FULLY-DEVELOPED LAMINAR MIXED CONVECTION IN UNIFORMLY HEATED PIPES

Approximate solutions are carried out for fully developed laminar mixe d convection in uniformly heated horizontal pipes. The problem conside red is steady state and validity of the Boussinesq approximation is as sumed. The analysis reveals that the relevant parameters are the Prand tl number and the product of the Rayleigh number based on temperature gradient along the pipe wall and of the Reynolds number based on press ure gradient along the pipe axis. Solutions for the velocity and tempe rature fields are obtained by a spectral Galerkin method, which proves capable of giving rapid convergence and, by implication, good accurac y, as demonstrated by the comparison with other numerical predictions. The results are presented in terms of fluid flow patterns, isotherms, and graphs of mass flow rate, local and average Nusselt number for va rious values of the parameters.