Environment Friendly Indirect-direct Type Evaporative Cooling Technology: A Review

This paper reports a review based study into the two stage indirect- direct evaporative cooling technology, which is referred as two-stage evaporative cooling (TSEC) system. The direct-type (evaporative) cooling system is widely using natural cooling technology for storage of agricultural produce particularly fruits and vegetables because of its simplicity, eco-friendly and low-cost. But EC system is environment based and got the limitation that cooling of air can be done up to wet bulb temperature. To overcome this and owing to the continuous progress in cooling technology innovations are done by combining other indirect methods with direct type evaporative cooling system. Such system is known as two stage evaporative cooling, includes indirect and direct type cooling system. The indirect cooling has potential to be an alternative to conventional mechanical vapour compression refrigeration system to take up the air conditioning duty. Indirect cooling system is mostly heat exchanger(s) whereas direct cooling is wet pad type system. Combination of these two systems has obtained significantly enhanced cooling performance, with near to 90% and high energy efficiency ratio up to 80. The experimental and research work done on the indirect and direct cooling technology on the basis of their design, structural, type of indirect cooler, materials of construction, pad materials, effectiveness and energy saving have been reviewed and presented. This review paper explains the working principles of two-stage evaporative cooling systems and its performance assessed. This system is energy efficient, environment friendly and having potential for cooling and storage of fruits and vegetables in countries where hot and dry weather prevails for most of the part.