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Fool, you are getting too caught up with gravity directly. The point is that if the man must climb to the top anyway, then it is a waste of energy to not raise weight on his way down. Of course there is no extra energy gained from the bricks going up, it's just energy being conserved. A separate argument can be made for further energy recovery that comes from the stopping of 390lbs in motion but that is for another day.

The important analog is human energy to heat energy. If you were tasked with bringing 190lbs of materials to the second story day in and day out, would you carry it at once, carry it in multiple trips, pull it up with block and tackle, or use the counterbalanced elevator system from above?

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I'm really not sure why you are exploring these mechanical efficiency questions. Some ways are inherently more wasteful than others. We can always dump fuel on the ground and burn it. We'd get zero caloric converted to mechanical efforts.

What if you counter weighted the man? 200# man with 200# weight? He could go up and down the ladder all day expending zero energy to lift himself. All energy would go into lifting the load each trip. Mgh 190# x g x 2nd story. 19# per trip. He might even be able to jump and let the inertia float him up without a ladder. A garden hose could be used to fill a variable counter weight for lifting a load.

I actually have brain stormed a system to do such. The problem I ran into is safety. The need for man ratings. The ingenious fool effect.

A ladder is still the cheapest, lightest, simplest, easiest, most versatile, and easy to setup way, to get materials up to the second floor. It's what I've used, and still use. Rope and pulley next, followed by block and tackle. Of course the easiest is a forklift or such, if you have the funds.

For our thermodynamics quest here. Load all the bricks onto a piston in a cylinder. Flip flop a hot-cold displacer in cylinder to change temperature. Piston elevates from pressure and volume increase.

Experiment further: Change parameters: isothermal, adiabatic, piston/cylinder size, precharge, locking piston into position until temperature fully changes, storing momentum on flywheel, or generator/motor super capacitor, counter weight, size of displacer chamber. Temperature hot or cold, single cylinder or multiples, one cycle verses many to the top, add a winch and gears, or even leverage, counter balanced teeter totter, etc.

Then add necessary processes to complete the cycle and return the piston, volume, and temperature, back to the starting point.

I recommend starting the design process using ideal gas calculators and reasonable temperatures and pressures. After that, use real gas steam tables, to see how much the numbers change. Stay far away from liquefaction temperatures and pressures.

Maybe, Matt, you, and I, can come up with some worked examples. It would be similar to the let's beat up Carnot thread.

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I'm really not sure why you are exploring these mechanical efficiency questions. Some ways are inherently more wasteful than others. We can always dump fuel on the ground and burn it. We'd get zero caloric converted to mechanical efforts.

What if you counter weighted the man? 200# man with 200# weight? He could go up and down the ladder all day expending zero energy to lift himself. All energy would go into lifting the load each trip. Mgh 190# x g x 2nd story. 19# per trip. He might even be able to jump and let the inertia float him up without a ladder. A garden hose could be used to fill a variable counter weight for lifting a load.

Because if the mechanical efficiency can't be locked down, then thermo efficiency sure can't.

If you counter weight the 200lb man with a 200lb load, you change the dynamic of the system. For a gain of only 10lbs of materials, you are now requiring the man to do more work to lower himself down against a 200lb load, and slowing down the system. You would be much better off at the end of the day with additional man power, or simply reducing the load 5%.

At the end of our day, the above is not what I meant to linger on. The following is what I believe to be most relevant for now.

...can we tie in a gaseous system where the internal(and opposing external) pressure and force is high enough compared to the workload that the thermodynamic work is substantially less significant.

Any scheme/system that only includes "some" thermo work will still require a focus on various thermo issues. The main issue with thermo work is that it's PV work akin the ideal gas law PV=nRT. If we consider a thermo expansion in a 500cc cylinder with single-acting piston, PV work will decline during stroke unless P is constant via isobaric heating/expansion. My previous steam engine example with zero cutoff doesn't qualify as thermo work, since it's not an isobaric 'expansion' (isobaric yes, expansion no).

Let's continue with a vertical 500cc cylinder with single-acting piston similar early steam engines (I like this config) where

(1) ambient pressure = 15 lb force
(2) each bar inside cylinder = 15 lb force
(3) piston weight = 0 lb force
(4) useful work = lb force stacked on piston

whereby

(a) 1 bar in 100cc merely offsets 1 bar ambient and nothing happens
(b) 2 bars in 100cc with isothermal expansion lifts piston until 1 bar in 200cc whereupon everything stops due to equal internal and external force on piston and the only thing that has happened was the 'work' of lifting some air
(c) to carry any meaningful piston load and achieve useful work, internal piston force must be far greater than external piston force when isothermal or adiabatic expansion

This is the thermo work dilemma where low P swing indicates high backwork ratio. Increasing charge P increases the output, but doesn't directly change the backwork ratio. Adding a flywheel is nearly mandatory since this allows one to mooch off the output gradient and store output from above MEP during expansion and supplement output below MEP during expansion. Any "smoothing" out of expansion (vibrations or whatever) is a distant secondary advantage.

(d) isobaric expansion escapes this constraint

I've been pondering various isobaric schemes lately. Not the typical isobaric flavor where deltaV=deltaT, but the early steam engine flavor with no cutoff...

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VincentG wrote:Because if the mechanical efficiency can't be locked down, then thermo efficiency sure can't.

Modeling thermo and mechanical systems, locks down both to the models. The models are ideal versions of reality. The only thing we can do for a real system is measure the thermodynamic and mechanical parameters, realizing that measurements are not perfect either.

The measuring tool for thermodynamics of a heat engine is an indicator diagram. From that, power, work, heat in, heat out can be obtained and thermodynamic efficiency can be determined.

From a dynamometer, power and work out can be obtained. From fuel burned heat supplied can be obtained. Overall efficiency is equal to work out divided by fuel heat supplied.

We can subtract thermodynamic efficiency from overall efficiency and call that mechanical efficiency. However it lumps in burner, and heat exchanger efficiency with mechanical efficiency. There are other refinements that can be done using temperature readings and such if needed to study burner or heat exchangers.

VincetG wrote:If you counter weight the 200lb man with a 200lb load, you change the dynamic of the system.

Yes that I agree. I was thinking of counter weighting the man with 200# so he effectively weighs nothing. Can now go up the ladder for free. So each load up is 100% efficient.

Oh well.

VincentG wrote:can we tie in a gaseous system where the internal(and opposing external) pressure and force is high enough compared to the workload that the thermodynamic work is substantially less significant.

There was an elevator system that was proposed that had a U-tube one going up one down. They counter weighted each other. It has no thermodynamics. The gas effects were insignificant to the pumps needed to overcome loads being moved. Same as a rope and pulley, or teeter totter.

An interesting note is that at the end of the day, a properly counter weighted elevator will come out at zero energy cost. The same number of people go up as come down. Hence, the only work put into an elevator, on average, is 100% mechanical inefficiency. Not true of a construction crane who's job it is to lift materials up high for permanent placement.

Thermodynamic heat engine cycle is about raising the temperature to produce the pressure to push a piston. Then subtracting that which is used to return to the starting point.

Matt's block diagrams can be used. I don't think they are as easy to use as a indicator diagram or PV diagram.

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Matt, waiting to see where you go with this.

The important thing is that the man has traded force for distance. By taking a longer path, the weight was raised without additional perceived force. No different than any other form of mechanical advantage, except that perhaps this example can be extended to thermodynamic work by allowing less force (lower delta T) to do more work.

In this way the lower temperature delta can be used like a lever to increase its effective force. Just like a prybar, the object being acted on must be as rigid as possible to make use of the mechanical advantage. For a gas, this means increasing its density and pressure as much as possible so that a small temperature increase results in a relatively large and useful effect.

As Matt has found, the smaller the delta T, the more efficient a cold connected piston becomes. That combined with much better thermal performance of low temperature materials makes a strong case for LTD engines. The problem of low overall efficiency is that LTD engines are essentially prying against a piece of foam (1bar). A turning point should arise when the low temperature delta is compelled to pry against pressure and energy levels that are "rigid" enough to affect practical work output. The increased pressure levels are allowing us to tap into the baseline internal energy levels of the gas. The same energy that would be contained in the rope but not available to us.

Phillips was obviously attempting this with megabar charge pressures, but maybe just took a wrong turn trying to hammer in more, and more heat instead of focusing on effective temperature delta.

In this forum, we're mainly focused on "common" heat engines where thermo issues have direct PVT etc cause and effect constraints, but I've often thought that maybe an engine could utilize heat indirectly and remove these constraints.

Consider a massive airplane which flies without Carnot nor Archimedes, but until fairly recently defied logic. What I'm suggesting is schemes where the heat does not do PV work, but where the heat provides the means for work. The first obvious example is the Minto Wheel, but this bugger has a host of other thermo issues.

Consider a massive airplane which flies without Carnot nor Archimedes, but until fairly recently defied logic.

Can't let that one go without asking for more details...

The first obvious example is the Minto Wheel, but this bugger has a host of other thermo issues.

In a way this is similar in that increasing diameter allow the heat to travel further in exchange for more effective force. It's obviously constrained by rpm, the diameter, and capacity for fluid so output can't be very impressive.

Even though caloric theory is outdated and heat itself is not a fluid, does it not propagate like a fluid? Instead of using the heat itself as defined by absolute temperature, could you instead use the force exerted by the flow of heat as a lever against a work load?

Airplanes fly by the reaction principle of an inclined plane, hence the name. Airplanes do not fly via "lift" of air moving faster over wing surface creating a local low pressure region over wing (pressure differential). Such lift is a very minor force since the air simply moves away from upper wing surface. Oddly, the magic of flight is still commonly taught akin Bernoulli principle. Nevertheless, an airplane flies without thermodynamics (for flight) and thereby nixes Carnot issues. Furthermore, this reaction principle is unrelated to Archimedes buoyancy (which is actually way more complicated than commonly thought).

The Minto Wheel is an xlnt example of an indirect heat engine which requires heat, but lacks PV work. What makes this fascinating is that within fixed thermo constraints, output is linear wheel diameter. The Qout of condensation vs Qin of evaporation for Minto Wheel is similar to the backwork ratio of gas engines, but gas engines have Wnet per cycle (rpm) related to Qin/Qout while the Minto Wheel does not.

A similar scheme without phase change should improve thermal eff AND speed. I've been scheming some weird isobaric stuff lately and pondering Minto Wheel details: (1) when heat of condensation equals heat of evaporation, I smell a free lunch (2) each lb of descending liquid has a known work value, but how about each lb of ascending vapor...

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Matt Brown wrote:Airplanes fly by the reaction principle of an inclined plane, hence the name. Airplanes do not fly via "lift" of air moving faster over wing surface creating a local low pressure region over wing (pressure differential). Such lift is a very minor force since the air simply moves away from upper wing surface. Oddly, the magic of flight is still commonly taught akin Bernoulli principle. Nevertheless, an airplane flies without thermodynamics (for flight) and thereby nixes Carnot issues. Furthermore, this reaction principle is unrelated to Archimedes buoyancy (which is actually way more complicated than commonly thought).

That is a modern myth. The Bernoulli Equations accurately describe pressures knowing velocity and are derived from Newton's Laws. There are some changes in density that Bernoulli ignores, so be careful applying it. There is not a battle between Newton and Bernoulli, camber verses angle of attack. Lift, or more accurately lift verses drag, is a result of camber and angle of attack. Bernoulli and Newton are complimentary and both are needed to fully understand lift.

The etymology of airplane is from air and plane. Plane means level or flat, it could also be from Greek meaning wandering. Inclined is not part of the name.

If you really want a definitive method of deriving lift, use the Navier-Stokes equations.

https://en.m.wikipedia.org/wiki/Lift_(f ... an_airfoil

https://www.physicsforums.com/threads/h ... e_vignette

It takes a lot of research on the Internet to understand what Internet areas are misleading and what areas are better. Most that have somethings better also have something bad.

For example there are some old videos on YouTube of wind tunnel testing. They completely expose the equal transfer times theory as being erroneous. Correct. But because the flow is confined in a wind tunnel, the downward flow after the wing is muffled. Not wrong but watch out. I think it is the beginning data of why many explanations leave this out. I.E., it reduces the observation of the inclined plane affect, angle of attack. However, it doesn't effect the accurate measurements of lift and drag. It's affect is forced upon the tunnel after the test section (You will not read this anywhere. My observation and point. And it might effect the measurements.).

One observation I've seen is that the air begins to rise up before it gets to the wing and then starts down on both the top and bottom. Also the top of the wind has a much greater delta-P than the bottom, thus providing a much greater amount of lift than the bottom, hmmm how's that explained by angle of attack only. The effect of a wing on the air mass goes out quite a distance from the wing in all directions.

Matt Brown wrote:The Minto Wheel is an xlnt example of an indirect heat engine which requires heat, but lacks PV work.

Oh no! Not the Drinking Bird again. LOL Isn't the PV work in a Minto wheel, and Drinking Bird, the pressure in the bottom vessel times the volume change of the bottom vessel, minus the pressure in the top vessel times that same volume change? Just a fluidic piston being pushed around.

Work=Pb•∆Vb-Pt•∆Vt

Where ∆Vb=∆Vt the fluid volume change.

Isn't it equal to mgh of the inside fluid?

Even though there is boiling in the bottom and condensing in the top, isn't the primary process higher pressure in the bottom pushing liquid fluid up the pipe, not vapor?

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

It is just a many spoked wheel made out of half as many slightly modified Drinking Birds, with a higher ∆T.

Matt Brown wrote:when heat of condensation equals heat of evaporation, I smell a free lunch

I don't.

I see zero lunch at a cost. Heat traveling completely through the engine with zero being converted to work.

And the two aren't equal. One happens at a lower temperature and pressure, than the other, so the energy of condensation will be lower. This is proof, that the second law disproves Caloric Theory. Caloric isn't conserved in a Carnot Engine. Only during an irreversible no work heat transfer.

You two should concentrate on the already successful Stirling Brothers Engine. Two displacer chambers interconnected by a double acting piston. Actuated by magnetic, or some other sealed connection to the outside. Play with displacer volume verses piston volume. Play with hot verses cold piston. Compare different sizes of hot-piston-engine and cold-piston-engine. I bet there is a trade off which makes them very similar in efficiency and power levels. Play with pressurization. Play with heat exchangers. Play with temperatures. Good day to all.

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Here is a variation on the theme adapted from my previous concept "fire piston" based engine:
The hot and cold regenerators now are composed of the hot and cold junctions of a thermopile to generate electricity directly.

A kind of little video tutorial on how a thermopile operates:

https://youtu.be/O6waiEeXDGo

What's interesting about the thermoelectric effect is that the free electrons in a cylindrical metal wire act remarkably similar to the way a gas behaves in a closed cylinder.

Expanding when heated or contracting when cooled.

I wonder if that is also due to outside atmospheric pressure as the two delusional nincompoops "Matt and fool" assert.
Particles of matter in a solid or a gas don't really behave so differently.

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I think that electrons in a wire behave more like a liquid than a gas. But both are just analogies and have limitations. The same is true for the waterwheel, or plumbing analogies, limited usefulness.

Electrons don't spontaneously flow out of a wire when the wire is put into the vacuum of space. Gas out of an open cylinder does. Electrons do if pushed out by high potential differences. Gas will flow out of a cylinder regardless of temperature.

Solids and liquids don't. They need to be pushed out by an external pressure force. Solids will sublime, and liquids will boil, off into space, but that is a process of turning to a gas and the gas's velocity carries itself away. Gasses have their own internal 'pushing outward pressure'.

I suppose if a volume of electrons were somehow magically released into space in a small volume, they would expand forever. Never contract, never pull, never condense. All they have is a mutual repulsive force. No need for an escape or boiling velocity. I don't know how such a cloud would respond to being heated.

I'm guessing their speed could increase, but they are already difficult to 'contain' in any sizable volume or density. Like trying to heard cats, LOL.

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https://m.youtube.com/watch?v=YKZtt2yEwfs

https://m.youtube.com/watch?v=bHIhgxav9LY

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