Investigation and performance rating of a horizontal counter-flow dew point evaporative cooler

The counter-flow dew point evaporative cooler has the potential for better cooling effectiveness with superior energy efficiency, when compared to the cross-flow cooler. However, the development of the counter-flow configuration is still at its infancy stages. In this paper, we proposed a horizontal counter-flow dew point evaporative cooler to overcome the possible problems in existing designs. The flow direction, as well as the water supply, is designated on a horizontal plane. A plate-type heat and mass exchanger was designed and fabricated for the cooler, and a test system was set up for experimental investigation. Both the transient-state and steady-state performance of the cooler were studied. Meanwhile a mathematical model has been developed to simulate the response of the dew point evaporative cooler. The model was able to accurately predict product air temperatures, cooling effectiveness, cooling capacity and COP, with the maximum discrepancy of ±8.0%. Key results that emerge from this study include: (1) at transient state, the change of product air temperature was relatively slow when the inlet air conditions were subjected to a continuous considerable variation. The maximum cooling capacity and COP were observed to be 6.4 W/channel and 8.9, respectively; (2) under the normal weather conditions, the cooler was able to deliver the product air at 22.3 °C when reaching the steady-state; and (3) the performance rating showed that the cooler could deliver the cooling capacity and room capacity with unit supply air flow at 4871 W/(m³/s) and 3437 W/(m³/s), when the ambient condition was 30 °C and 50% RH.