Mini Aleph heat sink, more than F-5?

[Russellc]

Just came across this thread, which is perfect timing. I just ordered a set of the 10" sinks in 8" lengths from HeatsinkUSA yesterday to do Aleph J. I calculated a thermal resistance after derating it by 25% of about .1000 to handle 200W. That gave me a target of two lengths of 10" but figure that by finishing them I can improve their C/W enough to get by. With a 10" length figured the chassis would look too boxy. I read somewhere that several members had great success using ceramic manifold paint on sinks.
Dan

BTW, does anyone know the difference between the IRFP240-ND

An externally hosted image should be here but it was not working when we last tested it.

and the IRFP240PBF-ND? they appear to have identical specs.

Lead free maybe?

Russellc

 

[Bill Fuss]

Just came across this thread, which is perfect timing. I just ordered a set of the 10" sinks in 8" lengths from HeatsinkUSA yesterday to do Aleph J. I calculated a thermal resistance after derating it by 25% of about .1000 to handle 200W. That gave me a target of two lengths of 10" but figure that by finishing them I can improve their C/W enough to get by. With a 10" length figured the chassis would look too boxy. I read somewhere that several members had great success using ceramic manifold paint on sinks.
Dan

BTW, does anyone know the difference between the IRFP240-ND

An externally hosted image should be here but it was not working when we last tested it.

and the IRFP240PBF-ND? they appear to have identical specs.

PBF does mean lead free, the new standard.

I wonder about the ceramic paint. Automotive racing exhaust systems are sometimes ceramic coated to keep the heat in and lower under hood temps. A little research would be wise I think.

Best, Bill

 

[Dmatuszak]

PBF does mean lead free, the new standard.

I wonder about the ceramic paint. Automotive racing exhaust systems are sometimes ceramic coated to keep the heat in and lower under hood temps. A little research would be wise I think.

Best, Bill

Interesting....I'm obviously not a mechanic. Just when you think you have things figured out ... guess the paint option will take some more research. There must be a reason manufacturers anodize their heatsinks instead of painting them. Might just have to have them anodized. Thanks Bill.

Thanks for the explanation on the 2 transistor parts codes.

Dan

 

[flg]

Anodize is only a very thin penetrating die like process. It does create a dielectric surface but it does very little in the way of impeading or improving radiated heat.
Conrad I believe powder coats there Black heat sinks. I think they claim improvement in Rth.
I have seen testing on motorcycle cylinders that showed reasonable improvement with a speacial sand/bead/Media? blasting(improves the fin surface area).
And yes, the purpose of painting your headers with high tech "paint" is to maintain high exaust gas temp inside the pipe for better flow(and lower emissions). It will reduce underhood temps but that is the opposite of our intentions with heat sinks.

 

[Dmatuszak]

For those so inclined check out the International Rectifier Technical Bulletins on heat sinks....particularily AN-1057.

 

[digits]

Surface - Emissivity
Polished aluminium 0.05
Polished copper 0.07
Rolled sheet steel 0.66
Oxidised copper 0.70
Black anodised aluminium 0.70 - 0.90
Black air-drying enamel 0.85 - 0.91
Dark varnish 0.89 - 0.93
Black oil paint 0.92 - 0.96

Table from ESP website

 

[flg]

If you have an infared camera, that table is usefull. It tells you that Polished aluminium @ 0.05, will actually be 5% of the reading your camera gives you without using the emissivity offset. Your camera view will basically appear black (Coldest) for Polished al, when in reality it could be the hottest object in the feild of veiw.
Polished metal objects typically reflect the heat signiture as if they were a mirror.