EFFECT OF DRYING AREA ON HEAT TRANSFER COEFFICIENT AND DRYING KINETICS OF HIGH-MOISTURE CROP DRIED IN A HYBRID ACTIVE GREENHOUSE SOLAR DRYER

A hybrid active greenhouse solar dryer (HAGSD) integrated with water in a tube-type evacuated solar collector is developed for drying high-moisture crops. The effect of three different drying areas (0.6 m(2), 1 m(2), and 1.5 m(2)) on the heat transfer coefficients and drying kinetics of bottle gourd, tomato, and ginger in winter and summer seasons is analyzed. The same quantity of the selected crops is dried to 10% (wb) moisture content in all three drying areas. The performance of dryer improves with increase in the drying area and the best result is obtained on the 1.5-m(2) drying area. The drying time on the 1.5-m(2) area is found to be 4-7 h and 4-9 h less than on the 0.6-m(2) area and 1-2 h and 1-3 h less than on the 1-m(2) area for all the three crops in winter and summer, respectively. The average convective heat transfer coefficient on the 1.5-m(2) drying area is found to be 34% to 134.58% higher than on the 0.6-m(2) area, while the evaporative heat transfer coefficient on the 1.5-m(2) area is 12.78% to 368.94% higher than on the 0.6-m(2) area for all the crops in both the seasons. The efficiency of the dryer is observed to be higher on the 1-m(2) area.