modelPlugFlowPipeEmbedded
Extends from AixLib.Fluid.Interfaces.PartialTwoPortInterface.
Information
This model represents an extension of AixLib.Fluid.DistrictHeatingCooling.Pipes.PlugFlowPipe by modelling the thermal capacity of the surrounding soil. For the description of the cylindric heat transfer within the surrounding soil AixLib.Utilities.HeatTransfer.CylindricHeatTransfer is used. The considered layer thickness of the surrounding soil is set as a parameter and divided into three capacities. For the heat transfer calculation within the material/soil, the density, the specific heat capacity, the thickness of the considered soil layer and the thermal conductivity of the material are used.
The default values for the soil are for sandy soil with clay content and based on: "Simulationsmodell Erdwärmekollektor zur wärmetechnischen Beurteilung von Wärmequellen, Wärmesenken und Wärme-/Kältespeicher" by Berd Glück
References
Full details on the model implementation and experimental validation can be found in:
van der Heijde, B., Fuchs, M., Ribas Tugores, C., Schweiger, G.,
Sartor, K., Basciotti, D., Müller, D., Nytsch-Geusen, C., Wetter, M.
and Helsen, L. (2017).
Dynamic equation-based thermo-hydraulic pipe model for district
heating and cooling systems.
Energy Conversion and Management, vol. 151, p. 158-169.
doi:
10.1016/j.enconman.2017.08.072.
- November 21, 2019, by Nils Neuland:
Model is now using PlugFlowPipe model from DistrictHeatingCooling - July, 2018 by Tobias Blacha:
First implementation.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | ReC | 4000 | Reynolds number where transition to turbulent starts |
| Dynamics › Equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
| Additional pressurelosses | |||
| Boolean | use_zeta | false | = true HydraulicResistance is implemented, zeta value has to be given next |
| Real | fac | 1 | Factor to take into account flow resistance of bends etc., fac=dp_nominal/dpStraightPipe_nominal |
| Real | sum_zetas | 0 | Sum of all zeta values. Takes into account additional pressure drops due to bends/valves/etc. |
| Advanced | |||
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Modelica.Units.SI.MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Material | |||
| Modelica.Units.SI.Length | dh | sqrt(4*m_flow_nominal/rho_default/v_nominal/Modelica.Constants.pi) | Hydraulic diameter (assuming a round cross section area) |
| Modelica.Units.SI.Height | roughness | 2.5e-5 | Average height of surface asperities (default: smooth steel pipe) |
| Modelica.Units.SI.Length | length | Pipe length | |
| Modelica.Units.SI.SpecificHeatCapacity | cPip | 2300 | Specific heat of pipe wall material. 2300 for PE, 500 for steel |
| Modelica.Units.SI.Density | rhoPip | 930 | Density of pipe wall material. 930 for PE, 8000 for steel |
| Modelica.Units.SI.Length | thickness | 0.0035 | Pipe wall thickness |
| Nominal condition | |||
| Modelica.Units.SI.Velocity | v_nominal | 1.5 | Velocity at m_flow_nominal (used to compute default value for hydraulic diameter dh) |
| Modelica.Units.SI.MassFlowRate | m_flow_nominal | Nominal mass flow rate | |
| Thermal resistance | |||
| Modelica.Units.SI.Length | dIns | Thickness of pipe insulation, used to compute R | |
| Modelica.Units.SI.ThermalConductivity | kIns | Heat conductivity of pipe insulation, used to compute R | |
| Real | R | 1/(kIns*2*Modelica.Constants.pi/Modelica.Math.log((dh/2 + dIns)/(dh/2))) | Thermal resistance per unit length from fluid to boundary temperature |
| Initialization | |||
| Modelica.Units.SI.Temperature | T_start_in | Medium.T_default | Initialization temperature at pipe inlet |
| Modelica.Units.SI.Temperature | T_start_out | T_start_in | Initialization temperature at pipe outlet |
| Boolean | initDelay | false | Initialize delay for a constant mass flow rate if true, otherwise start from 0 |
| Modelica.Units.SI.MassFlowRate | m_flow_start | 0 | Initial value of mass flow rate through pipe |
| Soil | |||
| Modelica.Units.SI.Density | rho_soi | 1630 | Density of material/soil |
| Modelica.Units.SI.SpecificHeatCapacity | c | 1046 | Specific heat capacity of material/soil |
| Modelica.Units.SI.Length | thickness_soi | 0.6 | thickness of soil layer for heat loss calulcation |
| Modelica.Units.SI.ThermalConductivity | lambda | 1.5 | Heat conductivity of material/soil |
| Modelica.Units.SI.Length | d_in | dh + 2*thickness | Inner diameter of pipe |
| Integer | nParallel | 1 | Number of identical parallel pipes |
| Modelica.Units.SI.Temperature | T0 | 289.15 | Initial temperature |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Velocity | v_med | Velocity of the medium in the pipe | |
| AixLib.Fluid.DistrictHeatingCooling.Pipes.PlugFlowPipeZeta | plugFlowPipeZeta | ||
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | heatPort | Heat transfer to or from surroundings (heat loss from pipe results in a positive heat flow) | |
| AixLib.Utilities.HeatTransfer.CylindricHeatTransfer | cylindricHeatTransfer_1 | ||
| AixLib.Utilities.HeatTransfer.CylindricHeatTransfer | cylindricHeatTransfer_2 | ||
| AixLib.Utilities.HeatTransfer.CylindricHeatTransfer | cylindricHeatTransfer_3 |