Filtration performance of glass fibrous air filter media under sinusoidal flow condition

Abstract

Air filter is one of the key equipments for sustainable built environment. However, the variation of incoming air velocity is usually neglected in previous studies. Therefore, we applied computational fluid dynamics techniques at micro-scale to study the filtration performance of a glass fibrous media under sinusoidal flow condition. The effects of different flow rates, fluctuation frequencies, fluctuation amplitudes and particle sizes on filtration performance were investigated. Results show that changing the incoming flow field can weaken the Brownian diffusion of particles, resulting in reduced capture efficiency for particles smaller than 0.1 μm. The ratio of particle penetration between sinusoidal flow condition and constant flow condition is calculated. When the fluctuating frequency of the airflow changes for particles less than 0.1 μm, the smaller the particle size is, the larger the ratio of particle penetration is. When the particle size is near the Most Penetrating Particle Size (MPPS), the fluctuating airflow with large amplitude makes the particles more easily trapped by the fiber. The fluctuating airflow with large amplitude will result in a significant reduction in the capture efficiency for particles larger than 1 μm, and the penetration ratio will be greater than that under constant flow condition by three times. For particles with size smaller than 0.1 μm and larger than 1 μm, the amplitude of 0.4 u‾ and smaller has little effect on the capture efficiency. The capture efficiency of particles with size near MPPS value is less susceptible to changes in sinusoidal gas velocity with small amplitude.