free convection
 

I used the groovyBC of foamExtend 4.1 to apply free convectio BC.
But I can not interprete the results.
In your opinion it is correct to use this:

internalField uniform 293.16;

boundaryField
{
"patch2|patch3"
{
type groovyBC;
value uniform 293.16;
gradientExpression "-h*(T-Tamb)/(DT*rho*cp)";
variables 4 (
"h=6.4;"
"rho=2700;"
"cp=896;"
"Tamb=293.16;"
);
}

patch1
{
type fixedValue;
value uniform 573.16;
}
}

In attached a picture for the results, and on the right the good results from Elmer solver.
Even if I change many values for the groovyBC, the solution dosn't change!!!