Investigation of the heat transfer through down clothing with quilting structure

Down clothing is commonly adopted as cold protective clothing to maintain human thermal comfort. However, its surface temperature distribution, heat transmission and thermal insulation are still not fully understood due to the complex heat and mass transfer caused by the quilting structure and varying mass density. In this work, we comprehensively explored the thermal behavior of down clothing with quilting structures. Objective tests were carried out by the thermal manikin and infrared thermal imager in a climate room at a fixed temperature of 10 +/- 1 degrees C and relative humidity of 40 +/- 5%. Four different down clothing were examined to investigate the effect of down lattice structure and mass density on heat flux, surface temperature distribution and thermal resistance. The results revealed a distinct valley in the surface temperature along the down lattice due to the quilting structure. A space-averaged method to estimate the thermal insulation of down clothing would neglect variation among different local positions. Besides, the thermal insulation performance significantly improved with the higher down mass density. Because the average clothing thickness as well as the thickness near quilting position both increased, resulting in an additional reduction of heat dissipation. Furthermore, the surface convective and radiative heat exchange decreased with the higher down mass density as a result of lower surface temperature. The lowest comfort temperature for clothing with various down mass density under activity level 2 met and 4 met was also estimated. The results can help to improve the design of down clothing's thermal performance and enhance human comfort in cold environments.