modelInternalHEXOneUTube

Internal heat exchanger of a borehole for a single U-tube configuration

Extends from Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.BaseClasses.PartialInternalHEX (Partial model to implement the internal heat exchanger of a borehole segment), Buildings.Fluid.Interfaces.FourPortHeatMassExchanger (Model transporting two fluid streams between four ports with storing mass or energy).

Information

Model for the heat transfer between the fluid and within the borehole filling for a single borehole segment. This model computes the dynamic response of the fluid in the tubes, the heat transfer between the fluid and the borehole filling, and the heat storage within the fluid and the borehole filling.

This model computes the different thermal resistances present in a single-U-tube borehole using the method of Bauer et al. (2011) and computing explicitely the fluid-to-ground thermal resistance R_b and the grout-to-grout resistance R_a as defined by Claesson and Hellstrom (2011) using the multipole method.

References

J. Claesson and G. Hellstrom. Multipole method to calculate borehole thermal resistances in a borehole heat exchanger. HVAC&R Research, 17(6): 895-911, 2011.

D. Bauer, W. Heidemann, H. Müller-Steinhagen, and H.-J. G. Diersch. Thermal resistance and capacity models for borehole heat exchangers . International Journal Of Energy Research, 35:312-320, 2011.

Parameters

Type	Name	Default	Description
Buildings.Fluid.Geothermal.Borefields.Data.Borefield.Template	borFieDat (from PartialInternalHEX)		Borefield parameters
Real	mSenFac (from PartialInternalHEX)	1	Factor for scaling the sensible thermal mass of the volume
Modelica.Units.SI.Length	hSeg (from PartialInternalHEX)		Length of the internal heat exchanger
Modelica.Units.SI.Volume	VTubSeg (from PartialInternalHEX)	hSegModelica.Constants.pi(borFieDat.conDat.rTub - borFieDat.conDat.eTub)^2	Fluid volume in each tube
Boolean	homotopyInitialization (from FourPortHeatMassExchanger)	true	= true, use homotopy method
Initialization
Modelica.Units.SI.Temperature	TFlu_start (from PartialInternalHEX)		Start value of fluid temperature
Modelica.Units.SI.Temperature	TGro_start (from PartialInternalHEX)		Start value of grout temperature
Assumptions
Boolean	allowFlowReversal1 (from PartialFourPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1
Boolean	allowFlowReversal2 (from PartialFourPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2
Nominal condition
Modelica.Units.SI.MassFlowRate	m1_flow_nominal (from PartialFourPortInterface)		Nominal mass flow rate
Modelica.Units.SI.MassFlowRate	m2_flow_nominal (from PartialFourPortInterface)		Nominal mass flow rate
Modelica.Units.SI.PressureDifference	dp1_nominal (from FourPortFlowResistanceParameters)		Pressure difference
Modelica.Units.SI.PressureDifference	dp2_nominal (from FourPortFlowResistanceParameters)		Pressure difference
Advanced
Medium1.MassFlowRate	m1_flow_small (from PartialFourPortInterface)	1E-4*abs(m1_flow_nominal)	Small mass flow rate for regularization of zero flow
Medium2.MassFlowRate	m2_flow_small (from PartialFourPortInterface)	1E-4*abs(m2_flow_nominal)	Small mass flow rate for regularization of zero flow
Advanced › Diagnostics
Boolean	show_T (from PartialFourPortInterface)	false	= true, if actual temperature at port is computed
Flow resistance › Medium 1
Boolean	computeFlowResistance1 (from FourPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp1 (from FourPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n1 (from FourPortFlowResistanceParameters)	2	Flow exponent for side 1, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance1 (from FourPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1 (from FourPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Flow resistance › Medium 2
Boolean	computeFlowResistance2 (from FourPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp2 (from FourPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n2 (from FourPortFlowResistanceParameters)	2	Flow exponent for side 2, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance2 (from FourPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2 (from FourPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics › Nominal condition
Modelica.Units.SI.Time	tau1 (from FourPortHeatMassExchanger)	30	Time constant at nominal flow
Modelica.Units.SI.Time	tau2 (from FourPortHeatMassExchanger)	30	Time constant at nominal flow
Dynamics › Conservation equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from FourPortHeatMassExchanger)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Type of energy balance: dynamic (3 initialization options) or steady state
Initialization › Medium 1
Medium1.AbsolutePressure	p1_start (from FourPortHeatMassExchanger)	Medium1.p_default	Start value of pressure
Medium1.Temperature	T1_start (from FourPortHeatMassExchanger)	Medium1.T_default	Start value of temperature
Medium1.MassFraction[Medium1.nX]	X1_start (from FourPortHeatMassExchanger)	Medium1.X_default	Start value of mass fractions m_i/m
Medium1.ExtraProperty[Medium1.nC]	C1_start (from FourPortHeatMassExchanger)	fill(0, Medium1.nC)	Start value of trace substances
Medium1.ExtraProperty[Medium1.nC]	C1_nominal (from FourPortHeatMassExchanger)	fill(1E-2, Medium1.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Initialization › Medium 2
Medium2.AbsolutePressure	p2_start (from FourPortHeatMassExchanger)	Medium2.p_default	Start value of pressure
Medium2.Temperature	T2_start (from FourPortHeatMassExchanger)	Medium2.T_default	Start value of temperature
Medium2.MassFraction[Medium2.nX]	X2_start (from FourPortHeatMassExchanger)	Medium2.X_default	Start value of mass fractions m_i/m
Medium2.ExtraProperty[Medium2.nC]	C2_start (from FourPortHeatMassExchanger)	fill(0, Medium2.nC)	Start value of trace substances
Medium2.ExtraProperty[Medium2.nC]	C2_nominal (from FourPortHeatMassExchanger)	fill(1E-2, Medium2.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)

Connectors

Type	Name	Description
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a	port_wall (from PartialInternalHEX)	Thermal connection for borehole wall
Modelica.Fluid.Interfaces.FluidPort_a	port_a1 (from PartialFourPort)	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_b	port_b1 (from PartialFourPort)	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_a	port_a2 (from PartialFourPort)	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
Modelica.Fluid.Interfaces.FluidPort_b	port_b2 (from PartialFourPort)	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)

Components

Type	Name	Default	Description
Medium1.MassFlowRate	m1_flow (from PartialFourPortInterface)	port_a1.m_flow	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction)
Modelica.Units.SI.PressureDifference	dp1 (from PartialFourPortInterface)	port_a1.p - port_b1.p	Pressure difference between port_a1 and port_b1
Medium2.MassFlowRate	m2_flow (from PartialFourPortInterface)	port_a2.m_flow	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction)
Modelica.Units.SI.PressureDifference	dp2 (from PartialFourPortInterface)	port_a2.p - port_b2.p	Pressure difference between port_a2 and port_b2
Medium1.ThermodynamicState	sta_a1 (from PartialFourPortInterface)	if allowFlowReversal1 then Medium1.setState_phX(port_a1.p, noEvent(actualStream(port_a1.h_outflow)), noEvent(actualStream(port_a1.Xi_outflow))) else Medium1.setState_phX(port_a1.p, inStream(port_a1.h_outflow), inStream(port_a1.Xi_outflow))	Medium properties in port_a1
Medium1.ThermodynamicState	sta_b1 (from PartialFourPortInterface)	if allowFlowReversal1 then Medium1.setState_phX(port_b1.p, noEvent(actualStream(port_b1.h_outflow)), noEvent(actualStream(port_b1.Xi_outflow))) else Medium1.setState_phX(port_b1.p, port_b1.h_outflow, port_b1.Xi_outflow)	Medium properties in port_b1
Medium2.ThermodynamicState	sta_a2 (from PartialFourPortInterface)	if allowFlowReversal2 then Medium2.setState_phX(port_a2.p, noEvent(actualStream(port_a2.h_outflow)), noEvent(actualStream(port_a2.Xi_outflow))) else Medium2.setState_phX(port_a2.p, inStream(port_a2.h_outflow), inStream(port_a2.Xi_outflow))	Medium properties in port_a2
Medium2.ThermodynamicState	sta_b2 (from PartialFourPortInterface)	if allowFlowReversal2 then Medium2.setState_phX(port_b2.p, noEvent(actualStream(port_b2.h_outflow)), noEvent(actualStream(port_b2.Xi_outflow))) else Medium2.setState_phX(port_b2.p, port_b2.h_outflow, port_b2.Xi_outflow)	Medium properties in port_b2
Modelica.Units.SI.HeatFlowRate	Q1_flow (from FourPortHeatMassExchanger)	vol1.heatPort.Q_flow	Heat flow rate into medium 1
Modelica.Units.SI.HeatFlowRate	Q2_flow (from FourPortHeatMassExchanger)	vol2.heatPort.Q_flow	Heat flow rate into medium 2
Buildings.Fluid.MixingVolumes.BaseClasses.MixingVolumeHeatPort	vol1 (from FourPortHeatMassExchanger)
Buildings.Fluid.MixingVolumes.MixingVolume	vol2 (from FourPortHeatMassExchanger)
Buildings.Fluid.FixedResistances.PressureDrop	preDro1 (from FourPortHeatMassExchanger)		Flow resistance of fluid 1
Buildings.Fluid.FixedResistances.PressureDrop	preDro2 (from FourPortHeatMassExchanger)		Flow resistance of fluid 2
Modelica.Blocks.Sources.RealExpression	RVol1		Convective and thermal resistance at fluid 1
Modelica.Blocks.Sources.RealExpression	RVol2		Convective and thermal resistance at fluid 2
Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.BaseClasses.InternalResistancesOneUTube	intResUTub		Internal resistances for a single U-tube configuration
Modelica.Thermal.HeatTransfer.Components.ConvectiveResistor	RConv2		Pipe convective resistance
Modelica.Thermal.HeatTransfer.Components.ConvectiveResistor	RConv1		Pipe convective resistance

Revisions

June 17, 2026, by Michael Wetter:
Removed stray annotation.
This is for IBPSA, #2139.
May 17, 2024, by Michael Wetter:
Updated model due to removal of parameter dynFil.
This is for IBPSA, #1885.
November 22, 2023, by Michael Wetter:
Corrected use of getInstanceName() which was called inside a function which is not allowed.
This is for IBPSA, #1814.
March 7, 2022, by Michael Wetter:
Removed massDynamics.
This is for #1542.
February 28, 2022, by Massimo Cimmino:
Removed printDebug parameter from call to Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.BaseClasses.Functions.internalResistancesOneUTube.
This is for IBPSA, #1582.
July 10, 2018, by Alex Laferrière:
Updated documentation following major changes to the Buildings.Fluid.HeatExchangers.Ground package. Additionally, implemented a partial InternalHex model.
June 18, 2014, by Michael Wetter:
Added initialization for temperatures and derivatives of capFil1 and capFil2 to avoid a warning during translation.
February 14, 2014, by Michael Wetter:
Removed unused parameters B0 and B1.
January 24, 2014, by Michael Wetter:
Revised implementation, added comments, replaced HeatTransfer.Windows.BaseClasses.ThermalConductor with resistance models from the Modelica Standard Library.
January 23, 2014, by Damien Picard:
First implementation.