Case Study on Thermal and Drying Performance Index of Hybrid Solar Dryer with Evacuated Collector

Solar drying is one of the oldest and most popular food preservation methods that involve moisture removal by a complex heat and mass transfer phenomenon. The process of the drying system is dependent on a number of operating parameters. In the present chapter determination of thermal and drying performance parameters is discussed. A hybrid solar drying system with the integration of an evacuated water tube solar water heater is installed and tested for drying hygroscopic leaf crops. The drying performance of the hybrid system is evaluated in terms of mass reduction and its derived influence on moisture content and drying rate. The derived parameters are compared with the corresponding evaluations under open sun drying. The rise in greenhouse environment temperature and crop surface temperature at hourly intervals as compared to the ambient condition were used as parameters for the thermal performance of dryer. The average values of SMER were 60% lesser than that of the simple PVT-hybrid system (without ETSC), but the drying performance parameters of mass reduction, drying rate and mass shrinkage ratio provide favourable results. The drying time was reduced by 3.5 and 2.5 hours, respectively, for the present sample size of two crops as compared to the open sun drying.

Keywords: Hybrid, Solar dryer, Evacuated tube, Solar collector, Drying.