Thermal convection in laminar boundary layers III

Summary

The exact value of the heat loss in laminar thermal convection at the surface of horizontal cylinders and spheres is as yet difficult to calculate explicitly with the aid of the so-called exact boundary layer theory. In this paper we shall therefore calculate the local heat transfer by an approximation method first introduced by Squire for a flat plate. The calculations are performed for horizontal cylinders and spheres in first approximation for some values of the Prandtl number between 0.7 and ∞ and in second approximation forPr = ∞. The results look reasonable in themselves, while the total heat transfer is in rather good agreement with experiment, especially for a horizontal cylinder in air. This more or less justifies the approximations introduced. In the last paragraph we consider some details of the second approximation for large values of the Prandtl number and compare the theoretical results for different shapes of the body.