Heat Dissipation - Cut Heat Sinks into Enclosure

[DesignDad]

Hello all,

First time post, long time reader.

I am designing IP65 Electrical Enclosure with 80w internal Heat load. It is small and dont have a lot of room for vents, the only IP65 vents I see are made for large off the shelf enclosures.

I have 2 questions:

1. What is the external solar load I need to consider?

Based on charts below, aluminum enclosure, clear anodized, with 20deg delta T between ambient and internal, should not have a solar heat gain. Correct?​

2. Calculate Internal Air temp with fan, inside of sealed enclosure?

What is the best way to calculate cooling effects in a sealed, small enclosure(12in x 8in x 6in )​

Most of the cooling effect comes from the temperature differential but I want to quantify the air movement effects and if increasing the fan flow rate would improve cooling 20-30%​

See my Calculation Page as an attached file,

http://files.engineering.com/getfil...7-4c95-9538-5482180f367e&file=Heat_Calcs.xlsx

it is based on surface area of the enclosure, plus the additional area of the fins that are cut into the side.

See also, the box geometry here,

http://files.engineering.com/getfil...3a709bc99ff9&file=Enclosure_Heat_Sink,_X3.pdf

Current Calc Sheet that I have going

Chart for Solar Heat Gain

Thanks for all of the help!

 

[IRstuff]

Solar load is best dealt with if you can reflect as much as possible to start with. White paint or mirror finish are good choices. An alternative is a sunshade, so you could mount some sort of shade above the box to keep it in the shadow. That would cut a huge amount of sunload. Then paint the box with white.

As mentioned before, thermal straps could help; they would basically be big copper braids that would provide a high conductance path for your hottest parts. Ideally, you should heatsink the hot parts directly to the chassis.

TECs could help, but they are extremely inefficient, and get progressively worse with larger temperature deltas. Likewise, internal fans do dissipate power internally to the box.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[DesignDad]

An alternative is a sunshade, so you could mount some sort of shade above the box to keep it in the shadow. That would cut a huge amount of sunload. Then paint the box with white.

As mentioned before, thermal straps could help; they would basically be big copper braids that would provide a high conductance path for your hottest parts. Ideally, you should heatsink the hot parts directly to the chassis.

TECs could help, but they are extremely inefficient, and get progressively worse with larger temperature deltas. Likewise, internal fans do dissipate power internally to the box

Thanks IRStuff

I agree that white will be a direction I push. The shade is ideal but the problem with this application is that it needs to be somewhat portable on a jobsite. They will move it and connect to a computer.

I think the solar strap is a good idea, I will have one full side of aluminum sink on board in contact with inner wall. I think on that wall I will have the outer ip68 fan and heatsink directly opposite. Something like this,

http://www.phanteks.com/PH-TC90LS.html

. and then put a cage around it.

 

[IRstuff]

Don't forget that surface temperatures as low as 40C are potential burn hazards

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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