New Results on the Thermal Conductivity of the Noble Gases and of Two Binary Mixtures
The paper discusses new data on the thermal conductivity of the noble gases and of the binary mixtures Ar-Ne and Ar-He, all at zero density and 27.5°C.
First a comparison is made between a third-approximation calculation for the pure gases, based on kinetic theory coupled with our extended law of corresponding states. The calculation reproduces our measurements with a systematic error of order 1%. The same calculational scheme reproduces viscosity with a marginally smaller systematic error of the same sign. This calculation (easy to program) is recommended if a 1% accuracy is adequate. Work on an improved scheme is in progress.
As far as binary mixtures are concerned, it is necessary to recognize that our transient hot-wire instrument measures the “steady-state” thermal conductivity which characterizes heat conduction in the presence of a composition gradient induced by thermal diffusion in the limit of zero mass flux. A comparison between measurement and first-order calculation results in a maximum deviation of 4.5%, whereas a correction to third order reduces it to 3%. Analogous data for viscosity show a deviation of no more than 3% from a first-order calculation. This calculation, not too difficult to program, can be recommended if an accuracy of 4–5% is adequate.
Since the deviations are systematic in all cases it is concluded that the inner consistency of our measurements is better than the preceding comparison would suggest. An improved scheme is here also possible.
KeywordsThermal Conductivity Binary Mixture Mass Flux Composition Gradient Calculational Scheme
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