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Showing papers on "Heat transfer published in 1984"


Book
01 Jan 1984
TL;DR: In this article, the Helmholtz Function is used to calculate the velocity of sound in the transport of compressed water and superheated steam in the critical region of a ship.
Abstract: : Contents of this document include: Thermodynamic Property Values-Saturation(Temperature); Saturation(Pressure); Compressed Water and Superheated Steam; Critical Region:Isochores for or = + subscripts; Specific Heat Capacity at Constant Pressure; Speed of Sound; Transport and other Thermophysical Property Values-Viscosity; Thermal Conductivity; Prandtl Number; Dielectric constant; Properties for Coexisting Phases: Viscosity, Thermal Conductivity, Prandtl Number, Dielectric Constant Surface Tension; The Helmholtz Function; Computer Programs for Thermodynamic Property Calculations; Equations for Transport and other Thermophysical Properties.

537 citations


Journal ArticleDOI
TL;DR: The extent of thermal destruction of tissue by visible and near-infrared lasers is governed by heat deposition in the tissue, heat transfer, and temperature-dependent rate reactions.
Abstract: The extent of thermal destruction of tissue by visible and near-infrared lasers is governed by heat deposition in the tissue, heat transfer, and temperature-dependent rate reactions. Often the thermal response has been analyzed by linear models with constant coefficients that presume exponential absorption of the laser irradiation with depth. However, for weakly absorbing tissues, light scattering dominates the optical properties. These properties may be altered by thermal damage of the tissue. Also, thermal properties for tissue vary with temperature and water content. Typical therapeutic laser irradiations vaporize water in the tissue causing sharp increases in temperature beyond 100°C, and continued irradiation causes ablation of the tissue. Models for all these events are discussed.

488 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of variable porosity and inertial forces on convective flow and heat transfer in porous media were analyzed and a numerical scheme for the solution of the governing equations was proposed to investigate the variable-porosity effects on the velocity and temperature fields inside the porous medium.
Abstract: The present work analyses the effects of variable porosity and inertial forces on convective flow and heat transfer in porous media. Specific attention is given to forced convection in packed beds in the vicinity of an impermeable boundary. After establishing the governing equations, a thorough investigation of the channelling effect and its influence on flow and heat transfer through variable-porosity media is presented. Based on some analytical considerations, a numerical scheme for the solution of the governing equations is proposed to investigate the variable-porosity effects on the velocity and temperature fields inside the porous medium. The method of matched asymptotic expansions is used to show the qualitative aspects of variable porosity in producing the channelling effect. These qualitative features are also confirmed by the numerical solution. The qualitative effects of the controlling parameters on flow and heat transfer in variable-porosity media are discussed at length. The variable-porosity effects are shown to be significant for most cases. For the same conditions as the perturbation solution, the numerical results are in excellent agreement with the perturbation analysis. The numerical results are also in very good agreement with the available experimental data of previous studies.

477 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed composite relations for the variation of the heat transfer coefficient along the plate surfaces, and the mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of the presentation.
Abstract: While component dissipation patterns and system operating modes vary widely, many electronic packaging configurations can be modeled by symmetrically or asymmetrically isothermal or isoflux plates. The idealized configurations are amenable to analytic optimization based on maximizing total heat transfer per unit volume or unit primary area. To achieve this anlaytic optimization, however, it is necessary to develop composite relations for the variation of the heat transfer coefficient along the plate surfaces. The mathematical development and verification of such composite relations as well as the formulation and solution of the optimizing equations for the various boundary conditions of interest constitute the core of this presentation.

462 citations


Book
01 Jan 1984
TL;DR: In this paper, the authors present several generalized analytical methods of solution for a variety of commonly incurred heat transfer problems, including time-dependent, linear heat-oriented, or involve mass diffusion.
Abstract: This text presents several generalized analytical methods of solution for a variety of classes of commonly incurred heat transfer problems. It covers problems that are time-dependent, linear heat-oriented, or involve mass diffusion.

395 citations


Journal ArticleDOI
Je-Chin Han1
TL;DR: Etude experimentale d'un ecoulement d'air turbulent dans des conduites carrees avec 2 parois opposees a nervures en vue de determiner l'influence des rapports pas/hauteur des nervures and hauteur nervure/diametre equivalent sur le coefficient de frottement and les coefficients de transfert de chaleur for un nombre de Reynolds variant de 7000 a 90000 as discussed by the authors.
Abstract: Etude experimentale d'un ecoulement d'air turbulent dans des conduites carrees avec 2 parois opposees a nervures en vue de determiner l'influence des rapports pas/hauteur des nervures et hauteur nervure/diametre equivalent sur le coefficient de frottement et les coefficients de transfert de chaleur pour un nombre de Reynolds variant de 7000 a 90000

369 citations


Journal ArticleDOI
TL;DR: In this paper, the relative importance of internal and external heat transfer and of the intrinsic (first order) pyrolysis kinetics can be determined from the Biot number (hR/K).

358 citations


Journal ArticleDOI
TL;DR: Vial heat transfer coefficients are sensitive to the geometry of the vial bottom, and even vials of nominally the same specifications may differ significantly in heat transfer characteristics.

318 citations


Journal ArticleDOI
TL;DR: In this article, heat transfer characteristics have been measured for the flow of gas in the fine channels of the heat exchangers used for microminiature J-T refrigerators.

315 citations


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional transient model for convective heat transfer and surface tension driven fluid flow is developed, which describes the transient behavior of the heat transfer process of a stationary band source.
Abstract: A two-dimensional transient model for convective heat transfer and surface tension driven fluid flow is developed. The model describes the transient behavior of the heat transfer process of a stationary band source. Semi-quantitative understanding of scanning is obtained by a coordinate transformation. The non-dimensional forms of the equations are derived and four dimensionless parameters are identified, namely, Peclet number (Pe), Prandtl number (Pr), surface tension number(S), and dimensionless melting temperature(@#@ Tm * @#@). Their governing characteristics and their effects on pool shape, cooling rate, velocity field, and solute redistribution are discussed. A numerical solution is obtained and presented. Quantitative effects of Prandtl number and surface tension number on surface velocity, surface temperature, pool shape, and cooling rate are presented graphically.

294 citations


Journal ArticleDOI
TL;DR: In this article, an improved version of the generalized correlation is successfully developed, being accompanied with a very clear-cut structure as compared with the previous correlation, and careful experiments have been attempted with an identical test tube covering all the main characteristic regimes of CHF.

Journal ArticleDOI
TL;DR: In this article, the authors developed a better understanding of the mechanisms controlling heat transfer through foams, which will aid future foam developments and form the basis of a fundamental model for the R value of foam.
Abstract: the development of improved foam insulations has been an evolutionary process. Current research efforts to develop higher R value foams are handicapped by the fact that the mechanisms of heat transfer through foam are not well understood and a basic model is not available. It is the goal of this paper to help develop a better understanding of the mechanisms controlling heat transfer through foams. This will aid future foam developments and form the basis of a fundamental model for the R value of foam. This work also applies to understanding the aging of foams. In a review of the foam literature, Valenzuela [1] showed that published heat transfer models underestimate the effective conductivity of foams, even when upper limits are used for the contribution of solid and gas conduction. Gas convection within the cells was shown to be negligible and hence could not account for the discrepancy. It was hypothesized that thermal radiation accounted for the balance of

Journal ArticleDOI
TL;DR: In this paper, a review of the literature on bubble columns is presented, where the authors extract formulae and guidelines as simply as possible on the basis of currently available material.

Patent
19 Jun 1984
TL;DR: A finned heat exchanger includes a plurality of elongated fins which are arranged at a predetermined interval in parallel with one another such that air flows between neighboring ones of the fins in a predetermined direction as discussed by the authors.
Abstract: A finned heat exchanger includes a plurality of elongated fins which are arranged at a predetermined interval in parallel with one another such that air flows between neighboring ones of the fins in a predetermined direction. A plurality of heat transfer tubes which contain refrigerant passing therethrough are orthogonally inserted through the fins so as to be arranged in a plurality of columns on the fins. When the finned heat exchanger is operated for condensation, the heat transfer tubes are provided in two paths in the vicinity of an inlet for the refrigerant and are provided in one path in the vicinity of an outlet for the refrigerant, such that the heat transfer tubes of the one path occupy about 5 to 30% of all the heat transfer tubes.

Book
01 Jan 1984
TL;DR: In this paper, a liquid partially fills an array of micron-wide repentant capillaries in the heat sink substrate, so that surface tension holds the polished back of an IC in intimate thermal contact with the sink.
Abstract: : The design of high-speed integrated circuits and systems is often constrained by thermal considerations. As late as 1981 it was authoritatively predicted that the maximum achievable power flux for liquid-cooled, densely-packed integrated circuits (ICs) would be about 20 W/sq cm. Convective heat-transfer theory indicates that well over 1000 W/sq cm can be compactly removed from ICs at normal operating temperatures, provided microscopic (e.g., 50-microns wide) extended-surface structures are used. The difficulty of constructing high-conductance, low-stress thermal interfaces between ICs and heat sinks suggests the use of an integral heat sink. Accordingly, IC microfabrication techniques were employed to design, fabricate, and test novel, ultracompact water-cooled, laminar-flow, optimized plate-fin and pin-fin heat sinks directly within standard-thickness silicon substrates. Worst-case thermal resistances as low as 0.083 deg C/W were measured from 1-sq cm thin-film resistors (e.g., a 108 deg C temperature rise at 1309 W), in good agreement with predictions. Further increases in heat transfer are achievable. The use of integral liquid-cooled heat sinks in multichip systems presents potential yield, reliability, cost and packaging problems. Attachment of unmodified ICs to micro-heat sinks seems a more attractive approach. A novel die-attachment technique has been developed which avoids the problems of conventional attachments. In this technique, a liquid partially fills an array of micron-wide repentant capillaries in the heat sink substrate, so that surface tension holds the polished back of an IC in intimate thermal contact with the heat sink. The bond is void-free, virtually stress-free, long-lived, and allows repeated detachment and replacement of ICs without damaging the heat sink substrate. The repentant grooves were fabricated by a novel process using electroless plating of nickel onto vertical silicon microgrooves.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of surface orientation on nucleate boiling heat transfer and proposed two mechanisms of the sensible heat transport by compulsory removal of the thermal layer by the rising bubble and the latent heat transfer by evaporation from thin liquid film underneath the bubble.

Journal ArticleDOI
TL;DR: In this paper, two families of pin fin array geometries which have potential for improving airfoil internal cooling performance were studied experimentally and the results indicated that the use of circular pins with array orientation between staggered and inline can increase heat transfer while decreasing pressure loss.
Abstract: Modern high-performance gas turbine engines operate at high turbine inlet temperatures and require internal convection cooling of many of the components exposed to the hot gas flow. Cooling air is supplied from the engine compressor at a cost to cycle performance and a design goal is to provide necessary cooling with the minimum required cooling air flow. In conjunction with this objective, two families of pin fin array geometries which have potential for improving airfoil internal cooling performance were studied experimentally. One family utilizes pins of a circular cross section with various orientations of the array with respect to the mean flow direction. The second family utilizes pins with an oblong cross section with various pin orientations with respect to the mean flow direction. Both heat transfer and pressure loss characteristics are presented. The results indicate that the use of circular pins with array orientation between staggered and inline can in some cases increase heat transfer while decreasing pressure loss. The use of elongated pins increases heat transfer, but at a high cost of increased pressure loss. In conjunction with the present measurements, previously published results were reexamined in order to estimate the magnitude of heat transfer coefficients on the pin surfaces relative to those of the endwall surfaces. The estimate indicates that the pin surface coefficients are approximately double the endwall values.


Journal ArticleDOI
TL;DR: In this article, an extensive numerical study of the heat transport by 2-D steady state convection with free boundaries and temperature dependent viscosity was carried out, and the results for convection in a square box were presented in several ways.

01 Jan 1984
TL;DR: In this article, the fabrication and purpose of very small wickless heat pipes are discussed, and a theoretical analysis of their performance characteristics is presented, showing that they have nearly the heat transport capability expected by scaling down from conventional heat pipes.
Abstract: The fabrication and purpose of very small wickless heat pipes are discussed. A theoretical analysis of their performance characteristics shows that they have nearly the heat transport capability expected by scaling down from conventional heat pipes. They appear attractive for applications calling for close temperature control, but having only modest cooling requirements.

Journal ArticleDOI
TL;DR: In this paper, analytical solutions are developed for the hyperbolic heat conduction equation describing the wave nature of thermal energy transport in a finite slab with insulated boundaries subjected to a volumetric energy source in the medium.

Journal ArticleDOI
TL;DR: In this article, a laminar hydrodynamic theory is developed to describe the phenomenon and to show that the enhanced heat conduction is one involving radial heat transfer across very thin Stokes boundary layers existing in these flows.
Abstract: Heat transfer between two fluid reservoirs maintained at different temperatures and connected to each other via a capillary bundle is examined when the fluid within the capillaries is oscillated axially. Very large effective axial heat conduction rates, exceeding those possible with heat pipes by several orders of magnitude, are found to be achievable. A laminar hydrodynamic theory is developed to describe the phenomenon and to show that the enhanced heat conduction is one involving radial heat transfer across very thin Stokes’s boundary layers existing in these flows. Experimental measurements using water as the working fluid show effective thermal diffusivities up to 17 900 times those existing in the absence of oscillations. Since the process involves no net convective mass transport, it offers considerable promise as a means for the rapid removal of heat from radioactive fluids.

Journal ArticleDOI
TL;DR: A closed form analytic solution for the boundary value problem coupling the three layers is obtained in terms of numerically evaluated integrals describing the detailed vascular geometry, a capillary bleed-off distribution function and parameters describing the shunting of blood to the cutaneous layer.
Abstract: In this paper the conceptual three-layer representation of surface tissue heat transfer proposed in Weinbaum, Jiji and Lemons [1], is developed into a detailed quantitative model. This model takes into consideration the variation of the number density, size and flow velocity of the countercurrent arterio-venous vessels as a function of depth from the skin surface, the directionality of blood perfusion in the transverse vessel layer and the superficial shunting of blood to the cutaneous layer. A closed form analytic solution for the boundary value problem coupling the three layers is obtained. This solution is in terms of numerically evaluated integrals describing the detailed vascular geometry, a capillary bleed-off distribution function and parameters describing the shunting of blood to the cutaneous layer. Representative heat transfer results for typical physiological conditions are presented.


Journal ArticleDOI
TL;DR: In this article, the Brinkman-Forchheimer-extended Darcy model is used as the momentum equation and the effect of porosity variation is taken into consideration.

Book
01 Jan 1984
TL;DR: In this article, the three mechanisms of heat exchange: Conduction, Convection, and Radiation are discussed. But they do not consider the effect of temperature transfer resistances.
Abstract: Fluid Flow: Basic Equations for Flowing Streams. Flow of Incompressible Newtonians in Pipes. Compressible Flow of Gases. Molecular Flow. Non-Newtonian Fluids. Flow Through Packed Beds. Flow in Fluidized Beds. Solid Particles Falling Through Fluids. Heat Exchange: The Three Mechanisms of Heat Transfer: Conduction, Convection, and Radiation. Combination of Heat transfer Resistances. Unsteady State Heating and Cooling of Solid Objects. Introduction to Heat Exchangers. Recuperators: Through-the-Wall Nonstoring Exchangers. Direct-Contact Gas-Solid Nonstoring Exchanger. Heat Regenerators: Direct Contact Heat Storing Exchangers. Potpourri of Problems. Appendix: Dimensions, Units, Conversions, Physical Data, and Other Useful Information. Index.

Book
01 Jan 1984

Journal ArticleDOI
TL;DR: In this paper, heat transfer characteristics and flow behaviors have been made clear for an elliptic cylinder of axis ratio 1 : 3, where the testing fluid was air and the Reynolds number ranged from about 8000 to 79000.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the departure from the Darcy flow model is dictated by the dimensionless number G = (v/K)(bgββΔT) − 1 2, with G → 0 representing the high pore Reynolds number limit, and G → ∞ representing the normal flow limit.

Journal ArticleDOI
TL;DR: In this paper, the authors describe an experimental investigation to determine the mechanism governing nucleate pool boiling heat transfer in refrigerant-oil mixtures, the role diffusion plays in this process, and the influence of the fluid mixture properties.
Abstract: This paper describes an experimental investigation to determine the mechanism governing nucleate pool boiling heat transfer in refrigerant-oil mixtures, the role diffusion plays in this process, and the influence of the fluid mixture properties. Boiling heat transfer date were taken in mixtures of up to 10 per cent oil by weight in R-113. Thermophysical properties of the mixtures (density, viscosity, surface, tension, specific heat, and contact angle) were measured. The decrease in heat transfer coefficient with incresing oil concentration is attributed to diffusion in an oil-enriched region surrounding the growing vapor bubbles. A correlation based on a postulated mechanism is presented which shows fair agreement with the experimental data from this study and with data obtained from the literature.