FORCED-CONVECTION IN THE THERMAL ENTRANCE REGION OF A CIRCULAR DUCT WITH SLUG FLOW AND VISCOUS DISSIPATION

Slug flow forced convection in a circular duct is studied. The effect of viscous dissipation is analysed in the thermal entrance region. The temperature field and the local Nusselt number are determined analyti cally for any prescribed axial distribution of wall heat flux. Three e xamples are considered: a uniform wall heat Bur, a linearly varying wa ll heat flux and an exponentially varying wall heat flux. In the case of a uniform wall heat flux, it is shown that viscous dissipation redu ces the value of the local Nusselt number in the whole duct. In the ca se of a linearly or exponentially increasing wall heat flux, viscous d issipation affects the local Nusselt number only in the thermal entran ce region and becomes negligible in the fully developed region. Copyri ght (C) 1996 Elsevier Science Ltd.