Buildings.Experimental.DHC.Networks.Combined
Package of models for DHC distribution networks
Information
This package contains models for heating, cooling or combined distribution networks.
Extends from Modelica.Icons.Package (Icon for standard packages).
Package Content
| Name | Description |
|---|---|
 UnidirectionalParallel
|
Hydronic network for unidirectional parallel DHC system |
 UnidirectionalSeries
|
Hydronic network for unidirectional series DHC system |
 BaseClasses
|
Package with base classes for Buildings.Experimental.DHC.Networks.Combined |
Buildings.Experimental.DHC.Networks.Combined.UnidirectionalParallel
Hydronic network for unidirectional parallel DHC system
Information
This model represents a two-pipe distribution network with built-in computation of the pipe diameters based on the pressure drop per pipe length at nominal flow rate.
Extends from Buildings.Experimental.DHC.Networks.BaseClasses.PartialDistribution2Pipe (Partial model for two-pipe distribution network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium model | |
| Integer | nCon | Number of connections | |
| replaceable model Model_pipDis | Buildings.Experimental.DHC.N... | Model for distribution pipe | |
| Integer | iConDpSen | nCon | Index of the connection where the pressure drop is measured |
| Boolean | show_entFlo | false | Set to true to output enthalpy flow rate difference at each connection |
| Real | dp_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate [Pa/m] |
| Length | lDis[nCon] | Length of the distribution pipe before each connection (supply only, not counting return line) [m] | |
| Length | lCon[nCon] | Length of each connection pipe (supply only, not counting return line) [m] | |
| Length | lEnd | Length of the end of the distribution line (supply only, not counting return line) [m] | |
| Length | dhDis[nCon] | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Length | dhDisRet[nCon] | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Length | dhCon[nCon] | Hydraulic diameter of each connection pipe [m] | |
| Length | dhEnd | Hydraulic diameter of the end of the distribution line [m] | |
| Nominal condition | |||
| MassFlowRate | mDis_flow_nominal | Nominal mass flow rate in the distribution line before the first connection [kg/s] | |
| MassFlowRate | mCon_flow_nominal[nCon] | Nominal mass flow rate in each connection line [kg/s] | |
| MassFlowRate | mEnd_flow_nominal | mDis_flow_nominal - sum(mCon... | Nominal mass flow rate in the end of the distribution line [kg/s] |
| MassFlowRate | mDisCon_flow_nominal[nCon] | cat(1, {mDis_flow_nominal}, ... | Nominal mass flow rate in the distribution line before each connection [kg/s] |
| Assumptions | |||
| Boolean | allowFlowReversal | false | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Dynamics | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 5*60 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPorts_a | ports_aCon[nCon] | Connection return ports |
| FluidPorts_b | ports_bCon[nCon] | Connection supply ports |
| FluidPort_a | port_aDisSup | Distribution supply inlet port |
| FluidPort_b | port_bDisSup | Distribution supply outlet port |
| replaceable model Model_pipDis | Model for distribution pipe | |
| FluidPort_b | port_bDisRet | Distribution return outlet port |
| FluidPort_a | port_aDisRet | Distribution return inlet port |
| output RealOutput | dp | Pressure difference at given location (measured) [Pa] |
| output RealOutput | dH_flow[nCon] | Difference in enthalpy flow rate between connection supply and return [W] |
| output RealOutput | mCon_flow[nCon] | Connection supply mass flow rate (measured) [kg/s] |
Modelica definition
model UnidirectionalParallel
"Hydronic network for unidirectional parallel DHC system"
extends Buildings.Experimental.DHC.Networks.BaseClasses.PartialDistribution2Pipe
(
tau=5*60,
redeclare Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionParallelAutosize
con[nCon](
each final dp_length_nominal=dp_length_nominal,
final lDis=lDis,
final lCon=lCon,
final dhDis=dhDis,
final dhDisRet=dhDisRet,
final dhCon=dhCon),
redeclare model Model_pipDis =
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.PipeAutosize (
roughness=7e-6,
fac=1.5,
final dp_length_nominal=dp_length_nominal,
final dh(fixed=true)=dhEnd,
final length=2*lEnd));
parameter Real dp_length_nominal(final unit="Pa/m") = 250
"Pressure drop per pipe length at nominal flow rate";
parameter Modelica.Units.SI.Length lDis[nCon]
"Length of the distribution pipe before each connection (supply only, not counting return line)";
parameter Modelica.Units.SI.Length lCon[nCon]
"Length of each connection pipe (supply only, not counting return line)";
parameter Modelica.Units.SI.Length lEnd
"Length of the end of the distribution line (supply only, not counting return line)";
parameter Modelica.Units.SI.Length dhDis[nCon](
each fixed=false,
each start=0.05,
each min=0.01)
"Hydraulic diameter of the distribution pipe before each connection";
parameter Modelica.Units.SI.Length dhDisRet[nCon](
each fixed=false,
each start=0.05,
each min=0.01)
"Hydraulic diameter of the distribution pipe before each connection";
parameter Modelica.Units.SI.Length dhCon[nCon](
each fixed=false,
each start=0.05,
each min=0.01) "Hydraulic diameter of each connection pipe";
parameter Modelica.Units.SI.Length dhEnd(
fixed=false,
start=0.05,
min=0.01) "Hydraulic diameter of the end of the distribution line";
end UnidirectionalParallel;
Buildings.Experimental.DHC.Networks.Combined.UnidirectionalSeries
Hydronic network for unidirectional series DHC system
Information
This model represents a one-pipe distribution network with built-in computation of the pipe diameter based on the pressure drop per pipe length at nominal flow rate.
Modeling considerations
Note that dhDis needs to be vectorized, even if the same value
is computed for each array element in case of a one-pipe network.
This is because the pipe diameter is computed at initialization by the model
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionSeriesAutosize
which is instantiated for each connection.
So the initialization system of equations would be overdetermined if using
a parameter binding with a scalar variable.
Extends from Buildings.Experimental.DHC.Networks.BaseClasses.PartialDistribution1Pipe (Partial model for one-pipe distribution network).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium model | |
| Integer | nCon | Number of connections | |
| replaceable model Model_pipDis | Buildings.Experimental.DHC.N... | Model for distribution pipe | |
| Boolean | show_entFlo | false | Set to true to output enthalpy flow rate difference at each connection |
| Boolean | show_TOut | false | Set to true to output temperature at connection outlet |
| Real | dp_length_nominal | 250 | Pressure drop per pipe length at nominal flow rate [Pa/m] |
| Length | lDis[nCon] | Length of the distribution pipe before each connection [m] | |
| Length | lCon[nCon] | Length of each connection pipe (supply only, not counting return line) [m] | |
| Length | lEnd | Length of the end of the distribution line (after last connection) [m] | |
| Length | dhDis[nCon] | Hydraulic diameter of the distribution pipe before each connection [m] | |
| Length | dhCon[nCon] | Hydraulic diameter of each connection pipe [m] | |
| Length | dhEnd | Hydraulic diameter of of the end of the distribution line (after last connection) [m] | |
| Nominal condition | |||
| MassFlowRate | mDis_flow_nominal | Nominal mass flow rate in the distribution line [kg/s] | |
| MassFlowRate | mCon_flow_nominal[nCon] | Nominal mass flow rate in each connection line [kg/s] | |
| Assumptions | |||
| Boolean | allowFlowReversal | false | = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
| Dynamics | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 5*60 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPorts_a | ports_aCon[nCon] | Connection return ports |
| FluidPorts_b | ports_bCon[nCon] | Connection supply ports |
| FluidPort_a | port_aDisSup | Distribution supply inlet port |
| FluidPort_b | port_bDisSup | Distribution supply outlet port |
| replaceable model Model_pipDis | Model for distribution pipe | |
| output RealOutput | dH_flow[nCon] | Difference in enthalpy flow rate between connection supply and return [W] |
| output RealOutput | mCon_flow[nCon] | Connection supply mass flow rate (measured) [kg/s] |
| output RealOutput | mByp_flow[nCon] | Bypass mass flow rate [kg/s] |
| output RealOutput | TOut[nCon] | Temperature in distribution line at each connection outlet [K] |
Modelica definition
model UnidirectionalSeries
"Hydronic network for unidirectional series DHC system"
extends Buildings.Experimental.DHC.Networks.BaseClasses.PartialDistribution1Pipe
(
tau=5*60,
redeclare Buildings.Experimental.DHC.Networks.Combined.BaseClasses.ConnectionSeriesAutosize
con[nCon](
each final dp_length_nominal=dp_length_nominal,
final lDis=lDis,
final lCon=lCon,
final dhDis=dhDis,
final dhCon=dhCon),
redeclare model Model_pipDis =
Buildings.Experimental.DHC.Networks.Combined.BaseClasses.PipeAutosize (
roughness=7e-6,
fac=1.5,
final dp_length_nominal=dp_length_nominal,
final dh(fixed=true)=dhEnd,
final length=lEnd));
parameter Real dp_length_nominal(final unit="Pa/m") = 250
"Pressure drop per pipe length at nominal flow rate";
parameter Modelica.Units.SI.Length lDis[nCon]
"Length of the distribution pipe before each connection";
parameter Modelica.Units.SI.Length lCon[nCon]
"Length of each connection pipe (supply only, not counting return line)";
parameter Modelica.Units.SI.Length lEnd
"Length of the end of the distribution line (after last connection)";
parameter Modelica.Units.SI.Length dhDis[nCon](
each fixed=false,
each start=0.05,
each min=0.01)
"Hydraulic diameter of the distribution pipe before each connection";
parameter Modelica.Units.SI.Length dhCon[nCon](
each fixed=false,
each start=0.05,
each min=0.01) "Hydraulic diameter of each connection pipe";
parameter Modelica.Units.SI.Length dhEnd(
fixed=false,
start=0.05,
min=0.01)
"Hydraulic diameter of of the end of the distribution line (after last connection)";
end UnidirectionalSeries;