Big Heat Sinks

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
These heatsinks can be placed face to face and the center channel that is formed is perfect for a standard 4 11/16" muffin fan. They ar rated at 0.28 C/W without airflow each. With airflow Aleph 1.2's may be within reach.

24.75" Heavy Duty Aluminum Heat Sink
Heavy duty heat sink comes in two lengths. 24.75" long x 7" wide x 3" tall Each has 5/8" holes and a place for our 1800V Phase Control Thysistor (280-0397) Great for big power supplies and amps.

MECI Part Number: 310-0282 Qty:
Price: $29.95

If I understand correctly, the heatsink rating given by the Aavid thermalloy website is based on a single point source of heat. If you spread 12 IRFP240's out per sink, I believe you will achieve much better dissipation than the .28 shown.

I think that the 500 watts could be dissipated by two of these without fan cooling.

One 3" section gives a .8 rating. Let's say you were mounting just 8 FETs per sink - we could calculate an aggregate .1 degree per watt for each sink. 250 watts per sink would give a 25 degree rise. This is not a completely accurate assumption because air flow over a 8 single 3" pieces is completely different than over one 24" section. However, I think that we can use the horseshoes and handgreandes principle and say close enough.

Any one out there have the sinks up and running yet? I would
like to know how close the theoretical calcs match up to the real world.

They have another 5 1/2" heavy duty heat sink $9.95

This one is shorter, they used the same picture to show the cross section of the sink. Apex gave me the idea to try them this way and they work. Both are excellent values. C'mon, build those Pass amps! Hmmm... 500 watts no air... Kilowatt Pass X's?
but (original question once again), 1 18" section per channel would be enough cooling? vertically or horizontally?

i assume that 2 18" sections per channel is enough also...

BrianGT said:
I was thinking of the wrong heatsinks... I was thinking of the other big heatsinks that they used to offer.

Cutting them in half seems like the best plan to me and would provide a better looking chassis.

Retired diyAudio Moderator
Joined 2002
I don't think that one 18" would be enough.

I would instead, cut the heatsink in 3 even pieces, buying 3 heatsinks total, and using 4 of these pieces per channel, orientating the fins vertically.

That would give you 2 chassis that would be ~8" high and 21" deep.

I would then use one of these chassis per channel. You could then mount 3 devices on each of the heat sinks in the big middle part.

Retired diyAudio Moderator
Joined 2002
Similar to this, but with your heatsinks:



Do you think a plastic/aluminum blade in a chop saw would work to cut these?

I assume a bandsaw would be best, but I don't have one of those. Table saw and a chop saw I do have, and I've cut aluminum in those (with backing), but these heatsinks have a lot of fins, I'm not sure how well that would work.

Correct, it's a woodworking saw, although it doesn't slide. It's a 12" compound miter saw.

I've seen problems with thin pieces (1/8") of Al (L piece) going through the table saw; sometimes the piece of Al 'flexes' and then it tends to 'shoot'. I started clamping a piece of wood on the top of the Al L, in addition to the wood fence behind it.

Kickback is not fun :bigeyes: but that should be less of an issue with the Compound Miter saw.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.