Direct Absorption Dryers
Direct drying consists of using incident radiation only, or incident radiation plus reflected
radiation. Most solar drying techniques that use only direct solar energy also use some means
to reflect additional radiation onto the product to further increase its temperature.
An example of direct absorption dryer is the hot box dryer as shown in Figure 1 (3). The aim
of this type of a dryer is mainly to improve product quality by reducing contamination by
dust, insect infestation, and animal or human interference. It consists of a hot box with a
transparent top and blackened interior surfaces. Ventilation holes in the base and upper parts
of slide walls maintained a natural air circulation.