# Talk:Heat transfer

## Discussion of Variables

In the mechanism section many equations and variables are introduced but not discussed in much detail. A couple short sections explaining and highlighting such variables would be beneficial. For example a section which defines heat capacity, discusses how properties of chemicals effect heat capacity, and gives examples of chemicals and their heat capacities.

It also seems as though the mechanism section sets a precedence that there will be a discussion of the math and physics behind much of the material presented throughout the page. However, after the first two sections, equations relating to the material discussed are no longer included. A few specific sections second that could benefit from the addition of equations are: The heat equation: it is defined and discussed but not included. Phase change: The discussion of heat of vaporization and heat of formation would enhance section. The device section: symbols for work and heat are introduced in images but not discussed in text. Maybe include energy balance equation and how it's used.

Llavecch (talk) 09:13, 13 January 2017 (UTC)

## Missing Citations

There are many areas where added citations would greatly improve this page. Many of these sections have already been identified; however, the phase change section has quite a few areas that need citations and have not been identified. The introduction could use one right after the main paragraph and mention of the mason equation. The boiling section could use at least two cites considering the length of the section and as of now there are 0 cited sources.

Llavecch (talk) 08:35, 13 January 2017 (UTC)

## Error found in the picture

The formula for radiation heat transfer coefficient (in the image showing thermal resistances for each mode of heat tranfer) contains a term for surface area. This is an error and should be removed.

-mbwittig 10:16, 23 November 2008 (PST)

I've changed the "Equations for different heat transfer modes and their thermal resistances" image into a wikitable. Given the age of this comment, I'm not sure if the change above happened, so mine is a literal conversion. I don't feel like I have the authority to change equations that I don't know/understand, but it should now be possible for you to change them! Sutekh.destroyer (talk) 00:22, 29 March 2010 (UTC)

## Peer Review

Thank you,

-Âme Errante 10:15, 29 July 2006 (UTC)

## References

I´ve been doing some search for information in this subject and found a couple of available textbooks on the internet that will surely be usefull for expanding and also refining the concepts of heat transfer.

A Heat Transfer Textbook, John H. Lienhard V, Professor, Massachusetts Institute of Technology.

Wolverine Engineering Data Book II, Dr. K.J. Bell and A.C. Mueller:

Wolverine Engineering Data Book III, Pr. John R. Thome:

Please comment what you think. WiKimik 19:39, 6 September 2006 (UTC)

## Don't confuse heat with energy

I removed the following statement from the intro paragraph:

energy in the form of heat,

because this is a misnomer. Heat is not, in fact, a type of energy; rather, heat is movement of energy (see the first sentence of the heat article). In reality, heat transfer is redundent: the transfer of the transfer of energy. A better name would perhaps be 'thermal transfer' in that one is transfering thermal energy. —Preceding unsigned comment added by Âme Errante (talkcontribs) 20:01, 4 October 2006 (UTC)

of course it is energy, check the units in any equation using heat(q).
BTW the heat article is also wrong, i don't know where this idea started, as a physicist with 20 years kicking around science, wikipedia is the first place i've heard of it, this is very basic stuff to be getting this badly wrong.

"Now although ice has a "rigid" crystalline form, its temperature can change-ice has heat. If we wish, we can change the amount of heat. What is the heat in the case of ice? The atoms are not standing still. They are jiggling and vibrating."

Feynman lectures on physics, chapter 1, lecture 1

Asplace 17:12, 5 February 2007 (UTC)

Of course it's a misnomer. Heat Transfer is the name given to the study of heat. Heat is a transfer of energy. The term "Heat Transfer" IS redundant. Heat is thermodynamically equivalent to work and has units of energy per time. Feynman is wrong, but Newton had it wrong too. Jean Baptiste Joseph Fourier was the first person to separate the concepts of heat and temperature. (A couple hundred years after Newton but a couple hundred years before Feynman.)

Combined with Heat? Maybe it could stay separate as the engineering subject that considers heat, and the Heat article can remain more physics-based? —Preceding unsigned comment added by 137.192.45.122 (talk) 13:45, 12 October 2007 (UTC)

The entire page should be deleted and combined with heat. As state above, heat transfer is a misnomer. Then why have a page entitled "Heat Transfer"? Makes no sense.

Norm —Preceding unsigned comment added by 68.44.91.155 (talk) 21:59, 1 July 2007 (UTC)

Norm, I disagree that this page should be deleted. The field of heat transfer may be misnamed (as are, I'm sure, many older areas of engineering and science), but it is nonetheless an applied field separate from the study of heat in physics. As long as engineering textbooks continue to be written about heat transfer, I propose we keep the article. -Âme Errante (talk) 19:11, 7 May 2008 (UTC)
But the present article claims to be about physics, not engineering, and therefore confusingly implies that physicists consider heat transfer a separate topic from heat. If the justification for the article is its engineering applications then the article should make this clear. --Vaughan Pratt (talk) 18:23, 20 June 2008 (UTC)

Ok -- I will explain just how wrong you are in 4 easy steps.

1. Heat is a form of energy. 2. Heat is classifed as a type of energy called thermal energy. 3. Therefore Heat Transfer is not a redundant statement because this is the field of science that studys the transfer of thermal energy as the name implies. 4. If heat is not energy, then explain please how we are able to utilize fire as a tool to say burn some coals which then spin a turbine blade above it to harvest power. Because if heat is not a form of energy then this would not be possible.

Granted many things in both the math and science fields have so strange annotation and many time the same letter such as Q, can mean discharge of a fluid in the field of fluid dynamics or it can mean total heat transfer in it respective field. Hope that wasn't too confusing... Heat Transfer is a special part of Thermodynamics. —Preceding unsigned comment added by 67.133.219.194 (talk) 17:52, 16 July 2009 (UTC)

What is the reliable source for the assertion that heat is energy transfer, not energy? I have no problem finding many reliable sources that define heat as energy, but I can't find any that define it as the transfer of energy. It does not do the reputation of Wiki any good to have such a radical change in a centuries old definition asserted without a reliable source to justify it.

John G Eggert (talk) 14:26, 30 May 2014 (UTC)

## What about phase change? / boiling heat transfer

Any serious treatment of heat transfer can not ignore phase change. Kjlgstp 14:27, 29 November 2006 (UTC)

Apropos the above - we need a decent article on boiling heat transfer - it's scattered around several places at present. I've bunged down a few thoughts and quotes from standard texts but much more is needed. Bob aka Linuxlad 18:58, 24 April 2007 (UTC)

transferring thermal energy from cold to hot is ok, (heat pumps), its only when no work is added, as in conductive, radiative and convective transfers that heat cannot, overall, move to a higher temperature.

also this article says heat transfer is by electrons and phonons only, if this were the case gases could not be conductors, missed out is heat carrying diffusion of any particles (atoms, molecules) in the system.

Asplace 03:09, 2 February 2007 (UTC)

Asplace, I think that your statement above, 'transferring thermal energy from cold to hot is ok', is wrong. Heat pumps do not transfer energy this way, and even with additional work it is impossible. For instance, the heat pump article states about refrigerators that 'In such a system it is essential that the refrigerant reaches a sufficiently high temperature when compressed, since the second law of thermodynamics prevents heat from flowing from a cold fluid to a hot heat sink. Similarly, the fluid must reach a sufficiently low temperature when allowed to expand, or heat cannot flow from the cold region into the fluid. In particular, the pressure difference must be great enough for the fluid to condense at the hot side and still evaporate in the lower pressure region at the cold side.' Thus, the work applied actually changes the temperature of the refrigerant by exploiting its physical properties, and at both sides energy still transfers from hot to cold. It's a subtle point, but it's very important in engineering. As for your second point, you're right on, and I believe this has since been changed. -Âme Errante (talk) 19:07, 7 May 2008 (UTC)
Nevertheless Asplace has a valid point. The first sentence of the article implies that the direction of heat transfer is from hot to cold. This is true for radiation and conduction but not for convection, at least for laminar flow. In the case of turbulent flow the turbulence causes mixing which has an averaging effect that resembles conduction, but the mechanism and its statistics are qualitatively different. --Vaughan Pratt (talk) 16:30, 20 June 2008 (UTC)

## ????What about liquid non-metals????also, read the first and second sentences regarding gas????

Someone posted this in the article. Assuming it wasn't vandalism, can someone comment on it or add something to the article? I've repressed most of what I learned in thermodynamics, and I'm much happier for it.-- joshschr (talk) 21:11, 16 November 2007 (UTC)

## What causes heat to burn things?

Since this is an article that is primarily scientific in nature, I thought someone here might be able to answer it. What is it that causes fire and heat to burn other things. And I mean this on a molecular level. I really have no clue myself, yet it's the only question I've ever had about anything that I couldn't find on the internet. Does it have something to do with the speed that molecules of fire/heat are moving and when this hits say the molecules of something like wood or flesh it separates them or something? Another example would be lasers. Some lasers are fine to hit other objects, they have no visible effect. However a more intense/powerful laser will burn through very hard substances. What is the intense laser actually doing to the substance at a molecular level that the weaker laser isn't. I assume the stronger laser simply has more energy being transferred to the material it is hitting. With human flesh is it a case that it can't properly contain the energy transferred to it, and thus it damages the cells? If so what is it that actually causes the damage at a molecular level, or maybe it would be better to say what is the actual damage at a molecular level? Is it that it breaks molecular bonds or what? Livingston 00:26, 18 September 2008 (UTC)

'Burning' is a chemical reaction that involves oxidation of a material. oxygen is consumed and the burning substance undergoes changes in its chemical composition. like any chemical reaction, oxidation of a compound has an activation energy. increasing the temperature of the substance to be burned increases the probability that it will undergo oxidation, and thus burn. the laser heats the material. that is, by some process the photons in the laser beam interact with the atoms in the material, and by absorption, increase the kinetic energy of the atoms. this energy will eventually be spread into all other modes, ie rotational, vibrational, in such a way that each quadratic mode has 3/2 kT energy, statistically (mechanically) speaking. —Preceding unsigned comment added by 18.187.0.59 (talk) 20:36, 2 November 2008 (UTC)

Answer- Objects burn/melt(change state) because the energy being transported by means of conduction qk, convection qc, or radiation G contains too much energy for that substance to be absorbed over that given time frame; so dE/dt, is too great for the substance trying to continue the transport.

Example - Burning/Freezing of Human skin- If you place your hand on a wall with a lower temperature then yours, in this case the temperature for skin can be denoted Ts and the temperature for the wall can be denoted Tw, respectively. The reason your hand starts to feel cold is not because the cold is traveling through the wall and into your hand(the 2nd law of thermodynamics says this is impossible) but that your hand is actually releasing heat(thermal energy) to the surface of the wall, in an effort to reach and maintain an equalibrium point.

The equalibrium point is where Ts and Tw are closer to being the same, so that the amount of thermal energy being transported through, in this case conduction, with respect to time is no longer as large as it once was; meaning the rate at which heat transfer is occuring, tf = final time(after equilibrium point) is less than that of ti=initial time (the instant you place your hand on the wall). Once this is reached your body becomes more adjusted to the situation and it will feel much less cold, if it still feels cold at all. The opposite is true if the temperature of your hand(skin), Ts is less than that of Tw, as the heat transfer is now in the reverse direction and your body is warming up because it is absorbing(transfering) that energy.

Burning and freezing occur in human skin when the rate of a heat(thermal energy) transfer is too great for human skin to handle. Meaning if the skin cannot safely transfer energy through it then damage occurs on the skin or worse. Too much energy is being transferred and your hand on the moleculur level can not deal with this great change of energy and electron bonds, especially weak secondary bonds, vanderwall(this needs to be spelled checked i apologize) bonds start to break apart and thus your hand is damaged.

Say you take a small flame (a flame with not much energy being released such as a lighter) and (accidently) have the flame pass under your hand and leave it there(you'll have to leave it there or you will not get a burn because the flame's low energy will not have enough time to break the bonds if you don't). So in this case low energy over a long period of time will break bonds you, as well as high amounts of energy over a very small period of time, such as a nuclear blast.

A nuclear blast contains so much energy that they literally just advance at you in a wave of energy that is far too great for you body to handle, breaking apart the bonds instantly.

Basically if the energy rate of change over time is large (either small energy over a large period of time, or a high amount of energy over a small period of time) things will break down on the molecular level.

Hope that answered your question. best regards, DBL —Preceding unsigned comment added by 67.133.219.194 (talk) 17:33, 16 July 2009 (UTC)

Yes, thank you. The only follow up I could think of is if a very minor burn, such as touching a hot plate, that doesn't do a lot of physical damage (only a small red mark) but still hurts for a few hours, if that is also due to the weakening of molecular bonds. In this instance have the bonds simply weakened or is there a breaking of the bonds, and if they were only weakened, but not broken, would it produce a noticeable physical effect? Also is the mark from the burn a physical indication of the molecular bonds breaking or weakening or is the physical appearance due to some other biological process. Obviously at the point where skin melts or blisters, that would be a result of the bonds breaking, but is it the same for less severe reactions. BTW I ask because I'm a First Aid instructor. So though it's not really essential to my courses, it's useful to know exactly what's going on. Thanks again. Livingston 15:21, 22 July 2009 (UTC)

According to skin the epidermis is a tougher outer layer that protects the dermis and subcutaneous tissue. Presumably the latter are more easily damaged (broken bonds) by a minor burn than the epidermis. On the other hand inflammation "is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants," and presumably excess heat counts as an irritant. So I would guess that inflammation could result even from a burn that irritated the dermis without seriously damaging it, in which case redness associated with minor burns could be as much an indication of inflammation as of any serious damage to the dermis. Not my area, just a guess. --Vaughan Pratt (talk) 07:42, 5 February 2010 (UTC)

## Possible error in the paragraph "Insulation and radiant barriers": assertion that "at any specific wavelength, reflectivity = 1 - emissivity"

"reflectivity = 1 - emissivity" is in fact true when integrated over all the wavelengths (Kirchhoff's thermal law of thermal radiation), but is not true at a specific wavelength. The wavelength distribution of the reflected energy is the same as that of the incident radiation, but the wavelength distribution of the emitted energy is usually quite different. This is for instance what explains the greenhouse effect, or the heating of the interior of a car in summer: the window of the car (the gas layer around the earth) is transparent to the incident radiation (which has a peak in its energy distribution at the visible wavelengths, since it is produced by the sun at about 6000°K), while it is much less transparent to the emitted radiation (that has a peak in lower infrared, since it is emitted by the interior of the car or by the earth, at about 330°K). If the law were true at any specific wavelength, the energy distribution of the emitted energy would be also the same as that of the incident radiation. The independence on wavelength for the emissivity (gray body assumption) is sometimes used - still, it only means that the dependence on wavelength is neglected for some wavelength band, not that reflectivity = 1 - emissivity in this band.

True. WP:SOFIXIT SBHarris 08:00, 28 January 2009 (UTC)
Not true (so it's a good thing it didn't get fixed). The greenhouse effect is merely a dependence of absorptivity on wavelength and is not a counterexample to reflectivity+emissivity = 1, which holds even for radiation at a specific wavelength and a specific direction. This is stated correctly at Radiant barrier#Reflectivity_and_emissivity but incorrectly at Kirchhoff's law of thermal radiation which brings in absorptivity incorrectly (on my list of things to fix). The statement "If the law were true at any specific wavelength, the energy distribution of the emitted energy would be also the same as that of the incident radiation" does not relate logically to the preceding sentence concerning glass because the incoming insolation and outgoing thermal radiation both originate outside the glass: the glass merely transmits the former from the sun while absorbing the latter from the ground or car interior. --Vaughan Pratt (talk) 07:26, 5 February 2010 (UTC)

Heat transmission redirects here, but this article has no explicit indication whether or not they refer to the same concept. Do they? Shouldn't that be mentioned?90.190.225.121 (talk) 04:47, 30 November 2009 (UTC)

## Nothing about Fourier or signal processing?

I've found nothing about Fourier in this article or in any of the articles bearing on climatology and the various atmospheric sciences. Why did Fourier invent spectral analysis, a fundamental tool of signal processing, and apply it to his study of heat transfer, if it is so irrelevant to the subject that no Wikipedia editor even mentions it in the context of heat? --Vaughan Pratt (talk) 18:00, 7 December 2009 (UTC)

If it's so important, why don't you put something in the article about it? WP:SOFIXIT. Wikipedia editors aren't omniscient-- we wait for experts to happy by and ask questions like yours. They we point out that it's a volunteer effort, so pitch in. SBHarris 18:29, 2 February 2010 (UTC)
It was a question, not a suggestion to add material. I wish I knew enough about Fourier's contribution to write something on it. For all I know it is irrelevant. --Vaughan Pratt (talk) 06:50, 5 February 2010 (UTC)

## Newton's Law of Cooling, solving differential equations

Am I correct in my belief that using non-absolute temperature scales (e.g. Celsius or Fahrenheit) when solving the differential equation given by Newton's law of cooling will lead to errors due to the natural logarithm of the ratio between temperatures? I seem to remember this being the case, but I cannot remember and I cannot find the information anywhere.

Thanks. --137.125.104.76 (talk) 15:46, 2 February 2010 (UTC)

No, because the log of the ratio of the temperatures never appears in solving Newtonian cooling problems, or any other cooling problem; heat flow problems tend to be linear in ΔT, due to Fourier's law. You're probably thinking of solving problems like entropy changes in non-isothermal conditions, where integration of dT/T type terms can give wrong answers if absolute temps aren't used. But they're only off by a constant if C vs K is used, because the degree size is the same. SBHarris 18:25, 2 February 2010 (UTC)

## Convection and Work

I'm a bit curious whether Convection occurs without 'Work'. Gravity plays a key role and hence there is work, indeed this 'work' is harvested in many ways by many machines?--Rjstott (talk) 17:47, 19 February 2010 (UTC)

## Needs edit

As written, the article misuses the languages of thermodynamics and radiative heat transfer, thus making a muddle of their concepts.

Thermodynamics features a body that is surrounded by a boundary. "Heat" flows through the boundary. "Work" is done on the boundary. The body has an "internal energy." The ideas of heat, work and internal energy are linked by the first law of thermodynamics. The second law of thermodynamics imposes a restriction on the flow of heat, namely that it can flow only from hotter to colder matter.

In radiative transfer, two or more bodies are said to "radiate against" one another.

Some of the article's deficiencies are:

• Asserts "Heat transfer is the transition of thermal energy..." but the ambiguous term "energy" is not used in thermodynamics. Could be modified to "Heat transfer is the transfer of heat..." but this would be redundant.
• Asserts "Radiation is the transfer of heat energy through empty space." but this is incorrect for radiation is not a transfer of heat. The correct idea is that when two bodies radiate against each other, heat is transferred from the hotter of the two bodies to the colder of the two.
• Asserts "All objects with a temperature above absolute zero radiate energy..." but the ambiguous term "energy" is not used in language of thermodynamics. To capture the idea of radiative heat transfer it is necessary to introduce the idea that two or more bodies "radiate against each other."
• Asserts "The energy from the Sun travels through the vacuum of space before warming the earth." but the ambigouous term "energy" is not used in the language of thermodynamics or heat transfer. Should be changed to something like "The Sun radiates against the Earth; as the Sun is hotter, heat is transferred to the Earth." —Preceding unsigned comment added by 99.38.149.90 (talk) 18:36, 28 March 2010 (UTC)
You seem to know a lot about it - go ahead, be bold! and edit the article. --Amaher (talk) 22:29, 28 March 2010 (UTC)

## Convection?

how does convection get the heat from one molecule to the next? Grabba (talk) 01:33, 18 May 2010 (UTC)

By diffusion (one molecule striking the next), which is also part of all convection. SBHarris 21:09, 28 July 2010 (UTC)

## First sentence

Why does the first sentence of this article state that heat transfer is only the transfer of heat by fluids? Convection in gasses, conduction and radiation are treated in the rest of the article. —Preceding unsigned comment added by 152.74.187.2 (talk) 20:19, 28 July 2010 (UTC)

Gases ARE fluids. "Fluids" include gases and liquids. Convection doesn't happen in solids. SBHarris 21:07, 28 July 2010 (UTC)

## Multiple issues with article

First of all, I agree with those below who say this article should be merged with heat. Heat transfer is a tautology.

Secondly, heat, denoted by a capital Q, is measured in Joules, not in Watts. In the section "Convection", Q is used (incorrectly) to denote the rate of heat transfer, whereas below, in the section "Newton's law of cooling", the quantities Q and dQ/dt are correctly defined.

I realize that many engineering textbooks use Q to denote the rate of heat transfer, but this is simply wrong. Q is heat, and it is measured in Joules. The first time derivative of Q, which can be written dQ/dt, or ${\displaystyle {\dot {Q}}}$, is the rate of heat transfer, which is measured in Watts. If any of you engineers out there are in any doubt about this, please look at the page on derived SI units.

I have gone ahead and made changes to the page where I think Q should be replaced by ${\displaystyle {\dot {Q}}}$. I leave it to other concerned editors to merge this page with heat

darkside2010 (talk) 12:47, 10 May 2010 (UTC)

We do not merge articles for the fun of it on Wikipedia. There is plenty of material on heat transfer to make a separate article from heat. It is, after all, an entire engineering discipline.
As for whether or not heat transfer is a tautology, that depends on whether or not the old or new definition of heat is used. The term comes from the days when heat was used synonymously with thermal energy, which is why today we still sometimes use "Q" to mean heat, when actually only dQ/dt is heat (Q is actually thermal energy, and "heat flow per time" is also that same tautology, if you want to be hardnosed about it).
Finally, please remember to use "watt" and "joule" when lecturing others about SI units. The use of capital letters are meant only to refer to the people of that name (as proper nouns), or in abbreviation (J and W), just as is the case with chemical elements. SBHarris 23:50, 14 May 2011 (UTC)

## Critical insulation thickness

The description on this page is wrong.This sentence has the logic reversed "The point where the added resistance of increasing insulation thickness becomes overshadowed by the effect of increased surface area is called the critical insulation thickness." It should read "The point where the added resistance of increasing insulation thickness overcomes the effect of increased surface area is called the critical insulation thickness."

For confirmation/explanation, see http://www.raeng.org.uk/education/diploma/maths/pdf/exemplars_engineering/2_SteamPipe.pdf or a heat transfer textbook.

131.111.85.79 (talk) 13:34, 20 January 2012 (UTC)

This section of the article is definitely a mess.

The concept of "critical insulation thickness" is interesting in theory but I'm not sure it occurs in practice often enough to merit a mention in this article. Infact I suspect that when you're looking at real insulation materials it often doesn't exist at all or exists at such a small thickness (somewhere far less than 1 mm) that there is no need to consider it.

The reason for this is that if you continually re-calculate the surface coeffient of heat transfer (h) from scratch every time you increase the insulation thickness the coefficient becomes smaller every time.

Yes, if you set the thermal conductivity to 0.15 W/(m K), then you'll get a critical insulation thickness but when you take the thermal conductivity down to a much lower level (how many insulation materials are sold with a conductivity greater than 0.05 W/(m K) in the 0-100 degree range?) the critical insulation thickness gets muted and shifted to lower thickness's. I suspect the natural reduction in the surface coefficient as the thickness increases could wipe it out entirely (especially since it has a greater influence as the thickness is lower).

There are things that should be pointed out about the relationship between thickness, surface coefficient and such (applying an insulation material with a higher emissivity finish than the pipe surface will definitely increase the heat flow than an un-insulated pipe for instance) but whether this is the right article to add this level of detail I'm not sure. Surely pipe insulation is a better place? 86.160.197.23 (talk) 16:31, 23 January 2012 (UTC)

Replaced cleanup tag with disputed accuracy; as 131.111..; says, it's the exact opposite. Small diameter pipes (or a thin hot wire for example) will lose more heat when a thin layer of insulation is applied. Total thermal resistance is the sum of conductive resistance and convection resistance. The critical thickness is where total resistance reaches a minimum, not a maximum. Should be obvious when one realises that convection resistance can't go lower than zero. Ssscienccce (talk) 03:07, 3 September 2012 (UTC)
removed the tag, description seems ok now. Changed symbol for radius to small letter r to avoid confusion with thermal resistance. Ssscienccce (talk) 11:14, 29 November 2013 (UTC)
Maybe we can move the part to thermal insulation? Prokaryotes (talk) 13:44, 7 April 2014 (UTC)
Moved to Thermal insulation prokaryotes (talk) 00:22, 18 April 2014 (UTC)

## Organization

I have re-organized some of the material to try and structure the article a bit better. I had in mind that this might clarify the contents of this article vs. the contents of Heat. Not that I necessarily think they must be separate articles, but at least for the time being this may improve the readability.

I also separated out some of the lumped capacitance / thermal circuit stuff to its own article (Lumped capacitance model) as there were bits of that topic scattered in various places and it seemed best to consolidate it there; this also had the effect of slightly shortening and focusing this article.

Also, Darkside2010, I moved your "multiple issues" section down here as I think it is the norm to add newer comments at the bottom of the talk page (as far as I can tell?) Hope that is okay. Dhollm (talk) 10:26, 10 August 2010 (UTC)

I further organized the page, made the part on engineering more clear and added some basic aspects missing. Prokaryotes (talk) 13:42, 7 April 2014 (UTC)

## Heat transfer physics

Please see Talk:Heat#Heat_transfer_physics. Staszek Lem (talk) 18:07, 13 September 2013 (UTC)

## Heat Transfer should be compatible with Second Law article

NOR

This article on Heat Transfer should not be saying something altogether different from what the article on the Second Law of Thermodynamics says. The end state of maximum attainable entropy is a state of thermodynamic equilibrium, not just a state of thermal equilibrium. The latter may not be a state of maximum entropy, unless you define thermal equilibrium as having no further net energy transfers across any boundary between objects and any boundary within objects. The Second Law says nothing at all about heat transfers being only from hot to cold. It talks about entropy never decreasing. All this is well established physics.

Douglas Cotton (talk) 03:01, 1 April 2014 (UTC)

A picture in the page says "Red-hot iron object, transferring heat to the surrounding environment primarily through thermal radiation".
I think this sentence is wrong and misleading, in fact if we put our hand near a red-hot iron object like that one showed in figure nothing happens, instead if we touch it we will have a burn. This means that the conduction contribute is predominant. To be predominant the radiant effect the body needs to be at a really high temperature.
Hence I think we can change the sentence in: "Red-hot iron object, transferring heat to the surrounding environment also through thermal radiation". If we want to maintain the word "predominant" we need to use another example instead or we need to specify "at distance", comparing in this way the radiant with only the convective contribution, but also in this case I think we need another example with higher temperature (for example the Sun, that exchanges only radiant heat with the Earth). --Daniele Pugliesi (talk) 10:06, 9 November 2014 (UTC)

## Newton's law of cooling

I would certainly support this becoming a separate page if an editor came along with decent reference works concerning the historical context of Newton's investigations. I didn't find a lot in a quick search. I did find one PPT which claimed that Newton used a modern-style thin tube thermometer filled with linseed oil, marked in a "Celsius" scale (perhaps centigrade would be the more correct term). It also pointed out that Newton's law is correct even though his own experiment disagreed, due to experimental effects such as convection within the thermometer itself. It wasn't up to cite-worthy standards, though. It seems Newton himself only regarded his law as valid for temperature differences up to 10 degrees C.— MaxEnt 10:48, 10 April 2014 (UTC)

Newton's law of cooling happens in many circumstances, some convective, some conductive. It deserves its own article as a mechanistic phenomenon, even absent a history section, and it used to have one. Then some lumper-editor person stuck it in the convective heat transfer article. I'll give everybody a few days to comment, and then assume that silence implies consent, start a Newton's Law of Cooling article, then spin this section off per WP:SS, leaving a small summary section behind. That needs be done also, referencing this "law" in several other heat transfer articles. SBHarris 19:56, 8 June 2015 (UTC)

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