Thermophysical properties of (diphenyl ether + biphenyl) mixtures for their use as heat transfer fluids

Experimental measurements of density, viscosity and thermal conductivity are reported for pure diphenyl ether and three different binary mixtures of diphenyl ether and biphenyl including the eutectic point. Density has been measured for the liquid phase at temperatures ranging from (298.15 to 363.15) K and for pressures up to 45 MPa using a high-pressure vibrating tube densimeter. A Tammann–Tait correlation of the experimental densities has been proposed for each composition. From these correlations, isothermal compressibility, isobaric thermal expansivity and internal pressure have been determined. Moreover, viscosity and thermal conductivity were experimentally determined at atmospheric pressure for several temperatures by using a rolling ball viscometer and a device based in the hot-wire technique, respectively. All the experimental devices used to determine the thermophysical properties were checked finding good agreements with previous literature data. The experimental viscosity values were correlated using the Vogel–Fulcher–Tammann, Avramov–Milchev and MYEGA equation.

► Densities at high pressure of mixtures of diphenyl ether and biphenyl were reported. ► The composition dependence on thermal conductivity and viscosity is very smooth. ► Crossing point in αp isotherms were detected around 38 MPa. ► MYEGA reproduces our experimental η(T) curves with deviations lower than 0.24%. ► The experimental devices were checked obtaining good agreements with literature.