Study On The Impact Of Local Air Flow On Human Thermal Sensation Under Hypobaric Environment

Adjusting in local thermal environment is an effective method to improve the thermal comfort of people. In the existing research, there are variable of ways to creat local thermal environment, like temperature seat, air station and local air movement. Most of the current research on local thermal comfort is carried out under the normal atmospheric pressure. However with the increase of the altitude, the air pressure and density decreases and the physiological reaction combining the thermal regulation will have impact on thermal sensation. In this paper, a local airflow experiments on human was conducted in low pressure environment, study how low pressure environment would impact the human thermal sensation.During the local airflow experiments, the ambient air temperature was set at 22℃, 25℃ and 28℃,which were conducted in a high altitude simulation chamber. And the environment pressure simulated were 1.00 atm, 0.87 atm and 0.74 atm separately. During the experiment the subject’s head, chest, hand and ankle were exposed to local isothermal airflow with the speed of 0.25m/s and 0.50m/s respectively. And subjects’ local thermal sensation, overall thermal sensation and general airflow sensation vote were collected. Furthermore, two physiological parameters of core temperature and skin temperature were tested.The results of the analysis of the experimental results showed that the general airflow sensation in the 0.50m/s local flow range with the increase of ambient temperature, decrease of air pressure and the increase of wind speed increased gradually, and little difference for local airflow blow to different parts of the body. The overall thermal sensation with the increase of ambient temperature, decrease of air pressure and the increase of wind speed decreased gradually, yet little difference for different parts of the body. The variance analysis showed that there was no significant difference in the overall thermal sensation of the different parts of the body blew, and the effect of environmental temperature, air pressure and air pressure on the overall thermal sensation descending order. There are some differences in the influence of the pressure and the local wind speed on the overall thermal sensation. Under the same conditions, the overall thermal sensation was negatively correlated with the air flu. There is a significant effect on the Tympanic temperature, and the fluctuation range of the temperature decreased gradually with the increase of the temperature. When the wind speed is constant, the Tympanic temperature variation is different with the decrease of the pressure in different ambient temperature environment. There is a significant effect of ambient temperature and hair dryer on mean skin temperature(P<0.05), With the increase of the temperature of the human body, the mean skin temperature increased; with the ambient temperature is constant, the skin temperature is high when head and hand were blew, chest and ankle blew is lower. In the partial cold environment, the average skin temperature decreases slightly with the decrease of pressure, however in the partial thermal environment is slightly higher.Local thermal sensation and the overall thermal sensation carries on the contrast analysis, and found that under the action of the local airflow, site of action of thermal sensation and overall thermal sensation significantly reduced and between the local thermal sensation exist certain correlation. Using principal component regression analysis between local thermal sensation and the overall thermal sensation weight relationship, showed that in the atmospheric environment the different parts of the influence weight from high to low in order to chest, head, foot and hand, the weight difference reduced between the local thermal sensation with the environment pressure reduced, head and ankle weights by the pressure changes have little effect, chest and hand weights by the influence of the pressure larger, with the pressure reduced the influence weight of chest decreases gradually and weight of hand increased gradually. Finally, using multiple linear regression method, respectively, in the head, chest, hand and ankle local blowing, the establishment of prediction model based on the ambient temperature, blowing speed and air pressure of the overall thermal sensation.