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.
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.)
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.
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.
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.
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).
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.
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.
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.
With the bulb covered by a foil shell alone and a surface temperature of 158.6C, the bulb drew slightly less, 288.7 milliamperes.
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.
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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
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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
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:
-Anthony
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.
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]
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 …
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!!!
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!
Absolutely flawless and very well explained. JEP’s response is typical of a troll.
@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.
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.
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.
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.
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.
@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.
@ur momisugly 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.
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.
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.
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.
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?