Development and Performance Evaluation of a Solar Dryer for Bulb Onion (Allium cepa L.)

An experimental solar dryer for dehydration of bulb onion (Allium cepa L.) had been designed by the first author and constructed at the workshop of South China Agricultural University- Guangzhou in which efficiency, cost and durability were optimally combined. The data were recorded by a programmable data acquisition system including microprocessor control, recorded data at ten minutes intervals. During winter season (Dec. 2000), solar heated air was 30.1 degrees C on average, relative humidity of 59.3 % on average, and flow rate of 72.7 m(3)/ (h.m(2). coll.surface). The temperatures rises of solar system was 1.7 degrees C and 16.1 degrees C, for those temperatures the average collection efficiency was about 54.7 %. Some drying parameters were calculated and results indicated that the numerical values were satisfactory. A techno-feasibility study gave a good result for the possibility of using the developed dryer in rural area.