Energy-Efficient Design Optimization of a Multistage Indirect Evaporative Cooler for Sustainable Cooling in Hot and Dry Climates

This study presents a detailed evaluation of the energy performance and design optimization of a novel four-stage indirect evaporative cooler (IEC) enhanced with a supplementary humidifier, examined under the summer design conditions of Riyadh. Although previous research has demonstrated the system’s high thermal effectiveness, its energy efficiency—expressed through the coefficient of performance (COP)—and the influence of key design parameters have not been thoroughly explored. To address this gap, we integrate a validated thermal model with a comprehensive energy consumption model to assess the COP of the system under varying operational and geometric conditions. Results show that the baseline design achieves a maximum COP of 14.3. Through parametric optimization of heat exchanger depth and air velocity, the maximum COP increases to 20.4—a 43% improvement, associated with a supply temperature of 13.2 °C and specific water consumption of 2.5 kg/kWh at a return ratio of 0.3. The optimal parameters—a heat exchanger depth of 1.5 m and a humid-path air velocity of 1 m/s—ensure both high efficiency and practical feasibility. Overall, the findings highlight the considerable potential of the optimized multistage IEC system as a highly energy-efficient and sustainable alternative to conventional vapor-compression cooling technologies, contributing to reduced energy consumption and enhanced environmental sustainability in hot and dry climates.