Thermodynamic analysis of the working states of the Stirling/pulse tube hybrid cryocooler

The Stirling/pulse tube hybrid cryocooler (SPC) is a kind of high efficiency multi -stage cryocooler which has the potential to be a competitive candidate in space detector cooling. This kind of hybrid cryocooler exhibits special thermodynamic characteristics that have significant influence on the performance and the working state of the Stirling stage of the SPC could be different from normal Stirling cryocooler. Focus on different working states of the Stirling stage of the SPC, a thermodynamic model is established. Altogether five working states of the Stirling stage are classified into two main types according to whether the phase shifter of the pulse tube stage is precooled by the Stirling stage. The detailed study indicates that the working states are closely related to the movement of the piston and the displacer. The criteria including both the swept volume ratio and the phase angle difference of the piston and the displacer for each working state are obtained. The boundaries between different working states are also presented. A non-dimensional parameter G is proposed to identify the working state. Theoretical results are compared with both the numerical simulation and the experiment and good agreement is achieved. This study will be of great significance to the proper design and optimization of the Stirling/pulse tube hybrid cryocooler.