Effects of capillary forces on laminar filmwise condensation on horizontal disk in porous medium

This study investigates the problem of steady filmwise condensation on a horizontal disk embedded in a porous medium. The disk surface is cold and faces upwards into the porous medium, which is filled with a dry vapor. Due to the effects of capillary forces in the porous medium, a two-phase zone is formed between the liquid film and the vapor zone. As in the classical filmwise condensation problem, this study assumes that the inertia within the liquid film is negligible and that the properties of the porous medium, dry vapor, and condensate are constant. Darcy’s law is used to analyze the liquid flow in both the liquid film and the two-phase zone. A capillary parameter, Bo_c, is introduced to characterize the liquid flow caused by capillary forces in the porous medium. It is shown that the mean Nusselt number, , increases at higher values of the capillary parameter, Bo_c. Finally, this study derives a simple closed form correlation for the Nusselt number for the case where the capillary forces are neglected.