Skip to content
GitLab
Projects Groups Snippets
  • /
  • Help
    • Help
    • Support
    • Community forum
    • Submit feedback
    • Contribute to GitLab
  • Sign in / Register
  • openfoam openfoam
  • Project information
    • Project information
    • Activity
    • Labels
    • Members
  • Repository
    • Repository
    • Files
    • Commits
    • Branches
    • Tags
    • Contributors
    • Graph
    • Compare
  • Issues 426
    • Issues 426
    • List
    • Boards
    • Service Desk
    • Milestones
  • Merge requests 9
    • Merge requests 9
  • Deployments
    • Deployments
    • Releases
  • Wiki
    • Wiki
  • Activity
  • Graph
  • Create a new issue
  • Commits
  • Issue Boards
Collapse sidebar
  • Development
  • openfoamopenfoam
  • Issues
  • #831
Closed
Open
Issue created May 16, 2018 by Admin@OpenFOAM-adminMaintainer

Documentation in header of humidityTemperatureCoupledMixedFvPatchScalarField.H possibly wrong

In the header of the file src/thermophysicalModels/thermophysicalPropertiesFvPatchFields/liquidProperties/humidityTemperatureCoupledMixed/humidityTemperatureCoupledMixedFvPatchScalarField.H the documentation might by incorrect:

Currently it states:

The mass transfer correlation used is:

\f[ h_m = D_{ab} \frac{Sc}{L} \f]

where:
\vartable
    D_{ab} | mass vapour difussivity
    L      | characteristic length
    Sc     | Schmidt number
\endvartable

The Schmidt number is calculated using:

\f{eqnarray*}{
        0.664 Re^\frac{1}{2} Sc^\frac{1}{3} & Re < 5.0E+05 \\
        0.037 Re^\frac{4}{5} Sc^\frac{1}{3} & Re > 5.0E+05
\f}

But in the first equation, not the Schmidt number Sc should be used, but the Sherwood number Sh. And Sh is calculated by the correlations depending on the Schmidt number Sc and the Reynolds number Re. This is also the way, it is used in the code:

Calculation of Schmidt number and its use in the calculation of the Sherwood number:

                    const scalar Sc = nuf/Dab;
                    const scalar Sh = this->Sh(Re, Sc);

Calculation of Sherwood number:

Foam::scalar Foam::humidityTemperatureCoupledMixedFvPatchScalarField::Sh
(
    const scalar Re,
    const scalar Sc
) const
{
    if (Re < 5.0E+05)
    {
        return 0.664*sqrt(Re)*cbrt(Sc);
    }
    else
    {
        return 0.037*pow(Re, 0.8)*cbrt(Sc);
    }
}

Use of Sherwood number in the calculation of the mass transfer:

                    // Mass transfer coefficient [m/s]
                    const scalar hm = Dab*Sh/L_;

So the header should read:

The mass transfer correlation used is:

\f[ h_m = D_{ab} \frac{Sh}{L} \f]

where:
\vartable
    D_{ab} | mass vapour difussivity
    L      | characteristic length
    Sh     | Sherwood number
\endvartable

The Sherwood number is calculated using:

\f{eqnarray*}{
        0.664 Re^\frac{1}{2} Sc^\frac{1}{3} & Re < 5.0E+05 \\
        0.037 Re^\frac{4}{5} Sc^\frac{1}{3} & Re > 5.0E+05
\f}
where:
\vartable
    Re     | Reynolds number
    Sc     | Schmidt number
\endvartable

(There is another typo: A space is missing between in \c p (currently \cp) in this line:

      - requires \c rho, \c thickness and \cp

)

Assignee
Assign to
Time tracking