[Waris6420]

I am doing a simulation for flow boiling in a vertical rectangular annular channel with a single heater rod in the center. R134a is the working media. RPI boiling model is being used. The geometry is a simple 2D rectangular with one side as wall and the opposite side as heat flux and adiabatic partitioned. I have to simulate both natural and forced convection cases. The issue is that the solution diverges as it is started. I have tried changing everything but cannot figure out where the problem is. Is there an issue with my material properties, boundary conditions or other parameters.
Boundary conditions I am using are
Inlet: Velocity inlet (o for natural convection)
Outlet: outflow
Wall
Operating pressure is 2.6 MPa and T_sat at this is 80 C.

Kindly help in this regard.