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Abstract
The free-piston Stirling machine has been used as either thermal engine, cryocooler, or heat pump, due to its compact structure, high efficiency, and reliability. A compact engine-refrigerator dual-functional coaxial free-piston Stirling engine was designed and fabricated. It could output 1000 W electricity power with a conversation rate of 20%, when the hot end was heated up to 530°C and the cold end cooled by water which was heated from room temperature to 65°C. The engine was reversely operated as a refrigerator without any modification, and its cooling performance was measured at different input power. The results indicate that, a none-load cooling temperature 142.4 K was obtained at a maximum power supply voltage of 300 VAC (50 Hz), and 193.1 K was reached at a minimum input power of 60 VAC (50 Hz). For a nominal power supply 220 VAC@50 Hz (i.e., 716.8 W), the cooling power increases from 2.4 to 276 W when the temperature at the cold head changes from 156.6 to 203 K. The relative Carnot coefficient of performance of the Stirling unit as a cooler is 18.6% at 203 K.