Heat transfer efficiency of metal honeycombs
T. J. Lu
1998-01-01
The efficiency of micro-cell aluminium honeycombs in augmenting heat transfer in compact heat exchangers is evaluated using analytical models. For convective cooling, the overall heat transfer rate is found to be elevated by about two order of magnitudes when an open channel is designed with an aluminium honeycomb core. The performance is comparable to that achieved by using open-celled aluminium
Transfer functions for efficient calculation of multidimensional transient heat transfer
J. E. Seem; S. A. Klein; W. A. Beckman; J. W. Mitchell
1989-01-01
Finite difference or finite element methods reduce transient multidimensional heat transfer problems into a set of first-order differential equations when thermal physical properties are time invariant and the heat transfer processes are linear. This paper presents a method for determining the exact solution to a set of first-order differential equations when the inputs are modeled by a continuous, piecewise linear
NSDL National Science Digital Library
Integrated Teaching and Learning Program,
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.
Effect of microfouling on heat-transfer efficiency
Little, B.; Berger, L.R.
1980-01-01
Field experiments, performed at Keahole Point, Hawaii and in the Gulf of Mexico, were designed to determine the relationship between decreased heat transfer efficiency and the accumulation of corrosion and/or biofouling films on heat exchanger surfaces. The sample tubes were maintained under conditions simulating those of an Ocean Thermal Energy Conversion (OTEC) system and data from the two sites have been compared. Seawater flowed through 2.54 (internal diameter) metal tubes at approximately 1.8m sec/sup -1/. Four types of tubes were used: 5052 Aluminum (A1), Grade 2 titanium (Ti), 90-10 copper-nickel (Cu-Ni) and Allegheny-Ludlum 6X stainless ssteel (SS). All surfaces were colonized by microorganisms, though colonization of the Cu-Ni surface was initially retarded. Total film weight was greatest for the Al and Cu-Ni surfaces which were characterized by corrosion as well as microbial fouling. The total organic carbon: total nitrogen ratios of the fouling films from Ti, Al, SS and Cu-Ni, 4.2, 4.0, 4.8 and 7.9 respectively, remained constant throughout the experiment. The degradation of heat transfer efficiency due to the formation of fouling layers on Ti and SS is neither linear nor a simple exponential function. A microfouling model is proposed for corrosion-resistant surfaces that is consistent with field observations.
Efficient Heat and Mass Transfer Formulations for Oil Shale Retorting
NASA Astrophysics Data System (ADS)
Parker, J. C.; Zhang, F.
2007-12-01
A mathematical model for oil shale retorting is described that considers kerogen pyrolysis, oil coking, residual carbon gasification, carbonate mineral decomposition, water-gas shift, and phase equilibria reaction. Reaction rate temperature-dependence is described by Arrhenius kinetics. Fractured rock is modeled as a bi-continuum consisting of fracture porosity in which advective and dispersive gas and heat transport occur, and rock matrix in which diffusive mass transport and thermal conduction occur. Heat transfer between fracture and matrix regions is modeled either by a partial differential equation for spherical conduction or by a linear first-order heat transfer formulation. Mass transfer is modeled in an analogous manner or assuming local equilibrium. First-order mass and heat transfer coefficients are computed by a theoretical model from fundamental rock matrix properties. The governing equations are solved using a 3-D finite element formulation. Simulations of laboratory retort experiments and hypothetical problems indicated thermal disequilibrium to be the dominant factor controlling retort reactions. Simulation accuracy was unaffected by choice of mass transfer formulation. However, computational effort to explicitly simulate diffusive mass transfer in the rock matrix increased computational effort by more than an order of magnitude compared with first-order mass transfer or equilibrium analyses. A first-order heat transfer approximation of thermal conduction can be used without significant loss of accuracy if the block size and/or heating rate are not too large, as quantified by a proposed dimensionless heating rate.
Fang, X.; Wang, Z.; Liu, H.
2006-01-01
This paper analyzes the influence of transfer efficiency of the outdoor pipe network and operating efficiency of the boiler on the building heat consumption index, on the premise of saving up to 65 percent energy in different climates. The results...
NASA Astrophysics Data System (ADS)
Laptev, A. G.; Lapteva, E. A.
2015-07-01
The efficiency of heat and mass transfer in the bubbling bed on the plate has been investigated with the use of the method of combined physical and mathematical modeling based on the representation of the physical process in the form of a combination of elementary phenomena having a hierarchy of scales that permits realizing a scale transition in designing a contact device. The mathematical modeling of the heat and mass transfer in the above bed is based on the idea that the structure of this bed is invariant with its size and the interaction of the phases in it. A parametric investigation of the interaction of various effects in the process of heat and mass transfer in the bubbling bed on the plate and their conjugation has been carried out on the basis of the variational formulation of the conservation laws. Examples of calculating the efficiencies of the heat and mass transfer processes on bubbling plates are given. The results of calculations were compared with the corresponding experimental data.
Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines
NASA Technical Reports Server (NTRS)
Ameri, A. A.; Steinthorsson, E.; Rigby, David L.
1998-01-01
Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E 3 first stage turbine, which represents a modem gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.
Improving the heat transfer efficiency of synthetic oil with silica nanoparticles.
Timofeeva, Elena V; Moravek, Michael R; Singh, Dileep
2011-12-01
The heat transfer properties of synthetic oil (Therminol 66) used for high temperature applications was improved by introducing 15 nm silicon dioxide nanoparticles. Stable suspensions of inorganic nanoparticles in the non-polar fluid were prepared using a cationic surfactant (benzalkonium chloride). The effects of nanoparticle and surfactant concentrations on thermo-physical properties (viscosity, thermal conductivity and total heat absorption) of these nanofluids were investigated in a wide temperature range. The surfactant-to-nanoparticle (SN) ratio was optimized for higher thermal conductivity and lower viscosity, which are both critical for the efficiency of heat transfer. The rheological behavior of SiO(2)/TH66 nanofluids was correlated to average agglomerate sizes, which were shown to vary with SN ratio and temperature. The conditions of ultrasonic treatment were studied and the temporary decrease of agglomerate size from an equilibrium size (characteristic to SN ratio) was demonstrated. The heat transfer efficiencies were estimated for the formulated nanofluids for both turbulent and laminar flow regimes and were compared to the performance of the base fluid. PMID:21889163
Urban Sewage Delivery Heat Transfer System (2): Heat Transfer
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...
Zhao, Ye; Luo, Yuting; Zhu, Jie; Li, Juan; Gao, Xuefeng
2015-06-10
We report a type of copper-based ultrathin nickel nanocone films with high-efficiency dropwise condensation heat transfer (DCHT) performance, which can be fabricated by facile electrodeposition and low-surface-energy chemistry modification. Compared with flat copper samples, our nanosamples show condensate microdrop self-propelling (CMDSP) function and over 89% enhancement in the DCHT coefficient. Such remarkable enhancement may be ascribed to the cooperation of surface nanostructure-induced CMDSP function as well as in situ integration and ultrathin nature of nanofilms. These findings are very significant to design and develop advanced DCHT materials and devices, which help improve the efficiency of thermal management and energy utilization. PMID:26011021
Zhu, Jie; Luo, Yuting; Tian, Jian; Li, Juan; Gao, Xuefeng
2015-05-27
We report that the dropwise condensation heat transfer (DCHT) effectiveness of copper surfaces can be dramatically enhanced by in situ grown clustered ribbed-nanoneedles. Combined experiments and theoretical analyses reveal that, due to the microscopically rugged and low-adhesive nature of building blocks, the nanosamples can not only realize high-density nucleation but constrain growing condensates into suspended microdrops via the self-transport and/or self-expansion mode for subsequently self-propelled jumping, powered by coalescence-released excess surface energy. Consequently, our nanosample exhibits over 125% enhancement in DCHT coefficient. This work helps develop advanced heat-transfer materials and devices for efficient thermal management and energy utilization. PMID:25966966
Li, Perry Y.
and expansion is both energy efficient and power-dense. An ex- ample would be compressed air energy storage. One transfer, in- crease the thermal capacitance of the air space, and promote mix- ing. Foams, strands, finsOPTIMAL EFFICIENCY-POWER TRADEOFF FOR AN AIR MOTOR/COMPRESSOR WITH VOLUME VARYING HEAT TRANSFER
J. E. Seem; S. A. Klein; W. A. Beckman; J. W. Mitchell
1989-01-01
This paper describes a method in which the transfer functions describingheat flow in building elements can be combined into a single tranfer functionfor an enclosure, referred to as a comprehensive room transfer function (CRTF).The method accurately models long-wave radiation exchange and convection in anenclosure through an approximate network, referred to as the ''star'' network.Resistances in the star network are determined
An efficient higher order compact scheme to capture heat transfer solutions in spherical geometry
NASA Astrophysics Data System (ADS)
Sekhar, T. V. S.; Hema Sundar Raju, B.
2012-11-01
A higher order compact scheme (HOCS) is developed for solving energy equation in spherical polar coordinates for the flow past a sphere. The velocity components are obtained by solving the Navier-Stokes equations using HOCS in spherical geometry. The convection terms in the momentum and energy equations are handled in an effective manner so as to get fourth order accurate solutions. The higher order compact scheme is made efficient by combining with the coarse grid correction based multigrid method. In the absence of an exact solution, the order of accuracy of the results is illustrated. The results are compared with first order accurate upwind scheme, second order accurate defect correction technique(DC) and other recent numerical results of the literature. It is found that HOCS captures heat transfer solutions accurately when compared to other conventional schemes at higher values of Re and Pr. The angular variation of thermal boundary layer thickness is also presented.
Lottes
1961-01-01
Text material for a graduate course in heat transfer applications to ; nuclear engineering is presented. Topics covered include fuel element heat ; transfer-steady state, fuel assembly calculations, maximum-to-average heat flux ; calculations, hot spot factors, power excursion equations, fuel element ; transients, shutdown cooling calculations, shield cooling calculations, boiling ; heat transfer-steady state, two-phase pressure drop with constant flow
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 ...
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.
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.
W. Nakayama
1982-01-01
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
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
Improving the heat transfer efficiency of synthetic oil with silica nanoparticles
Elena V. Timofeeva; Michael R. Moravek; Dileep Singh
2011-01-01
The heat transfer properties of synthetic oil (Therminol 66) used for high temperature applications was improved by introducing 15nm silicon dioxide nanoparticles. Stable suspensions of inorganic nanoparticles in the non-polar fluid were prepared using a cationic surfactant (benzalkonium chloride). The effects of nanoparticle and surfactant concentrations on thermo-physical properties (viscosity, thermal conductivity and total heat absorption) of these nanofluids were
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.
NASA Technical Reports Server (NTRS)
Eaton, L. R. (inventor)
1976-01-01
An improved heat transfer device particularly suited for use as an evaporator plate in a diffusion cloud chamber. The device is characterized by a pair of mutually spaced heat transfer plates, each being of a planar configuration, having a pair of opposed surfaces defining therebetween a heat pipe chamber. Within the heat pipe chamber, in contiguous relation with the pair of opposed surfaces, there is disposed a pair of heat pipe wicks supported in a mutually spaced relationship by a foraminous spacer of a planar configuration. A wick including a foraminous layer is contiguously related to the external surfaces of the heat transfer plates for uniformly wetting these surfaces.
NASA Astrophysics Data System (ADS)
Bell, Peter M.
The Subseabed Disposal Program (SDP) includes a set of heat-transfer experiments on the ocean floor, planned for 1986. The concept is to provide data on the local heating of seabed sediment released by buried radioactive waste materials. The In Situ Heat Transfer experiment (ISHTE) involves placing a 400-W isotopic heat source and related equipment frame on the seabed at a depth of approximately 6000 m. Data will be recorded at the site, some of which will be transmitted to a surface vessel by acoustic telemetry. The entire apparatus will be recovered within 1 year.
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.
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.
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…
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
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.
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.
Conjugated Heat Transfer in Microchannels
NASA Astrophysics Data System (ADS)
Nunes, J. S.; Cotta, R. M.; Avelino, M. R.; Kakaç, S.
Energy conservation and sustainable development demands have been driving research efforts, within the scope of thermal engineering, towards more energy efficient equipments and processes. In this context, the scale reduction in mechanical fabrication has been permitting the miniaturization of thermal devices, such as in the case of micro-heat exchangers [1]. More recently, heat exchangers employing micro-channels with characteristic dimensions below 500 ?m have been calling the attention of researchers and practitioners, towards applications that require high heat removal demands and/or space and weight limitations [2]. Recent review works [2, 3] have pointed out discrepancies between experimental results and classical cor-relation predictions of heat transfer coefficients in micro-channels. Such deviations have been stimulating theoretical research efforts towards a better agreement between experiments and simulations, through the incorporation of different effects that are either typically present in micro-scale heat transfer or are effects that are normally disregarded at the macro-scale and might have been erroneously not accounted for in micro-channels. Our own research effort was first related to the fundamental analysis of forced convection within micro-channels with and without slip flow, as required for the design of micro-heat exchangers in steady, periodic and transient regimen [4, 5]. Also recently in Refs. [6-11], the analytical contributions were directed towards more general problem formulations, including viscous dissipation, axial diffusion in the fluid and three-dimensional flow geometries. Then, this fundamental research was extended to include the effects of axial fluid heat conduction and wall corrugation or roughness on heat transfer enhancement [12]. The work of Maranzana et al. [13] further motivated the present analysis, dealing with longitudinal wall heat conduction effects in symmetric micro-channels.
Boiling Heat Transfer in Minichannels
V. V. Kuznetsov; O. V. Vitovsky; A. S. Shamirzaev
the capillary forces predominate, and they determine flow pattern and boiling heat transfer. The interest for study of boiling heat transfer in minichannels increases at last decade due to obtained possibility to makes the channels of millimeter’s and micron’s size for application in wide range of industrial devices for enhancement of heat and mass transfer. They could be used in
Thermodynamics of Flow Boiling Heat Transfer
NASA Astrophysics Data System (ADS)
Collado, F. J.
2003-05-01
Convective boiling in sub-cooled water flowing through a heated channel is essential in many engineering applications where high heat flux needs to be accommodated. It has been customary to represent the heat transfer by the boiling curve, which shows the heat flux versus the wall-minus-saturation temperature difference. However it is a rather complicated problem, and recent revisions of two-phase flow and heat transfer note that calculated values of boiling heat transfer coefficients present many uncertainties. Quite recently, the author has shown that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant) was tightly connected with the thermodynamic efficiency of a theoretical reversible engine placed in this thermal gap. In this work, whereas this correlation is checked again with data taken by General Electric (task III) for water at high pressure, a possible connection between this wall efficiency and the reversible-work theorem is explored.
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.
Nano materials for efficiently lowering the freezing point of heat transfer nanofluids
NASA Astrophysics Data System (ADS)
Hong, Haiping; Roy, Walter
2007-09-01
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 freezing point than the regular ionic materials (e.g. NaCl). The possible explanation for this interesting phenomenon is the colligative property of fluid and relative small size of nano material. It is quite certain that the carbon nanotubes and metal oxide nano particles could be a wonderful candidate for the nano coolant application because they could not only increase the thermal conductivity, but also efficiently lower the freezing point of traditional coolants.
Hydrodynamics, heat transfer and flow boiling instabilities in microchannels
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 ...
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.
NSDL National Science Digital Library
This introductory engineering textbook on heat and mass transfer, written by John H. Lienhard IV, Professor at University of Houston and John H. Lienhard IV, Professor at Massachusetts Institute of Technology is now available online without charge. One aim of this project is to "explore the possibilities of placing textbooks online." The idea is that the online format holds two key benefits -- ease of continuous updates or corrections, and the "potential for fundamentally altering the economics of higher education, particularly those in environments where money is scarce." To these ends, the website also posts a history of the various versions and statistics on downloads of the book worldwide.
Heat transfer from internally heated hemispherical pools
Gabor, J.D.; Ellsion, P.G.; Cassulo, J.C.
1980-01-01
Experiments were conducted on heat transfer from internally heated ZnSO/sub 4/-H/sub 2/O pools to the walls of hemispherical containers. This experimental technique provides data for a heat transfer system that has to date been only theoretically treated. Three different sizes of copper hemispherical containers were used: 240, 280, 320 mm in diameter. The pool container served both as a heat transfer surface and as an electrode. The opposing electrode was a copper disk, 50 mm in diameter located at the top of the pool in the center. The top surface of the pool was open to the atmosphere.
5. Heat transfer Ron Zevenhoven
Zevenhoven, Ron
= voltage difference / resistance; heat transfer = temperature difference / resistance; fluid flow-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
Anjun Jiao
2008-01-01
The heat pipe, as one of the most efficient heat transport devices, is a peerless choice in the electronic cooling field. In order to better understand the heat transfer mechanisms of the heat pipe, a heat transfer model, which considers the effects of the surface condition, disjoining pressure, gravity force, and contact angle on the thin film profile, heat flux
Conduction heat transfer solutions
NASA Astrophysics Data System (ADS)
Vansant, J. H.
1980-03-01
A collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc., are presented. 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.
Heater Composite Measures Heat Transfer
NASA Technical Reports Server (NTRS)
Hippensteele, S. A.; Russel, L. M.; Stepka, F. S.; Moffat, R. J.
1982-01-01
Composite consisting of commercially available elements has been developed to measure heat transfer. Composite provides a simple, convenient, low-cost device for use in heat-transfer work for rapid evaluation of thermal performance of both flat and simply curved objects. Device utilizes available off-the-shelf materials and provides a convenient method, with good resolution of local temperatures and heat transfer, with measurement accuracy at near-normal room conditions.
Tubing for augmented heat transfer
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)
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.
Flow and heat transfer enhancement in tube heat exchangers
NASA Astrophysics Data System (ADS)
Sayed Ahmed, Sayed Ahmed E.; Mesalhy, Osama M.; Abdelatief, Mohamed A.
2015-08-01
The performance of heat exchangers can be improved to perform a certain heat-transfer duty by heat transfer enhancement techniques. Enhancement techniques can be divided into two categories: passive and active. Active methods require external power, such as electric or acoustic field, mechanical devices, or surface vibration, whereas passive methods do not require external power but make use of a special surface geometry or fluid additive which cause heat transfer enhancement. The majority of commercially interesting enhancement techniques are passive ones. This paper presents a review of published works on the characteristics of heat transfer and flow in finned tube heat exchangers of the existing patterns. The review considers plain, louvered, slit, wavy, annular, longitudinal, and serrated fins. This review can be indicated by the status of the research in this area which is important. The comparison of finned tubes heat exchangers shows that those with slit, plain, and wavy finned tubes have the highest values of area goodness factor while the heat exchanger with annular fin shows the lowest. A better heat transfer coefficient ha is found for a heat exchanger with louvered finned and thus should be regarded as the most efficient one, at fixed pumping power per heat transfer area. This study points out that although numerous studies have been conducted on the characteristics of flow and heat transfer in round, elliptical, and flat tubes, studies on some types of streamlined-tubes shapes are limited, especially on wing-shaped tubes (Sayed Ahmed et al. in Heat Mass Transf 50: 1091-1102, 2014; in Heat Mass Transf 51: 1001-1016, 2015). It is recommended that further detailed studies via numerical simulations and/or experimental investigations should be carried out, in the future, to put further insight to these fin designs.
Heat Transfer: From Hot to Not
NSDL National Science Digital Library
Integrated Teaching and Learning Program, College of Engineering,
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.
Turbulent boundary layer heat transfer
NASA Technical Reports Server (NTRS)
Moffat, R. J.
1982-01-01
Several environmental parameters presently acknowledged to affect heat transfer are discussed including: (1) the experimental apparatus used, (2) uniform and variable wall temperatures, (3) acceleration effects, (4) deceleration, (5) free stream turbulence, (6) surface roughness, (7) unsteady effects, and (8) secondary flows. Calculation procedures, and some physically based models that are successful in computing heat transfer rates are discussed.
Jiang, Shaohui; Liu, Changhong; Fan, Shoushan
2014-03-12
In this work, we report our studies related to the natural-convective heat transfer properties of carbon nanotube (CNT) sheets. We theoretically derived the formulas and experimentally measured the natural-convective heat transfer coefficients (H) via electrical heating method. The H values of the CNT sheets containing different layers (1, 2, 3, and 1000) were measured. We found that the single-layer CNT sheet had a unique ability on heat dissipation because of its great H. The H value of the single-layer CNT sheet was 69 W/(m(2) K) which was about twice of aluminum foil in the same environment. As the layers increased, the H values dropped quickly to the same with that of aluminum foil. We also discussed its roles on thermal dissipation, and the results indicated that the convection was a significant way of dissipation when the CNT sheets were applied on macroscales. These results may give us a new guideline to design devices based on the CNT sheets. PMID:24548165
Apparatus for and method of heat transfer
1988-01-01
A heat transfer apparatus is described comprising a closed container enclosing therewithin, a nuclear fission reactor constituting a heat source having a heat transfer surface thereon, means for absorbing heat located apart from the nuclear reactor, and a heat transfer working medium of such quality so as to permit surface film evaporation thereof on the heat transfer surface of the
Heat transfer and thermal control
Crosbie, A.L.
1981-01-01
Radiation heat transfer is considered along with conduction heat transfer, heat pipes, and thermal control. Attention is given to the radiative properties of a painted layer containing nonspherical pigment, bidirectional reflectance measurements of specular and diffuse surfaces with a simple spectrometer, the radiative equilibrium in a general plane-parallel environment, and the application of finite-element techniques to the interaction of conduction and radiation in participating medium, a finite-element approach to combined conductive and radiative heat transfer in a planar medium. Heat transfer in irradiated shallow layers of water, an analytical and experimental investigation of temperature distribution in laser heated gases, numerical methods for the analysis of laser annealing of doped semiconductor wafers, and approximate solutions of transient heat conduction in a finite slab are also examined. Consideration is also given to performance testing of a hydrogen heat pipe, heat pipe performance with gravity assist and liquid overfill, vapor chambers for an atmospheric cloud physics laboratory, a prototype heat pipe radiator for the German Direct Broadcasting TV Satellite, free convection in enclosures exposed to compressive heating, and a thermal analysis of a multipurpose furnace for material processing in space.
Heat transfer in fluidized beds
Borodulya, V.A.; Epanov, Yu.G.; Ganzha, V.L.; Tephtskii, Yu.S.
1986-04-01
Recent research on the combustion and gasification of low-grade solid fuels in a fluidized bed indicates considerable interest in the development of models of external heat transfer in high-temperature beds with a high variation of particle sizes. A schematic diagram is presented of experimental equipment consisting of U-tube manometers; cyclone; coordinate device; heat-transfer probe; valve; blower; and gas distributing grid. The heat-transfer coefficient as a function of the air filtration rate for various locations of the probe in the bed is shown. The expressions used to calculate the average porosity of the bed are presented.
NASA Astrophysics Data System (ADS)
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-07-01
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body.
Sphere Drag and Heat Transfer.
Duan, Zhipeng; He, Boshu; Duan, Yuanyuan
2015-01-01
Modelling fluid flows past a body is a general problem in science and engineering. Historical sphere drag and heat transfer data are critically examined. The appropriate drag coefficient is proposed to replace the inertia type definition proposed by Newton. It is found that the appropriate drag coefficient is a desirable dimensionless parameter to describe fluid flow physical behavior so that fluid flow problems can be solved in the simple and intuitive manner. The appropriate drag coefficient is presented graphically, and appears more general and reasonable to reflect the fluid flow physical behavior than the traditional century old drag coefficient diagram. Here we present drag and heat transfer experimental results which indicate that there exists a relationship in nature between the sphere drag and heat transfer. The role played by the heat flux has similar nature as the drag. The appropriate drag coefficient can be related to the Nusselt number. This finding opens new possibilities in predicting heat transfer characteristics by drag data. As heat transfer for flow over a body is inherently complex, the proposed simple means may provide an insight into the mechanism of heat transfer for flow past a body. PMID:26189698
MODERN DEVELOPMENTS IN MULTIPHASE FLOW & HEAT TRANSFER
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
Rotary Joint for Heat Transfer
NASA Technical Reports Server (NTRS)
Shauback, R.
1986-01-01
Rotary joint exchanges heat between two heat pipes - one rotating and one stationary. Joint accommodates varying heat loads with little temperature drop across interface. According to concept, heat pipe enters center of disklike stationary section of joint. There, wicks in central artery of heat pipe separate into multiple strands that lead to concentric channels on rotaryinterface side of stationary disk. Thin layer of liquid sodium/potassium alloy carries heat from one member of rotary joint to other. Liquid conducts heat efficiently while permitting relative motion between members. Polypropylene rings contain liquid without interfering with rotation.
Electrohydrodynamically enhanced condensation heat transfer
Wawzyniak, Markus
1993-01-01
In a condenser the thickness of the liquid condensate film covering the cooled surface constitutes a resistance to the heat transfer. By establishing a non uniform electric field in the vicinity of the condensation surface the extraction of liquid...
Yilmaz, S.; Palen, J.W.; Taborek, J.
1981-12-01
Single enhanced boiling tubes perform up to an order of magnitude better than single plain tubes, depending strongly on the type of surface and physical properties and operating conditions of the liquid. It is most pronounced at low temperature differences, then decreases and eventually disappears with increase of the temperature difference. The heat flux for a plain tube bundle is considerably greater than that for a single plain tube. Enhanced and finned tube bundles produce appreciable augmentation in heat flux compared to an identical plain tube bundle. The effect usually has most practical significance at low ..delta..T. The augmentation for enhanced tube bundles is less than the augmentation for single tubes, due mainly to the relatively more pronounced convective transfer for plain tubes. Although the cost of enhanced tubes is always higher, their advantage lies not only in smaller units required but, most importantly, that enhanced tubes will produce nucleate boiling at very low temperature differences where plain tubes would not. (Thus, heat recovery is possible in cases which otherwise would have to be rejected). The advantages of enhanced boiling tubes are not only in smaller size of the exchangers, but, in process loops involving compressors, operation of the typical low temperature boiler/condenser at a lower temperature difference, thus resulting in substantial savings in compressor size and energy consumption. Increased application of enhanced boiling surfaces will be realized as less expensive techniques of manufacture become commercially available. Three abstracts are entered separately.
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.
NUCLEAR REACTOR HEAT TRANSFER TECHNOLOGY
Lapides
1961-01-01
Analytical and experimental data are presented on heat transfer by ; various classes of fluids (ordinary fluids, liquid metals, heat generating ; fluids, and boiling liquids) in simple duct geometries. The information is ; applied in an interpretation of tests of fuel element geometries where additional ; problems of assessing flow distribution and fluid mixing are encountered. The ; effects
Battaglia, Francine
. The specific heat of water pc , and the thermal conductivity of the fuel rod fk are constants. The systemSpring 2014 1 Heat Transfer - 1 Consider a cylindrical nuclear fuel rod of length L and diameter df to exist between the surface of the rod and the water. Axial conduction can be neglected in rod and fluid
Enhanced heat transfer using nanofluids
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.
Thermoacoustic convection heat-transfer phenomenon
NASA Astrophysics Data System (ADS)
Parang, M.; Salah-Eddine, A.
1984-07-01
In this paper the results of an experimental investigation of thermoacoustic convection (TAC) heat transfer phenomenon in both zero-gravity and gravity environment are presented and compared with pure conduction heat transfer. The numerical solutions of the governing equations obtained by others for TAC heat transfer phenomenon are also discussed. The experimental results show that for rapid heating rate at a boundary, the contribution of TAC heat transfer to a gas could be significantly (one order of magnitude) higher than heat transfer rate from pure conduction. The results also show significantly reduced transient time in heat transfer processes involving thermoacoustic convective heat transfer mode in both space and gravity environment.
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.
Nanofluid impingement jet heat transfer
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
Examination of Liquid Fluoride Salt Heat Transfer
Yoder Jr, Graydon L
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.
Heat transfer effects on hydropneumatic suspension systems
P. S Els; B Grobbelaar
1999-01-01
One of the problems experienced on hydropneumatic suspension systems, is the effect of temperature change on the spring characteristic, resulting in variations in spring rate and ride height. This problem can be analysed using an appropriate heat transfer model. Two major heat transfer modes are investigated, i.e. heat transfer between the gas and its surroundings and heat transfer between the
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.
Nuclear reactor safety heat transfer
O. C. Jr
1981-01-01
Nuclear Reactor Safety Heat Transfer is presented in five major sections.The first section presents the background material placing nuclear power in perspective. Starting with a historical overview, followed by fundamental concepts of nuclear energy and the philosphy of risk, the first three chapters: give the reader a brief but thorough introduction to nuclear power generation; describe the different types of
Host turbine heat transfer overview
NASA Technical Reports Server (NTRS)
Rohde, J. E.
1984-01-01
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.
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.
Heat and mass transfer in liquid boiling
Suogalev, I.P.
1986-10-01
This paper focuses on boiling in a large volume; calculation of the heat-transfer crisis is discussed. The influence of heater dimensions and liquid heating to the saturation temperature are examined. Heating transfer on boiling and the calculation of the heat-transfer crisis with slow water flow are considered. It is noted that the use of the law of locally turbulent diffusion and well-known physical models permits an analytical description of mass transfer in boiling and leads to the formulas required for practical calculations of heat transfer nad heat-transfer crisis.
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.
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.
Heat Transfer Characteristics of a Generalized Divided Flow Heat Exchanger
Singh, K. P.
1979-01-01
that the off-center nozzle location can be selected judiciously so as to maintain (or even improve heat transfer) while reducing the gross shellside pressure loss. Thus, the pumping costs are minimized without sacrificing heat transfer....
Fouling of heat transfer surfaces
Somerscales, E.F.C. (Rensselaer Polytechnic Inst., Troy, NY (USA))
1990-01-01
The history of the fouling of heat transfer surfaces is reviewed up to 1979. Four epochs of fouling are identified. Particular attention is paid to fouling in steam boilers and steam condensers. The origin of the cleanliness factor and the fouling factor are discussed. The introduction of scientific methods of studying fouling through the model of Kern and Seaton, and the application of models based on fundamental ideas in mass transfer are considered. The paper concludes by drawing attention to the successes in understanding fouling and pointing out the needs for future research.
Combustion, heat transfer and analysis
Not Available
1986-01-01
This book presents papers on diesel engines combustion. Topics considered include combustion control, high-speed photography, visual studies of diesel combustion, swirl chambers, heat insulated turbochargers, direct injection, autoignition, statistical analysis software, particulate emissions, improvements in exhaust gas emissions and cold startability of diesel engines with new injection-rate-control pumps, jet mixing processes, a thermodynamic simulation model, heat transfer in ceramic combustion chamber walls, temperature distribution in a diesel piston, and the application of a variable swirl device to a two-stroke engine.
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.
Debottlenecking using heat transfer enhancement
Polly, G.T.; Gibbard, I. [Cal Gavin Ltd. Process Intensification Engineering, Inc., Alcester (United Kingdom); Pretty, B. [Veritech, Inc., Reston, VA (United States)
1998-05-01
Vertical thermosiphon reboilers (VTRs) and multiple-effect evaporators, used widely in the process industries, are difficult to debottleneck. As a result, process engineers usually wind up buying expensive replacement units when they need to increase VTR or multiple-effect-evaporator throughput. Flow in these units depends on the buoyancy created by vaporization. Flowrate is thus linked not only to heat transfer rate, but also to vaporization and frictional and static pressure loss. Since these factors are closely linked, changing one affects the others. In this article, using a simulation model that has been validated against actual reboiler performance data, the authors show how tube inserts can be used to enhance heat transfer and to debottleneck some of these types of units. They conclude the article by working out a sample debottlenecking for a typical feed-forward, multi-effect evaporator operating at low pressure, using the simulation.
Heat transfer via dropwise condensation on hydrophobic microstructured surfaces
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 ...
Thermodynamics and heat transfer in fire fighting
P. N. Romanenko; Y. A. Koshmarov; M. P. Bashkirtsev
1985-01-01
The book presents the fundamental principles of thermodynamics and heat transfer with particular reference to their application in problems related to fire prevention. Special attention is given to the study of unsteady heat transfer, radiant heat transfer (including radiation from flames to the surrounding), thermodynamic analysis of the growth of fires and theoretical modeling of fires in building.
Thermodynamics and heat transfer in fire fighting
NASA Astrophysics Data System (ADS)
Romanenko, P. N.; Koshmarov, Y. A.; Bashkirtsev, M. P.
1985-05-01
The book presents the fundamental principles of thermodynamics and heat transfer with particular reference to their application in problems related to fire prevention. Special attention is given to the study of unsteady heat transfer, radiant heat transfer (including radiation from flames to the surrounding), thermodynamic analysis of the growth of fires and theoretical modeling of fires in building.
Heat transfer in GTA welding arcs
NASA Astrophysics Data System (ADS)
Huft, Nathan J.
Heat transfer characteristics of Gas Tungsten Arc Welding (GTAW) arcs with arc currents of 50 to 125 A and arc lengths of 3 to 11 mm were measured experimentally through wet calorimetry. The data collected were used to calculate how much heat reported to the cathode and anode and how much was lost from the arc column. A Visual Basic for Applications (VBA) macro was written to further analyze the data and account for Joule heating within the electrodes and radiation and convection losses from the arc, providing a detailed account of how heat was generated and dissipated within the system. These values were then used to calculate arc efficiencies, arc column voltages, and anode and cathode fall voltages. Trends were noted for variances in the arc column voltage, power dissipated from the arc column, and the total power dissipated by the system with changing arc length. Trends for variances in the anode and cathode fall voltages, total power dissipated, Joule heating within the torches and electrodes with changing arc current were also noted. In addition, the power distribution between the anode and cathode for each combination of arc length and arc current was examined. Keywords: Gas Tungsten Arc Welding, GTAW, anode fall, cathode fall, heat transfer, wet calorimetry
Heat exchanger device and method for heat removal or transfer
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.
Heat exchanger device and method for heat removal or transfer
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.
Heat Transfer Research, 2010, Vol. 41, No. 6 Turbine Aero-Heat Transfer Studies
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
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.
Spiraled channels improve heat transfer between fluids
NASA Technical Reports Server (NTRS)
Higa, W.; Wiebe, E. R.
1965-01-01
Spiral flow channels increase heat transfer between two fluids in a countercurrent heat exchanger of given volume. The heat exchanger is constructed by connecting a spiraled bellows-shaped ducting between two concentric cylindrical tubes.
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.
Energy-efficient water heating
1995-01-01
This fact sheet describes how to reduce the amount of hot water used in faucets and showers, automatic dishwashers, and washing machines; how to increase water-heating system efficiency by lowering the water heater thermostat, installing a timer and heat traps, and insulating hot water pipes and the storage tank; and how to use off-peak power to heat water. A resource list for further information is included.
Modeling of Heat Transfer in Geothermal Heat Exchangers
Cui, P.; Man, Y.; Fang, Z.
2006-01-01
/into the ground. This paper summarizes the authors' studies on heat transfer in ground-coupled heat pump systems. Taking the fluid axial convective heat transfer and thermal “short-circuiting” among U-tube legs into account, a quasi-3-D model has been solved...
Cueff, Sebastien; Labbe, Christophe; Cardin, Julien; Doualan, Jean-Louis; Khomenkova, Larysa; Hijazi, Khalil; Rizk, Richard
2010-09-15
This study investigates the influence of the deposition temperature T{sub d} on the Si-mediated excitation of Er ions within silicon-rich silicon oxide layers obtained by magnetron cosputtering. For T{sub d} exceeding 200 deg. C, an efficient indirect excitation of Er ions is observed for all as-deposited samples. The photoluminescence intensity improves gradually up to a maximum at T{sub d}=600 deg. C before decreasing for higher T{sub d} values. The effects of this ''growth-induced annealing'' are compared to those resulting from the same thermal budget used for the ''classical'' approach of postdeposition annealing performed after a room temperature deposition. It is demonstrated that the former approach is highly beneficial, not only in terms of saving time but also in the fourfold enhancement of the Er photoluminescence efficiency.
Evaporation heat transfer and pressure drop of refrigerant R-134a in a plate heat exchanger
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
Handbook of heat transfer applications (2nd edition)
W. M. Rohsenow; J. P. Hartnett; E. N. Ganic
1985-01-01
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
HEAT TRANSFER SYSTEMS FOR NUCLEAR REACTORS
B. Vrillon; R. Roche
1963-01-01
Heat transfer systems for gas-cooled heavy-watermoderated reactors for ; reduction of the detrimental effects of thermal expansion are described. The ; tubular header elements and the portions of the heat-transfer channels leading to ; the headers are arranged so that the headers are kept at low temperature by the ; combined action of an internal heat insulation and of an
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.
Flow characteristics and heat transfer in wavy walled channels
NASA Astrophysics Data System (ADS)
Mills, Zachary; Shah, Tapan; Monts, Vontravis; Warey, Alok; Balestrino, Sandro; Alexeev, Alexander
2013-11-01
Using lattice Boltzmann simulations, we investigated the effects of wavy channel geometry on the flow and heat transfer within a parallel plate heat exchanger. We observed three distinct flow regimes that include steady flow with and without recirculation and unsteady time-periodic flow. We determined the critical Reynolds numbers at which the flow transitions between different flow regimes. To validate our computational results, we compared the simulated flow structures with the structures observed in a flowing soap film. Furthermore, we examine the effects of the wavy channel geometry on the heat transfer. We find that the unsteady flow regime drastically enhances the rate of heat transfer and show that heat exchangers with wavy walls outperform currently used heat exchangers with similar volume and power characteristics. Results from our study point to a simple and efficient method for increasing performance in compact heat exchangers.
Heat-transfer device for heating of extended horizontal objects
Vasil'ev, L.L.; Rabetskii, M.I.; Kiselev, V.G.
1987-07-01
A heat pipe with total separation of vapor and liquid flows is described. The construction allows transfer of high thermal fluxes over a significant distance with horizontal orientation of the object being heated.
Phase change heat transfer device for process heat applications
Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson
2010-01-01
The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and\\/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up
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.
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.
Third heat transfer crisis at subcooling
NASA Astrophysics Data System (ADS)
Avksentyuk, B. P.; Ovchinnikov, V. V.
2008-06-01
The effect of liquid subcooling below the saturation temperature on the third heat transfer crisis was studied experimentally at pool boiling. Experimental data on the threshold values of superheating and heat fluxes, above which the evaporation front and third heat transfer crisis for acetone at subcooling from 0.3 to 10 K are formed, were shown. Formation of evaporation fronts is the necessary, but not sufficient condition for the third heat transfer crisis at subcooling. It was found that formation of a stable vapor film after propagation of condensation fronts over the heater surface is possible at heat fluxes considerably lower than the first critical one.
Boost heat-transfer system performance
Ballard, D.; Manning, W.P. (Coastal Chemical Co. (US))
1990-11-01
The ability to optimize heat-transfer systems is crucial to chemical engineers. Consider, for example, the number and breadth of applications that are affected: reaction vessels for intermediates, resins, and plastics, reboilers for regenerating amines and glycol, dyes and molds for injecting and extruding plastics, regeneration gas for solid desiccants, kilns and driers for wood and resin-impregnated fabrics, cogeneration, waste recovery, sulfur barges, and heavy oils and asphalt. Both design and plant engineers ask if the heat-transfer fluid can transport sufficient heat, if the heat transfer rate is adequate, and how aging of the fluid changes the performance. To answer these questions, a review of some commercially available fluids and their physical properties is given. The authors focus on heat-transfer coefficients at operating temperatures. The heat-transfer fluid system as a whole is examined as well. Several design and equipment options are considered.
HEAT TRANSFER IN WATER COOLED NUCLEAR REACTORS
Randles
1963-01-01
A theoretical study of heat transfer in water-cooled reactors is given ; in two parts, the first of which deals with steady-state heat transfer and the ; second with nonequilibrium conditions. In the part dealing with the steady ; state, the problem solved is that of a fuel rod situated in a neutron flux which ; changes appreciably over the
Radiative heat transfer between dielectric bodies
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.
Phase Change Heat Transfer Device for Process Heat Applications
Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson
2010-10-01
The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up to approx.1300 K) and industrial scale power transport (=50MW), but also due to a potentially large separation distance between the nuclear and industrial plants (100+m) dictated by safety and licensing mandates. The work reported here is the preliminary analysis of two-phase thermosyphon heat transfer performance with alkali metals. A thermosyphon is a thermal device for transporting heat from one point to another with quite extraordinary properties. In contrast to single-phased forced convective heat transfer via ‘pumping a fluid’, a thermosyphon (also called a wickless heat pipe) transfers heat through the vaporization/condensing process. The condensate is further returned to the hot source by gravity, i.e., without any requirement of pumps or compressors. 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. Two-phase heat transfer by a thermosyphon has the advantage of high enthalpy transport that includes the sensible heat of the liquid, the latent heat of vaporization, and vapor superheat. In contrast, single-phase forced convection transports only the sensible heat of the fluid. Additionally, vapor-phase velocities within a thermosyphon are much greater than single-phase liquid velocities within a forced convective loop. Thermosyphon performance can be limited by the sonic limit (choking) of vapor flow and/or by condensate entrainment. Proper thermosyphon requires analysis of both.
[A heat transfer model for liquid cooling garment (LCG) and its analysis].
Zhang, W X; Chen, J S; Li, T Q
2000-10-01
Objective. To establish the heat transfer model for liquid cooling garment (LCG) and, basing on this model, to find the relations between the design parameters and heat removing, as well as that between the design parameters and heat transfer efficiency. Method. Heat transfer process of the LCG was analyzed according to engineering facts. Result. The relations between the design parameters and heat removing, and also that between the design parameters and heat transfer efficiency were interelative and the optimal values of the parameters were essential to the design of LCG. Conclusion. The results might be useful in the design of LCG in extra vehicular activity (EVA) space suit. PMID:11894874
Code Number :.............. HEAT TRANSFER QUALIFYING EXAM
Feeny, Brian
, is perfectly insulated. What is the radiant heat loss from the floor? What is the temperature of the ceilingCode Number :.............. HEAT TRANSFER QUALIFYING EXAM August 2010 OPEN BOOK (only one book consider only the heat exchanges between the thermometer and the water. You should also assume
Influence of internal axial fins on condensation heat transfer in co-axial rotating heat pipes
P. J. Marto; A. S. Wanniarachchi
1987-01-01
The use of a stepped condenser section in a coaxial rotating heat pipe is experimentally demonstrated to yield efficient thermal transport. Turbulence may occur in the condensate film in the case of a smooth-walled cylindrical condenser; vibration may influence the onset of turbulence, and the geometry of the step between evaporator and condenser could affect heat transfer. Straight axial fins
Base fluid in improving heat transfer for EV car battery
NASA Astrophysics Data System (ADS)
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
NASA Astrophysics Data System (ADS)
Jiao, Anjun
The heat pipe, as one of the most efficient heat transport devices, is a peerless choice in the electronic cooling field. In order to better understand the heat transfer mechanisms of the heat pipe, a heat transfer model, which considers the effects of the surface condition, disjoining pressure, gravity force, and contact angle on the thin film profile, heat flux distribution, has been developed. The theoretical analyses showed that the heat transfer in the evaporator could be divided into three templates: CASE I, II, and III with increasing the heat load input. In order to verify the theoretical analysis, experimental investigations of a grooved heat pipe with micro trapezoid wicks, a miniature loop heat pipe with a copper sintered-layer flat evaporator, and a flat heat pipe with the wire core wicks were conducted, respectively. Comparison of the experimental data with theoretical results showed that the model can be used to predict the temperature response in evaporator at low heat load but is invalid at high heat load. The thin film evaporation heat transfer model is successful to address the heat transfer in a cell during the freezing process. In order to obtain ultra-high cooling rate and uniform temperature profiles at cryogenic temperature, one cryogenic oscillating heat pipe with the liquid nitrogen as its working fluid has been developed and experimentally studied. Experimental results showed that its heat transport capability reached 380W with DeltaTAve,e-c = 49°C at charged ratio of 48 percent. At steady state, the amplitude of temperature response in evaporator was smaller than that of condenser while the temperature response kept the same frequency in both evaporator and condenser. The Delta T amplitude between evaporator and condenser decreased with increasing the heat load.
Dynamics of heat transfer between nano systems
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.
Heat transfer in a rotary kiln
Kirslis, S.J.; Watson, J.S.
1989-01-01
An improved heat transfer model has been developed for a direct-fired rotary kiln. The treatment of radiant heat transfer was based on the Reflection Method developed by Succec and applied by Gorog, and was extended to account for radiation from a flame. Some elements of the Resistive Network Method and Zone Method were incorporated in the model. This method results in a more straightforward and flexible treatment of radiant heat transfer than other methods of analysis. The model also accounts for conductive and convective heat transfer within the kiln and heat conducted through the kiln wall and lost from the outer kiln shell to the ambient surroundings. 25 refs., 9 figs., 2 tabs.
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.
Crossflow boiling heat transfer in tube bundles
Hwang, T.H.; Yao, S.C.
1986-09-01
Experimental studies are conducted for two-phase crossflows in horizontal tube bundles at various mass fluxes and local flow qualities. The results are compared with those for a single tube in a channel at two-phase crossflow conditions. The difference between the heat transfer performance for a heated tube in an infinite pool and in a heated or non-heated bundle can be explained in terms of the different flow field geometry and thermal environment.
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...
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 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...
Heat transfer for water ow in trapezoidal silicon microchannels
Qu, Weilin
Heat transfer for water ¯ow in trapezoidal silicon microchannels Weilin Qu, Gh. Mohiuddin Mala to investigate heat transfer characteristics of water ¯owing through trapezoidal silicon microchannels a conjugate heat transfer problem involving simultaneous determination of the temperature ®eld in both
Nanofluids for heat transfer : an engineering approach.
Timofeeva, E. V.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L.
2011-02-28
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties.
Nanofluids for heat transfer: an engineering approach
2011-01-01
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties. PMID:21711700
Thermodynamics of enhanced heat transfer: a model study
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.
Heat-transfer characteristics in tert-butanol dehydration reaction used for heat transport
Kiguchi, Yuji; Watanabe, Takayuki; Kanzawa, Atsushi
1996-07-01
The reaction system of tert-butanol/isobutene/water was considered for use in chemical heat transport. In this study, the heat-transfer characteristics in an endothermic tert-butanol dehydration reaction which occurred in the heat-supply side of this reaction system was investigated. The heat flow was obtained by measuring the reactant composition change and temperature change in the catalyst bed. The heat flow consists of reaction heat, the latent heat of isobutene, and sensible heat in this reaction system. Numerical calculations based on a two-dimensional model were carried out and the results showed good agreement with experiment. It was noticed that the heat flow with chemical reaction was much higher than without reaction. These results indicated that the dehydration reaction promoted the heat-transfer rate, because of the increase in temperature difference between the heating medium and the wall by making use of chemical reaction for a heat transport. The apparent local heat-transfer coefficient with chemical reaction was higher than without reaction. The possibility of a high efficiency heat transport which used this reaction system was suggested.
Heat Transfer in Complex Fluids
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
Passive heat transfer means for nuclear reactors
Burelbach, James P. (Glen Ellyn, IL)
1984-01-01
An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler component operable to heat it. Each heat pipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. Means such as shrouding normally isolated the secondary condensing section from effective heat transfer with the heat sink, but a sensor responds to overheat conditions of the reactor to open the shrouding, which thereby increases the cooling capacity of the heat pipe. By having many such heat pipes, an emergency passive cooling system is defined that is operative without electrical power.
Heat transfer fluids -- too easy to overlook
Green, R.L.; Morris, R.C. [Monsanto Co., St. Louis, MO (United States)
1995-04-01
For process heating, distributed systems that transfer heat indirectly from a central combustion unit are usually preferable to either electrical heating of individual process units or direct fuel-fired heating. For indirect process heating, the engineer can choose either steam or heat transfer fluids (HTFs). The most common HTFs for heating are a variety of organic compounds or mixtures, among them alkylated or benzylated aromatics, hydrogenated and unhydrogenated polyphenyls, modified terphenyls, mixtures of bi and diphenyls and their oxides, and polymethyl siloxanes. Some of these fluids are stable at temperatures high as 750 F. Among other heat transfer fluids are mineral oils, molten nitrate salts, and polyalkylene glycols. Steam is in inherently attractive. It is inexpensive, it displays a high heat-transfer coefficient as it condenses, and it can be generated economically in large boiler plants. On the other hand, its vapor pressure is an order of magnitude larger than that of most organic HTFs. If heat is to be supplied to a process at below about 300 F and the expected temperature variations are not great, steam is widely (and usually rightly) recognized to be the better choice. Similarly, for temperatures above approximately 500 F, HTFs are the widely acknowledged correct option. However, choosing between steam and an HTF for the intermediate, 300--500 F range requires more care -- not only economic evaluation, but also awareness and consideration of a variety of process factors. This paper discusses these factors.
Heat transfer coefficients of shell and coiled tube heat exchangers
Salimpour, M.R. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran)
2009-01-15
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 instruments. Totally, 75 test runs were performed from which the tube-side and shell-side heat transfer coefficients were calculated. Empirical correlations were proposed for shell-side and tube-side. The calculated heat transfer coefficients of tube-side were also compared to the existing correlations for other boundary conditions and a reasonable agreement was observed. (author)
HEAT TRANSFER FOULING PART I -HEAT TRANSFER FOULING
Gudmundsson, Jon Steinar
corrosion and biological growth on the performance of transfer surfaces. Fouling affects both capital) are obtained from design correlations but R (tube wall) from the thermal conductivéty of the tube material
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.
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
Condensation heat transfer in a microgravity environment
NASA Technical Reports Server (NTRS)
Chow, L. C.; Parish, R. C.
1986-01-01
In the present treatment of the condensation heat transfer process in a microgravity environment, two mechanisms for condensate removal are analyzed in light of two problems: (1) film condensation on a flat, porous plate, with condensate being removed by wall suction; and (2) the analytical prediction of the heat transfer coefficient of condensing annular flows, where the condensate film is driven by vapor shear. Both suction and vapor shear can effectively drain the condensate, ensuring continuous operation in microgravity.
Regenerative heat transfer in rotary kilns
J. P. Gorog; T. N. Adams; J. K. Brimacombe
1982-01-01
A mathematical model has been developed to determine the temperature distribution in the wall of a rotary kiln. The model,\\u000a which incorporates a detailed formulation of the radiative and convective heat-transfer coefficients in a kiln, has been employed\\u000a to examine the effect of different kiln variables on both the regenerative and the overall heat transfer to the solids. The\\u000a variables
Heat and mass transfer in materials processing
NASA Astrophysics Data System (ADS)
Tanasawa, Ichiro; Lior, Noam
Various papers on heat and mass transfer in materials processing are presented. The topics addressed include: heat transfer in plasma spraying, structure of ultrashort pulse plasma for CVD processing, heat flow and thermal contraction during plasma spray deposition, metal melting process by laser heating, improved electron beam weld design and control with beam current profile measurements, transport phenomena in laser materials processing, perspectives on integrated modeling of transport processes in semiconductor crystal growth, numerical simulation of natural convection in crystal growth in space and on the earth, conjugate heat transfer in crystal growth, effects of convection on the solidification of binary mixtures. Also discussed are: heat transfer in in-rotating-liquid-spinning process, thermal oscillations in materials processing, modeling and simulation of manufacturing processes of advanced composite materials, reaction engineering principles of combustion synthesis of advanced materials, numerical evaluation of the physical properties of magnetic fluids suitable for heat transfer control, and measurement techniques of thermophysical properties of high temperature melts. (For individual items see A93-10827 to A93-10843)
Heat transfer performance of Al2O3/water nanofluids in a mini channel heat sink.
Dominic, A; Sarangan, J; Suresh, S; Sai, Monica
2014-03-01
The high density heat removal in electronic packaging is a challenging task of modern days. Finding compact, energy efficient and cost effective methods of heat removal is being the interest of researchers. In the present work, mini channel with forced convective heat transfer in simultaneously developing regime is investigated as the heat transfer coefficient is inversely proportional to hydraulic diameter. Mini channel heat sink is made from the aluminium plate of 30 mm square with 8 mm thickness. It has 15 mini channel of 0.9 mm width, 1.3 mm height and 0.9 mm of pitch. DI water and water based 0.1% and 0.2% volume fractions of Al2O3/water nanofluids are used as coolant. The flow rates of the coolants are maintained in such a way that it is simultaneously developing. Reynolds number is varied from 400 to 1600 and heat input is varied from 40 W to 70 W. The results showed that heat transfer coefficient is more than the heat transfer coefficient of fully developed flow. Also the heat transfer is more for nanofluids compared to DI water. PMID:24745233
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.
Improvement of heat transfer by means of ultrasound: Application to a double-tube heat exchanger.
Legay, M; Simony, B; Boldo, P; Gondrexon, N; Le Person, S; Bontemps, A
2012-11-01
A new kind of ultrasonically-assisted heat exchanger has been designed, built and studied. It can be seen as a vibrating heat exchanger. A comprehensive description of the overall experimental set-up is provided, i.e. of the test rig and the acquisition system. Data acquisition and processing are explained step-by-step with a detailed example of graph obtained and how, from these experimental data, energy balance is calculated on the heat exchanger. It is demonstrated that ultrasound can be used efficiently as a heat transfer enhancement technique, even in such complex systems as heat exchangers. PMID:22546297
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.
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.
Nonequilibrium Electromagnetic Fluctuations: Heat Transfer and Interactions
Krueger, Matthias; Kardar, Mehran [Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139 (United States); Emig, Thorsten [Laboratoire de Physique Theorique et Modeles Statistiques, CNRS UMR 8626, Ba circumflex timent 100, Universite Paris-Sud, 91405 Orsay cedex (France)
2011-05-27
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 environment, is at a different temperature. The formalism tracks the radiation from each body and its scatterings by the other objects. We discuss the radiation from a cylinder, emphasizing its polarized nature, and obtain the heat transfer between a sphere and a plate, demonstrating the validity of proximity transfer approximation at close separations and arbitrary temperatures.
Convective heat transfer in external flows
Zhukauskas, A.A.
1988-05-01
Research on convective heat transfer in single-phase external flows, carried out at the Institute of Physical and Technical Problems of Energetics over a broad interval of Reynolds and Prandtl numbers, is described and the principal results are presented. The institute uses a multidisciplinary approach to solve problems relating to the development of power engineering and the design of power plants and heat exchangers. Attention in this paper is focused on the turbulent boundary layer and on the question of heat transfer intensification and rational tube bundle geometry.
Heat transfer coefficients for atmospheric coolers
Robinson, Robert McCollum
1950-01-01
design could be studied. Outside heat trans- fer coefficients were determined for the section under var- ious condit1ons of flowrates and tube row depth. The flow- rates were varied from n1ne gallons per minute to twenty five gallons per minute... and the tube row depth was varied from two to ten tube rows. The outside heat transfer coef- ficients varied from 250 at the lower flowratss to 425 at the higher flowrates and from 360 at ten tube rows to 585 at two tube rows. The overall heat transfer...
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%.
Heat transfer in rocket combustion chambers
NASA Technical Reports Server (NTRS)
Anderson, P.; Cheng, G.; Farmer, R.
1993-01-01
Complexities of liquid rocket engine heat transfer which involve the injector faceplate and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis was used to describe localized heating phenomena associated with particular injector configurations and film coolant flows. These components were analyzed, and the analyses verified when appropriate test data were available. The component analyses are being synthesized into an overall flowfield/heat transfer model. A Navier-Stokes flow solver, the FDNS code, was used to make the analyses. Particular attention was given to the representation of the thermodynamic properties of the fluid streams. Unit flow models of specific coaxial injector elements have been developed and are being used to describe the flame structure near the injector faceplate.
Fluid dynamics at transition regions of enhanced heat transfer channels
NASA Astrophysics Data System (ADS)
Case, Jennifer C.; Pohlman, Nicholas A.
2012-11-01
Helical wire coil inserts are used to enhance heat transfer in high heat flux cooling channels. Past research using temperature probes has sufficiently proven that wire coils increase heat transfer by factors of three to five through the disruption of the boundary layer in the channels. The coils are passive devices that are inexpensive to manufacture and easily integrate into existing heat exchangers given the limited pressure drop they produce. Most of the fluid mechanics research in flow over helical coils has focused on the dynamics and vortex structure in fully developed regions rather than the short transition region where the enhanced heat transfer is often expected. Understanding how the development of the flow occurs over the axial length of the cooling channel will determine minimum dimensions necessary for enhanced heat transfer. Results of particle-shadow velocimetry (PSV) measurements report on the flow velocities and turbulence that occurs in the transition regions at the beginning of wire coil inserts. The ability to relate parameters such as flow rate, wire diameter, coil pitch, and the total tube length will increase fundamental knowledge and will allow for more efficient heat exchanger designs. Funding provided by NIU's Undergraduate Special Opportunities in Artistry & Research grant program.
Modeling microscale heat transfer using Calore.
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Progress in direct numerical simulation of turbulent heat transfer
Kasagi, Nobuhide; Iida, Oaki
1999-07-01
With high performance computers, reliable numerical methods and efficient post-processing environment, direct numerical simulation (DNS) offers valuable numerical experiments for turbulent heat transfer research. In particular, one can extensively study the turbulence dynamics and transport mechanism by visualizing any physical variable in space and time. It is also possible to establish detailed database of various turbulence statistics of turbulent transport phenomena, while systematically changing important flow and scalar field parameters. The present paper illustrates these novelties of DNS by introducing several examples in recent studies. Future directions of DNS for turbulence and heat transfer research are also discussed.
Characteristics of Transient Boiling Heat Transfer
Liu, Wei; Monde, Masanori; Mitsutake, Y.
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)
Heat transfer studies. Quarterly report
Boehm, R.; Chen, Y.T.; Ma, L.
1995-04-20
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 a steady-state heater temperature ({approx}238{degrees}C) close to the constant heater surface temperature used before. What occurs in the air annulus and in the porous medium with the different thermal boundary conditions and water quantities is reported.
Heat transfer in pressurized circulating fluidized beds
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.
Heat transfer 1990. Proceedings of the ninth international heat transfer conference
Hetsroni, G.
1990-01-01
This book contains the proceedings of the Ninth International Heat Transfer Conference. Included in Volume 3 are the following chapters: Refrigerant vapor condensation on a horizontal tube bundle. Local heat transfer in a reflux condensation inside a closed two-phase thermosyphon and surface temperature by means of a pulsed photothermal effects.
Secondary heat transfer circuits for nuclear reactor plant
1977-01-01
A secondary heat transfer circuit for a nuclear reactor comprises a steam generator module, an intermediate heat exchanger, and a pump which circulates a heat transfer liquid, e.g., liquid sodium, between the heat exchanger and steam generator module. The steam generator module includes a central return duct for cold heat transfer liquid and the pump intake is directly connected to
Thermodynamics and Heat Transfer Review
Colton, Jonathan S.
T t T = T = temperature x t = time = thermal diffusivity2l ME 6222: Manufacturing Processes and Systems Prof. J.S. Colton © GIT 2009 4 #12;Thermal Diffusivity ()y ( ) ( )tyconductivik ( ) ( ) ( )heatspecificdensity a 0.5 in. thick plate of copper from T=500oC to T=50oC. · It is cooled such that the heatIt is cooled
NASA Astrophysics Data System (ADS)
Utaka, Yoshio; Saito, Akio; Nakata, Naoki
The objectives of this report are to propose a new method of the high performance cold energy storage using ice as a phase change material and to clarify the heat transfer characteristics of the apparatus of ice cold energy storage based on the proposed principle. A working medium vapor layer a water layer and a working medium liquid layer stratified in this order from the top were kept in an enclosure composed of a condenser, an evaporator and a condensate receiver-and-return tube. The direct contact heat transfers between water or ice and a working medium in an enclosure were applied for realizing the high performance cold energy storage and release. In the storage and release processes, water changes the phase between the liquid and the solid, and the working medium cnanges between the vapor and the liquid with a natural circulation. Experimental apparatus was manufactured and R12 and R114 were selected as working media in the thermal energy storage enclosure. It was confirmed by the measurements that the efficient formation and melting of ice were achieved. Then, th e heat transfer characteristics were clarified for the effects of the initial water height, the initial height of woking medium liquid layer and the inlet coolant temperature.
Active heat transfer enhancement in integrated fan heat sinks
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 ...
M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction
Bahrami, Majid
M. Bahrami ENSC 388 (F09) Steady Conduction Heat Transfer 1 Steady Heat Conduction In thermodynamics, we considered the amount of heat transfer as a system the process takes. In heat transfer, we are more concerned about the rate of heat transfer. The basic
Heat transfer, condensation and fog formation in crossflow plastic heat exchangers
H. J. H. BROUWERSt; Geld van der C. W. M
1996-01-01
In this paper heat transfer of air-water-vapour mixtures in plastic crossflow heat exchangers is studied theoretically and experimentally. First, a model for heat transfer without condensation is derived, resulting in a set of classical differential equations. Subsequently, heat transfer with wall condensation and fog formation are considered in some detail. Separate attention is paid to the heat transfer and condensation
Direct contact heat transfer for thermal energy storage
Wright, J. D.
1980-11-01
Direct contact heat exchange offers the potential for increased efficiency and lower heat transfer costs in a variety of thermal energy storage sytems. SERI models of direct contact heat transfer based on literature information have identified dispersed phase drop size, the mechanism of heat transfer within the drop, and dispersed phase holdup as the parameters controlling direct contact system performance. However, current information is insufficient to predict these factors a priori. Therefore, tests have been defined and equipment constructed to provide independent determination of drop size, heat transfer mechanism, and hold up. In experiments with heptane dispersed in water, the equation of Kagen et. al. was found to most closely predict the drop size. The velocity at which drop formation changes from dropwise to jetting was overpredicted by all literature correlations. Further experiments are needed to conclusively determine whether the salt in a salt hydrate melt acts to block internal circulation. In addition, the potential of low temperature oil/salt hydrate latent heat storage systems is being evaluated in the laboratory.
Radiant heat transfer between nongray directional surfaces.
NASA Technical Reports Server (NTRS)
Fischer, W. D.; Hering, R. G.
1972-01-01
Real surface property effects on local and overall heat transfer are studied for a simple system of interacting opaque surfaces. Wavelength, temperature and directional dependence of surface properties is included in the analysis for equal and unequal temperature specularly reflecting surfaces. Tungsten is employed as a representative metal and Roberts' model is used to describe the wavelength and temperature dependence of its optical parameters. The relationships of electromagnetic theory are employed to describe the directional dependence of spectral properties. Numerical results establish that gray direction independent property analysis adequately predicts the general trends of real surface analysis. The results also establish that spectral and temperature dependence of surface properties influences radiant heat transfer to a greater degree than does directional dependence of properties. Property models which adequately account for the nongray character of engineering surfaces while neglecting directional dependence of properties can provide heat transfer results of acceptable engineering accuracy.
HOST turbine heat transfer program summary
Gladden, H.J.; Simoneau, R.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.
Heat transfer on accreting ice surfaces
NASA Technical Reports Server (NTRS)
Yamaguchi, Keiko; Hansman, R. John, Jr.
1993-01-01
Based on previous observations of glaze ice accretion on aircraft surfaces, a multizone model with distinct zones of different surface roughness is demonstrated. The use of surface roughness in the LEWICE ice accretion prediction code is examined. It was found that roughness is used in two ways: (1) to determine the laminar to turbulent boundary-layer transition location; and (2) to calculate the convective turbulent heat-transfer coefficient. A two-zone version of the multizone model is implemented in the LEWICE code, and compared with experimental convective heat-transfer coefficient and ice accretion results. The analysis of the boundary-layer transition, surface roughness, and viscous flowfield effects significantly increased the accuracy in predicting heat-transfer coefficients. The multizone model was found to significantly improve the ice accretion prediction for the cases compared.
Radiative Heat Transfer between Neighboring Particles
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.
Study of the Heat-Transfer Processes of Tubular Elements of Ground Heat Exchangers
NASA Astrophysics Data System (ADS)
Kusaiynov, K.; Shuyushbayeva, N. N.; Shaimerdenova, K. M.; Nurgalieva, Zh. G.; Omarov, N. N.
2015-06-01
In this paper, consideration is given to the efficiency of utilization of the low-potential heat of the ground. Also, the advantages and distinctive features of polyethylene tubes used in vertical tubular elements of heat pumps are described. This paper gives the results of investigation of the heat transfer of tubular elements of ground heat exchangers. The dependences of the temperature distributions in the ground in the vicinity of a tube and the change in the temperature with time in dry and moist grounds are determined.
Study of the Heat-Transfer Processes of Tubular Elements of Ground Heat Exchangers
NASA Astrophysics Data System (ADS)
Kusaiynov, K.; Shuyushbayeva, N. N.; Shaimerdenova, K. M.; Nurgalieva, Zh. G.; Omarov, N. N.
2015-05-01
In this paper, consideration is given to the efficiency of utilization of the low-potential heat of the ground. Also, the advantages and distinctive features of polyethylene tubes used in vertical tubular elements of heat pumps are described. This paper gives the results of investigation of the heat transfer of tubular elements of ground heat exchangers. The dependences of the temperature distributions in the ground in the vicinity of a tube and the change in the temperature with time in dry and moist grounds are determined.
Heat transfer analysis of boreholes in vertical ground heat exchangers
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
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.
Heat transfer during quenching of gases
NASA Astrophysics Data System (ADS)
Ambraziavichius, A.
Results of theoretical and experimental investigations of gas-side heat transfer of subsonic laminar or turbulent flows of diatomic gases (air or nitrogen) heated to 5000 K in cold-wall pipes are presented. While determining the mixing length, physical parameters which consider local temperatures of the boundary layer were adopted. Thus, the generalized fields of velocities and temperatures in the turbulent region of the boundary layer are identical for both moderate and high gas temperature ranges, and Pr-sub-t may be considered constant and approximately equal to 0.9. The temperature level of gases in turblent flow is shown to insignificantly affect heat transfer equations, provided the physical parameters in the similarity numbers are chosen according to the bulk flow temperature. A calculation technique is developed for heat transfer of dissociated diatomic gases in annular and rectangular channels, in slots, and over bundles of square tubes in cross flow. Also, a relation is shown between the heat transfer coefficient, quenching velocity, and nitrogen oxide concentration in the air exhaust of a nitrogen oxide quenching apparatus.
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-01
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985
Analysis of three-dimensional heat transfer in micro-channel heat sinks
Qu, Weilin
Analysis 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 a simplified means to modeling heat transfer in micro-channel heat sinks, some key assumptions introduced
An experimental study of premixed flame impingement heat transfer
Mizuno, K.; Mital, R.; Viskanta, R.
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.
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.
Noncontact heat transfer between two metamaterials
NASA Astrophysics Data System (ADS)
Joulain, Karl; Drevillon, Jérémie; Ben-Abdallah, Philippe
2010-04-01
Dispersive metamaterials are artificial composite media with magnetodielectric losses so that they naturally radiate in their surrounding. Here we theoretically investigate both radiative and nonradiative heat exchanges between two metamataterials. We show that the presence of magnetic surface modes and the ferromagnetic behavior of materials close to their magnetic resonance yield novel channels for energy transfer. These results pave the way to the design of innovative structures to manage the noncontact heat exchanges.
Handbook of numerical heat transfer
NASA Astrophysics Data System (ADS)
Minkowycz, W. J.; Sparrow, E. M.; Schneider, G. E.; Pletcher, R. H.
A comprehensive presentation is given of virtually all numerical methods that are suitable for the analysis of the various heat transverse and fluid flow problems that occur in research, practice, and university instruction. After reviewing basic methodologies, the following topics are covered: finite difference and finite element methods for parabolic, elliptic, and hyperbolic systems; a comparative appraisal of finite difference versus finite element methods; integral and integrodifferential systems; perturbation methods; Monte Carlo methods; finite analytic methods; moving boundary problems; inverse problems; graphical display methods; grid generation methods; and programing methods for supercomputers.
Heat flux sensors for infrared thermography in convective heat transfer.
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
Self supporting heat transfer element
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.
Combined heat and mass transfer device for improving separation process
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.
Combined heat and mass transfer device for improving separation process
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.
On Radiant Heat Transfer from Turbulent Flames
G. COX
1977-01-01
Turbulent flames fluctuate in temperature and emissivity. This note considers the effect that such fluctuations have on radiation heat transfer. With simplifying assumptions an expression is obtained for the intensity of radiation at a receiver which implies: (a) the instantaneous intensity at the receiver is independent of time; (b) the radiant intensity depends on the fluid dynamics of the flame;
Heat transfer analysis of an inclined radiator
C. W. Somerton; R. D. Bridges; R. W. Callihan; C. Taff
1985-01-01
A series of experiments have been conducted to study the effect of the inclination of an automobile radiative to the incoming air stream on the heat transfer. A heater core was used to model the radiator in the experiments. The heater core was positioned at different angles (0Â° to 60Â°) to the perpendicular for different air flow rates. It was
Heat Transfer in Rectangular Reflective Insulation Systems
B. M. Nebeker; T. W. Tong
1992-01-01
The results of a numerical study on simultaneous natural convection and radiation in air filled vertical rectangular enclosures are presented. A non- partitioned enclosure, one with a non-reflecting partition, and an enclosure with a reflective partition were considered. Heat transfer characteristics were studied for a wide range of the governing parameters. The mean enclosure temperature ranged from 250 to 350
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.
Heat transfer between two degrees of freedom
NASA Astrophysics Data System (ADS)
Hoover, William G.; Craig, Errol; Posch, Harald A.; Holian, Brad Lee; Hoover, Carol G.
1991-10-01
A particularly simple chaotic nonequilibrium open system with two Cartesian degrees of freedom, characterized by two distinct temperatures Tx and Ty, is introduced. The two temperatures are maintained by Nosé-Hoover canonical-ensemble thermostats. Both the equilibrium (no net heat transfer) and nonequilibrium (dissipative) Lyapunov spectra are characterized for this simple system.
A Review of Heat Transfer Physics
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
Heat transfer in a nuclear rocket engine
Konyukhov, G.V.; Petrov, A.I.
1995-02-01
Special features of heat transfer in the reactor of a nuclear rocket engine (NRE) are dealt with. It is shown that the design of the cooling system of the NRE reactor is governed by its stability to small deviations of the parameters from the corresponding calculated values and the possibility of compensating for effects due to nonuniformities and distrubances of various types and scales.
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…
Heat transfer design of an electrophoresis experiment
NASA Astrophysics Data System (ADS)
Clifton, M. J.; Marsal, O.
A mathematical model is presented to represent heat generation and transfer in a free-flow zone electrophoresis apparatus. The model is used to calculate inlet and cooling temperatures designed to minimize temperature variations in the separation compartment. The thermal operating mode has to be chosen so as to be compatible with satellite-based operation.
Heat transfer design of an electrophoresis experiment
NASA Astrophysics Data System (ADS)
Clifton, M. J.; Marsal, O.
1987-10-01
A mathematical model is presented to represent heat generation and transfer in a free-flow zone electrophoresis apparatus. The model is used to calculate inlet and cooling temperatures designed to minimize temperature variations in the separation compartment. The thermal operating mode has to be chosen so as to be compatible with satellite-based operation.
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.
Heat transfer in bioengineering and medicine
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.
Advanced Heat Transfer and Thermal Storage Fluids
Moens, L.; Blake, D.
2005-01-01
The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.
Effects of very high turbulence on heat transfer
NASA Technical Reports Server (NTRS)
Maciejewski, Paul K.; Moffat, Robert J.
1989-01-01
The effects of very high free stream turbulence on heat transfer were investigated experimentally by placing a flat plate, constant temperature heat transfer surface in a large diameter turbulent-free jet. The heat transfer rates measured were two to four times greater than those that would be predicted by accepted correlations for turbulent boundary layers. Thus, rather than establish a particular high turbulence flow field and then measure its effect on heat transfer, search for a flow field with very aggressive heat transfer characteristics and description of the aspects of the free stream turbulence associated with high levels of heat transfer is examined.
Heat Transfer between Graphene and Amorphous SiO2
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.
Ecological performance of an endoreversible Carnot heat engine with complex heat transfer law
Jun Li; Lingen Chen; Fengrui Sun
2011-01-01
The optimal ecological performance of an endoreversible Carnot engine, in which the transfer between the working fluid and the heat reservoirs obeys a complex heat transfer law, including generalized convective heat transfer law and generalized radiative heat transfer law, Q? (? T ), is derived by taking into account an ecological optimization criterion as the objective function, which consists of
Heat transfer in a pulsating heat pipe with open end Yuwen Zhang 1
Zhang, Yuwen
Heat transfer in a pulsating heat pipe with open end Yuwen Zhang 1 , Amir Faghri * Department 11 July 2000; received in revised form 6 June 2001 Abstract Heat transfer in the evaporator and condensation. The heat transfer solutions are applied to the thermal model of the pulsating heat pipe
Dust as a Working Fluid for Heat Transfer Project
NASA Technical Reports Server (NTRS)
Mantovani, James G.
2015-01-01
The project known as "Dust as a Working Fluid" demonstrates the feasibility of a dust-based system for transferring heat radiatively into space for those space applications requiring higher efficiency, lower mass, and the need to operate in extreme vacuum and thermal environments - including operating in low or zero gravity conditions in which the dust can be conveyed much more easily than on Earth.
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.
Some aspects of spacecraft equipment heat transfer technology
NASA Astrophysics Data System (ADS)
Haskin, William L.
1988-06-01
Developments in the study of thermal transfer methods for spacecraft are presented, including slurry transport loops which carry microencapsulated phase change materials, thermal energy units with rapid response capabilities, and ways of predicting two-phase fluid flow patterns and pressure drops. Simulation of two-phase fluid flow at zero gravity allowing for low-cost observations and measurements is discussed. Microencapsulated phase change materials are being used to develop more efficient heat transfer at intermediate loads. Dispersion of metals in phase change heatsinks provides for an enhanced capability for rapid absorption or supply of thermal energy to accommodate pulsed or periodic loads.
Influence of Spacer Systems on Heat Transfer in Evacuated Glazing
NASA Astrophysics Data System (ADS)
Swimm, K.; Weinläder, H.; Ebert, H.-P.
2009-06-01
One attractive possibility to essentially improve the insulation properties of glazing is to evacuate the space between the glass panes. This eliminates heat transport due to convection between the glass panes and suppresses the thermal conductivity of the remaining low pressure filling gas atmosphere. The glass panes can be prevented from collapsing by using a matrix of spacers. These spacers, however, increase heat transfer between the glass panes. To quantify this effect, heat transfer through samples of evacuated glazing was experimentally determined. The samples were prepared with different kinds of spacer materials and spacer distances. The measurements were performed with a guarded hot-plate apparatus under steady-state conditions and at room temperature. The measuring chamber of the guarded hot plate was evacuated to < 10-2 Pa. An external pressure load of 0.1 MPa was applied on the samples to ensure realistic system conditions. Radiative heat transfer was significantly reduced by preparing the samples with a low- ? coating on one of the glass panes. In a first step, measurements without any spacers allowed quantification of the amount of radiative heat transfer. With these data, the measurements with spacers could be corrected to separate the effect of the spacers on thermal heat transfer. The influence of the thermal conductivity of the spacer material, as well as the distance between the spacers and the spacer geometry, was experimentally investigated and showed good agreement with simulation results. For mechanically stable matrices with cylindrical spacers, experimental thermal conductance values ?0.44W·m-2 ·K-1 were found. This shows that U g -values of about 0.5W · m-2 · K-1 are achievable in evacuated glazing, if highly efficient low-emissivity coatings are used.
Radiative heat transfer in plastic welding process
NASA Astrophysics Data System (ADS)
Kurosaki, Yasuo
2005-06-01
This paper deals with a novel CO2 laser plastic welding procedure developed from the point of view of heat transfer containing simultaneous radiation and conduction processes and also gives a brief review of plastic welding development to date. The principle and features are shown by both the experiments using CO2 laser as a radiation source and numerical simulation considering heat transfer phenomena in simultaneous radiation and conduction in welding process. The feasibility of the proposed procedure is confirmed by applying the overlapped same plastic films with combination of infrared radiation absorbing heating and thermal diffusion cooling processes. A solid material transparent to infrared radiation with a high thermal diffusivity is used as a heat sink in contact with the irradiated surface of overlapped thermoplastics during radiation heating. The procedure is able to achieve both high welding strength and excellent surface appearance without causing surface thermal damage as often suffered in conventional direct infrared radiation welding process. In addition, pigmentation in welding material to increase absorption of radiation is unnecessary for this method.
Regenerative heat transfer in rotary kilns
NASA Astrophysics Data System (ADS)
Gorog, J. P.; Adams, T. N.; Brimacombe, J. K.
1982-06-01
A mathematical model has been developed to determine the temperature distribution in the wall of a rotary kiln. The model, which incorporates a detailed formulation of the radiative and convective heat-transfer coefficients in a kiln, has been employed to examine the effect of different kiln variables on both the regenerative and the overall heat transfer to the solids. The variables include rotational speed, pct loading, temperature of gas and solids, emissivity of wall and solids, convective heattransfer coefficients at the exposed and covered wall, and thermal diffusivity of the wall. The model shows that the regenerative heat flow is most important in the cold end of a rotary kiln, but that generally the temperature distribution and heat flows are largely independent of these variables. Owing to this insensitivity it has been possible to simplify the model with the aid of a resistive analog. Calculations are presented indicating that both the shell loss and total heat flow to the bed may be estimated to within 5 pct using this simplified model.
Heat transfer characteristics of tube bundles during boiling in vacuum
NASA Astrophysics Data System (ADS)
Slesarenko, V. N.; Zakharov, G. A.
1992-06-01
Heat transfer during boiling in vacuum was compared experimentally for single tubes, rows of tube, and tube bundles to analyze characteristic properties of vaporization under such conditions. Relations for calculating heat transfer coefficients are proposed.
Heat transfer during film condensation of potassium vapor
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 ...
Nanofluid heat transfer enhancement for nuclear reactor applications
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, ...
Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)
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.
Survey of heat transfer to near critical fluids
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Simoneau, R. J.; Smith, R. V.
1971-01-01
Survey topics include - heat transfer boundaries of near critical region, free, natural, and forced convection experiments, oscillations, geometric effects, parameters which appear to be significant to heat transfer in critical region, and theories which have been proposed for region.
Heat Transfer Problems of Mixed Refrigerants
NASA Astrophysics Data System (ADS)
Fujii, Tetsu; Koyama, Shigeru; Goto, Masao; Takamatsu, Hiroshi
From the point of view of the application of non-azeotropic mixed refrigerants to heat pump and refrigeration cycles, literatures on condensation and evaporation are surveyed and future problems to be studied are extracted. All researches on the relevant problems are recently started and still in developing way except for condensation on a single horizontal tube. Particularly, the studies for condensation and evaporation of mixed Freon refrigerant in a horizontal tube, which are the most important in practice, are far backward in comparison with single component refrigerant in every point of heat transfer characteristics, flow pattern and theoretical analysis.
Handbook of heat transfer fundamentals (2nd edition)
NASA Astrophysics Data System (ADS)
Rohsenow, W. M.; Hartnett, J. P.; Ganic, E. N.
Recent advances in heat transfer are discussed, providing data and methodology to solve a wide range of heat transfer problems. The topics considered include: basic concepts of heat transfer, mathematical methods, thermophysical properties, conduction, numerical methods in heat transfer, natural convection, and internal duct flow and external flows in forced convection. Also addressed are: rarefied gases, electric and magnetic fields, condensation, boiling, two-phase flow, and radiation.
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.
Various methods to improve heat transfer in exchangers
NASA Astrophysics Data System (ADS)
Pavel, Zitek; Vaclav, Valenta
2015-05-01
The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.
A diffuser heat transfer and erosion code
NASA Astrophysics Data System (ADS)
Buzzard, G. H.
1985-10-01
A computer code for diffuser heat transfer and erosion analysis (DHTE) has been developed which improves upon the earlier Rocket Engine Diffuser Thermal Analysis Program (REDTAP). Improvements contained within DHTE include provision for a radial temperature gradient within the diffuser wall, an improved model for the particle impingement accommodation coefficient, a model for particle debris shielding, and a model for wall erosion by particle impact. DHTE differs from an earlier diffuser heat transfer code (DHT) to the extent that it incorporates a simple erosion model and utilizes a more recent diffuser version of the JANNAF Standardized Plume Flow Field Model (SCP2ND). The 77-inch diffuser was instrumented to record the water side wall temperature and water jacket temperature at selected sites along the initial seven feet of the diffuser during routine test firings. Data is presented that supports the predictions of DHTE but is inadequate to validate the code.
Acquisition systems for heat transfer measurement
De Witt, R.J.
1983-01-01
Practical heat transfer data acquisition systems are normally characterized by the need for high-resolution, low-drift, low-speed recording devices. Analog devices such as strip chart or circular recorders and FM analog magnetic tape have excellent resolution and work well when data will be presented in temperature versus time format only and need not be processed further. Digital systems are more complex and require an understanding of the following components: digitizing devices, interface bus types, processor requirements, and software design. This paper discusses all the above components of analog and digital data acquisition, as they are used in current practice. Additional information on thermocouple system analysis will aid the user in developing accurate heat transfer measuring systems.
Low-melting point heat transfer fluid
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.
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.
Computer graphics in heat-transfer simulations
Hamlin, G.A. Jr.
1980-01-01
Computer graphics can be very useful in the setup of heat transfer simulations and in the display of the results of such simulations. The potential use of recently available low-cost graphics devices in the setup of such simulations has not been fully exploited. Several types of graphics devices and their potential usefulness are discussed, and some configurations of graphics equipment are presented in the low-, medium-, and high-price ranges.
Radiative heat transfer in rotary kilns
J. P. Gorog; J. K. Brimacombe; T. N. Adams
1981-01-01
Radiative heat transfer between a nongray freeboard gas and the interior surfaces of a rotary kiln has been studied by evaluating\\u000a the fundamental radiative exchange integrals using numerical methods. Direct gas-to-surface exchange, reflection of the gas\\u000a radiation by the kiln wall, and kiln wall-to-solids exchange have been considered. Graphical representations of the results\\u000a have been developed which facilitate the determination
An Exploration of Viral Transfer Efficiency Factors
NASA Astrophysics Data System (ADS)
Tamayo, F. J.; Julian, T.; Boehm, A.
2008-12-01
Viruses exist on common household surfaces and persist on them (Abad 1994, Rusin 2002). In addition to this, they are able to transfer from surface to surface, and when in contact with humans, can cause illness. In a previous study, we were able to test out the transfer efficiencies of three different phages. Transfer efficiency is defined as follows: Transfer Efficiency: Phage recovered from surface 2 / (Phage recovered from surface 2 + Phage recovered from surface 1) The phages tested have similar size and shape, but vary in isoelectric points and route of infection (Maier 2000). Preliminary studies have suggested that the transfer efficiencies for each phage may be different. Because of this, we are investigating what is the cause of this difference in phage transfer. Two possibilities for these differences are the phage's properties and the cotton tip swab elution from each surface. Using the statistical method known as the student t-test and the experimental methods for phage elution and a double agar overlay phage enumeration, we examined whether the cotton tip swab elution was responsible for phage transfer differences.
Heat transfer of finned tube bundles in crossflow
Stasiulevicius, J.; Skrinska, A.; Zukauskas, A.
1988-01-01
This volume correlates findings on heat transfer and hydraulic drag of bundles of finned tubes in crossflow at Reynolds numbers from 10/sup 4/ to 10/sup 6/. These studies illustrate fin, local, and mean heat transfer coefficients; effects of geometric parameters of the fins; effect of tube location within the bundle on heat transfer and hydraulic drag; and resistance of finned tube bundles.
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...Control Systems § 153.430 Heat transfer systems; general. Each cargo...manual regulation of the system's heat transfer rate. [CGD 73-96, 42...
Proceeding of the 1st International Forum on Heat Transfer
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
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...Control Systems § 153.430 Heat transfer systems; general. Each cargo...manual regulation of the system's heat transfer rate. [CGD 73-96, 42...
STEADY STATE LIQUID CRYSTAL THERMOGRAPHY AND HEAT TRANSFER MEASUREMENTS ON
Camci, Cengiz
Chapter V STEADY STATE LIQUID CRYSTAL THERMOGRAPHY AND HEAT TRANSFER MEASUREMENTS ON SURFACES Composite Heat Transfer Surface Liquid Crystal Image Processing Technique V . 4 Experimental Results and Discussion Test Conditions and Data Analysis Application to Endwall Heat Transfer Problem Further Application
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...
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...
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...
Film-Cooling Heat-Transfer Measurements Using Liquid Crystals
NASA Technical Reports Server (NTRS)
Hippensteele, Steven A.
1997-01-01
The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.
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…
An experimental study of the flow and heat transfer between enhanced heat transfer plates for PHEs
Li, Xiao-wei [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Meng, Ji-an; Li, Zhi-xin [School of Aerospace, Tsinghua University, Beijing 100084 (China)
2010-11-15
The flow and heat transfer between inclined discrete rib plates for plate heat exchangers have been experimentally studied. Dye injection method is used to visualize the flow structures. The visualization results show that front vortex, rear vortex and main vortex are formed between the plates. The rib parameter influence is also studied using visualization method. The pressure drop and heat transfer between the inclined discrete rib plates as well as that between inclined continuous rib plates and smooth plates are also measured. The measured results show that the inclined discrete rib plate can enhanced heat transfer 20-25% at the same pumping power compared with the commonly used inclined continuous rib plates. (author)
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.
HOST turbine heat transfer subproject overview
NASA Technical Reports Server (NTRS)
Gladden, Herbert J.
1986-01-01
The experimental part of the turbine heat transfer subproject consists of six large experiments, which are highlighted in this overview, and three of somewhat more modest scope. One of the initial efforts was the stator airfoil heat transfer program. The non-film cooled and the showerhead film cooled data have already been reported. The gill region film cooling effort is currently underway. The investigation of secondary flows in a 90 deg curved duct, was completed. The first phase examined flows with a relatively thin inlet boundary layer and low free stream turbulence. The second phase studied a thicker inlet boundary layer and higher free stream turbulence. A comparison of analytical and experimental cross flow velocity vectors is shown for the 60 deg plane. Two experiments were also conducted in the high pressure facility. One examined full coverage film cooled vanes, and the other, advanced instrumentation. The other three large experimental efforts were conducted in a rotation reference frame. An experiment to obtain gas path airfoil heat transfer coefficients in the large, low speed turbine was completed. Single-stage data with both high and low-inlet turbulence were taken. The second phase examined a one and one-half stage turbine and focused on the second vane row. Under phase 3 aerodynamic quantities such as interrow time-averaged and rms values of velocity, flow angle, inlet turbulence, and surface pressure distribution were measured.
Energy transfer simulation for radiantly heated and cooled enclosures
Chapman, K.S.; Zhang, P.
1996-11-01
This paper presents the development of a three-dimensional mathematical model to compute heat transfer within a radiantly heated or cooled room, which then calculates the mass-averaged room air temperature and the wall surface temperature distributions. The radiation formulation used in the model accommodates arbitrary placement of walls and objects within the room. The convection model utilizes Nusselt number correlations published in the open literature. The complete energy transfer model is validated by comparing calculated room temperatures to temperatures measured in a radiantly heated room. This three-dimensional model may be applied to a building to assist the heating/cooling system design engineer in sizing a radiant heating/cooling system. By coupling this model with a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater/cooler location. In addition, obstacles such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the radiant heating system performance.
Fluctuating-surface-current formulation of radiative heat transfer for arbitrary geometries
Rodriguez, Alejandro W.
We describe a fluctuating-surface-current formulation of radiative heat transfer, applicable to arbitrary geometries in both the near and far field, that directly exploits efficient and sophisticated techniques from the ...
Fluctuating-surface-current formulation of radiative heat transfer: Theory and applications
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 ...
Heat and mass transfer in bubble column dehumidifiers for HDH desalination
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 ...
Visualization study on pool boiling heat transfer
NASA Astrophysics Data System (ADS)
Kamei, Shuya; Hirata, Masaru
1991-04-01
The visualized boiling phenomena were observed by means of high speed photographic shadowgraphy using a rotating prism camera (nac HIGH SPEED CAMERA model-16HD) with the speed of about 3500 frames per second. The photographs show that pool boiling heat transfer phenomena are varied for the boiling curve based on the experiments. Experiments have been carried out to investigate pool boiling heat transfer phenomena on a horizontal thin filament in subcooled and saturated distilled water. The experiments were performed for atmospheric pressure,for filament diameters of about 0.3 mm, for region of natural convection to film boiling. The color-film made by high speed movie camera are converted to high speed color video-tape. It is convenient to edit and show the tape for visualization with teaching the students. The high speed color video showed that the successive motion and shape of bubbles during their process of detachment varied with increasing heat flux on the heated surface of a filament. From these results, it was confirmed that the high speed phenomena of boiling by the slow motion video pictures could be estimated clearly.
Heat Transfer Operators Associated with Quantum Operations
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.
Liquid metal heat exchanger for efficient heating of soils and geologic formations
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.
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%.
HEAT TRANSFER IN STEADY-PERIODIC FLOWS OVER HEATED S. Yesilyurt, M. Ozcan, G. Goktug
Yanikoglu, Berrin
HEAT TRANSFER IN STEADY-PERIODIC FLOWS OVER HEATED MICROWIRES S. Yesilyurt, M. Ozcan, G. Goktug frequency (Srp) and amplitude of y- oscillations in the flow on the heat transfer coefficient and its traveling with a range of phase velocities and frequencies. Heat transfer in oscillatory flows at high
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.
A Model of Respiratory Heat Transfer in a Small Mammal
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
Heating systems to maximise efficiency.
House, Jeff
2013-09-01
Jeff House, marketing and applications manager, Baxi Commercial, identifies some of the heating options available to the operators of healthcare facilities, and highlights practical examples of successful applications. PMID:24138002
NASA Astrophysics Data System (ADS)
Chen, Kaifeng; Santhanam, Parthiban; Fan, Shanhui
2015-08-01
We consider a near-field thermophotovoltaic device with metal as the emitter and semiconductor as the photovoltaic cell. We show that when the cell is a III-V semiconductor, such as GaSb, parasitic phonon-polariton heat transfer reduces efficiency in the near-field regime, especially when the temperature of the emitter is not high enough. We further propose ways to avoid the phonon-polariton heat transfer by replacing the III-V semiconductor with a non-polar semiconductor such as Ge. Our work provides practical guidance on the design of near-field thermophotovoltaic systems for efficient harvesting of low-quality waste heat.
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.
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.
Heat-transfer microstructures for integrated circuits
Tuckerman, D.B.
1984-02-01
Convective heat-transfer theory indicates that well over 1000 W/cm/sup 2/ can be compactly removed from ICs at normal operating temperatures, provided microscopic (e.g., 50-..mu..m wide) extended-surface structures are used. The difficulty of constructing high-conductance, low-stress thermal interfaces between ICs and heat sinks suggests the use of an integral heat sink. Accordingly, IC microfabrication techniques were employed to design, fabricate, and test novel, ultracompact water-cooled, laminar-flow, optimized plate-fin and pin-fin heat sinks directly within standard-thickness silicon substrates. Worst-case thermal resistances as low as 0.083/sup 0/C/W were measured from 1-cm/sup 2/ thin-film resistors. The use of integral liquid-cooled heat sinks in multichip systems presents potential yield, reliability, cost and packaging problems. Attachment of unmodified ICs to micro-heat sinks seems a more attractive approach. A novel die-attachment technique has been developed which avoids the problems of conventional attachments. In this technique, a liquid partially fills an array of micron-wide reentrant capillaries in the heat sink substrate, so that surface tension holds the polished back of an IC in intimate thermal contact with the heat sink. The bond is void-free, virtually stress-free, long-lived, and allows repeated detachment and replacement of ICs without damaging the heat sink substrate. The reentrant grooves were fabricated by a noval process using electroless plating of nickel onto vertical silicon microgrooves. For a 1-cm/sup 2/ area, typical interfacial thermal resistances of 0.022/sup 0/C/W at 300 W have been measured. In summary, microfabrication techniques have been employed to fabricate new, very high-performance liquid-cooled heat sinks having negligible volume (0.1 cm/sup 3/), and also to make a novel, stress-free, reusable microcapillary thermal interface between such heat sinks and integrated circuit substrates.
Heat Transfer Characterization Using Heat and Solute Tracer Tests in a Shallow Alluvial Aquifer
NASA Astrophysics Data System (ADS)
Dassargues, A.
2013-12-01
Very low enthalpy geothermal systems are increasingly considered for heating or cooling using groundwater energy combined with heat pumps. The design and the impact of shallow geothermal systems are often assessed in a semi-empirical way. It is accepted by most of the private partners but not by environmental authorities deploring a lack of rigorous evaluation of the mid- to long-term impact on groundwater. In view of a more rigorous methodology, heat and dye tracers are used for estimating simultaneously heat transfer and solute transport parameters in an alluvial aquifer. The experimental field site, is equipped with 21 piezometers drilled in alluvial deposits composed of a loam layer overlying a sand and gravel layer constituting the alluvial aquifer. The tracing experiment consisted in injecting simultaneously heated water and a dye tracer in a piezometer and monitoring evolution of groundwater temperature and tracer concentration in 3 control panels set perpendicularly to the main groundwater flow. Results showed drastic differences between heat transfer and solute transport due to the main influence of thermal capacity of the saturated porous medium. The tracing experiment was then simulated using a numerical model and the best estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale. On the field: view from the injection well in direction of the pumping well through the three monitoring panels Temperature monitoring in the pumping well and in the piezometers of the three panels: heat transfer is faster in the lower part of the aquifer (blue curves) than in the upper part (red curves). Breakthrough curves are also more dispersed in the upper part with longer tailings.
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.
Effects of winglets to augment tube wall heat transfer in louvered fin heat exchangers
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
Clark, G.L. Jr.; Clausing, A.M.; Mueller, M.H.; Weiner, J.G.; Kempka, S.N.
1980-01-01
The UIUC Cryogenic Heat Transfer Tunnel was built to exploit the spectacular gains in Reynolds and Grashof numbers which occur when convective experiments are performed at cryogenic temperatures. The program was motivated by the need to predict the convective loss from external solar thermal-electric receivers which will typically operate in the combined convection regime with Reynolds numbers above 10/sup 6/ and Grashof numbers exceeding 10/sup 11/. The tunnel facility is currently operational and forced convection heat transfer data have been taken from a vertical cylinder in cross-flow. The results of these validation tests indicate that the heat transfer coefficients measured are completely dependent upon the traditional non-dimensional parameters of forced convection.
Parametric study of boiling heat transfer in horizontal tube bundles
Hsu, J.T.
1987-01-01
Boiling heat transfer outside a section of a uniformly heated horizontal tube bundle in an upward crossflow was investigated using R-113 as the working fluid. Two in-line tube bundles with pitch-to-diameter ratios of 1.3 and 1.7 were tested. Each tube bundle had five columns and 27 rows. Heat transfer coefficients obtained from 14 instrumented tubes are reported for a variety of flow conditions. The effects of heat flux, mass velocity, pressure and pitch-to-diameter ratio of the heat transfer coefficient were determined. At high heat fluxes there was no significant variation in the heat transfer coefficient in the tube bundle. However, at low heat fluxes and mass velocities, the heat transfer coefficient increased at positions higher in the tube bundle. As pressure and mass velocity increased so did the heat transfer coefficients. The tube bundle with the larger pitch-to-diameter ration had higher heat transfer coefficients than the smaller test section at low heat fluxes. However, the differences decreased as heat flux increased. A Chen-type correlation was developed, with an S factor and an F factor being described for tube bundles, for the prediction of local tube-averaged heat transfer coefficients.
Transectional heat transfer in thermoregulating bigeye tuna (Thunnus obesus) - a 2D heat flux model.
Boye, Jess; Musyl, Michael; Brill, Richard; Malte, Hans
2009-11-01
We developed a 2D heat flux model to elucidate routes and rates of heat transfer within bigeye tuna Thunnus obesus Lowe 1839 in both steady-state and time-dependent settings. In modeling the former situation, we adjusted the efficiencies of heat conservation in the red and the white muscle so as to make the output of the model agree as closely as possible with observed cross-sectional isotherms. In modeling the latter situation, we applied the heat exchanger efficiencies from the steady-state model to predict the distribution of temperature and heat fluxes in bigeye tuna during their extensive daily vertical excursions. The simulations yielded a close match to the data recorded in free-swimming fish and strongly point to the importance of the heat-producing and heat-conserving properties of the white muscle. The best correspondence between model output and observed data was obtained when the countercurrent heat exchangers in the blood flow pathways to the red and white muscle retained 99% and 96% (respectively) of the heat produced in these tissues. Our model confirms that the ability of bigeye tuna to maintain elevated muscle temperatures during their extensive daily vertical movements depends on their ability to rapidly modulate heating and cooling rates. This study shows that the differential cooling and heating rates could be fully accounted for by a mechanism where blood flow to the swimming muscles is either exclusively through the heat exchangers or completely shunted around them, depending on the ambient temperature relative to the body temperature. Our results therefore strongly suggest that such a mechanism is involved in the extensive physiological thermoregulatory abilities of endothermic bigeye tuna. PMID:19880733
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.
Heat transfer measurements of internally finned rotating heat pipes
NASA Astrophysics Data System (ADS)
Nefesoglu, A.
1983-12-01
A rotating cylindrical heat pipe was tested using various internally finned condensers and was compared with a smooth-wall cylinder. Each condenser was tested at rotational speeds of 700, 1400 and 2800 rpm with film condensation. Distilled water was used as the working fluid. The heat transfer rate of each condenser was plotted versus the driving temperature difference between the vapor saturation temperature and the cooling water inlet temperature. The objective of this investigation was to study the performance with various fin configurations and to find an optimum fin geometry. As expected, in all cases, performance was improved with increasing rpm. The performance of internally finned condensers was found to be as much as 230 percent greater than that of the smooth condenser.
Mass transfer in oscillating flows: Efficient drying via pulse combustors
NASA Astrophysics Data System (ADS)
Arpaci, V. S.; Gemmen, R.; Selamet, A.
1990-04-01
Analytical and experimental methods are addressed for increasing industrial and home drying efficiency via pulse combustors. A fundamental scientific methodology is being developed for the momentum, heat, and mass transfer in oscillating (on the mean) turbulent flows. The approach follows the intuitive ideas of Taylor and Kolmogorov on the construction of microscales of turbulence. A parallel experimental program was carried out by the pulse combustor of the Continuous Combustion Lab of Sandia-Livermore National Labs. A droplet sizing technique and a quasi-steady computer model were developed. The unsteady analytical model determines the range of the quasi-steady model and provides also a mass transfer correlation beyond this range. The scales of mass transfer in oscillating turbulent flows were developed. A mass transfer correlation based on these scales was proposed. The correlation agrees well with the results so far obtained in the experimental program.
Advances in refrigeration and heat transfer engineering
Bansal, Pradeep; Cremaschi, Prof. Lorenzo
2015-01-01
This special edition of Science and Technology for the Built Environment (STBE) presents selected high quality papers that were presented at the 15th International Refrigeration and Air Conditioning Conference held at Purdue University during July 14-17 2014. All papers went through the additional review before being finally accepted for publication in this special issue of Science and Technology and the Built Environment. Altogether 20 papers made to this special issue that cover a wide range of topics, including advancements in alternative refrigerants, heat exchangers/heat transfer, nano-fluids, systems design and optimization and modeling approaches. Although CO2 may perhaps have been the most researched and popular refrigerant in the past decade, R32 is being seriously considered lately as an alternative and environmentally friendly refrigerant for small systems due to its low Global Warming Potential (GWP).
Convective Heat Transfer in Acoustic Streaming Flows
NASA Astrophysics Data System (ADS)
Gopinath, Ashok
1992-01-01
Convective heat transfer due to acoustic streaming has been studied in the absence of an imposed mean flow. The work is motivated by the need to design and control the thermal features of a suitable experimental rig for the containerless processing of materials by heat treatment of acoustically levitated alloy samples at near zero-gravity. First the problem of heat transfer from an isolated sphere (in a standing sound field) is explored in detail. The streaming Reynolds number, Rs, which characterizes the resulting steady flows, is determined from the acoustic signal. A scale analysis is used to ascertain the importance of buoyancy and viscous dissipation. The steady velocity and temperature fields are determined using asymptotic techniques and numerical methods for the limiting cases of Rs<<1 and Rsgg1. Working correlations for the average Nusselt number are obtained for a wide range of Prandtl numbers. A simple experiment is conducted to verify the predictions for the more relevant case of Rsgg1. The acoustic levitation chamber itself is modelled as a Kundt tube (supporting a plane axial standing sound wave) with insulated side-wall and isothermal end-walls. Analytical solution techniques are used to determine the steady fields close to the tube walls. For the steady recirculatory transport in the core, the numerical solver PHOENICS is adopted for the solution of the complete elliptic form of the governing equations. A study of the effects of a range of acoustic and geometric parameters on the flow and heat transfer is performed and Nusselt number correlations are obtained for air. PHOENICS is also used to study the effects of variable fluid properties and axial side-wall conduction (coupled with radiation). The role of normal/reduced gravity is assessed and suggestions made for terrestrial testing of the levitation apparatus. Finally, with the sample located at a node in the levitation chamber, the effect of the interaction of the streaming flows (on the sphere and the tube walls) is estimated. Representative calculations for the sample heating/cooling rates are presented and compared with existing data in the literature.
Heat transfer to impacting drops and post critical heat flux dispersed flow
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 ...
Study and Analysis of Heat Transfer Limitation of Separated Heat Pipe
NASA Astrophysics Data System (ADS)
Mou, Qizheng; Mou, Kai
2002-01-01
satellite and spacecraft. evaporator, heat isolation and condenser along the axial direction. The working fluid absorbs heat and evaporates in evaporator, and then the vapor flows to condenser and gives out heat. The condensed liquid is pumped to evaporator by wick. By the circulation, the heat can by transferred continuously. heat pipe as follow: - Vapor-liquid two phase flow inside pipe; - The manner of latent heat to transfer heat; - Automatic circulation by working fluid flowing - A certain extent of vacuum. and the traditional heat pipe, that is, the vapor fluid and liquid fluid flow along the same direction. So it is obviously that the separated heat pipe has special internal heat transfer characteristic and crisis. This paper has regard for the heat transfer crisis of the separated heat pipe, and meanwhile relevant calculation and analysis have been done. 1. FLOW TYPE OF THE WORKING FLUID IN SEPARATED HEAT PIPE 2. HEAT TRANSFER CRISIS IN THE EVAPORATOR 3. CARRYING PHENOMENON INSIDE SEPARATED HEAT PIPE 4. THE STAGNANT FLOW PHENOMENON AND THE BACKWARD FLOW PHENOMENON IN EVAPORATOR CONCLUSION transfer limitation of location burn-out, and the heat transfer limitation of flow unconventionality in erective pipe. The carrying phenomenon can occurs not only in evaporator but also in condenser of separated heat pipe. It is in the evaporator that should take place the heat transfer limitation of liquid film dry-out at first. Then with the increasing of heat flux, the heat transfer limitation of location burn-out would happen. In order to avoid the heat transfer limitation of flow unconventionality in erective pipe, the length and diameter of the outflow tube and inflow tube must be reasonably calculated to control the flow velocity of the working fluid inside pipe. Key words:Separated Heat PipeHeat Transfer LimitationDry-OutCarryingStagnancy
Thermal coherent sets and heat transfer in chaotic laminar flows
NASA Astrophysics Data System (ADS)
Naik, Shibabrat; Grover, Piyush
2013-11-01
The relation between the chaotic nature of the advection flow field and heat transfer in laminar flow heat exchangers is known to be subtle. We use the Perron-Frobenius transfer operator approach to analyze thermal transport in a coiled tube with 3D laminar flow and Dirichlet thermal boundary condition. The usual advection-only transfer operator is combined with a finite-difference diffusion operator via an operator-splitting technique. We compute various coherent sets of this approximate advection-diffusion operator. These coherent sets correspond to the important ``thermal structures'' which govern the heat transfer in this problem. This analysis gives an insight into the effect of chaotic advection field on the heat transfer performance of such devices. We study the dependence of heat transfer enhancement factor on Peclet number.This transfer operator based analysis could lead to systematic geometric optimization of micrometer sized heat exchangers.
Boiling local heat transfer enhancement in minichannels using nanofluids.
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
Efficiency bounds for nonequilibrium heat engines
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.
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.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, Michael J. (Richmond, CA); Rubenstein, Francis M. (Berkeley, CA); Whitman, Richard E. (Richmond, CA)
1992-01-01
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.
A novel infrared thermography heat transfer measurement technique
NASA Astrophysics Data System (ADS)
Eppich, Henry M.; Kreatsoulas, John C.
1989-01-01
This paper presents results of proof-of-concept experiments for a nonintrusive diagnostic technique capable of rapid measurement of convective heat transfer distributions over broad surface areas with high spatial resolution. IR thermography, based on video camera technology, is used to obtain surface temperature distributions. These distributions plus surface substrate temperatures obtained by a few thermocouples are all that is required to infer accurate, highly resolved distributions of local heat transfer coefficient behavior. Comparisons of heat transfer coefficient behavior measured by this technique with those by conventional techniques are presented to illustrate this technique's capabilities for convective heat transfer resulting from an air jet impinging on a heated plate.
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.
Heat transfer mechanisms in poplar wood undergoing torrefaction
NASA Astrophysics Data System (ADS)
Sule, Idris O.; Mahmud, Shohel; Dutta, Animesh; Tasnim, Syeda Humaira
2015-04-01
Torrefaction, a thermal treatment process of biomass, has been proved to improve biomass combustible properties. Torrefaction is defined as a thermochemical process in reduced oxygen condition and at temperature range from 200 to 300 °C for shorter residence time whereby energy yield is maximized, can be a bridging technology that can lead the conventional system (e.g. coal-fired plants) towards a sustainable energy system. In efforts to develop a commercial operable torrefaction reactor, the present study examines the minimum input condition at which biomass is torrefied and explores the heat transfer mechanisms during torrefaction in poplar wood samples. The heat transfer through the wood sample is numerically modeled and analyzed. Each poplar wood is torrefied at temperature of 250, 270, and 300 °C. The experimental study shows that the 270 °C-treatment can be deduced as the optimal input condition for torrefaction of poplar wood. A good understanding of heat transfer mechanisms can facilitate the upscaling and downscaling of torrefaction process equipment to fit the feedstock input criteria and can help to develop treatment input specifications that can maximize process efficiency.
FIN EFFICIENCY CALCULATION IN ENHANCED FIN-AND-TUBE HEAT EXCHANGERS IN DRY CONDITIONS
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
Increasing Boiling Heat Transfer using Low Conductivity Materials.
Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew
2015-01-01
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches. PMID:26281890
Increasing Boiling Heat Transfer using Low Conductivity Materials
NASA Astrophysics Data System (ADS)
Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew
2015-08-01
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches.
Increasing Boiling Heat Transfer using Low Conductivity Materials
Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew
2015-01-01
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches. PMID:26281890
Cross flow heat transfer in tube bundles
Hwang, T.H.
1985-01-01
The objective of the research described in this thesis is to understand the boiling heat transfer characteristics in tube bundles. The studies are performed both analytically and experimentally. Analyses are conducted for single phase flow in bundles with various geometries. The results are compared with the available experimental data. Recommendation for simple and general design correlations at special conditions are proposed. Experimental results of forced convective boiling of a horizontal tube in a channel as well as in a bundle are reported. The difference between a single tube in a channel and a tube in a bundle is attributed to the different flow-field environment and thermal environment. A modified Chen's correlation can be used to predict the heat transfer performance of a single tube in a channel or in a bundle. An empirical CHF correlation of forced convective boiling from a single tube in a channel is proposed. The agreement of this correlation with the experimental data is reasonable with the maximum deviation of 20%.
Heat Transfer in High Temperature Multilayer Insulation
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Miller, Steve D.; Cunnington, George R.
2007-01-01
High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heat transfer in multilayer insulations consisting of thin, gold-coated, ceramic reflective foils and Saffil(TradeMark) fibrous insulation spacers was studied both numerically and experimentally. A finite volume numerical thermal model using combined conduction (gaseous and solid) and radiation in porous media was developed. A two-flux model with anisotropic scattering was used for radiation heat transfer in the fibrous insulation spacers between the reflective foils. The thermal model was validated by comparison with effective thermal conductivity measurements in an apparatus based on ASTM standard C201. Measurements were performed at environmental pressures in the range from 1x10(exp -4) to 760 torr over the temperature range from 300 to 1300 K. Four multilayer samples with nominal densities of 48 kg/cu m were tested. The first sample was 13.3 mm thick and had four evenly spaced reflective foils. The other three samples were 26.6 mm thick and utilized either one, two, or four reflective foils, located near the hot boundary with nominal foil spacing of 1.7 mm. The validated thermal model was then used to study relevant design parameters, such as reflective foil spacing and location in the stack-up and coating of one or both sides of foils.
The heat transfer of cooling fins on moving air
NASA Technical Reports Server (NTRS)
Doetsch, Hans
1935-01-01
The present report is a comparison of the experimentally defined temperature and heat output of cooling fins in the air stream with theory. The agreement is close on the basis of a mean coefficient of heat transfer with respect to the total surface. A relationship is established between the mean coefficient of heat transfer, the dimensions of the fin arrangement, and the air velocity.
Heat transfer and fluid friction in bundles of twisted tubes
NASA Astrophysics Data System (ADS)
Dzyubenko, B. V.; Dreitser, G. A.
1986-06-01
The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.
National & 7th Heat and Mass Transfer Conference
Walker, D. Greg
, a fictitious event to regu- late the transfer of energy was devised so that heat pref- erentially moved onlyPaper No: 18th National & 7th ISHMT-ASME Heat and Mass Transfer Conference January 4-6, 2006 IIT/K) m electron effective mass N phonon occupation number p electron momentum q heat flux (W/m2 ) R
Wright, T.; Lackey, R.S.; Veyo, S.E.
1983-01-01
Efforts toward development of a high-efficiency outdoor air mover for an advanced electric heat pump are documented. The design goal was to halve the outdoor air-moving electrical power. The prototype air mover at 850 rpm delivers 3070 scfm through the prototype outdoor unit with a pressure drop through the coil of 0.09 inches of water and consumes 150 watts of electrical power. The overall air-moving efficiency is estimated at about 35 percent compared with 19 percent for the conventionally-applied heat pump fan. Although this air mover will cost twice as much as the conventional heat pump air mover, this premium cost should be recoverable in less than four years through energy savings. The sound rating (SRN) for this air mover is less than 20. Means for improving fan efficiency by 5 percentage points, motor efficiency by 2.5 points, and to further quiet the fan have been identified.
Nucleate Boiling Heat Transfer Studied Under Reduced-Gravity Conditions
NASA Technical Reports Server (NTRS)
Chao, David F.; Hasan, Mohammad M.
2000-01-01
Boiling is known to be a very efficient mode of heat transfer, and as such, it is employed in component cooling and in various energy-conversion systems. In space, boiling heat transfer may be used in thermal management, fluid handling and control, power systems, and on-orbit storage and supply systems for cryogenic propellants and life-support fluids. Recent interest in the exploration of Mars and other planets and in the concept of in situ resource utilization on the Martian and Lunar surfaces highlights the need to understand how gravity levels varying from the Earth's gravity to microgravity (1g = or > g/g(sub e) = or > 10(exp -6)g) affect boiling heat transfer. Because of the complex nature of the boiling process, no generalized prediction or procedure has been developed to describe the boiling heat transfer coefficient, particularly at reduced gravity levels. Recently, Professor Vijay K. Dhir of the University of California at Los Angeles proposed a novel building-block approach to investigate the boiling phenomena in low-gravity to microgravity environments. This approach experimentally investigates the complete process of bubble inception, growth, and departure for single bubbles formed at a well-defined and controllable nucleation site. Principal investigator Professor Vijay K. Dhir, with support from researchers from the NASA Glenn Research Center at Lewis Field, is performing a series of pool boiling experiments in the low-gravity environments of the KC 135 microgravity aircraft s parabolic flight to investigate the inception, growth, departure, and merger of bubbles from single- and multiple-nucleation sites as a function of the wall superheat and the liquid subcooling. Silicon wafers with single and multiple cavities of known characteristics are being used as test surfaces. Water and PF5060 (an inert liquid) were chosen as test liquids so that the role of surface wettability and the magnitude of the effect of interfacial tension on boiling in reduced gravity can be investigated.
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.
Transient critical heat flux and blowdown heat-transfer studies
Leung, J.C.
1980-05-01
Objective is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. A predictional method has been developed which 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. 234 figures, 13 tables.
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.
MODELING OF THE FLOW AND HEAT TRANSFER IN MICRO HEAT PIPES
CHOONDAL B. SOBHAN
The fluid flow and heat transfer characteristics of micro heat pipes are analyzed theoretically, in order to understand the physical phenomena and quantify the influence of various parameters on overall thermal performance of these devices. A one-dimensional model is utilized to solve the governing equations for the liquid\\/vapor flow and the heat transfer in the heat pipe channel. Variations in
Local heat transfer in the intertube space of a heat exchanger with spiral tubes
NASA Astrophysics Data System (ADS)
Dzyubenko, B. V.; Sakalauskas, A. V.; Vilemas, Yu. V.; Ashmantas, L. A.
1981-08-01
The article explains the methods and presents the results of the experimental investigation of local heat transfer in bundles of spiral tubes with heat supply to the heat carrier that is nonuniform over the cross section.
Field investigation on heat transfer in an urban canyon
Yoshida, A.; Tominaga, K.; Watatani, S. )
1991-01-01
This paper reports on field measurements of the heat transfer in an urban canyon running from east to west that were performed both in summer and winter as a preliminary investigation of the heat transfer in an urban surface boundary layer. The canyon consisted of concrete buildings (16m in height) with windows, standing face to face with an asphalt road (17 m in width) between them. The heat transfer in the urban canyon is represented by an energy balance at an imaginary surface called the top surface, which is a plane positioned above the heat transferred into the urban canyon was more than four times larger than that into the roof and reached about 50 percent of the net radiation heat transfer on a summer day regardless of the meteorological conditions. In the daytime, there was no significant difference in the convective heat transfer between the roof surface and the top surface.
Micro and nanostructured surfaces for enhanced phase change heat transfer
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, ...
Panchagnula, Mahesh
ME 6010 CONDUCTION HEAT TRANSFER 1998 Catalog Data: ME 6010. Conduction Heat Transfer. Lec. 3. Cr. 3. Conduction in steady, periodic, and transient systems; analytical and numerical techniques. Prerequisite: Math 4510, ME 3710 Textbook: S. Kakac and Y. Yener, Heat Conduction, Taylor & Francis Coordinator
Heat-transfer enhancement in natural convection enclosure flow
NASA Astrophysics Data System (ADS)
Bohn, M.; Anderson, R.
1984-08-01
The enhancement of natural convection heat transfer in an enclosure was studied experimentally in a water filled test cell at Rayleigh numbers of theta (10 to the 10th power). Surface average heat transfer, local heat transfer, and flow visualization were compared for a smooth and rough vertical heated wall. The facing cooled wall was smooth. The roughness was distributed over the entire heated wall and was of a height comparable to the velocity boundary layer thickness. Results indicate that the roughness promotes boundary layer transition giving fully turbulent behavior at overall Rayleigh numbers about half that for the smooth wall. Local increases in heat transfer of about 40% and surface averaged heat transfer increases of about 16% were observed.
Heat transfer in bundles of finned tubes in crossflow
Stasiulevicius, J.; Skrinska, A.; Zukauskas, A.; Hewitt, G.F.
1986-01-01
This book provides correlations of heat transfer and hydraulic data for bundles of finned tubes in crossflow at high Reynolds numbers. Results of studies of the effectiveness of the fin, local, and mean heat transfer coefficients are presented. The effect of geometric parameters of the fins and of the location of tubes in the bundle on heat transfer and hydraulic drag are described. The resistance of the finned tube bundles under study and other factors are examined.
Heat transfer in freeboard region of fluidized beds
Biyikli, S.; Tuzla, K.; Chen, J.C.
1983-10-01
This research involved the study of heat transfer and fluid mechanic characteristics around a horizontal tube in the freeboard region of fluidized beds. Heat transfer coefficients were experimetnally measured for different bed temperatures, particle sizes, gas flow rates, and tube elevations in the freeboard region of air fluidized beds at atmospheric pressure. Local heat transfer coefficients were found to vary significantly with angular position around the tube. Average heat transfer coefficients were found to decrease with increasing freeboard tube elevation and approach the values for gas convection plus radiation for any given gas velocity. For a fixed tube elevation, heat transfer coefficients generally increased with increasing gas velocity and with high particle entrainment they can approach the magnitudes found for immersed tubes. Heat transfer coefficients were also found to increase with increasing bed temperature. It was concluded that this increase is partly due to increase of radiative heat transfer and partly due to change of thermal properties of the fluidizing gas and particles. To investigate the fluid mechanic behavior of gas and particles around a freeboard tube, transient particle tube contacts were measured with a special capacitance probe in room temperature experiments. The results indicated that the tube surface experiences alternating dense and lean phase contacts. Quantitative information for local characteristics was obtained from the capacitance signals and used to develop a phenomenological model for prediction of the heat transfer coefficients around freeboard tubes. The packet renewal theory was modified to account for the dense phase heat transfer and a new model was suggested for the lean phase heat transfer. Finally, an empirical freeboard heat transfer correlation was developed from functional analysis of the freeboard heat transfer data using nondimensional groups representing gas velocity and tube elevation.
Sensitivity Analysis of the Gap Heat Transfer Model in BISON.
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.
Heat exchanger efficiently operable alternatively as evaporator or condenser
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.
Radiative heat transfer in rotary kilns
NASA Astrophysics Data System (ADS)
Gorog, J. P.; Brimacombe, J. K.; Adams, T. N.
1981-03-01
Radiative heat transfer between a nongray freeboard gas and the interior surfaces of a rotary kiln has been studied by evaluating the fundamental radiative exchange integrals using numerical methods. Direct gas-to-surface exchange, reflection of the gas radiation by the kiln wall, and kiln wall-to-solids exchange have been considered. Graphical representations of the results have been developed which facilitate the determination of the gas mean beamlength and the total heat flux to the wall and to the solids. These charts can be used to account for both kiln size and solids fill ratio as well as composition and temperature of the gas. Calculations using these charts and an equimolar CO2-H2O mixture at 1110 K indicate that gas-to-surface exchange is a very localized phenomenon. Radiation to a surface element from gas more than half a kiln diameter away is quite small and, as a result, even large axial gas temperature gradients have a negligible effect on total heat flux. Results are also presented which show that the radiant energy either reflected or emitted by a surface element is limited to regions less than 0.75 kiln diameters away. The radiative exchange integrals have been used, together with a modified reflection method, to develop a model for the net heat flux to the solids and to the kiln wall from a nongray gas. This model is compared to a simple resistive network/gray-gas model and it is shown that substantial errors may be incurred by the use of the simple models.
Multiscale simulations of heat transfer in nanocomposites
NASA Astrophysics Data System (ADS)
Bui, Khoa Nguyen Dang
The field of nanotechnology has been expanded by the discovery of fullerenes and carbon nanotubes (CNTs) in the 20th century. Geim and Novoselov won the Nobel prize in 2010 for their work on graphene sheets (GSs). Those materials with their outstanding properties have been suggested as reinforcement fillers in a variety of composite materials. By incorporating these nanomaterials into a polymer matrix, or dispersing them into a solution, the effective thermal conductivity of the resulting composite (Keff) can be increased. For example, this enhancement can range from 80% to 125% at 1.0wt% of CNTs over pure polymer for the case of epoxy composites or by a factor of almost 4 in the case of high concentration of single-walled carbon nanotubes (SWNTs) in poly-styrene. However, based on the properties of pristine CNTs and GSs, one would expect a much higher value of Keff of such composites, more than one order of magnitude according to the classical theory of Maxwell. The presence of resistance to heat transfer at the nanoinclusion-polymer interface, known as the interfacial thermal resistance or Kapitza resistance, is the reason for this difference. Experimentally measuring and characterizing heat transport at the nanoscale are not trivial tasks and current theory in this area is limited to simple cases only. The acoustic mismatch theory and the effective medium theory provide a rough estimation of Kapitza resistance and Keff of the composites, respectively. However, the effect of dispersion pattern and the orientation of nanoinclusions inside the polymer matrix on Keff is still an open question. For the case of multi-walled carbon nanotubes (MWCNTs) embedded in polymer matrix, it is unknown whether thermal transfer occurs solely via the outermost wall or through the center of the tube. In this work, Monte Carlo (MC) simulations were developed to investigate heat transfer in nanocomposites. This approach is capable of taking into account the effect of different geometries, realistic orientations, and dispersion patterns of nanoinclusions on Keff. Furthermore, molecular dynamics (MD) simulations were employed coherently with MC simulations to characterize interfacial thermal resistance. Results from this work provide suggestions for producing superior thermal nanocomposites through the controll of Kapitza resistance and the configurations of nanoinclusions inside the polymer matrix.
NASA Astrophysics Data System (ADS)
Arai, N.; Hasatani, M.; Kato, Y.; Sugiyama, S.
1980-06-01
The unsteady characteristics of heat transfer in an optically thick semitransparent liquid such as that used in solar ponds are investigated for the case of a horizontal fluid layer heated from above by a radiant heat source. The time-dependent temperature distribution in a liquid layer heated in a stepwise fashion is formulated in terms of a differential equation of unsteady radiative and conductive heat transfer, which is solved numerically by means of the multiband model of Viskanta et al. (1975) and the Planck mean model. The numerical results are compared with thermocouple determinations of time-dependent temperature distributions in diethylphthalate within a vertical glass tube with either a constant bottom temperature assured by a cooling flow or insulated bottom and side walls, which was irradiated by an infrared lamp bundle. Both numerical calculations are found to be in good agreement with experiment, with the multiband calculations displaying a closer correspondence.
2.51 Intermediate Heat and Mass Transfer, Fall 2001
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 ...
Nonlinear Transient Problems Using Structure Compatible Heat Transfer Code
NASA Technical Reports Server (NTRS)
Hou, Gene
2000-01-01
The report documents the recent effort to enhance a transient linear heat transfer code so as to solve nonlinear problems. The linear heat transfer code was originally developed by Dr. Kim Bey of NASA Largely and called the Structure-Compatible Heat Transfer (SCHT) code. The report includes four parts. The first part outlines the formulation of the heat transfer problem of concern. The second and the third parts give detailed procedures to construct the nonlinear finite element equations and the required Jacobian matrices for the nonlinear iterative method, Newton-Raphson method. The final part summarizes the results of the numerical experiments on the newly enhanced SCHT code.
EFFECT OF REACTOR HEAT TRANSFER LIMITATIONS ON CO PREFERENTIAL OXIDATION
Besser, Ronald S.
in PEM fuel cell applications. In order to prevent poisoning of the fuel cell electrodes, the CO: Preferential Oxidation; Microreactor; Fuel processor; Heat transfer limitation; Nonisothermal reactor; Reverse
Heat transfer coefficient in serpentine coolant passage for CCDTL
Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.
1998-12-31
A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.
Sandwich heating film boiling heat transfer research in narrow rectangle channel
NASA Astrophysics Data System (ADS)
Wang, Z. H.; Ni, M. J.
2010-03-01
The narrow rectangle channel heat transfer technique is a new developing heat transfer technique in recent years. In the narrow rectangle channel, film boiling is an important two-phase flow heat transfer process in many engineering application, including steam generator, nuclear reactor and engineering metallurgy. As the temperature of droplet, steam and wall are decided by forced convection heat transfer between the steam and the wall, the droplet and the wall, the steam and the droplet and radiation heat transfer process, which makes heat transfer mechanism of film boiling be difficultly interpretative. Film boiling in narrow rectangle channel is analyzed in the paper, investigating the influence of all kinds of heat transfer processes on film boiling. A rectangle channel film boiling model has been built up using thermodynamic non-equilibrium model.
Low-melting point heat transfer fluid
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.
Heat and mass transfer in flames
NASA Technical Reports Server (NTRS)
Faeth, G. M.
1986-01-01
Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.
Submersible pumping system with heat transfer mechanism
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.
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.
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.
Convective heat transfer in building energy analysis
Gadgil, A.J.
1980-05-01
In the ongoing efforts to study energy consumption in buildings through computer simulations, practically no attention has been given to modeling natural convective heat transfer in buildings. The main reason for this neglect is due to the difficulty of solving the problem numerically. This paper makes a contribution towards the solution of this difficulty by presenting a numerical code for modeling natural convection in rectangular enclosures at Rayleigh numbers up to 10/sup 10/. Chapter 2 develops the general equations of motion to be solved. Chapter 3 is devoted to simplification of these equations and description of the numerical scheme. Chapter 4 describes the comparisons of the predictions of the computer program based on the numerical scheme with various published experimental and numerical results of other investigators. Chapter 5 illustrates an application of the computer program to investigate the soundness of an assumption commonly made by all the building energy analysis programs.
Summary of NASA aerodynamic and heat transfer studies in turbine vanes and blades
NASA Technical Reports Server (NTRS)
Moffitt, T. P.; Stepka, F. S.; Rohlik, H. E.
1976-01-01
Aerodynamic effects of trailing edge geometry, hole size, angle, spacing, and shape were studied in two- and three-dimensional cascades and in a warm turbine test series. Heat transfer studies were carried out in various two- and three-dimensional test facilities in order to provide corresponding heat transfer data. Results are shown in terms of cooling effectiveness and aerodynamic efficiency for various coolant fractions, coolant-primary temperature ratios, and cooling configurations.
Evaluation of heat transfer surfaces for compact recuperator using a CFD code
NASA Astrophysics Data System (ADS)
Ashok Babu, T. P.; Talekala, Mohammad Shekoor
2009-04-01
Exhaust recovery recuperator is mandatory in order to realize a thermal efficiency of 30% or higher for micro turbines. In this work an attempt is made to select the cross corrugated heat transfer surface with minimum core volume of a recuperator matrix using a CFD code. Analysis is carried out for selected cross corrugated heat transfer surface configurations. The relation between the minimum core volume from design calculation and average skin friction coefficient from CFD analysis has been established.
Efficient thermoelectric cooling of concentrated heat loads
NASA Astrophysics Data System (ADS)
Hershberger, Jeff; Smythe, Robert; Gu, Xiaoyi; Hill, Richard F.
2013-02-01
An efficiency improvement of 87% is demonstrated in cooling of concentrated heat loads when using thermoelectric coolers (TECs) constructed with thermally conductive printed circuit boards (TCPCBs) as compared to traditional ceramic-based TECs. Laser diodes and infrared detectors must be actively cooled but are smaller than typical TECs. As a result, heat spreading must occur between the optical component and the semiconductor pellets near the edge of the TEC. Typically, TECs based on aluminum nitride circuit boards are chosen and in some cases an AlN plate is added between the optical component and the TEC. To address this, TECs have been developed that replace the ceramic circuit boards with laminated TCPCBs containing a thick copper backing. The copper backing improves heat spreading within the TEC. A study was conducted to quantify differences in coefficient of performance (COP, heat pumped divided by electrical power consumed) when cooling concentrated heat loads. A heat source 3 mm wide was cooled by TECs ~12 mm wide, comparing ceramic-based and TCPCB-based TECs of otherwise identical design. With a fixed hot side temperature and heat load, each TEC was powered to achieve a desired temperature at the heat source. Ceramic-based and TCPCB-based TECs exhibited COPs of 0.235 and 0.440 respectively, an 87% improvement. Further improvements are achievable: adding a thick copper plate between the heat source and the TEC resulted in a COP of ~0.59 for both TEC types.
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.
BASIC PROBLEMS OF HEAT TRANSFER IN NUCLEAR REACTORS
1958-01-01
In nuclear reactors large heat fluxes must be removed at high coolant ; temperatures, without which the permissible temperatures in the reactor and in ; the fuel elements would be exceeded. Three problems arising from this factor are ; considered: heat conduction in the fuel elements. heat transfer to the coolant, ; and heat removal with the ccolant from the
Uncertainty of Heat Transfer Measurements in an Engulfing Pool Fire
M. Alex Kramer; Miles Greiner; J. A. Koski; Carlos Lopez
A series of experiments were performed to measure heat transfer to a cylindrical steel calorimeter engulfed in a 30-minute pool fire. The calorimeter inner surface temperature history was measured at 46 locations. A one-dimensional inverse heat conduction technique was used to determine the net heat flux to the calorimeter as a function of time and location. The uncertainty in heat
Proceedings of HT'03 2003 Summer Heat Transfer Conference
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
Solar molten-salt heat-transfer loop. Final report
G. H. Eggers; J. R. Schuster
1981-01-01
Work is reported to design, fabricate, and operate a molten salt heat transfer loop in conjunction with a distributed solar concentrator. The collector consists of a fixed mirror solar concentrator with an aperture width of 2.13 m (7 ft) and a length of 22.86 m (75 ft). The heat transfer loop consists of a heated tank, heat-traced piping, and a
Solution of Radiation and Convection Heat-Transfer Problems
NASA Technical Reports Server (NTRS)
Oneill, R. F.
1986-01-01
Computer program P5399B developed to accommodate variety of fin-type heat conduction applications involving radiative or convective boundary conditions with additionally imposed local heat flux. Program also accommodates significant variety of one-dimensional heat-transfer problems not corresponding specifically to fin-type applications. Program easily accommodates all but few specialized one-dimensional heat-transfer analyses as well as many twodimensional analyses.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
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.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
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.
Methods for calculating conjugate problems of heat transfer
NASA Astrophysics Data System (ADS)
Kalinin, E. K.; Dreitser, G. A.; Kostiuk, V. V.; Berlin, I. I.
Methods are examined for calculating various conjugate problems of heat transfer in channels and closed vessels in cases of single-phase and two-phase flow in steady and unsteady conditions. The single-phase-flow studies involve the investigation of gaseous and liquid heat-carriers in pipes, annular and plane channels, and pipe bundles in cases of cooling and heating. General relationships are presented for heat transfer in cases of film, transition, and nucleate boiling, as well as for boiling crises. Attention is given to methods for analyzing the filling and cooling of conduits and tanks by cryogenic liquids; and ways to intensify heat transfer in these conditions are examined.
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.
The heat transfer coefficients of the heating surface of 300 MWe CFB boiler
NASA Astrophysics Data System (ADS)
Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai
2012-08-01
A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.
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.
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.
Heat transfer research on supercritical water flow upward in tube
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)
Wake Modes and Heat Transfer from Rotationally Oscillating Cylinder
NASA Astrophysics Data System (ADS)
Sellappan, Prabu; Pottebaum, Tait
2012-11-01
Wake formation is an important problem in engineering due to its effect on phenomena such as vortex induced vibrations and heat transfer. While prior work has focused on the wake formation due to vortex shedding from stationary and oscillating cylinders, limited information is available on the relationship between wake modes and heat transfer from rotationally oscillating cylinders. Experiments were carried out at Re=150 and 750, using an electrically heated cylinder, in a water tunnel for oscillation frequencies from 0.67 to 3.5 times the natural shedding frequency and peak-to-peak oscillation amplitudes up to 320. DPIV was used to identify and map wake modes to various regions of the parameter space. Temperature data from a thermocouple embedded in the cylinder was used to calculate heat transfer rates. Correlation between heat transfer enhancement and certain wake mode regions were observed in the parameter space. The relationship between wake formation and heat transfer enhancement will be described.
Tokyo, University of
2004-01-01
H. Wu & N. Kasagi, Int. J. Heat Mass Transfer 47, 4579-4591 (2004) Turbulent Heat Transfer. Heat Mass Transfer 47, 4579-4591 (2004) #12;H. Wu & N. Kasagi, Int. J. Heat Mass Transfer 47, 4579 thermal conductivity µ dynamic viscosity instantaneous temperature 2 #12;H. Wu & N. Kasagi, Int. J. Heat
Zhongliang Liu; Zengyi Wang; Chongfang Ma
2006-01-01
In this part of the paper, the performance of the simultaneous charging\\/discharging operation modes of the heat pipe heat exchanger with latent heat storage is experimentally studied. The experimental results show that the device may operate under either the fluid to fluid heat transfer with charging heat to the phase change material (PCM) or the fluid to fluid heat transfer
Kaminski, D.; Smith, A.M.; Smith, T.F.
1997-07-01
This volume contains a portion of the over 240 ASME papers which were presented at the conference. For over 40 years, the National Heat Transfer Conference has been the premiere forum for the presentation and dissemination of the latest advances in heat transfer. The work contained in these volumes range from studies of fundamental phenomena to applications in the latest heat transfer equipment. Radiative heat transfer is the subject covered by the papers in this volume. Separate abstracts were prepared for most papers in this volume.
Optimizing transfer efficiency in spray painting
Darvin, C.H.
1987-01-01
This paper describes an extensive program to define the effects of operating and maintenance practices on the transfer efficiency of spray painting. Three spray painting systems were used: air-atomized conventional, air-atomized electrostatic, and airless conventional. More than 30 operating variables were initially identified and evaluated. Eight were found to be most important and received intensive testing: restricted air lines, booth air rate, gun cleanliness, restricted paint lines, fan or shaping air, gun tip erosion, electrode position, and tip voltage.
Validation of efficiency transfer for Marinelli geometries.
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
Computational and experimental investigation of annulus heat transfer with swirl
NASA Astrophysics Data System (ADS)
Kim, Jay C.; Bennett, John C.
1992-08-01
Computational and experimental investigations were conducted to evaluate the effect of swirl on annulus heat transfer. In the computational approach, Reynolds-averaged turbulent Navier-Stokes equations were solved numerically using a standard K-epsilon turbulence model. For the near-wall regions, where accurate velocity and temperature profiles were needed for heat transfer calculations, the equations were solved down to the wall with a fine grid instead of using a wall function. Average convective heat transfer coefficients were measured with heat-flux gauges mounted on a large scale model. Swirl was found to cause a substantial increase in annulus heat transfer. With 45-deg swirl, average heat transfer coefficients on the outer and inner annulus wall were measured 1.5 to 2.5 times those of nonswirling flow. The comparison of the numerical results with the experimental data showed reasonable agreements in nonswirling heat transfer. In swirling flow, the calculated heat transfer agreed well with the measured data on the outer annulus wall, but the calculation overpredicted the inner heat transfer.
Heat transfer in turbulent bubbly flow in channels
NASA Astrophysics Data System (ADS)
Dabiri, Sadegh; Tryggvason, Gretar
2013-11-01
In many applications convective heat transfer occurs in the presence of a multiphase turbulent flow such as in boilers and bubble column reactors. Turbulence in channel and pipe flows significantly increases the heat transfer rate. Here we examine the effect of turbulent bubbly flows on the heat transfer inside a vertical channel with uniform heat flux on the walls and compare it with the heat transfer in single phase flow. Both bubbles and the turbulence are fully resolved through Direct Numerical Simulation. The distribution of the bubbles in the channel is affected by the deformability of the bubbles. A wall-peaked distribution is observed for nearly spherical bubbles and a core-peaked distribution is observed for deformable bubbles. This change in distribution of the bubbles significantly affects the flow rate in the channel and the heat transfer rate as well. The results of heat transfer for different flow configurations are presented and compared to the heat transfer in a single phase channel flow. In many applications convective heat transfer occurs in the presence of a multiphase turbulent flow such as in boilers and bubble column reactors. Turbulence in channel and pipe flows significantly increases the heat transfer rate. Here we examine the effect of turbulent bubbly flows on the heat transfer inside a vertical channel with uniform heat flux on the walls and compare it with the heat transfer in single phase flow. Both bubbles and the turbulence are fully resolved through Direct Numerical Simulation. The distribution of the bubbles in the channel is affected by the deformability of the bubbles. A wall-peaked distribution is observed for nearly spherical bubbles and a core-peaked distribution is observed for deformable bubbles. This change in distribution of the bubbles significantly affects the flow rate in the channel and the heat transfer rate as well. The results of heat transfer for different flow configurations are presented and compared to the heat transfer in a single phase channel flow. This research is partially supported by CASL project.
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.
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.
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
Condensation heat transfer enhancement by surface modification on a monolithic copper heat sink
Leu, Tzong-Shyng "Jeremy"
in the literature. The superhydrophobic copper heat sink surface was prepared using a hydrogen peroxide immersionCondensation heat transfer enhancement by surface modification on a monolithic copper heat sink surface modification is applied to a monolithic copper heat sink. A monolithic copper heat sink is used
Measurement of heat and moisture exchanger efficiency.
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
Efficiency of a Water Heating System
NSDL National Science Digital Library
2014-09-18
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.
A. J. Kuprys; V. V. Lappo; M. M. Tamonis; O. L. Tutlyte
1989-01-01
The problem of removal of heat in a heat exchanger consisting of concentric heating elements with an additional central heat exchanger in the form of a Field's tube is analyzed. It is shown that the central heat exchanger makes it possible to remove a significantly greater quantity of thermal power from the heating elements without raising the maximum temperature of
Fluid Flow and Heat Transfer in a Dual-wet Micro Heat Pipe
Jin Zhang; Stephen J. Watson; Harris Wong
2007-01-01
Micro heat pipes have been used to cool micro electronic devices, but their heat transfer coefficients are low compared with those of conventional heat pipes. In this talk, a dual-wet pipe is proposed as a model to study heat transfer in micro heat pipes. The dual-wet pipe has a long and narrow cavity. The bottom-half of the horizontal pipe is
Boiler efficiency methodology for solar heat applications
NASA Astrophysics Data System (ADS)
Maples, D.; Conwell, J. C.; Pacheco, J. E.
1992-08-01
This report contains a summary of boiler efficiency measurements which can be applied to evaluate the performance of steam-generating boilers via both the direct and indirect methods. This methodology was written to assist industries in calculating the boiler efficiency for determining the applicability and value of thermal industrial heat, as part of the efforts of the Solar Thermal Design Assistance Center (STDAC) funded by Sandia National Laboratories. Tables of combustion efficiencies are enclosed as functions of stack temperatures and the amount of carbon dioxide and carbon monoxide in the gas stream.
Analysis of Heat and Mass Transfer in a Desiccant Rotor
NASA Astrophysics Data System (ADS)
Hamamoto, Yoshinori; Murase, Sousuke; Akisawa, Atsushi; Kashiwagi, Takao; Okajima, Jirou; Matsuoka, Fumio
The study aims at clarifying the local heat and mass transfer in the desiccant rotor, and at obtaining the design aspects of high efficient desiccant rotor and operation method. In the paper, theoretical analysis is performed for rotary dehumidifier. Both surface diffusion and mass transfer coefficient are considered in the model. It is examined that the results of calculation agree well with the experimental data. The local temperature, humidity and the amount of adsorbed water vapor are calculated. It is clarified that temperature and humidity of air in the rotor change clockwise between each inlet air condition on the psychrometric chart. The outlet temperature and humidity distribution of the rotor is clarified in the system showing the optimum rotor speed. Furthermore, it is clarified that local desorption rate is higher than adsorption rate. It is attributed to the increase of mass transfer coefficient and surface diffusivity of the rotor during desorption process. And, it is clarified that the influence of surface diffusion on amount of adsorbed water vapor is much larger than that of mass transfer coefficient.
FINITE ELEMENT METHOD IN FLUID MECHANICS & HEAT TRANSFER
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
Proceedings of 28th national heat transfer conference
Santoro
1991-01-01
Recent advances in the design of various nuclear components and systems have called for the studies of many important heat transfer processes that occur either during normal operations or under accident conditions. These processes include, for example, heat transfer in reactor steam generators, mixed convection in tube bundles and rod assemblies, turbulent convection and flow instability, two-phase natural circulation, thermal
Reflective Coating on Fibrous Insulation for Reduced Heat Transfer
Derek D. Hass; B. Durga Prasad; David E. Glass; Karl E. Wiedemann
1997-01-01
Radiative heat transfer through fibrous insulation used in thermal protectionsystems (TPS) is significant at high temperatures (1200??C). Decreasing the radiative heattransfer through the fibrous insulation can thus have a major impact on the insulatingability of the TPS. Reflective coatings applied directly to the individual fibers in fibrousinsulation should decrease the radiative heat transfer leading to an insulation withdecreased effective thermal
Improving Heat Transfer Performance of Printed Circuit Boards
NASA Technical Reports Server (NTRS)
Schatzel, Donald V.
2009-01-01
This paper will explore the ability of printed circuit boards laminated with a Carbon Core Laminate to transfer heat vs. standard printed circuit boards that use only thick layers of copper. The paper will compare the differences in heat transfer performance of printed circuit boards with and without CCL.
MOLECULAR DYNAMICS SIMULATIONS OF HEAT TRANSFER OF CARBON NANOTUBES
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
Enhanced radiative heat transfer between nanostructured gold plates
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.
Effects of simulated combustor turbulence on boundary layer heat transfer
NASA Technical Reports Server (NTRS)
Ames, F. E.; Moffat, R. J.
1990-01-01
A simulated combustor flow field has been generated in order to study the effects of high intensity large scale turbulence on boundary layer heat transfer. Turbulence intensities of up to 19 percent and integral lengths scales of 4 to 6 centimeters have been generated. Heat transfer has been augmented by up to 28 percent for the flat plate constant velocity turbulent boundary layer.
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
Heat transfer in proteinwater interfaces Anders Lervik,ab
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
Gas Heat Transfer in a Heated Vertical Channel under Deteriorated Turbulent Heat Transfer Regime
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 ...
A study of the heat transfer characteristics of the micro-channel heat sink
Shun Wang; Yan Zhang; Yifeng Fu; Johan Liu; Xiaojing Wang; Zhaonian Cheng
2009-01-01
Micro-channels are generally regarded as an effective method for the heat transfer in electronic products, and much effort has been put into improving their capacities. At the same time, carbon nanotubes have shown great potential in the field of heat transfer. This paper focuses on the microchannel heat sinks combined with carbon nanotubes. A series of 3D models had been
Heat Transfer Enhancement of Spray Cooling on Flat Aluminum Tube Heat Exchanger
Chia-Wei Chen; Chien-Yuh Yang; Yuh-Tang Hu
2013-01-01
This study provides an experimental analysis on the heat transfer performance of a flat aluminum tube micro-channel heat exchanger with spray cooling. The effects of water spraying rate, air flow rate and relative humidity were investigated. The test results show that the heat transfer performance increased with increasing the water spraying rate but without the penalty of increased flow resistance
Calculation of overall heat transfer coefficients in a triple tube heat exchanger
Ediz Batmaz; K. P. Sandeep
2005-01-01
In previous studies, calculation of overall heat transfer coefficients in a triple tube heat exchanger (TTHE) involved assumptions or approaches those are not valid in all cases. In this study a more generic way of calculating overall heat transfer coefficients in a TTHE has been developed. Consequently, temperature profiles of all streams in a TTHE in the axial direction were
Heat transfer in open-cell metal foams
Lu, T.J.; Ashby, M.F.; Stone, H.A.
1998-06-12
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 inside the channel as a function of foam density, cell size and other pertinent heat transfer parameters. Two characteristic length scales of importance to the problem are discussed: the minimum channel length required for heating the fluid to its goal temperature and the thermal entry length beyond which the transfer of heat between fluid and channel wall assumes a constant coefficient. The overall heat transfer coefficient of the heat exchanging system is calculated, and the pressure drop experienced by the fluid flow obtained. The present model perhaps oversimplifies the calculation of transport in a metal foam consisting of non-circular, possibly sharp-edged ligaments, and so likely leads to overestimates. Nevertheless the trends of heat transfer predicted by the model (for dependence on foam relative density, duct geometries, fluid velocity, etc.) are expected to be valid for a wide range of open-cell foams and are in reasonable agreement with available experimental data on aluminum foams (Bastawros and Evans, Proceedings Symposium Application of Heat Transfer in Microelectronics Packaging, IMECE, Dallas, TX, 1997).
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.
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.
Heat transfer between elastic solids with randomly rough surfaces
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.
Erosion effects on TVC vane heat transfer characteristics
NASA Astrophysics Data System (ADS)
Gardner, Steven R.
1994-03-01
This work describes the effects of erosion on the heat transfer characteristics on thrust vector control vanes exposed to aluminized propellant exhaust flows. This was accomplished using an inverse heat transfer parameter identification of quarter scale models. The model is based on a four node lumped parameter system with two heat energy inputs. The erosion is modeled as decreasing the geometric dimensions linearly as function of time and percentage of aluminum in the propellant. Excellent agreement was found between experimental and model temperature profiles. The heat transfer coefficients of the vanes were found to decrease with increasing erosion rates.
Simplified method of estimating efficiency of radiant and convective heating systems
Hanibuchi, Haruo; Hokoi, Shuichi
2000-07-01
This paper investigates the thermal performance of radiant and convective heating systems in a house and proposes a simplified method for evaluating the efficiency of these systems. The characteristics of the systems--heat transfer on enclosed surfaces, temperature and velocity distribution--were examined both by experiment in a full-scale experimental room and by numerical analysis. Convective heat transfer was calculated using a two-equation turbulent model along with radiant analysis. The following conclusions were obtained: (1) With the convective heating system, convective heat transfer amounts to more than 70% of the total heat exchange. With radiant heating, the convective heat exchange is approximately half of the total heat exchange; (2) When convective heat exchange is dominant, the heat loss through poorly insulated windows is larger than when radiant heat exchange is dominant. (3) A simplified method to estimate the efficiency of radiant and convective heating systems is proposed. The simplified formula, which uses operative temperature as a criterion for thermal comfort, can give the ratio of heat load between convective and radiant systems that attains the same operative temperature.
Heat transfer of HTSC-ceramic cooled by liquid hydrogen
NASA Astrophysics Data System (ADS)
Kolod'Ko, I. M.; Levchenko, N. M.; Nozdrin, S. V.; Rusinov, K. V.; Tyurina, E. G.
1994-09-01
An experimental investigation of heat transfer and crises of bubble and film boiling of hydrogen on the YBa2Cu3O7 HTSC-ceramic is described. Heat transfer characteristics obtained at pressures from 17 to 100 kPa and heat flux densities from 0.1 to 120 kW/m2 are compared with well-known results for hydrogen boiling on metal heaters.
Heat transfer of dilute viscoelastic solutions in helical exchangers
NASA Astrophysics Data System (ADS)
Ismail, Z.; Karim, R.
2013-05-01
The study examined heat transfer of two dilute viscoelastic solutions in helical exchangers of circular cross-section. Ten helical coil heat exchangers with diameter ratios ranging from 4 to 50 were constructed. Results showed doubling the concentrations of polymer increased heat transfer performance by 12 %. The results were expressed in forms of some existing equations and were found to be in fair agreement to previous results.
Heat transfer performance of an external receiver pipe under unilateral concentrated solar radiation
Jianfeng, Lu; Jing, Ding; Jianping, Yang
2010-11-15
The heat transfer and absorption characteristics of an external receiver pipe under unilateral concentrated solar radiation are theoretically investigated. Since the heat loss ratio of the infrared radiation has maximum at moderate energy flux, the heat absorption efficiency will first increase and then decrease with the incident energy flux. The local absorption efficiency will increase with the flow velocity, while the wall temperature drops quickly. Because of the unilateral concentrated solar radiation and different incident angle, the heat transfer is uneven along the circumference. Near the perpendicularly incident region, the wall temperature and absorption efficiency slowly approaches to the maximum, while the absorption efficiency sharply drops near the parallelly incident region. The calculation results show that the heat transfer parameters calculated from the average incident energy flux have a good agreement with the average values of the circumference under different boundary conditions. For the whole pipe with coating of Pyromark, the absorption efficiency of the main region is above 85%, and only the absorption efficiency near the parallelly incident region is below 80%. In general, the absorption efficiency of the whole pipe increases with flow velocity rising and pipe length decreasing, and it approaches to the maximum at optimal concentrated solar flux. (author)
NASA Astrophysics Data System (ADS)
Stafford, Jason; Walsh, Ed; Egan, Vanessa
2009-10-01
Convective heat transfer, due to axial flow fans impinging air onto a heated flat plate, is investigated with infrared thermography to assess the heated-thin-foil technique commonly used to quantify two-dimensional heat transfer performance. Flow conditions generating complex thermal profiles have been considered in the analysis to account for dominant sources of error in the technique. Uncertainties were obtained in the measured variables and the influences on the resultant heat transfer data are outlined. Correction methods to accurately account for secondary heat transfer mechanisms were developed and results show that as convective heat transfer coefficients and length scales decrease, the importance of accounting for errors increases. Combined with flow patterns that produce large temperature gradients, the influence of heat flow within the foil on the resultant heat transfer becomes significant. Substantial errors in the heat transfer coefficient are apparent by neglecting corrections to the measured data for the cases examined. Methods to account for these errors are presented here, and demonstrated to result in an accurate measurement of the local heat transfer map on the surface.
Research on Convective Heat Transfer and Mass Transfer of the Evaporator in Micro/Mini-Channel
Su, J.; Li, J.
2006-01-01
With the development of science and technology, various heating and cooling equipment have a development trend of micromation. Micro-fabrication processes make it possible to conduct research on condensation heat transfer in micro-channels. Based...
A high-efficiency heat pump fan
Wright, T.; Lackey, R.S.; Veyo, S.E.
1983-06-01
This paper documents efforts toward development of a high-efficiency outdoor air mover for an advanced electric heat pump. The design goal was to halve the outdoor air-moving electrical power. The prototype air mover at 850 rpm delivers 3070 scfm (1449 l/s) through the prototype outdoor unit with a pressure drop through the coil of 0.09 in (2.29 mm) of water and consumes 150 W of electrical power. The overall air-moving efficiency is estimated at about 35% compared with 19% for the conventionally applied heat pump fan. Although this air mover will cost twice as much as the conventional heat pump air mover, this premium cost should be recoverable in less than four years through energy savings. The sound rating (SRN) for this air mover is less than 20. Means have been identified for improving fan efficiency by 5 percentage points and motor efficiency by 2.5 points and to further quiet the fan.
CFD Extraction of Heat Transfer Coefficient in Cryogenic Propellant Tanks
NASA Technical Reports Server (NTRS)
Yang, H. Q.; West, Jeff
2015-01-01
Current reduced-order thermal model for cryogenic propellant tanks is based on correlations built for flat plates collected in the 1950's. The use of these correlations suffers from inaccurate geometry representation; inaccurate gravity orientation; ambiguous length scale; and lack of detailed validation. This study uses first-principles based CFD methodology to compute heat transfer from the tank wall to the cryogenic fluids and extracts and correlates the equivalent heat transfer coefficient to support reduced-order thermal model. The CFD tool was first validated against available experimental data and commonly used correlations for natural convection along a vertically heated wall. Good agreements between the present prediction and experimental data have been found for flows in laminar as well turbulent regimes. The convective heat transfer between the tank wall and cryogenic propellant, and that between the tank wall and ullage gas were then simulated. The results showed that the commonly used heat transfer correlations for either vertical or horizontal plate over-predict heat transfer rate for the cryogenic tank, in some cases by as much as one order of magnitude. A characteristic length scale has been defined that can correlate all heat transfer coefficients for different fill levels into a single curve. This curve can be used for the reduced-order heat transfer model analysis.
Dual circuit embossed sheet heat transfer panel
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.
Dual circuit embossed sheet heat transfer panel
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.
Heat transfer through metal-graphene interfaces
NASA Astrophysics Data System (ADS)
Wejrzanowski, Tomasz; Grybczuk, Mateusz; Wasiluk, Mateusz; Kurzydlowski, Krzysztof J.
2015-07-01
The paper presents the results of Molecular Dynamics (MD) studies of the thermal properties of Cu and Ag composites with single- (SLG) and multi-layered (MLG) graphene. We show that the thermal boundary conductance (TBC) of the metal-graphene interface drops significantly for the systems containing more than one layer of graphene. It is also concluded that the TBC for a single graphene layer is significantly higher for silver than for copper. For both systems, however, we found that the interface is a barrier for heat transfer with the thermal conductance being at least two orders of magnitude lower than for metal. Moreover, we found that the TBC decreases with an increase in the number of graphene layers. The interfacial effect becomes negligible for a thickness bigger than two graphene layers. Above this thickness the thermal conductivity of the region of multilayered graphene is not influenced by the interface and becomes similar to that of graphite. The results are compared with available experimental data and discussed in terms of the rules for designing composites of a high thermal conductivity.
Enhanced two phase flow in heat transfer systems
Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D
2013-12-03
A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.
Heat transfer in open-cell metal foams
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
Thermodynamic efficiency of pumped heat electricity storage.
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
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.
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 ...
Nano-engineering the boiling surface for optimal heat transfer rate and critical heat flux
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 ...
Cheeti, Satish K.R.
1993-01-01
Heat transfer by free convection in air from an isothermal horizontal heated flat plate facing upward has been experimentally studied by using a non intrusive and accurate optical technique, Speckle photography or a specklegram technique. The local...
Bimonte, Giuseppe
We present a detailed derivation of heat radiation, heat transfer, and (Casimir) interactions for N arbitrary objects in the framework of fluctuational electrodynamics in thermal nonequilibrium. The results can be expressed ...
Heat transfer characteristics of a two-pass trapezoidal channel and a novel heat pipe
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 ...
The deterioration in heat transfer to fluids at supercritical pressure and high heat fluxes
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 ...
Mass transfer in oscillating flows: Efficient drying via pulse combustors
NASA Astrophysics Data System (ADS)
Arpaci, V. S.; Gemmen, R.; Selamet, A.
1989-04-01
The study addressed analytical and experimental methods for increasing industrial and home drying efficiency via pulse combustors. A fundamental scientific methodology is being developed for the momentum, heat and mass transfer in oscillating (on the mean) turbulent flows. The approach follows the intuitive ideas of Taylor and Kolmogorov on the construction of microscales of turbulence. A parallel experimental program is being carried out by the pulse combustor of the Continuous Combustion Laboratory of the Sandia-Livermore National Laboratories. A droplet sizing technique and a quasi-steady computer model have been developed. The unsteady analytical model will determine the range of the quasi-steady model and provide also a mass transfer correlation beyond this range.
Nere, Nandkishor K; Allen, Kimberley C; Marek, James C; Bordawekar, Shailendra V
2012-10-01
Drying an early stage active pharmaceutical ingredient candidate required excessively long cycle times in a pilot plant agitated filter dryer. The key to faster drying is to ensure sufficient heat transfer and minimize mass transfer limitations. Designing the right mixing protocol is of utmost importance to achieve efficient heat transfer. To this order, a composite model was developed for the removal of bound solvent that incorporates models for heat transfer and desolvation kinetics. The proposed heat transfer model differs from previously reported models in two respects: it accounts for the effects of a gas gap between the vessel wall and solids on the overall heat transfer coefficient, and headspace pressure on the mean free path length of the inert gas and thereby on the heat transfer between the vessel wall and the first layer of solids. A computational methodology was developed incorporating the effects of mixing and headspace pressure to simulate the drying profile using a modified model framework within the Dynochem software. A dryer operational protocol was designed based on the desolvation kinetics, thermal stability studies of wet and dry cake, and the understanding gained through model simulations, resulting in a multifold reduction in drying time. PMID:22753308
NASA Astrophysics Data System (ADS)
Cleveland, Mathew A.
We investigate several aspects of the numerical solution of the radiative transfer equation in the context of coal combustion: the parallel efficiency of two commonly-used opacity models, the sensitivity of turbulent radiation interaction (TRI) effects to the presence of coal particulate, and an improvement of the order of temporal convergence using the coarse mesh finite difference (CMFD) method. There are four opacity models commonly employed to evaluate the radiative transfer equation in combustion applications; line-by-line (LBL), multigroup, band, and global. Most of these models have been rigorously evaluated for serial computations of a spectrum of problem types [1]. Studies of these models for parallel computations [2] are limited. We assessed the performance of the Spectral-Line-Based weighted sum of gray gasses (SLW) model, a global method related to K-distribution methods [1], and the LBL model. The LBL model directly interpolates opacity information from large data tables. The LBL model outperforms the SLW model in almost all cases, as suggested by Wang et al. [3]. The SLW model, however, shows superior parallel scaling performance and a decreased sensitivity to load imbalancing, suggesting that for some problems, global methods such as the SLW model, could outperform the LBL model. Turbulent radiation interaction (TRI) effects are associated with the differences in the time scales of the fluid dynamic equations and the radiative transfer equations. Solving on the fluid dynamic time step size produces large changes in the radiation field over the time step. We have modified the statistically homogeneous, non-premixed flame problem of Deshmukh et al. [4] to include coal-type particulate. The addition of low mass loadings of particulate minimally impacts the TRI effects. Observed differences in the TRI effects from variations in the packing fractions and Stokes numbers are difficult to analyze because of the significant effect of variations in problem initialization. The TRI effects are very sensitive to the initialization of the turbulence in the system. The TRI parameters are somewhat sensitive to the treatment of particulate temperature and the particulate optical thickness, and this effect are amplified by increased particulate loading. Monte Carlo radiative heat transfer simulations of time-dependent combustion processes generally involve an explicit evaluation of emission source because of the expense of the transport solver. Recently, Park et al. [5] have applied quasi-diffusion with Monte Carlo in high energy density radiative transfer applications. We employ a Crank-Nicholson temporal integration scheme in conjunction with the coarse mesh finite difference (CMFD) method, in an effort to improve the temporal accuracy of the Monte Carlo solver. Our results show that this CMFD-CN method is an improvement over Monte Carlo with CMFD time-differenced via Backward Euler, and Implicit Monte Carlo [6] (IMC). The increase in accuracy involves very little increase in computational cost, and the figure of merit for the CMFD-CN scheme is greater than IMC.
HEAT TRANSFER IN VERTICAL AND HORIZONTAL ONE-SIDE-HEATED EVAPORATOR TUBES
W. Kohler; V. kefer; W. Kastner
1990-01-01
Heat transfer tests were carried out in a high-pressure test loop using a tube of 6.1-m heated length and 19.55-mm inner diameter. For simulation of nonuniform heating, the wall thickness of the electrically heated tube was reduced over half of its circumference. Experiments included not only vertical upward flow, but also horizontal tube installation with side heating and top heating.
D. E. Beasley; Y. A. Hassan; F. B. Cheung; B. Yang; C. Presser; D. A. Olsen; W. Tong; P. Phelan; L. W. Swanson; D. W. McEligot; D. G. Bogard
1997-01-01
This volume contains a portion of the over 240 ASME papers which were presented at the conference. For over 40 years, the National Heat Transfer Conference has been the premiere forum for the presentation and dissemination of the latest advances in heat transfer. The work contained in these volumes range from studies of fundamental phenomena to applications in the latest
Performance and heat transfer characteristics of a carbon monoxide/oxygen rocket engine
NASA Technical Reports Server (NTRS)
Linne, Diane L.
1993-01-01
The combustion and heat transfer characteristics of a carbon monoxide and oxygen rocket engine were evaluated. The test hardware consisted of a calorimeter combustion chamber with a heat sink nozzle and an eighteen element concentric tube injector. Experimental results are given at chamber pressures of 1070 and 3070 kPa, and over a mixture ratio range of 0.3 to 1.0. Experimental C efficiency was between 95 and 96.5 percent. Heat transfer results are discussed both as a function of mixture ratio and axial distance in the chamber. They are also compared to a Nusselt number correlation for fully developed turbulent flow.
Nanoscale heat transfer and thermoelectrics for alternative energy
NASA Astrophysics Data System (ADS)
Robinson, Richard
2011-03-01
In the area of alternative energy, thermoelectrics have experienced an unprecedented growth in popularity because of their ability to convert waste heat into electricity. Wired in reverse, thermoelectrics can act as refrigeration devices, where they are promising because they are small in size and lightweight, have no moving parts, and have rapid on/off cycles. However, due to their low efficiencies bulk thermoelectrics have historically been a niche market. Only in the last decade has thermoelectric efficiency exceeded ~ 20 % due to fabrication of nanostructured materials. Nanoscale materials have this advantage because electronic and acoustic confinement effects can greatly increase thermoelectric efficiency beyond bulk values. In this talk, I will introduce our work in the area of nanoscale heat transfer with the goal of more efficient thermoelectrics. I will discuss our experiments and methods to study acoustic confinement in nanostructures and present some of our new nanostructured thermoelectric materials. To study acoustic confinement we are building a nanoscale phonon spectrometer. The instrument can excite phonon modes in nanostructures in the ~ 100 s of GHz. Ballistic phonons from the generator are used to probe acoustic confinement and surface scattering effects. Transmission studies using this device will help optimize materials and morphologies for more efficient nanomaterial-based thermoelectrics. For materials, our group has synthesized nano-layer superlattices of Na x Co O2 . Sodium cobaltate was recently discovered to have a high Seebeck coeficent and is being studied as an oxide thermoelectric material. The thickness of our nano-layers ranges from 5 nm to 300 nm while the lengths can be varied between 10 ? m and 4 mm. Typical aspect ratios are 40 nm: 4 mm, or 1:100,000. Thermoelectric characterization of samples with tilted multiple-grains along the measurement axis indicate a thermoelectric efficiency on par with current polycrystalline samples. Due to phonon confinement in nano-structures, it is expected that the thermoelectric efficiency of these sheets will be much higher than that of single crystalline Na 0.7 Co O2 , when the nanosheets have single grains along the heat transport path. This work is supported by KAUST (KUS-C1-018-02), NSF (DMR 0520404), and the DOE (DE-SC0001086).
GAM-HEAT -- a computer code to compute heat transfer in complex enclosures. Revision 1
Cooper, R.E.; Taylor, J.R.; Kielpinski, A.L.; Steimke, J.L.
1991-02-01
The GAM-HEAT code was developed for heat transfer analyses associated with postulated Double Ended Guillotine Break Loss Of Coolant Accidents (DEGB LOCA) resulting in a drained reactor vessel. In these analyses the gamma radiation resulting from fission product decay constitutes the primary source of energy as a function of time. This energy is deposited into the various reactor components and is re- radiated as thermal energy. The code accounts for all radiant heat exchanges within and leaving the reactor enclosure. The SRS reactors constitute complex radiant exchange enclosures since there are many assemblies of various types within the primary enclosure and most of the assemblies themselves constitute enclosures. GAM-HEAT accounts for this complexity by processing externally generated view factors and connectivity matrices, and also accounts for convective, conductive, and advective heat exchanges. The code is applicable for many situations involving heat exchange between surfaces within a radiatively passive medium. The GAM-HEAT code has been exercised extensively for computing transient temperatures in SRS reactors with specific charges and control components. Results from these computations have been used to establish the need for and to evaluate hardware modifications designed to mitigate results of postulated accident scenarios, and to assist in the specification of safe reactor operating power limits. The code utilizes temperature dependence on material properties. The efficiency of the code has been enhanced by the use of an iterative equation solver. Verification of the code to date consists of comparisons with parallel efforts at Los Alamos National Laboratory and with similar efforts at Westinghouse Science and Technology Center in Pittsburgh, PA, and benchmarked using problems with known analytical or iterated solutions. All comparisons and tests yield results that indicate the GAM-HEAT code performs as intended.
Analogy Between Mass and Heat Transfer with Turbulent Flow
NASA Technical Reports Server (NTRS)
Callaghan, Edmund E.
1953-01-01
An analysis of combined heat and mass transfer from a flat plate has been made in terms of Prandtl t s simplified physical concept of the turbulent boundary layer. The results of the analysis show that for conditions of reasonably small heat and mass transfer, the ratio of the mass-and heat-transfer coefficients is dependent on the Reynolds number of the boundary layer, the Prandtl number of the medium of diffusion, and the Schmidt number of the diffusing fluid in the medium of diffusion. For the particular case of water evaporating into air, the ratio of mass-transfer coefficient to heat-transfer coefficient is found to be slightly greater than unity.
INVESTIGATIONS OF NON-UNIFORMLY HEAT TRANSFER IN NUCLEAR REACTOR HEAT RELEASING ELEMENTS
V. S. Ermakov; V. Ivanov
1958-01-01
The problem of heat distribution in a multi-layer fuel element (F E) for ; a one-dimensional transient temperature field is considered when there is a ; nonuniform heat source (which is a function of the space coordinates and time) ; and convective heat exchange of the FE with a heat transfer medium at a variable ; temperature. Two methods for
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
NASA Astrophysics Data System (ADS)
Stein, R. P.
Aspects of direct contact heat transfer are considered along with transport phenomena in fusion reactors, enhanced nucleate boiling, flow boiling, heat transfer in non-Newtonian systems, two-phase systems, heat transfer in fossil fuel conversion systems, process heat transfer, thermal and hydraulic behavior in rod and tube bundles, and two-phase systems in rod and tube bundles. Attention is also given to solar energy heat transfer, heat transfer in fluidized beds, and fire and combustion fundamentals, taking into account thermal stress oscillations induced by dynamic instabilities in radiation-heated boiler tubes, convection losses from a cavity receiver, numerical solutions of turbulent models for flow over a flat plate with angle of attack, and the heat transfer from smooth horizontal tubes immersed in gas fluidized beds. A description is provided of aspects of turbulent combustion modelling, the exhaust gas emission from a swirl stabilized combustor, the analytical solution for diffusion in the core of a droplet with internal circulation, and the radiant ignition of a thin combustible solid.
Heat transfer of nanofluids in a shell and tube heat exchanger
B. Farajollahi; S. Gh. Etemad; M. Hojjat
2010-01-01
Heat transfer characteristics of ?-Al2O3\\/water and TiO2\\/water nanofluids were measured in a shell and tube heat exchanger under turbulent flow condition. The effects of Peclet number, volume concentration of suspended nanoparticles, and particle type on the heat characteristics were investigated. Based on the results, adding of naoparticles to the base fluid causes the significant enhancement of heat transfer characteristics. For
Heat and Mass Transfer Processes in Scrubber of Flue Gas Heat Recovery Device
NASA Astrophysics Data System (ADS)
Veidenbergs, Ivars; Blumberga, Dagnija; Vigants, Edgars; Kozuhars, Grigorijs
2010-01-01
The paper deals with the heat and mass transfer process research in a flue gas heat recovery device, where complicated cooling, evaporation and condensation processes are taking place simultaneously. The analogy between heat and mass transfer is used during the process of analysis. In order to prepare a detailed process analysis based on heat and mass process descriptive equations, as well as the correlation for wet gas parameter calculation, software in the
Heat transfer near spacer grids in rod bundles
Yoder, G.L.
1985-01-01
Heat transfer data from several sources have been assembled which show the effect of spacer grids on local heat transfer within a rod bundle. Both single phase (air and steam) data and two phase (steam/water) data show heat transfer augmentation in the grid region. Heat transfer improvement immediately beyond the grid ranges from a few percent to over fifty percent in these experiments, depending on flow conditions. The data are examined using several nondimensional parameters which relate the above effects to known quantities. The relative effect of the grid on local heat transfer is altered by both the Reynolds number and blockage ratio. Twenty to thirty hydraulic diameters are required before the local effect of the grid dissipates. Locally, both the single phase and two phase data show the same trends. Comparison of the single and two phase data also shown some differences. Some film boiling data indicate that an altered heat transfer regime may exist near the grid. High rod heat transfer coefficients at the grid locations indicate either a rewet of the rods or at least a change from film boiling to transition boiling near the spacer. The comparison also indicates that the film boiling data is affected on a global as well as local basis. This is due to the effect of the grid on the liquid distribution.
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.
Heat Transfer of Confined Impinging Air-water Mist Jet
NASA Astrophysics Data System (ADS)
Chang, Shyy Woei; Su, Lo May
This paper describes the detailed heat transfer distributions of an atomized air-water mist jet impinging orthogonally onto a confined target plate with various water-to-air mass-flow ratios. A transient technique was used to measure the full field heat transfer coefficients of the impinging surface. Results showed that the high momentum mist-jet interacting with the water-film and wall-jet flows created a variety of heat transfer contours on the impinging surface. The trade-off between the competing influences of the different heat transfer mechanisms involving in an impinging mist jet made the nonlinear variation tendency of overall heat transfer against the increase of water-to-air mass-flow ratio and extended the effective cooling region. With separation distances of 10, 8, 6 and 4 jet-diameters, the spatially averaged heat transfer values on the target plate could respectively reach about 2.01, 1.83, 2.43 and 2.12 times of the equivalent air-jet values, which confirmed the applicability of impinging mist-jet for heat transfer enhancement. The optimal choices of water-to-air mass-flow ratio for the atomized mist jet required the considerations of interactive and combined effects of separation distance, air-jet Reynolds number and the water-to-air mass-flow ratio into the atomized nozzle.
NASA Astrophysics Data System (ADS)
Chen, Kaifeng; Santhanam, Parthiban; Sandhu, Sunil; Zhu, Linxiao; Fan, Shanhui
2015-04-01
We consider near-field heat transfer with nonzero chemical potential for photons, as can occur between two semiconductor bodies, held at different temperatures with at least one of the bodies under external bias. We show that the dependence of radiative heat flux on chemical potential enables electronic control of both the direction and magnitude of near-field heat transfer between the two bodies. Moreover such a configuration can operate as a solid-state cooling device whose efficiency can approach the Carnot limit in the ideal case. Significant cooling can also be achieved in the presence of inherent nonidealities including Auger recombination and parasitic phonon-polariton heat transfer.
Cryogenic apparatus for study of near-field heat transfer
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.
An analytical and experimental investigation of melting heat transfer
NASA Astrophysics Data System (ADS)
Wen, C.; Sheffield, J. W.; O'dell, M. P.; Leland, J. E.
1988-01-01
A computational model is presented for the prediction of the heat transfer between a heat transfer fluid (HTF) and a phase change material (PCM) of a latent heat storage unit. Two models of flow, hydrodynamically fully developed flow and developing flow, of the HTF were proposed in this study. A two-dimensional enthalpy method was used for the computation of the phase change heat transfer in the PCM. A fully implicit finite difference scheme was utilized for the calculation of convective heat transfer in the HTF. The unknown time dependent boundary condition between the HTF and the PCM was found iteratively. The predictions are substantiated by their excellent agreement with experimental data. Factors which affect the heat transfer rates between the HTF and the PCM were studied numerically for both hydrodynamically fully developed flow and developing flow. It is found that the Nusselt number is significantly increased by the developing temperature profiles. The developing velocity profiles also will increase the Nusselt number. However, the influence on Nusselt number due to the developing temperature profiles. Other factors which affect the Nusselt number are discussed. The heat transfer of this latent heat storage unit was also studied experimentally. The experimental results were compared with the numerical results for P116, a sun wax.
Wall-to-suspension heat transfer in circulating fluidized beds
Wirth, K.E.
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.
Radiative heat transfer in low-dimensional systems -- microscopic mode
NASA Astrophysics Data System (ADS)
Woods, Lilia; Phan, Anh; Drosdoff, David
2013-03-01
Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.
Heat transfer crisis on sintered porous surfaces - experimental investigations
NASA Astrophysics Data System (ADS)
Michal Wojcik, Tadeusz
2012-04-01
There were presented the results of theoretical analysis of boiling heat transfer on heating surfaces covered with thin-layered capillary porous structures. The paper discussed the results of experimental investigations into intralayer boiling crisis and accompanying phenomena. It was observed that the structural parameters of the porous covering affected the course of the process. Hysteresis phenomenon manifested itself when the heat flux initiating intralayer heat crisis was reached. The crisis mechanism hypotheses, the description of which was available in literature, were discussed.
A review on boiling heat transfer enhancement with nanofluids
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
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...
P. K. Sahoo; A. K. Datta
2003-01-01
An iterative technique is developed and reported for accurate estimation of heat transfer coefficients in a helical triple tube heat exchanger. Based on the experimental temperature rise of whole milk in a helical triple tube heat exchanger, accurate values of film heat transfer coefficients and overall heat transfer coefficients based on the outside area of the innermost tube and the
Numerical study of vorticity-enhanced heat transfer
NASA Astrophysics Data System (ADS)
Wang, Xiaolin; Alben, Silas
2013-11-01
Vortices produced by vibrated reeds and flapping foils can improve heat transfer efficiency in electronic hardware. Vortices enhance forced convection by boundary layer separation and thermal mixing in the bulk flow. In this work, we modeled and simulated the fluid flow and temperature in a 2-D channel flow with vortices injected at the upstream boundary. We classified four types of vortex streets depending on the Reynolds number and vortices' strengths and spacings, and studied the different vortex dynamics in each situation. We then used Lagrangian coherent structures (LCS) to study the effect of the vortices on mixing and determined how the Nusselt number and Coefficients of performance vary with flow parameters and Peclet numbers.
Passive heat transfer means for nuclear reactors
Burelbach; James P
1984-01-01
An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler
Nonlinear aspects of high heat flux nucleate boiling heat transfer. Part 1, Formulation
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.
Heat transfer through an extended surface containing He II
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.
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.
Boiling heat transfer and droplet spreading of nanofluids.
Murshed, S M Sohel; de Castro, C A Nieto
2013-11-01
Nanofluids- a new class of heat transfer fluids have recently been a very attractive area of research due to their fascinating thermophysical properties and numerous potential benefits and applications in many important fields. However, there are many controversies and inconsistencies in reported arguments and experimental results on various thermal characteristics such as effective thermal conductivity, convective heat transfer coefficient and boiling heat transfer rate of nanofluids. As of today, researchers have mostly focused on anomalous thermal conductivity of nanofluids. Although investigations on boiling and droplet spreading are very important for practical application of nanofluids as advanced coolants, considerably fewer efforts have been made on these thermal features of nanofluids. In this paper, recent research and development in boiling heat transfer and droplet spreading of nanofluids are reviewed together with summarizing most related patents on nanofluids published in literature. Review reveals that despite some inconsistent results nanofluids exhibit significantly higher boiling heat transfer performance compared to their base fluids and show great promises to be used as advanced heat transfer fluids in numerous applications. However, there is a clear lack of in-depth understanding of heat transport mechanisms during phase change of nanofluids. It is also found that the nanofluids related patents are limited and among them most of the patents are based on thermal conductivity enhancement and synthesising processes of specific type of nanofluids. PMID:24330044
Percolation induced heat transfer in deep unsaturated zones
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.
Fourier analysis of conductive heat transfer for glazed roofing materials
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.
NASA Astrophysics Data System (ADS)
Borodulya, V. A.; Malevich, V. L.; Sinkevich, A. E.
2012-01-01
Based on the earlier developed model of calculation of the local parameters of heat and mass transfer in deep cooling of flue gases (a vapor-gas mixture) in a bundle of tubes of a condensation heat-utilization unit, the distribution of the parameters of a condensing vapor-gas mixture both along the length of the tubes and in the depth of the tube bundle in a crossflow under various cooling conditions corresponding to the working parameters of heat-utilization units at industrial thermoelectric plants (TEP) and in boiler houses has been obtained. A comparison of the calculated values of the heating efficiency of the indicated heat-utilization unit with the results of tests of the condensation heat-utilization unit at the Ul'yanovsk TEP-3 (Russia) has demonstrated their satisfactory agreement.
Takeishi, K; Aoki, S
2001-05-01
This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of industrial gas turbines in order to attain efficient and environmentally benign engines. High efficiency film cooling, in the form of shaped film cooling and full coverage film cooling, is one of the most important cooling technologies. Corresponding heat transfer tests to optimize the film cooling effectiveness are shown and discussed in this first part of the contribution. PMID:11460641
Heat transfer intensification by increasing vapor flow rate in flat heat pipes
NASA Astrophysics Data System (ADS)
Sprinceana, Silviu; Mihai, Ioan; Beniuga, Marius; Suciu, Cornel
2015-02-01
Flat heat pipes have various technical applications, one of the most important being the cooling of electronic components[9]. Their continuous development is due to the fact that these devices permit heat transfer without external energetic contribution. The practical exploitation of flat heat pipes however is limited by the fact that dissipated power can only reach a few hundred watts. The present paper aims to advance a new method for the intensification of convective heat transfer. A centrifugal mini impeller, driven by a turntable which incorporates four permanent magnets was designed. These magnets are put in motion by another rotor, which in its turn includes two permanent magnets and is driven by a mini electrical motor. Rotation of the centrifugal blades generates speed and pressure increase of the cooling agent brought to vapor state within the flat micro heat pipe. It's well known that the liquid suffers biphasic transformations during heat transfer inside the heat pipe. Over the hotspot (the heat source being the electronic component) generated at one end of the heat pipe, convective heat transfer occurs, leading to sudden vaporization of the liquid. Pressures generated by newly formed vapors push them towards the opposite end of the flat heat pipe, where a finned mini heat sink is usually placed. The mini-heat exchanger is air-cooled, thus creating a cold spot, where vapors condensate. The proposed method contributes to vapor flow intensification by increasing their transport speed and thus leading to more intense cooling of the heat pipe.
Rheology and convective heat transfer of colloidal gas aphrons in horizontal mini-channels
Pilon, Laurent
Rheology and convective heat transfer of colloidal gas aphrons in horizontal mini-channels Howard rights reserved. Keywords: Foams; Microbubbles; Rheology; Heat transfer; Protein separation; Porous media
Kaji, N. (Institute of Vocational and Technical Education, Sagamihara (Japan)); Mori, Y.H. (Keio Univ., Yokahama (Japan)); Tochitani, Y. (Kabazawa Inst. of Tech., Nonoichi (Japan))
1988-08-01
The heat transfer enhancement caused by the application of a low-frequency (1 {approximately} 16 Hz) alternating field having the sinusoidal waveform has been studied experimentally with water drops in a medium of silicone oil. The heat transfer coefficients has been found to peak at three particular frequencies. The data newly obtained with the sinusoidal waveform are compared with earlier results obained with electric fields having other waveforms. The waveform and the frequency that yield the largest enhancement of heat transfer are sought.
Heat transfer in porous media considering phase change and capillarity - The heat pipe effect
K. S. Udell
1985-01-01
A one-dimensional, steady state analysis of the heat and mass transfer in porous media saturated with the liquid and vapor phases of a single component fluid was conducted. The effects of capillarity, gravity forces, and phase change were included. Theoretical results were compared to experimental data with excellent agreement. It was found that the heat transfer was increased several orders
The measurement of capsule heat transfer gaps using neutron radiography.
NASA Technical Reports Server (NTRS)
Thaler, L. A.
1971-01-01
The use of neutron radiographs to determine dimensional changes of heat transfer gaps in cylindrical nuclear fueled capsules is described. A method was developed which involves scanning a very fine grained neutron radiograph negative with a recording microdensitometer. The output of the densitometer is recorded on graph paper and the heat transfer gap is plotted as a well-defined optical density change. Calibration of the recording microdensitometer ratio arms permits measurements to be made of the heat transfer optical density change from the microdensitometer trace. Total heat transfer gaps, measured by this method, agree with the physical measurements within plus or minus 0.005 cm over a range of gaps from 0.061 to 0.178 cm.
Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces
Attinger, Daniel
Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces Amy Rachel in revised form 30 October 2012 Accepted 31 October 2012 Keywords: Superhydrophobic Superhydrophilic Biphilic- and nanofabrication, superhydrophilic and superhydrophobic surfaces have been developed. The statics and dynamics
Effects of operating conditions on a heat transfer fluid aerosol
Sukmarg, Passaporn
2000-01-01
of heat transfer fluid aerosols from process leaks. To simulate industrial leaks, aerosol formation from a plain orifice into ambient air is studied by measuring liquid drop sizes and size distributions at various distances from an orifice. Measurements...
Wellbore Heat Transfer Model for Wax Deposition in Permafrost Region
Cui, Xiaoting
2012-05-31
Producing waxy oil in arctic area may cause wax deposited on the well wall. Since wax deposition is strongly thermal related, accurate heat transfer model is necessary in predicting and preventing wax depostion. A mathematical model was derived...
Heat transfer during film condensation of a liquid metal vapor
Sukhatme, S. P.
1964-01-01
The object of this investigation is to resolve the discrepancy between theory and experiment for the case of heat transfer durirnfilm condensation of liquid metal vapors. Experiments by previous investigators have yielded ...
Survey and evaluation of techniques to augment convective heat transfer
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 ...
A foundation heat transfer algorithm for detailed building energy programs
Krarti, M.; Kreider, J.F. [Univ. of Colorado, Boulder, CO (United States). Joint Center for Energy Management; Claridge, D.E. [Texas A and M Univ., College Station, TX (United States). Mechanical Engineering Dept.
1994-12-31
This paper describes an algorithm that calculates heat transfer between the ground and buildings. The algorithm an handle more than 37 building foundation/insulation configurations, including basements, slabs, and crawl spaces with full, partial, and no insulation. The solution method on which the algorithm is based is outlined. The required input data are described and references are listed to help the user Determine the appropriate values for some of the input parameters. As an application of the algorithm, analyses of the effect of the insulation configuration on heat transfer from both slabs and basements are briefly presented. Spectral sensitivity analysis is conducted to determine the effect of cyclic changes of indoor and outdoor temperature on foundation heat transfer. Finally, implementation of the foundation heat transfer calculation algorithm in a commonly used hourly building simulation program is demonstrated.
Volume-energy parameters for heat transfer to supercritical fluids
NASA Technical Reports Server (NTRS)
Kumakawa, A.; Niino, M.; Hendricks, R. C.; Giarratano, P. J.; Arp, V. D.
1986-01-01
Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.
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.
Heat transfer enhancement in a channel with porous baffles
Ko, Kang-Hoon
2005-02-17
/3...........................................................68 xiii FIGURE Page 4.8 Heat transfer performance for /hh = 2/3...........................................................69 5................6 1.3 Objectives...........................................................................................................8 1.3.1 Experimental Investigation ....................................................................8 1.3.2 Numerical...
Promotion and retardation of heat transfer by electric fields
Y. Asakawa
1976-01-01
I REPORT here on the effects of an electric field on heat transfer. The effects depend on the applied voltage, the shapes, number and locations of the electrodes, and the frequency of the electric field1,2.
Scalable graphene coatings for enhanced condensation heat transfer.
Preston, Daniel J; Mafra, Daniela L; Miljkovic, Nenad; Kong, Jing; Wang, Evelyn N
2015-05-13
Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating to promote dropwise condensation of water in industrial conditions with the potential for scalable application via CVD. PMID:25826223
Non-intrusive characterization of heat transfer fluid aerosol formation
Krishna, Kiran
2001-01-01
Heat transfer fluids are widely used in the chemical process industry and are available in a wide range of properties. These fluids are flammable above their flash points and can cause explosions. Though the possibility of aerosol explosions has...
Mesoscopic near-field radiative heat transfer at low temperatures
NASA Astrophysics Data System (ADS)
Maasilta, Ilari; Geng, Zhuoran; Chaudhuri, Saumyadip; Koppinen, Panu
2015-03-01
Near-field radiative heat transfer has mostly been discussed at room temperatures and/or macroscopic scale geometries. Here, we discuss our recent theoretical and experimental advances in understanding near-field transfer at ultra-low temperatures below 1K. As the thermal wavelengths increase with lowering temperature, we show that with sensitive tunnel junction bolometers it is possible to study near-field transfer up to distances ~ 10 ?m currently, even though the power levels are low. In addition, these type of experiments correspond to the extreme near-field limit, as the near-field region starts at ~ mm distances at 0.1 K, and could have theoretical power enhancement factors of the order of 1010. Preliminary results on heat transfer between two parallel metallic wires are presented. We also comment on possible areas were such heat transfer might be relevant, such as densely packed arrays of low-temperature detectors.
Transient Heat Transfer in TCAP Coils
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.
Transient Heat Transfer in TCAP Coils
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.
Forced Convection Film Boiling Heat Transfer Over a Vertical Cylinder
Q. S. Liu; K. Fukuda; M. Shiotsu
2011-01-01
The knowledge of subcooled film boiling heat transfer is important as the basis of understanding the reflooding phenomenon during emergency cooling in a nuclear reactor under a loss-of-coolant accident. In this study, forced convection film boiling heat transfer from a vertical cylinder in Freon-113 flowing upward along the cylinder was measured for the flow velocities ranging from 0 to 1.3
Comparison of Methods for Calculating Radiative Heat Transfer
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.
Heat transfer enhancement resulting from induction electrohydrodynamic pumping
Margo, Bryan David
1992-01-01
HEAT TRANSFER ENHANCEMENT RESULTING FROM INDUCTION ELECTROHYDRODYNAMIC PUMPING A Thesis by BRYAN DAVID MARGO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1992 Major Subject: Mechanical Engineering HEAT TRANSFER ENHANCEMENT RESULTING FROM INDUCTION ELECTROHYDRODYNAMIC PUMPING A Thesis by BRYAN DAVID MARGO Approved as to style and content by: Jamal Seyed- Yagoobi (Chair...
Update on Condensation Heat Transfer and Pressure Drop inside Minichannels
Alberto Cavallini; Luca Doretti; Marko Matkovic; Luisa Rossetto
2006-01-01
The present paper reviews published experimental work focusing on condensation flow regimes, heat transfer, and pressure drop in minichannels. New experimental data are available with high (R410A), medium (R134a), and low (R236ea) pressure refrigerants in minichannels of different cross-section geometries and with hydraulic diameters ranging from 0.4 to 3 mm. Because of the influence of flow regimes on heat transfer
Boiling heat transfer on meshed surfaces of different aperture
NASA Astrophysics Data System (ADS)
Orman, ?ukasz J.
2014-08-01
The paper presents the results of investigations of the impact of mesh aperture on boiling heat transfer. The tests have been performed for distilled water and ethyl alcohol at ambient pressure. It was observed that the meshed surfaces performed much better than the smooth reference surface and that meshes of smaller aperture provided better results. The obtained results have been compared with selected models of boiling heat transfer from literature.
Heat transfer and evaporation in geothermal desalination units
K. Bourouni; R. Martin; L. Tadrist; M. T. Chaibi
1999-01-01
The heat transfer of air–water–vapour mixtures in a desalination plant, using the aero-evapo-condensation process, has been studied theoretically and experimentally. The present unit consists of a falling-film evaporator and condenser, made of polypropylene. It was designed to work at low temperatures (of 60–90°C) utilizing geothermal energy. A model for heat-and-mass transfers in the plant is developed, resulting in a set
Mpemba effect, Newton cooling law and heat transfer equation
Vladan Pankovic; Darko V. Kapor
2012-12-11
In this work we suggest a simple theoretical solution of the Mpemba effect in full agreement with known experimental data. This solution follows simply as an especial approximation (linearization) of the usual heat (transfer) equation, precisely linearization of the second derivation of the space part of the temperature function (as it is well-known Newton cooling law can be considered as the effective approximation of the heat (transfer) equation for constant space part of the temperature function).
Heat Transfer of Confined Impinging Air-water Mist Jet
Shyy Woei Chang; Lo May Su
2001-01-01
This paper describes the detailed heat transfer distributions of an atomized air-water mist jet impinging orthogonally onto a confined target plate with various water-to-air mass-flow ratios. A transient technique was used to measure the full field heat transfer coefficients of the impinging surface. Results showed that the high momentum mist-jet interacting with the water-film and wall-jet flows created a variety
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.
Heat transfer and pressure drop in tubes with short turbulators
A. Klaczak
1996-01-01
The results of investigations concerning heat transfer and pressure drop in a tube with short single-turn turbulators in form of a twisted tape are presented here. The experiments were carried out in the range: 1300hRe 4,3hPrЗ,0, 2,9hS\\/dД,4 with water as the test fluid. The results were compared with those obtained when investigating heat transfer and flow resistance in a tube
One dimensional lunar ash flow with and without heat transfer
NASA Technical Reports Server (NTRS)
Pai, S. I.; Hsieh, T.
1971-01-01
The characteristics of lunar ash flow are discussed in terms of the two phase flow theory of a mixture of a gas and small solid particles. A model is developed to present the fundamental equations and boundary conditions. Numerical solutions for special ash flow with and without heat transfer are presented. In the case of lunar ash flow with small initial velocity, the effect of the heat transfer makes the whole layer of ash flow more compacted together than the corresponding isothermal case.
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.
Effect of Channel Configurations for Tritium Transfer in Printed Circuit Heat Exchangers
Chang Oh; Eung Kim; Robert Shrake; Mike Patterson
2009-05-01
The Next Generation Nuclear Plant (NGNP), a very High temperature Gas-Cooled Reactor (VHTR) concept, will provide the first demonstration of a closed-loop Brayton cycle at a commercial scale of a few hundred megawatts electric and hydrogen production. The power conversion system (PCS) for the NGNP will take advantage of the significantly higher reactor outlet temperatures of the VHTR to provide higher efficiencies than can be achieved in the current generation of light water reactors. Besides demonstrating a system design that can be used directly for subsequent commercial deployment, the NGNP will demonstrate key technology elements that can be used in subsequent advanced power conversion systems for other Generation IV reactors. In anticipation of the design, development and procurement of an advanced power conversion system for the NGNP, the system integration of the NGNP and hydrogen plant was initiated to identify the important design and technology options that must be considered in evaluating the performance of the proposed NGNP. In the VHTR system, an intermediate heat exchanger (IHX), which transfers heat from the reactor core to the electricity or hydrogen production system is one key component, and its effectiveness is directly related to the system overall efficiency. In the VHTRs, the gas fluids used for coolant generally have poor heat transfer capability, so it requires very large surface area for a given condition. For this reason, a compact heat exchanger (CHE), which is widely used in industry especially for gasto-gas or gas-to-liquid heat exchange is considered as a potential candidate for an IHX replacing the classical shell and tube type heat exchanger. A compact heat exchanger is arbitrary referred to be a heat exchanger having a surface area density greater than 700 m2/m3. The compactness is usually achieved by fins and micro-channels, and leads to the enormous heat transfer enhancement and size reduction. The surface area density is the total heat transfer area divided by the volume of the heat exchanger. In the case of PCHE units, the heat transfer surface area density may be as high as 2,500 m2/m3. This high compactness implies an appreciable reduction in material reducing cost. In this study, heat transfer and tritium penetration analyses have been performed for two different channel configurations of the PCHE; (1) standard and (2) off-set. One of the goals of this study was to determine whether offsetting the hot and cold streams would significantly reduce the tritium flux, and whether or not it would affect the heat transfer significantly.
Spinodal turbulence enhances heat transfer in micro devices
NASA Astrophysics Data System (ADS)
Farisé, Stefano; Poesio, Pietro; Beretta, Gian Paolo
2012-11-01
We experimentally prove the possibility of using spinodal mixtures to increase heat transfer in micro devices as a consequence of an evenly distributed micro agitation, which increases the effective diffusivity. Despite the Re -number is as low as 5, turbulence-like mixing can be achieved by mass transfer effects. A mixture of acetone-hexadecane is quenched in a micro heat exchanger to induce spinodal decomposition. The heat transfer rate is enhanced by self-induced convective motion (spinodal turbulence) because the drops of one phase move against each others under the influence of non-equilibrium capillary forces, Korteweg stresses,which are sustained by the free energy liberated during phase separation. The heat transfer is increased up to the 200% and the effect become larger as the bulk Re decreses, while no dramatic increase in the pressure drop is observed. We built two different experimental set-ups: in the first we measure the heat transfer with a feedback method and in the second we measure the pressure drop and we visualize the induced convection. High-speed camera visualization,pressure drop and temperature measurements allow a complete characterization of the phenomenon, with a special attention to the quantification of the heat transfer coefficent enhancement.
Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.
2012-01-01
Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.
Revealing the complex conduction heat transfer mechanism of nanofluids
NASA Astrophysics Data System (ADS)
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects. PMID:26058515
Two phase flow and heat transfer characteristics of a separate-type heat pipe
NASA Astrophysics Data System (ADS)
Tang, Zhiwei; Liu, Aijie; Jiang, Zhangyan
2011-07-01
Two phase flow and heat transfer characteristics of a separate-type heat pipe have been studied experimentally and theoretically. The experimental apparatus have the same geometry for the evaporator and the condenser which consist of 5-tube-banks, with working temperature ranges of 80-125°C. The experimental working fluid is dual-distilled water with corrosion-resistant agents. Heat transfer coefficients for boiling and condensation along with heat flux and working temperature are measured at different filling ratio. According to the results of the experiments, the optimized filling ratio ranges from 16 to 36%. Fitted correlations of average heat transfer coefficients of the evaporator and Nusselt numbers of the condenser at the proposed filling ratio are obtained. Two phase flow characteristics of the evaporator and the condenser as well as their influence on heat transfer are described on the basis of simplified analysis. Reasons for the pulse-boiling process remain to be studied.
Unsteady radiative-convective heat transfer on a radiating surface
NASA Astrophysics Data System (ADS)
Salomatov, Vasily; Puzyrev, Evgeniy; Salomatov, Vladimir
2012-11-01
Research of radiation-convective heat exchange on radiating surfaces at natural and forced convection is complex mathematical task and here we obtain approximate analytical formulations for this process. We consider two dimensional unsteady heat transfer between solid surface and fluid under the natural laminar convection within optically transparent grey media. Also we assume constant thermo-physical properties except density which is decreasing linearly with temperature. Complex radiative-convective unsteady heat transfer approximately can be considered as a multi-stage process. At the beginning heat transfer coefficient is time dependent but almost independent on longitudinal coordinate. Afterwards heat transfer coefficient becomes dependent on longitudinal coordinate but does not change over time. Analytic formulations obtained for those two stages could be merged along the "time-space" characteristic basing on the equality of heat flows and temperatures there. Solutions are constructed using asymptotic expansions. Theoretical analysis of the solutions revealed the following: effect of radiation leads to a change in the heat transfer coefficient from the values that are characteristic to the second order boundary conditions to the values that are characteristic for the first order boundary conditions. The rate of this transition depends on ß radiation coefficient. Experimental research confirmed correctness of the simplifications introduced.
Heat and mass transfer during low intensity convection drying
Zhao Hui Wang; Guohua Chen
1999-01-01
A diffusion model of heat and mass transfer in moist porous media is obtained for low intensity convection drying found typically in food products and vegetable dehydration. The effective diffusivity was analyzed based on the coupled effects of moisture content and temperature on mass transfer in capillary flow, evaporation–condensation, and transition regions. The temperature effect was found to be significant
NASA Astrophysics Data System (ADS)
Wu, Yan-Qiu
2015-07-01
In this paper, an endoreversible Carnot heat engine with irreversible heat transfer processes is analyzed based on generalized heat transfer law. The applicability of the entropy generation minimization, exergy analyses method, and entransy theory to the analyses is discussed. Three numerical cases are presented. It is shown that the results obtained from the entransy theory are different from those from the entropy generation minimization, which is equivalent to the exergy analyses method. For the first case in which the application preconditions of the entropy generation minimization and entransy loss maximization are satisfied, both smaller entropy generation rate and larger entransy loss rate lead to larger output power. For the second and third cases in which the preconditions are not satisfied, the entropy generation minimization does not lead to the maximum output power, while larger entransy loss rate still leads to larger output power in the third case. For the discussed cases, the concept of entransy dissipation is not applicable for the analyses of output power. The problems in the negative comments on the entransy theory are pointed out and discussed. The related researchers are advised to focus on some new specific application cases to show if the entransy theory is the same as some other theories. Project supported by the Youth Programs of Chongqing Three Gorges University, China (Grant No. 13QN18).
Thermal modelling of DC continuous casting including submould boiling heat transfer
S. K. Das
1999-01-01
The steady-state thermal problem associated with the direct-chill continuous casting of aluminium–magnesium (Al–Mg) alloy cylindrical ingots is solved by an efficient numerical simulation method which also includes secondary cooling with submould boiling heat transfer. A nonorthogonal control volume discretisation and coordinate transformation technique has been applied for solving the heat transport phenomena in a multi-domain framework which involves detrmination of
Chi-Chuan Wang; Kuan-Yu Chi; Chun-Jung Chang
2000-01-01
A correlation for fin-and-tube heat exchanger having plain fin geometry is proposed in this study. A total of 74 samples were used to develop the correlation. For practical considerations, the proposed heat transfer correlation had absorbed the contact conductance in the development of correlation. The proposed heat transfer correlation can describe 88.6% of the database within ±15%, while the proposed
Heat transfer enhancement in fin-tube heat exchangers by winglet type vortex generators
G. Biswas; N. K. Mitra; M. Fiebig
1994-01-01
Numerical investigations of the flow structure and heat transfer enhancement in a channel with a built-in-circular tube and a winglet type vortex generator are presented. The geometrical configuration represents an element of a gas-liquid fin-tube crossflow heat exchanger. In the absence of the winglet type vortex generator, relatively little heat transfer takes place in the downstream of the circular tube
Convective heat transfer through complex structures
Kuo; Shiaomin
1989-01-01
Complex structures such as fin arrays, foam materials, and packed beds have extensive industrial applications, e.g., heat sinks in electronics cooling, compact heat exchangers, regenerators, and chemical catalytic reactors. Forced convection through such systems poses a complex problem of mass, momentum, and energy exchanges between the solid matrix and the surrounding fluid. A general model would require the energy equations
Studies of heat transfer and aerodynamics in bundles assembled from oval tubes
NASA Astrophysics Data System (ADS)
Burkov, V. K.; Medvedskii, V. P.; Kochegarova, I. Yu.; Lafa, Yu. I.
2010-03-01
Results from studies of heat transfer and airdynamic drag in bundles assembled from oval tubes spaced at relative transverse pitches equal to 2.07, 2.24, and 2.62 and with a constant relative longitudinal pitch equal to 2.24 are presented. The influence of the bundle’s geometrical characteristics on its power efficiency is analyzed.
Secondary heat transfer circuit for a nuclear reactor
A. Brachet; J. Figuet; J. Guidez; N. Lions
1985-01-01
The invention relates to a secondary heat transfer circuit for a liquid metal nuclear reactor. Each loop of the main circuit has in order a steam generator, a pump, and at least one heat exchanger positioned in the reactor vessel. A downstream buffer tank is located in the pipe connecting the generator to the pump, whilst the upstream buffer tank
Students' Misconceptions about Heat Transfer Mechanisms and Elementary Kinetic Theory
ERIC Educational Resources Information Center
Pathare, S. R.; Pradhan, H. C.
2010-01-01
Heat and thermodynamics is a conceptually rich area of undergraduate physics. In the Indian context in particular there has been little work done in this area from the point of view of misconceptions. This prompted us to undertake a study in this area. We present a study of students' misconceptions about heat transfer mechanisms, i.e. conduction,…
Heat Transfer from Finned Metal Cylinders in an Air Stream
NASA Technical Reports Server (NTRS)
Biermann, Arnold, E; Pinkel, Benjamin
1935-01-01
This report presents the results of tests made to supply design information for the construction of metal fins for the cooling of heated cylindrical surfaces by an air stream. A method is given for determining fin dimensions for a maximum heat transfer with the expenditure of a given amount of material for a variety of conditions of air flow and metals.
Instabilities encountered during heat transfer to a supercritical fluid
NASA Technical Reports Server (NTRS)
Cornelius, A. J.
1969-01-01
Investigation was made of the unstable behavior of a heat-transfer loop operating at a supercritical pressure. Natural convection operation of the loop, with observations on acoustic and slow oscillatory behavior, was emphasized during testing. The basic cause of both types of behavior appeared to originate in the heated boundary layer.
Modeling of transient natural convection heat transfer in electric ovens
Hitesh Mistry; Ganapathi-subbu; Subhrajit Dey; Peeush Bishnoi; Jose Luis Castillo
2006-01-01
Prediction of transient natural convection heat transfer in vented enclosures has multiple applications such as understanding of cooking environment in ovens and heat sink performance in electronic packaging industry. The thermal field within an oven has significant impact on quality of cooked food and reliable predictions are important for robust design and performance evaluation of an oven. The CFD modeling
Unsteady heat transfers through a multi-layer wall
En-Hai Wang; W. H. Liu
1988-01-01
This paper presents a numerical analysis of the heat transfers through a multi-layer wall subjected to complicated time-dependent boundary conditions. A layer of insulating material at the exterior side or at the interior side has significant influences on the daily total heat gain or loss of the associated building. Averaged total incident solar radiation and ambient temperature functions can be
Thinking about Heat Transfer Fouling: A 5 × 5 Matrix
Norman Epstein
1981-01-01
Fouling of heat transfer surfaces, which leads to high economic penalties and is still dealt with by heat exchanger designers by the crude TEMA approach, is classified into five principal categories. The measurement of thermal fouling is considered critically, and this is followed by a discussion of the successive events, up to five in number, that characterize most fouling situations.
Komendantov, A.S.; Kuzma-Kichta, Y.A.; Vasil'eva, L.T.; Ovodkov, A.A. (Moscow Power Engineering Inst., Moscow (SU))
1991-01-01
In this paper burnout is investigated in tubes under nonuniform heating on the perimeter. Data on heat transfer and critical heat flux (q{sub chf}) in the case of water were obtained for ranges of mass velocity {rho}w = 200--3000 kg/m{sup 2} s, pressure p = 1--1 MPa, and inlet water temperature T = 25--98{degrees}C. The test section was a horizontal copper tube of 21 mm outer diameter, 8 mm inner diameter with a technically smooth surface and heat transfer-intensifying twisted tape and porous sintered coating. The test section was heated by bombardment with electrons. It is established that a redistribution of heat fluxes and an increase of wall temperature fluctuations occur at burnout. The range of regime parameters to prevent burnout of a heat transfer surface is determined.
Heat Transfer Over the Circumference of a Heated Cylinder in Transverse Flow
NASA Technical Reports Server (NTRS)
Schmidt, Ernst; Wenner, Karl
1943-01-01
A method for recording the local heat-transfer coefficients on bodies in flow was developed. The cylinder surface was kept at constant temperature by the condensation of vapor except for a narrow strip which is heated separately to the same temperature by electricity. The heat-transfer coefficient at each point was determined from the electric heat output and the temperature increase. The distribution of the heat transfer along the circumference of cylinders was recorded over a range of Reynolds numbers of from 5000 to 426,000. The pressure distribution was measured at the same time. At Reynolds numbers up to around 100,000 high maximums of the heat transfer occurred in the forward stagnation point at and on the rear side at 180C, while at around 80 the heat-transfer coefficient on both sides of the cylinder behind the forward stagnation point manifested distinct minimums. Two other maximums occurred at around 115 C behind the forward stagnation point between 170,000 and 426,000. At 426,000 the heat transfer at the location of those maximums was almost twice as great as in the forward stagnation point, and the rear half of the cylinder diffused about 60 percent of the entire heat, The tests are compared with the results of other experimental and theoretical investigations.
P. Malekzadeh; M. R. Golbahar Haghighi; Y. Heydarpour
2012-01-01
The transient heat transfer analysis of functionally graded (FG) hollow cylinders subjected to a distributed heat flux with a moving front boundary on its inner surface is presented. The heat flux is assumed to be axisymmetric, and its front boundary moves along the axis of the cylinder. A method composed of the finite element and differential quadrature methods is employed
AN INVESTIGATION OF THE PROCESSES OF HEAT TRANSFER IN HEAT EMANATING ELEMENTS OF A NUCLEAR REACTOR
Ermakov
1958-01-01
A solution of differential equations fer heat transfer from a variable ; internal heat source was developed for use with cylindrical reactor fuel element. ; The solution was obtained for the stationary temperature field under ideal heat ; flux conditions along the cylinder length. (R.V.J.);
Junseok Chang; Orgun Güralp; Zoran Filipi; Dennis Assanis; Tang-Wei Kuo; Paul Najt; Rod Rask
An experimental study has been carried out to provide qualitative and quantitative insight into gas to wall heat transfer in a gasoline fueled Homogeneous Charge Compression Ignition (HCCI) engine. Fast response thermocouples are embedded in the piston top and cylinder head surface to measure instantaneous wall temperature and heat flux. Heat flux measurements obtained at multiple locations show small spatial
Heat transfer regimes in nuclear-reactor-pumped gas lasers
J. R. Torczynski
1991-01-01
The flow induced in nuclear-reactor-pumped gas lasers by spatially nonuniform fission-fragment heating and by heat transfer to the walls is examined. The equations of motion are acoustically filtered, and the resulting equations have three time scales: the heating duration, the time over which an O(1) pressure rise is produced, and the thermal boundary-layer growth time. Three distinct regimes emerge from
Mathematical modelling of complex heat transfer in a rectangular enclosure
G. V. Kuznetsov; M. A. Sheremet
2009-01-01
Numerical simulation of convective-radiative heat transfer in an enclosure with a heat source in the presence of heat-conducting\\u000a walls of the finite thickness was carried out. The distributions of both local (streamlines, temperature fields) and integral\\u000a (mean Nusselt numbers at typical interfaces) characteristics describing specific features of the investigated process in a\\u000a real range of the variation of determining parameters
O'Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert
2002-08-01
A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numerical modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.
Non-equilibrium electromagnetic fluctuations: Heat transfer and interactions
Matthias Krüger; Thorsten Emig; Mehran Kardar
2011-06-01
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 non-equilibrium cases where each body, and the environment, is at a different temperature. The formalism tracks the radiation from each body and its scatterings by the other objects. We discuss the radiation from a cylinder, emphasizing its polarized nature, and obtain the heat transfer between a sphere and a plate, demonstrating the validity of proximity transfer approximation at close separations and arbitrary temperatures.
Qu, Weilin
Flow boiling heat transfer in two-phase micro-channel heat sinksI. Experimental investigation is the first of a two-part study concerning measurement and prediction of saturated flow boiling heat transfer the point of zero thermodynamic equilibrium quality, and reveal the dominant heat transfer mechanism
Heat transfer in serpentine passages with turbulence promoters
NASA Technical Reports Server (NTRS)
Boyle, R. J.
1984-01-01
Local heat transfer rates and overall pressure losses were determined for serpentine passages of square cross section. The flow entered an inlet leg, turned 180 deg and then passed through an outlet leg. Results were obtained for a passage with smooth walls for three different bend geometries and the effect of turbulence promoters was investigated. Turbulence promoters between 0.6 and 15% of the passage height were tested. Local heat transfer rates are determined from thermocouple measurements on a thin electrically heated Inconel foil and pressure drop is measured along the flow path.
Research Strategy for Modeling the Complexities of Turbine Heat Transfer
NASA Technical Reports Server (NTRS)
Simoneau, Robert J.
1996-01-01
The subject of this paper is a NASA research program, known as the Coolant Flow Management Program, which focuses on the interaction between the internal coolant channel and the external film cooling of a turbine blade and/or vane in an aircraft gas turbine engine. The turbine gas path is really a very complex flow field. The combination of strong pressure gradients, abrupt geometry changes and intersecting surfaces, viscous forces, rotation, and unsteady blade/vane interactions all combine to offer a formidable challenge. To this, in the high pressure turbine, we add the necessity of film cooling. The ultimate goal of the turbine designer is to maintain or increase the high level of turbine performance and at the same time reduce the amount of coolant flow needed to achieve this end. Simply stated, coolant flow is a penalty on the cycle and reduces engine thermal efficiency. Accordingly, understanding the flow field and heat transfer associated with the coolant flow is a priority goal. It is important to understand both the film cooling and the internal coolant flow, particularly their interaction. Thus, the motivation for the Coolant Flow Management Program. The paper will begin with a brief discussion of the management and research strategy, will then proceed to discuss the current attack from the internal coolant side, and will conclude by looking at the film cooling effort - at all times keeping sight of the primary goal the interaction between the two. One of the themes of this paper is that complex heat transfer problems of this nature cannot be attacked by single researchers or even groups of researchers, each working alone. It truly needs the combined efforts of a well-coordinated team to make an impact. It is important to note that this is a government/industry/university team effort.
Research Strategy for Modeling the Complexities of Turbine Heat Transfer
Simoneau, R.J.
1996-03-01
The subject of this paper is a NASA research program, known as the Coolant Flow Management Program, which focuses on the interaction between the internal coolant channel and the external film cooling of a turbine blade and/or vane in an aircraft gas turbine engine. The turbine gas path is really a very complex flow field. The combination of strong pressure gradients, abrupt geometry changes and intersecting surfaces, viscous forces, rotation, and unsteady blade/vane interactions all combine to offer a formidable challenge. To this, in the high pressure turbine, one adds the necessity of film cooling. The ultimate goal of the turbine designer is to maintain or increase the high level of turbine performance and at the same time reduce the amount of coolant flow needed to achieve this end. Simply stated, coolant flow is a penalty on the cycle and reduces engine thermal efficiency. Accordingly, understanding the flow field and heat transfer associated with the coolant flow is a priority goal. It is important to understand both the film cooling and the internal coolant flow, particularly their interaction. Thus, the motivation for the Coolant Flow Management Program. The paper will begin with a brief discussion of the management and research strategy, will then proceed to discuss the current attack from the internal coolant side, and will conclude by looking at the film cooling effort - at all times keeping sight of the primary goal the interaction between the two. One of the themes of this paper is that complex heat transfer problems of this nature cannot be attacked by single researchers or even groups of researchers, each working alone. It truly needs the combined efforts of a well-coordinated team to make an impact. It is important to note that this is a government/industry/university team effort.
Boiling heat transfer in a small horizontal rectangular channel
Tran, T.N.; Wambsganss, M.W.; Jendrzejczyk, J.A.; France, D.M.
1993-08-01
Compact heat exchangers have traditionally found wide application in the transportation industry, where they are used as evaporators and condensers in vapor compression cycles for air conditioning and refrigeration. Such heat exchangers possess numerous attractive features including high thermal effectiveness, small size, low weight, design flexibility, and pure counterflow, and they can accommodate multiple streams. Today, there is a widespread interest in expanding the range of application of compact heat exchangers to include phase-change heat transfer in the process industries, among others. An overall objective of this effort is to provide the basis for establishing design technology in this area. In the present study, small channel flow boiling heat transfer was extended to a rectangular channel (4.06 {times} 1.70 mm) using refrigerant 12 (R-12). As with the circular tube studies, the flow channel wall was electrically heated providing a constant heat flux. Tests were performed over a quality range of 0.15 to 0.80, and large ranges of mass fluxes (50 to 400 kg/m{sup 2}s) and heat flux (4 to 34 kW/m{sup 2}). Heat transfer was measured and results are compared with correlation predictions.
Heat Transfer Characteristics of Slush Nitrogen in Turbulent Pipe Flows
NASA Astrophysics Data System (ADS)
Ohira, K.; Ishimoto, J.; Nozawa, M.; Kura, T.; Takahashi, N.
2008-03-01
Slush fluids, such as slush hydrogen and slush nitrogen, are two-phase (solid-liquid) single-component cryogenic fluids containing solid particles in a liquid, and consequently their density and refrigerant capacity are greater than for liquid state fluid alone. This paper reports on the experimental results of the forced convection heat transfer characteristics of slush nitrogen flowing in a pipe. Heat was supplied to slush nitrogen by a heater wound around the copper pipe wall. The local heat transfer coefficient was measured in conjunction with changes in the velocity and the solid fraction. The differences in heat transfer characteristics between two-phase slush and single phase liquid nitrogen were obtained, and the decrease in heat transfer to slush nitrogen caused by the previously observed pressure drop reduction was confirmed by this study. Furthermore, for the purpose of establishing the thermal design criteria for slush nitrogen in the case of pressure drop reduction, the heat transfer correlation between the experimental results and the Sieder-Tate Equation was obtained.
Heat transfer in serpentine flow passages with rotation
Mochizuki, S.; Takamura, J. . Dept. of Mechanical Engineering); Yamawaki, S. . R D Dept.); Yang, W.J. . Dept. of Mechanical Engineering and Applied Mechanics)
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 stationary and rotating cases. The throughflow Reynolds, Rayleigh (centrifugal type), and rotation numbers are varied. It is revealed that three-dimensional flow structures cause the heat transfer rate at the bends to be substantially higher than at the straight flow passages. This mechanism is revealed by means of a flow visualization experiment for a nonrotating case. Along the first straight flow passage, the heat transfer rate is increased on the trailing surface but is reduced on the leading surface, due to the action of secondary streams induced by the Coriolis force. At low Reynolds numbers, the local heat transfer performance is primarily a function of buoyancy force. In the higher Reynolds number range, however, the circumferentially averaged Nusselt number is only a weak function of the Rayleigh and rotation numbers.
Turbulent heat transfer prediction method for application to scramjet engines
NASA Technical Reports Server (NTRS)
Pinckney, S. Z.
1974-01-01
An integral method for predicting boundary layer development in turbulent flow regions on two-dimensional or axisymmetric bodies was developed. The method has the capability of approximating nonequilibrium velocity profiles as well as the local surface friction in the presence of a pressure gradient. An approach was developed for the problem of predicting the heat transfer in a turbulent boundary layer in the presence of a high pressure gradient. The solution was derived with particular emphasis on its applicability to supersonic combustion; thus, the effects of real gas flows were included. The resulting integrodifferential boundary layer method permits the estimation of cooling reguirements for scramjet engines. Theoretical heat transfer results are compared with experimental combustor and noncombustor heat transfer data. The heat transfer method was used in the development of engine design concepts which will produce an engine with reduced cooling requirements. The Langley scramjet engine module was designed by utilizing these design concepts and this engine design is discussed along with its corresponding cooling requirements. The heat transfer method was also used to develop a combustor cooling correlation for a combustor whose local properties are computed one dimensionally by assuming a linear area variation and a given heat release schedule.
Effect of geometry of film flow passage in superfluid heat pipe on heat transfer
NASA Astrophysics Data System (ADS)
Takada, Suguru; Ishii, Soh; Murakami, Masahide
2014-01-01
A superfluid heat pipe is one of the excellent heat transfer devices below 2.17 K. The overall heat conductance of this type of heat pipe is extremely high below the critical heat flow. In this study, the critical heat flow rates through the heat pipes with different internal structures of superfluid film flow passage were measured. In the case of the heat pipe where straight stainless steel wires were inserted, the critical heat flow was proportional to the wetted perimeter as far as the porosity is high enough. On the other hand, for the heat pipe with inside porous structure composed of glass beads, the critical heat flow doesn't follow the simple linear equation.
Heat Transfer Enhancement: Second Generation Technology
Bergles, A. E.; Webb, R. L.
1984-01-01
or evaporators and waste heat recovery boilers. On a larger scale, the brick checkers used with glass or steel furnaces employ similar principles of boundary layer interruption. Figure 3d shows an the strip fin for use in The tube is manufactured... products, such as encountered in a rotary regenerator for combustion air preheat, must include consideration of fouling and corrosion. Surfaces with protective coatings are specified when corrosive condensate is expected. Shell-and-Tube Heat Exchan ers...
Modelling of heat and mass transfer processes in neonatology.
Ginalski, Maciej K; Nowak, Andrzej J; Wrobel, Luiz C
2008-09-01
This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices. PMID:18708705
Particle shape effect on heat transfer performance in an oscillating heat pipe.
Ji, Yulong; Wilson, Corey; Chen, Hsiu-Hung; Ma, Hongbin
2011-01-01
The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP) was investigated experimentally. A binary mixture of ethylene glycol (EG) and deionized water (50/50 by volume) was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP. PMID:21711830
Effect of Cu-water nanofluid on the heat transfer by rotating heat pipe
NASA Astrophysics Data System (ADS)
Hassan, Hamdy; Harmand, Souad
2013-10-01
This paper presents a study on the effect of using Cu-water nanofluid on the heat transfer by rotating heat pipe (RHP). A mathematical model is presented of the RHP including, vapor velocity, gravity effect and taper angle. The study is carried out at different rotation speeds, RHP temperatures differences (?T) and masses of working fluid of the RHP. Using of Cu-water nanofluid with RHP decreases the liquid film thickness adjacent to its walls and increases the heat transfer by RHP compared with ordinary fluid. The heat transfer by RHP increases with increasing ?T and volume fraction and radius of solid nanoparticles. The maximum heat transfer by RHP at ?T=20 oC and ?=3000rpm increases by about 56% due to using Cu-water nanofluid with volume fraction 0.04 and nanoparticles radius 5nm.
NASA Astrophysics Data System (ADS)
Galindo, P.
1984-06-01
Heat transfer coefficients, pressure distributions, and fluid flow patterns on the shell side of shell and tube heat exchangers are discussed. The main focus was to quantify the effect of the size of the baffle window on the heat transfer coefficient, which was measured at each tube in the bundle and at three Reynolds numbers. Pressure drops were obtained by measuring detailed pressure distributions within the exchangers. The flow visualizations provided fluid flow patterns adjacent to the shell wall, to the baffle plates, and at each tube of the array. Performance comparisons among the exchangers were carried out holding the heat transfer surface area fixed together with either the pumping power, the mass flow rate, or the pressure drop. Numerical evaluations of commonly employed design procedures are presented using the present data as a means for rank ordering their validity. Tinker's design method provided the best predictions of the present heat transfer and pressure drop results, which are unaffected by leakage and bypass.
Heat transfer enhancement accompanying Leidenfrost state suppression at ultrahigh temperatures.
Shahriari, Arjang; Wurz, Jillian; Bahadur, Vaibhav
2014-10-14
The well-known Leidenfrost effect is the formation of a vapor layer between a liquid and an underlying hot surface. This insulating vapor layer severely degrades heat transfer and results in surface dryout. We measure the heat transfer enhancement and dryout prevention benefits accompanying electrostatic suppression of the Leidenfrost state. Interfacial electric fields in the vapor layer can attract liquid toward the surface and promote wetting. This principle can suppress dryout even at ultrahigh temperatures exceeding 500 °C, which is more than 8 times the Leidenfrost superheat for organic solvents. Robust Leidenfrost state suppression is observed for a variety of liquids, ranging from low electrical conductivity organic solvents to electrically conducting salt solutions. Elimination of the vapor layer increases heat dissipation capacity by more than 1 order of magnitude. Heat removal capacities exceeding 500 W/cm(2) are measured, which is 5 times the critical heat flux (CHF) of water on common engineering surfaces. Furthermore, the heat transfer rate can be electrically controlled by the applied voltage. The underlying science is explained via a multiphysics analytical model which captures the coupled electrostatic-fluid-thermal transport phenomena underlying electrostatic Leidenfrost state suppression. Overall, this work uncovers the physics underlying dryout prevention and demonstrates electrically tunable boiling heat transfer with ultralow power consumption. PMID:25225852
NASA Astrophysics Data System (ADS)
Sheng, Shiqi; Tu, Z. C.
2013-10-01
A unified ?-criterion for heat devices (including heat engines and refrigerators), which is defined as the product of the energy conversion efficiency and the heat absorbed per unit time by the working substance (de Tomás et al 2012 Phys. Rev. E 85 010104), is optimized for tight-coupling heat engines and refrigerators operating between two heat baths at temperatures Tc and Th( > Tc). By taking a new convention on the thermodynamic flux related to the heat transfer between two baths, we find that for a refrigerator tightly and symmetrically coupled with two heat baths, the coefficient of performance (i.e., the energy conversion efficiency of refrigerators) at maximum ? asymptotically approaches \\sqrt{\\varepsilon _C} when the relative temperature difference between two heat baths \\varepsilon _C^{-1}\\equiv (T_h-T_c)/T_c is sufficiently small. Correspondingly, the efficiency at maximum ? (equivalent to maximum power) for a heat engine tightly and symmetrically coupled with two heat baths is proved to be \\eta _C/2+\\eta _C^2/8 up to the second order term of ?C ? (Th - Tc)/Th, which reverts to the universal efficiency at maximum power for tight-coupling heat engines operating between two heat baths at small temperature difference in the presence of left-right symmetry (Esposito et al 2009 Phys. Rev. Lett. 102 130602).
NASA Technical Reports Server (NTRS)
Morris, J. F. (inventor)
1985-01-01
This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. 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. If the receiver requires gratr 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 comparative low thermal power densities through the electrically nonconducting gap between the two heat pipes.
Heat-stop structure design with high cooling efficiency for large ground-based solar telescope.
Liu, Yangyi; Gu, Naiting; Rao, Changhui; Li, Cheng
2015-07-20
A heat-stop is one of the most important thermal control devices for a large ground-based solar telescope. For controlling the internal seeing effect, the temperature difference between the heat-stop and the ambient environment needs to be reduced, and a heat-stop with high cooling efficiency is required. In this paper, a novel design concept for the heat-stop, in which a multichannel loop cooling system is utilized to obtain higher cooling efficiency, is proposed. To validate the design, we analyze and compare the cooling efficiency for the multichannel and existing single-channel loop cooling system under the same conditions. Comparative results show that the new design obviously enhances the cooling efficiency of the heat-stop, and the novel design based on the multichannel loop cooling system is obviously better than the existing design by increasing the thermal transfer coefficient. PMID:26367826
Field Measurements of Heating System Efficiency in Nine Electrically-Heated Manufactured Homes.
Davis, Bob; Siegel, J.; Palmiter, L.; Baylon, D.
1996-07-01
This report presents the results of field measurements of heating efficiency performed on nine manufactured homes sited in the Pacific Northwest. The testing procedure collects real-time data on heating system energy use and heating zone temperatures, allowing direct calculation of heating system efficiency.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, Benjamin A. (Benton Harbor, MI); Zawacki, Thomas S. (St. Joseph, MI)
1998-07-21
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, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, B.A.; Zawacki, T.S.
1998-07-21
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, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration. 5 figs.
Kendall, C.M.; Holman, J.P.
1996-06-06
Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.
Heat transfer in heat storage arrangements under melting
NASA Astrophysics Data System (ADS)
Alexeev, Vladimir A.
Heat storage arrangements (HSA) are devices containing a medium, which for appropriately prescribed outside energy source, may experience phase change processes and alternate between liquid and solid states. We present computational results that were obtained for HSAs of realistic form and size. The mathematical description of the model is given for two-dimensional heat conduction incorporating possible phase changes, when either melting or freezing occur. The numerical results are compared with the corresponding experiments for HSAs of different size and form. On the basis of the two-dimensional analysis it was then possible to construct a one-dimensional model with equivalent parameters and producing equivalent results. The investigation suggests to use the model for the design of energy-saving-heat-storage-battery systems.
Heat transfer characteristics of a new helically coiled crimped spiral finned tube heat exchanger
Kwanchanok Srisawad; Somchai Wongwises
2009-01-01
In the present study, the heat transfer characteristics in dry surface conditions of a new type of heat exchanger, namely\\u000a a helically coiled finned tube heat exchanger, is experimentally investigated. The test section, which is a helically coiled\\u000a fined tube heat exchanger, consists of a shell and a helical coil unit. The helical coil unit consists of four concentric\\u000a helically