Air motion in the vicinity of air supply devices for displacement ventilation.

In displacement ventilation systems, air flow rates, temperature and the design of the air supply device strongly influence the parameters which decide the thermal comfort. This paper reviews experiments and theoretical models which show the connection between t.hese parameters. It is indicated that the Archimedes number of the supply air is the parameter which decides the air velocity in the area close to the floor. (The Archimedes number is the ratio between buoyancy and inertia forces). The width and shape of the air supply device has also been varied, and a porous media has been used on the inlet area of the air supply device. The results show that it is possible to remove considerable amounts of excess heat from a room without exceeding the limits for thermal comfort. Comparisons with commercial elements indicate that the design of the device is of minor importance as long as the air flow is horizontal and the perforation ratio of holes is high enough.