- 學位論文
氣體吸收薄膜接觸器之計算流體力學研究
CFD study on membrane contactors for gas absorption
摘要
本研究利用計算流體力學軟體(Computational Fluid Dynamics，CFD)模擬氣體吸收的薄膜接觸器之吸收性能與吸收器內之特徵。因系統涉及氣液兩相，本研究採用FLUENT內之VOF(Volume of Fluid)多相模式(Multiphase model)。氣液介面間之熱質傳，利用使用者定義函數(udf，user defined function)方式，將薄膜內部之熱質傳效應納入氣液介面之能量與質量平衡關係，並求解介面溫度。本研究模擬範圍涵概層流與紊流。 透過模擬建立了吸收器內部之特性分佈，顯示氣相存在濃度極化現象；網格細化程度探討顯示並非最細化之網格所得吸收量為最低；模擬與實驗吸收量之比較顯示相對高低結果為一致，但模擬值均高於實驗值；操作條件之影響分析顯示改變液相流體流量對吸收量影響最大，顯示此系統主要受控於液相；與熱質傳係數關聯式之比較結果顯示，紊流較層流之偏離程度為小。
並列摘要
This thesis uses Computational Fluid Dynamics software, FLUENT, to simulation the characteristics inside the absorber, for the flat plate membrane contactors used as gas absorbers. Since it is a vapor-liquid two phase system, the VOF (Volume of Fluid) multiphase model is adopted. The heat and mass transfer across vapor and liquid interface was calculated by solving the interface temperature as well as the corresponding phase equilibrium composition using User Defined Functions (UDF) in FLUENT. Both laminar and turbulent flow regimes are studied. The profiles of state variables inside the absorber are obtained. The effects of grid size and the flow rates and temperatures of inlet streams are studied. The heat and mass transfer coefficients in terms of relations between dimensionless groups, Nu vs. Re and Sh vs. Re, are analyzed and compared to reported correlations in the literature. The reported correlations are not applicable to the membrane absorbers.