WALL TEMPERATURES IN A TUBE WITH FORCED CONVECTION, INTERNAL RADIATION EXCHANGE, AND AXIAL WALL HEAT CONDUCTION

摘要

An analysis is presented in which a circular tube with uniform wall heat generation is cooled by a turbulent forced convection gas flow. The wall temperature is determined by taking into account the effects of (l) connective heat addition from the tube wall to the flowing gas, which includes a varying heat-transfer coefficient in the thermal entrance region, (2) radiation exchanges between wall elements on the internal surface of the tube, and (3) axial heat flow by conduction along the tube wall. The flowing gas is assumed transparent to radiation, and, hence, does not participate in the radiative exchange process. It is assumed that the outside surface of the tube is perfectly insulated, while the inside surface is a black radiator. The resulting nonlinear integodifferential equation is solved by a specially devised iterative technique, and a number of illustrative solutions are given. It was found that radiation exchanges can cause significant changes in the wall temperature distribution, but the effect of axial conduction was generally small. As in the illustrative case of convection alone presented herein, the high convective heat-transfer coefficient in the thermal entrance region considerably reduced the wall temperatures at the tube entrance but had a lesser effect on the peak wall temperatures.