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Old 13th October 2003, 07:41 PM   #1
OliverD is offline OliverD  Germany
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Question Yet another heat sink problem

Having completed 4 channels of Aleph 5 with conventional heatsinks, I recently acquired a forced air-flow heat sink for free (junk yard). As using a fan is no option (noise), my plan is to cut this heatsink into six "slices" and mount them in a 2 x 3 array next to each other. The fins will be vertically and the transistors will attach to the sides of the array. This array will be mounted in the middle of the amplifiers case, and air can flow from the bottom through the heatsink to the top of the case. Of course, no other device will be placed on top of the amplifier and the feet it stands on will be higher than usual to assure air convection.

The heatsink I have is 26 cm long (there will be 6 slices of 4 cm), 6 cm high and there are forty fins. The picture shows a similar heatsink.

Each section (40 fins * 4cm * 6cm) has a surface area of about 960 square cm, adding up to a total of 5760 square cm.

(1 inch = 2.54 cm)

Here is my question: Can anyone estimate what approximate K/W rating the resulting heat sink will have, taking into account the case which will force the air to flow through it? Will it be enough for two channels of Aleph 5?
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Old 13th October 2003, 08:37 PM   #2
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You did not specify the air flow rate.
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Old 13th October 2003, 09:18 PM   #3
OliverD is offline OliverD  Germany
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I have no clue what the air flow rate will be. I'm not using a fan.
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Old 13th October 2003, 09:27 PM   #4
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Then it will not run as cool as you are hoping. My guess:
1 deg C/watt
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Old 14th October 2003, 01:58 AM   #5
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Throw some big heatsink mounted power resistors on it and fire it up. Like this. That's the best way to get real world measurements.
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Old 14th October 2003, 03:37 AM   #6
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That's the spirit.

Say, I have some of that kind of tile too...

/pass/ - still playing Pirates of the Caribbean for all that a
pair of Zen Lites and J-Lows are worth

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Old 14th October 2003, 09:44 AM   #7
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You should definitely not use that sink without a fan. The guess of about 1 deg C/W doesn't sound too bad. You might have a look at the Fischer Elektronik Website (http://www.fischerelektronik.de/) for some data.
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Old 15th October 2003, 07:00 PM   #8
Mad_K is offline Mad_K  Norway
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you might be surpised how quiet a 12dB papst fan is...
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Old 15th October 2003, 09:47 PM   #9
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And add a labyrinth of foam for the intake and exhaust. You'ld be suprised how mush that quietens 100 KW turbodeisel portable generators
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Old 15th October 2003, 11:35 PM   #10
Cobra2 is offline Cobra2  Norway
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Talking A 100 KW generator ?

I could listen to one for hours, without music!

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