Characterization and measurements of thermal conductivity, density and rheological properties of zinc oxide nanoparticles dispersed in (ethane-1,2-diol + water) mixture

The stability of nanofluids obtained by dispersing ZnO commercial nanoparticles in ethane-1,2-diol (ED) and in a {ethane-1,2-diol (1) + water (2)} mixture with mole fraction, x1 = 0.2445 (volume fraction ϕ1 = 0.5, mass fraction w1 = 0.5271), has been analyzed by using two different methods. Density, thermal conductivity and the rheological behaviour have been experimentally determined for different ethane-1,2-diol + water (ϕ1 = 0.5) based ZnO nanofluids and also for the base fluid. Density has been measured at temperatures ranging from (278.15 to 363.15) K and for pressures up to 45 MPa using a high-pressure vibrating tube densimeter. Isothermal compressibility and isobaric thermal expansivity coefficients have been determined whereas an analysis of the excess volumes values of different nanofluids reported in the literature is also developed. Thermal conductivity was measured from T = (283.15 to 343.15)  K with a device based in the hot-wire technique, and the rheological characterization was performed from T = (283.15 to 323.15) K with a rheometer equipped with a cone-plate geometry. The tests carried out for the nanofluids at different concentrations evidence Newtonian behaviour. Experimental viscosity and thermal conductivity were also compared with the estimations provided by several theoretical modelling.

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► Stable nanofluids are prepared by dispersing ZnO with cylindrical shape (62 × 29 nm) in ED + W.
► A contractive volumetric behaviour is found which increases with concentration and temperature.
► Maximum enhancements in density, viscosity and thermal conductivity of 10%, 33%, and 15% are achieved, respectively.
► Murshed and HC models show the best results on thermal conductivity of the studied nanofluids.
► Rheology tests evidence that ethane-1,2-diol + water based ZnO nanofluids are Newtonian.