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Matching the critical point of associating fluids with the Cubic Plus Association equation of state
Fluid Phase Equilibria ( IF 2.6 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.fluid.2020.112674
Xiaodong Liang , Baoliang Peng , Yuan Chen , Jianhui Luo , Michael Locht Michelsen , Georgios M. Kontogeorgis

Abstract Simultaneous description of critical point, vapor pressure and liquid density with an equation of state has been a hot research topic. In this work, the possibilities and limitations of the Cubic Plus Association equation of state for describing these properties of associating fluids have been studied. First a procedure is developed to determine the energy and co-volume parameters by converting the system of three equations at the critical point to a single variable root-finding problem. The procedure is then used in parameter estimation to simultaneously match the critical temperature and pressure as well as fit the vapor pressure and liquid molar volume of typical associating fluids. The performance of the estimated parameters is subsequently compared with the parameters fitted only to vapor pressure and liquid molar volume. The possibility of introducing an extra adjustable parameter to improve the performance is further explored. The results show that, for the studied associating fluids, the Cubic Plus Association equation of state with the obtained parameters can match the critical temperature and pressure exactly, fit the vapor pressure within 2% and the liquid molar volume within 3–4% in the range of temperature up to 0.95 critical temperature, while the model overpredicts the critical volume up to 18%.

中文翻译:

将关联流体的临界点与 Cubic Plus Association 状态方程匹配

摘要 用状态方程同时描述临界点、蒸气压和液体密度一直是研究的热点。在这项工作中,研究了 Cubic Plus Association 状态方程用于描述缔合流体的这些特性的可能性和局限性。首先,通过将临界点的三个方程组转换为单个变量的求根问题,开发了一个程序来确定能量和协体积参数。然后在参数估计中使用该过程以同时匹配临界温度和压力以及拟合典型缔合流体的蒸气压和液体摩尔体积。随后将估计参数的性能与仅适用于蒸气压和液体摩尔体积的参数进行比较。进一步探讨了引入额外可调参数以提高性能的可能性。结果表明,对于所研究的缔合流体,得到参数的 Cubic Plus Association 状态方程可以精确匹配临界温度和压力,拟合蒸汽压在 2% 以内,液体摩尔体积在 3-4% 以内。温度范围高达 0.95 临界温度,而模型高估了临界体积高达 18%。
更新日期:2020-12-01
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