Experiments and Large-Eddy Simulations of Lobed and Swirling Turbulent Thermal Jets for HVAC's Applications

Abstract

The mixing improvement by passive control is of wide practical interest. The lobed diffuser, which mixes the primary and secondary streams with high efficiency, has been widely used for heat and mass transfer in the field of fluid engineering. In addition, the jets through lobed generate streamwise vortices, which mix the ambient air and the jet fluid more effectively. The main objective of the present work is to develop new air diffusers for heating, ventilation, air conditioning (HVAC) systems using different jet geometries, in order to improve the users' thermal comfort. Three free jets of air diffusers emitted from a tubular lobed, with six and five lobes, and from a swirl nozzle have been both studied experimentally and numerically. All diffusers have the same throat diameter. It turns out that the results obtained with the LES/WALE and LES/K-ET turbulence models are respectively in good agreement with the experimental results of the lobed and swirling jets. These results indicate that the best mixture is obtained using the six-lobed nozzle with respect to the five-lobed nozzle and the swirling nozzle. In addition, the importance of the jet type on the mixing capacity is highlighted.