modelVAVSystemCTControl
Extends from Modelica.Icons.Example (Icon for runnable examples).
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 |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | mMIT_flow | roo.m0Tot_flow | Nominal mass flow rate of MIT system model as in ASHRAE 825-RP |
| Modelica.Units.SI.PressureDifference | dpSuiSup_nominal | 95 | Pressure drop supply air leg with splitters of one suite (obtained from simulation) |
| Modelica.Units.SI.PressureDifference | dpSuiRet_nominal | 233 | Pressure drop return air leg with splitters of one suite (obtained from simulation) |
| Modelica.Units.SI.PressureDifference | dpFanSupMIT_nominal | 1050 | Pressure increase over supply fan in MIT system model as in ASHRAE 825-RP (obtained from simulation) |
| Modelica.Units.SI.PressureDifference | dpFanRetMIT_nominal | 347 | Pressure increase over supply fan in MIT system model as in ASHRAE 825-RP (obtained from simulation) |
| 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 |
| Damper coefficients | |||
| Real | l | 6.708204E-04 | Damper leakage, ratio of flow coefficients k(y=0)/k(y=1) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Sources.Constant | PAtm | ||
| Modelica.Blocks.Sources.Constant | yDam | ||
| Buildings.Fluid.FixedResistances.PressureDrop | res31 | ||
| Buildings.Fluid.FixedResistances.PressureDrop | res33 | ||
| Buildings.Fluid.FixedResistances.PressureDrop | res57 | ||
| Buildings.Examples.VAVCO2.BaseClasses.Suite | roo | ||
| Fluid.Actuators.Dampers.MixingBox | mixBox | mixing box | |
| Buildings.Fluid.Sources.Boundary_pT | bouIn | ||
| Buildings.Controls.Continuous.LimPID | conSupFan | Controller for supply fan | |
| Buildings.Fluid.Movers.FlowControlled_dp | fan32 | ||
| Buildings.Fluid.Movers.FlowControlled_dp | fan56 | ||
| Modelica.Blocks.Sources.BooleanPulse | onSig | On/off signal for plant | |
| Modelica.Blocks.Math.Gain | dp32 | Gain for fan | |
| Modelica.Blocks.Math.Gain | dp56 | Gain for fan | |
| Modelica.Blocks.Logical.Switch | switch1 | ||
| Modelica.Blocks.Sources.Constant | off | Off signal | |
| Controls.OBC.CDL.Conversions.BooleanToReal | booToRea | Boolean to real conversion, outputs static pressure set point | |
| Controls.OBC.CDL.Reals.LimitSlewRate | ramLim | Ramp limiter for fan control signal |
Contents
| Name | Description |
|---|---|
 Medium |
Revisions
-
July 12, 2019, by Michael Wetter:
Simplified computation of on/off signal. Used slew rate limiter for fan control signal rather than 2nd order filter, as this reduces computing time in JModelica by a factor of two. -
January 20, 2017, by Michael Wetter:
Changed the fan control so that they have a control signal of exactly zero if the setpoint for the duct static pressure is zero. This leads to about a four times faster simulation as previously, a very small control signal was received by the fan during the night hours.
This is for #628. -
March 22, 2016, by Michael Wetter:
Changed the fan model to use pressure as an input, which makes the model simulate twenty times faster. -
January 22, 2016, by Michael Wetter:
Corrected type declaration of pressure difference. This is for #404.