i need to stress a metal line (B31.3) connected to an exchanger noozle.
the problem is the exchanger material: ceramic.
(no comment about client choice.... )

any idea how to model the exchanger body and nozzle? what code and material can i use to simulate the "ceramic" material?

I think you do not need to model the exchanger. Estimate some displacements ( saw on internet some values for expansion coefficient) and stop at the flange. I guess that you will have very small allowable.

In case the ceramic exchanger (which may have the flange rating only) is in line or the line finishes on the exchanger flange, you need to know the coefficient of thermal expansion of the ceramic material, allowable nozzle/flange loads and allowable support load (if a support exist on the exchanger).

If you are given the flange rating only (for the in-line exchanger) you need to model the exchanger as rigid (depending on the size and type) with thermal load. You still need to get the coefficient of thermal expansion of the ceramic exchanger, and keep the flange loads under allowable by pipe flexibility.

You need to ask the values your client to obtain or you may obtain the values from the supplier on behalf of your client by informing your client first. The supplier or manufacturer has the obligation to provide them.

You need to inform your client that you need to get these information to be able to progress, and check the suitability of either your piping route or the exchanger (if you cannot provide more flexible piping to protect the exchanger under the allowable). Sometimes the exchangers require very low allowable loads on the flanges, sometime you order with higher allowables depending on the required design code on the exchanger.

Hope it helps.

thank you for the suggestions