Determination of evaporative area of hollow fiber membrane module for evaporative cooling based on surface morphology and hydrophobicity

Abstract

Hollow fiber membrane-based evaporative cooling is regarded as an efficient, energy-saving, hygienic, and versatile cooling solution. However, most existing studies simplify the calculation of evaporative area, leading to inaccurate estimates of heat and mass transfer behavior. This study proposes a theoretical model for determining evaporative area, addressing the physical phenomenon at the micro level by incorporating membrane surface morphology and hydrophobicity. Fractal theory is employed to quantify the roughness of the membrane surface, and the apparent contact angle and evaporative area calculation models are established based on the Wenzel model. The proposed model is validated through membrane material characterization and experimental testing of membrane modules. In addition, the influence of membrane properties on the evaporative area during the membrane-based evaporative cooling process is investigated. The results show that the theoretical model for evaporative area matches experimental data with a relative error of less than 5 %. Membranes with higher surface fractal dimension, intrinsic contact angle, and porosity are found to theoretically increase the evaporative area beyond the total membrane area, thereby enhancing heat and mass transfer performance. The developed evaporative area calculation method can be applied to numerical modeling of membrane-based evaporative cooling processes, enabling more accurate predictions of system behavior and providing theoretical guidance for membrane material selection and optimization.