Design and Performance Evaluation of an Indirect Solar Dryer.

Abstract

An attempt to minimize post harvest losses of tomato that gluts in Mubi, Adamawa State, Nigeria in the months of August to October annually, an indirect solar dryer was designed, fabricated and evaluated based on meteorological data of mean monthly values of ambient temperature, wind speed, and global solar radiation, which were 22.2ºC, 3.64 m/s, and 206 W/m2 respectively. The designed dryer has a solar collector tilted at an angle of 20.26ºC to the horizontal with the air mass-flow rate and overall mean drying rate of 3.106 X 10-3 kg/s and 0.140 kg/h. It also had a lagging material of thickness 0.065m and an air volumetric flow rate of 0.115 m3/s. Evaluation of the dryer revealed that within the studied months, the dryer requires 50.8 h to dry tomato from a postharvest moisture content of 95.6% (d.b) to a storage moisture content of 15.8% (d.b). In the light of the tomato-fruit dryers developed and evaluated in other regions of the world, further researches need to investigate the effects of incorporating either an additional source of heat or a heat reservoir to ensure day and night time drying, which will further enhance the drying rate and consequently minimize drying duration.