Forced Convection Heat Transfer From a Uniformly Heated Sphere

Abstract

An approximate analytical solution is presented for the variation of the local heat-transfer coefficient over the forward half of a uniformly heated sphere. Experimental measurements with water over a Reynolds number range of 5000 to 480,000 and a Prandtl number range of 2.2 to 6.8 give local coefficients which are in good agreement with analytical results. Average heat-transfer coefficients for the uniformly heated sphere are slightly higher than similar results reported earlier [1] for an isothermal sphere. The effect of variations of heat flux on the average heat-transfer coefficient is correlated in a manner similar to that which was used for the isothermal data. Three different duct sizes were used in the experiment to determine the effect of this variable, and the correlations which are presented are based on duct-to-sphere diameter ratios of 2, 2.67, and 4.