Experimental assessment of the velocity and temperature distribution in an indoor displacement ventilation jet

Abstract Displacement Ventilation (DV) offers a great opportunity to improve indoor air quality while reducing the energy consumption compared to mixing ventilation. A frequent problem with displacement ventilation is however the draft discomfort caused by the cold air movement at foot level and excessive temperature difference between head and ankle. Despite numerous past studies, there is still a lack of detailed data regarding the velocity and temperature distribution inside DV jets. In this experimental study, measurements of the air velocity and temperature are performed in the DV jet produced by a flat wall-mounted DV diffuser, using a fine mesh focused on the 0.00–0.20 m height range. Two supply conditions are studied. Three planes of measurements are covered: the vertical longitudinal plane, the vertical transversal plane, and the horizontal plane. Measurements at the outlet of the wall-mounted DV diffuser are also performed. The drop of the DV jet at the diffuser exit, the variation of jet thickness, and the lateral spreading of the flow are discussed. The non-uniformities of velocity and temperature in each plane of measurements are also highlighted and documented. Finally, the measured results are discussed in regard to thermal comfort. Although the measurements presented in this paper are obtained with one specific DV diffuser, the results allow for better understanding of this type of air jet.