Experimental Research On Improment Measure Of Thermal And Humidity Environment Based On Body Surface Impedance

From the beginning of last century, the relationship between thermoregulatory respones during exposure to thermal and humidity environments and the associated subjective perceptions, e.g., comfort, thermal sensation, etc., have been studied by numerous investigators. Skin temperature, mean body temperature, sweating, and percent of skin wettedness have been shown to have a role in thermal sensation and comfort. The discomfort associated with exposure to thermal and humidity environments is attributed to the conscious awareness of perspiration an elevated body temperature. In warm conditions in the resting individual and with increased metabolic levels associated with work and exercise, it was recognized that thermal discomfort are associated sweating.In this paper, regarding one of thermal regulation behaviors of human body——sweating as a breakthrough point. Sweating status of human body was tested by body surface impedance methed, and subjective sweating sense was investigated. The indoor thermal environment and its impact on human thermal comfort was explored by them. This paper mainly has done some research on the following aspects:(1)The sweating sensitivity and the sweating critical temperature were studied. The results showed:①the more sensitive parts of sweating are mainly in forehead, chest, back and neck;②the sweating critical temperature of forehead, chest and back are lower, slightly lower than 30℃, the sweating critical temperature of limbs are higher.(2)The relationgship between sweating sense and body surface impedance was analyzed, and considering body surface impedance as the quantitative indicator which can determine the sweating status of body. The results are as follows: As the frequency of AC signal is 1000Hz, when body surface impedance is higher than 24k?, skin is in a dry state; when body surface impedance is between 8k? and 20k?, skin is in a stick state; when body surface impedance is lower than 7k?, skin is a moist state.(3)The relationship between human sweating and thermal discomfort was studied, the concept of average body surface impedance was put forward, The results showed: when it is higher than 20k?, human body is mainly in the state of comfort, the interval from 18k? to 20k? is the critical transition zone between comfort and a little discomfort; when body surface impedance is between 10k? and 18k?, human body is mainly in the state of a little discomfort, the interval from 7k? to 10k? is the critical transition zone between a little discomfort and diacomfort.(4)The questionnaire of thermal sensation was analyzed, the results showed that, with the ambient temperature increasing, the chang rate of thermal sensation with ambient temperature in each part of body is different. And got the neutral temperature of each part of body. By the use of fuzzy statistical method, the membership function of thermal sensation under the ambient temperature was obtained, for any known indoor air temperature, the membership of different levels of thermal sensation can be easily obtained.(5)Aiming at the climate characteristics of Chongqing area in summer, which is"high-temperature, high humidity, slow wind", some measures were put forward, including"cooling, desiccant, ventilation", which can improve the indoor environment and meet people's demand for thermal comfort.