LAMINAR FORCED-CONVECTION WITH SINUSOIDAL WALL HEAT-FLUX DISTRIBUTION- AXIALLY PERIODIC REGIME

Stationary and laminar forced convection in a circular tube with a sin usoidal axial distribution of wall heat flux is studied under the hypo thesis that both axial heat conduction and viscous dissipation in the fluid are negligible. Two cases are considered: a sinusoidal wall heat flux distribution with a vanishing mean value; a sinusoidal wall heat flux distribution which does not change its sign. In both cases, the temperature field and the local Nusselt number are evaluated analytica lly in the fully developed region, i.e. where the local Nusselt number depends periodically on the axial coordinate. It is shown that, in th e first case, the fully developed region presents an infinite sequence of axial positions where the local Nusselt number is singular. In the se positions, the wall heat flux has a non-vanishing value even if the wall temperature equals the bulk temperature.