Abstract:
A double-pass indirect solar dryer has been designed, constructed, and evaluated that
can be used for drying chickpeas. The main aim of the study was to address the
problem associated with the fact that solar dryers only work efficiently when there is
enough solar energy.
The dryer mainly consists of a solar collector panel, drying chamber, and chimney.
The solar collector is made of 4 mm thick single-layer glass, 2 mm black painted mild
steel absorber plate, and 18 mm plywood insulation enclosed in a wooden housing.
The drying chamber is made of plywood with a thickness of 18 mm. The chimney is
made of a plastic pipe with a diameter of 12 cm.
Several tests have been performed to evaluate the performance of the dryer. An
unloaded test, i.e., a test without holding the material to be dried, was performed, and
it indicated that the temperature in the dryer could reach 54℃. The maximum and
average collector outlet temperatures recorded were 62℃ and 40℃, respectively. The
maximum and average temperatures of the absorber plate recorded were 90℃ and 54
℃, respectively.
Dryer performance was also evaluated using chickpeas. For the different tests
performed, the performance parameters used for the evaluation included moisture
content, drying rate, and drying efficiency.
The moisture content of chickpeas was reduced from 25% to 12% within two days.
Using only solar energy as the heat source, the drying rate for chickpeas on the first
and second day was found to be 97.12 g/h and 69.3 g/h, respectively. On the first day,
a higher drying rate was obtained. The maximum and average collector efficiency was
found to be 62.5% and 32%, respectively. The drying efficiency was also found to be
15% for solar drying.