Study of the Drying Behavior and Performance Evaluation of Gas Fired Hybrid Solar Dryer

摘要

The conventional drying methods are energy intensive and are not cost competitive. The severe energy crises in Pakistan during the last decade has decreased the interest in drying of farm produce which is resulting huge postharvest losses due to product spoilage and nonavailability of storage facilities. This study has been carried out for the performance evaluation of newly developed hybrid solar dryer for the drying of onion, ginger and cabbage under local climatic conditions. The hybrid solar dryer has a total cross-sectional area of 0.122m(2) out of which 34% is the collector while 64% is drying section. The dryer uses solar energy for drying during daytime while assisted with backup source during night for continuous product drying. The average initial moisture content of ginger, onion and cabbage batches was measured to be 88.45, 55.76 and 72.51%, respectively, while the final moisture content after drying was 10.27, 15.69 and 15.02%, respectively. The result also shows that the initial high moisture content of the products was removed in early hours of sunshine without any expense of primary energy cost. However, the remaining small amount of hygroscopic moisture was removed using backup energy source but with lower costs as compared with conventional drying. The final moisture content was achieved between 10 and 16h for all batches of the onion, ginger and cabbage. On an average, greater than 70% moisture of the products was removed on the expense of solar energy. The overall average efficiency of the dryer was found to be 42.79%.