Assessing heat stress relief measures to enhance outdoor thermal comfort: A field study in China's cold region

Abstract

We recruited 72 healthy college students on a university campus in Xi'an, China to investigate the effectiveness of heat stress relief measures (shade, mist spraying and shade+mist) on enhancing outdoor thermal comfort. Using the Universal Thermal Climate Index (UTCI) and mean skin temperature (MST), we evaluated respondents’ thermal and physiological responses. We found that: 1) Mist spraying and shade were effective in improving respondents’ outdoor thermal comfort. The cooling effect of mist spraying was more effective than shade, while shade+mist provided a wider thermal comfort range. 2) UTCI declined among cooling strategies by 12.31 °C (shade+mist), 8.03 °C (mist spraying) and 3.48 °C (shade) on average. 3) Shade and mist caused similar cooling effects on skin temperature (ST), but MST plateaued 5 min after exposure to these cooling environments in isolation. Shade+mist provided the greatest cooling effect with MST continuing to drop as the exposure continued. 4) Predictive models showed that MST in shade, mist spraying and shade+mist decreased 0.24, 0.21 and 0.16 °C, respectively when air temperature (Ta) declined 1 °C with constant relative humidity (RH) and mean radiation temperature (Tmrt). MST in shade, mist spraying and shade+mist decreased 0.05, 0.08 and 0.06 °C, respectively where RH increased 1% with constant Ta and Tmrt.