Viscous and Molecular Flow
Viscous Flow:
Distance between molecules is small; collisions between molecules dominate; flow through momentum transfer; generally P greater than 0.1 mbar
Transition Flow:
Region between viscous and molecular flow
Molecular Flow:
Distance between molecules is large; collisions between molecules and wall dominate; flow through random motion; generally P smaller than 10 mbar
Vacuum Pressure Ranges
Helderpad 