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wallHeatTransferCoeff + simpleFOAM ( OpenFoam7)

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Old   September 21, 2020, 05:15
Default wallHeatTransferCoeff + simpleFOAM ( OpenFoam7)
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giovanni
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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 ...
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Old   September 21, 2020, 08:10
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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}}

Last edited by Krapf; September 21, 2020 at 17:05.
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Old   September 21, 2020, 10:06
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giovanni
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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!
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Old   September 21, 2020, 17:03
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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)?
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Old   September 22, 2020, 06:08
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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?
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Old   September 23, 2020, 05:05
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Take a look here: Heat Transfer Coefficients from WallHeatFlux
Does this help you?


EDIT: Probably not, because due to simpleFoam you don't have a wall temperature.
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Old   September 23, 2020, 08:56
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Quote:
Originally Posted by Krapf View Post
Take a look here: Heat Transfer Coefficients from WallHeatFlux
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+..
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