Engine vs. heat pump

[Bumpkin]

With consistent direction of rotation, which end of a Stirling gets hot when it's powered as a heat pump instead of making power as an engine? I'm thinking it would be the same as an electrical motor/generator situation where the polarity is the same, but the more I think, the less sure I am. I'm just conversatin' here, but it is relevant to something I'm doing.

[Ian S C]

As a stirling engine rotates, it it extracting the heat energy from the heat source, and getting rid of it from the cooling system at the cold end. If you take away the heat source, and continue to drive the motor in the same direction, it will continue to extract heat from the surounding atmosphere, and the temperature of the displacer cylinder, or hot cap of an ALPHA motor will reduce, the heat being transfered to the cold end, which will heat up, if you'r really working it, and you have water cooling, it's possible to boil it, the lowest temp I'v had is -20*C, while the ambiant temp was 19*C, the cooling water went to just over 60*C, the motor was being turned by another stirling engine of similar power, a more powerful motor, and I would have got a better temp drop. The two motors are in my gallery. The driving motor is listed as my second motor, and the driven one is the Ross Yoke one. Ian S C

[Bumpkin]

Thanks Ian, that’s what I was thinking, but couldn't see it that clearly. Looking at it as the same heat pump, whether it's driving or driven, helps visualize. It would seem then, that if you throttle an engine by using variable displacer timing, if you took it far enough you could have a regenerative braking effect. 'Course it could easily overheat, but that's interesting.