Numerical investigation of the effect of static and dynamic air gap on heat and moisture transfer in steam protective clothing

The air gap between fabric layers or underneath clothing significantly affects heat and moisture transfer. To explore heat and moisture transfer mechanism of protective clothing with the air gap exposed to high pressurized steam, a robust numerical "steam-protective fabric-skin" heat and moisture transfer model was established, accounting for both static and dynamic air gaps. The model prediction results showed a strong agreement with experimental data, namely a relative error ranging from 0.63% to 3.60%. In addition, the effects of various air gap parameters on steam protective performance were investigated, including the thickness and position of interlayer air gaps, the thickness of underneath air gaps, and dynamic variations in air gaps. The findings show that the interlayer air gap prolong the skin burn time, but mitigate the influence of fabric properties. Also, increasing air gap thickness underneath clothing, particularly no bigger than 12 mm, yields a substantial increment in skin burn time. It reveals that motion amplitude emerges as the primary factor influencing steam protective performance of the fabric system during periodic air gap thickness fluctuations. Larger amplitudes causes weaker protective performance. These insights hold immense promise for engineering high performance protective clothing under exposure to hot steam environments.