A comprehensive correlating equation for laminar, assisting, forced and free convection

Abstract

Abstract A correlating equation for assisting convection was developed by combining correlating equations for pure free and pure forced convection. These component equations are based on laminar boundary‐layer theory for an isothermal, vertical plate. Theoretical values for assisting convection indicate that the third root of the sum of the third powers gives the best representation, as contrasted with the choice and rationalization of the second or fourth power by prior investigators. This expression was modified by the addition of a limiting value Nu o to obtain a better representation below the domain of boundary‐layer theory and was generalized for uniform heating and for spheres and horizontal cylinders by the appropriate choice of the characteristic length.