Buildings.Examples.VAVCO2

Information

Package Content

Name	Description
VAVSystemCTControl	Variable air volume flow system of MIT building with CO2 control and continuous time control for static pressure reset
BaseClasses	Package with base classes for Buildings.Examples.VAVCO2

Buildings.Examples.VAVCO2.VAVSystemCTControl

Information

This examples demonstrates the implementation of CO₂ control for a variable air volume flow system. Each room has a CO₂ source. Depending on the CO₂ concentrations, the air dampers in the room open or close. The supply and return fans are controlled to provide a constant static pressure.

Note that this example does not control the room temperature and the heat flow through the building envelope. It only implements the CO₂ source and the damper and fan control to maintain a CO₂ concentration in the room below 700 PPM.

Because the building envelope is idealized as having no leakage, the supply and return fan are controlled so that they both receive the same control signal. If the return fan were controlled so that it tracks the volume flow rate of the supply fan, then there would be multiple solutions for the control signal as the split between pressure raise of the supply fan and pressure raise of the return fan is arbitrary.

Parameters

Type	Name	Default	Description
MassFlowRate	mMIT_flow	roo.m0Tot_flow	Nominal mass flow rate of MIT system model as in ASHRAE 825-RP [kg/s]
Pressure	dpSuiSup_nominal	95	Pressure drop supply air leg with splitters of one suite (obtained from simulation) [Pa]
Pressure	dpSuiRet_nominal	233	Pressure drop return air leg with splitters of one suite (obtained from simulation) [Pa]
Pressure	dpFanSupMIT_nominal	1050	Pressure increase over supply fan in MIT system model as in ASHRAE 825-RP (obtained from simulation) [Pa]
Pressure	dpFanRetMIT_nominal	347	Pressure increase over supply fan in MIT system model as in ASHRAE 825-RP (obtained from simulation) [Pa]
Real	scaM_flow	1	Scaling factor for mass flow rate
Real	scaDpFanSup_nominal	1	Scaling factor for supply fan pressure lift with NSui number of suites
Real	scaDpFanRet_nominal	1	Scaling factor for supply fan pressure lift with NSui number of suites

Modelica definition

model VAVSystemCTControl 
  "Variable air volume flow system of MIT building with CO2 control and continuous time control for static pressure reset"
  extends Modelica.Icons.Example;
 package Medium = Buildings.Media.GasesPTDecoupled.SimpleAir(extraPropertiesNames={"CO2"});
 parameter Modelica.SIunits.MassFlowRate mMIT_flow = roo.m0Tot_flow 
    "Nominal mass flow rate of MIT system model as in ASHRAE 825-RP";
parameter Modelica.SIunits.Pressure dpSuiSup_nominal = 95 
    "Pressure drop supply air leg with splitters of one suite (obtained from simulation)";
parameter Modelica.SIunits.Pressure dpSuiRet_nominal = 233 
    "Pressure drop return air leg with splitters of one suite (obtained from simulation)";
parameter Modelica.SIunits.Pressure dpFanSupMIT_nominal = 1050 
    "Pressure increase over supply fan in MIT system model as in ASHRAE 825-RP (obtained from simulation)";
parameter Modelica.SIunits.Pressure dpFanRetMIT_nominal = 347 
    "Pressure increase over supply fan in MIT system model as in ASHRAE 825-RP (obtained from simulation)";
parameter Real scaM_flow = 1 "Scaling factor for mass flow rate";
parameter Real scaDpFanSup_nominal = 1 
    "Scaling factor for supply fan pressure lift with NSui number of suites";
parameter Real scaDpFanRet_nominal = 1 
    "Scaling factor for supply fan pressure lift with NSui number of suites";
  Modelica.Blocks.Sources.Constant PAtm(k=101325);
  Modelica.Blocks.Sources.Constant yDam(k=0.5);
Buildings.Fluid.FixedResistances.FixedResistanceDpM res31(
                                               dp_nominal=0.546,
  m_flow_nominal=scaM_flow*1,
  dh=sqrt(scaM_flow)*1,
  redeclare package Medium = Medium);
Buildings.Fluid.FixedResistances.FixedResistanceDpM res33(
  dp_nominal=0.164,
  dh=sqrt(scaM_flow)*1,
  m_flow_nominal=scaM_flow*1,
  redeclare package Medium = Medium);
Buildings.Fluid.FixedResistances.FixedResistanceDpM res57(
                                               dp_nominal=0.118000,
  m_flow_nominal=scaM_flow*1,
  dh=sqrt(scaM_flow)*1,
  redeclare package Medium = Medium);
Buildings.Examples.VAVCO2.BaseClasses.Suite roo(redeclare package Medium = Medium, scaM_flow=scaM_flow);
Fluid.Actuators.Dampers.MixingBox mixBox(
  dpOut_nominal=0.467,
  dpRec_nominal=0.665,
  AOut=scaM_flow*1.32,
  AExh=scaM_flow*1.05,
  ARec=scaM_flow*1.05,
  mOut_flow_nominal=scaM_flow*1,
  mRec_flow_nominal=scaM_flow*1,
  mExh_flow_nominal=scaM_flow*1,
  redeclare package Medium = Medium,
    dpExh_nominal=0.467,
    allowFlowReversal=true) "mixing box";
  Buildings.Fluid.Sources.Boundary_pT bouIn(
    redeclare package Medium = Medium,
    use_p_in=true,
    T=293.15,
    nPorts=2);
  inner Modelica.Fluid.System system;
   Buildings.Controls.Continuous.LimPID conSupFan(
    Ti=60,
    yMax=1,
    yMin=0,
    Td=60,
    k=0.1,
    initType=Modelica.Blocks.Types.InitPID.InitialState,
    controllerType=Modelica.Blocks.Types.SimpleController.P) 
    "Controller for supply fan";
  Fluid.Movers.FlowMachine_y fan32(
    redeclare package Medium = Medium,
    pressure(final V_flow={0,11.08,14.9}, dp={1508,743,100}),
    dynamicBalance=true,
    r_N(start=0));
  Fluid.Movers.FlowMachine_y fan56(
    redeclare package Medium = Medium,
    pressure(final V_flow={2.676,11.05}, dp={600,100}),
    dynamicBalance=true,
    r_N(start=0));
  Modelica.Blocks.Sources.Trapezoid
                                pSet(
    amplitude=120,
    period=86400,
    width=86400/2,
    falling=10,
    rising=120,
    startTime=6*3600) "Pressure setpoint (0 during night, 120 during day)";
equation 
  connect(PAtm.y, bouIn.p_in);
  connect(roo.p_rel, conSupFan.u_m);
  connect(yDam.y, mixBox.y);
  connect(roo.p, PAtm.y);
  connect(mixBox.port_Sup, res31.port_a);
  connect(res31.port_b, fan32.port_a);
  connect(res57.port_b, mixBox.port_Ret);
  connect(res33.port_b, roo.port_aSup);
  connect(bouIn.ports[1], mixBox.port_Out);
  connect(bouIn.ports[2], mixBox.port_Exh);
  connect(fan56.port_b, res57.port_a);
  connect(fan32.port_b, res33.port_a);
  connect(fan56.port_a, roo.port_bExh);
  connect(pSet.y, conSupFan.u_s);
  connect(conSupFan.y, fan32.y);
  connect(conSupFan.y, fan56.y);
end VAVSystemCTControl;