Comparison between the human physiological sweat and pre-wetting method on the heat and mass transfer of thermal protective clothing under radiant exposure

Abstract

In this study, a thorough investigation of human sweating behavior was conducted to ensure an accurate evaluation of the thermal protection performance of garments, addressing the lack of existing standardized methods. Three fabrics were compared at different sweating rates under radiant exposure, focusing on exploring heat and mass transfer mechanisms using the traditional pre-wetting method and the innovative continuous sweating method. It was found that the pre-wetting method was effective in situations where fabrics experienced transient moisture absorption, whereas the continuous sweating method excelled in scenarios requiring continuous moisture supply before saturation and was used to estimate liquid moisture transfer. In particular, for materials with low hygroscopicity, the pre-wetting method resulted in 86.24 kJ/m2 more absorbed thermal energy at the skin surface compared with the continuous sweating method, with a sweat rate of 10 μL/min/cm2, highlighting the tendency of the pre-wetting method to overestimate the thermal protective performance. Conversely, for fabrics with high hygroscopicity and testing with high sweat rate, a 32.81% reduction in absorbed thermal energy on the skin surface was observed when the continuous sweating method was used in place of the pre-wetting method, significantly reducing operational risks. This study provides valuable guidance in selecting appropriate sweat simulation methods to evaluate the thermal protection performance based on specific environmental conditions, and provides critical insights for further studies on heat and moisture transfer.