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Dear All,

I have to cauculate area of shell and tube heat exchanger but I have some points need to reconfirm again:

1. This heat exchanger use to exchange between hot oil and cool oil (The same type of oil but different temperature). The hot oil that we get after exchange will use for heating the vessel (Half coil)

--> My questions is Can I use heat duty for heating the chemical in vessel for calculate this heat exchange?
(Note : Hot in = 180 C, H out = 160 C, Cold in = 40 C , Cold out = 170 C)

2. From no.1 If yes, I've calculate the tube side velocity is only 0.2768 m/2 (As reference from typical design the tube velocity 1-2 m/sec, Max 4m/s) I'm not sure that there are anything wrong in my calculation.

(Calculation step :
1. Heat duty calculation : Q = m x Cp x deltaT (Cal from heating chemical in vessel)
2. Flow rate culculation : m = Q / (Cp x delta T)
3. Cal. Delta T log Mean
4. Cal. Ft --> Delta Tm
5. Assume U0 (Overall heat transfer coefficient)
6. Calculate area : A = Q/(U x Delata Tm)
7. Select type, size.
8. Cal no. of tube : In this case I get only 30 tubes (with OD 20 mm, ID 16 mm, Tube length 4.88 m.) This calculation can be possible or not?
9. Cal shell diameter : I get 8.5"

3. From no.1 If no, How can I calculate heat duty for design this heat exchanger?

4. How can I get the velocity of fluid in shell side? Can I use Q = m x Cp x Delta T (Q is the same as above) Find M for flow rate in shell : Also tube is the same method ???

Thank you very much for all of your comments

Nikki

[Art Montemayor]

Nikki:

Your explanation is more confusing than it is in giving basic data and information. For example, you say, “The hot oil that we get after exchange will use for heating the vessel (Half coil)”. WHAT vessel? WHAT half coil? Please simply take the time and draw a detailed, schematic drawing of your process, showing all the flows and their conditions. This will be much easier to understand.

You also ask, “My questions is Can I use heat duty for heating the chemical in vessel for calculate this heat exchange?” Again, WHAT chemical? Is it a liquid? Is it a solid? Is is a gas or vapor? We can’t be expected to know what is in your head.

You claim to have calculated the tube side velocity. Fine! But where is the calculation. Are we supposed to “trust” you to do the calculation correctly and without any errors? Even if my mother did the calculations, as an engineer I would still insist on checking her work. Don’t ask us questions regarding your calculations without you furnishing them – IN SPREADSHEET DETAIL, COMPLETE WITH ALL BASES, EQUATIONS, AND REFERENCES. That’s the only way that engineers work in the real world.

There are some workbooks that our Forum now makes available to members in the Hall of Fame section. One of these workboods deals with the calculation of heat exchangers. You should download this workbook and apply what is in in. In the meantime, I will await your Excel workbook with the process sketch and all the calculations.