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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)
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)
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 requested a peer review because I think that this article meets several of the Wikipedia criteria for becoming a featured article. I believe that this article is consise, covers the topic completely, is stable, and contains minimal point-of-view influence. I believe that this article describes a very complicated topic elegantly, and may be useful for both engineers and people with no engineering knowledge. If you agree that this article is a good candidate for becoming a featured article, please let me know. Otherwise, all of use who have worked on this article would appreciate your comments and edits.
Thank you,
- Âme Errante 10:15, 29 July 2006 (UTC)
The link "Heat Transfer Links - Heat Transfer Links" located in the domian onesmartclick.com is nothing more than a page filled with Google advertisements. I would guess that someone edited it into this article to make money off people clicking that link. I'm removing the offending link. Jason 18:16, 1 May 2006 (UTC)
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.
Please look at:
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)
I removed the following statement from the intro paragraph:
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 ( talk • contribs) 20:01, 4 October 2006 (UTC)
"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."
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)
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)
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)
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)
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)
"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.
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)
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)
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)
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)
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:
how does convection get the heat from one molecule to the next? Grabba ( talk) 01:33, 18 May 2010 (UTC)
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)
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 , 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 . I leave it to other concerned editors to merge this page with heat
darkside2010 ( talk) 12:47, 10 May 2010 (UTC)
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)
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)
Please see Talk:Heat#Heat_transfer_physics. Staszek Lem ( talk) 18:07, 13 September 2013 (UTC)
NOR
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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)
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)
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The article needs cleaning up. Heat is not a fluid, it does not "flow". Damorbel ( talk) 16:32, 1 January 2021 (UTC)
This is multiple times you've presented your personal fallacy, on thermal equilibrium Wikipedia pages.
""Heat is thermal energy associated with temperature-dependent motion of particles. The macroscopic energy equation for infinitesimal volume used in heat transfer analysis,
(∂T/∂t) /*snip
Once states and kinetics of the energy conversion and thermophysical properties are known, the fate of heat transfer is described by the above equation. These atomic-level mechanisms and kinetics are addressed in heat transfer physics. The microscopic thermal energy is stored, transported, and transformed by the principal energy carriers: phonons (p), electrons (e), fluid particles (f), and photons (ph).""
In layman's terms, I pour hot water into cold water, and via convection, you get tepid water.
Read this article again, where it says convection.
Heat "flows", that does an adequate job of conveying the meaning in writing. For everything else there's pictures.
Sorry if I sound harsh, but, the article is good, and doesn't deserve being yelled at. I for one value our editorial overlords.
Have a nice day. — Preceding unsigned comment added by 49.199.238.133 ( talk) 18:08, 22 April 2022 (UTC)
Hi. Isn’t the phrase “heat transfer” redundant, since “heat” is defined in thermodynamics already as energy being transferred by mechanisms other than work and transfer of matter? Alej27 ( talk) 00:13, 4 November 2021 (UTC)
.[8] An example of steady state conduction is the heat flow through walls of a warm house on a cold day—inside the house is maintained at a high temperature and, outside, the temperature stays low, so the transfer of heat per unit time stays near a constant rate determined by the insulation in the wall and the spatial distribution of temperature in the walls will be approximately constant over time.
This does not take into account the dew point of the walls. A better example could be found. 86.150.117.77 ( talk) 17:52, 5 October 2022 (UTC)
I have restored the History section, but moved it to the end of the article so as to deemphasize its importance. I agree with Sgubaldo that a History section is not really necessary, but I think it would be nice to have one. At the end of the article it will hopefully offer minimal distraction. As for now the section is woefully inadequate and unbalanced (my fault) consisting mainly of a long, quote-heavy account of just one series of experiments by Benjamin Thompson and subsections copied from other parts of Wikipedia. Some little editing has been done to the latter though, while leaving them mainly unchanged at their original pages.
The relevant parts of the History section could be moved to the articles Thermal conduction, Thermal conductivity, Convection (heat transfer), and Thermal radiation respectively, and I might try that if it is not suitable here. I was thinking of adding historical content to Convection (heat transfer), but found that there were two seemingly overlapping articles: Convection (heat transfer) and Convection; the former more relevant on account of its title, the latter—in my opinion—better and more complete. I wasn't sure where best to put it.
If some senior editor feels there should be no, or just a brief History section, I'll leave it at that. For all I have to offer is expansion. Unfortunately, I don't have time to scour the literature for a nice, balanced section covering all different time periods. My additions must rather happen as I come across them for other reasons, meaning—for now—few and far between additions of more Thompson and other 17th and 18th centuries investigators. The Cosmic Ocean (Please feel free to modify or undo any of my edits as deemed appropriate.) 16:07, 16 January 2024 (UTC)
![]() | This article is written in American English, which has its own spelling conventions (color, defense, traveled) and some terms that are used in it may be different or absent from other varieties of English. According to the relevant style guide, this should not be changed without broad consensus. |
![]() | Text has been copied to or from this article; see the list below. The source pages now serve to
provide attribution for the content in the destination pages and must not be deleted as long as the copies exist. For attribution and to access older versions of the copied text, please see the history links below.
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![]() | This page is not a forum for general discussion about Heat transfer. Any such comments may be removed or refactored. Please limit discussion to improvement of this article. You may wish to ask factual questions about Heat transfer at the Reference desk. |
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)
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)
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 requested a peer review because I think that this article meets several of the Wikipedia criteria for becoming a featured article. I believe that this article is consise, covers the topic completely, is stable, and contains minimal point-of-view influence. I believe that this article describes a very complicated topic elegantly, and may be useful for both engineers and people with no engineering knowledge. If you agree that this article is a good candidate for becoming a featured article, please let me know. Otherwise, all of use who have worked on this article would appreciate your comments and edits.
Thank you,
- Âme Errante 10:15, 29 July 2006 (UTC)
The link "Heat Transfer Links - Heat Transfer Links" located in the domian onesmartclick.com is nothing more than a page filled with Google advertisements. I would guess that someone edited it into this article to make money off people clicking that link. I'm removing the offending link. Jason 18:16, 1 May 2006 (UTC)
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.
Please look at:
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)
I removed the following statement from the intro paragraph:
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 ( talk • contribs) 20:01, 4 October 2006 (UTC)
"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."
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)
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)
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)
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)
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)
"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.
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)
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)
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)
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)
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:
how does convection get the heat from one molecule to the next? Grabba ( talk) 01:33, 18 May 2010 (UTC)
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)
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 , 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 . I leave it to other concerned editors to merge this page with heat
darkside2010 ( talk) 12:47, 10 May 2010 (UTC)
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)
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)
Please see Talk:Heat#Heat_transfer_physics. Staszek Lem ( talk) 18:07, 13 September 2013 (UTC)
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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)
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)
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The article needs cleaning up. Heat is not a fluid, it does not "flow". Damorbel ( talk) 16:32, 1 January 2021 (UTC)
This is multiple times you've presented your personal fallacy, on thermal equilibrium Wikipedia pages.
""Heat is thermal energy associated with temperature-dependent motion of particles. The macroscopic energy equation for infinitesimal volume used in heat transfer analysis,
(∂T/∂t) /*snip
Once states and kinetics of the energy conversion and thermophysical properties are known, the fate of heat transfer is described by the above equation. These atomic-level mechanisms and kinetics are addressed in heat transfer physics. The microscopic thermal energy is stored, transported, and transformed by the principal energy carriers: phonons (p), electrons (e), fluid particles (f), and photons (ph).""
In layman's terms, I pour hot water into cold water, and via convection, you get tepid water.
Read this article again, where it says convection.
Heat "flows", that does an adequate job of conveying the meaning in writing. For everything else there's pictures.
Sorry if I sound harsh, but, the article is good, and doesn't deserve being yelled at. I for one value our editorial overlords.
Have a nice day. — Preceding unsigned comment added by 49.199.238.133 ( talk) 18:08, 22 April 2022 (UTC)
Hi. Isn’t the phrase “heat transfer” redundant, since “heat” is defined in thermodynamics already as energy being transferred by mechanisms other than work and transfer of matter? Alej27 ( talk) 00:13, 4 November 2021 (UTC)
.[8] An example of steady state conduction is the heat flow through walls of a warm house on a cold day—inside the house is maintained at a high temperature and, outside, the temperature stays low, so the transfer of heat per unit time stays near a constant rate determined by the insulation in the wall and the spatial distribution of temperature in the walls will be approximately constant over time.
This does not take into account the dew point of the walls. A better example could be found. 86.150.117.77 ( talk) 17:52, 5 October 2022 (UTC)
I have restored the History section, but moved it to the end of the article so as to deemphasize its importance. I agree with Sgubaldo that a History section is not really necessary, but I think it would be nice to have one. At the end of the article it will hopefully offer minimal distraction. As for now the section is woefully inadequate and unbalanced (my fault) consisting mainly of a long, quote-heavy account of just one series of experiments by Benjamin Thompson and subsections copied from other parts of Wikipedia. Some little editing has been done to the latter though, while leaving them mainly unchanged at their original pages.
The relevant parts of the History section could be moved to the articles Thermal conduction, Thermal conductivity, Convection (heat transfer), and Thermal radiation respectively, and I might try that if it is not suitable here. I was thinking of adding historical content to Convection (heat transfer), but found that there were two seemingly overlapping articles: Convection (heat transfer) and Convection; the former more relevant on account of its title, the latter—in my opinion—better and more complete. I wasn't sure where best to put it.
If some senior editor feels there should be no, or just a brief History section, I'll leave it at that. For all I have to offer is expansion. Unfortunately, I don't have time to scour the literature for a nice, balanced section covering all different time periods. My additions must rather happen as I come across them for other reasons, meaning—for now—few and far between additions of more Thompson and other 17th and 18th centuries investigators. The Cosmic Ocean (Please feel free to modify or undo any of my edits as deemed appropriate.) 16:07, 16 January 2024 (UTC)