foam-extend4.1-coherent-io/applications/solvers/compressible/rhoPimpleFoam/hEqn.H

{
    fvScalarMatrix hEqn
    (
        fvm::ddt(rho, h)
      + fvm::div(phi, h)
      - fvm::laplacian(turbulence->alphaEff(), h)
     ==
        DpDt
    );

    if (oCorr == nOuterCorr-1)
    {
        hEqn.relax();
        hEqn.solve(mesh.solutionDict().solver("hFinal"));
    }
    else
    {
        hEqn.relax();
        hEqn.solve();
    }

    thermo.correct();
}