Impact Of Exhaust Heat Fan Operation Mode On Air Quality Of Subway Platform

With the rapid development of China’s rail transport,the construction of urban rail transit networks has become a trend,and the energy consumption of subway ventilation and air-conditioning systems accounts for 30%-40%of the total energy consumption of subway operations.Under the premise of ensuring passenger comfort,reducing the energy consumption of the subway environmental control system is of great significance.As an important part of the subway environmental control system,the station tunnel heat removal system has the disadvantages of long running time and large energy consumption in many cities in China.In recent years,more and more urban subway operating companies are exploring energy-saving operation modes of exhaust heat fans to achieve the goal of satisfying passenger thermal comfort and energy saving.This article takes the Wuhan Metro Line 2 Guangbutun Station as the research object,and uses field measurements and numerical simulations to explore the impact of different operation mode of exhaust heat fan（open two fans,open one and close one,close two fans）on air quality of subway platform。The temperature of the station tunnel track area and the exhaust CO₂ concentration were tested under different operating modes of the exhaust heat fan.From the test data,it is known that the air quality of the station track can still meet the subway design specifications when closing one or two exhaust fans,which shows that changing the operation mode of the exhaust heat fans has a large space for energy saving.At the same time,the air quality of the public area of the platform is continuously and dynamically tested under different operating modes of the exhaust heat fan.The test temperature is 24.3-26.5℃,the CO₂ concentration is 500ppm-720ppm,the PM₁₀concentration is less than 128ug/m³,and the PM_2.5 concentration is less than 70ug/m³,tests show that changing the operation mode of the exhaust heat fan has a small impact on the platform air quality,and can meet the subway design specifications and indoor air quality requirements of public building.In order to further explore the impact of different operation modes of the exhaust heat fans on the air quality of the public areas of the platform,using ICEM CFD and Fluent software to numerically simulate the air quality of the public areas of the platform,the simulation results show that the average temperature of the platform is slightly rises,the relative humidity decreases,and the average CO₂ concentration rises when the exhaust heat fans are turned off.At the height of Z=1.8m,the average temperature in the three different operating modes is 24.5℃、25.1℃、25.6℃,the average relative humidity is 45.7%、44.3%、42.9%,and the average CO₂ concentration is 516ppm、529ppm、540ppm.The temperature、relative humidity and CO₂ concentration can meet the requirements of subway design codes.According to the field measurement and simulation results,it can be inferred that changing the operation mode of the exhaust heat fan will not have much impact on the air quality of the station track area and the platform,and the energy consumption of the exhaust heat fan will be greatly reduced.