Experiment: Can an externally heated object actually heat its heat source?

The Watercooler
1

I realize I really don’t know how the physical world actually behaves in terms of how heat works!

Particularly re Point 11 in Richard’s article: “In the physical world no externally heated substance can raise the temperature of its heat-source.”

Even though the result of this experiment won’t affect the validity of the article as a whole (as the other 11 points would still remain, namely the Earth is not flat, not black, not irradiated by 1/4th the rays, etc…), I like to be thorough and I also want to actually know how the world behaves.

So I devised a little experiment to actually see what happens… it involves the following equipment which will arrive Tuesday (total cost under 150 EUR):

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It consists of the following setup:

  • Induction Skillet: a 22cm (16.3cm base) skillet that works on an induction plate
  • Induction Plate: This can be set to generate a constant 200W of power into the skillet
  • Glass Cover: to fit snugly over the skillet
  • Aluminum Foil: which is said to reflect ~95% infrared light[1]

The experiment consists of 4 steps:

  1. Baseline: let everything sit out and get to room temperature. Measure the temperature of everything with the IR thermometer, should all be the same (e.g. ~20°C).
  2. Open: Put the skillet on the induction plate, uncovered. Turn it on to 200W. Let it sit until temperature equilibrium is reached. Measure the temperature of the skillet (the top of the base, the inside side, and the outside side, to get a good idea of how the heat distributing)
  3. Covered: Start as with “Open”. Once equilibrium reached, place the bare glass cover on it (no foil). Let everything reach equilbrium again. Measure temperature of the glass top and bottom, and the skillet.
  4. Foiled: Layer the bottom of the glass cover with aluminum foil. Repeat same steps as in “Covered”.
  5. Gassed: covered or foiled but adding CO2 gas in it with vinegar and baking soda!

The question is: how will the temperature of the base of the skillet compare between 2, 3, and 4?

With some rough math using the Stefan-Boltzmann Law and assuming room temperature of 20°C, and that the skillet is 5cm tall, and that it emits radiation across one side of the base and both sides of the sides (inside and outside), I figure that on the “Open” setup it should reach ~151°C. This can be wildly off, but we shall see.

Then…

Hypothesis 1: If you follow the same reasoning as with the “greenhouse gases” warming up the planet above what it otherwise would be, then when you cover it, the glass lid will heat up. Now the glass lid will itself emit infrared radiation back down to the skillet. Now the skillet is receiving more radiation than it otherwise would be. Rough calculation is it should get to ~192°C instead, with the glass being around the same temperature (somehow I got ~207°C for the glass, which seems wrong, but it’s enough to get a rough idea).

Then when you cover the bottom of the glass with foil, now it should be reflecting 95% of the radiation back, instead of just absorbing and basically emitting 50%, so the skillet should get much, much hotter. It should get to at least 255°C and maybe a lot more – I didn’t fully do all the math but it’s enough to get an idea. Meanwhile the glass itself should stay at the same temperature as without being covered since it’s absorbing less of it.

Hypothesis 2: Following the immediate common sense logic of how the world behaves, the glass cover, since it’s being heated by the skillet, won’t end up heating the skillet more than it started at. The glass will get to at most the same temperature as in the “Open” scenario (~151°C), while the skillet temp will be unchanged. The addition of the foil likewise won’t change anything (except maybe the glass will not get as hot since it absorbing less).

Hypothesis 3: “Covered” will lose less heat to convection so surface will be a bit hotter than otherwise. “Foiled” won’t increase temp much or at all since that effect already will be saturated by then.

Possible Problems/Issues/Thoughts:

  • I will have to take the glass lid off to measure the skillet temp. But if the skillet does really get hotter it should remain at the higher temp long enough to get a good reading (~0.5s according to the IR thermometer specs).

  • The predicted temp ranges might be wildly off with the math, but I calculate it should be different enough (at least ~50°C between each setup) that a difference should be noticeable. And they are all within the IR thermometer’s range (-50°C to 600°C)

  • The actual heat source isn’t the skillet base per se, but the coils inside the skillet, that the induction plate passes a current through to heat up. It is possible these coils themselves are hotter than the skillet gets to in the initial “Open” set up. In fact according to the Stefan-Boltzmann equation math, if their surface area is smaller then they have to be (lower surface area means higher W/m^2 and thus higher temperature). But as they are coils vs a solid surface their surface area may be greater…

    In any case in this case the skillet base will get hotter when “Covered” and “Foiled”, and this could invalidate the experiment as I’m not sure if I could measure the temp of the coils themselves vs. the skillet. Any thoughts??

Curious to see the result. What do you guys think will happen? Anyone see issues with the experimental setup?

  1. “The surface of aluminum has the ability NOT TO ABSORB, but TO REFLECT 95% of the infrared rays which strike it. Since aluminum foil has such a low mass to air ratio, very little conduction can take place, particularly when only 5% of the rays are absorbed.” (source) ↩︎

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@claudiu , dude, you are my hero!

I have been holding back from buying an IR sensor and setting up my own makeshift lab over this topic!

I will read it again, and comment.

3

From my accumulated knowledge, the issue of insulation is the “thermal gradient curve”.

Not sure if that is the correct way of saying it.

Basically, it’s absolutely true that one can’t make the heat source hotter by reflecting it’s own heat back into it but one can maintain the surface at its maximum temperature, by moving the “thermal gradient” outside of it.

Which is what we do when we put on a jumper (sweater). Our own body reacts with goose bumps and the hairs stand on end, and the blood restriction in the skin starts to happen; the body is attempting to create a “gradient” bigger than it’s physical size on one hand, and moving the gradient away from the surface of the skin on the other.

Basically, to loose heat, it has to make it to the surface of the body. Homeostasis responds in both directions; put on more clothes/raise the hairs to trap air; move the gradient further into the body so that the outer layers act as insulation.

My fantasy of buying an IR detector was to go out into the back yard and take some measurements of the sand/dirt and my own “blackbody” (a painted piece of steel), and feed it all into MATLAB/python and see if I could build the virtual model of the bare planet which is so glaring absent from the Climatology propaganda.

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(90% pass in year 12 human biology without studying; it’s easy when one is the very thing in question)

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For ref the one I’m getting on Amazon is like 20EUR. Less than the few hundred you were thinking ! It may be crap but it says it’s within 0.2C accuracy which is enough for this …

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So Richard’s point is absolutely correct. It’s impossible to raise the temperature of the heat source by reflecting it’s own heat back into it.

Of course, in the case of the earth, we have the curious situation where the primary heat source is the sun.

Which is why the first points that Richard makes are so crucial; there is a gaping hole in the burden of proof. My comments on it being a “very long pole” is that the audacity of the leap from basically small scale “blackbody” experiments, to an entire planet is utterly absurd.

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Yeah, I was looking them up, trying to understand if the cheap ones were worth it.

The " science" of the detectors is another kettle of fish.

I was looking up how they worked, and was less than impressed by the details.

I don’t think any meaningful results will come from the budget ones.

I was so close, to actually switching on the laptop and going to work on a virtual globe, sans atmosphere etc. Well, not that close, I was too busy enjoying the combined happiness of seeing what Richard and yourself were pointing to with the whole topic, and also really “completing a circle” in my other ongoing investigation into rebellion, that it wasn’t that appealing.

Appart from the vague fantasy of a Nobell Prize, I am happy to be looking at the clouds with fresh eyes.

8

So you predict that the temperature of the skillet will not get hotter with the addition of cover and cover with foil?

9

Correct. It will reach it’s maximum temperature, and no more.

The surface will be at maximum temperature, given the lid and foil.

Which is why we use lids and foil.

10

If it was able to reach a higher temperature, then we just created “free energy”.

11

The issue with the whole “greenhouse” thingy, is the starting temperature.

If, the starting temperature is -18c, then indeed we have a very remarkable atmosphere and ocean system. It’s doing a fine job of providing 33c.

If we have a starting point of 5c (to pick a number) we have a otherwise also awesome atmosphere/oceans, but they are WAY less important to the overall energy balance.

The way I see it right now is the models are having all sorts of problems because the starting temperature is potentially wrong.

12

To your point of spending money on this; I found a guy who did his thesis on modelling exoplanets.

He created an entire python library for it.

Being the “knows enough to be dangerous” kind of computerfile, I was thinking of engaging his services to create the missing model.

The only reference I could find to someone actually modelling a “bare earth” sans atmosphere et al, was a reference to Dennis Hartmann in a 1994 book “Global Physical Climatology” chapter 8, where according to chatGPT, he claimed to have confirmed the -18c in a computer model.

I had a go at trying to get the pdf, but you know how that goes.

I still object to it however. Chapter 8? For crying out loud! When pressed, chatGPT couldn’t quote it, and otherwise said it was using Stefan-Blotzmann equations afterall.

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A post was merged into an existing topic: Global warming/climate change

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Hi @lexej ,

Welcome to the Forum!

It sounds like you know a thing or two on the subject. That’s indeed welcome.

These posts will probably be moved to another thread, but I am sure no one is going to object to your input.

What do you make of the Stefan-Blotzmann (modified) equation being used to model the entire planet, when it seems reasonable to me that an simulation could be run (in this age of beyond “super-computers”)?

I find it bizarre, after a week of fruitless searches, that I don’t see anything close to a simulation of this basic assumption of the greenhouse model.

Are you aware of anyone who has modelled the earth, with all it’s quite well known properties, to confirm the starting temperature of -18C?

Genuine enquiry here. I am all of a week or so old on actually looking into any of this.

15

Hmm it’s not quite the question.

Say without lid and without foil the surface temperature is T1.

With lid without foil: T2

With lid and foil: T3

Is T1 = T2 = T3? Or is T2 > T1 and T3 > T2?

16

Hmm the point of point 11 is that if the temperature without atmosphere would be -18C, then adding an atmosphere would not be able to raise this temperature because then the externally heated object (the atmosphere) would be increasing the temperature of its heat source (the -18C surface).

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Hi @lexej and welcome.

I pose the same question to you (Experiment: Can an externally heated object actually heat its heat source? - #15 by claudiu): what do you predict will be the result of this hot plate / glass dome / foil experiment?

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It depends on the input energy.

T1: let’s say it to 150f. (No idea what that means, I have little experience converting from “bald eagles”).

T1 is going to be that temperature given that the thermal curve is outside the surface. That is, the maximum temperature is maintained at the surface because the input energy in this case is ensuring it is so.

The thermal gradient is outside the surface.

In the case of a skillet, how much energy is required will depend on the efficiency of the entire system.

What will happen at T2, is the input energy required to maintain 150 bald eagles, at the surface, will be less because we compressed the thermal gradient. We put a sweater on the pan.

At T3, we brought in the reflected IR, and made the system even more efficient. The input energy is now not only being insulated, but “bounced around” and recycled.

At no point though will the surface temperature rise above the input energy.

This of course means that it’s going to be the efficiency of the system which determines the surface temperature.

If it’s really struggling to maintain it’s 150 BE, without a lid or foil, then we may see an increase in T2, and T3 for the same input energy. If we observe an increased surface temperature, it’s because we created a more efficient system. At no point did the surface temperature become more than it’s possible input energy potential.

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A post was merged into an existing topic: Global warming/climate change

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200 watts :slight_smile:

The input energy will be the same in all 3 scenarios.

So the answer is either it will or it won’t increase? That is not very definitive :sweat_smile:

Basically I am asking for your (and mine and everyone’s) predictions up front, before I do the experiment. That way it will actually demonstrate something and we can learn something.

Otherwise we will just rationalize away whatever the result is and make back-explanations to fill it in.

So… what do you think will happen? :slight_smile:

EDIT: Just realized from the glass jar link that I should do a “Covered” and “Foiled” baseline too where I leave them covered without the input energy on. To control for any effect not related to the induction heating … I will do it in garage anyway away from sunlight.