Design and Performance Evaluation of an Indirect Solar Dryer: A Recent Study

Abstract

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, in an attempt to minimise post harvest losses of tomato that gluts in Mubi, Adamawa State, Nigeria in the months of August to October annually. With an air mass-flow rate of 3.106 X 10-3 kg/s and an overall mean drying rate of 0.140 kg/h, the planned dryer features a solar collector inclined at an angle of 20.26oC to the horizontal. And it had a 0.065m thick lagging material and a 0.115 m3/s air volumetric flow rate. The dryer's evaluation found that drying tomatoes from a postharvest moisture content of 95.6 percent (d.b) to a storage moisture content of 15.8 percent (d.b) takes 50.8 hours throughout the study months (d.b). Following the development and evaluation of tomato-fruit dryers in other parts of the world, more research is needed to determine the effects of incorporating either an additional source of heat or a heat reservoir to ensure day and night drying, which will improve the drying rate and, as a result, reduce drying time. Color of the fruit, its firmness, flavor, nutritive value & safety of tomatoes are related to their composition at the time of harvest and compositional changes during the postharvest handling.