Construction and Comparative Analysis of Passive and Active Indirect Hybrid Solar Dryer’s for Drying Tomatoes

Abstract

The surplus agricultural products needed to be preserved by drying during harvesting period for long term storage. The application of modern techniques of solar thermal systems using solar dryers substitutes the use of an olden day’s method of direct sun radiation. This research entailed construction and comparative performances analysis of two different hybrid indirect solar dryers. The average daily air flow rates and temperatures in the dryer’s chamber, the weight reductions, percentage moisture contents and moisture removed, and the drying rates and dryer’s efficiencies were analyzed and compared. It has been found that the weight of tomatoes has reduced by 45.4% in a passive dryer’s chamber with temperature 43.1^oC when the air flow rate was 1.83m3/s. While in an active mode dryer’s chamber, the tomatoes weight has reduced by 49.2% at temperatures of 50^oC and 2.04m³/s air flow rate. Furthermore, out of 64.6% moisture content of tomatoes placed in a passive mode dryer, 61% has been removed due to drying rates of 31.1% attaining 64.8% drying efficiency. While, in an active dryer, 61.2% of the tomatoes moisture had been removed out of 64.8% of its contents, due to drying rate of 46.1%, enhancing 77.9% drying efficiency. It has been noted that both tomatoes got dried in two days through an active drying mode; however, it took them three days to be dried in passive mode dryer. Therefore, active mode dryer is more efficient than the passive, and it can be effectively used for drying tomatoes.