Stirlingengineforum.com

Posted: **Tue Jun 18, 2024 2:05 am**

Tom you are taking about an incomplete cycle. You are missing the fact that to get work out of a gas it must have two pressures, higher and lower. Sure, once there is two pressures what you say is true, however how those two pressures are obtained, is sadly lacking from your theory.

The only way I know of the obtain two pressures is by the addition of work, either for compression, or pulling a vacuum.

Linde and Claude process from Wikipedia, both start from highly compressed gas pressures:

Linde's process

Air is liquefied by the Linde process, in which air is alternately compressed, cooled, and expanded, each expansion results in a considerable reduction in temperature. With the lower temperature the molecules move more slowly and occupy less space, so the air changes phase to become liquid.

Claude's process

Air can also be liquefied by Claude's process in which the gas is allowed to expand isentropically twice in two chambers. While expanding, the gas has to do work as it is led through an expansion turbine. The gas is not yet liquid, since that would destroy the turbine. Commercial air liquefication plants bypass this problem by expanding the air at supercritical pressures.[1] Final liquefaction takes place by isenthalpic expansion in a thermal expansion valve.

https://en.m.wikipedia.org/wiki/Liquefaction_of_gases

You can't get expansion without either a man made higher pressure or man made lower pressure. They both require work input. You always leave out the work being input, thus nullifying any evidence you might think you have, but don't, against the second law. Higher pressures potentially have higher expansions than atmospheric and vacuum systems.

Again, the colonialism "heat converted to work", only applies to a full cycle. The second law only applies to a full cycle.

Posted: **Tue Jun 18, 2024 3:38 am**

Tom you are too focused on temperature. I am specifically focused on internal energy per mole.

You can compress air and cool it down, then when expanded through the ACM, temperature goes down but not necessarily internal energy per mole.

Posted: **Tue Jun 18, 2024 4:14 am**

VincentG wrote: ↑Tue Jun 18, 2024 3:38 am Tom you are too focused on temperature. I am specifically focused on internal energy per mole.

You can compress air and cool it down, then when expanded through the ACM, temperature goes down but not necessarily internal energy per mole.

AFAIK VincentG your questioning if it is possible for heat to be converted into work at all, ever, in principle by any means whatsoever.

Is expansion of a gas doing work any different from expansion of a gas not doing work?

For a gas temperature is the measure of its internal energy. The number of moles does not change by expanding and doing or not doing work while expanding.

"Experimentally confirming the conversion of heat energy to work"

Nothing in the thread title about cycles, or systems (open or closed), Carnot, the second law, perpetual motion or the exact method or means employed.

As I said, you don't really seem to be interested in your own question, you seem to just want to join the club in trying to debunk it. If so, no point in this discussion. Believe whatever you like. I don't care.

Anyway;

Suppose we start out by wheeling a tank of room temperature compressed air into a "perfectly insulated room".

If we just open a valve and let the air out of the tank without doing any useful work, we know the expanding gas will get a little bit colder as the air expands into the room and the pressure in the tank equalized with the pressure of the air in the room. There will be a certain amount of "internal energy per mole" in the room.

Taking the exact same setup, if we let the gas leaving the tank do useful work lifting weights as it expands will it get any colder than when it just expanded without doing any useful work?

That is your question isn't it?

If so, if the air gets colder doing work than by expansion alone, was heat that started out in the air in the tank full of room temperature compressed air actually converted into the "gravitational potential energy" of the lifted weights?

Is the room in the second scenario now colder than in the first (less internal energy per mole) for having converted some of the total heat in the room (including the tank of compressed air) into work?

Same room, same tank of compressed air, same total number of moles, same starting temperature.

But the air in the second room full of all the lifted weights is colder than the first.

Incidentally, if the room is also air tight, I suppose the air pressure in the second colder room would be a bit lower as well.

Posted: **Tue Jun 18, 2024 4:45 am**

All the literature that touches on this subject, past experiments etc. indictate that the gas when expanding and doing work gets much much colder (less energy per mole) than gas that is allowed to expand without doing work.

Would it matter or make any difference if the air in the tank was compressed beforehand outside the room or inside the room?

I don't think so.

In compressing the gas heat would be dissipated into the room until the temperature of the tank and room equalized.

Same situation either way.

Same room, same tank full of compressed air.

The only variable is the compressed gas does work while escaping the tank or the gas doesn't do work while escaping the tank.

I suppose both rooms should have the weights present so the starting mass in the room is the same.

Posted: **Tue Jun 18, 2024 4:55 am**

internal energy per mole.

AFAIK VincentG your questioning if it is possible for heat to be converted into work at all, ever, in principle by any means whatsoever.

No, my inquiry is specifically related to a piston based engine. I was using the thought experiment of the perfectly insulated room to help get my point across.

Is the room in the second scenario now colder than in the first (less internal energy per mole) for having converted some of the total heat in the room (including the tank of compressed air) into work?

I don't know.

All the literature that touches on this subject, past experiments etc. indictate that the gas when expanding and doing work gets much much colder (less energy per mole) than gas that is allowed to expand without doing work.

You are still mixing temperature and internal energy. The same mole, expanded, can have the same internal energy while having a lower "temperature".

Posted: **Tue Jun 18, 2024 5:28 am**

VincentG wrote: ↑Tue Jun 18, 2024 4:55 am ...

You are still mixing temperature and internal energy. The same mole, expanded, can have the same internal energy while having a lower "temperature".

Not in an "ideal gas" it can't

Joule's Law.

Ideal gases are a very simple system of non-interacting particles. The only energy
involved is the kinetic energy of the gas particles. There is no potential energy. Let’s
study this system as a way to illustrate some of the concepts that we have been discussing such as internal energy, specific heat, etc.

First of all, the internal energy of an ideal gas is solely a function of its temperature
and is independent of its volume.
(...)

Perhaps this is not surprising since the energy is solely kinetic and hence just depends on the temperature. The energy does not depend on interactions between the particles, so it doesn’t matter how close together the particles are, i.e., the density and volume don’t matter.

One can prove that the energy is solely a function of the temperature in 2 different
ways. One way is microscopic and uses phase space (Reif section 2.5); the other way is macroscopic and just uses the equation of state pV = νRT (Reif section 5.1).

Skipping over all the mathematical proofs. If you are REALLY interested, just look it up.

https://ps.uci.edu/~cyu/p115A/LectureNo ... cture6.pdf

There are a gazillion other similar references. As I said this was all worked out by Joule and others decades ago.

I think your being disingenuous. Not really interested in the facts, just interested in debunking Tom Booth.

Join the club.

Posted: **Tue Jun 18, 2024 5:50 am**

Tom I don't care to invest any time debunking you. I'm simply asking for legitimate experimental evidence that shows heat energy directly convering to work. And as of yet it has not been presented.

I will however argue that in real gas, density and volume does matter. And that the same gas molecules when spread out can have the same kinetic motion (internal energy), even if the apparent "temperature" is lower.

Posted: **Tue Jun 18, 2024 6:29 am**

VincentG wrote: ↑Tue Jun 18, 2024 5:50 am Tom I don't care to invest any time debunking you. I'm simply asking for legitimate experimental evidence that shows heat energy directly convering to work. And as of yet it has not been presented.

I will however argue that in real gas, density and volume does matter. And that the same gas molecules when spread out can have the same kinetic motion (internal energy), even if the apparent "temperature" is lower.

Well I guess nobody has yet performed the exact experiment according to your strict parameters, lifting weights in a perfectly insulated room or whatever.

The whole history of the science of liquifying gases, air cycle refrigeration etc. is replete with examples at least from Joule onward to today.

All I ever get is people throwing the "ideal gas law" at me, all of a sudden you want to talk about real gases.

Well, an "ideal gas" is a generalization that hold true at most common temperatures and pressures. You may get some variation one way or the other with real gases, such as the exact amount of cooling or something for different types of gas but the general principle holds.

A gas expanding and doing work gets much much colder (internal energy per mole) than a gas just expanding and not doing work.

Part of the problem in talking about this, I think is that there is a lot of money in liquifying gases and other cryogenic type processes. To really learn something about it, in depth, you'd probably have to work for Air Liquide or the DOD or something and enter into a NDA because it mostly all involves proprietary processes.

Liquefaction of air

In 1902 Claude devised what is now known as the Claude system for liquifying air.[9] The system enabled the production of industrial quantities of liquid nitrogen, oxygen, and argon; Claude's approach competed successfully with the earlier system of Carl von Linde (1895).[10] Claude and businessman Paul Delorme founded Air Liquide (L'Air Liquide), which is presently a large multinational corporation headquartered in Paris, France.

From the start this became big business with its "trade secrets".

Your privileged to benefit from my decade or so of research, gleaning tidbits of information here and there on the subject over the years. Take it or leave it. I don't care.

As they say, you can lead a horse to water but you can't make him drink.

There is plenty of evidence. A machine that transforms or converts heat into work is the accepted definition of a heat engine

What sort of experiment, in your opinion, would constitute "confirmation"?

If you were really interested you could run the experiment described.

Get a compressor and release the air. Then release the air through an air tool doing some kind of work.

Your not looking for confirmation, IMO, you just seem to be looking for any excuse to just dismiss the subject.

I've done plenty of my own experiments of that nature. They all appear to confirm that heat is a form of energy and can be converted into work.

I'd always like to see more, but personally I've seen enough to be convinced that heat is just a form of energy that is converted into work by a heat engine.

It's a well established and accepted fact.

The evidence has been presented or is readily available to you, you'd just rather wear a blindfold. Willful ignorance.

Posted: **Tue Jun 18, 2024 7:02 am**

Again, I am specifically referring to a piston engine. Air expanding through a turbine is interesting but beyond the scope of my development currently.

When I presented my question, the response I received(in the opening post of this thread) from Stroller, who has an engineering background, went along with my suspicions.

It also seemed from the original discussion around that response that no one here is in agreement on the true nature of heat energy and how it relates to work.

I have spent countless hours designing and fabricating my epoxy engine to help my understanding of the true nature of a heat engine.

It remains the best example of a closed cycle (and fast acting) demonstration of PV=nRT that I have seen. If you have seen a better model please bring it to our attention.

I consider it a real scientific instrument. A standard model LTD Stirling engine is, by scientific comparison, a toy.

Posted: **Tue Jun 18, 2024 7:41 am**

VincentG wrote: ↑Tue Jun 18, 2024 7:02 am Again, I am specifically referring to a piston engine. Air expanding through a turbine is interesting but beyond the scope of my development currently.

...

Claude's experiments originally used an expansion engine (with a piston, not a turbine). Numerous references to that effect have already been posted in abundance.

When presented with evidence or references you just keep narrowing down the scope. Again, looks to me like willful ignorance.

It is universally accepted in physics and science generally that at least SOME heat can be converted into work. The only real question is how much. If you accept the Carnot limit that's one thing but you seem to think your device being spun up by a Dremel tool has overturned even the Carnot limit. You say no heat at all is converted.

You do realize you are going against accepted science at least as much if not moreso than me in just questioning the "limit". but in the opposite direction.

Anyway, I don't really see anything very extraordinary in your demonstration. You seem to be seeing what you want to see. Or, maybe I am and your just being objective, but your results can be interpreted differently, just as my so-called "results" with my LTD "toy".

That's why I'm working on experiments that hopefully remove any ambiguity.

With two engines "running on ice" either the ice will melt fairly rapidly or theoretically, if heat is REALLY being converted into work, much much more slowly, or potentially not at all

I think you are right at least that real incontrovertible experimental evidence, (though available to one degree or another, mostly as historical references, with diligent effort), is generally pretty scarce and/or undisclosed "trade secrets".

You and I seem to be about the only two people trying to answer the question with relatively easy to engineer experiments.

There is something of a void to fill or I don't think we would be having any debate about it

Posted: **Tue Jun 18, 2024 8:09 am**

But experimenting with this does not necessarily require a turbine or extremely sophisticated or expensive equipment.

These guys apparently got some modest cooling by running a slightly modified IC engine on compressed air.

https://youtu.be/MQuQEY9XEK0

There are lots of videos on how to convert a gasoline engine to an air motor.

It doesn't, or shouldn't matter if the air is expanded and does work through a turbine or a modified lawnmower engine. Work is work.

The cooling doesn't seem very impressive in that video, but I don't know what the ambient temperature is. They also don't have the engine insulated so any cooling effect from converting heat into work is being largely nullified by the hot (ambient) metal, friction, exhaust mixing with the air, probably aluminum engine transfers a lot of heat, so not very conclusive at all

My point is just that if you really want to do an experiment demonstrating heat being converted to work it's not impossible.

How do you think a Stirling engine runs? Even a "toy" is an example of heat being converted into mechanical motion or "work". Or if not, why not?

You seem to be returning to Caloric theory then?

Posted: **Tue Jun 18, 2024 8:22 am**

VincentG wrote:I will however argue that in real gas, density and volume does matter. And that the same gas molecules when spread out can have the same kinetic motion (internal energy), even if the apparent "temperature" is lower.

There are formulas that more accurately predict real gas behavior. They can be found in the following link:

https://en.m.wikipedia.org/wiki/Real_gas

And for internal energy:

https://en.m.wikipedia.org/wiki/Internal_energy

Wikipedia wrote:Therefore, the internal energy of an ideal gas depends solely on its temperature (and the number of gas particles): 𝑈=𝑈(𝑁,𝑇). It is not dependent on other thermodynamic quantities such as pressure or density.

It seems to me that temperature and internal energy run hand in hand. This is unlike "heat" in that the same amount can be transfered between any two temperature differences. Or any amount between fixed temperature differences. Temperature is the measurement of internal energy.

There appears to only be internal energy per mass/mole, not density, or volume mole, just the total isolated mass.

I was a little confused on this years ago, as I thought number of impacts dictated temperature too. I now think, it's just speed of impact. Number just dictates Wattage of heat flow. The more dense, the faster the thermometer will heat up. The faster the molecules, the higher the temperature reading will eventually be.

That is one of the reasons highly pressurized engines are more powerful, better conduction of heat into the gas. It's not because the compressed gas appears hotter.

The problem I see with the thoughts of this thread is, are we describing heat or internal energy being converted?

Internal energy is converted to work in an adiabatic with work process. Many tests have shown this. The diesel engine, or fire Piston, come to mind. Work of compression makes the internal gas hotter, for a higher temperature and higher internal energy. Single stroke. Compressing it slowly, so energy can leave, keeps the temperature rise lower.

Heat going into an engine does one of to things, it either raises the temperature of the working gas, or keeps it from going down or down as fast. It is, IMHO, misleading ones self, to describe heat being converted to work, as it really isn't something that exists anyway. For that mater neither does work. Internal energy gets converted to potential or kinetic energy.

Those links provided, and others, take some serious studying time to understand. That is why I try to avoid the confusion between, heat, work, internal energy, enthalpy, entropy, kinetic, potential, electrical, chemical, etc..., and all the measurable energy effects.

One more confusing point, heat entering, or exiting, an isothermal process, stroke, equals the work coming out, or in, during that process. The heat and work are still mathematical concepts, so the real conversion is between the internal energy's of the hot, cold, and height masses. If you want to avoid the confusion, think of those values, rather than heat and work.

Tom and my disagreement appears to be how much energy possibly gets converted to work verses how much gets cooled down to Tc and rejected as heat. No arguments about whether any come out as work, therefore less as heat. The reason for the disagreement is washed out buy eliminating the confusing terms. He is beginning to see the difference a little at a time, as he's using the terms more and more and in more correct ways. He's learning this by studying links like the ones I post. Doesn't take my word for it, as it should be.

My beef now is that when I think I've put out an obvious point, he slips back into single stroke process and ignores the completion of the cycle.

If a compressed tank of gas at room temperature is released in an isolated room, the room will become hotter. PV=MRT. The pressure of the room will be higher. The tank will cool. Eventually the two temperatures will equalize as slightly higher. Energy has been released into the room. The room pressure will be higher. Overall entropy will be higher. Any energy saved by lifting a weight will leave the room cooler by the same amount of potential energy saved. T=Q/CvM. Density unimportant, only the total mass isolated.

If the tank is compressed in the room temperature will be higher, by the amount of electrical energy put into the room minus the energy stored in the tank.

Posted: **Tue Jun 18, 2024 8:41 am**

Fool wrote: ↑Tue Jun 18, 2024 8:22 am
... Any energy saved by lifting a weight will leave the room cooler ...

Fool and I seem to agree on this point at least. Theoretically anyway.

As I said before though, agreeing with "fool" doesn't necessarily make it true.

I'd still reserve judgement until someone does the actual experiment.

It seems pretty extraordinary if actual heat can be "disappeared" by lifting a weight.

Posted: **Tue Jun 18, 2024 9:43 am**

I was a little confused on this years ago, as I thought number of impacts dictated temperature too. I now think, it's just speed of impact. Number just dictates Wattage of heat flow. The more dense, the faster the thermometer will heat up. The faster the molecules, the higher the temperature reading will eventually be.

Perfect description. My contention would be that with less impacts, the effective temperature is essentially lower.

That is one of the reasons highly pressurized engines are more powerful, better conduction of heat into the gas. It's not because the compressed gas appears hotter.

Agreed.

The problem I see with the thoughts of this thread is, are we describing heat or internal energy being converted?

Still not sure. I think it's whatever would raise the temperature of the room.

Internal energy is converted to work in an adiabatic with work process. Many tests have shown this. The diesel engine, or fire Piston, come to mind. Work of compression makes the internal gas hotter, for a higher temperature and higher internal energy. Single stroke. Compressing it slowly, so energy can leave, keeps the temperature rise lower.

This is in contrast to another description I have read, that the fire piston has the same internal energy at "TDC", just bunched up in a smaller space, manifested as higher temperature.

Posted: **Tue Jun 18, 2024 9:48 am**

Tom, like Fool said the compressed air expansion is leaving out part of the cycle. If the air compressor was in the same room, temperature would be greatly affected.

I'd still reserve judgement until someone does the actual experiment.

Me too.

It seems pretty extraordinary if actual heat can be "disappeared" by lifting a weight.

My thoughts exactly.

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Experimentally confirming the conversion of heat energy to work

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Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work

Re: Experimentally confirming the conversion of heat energy to work