Simultaneous heat and moisture transfer in fiberglass insulation with transient boundary conditions

The coupled problem of heat and vapor diffusion within porous fiberglass insulation materials is considered under transient conditions of heat conduction and water vapor adsorption/desorption, condensation, and frosting. A special laboratory test facility is described for measuring transient, one-dimensional temperature, heat flux and moisture accumulation for a range of cold-plate temperatures near 10 C (50 F) down to {minus}20 C ({minus}4 F) and warm-side relative humidities from 35% to 90%. The measured boundary conditions were used as input conditions for a numerical model for heat and water vapor diffusion. The simulation results compared well with measured data within the experimental uncertainty for all the results except heat flux when the insulation slab was subjected to repeated temperature cycles. The discussion also includes results for a cyclic cold temperature case.