modelDistribution2Pipe_R

Model of a two-pipe distribution network with hydraulic diameter of main line pipes calculated from pressure drop per length
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Extends from Buildings.DHC.Networks.BaseClasses.PartialDistribution2Pipe (Partial model for two-pipe distribution network).

Information

This is a model of a two-pipe distribution network using a connection model with pipes in the main lines whose hydraulic diameters are calculated at initialization based on the pressure drop per pipe length at nominal flow rate Buildings.DHC.Networks.Connections.Connection2Pipe_R. The same pipe model is also used at the end of the distribution line (after the last connection) only on the supply side.

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.DHC.Networks.Pipes.PipeAutosize which is instantiated for each connection. So the initialization system of equations would be overdetermined if using a parameter binding with a scalar variable.

Parameters

TypeNameDefaultDescription
Booleanshow_entFlo (from PartialDistribution2Pipe)falseSet to true to output enthalpy flow rate difference at each connection
Realdp_length_nominal250Pressure drop per pipe length at nominal flow rate
Modelica.Units.SI.Length[nCon]lDisLength of the distribution pipe before each connection (supply only, not counting return line)
Modelica.Units.SI.LengthlEndLength of the end of the distribution line (supply only, not counting return line)
Modelica.Units.SI.Length[nCon]dhDisHydraulic diameter of the distribution pipe before each connection
Modelica.Units.SI.Length[nCon]dhDisRetHydraulic diameter of the distribution pipe before each connection
Modelica.Units.SI.LengthdhEndHydraulic diameter of the end of the distribution line
General
IntegernCon (from PartialDistribution2Medium)Number of connections
IntegeriConDpSen (from PartialDistribution2Pipe)nConIndex of the connection where the pressure drop is measured
Assumptions
BooleanallowFlowReversal (from PartialDistribution2Medium)false= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
General › Nominal condition
Modelica.Units.SI.MassFlowRatemDis_flow_nominal (from PartialDistribution2Pipe)Nominal mass flow rate in the distribution line before the first connection
Modelica.Units.SI.MassFlowRate[nCon]mCon_flow_nominal (from PartialDistribution2Pipe)Nominal mass flow rate in each connection line
Modelica.Units.SI.MassFlowRatemEnd_flow_nominal (from PartialDistribution2Pipe)mDis_flow_nominal - sum(mCon_flow_nominal)Nominal mass flow rate in the end of the distribution line
Modelica.Units.SI.MassFlowRate[nCon]mDisCon_flow_nominal (from PartialDistribution2Pipe)cat(1, {mDis_flow_nominal}, {mDis_flow_nominal - sum(mCon_flow_nominal[1:i]) for i in 1:(nCon - 1)})Nominal mass flow rate in the distribution line before each connection
Dynamics › Conservation equations
Modelica.Fluid.Types.DynamicsenergyDynamics (from PartialDistribution2Pipe)Modelica.Fluid.Types.Dynamics.FixedInitialType of energy balance: dynamic (3 initialization options) or steady state
Dynamics › Nominal condition
Modelica.Units.SI.Timetau (from PartialDistribution2Pipe)10Time constant at nominal flow for dynamic energy and momentum balance

Connectors

TypeNameDefaultDescription
Modelica.Fluid.Interfaces.FluidPorts_a[nCon]ports_aCon (from PartialDistribution2Medium)Connection return ports
Modelica.Fluid.Interfaces.FluidPorts_b[nCon]ports_bCon (from PartialDistribution2Medium)Connection supply ports
Modelica.Fluid.Interfaces.FluidPort_aport_aDisSup (from PartialDistribution2Medium)Distribution supply inlet port
Modelica.Fluid.Interfaces.FluidPort_bport_bDisSup (from PartialDistribution2Medium)Distribution supply outlet port
Modelica.Fluid.Interfaces.FluidPort_bport_bDisRet (from PartialDistribution2Pipe)Distribution return outlet port
Modelica.Fluid.Interfaces.FluidPort_aport_aDisRet (from PartialDistribution2Pipe)Distribution return inlet port
Buildings.Controls.OBC.CDL.Interfaces.RealOutputdp (from PartialDistribution2Pipe)Pressure difference at given location (measured)
Buildings.Controls.OBC.CDL.Interfaces.RealOutput[nCon]dH_flow (from PartialDistribution2Pipe)Difference in enthalpy flow rate between connection supply and return
Buildings.Controls.OBC.CDL.Interfaces.RealOutput[nCon]mCon_flow (from PartialDistribution2Pipe)Connection supply mass flow rate (measured)

Components

TypeNameDefaultDescription
Buildings.DHC.Networks.BaseClasses.PartialConnection2Pipe[nCon]con (from PartialDistribution2Pipe)Connection to agent
Model_pipDispipEnd (from PartialDistribution2Pipe)Pipe representing the end of the distribution line (after last connection)
Fluid.Sensors.RelativePressuresenRelPre (from PartialDistribution2Pipe)Relative pressure sensor

Revisions

  • March 15, 2024, by David Blum:
    Renamed. This is for issue 3712.
  • December 20, 2023, by Ettore Zanetti:
    This is for issue 3431.
  • February 23, 2021, by Antoine Gautier:
    First implementation.