Design and performance evaluation of a passive flat plate collector solar dryer for agricultural products

A passive flat plate collector solar dryer (FPC-SD) was designed and fabricated for drying of agricultural products. It has drying capacity of 7.5 kg, drying chamber cross sectional area of 0.74 m x 0.58 m, collector aspect ratio 2, collector depth of 0.25 m and hence volume of 0.5 m(3). Total pressure drop across drying bed Delta P(T)was 1.29 kg/m(2). The difference between the dryer inlet and ambient temperature was recorded for certain days and was 24.6 degrees C at 1.30 p.m. with average solar insolation of 882.35 W/m(2). Performance of FPC-SD was evaluated by drying mushroom under sun drying and passive FPC solar dryer. The moisture ratio of the samples reached zero in 33 hr for sun drying while 21 hr for FPC-SD. Solar drying took 36.36% lesser time than open sun drying. Practical applications The designed and fabricated flat plate collector (FPC) solar dryer incorporated with a phase change material is a farmer's friendly unit, which can dry agricultural products at farm level. Traditional open sun drying is usually practiced by farmers for drying of fruits and vegetables which generates wastage and also is an energy inefficient process. It also results in loss of nutritional quality due to slow and intermittent drying. The solar dryer is a sustainable and environment friendly farmer's gadget for drying of fruit and vegetables with better retention of the quality. The phase change material helps to prolong the operation even after sunset and thus this continuous operation accomplishes the drying process sooner. Incorporation of phase change material as thermal storage unit helps in improving its performance. Present FPC-SD helps carry out drying in nearly 35 to 40% lesser time than open sun drying.