F6 heatsink Calculations
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dantwomey
diyAudio Member

Join Date: Feb 2002
Location: Canada
F6 heatsink Calculations

Revisiting the neverending discussion of heatsink calculations........

Refering to this webpage
ESP - Heatsink design and transistor mounting

I have,
Quote:
 You will use the following terms - Tr - Temperature rise Ta - Ambient temperature (example 22°C) Th - Heatsink temperature (example 54°C) Vh - Voltage to heater (example 12V) Ih - Current to heater (example 3.5A) Ph - Power applied to heatsink Rth - Thermal resistance (in °C/W) so ... Tr = Th - Ta = 54 - 22 = 32°C Ph = Vh * Ih = 12 * 3.5 = 42W Rth = Tr / Ph = 32 / 42 = 0.76°C/W
I'd to like mount three or four of these heatsinks vertically on a piece of 1/4" plate aluminum. At there 100mm length they are rate at .85K/C.

How do I calculate the effect of multiple heatsinks bolted to a base?

Regards,
Dan

 14th November 2012, 12:37 PM #2 Eric   diyAudio Member     Join Date: Nov 2000 Location: Central PA, USA If you orient this sink on its "edge" (closest surface in your image) with the fins running up and down and place multiple sinks side by side, you simply divide the c/w figure by the number of sinks you are using. For example, at 0.85k/w each, having 2 of them side by side will result in net dissipation of 0.42c/w. Having 4 of them will result in 0.21c/w dissipation. However, is you take these sinks and stack them one on top of the other (effectively making a column of them), the impact of adding more is significantly decreased. One will dissipate 0.85c/w. Two (one of top of the other -effectively making it look like a single sink that is twice as tall) will increase your cooling by 0.85 / sqrt(2) or about 0.60c/w. Thus it is much less efficient to stack them than to place them side by side. You might want to see the "heatsinking" section of my Aleph-X page for a more thorough description... __________________ My DIY Basement Theater, Aleph-X Amps, Avro Open Baffle Speakers, LDR based DCB1 + BA-3 pre, Pearl II, highly modded Technics SL-1200, F4, a40, several ACAs, FHXL, Tang Band 1772 bass-reflex

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