Analysis of condensation in porous insulation

Abstract

The present work analyzes the problem of condensation in porous insulation. Specific consideration is given to a steady-state one-dimensional formulation, representing a porous slab exposed to two different humid environments on both sides. The analysis includes both the convective and the diffusive transport mechanisms along with phase change. Condensation (or freezing) is shown to take place in a wet zone in which the air-vapor mixture is saturated. When the two external environments are not saturated, the wet zone is bounded by two dry zones with no condensation. The effect of condensation, due to release of latent heat, on the overall thermal performance is found to be significant. Both the condensation rate and the resulting increase in heat transfer depend on the Peclet number, the Lewis number, and the Biot number, as well as on the temperatures and humidities of the two external environments.