modelHexInternalElement
Internal part of a borehole
Extends from 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. 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 explicitly the fluid-to-ground thermal resistance Rb and the grout-to-grout resistance Ra as defined by Hellstroem (1991) using the multipole method. The multipole method is implemented in Buildings.Fluid.Geothermal.Boreholes.BaseClasses.singleUTubeResistances. The convection resistance is calculated using the Dittus-Boelter correlation as implemented in Buildings.Fluid.Geothermal.Boreholes.BaseClasses.convectionResistance.
The figure below shows the thermal network set up by Bauer et al. (2010).
References
G. Hellström. Ground heat storage: thermal analyses of duct storage systems (Theory). Dept. of Mathematical Physics, University of Lund, Sweden, 1991.
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 |
|---|---|---|---|
| Boolean | homotopyInitialization (from FourPortHeatMassExchanger) | true | = true, use homotopy method |
| Modelica.Units.SI.ThermalConductivity | kSoi | Thermal conductivity of the soil used for the calculation of the internal interference resistance | |
| Modelica.Units.SI.Height | hSeg | Height of the element | |
| Modelica.Units.SI.Radius | rBor | Radius of the borehole | |
| Modelica.Units.SI.Length | xC | 0.05 | Shank spacing, defined as half the center-to-center distance between the two pipes |
| 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.) |
| Filling material | |||
| Buildings.HeatTransfer.Data.BoreholeFillings.Generic | matFil | Thermal properties of the filling material | |
| Modelica.Units.SI.Temperature | TFil_start | 283.15 | Initial temperature of the filling material |
| Soil | |||
| Buildings.HeatTransfer.Data.Soil.Generic | matSoi | Thermal properties of soil | |
| Pipes | |||
| Modelica.Units.SI.Radius | rTub | 0.02 | Radius of the tubes |
| Modelica.Units.SI.ThermalConductivity | kTub | 0.5 | Thermal conductivity of the tubes |
| Modelica.Units.SI.Length | eTub | 0.002 | Thickness of the tubes |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| 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) | |
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | port | Heat port that connects to filling material |
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.Thermal.HeatTransfer.Components.HeatCapacitor | capFil1 | Heat capacity of the filling material | |
| Modelica.Thermal.HeatTransfer.Components.HeatCapacitor | capFil2 | Heat capacity of the filling material |
Contents
| Name | Description |
|---|---|
 Medium | Medium in the component |
Revisions
-
May 6, 2015, by Michael Wetter:
Removed assignement ofvol.allowFlowReversalas this is done in the base class. -
June 18, 2014, by Michael Wetter:
Added initialization for temperatures and derivatives ofcapFil1andcapFil2to avoid a warning during translation. -
February 14, 2014, by Michael Wetter:
Removed unused parametersB0andB1. -
January 24, 2014, by Michael Wetter:
Revised implementation, added comments, replacedHeatTransfer.Windows.BaseClasses.ThermalConductorwith resistance models from the Modelica Standard Library. -
January 23, 2014, by Damien Picard:
First implementation.