I am implementing the ValveLinear model from the Modelica standard fluid library into a model of mine using Dymola. I have some questions regarding its parameters which I can hopefully clear up: The key parameters for this valve are as follows:
parameter Medium.MassFlowRate m_flow_nominal
"Nominal mass flowrate at full opening";
final parameter Types.HydraulicConductance k = m_flow_nominal/dp_nominal
"Hydraulic conductance at full opening";
Modelica.Blocks.Interfaces.RealInput opening(min=0,max=1)
"=1: completely open, =0: completely closed"
The mass flow over the valve is then caclulated as
m_flow = opening*k*dp;
Am I right in assuming that m_flow_nominal
is the maximum mass flow rate with a linear drop off in mass_flow
down to zero as opening goes from 1 to 0?
Furthermore is dp_nominal the corresponding minimum pressure drop across the valve? (i.e. at fully open). Therefore would we see a linear increase in dp from dp_nominal to some maximum value as opening goes from 1 to 0?
The answer may seem trivial but I have run some examples with valves in Dymola so far and in some cases it seems that dp remains constant across the valve as the opening in varied which doesn't make sense to me.