Prediction of Filtering Efficiency of an Air Filter Using Light Shading Rate

Abstract

There have been some studies on the theoretical formula for predicting the filtering efficiency of an air filter. However, accurate predictions remain challenging even today. Measurement of the filtering efficiency of an air filter requires multiple devices, including an air compressor, a particle generator, and a particle counter. Therefore, utilizing easily measurable performance parameters for prediction is advantageous as it eliminates the need for measuring equipment, resulting in significant cost reduction in manufacturing process for an air filter. This study focuses on the light shading rate (LSR) as a readily measurable parameter that potentially correlates with logarithm of penetration (− lnP). To predict the − lnP, an empirical formula using the LSR was attempted to be developed. Four types of test filters were produced using glass wool with different fiber diameters (d_f) as materials. The packing density (α), the thickness (T), the LSR, and the − lnP were measured and analyzed. In modeling the LSR, the number of fibers (N_f) for thickness direction was obtained by calculating the inter-fiber distance (D_i) using the packing density and the fiber diameter. The LSR per fiber (LSR/N_f) was determined based on the number of fibers (N_f). The results of comparing calculated values with actual measurements showed a good fit. Additionally, an experimental formula was constructed to predict the − lnP based on the correlation between the LSR and the − lnP. The experimental formula for predicting the − lnP exhibited a high level of agreement. However, it should be noted that its effectiveness is limited to a certain range of fiber diameter, thickness, packing density, LSR, and transparent glass wool as the fiber material.