Heat transfer in porous media considering phase change and capillarity - The heat pipe effect

A one-dimensional, steady state analysis of the heat and mass transfer in porous media saturated with the liquid and vapor phases of a single component fluid was conducted. The effects of capillarity, gravity forces, and phase change were included. Theoretical results were compared to experimental data with excellent agreement. It was found that the heat transfer was increased several orders of magnitude beyond pure conduction due to an evaporation, convection and condensation phenomenon similar to conventional heat pipe operation. The dry-out heat flux was predicted and verified for the bottom heating orientation. Theoretical temperature, pressure and saturation profiles within the two-phase region were obtained. Apparent thermal conductivities were evaluated for various gravitational orientations and medium permeabilities.