How to check if heatsink is big enough

[shattered_dream]

Got here some heatsinks in the closet....
300 x 180 x 50 mm.
Is there a chance how to measure/calculate the thermal coefficient of this heatsink ?

 

[HalFoster]

There is a link to a extremely useful design spreadsheet at the end of the first artical:

https://sound-au.com/heatsinks.htm
https://sound-au.com/articles/heatsink-amp.htm

Hal

 

[shattered_dream]

Great thanks...

 

[e_fortier]

You can have a rough estimate below from the DIYaudio store.

I’d guess 0.25C/W

 

[pinholer]

If you already have the heatsinks, you can clamp chassis mount power resistors to it, connect them to a power supply and actually measure temperature rise. Power = V x I = I x I x R.

 

[profiguy]

I use the resistor method as well. Easiest way to practically do it.

When I build a large class AB amp, it has to run up to rated power continuously without forced air cooling and not exceed 130 degrees F. Thats about what you can tolerate touching with bare hands for several seconds. I hate fan noise, even the tiniest amount.

Based on previous experiences, about 300W is easily possible long term at typical class AB efficiency levels and 70 deg F ambient air temp with your heat sink if the fins are vertically orientated. This may not be your specific application but it gives you a guideline.