Buildings.Fluids.Movers

Package with fan and pump models

Package Content

NameDescription
Buildings.Fluids.Movers.BaseClasses BaseClasses Package with basic models for fans and pumps
Buildings.Fluids.Movers.FlowMachinePolynomial FlowMachinePolynomial Pump with head and efficiency given by a non-dimensional polynomial


Buildings.Fluids.Movers.FlowMachinePolynomial Buildings.Fluids.Movers.FlowMachinePolynomial

Pump with head and efficiency given by a non-dimensional polynomial

Buildings.Fluids.Movers.FlowMachinePolynomial

Information


This is a model of a flow machine (pump or fan).

The normalized pressure difference is computed using a function of the normalized mass flow rate. The function is a polynomial for which a user needs to supply the coefficients and two values that determine for what flow rate the polynomial is linearly extended.


Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
LengthD Diameter [m]
Reala[:] Polynomial coefficients for pressure=p(mNor_flow)
Realb[:] Polynomial coefficients for etaSha=p(mNor_flow)
RealmNorMin_flow Lowest valid normalized mass flow rate
RealmNorMax_flow Highest valid normalized mass flow rate
RealscaM_flow1Factor used to scale the mass flow rate of the fan (used for quickly adjusting fan size)
RealscaDp1Factor used to scale the pressure increase of the fan (used for quickly adjusting fan size)
Initialization
MassFlowRatem_flow Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressuredp Pressure difference between port_a and port_b [Pa]
Advanced
TempflowDirectionModelica_Fluid.Types.FlowDir...Unidirectional (port_a -> port_b) or bidirectional flow component

Connectors

TypeNameDescription
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
input RealInputN_inPrescribed rotational speed

Modelica definition

model FlowMachinePolynomial 
  "Pump with head and efficiency given by a non-dimensional polynomial" 
  extends Buildings.Fluids.Interfaces.PartialStaticTwoPortTransformer;
  
  
  Modelica.Blocks.Interfaces.RealInput N_in(redeclare type SignalType = 
        Modelica.SIunits.AngularVelocity) "Prescribed rotational speed";
  
  parameter Modelica.SIunits.Length D "Diameter";
  parameter Real[:] a "Polynomial coefficients for pressure=p(mNor_flow)";
  parameter Real[:] b "Polynomial coefficients for etaSha=p(mNor_flow)";
  parameter Real mNorMin_flow "Lowest valid normalized mass flow rate";
  parameter Real mNorMax_flow "Highest valid normalized mass flow rate";
  parameter Real scaM_flow = 1 
    "Factor used to scale the mass flow rate of the fan (used for quickly adjusting fan size)";
  parameter Real scaDp = 1 
    "Factor used to scale the pressure increase of the fan (used for quickly adjusting fan size)";
  
  Real pNor(min=0) "Normalized pressure";
  Real mNor_flow(start=mNorMax_flow) "Normalized mass flow rate";
  Real etaSha(min=0, max=1) "Efficiency, flow work divided by shaft power";
  Modelica.SIunits.Power PSha "Power input at shaft";
protected 
  parameter Real pNorMin1(fixed=false) 
    "Normalized pressure, used to test slope of polynomial outside [xMin, xMax]";
  parameter Real pNorMin2(fixed=false) 
    "Normalized pressure, used to test slope of polynomial outside [xMin, xMax]";
  parameter Real pNorMax1(fixed=false) 
    "Normalized pressure, used to test slope of polynomial outside [xMin, xMax]";
  parameter Real pNorMax2(fixed=false) 
    "Normalized pressure, used to test slope of polynomial outside [xMin, xMax]";
initial equation 
 // check slope of polynomial outside the domain [mNorMin_flow, mNorMax_flow]
 pNorMin1 = Buildings.Fluids.Utilities.extendedPolynomial(
                                        c=a, x=mNorMin_flow/2, xMin=mNorMin_flow, xMax=mNorMax_flow);
 pNorMin2 = Buildings.Fluids.Utilities.extendedPolynomial(
                                        c=a, x=mNorMin_flow, xMin=mNorMin_flow, xMax=mNorMax_flow);
 pNorMax1 = Buildings.Fluids.Utilities.extendedPolynomial(
                                        c=a, x=mNorMax_flow, xMin=mNorMin_flow, xMax=mNorMax_flow);
 pNorMax2 = Buildings.Fluids.Utilities.extendedPolynomial(
                                        c=a, x=mNorMax_flow*2, xMin=mNorMin_flow, xMax=mNorMax_flow);
 assert(pNorMin1>pNorMin2,
    "Slope of pump pressure polynomial is non-negative for mNor_flow < mNorMin_flow. Check parameter a.");
 assert(pNorMax1>pNorMax2,
    "Slope of pump pressure polynomial is non-negative for mNorMax_flow < mNor_flow. Check parameter a.");
equation 
  -dp = scaDp     * pNor      * medium_a.d * D*D   * N_in * N_in;
  m_flow = scaM_flow * mNor_flow * medium_a.d * D*D*D * N_in;
  pNor = Buildings.Fluids.Utilities.extendedPolynomial(
                                        c=a, x=mNor_flow, xMin=mNorMin_flow, xMax=mNorMax_flow);
  etaSha = max(0.1, Buildings.Fluids.Utilities.polynomial(
                                                      c=b, x=mNor_flow));
                                                                // for OpenModelica 1.4.3 sum(mNor_flow^(i - 1)*b[i] for i in 1:size(b,1));
  etaSha * PSha = -dp * m_flow / medium_a.d; // dp<0 and m_flow>0 for normal operation
  
  // interface ports and state conservation equations
  port_a.H_flow + port_b.H_flow + PSha = 0;
  port_a.m_flow + port_b.m_flow = 0;
  port_a.mXi_flow + port_b.mXi_flow = zeros(Medium.nXi);
end FlowMachinePolynomial;

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