Thermal diffusivities and sound velocities of supercritical methanol and ethanol measured by the transient grating method

Abstract

We have applied the transient grating (TG) method to the measurement of the thermal diffusivities and sound velocities of supercritical methanol (MeOH) and ethanol (EtOH) in the density region from 0.14 to 2.3, in reduced units scaled by the critical density, at T = 513 and 540 K in MeOH, and T = 518 and 543 K in EtOH. We estimated the thermal conductivity of MeOH in the same density range from the thermal diffusivities and ensured that it increases in the medium-density region, which is similar to those of other fluids. The sound velocity does not show meaningful dispersion on the sound frequency from 50 to 350 MHz in the measured density region.