# wallHeatTransferCoeff + simpleFOAM ( OpenFoam7)

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 September 21, 2020, 05:15 wallHeatTransferCoeff + simpleFOAM ( OpenFoam7) #1 Member   giovanni Join Date: Sep 2017 Posts: 48 Rep Power: 5 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 ...

 September 21, 2020, 08:10 #2 Member   Join Date: Oct 2017 Posts: 56 Rep Power: 5 Never used it myself, but I think the unit is W/(m*K). wallHeatTransferCoeff.C Code: tmp twallHeatTransferCoeff ( volScalarField::New ( type(), mesh_, dimensionedScalar ( dimMass/pow3(dimTime)/(dimTemperature/dimLength), 0 ) ) ); Last edited by Krapf; September 21, 2020 at 17:05.

 September 21, 2020, 10:06 #3 Member   giovanni Join Date: Sep 2017 Posts: 48 Rep Power: 5 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!

 September 21, 2020, 17:03 #4 Member   Join Date: Oct 2017 Posts: 56 Rep Power: 5 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)?

 September 22, 2020, 06:08 #5 Member   giovanni Join Date: Sep 2017 Posts: 48 Rep Power: 5 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?

 September 23, 2020, 05:05 #6 Member   Join Date: Oct 2017 Posts: 56 Rep Power: 5 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.

September 23, 2020, 08:56
#7
Member

giovanni
Join Date: Sep 2017
Posts: 48
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Quote:
 Originally Posted by Krapf 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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