[regard]

hi every one

i have a question about total pressure drop in open foam
my geometry is Vertical rectangular channel .The fluid moves from the bottom to upwards and wall is heated by constant heat flux and we have phase change in this channel....i calculate the pressure drop by following code

deltap

{
type patchExpression;
variables
(
"pout{patch'outlet}=sum(p*area())/sum(area());"
);
patches (
inlet
);
expression "p-pout";
accumulations (
average
);
verbose true;
outputControlMode timeStep;//outputTime;//
outputInterval 100;
}
but this answer is more less than Experimental data how can i calculate the total pressure loss in this case?(solver:PhaseChangeHeatFoam)

thanks in advance