Zervaki Orthodoxia, Dionysiou Dionysios D, Kulkarni Pramod
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA.
Environmental Engineering and Science Program, Department of Chemical and Environmental Engineering (ChEE), University of Cincinnati, Cincinnati, Ohio, USA.
Aerosol Sci Technol. 2024;58(8):889-901. doi: 10.1080/02786826.2024.2361050.
A new high-flow, compact aerosol concentrator, using rapid, turbulent mixing to grow aerosol particles into droplets for dry spot sample collection, has been designed and tested. The "TCAC (Turbulent-mixing, Condensation Aerosol Concentrator)" is composed of a saturator for generating hot vapor, a mixing section where the hot vapor mixes with the cold aerosol flow, a growth tube where condensational droplet growth primarily occurs, and a converging nozzle that focuses the droplets into a beam. The prototype concentrator utilizes an aerosol sample flow rate of 4 L min. The TCAC was optimized by varying the operating conditions, such as relative humidity of the aerosol flow, mixing flow ratio, vapor temperature, and impaction characteristics. The results showed that particles with a diameter ≥ 25 nm can be grown to a droplet diameter > 1400 nm with near 100% efficiency. Complete activation and growth were observed at relative humidity ≥ 25% of the aerosol sample flow. A consistent spot sample with a diameter of (the diameter of a circle containing 90% of the deposited particles) was obtained regardless of the aerosol particle diameter ( ). For fiber counting applications using phase contrast microscopy, the TCAC can reduce the sampling time, or counting uncertainty, by two to three orders of magnitude, compared to the 25-mm-filter collection. The study shows that the proposed mixing-flow scheme enables a compact spot sample collector suitable for handheld or portable applications, while still allowing for high flow rates.
一种新型的高流量、紧凑型气溶胶浓缩器已被设计并测试，它利用快速、湍流混合将气溶胶颗粒生长成液滴以进行干点样品采集。“TCAC（湍流混合、冷凝气溶胶浓缩器）”由用于产生热蒸汽的饱和器、热蒸汽与冷气溶胶流混合的混合段、主要发生冷凝液滴生长的生长管以及将液滴聚焦成束的收敛喷嘴组成。该原型浓缩器的气溶胶样品流速为4 L/min。通过改变操作条件，如气溶胶流的相对湿度、混合流率、蒸汽温度和撞击特性，对TCAC进行了优化。结果表明，直径≥25 nm的颗粒能够以近100%的效率生长成直径>1400 nm的液滴。在气溶胶样品流的相对湿度≥２５％时观察到完全活化和生长。无论气溶胶颗粒直径（）如何，均获得了直径为（包含90%沉积颗粒的圆的直径）的一致点样。对于使用相差显微镜的纤维计数应用，与25-mm过滤器采集相比，TCAC可以将采样时间或计数不确定度降低两到三个数量级。研究表明，所提出的混合流方案能够实现一种适用于手持或便携式应用的紧凑型点样采集器，同时仍允许高流速。
