Design and Testing of a Desiccant-Enhanced Evaporative Cooler

Abstract

Evaporative cooling is one method that could help reduce post-harvest losses. However, its increased acceptability has been hindered by its poor performance in humid regions or during humid periods of the day or year, resulting in its inability to produce cooling during those periods. To address this challenge, an enhanced evaporative cooler for the preservation of fruits and vegetables was designed and tested. The system, an active direct evaporative cooler type, incorporated desiccant (activated carbon) and addressed the challenge of frequent desiccant saturation by using a sensor to control the regeneration process. Its major components are a desiccant wheel made of galvanised steel sheet, driven by a 12 V DC motor; a 220 V, 0.14 A-rated extractor fan; a 12 V DC, 70 W adsorbent regeneration heater-fan assembly; a humidification pad; and a water tank. Activated carbon was used as the desiccant. From the results obtained, when the system was tested during humid periods, the storage chamber temperature was maintained below the ambient value throughout the experimental periods, with an average difference of 4.14–5.13 °C. The average cooling power was 259–323 W, while the average COP was 2.95–3.67. Relative humidity within the storage chamber remained above 88% throughout the period. Thus, the designed system can produce cooling, even in a very humid region.