Experimental on a new mixed-flow 2-stage regenerative indirect evaporative cooler

Abstract

This work proposes a mixed-flow prototype to balance the better thermal performance of counter flow and the smaller size of cross-flow configuration. The heat exchanger is made of polycarbonate plates, while water distribution is optimized thanks to outlet nozzles and wicking material located on the wet side. The device measures 0.025 m3 and supplies 40 l/s of cooled air, with a cooling capacity above 325 W at 40 °C and 30% relative humidity inlet air conditions, while consuming 1.9 l/h. Experimental characterization demonstrates that increasing the inlet dry bulb temperature and decreasing the inlet air relative humidity yield notably higher temperature drops and cooling capacities, but with lower effect on the thermal effectiveness. Compared to a previous one-stage prototype, the two-stage configuration increases the temperature drop and both the wet bulb and dew point effectiveness by about 50%. However, cooling capacity barely improves to less than 17%, due to the bleed off the product air as working air.