Abstract
ABSTRACT In this paper, a proposed method based on a microfluidic chip that can arrange the collected particles in radial positions according to their sizes before virtual impactor separation was introduced. The main objective of this paper was to design a novel micro-separator structure composed of two major parts: a virtual impactor, and a pretreatment that consists of a sheath flow and a backward-facing step flow configuration. In the separation process, the particles firstly were aggregated on the middle channel by the sheath flow, then ordered in radial position of backward-facing step flow, and finally separated in virtual impactor. To determine the effects of the pretreatment, both simulations and experiments were conducted. A parameter optimization was performed on the micro-separator where the cut-off size of the virtual impactor was 2.5 µm. The results demonstrated that when the flow ratio between inlet flow rate and the total flow rate was set to 50% and the expansion ratio (Er) was 2. The cut-off size of the micro-separator was reduced by 20.77% from 2.436 µm to 1.93 µm, and the wall loss (WL) was acceptable compared with the result only using PM2.5 virtual impactor. The effect of pretreatment on PM1 and PM5 virtual impactor also saw an improvement of collection efficiency even when the additional pretreatment had varying Reynold numbers and nozzle sizes. Accordingly, the stk50 value was reduced by 44.39% from 0.669 to 0.372 by adding pretreatment before the virtual impactor.
Highlights
Publisher: Taiwan Association for Aerosol Research ISSN: 1680-8584 print ISSN: 2071-1409 onlineCopyright: The Author(s)
The flow ratio was defined as the flow rate of particle inlet to the total flow rate of the microfluidic chip, and expansion ratio (Er) were optimized based on the micro-separator, in which the cut-off size of the virtual impactor is 2.5 μm
A novel method enabling particles to be arranged firstly according to the sizes before the virtual impactor separation was proposed to improve the collection efficiency curve of the traditional virtual impactor
Summary
Publisher: Taiwan Association for Aerosol Research ISSN: 1680-8584 print ISSN: 2071-1409 onlineCopyright: The Author(s). Bioaerosols such as viruses, bacteria, and fungal spores pose a great threat to human lives and health, especially for patients with respiratory diseases (Blachere et al, 2009; Tsuda et al, 2013; Cui et al, 2015). To improve the collection efficiency of the impactor, various parameters of inertial impactor have been studied Such as Reynolds number (Marple et al, 1974; Marple et al, 1975), the jet-to-plate distance (Marple et al, 1967; Grinshpun et al, 2005), the particle density (Huang et al, 2002), gravitational force (May et al, 1975; Huang et al, 2001) and etc. Cheon et al (2017) added an additional punched impaction plate between
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