The heat flux between two coaxial cylinders was measured in the range from the free molecular to the early transitional flow regimes for extraction of the thermal accommodation coefficient using an approximate relation on the pressure dependence of the heat flux. The experimental coaxial cylinders' geometry has been traditionally implemented for the measurement of the thermal accommodation coefficient using the low-pressure method; however, the actual experimental setup was characterized by large temperature difference and large cylinders' radius ratio. Compared to the original low-pressure method, much higher pressure range was applied. In order to verify assumptions in the accommodation coefficient extraction, the heat flux under measurement conditions was simulated numerically by the nonlinear S-model kinetic equation. Very good agreement was found between the measured and the simulated heat flux. The proposed procedure of the thermal accommodation coefficient extraction was discussed in detail and verified. The temperature dependence of the thermal accommodation coefficient was also found.
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