Numerical Study of an Electret Filter Composed of an Array of Staggered Parallel Rectangular Split-Type Fibers

In this article, the particle filtration processes of five noncircular fibers with triangular, quatrefoil, trilobal, rectangular, and elliptical cross-sections were numerically investigated, and the pressure drop, capture efficiency, and quality factor due to three main capture mechanisms (diffusion, interception, and inertial impaction) were calculated. By comparing the results with circular fiber, which has the same volume fraction as the five noncircular fibers, the following results can be found. The diffusional capture efficiency, which is highly dependent on the superficial area of fibers, is almost independent of the orientation angle for all fibers. For the quatrefoil, trilobal, and elliptical fibers, as the aspect ratio of component ellipse increases, the capture range also increases, as does the capture efficiency due to three different mechanisms. When considering submicron particles with medium size, which are difficult to capture with circular fibers (especially when dominated by the interception mechanism), triangle and trilobal fibers have higher capture efficiency when the orientation angle is 0 and 60 , respectively. The quality factors of these fibers due to the three capture mechanisms were also investigated in this article. The triangular and rectangular fibers placed horizontally perform better for intermediate and high-inertia particles, and the elliptical fiber placed horizontally shows an advantage in capturing small particles with strong Brownian diffusion.

Section: Introductionmentioning

confidence: 99%

The Influence of Fiber Geometry and Orientation Angle on Filtration Performance

Wang

2015

“…More common are the filters with bipolarly charged fibers; however, there are not many information in the literature concerning the calculation of aerosol particle deposition onto such fibers. The simulations for bipolarly charged fibers of rectangular cross-section were done, e.g., by Cao et al (2004) and Cheung et al (2005), while the deposition on a cylindrical fiber with a line dipole charge distribution was investigated theoretically, e.g., by Brown (1981). The experimental data of filtration efficiency of neutral aerosol particles in electret filters were reported, e.g., by Lee et al (2002), Kim et al (2005), and Ba lazy et al (2006).…”

Section: Introductionmentioning

confidence: 99%

“…Electret fibers can be classified as spun and split types. The former ones are unipolarly charged, whereas the latter fibers carry a high bipolar charge (Baumgartner and Löffler 1986;Cao et al 2004). Unipolarly charged fibers were investigated, e.g., by Baumgartner and Löffler (1987), who assumed that the mechanisms of particle deposition act independently, and by Oh et al (2002), who used the Brownian dynamics method to calculate the collection efficiency of charged and 124 A. PODGÓRSKI AND A. BA LAZY uncharged monodisperse aerosols of submicron size.…”

Section: Introductionmentioning

confidence: 99%

Novel Formulae for Deposition Efficiency of Electrically Neutral, Submicron Aerosol Particles in Bipolarly Charged Fibrous Filters Derived Using Brownian Dynamics Approach

Podgórski

Bałazy

2008

Brownian dynamics (BD) method was employed to calculate the single fiber deposition efficiencies of electrically neutral, submicron aerosol particles in bipolarly charged and non-charged fibrous filters. It was found that a considerable increase in the deposition efficiency can be achieved by increasing the fiber charge density and that it is accompanied by a noticeable shift of the most penetrating particles size towards smaller particles. The results of the BD simulations obtained for various fiber charge densities and various particle diameters allowed us to derive new formulae relating a gain in the deposition efficiency due to action of the electrostatic force to the dimensionless polarization parameter, N σ0 . These equations are applicable in much wider range of N σ0 than other correlations available in the literature. A simple approximate rule for recalculating the form of the proposed formulae for another filter packing density was also presented. Theoretically predicted values of the deposition efficiency in bipolar electret filters were compared with our own experimental data as well as with the data available in the literature and a satisfactory agreement, better than in the case of other existing correlations, was obtained.

“…As noncircular fibers per unit volume can offer more surface area than circular fibers, so noncircular fibers can improve the filter performance. Some researchers have utilized analytical and numerical procedures to predict velocity fields and drag for fluid flow around fibers with square or rectangular cross sections (Brown 1984;Liu 1992a, 1992b;Wang 1996;Ouyang and Liu 1998;Zhu et al 2000;Cao et al 2004). As elliptical fibers may be used in a simple model of dust loading, the studying of elliptical fibers has extra significance.…”

Section: Introductionmentioning

confidence: 99%

An Exact Solution of Interception Efficiency Over an Elliptical Fiber Collector

Wang¹,

Xie²,

Lian-ping³

2012

An exact solution for the interception efficiency of a particle carried by potential flow over an elliptical fiber acting as the collector has been developed based on the Zhukovsky conversion. It is shown that the interception efficiency depends on fiber geometric properties such as size, aspect ratio, the orientation angle of the incoming flow, and the particle diameter. The results show that the noncircular collector shape can improve the interception efficiency significantly when compared to a circular collector, and the maximum efficiency occurs when the incoming flow is parallel to the major axis of the elliptical fiber.