The Reversible engine

[Tom Booth]

Really, if you were to say that, adding 10 joules of heat energy causes the gas to expand and do ten joules of work moving the piston and increasing the volume, then

To get the piston to return you now have to remove ten joules of heat, that would be a clear violation of conservation of energy.

10 joules in as heat -> [gas] -> 10 joules out as work

Then

10 joules back out as heat <- [gas]

When the ten joules go out as work, this causes the temperature and pressure to drop and that SHOULD cause the piston to immediately return to restore the original volume.

Tom, why do keep trying to cheat the system when this is all VERY simple...

(...)

(4) if you add a flywheel (by option or necessity with whatever back pressure you favor) this taxes the available shaft output during each isothermal expansion process, and is returned during similar iosthermal compression process

(5) any momentum, angular velocity, or whatever other mumbo-jumbo you care to add is bogus, since ALL these 'downstream' effects originate from input, and at best, can only be returned later in cycle

(...)

Let's say the first (...) I don't think I have a problem with.

The last (...) is your assertion, not worth arguing about.

What's left, theoretically SOME momentum/energy COULD be returned, if needed, but for the most part once set in motion the flywheel stays in motion eventually dissipating energy to air resistance, bearing friction etc.

Other shaft work you call "mumbo jumbo" is not returned.

This other positive work output is the whole point of having an engine,; to do external shaft work, turning a saw blade to cut logs or driving a generator to light lights, operate machinery etc.

Real work output, not "mumbo Jumbo".

If I'm running a generator from a Stirling engine to power my house; lights, refrigerator, air conditioner, cook stove, toaster, water hester, TV, computer, shop tools power washer, sand blaster, table saw, drill press, washer and dryer, dish washer, angle grinder, welder, battery charger, radio, vacuum cleaner, microwave, toaster, etc. ... All the things running an engine is used for

How is all this work output "returned later in the cycle"?

I'm not trying to "chest the system". You are, if you think you can get all this work output "mumbo jumbo" back into the engine, somehow "returned later in the cycle".

[matt brown]

In ICE terms, if all expansion work went to the flywheel then there would be no shaft output, but some of the expansion work can go to the flywheel and return later in the cycle. Just what do you think is going on when a big block ICE is running ~3000rpm and that mega load on EACH piston takes a reversal each rpm??? One of the main reasons we still have pistons and slider-cranks is due to exactly this 'flywheel effect' where a constantly rotating flywheel can remove and add work from a variable speed piston.

[Tom Booth]

In ICE terms, if all expansion work went to the flywheel then there would be no shaft output, but some of the expansion work can go to the flywheel and return later in the cycle. Just what do you think is going on when a big block ICE is running ~3000rpm and that mega load on EACH piston takes a reversal each rpm??? One of the main reasons we still have pistons and slider-cranks is due to exactly this 'flywheel effect' where a constantly rotating flywheel can remove and add work from a variable speed piston.

I acknowledge a flywheel could, theoretically return some work, but in reality, Stirling engines don't require flywheels.

Regardless, the flywheel is not work output to an external load; lights, electrical generator or whatever.

The flywheel, if there is one in a Stirling engine, would be only a small fraction of the work output. You are still ignoring the bulk of the real "work" output from the engine used to power my house or workshop. You know, all that "other mumbo jumbo".

If I have a Stirling engine driving a 3000 watt generator and that work output is running 3000 watts worth of lights and other electrical equipment, how is that 3000 watts of work output insignificant, or how is all that energy (3000 watts) "returned" "later in the cycle"?

[Fool]

Heat is converted to work at the instant a gas particle impacts the piston and transfers energy to the piston.

Internal energy is like a bank account. Pay-Joules/money coming in is like heat. Your balance-Jouels/money saved is like internal energy, in that they are not the same.

Internal energy is converted to piston speed, no heat involved. If heat is involved, it just adds to, or subtracts from, the internal energy/bank ballance.

The speed of the molecules are just internal kinetic energy/measured by temperature and pressure.

work output decreases internal energy, and lower internal energy is reflected by a decrease of pressure and or volume.

Work output, from the gas, never is associated with decreased volume. Decreased volume is associated with work input to the gas. Work and heat do different things to a contained gas. Those different things show up differently on a PV diagram.

The gas is only affected by: volume, temperature and amount/total mass and to a lesser degree piston speed.

Speed is ignored if it is significantly lower than the speed of sound. In our case, 2000 rpm or less, is way acceptable.

Total mass is ignored because it doesn't change in our system.

Gravity and atmospheric pressure can be ignored if the system is completing a full cycle.

The working gas doesn't care what is manipulating the piston, just the direction of the inside piston wall, volume. It can be a crank, atmospheric pressure, or gravity.

Whatever volume increase took place or should have taken place due to heat addition is canceled or reversed due to the equivalent work output.

You got to stop this. Heat addition and then adiabatic work will end up with a larger volume than you started even if the temperature becomes the same as before the heat was added. Or, it will have a larger volume at a higher temperature if pressure returns to the initial. They are two different points on the new adiabatic line. It won't return to the original line or point unless heat is rejected. If at a lower temperature, it will be less rejected heat than what was added, thus giving the possibility of some net work output for the cycle.

Matt and Tom,

A flywheels main purpose is to smooth out torque ripple. Sure, an ICE can spin up, storing energy, for the lung effect off the line acceleration. A flywheel reduces the speed increase during a power stroke, and caries that energy through the non power strokes at a smaller drop in speed. It reduces shock to the drivetrain.

It can also be used in reverse to reduce shock to a motor in the case of a trip hammer where output torque changes abruptly. It also allows for a smaller motor to compensate for the uneven load.

Slider cranks are there own flywheel because they mimic harmonic motion. Slowing a piston down speeds up the crank. The crank then speeds up the piston. It is more difficult to do this with one piston. The slowing down and speeding up are balanced.

Even if the crank is missing and one is dependent on atmospheric pressure or gravity (pile driver) to return the piston, the mass in motion (piston) becomes the "flywheel". It is purely an mV momentum kinetic energy process.

Even if there is no piston, laminar flow, pulse jet, etc, the mass-in-flow becomes the mV energy storage device.

In the case of the pile driver mV converts to mgh to reverse the direction. Pretty cool. I know you all know this stuff, but, it helps to hear it again.

[Tom Booth]

(...)

Whatever volume increase took place or should have taken place due to heat addition is canceled or reversed due to the equivalent work output.

You got to stop this.

LOL

Heat addition and then adiabatic work will end up with a larger volume than you started even if the temperature becomes the same as before the heat was added....

Yes, of course, but that larger volume will be a low pressure partial vacuum. Also the temperature doesn't necessarily just end up "the same" as before the heat was added, it can apparently drop lower.

We can agree to disagree, but I think some of my experiments demonstrate, unequivocally, that heat rejection to a sink is at times, completely unnecessary.

Not having done any such experiments, not having made these observations, it's easy to dismiss, but after so many dozen experiments seeing essentially the same thing over and over I've been forced to re-evaluated the situation and reject the former hypothesis as incapable of explaining observable phenomena.

"When a hypothesis no longer suffices to explain
phenomena, it should be abandoned." -- Sadi Carnot:

https://en.m.wikisource.org/wiki/Reflec ... Appendix_A

Good advice IMO

[Fool]

I'm still waiting for your hypothesis to start explaining something. So far no hypothesis. Perhaps 200 years of predicting, building successful engines, refrigerators, heat pumps, such as the Ericsson, Malone, Stirling, Phillips, Ryder, ST-5, free position, LTDS's all by engineers using classical theory should be discarded because Tom says so. And he says his experiment can't be interpreted any other way. Of course we are trying to help look for ways to explain it using classical thermodynamics, but he seems very unwilling to consider any, choosing instead to deny factual points about the tools scientists and mathematicians use for thermodynamics and mechanics and the foundations of calculus, etc.

Do you have an alternate theory to use in calculating these engine parameters? If so please, give us some numbers, formula, charts, or graphs, so we can again be successful at designing engines as good or better than current theory. Otherwise it is your viewpoint that we should throw out as being unfitting.

[Tom Booth]

I'm still waiting for your hypothesis to start explaining something. So far no hypothesis. Perhaps 200 years of predicting, building successful engines, refrigerators, heat pumps, such as the Ericsson, Malone, Stirling, Phillips, Ryder, ST-5, free position, LTDS's all by engineers using classical theory should be discarded because Tom says so. And he says his experiment can't be interpreted any other way. Of course we are trying to help look for ways to explain it using classical thermodynamics, but he seems very unwilling to consider any, choosing instead to deny factual points about the tools scientists and mathematicians use for thermodynamics and mechanics and the foundations of calculus, etc.

Do you have an alternate theory to use in calculating these engine parameters? If so please, give us some numbers, formula, charts, or graphs, so we can again be successful at designing engines as good or better than current theory. Otherwise it is your viewpoint that we should throw out as being unfitting.

Hypothesis to explain....? Alternative theory to calculate...?

What exactly???

A "reversible engine"?

What's to explain? There's no such thing. No Carnot engines, no "reversible" engines.

Why don't you explain why anyone, in particular, any kind of engineer, should be required to waste brain cells contemplating fiction.

[Fool]

And very few engines that exceed half of the Carnot formula efficiency. Perhaps we study ideal cases to give an idea of how close to perfect effiency we are getting.

[Tom Booth]

And very few engines that exceed half of the Carnot formula efficiency. Perhaps we study ideal cases to give an idea of how close to perfect effiency we are getting.

Define 'perfect".

The Carnot engine doesn't work. That's not "perfect" in my book.

The Carnot engine is based on caloric theory.

Kelvin bet caloric theory was going to triumph and developed thermodynamics on the basis of caloric theory.

He also said that heavier-than-air flying machines were impossible, that radio would never have any practical use, that X-rays were a hoax, and that all useful discoveries in science had already been made.

Today I suppose he would be down at the airport on the runway frantically trying to convince passengers to get off the plane.

When a distinguished but elderly scientist says that something is possible, he is very likely right. When a distinguished but elderly scientist says that something is impossible, he is very likely wrong. - Arthur C. Clarke

I've been looking over this "Carnot efficiency limit" along with it's implications and ramifications and supposed basis and can find nothing whatsoever to recommend it. It is a fallacy, based on a fallacy.

If you wish to adhere to a nonsensical theory from the 1820's that's your prerogative but please try not interfere with the progress of others.

This whole "perfect Carnot engine" concept is so full of absurdities and logical contradictions I have no real idea how any rational person ever took it seriously.

https://pressbooks.bccampus.ca/collegep ... -restated/

[Fool]

Is that what our progress has boiled down to, disagreement as to the definition of "perfect"? Perfect is a mythical beast. A perfect Carnot engine model, and the mathematics describing it, allow us to progress to building similar devices and test them.

You have defined imperfect as, a Carnot engine that doesn't work. I say that is only a human claiming it is impossible. He might likely be wrong, according to a science fiction writer.

Does the perfect, 100% efficient, Tom Booth Hot Potato Engine work? How much theory behind it can we used to model and design new progressively better engines? The theory of 100% of the heat in, comes out as work, even if it is going into grinding paste, doesn't seem very helpful for sizing mechanical and electrical components. And the progress as of yet hasn't yielded any useable power. Perhaps seeking your mythical beast is impeding your progress instead of benefiting from 200 years of progress and improvement following the Carnot theories.

Carnot and classical thermodynamics, even caloric theory, gives us equations that can be useful for sizing components.

The Carnot theory has been revalidated many times using, current, kinetic, quantum, and other, theories. Revalidated theories are not invalidated by their origins. It is good to question them. It is bad to denounce them prematurely.

Side bets by notable scientists do not invalidate a theory.

I find it interesting that you believe that 200 years of the lure of the perfect Carnot engine has so baffled rational engineers and instructors that they have failed to point out the absurdities and logical contradictions. Please... I have seen instructions/warning/helpful points regarding the limits of modeling any system and why the model, even when imperfect, can be very useful, and a good learning tool and how it fits into other areas of physics. Your hot potato engine theory doesn't fit any that I know, and your insulation experiment is insufficient for any conclusion. It has been a good learning and study incentive. Thanks.

[Tom Booth]

The "hot potato" engine has no relevance to this discussion. It was an idea for an engine design I had ten years ago, not any theory of operation.

My only theory is that a Stirling engine appears to be oscillating between two forces.

1) Pressure due to expansion from applied heat.

2) atmospheric or buffer pressure.

#1 results in a power stroke
#2 results in a return stroke

In order for #2 to be realized, all the heat from #1 must be utilized.

Now the same result could be due to "heat rejection" then all the heat from #1 does not need to be utilized. I don't deny that that can happen and often does, but if you can rule that out and the engine still runs then there seems to be a problem with the old conception that the engine cannot operate without heat rejection.

[Tom Booth]

Now if you are going to include FRICTION in the equation as heat rejected, the whole thing is completely meaningless.

ALL the energy produced will end up back in the environment eventually. Run a generator to produce electricity to run a power saw that cuts wood producing "friction" while cutting the wood.

Are we supposed to include that friction? Heat from the motor driving the saw?

I draw the line at the working fluid. The working fluid does work on the piston, OR the working fluid looses waste heat to the "cold reservoir". Period.

Heat from FRICTION is, or should be irrelevant. The engine has to have already converted the heat to work to produce any friction.

The whole ""Carnot limit" is utter meaningless nonsense. Nothing more than a measure of the ∆T on the Kelvin scale.

No engine can possibly exceed the "carnot efficiency limit" because it has nothing whatsoever to do with the actual engine, or the actual quantity of heat entering or leaving the engine. Or heat utilization or efficiency. It's a thermometer reading.

[Fool]

In order for #2 to be realized, all the heat from #1 must be utilized.

Zero heat is utilized in an adiabatic expansion. Internal energy is utilized. All that energy will need to be put back into the volume of gas if the return stroke is also adiabatic.

That is why adiabatic bounce decays to a stop. It will be impossible to add more heat after the return stroke rases the temperature to the same temperature as the hot plate. Thermal equilibrium between hot plate and the volume of gas prevents it.

My only theory is that a Stirling engine appears to be oscillating between two forces.

One of the forces must increase and then decrease. Your proposal to use work will, when reversed, produce hot. The work into the gas volume will consume the work put out by the gas volume.

Can you see that a compressed adiabatic gas spring will push out with positive work, and must be pushed back in with an equivalent but opposite amount of work into the gas volume?

[Tom Booth]

In order for #2 to be realized, all the heat from #1 must be utilized.

Zero heat is utilized in an adiabatic expansion. Internal energy is utilized.

You seriously do not know what you're talking about.

For a gas, heat and "internal energy" are the same thing. When the gas loses "internal energy" for expansion work it drops in temperature.

You obviously do not understand the concept of the equivalence of work and heat, no matter how many times it is explained to you.

All that energy will need to be put back into the volume of gas if the return stroke is also adiabatic.

When heat is converted to work, yes, of course additional heat must be added so THAT additional heat can also be converted, then more heat is added so that can be converted etc. etc. That is what a heat engine does, you keep adding heat and it keeps converting the heat into work.

That is why adiabatic bounce decays to a stop. It will be impossible to add more heat after the return stroke rases the temperature to the same temperature as the hot plate. Thermal equilibrium between hot plate and the volume of gas prevents it.

When work from atmospheric pressure returns the piston and adds some heat of compression, then LESS heat needs to be added. The two sources of heat collide to produce more power and torque at TDC. That is why Stirling engines are so efficient.

My only theory is that a Stirling engine appears to be oscillating between two forces.

One of the forces must increase and then decrease. Your proposal to use work will, when reversed, produce hot. The work into the gas volume will consume the work put out by the gas volume.

No, because the heat is being continually converted to work during the expansion stroke, a fact you refuse to acknowledge. A fact you repeatedly ignore or deny the reality of with your words above: "Zero heat is utilized in an adiabatic expansion. Internal energy is utilized."

For a gas, heat and "internal energy" are the same thing. Heat IS energy. Heat IS energy. Heat = Energy. In a gas HEAT and INTERNAL ENERGY are exactly equivalent. When "internal energy" is utilized "Heat" is utilized and the temperature of the gas drops. The gas gets cold and the pressure drops.

Can you see that a compressed adiabatic gas spring will push out with positive work, and must be pushed back in with an equivalent but opposite amount of work into the gas volume?

No because on expansion the heat (internal energy) of the gas is converted to work output with the result that the gas cools and by the time the piston reaches BDC the pressure drops and a vacuum is formed, so atmospheric pressure can drive the piston back in without resistance. (Until the last moment when the new heat added and the heat of compression combine for the next power stroke at TDC).

[Fool]

Tom,

"For a gas, heat and "internal energy" are the same thing. "

Heat and internal energy are never the same thing. This is no more ture than, a paycheck and bank balance are the same.

"equivalence of work and heat,"

Work and heat share an equivalence, just as: paycheck and bank-balance: mass and energy: work and potential: do. None are the same thing. Big difference.

Heat is the energy transferred between a hot and a cold difference.

Internal energy is agitation of mass molecules. The hotter they are (temperature), the more agitated.

Work is similar in that it is energy moving between systems in the form of force times a distance. But it too, is not heat.

This discussion may help, but only if you have an open mind:

https://physics.stackexchange.com/quest ... der%20body.

From that link:
"Saying that a body possesses heat energy is as absurd as saying it possesses work! "

Learning the difference is an important first principal in the field of thermodynamics. Work is energy, but, not all energy is work. Heat and internal energy are separate. Both are energy measured in Joules. Similar to a paycheck and a bank balance. Both are money measured in dollars.

"so atmospheric pressure can drive the piston back in without resistance."

The pressure inside the cylinder never goes away during an adiabatic process cooling. Pressure is always there and both heat and pressure build, in the same amount, when being compressed, except in reverse. The pressure inside always provides an opposing force. Minimizing it's build up, heat rejection, is the only way to have a net work output from any heat engine cycle. If the heat buildup, compression, is not minimized there will be zero work output. Your experiments haven't disproven that, even tho you have falsely jumped to that viewpoint.

I don't understand why you talk of the work done by atmospheric pressure when it's beneficial, but, ignore it on the power stroke were it's detrimental. Why?

Heat one liter of gas at one bar from 300K to 600K and pressure will rise to 2 bars. Expand it to 2 liters, if it becomes 300K it will be at a pressure of 1/2 bars. If it is pushed back in again it will become a temperature of 600K and 2 bars. Cooling it, heat rejection, during compression will return to the start where it is one liter at one bar.

"Until the last moment when the new heat added"

You have made the claim that the Stirling Engines we talk about move too fast for isothermal heat to come in during an entire expansion stroke. But, you are now making the claim that, after adiabatic compression where the gas volume has returned to the hot plate temperature, that instantly (last moment) heat is added. Why do you think heat can transfer from a hot plate (temperature T-high) to a gas volume (temperature T-high), instantaneously?

Putting work back into an adiabatic gas volume will raise the temperature back to it's original temperature and cost you the work of expansion. Work of expansion equals work of compression, adiabatic bounce, for a full cycle. You need to include the entire cycle for all parameters.