Study on Heat and Vapor-Dominated Moisture Transfer Properties of Polyester Fabric with Irregular Cross-Section Based on Thermal–Moisture Coupling Numerical Simulation

In order to design suitable heat-dissipating clothing for people engaged in high-temperature conditions, the vapor-dominated moisture transfer and heat dissipation properties of polyester fabric (Coolmax) with irregular cross-section in sweat-wicking protective clothing were analyzed by establishing a three-dimensional thermal–moisture coupled numerical model. In this study, moisture transport was mainly considered as water vapor transport within the porous fabric domain under a prescribed vapor-input boundary condition, rather than as a complete liquid-sweat-wicking, condensation, and re-evaporation process. The effects of convective heat transfer coefficient, ambient temperature, fabric thickness, and porosity on the thermal and moisture regulation behavior of the fabric were analyzed. The results show that Coolmax fabric can realize more efficient vapor transfer and heat diffusion under different ambient conditions due to its irregular grooved fiber structure, and its skin-side temperature is lower, and the relative-humidity distribution is more uniform than that of cotton material. Through the comparative analysis of temperature and relative humidity under different parameter combinations, the reasonable structural parameter range considering heat dissipation efficiency and perspiration ability is determined as follows: a fabric thickness of 0.8–1.2 mm and a porosity of 0.70–0.80, which can effectively improve the heat and moisture regulation performance of fabrics. This study provides a theoretical basis and numerical simulation reference for material selection and structure design of sweat-protective clothing and functional sportswear, which is helpful to improve wearing comfort and reduce thermal stress.