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Old 16th October 2013, 12:15 AM   #11
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Quote:
Well back it up with some real physics assuming typical steel
cased or tabbed devices
I can't find the reference I was thinking of, but these links should substitute.
List of thermal conductivities
Properties of metals
I like CanAm Man's last suggestion, as the finned side of the heatsink has much greater surface area and is where most convection will occur.
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Old 16th October 2013, 12:24 AM   #12
sreten is offline sreten  United Kingdom
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Hi,

Somebody quote some real numbers rather than talking crap.

rgds, sreten.

Real numbers for a steel output device via a steel chassis to
an aluminium heat sink are such its hardly worth the effort.

An aluminium heatsink designed to fit a steel case will
typically take into account the heat spreading of the
steel layer, for such a heatsink directly mounting
devices has no real benefit, it may be worse.
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Old 16th October 2013, 12:34 AM   #13
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Quote:
Originally Posted by sreten View Post
Hi,

Somebody quote some real numbers rather than talking crap.
Built a bunch of Class A amps, have ya, sreten?

I have. And also a number semiconductor 1-kilowatt HF and VHF power amps.

Funny, but when we want to improve thermal coupling between power semi's and a large heatsink area, we use thick COPPER bar stock as a heat spreader. Next best engineering practice is to "direct mount" the semi on the heatsink.

If you desire to use steel as a medium between a semi and a heatsink, please do. Please send pictures of the finished product, when you fire it up under load. ("Fire it up" is probably an accurate description)

I won't bore you with my background in physics and thermodynamics. Besides, I'm not going to sway your opinion, am I?
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Old 16th October 2013, 12:35 AM   #14
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by sofaspud View Post
I can't find the reference I was thinking of, but these links should substitute.
List of thermal conductivities
Properties of metals
Hi,

Quoting facts is no substitute for understanding the physics,
and that you have implies you don't understand the physics.

rgds, sreten.
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Old 16th October 2013, 12:38 AM   #15
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Heat sink - Wikipedia, the free encyclopedia

If you can't follow the transition equations, there are some pictures that might amuse you..........
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Old 16th October 2013, 12:48 AM   #16
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Getting competitive performance through a steel chassis is harder than making some holes in it.
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Old 16th October 2013, 12:49 AM   #17
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Quote:
Originally Posted by Andrew Eckhardt View Post
Getting competitive performance through a steel chassis is harder than making some holes in it.
Yep...that's why you do NOT want to sandwich a steel chassis between a semiconductor and it's heatsink. Q.E.D.....
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Old 16th October 2013, 12:55 AM   #18
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Katie: Can you show us pics of the heat sinks and the steel chassis you intend to use, so we can offer some practical suggestions?
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Old 16th October 2013, 01:03 AM   #19
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Quote:
Originally Posted by sreten View Post
Hi,

Quoting facts is no substitute for understanding the physics,
and that you have implies you don't understand the physics.

rgds, sreten.
Before I continue reading the replies I'd like to respond.
I've yet to see your numbers, and until I do I'd appreciate you keeping the personal comments to yourself. Thank you.
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Old 16th October 2013, 01:05 AM   #20
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by CanAm Man View Post
Built a bunch of Class A amps, have ya, sreten?

I have. And also a number semiconductor 1-kilowatt HF and VHF power amps.

Funny, but when we want to improve thermal coupling between power semi's and a large heatsink area, we use thick COPPER bar stock as a heat spreader. Next best engineering practice is to "direct mount" the semi on the heatsink.

If you desire to use steel as a medium between a semi and a heatsink, please do. Please send pictures of the finished product, when you fire it up under load. ("Fire it up" is probably an accurate description)

I won't bore you with my background in physics and thermodynamics. Besides, I'm not going to sway your opinion, am I?
Hi,

No because your being an idiot. As I've said all along it depends
on design what is best, here it simply whether its worth it or
not to bypass the steel case and IMO it basically usually isn't.

The real physics indicate a minor loss of heat flow.

Don't try and tell me how to implement a "heat spreader",
that you think you can just shows how little you really know.

rgds, sreten.
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Last edited by sreten; 16th October 2013 at 01:28 AM.
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