Comparative Analysis of Ventilation and Air Conditioning Systems in Subway Stations and Above-Ground Buildings

Most subway stations are constructed underground, resulting in a closed, poorly ventilated environment with a high volume of regular passenger traffic. This creates significant differences between subway stations and above-ground buildings, and the subway environment exhibits the following key characteristics: (1) Closed environment: Ventilation is limited to inlet and outlet entrances and ventilation shafts, creating a highly enclosed atmosphere. (2) High heat emissions and pollutant concentration: The large volume of passengers, combined with significant lighting and equipment, generates substantial amounts of heat and pollutants. (3) Thermal inertia: Due to the station's soil covering, the station envelope has a high thermal inertia, making it challenging to dissipate heat quickly.

These environmental characteristics clearly distinguish subway stations from above-ground buildings. Consequently, the ventilation and air conditioning systems of subway stations differ substantially from those of above-ground buildings in numerous ways. Firstly, subway station ventilation and air conditioning systems must provide both a comfortable riding environment for passengers and the capability to remove smoke in the event of a fire or other disasters. Secondly, subway stations have a higher flow of people, equipment, and building space, resulting in a greater load and requiring larger equipment selection than above-ground buildings. Thirdly, since subway stations have many internal heat sources and are difficult to dissipate quickly, the ventilation and air conditioning system only needs to provide cooling in the summer and doesn't need to be heated in the winter. Finally, as most subway stations are only two underground floors, they don't have the same high-rise cooling requirements as above-ground buildings, and the water system can operate with a lower pressure. Instead, the subway station ventilation and air conditioning system is powered by pumps to meet demand.