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Old 30th July 2012, 06:35 PM   #1
ChrisA is offline ChrisA  United States
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Default Help me guess heat sink specs

Is there a rule of thumb for estimating how well a given heat sink will work in free air. I need to make a rough guess for a pair of heat sinks I found in a pile of salvaged junk.

Each heatsink is a simple 2 x 2 inch "U" channel with small grooves and is 9.5 inches long. about 1/8th inch thick. What makes these nice is they have a socket for to-6 transistors. Here is a photo

https://www.dropbox.com/sh/ujepcbbgevxj75s/OMcwO7YYKT

Yes, I know I could measure then by bonding a dummy load resister to the heat sink and measuring temperature vs current in the resistor. But "what a lot of work" and I'd STILL need to make an initial guess.
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Old 31st July 2012, 12:58 AM   #2
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Here are a few links that might help you, One of them calculates them by just the surface area,

HEATSINK QUESTION

jer
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Old 31st July 2012, 03:55 AM   #3
ChrisA is offline ChrisA  United States
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Thanks, So by several methods it looks like about 20W continuous. But music is not a flat sine wave. Next I'll have to figure out how to set up a VI limiter to get the most possible use of this heat sink.
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Old 31st July 2012, 04:02 AM   #4
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That is about what I guessed 10 to 20 watts or so.

You'd be surprised what a small fan would do.
Maybe closer to 40 or 50 watts but at around 80 degrees celsius though.

jer

Last edited by geraldfryjr; 31st July 2012 at 04:07 AM.
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