Unsteady thermal entrance heat transfer of laminar duct flows with wall suction and injection

Abstract

Abstract The unsteady thermal entrance heat transfer problem is analyzed by the instant‐local similarity method for the system of fully‐developed laminar incompressible flow into the region of porous wall which permits uniform suction or injection and with a step change in wall temperature. Both the circular tube and flat duct between parallel plates are considered in this work. Numerical solutions of the transient heat transfer rates and the development of temperature profiles are presented for some selective values of suction Reynolds number, Prandtl number, and Graetz number. The numerical solutions at the asymptotic small and large time are in agreement excellently with the transient condution solution and steady‐state solution, respectively. The corresponding steady‐state heat transfer problems are also analyzed by the local similarity and local nonsimilarity methods. The numerical solutions of these methods are in agreement very closely.