Design, construction and testing of an improved solar powered evaporative cooling system
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A solar powered evaporative cooler of 0.216 m3 capacity was designed, constructed and tested with the objective to increase the shelf life of stored vegetables and fruits. The evaporative cooler was tested and assessed using fresh tomatoes. The system operates on the principle of evaporative cooling and thus increasing the relative humidity (RH %) in the storage chamber. The frame of the storage system was constructed out of metallic material and sides of the system packed with jute pad which get moist by water flowing through a series of perforated piping system from the reservoir placed at 10cm above the system to allow water flow by gravity. The daily temperature in the system dropped significantly in a range of 40C to 7°C with corresponding daily RH range of 73% to 90% and cooling efficiency of 78.4% to 82.9% unlike the ambient condition which showed a daily temperature variation of 220C to 260C. The temperature change, relative humidity and weight loss of tomato was statistically analyzed using t–test and the result exposed that there was significant difference in using the designed evaporative cooler for storing tomatoes at a 5% and 1% significance level. However, the testing of the evaporative cooler showed that the tomatoes can be stored for an average of five days with negligible changes in weight, color, firmness and rotting as compared to ambient condition which showed rotting in a period of five days of storage. Hence, it is on this note that householders, farmers, and tomatoes processing factories should make use of such evaporative coolers for temporal storage of fresh tomatoes as this will increases the shelf life of tomatoes.