Heat Exchanger design problem 1

[MecEngSelli]

Good morning Everyone.

I'm developing and evaporator with Ø2580mm and 1760 tubes of 15.000mm, it is vertical and the materials of the head and tubes are AISI 316 and the shell is ASTM A 285 Gr C

So when i run the calculation it appears the following message.

ASME: Shell side MAWP 0,14 kPa < Shell side design pressure 150 kPa. (Operating)
ASME: Tube side MAWP 0,14 kPa < Tube side design pressure 100 kPa. (Operating)
Front Tubesheet: UHX-13.5.9 Step 9: Tube buckling stress (50,022 MPa greater than 34,658 MPa) is excessive. Operating, load case 6, New condition.

But, when i make all the components with the SAME material, or if i take the corrosion thickness of the carbon shell the message disappears.

Can anyone shed a light about this little problem?

thanks a lot!

 

[Afox88]

It is a differential thermal growth issue. That is, the tubes or shell is expanding due to temperature more than the other. Try more baffles, thicker or thinner shell/tubesheet, or just settle with an expansion joint.

 

[MecEngSelli]

I will try that thanks Afox88