Forced convection film condensation of flowing vapour on an inclined circular tube

In this work, an analytical study is made on the process of forced-convecti on-dominated laminar-film condensation on an inclined circular tube for a p ure saturated vapour with vertical downflow. The resultant partial differen tial equation for the local film thickness has been solved analytically by applying the method of characteristics. Thus, an explicit analytical soluti on; in closed-form, has been obtained for calculating the local and average Nusselt numbers. The general solution yields, in special cases, the known analytical solutions of vertical and horizontal tubes. The results show tha t an optimum inclination of the tube, at which the rate of condensation on the whole surface is maximum, is a function of the ratio L/D.