Testing and Evaluation of Double Layer Evaporative Cooler for Vegetables Preservation in North

Sri Lanka is faced a problematic issue of post- harvest preservation and processing of agricultural produces. Introduction of cost effective method for storage of vegetables is necessary to maintain freshness until marketing. The evaporative cooling principle was introduced under the construction of cooling chamber system. Therefore low cost zero energy double layer cool chambers were designed using clay bricks, anthill clay. Space between double layers was filled with saw dust and charcoal separately and water circulated from top to bottom. The cool chambers were made to enhance the shelf life and minimize the weight loss of vegetables. Temperature and relative humidity inside and outside of chamber were measured in hourly intervals in day time. The samples of Spinach, brinjal and carrot were selected for evaluation. Weight loss was measured at hourly intervals to check the effectiveness of the design. Physiological weight loss for all selected vegetables was low for samples placed charcoal media cool-chamber than the saw dust media cool-chamber than outside. Evaporative cooler design tested by the regression analysis was implied to fit the relationship between log mean temperature ratio against time duration of cooling in saw dust media and charcoal media cool-chambers. The cooling rate (CR) was expressed by the equation, respectively. The relationship derived to charcoal media cool-chamber was y= -0.015x + 0.063 with regression value of Ris 0.978 and saw dust media cool-chamber y = -0.033x +0.079 with regression value of R is 0.856. The cooling rate and efficiency were higher in charcoal as a filling media cooler. Since the regression value was more than 80%, in the both design. Design evaporative coolers are satisfied the requirements of safe storage.