Ron,
For example the Jandy Model AE 2500 claims COP 5.4, while the Ice Breaker Model H100R is rated at 5.6 and its big brother at 6.1, or http://www.sortprice.com/search-CQ-Pool_and_Spa-Heat_Pump which all have claims of COP's that are higher.
Wow, I had no idea that they were getting that kind of performance.
I do realize in the application being discussed that ( W/Qh = Qh-Qc/Qh ) would apply.
Yes. Now we need to locate that elusive Stirling. BTW, an exciting subset of the Stirling is the thermoacoustic Stirling. NASA and LANL have been involved, and one suspects that the cutting-edge of thermoacoustic conversion has gone beyond what they are admitting to, in public:
http://www.lanl.gov/mst/engine/ Jones
