Experimental Investigation of the Performance of Two-Stage Evaporative Coolers

Abstract

Experiments have been conducted to investigate the thermal effectiveness and the air-side pressure drop of single- and two-stage evaporative coolers. Two different configurations of the two-stage evaporative cooler have been tested. The first one uses an external cooling tower to cool the water required to precool the air in the indirect water-to-air precooler. In the second design the cooled water in the direct-contact evaporative cooler is used as the cooling medium in the air precooler. Tlie variables considered are packing thickness, mass flow rate of water to the precooler, and mass flux of water irrigating the packing. The data obtained indicate that the thermal effectiveness of the two-stage evaporative cooler with a cooling tower is high compared to that of the system without a cooling tower, which in turn is superior to that of the single-stage, direct-contact evaporative cooler. Increasing the mass flow rate of water to the air precooler improves the effectiveness of the two-stage evaporative coolers. The effectiveness of the two-stage cooler without a cooling tower dimensions uniformly with the increase in the mass flux of water irrigating the packing. The effectiveness of the single-stage and the two-stage design using a cooling tower was found to be independent of the mass flux of water flowing over the packing. For the three configurations tested, the thermal performance increases with the packing thickness, and the air-side pressure is nearly constant.