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K&K Audio / Lundahl Transformers Welcome! Need support, you got it. Or share youe ideas and experiences. |
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K&K Audio / Lundahl Transformers Welcome! Need support, you got it. Or share youe ideas and experiences. |
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In Reply to: Shunt Regulation Question Part2 posted by amandarae on January 18, 2013 at 16:54:20:
Your calculations are correct. Perhaps you will be sorry you asked, but the answer to the how big question isn't so simple.
The size of a heat sink needed for a given power dissipation depends mainly on four things:
1. the wattage needing to be dissipated = 11 watts
2. the ambient temperature in the heat sink's environment
3. the maximum heat sink temperature that you or the semiconductor devices will tolerate
4. the thermal resistance of the heat sink candidates that you have available (under the mounting conditions that they will be used in, which affects airflow over the heat sink)
Heat sinks are normally specified in units of degrees Celsius of temperature rise per watt of heat input (thermal resistance). If you were using a flat aluminum chassis surface for a heat sink you would also need to know the thermal resistance for the specific unobstructed area of the chassis surface available for use as a heat sink. If the chassis surface to be used is horizontal the result will be different than if it were to be vertical, due to the obvious heated airflow differences. There are websites such as this one (http://www.electronics-cooling.com/2003/02/estimating-parallel-plate-fin-heat-sink-thermal-resistance/) that will allow you to calculate the results, but the calculations are laborious. It's easier to "cheat" and use nearly flat heat sink profiles to get an idea how much area you need. I use the Aavid Thermaloy webpage to find profiles that are helpful, when I need estimates. Without describing the estimation process, because typing so many words would not be pleasant, I would estimate that to keep the surface of your chassis from exceeding 60 degrees C, you would need about 16in x 16in, assuming a horizontal plate that has contact with ambient air on one side only and has no other heat generating devices confined inside. In other words, you'd be better off with a real heat sink!
Kevin Carter
K&K Audio
www.kandkaudio.com
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Follow Ups
- RE: Shunt Regulation Question Part 2 - KevinC 06:44:42 01/21/13 (1)
- RE: Shunt Regulation Question Part 2 - amandarae 10:58:38 01/21/13 (0)
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