Performance, Exergy, and Economic Analysis of an Evaporative Cooling System With Air Gap: An Experimental Investigation

As global energy demands rise and environmental concerns intensify, evaporative cooling systems emerge as a promising solution to reduce energy consumption and environmental impact. While some studies have demonstrated that air gap spacing between cooling pads improves the energy performance of direct evaporative cooling (DEC) systems, none have explored their exergy and economic performance. This study provides a comprehensive thermal, exergetic, and economic analysis of a DEC system across a broad range of operating circumstances, comparing configurations with and without an air gap between the cooling pads. Tests were carried out using water flow rates of 60 and 35 L/(min·m²) and air velocities ranging from 1 to 3 m/s, under constant inlet conditions of approximately 32°C−33°C dry-bulb temperature and 28%−30% relative humidity. The results showed that the outlet air temperature decreased by 4%–6%, while heat and mass transfer flux increased by 8.2%–10%, leading to improved cooling efficiency. Performance evaluation criterion and water consumption criterion analyses identified a 200-mm pad thickness with an air gap at a flow rate of 35 L/(min·m²) as the most thermally efficient configuration, striking a perfect equilibrium between thermal performance, power consumption, and water usage. Moreover, configurations with an air gap proved to be the most cost-effective, reducing the specific total cost by 6%–9.6%. These findings highlight the potential of air gap configurations to enhance the sustainability and performance of DEC systems, offering an energy-efficient cooling solution that is particularly suitable for environments with limited water resources.