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Heat pipe transports large quantities of heat from source to sink with only small temperature drop. Thermal energy is transferred to and from heat pipe by any combination of conduction, convection, or radiation heattransfer. Pipes transport energy from open flames, nuclear sources, and electronic equipment.

This site published by the British Broadcasting Corporation explains how heat energy is transferred by the processes of radiation, conduction, and convection. It is written in "bite-size" pieces so that adolescent learners can grasp the concepts more easily and connect information with prior knowledge. Each page is supplemented with multiple images and animations.

Field experiments, performed at Keahole Point, Hawaii and in the Gulf of Mexico, were designed to determine the relationship between decreased heattransferefficiency and the accumulation of corrosion and/or biofouling films on heat exchanger surfaces. T...

Students explore heattransfer and energy efficiency using the context of energy efficient houses. They gain a solid understanding of the three types of heattransfer: 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 heattransfer to produce a beneficial result. They are given the tools to calculate the heattransferred between a system and its surroundings.

Field experiments, performed at Keahole Point, Hawaii and in the Gulf of Mexico, were designed to determine the relationship between decreased heattransferefficiency 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 heattransferefficiency 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.

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. Heattransfer between fracture and matrix regions is modeled either by a partial differential equation for spherical conduction or by a linear first-order heattransfer formulation. Mass transfer is modeled in an analogous manner or assuming local equilibrium. First-order mass and heattransfer 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 heattransfer 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.

Computationally efficientheattransfer models of keyhole mode laser welding ignore fluid flow in the gas, liquid, and the two phase solid-liquid regions. These models cannot be applied to high Peclet number systems where convective heattransfer affects weld pool geometry, cooling rate, and other weld attributes. Here we show that by synthesizing features of an existing model to determine keyhole shape and size with rigorous fluid flow and heattransfer calculations in the liquid and the two phase solid-liquid regions, important features of both high and low Peclet number systems can be satisfactorily simulated. The geometry of the keyhole is calculated by assuming thermal equilibrium at the gas/liquid interface and point by point heat balance at the keyhole wall. The heattransfer outside the vapor cavity is calculated by numerically solving the equations of conservation of mass, momentum, and energy. A vorticity based turbulence model is used to estimate the values of effective viscosity and effective thermal conductivity of the liquid metal in the weld pool. It is shown that the temperature profile and the weld pool shape and size depend strongly on the convective heattransfer for low thermal conductivity alloys like stainless steel. For high thermal conductivity aluminum alloys, on the other hand, convection does not play a significant role in determining the shape and size of the weld pool. The computed solidification parameters indicated that the solidification structure becomes less dendritic and coarser with the decrease in welding velocity. The results demonstrate that a numerically efficient convective heattransfer model of keyhole mode laser welding can significantly improve the current understanding of weld attributes for different materials with widely different thermal properties.

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

Calculations were performed to assess the effect of the tip leakage flow on the rate of heattransfer 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 heattransfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heattransfer 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 heattransfer 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.

Calculations were performed to assess the effect of the tip leakage flow on the rate of heattransfer 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{sup 3} first-stage turbine, which represents a modern gas turbine blade, were used for the analysis. Clearance heights of 0, 1, 1.5, and 3 percent 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 heattransfer surfaces considered due to enlargement of the clearance gap. Introduction, of recessed casing resulted in a drop in the rate of heattransfer 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 heattransfer 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 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.

Heattransfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heattransfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heattransfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heattransfer process in microwave heating of magnetite, which is a typical magnetic dielectric, was simulated by using an explicit finite-difference approach. It is demonstrated that the heat generation due to microwave irradiation dominates the initial temperature rise in the heating and the heat radiation heavily affects the temperature distribution, giving rise to a hot spot in the predicted temperature profile. Microwave heating at 915 MHz exhibits better heating homogeneity than that at 2450 MHz due to larger microwave penetration depth. To minimize/avoid temperature nonuniformity during microwave heating the optimization of object dimension should be considered. The calculated reflection loss over the temperature range of heating is found to be useful for obtaining a rapid optimization of absorber dimension, which increases microwave absorption and achieves relatively uniform heating. To further improve the heating effectiveness, a function for evaluating absorber impedance matching in microwave heating was proposed. It is found that the maximum absorption is associated with perfect impedance matching, which can be achieved by either selecting a reasonable sample dimension or modifying the microwave parameters of the sample.

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 from a network that uses viewfactors to model long-wave radiation exchange. The Pade approximation andbilinear transformation are used to reduce the number of coefficients in a CRTF.

Seem, J. E.; Klein, S. A.; Beckman, W. A.; Mitchell, J. W.

Conventional multi-effect and multi-stage flash distillation use aluminium brass, cupro-nickel and\\/or titanium heattransfer surfaces. Polyolefins such as high density polyethylene (HDPE) and polypropylene (PP) have better corrosion resistance than these, which permits thinner walls. For identical internal & external convection coefficients, 20–50 ?m thick HDPE and PP film heattransfer elements have from 71–105% of the U value of

The basic concepts of heattransfer are set forth, and the fundamentals of numerical analysis appropriate to solving heattransfer problems are covered. In some example problems, numerical solutions, flow charts, example FORTRAN programs, and computer output are given. Conduction, convection, thermal radiation, and combined mechanisms of heattransfer are investigated. A chapter on heattransfer equipment is given, and

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

A heattransfer system for a nuclear reactor. Heattransfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heattransfer medium, which is liquid at the design operating temperatures, transfersheat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heattransfer 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.

A heattransfer system for a nuclear reactor is described. Heattransfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heattransfer medium, which is liquid at the design operating temperatures, transfersheat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heattransfer 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.

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

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

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 heattransfer is convection. Because of the locally high rate of heattransfer 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.

Although near-field microscopy has allowed optical imaging with sub-20 nm resolution, the optical throughput of this technique is notoriously small. As a result, applications such as optical data storage have been impractical. However, with an optimized near-field transducer design, we show that optical energy can be transferredefficiently to a lossy metallic medium and yet remain confined in a spot

W. A. Challener; Chubing Peng; A. V. Itagi; D. Karns; Wei Peng; Yingguo Peng; Xiaomin Yang; Xiaobin Zhu; N. J. Gokemeijer; Y.-T. Hsia; G. Ju; Robert E. Rottmayer; Michael A. Seigler; E. C. Gage

Heat is transferred through fabrics by convection, conduction and radiation and under certain circumstances by vaporization. Each mode is subject to different physical principles but the effect of the total heat absorbed by underlying skin is the same: if...

Using molecular dynamics simulations, we demonstrate that the efficiency of heat exchange between a solid and a gas can be maximized by functionalizing solid surface with organic self-assembled monolayers (SAMs). We observe that for bare metal surfaces, the thermal accommodation coefficient (TAC) strongly depends on the solid-gas interaction strength. For metal surfaces modified with organic SAMs, the TAC is close to its theoretical maximum and is essentially independent from the SAM-gas interaction strength. The analysis of the simulation results indicates that softer and lighter SAMs, compared to the bare metal surfaces, are responsible for the greatly enhanced TAC.

A comprehensive presentation is made of state-of-the-art configurations and design methodologies for heattransfer devices applicable to industrial processes, automotive systems, air conditioning/refrigeration, cryogenics, and petrochemicals refining. Attention is given to topics in heat exchanger mechanical design, single-phase convection processes, thermal design, two-phase exchanger thermal design, heat-transfer augmentation, and rheological effects. Computerized analysis and design methodologies are presented for the range of heattransfer systems, as well as advanced methods for optimization and performance projection.

Shah, R. K.; Subbarao, Eleswarapu Chinna; Mashelkar, R. A.

In this letter, it is shown that the applied relations in the paper by Hakan Özcan [H. Özcan, The effects of heattransfer on the exergy efficiency of an air-standard Otto cycle, Heat and Mass Transfer (2011) 47:571-577] are erroneous and thus the reported results are invalid. These incorrect relations [Eqs. (8), (9), (10), (14) and (16) of HÖ2011] are replaced by correct ones. Moreover, the obtained results (graphs and tables) are modified based on the correct relations. Finally, to achieve more realistic results, the internal irreversibility described by using the compression and expansion efficiencies is added to the analysis.

Heattransfer principles are discussed with emphasis on the practical aspects of the problems. Correlations for heattransfer and pressure drop from several worldwide sources for flow inside and outside of tubes, including finned tubes are presented, along with design and performance calculations of heat exchangers economizers, air heaters, condensers, waste-heat boilers, fired heaters, superheaters, and boiler furnaces. Vibration analysis for tube bundles and heat exchangers are also discussed, as are estimating gas-mixture properties at atmospheric and elevated pressures and life-cycle costing techniques. (JMT)

Calculate temperature profile and Biot number in mixed conduction and convection/radiation heattransfer 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.

Recent advances in electronics lead to smaller sizes and higher heat generation rates. Heat removal at a very tight thermal envelope is only possible with liquid cooling technologies such as the microchannel heat sink cooling. While a large number of studies have focused on experimental analysis, there is a limited number of computational data to understand the interaction between flow,

This item is an interactive Flash animation for Grades 5-8 on the topic of heat. Users explore methods of heattransfer and classify examples from everyday life. Three methods of heattransfer are depicted: conduction, convection, and radiation. Teachers' Domain is an NSF-funded pathway of the National Science Digital Library (NSDL). It is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

The present volume on heattransfer in turbulent flow discusses heattransfer through a pressure-driven 3D boundary layer, the effects of simulated combustor turbulence on boundary layer heattransfer, an experiment on spatial and temporal turbulent structures of a natural convection boundary layer, and the influence of high mainstream turbulence on leading edge heattransfer. Attention is given to turbulent

The heattransferefficiency in turbulent Rayleigh-Bénard convection is investigated experimentally, in a cylindrical cell of height 0.3 m, diameter 0.3 m. We show that for Rayleigh numbers 1012?Ra?1015 the Nusselt number closely follows Nu?Ra1/3 if the mean temperature of the working fluid—cryogenic helium gas—is measured by small sensors directly inside the cell at about half of its height. In contrast, if the mean temperature is determined in a conventional way, as an arithmetic mean of the bottom and top plate temperatures, the Nu(Ra)?Ra? displays spurious crossover to higher ? that might be misinterpreted as a transition to the ultimate Kraichnan regime.

In a perforated heat conductive surface structure having voids under an outer surface and openings in the outer surface, in order to obtain a high performance in particular at a low pressure and low temperature region, there is provided a heattransfer wall in which a thickness of a wall at a ceiling of each void and a length of a passage of the respective openings are increased in predetermined ranges.

Understanding HeatTransfer 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.

This module on heattransfer 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…

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 heattransfer 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.

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 heattransfer 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.

Optimization for convective heattransfer plays a significant role in energy saving and high-efficiency utilizing. We compared two optimization principles for convective heattransfer, the minimum entropy generation principle and the entransy dissipation extremum principle, and analyzed their physical implications and applicability. We derived the optimization equation for each optimization principle. The theoretical analysis indicates that both principles can be

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

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

Aspects of direct contact heattransfer are considered along with transport phenomena in fusion reactors, enhanced nucleate boiling, flow boiling, heattransfer in non-Newtonian systems, two-phase systems, heattransfer in fossil fuel conversion systems, process heattransfer, thermal and hydraulic behavior in rod and tube bundles, and two-phase systems in rod and tube bundles. Attention is also given to solar

The program consisted of two inter-related tasks: Theoretical modeling and experimental verification. Task I of the effort focused on thermodynamic modeling of the SHS reactions, and modeling of the heattransferefficiency between the SHS reaction and th...

K. V. Logan G. R. Villalobos J. N. Harris P. Mackle S. C. Neel

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

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

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.

In a real plate heat exchanger (PHX), heattransfer from the hot to the cold fluid is a conjugate problem, in which longitudinal heat conduction (LHC) along the walls plays some role. Large-scale LHC is always detrimental to the exchanger's effectiveness. On the contrary, if significant non-uniformities exist in the distribution of either convective heattransfer coefficient, small-scale LHC may

Proposed welded heat-transfer coupling joins set of heat pipes to thermoelectric converter. Design avoids difficult brazing operation. Includes pair of mating flanged cups. Upper cup integral part of housing of thermoelectric converter, while lower cup integral part of plate supporting filled heat pipes. Heat pipes prefilled. Heat of welding applied around periphery of coupling, far enough from heat pipes so it would not degrade working fluid or create excessive vapor pressure in the pipes.

Modeling microscale heattransfer with the computational-heat-transfer code Calore is discussed. Microscale heattransfer problems differ from their macroscopic counterparts in that conductive heattransfer in both solid and gaseous materials may have imp...

C. C. Wong D. J. Rader E. S. Piekos J. R. Torczynski M. A. Gallis

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

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

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

In this work, we report our studies related to the natural-convective heattransfer properties of carbon nanotube (CNT) sheets. We theoretically derived the formulas and experimentally measured the natural-convective heattransfer 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

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

Integrated Teaching and Learning Program, College of Engineering,

With reference to numerical simulation of turbulent flow and heattransfer, some of the most frequently used turbulence models and boundary conditions are described with special attention given to heattransfer. The near-wall turbulence is a main focus an...

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, heattransfer rates on the gas-side of airfoils, cooling air flow inside airfoils, and heattransfer rates on the coolant-side of airfoils. A systematic building block research approach is

The present invention relates to an arrangement for the heattransfer between a tubular body suitable for conducting a fluid and a contact body that is in contact with said tubular body, wherein the contact body comprises a contact side facing the tubular body, with which the contact body is in contact with an outside of the tubular body facing the contact body, wherein in a tensioned state of the arrangement a preload force presses the contact body against the tubular body in a preload direction. A high heattransferefficiency even over an operating temperature range can be achieved if the outside in an un-tensioned state of the arrangement is convexly curved towards the contact body, if the outside in the tensioned state is deformed relative to the un-tensioned state and bears against the contact side surface-to-surface, and if in the interior of the support body a support structure is arranged, which in the tensioned state supports itself on two inner sides of the tubular body located opposite each other in the preload direction.

The power output and efficiency expressions for thermoelectric (semiconductor) generators which is composed of multi-elements are derived with considerations of heattransfer irreversibility in the heat exchangers between the generator and the heat reservoirs. Numerical examples are provided. The effects of heattransfer and the number of elements on the performance are analyzed.

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.

Boiling is a common mechanism for liquid-vapor phase transition and is widely exploited in power generation and refrigeration devices and systems. The efficacy of boiling heattransfer is characterized by two parameters: (a) heattransfer coefficient (HTC) or the thermal conductance; (b) the critical heat flux (CHF) limit that demarcates the transition from high HTC to very low HTC. While increasing the CHF and the HTC has significant impact on system-level energy efficiency, safety, and cost, their values for water and other heattransfer fluids have essentially remained unchanged for many decades. Here we report that the high surface tension forces offered by liquids in nanowire arrays made of Si and Cu can be exploited to increase both the CHF and the HTC by more than 100%. PMID:19152275

Fully coupled thermo-mechanical analysis of civil engineering problems is studied. The mechanical analysis is based on damage mechanics which is useful for modeling of behaviour of quasi-brittle materials, especially in tension. The damage is assumed to be isotropic. The heattransfer is assumed in the form of heat conduction governed by the Fourier law and heat radiation governed by the Stefan-Boltzmann law. Fully coupled thermo-mechanical problem is formulated.

This invention is directed to a method of and apparatus for enhancing heattransfer 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.

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

Experimental investigation to study the heattransfer 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 heattransfer carrier can enhance the heattransfer 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 heattransfer. 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 heattransfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669

Experimental investigation to study the heattransfer 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 heattransfer carrier can enhance the heattransfer 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 heattransfer. 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 heattransfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters.

In this paper the results of an experimental investigation of thermoacoustic convection (TAC) heattransfer phenomenon in both zero-gravity and gravity environment are presented and compared with pure conduction heattransfer. The numerical solutions of the governing equations obtained by others for TAC heattransfer phenomenon are also discussed. The experimental results show that for rapid heating rate at a boundary, the contribution of TAC heattransfer to a gas could be significantly (one order of magnitude) higher than heattransfer rate from pure conduction. The results also show significantly reduced transient time in heattransfer processes involving thermoacoustic convective heattransfer mode in both space and gravity environment.

This paper deals with the transfer of heat-driven heattransfer 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 heattransfer 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.

One of the main applications of microscale flow is miniature, high-efficiencyheattransfer. The most simple and immediate solution to the problem of concentrated heat exchange is the use of small diameter channels with single-phase water flow, but there is a lack of publicised knowledge about the heattransfer performance in these conditions. In this article, an experimental investigation is

G. P. Celata; M. Cumo; V. Marconi; S. J. McPhail; G. Zummo

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

Heattransfer in the evaporator and condenser sections of a pulsating heat pipe (PHP) with open end is modeled by analyzing thin film evaporation and condensation. The heattransfer solutions are applied to the thermal model of the pulsating heat pipe and a parametric study was performed. The results show that the heattransfer in a PHP is mainly due

In current and advanced gas turbine engines, increased speeds, pressures and temperatures are used to reduce specific fuel consumption and increase thrust/weight ratios. Hence, the turbine airfoils are subjected to increased heat loads escalating the cooling requirements to satisfy life goals. The efficient use of cooling air requires that the details of local geometry and flow conditions be adequately modeled to predict local heat loads and the corresponding heattransfer coefficients. The objective of this program is to develop a heattransfer and pressure drop data base, computational fluid dynamic techniques and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.

Developments in heattransfer research during 1983 are reviewed. The topics addressed include: conduction, channel flow, boundary layer and external flows, flow with separated regions, heattransfer in porous media, internal and external flows in natural convection, convection from rotating surfaces, combined heat and mass transfer, boiling, condensation, freezing and melting, radiation, MHD, and applications to heat exchangers and heat pipes, to solar energy, to plasma heattransfer, and elsewhere.

Eckert, E. R. G.; Goldstein, R. J.; Patankar, S. V.; Pfender, E.; Ramsey, J. W.; Simon, T. W.; Decker, N.; Kuehn, T. H.

This paper is dedicated to reviewing and assessing the various models, embodied in a calculation procedure, that are employed in order to calculate heattransfer characteristics (the flux models, the Spherical Harmonics model, the Discrete Ordinate model, etc). The calculation procedure solves the governing conservation equation of mass, momentum and energy, expressed in a finite difference form, and employs a

Text of a paper presented at the American Nuclear Scciety Meeting held ; in Los Angeles, Calif., June 2, 3, 4, and 5, 1958. This report was issued May ; 10, 1958 as PTR-307. A critical review of the heattransfer in the ETR fuel ; elements was undertaken to establish the reactor operating parameters. The basic ; criterion was

Nuclear Reactor Safety HeatTransfer 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

Heattransfer in presence of a high viscosity fluid may be substantially enhanced using heat exchangers supported by a mechanical agitation system that can also “scrape” the exchange surface (Scraped Surface Heat Exchanger, SSHE). In this case, heattransferefficiency depends strongly on exchanger and agitator geometries, agitation methods as well as fluid characteristics and heattransfer conditions. Correlations used

L. Saraceno; G. Boccardi; G. P. Celata; R. Lazzarini; R. Trinchieri

The Fluidfire shallow fluidized bed heattransfer facility was modified during this program to give increased air flow capacity and to allow testing with different distributor plates and with two-stage heat exchangers. Tests were conducted using this heattransfer facility to investigate the effect of reduced distributor plate pressure loss and amount and type of bed material on the heattransfer performance of a single-stage fluidized bed heat exchanger. Elutriation from the bed was measured for different bed materials and distributor plates; alternate heat exchanger surfaces having different fin spacings were also tested. Two types of two-stage fluidized bed heat exchangers were tested: one having a baffle (having almost no pressure loss) located between the stages and which allowed bed material to recirculate between upper and lower beds; the second having two distributor plates in series with no recirculation of the bed material. The results obtained in the experimental program were used in conceptual design studies of multi-stage fluidized bed heat exchangers for waste heat recovery from diesel engine exhaust gases. Information was obtained from the literature and from diesel engine manufacturers to determine allowable diesel engine operating back pressures. The costs were estimated for two- and three-stage designs and were compared with costs obtained previously for single-stage fluidized bed and conventional heat exchanger designs.

The integrated solar collector is considered to be a promising direction for increasing the economic feasibility of low-temperature solar systems for heating water in domestic and industrial applications. Phase change material (paraffin) energy storage can be used in solar water heaters. The paraffin-integrated solar collector eliminates the need of conventional storage tanks, thus reducing cost and space. But a negative

This paper presents the results of a project to develop a simple and accurate predictive algorithm for heat pump heatingefficiency. Field test data are gathered. Cycling losses are then predicted by means of a model. Laboratory tests were performed to evaluate the capacity and power transients during startup, and the effect of off cycle period on the startup transients. Frost-defrost tests were performed. Seasonal efficiency comparison for seven residences for field tests, steady state, cycling only, timed frost, and demand frost schemes are given. The performance predictions for the entire heating season are provided.

The history of the fouling of heattransfer 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.

Somerscales, E.F.C. (Rensselaer Polytechnic Inst., Troy, NY (USA))

Purpose – To fabricate and characterise novel heat sinks manufactured by selective laser melting (SLM). The investigation explores features of SLM produced heat sinks that may be exploited to improve their heattransfer capability. Design\\/methodology\\/approach – The study was conducted on heat sinks manufactured from 316L stainless steel and aluminium 6061. The heattransfer devices' thermal and pressure drop performances

Matthew Wong; Sozon Tsopanos; Chris J. Sutcliffe; Ieuan Owen

The performance of multi-element thermoelectric-generators, assuming heat-transfer irreversibilities which obey the linear phenomenological heat-transfer law Q?(?T?1), is studied in this paper by combining finite-time thermodynamics with non-equilibrium thermodynamics. The performance characteristics of the output power, efficiency and working electrical-current are described by numerical examples.

The global promotion of energy conservation and environmental protection is establishing new standards for more efficient production and utilization of energy in various industrial sectors. In the refrigeration and air conditioning industry, substitution of CFCs with ozone-safe refrigerants has presented new challenges. Many of the newly introduced substitutes are considerably more expensive and in most cases exhibit poor thermal characteristics.

The global promotion of energy conservation and environmental protection is establishing new standards for more efficient production and utilization of energy in various industrial sectors. In the refrigeration and air conditioning industry substitution of CFCs with ozone-safe refrigerants has presented new challenges. Many of the newly introduced substitutes are considerably more expensive than CFCs and in most cases exhibit poor

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 heattransfer 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 heattransfer 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.

Polly, G.T.; Gibbard, I. [Cal Gavin Ltd. Process Intensification Engineering, Inc., Alcester (United Kingdom); Pretty, B. [Veritech, Inc., Reston, VA (United States)

Impinging jets are used for heat and mass transfer in some industries. Previous impinging jet studies used thermocouples or liquid crystals to determine convection coefficients. These methods have inaccuracies that can be avoided with an infrared image temperature measurement. For this research, an infrared camera with a resolution of 0.025 degree(s)C was used to store images containing 52785 temperatures. The camera was checked for accuracy with a thermometer calibrated with a NIST standard. A facility for measuring surface heattransfer coefficients due to an impinging jet was developed. The infrared images obtained with the facility were used to identify impingement flow characteristics and to calculate local convection coefficients for in-line and radial jets. The results include photographs and convection coefficient graphs.

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

The mechanism of heattransfer enhancement across solid gaseous interfaces by corona wind directed towards the heattransfer surface is investigated. Corona wind may adequately be described by the Navier-Stokes equations of motion. The Coulomb ion drag fo...

Nanoparticle morphology is thought to be an important factor influencing heat and mass transfer rates in liquid systems. How nanoparticles mechanistically increase heat and mass transfer rates is not well understood. Both dispersed nanoparticles and aggre...

A new method for convective heattransfer enhancement is described. The technique involves the use of a pulse combustor to generate a transient jet that impinges on a flat plate. Enhancements in convective heattransfer of a factor of up to 2.5, compared to a steady impinging jet at approximately the same Reynolds number, have been obtained. Heattransfer data

R A. EIBECK; J. O. KELLER; T. T. BRAMLETTE; D. J. SAILOR

Research in convective heattransfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heattransfer characteristics of the suspension. This review summarizes recent research on fluid flow and heattransfer characteristics of

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

Heattransfer 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, heattransfer, wet calorimetry

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

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

Heattransfer enhancement is an active and important field of engineering research since increases in the effectiveness of heat exchangers through suitable heattransfer augmentation techniques can result in considerable technical advantages and savings of costs. Considerable enhancements were demonstrated in the present work by using small cylindrical pins on surfaces of heat exchangers. A partly quantitative theoretical treatment of

Heat storage in geological strata (geostorage) is considered with attention given to single phase hat transfer in porous media, reservoir stability and heattransfer by conduction in rocks and soils. Also considered are solid and liquid heat storage systems, heat exchanger design, phase change systems for low and high temperature applications (melting and solidification, and encapsulation (of molten salts), fluidized

J. L. Peube; G. F. Hewitt; E. R. G. Eckert; E. Hahne; H. W. Hoffman; P. Le Goff; H. Sandner; D. G. Stephenson; A. C. Gringarten; N. Kurti

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

Latent heat models were developed to calculate heat-transfer coefficients in agitated vessels for two cases: (1) heating with a condensable fluid flowing through coils and jackets; (2) vacuum reflux cooling with an overhead condenser. In either case the mathematical treatment, based on macroscopic balances, requires no iterative schemes. In addition to providing heat-transfer coefficients, the models predict flow rates of

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 heattransfer structure immersed in a surrounding medium such as air.

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 heattransfer structure immersed in a surrounding medium such as air.

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.

New common heat-transfer head for two cylinders of opposed-cylinder Stirling-cycle machine performs function formerly performed by two heat acceptors-one for each cycle. Simplifies structure of machine and increases efficiency of operation by reducing resistance to flow of working gas and/or increasing transfer of heat to or from working gas during flow between compression and expansion spaces of machine.

Emigh, Stuart G.; Lehmann, Gregory A.; Noble, Jack E.

Reviewed is a book which has 5 parts: Overview, Fundamental Concepts, Design Basis Accident-Light Water Reactors (LWRs), Design Basis Accident-Liquid-Metal Fast Breeder Reactors (LMFBRs), and Special Topics. It combines a historical overview, textbook material, handbook information, and the editor's personal philosophy on safety of nuclear power plants. Topics include thermal-hydraulic considerations; transient response of LWRs and LMFBRs following initiating events; various accident scenarios; single- and two-phase flow; single- and two-phase heattransfer; nuclear systems safety modeling; startup and shutdown; transient response during normal and upset conditions; vapor explosions, natural convection cooling; blockages in LMFBR subassemblies; sodium boiling; and Three Mile Island.

This paper is dedicated to reviewing and assessing the various models, embodied in a calculation procedure, that are employed in order to calculate heattransfer characteristics (the flux models, the Spherical Harmonics model, the Discrete Ordinate model, etc). The calculation procedure solves the governing conservation equation of mass, momentum and energy, expressed in a finite difference form, and employs a two-equation turbulence model and a reaction model. Calculated results obtained using the flux and the Discrete Ordinate models were compared with experimental data for three furnaces. The resulting agreement promises greater economy and better performance in furnaces and combustion chambers.

The design of a fusion reactor blanket concept based on a bed of lithium containing ceramic pebbles or a mixture of ceramic and beryllium pebbles is studied. Effective thermal conductivity of pebble beds, including beds formed by a binary mixture of high conducting metallic pebbles and poorly conducting pebbles is analyzed. Binary mixtures of spheres of same diameter and different conductivities as well as beds formed by one type of spheres were investigated. The experimental apparatus consists of a stainless steel cylinder with a heating rod along the symmetry axis. Experiments with stagnant and flowing gas were performed. The pebbles are of Al2O3 (diameter 1, 2, 4 mm), Li4SiO4 (diameter 0.5 mm), Al (diameter 2 mm) and steel (diameter 2, 4 mm). Experimental values of the thermal conductivity and of the wall heattransfer coefficient are compared with the predicted ones.

Strongly thermophilic nanofluids are able to transfer either small or large quantities of heat when subjected to a stable temperature difference. We investigate the bistability diagram of the heattransferred by this class of nanofluids. We show that bistability can be exploited to obtain a controlled switching between a conductive and a convective regime of heattransfer, so as to achieve a controlled modulation of the heat flux. PMID:23005220

Bernardin, Michele; Comitani, Federico; Vailati, Alberto

Studies in the field of heattransfer published during 1985 are presented. The topics of conduction and flow, including channel flow, boundary-layer and external flows (with special consideration given to the laminar and transition flows and to turbulent and separated flows), and flow with separated regions, are covered. Studies on heattransfer in porous media, combined heattransfer and mass transfer, as well as on heattransfer applications, and the experimental techniques and instrumentation used in heattransfer measurements and in measurements of the coefficients of diffusion, thermal conductivity, and viscosity, are discussed. Special consideration is given to the processes of natural convection (including internal and external flows) and convection from rotating surfaces, as well as to boiling, evaporation, and condensation processes. In addition, studies on the subjects of radiation in participating area and surface radiation and change of phase are discussed. Also presented are numerical methods employed in heattransfer analysis.

Eckert, E. R. G.; Goldstein, R. J.; Patankar, S. V.; Pfender, E.; Ramsey, J. W.

The mechanism of radial heattransfer in two-phase flow through packed beds is examined. A model with 2 parameters: an effective radial thermal conductivity in the bed, ke, and a heattransfer coefficient, hw, at the wall, give a satisfactory interpretation of the radial temperature profile.ke was expressed in terms of a stagnant contribution, due to the heat conduction through

This paper reports a numerical study of the heattransfer characteristics of porous radiant burners, which have significant advantages over conventional burners. The heattransfer characteristics are investigated using a one-dimensional conduction, convection, and radiation model. The combustion phenomenon is modeled as spatially dependent heat generation. Nonlocal thermal equilibrium between the gas and solid phases is accounted for by using

Heattransfer 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.

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

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

Heattransfer plays an important role in thermoelectric (TE) power generation because the higher the heat-transfer rate from the hot to the cold side of the TE material, the higher is the generation of electric power. However, high heat-transfer rate is difficult to achieve compactly when the hot and\\/or the cold sources are maintained by a flow of gas such

Organic Rankine Cycles (ORC's) are being used in the generation of electrical or mechanical power in situations where little demand exists for process steam. Using organic fluids in Rankine cycles improves the potential for economic recovery of waste heat. The right organic fluid can enhance the conversion efficiency by tailoring the ORC heat recovery cycle to the thermodynamic characteristics of the waste heat stream. The selection of the working fluid is affected by its flammability, toxicity, environmental impact, materials compatibility, and cost. Water, ethanol, 2-methyl Pyridine/H2O, Flourinol, Toluene, Freon R-11, and Freon R-113 are compared. An organic cycle using toluene as the working fluid is schematicized.

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 heattransfer coefficient and pressure drop for

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

Technical papers in the area of numerical heattransfer published from 1977 through 1981 are reviewed. The journals surveyed include: (1) ASME Journal of HeatTransfer, (2) International Journal of Heat and Mass Transfer, (3) AIAA Journal, (4) Numerical HeatTransfer, (5) Computers and Fluids, (6) International Journal for Numerical Methods in Engineering, (7) SIAM Journal of Numerical Analysis, and (8) Journal of Computational Physics. This survey excludes experimental work in heattransfer and numerical schemes that are not applied to equations governing heattransfer phenomena. The research work is categorized into the following areas: (A) conduction, (B) boundary-layer flows, (C) momentum and heattransfer in cavities, (D) turbulent flows, (E) convection around cylinders and spheres or within annuli, (F) numerical convective instability, (G) radiation, (H) combustion, (I) plumes, jets, and wakes, (J) heattransfer in porous media, (K) boiling, condensation, and two-phase flows, (L) developing and fully developed channel flows, (M) combined heat and mass transfer, (N) applications, (O) comparison and properties of numerical schemes, and (P) body-fitted coordinates and nonuniform grids.

In air conditioning, regenerators are widely used for heat recovery of exhaust air. A regenerator can simultaneously transferheat and water or other compounds from exhaust to supply air. In particular the regenerators with hygroscopic matrix materials ca...

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

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

Heattransfer enhancement was investigated in a coaxial-pipe heat exchanger using dimples as the heattransfer modification on the inner tube. Tube-side Reynolds numbers were in the range of 7.5×103–5.2×104 for water flow. A constant annular mass flow rate was chosen to obtain the highest possible Reynolds number of 1.1×104. Typically, the heating water inlet temperature was 68.1±0.1?C.All six variants

Juin Chen; Hans Müller-Steinhagen; Geoffrey G Duffy

A study was conducted of heattransfer enhancement in a heated tube in which a supercritical-pressure kerosene and oil flowed under the conditions of carbon deposit. This technique proved to be very effective when applied to boiling of heat carriers. At disperse and slug film boiling inside tubes, heattransfer increases three to eight times, and at surface boiling of water and water-glycerine mixtures, by 30-40 percent.

Kalinin, E. K.; Dreitser, G. A.; Paramonov, N. V.; Miakochin, A. S.; Tikhonov, A. I.; Zakirov, S. G.; Levin, E. S.; Ianovskii, L. S.

Because of its order-of-magnitude higher heattransfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and t...

BEAM computer program enables user to calculate microwave power-transferefficiency between two circular apertures at arbitrary range. Power-transferefficiency obtained numerically. Two apertures have generally different sizes and arbitrary taper illuminations. BEAM also analyzes effect of distance and taper illumination on transmission efficiency for two apertures of equal size. Written in FORTRAN.

A common of finite-time heattransfer processes between high- and low-temperature sides with generalized radiative heattransfer law [q??(Tn)] is studied in this paper. In general, the minimization of entropy generation in heattransfer processes is taken as the optimization objective. A new physical quantity, entransy, has been identified as a basis for optimizing heattransfer processes in terms of

A packed bed is modeled as a homogeneous gray medium in which heat is transferred by conduction, convection, and radiation. The problem is formulated wherein the packed bed is contained between concentric gray cylinders that are axially isothermal. The outer cylinder is at a high temperature, and heattransfer is radial through the bed to the low temperature inner cylinder.

The objective of this summer research was to examine heattransfer in thin liquid films. A successful formulation was accomplished on the effect of electrostatic field on the stability of isothermal non-evaporating thin films and on the heattransfer in e...

An improved heattransfer model has been developed for a direct-fired rotary kiln. The treatment of radiant heattransfer was based on the Reflection Method developed by Succec and applied by Gorog, and was extended to account for radiation from a flame. ...

Local heattransfer measurements were experimentally mapped using a transient liquid-crystal heattransfer 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 a...

The primary basis for heattransfer analysis of turbine blades is experimental data obtained in linear cascades. These data have been very valuable in identifying the major heattransfer and fluid flow features of a turbine airfoil. The question of major interest is how well all of these data translate to the rotating turbine blade. It is known from the

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

The internal heattransfer coefficient in a pulsating circular pipe flow was determined for both dry and condensing surfaces. The fully-reversing flow was driven by a pulse combustion process at a frequency of 34 Hz. The mean Reynolds numbers ranged from approximately 2600 to 4300, while the instantaneous Reynolds number had a maximum of 18,000. The internal heattransfer is

Scott E. Hommema; Keith A. Temple; James D. Jones; Victor W. Goldschmidt

The gas turbine has the potential for power production at the highest possible efficiency. The challenge is to ensure that gas turbines operate at the optimum efficiency so as to use the least fuel and produce minimum emissions. A key component to meeting this challenge is the turbine. Turbine performance, both aerodynamics and heattransfer, is one of the barrier

Three-dimensional numerical simulations were performed for laminar flow of wavy fin-and-tube heat exchangers by using body-fitted coordinates (BFC) method with fin efficiency effect accounted. The prediction results of average Nusselt number, friction factor and fin efficiency were compared with the related experimental correlations [R.C. Xin, H.Z. Li, H.J. Kang, W. Li, W.Q. Tao, An experimental investigation on heattransfer and

Y. B. Tao; Y. L. He; J. Huang; Z. G. Wu; W. Q. Tao

Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heattransfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heattransfer results by liquid crystal thermography in a wind tunnel. The thermographic technique allowed the rapid and inexpensive measurement of wall heattransfer coefficients along flat walls of arbitrary boundary shapes with an accuracy of about 5 percent. The results show that an increase in secondary flow velocities near the heated wall causes an increase in the local wall heattransfer coefficient, and quantify the variation for maximum secondary-flow velocities in a range from 1.5 to 17 percent of the bulk flow velocity.

A summary of cryogenic rotatable heattransfer joint technology development, at Rockwell International Space Division, is presented. Starting with the flight qualified radiative joint on the RM-20B IR sensor of the early 70's, leading to rotatable heat pipe joint, gas conductive joints, rolling-contact-conductance joints, and the more recent work on development and evaluation of cryogenic rotatable seals and mechanical interfaces. Potential applications, joint design optimization, heattransfer, seal leakage and torque test data are presented.

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

Working lengths of heat pipes electronically controlled. Rate of heattransfer controlled by electrical heaters shorten effective working lengths of heat pipes. Concept not limited to right circular cylindrical shape. Concept adaptable to terrestrial instruments or processes in which atmospheres or fluids must be cooled and returned to instruments or processes at fixed lower temperatures.

Contact evaporators with HHTAs differ from other types of evaporators by their simplicity of construction. They can also be used to capture waste heat from exit gases coming from industrial furnaces. A column type apparatus was proposed as an evaporator with a HHTA in which the heatedheat-transfer agent is atomized into drops in order to create a large surface

Experiments have been performed in a facility designed for steady state heattransfer through coal ash deposits obtained from utility boilers. A one-dimensional heat flux through the ash deposits was achieved by subjecting one surface to intense irradiation from SiC electrodes and the other surface to allow temperature heat sink. Temperature profiles and \\

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

Transient models for sensible heat were developed to assess the thermal performance of agitated vessels with coils and jackets. Performance is quantified with the computation of heat-transfer coefficients by introducing vessel heating and cooling data into model equations. Of the two model categories studied, differential and macroscopic, the latter is preferred due to mathematical simplicity and lower sensitivity to experimental

Wireless power transfer systems using near-field magnetic coupling are attractive as they allow power transfer with high efficiency and do not require an unobstructed path between transmitter and receiver. In this work a two coil wireless power transmission system is analyzed, including the driving amplifier, and a demonstration system is built and characterized. The system achieves 76% efficiency for a

Fundamental heattransfer experiments were carried out for three kinds of heat pipes that may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heattransfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B, and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium (Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium (NaK). Heat pipes B and C included noncondensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, an infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm{sup 2}. The start-up time was about 6 minutes for heat pipe B and about 6 minutes for heat pipe A. Thus, adding noncondensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the start-up time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 deg. There was no significant gravitational dependence on heat transport for heat pipes including noncondensible gas.

Yamawaki, S. [Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan); Yoshida, T.; Taki, M.; Mimura, F. [National Aerospace Lab., Tokyo (Japan)

This invention relates to a thermodynamic system for effectively and economically removing waste heat from space within a building or other enclosed structure containing a source of the waste heat. In particular, this invention relates to a system for acc...

An improved heattransfer model has been developed for a direct-fired rotary kiln. The treatment of radiant heattransfer 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 heattransfer than other methods of analysis. The model also accounts for conductive and convective heattransfer 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.

The finite difference method in conjunction with the least-squares scheme and the experimental temperature data is proposed to predict the average natural-convection heattransfer coefficient and the fin efficiency on a vertical square fin of one-circular tube plate finned-tube heat exchangers. In the present study, the radiation and convection heattransfer coefficients are simultaneously taken into consideration. The heattransfer

Cooling technology of gas turbine blades, primarily ensured via internal forced convection, is aimed towards withdrawing thermal energy from the airfoil. To promote heat exchange, the walls of internal cooling passages are lined with repeated geometrical flow disturbance elements and surface non-uniformities. Raising the heattransfer at the expense of increased pressure loss; the goal is to obtain the highest possible cooling effectiveness at the lowest possible pressure drop penalty. The cooling channel heattransfer problem involves convection in the fluid domain and conduction in the solid. This coupled behavior is known as conjugate heattransfer. This experimental study models the effects of conduction coupling on convective heattransfer by applying iso-heat-flux boundary condition at the external side of a scaled serpentine passage. Investigations involve local temperature measurements performed by Infrared Thermography over flat and ribbed slab configurations. Nusselt number distributions along the wetted surface are obtained by means of heat flux distributions, computed from an energy balance within the metal domain. For the flat plate experiments, the effect of conjugate boundary condition on heattransfer is estimated to be in the order of 3%. In the ribbed channel case, the normalized Nusselt number distributions are compared with the basic flow features. Contrasting the findings with other conjugate and convective iso-heat-flux literature, a high degree of overall correlation is evident.

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 heattransfer evaluated in this article allows engineering nanofluids with desired set of properties.

Timofeeva, E. V.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L. (Energy Systems); ( NE); (Univ. of Illinois at Chicago)

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 heattransfer evaluated in this article allows engineering nanofluids with desired set of properties.

Timofeeva, Elena V.; Yu, Wenhua; France, David M.; Singh, Dileep; Routbort, Jules L.

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 heattransfer evaluated in this article allows engineering nanofluids with desired set of properties. PMID:21711700

Timofeeva, Elena V; Yu, Wenhua; France, David M; Singh, Dileep; Routbort, Jules L

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 heattransfer evaluated in this article allows engineering nanofluids with desired set of properties.

To quantify the effect of roll chilling on the thermal history of a slab during hot rolling, tests were conducted at the Canada Center for Mineral and Energy Technology (CANMET) and at the University of British Columbia (UBC). In these tests, the surface and the interior temperatures of specimens were recorded during rolling using a data acquisition system. The corresponding heat-transfer coefficients in the roll bite were back-calculated by a trial-and-error method using a heat-transfer model. The heat-transfer coefficient was found to increase along the arc of contact and reach a maximum, followed by a decrease, until the exit of the roll bite. Its value was influenced by rolling parameters, such as percent reduction, rolling speed, rolling temperature, material type, etc. It was shown that the heat-transfer coefficient in the roll gap was strongly dependent on the roll pressure, and the effect of different variables on the interfacial heat-transfer coefficient can be related to their influence on pressure. At low mean roll pressure, such as in the case of rolling plain carbon steels at elevated temperature, the maximum heat-transfer coefficient in the roll bite was in the 25 to 35 kW/m2 °C range. As the roll pressure increased with lower rolling temperature and higher deformation resistance of stainless steel and microalloyed grades, the maximum heat-transfer coefficient reached a value of 620 kW/m2 °C. Obviously, the high pressure improved the contact between the roll and the slab surface, thereby reducing the resistance to heat flow. The mean roll-gap heat-transfer coefficient at the interface was shown to be linearly related to mean roll pressure. This finding is important because it permitted a determination of heat-transfer coefficients applicable to industrial rolling from pilot mill data. Thus, the thermal history of a slab during rough rolling was computed using a model in which the mean heat-transfer coefficient between the roll and the slab was determined from an estimate of the rolling load. It was found that the heat loss of a slab to the roll was 33 pet of the total, which emphasizes the importance of accurately characterizing the heat-transfer coefficient in the roll bite during hot rolling.

Strong short laser pulses can give rise to a strong increase in the electronic temperature at metal surfaces. Energy transfer from the hot electrons to adsorbed molecules may result in adsorbate reactions, e.g. desorption or diffusion. We point out the limitations of an often used equation to describe the heattransfer process in terms of a friction coupling. We propose a simple theory for the energy transfer between the adsorbate and hot electrons using a newly introduced heattransfer coefficient, which depends on the adsorbate temperature. We calculate the transient adsorbate temperature and the reaction yield for a Morse potential as a function of the laser fluency. The results are compared to those obtained using a conventional heattransfer equation with temperature-independent friction. It is found that our equation of energy (heat) transfer gives a significantly lower adsorbate peak temperature, which results in a large modification of the reaction yield. We also consider the heattransfer between different vibrational modes excited by hot electrons. This mode coupling provides indirect heating of the vibrational temperature in addition to the direct heating by hot electrons. The formula of heattransfer through linear mode-mode coupling of two harmonic oscillators is applied to the recent time-resolved study of carbon monoxide and atomic oxygen hopping on an ultrafast laser-heated Pt(111) surface. It is found that the maximum temperature of the frustrated translation mode can reach high temperatures for hopping, even when direct friction coupling to the hot electrons is not strong enough.

The determination of the space- or time-dependent heattransfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heattransfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.

Investigations were performed on instrumentation concepts for the purpose of acquiring heattransfer and recovery temperature measurements on models to be tested in cold wind tunnels. The problem in cold wind tunnels is the recovery and model initial (or ...

Two 3D CFD solvers for internal flow applications are briefly presented and applied for the investigation of heattransfer problems in gas turbine components. The numerical approaches considered are respectively based on a structured (XFLOS) and on an uns...

Using transition region fluxes and high resolution spectra of the Ly-alpha and Mg II h and k lines observed by the GHRS spectrograph, I determine the total flux radiated from each temperature regime in the Capella upper chromosphere and transition region. This contains essentially the same information as the emission measure distribution, but to better suggest physical interpretations of the heating mechanisms it is expressed instead in terms of the efficiency for extracting convection zone energy flux and depositing it over the temperature ranges considered.

The heating apparatus for applying heat to the interior of a chamber includes a modular, removable, electrical, heat-producing unit and a heat pipe mountable in a wall of the chamber with one end of the pipe arranged to receive heat from the electrical heat producing unit exterior of the housing and with another end of the pipe constructed and arranged

The objective is to develop a heattransfer and pressure drop data base, computational fluid dynamic techniques and heattransfer correlations for rotating multipass coolant passages, with and without flow tabulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.

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 heattransfer to the solids. The\\u000a variables

During the solidification of metal castings, an interfacial heattransfer resistance exists at the boundary between the metal\\u000a and the mold. This heattransfer resistance usually varies with time even if the cast metal remains in contact with the mold,\\u000a due to the time dependence of plasticity of the freezing metal and oxide growth on the surface. The present work

A brief survey is given of the properties, compared to water, of three commercially available heattransfer fluids -- ethylene glycol, propylene glycol and silicone oil. Their physical and chemical properties and toxicity are discussed as well as factors ...

In this paper, in order to optimize the heattransfer structure of LED light bulb, the effects of various parameters on the temperature of the LED device were systematically analyzed, and a design guideline was shown. Although LED device has become popular due to its high-efficiency and long life, the design issues on the heattransfer structure of LED light bulbs has still remained. Because the original efficiency and life of the LED device can not be obtained due to the local temperature rise of LED element and the surrounding polymer molding material. Therefore, heattransfer analysis by finite element method was conducted systematically by changing parameters such as the shape, number and thickness of the radiating fin of the LED. As a result, advantage of open type structure was shown, and the proper design guidance for the structure of the fin shape was obtained.

Natural convection heattransfers inside horizontal pipes were measured. The Rayleigh numbers were varied from 6.8 × 108 to 1.5 × 1012, while the Prandtl number was fixed at 2,094. Based on the analogy concept, a copper sulfate electroplating system was adopted to measure mass transfer rates in place of heattransfer rates. Test results using single-piece electrodes were in good agreement with the work of Sarac and Korkut. The angle-dependent mass transfer rates, measured using piecewise electrodes, were compared with the results of studies on natural convection in concentric annuli, and showed similar trends. The experiments were expanded to the turbulent region, and a transition criterion was proposed. Angle-dependent natural convection heattransfer correlations for the laminar and turbulent regions were derived.

With rapid advances in micro-device fabrication, computational techniques, and diagnostic tools, there is a significant interest in applying micro-scale fluid dynamics and heattransfer to flow control, flight vehicle protection, and thermal management. Utilizing energy transfer associated with phase change, multiphase systems offer many new opportunities. To elucidate the main scientific issues and technical implications, recent research addressing the interplay

Radiative heattransfer in emitting, absorbing, and scattering spherical media is analyzed. The medium is assumed to be gray, isothermal, and linear-anisotropically scattering. The medium is confined in the space between two gray concentric spheres, which diffusely emit, and specularly and diffusely reflect radiation. Approximate solutions of the equation of radiative transfer are obtained using the spherical harmonics method. Results

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

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

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

The NASA Glenn Research Center General Multi-Block Navier-Stokes Convective HeatTransfer Code, Glenn-HT, has been used extensively to predict heattransfer 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 heattransfer 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 heattransfer 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.

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

The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heattransfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heattransfer 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, heattransfer hysteresis loss, and other heattransfer-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 heattransfer 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 heattransfer as a function of overall nondimensional parameter. Heattransfer 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 heattransfer 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.

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

Mathematical analysis was carried out for the heattransfer in lead--acid batteries designed for use in electric vehicles. This analysis showed that the heat generated in the battery during recharge cycles may cause a noticeable rise of battery temperatur...

The convective heattransfer at a fluid/solid interface is investigated from a mathematical point of view. Through the use of a transformation, Th, a number of exact solutions of the heat equation satisfying convection or radiation type boundary condition...

A theoretical study is presented of the convective heattransfer in the hydrodynamically and thermally fully developed region of rotating radial rectangular ducts. A pair or pairs of vortices superimposed on the main flow are introduced in the duct by the coriolis force. The fluid is heated by the duct wall, and the fluid bulk temperature may increase exponentially after

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

The finite difference method in conjunction with the least-squares scheme and experimental temperature data is used to predict the average heattransfer coefficient and fin efficiency on the fin of annular-finned tube heat exchangers in natural convection for various fin spacings. The radiation and convection heattransfer coefficients are simultaneously taken into consideration in the present study. The heattransfer

The present work is a simplified calculation procedure of heattransfer in oil-fired flame tubes. The relations for the distribution of heat liberation and soot concentration along the tube and which are needed in the calculations were based on experimental data obtained on a horizontal, segmented, water-cooled flame tube, under operating conditions close to those occurring in actual cases. The

Pulse combustion devices offer several potential advantages over conventional burners, including enhanced efficiency, reduced size, automatic rejection of exhaust gases and consistency of operation over long time periods. This project was conducted in order to acquire an understanding of the heattransfer characteristics and pressure oscillations occurring in pulse combustion devices.^ A gas-fired pulse combustion water heater was utilized. This

Convective heattransfer in a heat sink consisting of rectangular minichannels and cooled with alumina and titania nanofluids has been investigated experimentally and numerically. Numerical simulations were carried out in a three dimensional domain employing homogeneous mixture model with effective thermo-physical properties of nanofluids. The predictions of base temperature profiles of the heat sink cooled with both water and nanofluids agree well with the experimental data. Experimental and numerical results show that the investigated nanofluids neither exhibits unusual enhancement of heattransfer coefficient nor decreases the heat sink base temperature. Although both nanofluids showed marginal thermal conductivity enhancements, the presence of solid nanoparticles lowers the specific heat capacity of nanofluids offseting the advantage of thermal conductivity enhancement. For all investigated flow rates, the Nusselt number of both nanofluids overlaps with that of water indicating that both nanofluids behave like single-phase fluids.

Utomo, Adi T.; Zavareh, Ashkan I. T.; Poth, Heiko; Wahab, Mohd; Boonie, Mohammad; Robbins, Phillip T.; Pacek, Andrzej W.

Heat being transferred supplies operating power. Capillary-condenser-pumped heat-transfer loop similar to heat pipe and to capillary-evaporator-pumped heat-transfer loop in that heat-transfer fluid pumped by evaporation and condensation of fluid at heat source and sink, respectively. Capillary condenser pump combined with capillary evaporator pump to form heat exchanger circulating heat-transfer fluids in both loops. Transport of heat more nearly isothermal. Thermal stress in loop reduced, and less external surface area needed in condenser section for rejection of heat to heat sink.

In the present work, we consider the problem of the forced convection flow of water– ?Al2O3 and ethylene glycol– ?Al2O3 nanofluids inside a uniformly heated tube that is submitted to a constant and uniform heat flux at the wall. In general, it is observed that the inclusion of nanoparticles has increased considerably the heattransfer at the tube wall for

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 heattransferred as well as the rate of heattransfer 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.

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 heattransfer in simultaneously developing regime is investigated as the heattransfer 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 heattransfer coefficient is more than the heattransfer coefficient of fully developed flow. Also the heattransfer is more for nanofluids compared to DI water. PMID:24745233

An investigation of finite-time heattransfer processes between high- and low-temperature sides with a generalized heattransfer law (q~[?(Tn)]m) is presented in this paper. Optimal heating and cooling strategies for minimizing entropy generation are derived for the fixed initial and final temperatures of the low-temperature side working fluid. Optimal paths are compared with the common strategies of constant heat flux and constant source temperature operation by numerical examples. The condition corresponding to the minimum entropy generation strategy is not only valid for Newton's [q~(?T)] and linear phenomenological [q~?(T-1)] heattransfer laws but also valid for heattransfer law (q~[?(T-1)]m). The obtained results are general and can provide some theoretical guidelines for the designs and operations of practical heat exchangers.

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 transferefficiencies of three different phages. Transferefficiency is defined as follows: TransferEfficiency: 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 transferefficiencies 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.

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

Heattransfer over a sub-millimeter spheroidal solid is of interest in many engineering processes. One important mechanism of heattransfer in the above processes is natural convection which leads to heattransfer rates many times larger than that of pure conduction. Despite the huge literature devoted to natural convection heattransfer rates over spheres (and to a smaller extent over

Margaritis Kostoglou; Sotiris P. Evgenidis; Konstantinos A. Zacharias; Thodoris D. Karapantsios

Researches in heattransfer have been carried out over the previous several decades, leading to the development of the currently used heattransfer enhancement techniques. The use of additives is a technique applied to enhance the heattransfer performance of base fluids. Recently, as an innovative material, nanometer-sized particles have been used in suspension in conventional heattransfer fluids. The

Natural convection heattransfer is found in many industrial applications such as nuclear technologies, electronic circuit board cooling, solar panel cooling and many other fields. When natural convection heattransfer coefficients are insufficient, passive heattransfer enhancement devices (called ribs\\/fins) are often used. In this paper, the effect of periodic patterns of protrusions (ribs) on the free-convection heattransfer of

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

Extended performance evaluation criteria equations for enhanced heattransfer surfaces based on the entropy production theorem are developed to include the effect of fluid temperature variation along the length of a tubular heat exchanger. The equations originate from various design constraints and generalize the performance evaluation criteria (PEC) for enhanced heattransfer techniques obtained by means of first law analysis.

The objectives of the HOST Turbine HeatTransfer 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 heattransfer 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 heattransfer design technology base.

A mathematical model was developed to describe the heattransfer characteristics of a hot strand emerging into a surrounding coolant. A stable strand of constant efflux velocity is analyzed, with a constant (average) heattransfer 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.

This paper describes a course developed by the author on the use of fins to enhance heattransfer from surfaces. The wide range of applications of fins makes it almost mandatory to include the subject in the teaching of heattransfer. At the graduate level, the tradition has been to offer a sequence of separate courses in conduction, convection, and radiation. A separate course on conduction provides the opportunity to expand the fin theory, but the coverage is limited to make room for other equally important topics.

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

Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane possage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Resutls were obtained for Reynolds numbers based on inlet velocity and axial chord between 75,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heattransfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heattransfer. Endwall heattransfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heattransfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.

Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane passage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Results were obtained for Reynolds numbers based on inlet velocity and axial chord between 73,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heattransfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heattransfer. Endwall heattransfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heattransfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.

In this experimental study, two surface modification techniques were investigated for their effect on heattransfer 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 heattransfer 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 heattransfer 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 heattransfer process. PMID:24003985

Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C

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.

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

Direct contact heat exchange offers the potential for increased efficiency and lower heattransfer costs in a variety of thermal energy storage sytems. SERI models of direct contact heattransfer based on literature information have identified dispersed phase drop size, the mechanism of heattransfer 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, heattransfer 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.

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

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

The advantages of direct contact heattransfer over heattransfer utilizing conventional metallic heat exchangers are listed. The performance characteristics of a three-phase direct contact heat exchanger in near counterflow operation were evaluated using...

A high efficiency absorption heat pump for the residential market is investigated. The performance targets established for this high efficiency absorption heat pump are a heating coefficient of performance of 1.5 and a cooling coefficient of performance of 0.8 at rating conditions, including parasitic electric power consumption. The resulting heat pump would have a space heating capacity of 68,000 BTU/hour, and a space cooling capacity of 36,000 BTU/hour at rating conditions. A very simplified schematic block diagram of the high efficiency absorption heat pump cycle is shown. High temperature, high pressure, refrigerant vapor is produced in the refrigerant generator and heat exchange system, is condensed to a liquid in the condenser, expanded to a low pressure vapor in the evaporator, and mixed with and reabsorbed into the weakened solution returned from the refrigerant generator and heat exchange system in the absorber.

A workshop on heat-transfer enhancement by additives in absorption processes was held last year at the Bavarian Center for Applied Energy Research (ZAE Bayern) in Garching, Germany, in collaboration with the Technical University München. The workshop was the first in a series of München Discussion Meetings, designed to bring together a limited number of researchers active in specific fields in

With rising science contents of the engineering research and education, we give examples of the quest for fundamental understanding of heattransfer 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

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

Fluid flow and heattransfer characteristics in microchannels of different cross-sections; parallel plate, cylindrical and trapezoidal microchannels were studied. The trapezoidal microchannels were etched in silicon and glass by photolithographic techniques. The cylindrical microchannels of fused silica and stainless steel were readily available. Channels with depths of 18 mum to 300 mum were studied. The study was divided into three

Heattransfer enhancement with electrohydrodynamic (EHD) technique in laminar forced convection inside a wavy channel with different wire electrode arrangements is numerically investigated. The electric field is generated by the wire electrodes charged with DC high voltage. The mathematical modeling includes the interactions among electric field, flow field, and temperature field. The simulation is firstly conducted with the experimental data

TACO is a two-dimensional implicit finite element code for heattransfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Either plane or axisymmetric geometries can be analyze...

TACO is an implicit finite element code for heattransfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Presently, TACO is specialized for two-dimensional problems of either...

One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heattransfer (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…

Work is currently underway to develop and characterize an analytical approach, based on boundary layer theory, for predicting the effects of leading edge (showerhead) film cooling on downstream gas side heattransfer rates. Parallel to this work, experiments are being conducted to build a relevant data base for present and future methods verification.

Quality of semiconductor and oxide crystals which are grown from the melts plays an important role for electronic and\\/or optical devices. The crystal quality is significantly affected by the heat and mass transfer in the melts during crystal growth in a growth furnace such as Czochralski or horizontal Bridgman methods. This paper reviews the present understanding of phenomena of the

This article presents results from a numerical study of pulsating jet impingement heattransfer. The motivation is to seek conditions offering a significant enhancement compared to steady flow impingement drying. The CFD software package FLUENT was used for simulating slot-type pulsating jet impingement flows with confinement. The parameter study included velocity amplitude ratio, mean jet velocity, and pulsation frequency. The

The aim of this work is to study heattransfer in a laboratory scale crater bed, which was set up from a cylindrical acrylic\\/quartz tube, using sand as the bed particle. The bed employs a downward gas jet from a nozzle which causes the particles to ascend fountain-like into the freebroad, leaving a crater on the bed surface. After reaching

A micromachined thermal accelerometer that is simple, reliable, and inexpensive to make has been developed at Simon Fraser University. The operating principle of this accelerometer is based on the free-convection heattransfer of a small hot air bubble in a sealed chamber. An experimental device that requires only four masking steps to fabricate has been built. This device has demonstrated

A. M. Leung; J. Jones; E. Czyzewska; J. Chen; B. Woods

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

Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ?10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation.

The hot section facility at the Lewis Research Center was used to demonstrate the capability of instruments to make required measurements of boundary conditions of the flow field and heattransfer processes in the hostile environment of the turbine. The results of thermal scaling tests show that low temperature and pressure rig tests give optimistic estimates of the thermal performance of a cooling design for high pressure and temperature application. The results of measuring heattransfer coefficients on turbine vane airfoils through dynamic data analysis show good comparison with measurements from steady state heat flux gauges. In addition, the data trends are predicted by the STAN5 boundary layer code. However, the magnitude of the experimental data was not predicted by the analysis, particularly in laminar and transitional regions near the leading edge. The infrared photography system was shown capable of providing detailed surface thermal gradients and secondary flow features on a turbine vane and endwell.

A two-phase small channel heat exchange matrix simultaneously provides for heattransfer 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 heattransfer 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.

Convective boiling heattransfer is an efficient cooling mechanism to dissipate amount of thermal energy by accompanying the phase transition of the working fluids. Particularly, the amount of heat dissipation capacity can be readily extensible by increasing the degree of subcooling due to initial demands requiring for coolant saturation. Under severely subcooled condition of 60°, we investigate boiling heattransfer phenomena regarding spatial heattransfer uniformity and stability on a planar surface. Severe subcooling can induce locally concentrated thermal loads due to poor spatial uniformity of the heattransfer. For reliable cooling, a high degree of spatial uniformity of the heattransfer should be guaranteed with minimized spatial deviation of heattransfer characteristics. Under pre-requisite safeguards below CHF, we experimentally elucidate the principal factors affecting the spatial uniformity of the heattransfer for a flow/thermal boundary layer considering heattransfer domains from a single-phase regime to a fully-developed boiling regime. Based on the local heattransfer evaluation, we demonstrate that full nucleation boiling over the entire heattransfer surface under subcooling conditions is favorable in terms of the uniformity of heat dissipation through the phase-change of the working fluid.

Kim, Beom Seok; Yang, Gang Mo; Shin, Sangwoo; Choi, Geehong; Cho, Hyung Hee

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

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

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

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

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

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

The primary basis for heattransfer analysis of turbine airfoils is experimental data obtained in linear cascades. A detailed set of heattransfer coefficients was obtained along the midspan of a stator and a rotor in a rotating turbine stage. The data are to be compared to standard analyses of blade boundary layer heattransfer. A detailed set of heat

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

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

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

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

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.

Heattransfer to drops impacting on a hot surface is examined in context of dispersions of flowing, boiling fluids. The liquid contribution to heattransfer from a hot tube to a two-phase dispersion is formulated in terms of heattransfer contributions due to surface impacts of individual drops. High heattransfer rates are associated with liquid wetting of the surface

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 heattransfer characteristics, flow pattern and theoretical analysis.

Heattransfer in microchannels has gained more interest in the last decade due to developments in the aerospace, biomedical and electronics industries. It has been a critical issue since the performance of the devices is primarily determined by temperature. As the size decreases, more efficient ways of cooling are sought due to the reduction in the heattransfer area. Convection

Although pulse combustion devices exhibit a high thermal efficiency and low pollutant emission when used in a drying process, a broad application of these dryers has been limited because of a lack of understanding of the fundamental controlling heat and mass transfer. This paper reports the results of an experimental investigation of heattransfer between unsteady airflow and a brass

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

The Cascade ICF reactor features a flowing blanket of solid BeO and LiAlO/sub 2/ granules with very high temperature capability (up to approx. 2300 K). The authors present here the design of a high temperature granule transport and heat exchange system, and two options for high efficiency power conversion. The centrifugal-throw transport system uses the peripheral speed imparted to the granules by the rotating chamber to effect granule transport and requires no additional equipment. The heat exchanger design is a vacuum heattransfer concept utilizing gravity-induced flow of the granules over ceramic heat exchange surfaces. A reference Brayton power cycle is presented which achieves 55% net efficiency with 1300 K peak helium temperature. A modified Field steam cycle (a hybrid Rankine/Brayton cycle) is presented as an alternate which achieves 56% net efficiency.

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

A solution methodology based on integral equations is presented for the problem of heattransfer to laminar duct flow subjected to an axial variation of the external heattransfer coefficient. The technique offers an efficient and accurate calculation procedure which combines standard analytical methods with a simple numerical integration. In order to examine the effect of external finning, results are calculated for the cases of a stepwise periodic and a harmonic variation of the heattransfer coefficient for both fully developed laminar flow and slug flow. The general procedure is applicable to a wide class of problems in heat and mass transfer involving variable boundary condition parameters.

The objective is to develop a heattransfer and pressure drop data base, computational fluid dynamic techniques, and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.

Various heattransfer problems that are currently investigated computationally, and some emerging computational trends are reviewed with reference to specific examples. In particular, attention is given to radiation problems, evaporation and interfaces, coupled and integrated problems, finite difference, finite volume, and finite element methods, and spectral elements. The discussion also covers internal forced flows and turbulence, free convection, mesh generation, adaptive grids and solvers, turbulence modeling, commercial software, and computer hardware trends.

Radiative heattransfer 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

We studied numerically the heattransfer for a turbulent flow of supercritical helium. A finite difference model is constructed\\u000a with three different models of turbulence: the mixing length,k- andk-? model. The stationary results compared to experimental data reveal that the mixing length model gives the best prediction\\u000a of turbulence in this situation. A severe deterioration from the widely used Nusselt

Local heattransfer measurements were experimentally mapped using a transient liquid-crystal heattransfer 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 heattransfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heattransfer 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.

Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven

A low-melting point, heattransfer 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.

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

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

The report contains techniques for calculating the heattransfer of a Standard Hardware module, designing a module with respect to heattransfer, test data from a specially constructed module, and comparison of test data with theoretical data. (Author)

The Primary basis for heattransfer analysis of turbine airfoils is experimental data obtained in linear cascades. These data were very valuable in identifying the major heattransfer and fluid flow features of a turbine airfoil. The first program objecti...

A transcript is presented of a lecture concerning recent developments in predicting heattransfer performance. Topics discussed include: the designer's problem, calculation of local heattransfer conductances, calculations of convective interactions, and ...

Numerical simulations of heat- and mass-transfer and heterogeneous reactions in catalytic monoliths are reported with the focus on the influence of radiation heattransfer on the thermal behavior of the monolith. Appropriate heterogeneous kinetics and boundary conditions were calculated for two cases including: an automobile catalytic converter in which carbon monoxide is oxidized over a platinum (Pt) catalyst and a catalytic combustor for gas turbine power generation in which methane is oxidized over a palladium oxide (PdO) catalyst. Surface oxidation rates of carbon monoxide are based on measurements of Pt catalyst activity in a catalytic flow reactor, and rates for methane oxidation are based on reaction kinetics for a supported PdO catalyst assigned from differential reactor measurements. These simulations show that in the high aspect ratio passageways (length to diameter) in catalytic monoliths, radiation heattransfer can play a major role in the energy balance on the catalytic surfaces, which determines the transient warm-up behavior and the steady-state location of catalyst light-off. For gray surfaces, however, the predicted steady-state and transient behaviors are not sensitive to the emissivity of the monolith walls.

Boehman, A.L. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Energy and Geo-Environmental Engineering] [Pennsylvania State Univ., University Park, PA (United States). Dept. of Energy and Geo-Environmental Engineering

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

A HeatTransfer Monitor (HTM) is a sensitive device which quantifies development of biofouling in the OTEC heat exchanger surfaces in terms of degrading heattransfer coefficient as biofouling progresses. The Carnegie-Mellon University (CMU) type HTM has ...

A 3D mathematical model has been developed to investigate the heattransfer augmentation in a circular tube with a helical turbulator. Glycol–water blends of various concentrations were used in the inner tube, and pure water was used in the outer tube. Changes in fluid physical properties with temperature were taken into account, and k–?,k-?, and large eddy simulations were developed

The flow and heattransfer 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 heattransfer 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 heattransfer 20-25% at the same pumping power compared with the commonly used inclined continuous rib plates. (author)

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)

A theoretical and experimental investigation of the transient heattransfer during sterilization of the canned foods was conducted in order to determine the heattransfer rate variations. The present model is based on the heat balance equation using the boundary condition of the first kind in the transient heattransfer, which expresses a simple relationship between the time and temperatures of the canned foods. The experimental heattransfer rates were compared with the predictions obtained from the present model and good agreement was found. The results confirmed that the present model is capable of estimating the heattransfer rates in a simple manner.

Dincer, I.; Varlik, C.; Gun, H. (TUBITAK-Marmara Research Center, Gebze (Turkey))

Heattransfer enhancement is one of the key issues of saving energies and compact designs for mechanical and chemical devices and plants. We discover an ultrahigh convective heattransfer performance compared to the well-known heattransfer correlations caused by a nano-particle porous surface: the maximum increase of heattransfer coefficient was around 180%. This nano-particle porous layer can be formed

In order to investigate the contribution of radiative heattransfer to total heattransfer in a circulating fluidized bed coal combustor, heattransfer experiments were carried out. The test facility has the dimension of 6.0 m in height and 0.2 m×0.2 m rectangular cross-section. Anthracite coal was used for the fuel, and the heattransfer tubes were installed near the

Two-phase closed thermosiphons are highly efficientheat-transfer elements with applications in terrestrial heat-transport and heat-recovery systems. In this paper, a corrugated copper tube was used as the container of the thermosiphons and distilled water was used as the working fluid. The influences of the liquid charge ratio and inclination angle on the heat-transfer performance were studied. It was found that the optimum liquid charge ratio to evaporator volume is 40 percent and the maximum performance is obtained at an inclination angle of 30 degrees. A useful formula to calculate the heat-transfer coefficient in the evaporator has been derived.

Negishi, K. (Tokyo Metropolitan Inst. of Technology (JP)); Kaneko, K. (Univ. of Osaka Prefecture (JP)); Matsuoka, T. (Nissan Motor Co., Ltd. (JP)); Hirashima, M.; Nishikawa, Y.; Taguchi, M. (Takuma Research and Development Co., Ltd. (JP))

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

A theoretical study is presented of the convective heattransfer in the hydrodynamically and thermally fully developed region of rotating radial rectangular ducts. A pair or pairs of vortices superimposed on the main flow are introduced in the duct by the coriolis force. The fluid is heated by the duct wall, and the fluid bulk temperature may increase exponentially after a sufficiently long heating length. The three-dimensional energy equation can then be reduced to a two-dimensional eigenvalue problem. The axial conduction is also considered for a small Peclet number. The study covers parameters Pr = 0.7 and 7.0, Pe = infinity, 5, 1, and Re, and Re(omega) = 0-2 x 10 to the 5 for rectangular channels with aspect ratios of 0.2, 0.5, 1, 2, and 5. The results are compared with existing data.

Heattransfer 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%.

Four general Monte Carlo codes (GEANT3, PENELOPE, MCNP and EGS4) and five dedicated packages for efficiency determination in gamma-ray spectrometry (ANGLE, DETEFF, GESPECOR, ETNA and EFFTRAN) were checked for equivalence by applying them to the calculation of efficiencytransfer (ET) factors for a set of well-defined sample parameters, detector parameters and energies typically encountered in environmental radioactivity measurements. The differences between the results of the different codes never exceeded a few percent and were lower than 2% in the majority of cases. PMID:19892558

Vidmar, T; Celik, N; Cornejo Díaz, N; Dlabac, A; Ewa, I O B; Carrazana González, J A; Hult, M; Jovanovi?, S; Lépy, M-C; Mihaljevi?, N; Sima, O; Tzika, F; Jurado Vargas, M; Vasilopoulou, T; Vidmar, G

We have performed detailed measurements of the charge transferefficiency (CTE) in a thinned, backside-illuminated imaging charge-coupled device (CCD). The device had been damaged in three separate sections by proton radiation typical of that which a CCD would receive in space-borne experiments, nuclear imaging, or particle detection. We examined CTE as a function of signal level, temperature, and radiation dose.

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 efficiencytransfer 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

In the paper, a heat-transfer model considering thermal degradation of heat-resistant fabrics when subjected to the radiant heat flux has been proposed. The model incorporates the heat-induced changes in fabric thermo physical properties. The new model has been validated by experimental data from modified Radiant Protective Performance (RPP) tests of heat-resistant fabrics. Comparisons with experimental data show that the predictions

A test set-up was developed for the determination of the external heattransfer coefficient of walls under actual outdoor conditions. The set-up was used to measure the convective heattransfer coefficient for the central region of a vertical wall. Outdoor tests were carried out under a wide range of conditions and the heattransfer coefficient was correlated with wind speed.

For heattransfer between a gas and a fluid medium, the surface of the gas medium was optimized by using rectangular ribs. To intensify the heattransfer in pipes, a systematic roughening of the surface is proposed and its influence on the flow resistance discussed. A model for the relevant information on the turbulent convective heattransfer in relation to surface roughness is presented.

The bio-heattransfer equation is a macroscopic model for describing the heattransfer in microvascular tissue. In (8) the authors applied homog- enization techniques to derive the bio-heattransfer equation as asymptotic result of boundary value problems which provide a microscopic descrip tion for microvascular tissue. Here those results are generalized to a geo metrical setting where the regions of

Nanofluids are considered to offer important advantages over conventional heattransfer fluids. Over a decade ago, researchers focused on measuring and modeling the effective thermal conductivity and viscosity of nanofluids. Recently important theoretical and experimental research works on convective heattransfer appeared in the open literatures on the enhancement of heattransfer using suspensions of nanometer-sized solid particle materials, metallic

For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heattransfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heattransfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heattransfer over microscopic distances between metallic and non-metallic surfaces. Using a

T. Kralik; P. Hanzelka; V. Musilova; A. Srnka; M. Zobac

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 heattransfer fundamentals are described. Heattransfer coefficients and the resistance to heattransfer offered…

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

The Primary basis for heattransfer analysis of turbine airfoils is experimental data obtained in linear cascades. These data were very valuable in identifying the major heattransfer and fluid flow features of a turbine airfoil. The first program objective is to obtain a detailed set of heattransfer coefficients along the midspan of a stator and a rotor in

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

Results of studies concerned with the convective and radiation heattransfer in the combustion chambers of gas turbines are examined. In particular, the existing methods for cooling flame tubes are analyzed, and heattransfer calculations are carried out for highly augmented combustion chambers. A method is also presented for calculating complex heattransfer in the flame zone for various types

This research involved the study of heattransfer and fluid mechanic characteristics around a horizontal tube in the freeboard region of fluidized beds. Heattransfer 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 heattransfer coefficients were found to vary

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

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...

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

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

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

In this study time dependant heat flow through superfluid helium (He II) contained in porous media is examined. Using a porous insulation instead of fully epoxy-impregnated insulation could potentially increase cooling efficiency by allowing an intimate contact of He II with the conductor. The present work focuses on understanding heattransfer in He II contained in a bed of polyethylene spheres of uniform size arranged in a random pack. Measured results include the transient temperature decay across the bed of packed spheres (diameters of 35, 49 and 98 microns) when heat addition is removed on one side of the porous media while the other is held at bath temperature. Bath temperatures range from 1.7 to 2.1 K. Two flow regimes (transitional and turbulent) are decipherable from the dependence of the temperature gradient on the heat flux. Past steady state, turbulent He II heattransfer experiments in the same media have concluded that the Gorter-Mellink exponent varies from 3.3 to 3.4 in this temperature range. Transient results compare favorably to a one-dimensional numerical solution that considers a variable Gorter-Mellink exponent and a piece-wise determination of the heat flux.

The "general Prandtl number" Pr(exp 1) - A(sub q)/A Pr, aside from the Reynolds number determines the ratio of turbulent to molecular heattransfer, 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 heattransfer 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.

A novel porous micro heat sink system is presented for thermal management of high power LEDs, which has high heat transport capability. The operational principle and heattransfer characteristics of porous micro heat sink are analyzed. Numerical model for the micro heat sink is developed to describe liquid flow and heattransfer based on the local thermal equilibrium of porous

Apparatus for efficientheating 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 heattransfer 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.

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

In the second part of review, we have considered the problems related to momentum and heattransfer in nanofluids. Results on hydrodynamic friction, forced and free convection in the laminar and turbulent flows are analysed; heattransfer at boiling is considered. The available models describing heattransfer intensification and suppression in nanofluids are studied. It is shown that for some problems on convective heattransfer there is a contradiction in data of different authors; possible reasons for this contradiction are analysed.

Aspects of direct contact heattransfer are considered along with transport phenomena in fusion reactors, enhanced nucleate boiling, flow boiling, heattransfer in non-Newtonian systems, two-phase systems, heattransfer in fossil fuel conversion systems, process heattransfer, thermal and hydraulic behavior in rod and tube bundles, and two-phase systems in rod and tube bundles. Attention is also given to solar

The fuel consumed to supply the thermal demands in buildings can be reduced by improving the thermal integrity of buildings or by relying on more efficient methods of converting the fuel energy into heat. It is shown that one conversion option, district heating with cogeneration, requires about the same amount of capital investment per unit of energy saved as required

G. D. Pine; M. A. Karnitz; M. A. Broders; W. R. Mixon

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

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.

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

Advanced computers are facing thermal engineering challenges from both high heat generation due to rapid performance improvement and the reduction of an available heat removal surface due to large packaging density. Efficient cooling technology is desired to provide reliable operation of microelectronic devices. This paper investigates the feasibility of heattransfer enhancement in laminar flow using the flow-induced vibration of

Jeung Sang Go; Sung Jin Kim; Geunbae Lim; Hayong Yun; Junghyun Lee; Inseob Song; Y. Eugene Pak

Supercritical fuel reforming is being studied as a technology for reducing emissions of industrial gas turbine engines. In this study, experiments were performed in a 2.67-mm-inside-diameter stainless steel tube with a heated length of 0.610 m for the purpose of investigating the characteristics of supercritical heattransfer with endothermic fuel reforming. Thermocouples were positioned along the tube both in the fluid stream and on the heated wall for local heattransfer measurements. Both heattransfer coefficients and endotherms were calculated from the measured results. State-of-the-art correlations for heattransfer were evaluated, and a correlation for supercritical heattransfer to hydrocarbon fuel has been developed. The results provide a basis for supercritical fuel heat-exchanger/reactor design and its practical applications, in an area that has received relatively little attention in the engineering literature, viz., supercritical forced convection heattransfer with endothermic chemical reaction.

Yu, W.; France, D. M.; Wambsganss, M. W.; Energy Technology; Univ. of Illinois at Chicago

A visualization technique is used to measure the heattransfer coefficient distribution on a flat plate on which either a single jet or an array of jets impinges. Liquid crystals coated on a mylar sheet are used to locate isotherms on a heated surface. By adjusting the surface heat flux, contours of constant heattransfer coefficient are obtained.

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

This paper investigates a two-phase non-boiling slug flow regime for the purposes of enhancing heattransfer in microchannel heat sinks or compact heat exchangers. The primary focus is upon understanding the mechanisms leading to enhanced heattransfer and also the effect of utilizing different Prandtl number fluids. Experiments were conducted using Infrared thermography and results presented in terms of Nusselt

James A. Howard; Patrick A. Walsh; Edmond J. Walsh; Yu. S. Muzychka

A parametric study of the heattransfer 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 heattransfer 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.

Interfaces usually impede heattransfer in heterogeneous structures. Recent experiments show that van der Waals (vdW) interactions can significantly enhance thermal conductivity parallel to the interface of a bundle of nanoribbons compared to a single layer of freestanding nanoribbon. In this paper, by simulating heattransfer in nanostructures based on a model of nonlinear one-dimensional lattices interacting via van der Waals interactions, we show that the vdW interface interaction can adjust the thermal conductivity parallel to the interface. The efficiency of the adjustment depends on the intensity of interactions and temperature. The nonlinear dependence of the conductivity on the intensity of interactions agrees well with experimental results for carbon nanotube bundles, multi-walled carbon nanotubes, multi-layer graphene, and nanoribbons. PMID:23147396

A novel high-heattransfer low NO(sub x) natural gas combustion system. The objectives of this program are to research, develop, test, and commercialize a novel high-heattransfer low-NOâ natural gas combustion system for oxygen-, oxygen-enriched air, and air-fired furnaces. This technology will improve the process efficiency (productivity and product quality) and the energy efficiency of high-temperature industrial furnaces by at

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.

The feasibility of adding phase change materials (PCMS) and surfactants to the heattransfer fluids in district cooling systems was investigated. It increases the thermal capacity of the heattransfer fluid and therefore decreases the volume that needs to be pumped. It also increases the heattransfer rate, resulting in smaller heat exchangers. The thermal behavior of two potential PCMS,

Fusion power plant studies have found helium to be an attractive coolant based on its safety advantages and compatibility with structural materials at high temperature. However, gas coolants in general tend to provide modest heattransfer performance due to their inherently low heat capacity and heattransfer coefficient. Innovative techniques have been proposed previously using porous metal heattransfer media

Flow and heattransfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heattransfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heattransfer was 22 percent greater than the straight-channel correlation.

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

Heattransfer in gas fluidization is investigated at a particle scale by means of a combined discrete element method and computational fluid dynamicsapproach. To develop understanding of heattransfer at various conditions, the effects of a few important material properties such as particle size, the Hamaker constant and particle thermal conductivity are examined through controlled numerical experiments. It is found that the convective heattransfer is dominant, and radiative heattransfer becomes important when the temperature is high. Conductive heattransfer also plays a role depending on the flow regimes and material properties. The heattransfer between a fluidized bed and an immersed surface is enhanced by the increase of particle thermal conductivity while it is little affected by Young's modulus. The findings should be useful for better understanding and predicting the heattransfer in gas fluidization.

Theoretical results derived in this article are combined with experimental data to conclude that, while there is no improvement in the effective thermal conductivity of nanofluids beyond the Maxwell's effective medium theory (J.C. Maxwell, Treatise on Electricity and Magnetism, 1891), there is substantial heattransfer augmentation via nanofins. The latter are formed as attachments on the hot wire surface by yet an unknown mechanism, which could be related to electrophoresis, but there is no conclusive evidence yet to prove this proposed mechanism.

This paper describes heat and mass transfer characteristics of organic sorbent coated on heattransfer surface of a fin-tube heat exchanger. The experiments in which the moist air was passed into the heat exchanger coated with sorption material were conducted under various conditions of air flow rate (0.5 1.0 m/s) and the temperature of brine (14 20°C) that was the heattransfer fluid to cool the air flow in the dehumidifying process. It is found that the sorption rate of vapor is affected by the air flow rate and the brine temperature. Meanwhile, the attempt of clarifying the sorption mechanism is also conducted. Finally the average mass transfer coefficient of the organic sorbent coated on heattransfer surface of a fin-tube heat exchanger is non-dimensionalzed as a function of Reynolds number and non-dimensional temperature, and it is found that the effect of non-dimensional temperature on them is larger than Reynolds number .

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.

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

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

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 heattransfer 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 heattransfer 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 heattransfer 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: heattransfer 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.

This paper describes a subroutine, GETQ, which was developed to compute the heattransfer 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 heattransfer rate computation is desired. The returned heattransfer rate values are broken down into linear, nonlinear, source and combined heat loads.

A supercritical water heattransfer facility has been built at the University of Wisconsin to study heattransfer in ancircular and square annular flow channel. A series of integral heattransfer measurements has been carried out over a wide range of heat flux, mas velocity and bulk water temperatures at a pressure of 25 MPa. The circular annular test section geometry is a 1.07 cm diameter heater rod within a 4.29 diameter flow channel.

Mark H. Anderson; MichaelL. Corradini; Riccardo Bonazza; Jeremy R. Licht

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

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

This paper discusses three-dimensional combined radiative and convective heat-transfer process in a furnace for LPG reforming which is simulated by introducing the radiosity concept into the radiative heat ray method for accurate radiative heat-transfer analysis. Together with an analysis of the chemical reaction in the reactor tubes of the furnace, the heat-transfer simulation gives the three-dimensional profile of the combustion

K. Kudo; H. Taniguchi; K. Guo; T. Katayama; T. Nagata

This paper describes quantitatively new mechanisms in the post-CHF regime which provide understanding and predictive capability for several current two-phase forced convective heattransfer problems. These mechanisms are important in predicting rod temperature turnaround and quenching during the reflood phase of either a hypothetical loss-of-coolant accident (LOCA) or the FLECHT and Semiscale experiments. The mechanisms are also important to the blowdown phase of a LOCA or the recent Loss-of-Fluid Test (LOFT) experiments L2-2 and L2-3, which were 200% cold leg break transients. These LOFT experiments experienced total core quenching in the early part of the blowdown phase at high (1000 psia) pressures. The mechanisms are also important to certain pressurized water reactor (PWR) operational transients where the reactor may operate in the post-CHF regime for short periods of time. Accurate prediction of the post-CHF heattransfer including core quench during these transients is of prime importance to limit maximum cladding temperatures and prevent cladding deformation.

High temperature multilayer insulations have been investigated as an effective component of thermal-protection systems for atmospheric re-entry of reusable launch vehicles. Heattransfer 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 heattransfer 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.

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

Fluid flow and heattransfer characteristics in microchannels of different cross-sections; parallel plate, cylindrical and trapezoidal microchannels were studied. The trapezoidal microchannels were etched in silicon and glass by photolithographic techniques. The cylindrical microchannels of fused silica and stainless steel were readily available. Channels with depths of 18 ?m to 300 ?m were studied. The study was divided into three parts viz. theoretical modeling, numerical simulation and experimentation. Electrokinetic effects such as the effects of electrical double layer (EDL) at the solid-liquid interface and surface roughness effects were considered. An experimental apparatus was constructed and a procedure devised to measure the flow rate, pressure drop, temperatures and electrokinetic parameters like streaming potential, streaming current, and conductivity of the working fluid. Great care was taken so that the measurements were accurate and repeatable. For steady state laminar flow and heattransfer in microchannels, mathematical models were developed that consider the effects of electrical double layer and surface roughness at the microchannel walls. The non- linear, 2-D, Poisson-Boltzmann equation that describes the potential distribution at the solid liquid interface was solved numerically and results were compared with a linear approximate solution that overestimates the potential distribution for higher values of zeta potential. Effects of the EDL field at the solid-liquid interface, surface roughness at the microchannel walls and the channel size, on the velocity distribution, streaming potential, apparent viscosity, temperature distribution and heattransfer characteristics are discussed. The experimental results indicate significant departure in flow characteristics from the predictions of the Navier-Stokes equations, referred to as conventional theory. The difference between the experimental results and theoretical predictions decreases as the hydraulic diameter increases. For higher hydraulic diameters, the experimental results are in rough agreement with the predictions of Navier-Stokes equations. For the same volume flow rate, experimentally measured pressure gradients are significantly higher than conventional theory predictions. Therefore, the friction factor and apparent viscosity are higher. The results also indicate material dependence of the flow behavior. The observed effects are attributed to either to an early transition from laminar flow to turbulent flow or to the surface effects; electrokinetic and surface roughness effects. For parallel plate microchannels, the electrokinetic effects explain the observed differences. For cylindrical and trapezoidal silicon microchannels, experimentally measured pressure drop is significantly higher than conventional theory prediction; with and without electrokinetic effects. For cylindrical microchannels, the electrokinetic effects were not measured as one material was conducting while as for the fused silica the diameter of microchannels was greater than 50 ?m. For such large microchannels the EDL effects are negligible as shown by theory. For trapezoidal microchannels, flow rate, pressure drop, temperature and electrokinetic parameters were measured for three different electrolyte concentrations. It was found that the electrokinetic effects are negligible for trapezoidal microchannels having hydraulic diameters greater than 50 ?m, and the higher-pressure requirement is because of surface roughness. The roughness-viscosity model developed for cylindrical and trapezoidal microchannels explains the higher-pressure requirement as measured experimentally. The predictions of the roughness viscosity model agree well with the experimental data. The heattransfer characteristics are similar to as obtained by various other researchers. The measured Nusselt numbers were lower than the conventional theoretical predictions but agree well with the modified conventional equation by considering the roughness effects on heattransfer.

Research results on curved surface heattransfer, airfoil heattransfer, film cooling and end-wall heattransfer are presented. In particular these studies focus on the recovery process of a turbulent boundary layer from curvature, heattransfer measureme...

E. R. Eckert R. J. Goldstein S. V. Patankar T. W. Simon

This paper is basically the text of the Kern Lecture for 1991 (the 1990 Kern Award). The paper begins with some remarks about Dr. Kern. By way of introduction to heattransfer enhancement, historical notes and the evolution of literature in this area are presented. Comments are made about the increasing practical applications of enhancement technology. Developments in single-phase convection

This paper reports an experimental study on nanofluid convective boiling heattransfer 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 heattransfer 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 heattransfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heattransfer results. The boiling local heattransfer 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 heattransfer are obtained at the minichannels entrance.

This paper reports an experimental study on nanofluid convective boiling heattransfer 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 heattransfer 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 heattransfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heattransfer results. The boiling local heattransfer 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 heattransfer are obtained at the minichannels entrance. PMID:23506445

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

Arctic people living throughout the circumpolar region have time tested their caribou skin clothing ensembles for 3000 to 8000 years (Stefansson 1944 and 1955). The traditional clothing system developed and used by the Inuit is the most effective cold weather clothing developed to date (Oakes et al. 1995). One of the key elements used by the Inuit is a fur ruff attached to the hood, hem, and cuffs of their parkas. This paper determines why the fur ruff is so critical to the effectiveness of cold weather clothing, especially in protecting the face, without impeding movement or view, so essential to the Inuit hunter. The effectiveness of this clothing is established using both traditional and scientific knowledge. To quantify the effectiveness of this clothing, the heattransfer was measured on a model, placed into a wind tunnel. The wind velocity and angle to the wind were varied. A boundary layer forms on the face, the heattransfer was measured across that layer using thermocouples. It is essential to minimize that heattransfer for survival and frostbite prevention. Different fur ruffs geometries were examined to determine the most efficient one. This information was combined with data collected using ethno-historical methods. Data for this portion of the research has been collected since 1970 and 1983 by two of the co-researchers. This unique combination of scientific and traditional Aboriginal knowledge provides a wholistic perspective on new insights on the effectiveness of cold weather clothing systems.

In a lighting fixture including a lamp and a housing, a heattransfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heattransfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferringheat 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 heattransfer structure.

Siminovitch, Michael J. (Richmond, CA); Rubenstein, Francis M. (Berkeley, CA); Whitman, Richard E. (Richmond, CA)

In a lighting fixture including a lamp and a housing, a heattransfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heattransfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferringheat 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 heattransfer structure. 11 figs.

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

In order to obtain a semitheoretical correlation for the heattransfer coefficients in three phase fluidized beds, Deckwer's semitheoretical correlation for the heattransfer coefficients in the bubble column, which was derived from Higbie's surface renewal theory of interphase mass transfer with the concept of isotropic turbulence, has been extended to three phase fluidized beds with the modification of the

We present an updated version of SKIRT, a three-dimensional (3D) Monte Carlo radiative transfer code developed to simulate dusty galaxies. The main novel characteristics of the SKIRT code are the use of a stellar foam to generate random positions, an efficient combination of eternal forced scattering and continuous absorption, and a new library approach that links the radiative transfer code to the DustEM dust emission library. This approach enables a fast, accurate, and self-consistent calculation of the dust emission of arbitrary mixtures of transiently heated dust grains and polycyclic aromatic hydrocarbons, even for full 3D models containing millions of dust cells. We have demonstrated the accuracy of the SKIRT code through a set of simulations based on the edge-on spiral galaxy UGC 4754. The models we ran were gradually refined from a smooth, two-dimensional, local thermal equilibrium (LTE) model to a fully 3D model that includes non-LTE (NLTE) dust emission and a clumpy structure of the dusty interstellar medium. We find that clumpy models absorb UV and optical radiation less efficiently than smooth models with the same amount of dust, and that the dust in clumpy models is on average both cooler and less luminous. Our simulations demonstrate that, given the appropriate use of optimization techniques, it is possible to efficiently and accurately run Monte Carlo radiative transfer simulations of arbitrary 3D structures of several million dust cells, including a full calculation of the NLTE emission by arbitrary dust mixtures.

We visualize unsteady temperature fields in the grooved channel with curved vanes using holographic interferometry. The heattransfer performance of the investigated channel is compared with that of the basic grooved channel. The addition of curved vanes above the downstream end of the heated block redirects the flow from the main channel into the groove. Heattransfer shows an increase

An experimental study was performed to characterize the boiling heattransfer of impinging circular submerged jets on simulated microelectronic chips with a nominal area of 5 mm × 5 mm. The heattransfer modes included natural convection, partially developed nucleate boiling, fully developed nucleate boiling and critical heat flux. The study included the effects of jet parameters and fluid subcooling

Heattransfer 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 heattransfer performance on the four side walls of the three straight flow passages and two turning elbows are determined for both

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

This work deals with a measurement of heattransfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heattransfer coefficient (HTC) is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.

Complexities of liquid rocket engine heattransfer which involve the injector faceplate and regeneratively and film cooled walls are being investigated by computational analysis. A conjugate heattransfer analysis will be used to describe localized heating phenomena associated with particular injector configurations and coolant channels and film coolant dumps. These components are being analyzed, and the analyses verified with appropriate

Applications of heattransfer to electronic components and devices are presented and discussed. The major objectives are to review the state of the art in such applications and to indicate the need for a better grasp of the science of heattransfer in aiding the creative engineering of new electronic devices operating at extreme conditions of temperature, heat flux, air

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

Maciej K. Ginalski; Andrzej J. Nowak; Luiz C. Wrobel

Boiling is known to be a very efficient mode of heattransfer, and as such, it is employed in component cooling and in various energy-conversion systems. In space, boiling heattransfer 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 heattransfer. Because of the complex nature of the boiling process, no generalized prediction or procedure has been developed to describe the boiling heattransfer 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.

This article presents an analytical model for analyzing transient heattransfer between a brick particle and air flow during heating in a fluidized bed combustor. Both experimental and theoretical studies were carried out. The experimental investigation provided the temperature distributions at the centers of the spherical particles during heating. These data were presented in the dimensionless form and were compared with the results of the present analytical model. The modeling includes two heattransfer coefficient cases. In the first case, heattransfer coefficient is the only convection heattransfer coefficient, and in the second case, it is the sum of the convection and radiation heattransfer coefficients. In the comparison between experimental data and theoretical results, better agreement was found for the second case. The present results indicate that the radiation heattransfer coefficient has a significant effect on transient heattransfer from the single object and should be taken into consideration.

Dincer, I. [TUBITAK-Marmara Research Center, Gebze (Turkey)

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 transferheat; - 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 heattransfer characteristic and crisis. This paper has regard for the heattransfer 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. HEATTRANSFER 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 heattransfer 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 heattransfer limitation of liquid film dry-out at first. Then with the increasing of heat flux, the heattransfer limitation of location burn-out would happen. In order to avoid the heattransfer 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 PipeHeatTransfer LimitationDry-OutCarryingStagnancy

This paper presents a mathematical analysis of the heattransfer 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.

Combined convective-radiative heattransfer in the hydrodynamically and thermally developing region of rectangular and equilateral-triangular ducts is numerically investigated. The radiative heattransfer contribution is modeled by a differential method, the method of moments. The 3D governing equations of momentum and energy are discretized by an explicit finite-difference algorithm, the method of lines. This system of discretized algebraic equations are then solved by the fourth-order Runge-Kutta method. The effects of three major parameters affecting combined heattransfer, namely, conduction-radiation parameter, optical thickness, and wall emissivity, are analyzed in detail. This numerical scheme is found to be simple, accurate and efficient, and it is especially suited for combined heattransfer. The predicted results for pure convective heattransfer are in good agreement with available data published in open literature.

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

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

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 efficientheattransfer material for transferringheat between the first and second fluids. Also disclosed are specific materials and configurations.

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.

Combined radiation and conduction heattransfer 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 heattransfer in the optically thick insulations. The relevant parameters needed for the heattransfer model were derived from experimental data. Semi-empirical formulations were used to model the solid conduction contribution of heattransfer in fibrous insulations with the relevant parameters inferred from thermal conductivity measurements at cryogenic temperatures in a vacuum. The specific extinction coefficient for radiation heattransfer 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 heattransfer formulation. This heattransfer 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 heattransfer. The heattransfer modeling methodology was validated by comparison with more rigorous analytical solutions and with standard thermal conductivity measurements. The validated heattransfer 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 heattransfer 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.

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

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/heattransfer 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 heattransfer 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 heattransfer 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.

Interface elements are desirable in finite element heattransfer analyses in situations where dissimilar meshes are to be joined or where contact resistances occur between various parts of a body. In stress codes, such elements are often termed master/slave. A general algorithm for interface elements will be described. The algorithm allows development of interface elements for both two- and three-dimensional applications. Surfaces in contact are automatically determined so that a minimum of input data is required. In addition, the algorithm allows for compatibility in thermal stress calculations with mechanical codes which have sliding interface capabilities. Implementation of the algorithm into the TACO codes will be discussed and examples will be given.

A low-melting point, heattransfer 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.

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

Heat-transfer augmentation by straight grid spacers in rod bundles is studied for single-phase flow and for post-critical heat flux dispersed flow. The heattransfer effect of swirling grid spacers in single-phase flow is also examined. Governing heat-transfer mechanisms are analyzed, and predictive formulations are established. For single-phase flow, the local heattransfer at a straight spacer and at its upstream or downstream locations are treated separately. The effect of local velocity increasing near swirling spacer is considered. For post critical heat flux (CHF) dispersed flow, the heattransfer by thermal radiation, fin cooling, and vapor convection near the spacer are calculated. The predictions are compared with experimental data with satisfactory agreement.

Vortex-induced heattransfer enhancement exploits longitudinal and transverse pressure-driven vortices through the deliberate artificial generation of large-scale vortical flow structures. Thermal-hydraulic performance, Nusselt number and friction factor are experimentally investigated in a HEV (high-efficiency vortex) mixer, which is a tubular heat exchanger and static mixer equipped with trapezoidal vortex generators. Pressure gradients are generated on the trapezoidal tab initiating a streamwise swirling motion in the form of two longitudinal counter-rotating vortex pairs (CVP). Due to the Kelvin-Helmholtz instability, the shear layer generated at the tab edges, which is a production site of turbulence kinetic energy (TKE), becomes unstable further downstream from the tabs and gives rise to periodic hairpin vortices. The aim of the study is to quantify the effects of hydrodynamics on the heat- and masstransfer phenomena accompanying such flows for comparison with the results of numerical studies and validate the high efficiency of the intensification process implementing such vortex generators. The experimental results reflect the enhancement expected from the numerical studies and confirm the high status of the HEV heat exchanger and static mixer.

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

CPU time for radiative heattransfer analysis using the zone method is greatly reduced. Reduction in CPU time is attributed to the development of a simplified version of the plating algorithm for calculation of total exchange areas (TEAs) and of a model reduction algorithm for eliminating low-energy-level exchange areas from the matrix of radiative transfer. The accuracy and efficiency of

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

In order to determine the effect of surface irregularities on local convective heattransfer, the variation in heattransfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heattransfer enhancement was observed to vary over the roughness elements with the maximum heattransfer on the upstream face. This heattransfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heattransfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heattransfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heattransfer was observed on the downstream elements. Implications of the observed roughness enhanced heattransfer on ice accretion modeling are discussed.

Henry, Robert C.; Hansman, R. John, Jr.; Breuer, Kenneth S.

A series of heattransfer 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 heattransfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heattransfer 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 heattransfer rates were much better (approximately 2.5 times) than expected.

Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.

Seven types of pyrotechnic igniters were each mounted at one end of a closed cylindrical bore hole representative of the center hole in a thermal battery. Measurements of local bore wall temperature, T/sub w/, using commercially available, fast response (10 /mu/sec) sheathed chromel-constantan thermocouples allowed calculation of local heattransfer rates, q, and wall heat flows, Q. The principal charge constituents of all these igniters were titanium and potassium perchlorate, while three types also contained barium styphnate as an ignition sensitizer. Igniter closure disc materials included glass-ceramic, glass, metal (plain, scored, with and without capture cone), and kapton/RTV. All igniters produced the lowest values of T/sub w/ and q at the beginning of the bore, and, except for the igniter with the kapton/RTV closure disc, these quantities increased with distance along the bore. For igniters containing only titanium/potassium perchlorate, the rates of increase of Q along the bore length, compared with those for T/sub w/ and q, were generally lower and more variable. The inclusion of barium styphnate produced rates of change in Q that were essentially constant to the end of the bore. The highest overall average wall temperatures were achieved by two igniter types with metal closure discs and no capture cone. No clear correlation was established between peak bore pressure and maximum wall temperature. 3 refs., 8 figs., 1 tab.

Spray cooling is an integral part of many manufacturing processes and is particularly relevant to high-temperature process. It may be used to simply allow the survival of a unit or to insure that a unit operates at an acceptable temperature. A more recent trend is to use spray cooling to control the final properties of the product. Particular problems are experienced when cooling from the high temperature, stable film boiling regime through Leidenfrost to nucleate boiling. In this case, the published relationships between spray impact density (liters/s/sq meter) and heattransfer coefficient (HTC) are of little use, becoming very inaccurate as cooling proceeds. Mathematical models of cooling are well developed and reliable but need accurate information on the heat removal conditions at the surface of the stock. A test apparatus using a stainless steel specimen cooled from 1,200 C to ambient has been used to investigate the HTC`s from various types of spray, both pressure atomized and air mist, by a transient method. The temperature history is supplied to a mathematical model which works in a reverse iterative manner but with a convergence function. This gives a relationship between HTC and stock temperature over the entire temperature range. Relationships between impact density and HTC are presented for various nozzles and suggestions for further work are made.

Stewart, I.; Massingham, J.D. [British Steel Technical, Moorgate (United Kingdom). Swinden Technology Center; Hagers, J. [Spraying Systems Co., Wheaton, IL (United States)

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

A numerical study of the aerodynamic and thermal environment associated with axial turbine stages is presented. Computations were performed using a modification of the unsteady NASA Ames viscous code, ROTOR1, and an improved version of the NASA Lewis steady inviscid cascade system MERIDL-TSONIC coupled with boundary layer codes BLAYER and STAN5. Two different turbine stages were analyzed: the first stage of the United Technologies Research Center Large Scale Rotating Rig (LSRR) and the first stage of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine. The time-averaged airfoil midspan pressure and heattransfer profiles were predicted for numerous thermal boundary conditions including adiabatic wall, prescribed surface temperature, and prescribed heat flux. Computed solutions are compared with each other and with experimental data in the case of the LSRR calculations. Modified ROTOR1 predictions of unsteady pressure envelopes and instantaneous contour plots are also presented for the SSME geometry. Relative merits of the two computational approaches are discussed.

Seven types of pyrotechnic igniters were each mounted at one end of a closed cylindrical bore hole representative of the center hole in a thermal battery. Measurements of local bore wall temperature, T(sub w), using commercially available, fast response (10 microsec) sheathed chromel-constantan thermocouples allowed calculation of local heattransfer rates, q, and wall heat flows, Q. The principal charge constituents of all these igniters were titanium and potassium perchlorate, while three types also contained barium styphnate as an ignition sensitizer. Igniter closure disc materials included glass-ceramic, glass, metal (plain, scored, with and without capture cone), and kapton/RTV. All igniters produced the lowest values of T(sub w) and q at the beginning of the bore, and, except for the igniter with the kapton/RTV closure disc, these quantities increased with distance along the bore. For igniters containing only titanium/potassium perchlorate, the rates of increase of Q along the bore length, compared with those for T(sub w) and q, were generally lower and more variable. The inclusion of barium styphnate produced rates of change in Q that were essentially constant to the end of the bore. The highest overall average wall temperatures were achieved by two igniter types with metal closure discs and no capture cone. No clear correlation was established between peak bore pressure and maximum wall temperature.

A simplified model of heattransfer was developed to investigate the thermal behavior of heat exchangers and stack plates of thermoacoustic devices. The model took advantage of previous results describing the thermal behavior of the thermoacoustic core and heattransfer in oscillating flow to study the performance of heat exchangers attached to the core. The configuration considered is a flat

This paper presents the experimental heattransfer coefficients and pressure drop measured during HFC refrigerant 134a, 410A and 236fa vaporisation inside a small brazed plate heat exchanger: the effects of heat flux, refrigerant mass flux, saturation temperature, outlet conditions and fluid properties are investigated. The experimental results are reported in terms of refrigerant side heattransfer coefficients and frictional pressure

An experimental study is conducted on natural convection heattransfer from square pin fin heat sinks subject to the influence of orientation. A total of six pin fin heat sinks with various arrangements are tested under controlled environment. Test results show that the upward facing orientation yields the highest heattransfer coefficient, followed by the sideward facing and the downward

Ren-Tsung Huang; Wen-Junn Sheu; Hsing-Yung Li; Chi-Chuan Wang; Kai-Shing Yang

Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants for use in HVAC applications, internal combustion engines, personal cooling devices, thermal energy storage, or other heating or cooling...

Products with high thermal capacities used to facilitate the transfer of heat from one location to another, including coolants or refrigerants for use in HVAC applications, internal combustion engines, personal cooling devices, thermal energy storage, or other heating or cooling...

Analysis of heattransfer in solar collectors with heat pipe absorbers is compared to that for collectors with flow through absorbers. Both pumped and thermosiphon systems that produce hot water or other heated fluids are discussed. In these applications the heat pipe absorber suffers a heattransfer penalty compared with the flow through absorber, but in many cases the penalty can be minimized by proper design at the heat pipe condenser and system manifold. When the solar collector is used to drive an absorption chiller, the heat pipe absorber has better heattransfer characteristics than the flow through absorber.

In this article a review of heat storage technologies with phase change materials (PCMs) is given. In addition, we present paraffin as phase change material in solar heat storage wall with proposals of heattransfer enhancement. The mathematical model for heat transport in heat storage is made. The results obtained with the simulation gives the time dynamics of heat accumulation

Experiments were performed on natural convection heattransfer from circular pin fin heat sinks subject to the influence of its geometry, heat flux and orientation. The geometric dependence of heat dissipation from heat sinks of widely spaced solid and hollow\\/perforated circular pin fins with staggered combination, fitted into a heated base of fixed area is discussed. Over the tested range

The article explains the methods and presents the results of the experimental investigation of local heattransfer in bundles of spiral tubes with heat supply to the heat carrier that is nonuniform over the cross section.

Dzyubenko, B. V.; Sakalauskas, A. V.; Vilemas, Yu. V.; Ashmantas, L. A.

Direct contact heattransfer is an attractive method to reduce the cost of heat exchange for latent heat thermal energy storage systems. However, current performance information is insufficient to allow an accurate appraisal of its economic and technical ...

An analog between convection and conduction with heat sources is made to have a further understanding of the mechanism of convective heattransfer. There are three ways to raise the strength of heat sources\\/convection terms, and consequently to enhance the heattransfer: (a) increasing Reynolds and\\/or Prandtl number, (b) increasing the fullness of dimensionless velocity and\\/or temperature profiles, (c) increasing

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 heattransfer. 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.

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

The results of a thermal engineering analysis of a bath furnace heated by natural gas with the surface area of the melting part equal to 303.3 m2 and equipped with six pairs of burners are presented. Practical recommendations are given for increasing the efficiency of the furnace. The data can be used for developing a mathematical model of heattransfer

V. G. Lisienko; V. B. Kut'in; S. N. Gushchin; B. A. Fetisov

Two ways of determining the convective fluxes from the nonsteady temperatures are discussed: the passive method of classical thermography, in which the heating due to convection alone is used; and the active method of stimulated thermography in which the heattransfer coefficients are found directly from the heating due to a source of radiation, which is added to the convection for very brief intervals. The various algorithms used for identification of the heattransfer coefficient are presented together with some experimental results. For heattransfer identification, monodimensional models are used in both the passive and active modes. Moreover, considering the fact that supersonic or hypersonic flows are being dealt with, it is assumed that the linearized transfer coefficient corresponding to the radiative transfers between the model and the wind tunnel wall is negligible compared with the convective transfer coefficient.

Experiments were carried out to study the heattransfer performance of a heated circular cylinder in turbulent pulsating crossflows. For a single heated circular cylinder, heattransfer enhancement factors up to 1.26 were observed in the studied parameter range. Two empirical correlations with different deviations were developed. The heattransfer enhancement factor was found to decrease with Strouhal number and Reynolds number, but increase in trend with the ratio of pulsating to steady Reynolds number.

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

Aerodynamic effects of trailing edge geometry, hole size, angle, spacing, and shape have been studied in two- and three-dimensional cascades and in a warm turbine test series. Heattransfer studies have been carried out in various two- and three-dimensional test facilities in order to provide corresponding heattransfer data. Results are shown in terms of cooling effectiveness and aerodynamic efficiency for various coolant fractions, coolant-primary temperature ratios, and cooling configurations.

Radiative heattransfer is a dominant heattransfer phenomenon in high temperature systems. With the rapid development of massive supercomputers, the Monte-Carlo ray tracing (MCRT) method starts to see its applications in combustion systems. This research is to find out if Monte-Carlo ray tracing can offer more accurate and efficient calculations than the discrete ordinates method (DOM). Monte-Carlo ray tracing

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 heattransfer surface with minimum core volume of a recuperator matrix using a CFD code. Analysis is carried out for selected cross corrugated heattransfer surface configurations. The relation between the minimum core volume from design calculation and average skin friction coefficient from CFD analysis has been established.

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

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

The narrow rectangle channel heattransfer technique is a new developing heattransfer technique in recent years. In the narrow rectangle channel, film boiling is an important two-phase flow heattransfer 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 heattransfer between the steam and the wall, the droplet and the wall, the steam and the droplet and radiation heattransfer process, which makes heattransfer 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 heattransfer processes on film boiling. A rectangle channel film boiling model has been built up using thermodynamic non-equilibrium model.

This volume contains a portion of the over 240 ASME papers which were presented at the conference. For over 40 years, the National HeatTransfer Conference has been the premiere forum for the presentation and dissemination of the latest advances in heattransfer. The work contained in these volumes range from studies of fundamental phenomena to applications in the latest heattransfer equipment. Radiative heattransfer is the subject covered by the papers in this volume. Separate abstracts were prepared for most papers in this volume.

The irreversible generation of entropy for two limiting cases of combined forced-convection heat and mass transfer in a two-dimensional channel are investigated. First, convective heattransfer in a channel with either constant heat flux or constant surface temperature boundary conditions are considered for laminar and turbulent flow. The entropy generation is minimized to yield expressions for optimum plate spacing and

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 heattransfer 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.

This paper presents an analytical model for analyzing transient heattransfer between a brick particle and air flow during heating in a fluidized bed combustor. Both experimental and theoretical studies were carried out. The experimental investigation provided the temperature distributions at the centers of the spherical particles during heating. These data were presented in the dimensionless form and were compared with the results of the present analytical model. The theoretical investigation included two cases: e.g. Case 1 considered that the surface heattransfer coefficient is only the convection heattransfer coefficient; Case 2 also considered that the surface heattransfer coefficient is the sum of the convection and radiation heattransfer coefficients. Better agreement was found between the experimental data and the theoretical Case 2. The results of this study show that there is a dominant effect of the radiation heattransfer on the temperature distribution.

Dincer, I.; Kilic, Y.A.; Kahveci, N. [TUBITAK-Marmara Research Center, Gebze (Turkey)] [TUBITAK-Marmara Research Center, Gebze (Turkey)

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.

An evaporative surface is described for heat pipes and other two-phase heattransfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heattransfer 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, heattransfer 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 heattransfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

To uncover the intriguing non-thermal microwave effect, an experiment was conducted using an amplifier rather than an oscillator as the radiation source, which was injected into an applicator with strong electromagnetic field enhancement. The characteristics of the applicator are discussed and the enhancement of the microwave field is illustrated and explained. Thermal distribution is simulated based on the calculated microwave field profile. It was demonstrated that the proposed system heated a SiC susceptor to a temperature of 637 °C with the input power of 60 W. The reasons for such an efficientheating are discussed.

Chang, T. H.; Chao, H. W.; Syu, F. H.; Chiang, W. Y.; Fong, S. C.; Chin, T. S.

To uncover the intriguing non-thermal microwave effect, an experiment was conducted using an amplifier rather than an oscillator as the radiation source, which was injected into an applicator with strong electromagnetic field enhancement. The characteristics of the applicator are discussed and the enhancement of the microwave field is illustrated and explained. Thermal distribution is simulated based on the calculated microwave field profile. It was demonstrated that the proposed system heated a SiC susceptor to a temperature of 637 °C with the input power of 60 W. The reasons for such an efficientheating are discussed. PMID:22225237

Chang, T H; Chao, H W; Syu, F H; Chiang, W Y; Fong, S C; Chin, T S

A study of the heattransfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heattransfer 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 heattransfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heattransfer coefficients of these heating surface increases, and the heattransfer coefficient of the water wall is higher than that of the platen heating surface. The heattransfer coefficient of the EHE is the highest in high boiler load, the heattransfer 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 heattransfer 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.

A reliable computational heattransfer model has been investigated to define the heattransfer characteristics of a spray\\u000a column direct contact heat exchanger, which is often utilized in the process involving counterflows for heat and mass transfer\\u000a operations. Most of the previous studies investigated are one-dimensional unsteady solutions based on rather fragmentary experimental\\u000a data. Development of a multidimensional numerical model

Yong Heack Kang; Nam Jin Kim; Byung Ki Hur; Chong Bo Kim

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

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

The principal problems in physics, gas dynamics, and applied fields where radiative heattransfer is of major importance are reviewed, and the existing methods for calculating radiative transfer in heated gases are examined. Particular attention is given to the asymptotic integral method of partial characteristics which makes it possible to achieve substantial savings in computer time by separately calculating the

I. F. Golovnev; V. P. Zamuraev; S. S. Katsnelson; G. A. Kovalskaia; V. G. Sevastianenko; R. I. Soloukhin

We propose theoretical model of the heattransfer in the axisymmetric swirl pipe flows. The model is used to study influences of the type of vortex symmetry and of the vorticity distribution in the vortex core on the heattransfer enhancement.The study shows that traditional empirical correlations for swirl flows are, in general, insufficient. Indeed, two types of vortex structures

The effect of three-dimensional hydrodynamics on the enhancement of steady, laminar heattransfer in corrugated channels is studied using a combination of analytical and numerical techniques. Reynolds numbers are considered in the range of 0 < Re < 250 to avoid unsteady flow. Two-dimensional sinusoidal corrugations with flow perpendicular to the corrugations is taken as the base. The heattransfer

In order to determine the effect of surface irregularities on local convective heattransfer, the variation in heattransfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR te...

The heattransfer near stagnation point of blunt bodies in hypersonic low density gas flow was investigated. The dissipation effects of vibration relaxation, as well as that of friction and thermal conduction, were considered. Heattransfer was calculated under space environment conditions and under wind tunnel simulation conditions. Theoretical results agree well with experimental results obtained by various authors.

This paper presents an investigation of the radiative heattransfer process in two fixed bed furnaces firing biomass fuels and the performance of several widely used models for calculation of radiative heattransfer in the free-room of fixed bed furnaces. The simple optically thin (OT) model, the spherical harmonic P1-approximation model, the grey gas model based on finite volume discretization

T. Klason; X. S. Bai; M. Bahador; T. K. Nilsson; B. Sundén

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

A new geometric model is used to model the flow and heattransfer in a porous medium. Solutions to the governing equations of the model show that this type of simple physical model is successful in predicting the flow characteristics of porous media at a large range of Reynolds numbers and heattransfer characteristics of porous media at lower Reynolds

Recent advances in the design of various nuclear components and systems have called for the studies of many important heattransfer processes that occur either during normal operations or under accident conditions. These processes include, for example, heattransfer in reactor steam generators, mixed convection in tube bundles and rod assemblies, turbulent convection and flow instability, two-phase natural circulation, thermal

The paper is concerned about formulation of aqueous based nanofluids and its application under natural convective heattransfer conditions. Titanium dioxide nanoparticles are dispersed in distilled water through electrostatic stabilization mechanisms and with the aid of a high shear mixing homogenizer. Nanofluids formulated in such a way are found very stable and are used to investigate their heattransfer behaviour

Cooling designs of superconducting generator rotors are important for maintaining a stable superconducting state of field windings, and it is essential to comprehend the heattransfer characteristics of helium in rotating fields. Experiments were carried out using a large-scale rotating cryostat with a cold rotor diameter of approximately 800 mm. Clear differences among the steady-state heattransfer characteristics of helium

R. Nakajima; K. Sato; K. Miyaike; M. Kumagai; Y. Kobayashi

The paper intends to discuss the use of IR thermography as a new technology tool in various heattransfer and fluid dynamics problems. Different operating modes and their implementation are presented. Particular emphasis is given to the measurement of convective heattransfer coefficients. The development of appropriate software is also presented. Basic Principles of Infrared Thermography Thermography is a measurement

Modeling using CFD was performed to obtain the magnitude of heattransfer from the surface of an airfoil along its entire chord length. The computations were performed on various shapes of airfoils at different angles of attack and Reynolds numbers for the purpose of giving a good representation of the behavior of heattransfer throughout varying flight conditions. The results

A study program is presented on the effects of strong electric fields on condensation heattransfer and two-phase flow. It has been confirmed that significant changes in the flow regimes and heattransfer are possible with negligible electrical power expe...

The heattransfer conditions in automotive exhaust piping are only recently being studied in depth because of their important role in the design and optimization phases of exhaust after-treatment systems. The complex geometry of the exhaust line and the special flow conditions complicate the problem of accurately estimating several important heattransfer parameters. This paper initially summarizes the current status

A mathematical model is proposed to describe the heattransfer in quartz glass axisymmetric tubes. Heat is transferred inside the glass by radiation and conduction. Scattering of thermal radiation inside the glass is ignored. At the boundaries of the tube the radiative intensity is specularly reflected. The spectral dependent radiative intensity and the temperature distribution inside the tube are determined.

A detailed numerical study is performed to investigate radiative and convective heattransfer enhancement in pipes filled with small diameter (?100 ?m) silicon carbide fibers. Radiation between fibers and the tube wall, conduction within fibers and convection from the fibers to the surrounding fluid drive the heattransfer enhancement. Macroscopic (porous media) modeling is used to determine the velocity, pressure,

This paper presents a theoretical study of heattransfer from magneto-rheological fluid (MRF) dampers. A lumped system model is developed which is capable of predicting the temperature rise for any size MRF damper. As a case study example, finned and unfinned dampers are compared for automotive-size MRF dampers. The results demonstrate that heattransfer from these devices can be enhanced

M. Baris Dogruoz; Faramarz Gordaninejad; Eric L. Wang; Arthur J. Stipanovich

This paper reports the numerical determination of the entropy generation due to heattransfer, mass transfer and fluid friction in steady state for laminar double diffusive convection, in an inclined enclosure with heat and mass diffusive walls, by solving numerically the mass, momentum, species conservation and energy balance equations, using a Control Volume Finite-Element Method. The influences of the inclination angle, the thermal Grashof number and the buoyancy ratio on total entropy generation were investigated. The irreversibilities localization due to heattransfer, mass transfer and fluid friction is discussed for three inclination angles at a fixed thermal Grashof number.

Magherbi, M.; Abbassi, H.; Hidouri, N.; Brahim, A. B.

A heattransfer 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.

A heattransfer 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.

Several novel ideas to use heat pipes in adsorption water chiller or ice maker are presented in this paper. Experimental results have shown that the adsorption refrigerators are very efficient. The first example of such systems is a small scale silica gel–water adsorption water chiller with cooling power rated as 10kW; the system could be powered by 60–100°C hot water,

The thermal design of the combustor and turbine of a gas turbine engine poses a number of difficult heattransfer problems. The importance of improved prediction techniques becomes more critical in anticipation of future generations of gas turbine engines which will operate at higher cycle pressure and temperatures. Research which addresses many of the complex heattransfer processes holds promise for yielding significant improvements in prediction of metal temperatures. Such research involves several kinds of program including: (1) basic experiments which delineate the fundamental flow and heattransfer phenomena that occur in the hot sections of the gas turbine but at low enthalpy conditions; (2) analytical modeling of these flow and heattransfer phenomena which results from the physical insights gained in experimental research; and (3) verification of advanced prediction techniques in facilities which operate near the real engine thermodynamic conditions. In this paper, key elements of the NASA program which involves turbine and combustor heattransfer research will be described and discussed.

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

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

This project developed quantitative methods for obtaining heattransfer 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 heattransfer. Previous difficulties with inferring heattransfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heattransfer 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 heattransfer 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.

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 heattransfer 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 heattransfer 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 heattransfer 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 heattransfer 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 HeatTransfer in Microelectronics Packaging, IMECE, Dallas, TX, 1997).

Lu, T.J.; Ashby, M.F. [Univ. of Cambridge (United Kingdom). Dept. of Engineering] [Univ. of Cambridge (United Kingdom). Dept. of Engineering; Stone, H.A. [Harvard Univ., Cambridge, MA (United States). Div. of Engineering and Applied Sciences] [Harvard Univ., Cambridge, MA (United States). Div. of Engineering and Applied Sciences

Numerical study was performed to evaluate the characteristics of combined heattransfer of radiation, conduction and convection\\u000a in indirect near infrared ray (NIR) heating chamber. The effects of important design parameters such as the shape of heat\\u000a absorbing cylinder and heat releasing fin on the pressure drop and heattransfer coefficient were analyzed with different\\u000a Reynolds numbers. The Reynolds numbers

Available two-component two phase heattransfer data in tubes have been reviewed. Based on momentum transfer considerations and the important influence of turbulence in the continuous phase, two phase heattransfer data in tubes for liquid Reynolds number varying from 600-190,000 and void fraction varying from 0.01-0.35 have been correlated. New two phase data obtained on rod bundles are also

M. I. Drucker; V. K. Dhir; R. B. Duffey; G. Ford; B. Hagemeyer

An advanced heattransfer model for both unlooped and looped Pulsating Heat Pipes (PHPs) with multiple liquid slugs and vapor plugs has been developed. The thin film evaporation and condensation models have been incorporated with the model to predict the behavior of vapor plugs and liquid slugs in the PHP. The results show that heattransfer in both looped and

Heattransfer in the gas layer of a horizontal cylindrical tank with a fluctuating level of boiling liquid nitrogen is investigated experimentally. Criterial equations for heattransfer in the gas cavity of the tank are obtained. A procedure is proposed for calculating heat fluxes, temperature fields, and cryogenic fluid evaporation during the filling and draining of the tank.

Enhanced heat-transfer techniques, used to significantly reduce temperatures and thermally induced stresses on beam-strike surfaces, are routinely used at the APS in all critical high-heat-load components. A new heat-transfer enhancement technique being e...

J. T. Collins C. M. Conley J. N. Attig M. M. Baehl

This study provides an experimental analysis on the heattransfer 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 heattransfer performance increased with increasing the water spraying rate but without the penalty of increased flow resistance

Using the Buckingham Pi theorem, this study derives dimensionless correlations to characterize the heattransfer performance of the corrugated channel in a plate heat exchanger. The experimental data are substituted into these correlations to identify the flow characteristics and channel geometry parameters with the most significant influence on the heattransfer performance. Simplified correlations by omitting the factors with less

This paper presents selected results on heattransfer to supercritical water flowing upward in a 4-m-long vertical bare tube. Supercritical-water heat-transfer data were obtained at pressures of about 24MPa, mass fluxes of 200–1500kg\\/m2s, heat fluxes up to 884kW\\/m2 and inlet temperatures from 320 to 350°C for several combinations of wall and bulk-fluid temperatures that were below, at or above the

Sarah Mokry; Igor Pioro; Pavel Kirillov; Yevgeniy Gospodinov

In this paper, we study the boiling heattransfer of upward flow of R21 in a vertical mini-channel with a size of 1.6 × 6.3 mm. The heattransfer coefficient was measured as a function of heat flux for a wide range of vapor quality and for two levels of mass flow rate, G = 215 kg\\/ms and G =

Experiments were performed to study the flow regimes and heattransfer in air–water flow in 8° inclined tubes of inner diameter of 49.2 and 25 mm. The flow regimes were investigated by using high-speed video technique and conductive tomography. The thermal patterns on the heated wall and local heattransfer coefficients were obtained by infrared thermography. Under the conditions studied,

G. Hetsroni; D. Mewes; C. Enke; M. Gurevich; A. Mosyak; R. Rozenblit

A facility for making heattransfer measurements on solid surfaces using transient techniques is constructed. The facility being constructed is a Ludweig tube with isentropic compression heating (LICH tube). The work completed is detailed as is the work remaining in order to complete the facility and make useful heattransfer measurements. The scope of the project is briefly discussed along with an overall appraisal of the progress.

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

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

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

This paper presents results from heattransfer studies performed in 7.5 MWt and 15 MWt direct coal-fired magnetohydrodynamic systems for electrical power generation. Heattransfer from the various components is measured to determine system heat balance and the influence of parameters related to coal combustion on heattransfer. The measured heat flux from electrode walls is compared with a quasi-one-dimensional model and extended for off-design operation. The heat flux values are used in a computer model to evaluate temperature distributions in electrode frames and caps and are compared with measurements taken during power runs.

An attempt is made to obtain historical perspectives on the development of the mathematical theory of heat conduction considering Newton's law of cooling (1701) and its close connection with Fourier's work from 1807 to 1822 resulting in his epoch-making treatise on "The Analytical Theory of Heat". Fourier was the principal architect of the heat conduction theory. Fourier's work established a new methodology for the formulation and solution of physical problems, based on partial differential equations and marked a major turning point in the history of physics. The developments in the periods 1822 to 1900 and 1900 to 1950 are also briefly reviewed as are the classical (analytical) and numerical methods of solution for heat conduction problems. The analogy in heat, momentum, and mass transfer for transport phenomena is discussed. A list of recent conduction heattransfer books is presented to show the scope of recent developments. Some observations on conduction heattransfer are noted.

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 heattransfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heattransfer coefficient of the evaporation phase change process with comparable or lower pressure drop.

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

Numerical evaluations of heattransfer in a fissioning uranium plasma core reactor cavity, operating with seeded hydrogen propellant, was performed. A two-dimensional analysis is based on an assumed flow pattern and cavity wall heat exchange rate. Various iterative schemes were required by the nature of the radiative field and by the solid seed vaporization. Approximate formulations of the radiative heat

Characteristics of wall-to-air heattransfer for a fully developed forced convection have been studied in a large rectangular packed duct with 160 cm heated length, 40 cm width, and for low bed equivalent diameter to particle diameter ratio. The separation distance between the top and bottom walls is 10 cm. A uniform heat flux is supplied at the top wall,

Yasar Demirel; Habib H. Al-Ali; Basem A. Abu-Al-Saud

Heattransfer was studied between intact leaves of various sizes and shapes in vivo under free and forced air conditions. Use of a wind tunnel and a microwave transmitter to heat the leaves facilitated measurements of convective, along with radiative and evaporative, heat losses from plant leaves. Knowledge of input energy, analysis of cooling curves, and established formulae, respectively, formed

Proposed heat-exchange scheme boosts heattransfer per unit area. Key component is generator that fires uniform size droplets of subcooled liquid at hot plate. On impact, droplets spread out and evaporate almost instantly, removing heat from plate. In practice, many generator nozzles arrayed over evaporator plate.

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 heattransfer data on convective crossflow through cylinder banks. A foam-filled channel having constant wall temperatures is analyzed to obtain the temperature distribution

The heattransfer 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 heattransfer 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 heattransfer 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)

Jianfeng, Lu; Jing, Ding [School of Engineering, Sun Yat-Sen University, Guangzhou 510006 (China); Jianping, Yang [Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education, South China University of Technology, Guangzhou 510640 (China)

This paper represents and describes the experimental results for heattransfer characteristics and optimization strategies for the blade design through the obtained heattransfer correlations carried out at Mechanical Systems and Control Lab., Jadavpur University, Kolkata, India. Impingement heattransfer is considered as a promising heattransfer enhancement technique. In particular, in gas turbine cooling, jet impingement heattransfer is

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 heattransfer 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 ˜100s 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 NaxCoO2. 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 Na0.7CoO2, when the nanosheets have single grains along the heat transport path.

Impinging jets provide a means of achieving high heattransfer coefficients both locally and on an area averaged basis. The current work forms the first stage of a two part investigation of heattransfer distributions from a heated flat surface subject to an impinging air jet for Reynolds numbers from 10,000 to 30,000 and non-dimensional surface to jet exit spacing,

This volume contains a portion of the over 240 ASME papers which were presented at the conference. For over 40 years, the National HeatTransfer Conference has been the premiere forum for the presentation and dissemination of the latest advances in heattransfer. The work contained in these volumes range from studies of fundamental phenomena to applications in the latest

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

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

Heattransfer data from several sources have been assembled which show the effect of spacer grids on local heattransfer within a rod bundle. Both single phase (air and steam) data and two phase (steam/water) data show heattransfer augmentation in the grid region. Heattransfer 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 heattransfer 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 heattransfer regime may exist near the grid. High rod heattransfer 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.

A computational approach to modeling transient, compressible fluid flow with heattransfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heattransfer 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 heattransfer. 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 heattransfer 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 heattransfer solver to analyze heattransfer between the fluid and surrounding structure. Conjugate fluid flow and heattransfer 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.

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

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

In this paper, we address the problem of choosing the right topology for a wireless power transfer (WPT) application to obtain maximum power transferefficiency. We analyze the series and parallel resonant topologies used in inductively coupled links, derive the efficiency expressions and verify them experimentally using planar inductors built on a PCB. We compare and contrast the two topologies

Low-temperature process heat is utilized for concentration of the acid residues of gas purification and other recirculation processes. The most efficientheat recovery process is by indirect heattransfer from the acid circuits of the sulphuric acid produ...

For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heattransfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heattransfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heattransfer 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 100 to 103 ?m. The heattransferred from the hot (10 - 100 K) to the cold sample (~5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferredheat power within ~2 nW/cm2 and ~30 ?W/cm2 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 heattransfer.

Kralik, T.; Hanzelka, P.; Musilova, V.; Srnka, A.; Zobac, M.

For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heattransfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heattransfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heattransfer 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 heattransferred 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. Transferredheat 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 heattransfer.

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)

For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heattransfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heattransfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heattransfer 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(0) to 10(3) ?m. The heattransferred from the hot (10 - 100 K) to the cold sample (?5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferredheat power within ?2 nW?cm(2) and ?30 ?W?cm(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 heattransfer. PMID:21639537

Kralik, T; Hanzelka, P; Musilova, V; Srnka, A; Zobac, M

The effects of carbon-fiber chips and carbon brushes as additives on the thermal conductivity enhancement of phase change materials (PCMs) using in latent heat thermal energy storage are investigated experimentally and numerically by considering the wall effect of the additives. The carbon-fiber chips are effective for improving the heattransfer rate in PCMs. However, the thermal resistance near the heat

Extended performance evaluation criteria equations for enhanced heattransfer surfaces based on the entropy production theorem have been developed to include the effect of fluid temperature variation along the length of a tubular heat exchanger with constant wall temperature as a boundary condition. The equations originate from various design constraints and generalize the performance evaluation criteria (PEC) for enhanced heat

The dynamics of heat exchange between helium gas and a matrix material, in a Gifford-McMahon cryocooler, is simulated using a generalized Hausen equations system. The temperature dependence of heat exchange is taken into account by introducing a time dependent heattransfer coefficient. A profile of gas outlet temperature versus time is obtained which is in good agreement with experimental data.

Enhancement of heattransfer is relatively a new topic of research and its evaluation is needed to measure the performance of any enhanced technique. Lattice Boltzmann method is also a quite new numerical technique specifically the implementation of thermal models. In this research, thermal lattice Boltzmann method was utilized to simulate heattransfer enhancement in channels of two and three dimensions. Implementation of extended surfaces is a common practice for heattransfer enhancement from hot surfaces due to its significance in different fields of engineering application. The effect of varying the heattransfer surface's geometry and the dynamics of the flow play significant role on the enhancement process. In this work, the implementation of the extended surfaces as a method for heattransfer enhancement in channels is investigated. Several geometries are considered and the effect of several parameters on the flow characteristics and the heattransfer enhancement is investigated as well. The parameters of interest are the extended surfaces' height, thickness, in-between spacing, and the Reynolds number. In addition, the effect of changing the shapes of the extended surfaces tips' on the fluid flow characteristics and heattransfer is also investigated. Seven different geometries of the tips' shapes are presented for the investigation purposes. The performance of the enhancement method is evaluated through the Nusselt number, the pressure drop, and the minimization of entropy generation. As expected the rate of heattransfer was enhanced by increasing the flow velocity. In addition, heattransfer was found to be highly augmented for extended surfaces' height close to the channel's mid-height. The in-between spacing affected the enhancement method as well, the closer the better for all values of Reynolds number within the tested range. Several correlations are proposed to describe the relationship between the rate of heattransfer and the investigated parameter in conjunction with the effect of flow velocity. In addition, the effect of changing the tips' shapes of the extended surfaces was found to enhance the heattransfer process. For the three-dimensional flows, changing the transversal spacing was found to enhance the heattransfer rate better than what longitudinal spacing does.

An experimental and theoretical study of convective heattransfer in a coolant channel consisting of a rectangular-sectioned duct rotating around an orthogonal axis is presented, with application to cooled turbine rotor blades. Transient and steady-state techniques are used to measure the convective heattransfer coefficients. It is found that Coriolis acceleration has a beneficial influence on mean heattransfer. The results are analyzed using a three-dimensional Navier-Stokes model, and are explained by the influence of the Coriolis force which induces a secondary flow and distorts the velocity and temperature profiles.

Multiphase thermal systems (involving more than one phase or one component) have numerous applications in aerospace, heat-exchanger, transport of contaminants in environmental systems, and energy transport and energy conversion systems. Advances in understanding the behaviour of multiphase thermal systems could lead to higher efficiency energy production systems, improved heat-exchanger design, and safer and enhanced treatment of hazardous waste. But such advances have been greatly hindered by the strong effect of gravitational acceleration on the flow. Depending on the flow orientation and the phase velocities, gravitational forces could significantly alter the flow regime, and hence the pressure-drop and heat-transfer coefficients associated with the flow. A reduced gravity environment (or "microgravity"), provides an excellent tool to study the flow without the masking effects of gravity. This book presents for the first time a comprehensive coverage of all aspects of two-phase flow behaviour in the virtual absence of gravity. Link: http://www.springer.com/east/home?SGWID=5-102-22-173662745-0&changeHeader=true

A study of the engineering and economic effects of heat exchangers in conventional maple syrup evaporators indicated that: (1) Efficiency was increased by 15 to 17 percent with heat exchangers; (2) Syrup produced in evaporators with heat exchangers was si...

L. D. Garrett H. Duchacek M. Morselli F. M. Laing N. K. Huyler

There has been increasing interest of late in nanofluid boiling and its use in heattransfer 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 heattransfer 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.

There has been increasing interest of late in nanofluid boiling and its use in heattransfer 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 heattransfer 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

The combustion and heattransfer 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. Heattransfer 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.

If no valid data on the temperature state of heat stressed units are available, it is impossible to assess the strength reserves of pieces. Also, it is impossible, in this case, to develop efficient cooling systems and systems for controlling radial clearances. That's why the paper presents experimental results, showing heattransfer on the surface of the blade profile and on the end surfaces of the interblade channel of flat compressor lattices. Dependences, considering the effect of geometric and regime parameters on heattransfer, have been obtained.

Microstructure heat exchangers have unique properties that make them useful for numerous scientific and industrial applications. The power transferred per unit volume is mainly a function of the distance between heat source and heat sink-the smaller this distance, the better the heattransfer. Another parameter governing for the heattransfer is the lateral characteristic dimension of the heattransfer structure; in the case of microchannels, this is the hydraulic diameter. Decreasing this characteristic dimension into the range of several 10s of micrometers leads to very high values for the heattransfer rate. Another possible way of increasing the heattransfer rate of a heat exchanger is changing the flow regime. Microchannel devices usually operate within the laminar flow regime. By changing from microchannels to three dimensional structures, or to planar geometries with microcolumn arrays, a significant increase of the heattransfer rate can be achieved. Microheat exchangers in the form of both microchannel devices (with different hydraulic diameters) and microcolumn array devices (with different microcolumn layouts) are presented and compared. Electrically heated microchannel devices are presented, and industrial applications are briefly described. (author)

Brandner, J.J.; Anurjew, E.; Bohn, L.; Hansjosten, E.; Henning, T.; Schygulla, U.; Wenka, A.; Schubert, K. [Forschungszentrum Karlsruhe, Institute for Micro Process Engineering IMVT, P.O. Box 3640, DE-76021 Karlsruhe (Germany)

This paper presents an experimental study of flow boiling heattransfer in a microchannel heat sink. The dielectric fluid Fluorinert FC-77 is used as the boiling liquid after it is fully degassed. The experiments were performed at three flow rates ranging from 30-50ml\\/min. The heattransfer coefficients, as well as the critical heat flux (CHF), were found to increase with

Flow boiling of R-123 in a hydrofoil-based micro pin fin heat sink was investigated. Average two-phase heattransfer coefficients were obtained over effective heat fluxes ranging from 19 to 312W\\/cm2 and mass fluxes from 976 to 2349kg\\/m2s. The paper presents a flow map, which divides the data into three flow pattern regions: bubbly, wavy intermittent and spray-annular flows. Heattransfer

The air-side heattransfer from wire-and-tube heat exchangers of the kind widely used in small refrigeration appliances has been studied. Radiation and free-convection components have been separately investigated. The radiation component was theoretically computed using a diffuse, gray-body network with interactions between each part of the heat exchanger and the surroundings. For the free-convection heattransfer component, a semiempirical correlation

A one-dimensional (1D) laminar oscillating flow heattransfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heattransfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heattransfer. PMID:24606258

This paper describes numerical methodologies of the flow and heattransfer analysis in heat exchangers of various types. Heat\\u000a exchangers considered in the present study include a louver fin radiator for a vehicle, a shell and tube heat exchanger for\\u000a HVAC and plate heat exchangers with patterns of herringbone and of dimple used in waste heat recovery. For the analysis

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

In this paper, heattransfer characteristics of a miniature heat sink cooled by SiO 2-water nanofluids were investigated both experimentally and numerically. The heat sink was fabricated from aluminum and insulated by plexiglass cover plates. The heat sink consisted of an array of 4 mm diameter circular channels with a length of 40 mm. Tests were performed while inserting a 180 W/cm 2 heat flux to the bottom of heat sink and Reynolds numbers ranged from 400 to 2000. The three-dimensional heattransfer characteristics of the heat sink were analyzed numerically by solving conjugate heattransfer problem of thermally and hydrodynamically developing fluid flow. Experimental results showed that dispersing SiO 2 nanoparticles in water significantly increased the overall heattransfer coefficient while thermal resistance of heat sink was decreased up to 10%. Numerical results revealed that channel diameter, as well as heat sink height and number of channels in a heat sink have significant effects on the maximum temperature of heat sink. Finally, an artificial neural network (ANN) was used to simulate the heat sink performance based on these parameters. It