A new approach to evaluate the effect of body motion on heat transfer of thermal protective clothing during flash fire exposure

The effect of dynamic change of air gap between protective clothing and skin caused by continuous human body motion on thermal protective performance of protective fabric cannot be simulated in current bench-top test. In this study, a newly modified TPP test apparatus with a dynamic air gap manufacturing system was applied to investigate the effect of body motion on heat transfer of fabrics exposed to flash fires. Three different velocities of body motion were simulated respectively. The results indicated that the dynamic air gap with variation range of 0–25 mm significantly improved thermal protection of fabric comparing with no air gap, but approximated to static air gap of 6.4 mm width for different heat transfer modes. It was manifested that thermal protection had no linear relationship with the air gap width variation frequency due to convection heat in microclimate, and the TPP values was shown as 0.5 rps < 0.25 rps, 0.5 rps < 1 rps and uncertain for 0.25 rps with 1 rps. The amplitude of simulate epidermis surface temperature fluctuation had a negative correlation with air gap variation frequency. Most of the temperature curves rose smoothly along with periodical variation, only the temperature fluctuation of 0.25 rps could be observed in a variation cycle.