Thermal-frictional and energetic analysis and improvement of the commercial evaporative cellulose cooling pad using experimentally validated 3D CFD modeling

This work provides a robust framework for enhancing the development of cellulose-honeycomb cooling technologies while offering insights into the practical implications for industrial applications. Honeycomb cellulose pads, made from paper or fiberglass, are widely used as the primary medium in modern direct evaporative cooling technologies. However, commercialized pads have typically been developed through limited experimental trial-and-error approaches, with no deep scientific investigation conducted to evaluate their thermal, economic, and frictional performance across a broad range of parameters. Two attack angles, corrugation height, corrugation pitch, pad depth, pad height, and air velocity not only significantly affect the water distribution quality, evaporation rate, and required fan power but also impact the thermal/frictional performance of the pad. Hundreds of trials are needed to investigate the impact of each parameter while other parameters may also vary, which is not cost-effective. Therefore, in this study, experimentally validated 3D CFD modeling is employed to comprehensively address this research gap and explore the key features of the cellulose cooling pad. A systematic arrangement of geometric and fluid flow parameters (up to 120 runs) was developed to evaluate their impact on convective heat transfer, the Nusselt number, friction factor, required fan power, turbulence intensity, and other relevant factors. The findings reveal key correlations between geometric variations and cooling performance, highlighting optimal design configurations that improve efficiency and reduce energy consumption. As a small example of the findings, for a given corrugation pitch, a critical corrugation height was discovered where the Nusselt number reaches its maximum. This peak occurs at larger heights for higher corrugation pitches. Additionally, a minimum extremum point was detected for the impact of attack angles on the Nusselt number. Additional fan power is required when the attack angle is high to achieve higher thermal performance. Hence, the final decision depends on several factors, including the acceptable pressure drop relative to the available fan power, desired power consumption, permissible noise level of the fan, uniform water distribution, and so on. For industrial consultation or access to the raw data from this research (temperature, pressure, etc.) covering a wider range of parameters, please contact the corresponding author.