A modified model to assess the thermal protective performance of fire-retardant clothing exposed to both flame and radiant source

Abstract

The present work evaluates the thermal protective performance (TPP) of a multi-layered fire-resistant fabric system subjected to a high intensity risky thermal environment integrating both flame and radiant heat exposure by developing a modified model for the fabric as well as the skin. The present numerical analysis takes into consideration a multiple-layer flameproof gear (outer shell, moisture barrier, and thermal liner), an airgap separating fabric and skin, and a three-layer of skin (epidermis, dermis, and fat layer). The present model is formulated by considering a two-flux model for the radiative heat interaction in the porous fabric medium and a nonlinear bioheat transfer model for the multi-layered skin. The radiative part of the total incident energy from the flame and the radiant heater is considered to be absorbed, emitted, reflected, and transmitted through the porous fibrous layer. Here, a two-flux model is implemented to simulate the self-emission of hot gas trapped inside the porous fabrics. The thermal response in multi-layered skin is analysed using a non-linear bioheat transfer model considering a temperature dependent thermal conductivity of the living tissue. Purely radiant exposure markedly impairs turnout gear protection, while performance deteriorates more gradually with increased convective thermal energy. Greater fabric transmissivity negatively affects skin temperature distribution and TPP ratings more than equivalent reflection reduction. These study results aid in enhancing flame-resistant fabric thermal protection.