Study On Thermal Environment Evaluation And Design Temperature Criterion Of Xi'an Metro Station

The reasonable temperature criteria of subway can make more passengers get thermal comfort during waiting period.We took two typical subway stations in Xi'an as the research object,based on the field measurement and investigation to study the thermal environment of metro station and thermal comfort of human body,furthermore,used the Relative Warmth Index(RWI)and the Heat Deficit Rate(HDR)to analysis the changes of patrons' RWI value,HDR value and thermal comfort in the current operating environment and temperature criteria,respectively.The RWI is used to study the warm environment,while the HDR is used to design subway environment-control system in cold weather.The prediction results of RWI method and HDR method were compared with the questionnaire method,and then revised the RWI method and HDR method.Based on the modified RWI value and HDR value,the suitable temperature criteria of Xi'an subway in summer and winter is discussed,and the operation control strategy for different outdoor climate is established.The results show that if the temperature is operated under the Code for the Design of Metro(GB 50157-2013),the thermal comfort of most passengers can not be satisfied;and the platform temperature should be at least 1 ? below the mezzanine in order to ensure that the RWI is decreasing and passengers could get a temporary thermal comfort.To control the ratio of 25% passengers who want a cooler environment,it is suggested that the air-conditioning temperature of Xi'an subway should be 25.5 ? for mezzanine and 24.5 ?for platform.In winter,if there is no upper limit to the design temperature,this could lead to overheating in the public area of the subway station;and when the outdoor temperature is above 6 ?,the lower temperature limit of 12 ? set by the code will cause the station to be cold;assuming that the outdoor air temperature is at-1 ?(the Winter ventilation outdoor air temperature of Xi'an),we recommends that the design temperature range of Xi'an subway in winter should be controlled at 10 ? to 13.2 ?,if there is a higher requirement for comfort,the median temperature of 11.6 ? can be taken as the center and the temperature range can be reduced appropriately.The study also found that to satisfy the thermal comfort of passengers,the design temperature of the station should vary with the outdoor temperature rather than the fixedvalue.In summer,as long as the outdoor temperature is not lower than 24.7?,the recommended design temperature of station and platform,25.5? and 24.5?,can satisfy more than 75% of passengers;and in winter,when the outdoor temperature is higher than 6 ?,in order to ensure that passengers do not feel too cold,it is necessary to raise the corresponding design temperature according to the rising outdoor temperature.