MEMS Flow Controller for Cryocoolers

"There is a strong interest in pulse tube cryocoolers that is driven by the reliability inherent in cryocooler expander designs that eliminate moving parts. Pulse tube cryocooler performance is strongly dependent on accurate control of gas flow andeffective phasing of the gas volumes. Present pulse-tube technology relies on flow control that is achieved using fixed geometry restrictions. This requires some degree of physical disassembly of the expander for access to the flow restrictor. It is highlydesirable to control flow characteristics remotely with the flexibility to tailor flow into and out of the pulse tube. The primary objective of this proposed development effort is to determine the feasibility of incorporating miniature flow controlassemblies into pulse tube refrigerator designs. For the past two years, TAI has under development a MEMS-based valve that is remotely operated through electrostatic force. This miniature valve has remote flow control capability at high frequency suitablefor operation in the pulse tube cryocooler. Among the benefits this program offers in the area of cryocooler technology are engineering evaluation of flow restrictor designs, dynamic optimization of flow restrictor performance, and real time tunable flowcontrol that enables active load shifting and maximizes dynamic and steady-state efficiencies. Benefits include adjustable flow restrictions to effectively tune pulse tube cryocooler performance