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ABSTRACT
In this study, the modified square well model is combined with perturbed-hard-trimer-chain (PHTC) EOS to correlate the surface tension of normal alkanes and refrigerant fluids. The performance of the proposed model has been evaluated by calculating the surface tension of 15 hydrocarbons range within 112–440 K and pressures up to 4.72 × 10−6 MPa. From 251 data points examined the average relative deviation (ARD) of the correlated and calculated densities and surface tension from the experimental ones was found to be 1.63% and 2.46%. Besides, some surface thermodynamic functions such as the surface entropy (SS) and surface enthalpy (HS) of studied liquids were also computed via our method. The ARD (in %) were found to be equal to 3.94 and 2.44, respectively. Finally, our method has also been employed to estimate the critical temperature of 15 hydrocarbons with ARD (in %) equal to 7.92.
Abbreviations
R13: Chlorotrifluoromethane, R12: Dichlorodifluoromethane, R143a: Ethane, 1,1,1-trifluoro
Nomenclature and units
| H | = | Enthalpy/J |
| S | = | Entropy/J·K−1 |
| G | = | Gibbs free energy/J |
| T | = | Absolute temperature/K |
| u(r) | = | Pair potential/J |
| LJ | = | Lennard-Jones |
| kB | = | Boltzmann constant/J·K−1 |
| kBT | = | Thermal energy per molecule |
| σ | = | Segment hard-core diameter |
| d | = | Effective soft-sphere diameter/nm |
| r* | = | Inter-molecular distance in the first coordination shell/nm |
| r** | = | Outer radius of the first coordination shell/nm |
| b | = | van der Waals co-volume, m3 |
| P | = | Pressure, Pa |
| R | = | Gas constant, J/mol K |
| Mw | = | Molecular weight |
| a(T) | = | Strengths of attractive forces, J m−3 |
| Fa and Fb | = | Universal functions |
| Greek letters | = | |
| ε | = | Non-bonded interaction energy parameter, J |
| σ | = | Hard-core diameter, nm |
| η | = | Packing fraction |
| ρ | = | Molar density, mol/m3 |
| γ | = | Surface tension/N·m−1 |
| ε | = | Dispersive energy parameter/J |
| Subscript | = | |
| exp | = | Experimental |
| Calc | = | Calculated |
| Superscripts | = | |
| c | = | Critical state |
| S | = | Surface property |
Acknowledgments
The research committee of Shiraz University of Technology is acknowledged for supporting this project.
Disclosure statement
No potential conflict of interest was reported by the authors.