Sample records for heat transfer efficient

  1. Investigation of heat transfer efficiency in coplanar channels

    NASA Astrophysics Data System (ADS)

    Pelevin, F. V.; Yaroslavtsev, N. L.; Vikulin, A. V.; Orlin, S. A.; Ponomarev, A. V.

    2015-03-01

    Achieving more efficient heat transfer in heat-transfer devices is a topical problem. Heat transfer and pressure drop in paths containing coplanar channels of different shapes are experimentally studied in this work. It is found that the mutual crossing angles of coplanar channels, finning ratio, and the dimensions of coplanar channels are the main parameters influencing heat transfer enhancement. The best effect from using coplanar channels is achieved at the values of Reynolds number Re = 103-104. The coefficient of heat transfer in coplanar channels can be increased by a factor of 3-10 as compared with that for a smooth channel. The pressure drop coefficient ? increases with increasing the total mutual channel crossing angle. It is found that heat transfer in flat paths with coplanar channels becomes less efficient with decreasing the coplanar channel's equivalent hydraulic diameter to 0.5-1.0 mm, whereas more efficient heat transfer is obtained by fitting these channels with flow microturbulizers. It is shown that increasing the finning height in cylindrical paths with coplanar channels has no effect on vortex formation in them; however, it results in a higher finning ratio, due to which more efficient heat transfer is obtained

  2. Heat Transfer

    NSDL National Science Digital Library

    2014-09-18

    Students explore heat transfer and energy efficiency using the context of energy efficient houses. They gain a solid understanding of the three types of heat transfer: radiation, convection and conduction, which are explained in detail and related to the real world. They learn about the many ways solar energy is used as a renewable energy source to reduce the emission of greenhouse gasses and operating costs. Students also explore ways in which a device can capitalize on the methods of heat transfer to produce a beneficial result. They are given the tools to calculate the heat transferred between a system and its surroundings.

  3. Surface heat transfer coefficient, heat efficiency, and temperature of pulsed solid-state lasers

    SciTech Connect

    Mann, K.; Weber, H.

    1988-08-01

    The temperature of solid-state lasers is a critical parameter. Efficiency and output power are strongly influenced by it. The two parameters which determine the temperature are the heat generation efficiency (HGE) and the surface heat transfer coefficient (SHTC) of the laser rod. These parameters allow the scaling of the rod temperature up to high pumping powers. Moreover, from the temperature inside the rod, the temperature gradients and the mechanical stress can be evaluated. Using transient temperature measurements, the SHTC and the HGE were determined for air- and water-cooled Nd:YAG and alexandrite lasers. The SHTC can be confirmed by theoretical considerations.

  4. Field-structured composites for efficient, directed heat transfer

    NASA Astrophysics Data System (ADS)

    Martin, James E.; Gulley, G.

    2009-10-01

    Thermally conductive composites are needed for a variety of applications, especially as thermal interface materials. Unfortunately, the addition of even highly conductive particles to a polymer raises its conductivity only slightly and incurs a commensurate increase in the viscosity of the prepolymer resin. Meaningful increases in the thermal conductivity of the final composite require a filled resin that has the rheology of a typical paste. In this paper, we report on the use of uniaxial, biaxial, and triaxial ac magnetic fields to organize thermally conductive magnetic particles into structures that conduct heat more efficiently. Experimental results are compared to an extension of the Maxwell-Eucken theory that takes into account spatial correlations between particles. Both theory and experiment show that the thermal conductivity of field-structured composites increases essentially linearly with particle loading, and that the enhancement is significantly greater than that of unstructured composites. The measured conductivity enhancements are found to be comparable to the enhancements in magnetic permeability of these composites and are far less than the enhancements in the electrical conductivity. These results indicate the value of field structuring in enhancing the performance of a thermal interface material and show that particle percolation is not a critical factor in achieving high performance.

  5. Efficiency of a Curzon and Ahlborn engine with Dulong-Petit heat transfer law

    NASA Astrophysics Data System (ADS)

    Ladino-Luna, D.

    2003-02-01

    Using the maximization of the power output per cycle, the optimization of a thermal engine performing a Carnot-type cycle is considered. It is assumed that the heat transfer between the reservoirs and the engine occurs according to the Dulong and Petit's heat transfer law. It is, found that the efficiency obtained with this heat transfer law can be written as a power series in the parameter lambda similar to 1/(In V-max - InVmin), where V-max and V-min are the maximum volume and minimum volume spanned by the cycle, respectively. It is also shown that the calculated efficiency verifies the semi-sum property of the ecological efficiency.

  6. The effect of heat transfer on the volumetric efficiency for refrigerant compressors

    SciTech Connect

    Chen, L.T.

    1985-09-01

    A cylinder thermodynamic model considering the effect of heat transfer for a reciprocating compressor has been developed. A sample calculation for a typical R-22 compressor was carried out. The prediction of volumetric efficiency was found to be good when compared with some available experimental data.

  7. USING LIGA BASED MICROFABRICATION TO IMPROVE OVERALL HEAT TRANSFER EFFICIENCY OF PRESSURIZED WATER REACTOR: I. Effects of Different Micro Pattern on Overall Heat Transfer.

    SciTech Connect

    Zhang, M.; Ibekwe, S.; Li, G.; Pang, S.S.; and Lian, K.

    2006-07-01

    The Pressurized Water Reactors (PWRs in Figure 1) were originally developed for naval propulsion purposes, and then adapted to land-based applications. It has three parts: the reactor coolant system, the steam generator and the condenser. The Steam generator (a yellow area in Figure 1) is a shell and tube heat exchanger with high-pressure primary water passing through the tube side and lower pressure secondary feed water as well as steam passing through the shell side. Therefore, a key issue in increasing the efficiency of heat exchanger is to improve the design of steam generator, which is directly translated into economic benefits. The past research works show that the presence of a pin-fin array in a channel enhances the heat transfer significantly. Hence, using microfabrication techniques, such as LIGA, micro-molding or electroplating, some special microstructures can be fabricated around the tubes in the heat exchanger to increase the heat-exchanging efficiency and reduce the overall size of the heat-exchanger for the given heat transfer rates. In this paper, micro-pin fins of different densities made of SU-8 photoresist are fabricated and studied to evaluate overall heat transfer efficiency. The results show that there is an optimized micro pin-fin configuration that has the best overall heat transfer effects.

  8. Heat Transfer

    NSDL National Science Digital Library

    Ms. Leslie Van (Montgomery Blair High School)

    2006-04-01

    In this inquiry activity students explore how heat transfers from one substance to another This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÂ?s 2006 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

  9. A new method of efficient heat transfer and storage at very high temperatures

    NASA Technical Reports Server (NTRS)

    Shaw, D.; Bruckner, A. P.; Hertzberg, A.

    1980-01-01

    A unique, high temperature (1000-2000 K) continuously operating capacitive heat exchanger system is described. The system transfers heat from a combustion or solar furnace to a working gas by means of a circulating high temperature molten refractory. A uniform aggregate of beads of a glass-like refractory is injected into the furnace volume. The aggregate is melted and piped to a heat exchanger where it is sprayed through a counter-flowing, high pressure working gas. The refractory droplets transfer their heat to the gas, undergoing a phase change into the solid bead state. The resulting high temperature gas is used to drive a suitable high efficiency heat engine. The solidified refractory beads are delivered back to the furnace and melted to continue the cycle. This approach avoids the important temperature limitations of conventional tube-type heat exchangers, giving rise to the potential of converting heat energy into useful work at considerably higher efficiencies than currently attainable and of storing energy at high thermodynamic potential.

  10. Urban Sewage Delivery Heat Transfer System (2): Heat Transfer

    E-print Network

    Zhang, C.; Wu, R.; Li, X.; Li, G.; Zhuang, Z.; Sun, D.

    2006-01-01

    The thimble delivery heat-transfer (TDHT) system is one of the primary modes to utilize the energy of urban sewage. Using the efficiency-number of transfer units method ( ), the heat-transfer efficiencies of the parallel-flow and reverse-flow TDTH...

  11. OPTIMAL EFFICIENCY-POWER TRADEOFF FOR AN AIR MOTOR/COMPRESSOR WITH VOLUME VARYING HEAT TRANSFER CAPABILITY

    E-print Network

    Li, Perry Y.

    OPTIMAL EFFICIENCY-POWER TRADEOFF FOR AN AIR MOTOR/COMPRESSOR WITH VOLUME VARYING HEAT TRANSFER, also at 90% effiency, power gains are expected to be around 500­1500%. 1 Introduction Gas compression compressed air storage concept, an efficient and powerful air motor/compressor is needed. These two criteria

  12. Heat transfer -- Portland 1995

    SciTech Connect

    El-Genk, M.S. [ed.] [Univ. of New Mexico, Albuquerque, NM (United States)

    1995-12-31

    This Volume contains a total of forty seven papers, plus two abstracts, divided among eleven technical sessions on the following topics: Multiphase flow in waste management and environmental restoration, Parts 1 and 2; forced convection interphase transfer with particles; thermal-hydraulics in nuclear reactor systems, heat transfer phenomena in non-commercial reactors; heat transfer in containment; erosion, corrosion, and process heat transfer in power plant systems; innovative applications of solar energy; heat transfer aspects of space power and propulsion; fundamentals of heat pipes in space applications; and heat transfer and energy conversion in dual use power systems. Papers have been abstracted separately for inclusion on the data base.

  13. HEAT TRANSFER FLUIDS

    E-print Network

    Lenert, Andrej

    2012-01-01

    The choice of heat transfer fluids has significant effects on the performance, cost, and reliability of solar thermal systems. In this chapter, we evaluate existing heat transfer fluids such as oils and molten salts based ...

  14. Heat transfer system

    DOEpatents

    Not Available

    1980-03-07

    A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

  15. Heat transfer system

    DOEpatents

    McGuire, Joseph C. (Richland, WA)

    1982-01-01

    A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.

  16. Methods of Heat Transfer

    NSDL National Science Digital Library

    Mrs. Carlone

    2006-11-12

    To help students better understand conduction, convection, and radiation as methods of heat transfer in solids, liquids and gases. Let's look at all three methods of heat transfer ... Overview of Conduction, Convection, Radiation Conduction- 1. Explain what happens as heat energy is supplied to one part of a solid. 2. Explain how energy is transferred by conduction through a solid. Convection- 1. What is ?anything fluid? ? Include two examples. 2. Describe how and why heat is transferred in ...

  17. Application of Combined Enhanced Techniques for Design of Highly Efficient Air Heat Transfer Surface

    Microsoft Academic Search

    Ju-Fang Fan; Ya-Ling He; Wen-Quan Tao

    2012-01-01

    In order to reduce the size and cost of heat exchanger, an air side wavy fin-and-tube heat transfer surface with three-row tubes is required to be replaced by two-row tubes with some appropriate enhancing techniques. The major purpose of the present paper is to search for such new structure by numerical simulation. First longitudinal vortex generators of Delta-winglet type are

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

    NASA Astrophysics Data System (ADS)

    Pis'mennyi, E. N.

    2011-04-01

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

  19. Heat Transfer Guest Editorial

    E-print Network

    Kandlikar, Satish

    Journal of Heat Transfer Guest Editorial We are indeed delighted in bringing out this special issue was showcased in diverse areas such as traditional heat and mass transfer, lab-on-chip, sensors, biomedical applica- tions, micromixers, fuel cells, and microdevices. Selected papers in the field of heat transfer

  20. Enhancement of heat transfer

    NASA Astrophysics Data System (ADS)

    Nakayama, W.

    Recent publications on enhancement of heat transfer are reviewed, emphasizing the effects of roughness elements, fins, and porous surfaces. Enhancement of forced convective heat transfer on roughened surfaces, performance evaluation of enhanced surfaces, viscous flows in cooled tubes and tubes with swirlers, and active methods of enhancement are addressed. Aspects of pool boiling heat transfer are considered, including nucleate boiling heat transfer on rough surfaces and porous surfaces, and maximum and minimum heat fluxes. Evaporative heat transfer is discussed for thin-film evaporation on structured surfaces and liquid spray cooling of a heated surface. Condensation heat transfer on external surfaces is covered, including filmwise condensation on vertical finned and fluted surfaces and on horizontal tubes. In-tube boiling and condensation are treated, discussing their enhancement by fins and inserts, as well as critical heat flux in coiled, rifled, and corrugated tubes.

  1. An efficient algorithm for finite difference analyses of heat transfer with melting and solidification

    NASA Astrophysics Data System (ADS)

    Hsiao, J. S.

    1984-12-01

    A simple algorithm incorporating with the equivalent heat-capacity model is described for the finite-difference heat-transfer analysis with phase change. The specific heats associated to those nodes adjacent to the fusion front are determined using a linear interpolation of nodal temperatures to properly account for the latent heat effect. Numerical results for both one-dimensional and two-dimensional problems are in good agreement with those existing in the literature. This scheme is proven to be insensitive to the selection of temperature interval 2 delta T assumed for phase change to take place. Therefore, very small or large temperature interval 2 delta T can be used to properly simulate the fusion of pure metal or alloy, respectively. The present algorithm also could be extended to a three-dimensional phase change problem and other nonlinear heat-conduction analyses.

  2. Heat transfer efficiency evaluation for outward and inward multi-flame-hole gas burner

    NASA Astrophysics Data System (ADS)

    Morita, Shin-ichi; Hayamizu, Yasutaka; Katayama, Takashi; Inaba, Hideo

    2012-04-01

    The purpose of this study is to understand the factor that influence the heating efficiency of the outward and inward multi-hole gas burner. The flame-hole angle and the distance from flame hole to heating object are chosen as the experimental parameters. The measurement of the flame temperature distribution is carried out on each experimental condition. The observation of combustion flame, by the Schlieren method, is done from the purpose to understand the combustion phenomenon on the heating efficiency. LPG (Liquefied petroleum gas) is used for the test fuel gas. The compositions of LPG are propane 97.5vol%, butane 0.2vol% and methane + ethylene 2.3vol%. The optimum ranges of the flame-hole angle and the distance from flame hole to heating object are clarified. The experimental correlation equations for the outward and inward multi-flame-hole gas burner are proposed.

  3. Development and Demonstration of a High Efficiency, Rapid Heating, Low NOx Alternative to Conventional Heating of Round Steel Shapes, Steel Substrate (Strip) and Coil Box Transfer Bars

    SciTech Connect

    Kurek, Harry; Wagner, John

    2010-01-25

    Direct Flame Impingement involves the use of an array of very high-velocity flame jets impinging on a work piece to rapidly heat the work piece. The predominant mode of heat transfer is convection. Because of the locally high rate of heat transfer at the surface of the work piece, the refractory walls and exhaust gases of a DFI furnace are significantly cooler than in conventional radiant heating furnaces, resulting in high thermal efficiency and low NOx emissions. A DFI furnace is composed of a successive arrangement of heating modules through or by which the work piece is conveyed, and can be configured for square, round, flat, and curved metal shapes (e.g., billets, tubes, flat bars, and coiled bars) in single- or multi-stranded applications.

  4. Heat transfer dynamics

    SciTech Connect

    Smith, T.M. (Marsden, Inc., Pennsauken, NJ (United States))

    1994-08-01

    As heat transfer technology increases in complexity, it becomes more difficult for those without thermal dynamics engineering training to choose between competitive heat transfer systems offered to meet their drying requirements. A step back to the basics of heat transfer can help professional managers and papermakers make informed decisions on alternative equipment and methods. The primary forms of heat and mass transfer are reviewed with emphasis on the basics, so a practical understanding of each is gained. Finally, the principles and benefits of generating infrared energy by combusting a gaseous hydrocarbon fuel are explained.

  5. Containment condensing heat transfer

    NASA Astrophysics Data System (ADS)

    Gido, R. G.; Koestel, A.

    A mechanistic heat transfer model that is valid for large scale containment heat sinks was presented. The model development is based on the determination that the condensation is controlled by mass diffusion through the vapor-air boundary layer, and the application of the classic Reynolds' analog to formulate expressions for the transfer of heat and mass based on hydrodynamic measurements of the momentum transfer. As a result, the analysis depends on the quantification of the shear stress (momentum transfer) at the interface between the condensate film and the vapor-air boundary layer. In addition, the currently used Tagami and Uchida test observations and their range of applicability are explained.

  6. BOILING CRISIS:THEORY,SIMULATION,AND EXPERIMENTSBOILING CRISIS: THEORY, SIMULATION, AND EXPERIMENTS Boiling is a very efficient way to transfer heat from a heater to the liquid heat carrier. We discuss the

    E-print Network

    Nikolayev, Vadim S.

    BOILING CRISIS:THEORY,SIMULATION,AND EXPERIMENTSBOILING CRISIS: THEORY, SIMULATION, AND EXPERIMENTS Boiling is a very efficient way to transfer heat from a heater to the liquid heat carrier. We discuss the boiling crisis, a sharp decrease in the heat transfer rate, which can cause a major accident in industrial

  7. Proceedings of Heat Transfer 2003: ASME Summer Heat Transfer Conference

    E-print Network

    Kandlikar, Satish

    Proceedings of Heat Transfer 2003: ASME Summer Heat Transfer Conference Las Vegas, Nevada, USA July 21-23, 2003 HT2003-47449 HEAT TRANSFER FROM A MOVING AND EVAPORATING MENISCUS ON A HEATED SURFACE meniscus with complete evaporation of water without any meniscus break-up. The experimental heat transfer

  8. Heat transfer in pipes

    NASA Technical Reports Server (NTRS)

    Burbach, T.

    1985-01-01

    The heat transfer from hot water to a cold copper pipe in laminar and turbulent flow condition is determined. The mean flow through velocity in the pipe, relative test length and initial temperature in the vessel were varied extensively during tests. Measurements confirm Nusselt's theory for large test lengths in laminar range. A new equation is derived for heat transfer for large starting lengths which agrees satisfactorily with measurements for large starting lengths. Test results are compared with the new Prandtl equation for heat transfer and correlated well. Test material for 200- and to 400-diameter test length is represented at four different vessel temperatures.

  9. Investment casting heat transfer

    NSDL National Science Digital Library

    Powell, Adam C., IV

    2004-12-15

    Calculate temperature profile and Biot number in mixed conduction and convection/radiation heat transfer from liquid metal through a ceramic mold to the environment, and suggest a design change to reduce the probability of shattering due to thermal stress.

  10. Heat transfer studies

    Microsoft Academic Search

    R. Boehm; Y. T. Chen; A. K. Sathappan

    1995-01-01

    Work continued from last quarter related to studies of heat transfer and fluid flow in porous media. One experiment focused on issues of drying in subresidually-saturated systems. The other experiment deals with studies of flows in a repository-like geometry around a heated horizontal annulus. In the subresidual saturation studies, elevated temperature environments were considered during this quarter. A 1 in.

  11. Convective heat transfer in planetary dynamo models

    Microsoft Academic Search

    Eric M. King; Krista M. Soderlund; Ulrich R. Christensen; Johannes Wicht; Jonathan M. Aurnou

    2010-01-01

    The magnetic fields of planets and stars are generated by the motions of electrically conducting fluids within them. These fluid motions are thought to be driven by convective processes, as internal heat is transported outward. The efficiency with which heat is transferred by convection is integral in understanding dynamo processes. Several heat transfer scaling laws have been proposed, but the

  12. Understanding heat transfer

    NSDL National Science Digital Library

    2010-01-01

    Understanding Heat Transfer is a graduate-level professional development course designed for middle school teachers to enhance understanding and teaching of physical science. In two sessions, you will investigate physical science topics using hands-on activities and online resources including video segments, interactive activities, readings, and other multimedia materials. These resources are drawn from Teachers' Domain, WGBH's digital library service.

  13. Solar Energy: Heat Transfer.

    ERIC Educational Resources Information Center

    Knapp, Henry H., III

    This module on heat transfer is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies. The…

  14. Heat Transfer Technical Brief

    E-print Network

    Banerjee, Debjyoti

    Journal of Heat Transfer Technical Brief Pool Boiling Experiments on Multiwalled Carbon Nanotube with verti- cally aligned multiwalled carbon nanotubes (MWCNT) "forests" and were used for pool boiling chemical vapor deposition (CVD) process. The sub- strates were clamped on a cylindrical copper block

  15. Methane heat transfer investigation

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Future high chamber pressure LOX/hydrocarbon booster engines require copper base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and reusable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper base alloy material adjacent to he fuel coolant. High pressure methane cooling and coking characteristics recently evaluated at Rocketdyne using stainless steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.

  16. Methane heat transfer investigation

    NASA Technical Reports Server (NTRS)

    Cook, R. T.

    1984-01-01

    Future high chamber pressure LOX/hydrocarbon booster engines require copper-base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and resuable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper-base alloy material adjacent to the fuel coolant. High-pressure methane cooling and coking characteristics were recently evaluated using stainless-steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper-base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.

  17. Geothermal Heat Transfer

    SciTech Connect

    Basmajian, V.V.

    1986-01-28

    This patent describes a heat transfer apparatus which consists of: heat exchanging means for orientation in the earth below ground substantially vertically, having a hollow conduit of length from top to bottom much greater than the span across the hollow conduit orthogonal to its length with a top, bottom and an intermediate portion contiguous and communicating with the top and bottom portions for allowing thermally conductive fluid to flow freely between the top, intermediate and bottom portions for immersion in thermally conductive fluid in the region around the heat exchanging means for increasing the heat flow between the latter and earth when inserted into a substantially vertical borehole in the earth with the top portion above the bottom portion. The heat exchanger consists of heat exchanging conduit means in the intermediate portion for carrying refrigerant. The heat exchanging conduit consisting of tubes of thermally conductive material for carrying the refrigerant and extending along the length of the hollow conduit for a tube length that is less than the length of the hollow conduit. The hollow conduit is formed with port means between the top and the plurality of tubes for allowing the thermally conductive fluid to pass in a flow path embracing the tubes, the bottom portion, an outer channel around the hollow conduit and the port means.

  18. Faculty Positions Heat Transfer and

    E-print Network

    Faculty Positions Heat Transfer and Thermal/Energy Sciences Naval Postgraduate School Monterey-track faculty position at the assistant professor level in the areas of Heat Transfer and Thermal/Fluid Sciences

  19. Nano materials for efficiently lowering the freezing point of heat transfer nanofluids

    Microsoft Academic Search

    Haiping Hong; Walter Roy

    2007-01-01

    In this paper, we report, for the first time, the effect of the lowered freezing point in a 50% water \\/ 50% antifreeze coolant (PAC) or 50% water \\/ 50% ethylene glycol (EG) solution by the addition of carbon nanotubes and other particles. The experimental results indicated that the nano materials are much more efficient (hundreds fold) in lowering the

  20. Heat transfer in geothermal systems

    Microsoft Academic Search

    P. Cheng

    1978-01-01

    Theoretical and experimental investigations of convective heat transfer in geothermal systems are reviewed. The governing equations for such heat transfer in geothermal systems are examined, along with heat transfer in hot-water, water-steam two-phase, and geopressured geothermal systems. Lumped-parameter analyses for predicting averaged reservoir characteristics during production are considered, heat transfer in other geothermal systems (e.g., dry hot rock and magma)

  1. Laser Generated Heat Transfer

    Microsoft Academic Search

    Kenneth R. Diller

    \\u000a The irradiation of tissue by laser light results in the absorption of energy. Since this is a fully dissipative process, the\\u000a consequence is that the increment in energy is expressed entirely as a heat transfer absorbed by the tissue. In conjunction\\u000a with this absorption, there will be an increase in the energy stored locally in the tissue as a function

  2. "Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"

    SciTech Connect

    Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann

    2008-06-12

    ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers

  3. Heat transfer in aeropropulsion systems

    NASA Technical Reports Server (NTRS)

    Simoneau, R. J.

    1985-01-01

    Aeropropulsion heat transfer is reviewed. A research methodology based on a growing synergism between computations and experiments is examined. The aeropropulsion heat transfer arena is identified as high Reynolds number forced convection in a highly disturbed environment subject to strong gradients, body forces, abrupt geometry changes and high three dimensionality - all in an unsteady flow field. Numerous examples based on heat transfer to the aircraft gas turbine blade are presented to illustrate the types of heat transfer problems which are generic to aeropropulsion systems. The research focus of the near future in aeropropulsion heat transfer is projected.

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

    E-print Network

    Barber, Jacqueline Claire

    2010-01-01

    Boiling in microchannels is a very efficient mode of heat transfer with high heat and mass transfer coefficients achieved. Less pumping power is required for two-phase flows than for single-phase liquid flows to achieve ...

  5. Heat transfer probe

    DOEpatents

    Frank, Jeffrey I.; Rosengart, Axel J.; Kasza, Ken; Yu, Wenhua; Chien, Tai-Hsin; Franklin, Jeff

    2006-10-10

    Apparatuses, systems, methods, and computer code for, among other things, monitoring the health of samples such as the brain while providing local cooling or heating. A representative device is a heat transfer probe, which includes an inner channel, a tip, a concentric outer channel, a first temperature sensor, and a second temperature sensor. The inner channel is configured to transport working fluid from an inner inlet to an inner outlet. The tip is configured to receive at least a portion of the working fluid from the inner outlet. The concentric outer channel is configured to transport the working fluid from the inner outlet to an outer outlet. The first temperature sensor is coupled to the tip, and the second temperature sensor spaced apart from the first temperature sensor.

  6. Heat transfer coefficient of cryotop during freezing.

    PubMed

    Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

    2013-01-01

    Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K). PMID:23812315

  7. 5. Heat transfer Ron Zevenhoven

    E-print Network

    Zevenhoven, Ron

    -moving medium (i.e. a solid, or stagnant fluid) in the presence of a temperature gradient, heat is transferred from high to low temperature as a result of molecular movement: heat conduction (sv: värmeledning) For a one-dimensional temperature gradient T/x or dT/dx, Fourier's Law gives the conductive heat transfer

  8. Conduction heat transfer solutions

    SciTech Connect

    VanSant, J.H.

    1983-08-01

    This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.

  9. Conduction heat transfer solutions

    SciTech Connect

    VanSant, J.H.

    1980-03-01

    This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references.

  10. Heat Transfer Discussion: "Heat Transfer and Wall

    E-print Network

    Kandlikar, Satish

    flow boiling curve extending from the single-phase region at point C to the fully developed boiling During Subcooled Flow Nucleate Boiling­A Review" (Warrier, G.R., and Dhir, V.K., 2006, Journal of Heat in the partial boiling region, along with Eqs. 13 - 14 . The authors of 1 further state that Kandlikar 3 in 1998

  11. Heat transfer in turbulent flow

    SciTech Connect

    Amano, R.S.; Crawford, M.E.; Anand, N.K.

    1990-01-01

    The present volume on heat transfer in turbulent flow discusses heat transfer through a pressure-driven 3D boundary layer, the effects of simulated combustor turbulence on boundary layer heat transfer, an experiment on spatial and temporal turbulent structures of a natural convection boundary layer, and the influence of high mainstream turbulence on leading edge heat transfer. Attention is given to turbulent heat transfer in an axisymmetric cavity with a small expansion ratio, a temperature turbulence spectrum for high temperature radiating gases, and the development of a two-scale turbulence model and prediction of buoyant shear flows. Topics addressed include prediction of film cooling with lateral injection, the computation of turbulent flow in a thin liquid layer of fluid involving a hydraulic jump, 3D laminar and turbulent natural convection cooling of heated blocks, and critical heat flux in subcooled flow boiling on finned and unfinned tube geometries.

  12. Heat Transfer through Rockfall

    NASA Astrophysics Data System (ADS)

    Green, R. T.; Pohle, J.; Prikryl, J.

    2004-12-01

    Thermally induced rock stresses at the potential high-level nuclear waste (HLW) repository at Yucca Mountain, Nevada, can degrade the drifts, possibly causing rockfall onto the dripshield overlying the emplaced waste packages. Thermal-hydrological processes will be altered by changes in thermal conductivity, ventilation, radiation, and convection resulting from such rockfalls. Determining the effects of collapse materials on repository performance is difficult because heat and mass transfer through the engineered barrier and highly heterogeneous collapse materials is a complex and coupled process. Measurements and estimates of thermal conductivity of intact rock samples from geologic units at Yucca Mountain are available, but collapsed rock will be a mixture of broken rock and air. The purpose of this investigation is to assess the thermal conductivity of crushed tuff from the Topopah Spring lower lithophysal unit at Yucca Mountain and identify the important heat and mass transfer mechanisms in the collapsed rock for the range of conditions expected at a potential geologic HLW repository. A laboratory apparatus was used to directly measure steady-state bulk thermal conductivity of crushed tuff for a range of temperatures up to 197ºC and thermal gradients as large as 990ºC/m. Measured thermal conductivities varied from 0.38 to 0.56 W/m-K. In general, thermal conductivity increased with either increased temperature or increased thermal gradient. This abstract is an independent product of the CNWRA and does not necessarily reflect the views or regulatory position of the NRC. The NRC staff views expressed herein are preliminary and do not constitute a final judgement of determination of the matters addressed or the acceptability of a license application for a geologic repository at Yucca Mountain.

  13. Tubing for augmented heat transfer

    SciTech Connect

    Yampolsky, J.S.; Pavlics, P.

    1983-08-01

    The objectives of the program reported were: to determine the heat transfer and friction characteristics on the outside of spiral fluted tubing in single phase flow of water, and to assess the relative cost of a heat exchanger constructed with spiral fluted tubing with one using conventional smooth tubing. An application is examined where an isolation water/water heat exchanger was used to transfer the heat from a gaseous diffusion plant to an external system for energy recovery. (LEW)

  14. Preparation and heat transfer properties of nanoparticle-in-transformer oil dispersions as advanced energy-efficient coolants

    Microsoft Academic Search

    C. Choi; H. S. Yoo; J. M. Oh

    2008-01-01

    Three kinds of nanofluids are prepared by dispersing Al2O3 and AlN nanoparticles-in-transformer oil. The thermal conductivity of the nanoparticle–oil mixtures increases with particle volume fraction and thermal conductivity of the solid particle itself. The AlN nanoparticles at a volume fraction of 0.5% can increase the thermal conductivity of the transformer oil by 8% and the overall heat transfer coefficient by

  15. Heat Transfer: From Hot to Not

    NSDL National Science Digital Library

    2014-09-18

    Students learn the fundamental concepts of heat transfer and heat of reaction. This includes concepts such as physical chemistry, an equation for heat transfer, and a basic understanding of energy and heat transfer.

  16. Heat transfer in gas tungsten arc welding

    SciTech Connect

    Smartt, H.B.; Stewart, J.A.; Einerson, C.J.

    1986-05-01

    The heat transferred from an electrode negative, argon gas tungsten arc to an anode has been measured for a wide range of conditions suitable for mechanized welding applications. The results are given as (1) the arc efficiency; and (2) the anode heat and current input distribution functional shapes and radii for various anode materials and groove shapes over a wide range of current and voltage, using different electrode geometries, as well as both He and Ar-He shielding gases. The nominal arc is Gaussian with a diameter of about 4 mm and a heat transfer efficiency to the anode of about 75%. Variations from these values are discussed in terms of current knowledge of the electrical and thermal energy transport mechanisms. A new method of measuring the heat transferred from the arc to the anode, using a boiling liquid nitrogen calorimeter, has been developed which gives rapid, accurate values.

  17. Spring 2014 Heat Transfer -2

    E-print Network

    Virginia Tech

    Spring 2014 Heat Transfer - 2 A thin electronic chip is in the shape of a square wafer, b = 1 cm surface of the chip with a heat transfer coefficient of h = 100 W/m2 -K. Assume the chip has a uniform per side with a mass of m = 0.3 grams and specific heat of C = 103 J/kg-K. The chip is mounted

  18. Spring 2014 Heat Transfer -1

    E-print Network

    Virginia Tech

    Spring 2014 1 Heat Transfer - 1 Consider a cylindrical nuclear fuel rod of length L and diameter df and the tube at a rate m , and the outer surface of the tube is well insulated. Heat generation occurs within. The specific heat of water pc , and the thermal conductivity of the fuel rod fk are constants. The system

  19. MODERN DEVELOPMENTS IN MULTIPHASE FLOW & HEAT TRANSFER

    E-print Network

    Lahey, Richard T.

    MODERN DEVELOPMENTS IN MULTIPHASE FLOW & HEAT TRANSFER "ENGINEERING APPLICATIONS OF FRACTAL and multiphase flow & heat transfer will be stressed. This paper will begin by reviewing some important concepts

  20. Heat transfer in internal combustion engines

    Microsoft Academic Search

    C. S. Wang; G. F. Berry

    1985-01-01

    A heat transfer model has been developed that uses quasi-steady heat flux relations to calculate the heat transfer from combustion gases through the cylinder wall to the coolant in an internal combustion engine. The treatment of convective heat transfer accounts for the physical problems of rotating and impinging axial flow inside the engine cylinder. The radiative heat transfer includes gas

  1. Heat transfer characteristics for disk fans

    NASA Astrophysics Data System (ADS)

    Prikhodko, Yu. M.; Chekhov, V. P.; Fomichev, V. P.

    2014-08-01

    Multiple-disk fans belong to the class of friction machines; they can be designed in two variants: centrifugal disk fans and diametrical disk fans. Flow patterns in these two types of machines are different, and they possess different heat transfer characteristics. The paper presents results of experimental study for a centrifugal disk fan under atmospheric pressure with air taken as working gas. The radial temperature distribution for a disk was obtained at different rotation speed of the rotor and different heating of the disks. Heat transfer characteristics of a centrifugal disk fan and a diametrical disk fan were compared. The research results demonstrate a higher heat transfer efficiency for centrifugal design versus diametrical disk design.

  2. Introductory heat-transfer

    NASA Technical Reports Server (NTRS)

    Widener, Edward L.

    1992-01-01

    The objective is to introduce some concepts of thermodynamics in existing heat-treating experiments using available items. The specific objectives are to define the thermal properties of materials and to visualize expansivity, conductivity, heat capacity, and the melting point of common metals. The experimental procedures are described.

  3. Influence of structural design condensing part of NH3 heat pipe to heat transfer

    NASA Astrophysics Data System (ADS)

    Vantúch, Martin; Malcho, Milan

    2014-03-01

    The article describes influence design heat exchangers to efficiency condensation liquid ammonia in the gravitational heat pipe. Analyse adverse factors in the operation and flow of ammonia in heat pipe. Also describes heat transfer characteristics of heat pipe in low-potential geothermal heat transport simulations.

  4. Enhanced heat transfer using nanofluids

    DOEpatents

    Choi, Stephen U. S. (Lisle, IL); Eastman, Jeffrey A. (Naperville, IL)

    2001-01-01

    This invention is directed to a method of and apparatus for enhancing heat transfer in fluids such as deionized water. ethylene glycol, or oil by dispersing nanocrystalline particles of substances such as copper, copper oxide, aluminum oxide, or the like in the fluids. Nanocrystalline particles are produced and dispersed in the fluid by heating the substance to be dispersed in a vacuum while passing a thin film of the fluid near the heated substance. The fluid is cooled to control its vapor pressure.

  5. Unsteady heat transfer in heat pipes

    NASA Astrophysics Data System (ADS)

    Beam, J. E.

    The purpose was to investigate the unsteady heat transfer associated with a heat pipe during start up operation. Initial studies were conducted with a variety of heat pipe screen wick configurations in order to develop a mathematical expression for the flow velocity of a fluid inducted by the capillary structure of the wick. This mathematical model was solved first numerically and then simplified to provide a closed form solution. The results were compared with the experimental data and proved to provide consistent results with plus or minus 10%. A lumped parameter model of the heat pipe was next developed so that the transient operation of the heat pipe could be predicted. Upon evalaution of the model it was shown that the model and the experimental data agreed quite well in overall performance but an initial period of performance was identified where the experimental results differed significantly from the lumped parameter model. During this initial period of operation, large temperature gradients were observed, and it was theorized that the effect was a result of the interdependence of the hydrodynamics and the heat transfer characteristics of the heat pipe.

  6. Nanofluid impingement jet heat transfer

    PubMed Central

    2012-01-01

    Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669

  7. Heat transfer from oriented heat exchange areas

    NASA Astrophysics Data System (ADS)

    Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej

    2014-03-01

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

  8. Examination of Liquid Fluoride Salt Heat Transfer

    SciTech Connect

    Yoder Jr, Graydon L [ORNL] [ORNL

    2014-01-01

    The need for high efficiency power conversion and energy transport systems is increasing as world energy use continues to increase, petroleum supplies decrease, and global warming concerns become more prevalent. There are few heat transport fluids capable of operating above about 600oC that do not require operation at extremely high pressures. Liquid fluoride salts are an exception to that limitation. Fluoride salts have very high boiling points, can operate at high temperatures and low pressures and have very good heat transfer properties. They have been proposed as coolants for next generation fission reactor systems, as coolants for fusion reactor blankets, and as thermal storage media for solar power systems. In each case, these salts are used to either extract or deliver heat through heat exchange equipment, and in order to design this equipment, liquid salt heat transfer must be predicted. This paper discusses the heat transfer characteristics of liquid fluoride salts. Historically, heat transfer in fluoride salts has been assumed to be consistent with that of conventional fluids (air, water, etc.), and correlations used for predicting heat transfer performance of all fluoride salts have been the same or similar to those used for water conventional fluids an, water, etc). A review of existing liquid salt heat transfer data is presented, summarized, and evaluated on a consistent basis. Less than 10 experimental data sets have been found in the literature, with varying degrees of experimental detail and measured parameters provided. The data has been digitized and a limited database has been assembled and compared to existing heat transfer correlations. Results vary as well, with some data sets following traditional correlations; in others the comparisons are less conclusive. This is especially the case for less common salt/materials combinations, and suggests that additional heat transfer data may be needed when using specific salt eutectics in heat transfer equipment designs. All of the data discussed above were taken under forced convective conditions (both laminar and turbulent). Some recent data taken at ORNL under free convection conditions are also presented and results discussed. This data was taken using a simple crucible experiment with an instrumented nickel heater inserted in the salt to induce natural circulation within the crucible. The data was taken over a temperature range of 550oC to 650oC in FLiNaK salt. This data covers both laminar and turbulent natural convection conditions, and is compared to existing forms of natural circulation correlations.

  9. Heat transfer in oscillating flows

    NASA Technical Reports Server (NTRS)

    El-Mehlawy, F.; Mankbadi, R. R.

    1990-01-01

    The heat transfer in a sudden-expansion flow subjected to upstream periodic disturbances is investigated. In order to study the unsteady turbulent flow for the present symmetrical sudden-expansion flow, the phase-averaging technique of Hussain and Reynolds (1970) is used to derive the governing equations. The imposed periodic disturbances are found to increase the turbulent kinetic energy and the heat transfer rates at the wall. The phenomenon is discovered to be sensitive to the frequency of the imposed disturbances. At the optimum frequency and at a 3 percent disturbance level, the time-averaged heat transfer rate near the reattachment point can be increased by as much as 14 percent.

  10. Energy Efficient Steam Trapping of Trace Heating Systems

    E-print Network

    Krueger, R. G.; Wilt, G. W.

    1981-01-01

    desired product temperatures and greatly reduce steam losses. Factors related to achieving uniform product temperatures and maximum heat transfer rates and energy efficiency are: 1.Types and Methods used for Steam Tracing; 2. Systematic heat balance...

  11. Sodium heat transfer system modeling

    NASA Astrophysics Data System (ADS)

    Baker, A. F.; Fewell, M. E.

    1983-11-01

    The sodium heat transfer system of the international energy agency (IEA) small solar power systems (SSPS) central receiver system (CRS), which includes the heliostat field, receiver, hot and cold storage vessels, and sodium/water steam generator was modeled. The computer code SOLTES (simulator of large thermal energy systems), was used to model this system. The results from SOLTES are compared to measured data.

  12. Host turbine heat transfer overview

    NASA Astrophysics Data System (ADS)

    Rohde, J. E.

    1984-10-01

    Improved methods of predicting airfoil local metal temperatures require advances in the understanding of the physics and methods of analytically predicting the following four aerothermal loads: hot gas flow over airfoils, heat transfer rates on the gas-side of airfoils, cooling air flow inside airfoils, and heat transfer rates on the coolant-side of airfoils. A systematic building block research approach is being pursued to investigate these four areas of concern from both the experimental and analytical sides. Experimental approaches being pursued start with fundamental experiments using simple shapes and flat plates in wind tunnels, progress to more realistic cold and hot cascade tests using airfoils, continue to progress in large low-speed rigs and turbines and warm turbines, and finally, combine all the interactive effects in tests using real engines or real engine type turbine rigs. Analytical approaches being pursued also build from relatively simple steady two dimensional inviscid flow and boundary layer heat transfer codes to more advanced steady two and three dimensional viscous flow and heat transfer codes. These advanced codes provide more physics to model better the interactive effects and the true real-engine environment.

  13. Radiative heat transfer

    NASA Astrophysics Data System (ADS)

    Chapman, K.; Ramadhyani, S.; Ramamurthy, H.; Viskanta, R.

    1989-03-01

    A simple two-dimensional mathematical model was developed to predict the steady state thermal performance and combustion characteristics of a natural gas indirectly fired once-through radiant tube. Different burner geometries were studied and a grid size analysis was performed to determine the optimum grid spacing for each case. The rate of fuel burn-up was correlated using the burner geometry, the equivalence ratio, the fuel firing rate and air preheat temperatures as variables for non-swirling diffusion flames in the radiant tube. The model predictions were also compared with available experimental data for the purpose of validating the model. The transient, zero-dimensional model was used to conduct a detailed parametric study of a directly-fired batch reheating furnace. The parameters that were investigated are the load and refractory emissivities, the air preheat temperature, the heat capacity of the load, and the height of the combustion space. A one-dimensional model of a directly-fired continuous reheating furnace was also developed. A parametric study was completed to examine the effect of the local throughput on the furnace performance.

  14. Preliminary analysis of rapid boiling heat transfer

    Microsoft Academic Search

    Jinliang Wang

    2000-01-01

    Rapid boiling is a transient heat transfer phenomenon which occurs when a subcooled or saturated liquid quickly enters a highly metastable state. The preliminary analyses of the rapid boiling heat transfer are carried out in the paper. A physical process model is suggested for describing the rapid boiling heat transfer and a boundary microlayer on the heating surface is put

  15. Heat transfer in aerospace propulsion

    NASA Technical Reports Server (NTRS)

    Simoneau, Robert J.; Hendricks, Robert C.; Gladden, Herbert J.

    1988-01-01

    Presented is an overview of heat transfer related research in support of aerospace propulsion, particularly as seen from the perspective of the NASA Lewis Research Center. Aerospace propulsion is defined to cover the full spectrum from conventional aircraft power plants through the Aerospace Plane to space propulsion. The conventional subsonic/supersonic aircraft arena, whether commercial or military, relies on the turbine engine. A key characteristic of turbine engines is that they involve fundamentally unsteady flows which must be properly treated. Space propulsion is characterized by very demanding performance requirements which frequently push systems to their limits and demand tailored designs. The hypersonic flight propulsion systems are subject to severe heat loads and the engine and airframe are truly one entity. The impact of the special demands of each of these aerospace propulsion systems on heat transfer is explored.

  16. Glycol coolants improve heat transfer and corrosion control

    Microsoft Academic Search

    Holfield

    1995-01-01

    Various liquids from plain water to exotic fluids have been used as coolants in large stationary diesel engines that drive compressors on natural gas pipeline distribution systems. Although water is an efficient heat transfer medium, its drawbacks of freezing at -32 F and boiling at 212 F seriously limit its usefulness. Special glycol-based heat transfer fluids are available and refined

  17. Journal of Heat Transfer1999 JHT Heat Transfer Gallery Department of Mechanical 8. Aerospace Engineering

    E-print Network

    Kihm, IconKenneth David

    Journal of Heat Transfer1999 JHT Heat Transfer Gallery S. M. You Department of Mechanical 8 Transfer Visualization Committee organized two photo gallery sessions in 1998. The International Heat Transfer Photo Gallery was held at the l la' International Heat Transfer Conference (IHTC) in Kyongju

  18. Investigation of heat transfer and pressure drop in an annular channel with heat transfer intensifiers

    NASA Astrophysics Data System (ADS)

    Boltenko, E. A.; Varava, A. N.; Dedov, A. V.; Zakharenkov, A. V.; Komov, A. T.; Malakhovskii, S. A.

    2015-03-01

    Results from systematic investigations of heat transfer and pressure drop for water flow in an annular channel using an efficient method for enhancing heat transfer on a convex heating surface are presented. The main technical data of the thermal-hydraulic experimental setup are given together with a brief description of the control, monitoring, and physical parameters measurement and recording systems, as well as primary experimental data processing and storage system. The test section, the enhancement method based on setting up swirl flows, the geometrical characteristics of intensifiers, their schematic design, and installation technology are described. The experimental data are obtained in a wide range of coolant flow parameters under the conditions of single-phase convection with using intensifiers having different shapes. The test measurements carried out on a smooth annular channel showed good agreement with the classic correlations both for heat transfer and pressure drop, thereby confirming reliability of the experimental data. A considerable improvement in heat removal efficiency on the convex heating surface is obtained. The value of heat transfer coefficient is a factor of 1.8 higher than it is for smooth annular channels. The region of the values of intensifier geometrical characteristics and Reynolds numbers for which the growth of heat transfer prevails over the growth of pressure drop is established. It is shown that the maximums of heat transfer and pressure drop are observed at quite definite values of intensifier geometrical characteristics. The primary experimental data are processed and presented as a dependence of the Nusselt number on the Reynolds number for different values of the intensifier's relative fin height ?. The value of ? at which heat transfer reaches its maximum is found. The experiments were carried out in the pressure range p = 3.0-10.0 MPa and at the constant temperature of liquid at the test section inlet equal to 100°C. The influence of peripheral liquid flow swirling pitch on heat transfer and pressure drop is studied. An empirical correlation describing the dependence of heat transfer on the intensifier geometrical characteristics is obtained.

  19. Acoustically enhanced boiling heat transfer

    NASA Astrophysics Data System (ADS)

    Douglas, Zachary; Boziuk, Thomas R.; Smith, Marc K.; Glezer, Ari

    2012-05-01

    An acoustic field generated by a light-weight, low-power acoustic driver is shown to increase the critical heat flux during pool boiling by about 17%. It does this by facilitating the removal of vapor bubbles from the heated surface and suppressing the instability that leads to the transition to film boiling at the critical heat flux. Bubble removal is enhanced because the acoustic field induces capillary waves on the surface of a vapor bubble that interact with the bubble contact line on the heated surface causing the contact line to contract and detach the bubble from the surface. The acoustic field also produces a radiation pressure that helps to facilitate the bubble detachment process and also suppresses the transition to film boiling. The mechanisms associated with these interactions are explored using three different experimental setups with acoustic forcing: an air bubble on the underside of a horizontal surface, a single vapor bubble on the top side of a horizontal heated surface, and pool boiling from a horizontal heated surface. Measurements of the capillary waves induced on the bubbles, bubble motion, and heat transfer from the heated surface were performed to isolate and identify the dominant forces involved in these acoustically forced motions.

  20. A study on a flexible wing with up-down vibration in a pulsating flow of cooling air to improve heat transfer efficiency

    NASA Astrophysics Data System (ADS)

    Park, Ki-Hong; Min, June Kee; Kim, Jin-Kyu; Park, Sang-Hu; Ha, Man Yeong

    2013-10-01

    We investigated a flexible wing that can function as a folding fan by vibrating smoothly on a heated surface, and the effects of this vibration on heat transfer. For flexible up-down vibrations of the wing in a pulsating flow, we propose a novel milli-scale flexible wing shape with a relatively large body and a narrow connecting leg. The shape was optimized such that its deformation became much larger at a low air flow. We performed two-way fluid-structure interaction analyses to predict performance, and an experimental validation was also conducted. The details of flow, heat transfer, and structural deformation are summarized qualitatively. Our results show that the heat transfer coefficient of a heated surface with a single flexible wing was approximately 11.3 % greater than that of a flat plate.

  1. Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants

    NASA Astrophysics Data System (ADS)

    Yoshida, Suguru; Fujita, Yasunobu

    The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.

  2. Heat transfer and planetary evolution

    NASA Astrophysics Data System (ADS)

    Tozer, D. C.

    1985-06-01

    The object of this account is to show how much one can interprete and predict about the present state of material forming planet size objects, despite the fact we do not and could never have the kind of exact or prior knowledge of initial conditions and in situ material behaviour that would make a formal mathematical analysis of the dynamical problems of planetary evolution an efficient or meaningful exercise The interest and usefulness of results obtained within these limitations stem from the highly non linear nature of planetary scale heat transfer problems when posed in any physically plausible form. The non linearity arising from a strongly temperature dependent rheology assumed for in situ planetary material is particularly valuable in deriving results insensitive to such uncertainties. Qualitatively, the thermal evolution of a planet is quite unlike that given by heat conduction calculation below a very superficial layer, and much unnecessary argument and confusion results from a persistent failure to recognise that fact. At depths that are no greater on average than a few tens of kilometres in the case of Earth, the temperature distribution is determined by a convective flow regime inaccessble to the laboratory experimenter and to the numerical methods regularly employed to study convective movement. A central and guiding quantitative result is the creation in homogeneous planet size objects having surface temperatures less than about half the absolute melting temperature of their material, of internal states with horizontally a veraged viscosity values ˜1021 poise. This happens in times short compared with the present Solar System age. The significance of this result for an understanding of such processes and features as isostasy, continental drift, a minimum in seismic S wave velocity in Earth's upper mantle, a uniformity of mantle viscosity values, the survival of liquid planetary cores and the differentiation of terrestrial planet material is examined. After a discussion and definition of ‘lithospheric’ material, it is concluded that endogenous tectonic activity only continues on Earth's surface on account of water enhancing the deformability of its rocks. Metal/silicate differentiation of terrestrial planet material is predicted to have been a global scale catastrophic process in the many objects it formed predating the existing planets, but intersilicate and volatile/silicate separations are necessarily protracted, quasi continous processes arising from local shear instabilties in the convective flow of such a viscous material. In particular, these local magma producing instabilities require the involvement of ‘lithospheric’ planetary material in convective movements and it is shown how this unsteadiness accounts for the distribution and salient features of planetary seismicity and vulcanicity at the present time. The picture that emerges for the state of Earth's silicate shell material after more than four billion years of average viscosity regulation and shear instability is one of chemical and isotopic heterogeneity on a wide range of length scales. The larger length scales of this range are introduced by the pattern of heterogeneity remixing rather than its generation. For example, at the largest scale, the predicted heterogeneity is radial and a feature indirectly arising from properties conferred on the shell material by major mineral phase transitions at depths ˜700km. These increase the adiabatic temperature gradient and have the effect of a barrier adequate in strength to prevent wholesale mixing of the material above and below for at least a large fraction of the Earth's history in which radiogenic heat has been the dominant cause of large scale internal movements. That such a barrier actually marks a chemical and isotopic heterogeneity of the mantle is because only the convective movements above it are prone to the shear heating instabilities on which differentiation absolutely depends. Many millions of such instabilities in this shallower shell material would by now have created a thre

  3. Enhanced heat transfer techniques for industrial heat exchangers

    Microsoft Academic Search

    A. E. Bergles

    1991-01-01

    An introductory lecture on the enhancement of convective heat transfer which provides background for the many applications of this 'second generation heat transfer technology' is presented. The many available enhancement techniques are described, and some representative performance data and correlations are given for the popular passive techniques. The discussion is organized according to the modes of heat transfer ranging from

  4. Conceptions for heat transfer correlation of nanofluids

    Microsoft Academic Search

    Yimin Xuan; Wilfried Roetzel

    2000-01-01

    The nanofluid is a solid–liquid mixture in which metallic or nonmetallic nanoparticles are suspended. The suspended ultrafine particles change transport properties and heat transfer performance of the nanofluid, which exhibits a great potential in enhancing heat transfer. The mechanism of heat transfer enhancement of the nanofluid is investigated. Based on the assumption that the nanofluid behaves more like a fluid

  5. ME 519: THEORY OF HEAT TRANSFER Instructor

    E-print Network

    Lin, Xi

    ME 519: THEORY OF HEAT TRANSFER Fall 2014 Instructor: Class time: Classroom: Office Hours: Prof Tuesday 4­5pm or by appointment Class description This course will cover the fundamentals of heat transfer. An introductory course in heat transfer (ME 419 or equivalent) is pre-requisite. Grading 20% Homework 25% Exam 1

  6. Heat transfer via dropwise condensation on hydrophobic microstructured surfaces

    E-print Network

    Ruleman, Karlen E. (Karlen Elizabeth)

    2009-01-01

    Dropwise condensation has the potential to greatly increase heat transfer rates. Heat transfer coefficients by dropwise condensation and film condensation on microstructured silicon chips were compared. Heat transfer ...

  7. Utilization of heat pipes for transfer heat from the flue gas into the heat transfer medium

    NASA Astrophysics Data System (ADS)

    Lenhard, Richard; Kaduchová, Katarína; Papu?ík, Štefan; Janda?ka, Jozef

    2014-03-01

    The contribution is listed possible application of heat pipes in systems for obtaining heat from flue gas of small heat sources. It is also stated in the contribution design an experimental device on which to study the impact of fill (the quantity, type of load) at various temperature parameters (temperature heating and cooling) thermal power transferred to the heat pipe. Is listed measurement methodology using heat pipes designed experimental facility, measurement results and analysis of the results obtained.

  8. Acoustically Enhanced Boiling Heat Transfer

    E-print Network

    Z. W. Douglas; M. K. Smith; A. Glezer

    2008-01-07

    An acoustic field is used to increase the critical heat flux (CHF) of a flat-boiling-heat-transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid-heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flatboiling surface for better study of an individual vapor bubble's reaction to the acoustic field. Work also includes application of the results from the single-bubble heater to a calibrated-copper heater used for quantifying the improvements in CHF.

  9. Heat Transfer Research, 2010, Vol. 41, No. 6 Turbine Aero-Heat Transfer Studies

    E-print Network

    Camci, Cengiz

    AU TH O R PR O O F Heat Transfer Research, 2010, Vol. 41, No. 6 Turbine Aero-Heat Transfer Studies in Rotating Research Facilities CENGIZ CAMCI Turbomachinery Aero-Heat Transfer Laboratory, Department The present paper deals with the experimental aero-heat transfer studies performed in rotating turbine

  10. Bubble Enhanced Heat Transfer from a Vertical Heated Surface

    Microsoft Academic Search

    Brian Donnelly; Darina B. Murray; Tadhg S. O'Donovan

    2008-01-01

    A rising bubble in a liquid can greatly enhance heat transfer from heated surfaces by acting like a bluff body, displacing fluid as it moves and via the wake generated by the bubble, increasing the mixing of the liquid. The current research quantifies the effect a single free rising ellipsoidal air bubble has on heat transfer from a vertical heated

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

    DOEpatents

    Koplow, Jeffrey P

    2013-12-10

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

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

    SciTech Connect

    Koplow, Jeffrey P. (San Ramon, CA)

    2012-07-24

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

  13. Heat Transfer in a Thermoacoustic Process

    ERIC Educational Resources Information Center

    Beke, Tamas

    2012-01-01

    Thermoacoustic instability is defined as the excitation of acoustic modes in chambers with heat sources due to the coupling between acoustic perturbations and unsteady heat addition. The major objective of this paper is to achieve accurate theoretical results in a thermoacoustic heat transfer process. We carry out a detailed heat transfer analysis…

  14. Handbook of heat transfer applications (2nd edition)

    NASA Astrophysics Data System (ADS)

    Rohsenow, W. M.; Hartnett, J. P.; Ganic, E. N.

    The applications of heat transfer in engineering problems are considered. Among the applications discussed are: mass transfer cooling; heat exchangers; and heat pipes. Consideration is also given to: heat transfer in nonNewtonian fluids; fluidized and packed beds; thermal energy storage; and heat transfer in solar collectors. Additional topics include: heat transfer in buildings; cooling towers and ponds; and geothermal heat transfer.

  15. New heat transfer factors for flat plate solar collectors

    NASA Astrophysics Data System (ADS)

    Lunde, P. J.

    1981-01-01

    It is shown that, for flat plate collectors operating in economically viable applications, three equations presented give suitable heat transfer factors for collector efficiency equations based on inlet, mean, and outlet fluid temperatures, respectively. The equations can be solved explicitly for any variable and do not become indeterminate as the flow approaches infinity. In addition, simple equations can be derived with which to convert any efficiency curve to one based on an alternate fluid temperature if (1) the flow rate is known, and (2) curves based on a particular fluid and flow rate can be adjusted to another flow rate without additional information. When a new heat transfer fluid is used, the heat transfer coefficient changes and the new heat transfer factor can be derived from the known transmissivity-absorptivity product and absorber plate fin efficiency.

  16. Experimental comparison of heat transfer enhancement methods in heat exchangers

    Microsoft Academic Search

    Hosni I. Abu-Mulaweh

    This paper presents an experimental comparison of four different types of heat transfer enhancement techniques or methods in heat exchangers: two insert devices (a displacement device and a swirl flow device), extended surfaces, and obstruction devices. The objective of these experiments is to assist undergraduate mechanical engineering students in understanding the basic heat transfer processes and the methods and devices

  17. Heat Transfer: No Magic About It

    NSDL National Science Digital Library

    National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs,

    Heat transfer is an important concept that is a part of everyday life yet often misunderstood by students. In this lesson, students learn the scientific concepts of temperature, heat and the transfer of heat through conduction, convection and radiation. These scientific concepts are illustrated by comparison to magical spells used in the Harry Potter stories.

  18. Solar collector-type heat transfer apparatus

    SciTech Connect

    Nelson, K.L.

    1984-01-17

    A conduit is arranged in a generally serpentine configuration and is provided with a plurality of heat transfer elements which are disposed interjacent spaced parallel sections of the conduit. An application of the assemblage consisting of the aforesaid serpentine conduit and associated heat transfer elements is a solar collector for use with solar heating systems and the like.

  19. Regenerative heat transfer lowers compressor performance. [Heat losses in natural gas compressor systems affect performance

    Microsoft Academic Search

    Prasad

    1993-01-01

    Regenerative heat in gas compressors diminishes performance, according to recent experiments. The results emphasize the importance of understanding and modeling the process to maximize operating efficiency. This paper presents results of experimental measurements done to determine regenerative heat transfer' contribution to suction gas heating and to compare its effect with earlier empirical models. These results form part of an ongoing

  20. Evaporation heat transfer and pressure drop of refrigerant R-134a in a plate heat exchanger

    Microsoft Academic Search

    Y.-Y. Yan; T.-F. Lin

    1999-01-01

    Plate heat exchangers (PHE) have been widely used in food processing, chemical reaction processes, and other industrial applications for many years. Particularly, in the last 20 years plate heat exchangers have been introduced to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. Here, the evaporation heat transfer coefficient and pressure drop for

  1. Heat transfer, cost modeling and process selection

    NSDL National Science Digital Library

    Kirchain, Randolph E., Jr.

    2006-02-12

    Case study of polymer matrix composite process selection between resin transfer molding and chopped fiber injection molding, including heat conduction to calculate solidification time and technical cost modeling.

  2. Heat Transfer in Gas Turbines

    NASA Technical Reports Server (NTRS)

    Garg, Vijay K.

    2001-01-01

    The turbine gas path is a very complex flow field. This is due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center. Also, based on the author's preference, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. While much has been achieved, more needs to be done in terms of validating the predictions against experimental data. More experimental data, especially on film cooled and rough turbine blades, are required for code validation. Also, the combined film cooling and internal cooling flow computation for a real blade is yet to be performed. While most computational work to date has assumed steady state conditions, the flow is clearly unsteady due to the presence of wakes. All this points to a long road ahead. However, we are well on course.

  3. Advanced turbine cooling, heat transfer, and aerodynamic studies

    SciTech Connect

    Han, Je-Chin; Schobeiri, M.T. [Texas A & M Univ., College Station, TX (United States). Dept. of Mechanical Engineering

    1995-12-31

    The contractual work is in three parts: Part I - Effect of rotation on enhanced cooling passage heat transfer, Part II - Effect of Thermal Barrier Coating (TBC) spallation on surface heat transfer, and Part III - Effect of surface roughness and trailing edge ejection on turbine efficiency under unsteady flow conditions. Each section of this paper has been divided into three parts to individually accommodate each part. Part III is further divided into Parts IIIa and IIIb.

  4. Low heat transfer oxidizer heat exchanger design and analysis

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  5. Radiative heat transfer in porous uranium dioxide

    SciTech Connect

    Hayes, S.L. [Texas A and M Univ., College Station, TX (United States)] [Texas A and M Univ., College Station, TX (United States)

    1992-12-01

    Due to low thermal conductivity and high emissivity of UO{sub 2}, it has been suggested that radiative heat transfer may play a significant role in heat transfer through pores of UO{sub 2} fuel. This possibility was computationally investigated and contribution of radiative heat transfer within pores to overall heat transport in porous UO{sub 2} quantified. A repeating unit cell was developed to model approximately a porous UO{sub 2} fuel system, and the heat transfer through unit cells representing a wide variety of fuel conditions was calculated using a finite element computer program. Conduction through solid fuel matrix as wekk as pore gas, and radiative exchange at pore surface was incorporated. A variety of pore compositions were investigated: porosity, pore size, shape and orientation, temperature, and temperature gradient. Calculations were made in which pore surface radiation was both modeled and neglected. The difference between yielding the integral contribution of radiative heat transfer mechanism to overall heat transport. Results indicate that radiative component of heat transfer within pores is small for conditions representative of light water reactor fuel, typically less than 1% of total heat transport. It is much larger, however, for conditions present in liquid metal fast breeder reactor fuel; during restructuring of this fuel type early in life, the radiative heat transfer mode was shown to contribute as much as 10-20% of total heat transport in hottest regions of fuel.

  6. Convective heat transfer as a function of wavelength: Implications for the cooling of the Earth

    E-print Network

    Convective heat transfer as a function of wavelength: Implications for the cooling of the Earth C, in particular, on its variation with the wavelength of convection. The heat transfer strongly depends in Earth's mantle can significantly reduce the efficiency of heat transfer. The likely variations

  7. Influence of nanoparticles on boiling heat transfer

    Microsoft Academic Search

    Dongsheng Wen

    Two sets of experiments are performed in this work to reveal the potential effect of nanoparticles on boiling heat transfer: i) pool boiling of nanofluids on two well-defined boiling surfaces and ii) bubble formation in a quiescent pool of nanofluids under adiabatic conditions. Different to the conventional thoughts that the modification of boiling heat transfer is the result of solid

  8. Temperature and Heat Transfer Measurements Cengiz Camci

    E-print Network

    Camci, Cengiz

    EAE077 Chapter 11 Temperature and Heat Transfer Measurements Cengiz Camci Turbomachinery Aero Resistive Temperature Transducers 2 3 Thermocouples 3 4 Bi-Metallic Temperature Sensors 7 5 Diode-Based Temperature Sensors 7 6 Liquid Crystal Thermometry 7 7 Infrared Thermometry and Pyrometer 9 8 Heat Transfer

  9. Radiation heat transfer in combustion systems

    Microsoft Academic Search

    R. Viskanta; M. P. Menguc

    1987-01-01

    An adequate treatment of thermal radiation heat transfer is essential to a mathematical model of the combustion process or to a design of a combustion system. This paper reviews the fundamentals of radiation heat transfer and some recent progress in its modeling in combustion systems. Topics covered include radiative properties of combustion products and their modeling and methods of solving

  10. ON THE STABILITY OF BOILING HEAT TRANSFER

    Microsoft Academic Search

    N. Zuber

    1958-01-01

    Boiling heat transfer in the nucleate region is reviewed. The ; transition film-boiling region is analyzed by considering the stability of a ; plane vortex sheet separating two inviscid fluids. Using the classical results ; of Helmholtz Kelvan and Rayleigh expressions have been derived that predict the ; maximum and minimum heat-transfer rates in the nucleate and the film-boiling ;

  11. Heat transfer in rotor/stator cavity

    NASA Astrophysics Data System (ADS)

    Tuliszka-Sznitko, Ewa; Majchrowski, Wojciech; Kie?czewski, Kamil

    2011-12-01

    In the paper we analyze the results of DNS/LES of the flow with heat transfer in the rotor/stator cavity. The rotor and the outer cylinder are heated. Computations have been performed for wide range of Reynolds numbers and aspect ratios. Computations are based on the efficient pseudo-spectral Chebyshev-Fourier method. In LES we used a Lagrangian dynamic subgrid-scale model of turbulence. Analysis allowed to check the influence of the aspect ratio and Reynolds number on the statistics and the structure of the flow. We analyzed all six Reynolds stress tensor components, turbulent fluctuations, three turbulent heat fluxes and different structural parameters which can be useful for modeling purposes. The distributions of Nusselt numbers obtained for different Re and aspect rations along disks are given. We also investigated influence of thermal Rosssby number as well as distributions of temperature along heated disk on statistics. Computations have shown that turbulence is mostly concentrated in the stator boundary layer with a maximum at the junction between the stator and the outer cylinder. The results are compared to the experimental and numerical data taken from literature.

  12. Heat Transfer in Complex Fluids

    SciTech Connect

    Mehrdad Massoudi

    2012-01-01

    Amongst the most important constitutive relations in Mechanics, when characterizing the behavior of complex materials, one can identify the stress tensor T, the heat flux vector q (related to heat conduction) and the radiant heating (related to the radiation term in the energy equation). Of course, the expression 'complex materials' is not new. In fact, at least since the publication of the paper by Rivlin & Ericksen (1955), who discussed fluids of complexity (Truesdell & Noll, 1992), to the recently published books (Deshpande et al., 2010), the term complex fluids refers in general to fluid-like materials whose response, namely the stress tensor, is 'non-linear' in some fashion. This non-linearity can manifest itself in variety of forms such as memory effects, yield stress, creep or relaxation, normal-stress differences, etc. The emphasis in this chapter, while focusing on the constitutive modeling of complex fluids, is on granular materials (such as coal) and non-linear fluids (such as coal-slurries). One of the main areas of interest in energy related processes, such as power plants, atomization, alternative fuels, etc., is the use of slurries, specifically coal-water or coal-oil slurries, as the primary fuel. Some studies indicate that the viscosity of coal-water mixtures depends not only on the volume fraction of solids, and the mean size and the size distribution of the coal, but also on the shear rate, since the slurry behaves as shear-rate dependent fluid. There are also studies which indicate that preheating the fuel results in better performance, and as a result of such heating, the viscosity changes. Constitutive modeling of these non-linear fluids, commonly referred to as non-Newtonian fluids, has received much attention. Most of the naturally occurring and synthetic fluids are non-linear fluids, for example, polymer melts, suspensions, blood, coal-water slurries, drilling fluids, mud, etc. It should be noted that sometimes these fluids show Newtonian (linear) behavior for a given range of parameters or geometries; there are many empirical or semi-empirical constitutive equations suggested for these fluids. There have also been many non-linear constitutive relations which have been derived based on the techniques of continuum mechanics. The non-linearities oftentimes appear due to higher gradient terms or time derivatives. When thermal and or chemical effects are also important, the (coupled) momentum and energy equations can give rise to a variety of interesting problems, such as instability, for example the phenomenon of double-diffusive convection in a fluid layer. In Conclusion, we have studied the flow of a compressible (density gradient type) non-linear fluid down an inclined plane, subject to radiation boundary condition. The heat transfer is also considered where a source term, similar to the Arrhenius type reaction, is included. The non-dimensional forms of the equations are solved numerically and the competing effects of conduction, dissipation, heat generation and radiation are discussed. It is observed that the velocity increases rapidly in the region near the inclined surface and is slower in the region near the free surface. Since R{sub 7} is a measure of the heat generation due to chemical reaction, when the reaction is frozen (R{sub 7}=0.0) the temperature distributions would depend only on R{sub 1}, and R{sub 2}, representing the effects of the pressure force developed in the material due to the distribution, R{sub 3} and R{sub 4} viscous dissipation, R{sub 5} the normal stress coefficient, R{sub 6} the measure of the emissivity of the particles to the thermal conductivity, etc. When the flow is not frozen (RP{sub 7} > 0) the temperature inside the flow domain is much higher than those at the inclined and free surfaces. As a result, heat is transferred away from the flow toward both the inclined surface and the free surface with a rate that increases as R{sub 7} increases. For a given temperature, an increase in {zeta} implies that the activation energy is smaller and thus, the reaction ra

  13. Radiative heat transfer between dielectric bodies

    E-print Network

    Svend-Age Biehs

    2011-03-16

    The recent development of a scanning thermal microscope (SThM) has led to measurements of radiative heat transfer between a heated sensor and a cooled sample down to the nanometer range. This allows for comparision of the known theoretical description of radiative heat transfer, which is based on fluctuating electrodynamics, with experiment. The theory itself is a macroscopic theory, which can be expected to break down at distances much smaller than 10-8m. Against this background it seems to be reasonable to revisit the known macroscopic theory of fluctuating electrodynamics and of radiative heat transfer.

  14. Cavitation Enhanced Heat Transfer in Microchannels

    Microsoft Academic Search

    Brandon Schneider; Ali Kos?ar; Chih-Jung Kuo; Gregory S. Cole; Robert P. Scaringe; Yoav Peles

    2006-01-01

    Heat transfer has been investigated in the presence of hydrodynamic cavitation instigated by 20-m wide inlet micro-orifices entrenched inside 227-m hydraulic diameter micro- channels. Average surface temperatures, heat transfer coefficients, and pressure drops have been obtained over effective heat fluxes ranging from 39 to 558 W\\/cm2 at mass flux of 1814 kg\\/m2 s under noncavitating and three cavitating conditions. Significant

  15. Efficient Phase-Change Materials: Development of a Low-Cost Thermal Energy Storage System Using Phase-Change Materials with Enhanced Radiation Heat Transfer

    SciTech Connect

    None

    2011-12-05

    HEATS Project: USF is developing low-cost, high-temperature phase-change materials (PCMs) for use in thermal energy storage systems. Heat storage materials are critical to the energy storage process. In solar thermal storage systems, heat can be stored in these materials during the day and released at night—when the sun is not out—to drive a turbine and produce electricity. In nuclear storage systems, heat can be stored in these materials at night and released to produce electricity during daytime peak-demand hours. Most PCMs do not conduct heat very well. Using an innovative, electroless encapsulation technique, USF is enhancing the heat transfer capability of its PCMs. The inner walls of the capsules will be lined with a corrosion-resistant, high-infrared emissivity coating, and the absorptivity of the PCM will be controlled with the addition of nano-sized particles. USF’s PCMs remain stable at temperatures from 600 to 1,000°C and can be used for solar thermal power storage, nuclear thermal power storage, and other applications.

  16. Efficient numerical modeling of borehole heat exchangers

    NASA Astrophysics Data System (ADS)

    Al-Khoury, R.; Kölbel, T.; Schramedei, R.

    2010-10-01

    This paper presents a finite element modeling technique for double U-tube borehole heat exchangers (BHE) and the surrounding soil mass. Focus is placed on presenting numerical analyses describing the capability of a BHE model, previously reported, to simulate three-dimensional heat transfer processes in multiple borehole heat exchangers embedded in a multi-layer soil mass, in a computationally efficient manner. Geothermal problems which require very fine meshes, of the order of millions of finite elements, can be simulated using coarse meshes, of the order of a few hundred to a few thousand elements. Accordingly, significant reduction of CPU time is gained, rendering the model suitable for utilization in engineering practice. A validation example comparing computed results with measured results is presented. Parametric analyses are also presented describing the possible utilization of the model for research works and design optimization.

  17. Prediction of Unshsrouded Rotor Blade Tip Heat Transfer

    NASA Technical Reports Server (NTRS)

    Ameri, A. A.; Steinthorsson, E.

    1994-01-01

    The rate of heat transfer on the tip of a turbine rotor blade and on the blade surface in the vicinity of the tip, was successfully predicted. The computations were performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations using an efficient multigrid method. The case considered for the present calculations was the Space Shuttle Main Engine (SSME) high pressure fuel side turbine. The predictions of the blade tip heat transfer agreed reasonably well with the experimental measurements using the present level of grid refinement. On the tip surface, regions with high rate of heat transfer was found to exist close to the pressure side and suction side edges. Enhancement of the heat transfer was also observed on the blade surface near the tip. Further comparison of the predictions was performed with results obtained from correlations based on fully developed channel flow.

  18. Heat transfer characteristics of rotating triangular thermosyphon

    NASA Astrophysics Data System (ADS)

    Ibrahim, E.; Moawed, M.; Berbish, N. S.

    2012-09-01

    An experimental investigation is carried out to study heat transfer characteristics of a rotating triangular thermosyphon, using R-134a refrigerant as the working fluid. The tested thermosyphon is an equilateral triangular tube made from copper material of 11 mm triangular length, 2 mm thickness, and a total length of 1,500 mm. The length of the evaporator section is 600 mm, adiabatic section is 300 mm, and condenser section is 600 mm. The effects of the rotational speed, filling ratio, and the evaporator heat flux on each of the evaporator heat transfer coefficient, he, condenser heat transfer coefficient, hc, and the overall effective thermal conductance, Ct are studied. Experiments are performed with a vertical position of thermosyphon within heat flux ranges from 11 to 23 W/m2 for the three selected filling ratios of 10, 30 and 50 % of the evaporator section volume. The results indicated that the maximum values of the tested heat transfer parameters of the rotational equilateral triangular thermosyphon are obtained at the filling ratio of 30 %. Also, it is found that the heat transfer coefficient of the condensation is increased with increasing the rotational speed. The tested heat transfer parameters of the thermosyphon are correlated as a function of the evaporator heat flux and angular velocity.

  19. Air-Side Heat Transfer in Finned Tube Heat Exchangers

    Microsoft Academic Search

    R. L. WEBB

    1980-01-01

    Because of the low heat transfer coefficient of gases, it is necessary to use extended surfaces on the gas side when exchanging heat with liquids or two-phase fluids. Such finned tube exchangers are a very important basic class of heat exchangers. Although finned tube exchangers have been in existence for 50 yr, there have been numerous developments in the technology.

  20. Natural convection heat transfer in liquid metals

    Microsoft Academic Search

    J. R. Welty

    1973-01-01

    Research progress for the reporting period is reported on: (1) natural convection studies in mercury confined between two vertical heated pipes, and (2) natural convection heat transfer studies in mercury adjacent to a vertical cylinder with constant heat flux. A bibliography of publications developed on the project for prior years is presented.

  1. Dynamics of heat transfer between nano systems

    E-print Network

    Svend-Age Biehs; Girish S. Agarwal

    2012-10-18

    We develop a dynamical theory of heat transfer between two nano systems. In particular, we consider the resonant heat transfer between two nanoparticles due to the coupling of localized surface modes having a finite spectral width. We model the coupled nanosystem by two coupled quantum mechanical oscillators, each interacting with its own heat bath, and obtain a master equation for the dynamics of heat transfer. The damping rates in the master equation are related to the lifetimes of localized plasmons in the nanoparticles. We study the dynamics towards the steady state and establish connection with the standard theory of heat transfer in steady state. For strongly coupled nano particles we predict Rabi oscillations in the mean occupation number of surface plasmons in each nano particle.

  2. Internal heat transfer coefficients of porous metals

    NASA Technical Reports Server (NTRS)

    Kar, K. K.; Dybbs, A.

    1982-01-01

    The internal heat transfer coefficients of porous metals have been experimentally determined in order to develop correlations between approximately defined Nusselt and Reynolds numbers. Scaled-up models of porous materials, and actual porous metal specimens, were subjected to countercurrent heat and mass transfer boundary conditions. Solid and gas phase temperatures were measured for both the scaled-up models and the actual porous metal specimens. On the basis of these measurements, the average internal heat transfer coefficient was evaluated, and a correlation between the Nusselt and Reynolds numbers was derived.

  3. Thermodynamics of enhanced heat transfer: a model study

    E-print Network

    Karen Hovhannisyan; Armen E. Allahverdyan

    2010-07-20

    Situations where a spontaneous process of energy or matter transfer is enhanced by an external device are widespread in nature (human sweating system, enzyme catalysis, facilitated diffusion across bio-membranes, industrial heat exchangers). The thermodynamics of such processes remains however open. Here we study enhanced heat transfer by a model junction immersed between two thermal baths at different temperatures $T_h$ and $T_c$ ($T_h>T_c$). The transferred heat power is enhanced via controlling the junction by means of external time-dependent fields. Provided that the spontaneous heat flow process is optimized over the junction Hamiltonian, any enhancement of this spontaneous process does demand consumption and subsequent dissipation of work. The efficiency of enhancement is defined via the increment in the heat power divided over the amount of consumed work. We show that this efficiency is bounded from above by $T_c/(T_h-T_c)$. Formally this is identical to the Carnot bound for the efficiency of ordinary refrigerators which transfer heat from cold to hot. It also shares some (but not all) physical features of the Carnot bound.

  4. 7 CFR 3201.54 - Heat transfer fluids.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...2013-01-01 false Heat transfer fluids. 3201.54 Section 3201.54 Agriculture...Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products...for qualifying biobased heat transfer fluids. By that date, Federal agencies...

  5. 7 CFR 3201.54 - Heat transfer fluids.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...2014-01-01 false Heat transfer fluids. 3201.54 Section 3201.54 Agriculture...Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products...for qualifying biobased heat transfer fluids. By that date, Federal agencies...

  6. 7 CFR 3201.54 - Heat transfer fluids.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...2012-01-01 false Heat transfer fluids. 3201.54 Section 3201.54 Agriculture...Designated Items § 3201.54 Heat transfer fluids. (a) Definition. Products...for qualifying biobased heat transfer fluids. By that date, Federal agencies...

  7. 7 CFR 2902.54 - Heat transfer fluids.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...2011-01-01 false Heat transfer fluids. 2902.54 Section 2902.54 Agriculture...Designated Items § 2902.54 Heat transfer fluids. (a) Definition. Products...for qualifying biobased heat transfer fluids. By that date, Federal agencies...

  8. Nonequilibrium Electromagnetic Fluctuations: Heat Transfer and Interactions

    E-print Network

    Kruger, Matthias

    The Casimir force between arbitrary objects in equilibrium is related to scattering from individual bodies. We extend this approach to heat transfer and Casimir forces in nonequilibrium cases where each body, and the ...

  9. Prerequisite: ME 303, 304 Heat Transfer

    E-print Network

    Lin, Xi

    understanding of the three modes of heat transfer (conduction, convection, radiation). Topics Covered: 1. Steady and unsteady conduction 2. Numerical analysis of conduction 3. Natural and forced convection 4. Introduction

  10. Heat Transfer Enhancement: Second Generation Technology

    E-print Network

    Bergles, A. E.; Webb, R. L.

    1984-01-01

    This paper reviews current activity in the field of enhanced heat transfer, with the aim of illustrating the technology and typical applications. Guidelines for application of enhanced surfaces are given, and practical concerns and economics...

  11. Quantification of convective heat transfer inside tree structures

    NASA Astrophysics Data System (ADS)

    Collin, Anthony; Lamorlette, Aymeric

    2012-11-01

    Convective heat transfer between a vegetal structure and its surrounding medium remains poorly described. However, for some applications, such as forest fire propagation studies, convective heat transfer is one of the main factors responsible for vertical fire transitions, from ground level to the tree crowns. These fires are the most dangerous because their rates of spread can reach high speeds, around one meter per second. An accurate characterization of this transfer is therefore important for fire propagation modelling. This study presents an attempt to formulate a theoretical modelling of the convective heat transfer coefficient for vegetal structures generated using an Iterated Function Systems (IFS). This model depends on the IFS parameters. The results obtained using this approach were compared with previously computed numerical results in order to evaluate their accuracy. The maximal discrepancies were found to be around 12% which proves the efficiency of the present model.

  12. Pool boiling heat transfer in microgravity

    Microsoft Academic Search

    J. F. Zhao; S. X. Wan; G. Liu; Z. D. Li; W. R. Hu

    2007-01-01

    A temperature-controlled pool boiling (TCPB) device has been developed to study the bubble behaviors and heat transfer in\\u000a pool boiling phenomenon both in normal gravity and in microgravity. The results on heat transfer and bubble dynamic behavior\\u000a in the experiments aboard the 22nd Chinese recoverable satellite and those in normal gravity before and after the flight experiment are reported and

  13. Code for Multiblock CFD and Heat-Transfer Computations

    NASA Technical Reports Server (NTRS)

    Fabian, John C.; Heidmann, James D.; Lucci, Barbara L.; Ameri, Ali A.; Rigby, David L.; Steinthorsson, Erlendur

    2006-01-01

    The NASA Glenn Research Center General Multi-Block Navier-Stokes Convective Heat Transfer Code, Glenn-HT, has been used extensively to predict heat transfer and fluid flow for a variety of steady gas turbine engine problems. Recently, the Glenn-HT code has been completely rewritten in Fortran 90/95, a more object-oriented language that allows programmers to create code that is more modular and makes more efficient use of data structures. The new implementation takes full advantage of the capabilities of the Fortran 90/95 programming language. As a result, the Glenn-HT code now provides dynamic memory allocation, modular design, and unsteady flow capability. This allows for the heat-transfer analysis of a full turbine stage. The code has been demonstrated for an unsteady inflow condition, and gridding efforts have been initiated for a full turbine stage unsteady calculation. This analysis will be the first to simultaneously include the effects of rotation, blade interaction, film cooling, and tip clearance with recessed tip on turbine heat transfer and cooling performance. Future plans call for the application of the new Glenn-HT code to a range of gas turbine engine problems of current interest to the heat-transfer community. The new unsteady flow capability will allow researchers to predict the effect of unsteady flow phenomena upon the convective heat transfer of turbine blades and vanes. Work will also continue on the development of conjugate heat-transfer capability in the code, where simultaneous solution of convective and conductive heat-transfer domains is accomplished. Finally, advanced turbulence and fluid flow models and automatic gridding techniques are being developed that will be applied to the Glenn-HT code and solution process.

  14. Heat Transfer Characteristics of a Generalized Divided Flow Heat Exchanger

    E-print Network

    Singh, K. P.

    1979-01-01

    The concept of a "Divided-flow" heat exchanger is generalized by locating the shell inlet (or outlet) nozzle off-center such that the two shell sub-streams are unequal and traverse unequal flow paths. The governing equations for heat transfer...

  15. Heat transfer measurements for Stirling machine cylinders

    NASA Technical Reports Server (NTRS)

    Kornhauser, Alan A.; Kafka, B. C.; Finkbeiner, D. L.; Cantelmi, F. C.

    1994-01-01

    The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heat transfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heat transfer in gas springs without inflow. The apparatus for the experiment consisted of a varying-volume piston-cylinder space connected to a fixed volume space by an orifice. The orifice size could be varied to adjust the level of inflow-produced turbulence, or the orifice plate could be removed completely so as to merge the two spaces into a single gas spring space. Speed, cycle mean pressure, overall volume ratio, and varying volume space clearance ratio could also be adjusted. Volume, pressure in both spaces, and local heat flux at two locations were measured. The pressure and volume measurements were used to calculate area averaged heat flux, heat transfer hysteresis loss, and other heat transfer-related effects. Experiments in the one space arrangement extended the range of previous gas spring tests to lower volume ratio and higher nondimensional speed. The tests corroborated previous results and showed that analytic models for heat transfer and loss based on volume ratio approaching 1 were valid for volume ratios ranging from 1 to 2, a range covering most gas springs in Stirling machines. Data from experiments in the two space arrangement were first analyzed based on lumping the two spaces together and examining total loss and averaged heat transfer as a function of overall nondimensional parameter. Heat transfer and loss were found to be significantly increased by inflow-produced turbulence. These increases could be modeled by appropriate adjustment of empirical coefficients in an existing semi-analytic model. An attempt was made to use an inverse, parameter optimization procedure to find the heat transfer in each of the two spaces. This procedure was successful in retrieving this information from simulated pressure-volume data with artificially generated noise, but it failed with the actual experimental data. This is evidence that the models used in the parameter optimization procedure (and to generate the simulated data) were not correct. Data from the surface heat flux sensors indicated that the primary shortcoming of these models was that they assumed turbulence levels to be constant over the cycle. Sensor data in the varying volume space showed a large increase in heat flux, probably due to turbulence, during the expansion stroke.

  16. The solar ultraviolet heating efficiency of the midlatitude thermosphere

    NASA Technical Reports Server (NTRS)

    Torr, M. R.; Torr, D. G.; Richards, P. G.

    1980-01-01

    In this paper we quantify the major channels by which solar UV energy is transferred to the atmosphere, and determine the UV heating efficiency for the thermosphere. Current knowledge of the solar ultraviolet fluxes, thermospheric chemistry and neutral atmosphere is used in a steady state, interhemispheric solution of the ionospheric continuity, momentum and energy equations. The heating efficiency is found to be a strong function of altitude, and peaks near the altitude of maximum EUV deposition at a value of approximately 50%.

  17. Interactive Heat Transfer Simulations for Everyone

    ERIC Educational Resources Information Center

    Xie, Charles

    2012-01-01

    Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…

  18. Prerequisite: ME 303, 304 Heat Transfer

    E-print Network

    Lin, Xi

    of a physical and analytical understanding of the three modes of heat transfer (conduction, convection, radiation). Topics Covered: 1. Steady and unsteady conduction 2. Numerical analysis of conduction 3. Natural and forced convection 4. Introduction to boiling, condensation and evaporation 5. Radiant heat exchange

  19. Heat transfer problems in nuclear waste management

    Microsoft Academic Search

    E. V. McAssey; V. E. Schrock

    1987-01-01

    This book contains five selections. They are: Heat Transfer Aspects of Nuclear Waste Disposal; Natural Convection in a Porous Layer Locally Heated From Below - A Regional Laboratory Model for A Nuclear Waste Repository; Thermal-Hydraulic Analysis of Spent Fuel Storage Systems; An Experimental and Analytical Evaluation of a Type B Radioactive Transport Container; and Theoretical Evaluation of Consolidated Rod Temperature

  20. Nucleation and Heat Transfer in Liquid Nitrogen

    Microsoft Academic Search

    Eric Warner Roth

    1993-01-01

    With the advent of the new high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states

  1. Heat transfer coefficients of shell and coiled tube heat exchangers

    Microsoft Academic Search

    M. R. Salimpour

    2009-01-01

    In the present study, the heat transfer coefficients of shell and helically coiled tube heat exchangers were investigated experimentally. Three heat exchangers with different coil pitches were selected as test section for both parallel-flow and counter-flow configurations. All the required parameters like inlet and outlet temperatures of tube-side and shell-side fluids, flow rate of fluids, etc. were measured using appropriate

  2. Experimental and numerical investigation of HyperVapotron heat transfer

    NASA Astrophysics Data System (ADS)

    Wang, Weihua; Deng, Haifei; Huang, Shenghong; Chu, Delin; Yang, Bin; Mei, Luoqin; Pan, Baoguo

    2014-12-01

    The divertor first wall and neutral beam injection (NBI) components of tokamak devices require high heat flux removal up to 20–30 MW m?2 for future fusion reactors. The water cooled HyperVapotron (HV) structure, which relies on internal grooves or fins and boiling heat transfer to maximize the heat transfer capability, is the most promising candidate. The HV devices, that are able to transfer large amounts of heat (1–20 MW m?2) efficiently, have therefore been developed specifically for this application. Until recently, there have been few attempts to observe the detailed bubble characteristics and vortex evolvement of coolant flowing inside their various parts and understand of the internal two-phase complex heat transfer mechanism behind the vapotron effect. This research builds the experimental facilities of HyperVapotron Loop-I (HVL-I) and Pressure Water HyperVapotron Loop-II (PWHL-II) to implement the subcooled boiling principle experiment in terms of typical flow parameters, geometrical parameters of test section and surface heat flux, which are similar to those of the ITER-like first wall and NBI components (EAST and MAST). The multiphase flow and heat transfer phenomena on the surface of grooves and triangular fins when the subcooled water flowed through were observed and measured with the planar laser induced fluorescence (PLIF) and high-speed photography (HSP) techniques. Particle image velocimetry (PIV) was selected to reveal vortex formation, the flow structure that promotes the vapotron effect during subcooled boiling. The coolant flow data for contributing to the understanding of the vapotron phenomenon and the assessment of how the design and operational conditions that might affect the thermal performance of the devices were collected and analysed. The subcooled flow boiling model and methods of HV heat transfer adopted in the considered computational fluid dynamics (CFD) code were evaluated by comparing the calculated wall temperatures with the experimentally measured values. It was discovered that the bubble and vortex characteristics in the HV are clearly heavily dependent on the internal geometry, flow conditions and input heat flux. The evaporation latent heat is the primary heat transfer mechanism of HV flow under the condition of high heat flux, and the heat transfer through convection is very limited. The percentage of wall heat flux going into vapour production is almost 70%. These relationships between the flow phenomena and thermal performance of the HV device are essential to study the mechanisms for the flow structure alterations for design optimization and improvements of the ITER-like devices' water cooling structure and plasma facing components for future fusion reactors.

  3. Heat Transfer to Fuel Sprays Injected into Heated Gases

    NASA Technical Reports Server (NTRS)

    Selden, Robert F; Spencer, Robert C

    1938-01-01

    This report presents the results of a study made of the influence of several variables on the pressure decrease accompanying injection of a relatively cool liquid into a heated compressed gas. Indirectly, this pressure decrease and the time rate of change of it are indicative of the total heat transferred as well as the rate of heat transfer between the gas and the injected liquid. Air, nitrogen, and carbon dioxide were used as ambient gases; diesel fuel and benzene were the injected liquids. The gas densities and gas-fuel ratios covered approximately the range used in compression-ignition engines. The gas temperatures ranged from 150 degrees c. to 350 degrees c.

  4. Interactive Heat Transfer Simulations for Everyone

    NASA Astrophysics Data System (ADS)

    Xie, Charles

    2012-04-01

    Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy, temperature distribution, and heat transfer may provide a straightforward method for teaching and learning these concepts. Through interacting with visual representations of the concepts and observing how they respond to manipulations, the misconceptions may be dispelled more effectively. This paper presents a new educational simulation tool called Energy2D developed to explore this idea.

  5. Heat transfer studies. Quarterly report

    Microsoft Academic Search

    R. Boehm; Y. T. Chen; L. Ma

    1995-01-01

    Nitrogen gas has been replaced by room air in the extension of multi-phase models to sub-residual saturation experiments on drying. The TOUGH2 code has been used to simulate the same problem with the identical boundary conditions. A constant heat flux boundary condition on the heater has been performed in the repository drift experiment. The desired constant heat flux can produce

  6. Heat Transfer in Underground Rail Tunnels

    E-print Network

    Sadokierski, Stefan

    2007-01-01

    The transfer of heat between the air and surrounding soil in underground tunnels ins investigated, as part of the analysis of environmental conditions in underground rail systems. Using standard turbulent modelling assumptions, flow profiles are obtained in both open tunnels and in the annulus between a tunnel wall and a moving train, from which the heat transfer coefficient between the air and tunnel wall is computed. The radial conduction of heat through the surrounding soil resulting from changes in the temperature of air in the tunnel are determined. An impulse change and an oscillating tunnel air temperature are considered separately. The correlations between fluctuations in heat transfer coefficient and air temperature are found to increase the mean soil temperature. Finally, a model for the coupled evolution of the air and surrounding soil temperature along a tunnel of finite length is given.

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

    PubMed

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

    2014-08-30

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  9. Micro heat spreader enhanced heat transfer in MCMs

    SciTech Connect

    Shen, D.S.; Mitchell, R.T.; Dobranich, D.; Adkins, D.R.; Tuck, M.R.

    1994-12-31

    The peak thermal power generated in microelectronics assemblies has risen from less than 1 W/cm{sup 2} in 1980 to greater than 40 W/cm{sup 2} today, due primarily to increasing densities at both the IC and packaging levels. The authors have demonstrated enhanced heat transfer in a prototype Si substrate with a backside micro heat channel structure. Unlike conventional micro heat pipes, these channels are biaxial with a greater capacity for fluid transfer. Thermal modeling and preliminary experiments have shown an equivalent increase in substrate thermal conductivity to over 500 W/m{center_dot}K, or a four times improvement. Optimization of the structure and alternative liquids will further increase the thermal conductivity of the micro heat channel substrate with the objective being polycrystalline diamond, or about 1,200 W/m{center_dot}K. The crucial design parameters for the micro heat channel system and the thermal characteristics of the system will be covered.

  10. Heat transfer in pressurized circulating fluidized beds

    SciTech Connect

    Wirth, K.E. [Univ. Erlangen-Nuernberg, Erlangen (Germany). Lehrstuhl fuer Mechanische Verfahrenstechnik

    1997-12-31

    The wall-to-suspension heat transfer in circulating fluidized beds (CFBs) operated at almost atmospheric pressure depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. No influence of the superficial gas velocity adjusted is present. Consequently, the wall-to-suspension heat transfer coefficient in the form of the Nusselt number can be described by the Archimedes number of the gas-solid-system and the pressure drop number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. However, with pressurized CFBs an influence of the superficial gas velocity on the wall-to-suspension heat transfer can be observed. Normalizing the superficial gas velocity in the form of the particle Froude number, two cases for the heat transfer in pressurized CFBs can be detected: with small particle Froude numbers (smaller than four) the same flow behavior and consequently the same heat transfer correlation is valid as it is for CFBs operated at almost atmospheric conditions; and with high particle Froude numbers (for example higher than four) the flow behavior immediately near the heat exchanger surface (CFB wall) can change. Instead of curtains of solids falling down with almost atmospheric pressure swirls of gas and solids can occur in the vicinity of the CFB wall when the static pressure is increased. With the change of the flow pattern near the CFB wall, i.e., the heat exchanger surface, a change of the heat transfer coefficient takes place. For the same Archimedes number, i.e., the same gas-solid system, and the same pressure drop number, i.e., the same cross-sectional average solids concentration, the Nusselt number, i.e., the heat transfer coefficient, increases when the flow pattern near the CFB wall changes from the curtain-type flow to that of the swirl-type flow. From experimentally obtained data in a cold running CFB a very simple correlation was obtained for the heat transfer coefficient.

  11. Characteristics of Transient Boiling Heat Transfer

    SciTech Connect

    Liu, Wei; Monde, Masanori; Mitsutake, Y. [Saga University, 1 Honjo Saga City, Saga 840-8502 (Japan)

    2002-07-01

    In this paper, one dimensional inverse heat conduction solution is used for a measurement of pool boiling curve. The experiments are performed under atmospheric pressure for copper, brass, carbon steel and gold. Boiling curves, including unsteady transition boiling region, are found can be traced fairly well from a simple experiment system by solving inverse heat conduction solution. Boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Surface behavior around CHF point, transition boiling and film-boiling regions are observed by using a high-speed camera. The results show the practicability of the inverse heat conduction solution in tracing boiling curve and thereby supply us a new way in boiling heat transfer research. (authors)

  12. Indirect Heat Transfer Technology For Waste Heat Recovery Can Save You Money

    E-print Network

    Beyrau, J. A.; Bogel, N. G.; Seifert, W. F.; Wuelpern, L. E.

    1984-01-01

    constraints of an existing installation makes the conventional flue gas to air energy recovery technology impractical to employ. A successful alternative is the transfer of waste heat to an intermediate heat transfer fluid (i.e., DOWTHERM Heat Transfer Fluid...

  13. HEAT TRANSFER DURING GLASS FORMING

    Microsoft Academic Search

    IHAB H. FARAG; MICHAEL J. BELIVEAU; RICHARD L. CURRAN

    1987-01-01

    An important step in the optimization of a glass container production cycle is the determination of the glass temperature distribution during heat treatment. The ideal approach to this problem is to formulate a theoretical model for comparison against experimental data measured in a well-determined system. Discrepancies between theory and experiment may then give further direction for model improvement. This approach,

  14. Analysis of heat transfer in unlooped and looped pulsating

    E-print Network

    Zhang, Yuwen

    Analysis of heat transfer in unlooped and looped pulsating heat pipes M.B. Sha®i and A. Faghri of Mechnical Engineering, New Mexico State University, Las Cruces, USA Keywords Heat transfer, Condensation, Tubing Abstract An advanced heat transfer model for both unlooped and looped Pulsating Heat Pipes (PHPs

  15. Active heat transfer enhancement in integrated fan heat sinks

    E-print Network

    Staats, Wayne Lawrence

    2012-01-01

    Modern computer processors require significant cooling to achieve their full performance. The "efficiency" of heat sinks is also becoming more important: cooling of electronics consumes 1% of worldwide electricity use by ...

  16. (Transfer of heat pump technology)

    SciTech Connect

    Broders, M.A.

    1990-02-23

    The traveler participated in the activities of the first meeting of the IEA Heat Pump Center National Team Working Group. The meeting provided a forum for National Team representatives from seven participating countries to share information about their respective National Team organization, activities and priorities; and the status of heat pumps in their countries. Particular attention was given to discussion of topics and content of future IEA-HPC Newsletters, analysis studies and workshops. In-depth, follow-up discussions of US National Team activities with both the IEA-HPC and IEA-CADDET were held with staff personnel at the operating agent Netherlands Agency for Energy and the Environment (NOVEM) headquarters in Sittard, The Netherlands.

  17. Solar heat transfer and storage system

    SciTech Connect

    McCall, D.

    1986-11-25

    This patent describes a heat transfer and storage system comprising: (a) a heat storage chamber having a phase change material contained therein; (b) water heater means for containing potable water, and including first conduit means through which the water flows, the first conduit means having a portion thereof extending through the phase change material in the chamber; (c) means for collecting heat energy, and including second conduit means through which a heat transfer liquid flows. The second conduit has a portion thereof extending through the phase change material in the chamber in adjacent parallel relation to the portion of the first conduit means; (d) fin means extending outwardly from the portion of the first and second conduit means to transfer heat between the conduit portions and the phase change material; and (e) connecting means simultaneously holding the portions of the first and second conduit means in adjacent heat conducting relationship to one another and holding the fin means interposed between the portions of the first and second conduit means in a heat conducting relationship therewith.

  18. Inner heat source model with heat and moisture transfer in soil around the underground heat exchanger

    Microsoft Academic Search

    Xinguo Li; Jun Zhao; Qian Zhou

    2005-01-01

    This paper presents an inner heat source model of underground heat exchanger based on the heat and mass transfer theory in soil. A number of factors such as moisture movement in soil, soil type, and soil property were taken into account in the model. The underground heat exchanger was simplified as the equivalent inner heat source term in the model.

  19. Convective heat transfer law for an endoreversible engine

    NASA Astrophysics Data System (ADS)

    Huleihil, Mahmoud; Andresen, Bjarne

    2006-07-01

    A generic model of an endoreversible engine is developed for studying the effect of convective heat transfer, the rate of which depends on the temperature difference to the power n where n is close to unity. The efficiency at maximum power production is found to have as its principal part the Curzon-Ahlborn [Am. J. Phys. 43, 22 (1975)] expression and a small correction which depends slightly on the temperature ratio of the heat engine reservoirs and the relative heat conductances to the hot and cold sides. By a proper choice of the independent variables it is demonstrated that the analysis becomes simple and approximate analytical expressions are easily derived.

  20. Radiative Heat Transfer between Neighboring Particles

    E-print Network

    Alejandro Manjavacas; F. Javier Garcia de Abajo

    2012-01-26

    The near-field interaction between two neighboring particles is known to produce enhanced radiative heat transfer. We advance in the understanding of this phenomenon by including the full electromagnetic particle response, heat exchange with the environment, and important radiative corrections both in the distance dependence of the fields and in the particle absorption coefficients. We find that crossed terms of electric and magnetic interactions dominate the transfer rate between gold and SiC particles, whereas radiative corrections reduce it by several orders of magnitude even at small separations. Radiation away from the dimer can be strongly suppressed or enhanced at low and high temperatures, respectively. These effects must be taken into account for an accurate description of radiative heat transfer in nanostructured environments.

  1. HOST turbine heat transfer program summary

    NASA Astrophysics Data System (ADS)

    Gladden, Herbert J.; Simoneau, Robert J.

    1988-01-01

    The objectives of the HOST Turbine Heat Transfer subproject were to obtain a better understanding of the physics of the aerothermodynamic phenomena and to assess and improve the analytical methods used to predict the flow and heat transfer in high temperature gas turbines. At the time the HOST project was initiated, an across-the-board improvement in turbine design technology was needed. A building-block approach was utilized and the research ranged from the study of fundamental phenomena and modeling to experiments in simulated real engine environments. Experimental research accounted for approximately 75 percent of the funding with the remainder going to analytical efforts. A healthy government/industry/university partnership, with industry providing almost half of the research, was created to advance the turbine heat transfer design technology base.

  2. Heat transfer characteristics of an emergent strand

    NASA Technical Reports Server (NTRS)

    Simon, W. E.; Witte, L. C.; Hedgcoxe, P. G.

    1974-01-01

    A mathematical model was developed to describe the heat transfer characteristics of a hot strand emerging into a surrounding coolant. A stable strand of constant efflux velocity is analyzed, with a constant (average) heat transfer coefficient on the sides and leading surface of the strand. After developing a suitable governing equation to provide an adequate description of the physical system, the dimensionless governing equation is solved with Laplace transform methods. The solution yields the temperature within the strand as a function of axial distance and time. Generalized results for a wide range of parameters are presented, and the relationship of the results and experimental observations is discussed.

  3. Heat transfer enhancement by chaotic mixing

    NASA Astrophysics Data System (ADS)

    Sen, M.; Chang, H. C.

    1991-11-01

    The feasibility of using chaotic mixing to enhance heat transfer is studied theoretically and experimentally. The study begins by an examination of the role of chaotic dynamics in transport enhancement in a counter-rotating eccentric annulus. Significant enhancement is seen to be attainable over that of regular mixing for a suitable choice of system parameters. Chaotic advection is then studied in a coiled pipe where the coiling geometry is suitably modified. Numerical investigation in the Dean's limit is used to explore the role of chaotic mixing in furthering heat transfer. These qualitative trends are tested on two coil geometries and an enhancement of between 6-8 percent is experimentally obtained.

  4. Metallized Gelled Propellant Heat Transfer Tests Analyzed

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan A.

    1997-01-01

    A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted at the NASA Lewis Research Center. These experiments used a small 20- to 40-lbf thrust engine composed of a modular injector, an igniter, a chamber, and a nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt % loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each channel used water flow to carry heat away from the chamber and the attached thermocouples; flow meters allowed heat flux estimates at each of the 31 stations.

  5. Heat transfer mechanisms in pulsating heat-pipes with nanofluid

    NASA Astrophysics Data System (ADS)

    Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo

    2015-01-01

    In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.

  6. Electrohydrodynamically enhanced condensation heat transfer

    E-print Network

    Wawzyniak, Markus

    1993-01-01

    of the Plexiglas container, (b) view of cooled plate with corona wire. [Velkoff and Miller, 1965] . . . . Fig. 1. 4 Effect of electric field on condensation. 5 mesh screen grid parallel to plate. [Velkoff and Miller, 1965]. Fig. 1. 5 Variation of h (mean heat...) overall view of the Plexiglas container, (b) view of cooled plate with corona wire. [Velkoff and Miller, 1965] non-uniform electric field with sufficient strength to form ions in the fluid, was spaced 25. 4 mm (1H) away from the condensation surface...

  7. Thermal transfer printing with heat amplification

    NASA Astrophysics Data System (ADS)

    Aviram, Ari; Shih, Kwang K.; Sachdev, Krishna

    1991-08-01

    A major advance in the field of thermal printing was the introduction of the QuietwriterR marketed by IBM which is based on resistive ribbon and utilizes the most advanced thermal printing technology. This printing technology is also termed Resistive Ribbon Thermal Transfer (R2T2) printing (1), because it is based on an electrically conductive ribbon. A recent detailed review of resistive ribbon printing is provided in ref. 2. In conventional thermal printing processes (3), the gating factor for the speed is the time it takes for the print head to cool down between cycles. Due to this limitation, the printing cycle for each successive printing element is about 2m seconds. A further drawback of this thermal printing technology, is the dependence of print quality on the type of paper used requiring very smooth paper for reasonable quality printing. This is probably due to inadequate heating of the ink resulting in high melt viscosity and consequently poor ink flow from ribbon to paper. This problem is alleviated in resistive printing where ink transfer temperatures are much higher than in the case of thermal head printing (4). In this technology the ink reaches temperatures far above the melting point of the ink. This is achieved by pumping enough energy into the ribbon to reach the necessary threshold temperature. however, there is a practical limit to the energy that the ribbon can withstand in a certain pulse without undergoing decomposition. Therefore, a need was recognized for approaches to improve thermal printing efficiency while minimizing the input energy requirement.

  8. Heat transfer analysis of boreholes in vertical ground heat exchangers

    Microsoft Academic Search

    Heyi Zeng; Nairen Diao; Zhaohong Fang

    2003-01-01

    A ground heat exchanger (GHE) is devised for extraction or injection of thermal energy from\\/into the ground. Bearing strong impact on GHE performance, the borehole thermal resistance is defined by the thermal properties of the construction materials and the arrangement of flow channels of the GHEs. Taking the fluid axial convective heat transfer and thermal “short-circuiting” among U-tube legs into

  9. Heat transfer characteristics of porous media

    NASA Technical Reports Server (NTRS)

    Singh, B. S.; Dybbs, A.

    1974-01-01

    An investigation was conducted regarding the relative effects of conduction and convection in a saturated porous medium. A method reported by Singh et al. (1973) is used to determine the effective thermal conductivity of the saturated porous material. Heat transfer measurements are conducted under conditions of forced convection of the saturated liquid parallel and countercurrent to the flow of heat. The results are compared with the data obtained with the aid of an analytical model.

  10. An experimental study of premixed flame impingement heat transfer

    SciTech Connect

    Mizuno, K.; Mital, R.; Viskanta, R. [Purdue Univ., West Lafayette, IN (United States). School of Mechanical Engineering

    1996-12-31

    This paper reports results of an experimental study to determine the flame structure and heat transfer characteristics of a premixed methane-air flame impinging on a calorimeter. The flame structure is studied photographically and through temperature measurements. The convection and radiation heat transfer contributions of the flame are separated using a black and a highly reflecting water cooled calorimeter. The effects of nozzle-to-plate spacing, firing rate and equivalence ratio on the flame structure and average heat flux are reported. The axial temperature profiles are found to be a strong function of the gap between burner and calorimeter. The radial temperature profiles show a sharp decline near the burner edge. The photographs reveal that multiple jets, arranged in a circular configuration, exit between the cup-shaped ceramic burner and the calorimeter plate. The length of the flame increases with both the firing rate and the equivalence ratio. The heat flux is highest when the burner is closest to the calorimeter, except for the high firing rates when quenching occurs. Even though the heat flux increases, the heat transfer efficiency decreases with increasing firing rate. Heat flux is also found to increase as the flame becomes air rich in the range of parameters investigated.

  11. Evaporation heat transfer and pressure drop of refrigerant R-134a in a plate heat exchanger

    SciTech Connect

    Yan, Y.Y.; Lin, T.F. [National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Dept. of Mechanical Engineering

    1999-02-01

    Plate heat exchangers (PHE) have been widely used in food processing, chemical reaction processes, and other industrial applications for many years. Particularly, in the last 20 years plate heat exchangers have been introduced to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. Here, the evaporation heat transfer coefficient and pressure drop for refrigerant R-134a flowing in a plate heat exchanger were investigated experimentally in this study. Two vertical counterflow channels were formed in the exchanger by three plates of commercial geometry with a corrugated sine shape of a chevron angle of 60 deg. Upflow boiling of refrigerant R-134a in one channel receives heat from the hot downflow of water in the other channel. The effects of the mean vapor quality, mass flux, heat flux, and pressure of R-134a on the evaporation heat transfer and pressure drop were explored. The quality change of R-134a between the inlet and outlet of the refrigerant channel ranges from 0.09 to 0.18. Even at a very low Reynolds number, the present flow visualization of evaporation in a plate heat exchanger remains turbulent. It is found that the evaporation heat transfer coefficient of R-134a in the plates is much higher than that in circular pipes and shows a very different variation with the vapor quality from that in circular pipes, particularly in the convective evaporation dominated regime at high vapor quality. Relatively intense evaporation on the corrugated surface was seen from the flow visualization. Moreover, the present data showed that both the evaporation heat transfer coefficient and pressure drop increase with the vapor quality. At a higher mass flux the pressure drop is higher for the entire range of the vapor quality but the evaporation heat transfer is clearly better only at the high quality. Raising the imposed wall heat flux was found to slightly improve the heat transfer, while at a higher refrigerant pressure, both the heat transfer and pressure drop are slightly lower. Based on the present data, empirical correlations for the evaporation heat transfer coefficient and friction factor were proposed.

  12. Heat transfer analysis in Stirling engine heat input system

    SciTech Connect

    Chung, W.; Kim, S. [LG Electronics Inc., Seoul (Korea, Republic of). Living System Lab.

    1995-12-31

    One of the major factor in commercialization of Stirling engine is mass productivity, and the heat input system including tubular heater is one of the obstacles to mass production because of its complexity in shape and difficulty in manufacturing, which resulted from using oxidation-resistant, low-creep alloys which are not easy to machine and weld. Therefore a heater heat exchanger which is very simple in shape and easy to make has been devised, and a burner system appropriate to this heater also has been developed. In this paper specially devised heat input system which includes a heater shell shaped like U-cup and a flame tube located in the heater shell is analyzed in point of heat transfer processes to find optimum heat transfer. To enhance the heat transfer from the flame tube to the heater shell wall, it is required that the flame tube diameter be enlarged as close to the heater shell diameter as possible, and the flame tube temperature be raised as high as possible. But the enlargement of the flame tube diameter should be restricted by the state of combustion affected by hydraulic resistance of combustion gas, and the boost of the flame tube temperature should be considered carefully in the aspects of the flame tube`s service life.

  13. Analysis of natural convective heat transfer of nano coated aluminium fins using Taguchi method

    NASA Astrophysics Data System (ADS)

    Senthilkumar, R.; Nandhakumar, A. J. D.; Prabhu, S.

    2013-01-01

    Rectangular aluminium fins were preferred for analysis and coated by carbon nano tubes using PVD to enhance the heat transfer rate of fins. Convective heat transfer rates for coated and non-coated surfaces were calculated and compared. The temperature and heat transfer characteristics were investigated using Nusselt, Grashof, Prandtl and Rayleigh numbers and also optimized by Taguchi method and ANOVA analysis. The average percentage of increase in fin efficiency is 5 %.

  14. Self supporting heat transfer element

    DOEpatents

    Story, Grosvenor Cook (Livermore, CA); Baldonado, Ray Orico (Livermore, CA)

    2002-01-01

    The present invention provides an improved internal heat exchange element arranged so as to traverse the inside diameter of a container vessel such that it makes good mechanical contact with the interior wall of that vessel. The mechanical element is fabricated from a material having a coefficient of thermal conductivity above about 0.8 W cm.sup.-1.degree. K.sup.-1 and is designed to function as a simple spring member when that member has been cooled to reduce its diameter to just below that of a cylindrical container or vessel into which it is placed and then allowed to warm to room temperature. A particularly important application of this invention is directed to a providing a simple compartmented storage container for accommodating a hydrogen absorbing alloy.

  15. Cooperative heat transfer and ground coupled storage system

    DOEpatents

    Metz, Philip D. (Rocky Point, NY)

    1982-01-01

    A cooperative heat transfer and ground coupled storage system wherein collected solar heat energy is ground stored and permitted to radiate into the adjacent ground for storage therein over an extended period of time when such heat energy is seasonally maximally available. Thereafter, when said heat energy is seasonally minimally available and has propagated through the adjacent ground a substantial distance, the stored heat energy may be retrieved by a circumferentially arranged heat transfer means having a high rate of heat transfer.

  16. Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer

    PubMed Central

    Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso

    2014-01-01

    This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758

  17. Coupling heat and chemical tracer experiments for estimating heat transfer parameters in shallow alluvial aquifers

    NASA Astrophysics Data System (ADS)

    Wildemeersch, S.; Jamin, P.; Orban, P.; Hermans, T.; Klepikova, M.; Nguyen, F.; Brouyère, S.; Dassargues, A.

    2014-11-01

    Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54 MJ/m3/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modeling.

  18. Coupling heat and chemical tracer experiments for estimating heat transfer parameters in shallow alluvial aquifers.

    PubMed

    Wildemeersch, S; Jamin, P; Orban, P; Hermans, T; Klepikova, M; Nguyen, F; Brouyère, S; Dassargues, A

    2014-11-15

    Geothermal energy systems, closed or open, are increasingly considered for heating and/or cooling buildings. The efficiency of such systems depends on the thermal properties of the subsurface. Therefore, feasibility and impact studies performed prior to their installation should include a field characterization of thermal properties and a heat transfer model using parameter values measured in situ. However, there is a lack of in situ experiments and methodology for performing such a field characterization, especially for open systems. This study presents an in situ experiment designed for estimating heat transfer parameters in shallow alluvial aquifers with focus on the specific heat capacity. This experiment consists in simultaneously injecting hot water and a chemical tracer into the aquifer and monitoring the evolution of groundwater temperature and concentration in the recovery well (and possibly in other piezometers located down gradient). Temperature and concentrations are then used for estimating the specific heat capacity. The first method for estimating this parameter is based on a modeling in series of the chemical tracer and temperature breakthrough curves at the recovery well. The second method is based on an energy balance. The values of specific heat capacity estimated for both methods (2.30 and 2.54MJ/m(3)/K) for the experimental site in the alluvial aquifer of the Meuse River (Belgium) are almost identical and consistent with values found in the literature. Temperature breakthrough curves in other piezometers are not required for estimating the specific heat capacity. However, they highlight that heat transfer in the alluvial aquifer of the Meuse River is complex and contrasted with different dominant process depending on the depth leading to significant vertical heat exchange between upper and lower part of the aquifer. Furthermore, these temperature breakthrough curves could be included in the calibration of a complex heat transfer model for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modeling. PMID:25201639

  19. Combined heat and mass transfer device for improving separation process

    DOEpatents

    Tran, T.N.

    1999-08-24

    A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area. 12 figs.

  20. Combined heat and mass transfer device for improving separation process

    DOEpatents

    Tran, Thanh Nhon (Flossmoor, IL)

    1999-01-01

    A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area.

  1. Development of Technologies on Innovative-Simplified Nuclear Power Plant Using High-Efficiency Steam Injectors (12) Evaluations of Spatial Distributions of Flow and Heat Transfer in Steam Injector

    SciTech Connect

    Yutaka Abe; Yujiro Kawamoto [University of Tsukuba, Tsukuba, Ibaraki (Japan); Chikako Iwaki [Toshiba Corporation (Japan); Tadashi Narabayashi [Hokkaido University, Kita-ku, Sapporo (Japan); Michitsugu Mori; Shuichi Ohmori [Tokyo Electric Power Company (Japan)

    2006-07-01

    Next-generation nuclear reactor systems have been under development aiming at simplified system and improvement of safety and credibility. One of the innovative technologies is the supersonic steam injector, which has been investigated as one of the most important component of the next-generation nuclear reactor. The steam injector has functions of a passive pump without large motor or turbo-machinery and a high efficiency heat exchanger. The performances of the supersonic steam injector as a pump and a heat exchanger are dependent on direct contact condensation phenomena between a supersonic steam and a sub-cooled water jet. In previous studies of the steam injector, there are studies about the operating characteristics of steam injector and about the direct contact condensation between static water pool and steam in atmosphere. However, there is a little study about the turbulent heat transfer and flow behavior under the great shear stress. In order to examine the heat transfer and flow behavior in supersonic steam injector, it is necessary to measure the spatial temperature distribution and velocity in detail. The present study, visible transparent supersonic steam injector is used to obtain the axial pressure distributions in the supersonic steam injector, as well as high speed visual observation of water jet and steam interface. The experiments are conducted with and without non-condensable gas. The experimental results of the interfacial flow behavior between steam and water jet are obtained. It is experimentally clarified that an entrainment exists on the water jet surface. It is also clarified that discharge pressure is depended on the steam supply pressure, the inlet water flow rate, the throat diameter and non-condensable flow rate. Finally a heat flux is estimated about 19 MW/m{sup 2} without non-condensable gas condition in steam. (authors)

  2. Radiative heat transfer calculations in real gases

    Microsoft Academic Search

    B. Leckner

    1974-01-01

    A general formulation for radiative heat transfer calculations is presented, based on integrated quantities such as total emissivities and absorptivities. The procedure is intended particularly for combustion chamber applications of varying degree of complexity, the radiative active medium consisting of gases such as H2O and CO2 and of soot. First, some preliminary calculations are given for the often treated radiative

  3. INVERSE PROBLEMS IN HEAT TRANSFER Nicholas Zabaras

    E-print Network

    Zabaras, Nicholas J.

    CHAPTER 17 INVERSE PROBLEMS IN HEAT TRANSFER Nicholas Zabaras Materials Process Design and Control points in the domain and time. Hadamard classified inverse problems as ill-posed in the sense be unstable to perturbations in input data [5]. 2 #12;In many respects, inverse problems driven by discrete

  4. A Review of Heat Transfer Physics

    Microsoft Academic Search

    V. P. Carey; G. Chen; C. Grigoropoulos; M. Kaviany; A. Majumdar

    2008-01-01

    With rising science contents of the engineering research and education, we give examples of the quest for fundamental understanding of heat transfer at the atomic level. These include transport as well as interactions (energy conversion) involving phonon, electron, fluid particle, and photon (or electromagnetic wave). Examples are 1. development of MD and DSMC fluid simulations as tools in nanoscale and

  5. Thermodynamics and heat transfer of ice slurries

    Microsoft Academic Search

    Peter W. Egolf; Andrej Kitanovski; Derrick Ata-Caesar; Evangelos Stamatiou; Masahiro Kawaji; Jean-Pierre Bedecarrats; Francoise Strub

    2005-01-01

    The thermodynamics and heat transfer of ice slurries is reviewed. It starts with a collection of models to calculate the effective thermal conductivity. These relations were derived for suspensions with solid particles that do not change its phase. Therefore, they can only be first approximations. Then dimensionless numbers are introduced, once based on the physical properties of the carrier fluid

  6. Circulation (Cont) Means of Transferring Heat

    E-print Network

    Johnson, Robert E.

    Part-6c Circulation (Cont) Means of Transferring Heat Global Circulation Easterlies /Westerlies Polar Front Planetary Waves Gravity Waves Mars Circulation Giant Planet Atmospheres Zones and Belts #12 in T and/ or Geostrophic flow can intensify with z Horizontal temperature differences causes increasing

  7. Heat and mass transfer in porous media

    SciTech Connect

    Cook, T.L.; Harlow, F.H.; Travis, B.J.; Bartel, T.J.; Tyner, C.E.

    1981-01-01

    Field test data on the OOSI MR3 experiments are used as a basis for exhibiting the computational capabilities of the WAFE computer code, which is a generalized tool for the analysis of heat and mass transfer in multi-dimensional domains of porous geothermal materials.

  8. Natural convective heat transfer from isothermalconic

    Microsoft Academic Search

    W. M. Lewandowski; S. Szyma?ski; P. Kubski; E. Radziemska; H. Bieszk; T. Wilczewski

    1999-01-01

    Theoretical considerations on convective heat transfer from isothermal upward conicalsurfaces have been presented. The physical model of this phenomenon consists of an isothermalcone of inclination angle (?) between the cone generating line (X) and the radius (R) of the cone base. The angle is a parameter of conical surface which varied from (? = 0?circular horizontal plate) to (? =

  9. Heat Transfer and Thermodynamics: a Compilation

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A compilation is presented for the dissemination of information on technological developments which have potential utility outside the aerospace and nuclear communities. Studies include theories and mechanical considerations in the transfer of heat and the thermodynamic properties of matter and the causes and effects of certain interactions.

  10. CONVECTIVE HEAT TRANSFER EFFECTS IN AIRFOIL ICING

    Microsoft Academic Search

    Luciano Martinez Stefanini

    2007-01-01

    Various classic icing codes have been developed and used by t he aircraft manufacturers to predict the ice shapes evolution. These codes apply boundary layer integra l analysis, based on sand grain roughness, to estimate the convective heat transfer coefficient around the iced airfoi l and adopt abrupt transition between laminar and turbulent flow. In the present work, the integral

  11. Computational Aspects of Heat Transfer in Structures

    NASA Technical Reports Server (NTRS)

    Adelman, H. M. (compiler)

    1982-01-01

    Techniques for the computation of heat transfer and associated phenomena in complex structures are examined with an emphasis on reentry flight vehicle structures. Analysis methods, computer programs, thermal analysis of large space structures and high speed vehicles, and the impact of computer systems are addressed.

  12. Forced Convection Heat Transfer in Circular Pipes

    ERIC Educational Resources Information Center

    Tosun, Ismail

    2007-01-01

    One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…

  13. Numerical analysis of heat and mass transfer in a compact finned tubes air heat exchanger under dehumidification conditions

    NASA Astrophysics Data System (ADS)

    Benelmir, Riad; Mokraoui, Salim

    2012-04-01

    A simulation model of a fin-and-tube heat exchanger is presented. The effect of the relative humidity, air speed, fin base temperature, and inlet air temperature on the estimation of the overall heat-transfer coefficient and fin efficiency under wet conditions is also investigated. This model considers a non-uniform airflow velocity as well as a variable sensible heat transfer coefficient.

  14. ME 339 Heat Transfer ABET EC2000 syllabus

    E-print Network

    Ben-Yakar, Adela

    : Introduction to the fundamental mechanisms of heat transfer; conduction, convection and radiation processes governing heat transfer; be able to analyze and solve conduction, convection, and radiation convection; radiation; introduction to phase change heat transfer and to heat exchangers. Prerequisite(s): ME

  15. Analysis of a heat transfer device for measuring film coefficients

    NASA Technical Reports Server (NTRS)

    Medrow, R. A.; Johnson, R. L.; Loomis, W. R.; Wedeven, L. D.

    1975-01-01

    A heat transfer device consisting of a heated rotating cylinder in a bath was analyzed for its effectiveness to determine heat transfer coefficient of fluids. A time dependent analysis shows that the performance is insensitive to the value of heat transfer coefficient with the given rig configuration.

  16. Forced convective heat transfer with impinging rectangular jets

    Microsoft Academic Search

    D. W. Zhou; Sang-Joon Lee

    2007-01-01

    The fluid flow and heat transfer characteristics of a rectangular air jet impinging on a heated flat plate have been investigated experimentally. The effects of jet Reynolds number and nozzle-to-plate spacing on local and average Nusselt number were studied. Results show that both have a significant influence on heat transfer behaviors of impinging jets. Local and average heat transfer data

  17. Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor

    NASA Technical Reports Server (NTRS)

    Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.

    2013-01-01

    This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.

  18. Heat transfer characteristics of Turbotec tubing

    NASA Astrophysics Data System (ADS)

    Bergles, A. E.

    1980-06-01

    The thermal/hydraulic performance of Turbotec spirally fluted tubes was evaluated. The emphasis is on individual heat transfer coefficients for the inside and outside surfaces so that the designer can calculate the overall heat transfer coefficient for any type of heat exchanger. The data for Turbotec tubes are presented in terms of an envelope diameter so that direct comparisons can be made with the performance of smooth tubes. The specific flow conditions considered are free convection external flow, laminar internal flow, turbulent internal flow (including fouling), turbulent external flow, fluidized beds, vapor space condensation, and in-tube condensation. The Turbotec tubes exhibit large increases in performance for forced convection single-phase flow.

  19. Heat transfer in bioengineering and medicine

    SciTech Connect

    Chato, J.C.; Diller, T.E.; Diller, K.R.; Roemer, R.B.

    1987-01-01

    This book contains the following papers: New ideas in heat transfer for agricultural animals; Issues in heat transfer and tumor blood flow in localized hyperthermia treatments of cancer; Ultrasound enhances adriamycin toxicity in vitro; Scanned, focused ultrasound hyperthermia treatment of brain tumors; Mathematical prediction and phantom studies of the clinical target ''hot spot'' using a three applicator phased array system (TRIPAS); Development of an endoscopic RF hyperthermia system for deep tumor therapy; Simultaneous measurement of intrinsic and effective thermal conductivity; Determination of the transport of thermal energy by conduction in perfused tissue; A whole body thermal model of man with a realistic circulatory system; and Canine muscle blood flow changes in response to initial heating rates.

  20. Heat Transfer between Graphene and Amorphous SiO2

    E-print Network

    B. N. J. Persson; H. Ueba

    2010-07-22

    We study the heat transfer between graphene and amorphous SiO2. We include both the heat transfer from the area of real contact, and between the surfaces in the non-contact region. We consider the radiative heat transfer associated with the evanescent electromagnetic waves which exist outside of all bodies, and the heat transfer by the gas in the non-contact region. We find that the dominant contribution to the heat transfer result from the area of real contact, and the calculated value of the heat transfer coefficient is in good agreement with the value deduced from experimental data.

  1. Heat transfer enhancement and performance of the molten salt receiver of a solar power tower

    Microsoft Academic Search

    Minlin Yang; Xiaoxi Yang; Xiaoping Yang; Jing Ding

    2010-01-01

    This paper investigates the interaction between the heat transfer performance and the thermal efficiency of a molten salt receiver used in the solar power tower plant. A test-bed is built, and a series of experiments of heat transfer enhancement for two types of molten salt receiver tubes, including smooth and spiral tubes, have been carried out under the high temperature

  2. Macroscopic turbulent models for heat and mass transfer in catalyst reactors

    NASA Astrophysics Data System (ADS)

    Mathey, Fabrice

    2012-05-01

    Tthis paper reports the development and validation of a Computational Fluid Dynamics (CFD) up-scaling approach to predict wit a porous media approximation the heat transfer efficiency of arbitrary randomly packed bed tubular reactors. The results demonstrate the feasibility to predict the flow, temperature and global heat transfer with macroscopic simulations with a good accuracy.

  3. Oscillatory flow with heat transfer in a square cavity

    NASA Technical Reports Server (NTRS)

    Biringen, S.; Danabasoglu, G.

    1989-01-01

    A computational study is presented for the flow inside an oscillatory cavity. The numerical scheme employs a semi-implicit, time-splitting method to integrate the two-dimensional full Navier-Stokes equations satisfying continuity to machine accuracy. The efficient use of direct solvers for the uncoupled momentum and pressure equations is demonstrated. The oscillatory cavity flow is studied considering the effects of heat transfer, Reynolds number, and oscillatory Stokes number.

  4. Heterogeneous nanofluids: natural convection heat transfer enhancement

    PubMed Central

    2011-01-01

    Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration ? and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case. PMID:21711755

  5. Application of transfer matrix method in heat transfer performance analysis of multi-re-entrant honeycomb structures

    NASA Astrophysics Data System (ADS)

    Hou, Xiuhui; Deng, Zichen; Yin, Guansheng

    2014-12-01

    The thermal properties for the multi-re-entrant honeycomb are investigated, where the hexagon and re-entrant topologies are applied for comparison. A compact model was adopted for the local heat transfer rate and pressure drop estimations while the total heat transfer rate was analyzed using the transfer matrix method. A thermal performance index was specified to characterize a good heat exchange medium that can transfer more heat at the expense of lower pressure loss. Numerical results reveal better thermal performances of multi-re-entrant honeycombs over hexagon and re-entrant topologies, attributed to the presence of added base walls. Auxetic effect introduced in multi-re-entrant honeycomb generally provides enhanced out-of-plane thermal conductivity and increased total heat transfer efficiency due to higher surface area density.

  6. Mean Overall Heat Transfer Coefficient in Heat Exchangers Allowing for Temperature-Dependent Fluid Properties

    Microsoft Academic Search

    Wilfried Roetzel; Xing Luo

    2011-01-01

    For temperature-dependent heat transfer coefficients and heat capacities, fast approximation methods are presented for the estimation of the effective overall heat transfer coefficient. The heat transfer coefficients are calculated for two, three, or four reference temperatures. For the parallel and countercurrent flow a known method is described that uses a hypothetical fluid temperature for the iteration-free consideration of variable heat

  7. High heat transfer oxidizer heat exchanger design and analysis. [RL10-2B engine

    NASA Technical Reports Server (NTRS)

    Kmiec, Thomas D.; Kanic, Paul G.; Peckham, Richard J.

    1987-01-01

    The RL10-2B engine, a derivative of the RL10, is capable of multimode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2% of full thrust, and pumped idle (PI), which is 10% of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for low-g deployment. Stable combustion of the RL10-2B engine during the low thrust operating modes can be accomplished by using a heat exchanger to supply gaseous oxygen to the propellant injector. The oxidizer heat exchanger (OHE) vaporizes the liquid oxygen using hydrogen as the energy source. The design, concept verification testing and analysis for such a heat exchanger is discussed. The design presented uses a high efficiency compact core to vaporize the oxygen, and in the self-contained unit, attenuates any pressure and flow oscillations which result from unstable boiling in the core. This approach is referred to as the high heat transfer design. An alternative approach which prevents unstable boiling of the oxygen by limiting the heat transfer is referred to as the low heat transfer design and is reported in Pratt & Whitney report FR-19135-2.

  8. In-Space technology experiments program. A high efficiency thermal interface (using condensation heat transfer) between a 2-phase fluid loop and heatpipe radiator: Experiment definition phase

    NASA Technical Reports Server (NTRS)

    Pohner, John A.; Dempsey, Brian P.; Herold, Leroy M.

    1990-01-01

    Space Station elements and advanced military spacecraft will require rejection of tens of kilowatts of waste heat. Large space radiators and two-phase heat transport loops will be required. To minimize radiator size and weight, it is critical to minimize the temperature drop between the heat source and sink. Under an Air Force contract, a unique, high-performance heat exchanger is developed for coupling the radiator to the transport loop. Since fluid flow through the heat exchanger is driven by capillary forces which are easily dominated by gravity forces in ground testing, it is necessary to perform microgravity thermal testing to verify the design. This contract consists of an experiment definition phase leading to a preliminary design and cost estimate for a shuttle-based flight experiment of this heat exchanger design. This program will utilize modified hardware from a ground test program for the heat exchanger.

  9. Two Heat-Transfer Improvements for Gas Liquefiers

    NASA Technical Reports Server (NTRS)

    Martin, Jerry L.

    2005-01-01

    Two improvements in heat-transfer design have been investigated with a view toward increasing the efficiency of refrigerators used to liquefy gases. The improvements could contribute to the development of relatively inexpensive, portable oxygen liquefiers for medical use. A description of the heat-transfer problem in a pulse-tube refrigerator is prerequisite to a meaningful description of the first improvement. In a pulse-tube refrigerator in particular, one of in-line configuration heat must be rejected from two locations: an aftercooler (where most of the heat is rejected) and a warm heat exchanger (where a small fraction of the total input power must be rejected as heat). Rejection of heat from the warm heat exchanger can be problematic because this heat exchanger is usually inside a vacuum vessel. When an acoustic-inertance tube is used to provide a phase shift needed in the pulse-tube cooling cycle, another problem arises: Inasmuch as the acoustic power in the acoustic-inertance tube is dissipated over the entire length of the tube, the gas in the tube must be warmer than the warm heat exchanger in order to reject heat at the warm heat exchanger. This is disadvantageous because the increase in viscosity with temperature causes an undesired increase in dissipation of acoustic energy and an undesired decrease in the achievable phase shift. Consequently, the overall performance of the pulse-tube refrigerator decreases with increasing temperature in the acoustic-inertance tube. In the first improvement, the acoustic-inertance tube is made to serve as the warm heat exchanger and to operate in an approximately isothermal condition at a lower temperature, thereby increasing the achievable phase shift and the overall performance of the refrigerator. This is accomplished by placing the acoustic-inertance tube inside another tube and pumping a cooling fluid (e.g., water) in the annular space between the tubes. Another benefit of this improvement is added flexibility of design to locate the warm heat-rejection components outside the vacuum vessel. The second improvement is the development of a compact radial-flow condenser characterized by a very high heat transfer coefficient and a small pressure drop.

  10. Experimental evaluation of heat transfer characteristics of silica nanofluid

    E-print Network

    Zhang, Zihao, S.B. Massachusetts Institute of Technology

    2010-01-01

    The laminar convective heat transfer characteristics were investigated for silica nanofluid. An experimental loop was built to obtain heat transfer coefficients for single-phase nanofluids in a circular conduit in laminar ...

  11. Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)

    SciTech Connect

    Not Available

    2010-08-01

    Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.

  12. Nanofluid heat transfer enhancement for nuclear reactor applications

    E-print Network

    Buongiorno, Jacopo

    Colloidal dispersions of nanoparticles are known as `nanofluids'. Such engineered fluids offer the potential for enhancing heat transfer, particularly boiling heat transfer, while avoiding the drawbacks (i.e., erosion, ...

  13. Heat transfer during film condensation of potassium vapor

    E-print Network

    Kroger, Detlev Gustav

    1966-01-01

    The object of this work is to investigate theoretically and experimentally the following two phases of heat transfer during condensation of potassium vapore, a. Heat transfer during film condensation of pure saturated ...

  14. Thermodynamic and heat transfer analysis of heat recovery from engine test cell by Organic Rankine Cycle

    NASA Astrophysics Data System (ADS)

    Shokati, Naser; Mohammadkhani, Farzad; Farrokhi, Navid; Ranjbar, Faramarz

    2014-12-01

    During manufacture of engines, evaluation of engine performance is essential. This is accomplished in test cells. During the test, a significant portion of heat energy released by the fuel is wasted. In this study, in order to recover these heat losses, Organic Rankine Cycle (ORC) is recommended. The study has been conducted assuming the diesel oil to be composed of a single hydrocarbon such as C12H26. The composition of exhaust gases (products of combustion) have been computed (and not determined experimentally) from the stoichiometric equation representing the combustion reaction. The test cell heat losses are recovered in three separate heat exchangers (preheater, evaporator and superheater). These heat exchangers are separately designed, and the whole system is analyzed from energy and exergy viewpoints. Finally, a parametric study is performed to investigate the effect of different variables on the system performance characteristics such as the ORC net power, heat exchangers effectiveness, the first law efficiency, exergy destruction and heat transfer surfaces. The results of the study show that by utilizing ORC, heat recovery equivalent to 8.85 % of the engine power is possible. The evaporator has the highest exergy destruction rate, while the pump has the lowest among the system components. Heat transfer surfaces are calculated to be 173.6, 58.7, and 11.87 m2 for the preheater, evaporator and superheater, respectively.

  15. Measuring Furnace/Sample Heat-Transfer Coefficients

    NASA Technical Reports Server (NTRS)

    Rosch, William R.; Fripp, Archibald L., Jr.; Debnam, William J., Jr.; Woodell, Glenn A.

    1993-01-01

    Complicated, inexact calculations now unnecessary. Device called HTX used to simulate and measure transfer of heat between directional-solidification crystal-growth furnace and ampoule containing sample of crystalline to be grown. Yields measurement data used to calculate heat-transfer coefficients directly, without need for assumptions or prior knowledge of physical properties of furnace, furnace gas, or specimen. Determines not only total heat-transfer coefficients but also coefficients of transfer of heat in different modes.

  16. Heat transfer coefficients for atmospheric coolers

    E-print Network

    Robinson, Robert McCollum

    1950-01-01

    the area required for heat transfer to the water inside the heater, The heater with the tube bundle is shown in Photograph I? Ths hot water is taken from the heater at a point close to the bottom on the side opposite the tube bundle by a Hom- ing.... . . . . . . . . . . . . . . . . . . . . ~ . . . . l00 PHOTOGRAPHS Page l. Heater and V Tube Bundle. . . . . . ~ . . . . , . . . ~ ~ . . ~ ~ ~ ~ 26 2. Cooling Section. . . . . . . . . . . . . . . . . . . . . ~ . . . . . . . . ~ . 26 3. Condensate Tanks...

  17. Heat Transfer in a Superelliptic Transition Duct

    NASA Technical Reports Server (NTRS)

    Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven

    2008-01-01

    Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.

  18. Computational fluid mechanics and heat transfer

    Microsoft Academic Search

    D. A. Anderson; J. C. Tannehill; R. H. Pletcher

    1984-01-01

    This book is intended to serve as a text for introductory courses in computational fluid mechanics and heat transfer for advanced undergraduates and\\/or first-year graduate students. The first part of the book presents basic concepts and provides an introduction to the fundamentals of finite-difference methods, while the second part is devoted to applications involving the equations of fluid mechanics and

  19. Heat transfer enhancement in metal hydride systems

    NASA Astrophysics Data System (ADS)

    Rosso, M. J., Jr.; Strickland, G.

    An attempt has been made to enhance the heat transfer of hydrogen storage metal hydride systems by the addition of small fraction of high conductivity materials in various configurations. Results indicate that the form of the enhancement material rather than its composition is the more critical factor. The addition of over 6% aluminum foam enhances the effective thermal conductivity of a hydride bed by a factor of 2.6.

  20. Low-melting point heat transfer fluid

    DOEpatents

    Cordaro, Joseph Gabriel (Oakland, CA); Bradshaw, Robert W. (Livermore, CA)

    2010-11-09

    A low-melting point, heat transfer fluid made of a mixture of five inorganic salts including about 29.1-33.5 mol % LiNO.sub.3, 0-3.9 mol % NaNO.sub.3, 2.4-8.2 mol % KNO.sub.3, 18.6-19.9 mol % NaNO.sub.2, and 40-45.6 mol % KNO.sub.2. These compositions can have liquidus temperatures below 80.degree. C. for some compositions.

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

    PubMed

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

    2011-07-01

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

  2. Liquid metal heat exchanger for efficient heating of soils and geologic formations

    DOEpatents

    DeVault, Robert C. (Knoxville, TN) [Knoxville, TN; Wesolowski, David J. (Kingston, TN) [Kingston, TN

    2010-02-23

    Apparatus for efficient heating of subterranean earth includes a well-casing that has an inner wall and an outer wall. A heater is disposed within the inner wall and is operable within a preselected operating temperature range. A heat transfer metal is disposed within the outer wall and without the inner wall, and is characterized by a melting point temperature lower than the preselected operating temperature range and a boiling point temperature higher than the preselected operating temperature range.

  3. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 2013-10-01 false Heat transfer systems; general. 153.430...Control Systems § 153.430 Heat transfer systems; general. Each cargo...manual regulation of the system's heat transfer rate. [CGD 73-96, 42...

  4. Proceedings of NHTC'00: 34 th National Heat Transfer Conference

    E-print Network

    Kandlikar, Satish

    Proceedings of NHTC'00: 34 th National Heat Transfer Conference Pittsburgh, Pennsylvania, August 20 ON SINGLE- AND TWO-PHASE HEAT TRANSFER CHARACTERISTICS IN A MICROCHANNEL Michael S June Graduate Student study investigates the heat transfer characteristics of single and two-phase flows in a 200 m wide

  5. Heat transfer from nanoparticles: a corresponding state analysis

    E-print Network

    Paris-Sud XI, Université de

    Heat transfer from nanoparticles: a corresponding state analysis Samy Merabia , Sergei Shenogin that inhibits the formation of an insulating vapor film. heat transfer | nanoparticles | liquids | phase transitions Introduction Sub-micron scale heat transfer is attracting a growing inter- est, motivated by both

  6. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 2012-10-01 false Heat transfer systems; general. 153.430...Control Systems § 153.430 Heat transfer systems; general. Each cargo...manual regulation of the system's heat transfer rate. [CGD 73-96, 42...

  7. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 2014-10-01 false Heat transfer systems; general. 153.430...Control Systems § 153.430 Heat transfer systems; general. Each cargo...manual regulation of the system's heat transfer rate. [CGD 73-96, 42...

  8. Dt2boool2> Nora Heat Transfer Correlations

    E-print Network

    Dt2boool2> Nora Heat Transfer Correlations in Nuclear Reactor Safety Calculations VW �Aiiatt�aii #12;fcflison cufiMiMltt lor yhdyiifci aomicantfgy RIS0-M-25O4 6«.*). HEAT TRANSFER of work 26 3. PRESENT KNOWLEDGE 27 3.1. General considerations 27 3.2. Heat transfer in different flow

  9. Proceeding of the 1st International Forum on Heat Transfer

    E-print Network

    Maruyama, Shigeo

    Proceeding of the 1st International Forum on Heat Transfer November 24-26, 2004, Kyoto, Japan Paper No. HEAT TRANSFER PROBLEMS RELATED WITH CARBON NANOTUBES BY MOLECULAR DYNAMICS-BASED SIMULATIONS Dynamics Simulation, Thermal Conductance ABSTRACT Several heat transfer problems related to single

  10. Proceedings of HT2009 2009 ASME Summer Heat Transfer Conference

    E-print Network

    Guo, Zhixiong "James"

    Proceedings of HT2009 2009 ASME Summer Heat Transfer Conference July 19-23, 2009, San Francisco, CA, USA HT2009-88261 SIMULATION OF FOCUSED RADIATION PROPAGATION AND TRANSIENT HEAT TRANSFER IN TURBID-dependent radiation and conduction bio-heat transfer model. Ultrashort pulsed radiation transport in the cylindrical

  11. Theory and methods of calculating radiative heat transfer

    Microsoft Academic Search

    Iu. A. Surinov

    1976-01-01

    Attention is given to the solution of integral equations of radiative heat transfer in an absorbing and isotropically scattering medium, unsteady problems of thermoelasticity, solar activity effects on the earth atmosphere, radiative heat transfer between a conical body and a shock front, and the local characteristics of radiative heat transfer between concentric cylinders separated by an absorbing medium. Also considered

  12. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 2011-10-01 false Heat transfer systems; general. 153.430...Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo...Allow manual regulation of the system's heat transfer rate. [CGD 73-96, 42...

  13. 46 CFR 153.430 - Heat transfer systems; general.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430...Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo...Allow manual regulation of the system's heat transfer rate. [CGD 73-96, 42...

  14. HEAT TRANSFER ENHANCEMENT THROUGH THE USE OF TRANSVERSE VORTEX GENERATORS

    Microsoft Academic Search

    Slawomir Blonski; Tomasz Kowalewski; Dariusz Mikielewicz; Adam Stasiek; Jan Stasiek

    Vortices and generation contain three passive elements to influence heat transfer: swirl, flow destabilization and developing viscous layers. They increase heat transfer by several hundred percent. Prior to the use of vortices to influence heat transfer it must be known how different vortices are generated and controlled and how they interact with the original or base flow and temperature field.

  15. Heat Transfer Characteristics of Nanofluids in an Acoustic Cavitation Field

    Microsoft Academic Search

    D. W. ZHOU; Deng-Ying Liu

    2004-01-01

    Heat transfer characteristics of nanofluids in an acoustic cavitation field have been investigated experimentally. The effects of acoustical parameters, nanofluids concentration, and fluid subcooling on heat transfer are determined in detail. Results show that acoustic cavitation and nanometer particles have a profound influence on single-phase convection and boiling heat transfer of a horizontal circular copper tube. The former is mainly

  16. Characterizations and Convective Heat Transfer Performance of Nanofluids

    Microsoft Academic Search

    Yijun Yang

    2011-01-01

    In recent years, many experimental studies have reported anomalous thermal conductivity enhancement and heat transfer increase in liquid suspensions of nanoparticles. In order to understand the mechanism of this phenomenon and examine the possible applications of nanofluids in heat transfer, the present study experimentally investigated thermal, rheological and heat transfer properties of nanofluids. In the first part of the work,

  17. Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles

    ERIC Educational Resources Information Center

    Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.

    2010-01-01

    This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…

  18. Boiling heat transfer and bubble dynamics in microgravity

    Microsoft Academic Search

    Johannes Straub

    2001-01-01

    This article presents results for pool boiling heat transfer under microgravity conditions that the author and his team have gained in a succession of experiments during the past two decades. The objective of the research work was to provide answers to the following questions: Is boiling an appropriate mechanism of heat transfer for space application? How do heat transfer and

  19. Investigation on Convective Heat Transfer and Flow Features of Nanofluids

    Microsoft Academic Search

    Yimin Xuan; Qiang Li

    2003-01-01

    With progresses of thermoscience and thermal engineering, many efforts have been devoted to heat transfer enhancement. Among them, application of additives to liquids is often involved. Since the flow media themselves may be the controlling factor of limiting heat transfer performance, solid additives are suspended in the base liquids in order to change transport properties, flow and heat transfer features

  20. Fluctuating-surface-current formulation of radiative heat transfer: Theory and applications

    E-print Network

    Rodriguez, Alejandro W.

    We describe a fluctuating-surface current formulation of radiative heat transfer between bodies of arbitrary shape that exploits efficient and sophisticated techniques from the surface-integral-equation formulation of ...

  1. Heat and mass transfer in bubble column dehumidifiers for HDH desalination

    E-print Network

    Tow, Emily W

    2014-01-01

    Heat and mass transfer processes governing the performance of bubble dehumidifier trays are studied in order to develop a predictive model and design rules for efficient and economical design of bubble column dehumidifiers ...

  2. Visualisation of heat transfer in 3D unsteady flows

    Microsoft Academic Search

    M. F. M. Speetjens; A. A. van Steenhoven

    2010-01-01

    Heat transfer in fluid flows traditionally is examined in terms of temperature field and heat-transfer coefficients at non-adiabatic walls. However, heat transfer may alternatively be considered as the transport of thermal energy by the total convective–conductive heat flux in a way analogous to the transport of fluid by the flow field. The paths followed by the total heat flux are

  3. Enhancement of heat and mass transfer by cavitation

    NASA Astrophysics Data System (ADS)

    Zhang, Y. N.; Zhang, Y. N.; Du, X. Z.; Xian, H. Z.

    2015-01-01

    In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment.

  4. Heat Transfer Operators Associated with Quantum Operations

    E-print Network

    Ç. Aksak; S. Turgut

    2011-04-14

    Any quantum operation applied on a physical system is performed as a unitary transformation on a larger extended system. If the extension used is a heat bath in thermal equilibrium, the concomitant change in the state of the bath necessarily implies a heat exchange with it. The dependence of the average heat transferred to the bath on the initial state of the system can then be found from the expectation value of a hermitian operator, which is named as the heat transfer operator (HTO). The purpose of this article is the investigation of the relation between the HTOs and the associated quantum operations. Since, any given quantum operation on a system can be realized by different baths and unitaries, many different HTOs are possible for each quantum operation. On the other hand, there are also strong restrictions on the HTOs which arise from the unitarity of the transformations. The most important of these is the Landauer erasure principle. This article is concerned with the question of finding a complete set of restrictions on the HTOs that are associated with a given quantum operation. An answer to this question has been found only for a subset of quantum operations. For erasure operations, these characterizations are equivalent to the generalized Landauer erasure principle. For the case of generic quantum operations however, it appears that the HTOs obey further restrictions which cannot be obtained from the entropic restrictions of the generalized Landauer erasure principle.

  5. Numerical methods in heat transfer. Volume 2

    NASA Astrophysics Data System (ADS)

    Lewis, R. W.; Morgan, K.; Schrefler, B. A.

    A unified approach free from restrictive hypotheses is presented for the computation of time-dependent thermal structural effects by means of influence functions pertaining to 'unit temperature distributions'. Exact finite element solutions for linear steady-state thermal problems are considered along with steep gradient modelling in diffusion problems, the variational formulation and approximate solutions of the thermal diffusion equation, and penalty-finite element methods in conduction and convection heat transfer. Attention is given to predictions of laminar natural convection in heated cavities, the influence of thermal wall conditions on the natural convection in heated cavities, the numerical solution of coupled conduction-convection problems using lumped-parameter methods, and the accuracy of the boundary element method for three-dimensional conduction problems. Other topics explored are related to the prediction of turbulent heat transfer by the finite element method, and the analysis of the transient thermal performances of composite devices by network methods. For individual items see A84-22202 to A84-22205

  6. Heat transfer coefficients during quenching of steels

    NASA Astrophysics Data System (ADS)

    Hasan, H. S.; Peet, M. J.; Jalil, J. M.; Bhadeshia, H. K. D. H.

    2011-03-01

    Heat transfer coefficients for quenching in water have been measured as a function of temperature using steel probes for a variety of iron alloys. The coefficients were derived from measured cooling curves combined with calculated heat-capacities. The resulting data were then used to calculate cooling curves using the finite volume method for a large steel sample and these curves have been demonstrated to be consistent with measured values for the large sample. Furthermore, by combining the estimated cooling curves with time-temperature-transformation (TTT) diagrams it has been possible to predict the variation of hardness as a function of distance via the quench factor analysis. The work should prove useful in the heat treatment of the steels studied, some of which are in the development stage.

  7. Supercritical oxygen heat transfer. [regenerative cooling

    NASA Technical Reports Server (NTRS)

    Spencer, R. G.; Rousar, D. C.

    1977-01-01

    Heat transfer to supercritical oxygen was experimentally measured in electrical heated tubes. Experimental data were obtained for pressures ranging from 17 to 34.5 MPa (2460 to 5000 psia), and heat fluxes from 2 to 90 million w/sq cm (1.2 to 55 Btu/(sq in. sec)). Bulk temperatures ranged from 96 to 217 K (173 to 391 R). Experimental data obtained by other investigators were added to this to increase the range of pressure down to 2 MPa (290 psia) and increase the range of bulk temperature up to 566 K (1019 R). From this compilation of experimental data a correlating equation was developed which predicts over 95% of the experimental data within + or - 30%.

  8. Experimental Investigation on Heat Transfer and Frictional Characteristics of Shell-and-tube Heat exchangers with Different Baffles and Tubes

    NASA Astrophysics Data System (ADS)

    Wang, C.; Zhu, J. G.; Sang, Z. F.

    2010-03-01

    In this study, the heat transfer and tube frictional characteristics of the helixchangers (shell-and-tube heat exchanger with helical baffles) with spirally corrugated and smooth tubes and the conventional shell-and-tube heat exchanger with smooth tubes were experimentally obtained. The results show that the helixchangers with the spirally corrugated tube and the smooth tubes enhance the total heat transfer coefficient about 26% and 7% on the average than the segmental baffled heat exchanger. In the tube side, the spirally corrugated tube leads to about 28% average increase on convective heat transfer performance and about 24% average increase on pressure drop than the smooth tube, but its conversion efficiency is still higher. The helical baffle could enhance the shell-side condensation coefficient by 13%, and the spirally corrugated tube could help the helixchanger with it enhance remarkably the condensation performance by 53% than the segmental baffled heat exchanger.

  9. A Model of Respiratory Heat Transfer in a Small Mammal

    PubMed Central

    Collins, J. C.; Pilkington, T. C.; Schmidt-Nielsen, K.

    1971-01-01

    A steady-state model of the heat and water transfer occurring in the upper respiratory tract of the kangaroo rat, Dipodomys spectabilis, is developed and tested. The model is described by a steady-state energy balance equation in which the rate of energy transfer from a liquid stream (representing the flow of heat and blood from the body core to the nasal region) is equated with the rate of energy transfer by thermal conduction from the nose tip to the environment. All of the variables in the equation except the flow rate of the liquid stream can be either measured directly or estimated from physiological measurements, permitting the solution of the equation for the liquid stream flow rate. After solving for the liquid stream flow rate by using data from three animals, the energy balance equation is used to compute values of energy transfer, expired air temperature, rates of water loss, and efficiency of vapor recovery for a variety of ambient conditions. These computed values are compared with values measured or estimated from physiological measurements on the same three animals, and the equation is thus shown to be internally consistent. To evaluate the model's predictive value, calculated expired air temperatures are compared with measured expired air temperatures of eight additional animals. Finally, the model is used to examine the general dependence of expired air temperature, of rates of water loss, and of efficiency of vapor recovery on ambient conditions. PMID:5113001

  10. Heat transfer enhancement of copper nanofluid with acoustic cavitation

    Microsoft Academic Search

    D. W. Zhou

    2004-01-01

    Heat transfer characteristics of copper nanofluids with and without acoustic cavitation were investigated experimentally. The effects of such factors as acoustical parameters, nanofluid concentration and fluid subcooling on heat transfer enhancement around a heated horizontal copper tube were discussed in detail. The results indicated that the copper nanoparticles and acoustic cavitation had profound and significant influence on heat transport in

  11. Length Scale and Gravity Effects on Microgravity Boiling Heat Transfer

    Microsoft Academic Search

    Jungho Kim; John McQuillen; Joe Balombin

    2002-01-01

    Boiling is a complex phenomenon where hydrodynamics, heat transfer, mass transfer, and interfacial phenomena are tightly interwoven. An understanding of boiling and critical heat flux in microgravity environments is of importance to space based hardware and processes such as heat exchange, cryogenic fuel storage and transportation, electronic cooling, and material processing due to the large amounts of heat that can

  12. High efficiency pump for space helium transfer

    NASA Technical Reports Server (NTRS)

    Hasenbein, Robert; Izenson, Michael G.; Swift, Walter L.; Sixsmith, Herbert

    1991-01-01

    A centrifugal pump was developed for the efficient and reliable transfer of liquid helium in space. The pump can be used to refill cryostats on orbiting satellites which use liquid helium for refrigeration at extremely low temperatures. The pump meets the head and flow requirements of on-orbit helium transfer: a flow rate of 800 L/hr at a head of 128 J/kg. The overall pump efficiency at the design point is 0.45. The design head and flow requirements are met with zero net positive suction head, which is the condition in an orbiting helium supply Dewar. The mass transfer efficiency calculated for a space transfer operation is 0.99. Steel ball bearings are used with gas fiber-reinforced teflon retainers to provide solid lubrication. These bearings have demonstrated the longest life in liquid helium endurance tests under simulated pumping conditions. Technology developed in the project also has application for liquid helium circulation in terrestrial facilities and for transfer of cryogenic rocket propellants in space.

  13. Orbiter catalytic/noncatalytic heat transfer as evidenced by heating to contaminated surfaces on STS-2 and STS-3

    NASA Technical Reports Server (NTRS)

    Throckmorton, D. A.; Zoby, E. V.; Hamilton, H. H., II

    1983-01-01

    During that portion of Space Shuttle orbiter entry when significant aerodynamic heat transfer occurs, the flow over the vehicle is in chemical nonequilibrium. The parameter which most significantly influences the level of surface heat transfer in such a flow field is the catalytic efficiency of the surface with respect to the recombination of dissociated oxygen atoms. Significant, and instantaneous, changes were observed in the level of heat transfer at several lower surface centerline locations on STS-2 and STS-3. This phenomenon apparently resulted from a sudden change in the surface catalytic efficiency at these locations due to contamination of the surface by metallic oxides. As a result, data obtained from affected measurements cannot be considered as benchmark data with which to attempt to characterize nonequilibrium heat transfer to the orbiter's lower surface centerline.

  14. Manufacture of a biporous nickel wick and its effect on LHP heat transfer performance enhancement

    NASA Astrophysics Data System (ADS)

    Wu, S. C.; Hsieh, B. H.; Wang, D.; Chen, Y. M.

    2015-02-01

    This work describes a mixed powder sintering method that uses polymer as sacrificial substance to manufacture wicks for LHPs to improve the heat transfer performance of a conventional monoporous wick during high heat flux in LHP. The proposed porous manufacturing method is simple, efficient, structurally sound, and easily managed. Compared to findings in literatures for LHPs with monoporous wicks, the heat transfer performance of the proposed method is enhanced by nearly 80 %.

  15. A review of turbine blade tip heat transfer.

    PubMed

    Bunker, R S

    2001-05-01

    This paper presents a review of the publicly available knowledge base concerning turbine blade tip heat transfer, from the early fundamental research which laid the foundations of our knowledge, to current experimental and numerical studies utilizing engine-scaled blade cascades and turbine rigs. Focus is placed on high-pressure, high-temperature axial-turbine blade tips, which are prevalent in the majority of today's aircraft engines and power generating turbines. The state of our current understanding of turbine blade tip heat transfer is in the transitional phase between fundamentals supported by engine-based experience, and the ability to a priori correctly predict and efficiently design blade tips for engine service. PMID:11460670

  16. Rocket engine thrust chamber heat transfer calculation and analysis

    NASA Technical Reports Server (NTRS)

    Saha, H.

    1974-01-01

    A parametric study of the heat transfer rate along the wall of a rocket nozzle is presented. The influences of different parameters; laminar and turbulent Lewis number, mixture ratio, initial wall temperature distribution, and eddy viscosity, were considered. The numerical evaluation of these influences on heat transfer rate was done by using three different compressible, reacting laminar and turbulent boundary layer computer programs; MABL (Mass Addition Boundary Layer Program), MABL-KE (MABL program is modified to include turbulent kinetic energy equation), and BLIMP (Boundary Layer Integral Matrix Procedure). This study also provided an excellent opportunity to evaluate the efficiencies of these three computer programs and to suggest one of them for future computational purposes.

  17. Heat Transfer Through Turbulent Friction Layers

    NASA Technical Reports Server (NTRS)

    Reichardt, H.

    1943-01-01

    The "general Prandtl number" Pr(exp 1) - A(sub q)/A Pr, aside from the Reynolds number determines the ratio of turbulent to molecular heat transfer, and the temperature distribution in turbulent friction layers. A(sub q) = exchange coefficient for heat; A = exchange coefficient for momentum transfer. A formula is derived from the equation defining the general Prandtl number which describes the temperature as a function of the velocity. For fully developed thermal boundary layers all questions relating to heat transfer to and from incompressible fluids can be treated in a simple manner if the ratio of the turbulent shear stress to the total stress T(sub t)/T in the layers near the wall is known, and if the A(sub q)/A can be regarded as independent of the distance from the wall. The velocity distribution across a flat smooth channel and deep into the laminar sublayer was measured for isothermal flow to establish the shear stress ratio T(sub t)/T and to extend the universal wall friction law. The values of T(sub t)/T which resulted from these measurements can be approximately represented by a linear function of the velocity in the laminar-turbulent transition zone. The effect of the temperature relationship of the material values on the flow near the wall is briefly analyzed. It was found that the velocity at the laminar boundary (in contrast to the thickness of the laminar layer) is approximately independent of the temperature distribution. The temperature gradient at the wall and the distribution of temperature and heat flow in the turbulent friction layers were calculated on the basis of the data under two equations. The derived formulas and the figures reveal the effects of the Prandtl number, the Reynolds number, the exchange quantities and the temperature relationship of the material values.

  18. Analysis of roll gap heat transfers in hot steel strip rolling through roll temperature sensors and heat transfer models

    E-print Network

    Paris-Sud XI, Université de

    Analysis of roll gap heat transfers in hot steel strip rolling through roll temperature sensors and heat transfer models N. Legrand1,a , N. Labbe1,b D. Weisz-Patrault2,c , A. Ehrlacher2,d , T. Luks3,e heat transfers during pilot hot steel strip rolling. Two types of temperature sensors (drilled and slot

  19. Journal of Enhanced Heat Transfer, 19 (5): 457476 (2012) EXPERIMENTAL INVESTIGATION OF HEAT

    E-print Network

    Ghajar, Afshin J.

    Journal of Enhanced Heat Transfer, 19 (5): 457­476 (2012) EXPERIMENTAL INVESTIGATION OF HEAT microfin tubes, most of the heat transfer and friction factor studies were focused on the turbulent region. However, there is a lack of information about the heat transfer and friction factor behavior of microfin

  20. The overall heat transfer of greenhouses and its application to the heating load

    Microsoft Academic Search

    T. Kazuo; M. Hideo

    1983-01-01

    The overall heat transfer of greenhouses covered with glass, polyvinyl chloride and polyethylene films was investigated and is reported in this paper. This heat transfer has heretofore been considered to be proportional to the difference between inside and outside air temperature and the heat requirement has been calculated with the overall heat transfer coefficient. However, this consideration is based on

  1. Numerical study of high heat ux pool boiling heat transfer Ying He a,*, Masahiro Shoji b

    E-print Network

    Maruyama, Shigeo

    Numerical study of high heat ¯ux pool boiling heat transfer Ying He a,*, Masahiro Shoji b , Shigeo simulation model of boiling heat transfer is proposed based on a numerical macrolayer model [S. Maruyama, M. Shoji, S. Shimizu, A numerical simulation of transition boiling heat transfer, in: Proceedings

  2. Thermodynamic Efficiency of Heat Exchange Devices

    E-print Network

    Witte, L. C.; Shamsundar, N.

    1982-01-01

    is defined for heat exchange devices. The efficiency can be simply written in terms of the mean absolute temperature levels of the two fluids exchanging heat, and an appropriate environment temperature. It is also shown that for a given ratio of hot to cold...

  3. Literature survey on numerical heat transfer (1992--1993)

    SciTech Connect

    Shih, T.M.; Ohadi, M.M.; Liu, W. [Univ. of Maryland, College Park, MD (United States). Dept. of Mechanical Engineering

    1996-04-01

    The present survey is a review of technical papers of the subject of numerical heat transfer (NHT) published in 1992 and 1993 and is a continuation of past literature surveys. The journals surveyed in this article are Numerical Heat Transfer Part A, Numerical Heat Transfer Part B, ASME Journal of Heat Transfer, International Journal of Heat and Mass Transfer, and International Journal for Numerical Methods in Fluids. Several other archival journals, such as AIAA Journal, Journal of Computational Physics, Journal of Fluid Mechanics, SIAM Journal of Numerical Analysis, and Computers and Fluids, occasionally publish works in the area of NHT. However, they are not surveyed.

  4. Effect of nanoparticles on heat transfer in mini double-pipe heat exchangers in turbulent flow

    NASA Astrophysics Data System (ADS)

    Aghayari, Reza; Maddah, Heydar; Ashori, Fatemeh; Hakiminejad, Afshin; Aghili, Mehdi

    2015-03-01

    In this work, heat transfer of a fluid containing nanoparticles of aluminum oxide with the water volume fraction (0.1-0.3) percent has been reported. Heat transfer of the fluid containing nano water aluminum oxide with a diameter of about 20 nm in a horizontal double pipe counter flow heat exchanger under turbulent flow conditions was studied. The results showed that the heat transfer of nanofluid in comparison with the heat transfer of fluid is slightly higher than 12 percent.

  5. On the efficiency of solar heating in the middle atmosphere

    NASA Technical Reports Server (NTRS)

    Mlynczak, Martin G.; Solomon, Susan

    1991-01-01

    The efficiency at which solar ultraviolet radiation absorbed in the Hartley band of ozone is directly converted to heat in the terrestrial mesosphere and lower thermosphere (50-110 km) is calculated. The ozone molecule undergoes photolysis to yield the excited species O(1D) and O2(1Delta) with a quantum yield of about 0.9. Spontaneous emission from O2(1Delta) and from O2(1Sigma) (excited by energy transfer from O/1D/) significantly decreases the amount of energy available for heat. Similarly, the efficiency at which solar ultraviolet radiation absorbed by O2 in the Schumann-Runge continuum is directly converted to heat in the lower thermosphere (95-110 km) is calculated. The O2 undergoes photolysis and the excited product O(1D) is generated. Spontaneous emission from O2(1Sigma) (excited by energy transfer from O/1D/) reduces the amount of energy available for heat in the lower thermosphere. The consideration of these energy transfer and loss processes results in significantly reduced heating rates as compared to those conventionally calculated in models of the middle atmosphere.

  6. Boiling Heat Transfer in a Narrow Channel with Thermal Spray Coating

    NASA Astrophysics Data System (ADS)

    Asano, Hitoshi; Aoki, Koichi; Inoue, Masashi; Sugimoto, Katsumi; Takenaka, Nobuyuki

    Boiling heat transfer enhancement is efficient for development of a cold plate used in a two-phase flow loop type thermal control system. This study deals with boiling heat transfer enhancement for a narrow channel by thermal spray coating of metal. Copper particles were coated on the heating surface by vacuum plasma spraying. Two kinds of surface were manufactured using different particle size, about 200 and 50 µm. The heat transfer performance was evaluated in saturated flow boiling experiments of HCFC123 for ranges of mass flux of 100 to 400 kg/(m2•s), inlet quality of 0 to 0.60, and heat flux of 25 to 251 kW/m2. The test channel with the width of 20 mm, and heated length of 100 mm was placed horizontally. The lower side of heating area was heated by cartridge heaters through a copper block. The channel gap was set to 2 and 4 mm. As the result, the coating surface produced higher heat transfer coefficient than the smooth surface, especially, the heat transfer performance of the surface using finer particle was higher and was about 5 to 10 times higher than that of the smooth surface. While the effect of gaps on the heat transfer coefficient was a little, the critical heat flux increased with increasing the channel gap. Critical heat flux was increased a little by thermal spray coating.

  7. Characteristic of Local Boiling Heat Transfer of Ammonia / Water Binary Mixture on the Plate Type Evaporator

    NASA Astrophysics Data System (ADS)

    Okamoto, Akio; Arima, Hirofumi; Kim, Jeong-Hun; Akiyama, Hirokuni; Ikegami, Yasuyuki; Monde, Masanori

    Ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC) are expected to be the next generation energy production systems. Both systems use a plate type evaporator, and ammonia or ammonia/water mixture as a working fluid. It is important to clarify heat transfer characteristic for designing efficient power generation systems. Measurements of local boiling heat transfer coefficients and visualization were performed for ammonia /water mixture (z = 0.9) on a vertical flat plate heat exchanger in a range of mass flux (7.5 - 15 kg/m2s), heat flux (15 - 23 kW/m2), and pressure (0.7 - 0.9 MPa). The result shows that in the case of ammonia /water mixture, the local heat transfer coefficients increase with an increase of vapor quality and mass flux, and decrease with an increase of heat flux, and the influence of the flow pattern on the local heat transfer coefficient is observed.

  8. CAV2001:sessionB4.002 1 TOWARD EFFICIENT COMPUTATION OF HEAT AND

    E-print Network

    Dabiri, John O.

    CAV2001:sessionB4.002 1 TOWARD EFFICIENT COMPUTATION OF HEAT AND MASS TRANSFER EFFECTS in a converging-diverging nozzle and showed good agreement to experiments both with and without shock waves. While are formed inside the bubble, and heat and mass transfer have a great influence on the bubble motion. While

  9. Efficiency bounds for nonequilibrium heat engines

    SciTech Connect

    Mehta, Pankaj; Polkovnikov, Anatoli, E-mail: asp@bu.edu

    2013-05-15

    We analyze the efficiency of thermal engines (either quantum or classical) working with a single heat reservoir like an atmosphere. The engine first gets an energy intake, which can be done in an arbitrary nonequilibrium way e.g. combustion of fuel. Then the engine performs the work and returns to the initial state. We distinguish two general classes of engines where the working body first equilibrates within itself and then performs the work (ergodic engine) or when it performs the work before equilibrating (non-ergodic engine). We show that in both cases the second law of thermodynamics limits their efficiency. For ergodic engines we find a rigorous upper bound for the efficiency, which is strictly smaller than the equivalent Carnot efficiency. I.e. the Carnot efficiency can be never achieved in single reservoir heat engines. For non-ergodic engines the efficiency can be higher and can exceed the equilibrium Carnot bound. By extending the fundamental thermodynamic relation to nonequilibrium processes, we find a rigorous thermodynamic bound for the efficiency of both ergodic and non-ergodic engines and show that it is given by the relative entropy of the nonequilibrium and initial equilibrium distributions. These results suggest a new general strategy for designing more efficient engines. We illustrate our ideas by using simple examples. -- Highlights: ? Derived efficiency bounds for heat engines working with a single reservoir. ? Analyzed both ergodic and non-ergodic engines. ? Showed that non-ergodic engines can be more efficient. ? Extended fundamental thermodynamic relation to arbitrary nonequilibrium processes.

  10. Analysis of three-dimensional heat transfer in micro-channel heat sinks

    E-print Network

    Qu, Weilin

    . For the micro- channel heat sink investigated, it is found that the temperature rise along the flow directionAnalysis of three-dimensional heat transfer in micro-channel heat sinks Weilin Qu, Issam Mudawar, the three-dimensional fluid flow and heat transfer in a rectangular micro-channel heat sink are ana- lyzed

  11. Effects of winglets to augment tube wall heat transfer in louvered fin heat exchangers

    E-print Network

    Thole, Karen A.

    Effects of winglets to augment tube wall heat transfer in louvered fin heat exchangers Paul A Abstract The louvered fin heat exchanger, a type of compact heat exchanger, has been used heavily transfer along the tube wall of the compact heat exchanger through the use of winglets placed

  12. CORRELATING EVAPORATION HEAT TRANSFER COEFFICIENT OF REFRIGERANT R-134a IN A PLATE HEAT EXCHANGER

    E-print Network

    Kandlikar, Satish

    1 CORRELATING EVAPORATION HEAT TRANSFER COEFFICIENT OF REFRIGERANT R-134a IN A PLATE HEAT EXCHANGER for evaporation heat transfer coefficient of refrigerant R-134a flowing in a plate heat exchanger. Correlation heat exchanger are found to result in large discrepancies with their own experimental data

  13. A SINDA '85 nodal heat transfer rate calculation user subroutine

    NASA Technical Reports Server (NTRS)

    Cheston, Derrick J.

    1992-01-01

    This paper describes a subroutine, GETQ, which was developed to compute the heat transfer rates through all conductors attached to a node within a SINDA '85 thermal submodel. The subroutine was written for version 2.3 of SINDA '85. Upon calling GETQ, the user supplies the submodel name and node number which the heat transfer rate computation is desired. The returned heat transfer rate values are broken down into linear, nonlinear, source and combined heat loads.

  14. Boiling heat transfer in a horizontal small-diameter tube

    Microsoft Academic Search

    M. W. Wambsganss; J. A. Jendrzejczyk; T. N. Tran; D. M. France

    1993-01-01

    Results of a study on boiling heat transfer of refrigerant R-113 in a small-diameter (2.92 mm) tube are reported. Local heat transfer coefficients are measured for a range of heat flux (8.8-90.75 kW\\/m[sup 2]), mass flux (50-300 kg\\/m[sup 2]s), and equilibrium mass quality (0-0.9). The measured coefficients are used to evaluate 10 different heat transfer correlations, some of which have

  15. Solar pond fluid dynamics and heat transfer

    SciTech Connect

    Jones, G.F.

    1984-08-01

    The primary objective of the solar pond research was to obtain an indepth understanding of solar pond fluid dynamics and heat transfer. The key product was the development of a validated one-dimensional computer model with the capability to accurately predict time-dependent solar pond temperature, salinities, and interface motions. Laboratory scale flow visualization experiments were conducted to better understand layer motion. Two laboratory small-scale ponds and a large-scale outdoor solar pond were designed and built to provide quantitative data. This data provided a basis for validating the model and enhancing the understanding of pond dynamic behavior.

  16. Solar Pond Fluid Dynamics and Heat Transfer

    NASA Technical Reports Server (NTRS)

    Jones, G. F.

    1984-01-01

    The primary objective of the solar pond research was to obtain an indepth understanding of solar pond fluid dynamics and heat transfer. The key product was the development of a validated one-dimensional computer model with the capability to accurately predict time-dependent solar pond temperature, salinities, and interface motions. Laboratory scale flow visualization experiments were conducted to better understand layer motion. Two laboratory small-scale ponds and a large-scale outdoor solar pond were designed and built to provide quantitative data. This data provided a basis for validating the model and enhancing the understanding of pond dynamic behavior.

  17. Convective heat transfer and infrared thermography.

    PubMed

    Carlomagno, Giovanni M; Astarita, Tommaso; Cardone, Gennaro

    2002-10-01

    Infrared (IR) thermography, because of its two-dimensional and non-intrusive nature, can be exploited in industrial applications as well as in research. This paper deals with measurement of convective heat transfer coefficients (h) in three complex fluid flow configurations that concern the main aspects of both internal and external cooling of turbine engine components: (1) flow in ribbed, or smooth, channels connected by a 180 degrees sharp turn, (2) a jet in cross-flow, and (3) a jet impinging on a wall. The aim of this study was to acquire detailed measurements of h distribution in complex flow configurations related to both internal and external cooling of turbine components. The heated thin foil technique, which involves the detection of surface temperature by means of an IR scanning radiometer, was exploited to measure h. Particle image velocimetry was also used in one of the configurations to precisely determine the velocity field. PMID:12496015

  18. Fibre optic sensors for heat transfer studies

    NASA Astrophysics Data System (ADS)

    Sinha, Pranay G.

    This thesis describes the design and development of a prototype sensor, based on a miniature optical fiber Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer rates, spatial resolution, electromagnetic interference, calibration and signal processing. The special features of the optical sensor are: (1) short length (less than 5 mm), and therefore embeddable in thin structures of model components; (2) direct measurement of heat flux rates; (3) calorimetric operation with temperature resolution of less than 25 mK over a measurement bandwidth of 100 kHz; (4) capability of measuring heat flux less than 5 kWm(exp -2) with measurement range in excess of 10 MWm(exp -2); (5) temporal response time of less than 10 microseconds; (6) minimal thermal disturbances because models are often made of ceramic materials with thermal properties similar to those of the optical fiber from which sensors are made;(7) possibility of using in models with dissimilar thermal properties to the optical fiber, for example, metals; (8) spatial resolution of less than 5 microns; (9) remote operation; (10) an ability to be multiplexed; and (11) immunity to electromagnetic interference. A detailed discussion of the design considerations for the sensor, system development, evaluation of the sensor performance both in the laboratory and wind tunnel environments is presented in this thesis. The performance of the sensor compared favorably with electrical gauges namely, platinum thin-film resistance thermometers. A 4-sensor multiplexed system has been successfully operated, and is reported in the thesis. A brief discussion is also included to indicate that the same sensor design may be considered for applications in other engineering areas.

  19. Fibre Optic Sensors for Heat Transfer Studies.

    NASA Astrophysics Data System (ADS)

    Sinha, Pranay G.

    Available from UMI in association with The British Library. This thesis describes the design and development of a prototype sensor, based on a miniature optical fibre Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer rates, spatial resolution, electromagnetic interference, calibration and signal processing. The special features of the optical sensor are: (i) short length (<5 mm), and therefore embeddable in thin structures of model components; (ii) direct measurement of heat flux rates; (iii) calorimetric operation with temperature resolution of <25 mK over a measurement bandwidth of 100 kHz: (iv) capability of measuring heat flux <5 kWm^ {-2} with measurement range in excess of 10 MWm^{-2}; (v) temporal response time of <10 mus; (vi) minimal thermal disturbances because models are often made of ceramic materials with thermal properties similar to those of the optical fibre from which sensors are made; (vii) possibility of using in models with dissimilar thermal properties to the optical fibre, for example, metals; (viii) spatial resolution of <5 mu m; (ix) remote operation; (x) an ability to be multiplexed; and (xi) immunity to electromagnetic interference. A detailed discussion of the design considerations for the sensor, system development, evaluation of the sensor performance both in the laboratory and wind tunnel environments is presented in this thesis. The performance of the sensor compared favourably with electrical gauges namely, platinum thin-film resistance thermometers. A 4-sensor multiplexed system has been sucessfully operated, and is reported in the thesis. A brief discussion is also included to indicate that the same sensor design may be considered for applications in other engineering areas.

  20. Heat and mass transfer in the gas tungsten and gas metal arc welding processes

    SciTech Connect

    Watkins, A.D; Smartt, H.B.; Einerson, C.J.; Watkins, J.A.

    1990-01-01

    The heat transferred from an electrode negative, argon gas tungsten arc to an anode was measured for a wide range of conditions suitable for mechanized welding. The results are given as (1) the arc efficiency and (2) the anode heat and current input distributions for various anode materials over a range of current and voltage. The nominal arc is Gaussian, {approximately}4 mm in diameter, with {approximately}75{percent}heat transfer efficiency. Variations from these values are discussed in terms of the electrical and thermal energy transport mechanisms. Heat transferred to the workpiece (cathode) during direct current, electrode positive gas metal arc welding (GMAW) was measured for various parameters applicable to machine welding. The results are presented as a function of electrode speed for changing voltages and contact tip to workpiece distances. The total heat transfer efficiency was nominally 85{percent} for a 0.89 mm diameter steel electrode using an argon-2{percent} oxygen shielding gas; the nominal heat transfer efficiency of the droplet component was 40{percent}. The average droplet temperatures ranged from 2400 to 3100 K, depending on the process parameters. A new method of measuring the heat transferred from the arc to the workpiece, using a boiling liquid nitrogen calorimeter, has been developed that gives rapid, accurate values. 20 refs., 8 figs., 2 tabs.

  1. Microscale heat transfer enhancement using spinodal decomposition

    NASA Astrophysics Data System (ADS)

    Poesio, Pietro; Molin, Dafne; Hadjiconstantinou, Nicolas G.; Beretta, Gian Paolo

    2011-11-01

    In many cases, miniaturization is limited by our ability to quickly remove heat; current state-of-the-art cooling approaches have significant limitations, particularly for high heat flux applications. Recent studies have shown that phase separation of a binary liquid-liquid mixture quenched to a temperature below the spinodal curve can be used to enhance heat transfer in small-scale devices. In particular, it has been shown that the self propulsion of single droplets formed during the intermediate stage of spinodal decomposition can produce considerable agitation and, as a result, enhanced heat transport. Spinodal phase separation dynamics can be described by the coupled Cahn-Hilliard/Navier-Stokes equations; unfortunately, simulation of these equations at the device scale is computationally costly due to the mulltiscale nature of spinodal decomposition, which requires resolution of the phase interface between the two fluids which is of atomistic size. In this talk we discuss possible approaches for reducing this computational cost by calculating the resulting transport from synthetic fluctuating fields that simulate the effect of spinodal decomposition but are generated stochastically without solving the Cahn-Hilliard equation at close-to-atomistic resolution.

  2. FIN EFFICIENCY CALCULATION IN ENHANCED FIN-AND-TUBE HEAT EXCHANGERS IN DRY CONDITIONS

    Microsoft Academic Search

    Thomas PERROTIN; Denis CLODIC

    Fin efficiency calculation is of the greatest importance in refrigerant-to-air heat exchanger engineering, for the evaluation of the finned surface performance or for the determination of the air-side heat transfer coefficient from experimental data. High efficiency heat exchangers use enhanced fin geometry (louvered and slit fins) for which the fin efficiency could be overestimated by usual formulations and more precisely

  3. Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor transfer

    E-print Network

    Martin, Timothy

    Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become diffusion, the boundary layer around a leaf also provides resistance to the transfer of heat between a leaf

  4. Heat transfer to impacting drops and post critical heat flux dispersed flow

    E-print Network

    Kendall, Gail E.

    1978-01-01

    Heat transfer to drops impacting on a hot surface is examined in context of dispersions of flowing, boiling fluids. The liquid contribution to heat transfer from a hot tube to a two-phase dispersion is formulated in terms ...

  5. Boiling local heat transfer enhancement in minichannels using nanofluids.

    PubMed

    Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony

    2013-01-01

    This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 ?m hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445

  6. Boiling local heat transfer enhancement in minichannels using nanofluids

    PubMed Central

    2013-01-01

    This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 ?m hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445

  7. Preparation, thermo-physical properties and heat transfer enhancement of nanofluids

    NASA Astrophysics Data System (ADS)

    Rashmi, W.; Khalid, M.; Ong, S. S.; Saidur, R.

    2014-09-01

    Research interest in convective heat transfer using suspensions of nano-sized solid particles has been growing rapidly over the past decade, seeking to develop novel methods for enhancing the thermal performance of heat transfer fluids. Due to their superior transport properties and significant enhancement in heat transfer characteristics, nanofluids are believed to be a promising heat transfer fluid for the future. The stability of nanofluids is also a key aspect of their sustainability and efficiency. This review summarizes the recent research findings on stability, thermophysical properties and convective heat transfer of nano-sized particles suspended in base fluids. Furthermore, various mechanisms of thermal conductivity enhancement and challenges faced in nanofluid development are also discussed.

  8. Heat transfer assembly for a fluorescent lamp and fixture

    DOEpatents

    Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.

    1992-12-29

    In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.

  9. Exact microscopic theory of electromagnetic heat transfer between a dielectric sphere and plate

    E-print Network

    Clayton Otey; Shanhui Fan

    2011-10-10

    Near-field electromagnetic heat transfer holds great potential for the advancement of nanotechnology. Whereas far-field electromagnetic heat transfer is constrained by Planck's blackbody limit, the increased density of states in the near-field enhances heat transfer rates by orders of magnitude relative to the conventional limit. Such enhancement opens new possibilities in numerous applications, including thermal-photo-voltaics, nano-patterning, and imaging. The advancement in this area, however, has been hampered by the lack of rigorous theoretical treatment, especially for geometries that are of direct experimental relevance. Here we introduce an efficient computational strategy, and present the first rigorous calculation of electromagnetic heat transfer in a sphere-plate geometry, the only geometry where transfer rate beyond blackbody limit has been quantitatively probed at room temperature. Our approach results in a definitive picture unifying various approximations previously used to treat this problem, and provides new physical insights for designing experiments aiming to explore enhanced thermal transfer.

  10. Nanoscale heat transfer and phase transformation surrounding intensely heated nanoparticles

    NASA Astrophysics Data System (ADS)

    Sasikumar, Kiran

    Over the last decade there has been significant ongoing research to use nanoparticles for hyperthermia-based destruction of cancer cells. In this regard, the investigation of highly non-equilibrium thermal systems created by ultrafast laser excitation is a particularly challenging and important aspect of nanoscale heat transfer. It has been observed experimentally that noble metal nanoparticles, illuminated by radiation at the plasmon resonance wavelength, can act as localized heat sources at nanometer-length scales. Achieving biological response by delivering heat via nanoscale heat sources has also been demonstrated. However, an understanding of the thermal transport at these scales and associated phase transformations is lacking. A striking observation made in several laser-heating experiments is that embedded metal nanoparticles heated to extreme temperatures may even melt without an associated boiling of the surrounding fluid. This unusual phase stability is not well understood and designing experiments to understand the physics of this phenomenon is a challenging task. In this thesis, we will resort to molecular dynamics (MD) simulations, which offer a powerful tool to investigate this phenomenon, without assumptions underlying continuum-level model formulations. We present the results from a series of steady state and transient non-equilibrium MD simulations performed on an intensely heated nanoparticle immersed in a model liquid. For small nanoparticles (1-10 nm in diameter) we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, we report the existence of a critical nanoparticle size (4 nm in diameter) below which we do not observe formation of vapor even when local fluid temperatures exceed the critical temperature. Instead, we report the existence of a stable fluid region with a density much larger than that of the vapor phase. We explain this stability in terms of the Laplace pressure associated with the formation of a vapor nanocavity and the associated effect on the Gibbs free energy. Separately, we also demonstrate the role of extreme temperature gradients (108-1010 K/m) in elevating the boiling point of liquids. We show that, assuming local thermal equilibrium, the observed elevation of the boiling point is associated with the interplay between the "bulk" driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. In transient simulations that mimic laser-heating experiments we observe the formation and collapse of vapor bubbles around the nanoparticles beyond a threshold. Detailed analysis of the cavitation dynamics indicates adiabatic formation followed by an isothermal final stage of growth and isothermal collapse.

  11. Proceedings of HTSC 2005: Heat Transfer Summer Conference

    E-print Network

    Guo, Zhixiong "James"

    for describing radiation transfer and heat transfer in the micro/nanoscale devices is presented firstProceedings of HTSC 2005: Heat Transfer Summer Conference San Francisco, CA, July 17-22, 2005 HT's equations which govern the propagation of electromagnetic field and the radiation energy transport

  12. Partial moment entropy approximation to radiative heat transfer

    Microsoft Academic Search

    Martin. Frank; Bruno. Dubroca; Axel. Klar

    2006-01-01

    We extend the half moment entropy closure for the radiative heat transfer equations presented in Dubroca and Klar [B. Dubroca, A. Klar, Half moment closure for radiative transfer equations, J. Comput. Phys. 180 (2002) 584–596] and Turpault et al. [R. Turpault, M. Frank, B. Dubroca, A. Klar, Multigroup half space moment approximations to the radiative heat transfer equations, J. Comput.

  13. Radiative heat transfer in participating media — A review

    Microsoft Academic Search

    Subhash C Mishra; Manohar Prasad

    1998-01-01

    This paper presents an overview of various exact analytic and approximate numerical methods for the solution of radiative\\u000a heat transfer problems in participating media. Review of each method is followed by its strengths and limitations. Importance\\u000a of radiative heat transfer analysis and difficulties in the solution of radiative transfer problems have been emphasized.

  14. Analogous studies of simultaneous conductive and radiative heat transfer

    Microsoft Academic Search

    D W Stops; R E Pearson

    1966-01-01

    The process of radiative heat transfer is electrically simulated by using voltage-dependent resistors in conjunction with current transference circuits, and so an analogue is devised which shows how the overall uni-directional heat transfer by simultaneous conduction and radiation across a transparent gas space is a function of the positions of radiation shields which may be interposed between the bounding surfaces.

  15. Heat transfer from extended surfaces subject to variable heat transfer coefficient

    Microsoft Academic Search

    Esmail M. A. Mokheimer

    2003-01-01

    The present article investigates the effect of locally variable heat transfer coefficient on the performance of extended surfaces (fins) subject to natural convection. Fins of different profiles have been investigated. The fin profiles presently considered are namely; straight and pin fin with rectangular (constant diameter), convex parabolic, triangular (conical) and concave parabolic profiles and radial fins with constant profile with

  16. M. Bahrami ENSC 388 (F09) Forced Convection Heat Transfer 1 Forced Convection Heat Transfer

    E-print Network

    Bahrami, Majid

    heat transfer is expressed by Newton's law of cooling: WTThAQ mWTThq sconv sconv 2 in the presence of bulk fluid motion. Convection is classified as natural (or free) and forced convection depending on how the fluid motion is initiated. In natural convection, any fluid motion

  17. Ceramic or metallic? - material aspects of compact heat regenerator energy efficiency

    Microsoft Academic Search

    M Wnek

    2012-01-01

    The metal industry cannot afford the financial mismanagement in the era of rising energy prices and thus, the high efficiency devices should be used. In the metallurgical thermal processes the combustion air temperature increasing is one of the methods for obtaining the heat transfer intensification and the furnaces efficiency rising. Therefore the new and effective heating technologies in thermal processes

  18. Validation of efficiency transfer for Marinelli geometries.

    PubMed

    Ferreux, Laurent; Pierre, Sylvie; Thanh, Tran Thien; Lépy, Marie-Christine

    2013-11-01

    In the framework of environmental measurements by gamma-ray spectrometry, some laboratories need to characterize samples in geometries for which a calibration is not directly available. A possibility is to use an efficiency transfer code, e.g., ETNA. However, validation for large volume sources, such as Marinelli geometries, is needed. With this aim in mind, ETNA is compared, initially to a Monte Carlo simulation (PENELOPE) and subsequently to experimental data obtained with a high-purity germanium detector (HPGe). PMID:23623315

  19. Heat transfer investigations in a slurry bubble column

    SciTech Connect

    Saxena, S.C.; Rao, N.S.; Vadivel, R.; Shrivastav, S.; Saxena, A.C.; Patel, B.B.; Thimmapuram, P.R.; Kagzi, M.Y.; Khan, I.A.; Verma, A.K.

    1991-02-01

    Slurry bubble columns, for use in Fischer-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven-, or thirty-seven tubes. the experiments were conducted for two- and three phase systems; employing for gas phase: air and nitrogen, liquid phase: water and Therminol-66, and solid phase: red iron oxide (1.02, 1.70 and 2.38 {mu}m), glass beads (50.0, 90.0, 119.0 and 143.3 {mu}m), silica sand (65 {mu}m), and magnetite (28.0, 35.7, 46.0, 58.0, 69.0, 90.5, 115.5 and 137.5 {mu}m). The column temperature was varied between 298--523 K, gas velocity between 0--40 cm/s, and solids concentration between 0--50 weight percent. The holdup and heat transfer data as a function of operating and system parameters were employed to assess the available correlations and semitheoretical models, and to develop new correlations. Information concerning the design and scale-up of larger units is presented. Specific research work that need to be undertaken to understand the phenomena of heat transfer and gas holdup is outlined so that efficient gas conversion and catalyst usage may be accomplished in slurry bubble columns. 28 refs., 102 figs., 42 tabs.

  20. Heat transfer investigations in a slurry bubble column

    SciTech Connect

    Saxena, S.C.; Rao, N.S.; Vadivel, R.; Shrivastav, S.; Saxena, A.C.; Patel, B.B.; Thimmapuram, P.R.; Kagzi, M.Y.; Khan, I.A.; Verma, A.K.

    1991-02-01

    Slurry bubble columns, for use in Fisher-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven- or thirty-seven tubes. The experiments were conducted for two- and three-phase systems; employing for gas phase: air and nitrogen, liquid phase: water and Therminol-66, and solid phase: red iron oxide (1.02, 1.70 and 2.38 {mu}m), glass beads (50.0, 90.0, 119.0 and 143.3 {mu}m), silica sand (65 {mu}), and magnetite (28.0, 35.7, 46.0, 58.0, 69.0, 90.5, 115.5, and 137.5 {mu}m). The column temperature was varied between 298--523 K, gas velocity between 0--40 cm/s, and solids concentration between 0--50 weight percent. The holdup and heat transfer data as a function of operating and system parameters were employed to assess the available correlations and semitheoretical models, and to develop new correlations. Information concerning the design and scale-up of larger units is presented. Specific research work that need to be undertaken to understand the phenomena of heat transfer and gas holdup is outlined so that efficient gas conversion and catalyst usage may be accomplished in slurry bubble columns. 130 refs., 177 figs., 54 tabs.

  1. CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011

    E-print Network

    Dyer, Bill

    ME 525 CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011 Office: 201C Roberts Hall Lecture Room of conduction heat transfer. Important results which are useful for engineering application will also: 121 Roberts Hall Phone: 994-6295 Lecture Periods: 12:45- 2:00, TR TEXT: Heat Conduction, M. N. Ozisik

  2. Proceedings of NHTC'00 34th National Heat Transfer Conference

    E-print Network

    Wang, Chao-Yang

    Proceedings of NHTC'00 34th National Heat Transfer Conference Pittsburgh, Pennsylvania, August 20­22, 2000 NHTC2000-12151 HEAT TRANSFER IN A FUEL CELL ENGINE J. Musser and C.Y. Wang Department-4848 E-mail: cxw31@psu.edu KEYWORDS: PEM, Fuel Cell Engine, Heat Generation, Current Density, System

  3. Intensification of heat transfer in flash film evaporators

    Microsoft Academic Search

    L. P. Pertsev; P. E. Novikov; E. P. Novikov; P. A. Kapustenko

    1992-01-01

    The horizontal arrangement of the panels in the evaporator was selected after analysis of the process of heat transfer in different sections of the heat-exchange elements of known panel-type vertical gravity film evaporators, which showed a low local heat transfer in the first upper section of the panel (because of the instability of the film flow of the solution being

  4. High flux heat transfer in a target environment

    E-print Network

    McDonald, Kirk

    velocity [m/s] (Mach=0.3 for gases) Pr Re Nu heat transfer coefficient [W/m 2 K] allowable temp rise [KHigh flux heat transfer in a target environment T. Davenne High Power Targets Group Rutherford · Radiation Cooling · Forced Convection · Nucleate Boiling · Critical Heat Flux · Other ideas · Summary #12

  5. Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces

    E-print Network

    Attinger, Daniel

    that describes how biphilic surfaces effectively manage the vapor and liquid transport, delaying critical heat flux and maximizing the heat transfer coef- ficient. Finally, we manufacture and test the first, with the exception of experiments involving single nucleation [14] or condensation [15]. The high heat transfer rates

  6. Heat transfer in serpentine flow passages with rotation

    Microsoft Academic Search

    S. Mochizuki; J. Takamura; S. Yamawaki; Wen-Jei Yang

    1994-01-01

    Heat transfer characteristics of a three-pass serpentine flow passage with rotation are experimentally studied. The walls of the square flow passage are plated with thin stainless-steel foils through which electrical current is applied to generate heat. The local heat transfer performance on the four side walls of the three straight flow passages and two turning elbows are determined for both

  7. Mathematical model for heat transfer mechanism for particulate system

    Microsoft Academic Search

    A. R. Khan; A. Elkamel

    2002-01-01

    Various theoretical models for fluidized bed to surface heat transfer have been considered to explain the mechanism of heat transport. The particulate fluidized bed which is the common case for liquid–solid fluidized bed is much simpler and homogeneous and transport operation can be easily modeled. The heat transfer coefficient increases to a maximum and then steadily decreases as the bed

  8. ME 139L Experimental Heat Transfer ABET EC2000 syllabus

    E-print Network

    Ben-Yakar, Adela

    Edition, 2002. Other Required Material: None Course Objectives: The objective of this course is to provideME 139L ­ Experimental Heat Transfer Page 1 ABET EC2000 syllabus ME 139L ­ Experimental Heat, Convection Over a Cylinder. #12;ME 139L ­ Experimental Heat Transfer Page 2 ABET EC2000 syllabus Contribution

  9. Heat Transfer Analysis of a Closed Brayton Cycle Space Radiator

    NASA Technical Reports Server (NTRS)

    Juhasz, Albert J.

    2007-01-01

    This paper presents a mathematical analysis of the heat transfer processes taking place in a radiator for a closed cycle gas turbine (CCGT), also referred to as a Closed Brayton Cycle (CBC) space power system. The resulting equations and relationships have been incorporated into a radiator sub-routine of a numerical triple objective CCGT optimization program to determine operating conditions yielding maximum cycle efficiency, minimum radiator area and minimum overall systems mass. Study results should be of interest to numerical modeling of closed cycle Brayton space power systems and to the design of fluid cooled radiators in general.

  10. Effects of fouling on the efficiency of heat exchangers in lignite utility boilers

    Microsoft Academic Search

    G. Bergeles; D. Bouris; M. Yianneskis; S. Balabani; A. Kravaritis; S. Itskos

    1997-01-01

    The work presented in this article is directed towards the understanding of the mechanism of ash deposition on the surfaces of tubes of heat exchangers in lignite utility boilers and the evaluation of the influence of fouling on heat exchanger efficiency. For this purpose a numerical model was developed to predict the deposition of particles onto the heat transfer surfaces.

  11. Combined Heat Transfer in High-Porosity High-Temperature Fibrous Insulations: Theory and Experimental Validation

    NASA Technical Reports Server (NTRS)

    Daryabeigi, Kamran; Cunnington, George R.; Miller, Steve D.; Knutson, Jeffry R.

    2010-01-01

    Combined radiation and conduction heat transfer through various high-temperature, high-porosity, unbonded (loose) fibrous insulations was modeled based on first principles. The diffusion approximation was used for modeling the radiation component of heat transfer in the optically thick insulations. The relevant parameters needed for the heat transfer model were derived from experimental data. Semi-empirical formulations were used to model the solid conduction contribution of heat transfer in fibrous insulations with the relevant parameters inferred from thermal conductivity measurements at cryogenic temperatures in a vacuum. The specific extinction coefficient for radiation heat transfer was obtained from high-temperature steady-state thermal measurements with large temperature gradients maintained across the sample thickness in a vacuum. Standard gas conduction modeling was used in the heat transfer formulation. This heat transfer modeling methodology was applied to silica, two types of alumina, and a zirconia-based fibrous insulation, and to a variation of opacified fibrous insulation (OFI). OFI is a class of insulations manufactured by embedding efficient ceramic opacifiers in various unbonded fibrous insulations to significantly attenuate the radiation component of heat transfer. The heat transfer modeling methodology was validated by comparison with more rigorous analytical solutions and with standard thermal conductivity measurements. The validated heat transfer model is applicable to various densities of these high-porosity insulations as long as the fiber properties are the same (index of refraction, size distribution, orientation, and length). Furthermore, the heat transfer data for these insulations can be obtained at any static pressure in any working gas environment without the need to perform tests in various gases at various pressures.

  12. Understanding fast heat transfer in the shallow subsurface

    NASA Astrophysics Data System (ADS)

    Rutten, Martine; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick

    2010-05-01

    Understanding the temperature profile of the shallow subsurface is of great importance for interpreting remote sensing observations and modeling land-atmosphere interaction. Remote sensing observations are translated to surface characteristics, such as vegetation and soil moisture, using radiative transfer schemes that are sensitive to skin temperature estimation. The surface temperature is also a key variable in the heat partitioning of net radiation into sensible, latent and soil heat flux at the interface between land and atmosphere. The temperature profile of the soil is determined by the processes of radiative, convective and conductive heat transfer. Whereas radiative and convective heat transfer are dominant at the soil-air interface, heat transfer within the soil is typically assumed to be governed by conduction and as such is described with a diffusion model. The thermal diffusivity of the soil depends mainly on mineral composition and moisture content and is described in many empirical models. Using temperature data from experiments conducted in Florida (MicroWex 2) and the Netherlands (Monster), we show that diffusion cannot describe heat transfer within approximately the upper ten centimeters of the soil. The heat transfer is significantly faster than would be predicted with a diffusion equation. Diffusivity values, estimated using an inversion approach to the diffusion equation, fall outside the physically reasonable range, which is defined by available soil diffusivity models. The extent of this strongly thermally active layer depends on vegetation conditions, and possibly moisture conditions. We investigate mechanisms that may explain the fast heat transfer in the shallow subsurface. Possible mechanisms include heat transfer by convective heat transfer processes such as latent heat formation and heat transfer due to water percolation. We estimated the size of the heat sink-source at depth and compared these to observations of latent heat and estimates of heat transfer by percolation. The magnitude of the sink-source reached values up to the same order of magnitude as the latent heat flux and decreased with depth. The sink-source terms were large, especially for low vegetation conditions and showed a distinct diurnal cycle. The possible contribution of percolation to heat transfer was minor compared to the magnitude of the sink-source term. Finally, we compared an empirical heat flow model, which includes formation of latent heat in the shallow subsurface, with our data. We found this model could not sufficiently describe the fast heat transfer in the shallow subsurface. Ongoing work is on a physically based model to describe fast heat transfer in the shallow subsurface.

  13. Transient critical heat flux and blowdown heat-transfer studies

    SciTech Connect

    Leung, J.C.

    1980-05-01

    Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.

  14. Heat Transfer in Turbulent Rotating Convection

    NASA Astrophysics Data System (ADS)

    Clercx, H. J. H.; Kunnen, R. P. J.; Geurts, B. J.

    2006-11-01

    Rayleigh-B'enard convection is a classical problem in which a fluid layer enclosed between two parallel horizontal walls is heated from below. In a rotating frame of reference the dynamics can change considerably through the fundamental involvement of a combination of buoyancy and Coriolis forces. The rotating Rayleigh-B'enard (RRB) setting is important for many applications, e.g., in engineering and climate modelling. Direct numerical simulation (DNS) is used to calculate the heat transfer at systematically varied rotation rates. The DNS code solves the incompressible Navier-Stokes equations in a rotating frame of reference, coupled to the heat equation within the Boussinesq approximation. Periodic boundary conditions are adopted in the horizontal directions and the vertical boundaries are treated as isothermal, no-slip walls. The velocity and temperature averages from this DNS will be compared to measurements in a water-filled cylindrical convection cell. Detailed velocity and temperature data will be obtained using stereoscopic particle image velocimetry and laser induced fluorescence, respectively.

  15. Heat exchanger efficiently operable alternatively as evaporator or condenser

    DOEpatents

    Ecker, Amir L. (Dallas, TX)

    1981-01-01

    A heat exchanger adapted for efficient operation alternatively as evaporator or condenser and characterized by flexible outer tube having a plurality of inner conduits and check valves sealingly disposed within the outer tube and connected with respective inlet and outlet master flow conduits and configured so as to define a parallel flow path for a first fluid such as a refrigerant when flowed in one direction and to define a serpentine and series flow path for the first fluid when flowed in the opposite direction. The flexible outer tube has a heat exchange fluid, such as water, flowed therethrough by way of suitable inlet and outlet connections. The inner conduits and check valves form a package that is twistable so as to define a spiral annular flow path within the flexible outer tube for the heat exchange fluid. The inner conduits have thin walls of highly efficient heat transfer material for transferring heat between the first and second fluids. Also disclosed are specific materials and configurations.

  16. Heat and mass transfer for micropolar flow with radiation effect past a nonlinearly stretching sheet

    NASA Astrophysics Data System (ADS)

    Hsiao, Kai-Long

    2010-04-01

    In this study, an analysis has been performed for heat and mass transfer with radiation effect of a steady laminar boundary-layer flow of a micropolar flow past a nonlinearly stretching sheet. Parameters n, K, k 0, Pr, Ec, and Sc represent the dominance of the nonlinearly effect, material effect, radiation effect, heat and mass transfer effects which have presented in governing equations, respectively. The similar transformation, the finite-difference method and Runge-Kutta method have been used to analyze the present problem. The numerical solutions of the flow velocity distributions, temperature profiles, the wall unknown values of ?'(0) and ?'(0) for calculating the heat and mass transfer of the similar boundary-layer flow are carried out as functions of n, Ec, k 0, Pr, Sc. The value of n, k 0, Pr and Sc parameters are important factors in this study. It will produce greater heat transfer efficiency with a larger value of those parameters, but the viscous dissipation parameter Ec and material parameter K may reduce the heat transfer efficiency. On the other hand, for mass transfer, the value of Sc parameter is important factor in this study. It will produce greater heat transfer efficiency with a larger value of Sc.

  17. Efficiency improvement in multi-sensor wireless network based estimation algorithms for distributed parameter systems with application at the heat transfer

    NASA Astrophysics Data System (ADS)

    Volosencu, Constantin; Curiac, Daniel-Ioan

    2013-12-01

    This paper gives a technical solution to improve the efficiency in multi-sensor wireless network based estimation for distributed parameter systems. A complex structure based on some estimation algorithms, with regression and autoregression, implemented using linear estimators, neural estimators and ANFIS estimators, is developed for this purpose. The three kinds of estimators are working with precision on different parts of the phenomenon characteristic. A comparative study of three methods - linear and nonlinear based on neural networks and adaptive neuro-fuzzy inference system - to implement these algorithms is made. The intelligent wireless sensor networks are taken in consideration as an efficient tool for measurement, data acquisition and communication. They are seen as a "distributed sensor", placed in the desired positions in the measuring field. The algorithms are based on regression using values from adjacent and also on auto-regression using past values from the same sensor. A modelling and simulation for a case study is presented. The quality of estimation is validated using a quadratic criterion. A practical implementation is made using virtual instrumentation. Applications of this complex estimation system are in fault detection and diagnosis of distributed parameter systems and discovery of malicious nodes in wireless sensor networks.

  18. Kissing heat transfer between the wraps of a scroll pump

    SciTech Connect

    Sunder, S.; Smith, J.L. Jr. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Mechanical Engineering

    1996-12-31

    Conductances associated with the various modes of internal heat transfer in a scroll pump are estimated. Heat transfer through transient contact between scroll wraps (kissing heat transfer) is found to be a dominant mode of heat transfer between discharge and suction sides of the pump. Such heat transfer is characterized by significant steady-state heat fluxes across the wraps of a scroll pump. Experiments on a specially instrumented scroll compressor provide evidence of significant heat fluxes across the wraps of the scroll pump. Estimation of the contact angle between wraps based on Hertzian stresses, as well as an oil film demonstrate that kissing heat transfer is a plausible mechanism of heat transfer in these pumps. Contact angles inferred from experimental data are also shown to be of the same order of magnitude as those predicted by Hertzian stress calculations. It is shown that the heat fluxes observed in the kissing heat transfer experiment are too large to be explained by convection between gas and wall in the scroll pump.

  19. Local heat transfer in a rotating serpentine flow passage

    NASA Astrophysics Data System (ADS)

    Yang, Wen-Jei; Zhang, Nengli; Chiou, Jeff

    1992-05-01

    An experimental study is performed on the internal cooling of a rotating serpentine flow passage of square cross section with throughflow. The test section is not preceded by a hydrodynamic calming region, i.e., a leading arm, and is rotated at low Rossby numbers. The local heat transfer coefficients along the flow passage, including the leading wall, trailing wall, and sidewalls, are determined together with the circumferentially averaged values. The Reynolds, Rossby, and rotating Rayleigh numbers are varied to determine their effects on heat transfer performance. It is shown that heat transfer augmentation is significant at all sharp turns due to the presence of strong secondary flow. The rotational effect is very obvious and complicated in the local heat transfer performance but it is very minor for the average heat transfer performance. The throughflow rate plays an important role in the heat transfer performance.

  20. Proceedings of IWHT2011 2011 International Workshop on Heat Transfer Advances for

    E-print Network

    Guo, Zhixiong "James"

    . These processes range from determining the thermal efficiency and performance of solar collectors and combustion Phase Functions and Radiative Transfer Analysis in a Solar Absorber Tube Brian Hunter, Zhixiong Guo is applied to the DOM for predicting radiative heat transfer in a solar absorber tube. Analysis of previous

  1. Micro and nanostructured surfaces for enhanced phase change heat transfer

    E-print Network

    Chu, Kuang-Han, Ph. D. Massachusetts Institute of Technology

    2013-01-01

    Two-phase microchannel heat sinks are of significant interest for thermal management applications, where the latent heat of vaporization offers an efficient method to dissipate large heat fluxes in a compact device. However, ...

  2. Downward heat transfer from heat-generating boiling pools pertaining to PAHR and transition phase. [LMFBR

    Microsoft Academic Search

    T. C. Chawla; J. D. Bingle

    1983-01-01

    The phenomenon of heat transfer from volume heated boiling pools in the downward direction is of considerable interest in nuclear reactor safety analysis. For example, in the post-accident heat removal studies of LMFBRs the downward heat transfer to a boiling steel layer in molten pool penetration of the MgO substrate is of interest. The bubbles rising from the boiling of

  3. INVESTIGATING THE EFFECT OF HEATING METHOD ON POOL BOILING HEAT TRANSFER

    E-print Network

    Kandlikar, Satish

    INVESTIGATING THE EFFECT OF HEATING METHOD ON POOL BOILING HEAT TRANSFER Satish G. Kandlikar-mail: SGKEME@RIT.EDU ABSTRACT Pool boiling experiments are generally conducted with electrically heated. Similar concerns have been expressed in literature for flow boiling heat transfer. The present

  4. Surface-Phonon Polariton Contribution to Nanoscale Radiative Heat Transfer

    Microsoft Academic Search

    Emmanuel Rousseau; Marine Laroche; Jean-Jacques Greet

    Heat transfer between two plates of polar materials at nanoscale distance is known to be enhanced by several orders of magnitude as compared with its far-field value. In this article, we show that nanoscale heat transfer is dominated by the coupling between surface phonon-polaritons located on each interface. Furthermore, we derive an asymptotic closed-form expression of the radiative heat transfer

  5. Sensitivity Analysis of the Gap Heat Transfer Model in BISON.

    SciTech Connect

    Swiler, Laura Painton; Schmidt, Rodney C.; Williamson, Richard (INL); Perez, Danielle (INL)

    2014-10-01

    This report summarizes the result of a NEAMS project focused on sensitivity analysis of the heat transfer model in the gap between the fuel rod and the cladding used in the BISON fuel performance code of Idaho National Laboratory. Using the gap heat transfer models in BISON, the sensitivity of the modeling parameters and the associated responses is investigated. The study results in a quantitative assessment of the role of various parameters in the analysis of gap heat transfer in nuclear fuel.

  6. Generalized dynamic modeling of local heat transfer in bubble columns

    Microsoft Academic Search

    Wei Chen; Tatsuya Hasegawa; Atsushi Tsutsumi; Kentaro Otawara; Yoshiki Shigaki

    2003-01-01

    Instantaneous local heat transfer rates were measured by using a hot-wire probe in three bubble columns of different diameters of 200, 400 and 800mm. The time series of heat transfer rates were analyzed by means of rescaled range (R\\/S) and deterministic chaos analyses. Due to the influence of highly chaotic bubble motions, the instantaneous local heat transfer exhibits low-dimensional chaotic

  7. Natural convection heat transfer from sinusoidal wavy surfaces

    Microsoft Academic Search

    S. H. Bhavnani; A. E. Bergles

    1991-01-01

    This paper presents the results of an experimental study of the natural convection heat transfer characteristics of sinusoidal wavy surfaces on vertical plates maintained at a constant temperature. Local heat transfer coefficients were obtained with a Mach-Zehnder interferometer. The heat transfer from the wavy surfaces, compared to a plane plate of equal projected area, increased with increasing amplitude-to-wavelength ratio. The

  8. Numerical Simulation and Optimization of Heat Transfer in Microchannel by Implementing Nonuniform Electrokinetic Forces

    Microsoft Academic Search

    V. Esfahanian; F. Kowsary; N. Noroozi; M. Rezaei Barmi

    2008-01-01

    The increasing power dissipation and decreasing dimensions of microelectronic devices have emphasized the demand for extremely efficient compact cooling technology. Microchannel heat sinks are of particular interest due to high rates of heat transfer, which have become known as one of the effective cooling technologies. In the present work, numerical simulation of incompressible flow in two dimensional microchannels by implementing

  9. Heat transfer coefficients for drying in pulsating flows

    SciTech Connect

    Fraenkel, S.L. [DEM/UFRJ, Rio de Janeiro (Brazil)] [DEM/UFRJ, Rio de Janeiro (Brazil); Nogueira, L.A.H. [IEM/EFEI, Itajuba, Minas Gerais (Brazil)] [IEM/EFEI, Itajuba, Minas Gerais (Brazil); Carvalho, J.A. Jr.; Costa, F.S. [LCP/INPE, Cachoeira Paulista, Sao Paulo (Brazil)] [LCP/INPE, Cachoeira Paulista, Sao Paulo (Brazil)

    1998-05-01

    Pulsating flows generated by a Rijke type combustor are studied for drying of grains and food particles. It is assumed that the velocity fluctuations are the main factor in the enhancement of the drying process. The heat transfer coefficients for drying in vibrating beds are utilized to estimate the heat transfer coefficients of fixed beds in pulsating and permeating flows and are compared to the steady flow heat transfer coefficients obtained for solid porous bodies, after perturbing the main flow. The cases considered are compared to the convective heat transfer coefficients employed in non-pulsating drying.

  10. Measurement of airfoil heat transfer coefficients on a turbine stage

    NASA Technical Reports Server (NTRS)

    Dring, R. P.; Blair, M. F.

    1984-01-01

    The primary basis for heat transfer analysis of turbine airfoils is experimental data obtained in linear cascades. A detailed set of heat transfer coefficients was obtained along the midspan of a stator and a rotor in a rotating turbine stage. The data are to be compared to standard analyses of blade boundary layer heat transfer. A detailed set of heat transfer coefficients was obtained along the midspan of a stator located in the wake of a full upstream turbine stage. Two levels of inlet turbulence (1 and 10 percent) were used. The analytical capability will be examined to improve prediction of the experimental data.

  11. Combustion chambers of gas-turbine plants - Heat transfer

    NASA Astrophysics Data System (ADS)

    Sudarev, A. V.; Antonovskii, V. I.

    Results of studies concerned with the convective and radiation heat transfer in the combustion chambers of gas turbines are examined. In particular, the existing methods for cooling flame tubes are analyzed, and heat transfer calculations are carried out for highly augmented combustion chambers. A method is also presented for calculating complex heat transfer in the flame zone for various types of the cooling system. Finally, experimental techniques for studying convective and radiation heat transfer in the combustion chambers of test and commercial gas turbines are discussed.

  12. Low-melting point heat transfer fluid

    DOEpatents

    Cordaro, Joseph G. (Oakland, CA); Bradshaw, Robert W. (Livermore, CA)

    2011-04-12

    A low-melting point, heat transfer fluid comprising a mixture of LiNO.sub.3, NaNO.sub.3, KNO.sub.3, NaNO.sub.2 and KNO.sub.2 salts where the Li, Na and K cations are present in amounts of about 20-33.5 mol % Li, about 18.6-40 mol % Na, and about 40-50.3 mol % K and where the nitrate and nitrite anions are present in amounts of about 36-50 mol % NO.sub.3, and about 50-62.5 mol % NO.sub.2. These compositions can have liquidus temperatures between 70.degree. C. and 80.degree. C. for some compositions.

  13. Heat transfer characteristics in film cooling applications

    NASA Astrophysics Data System (ADS)

    Licu, Dragos Nicolae

    1998-11-01

    The leading edge region of gas turbine blades and vanes experiences high thermal and mechanical stresses and has to be properly cooled. External cooling of the leading edge region is typically achieved by a film cooling technique. An investigation into the film cooling effectiveness of three different large scale leading edge geometries is presented in this study. One of the geometries investigated represents an original design and is an example of an improved film cooling layout. AD geometries used have four rows of cooling holes placed symmetrically about the geometrical leading edge, but the layout of the cooling holes is different from one leading edge geometry to another. A broad range of variables is considered including mass flow ratio, coolant density, and jet Reynolds number. Film cooling effectiveness measurements were made in a low speed wind tunnel environment using a flame ionization detector technique and the mass/heat transfer analogy. These measurements significantly extend the insight into the effects of hole geometry on the film cooling characteristics of the leading edge of turbine blades and provide new data for design purposes. The effect of geometry is more important for the case of double row injection where spanwise-averaged film cooling effectiveness is improved by the use of compound angle holes. The spanwise-averaged film cooling effectiveness is higher at lower mass flow ratios and decreases typically as the mass flow ratio increases. At higher mass flow ratios, the newly designed leading edge geometry produces higher spanwise-averaged film cooling effectiveness than the other two geometries investigated thus providing the necessary backflow margin at operating conditions more relevant to gas turbine use. For the case of single row injection, the effects of geometry scale reasonably well when the local mass flow ratio is used in the analysis of the spanwise-averaged film cooling effectiveness immediately downstream of the injection holes. The local momentum flux ratio is a more appropriate scaling parameter when coolants with different densities are used. A film cooling effectiveness correlation was also developed for one of the geometries investigated based on an area-averaged film cooling effectiveness and on a newly defined blowing parameter. This correlation accounts implicitly for the particular geometrical layout used and explicitly for the main injection parameters investigated. The results can be now more directly used in existing design procedures. A new experimental technique based on wide-band liquid crystal thermography and transient one-dimensional heat conduction has been developed and implemented. The technique combines a real-time, true colour imaging system with the use of a wide-band liquid crystal and multiple event sampling for the simultaneous determination of the film cooling effectiveness and heat transfer coefficient from one transient test. A comparison of different image capture techniques is also presented and computer codes are developed for data processing. For a test case of compound angle square jets in a crossflow, very good agreement was obtained between the film cooling effectiveness calculated from the transient heat transfer experiments and the film cooling effectiveness measured in isothermal mass transfer experiments using a flame ionization detector technique. This new approach has been developed as a major part of this thesis and represents a significant contribution to the use of liquid crystal thermography in film cooling applications.

  14. Radiative heat transfer in nonlinear Kerr media

    NASA Astrophysics Data System (ADS)

    Khandekar, Chinmay; Pick, Adi; Johnson, Steven G.; Rodriguez, Alejandro W.

    2015-03-01

    We obtain a fluctuation-dissipation theorem describing thermal electromagnetic fluctuation effects in nonlinear media that we exploit in conjunction with a stochastic Langevin framework to study thermal radiation from Kerr (?(3 )) photonic cavities coupled to external environments at and out of equilibrium. We show that, in addition to thermal broadening due to two-photon absorption, the emissivity of such cavities can exhibit asymmetric, non-Lorentzian line shapes due to self-phase modulation. When the local temperature of the cavity is larger than that of the external bath, we find that the heat transfer into the bath exceeds the radiation from a corresponding linear blackbody at the same local temperature. We predict that these temperature-tunable thermal processes can be observed in practical, nanophotonic cavities operating at relatively small temperatures.

  15. Submersible pumping system with heat transfer mechanism

    DOEpatents

    Hunt, Daniel Francis Alan; Prenger, F. Coyne; Hill, Dallas D; Jankowski, Todd Andrew

    2014-04-15

    A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.

  16. Convective heat transfer in rotating cylindrical cavity

    NASA Astrophysics Data System (ADS)

    Owen, J. M.; Onur, H. S.

    1983-04-01

    In order to gain an understanding of the conditions inside air-cooled, gas-turbine rotors, flow visualization, laser-doppler anemometry, and heat-transfer measurements have been made in a rotating cavity with either an axial throughflow or a radial outflow of coolant. For the axial throughflow tests, a correlation has been obtained for the mean Nusselt number in terms of the cavity gap ratio, the axial Reynolds number, and rotational Grashof number. For the radial outflow tests, velocity measurements are in good agreement with solutions of the linear (laminar and turbulent) Ekman layer equations, and flow visualization has revealed the destabilizing effect of buoyancy forces on the flow structure. The mean Nusselt numbers have been correlated, for the radial outflow case, over a wide range of gap ratios, coolant flow rates, rotational Reynolds numbers and Grashof numbers. As well as the three (forced convection) regimes established from previous experiments, a fourth (free convection) regime has been identified.

  17. Turbine disk cavity aerodynamics and heat transfer

    NASA Technical Reports Server (NTRS)

    Johnson, B. V.; Daniels, W. A.

    1992-01-01

    Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.

  18. Methods for increasing the efficiency of heating scrap metal in electric arc furnaces

    NASA Astrophysics Data System (ADS)

    Raile, V.

    2013-06-01

    The type of heating, which determines heat transfer from an external energy source to a metallic charge, plays a key role in the process of preliminary heating of scrap metal. The type of charge heating during preliminary heating of scrap metal mainly determines the average scrap metal heating temperature and the formation of harmful substances. This article considers the existing types of charge heating in EAF baths and shaft heaters. The types of scrap metal heating that increase the energy efficiency and weaken the ecological problems related to this process in electric furnace steelmaking units are found.

  19. Efficiency bounds for nonequilibrium heat engines

    NASA Astrophysics Data System (ADS)

    Mehta, Pankaj; Polkovnikov, Anatoli

    2012-05-01

    We analyze the efficiency of thermal engines (either quantum or classical) working with a single heat reservoir like an atmosphere. The engine first gets an energy intake, which can be done in an arbitrary nonequilibrium way e.g. combustion of fuel. Then the engine performs the work and returns to the initial state. We distinguish two general classes of engines where the working body first equilibrates within itself and then performs the work (ergodic engine) or when it performs the work before equilibrating (non-ergodic engine). We show that in both cases the second law of thermodynamics limits their efficiency. For ergodic engines we find a rigorous upper bound for the efficiency, which is strictly smaller than the equivalent Carnot efficiency. I.e. the Carnot efficiency can be never achieved in single reservoir heat engines. For non-ergodic engines the efficiency can be higher and can exceed the equilibrium Carnot bound. By extending the fundamental thermodynamic relation to nonequilibrium processes, we find a rigorous thermodynamic bound for the efficiency of both ergodic and non-ergodic engines and show that it is given by the relative entropy of the nonequilibrium and initial equilibrium distributions. These results suggest a new general strategy for designing more efficient engines. We illustrate our ideas by using simple examples.

  20. Efficiency bounds for nonequilibrium heat engines

    NASA Astrophysics Data System (ADS)

    Mehta, Pankaj; Polkovnikov, Anatoli

    2013-05-01

    We analyze the efficiency of thermal engines (either quantum or classical) working with a single heat reservoir like an atmosphere. The engine first gets an energy intake, which can be done in an arbitrary nonequilibrium way e.g. combustion of fuel. Then the engine performs the work and returns to the initial state. We distinguish two general classes of engines where the working body first equilibrates within itself and then performs the work (ergodic engine) or when it performs the work before equilibrating (non-ergodic engine). We show that in both cases the second law of thermodynamics limits their efficiency. For ergodic engines we find a rigorous upper bound for the efficiency, which is strictly smaller than the equivalent Carnot efficiency. I.e. the Carnot efficiency can be never achieved in single reservoir heat engines. For non-ergodic engines the efficiency can be higher and can exceed the equilibrium Carnot bound. By extending the fundamental thermodynamic relation to nonequilibrium processes, we find a rigorous thermodynamic bound for the efficiency of both ergodic and non-ergodic engines and show that it is given by the relative entropy of the nonequilibrium and initial equilibrium distributions. These results suggest a new general strategy for designing more efficient engines. We illustrate our ideas by using simple examples.

  1. Efficiency bounds for nonequilibrium heat engines

    E-print Network

    Pankaj Mehta; Anatoli Polkovnikov

    2013-01-22

    We analyze the efficiency of thermal engines (either quantum or classical) working with a single heat reservoir like atmosphere. The engine first gets an energy intake, which can be done in arbitrary non-equilibrium way e.g. combustion of fuel. Then the engine performs the work and returns to the initial state. We distinguish two general classes of engines where the working body first equilibrates within itself and then performs the work (ergodic engine) or when it performs the work before equilibrating (non-ergodic engine). We show that in both cases the second law of thermodynamics limits their efficiency. For ergodic engines we find a rigorous upper bound for the efficiency, which is strictly smaller than the equivalent Carnot efficiency. I.e. the Carnot efficiency can be never achieved in single reservoir heat engines. For non-ergodic engines the efficiency can be higher and can exceed the equilibrium Carnot bound. By extending the fundamental thermodynamic relation to nonequilibrium processes, we find a rigorous thermodynamic bound for the efficiency of both ergodic and non-ergodic engines and show that it is given by the relative entropy of the non-equilibrium and initial equilibrium distributions.These results suggest a new general strategy for designing more efficient engines. We illustrate our ideas by using simple examples.

  2. 2.51 Intermediate Heat and Mass Transfer, Fall 2001

    E-print Network

    Lienhard, John H., 1961-

    Analysis, modeling, and design of heat and mass transfer processes with application to common technologies. Unsteady heat conduction in one or more dimensions, steady conduction in multidimensional configurations, numerical ...

  3. Heat transfer and pressure drop in tape generated swirl flow

    E-print Network

    Lopina, Robert F.

    1967-01-01

    The heat transfer and pressure drop characteristics of water in tape generated swirl flow were investigated. The test sections were electrically heated small diameter nickel tubes with tight fitting full length Inconel ...

  4. Experimental Study on Heat Transfer of Plate Heat Exchanger and Application to Waste Heat Power Generation

    NASA Astrophysics Data System (ADS)

    Tang, X. Y.; Zhu, D. S.; Guo, C. Q.

    2010-03-01

    According to investigation on the steel plant, a large amount of low thermal energy is emitted directly to the environment without any utilization. It is apparent that energy cogeneration and energy conversion become a problem concerned by all countries. At present, the utilization of thermal energy stored in slag washing water is mainly confined to transformation to heating rather than electricity generation. The working mechanism of electricity generation using slag washing water and experimental study on heat transfer characteristics of plate heat exchanger are presented in this paper. The experimental results show the non-linear relationship between heat transfer coefficient of plate heat exchanger made by different materials and different flow velocity of clean water in the pipe. When the flow velocity is greater than 1 m/s, K retains a certain value while the resistance coefficient increases dramatically. By comparison of experimental data, it is found that the heat resistance outside plate heat exchanger is the main factor that influences performance of plate heat transfer.

  5. Heat Sponge: A Concept for Mass-Efficient Heat Storage

    NASA Technical Reports Server (NTRS)

    Splinter, Scott C.; Blosser, Max L.; Gifford, Andrew R.

    2008-01-01

    The heat sponge is a device for mass-efficient storage of heat. It was developed to be incorporated in the substructure of a re-entry vehicle to reduce thermal- protection-system requirements. The heat sponge consists of a liquid/vapor mixture contained within a number of miniature pressure vessels that can be embedded within a variety of different types of structures. As temperature is increased, pressure in the miniature pressure vessels also increases so that heat absorbed through vaporization of the liquid is spread over a relatively large temperature range. Using water as a working fluid, the heat-storage capacity of the liquid/vapor mixture is many times higher than that of typical structural materials and is well above that of common phase change materials over a temperature range of 200 F to 700 F. The use of pure ammonia as the working fluid provides a range of application between 432 deg R and 730 deg R, or the use of the more practical water-ammonia solution provides a range of application between 432 deg R and 1160 deg R or in between that of water and pure ammonia. Prototype heat sponges were fabricated and characterized. These heat sponges consisted of 1.0-inch-diameter, hollow, stainless-steel spheres with a wall thickness of 0.020 inches which had varying percentages of their interior volumes filled with water and a water-ammonia solution. An apparatus to measure the heat stored in these prototype heat sponges was designed, fabricated, and verified. The heat-storage capacity calculated from measured temperature histories is compared to numerical predictions.

  6. Carbon dioxide local heat transfer coefficients during flow boiling in a horizontal circular smooth tube

    Microsoft Academic Search

    R. Mastrullo; A. W. Mauro; A. Rosato; G. P. Vanoli

    2009-01-01

    Carbon dioxide is gaining renewed interest as an environmentally safe refrigerant. In order to improve the energy efficiency of R744 systems, an accurate knowledge of heat transfer coefficients is fundamental.In this paper experimental heat transfer coefficients during flow boiling of R744 in a smooth, horizontal, circular, 6.00mm inner diameter tube are presented. We obtained 217 experimental points in 18 operating

  7. In - line determination of heat transfer coefficients in a plate heat exchanger

    NASA Astrophysics Data System (ADS)

    Sotelo, S. Silva; Domínguez, R. J. Romero

    This paper shows an in - line determination of heat transfer coefficients in a plate heat exchanger. Water and aqueous working solution of lithium bromide + ethylene glycol are considered. Heat transfer coefficients are calculated for both fluids. "Type T" thermocouples were used for monitoring the wall temperature in a plate heat exchanger, which is one of the main components in an absorption system. Commercial software Agilent HP Vee Pro 7.5 was used for monitoring the temperatures and for the determination of the heat transfer coefficients. There are not previous works for heat transfer coefficients for the working solution used in this work.

  8. Effects of Solar Photovoltaic Panels on Roof Heat Transfer

    NASA Technical Reports Server (NTRS)

    Dominguez, A.; Klessl, J.; Samady, M.; Luvall, J. C.

    2010-01-01

    Building Heating, Ventilation and Air Conditioning (HVAC) is a major contributor to urban energy use. In single story buildings with large surface area such as warehouses most of the heat enters through the roof. A rooftop modification that has not been examined experimentally is solar photovoltaic (PV) arrays. In California alone, several GW in residential and commercial rooftop PV are approved or in the planning stages. With the PV solar conversion efficiency ranging from 5-20% and a typical installed PV solar reflectance of 16-27%, 53-79% of the solar energy heats the panel. Most of this heat is then either transferred to the atmosphere or the building underneath. Consequently solar PV has indirect effects on roof heat transfer. The effect of rooftop PV systems on the building roof and indoor energy balance as well as their economic impacts on building HVAC costs have not been investigated. Roof calculator models currently do not account for rooftop modifications such as PV arrays. In this study, we report extensive measurements of a building containing a flush mount and a tilted solar PV array as well as exposed reference roof. Exterior air and surface temperature, wind speed, and solar radiation were measured and thermal infrared (TIR) images of the interior ceiling were taken. We found that in daytime the ceiling surface temperature under the PV arrays was significantly cooler than under the exposed roof. The maximum difference of 2.5 C was observed at around 1800h, close to typical time of peak energy demand. Conversely at night, the ceiling temperature under the PV arrays was warmer, especially for the array mounted flat onto the roof. A one dimensional conductive heat flux model was used to calculate the temperature profile through the roof. The heat flux into the bottom layer was used as an estimate of the heat flux into the building. The mean daytime heat flux (1200-2000 PST) under the exposed roof in the model was 14.0 Watts per square meter larger than under the tilted PV array. The maximum downward heat flux was 18.7 Watts per square meters for the exposed roof and 7.0 Watts per square meters under the tilted PV array, a 63% reduction due to the PV array. This study is unique as the impact of tilted and flush PV arrays could be compared against a typical exposed roof at the same roof for a commercial uninhabited building with exposed ceiling and consisting only of the building envelope. Our results indicate a more comfortable indoor environment in PV covered buildings without HVAC both in hotter and cooler seasons.

  9. Dimensioning of ducts for maximal volumetric heat transfer taking both laminar and turbulent flow possibilities into consideration

    NASA Astrophysics Data System (ADS)

    Yilmaz, Alper

    2015-04-01

    It is intended to design compact heat exchangers which can transfer high heat flow for a given volume and temperature difference with high efficiency. This work presents the optimal design of heat exchangers for a given length or hydraulic diameter with a constraint of a certain pressure loss and constant wall temperature. Both volumetric heat transfer and heat transfer efficiency are taken into consideration for the design in laminar or turbulent flow regions. Equations are derived which easily enable optimal design for all shapes of ducts and for all Pr numbers. It is found that optimum conditions for turbulent flow is possible for all duct hydraulic diameters; however, it is possible to have optimum conditions till a certain dimensionless duct hydraulic diameter for laminar flow. Besides maximal volumetric heat flow, heat transfer efficiency should be taken into consideration in turbulent flow for optimum design.

  10. Proceedings of HT'03 2003 Summer Heat Transfer Conference

    E-print Network

    Walker, D. Greg

    Proceedings of HT'03 2003 Summer Heat Transfer Conference July 21­23, 2003, Las Vegas, Nevada, USA HT2003-47016 A NEW TECHNIQUE FOR HEAT FLUX DETERMINATION D.G. Walker Department of Mechanical@vt.edu ABSTRACT A new method for estimating heat fluxes from heating rate measurements and an approach to measure

  11. Efficiency of a Water Heating System

    NSDL National Science Digital Library

    Office of Educational Partnerships,

    Students use a watt meter to measure energy input into a hot plate or hot pot used to heat water. The theoretical amount of energy required to raise the water by the measure temperature change is calculated and compared to the electrical energy input to calculate efficiency.

  12. Measurement of heat and moisture exchanger efficiency.

    PubMed

    Chandler, M

    2013-09-01

    Deciding between a passive heat and moisture exchanger or active humidification depends upon the level of humidification that either will deliver. Published international standards dictate that active humidifiers should deliver a minimum humidity of 33 mg.l(-1); however, no such requirement exists, for heat and moisture exchangers. Anaesthetists instead have to rely on information provided by manufacturers, which may not allow comparison of different devices and their clinical effectiveness. I suggest that measurement of humidification efficiency, being the percentage moisture returned and determined by measuring the temperature of the respired gases, should be mandated, and report a modification of the standard method that will allow this to be easily measured. In this study, different types of heat and moisture exchangers for adults, children and patients with a tracheostomy were tested. Adult and paediatric models lost between 6.5 mg.l(-1) and 8.5 mg.l(-1) moisture (corresponding to an efficiency of around 80%); however, the models designed for patients with a tracheostomy lost between 16 mg.l(-1) and 18 mg.l(-1) (60% efficiency). I propose that all heat and moisture exchangers should be tested in this manner and percentage efficiency reported to allow an informed choice between different types and models. PMID:24047355

  13. Contribution of heat transfer to turbine blades and vanes for high temperature industrial gas turbines. Part 2: Heat transfer on serpentine flow passage.

    PubMed

    Takeishi, K; Aoki, S

    2001-05-01

    The improvement of the heat transfer coefficient of the 1st row blades in high temperature industrial gas turbines is one of the most important issues to ensure reliable performance of these components and to attain high thermal efficiency of the facility. This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of such gas turbines in order to attain efficient and environmentally benign engines. Following the experiments described in Part 1, a set of trials was conducted to clarify the influence of the blade's rotating motion on the heat transfer coefficient for internal serpentine flow passages with turbulence promoters. Test results are shown and discussed in this second part of the contribution. PMID:11460663

  14. TACO: a finite element heat transfer code

    SciTech Connect

    Mason, W.E. Jr.

    1980-02-01

    TACO is a two-dimensional implicit finite element code for heat transfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Either plane or axisymmetric geometries can be analyzed. TACO has the capability to handle time or temperature dependent material properties and materials may be either isotropic or orthotropic. A variety of time and temperature dependent loadings and boundary conditions are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additionally, TACO has some specialized features such as internal surface conditions (e.g., contact resistance), bulk nodes, enclosure radiation with view factor calculations, and chemical reactive kinetics. A user subprogram feature allows for any type of functional representation of any independent variable. A bandwidth and profile minimization option is also available in the code. Graphical representation of data generated by TACO is provided by a companion post-processor named POSTACO. The theory on which TACO is based is outlined, the capabilities of the code are explained, the input data required to perform an analysis with TACO are described. Some simple examples are provided to illustrate the use of the code.

  15. High thermal power density heat transfer. [thermionic converters

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (inventor)

    1980-01-01

    Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. The heat pipe is used to cool the nuclear reactor while the heat pipe is connected thermally and electrically to a thermionic converter. If the receiver requires greater thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparatively low thermal power densities through the electrically non-conducting gap between the two heat pipes.

  16. Energy Efficient Design of a Waste Heat Rejection System

    E-print Network

    Mehta, P.

    In small and medium sized manufacturing facilities, several situations exist where sources of waste heat and sinks needing heat transfer coexist. Examples of waste heat include but are not limited to: drained hot water streams from water cooled...

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

    DOEpatents

    Phillips, Benjamin A. (Benton Harbor, MI); Zawacki, Thomas S. (St. Joseph, MI)

    1996-12-03

    Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use the working solution of the absorption system for the heat transfer medium. A combination of weak and rich liquor working solution is used as the heat transfer medium.

  18. Study on heat transfer of heat exchangers in the Stirling engine - Performance of heat exchangers in the test Stirling engine

    Microsoft Academic Search

    Mitsuo Kanzaka; Makio Iwabuchi

    1992-01-01

    The heat transfer performance of the actual heat exchangers obtained from the experimental results of the test Stirling engine is presented. The heater for the test engine has 120 heat transfer tubes that consist of a bare-tube part and a fin-tube part. These tubes are located around the combustion chamber and heated by the combustion gas. The cooler is the

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

    DOEpatents

    Phillips, Benjamin A. (Benton Harbor, MI); Zawacki, Thomas S. (St. Joseph, MI); Marsala, Joseph (Glen Ellyn, IL)

    1994-11-29

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

  20. Heat transfer research on supercritical water flow upward in tube

    SciTech Connect

    Li, H. B.; Yang, J. [China Nuclear Power Technology Research Inst., Shenzhen, Guangdong (China); Gu, H. Y.; Zhao, M. [Shanghai Jiao Tong Univ., Shanghai (China); Lu, D. H.; Zhang, J. M.; Wang, F.; Zhang, Y. [China Nuclear Power Technology Research Inst., Shenzhen, Guangdong (China)

    2012-07-01

    The experimental research of heat transfer on supercritical water has been carried out on the supercritical water multipurpose test loop with a 7.6 mm upright tube. The experimental data of heat transfer is obtained. The experimental results of thermal-hydraulic parameters on flow and heat transfer of supercritical water show that: Heat transfer enhancement occurs when the fluid temperature reaches pseudo-critical point with low mass flow velocity, and peters out when the mass flow velocity increases. The heat transfer coefficient and Nusselt number decrease with the heat flux or system pressure increases, and increase with the increasing of mass flow velocity. The wall temperature increases when the mass flow velocity decreases or the system pressure increases. (authors)

  1. Numerical computation of 3D heat transfer in complex parallel heat exchangers using generalized Graetz modes

    NASA Astrophysics Data System (ADS)

    Pierre, Charles; Bouyssier, Julien; de Gournay, Frédéric; Plouraboué, Franck

    2014-07-01

    We propose and develop a variational formulation dedicated to the simulation of parallel convective heat exchangers that handles possibly complex input/output conditions as well as connection between pipes. It is based on a spectral method that allows to re-cast three-dimensional heat exchangers into a two-dimensional eigenvalue problem, named the generalized Graetz problem. Our formulation handles either convective, adiabatic, or prescribed temperature at the entrance or at the exit of the exchanger. This formulation is robust to mode truncation, offering a huge reduction in computational cost, and providing insights into the most contributing structure to exchanges and transfer. Several examples of heat exchangers are analyzed, their numerical convergence is tested and the numerical efficiency of the approach is illustrated in the case of Poiseuille flow in tubes.

  2. An experimental investigation of heat transfer enhancement for a shell-and-tube heat exchanger

    Microsoft Academic Search

    Simin Wang; Jian Wen; Yanzhong Li

    2009-01-01

    For the purpose of heat transfer enhancement, the configuration of a shell-and-tube heat exchanger was improved through the installation of sealers in the shell-side. The gaps between the baffle plates and shell is blocked by the sealers, which effectively decreases the short-circuit flow in the shell-side. The results of heat transfer experiments show that the shell-side heat transfer coefficient of

  3. Fabrication of copper-based microchannel devices and analysis of their flow and heat transfer characteristics

    NASA Astrophysics Data System (ADS)

    Mei, Fanghua; Phillips, W. A.; Lu, B.; Meng, W. J.; Guo, S.

    2009-03-01

    Metal-based microchannel heat exchangers (MHEs) offer potential solutions to high heat flux removal applications, such as cooling of high-performance microelectronic and energy-efficient lighting modules. Efficient fabrication of metal-based MHEs and quantitative flow and heat transfer measurements on them are critical for establishing the economic and technical feasibility of such devices. In this paper, all-Cu MHE prototypes were fabricated. Results of flow and heat transfer testing made on these Cu-based MHE prototypes are reported. Efficient fabrication of Cu-based high-aspect-ratio microscale structures (HARMSs) was achieved through direct molding replication using surface-engineered metallic mold inserts. Replicated Cu HARMSs were assembled through solid-state bonding to form all-Cu MHE prototypes. Flow and heat transfer testing of the Cu MHE prototypes was conducted to determine the average rate of heat transfer from the solid Cu body to water flowing within the enclosed microchannel array. Experimentally observed flow and heat transfer data are analyzed and shown to agree with known macroscale correlations once surface roughness and entrance length effects are taken into account.

  4. Study of a high performance evaporative heat transfer surface

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.; Hamasaki, R. H.

    1977-01-01

    An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

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

    SciTech Connect

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

    2006-07-01

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

  6. Enhanced heat transfer is dependent on thickness of graphene films: the heat dissipation during boiling

    NASA Astrophysics Data System (ADS)

    Ahn, Ho Seon; Kim, Jin Man; Kim, Taejoo; Park, Su Cheong; Kim, Ji Min; Park, Youngjae; Yu, Dong In; Hwang, Kyoung Won; Jo, Hangjin; Park, Hyun Sun; Kim, Hyungdae; Kim, Moo Hwan

    2014-09-01

    Boiling heat transfer (BHT) is a particularly efficient heat transport method because of the latent heat associated with the process. However, the efficiency of BHT decreases significantly with increasing wall temperature when the critical heat flux (CHF) is reached. Graphene has received much recent research attention for applications in thermal engineering due to its large thermal conductivity. In this study, graphene films of various thicknesses were deposited on a heated surface, and enhancements of BHT and CHF were investigated via pool-boiling experiments. In contrast to the well-known surface effects, including improved wettability and liquid spreading due to micron- and nanometer-scale structures, nanometer-scale folded edges of graphene films provided a clue of BHT improvement and only the thermal conductivity of the graphene layer could explain the dependence of the CHF on the thickness. The large thermal conductivity of the graphene films inhibited the formation of hot spots, thereby increasing the CHF. Finally, the provided empirical model could be suitable for prediction of CHF.

  7. Enhanced heat transfer is dependent on thickness of graphene films: the heat dissipation during boiling.

    PubMed

    Ahn, Ho Seon; Kim, Jin Man; Kim, TaeJoo; Park, Su Cheong; Kim, Ji Min; Park, Youngjae; Yu, Dong In; Hwang, Kyoung Won; Jo, HangJin; Park, Hyun Sun; Kim, Hyungdae; Kim, Moo Hwan

    2014-01-01

    Boiling heat transfer (BHT) is a particularly efficient heat transport method because of the latent heat associated with the process. However, the efficiency of BHT decreases significantly with increasing wall temperature when the critical heat flux (CHF) is reached. Graphene has received much recent research attention for applications in thermal engineering due to its large thermal conductivity. In this study, graphene films of various thicknesses were deposited on a heated surface, and enhancements of BHT and CHF were investigated via pool-boiling experiments. In contrast to the well-known surface effects, including improved wettability and liquid spreading due to micron- and nanometer-scale structures, nanometer-scale folded edges of graphene films provided a clue of BHT improvement and only the thermal conductivity of the graphene layer could explain the dependence of the CHF on the thickness. The large thermal conductivity of the graphene films inhibited the formation of hot spots, thereby increasing the CHF. Finally, the provided empirical model could be suitable for prediction of CHF. PMID:25182076

  8. Enhanced heat transfer is dependent on thickness of graphene films: the heat dissipation during boiling

    PubMed Central

    Ahn, Ho Seon; Kim, Jin Man; Kim, TaeJoo; Park, Su Cheong; Kim, Ji Min; Park, Youngjae; Yu, Dong In; Hwang, Kyoung Won; Jo, HangJin; Park, Hyun Sun; Kim, Hyungdae; Kim, Moo Hwan

    2014-01-01

    Boiling heat transfer (BHT) is a particularly efficient heat transport method because of the latent heat associated with the process. However, the efficiency of BHT decreases significantly with increasing wall temperature when the critical heat flux (CHF) is reached. Graphene has received much recent research attention for applications in thermal engineering due to its large thermal conductivity. In this study, graphene films of various thicknesses were deposited on a heated surface, and enhancements of BHT and CHF were investigated via pool-boiling experiments. In contrast to the well-known surface effects, including improved wettability and liquid spreading due to micron- and nanometer-scale structures, nanometer-scale folded edges of graphene films provided a clue of BHT improvement and only the thermal conductivity of the graphene layer could explain the dependence of the CHF on the thickness. The large thermal conductivity of the graphene films inhibited the formation of hot spots, thereby increasing the CHF. Finally, the provided empirical model could be suitable for prediction of CHF. PMID:25182076

  9. Heat transfer of horizontal parallel pipe ground heat exchanger and experimental verification

    Microsoft Academic Search

    Hakan Demir; Ahmet Koyun; Galip Temir

    2009-01-01

    The ground heat exchangers (GHE) consist of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger pipes of the ground source heat pump (GSHP). Because of the complexity of the boundary conditions, the heat conduction equation has been solved numerically using alternating direction implicit finite difference formulation. A software was developed

  10. Performance characteristics of a multi-element thermoelectric generator with radiative heat transfer law

    Microsoft Academic Search

    Fankai Meng; Lingen Chen; Fengrui Sun

    2011-01-01

    A finite-time thermodynamic model of multi-element thermoelectric generator with radiative heat transfer law Q? ? (T ) is built by combining finite-time thermodynamics with non-equilibrium thermodynamics. The characteristics of the power output and efficiency versus working electrical current are analysed. The effects of total number of thermoelectric elements and generator heat source temperature on the power output and efficiency are

  11. Performance characteristics of a multi-element thermoelectric generator with radiative heat transfer law

    Microsoft Academic Search

    Fankai Meng; Lingen Chen; Fengrui Sun

    2012-01-01

    A finite-time thermodynamic model of multi-element thermoelectric generator with radiative heat transfer law Q? ? (T ) is built by combining finite-time thermodynamics with non-equilibrium thermodynamics. The characteristics of the power output and efficiency versus working electrical current are analysed. The effects of total number of thermoelectric elements and generator heat source temperature on the power output and efficiency are

  12. Heat transfer in proteinwater interfaces Anders Lervik,ab

    E-print Network

    Kjelstrup, Signe

    Heat transfer in protein­water interfaces Anders Lervik,ab Fernando Bresme,*ac Signe Kjelstrup of the heat diffusion equation we compute the thermal conductivity and thermal diffusivity of the proteins by about 4 nm.4 It is expected that the energy transfer between these sites may involve the concerted

  13. Heat Transfer Study of Polymer Solutions with Different Rigidities

    E-print Network

    Huang, Yao

    2014-05-08

    ...................................................................... 14 2.4 Intrinsic Viscosity ........................................................................................... 18 ix DESCRIPTION OF DILUTE POLYMER SOLUTION (DPS) FORMULATION AND NUMERICAL HEAT TRANSFER AND FLUID DYNAMICS SIMULATION... SCHEME FOR DPS ......................................................................................................... 20 3.1 Formulation of the Convective Heat Transfer Problem .................................. 20 3.1.1 Governing Equation...

  14. Theory of Radiative Heat Transfer between Closely Spaced Bodies

    Microsoft Academic Search

    D. Polder; M. van Hove

    1971-01-01

    A general formalism is developed by means of which the radiative heat transfer between macroscopic bodies of arbitrary dispersive and absorptive dielectric properties can be evaluated. The general formalism is applied to the heat transfer across a vacuum gap between two identical semi-infinite bodies at different temperatures. The peculiarities arising when the gap width is of the order of, or

  15. Radiative heat transfer in a rectangular enclosure with gray medium

    Microsoft Academic Search

    W. W. Yuen; L. W. Wong

    1980-01-01

    Radiative heat transfer in a rectangular enclosure with gray medium is considered. The method of undetermined parameters is shown to be applicable to yield successive approximate solutions for the problem. Both heat transfer and temperature profile results can be readily generated. All results are demonstrated to be expressible in closed form as sums of standard mathematical function and simple numerical

  16. HEAT TRANSFER IN PACKED BED REACTORS WITH ONE PHASE FLOW

    Microsoft Academic Search

    V. SPECCHIA; G. BALDI; S. SICARDI

    1980-01-01

    An extensive array of literature data on the heat transfer from a reactor wall to a fluid flowing through a packed bed and those obtained from some experimental runs were interpreted with a model containing two parameters: ke, (effective radial thermal conductivity within the bed) and hw (heat transfer coefficient at the wall).Both parameters were considered in terms of a

  17. Fluid Flow and Heat transfer Model of the HEATHYD Code

    NASA Astrophysics Data System (ADS)

    Hansen, G.; von Zahn, U.

    1991-01-01

    The following sections are included: * BACKGROUND OF CORE THERMOHYDRAULICS * Fluid Flow in channels * Heat Transfer Model of HEATHYD * Correlations for Heat Transfer coefficient * Physical Properties of Water * Onset of Nucleate Boiling (ONB) * Nodular Computation Model * MODELS OF CRITICAL COOLING * Flow instability * Departure from Nucleate Boiling (DNB) * NOMENCLATURE * References

  18. Ultrasonic enhancement of heat transfer on narrow surface

    Microsoft Academic Search

    Shinfuku Nomura; Masafumi Nakagawa

    1994-01-01

    Ultrasonic enhancement of heat transfer on a narrow surface was measured by changing the width of the surface from 8 to 0.1 mm. Ultrasonic power of 600 W with a frequency of 40 kHz was used. Heat transfer on the narrow surface without ultrasonic vibration was correlated by the experimental equation for a thin wire. The cavitation intensity was measured

  19. Effect of acoustic cavitation on boiling heat transfer

    Microsoft Academic Search

    D. W. Zhou; D. Y. Liu; X. G. Hu; C. F. Ma

    2002-01-01

    Boiling heat transfer on a horizontal circular copper tube in an acoustical field is investigated experimentally and the relation between the liquid cavitation, the boiling and the micro bubble radii are analyzed theoretically. The results show that cavitation bubbles have an important influence on the nucleation, growth and collapse of vapor embryo within cavities on the heat transfer surface and

  20. Heat-transfer coefficients of pin-finned cylinders

    NASA Technical Reports Server (NTRS)

    Van Fossen, G. J., Jr.

    1977-01-01

    Pin-finned cylinder can increase heat-transfer rate to more than 4 times that of plain cylinder, depending on pin diameter and spacing. Smallest diameter, closest spacing, and largest pin length-to-diameter ratio gives highest average effective heat-transfer coefficients.

  1. MOLECULAR DYNAMICS SIMULATIONS OF HEAT TRANSFER OF CARBON NANOTUBES

    E-print Network

    Maruyama, Shigeo

    MOLECULAR DYNAMICS SIMULATIONS OF HEAT TRANSFER OF CARBON NANOTUBES J. Shiomi, Y. Igarashi, Y-ku, Tokyo 113-8656, JAPAN Several heat transfer problems related to single-walled carbon nanotubes (SWNTs] is employed as the potential function between carbon and carbon within a nanotube. MD simulations of thermal

  2. Fluid mechanics and heat transfer spirally fluted tubing

    Microsoft Academic Search

    J. S. Yampolsky; P. A. Libby; B. E. Launder; J. C. Larue

    1984-01-01

    The objective of this program is to develop an understanding of the fluid mechanics and heat transfer mechanisms that result in the demonstrated performance of the spiral fluted tubing under development at GA Technologies Inc. Particularly emphasized are the processes that result in the augmentation of the heat transfer coefficient without an increase in friction coefficient in the single-phase flow.

  3. FINITE ELEMENT METHOD IN FLUID MECHANICS & HEAT TRANSFER

    E-print Network

    Camci, Cengiz

    FINITE ELEMENT METHOD IN FLUID MECHANICS & HEAT TRANSFER AERSP-560 Department : Aerospace element techniques to especially fluid flow and heat transfer problems. A student who successfully completed this course should be able to perform quick analysis of small problems using the finite element

  4. Measurement and analysis of gas turbine blade endwall heat transfer

    E-print Network

    Lee, Joon Ho

    2001-01-01

    the aerodynamic flow and external heat transfer distribution around the airfoils and end-wall surfaces. A stationary 5 vane linear cascade is designed and developed to investigate gas turbine blade endwall heat transfer and flow. The test cascade is instrumented...

  5. Enhanced radiative heat transfer between nanostructured gold plates

    E-print Network

    R. Guérout; J. Lussange; F. S. S. Rosa; J. -P. Hugonin; D. A. R. Dalvit; J. -J. Greffet; A. Lambrecht; S. Reynaud

    2012-03-07

    We compute the radiative heat transfer between nanostructured gold plates in the framework of the scattering theory. We predict an enhancement of the heat transfer as we increase the depth of the corrugations while keeping the distance of closest approach fixed. We interpret this effect in terms of the evolution of plasmonic and guided modes as a function of the grating's geometry.

  6. Heat transfer to impinging isothermal gas and flame jets

    Microsoft Academic Search

    R. Viskanta

    1993-01-01

    Heat transfer characteristics of single and multiple isothermal turbulent air and flame jets impinging on surfaces are reviewed. Both circular and slot two-dimensional jets are considered, and the effect of crossflow on impingement heat transfer is included. The emphasis is on physical phenomena and not on comparison of published empirical correlations or comparisons of theory and experiments. The review focuses

  7. MSG: A Computer System for Automated Modeling of Heat Transfer

    E-print Network

    Steinberg, Louis

    MSG: A Computer System for Automated Modeling of Heat Transfer Sui­ky Ringo Ling Louis Steinberg a computer system, MSG for generating mathematical models to analyze physical systems involving heat transfer equations and partial differential equations. MSG uses the strong domain theory to guide model construction

  8. A new model for nucleate boiling heat transfer

    Microsoft Academic Search

    P. Stephan; J. Hammer

    1994-01-01

    A new model to calculate heat transfer coefficients in nucleate boiling is presented. Heat transfer and fluid flow around a single bubble are investigated taking into account the influence of meniscus curvature, adhesion forces and interfacial thermal resistance on the thermodynamic equilibrium at the gas-liquid interface. The model requires only bubble site densities and departure diameters. Further quantities except the

  9. CONVECTIVE HEAT TRANSFER OF BINARY MIXTURES UNDER FLOW BOILING CONDITIONS

    E-print Network

    Kandlikar, Satish

    CONVECTIVE HEAT TRANSFER OF BINARY MIXTURES UNDER FLOW BOILING CONDITIONS E. V. McAssey Jr results are presented for the heat transfer coefficient under flow boiling conditions for water-phase non-boiling region through the fully developed subcooled flow boiling region to saturated boiling

  10. EFFECT OF SURFACE CHARACTERISTICS ON FLOW BOILING HEAT TRANSFER

    E-print Network

    Kandlikar, Satish

    EFFECT OF SURFACE CHARACTERISTICS ON FLOW BOILING HEAT TRANSFER Satish G. Kandlikar and Paul H ABSTRACT It is well known that the surface structure affects the pool boiling heat transfer from a heater characteristics. This fact is utilized in developing structured and sintered surfaces for enhanced boiling

  11. Heat Transfer from an ESF Radial Plate Clutch Surface

    Microsoft Academic Search

    D. J. Ellam; W. A. Bullough; V. Oravský

    2003-01-01

    The aim of this work was to investigate the rate of heat transfer from a radial plate clutch surface. The paper presents experimental results over a range of angular speeds (&OHgr;) and fluid gap widths (h), which are then favourably compared to analytical and computational fluid dynamics (CFD) solutions for the same geometry and operating conditions. Verifying the heat transfer

  12. INFLUENCE OF NONUNIFORM TWISTED TAPE ON HEAT TRANSFER ENHANCEMENT CHARACTERISTICS

    Microsoft Academic Search

    Smith Eiamsa-ard; Khwanchit Wongcharee; Pongjet Promvonge

    2012-01-01

    An experimental study of heat transfer and friction factor characteristics in a circular tube fitted by twisted tapes with nonuniform twist ratios is reported. The twisted tapes are used as swirl generators playing roles as heat transfer enhancers. The nonuniform twisted tapes examined in the present work have (1) sequentially increasing twist ratios (SL), (2) sequentially decreasing twist ratios (LS),

  13. Gas Heat Transfer in a Heated Vertical Channel under Deteriorated Turbulent Heat Transfer Regime

    E-print Network

    Lee, Jeongik

    Passive cooling via natural circulation of gas after a loss of coolant (LOCA) accident is one of the major goals of the Gas-cooled Fast Reactor (GFR). Due to its high surface heat flux and low coolant velocities under ...

  14. Gas heat transfer in a heated vertical channel under deteriorated turbulent heat transfer regime

    E-print Network

    Lee, Jeongik

    2007-01-01

    Passive cooling via natural circulation of gas after a loss of coolant (LOCA) accident is one of the major goals of the Gas-cooled Fast Reactor (GFR). Due to its high surface heat flux and low coolant velocities under ...

  15. Experimental Study on the Heat Transfer Enhancement of Oscillating-Flow Heat Pipe by Acoustic Cavitation

    Microsoft Academic Search

    H. Xian; D. Liu; F. Shang; Y. Yang; G. Chen

    2009-01-01

    Experimental investigations on the heat transfer characteristics of an oscillating-flow heat pipe with acoustic cavitation in comparison with the ordinary oscillating-flow heat pipe are given in this article. The experimental results showed that the heat transfer rate of an oscillating-flow heat pipe with an acoustic cavitation field imposed on the evaporator section was higher than that without a cavitation field

  16. Experimental and numerical study of laminar forced convection heat transfer for a dimpled heat sink

    E-print Network

    Park, Do Seo

    2009-05-15

    Chair of Advisory Committee: Dr. Egidio (Ed) Marotta An investigation was conducted to determine whether dimples on a heat sink fin can increase heat transfer for laminar airflows. This was accomplished by performing an experimental and numerical... the cooling fluid to reach all cooling fins and to allow good heat transfer from the heat source to the fins. Heat sink performance also depends on the type of fluid moving device used because airflow rates have a direct influence on its enhancement...

  17. Mixed convection heat transfer in concave and convex channels

    SciTech Connect

    Moukalled, F.; Doughan, A.; Acharya, S.

    1997-07-01

    Mixed convection heat transfer studies in the literature have been primarily confined to pipe and rectangular channel geometry's. In some applications, however, heat transfer in curved channels may be of interest (e.g., nozzle and diffuser shaped passages in HVAC systems, fume hoods, chimneys, bell-shaped or dome-shaped chemical reactors, etc.). A numerical investigation of laminar mixed convection heat transfer of air in concave and convex channels is presented. Six different channel aspects ratios (R/L = 1.04, 1.25, 2.5, 5, 10, and {infinity}) and five different values of Gr/Re{sup 2} (Gr/Re{sup 2} = 0, 0.1, 1, 3, 5) are considered. Results are displayed in terms of streamline and isotherm plots, velocity and temperature profiles, and local and average Nusselt number estimates. Numerical predictions reveal that compared to straight channels of equal height, concave channels of low aspect ratio have lower heat transfer at relatively low values of Gr/Re{sup 2} and higher heat transfer at high values of Gr/Re{sup 2}. When compared to straight channels of equal heated length, concave channels are always found to have lower heat transfer and for all values of Gr/Re{sup 2}. On the other hand, predictions for convex channels revealed enhancement in heat transfer compared to straight channels of equal height and/or equal heated length for all values of Gr/Re{sup 2}.

  18. Using supercritical heat recovery process in Stirling engines for high thermal efficiency

    Microsoft Academic Search

    Zhaolin Gu; Haruki Sato; Xiao Feng

    2001-01-01

    Stirling engine, using a composite working fluid, such as two-component fluid: gaseous carrier and phase-change component and single multi-phase fluid as the working fluid is studied to get high thermal efficiency. In Stirling engine with a composite fluid, a thermodynamic supercritical heat recovery and heating process is proposed and demonstrated to improve the heat transfer of the heat regenerator and

  19. Investigation of the characteristics of heat transfer in the heating zone of heat pipes with metal fiber capillary structures

    NASA Astrophysics Data System (ADS)

    Semena, M. G.; Zaripov, V. K.; Gershuni, A. N.

    1982-09-01

    Experimental results from the study of heat transfer in radially configured heat pipes which feature metal fiber capillary structures are discussed. Examinations were made with water, ethanol, methanol, acetone, ammonia, Freon, and nitrogen as heat transfer fluids. The heat pipes were equipped with cylindrical and flat casings, and were fitted with copper, stainless steel, and nickel capillary structures. Quantitative results are presented for the heat transfer coefficients for a smooth heating surface in a large volume, for surfaces sintered with the metal fiber structures with low porosity, and with the same surface with high porosity. The heat flux density increased with decreasing porosity, which formed centers where bubble boiling could occur.

  20. Study on heat transfer of heat exchangers in the Stirling engine - Performance of heat exchangers in the test Stirling engine

    NASA Astrophysics Data System (ADS)

    Kanzaka, Mitsuo; Iwabuchi, Makio

    1992-11-01

    The heat transfer performance of the actual heat exchangers obtained from the experimental results of the test Stirling engine is presented. The heater for the test engine has 120 heat transfer tubes that consist of a bare-tube part and a fin-tube part. These tubes are located around the combustion chamber and heated by the combustion gas. The cooler is the shell-and-tube-type heat exchanger and is chilled by water. It is shown that the experimental results of heat transfer performance of the heater and cooler of the test Stirling engine are in good agreement with the results calculated by the correlation proposed in our previous heat transfer study under the periodically reversing flow condition. Our correlation is thus confirmed to be applicable to the evaluation of the heat transfer coefficient and the thermal design of the heat exchangers in the Stirling engine.

  1. CFD study of the heat transfer between a dilute gas particle suspension flow and an obstruction

    SciTech Connect

    Nguyen, A.V.; Fletcher, C.A.J. [Univ. of New South Wales, Sydney, New South Wales (Australia). Centre for Advanced Numerical Computation in Engineering and Science; Tu, J.Y. [Australian Nuclear Science and Technology Organization, Menai, New South Wales (Australia)

    1999-04-01

    The effect on heat transfer of solid particles suspended in a gas flow is of considerable importance in a number of industrial applications, ranging from coal combustion equipment and heat exchangers to catalytic reaction or cooling of nuclear reactors using gas graphite dust suspensions. Here, the heat transfer process between a dilute gas-particle suspension flow and an obstruction has been numerically investigated employing a novel Eulerian formulation for dilute gas particle suspension flows, which allows interaction of the key mechanisms to be quantified for the first time. As the particle reflection occurs around the obstruction, the heat transfer process has been modeled taking into account the incident and reflected particles explicitly. In the energy equations these particle families are treated separately. Only the effect on the gas convective heat transfer is expected to be of primary significance and investigated. The numerical computation is performed using the commercial computational fluid dynamics code, FLUENT, with the User Defined Subroutines. The authors study the heat transfer process between a dilute gas particle flow and an obstruction with simple geometries such as a 45{degree} ramp and a cylindrical tube. The theoretical results for the latter case are compared with the available experimental data. The numerical simulation shows that both the particle size and the particle concentration (in the thermal boundary layer) affect the heat transfer process. Since both the particle incidence and reflection depend on the particle size and strongly influence the particle concentration distribution, they have to be physically correctly treated in the modeling of the heat transfer, as is demonstrated in the novel formulation. There is an optimum particle size for a maximum enhancement of the heat transfer. The particle concentration increases the efficiency of the heat transfer process expressed in terms of the local Nusselt numbers.

  2. Capillary Pumped Heat Transfer (CHT) Experiment

    NASA Technical Reports Server (NTRS)

    Hallinan, Kevin P.; Allen, J. S.

    1998-01-01

    The operation of Capillary Pumped Loops (CPL's) in low gravity has generally been unable to match ground-based performance. The reason for this poorer performance has been elusive. In order to investigate the behavior of a CPL in low-gravity, an idealized, glass CPL experiment was constructed. This experiment, known as the Capillary-driven Heat Transfer (CHT) experiment, was flown on board the Space Shuttle Columbia in July 1997 during the Microgravity Science Laboratory mission. During the conduct of the CHT experiment an unexpected failure mode was observed. This failure mode was a result of liquid collecting and then eventually bridging the vapor return line. With the vapor return line blocked, the condensate was unable to return to the evaporator and dry-out subsequently followed. The mechanism for this collection and bridging has been associated with long wavelength instabilities of the liquid film forming in the vapor return line. Analysis has shown that vapor line blockage in present generation CPL devices is inevitable. Additionally, previous low-gravity CPL tests have reported the presence of relatively low frequency pressure oscillations during erratic system performance. Analysis reveals that these pressure oscillations are in part a result of long wavelength instabilities present in the evaporator pores, which likewise lead to liquid bridging and vapor entrapment in the porous media. Subsequent evaporation to the trapped vapor increases the vapor pressure. Eventually the vapor pressure causes ejection of the bridged liquid. Recoil stresses depress the meniscus, the vapor pressure rapidly increases, and the heated surface cools. The process then repeats with regularity.

  3. Heat transfer between immiscible liquids enhanced by gas bubbling

    NASA Astrophysics Data System (ADS)

    Greene, G. A.; Schwarz, C. E.; Klages, J.; Klein, J.

    1982-08-01

    The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments were performed with nonreactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies were performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model.

  4. Condensation Heat Transfer Performance of Nano- Engineered Cu Surfaces

    NASA Astrophysics Data System (ADS)

    Kim, Hyunsik; Nam, Youngsuk

    2014-11-01

    We investigated condensate mobility and resulting heat transfer performance on Cu based water repellent surfaces including hydrophobic, superhydrophobic and oil-infused surfaces. We observed the transient microscale condensation behaviours up to 3 hours with controlling the supersaturation level at 1.64. We experimentally characterized the nucleation density, droplet size distribution and growth rate, and then incorporated them into the developed condensation heat transfer model to compare the condensation heat transfer performance of each surface. Due to the spontaneous coalescence induced jumping, superhydrophobic surface can maintain the high heat transfer performance while other surfaces show a gradual decrease in heat transfer performance due to the increase in the thermal resistance across the growing droplets. We also quantified each thermal resistance values from the vapor to the surface through the droplets to find out the relative importance of each thermal resistance term.

  5. Heat transfer between elastic solids with randomly rough surfaces

    E-print Network

    B. N. J. Persson; B. Lorenz; A. I. Volokitin

    2009-08-27

    We study the heat transfer between elastic solids with randomly rough surfaces. We include both the heat transfer from the area of real contact, and the heat transfer between the surfaces in the noncontact regions. We apply a recently developed contact mechanics theory, which accounts for the hierarchical nature of the contact between solids with roughness on many different length scales. For elastic contact, at the highest (atomic) resolution the area of real contact typically consists of atomic (nanometer) sized regions, and we discuss the implications of this for the heat transfer. For solids with very smooth surfaces, as is typical in many modern engineering applications, the interfacial separation in the non-contact regions will be very small, and for this case we show the importance of the radiative heat transfer associated with the evanescent electromagnetic waves which exist outside of all bodies.

  6. Measurement of airfoil heat transfer coefficients on a turbine stage

    NASA Technical Reports Server (NTRS)

    Dring, Robert P.; Blair, Michael F.; Joslyn, H. David

    1986-01-01

    The Primary basis for heat transfer analysis of turbine airfoils is experimental data obtained in linear cascades. These data were very valuable in identifying the major heat transfer and fluid flow features of a turbine airfoil. The first program objective is to obtain a detailed set of heat transfer coefficients along the midspan of a stator and a rotor in a rotating turbine stage. The data are to be compared to some standard analysis of blade boundary layer heat transfer which is in use today. A second program objective is to obtain a detailed set of heat transfer coefficients along the midspan of a stator located in the wake of an upstream turbine stage.

  7. Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel

    NASA Technical Reports Server (NTRS)

    Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo; Woodiga, Sudesh

    2012-01-01

    This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.

  8. Modelling of Heat Transfer in Single Crystal Growth

    E-print Network

    Zhmakin, Alexander I

    2014-01-01

    An attempt is made to review the heat transfer and the related problems encountered in the simulation of single crystal growth. The peculiarities of conductive, convective and radiative heat transfer in the different melt, solution, and vapour growth methods are discussed. The importance of the adequate description of the optical crystal properties (semitransparency, specular reflecting surfaces) and their effect on the heat transfer is stresses. Treatment of the unknown phase boundary fluid/crystal as well as problems related to the assessment of the quality of the grown crystals (composition, thermal stresses, point defects, disclocations etc.) and their coupling to the heat transfer/fluid flow problems is considered. Differences between the crystal growth simulation codes intended for the research and for the industrial applications are indicated. The problems of the code verification and validation are discussed; a brief review of the experimental techniques for the study of heat transfer and flow structu...

  9. Thermodynamic Efficiency of Pumped Heat Electricity Storage

    NASA Astrophysics Data System (ADS)

    Thess, André

    2013-09-01

    Pumped heat electricity storage (PHES) has been recently suggested as a potential solution to the large-scale energy storage problem. PHES requires neither underground caverns as compressed air energy storage (CAES) nor kilometer-sized water reservoirs like pumped hydrostorage and can therefore be constructed anywhere in the world. However, since no large PHES system exists yet, and theoretical predictions are scarce, the efficiency of such systems is unknown. Here we formulate a simple thermodynamic model that predicts the efficiency of PHES as a function of the temperature of the thermal energy storage at maximum output power. The resulting equation is free of adjustable parameters and nearly as simple as the well-known Carnot formula. Our theory predicts that for storage temperatures above 400°C PHES has a higher efficiency than existing CAES and that PHES can even compete with the efficiencies predicted for advanced-adiabatic CAES.

  10. Thermodynamic efficiency of pumped heat electricity storage.

    PubMed

    Thess, André

    2013-09-13

    Pumped heat electricity storage (PHES) has been recently suggested as a potential solution to the large-scale energy storage problem. PHES requires neither underground caverns as compressed air energy storage (CAES) nor kilometer-sized water reservoirs like pumped hydrostorage and can therefore be constructed anywhere in the world. However, since no large PHES system exists yet, and theoretical predictions are scarce, the efficiency of such systems is unknown. Here we formulate a simple thermodynamic model that predicts the efficiency of PHES as a function of the temperature of the thermal energy storage at maximum output power. The resulting equation is free of adjustable parameters and nearly as simple as the well-known Carnot formula. Our theory predicts that for storage temperatures above 400?°C PHES has a higher efficiency than existing CAES and that PHES can even compete with the efficiencies predicted for advanced-adiabatic CAES. PMID:24074066

  11. Heat Transfer Performance of Absorber of Absorption Refrigerating Machine

    NASA Astrophysics Data System (ADS)

    Kunugi, Yoshifumi; Ouchi, Tomihisa; Usui, Sanpei; Fukuda, Tamio

    Experimental studies on heat transfer performance of absorber for lithium bromide-water absorption refrigerating machine are presented in this paper. Experimental apparatus for 35 kW evaporator and absorber, and outer grooved tubes are used. As a result, over-al1 coefficient of heat transmission of absorber has a maximum value, in the case of heat transfer area ratio of absorber to evaporator, is about 0.8. Heat transfer rate of absorber is increased by 60% by using the outer grooved tube compared with the plane surfaced tube.

  12. Heat transfer monitor for measurements of fouling of industrial heat exchangers

    Microsoft Academic Search

    C. B. Panchal

    1985-01-01

    A Heat Transfer Monitor (HTM) is a sensitive device that quantifies development of fouling on heat exchanger surfaces in terms of degradation in the heat transfer coefficient as fouling progresses. The Argonne HTM was originally developed by Carnegie-Mellon University for Ocean Thermal Energy Conversion (OTEC) applications and later modified by Argonne National Laboratory. The HTM has been used for the

  13. Boiling heat transfer in a hydrofoil-based micro pin fin heat sink

    E-print Network

    Peles, Yoav

    Boiling heat transfer in a hydrofoil-based micro pin fin heat sink Ali Kosßar, Yoav Peles, USA Received 1 May 2006 Available online 23 October 2006 Abstract Flow boiling of R-123 in a hydrofoil boiling heat transfer mechanisms. Existing conventional scale correlations for circular tubes resulted

  14. Using Exergy Analysis Methodology to Assess the Heating Efficiency of an Electric Heat Pump

    E-print Network

    Ao, Y.; Duanmu, L.; Shen, S.

    2006-01-01

    exergy loss and heating exergy efficiency for the HP set, presented an average heating temperature ranges for the heating exchanger with four different refrigerants, in which the HP set runs efficiently. Compared to the COP assessment standard...

  15. Dual circuit embossed sheet heat transfer panel

    DOEpatents

    Morgan, G.D.

    1984-02-21

    A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet. 6 figs.

  16. Dual circuit embossed sheet heat transfer panel

    DOEpatents

    Morgan, Grover D. (St. Louis County, MO)

    1984-01-01

    A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet.

  17. Dynamic heat transfer mechanism of two-phase closed thermosyphon

    NASA Astrophysics Data System (ADS)

    Negishi, K.; Kaneko, K. I.; Kusumoto, F.

    The heat transfer mechanism of a two phase closed thermosyphon was dynamically analysed in the periodically motive behavior of working fluid with boiling. It is an important problem in order to obtain high heat transfer performance, how the liquid film of the working fluid can be held for longer time on the wider area of the evaporator heating wall, and how the active evaporation can be kept there.

  18. Laser Measurement Of Convective-Heat-Transfer Coefficient

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

    1994-01-01

    Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

  19. Consideration of heat transfer enhancement mechanism using nano- and micro-scale porous layer

    Microsoft Academic Search

    T. Kunugi; Y. Ueki; T. Naritomi; H. Son; Z. Kawara; S. Muko; S. Wakamori

    2008-01-01

    A convective heat transfer enhancement using nano- and micro-scale porous layer surface was discovered by Kunugi et al. The heat transfer experiments, analytical considerations, flow visualization near the porous layer, and the porous layer surface observation were performed to grasp the heat transfer characteristics and the heat transfer enhancement mechanism. The heat transfer experiments revealed the porous layers were capable

  20. Heat transfer to the adsorbent in solar adsorption cooling device

    NASA Astrophysics Data System (ADS)

    Pilat, Peter; Patsch, Marek; Papucik, Stefan; Vantuch, Martin

    2014-08-01

    The article deals with design and construction of solar adsorption cooling device and with heat transfer problem in adsorber. The most important part of adsorption cooling system is adsorber/desorber containing adsorbent. Zeolith (adsorbent) type was chosen for its high adsorption capacity, like a coolant was used water. In adsorber/desorber occur, at heating of adsorbent, to heat transfer from heat change medium to the adsorbent. The time required for heating of adsorber filling is very important, because on it depend flexibility of cooling system. Zeolith has a large thermal resistance, therefore it had to be adapted the design and construction of adsorber. As the best shows the tube type of adsorber with double coat construction. By this construction is ensured thin layer of adsorbent and heating is quick in all volume of adsorbent. The process of heat transfer was experimentally measured, but for comparison simulated in ANSYS, too.

  1. Enhanced two phase flow in heat transfer systems

    SciTech Connect

    Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D

    2013-12-03

    A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.

  2. Proceedings of HT2008 2008 ASME Summer Heat Transfer Conference

    E-print Network

    Ghajar, Afshin J.

    An important design problem in industrial heat exchangers arises when the flow inside the tubes falls with a rounded entrance. If the flow has a disturbed entrance typical of heat exchangers, in whichProceedings of HT2008 2008 ASME Summer Heat Transfer Conference August 10-14, 2008, Jacksonville

  3. Heat transfer in open-cell metal foams

    Microsoft Academic Search

    T. J. Lu; H. A. Stone; M. F. Ashby

    1998-01-01

    The paper explores the use of open-celled metal foams as compact heat exchangers, exploiting convective cooling. An analytical model is developed for model foams with simple cubic unit cells consisting of heated slender cylinders, based on existing heat transfer data on convective crossflow through cylinder banks. A foam-filled channel having constant wall temperatures is analyzed to obtain the temperature distribution

  4. Solar power plant equipped with high efficiency heat exchangers

    Microsoft Academic Search

    Moisdon

    1981-01-01

    This is a description of solar power plant having a plurality of modular units, which form improved heat exchangers by enhancement of heat transfer surfaces, through the action of wipers and the draining down of transfer surfaces. The whole structure is insulated by a film of lubricant, and a solar heater booster provides additional heating capabilities.

  5. Natural convection heat transfer and fluid dynamics for a pair of vertically aligned isothermal horizontal cylinders

    Microsoft Academic Search

    Tim Persoons; Ian M. O’Gorman; David B. Donoghue; Gerry Byrne; Darina B. Murray

    2011-01-01

    This paper discusses the close interaction between local fluid dynamics and natural convection heat transfer from a pair of isothermally heated horizontal cylinders submerged in water. The presence of a second heated cylinder induces heat transfer enhancements of up to 10%, and strong fluctuations in local heat transfer rate. Therefore specific attention is focused on how the local heat transfer

  6. Conjugate heat transfer and thermal stress analysis of wire coil inserted tubes that are heated externally with uniform heat flux

    Microsoft Academic Search

    Veysel Özceyhan

    2005-01-01

    Wire coil inserted tubes are important in engineering applications. The conjugate heat transfer and thermal stress, which is induced by temperature differences in the wire coil inserted tube sheet of heat transfer equipment, were studied numerically in the paper. Three different wire coil inserts, which have different pitches, are considered. The smooth tube is also considered for comparison. Uniform heat

  7. Efficient Gene Transfer in Bacterial Cell Chains

    E-print Network

    Babic, Ana

    Horizontal gene transfer contributes to evolution and the acquisition of new traits. In bacteria, horizontal gene transfer is often mediated by conjugative genetic elements that transfer directly from cell to cell. Integrative ...

  8. Heat transfer characteristics of a two-pass trapezoidal channel and a novel heat pipe

    E-print Network

    Lee, Sang Won

    2009-06-02

    The heat transfer characteristics of airflows in serpentine cooling channels in stator vanes of gas turbines and the novel QuTech® Heat Pipe (QTHP) for electronic cooling applications were studied. The cooling channels are modeled as smooth...

  9. Systematic investigation of the effects of hydrophilic porosity on boiling heat transfer and critical heat flux

    E-print Network

    Tetreault-Friend, Melanie

    2014-01-01

    Predicting the conditions of critical heat flux (CHF) is of considerable importance for safety and economic reasons in heat transfer units, such as in nuclear power plants. It is greatly advantageous to increase this thermal ...

  10. The deterioration in heat transfer to fluids at supercritical pressure and high heat fluxes

    E-print Network

    Shiralkar, B. S.

    1968-01-01

    At slightly supercritical pressure and in the neighborhood of the pseudo-critical temperature (defined as the temperature corresponding to the peak in specific heat at the operating pressure), the heat transfer coefficient ...

  11. Nano-engineering the boiling surface for optimal heat transfer rate and critical heat flux

    E-print Network

    Phillips, Bren Andrew

    2011-01-01

    The effects on pool boiling characteristics such as critical heat flux and the heat transfer coefficient of different surface characteristics such as surface wettability, roughness, morphology, and porosity are not well ...

  12. Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

    NASA Technical Reports Server (NTRS)

    Cross, M. F.

    2011-01-01

    A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.

  13. Local heat transfer in a rotating serpentine flow passage

    SciTech Connect

    Wenjei Yang; Nengli Zhang; Chiou, J. (Univ. of Michigan, Ann Arbor (United States))

    1992-05-01

    An experimental study is performed on the internal cooling of a rotating serpentine flow passage of square cross section with throughflow. The test section is not proceeded by a hydrodynamic calming region, i.e., a leading arm, and is rotated at low Rossby numbers. The local heat transfer coefficients along the flow passage, including the leading wall, trailing wall, and sidewalls, are determined together with the circumferentially averaged values. The Reynolds, Rossby, and rotating Rayleigh numbers are varied to determine their effects on heat transfer performance. It is disclosed that heat transfer augmentation is significant at all sharp turns due to the presence of strong secondary flow. The rotational effect is very obvious and complicated in the local heat transfer performance but it is very minor on the average heat transfer performance. The throughflow rate plays an important role on the heat transfer performance. The results may serve as a baseline for comparison with the results from a model with a leading arm to determine the effects of a hydro-dynamic calming section on the heat transfer performance of a rotating serpentine flow passage.

  14. Radiation Heat Transfer Procedures for Space-Related Applications

    NASA Technical Reports Server (NTRS)

    Chai, John C.

    2000-01-01

    Over the last contract year, a numerical procedure for combined conduction-radiation heat transfer using unstructured grids has been developed. As a result of this research, one paper has been published in the Numerical Heat Transfer Journal. One paper has been accepted for presentation at the International Center for Heat and Mass Transfer's International Symposium on Computational Heat Transfer to be held in Australia next year. A journal paper is under review by my NASA's contact. A conference paper for the ASME National Heat Transfer conference is under preparation. In summary, a total of four (4) papers (two journal and two conference) have been published, accepted or are under preparation. There are two (2) to three (3) more papers to be written for the project. In addition to the above publications, one book chapter, one journal paper and six conference papers have been published as a result of this project. Over the last contract year, the research project resulted in one Ph.D. thesis and partially supported another Ph.D. student. My NASA contact and myself have formulated radiation heat transfer procedures for materials with different indices of refraction and for combined conduction-radiation heat transfer. We are trying to find other applications for the procedures developed under this grant.

  15. Heat transfer and flow characteristics on a gas turbine shroud.

    PubMed

    Obata, M; Kumada, M; Ijichi, N

    2001-05-01

    The work described in this paper is an experimental investigation of the heat transfer from the main flow to a turbine shroud surface, which may be applicable to ceramic gas turbines. Three kinds of turbine shrouds are considered with a flat surface, a taper surface and a spiral groove surface opposite to the blades in an axial flow turbine of actual turbo-charger. Heat transfer measurements were performed for the experimental conditions of a uniform heat flux or a uniform wall temperature. The effects of the inlet flow angle, rotational speed, and tip clearance on the heat transfer coefficient were clarified under on- and off-design flow conditions. The mean heat transfer coefficient was correlated to the blade Reynolds number and tip clearance, and compared with an experimental correlation and measurements of a flat surface. A comparison was also made for the measurement of static pressure distributions. PMID:11460639

  16. Heat and mass transfer study of impinging turbulent premixed flames

    NASA Astrophysics Data System (ADS)

    Liakos, H. H.; Keramida, E. P.; Founti, M. A.; Markatos, N. C.

    Impinging jet combusting flows on granite plates are studied. A mathematical model for calculating heat release in turbulent impinging premixed flames is developed. The combustion including radiative heat transfer and local extinction effects, and flow characteristics are modeled using a finite volume computational approach. Two different eddy viscosity turbulence models, namely the standard k-? and the RNG k-? model with and without radiation (discrete transfer model) are assessed. The heat released predictions are compared with experimental data and the agreement is satisfactory only when both radiative heat transfer and local extinction modeling are taken into account. The results indicate that the main effect of radiation is the decrease of temperature values near the jet stagnation point and along the plate surface. Radiation increases temperature gradients and affects predicted turbulence levels independently of the closure model used. Also, the RNG k-? predicts higher temperatures close the solid plate, with and without radiative heat transfer.

  17. Heat Transfer For Subcooled Flow Boiling In Hypervapotron Configuration

    SciTech Connect

    Chena, Peipei; Wua, Wen; Jonesa, Barclay G. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign Urbana, IL, 61801 (United States); Newell, Ty A [Mechanical and Industrial Engineering, University of Illinois at Urbana Champaign Urbana, IL, 61801 (United States)

    2006-07-01

    This work reports on experimental studies that examine subcooled boiling on the enhanced heat transfer surface of hypervapotron structures. The use of simulant fluid (refrigerant R134a) instead of prototypic water allows examination of a full range of subcooled boiling, including up to critical heat flux (CHF). The experimental results are compared to Bjorge's model and Kandlikar's heat transfer correlation in the subcooled boiling region. It is found that the fully developed boiling curve has a slope of about 2.96 (q{sup {approx}} {delta}{sub sat} {sup 2}.{sup 96}), which shows good agreement with Bjorge's recognition for flat surface channels. In addition, Kandlikar's correlation is also able to predict the heat transfer coefficient for the range from net vapor generation (NVG) to the fully developed boiling region with acceptable accuracy. However, the heat transfer curve shows a significant deviation when subcooled boiling approaches CHF. (authors)

  18. Cryogenic apparatus for study of near-field heat transfer

    SciTech Connect

    Kralik, T.; Hanzelka, P.; Musilova, V.; Srnka, A.; Zobac, M. [Institute of Scientific Instruments of the ASCR, v.v.i., Kralovopolska 147, Brno (Czech Republic)

    2011-05-15

    For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10{sup 0} to 10{sup 3} {mu}m. The heat transferred from the hot (10 - 100 K) to the cold sample ({approx}5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within {approx}2 nW/cm{sup 2} and {approx}30 {mu}W/cm{sup 2} is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer.

  19. Simulation Approach for Microscale Noncontinuum Gas-Phase Heat Transfer

    NASA Astrophysics Data System (ADS)

    Torczynski, J. R.; Gallis, M. A.

    2008-11-01

    In microscale thermal actuators, gas-phase heat transfer from the heated beams to the adjacent unheated substrate is often the main energy-loss mechanism. Since the beam-substrate gap is comparable to the molecular mean free path, noncontinuum gas effects are important. A simulation approach is presented in which gas-phase heat transfer is described by Fourier's law in the bulk gas and by a wall boundary condition that equates the normal heat flux to the product of the gas-solid temperature difference and a heat transfer coefficient. The dimensionless parameters in this heat transfer coefficient are determined by comparison to Direct Simulation Monte Carlo (DSMC) results for heat transfer from beams of rectangular cross section to the substrate at free-molecular to near-continuum gas pressures. This simulation approach produces reasonably accurate gas-phase heat-transfer results for wide ranges of beam geometries and gas pressures. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  20. Effects of Nonsteady Hot-water Greenhouse Heating on Heat Transfer and Microclimate

    Microsoft Academic Search

    M. Teitel; A. Shklyar; I. Segal; M. Barak

    1996-01-01

    Hot-water tubes are used for heating in many agricultural buildings. Owing to the thermostatic control of the heating system, the tubes usually operate under non-steady-state conditions. Experiments were carried out to determine the effects of non-steady heating on the heat transfer coefficients of the heating tubes, on the amount of energy supplied in the different phases of the heating cycle

  1. An experimental apparatus measuring convective heat transfer coefficient from a heated fine wire traversing in nanofluids

    Microsoft Academic Search

    Shinpyo Lee

    2011-01-01

    Most of the previous convection experiments for nanofluids have been performed for internal tube flow with constant heat flux\\u000a boundary condition. In contrast, a simple experimental apparatus measuring convective heat transfer coefficient from a heated\\u000a wire to external nanofluids is proposed and its working principles are explained in detail. The convective heat transfer coefficient\\u000a provided by the present system might

  2. In - line determination of heat transfer coefficients in a plate heat exchanger

    Microsoft Academic Search

    S. Silva Sotelo; R. J. Romero Domínguez

    2008-01-01

    \\u000a This paper shows an in – line determination of heat transfer coefficients in a plate heat exchanger. Water and aqueous working\\u000a solution of lithium bromide + ethylene glycol are considered. Heat transfer coefficients are calculated for both fluids. “Type\\u000a T” thermocouples were used for monitoring the wall temperature in a plate heat exchanger, which is one of the main components

  3. Thermal response in thermal energy storage material around heat transfer tubes: effect of additives on heat transfer rates

    Microsoft Academic Search

    Yuichi Hamada; Wataru Ohtsu; Jun Fukai

    2003-01-01

    The effects of carbon-fiber chips and carbon brushes as additives on the thermal conductivity enhancement of phase change materials (PCMs) using in latent heat thermal energy storage are investigated experimentally and numerically by considering the wall effect of the additives. The carbon-fiber chips are effective for improving the heat transfer rate in PCMs. However, the thermal resistance near the heat

  4. Heat Transfer of a Multiple Helical Coil Heat Exchanger Using a Microencapsulated Phase Change Material Slurry

    E-print Network

    Gaskill, Travis

    2012-02-14

    sides, respectively. The NTU-effectiveness relationship of the CHE when MPCM fluid is used approaches that of a heat exchanger with a heat capacity ratio of zero. The heat transfer results have shown that when using a MPCM slurry, an increase in heat...

  5. Heat transfer mechanisms during short-pulse laser heating of metals

    Microsoft Academic Search

    T. Q. Qiu; C. L. Tien

    1993-01-01

    This work studies heat transfer mechanisms during ultrafast laser heating of metals from a microscopic point of view. The heating process is composed of three processes: the deposition of radiation energy on electrons, the transport of energy by electrons, and the heating of the material lattice through electron-lattice interactions. The Boltzmann transport equation is used to model the transport of

  6. Numerical investigation of fouling on cross-flow heat exchanger tubes with conjugated heat transfer approach

    Microsoft Academic Search

    Y. Kaptan; E. Buyruk; A. Ecder

    2008-01-01

    Although fouling on heat exchanger tubes is extensively investigated, due to the lack of energy resources, the effects of fouling on heat exchangers is still an important area of study and gaining more and more attention every day. In this study we investigated the effects of fouling on heat transfer and flow structures numerically for cross-flow heat exchanger tube geometry.

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

    E-print Network

    Boyer, Edmond

    Measurement of flow field and local heat transfer distribution on a scraped heat exchanger.ravelet@laposte.net Geert-Jan Witkamp G.J.Witkamp@xs4all.nl Abstract In a cylindrical scraped heat exchanger crystallizer exchanger surface has been studied by direct measurements of the heat exchanger surface temperature

  8. Wall-to-suspension heat transfer in circulating fluidized beds

    SciTech Connect

    Wirth, K.E. [Univ. Erlangen-Nuernberg, Erlangen (Germany). Lehrstuhl fuer Mechanische Verfahrenstechnik

    1995-12-31

    The wall-to-suspension heat transfer in circulating fluidized beds depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. Experimental investigations of circulating fluidized beds of low dimensionless pressure gradients with different solid particles like bronze, glass and polystyrene at ambient temperatures showed no influence of the conductivity and the heat capacity of the solids on the heat transfer coefficient. Consequently the heat transfer coefficient in the form of the dimensionless Nusselt number can be described by the dimensionless numbers which characterize the gas-solid-flow near the wall. These numbers are the Archimedes number and the pressure drop-number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. With the aid of a model of segregated vertical gas-solid flow, the flow pattern in the wall region can be calculated and thus the wall heat transfer which depends only on heat conduction in the gas and on the convective heat transfer by the gas. With elevated suspension temperatures, radiation contributes additionally to the heat transfer. When the solids concentration is low, the effect of the radiation on the heat transfer is high. Increasing solids concentration results in a decrease of the radiation effect due to the wall being shielded from the radiation of the hot particles in the core region by the cold solids clusters moving down the wall. A simple correlation is presented for calculating the wall-to-suspension heat transfer in circulating fluidized beds.

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

    PubMed

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

    2014-03-01

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

  10. Microgravity Two-phase Flow and Heat Transfer

    NASA Astrophysics Data System (ADS)

    Gabriel, Kamiel

    2006-12-01

    Multiphase thermal systems (involving more than one phase or one component) have numerous applications in aerospace, heat-exchanger, transport of contaminants in environmental systems, and energy transport and energy conversion systems. Advances in understanding the behaviour of multiphase thermal systems could lead to higher efficiency energy production systems, improved heat-exchanger design, and safer and enhanced treatment of hazardous waste. But such advances have been greatly hindered by the strong effect of gravitational acceleration on the flow. Depending on the flow orientation and the phase velocities, gravitational forces could significantly alter the flow regime, and hence the pressure-drop and heat-transfer coefficients associated with the flow. A reduced gravity environment (or "microgravity"), provides an excellent tool to study the flow without the masking effects of gravity. This book presents for the first time a comprehensive coverage of all aspects of two-phase flow behaviour in the virtual absence of gravity. Link: http://www.springer.com/east/home?SGWID=5-102-22-173662745-0&changeHeader=true

  11. Modeling of Heat Transfer in Geothermal Heat Exchangers

    E-print Network

    Cui, P.; Man, Y.; Fang, Z.

    2006-01-01

    Ground-coupled heat pump (GCHP) systems have been gaining increasing popularity for space conditioning in residential and commercial buildings. The geothermal heat exchanger (GHE) is devised for extraction or injection of thermal energy from...

  12. Heat transfer in the pneumatic transport of massive particles

    NASA Astrophysics Data System (ADS)

    Louge, Michel; Yusof, Jamaludin M.; Jenkins, James T.

    1993-01-01

    The steady, fully developed heat transfer to the walls of a vertical pipe from a dilute suspension of relatively massive particles of low Biot number in a turbulent gas is analyzed. In this flow, particle collisions play a significant role. The thermal energies of the particle and gas phases are balanced using two coupled equations. In the particle phase, conduction is calculated from the kinetic theory as a self-diffusive transport flux and, assuming negligible transfer of heat during collisions, homogeneous boundary conditions are prescribed for the temperature. Solutions of the balance laws highlight the mechanisms governing the heat transfer in this regime.

  13. Optimization of Heat Transfer Rate in the Rectangular Microchannel of Different Aspect Ratios with Constant Cross Sectional Area

    Microsoft Academic Search

    F. Kowsari; N. Noroozi; M. Rezaei Barmi

    2008-01-01

    The increased power dissipation and reduced dimensions of microelectronics devices have emphasized the need for highly efficient compact cooling technologies. Microchannel heat sinks are of particular interest due to the very high rates of heat transfer they enable in conjunction with greatly reduced heat sink length scales and coolant mass flow rate. Therefore, in the present work, optimization of laminar

  14. Determination of the heat transfer coefficients in porous media

    SciTech Connect

    Kim, L.V.

    1994-06-01

    The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.

  15. A review on boiling heat transfer enhancement with nanofluids

    PubMed Central

    2011-01-01

    There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794

  16. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 2012-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...

  17. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 2010-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...

  18. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 2014-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...

  19. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 2013-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...

  20. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 2011-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...

  1. Design, Construction, and Qualification of a Microscale Heater Array for Use in Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Rule, T. D.; Kim, J.; Kalkur, T. S.

    1998-01-01

    Boiling heat transfer is an efficient means of heat transfer because a large amount of heat can be removed from a surface using a relatively small temperature difference between the surface and the bulk liquid. However, the mechanisms that govern boiling heat transfer are not well understood. Measurements of wall temperature and heat flux near the wall would add to the database of knowledge which is necessary to understand the mechanisms of nucleate boiling. A heater array has been developed which contains 96 heater elements within a 2.5 mm square area. The temperature of each heater element is held constant by an electronic control system similar to a hot-wire anemometer. The voltage that is being applied to each heater element can be measured and digitized using a high-speed A/D converter, and this digital information can be compiled into a series of heat-flux maps. Information for up to 10,000 heat flux maps can be obtained each second. The heater control system, the A/D system and the heater array construction are described in detail. Results are presented which show that this is an effective method of measuring the local heat flux during nucleate and transition boiling. Heat flux maps are obtained for pool boiling in FC-72 on a horizontal surface. Local heat flux variations are shown to be three to six times larger than variations in the spatially averaged heat flux.

  2. Efficiency of Plasma Heating with Beating Electrostatic Waves

    E-print Network

    Choueiri, Edgar

    plasma is used to predict the efficiency of heating in a rectilinear geometry for waves with phaseEfficiency of Plasma Heating with Beating Electrostatic Waves Benjamin Jorns and Edgar Y. Choueiri-dimensional efficiency model is derived for the heating of a uniformly magnetized plasma with beating electrostatic waves

  3. Heat transfer with very high free-stream turbulence and heat transfer with streamwise vortices

    NASA Technical Reports Server (NTRS)

    Moffat, Robert J.; Maciejewski, Paul; Eaton, John K.; Pauley, Wayne

    1987-01-01

    Two experimental programs related to augmentation of heat transfer by complex flow characteristics are reviewed. The first program deals with very high turbulence (up to 63 percent) which was shown to result in Stanton numbers as much as five times the expected values. Results from a number of trials show that fixing the free stream velocity, x-Reynolds number, turbulence intensity and integral length scale does not fix the Stanton number. Two such cases were found in which the Stanton number of one was 40 percent larger than the other. Mean velocity and mean temperature profiles are presented, as well as profiles of turbulence intensity within the boundary layer. The second program deals with vortices originating at bluff bodies and traveling downstream embedded in the wall boundary layer. Velocity vector maps from the boundary layers and distributions of Stanton number on the wall are presented for three types of bodies: square, cylindrical and teardrop. The heat transfer and velocity maps do not show evidence of the expected horseshoe vortices but, instead, show a strong common flow up vortex pair. The fluid mechanic mechanism responsible for this secondary flow field has not yet been identified.

  4. Experimental and numerical study of pressure drop and heat transfer in a single-phase micro-channel heat sink

    E-print Network

    Qu, Weilin

    Experimental and numerical study of pressure drop and heat transfer in a single-phase micro Received 6 July 2001; received in revised form 26 October 2001 Abstract The pressure drop and heat transfer-dimensional heat transfer characteristics of the heat sink were analyzed numerically by solving the conjugate heat

  5. Theoretical Design of a Thermosyphon for Efficient Process Heat Removal from Next Generation Nuclear Plant (NGNP) for Production of Hydrogen

    SciTech Connect

    Piyush Sabharwall; Fred Gunnerson; Akira Tokuhiro; Vivek Utgiker; Kevan Weaver; Steven Sherman

    2007-10-01

    The work reported here is the preliminary analysis of two-phase Thermosyphon heat transfer performance with various alkali metals. Thermosyphon is a device for transporting heat from one point to another with quite extraordinary properties. Heat transport occurs via evaporation and condensation, and the heat transport fluid is re-circulated by gravitational force. With this mode of heat transfer, the thermosyphon has the capability to transport heat at high rates over appreciable distances, virtually isothermally and without any requirement for external pumping devices. For process heat, intermediate heat exchangers (IHX) are required to transfer heat from the NGNP to the hydrogen plant in the most efficient way possible. The production of power at higher efficiency using Brayton Cycle, and hydrogen production requires both heat at higher temperatures (up to 1000oC) and high effectiveness compact heat exchangers to transfer heat to either the power or process cycle. The purpose for selecting a compact heat exchanger is to maximize the heat transfer surface area per volume of heat exchanger; this has the benefit of reducing heat exchanger size and heat losses. The IHX design requirements are governed by the allowable temperature drop between the outlet of the NGNP (900oC, based on the current capabilities of NGNP), and the temperatures in the hydrogen production plant. Spiral Heat Exchangers (SHE’s) have superior heat transfer characteristics, and are less susceptible to fouling. Further, heat losses to surroundings are minimized because of its compact configuration. SHEs have never been examined for phase-change heat transfer applications. The research presented provides useful information for thermosyphon design and Spiral Heat Exchanger.

  6. Fourier analysis of conductive heat transfer for glazed roofing materials

    SciTech Connect

    Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah [Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Zakaria, Nor Zaini [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)

    2014-07-10

    For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.

  7. Fourier analysis of conductive heat transfer for glazed roofing materials

    NASA Astrophysics Data System (ADS)

    Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini

    2014-07-01

    For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.

  8. Percolation induced heat transfer in deep unsaturated zones

    USGS Publications Warehouse

    Lu, N.; LeCain, G.D.

    2003-01-01

    Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997-1998 El Ni??no precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997-1998 El Ni??no precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.

  9. Heat transfer through an extended surface containing He II

    SciTech Connect

    Van Sciver, S.W. [FAMU-FLU Coll. of Engineering, Tallahassee, FL (United States)

    1999-02-01

    A semi-analytic solution for the heat transfer process between a He II pressurized bath and a saturated tube-type heat exchanger is presented. The problem is modeled with an extended surface heat transfer formulation analogous to that in conventional conduction. The process is governed by Kapitza conductance and counterflow within the bulk fluid in the tube. The resulting nonlinear differential equation may be integrated for the special case of constant properties, yielding a simple solution applicable to design and analysis of practical heat exchangers.

  10. Nonlinear aspects of high heat flux nucleate boiling heat transfer. Part 1, Formulation

    SciTech Connect

    Sadasivan, P.; Unal, C.; Nelson, R.

    1994-04-01

    This paper outlines the essential details of the formulation and numerical implementation of a model used to study nonlinear aspects of the macrolayer-controlled heat transfer process associated with high heat flux nucleate boiling and the critical heat flux. The model addresses the three-dimensional transient conduction heat transfer process within the problem domain comprised of the macrolayer and heater. Heat dissipation from the heater is modeled as the sum of transient transport into the macrolayer, and the heat loss resulting from evaporation of menisci associated with vapor stems.

  11. Heat transfer performance of a horizontal micro-grooved heat pipe using CuO nanofluid

    NASA Astrophysics Data System (ADS)

    Yang, Xue Fei; Liu, Zhen-Hua; Zhao, Jie

    2008-03-01

    An experiment was carried out to study the heat transfer performance of a horizontal micro-grooved heat pipe using CuO nanofluid as the working fluid. CuO nanofluid was a uniform suspension of CuO nanoparticles and deionized water. The average diameter of CuO nanoparticles was 50 nm. Mass concentration of CuO nanoparticles varied from 0.5 wt% to 2.0 wt%. The experiment was performed at three steady operating pressures of 7.45 kPa, 12.38 kPa and 19.97 kPa, respectively. Effects of the mass concentration of CuO nanoparticles and the operating pressure on both the heat transfer coefficients of the evaporator and the condenser sections, the critical heat flux (CHF) and the total heat resistance of the heat pipe were discussed. Experimental results show that CuO nanofluid can improve the thermal performance of the heat pipe and there is an optimal mass concentration which is estimated to be 1.0 wt% to achieve the maximum heat transfer enhancement. Operating pressure has apparent influences on both the heat transfer coefficients and the CHF of nanofluids. The minimum pressure corresponds to the maximum heat transfer enhancement. Under an operating pressure of 7.45 kPa, the heat transfer coefficients of the evaporator can be averagely enhanced by 46% and the CHF can be maximally enhanced by 30% when substituting CuO nanofluids for water.

  12. Experimental improvements of heat transfer in a latent heat thermal energy storage unit with embedded heat sources

    Microsoft Academic Search

    M. Lacroix; T. Duong

    1998-01-01

    An experimental study was conducted in order to improve the heat transfer in a single layer latent heat thermal energy storage unit with embedded electrical heat sources. This study is motivated by the need to increase the performance of a more complex multi-layer latent heat thermal energy storage system used for smoothing daily electrical load profiles. In the first part,

  13. Survey and evaluation of techniques to augment convective heat transfer

    E-print Network

    Bergles A. E.

    1965-01-01

    This report presents a survey and evaluation of the numerous techniques which have been shown to augment convective heat transfer. These techniques are: surface promoters, including roughness and treatment; displaced ...

  14. 16 Heat Transfer and Air Flow in a Domestic Refrigerator

    E-print Network

    Paris-Sud XI, Université de

    445 16 Heat Transfer and Air Flow in a Domestic Refrigerator Onrawee Laguerre UMR Génie Industriel...............................................447 16.2.1 Studies in Domestic Refrigerators...................................................................................... 451 16.3 Cold Production System in Domestic Refrigerators

  15. Small distance expansion for radiative heat transfer between curved objects

    E-print Network

    Golyk, Vladyslav A.

    We develop a small distance expansion for the radiative heat transfer between gently curved objects, in terms of the ratio of distance to radius of curvature. A gradient expansion allows us to go beyond the lowest-order ...

  16. Two-dimensional radiative heat transfer with allowance for shading

    Microsoft Academic Search

    V. F. Kravchenko; V. M. Yudin

    1976-01-01

    Radiative heat transfer with account taken for shading in an infinite cylinder whose contour is made up of arbitrary straight-line segments and which has variable temperature and emissivity on its two sides is examined.

  17. Heat transfer and pressure drop measurement in minichannels

    NASA Astrophysics Data System (ADS)

    Hej?ík, Ji?í; Jícha, Miroslav

    2012-04-01

    This paper describes the suitable techniques for the heat transfer and pressure drop measurement in smooth tubular channels with the internal diameter less than 5 mm. The first experimental data are mentioned and their evaluation is presented.

  18. Navier-Stokes analysis of turbine blade heat transfer

    NASA Technical Reports Server (NTRS)

    Boyle, R. J.

    1990-01-01

    Comparisons with experimental heat transfer and surface pressures were made for seven turbine vane and blade geometries using a quasi-three-dimensional thin-layer Navier-Stokes analysis. Comparisons are made for cases with both separated and unseparated flow over a range of Reynolds numbers and freestream turbulence intensities. The analysis used a modified Baldwin-Lomax turbulent eddy viscosity mode. Modifications were made to account for the effects of: (1) freestream turbulence on both transition and leading edge heat transfer; (2) strong favorable pressure gradients on relaminarization; and (3) variable turbulent Prandtl number heat transfer. In addition, the effect of heat transfer on the near wall model of Deissler is compared with the Van Driest model.

  19. Surface heat transfer coefficients of pin-finned cylinders

    NASA Technical Reports Server (NTRS)

    Vanfossen, G. J., Jr.

    1975-01-01

    An experimental investigation was conducted to measure heat-transfer coefficients for a 15.24-centimeter-diameter cylinder with pin fins on its surface. Pin diameters of 0.3175 and 0.6350 centimeter with staggered pin spacings of 3 and 4 pin diameters and pin lengths of 5, 7, and 9 pin diameters were tested. Flow was normal to the axis of the cylinder, and local heat-transfer coefficients were measured as a function of angle around the circumference of the cylinder. The average heat-transfer coefficient was also computed. Reynolds number based on pin diameter ranged from 3600 to 27,750. The smallest diameter, closest spacing, and largest pin-length-to-diameter ratio gave the highest average effective heat-transfer coefficients.

  20. Electric simulator for solving heat- and mass-transfer problems

    Microsoft Academic Search

    V. S. Shklyar

    1970-01-01

    An electric analog simulation method is described for heat- or mass-transfer based on the decomposition of the transport equation and the simulation of a system of locally-one-di-mensional equations by resistors.

  1. Influence of Infrared Radiation on Attic Heat Transfer

    E-print Network

    Katipamula, S.; Turner, W. D.; Murphy, W. E.; O'Neal, D. L.

    1985-01-01

    An experimental study concerned with different modes of heal transfer in fibrous and cellulose insulating material is presented. A series of experiments were conducted using an attic simulator to determine the effects of ventilation on attic heat...

  2. The Advantages of Sealless Pumps in Heat Transfer Fluid Services

    E-print Network

    Smith, M. D.

    The expectations for heat transfer fluid (HTF) system safety and reliability are continuing to increase. The challenges are many. Leaks produce vapors that ignite readily, fluid viscosity is very low, and many of the fluids react with oxygen...

  3. Heat Transfer Enhancement in Rectangular Channel with Compound Cooling Techniques

    E-print Network

    Krad, Belal

    2013-11-27

    Various compound internal cooling techniques were investigated in this experiment to see which combinations can offer the greatest heat transfer. Combinations of rib turbulators as well as pin0fins were used in different configurations in order...

  4. Heat Transfer Performance for Evaporator of Absorption Refrigerating Machine

    NASA Astrophysics Data System (ADS)

    Kunugi, Yoshifumi; Usui, Sanpei; Ouchi, Tomihisa; Fukuda, Tamio

    An experiment was conducted to check the heat transfer performance of evaporators with grooved tubes for absorption refrigerating machines. Heat transfer rate of evaporators were 35kW and 70kW. The range of the flow rate of the sprayed refrigerant per unit length ? was 1 to 50kg/hm, and the outside diameters of the tubes, D0 were 16 and 19.6 mm. About 80 to 100 % increase of heat transfer rate over a plane surfaced tube is obtained by using grooved tube. The heat transfer coefficients for evaporation are correlated by the equation ?E0=(?/D0)1/2. The substantial surface area, which is about three times larger than that of plane surfaced tube, is used in the above correlation.

  5. Heat transfer during condensation of refrigerants in tubular minichannels

    NASA Astrophysics Data System (ADS)

    Bohdal, Tadeusz; Charun, Henryk; Sikora, Ma?gorzata

    2012-10-01

    The present paper describes the results of experimental investigations of heat transfer during condensation of R134a, R404A and R407C in pipe minichannels with internal diameters 0.31-3.30 mm. The results concern investigations of the local heat transfer coefficient. The results were compared with the correlations proposed by other authors. Within the range of examined parameters of the condensation process in minichannels made of stainless steel, it was established that the values of the heat transfer coefficient may be described with Akers et al., Mikielewicz and Shah correlations within a limited range of the mass flux density of the refrigerant and the minichannel diameter. On the basis of experimental investigations, the authors proposed their own correlation for the calculation of local heat transfer coefficient.

  6. Transient Heat Transfer in TCAP Coils

    SciTech Connect

    Steimke, J.L.

    1999-03-09

    The Thermal Cycling Absorption Process (TCAP) is used to separate isotopes of hydrogen. TCAP involves passing a stream of mixed hydrogen isotopes through palladium deposited on kieselguhr (Pd/k) while cycling the temperature of the Pd/k. Kieselguhr is a silica mineral also called diatomite. To aid in the design of a full scale facility, the Thermal Fluids Laboratory was used by the Chemical and Hydrogen Technology Section to compare the heat transfer properties of three different configurations of stainless steel coils containing kieselguhr and helium. Testing of coils containing Pd/k and hydrogen isotopes would have been more prototypical but would have been too expensive. Three stainless steel coils filled with kieselguhr were tested; one made from 2.0 inch diameter tubing, one made from 2.0 inch diameter tubing with foam copper embedded in the kieselguhr and one made from 1.25 inch diameter tubing. It was known prior to testing that increasing the tubing diameter from 1.25 inch to 2.0 inch would slow the rate of temperature change. The primary purpose of the testing was to measure to what extent the presence of copper foam in a 2.0" tubing coil would compensate for the effect of larger diameter. Each coil was connected to a pressure gage and the coil was evacuated and backfilled with helium gas. Helium was used instead of a mixture of hydrogen isotopes for reasons of safety. Each coil was quickly immersed in a stirred bath of ethylene glycol at a temperature of approximately 100 degrees Celsius. The coil pressure increased, reflecting the increase in average temperature of its contents. The pressure transient was recored as a function of time after immersion. Because of the actual process will use Pd/k instead of kieselguhr, additional tests were run to determine the differences in thermal properties between the two materials. The method was to position a thermocouple at the center of a hollow sphere and pack the sphere with Pd/k. The sphere was sealed, quickly submerged in a bath of boiling water and the temperature transient was recorded. There sphere was then opened, the Pd/k was replaced with kieselguhr and the transient was repeated. The response was a factor of 1.4 faster for Pd/k than for kieselguhr, implying a thermal diffusivity approximately 40 percent higher than for kieselguhr. Another implication is that the transient tests with the coils would have proceeded faster if the coils had been filled with Pd/k rather than kieselguhr.

  7. An assessment of RELAP5 MOD3.1.1 condensation heat transfer modeling with GIRAFFE heat transfer tests

    SciTech Connect

    Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.

    1995-09-01

    RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {+-}5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.

  8. Transfer heat in a resin sheath

    SciTech Connect

    Wharry, S.R. Jr. [Ametek, Wilmington, DE (United States). Haveg Div.

    1996-02-01

    As a material of construction for heat exchangers, fluoropolymers offer a combination of low cost and performance that is difficult for other materials to match. Durable, pliable, and less brittle than glass and graphite, fluoropolymers are generally specified over those materials in heat exchangers. Fluoropolymers have also displaced certain metals, depending on their susceptibility to corrosion from aggressive chemicals. Since making their debut in shell-and-tube models more than 30 years ago, fluoropolymers have also found their way into other configurations, namely reactor coils and immersion coils. Although fluoropolymer exchangers have proven their worth, there are still obstacles to overcome. One is the bias that exists toward process equipment that is made of plastic or other synthetic resins, particularly in high-heat environments. Secondly, there is the assumption that because fluoropolymers are inherently poor conductors of heat, they are odd candidates for heat exchangers. The paper discusses the advantages of fluoropolymer use in heat exchangers.

  9. M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction

    E-print Network

    Bahrami, Majid

    requirement for heat transfer is the presence of a temperature difference. The temperature difference gradient, which is the slope of the temperature curve (the rate of change of temperature T with length x and surface area A. The temperature difference across the wall is T = T2 ­ T1. Note that heat transfer

  10. Heat transfer enhancement in latent heat thermal energy storage system by using the internally finned tube

    Microsoft Academic Search

    Yuwen Zhang; A. Faghri

    1996-01-01

    The heat transfer enhancement in the latent heat thermal energy storage system by using an internally finned tube is presented in this paper. The phase change material fills the annular shell space around the tube, while the transfer fluid flows within the internally finned tube. The melting of the phase change material is described by a temperature transforming model coupled

  11. The Little Heat Engine: Heat Transfer in Solids, Liquids and Gases

    Microsoft Academic Search

    Pierre-Marie Robitaille

    2007-01-01

    In this work, an introductory exposition of the laws of thermodynamics and radiative heat transfer is presented while exploring the concepts of the ideal solid, the lattice, and the vibrational, translational, and rotational degrees of freedom. Analysis of heat transfer in this manner helps scientists to recognize that the laws of thermal radiation are strictly applicable only to the ideal

  12. Heat and Mass Transfer in Air to Air Enthalpy Heat Exchangers

    Microsoft Academic Search

    Mohammad Shakir Nasif; Graham L. Morrison; Masud Behnia

    The effectiveness of a Z type flow membrane based heat exchanger utilizing porous paper as the heat and moisture transfer media used in ventilation energy recovery systems is presented. A mathematical model is developed and validated against the experimental results. The moisture transfer resistance of the paper is determined using permeability measurements. A computational fluid dynamics code is used to

  13. Nanofluid jet impingement heat transfer characteristics in the rectangular mini-fin heat sink

    NASA Astrophysics Data System (ADS)

    Naphon, Paisarn; Nakharintr, Lursukd

    2012-11-01

    The nanofluid jet impingement heat transfer characteristics in a rectangular mini-fin heat sink are studied. The heat sink is fabricated from aluminum by a wire electrical discharge machine. The nanofluid is a mixture of deionized water and nanoscale TiO2 particles with a volume nanoparticle concentration of 0.2%. The results obtained for nanofluid jet impingement cooling in the rectangular mini-fin heat sink are compared with those found in the water jet impingement cooling. The effects of the inlet temperature of the nanofluid, its Reynolds number, and the heat flux on the heat transfer characteristics of the rectangular mini-fin heat sink are considered. It is found that the average heat transfer rates for the nanofluid as coolant are higher than those for deionized water.

  14. Heat Transfer Research 44(1), 130 (2013) ENTROPY GENERATION ANALYSIS

    E-print Network

    Zhang, Yuwen

    Heat Transfer Research 44(1), 1­30 (2013) ENTROPY GENERATION ANALYSIS FOR A PULSATING HEAT­vapor phase 2 Kim, Zhang, & Choi Heat Transfer Research NOMENCLATURE A area, m2 Qin,s,l sensible heat transfer into cp specific heat at constant liquid slug, W pressure, Qout,s,l sensible heat transfer out cv specific

  15. Numerical Modeling of Conjugate Heat Transfer in Fluid Network

    NASA Technical Reports Server (NTRS)

    Majumdar, Alok

    2004-01-01

    Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.

  16. Comparison of Methods for Calculating Radiative Heat Transfer

    SciTech Connect

    Schock, Alfred; Abbate, M J

    2012-01-19

    Various approximations for calculating radioactive heat transfer between parallel surfaces are evaluated. This is done by applying the approximations based on total emissivities to a special case of known spectral emissivities, for which exact heat transfer calculations are possible. Comparison of results indicates that the best approximation is obtained by basing the emissivity of the receiving surface primarily on the temperature of the emitter. A specific model is shown to give excellent agreement over a very wide range of values.

  17. Application of ray tracing in radiation heat transfer

    NASA Technical Reports Server (NTRS)

    Baumeister, Joseph F.

    1993-01-01

    This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.

  18. Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids)

    Microsoft Academic Search

    Yulong Ding; Hajar Alias; Dongsheng Wen; Richard A. Williams

    2006-01-01

    This paper is mainly concerned about the heat transfer behaviour of aqueous suspensions of multi-walled carbon nanotubes (CNT nanofluids) flowing through a horizontal tube. Significant enhancement of the convective heat transfer is observed and the enhancement depends on the flow conditions (Reynolds number, Re), CNT concentration and the pH, with the effect of pH smallest. Given other conditions, the enhancement

  19. High-Power Liquid-Metal Heat-Transfer Loop

    NASA Technical Reports Server (NTRS)

    Bhandari, Pradeep; Fujita, Toshio

    1991-01-01

    Proposed closed-loop system for transfer of thermal power operates at relatively high differential pressure between vapor and liquid phases of liquid-metal working fluid. Resembles "capillary-pumped" liquid-metal heat-transfer loop except electric field across permselective barrier of beta alumina keeps liquid and vapor separate at heat-input end. Increases output thermal power, contains no moving parts, highly reliable and well suited to long-term unattended operation.

  20. Heat transfer in airplane fuel tanks at low temperatures

    Microsoft Academic Search

    P. M. McConnell; L. A. Desmarais; F. F. Tolle; C. L. Delaney

    1983-01-01

    A 1D unsteady convection\\/conduction heat-transfer model is developed to calculate the effects of flight through cold regions on the temperature distribution of fuel in aircraft wing tanks. The thermal environment of the aircraft is described, the mechanisms of internal and external heat transfer are characterized, the governing equations are set forth, and a finite-difference scheme is employed in their solution.