Talk:Heat/Archive 11

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convection of heat

Latest comment: 12 years ago19 comments5 people in discussion

There are various views on the notion of convection of heat. A a child at school I was taught that heat can be convected. Many engineers talk of convection of heat. The present Wikipedia article on heat transfer talks freely about the convection of heat, but does not contain the phrase 'internal energy'; it also talks freely of 'thermal energy'. The present Wikipedia article on heat cites two sources for the definition of heat, Kittel & Kroemer, and Reif. Kittel & Kroemer in their index have an entry "Convective isentropic equilibrium". It refers to problem set on page 179. The word heat does not appear in the text of that problem. Reif has no entry for convection in his index. In thermodynamics, the phrase 'convection of heat' might be anticipated to refer to open systems. In general, transfer of energy as heat is not defined for open systems.(Münster, A., 1970, Classical Thermodynamics, translated by E.S. Halberstadt, Wiley–Interscience, London, ISBN 0-471-62430-6, pp. 50–51. The index of this text does not contain an entry for convection.)Chjoaygame (talk) 22:05, 16 November 2012 (UTC)

response by Waleswatcher

What would you call the transfer of energy from a high temperature solid object to a cold gas surrounding it, and then to a colder container surrounding the gas? Waleswatcher (talk) 23:47, 16 November 2012 (UTC)

Good question. It depends on how the transfer takes place. The system as described as a whole seems to consist initially of several bodies in thermal contact, initially at different temperatures. The problem as stated refers to a colder container, but does not explicitly say what determines the temperature of its walls, whether they are kept at controlled steady temperature or whatever. I will treat the problem as intending no external energy source, so that the system as a whole is isolated. It seems intended to assume that the solid body does not evaporate and the gas does not condense?

If the temperature differences are small so that the process is very slow, it might occur without hydrodynamic instability, and thus without convection. Then conduction would be important, and radiation between the internal solid body and the walls might be significant. If the gas volume were very large, radiation within the gas might also come into it.

If the temperature differences are larger, hydrodynamical instability might occur, and convection. Classical thermodynamics does not talk about intermediate stages of the process, but restricts its attention to the initial and final equilibrium states. The final equilibrium state is one of thermal equilibium, in which the temperatures of the several bodies are equal.

Non-equilibrium thermodynamics could well take an interest in the intermediate stages of the process, and would be concerned with hydrodynamic stability and convection. Both bulk movement of the parts of the gas and conduction would be of much concern. The energetic quantity considered to be transported by bulk movement of parts of the gas would be depend on the variables chosed for the formulation of the analysis. Internal energy density would be suitable if the relevant variables were chosen. Some treatments, that did not respect the strict physical definition, would call that internal energy density a density of heat, and would talk of convection of heat; I think the Wikipedia article Heat transfer would likely do that. But you are asking me what I would call it. I would follow the strict physical definition, and call it transport of internal energy by bulk flow.

If the convection were very strong, then turbulence might occur, and a precise thermodynamic treatment would not be feasible.Chjoaygame (talk) 02:27, 17 November 2012 (UTC)

Enough time has elapsed to let Waleswatcher respond to this. He hasn't. It seems reasonable to infer that he concedes the point, that the strict thermodynamic definition of heat allows it to transfer itself only by conduction and radiation, and not by convection. Convection of heat is for some engineers and schoolboys.Chjoaygame (talk) 03:38, 20 November 2012 (UTC)

response by Waleswatcher

I've simply been very busy. I do not "concede" that point, nor is that point relevant. This article is not about "the strict thermodynamic definition of heat". It is about heat. Along with radiation and conduction, convection is one of the primary and common mechanisms of heat transfer. Therefore, this article should discuss it. Since the lead should summarize the article, it's reasonable for the lead to mention convection. Waleswatcher (talk) 12:54, 20 November 2012 (UTC)

We have been patient while you attend to your important "very busy" activities, but we do not get the same consideration from you, in your habit of violent onslaughts in bursts of editing, that largely ignore the talk page, and overwrite contrary opinions as if you own the lead.

For some time, the article suffered from your violent removal from the lead of the advice that the article is written from the technical viewpoint of physics, and especially of thermodynamics. Now you have conceded by your actions that your former removal was wrong. Your former removal of that reservation survived because other editors, though knowing it was wrong, did not wish to engage in the violent and unethical kind of editing that you inflict. So for a while you got your way by violence.

The article is not, as you assert just above, about heat as read in ordinary language. It is about heat as viewed from the viewpoint of physics and chemistry, with thermodynamics of particular importance, as you now admit in the article.

The lead you have inflicted on the article now seems smooth talk, as is your taste. But its logic is poor and fuzzy. The term 'thermal interaction', imposed by you, is an evasion, because the word 'thermal' is eventually not clearly defined. The references for the first sentence are from Reif and from Kittel & Kroemer, introductory student textbooks of statistical mechanics, that take the pedagogical viewpoint that thermodynamics should be taught simultaneously with statistical mechanics, but hardly mention the more serious parts of thermodynamics, such as Legendre transforms and the choice of working with energetic potentials versus Massieu-Planck functions, and thermodynamic stability theory. They do not consider convection as a form of heat transfer. The second sentence of the lead as it is worded could easily suggest to a naive reader that convection of heat is transfer by bulk flow of something that is conserved, and could be represented by a state variable of the bulk fluid, in contradiction of the vaguely worded third sentence of the lead, "Heat is not a property of a system or body, but instead is always associated with a process of some kind", which omits reference to the important idea that a property of a body is represented by a state variable, and leaves the kind of process unduly wide open. From what you write, it seems possible or even likely that you yourself do not understand that heat in physics, not being subject to a conservation law, cannot in logic be convected. Engineers can think in terms of convection of heat by considering restricted classes of process. While thermodynamics of open systems allows, in general, diffusion to occur where internal energy is also being transferred, or produced from external potential energy, engineers can deal with many of their problems by treating restricted processes which do not involve such simultaneous transfers, and so avoid the problems that a general thermodynamic treatment considers. Leaving convection there in the lead invites confusion, which is partly your aim, in order to evade a clarity that would expose your sloppy thinking.Chjoaygame (talk) 15:39, 20 November 2012 (UTC)

Your talk page comments are as wordy and incoherent as your edits to the article. Waleswatcher (talk) 17:12, 20 November 2012 (UTC)

Waleswatcher, you thus confirm your violent and unethical character. The talk page is too much for you. In particular, you offer no physical reason for your violently imposed view that heat can be convected, while you still say below to Damorbel that the definition of heat that we are using is that of physics, not of ordinary language.Chjoaygame (talk) 21:14, 20 November 2012 (UTC)Chjoaygame (talk) 21:27, 20 November 2012 (UTC)

Wikipedia is based on reliable sources, Chjoaygame. Find us a source that states explicitly that radiation and conduction are the only mechanisms of heat transfer, and we can compare it to the multiple sources that say otherwise (and explicitly include convection). Until then, no such statement can be added to the article. Apart from wiki policy, the purpose of this article is to explain a basic concept of physics. People reading it want to know what's the underlying physics of heat, and why they feel warmth when they stand near a vent blowing heated air. Waleswatcher (talk) 12:00, 21 November 2012 (UTC)

Dear Waleswatcher, you can spin this by violence and Wikilawyering, but you can't get the physics right.Chjoaygame (talk) 20:44, 21 November 2012 (UTC)

response by Damorbel

Chjoaygame your argument: the strict thermodynamic definition of heat allows it to transfer itself only by conduction and radiation is completely without foundation.

Heat transfer is a subset of the processes that lead to thermal equilibrium. Thermal equilibrium is the condition where the temperature is uniform - full stop. Now a mole of an material contains 6.02214X×10²³ (Avogadro's number) particles, I invite you to estimate how many ways these 6.02214X×10²³ particles can go from any state of disequilibrium to equilibrium. Your idea that only conduction and radiation exist surely is not supported by the facts; does diffusion not play a role, particle collisions in gases. Equilibrium implies that the probability of a particle has a given energy is uniform throughout the system - that is what it's all about, not imginary restrictions. Oh, and don't forget there is no restriction on the size of the particles!. --Damorbel (talk) 08:08, 20 November 2012 (UTC)

response by Damorbel

Convection is mass transport in fluids in a gravitational field (a kettle of water, a planetary atmosphere) when a (mass) density differential arises due to thermal disequilibrium. Convection is not to be confused with forced convection which is quite distinct; in forced convection momentum is added to the system from an external source, the energy implied most likely being converted to heat by friction. --Damorbel (talk) 07:21, 17 November 2012 (UTC)

Chjoaygame, you mention neither gravity nor (mass) density in your explanation of convection above; nor do you distinguish between convection and forced convection. I think these are important matters in regard to convection since they are all related to the concept of heat as energy in the motion of particles. I'm sure your omission was inadvertent and not on technical grounds. Thanking you in advance for your attention. --Damorbel (talk) 07:21, 17 November 2012 (UTC)

I was not seeking to explain convection. I was seeking only to specify what might be convected. I was not trying to consider "a concept of heat as energy in the motion of particles". That is not the notion of heat that is considered in thermodynamics, the main theory for the present article. Dear Damorbel, we are all well aware that you would like to change the viewpoint of the article so as consider "a concept of "heat as energy in the motion of particles", but mostly we are not attracted by the idea; I think you are very well aware of this. Not even in statistical mechanics is that a very satisfactory definition, as you will find by reading some textbooks on the subject, with an open mind. We have mostly found by experience that our explanations here of the reasons for this do not satisfy you. That is why I suggest you do some reading for yourself, with an open mind.Chjoaygame (talk) 07:59, 17 November 2012 (UTC)

Chjoaygame, "but mostly we [sic] are not attracted by the idea"; is of absolutely of no relevance to the Heat articles in Wikipedia

It should be clear to all that the concept of heat is the relation of temperature and energy incorporated in the Boltzmann constant. As far as I can see the Boltzmann constant does not appear in your arguments. I suggest that until it does you will not be able to sustain them. Please comment. --Damorbel (talk) 08:33, 17 November 2012 (UTC)

No comment.Chjoaygame (talk) 11:13, 17 November 2012 (UTC)

This won't do, Chjoaygame. You dismiss my claim that a Wiki article on heat should be based on the energy of the particles of the system and when I invite you to discuss the key relation between particles, their temperature and energy - the Boltzmann constant - you reply 'No comment'. If you are not able to progress this discussion at such basic level, are you able to say how I am to respond to your contributions to the heat article? --Damorbel (talk) 11:41, 17 November 2012 (UTC)

The basic level of discussion includes a fact that you will not absorb, which is that heat is not temperature, which is what the Boltzmann constant is about. To get from temperature to heat, you must consider the defining relation between them, which is heat capacity. This is a complex function which is not constant, not obvious, and which makes the whole matter of heat nontrivial and not capable of being easily defined in terms of temperature (and thus motion) alone. Okay? We've told you this a dozen times and yet it does not penetrate. What is your mental block? S B H arris 17:07, 17 November 2012 (UTC)

response by editor 186.32.17.47

Heat is not based on the energy of the particles. Damorbel, you are confusing internal energy with heat. Heat and work are trasnfer phenomena, temperature is part of the state of the system. In classical equilibrium thermodynamic processes what one has is an equilibrium initial state and an equilibrium final state. In these internal energy is a function of temperature (and so of the microconfigurations of constituent particles), and also entropy, free energy, enthalpy, and other functions of state are functions of the microconfigurations of constituent particles. Transfer phenomena, mechanics, the study of heat tranfer, are another matter entirely, dependant on the process and used to provide descriptions of the dynamics of processes, not of it's equilibrium state conditions...--186.32.17.47 (talk) 16:49, 19 November 2012 (UTC)

Incompatible statements?

Latest comment: 12 years ago20 comments5 people in discussion

I suggest that these four statements in the article are not consistent:-

1/ "Heat flow from a high to a low temperature body occurs spontaneously." (Opening statement, 2nd paragraph)

2/ "The SI unit of heat is the joule." (Opening statement, 3nd paragraph)

3/ "Heat in physics is defined as energy transferred by thermal interactions." (Overview - 1st line)

4/ "The first law of thermodynamics describes the principle that the internal energy of an isolated system is conserved." (Overview - 1st line, 2nd paragraph)

I invite comments since there appears to be no consensus on the physics involved. --Damorbel (talk) 07:55, 17 November 2012 (UTC)

I do think that the first one is correct: if both systems are in thermodynamic contact heat will flow until both have the same temperature, either by radiation, conduction or more complex phenomena. Also the unit for heat is the same as the unit for energy and work (the joule). When there is a thermal interaction between two systems heat is transfered if there is a gradient of temperature. The first law of thermodynamics does state this and then can be generalized to a conservation of energy law and even a conservation of mass energy law (regarding the derivation of the equivalence of mass and energy of Einstein).--186.32.17.47 (talk) 16:58, 19 November 2012 (UTC)

Thanks for you response 186.32.17.47 (I wish you had a name!)

This section I started is really FAR TOO OBSCURE!

I am trying to make the point that the article is self-contradictory.

It is section 3/ that is the problem, You are quite right, section 1/ is OK.

However, if the unit of heat is the Joule - section 2/ (energy - conserved)

then it does not just appear during transfer, it is here all the time (sections 1/, 2/, & 4/.

--Damorbel (talk) 21:34, 19 November 2012 (UTC)

Nope: the unit of work is the Joule too and it is also a function of time. http://en.wikipedia.org/wiki/Joule "The joule ( /ˈdʒuːl/ or sometimes /ˈdʒaʊl/); symbol J) is a derived unit of energy, work, or amount of heat in the International System of Units.[1] It is equal to the energy expended (or work done) in applying a force of one newton through a distance of one metre (1 newton metre or N·m), or in passing an electric current of one ampere through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889).[2][3][4]" The first law of thermodynamics states that energy is conserved in an isolated system: the total change of energy of "the universe" (being the universe an isolated system) is always zero. Energy is a function of state. Energy is transfered between the system in study and it's sorroundings through two distinct quantities or phenomena: heat and work. Both, heat and work, are functions of _path_, both are dynamic quantities, both are not functions of state; heat and work are how energy is transfered between a system and it's sorroundings, not related to the energy content but to the transfer phenomena. According to the second law of thermodynamics there is a minimum ammount of heat that _always_ has to be transfered in order to "move" a system between two states: the process that uses up the minimum quantity of heat possible is a reversible process such as dS=δQrev/T. The "δ" means that it is not a function of state, that the differential is not an "exact differential", that it is a function of _path_. Most of the work of Gibbs and others is a mathematical framework to deal with exact differentials in equilibrium states and the relationships between G, T, S, U, H, A, and variables of state (T,P, Vmol, Ni) and amongst themselves, including the use of Maxwell relations http://en.wikipedia.org/wiki/Maxwell_relations between the second derivatives of thermodynamic potentials http://en.wikipedia.org/wiki/Thermodynamic_potentials. In order to simplify: first the system is in equilibrium, then there are some dynamical aspects that involve "heat" and "work" and then we have another equilibrium state. In a system in equilibrium with it's sorroundings there is no heat and no work performed. Heat and work exist as distinct path functions in a given physical process. The first and second law also imply the non possibility of perpetuum mobile. The confusion arises when (lacking proper thermodynamic discourse) such thing as "heat content" is instead of internal energy and or enthalpy. dH=δQ+VdP+δW' where if pressure is constant and δW' (other work, not related to pressure volume work) is zero then dH=δQ if the only work done is expansion work and there is no other work involved. But dH is a change in the _enthalpy_ of the system (a function of state: i.e. a function of the state of the system before and after a process that involves a certain ammount of heat δQ). That is one of the reasons why enthaply is so important in physical chemistry and thermodynamic equilibrium. In order to establish these relations there is no need to take into account statistical thermodynamics (even though they are compatible with it) nor is "heat contained" on any system ever. Heat is exchanged between the system in analysis and the sorroundings. --186.32.17.47 (talk) 22:25, 19 November 2012 (UTC)

186.32.17.47, Thank you for your reply.

What do you mean by 'nope'?

You write "the unit of work is the Joule too". Work, as you acknowledge is measured in Joules, it is the integral of force (Newtons) over a period of time, the joule is a measure of energy; energy is a conserved so when an amount of work is done the energy is transformed into another manifestation PV^γ for a gas, δT xC (C = heat capacity in joules/K). But there are other manifestations of energy transformation, electrical and chemical energy can also be transformed into heat, the actions in this case may or may not involve time the heat (in joules) is equal to the chemical or electrical energy received from the source.

How is "heat and work, are functions of _path_"? Chemical energy is not a function of path; electrical energy stored in the electrical field of a capacitor is not a function of path, neither is gravitational energy. Conserved quantities like energy are independent of path.

A bit of clarifiation would be appreciated! --Damorbel (talk) 15:24, 20 November 2012 (UTC)

"However, if the unit of heat is the Joule - section 2/ (energy - conserved)

then it does not just appear during transfer, it is here all the time" = Nope. Heat, as work, as you clearly state, is a path function or a process function see:

http://en.wikipedia.org/wiki/Path_function One thing is _heat_ which is a process function, another thing is _work_ which is another process function, another thing is energy which is a function of state. All are measured in joules. It seems to me you could not understand how thermodynamic analysis is done: one first must establish a sytem and an initial equilibrium state for the system. Then there is a process that changes the state of the system, generating an interaction with the system sourroundings that changes it's energy through work and heat. Finally there is another equilibrium state. Heat and work are processes where energy is transfered. The do not 'exist' when the process is not occuring and they are _path_dependent_. Energy is conserved, but it is transfered between the system and it's sorroundings through heat and work during a process. It is the energy of an isolated system that is conserved, not the energy of any system. If you divide the universe in two sytems ('the system of study' and 'the sorroundings' the sum of both sytems is an isolated system for the process that is being analyzed).--186.32.17.47 (talk) 16:06, 20 November 2012 (UTC)

186.32.17.47 You have not understood the argument being presented. Perhaps it would help if you told me what you call the energy of the vibrating particles in as system of particles when such a system has a uniform temperature and the particles are able to exchange energy freely.

I ask this because, when you describe 'heat' as a process (above) you are not describing (nor is your link) a system with a uniform temperature but one with more than one temperature; so what you are describing is indeed a heat transfer process which is essentially a process in a system that is in disequilibrium. Calling this heat is a shorthand or jargon term; the full expression should be heat transfer the word transfer, standing as it does for disequilibrium, has been left out. --Damorbel (talk) 20:14, 20 November 2012 (UTC)

reponse by Waleswatcher: Damorbel, there is nothing incompatible about those statements. Heat is indeed energy transferred by a specific means (thermal interactions). Can I make an analogy? You have a certain amount of money in your bank account, measured in euros. Your salary is money transferred into your bank account by your employer because of work you have performed. Your salary is also measured in euros. Energy is like the money in your account, while heat is like salary - they're measured in the same units, but they're not the same thing, and you would never refer to the money in people's bank accounts as "salary". Does that make sense? Waleswatcher (talk) 17:15, 20 November 2012 (UTC)

Rubbish, Waleswatcher. What I have in the bank is money (I wish it was!). My salary is (a little) money per month, I have to integrate it wrt time before it becomes money. The money in the bank represents energy in the system, it is conserved (Oh dear!); whereas the income is a variable function of time from outside the system and may well not be predictable i.e. it is not conserved.

The system may undergo expenditure in which case the money in the bank is not isolated but is transferred somewhere else. --Damorbel (talk) 20:14, 20 November 2012 (UTC)

Nope: ΔE=Q+W. All three use the same units. I do not see how these comparissions with bank accounts help, but if you receive a couple of bucks and have a million in the account they are all bucks. W=INTEGRAL(F.vdt). I think you might be confusing _force_ with _work_ Work is work, wether it is an infinitesimal ammount (δW) or the total ammount involved in a process: it has the same units. δW=F.vδt. http://en.wikipedia.org/wiki/Work_(physics) In a similar way, we have Fourier's law to model heat transfered through conduction (http://en.wikipedia.org/wiki/Thermal_conduction)or the equations for radiative heat transfer (http://en.wikipedia.org/wiki/Thermal_radiation). In all cases heat has the same units as does work and energy (ΔE=Q+W), both heat and work are functions of the path taken by the process, meanwhile energy is a function of state (i.e. kinetic energy is a function of velocity, potential energy a function of position in a force field...). Heat and work are energy being transfered. This is why the "money" example does not add up to me: it is as if some of the money that is "useful" was destroyed with each transfer and depended on the path, which is not the case: I can´t think of a proper analogy regarding money. --Crio (talk) 21:59, 20 November 2012 (UTC)

Perhaps it would help if you told me what you call the energy of the vibrating particles in as system of particles when such a system has a uniform temperature and the particles are able to exchange energy freely. That wasn't addressed to me, but I'll answer: thermal energy, or internal energy, or simply energy. Heat is the transfer of that energy to another system or part of the system. Again: energy is money in the bank, heat is deposits or withdrawals (that works slightly better than salary). I've seen you question this over and over and over again, but that is in fact the way these terms are defined in physics, and there's nothing inconsistent or even particularly confusing about it other than semantic confusion with the common usage. Waleswatcher (talk) 21:17, 20 November 2012 (UTC)

Waleswatcher, perhaps the question "...what [do] you call the energy of the vibrating particles... " wasn't addressed to you but neither have you answered it. Your 'answer' is that the transfer of energy is 'Heat'; my question can be rephrased as: - 'what do you call the energy before it is transferred'? In my opinion this is the energy that gives a system its temperature.--Damorbel (talk) 08:35, 21 November 2012 (UTC)

Question:' what [do] you call the energy of the vibrating particles?

Answer: thermal energy, or internal energy, or simply energy. Waleswatcher (talk) 11:49, 21 November 2012 (UTC)

No,Waleswatcher, the question was about the energy of the vibrating particles (energy per particle) which is, through the Boltzmann constant, their temperature measured in Kelvins, Celsius etc. and thus their hotness which of course is the common interpretation of heat. Your response thermal energy, which is of course measured in Joules, depends on the number of particles in the system - N_A if the system is a mole(unit), but the system can be any size you like, having energy corresponding to its size. The amount of thermal energy a system does not require it to be in equilibrium; however to know the temperature of any system there are two requirement 1/ the system must be in equilibrium and 2/ the number of particles and the total (thermal energy Q in it must be known. Average particle energy is given by the total thermal energy Q divided by the number of particles (N) in the system.

So Ts = Q/Nk_B where Ts is the system temperature Q = thermal energy and N is the number of particles the system. --Damorbel (talk) 14:22, 21 November 2012 (UTC)

You didn't specify "energy per particle". I don't know of a specific term for that other than "energy per particle". The term "heat" does not in any way or any context (technical or otherwise) describe that. In any case, since I don't see any discussion here of the article, we're done. Waleswatcher (talk) 14:33, 21 November 2012 (UTC)

What I wrote (above) was Perhaps it would help if you told me what you call the energy of the vibrating particles in as system of particles. Seems there is room here for misunderstanding.

The connection with the article is that 'Heat' should be measured by temperature - the long standing measure. Temperature is an intensive (local) parameter - the greater the temperature the more powerful the action. Attempts in the Heat article to characterise it as an extensive quantity (energy - joules) cannot be sustained, certainly the second law of thermodynamics would collapse! Because it contains so many inconsistencies arising from this energy in transit meme, the article has very little value, it needs extensive revision. --Damorbel (talk) 15:18, 21 November 2012 (UTC)

Hi Damorbel, what you have written is of course nonsense. But that isn't really the point. The point is that your view is contrary to every reliable source on physics, thermodynamics, stat mech, etc. Therefore, it cannot go into a wiki article as per wiki policy (that all statements in articles be supported by reliable, published, secondary sources). As such, there is no point in discussing your views here any longer. Waleswatcher (talk) 20:21, 21 November 2012 (UTC)

Waleswatcher is right: the internal energy of a system is related to it's temperature. One might try to isolate, from the generalized internal energy of the system, the "thermal" energy (the energy that is directly related to temperature) from "other types of energy (the energy that the system has with respect to a frame of reference regarding which it is moving, the energy the system has because of it's position in a force field, the energy contained in it's mass as E=mc2, the chemical bonding enegy in it's components, or the energy related with the weak or strong nuclear forces...) but in a generalized theory of thermdynamics it is usually not that important which "type" of energy one is talking about... --Crio (talk) 22:09, 20 November 2012 (UTC)

Crio, my question is not 'related to it's temperature', it is about the energy that gives rise to the system temperature(s). My position is that the temperature(s), that is to say the heat, of a system derives directly from the microscopic kinetic energy of the particles comprising that system. --Damorbel (talk) 08:52, 21 November 2012 (UTC)

Then, Darmobel, your position is _wrong_ You _are_ confussing the concept of "thermal energy" and "internal energy" with the concept of "heat", in regard to thermodynamics and physics. From a statistical mechanics point of view, the temperature, that is to say the _thermal_energy_ (not the heat), of a system derives directly from the microscopic kinetic energy of the particles comprising that system, to put it in your words.

ΔU(T)=Q+W, for a given _process_ where U(T) is the internal energy of the system, composed, if you will (although this is unnecesary from a classical thermodynamics point of view) from the "thermal energy", "chemical energy", "nuclear energy", etc. of the system. These are _functions_of_state_, energy is a function of state, Temperature is a state variable. Then for a thermodynamic process that changes the internal energy of a system this change is equal to the _net_ work done on the system plus the ammount of heat transfered into the system. Heat and work are two distinct functions of path: through different paths between the initial and final states of the system different ammounts of work are done on the system _and_ different ammounts of heat are exchanged between the sorroundings and the system. Entropy is also a function of state dS(T)=δQrev/T. dS(T)>=δQ/T,

ΔS(T)>=INTEGRAL(δQ/T).

See: http://en.wikipedia.org/wiki/Thermal_energy

Where "thermal energy" is defined as : $U_{thermal}=N\cdot f\cdot {\tfrac {1}{2}}kT.$

From a statistical mechanics point of view.

There you can read "

Distinction of thermal energy and heat

In thermodynamics, heat must always be defined as energy in exchange between two systems, or a single system and its surroundings.[8] According to the zeroth law of thermodynamics, heat is exchanged between thermodynamic systems in thermal contact only if their temperatures are different, as this is the condition when the net exchange of thermal energy is non-zero. For the purpose of distinction, a system is defined to be enclosed by a well-characterized boundary. If heat traverses the boundary in direction into the system, the internal energy change is considered to be a positive quantity, while exiting the system, it is negative. As a process variable, heat is never a property of the system, nor is it contained within the boundary of the system.[2]"

The thermal energy of a sytem _can_ be used to produce work, see:

http://en.wikipedia.org/wiki/Thermal_efficiency

There you will be able to see also the maximum efficiency of a thermal engine, given by Carnot's cycle.

Heat (physics)is what it _is_ not what one want's it to be. It is as if I thought Ring (abstract algebra) was, somehow a ring like my wedding ring, or that the color(quantum mechanics) was actually blue.

Heat _is_not_ Thermal Energy.

--Crio de la Paz (talk) 00:47, 22 November 2012 (UTC)

laws and principles and requirements

Latest comment: 12 years ago13 comments5 people in discussion

Editor Rjstott made a well-intentioned but not well justified edit, when he changed "The first law of thermodynamics requires that the internal energy of an isolated system is conserved" to "The first law of thermodynamics describes the principle that the internal energy of an isolated system is conserved."

The use of the word law to refer to generally true scientifically intended propositions about nature is in a sense allegorical or metaphorical or it may be called a trope. A principle is not the same thing as a law. A principle is a proposition from which other propositions are deduced; more than that, it is an initial proposition for a wide range of deductions. Another word that means nearly the same as principle is axiom, though these two words are usually used in different contexts. The first law of thermodynamics is sometimes called the first principle of thermodynamics, and sometimes it is called a theorem of experience.

To say that it requires something is not to say it causes that thing. Editor Rjstott's well-intentioned edit seems to assume that is so to say, and this assumption is not right. It is proper to say that the first law of thermodynamics requires that the internal energy of an isolated system is conserved.

It is simply poor language use to say that the first law of thermodynamics describes the principle that the internal energy of an isolated system is conserved. The first law does not describe any principle. It states something, a principle if you like. Moreover, the statement that the first law is not that the internal energy of an isolated system is conserved. The law explicitly refers to changes in the internal energy of any system that is covered by thermodynamics, and is thus more general than the statement about isolated systems. The phrase 'describes the principle' is pleonastic; that is to say, it says the same thing twice over in a way that does not add to the meaning; it is faulty language usage.

But it is true that the law includes as one of its essential implications that the internal energy of an isolated system is conserved. The word requires here means the same as 'includes as one of its essential implications'. This is ordinary language usage, consistent with the semantics of the word law in this context, as a metaphor, and is appropriate here.

It is very good that editor Rjstott should be alert for matters of language, but on this occasion he acted too enthusiastically.Chjoaygame (talk) 02:12, 18 November 2012 (UTC)

I undid your reversal of Rjstott's contribution. I think the vast number of words you needed to explain your point is more than sufficient to show you have not got one. --Damorbel (talk) 07:49, 18 November 2012 (UTC)

Damorbel, this utterly unjustified undo of yours is most naturally, in view of current activity here, read as a mere personal attack on me.

You have been doing this kind of thing for some time now, but I have not pointed to it till now because such things are hard to demonstrate unequivocally, or would need too much time and effort to demonstrate, and because I have not wanted to encourage your predatory and irrational editing behaviour by responding to it. This one seems unequivocally clear. Your "justification" just above makes no reference to the issues at stake, and has no weight as rational argument. Many words are needed to explain subtle abstract ideas to novices. If I write a careful justification for my action, you attack me for wordiness. If I do not, you attack me for lack of detail. You seem to have lost the plot. I will not respond by undoing your undo because such a response would only reward your inordinate appetite for irrational and destructive edit conflict, which you continue to try to arouse.Chjoaygame (talk) 08:51, 18 November 2012 (UTC)

Laws simply STATE relationships. So simply state what this one states. Simplify! S B H arris 09:19, 18 November 2012 (UTC)

SBHarris' compromise, that "the law states" may be acceptable, but is not as precise as the previous version, that "the law requires". The law states more than this requirement, and this is signalled by the word 'requires', which is perfectly good English. His appeal to simplicity seems to be motivated by a desire to compromise. And the compromise reduces the explicit specificity of the article entry, for no reason that I can see other than to appease Damorbel, and perhaps editor Rjstott, whose English fairly deserved censure.Chjoaygame (talk) 10:03, 18 November 2012 (UTC)

Sbharris has it right. --Damorbel (talk) 09:28, 18 November 2012 (UTC)

Damorbel makes no response to my observing that his undo is most naturally read as a mere personal attack on me. If Damorbel really thought for himself that the edit of SBHarris was appropriate, why didn't he make it himself when it was called for?Chjoaygame (talk) 10:03, 18 November 2012 (UTC)

This is called "fiddling while the article burns!". Chjoaygame, it is far more important that an encyclopedia article should recognise that any article on heat should fully explain why the theory of heat is about the energy of particles - which is absolutely not the case at present. I find it quite bizarre that the present article does not show the proper relationship between the system energy, the number of particles in the system, its entropy and the role of temperature. Please stop going on about your personal feelings and get involved with the physics of heat - please! --Damorbel (talk) 12:03, 18 November 2012 (UTC)

Damorbel was so keen to attack me that he was blind that his edit, solely of a grammatical nature, was restoring a faulty pleonasm, "the law describes the principle". Then, blind that a personal attack of the kind he made is unethical here, he suggests that it is my feelings that are the problem here. Dear Damorbel, you flatter yourself to suggest that your personal attack on me might have affected my feelings, no, it seemed a joke to me, that you would so demean yourself. But it is right that I should point out that your action is unethical. You ask to focus on the physics, but your edit was merely grammatical, and mistaken at that. It is you who is burning the article, still blind to your personal attack on me, blind because of your above noted mental block. You have lost the plot.Chjoaygame (talk) 13:30, 18 November 2012 (UTC)

Damorbel seems to have a persistent confusion bewteen the concepts of temperature, "thermal" energy or, in a more general fashion, internal energy, and heat. He seems to think that "heat" is "internal energy" and that is _not_ the definition in physics: heat is not temperature, heat is the phenomena that occurs when two systems with different temperatures are in thermodynamic contact: heat flows from the hotter body to the colder body. A gradient in temperature is the "cause" of heat being exchanged, it is not the "heat" being exchanged. The energy contained within a system (internal energy) is not "heat". "Heat" is a function of path. Energy a function of state. In classical thermodynamics temperature is not defined in terms of particles. In statistical mechanics the concept is linked, succesfully, with the behavior of the atomic structure of matter. --Crio (talk) 22:26, 20 November 2012 (UTC)

The reading of http://en.wikipedia.org/wiki/Calorimetry could prove--Crio (talk) 22:30, 20 November 2012 (UTC) interesting.

Crio you are missing my point entirely by introducing into the argument, when you write "heat is ... when two systems with different temperatures are in .... contact:" a matter with has nothing to do with my point, because your system, having two (or more) temperatures, is not in thermal equilibrium. Thus, according to the 2^nd law of thermodynamics, there is a transfer of energy in your system. My question has nothing to do with the transfer of energy since it applies equally well to a system in equilibrium. All I want to know is, what the energy (if you think it exists at all) is called that makes the system hot i.e. gives a system its temperature(s), makes it above zero K, etc. etc. --Damorbel (talk) 09:21, 21 November 2012 (UTC)

Actually "hot" implies with respect to what?. Internal energy is a function of T: the internal energy of a system is related to it's temperature. In a more specific way "thermal energy" even when it is difficult to stablish what part of internal energy is "thermal" in nature and what is not. This involves studying the internal structure of the system or dedifining the system. See: http://en.wikipedia.org/wiki/Thermal_energy

"Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system temperature.[1] This quantity may be difficult to determine or even meaningless unless the system has attained its temperature only through heating, and not been subjected to work input or output, or any other energy-changing processes. "

Now this is _not_ a matter of what "I think" or "Darmobel thinks" it is a matter of how quantities _are_ defined in physics, and, in this case, in thermodynamics. Classical thermodynamics defines a system and it's sorroundings, it does not study the internal structure of the system. Statistical mechanics is a mechanistic science that is compatible with classical thermodynamics and that studies how the atomic structure of matter is compatible with classical thermodynamics. but "heat(physics)" is still a transfer phenomena, not a state function. Temperature is a state variable and internal energy is a state function. I think Darmobel is confussing "heat(physics)" with "thermal energy" "internal energy" and "temperature". That is where his confussion arises whe writing about the general theory of classical thermodynamics, which he seems to think reduced to one of it's mechanistical interpretations (statistical mechanics). Classical thermodynamics theory seems to be compatible with other theories as well, including a generalized theory of gravitation (general relativity) and information physicis, even though not all of these theories have been unified as of yet. The basic concepts that prevail with the basic laws of thermodynamics seem to be a set of rules for all procecess, disregaring it's internal mechanics (how work and heat are computed as functions of path), up until now. That is what is so interesting about thermodynamic theory (classical), specially since it was born out of an analysis of "heat engines". Chjoaygame is _right_ when he mentions that the problem is regarding heat(physics,thermodynamics) and a common language use of the word "heat". This is similar with regard to a generalized concept of the word "work" (I shoud be doing some "work" right now instead of writing on the wiki). Or action, or force, or anyother quantity that has a specific meaning in physics. It is similar to what happens in mathematics when you talk of a "field" or a "group" or a "ring" or a "set" or a "lattice"). And it is true that, when one goes into "engineering topics" one stops using the most rigorous definitions if they are not "useful" to solve an engineering problem.

--Crio de la Paz (talk) 17:02, 21 November 2012 (UTC)

Rewording

Latest comment: 12 years ago2 comments2 people in discussion

I did some rewording of the first parragraphs.

Please review.

Cheers!

--Crio de la Paz (talk) 01:14, 22 November 2012 (UTC)

Very well done!Chjoaygame (talk) 04:59, 22 November 2012 (UTC)

Boltzmann constant

Latest comment: 12 years ago11 comments4 people in discussion

Can anybody tell me why the Heat article does not mention of the Boltzmann constant? --Damorbel (talk) 21:44, 21 November 2012 (UTC)

Yes, the reason is that instead of putting your heart's desire into the right place in the article, you have frittered your efforts into sabotaging the efforts of others in other parts of the article. No one would have hindered you from putting it in the right place.Chjoaygame (talk) 23:50, 21 November 2012 (UTC)

Frankly I don't know what we'd do with k_B in this article (or R = N k_B, either). These constants don't have anything to do with heat. R and k_B act as the simple proportionality constants, that arise because we need constants to mediate between the (arbitrarily produced) kinetic energy and temperature scales that we happen to have independently developed, and that we want to continue to use (thus requiring conversion factors between them). But neither energy or temperature is heat. S B H arris 01:06, 22 November 2012 (UTC)

"These constants don't have anything to do with heat" How so, Sbharris?

You argue "But neither energy or temperature is heat." Who is arguing this? Certainly not me!

Then:-

1/ what is energy? Is work energy? Do chemical bonds contain energy? Is there potential energy in an elevated mass?

2/Do joules measure energy

3/Does a lump of iron at 10K; 100K; 1000K contain heat? Does it contain energy?

If so, how can you calculate the energy at 10K; 100K; 1000K? If you... ...calculate the heat at 10K; 100K; 1000K?

I would like to discuss the article but as the above shows, your response, addressed to me, has nothing to do with my

arguments. --Damorbel (talk) 07:08, 23 November 2012 (UTC)

Yes. But think of the possibility of some happiness for Damorbel if it is in the article!! And we are admitting that heat has a microscopic explanation and saying something about that in the article.Chjoaygame (talk) 05:02, 22 November 2012 (UTC)

Chjoaygame, for long enough you have denied the role of the energy of particles in the thermodynamics of heat; now with your inclusion the Boltzmann constant with its dimension joules per particle per K you may have changed your position.

I have always argued for revising the article to include what you were determined to reject, that thermodynamics, and thereby Heat, is all about the energy of particles.

Now, after what seems to be a small step for you; we can proceed to a giant step for the article; so to speak. --Damorbel (talk) 11:22, 22 November 2012 (UTC)

Dear Damorbel, you endlessly muddle yourself, and try to drag us into your muddle.

You write: "you may have changed your position." I have not changed my position. At 03:39, 24 March 2012, I originated the section of the article initially entitled Motion of microscopic particles explains heat. It has been there, ready for you to put in details to your heart's content. But instead of doing that good thing, you frittered away your energy in sabotaging the work of other editors on other parts of the article.

You write: "you have denied the role of the energy of particles in the thermodynamics of heat". I have denied that thermodynamics is concerned with particles, in which I am correct. I have not denied that the statistical mechanical explanation of thermodynamics is concerned with particles. The problem for us here is that you have persistently ignored the distinction between thermodynamics and statistical mechanics, and have tried to put the statistical mechanical explanation as primary without recognizing that it is an explanation of something more general and primarily empirically based. You still give yourself away here, when you write that "Heat is all about the energy of particles", which is a denial of the primary status of thermodynamics here.

Well, at least we seem to agree that it is a fair thing that I did actually put in information including the Boltzmann constant into the section that evolved from my original one, and is now, owing to Waleswatcher, renamed Heat#Microscopic origin of heat. Sad to say, the ever destructive Waleswatcher has removed the reference to Boltzmann's constant. Perhaps you might take that up with him. Indeed I have noticed that you are very skilled at undoing edits. You are free to undo Waleswatcher's unjustified removal of the comment about the Boltzmann constant, or to replace it as you think fit with your own preferred version; I would urge you to keep it to the right part of the article, whence it was removed.Chjoaygame (talk) 19:19, 22 November 2012 (UTC)Chjoaygame (talk) 00:45, 23 November 2012 (UTC)

I did actually put in information including the Boltzmann constant into the section.

Can you give me a diff. for this? I couldn't find it. --Damorbel (talk) 09:40, 23 November 2012 (UTC)

I put it in twice for you. First time that was subsequently removed by Waleswatcher. Second time that was subsequently removed by Waleswatcher.Chjoaygame (talk) 12:04, 23 November 2012 (UTC)

Thanks! --Damorbel (talk) 12:15, 23 November 2012 (UTC)

I removed it not because I think it's a bad idea to mention it, although it's not particularly central here, but just because it complicated that passage and wasn't needed to make the relevant point there. Where do you think it should go, Damorbel? Waleswatcher (talk) 14:13, 23 November 2012 (UTC)

Waleswatcher's current backward step

Latest comment: 12 years ago2 comments2 people in discussion

Waleswatcher, you have practically reverted the most recent improvements in the article. Your reversions mostly just restore word for word your previous edits. It seems you feel a need to dictate the article, word for word, even when faults are pointed out in your dictated version.Chjoaygame (talk) 19:58, 22 November 2012 (UTC)

I can't recall a time when you pointed out a single fault in any of my edits. Not that there aren't any - there are many - but you seem to be incapable of constructive or even specific discussion. Instead, you go off on vague rants such as this one, accusing me (and others) of all sorts of evils. Worse, your writing (in this and other articles) is stilted to the point of incomprehensibility.

Physics is difficult and abstract, and it needs to be explained simply and clearly, using language most people can understand. It's hard to do this kind of writing well. Please try to contribute constructively. Waleswatcher (talk) 03:47, 23 November 2012 (UTC)

Waleswatcher, where on the talk page?

Latest comment: 12 years ago5 comments2 people in discussion

Waleswatcher made an edit at 05:23, 23 November 2012 with the cover note (rv as per talk page), but I don't find a corresponding entry on the talk page. The next edit by Waleswatcher, at 05:25, 23 November 2012 has the cover note (restored Chjoaygame's last edit which was unintentionally reverted), but that edit was not fully restored; only part of it was restored. Please, Waleswatcher, where is the talk page entry to which you refer?Chjoaygame (talk) 05:45, 23 November 2012 (UTC)

It's all over the place. No one has given any physical reason or reliable source for separating convection from radiation and conduction. On the other side, both physics and a large number of sources list convection as one of the primary mechanisms for heat transfer. Waleswatcher (talk) 14:11, 23 November 2012 (UTC)

In other words, you can't point to where it is. You are just bluffing us; or perhaps you are just bluffing yourself?

In reality, there are three editors here who reject your bizarre story that there is very little physical distinction between radiative heat transfer and convective heat transfer. If you really believe that, let's see you source it and put it in the article!!! You respond to SBHarris thus: "Purely advected heat is not actually heat. I have no idea what you mean by that." Indeed it does seem that you have very little idea. I have given clear physical reasons: "The energy that is carried by convection is carried partly and importantly through the cooperation of the particles including their mutual potential energy, whereas for the most part, energy carried by a photon is the sole property of the photon. Also, convection is mainly one-way. One can have convection that is entirely one way. But radiative transfer is essentially two-way. This is because of the Helmholtz reciprocity principle. The heat transfer is the difference between the two ways. Photons carry energy from a source body constituent directly to a target body constituent, in one step. Convection essentially involves many particles on the way." Your response to this was evasive in the area of physics, and then wandered off into your views on pedagogy in the Wikipedia. Crio de la paz recognizes a difference between the physical and engineering accounts: "There _is_ an specific notion of _heat_ in _physics_thermodynamics_ that is fundamental to all of physics and it's applications. In engineering one deals with "heat transfer" phenomena ...", but he does seem to give you some vague support, which I think is indecisive. Reif, one of your two defining sources, does not mention convection, but talks at great length about conduction and radiation. The other of your defining sources, Kittel & Kroemer, mentions convection but not convection of heat, and that only once, in a problem. For the rest, it talks about conduction and radiation. That separates them. The difference is so obvious that no one would bother to make it explicit. It is amazing that you seem unable to see the difference, considering how obvious it is. If they really were the same, why would they be listed as three, instead of people routinely pointing out that they are the same? The idea that convection is of the same character as conduction and radiation is bizarre, an unsourced invention by you to justify your position. I do not deny that many sources list all three; I started by saying that I had been taught it when I was a schoolboy. That is not the point. The point is that the strict physical definition, upon which people here have been so dogmatic and insistent, refers only to conduction and radiation. SBHarris has pointed out that three steps are needed for convection: (1) conduction or radiation from the source heat bath into the carrier fluid, or work done on the carrier fluid, which add to its internal energy; (2) bulk flow of the carrier fluid with its contained internal energy; (3) conduction or radiation into the destination heat bath, or work done by the carrier fluid, by which it unloads the internal energy that it has carried. This is more complex than simple conduction or radiation, which you are trying to deny.

And you have made no answer to my pointing out that when you said you had reverted, you had done so only partially, so that your statement was misleading.Chjoaygame (talk) 15:03, 23 November 2012 (UTC)

Just FYI, I only read the beginning and end of your ridiculously long comments. Convection is discussed at length on this page; I have no idea what you expect me to point out to you other than that. Waleswatcher (talk) 20:50, 23 November 2012 (UTC)

It is not news to me that you ignore what I write. You can ridicule it, and repeatedly say that you "have no idea"; no problem there. But you can't get the physics right; that's a problem.Chjoaygame (talk) 21:44, 23 November 2012 (UTC)

difference between physics and the discipline of heat transfer about the idea of "convection of heat"

Latest comment: 12 years ago35 comments6 people in discussion

The Wikipedia article on transfer of heat says that it is concerned with a discipline of thermal engineering, concerned with thermal energy. It classifies heat transfer mechanisms as conduction, radiation, and convection. It also admits the engineering idea that a mass transfer can comprise an associated heat transfer. In this engineering terminology, sometimes mass transfer might refer to transfer of mass by diffusion between open systems, but very often it refers simply to motion of a body of fluid, considered as a mass transfer as a body moving from place to place rather than as diffusion between open systems.

This thermal engineering terminology differs from that of physics.

In physics, the energy associated with mass transfer by motion of a body from place to place is represented by kinetic energy of bulk movement, by potential energy with respect to long-range external forces such as gravity, and by internal energy belonging to the body considered without regard to its motion from place to place.

In physics mass transfer on a microscopic scale, known as diffusion, can occur between open systems, but not between closed systems. In physics, transfer of energy as heat is defined for transfer between closed systems, but is not defined in general for transfer between open systems.(Münster, A., 1970, Classical Thermodynamics, translated by E.S. Halberstadt, Wiley–Interscience, London, ISBN 0-471-62430-6, pp. 50–51. Kittel, C. Kroemer, H. (1980). Thermal Physics, second edition, W.H. Freeman, San Francisco, ISBN 0-7167-1088-9, p. 227. Reif, F. (1965). Fundamentals of Statistical and Thermal Physics, McGraw-Hill Book Company, New York. Carathéodory, C. (1909), Untersuchungen über die Grundlagen der Thermodynamik, Mathematische Annalen, 67: 355–386 doi=10.1007/BF01450409. A partly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA.) It follows that in physics, mass transfer by diffusion can be associated with transfer of internal energy, but not with a uniquely defined quantity of energy transferred as heat.

In physics, there are several well recognized extensive variables of state that represent well defined quantities of energy that belong to a body: internal energy, Helmholtz free energy, enthalpy, Gibbs free energy. These represent quantities of energy that, besides being state variables belonging to a body that can move with its bulk motion, can also be transferred between bodies, including transfers by diffusion. The thermal engineering term 'thermal energy' is loosely defined and may perhaps loosely refer to one or all of these quantities, but, unlike in thermal engineering, in physics the phrase 'thermal energy' is not recognized as an extensive state variable that represents a well defined quantity of energy that belongs to a body. Likewise, in physics, heat is not an extensive state variable of a body; heat is always energy in a process of transfer.

In physics, one can consider convection of internal energy, Helmholtz free energy, enthalpy, Gibbs free energy, and indeed also of convection of entropy.

This is because convection means transfer by bulk motion of a quantity that is indicated by an extensive state variable of a body of fluid.

From this, it follows that, differing from thermal engineering, physics speaks of convection neither of thermal energy nor of heat. In physics, heat transfer is by conduction and radiation.Chjoaygame (talk) 06:01, 21 November 2012 (UTC)

Response by Damorbel

Chjoaygame you write "This thermal engineering terminology differs from that of physics." Interesting. But what makes you think engineers are somehow constrained in the language they use? Engineers somtimes need to describe complex system built up of already complex subsystems. For a time I was responsible for the power subsystem of a communications satellite, to do my job I needed to understand the thermal control of the satellite, the design of the solar arrays, the orbit of the satellite, the control and regulation and storage of on board power and much, much more. To handle this massive comunications problem engineers use a restricted set of terms that frequently summarise the physics involved i.e. they don't go back to basics on every occasion, it would waste far too much time. An unfortunate side effect is that this obscurity, unless one is up to date with the functioning of the new design, one will be effectively excluded from discussions.

I did not actually design these various aspects but I needed to be able to talk to those who were in a meaningful way, otherwise I would have been speedily shown the door. In my job I learned a lot and I taught my colleagues a lot, that meant that, on occasions, I had to correct some of my ideas. Good engineering practice requires that designs are tested to see if they perform as predicted; in this way the validity of the communications is finally checked.

In physics the problem is quite different. Theories in physical science, (unlike mathematics) come and go, think of phlogiston and caloric. Physicists (should) want their work to be understood as widely as possible so they should use terminology that is not only widely understood but self consistent. This last requirement is generally upset when improved theories emerge, for many physicists it is almost impossible to accept changes to the ideas of their youth, a good example is Joseph Priestly who carried the idea of heat as a substance phlogiston to his grave, he would not accept the new idea of caloric. In turn Sir Humphry Davy and members of the Royal Society actively suppressed the new kinetic theory of heat (with energetic particles) as expounded by John Herapath, in 1821, and again by John Waterston in 1843; you can read about this here. This is a good example of the importance of scientific experiment, a hypothesis must be tested. Sir Humphry and other members of the Royal Society did not test the new theory, they rejected it out of hand as ridiculous. Not all physics can be tested in a laboratory but there must be some evidence of its validity that is availble to all; being available to all requires a universal terminology, very different from engineers who do not rely on terminology for success. --Damorbel (talk) 07:32, 21 November 2012 (UTC)

Response by Crio de la paz

This page should be about how "heat" should be dealt with on the wiki, not "a contest of wills"; and it should not be a contest between "engineering" and "physics". There _is_ an specific notion of _heat_ in _physics_thermodynamics_ that is fundamental to all of physics and it's applications. In engineering one deals with "heat transfer" phenomena and equipment design and uses thermodynamics, transfer phenomena theory, dimensional analysis, empirical data that has not been well modeled mechanistically, "rules of thumb" and whatever is handy to solve engineering procecess. Thermodynamic analysis (in it's classical, general form) has been one of the most fundamental aspects of how the world we live in is described: it has hold true where Newton's laws of motion haven't (and others). In "chemical engineering" "modeling of procecess" first a system is defined, then the fundamental conservation laws that apply are stated, including the second law of thermodynamics (which is not a conservation law but the law that governs the increase of entropy of the universe in most procecess). Then the constitutive realationships and parameters that are going to be used are introduced to solve for the model in question. The laws of conservation of mass, momentum, angular momentum, charge, energy, the second law of thermodynamics they are regarded as fundamental laws, not constitutive relationships (as are most physical "laws"). In "heat transfer" one deals with transport phenomena related to the subject matter and desing of equipment (heat exchangers, evaporators, cooling towers, boilers, furnaces, jacketed vessels, etc.)--Crio de la Paz (talk) 17:28, 21 November 2012 (UTC)

Response by SBHarris

Perhaps we can simplify this some. The article itself says that heat is a process of energy flow down a thermal gradient, as the result of the thermal interaction. That means that only diffusion and radiation count as pure forms of heat which fit the simple definition. Everything else which results in a "net" flow of heat from A to B, has some tricky step "in between" where heat is not being transfered (by the above definition) but rather internal energy is transferred without heat flow. The simplest example is a "heat pump" which is a beloved engineering term. But by definition one cannot pump heat against a thermal gradient, which is what heat pumps are supposed to do (that's what the name says, right?). Thus, actually it is internal energy that is pumped up the temperature gradient, not heat. At either end of this process, heat indeed flows down a thermal gradient in the normal way. The heat energy just finds that at its new home, it is in a place where it would not have gotten to on its own, in a single step or by any series of purely thermal interactions.

Now, consider convection (free or forced). In the intermediate step, a fluid "advects" (carries) energy from one place to another, like water carrying silt down a river. But does the fluid here carry "heat"? Not by the definition in this article, and not even by the definition of most engineers. When you carry a cup of hot coffee from one end of the room to the other end, not letting it cool at all, would an engineer say that you're carrying "heat"? Even engineers who believe loosely in thermal energy would not say you're carrying "heat" but would say you're carrying thermal energy. We prefer "internal energy". Heat is when something hot transfers energy to something cold, not when when some peice of mass at the same temperature is moved mechanically and grossly from here to there, not changing temperature while it changes position.

Likewise, an engineer would not say that a (perfectly insulated) pipe carrying hot water was carrying heat, if (again) the temperature was constant over the length and there was no heat exchange. When heat transfer happens at either end of such a pipe, then at those places, heat appears. The entire process is lumped by engineers into "(forced) convective heat transfer," but actually the only heat transfer happens at either "end" of the mass flow, and doesn't happen in between (or doesn't NEED to). And when this heating process (true and simple heat transfer) DOES happen, it happens by good-old-fashioned thermal diffusion. Down a thermal gradient. So convection is also like a heat pump-- there is heat at the ends, going in an coming out, but in between, there is none. It's like money wire transfer-- I take bills into one bank and across the country some minutes later, somebody else takes bills out. That's not bill transfer-- it just looks like it. For all intents and purposes it could be (and an engineer might be satisfied). But mechanistically, it isn't. It's money transfer, not paper currency transfer. Don't be fooled. S B H arris 01:31, 22 November 2012 (UTC)

Response by Crio

SBharris: Actually a "heat pump" is a thermodynamic cycle. It involves (as most usual) four steps. i.e. the fluid is compressed, it then releases _heat_. The fluid then goes through an expansionary valve (or a capillary tube, or a turbine) that lowers it pressure. Then it absorbs _heat_ from it's sorroundigs and goes again into the compressor. In an idealized system heat is absorbed from the environment on one side and heat is realeased on the environment on the other side. Work is done in the compressor and some work might be extracted on the turbine. The thing here is that _heat_ is that which is transfered at both ends. See:

http://en.wikipedia.org/wiki/Thermodynamic_cycle

http://en.wikipedia.org/wiki/Temperature-entropy_diagram

There you can see how thermodynamic cycles are calculated.

But now I realize we agree: heat is transfered _at_both_ends_ (in an idealized system, in a real system the compressor also releases heat, etc.) not "in between" in between we are changing the _state_ of the fluid.

Convection is a more complicated subject as you can see in:

http://en.wikipedia.org/wiki/Convection

"Convective heat transfer is one of the major modes of heat transfer and convection is also a major mode ofmass transfer in fluids. Convective heat and mass transfer take place through both diffusion – the randomBrownian motion of individual particles in the fluid – and by advection, in which matter or heat is transported by the larger-scale motion of currents in the fluid. In the context of heat and mass transfer, the term "convection" is used to refer to the sum of advective and diffusive transfer.[1] "

Of course it all depends on the system being analyzed and wether you are establishing a "volume control" or a "mass control" for the system in order to establish your conservation laws for the ssytem. Since the system might not be "closed" depending on the definiton of the system, when doing an energy balance on the system you have to take into account the energy brought into the volume of control by mass that enters the system and mass that leaves the system, in your energy balance. And of course, if one tries to model turbulent flow of compressible fluids one might run into situations where Navier Stokes prove unsolvable and only empirical approaches are "doable".

--Crio de la Paz (talk) 03:17, 22 November 2012 (UTC)

response by SBHarris

To Crio: thanks, I know how a modern heat pump works. The point is how a minimal heat pump works. Without the gizmos. You don't need phase changes-- they only increase efficiency. And you don't need convection-- if you do it slowly you won't get enough to count. To make a refrigerator for your house, take a cylinder of air (or any gas) outside into the hot day, and compress it until it's higher temp than the hot environment. Let the heat bleed out by conduction. Carry it indoors and let it expand against as much pressure as possible, slowly reversibly. If you've compressed it enough outside, it will cool inside to lower than room temp. Let heat flow in by diffusion. Then carry it outside and repeat. It's not a great refrigerator, but (absent your body heat) it will cool the room. The heat-equivalent of the work you do, will be ejected outside, plus whatever heat is absorbed inside. To pump heat the other way from cold outside to warm inside, simply reverse the cycle with compression phase inside, and expansion outside. Now, when I'm carrying the cylinder of gas inside to outside and vice, versa, do you think I'm moving heat? I'm not. No entropy change is involved in me moving a cylinder of gas. Entropy changes only when heat diffuses into or out of the cylinder. In fact, that's how we know it's heat: a bit of heat flow δQ is always TdS. But dS is zero when I advect, as it's reversible.S B H arris 05:05, 22 November 2012 (UTC)

Respose by Crio

SBHarris:

Actually when there is passive difussion there is an increase in entropy, see: http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/061/Why%20passive%20transport%20happens%20entropy.pdf?v=1352425760476 For a TS diagram of a heat pump figure 2 in http://en.wikipedia.org/wiki/Heat_pump_and_refrigeration_cycle is quite a good example. For a TS diagram of Carnot cycle see: http://en.wikipedia.org/wiki/Carnot_cycle Figure 2. Specially http://en.wikipedia.org/wiki/File:Carnot_Cycle2.png is of interest. The Carnot cycle is _the_most_eficient_ thermodynamic process between to different temperatures, where work is done isentropically and heat is released isothermally. Actually the example of you moving a cylinder of has is flawed: it is _quite_ inefficient ;-) and it is not reversible (you need to expend a lot of work in doing so: it is not reversible, it does not happen spontaneously). Advection and convection are not reversible, quite the contrary: they tend to be quite irreversible process: when a mass of fluid is heated up by a hot surface it rises. But it will not lower itself heating the surface back without external work. I forced convection one is _introducing_ an external force into the system in order to perform work in order to do process that _are_ irreversible. A reversible process is that which occurs spontaneously.

Cheers!--186.32.17.47 (talk) 19:02, 22 November 2012 (UTC)

I have moved the immediately forgoing to this point in the page because it seems that this is its home. I hope this is right.

Whatever. A reversible process is a theoretical idealization, and cannot occur in nature; it can be closely approximated by a slow enough process, but not exactly realized in a finite time. Spontaneous processes, the only ones that occur in nature, are always irreversible. This is fundamental thermodynamics.Chjoaygame (talk) 04:32, 23 November 2012 (UTC)

Response by Waleswatcher

There is very little physical distinction between radiative heat transfer - where a flow of photons carries energy from a hot to cold body - and convective heat transfer - where a flow of molecules carries energy from a hot to cold body (or for that matter conduction, where a flow of phonons carries energy from a hot to cold body or part of the body). I'm not opposed to differentiating them in the article, but we have to be careful asserting that one is more "direct" or "fundamental" than the other. Such statements need to be referenced. Waleswatcher (talk) 03:16, 22 November 2012 (UTC)

response by Crio de la paz

Waleswatcher has a point, though photons have zero rest mass... that ought to be a difference... --Crio de la Paz (talk) 03:29, 22 November 2012 (UTC)

Another thing: most probably what will happen in most "heat pumps" at "both ends" would not be "thermal difussion" or "conduction" but "convection".

Cheers!--Crio de la Paz (talk) 03:31, 22 November 2012 (UTC)

Walesatcher: why is heat transfered "indirectly" in convection? I do not understand the term "indirectly" aplied in this context. Thnks! --Crio de la Paz (talk) 03:42, 22 November 2012 (UTC)

Phonons typically also have a mass, so rest mass doesn't distinguish convection from conduction. Also I'm not sure why it's important in this context. The term "indirectly" isn't very good, it was a compromise to try to preserve the sense that convection is somehow less fundamental, as was written there by another editor. I'd prefer to remove it and go back to what I had originally. Waleswatcher (talk) 13:09, 22 November 2012 (UTC)

Phonons typically also have a mass. They do? Never heard of it. Phonons are the mechanical equivalent of photons i.e. they derive their properties from wave motion in a mechanical lattice, but the massive particles in the lattice are not transferred. What is transferred, as with photons, is momentum.

Have you got an explanation, or better still, a link? --Damorbel (talk) 14:58, 22 November 2012 (UTC)

So called "optical" phonons, for example, or any other where omega doesn't go to zero with k. Waleswatcher (talk) 05:22, 23 November 2012 (UTC)

response by SBHarris

To Waleswatcher, you've missed the fundamental property of heat, which is that as it flows, the entropy of the system increases due to the heat flow. But there is no entropy increase when I move a hot object from here to there. Or a hot stream of fluid from here to there. That part of the "convection" scheme, the purely "advective" part, involves no entropy changes. That is because heat is not being moved. ENERGY is being moved. Do you see? Photons radiated from a hot object expand into a larger volume; entropy goes up. The same when a gas expands, even isothermally. And of course, always in all heat conduction processes, as those little phonons multiply and occupy more states. The system occupies more of phase space. But again, pure advection of hot things does not push phase space. It's (obviously) reversible. If I can move a hot object THERE, I can just as easily move it BACK. Try putting those photons that radiated from a hot object back where they came from, or the phonons conducted away for that matter. You'll pay for it in entropy cost, if you do. Ditto for everything else that has to do with REAL heat transfer. S B H arris 05:05, 22 November 2012 (UTC)

That's not the case. Convection - at least when it occurs as a result of heating of a gas, as we are discussing here - is a spontaneous process that is always associated with an increase in entropy. You cannot separate the "advection" part from the "heat" part in this context (which is rather the point). Advection is simply the motion of a lot of molecules, gas in this case; if that motion carries hot gas molecules into a region occupied by cold gas molecules, the entropy of course increases even in the absence of any molecular collisions. As you say, try putting the hot molecules back in the corner where they came from after advection has carried them into and a region of cold molecules. Waleswatcher (talk) 13:13, 22 November 2012 (UTC)

In the absence of diffusive energy transfer (which would be better approximated in free convection in a viscous fluid like heavy oil), you could partly reverse it, simply by turning the system over, so that buoyancy forces put the plume back where it was. In high viscosity systems where diffusion is limited, very strange and odd-looking reversible things like that, actually happen. Have you seen the demo with the blob of colored fluid that starts in the thin space between two counter rotating concentric cylinders? You rotate them, and the color smears out and you think entropy has gone up a lot. Wrong, because when you turn it backwards the blob puts itself back together! Surprising degree of reversibility there is due to relatively little entropy of diffusion. You say "even in the absence of molecular collisions", then specify a *gas*, where all the irreversibility happens for precisely that reason! In any case my example of forced convection where these two parts of convection (advection and diffusion) CAN be separated, demonstrates the truth of my point. Purely advected heat is not actually heat. Throwing a hot object is not "heat transfer". That's just silly. S B H arris 16:29, 22 November 2012 (UTC)

I am very familiar with that demo - but its relevance to this discussion is close to zero. Yes, it's possible to have advection that is approximately reversible, and I never claimed otherwise. But when flows of particles occur because of heating, that is never the case.

You say "even in the absence of molecular collisions", then specify a *gas*, where all the irreversibility happens for precisely that reason! Sorry, but that's simply wrong. For example, the free expansion of a gas is irreversible and generates entropy even with no molecular collisions whatsoever.

Purely advected heat is not actually heat. I have no idea what you mean by that. Look - take a high temperature object and put it into a cold enclosure. If the enclosure is completely empty initially, the object will radiate photons, filling the container with a gas of photons that will eventually equilibrate with the object. During the equilibration, there will be convection in the photon gas (let's say the container is very large, so it takes significant time for the photons to cross it) as photons flow out from the object, but not - at least initially - back into it. In that instance, convection and radiation are identical If the enclosure is full of a cold gas - photonic or molecular - there will again be convection of gas particles as the hot particles near the object expand outwards. If the enclosure is full of solid, there will be convection of phonons. In that case, conduction and convection are identical. If a hot gas and a cold gas are brought into contact, there will be a net flow from hot to cold initially, because the hot gas diffuses faster. etc. etc.

The point is, convection is an important and fundamental mechanism of heat transfer, and is described as such in multiple reliable sources. Until and unless anyone finds a reliable source that explicitly states that convection is not heat or some such, the article should not imply it. A source not mentioning convection does not indicate anything of the kind, and interpreting as such is in contravention of wiki policy (it's unjustified synthesis and/or original research). I'm perfectly happy for the article to explain the usage and differences between convection, conduction, and radiation - that's a good idea - but I do not agree that it should ignore convection or treat it as if only ignorant engineers regard it as a form of heat. Waleswatcher (talk) 00:35, 23 November 2012 (UTC)

What you term convection of photons (or EM radiation classically) is diffusion. Diffusion needs a concentration gradient. That can be mass per volume or energy per volume. Entropy goes up in either case and I never said otherwise.

But entropy does not go up in advection, which doesn't involve concentration driven processes or increases in volume. Advection just means carrying along. When I move a thermos of hot coffee from my desk to yours, that's advection. Advection of caffeine, for instance (mass transfer). Advection of energy (internal energy transfer). But unless I open the thermos and allow energy out, there is no HEAT transfer. There is no change in entropy. It is reversible. I have not moved (transferred) heat, because there is no heat! Can you find the heat? So, do you now understand my meaning, when I say that pure advection of heat is an oxymoron? Heat cannot advect by definition. It can only diffuse, and radiative transfer is only a type of diffusion. Whether one-way or two-way makes no difference. The point is that entropy increases more in one direction than it decreases in the other. But there is always a change, in diffusion. S B H arris 23:25, 23 November 2012 (UTC)

Diffusion needs a concentration gradient. That can be mass per volume or energy per volume. Entropy goes up in either case and I never said otherwise. Actually, yes you did - you said that molecular collisions are the only source of irreversibility in a gas. That's wrong. Diffusion, or simply free expansion, or convection, all increase the entropy and are irreversible, and all can happen in the absence of any molecular collisions whatsoever.

As for advection, I didn't term anything "advection" or use it anywhere in the article - that's a term that you introduced into the discussion. The term I used is "convection". In standard usage, "convection" includes diffusion from a heat source. So if you agree that diffusion is a form of heat or heat transfer, then unless you have a different definition of convection than the standard one, it sounds like you agree with the text of the article as it is now. In that case, we are done here. Waleswatcher (talk) 00:12, 24 November 2012 (UTC)

Convection is advection plus diffusion. I brought in the word because it's a simple way to separate out the physical processes in convection where heat transfer happens, from those where it does not. Heat is transferred by diffusion not by advection. All the heat transfer in convection is by diffusion, so why confuse the issue for the poor reader that takes this article at its word that heat cannot "reside" in materials and thus clearly cannot be transferred by material motion. The last being essential for the idea of convection as some kind of process in heat transfer differentiable from diffusion , no?

I've sorry that you apparently had some volume-expanding process in mind as part of what makes convective heat flow irreversible. I didn't visualize your model. Gas expands as it rises but in an adiabatic system it also is compresses when it sinks. That is the cause of the lapse rare in the atmosphere. It means a parcel of air can rise or fall reversibly and pure temperature differences cause no convection unless temperature gradient exceeds this lapse. Adiabatic expansion is reversible as entropy doesn't change.

in any case what do we tell the reader who wants to know if hot water flowing along an insulated pipe is "heat transfer"? An engineer, thinking very loosely, would say yes. A thermodynamicist clearly "no". By this article's definitions, no. But that's a textbook case of forced convection of "heat". Since most texts make no distinction between "thermal energy in motion" and heat. This article would rather not talk about thermal energy and it's easy to see why. S B H arris 01:38, 24 November 2012 (UTC)

A more common and familiar case of convection is hot air rising or being blown from a vent or space heater. That is a form of heat transfer, both because the hot air diffuses into the surrounding cold air, but also because (at least if it's blown by a fan) there's an bulk flow that carries hot air some distance. After it arrives, it diffuses... except that diffusion happens all along the flow, and cannot be separated in any clear way from the flow itself. And in some cases, the flow itself is diffusion. For these reasons, convection can't really be split into diffusion+advection, nor does diffusion as a term really suffice to describe it.

I'm perfectly happy describing all of this in more detail in the body of the article, but for the lead, I think the word "convection" suffices - and that's why in many reliable sources, convection, radiation, and conduction are described as the three primary mechanisms of heat transfer. Waleswatcher (talk) 02:46, 24 November 2012 (UTC)

A valuable comment by true hot air expert!Chjoaygame (talk) 07:25, 24 November 2012 (UTC)

I fail to understand your approach. In science when we have two simultaneous effects we cannot disentangle, normally we look for a controlled situation where one or the other is minimized so we can tell what each one by itself is doing, We do that all the time to separate out separate contributions of radiative and diffusive heat transport for example. We don't just throw up our hands and say "Oh dear me, they happen together so I can't tell what each one contributes!"

There are many convection problems where advection can be nearly separated from diffusion, as in an auto radiator , and in those cases it's obvious that the advection phase does not transport heat as we define heat in this article. It follows logically that if heat cannot be stored in constant temp objects, that heat cannot be advected or convected (except as diffusion). If you don't like that, then change the definition given here!

It gets even worse with energy transport systems constructed so you do without heat transport at all. When you compress a gas adiabatically to make it warmer, do you produce heat? Not according to this article, as δq= 0. When you conduct (or simply carry) that hot gas outside and allow it to do adiabatic work on the environment, even work that increases the environment's temperature indirectly (like turning a paddle wheel that heats water by friction), is heat involved? No, according to this article's definition. So, does this entire chain of events transfer heat? No. Heat is never seen here. Just because you have a hot gas at some point does not mean you have heat, or ever had heat. With no thermal gradients, no entropy change, no thermal diffusion, there never exists heat. Only advected internal energy. S B H arris 18:29, 24 November 2012 (UTC)

It follows logically that if heat cannot be stored in constant temp objects, that heat cannot be advected or convected (except as diffusion) Again, it appears you acknowledge that heat can be convected. If so, we can finish this discussion, which doesn't seem to be aimed at improving the article. Waleswatcher (talk) 18:54, 24 November 2012 (UTC)

The article would be improved by pointing out that heat "convection" is only heat diffusion, and that any extra energy transported by convection is not transported as heat but rather as internal energy, which is not the same thing. Further, you're probably the only editor here who does not agree with this point of view (though I don't know about clueless DamὊorbel), so you are outvoted. S B H arris 19:18, 24 November 2012 (UTC)

If you can find a reliable source that says that, go ahead and add it (not to the lead, it's too detailed for that). Waleswatcher (talk) 19:20, 24 November 2012 (UTC)

I see you've come back and edited your comment. First, off, "outvoted"? Huh? That's (a) not how wiki works, (b) there's been no such vote, (c) Crio de la paz has listed convection along with radiation and conduction as one of three mechanisms - so that's three editors to two, I guess (although I don't know, see (d)), and (d) I have no idea what you even believe any more. You've acknowledged that convection is indeed a mechanism of heat transfer. It's just that you (erroneously, I think) believe there's a clear and useful distinction between the diffusive and advective parts of convection. As I said, in accord with wiki policy, if you can find a reliable source that supports your view - whatever it is - feel free to edit it in. Meanwhile, we have tons of sources that list convection as one of the primary mechanisms for heat, so it's staying in the article like that. Waleswatcher (talk) 23:36, 24 November 2012 (UTC)

response by Chjoaygame

Perhaps very little difference, but still significant. The energy that is carried by convection is carried partly and importantly through the cooperation of the particles including their mutual potential energy, whereas for the most part, energy carried by a photon is the sole property of the photon. Also, convection is mainly one-way. One can have convection that is entirely one way. But radiative transfer is essentially two-way. This is because of the Helmholtz reciprocity principle. The heat transfer is the difference between the two ways. Photons carry energy from a source body constituent directly to a target body constituent, in one step. Convection essentially involves many particles on the way.Chjoaygame (talk) 05:31, 22 November 2012 (UTC)

response by SBHarris

§ Photons and diffusion, transfer heat only one way, if the cold reservoir is at zero K. The two way thing is not necessary, nor is potential interaction in a fluid, which would work just as well with an ideal gas. Nor is forced convection needed if you stop diffusion aka heating by use of an insulated thin pipe. Take a partitioned cubical container with warm gas in the lower level and cold in the upper. Or separate containers, for that matter. Make sure pressures are equal or else you'd get flow even in 0 g and it wouldn't be free convection type flow, but forced by non buoyancy pressures. Connect the spaces with a thin insulated vertical pipe. Warm gas now moves up the pipe. Before it hits the end of the pipe, is there "heat transfer" by free convection of gas? No! At any point before diffusion of heat happens you can just turn the whole assembly over and it will all go back to initial state. It's reversible. Entropy didn't increase. Energy flowed but heat did not. S B H arris 17:47, 22 November 2012 (UTC)

Talking about processes with a cold reservoir at zero K !! Surely you are clutching at straws !! In the history of the discovery of the Stefan-Boltzmann law, it was recognized that the law had to be tested by formulas of the form 'heat transfer = function of T₁ − function of T₂. The Helmholtz reciprocity principle of 1847 points out that if radiation can pass from A to B, then it can pass with the same attenuation from B to A. This means that heat transfer by radiation is essentially two-way, the actual heat transferred being the difference between the two ways. In a sense, you are acknowledging this by asking that the cold reservoir have a temperature that you prescribe, even if your prescription is rather demanding.

In an ideal gas the molecules interact by colliding. That is an idealized kind of interaction, because it restricts the interaction to the collisions, requiring it to be zero in between collisions.

When you point to forced convection as an example of one-way transfer, you are agreeing with what I am saying. That convection is different from radiation in this way.Chjoaygame (talk) 19:39, 22 November 2012 (UTC)

I didn't really want to discuss radiative transfer of energy from a cold to a hot object because strictly speaking this subprocess isn't heating since by definition heat doesn't flow against temperature gradients. You cannot break this down without losing the meaning of the macro process of heat transfer that must refer to the sum of this interaction, or nothing. Break down a process into its various parts, some of which increase entropy and some of which decrease it , and you have passes into a subrealm where heat is no longer a useful concept. Heat is what happens overall. S B H arris 23:45, 23 November 2012 (UTC)

response by Waleswatcher

§ I'm not saying the difference isn't significant. I'm saying they are equally valid mechanisms of heat transfer on more or less the same basic footing. I suppose in some vague sense photons are more fundamental than molecules, but by the same token they are more fundamental than phonons too. And in the real world, all three are more or less equally common in people's experience. So for explaining heat on wikipedia, it makes no sense to exclude convection. Waleswatcher (talk)

Dear Waleswatcher, you are making it up off the top of your head as you go along, or perhaps I should say spinning it as you go along.

We are not seeking to exclude convection, as you allege. We are just pointing out that it has a status different in physics from that of the primary pair, conduction and radiation. As I have noted above, and as you have ignored, your chosen sources for the definition of transfer of energy as heat, Kittel & Kroemer, and Reif, do not actually mention convection of heat in those exact words; Reif does not mention it at all. As is your habit, you are seeking to hide this basic point of physics.Chjoaygame (talk) 19:49, 22 November 2012 (UTC)

response by Damorbel

§ If progress is to made in this article it is necessary to be pedantic about language. Chjoaygame you write The heat transfer is the difference.... Isn't it energy, the conserved quantity, that is transferred? With 'heat transfer' surely we are back in the days of caloric. --Damorbel (talk) 11:06, 22 November 2012 (UTC)