Buildings.Experimental.DHC.Networks.Steam

Collection of models for distribution networks involving steam

Information

This package contains models for steam heating distribution networks.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name	Description
ConnectionCondensatePipe	Connection for a steam district heating network featuring the condensate return pipe
DistributionCondensatePipe	Model of a steam distribution network using fixed resistance pipe model for condensate returns
Examples	Collection of models that illustrate model use and test models

Buildings.Experimental.DHC.Networks.Steam.ConnectionCondensatePipe

Connection for a steam district heating network featuring the condensate return pipe

Buildings.Experimental.DHC.Networks.Steam.ConnectionCondensatePipe

Information

This network connection model contains one pipe declaration for the condensate pipe, featuring a fixed hydraulic resistance. This model is intended for steam heating systems that utilize a split-medium approach with two separate medium declarations between liquid and vapor states.

In this model, it is assumed that there are no mass losses in the network connection. Further, heat transfer with the external environment and transport delays are also not included.

Reference

Hinkelman, Kathryn, Saranya Anbarasu, Michael Wetter, Antoine Gautier, and Wangda Zuo. 2022. “A Fast and Accurate Modeling Approach for Water and Steam Thermodynamics with Practical Applications in District Heating System Simulation.” Preprint. February 24. doi:10.13140/RG.2.2.20710.29762.

Extends from Buildings.Experimental.DHC.Networks.BaseClasses.PartialConnection2Pipe2Medium (Partial model for connecting an agent to a two-pipe distribution network with two medium declarations).

Parameters

Type	Name	Default	Description
replaceable package MediumSup		PartialMedium	Medium model for supply fluid
replaceable package MediumRet		PartialMedium	Medium model for return fluid
replaceable model Model_pipDisSup		PartialTwoPortInterface	Interface for inlet pipe for the distribution supply
replaceable model Model_pipDisRet		PartialTwoPortInterface	Interface for outlet pipe for the distribution return
Nominal condition
MassFlowRate	mDis_flow_nominal		Nominal mass flow rate in the distribution line [kg/s]
MassFlowRate	mCon_flow_nominal		Nominal mass flow rate in the connection line [kg/s]
PressureDifference	dp_nominal		Pressure drop at nominal mass flow rate [Pa]
Assumptions
Boolean	allowFlowReversal	false	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Dynamics
Equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Nominal condition
Time	tau	10	Time constant at nominal flow for dynamic energy and momentum balance [s]

Connectors

Type	Name	Description
replaceable model Model_pipDisSup		Interface for inlet pipe for the distribution supply
replaceable model Model_pipDisRet		Interface for outlet pipe for the distribution return
FluidPort_a	port_aDisSup	Distribution supply inlet port
FluidPort_b	port_bDisSup	Distribution supply outlet port
FluidPort_a	port_aDisRet	Distribution return inlet port
FluidPort_b	port_bDisRet	Distribution return outlet port
FluidPort_b	port_bCon	Connection supply port
FluidPort_a	port_aCon	Connection return port

Modelica definition

model ConnectionCondensatePipe "Connection for a steam district heating network featuring the condensate return pipe" extends Buildings.Experimental.DHC.Networks.BaseClasses.PartialConnection2Pipe2Medium ( redeclare final model Model_pipDisRet = Buildings.Fluid.FixedResistances.PressureDrop ( final dp_nominal=dp_nominal), redeclare model Model_pipDisSup = Buildings.Fluid.FixedResistances.LosslessPipe); parameter Modelica.Units.SI.PressureDifference dp_nominal(displayUnit="Pa") "Pressure drop at nominal mass flow rate"; Buildings.Fluid.FixedResistances.PressureDrop pipConRet( redeclare package Medium = MediumRet, m_flow_nominal=mCon_flow_nominal, final dp_nominal=dp_nominal) "Connection return pipe"; equation connect(port_aCon, pipConRet.port_a); connect(pipConRet.port_b, junConRet.port_3); connect(port_bCon, junConSup.port_3); end ConnectionCondensatePipe;

Buildings.Experimental.DHC.Networks.Steam.DistributionCondensatePipe

Model of a steam distribution network using fixed resistance pipe model for condensate returns

Buildings.Experimental.DHC.Networks.Steam.DistributionCondensatePipe

Information

This is a model of a distribution network for steam heating systems. The model utilizes a split-medium approach with two separate medium declarations between liquid (condensate return) and vapor (steam supply) states. The piping network features:

a connection model with fixed hydraulic resistance and no heat loss in the condensate return pipe segments;
a dummy pipe model with no hydraulic resistance and no heat loss for the steam supply pipes; and
a dummy pipe model with no hydraulic resistance and no heat loss for the end of the distribution line (after the last connection).

Reference

Extends from Buildings.Experimental.DHC.Networks.BaseClasses.PartialDistribution2Pipe2Medium (Partial model for a two-pipe distribution network with two medium declarations).

Parameters

Type	Name	Default	Description
replaceable package MediumSup		PartialMedium	Medium model for supply fluid
replaceable package MediumRet		PartialMedium	Medium model for return fluid
Integer	nCon		Number of connections
replaceable model Model_pipDis		PartialTwoPortInterface	Model for distribution pipe
Boolean	show_heaFlo	false	Set to true to output the heat flow rate transferred to each connected load
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]
PressureDifference	dp_nominal		Pressure drop at nominal mass flow rate [Pa]
Assumptions
Boolean	allowFlowReversal	false	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Dynamics
Equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Nominal condition
Time	tau	10	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

Modelica definition

model DistributionCondensatePipe "Model of a steam distribution network using fixed resistance pipe model for condensate returns" extends Buildings.Experimental.DHC.Networks.BaseClasses.PartialDistribution2Pipe2Medium ( redeclare ConnectionCondensatePipe con[nCon]( each final dp_nominal=dp_nominal), redeclare model Model_pipDis=Buildings.Fluid.FixedResistances.LosslessPipe); parameter Modelica.Units.SI.PressureDifference dp_nominal(displayUnit="Pa") "Pressure drop at nominal mass flow rate"; end DistributionCondensatePipe;