Further Investigation On Single-stage G-M Type Pulse Tube Cryocooler

Compared with the traditional cryocoolers, such as G-M and Stirling cryocooler, pulse tube cooler (PTC) without moving parts at the low temperature range has simpler structure, higher reliability and longer lifetime. With the development of zero boil-off liquid hydrogen storage, high temperature superconductor MgB₂ and cryogenic pumps, the application of cryocoolers working at 20 K becomes more extensive. The research and development of G-M type PTC has been reviewed. Theoretical and experimental investigations on a single-stage G-M type PTC have been carried out. to improve the coefficient of performance (COP), cooling capacity at 20 K and meet the requirement for practical applications. The present work focuses on the following sections:1. Numerical calculation and analysis of G-M type PTC based on REGEN3.3. The effects of some important parameters on the performance of the regenerator of a single-stage G-M type PTC working at low frequency are calculated and analyzed, including phase angle, regenerator length, mass flow rate, diameter of lead sphere, charging pressure and frequency. Some useful conclusions can provide theoretical foundation for the experimental optimization of the PTC.2. Experimental study on a single-stage G-M type PTC. The effects of regenerator length, regenerative materials below 80K, filling pressure and frequency on the performance of a single-stage G-M type PTC are tested and analyzed. The lowest no-load temperature of 10.6K has been obtained, which is a new record for the single-stage PTC. The cooling capacity of 20W at 20.6K has been obtained with an input power of 7.5kW. Meanwhile, the performance of the PTC in long-time run has been tested. The temperature fluctuation of the cold head of the PTC is less than 0.4K, which can meet the requirement for practical applications.3. Improvement of valve core rotary valve. In order to improve the reliability of rotary valve, four air-chambers on the interface between valve core and chassis have been proposed. The wear and the torque required of the valve core can be significantly reduced by this method. Preliminary experiments have confirmed that the new type of valve structure do not affect the cooling performance of the PTC.