Experimental and numerical investigation of a turbulent lobed diffuser jet: application to residential comfort

Abstract

In this work, we present an experimental and numerical study of a turbulent jet from a lobed diffuser, applied to residential comfort. The main aim is the improvement of the air diffusion efficiency, of the ventilation driving flow in the occupancy zone, with least cost. The experiments have been conducted in a room where the dimensions enable a better execution in the conditions of free and hot vertical jet at unfavorable pushing forces. The room has been isolated from the environment during experiments. The temperature difference between the jet and the environment has been controlled by readjusting the blowing jet temperature. Consequently, the jet's Archimedes number is kept constant during tests. The installation includes a hot air blowing diffuser oriented from top to bottom. The temperatures and velocities of the flow have been measured by a multi-functional thermo-anemometer. The probe is supported by a stem that is guided vertically and horizontally in order to sweep a maximum space. The numerical study has been carried out using the Fluent code (V.6). The numerical results obtained with the turbulence model (RNG k-ε) turned out to be in a good accordance with the experimental results.

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

“…The axial temperature of jet measurements, up to 20 De, for the diffuser with lobes, at a low height and at wider opening, and for the diffuser without and with swirling, show that in the same blowing conditions, the jet of lobed provides better temperature stability in the radial direction while the swirling jet, at an inclination angle of 60°, ensures a better expansion of the radial temperatures. In a recent study, Bennia et al (2016;2018) also interested in improving air diffusion in the building by using diffusers with lobes. The numerical results obtained with the RNG k-and SST k-ω models are found in good agreement with the results of experimental.…”

Numerical models development for unidirectional air flow diffusers with lobed and circular orifices

“…This approach can give a deeper understanding in the studies carried out in the field of air distribution and the predicted results can be closer to the real in-situ developing flows. There are studies which state that the orifices of a diffuser can be used as a passive control method of the air jet type flows to improve the mixing of the injected air with its ambient air [1][2][3][4][5]. The mixing process is closely correlated to the turbulence transition [6], while the geometry and the initial flow perturbation significantly affect its generation and transition.…”