Expansion or compression -- which is more energy efficient?

[T C]

Have you considered all possible scenarios. I think you should read up on the concept of exergy.

For now, I haven't considered phase change. Do you have other scenarios in mind?

 

[jack action]

If you want to include the work required to compress the atmosphere is fine, but it doesn't add any value to the calculations.

You have to see the atmosphere as a spring, and whatever work you put into compressing it while pulling the piston will come back when pushing it back. So it has no effect on the cycle.

But inside the cylinder, compressing a hot fluid requires more work than what was given by its expansion when cold. You cannot go around it, even if you keep the fluid below the atmospheric pressure. The atmosphere will not magically give more on the compressing stoke than what it was given on the expansion stroke. (Again, imagine the cylinder in a vacuum but acting against a mechanical spring instead.)

 

[T C]

But inside the cylinder, compressing a hot fluid requires more work than what was given by its expansion when cold. You cannot go around it, even if you keep the fluid below the atmospheric pressure. The atmosphere will not magically give more on the compressing stoke than what it was given on the expansion stroke. (Again, imagine the cylinder in a vacuum but acting against a mechanical spring instead.)

Compressing the hot fluid inside doesn't require any extra work until the pressure on both side of the piston will be the same.
Kindly go through the document made by my Engineer friend.

 

[jack action]

Do you really think people have overlooked the barometric pressure and used unnecessary work from electric motors to compress the fluid all these years?

Or do you think YOU might have overlooked something?

Maybe it is time you - and your engineer - do a PV diagram and the complete calculations for your cycle (including the outside atmospheric pressure or not, because its value doesn't matter).

Kindly go through the document made by my Engineer friend.

The 4480 J of work calculated in your document for $W_{atm}$ in phase 1 is the exact same value you should have for $W_{atm\_in}$ in phase 3. Therefore (according to the nomenclature of the document):
$$
\begin{align}
W_{net} &= (W_{atm} - W_{gas}) - (W_{atm\_in} - W_{comp}) \nonumber \\
&= (W_{atm} - W_{atm\_in}) + (W_{comp} - W_{gas}) \nonumber \\
&= 0 + (W_{comp} - W_{gas}) \nonumber \\
&= W_{comp} - W_{gas} \nonumber
\end{align}
$$
Proving that the work to and from the fluid making up the atmosphere does not affect the cycle happening inside the cylinder.

 

[T C]

Do you really think people have overlooked the barometric pressure and used unnecessary work from electric motors to compress the fluid all these years?

Without AI and electronic control, it's simply impossible to use that. Using compression was far easier from the age of industrial revolution. And later that has become trend as people have forgot to look at that part.

The 4480 J of work calculated in your document for Watm in phase 1 is the exact same value you should have for Watm_in in phase 3. Therefore (according to the nomenclature of the document):

Wrong! In the phase 3, the pressure and temperature of the enclosed gas has risen due to flow of heat from outside. Those can't be the same.

 

[Chestermiller]

For now, I haven't considered phase change. Do you have other scenarios in mind?

Counter current heat exchangers, flash vaporizers, cooling towers, heat pumps, refrigeration units, mixing with ice, '''

 

[jack action]

Wrong! In the phase 3, the pressure and temperature of the enclosed gas has risen due to flow of heat from outside. Those can't be the same.

From my understanding of your notation, that is $W_{comp}$.

$W_{atm\_in}$ would be the work done by the atmosphere on the piston, which is equal to whatever work was done in phase 1 because the pressure and temperature of the atmosphere did not change. It is just a spring releasing the energy that was previously stored in it.

But your calculations are not very clear, nor are your variables well-defined, in your posts or your document. We have to guess because you refuse to do the work correctly.

Edit: Whoops! Just noticed we lost T C through a ban.

 

[berkeman]

Edit: Whoops! Just noticed we lost T C through a ban.

Yes. He has a long history here of posting about PMMs and Over-Unity mechanisms, even though he usually would not admit it. His numerous infractions finally piled up too high, and he is now no longer at PF.

Thread can be closed now since he is gone. Thank you to everyone who was trying to help him see the issues with this latest idea.