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Liquid "Stirling" Hot Air Engine

rotate the cooling/heating liquid instead of the air
(+1, -1)
  [vote for,

[Edited for clarity, also changed Name]

The cylinder is filled with air. In it sits a radiator which receives a closed loop of coolant liquid (water). The liquid is sent to the heat or cooling source, and then back to the radiator. Instead of air moving with the air displacer, the power from the piston moves the water back and forth to the cooler/heater, and then to the radiator. The air in the cylinder is heated/cooled alternatively. This causes the air to compress or expand, and pushes the piston.

Much more heat can be absorbed and more cooling can be achieved using regular radiators which are cheaply available, and thus much more power can be achieved in the same area, and probably in a more quiet way. (Why do all claims to Stirling engines say "quiet" but a silent Stirling engine has never been shown?)

pashute, Jun 01 2010

Liquid Piston Stirling Engine http://www.engin.sw...rts/FK_AO_Final.pdf
Been around since the '70s [8th of 7, Jun 01 2010]

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       Widely known to exist.   

8th of 7, Jun 01 2010

       NOT baked, not known to exist.   

       "...which compresses or decompresses the AIR".   

       I'll edit the entry to make it more clear. The engine works on AIR being compressed or decompressed. The piston can be ANY type of piston (including but not necessarily liquid)   

       But the heating and cooling is done by bringing hot or cold liquid into the RADIATOR which is INSIDE the cylinder, heating or cooling the air in the cylinder and pushing the piston up and pulling it back down.   

       Very different from the Fluidine and other liquid piston engines.   

pashute, Jun 01 2010

       //works on AIR// sp. Hydrogen.   

FlyingToaster, Jun 01 2010

       So the radiator inside the cylinder is alternately hot and cold? [-]   

       If so, then the thermal mass of the radiator itself is huge source of inefficiency -- when switching from hot liquid in the radiator to cold liquid in it, a significant amount of heat must be used to heat up the radiator before the radiator can heat the surrounding air; similarly, when switching from hot to cold, a large amount of heat must be removed from the radiator, before the radiator can cool the surrounding air.   

       As for a "silent" Stirling engine, I'm sure that a thermoacoustic engine whose operating frequency is above the range of human hearing could be built. It would make sound, but you wouldn't be able to hear that sound :)
goldbb, Jun 01 2010

       Radiators can be made of surprisingly little material, its the area of contact the 'surface area' that's important, and that should pass the heat as fast as possible.   

       I'm not talking about a home radiator that has to give heat for a long time, and for that reason is made heavy and massive.
pashute, Jun 01 2010

       I'm afraid I still have to leave my [-] in place, even with a radiator of low thermal mass. A highly efficient radiator will need to have a very high surface area, both inside and outside. A high inner surface area translates to small diameter capillary-like channels, which in turn will produce a very high resistance to flow.   

       This in turn means that it takes a significant amount of mechanical energy to move the cooling/heating liquid through the radiator.
goldbb, Jun 01 2010

       it would be a trade off worth a try. No energy lost just maybe time for heat xchange, compensated by much larger power output for same size (better energy density).
pashute, Jun 02 2010

       Power is a time-related function. Less energy per unit time, less power. I presume you mean "power density", rather than "energy density" - the latter is used to refer to fuels and energy stores such as batteries, not motor/generators. Either way, a slower working motor has by definition a lower power density (power/weight).   

       I've been trying to nut out a similar idea to yours myself, something like a cross between that and the liquid piston engine [8th] linked. I came to the same stumbling block that [goldbb] points out - the thermal lag involved in cooling down the working gas AND the piston AND any and all other surrounding infrastructure makes this highly INefficient, not more efficient.
BunsenHoneydew, Jun 18 2010


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