Generation of 2-Dimensional Models for CFD Simulation of Fibrous Filter Media with Binder

Accurate modeling of fibrous filter pressure drop and particle capture/loading behavior includes many phenomena, including partial-to-full slip flow at fiber boundaries, random fiber location and orientation, particle/fiber and particle/particle adhesion and bouncing. Filter media fibers are usually joined together by binders which form significant percentages of the solid material in the media. Complete simulation of media geometry would be three-dimensional (3-D). However, complex 3-D geometries in computational fluid dynamics (CFD) demand powerful computing resources, and hence have been limited to a few fibers. Studies using 2-Dimensional (2D) models were effective in predicting media airflow resistance and particle capture for simple geometries. More realistic 2-D simulations reflecting the random diameter distribution and positioning of fibers with appropriate local boundary conditions should allow still better predictions. To this end we measured the geometric properties of three glass fiber media. 2-D models of fibers with binder links were developed. Statistical fiber diameter distributions were evaluated to determine which provided closer agreement with the measured fiber diameter distributions under the geometric constraints present. For the high standard deviations of fiber diameters present in these media, the number of fibers needed for valid statistics is rather large, which means that complete 3-D simulations are probably not practical.