Thermodynamic Calculation And Experimental Study Of 4K Two Stage Pulse Tube Cryocooler

As a new type of refrigerator, pulse tube refrigerator has no moving parts in the low temperature region compared with G-M and Stirling refrigerators, which gives it a lot of advantages such as simple structure, low cost, high reliability, low mechanical vibration and electromagnetism noise, etc. Along with its gradually improvement of performance, pulse tube refrigerator shows great competitive abilities in many application fields, including space, military, cryo-electronics, cryo-medicine, gas liquefaction, etc. In this paper, research on the two-stage pulse tube refrigerator which works at 4K is carried out based on the development history of pulse tube refrigerator and latest researches Detailed work is as follows:Firstly, calculation of the actual refrigeration capacity of the second stage at 4K is done. Consulting the separate theoretical refrigeration capacity computational methods of G-M refrigerator, the theoretical refrigeration capacity and various types of irreversible losses of the second stage are calculated, so the actual refrigeration capacity is obtained by subtracting theoretical refrigeration capacity by all loses. Based on the calculation, the actual refrigeration capacity of the second stage at 4K is determined.Secondly, CFD software Fluent has been applied for the numerical simulation of the second stage regenerator. The physical and computational models of the second stage regenerator are established and the calculation methods of the parameters which are important to the porous zone are given. Through the results of the simulation, the temperature and volumetric specific heat distributions of the second stage regenerator are obtained. Parameterξis introduced to prescribe the ratio of volumetric specific heat of helium and regenerative materials. Theoretically, the value ofξshould be close to 1, which means the effect of the arrangement of the regenerative materials is good. The result of the simulation is used to determine the arrangement of the second stage regenerative materials.Lastly, the experimental setup of the two-stage pulse tube refrigerator is introduced and the performance test of the refrigeratorr is conducted. The opening of the orifice and double-inlet are adjusted by needle valves. During the experiment, the cooling-down curve of the refrigerator and the optimal opening curve of the valves are gained. The temperature fluctuation of the cold-head which is influenced by the double-inlet valve opening is analyzed. Theoretical and computational analyses of the phenomena which are found in the experiment are done. According to these analyses, the problems of the cooler are concluded and measures to figure out these problems are also put forward, so that the refrigerator could be improved.