Study On Thermal Characteristics And Ventilation System Of Subway Tunnel In Severe Cold Region

The environmental control system of metro in severe cold region is faced with the great challenge of extremely low temperature outside in winter.Therefore,many special schemes such as circulating ventilation and adjustable platform door in cold winter are adopted,which are different from other climatic regions in China.Taking the typical station and interval tunnel of Harbin Metro Line 1 in the severe cold region as an example,this paper analyses and studies the ventilation heat environment and its influencing factors of subway tunnel in severe cold region by using the method of theoretical calculation,numerical simulation and theoretical analysis.In this paper,the calculation method of the piston wind speed in the subway tunnel is theoretically deduced,and the gain and loss of heat in the tunnel is analyzed comprehensively,and then calculated with the actual engineering parameters.The results show that the speed of train and the ratio of tunnel blocking are the main factors affecting the piston wind speed.The unfavorable condition of high tunnel temperature may occur near the railway station and the two-track section of single hole.Then,the one-dimensional ventilation network model of the research object is established by using subway thermal environment simulation software STESS.The existing subway design and operation scheme is taken as the benchmark scheme of simulation.Using the actual engineering parameters,the temporal and spatial distributions of velocity field and temperature field in the tunnel under normal working conditions are obtained by numerical simulation.According to the simulation results,under the present ventilation scheme,in summer the average temperature of station is about 26 ?,the temperature of tunnel is 17~24 ?,while in winter the temperature of station is 12~16 ?,and the temperature of tunnel is 5~15 ?.However,the number of air exchange is small and the winter temperature is low in the two-track section of single hole.The extreme minimum temperature in some sections is close to 0 ?,which may lead to the disadvantage of local freezing.On this basis,this paper contrasts and studies the influence of the configuration of piston air well,the setting of Track Exhaust System and the switch of platform door system on the ventilation & heat environment of tunnel.It is found that increasing the number of piston air wells,installing the wells at the exit station,and increasing their area is beneficial to the ventilation and air exchange of the tunnel.Reducing the area of the piston air well in summer,increasing the number of exhaust fans is beneficial to the cooling of the tunnel and the station in summer.Converting the platform doors into platform screen doors and closing the exhaust fans can effectively increase the tunnel temperature in winter.Finally,considering the comfort of subway station and tunnel thermal environment and the energy saving of ventilation system,a more reasonable improvement and optimization scheme is put forward for the ventilation system of subway tunnel in severe cold region.This scheme can ensure that the air temperature of stations and tunnels is no higher than 30 ? in summer,and no lower than 7 ? in winter,as well as having good economical efficiency.