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Showing papers by "Ephraim M Sparrow published in 1984"


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: In this paper, two different degrees of corrugation-peak roundedness were used in addition to sharp (i.e. unrounded) corrugations peaks. But the results showed that the Nusselt number was relatively insensitive to whether the peaks were sharp or rounded.

102 citations


Journal ArticleDOI
TL;DR: Etude experimentale du refroidissement par convection de dispositifs electroniques constitues de differents modules is described in this paper, where influence de modules de hauteurs differentes ou d'espacements entre les modules are discussed.

61 citations


Journal ArticleDOI
TL;DR: In this article, a non-orthogonal, algebraic coordinate transformation is used which yields a rectangular solution domain, which avoids the task of numerically generating boundary-fitted coordinates.
Abstract: A solution methodology has been developed for convection-diffusion problems in which one boundary of the solution domain does not lie along a coordinate line. A nonorthogonal, algebraic coordinate transformation is used which yields a rectangular solution domain. This transformation avoids the task of numerically generating boundary-fitted coordinates. The discretized conservation equations are derived on a control-volume basis. These equations contain pseudodiffusion terms that result from the nonorthogonal nature of the transformation. The entire discretization procedure is documented in detail. Although it is not an essential feature of the method, the discretized equations and their solutions are tied in with the well-documented practices of the Patankar solution scheme for orthogonal systems. Application of the methodology is illustrated by two numerical examples.

57 citations


Journal ArticleDOI
TL;DR: In this article, a double-pipe heat-exchanger with an annular duct of streamwise-periodic-varying cross-sectional area is investigated analytically for Reynolds numbers 50-1000 and Prandtl numbers 2-10.
Abstract: The fully developed laminar-flow and temperature fields of a double-pipe heat-exchanger with an annular duct of streamwise-periodic-varying cross-sectional area are investigated analytically for Reynolds numbers 50-1000 and Prandtl numbers 2-10. Numerical results are presented graphically and discussed. At Re 1000 and Pr 10, the Nusselt number is found to be four times that of a similar configuration with constant cross section the pressure drop is increased by a factor of two. Nusselt numbers for two different boundary conditions (constant wall temperature or uniform wall heat flux) are shown to differ by only 10-15 percent. 8 references.

47 citations


Journal ArticleDOI
TL;DR: In this article, an experiment experimentale de l'ecoulement et des caracteristiques du transfert de chaleur for un ecoulement turbulent d'air dans un tube avec un tourbillon axisymetrique decroissant is presented.
Abstract: Etude experimentale de l'ecoulement et des caracteristiques du transfert de chaleur pour un ecoulement turbulent d'air dans un tube avec un tourbillon axisymetrique decroissant

42 citations


Journal ArticleDOI
TL;DR: In this paper, the authors measured local and fully developed turbulent heat transfer coefficients for a flat rectangular duct having streamwise-periodic, two-dimensional disturbances symmetrically positioned at both principal walls.

41 citations


Journal ArticleDOI
TL;DR: In this paper, the authors performed wind tunnel experiments to determine heat transfer coefficients in the region of wall-cylinder interaction for a wall-attached cylinder in cross-flow.

41 citations


Journal ArticleDOI
TL;DR: In this article, the caracteristiques de transfert de chaleur en convection naturelle d'un cylindre horizontal chauffeur place dans un canal vertical and dans l'air.
Abstract: Etude experimentale des caracteristiques de transfert de chaleur en convection naturelle d'un cylindre horizontal chauffe place dans un canal vertical et dans l'air. Utilisation de 15 configurations differentes de canal, les parois ayant egalement des caracteristiques thermiques differentes. Pour chaque configuration, variation du nombre de Rayleigh du cylindre de 1,5×10 4 a 2×10 5 . Resultats mettant en evidence un accroissement du transfert de chaleur par rapport a un cylindre place dans un espace non limite, cet accroissement pouvant aller jusqu'a 40%

37 citations



Journal ArticleDOI
TL;DR: In this article, the coefficients quasi-locaux de transfert de chaleur sur un cylindre frappe normalement par un jet d'air cylindrique were investigated.
Abstract: Mesure des coefficients quasi-locaux de transfert de chaleur sur un cylindre frappe normalement par un jet d'air cylindrique en faisant varier parametriquement le diametre du jet, la distance entre le depart du jet et la surface du cylindre et le nombre de Reynolds. Etablissement de correlations entre le nombre de Musselt maximal et les parametres geometriques et le nombre de Reynolds

Journal ArticleDOI
TL;DR: In this article, a computationally efficient and highly accurate solution scheme for phase change problems is described which combines an implicit treatment of the temperature field equations with an explicit treatment of interface energy balance (s).
Abstract: A computationally efficient and highly accurate solution scheme for phase-change problems is described which combines an implicit treatment of the temperature field equations with an explicit treatment of the interface energy balance (s). This scheme avoids the iterative interaction between the field and interface solutions which characterizes a fully implicit treatment. No time-step limitations were encountered in the wide range of numerical solutions that were carried out with the methodology. The accuracy characteristics were established by comparisons with alternative solutions of a number of specific problems involving plane or radial freezing, one or two solid phases, and, in some cases, convective heating at the solid-liquid interface. Depending on the problem, the alternative solutions were analytical, semianalytical, or numerical. The accuracy level of the solid layer thicknesses given by the solution scheme were found to be in the 0.1% range.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the heat transfer coefficient on a circular cylinder subjected to the crossflow impingement of a slot jet and found that the effect of offset is accentuated for narrow slots and at small slot-to-cylinder separation distances.

Journal ArticleDOI
TL;DR: In this paper, a computational model was formulated for determining the array heat transfer rates, with account being taken of the fact that the same rate of airflow does not wash over all of the fin in the array.

Journal ArticleDOI
TL;DR: In this article, experiments were performed to study the heat transfer processes that occur during freezing inside of a sealed cylindrical capsule when the inclination of the capsule is varied parametrically from vertical to horizontal.
Abstract: Experiments were performed to study the heat transfer processes that occur during freezing inside of a sealed cylindrical capsule when the inclination of the capsule is varied parametrically from vertical to horizontal. The phase-change medium was 99 percent pure n-eicosane paraffin. It was found that the amount of mass that solidified during a given freezing period was insensitive to the inclination of the capsule, as was the amount of energy extracted from the capsule. Only highly localized quantities such as the local frozen layer thickness reflected the inclination of the cylinder. Parametric variations were also performed for the degree of subcooling of the capsule wall below the fusion temperature and for the degree of superheating of the liquid phase at the onset of freezing. These variations facilitated the identification of the relative importance of the latent and sensible energies to the total extracted energy.

Journal ArticleDOI
TL;DR: In this article, the average Nusselt number at a small innerbody situated in an enclosed space, with the innerbody and the bounding wall of the enclosure maintained at different uniform temperatures Natural convection occurred in the air which occupied the enclosed space.

Journal ArticleDOI
TL;DR: In this paper, local heat transfer coefficients were determined for turbulent flow in an isothermal-walled circular tube whose inlet was either built into a large wall or was supported so as to be in free space.

Journal ArticleDOI
TL;DR: In this paper, the authors measured the heat transfer due to all participating modes for a heated horizontal cylinder in the presence of adjacent adiabatic walls which partially enclose the space in which the cylinder is situated.

Journal ArticleDOI
TL;DR: Etude experimentale, par la methode de la sublimation du naphtalene, des caracteristiques de transfert de chaleur de barres fixees perpendiculairement sur un arbre tournant en fonction de differents parametres: longueur et diametre, nombre de bars sur la circonference, distance aux extremites libres de l'arbre and nomes de Reynolds rotationnel as discussed by the authors.
Abstract: Etude experimentale, par la methode de la sublimation du naphtalene, des caracteristiques de transfert de chaleur de barres fixees perpendiculairement sur un arbre tournant en fonction de differents parametres: longueur et diametre, nombre de barres sur la circonference, distance aux extremites libres de l'arbre et nombre de Reynolds rotationnel

Journal ArticleDOI
TL;DR: In this paper, the authors employed the oil-lampblack technique to reveal the patterns of fluid flow in a shell-and-tube heat exchanger and visualized flow patterns adjacent to the shell wall, to the baffle plates, and to each tube of the array.
Abstract: The oil-lampblack technique was employed to reveal the patterns of fluid flow in a shell-and-tube heat exchanger. Flow patterns were visualized adjacent to the shell wall, to the baffle plates, and to each tube of the array. From the flow patterns adjacent to the shell, three recirculation zones were identified. The patterns adjacent to the baffles were similar to those for cross flow over a tube bank, with curvature-related deviations near the shell. The flow patterns adjacent to the tubes showed, typically, a stagnation line/circumferential flow system on the upstream face of each tube and a recirculation tone dominating the tee side. Turn-related deviations from these patterns were in evidence at the window region.

Journal ArticleDOI
TL;DR: In this article, a tube-bank-type crossflow heat exchanger situated downstream of a right-angle bend was investigated, and it was found that the presence of the bend did not have a major effect on the heat transfer characteristics of the tube bank.

Journal ArticleDOI
TL;DR: In this paper, numerical solutions for planar or radial freezing on a cooled wall or cylinder maintained at a uniform temperature lower than the fusion temperature were obtained by using an implicit/explicit method developed in the preceding paper.
Abstract: Numerical solutions have been carried out for planar or radial freezing on a cooled wall or cylinder maintained at a uniform temperature lower than the fusion temperature. The solutions were obtained by using an implicit/explicit method developed in the preceding paper in this issue. Results are presented for the frozen layer thick-ness, the instantaneous heat flux at the cooled surface, and the time-integrated heat transfer at the surface, all as a function of time from the beginning of the freezing period. These quantities are normalized in various ways to illuminate their short-time and long-time behaviors and to enable comparisons between planar and radial freezing. Convection at the solid-liquid interface had virtually no effect on the freezing process at short times, but at longer times the convection significantly slowed the freezing and ultimately terminated it. Solid-solid transitions tended to slow the freezing and also to increase the heat transfer at the cooled surface.