VOF simulation troubleshooting required
 

I am new to ANSYS and doing an Implicit VOF transient simulation on single tube parrallel heat exchanger.*

Viscous Model:

K-Epsilon with realizable and Enhanced wall function*

VOF Model:*

Primary phase = water liquid (as I don’t need it to put in boundry condition volume fraction)

Secondary phases = water vapor, ammonia liquid, ammonia vapor.

*Material:

Tube side = Hot fluid =water that converts from vapor to liquid with VOF Lee’s Model at frequency 180/s.

Shell side = Cold fluid = ammonia that converts from liquid to water with Lee’s model frequency 89/s.

Boundry conditions:*

Velocity inlet and pressure outlet.

Tube side = I put water vapor Volume fraction = 1

Shell side = I put ammonia liquid volume fraction = 1

Method:

Piso Scheme with all second order upwind

Control:*

Initially all are at 1 UR factor and then reduced the convergence UR till 0.7.

Initialization:*

Hybrid.

Patch:*

Water vapor VF = 1 in tube domain

Ammonia liquid VF = 1 in shell domain.

Problem:

I am facing two big issues.

1- Continity residual is showing a straight line. It is not converging to 1e-3 or 1e-4. it stays at 1e-1 as a straight line. All other residuals are below 1e-6.

2- As water liquid is primary phase so I can’t assign it to any domain. I did the patch to avoid any water liquid in shell domain. After the simulation. What I find out through volume fraction surface and volume intergrals is that “the water liquid is present in both the tube and shell domain”. In tube domain it is condensed from water vapor but from where it comes to shell domain.



Can you guide me on this?

hello, can anyone guide me on this issue