modelInternalHEXTwoUTube

Internal heat exchanger of a borehole for a double U-tube configuration. In loop 1, fluid 1 streams from a1 to b1 and comes back from a2 to b2. In loop 2: fluid 2 streams from a3 to b3 and comes back from a4 to b4.

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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.EightPortHeatMassExchanger (Model transporting four fluid streams between eight ports with storing mass or energy).

Information

Model for the heat transfer between the fluid and within the borehole filling. 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 EightPortHeatMassExchanger)	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 EightPort)	true	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal2 (from EightPort)	true	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal3 (from EightPort)	true	= true to allow flow reversal in medium 3, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal4 (from EightPort)	true	= true to allow flow reversal in medium 4, false restricts to design direction (port_a -> port_b)
Advanced › Initialization
Modelica.Units.SI.SpecificEnthalpy	h_outflow_a1_start (from EightPort)	Medium1.h_default	Start value for enthalpy flowing out of port a1
Modelica.Units.SI.SpecificEnthalpy	h_outflow_b1_start (from EightPort)	Medium1.h_default	Start value for enthalpy flowing out of port b1
Modelica.Units.SI.SpecificEnthalpy	h_outflow_a2_start (from EightPort)	Medium2.h_default	Start value for enthalpy flowing out of port a2
Modelica.Units.SI.SpecificEnthalpy	h_outflow_b2_start (from EightPort)	Medium2.h_default	Start value for enthalpy flowing out of port b2
Modelica.Units.SI.SpecificEnthalpy	h_outflow_a3_start (from EightPort)	Medium3.h_default	Start value for enthalpy flowing out of port a1
Modelica.Units.SI.SpecificEnthalpy	h_outflow_b3_start (from EightPort)	Medium3.h_default	Start value for enthalpy flowing out of port b1
Modelica.Units.SI.SpecificEnthalpy	h_outflow_a4_start (from EightPort)	Medium4.h_default	Start value for enthalpy flowing out of port a1
Modelica.Units.SI.SpecificEnthalpy	h_outflow_b4_start (from EightPort)	Medium4.h_default	Start value for enthalpy flowing out of port b1
Nominal condition
Modelica.Units.SI.MassFlowRate	m1_flow_nominal (from PartialEightPortInterface)		Nominal mass flow rate
Modelica.Units.SI.MassFlowRate	m2_flow_nominal (from PartialEightPortInterface)		Nominal mass flow rate
Modelica.Units.SI.MassFlowRate	m3_flow_nominal (from PartialEightPortInterface)		Nominal mass flow rate
Modelica.Units.SI.MassFlowRate	m4_flow_nominal (from PartialEightPortInterface)		Nominal mass flow rate
Modelica.Units.SI.Pressure	dp1_nominal (from EightPortFlowResistanceParameters)		Pressure difference
Modelica.Units.SI.Pressure	dp2_nominal (from EightPortFlowResistanceParameters)		Pressure difference
Modelica.Units.SI.Pressure	dp3_nominal (from EightPortFlowResistanceParameters)		Pressure difference
Modelica.Units.SI.Pressure	dp4_nominal (from EightPortFlowResistanceParameters)		Pressure difference
Advanced
Medium1.MassFlowRate	m1_flow_small (from PartialEightPortInterface)	1E-4*abs(m1_flow_nominal)	Small mass flow rate for regularization of zero flow
Medium2.MassFlowRate	m2_flow_small (from PartialEightPortInterface)	1E-4*abs(m2_flow_nominal)	Small mass flow rate for regularization of zero flow
Medium3.MassFlowRate	m3_flow_small (from PartialEightPortInterface)	1E-4*abs(m3_flow_nominal)	Small mass flow rate for regularization of zero flow
Medium4.MassFlowRate	m4_flow_small (from PartialEightPortInterface)	1E-4*abs(m4_flow_nominal)	Small mass flow rate for regularization of zero flow
Advanced › Diagnostics
Boolean	show_T (from PartialEightPortInterface)	false	= true, if actual temperature at port is computed
Flow resistance › Medium 1
Boolean	computeFlowResistance1 (from EightPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp1 (from EightPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n1 (from EightPortFlowResistanceParameters)	2	Flow exponent for side 1, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance1 (from EightPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1 (from EightPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Flow resistance › Medium 2
Boolean	computeFlowResistance2 (from EightPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp2 (from EightPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n2 (from EightPortFlowResistanceParameters)	2	Flow exponent for side 2, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance2 (from EightPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2 (from EightPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Flow resistance › Medium 3
Boolean	computeFlowResistance3 (from EightPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp3 (from EightPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n3 (from EightPortFlowResistanceParameters)	2	Flow exponent for side 3, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance3 (from EightPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM3 (from EightPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Flow resistance › Medium 4
Boolean	computeFlowResistance4 (from EightPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp4 (from EightPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n4 (from EightPortFlowResistanceParameters)	2	Flow exponent for side 4, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance4 (from EightPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM4 (from EightPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics › Nominal condition
Modelica.Units.SI.Time	tau1 (from EightPortHeatMassExchanger)	30	Time constant at nominal flow
Modelica.Units.SI.Time	tau2 (from EightPortHeatMassExchanger)	30	Time constant at nominal flow
Modelica.Units.SI.Time	tau3 (from EightPortHeatMassExchanger)	30	Time constant at nominal flow
Modelica.Units.SI.Time	tau4 (from EightPortHeatMassExchanger)	30	Time constant at nominal flow
Dynamics › Conservation equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from EightPortHeatMassExchanger)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Formulation of energy balance
Initialization › Medium 1
Medium1.AbsolutePressure	p1_start (from EightPortHeatMassExchanger)	Medium1.p_default	Start value of pressure
Medium1.Temperature	T1_start (from EightPortHeatMassExchanger)	Medium1.T_default	Start value of temperature
Medium1.MassFraction[Medium1.nX]	X1_start (from EightPortHeatMassExchanger)	Medium1.X_default	Start value of mass fractions m_i/m
Medium1.ExtraProperty[Medium1.nC]	C1_start (from EightPortHeatMassExchanger)	fill(0, Medium1.nC)	Start value of trace substances
Medium1.ExtraProperty[Medium1.nC]	C1_nominal (from EightPortHeatMassExchanger)	fill(1E-2, Medium1.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Initialization › Medium 2
Medium2.AbsolutePressure	p2_start (from EightPortHeatMassExchanger)	Medium2.p_default	Start value of pressure
Medium2.Temperature	T2_start (from EightPortHeatMassExchanger)	Medium2.T_default	Start value of temperature
Medium2.MassFraction[Medium2.nX]	X2_start (from EightPortHeatMassExchanger)	Medium2.X_default	Start value of mass fractions m_i/m
Medium2.ExtraProperty[Medium2.nC]	C2_start (from EightPortHeatMassExchanger)	fill(0, Medium2.nC)	Start value of trace substances
Medium2.ExtraProperty[Medium2.nC]	C2_nominal (from EightPortHeatMassExchanger)	fill(1E-2, Medium2.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Initialization › Medium 3
Medium3.AbsolutePressure	p3_start (from EightPortHeatMassExchanger)	Medium3.p_default	Start value of pressure
Medium3.Temperature	T3_start (from EightPortHeatMassExchanger)	Medium3.T_default	Start value of temperature
Medium3.MassFraction[Medium3.nX]	X3_start (from EightPortHeatMassExchanger)	Medium3.X_default	Start value of mass fractions m_i/m
Medium3.ExtraProperty[Medium3.nC]	C3_start (from EightPortHeatMassExchanger)	fill(0, Medium3.nC)	Start value of trace substances
Medium3.ExtraProperty[Medium3.nC]	C3_nominal (from EightPortHeatMassExchanger)	fill(1E-2, Medium3.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Initialization › Medium 4
Medium4.AbsolutePressure	p4_start (from EightPortHeatMassExchanger)	Medium4.p_default	Start value of pressure
Medium4.Temperature	T4_start (from EightPortHeatMassExchanger)	Medium4.T_default	Start value of temperature
Medium4.MassFraction[Medium4.nX]	X4_start (from EightPortHeatMassExchanger)	Medium4.X_default	Start value of mass fractions m_i/m
Medium4.ExtraProperty[Medium4.nC]	C4_start (from EightPortHeatMassExchanger)	fill(0, Medium4.nC)	Start value of trace substances
Medium4.ExtraProperty[Medium4.nC]	C4_nominal (from EightPortHeatMassExchanger)	fill(1E-2, Medium4.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 EightPort)	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_b	port_b1 (from EightPort)	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_a	port_a2 (from EightPort)	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
Modelica.Fluid.Interfaces.FluidPort_b	port_b2 (from EightPort)	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
Modelica.Fluid.Interfaces.FluidPort_a	port_a3 (from EightPort)	Fluid connector a1 (positive design flow direction is from port_a3 to port_b3)
Modelica.Fluid.Interfaces.FluidPort_b	port_b3 (from EightPort)	Fluid connector b2 (positive design flow direction is from port_a3 to port_b3)
Modelica.Fluid.Interfaces.FluidPort_a	port_a4 (from EightPort)	Fluid connector a1 (positive design flow direction is from port_a4 to port_b4)
Modelica.Fluid.Interfaces.FluidPort_b	port_b4 (from EightPort)	Fluid connector b2 (positive design flow direction is from port_a4 to port_b4)

Components

Type	Name	Default	Description
Medium1.MassFlowRate	m1_flow (from PartialEightPortInterface)	port_a1.m_flow	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction)
Modelica.Units.SI.Pressure	dp1 (from PartialEightPortInterface)	port_a1.p - port_b1.p	Pressure difference between port_a1 and port_b1
Medium2.MassFlowRate	m2_flow (from PartialEightPortInterface)	port_a2.m_flow	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction)
Modelica.Units.SI.Pressure	dp2 (from PartialEightPortInterface)	port_a2.p - port_b2.p	Pressure difference between port_a2 and port_b2
Medium3.MassFlowRate	m3_flow (from PartialEightPortInterface)	port_a3.m_flow	Mass flow rate from port_a3 to port_b3 (m3_flow > 0 is design flow direction)
Modelica.Units.SI.Pressure	dp3 (from PartialEightPortInterface)	port_a3.p - port_b3.p	Pressure difference between port_a3 and port_b3
Medium4.MassFlowRate	m4_flow (from PartialEightPortInterface)	port_a4.m_flow	Mass flow rate from port_a4 to port_b4 (m4_flow > 0 is design flow direction)
Modelica.Units.SI.Pressure	dp4 (from PartialEightPortInterface)	port_a4.p - port_b4.p	Pressure difference between port_a4 and port_b4
Medium1.ThermodynamicState	sta_a1 (from PartialEightPortInterface)	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 PartialEightPortInterface)	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 PartialEightPortInterface)	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 PartialEightPortInterface)	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
Medium3.ThermodynamicState	sta_a3 (from PartialEightPortInterface)	if allowFlowReversal3 then Medium3.setState_phX(port_a3.p, noEvent(actualStream(port_a3.h_outflow)), noEvent(actualStream(port_a3.Xi_outflow))) else Medium3.setState_phX(port_a3.p, inStream(port_a3.h_outflow), inStream(port_a3.Xi_outflow))	Medium properties in port_a3
Medium3.ThermodynamicState	sta_b3 (from PartialEightPortInterface)	if allowFlowReversal3 then Medium3.setState_phX(port_b3.p, noEvent(actualStream(port_b3.h_outflow)), noEvent(actualStream(port_b3.Xi_outflow))) else Medium3.setState_phX(port_b3.p, port_b3.h_outflow, port_b3.Xi_outflow)	Medium properties in port_b3
Medium4.ThermodynamicState	sta_a4 (from PartialEightPortInterface)	if allowFlowReversal4 then Medium4.setState_phX(port_a4.p, noEvent(actualStream(port_a4.h_outflow)), noEvent(actualStream(port_a4.Xi_outflow))) else Medium4.setState_phX(port_a4.p, inStream(port_a4.h_outflow), inStream(port_a4.Xi_outflow))	Medium properties in port_a4
Medium4.ThermodynamicState	sta_b4 (from PartialEightPortInterface)	if allowFlowReversal4 then Medium4.setState_phX(port_b4.p, noEvent(actualStream(port_b4.h_outflow)), noEvent(actualStream(port_b4.Xi_outflow))) else Medium4.setState_phX(port_b4.p, port_b4.h_outflow, port_b4.Xi_outflow)	Medium properties in port_b4
Modelica.Units.SI.HeatFlowRate	Q1_flow (from EightPortHeatMassExchanger)	vol1.heatPort.Q_flow	Heat flow rate into medium 1
Modelica.Units.SI.HeatFlowRate	Q2_flow (from EightPortHeatMassExchanger)	vol2.heatPort.Q_flow	Heat flow rate into medium 2
Modelica.Units.SI.HeatFlowRate	Q3_flow (from EightPortHeatMassExchanger)	vol3.heatPort.Q_flow	Heat flow rate into medium 1
Modelica.Units.SI.HeatFlowRate	Q4_flow (from EightPortHeatMassExchanger)	vol4.heatPort.Q_flow	Heat flow rate into medium 2
Buildings.Fluid.MixingVolumes.MixingVolume	vol1 (from EightPortHeatMassExchanger)		Volume for fluid 1
Buildings.Fluid.MixingVolumes.MixingVolume	vol2 (from EightPortHeatMassExchanger)		Volume for fluid 2
Buildings.Fluid.MixingVolumes.MixingVolume	vol3 (from EightPortHeatMassExchanger)		Volume for fluid 3
Buildings.Fluid.MixingVolumes.MixingVolume	vol4 (from EightPortHeatMassExchanger)		Volume for fluid 4
Buildings.Fluid.FixedResistances.PressureDrop	preDro1 (from EightPortHeatMassExchanger)		Pressure drop model for fluid 1
Buildings.Fluid.FixedResistances.PressureDrop	preDro2 (from EightPortHeatMassExchanger)		Pressure drop model for fluid 2
Buildings.Fluid.FixedResistances.PressureDrop	preDro3 (from EightPortHeatMassExchanger)		Pressure drop model for fluid 3
Buildings.Fluid.FixedResistances.PressureDrop	preDro4 (from EightPortHeatMassExchanger)		Pressure drop model for fluid 4
Modelica.Blocks.Sources.RealExpression	RVol1		Convective and thermal resistance at fluid 1
Modelica.Blocks.Sources.RealExpression	RVol2		Convective and thermal resistance at fluid 2
Modelica.Blocks.Sources.RealExpression	RVol3		Convective and thermal resistance at fluid 1
Modelica.Blocks.Sources.RealExpression	RVol4		Convective and thermal resistance at fluid 1
Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.BaseClasses.InternalResistancesTwoUTube	intRes2UTub		Internal resistances for a double U-tube configuration
Modelica.Thermal.HeatTransfer.Components.ConvectiveResistor	RConv1		Pipe convective resistance
Modelica.Thermal.HeatTransfer.Components.ConvectiveResistor	RConv2		Pipe convective resistance
Modelica.Thermal.HeatTransfer.Components.ConvectiveResistor	RConv3		Pipe convective resistance
Modelica.Thermal.HeatTransfer.Components.ConvectiveResistor	RConv4		Pipe convective resistance

Revisions

August 3, 2026, by Michael Wetter:
Removed duplicate empty Diagram annotation.
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.internalResistancesTwoUTube.
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.