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Experimental research on performance of an oil-free moving-coil symmetrical dual-piston linear compressor for the J - T throttle refrigerator

In order to improve the efficiency of the Joule-Thomson (J-T) throttling refrigerator, an oil-free symmetrical dual-piston moving-coil linear compressor was developed, and its principle was demonstrated in detail. As the core component of the J-T throttling refrigerator, the linear compressor provides the pressure ratio and mass flow rate required by the throttling cycle. The linear compressor prototype was tested with nitrogen to evaluate its performance at different pressure ratios, strokes, and driving frequencies. Key performance parameters have been obtained, and the experimental results show that the input power is 175.2 W, the mass flow is 1.128 g/s, the unit power mass flow is 6.438 mg/s/W, the motor efficiency, volumetric efficiency, isentropic efficiency, and isothermal efficiency is 87.7%, 81.5%, 74.9%, and 63.7% at the design parameter (pressure ratio of 3.0, stroke of 10.0 mm, frequency of 60.0 Hz), respectively. The maximum mass flow rate is 1.742 g/s, and the maximum motor efficiency, volumetric efficiency, isentropic efficiency, and isothermal efficiency is 88.1%, 94.0%, 81.2%, and 73.4%, respectively. The symmetrical dual-piston linear compressor brings large-capacity and high efficiency, which provide a useful attempt and reference for the optimization of the linear compressors for the J-T throttling refrigerator.