Effect of boundary layer on drying mechanisms of beach and desert sand

A boundary layer developed over a flat-plate surface plays a great role in the mechanisms of convective drying. Beds of desert sand, beach sand and glass beads were subjected to forced convective drying in a scaled-up wind tunnel. The resulting temperature distribution profiles demonstrated clearly the stages of the drying process. A mathematical model is proposed to predict the temperature profile along the surface at various intervals. Good agreement was obtained between predicted and measured temperature profiles throughout the bed. The results showed a significant difference in the temperature along the bed. Surface temperature decreased gradually with increase in the distance from the leading edge. In a bed of 1 m long, the difference in the surface temperature was 11°C for the case of desert sand, and was 8°C for the case of beach sand. The results also revealed that the part of the bed closest to the leading edge dried faster. The reported results give a clear picture for the great role of the boundary layer in the drying mechanisms of the beach and desert sand.