1. Introduction
The advantages of solar drying over open sun drying are well documented [1,2].
Among the different types of natural convection solar dryers, the mixed-mode type
has been demonstrated to be superior in the speed of drying [3–5]. In this type of
dryer, grain is dried on a perforated surface and is subjected to direct radiation on
its top surface through the transparent drying chamber cover, and an air current
passing through the grain bed from a solar air heater [6].