Spiral channel flows in a disk-type drag pump

Pumping performance of a disk-type drag pump is studied numerically and exp erimentally. Molecular transition and slip flows that arise in a spiral cha nnel on the rotating disk are simulated by using molecular and continuum me thods. The molecular approach employs the direct simulation Monte Carlo (DS MC) method, and the continuum approach solves the Navier-Stokes (NS) equati ons. The formulation of second-order slip boundary conditions is utilized i n the NS method. Particular attention is paid to matching the DSMC method w ith the solutions obtained by the NS method in the slip flow regime. In the experimental study, the inlet pressures are measured for various outlet pr essures of a test pump. Comparison between the experimental data and the nu merical results reveals that the DSMC method provides the more accurate sol ution of the rarefied channel flow for the range of Knudsen number Kn>0.02 than does the NS method. (C) 2001 American Vacuum Society.