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

[Tom Booth]

Tom
....I always found it comical that Kelvin and others said a self-acting engine was impossible then when Tesla gave them a simple example of how they were wrong they changed the context by saying it was impractical, as if the truth was a matter of practicality, priceless.

Can you point me to or cite a reference for this i.e. "they said it was impractical" (implying - not impossible), I haven't come across that. Really ?

----

Here are a couple variations on the theme (Heat Engines):

This little engine appears to be mounted on a rather heavy base but again, it has a tendency to creep towards the flame. Certainly this cannot be due to the flywheel being out of balance as there isn't any flywheel.

I'm not quite certain where one might locate the "heat sink", In fact, I don't see any heat sink. The heat source is virtually sandwiched up against the power cylinder.

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

This engine is of a somewhat different design, but still there is no flywheel.

But what interests me about this second engine is; by turning the engine vertically and incorporating several other ingenious modifications this guy has seemingly managed to eliminate friction in the engine by using a diaphragm rather than a piston.

He is applying a rather serious gas flame to the enginel, yet he makes note of the fact, apparently with some genuine surprise,  that the engine seems to be keeping rather cool. He thinks this may be due to the vibrations of the diaphragm moving the air over the engine. Of course, as you know by now, I have a different theory.

Although the guy says he is just giving the engine a "wee bit" more flame, it appears to me to be enough to easily cook a pot of stew,  but after several minutes, and even after turning up the flame he remarks that the metal is staying relatively cool towards the top, not too hot  to touch anyway. A result he did not expect. When he built the engine he equipped it for water cooling.

This engine is running at a rather high "frequency", possibly in the "acoustic" range, I'm not really sure.  The "Piston" actually consisting of a diaphragm does not move in a cylinder but rather vibrates like a drum head at the very top of the engine (discounting the attached generator unit).

I'm not quite sure where to look for a heat sink for this engine either.

http://www.youtube.com/watch?v=QcppEhp2RfA

Basically, I'm noticing from time to time, when observing various heat engines in operation, clues or indications that Tesla's theory may have been correct.

If these type of heat engines can run without any discernible "Heat Sink" or if they can actually keep themselves cool (even while being supplied with a generous amount of heat) then I think Tesla's idea can be more than realized. It could possibly be surpassed.

By that I mean, Tesla surmised that SOME heat would undoubtedly reach the sink and so it would require "continual pumping out". I don't think he ever considered that the sink could be dispensed with entirely. Not even in a "perfect" engine.

To get a clearer picture. That is, to determine if this could really work EXPERIMENTALLY , the heat INPUT would have to be much more carefully regulated than what is shown in these videos. The heat would likely have to be supplied in carefully measured doses rather than just cranking up the flame. The idea being not to apply the heat at a rate which would exceed the rate at which the heat can be converted by the engine.

Supplying too much heat to the engine would be the equivalent of adding too powerful a charge to the cannon with the result that nothing can be determined with any degree of certainty.

[Tom Booth]

People believed him because it stood up to scientific scrutiny. Scrutiny that continues to this day.

Well, actually Carnots theory of, what the heck did he call it? That heat is an indestructible "fluid" that traveled from heat source to heat sink was proven false experimentally, and most of his calculations were thrown out and eventually abandoned, even by Carnot himself.

In something like a Steam Engine, which was what they were mostly going by in those days, there HAS TO BE a transfer of heat. At least in a cyclic system where the steam is condensed back into water and recirculated. Same with a Heat pump that relies on a change of state.

Heat boils water to make steam. Steam runs the steam engine, Steam is condensed by removing the excess heat back into water.

You have to add a lot of heat to boil water and boil it for a long time to get steam. Steam Engines in those days were rather inefficient so when the engine was through using it the steam was still hot. There was so much Latent Heat put into making the steam that it was ASSUMED that ALL the heat passed through. It was a long time before any actual measurements were taken and it was finally realized that at least SOME of the heat apparently vanished. The amount that vanished being equivalent to the WORK performed by the engine.

With a Hot Air Engine or Stirling Engine the heat is used more directly without any change of state involved. The gas performs "internal" work in expansion. The molecules working against their own mutual attraction, then there is the work done driving the piston. As a result, much more of the heat added, if not all of it, is converted into work.

...However ,  If you have to 'manufacture' the cold sink when one is not available then it will always take more energy to do that than can be recovered as work from the engine.

How so ?

If you "manufacture" a cold sink. Cold enough to run your engine on Ambient heat, and the majority of that heat, if not all of it is converted into work, then the heat does not reach your heat sink. Assuming it is otherwise well insulated.

The engine takes heat and takes out the energy which leaves cold.

If Ambient is your sink and you have to make the heat, then yes. If your engine takes the heat and leaves you with cold, you will have to heat the cold back up.

But if your engine runs on ambient and takes the ambient heat and leaves you with cold then your cold sink, once established STAYS COLD. So you only have to "manufacture" the cold ONCE.

When I studied thermodynamics we certainly didn't take these laws on faith alone. They were rigorously derived from first principles mathematically  and then shown to be experimentally valid.

Just out of curiosity, do you know of anyone having EVER tested Tesla's idea experimentally ?

I've scoured the internet as well as much of the Thermodynamics literature, even YouTube with all the hundreds of Stirling Engines to be seen there and I have uncovered nothing that suggests that anyone has ever given this idea any serious consideration. Certainly not to the point of actually DOING AN EXPERIMENT to either prove or disprove the idea. It is simply ASSUMED to be impossible and so no one has ever bothered.

If you have some other information or are aware of some experiment involving running a heat engine on a "manufactured" heat sink I would love to hear about it.

As far as I know, no one has ever even made the attempt.

The problem with the term 'ambient' heat engine is that it implies that no cold sink is available to receive the heat rejected during conversion to another energy form .

That is the false assumption IMO, that heat is "rejected during conversion".

Is that not a contradiction ?

I joined the Faith but I was rejected during conversion.

The heat cannot be BOTH rejected to the sink AND converted to another energy form.

The problem is that the guys who formulated the Second Law of Thermodynamics didn't understand the FIRST! And that's a FACT.

[Tom Booth]

I've been thinking about the little engine I posted a drawing of earlier and I'm sure that it wouldn't work. At least not without some minor alterations.

The reason being that a "Heat Engine" in reality, doesn't run on a temperature differential. It runs on a pressure differential. That the pressure differential is established by means of a temperature difference is almost incidental.

Anyway, the problem was that although there is a temperature difference (artificially established or "manufactured") because there is a diaphragm or "trap" to equalize pressure, there won't be any pressure difference, no mater how much of a temperature difference. Not with this simple of an engine at least. With a Stirling Engine with a displacer - sure, I think that might work, but with no displacer,... and with the diaphragm, any pressure difference established by a temperature difference would be destroyed due to the diaphragm equalizing the pressure.

So anyway, I made some modifications which I think could solve that problem.

Basically use a diaphragm piston, a wider piston and cylinder (probably, though not illustrated) eliminate the check vale, (which probably wasn't needed in the first place) and pump some of the air out of the insulated box to create a partial vacuum. It can't be a TOTAL VACUUM, I don't think, because there has to be some air pressure to push the piston back down the cylinder, but on average, the pressure in the cold chamber would have to be at least a little lower than the power cylinder. (indicated by the diaphragm drawn inward on top) On second thought, probably a regular piston would work, but the cold chamber would have to be maintained at a pressure a little below 1 atmosphere, I think. ?


In other words, Hot and Cold don't REALLY serve any purpose in a heat engine except that they cause air to expand and contract which creates high and low pressure. Most Stirling Engines have a "displacer" for the purpose of changing a volume of air from hot to cold and back, or for delivering heat in regulated doses.

These little engines however have no displacer, so getting one to run on ambient heat might be tricky.

If you ADD heat to the cylinder, naturally this will bring the pressure up above 1 atm. but if you take away heat. The cold does you no good if it is still at 1 atm.

If you just lowered the pressure in the chamber, at this point I'm not even that sure you would need a temperature difference.

Why? because it is not Heat, really, it is kinetic energy. Molecules bumping into the piston. So if you create a partial vacuum, there are fewer molecules inside the box. Then when you heat up the air in the cylinder, the extra kinetic energy of the more vigorous molecules moves the piston.

Pu another way, cold, if it doesn't effect a drop in pressure won't do any good I don't think, so the low temperature box wold probably also have to be a low pressure box, I think. Maybe. Maybe not. Might be worth a try though.

[Tom Booth]

Some of these terms like heat rejection have specific engineering meaning. Take the time to learn the definitions and you will see such statements are unfounded.

Poppycock. The term "heat rejection" in this context is no mystery to anybody. It is the portion of the heat added or given to the engine that is not converted into useful work or another form of energy (translation: waste heat)

You could have easily reconciled the contradiction in your statement by saying that SOME heat is converted and SOME is rejected as waste heat. But in fact, that contradicts Carnot's theory.

Carnot believed that work was accomplished by a transfer of heat, identical to that of a water wheel where work is accomplished by the transfer of water. He states explicitly that no heat is lost in the process and that the quantity of heat entering the system is exactly the same as the quantity "rejected", just as the quantity of water entering a turbine and passing through it to accomplish work is exactly the same as that leaving it.

He goes on to say: " This fact is not doubted ; it was assumed at first without investigation, and then established in many cases by calorimetric measurements. To deny it would overthrow the whole theory of heat, of which it is the foundation."

Well, like it or not the whole theory of heat was overthrown. The calorimetric measurements did not take into consideration the latent heat involved in phase changes of water first evaporated (boiled) and then condensed in a STEAM ENGINE. etc. The heat that produces work in a heat engine is not transfered as Carnot believed. Does not pass through the engine like water through a turbine. It is converted. Gone. Nowhere to be found in the thermodynamic cycle of the engine. 

If heat is viewed as what it actually is, a form of energy, then it can be seen that it is impossible for the same quantity of heat to be both converted AND rejected.

You are simply dodging the issue by asserting that I don't understand what "heat rejection" means, as the contradiction cannot be reconciled.

IMO, it seems the "Second Law" is rather schizophrenic, leading to such contradictory statements as "the heat rejected during conversion". Further, IMO, any calculations based on such an erroneous and contradictory view cannot be anything but flawed.

Feel free to dream up your own interpretations of the 2nd Law if you like but I can't be bothered taking it further. At the time it seemed logically self consistent and experimentally proven, such that I haven't need to question it since.

And that, IMO, is the problem. Unquestioning acceptance. Which is why I can find no account or reference to any experiments having been conducted that might prove or disprove Tesla's theory. And apparently, neither can you. There is rather this complacency or assurance that although Carnot's theory of heat was fundamentally wrong he somehow nevertheless came up with the right answers applicable to any and all circumstances. I find this rather presumptuous.

[Tom Booth]

Lets take the Carnot Engine or Cycle and see if it is Really the most efficient Engine or Cycle possible. We can use the simple "lamina flow Stirling" that has no flywheel for comparison and see if it is possible to apply the Carnot cycle to it so as to better understand or evaluate its performance or efficiency.

First we will examine the Carnot cycle:

The cycle starts with a gas in a cylinder. There is a heat source and a heat "sink".

The heat source is brought into contact with the cylinder. First there is isothermal expansion. The temperature of the gas remains constant as it absorbs heat and expands. Normally when a gas expands its temperature decreases but since the cylinder is in contact with the heat source, heat is transferred from the source to the gas to maintain the temperature. The heat transferred to the gas is represented by Q1 in a conventional PV diagram. Q1 is the heat transferred into the gas.

Next is adiabatic expansion. The heat source is removed but the volume of the cylinder continues to increase, presumably due to momentum of the piston and flywheel. Heat is no longer being transferred to the gas. Pressure in the gas drops and the temperature decreases as the volume continues to increases but no heat is being transferred.

In the third phase isothermal compression takes place. The heat source is replaced with a heat sink which is brought into contact with the cylinder, and "weight is added", presumably this weight, in a real engine is due to the momentum stored in the flywheel which is now effecting compression of the gas and raises the pressure in the gas. Although the gas is being compressed the temperature remains constant due to heat being ejected to the sink. Heat is transferred from the gas to heat sink to maintain the temperature. The heat transferred to the sink is designated by Q2 in a conventional PV diagram.

Lastly we have adiabatic compression. The "sink" is removed, but more "weight"  is added, i.e the momentum of the flywheel continues to compress the gas the pressure in the gas rises. The temperature increases and the volume decreases as the gas is compressed. No heat is transferred.

In the end the gas has returned to its original state and the cycle is completed. It was imagined that during the cycle, work W was produced by the gas, the amount of work being equal to the net heat transferredd during the process.

Thus: W = Q1 - Q2

The Carnot engine, converts the heat transferred into useful work.

Now lets take a look at the Stirling Lamina Flow Engine operating without any flywheel.

The cycle begins in much the same way, heat is applied and the gas expands. From then on however we are presented with a number of difficulties. There is no momentum stored in any revolving flywheel that could reduce the "weigh" on the piston so as to effect isothermal expansion. If by chance the temperature of the gas remains constant it cannot be due to the removal of weight. The pressure of the atmosphere that the expanding gas is working against cannot be reduced, therefore if the temperature of the gas remains constant it must be due to the fact that it is doing work to push the piston out against the pressure being exerted against it.

The next problem is that the heat source is not replaced by any heat sink. In the little Stirling Engine in question the application of heat remains constant.

We can however imagine that due to some momentum being stored in the piston the gas is expanded somewhat beyond its natural limit which could effect some cooling. We might also imagine that the air of the atmosphere on the other side of the piston has been to one degree or another rarefied. That is, knocked out of the cylinder away from the piston. What then is there to effect a return of the piston to its starting location other than its having given up heat in performing work and so contracts due to the mutual attraction of the cooled air molecules in the cylinder.

There again, is no flywheel with stored momentum revolving around to effect compression, therefore it might be surmised that the gas is, in a sense, compressing itself or contracting i.e. performing work.

If it is imagined that the gas in being thus "compressed" or in the process of contracting is liberating some heat, where is there for that heat to go but back to the source, as the heat source has in no way been "replaced" by any "sink". The heat generated by "compression", if any, is, rather, absorbed or accumulated by the same air molecules present in the cylinder in the process of contracting. On the other hand, if the gas has given up ALL the heat added to it from the heat source, there is no need for accounting for the heat generated by the "compression stroke" of the engine. There is, infact NO COMPRESSION STROKE but rather a CONTRACTION of the gas. Upon contracting the gas again is in the proximity of the heat source and the process is repeated, but no "transfer" of heat from heat source to heat sink is evident.

The heat was not "transferred" but rather WHOLLY AND COMPLETELY TRANSFORMED OR CONVERTED INTO WORK. GONE. If not wholly converted the remainder has nowhere to go but back where it originated, back into the gas molecules confined within the cylinder.

As the gas contracts and returns to proximity with the heat source another quantity of heat is delivered and the process repeats.

There is no Q2. (The heat source is never at any time replaced with a heat sink)

Therefore Q2 if anything must equal zero.

WORK = Q1 - Q2

Q1 - 0 = Q1

Work therefore = Q1

Heat "rejected to the sink" is zero.