Query on some regular practice of HVAC system design in domestic urban rail transit engineering By Liu Yijiang

In urban rail transit construction, the regular practice during the design of HVAC system are transversal ventilation in station tunnel, jet fans installed in non-typical section tunnel, primary return air all-air system with dual fans, up-supply and up-return air distribution, constant outdoor air volume, 5 h^-1 minimal air change rate, constant water volume system with primary pump, central cooling, etc. Combining with the characteristics of urban rail transit engineering, discusses the rationality of these regular practice from the points of view of the economy and safety of the system.