DESIGN OF AIR DIFFUSION TERMINAL DEVICES IN PASSENGER TRAIN VEHICLE

The ventilation system design for better environment in the passenger train vehicles in Hong Kong is discussed. Mean air speed is an importa nt factor on thermal comfort. Macroscopic flow numbers including the A rchimedes number, the Reynolds number, and the throw of diffusers are recommended to be design parameters, for determining the mean air spee d in the occupied zone of the train compartment. Empirical equations d erived earlier are recommended to be used in the design of air diffusi on terminal devices for providing a better environment in the passenge r train vehicles. It is found that the supply inlet air jet would not sufficiently penetrate into the occupied zone when passengers are clos ely packed together in it train vehicle. For maintaining an acceptable mean air speed of 0.15 m s(-1) at the occupied zone in this example, supply air inlet jet of high inlet velocity (15.2 m s(-1)) and low tem perature (6 degrees C) should be provided. Air diffusion terminal devi ces have to be selected carefully in order to improve the indoor air q uality inside train vehicles. Diffusers of thinner width are recommend ed, and they should be placed closely together (0.406 m).