Operating characteristics of a linear compressor in the cryocooler

Abstract

l A new efficiency map under the total impedance is proposed. l Displacement and current cannot affect maximum efficiency (0.86 at 963+0i N s m −1 ). l Non-resonant state may have higher efficiency than resonant state. l Different routines of achieving impedance matching are verified by experiments. Linear compressors have been widely used in the cryocoolers and refrigerators due to the advantages of high efficiency, low vibration level and compact construction. However, due to the complicated dynamic characteristics of the linear compressor, the impedance matching of the cryocooler is still an issue. In this study, the operating characteristics of a linear compressor are studied based on the electrical and mechanical impedance. The influences of the load impedance on the displacement and efficiency are analyzed. A new efficiency map under the total impedance is proposed. Experiments on a pulse tube cryocooler with a linear compressor are conducted to verify the theoretical analyses. The maximum theoretical efficiency of 0.86 is obtained at 963+0i N s m −1 . It is not affected by the displacement or the current. Two different routines by fixing the current at 20 A or fixing the voltage at 50 V are tested on the new efficiency map. The results show the feasibility of using the new map to find a better impedance matching and to achieve an efficiency of 0.68. The research is helpful to improve the whole cryocooler performance.