Analysis Of Cooling Effect And Energy Saving Of Tunnel Ventilation System In Metro Station

As a large public space,the subway station has its particularity compared with the ground building.The subway station is basically isolated from the outside world and is in a relatively closed place,except the entrances and exits of each station,and the ventilation shafts of the upper part of the tunnel.The ventilation and air conditioning system is a necessity of the subway station.The subway ring control system has huge energy consumption,while it creats a comfortable and safe environment for passengers.Therefore it has great potential for energy saving.The subway station is built at the bottom of the ground,surrounded by soil.Based on the buried depth of the subway station,it is a huge natural cold and heat source,which can be fully utilized in the ventilation and air conditioning system of the subway station.In this paper,the unsteady-state method is used to analyze the cooling effect and energy-saving of the tunnel ventilation system in subway station running one typical working-day.Firstly,the paper takes the summer working condition of the ventilation and air conditioning system of a subway station in Chongqing as the research background.Based on the characteristics of the buried depth of the subway station,this paper makes a theoretical analysis on the unsteady cooling process of the tunnel ventilation system,establishes the unsteady physical and mathematical model of the subway system,and verifies the model with the measured data of a similar system.Secondly,the paper uses the numerical simulation software to simulate the airflow of a typical working-day 17 h in the ventilation system,analyses the influences of the tunnel length,inlet wind speed,cross section area and inlet temperature on the average temperature and cooling efficiency of the tunnel outlet,and calculates the heat transfer for one day in the typical year of the summer working condition.Finally,the results show that the air cooled is obvious and the heat transfer increases with the length of the tunnel.For the tunnel with 120~270m length,running one typical working-day,the minimum heat transfer is about 578,000 kJ,and the maximum heat transfer is about 1,022,000 kJ.It shows that the tunnel ventilation system has great potential for energy saving in the subway station,which provides a reference for the actual engineering design.