modelPipe

Pipe with finite volume discretization along flow path

Extends from Buildings.Fluid.FixedResistances.BaseClasses.Pipe.

Information

Model of a pipe with flow resistance and optional heat exchange with environment.

Heat loss calculation

There are two possible configurations:

  1. If useMultipleHeatPorts=false (default option), the pipe uses a single heat port for the heat exchange with the environment. Note that if the heat port is unconnected, then all volumes are still connected through the heat conduction elements conPipWal. Therefore, they exchange a small amount of heat, which is not physical. To avoid this, set useMultipleHeatPorts=true.
  2. If useMultipleHeatPorts=true, then one heat port for each segment of the pipe is used for the heat exchange with the environment. If the heat port is unconnected, then the pipe has no heat loss.

Pressure drop calculation

The default value for the parameter diameter is computed such that the flow velocity is equal to v_nominal=0.15 for a mass flow rate of m_flow_nominal. Both parameters, diameter and v_nominal, can be overwritten by the user. The default value for dp_nominal is two times the pressure drop that the pipe would have if it were straight with no fittings. The factor of two that takes into account the pressure loss of fittings can be overwritten. These fittings could also be explicitly modeled outside of this component using models from the package Modelica.Fluid.Fittings. For mass flow rates other than m_flow_nominal, the model Buildings.Fluid.FixedResistances.PressureDrop is used to compute the pressure drop.

For a steady-state model of a flow resistance, use Buildings.Fluid.FixedResistances.PressureDrop instead of this model.

Parameters

TypeNameDefaultDescription
Modelica.Units.SI.Velocityv_nominal0.15Velocity at m_flow_nominal (used to compute default diameter)
Modelica.Units.SI.Lengthroughness2.5e-5Absolute roughness of pipe, with a default for a smooth steel pipe (dummy if use_roughness = false)
Modelica.Units.SI.PressureDifferencedpStraightPipe_nominalModelica.Fluid.Pipes.BaseClasses.WallFriction.Detailed.pressureLoss_m_flow(m_flow = m_flow_nominal, rho_a = rho_default, rho_b = rho_default, mu_a = mu_default, mu_b = mu_default, length = length, diameter = diameter, roughness = roughness, m_flow_small = m_flow_small)Pressure loss of a straight pipe at m_flow_nominal
BooleanuseMultipleHeatPortsfalse= true to use one heat port for each segment of the pipe, false to use a single heat port for the entire pipe

Components

TypeNameDefaultDescription
Modelica.Thermal.HeatTransfer.Components.ThermalConductor[nSeg]conPipWalThermal conductance through pipe wall
Modelica.Thermal.HeatTransfer.Components.ThermalCollectorcolAllToOneConnector to assign multiple heat ports to one heat port
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_aheatPortSingle heat port that connects to outside of pipe wall (default, enabled when useMultipleHeatPorts=false)
Modelica.Fluid.Interfaces.HeatPorts_a[nSeg]heatPortsMultiple heat ports that connect to outside of pipe wall (enabled if useMultipleHeatPorts=true)

Revisions

  • January 22, 2016, by Michael Wetter:
    Corrected type declaration of pressure difference. This is for #404.
  • October 30, 2015, by Michael Wetter:
    Improved documentation for #455.
  • February 5, 2015, by Michael Wetter:
    Renamed res to preDro for #292.
  • September 13, 2013 by Michael Wetter:
    Replaced nominal with default values as they are computed using the default Medium values.
  • February 22, 2012 by Michael Wetter:
    Renamed useMultipleHeatPort to useMultipleHeatPorts and used heat port connector from Modelica.Fluid package for vector of heat ports.
  • February 15, 2012 by Michael Wetter:
    Revised implementation and added default values.
  • February 12, 2012 by Wangda Zuo:
    First implementation.