EFFECT OF VISCOUS DISSIPATION ON THE ASYMPTOTIC-BEHAVIOR OF LAMINAR FORCED-CONVECTION IN CIRCULAR TUBES

The asymptotic behaviour of laminar forced convection in a circular tu be, for a Newtonian fluid at constant properties, is analysed by takin g into account the viscous dissipation effects. The axial heat conduct ion in the fluid is neglected. A sufficient condition for the existenc e of a fully developed region is determined. This condition includes, for instance, any asymptotically vanishing axial distribution of the w all heat flux, uniform wall temperature, convection with an external f luid. The asymptotic temperature field and the asymptotic value of the Nusselt number are determined analytically, for every boundary condit ion which allows a fully developed region. In particular, it is proved that, whenever the wall heat flux tends to zero, the asymptotic Nusse lt number is zero. Copyright (C) 1996 Elsevier Science Ltd.