Uniformity and energy evaluation of equal cross-section ventilation system(ECVS) for long tunnel in underground buildings

Uniform ventilation is important for the safety of long tunnel in underground buildings, it is difficult to install the large size air duct to ensure the centerline of each cross-section of the traditional variable cross-section ventilation system(VCVS) superimposed on the same horizontal axis, which is significant to the ventilation uniformity, energy consumption and installation convenience of the VCVS. On the contrary, each cross-section of the Equal Cross-section Ventilation System (ECVS) has the same horizontal axis, therefore, it is more convenient to manufacture and install the large size air duct in the underground long tunnel and achieve uniform ventilation. This study proposes an ECVS, using computational fluid dynamics(CFD) numerical simulation analyzed the influences of main duct velocity, aspect ratio, and outlet numbers on uniformity and energy consumption per unit air volume(ECPV). It revealed that when each ventilation equalizer's valve Angle β is given, uniformity of air supply decreases slightly with an increase in the inlet velocity. When the air supply main duct aspect ratio increases, the outlet velocity standard deviation range is from 0.22 to 0.34. When outlet numbers N=7~12 and β are constant, air supply uniformity and resistance coefficient ξ also decrease with the decrease of outlet numbers. The outlet number has a significant influence on the uniformity of system air supply, main duct velocity, and aspect ratio are relatively small. ECPV is positively correlated with the main duct velocity and outlet number, and is negatively correlated with aspect ratio.