Development and characterization of an inclined quad-vortex range hood.

In order to increase containment efficiency and reduce energy consumption, an inclined quad-vortex range hood (IQV range hood) was developed and tested by experimental methods. The flow structure was observed by a laser-assisted flow visualization technique and laser Doppler velocimetry (LDV). Leakage characteristics were measured by the tracer gas (sulfur hexafluoride) detection method. By arranging a narrow suction slot on the bottom face of the hood and two side plates hanging under lateral faces of the hood, a flow field featuring four backwards-inclined vortical flow structures was formed at suction velocities of larger than about 10 m s(-1) (suction flow rate 7.2 m(3) min(-1)). Oil mists were coherently contained in the vortical flow structures without observable dispersion out of the vortices; they rose up spirally with inclination towards the rear wall and were inducted into the suction slot. The backwards inclination of the oil-mist-containing vortical flow structures, caused by the backwards offset arrangement of the suction slot and the Coanda effect, benefited from the reduction in pollutant leakage induced by the influence of a mannequin's presence. Experimental results using the tracer gas concentration detection method showed a close correlation with the results from the flow visualization and LDV measurements. Under both occupied and unoccupied conditions, in which the mannequin was either present or not present, the IQV range hood provided low SF6 leakage concentration levels.