Shell in Tube Heat Exchangers with multiple tube passes: Heat Transfer for Mechanical Engineers

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In this problem, we design a shell and tube heat exchanger with multiple tubes that make multiple passes through the shell. Specifically, we find how long each tube pass must be for a given required heat load.
Heat exchanger problems typically have one of two potential main goals: (a) find the heat transferred between two fluids, OR (b) find the area needed to achieve a required target heat transfer between two fluids. In this example, we go through a systematic process to find the area required for shell and tube heat exchangers with multiple tube basses using the effectiveness-NTU method. We then use this required area to find the length of each tube pass. I believe that understanding this process will allow you to solve any heat exchanger problem.

Опубликовано:

22 мар 2020

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Комментарии : 14

@eduardosuarez7403 2 года назад

I really like the lectures content, the clarity and the graphics. Thank you very much. I think you are helping a lot of aspiring professional Engineers. [Q=731,850 W, Re=232,401, NU=750, A=27sq.m, L=4.30m]

@mikeschertzer941 2 года назад

That is very kind of you Eduardo. I'm glad that you find the videos useful!

@pinghsiuhsieh Год назад

05:46 At T=323K, the dynamic viscosity (mu) should be 548*10^-6 Ns/m^2 (typo with the units on the slide). The density (1/specific volume) should be 987 kg/m^3 (not 0.987 kg/^3). 12:13 With these, I computed the Reynolds Number to be 2.32*10^5. Similar to Eduardo Suarez's result in the other comment. Thanks again for putting these videos up on RU-vid.

@mikeschertzer941 Год назад

Good catch. Looks like I was doing these too quickly. I appreciate you pointing out these errors.

@diyaazaghloul756 3 года назад

Amazing video thank you

@elv6mil10gwata3 2 года назад

Very helpful

@harrypascoe1281 4 месяца назад

At 8:31 you say Cmin is W/K but at 13:12 Cmin is W/kgK, I am a little confused by this?

@truongphamnhat7062 Год назад

can i have a document on thermophysics properties of saturated please? thank!

@AhmedTaha-ij8xj 3 года назад

hi .. thanks for the video can i ask you where are the ten tubes ? I know the 8 passes but can't figure out where are the 10 tubes?

@mikeschertzer941 3 года назад

The tubes aren't shown in the picture. The sketch shows a single cross section. There would be ten tubes lined up in parallel (into the page).

@a.alfaify5352 2 года назад

Was it better to use: Q= {mCp(T2-T1)}c = {hA(T1-T2)}h , and calculate HT area directly?

@mikeschertzer941 2 года назад

At first glance this looks like it would work. But we need to remember that the Delta(T) for convection is the temperature difference between the fluid and the tube surface. And the temperature of the tube surface varies along the length of the tube.

@wolesunday8087 Год назад

Can anyone how explain he got the Reynolds number please

@mikeschertzer941 Год назад

In problems like these, we need to (1) define fluid properties and (2) pick a good equation to find the Re. You can see where we get properties at around 5:00. We get properties for water at around 6:05. We put that information into the Re equation at ~ 11:55. This equation might look a bit different than you are used to, but you could also use (/rho)(U)(D)/(\mu) = (U)(D)/( u). Note that in the heat exchanger videos, I seem to have often made the mistake of taking the specific volume (v_f) instead of the kinematic viscosity (/nu). But in this problem, the equation with mass flow rate works better because (m\dot) is given in the problem, as is the tube diameter (remember to convert to m). So the only property we needed to look up for Re is the dynamic viscosity (\mu). Others have pointed out that there may be a clerical error in the math here...I didn't go back to check if they are correct. The general method is correct, but you might want to double check the algebra.