Modelica.Fluid.Fittings.Bends

Information

Package Content

Name	Description
CurvedBend	Curved bend flow model
EdgedBend	Edged bend flow model

Modelica.Fluid.Fittings.Bends.CurvedBend

Information

This component models a curved bend in the overall flow regime for incompressible and single-phase fluid flow through circular cross sectional area considering surface roughness. It is expected that also compressible fluid flow can be handled up to about Ma = 0.3. It is assumed that neither mass nor energy is stored in this component. In the model basically a function is called to compute the mass flow rate as a function of pressure loss for a curved bend. Also the inverse of this function is defined, and a tool might use this inverse function instead, in order to avoid the solution of a nonlinear equation.

The details of the model are described in the documentation of the underlying function.

Extends from Modelica.Fluid.Dissipation.Utilities.Icons.PressureLoss.Bend_i (Icon for bend), Modelica.Fluid.Interfaces.PartialPressureLoss (Base flow model for pressure loss functions with the same area at port_a and at port_b).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Geometry	geometry		Geometry of curved bend
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
AbsolutePressure	dp_start	0.01*system.p_start	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	system.m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
MassFlowRate	m_flow_small	system.m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_T	true	= true, if temperatures at port_a and port_b are computed
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed

Connectors

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

Modelica definition

model CurvedBend "Curved bend flow model"
  extends Modelica.Fluid.Dissipation.Utilities.Icons.PressureLoss.Bend_i;
  extends Modelica.Fluid.Interfaces.PartialPressureLoss;

  parameter Modelica.Fluid.Fittings.BaseClasses.Bends.CurvedBend.Geometry geometry 
    "Geometry of curved bend";

protected 
  parameter Medium.AbsolutePressure dp_small=
             Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_curvedOverall_DP(
                geometry,
                Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_curvedOverall_IN_var(
                  rho=Medium.density(state_dp_small),
                  eta=Medium.dynamicViscosity(state_dp_small)),
                m_flow_small) 
    "Default small pressure drop for regularization of laminar and zero flow (calculated from m_flow_small)";

equation 
  if allowFlowReversal then
     m_flow = Modelica.Fluid.Fittings.BaseClasses.Bends.CurvedBend.massFlowRate(
                dp, geometry, d_a, d_b, eta_a, eta_b, dp_small, m_flow_small);
  else
     m_flow = Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_curvedOverall_MFLOW(
                geometry,
                Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_curvedOverall_IN_var(rho=d_a, eta=eta_a), dp);
  end if;

end CurvedBend;

Modelica.Fluid.Fittings.Bends.EdgedBend

Information

This component models an edged bend in the overall flow regime for incompressible and single-phase fluid flow through circular cross sectional area considering surface roughness. It is expected that also compressible fluid flow can be handled up to about Ma = 0.3. It is assumed that neither mass nor energy is stored in this component. In the model basically a function is called to compute the mass flow rate as a function of pressure loss for an edged bend. Also the inverse of this function is defined, and a tool might use this inverse function instead, in order to avoid the solution of a nonlinear equation.

The details of the model are described in the documentation of the underlying function.

Extends from Modelica.Fluid.Dissipation.Utilities.Icons.PressureLoss.Bend_i (Icon for bend), Modelica.Fluid.Interfaces.PartialPressureLoss (Base flow model for pressure loss functions with the same area at port_a and at port_b).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Geometry	geometry		Geometry of curved bend
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
AbsolutePressure	dp_start	0.01*system.p_start	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	system.m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
MassFlowRate	m_flow_small	system.m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_T	true	= true, if temperatures at port_a and port_b are computed
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed

Connectors

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

Modelica definition

model EdgedBend "Edged bend flow model"
  extends Modelica.Fluid.Dissipation.Utilities.Icons.PressureLoss.Bend_i;
  extends Modelica.Fluid.Interfaces.PartialPressureLoss;

  parameter Modelica.Fluid.Fittings.BaseClasses.Bends.EdgedBend.Geometry geometry 
    "Geometry of curved bend";

protected 
  parameter Medium.AbsolutePressure dp_small=
             Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_edgedOverall_DP(
               Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_edgedOverall_IN_con(
                   d_hyd=geometry.d_hyd,
                   delta=geometry.delta,
                   K=geometry.K),
                Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_edgedOverall_IN_var(
                  rho=Medium.density(state_dp_small),
                  eta=Medium.dynamicViscosity(state_dp_small)),
                m_flow_small) 
    "Default small pressure drop for regularization of laminar and zero flow (calculated from m_flow_small)";

equation 
  if allowFlowReversal then
     m_flow = Modelica.Fluid.Fittings.BaseClasses.Bends.EdgedBend.massFlowRate(
                dp, geometry, d_a, d_b, eta_a, eta_b, dp_small, m_flow_small);
  else
     m_flow = Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_edgedOverall_MFLOW(
               Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_edgedOverall_IN_con(
                   d_hyd=geometry.d_hyd,
                   delta=geometry.delta,
                   K=geometry.K),
                Modelica.Fluid.Dissipation.PressureLoss.Bend.dp_edgedOverall_IN_var(rho=d_a, eta=eta_a), dp);
  end if;

end EdgedBend;