Tesla's Ambient Heat Engine Theory - Right or Wrong ?

[Tom Booth]

My last post contains some, what seems to me, obvious, or perhaps not so obvious contradictions. Yet, this is the way things are generally explained in thermodynamics texts.

When Carnot said that work was a result of heat transfer from source to sink he meant just like a water wheel with no heat being lost in the process.

In the equation W = Q1 - Q2 where work is equivalent to the "net heat transfer" something entirely different is meant. That is heat transferred INTO the system (minus "waste" heat).

There is some potential for confusion when virtually the same language is used to described two entirely different scenarios. One where no heat is lost or actually converted and the other where heat actually does "disappear" or is converted into work.

IMO it is not really possible to reconcile the difference, and Carnot's idea of a heat engine operating just like a water wheel needs to be entirely discarded. It just isn't so. Yet this equation is happily used in conjunction with "The Carnot Cycle" though the two are actually incompatable if not entirely in opposition to one another.

W = Q1 - Q2 means in reality that the WORK performed by the engine is equivalent to the heat that DOES NOT GET  TRANSFERRED TO THE SINK. As far as Carnot was concerned, such a circumstance was "inadmissible". It would overturn the whole theory of heat as an "indestructible fluid".

What we have then, discarding Carnot's concept is something more along these lines: (what really happens in the "Carnot" Cycle.)

During phase 1 Isothermal Expansion, heat Q1 is added from the reservoir T1 and WORK OUTPUT is done.

In phase 2, Isentropic Expansion there is again WORK OUTPUT by additional  expansion.

Phase 3, Isothermal compression, work is done to the system. It is here where "waste heat" Q2 is rejected to the sink. However, in the Lamina Flow Stirling running without any flywheel the "sink" is absent, so the atmospheric pressure pushes the piston inward. the energy is transferred from the piston to the gas, the gas is compressed but the heat generated by the gas under pressure is not lost to the sink.

Phase 4 Isentropic compression, the gas is compressed further, more heat is generated, but the "sink" was not removed as it wasn't there in the first place. The temperature of the gas continues to increase.

It seems to me that at this point it might very well be possible that the temperature of the gas, having gained some energy from compression due to atmospheric pressure and the momentum of the piston on its return stroke, momentarily exceeds the temperature of T1 (The heat source). It is rising in temperature due to compression and simultaneously heat is still being added.

It seems to me that there is a real possibility that at this point the engine is operating very much like a heat pump, in that work is being done to it by atmospheric pressure and stored momentum. In other words, "waste" heat is being transferred back to the heat source rather than to any "sink" and so properly speaking it is not "wasted" or "ejected" or "transferred".

Normally, in most heat engines it is assumed that work done BY the system is useful work but work done TO the system is wasted, ejected to the sink.

In the case of the Lamina Flow Stirling with no flywheel, and similar engines  however, the energy, or heat generated by work done TO the system is retained or returned to the heat source rather than ejected to the "sink".

HEAT SUPPLIED = WORK + HEAT REJECTED

Therefore, WORK DONE = HEAT SUPPLIED - HEAT REJECTED

W = Q1 - Q2

"waste heat" is then limited to heat loss due to friction and conduction or convection or infrared radiation but not due to heat ejection to any "sink".

These type of losses can be minimized. Friction can be virtually eliminated. Heat conduction can be reduced to near zero. Without these two, heat loss due to radiation can be practically eliminated as well. What's left ? a very nearly 100% conversion of heat into work.

Could the work output be used to maintain the temperature differential ? That is to in one way or another compensate for the small fraction of heat that was lost ?
I don't really see why not.

[Tom Booth]

There is, I think, another slight problem or difficulty with the notion that the "Carnot Engine" is a "perfect" or "ideal" engine whose performance or efficiency would be "impossible" for any real engine to approach or surpass.

In stage 1 of the Carnot Cycle a cylinder containing a gas is expanded.

This is generally illustrated in thermodynamics texts by a removal of weights. In Carnot's words: "The steam is received into an envelope capable of enlargement, such as a cylinder furnished with a piston. We then increase the volume of this envelope, and consequently also the volume of the steam."

In the reverse operation weights are added to the cylinder to effect compression of the gas: "We condense the steam by bringing it in contact with B and exerting on it at the same time a constant pressure until it becomes entirely condensed."

In the first half of the cycle weights are removed from the piston and heat absorbed by the gas from the heat source. In the second half of the cycle weights a are added back to effect compression and heat is ejected to the sink.

Nowhere is it explained exactly who or what or by what mechanism or by what means these weights are supposed to be removed and added back or by what means the source and sink are to be exchanged.

Imagine if you will trying to operate such an engine. First you have to remove weights from the piston, then replace the heat source with the sink and put the weights back.

The engine itself, apparently, cannot function without the assistance of some unidentified agency which effects the removal and replacement of said weights.

In other words, it is completely inoperative. It can't even advance through any 1/4 of its cycle without outside assistance.

Earlier, I advanced the idea that the energy for this removal of weights and their replacement which is supposed to effect expansion and compression MUST BE due to energy stored up in the flywheel. In a real engine, where else would it come from ?

But think about it....

Is this even remotely possible ?

The flywheel, apparently, is doing the work of removing weights in part 1 & 2 and replacing weights in part 3 & 4 (expending energy).

But in reality, is it the flywheel of an engine that powers an engine ?

Who or what is supposed to be removing and replacing the weights to make this "ideal" engine go ?

This is never explained. This Carnot engine appears to be completely dependent for its motive power on some unnamed unidentified agency that removes and replaces weights. It is fundamentally ludicrous. It cannot possibly function as described.

How can such an engine, entirely incapable of operation without outside assistance be held up as the most efficient engine possible ?

I ask you.

I would love to ask some teacher of thermodynamics trying to explain the Carnot cycle, how are these weights removed and replaced ?

Well, I don't know, it just happens.

http://www.youtube.com/watch?v=aAfBSJObd6Y

[Tom Booth]

Concepts like the Carnot cycle are stated in terms of processes that are not present in Nature. However we do know that any real system cannot exceed the efficiency of the Carnot thermodynamic cycle. My advice... give up now on understanding thermodynamics unless you are prepared to think in the abstract terms that the laws are expressed in. If you refuse to do that then by all means continue to waste your time on speculation over devices that would be able to break these laws.

There is nothing particularly abstract about pressure, volume and temperature.

If "efficiency" is defined in terms of "useful work" then it is clear that the Carnot Engine does no useful work. How can it ? It doesn't have any mechanism for work output. It can't even lift a few pebbles by itself.

You might as well say that no mode of transportation will ever be devised that is more fuel efficient than the Radio Flyer.

[Tom Booth]

I think the second law applies to "unstructured energy".

If you create a sink, you've provided "structure".

Think of it this way"

If you had a room full of fast moving bouncing balls and set up a flexible curtain and pushed or moved all the balls to one side of the room you would have "structure".

Now you could put some levers or something on the curtain and extract energy as the balls hit the curtain.

OK, that would work, you say, but eventually the balls would transmit all of their energy to the levers and you would run out of energy.

Ambient heat however provides a continuous supply of high energy "bouncing balls". Create a cold room with your curtain and expose it to ambient heat and the supply of "bouncing balls" will never run out.

The ones that give up their energy return to the atmosphere and take up more energy from the sun.

Conceptually I can see no reason why this could not work.

Heat after all, is really kinetic energy. The energy of the balls hitting the curtain can be converted by the levers or whatever into some other form of energy, like electricity, so there is no problem with the "cold" side of the room becoming filled up with bouncing balls of its own.

Of course this would not work in a "closed system". You just have to open the window, or set up your "cold room" outside where there is a continuous supply energetic "bouncing balls" (air molecules) or otherwise have your hot ambient air flow through the system.

[Tom Booth]

I suppose you might say : well maybe something like that would work on a quantum level but not on a macro scale.

Consider this.

Using the above illustration, lets replace the "flexible curtain" with a large piston and crankshaft.

Opposite the head of the piston we set up another wall, but leave some space for the "bouncing balls" to flow between.

Now on this opposite wall we set up some mechanisms with levers and springs. Here is how they work:

When a high energy bouncing ball hits one of these mechanisms the force of the impact compresses a spring and a trap closes to hold the ball.

The wall is covered with many such devices. We wait until the whole wall is covered and all the springs are "loaded".

Now we trip a master control lever and all the springs are released at the same time. All the balls hit the piston at once and drive it forward. From there on you can imagine that the piston operates as any other engine.

You might say that this is impossible, there is no such thing as a tiny lever or spring or whatever small enough to trap the heat from a small air molecules and then release it all at once, but in fact, this is the function of the "regenerator", the little wad of Stainless steel wool in our Stirling Engine.

I'm not really sure just how it works but by trial and error Model builders have found that Stainless Steel has the property of trapping heat but holds on to it very lightly so that it can be released all at once just by a change in the direction of air flow.

Perhaps the Stainless Steel attracts negative ions or something that create a thermal boundary layer so that the steel holds the heat. Then when there is a change in the direction of air flow or a sudden jolt of air across it, The boundary layer is disturbed and the heat is released. That's just a guess. Don't really know. As far as I know, it has never been investigated. Regardless, it works.

That is why all these little "lamina Flow" Stirling engines have a little wad of steel wool stuffed in the end of the cylinder opposite the head of the piston. It is the mechanism for trapping and releasing heat. The choke or orifice controls the air flow so that the heat is released in metered doses.

As the piston returns, a blast of air is sent through the orifice into the steel wool and the boundary layer of air around the steel wool is disturbed and the heat is released all at once sending the piston back out again.

As with the room with a curtain, there is no need for the "bouncing balls" to ever travel to the other side of the curtain, to the "sink", but the sink still has to be there. If you had the "bouncing balls" on both sides of the curtain the energy would just cancel out and the curtain wouldn't move enough to extract any energy. This would be "unstructured" rather than "structured" energy.

The little Stirling Engine with nothing much more than a wad of steel wool and a test tube is doing a very good job of structuring and directing heat energy.

edit: by the way the type of stainless steel wool generally used by Stirling Engine Model builders is just the common stainless steel wool scouring pad for washing dishes.