modelPartialIndirect

Partial indirect energy transfer station for district energy systems

Extends from Buildings.DHC.ETS.BaseClasses.PartialETS.

Information

Indirect cooling energy transfer station (ETS) model that controls the building chilled water supply temperature by modulating a primary control valve on the district supply side. The design is based on a typical district cooling ETS described in ASHRAE's District Cooling Guide. As shown in the figure below, the building pumping design (constant/variable) is specified on the building side and not within the ETS.

DHC.ETS.Indirect

Reference

American Society of Heating, Refrigeration and Air-Conditioning Engineers. (2019). Chapter 5: End User Interface. In District Cooling Guide, Second Edition and Owner's Guide for Buildings Served by District Cooling.

Parameters

TypeNameDefaultDescription
Nominal condition
Modelica.Units.SI.MassFlowRatemDis_flow_nominalNominal mass flow rate of district side
Modelica.Units.SI.MassFlowRatemBui_flow_nominalNominal mass flow rate of building side
Modelica.Units.SI.PressureDifferencedpConVal_nominal6000Nominal pressure drop of fully open control valve
Heat exchanger
Modelica.Units.SI.PressureDifferencedp1_nominalNominal pressure difference on primary side
Modelica.Units.SI.PressureDifferencedp2_nominalNominal pressure difference on secondary side
Booleanuse_Q_flow_nominaltrueSet to true to specify Q_flow_nominal and temeratures, or to false to specify effectiveness
Modelica.Units.SI.HeatFlowRateQ_flow_nominalNominal heat transfer (positive for heat transfer from district to building)
Modelica.Units.SI.TemperatureT_a1_nominalNominal temperature at port a1 (district supply)
Modelica.Units.SI.TemperatureT_a2_nominalNominal temperature at port a2 (building return)
Modelica.Units.SI.Efficiencyeta0.8Constant effectiveness
PID controller
Modelica.Blocks.Types.SimpleControllercontrollerTypeModelica.Blocks.Types.SimpleController.PIType of controller
Realk1Gain of controller
Modelica.Units.SI.TimeTi120Time constant of integrator block
Modelica.Units.SI.TimeTd0.1Time constant of derivative block
RealyMax1Upper limit of output
RealyMin0.01Lower limit of output

Components

TypeNameDefaultDescription
Modelica.Blocks.Interfaces.RealInputTBuiSupSetSetpoint temperature for building supply
Modelica.Blocks.Interfaces.RealOutputQ_flowMeasured heating demand at the ETS
Modelica.Blocks.Interfaces.RealOutputQMeasured energy consumption at the ETS
Buildings.Fluid.Sensors.TemperatureTwoPortsenTDisSupDistrict supply temperature sensor
Buildings.Fluid.Sensors.MassFlowRatesenMasFloDistrict supply mass flow rate sensor
Buildings.Fluid.Actuators.Valves.TwoWayEqualPercentageconValControl valve
Buildings.Fluid.HeatExchangers.PlateHeatExchangerEffectivenessNTUhexHeat exchanger
Buildings.Fluid.Sensors.TemperatureTwoPortsenTDisRetDistrict return temperature sensor
Buildings.Fluid.Sensors.TemperatureTwoPortsenTBuiRetBuilding return temperature sensor
Buildings.Fluid.Sensors.TemperatureTwoPortsenTBuiSupBuilding supply temperature sensor
Controls.OBC.CDL.Reals.PIDconBuilding supply temperature controller
Modelica.Blocks.Math.AdddTDisTemperature difference on the district side
Modelica.Blocks.Math.Productproproduct
Modelica.Blocks.Math.GaincpSpecific heat multiplier to calculate heat flow rate
Modelica.Blocks.Continuous.IntegratorintIntegration

Revisions

  • March 11, 2024, by Michael Wetter:
    Corrected wrong displayUnit string.
  • April 7, 2023, by David Blum:
    Changed to partial base class for indirect so can extend to heating and cooling ETS.
  • January 11, 2023, by Michael Wetter:
    Changed controls to use CDL. Changed PID to PI as default for controller.
  • March 21, 2022, by Chengnan Shi:
    Update with base class partial model.
  • Novermber 13, 2019, by Kathryn Hinkelman:
    First implementation.