Heat and Moisture Transfer Modeling and Performance Evaluation of Hygroscopic Fabrics for Thermal Comfort Across Different Body Parts in Extreme Heat

Extreme heat exposure in medical and occupational settings can elevate thermal strain, impair task performance, and increase dehydration risk, particularly when protective clothing restricts ventilation and traps moisture near the skin. This study presents a one-dimensional coupled heat-moisture transfer model to evaluate hygroscopic natural fabrics for wearable cooling applications. Fabric properties for linen, ramie, bamboo, tencel, and hemp were obtained from recent literature, and simulations were performed for ambient temperatures of 38-45°C, relative humidity of 90-95%, and wind speeds of 0-10 m/s over a 60 min exposure period. The numerical framework captures transient heat conduction and vapor diffusion through the skin?fabric system, with evaporation-driven latent cooling at the skin interface. Results show that cooling efficiency increases with wind speed and decreases with relative humidity due to reduced vapor-pressure driving potential. Linen achieved the highest cooling efficiency, followed by ramie and bamboo with peak temperature reductions of 5.11°C, 4.13°C, and 3.43°C, respectively, while Tencel and hemp showed lower responses of 2.54°C and 2.36°C. Body-region analysis indicates non-uniform cooling, where the thigh exhibited the highest temperature reduction (2.65°C at 90% RH), whereas the upper arm and forearm showed smaller reductions under near-saturated conditions. These findings provide quantitative guidance for fabric screening and region targeted design of medical workwear and protective garments for heat stress mitigation