NT-87-03-3 -- Further Developments in the Design of a Free-Piston Stirling Engine Heat Pump for Residential Applications PDF

During the past year (1986/1987), the development of an improved Stifling engine driver for the Free-Piston Stifling Engine Heat Pump (FPSE/HP) has led to a significant increase in heat pump performance. With the improved engine, the MARK I, the FPSE/HP has achieved its two critical milestones of producing 3.0 refrigeration tons (RT) at the 95°F (35°C) ambient temperature conditions and an engine efficiency of 25%, as measured from the fuel input energy, based on the higher heating value of the natural gas and mechanical power developed by the engine. The overall measured performance of the heat pump module (engine, transmission, and compressor) was:

Capacity:

• Q (heating @ 47 F) = (60,000 Btu/h) 63.28 MJ/h
• Q (cooling @ 95 F) = 3.2 RT*

Performance

• COP (heating @ 47 F) = 1.61
• COP (cooling @ 95 F) = 0.86

*Refrigeration tons = 12,000 Btu/h (12.66 MJ/h)

This paper describes the latest configuration of the FPSE/HP module and presents measured performance data. Performance has been measured over a broad range of ambient temperature conditions and engine operating parameters. The results obtained from this testing are presented.

Units: Dual