以模擬及實驗探討轉子-定子旋轉盤反應器中之氣液滯留量及流力特性

Simulation and Experimental Studies on the Gas-liquid Hold-up and Flow Characteristics in Rotor-stator Spinning Disk Reactor

羅立荇(Li-Hsing Lo)

指導教授 ： 陳昱劭

中原大學/工學院/化學工程研究所/碩士(2021年)

https://doi.org/10.6840/cycu202100643

摘要

超重力技術屬於製程強化其中的項目，其主要目的為提升程序之效率、減小設備體積及提升熱、質傳速率。轉子-定子旋轉盤反應器(Rotor-stator Spinning Disk Reactor)為一新穎之超重力裝置，其具備良好的熱、質傳反應，並可調控反應器中的流體滯留時間，本研究透過商用計算流體力學(Computational Fluid Dynamics , CFD)軟體Fluent 16.0進行轉子-定子旋轉盤反應器中氣、液兩相之三維模擬。為了進一步確認模擬結果之準確性，本研究比較各條件下反應器中氣體滯留量之模擬值與實驗值。
於模擬中，以水及空氣兩物質為反應器中之兩相流體，探討不同轉速、液體流率、氣體流率及氣液進出口模式下之氣液分布、流體流速分布及氣體體積分率。由氣液分布結果得知，Type I模式下，隨轉速增加，液封壓力增加使氣體累積區減小。隨液體流率增加，氣體累積區體積改變不明顯，然而，高液體流率下氣液交界面較不為平整。隨氣體流率增加，氣體累積區體積增加。Type II模式下，氣體傾向累積於下層中心，氣液分布對於轉速、液體流率改變之影響不明顯。低氣體流率下氣體流率增加使下層間隙之氣體累積體積增加，高氣體流率下則無明顯變化。
由流體流速分布結果得知，隨徑向位置與轉速的增加，靠近轉子流體離心流速、靠近定子向心流速及整體切線向流速皆增加。隨液體流率增加，上層間隙之離心流速增加，且回流比例減少。隨氣體流率增加下層徑向及切線向速度分布變化不明顯。由流速分布結果亦可得知反應器內液體流動型態皆為Batchelor flow。由氣體體積分率實驗值與模擬值之比對得知於Type I模式下，並於中高轉速(600~1200 rpm)及低液體流率(0.2 L/min)之區間時，模擬之結果較為準確，其誤差值較小，介於0.1%~27%之間。於Type II模式下，模擬皆低估其氣體體積分率，其誤差值較大，介於40%~80%之間(可能是因為無法對於小於網格大小之氣泡進行計算)。透過本研究得以確切得知轉子-定子旋轉盤反應器內部之氣液流動型態，可做為往後對此反應器進行優化設計與相關應用之重要依據，並應用於需要透過RSSDR提升氣液質傳之程序，如:吸收、氣提等程序。

關鍵字

轉子-定子旋轉盤反應器 ； 計算流體力學 ； 氣液分布

並列摘要

High gravity technology is one of the items in the process intensification , its purpose is to increase the mass and heat transfer rate and reduce the volume of the equipment. Rotor-stator spinning disk reactor (RSSDR) is one of the novel high gravity devices , it has high heat and mass transfer efficiency , and the resident time of the fluid flow inside of RSSDR can be controlled. In this study, gas-liquid flow in RSSDR is simulated with a 3-D model by a commercial Computational Fluid Dynamics (CFD) software, Fluent 16.0.The simulating results were compared with the experimental results of the air volume fraction in the reactor to confirm the reliability of the CFD model.
The influence of rotating speed, liquid flow rate and gas flow rate on the distribution of two phases and fluid velocity profile had been investigated in the simulating results. In the type I mode, the increasing rotating speed and air flow rate will increase the accumulation of air in the top gap. The increasing of liquid flow rate doesn’t have obvious effect on the distribution of two phases. In the type II mode, the gas tends to accumulate at the center of the lower gap, and the changing flow of two phases is insignificant.
Through the results of velocity profile, the flow type in RSSDR is recognized as the Batchelor flow. Increasing radial position and rotating speed will cause centrifugal flow and centripetal flow become faster. Increasing the liquid flow rate makes the centrifugal flow in the upper gap increase, so that the ratio of the backflow decreases.
By comparing of the experimental and simulating results of the air volume fraction in the reactor, the simulating results are more accurate under ether high rotating speed or lower liquid flow rate in the type I mode. The air volume fractions of simulating results are all lower than the experimental results’. Through this study, the gas-liquid flow characteristics in RSSDR can be known, it is an important basis of design intensification on RSSDR in the future.

並列關鍵字

rotor-stator spinning disk reactor ； CFD ； gas-liquid distributuin

參考文獻

參考文獻

G.W. Chu , X. Gao(2013) Distillation studies in a two-stage counter-current rotating packed bed. Separation and Purification Technology. 102, 62-66.

W. Li , H. Liu(2018) Removal of hydrophobic volatile organic compounds with sodium hypochlorite and surfactant in a co-current rotating packed bed. Journal of Environmental Sciences. 64, 190-196.

S. Poncet(2005) Batchelor versus Stewartson flow structures in a rotor-stator cavity with throughflow. Physics of fluids 7, 1-16.

M.M. de Beer, J.T.F. Keurentjes(2016) Bubble formation in co-fed gas–liquid flows in a rotor-stator spinning disc reactor. International Journal of Multiphase Flow. 83, 142-152.