Numerical investigation of the effect of air gap orientations and heterogeneous air gap in thermal protective clothing on skin burn

Numerical model for heat transfer through air gap in thermal protective clothing was coupled with bio-heat transfer model for multi-layer human skin. Coupled CFD-radiation heat transfer model was used for heat transfer through air gap and Pennes' bio-heat transfer model was used for heat transfer through human skin. First and second degree skin burn times were calculated using Henriques' burn integral. Effect of air gap width and air gap orientations were analyzed on heat transfer through air gap and skin burn injuries. Significant impact of air gap width and air gap orientations were observed in first and second degree burn times. First and second degree burn times and hence the thermal protection were found to be higher in case of vertical air gap orientations as compared to horizontal air gap orientations. Air gap orientation influences the thermal protection more at higher air gap widths. Analysis were also performed for determining outcome of heterogeneous air gaps on heat transfer through air gap and protective performance. Heterogeneous air gap cases results in more heat transfer and lower thermal protection as compared to homogeneous air gap cases for both the air gap orientations. Further, effect of fold aspect ratio was also analyzed on first and second degree burn times in case of the heterogeneous air gap.