Mango leather (Aam Papad) drying in hybrid greenhouse solar dryer with evacuated tube collector and finned drying tray: drying behavior and economic analysis

Abstract

ABSTRACT Mango is primarily produced in India, and being a seasonal fruit, its pulp is dried to make mango leather so that it can also be enjoyed in the off-season. Traditionally, it is dried under the open sun, which takes more time to dry, and quality gets compromised due to direct exposure to dirt, direct sunlight, birds, pests, and microbes. Hence, its drying behavior is analyzed in a standalone hybrid greenhouse solar dryer (HGSD) operating in active mode. An evacuated tube collector (ETC) is attached to the dryer for high room air temperature and high drying rate. An aluminum drying tray having fins is fixed over copper tubes of a heat exchanger. The copper tubes get fixed in the finned slots of the drying tray, which increases the heat exchange between tray and tube. Experimentation is performed under three conditions: dryer with a collector, dryer without a collector, and open sun drying (OSD). The drying time in the dryer with the collector is 4 hours, 7 hours less than the dryer without the collector and OSD, respectively. The average convective heat transfer coefficient (CHTC) for the dryer with and without the collector is 0.11 W/m2°C and 0.08 W/m2°C, respectively, while in OSD, it is 0.07 W/m2°C. The economic analysis of the dryer shows that the payback time is 0.25 years only; hence, the large amount invested on the dryer is recovered in very less time and the profit can be enjoyed for the remaining time.