Heat Exchange Question

[ControlConcepts]

I'm electrical not to good in thermo, so heres my question. I am needing to calculate the size of an enclosure for a VSD, I know how many BTU's are being put of by the drive, but I need to how many BTU's are being put off by the change in temperature between the desired inside temp and actual outside temp. I then need to know how surface area of steel is required to dissipate this heat. Any help would be appreciated.

 

[vpl]

Control Concepts:

This actually should be easy for you: think of it as a big resistance. The formula is q(in BTU/hr)= hA(To-Ti). h is the average unit thermal conductance and is defined as the thermal conductivity, K, divided by the area, A, so that hA=K. K for steel depends on type and temperature (for stainless it runs between 8 an 13 for a temperature range from 32F to 1000F), so you will need to look in a handbook for your application. You have your q and your outside temperature, that will tell you what your inside temperature will be. If it's higher than your "desired" temperature, then no matter what your area, you're not going to get the cooling you probably want. Hope this helps! Patricia Lougheed

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[ControlConcepts]

Thanks VPL, thats what I been using. I was just having a hard time explaining to my boss that the enclosure itself absorbs heat which also needs to be dissipated.

Thanks
Micky