Local variations of air velocity in the vicinity of filter pleats in transitional airflow regime – Experimental and numerical approaches

Abstract

This study combines experimental velocity measurements and numerical simulations to characterize the airflow in the vicinity of pleated filters used in ventilation systems. Experimental velocity and turbulence intensity profiles were measured using Hot Wire Anemometry (HWA), upstream and downstream of the filter. Significant local velocity gradients were detected downstream of the filter. The maximum local velocity detected was as much as three times the inlet velocity. The gradient was constant up to 2.5 cm from the pleat entrance. However, only slight velocity variations were observed upstream of the filter. Computational Fluid Dynamics (CFD) simulations were performed using the Ansys Fluent code. Since the flow regime of the airflow approaching filters was transitional, the three following flow models were tested: laminar, standard k -ε, and transition SST. The numerical velocity data were in fairly close agreement with the experimental velocity profiles upstream and downstream of the filter, especially in close proximity to the filter medium. No significant turbulence intensities were detected close to the medium surface for the filtration velocity tested.