wall jet

A non isothermal horizontal jet issuing from a round nozzle distanced from a wall is investigated experimentally. We consider four cases: an isothermal jet, a hot air jet, a cold air jet interacting with the wall and a cold air jet falling down without reaching the wall. The jet expansion rates show two categories. These are (1) an isothermal jet and cold jet not adhering to the wall, with a vertical expansion rate higher than the lateral rate and (2) a non isothermal jet adhering to the wall, with a lateral expansion rate higher than the vertical one.

In many buildings, for instance tunnels, underground, parking areas and industrial halls, the L/H is so large that the flow pattern induced by a two dimensional supply air jet along the ceiling can be completely different from that in rooms of normal sizes. Earlier model experiments indicate that, in this case, the supply jet will have a limited penetration length (Ire) because the entrainment generates a backward flow in the lower part of the ventilated space which at a given distance will disperse or deflect the jet.