[ashishmagar600]

Hello everyone,

I am trying to simulate a heat exchanger problem. I have split regions (3 regions, hot fluid cold fluid and solid) and defined corresponding properties in them.

However while solving, the rho values in the output shows that it is not taking the values I am providing:

Solving for fluid region shellSide
DILUPBiCGStab:  Solving for Ux, Initial residual = 1, Final residual = 0.0136616, No Iterations 1
DILUPBiCGStab:  Solving for Uy, Initial residual = 1, Final residual = 0.0130695, No Iterations 1
DILUPBiCGStab:  Solving for Uz, Initial residual = 1, Final residual = 0.0095, No Iterations 1
DILUPBiCGStab:  Solving for h, Initial residual = 1, Final residual = 0.0350493, No Iterations 1
Min/max T:300 300.011
GAMG:  Solving for p_rgh, Initial residual = 0.988378, Final residual = 0.00910654, No Iterations 4
time step continuity errors : sum local = 1856.54, global = -13.9992, cumulative = -13.9992
Min/max rho:2 2

Solving for fluid region tubeSide
DILUPBiCGStab:  Solving for Ux, Initial residual = 1, Final residual = 0.00932655, No Iterations 1
DILUPBiCGStab:  Solving for Uy, Initial residual = 1, Final residual = 0.0102043, No Iterations 1
DILUPBiCGStab:  Solving for Uz, Initial residual = 1, Final residual = 0.00692628, No Iterations 1
DILUPBiCGStab:  Solving for h, Initial residual = 1, Final residual = 0.000374168, No Iterations 1
Min/max T:300 350
GAMG:  Solving for p_rgh, Initial residual = 0.985978, Final residual = 0.00349933, No Iterations 5
time step continuity errors : sum local = 991.807, global = -31.1576, cumulative = -45.1567
Min/max rho:2 2

The values for rho are always [2,2] here. I don't know what is the issue.

This is just the first iteration and then I stopped.

This is the thermophysicalProperties file:

thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectFluid;
    specie          specie;
    energy          sensibleEnthalpy;
}

mixture
{
    specie
    {
        nMoles      1;
        molWeight   18.0;       // [g/mol]
    }
    equationOfState
    {
        R           3000;      // [J/(kg K)]
        rho0        996;      // [kg/m^3]
    }
    thermodynamics
    {
        Cp          4179;      // [J/(kg K)] at T = 293 K
        Hf          0;
    }
    transport
    {
        mu          0.000852;    // [kg/(m s)]
        Pr          0.7;
    }
}

Thanks for any suggestions.

[ashishmagar600]

Alright. I solved it by myself.

In the system/regions/fvSolution was:

...
    momentumPredictor yes;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       100000;
    rhoMin          0.2;
    rhoMax          2;
...

I changed to :

...
    momentumPredictor yes;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       100000;
    rhoMin          900;
    rhoMax          1000;
...

Could be helpful if anyone has to cross out one problem.


Thanks.