The numerical solution of gaseous slip flows in microtubes

The gaseous flow in a circular microtube is studied by using of a finite-difference technique. The influences of gas compressibility, rarefaction effect and temperature difference between inlet gas and tube wall on the mass flow rate are comprehensively described. The numerical results indicate that rarefaction effect decreases friction factor and increases mass flow rate due to velocity slip at tube wall. Although inlet Mach number in a microtube is low, gaseous compressibility effect may be significant, because in such a flow problem the length-diameter ratio of tube is usually large so that flow Reynolds number may change much more along the flow path.