Study On A Cascade Pulse Tube Cryocooler With Work Recovery

In a pulse tube cryocooler (PTC), a great amount of acoustic power is dissipated in the resistance of an impedance network at the ambientend of the pulse tube, while it is recoveredby the displacer or piston in the Stirling cryocoolers.Especially in the application of cooling superconductor with high-power PTC, the dissipated acoustic power would be worthwhile considering to be utilized. Thus, acascade pulse tube cryocooler, of which the secondary stage was driven by the dissipated acoustic power via a transmissiontube, was proposed in this paper. The function of the transmission tube is to transmit the acoustic power from the primary stage PTC to the secondary stage and to adjust the phase angle between the pressure wave and mass flow rate, so that it is proper to drive a secondary cooler. Numerical simulation and experimental results show that the COP of the cascade cryocoolerhas been significantly increased comparing with the original single stage PTC, which lays a solid foundation to improve the efficiency of the high-power PTC working at LN2temperature. The following three aspects of theoretical and experimental research were carried out in this paper:1. An elaborate literature research on the concept and development of pulse tube cryocooler with work recovery was carried out and summarized. Due to different configurations, work recovery methods can be classified into two types:Active method and Passive method. An improved configuration of PTC with work recovery was proposed based on Dr. GW Swift’s quarter-wave pulse tube theory in order to improve the efficiency of the whole unit.2. Numerical simulation software REGEN and Sage were employed in the modeling of the cooler. A detailed design process was elaborated based on the characteristics of the software. The phasor diagram and energy flow inside the cascade PTC were analyzed to explore the various loss mechanisms on performance.The theoretical results show that the cascade cooler can achieve252.5W of cooling power, which is far higher than196.3W of the single stage cooler with the same500W input electric power.3. Experimental results are presented demonstrating the feasibility of work recovery. Among them, the test of the single stage shows that the cryocooler can provide181.3W at233K with an electrical input powerof500W. As for two stages, with the same input power, the primary stage produces175.0W cooling power and the secondary stage produces66.6W at233K, the summation of which is45W higher than the theoretical cooling power196.3W of the single stage PTC, and COP is in increased from the36.26%of the single stage PTC to48.32%of the cascade PTC, which verified the basic concept of work recovery.