Theoretical and experimental study of an evaporative cooler embedded with parallel plates
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In the current investigation, a theoretical model predicting the temperature variation of ambient air flowing through an evaporative cooler embedded with parallel plates was developed which can be used for both dry and wet sections of an evaporative cooler. When air flows into the dry section of an evaporative cooler, air temperature decreases due to the cold plate being cooled by the wet section. As ambient air continues to flow through the wet section coating with a thin layer of water, evaporation takes place if the vapor partial pressure of ambient air is lower than the saturated pressure of water vapor corresponding to the local temperature. The cooling produced is transferred to the dry section through heat conduction and to the ambient air flowing through the wet section by convection. Considering heat transfer characteristics between ambient air and cold plates, three flow zones of developing region of dry section, fully developed region of dry section, and wet region are modeled. Based on continuity, momentum, energy and mass transfer equations, a mathematical model is developed which can be used for all three regions. Using this model, the temperature variation of ambient air flowing through an evaporative cooler embedded with parallel plates can be predicted including the effects of air flow rate, plate thickness, relative humidity, and plate spacing. To verify the model, an experimental investigation of a two-stage evaporative cooler was conducted. The experimental results show that the prediction from the model agrees well with the experimental data.