CFD modelling for swirl diffuser and its implications on air change effectiveness assessment to green star's IEQ-2

Swirl diffusers can create better air mixing to enhance indoor air quality and help achieve compliance with Green Star IEQ-2 through Air Change Effectiveness (ACE) measure but the lack of modelling guidelines gives rise to the use of various modelling approaches with different results. The ACE calculation depends strongly on the flow characteristics produced by the diffuser outlet that vary considerably between different modelling set ups. Proper calibration and correct definition of performance related parameters are important to effect the radially diffusing flow pattern along the ceiling (Coanda effect). This study demonstrates the common approaches, identifies the critical design parameters, analyses and discusses the differing outcomes in terms of flow pattern, air distribution and ACE. Comparisons of the simulated results from the proposed modelling method with experimental data are also carried out.