Slaying the 'Slayers' with Watts – part 2

Light Bulb Back Radiation Experiment

Guest essay by Curt Wilson

In the climate blogosphere, there have been several posts recently on the basic principles of radiative physics and how they relate to heat transfer. (see yesterday’s experiment by Anthony here) These have spawned incredibly lengthy streams of arguments in the comments between those who subscribe to the mainstream, or textbook view of radiative heat transfer, and those, notably the “Skydragon Slayers” who reject this view.

A typical statement from a Slayer is that if “you have initially a body kept at a certain temperature by its internal source of energy”, that if another body at a lower temperature is placed near to it, that the radiation from this colder body could not increase the temperature of the warmer body, this being a violation of the 2nd Law of Thermodynamics. They continue that if this were possible, both objects would continually increase the other’s temperature indefinitely, which would be an obvious violation of the 1st Law of Thermodynamics (energy conservation).

This is part of a more general claim by Slayers that radiation from a colder body cannot transfer any energy to a warm body and lead to a higher temperature of the warm body than would be the case without the presence of the colder body.

It occurred to me that these claims were amenable to simple laboratory experiments that I had the resources to perform. A light bulb is a classic example of a body with an internal source of energy. Several Slayers specifically used the example of reflection back to a light bulb as such an example.

In our laboratory, we often have to do thermal testing of our electronic products so we can ensure their reliability. Particularly when it comes to power electronics, we must consider the conductive, convective, and radiative heat transfer mechanisms by which heat can be removed from these bodies with an “internal source of energy”. We have invested in good thermocouple measurement devices, regularly calibrated by a professional service, to make the temperature measurements we need.

We often use banks of light bulbs as resistive loads in the testing of our power electronics, because it is a simple and inexpensive means to load the system and dissipate the power, and it is immediately obvious in at least a qualitative sense from looking at the bulbs whether they are dissipating power. So our lab bench already had these ready.

If you want to isolate the radiative effects, the ideal setup would be to perform experiments in a vacuum to eliminate the conductive/convective losses. However, the next best thing is to reduce and control these to keep them as much alike as possible in the different phases of the experiment.

So, on to the experiment. This first picture shows a standard 40-watt incandescent light bulb without power applied. The lead of the thermocouple measuring device is taped to the glass surface of the bulb with heat-resistant tape made for this purpose. The meter registers 23.2C. In addition, a professional-grade infrared thermometer is aimed at the bulb, showing a temperature of 72F. (I could not get it to change the units of the display to Celsius.) Note that throughout the experiment, the thermocouple measurements are the key ones.

clip_image002

Next, the standard North American voltage of 120 volts AC (measured as 120.2V) was applied to the bulb, which was standing in free air on a table top. The system was allowed to come to a new thermal equilibrium. At this new equilibrium, the thermocouple registered 93.5C. (The IR thermometer showed a somewhat lower 177F, but remember that its reported temperature makes assumptions about the emissivity of the object.)

clip_image004

Next, a clear cubic glass container about 150mm (6”) on a side, initially at the room temperature of 23 C, was placed over the bulb, and once again the system was allowed to reach a new thermal equilibrium. In this state, the thermocouple on the temperature of the bulb registers 105.5C, and the outer surface of the glass container registers 37.0C (equivalent to body temperature).

The glass container permits the large majority of the radiative energy to escape, both in the visible portion of the spectrum (obviously) and in the near infrared, as standard glass is highly transparent to wavelengths as long as 2500 nanometers (2.5 microns). However, it does inhibit the direct free convection losses, as air heated by the bulb can only rise as far as the top of the glass container. From there, it must conductively transfer to the glass, where it is conducted through the thickness of the glass, and the outside surface of the glass can transfer heat to the outside ambient atmosphere, where it can be convected away.

clip_image006

The next step in the experiment was to wrap an aluminum foil shell around the glass container. This shell would not permit any of the radiative energy from the bulb to pass through, and would reflect the large majority of that energy back to the inside. Once again the system was allowed to reach thermal equilibrium. In this new state, the thermocouple on the surface of the bulb registered 137.7C, and the thermocouple on the outer surface of the glass registered 69.6C. The infrared thermometer is not of much use here due to the very low emissivity (aka high reflectivity) of the foil. Interestingly, it did show higher temperatures when focused on the tape on the outside of the foil than on the foil itself.

clip_image008

Since adding the foil shell outside the glass container could be reducing the conductive/convective losses as well as the radiative losses, the shell was removed and the system with the glass container only was allowed to re-equilibrate at the conditions of the previous step. Then the glass container was quickly removed and the foil shell put in its place. After waiting for thermal equilibrium, the thermocouple on the surface of the bulb registered 148.2C and the thermocouple on the outside of the foil registered 46.5C. The transient response (not shown) was very interesting: the temperature increase of the bulb was much faster in this case than in the case of adding the foil shell to the outside of the glass container. Note also how low the infrared thermometer reads (84F = 29C) on the low-emissivity foil.

clip_image010

Further variations were then tried. A foil shell was placed inside the same glass container and the system allowed to reach equilibrium. The thermocouple on the surface of the bulb registered 177.3C, the thermocouple on the outer surface of the foil registered 67.6C, and the infrared thermometer reading the outside of the glass (which has high emissivity to the wavelengths of ambient thermal radiation) reads 105F (40.6C).

clip_image012

Then the glass container was removed from over the foil shell and the system permitted to reach equilibrium again. The thermocouple on the surface of the bulb registered 176.3C and the thermocouple on the outside of the foil registered 50.3C.

clip_image014

All of the above examples used the reflected shortwave radiation from the aluminum foil. What about absorbed and re-emitted longwave radiation? To test this, a shell of black-anodized aluminum plate, 1.5mm thick, was made, of the same size as the smaller foil shell. A black-anodized surface has almost unity absorption and emissivity, both in the shortwave (visible and near infrared) and longwave (far infrared). Placing this over the bulb (without the glass container), at equilibrium, the thermocouple on the bulb registered 129.1C and the thermocouple on the outside of the black shell registered 47.0C. The infrared thermometer read 122F (50C) on the tape on the outside of the shell.

clip_image016

The power source for this experiment was the electrical input. The wall voltage from the electrical grid was steady at 120.2 volts. The electrical current was measured under several conditions with a professional-grade clip-on current sensor. With the bulb in open air and a surface temperature of 96.0C, the bulb used 289.4 milli-amperes of current.

clip_image018

With the bulb covered by a foil shell alone and a surface temperature of 158.6C, the bulb drew slightly less, 288.7 milliamperes.

clip_image020

Summary of Results

The following table shows the temperatures at equilibrium for each of the test conditions:

Condition Bulb Surface Temperature Shell Temperature
Bulb open to room ambient 95C
Bulb covered by glass container alone 105C 37C
Bulb covered by glass container and outer reflective foil shell 138C 70C (glass)
Bulb covered by outer reflective foil shell alone 148C 46C (foil)
Bulb covered by inner reflective foil shell inside glass container 177C 68C (foil)
Bulb covered by inner reflective foil shell alone 176C 50C
Bulb covered by black-anodized aluminum shell alone 129C 47C

Analysis

Having multiple configurations permits us to make interesting and informative comparisons. In all cases, there is about a 35-watt (120V x 0.289A) electrical input to the system, and thermal equilibrium is reached when the system is dissipating 35 watts to the room as well.

I used a low-wattage (40W nominal) bulb because I had high confidence that it could take significant temperature increases without failure, as it has the same package design as much higher-wattage bulbs. Also, I would not be working with contraband high-wattage devices 😉

The case with the glass container alone is the important reference case. The glass lets virtually all of the radiant energy through, while inhibiting direct convection to the room ambient temperature of 23C. Conductive/convective losses must pass from the surface of the bulb, through the air under the container, to and through the glass, and then to the room atmosphere, where it is conducted/convected away. Under these conditions, the bulb surface temperature is 105C, which is 10C greater than when the bulb can conductively dissipate heat directly to the room atmosphere.

Compare this case to the case of the larger foil shell alone. The foil shell also inhibits direct conductive/convective losses to the room atmosphere, but it will not inhibit them to any greater extent. In fact, there are three reasons why it will inhibit these losses less than the glass container will. First, the material thermal conductivity of aluminum metal is far higher than that of glass, over 200 times greater (>200 W/(m*K) versus <1.0 W/(m*K)). Second, the foil, which is a small fraction of a millimeter thick, is far thinner than the glass container, which is about 4 mm thick on average. And third, the surface area of the foil is somewhat larger than the glass container, so it has more ability to conductively transfer heat to the outside air.

And yet, the surface of the bulb equilibrated at 146C under these conditions, over 40C hotter than with the glass container. With conductive/convective losses no less than with the glass container, and very probably greater, the only explanation for the higher temperature can be a difference in the radiative transfer. The glass container lets the large majority of the radiation from the bulb through, and the foil lets virtually none of it through, reflecting it back toward the bulb. The presence of the foil, which started at the room ambient of 23C and equilibrated at 46C, increased the temperature of the bulb, which started at 105C on the outside (and obviously warmer inside). The reflected radiation increased the temperature of the bulb, but did not produce “endless warming”, instead simply until the other losses that increase with temperature matched the input power of 35 watts.

Interestingly, the foil shell without the glass container inside led to a higher bulb temperature (148C) than the foil shell with the glass container inside (138C). Two layers of material around the bulb must reduce conductive/convective losses more than only one of them would, so the higher temperature must result from significantly more reflected radiation back to the bulb. With the glass inside, the reflected radiation must pass through two surfaces of the glass on the way back to the bulb, neither of which passes 100% through.

Another interesting comparison is the large foil shell that could fit outside of the glass container, about 160mm on a side, with the small foil shell that could fit inside the glass container, about 140mm on a side. With the large shell alone, the bulb temperature steadied at 148C; with the smaller shell, it steadied at 176C. With all direct radiative losses suppressed in both cases, the difference must come from the reduced surface area of the smaller shell, which lessens its conductive/convective transfer to the outside air at a given temperature difference. This is why halogen incandescent light bulbs, which are designed to run hotter than standard incandescent bulbs, are so much smaller for the same power level – they need to reduce conductive/convective losses to get the higher temperatures.

All of the above-discussed setups used directly reflected radiation from the aluminum foil. What happens when there is a barrier that absorbs this “shortwave” radiation and re-emits it as “longwave” radiation in the far infrared? Can this lead to higher temperatures of the warmer body? I could test this using black-anodized aluminum plate. Black anodizing a metal surface makes it very close to the perfect “blackbody” in the visible, near-infrared, and far-infrared ranges, with absorptivity/emissivity (which are the same at any given wavelength) around 97-98% in all of these ranges.

With a black plate shell of the same size as the smaller foil shell, the bulb surface temperature equilibrated at 129C, 24C hotter than with the glass container alone. Once again, the thin metal shell would inhibit conductive/convective losses no better, and likely worse than the glass container (because of higher material conductivity and lower thickness), so the difference must be from the radiative exchange. The presence of the shell, which started at the room ambient of 23C and increased to 47C, caused the bulb surface temperature to increase from 105C to 129C.

Another interesting comparison is that of the smaller foil shell, which led to a bulb surface temperature of 176C and a shell temperature of 50C, to the black plate shell of the same size, which led to a bulb surface temperature of 129C and a shell temperature of 46C. While both of these create significantly higher bulb temperatures than the glass container, the reflective foil leads to a bulb surface temperature almost 50C higher than the black plate does. Why is this?

Consider the outside surface of the shell. The foil, which is an almost perfect reflector, has virtually zero radiative absorptivity, and therefore virtually zero radiative emissivity. So it can only transfer heat to the external room by conduction to the air, and subsequent convection away. The black plate, on the other hand, is virtually the perfect absorber and therefore radiator, so it can dissipate a lot of power to the room radiatively as well as conductively/convectively. Remember that, since it is radiating as a function of its own temperature, it will be radiating essentially equally from both sides, there being almost no temperature difference across the thickness of the plate. (Many faulty analyses miss this.) The foil simply reflects the bulb’s radiation back to the inside and radiates almost nothing to the outside. This is why the infrared thermometer does not read the temperature of the foil well.

The electrical voltage and current measurements were made to confirm that the increased temperature did not come from a higher electrical power input. The current measurements shown above demonstrate that the current draw of the bulb was no higher when the bulb temperature was higher, and was in fact slightly lower. This is to be expected, since the resistivity of the tungsten in the filament, as with any metal, increases with temperature. If you measure the resistance of an incandescent bulb at room temperature, this resistance is less than 10% of the resistance at its operating temperature. In this case, the “cold” resistance of the bulb is about 30 ohms, and the operating resistance is about 415 ohms.

Let’s look at the dynamic case, starting with the thermal equilibrium under the glass container alone. 35 watts are coming into the bulb from the electrical system, and 35 watts are leaving the bulb through conductive losses to the air and radiative losses to the room through the glass. Now we replace the glass with one of the metal shells. Conductive losses are not decreased (and may well be increased). But now the bulb is receiving radiant power from the metal shell, whether reflected in one case, or absorbed and re-radiated back at longer wavelengths in the other. Now the power into the bulb exceeds the power out, so the temperature starts to increase. (If you want to think in terms of net radiative exchange between the bulb and the shell, this net radiative output from the bulb decreases, and you get the same power imbalance.)

As the temperature of the bulb increases, both the conductive losses to the air at the surface of the bulb increase (approximately proportional to the temperature increase) and the radiative losses increase as well (approximately proportional to the 4th power of the temperature increase). Eventually, these losses increase to where the losses once again match the input power, and a new, higher-temperature thermal equilibrium is reached.

I originally did these tests employing a cylindrical glass container 150mm in diameter and 150mm high with and without foil shells, and got comparable results. In the second round shown here, I changed to a cubic container, so I could also create a black-plate shell of the same shape.

It is certainly possible that improvements to these experiments could result in differences of 1 or 2C in the results, but I don’t see any way that they could wipe out the gross effect of the warming from the “back radiation”, which are several tens of degrees C.

All of these results are completely in line with the principles taught in undergraduate engineering thermodynamics and heat transfer courses. The idea that you could inhibit net thermal losses from an object with an internal power source, whether by conductive, convective, or radiative means, without increasing the temperature of that object, would be considered ludicrous in any of these courses. As the engineers and physicists in my group came by the lab bench to see what I was up to, not a single one thought for a moment that this back radiation would not increase the temperature of the bulb.

Generations of engineers have been taught in these principles of thermal analysis, and have gone on to design crucial devices and infrastructure using these principles. If you think all of this is fundamentally wrong, you should not be spending your time arguing on blogs; you should be out doing whatever it takes to shut down all of the erroneously designed, and therefore dangerous, industrial systems that use high temperatures.

Conclusions

This experiment permitted the examination of various radiative transfer setups while controlling for conductive/convective losses from the bulb. While conductive/convective losses were not eliminated, they were at least as great, and probably greater, in the cases where a metal shell replaced the glass shell over the bulb.

Yet the bulb surface temperature was significantly higher with each of the metal shells than with the glass shell. The only explanation can therefore be the radiative transfer from the shells back to the bulb. In both cases, the shells were significantly cooler than the bulb throughout the entire experiment, both in the transient and equilibrium conditions.

We therefore have solid experimental evidence that radiation from a cooler object (the shell) can increase the temperature of a warmer object (the bulb) with other possible effects well controlled for. This is true both for reflected radiation of the same wavelengths the warmer body emitted, and for absorbed and re-radiated emissions of longer wavelengths. The temperature effects are so large that they cannot be explained by minor setup effects.

Electrical measurements were made to confirm that there was not increased electrical power into the bulb when it was at higher temperatures. In fact, the electrical power input was slightly reduced at higher temperatures.

This experiment is therefore compatible with the standard radiative physics paradigm that warmer and cooler bodies can exchange radiative power (but the warmer body will always transfer more power to the cooler body). It is not compatible with the idea that cooler bodies cannot transfer any power by radiative means to warmer bodies and cause an increase in temperature of the warmer body.

=====================================

UPDATE: The Principia/Slayers group has post a hilarious rebuttal here:

http://principia-scientific.org/supportnews/latest-news/210-why-did-anthony-watts-pull-a-bait-and-switch.html

Per my suggestion, they have also enabled comments. You can go discuss it all there. – Anthony

Advertisements

  Subscribe  
newest oldest most voted
Notify of

This experiment makes the same mistakes than Anthony made in Part 1. It actually makes worse mistakes. Keep an eye at PSI, or possibly here if we are allowed to post a link/reply, for the analysis.
REPLY: Then point out the ‘mistakes’, or please do shut the hell up on this thread.
Principia might get a link here if they open up the web site to comments with the article, so people can go there and point out the ‘pink unicorns’ blocking the back radiation. Something tells me that O’Sullivan doesn’t have the integrity to allow that, though. – Anthony

Julian Flood

A neat illustration of the process is to use two hyperbolic reflectors, placed facing each other. At the focus of the first we place a thermoneter and at the second a cup of boiling water. The thermometer will show an increase in temperature as the heat from the water is focussed on it. Now remove the water and a new temperature, room temperature will show.
Now is the clever bit. Put a block of ice at the second focus. The temperature indicated by the thermometer will fall.
So, we’ve focussed the cold? No, all we have done is alter the state of equilibrium of the thermometer: essentially we have demonstated that the thermometer is recording its state of balance with the environment around it, and that the balance alters when we alter the environment.
I still like the ‘focussing the cold’ idea though, the stuff of fifties SF. Even Campbell might have fallen for that.
JF

Of course, I’ll point out again that these table-top experiments, beside being wrongly interpreted etc, are beside the point of our empirical real-world data which has already proven that there is no GHE.
REPLY: So, let me get this straight.
1. Principia/Slayers cites a table top experiment in your essay.
2. Two people (soon to be 3) replicate the experiment in different ways, showing the Principia tabletop experiment is flawed, and the premise you state is ridiculous, as is clear by the data.
3. Slayers go on record in comments saying “we don’t need to replicate the experiment”.
4. Ignoring the fact that you’ve never done the experiment in the first place, you say others have misinterpreted it.
5. Slayers specifically in comments claim absurd easily disprovable things, such as passive element microbolomters emit a signal and temperature is measured by the “shift” in the returned signal
Remote read IR thermometers are also used to ‘explain’ this back-radiation warming effect. These instruments work be sending out an IR signal and measuring the shift in the returned signal.
…and when shown to be wrong, slayers refuse to admit you’ve confused the laser aiming with the sensing system.
6. You state the table top experiment you promoted has errors, but refuse to divulge what the supposed errors are.
7. You plan a rebuttal on a website that doesn’t allow open comments to the article, while asking me to carry your rebuttal.
Do you listen to yourselves when you say these things and take these positions? Do you realize that you’ve made a fool of yourself and killed any scrap of integrity you had with these claims?
I think the Ron House pink Unicorn analogy to describe your membership is right on:

We have here a really strange phenomenon: a truly fantastic claim (that our understanding of radiation is dramatically wrong) is being put forward, without any evidence, as the reason why our understanding of something derivative (namely the greenhouse effect) is mistaken. Surely it is obvious why that is so very perverse a process? It differs in no substantive way from, for example, claiming that powered flight is impossible because invisible pink unicorns block the takeoff of aircraft.

-Anthony

richard

not sure if this makes sense. jut thinking how one body can cause the other to heat up.
how does it work with a fridge, two bodies of air , the outside and the inside- both the same temp. the only way to get the heat from the air inside to the outside is to switch the heat pump on.

LamontT

Joseph you again claim that the experiment makes critical errors but you don’t explain what the errors are. Nor do you do your own experiment demonstrating the correct way and I might add proving your point all in one neat and easy experiment. Or is it that you can’t craft an experiment that would prove your point?

Offhand, I’d say the experiment makes an invalid claim : that the foil is a cooler body radiating anything. Clearly the foil is not the source of the radiation being reflected, nor could any foil body at its claimed temperature radiate any such powerful heat radiation. Explanation please.

[ snip – if you want to point out errors, do so now. No other discussion from you is of any value at this point – Anthony]

JeffC

I am curious about the assumption that an object at a higher energy state (the light bulb) can absorb the energy being radiated by the objects at a lower energy state (the air and the glass) ? are you sure it can actually absorb the radiated energy ? I don’t see how you measure this ? I can think of several mechanisms that would slow the dissipation of the energy of the bulb that have nothing to do with the bulb actually absorbing energy … any slowing of the energy dissipation would raise the temperature of the bulb …
Plus you aren’t using 2 similar objects like 2 light bulbs side by side … you have the bulb and a 360 degree enclosure around that bulb … not exactly a hot and cold object assuming that by object you mean similar items …

intrepid_wanders

Awesome experiment Curt! While this experiment is quite satisfactory for the majority of us, a compliant that the ‘slayers’ will have is the convection was included. If you have the time, you can do a quick check by sampling 2-3 enclosed elements (glass, glass foil and foil), but just flip the enclosure to allow the the convection to escape and just have the radiative effects.
I know, nothing will satisfy the ‘slayers’, but the silly lightbulb-mirror figure is an open convection system…

The Temperature of the Filament is the only temperature that matters here. Did the Filament warm from back-radiation? Did heat actually “flow uphill?”
Did you measure the temperature of the filament? Could you, please, and end this ludicrous “debate?” You only mention the current twice. If the filament warmed its resistance would increase, and with a constant voltage the current would drop a little. A direct measurement of filament temperature would be better but obviously difficult to achieve.
“In all cases, there is about a 35-watt (120V x 0.289A) electrical input to the system” OK, I answered my own question, the filament did NOT warm, and the Second Law reigns supreme as always!!!

wsbriggs

Well done!
Just like the other group of D*ists, the music is on and the tap dancing starts. Unspecified mistakes, uncommentable blogs (I won’t say unspeakable), and no real science just arguments from “theory.”
In the meantime it appears to me that a number of recent papers UofH among others, show someone is paying attention to Bob T. and Willis E. and trying to at least explain (I caught myself using ex-pain) the observations. It’s still modeling all the way down, but at least other phenomena are being considered.
OT but pertinent to “consensus” science, there has be a major breakthrough in understanding part of how viruses are attacked by the body. A theory, roundly poo pooed by “experts,” has been found to describe a completely new mechanism of viral identification and destruction – can you say TRIM21, I knew you could.
http://online.wsj.com/article/SB10001424127887323582904578489743949572994.html
Hey, that science was settled too. Sheesh!

Nylo

Absolutely flawless and very well explained. JEP’s response is typical of a troll.

Bill Marsh

@jeffC,
1) There is no requirement that the objects be ‘similar’ for the experiment to work
2) The Aluminum foil is an ‘object’ just as the light bulb is an ‘object’.
3) Please elucidate on the several mechanisms you believe would slow the dissipation of the energy
4) I think you’re mixing energy absorption and temperature, they aren’t the same thing.

Darren Potter

Joseph E Postma says: “It actually makes worse mistakes. Keep an eye at PSI”
That is all you got “makes worse mistakes”, and you want people to hang around PSI waiting on PSI to fabricate some response?
Joseph E Postma says: “This experiment makes the same mistakes …”
Yes, both experiments made mistake of assuming each would be considered by people with enough forethought to know they lacked basic scientific knowledge to comment on experiments.

OldWeirdHarold

Thus proving what Max Planck knew over 100 years ago.

Thanks for taking the trouble Curt. Now sit back and be amazed/amused/frustrated by the misinterpretations which will shower down on your demonstration.

Nylo

Michael Moon, “The Temperature of the Filament is the only temperature that matters here”
Obviously, both the Earth and the bulb glass surface have a constant source of energy which allow their temperature to be constant despite radiative losses (the sun in one case, the filament in the other), and that source of energy is necesarily hotter. But dragonslayers’ claim is that GHGs cannot warm the EARTH, not the Sun. So the correct comparison is with the bulb’s GLASS, not the filament.

OldWeirdHarold

Michael Moon says:
May 28, 2013 at 8:52 am
The Temperature of the Filament is the only temperature that matters here. Did the Filament warm from back-radiation? Did heat actually “flow uphill?”
=====
That actually could be measured by a very precise measurement of current through the bulb. As the filament warms (and yes, it will warm), the resistance will go up, and the current will drop. By how much, I don’t know, but it should be calculable from the known resistivity properties of tungsten.
Go for it. Do it. And when the current drops (and it will, but possibly by a very small amount), tell me why that happened. Show all work.

Bill Marsh

@Michael Moon
““In all cases, there is about a 35-watt (120V x 0.289A) electrical input to the system” OK, I answered my own question, the filament did NOT warm, and the Second Law reigns supreme as always!!!”
You seem to have missed the significance of ‘about’ in that quote. It indicates that Anthony did not make exact measurements of the electrical current, therefore you can’t draw the conclusion you have drawn.

@ Curt Wilson, well-done. This is basic heat transfer ‘101’.
Millions upon millions of fired furnaces operate world-wide on the textbook principles.
If the textbook analysis were wrong, as Slayers insist, then the furnaces would not work. One suspects that we would have noticed, by now.

OldWeirdHarold

Matter of fact, based on this:
http://hypertextbook.com/facts/2004/DeannaStewart.shtml
Current measurement should be pretty robust. If someone can place a clamp-on ammeter on the wire to the bulb, and take a current measurement, I would expect to see a significant drop in current when the cover is placed over the bulb, and then when the cover is removed, the current should rise to the original value. Thus proving that the filament itself became hotter.

MattN

I vote Joseph gets no more posts unless his very next one lists the “mistakes”…

Nice!
I would expect current would drop a bit as the bulb got warmer.
And I wonder if the difference in temps between the large and small foils are due to the 4th power law and some of the energy is not reflecting back to the bulb.

Kevin Kilty

Michael Moon says:
May 28, 2013 at 8:52 am
The Temperature of the Filament is the only temperature that matters here. Did the Filament warm from back-radiation? Did heat actually “flow uphill?”
Did you measure the temperature of the filament? Could you, please, and end this ludicrous “debate?” You only mention the current twice. If the filament warmed its resistance would increase, and with a constant voltage the current would drop a little. A direct measurement of filament temperature would be better but obviously difficult to achieve.
“In all cases, there is about a 35-watt (120V x 0.289A) electrical input to the system” OK, I answered my own question, the filament did NOT warm, and the Second Law reigns supreme as always!!!

The filament did indeed become warmer as one can tell from the decline in current. As the author points out, the equation of state of tungsten is one of increasing resistance with increasing temperature. Use voltage and current to determine the resistance of the tungsten filament and obtain its absolute temperature in turn. But your assertion that the filament would become warmer from heat flowing “uphill” does not make sense. The filament temperature derives from an energy balance–input from the mains and output through radiation, convection, conduction, etc which are all functions of temperature. The radiation baffle impairs one branch of the energy output stream leading to a higher filament equilibrium temperature–there is no need to have heat flow uphill in this view.
However, radiation has an interesting characteristic in that one cannot tell if a photon came from a cool body or a hot one. So, in a microscopic view, photons emitted from a cold body can land on a hot one and transfer energy “uphill”. Cold bodies produce a less intense stream of photons than do hot bodies, so, statistically, net heat flows from hot to cold.

Nano Pope

I’m not sure you’re disproving the correct point. You’ve proved that radiation can be reflected and affect solids, but isn’t the point about energy transfer in gases under various pressures?

Peter Shaw

Your data may include something simpler and more remarkable:
Consider the filament as a tungsten resistance thermometer. Your “foil shell” change of 0.7 mA represents a 3-4C increase.
This is an impressive demonstration of “uphill” heat flow.
Measurement is a challenge, but this has the elegance of simplicity.

Michael Moon, you make the same fundamental mistake the Slayers do…equating energy input to temperature. Temperature is NOT determined by the rate of energy input alone.

Gary Hladik

Julian Flood says (May 28, 2013 at 8:05 am): [snip]
Yes, the Pictet Experiment. Joel Shore linked this article in a comment at Dr. Spencer’s site:
http://www2.ups.edu/faculty/jcevans/Pictet%27s%20experiment.pdf
Not surprisingly, the Slayers managed to misiterpret this one, too. 🙂

Ben Of Houston

To all those contrarians who are claiming this is wrong. Anyone with a cursory knowledge of heat transfer knows exactly how radiation works (it is by far the simplest mode of heat transfer, with conduction more complex and convection downright headache-inducing). If you think that it violates the second law then you have no idea how entropy works, do you? It’s simple. At every step, total entropy increases, from the absorbance of the infrared to the re-emittance, and then the re-absorbance when it hits the light.
Or you could try and explain how the re-emitted photons magically avoid striking the fillament or even more magically, strike it and are absorbed but do not warm it.
Seriously, grow up and take a freshman-level thermodynamics course before trying to proclaim yourselves the lord and master of physics.

Eustace Cranch

A better way to do this experiment is to heat a length of nichrome resistance wire. Its temp could be measured directly without the complications of the light bulb envelope. Wattage would be easily calculated from Ohm’s Law. Could a wire dissipating, say, 10W cause an adjacent wire dissipating 20W to rise in temperature? Hmmm….

Anton Eagle

If you’re going to get the science wrong… then at least be internally consistent. You acknowledge that the current and voltage don’t go up, and assert that the filament temperature doesn’t go up. So then what is the source of the increased temperature on the surface of the bulb?
Also, why would the temperature of the filament be the only one that “counts”? The surface of the bulb is a great analog the surface of the earth… a much better analog than the filament would be.
Your supposed rebuttal does nothing to address the observed temperature change on the surface of the bulb. It can’t be the filament, as its energy output is strictly a function of the current and voltage. It has to be back-radiation, and this experiment neatly demonstrates that it is so.
If you’re going to offer an alternative explanation, then you need to do more than assert that something else should have been measured… you need to account for the observed temperature increase. If you can’t, then you really have no valid argument, and should just keep quiet. Better to be quiet and be thought a fool, than to open your mouth and remove all doubt.
Lastly, when someone proves you wrong, just step up and admit you were wrong, learn from it, and move on; continuing to fight an argument that you already lost is just foolish.

Anton Eagle

Oops… my reply was directed to Michael Moon… somehow his quote didn’t end up in my post like I expected.

Konrad

Meh.
Yesterdays news.
If you couldn’t work out that PSI were not sceptics, how can you combat AGW promoters?

I find this entire discussion set absolutely hilarious but tedious.
As the captain said to Luke
    “what we have here, is a failure to communicate!”
Both sides seem to be wandering in the weeds, looking at details, focusing on mundane and arguing about nits and bits without conceptualizing.
(Neat prototypical science experiment, Curt, should be mandatory at elementary schools)
Key points that are muddled:
1. the “hotter body” has a source of energy:
    => if it doesn’t radiate/lose/use energy it will increase in temperature until doomsday.
2. the enclosing “cooler body” reduces the rate of energy flow away
Yes, the details are thrilling, but any object that has energy added, needs to
    use it or lose it!
The trivial analogy, that hopefully everyone likely understands, is your house:
-> the “cold” insulation” keeps the house warmer than what it would otherwise
        if your house is heated
    or “cooler than it would be otherwise” if your house is A/C’d
and, when the power dies, people get upset at the cold/heat.
The earth’s air, the glass in a greenhouse, windows in your house, etc
all let in energy and slow the rate of its departure,
=> like the insulation in the walls which slow the departure of the heat generated by your furnace. (the windows, not so much)
It’s the energy flow stu…
If you want to argue about the nits and bits of how fiber glass insulation
(or the earth’s air) slow the departure of thermal energy or how glass and air allow the influx of energy in some bands (when present), go for it.
It is usually entertaining, but mostly tedious.

Feeling is believing

My house is not very well insulated. That is true of many houses in New Zealand the same age as mine. Sadly, limited access to the ceiling cavity has made this problem difficult to completely rectify. Fortunately it seldom gets too far below freezing where I live. Often however when I get up in the morning at this time of year (winter) the temperature in my bathroom is unpleasantly cold.
I like to start my day with a nice hot shower. Before I start my shower however I always detach the shower head and hose down all four walls (two of them glass) of the shower box with hot water to take the chill off them. That way I can have a comfortable shower and not one where the parts of me not directly under the hot water feel cold. Taking the chill off the walls and windows of the shower box stops me losing so much heat to them by radiation and makes an amazing and quite perceptible difference to the comfort of my shower.
I’d be fascinated to see how a sky dragon slayer might explain this phenomenon.

Eustace Cranch

Another way to think about this: consider a double star system in space. One star will almost certainly be cooler that its mate. Could it possibly heat the hotter star without losing its own heat? Is the total radiation of the pair greater than the sum of each separately? I think not.

dp

These lamps are nearly constant current devices and this characteristic can be used to directly measure the thermal response of the lamp system. No thermisters needed. Use a precision voltage source or a precision current source, put the lamp in a vacuum, warm it by placing any other radiating object near by. Watch the voltage or current change, depending on which of the two you choose to regulate.
But none of this is necessary if one can explain what becomes of the radiated energy from the cooler object that strikes the warmer object. In fact that energy does to the warmer object what any energy does that strikes another object. It increases that object’s energy level. Oddly enough some of that energy is radiated back to the cooler object, warming it faster which creates greater emission back to the warmer object. Back and forth like this until equilibrium is achieved.
Any boy scout can tell you two burning logs adjacent will reach equilibrium and very high heat at the place of least distance even of only one log is initially lit. Neither log alone will reach the temperature of the pair, nor heat as quickly as the pair.
Objects that radiate have no awareness of what is around them. They are equivalent isotropic radiators if geometry permits, and anything that is illuminated by emissions from such an object is energized by that illumination. The sun is very bright – bright as it is we can still strike it with a powerful laser. That laser energy becomes part of the total energy of the sun. That we have no prayer of measuring it does not mean that laser energy has evaporated on the way to the sun.
The slayers are too ignorant to bother with further and it drags down the quality of the science to humor them.

Bryan

[snip – we aren’t getting off topic on this – we are discussing this experiment, not some pie in the sky theoretical one – Anthony]

Macro behavior in solids is not transferable to micro behavior in individual, three atom gas molecules. The Aluminum foil is at least several thousand molecules thick, the glass even more. Radiative and convective flux are both restricted by both materials based on mass, specific heat and in this case, the sealed cubic configuration. In a free gas environment there are limited restrictions to convective and radiative flows, and a three atom gas molecule, at virtual rest compared to a photons speed, is not capable of stopping or redirecting this high velocity OLR force for more than milliseconds. Atmospheric CO2 is a feather in the path of a howitzer round.

OldWeirdHarold

Years ago, in a statistical mechanics lesson in P-chem, the prof, after wading through an insufferable derivation, drew an interesting conclusion. In a hurricane, over 40% of the molecules are moving against the direction of the wind. If they were all moving the the same direction, they’d be moving at the speed of sound.
The conceptual error that the Skydragons are making is failing to distinguish between individual dynamics and population dynamics. Just as a large percentage of the molecules in a hurricane move against the wind, a large percentage of the photons can and do move counter to the net heat flow, which implies moving counter to the thermal gradient.
The Second Law is an emergent phenomenon that applies to populations. It doesn’t apply to individual particles. Skydragons don’t seem to get that concept.

I’m not a slayer, but some of the effect you’re getting is the glass-greenhouse effect..where heat from the bulb is conducted to the surrounding gases which cannot convectively cool. The gases surrounding the enclosed bulb are thus warmer and direct heat loss via conduction is reduced.
It is very hard to measure the direct effect of LWR. With the mirror you get reflected SW which at the very least promotes a faster equilibrium.

PeterH

Hypothesis,
Clearly described experimental procedure,
Clearly presented data,
Analysis of how the data relates to experimental conditions and theory,
Debate and input how the experiment might be done differently or better.
This is SCIENCE!

Joseph E Postma says May 28, 2013 at 8:01 am

This is the same guy who conflates ‘night vision’ (visible light amplified by light intensifier tubes and the like) with thermal LWIR ‘FLIR” imagery equipment with near wavelength IR viewers requiring an external source of that near IR ‘light’ for the viewer?
He conflates an awful lot I’d say … and more, probably, than just visual/thermal/near-IR imagery subjects …
.

wikeroy

Susan Corwin says:
May 28, 2013 at 9:36 am
“I find this entire discussion set absolutely hilarious but tedious.”
That was what came to my mind too !
For many, many years I have noticed that the insulation in the walls of my house has kept it warmer than without. But the word “backradiation” never came up.
And I did the basic course in thermodynamics 30 years ago. I went to the addict and looked through the books. Couldnt find the word. Probably some new definition.

Bryan

Anthony
My proposed experiment was addressing this experiment in particular the final comment
“It is not compatible with the idea that cooler bodies cannot transfer any power by radiative means to warmer bodies and cause an increase in temperature of the warmer body.”
This implies that the presence of a colder object will always increase the temperature of a warmer one.
It contradicts common sense.
Try putting a large block of ice in your living room.
This is more acceptable and perhaps is what Curt was really meaning.
‘It is not compatible with the idea that cooler bodies cannot transfer any power by radiative means to warmer bodies and SOMETIMES cause an increase in temperature of the warmer body.’

Slartibartfast

These guys are in effect claiming that some radiation is effective while other radiation is not. In other words, radiation only works if it’s going from hot to cold.
It’s bunk. It’s tantamount to saying that some photons are more privileged than others. Blackbodies don’t care where the photos came from; they just care that the photons came at all.

Michael Moon says May 28, 2013 at 8:52 am
The Temperature of the Filament is the only temperature that matters here. Did the Filament warm from back-radiation? Did heat actually “flow uphill?”
Did you measure the temperature of the filament? Could you, please, and end this ludicrous “debate?”

OK, I answered my own question, the filament did NOT warm, and the Second Law reigns supreme as always!!!

Premature jubilation; did you perchance read this tidbit:

The electrical voltage and current measurements were made to confirm that the increased temperature did not come from a higher electrical power input. The current measurements shown above demonstrate that the current draw of the bulb was no higher when the bulb temperature was higher, and was in fact slightly lower.
This is to be expected, since the resistivity of the tungsten in the filament, as with any metal, increases with temperature.

Pls join-up with Greg for some remedial education …
.

Slartibartfast

s/photos/photons

Nano Pope says:
May 28, 2013 at 9:20 am

I’m not sure you’re disproving the correct point. You’ve proved that radiation can be reflected and affect solids, but isn’t the point about energy transfer in gases under various pressures?

That’s what the point should be, but what it really is about is realizing an ill-designed experiment created by Dr. Siddons.
We don’t have a failure to communicate, we have a failure to comprehend. We have better things to do, but the Slayers have been so vocal and pig-headed that we have to spend an excessive amount of time to explain to everyone else why their claims are wrong.
“Follow the money” is often heard here. In this case, “Follow the photons” applies.

Carrick

OldWeirdHarold:

That actually could be measured by a very precise measurement of current through the bulb. As the filament warms (and yes, it will warm), the resistance will go up, and the current will drop. By how much, I don’t know, but it should be calculable from the known resistivity properties of tungsten.

That’s the thought I had too. The electrical properties of the filament allows it to be directly used as a temperature sensor.
It’d be interesting if Curt Wilson (or somebody else) were to calibrate the tungsten filament temperature as a function of power drawn (use a clear glass bulb so you can image the filament, vary the power applied using a variac), then repeat the experiment, tracking the resistance of the filament under the different experimental conditions.
What these experiments prove is how resilient the PSI group are to actual facts in addition to how very limited their own understanding of how science works is.
I nominate this for their official icon.