tunnel ventilation

A model tunnel (approximately ten hydraulic diameters) with different designs of the tunnel mouth has been placed in a wind tunnel and has been subjected to the effects of external wind by varying the wind direction at the mouth of the tunnel. In the experimental oriented study pressures have been measured and the airflow has been made visible with smoke and by the sand erosion method (semolina). The relation between the flow ratio and the direction of the wind has been explored.

A planned new train tunnel under the central parts of Stockholm was intended to be ventilated by natural ventilation and the movement of the trains. However, the amount of heat generated by the trains is so high that natural ventilation would give abnormal temperatures and velocities in the tunnel and at the stations. The heat adsorbed by the rock surrounding the tunnel can be neglected in comparison with the amount transported by air.

To validate the emergency operation modes of a 7 km long underground railway tunnel ventilation system, a full-scale experimental investigation has been performed. The results of the test showed that the tunnel ventilation system can successfully provide the critical air velocity necessary for a fire sized 13.6 MW. Alternatively, the large reservoir for smoke under the tunnel ceiling may give more time for escape and ought to be considered when planning for the emergency procedure. The system is now operating commercially.

A one-dimensional unsteady flow model with a moving pollutant source is used for calculating airflow velocity and pollutant distribution inside the single-track railway tunnel when a train passes through it. Calculations are made about the distribution of pollutant concentration inside the tunnel when a train passes through it under the conditions of different tunnel lengths, different amount of pollutant emissions, etc.

Describes a cooling design using ground water to prevent overheating in London's underground train network. More conventional air conditioning is unusable because of the problem of exhausting the excess heat. However the proposed system would require moderate extra ventilation for the carriages. Rising groundwater is a major problem in London, and remains at 12 deg. C year-round. Temperatures in summer in tube trains is as high as 28 deg. C in the tunnels rising to 34 deg. C in the crowded trains. The groundwater is passed through heat exchangers in the tunnels which cool the air.

This paper presents results of a study where computational fluid dynamics (CFD) was the numerical tool used to analyze the ventilation performance in stations of the Buenos Aires Metro subway system. Both natural and mechanical ventilation options were studied. The study showed that although natural ventilation was sufficient to maintain the temperature criteria, it presented a potential egress problem by letting hot gases leave through the entranceways.