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Tom keep in mind that Matt is suggesting the use of valves, so we can effectively focus on distinct events like any good cycle should have.

VincentG wrote: ↑Thu Jun 29, 2023 11:13 am Tom keep in mind that Matt is suggesting the use of valves, so we can effectively focus on distinct events like any good cycle should have.

I don't see any previous mention of valves on this thread, just Stirling cycle, alpha, gamma and "voodoo", and the illustrations presented do not show valves, just a "Regen". Presumably indicating a regenerator.

Also if he is asserting that "Tom is right" about a cold side not being required, I've.not made any such statement regarding anything other than in regard to my observation of Stirling engines, which do not have valves.

Anyway, perhaps Matt would like to clarify that here, I haven't really been following the other threads.

The main point I was bringing up with this, or trying to, is not that Matt is "wrong" but that I think maybe he's not going far enough, as not only is external cooling not necessary as presented by his idealized calculations, but if he were to also factor in the expansion work, he may find mathematical evidence for my observed refrigeration effect.

At any rate, I don't see how any air could be drawn into the upper cylinder from 2 to 3 through a closed valve, so if valves were involved, the valve must be open or where do the moles of gas come from to fill the cylinder? You can't draw gas into a cylinder at 3 Bar through a closed valve. Also the hot cylinder pressure drops from 6 to 3 Bar, which indicates where the gas came from.

I still would say you cannot get an expansion (with pressure drop from 6 down to 3 Bar) without a corresponding drop in temperature, except in an idealized "isothermal" process, In reality there would be an additional drop in temperature.

Yes I was referring to his thread on VooDoo cycle where he mentioned valves.

What Matt has shown us is that a cycle can self cool, but at the expense of available power output. Anything else would be creating energy from nothing. The refrigeration effect is real but at the expense of shaft power.

VincentG wrote: ↑Fri Jun 30, 2023 8:31 am Yes I was referring to his thread on VooDoo cycle where he mentioned valves.

What Matt has shown us is that a cycle can self cool, but at the expense of available power output. Anything else would be creating energy from nothing. The refrigeration effect is real but at the expense of shaft power.

Mostly true, refrigeration is at the expense of shaft power, nevertheless, the implication is; a "self cooling" hot air engine could, over time, incrementally increase its own ∆T, eventually cooling itself down to the point where ambient heat itself could serve as a significant power source. It raises the question; could a pre-cooled heat engine operate on the surrounding ambient heat while maintaining its own "cold hole"? keeping itself refrigerated.

If the heat does not actually need to pass through to the cold side, then a well insulated cold hole should be relatively easy to maintain as the ambient heat would not actually be flowing to the cold side to warm it up. If heat does not need to be removed then the refrigeration required can be intermittent, while power output is continuous.

I've found in experimenting with this idea that there are a number of practical difficulties, like the piston freezing up and seizing, but if this and other problems could be overcome, I would not consider this "creating energy from nothing", necessarily.

We have ambient heat from the Sun. It would be, in principle, no more "free energy from nothing" to convert solar energy or heat, directly to mechanical output, than to convert it from Sunlight to electricity by a photovoltaic panel.

This is an interesting piston arrangement which should help avoid the problem of the power cylinder freezing as it is surrounded by ambient heat and well up and away from the cold ice:

https://youtu.be/ZP2Rxvm5bxc

Also sources of heat from friction are kept a distance away from the ice.

Well, thinking about it a bit more, the statement "refrigeration is at the expense of shaft power" is not entirely true either.

If the gas is heated and expands and work goes out as shaft power, resulting in a refrigerating effect (conversion of heat into work) the "refrigerating" effect is at least in part, the result of, or assisted by such conversion.

In other words the work out (shaft power) uses up the heat/energy as a form of "fuel" which when spent leaves "cold".

Some expansion/cooling results from work against atmospheric or buffer pressure which acts as an air spring, returning at least some of that heat/energy in the next compression phase of the cycle.

VincentG wrote: ↑Wed Jun 28, 2023 10:04 am

 I don't have any problem buying into the idea that heat applied to gas increases molecular speed linear absolute temperature. 

Interesting that molecule speed and pressure increases linearly with temperature, while kinetic energy goes up exponentially with the velocity of a mass.

Perhaps basic thermo does not explain the difference in available energy of a hot and cold gas at the same pressure.

Good catch, Vincent !!! I screwed up here due to hasty editing (timeout here and edit potential is so limited). The correct spiel is (1) pressure is linear absolute temperature, but (2) the molecule speed varies by RMS function and if you sketch this out on paper you'll be left pondering how does the pressure vary linear temperature when the gas speed does not. This apparent dichotomy is what Boltzmann tackled and contributed to his suicide. So, I have no problem buying into pressure linear temperature (aka gas 'force' is linear temperature) and I'll ignore the statistical mechanics that rationalizes this apparent impossibility.

Tom Booth wrote: ↑Thu Jun 29, 2023 10:37 pm
Anyway, perhaps Matt would like to clarify that here, I haven't really been following the other threads.

The main point I was bringing up with this, or trying to, is not that Matt is "wrong" but that I think maybe he's not going far enough, as not only is external cooling not necessary as presented by his idealized calculations, but if he were to also factor in the expansion work, he may find mathematical evidence for my observed refrigeration effect.

At any rate, I don't see how any air could be drawn into the upper cylinder from 2 to 3 through a closed valve, so if valves were involved, the valve must be open or where do the moles of gas come from to fill the cylinder? You can't draw gas into a cylinder at 3 Bar through a closed valve. Also the hot cylinder pressure drops from 6 to 3 Bar, which indicates where the gas came from.

I still would say you cannot get an expansion (with pressure drop from 6 down to 3 Bar) without a corresponding drop in temperature, except in an idealized "isothermal" process, In reality there would be an additional drop in temperature.

It's a work in progress. I'm new to betas & gammas at this level, but think that expansion from the 'cold side' of the cycle changes a lot of stuff.

The graphic is meant to show that a cycle is possible without isothermal cooling/compression and depicted via distinct events. Whatever engine could achieve such a cycle is another matter. Valves would be required, but when these 3 events are grouped in pairs, no valves are required, since the gas is self regulating due to piston action.

Tom Booth wrote: ↑Fri Jun 30, 2023 11:37 am

VincentG wrote: ↑Fri Jun 30, 2023 8:31 am Yes I was referring to his thread on VooDoo cycle where he mentioned valves.

What Matt has shown us is that a cycle can self cool, but at the expense of available power output. Anything else would be creating energy from nothing. The refrigeration effect is real but at the expense of shaft power.

Mostly true, refrigeration is at the expense of shaft power, nevertheless, the implication is; a "self cooling" hot air engine could, over time, incrementally increase its own ∆T, eventually cooling itself down to the point where ambient heat itself could serve as a significant power source. It raises the question; could a pre-cooled heat engine operate on the surrounding ambient heat while maintaining its own "cold hole"? keeping itself refrigerated.

If the heat does not actually need to pass through to the cold side, then a well insulated cold hole should be relatively easy to maintain as the ambient heat would not actually be flowing to the cold side to warm it up. If heat does not need to be removed then the refrigeration required can be intermittent, while power output is continuous.

I like Vincent's wording, since it offers a simple explanation that heat and work cross cancel during some part of voodoo cycle. I sent this graphic to Urieli and Herzog for review, but haven't heard anything (both long retired). I'll try another guy this weekend (a physicist) but he's also getting along in years.

Yep, Tom, I had the same cold hole thought and wondering about Tesla's ambient engine.

Tom Booth wrote: ↑Fri Jun 30, 2023 1:13 pm Well, thinking about it a bit more, the statement "refrigeration is at the expense of shaft power" is not entirely true either.

If the gas is heated and expands and work goes out as shaft power, resulting in a refrigerating effect (conversion of heat into work) the "refrigerating" effect is at least in part, the result of, or assisted by such conversion.

In other words the work out (shaft power) uses up the heat/energy as a form of "fuel" which when spent leaves "cold".

Some expansion/cooling results from work against atmospheric or buffer pressure which acts as an air spring, returning at least some of that heat/energy in the next compression phase of the cycle.

Xlnt wording, Tom, and exactly the type of stuff I was pondering for a few hours a night. Your last line is the most interesting, since it begs the question whether the atmospheric or buffer pressure (when equal internal pressure) supplies heat from work during isobaric regen, whereby the cold space would need to dissipate this 'extra' heat. If so, then voodoo cycle also requires 'isothermal' cooling, just different from similar gamma.

matt brown wrote: ↑Fri Jun 30, 2023 7:23 pm

Tom Booth wrote: ↑Fri Jun 30, 2023 1:13 pm Well, thinking about it a bit more, the statement "refrigeration is at the expense of shaft power" is not entirely true either.

If the gas is heated and expands and work goes out as shaft power, resulting in a refrigerating effect (conversion of heat into work) the "refrigerating" effect is at least in part, the result of, or assisted by such conversion.

In other words the work out (shaft power) uses up the heat/energy as a form of "fuel" which when spent leaves "cold".

Some expansion/cooling results from work against atmospheric or buffer pressure which acts as an air spring, returning at least some of that heat/energy in the next compression phase of the cycle.

Xlnt wording, Tom, and exactly the type of stuff I was pondering for a few hours a night. Your last line is the most interesting, since it begs the question whether the atmospheric or buffer pressure (when equal internal pressure) supplies heat from work during isobaric regen, whereby the cold space would need to dissipate this 'extra' heat. If so, then voodoo cycle also requires 'isothermal' cooling, just different from similar gamma.

If I understand what you mean about "atmospheric or buffer pressure supplies heat...the cold space would need to dissipate..."

I don't believe so.

Using an illustration; a child bouncing on a pogo stick. The child puts energy into the bounce that lifts the child and the contraption into the air against gravity, akin to the piston working against atmospheric pressure on expansion of the working fluid.

Gravity returns the pogo stick and child so that they accelerate towards the ground akin to the compression phase of the Stirling cycle - the piston accelerating inward. The energy contributed by gravity goes into the next bounce on the pogo stick. Likewise the "heat" contributed by atmospheric pressure goes into the next "bounce" of the piston as it runs into the air spring of compressed hot gas.

Put another way, a Stirling engine (of the thermal lag type for instance) is really just a kind of Rüchardt bottle.

From Wikipedia"

A typical experiment,[4] consists of a glass tube of volume V, and of cross-section A, which is open on one of its end. A ball (or sometimes a piston) of mass m with the same cross-section, creating an air-tight seal, is allowed to fall under gravity g. The entrapped gas is first compressed by the weight of the piston, which leads to an increase in temperature. In the course of the piston falling, a gas cushion is created, and the piston bounces. Harmonic oscillation occurs, which slowly damps. The result is a rapid sequence of expansion and compression of the gas.

https://en.m.wikipedia.org/wiki/R%C3%BC ... experiment

This Rüchardt ENGINE in theory, discounting friction, could continue its oscillations indefinitely, only requiring a bit of makeup gas to compensate for air leakage.

What is the ∆T for a Rüchardt ENGINE ?

Suppose we plug that into the Carnot efficiency formula, and why not? Why should a Rüchardt ENGINE not be subject to the same rule as any other hot air or Stirling engine?

Do we need to remove the heat of compression each cycle on the pistons downward fall for the Rüchardt ENGINE to continue running? Does it complete a full compression/expansion cycle of oscillation without heat removal to a "sink"?

Tom Booth wrote: ↑Fri Jun 30, 2023 8:14 pm
If I understand what you mean about "atmospheric or buffer pressure supplies heat...the cold space would need to dissipate..."

I don't believe so.

Using an illustration; a child bouncing on a pogo stick. The child puts energy into the bounce that lifts the child and the contraption into the air against gravity, akin to the piston working against atmospheric pressure on expansion of the working fluid.

Gravity returns the pogo stick and child so that they accelerate towards the ground akin to the compression phase of the Stirling cycle - the piston accelerating inward. The energy contributed by gravity goes into the next bounce on the pogo stick. Likewise the "heat" contributed by atmospheric pressure goes into the next "bounce" of the piston as it runs into the air spring of compressed hot gas.

Your pogo stick example is typical bounce gas effect where work=heat and heat=work. I revised the 2nd half of voodoo graphic with a 3.5 'tween' between stg 3 and initial stage 1.


In this graphic, when ambient/buffer pressure equals the internal pressure, during stg 3 to 1, all internal and external pressures are equal. I now suspect that external work during isobaric regen is obscured by these equal pressures, but still being supplied. Note that graphic shows working gas relative spaces A, B, and C. If working gas flows from B to C via isochoric regen then the working gas after regen is 300k. But if working gas flows from B to C via isobaric regen AND this requires work, then heat of compression will occur (1) in B prior regen, or (2) in C post regen. If (2) then cycle has isothermal cooling, just different from typical gamma. But since an Ericsson cycle has isobaric regen similar (1), I think we can safely conclude that voodoo scheme adds heat of work during isobaric regen to regen matrix, and reduces source input required vs similar gamma. Of course, all in theory, but it least this explains where the heat went.

The original Vuilleumier patent US1275507 from 1918 starts off with a simple read regarding various pressures. I was reviewing it last night for clarity and highly recommend this popular patent.

Tom Booth wrote: ↑Fri Jun 30, 2023 8:14 pm
Likewise the "heat" contributed by atmospheric pressure goes into the next "bounce" of the piston...

I think this sums up voodoo cycle perfectly where isobaric regen during 'cooling' exceeds isochoric regen during heating, so this difference reduces source input.

However, since voodoo has less work per cycle than similar gamma, the question is which has better efficiency, and that may require actual calcs...

the lower 2 pistons represent a displacer

Is that correct?

I've been looking at this as some unusual engine having two displacers,, like a Vuilleumier heat pump or some such thing and wondering about the linkage. Attached to a crank or using a cam or cams, but the quote from earlier (opening post) says a (one) displacer?

Could that be (the two "pistons" representing one displacer) like a regenerative displacer? Or a single displacer with the regenerator on the side? Such as:
Why illustrate or represent one displacer as two pistons? Or was that a typo, or maybe you meant the lower two pistons each represent a displacer?