Abstract
In the present work, an unsteady analysis is carried out for the thermal characterisation of a firefighter protective clothing. Coupled radiative and conduction heat transfers are considered inside the clothing with a focus on the thermal level on the first skin layer. The protective garment is modelled as a 1D solid medium, featuring three layers of tissues, separated by several air-gaps. A parametric analysis is performed in the aim to predict the effect of conductive and radiative tissue's properties fluctuation on the first skin's layer temperature. The thermal balance equations are written in a finite element (FE) formulation and solved using the COMSOL Multiphysics® software. Predictions were provided for the temperature and heat flux distributions in the fabric, skin, and air-gap as a function of time, as well as the time to receive skin burn injuries. The results obtained were compared with stationary 2-D calculations, and faced to unsteady simulations, based on the finite volume method. A 50% relative reduction in the absorptivity of the skin (in the case of wearing a fine knitted fabric) makes it possible to reduce the surface temperature of the skin to a tolerable value.
Highlights
Improving the performances of a firefighter clothing require a good understanding of the thermal exchanges between the clothing and the ambient surrounding as well as the firefighter’s body
Recent firefighter clothing technologies have evidenced the multilayered configuration of the textile, which have to be separated by several air-gaps to enhance the thermal resistance [2]
They concluded that the air-gap can be considered as a significant shielding layer that can absorb a major part of the heat fluxes emitted and transferred by the fabrics
Summary
Improving the performances of a firefighter clothing require a good understanding of the thermal exchanges between the clothing and the ambient surrounding as well as the firefighter’s body. The net incoming heat fluxes to the skin should be kept at low values to avoid the burning injury threshold In this direction, some authors have concluded that thermal insulation of the skin can be enhanced by an increase in the thickness of the fabrics, but the lightness of the clothing was not considered [4]. Some recent studies have shown the importance of accounting for both conduction and radiation in each air-gap that separates two adjacent fabrics layers [10]. In their investigation, thermal conductivity of each fabrics and air layer was considered as a temperature-dependent quantity in the Fourier equation. Governing equations are solved in a finite element (FE) formulation using Comsol Multiphysics®, associated with the surface-to-surface (S2S) radiative model
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