Design And Experimental Investigation Of G-M/J-T Hybrid Cycle Helium Refrigerator System

Helium gas resource in the world is increasingly nervous,which develops cryogenic equipment toward miniaturization and intensification.Meanwhile the helium refrigerators and technology applied on the vacuum device are accelerated the development of miniaturization technologies.In this thesis,a throttling helium refrigerator system was precooled by a 3W@10K Gifforf-McMahon cryocooler which was called G-M/J-T hybrid cycle helium refrigerator,and the helium refrigerator system was theoretically and experimentally researched.The paper presents the process of the hybrid cycle by a thermodynamic analysis mode.The relationship between the effective procooling and refrigerating capacity is deepy analyzed.The paper discussed the design of some components in the 4.5K G-M/J-T hybrid cycle helium refrigerator system such as cold box,vacuum structure,supports,thermal shields,heat exchangers,valves,data collection system and so on.The heat transfer and flow characteristics in the refrigerator system is deeply analyzed.The theoretical analysis results proved the components design reasonable.A test facility is also built of an open G-M/J-T hybrid cycle helium refrigerator system.The experiment results proved the refrigerator system that can be obtained liquid helium temperature with some cooling capacity.The main parts are shown as follows:1.The cooling process of thermodynamic analysis is basic process.A thermodynamic cycle mode of the 4.5K G-M/J-T hybrid cycle helium refrigerator system is studied.Then the premise of dynamic cooling process is deeply analyzed by a calculated procedure edited with MATLAB.The helium physical property is demanded by NIST.The results show that the effective precooling of the second cold heat of a 5/100T G-M cryocooler is major factor for the cooling capacity.For the hybrid cycle,the optimum state of operation is achieved.Based on exergy analysis method,the objective function of the hybrid cycle is reasoned out.The thermodynamic parameters of all steady state points is calculated out and different operation modes are discussed.2.The structure of the main equipment including cold box,heat exchangers,thermal shields and vacuum are designed.The kind of material and seal of the G-M/J-T hybrid cycle helium refrigerator is deeply analyzed.The heat transfer and temperature analysis results show that the design and selection for all of the main components are reasonable3.Based on the above theoretic analysis,a test facility for the 4.5K G-M/J-T hybrid cycle helium refrigerator system is developed.The premise of dynamic cooling process of the refrigerator,the performance of heat leakage for thermal shields and throttling valve are tested.The cooling experimental results show that the time of cooling process and the mass flow of helium gas are influenced by the throttling valve opening.The tests results also prove the measurement and data acquistion system is able to the helium refrigerator needs.Finally,through the experiment the complex temperature distribution regularity along helium flow direction is obtained and the maximum cooling power of different operation state for the hybrid refrigerator cycle were tested.The dynamic pressure drop in the high pressure tube of throttling cycle is also discussed.