3 replies to this topic

[lolli]

Hi all,

I need help with heat transfer area in a reboiler!

How do I find out the heat transfer area if I don't know the overall heat transfer coefficient (U)? Is there any ways for estimating overall heat transfer coefficient (U)?

The problem is:-
Benzene is boiling in a reboiler at atmosphere pressure with horizontal tubes.
Boiling point of Benzene is 80.1 C, vapour density is 2.70 kg/m3 and liquid density is 816 kg/m3
Reboiler duty is 114000000 kJ/hr
Temperature difference is 60C.

Please help me!
Many thanks!

[Zauberberg]

You are missing some basic data - like heating fluid temperature and flow. Also, it could be sensible heat transfer (e.g. hot oil) or latent heat transfer (e.g. steam condensation) service. So it is not possible to come up with a calculated U-value in your case.

There are nice examples for sizing various types of reboilers in Coulson & Richardson (Vol.6 if I remember well). Get the missing data and go through the textbook examples.

[lolli]

You are missing some basic data - like heating fluid temperature and flow. Also, it could be sensible heat transfer (e.g. hot oil) or latent heat transfer (e.g. steam condensation) service. So it is not possible to come up with a calculated U-value in your case.

There are nice examples for sizing various types of reboilers in Coulson & Richardson (Vol.6 if I remember well). Get the missing data and go through the textbook examples.

Thank you for your reply!

The fluid is going in at 170C and flow rate is 300 kmol/h.
I have decided to stick with the simplest desing; using hot stream for the reboiler.

Also is it true that I cannot have a reboiler with heat transfer area more than 100m2?

Thank you very much!

[Zauberberg]

See attached pages for kettle reboiler design guidelines. I have to assume that you are referring to pool boiling application although this was not stated in your post.

The answer on your second question: No, surface area can be in excess of 1,000 m2 and more likely somewhere up to 750 m2 for a single piece of equipment.

Attached Files

•  Kettle Reboilers.pdf   123.36KB   81 downloads