請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/78377
標題: | 溫度對微粒分徑器截取粒徑的影響 Temperature effect on the cutoff size of aerosol separator |
作者: | Chun-Ting Li 李俊霆 |
指導教授: | 陳志傑(Chih-Chieh Chen) |
關鍵字: | 高溫採樣,旋風式分徑器,負載效應,再懸浮,分徑曲線, High temperature sampling,Cyclone separators,Loading effect,Resuspension,Separation curve, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 旋風器(cyclone)是在執行排放管道中細懸浮微粒(PM2.5)採樣時經常被使用的 前置分徑器。由於各排放管道的排氣溫度存在相當大的差異,因此,本研究透過 實驗的方法,探討入口氣流溫度對旋風器的分徑效率、空氣阻抗的影響。 研究中利用超音波霧化器產生微米多粒徑分布的 NaCl 微粒,並搭配氣動粒徑 分析儀(APS)即時監測微粒粒徑與數目濃度的變化。微粒經乾淨空氣的稀釋乾燥與 帶電中和之後,由 APS 與抽氣裝置之組合主動吸取一定流率的空氣樣本進入旋風 器。在旋風器入口前設有加熱裝置以調整氣體的溫度(25 ~ 200 °C );在出口端則 利用冰浴裝置先把氣體溫度降至常溫後再以 APS 進行採樣分析。旋風器的外層以 保溫棉包覆,並在入、出口端設置壓力測定孔。 結果顯示,當溫度由25 °C增加至200 °C時,需增加氣體的質量流率才能使旋 風器的初始分徑效率維持不變(從 10.4 sLPM 提升至 10.46 sLPM),此時由於氣體 速度(風速隨溫度而增加)與黏滯係數(黏滯度隨溫度而增加)的改變,使得旋風器的 空氣阻抗隨著溫度的提升而顯著增加(相同質量流率下,阻抗隨溫度增加而與溫度 的 0.26 次方呈現正相關)。史托克數會隨溫度升高而增加,透過增加史托克數的參 數來修正溫度的影響,將使史托克參數也能在不同溫度下使用。 美國環保署對於粒狀物的採樣規範中(Method 201A),關於 PM10 與 PM2.5 在 25 °C的標準採樣流量為為 10.7 sLPM,而當溫度升高至 200 °C時,美國環保署的採 樣流量( 11.65 sLPM)明顯高於實驗值,從實驗室中所得到的結果說明,當溫度增 加時(25~200 °C),體積採樣流率應該與溫度呈現正相關,並會因為溫度的增加而 增加些許標準採樣流量(200 °C時的標準採樣為 10.46 sLPM 比 25 °C增加 0.06 sLPM)。 This study presented a numerical result of gas-particle flow in cyclone separators. The results evaluated the performance of separators at different temperature, and analyzed the application of Stokes number when elevated temperature. In this study, micro NaCl particles would be generated by ultrasonic atomizer in multi-particle size distribution, and aerodynamic particulate sizer (APS) was used to monitor the changes in particle size and number concentration in real time. The freshly produced droplet particles were diluted, dried and neutralized by dilution air, and the certain flow rate of air sample was draw by APS and air extraction device into the cyclone. A heating device was installed in front of the cyclone inlet to adjust the temperature of the gas (25 ~ 200 °C). At the end of outlet, an ice bath device was used to cool down the gas to normal temperature before sampling from APS for sampling and analysis. The outer layer of the cyclone was covered with thermal insulation cotton, and pressure drop were measured from inlet and outlet of the cyclone. The results show that when the temperature was increased from 25 to 200 °C, the mass flow rate of the gas needed to be slightly increased to maintain the initial separation efficiency of the cyclone. Due to changed in gas velocity and viscosity coefficient, the pressure drop of cyclones significantly increased with increasing temperature. The Stokes number that expressed the separation efficiency of the particle diameter increased with increasing temperature. Therefore, the Stokes number can also be used at different temperatures. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/78377 |
DOI: | 10.6342/NTU202001545 |
全文授權: | 有償授權 |
電子全文公開日期: | 2023-08-04 |
顯示於系所單位: | 環境與職業健康科學研究所 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
U0001-1507202015325100.pdf 目前未授權公開取用 | 5.58 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。