Buildings.Fluid.Geothermal.Borefields

Package with borefield models

Information

Package with models for geothermal borefields.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name Description
Buildings.Fluid.Geothermal.Borefields.UsersGuide UsersGuide User's Guide
Buildings.Fluid.Geothermal.Borefields.OneUTube OneUTube Borefield model containing single U-tube boreholes
Buildings.Fluid.Geothermal.Borefields.TwoUTubes TwoUTubes Borefield model containing double U-tube boreholes
Buildings.Fluid.Geothermal.Borefields.Data Data Collection of data records for ground heat exchanger models
Buildings.Fluid.Geothermal.Borefields.Types Types Package with type definitions
Buildings.Fluid.Geothermal.Borefields.Examples Examples Example models for Buildings.Fluid.Geothermal.Borefields
Buildings.Fluid.Geothermal.Borefields.Validation Validation Validation models for Buildings.Fluid.Geothermal.Borefields
Buildings.Fluid.Geothermal.Borefields.BaseClasses BaseClasses Base classes used in Buildings.Fluid.HeatExchangers.Ground

Buildings.Fluid.Geothermal.Borefields.OneUTube Buildings.Fluid.Geothermal.Borefields.OneUTube

Borefield model containing single U-tube boreholes

Buildings.Fluid.Geothermal.Borefields.OneUTube

Information

This model simulates a borefield containing one or many single U-tube boreholes using the parameters in the borFieDat record.

Heat transfer to the soil is modeled using only one borehole heat exchanger. The fluid mass flow rate into the borehole is divided to reflect the per-borehole fluid mass flow rate. The borehole model calculates the dynamics within the borehole itself using an axial discretization and a resistance-capacitance network for the internal thermal resistances between the individual pipes and between each pipe and the borehole wall.

Extends from Buildings.Fluid.Geothermal.Borefields.BaseClasses.PartialBorefield (Borefield model using single U-tube borehole heat exchanger configuration.Calculates the average fluid temperature T_fts of the borefield for a given (time dependent) load Q_flow).

Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
TimetLoaAgg300Time resolution of load aggregation [s]
IntegernCel5Number of cells per aggregation level
IntegernSeg10Number of segments to use in vertical discretization of the boreholes
TemplateborFieDat Borefield data
Assumptions
BooleanallowFlowReversaltrue= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed
g-function
BooleanforceGFunCalcfalseSet to true to force the thermal response to be calculated at the start instead of checking whether this has been pre-computed
IntegernSegGFun12Number of segments to use in the calculation of the g-function
IntegernClu5Number of borehole clusters to use in the calculation of the g-function
Flow resistance
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Conservation equations
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state
BooleandynFiltrueSet to false to remove the dynamics of the filling material.
Initialization
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureTFlu_start[nSeg]TGro_startStart value of fluid temperature [K]
Soil
TemperatureTExt0_start283.15Initial far field temperature [K]
TemperatureTExt_start[nSeg]{if z[i] >= z0 then TExt0_st...Temperature of the undisturbed ground [K]
Filling material
TemperatureTGro_start[nSeg]TExt_startStart value of grout temperature [K]
Temperature profile
Heightz010Depth below which the temperature gradient starts [m]
RealdT_dz0.01Vertical temperature gradient of the undisturbed soil for h below z0 [K/m]

Connectors

TypeNameDescription
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
output RealOutputTBorAveAverage borehole wall temperature in the borefield [K]

Modelica definition

model OneUTube "Borefield model containing single U-tube boreholes" extends Buildings.Fluid.Geothermal.Borefields.BaseClasses.PartialBorefield( redeclare Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.OneUTube borHol); end OneUTube;

Buildings.Fluid.Geothermal.Borefields.TwoUTubes Buildings.Fluid.Geothermal.Borefields.TwoUTubes

Borefield model containing double U-tube boreholes

Buildings.Fluid.Geothermal.Borefields.TwoUTubes

Information

This model simulates a borefield containing one or many double U-tube boreholes using the parameters in the borFieDat record.

Heat transfer to the soil is modeled using only one borehole heat exchanger. The fluid mass flow rate into the borehole is divided to reflect the per-borehole fluid mass flow rate. The borehole model calculates the dynamics within the borehole itself using an axial discretization and a resistance-capacitance network for the internal thermal resistances between the individual pipes and between each pipe and the borehole wall.

Extends from Buildings.Fluid.Geothermal.Borefields.BaseClasses.PartialBorefield (Borefield model using single U-tube borehole heat exchanger configuration.Calculates the average fluid temperature T_fts of the borefield for a given (time dependent) load Q_flow).

Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
TimetLoaAgg300Time resolution of load aggregation [s]
IntegernCel5Number of cells per aggregation level
IntegernSeg10Number of segments to use in vertical discretization of the boreholes
TemplateborFieDat Borefield data
Assumptions
BooleanallowFlowReversaltrue= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed
g-function
BooleanforceGFunCalcfalseSet to true to force the thermal response to be calculated at the start instead of checking whether this has been pre-computed
IntegernSegGFun12Number of segments to use in the calculation of the g-function
IntegernClu5Number of borehole clusters to use in the calculation of the g-function
Flow resistance
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Conservation equations
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state
BooleandynFiltrueSet to false to remove the dynamics of the filling material.
Initialization
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureTFlu_start[nSeg]TGro_startStart value of fluid temperature [K]
Soil
TemperatureTExt0_start283.15Initial far field temperature [K]
TemperatureTExt_start[nSeg]{if z[i] >= z0 then TExt0_st...Temperature of the undisturbed ground [K]
Filling material
TemperatureTGro_start[nSeg]TExt_startStart value of grout temperature [K]
Temperature profile
Heightz010Depth below which the temperature gradient starts [m]
RealdT_dz0.01Vertical temperature gradient of the undisturbed soil for h below z0 [K/m]

Connectors

TypeNameDescription
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
output RealOutputTBorAveAverage borehole wall temperature in the borefield [K]

Modelica definition

model TwoUTubes "Borefield model containing double U-tube boreholes" extends Buildings.Fluid.Geothermal.Borefields.BaseClasses.PartialBorefield( redeclare Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.TwoUTube borHol); end TwoUTubes;