Buildings.Fluids.BaseClasses

Package Content

Name	Description
PartialResistance	Partial model for a hydraulic resistance
PartialThreeWayResistance	Flow splitter with partial resistance model at each port

Buildings.Fluids.BaseClasses.PartialResistance

Information

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

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
MassFlowRate	m_small_flow		Mass flow rate where transition to laminar occurs [kg/s]
Initialization
MassFlowRate	m_flow		Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressure	dp		Pressure difference between port_a and port_b [Pa]
Advanced
Temp	flowDirection	Modelica_Fluid.Types.FlowDir...	Unidirectional (port_a -> port_b) or bidirectional flow component
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

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

partial model PartialResistance 
  "Partial model for a hydraulic resistance" 
    extends Modelica_Fluid.Interfaces.PartialTwoPortTransport(
          medium_a(T(start = Medium.T_default), h(start=Medium.h_default),
                   p(start=Medium.p_default)),
          medium_b(T(start = Medium.T_default), h(start=Medium.h_default),
                   p(start=Medium.p_default)));
    extends Buildings.BaseClasses.BaseIcon;
  
  
  parameter Boolean from_dp = true 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  parameter Modelica.SIunits.MassFlowRate m_small_flow 
    "Mass flow rate where transition to laminar occurs";
  parameter Boolean linearized = false 
    "= true, use linear relation between m_flow and dp for any flow rate";
protected 
  Real k(unit="(kg*m)^(1/2)", start=1) "Flow coefficient, k=m_flow/sqrt(dp)";
  Real kInv(unit="1/kg/m", start=1) 
    "Flow coefficient for inverse flow computation, kInv=dp/m_flow^2";
  
  Modelica.SIunits.AbsolutePressure dp_small 
    "Turbulent flow if |dp| >= dp_small, not a parameter because k can be a function of time";
  parameter Medium.ThermodynamicState sta0(T=Medium.T_default, p=Medium.p_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) 
  
initial equation 
                 // this equation can be deleted, it here for debugging during library transition 
  assert(abs(eta0-Medium.dynamicViscosity(medium_a)) < 0.1*eta0, "Wrong parameter for eta.\n"
    + "  medium_a.T                              = " + realString(medium_a.T) + "\n"
    + "  medium_a.p                              = " + realString(medium_a.p) + "\n"
    + "  Medium.dynamicViscosity(medium_a)       = " + realString(Medium.dynamicViscosity(medium_a)) + "\n"
    + "  eta0                                    = " + realString(eta0) + "\n"
    + "  Medium.dynamicViscosity(medium_a)/ eta0 = " + realString(Medium.dynamicViscosity(medium_a)/eta0));
  
equation 
  1=k*k*kInv;
  dp_small = kInv * m_small_flow^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_small, k=k);
    else
       dp = Buildings.Fluids.Utilities.pressureLoss_m_flow(             m_flow=m_flow,m_small_flow=m_small_flow,k=kInv);
    end if;
  end if;
end PartialResistance;

Buildings.Fluids.BaseClasses.PartialThreeWayResistance

Information

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

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)
Temp	flowDirection	Modelica_Fluid.Types.FlowDir...	Unidirectional (port_1 -> port_2) or bidirectional flow component

Connectors

Type	Name	Description
FluidPort_b	port_1
FluidPort_b	port_2
FluidPort_b	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_b port_1(
        redeclare package Medium = Medium,
        m_flow(start=0,min=if allowFlowReversal then -Modelica.Constants.inf else 0));
  Modelica_Fluid.Interfaces.FluidPort_b port_2(
        redeclare package Medium = Medium,
        m_flow(start=0,max=if allowFlowReversal then +Modelica.Constants.inf else 0));
  // For port_3, allowFlowReversal must not be specified because the flow
  // direction is different for a mixer and splitter
  Modelica_Fluid.Interfaces.FluidPort_b port_3(redeclare package Medium = 
        Medium);
  
  Medium.AbsolutePressure pMix "Pressure";
  Medium.SpecificEnthalpy hMix "Mixing enthalpy";
  Medium.MassFraction XiMix[Medium.nXi] 
    "Independent mixture mass fractions m_i/m";
  
  parameter Boolean from_dp = true 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
 parameter Modelica_Fluid.Types.FlowDirection.Temp flowDirection=
                   Modelica_Fluid.Types.FlowDirection.Bidirectional 
    "Unidirectional (port_1 -> port_2) or bidirectional flow component";
  Modelica_Fluid.Junctions.Splitter spl(redeclare package Medium=Medium);
  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 Boolean allowFlowReversal=
     flowDirection == Modelica_Fluid.Types.FlowDirection.Bidirectional 
    "= false, if flow only from port_a to port_b, otherwise reversing flow allowed";
equation 
  pMix = spl.p;
  hMix = spl.hMix;
  XiMix   = spl.Xi;
  connect(port_1, res1.port_a);
  connect(res1.port_b, spl.port_1);
  connect(spl.port_2, res2.port_b);
  connect(res2.port_a, port_2);
  connect(spl.port_3, res3.port_b);
  connect(res3.port_a, port_3);
end PartialThreeWayResistance;