A three-dimensional conjugate heat transfer model for thermal protective clothing

Abstract

A three-dimensional heat transfer model for analyzing heat transfer through thermal protective clothing subjected to flame and radiant heat exposures is developed in the present work. The developed model takes into consideration coupled conduction-radiation heat transfer in the fabric. Heat transfer through air gaps that exist between clothing and human body is analyzed using a computational fluid dynamic (CFD) model which accounts for coupled conduction, natural convection and radiation heat transfer. Fabric and air properties are considered temperature dependent. The developed model is validated with experimental results for high intensity flame and radiant heat exposures. The developed model is also coupled with a bio-heat transfer model to predict second degree burn time. Analysis is carried out for horizontal and vertical orientations of two different air gap widths for both type of heat exposures. Detailed parametric study is conducted to analyze the effect of various fabric parameters such as fabric thickness, fabric extinction coefficient along with parameters related to heat exposure like flame heat transfer coefficient and types of heat exposure. Significant effect of these parameters are found on heat transfer results and second degree burn predictions. Effect of simplifying assumptions considered in previous heat transfer models for thermal protective clothing like consideration of constant thermo-physical properties of fabric and neglecting convection is the air gap is also analyzed and discussed. Results of the study suggest that such simplifying assumptions can lead to considerable deviation in the heat transfer analysis as well as second degree burn prediction and thus depicts the importance of the model developed in the present work.