WOLFRAM SYSTEMMODELER

SimpleGenericOrifice

Simple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b)

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.Fittings.SimpleGenericOrifice"]
Out[1]:=

Information

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

  • Δp is the pressure drop: Δp = port_a.p - port_b.p
  • D is the diameter of the orifice at the position where ζ is defined (either at port_a or port_b). If the orifice has not a circular cross section, D = 4*A/P, where A is the cross section area and P is the wetted perimeter.
  • ζ is the loss factor with respect to D that depends on the geometry of the orifice. In the turbulent flow regime, it is assumed that ζ is constant.
    For small mass flow rates, the flow is laminar and is approximated by a polynomial that has a finite derivative for m_flow=0.
  • v is the mean velocity.
  • ρ is the upstream density.

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.

Parameters (14)

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)

Inputs (1)

pathLength

Default Value: 0

Type: Length (m)

Description: Length flow path

Connectors (2)

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)

Components (3)

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

Used in Examples (1)

InverseParameterization

Modelica.Fluid.Examples

Demonstrates the parameterization of a pump and a pipe for given nominal values