Buildings.DHC.Examples.Combined
Package of example models for DHC systems
Information
This package contains example models for district heating and cooling systems.
Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).
Package Content
| Name | Description |
|---|---|
 SeriesConstantFlow
|
Example of series connection with constant district water mass flow rate |
| SeriesVariableFlow
|
Example of series connection with variable district water mass flow rate |
| SeriesVariableFlowAgentControl
|
Example of series connection with variable district water mass flow rate with updated agent controller |
 BaseClasses
|
Package with base classes that are used by multiple models |
Buildings.DHC.Examples.Combined.SeriesConstantFlow
Example of series connection with constant district water mass flow rate
Information
This is a model of a so-called "reservoir network" (Sommer 2020), i.e., a fifth
generation district system with unidirectional mass flow rate in the
district loop, and energy transfer stations connected in series.
In this model, the temperature of the district loop is stabilized through
the operation of the plant and the borefield.
The main circulation pump has a constant mass flow rate.
Each substation takes water from the main district loop and feeds its return water back
into the main district loop downstream from the intake.
The pipes of the main loop are designed for a pressure drop of
dpDis_length_nominal=250 Pa/m at the design flow rate.
References
Sommer T., Sulzer M., Wetter M., Sotnikov A., Mennel S., Stettler C. The reservoir network: A new network topology for district heating and cooling. Energy, Volume 199, 15 May 2020, 117418.
Extends from Buildings.DHC.Examples.Combined.BaseClasses.PartialSeries (Partial model for series network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | dpDis_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate - Distribution line [Pa/m] |
| Real | dpCon_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate - Connection line [Pa/m] |
| Length | dhSto | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Length | dhPla | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Integer | nBui | datDes.nBui | Number of buildings connected to DHC system |
| String | filNam[nBui] | {"modelica://Buildings/Resou... | Library paths of the files with thermal loads as time series |
| Assumptions | |||
| Boolean | allowFlowReversalSer | true | Set to true to allow flow reversal in the service lines |
| Boolean | allowFlowReversalBui | false | Set to true to allow flow reversal for in-building systems |
Modelica definition
model SeriesConstantFlow
"Example of series connection with constant district water mass flow rate"
extends Buildings.DHC.Examples.Combined.BaseClasses.PartialSeries(redeclare Buildings.DHC.Loads.Combined.BuildingTimeSeriesWithETS
bui[nBui](final filNam=filNam),
datDes(
mPumDis_flow_nominal=95,
mPipDis_flow_nominal=95,
dp_length_nominal=69.3,
epsPla=0.935),
pumSto(dp_nominal=30000));
parameter String filNam[nBui]={
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissOffice_20190916.mos",
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissResidential_20190916.mos",
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissHospital_20190916.mos"}
"Library paths of the files with thermal loads as time series";
Modelica.Blocks.Sources.Constant masFloMaiPum(
k=datDes.mPumDis_flow_nominal)
"Distribution pump mass flow rate";
Modelica.Blocks.Sources.Constant masFloDisPla(
k=datDes.mPla_flow_nominal)
"District water flow rate to plant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant THotWatSupSet[nBui](
k=fill(63 + 273.15, nBui))
"Hot water supply temperature set point";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant TColWat[nBui](
k=fill(15 + 273.15, nBui))
"Cold water temperature";
Networks.Distribution1Pipe_R dis(
redeclare final package Medium = Medium,
final nCon=nBui,
show_TOut=true,
final mDis_flow_nominal=datDes.mPipDis_flow_nominal,
final mCon_flow_nominal=datDes.mCon_flow_nominal,
final dp_length_nominal=datDes.dp_length_nominal,
final lDis=datDes.lDis,
final lEnd=datDes.lEnd,
final allowFlowReversal=allowFlowReversalSer) "Distribution network";
Modelica.Blocks.Sources.Constant TSewWat(k=273.15 + 17)
"Sewage water temperature";
equation
connect(masFloMaiPum.y, pumDis.m_flow_in);
connect(pumSto.m_flow_in, masFloMaiPum.y);
connect(masFloDisPla.y, pla.mPum_flow);
connect(THotWatSupSet.y, bui.THotWatSupSet);
connect(TColWat.y, bui.TColWat);
connect(TDisWatSup.port_b, dis.port_aDisSup);
connect(dis.port_bDisSup, TDisWatRet.port_a);
connect(TSewWat.y, pla.TSewWat);
connect(bui.port_bSerAmb, dis.ports_aCon);
connect(dis.ports_bCon, bui.port_aSerAmb);
end SeriesConstantFlow;
Buildings.DHC.Examples.Combined.SeriesVariableFlow
Example of series connection with variable district water mass flow rate
Information
This model is identical to Buildings.DHC.Examples.Combined.SeriesConstantFlow except for the pipe diameter and the control of the main circulation pump. Rather than having a constant mass flow rate, the mass flow rate is varied based on the mixing temperatures after each agent. If these mixing temperatures are sufficiently far away from the minimum or maximum allowed loop temperature, then the mass flow rate is reduced to save pump energy.
Extends from Buildings.DHC.Examples.Combined.BaseClasses.PartialSeries (Partial model for series network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | dpDis_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate - Distribution line [Pa/m] |
| Real | dpCon_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate - Connection line [Pa/m] |
| Length | dhSto | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Length | dhPla | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Integer | nBui | datDes.nBui | Number of buildings connected to DHC system |
| String | filNam[nBui] | {"modelica://Buildings/Resou... | Library paths of the files with thermal loads as time series |
| Assumptions | |||
| Boolean | allowFlowReversalSer | true | Set to true to allow flow reversal in the service lines |
| Boolean | allowFlowReversalBui | false | Set to true to allow flow reversal for in-building systems |
Modelica definition
model SeriesVariableFlow
"Example of series connection with variable district water mass flow rate"
extends Buildings.DHC.Examples.Combined.BaseClasses.PartialSeries(redeclare Buildings.DHC.Loads.Combined.BuildingTimeSeriesWithETS
bui[nBui](final filNam=filNam),
datDes(
mPumDis_flow_nominal=97.3,
mPipDis_flow_nominal=69.5,
dp_length_nominal=69.3,
epsPla=0.91),
pumSto(dp_nominal=30000));
parameter String filNam[nBui]={
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissOffice_20190916.mos",
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissResidential_20190916.mos",
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissHospital_20190916.mos"}
"Library paths of the files with thermal loads as time series";
Modelica.Blocks.Sources.Constant masFloDisPla(
k=datDes.mPla_flow_nominal)
"District water flow rate to plant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant THotWatSupSet[nBui](
k=fill(63 + 273.15, nBui))
"Hot water supply temperature set point";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant TColWat[nBui](
k=fill(15 + 273.15, nBui))
"Cold water temperature";
Buildings.DHC.Networks.Controls.MainPump1Pipe conPum(
nMix=nBui,
nSou=2,
nBui=nBui,
TMin=279.15,
TMax=290.15,
use_temperatureShift=false) "Main pump controller";
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter gai(k=datDes.mPumDis_flow_nominal)
"Scale with nominal mass flow rate";
Networks.Distribution1Pipe_R dis(
redeclare final package Medium = Medium,
final nCon=nBui,
show_TOut=true,
final mDis_flow_nominal=datDes.mPipDis_flow_nominal,
final mCon_flow_nominal=datDes.mCon_flow_nominal,
final dp_length_nominal=datDes.dp_length_nominal,
final lDis=datDes.lDis,
final lEnd=datDes.lEnd,
final allowFlowReversal=allowFlowReversalSer) "Distribution network";
Modelica.Blocks.Sources.Constant TSewWat(k=273.15 + 17)
"Sewage water temperature";
equation
connect(THotWatSupSet.y, bui.THotWatSupSet);
connect(TColWat.y, bui.TColWat);
connect(pumDis.m_flow_in, gai.y);
connect(conPum.y, gai.u);
connect(dis.TOut, conPum.TMix);
connect(TDisWatRet.T, conPum.TSouIn[1]);
connect(TDisWatBorLvg.T, conPum.TSouIn[2]);
connect(TDisWatBorLvg.T, conPum.TSouOut[1]);
connect(TDisWatSup.T, conPum.TSouOut[2]);
connect(gai.y, pumSto.m_flow_in);
connect(masFloDisPla.y, pla.mPum_flow);
connect(TSewWat.y, pla.TSewWat);
connect(TDisWatSup.port_b, dis.port_aDisSup);
connect(TDisWatRet.port_a, dis.port_bDisSup);
connect(bui.port_aSerAmb, dis.ports_bCon);
connect(bui.port_bSerAmb, dis.ports_aCon);
connect(bui.QCoo_flow, conPum.QCoo_flow);
end SeriesVariableFlow;
Buildings.DHC.Examples.Combined.SeriesVariableFlowAgentControl
Example of series connection with variable district water mass flow rate with updated agent controller
Information
This model is an updated version of Buildings.DHC.Examples.Combined.SeriesVariableFlow. In particular the following have been updated:
- The sewage water temperature, mass flow rate and ground temperature are not constant and instead have a seasonal yearly profile.
- The distribution network pripes now use the plug-flow model to add transport delay and ground coupling to the distribution network.
- The borefield and sewagre heat exchanger circulation pumps are controlled by an agent specific controller Buildings.DHC.Networks.Controls.AgentPump1Pipe.
References
Ettore Zanetti, David Blum, Michael Wetter (2023) Control development and sizing analysis for a 5th generation district heating and cooling network using Modelica, In Proceedings of the 15th International Modelica Conference. Aachen, Germany, Oct 9-11, 2023.
Extends from Buildings.DHC.Examples.Combined.BaseClasses.PartialSeries (Partial model for series network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | dpDis_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate - Distribution line [Pa/m] |
| Real | dpCon_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate - Connection line [Pa/m] |
| Length | dhSto | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Length | dhPla | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Integer | nBui | datDes.nBui | Number of buildings connected to DHC system |
| String | filNam[nBui] | {"modelica://Buildings/Resou... | Library paths of the files with thermal loads as time series |
| Length | diameter | sqrt(4*datDes.mPipDis_flow_n... | Pipe diameter (without insulation) [m] |
| Height | lDisPip | 200 | Distribution pipes length [m] |
| Radius | rPip | diameter/2 | Pipe external radius [m] |
| Radius | thiGroLay | 0.5 | Dynamic ground layer thickness [m] |
| Assumptions | |||
| Boolean | allowFlowReversalSer | true | Set to true to allow flow reversal in the service lines |
| Boolean | allowFlowReversalBui | false | Set to true to allow flow reversal for in-building systems |
Modelica definition
model SeriesVariableFlowAgentControl
"Example of series connection with variable district water mass flow rate with updated agent controller"
extends Buildings.DHC.Examples.Combined.BaseClasses.PartialSeries(redeclare Buildings.DHC.Loads.Combined.BuildingTimeSeriesWithETS
bui[nBui](final filNam=filNam),
datDes(
mPumDis_flow_nominal=97.3,
mPipDis_flow_nominal=69.5,
mSto_flow_nominal=75,
dpPla_nominal(displayUnit="bar") = 50000,
TLooMin=279.15,
dp_length_nominal=250,
epsPla=0.91),
pumSto(dp_nominal=40000));
parameter String filNam[nBui]={
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissOffice_20190916.mos",
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissResidential_20190916.mos",
"modelica://Buildings/Resources/Data/DHC/Loads/Examples/SwissHospital_20190916.mos"}
"Library paths of the files with thermal loads as time series";
parameter Modelica.Units.SI.Length diameter=sqrt(4*datDes.mPipDis_flow_nominal/1000/1.5/Modelica.Constants.pi)
"Pipe diameter (without insulation)";
parameter Modelica.Units.SI.Height lDisPip=200 "Distribution pipes length";
parameter Modelica.Units.SI.Radius rPip=diameter/2 "Pipe external radius";
parameter Modelica.Units.SI.Radius thiGroLay=0.5
"Dynamic ground layer thickness";
Modelica.Blocks.Sources.Constant masFloDisPla(
k=datDes.mPla_flow_nominal)
"District water flow rate to plant";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant THotWatSupSet[nBui](
k=fill(63 + 273.15, nBui))
"Hot water supply temperature set point";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant TColWat[nBui](
k=fill(15 + 273.15, nBui))
"Cold water temperature";
Buildings.DHC.Networks.Controls.MainPump1Pipe conPum(
nMix=nBui,
nSou=2,
nBui=nBui,
TMin=279.15,
TMax=290.15,
dTSlo=1.5) "Main pump controller";
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter gai(k=datDes.mPumDis_flow_nominal)
"Scale with nominal mass flow rate";
Modelica.Blocks.Sources.CombiTimeTable HXtemperature(table=[0,14 + 273.15; 60
*86400,12 + 273.15; 210*86400,20 + 273.15; 365*86400,14 + 273.15],
extrapolation=Modelica.Blocks.Types.Extrapolation.Periodic);
Modelica.Blocks.Math.Product product1;
.Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter gai1(k=datDes.mSto_flow_nominal)
"Scale with nominal mass flow rate";
Fluid.Sensors.TemperatureTwoPort TDisWatSup1(redeclare final package Medium =
Medium, final m_flow_nominal=datDes.mPumDis_flow_nominal)
"District water supply temperature";
Fluid.Sensors.TemperatureTwoPort TDisWatRet1(redeclare final package Medium =
Medium, final m_flow_nominal=datDes.mPumDis_flow_nominal)
"District water return temperature";
Fluid.FixedResistances.BuriedPipes.PipeGroundCoupling pipeGroundCouplingMulti[nBui + 3](
each lPip=lDisPip,
each rPip=rPip,
each thiGroLay=thiGroLay,
each nSeg=1,
redeclare parameter Buildings.HeatTransfer.Data.Soil.Generic soiDat(
each k=2.3,
each c=1000,
each d=2600));
Buildings.DHC.Networks.Controls.AgentPump1Pipe pumPlantControlNsew(
yPumMin=0,
dToff=0.5,
k=0.8,
Ti=600,
uLowHea=0.75,
uHighHea=1.5,
h=0.5);
Buildings.DHC.Networks.Controls.AgentPump1Pipe pumPlantControlNsewSto(
yPumMin=0,
dToff=0.45,
k=1.1,
Ti=600,
uLowHea=0.25,
uHighHea=0.5,
uLowCoo=0.15,
uHighCoo=0.4);
Networks.Distribution1PipePlugFlow_v dis(
nCon=nBui,
allowFlowReversal=allowFlowReversalSer,
redeclare package Medium = Medium,
show_TOut=true,
mDis_flow_nominal=datDes.mPipDis_flow_nominal,
mCon_flow_nominal=datDes.mCon_flow_nominal,
lDis=datDes.lDis,
lEnd=datDes.lEnd,
dIns=0.02,
kIns=0.2);
Fluid.FixedResistances.PlugFlowPipe supDisPluFlo(
redeclare package Medium = Medium,
allowFlowReversal=allowFlowReversalSer,
m_flow_nominal=datDes.mPipDis_flow_nominal,
length=lDisPip,
dIns=0.02,
kIns=0.2);
Fluid.FixedResistances.PlugFlowPipe retDisPluFlo(
redeclare package Medium = Medium,
allowFlowReversal=allowFlowReversalSer,
m_flow_nominal=datDes.mPipDis_flow_nominal,
length=lDisPip,
dIns=0.02,
kIns=0.2);
equation
connect(THotWatSupSet.y, bui.THotWatSupSet);
connect(TColWat.y, bui.TColWat);
connect(pumDis.m_flow_in, gai.y);
connect(conPum.y, gai.u);
connect(TDisWatRet.T, conPum.TSouIn[1]);
connect(TDisWatBorLvg.T, conPum.TSouIn[2]);
connect(TDisWatBorLvg.T, conPum.TSouOut[1]);
connect(TDisWatSup.T, conPum.TSouOut[2]);
connect(masFloDisPla.y, product1.u1);
connect(product1.y, pla.mPum_flow);
connect(gai1.y, pumSto.m_flow_in);
connect(TDisWatBorLvg.T, pumPlantControlNsew.TSouIn);
connect(TDisWatSup.T,pumPlantControlNsew.TSouOut);
connect(TDisWatSup1.T,pumPlantControlNsew.TSupDis);
connect(TDisWatRet1.T,pumPlantControlNsew.TRetDis);
connect(borFie.TBorAve, pumPlantControlNsewSto.TSou);
connect(TDisWatRet.T, pumPlantControlNsewSto.TSouIn);
connect(TDisWatBorLvg.T,pumPlantControlNsewSto.TSouOut);
connect(TDisWatSup1.T,pumPlantControlNsewSto.TSupDis);
connect(TDisWatRet1.T,pumPlantControlNsewSto.TRetDis);
connect(pumPlantControlNsewSto.y, gai1.u);
connect(pumPlantControlNsew.y, product1.u2);
connect(TDisWatSup1.port_b, dis.port_aDisSup);
connect(dis.port_bDisSup, TDisWatRet1.port_a);
connect(dis.ports_bCon, bui.port_aSerAmb);
connect(dis.ports_aCon, bui.port_bSerAmb);
connect(dis.TOut, conPum.TMix);
connect(TDisWatSup.port_b, supDisPluFlo.port_a);
connect(supDisPluFlo.port_b, TDisWatSup1.port_a);
connect(TDisWatRet1.port_b, retDisPluFlo.port_a);
connect(retDisPluFlo.port_b, TDisWatRet.port_a);
connect(pipeGroundCouplingMulti[1:(nBui+1)].heatPorts[1], dis.heatPorts);
connect(supDisPluFlo.heatPort, pipeGroundCouplingMulti[nBui + 2].heatPorts[1]);
connect(retDisPluFlo.heatPort, pipeGroundCouplingMulti[nBui + 3].heatPorts[1]);
connect(HXtemperature.y[1], pla.TSewWat);
connect(HXtemperature.y[1], pumPlantControlNsew.TSou);
connect(bui.QCoo_flow, conPum.QCoo_flow);
end SeriesVariableFlowAgentControl;