Heat Transfer Questions & Answers  
Question by Student #201227127
professor, I wonder about question 1 of assignment 6. to solve it, I checked Reynolds number to know flow is laminar or turbulent. so I found Re>$5X10^5$, it is turbulent flow. in class, you talked laminar flow means same as steady-state. but in problem, find wall temperature in steady-state. but this flow is turbulent. so I wonder in steady-state, can turbulent flow appear?
05.16.17
Strictly speaking, no, a turbulent flow is always unsteady. But, if you take a time average of the flow properties within the turbulent boundary layer over a small amount of time (like 1-10 ms or so), then the turbulent flow can appear steady. In this course we're not concerned with the dynamics of turbulence, we simply consider the averaged properties of turbulence, so we call such turbulent flows “steady”. Good question. 2 points bonus.
Question by Student #201227153
Dear professor, I haver question about laminar and turbulent flow. The criteria Reynold's number is $Re_{x cret}=5*10^5$. If $Re_{x}<5*10^5$, the flow is laminar. Also, if $5*10^5<Re_{x}$, the flow is laminar-turbulent mixed. My question is $Re_{x}$ is only laminar or mixed flow along x. Turbulent flow depends on the point like Q2 of assignment#6. In summary, along x, the flow is laminar or mixed. However, along with the point, the flow is laminar or turbulent. Is it right?
05.17.17
In this course, the flow is considered fully turbulent at a location where the Reynolds number is larger than $5\times 10^5$. The flow is considered “mixed” if integrating both the laminar and the turbulent regions. 1.5 point bonus.
Question by Student #201227127
professor, in A6 Q1, I found $Re_L=1.45x10^7$. To find $T_w$, we need to find h. flow is mixed with laminar & turbulent, so in table, I choose "laminar-Turbulent average" but the restrictions are $T_w = const, Re_L <10^7$ in both 2 options. so I don't know what I choose ?
Well then you can not use these correlations. So you need to find another way..
Question by Student #201427132
I have some questions about previous the lecture at 5/11.
While you give an example, you missed the assumptions and let assumptions as blank. So, i try to fill it out and here's my idea. :
1. Steady-state flow 2. Plate should be flat and thin plate
3.$\rho$, c, k are constant 4. $E_c$<<$\frac{1}{Pr}$
I wonder whether my guess is right or wrong.
05.18.17
Hm, that lecture was more than one week ago.. I forget what that problem was. You should explain this in your question.
05.19.17
Question by Student #201427132
I rewrite my question with picture.
.jpg  ./download/file.php?id=3492&sid=2d995ee0b854d9af0d46c82c67ab8b29  ./download/file.php?id=3492&t=1&sid=2d995ee0b854d9af0d46c82c67ab8b29
The example wanted whether flow is turbulence or laminar at x = 1m. While you give this example, you missed the assumptions and let assumptions as blank. So, i try to fill it out and here's my idea. : 1. Steady-state flow 2. Plate should be flat and thin plate 3.ρρ, c, k are constant 4. EcEc<<1Pr I wonder whether my guess is right or wrong.
This time, the typesetting is hard to read. Please rewrite the question with proper typesetting and I'll answer it.
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