.ThermalSeparation.Components.Columns.BaseClasses.BaseColumn_external .ThermalSeparation.Components.Columns.BaseClasses.BaseColumn_externalStages are counted from the bottom (n=1: lowest stage). The minimum number of stages is n=1.
Startup operation
If a rectification column at time t = 0s shall be empty and cold and the starup operation from such an empty and cold state shall be modeled, the boolean parameter "considerStartUp" has to be set to true (default value = false). An initial pressure has to be provided.
During start-up the inert gas in the column is not modelled. A variable "startUp" is used in order to determine wether the switching condition on a stage is already fulfilled or not. The switching condition is fulfilled, when the bubble pressure of the mixture attains the initial pressure specified by the user. At this time instant the variable "startUp" is set to false, vapour is leaving the stage and the equilibrium condition at the phase boundary is valid.
The equations for the liquid phase for start up have to be provided in the extending classes.
Medium Models
The liquid medium models and the vapour medium models can differ both in the number of mediums they contain as well as in the substance types. The parameter nSL is the number of substances in the liquid and nSV is the number of substances in the vapour. The parameter nS is the number of substances which are in the liquid as well as in the vapour phase. This parameter has to be supplied by the user. The arrangement of the different substances in the medium models in in theory arbitrary. The parameter mapping has to be used to map the different vectors one to another.
Example: Vapour = {N2, H2O, CO2}, Liquid = {N2, H+, HCO3- H2O, CO2} , mapping = {{1,1},{2,4},{3,5}}.
Mole Balances
The mole balances are written separately for vapour and liquid. There exist one mole balance for each component of each stage. The vapour balance is of the following structure:
Mole storage = convective molar flow rate in - convective molar flow rate out + molar flow rate over phase boundary + feed molar flow rate
The liquid balance is of the following structure:
Mole storage = convective molar flow rate in - convective molar flow rate out + molar flow rate over phase boundary + molar flow rate due to reaction + feed molar flow rate
Energy Balances
The energy balances are also written separately for vapour and liquid. There exist one energy balance for each stage. The vapour balance is of the following structure:
Energy storage of the vapour = convective enthaply flow rate in - convective enthalpy flow rate out + heat transfer between the phases + enthalpy flow rate from the liquid to the vapour phase - enthalpy flow rate from the vapour to the liquid phase + enthalpy flow rate of the feed
The liquid balance is of the following structure:
Energy storage of the vapour + energy storage of the solid material = convective enthaply flow rate in - convective enthalpy flow rate out + heat transfer to the wall + heat transfer between the phases + enthalpy flow rate from the liquid to the vapour phase - enthalpy flow rate from the vapour to the liquid phase + enthalpy flow rate of the feed
Mass Transfer and thermodynamic equilibrium
The mass transfer equations and the equations for the thermodynamic equilibrium are provided in the film model, which is instantiated in the column specific classes StructuredPackedColumn, RandomPackedColumn, TrayColumn and SprayColumn.
| Name | Description |
|---|---|
 MediumVapour | medium to be used in vapour phase |
 MediumLiquid | medium to be used in liquid phase |
 ThermoEquilibrium | model for phase equilibrium |
created by |
|
creation date |
01.01.2009 |
revised by |
nobody so far |
last revision |
this is an alpha version... |
based on |
Documentation last revised: 18.7.2011