Buildings.Fluid.Geothermal.ZonedBorefields
Package with borefield models for thermal energy storage with multiple parallel loops
Information
Package with models for zoned borehole thermal energy storage systems.
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 |
 Examples
|
Example models for zoned borefields |
| Validation
|
Validation models for zoned geothermal energy storage |
 Interfaces
|
Package with interface for bore field models |
 BaseClasses
|
Base classes used in Buildings.Fluid.Geothermal.ZonedBorefields |
Buildings.Fluid.Geothermal.ZonedBorefields.OneUTube
Borefield model containing single U-tube boreholes
Information
This model simulates a borehole thermal energy storage system with multiple
zones of single U-tube boreholes. Boreholes within the same zone are connected
in parallel. The borefield configuration and thermal parameters are defined in
the borFieDat record.
Heat transfer to the soil is modeled using only one borehole heat exchanger per zone. The fluid mass flow rate into each 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.
The ground thermal response at each borehole segment is evaluated using analytical thermal response factors. Spatial and temporal superposition are used to evaluate the total temperature change at each of the borehole segments.
Extends from Buildings.Fluid.Geothermal.ZonedBorefields.BaseClasses.PartialStorage (Partial model for borehole thermal energy storage with independent borefield zones).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Time | tLoaAgg | 3600.0 | 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 record | |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| MassFlowRate | m_flow_small[nPorts] | 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 |
| Flow resistance | |||
| Boolean | from_dp[nPorts] | fill(false, nPorts) | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance[nPorts] | fill(false, nPorts) | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM[nPorts] | fill(0.1, nPorts) | 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 |
| 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[nPorts] | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b[nPorts] | Fluid connector b (positive design flow direction is from port_a to port_b) |
| output RealOutput | TBorAve[nZon] | Average borehole wall temperature in the borefield [K] |
| output RealOutput | QBorAve[nZon] | Average (per borehole) heat transfer rate in each zone [W] |
Modelica definition
Buildings.Fluid.Geothermal.ZonedBorefields.TwoUTubes
Borefield model containing double U-tube boreholes
Information
This model simulates a borehole thermal energy storage system with multiple
zones of double U-tube boreholes. Boreholes within the same zone are connected
in parallel. The borefield configuration and thermal parameters are defined in
the borFieDat record.
Heat transfer to the soil is modeled using only one borehole heat exchanger per zone. The fluid mass flow rate into each 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.
The ground thermal response at each borehole segment is evaluated using analytical thermal response factors. Spatial and temporal superposition are used to evaluate the total temperature change at each of the borehole segments.
Extends from Buildings.Fluid.Geothermal.ZonedBorefields.BaseClasses.PartialStorage (Partial model for borehole thermal energy storage with independent borefield zones).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Time | tLoaAgg | 3600.0 | 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 record | |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| MassFlowRate | m_flow_small[nPorts] | 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 |
| Flow resistance | |||
| Boolean | from_dp[nPorts] | fill(false, nPorts) | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance[nPorts] | fill(false, nPorts) | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM[nPorts] | fill(0.1, nPorts) | 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 |
| 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[nPorts] | Fluid connector a (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_b[nPorts] | Fluid connector b (positive design flow direction is from port_a to port_b) |
| output RealOutput | TBorAve[nZon] | Average borehole wall temperature in the borefield [K] |
| output RealOutput | QBorAve[nZon] | Average (per borehole) heat transfer rate in each zone [W] |