Talk:Thermal conductance and resistance

Thermal resistance

Here it says

   RθJC = 1.5 K/W (for a typical TO-220 package)
   RθB = 0.1 K/W (a typical value for an elastomer heat-transfer pad for a TO-220 package)

I think the values ar more like 100K/W - 10K/W. Here is an example http://www.ortodoxism.ro/datasheets/philips/BD139-16.pdf I'm trying to find one that has those properties. --(unsigned edit was by ) Zuperman 2007-05-30T09:44:01

No, 1.5K/W is OK: http://www.st.com/stonline/products/literature/ds/10073/stb200nf04.pdf I've seen a TO-220 regulator one with 3K/W also. The one in BS129-16.pdf has a lower power case style. Kallog 13:24, 24 June 2007 (UTC)

Cleanup tag status

There's been lots of cleanup since 2006 - is it time to remove the cleanup tag? It looks pretty good to me. --Lexein (talk) 22:22, 19 March 2010 (UTC)

I think the example calculation section is still over complicated. But yea apart from that. Kallog (talk) 01:49, 20 March 2010 (UTC)

Agreed. That cleanup tag was a hit & run - the user didn't make any edits. --Lexein (talk) 02:23, 20 March 2010 (UTC)

example confused

The formula in the example does not match the formula with numbers substituted. The latter doesn't have deltaThs but has Rha. Also the concept of deltaThs is not clear. Hoemaco (talk) 07:27, 5 April 2011 (UTC)

Agreed. DeltaThs from the formula is not in the example. More importantly, Deltahs shouldn't be in the equations anyway, as this is accounted for by Q*Rha (i.e. = the temperature drop across the heatsink). Comment that "THS appears to be undefined." in earlier paragraph may be eluding to this. — Preceding unsigned comment added by ASearcher (talk • contribs) 19:14, 20 March 2013 (UTC)

Requested move to Thermal resistance

The following discussion is an archived discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

The result of the move request was: page moved. Vegaswikian (talk) 22:03, 21 September 2011 (UTC)

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Thermal resistance in electronics → Thermal resistance – most of the article is about thermal resistance - not specifically electronics. Only one paragraph is specifically about electronics. --Glenn (talk) 18:48, 14 September 2011 (UTC)

• Support, Reasonable to have main articles before sub-articles. Marcus Qwertyus 03:12, 15 September 2011 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

Units are not consistent

Can anyone tell me why meters squared are included?

Keeping them would make calculations & understanding

so much easier.

But nobody else does that

except the thermal resistance page & the thermal conduction page.

The thermal conductivity page does not have meters squared

for thermal resistance or thermal conductance.

77.2.97.53 (talk) 02:00, 4 July 2014 (UTC)

Peter Sheedy PS20100401@gmx.de

I agree this needs to be fixed. The m2 should not be there. — Preceding unsigned comment added by 169.237.42.20 (talk) 01:33, 5 February 2015 (UTC)

My edits that user DVdm just undid

Regarding: "09:24, 3 August 2018 DVdm (talk | contribs) . . (20,374 bytes) (-6,928) . . (Reverted to revision 847787594 by InternetArchiveBot (talk): Was better before - various problems. PLease propose on article talk page. (TW)) (undo | thank) (Tag: Undo)"

DVdm claims my version of the article, where I made use of excellent examples that I meticulously wrote and checked to be correct (https://en.wikipedia.org/w/index.php?title=Thermal_resistance&oldid=853126417) is worse than the previous (and now current) version of the article (https://en.wikipedia.org/w/index.php?title=Thermal_resistance&oldid=847787594) which had a very poor and confusing example. I believe the only way he could have come to this conclusion is that he didn't read the version before, nor did he read my version. I am forced to believe he simply saw something wrong where I didn't perfectly follow the wikipedia style, or where I didn't quote perfectly, or something to that effect, and rather than focusing on the content he simply clicked the "undo" button to undo my 6 hrs of work.

I'd like to open up a discussion as to what, if anything, about my content is wrong and worth deleting, verses the current content in the sections which I had replaced, which is poor.

I was hoping people would simply improve upon the vast improvements I had made, rather than deleting them entirely, which is rather upsetting to me considering the great effort and meticulous detail I put into it.

Click the article's history button to see the changes I had made. I added correct detail, correct examples, correct explanations, and ample sources.

Sincerely, ERCaGuy (talk) 17:32, 3 August 2018 (UTC)

Good that you came here. I undid your edit for a couple of reasons:

• Unsourced section Conversion from specific thermal conductivity to absolute thermal resistance: see wp:CIRCULAR.
• In inline sentences we tend to use italicised variables, not <math>...</math>.
• replacing "modeled" with "modelled", see wp:ENGVAR and wp:RETAIN.

That is where I stopped verifying. Perhaps to soon, in which case my apologies.

Other contributors to the article might have a further look. - DVdm (talk) 17:54, 3 August 2018 (UTC)

DVdm, thanks for the response. You just confirmed my assumption: that you had undid my major changes based on minor problems. Please read the content in its entirety. Those minor things can be easily fixed, but the *content* of what I provided was significant, correct, and a vast improvement. I'd like to see my changes put back in place then the minor things you mentioned fixed.

• The unsourced section is easily fixed. I can add a source. For your information, the entire example section I replaced had not a single source. I vastly improved that section and used many sources.
• The "modelled" thing is trivial. Change that back. Who cares.
• The "circular reference" thing is minor: it's an easy fix.
• The italics things vs "< math >", I never knew. Again, easy fix.

But let's not jump to conclusions please unless you read the content to see if what I have added is worse or better. 6900 characters is no trivial edit. ::I did not take that task lightly. I believe my edits alone may have taken this article from a "Start-Class" to a "C" or "B" class (see: https://en.wikipedia.org/wiki/Wikipedia:Content_assessment), and you undid the whole thing in a single click. ERCaGuy (talk) 18:07, 3 August 2018 (UTC)

Please indent your talk page messages as outlined in wp:THREAD and wp:INDENT — See Help:Using talk pages. Hoping you don't mind, I have slightly reformatted your reply along these guidelines. Thanks.

Ok, no problem here. If other contributors don't object, go ahead. Cheers. - DVdm (talk) 18:16, 3 August 2018 (UTC)

Not entirely oppose, but I'm not a fan of such as explicit examples, the article gets cumbersome.MaoGo (talk) 18:27, 3 August 2018 (UTC)

I don't want to take it to an extreme, but I think Wikipedia needs to be clear enough that someone can learn a new skill or vocation from the technical (physics, engineering, etc) pages on Wikipedia. At a minimum, I think technical Wikipedia pages need to provide enough detail and examples, at a simple-enough level, that an engineer can learn how to do a new type of engineering. That's the intent I had in mind when writing these examples. They are clear, concise, and teach basic principles required in industry to actually use the concept of Thermal Resistance in the real-world. Articles which are overly academic, or purely academic, won't help our world progress because no one will know what to actually do with the information. In the case of my example, it could become a regular reference for students, designers, and engineers who are trying to understand how to calculate basic temperature and power requirements for circuits, which is a primary use-case for the concept of "thermal resistance" in the real-world. That's my logic. ERCaGuy (talk) 20:22, 3 August 2018 (UTC)

Maybe some of those examples, if correct could go into Wikiversity or a Wikibook.--MaoGo (talk) 17:43, 4 August 2018 (UTC)

• Comment. I think the current (reverted) version is better as less clumsy. Thanks to ERCaGuy for his hard work, but hours put in does not not necessarily result in improvement. Xxanthippe (talk) 22:44, 3 August 2018 (UTC).

I agree that hours don't equate to usefulness, but have you carefully read the previous (and current version), as well as mine? the current version doesn't even entirely make sense. I'm not even sure what this is supposed to mean: "the transistor to a metal surface (or heat sink) that is guaranteed to be less than $\Delta T_{HS}$ above the ambient temperature. Note: T_HS appears to be undefined." then: "Maximum temperature drop from junction to ambient = $T_{JMAX}-(T_{AMB}+\Delta T_{HS})$". Read my version and it is crystal clear what an engineer is supposed to do to make these calculations. The version I wrote also follows the terms and layout in the thermal diagram at the right of the page perfectly, including using the same symbols. ERCaGuy (talk) 00:41, 4 August 2018 (UTC)

Let me expound a little further. Imagine you are an electrical engineering student, or a (non-EE) engineer, asking yourself: "I have this heat sink and this transistor", how much power can it dissipate?" "What if I don't have a heat sink?" "What if I use thermal grease on the heat sink?" "Does forced airflow matter?" "How do I read a datasheet anyway?" "What terms can I expect to find in a datasheet?" "What the heck is absolute thermal resistance verses thermal resistivity and why does one have meters in the units?" "How do I convert between the two?" (NB: some datasheets use one form but not the other so this matters). In its current state, your best bet is to leave Wikipedia alone and go find a more useful resource since Wikipedia just won't help you much here. It won't help you answer these questions. It's incomplete, and confusing at best. With my edit, all of those questions become crystal clear, and you have an "ah ha!" moment and solve the problem. Which version of Wikipedia would you like? (If you're not an engineer and don't solve these problems, I agree with you: it doesn't matter. Wikipedia can continue being just a place where academics can pontificate, instead of a place where you can learn correct principles to solve real problems). ERCaGuy (talk) 00:57, 4 August 2018 (UTC)

WP:NOTTEXTBOOK. Xxanthippe (talk) 02:50, 4 August 2018 (UTC).

Providing a link with no explanation to provide your point of view is not very useful. I'd prefer you spoke with your voice and a link instead of with just a link. Nevertheless, from your source: "Describing to the reader how people or things use or do something is encyclopedic". So, my edit is encyclopedic. "Wikipedia is an encyclopedic reference, not a textbook. The purpose of Wikipedia is to present facts, not to teach subject matter. It is not appropriate to create or edit articles that read as textbooks, with leading questions and systematic problem solutions as examples. These belong on our sister projects, such as Wikibooks, Wikisource, and Wikiversity. Some kinds of examples, specifically those intended to inform rather than to instruct, may be appropriate for inclusion in a Wikipedia article." So the question is simply: do my examples inform rather than instruct? Or, are they "with leading questions and systematic problem solutions"? I assert they are the former, which are permitted on Wikipedia. If they become any more thorough or instructional than what I did, however, I agree they should be placed on Wikiversity instead, with a link to there from the Wikipedia page. If you disagree with having a link to the Wikiversity page from the Wikipedia page (and your or another deletes such a link if I add it), I see no point in contributing to Wikipedia further because it will not allow people to find the resources they need to be successful. If at least one person can agree my examples inform rather than instruct, and describe "how people or things use or do something," then I'll put them back onto Wikipedia. Regardless of what I do, though, how do you plan on addressing the current major shortcomings of the article as it is written now, such as using terms that are undefined, having "notes", being incomplete, not addressing the conversion between absolute and specific resistivity, etc.? The current example is so confusing and incomplete (and uses undefined terms), that it does NOT describe to the reader "how people or things use or do something", and it should be removed...or improved. My edit did the latter. ERCaGuy (talk) 19:19, 4 August 2018 (UTC)

Case and point about the current example being flawed:

$Q_{MAX}={{T_{JMAX}-(T_{AMB}+\Delta T_{HS})} \over {R_{\theta JC}+R_{\theta B}+R_{\theta HA}}}$

$Q={{125-(21)} \over {1.5+0.1+4}}=18.6\ \mathrm {W}$

What happend to $\Delta T_{HS}$? Why is it not even present in the part of the solution with actual numbers just above? Nobody knows: because this example literally doesn't make sense as written. It gets the right answer, but in a very poorly-explained way. It's like saying: to solve this problem you must know A, B, and C. Now, the answer is A*B (what happened to C!?).

If you know how to do these calculations yourself, somehow convince me this current article is better. I really can't see where you (or DVdm) are coming from to call my example "clumsy" and this example good. It doesn't make any sense at all. ERCaGuy (talk) 19:49, 4 August 2018 (UTC)

Insulance, R-value

'Thermal insulance ... is the thermal resistance of unit area of a material.' appears to imply 'per unit area' which is untrue: it is the inverse of that. Would this be better as 'the area of material for one unit of power to flow for each unit of temperature difference'? SciberDoc (talk) 09:49, 19 January 2023 (UTC)

Requested move 2 October 2023

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion.

The result of the move request was: moved. (closed by non-admin page mover) — MaterialWorks 14:34, 9 October 2023 (UTC)

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• Thermal resistance → Thermal conductance and resistance
• Thermal conductivity → Thermal conductivity and resistivity

– For the same reason as Electrical resistance and conductance & Electrical resistivity and conductivity Jeaucques Quœure (talk) 13:06, 2 October 2023 (UTC)

• Um, please explain to me the difference between thermal resistance and thermal resistivitiy, and the difference between thermal conductivity and thermal conductance. They appear to be the same thing, so how would the scope of either of your suggested titles differ from each other? Rreagan007 (talk) 07:44, 4 October 2023 (UTC)

Explanation

Thermal Resistance vs Thermal Resistivity

• Thermal Resistance (R) is a measure of how a material or an object opposes the flow of heat. It is expressed in units like Kelvin per Watt (K/W) and indicates how much temperature difference (in Kelvin) is required to transfer a unit of heat energy (in Watts) through the material or object. Lower thermal resistance means better heat conduction.

• Thermal Resistivity (ρ) is a property of a material that quantifies its inherent resistance to heat flow. It is expressed in units like Kelvin meter per Watt (K·m/W). Thermal resistivity is an intrinsic property of a material, whereas thermal resistance depends on the geometry and thickness of the material. Higher thermal resistivity means poorer heat conduction.

Thermal Conductivity vs Thermal Conductance

• Thermal Conductivity (κ) is a material property that measures how well a material conducts heat. It is expressed in units like Watts per meter-Kelvin (W/(m·K)). It is a characteristic of the material itself and does not depend on the size or shape of the object. Materials with higher thermal conductivity transfer heat more efficiently.

• Thermal Conductance (C) is a measure of how well a specific object or assembly of materials conducts heat. It is expressed in units like Watts per Kelvin (W/K). Thermal conductance takes into account both the material's thermal conductivity and the object's dimensions. It quantifies the ability of an object to conduct heat under given conditions.

In summary, thermal conductivity and thermal conductance are related but represent different aspects of heat transfer – one is a material property, and the other is a property of an object or assembly of materials. Jeaucques Quœure (talk) 15:52, 4 October 2023 (UTC)

• Okay, fair enough. Support. Rreagan007 (talk) 00:02, 5 October 2023 (UTC)
  • Thanks! Jeaucques Quœure (talk) 05:30, 5 October 2023 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Dimensional Analysis

Why are the dimensions given for Thermal Resistance and Conductance shown to be the same? One should be the invert of the other. I believe this is the correct analysis: C = L² M T^-3 Θ^-1 109.158.34.144 (talk) 11:53, 9 January 2024 (UTC)

The dimensions were generated automatically from wikidata. I think now should be correct.--ReyHahn (talk) 13:14, 9 January 2024 (UTC)