Effect Of Low Air Humidity On Human Comfort Sensation

In the society, People pay more attention to comfortable of indoor environment. This is an important aspect of human body thermal comfort research in building. Each climate zones in China the summer temperature is high, but the humidity is different. Different air conditioning system can create different temperature and humidity environment, and different temperature and humidity are differently effect on thermal comfort of human body. In southern China, especially in hot summer and cold winter area, both in summer and winter the relative humidity is high. Humidity is one of the six important factors which would influence human thermal comfort, humidity also affects the health of the body. Compared with the foreign, the domestic research less about relative humidity influencing on human thermal sensation. Previous research has shown that high relative humidity will increase the thermal sensation of the body in partial hot environment, and there were very few studies about the effect of low air humidity on human thermal comfort under air conditioning. There was no central heating in southern China, but many people want to provide heating in cold winter. If we provide heating, the indoor humidity will decrease, how will be the people who has accustomed to the high humidity environment response to the low humidity. The ASHRAE standards have no established lower humidity limits for thermal comfort. Based on this, it is necessary to research low humidity environment in summer and winter, to find out how the low humidity influence on human thermal comfort, and the acceptable temperature range, which is great significance for determining the design parameters of heating standards of southern. Experiments were conducted in artificial climate chamber, the subjects filled in the questionnaire according to the feeling and meanwhile recorded the environment and physiological parameters, studing the effect of low humidity on human thermal response.Experimental study consists of two seasons: summer and winter. 16 healthy college students were chosen as the subjects, including 8 women and 8 men in summer. In summer experiment, where 12 different air temperature and humidity conditions, 23/26/29/32℃and 15/30/50%RH were examined. Clothing insulation was 0.39, air velocity was 0.05m/s and metabolic rate was 1.0 for all conditions. 20 healthy college students were chosen as the subjects, including 10 women and 10 men in winter. In winter experiment, where 12 different air temperature and humidity conditions, 16/20/24/28℃and 15/30/50%RH were examined. Clothing insulation was 1.2 and metabolic rate was 1.0 for all conditions.Temperature is 26℃ and 29℃ in Summer and Temperature is 20℃ and 24℃ in winter, relative humidity has no effect on human thermal sensation and thermal comfort. The environment temperature is slants cold or partial hot, the relative humidity will effect obviously on the human thermal sensation and thermal comfort. The relationship between thermal comfort and thermal sensation are one-to-one correspondence in summer and winter. Different relative humidity has no effect on the skin temperature iin summer, relative humidity has also no effect on skin temperature basic in addition to 28℃ in winter. Air humidity can make peopel feel stimulation and dry, besides, parts of human body feel obviously stimulated and dry with the reduction of air relative humidity, especially in winter. In 16℃~28℃, between 15% and 50% relative humidity, nose, mouth and other parts have significant difference.Respectively research the relationship between overall comfort sensation and thermal comfort、wet comfort, found temperature strongly affect the overall comfort in summer, and temperature and humidity have same influence on the human body comfort in winter.PMV model and two node model can not accurately predict all the condition of the human thermal reaction, in partial cold and hot environment, there are a big difference between predicted and actual values, especially in 15% humidity environment.Comfort zone is calculated by using the ASHRAE standard method, besides adopted the humidity ratio at or below 0.012. If ignore the lower humidity limits, the summer comfort zone temperature scope is 23.5℃~30℃, the winter comfort zone temperature scope is 19.2℃~24.2℃.When considering relative humidity above 30%, the range of summer comfort zone temperature is 23.5℃~38.75℃, the range of the winter comfort zone temperature is 19.2℃~ 23.25℃. When relative humidity is 30% ~ 30%, the summer and winter acceptable temperature range are 23.8℃~28.9℃, 19.8℃~ 23.3℃.