The calculated optimum dimensions for both the mixed and indirect-mode dryers
are shown in Table 3. Optimization gave a shorter collector length for the mixedmode solar dryer than for the indirect-mode dryer of the same capacity. This is due
to the extra energy received through the drying chamber transparent cover of the
mixed-mode dryer that gives rise to another drying front at the top of the grain bed,
moving downwards, and therefore reducing on the energy demand from the collector.
The grain depths for both dryers are equal (about 83.5 mm), but the mixed-mode
has a slightly wider drying chamber.