The evaporator is designed for vaporizing liquid N2 to gas N2. Tube is N2 and shell is warm water.
It is not a standard type shell & tube HX. There is a cap collecting all the tubes at the outlet, but cap is not connecting with the shell. So small piece of tube is exposured in atmosphere. This small piece is covered with ice on several tubes. The outlet gas temperature should be around 20 C.
Anybody has encountered this kind of problem before?
Any possible causes?
Thanks.