Experimentally confirming the conversion of heat energy to work

[Tom Booth]

The first paragraph above could be rewritten:
Try to visualize a double ended piston with a chamber on each end. Piston dead centered, equal pressure, temperature, and volume both sides equal. Disturb the system by putting in HEAT moving the piston towards one side. One side increases in pressure, second/two side decreases. Let go piston returns to the center, it may oscillate some before stopping at dead center. If frictionless, and adiabatic, it will oscillate forever, unless the initial HEAT is taken back out. The HEAT out will equal the HEAT put in, or less. First law of thermodynamics.
Substitute heat for work and the resulting effect would be exactly the same. Your second paragraph, implying that the response would be different for heat is absolutely wrong.

The piston will be offset from center towards the cooler section, unless pv=nRT, and Q=MCvT are wrong.

VincentG has been demonstrating this by his manual displacer operations.

Adding heat to one side displaces the piston towards the cooler side. It will return only after the heat is removed.

He hasn't demonstrated anything regarding a running engine. No offense to VincentG, he put a lot of hard work and effort into that but spinning up a non-functional engine with a Dremel tool demonstrates exactly nothing.

The piston will behave as you describe, only if the heat addition is relatively slow (isothermal) with no adiabatic expansion from the piston momentum.

That is what happens while a Stirling engine is initially being heated up. The piston SLOWLY moves out to BDC and stays there.

But that is not a running engine, or oscillating system.

To actually start the engine you need to give it a nudge to get the oscillation started by intermittent bursts of heat input at just the right time as controlled by the engines gearing or other heat input timing agency.

You could give it a quick spin, but just turning it over very slowly until the displacer lifts at just the right time will also get the engine started.

Heating the engine up to operating temperature does not get the engine started. Intermittent or a rapid burst of heat input to get an oscillation going will.

[Fool]

The piston will behave as you describe, only if the heat addition is relatively slow (isothermal) with no adiabatic expansion from the piston momentum.

It doesn't have to be isothermal. Any heat getting in is sufficient to make it not adiabatic. The first scenario, where the piston recenters after work input, must be adiabatic, or it won't perfectly recenter. The work input must decay or be removed by extracting work.

Heat input, converted to work will have the same oscillation potential, until work is extracted or dissipates. The work will be less than the direct work input, it will oscillate around a point closer to the cold end, and it will stop, offset towards the cold end, until the heat is removed restoring it to the cycle's beginning state/position/volumes.

But that is not a running engine, or oscillating system.

Form VincentG's description, he ran it with a Dremel. That sounds like driven oscillation to me. Sorry, same dynamics, but zero power out, zero electrical energy generated. All work coming out of the gas went into the pistons momentum and oscillations, just as if "running" as any other demonstration here is. It just wasn't self driven. Maybe that will be next on his list of experiments. I'm looking forward to them. Thanks VincentG.

[Fool]

You could give it a quick spin, but just turning it over very slowly until the displacer lifts at just the right time will also get the engine started.

When cold, there are varying torques needed to turn one of these little engines over by hand. Those torques could be measured relative to position. That could then be compared to the torques in those same positions as the engine warms up and reaches operating temperature. My guess is they will all increase, but the forward stroke will increase significantly more than the rest. This is measured while moving it slowly. It may even be noticeable by 'hand feel'.

My guess is that if all the torques are added up, some positive, some negative, the resultant will be the maximum running torque. It will probably be at a slower running speed than full speed, but not at stall speed either, maybe close to stall speed.

[VincentG]

He hasn't demonstrated anything regarding a running engine. No offense to VincentG, he put a lot of hard work and effort into that but spinning up a non-functional engine with a Dremel tool demonstrates exactly nothing.

I have realized that to build a complete Stirling engine and hope for the best is a waste of my time.

The displacer chamber is the heart of these engines, so testing chamber performance is all I am interested in at the moment.

Pistons will do what they always do, make power when pressure is added at the right time.


And if you think I have demonstrated nothing, I encourage you to spin your LTD displacer to 1500rpm with the same temperature conditions and observe piston movement with high speed film.

If the motion of the power piston is discontinuous(dwell at tdc/bdc) like mine, than yes perhaps I have demonstrated nothing.

[VincentG]

Tom, I hope this didn't go unnoticed.

The following is from this paper on entropy.
https://www.sfu.ca/~mbahrami/ENSC%20388 ... ntropy.pdf

Entropy Change 
The entropy balance is easier to apply that energy balance, since unlike energy (which has  many forms such as heat and work) entropy has only one form. The entropy change for a  system during a process is: 
 Entropy change = Entropy at final state ‐ Entropy at initial state  system  S final
S  S initial
  
Therefore, the entropy change of a system is zero if the state of the system does not  change during the process. For example entropy change of steady flow devices such as  nozzles,  compressors,  turbines,  pumps,  and  heat  exchangers  is  zero  during  steady  operation. 
Mechanisms of Entropy Transfer 
Entropy can be transferred to or from a system in two forms: heat transfer and mass flow.  Thus, the entropy transfer for an adiabatic closed system is zero. 
Heat Transfer: heat is a form of disorganized energy and some disorganization (entropy)  will flow with heat. Heat rejection is the only way that the entropy of a fixed mass can be  decreased. The ratio of the heat transfer Q/ T (absolute temperature) at a location is  called entropy flow or entropy transfer 
Sheat  Q Entropy tr  
T
ansfer with heat (T  const.)
Since T (in Kelvin) is always positive, the direction of entropy transfer is the same of the  direction of heat transfer. 
When two systems are in contact, the entropy transfer from warmer system is equal to  the  entropy  transfer to the colder system  since the  boundary has no  thickness  and  occupies no volume. 
Note that work is entropy‐free, and no entropy is transferred with work.  
Mass Flow: mass contains entropy as well as energy, both entropy and energy contents of  a system are proportional to the mass. When a mass in the amount of m enters or leaves  a system, entropy in the amount of ms (s is the specific entropy) accompanies it. 
Entropy Balance for a Closed System 
A closed system includes no mass flow across its boundaries, and the entropy change is  simply the difference between the initial and final entropies of the system.  
The entropy change of a closed system is due to the entropy transfer accompanying heat  transfer and the entropy generation within the system boundaries: 

[Fool]

Unless you can show us your magic path hypothesizing how it's done, your opinion is just blowing in the wind. To deny any PV diagram is to deny science.

If this is for me, I haven't got to that point, but I don't deny PV diagrams.

No, not for you. You are proceeding very methodically. It's Tom I have reservations. He seems to be challenging 200 years of thermodynamics with very shaky data. It was a challenge to him to show how his theory works with mathematical precision. He won't.

[Tom Booth]

Unless you can show us your magic path hypothesizing how it's done, your opinion is just blowing in the wind. To deny any PV diagram is to deny science.

If this is for me, I haven't got to that point, but I don't deny PV diagrams.

No, not for you. You are proceeding very methodically. It's Tom I have reservations. He seems to be challenging 200 years of thermodynamics with very shaky data. It was a challenge to him to show how his theory works with mathematical precision. He won't.

Take it up with the two professional turbo-expander engineers who wrote the article, with sources. They are professionals in the field who obviously know 1000X more than our resident blowhard "fool" who can't seem to write a coherent sentence.

[VincentG]

Tom, that article is equivalent to the following...

Why is the sky blue?

The sky is blue, because when you look at the sky, it's blue. Case closed.

Fool had taken the time to provide pages of formula, which even if disagreed with, represents quite alot of effort.

I have simply asked for experimental evidence that a piston engine directly converts heat energy to work.

[Tom Booth]

Tom, that article is equivalent to the following...

Why is the sky blue?

The sky is blue, because when you look at the sky, it's blue. Case closed.

Fool had taken the time to provide pages of formula, which even if disagreed with, represents quite alot of effort.

I have simply asked for experimental evidence that a piston engine directly converts heat energy to work.

Actually your thread title says nothing whatsoever about "piston engine" being the exclusive domain you were interested in just "Experimentally confirming the conversion of heat energy to work" period.

The article is about expansion turbines converting heat into work. Same principle as it's predecessor: an expansion PISTON engine. Same principle as an air-cycle machine, same principle as any Stirling or other heat engine. You have at least a century of experimental evidence and nearly as much practical application on an industrial scale. You choose to ignore it all and make lame excuses for not doing simple experiments.

Factually though, I seriously doubt anyone fully understands exactly how or why in full detail. Science still can't agree fully on the nature of existence itself. Is matter particles, waves, quanta, strings, pure mathematical probability?

Engineers aren't much concerned. They just use what works. Experiments don't always explain the why. Sometimes the results are counterintuitive. Sometimes completely incomprehensible. But you asked for experimental evidence not an intuitive understanding. Hell, I said from the begining of the thermodynamics thread I had a hard time wrapping my head around the idea of heat being converted into work, and probably spent months or years just trying to figure out if that meant what it sounded like, heat literally transforming or changing or disappearing leaving COLD behind as WORK appears.

The wording may not be an accurate description of what's actually going on at an atomic level, but I don't think anybody really knows that for sure.

Even "atomic" is an obsolete model these days, I think.

[VincentG]

From the opening post...

So I would like this discussion to stay focused on proving that heat energy is directly converted to gravitational potential energy as the gas expands against the piston and lifts a weight. A crankshaft need not be considered for this example, just a piston lifting a weight vertically.

Factually though, I seriously doubt anyone fully understands exactly how or why in full detail. Science still can't agree fully on the nature of existence itself. Is matter particles, waves, quanta, strings, pure mathematical probability?

Engineers aren't much concerned. They just use what works. Experiments don't always explain the why. 

This is precisely what is motivating my efforts.

You choose to ignore it all and make lame excuses for not doing simple experiments.

Maybe I'm lazy and should invest more time in this.

[Tom Booth]

From the opening post...

So I would like this discussion to stay focused on proving that heat energy is directly converted to gravitational potential energy as the gas expands against the piston and lifts a weight.

Well, if you want to get technical about it, your asking for the impossible.

Whoever said "directly"?

Heat is not "directly" converted into gravitational potential energy.

Heat is generated by a flame perhaps, transfered to the engine hot plate whose molecules get vibrating faster. Those molecules transfer energy to the gas inside the engine.. the gas molecules "expand", maybe by moving further and faster, maybe by increasing "repulsive force", apparently not actually touching or colliding. The gas "Pressure" increases. Things get a bit vague as far as pressure, kinetic energy, molecular forces. Why do gases "expand"?

Whatever the reason, it took "energy" to expand. What's energy? What's "potential energy"?

You're demanding answers to existential questions nobody has any answers for.

Regardless, nothing "directly" about it. Multiple energy transformations going on even in something as simple as the power stroke of the engine. Gas expansion, piston inertia, velocity, momentum, displacement, thermal energy to "internal energy" to kinetic energy etc. etc.

A crankshaft need not be considered for this example, just a piston lifting a weight vertically.

Factually though, I seriously doubt anyone fully understands exactly how or why in full detail. Science still can't agree fully on the nature of existence itself. Is matter particles, waves, quanta, strings, pure mathematical probability?

Engineers aren't much concerned. They just use what works. Experiments don't always explain the why. 

This is precisely what is motivating my efforts.

You choose to ignore it all and make lame excuses for not doing simple experiments.

Maybe I'm lazy and should invest more time in this.

I don't think your lazy. Not at all. Maybe too driven or too ambitious.

The quote from Arthur C. Clarke comes to mind for some reason:

“Any sufficiently advanced technology is indistinguishable from magic”

Heat "disappears" and "work" appears. The weights are lifted. Seems like magic to me.

We can do an experiment to demonstrate what happens. "Heat" goes in and "work" comes out.

If you want to know WHY.

Don't ask me, to me the whole world is a beautiful mystery.

Maybe "fool" can tell you. He seems to think he has the answers to just about anything and everything

[Fool]

Thermal energy is quite interesting. Vibration of molecules in solid, liquid, gas, and plasma. Moves out into the universe by touch, dispersion of mass, and infrared radiation. The movement/transfer of that energy is called heat. Heat is not something that exists other than in mathematics. It is a transfer of a masses vibration. When vibration transfers, something vibrates more, leaving something vibrating less. It may be both speed/velocity and vibration. Even a photon has vibration and speed.

Maybe "fool" can tell you. He seems to think he has the answers to just about anything and everything

No. I do not know everything. Knowing things that others don't know is called trivia. Some trivia is very useful, science, some is not, such as errors. I try to only give useful information or entertaining stories. I strive very hard to not, make errors, nor vituperation.

I have a lot of interests and like to comment. I have an Engineering degree and am educated to know engineering principals. Perfect no. All the answers, no. Human, yes. Humble, try to be. Patient, try to be. Polite, maybe not so much. A fool, aren't we all?

[Fool]

I find it interesting that vibrations transferring into a gas makes the gas vibrate more manifesting into the macro world as higher, temperature and pressure. That pressure can push on a piston making it move and the gas vibration reduces without making the piston hotter. Thermal to kinetic energy conversion.

I find it also interesting that not all the added vibrations goes into the motion of the piston. Some must stay in the gas to maintain that larger volume. The only way to reduce that volume is to reduce the internal temperature by cooling and or compression and cooling.

[Fool]

We can do an experiment to demonstrate what happens. "Heat" goes in and "work" comes out.

We can do an experiment to demonstrate what happens. "Heat" goes in and "work" and less heat comes out.

Or

We can do an experiment to demonstrate what happens. "Heat" goes in and "less work than heat in" comes out.

[VincentG]

I find it interesting that vibrations transferring into a gas makes the gas vibrate more manifesting into the macro world as higher, temperature and pressure. That pressure can push on a piston making it move and the gas vibration reduces without making the piston hotter. Thermal to kinetic energy conversion.

Thats the interesting part to me. In a closed system with no mass flow, the gas is equally pushing the cylinder head and cylinder walls. If the piston is fixed, it's a Cv/zero work condition, and "possibly" the gas temperature can rise above Tmax.

But let the piston move, and the gas "knows", and loses temperature?