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NSDL National Science Digital Library

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

Integrated Teaching and Learning Program,

2

Effect of microfouling on heat-transfer efficiency

Field experiments, performed at Keahole Point, Hawaii and in the Gulf of Mexico, were designed to determine the relationship between decreased heat transfer efficiency and the accumulation of corrosion and/or biofouling films on heat exchanger surfaces. The sample tubes were maintained under conditions simulating those of an Ocean Thermal Energy Conversion (OTEC) system and data from the two sites have been compared. Seawater flowed through 2.54 (internal diameter) metal tubes at approximately 1.8m sec/sup -1/. Four types of tubes were used: 5052 Aluminum (A1), Grade 2 titanium (Ti), 90-10 copper-nickel (Cu-Ni) and Allegheny-Ludlum 6X stainless ssteel (SS). All surfaces were colonized by microorganisms, though colonization of the Cu-Ni surface was initially retarded. Total film weight was greatest for the Al and Cu-Ni surfaces which were characterized by corrosion as well as microbial fouling. The total organic carbon: total nitrogen ratios of the fouling films from Ti, Al, SS and Cu-Ni, 4.2, 4.0, 4.8 and 7.9 respectively, remained constant throughout the experiment. The degradation of heat transfer efficiency due to the formation of fouling layers on Ti and SS is neither linear nor a simple exponential function. A microfouling model is proposed for corrosion-resistant surfaces that is consistent with field observations.

Little, B.; Berger, L.R.

1980-01-01

3

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

4

Improving the heat transfer efficiency of synthetic oil with silica nanoparticles.

The heat transfer properties of synthetic oil (Therminol 66) used for high temperature applications was improved by introducing 15 nm silicon dioxide nanoparticles. Stable suspensions of inorganic nanoparticles in the non-polar fluid were prepared using a cationic surfactant (benzalkonium chloride). The effects of nanoparticle and surfactant concentrations on thermo-physical properties (viscosity, thermal conductivity and total heat absorption) of these nanofluids were investigated in a wide temperature range. The surfactant-to-nanoparticle (SN) ratio was optimized for higher thermal conductivity and lower viscosity, which are both critical for the efficiency of heat transfer. The rheological behavior of SiO(2)/TH66 nanofluids was correlated to average agglomerate sizes, which were shown to vary with SN ratio and temperature. The conditions of ultrasonic treatment were studied and the temporary decrease of agglomerate size from an equilibrium size (characteristic to SN ratio) was demonstrated. The heat transfer efficiencies were estimated for the formulated nanofluids for both turbulent and laminar flow regimes and were compared to the performance of the base fluid. PMID:21889163

Timofeeva, Elena V; Moravek, Michael R; Singh, Dileep

2011-12-01

5

Heat transfer in microwave heating

NASA Astrophysics Data System (ADS)

Heat transfer 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 heat transfer 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 heat transfer, 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 heat transfer 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.

Peng, Zhiwei

6

The work is in three sections: conduction, convection, and radiation heat transfer. The contents includes: The general conduction equation. Heat transfer from extended surfaces. Steady-state conduction in multiple dimensions. Convection heat transfer in a closed conduit. Natural-convection systems. Heat exchangers. Condensation and vaporization heat transfer. Radiation heat transfer between surfaces.

Janna, W.S.

1986-01-01

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Fabrication of polymer film heat transfer elements for energy efficient multi-effect distillation

Conventional multi-effect and multi-stage flash distillation use aluminium brass, cupro-nickel and\\/or titanium heat transfer 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 heat transfer elements have from 71–105% of the U value of

T. B. Scheffler; A. J. Leao

2008-01-01

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This book consists of eight chapters which cover the following topics: fundamental concepts of heat transfer; the general conduction equation; steady state conduction in one dimension; heat transfer from extended surfaces; steady state conduction in multiple dimensions; unsteady state heat conduction; introduction to convection; and convection heat transfer in a closed conduit. Each chapter includes a summary and problems.

Janna, W.

1986-01-01

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The optimization of drying processes as well as the design of drying equipment can be accomplished by computer simulation. In order to predict the drying behavior of capillary porous, hygroscopic materials a numerical model simulating the convective heat and mass transfer and an efficient method in determining the coefficients for the moisture conductivity and the vapor diffusion resistance by an

Christian Dietl; Edgar R. F. Winter; Raymond Viskanta

1998-01-01

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

Lenert, Andrej

2012-01-01

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

McGuire, Joseph C. (Richland, WA)

1982-01-01

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

Not Available

1980-03-07

13

NSDL National Science Digital Library

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

Carlone, Mrs.

2006-11-12

14

Improving the heat transfer efficiency of synthetic oil with silica nanoparticles

The heat transfer properties of synthetic oil (Therminol 66) used for high temperature applications was improved by introducing 15nm silicon dioxide nanoparticles. Stable suspensions of inorganic nanoparticles in the non-polar fluid were prepared using a cationic surfactant (benzalkonium chloride). The effects of nanoparticle and surfactant concentrations on thermo-physical properties (viscosity, thermal conductivity and total heat absorption) of these nanofluids were

Elena V. Timofeeva; Michael R. Moravek; Dileep Singh

2011-01-01

15

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

Kurek, Harry; Wagner, John

2010-01-25

16

NASA Technical Reports Server (NTRS)

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

Burbach, T.

1985-01-01

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Investment casting heat transfer

NSDL National Science Digital Library

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

Powell, Adam C., IV

2004-12-15

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NASA Astrophysics Data System (ADS)

The paper gives a brief description of some of the better understood aspects of condensation heat transfer and includes discussion of the liquid-vapour interface, natural and forced convection laminar film condensation and dropwise condensation.

Rose, J. W.

19

Convective heat transfer in planetary dynamo models

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

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

2010-01-01

20

Heat and mass transfer in rotating machinery

NASA Astrophysics Data System (ADS)

The present conference on turbomachine aerodynamics and thermodynamics considers the subjects of rotating tubes and channels, rotating surfaces and enclosures, experimental techniques, gas and steam turbines, and rotating heat pipes and thermosiphons. Attention is given to mass force effects on heat transfer in turbine rotor blades and on the hydraulic resistance of cooling channels, experiments on friction, velocity and pressure distributions in rotating disks, the turbulent field in the blade passages of a radial compressor, wide bandwidth analog circuits for heat transfer instrumentation, steam condensate droplet evolution, and heat transfer problems in aircraft engines. Also discussed are heat transfer to turbine blading, film cooling effectiveness and heat transfer on a flat plate, the prediction of blade erosion in wet steam turbines, a regenerative thermosiphon blade cooling system for high efficiency gas turbines, and heat transfer in rotating, coaxial and parallel heat pipes.

Metzger, D. E.; Afgan, N. H.

21

Fibrous insulation heat-transfer model

A mathematical model is developed for the transfer of heat through fibrous insulating materials. The mathematical derivation of the model based upon fundamental concepts of heat transfer and certain simplifying assumptions is described. It is shown that the efficiency of a fibrous insulation may be characterized by three model constants. One constant is calculated from fiber emissivity data and the

1978-01-01

22

Heat transfer in geothermal systems

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

P. Cheng

1978-01-01

23

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

NASA Astrophysics Data System (ADS)

In this paper, we report, for the first time, the effect of the lowered freezing point in a 50% water / 50% antifreeze coolant (PAC) or 50% water / 50% ethylene glycol (EG) solution by the addition of carbon nanotubes and other particles. The experimental results indicated that the nano materials are much more efficient (hundreds fold) in lowering the freezing point than the regular ionic materials (e.g. NaCl). The possible explanation for this interesting phenomenon is the colligative property of fluid and relative small size of nano material. It is quite certain that the carbon nanotubes and metal oxide nano particles could be a wonderful candidate for the nano coolant application because they could not only increase the thermal conductivity, but also efficiently lower the freezing point of traditional coolants.

Hong, Haiping; Roy, Walter

2007-09-01

24

Hydrodynamics, heat transfer and flow boiling instabilities in microchannels

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

Barber, Jacqueline Claire

2010-01-01

25

Conduction heat transfer solutions

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

VanSant, J.H.

1980-03-01

26

Conduction heat transfer solutions

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

VanSant, J.H.

1983-08-01

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Unsteady heat transfer in heat pipes

The purpose was to investigate the unsteady heat transfer associated with a heat pipe during start up operation. Initial studies were conducted with a variety of heat pipe screen wick configurations in order to develop a mathematical expression for the flow velocity of a fluid inducted by the capillary structure of the wick. This mathematical model was solved first numerically

J. E. Beam

1985-01-01

28

High temperature heat transfer equipment

Various alternative methods of high temperature heat transfer in the range of 300 to 750 F, such as direct firing, forced\\u000a circulation of heat transfer fluids such as water, oil, Therminol, Dowtherm and other fluids are outlined. Advantages and\\u000a disadvantages of each are discussed. Important considerations include design of heaters, temperature uniformity, heat transfer\\u000a rates, safety precautions, hardware required, control

E. E. magnuson

1971-01-01

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The heat pipe, as one of the most efficient heat transport devices, is a peerless choice in the electronic cooling field. In order to better understand the heat transfer mechanisms of the heat pipe, a heat transfer model, which considers the effects of the surface condition, disjoining pressure, gravity force, and contact angle on the thin film profile, heat flux

Anjun Jiao

2008-01-01

30

Heat Transfer: From Hot to Not

NSDL National Science Digital Library

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

2014-09-18

31

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

Virginia Tech

32

The idea was to combine an endothermic chemical reaction, steam reforming of methane, to provide a heat sink for an exothermic electrochemical reaction. The overall minimal entropy change reaction promised to produce a high efficiency, high temperature fuel cell without requiring external processing equipment for hydrogen production from fuels such as natural gas. The problem was to develop a theoretical model of the system. All the while the basic heat transfer problems were being analyzed, experimental and developmental work was being continued at the Institute of Gas Technology and later at MC Power Corporation and Energy Research Corporation and numerous other organizations in the US, Europe and Japan. At Energy Research Corporation, high temperature fuel cell development began in 1977 and the internal reforming approach was begun in 1981. By the mid-1980's, fuel cells in the 5 kW size range were built and tested. In 1991, a 70 kW power plant employing internal reforming, under the name the Direct Fuel Cell, was tested at a Pacific Gas and Electric Co. site in California. In 1995, the world's largest advanced fuel cell--the Direct Fuel Cell--and largest fuel cell power plant operated in North America was commissioned. This nominal 1800 kW power plant was operated in 1996 and 1997 in Santa Clara, California setting records for efficiency, low emissions, and quietness.

Baker, B.S.

1999-07-01

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A heat exchanger is adapted to unifomly cool a spherical surface. ; Equations for the design of a spherical heat exchanger hav~g tubes with a uniform ; center-to-center spining are given. The heat exchanger is illustrated in ; connection with a liquid-fueled reactor.

A. P. Fraas; G. F. Wislicenus

1961-01-01

34

Heat transfer, diffusion, and evaporation

NASA Technical Reports Server (NTRS)

Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.

Nusselt, Wilhelm

1954-01-01

35

Heat transfer characteristics for disk fans

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

36

NASA Technical Reports Server (NTRS)

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.

Widener, Edward L.

1992-01-01

37

Heat transfer in rectangular microchannels

Convection heat transfer in a rectangular microchannel is investigated. The flow is assumed to be fully developed both thermally and hydrodynamically. The H2-type boundary condition, constant axial and peripheral heat flux, is applied at the walls of the channel. Since the velocity profile for a rectangular channel is not known under the slip flow conditions, the momentum equation is first

Gokturk Tunc; Yildiz Bayazitoglu

2002-01-01

38

HEAT AND MASS TRANSFER IN IMPINGEMENT DRYING

In industrial drying applications, efficient transfer of heat and mass between a drying medium and the material being dried is very critical for the overall economics of the operation. Impinging jets are therefore widely used for their enhanced tmnsport characteristics, especially for drying of continuous sheets of materials such as paper and textiles. In such applications, a thin sheet of

Suna Polat

1993-01-01

39

Nanofluid impingement jet heat transfer

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

2012-01-01

40

Microtube liquid single-phase heat transfer in laminar flow

One of the main applications of microscale flow is miniature, high-efficiency heat transfer. 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 heat transfer performance in these conditions. In this article, an experimental investigation is

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

2006-01-01

41

Examination of Liquid Fluoride Salt Heat Transfer

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

Yoder Jr, Graydon L [ORNL] [ORNL

2014-01-01

42

Coolant passage heat transfer with rotation

NASA Astrophysics Data System (ADS)

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 heat transfer coefficients. The objective of this program is to develop a heat transfer 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.

Hajek, T. J.; Wagner, J.; Johnson, B. V.

1986-10-01

43

Systems for Steam-Electric Power Plants. M.G. Mann, M.F. Rosenfeld, N.A. Blum. American Power Conference, April 1979. (2) Waste Heat Management and Utilization Proceedings Conference, May 9-11, 1976, Miami Beach, Florida. University of Miami.... (3) EPA-600/7-78-l57. Water consumption and Costs for Various Steam Electric Power Plant Cooling Systems. (4) Assessment of Cooling Water Supply in the United States. D.E. Peterson and J.C. Sonnichsen. American Power Conference, Chicago...

Lefevre, M. R.

1984-01-01

44

Acoustically enhanced boiling heat transfer

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

45

Convective heat transfer in planetary dynamo models

NASA Astrophysics Data System (ADS)

The magnetic fields of planets and stars are generated by the motions of electrically conducting fluids within them. These fluid motions are thought to be driven by convective processes, as internal heat is transported outward. The efficiency with which heat is transferred by convection is integral in understanding dynamo processes. Several heat transfer scaling laws have been proposed, but the range of parameter space to which they apply has not been firmly established. Following the plane layer convection study by King et al. (2009), we explore a broad range of buoyancy forcing (Ra) and rotation strength (E-1) to show that heat transfer (Nu) in spherical dynamo simulations occurs in two distinct regimes. We argue that heat transfer scales as Nu ˜ Ra6/5 in the rapidly rotating regime and Nu ˜ Ra2/7 in the weakly rotating regime. The transition between these two regimes is controlled by the competition between the thermal and viscous boundary layers. Boundary layer scaling theory allows us to predict that the transition between the regimes occurs at a transitional Rayleigh number, Rat = E-7/4. Furthermore, boundary layer control of heat transfer is shown to relate to the interior temperature profiles of the models. In the weakly rotating regime, the interior fluid is nearly adiabatic. In the rapidly rotating regime, adverse mean temperature gradients abide, irrespective of the Reynolds number (Re). Extrapolating our results to Earth's core, we estimate that core convection resides in the rapidly rotating regime, with Ra ? 2 × 1024 (Ra/Rat ? 0.02), corresponding to a superadiabatic density variation of ??/?o ? 10-7, which is significantly below the sensitivity of present seismic observations.

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

2010-06-01

46

HEAT TRANSFER ANALYSIS OF A PULSE DETONATION

HEAT TRANSFER ANALYSIS OF A PULSE DETONATION ENGINE by NEELIMA KALIDINDI Presented to the Faculty support. November 23, 2009 #12;iv ABSTRACT HEAT TRANSFER ANALYSIS OF A PULSE DETONATION ENGINE NEELIMA ........................................................................................... 1 1.1 Pulse Detonation Engine ................................................................. 1 1

Texas at Arlington, University of

47

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

48

Convective heat transfer in microchannels

Heat-transfer microstructures for cooling silicon chips wherein water flows through mi-crochannels etched in the back of silicon\\u000a wafers have been considered by a number of authors. Under a set of reasonable assumptions, the problem can be reduced to a\\u000a quasi-two-dimensional differential equation. To date, these equations have only been solved approximately. We present exact\\u000a solutions to these equations and analytically

Vijay K. Samalam

1989-01-01

49

Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants

NASA Astrophysics Data System (ADS)

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

Yoshida, Suguru; Fujita, Yasunobu

50

Heat transfer and planetary evolution

NASA Astrophysics Data System (ADS)

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

Tozer, D. C.

1985-06-01

51

such con- figuration proposed in [1], the Open Accumulator, consists of dual liquid and compressed air pressure can also be maintained at a high level even as air mass depletes. Nevertheless, as with any transfer, in- crease the thermal capacitance of the air space, and promote mix- ing. Foams, strands, fins

Li, Perry Y.

52

Heat Transfer Characteristics of a Generalized Divided Flow Heat Exchanger

HEAT TRANSFER CHARACTERISTICS OF A GENERALIZED DIVIDED FLrnJ HEAT EXCHANGER KRISHNA P. SINGH, CHIEF ENGINEER JOSEPH OAT CORPORATION 2500 Broadway, Camden, New Jersey 08104 ,l\\bstract The concept of a "Di vi ded-fl O~I" heat exchanger...-Pass Split-Flow Shell Trans. of the ASME, Journal of Heat Transfer, pp 408-416, Aug. 1964. (4) Singh, K. P. and Holtz, ~I.J., "Generalization of the Split Flow Heat Exchanger - Geometry for Enhanced Heat Transfer", 18th National ASME/AICHE Heat Transfer...

Singh, K. P.

1979-01-01

53

A Numerical Study on Heat Transfer of High Efficient Solar Flat-Plate Collectors with Energy Storage

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

Zhenqian Chen; Mingwei Gu; Donghua Peng; Changhai Peng; Zhishen Wu

2010-01-01

54

Acoustically Enhanced Boiling Heat Transfer

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

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

2008-01-07

55

Heat transfer via dropwise condensation on hydrophobic microstructured surfaces

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

Ruleman, Karlen E. (Karlen Elizabeth)

2009-01-01

56

Enhancement of Pool Boiling Heat Transfer in Confined Space

Pool boiling is an effective method used in many technical applications for a long time. Its highly efficient heat transfer performance results from not only the convection effect but also the phase change process in pool boiling. Pool boiling...

Hsu, Chia-Hsiang

2014-05-05

57

Heat Transfer in a Thermoacoustic Process

ERIC Educational Resources Information Center

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

Beke, Tamas

2012-01-01

58

Heat exchanger device and method for heat removal or transfer

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

Koplow, Jeffrey P. (San Ramon, CA)

2012-07-24

59

Sodium heat transfer system modeling

The sodium heat transfer system of the International Energy Agency (IEA) Small Solar Power Systems (SSPS) Central Receiver System (CRS), which includes the heliostat field, receiver, hot and cold storage vessels, and sodium/water steam generator has been modeled. The computer code SOLTES (Simulator of Large Thermal Energy Systems), developed by Sandia National Laboratories, was used to model this system. Based on data provided to Sandia by the IEA-SSPS/CRS project, the results from SOLTES are compared to measured data. The comparison between measured data and predictions from SOLTES is very good for the day evaluated.

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

1983-01-01

60

Liquid metal heat transfer issues

An alkali liquid metal cooled nuclear reactor coupled with an alkali metal Rankine cycle provides a practicable option for space systems/missions requiring power in the 1 to 100 MW(e) range. Thermal issues relative to the use of alkali liquid metals for this purpose are identified as these result from the nature of the alkali metal fluid itself, from uncertainties in the available heat transfer correlations, and from design and performance requirements for system components operating in the earth orbital microgravity environment. It is noted that, while these issues require further attention to achieve optimum system performance, none are of such magnitude as to invalidate this particular space power concept.

Hoffman, H.W.; Yoder, G.L.

1984-01-01

61

Recovering waste industrial heat efficiently

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

J. G. Hnat; L. M. Bartone; J. S. Patten

1983-01-01

62

Heat recovery Energy efficiency

The petroleum refiing case study of Pennzoil's Atlas refinery at Shreveport, LA demonstrates how process integration or pinch technology can identify practical and cost-effective ways to substantially reduce energy costs. Suggested cost-saving measures include steam and power system improvements and optimum heat exchanger network design. Energy savings in excess of $1,640,000 were identified with an overall payback of 0.72 years.

unknown authors

1995-01-01

63

Heat Transfer: No Magic About It

NSDL National Science Digital Library

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

2014-09-18

64

Heat transfer characteristics of porous radiant burners

This paper reports a numerical study of the heat transfer characteristics of porous radiant burners, which have significant advantages over conventional burners. The heat transfer 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

T. W. Tong; S. B. Sathe

1991-01-01

65

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

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

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

1999-01-01

66

Heat transfer enhancement in heat exchangers

In the power generation industry, high performance heat exchangers are needed to promote substantial improvements in effective utilization of waste heat in low temperature heat recovery applications. High performance heat exchangers are also seriously needed in low temperature power and refrigeration cycles that operate on renewable base energy sources such as ocean thermal energy conversion, geothermal and solar energy systems.

Ohadi

1991-01-01

67

NASA Technical Reports Server (NTRS)

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

Garg, Vijay K.

2001-01-01

68

A literature survey on numerical heat transfer

NASA Astrophysics Data System (ADS)

Technical papers in the area of numerical heat transfer published from 1977 through 1981 are reviewed. The journals surveyed include: (1) ASME Journal of Heat Transfer, (2) International Journal of Heat and Mass Transfer, (3) AIAA Journal, (4) Numerical Heat Transfer, (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 heat transfer and numerical schemes that are not applied to equations governing heat transfer phenomena. The research work is categorized into the following areas: (A) conduction, (B) boundary-layer flows, (C) momentum and heat transfer 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) heat transfer 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.

Shih, T. M.

1982-12-01

69

MODELLING OF CAVITY RECEIVER HEAT TRANSFER COMPACT LINEAR FRESNEL REFLECTOR

MODELLING OF CAVITY RECEIVER HEAT TRANSFER FOR THE COMPACT LINEAR FRESNEL REFLECTOR John D Pye, for the purpose of determining the design parameters for an initial prototype plant. New heat loss correlation) linear absorbers, achieving higher ground area efficiency. Â· Receiver is an inverted, trapezoidal, linear

70

Heat transfer in ground heat exchangers with groundwater advection

In order to estimate the impact of groundwater flow on performance of geothermal heat exchangers in ground source heat pump systems, an equation of conduction–advection is established for heat transfer in porous media, and an analytical transient solution is obtained for a line heat source in an infinite medium by means of the Green function analysis. An explicit expression has

Nairen Diao; Qinyun Li; Zhaohong Fang

2004-01-01

71

Phase change heat transfer device for process heat applications

The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and\\/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up

Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson

2010-01-01

72

Recovering waste industrial heat efficiently

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.

Hnat, J.G.; Bartone, L.M.; Cutting, J.C.; Patten, J.S.

1983-03-01

73

ORNL small-break LOCA heat transfer test series I: rod bundle heat transfer analysis

ORNL has experimentally investigated heat transfer and reflood under conditions similar to those expected in small-break loss-of-coolant accidents (SBLOCAs). Presented are results and analysis of the first of two series of uncovered bundle heat transfer tests. Specifically, a high-pressure high-temperature data base of experimental heat transfer coefficients and local fluid conditions has been compiled. In addition, a heat transfer model

Anklam

1981-01-01

74

"Developing novel heat transfer diagnostics for nanosystems."

"Developing novel heat transfer diagnostics for nanosystems." Patrick Hopkins Assistant Professor Young Investigator Award for heat transfer across solid/fluid interfaces Â· 2013 AFOSR Young Investigator with lowest thermal conductivity of any fully dense solid (Physical Review Letters, v.110, 015902 (2013

Acton, Scott

75

Temperature and Heat Transfer Measurements Cengiz Camci

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

Camci, Cengiz

76

Fibre optic sensors for heat transfer studies

This thesis describes the design and development of a prototype sensor, based on a miniature optical fiber Fabry-Perot interferometer, for heat transfer studies on model turbomachinery components in transient flow wind tunnels. These sensors overcome a number of difficulties which are often encountered in using conventional electrical thin-film resistance gauges such as in the measurement of rapidly varying heat transfer

Pranay G. Sinha

1991-01-01

77

Heat transfer optimization in corrugated wall channels

In this work, the heat transfer in a channel composed of a smooth and a corrugated wall is studied under laminar flow conditions. The velocity and temperature distributions are determined with the help of a finite element model. The heat transfer performance of the corrugated wall channel is compared with that of a smooth wall duct. The numerical model is

Giampietro Fabbri

2000-01-01

78

Second law analysis in heat transfer

The second law of thermodynamics is used as a basis for evaluating the irreversibility (entropy generation) associated with simple heat transfer processes. In the first part of this paper, the irreversibility production is analyzed from the local level, at one point in a convective heat transfer arrangement. The second part of the paper is devoted to a limited review of

A. Bejan

1980-01-01

79

Numerical Simulation of Flow Instability and Heat Transfer

NASA Astrophysics Data System (ADS)

This paper numerically investigates the physical mechanism of flow instability and heat transfer of natural convection in a cavity with thin fin(s). The left and the right walls of the cavity are differentially heated. The cavity is given an initial temperature, and the thin fin(s) is fixed on the hot wall in order to control the heat transfer. The finite volume method with the SIMPLE scheme is used to simulate the flow. Distributions of the temperature, the pressure, the velocity and the total pressure are achieved. Then, the energy gradient method is employed to study the physical mechanism of flow instability and the effect of the thin fin(s) on heat transfer. Based on the energy gradient method, the energy gradient function K represents the characteristic of flow instability. It is observed from the simulation results that the positions where instabilities take place in the temperature contours accord well with those of higher K value, which demonstrates that the energy gradient method reveals the physical mechanism of flow instability. Furthermore, the effect of the fin length, the fin position, the fin number, and Ra on heat transfer is also investigated. It is found that the effect of the fin length on heat transfer is negligible when Ra is relatively high. When there is only one fin, the most efficient heat transfer rate is achieved as the fin is fixed at the middle height of the cavity. The fin blocks heat transfer with a relatively small Ra, but the fin enhances heat transfer with a relatively large Ra. The fin(s) enhances heat transfer gradually with the increase of Ra under the influence of the thin fin(s). Finally, it is observed that both Kmax and Ra can reveal the physical mechanism of natural convection from different approaches.

Dou, Hua-Shu; Jiang, Gang

2014-11-01

80

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

None

2011-12-05

81

charge reduction. The third air-to-air heat exchanger recovers heat from exhaust air and transfers for the ventilation and the exhaust air. Both latent and sensible heats are transferred. Figure 2: Schematic00149 -1- 10th IEA Heat Pump Conference 2011, 16 - 19 May 2011, Tokyo, Japan ENERGY EFFICIENT AIR

Paris-Sud XI, UniversitÃ© de

82

Heat Transfer Derivation of differential equations for heat transfer conduction

;Collect global force terms. In this example, there is no heat source (Q = 0) or heat flux (q = 0 conducted (heat flux) into the control volume at surface edge x, in units of kW/m2 or Btu/(h-ft2). qx of temperature increase. #12;Similar to The heat flux can be stated as: Expanding this using a two term Taylor

Veress, Alexander

83

Local, instantaneous heat transfer in pulse-stabilized fluidization

The Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), a hybrid combustor concept that couples a pulsed combustor with an atmospheric bubbling fluidized bed, has technical advantages in energy efficiency and emissions. The present study examines the effect of an opposing oscillatory flow on the local, instantaneous heat transfer in a laboratory scale bubbling gas-fluidized bed. This opposing secondary flow consisted of a steady mean component and an oscillating component thereby modeling the flow in the tailpipe of a pulsed combustor. Spectral and contact time analyses of local, instantaneous heat flux measurements from a heated, submerged horizontal cylinder clearly indicate that the bed hydrodynamics were significantly altered by the opposing secondary flow. These heat flux measurements were accomplished by employing an isothermal platinum film heat flux gage. For the present investigation, data were acquired for a monodisperse distribution of particles with a mean diameter of 345 {micro}m and total fluidization ratios ranging from 1.1 through 2.7. Heat transfer observed under conditions of secondary flows with a superimposed waveform exhibit characteristics of globally dominated, as opposed to locally dominated, hydrodynamics. For low primary and secondary flow rates and a forcing frequency of 5 Hz, a substantial enhancement in heat transfer was observed. Increases in the bubble phase and emulsion phase heat transfer coefficients were identified as the primary contributors to the observed increases in time-averaged local heat transfer coefficients.

Pence, D.V. [Univ. of Rhode Island, Kingston, RI (United States). Dept. of Mechanical Engineering and Applied Mechanics; Beasley, D.E. [Clemson Univ., SC (United States). Dept. of Mechanical Engineering

1996-12-31

84

Heat Transfer Enhancement: Second Generation Technology

. More complete information can be found in other survey articles [4-9 j . APPLICATIONS OF ENHANCED HEAT TRANSFER General Consid rations The heat transfer rate (q) for a two-fluid heat-exchanger (Fig. 2a) is given by (1) An enhanced tube surface... atures, increased U allows reduced A. 2a. Typical shell-and-tube heat exchanger: two tube passes (condensing) and one shell pass (heating). Table I Enhancement Techniques PassIve Treated surfaces Rough surfaces Extended surfaces Displaced...

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

1984-01-01

85

Heat transfer and nucleation in pool-boiling

The creation of bubbles is a fundamental process in boiling heat transfer. There must be a correlation between heat transfer and bubble action. In order to find out more about it a number of tubes of different materials, diameters and surface finish were investigated and their heat transfer coefficients were determined. Besides the overall heat transfer coefficient, local heat transfer

Erich Hahne; Gerrit Barthau

2006-01-01

86

Microgravity Heat Transfer in Flow Boiling

To investigate flow boiling in microgravity, test sections of transparent heated tube and transparent heating surface were developed, and heat transfer characteristics were directly related to the liquid–vapor behaviors observed. The experiments were performed on board aircraft where the boiling system was exposed in series to normal, hyper and reduced gravity fields along a parabolic trajectory. In the experiments using

Haruhiko Ohta

2003-01-01

87

Equivalent circuit model of radiative heat transfer

NASA Astrophysics Data System (ADS)

Here, we develop a theory of radiative heat transfer based on an equivalent electrical network representation for the hot material slabs in an arbitrary multilayered environment with arbitrary distribution of temperatures and electromagnetic properties among the layers. Our approach is fully equivalent to the known theories operating with the fluctuating current density, while being significantly simpler in analysis and applications. A practical example of the near-infrared heat transfer through the micron gap filled with an indefinite metamaterial is considered using the suggested method. The giant enhancement of the transferred heat compared to the case of the empty gap is shown.

Maslovski, Stanislav I.; Simovski, Constantin R.; Tretyakov, Sergei A.

2013-04-01

88

Nanofluids for heat transfer : an engineering approach.

An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties.

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

2011-02-28

89

Pumped two-phase heat transfer loop

NASA Technical Reports Server (NTRS)

A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

Edelstein, Fred (inventor)

1987-01-01

90

Pumped two-phase heat transfer loop

NASA Technical Reports Server (NTRS)

A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.

Edelstein, Fred

1988-01-01

91

Passive heat transfer means for nuclear reactors

An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler component operable to heat it. Each heat pipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. Means such as shrouding normally isolated the secondary condensing section from effective heat transfer with the heat sink, but a sensor responds to overheat conditions of the reactor to open the shrouding, which thereby increases the cooling capacity of the heat pipe. By having many such heat pipes, an emergency passive cooling system is defined that is operative without electrical power.

Burelbach, James P. (Glen Ellyn, IL)

1984-01-01

92

Heat-transfer characteristics in tert-butanol dehydration reaction used for heat transport

The reaction system of tert-butanol/isobutene/water was considered for use in chemical heat transport. In this study, the heat-transfer characteristics in an endothermic tert-butanol dehydration reaction which occurred in the heat-supply side of this reaction system was investigated. The heat flow was obtained by measuring the reactant composition change and temperature change in the catalyst bed. The heat flow consists of reaction heat, the latent heat of isobutene, and sensible heat in this reaction system. Numerical calculations based on a two-dimensional model were carried out and the results showed good agreement with experiment. It was noticed that the heat flow with chemical reaction was much higher than without reaction. These results indicated that the dehydration reaction promoted the heat-transfer rate, because of the increase in temperature difference between the heating medium and the wall by making use of chemical reaction for a heat transport. The apparent local heat-transfer coefficient with chemical reaction was higher than without reaction. The possibility of a high efficiency heat transport which used this reaction system was suggested.

Kiguchi, Yuji; Watanabe, Takayuki; Kanzawa, Atsushi [Tokyo Inst. of Tech. (Japan). Dept. of Chemical Engineering

1996-07-01

93

Cooling Heat Transfer of Supercritical Carbon Dioxide

NASA Astrophysics Data System (ADS)

The characteristics of carbon dioxide cooled under supercritical condition were investigated theoretically and experimentally. Based on the results of numerical calculation and experimental measurements described in the 1st report, a new correlation was proposed to predict the heat transfer coefficient, and the Filonenko's equation was found adequate to predict the pressure drop inside as mall seized tube. Those correlations were compared with measurement results and the deviations were found lower than ±20%. Furthermore, a compressor cycle was assembled to investigate the effect of lubricant oil on heat transfer and pressure drop. The oil content in CO2 was set to be about 0.5% during the measurements. This amount of lubricant oil was found affected the heat transfer coefficient significantly, with largest degradation of heat transfer coefficient at the pseudocritical point to nearly 50%. The effect of lubricant oil at small concentration on the pressure drop was found negligible.

Dang, Chaobin; Hihara, Eiji

94

Coolant passage heat transfer with rotation

NASA Astrophysics Data System (ADS)

The objective is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques and heat transfer 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.

Hajek, T. J.; Wagner, J. H.; Johnson, B. V.

1987-10-01

95

Nanoparticle enhanced ionic liquid heat transfer fluids

A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.

Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.

2014-08-12

96

Metal-Mold interfacial heat transfer

During the solidification of metal castings, an interfacial heat transfer resistance exists at the boundary between the metal\\u000a and the mold. This heat transfer 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

Kai Ho; Robert D. Pehlke

1985-01-01

97

Code for Multiblock CFD and Heat-Transfer Computations

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

98

Heat transfer measurements for Stirling machine cylinders

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

99

Interactive Heat Transfer Simulations for Everyone

ERIC Educational Resources Information Center

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

Xie, Charles

2012-01-01

100

ORNL PWR Blowdown Heat Transfer Program

The PWR-Blowdown Heat Transfer Program is an experimental, separate ; effects, study of the relations among the principal variables that can alter the ; rate of blowdown, the presence of flow reversal and re-reversal, and time delay ; to critical heat flux, the rate at which dryout progresses, and similar time-; related functions that are important to LOCA analysis. Primary

D. G. Thomas; R. F. Bennett; R. A. Hedrick; J. D. Sheppard; B. G. Eads; R. E. Helms; J. D. White

1975-01-01

101

ME 519: THEORY OF HEAT TRANSFER Instructor

.1Â7.2) Homework 4 10 11/4 Heat exchangers (3) 11/6 Convection: boundary layers, external flow 11 11/11 Convection: correlations Project topic 11/13 Natural convection & phase change 12 11/18 Quiz 4, Radiative propertiesME 519: THEORY OF HEAT TRANSFER Fall 2014 Instructor: Class time: Classroom: Office Hours: Prof

Lin, Xi

102

Measurements of heat transfer in microchannel heat sinks

The paper presents new experimental measurements for pressure drop and heat transfer coefficient in microchannel heat sinks. Tests were performed with devices fabricated using standard Silicon 100 wafers. Two different channel patterns were studied. The parallel pattern distributed the fluid through several parallel passages between the inlet and the outlet headers located at two ends of the wafer. The series

Muhammad Mustafizur Rahman

2000-01-01

103

Capillary-Condenser-Pumped Heat-Transfer Loop

NASA Technical Reports Server (NTRS)

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.

Silverstein, Calvin C.

1989-01-01

104

Nonequilibrium Electromagnetic Fluctuations: Heat Transfer and Interactions

The Casimir force between arbitrary objects in equilibrium is related to scattering from individual bodies. We extend this approach to heat transfer and Casimir forces in nonequilibrium cases where each body, and the environment, is at a different temperature. The formalism tracks the radiation from each body and its scatterings by the other objects. We discuss the radiation from a cylinder, emphasizing its polarized nature, and obtain the heat transfer between a sphere and a plate, demonstrating the validity of proximity transfer approximation at close separations and arbitrary temperatures.

Krueger, Matthias; Kardar, Mehran [Massachusetts Institute of Technology, Department of Physics, Cambridge, Massachusetts 02139 (United States); Emig, Thorsten [Laboratoire de Physique Theorique et Modeles Statistiques, CNRS UMR 8626, Ba circumflex timent 100, Universite Paris-Sud, 91405 Orsay cedex (France)

2011-05-27

105

Heat Transfer to Fuel Sprays Injected into Heated Gases

NASA Technical Reports Server (NTRS)

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

Selden, Robert F; Spencer, Robert C

1938-01-01

106

Outline of Pool Boiling Experiment for Nucleate Boiling Heat Transfer by Aircraft Experiment

Investigation of mechanisms in nucleate boiling in microgravity is essential for the development of high efficiency thermal management systems in space. A transparent heating surface with multiple arrays of 88 thin film temperature sensors and mini-heaters was developed for the clarification of boiling heat transfer mechanisms in microgravity through the study of the relation between local heat transfer coefficients and

Oleg Kabov; Queeckers Patrick; Sergey Chikov; Yusuke Kotani; Yoshino Sakata; Yuka Asada; Tadashi Nagayasu; Yoichi Sato; Yasuhisa Shinmoto; Osamu Kawanami; Haruhiko Ohta

2009-01-01

107

Heat Transfer in Underground Rail Tunnels

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

Sadokierski, Stefan

2007-01-01

108

Modeling microscale heat transfer using Calore.

Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.

Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley

2005-09-01

109

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

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

2014-08-30

110

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

forms are analyzed and the calculation formulas and characteristic are also given. The results indicate that the efficiency of the parallel-flow form is greater than that of the reverse-flow, so the TDTH system must choose the parallel-flow form...

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

2006-01-01

111

Micro heat spreader enhanced heat transfer in MCMs

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

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

1994-12-31

112

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

113

Heat transfer in pressurized circulating fluidized beds

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

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

1997-12-31

114

Heat transfer near spacer grids in rod bundles

Heat transfer data from several sources have been assembled which show the effect of spacer grids on local heat transfer within a rod bundle. Both single phase (air and steam) data and two phase (steam\\/water) data show heat transfer augmentation in the grid region. Heat transfer improvement immediately beyond the grid ranges from a few percent to over fifty percent

Yoder

1985-01-01

115

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

where Cf is the friction coefficient or the drag coefficient which is determined / The convective heat transfer coefficient h strongly depends on the fluid properties and roughness of the solid ./ 20 0 The convection heat transfer coefficient, in general, varies along

Bahrami, Majid

116

Heat transfer on accreting ice surfaces

NASA Technical Reports Server (NTRS)

Based on previous observations of glaze ice accretion on aircraft surfaces, a multizone model with distinct zones of different surface roughness is demonstrated. The use of surface roughness in the LEWICE ice accretion prediction code is examined. It was found that roughness is used in two ways: (1) to determine the laminar to turbulent boundary-layer transition location; and (2) to calculate the convective turbulent heat-transfer coefficient. A two-zone version of the multizone model is implemented in the LEWICE code, and compared with experimental convective heat-transfer coefficient and ice accretion results. The analysis of the boundary-layer transition, surface roughness, and viscous flowfield effects significantly increased the accuracy in predicting heat-transfer coefficients. The multizone model was found to significantly improve the ice accretion prediction for the cases compared.

Yamaguchi, Keiko; Hansman, R. John, Jr.

1993-01-01

117

Microscale surface modifications for heat transfer enhancement.

In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985

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

2013-10-01

118

Heat transfer in counterflow heat exchangers with helical turbulators

NASA Astrophysics Data System (ADS)

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

Zamankhan, Piroz

2010-10-01

119

Heat transfer mechanisms in pulsating heat-pipes with nanofluid

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

120

Heat transfer analysis of boreholes in vertical ground heat exchangers

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

Heyi Zeng; Nairen Diao; Zhaohong Fang

2003-01-01

121

Mounting for diodes provides efficient heat sink

NASA Technical Reports Server (NTRS)

Efficient heat sink is provided by soldering diodes to metal support bars which are brazed to a ceramic base. Electrical connections between diodes on adjacent bars are made flexible by metal strips which aid in heat dissipation.

1964-01-01

122

Self supporting heat transfer element

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)

2002-01-01

123

Cooperative heat transfer and ground coupled storage system

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

Metz, Philip D. (Rocky Point, NY)

1982-01-01

124

Numerical characterization of heat transfer in closed-loop vertical ground heat exchanger

A series of numerical analyses has been performed on the characteristics of heat transfer in a closed-loop vertical ground heat exchanger (U-loop). A 2-D finite element analysis was conducted to evaluate the temperature distribution over the cross section of the U-loop system involving high-density polyethylene (HDPE) pipe\\/grout\\/soil to compare the sectional efficiency between the conventional U-loop and a new latticed

Chulho Lee; Hujeong Gil; Hangseok Choi; Shin-Hyung Kang

2010-01-01

125

Heat Flux Sensors for Infrared Thermography in Convective Heat Transfer

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

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

2014-01-01

126

Local nucleation propagation on heat transfer uniformity during subcooled convective boiling

NASA Astrophysics Data System (ADS)

Convective boiling heat transfer 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 heat transfer phenomena regarding spatial heat transfer uniformity and stability on a planar surface. Severe subcooling can induce locally concentrated thermal loads due to poor spatial uniformity of the heat transfer. For reliable cooling, a high degree of spatial uniformity of the heat transfer should be guaranteed with minimized spatial deviation of heat transfer characteristics. Under pre-requisite safeguards below CHF, we experimentally elucidate the principal factors affecting the spatial uniformity of the heat transfer for a flow/thermal boundary layer considering heat transfer domains from a single-phase regime to a fully-developed boiling regime. Based on the local heat transfer evaluation, we demonstrate that full nucleation boiling over the entire heat transfer 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

2015-01-01

127

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

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

2014-11-15

128

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

129

Turbine disk cavity aerodynamics and heat transfer

Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant

B. V. Johnson; W. A. Daniels

1992-01-01

130

Heat Transfer and Thermodynamics: a Compilation

NASA Technical Reports Server (NTRS)

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

1974-01-01

131

Convective heat transfer in rotating, circular channels

Nusselt number values for flow in a rotating reference frame are obtained through computational fluid dynamic (CFD) analysis for Rossby numbers Ro ~1-4 and Reynolds numbers Re ~1,000-2,000. The heat-transfer model is first ...

Hogan, Brenna Elizabeth

2012-01-01

132

Recombinant retroviruses offer many advantages for the genetic modification of human hematopoietic cells, although their use in clinical protocols has thus far given disappointing results. There is therefore an important need to develop new strategies that will allow effectively transduced primitive hematopoietic target populations to be both rapidly characterized and isolated free of residual nontransduced but biologically equivalent cells. To address this need, we constructed a murine stem cell virus (MSCV)-based retroviral vector containing the 228-bp coding sequence of the murine heat-stable antigen (HSA) and generated helper virus-free amphotropic MSCV-HSA producer cells by transfection of GP-env AM12 packaging cells. Light density and, in some cases, lineage marker-negative (lin-) normal human marrow or mobilized peripheral blood cells preactivated by exposure to interleukin-3 (IL-3), IL-6, and Steel factor in vitro for 48 hours were then infected by cocultivation with these MSCV-HSA producer cells for a further 48 hours in the presence of the same cytokines. Fluorescence-activated cell sorting (FACS) analysis of the cells 24 hours later showed 21% to 41% (mean, 27%) of those that were still CD34+ to have acquired the ability to express HSA. The extent of gene transfer to erythroid and granulopoietic progenitors (burst-forming unit-erythroid and colony-forming unit-granulocyte-macrophage), as assessed by the ability of these cells to form colonies of mature progeny in the presence of normally toxic concentrations of G418, averaged 11% and 12%, respectively, in 6 experiments. These values could be increased to 100% and 77%, respectively, by prior isolation of the CD34+HSA+ cell fraction and were correspondingly decreased to an average of 2% and 5%, respectively, in the CD34+HSA- cells. In addition, the extent of gene transfer to long-term culture-initiating cells (LTC-IC) was assessed by G418 resistance. The average gene transfer to LTC-IC-derived colony-forming cells in the unsorted population was < or = 7% in 4 experiments. FACS selection of the initially CD34+HSA+ cells increased this value to 86% and decreased it to 3% for the LTC-IC plated from the CD34+HSA- cells. Transfer of HSA gene expression to a phenotypically defined more primitive subpopulation of CD34+ cells, ie, those expressing little or no CD38, could also be shown by FACS analysis of infected populations 24 hours after infection. These findings underscore the potential use of retroviral vectors encoding HSA for the specific identification and non-toxic selection immediately after infection of retrovirally transduced populations of primitive human hematopoietic cells. In addition, such vectors should facilitate the subsequent tracking of their marked progeny using multiparameter flow cytometry. PMID:8555466

Conneally, E; Bardy, P; Eaves, C J; Thomas, T; Chappel, S; Shpall, E J; Humphries, R K

1996-01-15

133

Heat transfer performance of axially grooved heat pipes

NASA Astrophysics Data System (ADS)

Experiments and analysis of the heat transport capability of axially grooved heat pipes are described. The heat pipes were made of aluminum axially grooved extruded pipes and the working fluid was R11. The effects of fluid inventory and inclination angle on the capillary pumping limit were investigated. A theoretical model was developed to predict the temperature rise in the evaporator and the heat transfer capability. In this model, the puddling effect, liquid recession into the groove bottom and the heat conduction in the evaporator were taken into consideration and the prediction agreed well with the experimental data. It was found that the temperature at the evaporator end began to increase just after all the grooves dried out at the evaporator end. The flooding limit and the evaporator and condenser film coefficients in the case of the gravity-supported operation were also investigated and compared with the performance of closed two-phase thermosyphons.

Ogushi, Tetsurou; Yamanaka, Gorou

1987-03-01

134

Heat transfer characteristics of Turbotec tubing

NASA Astrophysics Data System (ADS)

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

Bergles, A. E.

1980-06-01

135

Heat transfer in bioengineering and medicine

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

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

1987-01-01

136

Numerical Modeling of Ablation Heat Transfer

NASA Technical Reports Server (NTRS)

A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

Ewing, Mark E.; Laker, Travis S.; Walker, David T.

2013-01-01

137

Advanced Heat Transfer and Thermal Storage Fluids

The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.

Moens, L.; Blake, D.

2005-01-01

138

Instantaneous pressure and heat transfer in pulse-stabilized fluidization

A hybrid combustor concept that couples a pulsed combustor with an atmospheric bubbling fluidized bed was developed by Manufacturing Technology Conversion International, Inc. (MTCI, Inc.) and licensed to Thermo-Chem, Inc. This Pulsed Atmospheric Fluidized Bed technology has technical advantages in energy efficiency and emissions and is currently in pilot scale demonstration on the campus of Clemson University. The present study examines the effect of an opposing oscillatory flow on the pressure and overall heat transfer in a bubbling gas-fluidized bed. This opposing flow models the flow in the tailpipe of a pulsed combustor. Pressure measurements at the wall and on a submerged horizontal cylinder clearly indicate that the bed hydrodynamics are significantly altered by the opposing secondary flow. Under operating conditions of low secondary flow rates and pulse frequencies, the dominant frequency of the pressure fluctuations measured in the bed shifts from the natural, unforced response of the bed to the imposed frequency. For higher fluidization and secondary flow rates both the natural and forced response of the bed are present. Overall and time-averaged local heat transfer measurements from a submerged horizontal cylinder clearly indicate that the heat transfer rates are significantly altered by the opposing secondary flow. The most dramatic increases in heat transfer, on the order of 12%, were identified with operating conditions with low primary and secondary flow rates and pulse frequencies near the natural frequency of the bed. The local heat transfer was most significantly altered at the stagnation point. A modified form of the Strouhal number is shown to effectively describe the effect of pulse stabilization on overall heat transfer.

Beasley, D.E.; Postle, M.C. [Clemson Univ., SC (United States). Dept. of Mechanical Engineering; Pence, D.V. [Univ. of Rhode Island, Kingston, RI (United States). Dept. of Mechanical Engineering and Applied Mechanics

1996-12-31

139

Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

140

In this study, heat transfer and thermal performance of a periodically dimple-protrusion patterned surface have been investigated to enhance energy-efficiency in compact heat exchangers. The local heat transfer coefficients on the dimple\\/protrusion walls are derived using a transient TLC (Thermochromic Liquid Crystal) technique. The periodically patterned surface is applied to the bottom wall only or both the bottom and top

Sang Dong Hwang; Hyun Goo Kwon; Hyung Hee Cho

2010-01-01

141

An efficient tool to deal with multidimensional radiative heat transfer is in strong demand to analyze the various thermal problems combined either with other modes of heat transfer or with combustion phenomena. The current study examines the discrete ordinates method (DOM) for coupled radiative and conductive heat transfer in rectangular enclosures in which either a nonscattering or scattering medium is

Taik Young Kim; Seung Wook Baek

1991-01-01

142

Heat-transfer augmentation in rod bundles near grid spacers

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 heat transfer 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 heat transfer at a straight spacer and at its upstream

S. C. Yao; L. E. Hochreiter; W. J. Leech

1982-01-01

143

Heat Transfer between Graphene and Amorphous SiO2

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

B. N. J. Persson; H. Ueba

2010-07-22

144

NASA Astrophysics Data System (ADS)

We present a highly efficient lattice Boltzmann model for simulating compressible flows. This model is based on the combination of an appropriate finite difference scheme, a 16-discrete-velocity model [Kataoka and Tsutahara, Phys. Rev. E 69 (2004) 035701(R)] and reasonable dispersion and dissipation terms. The dispersion term effectively reduces the oscillation at the discontinuity and enhances numerical precision. The dissipation term makes the new model more easily meet with the von Neumann stability condition. This model works for both high-speed and low-speed flows with arbitrary specific-heat-ratio. With the new model simulation results for the well-known benchmark problems get a high accuracy compared with the analytic or experimental ones. The used benchmark tests include (i) Shock tubes such as the Sod, Lax, Sjogreen, Colella explosion wave, and collision of two strong shocks, (ii) Regular and Mach shock reflections, and (iii) Shock wave reaction on cylindrical bubble problems. With a more realistic equation of state or free-energy functional, the new model has the potential tostudy the complex procedure of shock wave reaction on porous materials.

Chen, Feng; Xu, Ai-Guo; Zhang, Guang-Cai; Gan, Yan-Biao; Cheng, Tao; Li, Ying-Jun

2009-10-01

145

ME 6010 CONDUCTION HEAT TRANSFER 1998 Catalog Data: ME 6010. Conduction Heat Transfer. Lec. 3. Cr. Prerequisite: Math 4510, ME 3710 Textbook: S. Kakac and Y. Yener, Heat Conduction, Taylor & Francis Coordinator. Undergraduate conduction and convection heat transfer, or equivalent 2. Advanced undergraduate mathematics

Panchagnula, Mahesh

146

Numerical analysis of heat transfer in supercritical water cooled flow channels

Research activities are ongoing worldwide to develop nuclear power plants with a supercritical water cooled reactor (SCWR) with the purpose to achieve a high thermal efficiency and to improve their economical competitiveness. However, there is still a big deficiency in understanding and prediction of heat transfer in supercritical fluids. In this paper, heat transfer of supercritical water has been investigated

X. Cheng; B. Kuang; Y. H. Yang

2007-01-01

147

Proceedings of IWHT2011 2011 International Workshop on Heat Transfer Advances for

For the heat transfer enhancement, internally micro-fin tubes are widely used in commercial HVAC applications. It is commonly understood that the micro-fin enhances heat transfer but at the same time increases the pressure adopted to find out the efficiency index. For comparison purposes, the Genetic Algorithms (GA) was also

Ghajar, Afshin J.

148

Oscillatory flow with heat transfer in a square cavity

NASA Technical Reports Server (NTRS)

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

Biringen, S.; Danabasoglu, G.

1989-01-01

149

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

150

NASA Astrophysics Data System (ADS)

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

Hou, Xiuhui; Deng, Zichen; Yin, Guansheng

2014-12-01

151

Heat Transfer and Energy Diffusion Analysis of Cannula Ground Heat Exchanger

A heat transfer model about fluid flow and heat conduct in cannula ground heat exchanger were given in this article. The heat transfer characteristics were analyzed by means of numerical method of finite element. Affect of difference size of buried tubes and the velocity of flow in the tube, on fluid outlet temperature and unit heat transfer of burned pipe

Jiang Yan; Gao Qing; Li Ming

2010-01-01

152

Analysis on Model and Affected Factors of Heat Transfer of Floor Heating System

High error in calculating the heat transfer of floor heating system can be introduced by existing models, considering the heat transfer of the floor slab and different temperature between interior wall and exterior wall. A modified calculation model of heat transfer of floor heating system was proposed, analyzed the influence of the interior or exterior wall and the floor slab,

Wu Guozhong; Xue Kang; Qi Hangbing; Li Dong

2010-01-01

153

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

154

IR Radiative Transfer with Transient Heating

NASA Astrophysics Data System (ADS)

In order to study the evolutionary history of most astrophysical systems an accurate account of the effects of dust is necessary. We are currently extending our radiative transfer models to include infrared emission from dust. Presently,the model tracks UV and optical photons through an arbitrary mixture of gas, stars, and dust. Emission from dust includes emission from large grains in thermodynamic equilibrium with the radiation field as well as small grains and molecules that undergo transient heating. Here we present results from our model which include the effects of the transient heating and apply it to systems with simple geometries.

Misselt, K. A.; Gordon, K. D.; Clayton, G. C.; Wolff, M. J.

1999-05-01

155

Two Heat-Transfer Improvements for Gas Liquefiers

NASA Technical Reports Server (NTRS)

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

Martin, Jerry L.

2005-01-01

156

Heat transfer during film condensation of potassium vapor

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

Kroger, Detlev Gustav

1966-01-01

157

Nanofluid heat transfer enhancement for nuclear reactor applications

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

Buongiorno, Jacopo

158

Heat transfer in earth science studies

Earth scientists have long recognized that quantitative models of heat and mass transfer are fundamental to understanding many geophysical phenomena. Transport models have been used to simulate a wide range of earth processes from the crystallization of rock melts to those global mechanisms responsible for driving lithospheric plates and the geodynamo. Since the elegant conductive cooling models of igneous instrusions by Lovering and Jaeger in the 1930's and 1940's, calculations have evolved in their sophistication with the realization of the importance of convective transport and the advent of new methods and supercomputers. Many of the modeling techniques currently used by geoscientists have been adapted from techniques that were originally developed to solve engineering problems. Processes, such as those involving magma transport in volcanic systems, may often be understood by establishing their dynamical similarity with a well-studied engineering application. This book contains a series of papers regarding heat transfer and earth science studies.

Carrigan, C. (Lawrence Livermore National Lab., CA (United States)); Chu, T.Y. (Sandia National Labs., Albuquerque, NM (United States))

1990-01-01

159

Coolant passage heat transfer with rotation

NASA Astrophysics Data System (ADS)

The objective is to develop a heat transfer 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.

Hajek, T. J.; Higgins, A. W.

1985-10-01

160

Heat transfer and fluid flow in microchannels

This paper investigates the effects of the EDL at the solid-liquid interface on liquid flow and heat transfer through a microchannel between two parallel plates at constant and equal temperatures. A linear approximate solution of the Poisson-Boltzmann equation is used to describe the EDL field near the solid-liquid interface. The electrical body force resulting from the double layer field is

G. Mohiuddin Mala; Dongqing Li; J. D. Dale

1997-01-01

161

Low-melting point heat transfer fluid

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

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

2010-11-09

162

Computational fluid mechanics and heat transfer

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

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

1984-01-01

163

Heat transfer enhancement in metal hydride systems

NASA Astrophysics Data System (ADS)

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

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

164

HOST turbine heat transfer subproject overview

NASA Technical Reports Server (NTRS)

The experimental part of the turbine heat transfer subproject consists of six large experiments, which are highlighted in this overview, and three of somewhat more modest scope. One of the initial efforts was the stator airfoil heat transfer program. The non-film cooled and the showerhead film cooled data have already been reported. The gill region film cooling effort is currently underway. The investigation of secondary flows in a 90 deg curved duct, was completed. The first phase examined flows with a relatively thin inlet boundary layer and low free stream turbulence. The second phase studied a thicker inlet boundary layer and higher free stream turbulence. A comparison of analytical and experimental cross flow velocity vectors is shown for the 60 deg plane. Two experiments were also conducted in the high pressure facility. One examined full coverage film cooled vanes, and the other, advanced instrumentation. The other three large experimental efforts were conducted in a rotation reference frame. An experiment to obtain gas path airfoil heat transfer coefficients in the large, low speed turbine was completed. Single-stage data with both high and low-inlet turbulence were taken. The second phase examined a one and one-half stage turbine and focused on the second vane row. Under phase 3 aerodynamic quantities such as interrow time-averaged and rms values of velocity, flow angle, inlet turbulence, and surface pressure distribution were measured.

Gladden, Herbert J.

1986-01-01

165

Investigation on Convective Heat Transfer and Flow Features of Nanofluids

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

Yimin Xuan; Qiang Li

2003-01-01

166

Heat Transfer Enhancement in Separated and Vortex Flows

This document summarizes the research performance done at the Heat Transfer Laboratory of the University of Minnesota on heat transfer and energy separation in separated and vortex flow supported by DOE in the period September 1, 1998--August 31, 2003. Unsteady and complicated flow structures in separated or vortex flows are the main reason for a poor understanding of heat transfer

Richard J. Goldstein

2004-01-01

167

Radial base heat-transfer gradients in turbulent flow

An experimental analysis of radial base heat-transfer gradients was conducted to determine the application to base heatshield design for various hypersonic entry vehicles. A geometric relation is derived from previous results to determine the radial base heat-transfer distribution for a slender cone at zero angle of attack. Turbulent heat transfer is shown to vary nearly linearly across a flat base.

B. M. Bulmer

1974-01-01

168

Non-conductive heat transfer associated with frozen soils

The assertion that pure conductive heat transfer always dominates in cold climates is at odds with decades of research in soil physics which clearly demonstrate that non-conductive heat transfer by water and water vapor are significant, and frequently are for specific periods the dominant modes of heat transfer near the ground surface. The thermal regime at the surface represents the

Douglas L Kane; Kenneth M Hinkel; Douglas J Goering; Larry D Hinzman; Samuel I Outcalt

2001-01-01

169

Boiling heat transfer and bubble dynamics in microgravity

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

Johannes Straub

2001-01-01

170

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2010 CFR

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

2010-10-01

171

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2012 CFR

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

2012-10-01

172

7 CFR 3201.54 - Heat transfer fluids.

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Heat transfer fluids. 3201.54 Section...PROCUREMENT Designated Items § 3201.54 Heat transfer fluids. (a) Definition...capacities used to facilitate the transfer of heat from one location to another,...

2012-01-01

173

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2013 CFR

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

2013-10-01

174

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2014 CFR

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

2014-10-01

175

46 CFR 153.430 - Heat transfer systems; general.

Code of Federal Regulations, 2011 CFR

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

2011-10-01

176

Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles

ERIC Educational Resources Information Center

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

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

2010-01-01

177

7 CFR 3201.54 - Heat transfer fluids.

Code of Federal Regulations, 2014 CFR

...2014-01-01 2014-01-01 false Heat transfer fluids. 3201.54 Section...PROCUREMENT Designated Items § 3201.54 Heat transfer fluids. (a) Definition...capacities used to facilitate the transfer of heat from one location to another,...

2014-01-01

178

7 CFR 3201.54 - Heat transfer fluids.

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Heat transfer fluids. 3201.54 Section...PROCUREMENT Designated Items § 3201.54 Heat transfer fluids. (a) Definition...capacities used to facilitate the transfer of heat from one location to another,...

2013-01-01

179

Heat Transfer Characteristics of Nanofluids in an Acoustic Cavitation Field

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

D. W. ZHOU; Deng-Ying Liu

2004-01-01

180

Film-Cooling Heat-Transfer Measurements Using Liquid Crystals

NASA Technical Reports Server (NTRS)

The following topics are discussed: (1) The Transient Liquid-Crystal Heat-Transfer Technique; (2) 2-D Film-Cooling Heat-Transfer on an AlliedSignal Vane; and (3) Effects of Tab Vortex Generators on Surface Heat Transfer. Downstream of a Jet in Crossflow.

Hippensteele, Steven A.

1997-01-01

181

Heat Transfer Operators Associated with Quantum Operations

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

Ç. Aksak; S. Turgut

2011-04-14

182

Enhancement of heat and mass transfer by cavitation

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

183

Optimal second-law efficiency for a Brayton cycle with an internal heat source

Net work of an endoreversible Brayton cycle and its second-law efficiency are examined for a heat source (hot air) that is initially at a temperature typical of adiabatic and stoichiometric combustion. That temperature is take to be well above maximum cycle temperature. When heat is transferred to the cycle via a heat exchanger, maximum work per unit of heat source

J. B. Woodward

1995-01-01

184

Heat and mass transfer in bubble column dehumidifiers for HDH desalination

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

Tow, Emily W

2014-01-01

185

High efficiency pump for space helium transfer

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

186

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

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

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

2010-02-23

187

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

R. P. Stein

1981-01-01

188

A Model of Respiratory Heat Transfer in a Small Mammal

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

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

1971-01-01

189

Numerical computation of fluid flow and heat transfer in microchannels

Three-dimensional fluid flow and heat transfer phenomena inside heated microchannels is investigated. The steady, laminar flow and heat transfer equations are solved using a finite-volume method. The numerical procedure is validated by comparing the predicted local thermal resistances with available experimental data. The friction factor is also predicted in this study. It was found that the heat input lowers the

K. C Toh; X. Y Chen; J. C Chai

2002-01-01

190

Heat transfer enhancement of copper nanofluid with acoustic cavitation

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

D. W. Zhou

2004-01-01

191

Rocket engine thrust chamber heat transfer calculation and analysis

NASA Technical Reports Server (NTRS)

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

Saha, H.

1974-01-01

192

A review of turbine blade tip heat transfer.

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

Bunker, R S

2001-05-01

193

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

194

Flow and heat transfer in a curved channel

NASA Technical Reports Server (NTRS)

Flow and heat transfer 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 heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.

Brinich, P. F.; Graham, R. W.

1977-01-01

195

NASA Astrophysics Data System (ADS)

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

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

196

Turbulence convective heat transfer for cooling the photovoltaic cells

NASA Astrophysics Data System (ADS)

Solar PV (photovoltaic) is a rapidly advancing renewable energy technology which converts sunlight directly into electricity. One of the outstanding challenges of the current PV technology is the reduction in its conversion efficiency with increasing PV panel temperature, which is closely associated with the increase in solar intensity and the ambient temperature surrounding the PV panels. To more effectively capture the available energy when the sun is most intense, significant efforts have been invested in active and passive cooling research over the last few years. While integrated cooling systems can lead to the highest total efficiencies, they are usually neither the most feasible nor the most cost effective solutions. This work examines some simple passive means of manipulating the prevailing wind turbulence to enhance convective heat transfer over a heated plate in a wind tunnel.

Arianmehr, Iman

197

Heat transfer augmentation in nanofluids via nanofins

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 heat transfer 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. PMID:21711695

2011-01-01

198

Measurement of flow field and local heat transfer distribution on a scraped heat exchanger.ravelet@laposte.net Geert-Jan Witkamp G.J.Witkamp@xs4all.nl Abstract In a cylindrical scraped heat exchanger crystallizer geometry the flow field influence on the local heat transfer distribution on an evenly cooled scraped heat

Boyer, Edmond

199

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

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

Thole, Karen A.

200

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

Analysis of three-dimensional heat transfer in micro-channel heat sinks Weilin Qu, Issam Mudawar, the three-dimensional fluid flow and heat transfer in a rectangular micro-channel heat sink are ana- lyzed numerically using water as the cooling fluid. The heat sink consists of a 1-cm2 silicon wafer. The micro

Qu, Weilin

201

INVESTIGATING THE EFFECT OF HEATING METHOD ON POOL BOILING HEAT TRANSFER

of heat transfer involving a change of phase. The presence of nucleating bubbles on the heating surface the bubble, vapor liquid exchange mechanisms, etc. The heat flux supplied by the surface is takenINVESTIGATING THE EFFECT OF HEATING METHOD ON POOL BOILING HEAT TRANSFER Satish G. Kandlikar

Kandlikar, Satish

202

Thermal performance analysis for heat exchangers having a variable overall heat transfer coefficient

The classic, conventional analysis for the thermal performance of heat exchangers is based on three assumptions: constant fluid flow rate, constant specific heat fluids, and constant overall heat transfer coefficient. Our analysis describes a general approach for analyzing the thermal performance of heat exchangers in which the overall heat transfer coefficient varies as a function of enthalpy, with the other

J. C. Conklin; E. Granryd

1991-01-01

203

Liquid-metal heat transfer in a cocurrent- flow, double-pipe heat exchanger is investigated

NASA Technical Reports Server (NTRS)

Analysis of liquid-metal heat transfer in cocurrent-flow, double-pipe heat exchangers shows that heat-transfer coefficients depend upon the operating conditions of the heat exchanger and that use of the customary design equation to predict heat-exchanger performance leads to significant errors.

Merriam, R. L.

1969-01-01

204

A SINDA '85 nodal heat transfer rate calculation user subroutine

NASA Technical Reports Server (NTRS)

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

Cheston, Derrick J.

1992-01-01

205

Study of hydraulic resistance and heat transfer in perforated-plate heat exchangers

NASA Astrophysics Data System (ADS)

An experimental study is made of the hydraulic resistance and heat transfer in heat exchangers made of perforated plates with different internal geometries. Generalizing theoretical relations are obtained.

Shevyakova, S. A.; Orlov, V. K.

1983-07-01

206

Efficiency bounds for nonequilibrium heat engines

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.

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

2013-05-15

207

Efficient clocked electron transfer on superfluid helium.

Unprecedented transport efficiency is demonstrated for electrons on the surface of micron-scale superfluid helium-filled channels by co-opting silicon processing technology to construct the equivalent of a charge-coupled device. Strong fringing fields lead to undetectably rare transfer failures after over a billion cycles in two dimensions. This extremely efficient transport is measured in 120 channels simultaneously with packets of up to 20 electrons, and down to singly occupied pixels. These results point the way towards the large scale transport of either computational qubits or electron spin qubits used for communications in a hybrid qubit system. PMID:22243176

Bradbury, F R; Takita, Maika; Gurrieri, T M; Wilkel, K J; Eng, Kevin; Carroll, M S; Lyon, S A

2011-12-23

208

Boiling local heat transfer enhancement in minichannels using nanofluids

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

209

Boiling local heat transfer enhancement in minichannels using nanofluids

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

2013-01-01

210

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

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

Kendall, Gail E.

1978-01-01

211

Micro-grooved heat transfer combustor wall

NASA Technical Reports Server (NTRS)

A gas turbine engine hot section combustor liner is provided a non-film cooled portion of a heat transfer wall having a hot surface and a plurality of longitudinally extending micro-grooves disposed in the portion of the wall along the hot surface in a direction parallel to the direction of the hot gas flow. The depth of the micro-grooves is very small and on the order of magnitude of a predetermined laminar sublayer of a turbulent boundary layer. The micro-grooves are sized so as to inhibit heat transfer from the hot gas flow to the hot surface of the wall while reducing NOx emissions of the combustor relative to an otherwise similar combustor having a liner wall portion including film cooling apertures. In one embodiment the micro-grooves are about 0.001 inches deep and have a preferred depth range of from about 0.001 inches to 0.005 inches and which are square, rectangular, or triangular in cross-section and the micro-grooves are spaced about one width apart.

Ward, Steven D. (Inventor)

1994-01-01

212

Heat transfer assembly for a fluorescent lamp and fixture

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

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

1992-01-01

213

Study and Analysis of Heat Transfer Limitation of Separated Heat Pipe

NASA Astrophysics Data System (ADS)

satellite and spacecraft. evaporator, heat isolation and condenser along the axial direction. The working fluid absorbs heat and evaporates in evaporator, and then the vapor flows to condenser and gives out heat. The condensed liquid is pumped to evaporator by wick. By the circulation, the heat can by transferred continuously. heat pipe as follow: - Vapor-liquid two phase flow inside pipe; - The manner of latent heat to transfer heat; - Automatic circulation by working fluid flowing - A certain extent of vacuum. and the traditional heat pipe, that is, the vapor fluid and liquid fluid flow along the same direction. So it is obviously that the separated heat pipe has special internal heat transfer characteristic and crisis. This paper has regard for the heat transfer crisis of the separated heat pipe, and meanwhile relevant calculation and analysis have been done. 1. FLOW TYPE OF THE WORKING FLUID IN SEPARATED HEAT PIPE 2. HEAT TRANSFER CRISIS IN THE EVAPORATOR 3. CARRYING PHENOMENON INSIDE SEPARATED HEAT PIPE 4. THE STAGNANT FLOW PHENOMENON AND THE BACKWARD FLOW PHENOMENON IN EVAPORATOR CONCLUSION transfer limitation of location burn-out, and the heat transfer limitation of flow unconventionality in erective pipe. The carrying phenomenon can occurs not only in evaporator but also in condenser of separated heat pipe. It is in the evaporator that should take place the heat transfer limitation of liquid film dry-out at first. Then with the increasing of heat flux, the heat transfer limitation of location burn-out would happen. In order to avoid the heat transfer limitation of flow unconventionality in erective pipe, the length and diameter of the outflow tube and inflow tube must be reasonably calculated to control the flow velocity of the working fluid inside pipe. Key words:Separated Heat PipeHeat Transfer LimitationDry-OutCarryingStagnancy

Mou, Qizheng; Mou, Kai

2002-01-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

215

Some characteristics of flow pattern and heat transfer past a circular cylindrical cavity

NASA Astrophysics Data System (ADS)

A turbulent vortex in a two or three-dimensional cavity appears to promote an increase in the efficiency of heat transfer. Various cases related to an increase of heat transfer on the basis of the considered phenomenon have been studied. However, there is no report regarding an investigation of the heat transfer from a circular cavity. The present study is, therefore, concerned with the conduction of experiments which were designed to provide information regarding the flow pattern and local heat transfer in the case of such a circular cavity. A single circular cavity in a turbulent boundary layer on a flat plate is considered. Attention is given to the experimental apparatus, the isopleths of Cp on the walls in the cavity, pressure fluctuations in the cavity flow, flow visualization by the oil-film method, local heat transfer characteristics, and two kinds of unstable phenomena in the cavity flow.

Hiwada, M.; Mabuchi, I.; Kumada, M.; Kawamura, T.

1983-10-01

216

Erosion effects on TVC vane heat transfer characteristics

This work describes the effects of erosion on the heat transfer characteristics on thrust vector control vanes exposed to aluminized propellant exhaust flows. This was accomplished using an inverse heat transfer parameter identification of quarter scale models. The model is based on a four node lumped parameter system with two heat energy inputs. The erosion is modeled as decreasing the

Steven R. Gardner

1994-01-01

217

Challenges in microscale conductive and radiative heat transfer

This work addresses challenges in the emerging field of microlength scale radiative and conductive heat transfer in solids and recommends specific directions of future research. Microlength scale heat transfer involves thermal energy transport processes in which heat carrier characteristic lengths become comparable to each other or the characteristic device dimension. Identification of these characteristic lengths leads to the definition of

C. L. Tien; G. Chen

1994-01-01

218

CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011

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

Dyer, Bill

219

Heat transfer investigations in a slurry bubble column

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

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

1991-02-01

220

Heat transfer investigations in a slurry bubble column

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

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

1991-02-01

221

An analysis is presented to predict the heat transfer characteristics of a plane layer of a semitransparent, high-temperature, porous material which is irradiated by an intense solar flux. A transient, combined conduction and radiation heat transfer model, which is based on a two-flux approximation for the radiation, is used to predict the temperature distribution and heat transfer in the material.

L. K. Matthews; F. P. Incropera; R. Viskanta

1985-01-01

222

Transient critical heat flux and blowdown heat-transfer studies

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

Leung, J.C.

1980-05-01

223

Transient critical heat flux and blowdown heat-transfer studies

Objective is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. A predictional method has been developed which involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous local-conditions hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis. 234 figures, 13 tables.

Leung, J.C.

1980-05-01

224

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

225

NASA Astrophysics Data System (ADS)

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

Volosencu, Constantin; Curiac, Daniel-Ioan

2013-12-01

226

Heat transfer in horizontal tubes immersed in fluidized beds

NASA Astrophysics Data System (ADS)

A theoretical model is proposed, and experimental data presented and analyzed, for the overall convective heat transfer coefficient at ambient conditions between horizontally immersed tubes and a gas fluidized bed of particle sizes usually applicable in fluidized bed combustion of coal. The overall heat transfer coefficient is a function of gas and particle heat transfer coefficients. The bubbling flow assumption, together with the two phase theory of fluidization, is used to obtain a simple analytical solution for the particle convective heat transfer coefficient. The equation for gas convective heat transfer coefficient is obtained through an analogy with heat transfer in packed beds. To a first order approximation the particle and gas convective components are additive.

Anekwe, C. I.

227

Micro and nanostructured surfaces for enhanced phase change heat transfer

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

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

2013-01-01

228

Investigation of local heat transfer in compact heat exchangers by holographic interferometry

Compact heat exchangers are key components for the development of future aircraft devices. An enhancement of the heat transfer results in a decrease in the heat exchanger size and thus in lower weight and lower investment costs. Exact knowledge of the temperature distribution in the boundary layer is necessary for a specific augmentation of heat transfer. Holographic interferometry was applied

R. Fehle; J. Klas; F. Mayinger

1995-01-01

229

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

1 CORRELATING EVAPORATION HEAT TRANSFER COEFFICIENT OF REFRIGERANT R-134a IN A PLATE HEAT EXCHANGER for evaporation heat transfer coefficient of refrigerant R-134a flowing in a plate heat exchanger. Correlation water-to-water experiment and a two-phase evaporation experiment with refrigerant R- 134a in a plate

Kandlikar, Satish

230

Heat-Transfer Enhancement by Artificially Generated Streamwise Vorticity

NASA Astrophysics Data System (ADS)

Vortex-induced heat transfer 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.

Ghanem, Akram; Habchi, Charbel; Lemenand, Thierry; Della Valle, Dominique; Peerhossaini, Hassan

2012-11-01

231

Sensitivity Analysis of the Gap Heat Transfer Model in BISON.

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

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

2014-10-01

232

Turbine disk cavity aerodynamics and heat transfer

NASA Astrophysics Data System (ADS)

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

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

1992-07-01

233

Submersible pumping system with heat transfer mechanism

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

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

2014-04-15

234

Turbine disk cavity aerodynamics and heat transfer

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

235

Heat Transfer Variation on Protuberances and Surface Roughness Elements

NASA Technical Reports Server (NTRS)

In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer 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 heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed.

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

1995-01-01

236

Nonlinear Transient Problems Using Structure Compatible Heat Transfer Code

NASA Technical Reports Server (NTRS)

The report documents the recent effort to enhance a transient linear heat transfer code so as to solve nonlinear problems. The linear heat transfer code was originally developed by Dr. Kim Bey of NASA Largely and called the Structure-Compatible Heat Transfer (SCHT) code. The report includes four parts. The first part outlines the formulation of the heat transfer problem of concern. The second and the third parts give detailed procedures to construct the nonlinear finite element equations and the required Jacobian matrices for the nonlinear iterative method, Newton-Raphson method. The final part summarizes the results of the numerical experiments on the newly enhanced SCHT code.

Hou, Gene

2000-01-01

237

2.51 Intermediate Heat and Mass Transfer, Fall 2001

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

Lienhard, John H., 1961-

238

Heat Transfer Study of Polymer Solutions with Different Rigidities

The heat transfer behaviors of non-Newtonian fluids under laminar flow conditions in circular tubes are presented in this study. The constant wall heat flux is considered as a boundary condition for dilute polymer solutions with different polymer...

Huang, Yao

2014-05-08

239

An improved model of heat transfer through penguin feathers and down

Penguins, mostly live in the extremely cold Antarctic, are known to have feathers and down, which are light weight, compact and extremely efficient in preventing heat loss. Nevertheless, the mechanisms of heat transfer through the penguin feathers and down, and how the unique characteristics of penguin feathers and down make them such good thermal insulators are not fully understood.In this

Ning Du; Jintu Fan; Huijun Wu; Shuo Chen; Yang Liu

2007-01-01

240

Effects of Solar Photovoltaic Panels on Roof Heat Transfer

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

241

Optimal placement depth for air–ground heat transfer systems

Heat transfer between the air and the ground is important for a variety of applications including buried pipes and cables, ground source heat pumps, and building insulation. A recent application considered a ground-source heat engine using a thermoelectric module sandwiched between two heat exchangers to produce a very small amount of electricity from the daily temperature difference between the air

James W. Stevens

2004-01-01

242

ME 339 Heat Transfer ABET EC2000 syllabus

convection; radiation; introduction to phase change heat transfer and to heat exchangers. Prerequisite(s): ME equipment and devices including extended surfaces and heat exchangers. These skills are highly valued. Internal Tube Flow 16. Internal Tube Flows 17. Heat Exchangers 18. Free convection 19. Review of Convection

Ben-Yakar, Adela

243

Heat transfer characteristics of igniter output plumes

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 heat transfer 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.

Evans, N.A.; Durand, N.A.

1989-01-01

244

Heat transfer characteristics of igniter output plumes

NASA Astrophysics Data System (ADS)

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 heat transfer 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.

Evans, N. A.; Durand, N. A.

245

TACO: a finite element heat transfer code

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

Mason, W.E. Jr.

1980-02-01

246

Application of Industrial Heat Improving energy efficiency of

Application of Industrial Heat Pumps Improving energy Â efficiency of industrial processes . H Session Application of Industrial Heat Pumps Improving energy Â efficiency of industrial processes Agency (IEA) - Agreements "Heat Pump Programme" "Industrial Energy-related Technologies and Systems #12

Oak Ridge National Laboratory

247

High thermal power density heat transfer. [thermionic converters

NASA Technical Reports Server (NTRS)

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

Morris, J. F. (inventor)

1980-01-01

248

NASA Astrophysics Data System (ADS)

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

Yilmaz, Alper

2014-09-01

249

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

Takeishi, K; Aoki, S

2001-05-01

250

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

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

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

1996-12-03

251

Measurement of heat and moisture exchanger efficiency.

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

Chandler, M

2013-09-01

252

Efficiency of a Water Heating System

NSDL National Science Digital Library

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

Office Of Educational Partnerships

253

Combined conductive-radiative heat transfer in a two-dimensional enclosure is considered. The numerical procedure is based on a combination of two previous techniques that have been demonstrated to be successful for a two-dimensional pure radiation problem and a one-dimensional combined conductive-radiative heat transfer problem, respectively. Both temperature profile and heat transfer distributions are generated efficiently and accurately. Numerical data are presented

W. W. Yuen; E. E. Takara

1988-01-01

254

... Performance Characteristics Â·Engine waste heat and exhaust heat is used at low temperatures as heating energy in the exhaust heat exchanger 100% Heating Energy Heating Mode Cooling Mode #12;Gas Heat Pump Â Performance#12;Ecological and Economical efficient Heating and Cooling by innovative Gas Motor Heat Pump

Oak Ridge National Laboratory

255

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

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

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

1994-11-29

256

Study of a high performance evaporative heat transfer surface

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

257

Power Transfer Efficiency of Plasma Sources

NASA Astrophysics Data System (ADS)

There are many devices to produce gas discharge plasmas. They differ by the method of plasma coupling to the electrical energy source. In order to create self-sustained gas-discharge plasma with given gas pressure and plasma density, a certain amount of power Pp has to be delivered to plasma electrons to compensate for electron energy losses. As shown in this presentation, this power does not depend on the specifics of electron interaction with electromagnetic field and is basically the same for all types of discharges. Some additional power loss Pc associated with power dissipation in the plasma supporting means (like thermionic cathode, cathode fall, rf antenna and matching network) is unavoidable to maintain self-sustained plasma. That is accounted for by the power transfer efficiency ? =Pp /(Pp +Pc ). Efficiency analysis of different plasma sources is given in this presentation. It is shown that the largest values of efficiency are found in the plasma sources for lighting and the lowest in the plasma for processing of materials. The presentation explains this disparity and challenges some wide spread mythology about unique efficiency of some plasma sources.

Godyak, Valery

2004-09-01

258

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

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

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

2006-07-01

259

This report presents the description of a liquid sodium heat transfer facility (sodium loop) constructed to support the study of transient response of heat pipes. The facility, consisting of the loop itself, a safety system, and a data acquisition system, can be safely operated over a wide range of temperature and sodium flow rate. The transient response of a heat

L. C. Chow; O. J. Hahn; H. X. Nguyen

1992-01-01

260

ADAPTIVE TRANSFER ADJUSTMENT IN EFFICIENT BULK DATA TRANSFER MANAGEMENT FOR CLIMATE DATASET

ADAPTIVE TRANSFER ADJUSTMENT IN EFFICIENT BULK DATA TRANSFER MANAGEMENT FOR CLIMATE DATASET Alex from the adaptive transfer adjustment methodology. KEY WORDS Bulk data movement, Climate datasets physics, astrophysics, climate observation and modeling, combustion, nano-scale material sciences

261

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

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

2014-01-01

262

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

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

2014-01-01

263

In this part of the paper, the performance of the simultaneous charging\\/discharging operation modes of the heat pipe heat exchanger with latent heat storage is experimentally studied. The experimental results show that the device may operate under either the fluid to fluid heat transfer with charging heat to the phase change material (PCM) or the fluid to fluid heat transfer

Zhongliang Liu; Zengyi Wang; Chongfang Ma

2006-01-01

264

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

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

Lee, Jeongik

2007-01-01

265

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

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

Hakan Demir; Ahmet Koyun; Galip Temir

2009-01-01

266

Heat transfer for water flow in trapezoidal silicon microchannels

Experiments were conducted to investigate heat transfer characteristics of water flowing through trapezoidal silicon microchannels with a hydraulic diameter ranging from 62 to 169 ?m. A numerical analysis was also carried out by solving a conjugate heat transfer problem involving simultaneous determination of the temperature field in both the solid and the fluid regions. The experimental results were compared with

Weilin Qu; Gh. Mohiuddin Mala; Dongqing Li

2000-01-01

267

A Reference Model for Ground Coupled Heat Transfer

A recently completed extension to IEA BESTEST includes further work on tests suitable for the validation of ground coupled heat transfer modules within building energy simulation software. The model described here forms part of this work. A finite difference model was prepared and applied to ground coupled heat transfer in the environs of a building for a range of geometries

Michael Crowley

2009-01-01

268

Heat transfer to impinging isothermal gas and flame jets

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

R. Viskanta

1993-01-01

269

Enhanced radiative heat transfer between nanostructured gold plates

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

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

2012-03-07

270

Ultrasonic enhancement of heat transfer on narrow surface

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

Shinfuku Nomura; Masafumi Nakagawa

1994-01-01

271

Effect of acoustic cavitation on boiling heat transfer

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

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

2002-01-01

272

Mixed convection heat transfer in concave and convex channels

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

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

1997-07-01

273

Capillary Pumped Heat Transfer (CHT) Experiment

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

274

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

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

2009-01-01

275

Heat and mass transfer in fixed and fluidized beds

This book includes papers reviewing the fundamentals of heat and mass transfer and features studies on special processes in packed and fluidized beds, new application areas, and special orientation regimes. The topics presented cover: fluid particle transfer in packed beds; heat transfer in fixed submerged surfaces in fluidized beds; fundamentals and measurements and applications; heat and mass transfer to suspended objects in fluidized beds; modeling of fluidized bed reactors; fluidized bed combustion and gasification; special fluidized bed processes; liquid and three-phase fluidization; packed bed reactor; and special operations in fluidized beds.

Van Swaaij, W.P.M.; Afgan, N.H.

1985-01-01

276

Condensation Heat Transfer Performance of Nano- Engineered Cu Surfaces

NASA Astrophysics Data System (ADS)

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

Kim, Hyunsik; Nam, Youngsuk

2014-11-01

277

A review of NASA combustor and turbine heat transfer research

NASA Technical Reports Server (NTRS)

The thermal design of the combustor and turbine of a gas turbine engine poses a number of difficult heat transfer 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 heat transfer 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 heat transfer phenomena that occur in the hot sections of the gas turbine but at low enthalpy conditions; (2) analytical modeling of these flow and heat transfer 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 heat transfer research will be described and discussed.

Rudey, R. A.; Graham, R. W.

1984-01-01

278

Heat transfer between elastic solids with randomly rough surfaces

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

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

2009-08-27

279

Two phase heat transfer in tubes, rod bundles and blockages

Available two-component two phase heat transfer data in tubes have been reviewed. Based on momentum transfer considerations and the important influence of turbulence in the continuous phase, two phase heat transfer 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

1982-01-01

280

Dual circuit embossed sheet heat transfer panel

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

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

1984-01-01

281

Dual circuit embossed sheet heat transfer panel

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

Morgan, G.D.

1984-02-21

282

of tube is widely used in high flow rate applications because the heat transfer enhancement in high flow rates (turbulent region) is more pronounced than that in the low flow rates (laminar region). Khanpara and shell-side condensers to increase heat transfer. This enables water chillers to reach high efficiency

Ghajar, Afshin J.

283

Predicting spacecraft multilayer insulation performance from heat transfer measurements

NASA Technical Reports Server (NTRS)

Multilayer insulation (MLI) ideally consists of a series of radiation shields with low-conductivity spacers. When MLI blankets were installed on cryogenic tanks or spacecraft, a large discrepancy between the calorimeter measurements and the performance of the installed blankets was discovered. It was found that discontinuities such as exposed edges coupled with high lateral heat transfer created 'heat leaks' which overshadowed the basic heat transfer of the insulation. Approaches leading to improved performance predictions of MLI units are discussed.

Stimpson, L. D.; Hagemeyer, W. A.

1974-01-01

284

Heat transfer and film cooling with steam injection

HEAT TRANSFER AND FILM COOLING WITH STEAM INJECTION A Thesis by GARY EUGENE CONKLIN Submitted to the Graduate College of Texas AIM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1982 Major... Subject: Mechanical Engineering HEAT TRANSFER AND FILM COOLING WITH STEAM INJECTION A Thesis by GARY EUGENE CONKLIN Approved as to style and content by: (Chairm of Committee) (Member) (Memb e r) (Me r (Head Departme ) May 1982 ABSTRACT Heat...

Conklin, Gary Eugene

2012-06-07

285

Mixture effects on horizontal convective boiling heat transfer

Mixture effects were studied in horizontal convective heat transfer for both nonazeotropic, R22\\/R114, and azeotropic, R12\\/R152a, mixtures. A test facility was designed, constructed, and operated to simulate evaporators in heat pump and refrigeration systems. More than 3000 local two-phase heat transfer coefficients were obtained under steady state condition for annular flow at a reduced pressure of 0.08. The ranges of

1988-01-01

286

Laser Measurement Of Convective-Heat-Transfer Coefficient

NASA Technical Reports Server (NTRS)

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.

1994-01-01

287

Heat transfer performance of an external receiver pipe under unilateral concentrated solar radiation

The heat transfer and absorption characteristics of an external receiver pipe under unilateral concentrated solar radiation are theoretically investigated. Since the heat loss ratio of the infrared radiation has maximum at moderate energy flux, the heat absorption efficiency will first increase and then decrease with the incident energy flux. The local absorption efficiency will increase with the flow velocity, while the wall temperature drops quickly. Because of the unilateral concentrated solar radiation and different incident angle, the heat transfer is uneven along the circumference. Near the perpendicularly incident region, the wall temperature and absorption efficiency slowly approaches to the maximum, while the absorption efficiency sharply drops near the parallelly incident region. The calculation results show that the heat transfer parameters calculated from the average incident energy flux have a good agreement with the average values of the circumference under different boundary conditions. For the whole pipe with coating of Pyromark, the absorption efficiency of the main region is above 85%, and only the absorption efficiency near the parallelly incident region is below 80%. In general, the absorption efficiency of the whole pipe increases with flow velocity rising and pipe length decreasing, and it approaches to the maximum at optimal concentrated solar flux. (author)

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)

2010-11-15

288

Efficient Gene Transfer in Bacterial Cell Chains

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

Babic, Ana

289

Natural convection heat transfer from two horizontal cylinders

Natural convection heat transfer from a single horizontal cylinder and a pair of vertically aligned horizontal cylinders is investigated. Surface heat transfer distributions around the circumference of the cylinders are presented for Rayleigh numbers of 2 x 10{sup 6}, 4 x 10{sup 6} and 6 x 10{sup 6} and a range of cylinder spacings of 1.5, 2 and 3 diameters. With a cylinder pairing the lower cylinder is unaffected by the presence of the second cylinder; the same is true of the upper cylinder if the lower one is not heated. However, when both cylinders are heated it has been found that a plume rising from the heated lower cylinder interacts with the upper cylinder and significantly affects the surface heat transfer distribution. Spectral analysis of surface heat transfer signals has established the influence of the plume oscillations on the heat transfer. Thus, when the plume from the lower cylinder oscillates out of phase with the flow around the upper cylinder it increases the mixing and results in enhanced heat transfer. (author)

Reymond, Olivier; Murray, Darina B. [Department of Mechanical and Manufacturing Engineering, Trinity College Dublin (Ireland); O'Donovan, Tadhg S. [School of Engineering and Physical Sciences, Heriot-Watt University, Nasmyth Building, Edinburgh EH14 4AS (United Kingdom)

2008-09-15

290

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

Purna Chandra Mishra

291

Droplet Evaporator For High-Capacity Heat Transfer

NASA Technical Reports Server (NTRS)

Proposed heat-exchange scheme boosts heat transfer 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.

Valenzuela, Javier A.

1993-01-01

292

Heat transfer in a combination microwave–jet impingement oven

Combination heating of food using microwave and jet impingement has been simulated by coupling Maxwell’s equations of electromagnetics with energy equation and using experimentally measured heat transfer coefficient values for jet impingement in a novel domestic oven. Transient food temperatures from the model and experiment for each separate heating mode and their combination revealed the characteristic nature of each of

S. Geedipalli; A. K. Datta; V. Rakesh

2008-01-01

293

Heat transfer in open-cell metal foams

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

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

1998-01-01

294

Convective heat transfer measurements of plants in a wind tunnel

Heat transfer 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

A. Kumar; N. Barthakur

1971-01-01

295

Experiments on microgravity boiling heat transfer by using transparent heaters

To clarify the relation between the liquid–vapor behavior and the heat transfer characteristics in the boiling phenomena, the structures of transparent heaters were developed for both flow boiling and pool boiling experiments and were applied to the microgravity environment realized by the parabolic flight of aircraft. In the flow boiling experiment, a transparent heated tube makes the heating, the observation

H Ohta

1997-01-01

296

Solar power plant equipped with high efficiency heat exchangers

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

Moisdon

1981-01-01

297

NASA Astrophysics Data System (ADS)

The performance of real heat engines can be characterized by their power versus efficiency curves. Real heat engines with sources of irreversibility that include friction and heat leaks exhibit fundamentally different power versus efficiency curves than those predicted by many previous studies in the finite-time thermodynamics of endoreversible heat engines, in which finite-rate heat transfer was the only irreversibility considered. It is shown that the thermoelectric generator provides an instructive illustration of a cyclic, irreversible heat engine with a power versus efficiency curve that qualitatively reproduces the key features of the corresponding curves for real heat engines. The generic sources of irreversibility are easily identifiable and analytically expressed so as to reveal more transparently the basis for the power versus efficiency characteristic.

Gordon, J. M.

1991-06-01

298

Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

NASA Technical Reports Server (NTRS)

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

Cross, M. F.

2011-01-01

299

??The spectacular heat transfer enhancement revealed experimentally in nanofluids suspensions is being investigated theoretically at the macro-scale level aiming at explaining the possible mechanisms that… (more)

Vadasz, Johnathan J.

2005-01-01

300

Heat transfer and flow characteristics on a gas turbine shroud.

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

Obata, M; Kumada, M; Ijichi, N

2001-05-01

301

Enhancement of heat transfer and the potential for energy conservation in industrial oil coolers

NASA Astrophysics Data System (ADS)

Problems relating to enhancement of heat transfer and energy conservation in oil-water and oil-air oil coolers used at thermal and nuclear power stations are considered. Results from a calculation study on analyzing the efficiency of a few most advanced intensifiers of heat transfer are presented. The most efficient intensifiers are determined, and their considerable possibilities for energy conservation and saving of structural materials are estimated. industrial recommendations for improving the design of coolers and using preferable intensifiers are proposed and substantiated.

Olimpiev, V. V.

2010-08-01

302

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

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

Shiralkar, B. S.

1968-01-01

303

Thermal entrance length in falling liquid film heat transfer

Subcooled and evaporating falling liquid films are frequently encountered in the process industry, desalination, and nuclear reactor safety. Thermal entrance lengths in a subcooled falling liquid film were studied experimentally on a vertical cylindrical heater preceded by an adiabatic section. A wavy-laminar flow regime close to the transition to turbulent flow was achieved. Water at atmospheric pressure was used as the test fluid. Heating surface temperatures were measured at eight axial locations along the flow direction and the local heat transfer coefficients were obtained as functions of heat flux and mass flow rate. Heat transfer coefficients were observed decreasing along the heater and reaching a minimum. The influences of the Reynolds number and heat flux on the thermal entrance length at low heat fluxes were weak. Both the Reynolds number and the heat flux strongly influenced the thermal entrance length at relatively high heat fluxes.

Ulucakli, E. [Lafayette Coll., Easton, PA (United States). Dept. of Mechanical Engineering

1996-06-01

304

Wall-to-suspension heat transfer in circulating fluidized beds

The wall-to-suspension heat transfer in circulating fluidized beds depends on the fluid mechanics immediately near the wall and on the thermal properties of the gas used. Experimental investigations of circulating fluidized beds of low dimensionless pressure gradients with different solid particles like bronze, glass and polystyrene at ambient temperatures showed no influence of the conductivity and the heat capacity of the solids on the heat transfer coefficient. Consequently the heat transfer coefficient in the form of the dimensionless Nusselt number can be described by the dimensionless numbers which characterize the gas-solid-flow near the wall. These numbers are the Archimedes number and the pressure drop-number. The last number relates the cross-sectional average solids concentration to the solids concentration at minimum fluidization condition. With the aid of a model of segregated vertical gas-solid flow, the flow pattern in the wall region can be calculated and thus the wall heat transfer which depends only on heat conduction in the gas and on the convective heat transfer by the gas. With elevated suspension temperatures, radiation contributes additionally to the heat transfer. When the solids concentration is low, the effect of the radiation on the heat transfer is high. Increasing solids concentration results in a decrease of the radiation effect due to the wall being shielded from the radiation of the hot particles in the core region by the cold solids clusters moving down the wall. A simple correlation is presented for calculating the wall-to-suspension heat transfer in circulating fluidized beds.

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

1995-12-31

305

Concepts and realization of microstructure heat exchangers for enhanced heat transfer

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 heat transfer. Another parameter governing for the heat transfer is the lateral characteristic dimension of the heat transfer 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 heat transfer rate. Another possible way of increasing the heat transfer 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 heat transfer 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)

2006-08-15

306

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

Flow boiling of R-123 in a hydrofoil-based micro pin fin heat sink was investigated. Average two-phase heat transfer 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. Heat transfer

Ali Ko?ar; Yoav Peles

2007-01-01

307

Heat and Mass Transfer Processes in Scrubber of Flue Gas Heat Recovery Device

NASA Astrophysics Data System (ADS)

The paper deals with the heat and mass transfer process research in a flue gas heat recovery device, where complicated cooling, evaporation and condensation processes are taking place simultaneously. The analogy between heat and mass transfer is used during the process of analysis. In order to prepare a detailed process analysis based on heat and mass process descriptive equations, as well as the correlation for wet gas parameter calculation, software in the

Veidenbergs, Ivars; Blumberga, Dagnija; Vigants, Edgars; Kozuhars, Grigorijs

2010-01-01

308

Heat transfer in a pulsating heat pipe with open end Yuwen Zhang 1

and condenser sections of a pulsating heat pipe (PHP) with open end is modeled by analyzing thin Â®lm evaporation and condensation. The heat transfer solutions are applied to the thermal model of the pulsating heat pipe to the exchange of sensible heat. The frequency and amplitude of the oscillation is almost unaected by surface

Zhang, Yuwen

309

Although fouling on heat exchanger tubes is extensively investigated, due to the lack of energy resources, the effects of fouling on heat exchangers is still an important area of study and gaining more and more attention every day. In this study we investigated the effects of fouling on heat transfer and flow structures numerically for cross-flow heat exchanger tube geometry.

Y. Kaptan; E. Buyruk; A. Ecder

2008-01-01

310

The present study has been carried out to predict the heat transfer characteristics of a residential refrigerator through insulation wall by using reverse heat loss method. The temperature time history characteristics were measured to achieve the steady state condition. In this experiment the steady state condition was reached at about 20h of heating. The temperature and heat inputs were then

Jae Seong Sim; Ji Soo Ha

2011-01-01

311

A review on boiling heat transfer enhancement with nanofluids

There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794

2011-01-01

312

Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor of transpiration). The boundary layer conductance to heat transfer is small enough that leaf temperature can become that produces clumped shoot morphol- ogy on sun-formed branches. Boundary layer conductances estimated

Martin, Timothy

313

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2013 CFR

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2013-10-01

314

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Heat transfer fluids: compatibility with cargo...Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo...

2011-10-01

315

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 false Heat transfer fluids: compatibility with cargo...Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo...

2014-10-01

316

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Heat transfer fluids: compatibility with cargo...Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo...

2010-10-01

317

46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Heat transfer fluids: compatibility with cargo...Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo...

2012-10-01

318

Fourier analysis of conductive heat transfer for glazed roofing materials

NASA Astrophysics Data System (ADS)

For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.

Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini

2014-07-01

319

Boiling heat transfer and droplet spreading of nanofluids.

Nanofluids- a new class of heat transfer fluids have recently been a very attractive area of research due to their fascinating thermophysical properties and numerous potential benefits and applications in many important fields. However, there are many controversies and inconsistencies in reported arguments and experimental results on various thermal characteristics such as effective thermal conductivity, convective heat transfer coefficient and boiling heat transfer rate of nanofluids. As of today, researchers have mostly focused on anomalous thermal conductivity of nanofluids. Although investigations on boiling and droplet spreading are very important for practical application of nanofluids as advanced coolants, considerably fewer efforts have been made on these thermal features of nanofluids. In this paper, recent research and development in boiling heat transfer and droplet spreading of nanofluids are reviewed together with summarizing most related patents on nanofluids published in literature. Review reveals that despite some inconsistent results nanofluids exhibit significantly higher boiling heat transfer performance compared to their base fluids and show great promises to be used as advanced heat transfer fluids in numerous applications. However, there is a clear lack of in-depth understanding of heat transport mechanisms during phase change of nanofluids. It is also found that the nanofluids related patents are limited and among them most of the patents are based on thermal conductivity enhancement and synthesising processes of specific type of nanofluids. PMID:24330044

Murshed, S M Sohel; de Castro, C A Nieto

2013-11-01

320

Heat transfer through an extended surface containing He II

A semi-analytic solution for the heat transfer process between a He II pressurized bath and a saturated tube-type heat exchanger is presented. The problem is modeled with an extended surface heat transfer formulation analogous to that in conventional conduction. The process is governed by Kapitza conductance and counterflow within the bulk fluid in the tube. The resulting nonlinear differential equation may be integrated for the special case of constant properties, yielding a simple solution applicable to design and analysis of practical heat exchangers.

Van Sciver, S.W. [FAMU-FLU Coll. of Engineering, Tallahassee, FL (United States)

1999-02-01

321

Heat transfer in large-scale heavy-gas dispersion.

Heavy-gas dispersion of practical interest is usually cold gas dispersion with the enthalpy deficit as the main cause of the density effect. New analysis of existing field experiment data suggests that heat transfer from the ground sometimes reduces this thermally induced density effect considerably. The limited heat capacity of the ground implies that heat transfer to a gas plume must disappear eventually, and our interpretation of Desert Tortoise measurements indicates that the surface heat flux decreased by 38% during a 3-min long release period. PMID:10334831

Nielsen, M; Ott, S

1999-05-31

322

Heat transfer performance of internally finned tubes in turbulent flow

NASA Astrophysics Data System (ADS)

The heat transfer performance for heating water in turbulent flow was experimentally determined for 11 tubes having integral internal spiral and longitudinal fins. Individual tube performance is presented and compared with a smooth tube datum at constant pumping power. A longitudinal and spiral fin tube from within the 11 tubes and a smooth tube were also tested heating a 50% w/w ethylene glycol-water solution, and these data are included. These data are compared with relevant data available in the literature. Correlating equations are presented for heat transfer and Fanning friction factor that describe the air, water, and ethylene glycol-water data within + or - 10%.

Carnavos, T. C.

1980-06-01

323

NASA Astrophysics Data System (ADS)

An adjoint-based shape optimization method of heat exchangers, which takes into account the heat transfer performance with the pressure loss penalty, is proposed, and its effectiveness is examined through a series of numerical simulation. Undulated heat transfer surface is optimized under an isothermal heated condition based on the variational method with the first derivative of the cost function, which is determined by an adjoint analysis of momentum and heat transfer. When applied to a modeled heat-exchanger passage with a pair of oblique wavy walls, the present optimization method refines the duct shape so as to enhance the heat transfer while suppressing the flow separation. It is shown that the j/f factor is further increased by 4% from the best value of the initial obliquely wavy duct. The effects of the initial wave amplitude upon the shape evolution process are also investigated.

Morimoto, Kenichi; Suzuki, Yuji; Kasagi, Nobuhide

324

Transient Heat Transfer in TCAP Coils

The Thermal Cycling Absorption Process (TCAP) is used to separate isotopes of hydrogen. TCAP involves passing a stream of mixed hydrogen isotopes through palladium deposited on kieselguhr (Pd/k) while cycling the temperature of the Pd/k. Kieselguhr is a silica mineral also called diatomite. To aid in the design of a full scale facility, the Thermal Fluids Laboratory was used by the Chemical and Hydrogen Technology Section to compare the heat transfer properties of three different configurations of stainless steel coils containing kieselguhr and helium. Testing of coils containing Pd/k and hydrogen isotopes would have been more prototypical but would have been too expensive. Three stainless steel coils filled with kieselguhr were tested; one made from 2.0 inch diameter tubing, one made from 2.0 inch diameter tubing with foam copper embedded in the kieselguhr and one made from 1.25 inch diameter tubing. It was known prior to testing that increasing the tubing diameter from 1.25 inch to 2.0 inch would slow the rate of temperature change. The primary purpose of the testing was to measure to what extent the presence of copper foam in a 2.0" tubing coil would compensate for the effect of larger diameter. Each coil was connected to a pressure gage and the coil was evacuated and backfilled with helium gas. Helium was used instead of a mixture of hydrogen isotopes for reasons of safety. Each coil was quickly immersed in a stirred bath of ethylene glycol at a temperature of approximately 100 degrees Celsius. The coil pressure increased, reflecting the increase in average temperature of its contents. The pressure transient was recored as a function of time after immersion. Because of the actual process will use Pd/k instead of kieselguhr, additional tests were run to determine the differences in thermal properties between the two materials. The method was to position a thermocouple at the center of a hollow sphere and pack the sphere with Pd/k. The sphere was sealed, quickly submerged in a bath of boiling water and the temperature transient was recorded. There sphere was then opened, the Pd/k was replaced with kieselguhr and the transient was repeated. The response was a factor of 1.4 faster for Pd/k than for kieselguhr, implying a thermal diffusivity approximately 40 percent higher than for kieselguhr. Another implication is that the transient tests with the coils would have proceeded faster if the coils had been filled with Pd/k rather than kieselguhr.

Steimke, J.L.

1999-03-09

325

The heat transfer enhancement caused by the application of a low-frequency (1 {approximately} 16 Hz) alternating field having the sinusoidal waveform has been studied experimentally with water drops in a medium of silicone oil. The heat transfer coefficients has been found to peak at three particular frequencies. The data newly obtained with the sinusoidal waveform are compared with earlier results obained with electric fields having other waveforms. The waveform and the frequency that yield the largest enhancement of heat transfer are sought.

Kaji, N. (Institute of Vocational and Technical Education, Sagamihara (Japan)); Mori, Y.H. (Keio Univ., Yokahama (Japan)); Tochitani, Y. (Kabazawa Inst. of Tech., Nonoichi (Japan))

1988-08-01

326

Overview of NASA Glenn Research Center Programs in Aero-Heat Transfer and Future Needs

NASA Technical Reports Server (NTRS)

This presentation concentrates on an overview of the NASA Glenn Research Center and the projects that are supporting Turbine Aero-Heat Transfer Research. The principal areas include the Ultra Efficient Engine Technology (UEET) Project, the Advanced Space Transportation Program (ASTP) Revolutionary Turbine Accelerator (RTA) Turbine Based Combined Cycle (TBCC) project, and the Propulsion & Power Base R&T - Smart Efficient Components (SEC), and Revolutionary Aeropropulsion Concepts (RAC) Projects. In addition, highlights are presented of the turbine aero-heat transfer work currently underway at NASA Glenn, focusing on the use of the Glenn-HT Navier- Stokes code as the vehicle for research in turbulence & transition modeling, grid topology generation, unsteady effects, and conjugate heat transfer.

Gaugler, Raymond E.

2002-01-01

327

Heat transfer during film condensation of a liquid metal vapor

The object of this investigation is to resolve the discrepancy between theory and experiment for the case of heat transfer durirnfilm condensation of liquid metal vapors. Experiments by previous investigators have yielded ...

Sukhatme, S. P.

1964-01-01

328

Survey and evaluation of techniques to augment convective heat transfer

This report presents a survey and evaluation of the numerous techniques which have been shown to augment convective heat transfer. These techniques are: surface promoters, including roughness and treatment; displaced ...

Bergles A. E.

1965-01-01

329

Non-intrusive characterization of heat transfer fluid aerosol formation

involves non-intrusive measurement of such aerosol sprays using a Malvern Instrument Diffraction Particle Analyzer. The aerosol is generated by plain orifice atomization to simulate the formation and dispersion of heat transfer fluid aerosols through leaks...

Krishna, Kiran

2012-06-07

330

Effects of operating conditions on a heat transfer fluid aerosol

of heat transfer fluid aerosols from process leaks. To simulate industrial leaks, aerosol formation from a plain orifice into ambient air is studied by measuring liquid drop sizes and size distributions at various distances from an orifice. Measurements...

Sukmarg, Passaporn

2012-06-07

331

The Advantages of Sealless Pumps in Heat Transfer Fluid Services

The expectations for heat transfer fluid (HTF) system safety and reliability are continuing to increase. The challenges are many. Leaks produce vapors that ignite readily, fluid viscosity is very low, and many of the fluids react with oxygen...

Smith, M. D.

332

RELAP5 MOD3.1.1 is being used to simulate Loss of Coolant Accidents (LOCA) for the Simplified Boiling Water Reactor (SBWR) being proposed by General Electric (GE). One of the major components associated with the SBWR is the Passive Containment Cooling System (PCCS) which provides the long-term heat sink to reject decay heat. The RELAP5 MOD3.1.1 code is being assessed for its ability to represent accurately the PCCS. Data from the Phase 1, Step 1 Heat Transfer Tests performed at Toshiba`s Gravity-Driven Integral Full-Height Test for Passive Heat Removal (GIRAFFE) facility will be used for assessing the ability of RELAP5 to model condensation in the presence of noncondensables. The RELAP5 MOD3.1.1 condensation model uses the University of California at Berkeley (UCB) correlation developed by Vierow and Schrock. The RELAP5 code uses this heat transfer coefficient with the gas velocity effect multiplier being limited to 2. This heat transfer option was used to analyze the condensation heat transfer in the GIRAFFE PCCS heat exchanger tubes in the Phase 1, Step 1 Heat Transfer Tests which were at a pressure of 3 bar and had a range of nitrogen partial pressure fractions from 0.0 to 0.10. The results of a set of RELAP5 calculations al these conditions were compared with the GIRAFFE data. The effects of PCCS cell nodings on the heat transfer process were also studied. The UCB correlation, as implemented in RELAP5, predicted the heat transfer to {+-}5% of the data with a three-node model. The three-node model has a large cell in the entrance region which smeared out the entrance effects on the heat transfer, which tend to overpredict the condensation. Hence, the UCB correlation predicts condensation heat transfer in the presence of noncondensable gases with only a coarse mesh. The cell length term in the condensation heat transfer correlation implemented in the code must be removed to allow for accurate calculations with smaller cell sizes.

Boyer, B.D.; Parlatan, Y.; Slovik, G.C.; Rohatgi, U.S.

1995-09-01

333

NASA Astrophysics Data System (ADS)

Based on the earlier developed model of calculation of the local parameters of heat and mass transfer in deep cooling of flue gases (a vapor-gas mixture) in a bundle of tubes of a condensation heat-utilization unit, the distribution of the parameters of a condensing vapor-gas mixture both along the length of the tubes and in the depth of the tube bundle in a crossflow under various cooling conditions corresponding to the working parameters of heat-utilization units at industrial thermoelectric plants (TEP) and in boiler houses has been obtained. A comparison of the calculated values of the heating efficiency of the indicated heat-utilization unit with the results of tests of the condensation heat-utilization unit at the Ul'yanovsk TEP-3 (Russia) has demonstrated their satisfactory agreement.

Borodulya, V. A.; Malevich, V. L.; Sinkevich, A. E.

2012-01-01

334

Particle-water heat transfer during explosive volcanic eruptions

NASA Astrophysics Data System (ADS)

Thermal interaction between volcanic particles and water during explosive eruptions has been quantified using a numerical heat transfer model for spherical particles. The model couples intraparticle conduction with heat transfer from the particle surface by boiling water in order to explore heat loss with time for a range of particle diameters. The results are combined with estimates of particle settling times to provide insight into heat removal during eruption from samples of volcanic particles produced by explosive eruption. Heat removal is restricted by resistance to heat transfer from the volcanic particles with intraparticle thermal conduction important for large particles and surface cooling by boiling dominating for small particles. In most cases, volcanic particles approach thermal equilibrium with the surrounding fluid during an explosive eruption. Application of the results to a sample from the Gjálp 1996, Iceland eruption indicates that, relative to 0?C, 70-80% of the heat is transferred from the particles to boiling water during the settling time before burial in the stratigraphic succession. The implication is that, for subglacial explosive eruptions, much of the heat content of the magma is coupled into melting ice extremely rapidly. If all particles of the Gjálp 1996 deposit were cooled to the local boiling point by the end of the eruption then approximately 78% of the initial heat content was removed from the erupting magma during the eruption. This is consistent with calorimetric calculations based on volumes of ice melted during and after the eruption.

Woodcock, D. C.; Gilbert, J. S.; Lane, S. J.

2012-10-01

335

High-Power Liquid-Metal Heat-Transfer Loop

NASA Technical Reports Server (NTRS)

Proposed closed-loop system for transfer of thermal power operates at relatively high differential pressure between vapor and liquid phases of liquid-metal working fluid. Resembles "capillary-pumped" liquid-metal heat-transfer loop except electric field across permselective barrier of beta alumina keeps liquid and vapor separate at heat-input end. Increases output thermal power, contains no moving parts, highly reliable and well suited to long-term unattended operation.

Bhandari, Pradeep; Fujita, Toshio

1991-01-01

336

Enhanced heat transfer in inclined solar chimneys by electrohydrodynamic technique

Heat transfer enhancement of natural convection inside the inclined solar chimneys is investigated using electrohydrodynamic technique. The interactions between electric field, flow field, and temperature field are analyzed. The ranges of parameters considered are 104?Ra?107, 7.5kV?V0?17.5kV, 30°???120°, and 2?aspect ratio?14. Flow and heat transfer enhancements are significantly influenced at low Rayleigh number. The optimum inclined angle which obtains maximum volume

Nat Kasayapanand

2008-01-01

337

Prediction of electronic component-board transient conjugate heat transfer

Numerical analysis of electronic component transient heat transfer has generally been confined to nonconjugate methods. This study discusses the need for conjugate (conduction\\/convection) analysis, both for component temperature and thermo-mechanical behavior prediction in operational, assembly and reliability qualification environments. The capability of computational fluid dynamics (CFD) analysis to predict component transient conjugate heat transfer is investigated using an industry-standard CFD

Valérie Eveloy; Peter Rodgers

2005-01-01

338

Heat transfer investigations in a slurry bubble column

Slurry bubble columns, for use in Fisher-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven- or thirty-seven tubes. The experiments were conducted

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

1991-01-01

339

Heat transfer investigations in a slurry bubble column

Slurry bubble columns, for use in Fischer-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven-, or thirty-seven tubes. the experiments were conducted

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

1991-01-01

340

Application of ray tracing in radiation heat transfer

NASA Technical Reports Server (NTRS)

This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.

Baumeister, Joseph F.

1993-01-01

341

Augmentation of natural convective heat transfer by acoustic cavitation

An experimental study was conducted to investigate the effects of acoustic cavitation on natural convective heat transfer\\u000a from a horizontal circular tube. The experimental results indicated that heat transfer could be enhanced by acoustic cavitation\\u000a and had the best effect when the head of the ultrasonic transducer was over the midpoint of the circular tube, and the distance\\u000a between the

Jun Cai; Xiulan Huai; Shiqiang Liang; Xunfeng Li

2010-01-01

342

The heat transfer enhancement in the latent heat thermal energy storage system by using an internally finned tube is presented in this paper. The phase change material fills the annular shell space around the tube, while the transfer fluid flows within the internally finned tube. The melting of the phase change material is described by a temperature transforming model coupled

Yuwen Zhang; A. Faghri

1996-01-01

343

The Experimental Study on Heat Transfer Characteristics of The External Heat Exchanger

NASA Astrophysics Data System (ADS)

Using the external heat exchanger in large-scale CFB boilers can control combustion and heat transfer separately, make the adjustments of bed temperature and steam temperature convenient. The state of gas-solid two phase flow in the external heat exchanger is bubbling fluidized bed, but differs from the regular one as there is a directional flow in it. Consequently, the temperature distribution changes along the flow direction. In order to study the heat transfer characteristics of the water cooled tubes in the bubbling fluidized bed and ensure the uniformity of heat transfer in the external heat exchanger, a physical model was set up according to the similarity principle and at the geometric ratio of 1?28 to an external heat exchanger of a 300MW CFB boiler. The model was connected with an electrically heated CFB test-bed which provides the circulating particles. The influencing factors and the distribution rule of the particles' heat transfer coefficient in the external heat exchanger were assessed by measuring the temperature changes of the water in the tubes and different parts of particles flow along the flow direction. At the end, an empirical correlation of particles' heat transfer coefficient in external heat exchanger was given by modifying the Veedendery empirical correlation.

Ji, X. Y.; Lu, X. F.; Yang, L.; Liu, H. Z.

344

High Reynolds Number and Turbulence Effects on Turbine Heat Transfer

NASA Technical Reports Server (NTRS)

Experimental data on pressure distribution and heat transfer on a turbine airfoil were obtained over a range of Reynolds numbers from 0.75 to 7.0 x 10(exp 6) and a range of turbulence intensities from 1.8 to about 15%. The purpose of this study was to obtain fundamental heat transfer and pressure distribution data over a wide range of high Reynolds numbers and to extend the heat transfer data base to include the range or Reynolds numbers encountered in the Space Shuttle main engine turbopump turbines. The results of this study indicated that Reynolds number and turbulence intensity have a large effect on both the transition from laminar to turbulent flow and the resulting heat transfer. For a given turbulence intensity, heat transfer for all Reynolds numbers at the leading edge can generally be correlated with the Frossling number developed for lower Reynolds numbers. For a given turbulence intensity, heat transfer for the airfoil surfaces downstream of the leading edge can be approximately correlated with a dimensionless parameter. Comparisons of the experimental results were also made with a numerical solution from a two-dimensional Navier-Stokes code.

Yeh, Frederick C.; Hippensteele, Steven A.; vanFossen, G. James; Poinsatte, Philip E.; Ameri, Ali

1994-01-01

345

Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation

NASA Technical Reports Server (NTRS)

Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.

Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.

2012-01-01

346

Literature survey of heat transfer enhancement techniques in refrigeration applications

A survey has been performed of the technical and patent literature on enhanced heat transfer of refrigerants in pool boiling, forced convection evaporation, and condensation. Extensive bibliographies of the technical literature and patents are given. Many passive and active techniques were examined for pure refrigerants, refrigerant-oil mixtures, and refrigerant mixtures. The citations were categorized according to enhancement technique, heat transfer mode, and tube or shell side focus. The effects of the enhancement techniques relative to smooth and/or pure refrigerants were illustrated through the discussion of selected papers. Patented enhancement techniques also are discussed. Enhanced heat transfer has demonstrated significant improvements in performance in many refrigerant applications. However, refrigerant mixtures and refrigerant-oil mixtures have not been studied extensively; no research has been performed with enhanced refrigerant mixtures with oil. Most studies have been of the parametric type; there has been inadequate examination of the fundamental processes governing enhanced refrigerant heat transfer, but some modeling is being done and correlations developed. It is clear that an enhancement technique must be optimized for the refrigerant and operating condition. Fundamental processes governing the heat transfer must be examined if models for enhancement techniques are to be developed; these models could provide the method to optimize a surface. Refrigerant mixtures, with and without oil present, must be studied with enhancement devices; there is too little known to be able to estimate the effects of mixtures (particularly NARMs) with enhanced heat transfer. Other conclusions and recommendations are offered.

Jensen, M.K.; Shome, B. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Mechanical Engineering, Aeronautical Engineering and Mechanics

1994-05-01

347

A general application heat transfer computer program

A computer program is proposed for accurate and rapid determination of transient temperature distributions in heated structures. The program has at its core the ability to calculate the finite difference approximations to the differential equations governing heat conduction in a solid. Boundary conditions that can be simulated include fixed or independently time varying boundary temperatures, fixed or independently time varying

R. K. Frazer

1975-01-01

348

Heat Transfer and Flow Structure Evaluation of a Synthetic Jet Emanating from a Planar Heat Sink

NASA Astrophysics Data System (ADS)

Direct impinging synthetic jets are a proven method for heat transfer enhancement, and have been subject to extensive research. However, despite the vast amount of research into direct synthetic jet impingement, there has been little research investigating the effects of a synthetic jet emanating from a heated surface, this forms the basis of the current research investigation. Both single and multiple orifices are integrated into a planar heat sink forming a synthetic jet, thus allowing the heat transfer enhancement and flow structures to be assessed. The heat transfer analysis highlighted that the multiple orifice synthetic jet resulted in the greatest heat transfer enhancements. The flow structures responsible for these enhancements were identified using a combination of flow visualisation, thermal imaging and thermal boundary layer analysis. The flow structure analysis identified that the synthetic jets decreased the thermal boundary layer thickness resulting in a more effective convective heat transfer process. Flow visualisation revealed entrainment of local air adjacent to the heated surface; this occurred from vortex roll-up at the surface of the heat sink and from the highly sheared jet flow. Furthermore, a secondary entrainment was identified which created a surface impingement effect. It is proposed that all three flow features enhance the heat transfer characteristics of the system.

Manning, Paul; Persoons, Tim; Murray, Darina

2014-07-01

349

HEAT AND MASS TRANSFER MODEL OF A GROUND HEAT EXCHANGER

A new approach to the simulation of a horizontal type Ground Heat Exchanger is proposed resulting in a better accuracy and at the same time a reduced computational effort. These results come from the concentration of the computational effort at the locations with the largest temperature and moisture gradients, i.e. the pipe-soil interface. The model takes into account heat and

Mirek Piechowski

350

D Simulation for Maximizing Electron Transfer Efficiency in Thick GEMS

NASA Astrophysics Data System (ADS)

Thick GEM for UV detector applications must provide high detection efficiency for a single photoelectron produced by UV light. Electron Transfer Efficiency (ETE) of GEM detector determines the detection efficiency. We have used GARFIELD simulation for estimation of ETE at various operating parameters, which are to be optimized for high detection efficiency.

Garai, Baishali; Rajanna, K.; Radhakrishna, V.

2012-08-01

351

A high-efficiency double quantum dot heat engine

NASA Astrophysics Data System (ADS)

High-efficiency heat engine requires a large output power at the cost of less input heat energy as possible. Here we propose a heat engine composed of serially connected two quantum dots sandwiched between two metallic electrodes. The efficiency of the heat engine can approach the maximum allowable Carnot efficiency ?C. We also find that the strong intradot Coulomb interaction can induce additional work regions for the heat engine, whereas the interdot Coulomb interaction always suppresses the efficiency. Our results presented here indicate a way to fabricate high-efficiency quantum-dot thermoelectric devices.

Liu, Y. S.; Yang, X. F.; Hong, X. K.; Si, M. S.; Chi, F.; Guo, Y.

2013-08-01

352

Rocket engine heat transfer and material technology for commercial applications

NASA Technical Reports Server (NTRS)

Liquid fueled rocket engine combustion, heat transfer, and material technology have been utilized in the design and development of compact combustion and heat exchange equipment intended for application in the commercial field. An initial application of the concepts to the design of a compact steam generator to be utilized by electrical utilities for the production of peaking power is described.

Hiltabiddle, J.; Campbell, J.

1974-01-01

353

Students' Misconceptions about Heat Transfer Mechanisms and Elementary Kinetic Theory

ERIC Educational Resources Information Center

Heat and thermodynamics is a conceptually rich area of undergraduate physics. In the Indian context in particular there has been little work done in this area from the point of view of misconceptions. This prompted us to undertake a study in this area. We present a study of students' misconceptions about heat transfer mechanisms, i.e. conduction,…

Pathare, S. R.; Pradhan, H. C.

2010-01-01

354

Entrance heat transfer in isosceles and right triangular ducts

Heat transfer in noncircular ducts is an important factor in the design of compact heat exchangers. A Galerkin-based integral method is presently used to conduct the requisite computations. The fully developed velocity distribution is obtained independent of the energy equation, because the physical properties do not depend on temperature. More accurate results may be obtained for right-triangular ducts with small

R. Lakshminarayanan; A. Haji-Sheikh

1992-01-01

355

Recent developments in modeling heat transfer in blood perfused tissues

Successful hyperthermia treatment of tumors requires understanding the attendant thermal processes in both diseased and healthy tissue. Accordingly, it is essential for developers and users of hyperthermia equipment to predict, measure and interpret correctly the tissue thermal and vascular response to heating. Modeling of heat transfer in living tissues is a means towards this end. Due to the complex morphology

H. Arkin; L. X. Xu; K. R. Holmes

1994-01-01

356

Recent Developments in Modeling Heat Transfer in Blood Perfused Tissues

Abstracf- Successful hyperthermia treatment of tumors re- quires understanding the attendant thermal processes in both diseased and healthy tissue. Accordingly, it is essential for devel- opers and users of hyperthermia equipment to predict, measure and interpret correctly the tissue thermal and vascular response to heating. Modeling of heat transfer in living tissues is a means towards this end. Due to

H. Arkin; L. X. Xu; K. R. Holmes

1994-01-01

357

Conductive heat transfer in salt gradient stabilized solar ponds

This paper deals with heat transfer in salt gradient solar ponds. Spatial variations in thermal properties have been considered and the resulting one-dimensional heat conduction equation with a source term is solved explicitly to obtain a closed form mathematical expression for temperature distribution in the non-convecting zone of the solar pond. The present analysis is not restricted to any one

Thakus

1983-01-01

358

ON SOME PROBLEMS OF HEAT TRANSFER IN FREE MOLECULE FLOW

The general theory for aerodynamic heating in free molecule flow is ; briefly presented. This is then applied to a cone and a paraboloid of revolution ; in an attempt to predict surface temperatures. Only the aerodynamic effects are ; considered, i.e., the entire heat transfer to the body is made by the energy ; exchange of the gas molecules

M. Z. v. Krzywoblocki; F. H. Bergonz

1959-01-01

359

Gas Turbine Blade Tip Heat Transfer and Cooling: A Literature Survey

Gas turbines are widely used for aircraft propulsion, land-base power generation, and other industrial applications like trains, marines, automobiles, etc. To satisfy the fast development of advanced gas turbines, the operating temperature must be increased to improve the thermal efficiency and output work of the gas turbine engine. However, the heat transferred to the turbine blade is substantially increased as

Bengt Sunden; Gongnan Xie

2010-01-01

360

An experimental study has been carried out for heat transfer and particle deposition during the outside vapor deposition process. The surface temperatures of deposited layers, and rates, efficiencies and porosities of particle deposition were measured. For the characterization of the burner used, temperature distributions in the flame were measured using thermocouples and the evolution of the particle sizes was obtained

Jaegeol Cho; Jaeyun Kim; Mansoo Choi

1998-01-01

361

Heat transfer phenomena are analyzed for test series 100 of the Thermal-Hydraulic Test Facility, part of the Pressurized-Water Reactor Blowdown Heat Transfer Separate-Effects Program. Heater rod surface temperatures are found to be sensitive to relatively small variations in flow. The mechanisms causing departure from nucleate boiling and rewetting are analyzed. Comparisons are made between heater rod surface temperatures calculated from

W. G. Craddick; C. R. Hyman; R. A. Hedrick; C. B. Mullins; K. G. Turnage

1978-01-01

362

A correlation for fin-and-tube heat exchanger having plain fin geometry is proposed in this study. A total of 74 samples were used to develop the correlation. For practical considerations, the proposed heat transfer correlation had absorbed the contact conductance in the development of correlation. The proposed heat transfer correlation can describe 88.6% of the database within ±15%, while the proposed

Chi-Chuan Wang; Kuan-Yu Chi; Chun-Jung Chang

2000-01-01

363

Heat transfer enhancement in fin-tube heat exchangers by winglet type vortex generators

Numerical investigations of the flow structure and heat transfer enhancement in a channel with a built-in-circular tube and a winglet type vortex generator are presented. The geometrical configuration represents an element of a gas-liquid fin-tube crossflow heat exchanger. In the absence of the winglet type vortex generator, relatively little heat transfer takes place in the downstream of the circular tube

G. Biswas; N. K. Mitra; M. Fiebig

1994-01-01

364

Investigation of heat transfer from a lead heat carrier to a tube streamlined longitudinally

Results of experimental studies on the local characteristics of heat transfer from a lead heat carrier to the surface of a\\u000a cooled tube in an annular gap are shown at control and alteration of oxygen admixture content under the conditions of power\\u000a circuits with heavy liquid-metal heat-transfer agent. This work is aimed at obtaining the grounded formulas for engineering\\u000a calculations

A. V. Beznosov; A. A. Molodtsov; A. V. Nazarov; S. Yu. Savinov; O. O. Kudrin

2007-01-01

365

The heat transfer coefficient and the power consumption of a laboratory scraped-surface heat exchanger (SSHE) were measured when it was used for freezing a 10wt.% sugar solution. Experimental results show that the heat transfer coefficient with phase change (ice formation) was about three to five times greater than that without phase change. Once onset of ice-growth occurred, the torque for

Frank Qin; Xiao Dong Chen; Shashini Ramachandra; Kevin Free

2006-01-01

366

Heat-transfer corrosion behaviour of cast Al alloy

Heat-transfer corrosion behaviour of an ISO 2379 cast Al alloy was studied in antifreeze radiator coolant under heat-rejecting condition. Extensive analyses of microstructures and corroded surfaces were carried out under the optical microscope, scanning electron microscope equipped with energy dispersive spectroscopy and X-ray diffractometer. Heat-rejecting condition led to a cavitation process and cavities were observed within the ?-Al matrix. Crevice

Wei Zhou; Naing Naing Aung; Anil Choudhary; Mouhcine Kanouni

2008-01-01

367

Heat transfer from a rod bundle under natural circulation conditions

A rectangular natural circulation loop with heat exchangers in the vertical legs was used to obtain heat transfer and fluid friction data from a tube bundle under natural circulation conditions. A 21 rod bundle arranged in a square array with a pitch-to-diameter ratio of 1.33 was used as the test heat exchanger. Deionized water at atmospheric pressure was used as

K. P. Hallinan; R. Viskanta

1986-01-01

368

Rod Bundle Heat Transfer: Steady-State Steam Cooling Experiments

Through the joint efforts of the Pennsylvania State University and the United States Nuclear Regulatory Commission, an experimental rod bundle heat transfer (RBHT) facility was designed and built. The rod bundle consists of a 7 x 7 square pitch array with spacer grids and geometry similar to that found in a modern pressurized water reactor. From this facility, a series of steady-state steam cooling experiments were performed. The bundle inlet Reynolds number was varied from 1 400 to 30 000 over a pressure range from 1.36 to 4 bars (20 to 60 psia). The bundle inlet steam temperature was controlled to be at saturation for the specified pressure and the fluid exit temperature exceeded 550 deg. C in the highest power tests. One important quantity of interest is the local convective heat transfer coefficient defined in terms of the local bulk mean temperature of the flow, local wall temperature, and heat flux. Steam temperatures were measured at the center of selected subchannels along the length of the bundle by traversing miniaturized thermocouples. Using an analogy between momentum and energy transport, a method was developed for relating the local subchannel centerline temperature measurement to the local bulk mean temperature. Wall temperatures were measured using internal thermocouples strategically placed along the length of each rod and the local wall heat flux was obtained from an inverse conduction program. The local heat transfer coefficient was calculated from the data at each rod thermocouple location. The local heat transfer coefficients calculated for locations where the flow was fully developed were compared against several published correlations. The Weisman and El-Genk correlations were found to agree best with the RBHT steam cooling data, especially over the range of turbulent Reynolds numbers. The effect of spacer grids on the heat transfer enhancement was also determined from instrumentation placed downstream of the spacer grid locations. The local heat transfer was found to be greatest at locations immediately downstream of the grid, and as the flow moved further downstream from the grid it became more developed, thus causing the heat transfer to diminish. The amount of heat transfer enhancement was found to depend not only on the spacer grid design, but also on the local Reynolds number. It was seen that decreasing Reynolds number leads to greater heat transfer enhancement. (authors)

Spring, J.P.; McLaughlin, D.M. [The Pennsylvania State University, 201 Shields Building University Park, PA 16802 (United States)

2006-07-01

369

Pool boiling heat transfer characteristics of nanofluids

Nanofluids are engineered colloidal suspensions of nanoparticles in water, and exhibit a very significant enhancement (up to 200%) of the boiling Critical Heat Flux (CHF) at modest nanoparticle concentrations (50.1% by ...

Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology

2007-01-01

370

Heat Transfer Over the Circumference of a Heated Cylinder in Transverse Flow

NASA Technical Reports Server (NTRS)

A method for recording the local heat-transfer coefficients on bodies in flow was developed. The cylinder surface was kept at constant temperature by the condensation of vapor except for a narrow strip which is heated separately to the same temperature by electricity. The heat-transfer coefficient at each point was determined from the electric heat output and the temperature increase. The distribution of the heat transfer along the circumference of cylinders was recorded over a range of Reynolds numbers of from 5000 to 426,000. The pressure distribution was measured at the same time. At Reynolds numbers up to around 100,000 high maximums of the heat transfer occurred in the forward stagnation point at and on the rear side at 180C, while at around 80 the heat-transfer coefficient on both sides of the cylinder behind the forward stagnation point manifested distinct minimums. Two other maximums occurred at around 115 C behind the forward stagnation point between 170,000 and 426,000. At 426,000 the heat transfer at the location of those maximums was almost twice as great as in the forward stagnation point, and the rear half of the cylinder diffused about 60 percent of the entire heat, The tests are compared with the results of other experimental and theoretical investigations.

Schmidt, Ernst; Wenner, Karl

1943-01-01

371

In this paper burnout is investigated in tubes under nonuniform heating on the perimeter. Data on heat transfer and critical heat flux (q{sub chf}) in the case of water were obtained for ranges of mass velocity {rho}w = 200--3000 kg/m{sup 2} s, pressure p = 1--1 MPa, and inlet water temperature T = 25--98{degrees}C. The test section was a horizontal copper tube of 21 mm outer diameter, 8 mm inner diameter with a technically smooth surface and heat transfer-intensifying twisted tape and porous sintered coating. The test section was heated by bombardment with electrons. It is established that a redistribution of heat fluxes and an increase of wall temperature fluctuations occur at burnout. The range of regime parameters to prevent burnout of a heat transfer surface is determined.

Komendantov, A.S.; Kuzma-Kichta, Y.A.; Vasil'eva, L.T.; Ovodkov, A.A. (Moscow Power Engineering Inst., Moscow (SU))

1991-01-01

372

Heat transfer in serpentine passages with turbulence promoters

NASA Astrophysics Data System (ADS)

Local heat transfer rates and overall pressure losses were determined for serpentine passages of square cross section. The flow entered an inlet leg, turned 180 deg and then passed through an outlet leg. Results were obtained for a passage with smooth walls for three different bend geometries and the effect of turbulence promoters was investigated. Turbulence promoters between 0.6 and 15% of the passage height were tested. Local heat transfer rates are determined from thermocouple measurements on a thin electrically heated Inconel foil and pressure drop is measured along the flow path.

Boyle, R. J.

373

Heat transfer analysis of ground heat exchangers with inclined boreholes

Consisting of closed-loop of pipes buried in boreholes, ground heat exchangers (GHEs) are devised for extraction or injection of thermal energy from\\/into the ground. Evolved from the vertical borehole systems, the configuration of inclined boreholes is considered in order to reduce the land plots required to install the GHEs in densely populated areas. A transient three-dimensional heat conduction model has

Ping Cui; Hongxing Yang; Zhaohong Fang

2006-01-01

374

An experimental study has been carried out to provide qualitative and quantitative insight into gas to wall heat transfer in a gasoline fueled Homogeneous Charge Compression Ignition (HCCI) engine. Fast response thermocouples are embedded in the piston top and cylinder head surface to measure instantaneous wall temperature and heat flux. Heat flux measurements obtained at multiple locations show small spatial

Junseok Chang; Orgun Güralp; Zoran Filipi; Dennis Assanis; Tang-Wei Kuo; Paul Najt; Rod Rask

375

Experimental study of heat transfer of buried finned pipe for ground source heat pump applications

Ground heat exchangers have vital importance for ground source heat pump applications. Various configurations tried to improve heat transfer in the soil. A new kind of aluminium finned pipe buried in the soil for this aim. In order to compare effectiveness of the Al finned pipe over the traditional PPRC pipe an experimental study carried out. The experimental GSHP system

Ahmet Koyun; Hakan Demir; Zakir Torun

2009-01-01

376

Numerical technique for modeling conjugate heat transfer in an electronic device heat sink

A fast running computational algorithm based on the volume averaging technique (VAT) is developed to simulate conjugate heat transfer process in an electronic device heat sink. The goal is to improve computational capability in the area of heat exchangers and to help eliminate some of empiricism that leads to overly constrained designs with resulting economic penalties.VAT is tested and applied

Andrej Horvat; Ivan Catton

2003-01-01

377

The Experimental Study on Heat Transfer Characteristics of The External Heat Exchanger

Using the external heat exchanger in large-scale CFB boilers can control combustion and heat transfer separately, make the adjustments of bed temperature and steam temperature convenient. The state of gas-solid two phase flow in the external heat exchanger is bubbling fluidized bed, but differs from the regular one as there is a directional flow in it. Consequently, the temperature distribution

X. Y. Ji; X. F. Lu; L. Yang; H. Z. Liu

2010-01-01

378

Heat and mass transfer in water-laden sandstone: microwave heating

Our previous theoretical model was extended to predict the heat and mass transfer phenomena in microwave-heated porous materials. A water-filled sandstone was heated in microwaves and its drying rates and temperature profiles were measured. Predictions agree well with observations. Besides moisture loss rates and temperature profiles, the model also predicts local moisture content, gas densities, and pressure. These latter quantities

Chen Kou Wei; H. T. Davis; E. A. Davis; Joan Gordon

1985-01-01

379

Influence of climatic factors on heat transfer in the upper zone of ground accumulators of heat

NASA Astrophysics Data System (ADS)

The boundary-value problem of nonstationary heat conduction in the upper zone of ground accumulators of heat has been formulated and solved numerically with account for the action of the net flux of solar radiation and convective component of heat transfer on the Earth's surface.

Nakorchevskii, A. I.

2012-03-01

380

Error Analysis of Heat Transfer for Finned-Tube Heat-Exchanger Text-Board

In order to reduce the measurement error of heat transfer in water and air side for finned-tube heat-exchanger as little as possible, and design a heat-exchanger test-board measurement system economically, based on the principle of test-board system...

Chen, Y.; Zhang, J.

2006-01-01

381

Boiling heat transfer in a small horizontal rectangular channel

Compact heat exchangers have traditionally found wide application in the transportation industry, where they are used as evaporators and condensers in vapor compression cycles for air conditioning and refrigeration. Such heat exchangers possess numerous attractive features including high thermal effectiveness, small size, low weight, design flexibility, and pure counterflow, and they can accommodate multiple streams. Today, there is a widespread interest in expanding the range of application of compact heat exchangers to include phase-change heat transfer in the process industries, among others. An overall objective of this effort is to provide the basis for establishing design technology in this area. In the present study, small channel flow boiling heat transfer was extended to a rectangular channel (4.06 {times} 1.70 mm) using refrigerant 12 (R-12). As with the circular tube studies, the flow channel wall was electrically heated providing a constant heat flux. Tests were performed over a quality range of 0.15 to 0.80, and large ranges of mass fluxes (50 to 400 kg/m{sup 2}s) and heat flux (4 to 34 kW/m{sup 2}). Heat transfer was measured and results are compared with correlation predictions.

Tran, T.N.; Wambsganss, M.W.; Jendrzejczyk, J.A. [Argonne National Lab., IL (United States); France, D.M. [Illinois Univ., Chicago, IL (United States). Dept. of Mechanical Engineering

1993-08-01

382

Radiative heat transfer in turbulent MHD channel flow

Radiative heat transfer in a MHD channel has been studied for fully developed turbulent flow of an electrically conducting fluid. A uniform magnetic field is imposed transverse to the flow direction between the electrically insulated parallel plates. Thermal entry region is analyzed for constant wall temperature including viscous dissipation and Joulean heating. A van Dreist mixing length model with Mei and Squire correction factor is used for eddy diffusivity of momentum and a modified Cebeci model is used for eddy conductivity. Both gray and real (non-gray) gas models of radiation are examined. An exponential wide band model is employed in evaluation of radiative heat flux for a real gas. Also, the contribution of a seed material to the radiative transfer is considered. The integro-differential equation for thermal energy transport is solved by a finite difference iterative method. Effects of control parameters such as Reynolds and Hartmann numbers, wall temperature, channel height, and partial pressures of participating gases on temperature profiles and heat transfer are studied. Results for Nusselt number, bulk temperature, and temperature profiles are reported for fully developed and developing thermal profiles. Furthermore, results are presented along the channel for these quantities for various parameters. Effect of variation of electrical conductivity with temperature is considered. For practical values of parameters as found in proposed MHD generators it is shown that radiative heat transfer is a major mechanism of heat transfer in the channel and accelerates the thermal development and results in reduced gas temperature profiles.

Alipour-Haghighi, F.

1981-01-01

383

Heat Transfer Enhancement in Separated and Vortex Flows

This document summarizes the research performance done at the Heat Transfer Laboratory of the University of Minnesota on heat transfer and energy separation in separated and vortex flow supported by DOE in the period September 1, 1998--August 31, 2003. Unsteady and complicated flow structures in separated or vortex flows are the main reason for a poor understanding of heat transfer under such conditions. The research from the University of Minnesota focused on the following important aspects of understanding such flows: (1) Heat/mass transfer from a circular cylinder; (2) study of energy separation and heat transfer in free jet flows and shear layers; and (3) study of energy separation on the surface and in the wake of a cylinder in crossflow. The current study used three different experimental setups to accomplish these goals. A wind tunnel and a liquid tunnel using water and mixtures of ethylene glycol and water, is used for the study of prandtl number effect with uniform heat flux from the circular cylinder. A high velocity air jet is used to study energy separation in free jets. A high speed wind tunnel, same as used for the first part, is utilized for energy separation effects on the surface and in the wake of the circular cylinder. The final outcome of this study is a substantial advancement in this research area.

Richard J. Goldstein

2004-05-27

384

He II heat transfer through superconducting cables electrical insulation

NASA Astrophysics Data System (ADS)

For NbTi magnets cooled by superfluid helium (He II), the most severe heat barrier comes from the electrical insulation of the cables. Tests on electrical multi-layer insulations, made of Kapton ®, dry fiber and epoxy resin impregnated fiberglass tapes, indicate that heat transfer is influenced by He II contained in the insulation. Electrical insulation can be considered as a composite material made of a solid matrix with a complicated helium channels network. For several insulations, this network is characterized by steady-state heat transfer experiment through an elementary insulation pattern. Measurements in Landau regime for low temperature difference (10 -5-10 -3 K) and in Gorter-Mellink (GM) regime for higher temperature differences permit to determine an equivalent He II channel cross-section (10 -6 m 2) with an equivalent channel thickness (25 ?m). We use the assumptions that He II heat transfer through the channels network and conduction in the insulation are decoupled and that the channels length is determined from the insulation overlap. It is observed that He II heat transfer is competing with conduction in the insulation. Furthermore, the measurements reveal an anomaly of heat transfer in the vicinity of the ? temperature which is associated to the phenomenon of ?-point depression.

Baudouy, B.; François, M. X.; Juster, F.-P.; Meuris, C.

2000-02-01

385

Numerical simulation of contact heat transfer between particles by TDEM

NASA Astrophysics Data System (ADS)

Heat transfer in particulate systems plays an important role in a range of industrial processes, such as drying, heating, cooling, and so on. However, the inter-particle heat transfer mechanism is comparatively less understood. Due to the multi-scale complexity of the system and the limitations of measurement techniques, the details of the processes are difficult to investigate experimentally. DEM is a powerful tool for us to obtain insight into the dynamics of particulate system. To extend the classical DEM to the Thermal Discrete Element Method (TDEM) for particulate system with heat transfer, the effect of softening treatment for TDEM was analyzed, which results in the change of some important micro-behaviors of inter-particle, such as impact time and contact area etc, and the unrealistic heat transfer between particles. Two coefficients, time restoration coefficient Crt and area restoration coefficient Cra, were derived to simulate the contact heat transfer between particles more realistically even if particle stiffness is artificially adjusted by several orders while a large time step is taken to save computational cost.

LU, L. Y.; Gu, Z. L.; Lei, K. B.; Kase, Kiwamu

2010-03-01

386

Experimental Investigation of Entrance-region Heat-transfer Coefficients

NASA Technical Reports Server (NTRS)

Experimental results of tests made at the Langley Memorial Aeronautical Laboratory are presented to show how heat-transfer coefficients can he increased by a method utilizing the high rate of heat transfer known to exist on any heat-transfer surface in the region adjacent to the edge on which the cooling or heating fluid impinges. The results show that, for the same pressure drop, the average surface heat-transfer.coefficient can be increased 50 to 100 percent when a cooling surface having a length of four inches in the direction of fluid flow is cut to form twenty fins with a length of 0.2 inch in the direction of fluid flow and the fins are sharpened and staggered in the air stream. The percentage of increase in the surface heat-transfer coefficient obtained as a result of shortening the length of the cooling surface varies with the pressure drop of the cooling fluid in passing the surface, the increase being largest when small pressure drop is used and smallest when high pressure drop is used.

Joyner, Upshur T

1943-01-01

387

Modelling of heat and mass transfer processes in neonatology.

This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices. PMID:18708705

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

2008-09-01

388

Study of the average heat transfer coefficient at different distances between wind tunnel models

NASA Astrophysics Data System (ADS)

The paper presents investigations of physical and climatic factors with regard to design and process variables having effect on heat transfer in the building model system at different distances between them in the airflow direction. The aim of this work is to improve energy efficiency of exterior walls of buildings. A method of physical simulation was used in experiments. Experimental results on the average values of the heat transfer coefficient in the building model system are presented herein. A series of experiments was carried out on a specific aerodynamic test bench including a subsonic wind tunnel, heat models and devices for giving thermal boundary conditions, transducers, and the record system equipment. The paper contains diagrams of the average heat transfer distribution at fixed Reynolds number and the airflow angle of attack; the average values of the heat transfer coefficient for each face and wind tunnel models as a whole at maximum, medium, and large distances between them. Intensification of the average heat transfer was observed on the downstream model faces depending on the distance between models.

Gnyrya, A.; Korobkov, S.; Mokshin, D.; Koshin, A.

2015-01-01

389

This paper is the second part of the experimental study on exploring the feasibility of inverse diffusion flame (IDF) for impingement heating. The structures and heat transfer characteristics of an impinging IDF jet have been studied. Four types of impinging flame structure have been identified and reported. The distributions of the wall static pressure are measured and presented. The influences

L. L. Dong; C. S. Cheung; C. W. Leung

2007-01-01

390

Infrared Thermography applied to measurement of Heat transfer coefficient of water in a pipe heated. It has been applied to measure heat transfer coefficients of water flowing in a round tube and in a multiport-flat tube. Models were developed to deduce heat transfer coefficient from wall temperature

Boyer, Edmond

391

NASA Astrophysics Data System (ADS)

Various papers on numerical heat transfer using PCs and supercomputing are presented. Individual topics addressed include: a generalized program for computing two-dimensional boundary layers on a PC, microcomputer software for heat transfer education, PC-based adaptive irregular triangular grid generation for transient diffusion problems, numerical studies of convective heat transfer in an inclined semiannular enclosure, capabilities of PCs for numerical convective heat transfer, one-dimensional analysis of plane and radial thin film flows including solid-body rotation, and analysis of the transient compressible vapor flow in heat pipes. Also considered are: transient combined mixed convection and radiation from a straight vertical fin, finite element method for fluid flow and heat transfer on a PC, use of finite elements and PCs in teaching heat transfer, application of supercomputers to computational heat transfer, heat transfer to a thin liquid film with a free surface, numerical simulation of internal supersonic flow, and numerical prediction of vortex shedding behind a square cylinder.

Shah, R. K.

1989-06-01

392

Efficient estimation of energy transfer efficiency in light-harvesting complexes

The fundamental physical mechanisms of energy transfer in photosynthetic complexes is not yet fully understood. In particular, the degree of efficiency or sensitivity of these systems for energy transfer is not known given ...

Mohseni, Masoud

393

Heat SET 2005 Heat Transfer in Components and Systems

Engineering Stanford University, Stanford, CA 94305 USA jbstein@stanford.edu ABSTRACT Polymer Electrolyte and mass transfer and axial pressure gradients. INTRODUCTION The Polymer Electrolyte Membrane (PEM) fuel of the diffusion layer and clogging of the gas channels. Design for optimal performance requires a thorough

Hidrovo, Carlos H.

394

Heat transfer in underground heating experiments in granite, Stipa, Sweden

Electrical heater experiments have been conducted underground in granite at Stripa, Sweden, to investigate the effects of heating associated with nuclear waste storage. Temperature data from these experiments are compared with closed-form and finite-element solutions. Good agreement is found between measured temperatures and both types of models, but especially for a nonlinear finite-element heat conduction model incorporating convective boundary conditions, measured nonuniform initial rock temperature distribution, and temperature-dependent thermal conductivity. In situ thermal properties, determined by least-squares regression, are very close to laboratory values. A limited amount of sensitivity analysis is undertaken.

Chan, T.; Javandel, I.; Witherspoon, P.A.

1980-04-01

395

NASA Astrophysics Data System (ADS)

A waste heat transportation system trans-heat (TH) system is quite attractive that uses the latent heat of a phase change material (PCM). The purpose of this paper is to study the thermophysical properties of various sugars and sodium acetate trihydrate (SAT) as PCMs for a practical TH system and the heat transfer property between PCM selected and heat transfer oil, by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA) and a heat storage tube. As a result, erythritol, with a large latent heat of 344 kJ/kg at melting point of 117°C, high decomposition point of 160°C and excellent chemical stability under repeated phase change cycles was found to be the best PCM among them for the practical TH system. In the heat release experiments between liquid erythritol and flowing cold oil, we observed foaming phenomena of encapsulated oil, in which oil droplet was coated by solidification of PCM.

Kaizawa, Akihide; Maruoka, Nobuhiro; Kawai, Atsushi; Kamano, Hiroomi; Jozuka, Tetsuji; Senda, Takeshi; Akiyama, Tomohiro

2008-05-01

396

NASA Technical Reports Server (NTRS)

This invention is directed to transferring heat from an extremely high temperature source to an electrically isolated lower temperature receiver. The invention is particularly concerned with supplying thermal power to a thermionic converter from a nuclear reactor with electric isolation. Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. If the receiver requires gratr thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparative low thermal power densities through the electrically nonconducting gap between the two heat pipes.

Morris, J. F. (inventor)

1985-01-01

397

Methamphetamine residue dermal transfer efficiencies from household surfaces.

Methamphetamine contamination from illegal production operations poses a potential health concern for emergency responders, child protective services, law enforcement, and children living in contaminated structures. The objective of this study was to evaluate dermal transfer efficiencies of methamphetamine from contaminated household surfaces. These transfer efficiencies are lacking for methamphetamine, and would be beneficial for use in exposure models. Surfaces were contaminated using a simulated smoking method in a stainless steel chamber. Household surfaces were carpet, painted drywall, and linoleum. Dermal transfer efficiencies were obtained using cotton gloves for two hand conditions, dry or saliva moistened (wet). In addition, three contact scenarios were evaluated for both hand conditions: one, two, or three contacts with contaminated surfaces. Dermal transfer efficiencies were calculated for both hand conditions and used as inputs in a Stochastic Human Exposure and Dose Simulation model (SHEDS-Multimedia, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, N.C.). Results of this study showed that average dermal transfer efficiencies of methamphetamine ranged from 11% for dry hands to 26% for wet hands. There was a significantly higher wet transfer as compared to dry transfer for all surfaces. For wet hands, dermal transfer depended on surface type with higher transfer from carpet and linoleum as compared to drywall. Based on our estimates of dermal transfer efficiency, a surface contamination clearance level of 1.5 ?g/100 cm(2) may not ensure absorbed doses remain below the level associated with adverse health effects in all cases. Additional dermal transfer studies should be performed using skin surrogates that may better predict actual skin transfer. PMID:24579754

Van Dyke, Mike; Martyny, John W; Serrano, Kate A

2014-01-01

398

Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.

Kendall, C.M. [Lawrence Livermore National Lab., CA (United States); Holman, J.P. [Southern Methodist Univ., Dallas, TX (United States). Dept. of Mechanical Engineering

1996-06-06

399

Heat transfer and pressure drop characteristics of a plate heat exchanger

pressure drop (Pa) 6P, BP, Pr Re T, hT AT?, manifold pressure drop (Pa) port pressure drop (Pa) total pressure drop (Pa) Prandtl number (/zc, /k) volumetric flowrate (m'/s) heat transfer (W) average heat transfer (W) Reynold's number (uD, p... Fig. Z Heat-Transfer Correlations: Turbulent :men eon 19673 Enier son 1967b F rrer eon 1967c Focke et crl. 1985 6 gp2 p~ 2 5 4 Fig. 3 Friction-Factor Correlations: Laminar/Transition Bell 1981 Cooper 197l Ed~mr ds et. al. 1970 Emerson 1967a...

Talik, Anthony Charles

2012-06-07

400

Advanced two-phase heat transfer systems

NASA Technical Reports Server (NTRS)

Future large spacecraft, such as the Earth Observing System (EOS) platforms, will require a significantly more capable thermal control system than is possible with current 'passive' technology. Temperatures must be controlled much more tightly over a larger surface area. Numerous heat load sources will often be located inside the body of the spacecraft without a good view to space. Power levels and flux densities may be higher than can be accommodated with traditional technology. Integration and ground testing will almost certainly be much more difficult with such larger, more complex spacecraft. For these and similar reasons, the Goddard Space Flight Center (GSFC) has been developing a new, more capable thermal control technology called capillary pumped loops (CPL's). CPL's represent an evolutionary improvement over heat pipes; they can transport much greater quantities of heat over much longer distances and can serve numerous heat load sources. In addition, CPL's can be fabricated into large cold plates that can be held to tight thermal gradients. Development of this technology began in the early 1980's and is now reaching maturity. CPL's have recently been baselined for the EOS-AM platform (1997 launch) and the COMET spacecraft (1992 launch). This presentation describes this new technology and its applications. Most of the viewgraphs are self descriptive. For those that are less clear additional comments are provided.

Swanson, Theodore D.

1992-01-01

401

Laminar heat transfer in annular sector ducts

The continuing interest in compact heat exchangeers has created the need for friction factor and Nusselt number data for different passage shapes. It has long been recognized that circular tube results are generally not applicable to noncircular passages even when the hydraulic diameter is used as the characteristic dimension. Hence, design data should be generated for each passage individually, and

H. M. Soliman

1987-01-01

402

An Experimental Study on Heat Transfer Coefficients of a CO2Filled Thermosyphon

Because carbon dioxide is ozone friendly and has negligible global warming potential, it has received renewed interest in recent years as an important alternative refrigerant. In this article, the heat transfer characteristics of a carbon dioxide-filled two-phase closed thermosyphon were investigated experimentally, and the empirical heat transfer correlations are reported. The heat transfer data were analyzed, and heat transfer coefficients

S. J. Jeong

2011-01-01

403

Analysis is carried out for dispersed flow heat transfer under reactor emergency cooling conditions. The present formulation explicitly reveals an extra dependence of the heat transfer coefficient and Nusselt number on the mean vapor temperature for droplet dispersed flow which is not found in single phase flow heat transfer. The heat transfer results obtained from three different geometries: an infinite

S. Wong; L. E. Hochreiter

1980-01-01

404

Improvement in Modeling of Heat Transfer in Vertical Ground Heat Exchangers

The heat transfer model of vertical ground heat exchangers for ground-source heat pump systems is discussed. An explicit solution of a finite line-source model has been derived to better describe temperature response of boreholes for long time steps, which can be easily incorporated into computer programs for thermal analysis of ground heat exchangers. A quasi-three-dimensional model is also presented for

N. R. Diao; H. Y. Zeng; Z. H. Fang

2004-01-01

405

Heat transfer characteristics of a new helically coiled crimped spiral finned tube heat exchanger

In the present study, the heat transfer characteristics in dry surface conditions of a new type of heat exchanger, namely\\u000a a helically coiled finned tube heat exchanger, is experimentally investigated. The test section, which is a helically coiled\\u000a fined tube heat exchanger, consists of a shell and a helical coil unit. The helical coil unit consists of four concentric\\u000a helically

Kwanchanok Srisawad; Somchai Wongwises

2009-01-01

406

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

Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration. 5 figs.

Phillips, B.A.; Zawacki, T.S.

1998-07-21

407

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

Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration.

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

1998-07-21

408

Condensing Heat Exchanger for Optimization of Energy Efficiency

? conder:sing heat exchangers are arranged in parallel and accept a slipstream of about one third of the plant flue gas flow from multiple boilers. The recovered heat is transferred to boiler make-up water. The cooled flue gas leaving the heat...

Carrigan, J. F.; Johnson, D. W.; DiVitto, J. G.; Schulze, K. H.

409

Heat transfer performance of submerged impinging jet using silver nanofluids

NASA Astrophysics Data System (ADS)

Silver-water nanofluids used in this paper, has been prepared by a one step method adopting an ultrasound-assisted membrane reaction. Experimental investigations on heat transfer of submerged jet in plate and pin-fin heat sinks were carried out with different concentrations of silver nanofluids. The results indicate that the silver nanoparticles can be uniformly distributed in the base fluid with an average grain size of 4.8 nm. The used surfactant had a great influence on the viscosity of the nanofluids. Compared with the base fluid (water and surfactant), the heat transfer coefficient of the nanofluids, for the same jet velocity, increases in average by 6.23, 9.24 and 17.53 % for the silver nanoparticles weight fractions of 0.02, 0.08 and 0.12 %, respectively. Compared with water, the heat transfer coefficient is enhanced by 6.61 % with a silver nanoparticles weight fraction of 0.12 %. The Nu of pin fin heat sink are obviously higher than that of plate one, at corresponding Re. The exit of nanoparticles can intense internal energy transmission of fluids, and then enhance the heat transfer, while the Re is small.

Zhou, Mingzheng; Xia, Guodong; Chai, Lei

2015-02-01

410

Heat transfer including radiation and slag particles evolution in MHD channel-I

Accurate estimates of convective and radiative heat transfer in the magnetohydrodynamic channel are provided. Calculations performed for a base load-size channel indicate that heat transfer by gas radiation almost equals that by convection for smooth walls, and amounts to 70% as much as the convective heat transfer for rough walls. Carbon dioxide, water vapor, and potassium atoms are the principal participating gases. The evolution of slag particles by homogeneous nucleation and condensation is also investigated. The particle-size spectrum so computed is later utilized to analyze the radiation enhancement by slag particles in the MHD diffuser. The impact of the slag particle spectrum on the selection of a workable and design of an efficient seed collection system is discussed.

Im, K.H.; Ahluwalia, R.K.

1980-01-01

411

Mixture effects on horizontal convective boiling heat transfer

Mixture effects were studied in horizontal convective heat transfer for both nonazeotropic, R22/R114, and azeotropic, R12/R152a, mixtures. A test facility was designed, constructed, and operated to simulate evaporators in heat pump and refrigeration systems. More than 3000 local two-phase heat transfer coefficients were obtained under steady state condition for annular flow at a reduced pressure of 0.08. The ranges of heat flux and mass flow rates were 10-45 kW/m{sup 2} and 16-46 g/s, equivalent to 250-720 kg/m{sup 2} s. The overall compositions of mixtures were 0, 23, 47, 77, and 100% R22 by mole for R22/R114 mixtures and 0, 21, 60 (Azeotrope), 89, and 100% R12 by mole for R12/R152a mixtures. The results indicated that there were two distinct heat transfer regions; partial boiling and convective evaporation. For a given heat and mass flux, nucleate boiling was suppressed at lower qualities for mixtures than for pure fluids. The unique phenomenon of loss of available superheat for mixtures caused nucleate boiling to be suppressed at lower qualities. An analytical study was performed to predict the transition quality by utilizing a theory of onset of nucleate boiling and phase equilibrium data. Local heat transfer coefficients for mixtures were as much as 36% lower than a weighted average of the pure components values in the convective region. The non-ideal variation of physical properties accounted for most of the heat transfer degradation.

Jung, D.

1988-01-01

412

Mass and heat transfer in crushed oil shale

Studies of heat and mass transfer in packed beds, which disagree substantially in their findings, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse irregular shapes and sizes. The authors, in 349 runs, measured mass-transfer rates front naphthalene particles buried in packed beds by passing through air at room temperature. An exact catalog between convection of heat and mass makes it possible to infer heat-transfer coefficients from measured mass-transfer coefficients and fluid properties. Some beds consisted of spheres, naphthalene and inert, of the same, contrasting or distributed sizes. In some runs, naphthalene spheres were buried in beds of crushed shale, some in narrow screen ranges and others with a wide size range. In others, naphthalene lozenges of different shapes were buried in beds of crushed shale in various bed axis orientations. This technique permits calculation of the mass-transfer coefficient for each active particle in the bed rather than, as in most past studies, for the bed as a whole. The data are analyzed by the traditional correlation of Colburn j{sub D} vs. Reynolds number and by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: local Reynolds number should be based on the active-particle size, not the average for the whole bed; differences between shallow and deep beds are not appreciable; mass transfer is 26% faster for spheres and lozenges buried in shale than in all-sphere beds; orientation of lozenges in shale beds has little or no effect on mass-transfer rate; and for mass or heat transfer in shale beds, log(j{center_dot}{epsilon}) = {minus}0.0747 - 0.6344 log N{sub Re} + 0. 0592 log {sup 2} N{sub Re}.

Carley, J.F.; Ott, L.L. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States); Swecker, J.L. [Corning, Inc., Wilmington, NC (United States). Telecommunication Products Division] [Corning, Inc., Wilmington, NC (United States). Telecommunication Products Division

1995-03-01

413

Heat transfer from a horizontal wafer-based disk of multi-chip modules

Convective heat transfer characteristics above a horizontal wafer-based disk heated with 15 simulated chips in unobstructed ambient air have been experimentally investigated under both stationary and rotating disk conditions. Relevant parameters influencing heat transfer performance studied are the Grashof number and rotational Reynolds number. Their effects on heat transfer characteristics in such configurations of stationary and rotational heated disks are

Y. R. Shieh; C. J. Li; Y. H. Hung

1999-01-01

414

Heat transfer performance of an oscillating heat pipe under ultrasonic field with dual frequency

NASA Astrophysics Data System (ADS)

The oscillating motion and heat transfer capacity in an oscillating heat pipe (OHP) under the effect of ultrasound was investigated experimentally. Using the electrically- controlled piezoelectric ceramics, the ultrasonic sound was applied to the evaporating section of the OHP. The heat pipe was tested with or without the ultrasonic sound. The effect of ultrasound on the heat transfer performance was conducted with ultrasound of single frequency or dual frequency. The experimental results demonstrate that the OHP under the effect of the ultrasonic sound with dual frequency performs better than that one with single frequency.

Fu, B. W.; Zhao, N. N.; Ma, H. B.; Su, F. M.

2015-01-01

415

NASA Astrophysics Data System (ADS)

Low-profile, Cu-based microchannel heat exchangers (MHEs) with different geometric dimensions were fabricated, bonded and assembled. A transient liquid phase (TLP) process was used for bonding of Cu-based MHEs with total thicknesses ranging from 600 µm to 1700 µm. The structural integrity of TLP-bonded Cu MHEs was examined. Device-level heat transfer testing was performed on a series of Cu-based MHEs to study the influence of microchannel dimensions on overall heat transfer performance, corroborated by computational results from a simple 2D finite element analysis. The present results demonstrate the promise of low-profile metallic MHEs for high heat flux cooling applications.

Lu, Bin; Chen, Ke; Meng, W. J.; Mei, Fanghua

2010-11-01

416

Numerical heat transfer and fluid flow

A mathematical description of physical phenomena is given and discretization methods are discussed. Heat conduction is considered along with convection and diffusion, and calculation of the flow field, source-term linearization, irregular geometries, two- and three-dimensional parabolic flow, partially parabolic flows, the finite-element method, and illustrative applications. Attention is given to governing differential equations, the nature of coordinates, the nature of

S. V. Patankar

1980-01-01

417

NASA Astrophysics Data System (ADS)

As one of the key devices in the high temperature gas turbine system, cross-corrugated recuperators provide high heat transfer capabilities with compact size, light weight, strong mechanical strength and are mandatory to achieve 30 % electrical efficiency or higher for micro turbine engines. Flow in such geometries is usually laminar with lower Reynolds numbers. In order to understand mechanisms of flowing and heat transfer, periodic fully developed fluid flow and heat transfer in two types of cross-corrugated structures with inclination angle at 90° are investigated numerically and experimentally. Periodicity was used to reduce the complexity of the channel geometry and enables the smallest possible segment of the flow channel to be modeled. The velocity and temperature distributions were obtained in the three-dimensional complex domain. Besides a detailed flow analysis, comparison of the local heat and mass transfer and the pressure losses for these geometries are presented. It is shown that the flow phenomena caused by the different geometries were of significant influence on the homogeneity and on the quantity of the local heat and mass transfer as well as on the pressure drop. As a recuperator for micro turbine engines, cross-corrugated sinusoidal channels are more preferable to triangular channels.

Zhou, Guo-Yan; Tu, Shan-Tung; Ma, Hu-gen

2014-09-01

418

Fusion blanket high-temperature heat transfer

Deep penetration of 14 MeV neutrons makes two-temperature region blankets feasible. A relatively low-temperature (approx. 300/sup 0/C) metallic structure is the vacuum/coolant pressure boundary, while the interior of the blanket, which is a simple packed bed of nonstructural material, operates at very high temperatures (>1000/sup 0/C). The water-cooled shell structure is thermally insulated from the steam-cooled interior. High-temperature steam can dramatically increase the efficiency of electric power generation, as well as produce hydrogen and oxygen-based synthetic fuels at high-efficiency.

Fillo, J.A.

1983-01-01

419

Reflective Coating on Fibrous Insulation for Reduced Heat Transfer

NASA Technical Reports Server (NTRS)

Radiative heat transfer through fibrous insulation used in thermal protection systems (TPS) is significant at high temperatures (1200 C). Decreasing the radiative heat transfer through the fibrous insulation can thus have a major impact on the insulating ability of the TPS. Reflective coatings applied directly to the individual fibers in fibrous insulation should decrease the radiative heat transfer leading to an insulation with decreased effective thermal conductivity. Coatings with high infrared reflectance have been developed using sol-gel techniques. Using this technique, uniform coatings can be applied to fibrous insulation without an appreciable increase in insulation weight or density. Scanning electron microscopy, Fourier Transform infrared spectroscopy, and ellipsometry have been performed to evaluate coating performance.

Hass, Derek D.; Prasad, B. Durga; Glass, David E.; Wiedemann, Karl E.

1997-01-01

420

Review of experimental investigations of liquid-metal heat transfer

NASA Technical Reports Server (NTRS)

Experimental data of various investigators of liquid-metal heat-transfer characteristics were reevaluated using as consistent assumptions and methods as possible and then compared with each other and with theoretical results. The reevaluated data for both local fully developed and average Nusselt numbers in the turbulent flow region were found still to have considerable spread, with the bulk of the data being lower than predicted by existing analysis. An equation based on empirical grounds which represents most of the fully developed heat-transfer data is nu = 0.625 pe(0.4) where nu represents the Nusselt number and pe the Peclet number. The theoretical prediction of the heat transfer in the entrance region was found to give lower values, in most cases, than those found in the experimental work.

Lubarsky, Bernard; Kaufman, Samuel J

1956-01-01

421

Near-field radiative heat transfer between metamaterial thin films.

We investigate near-field radiative heat transfer between two thin films made of metamaterials. The impact of film thickness on magnetic and electric surface polaritons (ESPs) is analyzed. It is found that the strength as well as the location of magnetic resonance does not change with film thickness until the film behaves as semi-infinite for the dielectric function chosen in this study. When the film is thinner than vacuum gap, both electric and magnetic polaritons contribute evenly to near-field radiative heat transfer. At larger film thicknesses, ESPs dominate heat transfer due to excitation of a larger number of modes. Results obtained from this study will facilitate applications of metamaterials as thin-film coatings for energy systems. PMID:24690723

Basu, Soumyadipta; Francoeur, Mathieu

2014-03-01

422

Ultrasonic enhancement of heat transfer on narrow surface

Ultrasonic enhancement of heat transfer on a narrow surface was measured by changing the width of the surface from 8 to 0.1 mm. Ultrasonic power of 600 W with a frequency of 40 kHz was used. Heat transfer on the narrow surface without ultrasonic vibration was correlated by the experimental equation for a thin wire. The cavitation intensity was measured by the cavitation erosion loss of an aluminum foil of 15 [mu]m thickness. The effects of acoustic streaming and cavitation were separated by this measurement. Heat transfer by acoustic streaming was predicted through forced convection. Enhancement by cavitation was explained by the turbulence thermal conductivity of the microjets.

Nomura, Shinfuku; Nakagawa, Masafumi (Toyohashi Univ. of Technology (Japan). Dept. of Energy Engineering)

1994-06-01

423

Radiant Heat Transfer in Reusable Surface Insulation

NASA Technical Reports Server (NTRS)

During radiant testing of mullite panels, temperatures in the insulation and support structure exceeded those predicted on the basis of guarded hot plate thermal conductivity tests. Similar results were obtained during arc tunnel tests of mullite specimens. The differences between effective conductivity and guarded hot plate values suggested that radiant transfer through the mullite was occurring. To study the radiant transport, measurements were made of the infrared transmission through various insulating materials and fibers of interest to the shuttle program, using black body sources over the range of 780 to 2000 K. Experimental data were analyzed and scattering coefficients were derived for a variety of materials, fiber diameters, and source temperature.

Hughes, T. A.; Linford, R. M. F.; Chmitt, R. J.; Christensen, H. E.

1973-01-01

424

Condensation heat transfer and flow friction in silicon microchannels

NASA Astrophysics Data System (ADS)

An experimental investigation was performed on heat transfer and flow friction characteristics during steam condensation flow in silicon microchannels. Three sets of trapezoidal silicon microchannels, with hydraulic diameters of 77.5 µm, 93.0 µm and 128.5 µm respectively, were tested under different flow and cooling conditions. It was found that both the condensation heat transfer Nusselt number (Nu) and the condensation two-phase frictional multiplier (phi2Lo) were dependent on the steam Reynolds number (Rev), condensation number (Co) and dimensionless hydraulic diameter (Dh/L). With the increase in the steam Reynolds number, condensation number and dimensionless hydraulic diameter, the condensation Nusselt number increased. However, different variations were observed for the condensation two-phase frictional multiplier. With the increase in the steam Reynolds number and dimensionless hydraulic diameter, the condensation two-phase frictional multiplier decreased, while with the increase in the condensation number, the condensation two-phase frictional multiplier increased. Based on the experimental results, dimensionless correlations for condensation heat transfer and flow friction in silicon microchannels were proposed for the first time. These correlations can be used to determine the condensation heat transfer coefficient and pressure drop in silicon microchannels if the steam mass flow rate, cooling rate and geometric parameters are fixed. It was also found that the condensation heat transfer and flow friction have relations to the injection flow (a transition flow pattern from the annular flow to the slug/bubbly flow), and with injection flow moving toward the outlet, both the condensation heat transfer coefficient and the condensation two-phase frictional multiplier increased.

Wu, Huiying; Wu, Xinyu; Qu, Jian; Yu, Mengmeng

2008-11-01

425

Heat transfer characteristics of the two-phase closed thermosyphon (wickless heat pipe)

NASA Astrophysics Data System (ADS)

Steady-state heat transfer characteristics and heat transfer limits (dry-out) for a vertical stainless steel tubular two-phase closed thermosyphon with Freon-113 working fluid are reported as a function of certain geometric parameters and liquid fill quantity. Condenser section heat transfer characteristics agreed reasonably well with existing laminar film condensation correlations and were found to be independent of the evaporator section, except for larger liquid fills. Evaporator characteristics were quite complex and appeared, under some conditions, to be coupled to condenser characteristics through effects of system pressure and/or surface wave as present on the descending condensate film. A laminar thin film evaporation model was found to give reasonable agreement with local evaporator temperature measurements in those regions of the evaporator where a continuous film apparently persisted. The measured heat transfer characteristics are interpreted relative to an earlier investigation by the authors in which flow characteristics in a similar device were visually and photographically observed.

Andros, F. E.; Florschuetz, L. W.

426

Uncertainty Analysis of Heat Transfer to Supercritical Hydrogen in Cooling Channels

NASA Technical Reports Server (NTRS)

Sound understanding of the cooling efficiency of supercritical hydrogen is crucial to the development of high pressure thrust chambers for regeneratively cooled LOX/LH2 rocket engines. This paper examines historical heat transfer correlations for supercritical hydrogen and the effects of uncertainties in hydrogen property data. It is shown that uncertainty due to property data alone can be as high as 10%. Previous heated tube experiments with supercritical hydrogen are summarized, and data from a number of heated tube experiments are analyzed to evaluate conditions for which the available correlations are valid.

Locke, Justin M.; Landrum, D. Brian

2005-01-01

427

S{sub n} solutions for radiative heat transfer in an L-shaped participating medium

The Third Symposium on Solution Methods for Radiative Heat Transfer in Participating Media is a continuing effort to benchmark solutions for problems of increasing complexity. This paper presents both the statement of a problem used for the benchmarking exercise and the results obtained using a finite-element S{sub 4} solution. Cases analyzed include rectangular and L-shaped enclosures, and homogeneous and nonhomogeneous media. Calculated surface radiative heat fluxes and divergence of radiative heat fluxes are tabulated at selected coordinates within the evaluated enclosures. Computation times for each of the solutions were recorded and are presented to permit a computational efficiency test against other solution techniques.

Hoover, R.L.; Li, W.; Benmalek, A.; Tong, T.W. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering

1996-11-01

428

Heat Transfer in High-Temperature Fibrous Insulation

NASA Technical Reports Server (NTRS)

The combined radiation/conduction heat transfer in high-porosity, high-temperature fibrous insulations was investigated experimentally and numerically. The effective thermal conductivity of fibrous insulation samples was measured over the temperature range of 300-1300 K and environmental pressure range of 1.33 x 10(exp -5)-101.32 kPa. The fibrous insulation samples tested had nominal densities of 24, 48, and 72 kilograms per cubic meter and thicknesses of 13.3, 26.6 and 39.9 millimeters. Seven samples were tested such that the applied heat flux vector was aligned with local gravity vector to eliminate natural convection as a mode of heat transfer. Two samples were tested with reverse orientation to investigate natural convection effects. It was determined that for the fibrous insulation densities and thicknesses investigated no heat transfer takes place through natural convection. A finite volume numerical model was developed to solve the governing combined radiation and conduction heat transfer equations. Various methods of modeling the gas/solid conduction interaction in fibrous insulations were investigated. The radiation heat transfer was modeled using the modified two-flux approximation assuming anisotropic scattering and gray medium. A genetic-algorithm based parameter estimation technique was utilized with this model to determine the relevant radiative properties of the fibrous insulation over the temperature range of 300-1300 K. The parameter estimation was performed by least square minimization of the difference between measured and predicted values of effective thermal conductivity at a density of 24 kilograms per cubic meters and at nominal pressures of 1.33 x 10(exp -4) and 99.98 kPa. The numerical model was validated by comparison with steady-state effective thermal conductivity measurements at other densities and pressures. The numerical model was also validated by comparison with a transient thermal test simulating reentry aerodynamic heating conditions.

Daryabeigi, Kamran

2002-01-01

429

Glove thermal insulation: local heat transfer measures and relevance

When exposed to cold, the hands need to be protected against heat loss not only in order to reduce thermal discomfort, but also to keep their efficiency. Although gloves are usually the most common protection, their thermal insulation is generally unknown. The aim of this study was to measure the heat losses from a gloved hand with a special interest

Hayet Sari; Maurice Gartner; Alain Hoeft; Victor Candas

2004-01-01

430

Heat Transfer from a Horizontal Cylinder Rotating in Oil

NASA Technical Reports Server (NTRS)

Measurements of the heat transfer from a horizontal cylinder rotating about its axis have been made with oil as the surrounding fluid to provide an addition to the heat-transfer results for this system heretofore available only for air. The results embrace a Prandtl number range from about 130 to 660, with Reynolds numbers up to 3 x 10(exp 4), and show an increasing dependence of free-convection heat transfer on rotation as the Prandtl number is increased by reducing the oil temperature. Some correlation of this effect, which agrees with the prior results for air, has been achieved. At higher rotative speeds the flow becomes turbulent, the free- convection effect vanishes, and the results with oil can be correlated generally with those for air and with mass-transfer results for even higher Prandtl numbers. For this system, however, the analogy calculations which have successfully related the heat transfer to the friction for pipe flows at high Prandtl numbers fail.

Seban, R. A.; Johnson, H. A.

1959-01-01

431

Heat transfer performance of metal fiber sintered surfaces

NASA Astrophysics Data System (ADS)

Boiling heat transfer performance on stainless steel metal fiber sintered surfaces is experimentally investigated with Freon 11 (R11) as the working fluid. The boiling heat transfer coefficient for the optimum surface structure gives a tenfold improvement over a smooth surface. The nondimensional specific parameter including all design parameters is introduced to explain the trend of the performance of various kinds of metal fiber sintered surfaces. Moreover, the metal fiber sintered surface clad with titanium film is suggested to be appropriate to an evaporator for Ocean Thermal Energy Conversion (OTEC) system.

Kajikawa, T.; Takazawa, H.; Mizuki, M.

1983-03-01

432

Predicted Turbine Heat Transfer for a Range of Test Conditions

NASA Technical Reports Server (NTRS)

Comparisons are shown between predictions and experimental data for blade and endwall heat transfer. The comparisons of computational domain parisons are given for both vane and rotor geometries over an extensive range of Reynolds and Mach numbers. Comparisons are made with experimental data from a variety of sources. A number of turbulence models are available for predicting blade surface heat transfer, as well as aerodynamic performance. The results of an investigation to determine the turbulence model which gives the best agreement with experimental data over a wide range of test conditions are presented.

Boyle, R. J.; Lucci, B. L.

1996-01-01

433

Dropwise condensation heat transfer of steam on a polytethefluoroethylene film

NASA Astrophysics Data System (ADS)

Excellent dropwise condensation of steam was observed on a polytethefluoroethylene (PTFE) coated plate. The experimental results indicated that the condensation heat transfer performance was increased by 30 to 47 times when compared with film condensation values at the same surface subcooling degrees. The random fluctuation of the surface temperature was resulted from the high thermal conductivity of the copper substrate and the ultra thin coated polymer film with lower surface free energy. The effect of the steam temperature for pressures near atmospheric pressure on the dropwise condensation heat transfer characteristics was investigated as well.

Ma, Xuehu; Tao, Bai; Chen, Jiabin; Xu, Dunqi; Lin, Jifang

2001-07-01

434

Heat transfer in jet assimilation into a uniform stream

The assimilation of a preheated jet into an aligned uniform stream is investigated. A formulation is developed that exploits inherent conservation properties of the flow and heat transfer. The formulation provides a unified framework for establishing flow and heat transfer characteristics at all stations downstream of the jet source. Numerical solutions are obtained for velocity and temperature distributions throughout the flow field. The study is complemented by an examination of the problem by series extension techniques. Favorable comparisons with exact numerical results are demonstrated.

Wilks, G.; Astin, P. [Univ. of Keele, Staffordshire (United Kingdom). Dept. of Mathematics

1997-02-21

435

Heat transfer coefficients of dilute flowing gas-solids suspensions

NASA Technical Reports Server (NTRS)

Heat transfer coefficients of air-glass, argon-glass, and argon-aluminum suspensions were measured in horizontal and vertical tubes. The glass, 21.6 and 36.0 micron diameter particles, was suspended at gas Reynolds numbers between 11,000 and 21,000 and loading ratios between 0 and 2.5. The presence of particles generally reduced the heat transfer coefficient. The circulation of aluminum powder in the 0.870 inch diameter closed loop system produced tenacious deposits on protuberances into the stream. In the vertical test section, the Nusselt number reduction was attributed to viscous sublayer thickening; in the horizontal test section to particle deposition.

Kane, R. S.; Pfeffer, R.

1973-01-01

436

Radial heat transfer from a moving plasma

from a plasma stream of air produced by a gas vortex stabilized dc-plasma jet to the stagnation region of a plane surface using a constant-flow water calorimeter. These measurements were of the rate of heat trans? fer through a central circular area...-temperature gas caused to emerge from one of the ends. A dc-plasma jet is then a device having two elec- trodes -- cathode and anode -- between which an arc has been "struck" and constricted to provide a continuous flame. The cathode or negative electrode...

Johnson, James Randall

2012-06-07

437

Shock tunnel measurements of heat transfer in a model scramjet

NASA Technical Reports Server (NTRS)

The results of heat transfer measurements to the walls of a two dimensional scramjet combustion chamber in a shock tunnel are presented. Thin film heat transfer gauges on a ceramic glass substrate were used. The range of experimental conditions covered produced boundary layers ranging from laminar to transitional, as was independently checked by flow visualization. Empirical flat plate correlations, corrected for local pressure disturbances were used to make a comparison with the experimental results. In the fully laminar regime the heating rates were found to give approximate agreement with the empirical estimates. In the nonlaminar tests the heating rate is found to be well below the fully turbulent levels. It is not known at present if this is a transition effect, or if the pressure corrected flat plate turbulent correlations do not apply to the configuration used.

Morgan, R. G.; Stalker, R. J.

1985-01-01

438

Convective heat transfer over thin ice covered coastal polynyas

NASA Astrophysics Data System (ADS)

Polynyas play an important role in the regional meteorology and oceanography of the high latitudes and in the global ocean circulation. Unique low-level observations of an Antarctic coastal polynya, the Ronne Polynya, were conducted using an instrumented aircraft. At the time of the observations, the polynya was mostly covered with thin ice perforated with holes and was composed of two distinct regimes: an inner region of newly formed and thin ice and an outer region of thicker more consolidated ice. The sensible heat flux over the polynya was ˜100 W m-2 and decreased with fetch, primarily as a result of the thickening ice cover. The mean sensible heat transfer and drag coefficients over the polynya were CHN10 = (0.7 ± 0.1) × 10-3 and CDN10 = (1.1 ± 0.2) × 10-3, respectively. The heat transfer coefficient is similar to that found over heterogeneous sea ice and is significantly lower than has been used in previous studies of heat fluxes over polynyas, which are often assumed to be open water. The transfer coefficients were not found to be a function of fetch or ice conditions as represented by the surface temperature and albedo. The data were used in an investigation of the output of sensible heat flux, potential temperature, and boundary layer depth from a simple fetch-dependent model. For this case study, surface temperatures and transfer coefficients appropriate to an ice-covered surface were required for an accurate simulation.

Fiedler, E. K.; Lachlan-Cope, T. A.; Renfrew, I. A.; King, J. C.

2010-10-01

439

Enhanced boiling heat transfer in horizontal test bundles

Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.

Trewin, R.R.; Jensen, M.K.; Bergles, A.E.

1994-08-01

440

Energy Efficient Storage and Transfer of Cryogens

NASA Technical Reports Server (NTRS)

Cryogenics is globally linked to energy generation, storage, and usage. Thermal insulation systems research and development is an enabling part of NASA's technology goals for Space Launch and Exploration. New thermal testing methodologies and materials are being transferred to industry for a wide range of commercial applications.

Fesmire, James E.

2013-01-01

441

Heat-transfer tests of aqueous ethylene glycol solutions in an electrically heated tube

NASA Technical Reports Server (NTRS)

As part of an investigation of the cooling characteristics of liquid-cooled engines, tests were conducted with an electrically heated single-tube heat exchanger to determine the heat-transfer characteristics of an-e-2 ethylene glycol and other ethylene glycol-water mixtures. Similar tests were conducted with water and commercial butanol (n-butyl alcohol) for check purposes. The results of tests conducted at an approximately constant liquid-flow rate of 0.67 pound per second (Reynolds number, 14,500 to 112,500) indicate that at an average liquid temperature 200 degrees f, the heat-transfer coefficients obtained using water, nominal (by volume) 30 percent-70 percent and 70 percent-30 percent glycol-water mixtures are approximately 3.8, 2.8, and 1.4 times higher, respectively, than the heat-transfer coefficients obtained using an-e-2 ethylene glycol.

Bernardo, Everett; Eian, Carroll S

1945-01-01

442

Nozzle-geometry effects in liquid jet impingement heat transfer

Experiments were conducted to determine the effect of nozzle geometry (diameter and aspect ratio) on the local heat transfer coefficients from a small heat source to a normally impinging, axisymmetric, submerged and confined liquid jet of FC-77. A single jet with nozzle diameters in the range of 0.79–6.35 mm and up to seven different nozzle aspect ratios in the range

Suresh V. Garimella; Boris Nenaydykh

1996-01-01

443

PWR-blowdown heat transfer separate effects program

The ORNL Pressurized-Water Reactor Blowdown Heat Transfer (PWR-BDHT) Program is an experimental separate-effects study of the relations among the principal variables that can alter the rate of blowdown, the presence of flow reversal and rereversal, time delay to critical heat flux, the rate at which dryout progresses, and similar time-related functions that are important to LOCA analysis. Primary test results

Thomas

1976-01-01

444

Theory of heat transfer and hydraulic resistance of oil radiators

NASA Technical Reports Server (NTRS)

In the present report the coefficients of heat transfer and hydraulic resistance are theoretically obtained for the case of laminar flow of a heated viscous liquid in a narrow rectangular channel. The results obtained are applied to the computation of oil radiators, which to a first approximation may be considered as made up of a system of such channels. In conclusion, a comparison is given of the theoretical with the experimental results obtained from tests on airplane oil radiators.

Mariamov, N B

1942-01-01

445

Natural convection heat transfer in horizontal rod-bundle enclosures

Natural convection heat transfer in enclosed horizontal N x N arrays (N = 3, 5, and 7) of electrically heated rods with a pitch-to-diameter ratio (P\\/d) of 1.35 has been experimentally investigated. Each array was positioned in an isothermal square enclosure with a width-to-diameter ratio (W\\/d) of 20.6. Pressurized air or helium was used as the working fluid. It was

M. Keyhani; T. Dalton

1996-01-01

446

Experimental investigation of flow-boiling heat transfer under microgravity

An experimental apparatus has been constructed and used to investigate one-component flow-boiling heat transfer under microgravity conditions. Freon-113 was injected at a constant rate between 35 cu cm\\/s and 75 cu cm\\/s into a cylindrical stainless steel test section (L 914.4 mm, O.D. 12.5 mm, I.D. 12.0 mm). The horizontal test section was heated externally up to 30 kW\\/sq m

R. K. Lui; M. Kawaji; T. Ogushi

1992-01-01

447

Heat transfer with phase change in plate-fin heat exchangers

NASA Astrophysics Data System (ADS)

A theoretical and experimental study was conducted for convective evaporation and condensation in plate-fin compact heat exchangers. The overall performance of a brazed-aluminum heat exchanger in the evaporation mode with ammonia and in the condensation mode with both ammonia and refrigerant R-22 as working fluids. The heat exchanger has straight perforated fins on the working-fluid side and extruded rectangular channels on the single-phase (water) side. The two-phase flow in narrow channels of the heat exchanger is modeled using a triangular relationship between pressure gradient, liquid film flow rate, and film thickness. The overall performance of the heat exchanger is calculated by employing local heat-transfer analysis and integrating mass- and heat-balance equations along the heat-exchanger length. Theoretical predictions are found to agree favorably with experimental results for a prototypical heat exchanger unit.

Panchal, C. B.

1984-08-01

448

NASA Astrophysics Data System (ADS)

Compact heat exchangers have been designed following the same basic methodology for over fifty years. However, with the present emphasis on energy efficiency and light weight of prime movers there is increasing demand for completely new heat exchangers. Moreover, new materials and mesoscale fabrication technologies offer the possibility of significantly improving heat exchanger performance over conventional designs. This work involves fundamental flow and heat transfer experimentation to explore two new heat exchange systems: in Part I, large arrays of impinging jets with local extraction and in Part II, metal foams used as fins. Jet impingement cooling is widely used in applications ranging from paper manufacturing to the cooling of gas turbine blades because of the very high local heat transfer coefficients that are possible. While the use of single jet impingement results in non-uniform cooling, increased and more uniform mean heat transfer coefficients may be attained by dividing the total cooling flow among an array of smaller jets. Unfortunately, when the spent fluid from the array's central jets interact with the outer jets, the overall mean heat transfer coefficient is reduced. This problem can be alleviated by locally extracting the spent fluid before it is able to interact with the surrounding jets. An experimental investigation was carried out on a compact impingement array (Xn/Djet = 2.34) utilizing local extraction of the spent fluid (Aspent/Ajet = 2.23) from the jet exit plane. Spatially resolved measurements of the mean velocity field within the array were carried out at jet Reynolds numbers of 2300 and 5300 by magnetic resonance velocimetry, MRV. The geometry provided for a smooth transition from the jet to the target surface and out through the extraction holes without obvious flow recirculation. Mean Nusselt number measurements were also carried out for a Reynolds number range of 2000 to 10,000. The Nusselt number was found to increase with the Reynolds number to the 0.6 power with peak Nusselt numbers near 75 at a Reynolds number of 10,000. Open-celled metallic foams offer three important characteristics which enable them to perform well in heat exchange applications. They contain a very large surface area to volume ratio, a highly complex flow passage through the foam, and in many cases, significant thermal conductivity in the solid phase. Unfortunately, difficulty arises when metal foams are implemented in heat exchanger designs. The performance of the foam has not been characterized in a way which is conducive to analytical design of high performance heat exchangers. The second part of this work provides both flow and heat transfer measurements for metal foam geometries. Full-field velocity measurements through a foam sample were acquired using MRV. The measurements show transverse velocities on the order of 25-30% of the Darcy velocity, UD, which produce enhanced thermal dispersion within the foam matrix. A mechanical dispersion coefficient, DM, was formed which demonstrates the transverse dispersion to be 13 times the kinematic viscosity and 9 times the thermal diffusivity of air at 20°C and 1 atm. To describe the heat transfer performance of the foam as a fin, we have developed a new method that utilizes a well documented, periodic heat exchanger core test and a new one heated wall (OHW) test which when used in conjunction are shown to determine the convective performance (hmAc), the conductive performance (ksAc), and the effective bond resistance associated to attaching metal foams to primary heat transfer surfaces (RBond). Small pore diameter foams, d ? 1 mm, where found to perform approximately a factor of 2 greater per unit volume than a comparable fine-fin heat exchanger surface at the same pumping power which points to the fact the foam as a system is conduction limited not convection limited.

Onstad, Andrew J.

449

Numerical prediction of turbulent oscillating flow and associated heat transfer

NASA Technical Reports Server (NTRS)

A crucial point for further development of engines is the optimization of its heat exchangers which operate under oscillatory flow conditions. It has been found that the most important thermodynamic uncertainties in the Stirling engine designs for space power are in the heat transfer between gas and metal in all engine components and in the pressure drop across the heat exchanger components. So far, performance codes cannot predict the power output of a Stirling engine reasonably enough if used for a wide variety of engines. Thus, there is a strong need for better performance codes. However, a performance code is not concerned with the details of the flow. This information must be provided externally. While analytical relationships exist for laminar oscillating flow, there has been hardly any information about transitional and turbulent oscillating flow, which could be introduced into the performance codes. In 1986, a survey by Seume and Simon revealed that most Stirling engine heat exchangers operate in the transitional and turbulent regime. Consequently, research has since focused on the unresolved issue of transitional and turbulent oscillating flow and heat transfer. Since 1988, the University of Minnesota oscillating flow facility has obtained experimental data about transitional and turbulent oscillating flow. However, since the experiments in this field are extremely difficult, lengthy, and expensive, it is advantageous to numerically simulate the flow and heat transfer accurately from first principles. Work done at the University of Minnesota on the development of such a numerical simulation is summarized.

Koehler, W. J.; Patankar, S. V.; Ibele, W. E.

1991-01-01

450

A vectorized heat transfer model for solid reactor cores

The new generation of nuclear reactors includes designs that are significantly different from light water reactors. Among these new reactor designs is the Modular High-Temperature Gas-Cooled Reactor (MHTGR). In addition, nuclear thermal rockets share a number of similarities with terrestrial HTGRs and would be amenable to similar types of analyses. In these reactors, the heat transfer in the solid core mass is of primary interest in design and safety assessment. One significant safety feature of these reactors is the capability to withstand a loss of pressure and forced cooling in the primary system and still maintain peak fuel temperatures below the safe threshold for retaining the fission products. To accurately assess the performance of gas-cooled reactors during these types of transients, a Helium/Hydrogen Cooled Reactor Analysis (HERA) computer code has been developed. HERA has the ability to model arbitrary geometries in three dimensions, which allows the user to easily analyze reactor cores constructed of prismatic graphite elements. The code accounts for heat generation in the fuel, control rods and other structures; conduction and radiation across gaps; convection to the coolant; and a variety of boundary conditions. The numerical solution scheme has been optimized for vector computers, making long transient analyses economical. Time integration is either explicit or implicit, which allows the use of the model to accurately calculate both short- or long-term transients with an efficient use of computer time. Both the basic spatial and temporal integration schemes have been benchmarked against analytical solutions. Also, HERA has been used to analyze a depressurized loss of forced cooling transient in a HTGR with a very detailed three-dimensional input model. The results compare favorably with other means of analysis and provide further validation of the models and methods. 18 refs., 11 figs.

Rider, W.J.; Cappiello, M.W.; Liles, D.R.

1990-01-01

451

Tube entrance heat transfer with deposit formation

NASA Technical Reports Server (NTRS)

A two-peak wall temperature profile was observed while flowing a kerosene-type gas turbine fuel through a direct-resistance heated tube at an entrance Reynolds number of about 1500. The downstream peak gradually diminished as deposits formed inside the tube, and only one peak remained after seven hours. The observation is explained qualitatively on the basis of analytical and experimental results reported in the literature. It is shown that the temperature profile can be divided into five regions: development of the thermal boundary layer, appearance of the secondary flows, fully developed thermal boundary layer, transition to turbulent flow, and turbulent flow. Deposits increase the tube roughness and reduce the length required for laminar-turbulent transition.

Szetela, E. J.; Sobel, D. R.

1982-01-01

452

Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

NASA Technical Reports Server (NTRS)

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

Jiang, Nan; Simon, Terrence W.

2006-01-01

453

Three-dimensional analysis of heat transfer in a micro-heat sink with single phase flow

A detailed numerical simulation of forced convection heat transfer occurring in silicon-based microchannel heat sinks has been conducted using a simplified three-dimensional conjugate heat transfer model (2D fluid flow and 3D heat transfer). The micro-heat sink model consists of a 10 mm long silicon substrate, with rectangular microchannels, 57 ?m wide and 180 ?m deep, fabricated along the entire length.

J. Li; G. P. Peterson; P. Cheng

2004-01-01

454

An experimental study was carried out to investigate enhancement of heat transfer in compact heat exchanger by keeping pressure drop constant in a given range. Two different test matrices, cylindrical and triangular, used to find the optimum ribs were compared with a smooth channel. The investigation was performed with both laminar and turbulent forced flow for Reynolds numbers from 250

Ibrahim Kilicaslan; H. Ibrahim Sarac

1998-01-01

455

Joule heating and heat transfer in poly(dimethylsiloxane) microfluidic systems

(using a 3D "whole-chip" finite element model) approach is used to examine Joule heating and heat transfer at a microchannel intersection in poly(dimethylsiloxane) (PDMS), and hybrid PDMS/Glass/PDMS chips over the PDMS/Glass systems. The detailed numerical analysis revealed that the vast majority

Erickson, David

456

Heat transfer and friction correlation for compact louvered fin-and-tube heat exchangers

General heat transfer and friction correlations for louver fin geometry having round tube configuration were proposed in the present study. A total of 49 samples of louvered fin-and-tube heat exchangers with different geometrical parameters, including louver pitch, louver height, longitudinal tube pitch, transverse tube pitch, tube diameter, and fin pitch were used to develop the correlations. The proposed correlation describes

C.-C. Wang; C.-J. Lee; C.-T. Chang; S.-P. Lin

1998-01-01

457

Local heat transfer measurements of plate finned-tube heat exchangers by infrared thermography

An experimental study is performed using an infrared thermovision to monitor temperature distribution over a plate-fin surface inside the plate finned-tube heat exchangers. The differentiation of the temperature function is derived to determine the local convective heat transfer coefficients on the tested fin, using a local element lumped conduction equation included the convective effect on the boundaries with experimental data.

Herchang Ay; JiinYuh Jang; Jer-Nan Yeh

2002-01-01

458

Heat transfer and pressure drop of ice slurries in plate heat exchangers

Ice slurries can be used both for cold storage in place of chilled water or ice and as a secondary refrigerant since, up to certain concentrations, they can be pumped directly through distribution pipeworks and heat exchangers. For ice slurries to become more widely accepted, however, more engineering information is required on fluid flow and heat transfer characteristics.This paper reports

J. Bellas; I. Chaer; S. A. Tassou

2002-01-01

459

Forced convective heat transfer across a pin fin micro heat sink

This paper investigates heat transfer and pressure drop phenomena over a bank of micro pin fins. A simplified expression for the total thermal resistance has been derived, discussed and experimentally validated. Geometrical and thermo-hydraulic parameters affecting the total thermal resistance have been discussed. It has been found that very low thermal resistances are achievable using a pin fin heat sink.

Yoav Peles; Ali Ko?ar; Chandan Mishra; Chih-Jung Kuo; Brandon Schneider

2005-01-01

460

ERIC Educational Resources Information Center

In this paper, some heat transfer characteristics through a sample that is uniformly heated on one of its surfaces by a power density modulated by a periodical square wave are discussed. The solution of this problem has two contributions, comprising a transient term and an oscillatory term, superposed to it. The analytical solution is compared to…

Rojas-Trigos, J. B.; Bermejo-Arenas, J. A.; Marin, E.

2012-01-01

461

An annular turbine shroud separates a hot gas path from a cooling plenum containing a cooling medium. Bumps are cast in the surface on the cooling side of the shroud. A surface coating overlies the cooling side surface of the shroud, including the bumps, and contains cooling enhancement material. The surface area ratio of the cooling side of the shroud with the bumps and coating is in excess of a surface area ratio of the cooling side surface with bumps without the coating to afford increased heat transfer across the element relative to the heat transfer across the element without the coating.

Chiu, Rong-Shi Paul (Glenmont, NY); Hasz, Wayne Charles (Pownal, VT); Johnson, Robert Alan (Simpsonville, SC); Lee, Ching-Pang (Cincinnati, OH); Abuaf, Nesim (Lincoln City, OR)

2002-01-01

462

Enhancement of heat transfers in counterflow plate heat exchanger due to presence of an intermediate auxiliary fluid flow is investigated. The intermediate auxiliary channel is supported by transverse conducting pins. The momentum and energy equations for the primary fluids are solved numerically and validated against a derived approximate analytical solution. A parametric study including the effect of the various plate heat exchanger, and auxiliary channel dimensionless parameters is conducted. Different enhancement performance indicators are computed. The various trends of parameters that can better enhance heat transfer rates above those for the conventional plate heat exchanger are identified. Large enhancement factors are obtained under fully developed flow conditions. The maximum enhancement factors can be increased by above 8.0- and 5.0-fold for the step and exponential distributions of the pins, respectively. Finally, counterflow plate heat exchangers with auxiliary fluid flows are recommended over the typical ones if these flows can be provided with the least cost. PMID:24719572

Khaled, A-R A

2014-01-01

463

Method of measuring heat influx of a cryogenic transfer system

A method is provided for measuring the heat influx of a cryogenic transfer system. A gaseous phase of the cryogen used during normal operation of the system is passed through the system. The gaseous cryogen at the inlet to the system is tempered to duplicate the normal operating temperature of the system inlet. The temperature and mass flow rate of the gaseous cryogen is measured at the outlet of the system, and the heat capacity of the cryogen is determined. The heat influx of the system is then determined from known thermodynamic relationships.

Niemann, Ralph C. (Downers Grove, IL); Zelipsky, Steven A. (Tinley Park, IL); Rezmer, Ronald R. (Lisle, IL); Smelser, Peter (Bruner, MO)

1981-01-01

464

Investigation of Drag and Heat Transfer for Martian Dust Particles

NASA Astrophysics Data System (ADS)

A Mars non-stop dust sample return project has been going on in a Mars exploration mission at Japan Aerospace Exploration Agency. In the project, sampling of Martian dust particles is planned between 35 and 45 km, and thus, the survivability of micron-size particles during traveling through a hot-temperature shock is crucial. In this work, the dust particle heating was investigated from macroscopic and microscopic viewpoints. Drag and heat transfer coefficients calculated by the direct simulation Monte Carlo method were found to agree well with Koshmarov and Svirshevskii and free-molecule models at both altitudes, and particle heating estimations calculated by these models were validated.

Ozawa, T.; Suzuki, T.; Takayanagi, H.; Fujita, K.

2011-05-01

465

Heat transfer and friction characteristics of typical wavy fin-and-tube heat exchangers

Extensive experiments on the heat transfer and pressure drop characteristics of typical wavy fin-and-tube heat exchangers were carried out. In the present study, 18 samples of wavy fin-and-tube heat exchangers with different geometrical parameters, including the number of tube rows, fin pitch, and flow arrangements, were tested in a wind tunnel. Results are presented as plots of the Fanning friction

W. L. Fu; C. T. Chang

1997-01-01

466

Finite Element Analysis for the Heat Transfer of Ground Heat Exchanger

A review of the analytical conduction models for ground heat exchangers was presented first, followed with the developed 3D finite element model based on the ANSYS. The developed model was constructed using a conduction-advection element and meshing trick that enabled the cost-effective simulation for complex heat transfer around ground buried heat exchangers. The validation of the developed model was performed

Xianlei Zong; Xiaohui Cheng

2010-01-01

467

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

In this study, the three-dimensional fluid flow and heat transfer in a rectangular micro-channel heat sink are analyzed numerically using water as the cooling fluid. The heat sink consists of a 1-cm2 silicon wafer. The micro-channels have a width of 57 ?m and a depth of 180 ?m, and are separated by a 43 ?m wall. A numerical code based

Weilin Qu; Issam Mudawar

2002-01-01

468

The Experimental Study on Heat Transfer Characteristics of The External Heat Exchanger

\\u000a Using the external heat exchanger in large-scale CFB boilers can control combustion and heat transfer separately, make the\\u000a adjustments of bed temperature and steam temperature convenient. The state of gas-solid two phase flow in the external heat\\u000a exchanger is bubbling fluidized bed, but differs from the regular one as there is a directional flow in it. Consequently,\\u000a the temperature distribution

X. Y. Ji; X. F. Lu; L. Yang; H. Z. Liu

469

Flow boiling heat transfer coefficients and pressure drops of FC72 in small channel heat sinks

In this study, the heat transfer and pressure drop characteristics of FC-72 in small channel heat sinks, which were designed for liquid cooling of electronic components, were measured by varying the mass flux, saturation temperature, and vapor quality. The small channels had circular cross-sections with diameters of 2 and 4mm and length of 100mm. The heat flux provided by the

Yonghee Jang; Yongtaek Lee; Yongchan Kim

2008-01-01

470

A Rotating Plug Model of Friction Stir Welding Heat Transfer

NASA Technical Reports Server (NTRS)

A simplified rotating plug model is employed to study the heat transfer phenomena associated with the fiction stir welding process. An approximate analytical solution is obtained based on this idealized model and used both to demonstrate the qualitative influence of process parameters on predictions and to estimate temperatures produced in typical fiction stir welding situations.

Raghulapadu J. K.; Peddieson, J.; Buchanan, G. R.; Nunes, A. C.

2006-01-01

471

Versatile Desktop Experiment Module (DEMo) on Heat Transfer

ERIC Educational Resources Information Center

This paper outlines a new Desktop Experiment Module (DEMo) engineered for a chemical engineering junior-level Heat Transfer course. This new DEMo learning tool is versatile, fairly inexpensive, and portable such that it can be positioned on student desks throughout a classroom. The DEMo system can illustrate conduction of various materials,…

Minerick, Adrienne R.

2010-01-01

472

Counterflow Heat Transfer in He II Contained in Porous Media

This dissertation presents a study of steady He II (superfluid helium) counter flow heat transfer in porous media. Porous insulation were suggested as potential alternatives to conventional fully impregnated insulations in superconducting magnet technology. Superconducting magnets are usually cooled with He II. Use of porous insulation requires thus a good knowledge of the behavior of He II within porous materials,

Matthieu Dalban-Canassy

2009-01-01

473

Prediction of Relaminarization Effects on Turbine Blade Heat Transfer

NASA Technical Reports Server (NTRS)

An approach to predicting turbine blade heat transfer when turbulent flow relaminarizes due to strong favorable pressure gradients is described. Relaminarization is more likely to occur on the pressure side of a rotor blade. While stators also have strong favorable pressure gradients, the pressure surface is less likely to become turbulent at low to moderate Reynolds numbers. Accounting for the effects of relaminarization for blade heat transfer can substantially reduce the predicted rotor surface heat transfer. This in turn can lead to reduced rotor cooling requirements. Two-dimensional midspan Navier-Stokes analyses were done for each of eighteen test cases using eleven different turbulence models. Results showed that including relaminarization effects generally improved the agreement with experimental data. The results of this work indicate that relatively small changes in rotor shape can be utilized to extend the likelihood of relaminarization to high Reynolds numbers. Predictions showing how rotor blade heat transfer at a high Reynolds number can be reduced through relaminarization are given.

Boyle, R. J.; Giel, P. W.

2001-01-01

474

Integration of Heat Transfer, Stress, and Particle Trajectory Simulation

Calabazas Creek Research, Inc. developed and currently markets Beam Optics Analyzer (BOA) in the United States and abroad. BOA is a 3D, charged particle optics code that solves the electric and magnetic fields with and without the presence of particles. It includes automatic and adaptive meshing to resolve spatial scales ranging from a few millimeters to meters. It is fully integrated with CAD packages, such as SolidWorks, allowing seamless geometry updates. The code includes iterative procedures for optimization, including a fully functional, graphical user interface. Recently, time dependent, particle in cell capability was added, pushing particles synchronically under quasistatic electromagnetic fields to obtain particle bunching under RF conditions. A heat transfer solver was added during this Phase I program. Completed tasks include: (1) Added a 3D finite element heat transfer solver with adaptivity; (2) Determined the accuracy of the linear heat transfer field solver to provide the basis for development of higher order solvers in Phase II; (3) Provided more accurate and smoother power density fields; and (4) Defined the geometry using the same CAD model, while maintaining different meshes, and interfacing the power density field between the particle simulator and heat transfer solvers. These objectives were achieved using modern programming techniques and algorithms. All programming was in C++ and parallelization in OpenMP, utilizing state-of-the-art multi-core technology. Both x86 and x64 versions are supported. The GUI design and implementation used Microsoft Foundation Class.

Thuc Bui; Michael Read; Lawrence ives

2012-05-17

475

A vectorized heat transfer model for solid reactor cores

The new generation of nuclear reactors includes designs that are significantly different from light water reactors. Among these new reactor designs is the Modular High-Temperature Gas-Cooled Reactor (MHTGR). In addition, nuclear thermal rockets share a number of similarities with terrestrial HTGRs and would be amenable to similar types of analyses. In these reactors, the heat transfer in the solid core

W. J. Rider; M. W. Cappiello; D. R. Liles

1990-01-01

476

Transient Analysis of Slip Flow and Heat Transfer in Microchannels

Hybrid analytical-numerical solutions for transient flow and transient convective heat transfer within microchannels are presented. Analytical solutions for flow transients in microchannels are obtained by making use of the integral transform approach. The proposed model involves the transient fully developed flow equation for laminar regime and incompressible flow with slip at the walls in simple channel geometries. The solution is

F. V. Castellões; C. R. Cardoso; P. Couto; R. M. Cotta

2007-01-01

477

Impingement Heat Transfer Effects on Baking of Flat Bread

An impingement oven designed for flat breads baking was instrumented to monitor the processing conditions and record variables responsible for changes in dough characteristics. Image processing was used to monitor the volume and surface color changes during baking. Fluctuations of oven temperature and jet velocity were minimized using electronic controllers, leading to better repeatability and accuracy. Impingement heat transfer distribution

S. Banooni; S. M. Hosseinalipour; A. S. Mujumdar; E. Taheran; M. Mashaiekhi

2008-01-01

478

Heat transfer in serpentine passages with turbulence promoters

Local heat transfer rates and overall pressure losses were determined for serpentine passages of square cross section. The flow entered an inlet leg, turned 180 deg and then passed through an outlet leg. Results were obtained for a passage with smooth walls for three different bend geometries and the effect of turbulence promoters was investigated. Turbulence promoters between 0.6 and

R. J. Boyle

1984-01-01

479

Wellbore Heat Transfer Model for Wax Deposition in Permafrost Region

was sufficient to produce the oil during the production process. Besides, a user friendly GUI was developed by VB and MATLAB to run the simulation. The effects of permafrost, thermal insulation, well geometry and wax deposition on the heat transfer calculation...

Cui, Xiaoting

2012-05-31

480

Heat Transfer Mechanisms During Flow Boiling in Microchannels

The forces due to surface tension, inertia, and momentum change during evaporation in microchannel govern the two- phase flow patterns and the