Heat Transfer Questions & Answers | |
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For convective heat transfer, the surface area when using the equation $q=A_s h \Delta T$ should always be measured at the fluid-solid interface (where the solid touches the fluid). Because the solid here has negligible thickness, the surface area is the same for the convective heat transfer taking place within or outside the pipe. 1.5 points bonus.
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As we saw in the first weeks of this course, $k$ is derived for a gas and extended by analogy to solids and liquids. This was explained already. 0.5 point bonus.
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Pe should be written as Pe$_d$: that's the Peclet number as defined on the second page of the tables. 2 points bonus.
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Sure, you should proceed iteratively as shown in class.
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Yes, $q_{\rm w}=q_{\rm in}$. The following is wrong: $$ \dot{m}c_{p}(T_{b2}-T_{b1}) = - \frac{h A_{s}(T_{b1}-T_{b2})}{\rm{ln}(\frac{T_{w}-T_{b2}}{T_{w}-T_{b1}})} $$ I guess I meant: $$ \dot{m}c_{p}(T_{b2}-T_{b1}) = - \frac{h A_{s}(T_{b2}-T_{b1})}{\rm{ln}(\frac{T_{w}-T_{b2}}{T_{w}-T_{b1}})} $$ Change the sign if necessary. 2 points bonus.
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$\pi$ |