A study of drying rate of some fruits and vegetables with passive solar dryers

摘要

The two passive solar dryers designed and constructed were with available local materials. The passive solar dryers which were direct and indirect type was tested with pepper, okro and vegetables in order to know the drying rate of these produce. 180gof freshly harvested pepper with moisture content of 78.9 % (w.b) were reduced to 24.0 % (w.b). The drying rate in the direct passive solar dryer was found to higher than the indirect passive solar direct. 1000 g of okro with initial moisture content of92 % (w.b) was reduced to 20% (w.b) The drying rate in the direct passive solar dryer was found to higher than the indirect passive solar direct. 400 g of vegetable with initial moisture content of 90 % (w.b) was reduced to 20 % (w.b). The drying rate in the direct passive solar dryer was found to higher than the indirect passive solar direct. During the course of drying after the crop is kept inside the drying system the temperature of each drying was monitored after one hour interval, the moisture content of the crop was also monitored after three hours interval until there is no more change in the weight of the crop. The crop dried inside the direct solar dryer driedfaster than the indirect passive solar dryer. As result of highest temperature attained in the direct passive solar dryer the rate of moisture removal was high in this dryer.