Application of the Bernoulli Effect for Improving Smoke Exhaust Efficiency in Tunnel Fires

Abstract

In South Korea, where mountainous terrain accounts for a significant proportion of the country, tunnels are essential for reaching destinations via the shortest possible route. Tunnels are high-traffic areas with only two exits, making them vulnerable to large-scale disasters in the event of a fire. However, existing longitudinal-flow-type exhaust systems (jet fans) are insufficient for effective smoke exhaust during a tunnel fire. Herein, a new ventilation system is proposed that uses a device with nozzles for expelling high-speed winds to generate a more robust ventilation flow at a tunnel entrance. A computational fluid dynamics (CFD) analysis showed that a jet fan system had a wind speed of 1.52 m/s at the tunnel exit. This system removed a total of 37,053.9 kg of air in 600 s. By contrast, the proposed Bernoulli ventilation system had a wind speed of 1.85 m/s at the tunnel exit and removed 53,308.4 kg air in 600 s. The simulation results from a scaleddown model of the tunnel safety testing facility were compared with the CFD analysis results. The ratio of the wind speeds between the tunnel entrance and exit was 2.7:1, exhibiting a similar trend. In conclusion, this study experimentally verified a CFD analysis of a Bernoulli ventilation system and provided a direction for improving longitudinal-flow-type exhaust systems. The results can be a foundational resource for government agencies (such as the Road Traffic Authority) in improving current ventilation systems.