Addendum to an Investigation of the Equilibrium Pressure Along Unequally Heated Tubes

Abstract:
This report presents results of an investigation of the error introduced in very low pressure measurements when small tubes with axial temperature gradients connect pressure tran ducer and the point where knowledge of the pressure is desired. The experiments reported in AEDC-TDR-62-26 were extended with air, argon, and helium to include higher Knudsen numbers and to include data taken with t e pressure transducer at the hot end of the tube. Although the form of the pressure-temperature relations ip was specified with good accuracy to a Knudsen number of 5.0, the degree of scatter for larger Knudsen numbers was s ch (!5%) tha it was not possible to fix accurately the free molecule limit. Also in the present analysis, what is considered to be a more accepted definition of mean free path is used, and the opportunity was taken to recalculate the earlier work using this definition.