Laminar film condensation from downward flowing superheated vapors onto a non-isothermal sphere

Abstract

A model is developed for the study of mixed convection film condensation from downward flowing superheated vapors onto a sphere with variable wall temperature. The model combined natural convection dominated and forced convection dominated film condensation, including effects of superheated vapor, pressure gradient and wall temperature variation can be solved numerically by the fourth-order Runge–Kutta technique. By the present numerical approach, the mean heat transfer is evaluated up to the critical angle of the condensate layer, φc. In general, the result of mean heat transfer shows that, as A, the wall-temperature amplitude, increases, the value of \(\) with inclusion of P, the pressure gradient effect, goes down slightly, however, the value of \(\) with the pressure gradient effect ignored will remain almost uniform. Further, for P=2.0, the mean heat transfer coefficient increases significantly, by 8.6–23.9%, depending on A, as the superheat parameter, Sp, increases within a practical range.