Experimental Study of Rarefied Argon Contained between Concentric Cylinders

Measurements were made in rarefied stationary argon contained between vertical concentric cylinders, with a fine wire probe aligned parallel to the axis of the cylinders. At different radial positions an equilibrium probe temperature was determined by measuring the temperature of the probe when there was no net energy exchange between the probe and the surrounding gas. When the center cylinder was in the transition regime ${\text{(0.15 < Kn}}_c\text{< 5)}$ , the experimental equilibrium probe temperatures were compared to equilibrium probe temperatures calculated using the moment method of Lees and Liu together with the assumptions that (a) the probe was in the free molecule regime, (b) the gas‐surface interaction at the probe could be described by Knudsen's thermal accommodation coefficient, and (c) the thermal accommodation coefficients at the probe and at the cylindrical surfaces remained constant. For ${\mathrm{Kn}}_c\text{> 0.5}$ agreement between the experimental and calculated equilibrium probe temperatures was within ∼2.5%. Equilibrium probe temperatures were also compared to local gas temperatures calculated by Smoluchowski's temperature jump approximation, and for ${\mathrm{Kn}}_c\text{< 0.15}$ agreement was found to be within ∼1%. In the range ${\text{0.15 < Kn}}_c\text{< 0.5}$ the results of both the moment method and the temperature jump approximation deviated (in opposite directions) from the data by a maximum of 4%.