[CFXer]

Hi All,

I'm doing two-fluid, conjugated heat transfer simulation. The whole domain is shown in figure 1.

Hot fluid is CO2, cold is water.

Boundary conditions are below:

CO2
- Ref Pressure = 7.9MPa
- inlet mass flow
- inlet T = 70℃
- outlet relative P = 0

Water
- Ref Pressure = 210kPa
- inlet mass flow
- inlet T = 35℃
- outlet relative P = 0

Turbulence model is k-e, heat transfer model is Total Energy win Ind. Viscous Work Term, and disabled Constant Physics to use two-fluid.

Fig 2. shows heat transfer at plate core(porous domain and solid domain), heat transfer between hot and cold fluid through solid domain.

As I applied these boundary conditions, it shows backflow error.
+--------------------------------------------------------------------+
| ****** Notice ****** |
| A wall has been placed at portion(s) of an OUTLET |
| boundary condition (at 100.0% of the faces, 100.0% of the area) |
| to prevent fluid from flowing into the domain. |
| The boundary condition name is: outlet_outlet_pipe_cold. |
| The fluid name is: Water. |
| If this situation persists, consider switching |
| to an Opening type boundary condition instead. |
+--------------------------------------------------------------------+

and shows backflow at water domain, Fig.3.

As I follow the error message and use opening boundary condition, it shows good flow but temperature reverse at outlet pipe, Fig.4.

I cannot understand why this happens. When I applied domain interface, I have checked non-overlap condition as adiabatic, as you can see in Fig.5 of postprocessing, It shows zero heat flux at pipe.

Anybody could help me please? I really want to solve this problem.

Thank you in advance.

[ghorrocks]

I would model the water domain by itself until you find a reliable way to fix this problem. So remove the CO2 domain for now.

With a water only model I would try different boundary conditions and initial conditions - at least to get it started, and then changing over to the final boundary conditions once convergence is progressing nicely.