A new low-cost design for a free-piston Stirling engine driven heat pump is presented. The new approach uses a linear-acting magnetic coupling to transfer engine power across a hermetic shell. Compliance in the coupling affects the performance and stability of the system, especially with regard to matching the engine dynamics to the compressor load. This paper first describes test results that were obtained with the Mark I diaphragm-coupled heat pump. Engine efficiencies exceeded 25% based on fuel higher heating value and heat pump COP was greater than .95 at the 95° ambient, 3-ton point. Following the description of Mark I test results, the Mark II compressor design is presented.
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