction uncertainties from spatially sparse sensor data; normalization of pipe experimental responses for measured input-condition differences among tests and for random and systematic uncertainties in measurement/processing/inference of experimental inputs and outputs; numerical solution uncertainty from model discretization and solver effects.

  6. Two-phase flow patterns of a top heat mode closed loop oscillating heat pipe with check valves (THMCLOHP/CV)

    Science.gov (United States)

    Thongdaeng, S.; Bubphachot, B.; Rittidech, S.

    2016-11-01

    This research is aimed at studying the two-phase flow pattern of a top heat mode closed loop oscillating heat pipe with check valves. The working fluids used are ethanol and R141b and R11 coolants with a filling ratio of 50% of the total volume. It is found that the maximum heat flux occurs for the R11 coolant used as the working fluid in the case with the inner diameter of 1.8 mm, inclination angle of -90°, evaporator temperature of 125°C, and evaporator length of 50 mm. The internal flow patterns are found to be slug flow/disperse bubble flow/annular flow, slug flow/disperse bubble flow/churn flow, slug flow/bubble flow/annular flow, slug flow/disperse bubble flow, bubble flow/annular flow, and slug flow/annular flow.

  7. Multi-objective shape optimization of double pipe heat exchanger with inner corrugated tube using RSM method

    International Nuclear Information System (INIS)

    Han, Huai-Zhi; Li, Bing-Xi; Wu, Hao; Shao, Wei

    2015-01-01

    Integrated a fully developing three-dimensional heat transfer and flow model, a multi-objective optimization aims to fulfill the geometric design for double-tube heat exchangers with inner corrugated tube is investigated in this work with RSM. Dimensionless corrugation pitch (p/D), dimensionless corrugation height (H/D), dimensionless corrugation radius (r/D) and Reynolds number (Re) are considered as four design parameters. Considering the process parameters, the characteristic numbers involving heat transfer characteristic, resistance characteristic and overall heat transfer performance calculated by CFD, and are served as objective functions to the RSM (Nu c , f c , Nu c /Nu s , f c /f s and h in this paper). The results of optimal designs are a set of multiple optimum solutions, called 'Pareto optimal solutions'. It reveals the identical tendency of Nu c /Nu s and f c /f s reflecting the conflict between them that means augmenting the heat transfer performance with various design parameters in the optimal situation inevitably sacrificed the increase of flow resistance. According to the Pareto optimal curves, the optimum designing parameters of double pipe heat exchanger with inner corrugated tube under the constrains of Nu c /Nu s ≥1.2 are found to be P/D = 0.82, H/D = 0.22, r/D = 0.23, Re = 26,263, corresponding to the maximum value of η = 1.12. (authors)

  8. Active Control of the Operating Temperature in a Loop Heat Pipe with Two Evaporators and Two Condensers

    Science.gov (United States)

    Ku, Jentung; Birur, Gaj; Powers, Edward I. (Technical Monitor)

    2001-01-01

    The operating temperature of a loop heat pipe (LHP) with multiple evaporators is a function of the total heat load, heat load distribution among evaporators, condenser temperature and ambient temperature. Because of the many variables involved, the operating temperature also showed more hystereses than an LHP with a single evaporator. Tight temperature control can be achieved by controlling its compensation chamber (CC) temperatures at the desired set point. This paper describes a test program on active control of the operating temperature in an LHP with two evaporators and two condensers. Temperature control was achieved by heating one or both CC's. Tests performed included start-up, power cycle, sink temperature cycle, CC temperature cycle, and capillary limit. Test results show that, regardless one or two CC's were heated to the set point temperature, one of CC's was always flooded with liquid. The loop could operate successfully at the desired set point temperature under most conditions, including some fast transients. At low heat loads, however, the CC temperature could suddenly increase above the set point temperature, possibly due to a sudden change of the vapor content inside the evaporator core.

  9. Sensor fault detection and isolation via high-gain observers: application to a double-pipe heat exchanger.

    Science.gov (United States)

    Escobar, R F; Astorga-Zaragoza, C M; Téllez-Anguiano, A C; Juárez-Romero, D; Hernández, J A; Guerrero-Ramírez, G V

    2011-07-01

    This paper deals with fault detection and isolation (FDI) in sensors applied to a concentric-pipe counter-flow heat exchanger. The proposed FDI is based on the analytical redundancy implementing nonlinear high-gain observers which are used to generate residuals when a sensor fault is presented (as software sensors). By evaluating the generated residual, it is possible to switch between the sensor and the observer when a failure is detected. Experiments in a heat exchanger pilot validate the effectiveness of the approach. The FDI technique is easy to implement allowing the industries to have an excellent alternative tool to keep their heat transfer process under supervision. The main contribution of this work is based on a dynamic model with heat transfer coefficients which depend on temperature and flow used to estimate the output temperatures of a heat exchanger. This model provides a satisfactory approximation of the states of the heat exchanger in order to allow its implementation in a FDI system used to perform supervision tasks. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

  10. Numerical and Experimental Study on Energy Performance of Photovoltaic-Heat Pipe Solar Collector in Northern China

    Directory of Open Access Journals (Sweden)

    Hongbing Chen

    2015-01-01

    Full Text Available Several studies have found that the decrease of photovoltaic (PV cell temperature would increase the solar-to-electricity conversion efficiency. Water type PV/thermal (PV/T system was a good choice but it could become freezing in cold areas of Northern China. This paper proposed a simple combination of common-used PV panel and heat pipe, called PV-heat pipe (PV-HP solar collector, for both electrical and thermal energy generation. A simplified one-dimensional steady state model was developed to study the electrical and thermal performance of the PV-HP solar collector under different solar radiations, water flow rates, and water temperatures at the inlet of manifold. A testing rig was conducted to verify the model and the testing data matched very well with the simulation values. The results indicated that the thermal efficiency could be minus in the afternoon. The thermal and electrical efficiencies decreased linearly as the inlet water temperature and water flow rate increased. The thermal efficiency increased while the electrical efficiency decreased linearly as the solar radiation increased.

  11. Studies on the characteristics of the separated heat pipe system with non-condensible gas for the use of the passive decay heat removal in reactor systems

    International Nuclear Information System (INIS)

    Hayashi, Takao; Ishi, Takayuki; Hayakawa, Hitoshi; Ohashi, Kazutaka

    1997-01-01

    Experiments on the separated heat pipe system of variable conductance type, which enclose non-condensible gas, have been carried out with intention of applying such system to passive decay heat removal of the modular reactors such as HTR plant. Basic experiments have been carried out on the experimental apparatus consisting of evaporator, vapor transfer tube, condenser tube and return tube which returns the condensed liquid back to the evaporator. Water and methanol were examined as the working fluids and nitrogen gas was enclosed as the non-condensible gas. The behaviors of the system were examined for the parametric changes of the heat input under the various pressures of nitrogen gas initially enclosed, including the case without enclosing N 2 gas for the comparison. The results of the experiments shows very clear features of self control characteristics. The self control mechanism was made clear, that is, in such system in which the condensing area in the condenser expands automatically in accordance with the increase of the heat input to keep the system temperature nearly constant. The working temperature of the system are clearly dependent on the pressure of the non-condensable gas initially enclosed, with higher system working temperature with higher initial gas pressure enclosed. The analyses were done on water and methanol as the working fluids, which show very good agreement with the experimental results. A lot of attractive applications are expected including the self switching feature with minimum heat loss during normal operation with maintaining the sufficient heat removal at accidents. (author)

  12. Horizontal Parallel Pipe Ground Heat Exchanger : Analytical Conception and Experimental Study

    International Nuclear Information System (INIS)

    Naili, Nabiha; Jemli, Ramzi; Farhat, Abdel Hamid; Ben Nasrallah, Sassi

    2009-01-01

    Due to limited amount of natural resources exploited for heating, and in order to reduce the environmental impact, people should strive to use renewable energy resources. Ambient low-grade energy may be upgraded by the ground heat exchanger (GH E), which exploits the ground thermal inertia for buildings heating and cooling. In this study, analytical performance and experiments analysis of a horizontal ground heat exchanger have been performed. The analytical study, relates to the dimensioning of the heat exchanger, shows that the heat exchanger characteristics are very important for the determination of heat extracted from ground. The experimental results were obtained during the period 30 November to 10 December 2007, in the heating season of the greenhouses. Measurements show that the ground temperature under a certain depth remains relatively constant. To exploit effectively the heat capacity of the ground, a horizontal heat exchanger system has to be constructed and tested in the Center of Research and Technology of Energy, in Tunisia

  13. Numerical study of the enhancement of heat transfer for hybrid CuO-Cu Nanofluids flowing in a circular pipe.

    Science.gov (United States)

    Balla, Hyder H; Abdullah, Shahrir; Mohdfaizal, Wan; Zulkifli, Rozli; Sopian, Kamaruzaman

    2013-01-01

    A numerical simulation model for laminar flow of nanofluids in a pipe with constant heat flux on the wall was built to study the effect of the Reynolds number on convective heat transfer and pressure loss. The investigation was performed for hybrid nanofluids consisting of CuO-Cu nanoparticles and compared with CuO and Cu in which the nanoparticles have a spherical shape with size 50, 50, 50nm respectively. The nanofluids were prepared, following which the thermal conductivity and dynamic viscosity were measured for a range of temperatures (10 -60°C). The numerical results obtained were compared with the existing well-established correlation. The prediction of the Nusselt number for nanofluids agrees well with the Shah correlation. The comparison of heat transfer coefficients for CuO, Cu and CuO-Cu presented an increase in thermal conductivity of the nanofluid as the convective heat transfer coefficient increased. It was found that the pressure loss increases with an increase in the Reynolds number, nanoparticle density and particle volume fraction. However, the flow demonstrates enhancement in heat transfer which becomes greater with an increase in the Reynolds number for the nanofluid flow.

  14. Simulation of Wickless-Heat Pipe as Passive Cooling System in Nuclear Spent Fuel Pool Using RELAP5/MOD3.2

    OpenAIRE

    Kusuma, Mukhsinun Hadi; Putra, Nandy; Ismarwanti, Sri; Widodo, Surip

    2017-01-01

    The lesson learned from the severe accident of Fukushima Daiichi nuclear power plant shows that the residual heat generated from nuclear spent fuel should be cooled properly. In order to absorb that residual heat when station blackout occurs, wickless-heat pipe is proposed to be used as an alternative of the passive cooling system in nuclear spent fuel pool. The objective of this research is to simulation the effect of initial pressure and evaporator filling ratio as factors that influence th...

  15. The Characteristics of natural convection heat transfer of Al2O3–water nano fluid flow in a vertical annulus pipe

    International Nuclear Information System (INIS)

    Reinaldy Nazar

    2016-01-01

    Results of several researches have shown that nano fluids have better thermal characteristics than conventional fluid (water). In this regard, ideas for using nano fluids as an alternative heat transfer fluid in the reactor coolant system have been well developed. Meanwhile the natural convection in a vertical annulus pipe is one of the important mechanisms of heat transfer and is found at the TRIGA research reactor, the new generation nuclear power plants and other energy conversion devices. On the other hand, the heat transfer characteristics of nano fluids in a vertical annulus pipe has not been known. Therefore, it is important to do research continuously to analyze the heat transfer nano fluids in a vertical annulus pipe. This study has carried out numerical analysis by using computer code of CFD (computational of fluids dynamic) on natural convection heat transfer characteristics of nano fluids flow of Al 2 O 3 -water 2 % volume in the vertical annulus pipe. The results showed an increase in heat transfer performance (Nusselt numbers - NU) by 20.5 % - 35 %. In natural convection mode with Rayleigh numbers 2.471 e +09 ≤ Ra ≤ 1.955 e +13 obtained empirical correlations for water is N U = 1.065 (R a (D H /x)) 0.179 and empirical correlations for Al 2 O 3 -water nano fluids is N U = 14.869 (R a (D H /x)) 0.115 .(author)

  16. Design Considerations for Lightweight Space Radiators Based on Fabrication and Test Experience With a Carbon-Carbon Composite Prototype Heat Pipe. Revised

    Science.gov (United States)

    Juhasz, Albert J.

    2002-01-01

    This report discusses the design implications for spacecraft radiators made possible by the successful fabrication and proof-of-concept testing of a graphite-fiber-carbon-matrix composite (i.e., carbon-carbon (C-C)) heat pipe. The prototype heat pipe, or space radiator element, consists of a C-C composite shell with integrally woven fins. It has a thin-walled furnace-brazed metallic (Nb-1%Zr) liner with end caps for containment of the potassium working fluid. A short extension of this liner, at increased wall thickness beyond the C-C shell, forms the heat pipe evaporator section which is in thermal contact with the radiator fluid that needs to be cooled. From geometric and thermal transport properties of the C-C composite heat pipe tested, a specific radiator mass of 1.45 kg/sq m can be derived. This is less than one-fourth the specific mass of present day satellite radiators. The report also discusses the advantage of segmented space radiator designs utilizing heat pipe elements, or segments, in their survivability to micrometeoroid damage. This survivability is further raised by the use of condenser sections with attached fins, which also improve the radiation heat transfer rate. Since the problem of heat radiation from a fin does not lend itself to a closed analytical solution, a derivation of the governing differential equation and boundary conditions is given in appendix A, along with solutions for rectangular and parabolic fin profile geometries obtained by use of a finite difference computer code written by the author.

  17. Design Considerations for Lightweight Space Radiators Based on Fabrication and Test Experience with a Carbon-Carbon Composite Prototype Heat Pipe

    Science.gov (United States)

    Juhasz, Albert J.

    1998-01-01

    This report discusses the design implications for spacecraft radiators made possible by the successful fabrication and Proof-of-concept testing of a graphite-fiber-carbon-matrix composite (i.e., carbon-carbon (C-C)) heat pipe. The proto-type heat pipe, or space radiator element, consists of a C-C composite shell with integrally woven fins. It has a thin-walled furnace-brazed metallic (Nb-1%Zr) liner with end caps for containment of the potassium working fluid. A short extension of this liner, at increased wall thickness beyond the C-C shell, forms the heat pipe evaporator section which is in thermal contact with the radiator fluid that needs to be cooled. From geometric and thermal transport properties of the C-C composite heat pipe tested, a specific radiator mass of 1.45 kg/m2 can be derived. This is less than one-fourth the specific mass of present day satellite radiators. The report also discusses the advantage of segmented space radiator designs utilizing heat pipe elements, or segments, in their survivability to micro-meteoroid damage. This survivability is further raised by the use of condenser sections with attached fins, which also improve the radiation heat transfer rate. Since the problem of heat radiation from a fin does not lend itself to a closed analytical solution, a derivation of the governing differential equation and boundary conditions is given in appendix A, along with solutions for rectangular and parabolic fin profile geometries obtained by use of a finite difference computer code written by the author.

  18. Domestic hot water. Measurements of consumption and heat loss from circulation pipes; Varmt brugsvand. Maaling af forbrug og varmetab fra cirkulationsledninger

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, B.; Schroeder, F.; Bergsoee, N.C.

    2009-07-01

    It is likely that the production and distribution of domestic hot water (DHW) in buildings will constitute a dominant share of both the present and in particular future energy design requirements. The goal of this project has been to propose more energy efficient and environmentally friendly solutions for DHW systems based on analyses of existing conditions. The possibilities include new types of circulation pipes, which have the potential of a 40 per cent reduction of heat losses. In addition to the reduction of heat losses inside the building, a low return temperature from the hot water system will have a large impact on the heat losses from the district heating network when the building is being heated by district heating. The results of this project could influence not only future buildings but also existing buildings in case of renovation of the installations. In this project measurements of water and energy consumptions have been carried out in a number of buildings, and heat losses from the production of domestic hot water and the distribution lines have been measured. In addition to the measurements, analyses and simulations have been carried out. Two models have been developed: One of an apartment room with vertical pipes passing through the room, and one of a room above a basement with horizontal heating pipes. The models make it possible to assess how much of the heat loss from the heating pipes is utilised for space heating. The following recommendations are pointed out: 1) In large buildings e.g. apartment buildings and office buildings the technical installations should be provided with meters so that it is possible to separate the energy consumption for DHW, space heating and ventilation, respectively. 2) In new buildings and in case of retrofitting existing buildings, careful planning of the placement and disposition of hot water taps compared with the location of the hot water tank or heat exchanger is recommended. Also, the necessity of a

  19. Flow and Heat Transfer Analysis of an Eyring-Powell Fluid in a Pipe

    Science.gov (United States)

    Ali, N.; Nazeer, F.; Nazeer, Mubbashar

    2018-02-01

    The steady non-isothermal flow of an Eyring-Powell fluid in a pipe is investigated using both perturbation and numerical methods. The results are presented for two viscosity models, namely the Reynolds model and the Vogel model. The shooting method is employed to compute the numerical solution. Criteria for validity of perturbation solution are developed. When these criteria are met, it is shown that the perturbation solution is in good agreement with the numerical solution. The influence of various emerging parameters on the velocity and temperature field is also shown.

  20. Loop Heat Pipe Transient Behavior Using Heat Source Temperature for Set Point Control with Thermoelectric Converter on Reservoir

    Science.gov (United States)

    Ku, Jentung; Paiva, Kleber; Mantelli, Marcia

    2011-01-01

    The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly done by cold biasing the reservoir and using electrical heaters to provide the required control power. With this method, the loop operating temperature can be controlled within 0.5K or better. However, because the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if the LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP was carried out to investigate the effects on the LHP operation when the control temperature sensor was placed on the heat source instead of the reservoir. In these tests, the LHP reservoir was cold-biased and was heated by a control heater. Test results show that it was feasible to use the heat source temperature for feedback control of the LHP operation. In particular, when a thermoelectric converter was used as the reservoir control heater, the heat source temperature could be maintained within a tight range using a proportional-integral-derivative or on/off control algorithm. Moreover, because the TEC could provide both heating and cooling to the reservoir, temperature oscillations during fast transients such as loop startup could be eliminated or substantially reduced when compared to using an electrical heater as the control heater.

  1. Effect of using ethanol and methanol on thermal performance of a closed loop pulsating heat pipe (CLPHP) with different filling ratios

    Science.gov (United States)

    Rahman, Md. Lutfor; Salsabil, Zaimaa; Yasmin, Nusrat; Nourin, Farah Nazifa; Ali, Mohammad

    2016-07-01

    This paper presents an experimental study of a closed loop Pulsating Heat Pipe (CLPHP) as the demand of smaller and effective heat transfer devices is increasing day by day. PHP is a two phase heat transfer device suited for heat transfer applications, especially suited for handling moderate to high heat fluxes in different applications. A copper made Pulsating Heat Pipe (PHP) of 250 mm length is used in this experimental work with 2 mm ID and 3 mm OD, closed end-to-end in 8 looped, evacuated and then partially filled with working fluids. The evaporation section is 50 mm, adiabatic section is 120 mm and condensation section is 80 mm. The performance characterization is done for two working fluids at Vertical (0°) orientations. The working fluids are Methanol and Ethanol and the filling ratios are 40%, 50%, 60% & 70% based on total volume, respectively. The results show that the influence of various parameters, the heat input flux, and different filling ratios on a heat transfer performance of CLPHP. Methanol shows better performance as working fluid in PHP than ethanol at present orientation for a wide range of heat inputs and can be used at high heat input conditions. Ethanol is better choice to be used in low heat input conditions.

  2. Prediction of the heat transfer coefficient for ice slurry flows in a horizontal pipe

    Energy Technology Data Exchange (ETDEWEB)

    Kousksou, T.; Jamil, A.; Zeraouli, Y. [Laboratoire de Thermique Energetique et Procedes, Avenue de l' Universite, BP 1155, 64013 Pau Cedex (France); El Rhafiki, T. [Laboratoire de Thermique Energetique et Procedes, Avenue de l' Universite, BP 1155, 64013 Pau Cedex (France); Laboratoire d' Energetique, Mecanique des Fluides et Sciences des Materiaux, Universite AbdelMalek Essaidi, 90000 Tetouan (Morocco)

    2010-06-15

    In this study, heat transfer for ice slurry flows was investigated. For the experiments, ice slurry was made from 9% ethanol-water solution flow in a 20 mm internal diameter, 1000 mm long horizontal copper tube. The ice slurry was heated by a cylindrical electrical resistance. Experiments of the melting process were conducted with changing the ice slurry mass flux rate and the heat flux. The enthalpy-porosity formulation was used to predict the ice slurry temperature and the local values of heat transfer coefficient in the exchanger. Measurements and data acquisition of ice slurry temperature and mass flow rate at the inlet and outlet are performed. It was found that the heat transfer rates increase with the mass flow rate, the ice fraction and the heat flux density. However, the effect of ice fraction appears not to be significant at high mass flow rates. In addition, the correlation proposed by Christensen and Kauffeld gives good agreement with numerical results. (author)

  3. Prediction of the heat transfer coefficient for ice slurry flows in a horizontal pipe

    International Nuclear Information System (INIS)

    Kousksou, T.; Jamil, A.; El Rhafiki, T.; Zeraouli, Y.

    2010-01-01

    In this study, heat transfer for ice slurry flows was investigated. For the experiments, ice slurry was made from 9% ethanol-water solution flow in a 20 mm internal diameter, 1000 mm long horizontal copper tube. The ice slurry was heated by a cylindrical electrical resistance. Experiments of the melting process were conducted with changing the ice slurry mass flux rate and the heat flux. The enthalpy-porosity formulation was used to predict the ice slurry temperature and the local values of heat transfer coefficient in the exchanger. Measurements and data acquisition of ice slurry temperature and mass flow rate at the inlet and outlet are performed. It was found that the heat transfer rates increase with the mass flow rate, the ice fraction and the heat flux density. However, the effect of ice fraction appears not to be significant at high mass flow rates. In addition, the correlation proposed by Christensen and Kauffeld gives good agreement with numerical results.

  4. Dynamic equation-based thermo-hydraulic pipe model for district heating and cooling systems

    OpenAIRE

    van der Heijde, Bram; Fuchs, Marcus; Ribas Tugores, Carles; Schweiger, Gerald; Sartor, Kevin; Basciotti, Daniele; Müller, Dirk; Nytsch-Geusen, Christoph; Wetter, Michael; Helsen, Lieve

    2017-01-01

    Simulation and optimisation of district heating and cooling networks requires efficient and realistic models of the individual network elements in order to correctly represent heat losses or gains, temperature propagation and pressure drops. Due to more recent thermal networks incorporating meshing decentralised heat and cold sources, the system often has to deal with variable temperatures and mass flow rates, with flow reversal occurring more frequently. This paper presents the mathematical ...

  5. Experimental and Statistical Analysis of MgO Nanofluids for Thermal Enhancement in a Novel Flat Plate Heat Pipes

    Science.gov (United States)

    Pandiaraj, P.; Gnanavelbabu, A.; Saravanan, P.

    Metallic fluids like CuO, Al2O3, ZnO, SiO2 and TiO2 nanofluids were widely used for the development of working fluids in flat plate heat pipes except magnesium oxide (MgO). So, we initiate our idea to use MgO nanofluids in flat plate heat pipe as a working fluid material. MgO nanopowders were synthesized by wet chemical method. Solid state characterizations of synthesized nanopowders were carried out by Ultraviolet Spectroscopy (UV), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) techniques. Synthesized nanopowders were prepared as nanofluids by adding water and as well as water/ethylene glycol as a binary mixture. Thermal conductivity measurements of prepared nanofluids were studied using transient hot-wire apparatus. Response surface methodology based on the Box-Behnken design was implemented to investigate the influence of temperature (30-60∘C), particle fraction (1.5-4.5 vol.%), and solution pH (4-12) of nanofluids as the independent variables. A total of 17 experiments were accomplished for the construction of second-order polynomial equations for target output. All the influential factors, their mutual effects and their quadratic terms were statistically validated by analysis of variance (ANOVA). The optimum stability and thermal conductivity of MgO nanofluids with various temperature, volume fraction and solution pH were predicted and compared with experimental results. The results revealed that increase in particle fraction and pH of MgO nanofluids at certain points would increase thermal conductivity and become stable at nominal temperature.

  6. Thermal resistance of rotating closed-loop pulsating heat pipes: Effects of working fluids and internal diameters

    Directory of Open Access Journals (Sweden)

    Kammuang-Lue Niti

    2017-01-01

    Full Text Available The objective of this study was to experimentally investigate the effects of working fluids and internal diameters on the thermal resistance of rotating closed-loop pul¬sating heat pipes (RCLPHP. The RCLPHP were made of a copper tube with internal diameters of 1.50 mm and 1.78 mm, bent into the shape of a flower petal, and arranged into a circle with 11 turns. The evaporator section was located at the outer end of the tube bundle. R123, ethanol, and water were filled as the working fluids. The RCLPHP was rotated at centrifugal accelerations 0.5, 1, 3, 5, 10, and 20 times of the gravitational acceleration considered at the connection between the evaporator and the condenser sections. The heat input was varied from 30 W to 50 W, and then to 100 W, 150 W, and 200 W. It can be concluded that when the latent heat of evaporation increases, the pressure difference between the evaporator and the condenser sections decreases, and the thermal resistance increases. Moreover, when the internal diameter increases, the driving force increases and the frictional force proportionally decreases, or the Karman number increases, and the thermal resistance decreases.

  7. An experimental study on the performance of closed loop pulsating heat pipe (CLPHP) with methanol as a working fluid

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Md. Lutfor; Nourin, Farah Nazifa, E-mail: farahnazifanourin@gmail.com; Salsabil, Zaimaa; Yasmin, Nusrat, E-mail: nusratyasmin015@gmail.com [Military Institute of Science and Technology, Mirpur Cantonment, Dhaka -1216 (Bangladesh); Ali, Mohammad [Bangladesh University of Engineering and Technology, Dhaka -1000 (Bangladesh)

    2016-07-12

    Thermal control is an important topic for thermal management of small electrical and electronic devices. Closed loop pulsating heat pipe (CLPHP) arises as the best solution for thermal control. The aim of this experimental study is to search a CLPHP of better thermal performance for cooling different electrical and electronic devices. In this experiment, methanol is used as working fluid. The effect of using methanol as a working fluid is studied on thermal performance in different filling ratios and angles of inclination. A copper capillary tube is used where the inner diameter is 2 mm,outer diameter is 2.5 mm and 250 mm long. The CLPHP has 8 loops where the evaporation section is 50 mm, adiabatic section is 120 mm and condensation section is 80 mm. The experiment is done using FR of 40%-70% with 10% of interval and angles of inclination 0° (vertical), 30°, 45°, 60° varying heat input. The results are compared on the basis of evaporator temperature, condenser temperature and their differences, thermal resistance, heat transfer co-efficient, power input and pulsating time. The results demonstrate the effect of methanol in different filling ratios and angles of inclination. M ethanol shows better performance at 30° inclination with 40% FR.

  8. An experimental study on the performance of closed loop pulsating heat pipe (CLPHP) with methanol as a working fluid

    Science.gov (United States)

    Rahman, Md. Lutfor; Nourin, Farah Nazifa; Salsabil, Zaimaa; Yasmin, Nusrat; Ali, Mohammad

    2016-07-01

    Thermal control is an important topic for thermal management of small electrical and electronic devices. Closed loop pulsating heat pipe (CLPHP) arises as the best solution for thermal control. The aim of this experimental study is to search a CLPHP of better thermal performance for cooling different electrical and electronic devices. In this experiment, methanol is used as working fluid. The effect of using methanol as a working fluid is studied on thermal performance in different filling ratios and angles of inclination. A copper capillary tube is used where the inner diameter is 2mm,outer diameter is 2.5mm and 250mm long. The CLPHP has 8 loops where the evaporation section is 50mm, adiabatic section is 120mm and condensation section is 80mm. The experiment is done using FR of 40%-70% with 10% of interval and angles of inclination 0° (vertical), 30°, 45°, 60° varying heat input. The results are compared on the basis of evaporator temperature, condenser temperature and their differences, thermal resistance, heat transfer co-efficient, power input and pulsating time. The results demonstrate the effect of methanol in different filling ratios and angles of inclination. M ethanol shows better performance at 30° inclination with 40% FR.

  9. An experimental study on the performance of closed loop pulsating heat pipe (CLPHP) with methanol as a working fluid

    International Nuclear Information System (INIS)

    Rahman, Md. Lutfor; Nourin, Farah Nazifa; Salsabil, Zaimaa; Yasmin, Nusrat; Ali, Mohammad

    2016-01-01

    Thermal control is an important topic for thermal management of small electrical and electronic devices. Closed loop pulsating heat pipe (CLPHP) arises as the best solution for thermal control. The aim of this experimental study is to search a CLPHP of better thermal performance for cooling different electrical and electronic devices. In this experiment, methanol is used as working fluid. The effect of using methanol as a working fluid is studied on thermal performance in different filling ratios and angles of inclination. A copper capillary tube is used where the inner diameter is 2 mm,outer diameter is 2.5 mm and 250 mm long. The CLPHP has 8 loops where the evaporation section is 50 mm, adiabatic section is 120 mm and condensation section is 80 mm. The experiment is done using FR of 40%-70% with 10% of interval and angles of inclination 0° (vertical), 30°, 45°, 60° varying heat input. The results are compared on the basis of evaporator temperature, condenser temperature and their differences, thermal resistance, heat transfer co-efficient, power input and pulsating time. The results demonstrate the effect of methanol in different filling ratios and angles of inclination. M ethanol shows better performance at 30° inclination with 40% FR.

  10. Vapor phase spectra and the pressure-temperature dependence of long-chain carboxyllic acids studied by a CO laser and the photoacoustic heat-pipe detector.

    NARCIS (Netherlands)

    Jalink, H.; Bicanic, D.; Franko, M.; Bozoki, Z.

    1995-01-01

    A resonant photoacoustic heat-pipe (PAHP) cell was constructed and used for spectral studies of four long-chain saturated fatty acids (C10:0 to C16:0) at CO laser wavelengths and temperatures above that of the ambient. Vapor-phase absorption spectra were recorded at temperatures of 383 K for capric

  11. Experimental investigation of thermo-physical properties, convective heat transfer and pressure drop of functionalized graphene nanoplatelets aqueous nanofluid in a square heated pipe

    International Nuclear Information System (INIS)

    Yarmand, Hooman; Gharehkhani, Samira; Shirazi, Seyed Farid Seyed; Amiri, Ahmad; Alehashem, Maryam Sadat; Dahari, Mahidzal; Kazi, S.N.

    2016-01-01

    Graphical abstract: Schematic of functionalization process and making of nanofluid. - Highlights: • Stable dispersion of GNP nanofluids are prepared with the functionalization method. • Remarkable thermal conductivity enhancement was observed for all nanofluid samples. • Overall heat transfer coefficient of nanofluids have been significantly enhanced. • Enhancement of friction factor as a negative parameter is negligible. - Abstract: In the present study, a facile method is used for preparation of functionalized graphene nanoplatelets (f-GNP) nanofluids. The effective thermal conductivity, density, viscosity, specific heat capacity, overall heat transfer coefficient and friction factor for fully developed turbulent flow of f-GNP/water nanofluids flowing through a square pipe at a constant heat flux were studied. f-GNP uniform nanocomposite was produced from a simple acid treatment reaction procedure. The surface characterization was performed by various techniques such as XRD, FESEM, FTIR and Raman. The f-GNP nanofluids were prepared by dispersing the functionalized nanoparticles in base fluid (water) without the assistance of a surfactant. As made nanofluids were stable for a long time and no sedimentation was observed. The experimental data for f-GNP nanofluids have shown significant enhancement in thermal conductivity and overall heat transfer coefficient in comparison to the corresponding water data. The percentage of enhancement is a function of weight concentration of nanoparticles and temperature. Highest improvement of overall heat transfer coefficient is 19.68% with 9.22% raise in friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to those data from the base fluid.

  12. Thermodynamic Analysis of Gravity-driven Liquid Film along an Inclined Heated Plate with Hydromagnetic and Viscous Dissipation Effects

    Directory of Open Access Journals (Sweden)

    Nouredine Meza

    2006-10-01

    Full Text Available The purpose of this work is to investigate the entropy generation in a laminar,gravity-driven conducting liquid film with fully developed velocity flowing along an inclineheated plate in the presence of a transverse magnetic field. The upper surface of the liquidfilm is considered free and adiabatic. The effect of heat generation by viscous dissipation isincluded in the analysis. The influence of the applied magnetic field and the viscousdissipation on velocity, temperature and entropy generation is examined.

  13. Semi-analytical prediction of hydraulic resistance and heat transfer for pipe and channel flows of water at supercritical pressure

    International Nuclear Information System (INIS)

    Laurien, E.

    2012-01-01

    Within the Generation IV International Forum the Supercritical Water Reactor is investigated. For its core design and safety analysis the efficient prediction of flow and heat transfer parameters such as the wall-shear stress and the heat-transfer coefficient for pipe and channel flows is needed. For circular pipe flows a numerical model based on the one-dimensional conservation equations of mass, momentum end energy in the radial direction is presented, referred to as a 'semi-analytical' method. An accurate, high-order numerical method is employed to evaluate previously derived analytical solutions of the governing equations. Flow turbulence is modeled using the algebraic approach of Prandtl/van-Karman, including a model for the buffer layer. The influence of wall roughness is taken into account by a new modified numerical damping function of the turbulence model. The thermo-hydraulic properties of water are implemented according to the international standard of 1997. This method has the potential to be used within a sub-channel analysis code and as wall-functions for CFD codes to predict the wall shear stress and the wall temperature. The present study presents a validation of the method with comparison of model results with experiments and multi-dimensional computational (CFD) studies in a wide range of flow parameters. The focus is laid on forced convection flows related to reactor design and near-design conditions. It is found, that the method can accurately predict the wall temperature even under deterioration conditions as they occur in the selected experiments (Yamagata el al. 1972 at 24.5 MPa, Ornatski et al. 1971 at 25.5 and Swenson et al. 1963 at 22.75 MPa). Comparison of the friction coefficient under high heat flux conditions including significant viscosity and density reductions near the wall with various correlations for the hydraulic resistance will be presented; the best agreement is achieve with the correlation of Pioro et al. 2004. It is

  14. Numerical analysis of magnetic field effects on hydro-thermal behavior of a magnetic nanofluid in a double pipe heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Shakiba, Ali, E-mail: Shakiba7858@yahoo.com [Department of Mechanical Engineering, Mazandaran Institute of Technology, Babol (Iran, Islamic Republic of); Vahedi, Khodadad, E-mail: Khvahedi@ihu.ac.ir [Department of Mechanical Engineering, Imam Hossein University, Tehran (Iran, Islamic Republic of)

    2016-03-15

    This study attempts to numerically investigate the hydro-thermal characteristics of a ferrofluid (water and 4 vol% Fe{sub 3}O{sub 4}) in a counter-current horizontal double pipe heat exchanger, which is exposed to a non-uniform transverse magnetic field with different intensities. The magnetic field is generated by an electric current going through a wire located parallel to the inner tube and between two pipes. The single phase model and the control volume technique have been used to study the flow. The effects of magnetic field have been added to momentum equation by applying C++ codes in Ansys Fluent 14. The results show that applying this kind of magnetic field causes kelvin force to be produced perpendicular to the ferrofluid flow, changing axial velocity profile and creating a pair of vortices which leads to an increase in Nusselt number, friction factor and pressure drop. Comparing the enhancement percentage of Nusselt number, friction factor and pressure drop demonstrates that the optimum value of magnetic number for Re{sub ff}=50 is between Mn=1.33×10{sup 6} and Mn=2.37×10{sup 6}. So applying non-uniform transverse magnetic field can control the flow of ferrofluid and improve heat transfer process of double pipe heat exchanger. - Highlights: • Effect of applying non-uniform transverse magnetic field on a ferrofluid for enhancing the cooling process in a double pipe heat exchanger is investigated. • Heat exchanger is exposed to a non-uniform transverse magnetic field with different intensities. • The magnetic field is generated by an electric current going through a wire located parallel to inner tube and between two pipes. • Applying this field produces kelvin force to change axial velocity profile and creating a pair of vortices increasing Nusselt number, friction factor and pressure drop.

  15. Regulation of heat shock protein message in Jurkat cells cultured under serum-starved and gravity-altered conditions

    Science.gov (United States)

    Lewis, M. L.; Hughes-Fulford, M.

    2000-01-01

    Although our understanding of effects of space flight on human physiology has advanced significantly over the past four decades, the potential contribution of stress at the cellular and gene regulation level is not characterized. The objective of this ground-based study was to evaluate stress gene regulation in cells exposed to altered gravity and environmentally suboptimal conditions. We designed primers to detect message for both the constitutive and inducible forms of the heat shock protein, HSP-70. Applying the reverse transcriptase-polymerase chain reaction (RT-PCR), we probed for HSP-70 message in human acute T-cell leukemia cells, Jurkat, subjected to three types of environmental stressors: (1) altered gravity achieved by centrifugation (hypergravity) and randomization of the gravity vector in rotating bioreactors, (2) serum starvation by culture in medium containing 0.05% serum, and (3) temperature elevation (42 degrees C). Temperature elevation, as the positive control, significantly increased HSP-70 message, while centrifugation and culture in rotating bioreactors did not upregulate heat shock gene expression. We found a fourfold increase in heat shock message in serum-starved cells. Message for the housekeeping genes, actin and cyclophilin, were constant and comparable to unstressed controls for all treatments. We conclude that gravitational perturbations incurred by centrifugal forces, exceeding those characteristic of a Space Shuttle launch (3g), and culture in rotating bioreactors do not upregulate HSP-70 gene expression. In addition, we found RT-PCR useful for evaluating stress in cultured cells. Copyright 2000 Wiley-Liss, Inc.

  16. Loop Heat Pipe with Thermal Control Valve for Passive Variable Thermal Link, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Future Lunar Landers and Rovers will require variable thermal links that can reject heat during daytime, and passively shut-off during lunar night. During the long...

  17. Low Cost Variable Conductance Heat Pipe for Balloon Payload, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — While continuously increasing in complexity, the payloads of terrestrial high altitude balloons need a thermal management system to reject their waste heat and to...

  18. A comparison of different methods for in-situ determination of heat losses form district heating pipes

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, Benny [Technical Univ. of Denmark, Dept. of Energy Engineering (Denmark)

    1996-11-01

    A comparison of different methods for in-situ determination of heat losses has been carried out on a 273 mm transmission line in Copenhagen. Instrumentation includes temperature sensors, heat flux meters and an infrared camera. The methods differ with regard to time consumption and costs of applying the specific method, demand on accuracy of temperature measurements, sensitivity to computational parameters, e.g. the thermal conductivity of the soil, response to transients in water temperature and the ground, and steady state assumptions in the model used in the interpretation of the measurements. Several of the applied methods work well. (au)

  19. Convective heat transfer in foams under laminar flow in pipes and tube bundles.

    Science.gov (United States)

    Attia, Joseph A; McKinley, Ian M; Moreno-Magana, David; Pilon, Laurent

    2012-12-01

    The present study reports experimental data and scaling analysis for forced convection of foams and microfoams in laminar flow in circular and rectangular tubes as well as in tube bundles. Foams and microfoams are pseudoplastic (shear thinning) two-phase fluids consisting of tightly packed bubbles with diameters ranging from tens of microns to a few millimeters. They have found applications in separation processes, soil remediation, oil recovery, water treatment, food processes, as well as in fire fighting and in heat exchangers. First, aqueous solutions of surfactant Tween 20 with different concentrations were used to generate microfoams with various porosity, bubble size distribution, and rheological behavior. These different microfoams were flowed in uniformly heated circular tubes of different diameter instrumented with thermocouples. A wide range of heat fluxes and flow rates were explored. Experimental data were compared with analytical and semi-empirical expressions derived and validated for single-phase power-law fluids. These correlations were extended to two-phase foams by defining the Reynolds number based on the effective viscosity and density of microfoams. However, the local Nusselt and Prandtl numbers were defined based on the specific heat and thermal conductivity of water. Indeed, the heated wall was continuously in contact with a film of water controlling convective heat transfer to the microfoams. Overall, good agreement between experimental results and model predictions was obtained for all experimental conditions considered. Finally, the same approach was shown to be also valid for experimental data reported in the literature for laminar forced convection of microfoams in rectangular minichannels and of macrofoams across aligned and staggered tube bundles with constant wall heat flux.

  20. Void fraction correlations analysis and their influence on heat transfer of helical double-pipe vertical evaporator

    International Nuclear Information System (INIS)

    Parrales, Arianna; Colorado, Dario; Huicochea, Armando; Díaz, Juan; Alfredo Hernández, J.

    2014-01-01

    Highlights: • 50 void fraction correlations were evaluated on heat transfer in vertical evaporators. • Two-phase flow model based on control volume formulation was used. • The drift flux parameter is common in all correlations with satisfactory results. - Abstract: An analysis of 50 void fraction correlations available in the literature was performed to describe two-phase flow mechanism inside two helical double-pipe vertical evaporators. The evaporators considered water as working fluid connected in countercurrent so the change of phase was carried out into the internal tube. The discretized equations of continuity, momentum and energy in each flow were coupled using an implicit step by step method. The selection of the void fraction correlations for the mathematical model was based on inclusion of some theoretical limits. The results of this analysis were compared with the experimental data in steady state for two different evaporators, obtaining good agreement in the evaporation process for only 7 void fraction correlations. The Armand and Massena correlation had a mean percentage error (MPE) of 3.08%, followed by Rouhanni and Axelsson I adquired MPE=3.16%, Chisholm and Armand obtained MPE=3.18%, Steiner as well as Rouhanni and Axelsson II with MPE=3.19%, Bestion reached MPE=3.20% and Flanigan presented MPE=3.21%. Furthermore, the experimental and simulated heat flux were acceptable (R 2 =0.939). Finally, the results showed that the drift flux parameter was important to evaluate the void fraction