Heat problems - should I paint my cab flat white?

[ScrubNinja]

Hey guys I've made the world's trippiest grow cab. It's micro and uses cold cathode lighting which is PC case modding equipment - it gives a glow from your pc tower if you know what I mean. Yes, I am clearly bonkers and it is a dumb idea, and very inefficient lighting but I just don't care, I'm doing it for science, and for the lulz. And for a pretty cool coffee table if it all goes tits up.

• The cab is only 1 cubic foot
• Exhaust fan is 20cfm and roars out fairly unrestricted
• Passive intakes are 3x the exhaust size and covered in foam
• Circulation fan is a 100+ CFM very strong fan inside to power a tornado effect to blow over the bulbs and their entire lengths get blown over by a lot of air.
• Lighting is approx 35w (humour me)

The *real* bulb though, is only a few millimetres in diameter, and is encased and enclosed virtually airtight in the outer protective tube.

I did one of those formulas for room air exchange and if I did it right, I only need like 1.5cfm. But my temps are super high at 9*f over ambient. To put that into perspective, I'd be getting close to 20cfm, but lets say 15 t'be sure. So that's approx 15 room changes per minute, right? Overkill I thought.

You think it would help if I painted the inside flat white? Otherwise is there some other way I can make it work with that exhaust fan or do I simply need more cfm to be exchanged? I had a similar spec/design fan cooling far more wattage in the past, in a small tent. Here is the fan setup in the lid/roof.



What do you reckon? Thanks.

 

[cork144]

its easy to think that 20cfm in 1cubic foot is enough airflow, but ive learnt that even with me about 90cfm on pc fans, i do have heat problems somtimes

i recommend you do try vamp up the cfm in there man, im sure you wont regrette it

 

[ScrubNinja]

Dammit, yeah I think you're right bro. I have noticed some irregularities trying to convert large scale things down to micro. *sigh* I really wanted to use that fan cos it fitted so perfectly! Ah well, cheers mate.

 

[cashmunny]

Dude, that's looks cool as hell. You're a mad scientist !!! I love the spiral placement of the cold cathode tubes. They have some art that kind of looks like that in Chicago's Ohare airport.

You could try attaching some cooling fins to the outside to help conduct heat to the outside. It would make it look even more like a warp drive time machine.

Actually I think they make liquid cooling systems for PCs if you want to stay with the computer themed grow. They are called heat pipes. Or peltier coolers.

You could make your own cooling system by wrapping a spiral coil of copper tubing around the inside and then run the ends through the wall of the cabinet and attach to a small water pump and a heat exchanger such as the heater core of an automobile. That's getting a little involved though.

The reflective material you added acts as a thermal barrier on the same principle of a heat shield. The technical term is multilayer insulation. So it's actually reflecting heat (infrared) back into the interior. That looks like reflective mylar. If you could switch to aluminum foil and thermally connect that foil to the exterior somehow that would help. Even white paint would probably work better since it would have a direct conduction path for heat through the cabinet wall.

9F over ambient isn't bad though. As long as ambient is about 80F or below you ought to be fine.

Good job! I hope you grow some multicolored weed with all those multicolored lights.

 

[touchofgrey]

Dammit, yeah I think you're right bro. I have noticed some irregularities trying to convert large scale things down to micro. *sigh* I really wanted to use that fan cos it fitted so perfectly! Ah well, cheers mate.

Hey Scrub, that little box looks cool! Could it be the air velocity is too high to do the cooling, did you say 100 cfm through there? I'm thinking it could be the air passes over the lights too fast to transfer the heat. Might try to experiment with lowering the cfm? Or look at how the airflow is directed? Are the inlets and exhaust on the lid?

 

[ScrubNinja]

Hey thanks a lot cashmunny! Great ideas. I think if I was to do it again, I would use a shiny metal garbage can, or at least use that as the base. Your ideas are friggin' awesome but I think the plastic walls are the big barrier to any heat conductivity. I mean, I can remove the tape, but the wall itself is insulating it.

Awesome, you have given me food for thought.

Hey touchofgrey! No it makes some sense to me bro, I hear what you're saying. But I did actually try that with a more typical not-so-strong 120mm fan and there was zero difference in temp diff. So I think cork was right really, just needs more cfm through the exhaust, well I hope so anyway. I think that's my basic error here.

So I have a more decent fan kind of like an S&P, that might be the next fan to try as I still have to introduce a carbon filter into the mix. Or some better pc fans. It's all good. Cheers all.

 

[Mycro]

That is sweet! I'll be watching this one!

 

[ScrubNinja]

Cheers Mycro! I really only started this to find out about the mylar/paint thing so I won't be updating this, but if you check the link in my sig, it's all going down there. A few others are building cabs as well, it's fun

Cashmunny, I forgot to say: I'm in the tropics, in the southern hemisphere so probably in the opposite season to you, and it's just hot all the time here pretty much. Can't run AC although I'm working on it.

Peace out.