Numerical study of heat and moisture transfer in thermal protective clothing against a coupled thermal hazardous environment

Abstract

The objective of the study was to examine the effect of heat and moisture transfer on steam burn under a coupled thermal hazardous environment. A coupled model on the heat and moisture transfer between heat source, protective clothing and air gap was proposed. The developed model considers the non-transient equilibrium between three phases, the impinging jet flow between steam nozzle and fabric, the steam flow within the fabric induced by the pressure gradient, the dynamic moisture absorption, and the possible phase changes. The model was validated by a test apparatus of thermal protective performance. The results demonstrated that the developed model presented the potential for reasonably accurate prediction of the skin temperature and the steam burn in the coupled thermal environment. For the dry heat exposure, the radiant heat transfer absorbed by the skin was the main reason causing the skin burn. However, the existence of hot steam greatly reduced radiant and conductive heat transfer. The moisture phase change on the skin surface was the primary reason of the skin burn, indicating the occurrence of skin steam burn in the wet heat exposure. The research findings provided theoretical foundation and instruction for development of new thermal protective material and scientific selection of thermal protective equipment, which would be of great importance and necessity on safety improvement of fire-fighting operation.