CFD Online Discussion Forums - wallHeatTransferCoeff + simpleFOAM ( OpenFoam7)

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wallHeatTransferCoeff + simpleFOAM ( OpenFoam7)

Hi All,
I think open a specific topic is more appropiate.
I want to calculate the heat transfer coefficient (called "virtual htc" as in star ccm +) after a steady state incompressible solver (simpleFoam). The simulation is about water in a cooling pipe.
I don't need energy equation so i decided to use simpleFoam. Infact the flow is steady and the cooling medium is water...
I have verified that wallHeatTransferCoeff function object is available for simpleFoam in openFOAM7.

This is the formula used in wallHeatTransferCoeff.C to calculate the heat transfer coefficient

PHP Code:


		
			
wallHeatTransferCoeffBf[patchi] =
                rho_*Cp_*(nuBf[patchi]/Prl_ + nutBf[patchi]/Prt_);

I have specified this in my controlDict

PHP Code:


		
			
wallHeatTransferCoeff1
    {
        type        wallHeatTransferCoeff;
        libs        ("libfieldFunctionObjects.so");
        //region      fluid;
        //patches     (".*Wall");  //default is all  walls
        rho         997;
        Cp          4215.7;
        Prl         1.64;
        Prt         0.9;
    }

No errors occours, neither warnings during the simulation..I use KEpsilon model for turbulence, inlet mass flow rate and fixed value for pressure at outlet. Flow velocity is about 3 m/s
Why when I visualize the results in paraview about the wallHeatTransferCoeff I obtain value from 1*10^0 to 6*10^0 and not in the order of 10^4 ?? they seems not to be in w/m^2k ...

Never used it myself, but I think the unit is W/(m*K).

wallHeatTransferCoeff.C

Code:

tmp<volScalarField> twallHeatTransferCoeff

(

    volScalarField::New

    (

        type(),

        mesh_,

        dimensionedScalar

        (

            dimMass/pow3(dimTime)/(dimTemperature/dimLength),

            0

        )

    )

);

$\mathrm{\frac{\frac{kg}{s^3}}{\frac{K}{m}} = \frac{kg}{s^3} \cdot \frac{m}{K} = \frac{kg \cdot m}{s^3 \cdot K} \cdot \frac{m}{m} = \frac{kg \cdot m^2}{s^3 \cdot K \cdot m} = \frac{W}{m \cdot K}}$

yes .. but why I obtain such different results between star CCM + and openfoam? Velocity and pressure gradient is failry the same in the two simulation!

Is the heat transfer coefficient in STAR-CCM+ calculated using the same or a similar equation? Or is it given there in W/(m^2*K)?

you are right... I did not notice that.. so stupid.
Star CCM + reports value in W/m^2K while openFOAM in W/mk
also formulations are quite different.

beside this, I'm much more confused because I' m not familiar with openFOAM local heat transfer formulation..
anyone has developed his localHTC post process utility similar to the Star ccm + one?

Take a look here: https://www.cfd-online.com/Forums/op...tml#post757226
Does this help you?

EDIT: Probably not, because due to simpleFoam you don't have a wall temperature.

Quote:

Originally Posted by Krapf (Post 783537)

Take a look here: https://www.cfd-online.com/Forums/op...tml#post757226
Does this help you?

EDIT: Probably not, because due to simpleFoam you don't have a wall temperature.

exactly..simpleFoam does not solve energy.

I have to implement a different local hct calculation similar to the one of star ccm+..