Abstract
This study deals with the analytic solutions for the two nonlinear problems arising in heat transfer. These problems are due to (i) temperature distribution in lumped system of combined convection-radiation and (ii) temperature distribution in a uniformly thick rectangular fin radiation to free space. Large symmetry algebras are obtained for the nonlinear ordinary differential equations (ODEs) describing the heat transfer. We use method of canonical variables to either linearize or transform the governing equations to integrable forms. Exact solutions are constructed. Finally, a comparison is given between the homotopy and symmetry solutions. (C) 2009 Published by Elsevier Inc.