The coupled effect of temperature, humidity, and air movement on human thermal response in hot-humid and hot-arid climates in summer in China

Apart from temperature, relative humidity (RH) and air velocity (V-a) also affect human thermal comfort, especially in hothumid and hot-arid climate regions. To explore the coupling effects of temperature, humidity, and air movement on human thermal response in summer, two long term field studies were conducted in Beihai (a typical hot-humid region in China) and Turpan (a typical hot-arid region in China), from which 610 and 1080 valid datasets were obtained respectively. Results show that the residents of hot-arid regions have higher tolerance to hot-environment compared with residents of hothumid regions. Within the same temperature range, the residents of hothumid regions want cooler temperatures compared with the residents of hot-arid regions. The variation in RH does not have much influence on human thermal sensation, thermal comfort and thermal acceptability in hothumid climates. However, in hot-arid climates, humidity shows an opposite effect on the thermal sensation of the human body in different thermal environments. In a slightly warm environment (30 degrees C-35 degrees C), humidity has no significant effect on thermal sensation. In an extremely hot-environment (>35 degrees C), an increase in humidity may negatively affect thermal sensation. Meanwhile, in hot-humid regions, when the operative temperature was lower than 33.5 degrees C, the mean thermal sensation was significantly reduced by increasing air velocity. When the operative temperature exceeded 33.5 degrees C, increasing air velocity could significantly reduce mean thermal sensation only when the air velocity exceeded 1.0 m/s. However, a slight increment in air velocity can significantly improve thermal sensation in an extremely dry environment. Moreover, the willingness to increase air movement was higher among the residents of hothumid regions than among the residents of hot-arid regions. These findings support climate adaptation theory and can serve as references for the design of low energy buildings.