Experimental analysis of mixing ventilation efficiency using a vortex diffuser - comparison to a lobed multi-cone diffuser

International audienceIn a recent work, an innovative multi-cone diffuser integrating lobed inserts as vortices promoters was proposed, and was compared to its counterpart without lobed inserts. The former offers better mixing of the jet with the ambient air, and significantly improves thermal comfort.In this study, the innovative diffuser is compared to a vortex diffuser under the same experimental conditions. The vortex diffuser is described in the scientific and technical literature as the best diffuser in terms of mixing efficiency due to the swirling effect, being thereby a reference for the innovative lobed diffuser.The results demonstrate that the vortex diffuser does not produce the expected swirling effect. The rotation of the jet is prevented by the immediate attachment of the flow to the ceiling due to the Coanda effect. The jet behaves as a radial ceiling-attached flow having a poor mixing performance. It is believed that such a diffuser would be efficient when mounted on a long duct far away from the ceiling. Hence, it will be better suited for high ceilings, such as in industrial or commercial spaces. In this case, the proposed lobed diffuser becomes an appropriate and efficient mixing ventilation solution for rooms having low ceiling heights