ON THE LAMINAR FORCED-CONVECTION WITH AXIAL CONDUCTION IN A CIRCULAR TUBE WITH EXPONENTIAL WALL HEAT-FLUX

The values of the fully developed Nusselt numb er for laminar forced c onvection in a circular tube with axial conduction in the fluid and ex ponential wall heat flux are determined analytically. Moreover, the di stinction between the concepts of bulk temperature and mixing-cup temp erature, at low values of the Peclet number, is pointed out. Finally i t is shown that, if the Nusselt number is defined with respect to the mixing-cup temperature, then the boundary condition of exponentially v arying wall heat flux includes as particular cases the boundary condit ions of uniform wall temperature and of convection with an external fl uid.