TEMA discusses maximum diametric clearance between baffle/support OD and shell design ID in Section V, RCB-4.3. Approximate outer tube limit can be extrapolated from there. Effects on shell-side local velocities, vibration, and resonance, as well as aggregate pressure drop should be considered when making changes.
As for minimums: remember, once you design it, someone is going to actually have to build it. Keep that in mind when getting aggressive with your OTL vs shell ID.
What type of exchanger are you dealing with , fixed tubesheet or floating head ?
In case of floating head exchangers floating head flange require large bundle to shell clearance as compared to fixed tubesheet exchangers. This clearance is function of design pressure , greater the design pressure larger is clearance.
If you have access to HTRI design manuals you can look into graph provided therein.
Following are some clearances between the tube OD and shell ID. The clearances were copied from a tube count manual. The clearances are for a heat exchanger where the tubesheets are welded to the shell. For example: a BEM type.
Shell ID clearance
6 -12 1/4"
13-24 5/16"
25-33 3/8"
34-47 1/2"
Following are some clearances between the tube OD and shell ID. The clearances were copied from a tube count manual. The clearances are for a heat exchanger where the tubesheets are welded to the shell. For example: a BEM type.Shell ID clearance
6 -12 1/4"
13-24 5/16"
25-33 3/8"
34-47 1/2"
