- 學位論文
二醇類水溶液之介電常數量測研究
Measurements of Dielectric Constants of Aqueous Glycols Solutions
摘要
本研究主要是利用介電分析儀量測在頻率範圍260 - 300 KHz及溫度範圍35 - 55℃之乙二醇及乙二醇水溶液的介電常數值。本研究所使用的濃度範圍介於0.06 - 1.0 mol％，所選用的系統為ethylene glycol (EG), diethylene glycols (DEG), triethylene glycol (TEG), tetraethylene glycol (T4EG), propylene glycol (PG), dipropylene glycol (DPG)及其水溶液。這些溶液的靜態介電常數值可藉由與頻率有關的介電常數外推至頻率為零下之介電常數值。本研究所量測出的靜態介電常數值 其不確定度為± 2%。我們可以從量測結果發現靜態介電常數值會隨著溫度上升而下降，且當二醇類水溶液之莫爾分率 < 0.6時， 會隨著 下降而上升，但在 > 0.6時並不明顯。量測的結果採用Redlich-Kister型的方程式求出過剩靜態介電常數值。本研究所計算之靜態介電常數值其絕對平均誤差(AAD%)皆小於0.6%。 鹽類水溶液及乙二醇水溶液常被用在乾燥系統中的液體除濕劑。混合溶劑鹽類水溶液例如LiCl/EG/H2O也被提出可以用在液體除濕劑以吸收水汽。本研究所量測出的靜態介電常數值可被應用在計算MSA(Mean Spherical Approximation)模式的混合溶劑鹽類水溶液的蒸氣壓。代入蒸氣壓的計算結果為2.3%。
關鍵字
介電常數並列摘要
The permittivity of various glycols and aqueous glycols solutions over the frequency range of 260 - 300 KHz for temperatures 35 - 55 ℃ are investigated using the dielectric analyzer. The concentration of the aqueous glycols solution ranges from mole fraction of glycols 0.06 to 1.0. The systems studied are: ethylene glycol (EG), diethylene glycols (DEG), triethylene glycol (TEG), tetraethylene glycol (T4EG), propylene glycol (PG), dipropylene glycol (DPG) and the corresponding aqueous solutions. The static dielectric constants of the fluids have been obtained by extrapolation of the frequency-dependent permittivity to zero frequency. The uncertainties of the measured static dielectric constants are estimated as ± 2%. The measured static dielectric constants of aqueous solutions decrease with increases in temperature and also decrease with increase with the mole fraction of glycols in the solution. The measured static dielectric constants of aqueous solutions were correlated by the Redlich-Kister type equation for the excess static dielectric constants of the system. The average absolute percentage deviation for the calculations of the static dielectric constants of aqueous solutions are less than 0.6%. The aqueous-salt solutions (i.e., LiCl/H2O) and aqueous glycol solutions (i.e., EG/H2O) are commonly used as liquid desiccants in absorption dehumidification systems. The mixed-solvent salt solutions such as LiCl/EG/H2O has been proposed as potential liquid desiccants in absorption of water vapor. The measured static dielectric constants have been applied to calculate the vapor pressures of mixed solvent salt solutions using the mean spherical approximation model. The results of the vapor pressure calculations are 2.3%.