modelStorageTankHex
Extends from BaseClasses.BaseStation.
Information
This is a model for a district heating substation storage tank with an internal heat exchanger. Its main components are the storage tank with internal heat exchanger, a flow regulating valve/pump, an expansion vessel and a controller that maintains the temperature in the selected tank layer by setting the position of the flow regulating valve/pump to open or closed.
A mismatch between the setpoint and the actual value of the secondary supply temperature can have different reasons:
- The differential pressure at the station is too low, resulting in a too low mass flow at the primary side even if the valve is completely open.
- The nominal mass flow rate at the primary side is too low, leading to a too low secondary supply temperature even with a fully opend valve.
- The supply temperature at the primary side is too low, i.e., lower than the tank temperature setpoint, leading to a fully opened valve
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Assumptions | |||
| Boolean | allowFlowReversal1 (from PartialFourPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1 |
| Boolean | allowFlowReversal2 (from PartialFourPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2 |
| Nominal condition | |||
| Modelica.SIunits.MassFlowRate | m1_flow_nominal (from PartialFourPortInterface) | Nominal mass flow rate | |
| Modelica.SIunits.MassFlowRate | m2_flow_nominal (from PartialFourPortInterface) | Nominal mass flow rate | |
| Advanced | |||
| Medium1.MassFlowRate | m1_flow_small (from PartialFourPortInterface) | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Medium2.MassFlowRate | m2_flow_small (from PartialFourPortInterface) | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialFourPortInterface) | false | = true, if actual temperature at port is computed |
| Flow resistance › Primary side | |||
| Boolean | from_dp (from BaseStation) | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance (from BaseStation) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Primary side | |||
| Modelica.SIunits.Power | Q1_flow_nominal (from BaseStation) | m1_flow_nominal*(TemSup1_nominal - TemRet1_nominal)*cp_default | Nominal heat flow rate at primary side |
| Modelica.SIunits.Temperature | TemSup1_nominal (from BaseStation) | 80.0 + 273.15 | Nominal supply temperature |
| Modelica.SIunits.Temperature | TemRet1_nominal (from BaseStation) | 45.0 + 273.15 | Nominal return temperature |
| Modelica.SIunits.PressureDifference | dp1_nominal (from BaseStation) | Nominal pressure difference | |
| Secondary side | |||
| Modelica.SIunits.Power | Q2_flow_nominal (from BaseStation) | m2_flow_nominal*(TemSup2_nominal - TemRet2_nominal)*cp_default | Nominal heat flow rate at primary side |
| Modelica.SIunits.Temperature | TemSup2_nominal (from BaseStation) | 60.0 + 273.15 | Nominal supply temperature |
| Modelica.SIunits.Temperature | TemRet2_nominal (from BaseStation) | 35.0 + 273.15 | Nominal return temperature |
| Boolean | OutsideDependent (from BaseStation) | false | Outside temperature dependent secondary supply temperature |
| Storage tank | |||
| Modelica.SIunits.Volume | VTan | Tank volume | |
| Modelica.SIunits.Length | hTan | Height of tank (without insulation) | |
| Modelica.SIunits.Length | dIns | 0.2 | Thickness of insulation |
| Modelica.SIunits.ThermalConductivity | kIns | 0.04 | Specific heat conductivity of insulation |
| Integer | nSeg | 4 | Number of volume segments |
| Modelica.SIunits.Temperature | TemRoom | 20.0 + 273.15 | Constant temperature surrounding the storage tank |
| Integer | nInit | nSeg | Number of volume segments initialized with TemSup2_nominal |
| Modelica.SIunits.PressureDifference | dp_hex_nominal | 0 | Nominal pressure difference at the heat exchanger at primary side |
| Modelica.SIunits.Height | hHex_a | storageTankHex.hTan/2 | Height of portHex_a of the heat exchanger, measured from tank bottom |
| Modelica.SIunits.Height | hHex_b | 0 | Height of portHex_b of the heat exchanger, measured from tank bottom |
| Integer | hexSegMult | 2 | Number of heat exchanger segments in each tank segment |
| Modelica.SIunits.Diameter | dExtHex | 0.025 | Exterior diameter of the heat exchanger pipe |
| Real | r_nominal | 0.5 | Ratio between coil inside and outside convective heat transfer at nominal heat transfer conditions |
| Flow controller | |||
| Modelica.SIunits.Temperature | T_const | TemSup2_nominal | Constant temperature setpoint |
| Modelica.SIunits.Time | Ti | 120 | Time constant of Integrator block |
| Real | k | 0.01 | Gain of controller |
| Integer | nSegMeasure | 1 | Volume segment to take temperature from |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a1 (from PartialFourPort) | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b1 (from PartialFourPort) | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) | |
| Modelica.Fluid.Interfaces.FluidPort_a | port_a2 (from PartialFourPort) | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b2 (from PartialFourPort) | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) | |
| Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a | port_ht (from BaseStation) | Outside temperature port | |
| Modelica.Blocks.Interfaces.RealOutput | P (from BaseStation) | Electric power |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium1.MassFlowRate | m1_flow (from PartialFourPortInterface) | port_a1.m_flow | Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) |
| Modelica.SIunits.PressureDifference | dp1 (from PartialFourPortInterface) | port_a1.p - port_b1.p | Pressure difference between port_a1 and port_b1 |
| Medium2.MassFlowRate | m2_flow (from PartialFourPortInterface) | port_a2.m_flow | Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) |
| Modelica.SIunits.PressureDifference | dp2 (from PartialFourPortInterface) | port_a2.p - port_b2.p | Pressure difference between port_a2 and port_b2 |
| Medium1.ThermodynamicState | sta_a1 (from PartialFourPortInterface) | Medium1.setState_phX(port_a1.p, noEvent(actualStream(port_a1.h_outflow)), noEvent(actualStream(port_a1.Xi_outflow))) | Medium properties in port_a1 |
| Medium1.ThermodynamicState | sta_b1 (from PartialFourPortInterface) | Medium1.setState_phX(port_b1.p, noEvent(actualStream(port_b1.h_outflow)), noEvent(actualStream(port_b1.Xi_outflow))) | Medium properties in port_b1 |
| Medium2.ThermodynamicState | sta_a2 (from PartialFourPortInterface) | Medium2.setState_phX(port_a2.p, noEvent(actualStream(port_a2.h_outflow)), noEvent(actualStream(port_a2.Xi_outflow))) | Medium properties in port_a2 |
| Medium2.ThermodynamicState | sta_b2 (from PartialFourPortInterface) | Medium2.setState_phX(port_b2.p, noEvent(actualStream(port_b2.h_outflow)), noEvent(actualStream(port_b2.Xi_outflow))) | Medium properties in port_b2 |
| Modelica.Blocks.Sources.RealExpression | total_power (from BaseStation) | sum of all power consumption/generation in component | |
| Storage.StorageTankHex | storageTankHex | ||
| DisHeatLib.Controls.flow_control | storage_control | ||
| DisHeatLib.BaseClasses.FlowUnit | flowUnit | ||
| Storage.BaseClasses.ThermostatMixer | thermostatMixer |