2019 NCEES T&F Problem #10

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BuffaloWings

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Could someone please explain why the solution just added the radiation and convection heat transfer coefficients instead of treating them like resistors in parallel?

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BuffaloWings said:
Could someone please explain why the solution just added the radiation and convection heat transfer coefficients instead of treating them like resistors in parallel?
Click to expand...
I have the 2011 NCEES Practice Exam, Thermal and Fluid Systems. ISBN 978-1-932613-61-2

There does not seem to be a problem #10. There's a #110 in the AM section and a #510 in the PM section, but none of those seem to match what you're describing.

Can you provide a screenshot of the question and answer?

 
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They did treat it as resistances in parallel.

The convection resistance is 1/(h_conv*A) and the radiation resistance is 1/(h_rad*A).

For parallel you find the total resistance as 1/R_total = 1/R_conv + 1/R_rad hence 1/R_total = (h_conv + h_rad)*A

 

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