Structure Improvement And Experimental Study On The10K Two Stage G-M Refrigerator

With the wide application of high performance cryo-pumps, high and low temperaturesuperconducting devices, MRI, infrared detectors and cryogenic electronics, thedevelopment of high performance cryocooler is of critical importance. With theadvantages of low running speed, low vibration, high operation stability, longlife-time and easy to operate, the G-M refrigerators have been widely used in theabove applications. In order to improve the operating stability，reliability and coolingperformance of the G-M refrigerators, detailed structure improvements andexperimental studies have been carried out, in particular on the low temperatureregenerator packing method, new sealing method, as well as the geometries of gasflow orifices at hot end of the low temperature regenerator.1) An experimental set-up of a4W/12K two-stage G-M refrigerator is theoreticalcalculated, designed, fabricated, and experimentally tested.2) The rectification meshes are proposed to improve the packing method, working gasdistributions and heat exchange inside low temperature regenerator. The regeneratorspacked with additional rectification meshes are optimal designed using REGEN3.3.The effects of main geometries of the rectification meshes and regenerator, as well assystem operating parameters on the performance of the G-M refrigerator are givenand analyzed. Meanwhile, the design principle of the rectification meshes is suggested.The rectification meshes are fabricated as this design principle and packed inside thelow temperature regenerator of the above10K two-stage G-M refrigerator. The effectsof the rectification meshes on the performance improvements of the G-M refrigeratorare experimentally studied.3) A new labyrinth sealing displacer is proposed to substitute the traditionalpiston-ring sealing displacer for improving the operating stability, reliability andlife-time of the two-stage G-M refrigerators. The displacers are optimal designedusing FLUENT. The effects of main geometries that influencing the performance ofthe labyrinth sealing, including the sealing clearance, the width, depth, quantity andshape of the grooves are given and analyzed. Meanwhile, the design principle of thelabyrinth sealing displacer is suggested. The labyrinth sealing displacers with differentgeometries are fabricated as this design principle. The effects of main geometries andmaterial of the labyrinth sealing displacers, as well as system charge pressure on theperformance of the G-M refrigerators are experimentally studied and compared withcalculation results. 4) The effects of main geometries of the gas flow orifices at hot end of the lowtemperature regenerator, including diameter, quantity and distribution method on thecooling performance of the two-stage G-M refrigerator are experimentallyinvestigated.