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Discussion > Simon Abingdon/Jonathan Jones/Radiative transfer

May 8, 2012 at 12:46 AM logicophilosophicus

They? Who are they?

May I respectfully recommend Steve Peters? He seems to have helped somebody to get their marbles together this week.

May 8, 2012 at 12:56 AM | Registered CommenterGreen Sand

Martin A. Thanks for the reference to ScienceOfDoom website. It is just the sort of straight talking science that I have been looking for.

May 8, 2012 at 4:45 AM | Unregistered CommenterBitBucket

I resent any implication that 'engineers' somehow abhor physical forumlae or scientific notation, and are thus the Morlocks to science's Eloi - my engineering degree was every bit as 'scientific' and 'theoretical' as any science degree, more so, because Engineering is applied science - so not only do you need to understand the scientific basis, you also MUST understand the real physical factors which affect the perfect theoretical model and carer for them when you come to use the formulae to build something.

There is enough line-drawing in this game, let's not draw a new set of us-and-them.

May 8, 2012 at 8:21 AM | Unregistered CommenterTheBigYinJames

Green Sand:

Steve Peters, jock shrink... So you think I am mentally unbalanced for holding the view that heated objects have added energy content? I suppose that's a continuation of RKS's "nutcase" remark - he who bleeds easy when he claims to have been insulted. Well, I don't. So, sticking to the argument rather than making abusive remarks, I suggest that you need some serious evidence if you doubt my energy-content statement; since it is "a truth universally acknowledged" you can take it that "they" means everyone, to an engineering approximation.

TBYJ You misread me if you thought my remark about "little x's" was meant to disparage engineers. That would have been odd, undermining my own argument. I am a wannabe engineer. I love engineering calculations - discarding what doesn't matter and cutting to the practical reality. That's why I was taken aback when RKS introduced his credentials ("as an engineer") to give weight to a very dubious scientific opinion. (BTW I enjoyed "forumlae" - intentional or accidental, it's a word which will nicely label some of the oddities that appear in web forums.)

May 8, 2012 at 9:34 AM | Unregistered Commenterlogicophilosophicus

I can spell, my fingers can't ;)

May 8, 2012 at 10:22 AM | Unregistered CommenterTheBigYinJames

Response from Scienceofdoom

ScienceofDoom has a page refuting the belief that radiation from a body cannot be absorbed by a body at a higher temperature.

http://scienceofdoom.com/2010/10/07/amazing-things-we-find-in-textbooks-the-real-second-law-of-thermodynamics/

They refer to several textbooks on heat transfer with the formula giving the power exchanged, in both directions, between a pair of bodies at differing temperatures.

I posted the queestion:

First, let me say that I have no problem with the principles of radiant heat transfer as described in the various texts. It's what I have always understood and it agrees with my understanding of Stefan–Boltzmann law and so on.

But I've been asked where someone can go to find details of physical measurements that confirm these results. I would imagine that the first year of a physics degree course would involve such experiments but I certainly found myself unable to come up with an answer.

Could you help me come up with an answer as to where one can find description of physical measurements that confitm these relations? Or maybe they follow inevitably as the consequence of simpler more fundamental laws that have been confirmed by physical measurements?

Thank you for any help you can give me.


Here are the responses:



on May 8, 2012 at 9:57 am Reply scienceofdoom

Martin A,

Good and interesting question. I wish I had the complete answer. The essence of radiant heat theory was worked out in the late 1800?s and early 1900?s and I'm sure that a reprint of some seminal papers from that era would be appreciated by many including me.

I have got Max Planck's The Theory of Heat Radiation from 1914 which includes little gems like:

This law, which states that the volume density and the specific intensity of black radiation are proportional to the fourth power of the absolute temperature, was first established by J. Stefan[1] on a basis of rather rough measurements. It was later deduced by L. Boltzmann[2] on a thermodynamics basis from Maxwell's radiation pressure and has more recently been confirmed by O. Lummer and E. Pringsheim[3] by exact measurements between 100?C and 1300?C, the temperature being defined by the gas thermometer..

[1] J.Stefan, Wien. Berichte, 79, p391, 1879
[2] L.Boltzmann, Wied. Annalen, 22, p.291, 1884
[3] O.Lummer und E.Pringsheim, Wied. Annalen, 63, p.395, 1897. Annalen d. Physik, 3, p.159, 1900

(This book is available from The Book Depository for only $26, free delivery worldwide).

Generally the results are presented as "known facts" in physics and engineering courses.

If any readers have some early papers or later experimental work, please post them. I have lots of papers which show experimental results of material properties like emissivity which of course rely on the fundamental theory being correct.

It's good to be skeptical of results presented without evidence, although I do generally work on the basis that when all the textbooks say the same thing and the science was worked out 100 years ago it's probably correct.

on May 8, 2012 at 10:26 am Bryan

Martin A

An experimental method of testing Stefan's Law is given on page 91 of
Experimental Physics for Students by Whittle and Yarwood.

Pub Chapman and Hall (1973)

May 8, 2012 at 12:52 PM | Registered CommenterMartin A

Have a mega day! Watch out for all those "thousands of trillions of trillions of Joules" You never know they might all eventually become yours!

May 7, 2012 at 11:59 PM | Green Sand>>>>

Nice to see another visitor to the 'discussion'.

We are being told to accept, in the most shrill manner' by these promoters of post normal science that within a steady state system, it is possible to have a greater energy flux at some point within that system than the total energy flux available to the system.

within an electronics circuit for one possible example, I is possible to create short term POWER pulses higher than that supplied to the overall circuit but the energy flux within the circuit can NEVER exceed that available by the POWER present at the terminals.

If someone can provide an empirical an example that refutes the accepted physics of the above example, I would honestly be keen to read this new knowledge which might have massive changes on our technology.

Also we must not lose sight of the subject of the thread which is with the interaction between a two body system of POWERED RADIATOR and PASSIVE BACK RADIATOR - and the quest to obtain empirical proof [see the start of the thread].

Not simply a discussion of Steffan - Boltzman and black bodies in abstraction.

I also asked for the same proof for the example and further asked for an opinion of the effect of this property of CO2, at various emissivities and at the accepted concentration of ~0.04%, on the amount of energy flux actually back radiated to the surface, [as per the IPCC pin up Trenberth].

And where does back radiated radiation at this wavelength, which stops it from passing through tropospheric CO2 because it is, as one new age scientist informs us opaque at that wavelength, go then? - Is it supposed to bounce up and down like the actions of a bell ad infinitum? - if not, how not?

Where the two body example is concerned I do look forward to a sensible experimental result as this may have uses in the world of industry.

As for the example I use with regard to the effects of CO2 on the climate, Nobody has yet come up with a simple mathematical description of the process using simple properties of CO2. It only need basic maths, with no references to black bodies or fancy accounting to allow more energy to exist within a system than that supplied to it.

Trenberth and the IPCC claim that 40% of the TOTAL energy flux, in terms of Wm^2, is due to back radiation from 0.04% of the atmosphere. I don't dispute back radiation as a thermodynamic property [awaiting experimental verification], I do find the supposed effect of CO2 on the climate to be simple metaphysics on a par with medieval alchemy.

If you want an interesting academic discussion by all means discuss the many ramifications of back radiation.

If you are scynical of the position of the IPCC and wish to discuss climate, why not grow a pair instead of not wanting to look silly by challenging the CO2 hypothesis and do, or support, actual scientific research attempting to describe other more likely drivers of climate.

Instead of discussing CO2 and back radiation on a scynical climate blog on the lines of ' it's IPCC Jim but not as we know it' why not discard the whole nonsensical notion of the 'climate driver' and stop giving even the smallest degree of comfort to those attempting to destroy our civilization by this crazy philosophy.

Sorry for the rant - This thread is very interesting in an academic sense and I'll continue 'lurking' in order to learn.

But why are so many apparently afraid to display by simple algebra how the proposed effects of CO2 are complete bollocks.

May 8, 2012 at 4:23 PM | Unregistered CommenterRKS

'RKS'

"We are being told to accept, in the most shrill manner by these promoters of post normal science that within a steady state system, it is possible to have a greater energy flux at some point within that system than the total energy flux available to the system."

A bit of a non sequitur, but I guess you are comparing the atmospheric back radiation energy flux of 324 Watts per sq m and the energy flux of incident sunlight minus the reflected fraction, i.e. 235 Watts per sq m. Then you are perhaps confusing two uses of the term "energy flux"? Imagine x solar photons per sq m per second passing through a translucent window and then reflecting back from a mirror towards the window. Imagine that y% of the photons escape through the window. When the set up achieves equilibrium, the photons per sq m at the mirror surface will always be greater than x, while the flux of escaping photons will be exactly x. That's always as in "inevitable", as opposed to your (implied) "impossible". Note that energy flux is not an amount of energy and is not conserved. As an easy example, moderately bright sunshine intercepted by a lens has an energy flux of a couple of hundred Watts per sq m. At the focus of the lens, the energy flux is much higher, enough to ignite paper for example, as in the Cambell-Stokes apparatus. What kind of engineer did you (not) say you are?

"I also asked for the same proof for the example and further asked for an opinion of the effect of this property of CO2, at various emissivities and at the accepted concentration of ~0.04%, on the amount of energy flux actually back radiated to the surface, [as per the IPCC pin up Trenberth]." Unless the emissivity is zero, again inevitable.

"And where does back radiated radiation at this wavelength, which stops it from passing through tropospheric CO2 because it is, as one new age scientist informs us opaque at that wavelength, go then? - Is it supposed to bounce up and down like the actions of a bell ad infinitum? - if not, how not?"

No - just "ad equilibrium", as described above.

"Where the two body example is concerned I do look forward to a sensible experimental result as this may have uses in the world of industry."

I think it already does, in the design and location of heat sinks. There is also quite a well known example when microwave emissions from a very cold object (2.7 K) was absorbed and detected by an antenna 300 degrees warmer, thus earning a Nobel Prize for Penzias and Wilson.

["As for the example I use with regard to the effects of CO2 on the climate, Nobody has yet come up with a simple mathematical description of the process using simple properties of CO2. It only need basic maths, with no references to black bodies or fancy accounting to allow more energy to exist within a system than that supplied to it. Trenberth and the IPCC claim that 40% of the TOTAL energy flux, in terms of Wm^2, is due to back radiation from 0.04% of the atmosphere. I don't dispute back radiation as a thermodynamic property [awaiting experimental verification], I do find the supposed effect of CO2 on the climate to be simple metaphysics on a par with medieval alchemy." You should already see that this is nonsense from the above.]

"If you are scynical of the position of the IPCC and wish to discuss climate, why not grow a pair instead of not wanting to look silly by challenging the CO2 hypothesis..."

If you are hell-bent on furthering the interests of the guys over at RealClimate, just let your balls-to-brain ratio take over, and challenge basic physics so they can rabbit on about scientifically illiterate deniers. ("Scynical"? Cynical is what Michael Mann is.)

"Instead of discussing CO2 and back radiation on a scynical climate blog on the lines of 'it's IPCC Jim but not as we know it' why not discard the whole nonsensical notion of the 'climate driver'..." But CO2 is a major climate driver, via the back-radiation mechanism - or we'd all be dead - and additional CO2 has an additional effect which IPCC dubiously claim to be subject to strong positive feedbacks.

"But why are so many apparently afraid to display by simple algebra how the proposed effects of CO2 are complete bollocks." I don't know - where is your simple algebraic disproof?

May 9, 2012 at 8:43 AM | Unregistered Commenterlogicophilosophicus

May 9, 2012 at 8:43 AM logicophilosophicus

I think it already does, in the design and location of heat sinks. There is also quite a well known example when microwave emissions from a very cold object (2.7 K) was absorbed and detected by an antenna 300 degrees warmer, thus earning a Nobel Prize for Penzias and Wilson.

Yes.

I've been accused of being daft (or something similar - can't quite remember) when I pointed out that radiation from the magnetron in a microwave at 2.45 GHz (wavelength about 12cm, equivalent to radiation from a body at around 0.024K) has no problem heating rice pudding at 370K. I was told this was different - the microwave heats rice pudding electrically.

I could not follow the argument - that's how electromagnetic radiation heats stuff, irrespectively of how it was generated.

May 9, 2012 at 5:43 PM | Registered CommenterMartin A

Martin A

I have found two papers that may be of interest. The first is by Max Planck showing the 1901 derivation of his law. The second is the often quoted paper by Rubens and Kurlbaum. This has the experimental data showing that the Planck equation was the best fit.

http://hermes.ffn.ub.es/luisnavarro/nuevo_maletin/Planck%20(1901),%20Energy%20distribution.pdf

http://adsabs.harvard.edu/full/1901ApJ....14..335R

Another interesting but detailed discussion on radiative heat transfer is given here:

http://webserver.dmt.upm.es/~isidoro/tc3/Heat%20transfer%20and%20thermal%20radiation%20modelling.pdf

Equation 27 is helpful as it shows how to calculate net heat transfer from one body to another. This takes into account the areas of the bodies, their emissivities and the view factor. This could have been used in our disc experiments if we wanted to use real materials with a greater separation of the discs.

Jorge

May 9, 2012 at 7:19 PM | Unregistered CommenterJorge

not sure about the reference to Hoyle - brilliant physicist but he did get hung up about how all the archaeopterxy fossils with feather imprints were fakes and how life originated on comets.

I would just like to see a lab demo. I don't want to read any more words by scientists or browse any more equations. People like to invoke the name of Feynman, but he was always clear on the topic of experimental proof and regretted how bad he was at that aspect of his profession - read his essays about trying to become a biologist or psychologist over the summer vacation and how it proved to be very difficult... Angstrom's experiment made Arrhenius change his mind. Has anyone updated the experiment? Does anyone perform it to show the effect?

May 9, 2012 at 10:29 PM | Registered Commenterdiogenes

May 9, 2012 at 7:19 PM Jorge

Jorge,
Thank you for the references.
Martin

May 9, 2012 at 10:51 PM | Registered CommenterMartin A

There are lots of lab demos on blackbody radiation - search YouTube - but here's a good standard example from real science:

"Radiometry of both the planets and stars did not bear full flower until the 1920's, with the work of W. W. Coblentz and C. O. Lampland at the Lowell Observatory, and E. Pettit and S. B. Nicholson at the Mount Wilson Obervatory. Nearly the same experimental technique was used by both groups. The image of the planet at the telescope fell upon one of two small receivers one millimeter or less in diameter, to which were attached two thermo-junctions of bismuth and bismuth-tin electrically connected to a galvanometer so that hey compensated for the heating of the background of the sky. When the junction is heated a minute current of electricity, which is proportional to the amount of radiation falling upon it, is generated. [paragraph] Filters were used to isolate the reflected solar radiation from the thermally emitted planetary radiation. A "water-cell" filter (opaque beyond 1.4 microns) or a piece of thin glass (opaque beyond 8 microns) removed the planet's heat radiation and left only he radiation due to reflected sunlight. By subtracting the deflection caused by the reflected solar energy from the deflection obtained with no filter, they obtained the deflection which would be caused by the heat radiation. With these indirect methods the temperature observations of Mercury, Venus, Mars, Jupiter, Saturn and the moon were made." The temperatures of Jupiter and Saturn are <150K, but their warming effect on a thermocouple at around 300K was observed and measured. For Saturn, that's equivalent, I very roughly calculate, to measuring the heating effect of a 1mm disc at 200K on a similar disc at 300K around a metre away.

May 9, 2012 at 11:20 PM | Unregistered Commenterlogicophilosophicus

wittgenstein


what was the search string you used on you tube?

May 9, 2012 at 11:28 PM | Registered Commenterdiogenes

Diogenes

I started with "Black body radiation experiment" and went with the flow.

May 10, 2012 at 7:27 AM | Unregistered Commenterlogicophilosophicus