bridgelux heat question

[Axkiker]

Hey im looking at using on of the white bridgelux rs series leds. looks like 4500 - 5000 lm at 2100ma....


what kind of heat issues am I going to have. any idea of heatsink capabilities ???


thanks

 

[blasterman]

Bridgelux Thermal Guide - page 15

Heatsink will either need a thermal resistance of .5 C/W (ouch) or a surface area of 580 sq inches. Spread out that's a plate of aluminum 1/4 inch thick by 17 inches square. Now imagine that folded up and it will get you in the ball park of how big a sink you need.

Note that Bridgelux thermal specs are for good longevity.

Now you see why I whine and gripe about thermal management for big emitters.

 

[Axkiker]

Bridgelux Thermal Guide - page 15

Heatsink will either need a thermal resistance of .5 C/W (ouch) or a surface area of 580 sq inches. Spread out that's a plate of aluminum 1/4 inch thick by 17 inches square. Now imagine that folded up and it will get you in the ball park of how big a sink you need.

Note that Bridgelux thermal specs are for good longevity.

Now you see why I whine and gripe about thermal management for big emitters.

That is a large heat sink!!!!! Good thing for me is this is an underwater project. I just was currious if I could somehow design them to be use out of water as well.... Doesnt look like its going to be possible for a long period of use.

 

[Walterk]

I read the Bridgelux datasheet, as I am not good with maths/physics, my eye catched the rule of thumb mentioning 10 square inch surface area for each Watt to dissapate.

For comparison some calculations for (fanless ) heatsink pictured below:

I have calculated the surface.
The 90dia x 30mm (3.5 x 1.18inch)
93.600mm2 or 145 sq inch, say 14.5 Watt

The 90dia x 75mm (3.5 x 2.9inch)
272.700mm2 or 423 sq inch, say 42 Watt.
(But due to depth probably less efficient.)

But thats only the rule of thumb...!

Wiki has a list of CPU's and their specific heat dissapation, that give some hint where to look. With a fan, is much more efficient cooling then without (passive).