Matching heatsink to led cob?

Hi folks,
I have just made a framework to mount an Aavid r186-70 heatsink with an arctic f12 fan on top. see photos.
Aavid say this heatsink is capable of dissapating 40w of heat passively.
My question is what would its capacity be with fan blowing at 74cfm (126m3/hr) in a 80x80x160m grow tent with extractor fan on as well?

I have a 3000k gen7 vero 29 array cob and want to know how hot i can run it?

Please advise

La belfasta

Impossible to say, but if that's 40w passive, I'd be comfortable at 80w with a decent fan.
It's not easy to calculate how much it can handle as there's too many variables involved.
The only way to find it is to try it with a fan and touch the heatsink every now and then over a few hours.

Thanks Goofy,
I was thinking of running the cob at various amps and taking temp readings every half hour to check rise in temp. Maybe starting at 1.8a and take it up to 2.7a and finding a happy medium.
Colin