Numerical investigation of the swirling air diffuser: Parametric study and optimization

During the recent decade, high induction diffusers have become more appealing in applications which require relatively high ventilation airflow rates, such as clean rooms. In this research, the effect of geometric parameters on the performance of a specific type of swirling air diffuser is investigated numerically. The results show that although the diffuser slots geometry, namely their angle and aspect ratio, is impressive on the diffuser performance, it is not as important as the swirling blade angle and the performance is almost constant in a wide range of slots specifications. The results also demonstrate that the diffuser performance and the resultant indoor airflow distribution highly depends on the blades angle and their sensitivity is surprisingly significant when the angle is between 30° and 35°. It is also worth mentioning that the optimum angle of 32° is almost independent of the diffuser airflow rate. Finally, the diffuser jet indexes, namely jet decay coefficient and entrainment ratio, are evaluated for the optimum diffuser and are compared with other common types of diffusers. This research and its results are useful in gaining a better understanding of the swirling diffuser airflow and the effect of diffuser geometry features on its performance.