Heat and mass transfer along a wetted porous plate in an air stream

This experimental study examines 2-D effects on long plate drying due to heat and moisture transfer through boundary layers and porous medium interaction. Many innovative techniques are used to measure accurately boundary layers (velocity, temperature, moisture), the wall surface (infrared sensors for temperature and moisture), and the medium (water content). Gradual decrease in surface saturation measured for several kinds of materials shows that their behavior is more complex than described by the Suzuki-Maeda model, which does not predict the mass exchange sufficiently. Based on the analysis of the transfer between the surrounding air and the porous medium at the scale of the pore on a rough surface, a flow classification is defined and other characteristics are proposed. The drying rate depends on the mass-transfer coefficient, which varies along the plate with the air flow. The study of boundary layers gives the corresponding profiles with an acceptable accuracy. The laminar-to-turbulent transition increases mass-transfer rates resulting in two drying fronts. The diffusive model proposed here predicts a gradual change in the drying rate along the plate similar to the experimental one.