Axial wall conduction preheating effects in high Péclet number laminar forced convection

An analytical solution for the preheating due to the wall axial conduction in forced convection heating of fully developed laminar flows, is presented. The geometry of interest consists of a long circular tube heated for a finite or semi-infinite length. It is proved that in the preheating region the wall heat flux varies with exponential law in the streamwise direction, so that the temperature profile becomes fully developed. Moreover, an exact functional relation between the exponent of the wall heat flux distribution and a single parameter, which depends on the Péclet number and the wall conductance, is derived. The practical significance of the analysis is finally discussed. Copyright © 1996 Elsevier Science Ltd.