Pad type impact on the economical direct- evaporative air cooler efficiency

Theoretical and experimental investigations were performed to study the impact of four pads in series on the thermal performance of an economical evaporative air cooler that works at a low voltage (12 Volts). Straw and cardboard pads were studied. The studied parameters were dry bulb temperature, the dry bulb temperature difference between inlet and outlet air, cooling efficiency, and the total heat transfer rate. Three draft fan speeds were considered, i.e. 2.8, 3.5, and 4.7 m/s. The results showed that adding multiple pads in series had an insignificant impact on the evaporative cooler thermal performance compared to one pad. The straw pads' cooling efficiency at 2.8 m/s was lower than that of the cardboard, i.e. 91.4% and 93.1%, respectively. Also, it was found that the velocity of the air passing through the cooler significantly impacted the cooling efficiency. The theoretical results for the lowest speed of 2.8 m/s showed an increase in the cooling efficiency of the cardboard pad by 46.6% compared to the speed of 4.7 m/s due to a long time for heat transfer. Therefore, the best air velocity entering the cooled space was 2.8 m/s.