Hello @1318980, yes I do see your point. One of my BC’s is wrong. I usually have a pressure BC on one surface (usually the outlet), and a Pressure + Temp BC on another surface (usually this is the inlet). I took a look at your project and for your inlet-outlet type BC, is there any difference if you just put a Temp and Pressure BC on the same surface? (it seems thats what the Custom Inlet Outlet BC achieves, I may be wrong).
Yes, running it Steady State first is a great idea…