For heat transfer in the microscale, the interaction between the gas and the solid surface is characterized by the thermal accommodation coefficient, and is important owing to the large surface-to-volume ratio existing as a consequence of the small size. However, there are few data of the thermal accommodation coefficients on the nonmetal surfaces often employed in microdevices. In this research, a novel simplified system in a spherically symmetric configuration is proposed, achieving a low-cost measurement of the thermal accommodation coefficient for both metal and nonmetal surfaces. Tiny flat-plate samples on a heater are placed at the center of a spherical vacuum chamber, and the conductive heat flux is measured and analyzed under the assumption of a concentric spherical shells geometry based on the low-pressure method. An approximate relation for the heat flux is also employed to measure under the near free-molecular and the transitional flow regimes. The proposed novel measurement system is validated by measurements of the thermal accommodation coefficient on a platinum surface with helium, argon and xenon. The measured heat fluxes as a function of pressure are well fitted by the approximate relation, and the obtained thermal accommodation coefficients agree well with the data in the literature. Finally, the measurement is demonstrated on a nonmetal surface of glass, showing good feasibility of the measurement system.
|ジャーナル||Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films|
|出版ステータス||Published - 2014 11月 1|
ASJC Scopus subject areas