Heat transfer model to predict skin burn injury for firefighters

Abstract

Skin burn injury is common among firefighters despite being encapsulated in the personal protective clothing. However, it is complex to predict skin burn during actual firefighting scenarios due to complex clothing geometries and thermal hazard environment. The objectives of this research were to develop a heat transfer model for predicting skin burn injury for firefighters and identify the causative factors affecting skin burn. A heat transfer model of a multilayer personal protective clothing furnished with human skin was developed using the Finite Element Method. The model considered bioheat equations that includes metabolic heat generation and blood perfusion for predicting skin burn injury. The model employed a quarter cylinder (radial) geometry to represent human limb overlays with Aralite material under wet and dry conditions. The factors such as air gap, heat flux and vapour were considered in skin burn analysis. The validation of the model was carried out by comparing skin temperatures at specified positions based on the published experimental data. The percentage error is less than 17% which is acceptable according to ASHRAE's prescription. The result shows that air gap thickness of 1 mm able to reduce the skin temperature by 10°C and the skin temperature can be reduced further as the air gap thickened. In dry conditions, each 1000 W/m2 increment of heat flux will increase the skin temperature by 2°C. While, in wet condition, a significant increase of 4°C of the skin temperature was observed for every 1000 W/m2 increment due the material properties of the personal protective clothing when it was altered and enhanced heat transfer across multiple layers of wet fabric. The presence of vapour under a constant heat flux of 7000 W/m2 for 25 seconds increases the skin temperature by 10°C. Based on transient heat transfer analysis, it was observed that steam burn injury occurred due to vapour. The research had developed a parametric study based on the three causative factors specifically for Aralite material. The model could benefit designers in producing and improving protective personal clothing for firefighters.