Heat transfer and density distribution measurements between parallel plates in the transition regime

TLDR: In this article, the heat conduction and density distributions for rarefied gases at rest contained between two unequally heated parallel plates were determined for argon and nitrogen in the transition regime where the ratio of plate spacing to free path was between 1 and 20.

Abstract: The heat conduction and density distributions were experimentally determined for rarefied gases at rest contained between two unequally heated parallel plates Both argon and nitrogen were used as test gases Particular attention was focused on obtaining measurements in the transition regime where the ratio of plate spacing to mean free path was between 1 and 20 The gas density distribution was measured by observing the luminescence produced by a high‐energy electron beam traversed between the plates The experimental results for argon were compared with the analytical results of Wang Chang and Uhlenbeck, Gross and Ziering, and Lees In computing these results the thermal accommodation coefficient measured in the free‐molecule regime was used with the assumption that its value remained constant over the entire pressure range The average agreement between the heat conduction data and the results of the four‐moment methods of Lees and Gross‐Ziering was about 2%, while the measured density profiles agreed with the results of these analyses within 3% Both the heat conduction and density distribution data differ by ∼10‐20% from the results of Gross‐Ziering's eight‐moment method