Design and construction of an evaporative cooler for citrus fruits.

Abstract

A Solar Powered and Temperature Controlled Evaporative Cooler of 45 kg capacity was designed and constructed to increase the shelf life of fresh citrus fruits. The cooler was tested using green freshly harvested lemon fruits and evaluated. The cooler operates on the principle of DEC. Freshly harvested citrus fruits are highly perishable. The cooler was made up of a 1.5mm mild steel sheet and lagged with cotton with one side made of sponge pad through which the water flew via a perforated half inch PVC pipe from the reservoir located at the top of the cooler. A 12 V battery powered two DC fans inserted on the side opposite to the side of sponge pad and a DHT22 sensor controlled the fans. A buzzer and LCD screen were also incorporated in the system. The temperature, RH and weight loss of fruits were statistically analysed and the results revealed that there was a marked difference in using the cooler for pre cooling of citrus fruits as compared to the shade. The temperature in the cooler reduced up to 19.0 °Σ when compared to the shade and the RH in a cooler chamber went up to 99%. However, the testing of the system disclosed that the citrus fruits can be pre cooled with minimal changes in weight, color and no putrefying as compared to the shade which started with notable changes in weight, color and severe putrefying after 3 days. Hence, it is on advisable that market dealers and citrus processing factories adopt the use of an evaporative cooler for their preservation as this increases their shelf life.