Experimental Investigation on the velocity profile of supply flow in impinging jet ventilation system

Abstract

Using the impinging jet ventilation system (IJV), it is possible to accomplish high ventilation effectiveness by creating temperature and contaminant stratification within the room. Since the air is supplied toward the floor and directly spreads into the occupied zone at the lower level, it is important to understand the flow feature of supplied jet around the floor. To understand this, the velocity profile of the jet over the floor at the central cross-section was measured using hotwire anemometer under isothermal conditions, and particle image velocimetry (PIV) under isothermal, cooling, and heating conditions. As a result, the obtained velocity profiles at the central cross-section by the hotwire anemometer and PIV are almost the same in the region more than 0.5 m horizontally away from the supply duct. The velocity in the region close to the supply duct was underestimated when using PIV, due to the insufficient entrainment of the seeding tracer. However, its measurement accuracy is assumed to be sufficient for the flow that goes into the occupied zone. In addition, it was also shown that at the central-cross section, the velocity profiles under isothermal and cooling conditions are almost the same.