Linking Viscosity to Equations of State Using Residual Entropy Scaling Theory

Abstract

In our previous work (J Chem Eng Data 2021, 66(3):1385–1398), a residual entropy scaling (RES) approach was developed to link viscosity to residual entropy [a thermodynamic property calculated with an equation of state (EoS)] using a simple polynomial equation for refrigerants. Here, we present an extension of this approach to a much wider range of fluids: all pure fluids and their mixtures whose reference EoS and experimental viscosity data are available. A total of 84 877 experimental points for 124 pure fluids and 351 mixtures are collected from 1846 references. The investigated pure fluids contain a wide variety of fluids from light gases with quantum effects at low temperatures to dense fluids and fluids with strong intermolecular association. More than 68.2 % (corresponding to the standard deviation) of the evaluated experimental data agree with the RES model within 3.2 % and 8.0 % for pure fluids and mixtures, respectively. Compared to the recommended models implemented in the REFPROP 10.0 software (the state-of-the-art for thermophysical property calculation), if the dilute gas viscosity is calculated in the same way, our RES approach yields similar statistical agreement with the experimental data while having a much simpler formulation and fewer parameters. To use our RES model, a software package written in Python is provided in the supporting information. Graphical Abstract

Residual Entropy Scaling for Long-Chain Linear Alkanes and Isomers of Alkanes

“…A similar linear trend is also obtained, when instead of the general parameters n g, k given in Table the general parameters of Yang et al given in Table are used in combination with the multiparameter equations of state. Figure (top right) shows the results for this fit (REF-MHC).…”

“…In this paper, different predictive methods were tested to determine the fluid-specific scaling factors ξ for alkanes based on the entropy scaling method proposed by Yang et al , In a first step, the reference equations of state in terms of the Helmholtz energy and two different sets of global parameters , were applied. A linear relationship between the fluid-specific scaling factors ξ and the longest carbon chain was found.…”

“…Yang et al 11 proposed to use different global parameters for different groups of fluids. In their article, the parameters given in Table 1 are applied to the hydrocarbons propane, n-pentane, isobutene, isopentane, ethane, and n-butane (group 3).…”

“…Furthermore, note that methane is in another group than all of the aforementioned fluids with again different global parameters (group 2). The global parameters of Yang et al 11 for the longer-chain hydrocarbons are given in Table 2.…”

“…Yang et al 11 extended the universal approach suggested by Yang et al 8 to 124 fluids and suggested that the investigated fluids should be grouped into eight different groups with different universal parameters for the entropy scaling model for each group. Taking the alkanes as an example, it can be seen in the results provided by Yang et al 9,11 that the proposed predictive relationship between ξ and s crit + is not always met well. The aim of this work is to study if there is a better method for estimating fluid-specific scaling factors for the residual entropy scaling of the viscosity than assuming ξ = 0.7 s crit + as suggested by Yang et al 9 For this purpose, linear alkanes and isomers of alkanes, for which multiparameter equations of state are available, have been studied in this work.…”