SimpleGenericOrificeSimple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b) 
This information is part of the Modelica Standard Library maintained by the Modelica Association.
This pressure drop component defines a simple, generic orifice, where the loss factor ζ is provided for one flow direction (e.g., from loss table of a book):
Δp = 0.5*ζ*ρ*v*v = 8*ζ/(π^2*D^4*ρ) * m_flow*m_flow
where
Since the pressure loss factor zeta is provided only for a mass flow from port_a to port_b, the pressure loss is not correct when the flow is reversing. If reversing flow only occurs in a short time interval, this is most likely uncritical. If significant reversing flow can appear, this component should not be used.
dp_start 
Value: dp_nominal Type: AbsolutePressure (Pa) Description: Guess value of dp = port_a.p  port_b.p 

m_flow_small 
Value: if system.use_eps_Re then system.eps_m_flow * m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Small mass flow rate for regularization of zero flow 
show_T 
Value: true Type: Boolean Description: = true, if temperatures at port_a and port_b are computed 
show_V_flow 
Value: true Type: Boolean Description: = true, if volume flow rate at inflowing port is computed 
allowFlowReversal 
Value: system.allowFlowReversal Type: Boolean Description: = true to allow flow reversal, false restricts to design direction (m_flow >= 0) 
momentumDynamics 
Value: Types.Dynamics.SteadyState Type: Dynamics Description: Formulation of momentum balance 
m_flow_start 
Value: system.m_flow_start Type: MassFlowRate (kg/s) Description: Start value of mass flow rates 
diameter 
Value: Type: Diameter (m) Description: Diameter of orifice 
zeta 
Value: Type: Real Description: Loss factor for flow of port_a > port_b 
use_zeta 
Value: true Type: Boolean Description: = false to obtain zeta from dp_nominal and m_flow_nominal 
m_flow_nominal 
Value: if system.use_eps_Re then system.m_flow_nominal else 1e2 * system.m_flow_small Type: MassFlowRate (kg/s) Description: Mass flow rate for dp_nominal 
dp_nominal 
Value: if not system.use_eps_Re then 1e3 else BaseClasses.lossConstant_D_zeta(diameter, zeta) / Medium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default) * m_flow_nominal ^ 2 Type: Pressure (Pa) Description: Nominal pressure drop 
use_Re 
Value: system.use_eps_Re Type: Boolean Description: = true, if turbulent region is defined by Re, otherwise by m_flow_small 
from_dp 
Value: true Type: Boolean Description: = true, use m_flow = f(dp) else dp = f(m_flow) 
pathLength 
Default Value: 0 Type: Length (m) Description: Length flow path 

port_a 
Type: FluidPort_a Description: Fluid connector a (positive design flow direction is from port_a to port_b) 


port_b 
Type: FluidPort_b Description: Fluid connector b (positive design flow direction is from port_a to port_b) 
state_a 
Type: ThermodynamicState Description: state for medium inflowing through port_a 


state_b 
Type: ThermodynamicState Description: state for medium inflowing through port_b 

system 
Type: System Description: System properties 
Modelica.Fluid.Examples Demonstrates the parameterization of a pump and a pipe for given nominal values 