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

[Tom Booth]

Phase change and latent heat etc is not important when considering a device with regard to the second law. A heat pump obeys the second law. It is just its cycle is reversed compared to a heat engine.

Ordinarily true, but I think Tesla was proposing something different.

One could not connect the output of a heatpump to the input of a heat engine and have it run 'self looped'. Such a system would be creating output work with no overall temperature differential and thus break the 2nd law.

What constitutes "the output of a heatpump" ?

Heat, right ?

But Tesla was not proposing running an engine on the output of a heat pump. Rather he was proposing running an engine on Ambient heat. Ambient heat does not have to be created or "pumped" it is just there.

So he was proposing something subtly different.

If what he proposes actually has a thermal gradient then there are plenty of Tesla devices out there already... One need not look any further than a thermo-electric device.

What he proposed is that one could convert all the ambient heat to another form of energy thus not requiring an actual cold sink.

He nowhere makes the assertion that a cold sink would not be required, quite the contrary.

"by expending initially a certain amount of work to create a sink for the heat ... to flow in..."

He recognized that a "sink" had to be created and that energy would have to be expended to create and maintain such a sink.

He also recognized that it is not possible to convert ALL the heat: "We do not know of any such absolutely perfect process of heat-conversion, and consequently some heat will generally reach the low level, ..."

Carnot had something to say about that as an impossibility, and Tesla didn't elaborate on how it his device could get around those limitations

Tesla was well aware of Carnot. He makes reference to Carnot in the quoted material above: "I read some statements from Carnot and Lord Kelvin (then Sir William Thomson) which meant virtually that it is impossible for an inanimate mechanism or self-acting machine to cool a portion of the medium below the temperature of the surrounding, and operate by the heat abstracted. These statements interested me intensely.... "

His whole article from that point on elaborates on how it is possible to get around those limitations.

I believe Tesla was proposing something quite different from using the heat from a heat pump to run a heat engine.

What he was proposing is removing heat from a given space which would then allow the Ambient heat to flow in naturally. The ambient heat does not have to be generated by a heat pump. Ultimately it is supplied by the sun. If a heat pump were used it would be only used as a means of throwing off EXCESS HEAT which was not converted by the engine. Such excess heat would only constitute some fraction of the ambient heat used to run the engine.

[Tom Booth]

...
An engine can be thought of as a heat converter. I takes heat and turns it into something that is not heat. You end up with less heat but that energy in now in another form, mechanical, for instance.

...You may end up with less heat...

Just for the sake of clarity, again, Tesla was not proposing running a heat engine on the output of a heat pump. He was proposing running the engine on Ambient Heat. So the problem is not ending up with LESS HEAT.

The heat in the ambient is vast so as to be practically inexhaustible. We are, in effect, living in a furnace heated by the sun continually, so the problem is not running out of heat. The problem is simply removing that fraction of excess heat not converted to some other form by the engine.

[Tom Booth]

That may be so, but what he proposed would not work.  You can't just 'disappear' the heat or convert all of it to another energy form.

He appears to have misunderstood Clausius , Carnot and Kelvin.

I've highlighted the word "ALL" above. Again, Tesla certainly recognized that you cannot convert ALL the heat or make it all "disappear".

He did say, speaking hypothetically: "If the process of heat transformation were absolutely perfect, no heat at all would arrive at the low level, since all of it would be converted into other forms of energy." but goes on: "We do not know of any such absolutely perfect process of heat-conversion, and consequently some heat will generally reach the low level."

By saying "You can't... convert all of it to another energy form." you just repeat what Tesla himself recognized and stated in his article making your statement a straw man argument.

What could not be converted would have to be removed, but he says: "But evidently there will be less to pump out than flows in"

Logically, if you have $100 US dollars and you convert SOME of that into a different currency, the number of US dollars you are left with is less than the $100 that you started with, NO?

Likewise with a heat engine. If you put Q heat energy in and some of that heat energy is converted into work, what you are left with is <Q. Right ?

Perhaps Tesla misunderstood. Perhaps his idea can't work. Perhaps.

But if we want to refute his claim or idea, we can't do so by refuting some other claim that he obviously did not make.

So if we re-frame your statement to more accurately reflect what Tesla actually did say, it would read something like this:

"...what he proposed would not work.  You can't just 'disappear' (some of) the heat or convert (some) of it to another energy form."

So does or does not a heat engine convert some of the heat into "work" or into something other than heat so that the heat thus converted effectively "disappears" leaving less heat than what we started with ?

If there is a flaw in Tesla's logic, I think we need to dig deeper to find it. Certainly we cannot refute him on the basis of your misrepresentation of his proposal.

[angryScientist]

I still assert that it must be true that Tesla was thinking correctly and ambient energy can be converted to useful work.

You must use every trick in the book to get around the inefficiencies that Gianna presents. It would be truly impossible if all you had to deal with is the contents of Gianna's presents in his opinions.

Luckily there is the latent heat trick of the heat pump, with out which there would be no way to create a heat sink at a cost in energy that would show any kind of benefit.

Here is another trick that can be employed.
Use of dissociating gases in Brayton Cycle space power systems 40% more efficient
http://www.overunity.com/7814/use-of-dissociating-gases-in-brayton-cycle-space-power-systems-40-more-efficien/msg192994/#msg192994

[Tom Booth]

Either there is a thermal gradient or there is not. If there is, then a device that produces work is a heat engine and it obeys the laws of thermodynamics.

Heat energy flows from the hot to cold regions.  The portion of work that can be extracted from that flow is limited by the Carnot efficiency which is predicated on the difference in temperature between the two regions.

In classical mechanics this statement is true even for infinitesimal and arbitrary geometries. Applying that to what Tesla proposed you can see that his idea could not work as proposed.

These are pronouncements and/or assertions and do not appear to address Tesla's specific proposals or ideas or statements of fact.

Tesla made specific assertions such as heat utilized by a heat engine is converted to another form or other forms of energy. That there will be less heat to remove as a consequence. etc. Making an appeal to "the laws of thermodynamics" does not make for a sound argument when considering a possible exception or "loophole" to those same laws, I don't think.

As an aside, An observation regarding Carnot and his "theoretical efficiencies".

Correct me if I'm wrong but....

If your TD (Temperature differential) is Th = 100k Tc =50k Carnot says your engine can be no more than 50% efficient. Likewise, Th 5000k Tc 2500 again 50%

1648k and 824k 50%
4000k - 1000k 75%
Tc 0k - Th (any number) 100%

It appears to me that what this is saying is that "Carnot efficiency" is calculated on a baseline of absolute zero.

In other words. If your actual ambient temperature were 300k (81F) and your sink was a bone chilling 150k (-190F) and your engine removed ALL OF THE AMBIENT HEAT GIVEN TO IT so that NO ADDED HEAT REACHED THE SINK AT ALL and your sink remained at -190F no matter how long your engine ran, Carnot would say that this engine was only 50% efficient!!!

Why? because theoretically there is still more heat that could have been converted into energy ALL THE WAY DOWN TO ABSOLUTE ZERO! Your engine only utilized half that. So it is only 50% efficient. 

This, IMO is moronic, too simplistic to have any real bearing on reality and not at all applicable to Tesla's proposal.

edit: (unless of course you use this as a basis to calculate that Tesla's engine would only have to muster something much less than 50% Carnot efficiency to realize his idea).