Field Survey And Collaborative Simulation Of Thermal And Humid Environment Of Several Subway Station In Xi’an

With the development of underground space in China,the number of subways in various cities is gradually increasing,and people have higher requirements for the thermal and humid environment in the subway.In order to improve people’s comfort in the process of taking the subway,this paper selected an underground transportation hub(North Railway Station),four standard stations(Beiyuan,Sports Park,Fengcheng fifth Road,City Library)and carriage of Xi’an Metro Line 2 as the research objects.Through the combination of field measurement and questionnaire survey,this paper analyzed the thermal and humid environment and comfort of subway station and carriage in autumn and winter.At the same time,through numerical simulation,it analyzed the air conditioning design scheme of environmental control system of Xi’an Metro Line 2 in summer,determined the thermal and humid environment improvement scheme of Xi’an metro station to meet the thermal and humid comfort requirements of passengers,and modified HDR(Heat Deficit Rate)to make it available to evaluate the thermal comfort of subway in cold area,enriched the data and research methods of subway thermal comfort research in cold area,and provided reference for the design of ventilation and air conditioning system of subway station.In the field survey,the thermal and humid environment parameters of five representative stations were obtained through field measurement.It was found that the temperature of North Railway Station is obviously different from that of the standard station in winter.Therefore,it is necessary to analyze the thermal and humid environment separately,at the same time,the dynamic thermal and humid comfort subjective evaluation questionnaire and real-time collection and monitoring of environmental parameters were used to analyze the thermal and humid environment of Xi’an Metro Line 2 in autumn and winter The heat and humidity feeling and comfort of passengers were obtained,the heat neutral temperature and humidity of the station hall,platform area and carriage of North Railway Station and four standard stations were obtained.Through the measured data,this paper compared and analyzed the temperature and humidity of five representative stations.It was found that in winter,the humidity in the public area of each station is low,and the temperature of the carriage is high,which leads to overheating.In order to understand the internal temperature and humidity changes of underground comprehensive transportation hub buildings,this paper took North Railway Station as an example,analyzed the temperature and humidity changes of outdoor,entrance and exit,high-speed railway exit,station hall and platform of North Railway Station in winter,and obtains the average temperature and temperature and humidity changes of each position,It was discovered that the cold air infiltration will lead to the low and fluctuating temperature at the entrance and exit of the high-speed railway,Piston wind is the main cause of temperature fluctuation in subway station hall and platform.In the research of thermal comfort and humidity comfort,TSV(Thermal Sensation Vote),TCV(Thermal Comfort Vote)and HPV(Humidity Perception Vote)were applied to analyze the change of thermal sensation and humidity perception of passengers in the whole process of taking the subway,the results showed that the change of state has different judgment on thermal sensation,but it will not affect the judgment of humidity perception;in addition,through a separate analysis of the thermal sensation and humidity perception of passengers who have lived in Xi’an for more than 10 years,It was found that the thermal perception of passengers who have lived in the same environment for more than 10 years is not consistent with the overall data of the questionnaire.In terms of humidity perception,due to the low humidity of the station in winter,it can not meet the basic comfort requirements of human body Based on the analysis of autumn data,it was found that the length of residence will affect the judgment of humidity perception of passengers in autumn;Through the fitting of MTS(Mean Thermal Sensation),PMV(Predicted Mean Vote),MHPV(Mean Humidity Perception Vote),the thermal neutral temperature,average neutral temperature and neutral relative humidity of the public area and carriage of North Railway Station and other four standard stations were obtained respectively.It was proved once again that the platform and carriage of the subway standard station are overheated in winter,the temperature in the station hall is low,and the humidity in the public area of the station is low.Passengers only stay in the station hall for a short time,considering the energy conservation,Therefore,it is necessary to reduce the temperature of platform and carriage of standard station and increase the humidity in the public area of the station in winter.By comparing the fitting results of MTS and PMV,it was discovered that PMV has deviation in predicting the neutral temperature of subway station in winter in cold regions.It is predicted that the temperature value of the standard station public area and the carriage is low.Through the study of 80%satisfaction rate thermal comfort zone,the temperature range of public area of station in autumn is 15.7℃-22.8℃,that of carriage in autumn is 18.7℃-24.3℃,and that of public area of station in winter is 12.3℃-16.1℃.The HDR of each station in winter was calculated,and then the temperature limit of each area of the station were calculated.Compared with the thermal neutral temperature obtained from the fitting curve,it was discovered that HDR is not accurate in evaluating the thermal comfort of subway stations in winter in cold regions.After correction,the HDR equation which can evaluate the colder environment in cold regions was obtained:(?).Finally,in order to analyze the heat transfer effect of the air conditioning system of Xi’an Metro Line 2 in summer,the field collaborative simulation was carried out.Based on the actual size,a three-dimensional geometric model of a double deck island platform was established.The boundary conditions are set according to the calculation method of actual project heat and moisture load,and the field synergy theory is applied to the model,The distribution of temperature field,humidity field,wind speed field and field synergy angle were obtained by numerical simulation of the public area of subway station hall and platform.It was discovered that the humidity of the platform is too high and dehumidification is needed.The wind speed field can affect the heat transfer effect and human thermal comfort by affecting the field synergy angle.