modelExpansionTank
Expansion Tank - lumped model
Information
Model ExpansionTank describes the storage of fluid in liquid phase in a closed volume filled with gas.
Pressure and enthalpy are selected as state variables.
The assumptions for this model are:
- The gas is considered ideal and using Boyle's law: p_gas*V_gas = Const = pstart*V_gas
- The gas is considered at the same temperature of the fluid
- The model is based on dynamic mass and energy balances of the fluid
- The static pressure head due to the liquid level is taken into account
- Thermal energy transfer due to external air convection through the tank surface (lateral+top+bottom) is ensured by the TankWall connector. The actual heat flow is computed by the thermal energy model
- Minimum liquid level with respect to tank height= 0
- Maximum liquid level with respect to tank height= 0.5
The model is characterized by one flow connector.
The thermal energy transfer through the tank surface is computed by the ConvectiveHeatTransfer model which is inerithed in the ExpansionTank model
Modelling options
In the General tab the following options are availabe:
- Medium: the user has the possibility to easly switch Medium.
- p_const:If true an user defined constant pressure is imposed to the fluid volume --> closed tank at constant pressure
- HeatTransfer: selection between the different heat transfer models available in ThermoCycle
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | g | Modelica.Constants.g_n | |
| Real | pi | Modelica.Constants.pi | pi-greco |
| Real | RR | Modelica.Constants.R | Molar gas constant [J/mol.K] |
| Real | H_D | Height to diameter ratio | |
| Modelica.SIunits.Volume | V_tank | Volume of the Tank | |
| Modelica.SIunits.Length | r_int | ((V_tank/(H_D)*4/pi)^(1/3))/2 | Internal tank radius |
| Modelica.SIunits.Length | D_int | r_int*2 | Internal tank Diameter |
| Modelica.SIunits.Length | H | V_tank/A_cross | Tank Height |
| Modelica.SIunits.Area | A_lateral | pi*H*D_int | Lateral External Area |
| Modelica.SIunits.Area | A_cross | pi*r_int^2 | Cross section of the tank External Area |
| Modelica.SIunits.Area | Atot_tank | A_lateral + 2*A_cross | Total External Area (lateral + bottom + top) |
| Boolean | p_const | false | Impose a constant pressure to the tank |
| Modelica.SIunits.Pressure | p_ext | 1e5 | Constant pressure value |
| Modelica.SIunits.MassFlowRate | Mdotnom | Nominal fluid flow rate | |
| Modelica.SIunits.CoefficientOfHeatTransfer | Unom | 1 | Nominal Heat transfer coefficient for the fluid. |
| Modelica.SIunits.Volume | V_lstart | A_cross*L_lstart | |
| Real | pV_gas | pstart*V_tank*(1 - L_lstart) | Initial value of |
| Initialization | |||
| Modelica.SIunits.Temperature | Tstart | Initial temperature | |
| Modelica.SIunits.Pressure | pstart | Initial pressure in the tank | |
| Modelica.SIunits.SpecificEnthalpy | hstart | Medium.specificEnthalpy_pTX(pstart, Tstart, fill(0, 0)) | Start value of enthalpy vector (initialized by default) |
| Real | L_lstart | Start value for the liquid level with respect to the tank height min=0,max=0.5 | |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| ThermoCycle.Interfaces.Fluid.FlangeA | InFlow | ||
| Modelica.Blocks.Interfaces.RealOutput | Level | ||
| ThermoCycle.Interfaces.HeatTransfer.ThermalPortL | TankWall |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| HeatTransfer | heatTransfer | ||
| Medium.ThermodynamicState | fluidState | ||
| Medium.AbsolutePressure | p | ||
| Medium.AbsolutePressure | p_fl | Water pressure at the bottom of the tank | |
| Modelica.SIunits.Volume | V_l | Volume of the liquid | |
| Modelica.SIunits.Length | L_l | Height of the liquid | |
| Modelica.SIunits.Mass | M_l | Liquid Mass | |
| Medium.SpecificEnthalpy | h | Fluid specific enthalpy | |
| Medium.SpecificEnthalpy | h_su | Enthalpy state variable at inlet node | |
| Medium.Density | rho | Fluid density | |
| Medium.Temperature | T | Fluid temperature | |
| Modelica.SIunits.MassFlowRate | M_dot | ||
| Modelica.SIunits.HeatFlux | qdot | heat flux with the external ambient | |
| Modelica.SIunits.DerDensityByEnthalpy | drdh | Derivative of average density by enthalpy | |
| Real | dMdt | ||
| Modelica.SIunits.Volume | V_gas | ideal gas volume | |
| Medium.AbsolutePressure | p_gas | Ideal gas pressure |
Contents
| Name | Description |
|---|---|
| Medium | |
 HeatTransfer |