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CFM Exhaust requirements

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CFM Exhaust requirements

(OP)
Have an enclosed space with 1700 c.f.  Has 1 intake opening of 6 s.f.at floor level. Has 2 ac compressors mounted on floor putting out combined cfm exhaust of 3400. In addition,there is radiant heat gain from sun through 378 s.f. of roof. Two part question: Based on existing intake size, how many cfm roof mounted exhaust fan would it take to remove heat? Would it be necessary to adjust intake opening size? Good luck with this one.

RE: CFM Exhaust requirements

You will need a laod calc on the building (building U value, OA temps etc), then see what heat the compressors are giving off to the space.  Find the difference between OA and indoor space, and that will calculate the airflow for the fan.

A calculation would be required to find the static pressure need to overcome the amount of air through the hole.

Not a difficult procedure, but can be tediuos/frustrating if it is not your profession.

knowledge is power

RE: CFM Exhaust requirements

(OP)
I want to thank cdxx139 for the info. Let me change the question just a bit.
If heat gain through the roof was a zero factor, could you answer
both parts of the intake air and exhaust requirements then?

RE: CFM Exhaust requirements

Assuming that you are a graduate ME, you should crack open two of your textbooks, thermo and heat transfer, since the questions you asked can be solved with an understanding of the basic equation: energy in - enrgy out=accumulation.

RE: CFM Exhaust requirements

sandbar, you can ignore any information you want, it just depends how accurate you want the answer to be.

You still need to figure the cfm before we can worry about the intake size.  So as chicopee stated what's the Energy in?  How much heat is the compressors putting into the space?

knowledge is power

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