Experimental validation and numeric optimization of a resonance tube-coupled duplex Stirling cooler

Combining thermoacoustic concepts with free piston Stirling systems, this paper puts forward a resonance tube-coupled duplex Stirling cooler which is thermally driven. The novel configuration consists of a free piston Stirling engine, a free piston Stirling cooler and a resonance tube to couple them. Possessing advantages of high exergy efficiency, high reliability and simple structure, it serves as a promising candidate for small scale natural gas liquefaction by burning a small part of natural gas to liquefy the rest and long lifetime space coolers. Using the off-the-shelf components in our laboratory, an experimental setup has been built and a no-load temperature of 110 K has been achieved. As the feasibility of the concept has been verified experimentally, further calculation was done to explore the potential of the configuration. Based on Sage software, the engine and the cooler subsystem were optimized respectively, then a system level numeric model was established and the performance of the system was studied. Among the numeric results, a heat-to-cooling-power exergy efficiency of 26.8% and a cooling power of 2.4 kW were obtained at 110 K with an inner diameter 60 mm resonance tube, charging pressure of 6 MPa, hot temperature of 923 K, ambient temperature of 303 K, working frequency of 75 Hz.