Thermal calculations - heat load vs. panel size

Hi all,

I have a project with 9 PowerFlex 525 drives inside an enclosure. I've done some calculations off the drive technical data, and worked out that I'll have around 2.7kW of heat loss from the drives. We're still arguing about whether the panel is going inside or outside - the installers say it will be much easier for them if it's outside, and I'm telling them that the difference between putting a panel in a hygienic, air conditioned area at 20°C (68°F) and putting it outside in a tropical climate where it routinely gets to 45°C (113°F) in the summer and would cop 4-5 hours of direct sunlight, is significant enough that they don't really have a leg to stand on. Let's assume that I'm going to win that argument, so the ambient temperature will be 20°C (68°F).

So now I need to work out how large a panel I need to ensure adequate heat dissipation, or how many fan/filter combinations I'll need to keep the internal temperature below 40°C (104°F for those of you still insisting that the metric system is the devil).

Does anyone know of any formulas/rules of thumb/lookup tables/calculation software that I can use to crunch some numbers?

Go here;
http://www.pentairprotect.com/en/na/thermal-management
scroll down to downloads for a 300 page Cooling Specifier's Guide.

You can download Rittal Therm App from the Android store, for a rough calculation, although this is not ideal as it doesn't take into account component position and some other factors.
http://www.rittal.com/com-en/content/en/support/software/projektieren/therm/Therm.jsp#rt-tab-3

You can also use solidworks to design your cabinet and airflows in three dimensions.

Also, stop spreading the myth that farenheit is still even a thing. Our colleagues in the US only use it ironically these days.

ASF said:

(104°F for those of you still insisting that the metric system is the devil).

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I assumed the metric fad died out much like disco and the pet rock.
I heard about the metric system back in the 80's when they were teaching us in school that it was going to be the next big thing. Are you telling me there are places in the world that still actually use it??



Will.

Thanks guys, some useful information here. Can't say I made it all the way through the 300-page document, but still!

Rockwell Tech Support came back with Technote 22022 (Access: Everyone) which goes right through the calculation process including panel dimensions and forced air cooling. It makes some assumptions about panel material and altitude, but they don't affect the outcome all that significantly, and I found that information elsewhere anyhow.

There's also this nifty little tool that doesn't take into account panel size, and so gave me a slightly different answer to the KB calculations, but it was in the same ballpark. I quite like it's description of "heat load" as "stray power", gave me quite an amusing mental picture of panel full of stray cats...that would certainly generate some heat!

willxfmr said:

I assumed the metric fad died out much like disco and the pet rock.
I heard about the metric system back in the 80's when they were teaching us in school that it was going to be the next big thing. Are you telling me there are places in the world that still actually use it??

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I have nothing to say to you except:

ASF said:

I have nothing to say to you except:

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I dang near shot coffee out my nose when I saw that! From the look of it, the good ol' USA might be just a little out of step with the rest of the world....

And thanks for the tech note link. Heat load in cabinets isn't something I deal with everyday, but it comes up often enough that I bookmarked it.


Will.

I don't know if it helps, but the company I work for has also made an enclosure that contains 9 powerflex drives, and an ethernet switch.

This enclosure will be mounted in the roof of the plant where it can get quite hot, even above 50 degrees C as an ambient temperature

This hasn't been commissioned yet, so we don't if our cooling system (a vortex cooler) will be up to the task, but one of the advantages of the powerflex 525 drive is that with a message instruction, you can obtain the drive temperature & monitor it if need be.

Ian

ianingram said:

This hasn't been commissioned yet, so we don't if our cooling system (a vortex cooler) will be up to the task, but one of the advantages of the powerflex 525 drive is that with a message instruction, you can obtain the drive temperature & monitor it if need be.

Ian

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I didn't know that...filing that one away for future reference!

Not that it's of any use to me in this application, because there's not actually a PLC in this panel