model SimpleGenericOrifice "Simple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b)"
extends Modelica.Fluid.Interfaces.PartialTwoPortTransport(dp_start = dp_nominal, m_flow_small = if system.use_eps_Re then system.eps_m_flow * m_flow_nominal else system.m_flow_small, m_flow(stateSelect = if momentumDynamics == Types.Dynamics.SteadyState then StateSelect.default else StateSelect.prefer));
extends Modelica.Fluid.Interfaces.PartialLumpedFlow(final pathLength = 0, final momentumDynamics = Types.Dynamics.SteadyState);
parameter SI.Diameter diameter "Diameter of orifice";
parameter Real zeta "Loss factor for flow of port_a -> port_b"
annotation (Dialog(enable = use_zeta));
parameter Boolean use_zeta = true "= false to obtain zeta from dp_nominal and m_flow_nominal";
parameter SI.MassFlowRate m_flow_nominal = if system.use_eps_Re then system.m_flow_nominal else 100 * system.m_flow_small "Mass flow rate for dp_nominal"
annotation (Dialog(group = "Nominal operating point"));
parameter SI.Pressure dp_nominal = if not system.use_eps_Re then 1000 else BaseClasses.lossConstant_D_zeta(diameter, zeta) / Medium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default) * m_flow_nominal ^ 2 "Nominal pressure drop"
annotation (Dialog(group = "Nominal operating point"));
parameter Boolean use_Re = system.use_eps_Re "= true, if turbulent region is defined by Re, otherwise by m_flow_small"
annotation (
Dialog(tab = "Advanced"),
Evaluate = true);
parameter Boolean from_dp = true "= true, use m_flow = f(dp) else dp = f(m_flow)"
annotation (
Evaluate = true,
Dialog(tab = "Advanced"));
protected
parameter Medium.AbsolutePressure dp_small(min = 0) = if system.use_eps_Re then dp_nominal / m_flow_nominal * m_flow_small else system.dp_small "Regularization of zero flow if |dp| < dp_small"
annotation (Dialog(
tab = "Advanced",
enable = not use_Re and from_dp));
public
Real zeta_nominal;
Medium.Density d = 0.5 * (Medium.density(state_a) + Medium.density(state_b));
Modelica.SIunits.Pressure dp_fg(start = dp_start) "pressure loss due to friction and gravity";
Modelica.SIunits.Area A_mean = 0.25 * Modelica.Constants.pi * diameter ^ 2 "mean cross flow area";
constant SI.ReynoldsNumber Re_turbulent = 10000 "cf. sharpEdgedOrifice";
SI.MassFlowRate m_flow_turbulent = if not use_Re then m_flow_small else max(m_flow_small, 0.125 * Modelica.Constants.pi * diameter * (Medium.dynamicViscosity(state_a) + Medium.dynamicViscosity(state_b)) * Re_turbulent);
SI.AbsolutePressure dp_turbulent = if not use_Re then dp_small else max(dp_small, BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal) / d * m_flow_turbulent ^ 2);
equation
if from_dp then
m_flow = homotopy(Utilities.regRoot2(dp_fg, dp_turbulent, Medium.density(state_a) / BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal), Medium.density(state_b) / BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal)), m_flow_nominal * dp_fg / dp_nominal);
else
dp_fg = homotopy(Utilities.regSquare2(m_flow, m_flow_turbulent, BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal) / Medium.density(state_a), BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal) / Medium.density(state_b)), dp_nominal * m_flow / m_flow_nominal);
end if;
if use_zeta then
zeta_nominal = zeta;
else
zeta_nominal = 2 * A_mean ^ 2 * d * dp_nominal / m_flow_nominal ^ 2;
end if;
F_fg = A_mean * dp_fg;
F_p = A_mean * (Medium.pressure(state_b) - Medium.pressure(state_a));
Ib_flow = 0;
port_a.h_outflow = inStream(port_b.h_outflow);
port_b.h_outflow = inStream(port_a.h_outflow);
annotation (
defaultComponentName = "orifice",
Icon(
coordinateSystem(
preserveAspectRatio = false,
extent = {
{-100, -100},
{100, 100}}),
graphics = {
Line(
points = {
{-60, -50},
{-60, 50},
{60, -50},
{60, 50}},
thickness = 0.5),
Line(
points = {
{-60, 0},
{-100, 0}},
color = {0, 127, 255}),
Line(
points = {
{60, 0},
{100, 0}},
color = {0, 127, 255}),
Text(
extent = {
{-173, 104},
{175, 62}},
textString = "zeta=%zeta")}),
Documentation(info = "<html>\n<p>\nThis pressure drop component defines a\nsimple, generic orifice, where the loss factor ζ is provided\nfor one flow direction (e.g., from loss table of a book):\n</p>\n\n<pre> Δp = 0.5*ζ*ρ*v*|v|\n = 8*ζ/(π^2*D^4*ρ) * m_flow*|m_flow|\n</pre>\n\n<p>\nwhere\n</p>\n<ul>\n<li> Δp is the pressure drop: Δp = port_a.p - port_b.p</li>\n<li> D is the diameter of the orifice at the position where\n ζ is defined (either at port_a or port_b). If the orifice has not a\n circular cross section, D = 4*A/P, where A is the cross section\n area and P is the wetted perimeter.</li>\n<li> ζ is the loss factor with respect to D\n that depends on the geometry of\n the orifice. In the turbulent flow regime, it is assumed that\n ζ is constant.<br>\n For small mass flow rates, the flow is laminar and is approximated\n by a polynomial that has a finite derivative for m_flow=0.</li>\n<li> v is the mean velocity.</li>\n<li> ρ is the upstream density.</li>\n</ul>\n\n<p>\nSince the pressure loss factor zeta is provided only for a mass flow\nfrom port_a to port_b, the pressure loss is not correct when the\nflow is reversing. If reversing flow only occurs in a short time interval,\nthis is most likely uncritical. If significant reversing flow\ncan appear, this component should not be used.\n</p>\n</html>"));
end SimpleGenericOrifice;