Binti Mohd Taib Malyanah, Trusler J P Martin
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
J Chem Phys. 2020 Apr 30;152(16):164104. doi: 10.1063/5.0002242.
In this work, we have investigated the mono-variant relationship between the reduced viscosity and residual entropy in pure fluids and in binary mixtures of hydrocarbons and hydrocarbons with dissolved carbon dioxide. The mixtures considered were octane + dodecane, decane + carbon dioxide, and 1,3-dimethylbenzene (m-xylene) + carbon dioxide. The reduced viscosity was calculated according to the definition of Bell, while the residual entropy was calculated from accurate multi-parameter Helmholtz-energy equations of state and, for mixtures, the multi-fluid Helmholtz energy approximation. The mono-variant dependence of reduced viscosity upon residual molar entropy was observed for the pure fluids investigated, and by incorporating two scaling factors (one for reduced viscosity and the other for residual molar entropy), the data were represented by a single universal curve. To apply this method to mixtures, the scaling factors were determined from a mole-fraction weighted sum of the pure-component values. This simple model was found to work well for the systems investigated. The average absolute relative deviation (AARD) was observed to be between 1% and 2% for pure components and a mixture of similar hydrocarbons. Larger deviations, with AARDs of up to 15%, were observed for the asymmetric mixtures, but this compares favorably with other methods for predicting the viscosity of such systems. We conclude that the residual-entropy concept can be used to estimate the viscosity of mixtures of similar molecules with high reliability and that it offers a useful engineering approximation even for asymmetric mixtures.
在本研究中，我们考察了纯流体以及烃类与溶解二氧化碳的二元混合物中比浓粘度与剩余熵之间的单变量关系。所考虑的混合物为辛烷 + 十二烷、癸烷 + 二氧化碳以及1,3 - 二甲基苯（间二甲苯）+ 二氧化碳。比浓粘度根据贝尔的定义进行计算，而剩余熵则由精确的多参数亥姆霍兹能量状态方程计算得出，对于混合物，则采用多流体亥姆霍兹能量近似法计算。在所研究的纯流体中观察到了比浓粘度对剩余摩尔熵的单变量依赖性，通过引入两个标度因子（一个用于比浓粘度，另一个用于剩余摩尔熵），数据可用一条单一的通用曲线表示。为了将该方法应用于混合物，标度因子由纯组分值的摩尔分数加权和确定。结果发现，这个简单模型对所研究的体系效果良好。对于纯组分和类似烃类的混合物，平均绝对相对偏差（AARD）在1%至2%之间。对于不对称混合物，观察到较大的偏差，AARD高达15%，但与预测此类体系粘度的其他方法相比，这一结果仍较为理想。我们得出结论，剩余熵概念可用于以高可靠性估算类似分子混合物的粘度，并且即使对于不对称混合物，它也提供了一种有用的工程近似方法。
