modelOneUTube
Borefield model containing single U-tube boreholes
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).
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.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | mSenFac (from PartialBorefield) | 1 | Factor for scaling the sensible thermal mass of the volume |
| Modelica.Units.SI.Time | tLoaAgg (from PartialBorefield) | 300 | Time resolution of load aggregation |
| Integer | nCel (from PartialBorefield) | 5 | Number of cells per aggregation level |
| Integer | nSeg (from PartialBorefield) | 10 | Number of segments to use in vertical discretization of the boreholes |
| Buildings.Fluid.Geothermal.Borefields.Data.Borefield.Template | borFieDat (from PartialBorefield) | Borefield data | |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal (from PartialTwoPortInterface) | Nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dp_nominal (from TwoPortFlowResistanceParameters) | Pressure difference | |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small (from PartialTwoPortInterface) | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortInterface) | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | computeFlowResistance (from TwoPortFlowResistanceParameters) | true | =true, compute flow resistance. Set to false to assume no friction |
| Boolean | from_dp (from TwoPortFlowResistanceParameters) | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Real | n (from TwoPortFlowResistanceParameters) | 2 | Flow exponent, n=1 for laminar, n=2 for turbulent |
| Boolean | linearizeFlowResistance (from TwoPortFlowResistanceParameters) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM (from TwoPortFlowResistanceParameters) | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics › Conservation equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics (from PartialBorefield) | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
| Initialization | |||
| Medium.AbsolutePressure | p_start (from PartialBorefield) | Medium.p_default | Start value of pressure |
| Modelica.Units.SI.Temperature[nSeg] | TFlu_start (from PartialBorefield) | TGro_start | Start value of fluid temperature |
| Advanced › g-function | |||
| Boolean | forceGFunCalc (from PartialBorefield) | 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 (from PartialBorefield) | 12 | Number of segments to use in the calculation of the g-function |
| Integer | nClu (from PartialBorefield) | 5 | Number of borehole clusters to use in the calculation of the g-function |
| Initialization › Soil | |||
| Modelica.Units.SI.Temperature | TExt0_start (from PartialBorefield) | 283.15 | Initial far field temperature |
| Modelica.Units.SI.Temperature[nSeg] | TExt_start (from PartialBorefield) | {if z[i] >= z0 then TExt0_start + (z[i] - z0)*dT_dz else TExt0_start for i in 1:nSeg} | Temperature of the undisturbed ground |
| Initialization › Filling material | |||
| Modelica.Units.SI.Temperature[nSeg] | TGro_start (from PartialBorefield) | TExt_start | Start value of grout temperature |
| Initialization › Temperature profile | |||
| Modelica.Units.SI.Height | z0 (from PartialBorefield) | 10 | Depth below which the temperature gradient starts |
| Real | dT_dz (from PartialBorefield) | 0.01 | Vertical temperature gradient of the undisturbed soil for h below z0 |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a (from PartialTwoPort) | Fluid connector a (positive design flow direction is from port_a to port_b) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b (from PartialTwoPort) | Fluid connector b (positive design flow direction is from port_a to port_b) | |
| Modelica.Blocks.Interfaces.RealOutput | TBorAve (from PartialBorefield) | Average borehole wall temperature in the borefield |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | m_flow (from PartialTwoPortInterface) | port_a.m_flow | Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp (from PartialTwoPortInterface) | port_a.p - port_b.p | Pressure difference between port_a and port_b |
| Medium.ThermodynamicState | sta_a (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow))) | Medium properties in port_a |
| Medium.ThermodynamicState | sta_b (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow)) | Medium properties in port_b |
| Buildings.Fluid.Geothermal.Borefields.BaseClasses.HeatTransfer.GroundTemperatureResponse | groTemRes (from PartialBorefield) | Ground temperature response | |
| Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.BaseClasses.PartialBorehole | borHol (from PartialBorefield) |
Revisions
-
July 2018, by Alex Laferrière:
Extended partial model and changed documentation to reflect the new approach used by the borefield models. -
July 2014, by Damien Picard:
First implementation.