A Diffusion Flame Adjacent to a Partially Saturated Porous Slab: Funicular State

The burning on the surface of a porous slab initially fully saturated with liquid fuel, and during the period where the liquid phase is continuous, is studied in order to determine the effects of the surface saturation, relative permeability, and vapor flow rate on the critical time. The critical time is defined as the time at which for the first time the surface saturation becomes zero, i.e., the first dry patches appear. The experimental and predicted results are in good agreement. The results show that unlike forced convection drying, the surface saturation does not influence the mass transfer rate significantly. Also, for the range of absolute permeabilities considered, the critical time is proportional to the absolute permeability.