[MMoataz]

I finished the simulation of each side of a shell and coil heat exchanger on its own and they give correct results, however, when I combine both sides together to simulate the whole system, I strangely get wrong pressure distribution in the shell side after convergence!

My questions are:
- How could the presence of the 2 domains together affect results?
- What can be done to fix this?

Summary of used settings:
- All solid and fluid bodies share topology
- Solver: Pressure based - Coupled
- Working fluid in shell: air
- Working fluid in coils: thermal oil (density 850 kg/m^3)
- Turbulence model: SST
- Both fluids have mass-flow-inlet and pressure-outlet BC
- Each fluid is initialized separately
- Default methods and controls

Note that the same mesh and same settings are used when simulating each side separately or when simulating both of them together!