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So I found this steam engine on the youtubes:
Consider the system not including the candles, only including the can that makes up the boiler shell and the piston, flywheel, etc. The boiler can acts as a hot reservoir; however, the Kelvin-Planck statement of the 2nd law says you can't have an engine put out net work per cycle with only a hot reservoir. This little steam gizmo is certainly doing work. What gives?
My best guess is that a tiny amount steam is condensing inside the syringe during the flywheel-driven compression, dropping the pressure in the cylinder so that the overall work is positive. The steam condensing would give off heat to the walls of the syringe, and that heat flow would act as the cold reservoir. I just can't seem to use maths to predict how much vapor condenses, because to do that I need to know the pressure and temperature (so I can do energy and entropy balance inside the syringe control volume).
Two questions:
1) what is the "cold reservoir" in this machine? (is it condensation in the syringe? something else?)
2) how would you analyze this engine if you were trying to calculate the efficiency knowing only say: the heat power in the boiler can, the piston volumes at top and bottom dead center, and the RPMs?
P.S. No, I'm not trying to build this piece of junk. I am aware that a few mm slip of the solder on that boiler joint makes the difference between an engine and a pipe bomb. This is purely a physics question. Just getting that out of the way.
Consider the system not including the candles, only including the can that makes up the boiler shell and the piston, flywheel, etc. The boiler can acts as a hot reservoir; however, the Kelvin-Planck statement of the 2nd law says you can't have an engine put out net work per cycle with only a hot reservoir. This little steam gizmo is certainly doing work. What gives?
My best guess is that a tiny amount steam is condensing inside the syringe during the flywheel-driven compression, dropping the pressure in the cylinder so that the overall work is positive. The steam condensing would give off heat to the walls of the syringe, and that heat flow would act as the cold reservoir. I just can't seem to use maths to predict how much vapor condenses, because to do that I need to know the pressure and temperature (so I can do energy and entropy balance inside the syringe control volume).
Two questions:
1) what is the "cold reservoir" in this machine? (is it condensation in the syringe? something else?)
2) how would you analyze this engine if you were trying to calculate the efficiency knowing only say: the heat power in the boiler can, the piston volumes at top and bottom dead center, and the RPMs?
P.S. No, I'm not trying to build this piece of junk. I am aware that a few mm slip of the solder on that boiler joint makes the difference between an engine and a pipe bomb. This is purely a physics question. Just getting that out of the way.
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