Train tunnels and subways are an interesting field of ventilation. Trains move air through tunnels at rates of 600 m³/s (over 2 x 10^6 m³ per hour) which is much more than flow rates in buildings. Air pressures can vary up to some 3000 Pa leading to air velocities in the range of 10 to 50 m/s. This can lead to unsafe situations and thermal discomfort. The development of high speed trains causes more concern for better tunnel design. Modern stations often house small shops and restaurants, that require lower air velocities for thermal comfort.
This paper presents the special needs and difficulties concerning cooling and ventilation of the SwissMetro high-speed ground transportation system. SwissMetro is based on four complementary technologies: a complete underground infrastructure, a partly evacuated tunnel system to reduce the aerodynamic drag of the vehicle with a maximum speed between 400 and 500 km/h, linear electric motors and a magnetic levitation and guiding system. Due to high internal and external heat loads permanent cooling and air-conditioning of the vehicle is required.
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