Design and Development of a Two-Stage Evaporative Cooling Transportation System for Fruits and Vegetables

Cooling and storage of fruits and vegetables using evaporative system is a well establish technique. Many evaporative cooling storage structures have been designed and developed using different construction and pad materials to improve system cooling efficiency. But the limitation with evaporative cooling is that, cooling of air can be achieved up to wet bulb temperature only. It can be overcome with the two-stage indirect- direct evaporative cooling system consisting of indirect cooling system and direct evaporative cooling. Therefore, two-stage evaporative cooling system was designed, constructed to improve the efficiency of evaporative cooling in order to reduce losses of fresh fruits and vegetables during transport and increase its availability. The developed system was evaluated for its performance with respect to three different air supply velocities (11.11, 14.00, 16.70 m/s), three pad thicknesses (100, 150, 200 mm) and three water flow rates (3, 4, 5 lpm) in terms of temperature drop and increase in relative humidity.. Significantly overall higher temperature drop of 14 +/- 2.9 degrees C was obtained for combination of 16.7 m/ s air velocity, 200 mm pad thickness and 5 lpm water flow rate. The overall cooling efficiency obtained varied from 54% to 100%. Maximum average relative humidity of 63% obtained for 14 m/s air velocity, 150 mm pad thickness and 3 lpm water flow rate.