Effect of environmental parameters on heat transfer characteristics and thermal sensation of human body with step change of temperature

Step change of thermal environment is often encountered in people's daily life. The purpose of this paper is to explore effects of temperature difference, wind speed and clothing thermal resistance on skin temperature, heat transfer characteristics and thermal comfort with step change of ambient temperature, and to find out relationship between human physiological parameters and subjective thermal evaluation. Thermal response experiment of 30 subjects under different temperature difference, wind speed and clothing thermal resistance were carried out in an artificial climate chamber to simulate step change of neutral-slightly hot/hot- neutral temperature. The results show that the larger the abrupt temperature difference, the larger the mean skin temperature increment, and the longer the time needs to reach stability. Thermal sensation appears "overshoot phenomenon" during step change, which is caused by step change of heat transfer between human body and environment. The increase of wind speed results in a decrease in skin temperature and thermal sensation after step change, but the effect was not significant. The greater the sudden temperature difference, the less significant the effect of wind speed. The increase of clothing thermal resistance results in a significant increase in skin temperature and thermal sensation after step change and the effect is significant. The greater the sudden temperature difference, the more significant the effect of clothing thermal resistance. Knothe function can quantify the regulation characteristics of mean skin temperature with time during temperature step change. There is a good linear correlation between thermal sensation and heat transfer on the skin surface, so heat transfer can be used to predict thermal sensation under step change condition. The regression coefficients are affected by wind speed and clothing thermal resistance.