Simulation Studies of Micro-Scale Gas Pumps Driven by Isolated Heating Elements Induced Thermal Creep Flows

Abstract

The Knudsen Pump (or Knudsen Compressor) is an unconventional micro-scale gas pump driven by the rarefied gas phenomenon of thermal creep, which is commonly induced by applying a temperature gradient along the wall of thermal creep channels. Previous experimental and simulation results have demonstrated satisfactory performances for Knudsen Pumps using the “linear wall temperature” heating concept. Employing a different heating mechanism, the present work used an isolated heating element placed in front of but not in direct contact with the thermal creep channel. The thermal creep flow was then induced by this isolated heating element instead of the direct temperature gradient along the thermal creep channel wall. Using the DSMC (Direct Simulation Monte Carlo) simulation technique, cases with various heaters’ sizes and operating pressures were studied here to investigate the limitation of thermal creep flows induced by an isolated heater. The maximum pressure ratio in the simulation domain was found to be varied with the heater sizes. This preliminary study of the “isolated heater” heating mechanism is proven to be viable for driving the thermal creep flows and be used in Knudsen Pumps.