Abstract:
Sun drying ofmqize grains on unperforated and perforatedsurfaceswas conducted under simulated solar
radiation intensity of afJout 800 Wlm: and in the field, where solar radiation intensity was variable. ,The
drying depths employed were 10, 20, 30 and 40 mm under simulated solar radiation conditions and 20
and 40 mm in the field The response variables measured were weight loss at all depths and moisture content
and temperature distributions in the 40-mm depth bed The results in terms of overall drying rates
indicate that, at depths greater than 10 mm, the perforated surface was superior (P < 0.05) to the
unperforated and at 40 mm th.e efJectwas about double that of the contro/. Changi,!gof dryingdepthfrom
10 to. either 20 or 30 mm on the perforated surface did not affoct the specific drying rates significantly (P <
0.05) 'except on 40/,;;n depth. On the unperforated surface the overall specific drying rates decreased significantly
(P<O. 05) with ~hange oj drying depth from 10 to 20 mm and above: Lolt'er moisture gradients
were achieved on th£! ierforaied surface and despite the higher drying rates temperatures in the bed were ,
lower than on the u;lperforated surface. In order for high drying throughput to be achieved, drying depth '
of about 30';"m on perforated surfaces is recommended. Sun drying in the field yielded results that were
similar to those obtained under simulated solar radiation conditions despite the fluctuating nature ofterrestrial
solar radiation intenSity. Further work in the field, focusing on theefJect of aperture size ofperforations
and 'the gap ~ize between the drying surface and the ground floor for perforated surfaces is
needed.'"
