Measurements of transport properties in the gas phase for hydrofluoroolefins by using a cylindrical acoustic resonator

Y. Kano1 and K. Fujii1

1National Institute of Advanced Industrial Science and Technology, Japan

Keywords: acoustic resonance, cylindrical cavity
property: viscosity, thermal conductivity
material: hydrofluoroolefin

We measured viscosity and thermal conductivity for hydrofluoroolefin refrigerants in the gas phase on the basis of the acoustic resonance method using a cylindrical cavity. The viscosity and thermal conductivity can be determined by measuring the resonant frequency response in the cylindrical resonator. The sample gas is filled in the resonator, then a condenser microphone transmits audio frequency sound signal into the resonator. The sound wave propagating in the sample gas is detected by another condenser microphone and its amplifier and phase shift are measured. The frequency of the sound signal is swiped so that the resonance curve is obtained. Based on the perturbation theory of the acoustic resonance in the cylindrical cavity, viscosity and thermal conductivity of the sample gas are related to the half-widths of the resonance curve. Therefore, effects by both transport properties can be split by measuring at least two asymmetric resonance mode, e. g. longitudinal mode and radial mode, in the cylindrical resonator. Inner length and radius of the cylindrical cavity are calibrated by measuring Ar as a reference gas. The measurement results for the hydrofluoroolefin samples are compared with RefProp developed by NIST.

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