Optimal operation of evaporative cooling pads: A review

Direct evaporative cooling is widely known for being an energy efficient air conditioning solution for arid and/or semi-arid climates. Commercialized evaporative cooling pads vary in material and construction characteristics, while existing research proposes several alternative wetted media and configurations. The most studied factors on the evaporative cooling pads operation are the air velocity or air mass flow rate, air psychrometric conditions; the pad thickness, its geometric characteristics and configuration, and the water flow rate supplied. The pads performance is commonly characterized through its saturation effectiveness, pressure drop, temperature drop and humidity increase achieved in the treated air, water evaporation and consumption, cooling capacity, coef ficient of performance and the heat and mass transfer coefficients. Present work conducts a critical review on the existing experimental and theoretical research on commercial and alternative wetted media, identifies the gaps in the literature, proposes uniform nomenclature and methodologies, and provides a critical view on the optimal operating conditions from wetted-surface evaporative coolers.