Buildings.Fluids.Movers

Package Content

Name	Description
BaseClasses	Package with basic models for fans and pumps
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

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Length	D		Diameter [m]
Real	a[:]		Polynomial coefficients for pressure=p(mNor_flow)
Real	b[:]		Polynomial coefficients for etaSha=p(mNor_flow)
Real	mNorMin_flow		Lowest valid normalized mass flow rate
Real	mNorMax_flow		Highest valid normalized mass flow rate
Real	scaM_flow	1	Factor used to scale the mass flow rate of the fan (used for quickly adjusting fan size)
Real	scaDp	1	Factor used to scale the pressure increase of the fan (used for quickly adjusting fan size)
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

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)
input RealInput	N_in	Prescribed 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;