Stirlingengineforum.com

Tim Booth wrote:All I'm saying, if you think the engine is 5% efficiency, on an 85 watt heat source there should be about 80 watts of that arriving at the "sink" (according to the Carnot formula) If that had been a test question for a thermo exam': "If Qh is 85 Joules and Qc is 1.32 Joules what is the efficiency of the engine" what would the correct answer be?

A. 5%
B. 98.5%

I would have to question the professor's motives, or at least consider what the professor has emphasized in lectures leading up to that question. I would also look at the rest of the test to see if other questions lead towards his emphasises.

Is he stressing Carnot? They all are. Is he talking Earth based normal materials and air engines? Atmospheric pressures? Or, exotic material and pressures and Pluto based engines and associated local ambient temperatures? Is he emphasizing good laboratory investigation?

As a non-multiple guess test question, I would begin by telling what I do know:

1: n=(Qh-Ql)/Qh=(85-1.32)/85•100
approximately equals 98.447%

2: Carnot Therom 0.98447 = (Th-Tl)/Th

If:
Th = 1000 K and Tc = 15 K
n = (1000-15)/1000 = about 0.985
It would be difficult to find a workable gas at that low a temperature. Helium might be an only choice. Even it might not work.

Or if 50 K for use of helium or hydrogen and 3333K:
n = (3333-50)/3333 = about .985
It might be difficult finding a material that would work at that high a temperature 3333 K and not melt. It might be too cold for even hydrogen and helium, especially if at a higher pressure. And nitrogen liquefies at 77 K and one atmosphere.

It would get progressively worse, hotter, as Tc is brought up to a workable temperature.

As a PhD level question, this would then need to go on to ponder if the the experimental results were flawed, and demand a relook with better instrumentation. It would be a question of accepting a very very extraordinary outcome with very limited single point data, or getting more data.

In other words, you have not verified that the steamer puts into your engine 85 Watts. It is only wishful thinking from the label on the bottom. A label that is required to show only absolute maximum for safety sake, and is probably conservative, or even boastful. You haven't verified that it even puts out 85 Watts of steam, let alone that all the heat from that steam enters your engine. You haven't even verified that the steamer absorbed 85 Watts from the power line. You haven't measured the temperature of the hot plate, which would potentially give some indication of how much heat maximum the amount of gas in the engine could possibly absorb per cycle assuming it gets cooled fully to ambient each cycle. A very bad set of assumptions. I don't remember if you took any Rpm readings, but that also would be needed. All those things must agree with your one claim of 85 Watts before even talking of the Qc rejected. Furthermore, the Qc rejected, as calculated, is a minimum amount, and it doesn't account for the heat lost by the cold plate being warmer than ambient. So it will definitely be a higher number. Lastly how much power output from even a simple homemade Dynamometer would be very important.

It really is very difficult to do good science because it requires a lot of cross checks, and mathematical theory. Things a good scientist is trained for in a good classroom and lab, or by good self training. Good science is not merely reading a thermometer, uncalibrated or even calibrated. It so much more. And even then can be very bad science. I'm thinking Ponds and Freshman, cold fusion.

Please be careful, but please cary on.

What I find most interesting in that experiment and data is that the cold plate warmed up, got hotter. That is interesting, not so much that it happened or how much, about par for tiny power output, but that you dismiss it from being a direct flaw in your quest to disprove 200 years of Thermodynamics, and you go on Bashing great men in many threads. Very entertaining though, thanks.

If you stuck to, why does a LTDS engine idle faster with the cold plate insulated, it would be great. You would, of course, need to fit it in with this data showing a significant increase in cold plate temperature.

A few thoughts.

First of all, I mostly respect and honor Carnot. He published his ideas in good faith, (or likely, mostly his engineer father's ideas, according to some accounts), but when by numerous further experiments caloric theory did not fit the available data he recommended that the theory be abandoned, though this recommendation was not published until years later.

Kelvin, by the time he wrote his analysis of Carnot's work certainly must have had access to the same experimental data. Regardless, he consciously and willfully chose to move forward using Caloric theory as the foundation though knowing full well the theory was beyond simply in question. It had long since been disproven. This seems like a course of action that is rather difficult to justify. He knew the theory was wrong but championed it forward making it the foundation of thermodynamics anyway, writing that the whole science of heat would have to be revised and rewritten on some new foundation someday.

But someday never arrived we are left with a deeply flawed and corrupted "science" that appears to perpetuate itself largely on the basis of "authority", and nothing more

The data resulting from my experiment was, of course, ridiculously flawed, resulting, from an accident. I hooked up the thermocouples cable backwards.

Correction for the error were made, but that is hardly conclusive of anything.

Nevertheless, if we are going to evaluate "the available data" the numbers are what they are.

They appear to indicate a vary very high efficiency, over 98%

It really is very difficult to do good science

That's just lame IMO.

Criticisms of the sort you've presented here are productive of nothing.

Such experiments are very simple and straightforward. Easy and simple and inexpensive for virtually anyone to carry out. To make all these excuses to avoid doing so is making mountains out of molehills.

There is a very simple way to disprove my so-called "claims".

Do the same experiment and record the results. Do your own calculations.

But will anyone take the time to do that?

Well, I think a Marine engineer here on the forum has said he has.

I hope more people in this forum will do some practical experiments with their small Stirling engines. I should not be so difficult to
isolate the cold side of the engine and see if there is something to Tom´s experience.

- And you don´t need high precession thermocouple's to do this. Look for the tendencies, not the "correct" temperature.

But have anyone in here done that ?

Yes, I have my self ;-)

viewtopic.php?p=19904&hilit=Goofy#p19900


Add to the available data.

I think furthermore, I would probably have never carried out any such experiments at all except for having happened upon that 1900 article by Tesla where he presented his own analysis of Kelvin.

Tesla theorized on the basis of the experimental evidence available at that time and concluded that heat is energy not a fluid "falling down" from a high to a low level and so, as a motion, should follow the laws of motion, the same as all other forms of energy, one form converting to another.

I don't think it could be said that as a Scientist, Tesla was incompetent.

Be that as it may, my experiments take a completely objective approach. Maybe Kelvin was right, maybe Tesla. I don't know.

I just tried to devise some simple experiments I could do myself to find out.

If Carnot was right there should be A LOT of heat that flows through to the "sink".

If Tesla was right, a "sink" would not be essential, or at a minimum, some of the heat going into the engine should "disappear".

Tesla wrote that in a "perfect" engine, no heat at all would arrive at the "cold side" but it might ALL be converted to mechanical output.

I don't make any preconceived judgement about the outcome, what to expect, or who might be right, and actually don't care one way or the other.

Objectively speaking, so far, I think the evidence is that Tesla was right.

I have not been able to get an engine to stop running by blocking the "flow" to the "lower level" and I've been able to measure at times, scarcely any heat at all flowing out from the cold side.

Another point. Before ever doing any experiments, I scoured the historic literature for any experimental proof of any kind whatsoever to verify the so-called "Carnot Limit".

I could find NOTHING. Nothing whatsoever.

I went on the various forums, Physics and Science forums for YEARS, asking about this. What is the empirical basis for the Carnot limit?

Rather than finding anything, I found several references that verified that there is NO EXPERIMENTAL BASIS. This is admitted.

A Carnot engine is admittedly impossible. It doesn't exist, so no experimental comparison with a Carnot engine can be made.

The whole thing rests upon supposition. Suppose heat is like a waterfall.

I did not find any satisfactory answer.

So, I devised some experiments, that IMO should have been carried out a century ago, at least. Simple common sense experiments. If heat really goes THROUGH the engine in the quantities predicted by the Carnot Limit, then it should be a simple matter to measure the heat LEAVING the engine at the sink.

The LESS efficient the engine, the MORE "waste heat" should, or according to the theory MUST be, "rejected" to the "cold reservoir".

For large quantities of heat to leave the cold side the temperature must be significantly elevated above the ambient.

In some of my experiments the cold side temperature, indicated by thermal image recordings, was slightly BELOW the surrounding ambient temperature, yet the engine continued running for hours on end.

Such results do not seem to support the Carnot limit "theory". Or unverified so-called "LAW".

If any previous experimental data were available, I never would have bothered going to all the trouble and expense of doing such experiments myself.

Sorry if I'm unwilling to accept that Kelvin was right and Tesla was wrong on authority or "faith" in "established science" alone.

In this case the "science" doesn't appear to be all that well established IMO.

I would have to question the professor's motives... your quest to disprove 200 years of Thermodynamics, and you go on Bashing great men

Presenting an alternative theory is not "bashing" anybody.

Why these extreme reactions to silly experiments with toy engines?

Why all the disparaging and alarming responses. "Please be careful" what?

I've been banned from every physics and science forum on the internet, and for what?

For posting videos of my experiments and asking questions, positing some theories and speculations to explain the results, that is all.

How dare I question 200 years of scientific AUTHORITY. How dare I question the opinions of these great AUTHORITIES?

All I get are these fallacious arguments. Appeal to authority and attacks on my motives and character or my scientific credentials or acumen.

I never claimed to be a great, or even a good "scientist".

I'm a retired lawnmower mechanic.

2: Carnot Therom 0.98447 = (Th-Tl)/Th

If:
Th = 1000 K and Tc = 15 K
n = (1000-15)/1000 = about 0.985
It would be difficult to find a workable gas at that low a temperature. Helium might be an only choice. Even it might not work.

Or if 50 K for use of helium or hydrogen and 3333K:
n = (3333-50)/3333 = about .985
It might be difficult finding a material that would work at that high a temperature 3333 K and not melt. It might be too cold for even hydrogen and helium, especially if at a higher pressure. And nitrogen liquefies at 77 K and one atmosphere.

It would get progressively worse, hotter, as Tc is brought up to a workable temperature.

As a PhD level question, this would then need to go on to ponder if the the experimental results were flawed, and demand a relook with better instrumentation.

Here it appears you are using the Carnot Limit to generate improbable outcomes to debunk criticism of the Carnot limit.

My argument is the Carnot formula is fallacious at its foundation. Temperature differences have no actual bearing on engine efficiency.

Concocting various scenarios out of thin air, based upon the formula in question proves zilch one way or the other.


If the Carnot efficiency formula based on ∆T alone is valid, I'd be interested to see the results when applied to the evaporation-condensation engine.

Water evaporates at 100°C

Water also condensed at 100°C

The temperature difference in these "toy" amateurishly constructed engines is, in many cases miniscule, and yet the potential power output based on the expansion ratio between liquid water and water vapor 1:1700 is enormous.

Tom Booth wrote:Water evaporates at 100°C

Water also condensed at 100°C

This is easily disproven using a PV diagram.

Water boils and condenses at 100 C, if and only if the pressure stays the same, and at approximately one atmosphere. This, on a PV diagram, would produce a cycle which contains zero area. Zero area on a PV diagram means zero work out per cycle. This means the efficiency for that cycle is zero. N = (373.15 - 373.15) / 373.15 = 0.0

Pressure out minus pressure in. Area under the curve out minus area under the curve in. Same pressures same but opposite areas.

But hey! That is only a two hundred year old reliable theory. So perhaps your opinions here weigh more. What would your theory predict, for an accurate testable number for work output?

Science is about making calculations that predict numerical outputs, instrumentation, and measurements that correlate, those predictions. Those numerical predictions are what makes it so difficult. That and accurate experimental setup.

Fool wrote: ↑Sun Mar 17, 2024 8:27 am

Tom Booth wrote:Water evaporates at 100°C

Water also condensed at 100°C

This is easily disproven using a PV diagram.

Water boils and condenses at 100 C, if and only if the pressure stays the same, and at approximately one atmosphere. This, on a PV diagram, would produce a cycle which contains zero area. ...

Right,

Which is why I've argued, PV diagrams, also used by Kelvin, based on Caloric theory are also invalid and misleading, as it does not illustrate simultaneous heat input with "internal thermal energy" conversion to mechanical output. As you point out, no change is evident on the diagram.

At any rate, it only takes a very slight temperature/pressure difference to tip the scales between evaporation and condensation. As can be seen in the "cloud in a bottle" experiment


https://youtu.be/G70y90BVes4?si=1qr4knPysnGCt68i


I mean, that guy isn't Hercules. How much pressure/temperature variation do you suppose is going on there? And he didn't even bother getting rid of the air in the bottle. His demonstration is not showing the full potential of a saturated vapor to undergo rapid, dramatic and powerful phase change.

I'd say this is why refrigeration systems that depend on phase change can have an efficiency (COP) greater than 100%

A heat pump violates the Carnot limit but we just get around that inconvenient truth by renaming "efficiency" to COP. Problem solved, the Carnot mythology is saved.

Fool wrote: ↑Sun Mar 17, 2024 8:27 am ...This means the efficiency for that cycle is zero. N = (373.15 - 373.15) / 373.15 = 0.0
...

Again, you're appealing to the Carnot efficiency limit formula itself to "prove" the Carnot efficiency limit formula. That is not a valid argument.

Now you are denying the reality of life. The PV diagram has nothing to do with Kelvin or Caloric Theory. It is merely a graph of pressure with respect to volume. It is a graph of real world measurable properties.

Those scientists that are more recent, and current such as myself, have reevaluated Carnot and Kelvin after discarding Caloric theory and still find it reliable. Even when others attempt to discredit it with scrambled logic, opinion, and lack of higher math tools. The Phillips Company has built many impressive machines using 200 year old theories. Others have as well.

Your bashing the findings of Kelin are unfounded. You are denying that others, such as myself, have found necessary improvements to your experiments before any conclusions can be made. You appear to forge on ignoring those flaws with obviously premature findings. Are your findings interesting, yes. Your conclusions, no. Your attempt to experiment more in the area of your conclusions, good idea. I predict you may learn from them, and why I and others talk the theory we talk. You aren't the first to try. Good luck. Please carry on. I'm really trying to be on your side and out for truth, we just disagree.

Pressurising the chamber both changes the temperature and pressure. That will show up on a PV diagram. A PV diagram is based on measuring Pressure and Volume. Of course that can lead to enough condensation to be visible. It puts work in. And allows work out. The two are reversible and equal and opposite. Zero work out per cycle. Adiabatic bounce.

I put in the Carnot Theorem to show that it also is consistent with zero work out. I proved it with the zero area on the PV diagram. It would be just a straight horizontal line under the pressure dome. No area. The Carnot Theorem also agrees.

Now if you squeeze it raising the temperature and pressure. Add heat to vaporizer condensed steam. Allow it to expand. Add heat during expansion if you want. Remove heat. Compress it, removing heat if you want. Back to the beginning. You will get more work out than you put in. Of course, since you are squeezing with your hand, temperature and pressure changes will be very little. Consequently it will have very low efficiency and power output.

A heat pump agrees with the Carnot Theorem.
n=(Qh-Qc)/Qh = (Th-Tc)/Th Engine

COP=Qh/(Qh-Qc) = Th/(Th-Tc) Heat Pump

Once you realize the heat coming out of a heat pump, going into a heat engine, can produce 100% return of the work, it becomes obvious what is happening.

Your Kelvin, Carnot, and Thermodynamics bashing is wasting your time and mine, and dragging others down with us. I would rather read about your material investigation, as you would probably like to read mine.

Go ahead and bash away. I've been very patient with this. Sorry if I haven't Explained it well enough. You have been patient too. Thanks.

Fool wrote: ↑Tue Mar 19, 2024 8:18 am Now you are denying the reality of life. The PV diagram has nothing to do with Kelvin or Caloric Theory. It is merely a graph of pressure with respect to volume. It is a graph of real world measurable properties.

In the majority of cases, PV diagrams are "ideal", hypothetical modeling, but aside from that, even a "real" PV reading is, IMO potentially misleading, as heat input would, under "normal" circumstances result in an increase in pressure and temperature.

While there is shaft work output happening simultaneously, however, there is energy leaving the system simultaneously. This would result in a simultaneous reduction in pressure and temperature.

I've previously given the illustration of an overflowing bathtub. You have input and output, but are measuring water level. The water level appears to be, and actually is constant. A measure of the water level is not an accurate representation of the actual input and output. Similarly, a static representation of pressure, volume and temperature does not fully represent the energy input and output. The levels appear more or less static, because there is input and output going on simultaneously.

....

Your Kelvin, Carnot, and Thermodynamics bashing is wasting your time and mine, and dragging others down with us. I would rather read about your material investigation, as you would probably like to read mine.

Go ahead and bash away. I've been very patient with this. Sorry if I haven't Explained it well enough. You have been patient too. Thanks.

Again, I'm not "bashing" anybody.

That Kelvin perpetuated Caloric theory as THE foundation of "all" thermodynamics is inescapable. He says so plainly, in his own words. He KNEW, and stated plainly in his writing that the evidence against Caloric theory was mounting, but regardless, it seemed to produce results.

He even states that someday the entire science of heat will need to be reconstructed on some new foundation, but, he chose to leave that for future generations.

Pointing out such facts as these is not "bashing", it's a necessary look at reality and the current state of affairs. Thermodynamics is a patchwork at best. It has been repaired and reinterpreted so many times it's mind boggling. There are dozens of versions of "the second law" alone. Some of which are actually contradictory or downright contrary to observable reality.

Characterizing such statements or observations as "bashing" is itself an unjustified attack on MY character and motives.

Do we at least agree, without reservation that SOME heat is converted to work (mechanical motion) in a heat engine?

Then even an engine that has purely adiabatic expansion and contraction is excuting some mechanical motion not represented as work on the PV diagram.

Let's take a single increment of expansion work. Do you agree that pressure increases with heat input?

Do you also agree that work out results in a lowering of internal energy?

Does a lowering of internal energy result in a lower temperature?

Does a lower temperature result in a lower pressure?

If yes, then for each incremental change that includes simultaneous heat input and work output the pressure on the PV diagram would only represent the mean pressure. Pressure increase due to heat input minus pressure reduction due to work output.

The ACTUAL work output is, at best, underrepresented.

A PV diagram, having originated with Kelvin, who based his methods, by his own account, on Caloric theory, does not recognize the actual CONVERSION of heat into work.