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1

BBC Bitesize: Heat Transfer and Efficiency  

NSDL National Science Digital Library

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

Bitesize, General C.

2006-07-09

2

An Efficient Localized Radial Basis Function Meshless Method for Fluid Flow and Conjugate Heat Transfer  

Microsoft Academic Search

A localized radial basis function (RBF) meshless method is developed for coupled viscous fluid flow and convective heat transfer problems. The method is based on new localized radial-basis function (RBF) expansions using Hardy Multiquadrics for the sought-after unknowns. An efficient set of formulae are derived to compute the RBF interpolation in terms of vector products thus providing a substantial computational

Eduardo Divo; Alain J. Kassab

2007-01-01

3

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

SciTech Connect

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

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

2006-07-01

4

Heat Transfer  

NSDL National Science Digital Library

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

Ms. Leslie Van (Montgomery Blair High School)

2006-04-01

5

Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines  

NASA Technical Reports Server (NTRS)

Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E 3 first stage turbine, which represents a modem gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.

Ameri, A. A.; Steinthorsson, E.; Rigby, David L.

1998-01-01

6

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

E-print Network

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

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

2006-01-01

7

Heat Transfer  

Microsoft Academic Search

\\u000a We are now stepping into the traditional physical chemistry area known as thermodynamics. Thermodynamics is concerned with a change of the total energy of a system. A system is a body which performs work (–w) or gives away heat (?q); the same body can also receive work (+w) or heat (+q). Notice the sign: when you carry out work or

Predrag-Peter Ilich

8

Heat transfer dynamics  

Microsoft Academic Search

As heat transfer technology increases in complexity, it becomes more difficult for those without thermal dynamics engineering training to choose between competitive heat transfer systems offered to meet their drying requirements. A step back to the basics of heat transfer can help professional managers and papermakers make informed decisions on alternative equipment and methods. The primary forms of heat and

1994-01-01

9

An Efficient Solver for the Algebraic Equations Resulting from Discretization of the Governing Equations for Fluid Flow and Heat Transfer  

Microsoft Academic Search

An efficient solver for the algebraic equations resulting from the discretization of governing equations of fluid flow and heat transfer problems is proposed. This method is based on the concept of the Gauss-Seidel point iteration method, but modifications are made in that not only the dependent variable itself but also the coefficients and the source term of the algebraic equations

Zhi-Gen Wu; Jin-Zhao Zhang; Dong-Liang Sun; Wen-Quan Tao

2009-01-01

10

Methods of Heat Transfer  

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

11

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

SciTech Connect

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

12

The oxygen mass transfer, carbon dioxide inhibition, heat removal, and the energy and cost efficiencies of high pressure fermentation.  

PubMed

This study focuses on the enhancement of oxygen transfer in aerobic fermentation processes through the use of the reactor headspace pressure as a process variable. Our investigation was performed using an example 5 m3 fermentor, and by applying the mass transfer (sorption) characteristics obtained from measurements with Pseudomonas putida CA-3 in a mineral medium. By applying reactor pressures up to 11 bar (10 bar overpressure) the oxygen transfer capacities of stirred tank reactors can theoretically be increased to values above 1 kmol m(-3) h(-1), although the problem of heat removal limits that value to levels of 0.7 kmol m(-3) h(-1). However, this is still sufficient for the oxygenation of most aerobic fermentation processes, even at very high cell densities. Possible inhibition by the carbon dioxide partial pressure at elevated total pressures is discussed. It is shown that increasing reactor pressure enhances the energy efficiency, defined as the ratio of the oxygen transfer capacity to the total power consumption of the reactor system. The cost efficiency of the oxygen mass transfer, defined as the ratio of the oxygen transfer capacity to the overall cost of the system (overall purchase cost divided by a project lifetime of ten years, plus total energy cost) also increases with reactor pressure up to 5.6 bar. PMID:15791933

Knoll, Arnd; Maier, Bernd; Tscherrig, Hermann; Büchs, Jochen

2005-01-01

13

Improvement of heat transfer efficiency at solid-gas interfaces by self-assembled monolayers  

NASA Astrophysics Data System (ADS)

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

Liang, Zhi; Evans, William; Desai, Tapan; Keblinski, Pawel

2013-02-01

14

Comment on "The effects of heat transfer on the exergy efficiency of an air-standard Otto cycle" by Hakan Özcan, Heat and Mass Transfer (2011) 47:571-577  

NASA Astrophysics Data System (ADS)

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

Rashidi, M. M.; Mousapour, A.; Hajipour, A.

2014-08-01

15

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

16

Teachers' Domain: Heat Transfer  

NSDL National Science Digital Library

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

2008-10-21

17

Heat Transfer Technical Brief  

E-print Network

in nucleate and film boiling regimes to investigate the effect of MWCNT height on pool boiling performance level, and working fluid on nucleate boiling were re- ported in this study. The thermal conductivityJournal of Heat Transfer Technical Brief Pool Boiling Experiments on Multiwalled Carbon Nanotube

Banerjee, Debjyoti

18

Understanding heat transfer  

NSDL National Science Digital Library

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

2010-01-01

19

Geothermal Heat Transfer  

SciTech Connect

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

Basmajian, V.V.

1986-01-28

20

Heat transfer within combusting droplets  

Microsoft Academic Search

The improvement of the basic understanding of heat transfer in sprays is a key point in many engineering applications. In this paper, the temperature field within combusting ethanol droplets in linear stream is investigated by the two-color laser induced fluorescence technique. Additionally, a heat transfer model within the droplet is developed, taking into account both heat conduction and heat advection

G. Castanet; F. Lemoine

2007-01-01

21

"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"  

SciTech Connect

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

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

2008-06-12

22

Heat Transfer Textbook  

NSDL National Science Digital Library

This introductory engineering textbook on heat and mass transfer, written by John H. Lienhard IV, Professor at University of Houston and John H. Lienhard IV, Professor at Massachusetts Institute of Technology is now available online without charge. One aim of this project is to "explore the possibilities of placing textbooks online." The idea is that the online format holds two key benefits -- ease of continuous updates or corrections, and the "potential for fundamentally altering the economics of higher education, particularly those in environments where money is scarce." To these ends, the website also posts a history of the various versions and statistics on downloads of the book worldwide.

2005-11-07

23

CONJUGATE HEAT TRANSFER IN PLATE HEAT EXCHANGERS  

Microsoft Academic Search

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

Michele Ciofalo

2004-01-01

24

Conduction heat transfer solutions  

SciTech Connect

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

25

Conduction heat transfer solutions  

SciTech Connect

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  

NASA Astrophysics Data System (ADS)

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

Vansant, J. H.

1980-03-01

27

5. Heat transfer Ron Zevenhoven  

E-print Network

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

Zevenhoven, Ron

28

Unsteady heat transfer in heat pipes  

Microsoft Academic Search

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

29

Efficient natural-convective heat transfer properties of carbon nanotube sheets and their roles on the thermal dissipation.  

PubMed

In this work, we report our studies related to the natural-convective heat transfer properties of carbon nanotube (CNT) sheets. We theoretically derived the formulas and experimentally measured the natural-convective heat transfer coefficients (H) via electrical heating method. The H values of the CNT sheets containing different layers (1, 2, 3, and 1000) were measured. We found that the single-layer CNT sheet had a unique ability on heat dissipation because of its great H. The H value of the single-layer CNT sheet was 69 W/(m(2) K) which was about twice of aluminum foil in the same environment. As the layers increased, the H values dropped quickly to the same with that of aluminum foil. We also discussed its roles on thermal dissipation, and the results indicated that the convection was a significant way of dissipation when the CNT sheets were applied on macroscales. These results may give us a new guideline to design devices based on the CNT sheets. PMID:24548165

Jiang, Shaohui; Liu, Changhong; Fan, Shoushan

2014-03-12

30

Tubing for augmented heat transfer  

SciTech Connect

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

Yampolsky, J.S.; Pavlics, P.

1983-08-01

31

Evaporative heat transfer in mesoscale heat exchangers  

SciTech Connect

An application for an integrated array of small (mesoscale) cooling devices is introduced and a survey of related research is provided. A test apparatus appropriate for experiments with small-scale, low-capacity evaporators is described. Two-phase pressure drop and heat transfer data are presented for R-134a in a heat exchanger consisting of an inlet manifold, 52 parallel channels, and an exit manifold. Each individual channel has a cross-sectional flow area 800 {micro}m by 800 {micro}m and 74 {micro}m long. Experiments are conducted over a range of conditions, with flow rates up to 0.48 g/s, inlet qualities from 7% to 15%, and an evaporating temperature of approximately 10 C. The heat exchanger operated with a pressure drop of less than about 8 kPa and provided a heat transfer coefficient greater than 8,000 W/(m{sup 2}{center_dot}K). The heat transfer data suggest that nucleate boiling dominates for flow rates below an equivalent Reynolds number (Re{sub eq}) of about 40 in a channel. A comparison of the pressure drop and heat transfer results to related data from the literature shows general agreement and supports these promising results for mesoscale heat exchangers.

Mehendale, S.S.; Jacobi, A.M.

2000-07-01

32

Heat transfer characteristics of radial liquid film flow (local heat transfer characteristics near the turbulent transition point)  

Microsoft Academic Search

It is well known that a circular liquid jet impinging on a flat plate has high heat transfer efficiency. Because such a high heat transfer efficiency can be achieved without sophisticated apparatus, the impinging jet is applied to heating and cooling of a wide range of industrial apparatus, such as the quenching of steel during the rolling process or, conversely,

Kenji Katoh; Tsuneo Azuma; Shinji Kano

1995-01-01

33

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

34

Introductory heat-transfer  

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

35

Rotary Joint for Heat Transfer  

NASA Technical Reports Server (NTRS)

Rotary joint exchanges heat between two heat pipes - one rotating and one stationary. Joint accommodates varying heat loads with little temperature drop across interface. According to concept, heat pipe enters center of disklike stationary section of joint. There, wicks in central artery of heat pipe separate into multiple strands that lead to concentric channels on rotaryinterface side of stationary disk. Thin layer of liquid sodium/potassium alloy carries heat from one member of rotary joint to other. Liquid conducts heat efficiently while permitting relative motion between members. Polypropylene rings contain liquid without interfering with rotation.

Shauback, R.

1986-01-01

36

Evaporative heat transfer in mesoscale heat exchangers  

Microsoft Academic Search

An application for an integrated array of small (mesoscale) cooling devices is introduced and a survey of related research is provided. A test apparatus appropriate for experiments with small-scale, low-capacity evaporators is described. Two-phase pressure drop and heat transfer data are presented for R-134a in a heat exchanger consisting of an inlet manifold, 52 parallel channels, and an exit manifold.

S. S. Mehendale; A. M. Jacobi

2000-01-01

37

Heat transfer in damaged material  

NASA Astrophysics Data System (ADS)

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

Kruis, J.

2013-10-01

38

Enhanced heat transfer using nanofluids  

DOEpatents

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

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

2001-01-01

39

Nanofluid impingement jet heat transfer.  

PubMed

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

Zeitoun, Obida; Ali, Mohamed

2012-01-01

40

Unsteady heat transfer in heat pipes  

NASA Astrophysics Data System (ADS)

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

Beam, J. E.

41

Heat transfer from oriented heat exchange areas  

NASA Astrophysics Data System (ADS)

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

Vantuch, Martin; Huzvar, Jozef; Kapjor, Andrej

2014-03-01

42

Measurement of thermoacoustic convection heat transfer phenomenon  

NASA Technical Reports Server (NTRS)

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

Parang, M.; Salah-Eddine, A.

1983-01-01

43

Boiling heat transfer in compact heat exchangers  

SciTech Connect

Small circular and noncircular channels are representative of flow passages in compact evaporators and condensers. This paper describes results of an experimental study on heat transfer to the flow boiling of refrigerant- 12 in a small circular tube of diameter = 2.46 mm. The objective of the study was to assess the effect of channel size on the heat transfer coefficient and to obtain additional insights relative to the heat transfer mechanisms. The flow channel was made of brass and had an overall length of 0.9 m. The channel wall was electrically heated, and temperatures were measured on the channel wall and in the bulk fluid stream. Voltage taps were located at the same axial locations as the stream thermocouples to allow testing over an exit quality range of 0.21 to 0.94 and a large range of mass flux (63 to 832 kg/m{sup 2}s) and heat flux (2.5 to 59 kW/m{sup 2}). Saturation pressure was nearly constant, averaging 0.82 MPa for most of the testing; a few test data were also taken at a constant lower pressure of 0.52 MPa. Local heat transfer coefficients were determined experimentally. Analysis provided additional support for the conclusion, arrived at from previous studies, that a nucleation mechanism dominates for flow boiling in small channels; nevertheless, a convective-dominant region was identified at very low values of wall superheat (<{approx}3{degrees}C). Previous flow boiling studies in small channels, that did not include wall superheats this low, did not encounter the convective dominant mechanism. Conversely, cryogenic studies at very low wall superheats ({approx}l{degree}C) did not encounter the nucleation dominant regime. The apparent discrepancy is explained by the results of this study.

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

1994-12-31

44

Heat Transfer Studies on Packed Bed Using Non Newtonian Fluid  

Microsoft Academic Search

This project aims to study and compare the heat transfer characteristics for Countercurrent flow and Parallel Flow through Packed Bed by determining the overall heat transfer coefficient, effectiveness, cold side efficiency and hot side efficiency for water-water system and Carboxymethylcellulose (CMC)-water system with various compositions on volume basis. In Packed Bed, the inlet temperatures of both hot and cold fluids

D. Priyadharisani; M. Thirumarimurugan; T. Kannadasan

2011-01-01

45

Investigation of Heat Transfer From  

NASA Technical Reports Server (NTRS)

The convective heat transfer from the surface of an ellipsoidal forebody of fineness ratio 3 and 20-inch maximum diameter was investigated in clear air for both stationary and rotating operation over a range of conditions including air speeds up to 240 knots, rotational speeds up to 1200 rpm, and angles of attack of 0 deg, 3 deg, and 6 deg. The results are presented in the form of heat-transfer coefficients and the correlation of Nusselt and Reynolds numbers. Both a uniform surface temperature and a uniform input heater density distribution were used. The experimental results agree well with theoretical predictions for uniform surface temperature distribution. Complete agreement was not obtained with uniform input heat density in the laminar-flow region because of conduction effects. No significant effects of rotation were obtained over the range of airstream and rotational speeds investigated. Operation at angle of attack had only minor effects on the local heat transfer. Transition from laminar to turbulent heat transfer occurred over a wide range of Reynolds numbers. The location of transition depended primarily on surface roughness and pressure and temperature gradients. Limited transient heating data indicate that the variation of surface temperature with time followed closely an exponential relation.

Lewis, James P.; Ruggeri, Robert S.

1956-01-01

46

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

NASA Astrophysics Data System (ADS)

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

Vantúch, Martin; Malcho, Milan

2014-03-01

47

Heat transfer - A review of 1983 literature  

Microsoft Academic Search

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

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

1984-01-01

48

Heat transfer - A review of 1983 literature  

NASA Astrophysics Data System (ADS)

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

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

1984-12-01

49

Cryo Power and Heat Transfer.  

National Technical Information Service (NTIS)

Over the past eight years, researchers at the University of Central Florida have studied high flux heat transfer by flow boiling, pool boiling and spray cooling. These techniques are targeted for cooling high power density devices such as power MOSFETs an...

L. C. Chow, M. Bass, J. Du Y. Lin, T. Chung

2004-01-01

50

Heat Transfer in Internal Combustion Engines.  

National Technical Information Service (NTIS)

A heat transfer model which uses quasi-steady heat flux relations to calculate the heat transfer from combustion gases through the cylinder wall to the coolant was developed. The convective heat transfer accounts for the physical problems of rotating and ...

C. S. Wang, G. F. Berry

1985-01-01

51

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

52

Selective laser melting of heat transfer devices  

Microsoft Academic Search

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

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

2007-01-01

53

Heat pump seasonal heating efficiency prediction  

SciTech Connect

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

Miller, R.S.

1983-06-01

54

Heat transfer variations of bicycle helmets.  

PubMed

Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets. PMID:16882634

Brühwiler, P A; Buyan, M; Huber, R; Bogerd, C P; Sznitman, J; Graf, S F; Rösgen, T

2006-09-01

55

Thermodynamics and Heat Transfer Review  

E-print Network

.S. Colton © GIT 2009 1 #12;Areas of Interest:Areas of Interest: Mechanical Engineering · MechanicsConduction · Convection to a limited extent via h­ to a limited extent via h · Radiation ­eb = T4 ME 6222: Manufacturing - Ex. 1-11D Heat Transfer Ex. 1 1 · You are interested in cooling a 0.5You are interested in cooling

Colton, Jonathan S.

56

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

57

Heat transfer by thermovision and CFD methods  

NASA Astrophysics Data System (ADS)

The report deals with using of thermovision for analysis of heat transfer. It discusses the use of these methods to analysis of heat transfer in experimental measurement of floor convector and tubular heater with natural convection.

Kapjor, Andrej; Gressak, Tomas; Huzvar, Jozef; Vantuch, Martin

2014-08-01

58

Advances in energy efficiency, heat\\/mass transfer enhancement. PID-Volume 2; HTD-Volume 338  

Microsoft Academic Search

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

M. M. Ohadi; S. V. Dessiatoun; A. R. Shekarriz

1996-01-01

59

Advances in enhanced heat\\/mass transfer and energy efficiency. HTD-Volume 320; PID-Volume 1  

Microsoft Academic Search

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

M. M. Ohadi; J. C. Conklin

1995-01-01

60

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

E-print Network

of air. These results could ben- efit applications such as compressed air energy storage where both high and expansion is both energy efficient and power-dense. An ex- ample would be compressed air energy storage. One such con- figuration proposed in [1], the Open Accumulator, consists of dual liquid and compressed air

Li, Perry Y.

61

Acoustically Enhanced Boiling Heat Transfer  

E-print Network

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

62

Heat transfer characteristics of nanofluids: a review  

Microsoft Academic Search

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

Xiang-Qi Wang; Arun S. Mujumdar

2007-01-01

63

Conceptions for heat transfer correlation of nanofluids  

Microsoft Academic Search

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

Yimin Xuan; Wilfried Roetzel

2000-01-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

65

Heat transfer via dropwise condensation on hydrophobic microstructured surfaces  

E-print Network

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

66

Heat transfer and thermal energy transport  

Microsoft Academic Search

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

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

1976-01-01

67

Pool boiling heat transfer to electrolyte solutions  

Microsoft Academic Search

Pool boiling heat transfer coefficients were measured for solutions of salts with positive solubility in water. The effect of the dissolved salts on nucleation site density, bubble departure diameter and bubble frequency was also investigated. The results show that at low heat fluxes heat transfer coefficients can be considerably lower than corresponding values for distilled water. At high heat fluxes

M. Jamialahmadi; A. Helalizadeh; H. Müller-Steinhagen

2004-01-01

68

Tunable heat transfer with smart nanofluids.  

PubMed

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

Bernardin, Michele; Comitani, Federico; Vailati, Alberto

2012-06-01

69

Energy-efficient water heating  

SciTech Connect

This fact sheet describes how to reduce the amount of hot water used in faucets and showers, automatic dishwashers, and washing machines; how to increase water-heating system efficiency by lowering the water heater thermostat, installing a timer and heat traps, and insulating hot water pipes and the storage tank; and how to use off-peak power to heat water. A resource list for further information is included.

NONE

1995-01-01

70

Heat Transfer Modeling During a Vapor Explosion  

SciTech Connect

A steam explosion is the result of the intense heat transfer that can occur when a cold and volatile fluid is brought into contact with a hot fluid. This heat transfer is linked to the fine fragmentation of the hot fluid, so on the explosion timescale, only part of the cold fluid is involved in this heat transfer. In this paper, two different ways of describing this heat transfer are presented. In the first one, i.e., the microinteraction concept, the amount of coolant involved is controlled by the fragmentation kinetics, while in the second one, it is controlled by phase change resulting from interfacial heat balance.

Berthoud, Georges [Commissariat a l'Energie Atomique, Grenoble (France)

2000-04-15

71

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.

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

72

Forced convective heat transfer in curved diffusers  

Microsoft Academic Search

Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal

J. Rojas; J. H. Whitelaw; M. Yianneskis

1987-01-01

73

Advances in heat transfer. Volume 16  

SciTech Connect

The diffusion of turbulent buoyant jets is considered along with the boiling of multicomponent liquid mixtures, heat flow rates in saturated nucleate pool boiling, and a review of turbulent-boundary-layer heat transfer research at Stanford, 1958-1983. In connection with the boiling of mulitcomponent liquid mixtures, attention is given to the fundamentals of vapor-liquid phase equilibria, the inception of boiling, bubble growth, bubble departure, nucleate pool boiling heat transfer, prediction of nucleate boiling heat transfer coefficients, peak nucleate heat flux, film boiling, and convective boiling. A wide-ranging examination using reduced properties is conducted in the study of heat flow rates in saturated nucleate pool boiling.

Hartnett, J.P.; Irvine, T.F. Jr.

1984-01-01

74

Sensible and latent heat transfer in cross-counterflow gas-to-gas heat exchangers  

SciTech Connect

Simultaneous heat and mass transfer during condensation in cross-counterflow gas-to-gas heat exchangers has been analyzed. The coupled heat and mass transfer equations are derived for boundary-layer controlled heat and mass transfer and include longitudinal heat conduction in the exchanger wall. A numerical method of the finite-difference type is applied to the steady-state performance. Temperature and absolute humidity distributions are calculated for exchanger parameters that are typical in air conditioning systems. Temperature and humidity efficiencies together with frosting limits are evaluated for different inlet air conditions.

Holmberg, R.B. (Flakt Evaporator AB, S-551 84 Jonkoping (SE))

1989-02-01

75

Heat transfer enhancement in heat exchangers  

Microsoft Academic Search

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

76

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

77

Heat transfer, cost modeling and process selection  

NSDL National Science Digital Library

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

Kirchain, Randolph E., Jr.; Powell, Adam C., IV

2006-02-12

78

Low heat transfer oxidizer heat exchanger design and analysis  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

79

Analysis of laminar convective heat transfer in micro heat exchanger for stacked multi-chip module  

Microsoft Academic Search

This article presents a numerical and experimental investigation for the single-phase forced laminar convective heat transfer through arrays of microchannels in micro heat exchangers to be used for cooling power-intensive semiconductor packages, especially the stacked multi-chip modules (MCMs). In the numerical analysis, a parametric study was carried out for the factors affecting the efficiency of heat transfer in the flow

Moon Koo Kang; Joong Han Shin; Hae-Hyung Lee; Kukjin Chun

2005-01-01

80

Heat Transfer in Complex Fluids  

SciTech Connect

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

Mehrdad Massoudi

2012-01-01

81

ON THE STABILITY OF BOILING HEAT TRANSFER  

Microsoft Academic Search

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

N. Zuber

1958-01-01

82

Radiative heat transfer in fire safety science  

Microsoft Academic Search

In fire safety science literature thermal radiation is commonly acknowledged as the dominant mode of heat transfer for medium or large scale fires, which determines the growth and spread of a number of fires. This paper is an attempt to overview the contribution of radiative heat transfer research to fire safety science over the last decade, and to highlight the

J. F. Sacadura

2005-01-01

83

Radiation heat transfer in combustion systems  

Microsoft Academic Search

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

R. Viskanta; M. P. Menguc

1987-01-01

84

Heat Transfer Characteristics of a Generalized Divided Flow Heat Exchanger  

E-print Network

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...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...

Singh, K. P.

1979-01-01

85

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

SciTech Connect

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

86

Forced convective heat transfer in curved diffusers  

NASA Technical Reports Server (NTRS)

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

Rojas, J.; Whitelaw, J. H.; Yianneskis, M.

1987-01-01

87

Heat and mass transfer considerations in advanced heat pump systems  

SciTech Connect

Advanced heat-pump cycles are being investigated for various applications. However, the working media and associated thermal design aspects require new concepts for maintaining high thermal effectiveness and phase equilibrium for achieving maximum possible thermodynamic advantages. In the present study, the heat- and mass-transfer processes in two heat-pump systems -- those based on absorption processes, and those using refrigerant mixtures -- are analyzed. The major technical barriers for achieving the ideal performance predicted by thermodynamic analysis are identified. The analysis provides general guidelines for the development of heat- and mass-transfer equipment for advanced heat-pump systems.

Panchal, C.B.; Bell, K.J.

1992-01-01

88

Heat and mass transfer considerations in advanced heat pump systems  

SciTech Connect

Advanced heat-pump cycles are being investigated for various applications. However, the working media and associated thermal design aspects require new concepts for maintaining high thermal effectiveness and phase equilibrium for achieving maximum possible thermodynamic advantages. In the present study, the heat- and mass-transfer processes in two heat-pump systems -- those based on absorption processes, and those using refrigerant mixtures -- are analyzed. The major technical barriers for achieving the ideal performance predicted by thermodynamic analysis are identified. The analysis provides general guidelines for the development of heat- and mass-transfer equipment for advanced heat-pump systems.

Panchal, C.B.; Bell, K.J.

1992-08-01

89

Prediction of Unshsrouded Rotor Blade Tip Heat Transfer  

NASA Technical Reports Server (NTRS)

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

Ameri, A. A.; Steinthorsson, E.

1994-01-01

90

Conjugate heat transfer characterization in cooling channels  

NASA Astrophysics Data System (ADS)

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

Cukurel, Beni; Arts, Tony; Selcan, Claudio

2012-06-01

91

Nanofluids for heat transfer : an engineering approach.  

SciTech Connect

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

92

The thermodynamics of enhanced heat transfer: a model study  

NASA Astrophysics Data System (ADS)

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

Hovhannisyan, Karen; Allahverdyan, Armen E.

2010-06-01

93

Heat transfer and fluid flow characteristics in microchannels heat exchanger using nanofluids: A review  

Microsoft Academic Search

Advancement in the electronics industry led to the development of microscale heat transfer devices which offered high heat transfer coefficient in a compact size. Nevertheless, the heat transfer characteristics were limited by the heat transfer fluids that were used. The recent development of nanotechnology led to the concept of using suspended nanoparticles in heat transfer fluids to improve the heat

H. A. Mohammed; G. Bhaskaran; N. H. Shuaib; R. Saidur

2011-01-01

94

Nucleate pool boiling heat transfer of pure liquids at low to moderate heat fluxes  

Microsoft Academic Search

A model based on an additive mechanism of heat transfer is proposed for pool boiling of single component systems. The contributing modes of heat transfer are: (i) the heat transferred as latent heat to the evaporating microlayer, (ii) the heat transferred by transient conduction during re-formation of the thermal boundary layer and (iii) the heat transferred by turbulent natural convection

R. J. Benjamin; A. R. BALAKRISHNANT

1996-01-01

95

Heat transfer coefficients of shell and coiled tube heat exchangers  

SciTech Connect

In the present study, the heat transfer coefficients of shell and helically coiled tube heat exchangers were investigated experimentally. Three heat exchangers with different coil pitches were selected as test section for both parallel-flow and counter-flow configurations. All the required parameters like inlet and outlet temperatures of tube-side and shell-side fluids, flow rate of fluids, etc. were measured using appropriate instruments. Totally, 75 test runs were performed from which the tube-side and shell-side heat transfer coefficients were calculated. Empirical correlations were proposed for shell-side and tube-side. The calculated heat transfer coefficients of tube-side were also compared to the existing correlations for other boundary conditions and a reasonable agreement was observed. (author)

Salimpour, M.R. [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran)

2009-01-15

96

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

SciTech Connect

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

97

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

98

Finite element methods in heat transfer  

Microsoft Academic Search

The application of the finite element method to problems in conduction and convection heat transfer is described. The formulation of the basic equations is presented for nonisothermal, incompressible, viscous flows and nonisothermal flows in porous media; typical solution algorithms for both transient and time-independent problems are described. Example analyses are included for problems in heat conduction, forced convection and free

D. K. Gartling

1992-01-01

99

Finite element methods in heat transfer  

SciTech Connect

The application of the finite element method to problems in conduction and convection heat transfer is described. The formulation of the basic equations is presented for nonisothermal, incompressible, viscous flows and nonisothermal flows in porous media; typical solution algorithms for both transient and time-independent problems are described. Example analyses are included for problems in heat conduction, forced convection and free convection.

Gartling, D.K.

1992-10-01

100

Radiative heat transfer in plastic welding process  

Microsoft Academic Search

This paper deals with a novel CO2 laser plastic welding procedure developed from the point of view of heat transfer containing simultaneous radiation and conduction processes and also gives a brief review of plastic welding development to date. The principle and features are shown by both the experiments using CO2 laser as a radiation source and numerical simulation considering heat

Yasuo Kurosaki

2005-01-01

101

Capillary-Pumped Heat-Transfer Loop  

NASA Technical Reports Server (NTRS)

New type of capillary-pumped heat-transfer loop primes itself at startup. Removes substantial quantities of heat like that generated by people and equipment in rooms and vehicles. Creates continuous path for its working fluid; both vapor and liquid move in same direction. Key element in operation of loop is formation of slugs of liquid, condensed from vapor and moved along loop by vapor bubbles before and after it. Both evaporator and condenser contain axial arteries carrying water. Heat entering evaporator from heat source provides energy for transport of fluid and heat. Dimensions in inches.

1989-01-01

102

RESEARCH CONCERNING DESIGN OF HIGH EFFICIENCY BRAZED PLATE HEAT EXCHANGERS  

E-print Network

Brazed plate heat exchangers are carving a big chunk out of the heat transfer industry with their compact size and high efficiency design. Brazed plate units are up to six times smaller than alternative methods of heat exchange with the same capacity. This is because of their unique construction: more then hundred corrugated stainless steel plates are brazed together with every second plate turned 180 degrees. This design creates two highly turbulent fluid channels that flow in opposite directions over a massive surface area. The result of this construction is a significantly higher heat transfer coefficient with less required surface area and outstanding performance characteristics.

Ionel Olaru; Codrin Cobrea

103

Conjugate heat transfer analysis of a heat generating vertical plate  

Microsoft Academic Search

This paper mainly deals with conjugate heat transfer problem pertinent to rectangular fuel element of a nuclear reactor dissipating heat into an upward moving stream of liquid sodium. Introducing boundary layer approximations, the equations governing the flow and thermal fields in the fluid domain are solved simultaneously along with two-dimensional energy equation in the solid domain by satisfying the continuity

S. Jahangeer; M. K. Ramis; G. Jilani

2007-01-01

104

Measurements of heat transfer in microchannel heat sinks  

Microsoft Academic Search

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

105

Heat transfer with freezing in a scraped surface heat exchanger  

Microsoft Academic Search

An experimental study was carried out on a scraped surface heat exchanger used for freezing of water–ethanol mixture and aqueous sucrose solution. The influence of various parameters on heat transfer intensity was established: product type and composition, flow rate, blade rotation speed, distance between blades and wall. During starting (transient period) the solution is first supercooled, then ice crystals appear

Mohamed Ben Lakhdar; Rosalia Cerecero; Graciela Alvarez; Jacques Guilpart; Denis Flick; André Lallemand

2005-01-01

106

Experimental Analysis of Heat Transfer Characteristics for Plate Heat Exchanger  

Microsoft Academic Search

According to analysis of heat transfer characteristics for heat exchanger, one kind of comprehensive performance experimental system is designed, which is high degree of automation, high measurement accuracy, simple operation and wide range of applications. Using Wilson Method to control experimental data and fit curve, one empirical formula is induced and corresponding rule curve is drawn. They are similar with

Yan Liu; Qing Gao; Guohua Wang; Chun Gao

2010-01-01

107

Radiative heat transfer in two-phase media  

Microsoft Academic Search

Physical processes occurring in radiating two-phase media are examined with emphasis on radiative heat transfer in the combustion chambers of thermal power plants. In particular, correct effective temperatures are determined for radiating and dissipating media with reflecting and radiating boundary surfaces; radiation characteristics and thermal efficiencies of the surfaces are calculated. An approximate method is developed for taking account of

Kazimir Serafimovich Adzerikho; Evgenii Fomich Nogotov; Vladimir Petrovich Trofimov

1987-01-01

108

HEAT TRANSFER IN A PULSE COMBUSTION WATER HEATER  

Microsoft Academic Search

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

HSIN-CHENG GARY HUANG; H. C. G

1984-01-01

109

Heat transfer behaviours of nanofluids in a uniformly heated tube  

Microsoft Academic Search

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

Cong Tam Nguyen; Nicolas Galanis; Gilles Roy

2004-01-01

110

Heat Transfer in Underground Rail Tunnels  

E-print Network

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

111

Heat transfer in rocket combustion chambers  

NASA Technical Reports Server (NTRS)

Complexities of liquid rocket engine heat transfer which involve the injector faceplate and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis was used to describe localized heating phenomena associated with particular injector configurations and film coolant flows. These components were analyzed, and the analyses verified when appropriate test data were available. The component analyses are being synthesized into an overall flowfield/heat transfer model. A Navier-Stokes flow solver, the FDNS code, was used to make the analyses. Particular attention was given to the representation of the thermodynamic properties of the fluid streams. Unit flow models of specific coaxial injector elements have been developed and are being used to describe the flame structure near the injector faceplate.

Anderson, P.; Cheng, G.; Farmer, R.

1993-01-01

112

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

113

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

114

Experimental and numerical investigation of HyperVapotron heat transfer  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

115

Heat transfer performance of Al2O3/water nanofluids in a mini channel heat sink.  

PubMed

The high density heat removal in electronic packaging is a challenging task of modern days. Finding compact, energy efficient and cost effective methods of heat removal is being the interest of researchers. In the present work, mini channel with forced convective heat transfer in simultaneously developing regime is investigated as the heat transfer coefficient is inversely proportional to hydraulic diameter. Mini channel heat sink is made from the aluminium plate of 30 mm square with 8 mm thickness. It has 15 mini channel of 0.9 mm width, 1.3 mm height and 0.9 mm of pitch. DI water and water based 0.1% and 0.2% volume fractions of Al2O3/water nanofluids are used as coolant. The flow rates of the coolants are maintained in such a way that it is simultaneously developing. Reynolds number is varied from 400 to 1600 and heat input is varied from 40 W to 70 W. The results showed that heat transfer coefficient is more than the heat transfer coefficient of fully developed flow. Also the heat transfer is more for nanofluids compared to DI water. PMID:24745233

Dominic, A; Sarangan, J; Suresh, S; Sai, Monica

2014-03-01

116

Experimental Study of Heat Transfer and Flow Characteristics for a New Type of Air Heater  

E-print Network

ICEBO2006, Shenzhen, China Heating technologies fo r energy efficiency Vol.III-1-1 Experimental Study of Heat Transfer and Flow Characteristics for a New Type of Air Heater Huifan Zheng Xiaowei Fan Angui Li Lecture...ICEBO2006, Shenzhen, China Heating technologies fo r energy efficiency Vol.III-1-1 Experimental Study of Heat Transfer and Flow Characteristics for a New Type of Air Heater Huifan Zheng Xiaowei Fan Angui Li Lecture...

Zheng, H.; Fan, X.; Li, A.

2006-01-01

117

Heat transfer in pressurized circulating fluidized beds  

SciTech Connect

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

118

Improvement of heat transfer by means of ultrasound: Application to a double-tube heat exchanger.  

PubMed

A new kind of ultrasonically-assisted heat exchanger has been designed, built and studied. It can be seen as a vibrating heat exchanger. A comprehensive description of the overall experimental set-up is provided, i.e. of the test rig and the acquisition system. Data acquisition and processing are explained step-by-step with a detailed example of graph obtained and how, from these experimental data, energy balance is calculated on the heat exchanger. It is demonstrated that ultrasound can be used efficiently as a heat transfer enhancement technique, even in such complex systems as heat exchangers. PMID:22546297

Legay, M; Simony, B; Boldo, P; Gondrexon, N; Le Person, S; Bontemps, A

2012-11-01

119

Characteristics of Transient Boiling Heat Transfer  

SciTech Connect

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

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

2002-07-01

120

Micro heat spreader enhanced heat transfer in MCMs  

SciTech Connect

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

121

Turbulent boundary layer heat transfer on curved surfaces  

Microsoft Academic Search

Heat transfer measurements for a turbulent boundary layer on a convex and concave, constant-temperature surface are presented. The heat transferred on the convex surface was found to be less than that for a flat surface, while the heat transferred to the boundary layer on the concave surface was greater. It was also found that the heat transferred on the convex

R. E. Mayle; M. F. Blair; F. C. Kopper

1979-01-01

122

Critical review of heat transfer characteristics of nanofluids  

Microsoft Academic Search

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

Visinee Trisaksri; Somchai Wongwises

2007-01-01

123

Boiling and Nonboiling Heat Transfer to Electrolyte Solutions  

Microsoft Academic Search

Heat transfer to electrolyte solutions is a common engineering problem in the chemical and petrochemical industries. Nevertheless, only a few experimental investigations of heat transfer to electrolyte solutions can be found in the literature. To improve design of heat transfer equipment and to understand fouling characteristics, it is important to know the clean heat transfer coefficient of electrolyte solutions, and

S. H. Najibi; H. Mueller-Steinhagen; M. Jamialahmadi

1996-01-01

124

Heat transfer for water ow in trapezoidal silicon microchannels  

E-print Network

that the heat transfer behaviors in microchannels International Journal of Heat and Mass Transfer 43 (2000) 3925Heat transfer for water ¯ow in trapezoidal silicon microchannels Weilin Qu, Gh. Mohiuddin Mala to investigate heat transfer characteristics of water ¯owing through trapezoidal silicon microchannels

Qu, Weilin

125

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

126

Condensation heat transfer under a microgravity environment  

NASA Technical Reports Server (NTRS)

A description of the condensation heat transfer process in microgravity is given. A review of the literature is also reported. The most essential element of condensation heat transfer in microgravity is the condensate removal mechanism. Two mechanisms for condensate removal are analyzed by looking into two problems. The first problem is concerned with film condensation on a flat porous plate with the condensate being removed by suction at the wall. The second problem is an analytical prediction of the heat transfer coefficient for condensing annular flows with the condensate film driven by the vapor shear. It is concluded that both suction and vapor shear can effectively drain the condensate to ensure continuous operation of the condensers operated under a microgravity environment. It is recommended that zero-g flight experiments be carried out to verify the prediction made in the present report. The results contained in this report should also aid in the design of future space condensers.

Chow, L. C.

1986-01-01

127

Radiative heat transfer between neighboring particles  

NASA Astrophysics Data System (ADS)

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

Manjavacas, Alejandro; García de Abajo, F. Javier

2012-08-01

128

HOST turbine heat transfer program summary  

NASA Technical Reports Server (NTRS)

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

Gladden, Herbert J.; Simoneau, Robert J.

1988-01-01

129

ME 360N Intermediate Heat Transfer ABET EC2000 syllabus  

E-print Network

or equivalent, with Grade of A. Textbook(s): Mills, Heat Transfer 2nd Ed., Prentice Hall, 1999 Other Required., LMTD & NTU (1) 25. Boiling Heat Transfer, Heat Pipes (1) 26. Network analogue, 1-Dim Steady, PlanarME 360N ­ Intermediate Heat Transfer Page 1 ABET EC2000 syllabus ME 360N ­ Intermediate Heat

Ben-Yakar, Adela

130

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

E-print Network

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

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

1984-01-01

131

Heat transfer in shrouded rectangular cavities  

NASA Technical Reports Server (NTRS)

Heat transfer with turbulent flow over shrouded rectangular cavities are numerically investigated. The geometry studied models flow through the clearance gap at the grooved tip of an axial turbine blade, where the blade rotates in close proximity to a stationary outer ring or shroud. The direction of relative shroud motion is always in opposition to the direction of the gas flow across the blade tip. Heat transfer characteristics and flow pattern in a cavity are found to be strongly influenced by the dimension of gap clearance, cavity geometry, and relative shroud movement.

Chyu, M. K.; Metzger, D. E.; Hwan, C. L.

1986-01-01

132

Metal-Mold interfacial heat transfer  

NASA Astrophysics Data System (ADS)

During the solidification of metal castings, an interfacial heat transfer resistance exists at the boundary between the metal and the mold. This heat transfer resistance usually varies with time even if the cast metal remains in contact with the mold, due to the time dependence of plasticity of the freezing metal and oxide growth on the surface. The present work has studied interfacial heat transfer on two related types of castings. In the first type, a copper chill was placed on the top of a cylindrical, bottom gated casting. Using the techniques of transducer displacements and electrical continuity, a clearance gap was detected between the solidified metal and the chill. The second type of casting had a similar design except that the chill was placed at the bottom. Owing to the effect of gravity, solid to solid contact was maintained at the metal-chill interface, but the high degree of interface nonconformity resulted in a relatively low thermal conductance as indicated by solution of the inverse heat conduction problem. Finally, the influence of interfacial heat transfer on solidification time with three mold ma-terials is compared by a numerical example, and criteria for utilizing Chvorinov's rule are discussed.

Ho, Kai; Pehlke, Robert D.

1985-09-01

133

Active heat transfer enhancement in integrated fan heat sinks  

E-print Network

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

Staats, Wayne Lawrence

2012-01-01

134

Self supporting heat transfer element  

DOEpatents

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

135

Noncontact heat transfer between two metamaterials  

NASA Astrophysics Data System (ADS)

Dispersive metamaterials are artificial composite media with magnetodielectric losses so that they naturally radiate in their surrounding. Here we theoretically investigate both radiative and nonradiative heat exchanges between two metamataterials. We show that the presence of magnetic surface modes and the ferromagnetic behavior of materials close to their magnetic resonance yield novel channels for energy transfer. These results pave the way to the design of innovative structures to manage the noncontact heat exchanges.

Joulain, Karl; Drevillon, Jérémie; Ben-Abdallah, Philippe

2010-04-01

136

Heat Transfer Enhancement: Second Generation Technology  

E-print Network

finned tube. e. Louvered tube-and-plate fin. f. Corrugated plates used in rotary regenerators [llJ. Finned Surfaces for Gases Heat exchange~ size or weight reduction may be an important objective in aeronautical and vehicular applications..." technique. a lower form drag than? tubes. This configuration prOVided in the tube-and offer potential for dry Some rotary regenerators use corrugated plate geometries such as that shown in Fig. 3f. The cor rugations provide considerable heat transfer...

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

1984-01-01

137

Heat transfer analysis of boreholes in vertical ground heat exchangers  

Microsoft Academic Search

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

138

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

139

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

E-print Network

transfer International Journal of Heat and Mass Transfer 45 (2002) 3973­3985 wwwAnalysis 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

Qu, Weilin

140

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

SciTech Connect

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

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

2006-07-01

141

Heat transfer enhancement by electric fields in several heat exchange regimes.  

PubMed

With the present article, the authors summarize over 15 years of work dedicated to studying the effects of the electrical and the gravitational force fields on two-phase and single-phase thermofluid dynamics. Results obtained on several microgravity platforms are presented and the role played by the electric field in the different heat transfer processes is analyzed. In particular, the regimes of nucleate boiling and film boiling are treated. Also, the parameters controlling the liquid-vapor interface instability and the main consequences regarding the critical heat flux (CHF) are outlined. In the final section, the promising technique of ion injection for efficient heat transfer enhancement in single-phase liquids is described, together with the main results obtained under different flow regimes and geometries. The following dielectrics were compared: R113, Vertrel XF, and FC-72 for the pool boiling research; again FC-72 and HFE-7100 for the single-phase convection heat transfer experiments. PMID:17124144

Grassi, Walter; Testi, Daniele

2006-09-01

142

A Review of Heat Transfer Physics  

Microsoft Academic Search

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

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

2008-01-01

143

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

144

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Highly Efficient Lattice Boltzmann Model for Compressible Fluids: Two-Dimensional Case  

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

Cooperative heat transfer and ground coupled storage system  

DOEpatents

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

146

Thermodynamic Efficiency of Heat Exchange Devices  

E-print Network

irreversibilities. The reclamation of what was formerly 'waste heat' by using additional, or more efficient, equipment has become not only economically feasible, but sometimes essential. A thermodynamic efficiency based on the second law of thermodynamics...

Witte, L. C.; Shamsundar, N.

1982-01-01

147

Combined heat and mass transfer device for improving separation process  

SciTech Connect

A two-phase small channel heat exchange matrix for providing simultaneous heat transfer and mass transfer at a single, predetermined location within a separation column, whereby the thermodynamic efficiency of the separation process is significantly improved. The small channel heat exchange matrix is comprised of a series of channels having a hydraulic diameter no greater than 5.0 mm. The channels are connected to an inlet header for supplying a two-phase coolant to the channels and an outlet header for receiving the coolant horn the channels. In operation, the matrix provides the liquid-vapor contacting surfaces within a separation column, whereby liquid descends along the exterior surfaces of the cooling channels and vapor ascends between adjacent channels within the matrix. Preferably, a perforated and concave sheet connects each channel to an adjacent channel, such that liquid further descends along the concave surfaces of the sheets and the vapor further ascends through the perforations in the sheets. The size and configuration of the small channel heat exchange matrix allows the heat and mass transfer device to be positioned within the separation column, thereby allowing precise control of the local operating conditions within the column and increasing the energy efficiency of the process.

Tran, Thanh Nhon

1997-12-01

148

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

149

Heat transfer in bioengineering and medicine  

SciTech Connect

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

150

Experimental Investigation on Heat Transfer Characteristics of a Gas-to-Gas Counterflow Microchannel Heat Exchanger  

Microsoft Academic Search

Heat transfer characteristics of a gas-to-gas counterflow microchannel heat exchanger have been experimentally investigated. Temperatures and pressures at inlets and outlets of the heat exchanger have been measured to obtain heat transfer rates and pressure drops. The heat transfer and the pressure drop characteristics are discussed. Since the partition wall of the heat exchanger is thick compared with the microchannel

K. Koyama; Y. Asako

2010-01-01

151

Heat and mass transfer in fixed and fluidized beds  

Microsoft Academic Search

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

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

1985-01-01

152

Combined heat and mass transfer device for improving separation process  

DOEpatents

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

Tran, Thanh Nhon (Flossmoor, IL)

1999-01-01

153

Combined heat and mass transfer device for improving separation process  

DOEpatents

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

Tran, T.N.

1999-08-24

154

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

155

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

NASA Astrophysics Data System (ADS)

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.

1990-07-01

156

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

NASA Technical Reports Server (NTRS)

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

157

Boiling heat transfer in rectangular microchannels with reentrant cavities  

E-print Network

@rpi.edu (Y. Peles). International Journal of Heat and Mass Transfer 48 (2005) 4867­4886 wwwBoiling heat transfer in rectangular microchannels with reentrant cavities Ali Kos�ar, Chih-phase heat transfer coefficients and CHF conditions have been obtained over a range of effective heat fluxes

Peles, Yoav

158

Porous media simplified simulation of single- and two-phase flow heat transfer in micro-channel heat exchangers  

Microsoft Academic Search

A numerical tool to simulate micro-channel flow and heat transfer in compact heat exchangers is developed. The method is based on a forced convection porous body approach combined with conventional pipe flow closure correlations. The proposed technique aims to provide developers of micro-channel heat exchangers with a fast efficient tool to estimate the thermodynamic behaviour dependent on geometry and operation

U Imke

2004-01-01

159

Heterogeneous nanofluids: natural convection heat transfer enhancement.  

PubMed

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

Oueslati, Fakhreddine Segni; Bennacer, Rachid

2011-01-01

160

Heterogeneous nanofluids: natural convection heat transfer enhancement  

PubMed Central

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

2011-01-01

161

Energy Efficient Steam Trapping of Trace Heating Systems  

E-print Network

Since as many as 40-60% of a plant's steam traps may be used on steam tracer lines, it is essential to select the correct, properly sized 'traps'; to optimize the efficient removal of condensate while providing maximum heat transfer to maintain...

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

1981-01-01

162

Analysis of Influencing Factors of Heat Transfer Performance of Heat Pipe Heat Exchanger  

Microsoft Academic Search

Heat transfer performance of heat pipe heat exchanger affected by many factors, such as the opening temperature of the heat pipe, the rate of fluid-filled, the physical nature of liquid refrigerant, the work temperature of tube, angle, tube spacing, tube length, hot and cold fluid flow and wind speed. The above-mentioned parameters can not be measured because of Test conditions,

Zhang Jie; Ren Yan; Zhang Lihong; Liang Huimin

2009-01-01

163

An implicit scheme for cascade flow and heat transfer analysis  

Microsoft Academic Search

A new efficient implicit scheme, based on the second-order time and spatial difference algorithm for solving steady flow by using time-marching Navier-Stokes equations, was developed for predicting turbine cascade flows and heat transfer. The difference scheme comprises an explicit part in the intermediate time-step and an implicit part in the local time-step. The viscous flux vectors are decomposed to simplify

C. Xu; R. S. Amano

2000-01-01

164

Heat transfer enhancement resulting from induction electrohydrodynamic pumping  

E-print Network

pump and one designed specifically for efficient pumping at high tilt angles were tested to examine the heat transfer enhancement that occurs as a result of induction pumping. Two fluids, Dodecylbenzene and n-Hexane, were tested in the pumps... in designing an induction EHD pump. Forced convection cooling of underground power cables using EHD pumping was investigated by Crowley et al. (1983). Kuo (1982) applied finite element techniques to induction EHD pumping in a horizontal pipe. The numerical...

Margo, Bryan David

2012-06-07

165

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

166

Radiative heat transfer in plastic welding process  

NASA Astrophysics Data System (ADS)

This paper deals with a novel CO2 laser plastic welding procedure developed from the point of view of heat transfer containing simultaneous radiation and conduction processes and also gives a brief review of plastic welding development to date. The principle and features are shown by both the experiments using CO2 laser as a radiation source and numerical simulation considering heat transfer phenomena in simultaneous radiation and conduction in welding process. The feasibility of the proposed procedure is confirmed by applying the overlapped same plastic films with combination of infrared radiation absorbing heating and thermal diffusion cooling processes. A solid material transparent to infrared radiation with a high thermal diffusivity is used as a heat sink in contact with the irradiated surface of overlapped thermoplastics during radiation heating. The procedure is able to achieve both high welding strength and excellent surface appearance without causing surface thermal damage as often suffered in conventional direct infrared radiation welding process. In addition, pigmentation in welding material to increase absorption of radiation is unnecessary for this method.

Kurosaki, Yasuo

2005-06-01

167

Heat and mass transfer modeling in air drying of foods  

Microsoft Academic Search

Heat and mass transfer modeling in the air drying of solids is considered as a two stage procedure. The former aims to discover the dominant heat and mass transfer phenomena (heat versus mass, internal versus external), the latter aims to formulate empirical equations for the calculation of the corresponding heat and mass transport properties (mass diffusivity, thermal conductivity, boundary heat

Z. B. Maroulis; C. T. Kiranoudis; D. Marinos-Kouris

1995-01-01

168

Analysis of heat transfer in unlooped and looped pulsating  

E-print Network

Analysis of heat transfer in unlooped and looped pulsating heat pipes M.B. Sha®i and A. Faghri, Tubing Abstract An advanced heat transfer model for both unlooped and looped Pulsating Heat Pipes (PHPs = speci®c heat (constant volume), J/kg K d = diameter, m g = gravitational acceleration, m2 /s h

Zhang, Yuwen

169

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

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

170

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.

171

Radiation heat transfer shapefactors for combustion systems  

NASA Technical Reports Server (NTRS)

The computation of radiation heat transfer through absorbing media is commonly done through the zoning method which relies upon values of the geometric mean transmittance and absorptance. The computation of these values is difficult and expensive, particularly if many spectral bands are used. This paper describes the extension of a scan line algorithm, based upon surface-surface radiation, to the computation of surface-gas and gas-gas radiation transmittances.

Emery, A. F.; Johansson, O.; Abrous, A.

1987-01-01

172

Coupled Heat Transfer in High Temperature Ceramic Wall with Heat Pipe under Aeroheating and Radiative Cooling  

Microsoft Academic Search

An effective heat transfer device such as heat pipe is used to reduce thermal stress and thermal gradients of inner material by transferring heat from one location to another with very large heat fluxes. Radiative transfer is important and complex at elevated temperature of the ceramic material. These temperatures in the two aeroheating regions and working fluid inside heat pipe

Du Shenghua; Ai Qing; Xia Xinlin

2010-01-01

173

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

E-print Network

.elsevier.com/locate/ijhmt International Journal of Heat and Mass Transfer 49 (2006) 4058­4069 #12;measurements within the heat exchangerEffects of winglets to augment tube wall heat transfer in louvered fin heat exchangers Paul A transfer along the tube wall of the compact heat exchanger through the use of winglets placed

Thole, Karen A.

174

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

175

Nanofluid heat transfer enhancement for nuclear reactor applications  

E-print Network

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

176

Experimental evaluation of heat transfer characteristics of silica nanofluid  

E-print Network

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

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

2010-01-01

177

Heat transfer during film condensation of potassium vapor  

E-print Network

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

178

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

179

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

180

An experimental study of the flow and heat transfer between enhanced heat transfer plates for PHEs  

SciTech Connect

The flow and heat transfer between inclined discrete rib plates for plate heat exchangers have been experimentally studied. Dye injection method is used to visualize the flow structures. The visualization results show that front vortex, rear vortex and main vortex are formed between the plates. The rib parameter influence is also studied using visualization method. The pressure drop and heat transfer between the inclined discrete rib plates as well as that between inclined continuous rib plates and smooth plates are also measured. The measured results show that the inclined discrete rib plate can enhanced heat transfer 20-25% at the same pumping power compared with the commonly used inclined continuous rib plates. (author)

Li, Xiao-wei [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Meng, Ji-an; Li, Zhi-xin [School of Aerospace, Tsinghua University, Beijing 100084 (China)

2010-11-15

181

Radiative heat transfer in nonisothermal combustion products  

NASA Astrophysics Data System (ADS)

Radiative heat transfer plays a significant and sometimes dominant role within combustion systems. Heat flux measurements in such systems are sometimes economically disadvantaged and difficult, if not impractical to perform. To demonstrate a feasible alternative, a simplified numerical model using total transmittance data, TTNH, was developed for predicting the heat flux from nonisothermal combustion systems containing variable concentrations of water vapor, carbon dioxide, and methane. Total and spectral experimental measurements were carried out, to test the numerical model, using nonisothermal mixtures of water vapor/carbon dioxide and methane/ethene, and using isothermal mixtures of methane and ethene. In general, the TTNH model was found to be reliable to predict the total emitted energy by nonisothermal mixtures of carbon dioxide and water vapor within 10%. However, the model was found not reliable to predict the theoretical emittance of methane.

Hamdan, M. A.

1985-12-01

182

EFFECT OF VORTICES ON JET IMPINGEMENT HEAT TRANSFER  

Microsoft Academic Search

Convective heat transfer to an impinging air jet is known to yield high local and area averaged heat transfer coefficients. Such jets are of interest in the cooling of electronic components and of turbine blades and in manufacturing processes such as grinding. The current research is concerned with the measurement of heat transfer to impinging air jets over a wide

T. S. O'Donovan; D. B. Murray

183

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

184

Heat transfer of a submerged round impacting jet  

Microsoft Academic Search

Heat transfer on a target impacted by an air jet was investigated experimentally using IR thermography. The experimentally determined temperature fields were processed on a minicomputer to determine circumferentially averaged radial distributions of heat transfer intensity. Two maxima of the radial heat transfer intensity distributions are identified, and the underlying mechanisms are discussed.

A. I. Abrosimov; M. A. Kosorotov; A. A. Paramonov; M. D. Parfent'ev

1991-01-01

185

Review of convective heat transfer enhancement with nanofluids  

Microsoft Academic Search

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

Sadik Kakaç; Anchasa Pramuanjaroenkij

2009-01-01

186

Investigation on Convective Heat Transfer and Flow Features of Nanofluids  

Microsoft Academic Search

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

187

Technical Note Theoretical analysis of film condensation heat transfer  

E-print Network

. In the International Journal of Heat and Mass Transfer 45 (2002) 2829­2842 wwwTechnical Note Theoretical analysis of film condensation heat transfer inside vertical mini of the inlet vapor flow rates, the inlet subcooling, and the channel size on the heat transfer coefficients

Zhao, Tianshou

188

Radiative heat transfer in inhomogeneous, nongray, and anisotropically scattering media  

E-print Network

and anisotropic scattering medium. Thus, the REM2 International Journal of Heat and Mass Transfer 43 (2000) 2325Radiative heat transfer in inhomogeneous, nongray, and anisotropically scattering media Zhixiong Radiative heat transfer in three-dimensional inhomogeneous, nongray and anisotropically scattering

Guo, Zhixiong "James"

189

7 CFR 3201.54 - Heat transfer fluids.  

...2014-01-01 2014-01-01 false Heat transfer fluids. 3201.54...Designated Items § 3201.54 Heat transfer fluids. (a) Definition...to facilitate the transfer of heat from one location to another...HVAC applications, internal combustion engines, personal...

2014-01-01

190

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...Designated Items § 3201.54 Heat transfer fluids. (a) Definition...to facilitate the transfer of heat from one location to another...HVAC applications, internal combustion engines, personal...

2013-01-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

192

Heat Transfer Through Turbulent Friction Layers  

NASA Technical Reports Server (NTRS)

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

Reichardt, H.

1943-01-01

193

A Model of Respiratory Heat Transfer in a Small Mammal  

PubMed Central

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

194

Testing efficiency transfer codes for equivalence.  

PubMed

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

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

2010-02-01

195

Heat transfer enhancement of copper nanofluid with acoustic cavitation  

Microsoft Academic Search

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

196

High flux heat transfer in a target environment  

E-print Network

Valid for: Consider turbulent heat transfer in a 1.5mm diameter pipe ­ Dittus Boelter correlation ideas Hypervapotrons ·Water cooled finned heat exchangers developed to cope with the high heat fluxesHigh flux heat transfer in a target environment T. Davenne High Power Targets Group Rutherford

McDonald, Kirk

197

Transient Heat Transfer in Zero Gravity Environment  

NASA Technical Reports Server (NTRS)

The objective is to provide computer codes and/or correlations for application in the design of transient heat transfer systems. The mathematical models in the computer codes are being tested by experimental data obtained in the laboratory using optical techniques. The elimination of natural convection (buoyancy) in the experimental data obtained in zero-g (KC-135) facilitates the study of thermal expansion effects which is of interest in the development and testing of the mathematical models of the transient heat transfer. Initial flight in the KC 135 (June 1983) suggested some modifications to the experimental apparatus and the data acquisition technique (high speed video will replace high speed movies for recording optical records generated during the experiments). A series of KC-135 flights with this experiment on board are scheduled for summer/fall 1984. The acquisition of the aforementioned data using interferometry and beam deflection optical techniques is anticipated. The measurements provide time dependent temperature fields above a horizontal heater surface submerged in a static fluid (Freon 13). The heater surface is electrically heated for a time interval approximately 0.100 sec. during which the data are optically recorded.

Giarratano, P. G.; Arp, V. D.; Kumakawa, A.

1985-01-01

198

Heat and mass transfer in bubble column dehumidifiers for HDH desalination  

E-print Network

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

199

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

200

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

Microsoft Academic Search

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

T. Kazuo; M. Hideo

1983-01-01

201

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

E-print Network

model based on Taylor instability and Helmholtz International Journal of Heat and Mass Transfer 44 (2001Numerical study of high heat ¯ux pool boiling heat transfer Ying He a,*, Masahiro Shoji b , Shigeo simulation model of boiling heat transfer is proposed based on a numerical macrolayer model [S. Maruyama, M

Maruyama, Shigeo

202

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

E-print Network

). www.elsevier.com/locate/ijhmt International Journal of Heat and Mass Transfer 50 (2007) 1018­1034 #12 presented by them were limited to low mass velocities (heat transfer coefficient 0017Boiling heat transfer in a hydrofoil-based micro pin fin heat sink Ali Kos�ar, Yoav Peles

Peles, Yoav

203

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

E-print Network

for convective ¯ow. International Journal of Heat and Mass Transfer 45 (2002) 755±764 wwwHeat transfer in a pulsating heat pipe with open end Yuwen Zhang 1 , Amir Faghri * Department 11 July 2000; received in revised form 6 June 2001 Abstract Heat transfer in the evaporator

Zhang, Yuwen

204

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Highly Efficient Lattice Boltzmann Model for Compressible Fluids: Two-Dimensional Case  

Microsoft Academic Search

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

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

2009-01-01

205

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

206

Heat transfer coefficients for atmospheric coolers  

E-print Network

of research done on atmospheric sections at Purdue University t For horizontal tubes carrying liquid to be cooled. , h =g5(7 )~g For slightly inclined tubes where the cooling liquid ripples on the outside surface of the tubes, For the case of a very large... of the tubes. m original data sheet is given in ths . ~ppendix and the method of taking this data is described more fully in the section titled Operation of the Cn1t, Counter flow mean temperature difference and clean heat transfer sur- faces...

Robinson, Robert McCollum

2012-06-07

207

Solar Pond Fluid Dynamics and Heat Transfer  

NASA Technical Reports Server (NTRS)

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

Jones, G. F.

1984-01-01

208

Numerical and experimental analysis of convection heat transfer in passive solar heating room with greenhouse and heat storage  

Microsoft Academic Search

In this paper, heat transfer and air flow in passive solar heating room with greenhouse and heat storage are studied. Thermal insulation of solar heating room has significant effects on temperature distribution and airflow in the heating chamber of this solar system. Heat transfer and air flow in a rock bed, which is used as solar absorber and storage layer,

Wei Chen; Wei Liu

2004-01-01

209

Convective Heat Transfer in Acoustic Streaming Flows  

NASA Astrophysics Data System (ADS)

Convective heat transfer due to acoustic streaming has been studied in the absence of an imposed mean flow. The work is motivated by the need to design and control the thermal features of a suitable experimental rig for the containerless processing of materials by heat treatment of acoustically levitated alloy samples at near zero-gravity. First the problem of heat transfer from an isolated sphere (in a standing sound field) is explored in detail. The streaming Reynolds number, Rs, which characterizes the resulting steady flows, is determined from the acoustic signal. A scale analysis is used to ascertain the importance of buoyancy and viscous dissipation. The steady velocity and temperature fields are determined using asymptotic techniques and numerical methods for the limiting cases of Rs<<1 and Rsgg1. Working correlations for the average Nusselt number are obtained for a wide range of Prandtl numbers. A simple experiment is conducted to verify the predictions for the more relevant case of Rsgg1. The acoustic levitation chamber itself is modelled as a Kundt tube (supporting a plane axial standing sound wave) with insulated side-wall and isothermal end-walls. Analytical solution techniques are used to determine the steady fields close to the tube walls. For the steady recirculatory transport in the core, the numerical solver PHOENICS is adopted for the solution of the complete elliptic form of the governing equations. A study of the effects of a range of acoustic and geometric parameters on the flow and heat transfer is performed and Nusselt number correlations are obtained for air. PHOENICS is also used to study the effects of variable fluid properties and axial side-wall conduction (coupled with radiation). The role of normal/reduced gravity is assessed and suggestions made for terrestrial testing of the levitation apparatus. Finally, with the sample located at a node in the levitation chamber, the effect of the interaction of the streaming flows (on the sphere and the tube walls) is estimated. Representative calculations for the sample heating/cooling rates are presented and compared with existing data in the literature.

Gopinath, Ashok

1992-01-01

210

Boiling heat transfer in a horizontal small-diameter tube  

Microsoft Academic Search

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

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

1993-01-01

211

Heat Transfer Phenomena in Supercritical Water Nuclear Reactors  

SciTech Connect

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

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

2007-10-03

212

Post CHF heat transfer and quenching. [PWR  

SciTech Connect

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

Nelson, R.A.; Condie, K.G.

1980-01-01

213

Performance of Counterflow Microchannel Heat Exchangers Subjected to External Heat Transfer  

Microsoft Academic Search

This article analyzes the effect of external heat transfer on the thermal performance of counterflow microchannel heat exchangers. Equations for predicting the axial temperature and the effectiveness of both fluids as well as the heat transferred between the fluids, while operating under external heating or cooling conditions, are provided in this article. External heating may decrease and increase the effectiveness

Bobby Mathew; Hisham Hegab

2010-01-01

214

The Critical Heat Transfer Characteristics of an Insulated Sphere Considering Heat Radiation  

Microsoft Academic Search

This study is to investigate the critical heat transfer characteristics of an insulated sphere considering heat radiation. It is found that the results considering heat radiation are very big different from those of neglecting heat radiation. The critical heat transfer characteristics deeply depend on the sphere surface emissivity, &Vegr;0, and insulation surface emissivity &Vegr;, surrounding temperature Tsur and the internal

King Leung Wong; Jose´ Luis Leo´n Salazar

2010-01-01

215

The Critical Heat Transfer Characteristics of an Insulated Sphere Considering Heat Radiation  

Microsoft Academic Search

This study is to investigate the critical heat transfer characteristics of an insulated sphere considering heat radiation. It is found that the results considering heat radiation are very big different from those of neglecting heat radiation. The critical heat transfer characteristics deeply depend on the sphere surface emissivity, epsilo0, and insulation surface emissivity V, surrounding temperature Tsur and the internal

King Leung Wong; José Luis León Salazar

2010-01-01

216

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

217

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

E-print Network

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

Kandlikar, Satish

218

Efficiency of vertical geothermal heat exchangers in the ground source heat pump system  

NASA Astrophysics Data System (ADS)

Taking the fluid temperature distribution along the borehole depth into account, a new quasi-three-dimensional model for vertical ground heat exchangers has been established, which provides a better understanding of the heat transfer processes in the geothermal heat exchangers. On this basis the efficiency of the borehole has been defined and its analytical expression derived. Comparison with the previous two-dimensional model shows that the quasi-three-dimensional model is more rational and more accurate to depict the practical feature of the conduction of geothermal heat exchanger, and the efficiency notion can be easily used to determine the inlet and outlet temperature of the circulating fluid inside the heat exchanger.

Zeng, Heyi; Diao, Nairen; Fang, Zhaohong

2003-02-01

219

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

NASA Astrophysics Data System (ADS)

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

220

Association between translation efficiency and horizontal gene transfer within  

E-print Network

Association between translation efficiency and horizontal gene transfer within microbial Horizontal gene transfer (HGT) is a major force in microbial evolution. Previous studies have sug- gested as barriers to the successful in- tegration of horizontally transferred genes. This study identifies

Ruppin, Eytan

221

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

E-print Network

in the presence of bulk fluid motion. Convection is classified as natural (or free) and forced convection depending on how the fluid motion is initiated. In natural convection, any fluid motion M. Bahrami ENSC 388 (F09) Forced Convection Heat Transfer

Bahrami, Majid

222

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

E-print Network

of heat transfer from the gas side to turbine blades in a linear cascade, annular cascade or turbine stage the full-scale operational conditions of a modern gas turbine dictate high temperatures well in excess research on the gas side of a rotating turbine environment is a techni- cally challenging task. The current

Camci, Cengiz

223

Boiling local heat transfer enhancement in minichannels using nanofluids.  

PubMed

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

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

2013-01-01

224

Transectional heat transfer in thermoregulating bigeye tuna (Thunnus obesus) - a 2D heat flux model.  

PubMed

We developed a 2D heat flux model to elucidate routes and rates of heat transfer within bigeye tuna Thunnus obesus Lowe 1839 in both steady-state and time-dependent settings. In modeling the former situation, we adjusted the efficiencies of heat conservation in the red and the white muscle so as to make the output of the model agree as closely as possible with observed cross-sectional isotherms. In modeling the latter situation, we applied the heat exchanger efficiencies from the steady-state model to predict the distribution of temperature and heat fluxes in bigeye tuna during their extensive daily vertical excursions. The simulations yielded a close match to the data recorded in free-swimming fish and strongly point to the importance of the heat-producing and heat-conserving properties of the white muscle. The best correspondence between model output and observed data was obtained when the countercurrent heat exchangers in the blood flow pathways to the red and white muscle retained 99% and 96% (respectively) of the heat produced in these tissues. Our model confirms that the ability of bigeye tuna to maintain elevated muscle temperatures during their extensive daily vertical movements depends on their ability to rapidly modulate heating and cooling rates. This study shows that the differential cooling and heating rates could be fully accounted for by a mechanism where blood flow to the swimming muscles is either exclusively through the heat exchangers or completely shunted around them, depending on the ambient temperature relative to the body temperature. Our results therefore strongly suggest that such a mechanism is involved in the extensive physiological thermoregulatory abilities of endothermic bigeye tuna. PMID:19880733

Boye, Jess; Musyl, Michael; Brill, Richard; Malte, Hans

2009-11-01

225

Radiative heat transfer in participating media — A review  

Microsoft Academic Search

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

Subhash C Mishra; Manohar Prasad

1998-01-01

226

Control of Impingement Heat Transfer Using Mist  

NASA Astrophysics Data System (ADS)

Impingement heat transfer from a circular orifice jet by using latent heat of water mists was studied experimentally. The amounts of mists of about Zauter's mean diameter 14 µm were from 60 to 200 g/h within a range where liquid films were not formed on the target plate and mists were added near the orifice edge. Experiments covered Reynolds numbers from 12,500 to 50,000 and a heat flux is 1,400 W/m2. The experimental results indicate that adding mists had little influence on free jet mean velocity profiles and target plate pressure coefficients. On the other hand, mists had a strong influence on temperature and humidity profiles of a free jet and they also influenced Nusselt number distributions on the target plate. Increases of mists and Reynolds number caused increases in Nusselt number on the developed region. In addition, we investigated influence of the way mists were added and these results showed that Nusselt number was influenced not only by the amounts of mists but also by the adding method. Local Nusselt number profiles with mists were closely related to temperature distributions of the free jet at the location corresponding to the target plate.

Kanamori, Azusa; Hiwada, Munehiko; Mimatsu, Junji; Sugimoto, Hiraku; Oyakawa, Kenyuu

227

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

E-print Network

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

228

Premixed flame impingement heat transfer with induced swirl  

Microsoft Academic Search

Experiments were performed to study the heat transfer characteristics of a swirling premixed flame impinging vertically normal to a horizontal plate. The effects of Reynolds number (Re), equivalence ratio (?) and nozzle-to-plate distance (H) on the heat flux were examined. Comparisons were also made between the heat transfer behaviors of the swirling premixed flame (SPF) with a non-swirling premixed flame

D. D. Luo; H. S. Zhen; C. W. Leung; C. S. Cheung

2010-01-01

229

July 2008 Mold heat transfer in continuous casting  

E-print Network

July 2008 Mold heat transfer in continuous casting is important to mold life, surface quality, breakouts and many aspects of the process. Heat transfer in the thin slab casting mold is being investigated aspects of the continuous casting process, including shell and mold temperatures, heat flux, interfacial

Thomas, Brian G.

230

Neural network methodology for heat transfer enhancement data  

Microsoft Academic Search

Purpose – The purpose of this paper is to study experimentally enhancement of heat transfer in a tube with axial swirling-flow promoters. The geometric features of flow geometry to improve heat transfer can be selected in order to yield the maximum opposite reduction in heat exchange flow irreversibility by using exergy-destruction method. The paper seeks to illustrate the use of

Betül Ayhan-Sarac; Bekir Karl?k; Tülin Bali; Teoman Ayhan

2007-01-01

231

Intensification of heat transfer in flash film evaporators  

Microsoft Academic Search

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

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

1992-01-01

232

EFFECT OF SURFACE CHARACTERISTICS ON FLOW BOILING HEAT TRANSFER  

E-print Network

ABSTRACT It is well known that the surface structure affects the pool boiling heat transfer from a heater that the surface condition of the boiling surface affects the pool boiling heat transfer. Surface conditions and the overall heat flux. Enhancement techniques such as sintering and specially fabricated surface geometries

Kandlikar, Satish

233

Heat transfer and fluid friction in bundles of twisted tubes  

NASA Astrophysics Data System (ADS)

The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.

Dzyubenko, B. V.; Dreitser, G. A.

1986-06-01

234

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

235

Transient critical heat flux and blowdown heat-transfer studies  

SciTech Connect

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

236

Heat Transfer Analysis of a Closed Brayton Cycle Space Radiator  

NASA Technical Reports Server (NTRS)

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

Juhasz, Albert J.

2007-01-01

237

Multiscale simulations of heat transfer in nanocomposites  

NASA Astrophysics Data System (ADS)

The field of nanotechnology has been expanded by the discovery of fullerenes and carbon nanotubes (CNTs) in the 20th century. Geim and Novoselov won the Nobel prize in 2010 for their work on graphene sheets (GSs). Those materials with their outstanding properties have been suggested as reinforcement fillers in a variety of composite materials. By incorporating these nanomaterials into a polymer matrix, or dispersing them into a solution, the effective thermal conductivity of the resulting composite (Keff) can be increased. For example, this enhancement can range from 80% to 125% at 1.0wt% of CNTs over pure polymer for the case of epoxy composites or by a factor of almost 4 in the case of high concentration of single-walled carbon nanotubes (SWNTs) in poly-styrene. However, based on the properties of pristine CNTs and GSs, one would expect a much higher value of Keff of such composites, more than one order of magnitude according to the classical theory of Maxwell. The presence of resistance to heat transfer at the nanoinclusion-polymer interface, known as the interfacial thermal resistance or Kapitza resistance, is the reason for this difference. Experimentally measuring and characterizing heat transport at the nanoscale are not trivial tasks and current theory in this area is limited to simple cases only. The acoustic mismatch theory and the effective medium theory provide a rough estimation of Kapitza resistance and Keff of the composites, respectively. However, the effect of dispersion pattern and the orientation of nanoinclusions inside the polymer matrix on Keff is still an open question. For the case of multi-walled carbon nanotubes (MWCNTs) embedded in polymer matrix, it is unknown whether thermal transfer occurs solely via the outermost wall or through the center of the tube. In this work, Monte Carlo (MC) simulations were developed to investigate heat transfer in nanocomposites. This approach is capable of taking into account the effect of different geometries, realistic orientations, and dispersion patterns of nanoinclusions on Keff. Furthermore, molecular dynamics (MD) simulations were employed coherently with MC simulations to characterize interfacial thermal resistance. Results from this work provide suggestions for producing superior thermal nanocomposites through the controll of Kapitza resistance and the configurations of nanoinclusions inside the polymer matrix.

Bui, Khoa Nguyen Dang

238

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

E-print Network

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

Clayton Otey; Shanhui Fan

2011-03-14

239

A microchannel heat exchanger design for microelectronics cooling correlating the heat transfer rate in terms of Brinkman number  

Microsoft Academic Search

Microchannel heat exchangers are a well known device in the application of microelectronics cooling. In this paper, liquid\\u000a microchannel heat exchangers were designed and investigated with varying channel width in order to find the maximum cooling\\u000a efficiency when combined with pumping performance. A recently developed correlation of heat transfer rate in terms of Nusselt\\u000a number and Brinkman number was adopted

HeeSung Park

2009-01-01

240

Low-melting point heat transfer fluid  

DOEpatents

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

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

2011-04-12

241

Heat transfer characteristics in film cooling applications  

NASA Astrophysics Data System (ADS)

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

Licu, Dragos Nicolae

1998-11-01

242

Heat and mass transfer in flames  

NASA Technical Reports Server (NTRS)

Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

Faeth, G. M.

1986-01-01

243

Efficient thermoelectric cooling of concentrated heat loads  

NASA Astrophysics Data System (ADS)

An efficiency improvement of 87% is demonstrated in cooling of concentrated heat loads when using thermoelectric coolers (TECs) constructed with thermally conductive printed circuit boards (TCPCBs) as compared to traditional ceramic-based TECs. Laser diodes and infrared detectors must be actively cooled but are smaller than typical TECs. As a result, heat spreading must occur between the optical component and the semiconductor pellets near the edge of the TEC. Typically, TECs based on aluminum nitride circuit boards are chosen and in some cases an AlN plate is added between the optical component and the TEC. To address this, TECs have been developed that replace the ceramic circuit boards with laminated TCPCBs containing a thick copper backing. The copper backing improves heat spreading within the TEC. A study was conducted to quantify differences in coefficient of performance (COP, heat pumped divided by electrical power consumed) when cooling concentrated heat loads. A heat source 3 mm wide was cooled by TECs ~12 mm wide, comparing ceramic-based and TCPCB-based TECs of otherwise identical design. With a fixed hot side temperature and heat load, each TEC was powered to achieve a desired temperature at the heat source. Ceramic-based and TCPCB-based TECs exhibited COPs of 0.235 and 0.440 respectively, an 87% improvement. Further improvements are achievable: adding a thick copper plate between the heat source and the TEC resulted in a COP of ~0.59 for both TEC types.

Hershberger, Jeff; Smythe, Robert; Gu, Xiaoyi; Hill, Richard F.

2013-02-01

244

Heat exchanger efficiently operable alternatively as evaporator or condenser  

DOEpatents

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

Ecker, Amir L. (Dallas, TX)

1981-01-01

245

FILM-30: A Heat Transfer Properties Code for Water Coolant  

SciTech Connect

A FORTRAN computer code has been written to calculate the heat transfer properties at the wetted perimeter of a coolant channel when provided the bulk water conditions. This computer code is titled FILM-30 and the code calculates its heat transfer properties by using the following correlations: (1) Sieder-Tate: forced convection, (2) Bergles-Rohsenow: onset to nucleate boiling, (3) Bergles-Rohsenow: partially developed nucleate boiling, (4) Araki: fully developed nucleate boiling, (5) Tong-75: critical heat flux (CHF), and (6) Marshall-98: transition boiling. FILM-30 produces output files that provide the heat flux and heat transfer coefficient at the wetted perimeter as a function of temperature. To validate FILM-30, the calculated heat transfer properties were used in finite element analyses to predict internal temperatures for a water-cooled copper mockup under one-sided heating from a rastered electron beam. These predicted temperatures were compared with the measured temperatures from the author's 1994 and 1998 heat transfer experiments. There was excellent agreement between the predicted and experimentally measured temperatures, which confirmed the accuracy of FILM-30 within the experimental range of the tests. FILM-30 can accurately predict the CHF and transition boiling regimes, which is an important advantage over current heat transfer codes. Consequently, FILM-30 is ideal for predicting heat transfer properties for applications that feature high heat fluxes produced by one-sided heating.

MARSHALL, THERON D.

2001-02-01

246

Heat transfer in ash deposits: A modelling tool-box  

Microsoft Academic Search

The objective of this paper is to review the present state-of-the-art knowledge on heat transfer to the surface of and inside ash deposits formed in solid fuel-fired utility boilers, and-based on the review-to propose models for calculation of heat transfer, e.g. in deposition models. Heat transfer will control the surface temperature of the deposit, thereby influencing the physical conditions at

Ana Zbogar; Flemming J. Frandsen; Peter Arendt Jensen; Peter Glarborg

2005-01-01

247

Micro and nanostructured surfaces for enhanced phase change heat transfer  

E-print Network

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

248

Heat Transfer in Regions of Separated and Reattached Flows  

NASA Technical Reports Server (NTRS)

Past experimental work has indicated that separated flow can greatly increase the heat transfer to a surface; whereas, some theoretical studies have indicated a possible decrease. Recent investigations have helped to clarify the effects of separation on heat transfer and have indicated a method of reducing separation. This paper considers the results of some of these investigations and shows the heat transfer in regions of separation and reattachment for a few specific shapes. These results show that the heat transfer in a separated region is strongly affected by the extent of separation, the location of the reattachment point, and the location of transition along the separated boundary.

Crawford, Davis H; Rumsey, Charles B

1957-01-01

249

Heat transfer coefficient in serpentine coolant passage for CCDTL  

SciTech Connect

A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.

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

1998-12-31

250

INVESTIGATING THE EFFECT OF HEATING METHOD ON POOL BOILING HEAT TRANSFER  

E-print Network

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

Kandlikar, Satish

251

2.51 Intermediate Heat and Mass Transfer, Fall 2001  

E-print Network

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-

252

Heat transfer and pressure drop in tape generated swirl flow  

E-print Network

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

Lopina, Robert F.

1967-01-01

253

Augmentation of heat transfer performance in coiled flow inverter vis-à-vis conventional heat exchanger  

Microsoft Academic Search

In the present work, primarily two studies were carried out to ascertain the performance of coiled flow inverter (CFI) as heat exchanger at pilot plant scale. In the first study, performance of CFI heat exchanger has been compared with conventional heat exchangers, i.e. shell and tube heat exchanger (SHE) and plate type heat exchanger (PHE) under identical heat transfer area

M. M. Mandal; Vimal Kumar; K. D. P. Nigam

2010-01-01

254

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

E-print Network

Joule heating and heat transfer in poly(dimethylsiloxane) microfluidic systems David Erickson (using a 3D "whole-chip" finite element model) approach is used to examine Joule heating and heat is the internal heat generation (commonly referred to as Joule heating) caused by current flow through the buffer

Erickson, David

255

Investigations on the heat transfer performance of edge-shaped finned-tubes  

NASA Astrophysics Data System (ADS)

The third generation enhanced heat transfer technologies, such as three-dimensional fin and dimple, are still important means of improving energy efficiency and will continue to be challenging issues. This paper concentrates on the analysis of the condensation heat transfer performance of an edge-shaped finned-tube fabricated by extrusion-ploughing process. Experimental results show that the overall heat transfer coefficient increases with increases of volumetric flow rate of cold water and heat flux whereas the shell side heat transfer coefficient decreases with volumetric flow rate and heat flux increasing. At the similar volumetric flow rate, the shell side heat transfer coefficient of the edge-shaped finned-tube is 4-6 times larger than that of the smooth tube. At the similar volumetric flow rate, the shell side heat transfer coefficient of edge-shaped finned-tube increases with ploughing depth increasing. At the same temperature difference between wall and vapor, the shell side heat transfer coefficient is also higher than what had been reported in the literature.

Wang, Xiao-wu; Wan, Zhen-ping; Tang, Yong

2014-09-01

256

Heat transfer measurements in the 1977 Kilauea Lava flow, Hawaii  

Microsoft Academic Search

The September-October 1977 eruption of Kilauea volcano, Hawaii, produced a river of basaltic lava which flowed for several days. A heat transfer probe containing two heat gauges measured the conduction-dominant heat transfer rates from molten lava into a cold probe inserted in an eddy in the lava river. During a 5-min test period the primary heat flux gauge indicated transient-decaying

H. C. Hardee

1979-01-01

257

Enhancement of nucleate boiling heat transfer using carbon nanotubes  

Microsoft Academic Search

The effect of carbon nanotubes (CNTs) on nucleate boiling heat transfer in R22 and water is investigated with the addition of 1.0vol% of CNTs. Test results showed that CNTs increase boiling heat transfer coefficients of these fluids. Especially, large enhancement up to 28.7% was observed at low heat fluxes of less than 30kW\\/m2. With increasing heat flux, however, the enhancement

Ki-Jung Park; Dongsoo Jung

2007-01-01

258

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

259

Comparisons of the heat transfer and pressure drop of the microchannel and minichannel heat exchangers  

Microsoft Academic Search

The present study investigated the comparisons of the heat transfer and pressure drop of the microchannel and minichannel\\u000a heat exchangers, both numerically and experimentally. The results obtained from this study indicated that the heat transfer\\u000a rate obtained from microchannel heat exchanger was higher than those obtained from the minichannel heat exchangers; however,\\u000a the pressure drops obtained from the microchannel heat

Thanhtrung Dang; Jyh-Tong Teng

2011-01-01

260

Measurement of heat and moisture exchanger efficiency.  

PubMed

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

261

Heat Sponge: A Concept for Mass-Efficient Heat Storage  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

262

Experimental investigation on heat transfer enhancement from a heated circular cylinder with constant heat input power in turbulent pulsating crossflows  

NASA Astrophysics Data System (ADS)

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

Li, Guoneng; Zheng, Youqu; Xu, Yousheng; Hu, Guilin; Zhang, Zhiguo

2014-10-01

263

Efficient Gene Transfer in Bacterial Cell Chains  

E-print Network

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

264

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

265

Heat transfer research on supercritical water flow upward in tube  

SciTech Connect

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

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

2012-07-01

266

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

PubMed

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

267

Zinc Oxide Nanowire Forest for Pool Boiling Heat Transfer  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanowire forest is applied for the electronics cooling by means of pool boiling heat transfer. The forest was composed of lengthwise grown backbone and branched nanowires, which were highly dense and tree-like hierarchical structures. The platinum heater and resistance temperature detector were fabricated by microfabrication on one side of silicon chips and nanowire forest was synthesized on the other side. The superheat and heat flux were evaluated at steady state while the voltage in the heater was increased gradually. The heat flux gradually increased linearly with superheat at the initial stage of heating due to convective heat transfer and abruptly increased once the coolant started to boil. It seemed that the nanowire forest played a role of increased bubble nucleation sites with superhydrophilic nature leading to enhancement of boiling heat transfer. This sheds light on application of nanostructured surface as an effective electronics cooling by boiling heat transfer.

Lee, Dongjin; Kim, Taehyun; Park, Sungsik; Lee, Seung Seob; Ko, Seung Hwan

2012-11-01

268

The heat transfer coefficients of the heating surface of 300 MWe CFB boiler  

NASA Astrophysics Data System (ADS)

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai

2012-08-01

269

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

E-print Network

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

270

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

E-print Network

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

271

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

272

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

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

273

The heat transfer analysis of a microinsulation for nuclear microbatteries  

NASA Astrophysics Data System (ADS)

Microelectromechanical Systems (MEMS) have not gained wide use because they lack the on-device power required by many important applications. Numerous studies have been carried out regarding technologies for providing electrical power to MEMS devices. Compared with solar or chemical energies, radioisotope sources have the advantage of large energy density and long lifetime. The radioisotope decay heat could be directly converted to electricity using thermoelectric or thermionic techniques. As a crucial part of this process, a microinsulation concept has been designed to maintain the radioisotope source temperature high in order to obtain good conversion efficiency. This paper reviews thermionic energy conversion technology and creates heat transfer models for a Micro Heat Barrier (MHB) and radioisotope powered thermionic microbattery developed by Sandia National Laboratory. The computed results indicate that the MHB has apparent thermal conductivity on the order of 10-4 W/mK at vacuum and is capable of providing sufficient thermal resistance to produce a high conversion efficiency for a thermionic microbattery. A new microinsulation concept using photo resist SU-8 is designed and the photolithography fabrication process is described. The microinsulation sample's apparent thermal conductivity is measured and compared with theoretical results. The experimental results show that a typical design has apparent thermal conductivity on the order of 10-4 W/mK at vacuum and have a good agreement with what the model predicts.

Yao, Rui

274

MSG: A Computer System for Automated Modeling of Heat Transfer  

E-print Network

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

Steinberg, Louis

275

Recent Trends in Computation of Turbulent Jet Impingement Heat Transfer  

Microsoft Academic Search

A review of the current status of computation of turbulent impinging jet heat transfer is presented. It starts with a brief introduction to flow and heat transfer characteristics of jet impinging flows considering the simplest jet impinging geometry: normal impingement of a single jet into a flat surface. Subsequently, a review of recent computational studies related to the same geometry

Anupam Dewan; Rabijit Dutta; Balaji Srinivasan

2012-01-01

276

Flow Visualization and Heat Transfer Characteristics of Liquid Jet Impingement  

Microsoft Academic Search

Equipment used to cool horticultural produce often involves three-phase porous media. The flow field and heat transfer processes that occur in such equipment are generally quantified by means of empirical relationships amongst dimensionless groups.This work represents a first step towards the goal of harnessing the power of computational fluid dynamics (CFD) to better understand the heat transfer processes that occur

Farial A. Jafar; Graham R. Thorpe; Özden F. Turan

2012-01-01

277

Recent Trends in Computation of Turbulent Jet Impingement Heat Transfer  

Microsoft Academic Search

A review of the current status of computation of turbulent impinging jet heat transfer is presented. It starts with a brief introduction to flow and heat transfer characteristics of jet impinging flows considering the simplest jet impinging geometry - normal impingement of a single jet into a flat surface. Subsequently a review of recent computational studies related to the same

Anupam Dewan; Rabijit Dutta; Balaji Srinivasan

2011-01-01

278

Heat transfer characteristics of an impinging premixed annular flame jet  

Microsoft Academic Search

The heat transfer behaviors of an annular jet flame impinging vertically normal to a flat surface were investigated experimentally. The relationship between the flow\\/flame structure of the annular jet flame and the local heat transfer behavior along the surface was analyzed. Further, the effects of Reynolds number (Re), equivalence ratio (?) and nozzle-to-plate distance (H) on the local and overall

H. S. Zhen; C. W. Leung; C. S. Cheung

279

Heat and mass transfer during the coffee drying process  

Microsoft Academic Search

For a better comprehension of heat and mass transfer during the coffee drying process and optimization of the industrial application transport coefficients and coffee properties were determined. Heat transfer coefficients were measured for different air velocities and were found to follow the known dimensionless equations for the flow surrounding a sphere. Thermal conductivities and effective diffusion coefficients were measured as

Katrin Burmester; Rudolf Eggers

2010-01-01

280

CONVECTIVE HEAT TRANSFER OF BINARY MIXTURES UNDER FLOW BOILING CONDITIONS  

E-print Network

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

Kandlikar, Satish

281

Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces  

E-print Network

Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces Amy Rachel Enhanced heat transfer Pool boiling Nucleation a b s t r a c t With recent advances in micro characterize pool boiling on surfaces with wettabilities varied from superhydrophobic to superhydrophilic

Attinger, Daniel

282

A new model for nucleate boiling heat transfer  

Microsoft Academic Search

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

P. Stephan; J. Hammer

1994-01-01

283

Enhanced radiative heat transfer between nanostructured gold plates  

E-print Network

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

284

HEAT TRANSFER IN PACKED BED REACTORS WITH ONE PHASE FLOW  

Microsoft Academic Search

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

V. SPECCHIA; G. BALDI; S. SICARDI

1980-01-01

285

Semiconductor Surface Thermocouples for Determining Heat-Transfer Rates  

Microsoft Academic Search

Possible methods of increasing the sensitivity capabilities for determining heat-transfer rates associated with wind tunnel testing have been investigated. Techniques utilizing surface thermocouples of conventional thermocouple materials do not provide the necessary temperature sensitivity to low heat-transfer rates. This need for increased sensitivity has resulted in development and evaluation of surface thermocouples fabricated from semiconductor materials. Calibration of the semiconductor

David N. Kendall; W. Paul Dixon; Edward H. Schulte

1967-01-01

286

A study of plate heat transfer surfaces with corrugated fins  

Microsoft Academic Search

The present article gives the results of studies that were made in the Institute of Technical Thermal Physics of the Academy of Sciences of the Ukrainian SSSR on the heat transfer and hydraulic resistance of plate heat transfer surfaces with corrugated fins; the thermal, dimensional, weight and energy characteristics of surfaces with different kinds of corrugated fins were compared. The

Z. V. Tishchenko; N. D. Butskii

1971-01-01

287

The critical heat transfer characteristics of an insulated oval duct  

Microsoft Academic Search

This study is to investigate the characteristics of critical and neutral thicknesses of an insulated oval duct by using two-dimensional numerical analysis and the one-dimensional PWTR model, coupled with accurate oval duct surfaces. Critical heat transfer occurs when the outer radius of an insulated circular duct is less than its critical insulation radius. The heat transfer rate increases with increasing

King-Leung Wong; Wen-Lih Chen; Tsung-Lieh Hsien; Huann-Ming Chou

2010-01-01

288

THE INFLUENCE OF HEAT TRANSFER EFFECTS ON TURBINE PERFORMANCE CHARACTERISTICS  

Microsoft Academic Search

A method allowing the evaluation of the effects related to heat transfer to the turbine blades on its performance characteristics is presented. The effects investigated are the change of passage dimensions, resulting from heat transfer and the change in flow field, exhibited mainly as a different boundary layer development. Change of hot gas temperature combined with cooling air temperature and

A. G. Stamatis; K. Mathioudakis

289

Formulation of nanofluids for natural convective heat transfer applications  

Microsoft Academic Search

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

Dongsheng Wen; Yulong Ding

2005-01-01

290

Steam condensation heat transfer on smooth and profiled vertical tubes  

Microsoft Academic Search

In this paper the results of an investigation into condensation heat transfer of quiescent steam on vertical smooth and profiled tubes with annular grooves are presented. The film REynolds number varied 20 to 3000, the Pradtl number from 1.14 to 1.77. The enhancement of heat transfer during steam condensation on profiled tubes was observed in the all regimes under investigation.

Mikhaylov

1991-01-01

291

Heat and Mass Transfer Wrme-und Stoffbertragung  

E-print Network

are important. List of symbols A Total surface area Cp Specific heat capacity (J kg-1 K-1 ) D Outer diameter transfer coefficient (W m-2 K-1 ) Greek symbols a Thermal diffusivity (m2 s-1 ) e Surface emissivity q tubes are widely used as a methodology for heat transfer enhancement in petroleum industry, chemical

Guo, Zhixiong "James"

292

FINITE ELEMENT METHOD IN FLUID MECHANICS & HEAT TRANSFER  

E-print Network

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

Camci, Cengiz

293

Modeling and simulation of heat transfer phenomena during investment casting  

Microsoft Academic Search

Determining the heat transfer phenomena during casting processes is an important parameter for measuring the overall performance of process. It gives information about the properties of the metal being casted and its possible behavior in the mold during casting process. Improper determination of heat transfer phenomena and use of improper molding materials and casting conditions leads to defects such as

M.M.A. Rafique; J. Iqbal

2009-01-01

294

Measurement and analysis of gas turbine blade endwall heat transfer  

E-print Network

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

Lee, Joon Ho

2012-06-07

295

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

SciTech Connect

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

296

INVERSE PROBLEMS IN HEAT TRANSFER Nicholas Zabaras  

E-print Network

stochastic inverse heat-conduction problem (SIHCP): Problem definition stochastic methods in inverse modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 17.3A BAYESIAN APPROACH TO THE INVERSE HEAT-CONDUCTION PROBLEM

Zabaras, Nicholas J.

297

Dual circuit embossed sheet heat transfer panel  

DOEpatents

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

298

Dual circuit embossed sheet heat transfer panel  

DOEpatents

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

299

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

PubMed Central

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

300

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

301

Modelling of Heat Transfer in Single Crystal Growth  

E-print Network

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

Zhmakin, Alexander I

2014-01-01

302

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

303

Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

304

Phononic heat transfer across an interface: thermal boundary resistance.  

PubMed

We present a general theory of phononic heat transfer between two solids (or a solid and a fluid) in contact at a flat interface. We present simple analytical results which can be used to estimate the heat transfer coefficient (the inverse of which is usually called the 'thermal boundary resistance' or 'Kapitza resistance'). We present numerical results for the heat transfer across solid-solid and solid-liquid He contacts, and between a membrane (graphene) and a solid substrate (amorphous SiO(2)). The latter system involves the heat transfer between weakly coupled systems, and the calculated value of the heat transfer coefficient is in good agreement with the value deduced from experimental data. PMID:21406883

Persson, B N J; Volokitin, A I; Ueba, H

2011-02-01

305

Efficient vector radiative transfer calculations in vertically inhomogeneous cloudy atmospheres  

E-print Network

in cloudy atmospheres are generally time consuming, limiting their practical use in satellite remote sensing radiative transfer calculations in cloudy atmospheres are generally time consuming. To overcome this, oftenEfficient vector radiative transfer calculations in vertically inhomogeneous cloudy atmospheres

306

Heat transfer effectiveness of three-fluid separated heat pipe exchanger  

NASA Astrophysics Data System (ADS)

A heat transfer model for three-fluid separated heat pipe exchanger was analyzed, and the temperature transfer matrix for general three-fluid separated heat exchanger working in parallel-flow or counter-flow mode was obtained. It was found that the forms of temperature transfer matrix are similar for heat pipe rows with equal or different heat transfer surface area. Furthermore, by using the temperature transfer matrix of the heat pipe exchanger, the relationship between heat transfer effectiveness ? 1, ? 2 and M, NTU, U, ?t i were derived for the exchanger operating in parallel-flow or counter-flow mode, and a simple special example was adopted to demonstrate the correctness of these relationships.

Shi, Chengming; Wang, Yang; Yang, Ying; Liao, Quan

2011-03-01

307

Erosion effects on TVC vane heat transfer characteristics  

NASA Astrophysics Data System (ADS)

This work describes the effects of erosion on the heat transfer characteristics on thrust vector control vanes exposed to aluminized propellant exhaust flows. This was accomplished using an inverse heat transfer parameter identification of quarter scale models. The model is based on a four node lumped parameter system with two heat energy inputs. The erosion is modeled as decreasing the geometric dimensions linearly as function of time and percentage of aluminum in the propellant. Excellent agreement was found between experimental and model temperature profiles. The heat transfer coefficients of the vanes were found to decrease with increasing erosion rates.

Gardner, Steven R.

1994-03-01

308

Thermodynamic efficiency of pumped heat electricity storage.  

PubMed

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

Thess, André

2013-09-13

309

Nonlinear aspects of high heat flux nucleate boiling heat transfer  

SciTech Connect

This paper deals with potential nonlinear effects in nucleate boiling systems as a result of the behavior of individual nucleation sites on the heater surface. This requires detailed microscopic modeling of the surface. A computational model has been formulated for this purpose. The model addresses the three-dimensional transient conduction heat transfer process within the problem domain comprised of the macrolayer and heater. Hydrodynamic effects are represented through boundary conditions. Individual nucleation sites are activated or deactivated depending on the thermal conditions that prevail at the site. The model has been used to examine the behavior of sites on a realistic heater surface. The results indicate that significant spatial and temporal temperature variations can occur on the surface, and that thermal interactions among sites can result in some sites operating intermittently. Surface-averaged temperatures show nonlinear period-doubling behavior. A chaotic case was found. Qualitative comparisons are made to both local instantaneous temperature measurements and recent experiments that showed chaotic behavior. We believe that such nonlinear behavior is one of the reasons that mechanistic predictive capabilities for the boiling process have remained elusive. 29 refs., 8 figs., 2 tabs.

Sadasivan, P.; Unal, C.; Nelson, R. [Los Alamos National Lab., NM (United States)

1995-11-01

310

Convective heat transfer from molten salt droplets in a direct contact heat exchanger  

Microsoft Academic Search

This paper presents a new predictive model of droplet flow and heat transfer from molten salt droplets in a direct contact\\u000a heat exchanger. The process is designed to recover heat from molten CuCl in a thermochemical copper–chlorine (Cu–Cl) cycle\\u000a of hydrogen production. This heat recovery occurs through the physical interaction between high temperature CuCl droplets\\u000a and air. Convective heat transfer

O. Jaber; G. F. Naterer; I. Dincer

2010-01-01

311

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

Microsoft Academic Search

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

312

Research on Convective Heat Transfer and Mass Transfer of the Evaporator in Micro/Mini-Channel  

E-print Network

With the development of science and technology, various heating and cooling equipment have a development trend of micromation. Micro-fabrication processes make it possible to conduct research on condensation heat transfer in micro-channels. Based...

Su, J.; Li, J.

2006-01-01

313

Modeling of nonisothermal heat and moisture transfer in capillary-porous media in periodic microwave heating  

NASA Astrophysics Data System (ADS)

The interrelated system of heat-and moisture-transfer and electrodynamic equations for modeling superhigh-frequency drying of capillary-porous materials has been formulated. An example of solving the problem of heat and moisture transfer in microwave heating of a wood sample with allowance for the influence of surface forces on the process of migration of moisture has been given.

Grinchik, N. N.; Akulich, P. V.; Adamovich, A. L.; Kuts, P. S.; Kundas, S. P.

2007-01-01

314

Heat transfer of HTSC-ceramic cooled by liquid hydrogen  

SciTech Connect

An experimental investigation of heat transfer and crises of bubble and film boiling of hydrogen on the YBa{sub 2}Cu{sub 3}O{sub 7} HTSC-ceramic is described. Heat transfer characteristics obtained at pressures from 17 to 100 kPa and heat flux densities from 0.1 to 120 kW/m{sup 2} are compared with well-known results for hydrogen boiling on metal heaters.

Kolod`ko, I.M.; Levchenko, N.M.; Nozdrin, S.V. [Physicotechnical Inst. of Low Temperatures, Khar`kov (Ukraine)] [and others

1995-04-01

315

Rayleigh-Bénard convection heat transfer in nanoparticle suspensions  

Microsoft Academic Search

Natural convection heat transfer of nanofluids in horizontal enclosures heated from below is investigated theoretically. The main idea upon which the present work is based is that nanofluids behave more like a single-phase fluid rather than like a conventional solid–liquid mixture, which implies that all the convective heat transfer correlations available for single-phase flows can be extended to nanoparticle suspensions,

Massimo Corcione

2011-01-01

316

Heat transfer from aluminum surfaces to pool boiling He I  

SciTech Connect

Heat transfer measurements between different aluminum surfaces and pool boiling He I at 4.21 K are reported. The samples are contained in a channel configuration similar to what might be found in a large bath cooled superconducting magnet. Results include heat transfer coefficients in the nucleate and film boiling regimes as well as values for the peak nucleate and minimum film boiling heat flux. The effects of sample orientation and surface condition are also studied.

Huang, Y.; Van Sciver, S.W. [Florida State Univ., Tallahassee, FL (United States)

1996-12-31

317

Unsteady transonic heat transfer in a transient facility  

NASA Technical Reports Server (NTRS)

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

Lagraff, J. E.

1985-01-01

318

Effects of bending on heat transfer performance of axial micro-grooved heat pipe  

Microsoft Academic Search

Heat pipe is always bent in the typical application of electronic heat dissipation at high heat flux, which greatly affects\\u000a its heat transfer performance. The capillary limit of heat transport in the bent micro-grooved heat pipes was analyzed in\\u000a the vapor pressure drop, the liquid pressure drop and the interaction of the vapor with wick fluid. The bent heat pipes

Le-lun Jiang; Yong Tang; Min-qiang Pan

2011-01-01

319

Enhanced two phase flow in heat transfer systems  

DOEpatents

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

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

2013-12-03

320

Heat transfer in open-cell metal foams  

Microsoft Academic Search

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

321

Ventilated-solar roof air flow and heat transfer investigation  

Microsoft Academic Search

The governing parameters for flows generated by heat transfer from solar cell modules to air gaps are discussed. Experimental results are presented from measurements in mock-ups of ventilated facades and roofs. The heat transmitted from the solar cells to the air have been mimicked by the use of heating foils. The inclination angle of the roof, position of solar cell

Mats Sandberg; Bahram Moshfegh

1998-01-01

322

Proceedings of HT2008 2008 ASME Summer Heat Transfer Conference  

E-print Network

For horizontal circular pipes under uniform wall heat flux boundary condition and three different inlet = local bulk Grashof number (= g2 D3 (Tw-Tb)/b 2 ) h= local peripheral heat transfer coefficient, W/(m2 -K-s = local bulk density, kg/m3 INTRODUCTION In a horizontal pipe, the secondary flow is produced by heating

Ghajar, Afshin J.

323

STEADY STATE LIQUID CRYSTAL THERMOGRAPHY AND HEAT TRANSFER MEASUREMENTS ON  

E-print Network

Chapter V STEADY STATE LIQUID CRYSTAL THERMOGRAPHY AND HEAT TRANSFER MEASUREMENTS ON SURFACES . 1 Introduction V . 2 Determination of the Non-Uniform Surface Heat Flux Analytical Model Numerical Computation of Local Heat Generation V . 3 Experimental Method and Apparatus Facility and Test Section

Camci, Cengiz

324

Cooperative Heat Transfer and Ground Coupled Storage System.  

National Technical Information Service (NTIS)

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 ma...

P. D. Metz

1979-01-01

325

An implicit scheme for cascade flow and heat transfer analysis  

SciTech Connect

A new efficient implicit scheme, based on the second-order time and spatial difference algorithm for solving steady flow by using time-marching Navier-Stokes equations, was developed for predicting turbine cascade flows and heat transfer. The difference scheme comprises an explicit part in the intermediate time-step and an implicit part in the local time-step. The viscous flux vectors are decomposed to simplify the flow calculation in the explicit step. The time difference terms are expressed in terms of the viscous dependent terms that appear in the diffusion terms in the form by adding eigenvalues of viscous flux matrices into the time derivation term. In the presently proposed scheme, the two-sweep procedure is used in the implicit step instead of employing a traditional matrix operation to save the computational time. This method has been used to calculate the flow around C3X and VKI cascades. The computed results were compared with experimental data as well as with other published computations. The comparisons for both surface pressure and heat transfer coefficient showed good agreement with the experiments.

Xu, C.; Amano, R.S.

2000-04-01

326

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

Microsoft Academic Search

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

Zhaolin Gu; Haruki Sato; Xiao Feng

2001-01-01

327

Combustion Air Preheat and Radiant Heat Transfer in Fired Heaters - A Graphical Method for Design and Operating Analysis  

E-print Network

heat transfer efficiency thereby enabling the transfer of the same amount of energy from a lower total heat release in the radiant box. This paper presents a graphical procedure that can be used (1) to estimate fuel savings obtained by combustion air...

Grantom, R. L.

1981-01-01

328

Jet impingement heat transfer – Part I: Mean and root-mean-square heat transfer and velocity distributions  

Microsoft Academic Search

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

Tadhg S. O’Donovan; Darina B. Murray

2007-01-01

329

Radiation Heat Transfer Procedures for Space-Related Applications  

NASA Technical Reports Server (NTRS)

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

Chai, John C.

2000-01-01

330

Outside heat transfer coefficients for atmospheric coolers  

E-print Network

the tubes in a shell and tube exchanger Atmospheric type heat exchangers are used in many dif- ferent industries, for example: brewery~ dairy, coke, heavy chemical, petroleum refining, and refzigeration. This type of heat exchanger first came into use... the tubes in a shell and tube exchanger Atmospheric type heat exchangers are used in many dif- ferent industries, for example: brewery~ dairy, coke, heavy chemical, petroleum refining, and refzigeration. This type of heat exchanger first came into use...

George, David Mark

2012-06-07

331

Heat Transfer For Subcooled Flow Boiling In Hypervapotron Configuration  

SciTech Connect

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

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

2006-07-01

332

Heat transfer and flow characteristics on a gas turbine shroud.  

PubMed

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

333

Simulation Approach for Microscale Noncontinuum Gas-Phase Heat Transfer  

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

334

Experimental and theoretical studies of convective heat transfer in a cylindrical porous medium  

Microsoft Academic Search

Convective heat transfer at constant heat flux through unconsolidated porous media has been studied both experimentally and theoretically. Heat transfer measurements have been performed for convective heat transfer over a wide range of operational parameters at constant heat fluxes. In addition to heat transfer coefficients, pressure drop and temperature profiles both in radial and axial direction have been recorded. The

M. R. Izadpanah; H. Müller-Steinhagen; M. Jamialahmadi

1998-01-01

335

Modeling of Heat Transfer in Geothermal Heat Exchangers  

E-print Network

Ground-coupled heat pump (GCHP) systems have been gaining increasing popularity for space conditioning in residential and commercial buildings. The geothermal heat exchanger (GHE) is devised for extraction or injection of thermal energy from...

Cui, P.; Man, Y.; Fang, Z.

2006-01-01

336

Wall-to-suspension heat transfer in circulating fluidized beds  

SciTech Connect

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

337

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

E-print Network

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

Phillips, Bren Andrew

2011-01-01

338

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

E-print Network

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

339

Heat Transfer Calculations for a Fixed CST Bed Column  

SciTech Connect

In support of the crystalline silicotitanate (CST) ion exchange project of High-Level Waste (HLW) Process Engineering, a transient two-dimensional heat transfer model that includes the conduction process neglecting the convection cooling mechanism inside the CST column has been constructed and heat transfer calculations made for the present design configurations. For this situation, a no process flow condition through the column was assumed as one of the reference conditions for the simulation of a loss-of-flow accident. The modeling and calculations were performed using a computational heat transfer approach.

Lee, S.Y.

2001-03-28

340

Experimental measurements of heat transfer in an internally finned tube  

SciTech Connect

This paper reports new experimental data for turbulent fluid flow and heat transfer in a tube having internal fins. An experimental set-up was designed to study the heat transfer performance in the entrance region as well as in the fully-developed region. The tube and the fin assembly was cast from aluminum to avoid any thermal contact resistance. The length of the test section was 15.2 m. The inner diameter of the tube was 70 mm. The tube contained six equally spaced fins of height 15 mm. Air was used as the working fluid in all experiments. The Reynolds number based on hydraulic diameter ranged from 2.6 {times} 10{sup 4} to 7.9 {times} 10{sup 4}. Heat was supplied from an electrical heating system providing an uniform heat flux around the tube periphery over the entire length of the test section. Results exhibited high pressure gradients and high heat transfer coefficients in the entrance region, approaching the fully developed values away from the entrance section. Nusselt numbers of the finned tube were compared with those for an unfinned (smooth) tube for both constant Reynolds number and constant pumping power. The enhancement of heat transfer rate due to integral fins was found to be very significant over the entire range of flow rates studied in this experiment. Heat transfer coefficient, based on inside diameter and nominal area of finned tube exceeded unfinned tube values by as much as 112%. When compared at constant pumping power, an improvement as high as 52% was observed for the overall heat transfer rate. The results of this study indicates that significant enhancement of heat transfer is possible by using internal fins without sacrificing any additional pumping power. The experimental results are expected to be very useful for the design of pipelines and heat exchanger tubes.

Huq, M.; Huq, A.M.A. [Bangladesh Univ. of Engineering and Technology, Dhaka (Bangladesh). Dept. of Mechanical Engineering] [Bangladesh Univ. of Engineering and Technology, Dhaka (Bangladesh). Dept. of Mechanical Engineering; Rahman, M.M. [Univ. of South Florida, Tampa, FL (United States). Dept. of Mechanical Engineering] [Univ. of South Florida, Tampa, FL (United States). Dept. of Mechanical Engineering

1998-07-01

341

Microgravity Two-phase Flow and Heat Transfer  

NASA Astrophysics Data System (ADS)

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

Gabriel, Kamiel

2006-12-01

342

Determination of the heat transfer coefficients in porous media  

SciTech Connect

The process of transpiration cooling is considered. Methods are suggested for estimating the volumetric coefficient of heat transfer with the use of a two-temperature model and the surface heat transfer coefficient at entry into a porous wall. The development of new technology under conditions of increasing heat loads puts the search for effective methods of heat transfer enhancement in the forefront of theoretical investigations. One of the promising trends in the solution of this problem is the use of porous materials (PM) in the elements of power units. For thermal protection against convective or radiative heat fluxes, the method of transpiration cooling is successfully used. The mechanism operative in the thermal protection involves the injection of a coolant through a porous medium to produce a screen over the contour of a body in a flow for removing heat energy from the skeleton of the porous material.

Kim, L.V.

1994-06-01

343

A review on boiling heat transfer enhancement with nanofluids.  

PubMed

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

Barber, Jacqueline; Brutin, David; Tadrist, Lounes

2011-01-01

344

Concepts and realization of microstructure heat exchangers for enhanced heat transfer  

SciTech Connect

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

345

Performance and heat transfer characteristics of a carbon monoxide/oxygen rocket engine  

NASA Technical Reports Server (NTRS)

The combustion and heat transfer characteristics of a carbon monoxide and oxygen rocket engine were evaluated. The test hardware consisted of a calorimeter combustion chamber with a heat sink nozzle and an eighteen element concentric tube injector. Experimental results are given at chamber pressures of 1070 and 3070 kPa, and over a mixture ratio range of 0.3 to 1.0. Experimental C efficiency was between 95 and 96.5 percent. Heat transfer results are discussed both as a function of mixture ratio and axial distance in the chamber. They are also compared to a Nusselt number correlation for fully developed turbulent flow.

Linne, Diane L.

1993-01-01

346

A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.  

PubMed

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

de Jong, J A; Wijnant, Y H; de Boer, A

2014-03-01

347

A Numerical Study on Flow and Heat Transfer Analysis of Various Heat Exchangers  

Microsoft Academic Search

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

Myungsung Lee; Chan-Shik Won; Nahmkeon Hur

348

Performance of a serpentine heat exchanger: Part I – Effectiveness and heat transfer characteristics  

Microsoft Academic Search

This work deals with the heat transfer performance of a cross-flow serpentine heat exchanger for waste heat recovery. The heat exchanger is made of rectangular tubes which afford a narrow spacing for the flow outside the tubes (channel flow). In the analysis, the channel flow and the tube flow were considered as an unmixed flow and a mixed flow, respectively.

Jung-Yang San; Gean-Sheng Lin; Kai-Li Pai

2009-01-01

349

Measurement of flow field and local heat transfer distribution on a scraped heat exchanger crystalliser surface  

E-print Network

Measurement of flow field and local heat transfer distribution on a scraped heat exchanger.ravelet@laposte.net Geert-Jan Witkamp G.J.Witkamp@xs4all.nl Abstract In a cylindrical scraped heat exchanger crystallizer exchanger surface has been studied by direct measurements of the heat exchanger surface temperature

Boyer, Edmond

350

Heat Transfer of a Multiple Helical Coil Heat Exchanger Using a Microencapsulated Phase Change Material Slurry  

E-print Network

sides, respectively. The NTU-effectiveness relationship of the CHE when MPCM fluid is used approaches that of a heat exchanger with a heat capacity ratio of zero. The heat transfer results have shown that when using a MPCM slurry, an increase in heat...

Gaskill, Travis

2012-02-14

351

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

352

Boiling heat transfer and droplet spreading of nanofluids.  

PubMed

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

353

Numerical Studies of Heat Transfer in Rarefied Gases at Head-Disk Interface  

NASA Astrophysics Data System (ADS)

In this article we derived a new heat transfer model by treating the heat conduction and viscous dissipation in the slip and transition flow regimes as an intermediate function of continuum heat transfer model and free molecular heat transfer model. We also employed this heat transfer model, together with our self-developed air bearing simulation code called ABSolution to analyze heat transfer behaviors at the head-disk interface (HDI) of two thermal flying height control (TFC) sliders. We found that slider design has a significant effect on the net heat flux from the slider to the disk. A properly designed TFC slider, which uses low pressure distribution around the reader/writer elements, can reduce air bearing cooling and compensation effects in this area and increase the thermal actuation efficiency of the slider. The thermal accommodation coefficient between the slider and the disk is also an important parameter to affect the heat flux at the HDI. Therefore, its effect should be considered carefully to improve the accuracy in simulating TFC sliders.

Zhou, Weidong; Liu, Bo; Yu, Shengkai; Hua, Wei

2009-10-01

354

Heat transfer through an extended surface containing He II  

SciTech Connect

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

355

AndreiG.Fedorov Title: George W. Woodruff Professorship in Heat Transfer, Combustion and  

E-print Network

Advisory Board; - 2012-Present, International Journal of Interfacial Phenomena and Heat Transfer Editorial ionization and imaging for bioanalytical mass spectrometry Thermal radiation heat transfer Thermal Transfer Division) Bergles-Rohsenow Young Investigator Award for sustained contributions to heat, mass

Garmestani, Hamid

356

Model and Method to Increase the Thermal Efficiency of Micro-Heat Exchangers for Aerospace Applications  

Microsoft Academic Search

The aim of this study is to test numerically the influence that incompressible flow pulsation has on heat transfer in configurations,\\u000a such as the backward facing step, that appear in micro-electro mechanical systems (MEMS) and that are not very efficient from\\u000a the thermal point of view. Two control parameters have been used to increase heat transfer: velocity pulsation frequency and

A. Velazquez; J. R. Arias; B. Mendez

357

Navier-Stokes analysis of turbine blade heat transfer  

NASA Technical Reports Server (NTRS)

Comparisons with experimental heat transfer and surface pressures were made for seven turbine vane and blade geometries using a quasi-three-dimensional thin-layer Navier-Stokes analysis. Comparisons are made for cases with both separated and unseparated flow over a range of Reynolds numbers and freestream turbulence intensities. The analysis used a modified Baldwin-Lomax turbulent eddy viscosity mode. Modifications were made to account for the effects of: (1) freestream turbulence on both transition and leading edge heat transfer; (2) strong favorable pressure gradients on relaminarization; and (3) variable turbulent Prandtl number heat transfer. In addition, the effect of heat transfer on the near wall model of Deissler is compared with the Van Driest model.

Boyle, R. J.

1990-01-01

358

Survey and evaluation of techniques to augment convective heat transfer  

E-print Network

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

359

The measurement of capsule heat transfer gaps using neutron radiography.  

NASA Technical Reports Server (NTRS)

The use of neutron radiographs to determine dimensional changes of heat transfer gaps in cylindrical nuclear fueled capsules is described. A method was developed which involves scanning a very fine grained neutron radiograph negative with a recording microdensitometer. The output of the densitometer is recorded on graph paper and the heat transfer gap is plotted as a well-defined optical density change. Calibration of the recording microdensitometer ratio arms permits measurements to be made of the heat transfer optical density change from the microdensitometer trace. Total heat transfer gaps, measured by this method, agree with the physical measurements within plus or minus 0.005 cm over a range of gaps from 0.061 to 0.178 cm.

Thaler, L. A.

1971-01-01

360

Non-intrusive characterization of heat transfer fluid aerosol formation  

E-print Network

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

361

Heat transfer during film condensation of a liquid metal vapor  

E-print Network

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

362

Volume-energy parameters for heat transfer to supercritical fluids  

NASA Technical Reports Server (NTRS)

Reduced Nusselt numbers of supercritical fluids from different sources were grouped by several volume-energy parameters. A modified bulk expansion parameter was introduced based on a comparative analysis of data scatter. Heat transfer experiments on liquefied methane were conducted under near-critical conditions in order to confirm the usefulness of the parameters. It was experimentally revealed that heat transfer characteristics of near-critical methane are similar to those of hydrogen. It was shown that the modified bulk expansion parameter and the Gibbs-energy parameter grouped the heat transfer data of hydrogen, oxygen and methane including the present data on near-critical methane. It was also indicated that the effects of surface roughness on heat transfer were very important in grouping the data of high Reynolds numbers.

Kumakawa, A.; Niino, M.; Hendricks, R. C.; Giarratano, P. J.; Arp, V. D.

1986-01-01

363

Heat Transfer Enhancement in Rectangular Channel with Compound Cooling Techniques  

E-print Network

to analyze heat transfer and pressure loss characteristics to determine which configuration had the overall best performance. Two different flow configurations were considered, a uniform channel flow setup as well as a jet impingement setup. There were a...

Krad, Belal

2013-11-27

364

Heat transfer between anisotropic nanopartricles: Enhancement and switching  

E-print Network

We theoretically study heat transfer between two anisotropic nanoparticles in vacuum, and derive closed expressions in terms of the anisotropic dipole polarizabilities. We show that transfer between two small spheroids can be many times as large as the one for two spheres of same volumes. Such increase with anisotropy is also found for the heat emission of an isolated small spheroid. Furthermore, we observe a strong dependence of transfer on the relative orientation, yielding the interpretation as a heat transfer switch. The switch quality, given as the ratio of transfer in the ``on'' and ``off'' positions, is observed to be as large as $10^3$ in the near field and even larger in the far field.

Roberta Incardone; Thorsten Emig; Matthias Krüger

2014-02-21

365

Design, Construction, and Qualification of a Microscale Heater Array for Use in Boiling Heat Transfer  

NASA Technical Reports Server (NTRS)

Boiling heat transfer is an efficient means of heat transfer because a large amount of heat can be removed from a surface using a relatively small temperature difference between the surface and the bulk liquid. However, the mechanisms that govern boiling heat transfer are not well understood. Measurements of wall temperature and heat flux near the wall would add to the database of knowledge which is necessary to understand the mechanisms of nucleate boiling. A heater array has been developed which contains 96 heater elements within a 2.5 mm square area. The temperature of each heater element is held constant by an electronic control system similar to a hot-wire anemometer. The voltage that is being applied to each heater element can be measured and digitized using a high-speed A/D converter, and this digital information can be compiled into a series of heat-flux maps. Information for up to 10,000 heat flux maps can be obtained each second. The heater control system, the A/D system and the heater array construction are described in detail. Results are presented which show that this is an effective method of measuring the local heat flux during nucleate and transition boiling. Heat flux maps are obtained for pool boiling in FC-72 on a horizontal surface. Local heat flux variations are shown to be three to six times larger than variations in the spatially averaged heat flux.

Rule, T. D.; Kim, J.; Kalkur, T. S.

1998-01-01

366

Effects of heat exchanger tube parameters on nucleate pool boiling heat transfer in a scaled IRWST  

SciTech Connect

In an effort to determine the combined effects of major parameters of heat exchanger tubes on the nucleate pool boiling heat transfer in the scaled in-containment refueling water storage tank (IRWST), a total of 1,966 data for q{double_prime} versus {Delta}T has been obtained using various combinations of tube diameters, surface roughness, and tube orientations. The experimental results show that (1) increased surface roughness enhances heat transfer for both horizontal and vertical tubes, (2) the two heat transfer mechanisms, i.e., enhanced heat transfer due to liquid agitation by bubbles generated and reduced heat transfer by the formation of large vapor slugs and bubble coalescence are different in two regions of low heat fluxes (q{double_prime} {le} 50 kW/m{sup 2}) and high heat fluxes (q{double_prime} > 50 kW/m{sup 2}) depending on the orientation of tubes and the degree of surface roughness, and (3) the heat transfer rate decreases as the tube diameter is increased for both horizontal and vertical tubes, but the effect of tube diameter on the nucleate pool boiling heat transfer for vertical tubes is greater than that for horizontal tubes. Two empirical heat transfer correlations for q{double_prime}, one for horizontal tubes and the other for vertical tubes, are obtained in terms of surface roughness ({var_epsilon}) and tube diameter (D). In addition, a simple empirical correlation for nucleate pool boiling heat transfer coefficient (h{sub b}) is obtained as a function of heat flux (q{double_prime}) only.

Chun, M.H.; Kang, M.G. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Nuclear Engineering

1996-08-01

367

Numerical Modeling of Conjugate Heat Transfer in Fluid Network  

NASA Technical Reports Server (NTRS)

Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.

Majumdar, Alok

2004-01-01

368

Heat transfer across the interface between nanoscale solids and gas.  

PubMed

When solid materials and devices scale down in size, heat transfer from the active region to the gas environment becomes increasingly significant. We show that the heat transfer coefficient across the solid-gas interface behaves very differently when the size of the solid is reduced to the nanoscale, such as that of a single nanowire. Unlike for macroscopic solids, the coefficient is strongly pressure dependent above ?10 Torr, and at lower pressures it is much higher than predictions of the kinetic gas theory. The heat transfer coefficient was measured between a single, free-standing VO(2) nanowire and surrounding air using laser thermography, where the temperature distribution along the VO(2) nanowire was determined by imaging its domain structure of metal-insulator phase transition. The one-dimensional domain structure along the nanowire results from the balance between heat generation by the focused laser and heat dissipation to the substrate as well as to the surrounding gas, and thus serves as a nanoscale power-meter and thermometer. We quantified the heat loss rate across the nanowire-air interface, and found that it dominates over all other heat dissipation channels for small-diameter nanowires near ambient pressure. As the heat transfer across the solid-gas interface is nearly independent of the chemical identity of the solid, the results reveal a general scaling relationship for gaseous heat dissipation from nanostructures of all solid materials, which is applicable to nanoscale electronic and thermal devices exposed to gaseous environments. PMID:22070645

Cheng, Chun; Fan, Wen; Cao, Jinbo; Ryu, Sang-Gil; Ji, Jie; Grigoropoulos, Costas P; Wu, Junqiao

2011-12-27

369

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

370

Heat transfer to a silicon carbide\\/water nanofluid  

Microsoft Academic Search

Heat transfer experiments were performed with a water-based nanofluid containing 170-nm silicon carbide particles at a 3.7% volume concentration and having potential commercial viability. Heat transfer coefficients for the nanofluid are presented for Reynolds numbers ranging from 3300 to 13,000 and are compared to the base fluid water on the bases of constant Reynolds number, constant velocity, and constant pumping

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

2009-01-01

371

Heat transfer enhancement in a channel with porous baffles  

E-print Network

HEAT TRANSFER ENHANCEMENT IN A CHANNEL WITH POROUS BAFFLES A Dissertation by KANG-HOON KO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR... OF PHILOSOPHY December 2004 Major Subject: Mechanical Engineering HEAT TRANSFER ENHANCEMENT IN A CHANNEL WITH POROUS BAFFLES A Dissertation by KANG-HOON KO Submitted to Texas A&M University in partial fulfillment of the requirements...

Ko, Kang-Hoon

2005-02-17

372

Mpemba effect, Newton cooling law and heat transfer equation  

E-print Network

In this work we suggest a simple theoretical solution of the Mpemba effect in full agreement with known experimental data. This solution follows simply as an especial approximation (linearization) of the usual heat (transfer) equation, precisely linearization of the second derivation of the space part of the temperature function (as it is well-known Newton cooling law can be considered as the effective approximation of the heat (transfer) equation for constant space part of the temperature function).

Vladan Pankovic; Darko V. Kapor

2010-05-06

373

Analysis of Radiative Heat Transfer in a Partitioned Idealized Furnace  

Microsoft Academic Search

In this article, the finite-volume method is applied, in conjunction with the blocked-off-region procedure, to solve the radiative heat transfer problem in a three-dimensional partitioned rectangular enclosure containing absorbing-emitting and isotropic scattering medium in the presence of heat generation. Three-dimensional test cases were chosen to benchmark this model against other methods, namely, the discrete transfer method, the discrete ordinates method,

Mohamed Naceur Borjini; Habib Farhat; Mohamed-Sassi Radhouani

2003-01-01

374

Experimental investigation of oxide nanofluids laminar flow convective heat transfer  

Microsoft Academic Search

In the present investigation nanofluids containing CuO and Al2O3 oxide nanoparticles in water as base fluid in different concentrations produced and the laminar flow convective heat transfer through circular tube with constant wall temperature boundary condition were examined. The experimental results emphasize that the single phase correlation with nanofluids properties (Homogeneous Model) is not able to predict heat transfer coefficient

S. Zeinali Heris; S. Gh. Etemad; M. Nasr Esfahany

2006-01-01

375

Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids)  

Microsoft Academic Search

This paper is mainly concerned about the heat transfer behaviour of aqueous suspensions of multi-walled carbon nanotubes (CNT nanofluids) flowing through a horizontal tube. Significant enhancement of the convective heat transfer is observed and the enhancement depends on the flow conditions (Reynolds number, Re), CNT concentration and the pH, with the effect of pH smallest. Given other conditions, the enhancement

Yulong Ding; Hajar Alias; Dongsheng Wen; Richard A. Williams

2006-01-01

376

Heat transfer augmentation of a car radiator using nanofluids  

NASA Astrophysics Data System (ADS)

The car radiator heat transfer enhancement by using TiO2 and SiO2 nanoparticles dispersed in water as a base fluid was studied experimentally. The test rig is setup as a car radiator with tubes and container. The range of Reynolds number and volume fraction are (250-1,750) and (1.0-2.5 %) respectively. Results showed that the heat transfer increases with increasing of nanofluid volume fraction. The experimental data is agreed with other investigator.

Hussein, Adnan M.; Bakar, R. A.; Kadirgama, K.; Sharma, K. V.

2014-05-01

377

Pool boiling heat transfer of non-Newtonian nanofluids  

Microsoft Academic Search

This paper reports on the investigation of pool boiling heat transfer of ?-Al2O3\\/CMC non-Newtonian nanofluids. To prepare nanofluids, ?-Al2O3 nanoparticles were dispersed in CMC solution (carboxy methyl cellulose in water) using ultrasonic mixing and mechanical mixer. Different concentrations of CMC non-Newtonian fluids and ?-Al2O3\\/CMC non-Newtonian nanofluids were tested under nucleate pool boiling heat transfer conditions. Experiments were carried out at

S. Soltani; S. Gh. Etemad; J. Thibault

2010-01-01

378

Heat transfer and fluid flow phenomena in electroslag refining  

Microsoft Academic Search

A mathematical formulation has been developed to represent the electromagnetic force field, fluid flow and heat transfer in\\u000a ESR units. In the formulation, allowance has been made for both electromagnetically driven flows and natural convection; furthermore,\\u000a in considering heat transfer the effect of the moving droplets has been taken into account. The computed results have shown\\u000a that the electromagnetic force

A. H. Dilawari; J. Szekely

1978-01-01

379

HYDRODYNAMICS AND HEAT TRANSFER OF LIQUID FLUIDIZED BED SYSTEMS  

Microsoft Academic Search

After some genera] remarks about liquid\\/solid fluidization, various aspects of liquid fluidization hydrodynamics and heat transfer have been analyzed on a coherent basis. For each of these cases, the state-of-the-art has been reported, together with some indication of areas that deserve further attention. Major emphasis is placed on the hydrodynamic behavior of fluidized beds, heat transfer mechanisms from surface-to-bed and

M. JAMIALAHMADI; H. MÜLLER-STEINHAGEN

2000-01-01

380

Boiling heat transfer on meshed surfaces of different aperture  

NASA Astrophysics Data System (ADS)

The paper presents the results of investigations of the impact of mesh aperture on boiling heat transfer. The tests have been performed for distilled water and ethyl alcohol at ambient pressure. It was observed that the meshed surfaces performed much better than the smooth reference surface and that meshes of smaller aperture provided better results. The obtained results have been compared with selected models of boiling heat transfer from literature.

Orman, ?ukasz J.

2014-08-01

381

A visual study of phase-change heat transfer in a two-dimensional porous structure with a partial heating  

E-print Network

studies on the heat International Journal of Heat and Mass Transfer 43 (2000) 1089±1102 0017A visual study of phase-change heat transfer in a two- dimensional porous structure with a partial. These visual observations explain heat transfer measurements: with an increase of the imposed heat ¯ux

Zhao, Tianshou

382

The Critical Heat Transfer Characteristics of an Insulated Sphere Considering Heat Radiation  

NASA Astrophysics Data System (ADS)

This study is to investigate the critical heat transfer characteristics of an insulated sphere considering heat radiation. It is found that the results considering heat radiation are very big different from those of neglecting heat radiation. The critical heat transfer characteristics deeply depend on the sphere surface emissivity, ?0, and insulation surface emissivity ?, surrounding temperature Tsur and the internal convection heat transfer coefficient hi. In situations of necessary critical heat transfer condition of insulated sphere radius R2 must less than critical radius Rcr = 2Ks/h0 (i.e., R2/Rcr<1), the critical heat transfer will occur for neglecting heat radiation (?0 = ? = 0). In situation of R2/Rcr<1, the external convection heat transfer coefficient h0 should be at small value, and thus heat radiation must be considered. For considering heat radiation, the critical heat transfer only occur at ?0 = ?with small value (for examples, the critical heat transfer only occur at ?0 = ??0.3 R2/Rcr = 0.75 in this study); the greater the value of ?0= ? is, the smaller the critical insulated thickness tcr and neutral insulted thickness te will be. While ?0heat transfer rate qa is greater than that of non-insulation qa0 (i.e., qa/qa0>1) at thinner insulation, the maximum value of qa/qa0 occurs at the near zero insulated thickness (t/R2?0); qa/qa0 = 0 locates at some insulated thickness te, then qa/qa0 is less than 1 after te; the greater the value of (?-?0) is, the higher the value of (qa/qa0)max at t/R2?0 and greater the te will be; the values of (qa/qa0)max and te of considering heat radiation are dependent on the internal convection heat transfer coefficient hi, other than those of neglecting heat radiation are independent of hi; the higher the hi, the greater the (qa/qa0)max and te will be. While ?0>?, all qa/qa0 are less than 1, thus there is no critical heat transfer will be occurred even in situation of R2/Rcr<1.

Leung Wong, King; León Salazar, José Luis

2010-05-01

383

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

384

Heat transfer coefficients for staggered arrays of short pin fins  

NASA Technical Reports Server (NTRS)

Short pin fins are often used to increase that heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat transfer surface area compared to a plain wall. A heat transfer data base for these short pins is not available in the literature. Heat transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).

Vanfossen, G. J.

1981-01-01

385

Heat transfer by a corona wind heat exchanger  

Microsoft Academic Search

A cold plate heat exchanger fitted with pin fins and having integral corona wind blowers was constructed and tested for thermal performance. The heat exchanger was operated in air at sea level pressure and at reduced pressures with Reynold's numbers up to 300. Test in sulphur hexafluoride gas at sea level pressures demonstrated that the thermal performance was considerably better

A. S. Mitchell

1978-01-01

386

Heat transfer of buried pipe for heat pump application  

Microsoft Academic Search

It is generally felt that the application of line source theory for ground coil design usually resulted in excessive overdesign. It was anticipated that in order for the ground coil heat pump systems to be economically competitive with other residential heating and cooling systems, ground coil overdesign had to be kept to a minimum. A new ground coil model was

Viung C. Mei

1991-01-01

387

Heat transfer enhancement in latent heat thermal energy storage system by using the internally finned tube  

Microsoft Academic Search

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

388

Modelling heat transfer in heterogeneous media using fractional calculus.  

PubMed

This paper presents the results of modelling the heat transfer process in heterogeneous media with the assumption that part of the heat flux is dispersed in the air around the beam. The heat transfer process in a solid material (beam) can be described by an integer order partial differential equation. However, in heterogeneous media, it can be described by a sub- or hyperdiffusion equation which results in a fractional order partial differential equation. Taking into consideration that part of the heat flux is dispersed into the neighbouring environment we additionally modify the main relation between heat flux and the temperature, and we obtain in this case the heat transfer equation in a new form. This leads to the transfer function that describes the dependency between the heat flux at the beginning of the beam and the temperature at a given distance. This article also presents the experimental results of modelling real plant in the frequency domain based on the obtained transfer function. PMID:23547224

Sierociuk, Dominik; Dzielinski, Andrzej; Sarwas, Grzegorz; Petras, Ivo; Podlubny, Igor; Skovranek, Tomas

2013-05-13

389

Boiling heat transfer of impacting liquid sprays on solid surfaces  

SciTech Connect

The nucleate spray boiling region and the film spray boiling region were investigated. In the nucleate regime, an exploratory experimental investigation was carried out with a unique spray generator which allowed independent control over the spray parameters. The liquids used in the study were water and FC-72,a dielectric fluid, and the surface was copper. Parametric studies revealed that the liquid mass flux and the liquid subcooling were the main parameters which affect nucleate spray boiling, while droplet parameters had little effect. Even under peak heat flux conditions, a large fraction of the sprayed liquid remained unvaporized. However, peak heat fluxes obtained were much higher than those for pool boiling and seem to be of the same order as free impinging jet boiling. The problem of temperature overshoot at boiling incipience was carefully checked for impacting liquid sprays. No evidence of it was found. For the film boiling region of impacting sprays, analysis of this complex heat transfer process was attempted by separating the region into dilute and dense sprays. The heat transfer of an impacting dilute spray was analyzed by dividing the process into three identified subprocesses-drop contact heat transfer, bulk air convective heat transfer and radiative heat transfer. Since the dense spray film boiling region is complicated tremendously by the presence of interaction, the approach found successful was to identify, analyze and predict the asymptotic conditions.

Deb, S.

1988-01-01

390

Contribution of heat transfer to turbine blades and vanes for high temperature industrial gas turbines. Part 1: Film cooling.  

PubMed

This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of industrial gas turbines in order to attain efficient and environmentally benign engines. High efficiency film cooling, in the form of shaped film cooling and full coverage film cooling, is one of the most important cooling technologies. Corresponding heat transfer tests to optimize the film cooling effectiveness are shown and discussed in this first part of the contribution. PMID:11460641

Takeishi, K; Aoki, S

2001-05-01

391

Pool boiling heat transfer characteristics of nanofluids  

E-print Network

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

392

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

393

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

394

Effects of corona on heat transfer in an enclosure  

Microsoft Academic Search

Experiments were conducted to determine the effects of corona wind on heat transfer rates for enclosures. Tests were performed with an enclosed cavity heated on the bottom and cooled on the top (and vice versa). A corona wind was established inside the cavity by applying high voltages to 0.004 inch diameter chromel wires placed along the hot and cold surfaces

Donald D. Dyer Jr.

1986-01-01

395

IntroductiontoProcessEngineering(PTG) 5. Heat transfer  

E-print Network

) in the presence of a temperature gradient, heat is transferred from high to low temperature as a result of molecular movement: heat conduction (sv: värmeledning) · For a one-dimensional temperature gradient T/x or d rz13 5/114 Fourier's Law /2 · For a general case with a 3-dimensional temperature gradient T = (T

Zevenhoven, Ron

396

Improved Heat-Transfer Calculations for Hypersonic Flow  

NASA Technical Reports Server (NTRS)

Lewis number corrected for extremely high airspeeds. Algorithm calculates improved, variable value of Lewis number, factor in equation for heat-transfer coefficient at stagnation point of body in hypersonic flow mach numbers of approximately 25. New algorithm improves accuracy of calculations of heat generated by hot air acting on moving body.

Greenschlag, S. N.

1987-01-01

397

Transient conduction and radiation heat transfer in porous thermal insulations  

Microsoft Academic Search

This paper analyzes transient radiation and conduction heat transfer through planar porous materials. The transient response considered is caused by a sudden increase of heat generation at the hot boundary. The objective was to establish the effect of radiation on the temperature rise of the hot wall. The problem investigated is relevant to the use of transient methods for measuring

T. W. Tong; D. L. McElroy; D. W. Yarbrough

1984-01-01

398

Transient Conduction and Radiation Heat Transfer in Porous Thermal Insulations  

Microsoft Academic Search

This paper analyzes transient radiation and conduction heat transfer through planar porous materials. The transient response considered is caused by a sudden increase of heat generation at the hot boundary. The objective was to establish the effect of radiation on the temperature rise of the hot wall. The problem investigated is relevant to the use of transient methods for measuring

T. W. Tong; D. L. McElroy; D. W. Yarbrough

1985-01-01

399

A Heat Transfer Model for Firefighters' Protective Clothing  

Microsoft Academic Search

An accurate and flexible model of heat transfer through firefighter protective clothing has many uses, including investigating the degree of protection, in terms of burn injury and heat stress, of a particular fabric assembly and analyzing cheaply and quickly the expected performance of new or candidate fabric designs or fabric combinations.

William E. Mell; J. Randall Lawson

2000-01-01

400

Gas\\/surface heat transfer in spray deposition processes  

Microsoft Academic Search

A numerical investigation of heat transfer dynamics between gas and solid surfaces during droplet spray impingement is presented. Aim of the work is to derive knowledge for control of spray deposition processes like spray painting or spray forming, analysing how the heat exchanged from the surface to the flowing gas is affected by the presence of impinging droplets.The investigation is

M. Garbero; M. Vanni; U. Fritsching

2006-01-01

401

Experimental study of surfactant effects on pool boiling heat transfer  

Microsoft Academic Search

In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is

Ying Liang Tzan; Yu Min Yang

1990-01-01

402

Power density of piezoelectric transformers improved using a contact heat transfer structure.  

PubMed

Based on contact heat transfer, a novel method to increase power density of piezoelectric transformers is proposed. A heat transfer structure is realized by directly attaching a dissipater to the piezoelectric transformer plate. By maintaining the vibration mode of the transformer and limiting additional energy losses from the contact interface, an appropriate design can improve power density of the transformer on a large scale, resulting from effective suppression of its working temperature rise. A prototype device was fabricated from a rectangular piezoelectric transformer, a copper heat transfer sheet, a thermal grease insulation pad, and an aluminum heat radiator. The experimental results show the transformer maintains a maximum power density of 135 W/cm(3) and an efficiency of 90.8% with a temperature rise of less than 10 °C after more than 36 h, without notable changes in performance. PMID:22293737

Shao, Wei Wei; Chen, Li Juan; Pan, Cheng Liang; Liu, Yong Bin; Feng, Zhi Hua

2012-01-01

403

Heat transfer measurements of the 1983 kilauea lava flow.  

PubMed

Convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of Kilauea volcano in Hawaii. Eight field measurements of induced natural convection were made, giving heat flux values that ranged from 1.78 to 8.09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees Celsius, respectively. These field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace-melted samples of molten lava, and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy. PMID:17810087

Hardee, H C

1983-10-01

404

Measurements of the overall heat transfer from combustion gases confined within elliptical tube heat exchangers  

Microsoft Academic Search

Measurements of the overall heat transfer for elliptical cylinders in cross-flow are presented for various flatness ratios and incidence angles. The measurements included the internal convective transfer of confined flowing (hot) gases combined with the external convective transfer. The internal hot gases were created using natural gas flames whereby combustion was completed prior to entering the elliptical test section. Results

Daniel K. Harris; Victor W. Goldschmidt

2002-01-01

405

The influence of oil on nucleate pool boiling heat transfer  

NASA Astrophysics Data System (ADS)

The influence of various oil contents in R134a is investigated for nucleate pool boiling on copper tubes either sandblasted or with enhanced heating surfaces (GEWA-B tube). Polyolester oils (POE) (Reniso Triton) with medium viscosity 55 cSt (SE55) and high viscosity 170 cSt (SE170) were used. Heat transfer coefficients were obtained for boiling temperatures between -28.6 and +20.1°C. The oil content varied from 0 to 5% mass fraction. For the sandblasted tube and the SE55 oil the heat transfer coefficients for the refrigerant/oil-mixture can be higher or lower than those for the pure refrigerant, depending on oil mass fraction, boiling temperature and heat flux. In some cases the highest heat transfer coefficients were obtained at a mass fraction of 3%. For the 170 cSt oil there is a clear decrease in heat transfer for all variations except for a heat flux 4,000 W/m2 and -10.1°C at 0.5% oil content. The heat transfer coefficients are compared to those in the literature for a smooth stainless steel tube and a platinum wire. For the enhanced tube and 55 cSt oil the heat transfer coefficients are clearly below those for pure refrigerant in all cases. The experimental results for the sandblasted tube are compared with the correlation by Jensen and Jackman. The calculated values are within +20 and -40% for the medium viscosity oil and between +50% and -40% for the high viscosity oil. A correlation for predicting oil-degradation effects on enhanced surfaces does not exist.

Spindler, Klaus; Hahne, Erich

2009-05-01

406

Effect of Channel Configurations for Tritium Transfer in Printed Circuit Heat Exchangers  

SciTech Connect

The Next Generation Nuclear Plant (NGNP), a very High temperature Gas-Cooled Reactor (VHTR) concept, will provide the first demonstration of a closed-loop Brayton cycle at a commercial scale of a few hundred megawatts electric and hydrogen production. The power conversion system (PCS) for the NGNP will take advantage of the significantly higher reactor outlet temperatures of the VHTR to provide higher efficiencies than can be achieved in the current generation of light water reactors. Besides demonstrating a system design that can be used directly for subsequent commercial deployment, the NGNP will demonstrate key technology elements that can be used in subsequent advanced power conversion systems for other Generation IV reactors. In anticipation of the design, development and procurement of an advanced power conversion system for the NGNP, the system integration of the NGNP and hydrogen plant was initiated to identify the important design and technology options that must be considered in evaluating the performance of the proposed NGNP. In the VHTR system, an intermediate heat exchanger (IHX), which transfers heat from the reactor core to the electricity or hydrogen production system is one key component, and its effectiveness is directly related to the system overall efficiency. In the VHTRs, the gas fluids used for coolant generally have poor heat transfer capability, so it requires very large surface area for a given condition. For this reason, a compact heat exchanger (CHE), which is widely used in industry especially for gasto-gas or gas-to-liquid heat exchange is considered as a potential candidate for an IHX replacing the classical shell and tube type heat exchanger. A compact heat exchanger is arbitrary referred to be a heat exchanger having a surface area density greater than 700 m2/m3. The compactness is usually achieved by fins and micro-channels, and leads to the enormous heat transfer enhancement and size reduction. The surface area density is the total heat transfer area divided by the volume of the heat exchanger. In the case of PCHE units, the heat transfer surface area density may be as high as 2,500 m2/m3. This high compactness implies an appreciable reduction in material reducing cost. In this study, heat transfer and tritium penetration analyses have been performed for two different channel configurations of the PCHE; (1) standard and (2) off-set. One of the goals of this study was to determine whether offsetting the hot and cold streams would significantly reduce the tritium flux, and whether or not it would affect the heat transfer significantly.

Chang Oh; Eung Kim; Robert Shrake; Mike Patterson

2009-05-01

407

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

Microsoft Academic Search

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

408

Heat transfer and friction characteristics of plain fin-and-tube heat exchangers, part II: Correlation  

Microsoft Academic Search

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

409

Direct contact heat exchange interfacial phenomena for liquid metal reactors : Part I - heat transfer.  

SciTech Connect

Experiments on direct-contact heat exchange between molten metal and water for steam production were conducted. These experiments involved the injection of water into molten lead-bismuth eutectic for heat transfer measurements in a 1-D geometry. Based on the initial results of the experiments, the effects of the water flow rate and the molten metal superheat (temperature difference between molten metal and saturated water) on the volumetric heat transfer coefficient were discussed.

Cho, D.H.; Page, R.J.; Hurtault, D.; Abdulla, S.; Liu, X.; Anderson, M.H.; Bonazza, R.; Corradini, M.

2002-02-26

410

Steam condensing – liquid CO 2 boiling heat transfer in a steam condenser for a new heat recovery system  

Microsoft Academic Search

In a new waste heat recovery system, waste heat is recovered from steam condensers through cooling by liquid CO2 instead of seawater, taking advantage of effective boiling heat transfer performance; the heat is subsequently used for local heat supply. The steam condensing – liquid CO2 boiling heat transfer performance in a steam condenser with a shell and a helical coil

Konstantin Nikitin; Yasuyoshi Kato; Takao Ishizuka

2008-01-01

411

Theoretical analysis of fin efficiency with frost deposition on heat exchanger surface  

SciTech Connect

Frosting phenomena are encountered in numerous fields of industry. Frosting process under unsteady conditions involves simultaneous heat and mass transfer. Since the heat exchanger is indispensable, it is obviously necessary to obtain an accurate fin efficiency under frosting condition. Several frosted fin efficiency functions have been discussed in the past. Different hypotheses had been made by different researchers. On the basis of linear and quadratic function of the saturated air enthalpy, two new algorithms are presented in this paper to determine the frosted fin efficiency when simultaneous heat and mass transfer occurs. Temperature distribution over fin surface is calculated by solving a nonlinear second-order differential equation. New fin efficiency function is more accurate. Analysis shows that the frosted fin efficiency is independent from the relative humidity. By using this function in frosting simulation, the simulation fits experimental data better.

Yu, B.; Feng, Y.; Tong, L.; Que, X.; Chen, Z.

1999-07-01

412

Turbulent heat transfer prediction method for application to scramjet engines  

NASA Technical Reports Server (NTRS)

An integral method for predicting boundary layer development in turbulent flow regions on two-dimensional or axisymmetric bodies was developed. The method has the capability of approximating nonequilibrium velocity profiles as well as the local surface friction in the presence of a pressure gradient. An approach was developed for the problem of predicting the heat transfer in a turbulent boundary layer in the presence of a high pressure gradient. The solution was derived with particular emphasis on its applicability to supersonic combustion; thus, the effects of real gas flows were included. The resulting integrodifferential boundary layer method permits the estimation of cooling reguirements for scramjet engines. Theoretical heat transfer results are compared with experimental combustor and noncombustor heat transfer data. The heat transfer method was used in the development of engine design concepts which will produce an engine with reduced cooling requirements. The Langley scramjet engine module was designed by utilizing these design concepts and this engine design is discussed along with its corresponding cooling requirements. The heat transfer method was also used to develop a combustor cooling correlation for a combustor whose local properties are computed one dimensionally by assuming a linear area variation and a given heat release schedule.

Pinckney, S. Z.

1974-01-01

413

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

414

Experimental validation of large eddy simulations of flow and heat transfer in a stationary ribbed duct  

E-print Network

configura- tions are commonly used in modern high temperature gas turbine vanes and blades to enhance Abstract Accurate prediction of ribbed duct flow and heat transfer is of importance to the gas turbine to build more powerful and efficient engines, the gas turbine industry has worked to enhance cooling

Thole, Karen A.

415

Radiative Heat Transfer in Curved Specular Surfaces in Czochralski Crystal Growth Furnace  

Microsoft Academic Search

A numerical investigation of radiative heat transfer constructed by curved surfaces with specular and diffuse reflection components is carried out. The ray tracing method is adopted for the calculation of view factors, in which a new ray emission model is proposed. The second-degree radiation ring elements are introduced, which are of engineering importance and numerical efficiency. The accuracy of the

Zhixiong Guo; Shigenao Maruyama; Takao Tsukada

1997-01-01

416

Fundamental Mechanisms That Influence the Estimate of Heat Transfer to Gas Turbine Blades  

Microsoft Academic Search

The quest for improved efficiency has motivated the elevation of turbine inlet temperatures in all types of advanced aircraft gas turbines. The accommodation of higher gas temperatures necessitates complex blade cooling schemes so as not to sacrifice structural integrity and operational life in advanced engine designs. Estimates of the heat transfer from the gas to stationary (vanes) or rotating blades

R. W. GRAHAM

1980-01-01

417

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

Microsoft Academic Search

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

418

Modeling high-temperature glass molding process by coupling heat transfer and viscous deformation analysis  

Microsoft Academic Search

Glass molding is as an effective approach to produce precision micro optical elements with complex shapes at high production efficiency. Since glass is deformed at a high temperature where the mechanical and optical properties depend strongly on temperature, modeling the heat transfer and high-temperature deformation behavior of glass is an important issue. In this paper, a two-step pressing process is

Jiwang Yan; Tianfeng Zhou; Jun Masuda; Tsunemoto Kuriyagawa

2009-01-01

419

Plasma actuated heat transfer Subrata Roya  

E-print Network

crossflow creating a three-dimensional flow field entraining some hot gas to bend toward the blade the domain of influence as shown in Fig. 2 schematic below. The momentum transfer between the plasma and gas introduce plasmas for film cooling enhancement in gas turbines and other engineering applications. We

Roy, Subrata

420

Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels  

SciTech Connect

Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were taken up. Experimental data were discussed for two kinds of enhanced surfaces formed by joined horizontal and vertical tunnels: tunnel structures (TS) and narrow tunnel structures (NTS). The experiments were carried out with water, ethanol and R-123 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil of 0.05 mm thickness (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 mm high rectangular fins and horizontal inter-fin surface. The effects of hole (pore) diameters, tunnel pitch for TS and tunnel width for NTS on nucleate pool boiling were examined. Substantial enhancement of heat transfer coefficient was observed. The investigated surfaces showed boiling heat transfer coefficients similar to those of existing structures with subsurface tunnels, but at higher heat fluxes range. (author)

Pastuszko, Robert [Chair of Thermodynamics and Fluids Mechanics, The Kielce University of Technology, Al. Tysiaclecia P.P. 7, 25-314 Kielce (Poland)

2008-09-15

421

Heat transfer from cylinders in subsonic slip flows  

NASA Technical Reports Server (NTRS)

The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.

Nagabushana, K. A.; Stainback, P. C.

1992-01-01

422

Radial heat transfer from a moving plasma  

E-print Network

to design reactors. A good review of plasma jet technology has been prepared by Dennis? Smith, Gates, ard Bord (I). In th s research? the total heat flux in the radial direction was measured experimertaily from a moving plasma or plasma jet with a water... the advances made 'ri plasma generatior technology, John and Bade (4) suggested that the convective heat losses from a plasma gas stre am to the walls of the conf ining chamber may be represented by the equatior 0. 023 0 (Hs ? H ) qc = prO 60 Reo ~ 20 (II-2...

Johnson, James Randall

2012-06-07

423

Shape factors in conductive heat transfer  

E-print Network

: q e -k(~)ZT hT q = Heat flow, Btu/Hr k = Thexmal conductivity, -Btu Jk ~ Lrea, ZtB I ~ length of. heat flow path& Jt 6 T = Temperatux e di f f er ence, dp. R Resistance, (op Zt)pt. ln othex simple cases, such as the cylinder and, the sphex'e.... It has 'been shown bg Andrews 1 and Jacob d that. q = -k (S. Z. ) ~ T Where S. Z. = Shape abactor ~ ! - ~d dk dx (1S) Hence; S. P. ]~i (lSa) Sic. lariy the flow of d. irect current in an electrical circuit may be represented as: (S. X. ) h e S...

Faulkner, Richard Campbell

2012-06-07

424

A generalized approach to heat transfer in pipe flow with internal heat generation  

Microsoft Academic Search

In the last few years, there has been a renewed interest in the molten salt reactor (MSR), one of the “Generation IV International Forum” concepts, which adopts a circulating molten salt mixture as both heat generator (fuel) and coolant. The heat transfer of a fluid with internal heat generation depends on the strength of the source whose influence on the

Valentino Di Marcello; Antonio Cammi; Lelio Luzzi

2010-01-01

425

Air-Side Flow and Heat Transfer in Compact Heat Exchangers: A Discussion of Enhancement Mechanisms  

Microsoft Academic Search

The behavior of air flows in complex Heat exchanger passages is reviewed with a focus on the heat transfer effects of boundary-layer development, turbulence, spanwise and streamwise vortices, and wake management. Each of these flow features is discussed for the plain, wavy, and interrupted passages found in contemporary compact Heat exchanger designs. Results from the literature are used to help

ANTHONY M. JACOBI; RAMESH K. SHAH

1998-01-01

426

Pressure Loss and Heat Transfer Through Heat Sinks Produced by Selective Laser Melting  

Microsoft Academic Search

Heat removal from electronic packages is often assisted with the use of heat sinks whose heat transfer surfaces come in a variety of forms such as cylindrical pins, flat fins, and corrugated sheet. These conventional designs are manufactured by traditional methods such as forging, machining, casting, stamping and bending, or a combination of processes. This article introduces a novel manufacturing

Matthew Wong; Ieuan Owen; Chris J. Sutcliffe

2009-01-01

427

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

E-print Network

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

428

Heat and mass transfer in two-phase porous materials under intensive microwave heating  

Microsoft Academic Search

Computational results for the intensive microwave heating of porous materials are presented in this work. A multi-phase porous media model has been developed to predict the heating mechanism. Combined finite difference time-domain and finite volume methods were used to solve equations that describe the electromagnetic field and heat and mass transfer in porous media. The coupling between the two schemes

D. D. Din?ov; K. A. Parrott; K. A. Pericleous

2004-01-01

429

Optimum Allocation Of Heat Transfer Surface In An Absorption Heat Pump  

Microsoft Academic Search

A simplified model of an absorption heat pump is used to enable a compact formulation of the problem of the optimum allocation of heat transfer surface. This optimization problem is similar to the power cycle optimizations that have appeared frequently in recent literature. The task is to maximize the cycle output by varying the heat exchanger sizes with the constraint

Keith E. Herold; Reinhard Radermacher

1990-01-01

430

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

Microsoft Academic Search

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

431

Heat transfer in the coolant channel of a heat-exchanger system based on fluctuation theories  

Microsoft Academic Search

We present a model to study the heat transfer in the coolant channel of a heat-exchanger system. Such a model introduces thermal fluctuations as well as external noises due to different mechanisms of heat interchange. A unified treatment of both kinds of noise is carried out. The stationary mean value of the channel temperature is studied, obtaining effective transport coefficients

A. Díaz-Guilera; M. A. Rodríguez; J. M. Rubí

1988-01-01

432

THE HEAT TRANSFER AND RESISTANCE OF TUBES DURING HIGH TEMPERATURE HEATING OF AIR  

Microsoft Academic Search

An experimental study was made of heat transfer and resistance when ; heating air under the conditions met in high-temperature recuperators. Tests ; were made in heat-resistant steel tubes of 1 mm wall thickness. Clean dry ; compressed air was passed through the tubes. Details are given of the ; experimental rig and of the measurements that were made. Various

Arseyev

1959-01-01

433

A model of large heat transfer surface combustion with radiant heat emission  

Microsoft Academic Search

A model is formulated for the surface combustion of a premixed gas mixture near the downstream surface of a porous solid. Large heat transfer occurs between the gas and porous solid, and there is significant radiant heat emission from the heated surface of the solid. Using large-activation-energy asymptotic methods an analytical solution is derived for the gas and solid temperature

A McIntosh

1991-01-01

434

Heat transfer enhancement accompanying leidenfrost state suppression at ultrahigh temperatures.  

PubMed

The well-known Leidenfrost effect is the formation of a vapor layer between a liquid and an underlying hot surface. This insulating vapor layer severely degrades heat transfer and results in surface dryout. We measure the heat transfer enhancement and dryout prevention benefits accompanying electrostatic suppression of the Leidenfrost state. Interfacial electric fields in the vapor layer can attract liquid toward the surface and promote wetting. This principle can suppress dryout even at ultrahigh temperatures exceeding 500 °C, which is more than 8 times the Leidenfrost superheat for organic solvents. Robust Leidenfrost state suppression is observed for a variety of liquids, ranging from low electrical conductivity organic solvents to electrically conducting salt solutions. Elimination of the vapor layer increases heat dissipation capacity by more than 1 order of magnitude. Heat removal capacities exceeding 500 W/cm(2) are measured, which is 5 times the critical heat flux (CHF) of water on common engineering surfaces. Furthermore, the heat transfer rate can be electrically controlled by the applied voltage. The underlying science is explained via a multiphysics analytical model which captures the coupled electrostatic-fluid-thermal transport phenomena underlying electrostatic Leidenfrost state suppression. Overall, this work uncovers the physics underlying dryout prevention and demonstrates electrically tunable boiling heat transfer with ultralow power consumption. PMID:25225852

Shahriari, Arjang; Wurz, Jillian; Bahadur, Vaibhav

2014-10-14

435

Heat transfer characteristics of an impinging inverse diffusion flame jet. Part II: Impinging flame structure and impingement heat transfer  

Microsoft Academic Search

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

436

Small distance expansion for radiative heat transfer between curved objects  

E-print Network

We develop a small distance expansion for the radiative heat transfer between gently curved objects, in terms of the ratio of distance to radius of curvature. A gradient expansion allows us to go beyond the lowest order proximity transfer approximation. The range of validity of such expansion depends on temperature as well as material properties. Generally, the expansion converges faster for the derivative of the transfer than for the transfer itself, which we use by introducing a near-field adjusted plot. For the case of a sphere and a plate, the logarithmic correction to the leading term has a very small prefactor for all materials investigated.

Vladyslav A. Golyk; Matthias Krüger; Alexander P. McCauley; Mehran Kardar

2012-10-12

437

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

438

Heat Transfer and Flammability of Fibrous Materials.  

National Technical Information Service (NTIS)

The need for nonflammable fibrous materials intended for incorporation into life support systems for aircrew protection from fires along with state-of-the-art of such materials is discussed. Fabrics are evaluated on the basis of heat transmission from dir...

R. M. Stanton

1971-01-01

439

Advanced two-phase heat transfer systems  

NASA Astrophysics Data System (ADS)

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.

1992-10-01

440

Heat and mass transfer through porous media  

Microsoft Academic Search

The behavior of liquid water in roof insulation is important in determining the conditions for which the insulation will tend to accumulate water or dry out. A one-dimensional, quasi-steady, analytical model is developed to simulate transient transport of heat and mass with phase change through a porous slab subjected to temperature and vapor concentration gradients. Small scale experiments examining the

S. Motakef; L. R. Glicksman

1989-01-01

441

Parallel Computations of Nongray Radiative Heat Transfer  

Microsoft Academic Search

Nongray radiative transfer calculations are demonstrated on parallel computers by spatially decomposing the discrete ordinates method to solve the radiative transport equation (RTE). The predictions from coupling different property models with the RTE are compared against benchmarks for model problems. A validation metric is employed to quantify the agreement with the benchmarks. The weighted-sum-of-gray-gases model, and Patch mean absorption coefficients

Gautham Krishnamoorthy; Rajesh Rawat; Philip J. Smith

2005-01-01

442

Heat transfer of buried pipe for heat pump application  

Microsoft Academic Search

Ground coil heat pump systems are well known for their potential of energy conservation. The majority of the ground coil designs were based on the application of the line source theory. A modified line source method was later derived to calculate the ground temperature distribution by dividing the ground around the coil into blocks. However, the line source approach has

Viung C. Mei

1989-01-01

443

Efficient radiative transfer modelling with SKIRT  

E-print Network

We present SKIRT, a three-dimensional Monte Carlo radiative transfer code developed to study dusty galaxies. We discuss SKIRT's most important characteristics and present a number of applications. In particular, we focus on the kinematical aspect of SKIRT. We demonstrate that dust attenuation mimics the presence of dark matter around elliptical galaxies and that it severely affects the rotation curves of edge-on galaxies.

Maarten Baes; Herwig Dejonghe; Jonathan Davies

2005-03-22

444

Heat transfer augmentation along the tube wall of a louvered fin heat exchanger using practical delta winglets  

E-print Network

.sciencedirect.com International Journal of Heat and Mass Transfer 51 (2008) 2346­2360 #12;shown by these past studiesHeat transfer augmentation along the tube wall of a louvered fin heat exchanger using practical the formation of streamwise vortices and increase heat transfer between a working fluid and the surface on which

Thole, Karen A.

445

Flow boiling heat transfer in two-phase micro-channel heat sinksI. Experimental investigation and assessment  

E-print Network

:10.1016/S0017-9310(03)00041-3 International Journal of Heat and Mass Transfer 46 (2003) 2755­2771 wwwFlow boiling heat transfer in two-phase micro-channel heat sinks­­I. Experimental investigation is the first of a two-part study concerning measurement and prediction of saturated flow boiling heat transfer

Qu, Weilin

446

Effects of Freestream Turbulence on Turbine Blade Heat Transfer  

NASA Technical Reports Server (NTRS)

Experiments have shown that moderate turbulence levels can nearly double turbine blade stagnation region heat transfer. Data have also shown that heat transfer is strongly affected by the scale of turbulence as well as its level. In addition to the stagnation region, turbulence is often seen to increase pressure surface heat transfer. This is especially evident at low to moderate Reynolds numbers. Vane and rotor stagnation region, and vane pressure surface heat transfer augmentation is often seen in a pre-transition environment. Accurate predictions of transition and relaminarization are critical to accurately predicting blade surface heat transfer. An approach is described which incorporates the effects of both turbulence level and scale into a CFD analysis. The model is derived from experimental data for cylindrical and elliptical leadng edges. Results using this model are compared to experimental data for both vane and rotor geometries. The comparisons are made to illustrate that using a model which includes the effects of turbulence length scale improves agreement with data, and to illustrate where improvements in the modeling are needed.

Boyle, Robert J.; Giel, Paul W.; Ames, Forrest E.

2004-01-01

447

Efficient and Robust Radiance Transfer for Probeless Photorealistic Augmented Reality  

E-print Network

Efficient and Robust Radiance Transfer for Probeless Photorealistic Augmented Reality Lukas Gruber transfer computations for probeless light estimation in Augmented Reality. (Left) Aug- mented Reality based Augmented Reality (AR) requires knowledge of the scene geometry and environment lighting to compute photomet

Sen, Pradeep

448

Two dimensional and axisymmetric heat transfer results with the CSCM upwind implicit algorithm  

NASA Technical Reports Server (NTRS)

The single level conservative supra characteristic method (CSCM-S) is an upwind implicit method that is very robust and in a single level relaxation format makes efficient use of computer resources, and is very rapidly convergent. These factors render the unconditionally stable algorithm a useful compromise between Parabolized Navier-Stokes methods and two level linearized implicit time dependent methods and, thus, the method is very attractive for multidimensional Navier-Stokes problems. In this paper the heat transfer prediction capabilities of the CSCM schemes for flat plate, nozzle, blunt cone and bluff body flows are reported for the first time. Results are compared with available experimental heat transfer measurements.

Bardina, J.; Venkatapathy, E.; Lombard, C. K.

1985-01-01

449

Electrohydrodynamic convective heat transfer in a square duct.  

PubMed

Laminar to weakly turbulent forced convection in a square duct heated from the bottom is strengthened by ion injection from an array of high-voltage points opposite the heated strip. Both positive and negative ion injection are activated within the working liquid HFE-7100 (C(4)F(9)OCH(3)), with transiting electrical currents on the order of 0.1 mA. Local temperatures on the heated wall are measured by liquid crystal thermography. The tests are conducted in a Reynolds number range from 510 to 12,100. In any case, heat transfer is dramatically augmented, almost independently from the flow rate. The pressure drop increase caused by the electrohydrodynamically induced flow is also measured. A profitable implementation of the technique in the design of heat sinks and heat exchangers is foreseen; possible benefits are pumping power reduction, size reduction, and heat exchange capability augmentation. PMID:19426338

Grassi, Walter; Testi, Daniele

2009-04-01

450

Efficient methods for finding transfer function zeros of power systems  

SciTech Connect

This paper is probably the first to describe algorithms suited to the efficient calculation of both proper and non-proper transfer function zeros of linearized dynamic models for large interconnected power systems. The paper also describes an improvement to the well known AESOPS algorithm, formulating it as an exact transfer function zero finding problem which is efficiently solved by a Newton-Raphson iterative scheme. Large power system results are presented in this paper.

Martins, N.; Pinto, H.J.C.P. (CEPEL, Centro de Pesquisas de Energia Electrica, Caixa Postal 2754, 20.001, Rio de Janeiro (BR)); Lima, L.T.G. (MARTE Engenharia, Av. Pres. Vargas 542/2202, 20.000, Rio de Janeiro (BR))

1992-08-01

451

Boiling heat transfer characteristics of nanofluids in a flat heat pipe evaporator with micro-grooved heating surface  

Microsoft Academic Search

An experimental study was performed to understand the nucleate boiling heat transfer of water–CuO nanoparticles suspension (nanofluids) at different operating pressures and different nanoparticle mass concentrations. The experimental apparatus is a miniature flat heat pipe (MFHP) with micro-grooved heat transfer surface of its evaporator. The experimental results indicate that the operating pressure has great influence on the nucleate boiling characteristics

Zhen-hua Liu; Jian-guo Xiong; Ran Bao

2007-01-01

452

Efficient gas hot-air furnace and heating process  

Microsoft Academic Search

This patent describes space heating apparatus in which fuel gas is burned and heat is transferred from the resulting combustion gases to a cool air stream to produce heated air. It comprises a combustion chamber, the chamber comprising an inlet for receiving combustion air and a burner for burning fuel gas in the combustion air to produce combustion gases; and

Astle; W. B. Jr

1991-01-01

453

Heat transfer enhancement by fins in the microscale regime  

SciTech Connect

The current literature contains many studies of microchannel and micro-pin-fin heat exchangers, but none of them consider the size effect on the thermal conductivity of channel and fin walls. The present study analyzes the effect of size (i.e., the microscale effect) on the microfin performance, particularly in the cryogenic regime where the microscale effect is often appreciable. The size effect reduces the thermal conductivity of microchannel and microfin walls and thus reduces the heat transfer rate. For this reason, heat transfer enhancement by microfins becomes even more important than for macroscale fins. The need for better understanding of heat transfer enhancement by microfins motivates the current study, which resolves three basic issues. First, it is found that the heat flow choking can occur even in the case of simple plate fins or pin fins in the microscale regime, although choking is usually caused by the accommodation of a cluster of fins at the fin tip. Second, this paper shows that the use of micro-plate-fin arrays yields a higher heat transfer enhancement ratio than the use of the micro-pin-fin arrays due to the stronger reduction of thermal conductivity in micro-pin-fins. The third issue is how the size effect influences the fin thickness optimization. For convenience in design applications, an equation for the optimum fin thickness is established which generalizes the case without the size effect as first reported by Tuckerman and Pease.

Chou, F.C.; Lukes, J.R.; Tien, C.L.

1999-11-01

454

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

2014-07-01

455

Vapor locking and heat transfer of multiple layers  

SciTech Connect

The cryogenic stability of a superconducting magnet depends on the heat transfer characteristics of the liquid helium cooling channels. One of the factors which affects the heat transfer to the channel is the amount of vapor accumulated in the channel. It is especially important to design a large magnet with cooling channels large enough to ensure the recovery of a normal zone produced in the magnet following the mechanical disturbances. A study of the vapor formation and heat transfer of multiple layers under both steady state and transient conditions is presented. The change in capacitance between the two sides of the heated channel is measured to determine the volume fraction of the vapor in the cooling channel. It is found that the heat transfer characteristics depend on the vapor accumulation and the velocity of vapor flow. The vapor locking heat flux is decreased when the vapor accumulation is increased. The samples were made to simulate the real cryostable superconductor and the cooling channels to be used in the large MHD superconducting magnet, designated as CFFF-SCMS, currently under construction at Argonne National Laboratory (ANL). (WHK)

Chen, C.J.; Wang, S.T.; Dawson, J.W.

1980-01-01

456

Heat transfer in rocket engine combustion chambers and nozzles  

NASA Technical Reports Server (NTRS)

The complexities of liquid rocket engine heat transfer which involve the injector faceplate and regeneratively and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis will be used to describe localized heating phenomena associated with particular injector configurations and coolant channels and film coolant dumps. These components are being analyzed, and the analysis verified with appropriate test data. Finally, the component analysis will be synthesized into an overall flowfield/heat transfer model. The FDNS code is being used to make the component analyses. Particular attention is being given to the representation of the thermodynamic properties of the fluid streams and to the method of combining the detailed models to represent overall heating. Unit flow models of specific coaxial injector elements have been developed and will be described. Film cooling simulations of film coolant flows typical of the subscale Space Transportation Main Engine (STME) being experimentally studied by Pratt and Whitney have been made, and these results will be presented. Other film coolant experiments have also been simulated to verify the CFD heat transfer model being developed. The status of the study and its relevance as a new design tool are covered. Information is given in viewgraph form.

Anderson, P. G.; Chen, Y. S.; Farmer, R. C.

1992-01-01

457

Heat transfer in rocket engine combustion chambers and nozzles  

NASA Technical Reports Server (NTRS)

Complexities of liquid rocket engine heat transfer which involve the injector faceplate and regeneratively and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis will be used to describe localized heating phenomena associated with particular injector configurations and coolant channels and film coolant dumps. These components are being analyzed, and the analyses verified with appropriate test data. Finally, the component analyses will be synthesized into an overall flowfield/heat transfer model. The FDNS code is being used to make the component analyses. Particular attention is being given to the representation of the thermodynamic properties of the fluid streams and to the method of combining the detailed models to represent overall heating. Unit flow models of specific coaxial injector elements have been developed and will be described. Since test data from the NLS development program are not available, new validation heat transfer data have been sought. Suitable data were obtained from a Rocketdyne test program on a model hydrocarbon/oxygen engine. Simulations of these test data will be presented. Recent interest in the hybrid motor have established the need for analyses of ablating solid fuels in the combustion chamber. Analysis of a simplified hybrid motor will also be presented.

Anderson, P. G.; Cheng, G. C.; Farmer, R. C.

1993-01-01

458

Heat transfer in cooled porous region with curved boundary  

NASA Technical Reports Server (NTRS)

Heat transfer characteristics are analyzed for a cooled two-dimensional porous medium having a curved boundary. A general analytical procedure is given in combination with a numerical conformal mapping method used to transform the porous region into an upper half plane. To illustrate the method, results are evaluated for a cosine shaped boundary subjected to uniform external heating. The results show the effects of coolant starvation in the thick regions of the medium, and the extent that internal heat conduction causes the heated surface to have a more uniform temperature.

Siegel, R.; Snyder, A.

1981-01-01

459

Heat Transfer Properties of Liquid 3He below 1K  

SciTech Connect

The characteristics of heat transfer from a flat copper surface to liquid 3He have been studied under saturated vapor pressure using two types of sample cells in which the flows of liquid 3He induced by convection were different from each other. The temperature difference between the heated copper surface and liquid 3He was measured as a function of heat flux in steady states in the regions of the nonboiling state and nucleate boiling state. The characteristic curves are analyzed in terms of the convective flow along the heated surface and the bubble nucleation rates.

Katagiri, M.; Shinn, K.; Tsurutani, T.; Fujii, Y.; Hatanaka, K. [Department of Applied Physics, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005 (Japan); Maeda, M. [Tsukuba Magnet Laboratory, NIMS, 3-13 Sakura, Tsukuba 305-0003 (Japan)

2006-09-07

460

Fusion blanket high-temperature heat transfer  

SciTech Connect

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

461

Correlation between Flow Pattern and Refrigerant Flow Boiling Heat Transfer in Microchannel Heat Sinks  

NASA Astrophysics Data System (ADS)

Flow boiling in microchannel heat sinks is significantly influenced by capillary forces and by boundary constrains affecting the flow pattern and the heat transfer. In the present work, some characteristics of flow boiling heat transfer are explained using measurements of statistical parameters of gas-liquid two-phase flow in a rectangular microchannel. Such statistical characteristics of the flow as length distributions of elongated bubbles and liquid plugs, and also velocity distribution of the elongated bubbles are determined by dual laser scanning of the horizontal adiabatic nitrogen-water flow in a microchannel with the cross-section of 370×217 ?m. Pressure gradients in gas-liquid flow are measured, and the results found well matching the predictions that account for capillary pressure on the gas-liquid interface. Heat transfer coefficients are measured for a horizontal copper microchannel heat sink with refrigerant R-21 as the working fluid. The heat sink contains 21 channels with cross section dimensions 930×335-?m. Distribution of local heat transfer coefficients along the length and the width of the microchannel plate is measured in the range of heat fluxes from 14 to 63 kW/m2; vapour quality was varied within 0.05-0.8, and pressure was about 1.6 bar. For flow boiling of R-21 refrigerant, contributions of nucleate boiling and forced convection are comparable. This allows us to examine the heat transfer mechanism for these complex conditions.

Kuznetsov, V. V.; Kozulin, I. A.; Shamirzaev, A. S.

2012-11-01

462

Field Measurements of Heating System Efficiency in Nine Electrically-Heated Manufactured Homes.  

SciTech Connect

This report presents the results of field measurements of heating efficiency performed on nine manufactured homes sited in the Pacific Northwest. The testing procedure collects real-time data on heating system energy use and heating zone temperatures, allowing direct calculation of heating system efficiency.

Davis, Bob; Siegel, J.; Palmiter, L.; Baylon, D.

1996-07-01

463

Subcooled nucleate boiling heat transfer from a large diameter tube  

SciTech Connect

Nucleate boiling heat transfer from the outside of large-diameter tubes has not been well studied. There are many large-diameter horizontal tubes in the core of a CANDU{reg_sign} nuclear reactor, and it is important to quantify the different modes of heat transfer from the tubes (known as calandria tubes) to the heavy water moderator. This paper describes a series of experiments performed to study nucleate boiling heat transfer from the outside surface of a horizontal calandria tube to subcooled and pressurized light water. When the circulating pump was on, it caused an upflow of water in the vicinity of the tube, estimated to be an average of 0.3 m/s. The flow cooled the tube and increased the surface temperature fluctuations, in contrast to the relatively steady temperatures observed by Dowlati and Byrne (1995) in a test section of similar diameter, but made from a solid copper block. The cooling effect of the pumped flow was the greatest for high subcooling, low heat flux and high pressure. The magnitudes of these fluctuations are explained in terms of transient heat conduction when the surface alternates between nucleation and cooling by the cold liquid. The heat transfer from the bottom of the tube was modelled by a combination of pool boiling, global single-phase natural convection and stagnation-point single-phase forced-convection correlations. The experiments showed that Rohsenow`s pool boiling correlation (with a single-phase free convection component) successfully modelled the outer surface temperatures on the large-diameter horizontal tube when the circulating pump was off. Even at high water subcooling (60 C) and low heat flux (200 kW/m{sup 2}), nucleate boiling dominated the heat transfer.

Brown, M.J. [Atomic Energy of Canada Limited, Whiteshell, Manitoba (Canada). Whiteshell Labs.; Fung, K.K. [Ontario Hydro Nuclear, Toronto, Ontario (Canada); Byrne, T.P. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

1996-12-31

464

Preliminary Heat Transfer Studies for the Double Shell Tanks (DST) Transfer Piping  

SciTech Connect

Heat transfer studies were made to determine the thermal characteristics of double-shell tank transfer piping under both transient and steady-state conditions. A number of design and operation options were evaluated for this piping system which is in its early design phase.

HECHT, S.L.

2000-02-15

465

Experimental research on convection heat transfer in sintered porous plate channels  

Microsoft Academic Search

Forced convection heat transfer of water and air in sintered porous plate channels was investigated experimentally. The effects of fluid velocity, particle diameter, type of porous media (sintered or non-sintered), and fluid properties on the convection heat transfer and heat transfer enhancement were investigated. The results showed that the convection heat transfer in the sintered porous plate channel was more

Pei-Xue Jiang; Meng Li; Tian-Jian Lu; Lei Yu; Ze-Pei Ren

2004-01-01