NSDL National Science Digital Library
Integrated Teaching and Learning Program,
Students explore heat transfer and energy efficiency using the context of energy efficient houses. They gain a solid understanding of the three types of heat transfer: radiation, convection and conduction, which are explained in detail and related to the real world. They learn about the many ways solar energy is used as a renewable energy source to reduce the emission of greenhouse gasses and operating costs. Students also explore ways in which a device can capitalize on the methods of heat transfer to produce a beneficial result. They are given the tools to calculate the heat transferred between a system and its surroundings.
Exergy efficiency optimization of a thermoacoustic engine with a complex heat transfer exponent
Xuxian Kan; Feng Wu; Lingen Chen; Fengrui Sun; Fangzhong Guo
2010-01-01
On the basis of exergetic analysis, the performance analysis and optimization of a generalized irreversible thermoacoustic engine with heat resistance, heat leakage, thermal relaxation and internal dissipation, in which heat transfer between the working fluid and heat reservoirs obeys a complex generalized heat transfer law , where n is a complex, is investigated by taking exergetic efficiency as the optimization
Heat transfer efficient thermal energy storage for steam generation
R. Adinberg; D. Zvegilsky; M. Epstein
2010-01-01
A novel reflux heat transfer storage (RHTS) concept for producing high-temperature superheated steam in the temperature range 350–400°C was developed and tested. The thermal storage medium is a metallic substance, Zinc–Tin alloy, which serves as the phase change material (PCM). A high-temperature heat transfer fluid (HTF) is added to the storage medium in order to enhance heat exchange within the
Fang, X.; Wang, Z.; Liu, H.
2006-01-01
This paper analyzes the influence of transfer efficiency of the outdoor pipe network and operating efficiency of the boiler on the building heat consumption index, on the premise of saving up to 65 percent energy in different climates. The results...
Quasi-one-dimensional nanostructures and efficient heat transfer in nanoscale devices
Chia-Yi Chen; Dmitry I. Kopelevich
2005-01-01
The steady decrease of the feature size of integrated circuits towards the nanometer scale leads to an increase in generated heat per unit area. Hence, efficient transfer of heat away from hotspots of integrated circuits becomes a crucial issue in the design of new generations of electronic devices. The importance of efficient thermal transport is even more pronounced in moving
Urban Sewage Delivery Heat Transfer System (2): Heat Transfer
Zhang, C.; Wu, R.; Li, X.; Li, G.; Zhuang, Z.; Sun, D.
2006-01-01
The thimble delivery heat-transfer (TDHT) system is one of the primary modes to utilize the energy of urban sewage. Using the efficiency-number of transfer units method ( ), the heat-transfer efficiencies of the parallel-flow ...
Efficiency of a Curzon and Ahlborn engine with Dulong-Petit heat transfer law
NASA Astrophysics Data System (ADS)
Ladino-Luna, D.
2003-02-01
Using the maximization of the power output per cycle, the optimization of a thermal engine performing a Carnot-type cycle is considered. It is assumed that the heat transfer between the reservoirs and the engine occurs according to the Dulong and Petit's heat transfer law. It is, found that the efficiency obtained with this heat transfer law can be written as a power series in the parameter lambda similar to 1/(In V-max - InVmin), where V-max and V-min are the maximum volume and minimum volume spanned by the cycle, respectively. It is also shown that the calculated efficiency verifies the semi-sum property of the ecological efficiency.
Zhang, M.; Ibekwe, S.; Li, G.; Pang, S.S.; and Lian, K.
2006-07-01
The Pressurized Water Reactors (PWRs in Figure 1) were originally developed for naval propulsion purposes, and then adapted to land-based applications. It has three parts: the reactor coolant system, the steam generator and the condenser. The Steam generator (a yellow area in Figure 1) is a shell and tube heat exchanger with high-pressure primary water passing through the tube side and lower pressure secondary feed water as well as steam passing through the shell side. Therefore, a key issue in increasing the efficiency of heat exchanger is to improve the design of steam generator, which is directly translated into economic benefits. The past research works show that the presence of a pin-fin array in a channel enhances the heat transfer significantly. Hence, using microfabrication techniques, such as LIGA, micro-molding or electroplating, some special microstructures can be fabricated around the tubes in the heat exchanger to increase the heat-exchanging efficiency and reduce the overall size of the heat-exchanger for the given heat transfer rates. In this paper, micro-pin fins of different densities made of SU-8 photoresist are fabricated and studied to evaluate overall heat transfer efficiency. The results show that there is an optimized micro pin-fin configuration that has the best overall heat transfer effects.
NSDL National Science Digital Library
Ms. Leslie Van (Montgomery Blair High School)
2006-04-01
In this inquiry activity students explore how heat transfers from one substance to another This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÂ?s 2006 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.
Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines
NASA Technical Reports Server (NTRS)
Ameri, A. A.; Steinthorsson, E.; Rigby, David L.
1998-01-01
Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E 3 first stage turbine, which represents a modem gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.
Urban Sewage Delivery Heat Transfer System (2): Heat Transfer
Zhang, C.; Wu, R.; Li, X.; Li, G.; Zhuang, Z.; Sun, D.
2006-01-01
The thimble delivery heat-transfer (TDHT) system is one of the primary modes to utilize the energy of urban sewage. Using the efficiency-number of transfer units method ( ), the heat-transfer efficiencies of the parallel-flow and reverse-flow TDTH...
Zhao, Ye; Luo, Yuting; Zhu, Jie; Li, Juan; Gao, Xuefeng
2015-06-10
We report a type of copper-based ultrathin nickel nanocone films with high-efficiency dropwise condensation heat transfer (DCHT) performance, which can be fabricated by facile electrodeposition and low-surface-energy chemistry modification. Compared with flat copper samples, our nanosamples show condensate microdrop self-propelling (CMDSP) function and over 89% enhancement in the DCHT coefficient. Such remarkable enhancement may be ascribed to the cooperation of surface nanostructure-induced CMDSP function as well as in situ integration and ultrathin nature of nanofilms. These findings are very significant to design and develop advanced DCHT materials and devices, which help improve the efficiency of thermal management and energy utilization. PMID:26011021
Zhu, Jie; Luo, Yuting; Tian, Jian; Li, Juan; Gao, Xuefeng
2015-05-27
We report that the dropwise condensation heat transfer (DCHT) effectiveness of copper surfaces can be dramatically enhanced by in situ grown clustered ribbed-nanoneedles. Combined experiments and theoretical analyses reveal that, due to the microscopically rugged and low-adhesive nature of building blocks, the nanosamples can not only realize high-density nucleation but constrain growing condensates into suspended microdrops via the self-transport and/or self-expansion mode for subsequently self-propelled jumping, powered by coalescence-released excess surface energy. Consequently, our nanosample exhibits over 125% enhancement in DCHT coefficient. This work helps develop advanced heat-transfer materials and devices for efficient thermal management and energy utilization. PMID:25966966
McGuire, Joseph C. (Richland, WA)
1982-01-01
A heat transfer system for a nuclear reactor. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
Not Available
1980-03-07
A heat transfer system for a nuclear reactor is described. Heat transfer is accomplished within a sealed vapor chamber which is substantially evacuated prior to use. A heat transfer medium, which is liquid at the design operating temperatures, transfers heat from tubes interposed in the reactor primary loop to spaced tubes connected to a steam line for power generation purposes. Heat transfer is accomplished by a two-phase liquid-vapor-liquid process as used in heat pipes. Condensible gases are removed from the vapor chamber through a vertical extension in open communication with the chamber interior.
Kandlikar, Satish
Journal of Heat Transfer Guest Editorial We are indeed delighted in bringing out this special issue was showcased in diverse areas such as traditional heat and mass transfer, lab-on-chip, sensors, biomedical applica- tions, micromixers, fuel cells, and microdevices. Selected papers in the field of heat transfer
Efficient heat-transfer surfaces assembled from partially finned flat-oval tubes
NASA Astrophysics Data System (ADS)
Pis'mennyi, E. N.
2011-04-01
The state of finned convective heat-transfer surfaces and prospects for using them in power engineering and industry are briefly reviewed. The characteristics of a heat-recovery economizer made of partially finned flat-oval tubes are presented by way of comparing them with design versions employing known types of finned tubes, and the results gained from its operation downstream of a PTVM-30M boiler are given.
Fang, X.; Wang, Z.; Liu, H.
2006-01-01
Zhenhua Wang Huaitao Liu Professor Master Master School of Municipal & Environmental Eng, Harbin Institute of Technology Harbin P. R. China, 150090 fxm490@163.com Abstract: This paper analyzes the influence of transfer efficiency...
Proceedings of Heat Transfer 2003: ASME Summer Heat Transfer Conference
Kandlikar, Satish
Proceedings of Heat Transfer 2003: ASME Summer Heat Transfer Conference Las Vegas, Nevada, USA July 21-23, 2003 HT2003-47449 HEAT TRANSFER FROM A MOVING AND EVAPORATING MENISCUS ON A HEATED SURFACE meniscus with complete evaporation of water without any meniscus break-up. The experimental heat transfer
NASA Astrophysics Data System (ADS)
Burbach, T.
1985-04-01
The heat transfer from hot water to a cold copper pipe in laminar and turbulent flow condition is determined. The mean flow through velocity in the pipe, relative test length and initial temperature in the vessel were varied extensively during tests. Measurements confirm Nusselt's theory for large test lengths in laminar range. A new equation is derived for heat transfer for large starting lengths which agrees satisfactorily with measurements for large starting lengths. Test results are compared with the new Prandtl equation for heat transfer and correlated well. Test material for 200- and to 400-diameter test length is represented at four different vessel temperatures.
NASA Technical Reports Server (NTRS)
Burbach, T.
1985-01-01
The heat transfer from hot water to a cold copper pipe in laminar and turbulent flow condition is determined. The mean flow through velocity in the pipe, relative test length and initial temperature in the vessel were varied extensively during tests. Measurements confirm Nusselt's theory for large test lengths in laminar range. A new equation is derived for heat transfer for large starting lengths which agrees satisfactorily with measurements for large starting lengths. Test results are compared with the new Prandtl equation for heat transfer and correlated well. Test material for 200- and to 400-diameter test length is represented at four different vessel temperatures.
Investment casting heat transfer
NSDL National Science Digital Library
Powell, Adam C., IV
2004-12-15
Calculate temperature profile and Biot number in mixed conduction and convection/radiation heat transfer from liquid metal through a ceramic mold to the environment, and suggest a design change to reduce the probability of shattering due to thermal stress.
Yadav, Rakesh K; Christensen, Ulrich R; Duarte, Lucia; Reiners, Ansgar
2015-01-01
We study rotating thermal convection in spherical shells as prototype for flow in the cores of terrestrial planets, gas planets or in stars. We base our analysis on a set of about 450 direct numerical simulations of the (magneto)hydrodynamic equations under the Boussinesq approximation. The Ekman number ranges from $10^{-3}$ to $10^{-6}$. Four sets of simulations are considered: non-magnetic simulations and dynamo simulations with either free-slip or no-slip flow boundary conditions. The non-magnetic setup with free-slip boundaries generates the strongest zonal flows. Both non-magnetic simulations with no-slip flow boundary conditions and self-consistent dynamos with free-slip boundaries have drastically reduced zonal-flows. Suppression of shear leads to a substantial gain in heat-transfer efficiency, increasing by a factor of 3 in some cases. Such efficiency enhancement occurs as long as the convection is significantly influenced by rotation. At higher convective driving the heat-transfer efficiency trends t...
NASA Astrophysics Data System (ADS)
Jaluria, Yogesh; Torrance, Kenneth E.
Numerical approaches to heat-transfer problems are examined in an introductory text for senior and graduate engineering students. The emphasis is on the application of physical criteria in selecting the computational method. Chapters are devoted to the mathematics of the governing equations, finite differences, and finite elements; the simulation of transport processes; numerical methods for convective and radiative heat transfer; and combined modes and process applications. Graphs, diagrams, flow charts, problems, tables of material parameters, and sample computer programs are provided.
Banerjee, Debjyoti
% higher heat flux at Leidenfrost point (film boiling regime) compared to control experiments. HoweverJournal of Heat Transfer Technical Brief Pool Boiling Experiments on Multiwalled Carbon Nanotube with verti- cally aligned multiwalled carbon nanotubes (MWCNT) "forests" and were used for pool boiling
Short duration heat transfer measurements
T. Arts; C. Camci
1985-01-01
Shock tunnels, blowdown cascades, and isentropic light piston compression tubes used to study heat transfer and aerodynamic phenomena in turbine components are described. Thin film heat transfer gages, calorimeter gages, and optical measurements methods are presented. Compression tube investigations of convective heat transfer on a flat plate, with and without film cooling; and convective heat transfer on a high pressure
Enhanced Condensation Heat Transfer
NASA Astrophysics Data System (ADS)
Rose, John Winston
The paper gives some personal observations on various aspects of enhanced condensation heat transfer. The topics discussed are external condensation (horizontal low-finned tubes and wire-wrapped tubes), internal condensation (microfin tubes and microchannels) and Marangoni condensation of binary mixtures.
Methane heat transfer investigation
NASA Technical Reports Server (NTRS)
1984-01-01
Future high chamber pressure LOX/hydrocarbon booster engines require copper base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and reusable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper base alloy material adjacent to he fuel coolant. High pressure methane cooling and coking characteristics recently evaluated at Rocketdyne using stainless steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.
Methane heat transfer investigation
NASA Technical Reports Server (NTRS)
Cook, R. T.
1984-01-01
Future high chamber pressure LOX/hydrocarbon booster engines require copper-base alloy main combustion chamber coolant channels similar to the SSME to provide adequate cooling and resuable engine life. Therefore, it is of vital importance to evaluate the heat transfer characteristics and coking thresholds for LNG (94% methane) cooling, with a copper-base alloy material adjacent to the fuel coolant. High-pressure methane cooling and coking characteristics were recently evaluated using stainless-steel heated tubes at methane bulk temperatures and coolant wall temperatures typical of advanced engine operation except at lower heat fluxes as limited by the tube material. As expected, there was no coking observed. However, coking evaluations need be conducted with a copper-base surface exposed to the methane coolant at higher heat fluxes approaching those of future high chamber pressure engines.
Faculty Positions Heat Transfer and
Faculty Positions Heat Transfer and Thermal/Energy Sciences Naval Postgraduate School Monterey-track faculty position at the assistant professor level in the areas of Heat Transfer and Thermal/Fluid Sciences
Heat Transfer Derivation of differential equations for heat transfer conduction
Veress, Alexander
Heat Transfer Derivation of differential equations for heat transfer conduction without convection/(hftF). T is the temperature, in C or F. dT=dx is the temperature gradient, in C/m or F/ft. This equation states that the heat sign in the above equation states heat flow is positive in the direction opposite the direction
"Nanotechnology Enabled Advanced Industrial Heat Transfer Fluids"
Dr. Ganesh Skandan; Dr. Amit Singhal; Mr. Kenneth Eberts; Mr. Damian Sobrevilla; Prof. Jerry Shan; Stephen Tse; Toby Rossmann
2008-06-12
ABSTRACT Nanotechnology Enabled Advanced industrial Heat Transfer Fluids” Improving the efficiency of Industrial Heat Exchangers offers a great opportunity to improve overall process efficiencies in diverse industries such as pharmaceutical, materials manufacturing and food processing. The higher efficiencies can come in part from improved heat transfer during both cooling and heating of the material being processed. Additionally, there is great interest in enhancing the performance and reducing the weight of heat exchangers used in automotives in order to increase fuel efficiency. The goal of the Phase I program was to develop nanoparticle containing heat transfer fluids (e.g., antifreeze, water, silicone and hydrocarbon-based oils) that are used in transportation and in the chemical industry for heating, cooling and recovering waste heat. Much work has been done to date at investigating the potential use of nanoparticle-enhanced thermal fluids to improve heat transfer in heat exchangers. In most cases the effect in a commercial heat transfer fluid has been marginal at best. In the Phase I work, we demonstrated that the thermal conductivity, and hence heat transfer, of a fluid containing nanoparticles can be dramatically increased when subjected to an external influence. The increase in thermal conductivity was significantly larger than what is predicted by commonly used thermal models for two-phase materials. Additionally, the surface of the nanoparticles was engineered so as to have a minimal influence on the viscosity of the fluid. As a result, a nanoparticle-laden fluid was successfully developed that can lead to enhanced heat transfer in both industrial and automotive heat exchangers
Nikolayev, Vadim S.
. It is true that boiling has been exten- sively studied from an empirical point of view for the most commonBOILING CRISIS:THEORY,SIMULATION,AND EXPERIMENTSBOILING CRISIS: THEORY, SIMULATION, AND EXPERIMENTS Boiling is a very efficient way to transfer heat from a heater to the liquid heat carrier. We discuss
Analysis of orbital heat transfer
NASA Technical Reports Server (NTRS)
Buna, T.
1974-01-01
Graphical representation of orbital heat balance in form of polar diagrams is obtained from integral expressions of orbital heat transfer whereby quantities of heat are represented as areas swept by ""thermal radii.''
Thermodynamics of Flow Boiling Heat Transfer
NASA Astrophysics Data System (ADS)
Collado, F. J.
2003-05-01
Convective boiling in sub-cooled water flowing through a heated channel is essential in many engineering applications where high heat flux needs to be accommodated. It has been customary to represent the heat transfer by the boiling curve, which shows the heat flux versus the wall-minus-saturation temperature difference. However it is a rather complicated problem, and recent revisions of two-phase flow and heat transfer note that calculated values of boiling heat transfer coefficients present many uncertainties. Quite recently, the author has shown that the average thermal gap in the heated channel (the wall temperature minus the average temperature of the coolant) was tightly connected with the thermodynamic efficiency of a theoretical reversible engine placed in this thermal gap. In this work, whereas this correlation is checked again with data taken by General Electric (task III) for water at high pressure, a possible connection between this wall efficiency and the reversible-work theorem is explored.
Radiant heat transfer from storage casks to the environment
R W Carlson; J Hovingh; G R Thomas
1999-01-01
A spent fuel storage cask must efficiently transfer the heat released by the fuel assemblies through the cask walls to the environment. This heat must be transferred through passive means, limiting the energy transfer mechanisms from the cask to natural convection and radiation heat transfer.. Natural convection is essentially independent of the characteristics of the array of casks, provided there
NASA Technical Reports Server (NTRS)
Kalkbrenner, R. W. (inventor)
1974-01-01
A heat transfer device is characterized by an hermetically sealed tubular housing including a tubular shell terminating in spaced end plates, and a tubular mesh wick concentrically arranged and operatively supported within said housing. The invention provides an improved wicking restraint formed as an elongated and radially expanded tubular helix concentrically related to the wick and adapted to be axially foreshortened and radially expanded into engagement with the wick in response to an axially applied compressive load. The wick is continuously supported in a contiguous relationship with the internal surfaces of the shell.
Anjun Jiao
2008-01-01
The heat pipe, as one of the most efficient heat transport devices, is a peerless choice in the electronic cooling field. In order to better understand the heat transfer mechanisms of the heat pipe, a heat transfer model, which considers the effects of the surface condition, disjoining pressure, gravity force, and contact angle on the thin film profile, heat flux
Conduction heat transfer solutions
VanSant, J.H.
1983-08-01
This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.
Heat Transfer Discussion: "Heat Transfer and Wall
Kandlikar, Satish
flow boiling curve extending from the single-phase region at point C to the fully developed boiling During Subcooled Flow Nucleate BoilingA Review" (Warrier, G.R., and Dhir, V.K., 2006, Journal of Heat in the partial boiling region, along with Eqs. 13 - 14 . The authors of 1 further state that Kandlikar 3 in 1998
Tubing for augmented heat transfer
Yampolsky, J.S.; Pavlics, P.
1983-08-01
The objectives of the program reported were: to determine the heat transfer and friction characteristics on the outside of spiral fluted tubing in single phase flow of water, and to assess the relative cost of a heat exchanger constructed with spiral fluted tubing with one using conventional smooth tubing. An application is examined where an isolation water/water heat exchanger was used to transfer the heat from a gaseous diffusion plant to an external system for energy recovery. (LEW)
Heat Transfer through Rockfall
NASA Astrophysics Data System (ADS)
Green, R. T.; Pohle, J.; Prikryl, J.
2004-12-01
Thermally induced rock stresses at the potential high-level nuclear waste (HLW) repository at Yucca Mountain, Nevada, can degrade the drifts, possibly causing rockfall onto the dripshield overlying the emplaced waste packages. Thermal-hydrological processes will be altered by changes in thermal conductivity, ventilation, radiation, and convection resulting from such rockfalls. Determining the effects of collapse materials on repository performance is difficult because heat and mass transfer through the engineered barrier and highly heterogeneous collapse materials is a complex and coupled process. Measurements and estimates of thermal conductivity of intact rock samples from geologic units at Yucca Mountain are available, but collapsed rock will be a mixture of broken rock and air. The purpose of this investigation is to assess the thermal conductivity of crushed tuff from the Topopah Spring lower lithophysal unit at Yucca Mountain and identify the important heat and mass transfer mechanisms in the collapsed rock for the range of conditions expected at a potential geologic HLW repository. A laboratory apparatus was used to directly measure steady-state bulk thermal conductivity of crushed tuff for a range of temperatures up to 197ºC and thermal gradients as large as 990ºC/m. Measured thermal conductivities varied from 0.38 to 0.56 W/m-K. In general, thermal conductivity increased with either increased temperature or increased thermal gradient. This abstract is an independent product of the CNWRA and does not necessarily reflect the views or regulatory position of the NRC. The NRC staff views expressed herein are preliminary and do not constitute a final judgement of determination of the matters addressed or the acceptability of a license application for a geologic repository at Yucca Mountain.
Heat Transfer: From Hot to Not
NSDL National Science Digital Library
Integrated Teaching and Learning Program, College of Engineering,
Students learn the fundamental concepts of heat transfer and heat of reaction. This includes concepts such as physical chemistry, an equation for heat transfer, and a basic understanding of energy and heat transfer.
Get the most out of heat transfer fluids
Shelley
1994-01-01
In the never-ending quest to squeeze more efficiency out of heat transfer systems, operators have two options: alter the system's mechanical attributes or better match the properties of the heat transfer fluid to the needs of the system. When it comes to liquid-phase heat transfer fluids, some property tradeoffs must be accepted. For example, glycols extend water's usefulness by depressing
Effect of heat transfer on the performance of thermoelectric generators
Lingen Chen; Jianzheng Gong; Fengrui Sun; Chih Wu
2002-01-01
The power output and efficiency expressions for thermoelectric (semiconductor) generators which is composed of multi-elements are derived with considerations of heat transfer irreversibility in the heat exchangers between the generator and the heat reservoirs. Numerical examples are provided. The effects of heat transfer and the number of elements on the performance are analyzed.
Jiang, Shaohui; Liu, Changhong; Fan, Shoushan
2014-03-12
In this work, we report our studies related to the natural-convective heat transfer properties of carbon nanotube (CNT) sheets. We theoretically derived the formulas and experimentally measured the natural-convective heat transfer coefficients (H) via electrical heating method. The H values of the CNT sheets containing different layers (1, 2, 3, and 1000) were measured. We found that the single-layer CNT sheet had a unique ability on heat dissipation because of its great H. The H value of the single-layer CNT sheet was 69 W/(m(2) K) which was about twice of aluminum foil in the same environment. As the layers increased, the H values dropped quickly to the same with that of aluminum foil. We also discussed its roles on thermal dissipation, and the results indicated that the convection was a significant way of dissipation when the CNT sheets were applied on macroscales. These results may give us a new guideline to design devices based on the CNT sheets. PMID:24548165
Virginia Tech
Spring 2014 Heat Transfer - 2 A thin electronic chip is in the shape of a square wafer, b = 1 cm surface of the chip with a heat transfer coefficient of h = 100 W/m2 -K. Assume the chip has a uniform per side with a mass of m = 0.3 grams and specific heat of C = 103 J/kg-K. The chip is mounted
Heat transfer in energy conservation
R. J. Goldstein; D. Didion; R. Gopal; K. Kreider; R. Schoenhals
1977-01-01
Seventeen papers by various authors are presented. The topics discussed are the many areas of heat transfer in energy conservation systems such as new techniques for measurement of quantities related to heat loss and energy use; monitoring and control instrumentation; potential energy savings in commercial\\/residential communities; total system design for building envelopes; and heat storage systems. Individual papers are abstracted
Virginia Tech
Spring 2014 1 Heat Transfer - 1 Consider a cylindrical nuclear fuel rod of length L and diameter df and the tube at a rate m , and the outer surface of the tube is well insulated. Heat generation occurs within. The specific heat of water pc , and the thermal conductivity of the fuel rod fk are constants. The system
MODERN DEVELOPMENTS IN MULTIPHASE FLOW & HEAT TRANSFER
Lahey, Richard T.
MODERN DEVELOPMENTS IN MULTIPHASE FLOW & HEAT TRANSFER "ENGINEERING APPLICATIONS OF FRACTAL and multiphase flow & heat transfer will be stressed. This paper will begin by reviewing some important concepts
NASA Technical Reports Server (NTRS)
Friedell, M. V.; Anderson, A. J.
1974-01-01
Thermal switch maintains temperature of planetary lander, within definite range, by transferring heat. Switch produces relatively large stroke and force, uses minimum electrical power, is lightweight, is vapor pressure actuated, and withstands sterilization temperatures without damage.
Heat transfer characteristics for disk fans
NASA Astrophysics Data System (ADS)
Prikhodko, Yu. M.; Chekhov, V. P.; Fomichev, V. P.
2014-08-01
Multiple-disk fans belong to the class of friction machines; they can be designed in two variants: centrifugal disk fans and diametrical disk fans. Flow patterns in these two types of machines are different, and they possess different heat transfer characteristics. The paper presents results of experimental study for a centrifugal disk fan under atmospheric pressure with air taken as working gas. The radial temperature distribution for a disk was obtained at different rotation speed of the rotor and different heating of the disks. Heat transfer characteristics of a centrifugal disk fan and a diametrical disk fan were compared. The research results demonstrate a higher heat transfer efficiency for centrifugal design versus diametrical disk design.
Rotary Joint for Heat Transfer
NASA Technical Reports Server (NTRS)
Shauback, R.
1986-01-01
Rotary joint exchanges heat between two heat pipes - one rotating and one stationary. Joint accommodates varying heat loads with little temperature drop across interface. According to concept, heat pipe enters center of disklike stationary section of joint. There, wicks in central artery of heat pipe separate into multiple strands that lead to concentric channels on rotaryinterface side of stationary disk. Thin layer of liquid sodium/potassium alloy carries heat from one member of rotary joint to other. Liquid conducts heat efficiently while permitting relative motion between members. Polypropylene rings contain liquid without interfering with rotation.
Heat transfer from interrupted plates
NASA Astrophysics Data System (ADS)
Zelenka, R. L.; Loehrke, R. I.
1983-02-01
Heat transfer coefficients were measured in single and multiple flat plates equipped with interior heating elements and immersed in low Re flows in a wind tunnel. The plates were located successively in the tunnel and spanned the width of the channel. Attention was initially given to blunt leading edges, which were gradually reshaped in order to study various flow separation conditions over the course of the trials. Each plate was heated to 6 C over room temperature. The average value of a heat transfer coefficient for a single plate was determined to depend on the plate length and thickness, and may be inhibited by the leading edge separation bubble in the case of a blunt leading edge. Higher Re enhances the value of the coefficient. Turbulence induced by the presence of the first plate was observed to enhance heat transfer from the second plate.
Heat Transfer Characteristics of a Quadratic Koch Island Fractal Heat Exchanger
Josua P. Meyer; Hilde van der Vyver
2005-01-01
Heat exchangers are widely used in the air conditioning and refrigeration industries, and any increase in their efficiency will have a positive effect on the industry as well. A new design of heat exchanger is proposed that will increase the heat transfer area significantly. The heat transfer area was increased by the use of fractals. Three techniques were used to
NASA Technical Reports Server (NTRS)
Widener, Edward L.
1992-01-01
The objective is to introduce some concepts of thermodynamics in existing heat-treating experiments using available items. The specific objectives are to define the thermal properties of materials and to visualize expansivity, conductivity, heat capacity, and the melting point of common metals. The experimental procedures are described.
Measurement of thermoacoustic convection heat transfer phenomenon
NASA Technical Reports Server (NTRS)
Parang, M.; Salah-Eddine, A.
1983-01-01
In this paper the results of an experimental investigation of thermoacoustic convection (TAC) heat transfer phenomenon in both zero-gravity and gravity environment are presented and compared with pure conduction heat transfer. The numerical solutions of the governing equations obtained by others for TAC heat transfer phenomenon are also discussed. The experimental results show that for rapid heating rate at a boundary, the contribution of TAC heat transfer to a gas could be significantly (one order of magnitude) higher than heat transfer rate from pure conduction. The results also show significantly reduced transient time in heat transfer processes involving thermoacoustic convective heat transfer mode in both space and gravity environment.
Enhanced heat transfer using nanofluids
Choi, Stephen U. S. (Lisle, IL); Eastman, Jeffrey A. (Naperville, IL)
2001-01-01
This invention is directed to a method of and apparatus for enhancing heat transfer in fluids such as deionized water. ethylene glycol, or oil by dispersing nanocrystalline particles of substances such as copper, copper oxide, aluminum oxide, or the like in the fluids. Nanocrystalline particles are produced and dispersed in the fluid by heating the substance to be dispersed in a vacuum while passing a thin film of the fluid near the heated substance. The fluid is cooled to control its vapor pressure.
Optimization of a Thermoacoustic Engine with a Complex Heat Transfer Exponent
Feng Wu; Chih Wu; Fangzhong Guo; Qing Li; Lingen Chen
2003-01-01
Heat transfer between a thermoacoustic engine and its surrounding heat reservoirs can be out of phase with oscillating working gas temperature. The paper presents a generalized heat transfer model using a complex heat transfer exponent. Both the real part and the imaginary part of the heat transfer exponent change the power versus efficiency relationship quantitatively. When the real part of
Examination of Liquid Fluoride Salt Heat Transfer
Yoder Jr, Graydon L [ORNL] [ORNL
2014-01-01
The need for high efficiency power conversion and energy transport systems is increasing as world energy use continues to increase, petroleum supplies decrease, and global warming concerns become more prevalent. There are few heat transport fluids capable of operating above about 600oC that do not require operation at extremely high pressures. Liquid fluoride salts are an exception to that limitation. Fluoride salts have very high boiling points, can operate at high temperatures and low pressures and have very good heat transfer properties. They have been proposed as coolants for next generation fission reactor systems, as coolants for fusion reactor blankets, and as thermal storage media for solar power systems. In each case, these salts are used to either extract or deliver heat through heat exchange equipment, and in order to design this equipment, liquid salt heat transfer must be predicted. This paper discusses the heat transfer characteristics of liquid fluoride salts. Historically, heat transfer in fluoride salts has been assumed to be consistent with that of conventional fluids (air, water, etc.), and correlations used for predicting heat transfer performance of all fluoride salts have been the same or similar to those used for water conventional fluids an, water, etc). A review of existing liquid salt heat transfer data is presented, summarized, and evaluated on a consistent basis. Less than 10 experimental data sets have been found in the literature, with varying degrees of experimental detail and measured parameters provided. The data has been digitized and a limited database has been assembled and compared to existing heat transfer correlations. Results vary as well, with some data sets following traditional correlations; in others the comparisons are less conclusive. This is especially the case for less common salt/materials combinations, and suggests that additional heat transfer data may be needed when using specific salt eutectics in heat transfer equipment designs. All of the data discussed above were taken under forced convective conditions (both laminar and turbulent). Some recent data taken at ORNL under free convection conditions are also presented and results discussed. This data was taken using a simple crucible experiment with an instrumented nickel heater inserted in the salt to induce natural circulation within the crucible. The data was taken over a temperature range of 550oC to 650oC in FLiNaK salt. This data covers both laminar and turbulent natural convection conditions, and is compared to existing forms of natural circulation correlations.
Nanofluid impingement jet heat transfer
NASA Astrophysics Data System (ADS)
Zeitoun, Obida; Ali, Mohamed
2012-02-01
Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters.
Nanofluid impingement jet heat transfer.
Zeitoun, Obida; Ali, Mohamed
2012-01-01
Experimental investigation to study the heat transfer between a vertical round alumina-water nanofluid jet and a horizontal circular round surface is carried out. Different jet flow rates, jet nozzle diameters, various circular disk diameters and three nanoparticles concentrations (0, 6.6 and 10%, respectively) are used. The experimental results indicate that using nanofluid as a heat transfer carrier can enhance the heat transfer process. For the same Reynolds number, the experimental data show an increase in the Nusselt numbers as the nanoparticle concentration increases. Size of heating disk diameters shows reverse effect on heat transfer. It is also found that presenting the data in terms of Reynolds number at impingement jet diameter can take into account on both effects of jet heights and nozzle diameter. Presenting the data in terms of Peclet numbers, at fixed impingement nozzle diameter, makes the data less sensitive to the percentage change of the nanoparticle concentrations. Finally, general heat transfer correlation is obtained verses Peclet numbers using nanoparticle concentrations and the nozzle diameter ratio as parameters. PMID:22340669
Solar concentrating collector heat transfer
Huang, Yuanhsiung.
1989-01-01
The purpose of this study was to obtain a correlation for a proposed solar concentrating collector element, which could be used for design of a large-scale collector. A mathematical model was developed to predict the velocity and temperature fields in a spirally grooved flow passage. The curvature produced a secondary flow and caused departures from the symmetric velocity profile. The analysis considered heat transfer in the developing and fully developed regions through the collector element. The experimental heat transfer values were compared with those values from the mathematical analysis. The numerical study of fully developed laminar flow in a spirally square groove gave satisfactory results for heat-transfer values in fully developed temperature field under the condition of uniform heat flux (on heated wall). The Nusselt number for a curved pipe flow was obtained as a function of Dean number De = Re(a/R){sup 1/2}. As the Dean number values increased, the heat-transfer coefficient and Nusselt number increased. The experimental study was carried out for water flow in a curved square groove. The outlet mean and wall temperatures were measured and the local Nusselt number values were obtained.
Heat transfer in oscillating flows
NASA Technical Reports Server (NTRS)
El-Mehlawy, F.; Mankbadi, R. R.
1990-01-01
The heat transfer in a sudden-expansion flow subjected to upstream periodic disturbances is investigated. In order to study the unsteady turbulent flow for the present symmetrical sudden-expansion flow, the phase-averaging technique of Hussain and Reynolds (1970) is used to derive the governing equations. The imposed periodic disturbances are found to increase the turbulent kinetic energy and the heat transfer rates at the wall. The phenomenon is discovered to be sensitive to the frequency of the imposed disturbances. At the optimum frequency and at a 3 percent disturbance level, the time-averaged heat transfer rate near the reattachment point can be increased by as much as 14 percent.
Heat transfer in oscillating flows
NASA Astrophysics Data System (ADS)
El-Mehlawy, F.; Mankbadi, R. R.
The heat transfer in a sudden-expansion flow subjected to upstream periodic disturbances is investigated. In order to study the unsteady turbulent flow for the present symmetrical sudden-expansion flow, the phase-averaging technique of Hussain and Reynolds (1970) is used to derive the governing equations. The imposed periodic disturbances are found to increase the turbulent kinetic energy and the heat transfer rates at the wall. The phenomenon is discovered to be sensitive to the frequency of the imposed disturbances. At the optimum frequency and at a 3 percent disturbance level, the time-averaged heat transfer rate near the reattachment point can be increased by as much as 14 percent.
Annual review of heat transfer
Tien, C.L. (California Univ., Berkeley, CA (United States))
1992-01-01
This book is designed to provide expository, state-of-the-art reviews of important new developments in the general field of heat transfer. These special characteristics were clearly exhibited in the previous volume which covered such topics as biological freezing, binary vapor condensation, film condensation interface, high-T[sub c] superconductors, multiphase transport in porous media, convection in packed beds and granular flow, microscales of turbulence, and scaling and asymptotic analysis in convection. Topics include chaos, fractal analysis, thermal shock in solids, thermal processing of materials, species-controlled condensation, heterogeneous propellant combustion, mixing of vaporizing droplet sprays and fouling heat transfer.
Heat transfer to turbine blading
NASA Astrophysics Data System (ADS)
Priddy, W. J.; Bayley, F. J.
This paper reports the most recent results of a continuing research program studying the factors determining the distribution of heat transfer to turbine blading. It is particularly concerned with the effects of mainstream turbulence parameters, including intensity and frequency of disturbance. A suggested correlation based on an earlier theoretical study (Ishigaki, 1971) shows clearly how different regions of the blade surface react to the perturbations in the mainstream flow. It is clear that laminar-turbulent transition for the blade boundary layer is crucial to this reaction and the large amount of heat transfer data from the present program is used to examine transition criteria in steady flows.
Sodium heat transfer system modeling
NASA Astrophysics Data System (ADS)
Baker, A. F.; Fewell, M. E.
1983-11-01
The sodium heat transfer system of the international energy agency (IEA) small solar power systems (SSPS) central receiver system (CRS), which includes the heliostat field, receiver, hot and cold storage vessels, and sodium/water steam generator was modeled. The computer code SOLTES (simulator of large thermal energy systems), was used to model this system. The results from SOLTES are compared to measured data.
A METHOD FOR IMPROVING HEAT TRANSFER TO A BOILING FLUID
C. W. Cowley; W. J. Timson; J. A. Sawdye
1962-01-01
Heat transfer rates from thermally conductive solids to boiling liquids ; can be improved by coating the solid with an insulator having sufficient ; insulation value to adjust the temperature difference between the coated solid ; and the liquid nitrogen to a value where more efficient heat transfer will result. ; The method is particularly applicable to conditions where the
Thermoelectric-generator with linear phenomenological heat-transfer law
Lingen Chen; Fengrui Sun; Chih Wu
2005-01-01
The performance of multi-element thermoelectric-generators, assuming heat-transfer irreversibilities which obey the linear phenomenological heat-transfer law Q?(?T?1), is studied in this paper by combining finite-time thermodynamics with non-equilibrium thermodynamics. The performance characteristics of the output power, efficiency and working electrical-current are described by numerical examples.
Kihm, IconKenneth David
Journal of Heat Transfer1999 JHT Heat Transfer Gallery S. M. You Department of Mechanical 8 Transfer Visualization Committee organized two photo gallery sessions in 1998. The International Heat Transfer Photo Gallery was held at the l la' International Heat Transfer Conference (IHTC) in Kyongju
Acoustically enhanced boiling heat transfer
NASA Astrophysics Data System (ADS)
Douglas, Zachary; Boziuk, Thomas R.; Smith, Marc K.; Glezer, Ari
2012-05-01
An acoustic field generated by a light-weight, low-power acoustic driver is shown to increase the critical heat flux during pool boiling by about 17%. It does this by facilitating the removal of vapor bubbles from the heated surface and suppressing the instability that leads to the transition to film boiling at the critical heat flux. Bubble removal is enhanced because the acoustic field induces capillary waves on the surface of a vapor bubble that interact with the bubble contact line on the heated surface causing the contact line to contract and detach the bubble from the surface. The acoustic field also produces a radiation pressure that helps to facilitate the bubble detachment process and also suppresses the transition to film boiling. The mechanisms associated with these interactions are explored using three different experimental setups with acoustic forcing: an air bubble on the underside of a horizontal surface, a single vapor bubble on the top side of a horizontal heated surface, and pool boiling from a horizontal heated surface. Measurements of the capillary waves induced on the bubbles, bubble motion, and heat transfer from the heated surface were performed to isolate and identify the dominant forces involved in these acoustically forced motions.
Heat transfer variations of bicycle helmets.
Brühwiler, P A; Buyan, M; Huber, R; Bogerd, C P; Sznitman, J; Graf, S F; Rösgen, T
2006-09-01
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
Heat transfer by thermovision and CFD methods
NASA Astrophysics Data System (ADS)
Kapjor, Andrej; Gressak, Tomas; Huzvar, Jozef; Vantuch, Martin
2014-08-01
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.
Urban, P; Hanzelka, P; Kralik, T; Musilova, V; Srnka, A; Skrbek, L
2012-10-12
The heat transfer efficiency in turbulent Rayleigh-Bénard convection is investigated experimentally, in a cylindrical cell of height 0.3 m, diameter 0.3 m. We show that for Rayleigh numbers 10(12) < or approximately equal to Ra < or approximately equal to 10(15) the Nusselt number closely follows Nu is proportional to Ra(1/3 if the mean temperature of the working fluid-cryogenic helium gas-is measured by small sensors directly inside the cell at about half of its height. In contrast, if the mean temperature is determined in a conventional way, as an arithmetic mean of the bottom and top plate temperatures, the Nu(Ra) is proportional to Ra(?) displays spurious crossover to higher ? that might be misinterpreted as a transition to the ultimate Kraichnan regime. PMID:23102312
Heat transfer in nonlinear media
NASA Astrophysics Data System (ADS)
Rodriguez, Alejandro
2015-03-01
We derive a fluctuation-dissipation theorem describing thermal electromagnetic fluctuation effects in nonlinear media, which we exploit in the context of a stochastic Langevin framework to study thermal radiation from Kerr photonic cavities coupled to external environments at and out of equilibrium. We find that in addition to inducing temperature-tunable, lineshape alterations, including asymmetric spectral broadening as well as stokes and anti-stokes emission peaks, non-equilibrium heat radiation from such an environment induced by either incident light or temperature gradients can lead to frequency-selective heat transfer greater than that of a linear black body.
Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants
NASA Astrophysics Data System (ADS)
Yoshida, Suguru; Fujita, Yasunobu
The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.
Heat transfer via dropwise condensation on hydrophobic microstructured surfaces
Ruleman, Karlen E. (Karlen Elizabeth)
2009-01-01
Dropwise condensation has the potential to greatly increase heat transfer rates. Heat transfer coefficients by dropwise condensation and film condensation on microstructured silicon chips were compared. Heat transfer ...
Enhancement of Pool Boiling Heat Transfer in Confined Space
Hsu, Chia-Hsiang
2014-05-05
Pool boiling is an effective method used in many technical applications for a long time. Its highly efficient heat transfer performance results from not only the convection effect but also the phase change process in pool boiling. Pool boiling...
ME 519: THEORY OF HEAT TRANSFER Instructor
Lin, Xi
ME 519: THEORY OF HEAT TRANSFER Fall 2014 Instructor: Class time: Classroom: Office Hours: Prof Tuesday 45pm or by appointment Class description This course will cover the fundamentals of heat transfer. An introductory course in heat transfer (ME 419 or equivalent) is pre-requisite. Grading 20% Homework 25% Exam 1
Conceptions for heat transfer correlation of nanofluids
Yimin Xuan; Wilfried Roetzel
2000-01-01
The nanofluid is a solid–liquid mixture in which metallic or nonmetallic nanoparticles are suspended. The suspended ultrafine particles change transport properties and heat transfer performance of the nanofluid, which exhibits a great potential in enhancing heat transfer. The mechanism of heat transfer enhancement of the nanofluid is investigated. Based on the assumption that the nanofluid behaves more like a fluid
Efficiency of short heat exchangers for helium vapor cooling
D. Steffensrud; J. Bahis; E. Christenson; K. Fassnacht; E. Guckel; D. Harriman; S. Nahn; P. Vu; J. Zhang
1991-01-01
The heat transfer efficiency of short heat exchangers along the vent tube of a helium cryostat and the temperature profile of the helium vapor along the vent tube are both measured. The results of the measurements show that the heat exchangers are in some cases considerably more efficient than indicated by simple model calculations. With a flow rate of 0.0044
Heat Transfer Research, 2010, Vol. 41, No. 6 Turbine Aero-Heat Transfer Studies
Camci, Cengiz
AU TH O R PR O O F Heat Transfer Research, 2010, Vol. 41, No. 6 Turbine Aero-Heat Transfer Studies in Rotating Research Facilities CENGIZ CAMCI Turbomachinery Aero-Heat Transfer Laboratory, Department The present paper deals with the experimental aero-heat transfer studies performed in rotating turbine
Radiation heat transfer in anisotropically scattering media
H. Lee
1985-01-01
Radiation heat transfer in anisotropically scattering media is considered. Scaling laws are formulated to predict the radiant heat flux in anisotropically scattering, one-dimensional planar media. The accuracy in scaling the radiative heat flux in isothermal, homogeneous media is shown to be excellent. The radiant scaling laws are applied to combined mode heat transfer problems which require the solution of the
Pool boiling heat transfer to electrolyte solutions
M. Jamialahmadi; A. Helalizadeh; H. Müller-Steinhagen
2004-01-01
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
Heat transfer in SiC compact heat exchanger
Y. Takeuchi; K. Noborio; Y. Yamamoto; S. Konishi
2010-01-01
For development of a compact SiC heat exchanger, numerical heat transfer analysis was conducted to investigate its performance for a wide range of thermal media, liquid LiPb and helium gas, flow rates. The numerical model used was based on the heat exchanger test module developed by the authors. Within the authors’ experimental range, the heat quantity transferred from high temperature
Heat exchanger device and method for heat removal or transfer
Koplow, Jeffrey P
2013-12-10
Systems and methods for a forced-convection heat exchanger are provided. In one embodiment, heat is transferred to or from a thermal load in thermal contact with a heat conducting structure, across a narrow air gap, to a rotating heat transfer structure immersed in a surrounding medium such as air.
Enhanced heat transfer for thermionic power modules
NASA Astrophysics Data System (ADS)
Johnson, D. C.
1981-07-01
Heat transfer systems required for high heat fluxes (20 w/sq cm) at high temperatures (1500 K) which advanced thermionic power modules upon combustion systems are described. Energy transfer from the hot combustion gases may take place by convection, radiation, or a combination of radiation and convection. Enhanced convective heat transfer with a jet impingement system was demonstrated in a thermionic converter. The cellular ceramic radiative heat transfer system was applied to a thermionic converter. By comparing the jet impingement and cellular ceramic radiative heat transfer systems, an appropriate system may be selected for utilization in advanced thermionic power modules.
G. S. Attey
1998-01-01
The heat transfer performance of conventional solid heat sinks in conjunction with thermoelectric modules is well known but little work has been carried out on liquid heat transfer systems as an alternative. A light weight, low cost, highly efficient liquid heat transfer system has been developed which operates on each side of standard TE modules. The system's basic properties and
A Numerical Study on Heat Transfer of High Efficient Solar Flat-Plate Collectors with Energy Storage
Zhenqian Chen; Mingwei Gu; Donghua Peng; Changhai Peng; Zhishen Wu
2010-01-01
The integrated solar collector is considered to be a promising direction for increasing the economic feasibility of low-temperature solar systems for heating water in domestic and industrial applications. Phase change material (paraffin) energy storage can be used in solar water heaters. The paraffin-integrated solar collector eliminates the need of conventional storage tanks, thus reducing cost and space. But a negative
Heat transfer and conditioning unit
Smith, R.J.
1986-10-28
This patent describes a heat transfer and conditioning unit connectively joining a fire chamber and an exhaust flue having an independent chamber for circulation of ambient air capable of transferring heat thereto comprising: a casing having exhaust inlets and exhaust outlets adapted for communication with a flue to the atmosphere; the casing containing adjacent walls, the opposing surfaces of the walls defining elongated passages arranged in longitudinal alignment for conducting exhaust gas containing products of combustion between the exhaust inlets and outlets; the walls being formed of a material suitable for the conductance of heat; each elongated passage having a passage inlet adjacent to the exhaust inlet and a passage outlet adjacent to the exhaust outlet, walls disposed parallel to each other and venturi. The venturi are located at each passage inlet and outlet and are periodically disposed along the elongated passage, each venturi is separated from adjacent venturi by portions of the wall disposed parallel to each other, the venturi and parallel portions of the wall defining compartments; the compartments containing a series of longitudinally and laterally extending fins; and the casing having an air inlet and an air outlet and a continuous chamber for the passage of ambient air between the inlet and the air outlet.
Sodium heat transfer system modeling
Baker, A.F.; Fewell, M.E.
1983-01-01
The sodium heat transfer system of the International Energy Agency (IEA) Small Solar Power Systems (SSPS) Central Receiver System (CRS), which includes the heliostat field, receiver, hot and cold storage vessels, and sodium/water steam generator has been modeled. The computer code SOLTES (Simulator of Large Thermal Energy Systems), developed by Sandia National Laboratories, was used to model this system. Based on data provided to Sandia by the IEA-SSPS/CRS project, the results from SOLTES are compared to measured data. The comparison between measured data and predictions from SOLTES is very good for the day evaluated.
Liquid metal heat transfer issues
Hoffman, H.W.; Yoder, G.L.
1984-01-01
An alkali liquid metal cooled nuclear reactor coupled with an alkali metal Rankine cycle provides a practicable option for space systems/missions requiring power in the 1 to 100 MW(e) range. Thermal issues relative to the use of alkali liquid metals for this purpose are identified as these result from the nature of the alkali metal fluid itself, from uncertainties in the available heat transfer correlations, and from design and performance requirements for system components operating in the earth orbital microgravity environment. It is noted that, while these issues require further attention to achieve optimum system performance, none are of such magnitude as to invalidate this particular space power concept.
Advances in enhanced heat\\/mass transfer and energy efficiency. HTD-Volume 320; PID-Volume 1
M. M. Ohadi; J. C. Conklin
1995-01-01
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.
Li, Perry Y.
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 density of compressed air storage (about 20 times greater than hydraulic accumulators), and the high power
Cueff, Sebastien; Labbe, Christophe; Cardin, Julien; Doualan, Jean-Louis; Khomenkova, Larysa; Hijazi, Khalil; Rizk, Richard [Centre de Recherche sur les Ions, les Materiaux et la Photonique (CIMAP), ENSICAEN, CNRS, CEA/IRAMIS, Universite de Caen, 14050 CAEN Cedex (France); Jambois, Olivier; Garrido, Blas [Dept. Electronica, MIND-IN2UB, Universitat de Barcelona, Marti i Fanques 1, 08028 Barcelona, CAT (Spain)
2010-09-15
This study investigates the influence of the deposition temperature T{sub d} on the Si-mediated excitation of Er ions within silicon-rich silicon oxide layers obtained by magnetron cosputtering. For T{sub d} exceeding 200 deg. C, an efficient indirect excitation of Er ions is observed for all as-deposited samples. The photoluminescence intensity improves gradually up to a maximum at T{sub d}=600 deg. C before decreasing for higher T{sub d} values. The effects of this ''growth-induced annealing'' are compared to those resulting from the same thermal budget used for the ''classical'' approach of postdeposition annealing performed after a room temperature deposition. It is demonstrated that the former approach is highly beneficial, not only in terms of saving time but also in the fourfold enhancement of the Er photoluminescence efficiency.
Nanowires for Enhanced Boiling Heat Transfer
Renkun Chen; Ming-Chang Lu; Vinod Srinivasan; Zhijie Wang; Hyung Hee Cho; Arun Majumdar
2009-01-01
ABSTRACT Boiling is a common mechanism for liquid-vapor phase transition and is widely exploited in power generation and refrigeration devices and systems. The efficacy of boiling heat transfer is characterized by two parameters: (a) heat transfer coefficient (HTC) or the thermal conductance; (b) the critical heat flux (CHF) limit that demarcates the transition from high HTC to very low HTC.
Industrial furnace with improved heat transfer
Hoetzl, M.; Lingle, T.M.
1992-07-07
This patent describes an industrial furnace for heating work which emits volatiles during heating. It comprises a generally cylindrical, closed end furnace section defining a sealable heat transfer chamber for heating work disposed therein; fan means for directing furnace atmosphere as a swirling wind mass about the interior of the furnace section over a portion thereof; heat means for heating the wind mass within the fan chamber; and an incineration track formed as a circumferentially extending groove about the exterior of the furnace section and in heat transfer relationship with and situated at least to extend about a portion of the fan chamber.
A literature survey on numerical heat transfer
NASA Astrophysics Data System (ADS)
Shih, T. M.
1982-12-01
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.
Gas-liquid flow and heat transfer
Hewitt, G.F.; Whalley, P.B.
1984-01-01
This book covers almost the total field of gas-liquid flow and heat transfer, reviewing and collating recent information. Contents (partial): Introduction. Regimes of flow. General analytical and empirical relationships in two phase flow. Interfacial waves. Creation and behaviour of entrained droplets. Bubble flow. Plug flow. Hydrodynamics of co-current vertical annular flow. Hydrodynamics and limits of counter-current flows. Stratified wavy and slug flow in horizontal tubes. Hydrodynamics of annular flows in nonvertical channels and complex. Introduction to two phase heat transfer. Heat transfer in annular flow. Burnout. Post burnout heat transfer. Rewetting and reflooding. Experimental techniques.
Heat transfer, cost modeling and process selection
NSDL National Science Digital Library
Kirchain, Randolph E., Jr.
2006-02-12
Case study of polymer matrix composite process selection between resin transfer molding and chopped fiber injection molding, including heat conduction to calculate solidification time and technical cost modeling.
Radiative heat transfer in porous uranium dioxide
Hayes, S.L. [Texas A and M Univ., College Station, TX (United States)] [Texas A and M Univ., College Station, TX (United States)
1992-12-01
Due to low thermal conductivity and high emissivity of UO{sub 2}, it has been suggested that radiative heat transfer may play a significant role in heat transfer through pores of UO{sub 2} fuel. This possibility was computationally investigated and contribution of radiative heat transfer within pores to overall heat transport in porous UO{sub 2} quantified. A repeating unit cell was developed to model approximately a porous UO{sub 2} fuel system, and the heat transfer through unit cells representing a wide variety of fuel conditions was calculated using a finite element computer program. Conduction through solid fuel matrix as wekk as pore gas, and radiative exchange at pore surface was incorporated. A variety of pore compositions were investigated: porosity, pore size, shape and orientation, temperature, and temperature gradient. Calculations were made in which pore surface radiation was both modeled and neglected. The difference between yielding the integral contribution of radiative heat transfer mechanism to overall heat transport. Results indicate that radiative component of heat transfer within pores is small for conditions representative of light water reactor fuel, typically less than 1% of total heat transport. It is much larger, however, for conditions present in liquid metal fast breeder reactor fuel; during restructuring of this fuel type early in life, the radiative heat transfer mode was shown to contribute as much as 10-20% of total heat transport in hottest regions of fuel.
Low heat transfer oxidizer heat exchanger design and analysis
NASA Technical Reports Server (NTRS)
Kanic, P. G.; Kmiec, T. D.; Peckham, R. J.
1987-01-01
The RL10-IIB engine, a derivative of the RLIO, is capable of multi-mode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2 percent of full thrust, and pumped idle (PI), which is 10 percent of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for log-g deployment. Stable combustion of the RL10-IIB engine at THI and PI thrust levels can be accomplished by providing gaseous oxygen at the propellant injector. Using gaseous hydrogen from the thrust chamber jacket as an energy source, a heat exchanger can be used to vaporize liquid oxygen without creating flow instability. This report summarizes the design and analysis of a United Aircraft Products (UAP) low-rate heat transfer heat exchanger concept for the RL10-IIB rocket engine. The design represents a second iteration of the RL10-IIB heat exchanger investigation program. The design and analysis of the first heat exchanger effort is presented in more detail in NASA CR-174857. Testing of the previous design is detailed in NASA CR-179487.
NASA Technical Reports Server (NTRS)
Garg, Vijay K.
2001-01-01
The turbine gas path is a very complex flow field. This is due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center. Also, based on the author's preference, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. While much has been achieved, more needs to be done in terms of validating the predictions against experimental data. More experimental data, especially on film cooled and rough turbine blades, are required for code validation. Also, the combined film cooling and internal cooling flow computation for a real blade is yet to be performed. While most computational work to date has assumed steady state conditions, the flow is clearly unsteady due to the presence of wakes. All this points to a long road ahead. However, we are well on course.
Heat transfer characteristics of a radical heat pipe
NASA Astrophysics Data System (ADS)
Kaminaga, Fumito; Okamoto, Yoshizo; Yotsukura, Terumitsu; Ito, Haruhiko; Saito, Takasi; Amezawa, Hiroo
1990-03-01
Heat transfer characteristics of a newly designed heat pipe which transports thermal energy in a radial direction of the heat pipe are examined experimentally, using Freon R-113 working fluid. The heat pipe produces a much higher overall heat transmission than the current heat pipe due to a direct contact condensation instead of a filmwise condensation. An unheated vapor space above a heated section and a higher charge rate over 70 percent are required to use it in a wide range of heat flux. A normal screen wick presents an insufficient capillary force to pump up the working fluid to the heated section against the gravity force.
Convective heat transfer as a function of wavelength: Implications for the cooling of the Earth
Convective heat transfer as a function of wavelength: Implications for the cooling of the Earth C, in particular, on its variation with the wavelength of convection. The heat transfer strongly depends in Earth's mantle can significantly reduce the efficiency of heat transfer. The likely variations
Subcooled flow boiling heat transfer from microporous surfaces in a small channel
Yan Sun; Li Zhang; Hong Xu; Xiaocheng Zhong
2011-01-01
The continuously increasing requirement for high heat transfer rate in a compact space can be met by combining the small channel\\/microchannel and heat transfer enhancement methods during fluid subcooled flow boiling. In this paper, the sintered microporous coating, as an efficient means of enhancing nucleate boiling, was applied to a horizontal, rectangular small channel. Water flow boiling heat transfer characteristics
Development of a Heat Transfer Model for the Integrated Facade Heating
Gong, X.; Archer, D. H.; Claridge, D. E.
2007-01-01
the heat transfer process of facade heating (mullion radiators) in a pilot research project in Pittsburgh, PA. The heat transfer model for facade heating is developed and verified by measured data. The comparison shows that the heat transfer model predicts...
Jie Yu; Huan Zhang; Shijun You
Seawater-source heat pump systems (SWHP) are recognized to be outstanding heating, cooling and water heating systems. A large number of SWHP systems have been used in residential and commercial buildings in coastal areas due to the attractive advantages of high efficiency and environmental friendliness. In this paper, two mathematical models that described heat transfer process of casted heat exchanger (CHE)
Heat transfer in the plate heat exchanger of an ammonia-synthesis column
Y. G. Obolentsev; M. S. Chus; O. A. Norobchanskii; Y. S. Teplitshi; L. L. Tovazhnyanskii
1983-01-01
The planning and construction of high-capacity synthetic ammonia plants requires the development and fabrication of unique, high unit-power equipment with high technical and economic characteristics. In foreign and domestic practice, tubular heat exchangers with relatively low heat-transfer coefficients are used. Plate heat exchangers are a promising alternative. They are compact and have a high heat energy efficiency and a relatively
Enhanced Condensation Outside Horizontal Heat Transfer
Tubes J. Li; H. F. Wang; Z. F. Sang
2010-01-01
Experimental investigation of heat transfer and friction characteristics was conducted on the out side of horizontal carbon steel heat transfer tubes under the pressure of saturated vapour 0.04 MP (gauge pressure). The test tubes included spiral-grooved tubes, corrugated tube and smooth tube. The use of water as test fluids has allowed to cover a wide range of turbulent fluid flow
Radiation heat transfer in combustion systems
R. Viskanta; M. P. Menguc
1987-01-01
An adequate treatment of thermal radiation heat transfer is essential to a mathematical model of the combustion process or to a design of a combustion system. This paper reviews the fundamentals of radiation heat transfer and some recent progress in its modeling in combustion systems. Topics covered include radiative properties of combustion products and their modeling and methods of solving
Radiative heat transfer between dielectric bodies
Svend-Age Biehs
2011-03-16
The recent development of a scanning thermal microscope (SThM) has led to measurements of radiative heat transfer between a heated sensor and a cooled sample down to the nanometer range. This allows for comparision of the known theoretical description of radiative heat transfer, which is based on fluctuating electrodynamics, with experiment. The theory itself is a macroscopic theory, which can be expected to break down at distances much smaller than 10-8m. Against this background it seems to be reasonable to revisit the known macroscopic theory of fluctuating electrodynamics and of radiative heat transfer.
Turbine tip and shroud heat transfer
NASA Astrophysics Data System (ADS)
Metzger, D. E.; Dunn, M. G.; Hah, C.
1990-06-01
A numerical computation of the leakage flow is used to link a simple flow and heat transfer model to a specific turbine geometry and operating point for which a unique set of measured local tip and shroud heat fluxes is available. Clearance leakage flow and accompanying heat-transfer are of interest because of long-obvious effects on structural durability and aerodynamic performance. This model should be useful in the understanding and interpretation of future measurements and also for providing early design estimates of the levels of tip and shroud heat transfer that need to be compensated for by active turbine cooling.
Heat Transfer in Complex Fluids
Mehrdad Massoudi
2012-01-01
Amongst the most important constitutive relations in Mechanics, when characterizing the behavior of complex materials, one can identify the stress tensor T, the heat flux vector q (related to heat conduction) and the radiant heating (related to the radiation term in the energy equation). Of course, the expression 'complex materials' is not new. In fact, at least since the publication 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
Development of cryogenic rotatable heat transfer joints
NASA Astrophysics Data System (ADS)
Sadunas, J. A.; Backovsky, Z. F.; Wilson, D. E.
1992-07-01
A summary of cryogenic rotatable heat transfer joint technology development, at Rockwell International Space Division, is presented. Starting with the flight qualified radiative joint on the RM-20B IR sensor of the early 70's, leading to rotatable heat pipe joint, gas conductive joints, rolling-contact-conductance joints, and the more recent work on development and evaluation of cryogenic rotatable seals and mechanical interfaces. Potential applications, joint design optimization, heat transfer, seal leakage and torque test data are presented.
Phase Change Heat Transfer Device for Process Heat Applications
Piyush Sabharwall; Mike Patterson; Vivek Utgikar; Fred Gunnerson
2010-10-01
The next generation nuclear plant (NGNP) will most likely produce electricity and process heat, with both being considered for hydrogen production. To capture nuclear process heat, and transport it to a distant industrial facility requires a high temperature system of heat exchangers, pumps and/or compressors. The heat transfer system is particularly challenging not only due to the elevated temperatures (up to approx.1300 K) and industrial scale power transport (=50MW), but also due to a potentially large separation distance between the nuclear and industrial plants (100+m) dictated by safety and licensing mandates. The work reported here is the preliminary analysis of two-phase thermosyphon heat transfer performance with alkali metals. A thermosyphon is a thermal device for transporting heat from one point to another with quite extraordinary properties. In contrast to single-phased forced convective heat transfer via ‘pumping a fluid’, a thermosyphon (also called a wickless heat pipe) transfers heat through the vaporization/condensing process. The condensate is further returned to the hot source by gravity, i.e., without any requirement of pumps or compressors. With this mode of heat transfer, the thermosyphon has the capability to transport heat at high rates over appreciable distances, virtually isothermally and without any requirement for external pumping devices. Two-phase heat transfer by a thermosyphon has the advantage of high enthalpy transport that includes the sensible heat of the liquid, the latent heat of vaporization, and vapor superheat. In contrast, single-phase forced convection transports only the sensible heat of the fluid. Additionally, vapor-phase velocities within a thermosyphon are much greater than single-phase liquid velocities within a forced convective loop. Thermosyphon performance can be limited by the sonic limit (choking) of vapor flow and/or by condensate entrainment. Proper thermosyphon requires analysis of both.
Enhanced Condensation Outside Horizontal Heat Transfer
NASA Astrophysics Data System (ADS)
Li, Tubes J.; Wang, H. F.; Sang, Z. F.
2010-03-01
Experimental investigation of heat transfer and friction characteristics was conducted on the out side of horizontal carbon steel heat transfer tubes under the pressure of saturated vapour 0.04 MP (gauge pressure). The test tubes included spiral-grooved tubes, corrugated tube and smooth tube. The use of water as test fluids has allowed to cover a wide range of turbulent fluid flow conditions: Reynolds number from 1×104 to 5×104. The heat transfer coefficients and amount of vapour condensation of spiral-grooved tube with different structure parameters are measured. The spiral-grooved tube has the best heat transfer performance compared with corrugated tube and smooth tube. The maximum heat transfer coefficients and amount of vapour condensation of spiral—groove tube is respectively 2.32 and 1.72 times as smooth tube. The maximum ? of spiral groove tube as comprehensive performance evaluation is 1.86. The corrugated tube increase heat transfer coefficients only in the Reynolds numbers lower than 1.5 104, but lower than spiral—groove tube, and transfer performance is worse than smooth tube with the Reynolds numbers grow. The structure parameters influence on spiral-grooved tube performance results show that the deeper of the groove, the better heat-exchange performance with the drag coefficient increased in the same Reynolds numbers. And the greater the fin pitch and trough radius, the poorer the heat exchange effectiveness with the drag coefficient decreased.
Heat and mass transfer considerations in advanced heat pump systems
Panchal, C.B.; Bell, K.J.
1992-01-01
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.
Heat and mass transfer considerations in advanced heat pump systems
Panchal, C.B.; Bell, K.J.
1992-08-01
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.
Variable-Conductance Heat-Transfer Module
NASA Technical Reports Server (NTRS)
Hewitt, D. R.
1984-01-01
Working lengths of heat pipes electronically controlled. Rate of heat transfer controlled by electrical heaters shorten effective working lengths of heat pipes. Concept not limited to right circular cylindrical shape. Concept adaptable to terrestrial instruments or processes in which atmospheres or fluids must be cooled and returned to instruments or processes at fixed lower temperatures.
Base fluid in improving heat transfer for EV car battery
NASA Astrophysics Data System (ADS)
Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.
2015-05-01
This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.
NASA Astrophysics Data System (ADS)
Jiao, Anjun
The heat pipe, as one of the most efficient heat transport devices, is a peerless choice in the electronic cooling field. In order to better understand the heat transfer mechanisms of the heat pipe, a heat transfer model, which considers the effects of the surface condition, disjoining pressure, gravity force, and contact angle on the thin film profile, heat flux distribution, has been developed. The theoretical analyses showed that the heat transfer in the evaporator could be divided into three templates: CASE I, II, and III with increasing the heat load input. In order to verify the theoretical analysis, experimental investigations of a grooved heat pipe with micro trapezoid wicks, a miniature loop heat pipe with a copper sintered-layer flat evaporator, and a flat heat pipe with the wire core wicks were conducted, respectively. Comparison of the experimental data with theoretical results showed that the model can be used to predict the temperature response in evaporator at low heat load but is invalid at high heat load. The thin film evaporation heat transfer model is successful to address the heat transfer in a cell during the freezing process. In order to obtain ultra-high cooling rate and uniform temperature profiles at cryogenic temperature, one cryogenic oscillating heat pipe with the liquid nitrogen as its working fluid has been developed and experimentally studied. Experimental results showed that its heat transport capability reached 380W with DeltaTAve,e-c = 49°C at charged ratio of 48 percent. At steady state, the amplitude of temperature response in evaporator was smaller than that of condenser while the temperature response kept the same frequency in both evaporator and condenser. The Delta T amplitude between evaporator and condenser decreased with increasing the heat load.
Dynamics of heat transfer between nano systems
Svend-Age Biehs; Girish S. Agarwal
2012-10-18
We develop a dynamical theory of heat transfer between two nano systems. In particular, we consider the resonant heat transfer between two nanoparticles due to the coupling of localized surface modes having a finite spectral width. We model the coupled nanosystem by two coupled quantum mechanical oscillators, each interacting with its own heat bath, and obtain a master equation for the dynamics of heat transfer. The damping rates in the master equation are related to the lifetimes of localized plasmons in the nanoparticles. We study the dynamics towards the steady state and establish connection with the standard theory of heat transfer in steady state. For strongly coupled nano particles we predict Rabi oscillations in the mean occupation number of surface plasmons in each nano particle.
Thermodynamics of enhanced heat transfer: a model study
Karen Hovhannisyan; Armen E. Allahverdyan
2010-07-20
Situations where a spontaneous process of energy or matter transfer is enhanced by an external device are widespread in nature (human sweating system, enzyme catalysis, facilitated diffusion across bio-membranes, industrial heat exchangers). The thermodynamics of such processes remains however open. Here we study enhanced heat transfer by a model junction immersed between two thermal baths at different temperatures $T_h$ and $T_c$ ($T_h>T_c$). The transferred heat power is enhanced via controlling the junction by means of external time-dependent fields. Provided that the spontaneous heat flow process is optimized over the junction Hamiltonian, any enhancement of this spontaneous process does demand consumption and subsequent dissipation of work. The efficiency of enhancement is defined via the increment in the heat power divided over the amount of consumed work. We show that this efficiency is bounded from above by $T_c/(T_h-T_c)$. Formally this is identical to the Carnot bound for the efficiency of ordinary refrigerators which transfer heat from cold to hot. It also shares some (but not all) physical features of the Carnot bound.
Ion beam texturing of heat transfer surfaces
NASA Technical Reports Server (NTRS)
Agarwal, P. K.; Park, E. L., Jr.; Weigand, A. J.
1981-01-01
Nucleate boiling heat transfer is examined as a means of energy conservation. Nucleate boiling curves were obtained for ion beam textured copper surfaces, untreated cooper surfaces, copper surfaces which had been polished and surfaces which had been coated with a plasma deposited polymer. Results show that texturing aids heat transfer while polishing has the opposite effect. The polymer coatings did not change nucleate boiling behavior. Aging effects were observed for untreated and for polished surfaces, while no such effects were noticed for textured surfaces. These data suggest that aging may be dependent on surface microgeometry, which is important in nucleate boiling heat transfer.
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred (inventor)
1987-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes a plurality of independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Pumped two-phase heat transfer loop
NASA Technical Reports Server (NTRS)
Edelstein, Fred
1988-01-01
A pumped loop two-phase heat transfer system, operating at a nearly constant temperature throughout, includes several independently operating grooved capillary heat exchanger plates supplied with working fluid through independent flow modulation valves connected to a liquid supply line, a vapor line for collecting vapor from the heat exchangers, a condenser between the vapor and the liquid lines, and a fluid circulating pump between the condenser and the heat exchangers.
Nanofluids for heat transfer : an engineering approach.
Timofeeva, E. V.; Yu, W.; France, D. M.; Singh, D.; Routbort, J. L. (Energy Systems); ( NE); (Univ. of Illinois at Chicago)
2011-02-28
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties.
Nanofluids for heat transfer: an engineering approach
2011-01-01
An overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented. A nanoparticle suspension is considered as a three-phase system including the solid phase (nanoparticles), the liquid phase (fluid media), and the interfacial phase, which contributes significantly to the system properties because of its extremely high surface-to-volume ratio in nanofluids. The systems engineering approach was applied to nanofluid design resulting in a detailed assessment of various parameters in the multivariable nanofluid systems. The relative importance of nanofluid parameters for heat transfer evaluated in this article allows engineering nanofluids with desired set of properties. PMID:21711700
Passive heat transfer means for nuclear reactors
Burelbach, James P. (Glen Ellyn, IL)
1984-01-01
An improved passive cooling arrangement is disclosed for maintaining adjacent or related components of a nuclear reactor within specified temperature differences. Specifically, heat pipes are operatively interposed between the components, with the vaporizing section of the heat pipe proximate the hot component operable to cool it and the primary condensing section of the heat pipe proximate the other and cooler component operable to heat it. Each heat pipe further has a secondary condensing section that is located outwardly beyond the reactor confinement and in a secondary heat sink, such as air ambient the containment, that is cooler than the other reactor component. Means such as shrouding normally isolated the secondary condensing section from effective heat transfer with the heat sink, but a sensor responds to overheat conditions of the reactor to open the shrouding, which thereby increases the cooling capacity of the heat pipe. By having many such heat pipes, an emergency passive cooling system is defined that is operative without electrical power.
Optimizing Structure of LED Light Bulb for Heat Transfer
NASA Astrophysics Data System (ADS)
Kobayashi, T.; Itami, D.; Hashimoto, R.; Takashina, T.; Kanematsu, H.; Mizuta, K.; Utsumi, Y.
2013-04-01
In this paper, in order to optimize the heat transfer structure of LED light bulb, the effects of various parameters on the temperature of the LED device were systematically analyzed, and a design guideline was shown. Although LED device has become popular due to its high-efficiency and long life, the design issues on the heat transfer structure of LED light bulbs has still remained. Because the original efficiency and life of the LED device can not be obtained due to the local temperature rise of LED element and the surrounding polymer molding material. Therefore, heat transfer analysis by finite element method was conducted systematically by changing parameters such as the shape, number and thickness of the radiating fin of the LED. As a result, advantage of open type structure was shown, and the proper design guidance for the structure of the fin shape was obtained.
Determination of the heat transfer coefficients in transient heat conduction
NASA Astrophysics Data System (ADS)
Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.
2013-09-01
The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.
ME 339 Heat Transfer ABET EC2000 syllabus
Ben-Yakar, Adela
ME 339 Heat Transfer Page 1 ABET EC2000 syllabus ME 339 Heat Transfer Spring 2010 Required convection; radiation; introduction to phase change heat transfer and to heat exchangers. Prerequisite(s): ME, Fundamentals of Heat and Mass Transfer, 6th ed., Wiley Other Required Material: NA Course Objectives
Nanoparticle enhanced ionic liquid heat transfer fluids
Fox, Elise B.; Visser, Ann E.; Bridges, Nicholas J.; Gray, Joshua R.; Garcia-Diaz, Brenda L.
2014-08-12
A heat transfer fluid created from nanoparticles that are dispersed into an ionic liquid is provided. Small volumes of nanoparticles are created from e.g., metals or metal oxides and/or alloys of such materials are dispersed into ionic liquids to create a heat transfer fluid. The nanoparticles can be dispersed directly into the ionic liquid during nanoparticle formation or the nanoparticles can be formed and then, in a subsequent step, dispersed into the ionic liquid using e.g., agitation.
Boiling Heat Transfer in a Narrow Channel with Thermal Spray Coating
Hitoshi Asano; Koichi Aoki; Masashi Inoue; Katsumi Sugimoto; Nobuyuki Takenaka
2009-01-01
Boiling heat transfer enhancement is efficient for development of a cold plate used in a two-phase flow loop type thermal control system. This study deals with boiling heat transfer enhancement for a narrow channel by thermal spray coating of metal. Copper particles were coated on the heating surface by vacuum plasma spraying. Two kinds of surface were manufactured using different
Heat transfer measurements for Stirling machine cylinders
NASA Technical Reports Server (NTRS)
Kornhauser, Alan A.; Kafka, B. C.; Finkbeiner, D. L.; Cantelmi, F. C.
1994-01-01
The primary purpose of this study was to measure the effects of inflow-produced heat turbulence on heat transfer in Stirling machine cylinders. A secondary purpose was to provide new experimental information on heat transfer in gas springs without inflow. The apparatus for the experiment consisted of a varying-volume piston-cylinder space connected to a fixed volume space by an orifice. The orifice size could be varied to adjust the level of inflow-produced turbulence, or the orifice plate could be removed completely so as to merge the two spaces into a single gas spring space. Speed, cycle mean pressure, overall volume ratio, and varying volume space clearance ratio could also be adjusted. Volume, pressure in both spaces, and local heat flux at two locations were measured. The pressure and volume measurements were used to calculate area averaged heat flux, heat transfer hysteresis loss, and other heat transfer-related effects. Experiments in the one space arrangement extended the range of previous gas spring tests to lower volume ratio and higher nondimensional speed. The tests corroborated previous results and showed that analytic models for heat transfer and loss based on volume ratio approaching 1 were valid for volume ratios ranging from 1 to 2, a range covering most gas springs in Stirling machines. Data from experiments in the two space arrangement were first analyzed based on lumping the two spaces together and examining total loss and averaged heat transfer as a function of overall nondimensional parameter. Heat transfer and loss were found to be significantly increased by inflow-produced turbulence. These increases could be modeled by appropriate adjustment of empirical coefficients in an existing semi-analytic model. An attempt was made to use an inverse, parameter optimization procedure to find the heat transfer in each of the two spaces. This procedure was successful in retrieving this information from simulated pressure-volume data with artificially generated noise, but it failed with the actual experimental data. This is evidence that the models used in the parameter optimization procedure (and to generate the simulated data) were not correct. Data from the surface heat flux sensors indicated that the primary shortcoming of these models was that they assumed turbulence levels to be constant over the cycle. Sensor data in the varying volume space showed a large increase in heat flux, probably due to turbulence, during the expansion stroke.
Free convection heat transfer thermoelectric refrigerators
I. I. Sochard
1962-01-01
Optimization equations for free convection heat transfer thermoelectric refrigerators have been derived and used to design several units. These devices successfully eliminate the blowers usually required for substantial performance in thermoelectric refrigerators. This results in totally silent operation and an indefinite operating life. The over-all power requirement is also reduced. A characteristic of these refrigerators is that substantial heat must
Interactive Heat Transfer Simulations for Everyone
ERIC Educational Resources Information Center
Xie, Charles
2012-01-01
Heat transfer is widely taught in secondary Earth science and physics. Researchers have identified many misconceptions related to heat and temperature. These misconceptions primarily stem from hunches developed in everyday life (though the confusions in terminology often worsen them). Interactive computer simulations that visualize thermal energy,…
Heat Transfer Characteristics of a Generalized Divided Flow Heat Exchanger
Singh, K. P.
1979-01-01
The concept of a "Divided-flow" heat exchanger is generalized by locating the shell inlet (or outlet) nozzle off-center such that the two shell sub-streams are unequal and traverse unequal flow paths. The governing equations for heat transfer...
Mixed convection heat transfer and flow in vertically heated channels
C. Gau; Win Aung; K. A. Yih
1990-01-01
Experiments are performed to study and understand buoyancy effect on the heat transfer process and flow in a finite vertical, rectangular channel. One wall is insulated and the opposite wall is heated uniformly. Uniform air flow is made to enter the channel. Both the case for buoyancy assisted flow and the case for opposed flow are studied. The mean velocity
Experimental and numerical investigation of HyperVapotron heat transfer
NASA Astrophysics Data System (ADS)
Wang, Weihua; Deng, Haifei; Huang, Shenghong; Chu, Delin; Yang, Bin; Mei, Luoqin; Pan, Baoguo
2014-12-01
The divertor first wall and neutral beam injection (NBI) components of tokamak devices require high heat flux removal up to 20–30 MW m?2 for future fusion reactors. The water cooled HyperVapotron (HV) structure, which relies on internal grooves or fins and boiling heat transfer to maximize the heat transfer capability, is the most promising candidate. The HV devices, that are able to transfer large amounts of heat (1–20 MW m?2) efficiently, have therefore been developed specifically for this application. Until recently, there have been few attempts to observe the detailed bubble characteristics and vortex evolvement of coolant flowing inside their various parts and understand of the internal two-phase complex heat transfer mechanism behind the vapotron effect. This research builds the experimental facilities of HyperVapotron Loop-I (HVL-I) and Pressure Water HyperVapotron Loop-II (PWHL-II) to implement the subcooled boiling principle experiment in terms of typical flow parameters, geometrical parameters of test section and surface heat flux, which are similar to those of the ITER-like first wall and NBI components (EAST and MAST). The multiphase flow and heat transfer phenomena on the surface of grooves and triangular fins when the subcooled water flowed through were observed and measured with the planar laser induced fluorescence (PLIF) and high-speed photography (HSP) techniques. Particle image velocimetry (PIV) was selected to reveal vortex formation, the flow structure that promotes the vapotron effect during subcooled boiling. The coolant flow data for contributing to the understanding of the vapotron phenomenon and the assessment of how the design and operational conditions that might affect the thermal performance of the devices were collected and analysed. The subcooled flow boiling model and methods of HV heat transfer adopted in the considered computational fluid dynamics (CFD) code were evaluated by comparing the calculated wall temperatures with the experimentally measured values. It was discovered that the bubble and vortex characteristics in the HV are clearly heavily dependent on the internal geometry, flow conditions and input heat flux. The evaporation latent heat is the primary heat transfer mechanism of HV flow under the condition of high heat flux, and the heat transfer through convection is very limited. The percentage of wall heat flux going into vapour production is almost 70%. These relationships between the flow phenomena and thermal performance of the HV device are essential to study the mechanisms for the flow structure alterations for design optimization and improvements of the ITER-like devices' water cooling structure and plasma facing components for future fusion reactors.
Heat transfer coefficient of nanofluids in minichannel heat sink
NASA Astrophysics Data System (ADS)
Utomo, Adi T.; Zavareh, Ashkan I. T.; Poth, Heiko; Wahab, Mohd; Boonie, Mohammad; Robbins, Phillip T.; Pacek, Andrzej W.
2012-09-01
Convective heat transfer in a heat sink consisting of rectangular minichannels and cooled with alumina and titania nanofluids has been investigated experimentally and numerically. Numerical simulations were carried out in a three dimensional domain employing homogeneous mixture model with effective thermo-physical properties of nanofluids. The predictions of base temperature profiles of the heat sink cooled with both water and nanofluids agree well with the experimental data. Experimental and numerical results show that the investigated nanofluids neither exhibits unusual enhancement of heat transfer coefficient nor decreases the heat sink base temperature. Although both nanofluids showed marginal thermal conductivity enhancements, the presence of solid nanoparticles lowers the specific heat capacity of nanofluids offseting the advantage of thermal conductivity enhancement. For all investigated flow rates, the Nusselt number of both nanofluids overlaps with that of water indicating that both nanofluids behave like single-phase fluids.
Heat transfer coefficients of shell and coiled tube heat exchangers
M. R. Salimpour
2009-01-01
In the present study, the heat transfer coefficients of shell and helically coiled tube heat exchangers were investigated experimentally. Three heat exchangers with different coil pitches were selected as test section for both parallel-flow and counter-flow configurations. All the required parameters like inlet and outlet temperatures of tube-side and shell-side fluids, flow rate of fluids, etc. were measured using appropriate
Heat transfer behaviours of nanofluids in a uniformly heated tube
Cong Tam Nguyen; Nicolas Galanis; Gilles Roy
2004-01-01
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
Heat transfer in rocket combustion chambers
NASA Astrophysics Data System (ADS)
Anderson, P.; Cheng, G.; Farmer, R.
1993-11-01
Complexities of liquid rocket engine heat transfer which involve the injector faceplate and film cooled walls are being investigated by computational analysis. A conjugate heat transfer analysis was used to describe localized heating phenomena associated with particular injector configurations and film coolant flows. These components were analyzed, and the analyses verified when appropriate test data were available. The component analyses are being synthesized into an overall flowfield/heat transfer model. A Navier-Stokes flow solver, the FDNS code, was used to make the analyses. Particular attention was given to the representation of the thermodynamic properties of the fluid streams. Unit flow models of specific coaxial injector elements have been developed and are being used to describe the flame structure near the injector faceplate.
Modeling microscale heat transfer using Calore.
Gallis, Michail A.; Rader, Daniel John; Wong, Chung-Nin Channy; Bainbridge, Bruce L.; Torczynski, John Robert; Piekos, Edward Stanley
2005-09-01
Modeling microscale heat transfer with the computational-heat-transfer code Calore is discussed. Microscale heat transfer problems differ from their macroscopic counterparts in that conductive heat transfer in both solid and gaseous materials may have important noncontinuum effects. In a solid material, three noncontinuum effects are considered: ballistic transport of phonons across a thin film, scattering of phonons from surface roughness at a gas-solid interface, and scattering of phonons from grain boundaries within the solid material. These processes are modeled for polycrystalline silicon, and the thermal-conductivity values predicted by these models are compared to experimental data. In a gaseous material, two noncontinuum effects are considered: ballistic transport of gas molecules across a thin gap and accommodation of gas molecules to solid conditions when reflecting from a solid surface. These processes are modeled for arbitrary gases by allowing the gas and solid temperatures across a gas-solid interface to differ: a finite heat transfer coefficient (contact conductance) is imposed at the gas-solid interface so that the temperature difference is proportional to the normal heat flux. In this approach, the behavior of gas in the bulk is not changed from behavior observed under macroscopic conditions. These models are implemented in Calore as user subroutines. The user subroutines reside within Sandia's Source Forge server, where they undergo version control and regression testing and are available to analysts needing these capabilities. A Calore simulation is presented that exercises these models for a heated microbeam separated from an ambient-temperature substrate by a thin gas-filled gap. Failure to use the noncontinuum heat transfer models for the solid and the gas causes the maximum temperature of the microbeam to be significantly underpredicted.
Boiling and Nonboiling Heat Transfer to Electrolyte Solutions
S. H. Najibi; H. Mueller-Steinhagen; M. Jamialahmadi
1996-01-01
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
Critical review of heat transfer characteristics of nanofluids
Visinee Trisaksri; Somchai Wongwises
2007-01-01
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
NASA Astrophysics Data System (ADS)
Xing, BaoYu; Liu, Kun; Huang, MinChao; Cheng, MouSen
2014-06-01
Solar thermal propulsion system includes solar thermal propulsion and nuclear thermal propulsion, and it is a significant issue to improve the heat transfer efficiency of the solar thermal thruster. This paper proposes a platelet configuration to be used in the heat exchanger core, which is the most important component of solar thermal system. The platelet passage can enhance the heat transfer between the propellant and the hot core heated by the concentrated sunlight. Based on fluid-solid coupled heat transfer, the paper utilized the platelet heat transfer characteristic to simulate the heat transfer and flow field of the platelet passage. A coupled system includes the coupled flow and heat transfer between the fluid region and solid region. The simulation result shows that the propellant can be heated to the design temperature of 2300K in platelet passage of the thermal propulsion system, and the fluid-solid coupled method can solve the heat transfer in the platelet structure more precisely.
Surface heat transfer due to particle impact
Sun, J.; Chen, M.M.; Chao, B.T. (Illinois Univ., Urbana, IL (USA). Dept. of Mechanical and Industrial Engineering)
1989-08-01
In a fluidized bed of high gas velocities, particle impact on an immersed surface is an important mechanism for heat transfer. The heat exchange between an impacting spherical particle and surface is analyzed by considering (1) the heat conduction through the time varying contact area during the period when the particle is in contact with the surface, and (2) the heat conduction through the surrounding gas during the period when the particle is approaching and rebounding from the surface. For the solid conduction problem, an analytical solution is obtained for small Fourier numbers, and a correction factor is computed numerically to be used for large Fourier numbers. For the gas conduction problem, a solution is obtained by combining three analytical solutions each valid in a certain region of the gas domain. Since heat transfer due to the impact of a stream of falling particles was also measured with a simple experimental set up. 53 refs., 15 figs., 1 tab.
Mixed convection heat transfer and flow in vertically heated channels
NASA Astrophysics Data System (ADS)
Gau, C.; Aung, Win; Yih, K. A.
1990-06-01
Experiments are performed to study and understand buoyancy effect on the heat transfer process and flow in a finite vertical, rectangular channel. One wall is insulated and the opposite wall is heated uniformly. Uniform air flow is made to enter the channel. Both the case for buoyancy assisted flow and the case for opposed flow are studied. The mean velocity is controlled at values that the channel flow is either laminar or turbulent when the plate is not heated. Both flow visualization and temperature fluctuation measurements are conducted and used to provide information on flow structure. Flow reversal occurs initially downstream and moves periodically upstream as the buoyancy parameters Gr/Re increases, which destabilizes the flow structure and enhances the heat transfer process in the range it transverses. The effect of buoyancy force on the local and averaged Nusselt number over the heated plate is studied. The buoyancy parameter studied ranges from 800 to 60,000.
Characteristics of Transient Boiling Heat Transfer
Liu, Wei; Monde, Masanori; Mitsutake, Y. [Saga University, 1 Honjo Saga City, Saga 840-8502 (Japan)
2002-07-01
In this paper, one dimensional inverse heat conduction solution is used for a measurement of pool boiling curve. The experiments are performed under atmospheric pressure for copper, brass, carbon steel and gold. Boiling curves, including unsteady transition boiling region, are found can be traced fairly well from a simple experiment system by solving inverse heat conduction solution. Boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Surface behavior around CHF point, transition boiling and film-boiling regions are observed by using a high-speed camera. The results show the practicability of the inverse heat conduction solution in tracing boiling curve and thereby supply us a new way in boiling heat transfer research. (authors)
Numerical methods in heat transfer
Emery, A.F.; Douglass, R.W.
1988-01-01
This book contains nine papers. Some of the titles are: Numerical calculation of bubble growth in nucleate boiling from inception through departure; An evaluation of a translator for finite element data to resistor/capacitor data for the heat diffusion; Thermophoretic deposition due to jet impingement on an inclined plane; and A three-dimensional boundary-fitted coordinate system.
Radiative Heat Transfer between Neighboring Particles
Alejandro Manjavacas; F. Javier Garcia de Abajo
2012-01-26
The near-field interaction between two neighboring particles is known to produce enhanced radiative heat transfer. We advance in the understanding of this phenomenon by including the full electromagnetic particle response, heat exchange with the environment, and important radiative corrections both in the distance dependence of the fields and in the particle absorption coefficients. We find that crossed terms of electric and magnetic interactions dominate the transfer rate between gold and SiC particles, whereas radiative corrections reduce it by several orders of magnitude even at small separations. Radiation away from the dimer can be strongly suppressed or enhanced at low and high temperatures, respectively. These effects must be taken into account for an accurate description of radiative heat transfer in nanostructured environments.
Active heat transfer enhancement in integrated fan heat sinks
Staats, Wayne Lawrence
2012-01-01
Modern computer processors require significant cooling to achieve their full performance. The "efficiency" of heat sinks is also becoming more important: cooling of electronics consumes 1% of worldwide electricity use by ...
Analysis of natural convective heat transfer of nano coated aluminium fins using Taguchi method
NASA Astrophysics Data System (ADS)
Senthilkumar, R.; Nandhakumar, A. J. D.; Prabhu, S.
2013-01-01
Rectangular aluminium fins were preferred for analysis and coated by carbon nano tubes using PVD to enhance the heat transfer rate of fins. Convective heat transfer rates for coated and non-coated surfaces were calculated and compared. The temperature and heat transfer characteristics were investigated using Nusselt, Grashof, Prandtl and Rayleigh numbers and also optimized by Taguchi method and ANOVA analysis. The average percentage of increase in fin efficiency is 5 %.
Heat transfer in liquids and gases
NASA Astrophysics Data System (ADS)
Tolubinskii, V. I.
The papers presented in this volume summarize results of heat transfer studies for various types of liquid and gas flows, including laminar and turbulent duct flows, flows past bodies, and changes in the state of aggregation. Some of the papers are concerned with the statistical theory of heat transfer and thermophysical principles of the theory of machines and apparatus. Papers are presented on swirling flow in the Laval nozzle, the principal characteristics of turbulent flows and their use in the study of transport processes, and an approximate theory and computational methods for three-dimensional thermal screens.
Heat transfer characteristics of an emergent strand
NASA Technical Reports Server (NTRS)
Simon, W. E.; Witte, L. C.; Hedgcoxe, P. G.
1974-01-01
A mathematical model was developed to describe the heat transfer characteristics of a hot strand emerging into a surrounding coolant. A stable strand of constant efflux velocity is analyzed, with a constant (average) heat transfer coefficient on the sides and leading surface of the strand. After developing a suitable governing equation to provide an adequate description of the physical system, the dimensionless governing equation is solved with Laplace transform methods. The solution yields the temperature within the strand as a function of axial distance and time. Generalized results for a wide range of parameters are presented, and the relationship of the results and experimental observations is discussed.
Heat transfer in slagging MHD radiant boilers
Im, K.H.; Ahluwalia, R.K.; Berry, G.F.
1981-01-01
A combined convection-radiation model is formulated to study heat transfer characteristics of slagging magnetohydrodynamic (MHD) radiant boilers. The model includes the contributions of carbon dioxide, water vapor, potassium atoms, and slag particles to gas radiation. The model also accounts for the presence of slag layer on the wall of the radiant boiler. In order to determine the slag layer dynamics, the mechanism of slag particle deposition by thermophoresis and by fluid turbulence is also investigated. The role of a slag layer in moderating the influence of refractory thickness on heat transfer is illustrated. 14 refs.
Heat transfer in shrouded rectangular cavities
NASA Technical Reports Server (NTRS)
Chyu, M. K.; Metzger, D. E.; Hwan, C. L.
1986-01-01
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.
Microscale surface modifications for heat transfer enhancement.
Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C
2013-10-01
In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985
Experimental determination of stator endwall heat transfer
NASA Technical Reports Server (NTRS)
Boyle, Robert J.; Russell, Louis M.
1989-01-01
Local Stanton numbers were experimentally determined for the endwall surface of a turbine vane passage. A six vane linear cascade having vanes with an axial chord of 13.81 cm was used. Results were obtained for Reynolds numbers based on inlet velocity and axial chord between 73,000 and 495,000. The test section was connected to a low pressure exhaust system. Ambient air was drawn into the test section, inlet velocity was controlled up to a maximum of 59.4 m/sec. The effect of the inlet boundary layer thickness on the endwall heat transfer was determined for a range of test section flow rates. The liquid crystal measurement technique was used to measure heat transfer. Endwall heat transfer was determined by applying electrical power to a foil heater attached to the cascade endwall. The temperature at which the liquid crystal exhibited a specific color was known from a calibration test. Lines showing this specific color were isotherms, and because of uniform heat generation they were also lines of nearly constant heat transfer. Endwall static pressures were measured, along with surveys of total pressure and flow angles at the inlet and exit of the cascade.
Heat transfer mechanisms in pulsating heat-pipes with nanofluid
NASA Astrophysics Data System (ADS)
Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo
2015-01-01
In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.
Local nucleation propagation on heat transfer uniformity during subcooled convective boiling
NASA Astrophysics Data System (ADS)
Kim, Beom Seok; Yang, Gang Mo; Shin, Sangwoo; Choi, Geehong; Cho, Hyung Hee
2015-01-01
Convective boiling heat transfer is an efficient cooling mechanism to dissipate amount of thermal energy by accompanying the phase transition of the working fluids. Particularly, the amount of heat dissipation capacity can be readily extensible by increasing the degree of subcooling due to initial demands requiring for coolant saturation. Under severely subcooled condition of 60°, we investigate boiling heat transfer phenomena regarding spatial heat transfer uniformity and stability on a planar surface. Severe subcooling can induce locally concentrated thermal loads due to poor spatial uniformity of the heat transfer. For reliable cooling, a high degree of spatial uniformity of the heat transfer should be guaranteed with minimized spatial deviation of heat transfer characteristics. Under pre-requisite safeguards below CHF, we experimentally elucidate the principal factors affecting the spatial uniformity of the heat transfer for a flow/thermal boundary layer considering heat transfer domains from a single-phase regime to a fully-developed boiling regime. Based on the local heat transfer evaluation, we demonstrate that full nucleation boiling over the entire heat transfer surface under subcooling conditions is favorable in terms of the uniformity of heat dissipation through the phase-change of the working fluid.
K. Koyama; Y. Asako
2010-01-01
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
Microscale Heat Transfer Transduced by Surface Plasmon Resonant Gold Nanoparticles
Roper, D. Keith; Ahn, W.; Hoepfner, M.
2008-01-01
Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ?10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation. PMID:19011696
Electrohydrodynamically enhanced condensation heat transfer
Wawzyniak, Markus
1993-01-01
. The occurrence of a corona discharge led to the appearance of a wavy motion on the condensate film. As the voltage was increased, rivulets of Freon were observed running down the plate and finally, at an even higher voltage, condensate was blown away f... of the Plexiglas container, (b) view of cooled plate with corona wire. [Velkoff and Miller, 1965] . . . . Fig. 1. 4 Effect of electric field on condensation. 5 mesh screen grid parallel to plate. [Velkoff and Miller, 1965]. Fig. 1. 5 Variation of h (mean heat...
Radial heat transfer from a moving plasma
Johnson, James Randall
1966-01-01
. The radiative heat flux from shock heat argor. to the stagr ation point of a blunt body has beer, investigated by Brown and Ross (13). Free ? free and free-bound electron-ion recombination in addition to tie characteristic line radiatior were the processes...RADIAL HEAT TRANSFER FROM A MOVING PLASMA A Thesis By JAMES RANDALL JOHNSON Submitted to the Graduate College of the Texas A!&I University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 1966 Major...
Boiling heat transfer from an excavated fin
NASA Astrophysics Data System (ADS)
Liaw, S. P.; Yeh, R. H.
1992-04-01
A single pin fin with excavation at base is proposed to enhance boiling heat transfer. The temperature distribution in the fin is obtained numerically by solving a 2D heat conduction equation. A copper fin boiling in isopropyl alcohol is taken as an example. When the operating temperature exceeds a specific value, the heat duty decreases drastically, and the whole fin is governed by film boiling. This highest operating temperature limit is raised by digging a hole at the fin base. Two distinct solutions are found by using different initial guesses into the code. This hysteresis effect becomes noticeable for a bigger hole. A model is also developed to predict the burnout temperatures.
Heat flux sensors for infrared thermography in convective heat transfer.
Carlomagno, Giovanni Maria; de Luca, Luigi; Cardone, Gennaro; Astarita, Tommaso
2014-01-01
This paper reviews the most dependable heat flux sensors, which can be used with InfraRed (IR) thermography to measure convective heat transfer coefficient distributions, and some of their applications performed by the authors' research group at the University of Naples Federico II. After recalling the basic principles that make IR thermography work, the various heat flux sensors to be used with it are presented and discussed, describing their capability to investigate complex thermo-fluid-dynamic flows. Several applications to streams, which range from natural convection to hypersonic flows, are also described. PMID:25386758
Mounting for diodes provides efficient heat sink
NASA Technical Reports Server (NTRS)
1964-01-01
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.
Microconvection heat transfer in electrorheological fluids in rotating electric field
NASA Astrophysics Data System (ADS)
Mokeev, A. A.; Gubarev, S. A.; Korobko, E. V.; Bedik, N. A.
2013-02-01
This work is dedicated to the study of heat transfer characteristics of electrorheological fluids in rotating electric fields. The problem of heat transfer in the electrosensitive heat carrier considering the microconvection transport mechanism is formulated and numerically solved. It is shown on the example of a flat layer, that internal rotations of elementary particles intensify heat transfer in ERF.
Flat plate heat transfer with impinging axial fan flows
Jason Stafford; Ed Walsh; Vanessa Egan; Ronan Grimes
2010-01-01
Axial flow fans are widely used for the augmentation of heat transfer. One such use is an axial flow fan impinging air on to a heated flat plate which has many practical applications and has been experimentally investigated to characterize local heat transfer distribution. Using infrared thermography, a two-dimensional profile of the heat transfer coefficient on a flat plate is
A Review of Heat Transfer Physics
V. P. Carey; G. Chen; C. Grigoropoulos; M. Kaviany; A. Majumdar
2008-01-01
With rising science contents of the engineering research and education, we give examples of the quest for fundamental understanding of heat transfer at the atomic level. These include transport as well as interactions (energy conversion) involving phonon, electron, fluid particle, and photon (or electromagnetic wave). Examples are 1. development of MD and DSMC fluid simulations as tools in nanoscale and
HEAT TRANSFER COEFFICIENTS WITH ANNULAR FLOW DURING \\
E. E. Polomik; S. Levy; S. G. Sawochka
1961-01-01
Results obtained in a study of once-through heat transfer are presented. ; Sufficient data were obtained for preliminary design of once-through boilers in ; the regions of departure from nucleate boiling, transition to film boiling, and ; film boiling at 800, 1100, and 1400 psi. Results are presented graphically and ; analyzed. (J.R.D.);
Unusual techniques employed in heat transfer programs
D. J. Campbell; D. B. Vollenweider
1959-01-01
A program for the IBM 704 to solve general transient and steady state heat transfer problems is described. The computer program was developed by Evendale Computations Operation in cooperation with the Jet Engine Department, General Electric Company, Flight Propulsion Division. Jet Engine Department personnel who were instrumental in the formulation of the problem are Mr. William K. Koffel and Dr.
FED. Zoning for TRUMP Heat Transfer Code
Elrod, D. [Oak Ridge National Lab., TN (United States)
1987-10-23
FED reduces the effort required to obtain the necessary geometric input for problems which are to be solved using the heat-transfer code, TRUMP. TRUMP calculates transient and steady-state temperature distributions in multidimensional systems. FED can properly zone any body of revolution in one, two, or three dimensions.
Forced Convection Heat Transfer in Circular Pipes
ERIC Educational Resources Information Center
Tosun, Ismail
2007-01-01
One of the pitfalls of engineering education is to lose the physical insight of the problem while tackling the mathematical part. Forced convection heat transfer (the Graetz-Nusselt problem) certainly falls into this category. The equation of energy together with the equation of motion leads to a partial differential equation subject to various…
Computational Aspects of Heat Transfer in Structures
NASA Technical Reports Server (NTRS)
Adelman, H. M. (compiler)
1982-01-01
Techniques for the computation of heat transfer and associated phenomena in complex structures are examined with an emphasis on reentry flight vehicle structures. Analysis methods, computer programs, thermal analysis of large space structures and high speed vehicles, and the impact of computer systems are addressed.
Hung-Wen Lin; Wei-Keng Lin
2007-01-01
This paper aims to study the capillary-pumped loop (CPL) vapor line temperature distributions. A simple axial heat transfer method is developed to predict the vapor line temperature from evaporator outlet to condenser inlet. CPL is a high efficiency two-phase heat transfer device. Since it does not need any other mechanical force such as pump, furthermore, it might be used to
Advanced Heat Transfer and Thermal Storage Fluids
Moens, L.; Blake, D.
2005-01-01
The design of the next generation solar parabolic trough systems for power production will require the development of new thermal energy storage options with improved economics or operational characteristics. Current heat-transfer fluids such as VP-1?, which consists of a eutectic mixture of biphenyl and diphenyl oxide, allow a maximum operating temperature of ca. 300 C, a limit above which the vapor pressure would become too high and would require pressure-rated tanks. The use of VP-1? also suffers from a freezing point around 13 C that requires heating during cold periods. One of the goals for future trough systems is the use of heat-transfer fluids that can act as thermal storage media and that allow operating temperatures around 425 C combined with lower limits around 0 C. This paper presents an outline of our latest approach toward the development of such thermal storage fluids.
Heat transfer in bioengineering and medicine
Chato, J.C.; Diller, T.E.; Diller, K.R.; Roemer, R.B.
1987-01-01
This book contains the following papers: New ideas in heat transfer for agricultural animals; Issues in heat transfer and tumor blood flow in localized hyperthermia treatments of cancer; Ultrasound enhances adriamycin toxicity in vitro; Scanned, focused ultrasound hyperthermia treatment of brain tumors; Mathematical prediction and phantom studies of the clinical target ''hot spot'' using a three applicator phased array system (TRIPAS); Development of an endoscopic RF hyperthermia system for deep tumor therapy; Simultaneous measurement of intrinsic and effective thermal conductivity; Determination of the transport of thermal energy by conduction in perfused tissue; A whole body thermal model of man with a realistic circulatory system; and Canine muscle blood flow changes in response to initial heating rates.
Numerical Modeling of Ablation Heat Transfer
NASA Technical Reports Server (NTRS)
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
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.
Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor
NASA Technical Reports Server (NTRS)
Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.
2013-01-01
This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.
Resonant self-pumped thermoacoustic heat transfer
NASA Astrophysics Data System (ADS)
Swift, Greg; Backhaus, Scott
2003-10-01
As a thermoacoustic engine or refrigerator is scaled up to higher power, it generally needs heat exchangers of a larger cross-sectional area. Constrained to lie adjacent to a stack or regenerator, large heat exchangers must use intricate geometries to interweave the thermoacoustic working gas and an external fluid (e.g., ambient cooling water or hot combustion gas) to bring them into intimate thermal contact. Such heat exchangers have many thermoacoustic passages in parallel, often entailing many parts and many joints that must be leak tight. Resonant self-pumped thermoacoustic heat transfer is a new alternative in which the thermoacoustic-to-external heat-transfer surface area is in the form of one long tube (or a few) extending far from the associated stack or regenerator. With a resonant sound wave in the tube and with diode-like nonlinear flow elements near the wave's velocity maxima, a strong time-averaged circulation of the working gas carries the heat. This concept will be described and preliminary experimental results will be presented. [Work supported by DOE's Office of Science and by Praxair, Inc.
Direct numerical simulation of turbulent heat transfer in annuli: effect of heat flux ratio.
Paris-Sud XI, Université de
Direct numerical simulation of turbulent heat transfer in annuli: effect of heat flux ratio. M-la-Vall´ee cedex 2, France (Dated: October 23, 2008) Abstract Fully developed turbulent flow and heat transfer square (rms) of temperature fluctuations, turbulent heat fluxes, heat transfer, ...). To validate
Conneally, E; Bardy, P; Eaves, C J; Thomas, T; Chappel, S; Shpall, E J; Humphries, R K
1996-01-15
Recombinant retroviruses offer many advantages for the genetic modification of human hematopoietic cells, although their use in clinical protocols has thus far given disappointing results. There is therefore an important need to develop new strategies that will allow effectively transduced primitive hematopoietic target populations to be both rapidly characterized and isolated free of residual nontransduced but biologically equivalent cells. To address this need, we constructed a murine stem cell virus (MSCV)-based retroviral vector containing the 228-bp coding sequence of the murine heat-stable antigen (HSA) and generated helper virus-free amphotropic MSCV-HSA producer cells by transfection of GP-env AM12 packaging cells. Light density and, in some cases, lineage marker-negative (lin-) normal human marrow or mobilized peripheral blood cells preactivated by exposure to interleukin-3 (IL-3), IL-6, and Steel factor in vitro for 48 hours were then infected by cocultivation with these MSCV-HSA producer cells for a further 48 hours in the presence of the same cytokines. Fluorescence-activated cell sorting (FACS) analysis of the cells 24 hours later showed 21% to 41% (mean, 27%) of those that were still CD34+ to have acquired the ability to express HSA. The extent of gene transfer to erythroid and granulopoietic progenitors (burst-forming unit-erythroid and colony-forming unit-granulocyte-macrophage), as assessed by the ability of these cells to form colonies of mature progeny in the presence of normally toxic concentrations of G418, averaged 11% and 12%, respectively, in 6 experiments. These values could be increased to 100% and 77%, respectively, by prior isolation of the CD34+HSA+ cell fraction and were correspondingly decreased to an average of 2% and 5%, respectively, in the CD34+HSA- cells. In addition, the extent of gene transfer to long-term culture-initiating cells (LTC-IC) was assessed by G418 resistance. The average gene transfer to LTC-IC-derived colony-forming cells in the unsorted population was < or = 7% in 4 experiments. FACS selection of the initially CD34+HSA+ cells increased this value to 86% and decreased it to 3% for the LTC-IC plated from the CD34+HSA- cells. Transfer of HSA gene expression to a phenotypically defined more primitive subpopulation of CD34+ cells, ie, those expressing little or no CD38, could also be shown by FACS analysis of infected populations 24 hours after infection. These findings underscore the potential use of retroviral vectors encoding HSA for the specific identification and non-toxic selection immediately after infection of retrovirally transduced populations of primitive human hematopoietic cells. In addition, such vectors should facilitate the subsequent tracking of their marked progeny using multiparameter flow cytometry. PMID:8555466
Heat-transfer performance of a corrugated-tube thermosiphon. Part 1; Evaporator performance
Negishi, K. (Tokyo Metropolitan Inst. of Technology (JP)); Kaneko, K. (Univ. of Osaka Prefecture (JP)); Matsuoka, T. (Nissan Motor Co., Ltd. (JP)); Hirashima, M.; Nishikawa, Y.; Taguchi, M. (Takuma Research and Development Co., Ltd. (JP))
1991-01-01
Two-phase closed thermosiphons are highly efficient heat-transfer elements with applications in terrestrial heat-transport and heat-recovery systems. In this paper, a corrugated copper tube was used as the container of the thermosiphons and distilled water was used as the working fluid. The influences of the liquid charge ratio and inclination angle on the heat-transfer performance were studied. It was found that the optimum liquid charge ratio to evaporator volume is 40 percent and the maximum performance is obtained at an inclination angle of 30 degrees. A useful formula to calculate the heat-transfer coefficient in the evaporator has been derived.
High heat transfer oxidizer heat exchanger design and analysis. [RL10-2B engine
NASA Technical Reports Server (NTRS)
Kmiec, Thomas D.; Kanic, Paul G.; Peckham, Richard J.
1987-01-01
The RL10-2B engine, a derivative of the RL10, is capable of multimode thrust operation. This engine operates at two low thrust levels: tank head idle (THI), which is approximately 1 to 2% of full thrust, and pumped idle (PI), which is 10% of full thrust. Operation at THI provides vehicle propellant settling thrust and efficient engine thermal conditioning; PI operation provides vehicle tank pre-pressurization and maneuver thrust for low-g deployment. Stable combustion of the RL10-2B engine during the low thrust operating modes can be accomplished by using a heat exchanger to supply gaseous oxygen to the propellant injector. The oxidizer heat exchanger (OHE) vaporizes the liquid oxygen using hydrogen as the energy source. The design, concept verification testing and analysis for such a heat exchanger is discussed. The design presented uses a high efficiency compact core to vaporize the oxygen, and in the self-contained unit, attenuates any pressure and flow oscillations which result from unstable boiling in the core. This approach is referred to as the high heat transfer design. An alternative approach which prevents unstable boiling of the oxygen by limiting the heat transfer is referred to as the low heat transfer design and is reported in Pratt & Whitney report FR-19135-2.
Heterogeneous nanofluids: natural convection heat transfer enhancement
2011-01-01
Convective heat transfer using different nanofluid types is investigated. The domain is differentially heated and nanofluids are treated as heterogeneous mixtures with weak solutal diffusivity and possible Soret separation. Owing to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces could be significant and interact with the initial thermal convection. A modified formulation taking into account the thermal conductivity, viscosity versus nanofluids type and concentration and the spatial heterogeneous concentration induced by the Soret effect is presented. The obtained results, by solving numerically the full governing equations, are found to be in good agreement with the developed solution based on the scale analysis approach. The resulting convective flows are found to be dependent on the local particle concentration ? and the corresponding solutal to thermal buoyancy ratio N. The induced nanofluid heterogeneity showed a significant heat transfer modification. The heat transfer in natural convection increases with nanoparticle concentration but remains less than the enhancement previously underlined in forced convection case. PMID:21711755
Thermal Storage and Advanced Heat Transfer Fluids (Fact Sheet)
Not Available
2010-08-01
Fact sheet describing NREL CSP Program capabilities in the area of thermal storage and advanced heat transfer fluids: measuring thermophysical properties, measuring fluid flow and heat transfer, and simulating flow of thermal energy and fluid.
Experimental evaluation of heat transfer characteristics of silica nanofluid
Zhang, Zihao, S.B. Massachusetts Institute of Technology
2010-01-01
The laminar convective heat transfer characteristics were investigated for silica nanofluid. An experimental loop was built to obtain heat transfer coefficients for single-phase nanofluids in a circular conduit in laminar ...
E. M. Sparrow; S. V. Patankar; H. Shahrestani
1978-01-01
Numerical techniques have been used to solve the thermally developed regime for a laminar pipe flow that exchanges heat with a fluid environment in the presence of a circumferentiatly varying external heat transfer coefficient. By making use of the fact that the temperature distributions have similar shapes at successive streamwise locations, the three-dimensional temperature field was scaled to two dimensions.
E. M. Sparrow; S. V. Patankar; H. Shahrestani
1978-01-01
Numerical techniques have been used to solve the thermally developed regime for a laminar pipe flow that exchanges heat with a fluid environment in the presence of a circumferentially varying external heat transfer coefficient. By making use of the fact that the temperature distributions have similar shapes at successive streamwise locations, the three-dimensional temperature field was scaled to two dimensions.
Various methods to improve heat transfer in exchangers
NASA Astrophysics Data System (ADS)
Pavel, Zitek; Vaclav, Valenta
2015-05-01
The University of West Bohemia in Pilsen (Department of Power System Engineering) is working on the selection of effective heat exchangers. Conventional shell and tube heat exchangers use simple segmental baffles. It can be replaced by helical baffles, which increase the heat transfer efficiency and reduce pressure losses. Their usage is demonstrated in the primary circuit of IV. generation MSR (Molten Salt Reactors). For high-temperature reactors we consider the use of compact desk heat exchangers, which are small, which allows the integral configuration of reactor. We design them from graphite composites, which allow up to 1000°C and are usable as exchangers: salt-salt or salt-acid (e.g. for the hydrogen production). In the paper there are shown thermo-physical properties of salts, material properties and principles of calculations.
Heat transfer and pressure drop characteristics of nanofluids in a plate heat exchanger.
Kwon, Y H; Kim, D; Li, C G; Lee, J K; Hong, D S; Lee, J G; Lee, S H; Cho, Y H; Kim, S H
2011-07-01
In this paper, the heat transfer characteristics and pressure drop of the ZnO and Al2O3 nanofluids in a plate heat exchanger were studied. The experimental conditions were 100-500 Reynolds number and the respective volumetric flow rates. The working temperature of the heat exchanger was within 20-40 degrees C. The measured thermophysical properties, such as thermal conductivity and kinematic viscosity, were applied to the calculation of the convective heat transfer coefficient of the plate heat exchanger employing the ZnO and Al2O3 nanofluids made through a two-step method. According to the Reynolds number, the overall heat transfer coefficient for 6 vol% Al2O3 increased to 30% because at the given viscosity and density of the nanofluids, they did not have the same flow rates. At a given volumetric flow rate, however, the performance did not improve. After the nanofluids were placed in the plate heat exchanger, the experimental results pertaining to nanofluid efficiency seemed inauspicious. PMID:22121605
High efficiency heat transport and power conversion system for cascade
Maya, I.; Bourque, R.F.; Creedon, R.L.; Schultz, K.R.
1985-02-01
The Cascade ICF reactor features a flowing blanket of solid BeO and LiAlO/sub 2/ granules with very high temperature capability (up to approx. 2300 K). The authors present here the design of a high temperature granule transport and heat exchange system, and two options for high efficiency power conversion. The centrifugal-throw transport system uses the peripheral speed imparted to the granules by the rotating chamber to effect granule transport and requires no additional equipment. The heat exchanger design is a vacuum heat transfer concept utilizing gravity-induced flow of the granules over ceramic heat exchange surfaces. A reference Brayton power cycle is presented which achieves 55% net efficiency with 1300 K peak helium temperature. A modified Field steam cycle (a hybrid Rankine/Brayton cycle) is presented as an alternate which achieves 56% net efficiency.
Heat transfer in slagging MHD radiant boilers
Im, K.H.; Ahluwalia, R.K.; Berry, G.
1981-01-01
A combined convection-radiation model is formulated to study heat-transfer characteristics of slagging MHD radiant boilers. The model includes the contributions of carbon dioxide, water vapor, potassium atoms, and slag particles to gas radiation. The model also accounts for the presence of slag layer on the wall of the radiant boiler. In order to determine the slag layer dynamics, the mechanism of slag-particle deposition by thermophoresis and by fluid turbulence is also investigated. The role of a slag layer in moderating the influence of refractory thickness on heat transfer is illustrated. From the viewpoint of NO/sub x/ decomposition, the calculations indicate that an adequately slow cooling rate of the combustion gas can be realized in the radiant boiler.
Acquisition systems for heat transfer measurement
De Witt, R.J.
1983-01-01
Practical heat transfer data acquisition systems are normally characterized by the need for high-resolution, low-drift, low-speed recording devices. Analog devices such as strip chart or circular recorders and FM analog magnetic tape have excellent resolution and work well when data will be presented in temperature versus time format only and need not be processed further. Digital systems are more complex and require an understanding of the following components: digitizing devices, interface bus types, processor requirements, and software design. This paper discusses all the above components of analog and digital data acquisition, as they are used in current practice. Additional information on thermocouple system analysis will aid the user in developing accurate heat transfer measuring systems.
Heat and mass transfer in bubble column dehumidifiers for HDH desalination
Tow, Emily W
2014-01-01
Heat and mass transfer processes governing the performance of bubble dehumidifier trays are studied in order to develop a predictive model and design rules for efficient and economical design of bubble column dehumidifiers ...
Numerical studies of heat transfer enhancements in laminar separated flows
Chung, Yongmann M.
heat transfer enhancements in grooved channel and sharp 180° bend flows of especial relevanceNumerical studies of heat transfer enhancements in laminar separated flows Yongmann M. Chung not always be valid over a significant system extent. For the bend flow, heat transfer enhancements due
RADIATIVE HEAT TRANSFER WITH QUASI-MONTE CARLO METHODS
RADIATIVE HEAT TRANSFER WITH QUASI-MONTE CARLO METHODS A. Kersch1 W. Moroko2 A. Schuster1 1Siemens of Quasi-Monte Carlo to this problem. 1.1 Radiative Heat Transfer Reactors In the manufacturing of the problems which can be solved by such a simulation is high accuracy modeling of the radiative heat transfer
Heat transfer from nanoparticles: a corresponding state analysis
Paris-Sud XI, Université de
Heat transfer from nanoparticles: a corresponding state analysis Samy Merabia , Sergei Shenogin that inhibits the formation of an insulating vapor film. heat transfer | nanoparticles | liquids | phase transitions Introduction Sub-micron scale heat transfer is attracting a growing inter- est, motivated by both
16 Heat Transfer and Air Flow in a Domestic Refrigerator
Paris-Sud XI, Université de
445 16 Heat Transfer and Air Flow in a Domestic Refrigerator Onrawee Laguerre UMR Génie Industriel........................................................................447 16.2.2 Heat Transfer and Airflow Near a Vertical Plate..................................................448 16.2.3 Heat Transfer and Airflow in Empty Closed Cavity
Proceeding of the 1st International Forum on Heat Transfer
Maruyama, Shigeo
Proceeding of the 1st International Forum on Heat Transfer November 24-26, 2004, Kyoto, Japan Paper No. HEAT TRANSFER PROBLEMS RELATED WITH CARBON NANOTUBES BY MOLECULAR DYNAMICS-BASED SIMULATIONS Dynamics Simulation, Thermal Conductance ABSTRACT Several heat transfer problems related to single
7 CFR 2902.54 - Heat transfer fluids.
Code of Federal Regulations, 2011 CFR
2011-01-01
...2011-01-01 2011-01-01 false Heat transfer fluids. 2902.54 Section...PROCUREMENT Designated Items § 2902.54 Heat transfer fluids. (a) Definition...capacities used to facilitate the transfer of heat from one location to another,...
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2011 CFR
2011-10-01
...2011-10-01 2011-10-01 false Heat transfer systems; general. 153.430...Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo...Allow manual regulation of the system's heat transfer rate. [CGD 73-96, 42...
46 CFR 153.430 - Heat transfer systems; general.
Code of Federal Regulations, 2010 CFR
2010-10-01
...2010-10-01 2010-10-01 false Heat transfer systems; general. 153.430...Temperature Control Systems § 153.430 Heat transfer systems; general. Each cargo...Allow manual regulation of the system's heat transfer rate. [CGD 73-96, 42...
Review of convective heat transfer enhancement with nanofluids
Sadik Kakaç; Anchasa Pramuanjaroenkij
2009-01-01
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
Heat Transfer in Glass, Aluminum, and Plastic Beverage Bottles
ERIC Educational Resources Information Center
Clark, William M.; Shevlin, Ryan C.; Soffen, Tanya S.
2010-01-01
This paper addresses a controversy regarding the effect of bottle material on the thermal performance of beverage bottles. Experiments and calculations that verify or refute advertising claims and represent an interesting way to teach heat transfer fundamentals are described. Heat transfer coefficients and the resistance to heat transfer offered…
Boiling heat transfer and bubble dynamics in microgravity
Johannes Straub
2001-01-01
This article presents results for pool boiling heat transfer under microgravity conditions that the author and his team have gained in a succession of experiments during the past two decades. The objective of the research work was to provide answers to the following questions: Is boiling an appropriate mechanism of heat transfer for space application? How do heat transfer and
Unsteady heat transfer on turbine blades
NASA Technical Reports Server (NTRS)
Cebeci, Tuncer; Simoneau, Robert J.; Platzer, Max F.
1990-01-01
This paper describes a method for calculating heat transfer on turbine blades subjected to passing wakes. It is based on the numerical solution of the boundary-layer equations for laminar, transitional, and turbulent flows with a novel procedure to account for the movement of the stagnation point. Results are presented for a model flow and show that the procedure is numerically sound and produces results that can give good agreement with measurements provided that the turbulence model is adequate.
Coolant passage heat transfer with rotation
NASA Technical Reports Server (NTRS)
Hajek, T. J.; Higgins, A. W.
1985-01-01
The objective is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques, and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades.
Low-melting point heat transfer fluid
Cordaro, Joseph Gabriel (Oakland, CA); Bradshaw, Robert W. (Livermore, CA)
2010-11-09
A low-melting point, heat transfer fluid made of a mixture of five inorganic salts including about 29.1-33.5 mol % LiNO.sub.3, 0-3.9 mol % NaNO.sub.3, 2.4-8.2 mol % KNO.sub.3, 18.6-19.9 mol % NaNO.sub.2, and 40-45.6 mol % KNO.sub.2. These compositions can have liquidus temperatures below 80.degree. C. for some compositions.
Heat Transfer in a Superelliptic Transition Duct
NASA Technical Reports Server (NTRS)
Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven
2008-01-01
Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.
Determining heat transfer coefficients using evolutionary algorithms
K. Tesch; M. A. Atherton; T. G. Karayiannis; M. W. Collins; P. Edwards
2009-01-01
This article presents a way of determining heat transfer calibrations for multi-objective and single-objective optimization by means of genetic algorithms. The need for optimization arises from the necessity for mathematical model validation and is very relevant to practical applications. The SPEA algorithm is used for multi-objective optimization. Scalarization of the fitness function is also addressed in combination with a small
Computer graphics in heat-transfer simulations
Hamlin, G.A. Jr.
1980-01-01
Computer graphics can be very useful in the setup of heat transfer simulations and in the display of the results of such simulations. The potential use of recently available low-cost graphics devices in the setup of such simulations has not been fully exploited. Several types of graphics devices and their potential usefulness are discussed, and some configurations of graphics equipment are presented in the low-, medium-, and high-price ranges.
Theoretical and experimental research on heat transfer performance of the semi-open heat pipe
Hua Zhu; Bo Zhuang; Jin-jun Tan; Rong-hua Hong
2008-01-01
This paper focuses on the heat transfer performance of semi-open heat pipe which is a new type of heat pipe. After analyzing\\u000a its condensation heat transfer mechanisms theoretically, several semi-open heat pipes in different length ratios and upper\\u000a hole diameters are studied experimentally and compared with the same dimensions closed heat pipes. Experimental results show\\u000a that the heat transfer performance
Enhancement of heat and mass transfer by cavitation
NASA Astrophysics Data System (ADS)
Zhang, Y. N.; Zhang, Y. N.; Du, X. Z.; Xian, H. Z.
2015-01-01
In this paper, a brief summary of effects of cavitation on the heat and mass transfer are given. The fundamental studies of cavitation bubbles, including its nonlinearity, rectified heat and mass diffusion, are initially introduced. Then selected topics of cavitation enhanced heat and mass transfer were discussed in details including whales stranding caused by active sonar activity, pool boiling heat transfer, oscillating heat pipe and high intensity focused ultrasound treatment.
NASA Technical Reports Server (NTRS)
Pohner, John A.; Dempsey, Brian P.; Herold, Leroy M.
1990-01-01
Space Station elements and advanced military spacecraft will require rejection of tens of kilowatts of waste heat. Large space radiators and two-phase heat transport loops will be required. To minimize radiator size and weight, it is critical to minimize the temperature drop between the heat source and sink. Under an Air Force contract, a unique, high-performance heat exchanger is developed for coupling the radiator to the transport loop. Since fluid flow through the heat exchanger is driven by capillary forces which are easily dominated by gravity forces in ground testing, it is necessary to perform microgravity thermal testing to verify the design. This contract consists of an experiment definition phase leading to a preliminary design and cost estimate for a shuttle-based flight experiment of this heat exchanger design. This program will utilize modified hardware from a ground test program for the heat exchanger.
Heat transfer at interfaces with graphene
NASA Astrophysics Data System (ADS)
Xu, Zhiping
2012-02-01
Graphene has an ultrahigh in-plane thermal conductivity (5500 W/mK), but simultaneously a much lower conductivity along the c-axis in graphite or at the interfaces with other materials. As graphene finds more and more applications in nanoelectronics and high-performance composites, these interfaces become critically important in defining their heat dissipation and conduction performance. Unlike conventional interfaces in materials such as grain boundaries, the interfaces with graphene can be tuned by chemically modifying the graphene monolayer or intercalating the interfaces. These nano-engineering proposals require fundamental understanding of the heat transfer mechanisms. In order to obtain some insights on the transfer processes of mechanical and thermal energy across these interfaces, we perform series of molecular dynamics simulations, in combination with theoretical analysis by considering the quasi-ballistic nature of phonon transport at nanoscale. The result shows that heat dissipation or transport can be divided into two stages, beginning with an interface-controlled process. The effects of interface structures and binding properties on the whole process will be covered in this talk, with several examples showing how the interfacial thermal transfer can be engineered.
Heat Transfer Operators Associated with Quantum Operations
Ç. Aksak; S. Turgut
2011-04-14
Any quantum operation applied on a physical system is performed as a unitary transformation on a larger extended system. If the extension used is a heat bath in thermal equilibrium, the concomitant change in the state of the bath necessarily implies a heat exchange with it. The dependence of the average heat transferred to the bath on the initial state of the system can then be found from the expectation value of a hermitian operator, which is named as the heat transfer operator (HTO). The purpose of this article is the investigation of the relation between the HTOs and the associated quantum operations. Since, any given quantum operation on a system can be realized by different baths and unitaries, many different HTOs are possible for each quantum operation. On the other hand, there are also strong restrictions on the HTOs which arise from the unitarity of the transformations. The most important of these is the Landauer erasure principle. This article is concerned with the question of finding a complete set of restrictions on the HTOs that are associated with a given quantum operation. An answer to this question has been found only for a subset of quantum operations. For erasure operations, these characterizations are equivalent to the generalized Landauer erasure principle. For the case of generic quantum operations however, it appears that the HTOs obey further restrictions which cannot be obtained from the entropic restrictions of the generalized Landauer erasure principle.
Visualization study on pool boiling heat transfer
NASA Astrophysics Data System (ADS)
Kamei, Shuya; Hirata, Masaru
1991-04-01
The visualized boiling phenomena were observed by means of high speed photographic shadowgraphy using a rotating prism camera (nac HIGH SPEED CAMERA model-16HD) with the speed of about 3500 frames per second. The photographs show that pool boiling heat transfer phenomena are varied for the boiling curve based on the experiments. Experiments have been carried out to investigate pool boiling heat transfer phenomena on a horizontal thin filament in subcooled and saturated distilled water. The experiments were performed for atmospheric pressure,for filament diameters of about 0.3 mm, for region of natural convection to film boiling. The color-film made by high speed movie camera are converted to high speed color video-tape. It is convenient to edit and show the tape for visualization with teaching the students. The high speed color video showed that the successive motion and shape of bubbles during their process of detachment varied with increasing heat flux on the heated surface of a filament. From these results, it was confirmed that the high speed phenomena of boiling by the slow motion video pictures could be estimated clearly.
Isao Tanaka; Youji Inoue; Norihiko Ishii; Katsu Tanaka; Yoshitaka Izumi; Shinji Okamoto
2002-01-01
The heat-transfer process described in this paper will be useful for controllably and selectively doping polymer films used to make hyperfine full-color polymer electroluminescent (EL) displays. A polymer receiver film is placed in direct contact with a dye-dispersed polymer film coated onto an efficient photo-absorbing substrate to permit heat-transfer dye diffusion. The widely used heat-mode magneto-optical storage material, TbFeCo was
Enhanced flow boiling heat transfer of FC72 on micro-pin-finned surfaces
Aixiang Ma; Jinjia Wei; Minzhe Yuan; Jiabin Fang
2009-01-01
For the purpose of cooling electronic components with high heat flux efficiently, some experiments were conducted to study the flow boiling heat transfer performance of FC-72 on silicon chips. Micro-pin-fins were fabricated on the chip surface using a dry etching technique to enhance boiling heat transfer. Three different fluid velocities (0.5, 1 and 2m\\/s) and three different liquid subcoolings (15,
Surface heat transfer due to sliding bubble motion
Brian Donnelly; Tadhg S. O’Donovan; Darina B. Murray
2009-01-01
The presence of a rising bubble in a fluid can greatly enhance heat transfer from adjacent heated surfaces such as in shell and tube heat exchangers and chemical reactors. One specific case of this is when a bubble impacts and slides along the surface. The result is heat transfer enhancement by two main mechanisms: first, the bubble itself acting as
Heat transfer enhancement of copper nanofluid with acoustic cavitation
D. W. Zhou
2004-01-01
Heat transfer characteristics of copper nanofluids with and without acoustic cavitation were investigated experimentally. The effects of such factors as acoustical parameters, nanofluid concentration and fluid subcooling on heat transfer enhancement around a heated horizontal copper tube were discussed in detail. The results indicated that the copper nanoparticles and acoustic cavitation had profound and significant influence on heat transport in
Paris-Sud XI, Université de
Analysis of roll gap heat transfers in hot steel strip rolling through roll temperature sensors and heat transfer models N. Legrand1,a , N. Labbe1,b D. Weisz-Patrault2,c , A. Ehrlacher2,d , T. Luks3,e heat transfers during pilot hot steel strip rolling. Two types of temperature sensors (drilled and slot
Numerical study of high heat ux pool boiling heat transfer Ying He a,*, Masahiro Shoji b
Maruyama, Shigeo
Numerical study of high heat ¯ux pool boiling heat transfer Ying He a,*, Masahiro Shoji b , Shigeo simulation model of boiling heat transfer is proposed based on a numerical macrolayer model [S. Maruyama, M. Shoji, S. Shimizu, A numerical simulation of transition boiling heat transfer, in: Proceedings
Journal of Enhanced Heat Transfer, 19 (5): 457476 (2012) EXPERIMENTAL INVESTIGATION OF HEAT
Ghajar, Afshin J.
2012-01-01
Journal of Enhanced Heat Transfer, 19 (5): 457476 (2012) EXPERIMENTAL INVESTIGATION OF HEAT microfin tubes, most of the heat transfer and friction factor studies were focused on the turbulent region. However, there is a lack of information about the heat transfer and friction factor behavior of microfin
Glycol coolants improve heat transfer and corrosion control
Holfield, R. [Dow Chemical Co., Midland, MI (United States)
1995-03-01
Various liquids from plain water to exotic fluids have been used as coolants in large stationary diesel engines that drive compressors on natural gas pipeline distribution systems. Although water is an efficient heat transfer medium, its drawbacks of freezing at {minus}32 F and boiling at 212 F seriously limit its usefulness. Special glycol-based heat transfer fluids are available and refined specifically for long-term needs of gas compressor engines. Appropriate corrosion inhibitors have been formulated for metallurgy and operating conditions encountered with these engines. Propylene glycol was developed as an alternative for use in environmentally sensitive areas. Glycol-based fluids must be specifically inhibited for industrial applications because uninhibited or improperly inhibited coolants can seriously damage reciprocating engines.
Rocket engine thrust chamber heat transfer calculation and analysis
NASA Technical Reports Server (NTRS)
Saha, H.
1974-01-01
A parametric study of the heat transfer rate along the wall of a rocket nozzle is presented. The influences of different parameters; laminar and turbulent Lewis number, mixture ratio, initial wall temperature distribution, and eddy viscosity, were considered. The numerical evaluation of these influences on heat transfer rate was done by using three different compressible, reacting laminar and turbulent boundary layer computer programs; MABL (Mass Addition Boundary Layer Program), MABL-KE (MABL program is modified to include turbulent kinetic energy equation), and BLIMP (Boundary Layer Integral Matrix Procedure). This study also provided an excellent opportunity to evaluate the efficiencies of these three computer programs and to suggest one of them for future computational purposes.
An Analysis of Efficiency Improvements in Residential Sized Heat Pumps
O'Neal, D. L.; Boecker, C. L.; Murphy, W. E.; Notman, J. R.
1986-01-01
the air handling unit. Limitations on the size of the indoor coil will limit the maximum efficiency that is feasible for a heat pump, Figure 3.1 shows the maximum SEER for optimized air source, single-speed, split heat pump systems built with "off... performance while ORNL emphasizes the total system effect. ORNL used much simpler algorithms to determine the coil heat transfer rate, but included calculations of air side pressure drop and computed fan power. NBS used very detailed refrigerant side...
Effect of nanoparticles on heat transfer in mini double-pipe heat exchangers in turbulent flow
NASA Astrophysics Data System (ADS)
Aghayari, Reza; Maddah, Heydar; Ashori, Fatemeh; Hakiminejad, Afshin; Aghili, Mehdi
2015-03-01
In this work, heat transfer of a fluid containing nanoparticles of aluminum oxide with the water volume fraction (0.1-0.3) percent has been reported. Heat transfer of the fluid containing nano water aluminum oxide with a diameter of about 20 nm in a horizontal double pipe counter flow heat exchanger under turbulent flow conditions was studied. The results showed that the heat transfer of nanofluid in comparison with the heat transfer of fluid is slightly higher than 12 percent.
Heat Transfer Through Turbulent Friction Layers
NASA Technical Reports Server (NTRS)
Reichardt, H.
1943-01-01
The "general Prandtl number" Pr(exp 1) - A(sub q)/A Pr, aside from the Reynolds number determines the ratio of turbulent to molecular heat transfer, and the temperature distribution in turbulent friction layers. A(sub q) = exchange coefficient for heat; A = exchange coefficient for momentum transfer. A formula is derived from the equation defining the general Prandtl number which describes the temperature as a function of the velocity. For fully developed thermal boundary layers all questions relating to heat transfer to and from incompressible fluids can be treated in a simple manner if the ratio of the turbulent shear stress to the total stress T(sub t)/T in the layers near the wall is known, and if the A(sub q)/A can be regarded as independent of the distance from the wall. The velocity distribution across a flat smooth channel and deep into the laminar sublayer was measured for isothermal flow to establish the shear stress ratio T(sub t)/T and to extend the universal wall friction law. The values of T(sub t)/T which resulted from these measurements can be approximately represented by a linear function of the velocity in the laminar-turbulent transition zone. The effect of the temperature relationship of the material values on the flow near the wall is briefly analyzed. It was found that the velocity at the laminar boundary (in contrast to the thickness of the laminar layer) is approximately independent of the temperature distribution. The temperature gradient at the wall and the distribution of temperature and heat flow in the turbulent friction layers were calculated on the basis of the data under two equations. The derived formulas and the figures reveal the effects of the Prandtl number, the Reynolds number, the exchange quantities and the temperature relationship of the material values.
Flow and heat transfer in a curved channel
NASA Technical Reports Server (NTRS)
Brinich, P. F.; Graham, R. W.
1977-01-01
Flow and heat transfer in a curved channel of aspect ratio 6 and inner- to outer-wall radius ratio 0.96 were studied. Secondary currents and large longitudinal vortices were found. The heat-transfer rates of the outer and inner walls were independently controlled to maintain a constant wall temperature. Heating the inner wall increased the pressure drop along the channel length, whereas heating the outer wall had little effect. Outer-wall heat transfer was as much as 40 percent greater than the straight-channel correlation, and inner-wall heat transfer was 22 percent greater than the straight-channel correlation.
Analysis of radial fin assembly heat transfer with dehumidification
Rosario, L.; Rahman, M.M. [Univ. of South Florida, Tampa, FL (United States). Dept. of Mechanical Engineering
1996-12-31
The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing heat transfer rate with and without fins under the same operating conditions. Numerical calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. Results were compared to those published for rectangular fin under humid condition showed excellent agreement when the present model was used to compute that limiting condition. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature.
Turbulence convective heat transfer for cooling the photovoltaic cells
NASA Astrophysics Data System (ADS)
Arianmehr, Iman
Solar PV (photovoltaic) is a rapidly advancing renewable energy technology which converts sunlight directly into electricity. One of the outstanding challenges of the current PV technology is the reduction in its conversion efficiency with increasing PV panel temperature, which is closely associated with the increase in solar intensity and the ambient temperature surrounding the PV panels. To more effectively capture the available energy when the sun is most intense, significant efforts have been invested in active and passive cooling research over the last few years. While integrated cooling systems can lead to the highest total efficiencies, they are usually neither the most feasible nor the most cost effective solutions. This work examines some simple passive means of manipulating the prevailing wind turbulence to enhance convective heat transfer over a heated plate in a wind tunnel.
Boiling heat transfer in a horizontal small-diameter tube
M. W. Wambsganss; J. A. Jendrzejczyk; T. N. Tran; D. M. France
1993-01-01
Results of a study on boiling heat transfer of refrigerant R-113 in a small-diameter (2.92 mm) tube are reported. Local heat transfer coefficients are measured for a range of heat flux (8.8-90.75 kW\\/m[sup 2]), mass flux (50-300 kg\\/m[sup 2]s), and equilibrium mass quality (0-0.9). The measured coefficients are used to evaluate 10 different heat transfer correlations, some of which have
High efficiency pump for space helium transfer
NASA Technical Reports Server (NTRS)
Hasenbein, Robert; Izenson, Michael G.; Swift, Walter L.; Sixsmith, Herbert
1991-01-01
A centrifugal pump was developed for the efficient and reliable transfer of liquid helium in space. The pump can be used to refill cryostats on orbiting satellites which use liquid helium for refrigeration at extremely low temperatures. The pump meets the head and flow requirements of on-orbit helium transfer: a flow rate of 800 L/hr at a head of 128 J/kg. The overall pump efficiency at the design point is 0.45. The design head and flow requirements are met with zero net positive suction head, which is the condition in an orbiting helium supply Dewar. The mass transfer efficiency calculated for a space transfer operation is 0.99. Steel ball bearings are used with gas fiber-reinforced teflon retainers to provide solid lubrication. These bearings have demonstrated the longest life in liquid helium endurance tests under simulated pumping conditions. Technology developed in the project also has application for liquid helium circulation in terrestrial facilities and for transfer of cryogenic rocket propellants in space.
The efficiencies of thermochemical energy transfer
P. O. Carden; O. M. Williams
1978-01-01
A general thermodynamic study of the thermochemical energy transfer and work production processes is presented. Gaseous systems in which the effluent of each reactor is not separated into the reactant and product species, as well as liquid\\/gas systems in which the effluent separates spontaneously into liquid and gas phases are treated. The overall system efficiency is derived as the product
Efficiency of vertical geothermal heat exchangers in the ground source heat pump system
NASA Astrophysics Data System (ADS)
Zeng, Heyi; Diao, Nairen; Fang, Zhaohong
2003-02-01
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.
Heat and mass transfer in fire
Kulkarni, A.K.; Jaluria, Y.
1987-01-01
This book contains eight selections. They are: Free Convection Diffusion Flames: A Review of Results; Evaporation of a Water Droplet Deposited on a Hot High Thermal Conductivity Solid Surface; A Study of Combustion of Slurry Drops in a Spray Flame; Thermal Measurements in Large Pool Fires; Measurements of Gas Velocities and Temperatures in a Large Open Pool Fire; A Numerical Model for Wind Flows Above Fire Areas; Heat Transfer in Compartment Fires Near Regions of Ceiling Jet-Wall Impingement; and Radiation-Convection Interactions of a Non-Gray Gas in a Square Enclosure.
On heat transfer in squish gaps
NASA Astrophysics Data System (ADS)
Spurk, J. H.
1986-06-01
Attention is given to the heat transfer characteristics of a squish gap in an internal combustion engine cylinder, when the piston is nearing top dead center (TDC) on the compression stroke. If the lateral extent of the gap is much larger than its height, the inviscid flow is similar to the stagnation point flow. Surface temperature and pressure histories during compression and expansion are studied. Surface temperature has a maximum near TDC, then drops and rises again during expansion; higher values are actually achieved during expansion than during compression.
Preparation, thermo-physical properties and heat transfer enhancement of nanofluids
NASA Astrophysics Data System (ADS)
Rashmi, W.; Khalid, M.; Ong, S. S.; Saidur, R.
2014-09-01
Research interest in convective heat transfer using suspensions of nano-sized solid particles has been growing rapidly over the past decade, seeking to develop novel methods for enhancing the thermal performance of heat transfer fluids. Due to their superior transport properties and significant enhancement in heat transfer characteristics, nanofluids are believed to be a promising heat transfer fluid for the future. The stability of nanofluids is also a key aspect of their sustainability and efficiency. This review summarizes the recent research findings on stability, thermophysical properties and convective heat transfer of nano-sized particles suspended in base fluids. Furthermore, various mechanisms of thermal conductivity enhancement and challenges faced in nanofluid development are also discussed.
Heat transfer enhancement of spray cooling with nanofluids
Christian David Martinez
2009-01-01
Spray cooling is a technique for achieving large heat fluxes at low surface temperatures by impinging a liquid in droplet form on a heated surface. Heat is removed by droplets spreading across the surface, thus removing heat by evaporation and by an increase in the convective heat transfer coefficient. The addition of nano-sized particles, like aluminum or copper, to water
HeeSung Park
2009-01-01
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
Boiling local heat transfer enhancement in minichannels using nanofluids.
Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony
2013-01-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 ?m hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445
Boiling local heat transfer enhancement in minichannels using nanofluids
2013-01-01
This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 ?m hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445
Efficient stream distributions in radiative transfer theory
NASA Technical Reports Server (NTRS)
Whitney, C.
1974-01-01
This paper discusses a new, computationally-efficient method for approximating the integro-differential equation of radiative transfer with a finite set of coupled differential equations for discrete streams. The method uses recommended spatial distributions of streams that are quite different from those typically used in that they are based on the symmetry of several regular Platonic solids. To facilitate the use of such distributions, an explicit, one-parameter relationship between the physical radiance and the abstract stream is formulated. The parameter is used to determine the minimum number of streams required in the radiative transfer model. Accuracy and computational efficiency are shown to be served best by choosing a stream distribution that is invariant to a large number of three space rotations. For various values of the above-mentioned parameter, the resulting recommended stream distribution is shown to be more computationally efficient than more conventional stream distributions. Finally, the incorporation of polarization in the stream definition is described.
Heat transfer assembly for a fluorescent lamp and fixture
Siminovitch, M.J.; Rubenstein, F.M.; Whitman, R.E.
1992-12-29
In a lighting fixture including a lamp and a housing, a heat transfer structure is disclosed for reducing the minimum lamp wall temperature of a fluorescent light bulb. The heat transfer structure, constructed of thermally conductive material, extends from inside the housing to outside the housing, transferring heat energy generated from a fluorescent light bulb to outside the housing where the heat energy is dissipated to the ambient air outside the housing. Also disclosed is a method for reducing minimum lamp wall temperatures. Further disclosed is an improved lighting fixture including a lamp, a housing and the aforementioned heat transfer structure. 11 figs.
Pool-Boiling Heat Transfer in Liquid Nitrogen
Muneo KIDA; Yoshihiro KIKUCHCI; Osamu TAKAHASHI; Itaru MICHIYOSHI
1981-01-01
An experimental study was conducted on pool-boiling heat transfer from an electrically heated horizontal wire to saturated liquid nitrogen at atmospheric pressure. Experimental results of heat transfer characteristics in both nucleate- and film-boiling regimes, critical heat flux and minimum heat flux were analyzed and compared with various correlations. In addition, photography was used to obtain information concerning the vapor-bubble and
RADIATIVE HEAT TRANSFER WITH QUASIMONTE CARLO METHODS \\Lambda
RADIATIVE HEAT TRANSFER WITH QUASIMONTE CARLO METHODS \\Lambda A. Kersch 1 W. Morokoff 2 A accuracy modeling of the radiative heat transfer from the heater to the wafer. Figure 1 shows the draft Carlo simulation is often used to solve radiative transfer problems where complex physical phenomena
Boiling heat transfer in rectangular microchannels with reentrant cavities
Peles, Yoav
been found to promote convective boiling, while Nucleate Boiling dominated at low Reynolds number transfer and fluid flow mechanisms governing boil- ing in microchannels, and has resulted in heat transferBoiling heat transfer in rectangular microchannels with reentrant cavities Ali Kosßar, Chih
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Cunnington, George R.; Miller, Steve D.; Knutson, Jeffry R.
2010-01-01
Combined radiation and conduction heat transfer through various high-temperature, high-porosity, unbonded (loose) fibrous insulations was modeled based on first principles. The diffusion approximation was used for modeling the radiation component of heat transfer in the optically thick insulations. The relevant parameters needed for the heat transfer model were derived from experimental data. Semi-empirical formulations were used to model the solid conduction contribution of heat transfer in fibrous insulations with the relevant parameters inferred from thermal conductivity measurements at cryogenic temperatures in a vacuum. The specific extinction coefficient for radiation heat transfer was obtained from high-temperature steady-state thermal measurements with large temperature gradients maintained across the sample thickness in a vacuum. Standard gas conduction modeling was used in the heat transfer formulation. This heat transfer modeling methodology was applied to silica, two types of alumina, and a zirconia-based fibrous insulation, and to a variation of opacified fibrous insulation (OFI). OFI is a class of insulations manufactured by embedding efficient ceramic opacifiers in various unbonded fibrous insulations to significantly attenuate the radiation component of heat transfer. The heat transfer modeling methodology was validated by comparison with more rigorous analytical solutions and with standard thermal conductivity measurements. The validated heat transfer model is applicable to various densities of these high-porosity insulations as long as the fiber properties are the same (index of refraction, size distribution, orientation, and length). Furthermore, the heat transfer data for these insulations can be obtained at any static pressure in any working gas environment without the need to perform tests in various gases at various pressures.
Heat transfer enhancement in a grooved channel with curved vanes
Cila Herman; Eric Kang
2002-01-01
We visualize unsteady temperature fields in the grooved channel with curved vanes using holographic interferometry. The heat transfer performance of the investigated channel is compared with that of the basic grooved channel. The addition of curved vanes above the downstream end of the heated block redirects the flow from the main channel into the groove. Heat transfer shows an increase
CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011
Dyer, Bill
ME 525 CONDUCTION HEAT TRANSFER Dr. Ruhul Amin Fall 2011 Office: 201C Roberts Hall Lecture Room of conduction heat transfer. Important results which are useful for engineering application will also: 121 Roberts Hall Phone: 994-6295 Lecture Periods: 12:45- 2:00, TR TEXT: Heat Conduction, M. N. Ozisik
Measurement of heat transfer coefficient using termoanemometry methods
NASA Astrophysics Data System (ADS)
Dan?ová, P.; Sitek, P.; Vít, T.
2014-03-01
This work deals with a measurement of heat transfer from a heated flat plate on which a synthetic jet impacts perpendicularly. Measurement of a heat transfer coefficient (HTC) is carried out using the hot wire anemometry method with glue film probe Dantec 55M47. The paper brings also results of velocity profiles measurements and turbulence intensity calculations.
THE INFRARED HEAT TRANSFER GAUGE. Research Note 265
M. Camac; R. Feinberg
1961-01-01
A heat transfer gage that operates in the presence of highly ionized ; plasmas and in strong electric and magnetic fields was developed. The principle ; of its operation is to use a thin opaque surface as the heat transfer element. ; Aerodynamic and radiative heating is applied to one side of this layer while ; measurements are made of
Heat transfer in food processing: ensuring product quality and safety
Peter J. Fryer; Phillip T. Robbins
2005-01-01
Heat transfer to foods is commonplace but critical; heating develops flavour and texture and ensures product safety. The food industry must ensure that all parts of the product have all been processed sufficiently, without unacceptable loss of quality. Conventionally, food is significantly over-processed to ensure safety. This paper reviews some problems which heat-transfer engineers face in the food industry, and
Heat transfer and fluid friction in bundles of twisted tubes
NASA Astrophysics Data System (ADS)
Dzyubenko, B. V.; Dreitser, G. A.
1986-06-01
The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes.
Theory of heat transfer from a surface covered with hair
A. Bejan
1990-01-01
This paper describes the fundamental mechanisms of heat transfer through a surface covered with perpendicular hair strands of uniform density. An air flow parallel to the skin seeps through the spaces created between the hair strands. It is shown that the total heat transfer rate from the surface is due to two contributions: (i) the heat conducted through the hair
Micro/Nanoscale Heat Transfer: Interfacial Effects Dominate the
Kostic, Milivoje M.
-probe method Pump laser is externally modulated and heats the sample Probe beam detects the transient3/15/2012 1 Micro/Nanoscale Heat Transfer: Interfacial Effects Dominate the Heat Transfer 1 Xing nanotransistors. Nanotechnology has been described as a new industrial revolution M. Chu, et al. Annu. Rev. Mater
Heat transfer from starlings sturnus vulgaris during flight
Ward; Rayner; MOLler; Jackson; Nachtigall; Speakman
1999-06-01
Infrared thermography was used to measure heat transfer by radiation and the surface temperature of starlings (Sturnus vulgaris) (N=4) flying in a wind tunnel at 6-14 m s-1 and at 15-25 degrees C. Heat transfer by forced convection was calculated from bird surface temperature and biophysical modelling of convective heat transfer coefficients. The legs, head and ventral brachial areas (under the wings) were the hottest parts of the bird (mean values 6.8, 6.0 and 5.3 degrees C, respectively, above air temperature). Thermal gradients between the bird surface and the air decreased at higher air temperatures or during slow flight. The legs were trailed in the air stream during slow flight and when air temperature was high; this could increase heat transfer from the legs from 1 to 12 % of heat transfer by convection, radiation and evaporation (overall heat loss). Overall heat loss at a flight speed of 10.2 m s-1 averaged 11. 3 W, of which radiation accounted for 8 % and convection for 81 %. Convection from the ventral brachial areas was the most important route of heat transfer (19 % of overall heat loss). Of the overall heat loss, 55 % occurred by convection and radiation from the wings, although the primaries and secondaries were the coolest parts of the bird (2.2-2.5 degrees C above air temperature). Calculated heat transfer from flying starlings was most sensitive to accurate measurement of air temperature and convective heat transfer coefficients. PMID:10333506
Experimental study of heat transfer to falling liquid films
N. E. Fagerholm; K. Kivioja; A. R. Ghazanfari; E. Jaervinen
1985-01-01
This project was initiated in order to obtain more knowledge about thermal design of falling film heat exchangers and to find methods to improve heat transfer in film flow. A short literature survey of film flow characteristics and heat transfer is presented. An experimental apparatus designed and built for studying falling film evaporation is described. The first experiments were made
Nucleate Boiling Heat Transfer Studied Under Reduced-Gravity Conditions
NASA Technical Reports Server (NTRS)
Chao, David F.; Hasan, Mohammad M.
2000-01-01
Boiling is known to be a very efficient mode of heat transfer, and as such, it is employed in component cooling and in various energy-conversion systems. In space, boiling heat transfer may be used in thermal management, fluid handling and control, power systems, and on-orbit storage and supply systems for cryogenic propellants and life-support fluids. Recent interest in the exploration of Mars and other planets and in the concept of in situ resource utilization on the Martian and Lunar surfaces highlights the need to understand how gravity levels varying from the Earth's gravity to microgravity (1g = or > g/g(sub e) = or > 10(exp -6)g) affect boiling heat transfer. Because of the complex nature of the boiling process, no generalized prediction or procedure has been developed to describe the boiling heat transfer coefficient, particularly at reduced gravity levels. Recently, Professor Vijay K. Dhir of the University of California at Los Angeles proposed a novel building-block approach to investigate the boiling phenomena in low-gravity to microgravity environments. This approach experimentally investigates the complete process of bubble inception, growth, and departure for single bubbles formed at a well-defined and controllable nucleation site. Principal investigator Professor Vijay K. Dhir, with support from researchers from the NASA Glenn Research Center at Lewis Field, is performing a series of pool boiling experiments in the low-gravity environments of the KC 135 microgravity aircraft s parabolic flight to investigate the inception, growth, departure, and merger of bubbles from single- and multiple-nucleation sites as a function of the wall superheat and the liquid subcooling. Silicon wafers with single and multiple cavities of known characteristics are being used as test surfaces. Water and PF5060 (an inert liquid) were chosen as test liquids so that the role of surface wettability and the magnitude of the effect of interfacial tension on boiling in reduced gravity can be investigated.
Micro-grooved heat transfer combustor wall
NASA Technical Reports Server (NTRS)
Ward, Steven D. (Inventor)
1994-01-01
A gas turbine engine hot section combustor liner is provided a non-film cooled portion of a heat transfer wall having a hot surface and a plurality of longitudinally extending micro-grooves disposed in the portion of the wall along the hot surface in a direction parallel to the direction of the hot gas flow. The depth of the micro-grooves is very small and on the order of magnitude of a predetermined laminar sublayer of a turbulent boundary layer. The micro-grooves are sized so as to inhibit heat transfer from the hot gas flow to the hot surface of the wall while reducing NOx emissions of the combustor relative to an otherwise similar combustor having a liner wall portion including film cooling apertures. In one embodiment the micro-grooves are about 0.001 inches deep and have a preferred depth range of from about 0.001 inches to 0.005 inches and which are square, rectangular, or triangular in cross-section and the micro-grooves are spaced about one width apart.
Algorithmic aspects of transient heat transfer problems in structures
NASA Astrophysics Data System (ADS)
Haftka, R. T.; Kadivar, M. H.
It is noted that the application of finite element or finite difference techniques to the solution of transient heat transfer problems in structures often results in a stiff system of ordinary differential equations. Such systems are usually handled most efficiently by implicit integration techniques which require the solution of large and sparse systems of algebraic equations. The assembly and solution of these systems using the incomplete Cholesky conjugate gradient algorithm is examined. Several examples are used to demonstrate the advantage of the algorithm over other techniques.
Understanding fast heat transfer in the shallow subsurface
NASA Astrophysics Data System (ADS)
Rutten, Martine; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick
2010-05-01
Understanding the temperature profile of the shallow subsurface is of great importance for interpreting remote sensing observations and modeling land-atmosphere interaction. Remote sensing observations are translated to surface characteristics, such as vegetation and soil moisture, using radiative transfer schemes that are sensitive to skin temperature estimation. The surface temperature is also a key variable in the heat partitioning of net radiation into sensible, latent and soil heat flux at the interface between land and atmosphere. The temperature profile of the soil is determined by the processes of radiative, convective and conductive heat transfer. Whereas radiative and convective heat transfer are dominant at the soil-air interface, heat transfer within the soil is typically assumed to be governed by conduction and as such is described with a diffusion model. The thermal diffusivity of the soil depends mainly on mineral composition and moisture content and is described in many empirical models. Using temperature data from experiments conducted in Florida (MicroWex 2) and the Netherlands (Monster), we show that diffusion cannot describe heat transfer within approximately the upper ten centimeters of the soil. The heat transfer is significantly faster than would be predicted with a diffusion equation. Diffusivity values, estimated using an inversion approach to the diffusion equation, fall outside the physically reasonable range, which is defined by available soil diffusivity models. The extent of this strongly thermally active layer depends on vegetation conditions, and possibly moisture conditions. We investigate mechanisms that may explain the fast heat transfer in the shallow subsurface. Possible mechanisms include heat transfer by convective heat transfer processes such as latent heat formation and heat transfer due to water percolation. We estimated the size of the heat sink-source at depth and compared these to observations of latent heat and estimates of heat transfer by percolation. The magnitude of the sink-source reached values up to the same order of magnitude as the latent heat flux and decreased with depth. The sink-source terms were large, especially for low vegetation conditions and showed a distinct diurnal cycle. The possible contribution of percolation to heat transfer was minor compared to the magnitude of the sink-source term. Finally, we compared an empirical heat flow model, which includes formation of latent heat in the shallow subsurface, with our data. We found this model could not sufficiently describe the fast heat transfer in the shallow subsurface. Ongoing work is on a physically based model to describe fast heat transfer in the shallow subsurface.
S. Downing; L. Haas; W. S. Chang; D. M. McEligot
1995-01-01
Papers in the first section present current research in topics such as meniscus subjected to a transient acceleration field, natural convection in a thermosyphon, a capillary pumped loop, and a mathematical model of axially grooved heat pipes. The papers in the second section deal with diverse topics included single-phase, two-phase, and supercritical heat transfer in component cooling, phase-change mechanisms in
Transient critical heat flux and blowdown heat-transfer studies
Leung, J.C.
1980-05-01
Objective of this study is to give a best-estimate prediction of transient critical heat flux (CHF) during reactor transients and hypothetical accidents. To accomplish this task, a predictional method has been developed. Basically it involves the thermal-hydraulic calculation of the heated core with boundary conditions supplied from experimental measurements. CHF predictions were based on the instantaneous ''local-conditions'' hypothesis, and eight correlations (consisting of round-tube, rod-bundle, and transient correlations) were tested against most recent blowdown heat-transfer test data obtained in major US facilities. The prediction results are summarized in a table in which both CISE and Biasi correlations are found to be capable of predicting the early CHF of approx. 1 s. The Griffith-Zuber correlation is credited for its prediction of the delay CHF that occurs in a more tranquil state with slowly decaying mass velocity. In many instances, the early CHF can be well correlated by the x = 1.0 criterion; this is certainly indicative of an annular-flow dryout-type crisis. The delay CHF occurred at near or above 80% void fraction, and the success of the modified Zuber pool-boiling correlation suggests that this CHF is caused by flooding and pool-boiling type hydrodynamic crisis.
Micro and nanostructured surfaces for enhanced phase change heat transfer
Chu, Kuang-Han, Ph. D. Massachusetts Institute of Technology
2013-01-01
Two-phase microchannel heat sinks are of significant interest for thermal management applications, where the latent heat of vaporization offers an efficient method to dissipate large heat fluxes in a compact device. However, ...
Assessment of an improved model for the heat transfer coefficient of grooved heat pipe evaporators
P. C. Stephan; C. A. Busse
1991-01-01
Predictions from an improved model of the radial heat transfer coefficient of grooved heat pipe evaporators are compared with experimental data from an Al\\/NH3 heat pipe. Good agreement is found. The observed temperature dependence of the heat transfer coefficient is explained.
Heat-transfer augmentation in rod bundles near grid spacers
Yao, S.C.; Hochreiter, L.E.; Leech, W.J.
1982-02-01
Heat-transfer augmentation by straight grid spacers in rod bundles is studied for single-phase flow and for post-critical heat flux dispersed flow. The heat transfer effect of swirling grid spacers in single-phase flow is also examined. Governing heat-transfer mechanisms are analyzed, and predictive formulations are established. For single-phase flow, the local heat transfer at a straight spacer and at its upstream or downstream locations are treated separately. The effect of local velocity increasing near swirling spacer is considered. For post critical heat flux (CHF) dispersed flow, the heat transfer by thermal radiation, fin cooling, and vapor convection near the spacer are calculated. The predictions are compared with experimental data with satisfactory agreement.
Heat-Transfer Enhancement by Artificially Generated Streamwise Vorticity
NASA Astrophysics Data System (ADS)
Ghanem, Akram; Habchi, Charbel; Lemenand, Thierry; Della Valle, Dominique; Peerhossaini, Hassan
2012-11-01
Vortex-induced heat transfer enhancement exploits longitudinal and transverse pressure-driven vortices through the deliberate artificial generation of large-scale vortical flow structures. Thermal-hydraulic performance, Nusselt number and friction factor are experimentally investigated in a HEV (high-efficiency vortex) mixer, which is a tubular heat exchanger and static mixer equipped with trapezoidal vortex generators. Pressure gradients are generated on the trapezoidal tab initiating a streamwise swirling motion in the form of two longitudinal counter-rotating vortex pairs (CVP). Due to the Kelvin-Helmholtz instability, the shear layer generated at the tab edges, which is a production site of turbulence kinetic energy (TKE), becomes unstable further downstream from the tabs and gives rise to periodic hairpin vortices. The aim of the study is to quantify the effects of hydrodynamics on the heat- and masstransfer phenomena accompanying such flows for comparison with the results of numerical studies and validate the high efficiency of the intensification process implementing such vortex generators. The experimental results reflect the enhancement expected from the numerical studies and confirm the high status of the HEV heat exchanger and static mixer.
Heat transfer in bundles of finned tubes in crossflow
Stasiulevicius, J.; Skrinska, A.; Zukauskas, A.; Hewitt, G.F.
1986-01-01
This book provides correlations of heat transfer and hydraulic data for bundles of finned tubes in crossflow at high Reynolds numbers. Results of studies of the effectiveness of the fin, local, and mean heat transfer coefficients are presented. The effect of geometric parameters of the fins and of the location of tubes in the bundle on heat transfer and hydraulic drag are described. The resistance of the finned tube bundles under study and other factors are examined.
Heat transfer in freeboard region of fluidized beds
Biyikli, S.; Tuzla, K.; Chen, J.C.
1983-10-01
This research involved the study of heat transfer and fluid mechanic characteristics around a horizontal tube in the freeboard region of fluidized beds. Heat transfer coefficients were experimetnally measured for different bed temperatures, particle sizes, gas flow rates, and tube elevations in the freeboard region of air fluidized beds at atmospheric pressure. Local heat transfer coefficients were found to vary significantly with angular position around the tube. Average heat transfer coefficients were found to decrease with increasing freeboard tube elevation and approach the values for gas convection plus radiation for any given gas velocity. For a fixed tube elevation, heat transfer coefficients generally increased with increasing gas velocity and with high particle entrainment they can approach the magnitudes found for immersed tubes. Heat transfer coefficients were also found to increase with increasing bed temperature. It was concluded that this increase is partly due to increase of radiative heat transfer and partly due to change of thermal properties of the fluidizing gas and particles. To investigate the fluid mechanic behavior of gas and particles around a freeboard tube, transient particle tube contacts were measured with a special capacitance probe in room temperature experiments. The results indicated that the tube surface experiences alternating dense and lean phase contacts. Quantitative information for local characteristics was obtained from the capacitance signals and used to develop a phenomenological model for prediction of the heat transfer coefficients around freeboard tubes. The packet renewal theory was modified to account for the dense phase heat transfer and a new model was suggested for the lean phase heat transfer. Finally, an empirical freeboard heat transfer correlation was developed from functional analysis of the freeboard heat transfer data using nondimensional groups representing gas velocity and tube elevation.
Heat transfer measurements in coal-water mixtures
Colombo, A.; Marcolongo, V. [CISE Tecnologie Innovative SpA, Segrate (Italy); Pedrelli, G.; Rossi, C. [ENEL/CRTN, Pisa (Italy)
1993-12-31
Experimental results of heat transfer measurements in Coal-Water Mixtures (CWM) for tubular geometry are presented. An increase in heat transfer was pointed out in comparison with predictions based on static thermophysical properties: this result was ascribed to dynamical phenomena in the particle size scale which can be explained through an effective dynamical thermal conductivity higher than the static conductivity. Finally, degradation of heat transfer was observed above a critical temperature.
Validation of efficiency transfer for Marinelli geometries.
Ferreux, Laurent; Pierre, Sylvie; Thanh, Tran Thien; Lépy, Marie-Christine
2013-11-01
In the framework of environmental measurements by gamma-ray spectrometry, some laboratories need to characterize samples in geometries for which a calibration is not directly available. A possibility is to use an efficiency transfer code, e.g., ETNA. However, validation for large volume sources, such as Marinelli geometries, is needed. With this aim in mind, ETNA is compared, initially to a Monte Carlo simulation (PENELOPE) and subsequently to experimental data obtained with a high-purity germanium detector (HPGe). PMID:23623315
R. Mastrullo; A. W. Mauro; A. Rosato; G. P. Vanoli
2009-01-01
Carbon dioxide is gaining renewed interest as an environmentally safe refrigerant. In order to improve the energy efficiency of R744 systems, an accurate knowledge of heat transfer coefficients is fundamental.In this paper experimental heat transfer coefficients during flow boiling of R744 in a smooth, horizontal, circular, 6.00mm inner diameter tube are presented. We obtained 217 experimental points in 18 operating
Heat Transfer Study of Polymer Solutions with Different Rigidities
Huang, Yao
2014-05-08
The heat transfer behaviors of non-Newtonian fluids under laminar flow conditions in circular tubes are presented in this study. The constant wall heat flux is considered as a boundary condition for dilute polymer solutions with different polymer...
Heat Transfer Applications for the Stimulated Reservoir Volume
Thoram, Srikanth
2011-10-21
shale gas well, after the gas production rate drops below the economic limit, for low grade geothermal heat extraction. Cold water is pumped into the fracture network through one horizontal well drilled at the fracture tips. Heat is transferred...
Heat Transfer Applications for the Stimulated Reservoir Volume
Thoram, Srikanth
2011-10-21
shale gas well, after the gas production rate drops below the economic limit, for low grade geothermal heat extraction. Cold water is pumped into the fracture network through one horizontal well drilled at the fracture tips. Heat is transferred...
2.51 Intermediate Heat and Mass Transfer, Fall 2001
Lienhard, John H., 1961-
Analysis, modeling, and design of heat and mass transfer processes with application to common technologies. Unsteady heat conduction in one or more dimensions, steady conduction in multidimensional configurations, numerical ...
Heat transfer coefficient in serpentine coolant passage for CCDTL
Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.
1998-12-31
A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.
Characterization and Development of Advanced Heat Transfer Technologie...
National Renewable Energy Laboratory (NREL)
heat transfer technologies through interactions with industry and research partners. - Literature search - Industry and research partner interactions * Objective and consistent...
Experimental study of heat transfer performance in a flattened AGHP
Han-Zhong Tao; Hong Zhang; Jun Zhuang; W. Jerry Bowman
2008-01-01
Round mini-axial grooved heat pipes (AGHP) with a diameter of 6mm and a length of 210mm were pressed into flattened heat pipes with a thickness of 3.5mm, 3mm, 2.5mm and 2mm, respectively. The article measured the heat transfer limit, thermal resistance and evaporation heat transfer coefficient of the said AGHPs and analyzed and studied the result. The result indicates: the
Takeishi, K; Aoki, S
2001-05-01
The improvement of the heat transfer coefficient of the 1st row blades in high temperature industrial gas turbines is one of the most important issues to ensure reliable performance of these components and to attain high thermal efficiency of the facility. This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of such gas turbines in order to attain efficient and environmentally benign engines. Following the experiments described in Part 1, a set of trials was conducted to clarify the influence of the blade's rotating motion on the heat transfer coefficient for internal serpentine flow passages with turbulence promoters. Test results are shown and discussed in this second part of the contribution. PMID:11460663
Proceedings of HT'03 2003 Summer Heat Transfer Conference
Walker, D. Greg
Proceedings of HT'03 2003 Summer Heat Transfer Conference July 2123, 2003, Las Vegas, Nevada, USA HT2003-47016 A NEW TECHNIQUE FOR HEAT FLUX DETERMINATION D.G. Walker Department of Mechanical@vt.edu ABSTRACT A new method for estimating heat fluxes from heating rate measurements and an approach to measure
Convective heat transfer in building energy analysis
Gadgil, A.J.
1980-05-01
In the ongoing efforts to study energy consumption in buildings through computer simulations, practically no attention has been given to modeling natural convective heat transfer in buildings. The main reason for this neglect is due to the difficulty of solving the problem numerically. This paper makes a contribution towards the solution of this difficulty by presenting a numerical code for modeling natural convection in rectangular enclosures at Rayleigh numbers up to 10/sup 10/. Chapter 2 develops the general equations of motion to be solved. Chapter 3 is devoted to simplification of these equations and description of the numerical scheme. Chapter 4 describes the comparisons of the predictions of the computer program based on the numerical scheme with various published experimental and numerical results of other investigators. Chapter 5 illustrates an application of the computer program to investigate the soundness of an assumption commonly made by all the building energy analysis programs.
Submersible pumping system with heat transfer mechanism
Hunt, Daniel Francis Alan; Prenger, F. Coyne; Hill, Dallas D; Jankowski, Todd Andrew
2014-04-15
A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.
Low-melting point heat transfer fluid
Cordaro, Joseph G. (Oakland, CA); Bradshaw, Robert W. (Livermore, CA)
2011-04-12
A low-melting point, heat transfer fluid comprising a mixture of LiNO.sub.3, NaNO.sub.3, KNO.sub.3, NaNO.sub.2 and KNO.sub.2 salts where the Li, Na and K cations are present in amounts of about 20-33.5 mol % Li, about 18.6-40 mol % Na, and about 40-50.3 mol % K and where the nitrate and nitrite anions are present in amounts of about 36-50 mol % NO.sub.3, and about 50-62.5 mol % NO.sub.2. These compositions can have liquidus temperatures between 70.degree. C. and 80.degree. C. for some compositions.
Interface elements for heat transfer analysis
NASA Astrophysics Data System (ADS)
Mason, W. E.
1984-08-01
Interface elements are desirable in finite element heat transfer analyses in situations where dissimilar meshes are to be joined or where contact resistances occur between various parts of a body. In stress codes, such elements are often termed master/slave. A general algorithm for interface elements will be described. The algorithm allows development of interface elements for both two- and three-dimensional applications. Surfaces in contact are automatically determined so that a minimum of input data is required. In addition, the algorithm allows for compatibility in thermal stress calculations with mechanical codes which have sliding interface capabilities. Implementation of the algorithm into the TACO codes will be discussed and examples will be given.
High thermal power density heat transfer. [thermionic converters
NASA Technical Reports Server (NTRS)
Morris, J. F. (inventor)
1980-01-01
Heat from a high temperature heat pipe is transferred through a vacuum or a gap filled with electrically nonconducting gas to a cooler heat pipe. The heat pipe is used to cool the nuclear reactor while the heat pipe is connected thermally and electrically to a thermionic converter. If the receiver requires greater thermal power density, geometries are used with larger heat pipe areas for transmitting and receiving energy than the area for conducting the heat to the thermionic converter. In this way the heat pipe capability for increasing thermal power densities compensates for the comparatively low thermal power densities through the electrically non-conducting gap between the two heat pipes.
Hydrodynamics and heat transfer during flow boiling instabilities in a single microchannel
Aussillous, Pascale
Hydrodynamics and heat transfer during flow boiling instabilities in a single microchannel July 2008 Keywords: Boiling Microchannels Visualisation Flow boiling instabilities Heat transfer a b intensification heat removal. Flow boiling heat transfer in microchannel geometry and the associated flow
The heat transfer coefficients of the heating surface of 300 MWe CFB boiler
NASA Astrophysics Data System (ADS)
Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai
2012-08-01
A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.
Heat transfer research on supercritical water flow upward in tube
Li, H. B.; Yang, J. [China Nuclear Power Technology Research Inst., Shenzhen, Guangdong (China); Gu, H. Y.; Zhao, M. [Shanghai Jiao Tong Univ., Shanghai (China); Lu, D. H.; Zhang, J. M.; Wang, F.; Zhang, Y. [China Nuclear Power Technology Research Inst., Shenzhen, Guangdong (China)
2012-07-01
The experimental research of heat transfer on supercritical water has been carried out on the supercritical water multipurpose test loop with a 7.6 mm upright tube. The experimental data of heat transfer is obtained. The experimental results of thermal-hydraulic parameters on flow and heat transfer of supercritical water show that: Heat transfer enhancement occurs when the fluid temperature reaches pseudo-critical point with low mass flow velocity, and peters out when the mass flow velocity increases. The heat transfer coefficient and Nusselt number decrease with the heat flux or system pressure increases, and increase with the increasing of mass flow velocity. The wall temperature increases when the mass flow velocity decreases or the system pressure increases. (authors)
TACO: a finite element heat transfer code
Mason, W.E. Jr.
1980-02-01
TACO is a two-dimensional implicit finite element code for heat transfer analysis. It can perform both linear and nonlinear analyses and can be used to solve either transient or steady state problems. Either plane or axisymmetric geometries can be analyzed. TACO has the capability to handle time or temperature dependent material properties and materials may be either isotropic or orthotropic. A variety of time and temperature dependent loadings and boundary conditions are available including temperature, flux, convection, and radiation boundary conditions and internal heat generation. Additionally, TACO has some specialized features such as internal surface conditions (e.g., contact resistance), bulk nodes, enclosure radiation with view factor calculations, and chemical reactive kinetics. A user subprogram feature allows for any type of functional representation of any independent variable. A bandwidth and profile minimization option is also available in the code. Graphical representation of data generated by TACO is provided by a companion post-processor named POSTACO. The theory on which TACO is based is outlined, the capabilities of the code are explained, the input data required to perform an analysis with TACO are described. Some simple examples are provided to illustrate the use of the code.
Heat transfer characteristics of igniter output plumes
NASA Astrophysics Data System (ADS)
Evans, N. A.; Durand, N. A.
Seven types of pyrotechnic igniters were each mounted at one end of a closed cylindrical bore hole representative of the center hole in a thermal battery. Measurements of local bore wall temperature, T(sub w), using commercially available, fast response (10 microsec) sheathed chromel-constantan thermocouples allowed calculation of local heat transfer rates, q, and wall heat flows, Q. The principal charge constituents of all these igniters were titanium and potassium perchlorate, while three types also contained barium styphnate as an ignition sensitizer. Igniter closure disc materials included glass-ceramic, glass, metal (plain, scored, with and without capture cone), and kapton/RTV. All igniters produced the lowest values of T(sub w) and q at the beginning of the bore, and, except for the igniter with the kapton/RTV closure disc, these quantities increased with distance along the bore. For igniters containing only titanium/potassium perchlorate, the rates of increase of Q along the bore length, compared with those for T(sub w) and q, were generally lower and more variable. The inclusion of barium styphnate produced rates of change in Q that were essentially constant to the end of the bore. The highest overall average wall temperatures were achieved by two igniter types with metal closure discs and no capture cone. No clear correlation was established between peak bore pressure and maximum wall temperature.
Application of Industrial Heat Improving energy efficiency of
Oak Ridge National Laboratory
Application of Industrial Heat Pumps Improving energy efficiency of industrial processes . H Session Application of Industrial Heat Pumps Improving energy efficiency of industrial processes Agency (IEA) - Agreements "Heat Pump Programme" "Industrial Energy-related Technologies and Systems #12
Heat transfer in turbulent bubbly flow in channels
NASA Astrophysics Data System (ADS)
Dabiri, Sadegh; Tryggvason, Gretar
2013-11-01
In many applications convective heat transfer occurs in the presence of a multiphase turbulent flow such as in boilers and bubble column reactors. Turbulence in channel and pipe flows significantly increases the heat transfer rate. Here we examine the effect of turbulent bubbly flows on the heat transfer inside a vertical channel with uniform heat flux on the walls and compare it with the heat transfer in single phase flow. Both bubbles and the turbulence are fully resolved through Direct Numerical Simulation. The distribution of the bubbles in the channel is affected by the deformability of the bubbles. A wall-peaked distribution is observed for nearly spherical bubbles and a core-peaked distribution is observed for deformable bubbles. This change in distribution of the bubbles significantly affects the flow rate in the channel and the heat transfer rate as well. The results of heat transfer for different flow configurations are presented and compared to the heat transfer in a single phase channel flow. In many applications convective heat transfer occurs in the presence of a multiphase turbulent flow such as in boilers and bubble column reactors. Turbulence in channel and pipe flows significantly increases the heat transfer rate. Here we examine the effect of turbulent bubbly flows on the heat transfer inside a vertical channel with uniform heat flux on the walls and compare it with the heat transfer in single phase flow. Both bubbles and the turbulence are fully resolved through Direct Numerical Simulation. The distribution of the bubbles in the channel is affected by the deformability of the bubbles. A wall-peaked distribution is observed for nearly spherical bubbles and a core-peaked distribution is observed for deformable bubbles. This change in distribution of the bubbles significantly affects the flow rate in the channel and the heat transfer rate as well. The results of heat transfer for different flow configurations are presented and compared to the heat transfer in a single phase channel flow. This research is partially supported by CASL project.
A structured surface for high performance evaporative heat transfer
NASA Technical Reports Server (NTRS)
Saaski, E. W.; Hamasaki, R. H.
1977-01-01
An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open faced screw thread surfaces. With a groove density of 12.6/cm and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm K have been measured, along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm K at 20 W/sq cm was measured with a 37.8/cm hybrid surface.
Study of a high performance evaporative heat transfer surface
NASA Technical Reports Server (NTRS)
Saaski, E. W.; Hamasaki, R. H.
1977-01-01
An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.
Heat transfer in thin, compact heat exchangers with circular, rectangular, or pin-fin flow passages
D. A. Olson
1992-01-01
The authors have measured heat transfer and pressure drop of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up
Heat transfer in thin, compact heat exchangers with circular, rectangular, or pin-fin flow passages
D. A. Olson
1992-01-01
Heat transfer and pressure drop have been measured of three thin, compact heat exchangers in helium gas at 3.5 MPa and higher, with Reynolds numbers of 450 to 36,000. The flow geometries for the three heat exchanger specimens were: circular tube, rectangular channel, and staggered pin fin with tapered pins. The specimens were heated radiatively at heat fluxes up to
Energy Efficient Design of a Waste Heat Rejection System
Mehta, P.
2000-01-01
In small and medium sized manufacturing facilities, several situations exist where sources of waste heat and sinks needing heat transfer coexist. Examples of waste heat include but are not limited to: drained hot water streams from water cooled...
Heat Sponge: A Concept for Mass-Efficient Heat Storage
NASA Technical Reports Server (NTRS)
Splinter, Scott C.; Blosser, Max L.; Gifford, Andrew R.
2008-01-01
The heat sponge is a device for mass-efficient storage of heat. It was developed to be incorporated in the substructure of a re-entry vehicle to reduce thermal- protection-system requirements. The heat sponge consists of a liquid/vapor mixture contained within a number of miniature pressure vessels that can be embedded within a variety of different types of structures. As temperature is increased, pressure in the miniature pressure vessels also increases so that heat absorbed through vaporization of the liquid is spread over a relatively large temperature range. Using water as a working fluid, the heat-storage capacity of the liquid/vapor mixture is many times higher than that of typical structural materials and is well above that of common phase change materials over a temperature range of 200 F to 700 F. The use of pure ammonia as the working fluid provides a range of application between 432 deg R and 730 deg R, or the use of the more practical water-ammonia solution provides a range of application between 432 deg R and 1160 deg R or in between that of water and pure ammonia. Prototype heat sponges were fabricated and characterized. These heat sponges consisted of 1.0-inch-diameter, hollow, stainless-steel spheres with a wall thickness of 0.020 inches which had varying percentages of their interior volumes filled with water and a water-ammonia solution. An apparatus to measure the heat stored in these prototype heat sponges was designed, fabricated, and verified. The heat-storage capacity calculated from measured temperature histories is compared to numerical predictions.
Ultrahigh heat transfer enhancement using nano-porous layer
NASA Astrophysics Data System (ADS)
Kunugi, Tomoaki; Muko, Katsumi; Shibahara, Masahiko
2004-03-01
Heat transfer enhancement is one of the key issues of saving energies and compact designs for mechanical and chemical devices and plants. We discover an ultrahigh convective heat transfer performance compared to the well-known heat transfer correlations caused by a nano-particle porous surface: the maximum increase of heat transfer coefficient was around 180%. This nano-particle porous layer can be formed on the substrate surface by an etching with some acids or alkalis including around 100 nm size nano-particles made from copper oxide, carbon nano-tube and aluminium oxide. Moreover, we have done some experiments using a co-current flow heat exchanger consisting of hot and cold water-channels and obtained an ultrahigh heat transfer performance: over 200% increase compared to the conventional correlation. On the other hand, in order to theoretically investigate effects of nano-particle porous layer structures on the surface energy transfer, the energy transfer from fluid to the heat transfer surface is calculated by a classical molecular dynamics method. Energy transfer to the surface from the fluid strongly depends on the surface structures in nanometre scale that affect the static structure and dynamic behaviours of fluid molecules in the vicinity of the surface.
Proceedings of HT2009 2009 ASME Summer Heat Transfer Conference
Guo, Zhixiong "James"
imaging [5-7]. The objective of hyperthermia treatment in cancer therapy is to raise the temperature, USA HT2009-88261 SIMULATION OF FOCUSED RADIATION PROPAGATION AND TRANSIENT HEAT TRANSFER IN TURBID-dependent radiation and conduction bio-heat transfer model. Ultrashort pulsed radiation transport in the cylindrical
A new model for nucleate boiling heat transfer
P. Stephan; J. Hammer
1994-01-01
A new model to calculate heat transfer coefficients in nucleate boiling is presented. Heat transfer and fluid flow around a single bubble are investigated taking into account the influence of meniscus curvature, adhesion forces and interfacial thermal resistance on the thermodynamic equilibrium at the gas-liquid interface. The model requires only bubble site densities and departure diameters. Further quantities except the
Heat transfer to impinging round jets with triangular tabs
N Gao; H Sun; D Ewing
2003-01-01
Experiments were performed to characterize the heat transfer enhancement produced by adding arrays of triangular tabs to the exit of turbulent round impinging jets issuing from a long pipe. For small nozzle-to-plate distances the local heat transfer was increased more than 25% in a series of distinct regions surrounding the impingement region. The largest increase in the average Nusselt number
Mechanical Engineering Laboratory of Heat and Mass Transfer
Diggavi, Suhas
of condensation heat transfer in vertical minichannels g g Motivation Two phase flow cooling, especially within the prediction methods. The local condensation heat transfer behavior of two new refrigerants(R236fa and R1234ze to be implemented in the power electronics system. Test facility Experimental results 1 y schematic diagram of test
Heat transfer in proteinwater interfaces Anders Lervik,ab
Kjelstrup, Signe
Heat transfer in proteinwater interfaces Anders Lervik,ab Fernando Bresme,*ac Signe Kjelstrup of the heat diffusion equation we compute the thermal conductivity and thermal diffusivity of the proteins by about 4 nm.4 It is expected that the energy transfer between these sites may involve the concerted
Heat transfer in gas-cooled annular channels
Vilemas, J.; Cesna, B.; Survila, V.; Zukauskas, A.; Hewitt, G.F.
1986-01-01
This book covers an industrial-scale study of heat transfer at high Reynolds numbers and large temperature differences. Local heat transfer and wall friction as a function of different physical properties of the fluid and surface ratios, for both steady-state and transient conditions, are presented. Design recommendations based on obtained correlations are also given.
Formulation of nanofluids for natural convective heat transfer applications
Dongsheng Wen; Yulong Ding
2005-01-01
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
Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces
Attinger, Daniel
, metallurgy, electronics cooling, and food processing. While flow boiling describes the boiling of liquidsBoiling 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
Reflective Coating on Fibrous Insulation for Reduced Heat Transfer
Derek D. Hass; B. Durga Prasad; David E. Glass; Karl E. Wiedemann
1997-01-01
Radiative heat transfer through fibrous insulation used in thermal protectionsystems (TPS) is significant at high temperatures (1200??C). Decreasing the radiative heattransfer through the fibrous insulation can thus have a major impact on the insulatingability of the TPS. Reflective coatings applied directly to the individual fibers in fibrousinsulation should decrease the radiative heat transfer leading to an insulation withdecreased effective thermal
Heat transfer in high-current thermal batteries
F. C. Kreiger
1992-01-01
Heat transfer studies at the Harry Diamond Laboratories are summarized and applied to a 100 A thermal battery that will be used for vehicular propulsion. The gas atmosphere in the thermal insulation is a major factor affecting the heat transfer. The remotely piloted vehicle (RPV) thermal battery was designed to serve as a silent energy source for a propeller-driven missile
Boiling helium heat transfer characteristics in narrow cooling channel
M. Nishi; T. Ando; T. Hiyama; T. Kato; S. Shimamoto
1983-01-01
For design of a stable superconducting magnet with pool cooling method, the size of the cooling channel is one of the important factors to determine its overall current density. The authors measured the steady state boiling helium heat transfer characteristics in a 600 mm long vertical cooling channel. The result shows that heat transfer characteristics in film boiling region do
Flow boiling heat transfer of refrigerant R21 in microchannel heat sink
V. V. Kuznetsov; A. S. Shamirzaev
2010-01-01
Boiling heat transfer in a refrigerant R 21 flow in a microchannel heat sink is studied. A stainless steel heat sink with\\u000a a length of 120 mm contains ten microchannels with a size of 640×2050 µm at cross-section with a wall roughness of 10 µm.\\u000a The local heat-transfer coefficient distribution along the heat sink length is obtained. The ranges of
Grantom, R. L.
1981-01-01
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...
Mixed convection heat transfer in concave and convex channels
Moukalled, F.; Doughan, A.; Acharya, S.
1997-07-01
Mixed convection heat transfer studies in the literature have been primarily confined to pipe and rectangular channel geometry's. In some applications, however, heat transfer in curved channels may be of interest (e.g., nozzle and diffuser shaped passages in HVAC systems, fume hoods, chimneys, bell-shaped or dome-shaped chemical reactors, etc.). A numerical investigation of laminar mixed convection heat transfer of air in concave and convex channels is presented. Six different channel aspects ratios (R/L = 1.04, 1.25, 2.5, 5, 10, and {infinity}) and five different values of Gr/Re{sup 2} (Gr/Re{sup 2} = 0, 0.1, 1, 3, 5) are considered. Results are displayed in terms of streamline and isotherm plots, velocity and temperature profiles, and local and average Nusselt number estimates. Numerical predictions reveal that compared to straight channels of equal height, concave channels of low aspect ratio have lower heat transfer at relatively low values of Gr/Re{sup 2} and higher heat transfer at high values of Gr/Re{sup 2}. When compared to straight channels of equal heated length, concave channels are always found to have lower heat transfer and for all values of Gr/Re{sup 2}. On the other hand, predictions for convex channels revealed enhancement in heat transfer compared to straight channels of equal height and/or equal heated length for all values of Gr/Re{sup 2}.
NASA Astrophysics Data System (ADS)
Semena, M. G.; Zaripov, V. K.; Gershuni, A. N.
1982-09-01
Experimental results from the study of heat transfer in radially configured heat pipes which feature metal fiber capillary structures are discussed. Examinations were made with water, ethanol, methanol, acetone, ammonia, Freon, and nitrogen as heat transfer fluids. The heat pipes were equipped with cylindrical and flat casings, and were fitted with copper, stainless steel, and nickel capillary structures. Quantitative results are presented for the heat transfer coefficients for a smooth heating surface in a large volume, for surfaces sintered with the metal fiber structures with low porosity, and with the same surface with high porosity. The heat flux density increased with decreasing porosity, which formed centers where bubble boiling could occur.
Effects of bending on heat transfer performance of axial micro-grooved heat pipe
Le-lun Jiang; Yong Tang; Min-qiang Pan
2011-01-01
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
Quantitative Global Heat Transfer in a Mach-6 Quiet Tunnel
NASA Technical Reports Server (NTRS)
Sullivan, John P.; Schneider, Steven P.; Liu, Tianshu; Rubal, Justin; Ward, Chris; Dussling, Joseph; Rice, Cody; Foley, Ryan; Cai, Zeimin; Wang, Bo; Woodiga, Sudesh
2012-01-01
This project developed quantitative methods for obtaining heat transfer from temperature sensitive paint (TSP) measurements in the Mach-6 quiet tunnel at Purdue, which is a Ludwieg tube with a downstream valve, moderately-short flow duration and low levels of heat transfer. Previous difficulties with inferring heat transfer from TSP in the Mach-6 quiet tunnel were traced to (1) the large transient heat transfer that occurs during the unusually long tunnel startup and shutdown, (2) the non-uniform thickness of the insulating coating, (3) inconsistencies and imperfections in the painting process and (4) the low levels of heat transfer observed on slender models at typical stagnation temperatures near 430K. Repeated measurements were conducted on 7 degree-half-angle sharp circular cones at zero angle of attack in order to evaluate the techniques, isolate the problems and identify solutions. An attempt at developing a two-color TSP method is also summarized.
Modelling of Heat Transfer in Single Crystal Growth
Zhmakin, Alexander I
2014-01-01
An attempt is made to review the heat transfer and the related problems encountered in the simulation of single crystal growth. The peculiarities of conductive, convective and radiative heat transfer in the different melt, solution, and vapour growth methods are discussed. The importance of the adequate description of the optical crystal properties (semitransparency, specular reflecting surfaces) and their effect on the heat transfer is stresses. Treatment of the unknown phase boundary fluid/crystal as well as problems related to the assessment of the quality of the grown crystals (composition, thermal stresses, point defects, disclocations etc.) and their coupling to the heat transfer/fluid flow problems is considered. Differences between the crystal growth simulation codes intended for the research and for the industrial applications are indicated. The problems of the code verification and validation are discussed; a brief review of the experimental techniques for the study of heat transfer and flow structu...
Condensation Heat Transfer Performance of Nano- Engineered Cu Surfaces
NASA Astrophysics Data System (ADS)
Kim, Hyunsik; Nam, Youngsuk
2014-11-01
We investigated condensate mobility and resulting heat transfer performance on Cu based water repellent surfaces including hydrophobic, superhydrophobic and oil-infused surfaces. We observed the transient microscale condensation behaviours up to 3 hours with controlling the supersaturation level at 1.64. We experimentally characterized the nucleation density, droplet size distribution and growth rate, and then incorporated them into the developed condensation heat transfer model to compare the condensation heat transfer performance of each surface. Due to the spontaneous coalescence induced jumping, superhydrophobic surface can maintain the high heat transfer performance while other surfaces show a gradual decrease in heat transfer performance due to the increase in the thermal resistance across the growing droplets. We also quantified each thermal resistance values from the vapor to the surface through the droplets to find out the relative importance of each thermal resistance term.
Experimental study of heat transfer to falling liquid films
NASA Astrophysics Data System (ADS)
Fagerholm, N. E.; Kivioja, K.; Ghazanfari, A. R.; Jaervinen, E.
1985-12-01
This project was initiated in order to obtain more knowledge about thermal design of falling film heat exchangers and to find methods to improve heat transfer in film flow. A short literature survey of film flow characteristics and heat transfer is presented. An experimental apparatus designed and built for studying falling film evaporation is described. The first experiments were made with smooth Cu tube 25/22 mm and refrigerant R114 as evaporating liquid. A significant amount of droplet entrainment was observed during the tests. The measured average heat transfer coefficient varied from 1000 to 1800 W/m K when Re=1300 to 11000 respectively and when the transfer mode is surface evaporation. This could be predicted accurately with the experimental correlation of Chun and Seban. When nucleate boiling is dominant the heat transfer could be predicted well with pool boiling correlation of VDI-84.
Heat Transfer Performance of Absorber of Absorption Refrigerating Machine
NASA Astrophysics Data System (ADS)
Kunugi, Yoshifumi; Ouchi, Tomihisa; Usui, Sanpei; Fukuda, Tamio
Experimental studies on heat transfer performance of absorber for lithium bromide-water absorption refrigerating machine are presented in this paper. Experimental apparatus for 35 kW evaporator and absorber, and outer grooved tubes are used. As a result, over-al1 coefficient of heat transmission of absorber has a maximum value, in the case of heat transfer area ratio of absorber to evaporator, is about 0.8. Heat transfer rate of absorber is increased by 60% by using the outer grooved tube compared with the plane surfaced tube.
Heat and mass transfer in impinging jet streams
Sheyman, V.; Rathod, M.S. [Wayne State Univ., Detroit, MI (United States). Division of Engineering Technology; Meltser, V.L. [Heat and Mass Transfer Inst., Minsk (Belarus)
1995-12-31
This paper considers high intensity heat and mass transfer of solid particulates in an impinging jet streams of mixture of solids and heat carrier. The theoretical analysis of the reversal jet streams is compared with the experimental data. The results of heat and mass transfer experimental research of drying solid particulates are presented and discussed. It is shown that the high intensity of the internal and external heat and mass transfer processes follow from the specifics of the process, namely frequent oscillation of the jet streams.
Heat transfer in micro region of a rotating miniature heat pipe
Lanchao Lin; Amir Faghri
1999-01-01
A theoretical model is established that describes the evaporating film flow in a rotating miniature heat pipe with an axial triangular grooved internal surface. The theory of thin liquid film vaporization heat transfer is used to predict the evaporation heat transfer in the micro region. The effects of disjoining pressure, surface tension and centrifugal force on the flow are discussed.
Hosny Z. Abou-Ziyan
2004-01-01
This paper presents the results of an experimental investigation of heat transfer from the heated bottom side of tee cross-section ducts to an internally flowing fluid. The idea of this work is derived from the cooling of critical areas in the cylinder heads of internal combustion engines. Fully developed single phase forced convection and subcooled flow boiling heat transfer data
Single phase forced convection heat transfer in microgeometries -- A review
Bailey, D.K.; Ameel, T.A.; Warrington, R.O. Jr.; Savoie, T.I. [Louisiana Technological Univ., Ruston, LA (United States). Inst. for Micromanufacturing
1995-12-31
As the field of microfluids and heat transfer continues to grow, it is becoming increasingly important to understand the mechanisms and fundamental differences involved with heat transfer and fluid flow in microgeometries. This paper presents a summary of the research in the area of single phase convective heat transfer in microtubes and microchannels with applications in devices such as micro heat pumps and heat exchangers that may be used for electronic equipment cooling, in biomedical applications, and potentially for macroscale cooling systems through many parallel configurations. While conclusive evidence is lacking, it appears that the friction factor for flow in microgeometries is less than that predicted by macroscale theory while heat transfer coefficients may increase relative to traditional correlations. The Reynolds analogy also appears to be invalid when the scale of the flow passages is on the order of 100 pm or less.
Research on Convective Heat Transfer and Mass Transfer of the Evaporator in Micro/Mini-Channel
Su, J.; Li, J.
2006-01-01
With the development of science and technology, various heating and cooling equipment have a development trend of micromation. Micro-fabrication processes make it possible to conduct research on condensation heat transfer in micro-channels. Based...
Research on Convective Heat Transfer and Mass Transfer of the Evaporator in Micro/Mini-Channel
Su, J.; Li, J.
2006-01-01
With the development of science and technology, various heating and cooling equipment have a development trend of micromation. Micro-fabrication processes make it possible to conduct research on condensation heat transfer in micro-channels. Based...
Boiling Heat Transfer for Freon R21 in Rectangular Minichannel
V. V. Kuznetsov; A. S. Shamirzaev
2007-01-01
In this paper, we study the boiling heat transfer of upward flow of R21 in a vertical mini-channel with a size of 1.6 × 6.3 mm. The heat transfer coefficient was measured as a function of heat flux for a wide range of vapor quality and for two levels of mass flow rate, G = 215 kg\\/ms and G =
G. V. Konyukhov; A. A. Koroteev; V. V. Novomlinskii; B. N. Baushev
1998-01-01
Modeling of radiative heat transfer and mass transfer in drop-flow-based heat exchangers for spacecraft is considered. A Monte\\u000a Carlo-based numerical model is presented. Results obtained with the aid of the model are analyzed and compared with existing\\u000a data.
Enhanced heat transfer in the entrance region of microchannels
Gui, F.; Scaringe, R.P. [Mainstream Engineering Corp., Rockledge, FL (United States)
1995-12-31
A detailed heat transfer analysis has been performed on the data from previously-reported experiments (Rahman and Gui 1993) to investigate the characteristics of high-heat-flux (10{sup 6} W/m{sup 2}) microchannel cooling in electronic chips. The use of microchannel directly etched into a silicon wafer has shortened the cooling path and improved the performance by significantly minimizing the thickness of the heat transfer layer. Experimental convective heat transfer coefficients (up to 45 kW/m{sup 2} K) for low temperature single-phase flow was an order of magnitude higher than conventional heat transfer coefficients; and reached the level of two-phase boiling heat transfer. The flow and heat transfer modes and their transitions in the experiments were investigated. The influence of the microchannel passage geometry, fluid property variation, and the fluid flow mode on the local Nusselt number in the entrance region of the microchannel has been analyzed. The analysis indicates that the significant enhancement obtained in microchannel cooling results from four key aspects: a thinner thermal boundary layer, entry effects, the roughness of the channel, and strong pre-existing turbulence at the inlet. The preexisting turbulence delayed the formation of the thermal boundaries, thereby increasing the entry effects on heat transfer. The critical Re shifted from 2,300 to 1,400 in microchannels, possibly due to the wall roughness which does not affect the Re{sub c} otherwise in normal size tubes.
Heat Transfer Research 44(1), 130 (2013) ENTROPY GENERATION ANALYSIS
Zhang, Yuwen
2013-01-01
Heat Transfer Research 44(1), 130 (2013) ENTROPY GENERATION ANALYSIS FOR A PULSATING HEATvapor phase 2 Kim, Zhang, & Choi Heat Transfer Research NOMENCLATURE A area, m2 Qin,s,l sensible heat transfer into cp specific heat at constant liquid slug, W pressure, Qout,s,l sensible heat transfer out cv specific
Experimental and theoretical studies of convective heat transfer in a cylindrical porous medium
M. R. Izadpanah; H. Müller-Steinhagen; M. Jamialahmadi
1998-01-01
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
Enhanced two phase flow in heat transfer systems
Tegrotenhuis, Ward E; Humble, Paul H; Lavender, Curt A; Caldwell, Dustin D
2013-12-03
A family of structures and designs for use in devices such as heat exchangers so as to allow for enhanced performance in heat exchangers smaller and lighter weight than other existing devices. These structures provide flow paths for liquid and vapor and are generally open. In some embodiments of the invention, these structures can also provide secondary heat transfer as well. In an evaporate heat exchanger, the inclusion of these structures and devices enhance the heat transfer coefficient of the evaporation phase change process with comparable or lower pressure drop.
Dual circuit embossed sheet heat transfer panel
Morgan, G.D.
1984-02-21
A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet. 6 figs.
Convective heat transfer measurements of plants in a wind tunnel
A. Kumar; N. Barthakur
1971-01-01
Heat transfer was studied between intact leaves of various sizes and shapes in vivo under free and forced air conditions. Use of a wind tunnel and a microwave transmitter to heat the leaves facilitated measurements of convective, along with radiative and evaporative, heat losses from plant leaves. Knowledge of input energy, analysis of cooling curves, and established formulae, respectively, formed
Heat transfer mechanisms in thin film with laser heat source
Shuichi Torii; Wen-Jei Yang
2005-01-01
The present study deals with the effect of laser radiation on the propagation phenomenon of a thermal wave in a very thin film subjected to a symmetrical heating on both sides. Pulsating laser heating is modelled as an internal heat source with various time characteristics. The Cattaneo heat flux law together with the energy conservation equation is solved by a
Heat transfer in the flow-through part of axial compressors
NASA Astrophysics Data System (ADS)
Lokaj, V. I.; Karimova, A. G.; Shigin, L. B.
1993-10-01
If no valid data on the temperature state of heat stressed units are available, it is impossible to assess the strength reserves of pieces. Also, it is impossible, in this case, to develop efficient cooling systems and systems for controlling radial clearances. That's why the paper presents experimental results, showing heat transfer on the surface of the blade profile and on the end surfaces of the interblade channel of flat compressor lattices. Dependences, considering the effect of geometric and regime parameters on heat transfer, have been obtained.
Nanoscale heat transfer and thermoelectrics for alternative energy
NASA Astrophysics Data System (ADS)
Robinson, Richard
2011-03-01
In the area of alternative energy, thermoelectrics have experienced an unprecedented growth in popularity because of their ability to convert waste heat into electricity. Wired in reverse, thermoelectrics can act as refrigeration devices, where they are promising because they are small in size and lightweight, have no moving parts, and have rapid on/off cycles. However, due to their low efficiencies bulk thermoelectrics have historically been a niche market. Only in the last decade has thermoelectric efficiency exceeded ~ 20 % due to fabrication of nanostructured materials. Nanoscale materials have this advantage because electronic and acoustic confinement effects can greatly increase thermoelectric efficiency beyond bulk values. In this talk, I will introduce our work in the area of nanoscale heat transfer with the goal of more efficient thermoelectrics. I will discuss our experiments and methods to study acoustic confinement in nanostructures and present some of our new nanostructured thermoelectric materials. To study acoustic confinement we are building a nanoscale phonon spectrometer. The instrument can excite phonon modes in nanostructures in the ~ 100 s of GHz. Ballistic phonons from the generator are used to probe acoustic confinement and surface scattering effects. Transmission studies using this device will help optimize materials and morphologies for more efficient nanomaterial-based thermoelectrics. For materials, our group has synthesized nano-layer superlattices of Na x Co O2 . Sodium cobaltate was recently discovered to have a high Seebeck coeficent and is being studied as an oxide thermoelectric material. The thickness of our nano-layers ranges from 5 nm to 300 nm while the lengths can be varied between 10 ? m and 4 mm. Typical aspect ratios are 40 nm: 4 mm, or 1:100,000. Thermoelectric characterization of samples with tilted multiple-grains along the measurement axis indicate a thermoelectric efficiency on par with current polycrystalline samples. Due to phonon confinement in nano-structures, it is expected that the thermoelectric efficiency of these sheets will be much higher than that of single crystalline Na 0.7 Co O2 , when the nanosheets have single grains along the heat transport path. This work is supported by KAUST (KUS-C1-018-02), NSF (DMR 0520404), and the DOE (DE-SC0001086).
Nano-engineering the boiling surface for optimal heat transfer rate and critical heat flux
Phillips, Bren Andrew
2011-01-01
The effects on pool boiling characteristics such as critical heat flux and the heat transfer coefficient of different surface characteristics such as surface wettability, roughness, morphology, and porosity are not well ...
Gaskill, Travis
2012-02-14
The present study has focused on the use of coil heat exchangers (CHEs) with microencapsulated phase change material (MPCM) slurries to understand if CHEs can yield greater rates of heat transfer. An experimental study was conducted using a...
The deterioration in heat transfer to fluids at supercritical pressure and high heat fluxes
Shiralkar, B. S.
1968-01-01
At slightly supercritical pressure and in the neighborhood of the pseudo-critical temperature (defined as the temperature corresponding to the peak in specific heat at the operating pressure), the heat transfer coefficient ...
Bimonte, Giuseppe
We present a detailed derivation of heat radiation, heat transfer, and (Casimir) interactions for N arbitrary objects in the framework of fluctuational electrodynamics in thermal nonequilibrium. The results can be expressed ...
Tetreault-Friend, Melanie
2014-01-01
Predicting the conditions of critical heat flux (CHF) is of considerable importance for safety and economic reasons in heat transfer units, such as in nuclear power plants. It is greatly advantageous to increase this thermal ...
NASA Astrophysics Data System (ADS)
Stein, R. P.
Aspects of direct contact heat transfer are considered along with transport phenomena in fusion reactors, enhanced nucleate boiling, flow boiling, heat transfer in non-Newtonian systems, two-phase systems, heat transfer in fossil fuel conversion systems, process heat transfer, thermal and hydraulic behavior in rod and tube bundles, and two-phase systems in rod and tube bundles. Attention is also given to solar energy heat transfer, heat transfer in fluidized beds, and fire and combustion fundamentals, taking into account thermal stress oscillations induced by dynamic instabilities in radiation-heated boiler tubes, convection losses from a cavity receiver, numerical solutions of turbulent models for flow over a flat plate with angle of attack, and the heat transfer from smooth horizontal tubes immersed in gas fluidized beds. A description is provided of aspects of turbulent combustion modelling, the exhaust gas emission from a swirl stabilized combustor, the analytical solution for diffusion in the core of a droplet with internal circulation, and the radiant ignition of a thin combustible solid.
Numerical Studies of Heat Transfer in Rarefied Gases at Head-Disk Interface
NASA Astrophysics Data System (ADS)
Zhou, Weidong; Liu, Bo; Yu, Shengkai; Hua, Wei
2009-10-01
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.
Simulation Approach for Microscale Noncontinuum Gas-Phase Heat Transfer
NASA Astrophysics Data System (ADS)
Torczynski, J. R.; Gallis, M. A.
2008-11-01
In microscale thermal actuators, gas-phase heat transfer from the heated beams to the adjacent unheated substrate is often the main energy-loss mechanism. Since the beam-substrate gap is comparable to the molecular mean free path, noncontinuum gas effects are important. A simulation approach is presented in which gas-phase heat transfer is described by Fourier's law in the bulk gas and by a wall boundary condition that equates the normal heat flux to the product of the gas-solid temperature difference and a heat transfer coefficient. The dimensionless parameters in this heat transfer coefficient are determined by comparison to Direct Simulation Monte Carlo (DSMC) results for heat transfer from beams of rectangular cross section to the substrate at free-molecular to near-continuum gas pressures. This simulation approach produces reasonably accurate gas-phase heat-transfer results for wide ranges of beam geometries and gas pressures. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Boiling heat transfer in a hydrofoil-based micro pin fin heat sink
Ali Ko?ar; Yoav Peles
2007-01-01
Flow boiling of R-123 in a hydrofoil-based micro pin fin heat sink was investigated. Average two-phase heat transfer coefficients were obtained over effective heat fluxes ranging from 19 to 312W\\/cm2 and mass fluxes from 976 to 2349kg\\/m2s. The paper presents a flow map, which divides the data into three flow pattern regions: bubbly, wavy intermittent and spray-annular flows. Heat transfer
Thermodynamic efficiency of pumped heat electricity storage.
Thess, André
2013-09-13
Pumped heat electricity storage (PHES) has been recently suggested as a potential solution to the large-scale energy storage problem. PHES requires neither underground caverns as compressed air energy storage (CAES) nor kilometer-sized water reservoirs like pumped hydrostorage and can therefore be constructed anywhere in the world. However, since no large PHES system exists yet, and theoretical predictions are scarce, the efficiency of such systems is unknown. Here we formulate a simple thermodynamic model that predicts the efficiency of PHES as a function of the temperature of the thermal energy storage at maximum output power. The resulting equation is free of adjustable parameters and nearly as simple as the well-known Carnot formula. Our theory predicts that for storage temperatures above 400?°C PHES has a higher efficiency than existing CAES and that PHES can even compete with the efficiencies predicted for advanced-adiabatic CAES. PMID:24074066
Yuichi Hamada; Wataru Ohtsu; Jun Fukai
2003-01-01
The effects of carbon-fiber chips and carbon brushes as additives on the thermal conductivity enhancement of phase change materials (PCMs) using in latent heat thermal energy storage are investigated experimentally and numerically by considering the wall effect of the additives. The carbon-fiber chips are effective for improving the heat transfer rate in PCMs. However, the thermal resistance near the heat
Heat transfer mechanisms during short-pulse laser heating of metals
T. Q. Qiu; C. L. Tien
1993-01-01
This work studies heat transfer mechanisms during ultrafast laser heating of metals from a microscopic point of view. The heating process is composed of three processes: the deposition of radiation energy on electrons, the transport of energy by electrons, and the heating of the material lattice through electron-lattice interactions. The Boltzmann transport equation is used to model the transport of
Gaskill, Travis
2012-02-14
sides, respectively. The NTU-effectiveness relationship of the CHE when MPCM fluid is used approaches that of a heat exchanger with a heat capacity ratio of zero. The heat transfer results have shown that when using a MPCM slurry, an increase in heat...
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.
de Jong, J A; Wijnant, Y H; de Boer, A
2014-03-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer. PMID:24606258
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 2012-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 2013-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 2014-10-01 false Heat transfer fluids: compatibility with cargo. 153.436...Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one...
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 2011-10-01 2011-10-01 false Heat transfer fluids: compatibility with cargo...Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo...
46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 2010-10-01 2010-10-01 false Heat transfer fluids: compatibility with cargo...Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo...
Radiative heat transfer in low-dimensional systems -- microscopic mode
NASA Astrophysics Data System (ADS)
Woods, Lilia; Phan, Anh; Drosdoff, David
2013-03-01
Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Radiative heat transfer between objects can increase dramatically at sub-wavelength scales. Exploring ways to modulate such transport between nano-systems is a key issue from fundamental and applied points of view. We advance the theoretical understanding of radiative heat transfer between nano-objects by introducing a microscopic model, which takes into account the individual atoms and their atomic polarizabilities. This approach is especially useful to investigate nano-objects with various geometries and give a detailed description of the heat transfer distribution. We employ this model to study the heat exchange in graphene nanoribbon/substrate systems. Our results for the distance separations, substrates, and presence of extended or localized defects enable making predictions for tailoring the radiative heat transfer at the nanoscale. Financial support from the Department of Energy under Contract No. DE-FG02-06ER46297 is acknowledged.
A review on boiling heat transfer enhancement with nanofluids
2011-01-01
There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794
Heat Transfer and Cooling Techniques at Low Temperature
Baudouy, B
2014-01-01
The first part of this chapter gives an introduction to heat transfer and cooling techniques at low temperature. We review the fundamental laws of heat transfer (conduction, convection and radiation) and give useful data specific to cryogenic conditions (thermal contact resistance, total emissivity of materials and heat transfer correlation in forced or boiling flow for example) used in the design of cooling systems. In the second part, we review the main cooling techniques at low temperature, with or without cryogen, from the simplest ones (bath cooling) to the ones involving the use of cryocoolers without forgetting the cooling flow techniques.
Experiments on heat transfer in a cryogenic engine thrust chamber
NASA Astrophysics Data System (ADS)
Sugathan, N.; Srinivasan, K.; Srinivasa Murthy, S.
1993-04-01
Tests are conducted on a cryogenic engine using liquid oxygen as oxidizer and gaseous hydrogen as fuel with water as a coolant. The coolant flow passage of the thrust chamber is of milled channel configuration. Measured heat transfer results compare well with those predicted by a thermal analysis using the standard Bartz correlation and the Hess and Kunz correlation for hot gas side and coolant side heat transfer coefficients, respectively. This confirms the conclusions of a recent theoretical study by the authors in which a comparison of various heat transfer correlations was made.
An Analysis of Efficiency Improvements in Residential Sized Heat Pumps, Final Report, May 1986
O'Neal, D. L.; Murphy, W. E.
1985-01-01
to the latter ORNL compressor model discussed above, but is more fundamental. It computes compression efficiencies from polytropic relationships. It also requires detailed motor performance characteristics that are not readily available. The NBS model cannot... of transfer units (NTU) is computed for the dry parts of the heat exchangers. A modified NTU form is used for the portions producing condensation. Heat transfer coefficients are calculated with existing correlations[3,4,5]. Because of its simplicity, the ORNL...
Takeishi, K; Aoki, S
2001-05-01
This paper deals with the contribution of heat transfer to increase the turbine inlet temperature of industrial gas turbines in order to attain efficient and environmentally benign engines. High efficiency film cooling, in the form of shaped film cooling and full coverage film cooling, is one of the most important cooling technologies. Corresponding heat transfer tests to optimize the film cooling effectiveness are shown and discussed in this first part of the contribution. PMID:11460641
Modeling of Heat Transfer in Geothermal Heat Exchangers
Cui, P.; Man, Y.; Fang, Z.
2006-01-01
Ground-coupled heat pump (GCHP) systems have been gaining increasing popularity for space conditioning in residential and commercial buildings. The geothermal heat exchanger (GHE) is devised for extraction or injection of thermal energy from...
Modeling of Heat Transfer in Geothermal Heat Exchangers
Cui, P.; Man, Y.; Fang, Z.
2006-01-01
Ground-coupled heat pump (GCHP) systems have been gaining increasing popularity for space conditioning in residential and commercial buildings. The geothermal heat exchanger (GHE) is devised for extraction or injection of thermal energy from...
Heat transfer performance of axially grooved heat pipes
Tetsurou Ogushi; Gorou Yamanaka
1987-01-01
Experiments and analysis of the heat transport capability of axially grooved heat pipes are described. The heat pipes were made of aluminum axially grooved extruded pipes and the working fluid was R11. The effects of fluid inventory and inclination angle on the capillary pumping limit were investigated. A theoretical model was developed to predict the temperature rise in the evaporator
Fourier analysis of conductive heat transfer for glazed roofing materials
NASA Astrophysics Data System (ADS)
Roslan, Nurhana Lyana; Bahaman, Nurfaradila; Almanan, Raja Noorliyana Raja; Ismail, Razidah; Zakaria, Nor Zaini
2014-07-01
For low-rise buildings, roof is the most exposed surface to solar radiation. The main mode of heat transfer from outdoor via the roof is conduction. The rate of heat transfer and the thermal impact is dependent on the thermophysical properties of roofing materials. Thus, it is important to analyze the heat distribution for the various types of roofing materials. The objectives of this paper are to obtain the Fourier series for the conductive heat transfer for two types of glazed roofing materials, namely polycarbonate and polyfilled, and also to determine the relationship between the ambient temperature and the conductive heat transfer for these materials. Ambient and surface temperature data were collected from an empirical field investigation in the campus of Universiti Teknologi MARA Shah Alam. The roofing materials were installed on free-standing structures in natural ventilation. Since the temperature data are generally periodic, Fourier series and numerical harmonic analysis are applied. Based on the 24-point harmonic analysis, the eleventh order harmonics is found to generate an adequate Fourier series expansion for both glazed roofing materials. In addition, there exists a linear relationship between the ambient temperature and the conductive heat transfer for both glazed roofing materials. Based on the gradient of the graphs, lower heat transfer is indicated through polyfilled. Thus polyfilled would have a lower thermal impact compared to polycarbonate.
Percolation induced heat transfer in deep unsaturated zones
Lu, N.; LeCain, G.D.
2003-01-01
Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997-1998 El Ni??no precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997-1998 El Ni??no precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.
Heat transfer with very high free-stream turbulence and heat transfer with streamwise vortices
NASA Technical Reports Server (NTRS)
Moffat, Robert J.; Maciejewski, Paul; Eaton, John K.; Pauley, Wayne
1987-01-01
Two experimental programs related to augmentation of heat transfer by complex flow characteristics are reviewed. The first program deals with very high turbulence (up to 63 percent) which was shown to result in Stanton numbers as much as five times the expected values. Results from a number of trials show that fixing the free stream velocity, x-Reynolds number, turbulence intensity and integral length scale does not fix the Stanton number. Two such cases were found in which the Stanton number of one was 40 percent larger than the other. Mean velocity and mean temperature profiles are presented, as well as profiles of turbulence intensity within the boundary layer. The second program deals with vortices originating at bluff bodies and traveling downstream embedded in the wall boundary layer. Velocity vector maps from the boundary layers and distributions of Stanton number on the wall are presented for three types of bodies: square, cylindrical and teardrop. The heat transfer and velocity maps do not show evidence of the expected horseshoe vortices but, instead, show a strong common flow up vortex pair. The fluid mechanic mechanism responsible for this secondary flow field has not yet been identified.
NASA Astrophysics Data System (ADS)
Borodulya, V. A.; Malevich, V. L.; Sinkevich, A. E.
2012-01-01
Based on the earlier developed model of calculation of the local parameters of heat and mass transfer in deep cooling of flue gases (a vapor-gas mixture) in a bundle of tubes of a condensation heat-utilization unit, the distribution of the parameters of a condensing vapor-gas mixture both along the length of the tubes and in the depth of the tube bundle in a crossflow under various cooling conditions corresponding to the working parameters of heat-utilization units at industrial thermoelectric plants (TEP) and in boiler houses has been obtained. A comparison of the calculated values of the heating efficiency of the indicated heat-utilization unit with the results of tests of the condensation heat-utilization unit at the Ul'yanovsk TEP-3 (Russia) has demonstrated their satisfactory agreement.
Heat transfer performance of a horizontal micro-grooved heat pipe using CuO nanofluid
NASA Astrophysics Data System (ADS)
Yang, Xue Fei; Liu, Zhen-Hua; Zhao, Jie
2008-03-01
An experiment was carried out to study the heat transfer performance of a horizontal micro-grooved heat pipe using CuO nanofluid as the working fluid. CuO nanofluid was a uniform suspension of CuO nanoparticles and deionized water. The average diameter of CuO nanoparticles was 50 nm. Mass concentration of CuO nanoparticles varied from 0.5 wt% to 2.0 wt%. The experiment was performed at three steady operating pressures of 7.45 kPa, 12.38 kPa and 19.97 kPa, respectively. Effects of the mass concentration of CuO nanoparticles and the operating pressure on both the heat transfer coefficients of the evaporator and the condenser sections, the critical heat flux (CHF) and the total heat resistance of the heat pipe were discussed. Experimental results show that CuO nanofluid can improve the thermal performance of the heat pipe and there is an optimal mass concentration which is estimated to be 1.0 wt% to achieve the maximum heat transfer enhancement. Operating pressure has apparent influences on both the heat transfer coefficients and the CHF of nanofluids. The minimum pressure corresponds to the maximum heat transfer enhancement. Under an operating pressure of 7.45 kPa, the heat transfer coefficients of the evaporator can be averagely enhanced by 46% and the CHF can be maximally enhanced by 30% when substituting CuO nanofluids for water.
M. Lacroix; T. Duong
1998-01-01
An experimental study was conducted in order to improve the heat transfer in a single layer latent heat thermal energy storage unit with embedded electrical heat sources. This study is motivated by the need to increase the performance of a more complex multi-layer latent heat thermal energy storage system used for smoothing daily electrical load profiles. In the first part,
Heat Transfer Performance for Evaporator of Absorption Refrigerating Machine
NASA Astrophysics Data System (ADS)
Kunugi, Yoshifumi; Usui, Sanpei; Ouchi, Tomihisa; Fukuda, Tamio
An experiment was conducted to check the heat transfer performance of evaporators with grooved tubes for absorption refrigerating machines. Heat transfer rate of evaporators were 35kW and 70kW. The range of the flow rate of the sprayed refrigerant per unit length ? was 1 to 50kg/hm, and the outside diameters of the tubes, D0 were 16 and 19.6 mm. About 80 to 100 % increase of heat transfer rate over a plane surfaced tube is obtained by using grooved tube. The heat transfer coefficients for evaporation are correlated by the equation ?E0=(?/D0)1/2. The substantial surface area, which is about three times larger than that of plane surfaced tube, is used in the above correlation.
Non-intrusive characterization of heat transfer fluid aerosol formation
Krishna, Kiran
2001-01-01
Heat transfer fluids are widely used in the chemical process industry and are available in a wide range of properties. These fluids are flammable above their flash points and can cause explosions. Though the possibility of aerosol explosions has...
Navier-Stokes analysis of turbine blade heat transfer
NASA Technical Reports Server (NTRS)
Boyle, R. J.
1990-01-01
Comparisons with experimental heat transfer and surface pressures were made for seven turbine vane and blade geometries using a quasi-three-dimensional thin-layer Navier-Stokes analysis. Comparisons are made for cases with both separated and unseparated flow over a range of Reynolds numbers and freestream turbulence intensities. The analysis used a modified Baldwin-Lomax turbulent eddy viscosity mode. Modifications were made to account for the effects of: (1) freestream turbulence on both transition and leading edge heat transfer; (2) strong favorable pressure gradients on relaminarization; and (3) variable turbulent Prandtl number heat transfer. In addition, the effect of heat transfer on the near wall model of Deissler is compared with the Van Driest model.
Heat transfer during film condensation of a liquid metal vapor
Sukhatme, S. P.
1964-01-01
The object of this investigation is to resolve the discrepancy between theory and experiment for the case of heat transfer durirnfilm condensation of liquid metal vapors. Experiments by previous investigators have yielded ...
Numerical Study of Flow and Heat Transfer in Rotating Microchannels
Roy, Pratanu
2014-10-07
Investigation of fluid flow and heat transfer in rotating microchannels is important for centrifugal microfluidics, which has emerged as an advanced technique in biomedical applications and chemical separations. The centrifugal force...
Influence of Infrared Radiation on Attic Heat Transfer
Katipamula, S.; Turner, W. D.; Murphy, W. E.; O'Neal, D. L.
1985-01-01
An experimental study concerned with different modes of heal transfer in fibrous and cellulose insulating material is presented. A series of experiments were conducted using an attic simulator to determine the effects of ventilation on attic heat...
The Advantages of Sealless Pumps in Heat Transfer Fluid Services
Smith, M. D.
The expectations for heat transfer fluid (HTF) system safety and reliability are continuing to increase. The challenges are many. Leaks produce vapors that ignite readily, fluid viscosity is very low, and many of the fluids react with oxygen...
Non-intrusive characterization of heat transfer fluid aerosol formation
Krishna, Kiran
2001-01-01
Heat transfer fluids are widely used in the chemical process industry and are available in a wide range of properties. These fluids are flammable above their flash points and can cause explosions. Though the possibility of aerosol explosions has...
Scalable graphene coatings for enhanced condensation heat transfer.
Preston, Daniel J; Mafra, Daniela L; Miljkovic, Nenad; Kong, Jing; Wang, Evelyn N
2015-05-13
Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating to promote dropwise condensation of water in industrial conditions with the potential for scalable application via CVD. PMID:25826223
Survey and evaluation of techniques to augment convective heat transfer
Bergles A. E.
1965-01-01
This report presents a survey and evaluation of the numerous techniques which have been shown to augment convective heat transfer. These techniques are: surface promoters, including roughness and treatment; displaced ...
Heat transfer intensification by increasing vapor flow rate in flat heat pipes
NASA Astrophysics Data System (ADS)
Sprinceana, Silviu; Mihai, Ioan; Beniuga, Marius; Suciu, Cornel
2015-02-01
Flat heat pipes have various technical applications, one of the most important being the cooling of electronic components[9]. Their continuous development is due to the fact that these devices permit heat transfer without external energetic contribution. The practical exploitation of flat heat pipes however is limited by the fact that dissipated power can only reach a few hundred watts. The present paper aims to advance a new method for the intensification of convective heat transfer. A centrifugal mini impeller, driven by a turntable which incorporates four permanent magnets was designed. These magnets are put in motion by another rotor, which in its turn includes two permanent magnets and is driven by a mini electrical motor. Rotation of the centrifugal blades generates speed and pressure increase of the cooling agent brought to vapor state within the flat micro heat pipe. It's well known that the liquid suffers biphasic transformations during heat transfer inside the heat pipe. Over the hotspot (the heat source being the electronic component) generated at one end of the heat pipe, convective heat transfer occurs, leading to sudden vaporization of the liquid. Pressures generated by newly formed vapors push them towards the opposite end of the flat heat pipe, where a finned mini heat sink is usually placed. The mini-heat exchanger is air-cooled, thus creating a cold spot, where vapors condensate. The proposed method contributes to vapor flow intensification by increasing their transport speed and thus leading to more intense cooling of the heat pipe.
Heat transfer enhancement resulting from induction electrohydrodynamic pumping
Margo, Bryan David
1992-01-01
HEAT TRANSFER ENHANCEMENT RESULTING FROM INDUCTION ELECTROHYDRODYNAMIC PUMPING A Thesis by BRYAN DAVID MARGO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1992 Major Subject: Mechanical Engineering HEAT TRANSFER ENHANCEMENT RESULTING FROM INDUCTION ELECTROHYDRODYNAMIC PUMPING A Thesis by BRYAN DAVID MARGO Approved as to style and content by: Jamal Seyed- Yagoobi (Chair...
Mpemba effect, Newton cooling law and heat transfer equation
Vladan Pankovic; Darko V. Kapor
2012-12-11
In this work we suggest a simple theoretical solution of the Mpemba effect in full agreement with known experimental data. This solution follows simply as an especial approximation (linearization) of the usual heat (transfer) equation, precisely linearization of the second derivation of the space part of the temperature function (as it is well-known Newton cooling law can be considered as the effective approximation of the heat (transfer) equation for constant space part of the temperature function).
Heat transfer near the contact line during boiling in microgravity
A. J. Robinson
2007-01-01
Although significant progress has been made, the mechanisms of heat transfer responsible for enhancement during nucleate boiling\\u000a are not fully understood. The primary barriers to a complete understanding of the heat transfer during boiling are due to\\u000a difficulties associated with performing rapid microscale measurements, ambiguity due to the interaction of previous and neighbouring\\u000a bubbles, uncertainty with regard to gravitational effects
HYDRODYNAMICS AND HEAT TRANSFER OF LIQUID FLUIDIZED BED SYSTEMS
M. JAMIALAHMADI; H. MÜLLER-STEINHAGEN
2000-01-01
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
Heat transfer enhancement resulting from induction electrohydrodynamic pumping
Margo, Bryan David
1992-01-01
HEAT TRANSFER ENHANCEMENT RESULTING FROM INDUCTION ELECTROHYDRODYNAMIC PUMPING A Thesis by BRYAN DAVID MARGO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1992 Major Subject: Mechanical Engineering HEAT TRANSFER ENHANCEMENT RESULTING FROM INDUCTION ELECTROHYDRODYNAMIC PUMPING A Thesis by BRYAN DAVID MARGO Approved as to style and content by: Jamal Seyed- Yagoobi (Chair...
Experimental investigation of oxide nanofluids laminar flow convective heat transfer
S. Zeinali Heris; S. Gh. Etemad; M. Nasr Esfahany
2006-01-01
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
Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids)
Yulong Ding; Hajar Alias; Dongsheng Wen; Richard A. Williams
2006-01-01
This paper is mainly concerned about the heat transfer behaviour of aqueous suspensions of multi-walled carbon nanotubes (CNT nanofluids) flowing through a horizontal tube. Significant enhancement of the convective heat transfer is observed and the enhancement depends on the flow conditions (Reynolds number, Re), CNT concentration and the pH, with the effect of pH smallest. Given other conditions, the enhancement
FATIGUE AND HEAT TRANSFER BEHAVIOUR OF SHOT ?El\\
V. S. Nadkarni
In the present investigation glass beads and zirconium oxide shots were used as media, to shot peen alluminium alloy specimens. Fatigue and boiling heat transfer behaviour of this alloy after . shot peenir-fg was studied. Out of 0.2N and 0.4N peening intensities, 0.4N gave higher improvement on fatigue strength and boiling heat transfer. Fatigue of butt welded aluminium joints were
Heat transfer of phase change materials (PCMs) in porous materials
C. Y. Zhao; D. Zhou; Z. G. Wu
2011-01-01
In this paper, the feasibility of using metal foams to enhance the heat transfer capability of phase change materials (PCMs)\\u000a in low- and high-temperature thermal energy storage systems was assessed. Heat transfer in solid\\/liquid phase change of porous\\u000a materials (metal foams and expanded graphite) at low and high temperatures was investigated. Organic commercial paraffin wax\\u000a and inorganic calcium chloride hydrate
Pool Boiling Heat Transfer in Dilute Water\\/Triethyleneglycol Solutions
S. A. Alavi Fazel; A. A. Safekordi; M. Jamialahmadi
2009-01-01
Boiling of water\\/triethyleneglycol (TEG) binary solution has a wide-ranging application in the gas processing engineering. Design, operation and optimization of the involved boilers require accurate prediction of boiling heat transfer coefficient between surface and solution. In this investigation, nucleate pool boiling heat transfer coefficient has been experimentally measured on a horizontal rod heater in water\\/TEG binary solutions in a wide
Theory of heat transfer from a surface covered with hair
Bejan, A. (Duke Univ., Durham, NC (USA))
1990-08-01
This paper describes the fundamental mechanisms of heat transfer through a surface covered with perpendicular hair strands of uniform density. An air flow parallel to the skin seeps through the spaces created between the hair strands. It is shown that the total heat transfer rate from the surface is due to two contributions: (i) the heat conducted through the hair strands, which act as fins, and (ii) the heat convected from the bare portions of the skin. When the air flow is slow enough to conform to the Darcy regime, there exists an optimum hair strand diameter for which the total heat transfer rate is minimum. The optimum diameter increases as the square root of the length swept by the air flow, that is the linear size of the body of the animal covered with hair.
Transient Heat Transfer in TCAP Coils
Steimke, J.L.
1999-03-09
The Thermal Cycling Absorption Process (TCAP) is used to separate isotopes of hydrogen. TCAP involves passing a stream of mixed hydrogen isotopes through palladium deposited on kieselguhr (Pd/k) while cycling the temperature of the Pd/k. Kieselguhr is a silica mineral also called diatomite. To aid in the design of a full scale facility, the Thermal Fluids Laboratory was used by the Chemical and Hydrogen Technology Section to compare the heat transfer properties of three different configurations of stainless steel coils containing kieselguhr and helium. Testing of coils containing Pd/k and hydrogen isotopes would have been more prototypical but would have been too expensive. Three stainless steel coils filled with kieselguhr were tested; one made from 2.0 inch diameter tubing, one made from 2.0 inch diameter tubing with foam copper embedded in the kieselguhr and one made from 1.25 inch diameter tubing. It was known prior to testing that increasing the tubing diameter from 1.25 inch to 2.0 inch would slow the rate of temperature change. The primary purpose of the testing was to measure to what extent the presence of copper foam in a 2.0 tubing coil would compensate for the effect of larger diameter. Each coil was connected to a pressure gage and the coil was evacuated and backfilled with helium gas. Helium was used instead of a mixture of hydrogen isotopes for reasons of safety. Each coil was quickly immersed in a stirred bath of ethylene glycol at a temperature of approximately 100 degrees Celsius. The coil pressure increased, reflecting the increase in average temperature of its contents. The pressure transient was recored as a function of time after immersion. Because of the actual process will use Pd/k instead of kieselguhr, additional tests were run to determine the differences in thermal properties between the two materials. The method was to position a thermocouple at the center of a hollow sphere and pack the sphere with Pd/k. The sphere was sealed, quickly submerged in a bath of boiling water and the temperature transient was recorded. There sphere was then opened, the Pd/k was replaced with kieselguhr and the transient was repeated. The response was a factor of 1.4 faster for Pd/k than for kieselguhr, implying a thermal diffusivity approximately 40 percent higher than for kieselguhr. Another implication is that the transient tests with the coils would have proceeded faster if the coils had been filled with Pd/k rather than kieselguhr.
NASA Astrophysics Data System (ADS)
Borovskoy, I. G.
2012-08-01
In a rigorous way, nonstationary problems of convective heat transfer should be treated in the conjugate statement where the condition of conjugation of the heat transfer medium and the channel wall temperature fields at their interface is used [1-3]. However, the difficulties, such as lack, as a rule, of complete data on the distribution of turbulent momentum and heat transfer coefficients over the channel cross-section, inherent restrictions of the existing models of turbulence, and the geometrical complexity of the solution domain, force researchers to consider an alternative approach where the heat transfer from the moving gas medium to the channel walls is described by the Newton-Richman law [4]. In this case, the local coefficient of convective heat transfer is determined by well-known criterial experimental relations, which are valid for a steady flow of the heat carrier [4, 5]. This simplified approach cannot be rigorously substantiated by invoking the quasistationarity principle or by introducing correction factors, and comparison of numerical and experimental data for evaluating the calculation accuracy is not always possible. An attempt is made to determine the domain of applicability of the simplified approach by evaluating the effect of the error that arises in the estimation of the heat transfer coefficient on the parameters of a convective flow.
Heat Transfer Modeling for Rigid High-Temperature Fibrous Insulation
NASA Technical Reports Server (NTRS)
Daryabeigi, Kamran; Cunnington, George R.; Knutson, Jeffrey R.
2012-01-01
Combined radiation and conduction heat transfer through a high-temperature, high-porosity, rigid multiple-fiber fibrous insulation was modeled using a thermal model previously used to model heat transfer in flexible single-fiber fibrous insulation. The rigid insulation studied was alumina enhanced thermal barrier (AETB) at densities between 130 and 260 kilograms per cubic meter. The model consists of using the diffusion approximation for radiation heat transfer, a semi-empirical solid conduction model, and a standard gas conduction model. The relevant parameters needed for the heat transfer model were estimated from steady-state thermal measurements in nitrogen gas at various temperatures and environmental pressures. The heat transfer modeling methodology was evaluated by comparison with standard thermal conductivity measurements, and steady-state thermal measurements in helium and carbon dioxide gases. The heat transfer model is applicable over the temperature range of 300 to 1360 K, pressure range of 0.133 to 101.3 x 10(exp 3) Pa, and over the insulation density range of 130 to 260 kilograms per cubic meter in various gaseous environments.
Heat transfer from a negatively buoyant wall jet
NASA Astrophysics Data System (ADS)
Kapoor, K.; Jaluria, Y.
1988-02-01
An experimental investigation is conducted on the heat transfer characteristics of a turbulent, negatively bouyant, 2-D wall jet. A jet of hot air is discharged adjacent to a water-cooled, isothermal surface in an extensive environment. The heat transfer to the surface from the elevated temperature jet is measured along the isothermal surface for several values of wall, jet and ambient temperatures. Wide ranges of Grashof (Gr) and Reynolds number (Re) are investigated. It is found that the total heat transfer rate to the isothermal vertical surface decreases with an increase in Gr/Re squared. The effect of the surface temperature T sub s on the downward penetration of the jet and on the heat transfer rate is also investigated. Correlating equations are derived from the experimental data to characterize the dependence of the surface heat transfer rate on the various physical parameters governing the transport process. An interesting flow circumstance arises when the surface temperature is higher than the ambient temperature but lower than the jet discharge temperature, since the downward wall jet flow interacts with an upward buoyancy induced flow adjacent to the wall. The heat transfer mechanisms are investigated in detail for this flow.
Revealing the complex conduction heat transfer mechanism of nanofluids
NASA Astrophysics Data System (ADS)
Sergis, A.; Hardalupas, Y.
2015-06-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects
Revealing the complex conduction heat transfer mechanism of nanofluids.
Sergis, A; Hardalupas, Y
2015-12-01
Nanofluids are two-phase mixtures consisting of small percentages of nanoparticles (sub 1-10 %vol) inside a carrier fluid. The typical size of nanoparticles is less than 100 nm. These fluids have been exhibiting experimentally a significant increase of thermal performance compared to the corresponding carrier fluids, which cannot be explained using the classical thermodynamic theory. This study deciphers the thermal heat transfer mechanism for the conductive heat transfer mode via a molecular dynamics simulation code. The current findings are the first of their kind and conflict with the proposed theories for heat transfer propagation through micron-sized slurries and pure matter. The authors provide evidence of a complex new type of heat transfer mechanism, which explains the observed abnormal heat transfer augmentation. The new mechanism appears to unite a number of popular speculations for the thermal heat transfer mechanism employed by nanofluids as predicted by the majority of the researchers of the field into a single one. The constituents of the increased diffusivity of the nanoparticle can be attributed to mismatching of the local temperature profiles between parts of the surface of the solid and the fluid resulting in increased local thermophoretic effects. These effects affect the region surrounding the solid manifesting interfacial layer phenomena (Kapitza resistance). In this region, the activity of the fluid and the interactions between the fluid and the nanoparticle are elevated. Isotropic increased nanoparticle mobility is manifested as enhanced Brownian motion and diffusion effects. PMID:26058515
Influence of high mainstream turbulence on leading edge heat transfer
Mehendale, A.B.; Han, J.C.; Ou, S. (Texas A and M Univ., College Station (United States))
1991-11-01
The influence of high mainstream turbulence on leading edge heat transfer was studied. High mainstream turbulence was produced by a bar grid (Tu = 3.3-5.1 percent), passive grid (Tu = 7.6-9.7 percent), and jet grid (Tu = 12.9-15.2 percent). Experiments were performed using a blunt body with a semicylinder leading edge and flat sidewalls. The mainstream Reynolds numbers based on leading edge diameter were 25,000, 40,000, and 100,000. Spanwise and streamwise distributions of local heat transfer coefficients on the leading edge and flat sidewall were obtained. The results indicate that the leading edge heat transfer increases significantly with increasing mainstream turbulence decay. Stagnation point heat transfer results for high turbulence intensity flows agree with the Lowery and Vachon correlation, but the overall heat transfer results for the leading edge quarter-cylinder region are higher than their overall correlation for the entire circular cylinder region. High mainstream turbulence tends not to shift the location of the separation-reattachment region. The reattachment heat transfer results are about the same regardless of mainstream turbulence levels and are much higher than the turbulent flat plate correlation.
Flow Film Boiling Heat Transfer in Water and Freon-113
NASA Astrophysics Data System (ADS)
Liu, Qiusheng; Shiotsu, Masahiro; Sakurai, Akira
Experimental apparatus and method for film boiling heat transfer measurement on a horizontal cylinder in forced flow of water and Freon-113 under pressurized and subcooled conditions were developed. The experiments of film boiling heat transfer from single horizontal cylinders with diameters ranging from 0.7 to 5mm in saturated and subcooled water and Freon-113 flowing upward perpendicular to the cylinders were carried out for the flow velocities ranging from 0 to 1m/s under system pressures ranging from 100 to 500kPa. Liquid subcoolings ranged from 0 to 50K, and the cylinder surface superheats were raised up to 800K for water and 400K for Freon-113. The film boiling heat transfer coefficients obtained were depended on surface superheats, flow velocities, liquid subcoolings, system pressures and cylinder diameters. The effects of these parameters were systematically investigated under wider ranges of experimental conditions. It was found that the heat transfer coefficients are higher for higher flow velocities, subcoolings, system pressures, and for smaller cylinder diameters. The observation results of film boiling phenomena were obtained by a high-speed video camera. A new correlation for subcooled flow film boiling heat transfer was derived by modifying authors' correlation for saturated flow film boiling heat transfer with authors' experimental data under wide subcooled conditions.
Heat Transfer and Flow Structure Evaluation of a Synthetic Jet Emanating from a Planar Heat Sink
NASA Astrophysics Data System (ADS)
Manning, Paul; Persoons, Tim; Murray, Darina
2014-07-01
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.
Heat transfer and pressure drop characteristics of a plate heat exchanger
Talik, Anthony Charles
1995-01-01
-transfer and pressure-drop data for a plate heat exchanger with water and a propylene-glycol/water (95, 5%/4. 5%) mixture as the working fluids. The plate heat exchanger was composed of 31 plates, each with a chevron angle of 30 degrees. All of the water data were... taken in the high Reynolds number range of 1450 to 11, 000 with heat-transfer rates of 6. 6 x 10' to 2. 2 x 10' W. All of the propylene-glycol data were taken in the low Reynolds number range of 10 to 720 with heat-transfer rates of 1. 1 x 10' to 6. 4...
Heat transfer and pressure drop characteristics of a plate heat exchanger
Talik, Anthony Charles
1995-01-01
-transfer and pressure-drop data for a plate heat exchanger with water and a propylene-glycol/water (95, 5%/4. 5%) mixture as the working fluids. The plate heat exchanger was composed of 31 plates, each with a chevron angle of 30 degrees. All of the water data were... taken in the high Reynolds number range of 1450 to 11, 000 with heat-transfer rates of 6. 6 x 10' to 2. 2 x 10' W. All of the propylene-glycol data were taken in the low Reynolds number range of 10 to 720 with heat-transfer rates of 1. 1 x 10' to 6. 4...
Application of the Chebyshev Method to Radiative Transfer Calculations for Laser Heated Targets
NASA Astrophysics Data System (ADS)
Bond, D. J.
1984-09-01
The Chebyshev semi-iterative method is used to accelerate the ? iteration for solving the radiative transfer equation for a spectral line. For conditions typical of laser heated targets this method may be more efficient than those used in present calculations.
Gas Turbine Blade Tip Heat Transfer and Cooling: A Literature Survey
Bengt Sunden; Gongnan Xie
2010-01-01
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
Modeling of heat transfer and fluid flow in keyhole mode welding
Rohit Rai
2008-01-01
In this work, computationally efficient numerical models have been developed for linear keyhole mode LBW and EBW processes. The models combine an energy balance based model for keyhole geometry calculation with a well tested 3D heat transfer and fluid flow model. For LBW, keyhole wall temperatures are assumed to be equal to the boiling point of the alloy at 1
The effect of turbulence–radiation interaction on radiative entropy generation and heat transfer
Miguel Caldas; Viriato Semião
2007-01-01
The analysis under the second law of thermodynamics is the gateway for optimisation in thermal equipments and systems. Through entropy minimisation techniques it is possible to increase the efficiency and overall performance of all kinds of thermal systems. Radiation, being the dominant mechanism of heat transfer in high-temperature systems, plays a determinant role in entropy generation within such equipments. Turbulence
The effects of topology upon fluid-flow and heat-transfer within cellular copper structures
Wadley, Haydn
, and the importance of achieving a quality (low thermal resistance) metal-to-metal bond (brazing or transient liquid The fluid-flow and heat-transfer features of copper cellular metal structures made by the transient liquid, they are not as structurally efficient as Thermally conductive ligaments 500¦Ìm (a) tetrahedral (b) pyramidal (c) 3D Kagom¨¦ (d
Characterization of Heat Transfer in Superhydrophobic Microchannels under Different Wetting Modes
NASA Astrophysics Data System (ADS)
Kim, Tae Jin; Hidrovo, Carlos
2013-11-01
Slip flow in microchannels is known to reduce the wall friction and consequently decreases the pumping power to drive the flow. One method to achieve slip flow is by trapping gas bubbles in the microchannel wall that is highly corrugated. While the use of rough walls to induce friction reduction is attractive, many microfluidic applications involve coupling of heat source in the microchip: the gas pockets may affect the heat transfer from the heaters to the microchannel walls. The purpose of this research is to explore the heat transfer efficiency of microchannels with corrugated surfaces heated from the side walls. The microchannel walls are modified to have an array of micro-trenches arranged transverse to the fluid flow along the axial direction, and a constant water pressure source is used to drive the flow and control the air pocket size. Advective heat transfer is then analyzed between the microchannel inlet and outlet using laser induced thermometry technique. Under identical flow rate conditions, it is expected that 1) the advective efficiency is affected by the degree of wetting of the corrugated walls and that 2) the advective heat transfer is lower for superhydrophobic microchannels with gas pockets trapped in the corrugated walls than those filled with water.
NASA Astrophysics Data System (ADS)
Wu, Yan-Qiu
2015-07-01
In this paper, an endoreversible Carnot heat engine with irreversible heat transfer processes is analyzed based on generalized heat transfer law. The applicability of the entropy generation minimization, exergy analyses method, and entransy theory to the analyses is discussed. Three numerical cases are presented. It is shown that the results obtained from the entransy theory are different from those from the entropy generation minimization, which is equivalent to the exergy analyses method. For the first case in which the application preconditions of the entropy generation minimization and entransy loss maximization are satisfied, both smaller entropy generation rate and larger entransy loss rate lead to larger output power. For the second and third cases in which the preconditions are not satisfied, the entropy generation minimization does not lead to the maximum output power, while larger entransy loss rate still leads to larger output power in the third case. For the discussed cases, the concept of entransy dissipation is not applicable for the analyses of output power. The problems in the negative comments on the entransy theory are pointed out and discussed. The related researchers are advised to focus on some new specific application cases to show if the entransy theory is the same as some other theories. Project supported by the Youth Programs of Chongqing Three Gorges University, China (Grant No. 13QN18).
Proceedings of HT2005 2005 ASME Summer Heat Transfer Conference
Aguilar, Guillermo
Proceedings of HT2005 2005 ASME Summer Heat Transfer Conference July 17-22, 2005, San Francisco absorption and increasing the thickness of the protected region. A 2D finite volume numerical code based interface location density (kg m-3 ) 1 Copyright © 2005 by ASME Proceedings of HT2005 2005 ASME Summer Heat
Heat transfer to blood flow in a small tube.
Wang, C Y
2008-04-01
Blood flow in a small tube (30-1000 mum) can be successfully modeled by the two-fluid model. The fully developed, constant heat flux convective heat transfer problem is studied. The velocity and temperature profiles are determined in closed form. Formulas for friction-factor-Reynolds number product, axial temperature gradient, and Nusselt number are found. PMID:18412512
A Heat Transfer Model for Firefighters' Protective Clothing
William E. Mell; J. Randall Lawson
2000-01-01
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.
Rocket engine heat transfer and material technology for commercial applications
NASA Technical Reports Server (NTRS)
Hiltabiddle, J.; Campbell, J.
1974-01-01
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.
Initial solidification phenomena: Factors affecting heat transfer in strip casting
Paolo Nolli
2007-01-01
In the last few years a few companies have announced the final stage of the commercial development of strip casting of steels. In strip casting heat extraction and productivity are limited by the thermal resistance at the interface between processed material and moving mold (rolls for twin-roll strip casters). Among many factors influencing interfacial heat transfer, films of various composition,
IntroductiontoProcessEngineering(PTG) 5. Heat transfer
Zevenhoven, Ron
) 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
Heat transfer between liquid3He and sintered metal heat exchangers
A. R. Rutherford; J. P. Harrison; M. J. Stott
1984-01-01
A new model to explain the unexpectedly large heat transfer between liquid3He and sintered metal heat exchangers is described and evaluated. The heat transfer results from a direct coupling of3He quasiparticles in the pores to vibrational modes of the sintered metal powder. It is proposed that for a range of temperatures below 20 mK the dominant vibrational modes of the
Heat transfer between liquid 3 He and sintered metal heat exchangers
A. R. Rutherford; J. P. Harrison; M. J. Stott
1984-01-01
A new model to explain the unexpectedly large heat transfer between liquid3He and sintered metal heat exchangers is described and evaluated. The heat transfer results from a direct coupling of3He quasiparticles in the pores to vibrational modes of the sintered metal powder. It is proposed that for a range of temperatures below 20 mK the dominant vibrational modes of the
Resonant self-pumped thermoacoustic heat transfer
Greg Swift; Scott Backhaus
2003-01-01
As a thermoacoustic engine or refrigerator is scaled up to higher power, it generally needs heat exchangers of a larger cross-sectional area. Constrained to lie adjacent to a stack or regenerator, large heat exchangers must use intricate geometries to interweave the thermoacoustic working gas and an external fluid (e.g., ambient cooling water or hot combustion gas) to bring them into
A general application heat transfer computer program
R. K. Frazer
1975-01-01
A computer program is proposed for accurate and rapid determination of transient temperature distributions in heated structures. The program has at its core the ability to calculate the finite difference approximations to the differential equations governing heat conduction in a solid. Boundary conditions that can be simulated include fixed or independently time varying boundary temperatures, fixed or independently time varying
HEAT TRANSFER ANALYSIS OF A PULSE DETONATION
Texas at Arlington, University of
analysis of the effect of sensible heat release on the walls of the detonation chamber for stoichiometric to operate at 20 Hz and cooled by a water jacket to dissipate the heat from the walls which ensures thermal conductivity. The study showed a slow temperature rise along the walls of the combustion chamber
Heat-transfer measurements of the 1983 Kilauea lava flow
Hardee, H.C.
1983-10-07
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.
Heat transfer of buried pipe for heat pump application
Viung C. Mei
1991-01-01
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
Heat Transfer of Airfoils and Plates
NASA Technical Reports Server (NTRS)
Seibert, Otto
1943-01-01
The few available test data on the heat dissipation of wholly or partly heated airfoil models are compared with the corresponding data for the flat plate as obtained by an extension of Prandtl's momentum theory, with differentiation between laminar and turbulent boundary layer and transitional region between both, the extent and appearance of which depend upon certain critical factors. The satisfactory agreement obtained justifies far-reaching conclusions in respect to other profile forms and arrangements of heated surface areas. The temperature relationship of the material quantities in its effect on the heat dissipation is discussed as far as is possible at tk.e present state of research, and it is shown that the profile drag of heated wing surfaces can increase or decrease with the temperature increase depending upon the momentarily existent structure of the boundary layer.
Heat pipes to increase the efficiency of fuel cells
Leonard L. Vasiliev; Leonid L. Vasiliev
2009-01-01
The goal of this work is to suggest, design and develop new heat pipe heat exchangers to increase the efficiency of fuel cells (FCs). At least two types of heat pipe coolers are considered. The first one is a heat pipe spreader used to equalize the temperature field inside the FC stack. The second one ensures the waste heat dissipation
Komendantov, A.S.; Kuzma-Kichta, Y.A.; Vasil'eva, L.T.; Ovodkov, A.A. (Moscow Power Engineering Inst., Moscow (SU))
1991-01-01
In this paper burnout is investigated in tubes under nonuniform heating on the perimeter. Data on heat transfer and critical heat flux (q{sub chf}) in the case of water were obtained for ranges of mass velocity {rho}w = 200--3000 kg/m{sup 2} s, pressure p = 1--1 MPa, and inlet water temperature T = 25--98{degrees}C. The test section was a horizontal copper tube of 21 mm outer diameter, 8 mm inner diameter with a technically smooth surface and heat transfer-intensifying twisted tape and porous sintered coating. The test section was heated by bombardment with electrons. It is established that a redistribution of heat fluxes and an increase of wall temperature fluctuations occur at burnout. The range of regime parameters to prevent burnout of a heat transfer surface is determined.
Effects of Nonequilibrium at Edge of Boundary Layer on Convective Heat Transfer to a Blunt Body
NASA Technical Reports Server (NTRS)
Goekcen, Tahir; Edwards, Thomas A. (Technical Monitor)
1996-01-01
This investigation is a continuation of a previous study on nonequilibrium convective heat transfer to a blunt body. In the previous study, for relatively high Reynolds number flows, it was found that: nonequilibrium convective heat transfer to a blunt body is not strongly dependent on freestream parameters, provided that the thermochemical equilibrium is reached at the edge of boundary layer; and successful testing of convective heat transfer in an arc-jet environment is possible by duplicating the surface pressure and total enthalpy. The nonequilibrium convective heat transfer computations are validated against the results of Fay and Riddell/Goulard theory. Present work investigates low Reynolds number conditions which are typical in an actual arc-jet flow environment. One expects that there will be departures from the Fay and Riddell/Goulard result since certain assumptions of the classical theory are not satisfied. These departures are of interest because the Fay and Riddell/Goulard formulas are extensively used in arc-jet testing (e.g., to determine the enthalpy of the flow and the catalytic efficiency of heat shield materials). For practical sizes of test materials, density of the test flow (and Reynolds number) in an arc-jet is such that thermochemical equilibrium may not be reached at the edge of boundary layer. For blunt body flows of nitrogen and air, computations will be presented to show the effects of thermochemical nonequilibrium at the boundary layer edge on nonequilibrium heat transfer.
Study of the average heat transfer coefficient at different distances between wind tunnel models
NASA Astrophysics Data System (ADS)
Gnyrya, A.; Korobkov, S.; Mokshin, D.; Koshin, A.
2015-01-01
The paper presents investigations of physical and climatic factors with regard to design and process variables having effect on heat transfer in the building model system at different distances between them in the airflow direction. The aim of this work is to improve energy efficiency of exterior walls of buildings. A method of physical simulation was used in experiments. Experimental results on the average values of the heat transfer coefficient in the building model system are presented herein. A series of experiments was carried out on a specific aerodynamic test bench including a subsonic wind tunnel, heat models and devices for giving thermal boundary conditions, transducers, and the record system equipment. The paper contains diagrams of the average heat transfer distribution at fixed Reynolds number and the airflow angle of attack; the average values of the heat transfer coefficient for each face and wind tunnel models as a whole at maximum, medium, and large distances between them. Intensification of the average heat transfer was observed on the downstream model faces depending on the distance between models.
Development of Heat Transfer Models for Gap Cooling
Tamio Kohriyama; Michio Murase; Tomohiko Tamaki
In a severe accident of a light water reactor(LWR), heat transfer models in a narrow annular gap between superheated core debris and a reactor pressure vessel(RPV)are important to evaluate the integrity of RPV and emergency procedures. This paper discusses the effects of superheat on the heat flux based on exisisting data. In low superheat conditions, the heat flux in the
Non-equilibrium electromagnetic fluctuations: Heat transfer and interactions
Matthias Krüger; Thorsten Emig; Mehran Kardar
2011-06-01
The Casimir force between arbitrary objects in equilibrium is related to scattering from individual bodies. We extend this approach to heat transfer and Casimir forces in non-equilibrium cases where each body, and the environment, is at a different temperature. The formalism tracks the radiation from each body and its scatterings by the other objects. We discuss the radiation from a cylinder, emphasizing its polarized nature, and obtain the heat transfer between a sphere and a plate, demonstrating the validity of proximity transfer approximation at close separations and arbitrary temperatures.
Evaporation heat transfer characteristics of a grooved heat pipe with micro-trapezoidal grooves
A. J. Jiao; H. B. Ma; J. K. Critser
2007-01-01
A detailed mathematical model predicting the effect of contact angle on the meniscus radius, thin film profile and heat flux distribution occurring in the micro-trapezoidal grooves of a heat pipe has been presented. The model can be used to determine the maximum evaporating heat transfer rate in the evaporator including the effects of disjoining pressure and surface tension. The equation
Heat and mass transfer in water-laden sandstone: microwave heating
Chen Kou Wei; H. T. Davis; E. A. Davis; Joan Gordon
1985-01-01
Our previous theoretical model was extended to predict the heat and mass transfer phenomena in microwave-heated porous materials. A water-filled sandstone was heated in microwaves and its drying rates and temperature profiles were measured. Predictions agree well with observations. Besides moisture loss rates and temperature profiles, the model also predicts local moisture content, gas densities, and pressure. These latter quantities
Error Analysis of Heat Transfer for Finned-Tube Heat-Exchanger Text-Board
Chen, Y.; Zhang, J.
2006-01-01
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...
Error Analysis of Heat Transfer for Finned-Tube Heat-Exchanger Text-Board
Chen, Y.; Zhang, J.
2006-01-01
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...
INVESTIGATING THE EFFECT OF HEATING METHOD ON POOL BOILING HEAT TRANSFER
Kandlikar, Satish
boiling performance is the focal point of this study. In the present study, experimental data is obtainedINVESTIGATING 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
S. Ferrouillat; P. Tochon; C. Garnier; H. Peerhossaini
2006-01-01
Compact heat exchangers are well known for their ability to transfer a large amount of heat while retaining low volume and weight. The purpose of this paper is to study the potential of using this device as a mixer as well as a chemical reactor, generally called a multifunctional heat exchanger (MHE). Indeed, the question arises: can these geometries combine
Thomas, Brian G.
and Yao [6] preheated a cylindrical copper plate to $450 °C, spray-cooled it, and solved a numerical one uniformity and a wide range of heat removal rates, including extremely high heat transfer. It is important] to calculate spray heat flux in transient cooling experiments on a preheated austenitic steel plate. Choi
Experimental study of heat transfer of buried finned pipe for ground source heat pump applications
Ahmet Koyun; Hakan Demir; Zakir Torun
2009-01-01
Ground heat exchangers have vital importance for ground source heat pump applications. Various configurations tried to improve heat transfer in the soil. A new kind of aluminium finned pipe buried in the soil for this aim. In order to compare effectiveness of the Al finned pipe over the traditional PPRC pipe an experimental study carried out. The experimental GSHP system
A Conceptual Change Model for Teaching Heat Energy, Heat Transfer and Insulation
ERIC Educational Resources Information Center
Lee, C. K.
2014-01-01
This study examines the existing knowledge that pre-service elementary teachers (PSETs) have regarding heat energy, heat transfer and insulation. The PSETs' knowledge of heat energy was initially assessed by using an activity: determining which container would be best to keep hot water warm for the longest period of time. Results showed that…
Gas flow and heat transfer in nanotube and nanowire arrays
NASA Astrophysics Data System (ADS)
Martin, Michael J.
2012-03-01
Gas flow through arrays of nanotube or nanowire structures is modeled by combining the one-dimensional equations for conservation of mass, momentum, and energy with the linearized free-molecular drag and heat transfer for a cylinder. The results show that the pressure gradient, temperature, and local velocity of the gas are governed by coupled ordinary differential equations. Three cases are considered: an isothermal system, a constant wall temperature, and a constant wall heat flux. While the coupled momentum, heat transfer, and continuity equations are nonlinear, the relatively low velocities encountered in these systems cause the nonlinear portions of pressure drops and thermal phenomena to be relatively small.
Heat transfer to a silicon carbide/water nanofluid.
Yu, W.; France , D. M.; Smith, D. S.; Singh, D.; Timofeeva, E. V.; Routbort, J. L.; Univ. of Illinois at Chicago
2009-07-01
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 power. Results were also compared to predictions from standard liquid correlations and a recently altered nanofluid correlation. The slip mechanisms of Brownian diffusion and thermophoresis postulated in the altered correlation were investigated in a series of heating and cooling experiments.
Computational heat transfer modeling of thermal energy storage canisters
NASA Astrophysics Data System (ADS)
Sokolov, Pavel Alexandrovich
A computer code has been developed for analyzing the phenomena occurring in cylindrical metal canisters containing a high temperature Phase Change Material (PCM). Such canisters are normally used as thermal storage elements in heat receivers of solar dynamic power systems for low orbit space vehicles. The code will be a useful canister design tool and it is able to predict the temperature distributions and the void behavior in the canisters. These in turn can be used for the canister thermal stress analyses. The emphasis in the development of the code is made on accurate descriptions of the solid-liquid phase change process, void dynamics and heat transfer, convective and radiative heat transfer modes in the PCM. The capabilities of the code include computations of three dimensional and axisymmetric heat transfer and fluid mechanics phenomena inside the canisters. The code validation has been made based on the results of ground tests and two Thermal Energy Storage flight experiments, TES-1 and TES-2. The validated code has been used for canister analyses. The following features have been examined: (1) the location of "hot spots" in the canister, especially canister walls; (2) the void location and heat transfer predictions; (3) the importance of radiative and convective heat transfer modes in the void and liquid PCM; and (4) influence of three-dimensional versus axisymmetric boundary conditions on the canister performance. The code could be also used to analyze canisters of geometries different from cylindrical and other phenomena involving solid-liquid phase change.
Heat Transfer Enhancement in Separated and Vortex Flows
Richard J. Goldstein
2004-05-27
This document summarizes the research performance done at the Heat Transfer Laboratory of the University of Minnesota on heat transfer and energy separation in separated and vortex flow supported by DOE in the period September 1, 1998--August 31, 2003. Unsteady and complicated flow structures in separated or vortex flows are the main reason for a poor understanding of heat transfer under such conditions. The research from the University of Minnesota focused on the following important aspects of understanding such flows: (1) Heat/mass transfer from a circular cylinder; (2) study of energy separation and heat transfer in free jet flows and shear layers; and (3) study of energy separation on the surface and in the wake of a cylinder in crossflow. The current study used three different experimental setups to accomplish these goals. A wind tunnel and a liquid tunnel using water and mixtures of ethylene glycol and water, is used for the study of prandtl number effect with uniform heat flux from the circular cylinder. A high velocity air jet is used to study energy separation in free jets. A high speed wind tunnel, same as used for the first part, is utilized for energy separation effects on the surface and in the wake of the circular cylinder. The final outcome of this study is a substantial advancement in this research area.
Experimental Investigation of Entrance-region Heat-transfer Coefficients
NASA Technical Reports Server (NTRS)
Joyner, Upshur T
1943-01-01
Experimental results of tests made at the Langley Memorial Aeronautical Laboratory are presented to show how heat-transfer coefficients can he increased by a method utilizing the high rate of heat transfer known to exist on any heat-transfer surface in the region adjacent to the edge on which the cooling or heating fluid impinges. The results show that, for the same pressure drop, the average surface heat-transfer.coefficient can be increased 50 to 100 percent when a cooling surface having a length of four inches in the direction of fluid flow is cut to form twenty fins with a length of 0.2 inch in the direction of fluid flow and the fins are sharpened and staggered in the air stream. The percentage of increase in the surface heat-transfer coefficient obtained as a result of shortening the length of the cooling surface varies with the pressure drop of the cooling fluid in passing the surface, the increase being largest when small pressure drop is used and smallest when high pressure drop is used.
Curvature dependence of the interfacial heat and mass transfer coefficients
NASA Astrophysics Data System (ADS)
Glavatskiy, K. S.; Bedeaux, D.
2014-03-01
Nucleation is often accompanied by heat transfer between the surroundings and a nucleus of a new phase. The interface between two phases gives an additional resistance to this transfer. For small nuclei the interfacial curvature is high, which affects not only equilibrium quantities such as surface tension, but also the transport properties. In particular, high curvature affects the interfacial resistance to heat and mass transfer. We develop a framework for determining the curvature dependence of the interfacial heat and mass transfer resistances. We determine the interfacial resistances as a function of a curvature. The analysis is performed for a bubble of a one-component fluid and may be extended to various nuclei of multicomponent systems. The curvature dependence of the interfacial resistances is important in modeling transport processes in multiphase systems.
Bibliography on augmentation of convective heat and mass transfer
Bergles, A.E.; Webb, R.L.; Junkhan, G.H.; Jensen, M.K.
1979-05-01
Heat transfer augmentation has developed into a major specialty area in heat transfer research and development. A bibliography of world literature on augmentation is presented. The literature is classified into passive augmentation techniques, which require no external power, and active techniques, which do require external power. The fourteen techniques are grouped in terms of their application to the various modes of heat transfer. Mass transfer is included for completeness. Key words are included with each citation for technique/mode identification. The total number of publications cited is 1,967, including 75 surveys of various techniques and 42 papers on performance evaluation of passive techniques. Patents are not included as they will be the subject of a future topical report.
M. Fiebig; Y. Chen; A. Grosse-Gorgemann; N. K. Mitra
1995-01-01
Numerical investigations of three-dimensional flow and heat transfer in a finned tube with punched longitudinal vortex generators( LVG's) are carried out for Reynolds numbers of 250 and 300. Air with a Prandtl number of 0.7 is used as the fluid. The flow is both thermally and hydrodynamically developing. The LVG is a delta winglet pair ( DWP) punched out of
Experimental determination of heat transfer coefficient with spray cooling
Bigzadeh, E.; Mignano, F. [Florida International Univ., Miami, FL (United States)
1995-12-31
Spray water cooling is used to cool the hot surface of metal cast in the continuous casting process. When the strand leaves the first cooling zone, i.e., the mold, further cooling takes place in a so-called secondary cooling zone, which consists of a system of support rollers and nozzles arranged in different positions. The strand surface temperature is close to its solidification temperature and the impinging water spray removes the heat from the surface due to its phase change. Heat transfer conditions in spray water cooling are similar to those of pool boiling. An experimental investigation is being conducted to determine the heat transfer coefficient of the impinging jet in the stable film boiling and partial stable film boiling ranges. It was found that the major parameters effecting the effective heat transfer coefficient are spray water mass flux and spray water temperature.
Heat transfer from cylinders in subsonic slip flows
NASA Technical Reports Server (NTRS)
Nagabushana, K. A.; Stainback, P. C.
1992-01-01
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.
Investigations of pool boiling heat transfer of binary refrigerant mixtures
Chiou, C.B. [Teco Electric and Machinery Co., Ltd., Tao-Yuan (Taiwan, Province of China); Lu, D.C. [National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Dept. of Mechanical Engineering; Wang, C.C. [Industrial Technology Research Inst., Hsinchu (Taiwan, Province of China). Energy and Research Labs.
1997-07-01
Pool boiling data for binary mixtures of R-22/R-124 on plain tubes are reported at reduced pressures of 0.1, 0.15, and 0.2. Significant reductions of heat transfer coefficients for mixtures are found as compared to pure refrigerant, and the reduction of heat transfer coefficient is especially pronounced in the vicinity of the pure component. This phenomenon is strongly related to the nonlinear variation of physical properties of liquid viscosity and latent heat of the mixtures. The available empirical and semiempirical correlations developed for mixtures are compared with the present data. In addition, a correlation based on the present R-22/R-124 experimental data is proposed. This correlation not only predicts the deterioration of heat transfer coefficients for the present data with success but also predicts the experimental data from other investigators with reasonably good accuracy.
Efficient wireless non-radiative mid-range energy transfer
Soljaèiæ, Marin
the devel- opment of schemes to transport energy over long distances without any carrier medium (e, can be efficiently used for energy transfer, even for long distances (transfer distance LTRANS » LDEVEfficient wireless non-radiative mid-range energy transfer Aristeidis Karalis a,*, J
Promotion of efficient heat pumps for heating (ProHeatPump)
and energy efficiency.............................................................................4 Note but slowly increasing. 2.2 Energy use in buildings 2.2.1 Buildings account for 38% of Norwegian energy use are driving increased use of energy for heating. Increasing energy efficiency is counteracted and surpassed
Heat transfer in geometrically similar cylinders
NASA Technical Reports Server (NTRS)
Riekert, P; Held, A
1941-01-01
The power and heat-stress conditions of geometrically similar engines are discussed. The advantages accruing from smaller cylinder dimensions are higher specific horsepower, lower weight per horsepower, lower piston temperature, and less frontal area, with reduced detonation tendency.
Pool boiling heat transfer characteristics of nanofluids
Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology
2007-01-01
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 ...
Particle shape effect on heat transfer performance in an oscillating heat pipe.
Ji, Yulong; Wilson, Corey; Chen, Hsiu-Hung; Ma, Hongbin
2011-01-01
The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP) was investigated experimentally. A binary mixture of ethylene glycol (EG) and deionized water (50/50 by volume) was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP. PMID:21711830
Particle shape effect on heat transfer performance in an oscillating heat pipe
2011-01-01
The effect of alumina nanoparticles on the heat transfer performance of an oscillating heat pipe (OHP) was investigated experimentally. A binary mixture of ethylene glycol (EG) and deionized water (50/50 by volume) was used as the base fluid for the OHP. Four types of nanoparticles with shapes of platelet, blade, cylinder, and brick were studied, respectively. Experimental results show that the alumina nanoparticles added in the OHP significantly affect the heat transfer performance and it depends on the particle shape and volume fraction. When the OHP was charged with EG and cylinder-like alumina nanoparticles, the OHP can achieve the best heat transfer performance among four types of particles investigated herein. In addition, even though previous research found that these alumina nanofluids were not beneficial in laminar or turbulent flow mode, they can enhance the heat transfer performance of an OHP. PMID:21711830
Zhen-hua Liu; Jian-guo Xiong; Ran Bao
2007-01-01
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
Heat Transfer Measurements for a Horizontal Micro-Tube Using Liquid Crystal Thermography
Ghajar, Afshin J.
62 TC02-007 Heat Transfer Measurements for a Horizontal Micro-Tube Using Liquid Crystal-tube and 1000m micro-tube. In the single-phase heat transfer experiments, the fully-developed flow heat transfer were also measured using thermocouples (TC). The results showed that the heat transfer coefficient
Heat transfer to supercritical fluids flowing in channels—empirical correlations (survey)
Igor L. Pioro; Hussam F. Khartabil; Romney B. Duffey
2004-01-01
This literature survey is devoted to the problem of heat transfer of fluids at supercritical pressures including near critical region.The objectives are to assess the work that was done in the area of heat transfer at supercritical pressures, to understand the specifics of heat transfer at these conditions, to compare different prediction methods for supercritical heat transfer in tubes and
An Experimental Study on Heat Transfer Coefficients of a CO2Filled Thermosyphon
S. J. Jeong
2011-01-01
Because carbon dioxide is ozone friendly and has negligible global warming potential, it has received renewed interest in recent years as an important alternative refrigerant. In this article, the heat transfer characteristics of a carbon dioxide-filled two-phase closed thermosyphon were investigated experimentally, and the empirical heat transfer correlations are reported. The heat transfer data were analyzed, and heat transfer coefficients
Process industry demand for more efficient, more cost-effective heat exchanger tubing
Thors, P.
1987-01-01
In the future the process industry will see a bigger selection of enhanced heat transfer tubes, one of the reasons being the continued production of special patented technology involved in making them. Here the author mentions only some of the factors that might influence the increased usage of these enhanced tubes. In using more efficient tubing in a heat exchanger the designer has available the options to increase the total heat duty per unit volume, lower operating costs by reducing the mean temperature difference at a given heat duty, save material, or reduce the size and/or pumping power, among others. This can be achieved, for example, by replacing plain tubes with appropriate enhanced tubes in retubing applications, where old heat exchangers need to be upgraded and total efficiency improved. When a new heat exchanger is to be built, it is easier for the designer to include the more efficient tubing to utilize all the benefits of the increased thermal performance.
NASA Astrophysics Data System (ADS)
Kaizawa, Akihide; Maruoka, Nobuhiro; Kawai, Atsushi; Kamano, Hiroomi; Jozuka, Tetsuji; Senda, Takeshi; Akiyama, Tomohiro
2008-05-01
A waste heat transportation system trans-heat (TH) system is quite attractive that uses the latent heat of a phase change material (PCM). The purpose of this paper is to study the thermophysical properties of various sugars and sodium acetate trihydrate (SAT) as PCMs for a practical TH system and the heat transfer property between PCM selected and heat transfer oil, by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA) and a heat storage tube. As a result, erythritol, with a large latent heat of 344 kJ/kg at melting point of 117°C, high decomposition point of 160°C and excellent chemical stability under repeated phase change cycles was found to be the best PCM among them for the practical TH system. In the heat release experiments between liquid erythritol and flowing cold oil, we observed foaming phenomena of encapsulated oil, in which oil droplet was coated by solidification of PCM.
Heat transfer evaluation in a plasma core reactor
NASA Technical Reports Server (NTRS)
Smith, D. E.; Smith, T. M.; Stoenescu, M. L.
1976-01-01
Numerical evaluations of heat transfer in a fissioning uranium plasma core reactor cavity, operating with seeded hydrogen propellant, was performed. A two-dimensional analysis is based on an assumed flow pattern and cavity wall heat exchange rate. Various iterative schemes were required by the nature of the radiative field and by the solid seed vaporization. Approximate formulations of the radiative heat flux are generally used, due to the complexity of the solution of a rigorously formulated problem. The present work analyzes the sensitivity of the results with respect to approximations of the radiative field, geometry, seed vaporization coefficients and flow pattern. The results present temperature, heat flux, density and optical depth distributions in the reactor cavity, acceptable simplifying assumptions, and iterative schemes. The present calculations, performed in cartesian and spherical coordinates, are applicable to any most general heat transfer problem.
Experimental Studies of the Enhanced Heat Transfer from a Heating Vertical Flat Plate by Ionic Wind
NASA Astrophysics Data System (ADS)
Yue, Yonggang; Hou, Junping; Ai, Zhongliang; Yang, Lanjun; Zhang, Qiaogen
2006-11-01
The effects of the ionic wind on the heat transfer rate from a heated vertical flat plate are described. The ionic wind is induced by three different types of discharge, corona discharge, dielectric barrier discharge (DBD) and dc glow discharge. The heat transfer coefficients for the heated copper plate under free convection conditions with and without an ionic wind are obtained by measuring the temperature and the heating power of the copper plate. It has been proved that the convective heat transfer coefficients increase by several times with the help of the ionic wind. With the ionic wind induced by a uniform dc glow discharge, the heat transfer coefficient of the heated copper plate is highly enhanced compared with those induced by a corona discharge or DBD. With the use of DBD, the breakdown voltage is increased significantly, which is helpful in avoiding a breakdown when heat transfer is enhanced by the ionic wind. In addition, it makes the application of the ionic wind much safer.
Generator-absorber-heat exchange heat transfer apparatus and method and use thereof in a heat pump
Phillips, B.A.; Zawacki, T.S.
1998-07-21
Numerous embodiments and related methods for generator-absorber heat exchange (GAX) are disclosed, particularly for absorption heat pump systems. Such embodiments and related methods use, as the heat transfer medium, the working fluid of the absorption system taken from the generator at a location where the working fluid has a rich liquor concentration. 5 figs.
Characterizations and Convective Heat Transfer Performance of Nanofluids
NASA Astrophysics Data System (ADS)
Yang, Yijun
In recent years, many experimental studies have reported anomalous thermal conductivity enhancement and heat transfer increase in liquid suspensions of nanoparticles. In order to understand the mechanism of this phenomenon and examine the possible applications of nanofluids in heat transfer, the present study experimentally investigated thermal, rheological and heat transfer properties of nanofluids. In the first part of the work, several types of suspensions of near spherical nanoparticles and base fluids were examined. The results show that particles in suspensions without stabilizers agglomerate over time. The thermal conductivity and viscosity of a range of nanofluids were measured. These measurements indicate that the thermal conductivities of nanofluids are in the range predicted using effective medium theory. For example, Bruggeman predicted a 13% thermal conductivity increase for a 3.86% concentration of particles by volume; our experimental measurement indicated a 15% increase for this concentration. Viscosity measurements indicate that dispersions with larger agglomeration experience a larger increase in shear thinning. The results also suggest that finer particles and a narrow particle size distribution should result in a large viscosity increase. The second part of this study examined heat transfer performance of nanofluids in both laminar and transitional flows. Within experimental uncertainty, the non-dimensional heat transfer behavior of nanofluids in laminar flow region was the same as for base fluids without particles. The laminar flow data indicates that nanoparticles migrate from regions of high shear rate to regions of low shear rate, causing them to migrate away from the boundaries of pipe flow. For transitional flow (2,600 migrate away from the boundaries of pipe flow. For transitional flow (2,600
Zhou, Feng; Catton, Ivan
2011-01-01
Longitudinally-Finned Cross-Flow Tube Banks and their HeatFlow and Heat Transfer in Plate-Pin Fin Heat Sinks with Various Pin Cross-Flow and Heat Transfer in Plate-Pin Fin Heat Sinks with Various Pin Cross-
AIAA Journal of Thermophysics and Heat Transfer Vol. 13(1), pp. 126-133, 1999
Zhao, Tianshou
Transfer in a Capillary Structure Heated by a Grooved Block Q. Liao* and T. S. Zhao The Hong Kong1 AIAA Journal of Thermophysics and Heat Transfer Vol. 13(1), pp. 126-133, 1999 Evaporative Heat of capillary-driven heat and mass transfer in a vertical rectangular capillary porous structure heated from
Gravity and Heater Size Effects on Pool Boiling Heat Transfer
NASA Technical Reports Server (NTRS)
Kim, Jungho; Raj, Rishi
2014-01-01
The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.
Heat-Traced Fluid Transfer Lines
Schilling, R. E.
1984-01-01
system. Traced lines are fluid conduits transporting air, gas, or liquids with an adjacent heat source designed to keep the fluid at a predetermined temperature throughout the run. There are four basic reasons for using heat-traced lines for fluid... primarily with proces gas chromatographs, combustion analyzers, and 0 gen, suIfer dioxide, and nitrogen analyzers. The temperatures of these fluids normally range b~tween 190 and 400 0 F and must be maintained within a ..:!: 5 to 10 degree F tolerance...
Radial heat transfer from a moving plasma
Johnson, James Randall
1966-01-01
!red to the arc. Although the heat flux data appeared to be a linear fui, ction of the power supplied to the arc, no correlation was given, Wet! arri (6) has also considered three models for predirtirig the stagnation heat flux to an object mme rsed in an air... plasma. Nitrogen, hydrogen, ard argon were the three gases used, The gererating unit was a dc-plasma jet capable of covering a range of 5 to 100 KW with 50 to &0% of this power absorbed by the gas. Test sections of I/2? 1, and 2 inc. , es in diameter...
Heat transfer in floating insulations for open cryogenic liquid containers
NASA Astrophysics Data System (ADS)
Srinivasa Murthy, S.; Krishna Murthy, M. V.
A transient heat transfer analysis of floating insulations in open cryogenic liquid containers is presented. The results are obtained in terms of three dimensionless parameters and are correlated to give the values of the cool down time, the total heat in-leak during cool down, the heat of sensible cooling of insulation and the steady state values of the temperature and heat flux at the exposed surface, as functions of the three parameters. The analysis facilitates the determination of the optimum insulation thickness for a given storage time. The utility of the analysis is demonstrated with a practical example of liquid nitrogen storage using expanded polystyrene beads as floating insulation.
Heat transfer in rocket engine combustion chambers and nozzles
NASA Astrophysics Data System (ADS)
Anderson, P. G.; Chen, Y. S.; Farmer, R. C.
1992-07-01
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.
Heat transfer enhancement by fins in the microscale regime
Chou, F.C.; Lukes, J.R.; Tien, C.L.
1999-11-01
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.
Heat transfer performance of submerged impinging jet using silver nanofluids
NASA Astrophysics Data System (ADS)
Zhou, Mingzheng; Xia, Guodong; Chai, Lei
2015-02-01
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.
Heat transfer including particle and gas radiation in subsonic MHD diffuser - II
NASA Astrophysics Data System (ADS)
Ahluwalia, R. K.; Im, K. H.
1980-01-01
Heat transfer by convection and gas and slag particle radiation in subsonic MHD diffusers is analyzed by simultaneously solving the radiation transport equation and the quasi-three-dimensional gasdynamic equations. The efficiency factors for extinction and scattering by particles are calculated from the Mie theory. For a reference diffuser geometry, heat transfer by convection is found to be 25 MW, and radiative heat transfer varies from 44 MW to 79 MW, depending on the rate of ash carryover into the channel. Results reveal that the heat transfer is sensitive to the ash carryover into the channel, slag particle spectrum, electrical conductivity of ash, gas composition, and wall emissivity. It is observed that, because of multiple scattering, the particles shield the short-wavelength radiation emitted by potassium atoms. The impacts of heat transfer enhancement by gas radiation in the channel and by gas-plus-particles radiation in the diffuser on MHD system design are assessed. It is suggested that, from the systems design point of view, the diffuser be regarded as a part of the radiant boiler. No significant effect of radiation enhancement on the ability to decompose NO(x) is anticipated.
Energy efficiency analysis of air cycle heat pump dryers
J. E. Braun; P. K. Bansal; E. A. Groll
2002-01-01
In this paper, the feasibility of an air heat pump (reversed Brayton) cycle for tumbler clothes dryers is investigated. The goal is to increase the energy efficiency as compared to conventional electrically heated driers. Relatively simple models were used to compare the energy efficiency of the heat pump drier with that of a conventional air vented drier. The components were
Subcooled nucleate boiling heat transfer from a large diameter tube
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
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.
Heat transfer and friction correlations for wavy plate fin-and-tube heat exchangers
Kim, N.H. [Univ. of Inchon (Korea, Republic of). Dept. of Mechanical Engineering; Youn, J.H. [Korea Academy of Industrial Technology, Seoul (Korea, Republic of); Webb, R.L. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering
1996-12-31
This paper deals with heat exchangers having plate fins of herringbone wave configuration. Correlations are developed to predict the air-side heat transfer coefficient and friction factor as a function of flow conditions and geometric variables of the heat exchanger. Correlations are provided for both staggered and in-line arrays of circular tubes. A multiple regression technique was used to correlate 41 wavy fin geometries by Beecher and Fagan (1987), Wang et al. (1995) and Beecher (1968). For the staggered layout, 92% of the heat transfer data are correlated within {+-}10%, and 91% of the friction data are correlated within {+-}15%.
Heat transfer performance of an oscillating heat pipe under ultrasonic field with dual frequency
NASA Astrophysics Data System (ADS)
Fu, B. W.; Zhao, N. N.; Ma, H. B.; Su, F. M.
2015-01-01
The oscillating motion and heat transfer capacity in an oscillating heat pipe (OHP) under the effect of ultrasound was investigated experimentally. Using the electrically- controlled piezoelectric ceramics, the ultrasonic sound was applied to the evaporating section of the OHP. The heat pipe was tested with or without the ultrasonic sound. The effect of ultrasound on the heat transfer performance was conducted with ultrasound of single frequency or dual frequency. The experimental results demonstrate that the OHP under the effect of the ultrasonic sound with dual frequency performs better than that one with single frequency.
Advanced two-phase heat transfer systems
NASA Technical Reports Server (NTRS)
Swanson, Theodore D.
1992-01-01
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.
Improved heat transfer from radioactive waste canisters
G. Jansen; J. D. Kaser
1974-01-01
From joint meeting of the American Nuclear Society and the Atomic ; lndustrial Forum and Nuclear Energy Exhibition; San Francisco, California, USA ; (11 Nov 1973). Since the radioisotope content that can be tolerated in a ; canister full of radioactive waste is limited by the amount of heat which can be ; dissipated from the waste to the surroundings,
Heat transfer analysis of blast furnace stave
Lijun Wu; Xun Xu; Weiguo Zhou; Yunlong Su; Xiaojing Li
2008-01-01
The three-dimensional mathematical model of temperature and thermal stress field of the blast furnace stave is built. The radiation heat transmitted from solid materials (coke and ore) to inner surface of the stave, which has been neglected by other studies, is taken into account. The cast steel stave is studied and the finite element method is used to perform the
Heat transfer of buried pipe for heat pump application
Viung C. Mei
1989-01-01
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
Preliminary Heat Transfer Studies for the Double Shell Tanks (DST) Transfer Piping
HECHT, S.L.
2000-02-15
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.
Martin, Timothy
Summary Weusedthreemethodstomeasureboundarylayer conductance to heat transfer (gbH) and water vapor (rsV) measured with a porometer from the total branch vapor phase resistance were unusually small, water vapor transfer. Introduction Water loss from plant leaves is controlled by boundary layer
Wake-induced unsteady stagnation region heat transfer measurements
NASA Astrophysics Data System (ADS)
Magari, Patrick Joseph
An experimental investigation of wake-induced unsteady heat transfer in the stagnation region of a cylinder is presented. The objective of the study was to create a quasi-steady representation of the stator/rotor interaction in a gas turbine using two stationary cylinders. In this simulation, a larger cylinder, representing the leading-edge region of a rotor blade was immersed in the wake of a smaller cylinder, representing the trailing-edge region of a stator vane. The experiment was conducted in a short-duration, compression-heated wind tunnel which allowed for independent control of Mach number, Reynolds number, and gas-to-wall temperature ratio. Measurements were performed at a gas-to-wall temperature ratio of 1.35 and Mach numbers of 0.1 and 0.5 with range of 67,500-112,000 and 112,000-383,000, respectively. The background freestream turbulence intensity was less than 0.5 percent, and turbulence grids were utilized to enhance these levels to 4.5 percent at M infinity = 0.08 and 1.75 percent at M infinity = 0.5. Low-speed, isolated-cylinder heat-transfer results compared well with the results of previous investigations, but at the transonic Mach number (M infinity = 0.5), the heat-transfer rate decreased faster with the circumferential distance from the stagnation point. The wake-interaction results were obtained with two wake-generating cylinder diameters of 0.25 and 0.125 times the instrumented cylinder diameter. The streamwise separations between the leading edge of the instrumented cylinder and the centerline of the wake-generating cylinder were 8 and 16 wake-generator diameters. The mean and rms variation of the heat-transfer signals, cross-correlations between various gauges, and spectral analyses of the unsteady heat-transfer signals are presented. The stagnation-point heat transfer was found to reach a maximum independent of the Reynolds number and wake-generator diameter when presented in terms of the Frossling number (NU/square root of Re) at high values of the turbulence parameter Tu/square root of Re. Freestream turbulence levels had no appreciable effect upon the results. The power spectra and wavelet transforms of the heat-transfer signals revealed the importance of large vortical structures in the wake to the unsteady component of the heat transfer in the stagnation region.
A laser-induced heat flux technique for convective heat transfer measurements in high speed flows
NASA Technical Reports Server (NTRS)
Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.
1991-01-01
A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.
Efficient estimation of energy transfer efficiency in light-harvesting complexes
Mohseni, Masoud
The fundamental physical mechanisms of energy transfer in photosynthetic complexes is not yet fully understood. In particular, the degree of efficiency or sensitivity of these systems for energy transfer is not known given ...