Effects of Ratio of Dynamic Circulation to Evaporation Rates on Exergy and Cooling Efficiencies an Evaporative Cooler

The expected performance characteristics of a wet media in an evaporative cooler with the specified geometric and material aspects are reducing the dry-bulb temperature and increasing the moisture content of the air outlet. Inlet air conditions are not under the control of the designer or the operator, but the choice of media geometry and fabric, the external factors such as the water circulation rate, and the velocity of air passing through the media could be controlled by the designer. Based on cooling performance for the excelsior of aspen wood pad, the minimum amount of ratio of the static circulation to evaporation rates is about 8 to 12, which has been mentioned in the literature. In this work, for the cellulosic pad by considering the exergy and cooling efficiencies, the optimal ratios of circulation to evaporation rates are presented for different air velocities. It can be seen that under the constant inlet air conditions, by increasing the air velocity as: 0.5, 1.0 and 1.5 m/s, the maximum exergy efficiency values are 0.10, 0.13 and 0.18 respectively and there are some specified values (minimum) for the ratios of water circulation to evaporation rates between 2 and 2.8 for the typical cellulose pad. However, for the same air velocities, maximum cooling efficiencies occur at lower exergy efficiencies, such as 0.03, 0.04, and 0.045, respectively.