The applications of carbon dioxide in heat pump and refrigeration systems are based on a good understanding of its thermophysical properties. Equations of state (EoSs) are largely used to describe the thermophysical behaviors of fluids and can usually give satisfactory results at conditions far from the critical region. However, in the vicinity of the critical point, the long-wavelength of density fluctuations induce an asymptotic singular behavior of fluids, which cannot be described properly by the classical mean-field based EoS. The use of the renormalization group (RG) method with EoSs can correct this nonanalytical behavior near the critical point and not affect the classical behavior far away from the critical region. In this work, an RG method is applied to the Cubic-Plus-Association (CPA) EoS to build a crossover equation. A comprehensive study on thermophysical properties of carbon dioxide, containing vapor–liquid phase equilibrium (VLE) of pure carbon dioxide and its binary mixtures with n-decane and water, compressed density, derivative properties, and transport properties, is performed using this crossover CPA (c-CPA) and the original CPA EoSs to analyze the effects of the RG method on these properties. Our results show that the RG approach can improve the EoS’s performances on VLE, compressed density, and some derivative properties such as isobaric heat capacity, while there is no remarkable influence observed on the calculation of transport properties.

中文翻译：

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通过立方加缔合和交叉立方加缔合状态方程对二氧化碳热物理性质的综合研究

二氧化碳在热泵和制冷系统中的应用是基于对二氧化碳的热物理性质的充分理解。状态方程（EoSs）主要用于描述流体的热物理行为，通常可以在远离临界区域的条件下给出令人满意的结果。但是，在临界点附近，密度波动的长波会引起流体的渐近奇异行为，这无法通过基于经典平均场的EoS正确描述。将重归一化组（RG）方法与EoS配合使用可以纠正临界点附近的这种非分析行为，而不会影响远离临界区域的经典行为。在这项工作中，将RG方法应用于立方加关联（CPA）EoS，以建立交叉方程。ñ -癸烷和水，压缩密度，衍生物的特性，和传输特性，使用该CPA交叉（C-CPA）和原始CPA EOSS来分析对这些性质的RG方法的效果进行。我们的结果表明，RG方法可以改善EoS的VLE性能，压缩密度以及一些诸如等压热容的派生属性，而对传输属性的计算没有显着影响。