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Buildings.Fluid.HeatExchangers.CoolingTowers.BaseClasses

Package with base classes for Buildings.Fluid.HeatExchangers.CoolingTowers

Information

This package contains base classes that are used to construct the models in Buildings.Fluid.HeatExchangers.CoolingTowers.

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

NameDescription
Buildings.Fluid.HeatExchangers.CoolingTowers.BaseClasses.CoolingTower CoolingTower Base class for cooling towers


Buildings.Fluid.HeatExchangers.CoolingTowers.BaseClasses.CoolingTower Buildings.Fluid.HeatExchangers.CoolingTowers.BaseClasses.CoolingTower

Base class for cooling towers

Buildings.Fluid.HeatExchangers.CoolingTowers.BaseClasses.CoolingTower

Information

Base class for steady-state and dynamic cooling tower models.

Extends from Buildings.Fluid.Interfaces.TwoPortHeatMassExchanger (Partial model transporting one fluid stream with storing mass or energy), Buildings.BaseClasses.BaseIcon (Base icon).

Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
Pressuredp_nominal Pressure [Pa]
Initialization
MassFlowRatem_flow.start0Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressuredp.start0Pressure difference between port_a and port_b [Pa]
Assumptions
BooleanallowFlowReversalsystem.allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Diagnostics
Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed
Booleanshow_Ttrue= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Nominal condition
Timetau30Time constant at nominal flow (if energyDynamics <> SteadyState) [s]
Equations
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Formulation of energy balance
DynamicsmassDynamicsenergyDynamicsFormulation of mass balance
Initialization
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureT_startMedium.T_defaultStart value of temperature [K]
MassFractionX_start[Medium.nX]Medium.X_defaultStart value of mass fractions m_i/m [kg/kg]
ExtraPropertyC_start[Medium.nC]fill(0, Medium.nC)Start value of trace substances

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)
output RealOutputTLvgLeaving water temperature

Modelica definition

partial model CoolingTower "Base class for cooling towers"
  extends Buildings.Fluid.Interfaces.TwoPortHeatMassExchanger(
    redeclare final Buildings.Fluid.MixingVolumes.MixingVolume vol,
    show_T=true);
  extends Buildings.BaseClasses.BaseIcon;
  Modelica.Blocks.Interfaces.RealOutput TLvg "Leaving water temperature";
  Modelica.SIunits.HeatFlowRate Q_flow = QWat_flow.y 
    "Heat input into water circuit";
  Modelica.SIunits.TemperatureDifference TAppAct(min=0, nominal=1, displayUnit="K") 
    "Actual approach temperature";

protected 
  Modelica.SIunits.Temperature TAirHT 
    "Air temperature that is used to compute the heat transfer with the water";
  Modelica.Thermal.HeatTransfer.Sources.PrescribedHeatFlow preHea 
    "Prescribed heat flow";
  Modelica.Blocks.Sources.RealExpression QWat_flow(y=m_flow*(
        Medium.specificEnthalpy(Medium.setState_pTX(
        p=port_b.p,
        T=TAirHT + TAppAct,
        X=inStream(port_b.Xi_outflow))) - inStream(port_a.h_outflow))) 
    "Heat input into water";
  Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor T_Vol 
    "Water temperature in volume, or leaving water temperature";

equation 
  connect(preHea.port, vol.heatPort);
  connect(QWat_flow.y, preHea.Q_flow);
  connect(T_Vol.port, vol.heatPort);
  connect(T_Vol.T, TLvg);
end CoolingTower;

Automatically generated Wed Feb 22 15:22:15 2012.