Application of perturbed hard-sphere equation of state to the study of volumetric properties of nano-fluids

• Assessment of analytical EOS based on PHS scheme for nanofluids.
• Estimation of their volumetric properties.
• Investigation of excess volumetric behavior of nanofluids by the help of crossed interaction parameters.

This paper aimed to examine the application of a perturbed hard-sphere (PHS) scheme for modeling the volumetric properties of nanofluids. In this regard, PHS scheme has been employed to develop an analytical equation of state (EOS) to correlate and predict the volumetric properties of some nanofluids containing SnO2,ZnO, Co3O4, TiO2-anatase (-A), TiO2-rutile (-R), CuO and Al2O3 as nanoparticles dispersed in ethylene glycol, poly ethylene glycol, water, poly ethylene glycol + water and ethylene glycol + water as base fluids. Two temperature-dependent parameters appeared in the EOS were expressed in terms of molecular scaling constants σ, the effective hard-sphere diameter, and ε, the non-bonded interaction energy. The aforementioned scaling constants were correlated with melting temperatures and true densities which demonstrated the rationality of these constants. The performance of the proposed model was assessed by predicting 1348 density data, for which their measured values were available in the literature over the pressure range from 0.1 to 45 MPa and temperature range from 273 to 363 K. The overall average absolute deviation (AAD) of the correlated (at 0.1 MPa) and predicted (at elevated pressures) densities of 9 studied nanofluids from the experimental data was found to be 0.44%. Generally, this work showed that PHS is an appropriate scheme for the correlation and prediction of the properties of this class of fluids by the help of crossed interaction parameters between nanoparticles and base fluid molecules. The isothermal compressibility coefficients and excess volumes of studied nanofluids have also been investigated by the proposed model.

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