Buildings.Fluids.Utilities

Package Content

Name	Description
BaseClasses	Library with base classes for utility functions
Examples	Collection of models that illustrate model use and test models
extendedPolynomial	Polynomial that is linearly extended at user specified values
massFlowRate_dp	Mass flow rate as a function of pressure drop
polynomial	Polynomial, used because OpenModelica 1.4.3 does not expand the sum() into a scalar
pressureLoss_m_flow	Pressure loss as a function of flow rate

Buildings.Fluids.Utilities.extendedPolynomial

Information

   y = c1 + c2 * x + ... + cN * x^(N-1)

Inputs

Type	Name	Default	Description
Real	c[:]		Polynomial coefficients
Real	x		x value
Real	xMin		Minimum x value for polynomial
Real	xMax		Maximum x value for polynomial

Outputs

Type	Name	Description
Real	y	y value

Modelica definition

function extendedPolynomial 
  "Polynomial that is linearly extended at user specified values" 
  annotation(derivative=BaseClasses.der_extendedPolynomial);  
  extends Modelica.Icons.Function;
  input Real[:] c "Polynomial coefficients";
  input Real x "x value";
  input Real xMin "Minimum x value for polynomial";
  input Real xMax "Maximum x value for polynomial";
  output Real y "y value";
protected 
 Integer N = size(c,1) "Number of coefficients";
algorithm 
if x < xMin then
   y := c[1];
   for i in 2:N loop
     y := y + xMin^(i - 1)*c[i] + (x - xMin)*(i - 1)*xMin^(i - 2)*c[i];
   end for;
  elseif x < xMax then
   y := c[1];
   for i in 2:N loop
     y := y + x^(i - 1)*c[i];
  end for;
  else
     y := c[1];
     for i in 2:N loop
       y := y + xMax^(i - 1)*c[i] + (x - xMax)*(i - 1)*xMax^(i - 2)*c[i];
    end for;
  end if;
end extendedPolynomial;

Buildings.Fluids.Utilities.massFlowRate_dp

Inputs

Type	Name	Default	Description
Pressure	dp		Pressure drop (dp = port_a.p - port_b.p) [Pa]
AbsolutePressure	dp_small	1	Turbulent flow if |dp| >= dp_small [Pa]
Real	k		Flow coefficient, k=m_flow/sqrt(dp) [(kg*m)^(1/2)]

Outputs

Type	Name	Description
MassFlowRate	m_flow	Mass flow rate from port_a to port_b [kg/s]

Modelica definition

function massFlowRate_dp 
  "Mass flow rate as a function of pressure drop" 
  extends Modelica.Icons.Function;
  import SI = Modelica.SIunits;
  input SI.Pressure dp "Pressure drop (dp = port_a.p - port_b.p)";
  input SI.AbsolutePressure dp_small = 1 "Turbulent flow if |dp| >= dp_small";
  input Real k(min=0, unit="(kg*m)^(1/2)") 
    "Flow coefficient, k=m_flow/sqrt(dp)";
  output SI.MassFlowRate m_flow "Mass flow rate from port_a to port_b";
protected 
   Real kk;
algorithm 
  kk:=k*k;
  m_flow:=Modelica_Fluid.Utilities.regRoot2(x=dp, x_small=dp_small, k1=kk, k2=kk);
end massFlowRate_dp;

Buildings.Fluids.Utilities.polynomial

Inputs

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

Outputs

Type	Name	Description
Real	y	Dependent variable

Modelica definition

function polynomial 
  "Polynomial, used because OpenModelica 1.4.3 does not expand the sum() into a scalar" 
  extends Modelica.Icons.Function;
  input Real[:] c "Coefficients";
  input Real x "Independent variable";
  output Real y "Dependent variable";
algorithm 
 y := c[1];
 for i in 2 : size(c,1) loop
   y := y + x^(i-1) * c[i];
 end for;
end polynomial;

Buildings.Fluids.Utilities.pressureLoss_m_flow

Inputs

Type	Name	Default	Description
MassFlowRate	m_flow		Mass flow rate from port_a to port_b [kg/s]
MassFlowRate	m_small_flow		Mass flow rate where function is approximated [kg/s]
Real	k		Flow coefficient, k=dp/m_flow^2 [1/kg/m]

Outputs

Type	Name	Description
Pressure	dp	Pressure drop (dp = port_a.p - port_b.p) [Pa]

Modelica definition

function pressureLoss_m_flow 
  "Pressure loss as a function of flow rate" 
  extends Modelica.Icons.Function;
  import SI = Modelica.SIunits;
  input SI.MassFlowRate m_flow "Mass flow rate from port_a to port_b";
  input SI.MassFlowRate m_small_flow 
    "Mass flow rate where function is approximated";
  input Real k(min=0, unit="1/kg/m") "Flow coefficient, k=dp/m_flow^2";
  output SI.Pressure dp "Pressure drop (dp = port_a.p - port_b.p)";
algorithm 
  dp:=Modelica_Fluid.Utilities.regSquare2(
    x=m_flow,
    x_small=m_small_flow,
    k1=k,
    k2=k);
end pressureLoss_m_flow;