An improved numerical model is developed for coupled heat and moisture transport in fire protective suit exposed to flash fire. This model is combined with Pennes' bio-heat transfer model and subsequently, second-degree burn time is estimated using Henriques' burn integral. Natural convection is considered inside the air gap present between the multilayer clothing ensemble and the skin. Comparisons of temperature and moisture distribution within the multilayer clothing, air gap, and the skin during the exposure are presented considering combined heat and moisture transport and only heat transport. Effect of moisture transport on the protective performance of the fire protective suit is shown. Impact of both horizontal and vertical air gap orientations on second-degree burn time is studied. Effect of temperature-dependent thermo-physical properties, relative humidity, fiber regain, different exposure conditions and fabric combinations for the fire protective suits on burn time is analyzed.
Prescribed burns are valuable tools utilized for land management. They serve the purpose of reducing the risk of wildfires by lowering the build-up of dry fuels, improving forest health, and controlling the growth of plants and insects. One of the crucial components that affects the execution of prescribed burns and controls the fire behaviour and smoke dispersal thereafter is the fuel moisture content, which needs to be considered when planning prescribed burns. The fuel moisture content variation is dependent on the meteorological variables, fuel properties, and the local turbulent fire dynamics, and so varies spatially and temporally over the land area before and during the fire advancement. In previous studies, the fuel moisture content was treated based on average properties, independent of the effect of local turbulence. In this study, the spatiotemporally varying fuel moisture content is obtained by a physics-based model that considers the coupled energy and moisture balance dynamics inside the fuel layers. This moisture model is implemented into the Wildland-urban Interface Fire Dynamics Simulator (WFDS) by means of a two-way coupling. Along with the local fuel properties, the model uses the instantaneous solar radiation and relative humidity, together with the instantaneous turbulent wind velocity and ambient air temperature at the boundary of each fuel sub-surface (grid) in the simulation domain. The coupled model is employed to study the effect of the dynamic variations of the fuel moisture on the turbulent evolution of the fire plume during a line fire propagation over a flat grassland. The findings of the study will provide insights into the effect of the fuel moisture content on the plume dynamics and smoke dispersal during prescribed burns and will assist in planning these burns.
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