A Knudsen pump using nanoporous zeolite for atmospheric pressure operation

This paper describes the use of naturally occurring nanoporous zeolite (clinoptilolite) for a miniature Knudsen pump. Based on the principle of thermal transpiration, these pumps have no moving parts, and are attractive for applications ranging from gas analyzers to cooling systems. The Knudsen pump requires flow channels that are in the free molecular or transitional flow regimes. Consequently, at atmospheric pressure, the pore diameters should be les100 nm, and large numbers of pores are necessary to permit meaningful flow. The initial prototype, operating at ap50 K above room temperature, achieves a flow rate of ap0.12 seem with a small pressure load at the output, or a maximum pressure of ap2.5 kPa when the flow is blocked. Its packaged volume is 55times55times12 mm .