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Bala Pullat
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Heat Transfer Coefficient

12/01/2008 12:58 AM

1. Can any one kindly confirm that heat transfer parameter W/MC and W/M-K are same?If not what is the conversion factor.

2. Thermal conductivity indicated for 20deg.C or @ 25 deg.C which is worst case scenario? Please any one confirm to me that the later is the worst case !

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Anonymous Poster
#1

Re: Heat Transfer Coeeficient

12/01/2008 1:20 AM

Yes - W/m·C and W/m·K are the same because they are based on a relative scale, not an absolute. (i.e. a temperature difference of Δ10 deg C = Δ10 K [note I left out the deg K for the purists out there )

It depends on what you mean by worst case. Are you looking at an insulator or conductor .

It really depends on your exact material and at what temperature range you are looking at because

  • thermal conductivity of iron initially decreases then increases slightly
  • thermal conductivity decreases with increase in temperature for aluminium
  • while it increases for platinum.
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PWSlack
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#2

Re: Heat Transfer Coeeficient

12/01/2008 2:56 AM

1. They are the same.

2. The question conveys little meaning in the absence of context. What material? At what pressure?

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Bala Pullat
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#3

Re: Heat Transfer Coeeficient

12/01/2008 6:43 AM

Thank you very much

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TVP45
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#4

Re: Heat Transfer Coeeficient

12/01/2008 7:48 AM

Wait! Don't go away. You did not get a clear answer to question number 2. Thermal conductivity sometimes goes up with temperature and sometimes goes down. Please tell us the material and the circumstances.

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editorgbanalysts
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#5
In reply to #4

Re: Heat Transfer Coeeficient

12/01/2008 7:16 PM

Apparently he did get answer to quest. #2 - it may be that one of the metals mentioned by "Guest" just might be the metal of use. Just my surmise.

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TVP45
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#6
In reply to #5

Re: Heat Transfer Coeeficient

12/01/2008 7:53 PM

Well, that's the matter. I don't know all aluminum alloys, but I surely know that 6061-T6 thermal conductivity goes up from 20°C to 25°C. So, if that was his metal, he got the wrong answer. Now, if he wanted 6063, then he got the right answer since it goes down. As does 1100, but 3003 goes up. And, for platinum, it decreases. So, I say again, he didn't get his question answered.

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Bala Pullat
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#8
In reply to #6

Re: Heat Transfer Coeeficient

12/02/2008 12:11 AM

mine is 1060..Please comment.Thanks !

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Bala Pullat
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#7
In reply to #5

Re: Heat Transfer Coeeficient

12/02/2008 12:09 AM

This is about specified Thermal Conductivity requirement of AA1060 Air fin cooler fin material .The requirement in Drawing is 198 W/MC.at 20 C. The T/C doesnot show any test results.

How do we check this with the bought material?

The web data on a certain brand of 1060 tabulates 294 W/M-K at 25 C .Can we readily extend this to all 1060s under the sky?That's where I sought CR4's help!

Is that brand strictly within spec?

Please comment.

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TVP45
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#9
In reply to #7

Re: Heat Transfer Coeeficient

12/02/2008 6:29 AM

No, you cn't extend that value. By the way, the question of up or down that several of us offered answers for is very small, perhaps 2% over a 5 degree range.

AA1060, or A91060 in UNS, should have a thermal conductivity of 230-234 W/m-K at 25°C. It varies a little depending on the hardness, but you didn't specify that. It won't very much at 20°C. Sounds like somebody is not controlling the composition very well (that's lawyer talk for "putting too much scrap in the pot").

I suggest a chemical analysis to see what's really in there.

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