Experimental Correlations on the Cooling Performance of a Two-Stage Evaporative Cooler During Hot and Less-Humid Climates at Chennai

Abstract This research work evaluates the cooling performance of a two-stage direct–indirect evaporative cooler (EC) during hot and less-humid conditions at Chennai. Experiments have been conducted in an indirect evaporative cooling (IDEC) circuit and a combined indirect–direct evaporative cooling (IDEC–DEC) circuit separately. Effects of air and spray water flow rates and IDEC heat exchanger surface area on the EC operational parameters have been studied, which include volumetric heat and mass transfer coefficients, cooler exit air dry bulb temperature (DBT), wet bulb temperature (WBT), relative humidity (RH), and cooling capacity of DEC, IDEC, and IDEC–DEC systems. These studies divulge that during hot and less-humid (35 °C DBT, 26 °C WBT, and 50% RH) conditions of Chennai, when an air flow rate of 200 CFM (5.7 m3/min) and a spray water flow rate of 15 LPM (15 kg/min) are maintained, DBT of exit air is reduced by 5.2 °C for DEC system, 3.3 °C for IDEC with a heat exchanger (HX) surface area of 2 m2, 4.5 °C for IDEC with an HX surface area of 4 m2, and 7.6 °C for two-stage EC system. Two-stage evaporative cooling is one of the effective cooling methods that shall be adopted for Chennai’s climate conditions. Correlations for Nusselt number and Sherwood number in terms of volumetric heat and mass transfer coefficients have been developed for two-stage EC systems with a maximum of ±25% error band.