Experimental Studies on Developed Direct Solar Dryer for Conversion of Grapes into Raisins with Temperature Control

Abstract

This chapter presents the experimental studies of the temperature variations in developed direct solar dryer while conversion of grapes into raisins. Optimum temperature of solar drying of grapes is in the range 28^oC to 55^oC so a small DC fan and speed control device running with solar PV panel is attached to the dryer to control the temperature in the dryer. The solar dryer is a flat plate solar collector with an aperture area as 2972.65cm². Experiments were performed without and with load, and the temperature profiles are reported. During load experiments with the developed solar dryer, the weight of 1kg of grapes reduced to 0.260 kg in five days and raisins were developed. The efficiency of the system was found to be in the range 4% to 7%. The efficiency of the system can be further improved with load optimization and slight modifications to make it suitable for households and cottage industries.