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Old 18th February 2012, 03:12 AM   #31
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One other detail, there are 37 2" fins and the overall size is 11.5"x5". Seems to be a good match based on what NP specifies in the manual (his example is 8"x6" with 2" fins at 0.6 C/W.)
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Old 18th February 2012, 03:25 AM   #32
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pr. device. total of 4 pc.
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Old 18th February 2012, 03:40 AM   #33
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Hmm... Uh oh. Did not catch that critical detail. But if I do my math...

0.6 C/W/" with 5" long heat sink = 3.0 C/W.

At idle, 62 watts divided by 3.0 is just over 20 C which is what I was aiming for.

Is there a mistake in my reasoning or am I good to go?

-J
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Old 18th February 2012, 05:09 AM   #34
lhquam is offline lhquam  United States
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Quote:
Originally Posted by oneplustwo View Post
Hmm... Uh oh. Did not catch that critical detail. But if I do my math...

0.6 C/W/" with 5" long heat sink = 3.0 C/W.

At idle, 62 watts divided by 3.0 is just over 20 C which is what I was aiming for.

Is there a mistake in my reasoning or am I good to go?

-J
My guess is that the Antek rating of .6 C/W is for that particular dimension heatsink, and the calculation should be dT(C) = .6 C/W * 62 = 37.2 C temperature rise above ambient.

Here is a useful resource about heatsinks: ESP - Heatsink design and transistor mounting.
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Old 18th February 2012, 05:16 AM   #35
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Quote:
Originally Posted by oneplustwo View Post
Hmm... Uh oh. Did not catch that critical detail. But if I do my math...

0.6 C/W/" with 5" long heat sink = 3.0 C/W.

At idle, 62 watts divided by 3.0 is just over 20 C which is what I was aiming for.

Is there a mistake in my reasoning or am I good to go?

-J
standar F5 like to see 0.3C/W. 65W/25C=0.38C/W.
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Old 18th February 2012, 05:40 AM   #36
lhquam is offline lhquam  United States
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I have used this thermal simulator for evaluating heatsink designs. It it capable of dealing with discrete heat sources so that MOSFET placement can be optimized.

Frigus Primore - Thermal Design for Electronics
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Old 18th February 2012, 05:46 AM   #37
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Wow, my math sucks after being out of school for so long. Couldn't even properly keep track of the units.

I will say, Antek claims it can dissipate up to 150W/channel so I have that going for me.

Thanks for the resources, I'll do some reading.

Ultimately, I'll probably just try it as is and see how much rise I get with an actual measurement.

Last edited by oneplustwo; 18th February 2012 at 05:55 AM.
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Old 18th February 2012, 06:26 AM   #38
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I believe (although I am still learning about heatsink's myself) if the material is rated at .6 C/W per inch then your 5 inches of heatsink material should be rated at .6/5= .12 C/W.

At 180 watts of dissipation the heatsink will be 180*.12= 21.6 degrees celsius above the ambient Temperature.

This seems to be just about right.

If I am wrong about this please somebody jump in here and correct me on this !!!

I have been scoping out heatsink's for my build and I have been thinking of using some Ximatec CPU coolers.


http://www.newegg.com/Product/Produc...82E16835233082

For $30 this one is rated at .15 C/W at least and is fairly quiet with a fan at 16-24 dba.

XIGMATEK

One of these will allow 333 watts of dissipation at temperature rise of 50 degrees celsius.
It maybe a bit on the warm side with a total heatsink temp. of 75 degrees celsius.
But, It is still below the safe limit for the devices as long as the heat pipe don't explode.
It is not uncommon for these to be run at levels of 200 watts or so.

I am considering about 2 to 4 of these would be good per channel for a Turbo F5 build.
I will mount these to a thick aluminium or copper bar heat spreader to mount the output devices to.

I am anxious to see how your build turns out.

The only thing holding me back right now is were to source the JFET's so I don't end up paying so much for the shipping for just a few pieces.

Keep on DIYin'

jer
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Old 18th February 2012, 06:33 AM   #39
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Yes, that's how I recalculated as well but it seemed too good to be true. Perhaps it's not a linear relationship? With every additional inch, you get less benefit.

We'll see!
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Old 18th February 2012, 06:46 AM   #40
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Here are a few more links to some more heatsink calculators that I found awhile back,


HEATSINK QUESTION

Enjoy !!!

jer
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