Integral Methods in Natural-Convection Flow

This paper presents an evaluation of the range of application, accuracy, and usefulness of integral methods in natural-convection flow. The study reveals (a) that integral methods may be utilized to obtain approximate answers to free-convection problems whenever exact analytical solutions become too involved. Specific-flow examples considered here (natural convection from inclined plate, horizontal cylinder, arbitrary body, or within enclosed channels) confirm their adaptability to complicated configurations. (b) Over-all accuracy of the solutions is good. For inclined plates the derived equations reduce at high Grashof numbers to the correlation proposed and verified by Rich (1) while in the case of horizontal cylinders the results compare satisfactorily with the theoretical values of Hermann (2) and the accepted experimental relations (12). (c) The integral method of solution may be extended to apply to low Prandtl number fluids, laminar or turbulent flow, variable wall temperature, and convection within confined spaces.