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

• Published in: Separation and purification technology 2021-08, Vol.268, p.118658, Article 118658
• Main Authors: Mrad, Walid, Theron, Félicie, Joubert, Aurélie, Zgheib, Nancy, Le Coq, Laurence
• Format: Article
• Language: English
• Subjects: Air filtration; Airflow pattern; CFD calculation; Chemical and Process Engineering; Engineering Sciences; Environmental Engineering; Environmental Sciences; Filter pleats; Hot wire anemometry
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2021.118658

•Airflow pattern studied in the vicinity of pleats for transitional regime.•HWA relevant to measure precisely velocity profiles inside filter pleats.•Validation of numerical airflow model from local experimental velocities.•Significant velocity gradients observed downstream of the filter media.•Mitigation of velocity fluctuations inside the pleats as approaching media surface. 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.