modelPipe

Discretized DynamicPipe with heat loss to ambient

Extends from Interfaces.PartialTwoPort.

Information

Overview

Dynamic Pipe with pipe wall and insulation wall which allows discretisation of pipe wall and pipe insulation. This model considers heat loss through radiation and convection if pipe is not embedded in wall. In case that the pipe is embedded in the wall, heat transfer between the pipe wall / insulation and the surrounding material is based on heat conduction.

Concept

Dynamic pipe model with heat losses for various applications. It is possible to choose whether the pipe is embedded in a wall or not. In addition, no insulation can be selected, if used for example for CCA ( concrete core activation).

The model already includes heat-transfer by convection and by radiation. Instead of modeling these phenomena outside the pipe, an ambient temperature can be prescribed at the heat-port and the star of the pipe, so the loss to ambient will be calculated within the pipe model.

For each discretisation of the pipe, there is a connector to the corresponding element of the discretized pipe wall. Each element of the discretised pipe wall is connected to a corresponding element of the discretized insulation wall. The heat-ports and stars of all nodes are then collected to form two single ports, which can be connected to an ambient temperature.

Example Results

AixLib.Fluid.FixedResistances.Examples.DPEAgg_ambientLoss

Parameters

Type	Name	Default	Description
Modelica.Units.SI.Diameter	diameter	parameterPipe.d_i	Diameter of circular pipe
Modelica.Units.SI.CoefficientOfHeatTransfer	hCon_i	1000	Heat tranfer coefficient from fluid to pipe wall
Geometry
Integer	nParallel	1	Number of identical parallel pipes
Modelica.Units.SI.Length	length	1	Length
Boolean	isCircular	true	=true if cross sectional area is circular
Modelica.Units.SI.Area	crossArea	Modelica.Constants.pidiameterdiameter/4	Inner cross section area
Modelica.Units.SI.Length	perimeter	Modelica.Constants.pi*diameter	Inner perimeter
Modelica.Units.SI.Height	roughness	2.5e-5	Average height of surface asperities (default: smooth steel pipe)
Static head
Modelica.Units.SI.Length	height_ab	0	Height(port_b)-Height(port_a)
Assumptions › Dynamics
Modelica.Fluid.Types.Dynamics	energyDynamics	system.energyDynamics	Formulation of energy balances
Modelica.Fluid.Types.Dynamics	massDynamics	system.massDynamics	Formulation of mass balances
Modelica.Fluid.Types.Dynamics	momentumDynamics	system.momentumDynamics	Formulation of momentum balances
Heat transfer
Boolean	Heat_Loss_To_Ambient	false	= true to internally simulate heat loss to ambient by convection and radiation
Boolean	isEmbedded	false	= true if pipe is embedded in a solid material, for example walls
Boolean	withInsulation	false	= true to use a pipe with insulation
Boolean	use_HeatTransferConvective	true	= true to use the convective HeatTransfer model
AixLib.DataBase.Pipes.PipeBaseDataDefinition	parameterPipe	AixLib.DataBase.Pipes.Copper.Copper_6x1()	Pipe type
AixLib.DataBase.Pipes.InsulationBaseDataDefinition	parameterIso	AixLib.DataBase.Pipes.Insulation.Iso50pc()	Insulation Type
Modelica.Units.SI.CoefficientOfHeatTransfer	hCon	8	Heat transfer coefficient to ambient
Modelica.Units.SI.Emissivity	eps	0.8	Emissivity
Initialization
Medium.AbsolutePressure	p_a_start	system.p_start	Start value of pressure at port a
Medium.AbsolutePressure	p_b_start	p_a_start	Start value of pressure at port b
Boolean	use_T_start	true	Use T_start if true, otherwise h_start
Medium.Temperature	T_start	if use_T_start then system.T_start else Medium.temperature_phX((p_a_start + p_b_start)/2, h_start, X_start)	Start value of temperature
Medium.SpecificEnthalpy	h_start	if use_T_start then Medium.specificEnthalpy_pTX((p_a_start + p_b_start)/2, T_start, X_start) else Medium.h_default	Start value of specific enthalpy
Medium.MassFraction[Medium.nX]	X_start	Medium.X_default	Start value of mass fractions m_i/m
Medium.ExtraProperty[Medium.nC]	C_start	fill(0, Medium.nC)	Start value of trace substances
Medium.MassFlowRate	m_flow_start	system.m_flow_start	Start value for mass flow rate
Advanced
Integer	nNodes	2	Number of discrete flow volumes
Modelica.Fluid.Types.ModelStructure	modelStructure	Modelica.Fluid.Types.ModelStructure.av_vb	Determines whether flow or volume models are present at the ports
Boolean	useLumpedPressure	false	=true to lump pressure states together
Boolean	useInnerPortProperties	false	=true to take port properties for flow models from internal control volumes

Components

Type	Name	Description
Modelica.Fluid.System	system	System wide properties
Utilities.HeatTransfer.CylindricHeatTransfer[nNodes]	PipeWall
Utilities.HeatTransfer.CylindricHeatTransfer[nNodes]	Insulation
Modelica.Fluid.Pipes.DynamicPipe	pipe
AixLib.Utilities.HeatTransfer.HeatConv[nNodes]	heatConv	Convection from pipe wall
AixLib.Utilities.HeatTransfer.HeatConv[nNodes]	heatConv_withInsulation	Convection from insulation
Utilities.HeatTransfer.HeatToRad[nNodes]	twoStar_RadEx	Radiation
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a	heatPort_outside
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	thermalCollector
AixLib.Utilities.Interfaces.RadPort	Star
Modelica.Thermal.HeatTransfer.Components.ThermalCollector	thermalCollector_Star

Name	Description
FlowModel
HeatTransferConvective

Revisions

February 03, 2020 by Alexander Kümpel:
Multiplication with nParallel in heatConv
April 25, 2017 by Tobias Blacha:
Parameter isEmbedded added and correction of connections for different applications
April 25, 2017 by Tobias Blacha:
Moved into AixLib
March 18, 2015 by Roozbeh Sangi:
Outputs for stored energy and temperature added
November 26, 2014 by Roozbeh Sangi:
Updated connectors to EBC Library 2.2, Updated documentation, Added example
May 19, 2014 by Roozbeh Sangi:
Added to the HVAC library
November 13, 2013 by Ole Odendahl:
Formatted documentation appropriately
August 3, 2011 by Ana Constantin:
Implemented