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Good agreement is obtained between the mass transfer j factor and other reported values for heat transfer, but comparison with the calculated frictional forces indicates that the equality proposed by Colburn (3) does not hold, because the distributions of the mass transfer and the skin friction over the surface differ.hlasa transfer from single spheres to a liquid has received little attention and the analogy between mass and momentum transfer has not been investigated, chiefly because of the lack of data for the values of the skin friction of a sphere.This work forms part of the more general study of mass transfer processes being undertaken a t present in the Chemical Engineering Department of Birmingham University and it was considered that this work would provide data of use for predicting not only mass transfer from solid surface but also for predicting outside film coefficients in liquid-liquid extraction and gas absorption.The relation between momentum and mass transfer from single spheres with liquid is unknown largely because of lack of knowledge of the skin friction around a sphere and there have bcen few investigations of the rate of solution at various points around a sphere corresponding to a sphere freely falling or rising in a iquid. that a solid sphere is the prototype of an undistorted liquid drop or gas bubble, and it has been shown that the flow conditions around a drop or bubble are precisely analogous to those around a solid sphere (lo), contrary to some of the supporters of the penetration theory who postulate slip a t fluid interfaces. Such knowledge is highly desira 6 le in MOMENTUM TRANSFERWhen a real fluid flows over a solid body there is normally no slip between the fluid and the solid surface and there is a velocity gradient outward from the surface, resulting'in a net force on the body acting in the direction of the fluid stream, called the skin jriction drag.For flow over cylinders or spheres the flow pattern is not symmetrical forward and aft of the body, owing to the dissipation of energy by the internal viscous forces. The pressure difference across the body results in another force, known as jorm drag, acting on the body in the direction of the fluid stream. Summation of these two drag forces gives the total drag force experienced by the body, and these forces are usually expressed in terms of a dimensionless drag coefficient which for a sphere may be written as For spheres the total drag is usually dekrmined by mcasurement of the terminal velocity of freely falling spheres, but this gives no indication of the relative importance of skin friction :md form drag. The contribution of the frictional drag can be found directly only from an analysis of the hydrodynamic conditions over the sphere surface, usually based upon the variation of the normal pressure over the surface. Values obtained in this of the skin friction, but as it is based upon pressure data determined a t a Reynolds number of 16.5 X lo4, it is not suitable for Reynolds numbers of 103 and below, since the conditions ov...

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