Thermal Humidity Environment And Thermal Comfort Analysis Of Xi’an Underground Transportation Hub

With the rapid development of Chinese economy,the increasingly intensified urbanization has made land use in some cities increasingly scarce,and the development and construction of underground buildings have entered a stage of rapid development.Therefore,more and more attention has been paid to the research on the mechanism of heat and humidity change and thermal comfort of underground buildings.In the study of the existing subway thermal comfort,because the subway construction with characteristics different with the ground,as the existence of "transitional space" makes the related thermal comfort study is less,especially in cold areas,because the subway construction late relative to other areas,there is a lack of relevant data used for the reference design,there are improper research methods and research content are comprehensive and thorough enough.In this paper,the underground building part of Xi’an North Railway Station is selected to test its air temperature and relative humidity data for 15 days from December 24,2020 to January 7,2021,so as to study the change rule of the underground transportation hub’s thermal and humid environment with the outdoor environment in cold areas.The moisture source of underground building is analyzed and corresponding moisture-proof measures are given.In view of the characteristics that underground building is wetter than aboveground building,the advantages and disadvantages of conventional air conditioning system and independent temperature and humidity control air conditioning system are analyzed from the perspective of control strategy.Different from the existing studies,this paper focuses on the thermal comfort of the subway in the transition season.This paper selects Xi’an Metro Line 2from October 15,2020 to November 12,2020,combines the dynamic subjective questionnaire survey with the field measurement,analyzes the obtained data to explore the variation rule of the thermal environment at different locations of the subway station,and calculates the thermal neutral temperature of the station based on the voting average of thermal sensation and the corresponding air temperature interval.Finally,by introducing the relative thermal index RWI developed by ASHRAE in the United States,the adaptability of RWI in the study of subway thermal comfort in the transition season in cold regions of China was studied,and the error was corrected.The mainly conclusions are as follows:(1)The internal temperature and humidity of the underground transportation hub are basically consistent with that of the outdoor temperature and humidity,but the internal temperature of the underground transportation hub is higher than that of the outdoor one and the fluctuation range is smaller than that of the outdoor one,and the temperature change lags significantly.When the general humidity of underground transportation hub is too high,from the perspective of reducing building energy consumption and improving air quality,"prevention should be the priority,and elimination should be the supplement",and the independent control of temperature and humidity can be adopted in the control strategy of air conditioning system.(2)In the transition season,passengers in Xi’an subway station feel hot on the whole,and the percentage of passengers’ thermal comfort satisfaction is 56%.Corresponding measures should be taken to improve the thermal comfort.(3)The relative warmth index(RWI)has deviation in the study of thermal comfort,which should be corrected in combination with the measured data.To sum up,this paper studies the variation law of temperature and humidity and the formation mechanism of heat and humidity in underground transportation hubs.In the pursuit of low-energy buildings and high-quality air in the design of underground buildings,independent control of temperature and humidity should be considered.In the study of the thermal comfort of underground buildings,the paper focuses on the thermal comfort of subway in the transition season in cold regions,which makes up for the scarcity of research on the thermal comfort in the transition season in cold regions,and also provides theoretical reference for the research on the air conditioning design and thermal comfort of subway stations in the future.