Fool wrote: ↑Fri Apr 05, 2024 6:53 am
....the big problem with those points is that Tom doesn't believe in 'constant T volume change', neither expansion nor compression. He believes in adiabatic. And
he thinks adding an electric generator will change that process. Granted, real processes are somewhere between adiabatic and constant T, unfortunately
adding heat during a Stirling Expansion is the only way it will work effectively. The pressure of expansion must be higher than the pressure of compression, and the only way to accomplish that is by adding heat and removing heat. It needs to be for a full cycle. He seems to always narrow the discussion to single processes ignoring the rest of them. Puts buffer pressure on for the return stroke, leaving it off for the forward stroke, etc...
I may start a tread on heat transfer and why
there is no such thing as Adiabatic.
Your (miss-) characterization of my views, opinions or observations is specious.
I tend to emphasize the adiabatic expansion phase because you fellows tend to discount it entirely.
There is most certainly heat addition during expansion. To imply that I don't "believe" heat needs to be added to effect expansion of the working fluid is disingenuous straw manning.
Ideally, though, heat input should be discontinued as early as possible allowing the later part of the expansion to be carried out adiabatically.
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- heat_input-expansion.jpg (208.73 KiB) Viewed 274 times
Adiabatic expansion without continued heat input allows the heat added to accelerate the engine at the beginning of the expansion to be utilized (converted to "work" output). The "internal energy" lost to "work" reduces the pressure.
"Adding an electric generator" or other external load increases the work output accelerating the cooling of the working fluid which brings the pressure down below atmospheric pressure more quickly, to make the return stroke more forceful.
The Carnot/caloric theory did not recognize the conversion of heat into work at all. Carnot and apparently Kelvin as well, believed that ALL the heat that entered into the engine would have to be removed
Later theoreticians conceded that "some" heat is converted, concocting the unsubstantiated so-called "Carnot Limit" which has no empirical basis and no sound or logical mathematical basis.
In reality ALL the heat added to expand the working fluid is converted to work output during the course of the expansion stroke leaving the piston at BDC and the working fluid at a reduced pressure with the result that atmospheric pressure accelerates the piston back towards TDC.
The heat addition at the early part of the expansion is like the push given to a child on a swing which carries the engine through the remainder of the cycle.
The piston returns completing the cycle in much the same way a swing returns to receive the next push.
Heat addition at, and to a limited extent after TDC is the requisite "push" given to the engine to keep it moving.