Characterization and Optimization of a Radiantly Driven Multi‐Stage Knudsen Compressor

The Knudsen Compressor is a micro/meso‐scale gas roughing pump that operates by utilizing the thermal transpiration effect. A Finite Element Knudsen Compressor Performance Model was constructed and used to investigate the pumpdown performance of large‐scale Knudsen Compressor cascades. Model predictions were compared to experimental measurements made for radiantly driven Knudsen Compressors of up to 15 stages. The temperature difference maintained across the thermal transpiration membrane was measured and agreed with analytically predicted values to within 15% except for gas pressures between 10mTorr and 1Torr, where the outward gas conduction cooling is transitioning to rarefied conditions and the 1D model is inadequate. A steady‐state pressure difference of 120 Torr was achieved for a 15 stage Knudsen Compressor operating with an average pressure of 760 Torr of air and illuminated with 20.9 mw/cm2 of radiant flux. Single stage optimization considerations are also discussed.