Sakoi Tomonori, Mochida Tohru, Kurazumi Yoshihito, Kuwabara Kohei, Horiba Yosuke, Sawada Shin-Ichi
Institute of Textile Science and Technology, Academic Assembly, Shinshu University, Ueda 386-8567, Japan.
Hokkaido University, Sapporo 060-0808, Japan.
J Therm Biol. 2018 Jan;71:1-9. doi: 10.1016/j.jtherbio.2017.10.002. Epub 2017 Oct 26.
The purpose of this study is to expand the empirically derived wet bulb globe temperature (WBGT) index to a rational thermal index based on the heat balance for a human body. We derive the heat balance model in the same form as the WBGT for a human engaged in moderate intensity work with a metabolic heat production of 174W/m while wearing typical vapor-permeable clothing under shady and sunny conditions. Two important relationships are revealed based on this derivation: (1) the natural wet bulb and black globe temperature coefficients in the WBGT coincide with the heat balance equation for a human body with a fixed skin wettedness of approximately 0.45 at a fixed skin temperature; and (2) the WBGT can be interpreted as the environmental potential to increase skin temperature rather than the heat storage rate of a human body. We propose an adjustment factor calculation method that supports the application of WBGT for humans dressed in various clothing types and working under various air velocity conditions. Concurrently, we note difficulties in adjusting the WBGT by using a single factor for humans wearing vapor-impermeable protective clothing. The WBGT for shady conditions does not need adjustment depending on the positive radiant field (i.e., when a radiant heat source exists), whereas that for the sunny condition requires adjustments because it underestimates heat stress, which may result in insufficient human protection measures.
本研究的目的是将根据经验得出的湿球黑球温度（WBGT）指数扩展为基于人体热平衡的合理热指数。我们推导了与WBGT形式相同的热平衡模型，该模型针对在阴凉和阳光条件下穿着典型透气服装、从事中等强度工作且代谢产热为174W/m²的人体。基于此推导揭示了两个重要关系：（1）WBGT中的自然湿球温度和黑球温度系数与皮肤湿润度固定在约0.45且皮肤温度固定的人体热平衡方程一致；（2）WBGT可被解释为增加皮肤温度的环境潜力，而非人体的蓄热率。我们提出了一种调整因子计算方法，该方法支持WBGT在穿着各种服装类型以及在各种风速条件下工作的人群中的应用。同时，我们注意到对于穿着不透水汽防护服的人群，使用单一因子调整WBGT存在困难。阴凉条件下的WBGT无需根据正辐射场（即当存在辐射热源时）进行调整，而阳光条件下的WBGT则需要调整，因为它低估了热应激，这可能导致人体防护措施不足。
