Showing papers by "Ephraim M Sparrow published in 1987"
••
TL;DR: In this article, a combined experimental and analytical/numerical investigation has been carried out for turbulent flow in a flat, rectangular duct with streamwise non-uniform heating at one of the principal walls.
19 citations
••
TL;DR: In this article, the axial distribution of the heat transfer coefficient downstream of an abrupt contraction in a flat rectangular duct was investigated, where the contraction was created by the presence of a forward-facing step in one of the walls of the duct.
Abstract: Experiments were performed to investigate the axial distribution of the heat transfer coefficient downstream of an abrupt contraction in a flat rectangular duct. The contraction was created by the presence of a forward-facing step in one of the walls of the duct. The flow arriving at the step was hydrodynamically developed and isothermal. In the contracted duct, the duct wall that constituted the continuation of the step was maintained at a uniform temperature different from that of the entering flow, while the other walls were adiabatic. During the course of the experiments, the Reynolds number of the flow in the contracted duct ranged from 4,000 to 24,000, while the ratio of the post-contraction to the precontraction duct heights took on values of 1 (no contraction), 0.8, 0.6, and 0.4. In the presence of the contraction, the axial distribution of the Sherwood number increased at first, attained a maximum, and then decreased monotonically to a fully developed value. In contrast, the no-contraction Sherwood number decreased monotonically and subsequently became fully developed. At a given Reynolds number, the peak Sherwood number for the contraction case was virtually independent of the contraction ratio and exceeded the largest measured Sherwood number for the no-contractionmore » case by about a factor of two.« less
11 citations
••
TL;DR: In this article, it was shown that the measured Nusselt numbers were truly representative of the uniform wall temperature boundary condition and were independent of the characteristics of the wind tunnel boundary layer.
10 citations
••
TL;DR: In this article, the thermal entrance region for turbulent flow in circular tube has been analytically investigated for two types of velocity distributions, one where the flow is hydrodynamically developed throughout the entire length of the thermal region and the other where the velocity is uniform at the inlet of the heated section, so that there is a hydrodynamic development of the flow which occurs simultaneously with the thermal development.
Abstract: The thermal entrance region for turbulent flow in circular tube has been analytically investigated for two types of velocity distributions. In one case, the flow is hydrodynamically developed throughout the entire length of the thermal entrance region. In the other, the velocity is uniform at the inlet of the heated section, so that there is a hydrodynamic development of the flow which occurs simultaneously with the thermal development. The latter situation is rarely, if ever, encountered in practice and is, in fact, difficult to achieve in a laboratory experiment. The effect of various types of velocity distributions on the turbulent heat transfer coefficients in the thermal entrance region of an isothermal-walled tube was investigated experimentally by Boelter et al. The different velocity distributions were attained by use of different configurations of the inlet of the heated section. As noted in Kays and Crawford, the insufficiencies of the experimental technique used by Boelter et al. suggest that the results be regarded as qualitative rather than quantitative. The objective of the present research is to provide definitive thermal entrance region heat transfer results for an isothermal-walled tube for two types of turbulent velocity distributions that are of practical relevance. The two setsmore » of results will be compared to yield the quantitative response of the thermal entrance region to the nature of the velocity condition at the tube inlet. The work to be reported here is experimental and covers the Reynolds number range from approximately 5,000 to 85,000.« less
4 citations
••
TL;DR: In this article, the effect of rotation on the local pattern of melting and on the overall rates of melting, energy storage were determined experimentally for melting in a rotating horizontal tube, where the tube was rotated about a vertical axis situated midway between the ends of the tube.
4 citations
••
TL;DR: In this paper, the combined natural convection and radiation heat transfer from a horizontal finned tube situated in a vertical channel open at the top and bottom was measured, where both walls of the channel were heavily insulated, while one of the insulated walls was replaced by an uninsulated metallic sheet.
Abstract: Measurements were made of the combined natural convection and radiation heat transfer from a horizontal finned tube situated in a vertical channel open at the top and bottom. In one set of experiments, both walls of the channel were heavily insulated, while in a second set of experiments, one of the insulated walls was replaced by an uninsulated metallic sheet. In general, the heat transfer coefficients were found to be lower with the metal wall in place, but only moderately. With the finned tube situated at the bottom of the channel, the differences in the heat transfer coefficients corresponding to the two types of walls were only a few percent. When the tube was positioned at the mid-height of the channel, larger differences were encountered, but in the practical range of Rayleigh numbers, the differences did not exceed 5 percent.
3 citations
••
TL;DR: In this article, the authors performed wind tunnel experiments to determine the response of the heat transfer coefficient at the base of an open-ended cylindrical cavity to yawed (i.e., nonperpendicular) impingement of the freestream flow on the cavity opening.
Abstract: Wind tunnel experiments were performed to determine the response of the heat transfer coefficient at the base of an open-ended cylindrical cavity to yawed (i.e., nonperpendicular) impingement of the freestream flow on the cavity opening. The experiments encompassed yaw angles from 0 (perpendicular impingement) to 45 deg, cavity depth-diameter ratios from 0 to 0.65, and Reynolds numbers from 4,500 to 45,000. In the absence of yaw, very large reductions of the base surface transfer coefficient were brought about by increases of cavity depth. Whent the freestream flow is yawed relative to the cavity opening the coefficient rebounds from its low no-yaw values, with the rebound being accentuated for large yaw, deep cavities, and high Reynolds numbers. Notwithstanding the rebound, the resulting base surface heat transfer coefficients are lower than those for the no-yaw, zero-depth cavity. Operating conditions are identified for which reductions of the transfer coefficient of 50% or more are encountered. On this basis, cavities and recesses appear to be an effective means for reducing heat loss.
3 citations