Question by Student #201127151 Professor, I am curious about the solution at question #3-(c) of assignment #6. Solving the problem, I obtained the following equation: at steady state with no heat generation and no radiation, $$\overline{q' '}=\overline{h}(T_{PLATE} - T_{\infty})$$ and isolate $T_{\infty}$ $$T_{\infty}=T_{PLATE}-\frac{\overline{q' '}}{\overline{h}}.$$ Here $\overline{q' '}$ and $\overline{h}$ are bigger than zero. Therefore I think the solution is $$T_{\infty}=20^{\circ}C-6^{\circ}Cm^{0.5}U_{\infty}^{-0.5}$$ rather than $$T_{\infty}=20^{\circ}C+6^{\circ}Cm^{0.5}U_{\infty}^{-0.5}$$ Is there any problem about the equations?
Hm, here $T_\infty$ should be higher than $T_{\rm w}$, so your solution can't be correct. I'll give you 1 point bonus boost.
 Question by Student #201700043 Dear professor, You said this morning the Reynolds number on a tube bank is equal to : $$Red = \frac{ \rho Umax D}{\mu}$$ Can we consider the Reynolds number is the same in all the bank ? Because the Temperature or Umax won't be exactly the same if we are on the middle or on the top of the bank...
Yes, the Reynolds number is function of $U_{\rm max}$ everywhere within the bank. But you're right, $U_{\rm max}$ may vary within the bank but this is taken into consideration by the empirical correlations in the tables. 1.5 point bonus: I would have given 2 if you would have typeset $Umax$ as $U_{\rm max}$.
 Question by Student #201327104 Professor, I have a question for Question 2 from Assignment 6. After I figured out that the $Re_{x}$ at one side of the plate is $3.2 \times 10^{5}$, I tried to find appropriate equation for this situation (Laminar,local). But, there are two equations available, and properties also fulfill both condition for the equations. In this case, Can I get same result with two equations? which equation is better for the situation in Question 2 ?
 $\pi$