Abstract
In this study, we developed a compact low-speed wind tunnel. First, we computationally analysed the flow quality of different wall shapes for the contraction section, the most critical part of a wind tunnel, and selected the design exhibiting minimal boundary layer separation at simulated flow velocities of 2 and 8 km h−1. Then, after constructing the wind tunnel, we experimentally evaluated its overall performance based on different parameters per the United States Environmental Protection Agency (U.S. EPA) guidelines (40 CFR 53.62). The air velocity and turbulence profiles were uniform, displaying ≤ 10% variation in the section we tested. Additionally, we measured the mass concentrations and size distributions of polydisperse dust particles, which were generated by a custom-made rotary dust feeder to ensure the homogeneity of the aerosol, inside the wind tunnel at air velocities of 2 and 8 km h−1 and found ≤ 10% deviation for the mean values across the test section relative to those for the central sampling point. We also assessed the effectiveness of the Well Impactor Ninety-Six (WINS) and Very Sharp Cut Cyclone (VSCC) in the wind tunnel at an air velocity of 8 km h−1 by determining the D50 cutoffs, which, being 2.44 ± 0.05 µm and 2.54 ± 0.05 µm, respectively, fulfilled U.S. EPA’s criteria. Furthermore, we compared the performance of a low-cost sensor against that of a reference instrument in measuring PM2.5 concentrations, and our results agreed with those from previous studies.
Highlights
Publisher: Taiwan Association for Aerosol Research ISSN: 1680-8584 print ISSN: 2071-1409 onlineCopyright: The Author(s)
Design based on high contraction ratio (CR; inlet/outlet area), and without any curvier designing to smoothly reduction in cross-section area of inlet to outlet often leads to boundary layer separation at the inlet which may create turbulence or eddy near the wall of wind tunnel (Mehta and Bradshaw, 1979)
The current square-shaped test section overcomes the impracticability of circular-shaped test section, e.g., in our case, it is needed to place additional aerosol instruments, and the alignment and arrangement for holding the instruments are convenient in square-shaped test section without the use of supportive system, i.e., without any obstacles which can create pressure gradients and affect the flow quality
Summary
Publisher: Taiwan Association for Aerosol Research ISSN: 1680-8584 print ISSN: 2071-1409 online. The design of a wind tunnel with the sole objective of keeping uniform distribution of particles in the test section is critical for evaluation of PM samplers. Design based on high contraction ratio (CR; inlet/outlet area), and without any curvier designing to smoothly reduction in cross-section area of inlet to outlet often leads to boundary layer separation at the inlet which may create turbulence or eddy near the wall of wind tunnel (Mehta and Bradshaw, 1979) Because of this instability, the dust mixing and dispersion inside the tunnel may vary from position to position at the test section. Apart from contraction and aerosol distribution system designing, settling chamber configuration is important task It is a place where high-efficiency particulate air (HEPA) filters and flow straighteners (honeycomb and screens) are placed. Our theoretical and experimental evaluation suggested that design of the developed wind
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