Measurement of conductive heat transfer through rarefied binary gas mixtures

The conductive heat transfer through a rarefied binary gas mixture of helium and argon is experimentally investigated as a function of a molar fraction. The heat flux is measured from the free-molecular to near free-molecular flow regimes, and it is analyzed both in dimensional and dimensionless forms to clarify the effect from the gas-surface interaction. Then, the thermal accommodation coefficient is obtained by assuming a gas mixture as a single “virtual” species gas. The measured thermal accommodation coefficients for single component gases of helium and argon show good agreement with our previous results and data in literature. The thermal accommodation coefficient for a binary gas mixture is compared with the theoretical value derived in the free-molecular flow regime as a superposition of an independent heat transfer by each gas component. The measured results are well explained by the theory. However, there is a little discrepancy between them, suggesting variation in the thermal accommodation coefficient with a molar fraction in flow regimes other than the free-molecular flow regime.