Heat Transfer Questions & Answers | |
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Before tackling internal flow in a pipe, I mentioned about external flow over a plate with and without VD as a reference point. But don't confuse the latter with flow in a pipe/duct. 1 point bonus.
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Hm, incompressible flow doesn't mean constant density flow. You can have an incompressible flow with a density change.. If the flow is a liquid, then yes you can assume the density to be constant, but not if the flow is a gas. I'm not sure if this answers your question..
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The air flows around all exposed surfaces of the cylinders as this is external flow on a tube bank. So, you can't cut a cylinder in half, this wouldn't make sense. I'll give you 1.5 point bonus boost. I would have given more if your typesetting would be better (you should have written $n_{\rm row}$ instead of $rows_{\rm deep}$ and $n_{\rm tubes}$ instead of $tubes_{\rm high}$ and define $n_{\rm row}$ and $n_{\rm tubes}$ after their first use.
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I don't understand.. Before the midterm, we didn't compute the Nusselt numbers (because $h$ was given) so there was no need to compute the film temperatures. Is this what you mean?
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Yes, exactly. I went quickly in class because of lack of time but when doing the assignments you need to follow the intructions in the tables carefully. Thus, when using the correlation for fully-developed flow in rough tubes, you have to evaluate the Stanton number at the mean bulk temperature and the Prandtl number and the friction factor at the film temperature. Because the mean bulk temperature and film temperature are not known apriori, you need to iterate. 2 points bonus.
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$\pi$ |