Field Study On Thermal And Humidity Environment And Thermal Comfort Evaluation In Xi’an Metro

In most urban areas of China,the metro is the most effective and convenient means of commuting,and taking the metro has gradually become the most popular way for citizens to travel.In this thesis,the comprehensive transportation hub（XI’AN BEI ZHAN Station）and transfer stations（XINGZHENGZHONGXIN Station,BEIDAJIE Station,and XIAOZHAI Station）and the carriages of Xi’an Metro Line 2,a representative city in cold regions,were selected as the research objects,and the thermal and humid environment tests and dynamic thermal comfort questionnaire surveys were carried out in summer and winter respectively,and the thermal comfort index was adopted to evaluate the thermal comfort of passengers in different seasons.Based on the measured data,the changes in temperature and humidity in the hall,platform,and carriages of XI’AN BEI ZHAN Station and transfer stations were analyzed,and the optimal temperature and humidity control range in different areas of each metro station were obtained.By analyzing the measured data,it can be found that the average temperature of the station hall of XI’AN BEI ZHAN Station in winter was 9.3℃,which is lower than the 12℃required by the code,while the public areas in each transfer station met the code requirements,because the structure and area of XI’AN BEI ZHAN Station were different from those of the transfer stations,and the station hall was greatly affected by the infiltration of outdoor cold air.At the same time,during the field study,it can be also found that the carriages of Xi’an Metro Line 2 was wet and cold in summer and dry and hot in winter.It is suggested that the environmental control system of the carriages should be adjusted to improve the comfort of passengers taking the metro.Through the measurement of CO₂ concentration in public areas and carriages of each representative station,it can be found that the CO₂ concentration in public areas and carriages of each representative station met the requirements of the specification in summer,and the air quality of metro stations was well.However,during the winter test,the average concentration of CO₂ in the carriages was 1517 ppm,which exceeded the concentration value required by the code,and the air quality in the carriages was poor.It is suggested that the fresh air volume sent into the carriages should be increased in winter to dilute the CO₂ in the carriages of the metro.In this thesis,the changes of thermal and humid sensation and thermal comfort of passengers during metro ride were obtained by means of dynamic questionnaire survey.Meanwhile,the average thermal sensation voting model and average humidity sensation voting model were established to obtain the thermal neutral temperature and neutral relative humidity of passengers in metro public areas and carriages in different seasons.In this way,the comfort zone temperature range of 80%satisfaction rate for passengers in different areas of the metro in summer and winter were obtained:the temperature range of public areas in summer was21.76～29.03℃,and that of carriages was 25.31～27.01℃;In winter,the temperature range of public areas was 7.70～22.1℃,and the temperature of carriages was 13.75～19.93℃.The research results of this thesis can provide reference for the parameter design of environmental control system of metro station.In this thesis,it explores the alteration of thermal comfort of passengers riding the metro by calculating the Relative Warmth Index（RWI）and Heat Deficit Rate（HDR）.By comparing the questionnaire results,it can be found that it is not accurate to directly predict the thermal comfort of Xi’an metro passengers in cold areas employing RWI and HDR.Therefore,it is necessary to modify RWI and HDR,and finally the thermal comfort evaluation indexes suitable for the Xi’an metro in summer and winter respectively were obtained,which has theoretical guiding significance for the design of metro air conditioning system.