Abstract

Displacement Ventilation (DV) is an air distribution method recognized to enhance indoor air quality, while having a great potential for energy savings, due to stratification, higher supply air temperature and opportunity of free cooling. A frequent complaint associated with displacement ventilation is however the draft discomfort caused by the colder air movement at foot level, and the local discomfort due to an excessive temperature difference between head and ankle. Insufficient information is currently available regarding the variations of temperature and velocity inside a DV jet. Correlation models also need to be developed to report the variation of air speed in the jet.
In this thesis, the DV jet is analyzed in depth through, first, experimental measurements and, then, the development of correlation models. Measurements are performed in an environmental chamber to study the DV jet coming from two different wall-mounted DV diffusers, for different supply conditions. The variations of air speed and temperature in the longitudinal, transversal, and horizontal planes are measured and analyzed. The thermal characteristics are discussed in terms of local thermal comfort. In the second part of the thesis, the experimental data are analyzed towards developing new models for the distribution of air speed and temperature in the air jets. A new mathematical model is proposed for the variation of air speed in the secondary zone of the jet, as well as a new model is suggested for the vertical air speed profile. The variation of the thickness of the DV jet is also studied. A new mathematical is model is proposed to account for the variation of minimal air temperature in the jet. The variations of air speed and temperature in the transversal direction are also discussed. Finally, the contributions are summarized and future work is proposed.