Model ID: 14313
Differentially pumped vacuum systems use a small orifice or tube to connect two parts of a vacuum system that are at very different pressures. Such systems are necessary when processes run at higher pressures and are monitored by detectors that require UHV for operation. In this model, gas flow through a narrow tube and into a high vacuum chamber is approximated using an analytic expression for the flow rate. The model can also be adapted to use experimental data directly. The results obtained by coupling the analytic model to the free molecular flow interface are compared with a simulation that incorporates free molecular flow in both the tube and the UHV part of the system.