EVALUATION AND CALCULATION OF GAS-FLOW THROUGH AXIALLY-SYMMETRIC TUBES

For vacuum technique the rate of the gas flow is the most important quantity. In the free molecular flow region there are known both correct results and approximate formulae for the transmission probabilities. In the near-free molecular flow region Monte-Carlo results and extrapolation terms are available. The precision required or the achievable accuracy determines the complexity of the calculations. For free molecular flow transmission probabilities of axially symmetric tubes a procedure to increase the accuracy is described. In the near-free molecular flow region Monte-Carlo results are presented with an indication of extrapolation possibilities. In the transmission probability calculations allowance is made for the roughness of the tube wall.