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Showing papers by "Ephraim M Sparrow published in 1964"


Journal ArticleDOI
TL;DR: In this article, the authors investigated the conditions marking the onset of convective motion in a horizontal fluid layer, in which a negative temperature gradient occurs somewhere within the layer, and they found that the Rayleigh number is greatest for the boundary conditions of fixed temperature and decreases monotonically as the condition of fixed heat flux is approached.
Abstract: An investigation is carried out to determine the conditions marking the onset of convective motion in a horizontal fluid layer in which a negative temperature gradient occurs somewhere within the layer. In such cases, fluid of greater density is situated above fluid of lesser density. Consideration is given to a variety of thermal and hydrodynamic boundary conditions at the surfaces which bound the fluid layer. The thermal conditions include fixed temperature and fixed heat flux at the lower bounding surface, and a general convective-radiative exchange at the upper surface which includes fixed temperature and fixed heat flux as special cases. The hydrodynamic boundary conditions include both rigid and free upper surfaces with a rigid lower bounding surface. It is found that the Rayleigh number marking the onset of motion is greatest for the boundary condition of fixed temperature and decreases monotonically as the condition of fixed heat flux is approached. Non-linear temperature distributions in the fluid layer may result from internal heat generation. With increasing departures from the linear temperature profile, it is found that the fluid layer becomes more prone to instability, that is, the critical Rayleigh number decreases.

472 citations


Journal ArticleDOI
TL;DR: In this paper, a new method of analysis has been devised for determining the developing laminar flow and corresponding pressure drop in the entrance region of tubes and ducts, formulated in a general manner which applies to ducts of any cross section.
Abstract: A new method of analysis has been devised for determining the developing laminar flow and corresponding pressure drop in the entrance region of tubes and ducts. The method is formulated in a general manner which applies to ducts of any cross section. Specific application is made for flow in a circular tube and in a parallel‐plate channel, and the velocity distribution and pressure‐drop results are compared with experimental data and prior analyses. These comparisons lend strong support to the findings of the present analysis.

235 citations



Journal ArticleDOI
TL;DR: In this paper, the conditions for instability in a viscous fluid contained between rotating coaxial cylinders of arbitrary radius ratio were investigated and a solution method was outlined and then applied to cylinders having radius ratios ranging from 0·95 to 0·1.
Abstract: An analytical investigation is carried out to determine the conditions for instability in a viscous fluid contained between rotating coaxial cylinders of arbitrary radius ratio. A solution method is outlined and then applied to cylinders having radius ratios ranging from 0·95 to 0·1. Consideration is given to both cases wherein the cylinders are rotating in the same direction and in opposite directions. Results are reported for the Taylor numbers and wave-numbers which mark the onset of instability. The present results are also employed to delineate the range of applicability of the closed-form instability predictions of Taylor and of Meksyn, which were derived for narrow-gap conditions.

115 citations



Journal ArticleDOI
TL;DR: In this paper, the effect of variable fluid properties was isolated by varying the local wall-to-bulk temperature difference at fixed values of the local Reynolds and Prandtl numbers.

50 citations


Journal ArticleDOI
TL;DR: Black body irradiation of metal surfaces to determine roughness effects on hemispherical and and specular reflectance for various temperatures and angles of incidence was used in this paper, and the results showed that the roughness effect on metal surfaces was negligible.
Abstract: Black body irradiation of metal surfaces to determine roughness effects on hemispherical and and specular reflectance for various temperatures and angles of incidence

46 citations





Journal ArticleDOI
TL;DR: In this paper, the distribution function at a point in a highly rarefied gas flow in a circular tube is shown to be made up of three parts which depend on whether reversed particle trajectories through the point strike the tube wall or pass into the chambers at the ends of the tube.
Abstract: The distribution function at a point in a highly rarefied gas flow in a circular tube is shown to be made up of three parts which depend on whether reversed particle trajectories through the point strike the tube wall or pass into the chambers at the ends of the tube. The distribution function is applied to the calculation of the velocity profile development along the length of the tube. It is found that the most rapid changes in the velocity profile occur near the tube inlet. For longer tubes, there is a substantial length in which the velocity profile is fully developed. In general, the velocity profile is quite flat and this characteristic is accentuated for longer tubes. Some numerical information is also given for the distribution of the particle density throughout the flow. The determination of other local quantities is discussed and illustrated.


Journal ArticleDOI
TL;DR: In this paper, an analysis was performed to determine the extent to which film-boiling heat transfer is affected by thermal radiation, considering both the direct radiation between the heated surface and the liquid and the emission and absorption of radiation in the vapor layer which lies between the surface and liquid.


Journal ArticleDOI
TL;DR: In this article, the kritische Reynoldszahl and the entsprechende Storungswellenzahl wurden fur reibungsbehaftete Stromung in gekrummten Kanalen with beliebigem Radienverhaltnis analytisch berechnet.
Abstract: Die kritische Reynoldszahl und die entsprechende Storungswellenzahl wurden fur reibungsbehaftete Stromung in gekrummten Kanalen mit beliebigem Radienverhaltnis analytisch berechnet. Im allgemeinen zeigt die Untersuchung, dass die ubliche Berechnung nach der fur den engen Kanal gultigen Theorie die kritische Reynoldszahl unterschatzt.

Journal ArticleDOI
TL;DR: In this paper, heat transfer rate, adiabatic wall temperature, and forces exerted for free molecule flow on concave cylindrical surface were investigated on a concave 3D polygonal surface.
Abstract: Heat transfer rate, adiabatic wall temperature and forces exerted for free molecule flow on concave cylindrical surface