Fabrication & performance analysis of direct type passive solar dryer for chilies and grapes drying

Now a days in the agriculture sector, agricultural drying has great importance. As compared to the open sun drying, a solar dryer has faster drying rates and it can remove moisture from vegetables and fruits in very short time. This study presents the very convenient method by using direct type passive solar dryer for drying of chilies and grapes. By removing moisture life of fruits and vegetables can be enhanced and these can be used and conserved for long time. This drying technique not only evaporates but also provides a controlled and safe storage of products. A closed wooden casing along with glass and black colored metallic sheet was employed to achieve the maximum temperature. An average inside air temperature of 60-70°C was achieved, whereas an average outside air temperature of 33-44°C was noted in the months of October and November. Solar illuminance was measured by lux meter. The maximum values for illuminance was in between 8000-12000 lux from 10:30 am to 4:30 am. 20-40% moisture lost per day for three days of drying session. Chilies and grapes were used as a test product. For chilies 85% of moisture was evaporated in 15 hours, while maximum inside air temperature gained inside the dryer was 70 °C. And for Grapes 75% moisture was dehydrated in 15 hours, while maximum inside air temperature noted within the dryer was 68°C.