[cfdsolve]

I am solving a case of conjugate heat transfer with phase change. The geometry is helical coil containing tube side fluid (which changes phase) and an annulus surrounding this coil containing shell side fluid. For boiling, I've used:
Eulerian (Boiling,CHF) model
Material properties are constant
OPerating pressure is atm (while both fluids are at different pressures)
BCs are two velocity inlets and two pressure outlets (no vapor at inlet, no liquid at outlet)
PV Coupling is SIMPLE with all discretization schemes of 1st order
Standard initialzation with default settings
URF's are all default, only vapor fraction URF is 0.01

Problem faced is that case diverges after performing about 600 iterations. Is there any way to stop the case divergence?
Mesh elements are about 4.5 million.

Any help in this regard by forum members will be greatly appreciated.