experience with medium size heatsinks in audio power amplifiers: My employer experimented with black anodized aluminum surface treatment.
The calculation posted here by another is good for still air and maybe even a vacuum. As soon as the air moves the situation changes dramatically and the relative emissivities rapidly become less significant. Our products are forced air cooled with shiny oxidized aluminum heatsinks. We stopped using black anodize treatment a long time ago except for one range of non-forced air ventilation models for low-noise environments. As an example of dissipation from shiny aluminum, we can get two channels of 5000W RMS 1kHz into 1 ohm out of a box measuring 19" x 9" x 20". The heatsinks are arranged as a 'tunnel' through the center with a 250 CFM fan at one end. This is class AB so reckon 50% efficiency maximum that means about 10kW of thermal energy is being dissipated, and this is with clean shiny, 'as extruded' aluminum. If the dissipation was limited by the emissivity quoted this would not be possible. So don't be put off by the low figure for shiny aluminum, natural convection sets up air flow and the real world result is greater dissipation. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
