Research On Impact Of Air Velocity On Human Thermal Comfort Under Low-pressure Environment

Air velocity is one of influential factors relevant to human thermal comfort. Because of the change of convection and evaporation heat exchange in different pressure environment, the effect of air velocity change on hunan thermal comfort is different. Supported by the National Natural Science Foundation (Project Number 50778091),this paper built an experimental table relying on the simulation cabin in plateau environment and simulated the low-pressure environment in the asymptomatic altitude reaction regions to experimentally study human thermal comfort in lower-pressure environment. Within this region, physiology of human body adapts to the environment change without pathology variation(At high altitude above 3000m, mountain disease is the most chief problem to be solved by physiological and medicinal methods).Fristly, human convective heat exchange and skin evaporative heat exchange with air velocity in different pressure environment are analyzed. Using experiment method, the influence of air pressure to human thermal sensation MTS and draught sensation vote is studied, then the effect of velocity change on human thermal sensation MTS and draught sensation vote under different pressure is compared. At the same time, the changes of PMV and PD calculated by programming and investigated by questionnaire with air velocity are compared and studied to analyse the applicability of PMV and PD in low-pressure environment. Finally, t-test analysis methodology is adopted to analyze the physiological indexes of human body, then a visible influence degree and trend of air velocities under different pressures on primary physiological indexes of human body is acquired.The research shows that human is more insensitive to air velocity in low-pressure environment. The subjects' predictive values of PMV and PD are less sensitive to air velocity than the measured values, so the prediction of PMV and PD evaluation indexes can not be simply and directly applied in low-pressure environment. At a certain temperature and with air velocity <0.20m/s, the increasing rate of the total heat loss with the increase of air velocity is higher under normal pressure. With the increase of air velociy, the change of subjects' sistolic blood pressure, diastolic blood pressure, heart rate and skin temperature is not obvious. In which the heart rate and skin temperature decreases slightly and the decrease rate is lower than in normal-pressure environment.With the development of western China, more and more people are entering plateau. Therefore, carrying research of the air velocity and human thermal sensation under low pressure is likely to deepen the understanding of some theoretic and experimental references to the research of the human thermal comfort in low-pressure environment and provide certain theoretical support for the establishment of relevant national standard.