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.