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Applied Science and Convergence Technology 1995; 4(4): 343-349

Published online December 1, 1995

Copyright © The Korean Vacuum Society.

Direct Simulation of Compression and Pumping Characteristics for a Gaede - Type Drag Pump

Young-Kyu Lee,Jin Won Lee


The pumping and compression characteristics for a Gaede-type drag pump model are simulated by the direct simulation Monte Carlo(DSMC) method using the hard sphere molecular model and No Time Counter(NTC) collision scheme. Model geometry is a 2-D channel of constant height, with the length-to-height ratio of the channel varied over 1 to 3000. Maximum compression ratio and throughput are calculated in the flow regime ranging from free molecular to continuum. The calculation results show that the existing theories for maximum compression ratio give inaccurate results when the pressure variation in the channel is large, and also that the transmission probability of the pumped gas molecules in the flow direction remains nearly constant irrespective of the channel length and the exhaust pressure under normal operating conditions.

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