A006 Diffuser in cabin

Design of air diffusion terminal devices in passenger train vehicle

Brief:

The ventilation system design for better environment in the passenger train vehicles in Hong Kong is discussed. Mean air speed is an important factor on thermal comfort. Macroscopic flow numbers including the Archimedes number, the Reynolds number, and the throw of diffusers are recommended to be design parameters, for determining the mean air speed in the occupied zone of the train compartment. Empirical equations derived earlier are recommended to be used in the design of air diffusion terminal devices for providing a better environment in the passenger train vehicles. It is found that the supply inlet air jet would not sufficiently penetrate into the occupied zone when passengers are closely packed together in a train vehicle. For maintaining an acceptable mean air speed of 0.15 ms^–¹ at the occupied zone in this example, supply inlet jet of high inlet velocity (15.2 ms^–¹) and low temperature (6°C) should be provided. Air diffusion terminal devices have to be selected carefully in order to improve the indoor air quality inside train vehicles. Diffusers of thinner width are recommended, and they should be placed closely together (0.406 m).

Further information:

Chow WK, Wong LT, 1997. Design of air diffusion terminal devices in passenger train vehicle, Journal of Environmental Engineering (ASCE) 123(12) 1203-1207.