Liquid dibromomethane under pressure: a computational study

Thermophysical properties of liquid dibromomethane are investigated by molecular dynamics simulations between 268 and 328 K at pressures up to 3000 bar. Notably, the isotherms of the isobaric thermal expansivity cross around 800 bar.

Volumetric Properties and Surface Tension of Few-Layer Graphene Nanofluids Based on a Commercial Heat Transfer Fluid

Volumetric properties such as density and isobaric thermal expansivity, and surface tension are of paramount importance for nanofluids to evaluate their ability to be used as efficient heat transfer fluids. In this work, the nanofluids are prepared by dispersing few-layer graphene in a commercial heat transfer fluid Tyfocor® LS (40:60 wt.% propylene-glycol/water) with the aid of three different nonionic surfactants: Triton X-100, Pluronic® P-123 and Gum Arabic. The density, isobaric thermal expansivity and surface tension of each of the base fluids and nanofluids are evaluated between 283.15 and 323.15 K. The influence of the mass content in few-layer graphene from 0.05 to 0.5% on these nanofluid properties was studied. The density behavior of the different proposed nanofluids is slightly affected by the presence of graphene, and its evolution is well predicted by the weight-average equation depending on the density of each component of the nanofluids. For all the analyzed samples, the isobaric thermal expansivity increases with temperature which can be explained by a weaker degree of cohesion within the fluids. The surface tension evolution of the graphene-based nanofluids is found to be sensitive to the used surfactant, its content and the few-layer graphene concentration.

Modeling of density and calculations of derived volumetric properties for n-hexane, toluene and dichloromethane at pressures 0.1-60 MPa and temperatures 288.15-413.15 K

Densities data of n-hexane, toluene and dichloromethane at temperatures 288.15-413.15 K and at pressures 0.1-60 MPa, determined in our previous work, were fitted to the modified Tait equation of state. The fitted temperature-pressure dependent density data were used to calculate the derived properties: the isothermal compressibility, the isobaric thermal expansivity, the difference between specific heat capacity at constant pressure and at constant volume and the internal pressure, over the entire temperature and pressure intervals specified above. In order to assess the proposed modeling procedure, a comparison of the obtained values for the isothermal compressibility and the isobaric thermal expansivity with the corresponding literature data were performed. The average absolute percentage deviations for isothermal compressibility were: for n-hexane 2.01-3.64%, for toluene 0.64-2.48% and for dichloromethane 1.81-3.20%; for the isobaric thermal expansivity: for n-hexane 1.31-4.17%, for toluene 0.71-2.45% and for dichloromethane 1.16-1.61%. By comparing the obtained deviations values with those found in the literature it can be concluded that the presented results agree good with the literature data.