DEVELOPMENT AND PERFORMANCE EVALUATION OF EVAPORATIVE COOLING SYSTEM USING SOME SELECTED COOLING PAD MATERIALS

Abstract

Post-harvest loss of fruits and vegetables in developing countries was due to the lack of proper storage facilities. Refrigerated cooling systems are the best method of preserving fruits and vegetables, however they are expensive to acquire and maintain. Food losses had been a major threat to securing foods for the teeming populace. Hence, a need to continue to invent in storage equipment that are not only effective but also affordable for rural farmers. A zero-based evaporative cooling system with a capacity of 0.06m3 was designed and constructed to increase the shelf life of stored fruits. The equipment uses the principle of evaporative cooling which increases the relative humidity and lowers the temperature in the cooling chamber. The cooling pads used are coconut husk and modified kenaf blast fibre and are moistened with water flowing under gravity through a series of perforated rubber hose from a reservoir located at the top of the storage system. An evaporative cooling structure without any pad and a refrigerator were used as control. The evaporative cooling system was evaluated using fresh African plum/Bush pear (dacryodes edulis). The relative humidity and temperatures of the cooling chambers were taken by using a weather station instrument coupled with data logger. The evaporative cooling structure shows reduction in the wet and dry bulb temperatures and relatively higher relative humidity when compared to ambient environmental temperatures and relative humidity. The result of saturation efficiency of the storage systems shows that the highest saturation efficiency was found in the coconut husk evaporative cooling system with an average value of 99.14 ± 0.27% and the least saturation efficiency was found in the control evaporative cooling system with a mean value of 86.19 % while the mean saturation efficiency of the modified kenaf blast fibre (86.33 ± 18.56 %) was slightly greater than that of the control throughout the storage period of 7 days. The results of the cooling capacity of the storage systems shows that the mean cooling capacity of the modified kenaf blast fibre (37.46 W) was slightly greater than that of the control storage system across the storage period of 7 days. Moreover, the result of the rate of weight loss of fruit throughout the storage period was recorded as 1.99 ± 0.14 %/day, 3.78 ± 0.63 %/day, 3.57 ± 0.15 %/day, and 3.9 ± 1.69 %/day for the refrigeration system, evaporative cooling system cooled with coconut husk, modified kenaf blast fibre and control system respectively. It was observed that the higher cooling capacity informs the low bacteria and fungi counts of 5.67 ± 1.17 x 10⁷cfu/g and 3.33 ± 1.53 x10⁵sfu/g respectively in Africa plum stored in the evaporative cooling system with Modified kenaf blast fibre pad when compared with the bacteria and fungi counts of 11.53 ± 0.81 x 10⁷cfu/g and 12.33 ± 2.52 x10⁵sfu/g respectively of the evaporative cooling system with coconut husk. The research provides a portable, efficient and cost-effective means of storing fruits for peasant farmers and retailers of African plum. Further studies with different leafy vegetables and fruits should be carried out on evaluation of the evaporative cooling systems in order to predict accurately the performance .