modelPartialDataCenter

Partial model that impliments cooling system for data centers
Diagram of PartialDataCenterOpen the diagram

Information

This is a partial model that describes the chilled water cooling system in a data center. The sizing data are collected from the reference.

Reference

  • Taylor, S. T. (2014). How to design & control waterside economizers. ASHRAE Journal, 56(6), 30-36.

Parameters

TypeNameDefaultDescription
IntegernumChi2Number of chillers
Modelica.Units.SI.MassFlowRatem1_flow_chi_nominal34.7Nominal mass flow rate at condenser water in the chillers
Modelica.Units.SI.MassFlowRatem2_flow_chi_nominal18.3Nominal mass flow rate at evaporator water in the chillers
Modelica.Units.SI.PressureDifferencedp1_chi_nominal46.2*1000Nominal pressure
Modelica.Units.SI.PressureDifferencedp2_chi_nominal44.8*1000Nominal pressure
Modelica.Units.SI.PowerQEva_nominalm2_flow_chi_nominal*4200*(6.67 - 18.56)Nominal cooling capaciaty(Negative means cooling)
Modelica.Units.SI.MassFlowRatem1_flow_wse_nominal34.7Nominal mass flow rate at condenser water in the chillers
Modelica.Units.SI.MassFlowRatem2_flow_wse_nominal35.3Nominal mass flow rate at condenser water in the chillers
Modelica.Units.SI.PressureDifferencedp1_wse_nominal33.1*1000Nominal pressure
Modelica.Units.SI.PressureDifferencedp2_wse_nominal34.5*1000Nominal pressure
Buildings.Fluid.Movers.Data.GenericperPumCWPerformance data for condenser water pumps
Modelica.Units.SI.TimetWai1200Waiting time
Modelica.Units.SI.ThermalConductanceUA_nominalnumChi*QEva_nominal/Buildings.Fluid.HeatExchangers.BaseClasses.lmtd(6.67, 11.56, 12, 25)Thermal conductance at nominal flow for sensible heat, used to compute time constant
Modelica.Units.SI.MassFlowRatemAir_flow_nominal161.35Nominal air mass flowrate
RealyValMinAHU0.1Minimum valve openning position
Modelica.Units.SI.TemperatureTCHWSet273.15 + 8Chilled water temperature setpoint
Modelica.Units.SI.TemperatureTSupAirSetTCHWSet + 10Supply air temperature setpoint
Modelica.Units.SI.TemperatureTRetAirSet273.15 + 25Supply air temperature setpoint
Modelica.Units.SI.PressuredpSetPoi80000Differential pressure setpoint
Fluid.HeatExchangers.CoolingTowers.Data.YorkCalc.GenericdatCooTowCooling tower performance data

Connectors

TypeNameDefaultDescription
Buildings.BoundaryConditions.WeatherData.BusweaBusWeather data bus

Components

TypeNameDefaultDescription
Buildings.Applications.DataCenters.ChillerCooled.Equipment.BaseClasses.PartialChillerWSEchiWSEChillers and waterside economizer
Buildings.Fluid.Sources.Boundary_pTexpVesCWExpansion tank
Buildings.Fluid.HeatExchangers.CoolingTowers.YorkCalc[numChi]cooTowCooling tower
Buildings.Fluid.Sensors.TemperatureTwoPortTCHWSupChilled water supply temperature
Buildings.BoundaryConditions.WeatherData.ReaderTMY3weaData
Buildings.Fluid.Sensors.TemperatureTwoPortTCWSupCondenser water supply temperature
Buildings.Fluid.Sensors.TemperatureTwoPortTCWRetCondenser water return temperature
Buildings.Fluid.Movers.FlowControlled_m_flow[numChi]pumCWCondenser water pump
Buildings.Applications.DataCenters.ChillerCooled.Equipment.CoolingCoilHumidifyingHeatingahuAir handling unit
Buildings.Fluid.Sensors.TemperatureTwoPortTCHWRetChilled water return temperature
Buildings.Fluid.Sources.Boundary_pTexpVesChiExpansion tank
Buildings.Fluid.Sensors.RelativePressuresenRelPreDifferential pressure
Buildings.Fluid.Sensors.TemperatureTwoPortTAirSupSupply air temperature
Buildings.Examples.ChillerPlant.DataCenter.BaseClasses.SimplifiedRoomrooRoom model
Buildings.Fluid.Actuators.Valves.TwoWayLinear[numChi]valShutoff valves
Modelica.Blocks.Sources.ConstantTCHWSupSetChilled water supply temperature setpoint
Buildings.Applications.DataCenters.ChillerCooled.Controls.ChillerStagechiStaConChiller staging control
Modelica.Blocks.Math.RealToBoolean[numChi]chiOnReal value to boolean value
Modelica.Blocks.Math.IntegerToBooleanintToBooInverse on/off signal for the WSE
Modelica.Blocks.Logical.NotwseOnTrue: WSE is on; False: WSE is off
Buildings.Applications.DataCenters.ChillerCooled.Controls.ConstantSpeedPumpStageCWPumConCondenser water pump controller
Modelica.Blocks.Sources.IntegerExpressionchiNumOnThe number of running chillers
Modelica.Blocks.Math.Gain[numChi]gaiGain effect
Buildings.Applications.DataCenters.ChillerCooled.Controls.CoolingTowerSpeedcooTowSpeConCooling tower speed control
Modelica.Blocks.Sources.RealExpressionTCWSupSetCondenser water supply temperature setpoint
Modelica.Blocks.Sources.ConstantTAirSupSetSupply air temperature setpoint
Buildings.Applications.BaseClasses.Controls.VariableSpeedPumpStagevarSpeConSpeed controller
Modelica.Blocks.Sources.RealExpressionmPum_flowMass flowrate of variable speed pumps
Buildings.Controls.Continuous.LimPIDpumSpePump speed controller
Modelica.Blocks.Sources.ConstantdpSetScaScaled differential pressure setpoint
Modelica.Blocks.Math.Product[numChi]pumSpeSigPump speed signal
Buildings.Controls.Continuous.LimPIDahuValSigValve position signal for the AHU
Modelica.Blocks.Math.Product[numChi]cooTowSpeCooling tower speed
Buildings.Controls.Continuous.LimPIDahuFanSpeConFan speed controller
Modelica.Blocks.Sources.ConstantTAirRetSetReturn air temperature setpoint
Utilities.Psychrometrics.X_pTphiXAirSupSetMass fraction setpoint of supply air
Modelica.Blocks.Sources.ConstantphiAirRetSetReturn air relative humidity setpoint
Modelica.Blocks.Math.Gaingai1Gain effect
Buildings.Controls.OBC.CDL.Reals.Switch[numChi]swiSwitch to assign pump signal if plant is on
Buildings.Controls.OBC.CDL.Logical.OrplaOnOutput true if plant is on
Buildings.Controls.OBC.CDL.Reals.Sources.Constant[numChi]zerOutputs zero
Modelica.Blocks.MathBoolean.OrchiOnStaOutput true if at least one chiller is on

Contents

NameDescription
MediumAMedium model
MediumWMedium model

Revisions

  • April 27, 2026, by Michael Wetter:
    Refactored for new cooling tower implementation.
    This is for issue 4567.
  • September 3, 2024, by Jianjun Hu:
    Added plant on signal to control the pump speed. This is for issue 3989.
  • January 2, 2022, by Kathryn Hinkelman:
    Passed the plaOn signal to the chilled water pump control to turn them off when the plant is off.
  • November 16, 2022, by Michael Wetter:
    Corrected control to avoid cooling tower pumps to operate when plant is off, because shut-off valves are off when plant is off.
  • November 1, 2021, by Michael Wetter:
    Corrected weather data bus connection which was structurally incorrect and did not parse in OpenModelica.
    This is for issue 2706.
  • October 6, 2020, by Michael Wetter:
    Set val.use_inputFilter=false because pump worked against closed valve at t=60 seconds, leading to negative pressure at pump inlet (because pump forces the mass flow rate).
  • January 12, 2019, by Michael Wetter:
    Removed wrong each.
  • December 1, 2017, by Yangyang Fu:
    Used scaled differential pressure to control the speed of pumps. This can avoid retuning gains in PID when changing the differential pressure setpoint.
  • September 2, 2017, by Michael Wetter:
    Changed expansion vessel to use the more efficient implementation.
  • July 30, 2017, by Yangyang Fu:
    First implementation.