The influence of air inlet angle in swirl diffusers of UFAD system on distribution and deposition of indoor particles

Abstract

The objective of the present study was to investigate the effect of swirl angle on the distribution and deposition of contaminant particles in a chamber with swirl diffuser in an under-floor air distribution (UFAD) system. In the desired model, the analysis of flow field and particle distribution for swirling diffusers at four angles 30°, 45°, 60°, and 90° has been conducted by OpenFOAM® with Eulerian-Lagrangian approach. The results show that under uniform initial distribution condition for particles, the percentage of inhalable particulate matter in the breathing zone decreases faster for the rotation angles of 45° and 60°. In other words, at the inlet angle of 45° and 60° after 600 s, the percentage of 2.5 μm particles removed is 79.2 and 79.5, respectively. While the same percentage for the inlet angle of 30° and 90° is 67.5 and 75.8, respectively. For the considered particles, the inlet angle of 45° and 60° can cause to increase the number of exited particles in comparison with the inlet angle of 30° and 90. Also, when the particles enter the chamber from inlet air diffusers, the concentration of 1, 2.5, and 5 μm particles in the breathing zone decreases by increasing the inlet air angle. But, for the 10, and 25 μm particles, the concentration of particles in the breathing zone increases by increasing the rotation angle of inlet swirl diffusers. The percentages of 2.5 μm particles exiting the outlet are 27.8, 46.9, 53.7, and 58 for the inlet angle of 30°, 45°, 60°, and 90°, respectively.