modelOneUTube
Single U-tube borehole heat exchanger
Extends from Buildings.Fluid.Geothermal.Borefields.BaseClasses.Boreholes.BaseClasses.PartialBorehole (Partial model to implement multi-segment boreholes).
Information
Model of a single U-tube borehole heat exchanger.
The borehole heat exchanger is vertically discretized into
nseg elements of height
h=hBor⁄nseg.
Each segment contains a model for the heat transfer in the borehole,
with a uniform borehole wall boundary temperature given by the
port_wall port.
The heat transfer in the borehole is computed using a convective heat transfer coefficient that depends on the fluid velocity, a heat resistance between the two pipes, and a heat resistance between the pipes and the borehole wall. The heat capacity of the fluid and the heat capacity of the grout are taken into account. The vertical heat flow is assumed to be zero.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | mSenFac (from PartialBorehole) | 1 | Factor for scaling the sensible thermal mass of the volume |
| Integer | nSeg (from PartialBorehole) | 10 | Number of segments to use in vertical discretization of the boreholes |
| Data.Borefield.Template | borFieDat (from PartialBorehole) | Borefield parameters | |
| 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 |
| Initialization | |||
| Modelica.Units.SI.Temperature[nSeg] | TGro_start (from PartialBorehole) | Start value of grout temperature | |
| Modelica.Units.SI.Temperature[nSeg] | TFlu_start (from PartialBorehole) | TGro_start | Start value of fluid temperature |
| Medium.AbsolutePressure | p_start (from PartialBorehole) | Medium.p_default | Start value of pressure |
| Dynamics › Conservation equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics (from PartialBorehole) | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
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.Thermal.HeatTransfer.Interfaces.HeatPort_a[nSeg] | port_wall (from PartialBorehole) | Thermal connection for borehole wall |
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.Boreholes.BaseClasses.InternalHEXOneUTube[nSeg] | intHex | Borehole segments |
Revisions
-
May 17, 2024, by Michael Wetter:
Updated model due to removal of parameterdynFil.
This is for IBPSA, #1885. -
July 2018, by Alex Laferrière:
Following major changes to the structure of the Buildings.Fluid.HeatExchangers.Ground package, the documentation has been changed to reflect the new role of this model. Additionally, this model now extends a partial borehole model. -
July 2014, by Damien Picard:
First implementation.