[Zoli]

Hello people

I am a PhD. student at the department of hydraulic machines in Slovakia. Till now a made all of my simulations in ANSYS Fluent, but want to know the basics of OpenFOAM simulations. As my first case i choosed a pipe in pipe heat exchanger, following the tutorials on site:

https://openfoamwiki.net/index.php/G..._-_planeWall2D

Everything looks fine, but this case deals with a co-current heat exchanger, so the both mediums are flowing in the same direction (1,0,0).

I want to change the direction of the bottom fluid to (-1,0,0) however when i change the vector in the \system\bottomAir\changeDictionaryDict file to

U
{
internalField uniform (0 0 0);

boundaryField
{
leftLet
{
type fixedValue;
value uniform ( -0.1 0 0 );
}

rightLet
{
type inletOutlet;
inletValue uniform ( 0 0 0 );
value uniform ( -0.1 0 0 );
}

bottomAir_bottom
{
type symmetryPlane;
}

"bottomAir_to_.*"
{
type fixedValue;
value uniform (0 0 0);
}
}
}

the direction does not change. I would appriciate You help.

Thank You.

Zoli

[Bloerb]

I have not opened the original files, but if you only changed the values this will not work. You want to change inlet and outlet. You therefore need to switch the boundary conditions for those and in addition the velocity at the inlet since it will enter the domain from the opposite direction. Maybe something like this:

U
    {
        internalField   uniform (0 0 0);

        boundaryField
        {
            leftLet
            {
                
                type            inletOutlet;
                inletValue      uniform ( 0 0 0 );
                value           uniform ( 0 0 0 );
            }

            rightLet
            {
                type            fixedValue;
                value           uniform ( -0.1 0 0 );
            }
    }

What i suppose you have done however is fix the velocity on the outlet side and put a inletOutlet on the inlet. But since inletOutlet switches to fixedValue if the flow is into the domain you have one side with fixed Velocity of zero and one with -0.1

[Zoli]

Hello Dear Bloerb!

I changed the BC as YOu written, and the simulation worked like a charm

Thank You very much for the help.
I think we can close this thread

Best regards:

Zoli