Buildings.Fluids.BaseClasses

Package with base classes for fluid models

Information

This package contains base classes that are used to construct the models in Buildings.Fluids.

Extends from Modelica_Fluid.Icons.BaseClassLibrary (Icon for library).

Package Content

Name Description

PartialResistance Partial model for a hydraulic resistance

PartialThreeWayResistance Flow splitter with partial resistance model at each port

polynomial Polynomial function

quadraticLinear Function that is quadratic in first argument and linear in second argument

Name	Description
PartialResistance	Partial model for a hydraulic resistance
PartialThreeWayResistance	Flow splitter with partial resistance model at each port
polynomial	Polynomial function
quadraticLinear	Function that is quadratic in first argument and linear in second argument

Buildings.Fluids.BaseClasses.PartialResistance

Partial model for a hydraulic resistance

Buildings.Fluids.BaseClasses.PartialResistance

Information

Partial model for a flow resistance, possible with variable flow coefficient.

Extends from Modelica_Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy).

Parameters

Type Name Default Description

replaceable package Medium Modelica.Media.Interfaces.Pa... Medium in the component

Nominal condition

MassFlowRate m0_flow Nominal mass flow rate [kg/s]

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 1E-4*m0_flow Small mass flow rate for regularization of zero flow [kg/s]

Boolean from_dp true = true, use m_flow = f(dp) else dp = f(m_flow)

Boolean linearized false = true, use linear relation between m_flow and dp for any flow rate

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

Type	Name	Default	Description
replaceable package Medium	Modelica.Media.Interfaces.Pa...	Medium in the component
Nominal condition
MassFlowRate	m0_flow		Nominal mass flow rate [kg/s]
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	1E-4*m0_flow	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp	true	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearized	false	= true, use linear relation between m_flow and dp for any flow rate
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)

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

partial model PartialResistance 
  "Partial model for a hydraulic resistance"
    extends Modelica_Fluid.Interfaces.PartialTwoPortTransport(m_flow_small = 1E-4*m0_flow);


  parameter Boolean from_dp = true 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  parameter Medium.MassFlowRate m0_flow(min=0) "Nominal mass flow rate";

  parameter Boolean linearized = false 
    "= true, use linear relation between m_flow and dp for any flow rate";
  parameter Medium.AbsolutePressure dp_start = 0.01*system.p_start 
    "Guess value of dp = port_a.p - port_b.p";
  Modelica.SIunits.Pressure dp(start=dp_start) 
    "Pressure difference between port_a and port_b (= port_a.p - port_b.p)";
protected 
  Real k(start=1) "Flow coefficient, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)";
  Real kInv(unit="1/(kg.m)", start=1) 
    "Flow coefficient for inverse flow computation, kInv=dp/m_flow^2";

  Modelica.SIunits.AbsolutePressure dp_laminar 
    "Turbulent flow if |dp| >= dp_small, not a parameter because k can be a function of time";
  Medium.MassFlowRate m_flow_laminar 
    "Turbulent flow if |m_flow| >= m_flow_laminar, not a parameter because k can be a function of time";

  parameter Medium.ThermodynamicState sta0=
     Medium.setState_pTX(T=Medium.T_default, p=Medium.p_default, X=Medium.X_default);
  parameter Modelica.SIunits.DynamicViscosity eta0=Medium.dynamicViscosity(sta0) 
    "Dynamic viscosity, used to compute laminar/turbulent transition";
  parameter Modelica.SIunits.SpecificEnthalpy h0=Medium.h_default 
    "Initial value for solver for specific enthalpy";           //specificEnthalpy(sta0)

equation 
  1=k*k*kInv;
  dp_laminar = kInv * m_flow_laminar^2;
  if linearized then
     m_flow = k * dp;
  else
    if from_dp then
       m_flow = Buildings.Fluids.Utilities.massFlowRate_dp(dp=dp, dp_small=dp_laminar, k=k);
    else
       dp = Buildings.Fluids.Utilities.pressureLoss_m_flow(m_flow=m_flow,m_small_flow=m_flow_laminar,k=kInv);
    end if;
  end if;

  // Isenthalpic state transformation (no storage and no loss of energy)
  port_a.h_outflow = inStream(port_b.h_outflow);
  port_b.h_outflow = inStream(port_a.h_outflow);

end PartialResistance;

Buildings.Fluids.BaseClasses.PartialThreeWayResistance

Flow splitter with partial resistance model at each port

Buildings.Fluids.BaseClasses.PartialThreeWayResistance

Information

Partial model for flow resistances with three ports such as a flow mixer/splitter or a three way valve.

Extends from Buildings.BaseClasses.BaseIcon (Base icon).

Parameters

Type Name Default Description

PartialTwoPortTransport res1 redeclare Modelica_Fluid.Int... Partial model, to be replaced with a fluid component

PartialTwoPortTransport res2 redeclare Modelica_Fluid.Int... Partial model, to be replaced with a fluid component

PartialTwoPortTransport res3 redeclare Modelica_Fluid.Int... Partial model, to be replaced with a fluid component

Advanced

Boolean from_dp true = true, use m_flow = f(dp) else dp = f(m_flow)

Type	Name	Default	Description
PartialTwoPortTransport	res1	redeclare Modelica_Fluid.Int...	Partial model, to be replaced with a fluid component
PartialTwoPortTransport	res2	redeclare Modelica_Fluid.Int...	Partial model, to be replaced with a fluid component
PartialTwoPortTransport	res3	redeclare Modelica_Fluid.Int...	Partial model, to be replaced with a fluid component
Advanced
Boolean	from_dp	true	= true, use m_flow = f(dp) else dp = f(m_flow)

Connectors

Type Name Description

FluidPort_a port_1

FluidPort_b port_2

FluidPort_a port_3

Type	Name	Description
FluidPort_a	port_1
FluidPort_b	port_2
FluidPort_a	port_3

Modelica definition

partial model PartialThreeWayResistance 
  "Flow splitter with partial resistance model at each port"
    extends Buildings.BaseClasses.BaseIcon;
  replaceable package Medium = Modelica.Media.Interfaces.PartialMedium 
    "Fluid medium model";

  Modelica_Fluid.Interfaces.FluidPort_a port_1(redeclare package Medium = 
        Medium, m_flow(min=if (portFlowDirection_1 == Modelica_Fluid.Types.PortFlowDirection.Entering) then 
                0.0 else -Modelica.Constants.inf, max=if (portFlowDirection_1
           == Modelica_Fluid.Types.PortFlowDirection.Leaving) then 0.0 else Modelica.Constants.inf));
  Modelica_Fluid.Interfaces.FluidPort_b port_2(redeclare package Medium = 
        Medium, m_flow(min=if (portFlowDirection_2 == Modelica_Fluid.Types.PortFlowDirection.Entering) then 
                0.0 else -Modelica.Constants.inf, max=if (portFlowDirection_2
           == Modelica_Fluid.Types.PortFlowDirection.Leaving) then 0.0 else Modelica.Constants.inf));
  Modelica_Fluid.Interfaces.FluidPort_a port_3(
    redeclare package Medium=Medium,
    m_flow(min=if (portFlowDirection_3==Modelica_Fluid.Types.PortFlowDirection.Entering) then 0.0 else -Modelica.Constants.inf,
    max=if (portFlowDirection_3==Modelica_Fluid.Types.PortFlowDirection.Leaving) then 0.0 else Modelica.Constants.inf));

 parameter Boolean from_dp = true 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  replaceable Modelica_Fluid.Interfaces.PartialTwoPortTransport res1(redeclare 
      package Medium = Medium) 
    "Partial model, to be replaced with a fluid component";
  replaceable Modelica_Fluid.Interfaces.PartialTwoPortTransport res2(redeclare 
      package Medium = Medium) 
    "Partial model, to be replaced with a fluid component";
  replaceable Modelica_Fluid.Interfaces.PartialTwoPortTransport res3(redeclare 
      package Medium = Medium) 
    "Partial model, to be replaced with a fluid component";

protected 
  parameter Modelica_Fluid.Types.PortFlowDirection portFlowDirection_1=Modelica_Fluid.Types.PortFlowDirection.Bidirectional 
    "Flow direction for port_1";
  parameter Modelica_Fluid.Types.PortFlowDirection portFlowDirection_2=Modelica_Fluid.Types.PortFlowDirection.Bidirectional 
    "Flow direction for port_2";
  parameter Modelica_Fluid.Types.PortFlowDirection portFlowDirection_3=Modelica_Fluid.Types.PortFlowDirection.Bidirectional 
    "Flow direction for port_3";

protected 
  Modelica_Fluid.Interfaces.FluidPort_b port_m(redeclare package Medium = 
        Medium) "Mixing port";
equation 
  connect(port_1, res1.port_a);
  connect(res2.port_b, port_2);
  connect(res3.port_a, port_3);
  connect(res1.port_b, port_m);
  connect(res2.port_a, port_m);
  connect(res3.port_b, port_m);
end PartialThreeWayResistance;

Buildings.Fluids.BaseClasses.polynomial

Polynomial function

Information

This function computes a polynomial of arbitrary order.

Inputs

Type Name Default Description

Real a[:] Coefficients

Real x Independent variable

Type	Name	Default	Description
Real	a[:]		Coefficients
Real	x		Independent variable

Outputs

Type Name Description

Real y Result

Type	Name	Description
Real	y	Result

Modelica definition

function polynomial "Polynomial function"
 input Real a[:] "Coefficients";
 input Real x "Independent variable";
 output Real y "Result";
protected 
 parameter Integer n = size(a, 1)-1;
 Real xp[n+1] "Powers of x";
algorithm 
  xp[1] :=1;
  for i in 1:n loop
     xp[i+1] :=xp[i]*x;
  end for;
  y :=a*xp;
end polynomial;

Buildings.Fluids.BaseClasses.quadraticLinear

Function that is quadratic in first argument and linear in second argument

Information

This function computes

  y =   a1 + a2 * x1 + a3 *x1^2 
     + (a4 + a5 * x1 + a6 *x1^2) * x2

Inputs

Type Name Default Description

Real a[6] Coefficients

Real x1 Independent variable for quadratic part

Real x2 Independent variable for linear part

Type	Name	Description
Real	a[6]	Coefficients
Real	x1	Independent variable for quadratic part
Real	x2	Independent variable for linear part

Outputs

Type Name Description

Real y Result

Type	Name	Description
Real	y	Result

Modelica definition

function quadraticLinear 
  "Function that is quadratic in first argument and linear in second argument"
 input Real a[6] "Coefficients";
 input Real x1 "Independent variable for quadratic part";
 input Real x2 "Independent variable for linear part";
 output Real y "Result";
protected 
 Real x1Sq;
algorithm 
  x1Sq :=x1*x1;
  y :=a[1] + a[2]*x1 + a[3]*x1Sq + (a[4] + a[5]*x1 + a[6]*x1Sq)*x2;

end quadraticLinear;

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