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guillaume May 11, 2008 19:59

Car park ventilation and impulse fans

I'd like to get the opinion of car park designers on the following point:

Impulse fan manufacturers claims that the instalation of impulse fans reduces dramaticaly the flow rates of exhaust and supply fans of the car park.

My model consistently showed that the tunnel analogy doesn't work in a car park and the CO concentration is very much set by the average air velocity throughout the carpark created by the exhaust/supply velocity in a car park of rectangular shapes with exhaust on one side and supply on the opposite side. The higher velocities created in the fan areas are only mixing the pollution, create recirculation zones, and destroy the vertical stratification of CO concentration.

In my opinion, impulse fans are only usefull for smoke dilution in the case of a rectangular car park. They can help with CO only when there are stagnation areas in car park with a complex shape (by bringing some fresher air in the stagnation area) or when the sides of the carpark are open and thus the impulse fans set the average velocity of the air through the car park (tunnel analogy is valid in this case).

Anybody to agree or disagree?

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