Theoretical and experimental study for the transient behavior of a linear compressor during pulse tube cryocooler cool down process

The working condition of the linear compressor greatly affects the performance of the cryocooler. When the cryocooler operates during a transient working state like the cool down process, the linear compressor is also in a transient working state and could lead to deviation from designed steady state condition. In order to study the transient behavior of a linear compressor during the cool down process, a theoretical model based on the finite difference method is proposed. The temperature distribution of the regenerator during the cool down process is calculated. The variation of the impedance of the cold finger is then calculated. The transient behavior of the linear compressor are studied according to the impedance match between the compressor and the cold finger. The theoretical model shows that the transient behavior of the linear compressor is determined by the variation of the cold finger impedance during the cool down process and the increase of the input power could be larger than 40% with constant input voltage through the whole cool down process. A Sage simulation model of the cryocooler is built and the cool down experiments are carried out. The simulation and the experiment results are consistent with the theoretical model. It's also shown that the theoretical model could provide better prediction of the transient behavior of the linear compressor. The study of the transient behavior of the linear compressor could help improve the design and control of the linear compressor especially for the transient process.