Study On The Potential Of Implementing Piston Wind To Minimize HVAC Energy Consumption In Subway Station

Rapid development of Metro and other rail transit has improved the overall development level of cities.But it has also brought about huge energy consumption at the same time.The ventilation and air conditioning system of underground railway station is very high in energy consumption,which accounts for about 50% of the total energy consumption in the southern cities,and nearly 30% in the northern cities of China.Therefore,one of the effective ways to reduce the power consumption of underground stations is to reduce the energy consumption of the subway environment control system.In recent years,many scholars have done a lot of research on reducing the energy consumption of ventilation and air conditioning system in underground stations,especially in the direct use of the tunnel piston wind.Shielding door with controllable draught is a hot spot at present,but it faces many problems in practical application.However,for the double Island underground station with shielding door system,there are 4 end doors on the platform layer of about 6 ?,that is,a total of 24 ?/station.When using the shield door system,the inner end door of the subway station can be changed into a ventilating type structure,which can provide a new idea for the subway station to use the piston wind energy and airflow organization.In this paper,theoretical analysis,measured data analysis,numerical simulation and technical-economic comparison are used to carry out the research.The measured data of the tunnel and platform temperature and humidity in the station hall of the typical subway station of Xi'an metro Line 2 are compared with the measured weather data of Xi'an.So it can be spotted that how the indoor temperature and humidity vary with the outdoors.Based on the measured data,the passengers' thermal comfort characteristics are calculated by using Relative Warmth Index and the Heat Deficit Rate while they get into the platform from outside of the station in Xi'an.The suggestions are given for the operating parameters of temperature and humidity in the subway station,and the energy saving effect is quantified from the angle of the cold load.In addition,according to the measured data,the changes of temperature and humidity in the platform and tunnel during subway operation are studied to find out the feasibility and timeliness of the direct use of the piston wind.The study found that passengers feel thermal comfort in typical station of XI'an metro Line 2 in summer.But the indoor and outdoor temperature difference is large,which may cause the passengers' discomfort and the energy waste.Therefore the proper enhancement platform air conditioning operating temperatures are proposed.Results pointed out that it is possible to guarantee the passengers' thermal comfort under the premise energy saving by using suggestion temperature.The passengers in the winter station are basically feeling warm and comfortable.The air condition in the tunnel is almost the same as that in the platform,and there is no obvious temperature rise during the test.Finally,set the measured temperature and velocity of the piston wind in Xi'an metro Line 2 as boundary conditions,using CFD software to simulate a single side of the train in a running cycle(out of a station ? into the platform ? out of the platform ? into the next platform).Characteristic of velocity distribution in the platform are analyzed with different end-door opening scheme,because of the train piston effect.According to the simulation results,the ventilating-type end-door is feasible in Xi'an metro station.Air distribution in the platform is more uniform under the condition of opening two end-doors at the entrance of the tunnels separately.