蒸氣凝結氣膠微粒收集器之效能評估與研發

Development and Performance Characterization of a Steam-based Aerosol Collector

張柏陽(Chang, Po Yang)

指導教授 ： 王竹方

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2015年)

摘要

本篇研究主要在評估一套具有高時間解析度的蒸氣凝結氣膠微粒收集器，並可以串接水相的化學分析儀器。此收集器可區分成以下幾個部分: 混合腔、蒸汽產生器、冷卻系統、慣性衝擊板以及幫浦。當顆粒性物質進入混合腔時，蒸氣與氣流方向平行，顆粒會開始與蒸氣進行混和，此時蒸氣將會附著於顆粒表面以增加顆粒的大小，以便後端慣性衝擊板收集。冷卻系統維持混合腔體的溫度維在20度C左右，以確保腔體內部具有較高的相對濕度以利於蒸氣冷凝於顆粒表面。此蒸氣凝結氣膠微粒收集器可操作在每分鐘5.0到16.7公升的流量範圍內，依照不同的採樣流速，顆粒於混合腔體內部停留時間為1.23秒到4.11秒。為了去評斷此台蒸氣凝結氣膠微粒收集器之效能，設計了一系列的實驗，藉由流量與顆粒大小等參數對其的性能作系統性的量測。首先針對慣性衝擊板對不同粒徑及流量做測試，而得到在每分鐘5.0、10.0以及16.7公升的流量下，慣性收集板所能收到的最小粒徑，此時如將氣動粒徑轉換成史托克數可以預測在此流量範圍內的所對應的流量的最小收集粒徑。第二部分是在量測不同的顆粒大小及流量，經過混合腔體後，顆粒長大的程度，數據顯示，大部分32.2-194.0 奈米的微粒均可長至 2-13微米左右。第三部分探討不同粒徑及流量下，顆粒的收集效率，在每分鐘5.0-16.7公升的流量範圍下，89.8-300.0奈米的微粒回收效率都接近百分之百。最後，將此蒸氣凝結氣膠微粒收集器串接狹縫虛擬衝擊器對周遭的空氣濃度利用慣性的方式做濃縮，得到的實驗濃縮效率大概為3到4倍左右。

關鍵字

顆粒性物質 ； 微粒長大 ； 微粒收集效率 ； 蒸氣凝結氣膠微粒收集器

並列摘要

In this study, a homemade steam-based aerosol collector with high time resolution is developed and discussed here in detail. This steam-based aerosol collector can be coupled with water-phase chemical analytical instruments and divided into a few separate parts, including a mixing chamber, steam generator, cooling system, inertial impactor, and vacuum pump. The particulate matter drawn into the system mixes with steam in parallel direction and forms droplets due to the water supersaturation in the mixing chamber. The cooling system maintaining the temperature around 20 °C enhances the steam condensation on the particle surface. In this study, the aerosol collector is operated in the flow rate range from 5.0 to 16.7 L min-1, and the residence time of droplets inside of the mixing chamber is from 1.23 to 4.11 seconds. For evaluating the performance of the collector, the following experiments were conducted. Firstly, the cut size of the inertial impactor was characterized by penetration experiments at 5.0, 10.0, and 16.7 L min-1. The penetration curves with the Stokes number as x-axis can be established to predict the cut size. Secondly, the sizes of particles from 32.2-194.0 nm are enlarged up to the cut size of the inertial impactor at 5.0 to 16.7 L min-1. Thirdly, the particle collection efficiencies were almost 100% at the sizes of test particles from 89.8 to 300.0 nm in 5.0, 10.0, and 16.7 L min-1. Finally, this steam-based aerosol collector with the slit virtual impactor can concentrate the air mass concentration by the inertial motion of particles. The concentrated ratio was around 3 to 4 times based on the experiments.

並列關鍵字

Particulate matter ； Particle growth ； Particle collection efficiency ； Steam-based aerosol collector

參考文獻

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