Sealed Enclosure Temperature Rise

[wintland]

Hey Guys,

I have an outdoor equipment enclosure with varios switches and computers that is sealed and normally has AC cooling. I am looking for a way to calculate the rise in temperature per min if the AC were to shut off so that I can establish the time to service for our operations crew.

Can anybody help me with a calculation? Or better yet, a calculator where I can plug in parameters to get the answer?

Thanks in advance for any help.

-Brian

 

[VEBill]

Quite a few variables - solar flux, orientation, surface characteristics, thermal mass, emissivity, spectral effects, etc., etc., ad infinitum...

Probably easier to add a small fan powered by the same back-up power supply as powers the gear. Add a sensor and comm system to call for help.

 

[itsmoked]

wintland; You need to read this entire post.

thread248-133761

 

[jraef]

I agee, there are a lot of variables there. Although you may be able to calculate your rise, or delta-T, the problem is in determining your rate of rise, delta-T/delta-t (change in time) in order to calculate safe time. That is the task that cannot be boiled down to a simplistic firmula IMHO. You may want to post this to the mechanical / HVAC engineers however, they are typically better at thermal dynamics that EEs are.

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more." Nikola Tesla
Read the Eng-Tips Site Policies at faq731-376
Member, [blue]P³[/blue]

 

[wintland]

I anticipated such a response. Nothing is ever easy is it

itsmoked I did read that entire thread, its actually how I stumbled upon this forum but I wasnt sure it applied to my situation as it was attempting to measure surface temperatures of an enclosure (transformer) inside another enclosure. I was hoping my problem would be much more simplistic.

Oh well, I guess we will just have to do some experimentation to figure it out.

Thanks very much for the help, at least now I can stop searching the net for a nifty little calculator.

-Brian

 

[ko99]

Wintland, your problem is much more complicated than the ohter thread.

For your test: Keep in mind the temperature that matters is the die temperature. The case temperature will rise at a slower rate than the die, perhaps much slower, depending on the mass of the case and the thermal resistance from die to case.

ko (

http://www.ecooling.biz)

 

[jraef]

Actually I think using emperical data is going to be the only really valid method anyway.

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more." Nikola Tesla
Read the Eng-Tips Site Policies at faq731-376
Member, [blue]P³[/blue]

 

[itsmoked]

wintland; It would be a relatively straight forward study for you, especially if this stuff is installed and in existence. Just put a couple of sensors in the cabinet next to points of interest and kill the cooling. You should then have a very accurate time/temp curve.