Thermodynamic work vs. real work

[Fool]

You make no significant sense.

Atmosphere assists an IC engine on compression and exhaust strokes.

Not all Stirling engines will run without the crankshaft and or flywheel.

A Stirling engine operates exactly as all heat engines. Power stroke higher internal pressure. Compression stroke lower internal pressure.

Explosions are moot. Engines don't run on gas impulse. The run on pressure differences.

A pendulum does not supply energy. Energy is supplied to a pendulum. A pendulum only stores energy. The same goes for spring oscillators.

Going from 10 m^3 to one, makes a perfect vacuum negligible. Close to a vacuum is good enough.


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[Tom Booth]

You make no significant sense.

Atmosphere assists an IC engine on compression and exhaust strokes.

Not all Stirling engines will run without the crankshaft and or flywheel.

A Stirling engine operates exactly as all heat engines. Power stroke higher internal pressure. Compression stroke lower internal pressure.

Explosions are moot. Engines don't run on gas impulse. The run on pressure differences.

A pendulum does not supply energy. Energy is supplied to a pendulum. A pendulum only stores energy. The same goes for spring oscillators.

Going from 10 m^3 to one, makes a perfect vacuum negligible. Close to a vacuum is good enough.


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Your opinions.

Mostly wrong, but hardly worth commenting on

[Fool]

Yes. But my science is spot on. You lack science.

[Tom Booth]

Yes. But my science is spot on. You lack science.

OK, maybe you can explain in detail exactly how "Atmosphere assists an IC engine on compression and exhaust strokes".

From inside the crankcase?

That seems unlikely in an engine running at over 3000 RPM.

You assert: "Not all Stirling engines will run without the crankshaft and or flywheel".

How many have you actually tested?

From what I've seen, all types of Stirling engine can, unless of course the displacer is mechanically attached to the crank making it physically impossible.

I doubt you've ever done an actual experiment with any Stirling engine in your entire life. Not very scientific of you IMO.

A pendulum does not supply energy. Energy is supplied to a pendulum. A pendulum only stores energy. The same goes for spring oscillators.

That is simply ignorant

A pendulum can supply energy. It takes in energy, stores energy and also returns or supplies energy, depending on the application.

Your so-called "science" is nothing more than crap opinions.

Edit: sorry VincentG. I'll try to ignore the moron for the sake of continuity on your thread.

[Tom Booth]

... With a displacer SEEMINGLY pushing air from side to side it APPEARS that the hot air is being transfered over to the cold side and vice-versa, so the idea that heat is "flowing through" appears to be obvious or a given.. Instead heat is being pushed or pumped from the cold side over to the hot side.

How then would you explain the operation of a displacer chamber with no work output?

All in all it's a driving engine, it shouldn't be pumping more heat than it's utilizing, otherwise it would be a driven heat pump

I'm not sure I understand your question.

A displacer chamber is not intended to have work output. The piston/power cylinder does the work output

The displacer uncovers the hot plate allowing heat to enter, like a "heat valve".

The heat introduced expands the gas. The gas, as it expands does work equivalent to the heat input, Joule for Joule.

Afterward the gas is left cold at BDC with low internal pressure. Higher external atmospheric pressure then drives the piston back to equilibrium and momentum carries the piston the rest of the way to TDC

Any heat pumping is usually virtually non-existent beyond .maintaining the ∆T.

But, I think there is a potential for increasing that slight heat pumping action so that the ∆T will gradually increase.

Ordinarily the piston is driven out by expansion to the point of pressure equilibrium, then travels a bit further due to momentum, resulting in a slight refrigerating effect.

The throw of the piston can be increased, or it's weight increased to extend the throw and increase the cooling.

If the backflow of ambient heat into the cold side is restricted by insulating the cold side a gradual refrigeration and increase in ∆T could be effected.

I think I've already demonstrated this experimentally. Without difficulty.

https://youtu.be/P11q-BAhvqk

But maybe the metal plate was acting as a kind of mirror reflecting some cold wall or window in the background. Maybe the "emissivity" of the aluminum gave a false reading.

I'd certainly like to see more testing and/or replication, but for the most part, I've done enough repeated and varied experiments to convince me it's worth building a larger model

Extending the throw on that little engine was limited to about 1/8" to the outer rim of the flywheel hub. It also lacked insulation, so any potential cooling was fighting against the surrounding ambient heat.

Personally I don't believe that if 80% of the heat entering the engine were just flowing straight through to the cold side we would need to be talking about any "margin or error". Or quirks of the instrumentation.

The heat flow through the engine would be obvious and an insulated engine would not operate at all, never mind running better.

The Carnot theory and so-called "limit" are crap pseudoscience based on obsolete theory long ago proven to be just plain wrong.

I don't personally care if the Carnot's had their own family secret society and deemed their opinions to be infallible, like the pope.

Too much political power and influence can go to people's heads.

[Fool]

A Stirling engine operates like a pendulum or any other oscillator around a point of equilibrium.

An oscillator can do "real work" in both directions.

You appear to ignore the input and removal of heat that makes a heat engine continue to oscillate while outputting work. It is the difference between the input heat and rejected heat that is work output. Not the oscillation. Conservation of energy. Overshooting, springing, bouncing, doesn't add energy, it just reverses motion. Conservation of energy and momentum.

Too much political power and influence can go to people's heads.

I don't know which is worse, that or ignorance. They are very similar.

How can you tell when a politician is ignorant? When they tell you they are going to fix something. Also a lie, but that is whenever their lips are moving.

.

[Tom Booth]

A Stirling engine operates like a pendulum or any other oscillator around a point of equilibrium.

An oscillator can do "real work" in both directions.

You appear to ignore the input and removal of heat that makes a heat engine continue to oscillate while outputting work. It is the difference between the input heat and rejected heat that is work output. Not the oscillation. Conservation of energy. Overshooting, springing, bouncing, doesn't add energy, it just reverses motion. Conservation of energy and momentum.

That goes without saying.

A heat engine, obviously is supplied with heat. I get sick and tired of your endless straw manning or simple inability to comprehend.

If you've read anything I've ever written on the subject here, I've described a Stirling engine as a damped "driven" oscillator already many times. I have an entire thread on the subject:

viewtopic.php?t=5683

To repeat it every sentence would be redundant, but I forgot, you chat bots have no long term memory for recalling such things.

[Tom Booth]

A Stirling engine operates like a pendulum or any other oscillator around a point of equilibrium.

An oscillator can do "real work" in both directions.

You appear to ignore the input and removal of heat that makes a heat engine continue to oscillate while outputting work. It is the difference between the input heat and rejected heat that is work output. Not the oscillation. Conservation of energy. Overshooting, springing, bouncing, doesn't add energy, it just reverses motion. Conservation of energy and momentum.

Just to be clear, I don't ignore, I deny and refute the supposed necessity for "removal" or "rejection" of "heat".

Energy goes in as heat and out, not as heat but as "work".

There is no "law of the universe" that necessitates throwing away 90% of the heat supplied to a heat engine as "waste heat".

"Heat" being defined as thermal energy actually transfered from outside -> into the engine. Not the pre-existing ambient or "internal" energy within the engine which is never transfered but simply exists as a given, as you and others interpret the "Carnot limit".

[Fool]

... With a displacer SEEMINGLY pushing air from side to side it APPEARS that the hot air is being transfered over to the cold side and vice-versa, so the idea that heat is "flowing through" appears to be obvious or a given.. Instead heat is being pushed or pumped from the cold side over to the hot side.

How then would you explain the operation of a displacer chamber with no work output?

All in all it's a driving engine, it shouldn't be pumping more heat than it's utilizing, otherwise it would be a driven heat pump

VincentG, operating a displacer chamber with no power piston or cylinder, by external means, as you have said produces zero work output. It does require a little work input, to overcome windage and friction.

Let us look at just the thermodynamics. First let's use one with a perfect frictionless chamber with zero friction compression, windage, and a perfect regenerator. As the gas is pushed back and forth heat is stored in the regenerator and emerges in the other section at that sections temperature Th or Tc.

Going from cold to hot would change the pressure as the temperature was increased. This would tend to make the gas in the cold space hotter. It would begin releasing heat to the cold plate, and rase the temperature of the entrance to the regenerator. It would also tend to make the gas in the hot space hotter, and it would release heat to the hot plate, and make the exit hole of the regenerator hotter.

The reverse would happen when the gas goes from hot to cold.

I suppose ultimately the gas in average and after mixing and sloshing back and forth many times, the gas would be transferred in and out with little new heat coming in or going out. There may be a hysteresis effect that pumps some heat through, but small amount.

This leads to why Stirling engines are so difficult to model.

If it had no regenerator it would pump a certain amount of heat across from hot to cold every cycle and the gas would absorb and release heat and tend towards a halfway temperature. Especially if running faster.

[Tom Booth]

... With a displacer SEEMINGLY pushing air from side to side it APPEARS that the hot air is being transfered over to the cold side and vice-versa, so the idea that heat is "flowing through" appears to be obvious or a given.. Instead heat is being pushed or pumped from the cold side over to the hot side.

How then would you explain the operation of a displacer chamber with no work output?

All in all it's a driving engine, it shouldn't be pumping more heat than it's utilizing, otherwise it would be a driven heat pump

VincentG, operating a displacer chamber with no power piston or cylinder, by external means, as you have said produces zero work output....

First of all, the passage of mine VincentG quoted was in regard to a Stirling engine with a power piston as was clearly stated. So where you get "operating a displacer chamber with no power piston" I don't know.

Let us look at just the thermodynamics. First let's use one with a perfect frictionless chamber with zero friction compression, windage, and a perfect regenerator. As the gas is pushed back and forth heat is stored in the regenerator and emerges in the other section at that sections temperature Th or Tc.

Going from cold to hot would change the pressure as the temperature was increased. This would tend to make the gas in the cold space hotter. It would begin releasing heat to the cold plate,...

This is wrong because ideally, when the displacer pushes the working fluid through the regenerator to the hot side and the temperature and pressure increase, what occupies the cold side is the displacer not the hot gas with the added heat of compression. So there would not be any "gas in the cold space" to make hotter. As usual your opinions are based on a faulty understanding of Stirling engine operation and made up nonsense.

The heat supplied by the hot plate with the additional heat of compression creates a potential for power output and the conversion of all that concentrated heat from both the hot plate along with the additional heat of compression into work.

Not very useful if there is no power piston to utilize it though.

But if there is a piston, it does work and the gas cools by energy loss to work output and expansion and so cools as the displacer moves the working fluid through the regenerator to the cold side. Ideally, no heat is transfered to the cold side. Granted, in a poorly designed engine that doesn't always happen with 100% isolation between the hot and cold side, but your description is incomplete.

A Stirling engine works like a heat pump, it is not just move the working fluid from side to side through the regenerator "sloshing back and forth" the way you describe, which is misleading.

VincentG's opening post states that in his example: "...the gas does work on the piston..."

As far as I know, nobody in this thread/topic has mentioned anything about a displacer chamber with no power piston.

This discussion started when I posted this image of a theoretical engine:

Compress_20240908_231001_1637.jpg (22.19 KiB) Viewed 831 times

There is certainly a power piston, but instead of a displacer, the regenerators move to better illustrate how there is no heat transfer between the hot and cold sides.

[VincentG]

I was just illustrating a different method of isolation that is easier to see or make obvious. With a displacer SEEMINGLY pushing air from side to side it APPEARS that the hot air is being transfered over to the cold side and vice-versa, so the idea that heat is "flowing through" appears to be obvious or a given, but that isn't really the case. Instead heat is being pushed or pumped from the cold side over to the hot side.

I was specifically referring to what seemed to be Tom suggesting that the displacer does not push air back and forth, but somehow it is just the heat being pumped that causes the movement of energy.

Take the power piston out of the equation and just look at the displacer. If both plates are room temperature, I don't think it can be argued that the displacer isn't just pushing the air back and forth.

Now add the delta T. Are you saying that the displacer alone is not responsible for pushing the air back and forth and that the heat is?

Can the chamber alone not drive a piston without the piston pumping extra heat into the cold side? I can provide proof that it can using what is essentially a repeating non-cyclical process.

[Tom Booth]

I was just illustrating a different method of isolation that is easier to see or make obvious. With a displacer SEEMINGLY pushing air from side to side it APPEARS that the hot air is being transfered over to the cold side and vice-versa, so the idea that heat is "flowing through" appears to be obvious or a given, but that isn't really the case. Instead heat is being pushed or pumped from the cold side over to the hot side.

I was specifically referring to what seemed to be Tom suggesting that the displacer does not push air back and forth, but somehow it is just the heat being pumped that causes the movement of energy.

Take the power piston out of the equation and just look at the displacer. If both plates are room temperature, I don't think it can be argued that the displacer isn't just pushing the air back and forth.

Now add the delta T. Are you saying that the displacer alone is not responsible for pushing the air back and forth and that the heat is?

Can the chamber alone not drive a piston without the piston pumping extra heat into the cold side? I can provide proof that it can using what is essentially a repeating non-cyclical process.

Sorry for any misunderstanding. Of course the displacer pushes AIR back and forth or side to side.

What I said was " it APPEARS that the HOT air is being transfered over to the cold side"

Emphasis on HOT.

As explained, or as I attempted to explain, the displacer and power piston work together in such a way that when the working fluid drops in temperature due to power output- losing energy the displacer simultaneously moves the COLD or cooling air over to the cold side

With compression the gas is subject to "heat of compression" and the displacer simultaneously moves the HOT air to the hot side.

So as the air gets hot, then cold, then hot again due to expansion/power output and cooling followed by contraction/compression with the motion of the power piston, the displacer shifts the air to the hot side when hot from heat of compression and back to the cold side when it is cold from power output and expansion.

The timing of these events, of course, is critical to the process.

So the displacer does not move hot air to the cold side or move cold air to the hot side, it moves the air to the cold side as, or after it does work and cools. Then during compression when the gas starts to get hot from the heat of compression the displacer shifts the gas back over to the hot side.

If the throw (or compression ratio) is high, then the cooling and heating from power output and compression, respectively, can be great enough that the gas is colder than the cold plate when on the cold side, so absorbs a little heat from the cold side, then with compression the gas may get hotter than the hot plate so there is a heat pumping action that continually tends to transfer heat in the opposite direction to its natural flow, concentrating the heat on the hot side.

But the heat does not flow backwards into the hot plate much, if any, because from there the gas is allowed to immediately expand for the power stroke and all that concentrated or collected heat goes towards expansion and power output.

Just as a side note:

IMO high compression has some effect that goes beyond "heat of compression".

Perhaps when the molecules are forced very close together they are subject to repulsion due to "spin" rather than ordinary collision.

Like two billiard balls spinning and slowly moving closer until they collide. Many "spinning" molecules forced together might "explode".

Otherwise, what is the advantage of high compression? You should only get back what you put in, but it seems clear that more power is derived from higher compression for some reason.

[Tom Booth]

....

Can the chamber alone not drive a piston without the piston pumping extra heat into the cold side? I can provide proof that it can using what is essentially a repeating non-cyclical process.

I'm not sure what you mean here.

I don't think the piston pumps "extra heat into the cold side".

I think it pumps extra heat from the cold side to the hot side.

Maybe you should go on and explain what you mean by "a repeating non-cyclical process".

[VincentG]

Sorry for any misunderstanding. Of course the displacer pushes AIR back and forth or side to side.

What I said was " it APPEARS that the HOT air is being transfered over to the cold side"

I see. I was trying to illustrate that the displacer can affect work without any heat pumping action of the piston or displacer itself. The heat pumping effect of the power piston is an unfortunate consequence of a power producing hot air engine and we try to mitigate that with isothermal compression.

[VincentG]

....

Can the chamber alone not drive a piston without the piston pumping extra heat into the cold side? I can provide proof that it can using what is essentially a repeating non-cyclical process.

I'm not sure what you mean here.

I don't think the piston pumps "extra heat into the cold side".

I think it pumps extra heat from the cold side to the hot side.

Maybe you should go on and explain what you mean by "a repeating non-cyclical process".

Consider a Gamma chamber at 1bar and 300k. At 600k it is allowed to drive out a piston that does work on a crankshaft or directly raising a weight. Now separate the chamber from the power producing system. The chamber returns to 300k and is repressurized by the atmosphere itself. The piston is allowed to return back to TDC without any compression work as pressure on both sides is 1 bar. The two systems (chamber and power) are reconnected. Repeat.

This I think would be considered a repetitive open process open cycle. Work is extracted on expansion at high efficiency and there is zero work negative from compression.

Hopefully Matt chimes in as this is somewhat similar to that non compression internal combustion engine that blows a weight up and extracts work from the weight falling, of which I can't remember the name.