Numerical analysis of heat and moisture transfer in waterproof and breathable composite fabric used for steam protective clothing

A coupled heat and moisture transfer model for waterproof and breathable composite fabrics was developed to examine the behavior of steam heat transfer in porous and hygroscopic membranes. The model accounted for the impact jet flow at outer boundary of fabric, Darcian flow, molecular diffusion, dynamical absorption and phase change of moisture in the fabric. The predictive model was validated by experimental data of hot steam exposure. The heat and moisture distribution in porous and hygroscopic membranes (PM and HM) fabrics was analyzed. The parameters affecting the steam protective performance of waterproof and breathable composite fabric were investigated. The results demonstrated that the HM fabric provided higher steam protective performance than the PM fabric, and placing the membrane on the outer layer of PM and HM fabrics significantly enhanced the steam protective performance. For the PM fabric, the steam protective performance was greatly determined by the thickness and porosity of membrane layer. However, the steam protective performance for the HM fabric was strongly affected by the thickness and thermal conductivity of the substrate layer. The findings obtained in this study can be used to engineer protective clothing that offer better protection against hot steam exposure.