Design and construction of a test rig for grouping of tiny particles using acoustic combined with flow oscillations

Abstract

To attain the high level of cleanliness which are required by clean rooms of the semi-conductor industries, High efficiency particulate arrestance filters, or better known as HEPA filters, are required. However, these HEPA filters are costly and are required to be replaced frequently. Therefore increasing their lifespan is desirable. The common use of pre-filters to improve this is well known. In this project, acoustic methods such as acoustic tweezing are identified as an alternative or an additional layer to the existing pre-filter to improve the efficiency and lifespan of the HEPA filters. Various agglomeration mechanisms are also considered. In part one of this project, Styrofoam balls are simulated as monodispersed aerosols. Standing waves of low frequencies from 100Hz to 2000Hz are identified. This information is used for part two and three of this project, designing and construction of a prototype acoustic agglomeration device for pre-filters. It was noted that at standing wave frequencies, it increases the efficiency of the grade G4 pre-filter that was used by almost 50%. This could possibly result in massive cost reduction in maintaining the HEPA filters. However, more studies need to be conducted on ultrasonic frequencies for this technique to be a viable option in the industry.