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Showing papers in "Journal of Heat Transfer-transactions of The Asme in 1984"


Journal ArticleDOI
W. A. Fiveland1
TL;DR: In this paper, the methode des ordonnees discretes discretees au calcul numerique du transfert radiatif de chaleur dans une enceinte rectangulaire bidimensionnelle remplie d'un milieu gris absorbant, emissif and diffusant isotrope.
Abstract: Utilisation de la methode des Sn ordonnees discretes au calcul numerique du transfert radiatif de chaleur dans une enceinte rectangulaire bidimensionnelle remplie d'un milieu gris absorbant, emissif et diffusant isotrope. Presentation des resultats pour les approximations S 2 , S 4 et S 6 et comparaison aux solutions exactes obtenues par la methode numerique des zones de Hottel

593 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


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 article, a three-part study encompassing both experiment and analysis has been performed for natural convection in an open-ended vertical channel, where one of the principal walls of the channel was maintained at a uniform temperature, while the other principal wall was unheated.
Abstract: A three-part study encompassing both experiment and analysis has been performed for natural convection in an open-ended vertical channel. One of the principal walls of the channel—the heated wall—was maintained at a uniform temperature, while the other principal wall was unheated. The experiments, which included flow visualization and Nusselt number measurements, were carried out with water in the channel and in the ambient which surrounds the channel. At Rayleigh numbers which exceeded a threshold value, the visualization revealed a pocket of recirculating flow situated adjacent to the unheated wall in the upper part of the channel. The recirculation was fed by fluid drawn into the top of the channel, adjacent to the unheated wall. Average Nusselt numbers for the heated wall were measured over a three orders of magnitude range of a single correlating parameter, which includes the Rayleigh number and the ratio of the channel length to the interwall spacing. The Nusselt numbers were found to be unaffected by the presence of the recirculation zone. Numerical solutions obtained via a parabolic finite difference scheme yielded Nusselt numbers in good agreement with those of experiment. The numerical results covered the Prandtl number range from 0.7 to 10.

184 citations




Journal ArticleDOI
TL;DR: Application of the visualisation of l'ecoulement, de la manometrie et de l'anemometrie laser a effet Doppler a un ecoulement approximativement bidimensionnel d'eau autour de chicanes de different caracteristiques geometriques for simuler les aspects importants de l'.
Abstract: Application de la visualisation de l'ecoulement, de la manometrie et de l'anemometrie laser a effet Doppler a un ecoulement approximativement bidimensionnel d'eau autour de chicanes de differentes caracteristiques geometriques pour simuler les aspects importants de l'ecoulement cote calandre dans des echangeurs a faisceau et calandre

134 citations


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.

129 citations


Journal ArticleDOI
TL;DR: In this article, an etude analytique et numerique de la convection naturelle dans a cavite rectangulaire remplie de fluide is presented.
Abstract: Etude analytique et numerique de la convection naturelle dans une cavite rectangulaire remplie de fluide, la caracteristique nouvelle de cette etude etant la presence de flux thermiques constants le long des parois laterales verticales. Resultats analytiques montrant que dans le regime de couche limite les champs d'ecoulement et de temperature different des configurations correspondantes dans une fente a parois isothermes. Bon accord entre les resultats analytiques et les resultats numeriques

111 citations


Journal ArticleDOI
TL;DR: In this paper, two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered, where the jet flow after impingement is constrained to exit in a single direction along the channel formed by the jet and heat transfer surfaces.
Abstract: Two-dimensional arrays of circular air jets impinging on a heat transfer surface parallel to the jet orifice plate are considered The jet flow, after impingement, is constrained to exit in a single direction along the channel formed by the jet orifice plate and the heat transfer surface In addition to the crossflow which originates from the jets following impingement, an initial crossflow is present which approaches the array through an upstream extension of the channel The temperature of the initial crossflow air may differ from the jet air temperature The configurations considered are intended to model the impingement cooled midchord region of gas turbine airfoils in cases where an initial crossflow is also present Nusselt numbers and dimensionless adiabatic wall temperatures resolved to one streamwise jet hole spacing were experimentally determined for ratios of the initial crossflow rate to the total jet flow rate ranging from zero to unity These are presented and discussed relative to the flow and geometric parameters

109 citations


Journal ArticleDOI
TL;DR: In this paper, a two-dimensional melting of a solid phase change material in a rectangular enclosure heated from one side is simulated numerically by dividing the process in a large number of quasi-static steps.
Abstract: Two-dimensional melting of a solid phase change material in a rectangular enclosure heated from one side is simulated numerically. The simulations are carried out by dividing the process in a large number of quasi-static steps. In each quasi-static step, steady-state natural convection in the liquid phase is calculated by directly solving the governing equations of motion with a finite difference technique. This is used to predict the shape and motion of the solid-liquid boundary at the beginning of the next step. The predictions are found to be in good agreement with experiment. Influence of some of the governing parameters on the time development of the melting process is studied using the numerical simulation procedure.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the local heat transfer coefficients to an air flow downstream of an axisymmetric abrupt expansion in a circular pipe with a constant wall heat flux.
Abstract: Measurements have been made of the local heat transfer coefficients to an air flow downstream of an axisymmetric abrupt expansion in a circular pipe with a constant wall heat flux. The experimental technique uses an electrically heated thin gold film on a plastic substrate. The flow upstream of the expansion was unheated and fully developed. Runs were made with small diameter to large diameter ratios of 0.267 to 0.800 and over the Reynolds numbers range of 5,300 to 87,000 (based on downstream diameter). The results include measurements near the expansion corner region where no previous measurements have been reported. These provide clear evidence of a secondary recirculation. Comparisons are also made with previous experimental results in the region of reattachment.

Journal ArticleDOI
TL;DR: In this article, the technique de la sublimation de naphtalene was used to determine the variations a circonferentielle et longitudinale du transfert de masse d'un cylindre circulaire lisse dans un ecoulement croise d'air.
Abstract: Utilisation de la technique de la sublimation de naphtalene pour determiner les variations a circonferentielle et longitudinale du transfert de masse d'un cylindre circulaire lisse dans un ecoulement croise d'air. Etude de l'influence des ecoulements secondaires tridimensionnels pres des extremites du cylindre liees aux parois de la soufflerie

Journal ArticleDOI
TL;DR: In this paper, an experiment was conducted to measure the heat transfer from a heated cylinder in crossflow in an array of circular cylinders, where cylinders were spaced 2.67 diameters apart center-to-center in both the axial and transverse directions to the flow.
Abstract: An experiment was conducted to measure the heat transfer from a heated cylinder in crossflow in an array of circular cylinders. All cylinders had a length-to-diameter ratio of 3.0. Both in-line and staggered array patterns were studied. The cylinders were spaced 2.67 diameters apart center-to-center in both the axial and transverse directions to the flow. The row containing the heated cylinder remained in a fixed position in the channel and the relative location of this row within the array was changed by adding up to five upstream rows. The working fluid was nitrogen gas at pressures from 100 to 600 kPa. The Reynolds number range based on cylinder diameter and average unobstructed channel velocity was from 5,000 to 125,000. Turbulence intensity profiles were measured for each case at a point one half space upstream of the row containing the heated cylinder. The basis of comparison for all the heat transfer data was the single row with the heated cylinder. For the in-line cases the addition of a single row of cylinders upstream of the row containing the heated cylinder increased the heat transfer by an average of 50 percent above the base case. Adding up to five more rows caused no increase or decrease in heat transfer. Adding rows in the staggered array cases resulted in average increases in heat transfer of 21, 64, 58, 46, and 46 percent for one to five upstream rows, respectively. Previously announced in STAR as N82-19493


Journal ArticleDOI
TL;DR: In this paper, a solution numerique, en utilisant la methode des elements finis, des equations exactes du transfert de chaleur couple par conduction and rayonnement thermiques, du champ de temperatures dans le milieu and de la repartition des flux thermiques sur toutes les parois grises d'une enceinte bidimensionnelle rectangulaire for un milieu presentant des proprietes uniformes d'absorption and d'emission.
Abstract: Presentation d'une solution numerique, en utilisant la methode des elements finis, des equations exactes du transfert de chaleur couple par conduction et rayonnement thermiques, du champ de temperatures dans le milieu et de la repartition des flux thermiques sur toutes les parois grises d'une enceinte bidimensionnelle rectangulaire pour un milieu presentant des proprietes uniformes d'absorption et d'emission

Journal ArticleDOI
TL;DR: In this paper, both constrained and unconstrained cavity geometries were studied and detailed velocity profiles were obtained using laser doppler velocimetry for Rayleigh numbers between 3 x 10/sup 10/ and 2 x 10 /sup 11/, corresponding to a constant elevated wall temperature boundary condition.
Abstract: Experimental results for natural convection in a cavity are reported. Both constrained andd unconstrained cavity geometries were studied. Detailed velocity profiles were obtained using Laser doppler velocimetry for Rayleigh numbers between 3 x 10/sup 10/ and 2 x 10/sup 11/, corresponding to a constant elevated wall temperature boundary condition. Characteristics of two-dimensional and three-dimensional flows obtained with dye flow visualization are discussed, including boundary layer transition to turbulence, flow patterns in the cavity, and flow outside of the cavity. Local Nusselt number is correlated with local Rayleigh number for constrained and unconstrained cavities.

Journal ArticleDOI
TL;DR: In this paper, a caracteriser un jet d'air chaud turbulent decharge d'un orifice a bords carres avec un rapport longueur/diametre egal a 1.
Abstract: Presentation d'experiences destinees a caracteriser un jet d'air chaud turbulent decharge d'un orifice a bords carres avec un rapport longueur/diametre egal a 1. Mesures des profils de temperature et de vitesse dans le jet et du champ de temperatures sur une plaque plane frappee normalement par le jet. Construction d'un modele de prediction du champ de temperatures sur la plaque

Journal ArticleDOI
TL;DR: In this article, the mean velocities and temperatures in buoyant turbulent, axisymmetric methane diffusion flames burning in still air have been extended to include mean species concentrations (CH/sub 4/, N/sub 2), O/sub 1/O, CO, and H/sub 3/O), and turbulence quantitites.
Abstract: Past measurements of mean velocities and temperatures in buoyant turbulent, axisymmetric methane diffusion flames burning in still air have been extended to included mean species concentrations (CH/sub 4/, N/sub 2/, O/sub 2/, CO/sub 2/, H/sub 2/O, CO, and H/sub 2/) and turbulence quantitites. The new measurements were used to evaluate a Favre-averaged, k-epsilon-g turbulence model of the process- with all empirical constants fixed by measurements in noncombusting flows. Use of the laminar flamelet method to treat scalar properties yielded reasonably good predictions of mean properties. Turbulence predictions were less satisfactory, generally underestimating fluctuation levels and Reynolds stresses in highly regions of the flows. Measurements indicating significant anisotropy of turbulence properties in the same regions. These findings suggest the need for multistress closure to adequately model turbulence properties in buoyant flames.

Journal ArticleDOI
TL;DR: Generalisation de la regle de Hottel et al. as discussed by the authors for estimation du coefficient d'absorption totale d'un gaz homogene a partir d'une table ou d'one expression donnant son emissivite totale.
Abstract: Generalisation de la regle de Hottel et de la regle de Penner pour l'estimation du coefficient d'absorption totale d'un gaz homogene a partir d'une table ou d'une expression donnant son emissivite totale

Journal ArticleDOI
TL;DR: In this article, the authors studied the condensation of steam on a subcooled water layer in a cocurrent horizontal channel at atmospheric pressure, and found that 50 to 90 percent of the steam condensed within 1.2 m from the entrance.
Abstract: Condensation of steam on a subcooled water layer was studied in a cocurrent horizontal channel at atmospheric pressure. The heat transfer coefficients were found to vary from 1.3 kWS/m/sup 20/C to 20 kW/m/sup 20/C, depending on whether the liquid interface was smooth or wavy, increased with increasing steam flow rates and water flow rates. For all cases, 50 to 90 percent of the steam condensed within 1.2 m from the entrance. The average Nusselt numbers were correlated with average steam and water Reynolds numbers an average liquid Prandtl numbers, for both smooth and wavy interface flows. Finally, a correlation of the average heat transfer coefficient and condensation rate for wavy interface flow was obtained as a function of inlet conditions and distance downstream.

Journal ArticleDOI
TL;DR: In this article, an effective finite difference model has been developed to study the temperature profiles of the work roll and the strip, and the effect of changing velocities was also studied.
Abstract: The lack of a practical mathematical model to simulate thermal behavior of the metal rolling process has forced mill operators and designers to rely on plant experience and testing, which is time consuming and expensive. An effective finite difference model has been developed to study the temperature profiles of the work roll and the strip. Several finite difference techniques have been successfully employed to cope with the special characteristics of the rolling process, such as very high velocity, high temperature variation in a very thin layer, curved boundary, and bimaterial interface. Typical rolling conditions were analyzed to provide temperature information on the roll and strip. Both cold and hot rollings were considered, and the effect of changing velocities was also studied. Good correspondence is found when present results are compared with either analytical solutions under simplified rolling conditions or measured data.

Journal ArticleDOI
TL;DR: In this paper, the infrared optical constants, n and k, (n = n-ik) of swelling and nonswelling coals, their respective char products, and limestone at room temperature have been obtained by a particle extinction technique using compressed KBr tables.
Abstract: The infrared optical constants, n and k, (n = n-ik) of swelling and nonswelling coals, their respective char products, and limestone at room temperature have been obtained by a particle extinction technique using compressed KBr tables. By assuming spherical particles and using Mie theory for the particle extinction measurements in conjunction with normal specular reflectance measurements from polished specimens, it is possible to obtain more accurate values for n and k than if the usual Fresnel reflectance technique is misapplied to samples that may appear specular but do not satisfy the stringent conditions necessary for invoking the Fresnel equations. Values of k for coal were found to be an order-of-magnitude smaller than previously reported values, with absorption due mainly to molecular vibration. The results for char evidenced that a significant increase in absorption by free electrons takes place upon devolatization and carbonization of coal. The limestone results demonstrated pronounced molecular absorption bands characteristic of CaCO/sub 3/.

Journal ArticleDOI
TL;DR: In this article, the authors calculate the variation of the temperature of a fluide d'un echangeur de chaleur a contrecourant due to a un saut de temperature d'entree de l'un ou l'autre des fluides.
Abstract: Calcul de la variation de la temperature de sortie d'un fluide d'un echangeur de chaleur a contrecourant due a un saut de temperature d'entree de l'un ou l'autre des fluides



Journal ArticleDOI
TL;DR: In this article, an experimental and theoretical study was made of the effect of the Reynolds number on the radiative heat flux of methane flames, and it was shown that the effect was negligible.
Abstract: An experimental and theoretical study was made of the effect of the Reynolds number on the radiative heat flux of methane flames. (AIP)

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the possibilite d'utiliser les elements finis standards de Galerkin for l'analyse bidimensionnelle du transfert de chaleur par les trois modes dans un milieu emissif, absorbant and diffusant si le produit des nombres de Reynolds et de Prandtl est inferieur ou egal a 1000.
Abstract: Demonstration de la possibilite d'utiliser les elements finis standards de Galerkin pour l'analyse bidimensionnelle du transfert de chaleur par les trois modes dans un milieu emissif, absorbant et diffusant si le produit des nombres de Reynolds et de Prandtl est inferieur ou egal a 1000. Applications numeriques a des conduites divergente et convergente. Etude de l'influence sur le champ de temperatures des nombres de Reynolds et de Prandtl, de l'albedo et de l'epaisseur optique

Journal ArticleDOI
TL;DR: In this paper, a modele aux differences finies d'un deshumidificateur rotatif a contre-courant for determiner l'influence of six proprietes de la matrice poreuse employee sur les performances de cet appareil en regime permanent.
Abstract: Utilisation d'un modele aux differences finies d'un deshumidificateur rotatif a contre courant pour determiner l'influence de six proprietes de la matrice poreuse employee sur les performances de cet appareil en regime permanent

Journal ArticleDOI
TL;DR: Etude experimentale des courants de convection naturelle et du transfert de chaleur dans une enceinte cubique remplie d'eau don chaque face peut etre chauffee ou refroidie as discussed by the authors.
Abstract: Etude experimentale des courants de convection naturelle et du transfert de chaleur dans une enceinte cubique remplie d'eau dont chaque face peut etre chauffee ou refroidie. Etablissement d'une correlation entre les nombres de Nusselt et de Rayleigh