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

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

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Time	tLoaAgg	300	Time resolution of load aggregation [s]
Integer	nCel	5	Number of cells per aggregation level
Integer	nSeg	10	Number of segments to use in vertical discretization of the boreholes
Template	borFieDat		Borefield data
Assumptions
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_T	false	= true, if actual temperature at port is computed
g-function
Boolean	forceGFunCalc	false	Set to true to force the thermal response to be calculated at the start instead of checking whether this has been pre-computed
Integer	nSegGFun	12	Number of segments to use in the calculation of the g-function
Integer	nClu	5	Number of borehole clusters to use in the calculation of the g-function
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Conservation equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Boolean	dynFil	true	Set to false to remove the dynamics of the filling material.
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	TFlu_start[nSeg]	TGro_start	Start value of fluid temperature [K]
Soil
Temperature	TExt0_start	283.15	Initial far field temperature [K]
Temperature	TExt_start[nSeg]	{if z[i] >= z0 then TExt0_st...	Temperature of the undisturbed ground [K]
Filling material
Temperature	TGro_start[nSeg]	TExt_start	Start value of grout temperature [K]
Temperature profile
Height	z0	10	Depth below which the temperature gradient starts [m]
Real	dT_dz	0.01	Vertical temperature gradient of the undisturbed soil for h below z0 [K/m]

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
output RealOutput	TBorAve	Average 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

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.

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Time	tLoaAgg	300	Time resolution of load aggregation [s]
Integer	nCel	5	Number of cells per aggregation level
Integer	nSeg	10	Number of segments to use in vertical discretization of the boreholes
Template	borFieDat		Borefield data
Assumptions
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_T	false	= true, if actual temperature at port is computed
g-function
Boolean	forceGFunCalc	false	Set to true to force the thermal response to be calculated at the start instead of checking whether this has been pre-computed
Integer	nSegGFun	12	Number of segments to use in the calculation of the g-function
Integer	nClu	5	Number of borehole clusters to use in the calculation of the g-function
Flow resistance
Boolean	from_dp	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics
Conservation equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
Boolean	dynFil	true	Set to false to remove the dynamics of the filling material.
Initialization
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Temperature	TFlu_start[nSeg]	TGro_start	Start value of fluid temperature [K]
Soil
Temperature	TExt0_start	283.15	Initial far field temperature [K]
Temperature	TExt_start[nSeg]	{if z[i] >= z0 then TExt0_st...	Temperature of the undisturbed ground [K]
Filling material
Temperature	TGro_start[nSeg]	TExt_start	Start value of grout temperature [K]
Temperature profile
Height	z0	10	Depth below which the temperature gradient starts [m]
Real	dT_dz	0.01	Vertical temperature gradient of the undisturbed soil for h below z0 [K/m]

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
output RealOutput	TBorAve	Average 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;