Excel Add-In for Thermodynamic Calculations

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Contents

[edit] Introduction

The DWSIM Excel Add-In enables usage of some low-level internal functions in DWSIM, exposed so far only to CAPE-OPEN compatible software. Some of the functions exposed include:

  • Single Compound Property Calculator
  • Single Phase Mixture Property Calculator
  • PT, PH, PS, PVF and TVF Flash Calculators, using an algorithm of your choice
  • Other auxiliary functions

Property and Equilibrium calculation functionality is now available to Excel just as any other add-in function.

[edit] Installation

The Excel add-in is included within the DWSIM software package and can be installed using the normal procedure for XLL add-ins. Just look for the “DWSIM.xll” file in the DWSIM installation directory and you’re set:

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[edit] Usage

Functions exposed by this add-in will be grouped in a category named “DWSIM”:

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Property and Equilibrium calculation functions require parameters that must be one or more values returned by GetPropPackList, GetCompoundList, GetPropList, GetCompoundPropList and GetPhaseList. They are self-explanatory, and will return values listed in a single column, so you probably will have to select some cells in a single column and call the functions using Ctrl+Shift+Enter:

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For example, the PTFlash function requires the name of the Property Package to use, the compound names and mole fractions, temperature in K, pressure in Pa and you may optionally provide new interaction parameters that will override the ones used internally by DWSIM. The calculation results will be returned as a (n+2) x (4) matrix, where n is the number of compounds. First row will contain the phase names (Vapor, Liquid, Liquid2 and Solid, in this order), the second will contain the phase mole fractions and the other lines will contain the compound mole fractions in the corresponding phases:

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For PH, PS, TVF and PVF flash calculation functions, and additional line is returned that will contain the temperature in K or pressure in Pa in the first column.

[edit] Overriding Interaction Parameters

You can directly override the interaction parameters used by Property Packages when calling calculations from Excel by providing n x n matrices containing the values, where n is the number of compounds. This feature is optional and should be used only when you know exactly what you are doing.

The following table shows the user-definable interaction parameters for each Property Package:

Property Package

IP Set #1
IP Set #2
IP Set #3
IP Set #4
IP Set #5
IP Set #6
IP Set #7
IP Set #8

PC-SAFT

PC-SAFT kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Peng-Robinson (PR)

PR kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Soave-Redlich-Kwong (SRK)

SRK kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Peng-Robinson-Stryjek-Vera 2 (PRSV2)

PRSV2-M kij
PRSV2-M kji
Not used
Not used
Not used
Not used
Not used
Not used

Peng-Robinson / Lee-Kesler (PR/LK)

PR kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

UNIFAC

PR kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

UNIFAC-LL

PR kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Modified UNIFAC (Dortmund)

PR kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

NRTL

PR kij
NRTL A12 (cal/mol)
NRTL A21 (cal/mol)
NRTL Alpha
NRTL B12 (cal/mol.K)
NRTL B21 (cal/mol.K)
NRTL C12 (cal/mol.K²)
NRTL C21 (cal/mol.K²)

UNIQUAC

PR kij
UNIQUAC A12 (cal/mol)
UNIQUAC A21 (cal/mol)
UNIQUAC B12 (cal/mol.K)
UNIQUAC B21 (cal/mol.K)
UNIQUAC C12 (cal/mol.K²)
UNIQUAC C21 (cal/mol.K²)
Not used

Chao-Seader

Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Grayson-Streed

Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Lee-Kesler-Plöcker

LKP kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

Raoult's Law

Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used

COSMO-SAC (JCOSMO)

PR kij
Not used
Not used
Not used
Not used
Not used
Not used
Not used

IAPWS-IF97 Steam Tables

Not used
Not used
Not used
Not used
Not used
Not used
Not used
Not used

[edit] Property Methods and Correlation Profiles

View the Property Methods and Correlation Profiles page for a list of Property Packages and their models/correlations used to calculate properties.

[edit] Flash Algorithms and Results Validation

[edit] Flash Algorithms

The Flash Algorithms in DWSIM are the components responsible for determining a particular set of phases at thermodynamic equilibrium, their amounts (and the amounts of the compounds on each phase) at the specified conditions like Temperature, Pressure, Total Enthalpy and Total Entropy. Some Flash Algorithms are capable of predicting equilibrium between one vapor and one liquid phase, while others support another co-existing liquid and/or solid phase. As the amount of phases considered in equilibrium increases, the calculation time/complexity also increases while the results' reliability decreases.

Some flash algorithms are more capable/reliable than others, depending on the mixture for which the flash calculation request is being requested. DWSIM features a selection of flash algorithms that are capable of calculating VLE, VLLE and SLE. They are:

  • Nested Loops (default): recommended for the vast majority of VLE systems;
  • Nested Loops (VLLE): recommended for mixtures which exhibit liquid phase splitting;
  • Inside-Out (2 or 3-Phase): recommended for petroleum simulations. The 3-phase option must be used when a second liquid phase is expected (i.e. free water);
  • Gibbs Minimization (2 or 3-phase): recommended for difficult, highly non-ideal chemical systems;
  • Nested Loops for Eutectic Solid Systems: Calculates Solid-Liquid Equilibria for eutectic systems considering the solid phase as being ideal.
  • Nested Loops for Solid Solution Systems: Calculates Solid-Liquid Equilibria for solid solution systems considering the solid phase as being ideal.
  • Nested Loops (3-phase immiscible VLLE): Fast algorithm for systems with an immiscible second liquid phase (VLLE). The first compound in the list will be the immiscible one.

[edit] Validation of Equilibrium Calculations

Not all thermodynamic models are adequate for all types of mixtures/systems. It is easy to be mistaken by an apparently suitable model for your system because it will always return a result, which may be correct or not depending on a number of factors:

  • Inadequate/limited background theory for thermodynamic calculations
  • Missing binary interaction parameters (BIPs)
  • Unsuitable flash algorithm

You must know a priori what to expect from a flash calculation. For example, for a mixture of hydrocarbons with water, a liquid phase split is expected because water and hydrocarbons are almost completely immiscible. In this case a VLE Flash Algorithm is not suitable for equilibrium calculations. You must use one of the three-phase flash algorithms available.

Validation of flash results is carried out automatically by DWSIM if you're doing a simulation through its own interface, but if you're using the Excel Add-In you must take some extra precautions to understand what's being given as a result.

To validate the equilibrium calculation results, you can take advantage of the fact that the Gibbs Free Energy will always decrease on a phase split. If there's no phase split, the Gibbs energy will remain the same, otherwise it must decrease. Using the definition G = H - TS (Gibbs Energy = Enthalpy - Temperature x Entropy), you can use the available functions in the DWSIM Excel Add-In to validate the results.

For more details, download this Excel sheet which contains an example of a flash calculation validation.

[edit] Property Identifiers and Units

The following tables show the property identifiers and their units of measure as returned by the Add-In. The tables were copied directly from the CAPE-OPEN Thermo 1.1 standard document.

Please note that not all properties are implemented in DWSIM – if you ask for a property that is not available, a NotImplemented exception will be returned by the Add-In.

[edit] Single compound constant properties

Identifier meaning units
acentricFactor Pitzer acentric factor
associationParameter association-parameter (Hayden-O’Connell)
bornRadius m
charge
criticalCompressibilityFactor critical compressibility factor Z
criticalDensity critical density mol/m3
criticalPressure critical pressure Pa
criticalTemperature critical temperature K
criticalVolume critical volume m3/mol
diffusionVolume diffusion volume m3
dipoleMoment dipole moment Cm
energyLennardJones Lennard-Jones energy parameter (divided by Boltzmann constant) K
gyrationRadius radius of gyration m
heatOfFusionAtNormalFreezingPoint enthalpy change on melting at normal freezing point (101325 Pa) J/mol
heatOfVaporizationAtNormalBoilingPoint enthalpy change on vaporization at normal boiling point (101325 Pa) J/mol
idealGasEnthalpyOfFormationAt25C J/mol
idealGasGibbsFreeEnergyOfFormationAt25C J/mol
liquidDensityAt25C liquid density at 25 ºC mol/m3
liquidVolumeAt25C liquid volume at 25 ºC m3/mol
lengthLennardJones Lennard-Jones length parameter m
molecularWeight relative molar mass
normalBoilingPoint boiling point temperature at 101325 Pa K
normalFreezingPoint melting point temperature at 101325 Pa K
Identifier meaning units
parachor Parachor m3 kg0.25/(s0.5 mol)
standardEntropyGas Standard entropy of gas J/mol
standardEntropyLiquid standard entropy of liquid J/mol
standardEntropySolid standard entropy of solid J/mol
standardEnthalpyAqueousDilution Standard aqueous infinite dilution enthalpy J/mol
standardFormationEnthalpyGas standard enthalpy change on formation of gas J/mol
standardFormationEnthalpyLiquid standard enthalpy change on formation of liquid J/mol
standardFormationEnthalpySolid standard enthalpy change on formation of solid J/mol
standardFormationGibbsEnergyGas standard Gibbs energy change on formation of gas J/mol
standardFormationGibbsEnergyLiquid standard Gibbs energy change on formation of liquid J/mol
standardFormationGibbsEnergySolid standard Gibbs energy change on formation of solid J/mol
standardGibbsAqueousDilution Standard aqueous infinite dilution Gibbs energy J/mol
triplePointPressure triple point pressure Pa
triplePointTemperature triple point temperature K
vanderwaalsArea van der Waals area m2
vanderwaalsVolume van der Waals volume m3

[edit] Single compound temperature-dependent properties

Identifier Meaning units
cpAqueousInfiniteDilution Heat capacity of a solute in an infinitely dilute aqueous solution. J/(mol K)
dielectricConstant The ratio of the capacity of a condenser with a particular substance as dielectric to the capacity of the same condenser with a vacuum for dielectric.
expansivity Coefficient of linear expansion for a solid: 1/K
(where L is the length) at 1 atm
fugacityCoefficientOfVapor Fugacity coefficient of vapour on the saturation line
glassTransitionPressure Glass transition pressure Pa
heatCapacityOfLiquid Heat capacity (Cp) of liquid on the saturation line J/(mol K)
heatCapacityOfSolid Solid heat capacity (Cp) at 1 atm J/(mol K)
heatOfFusion Enthalpy change on fusion for the solid on the melting line J/mol
heatOfSublimation Enthalpy change on evaporation of the solid on the sublimation line J/mol
heatOfSolidSolidPhaseTransition Enthalpy change on phase transition J/mol
heatOfVaporization Enthalpy change on evaporation of the liquid on the saturation line J/mol
idealGasEnthalpy Enthalpy of ideal gas J/mol
idealGasEntropy Temperature-dependent part of entropy of ideal gas J/(mol K)
idealGasHeatCapacity Heat capacity (Cp) of ideal gas J/(mol K)
meltingPressure Pressure on melting line Pa
selfDiffusionCoefficientGas Self-diffusion coefficient in gas phase at 1 atm M2/s
Identifier Meaning units
selfDiffusionCoefficientLiquid self-diffusion coefficient in liquid phase on saturation line M2/s
solidSolidPhaseTransitionPressure Pressure at phase transition Pa
sublimationPressure Vapour pressure of solid on the sublimation line Pa
surfaceTensionSatLiquid Surface tension of liquid on the saturation line N/m
thermalConductivityOfLiquid Thermal conductivity of liquid on saturation line W/(m K)
thermalConductivityOfSolid Thermal conductivity of solid at 1 atm W/(m K)
thermalConductivityOfVapor Thermal conductivity of dilute gas W/(m K)
vaporPressure Vapour pressure of saturated liquid Pa
virialCoefficient Second virial coefficient of gas M3/mol
viscosityOfLiquid Viscosity of liquid on saturation line Pas
viscosityOfVapor Viscosity in dilute gas state Pas
volumeChangeUponMelting Volume change for the solid on the melting line m3/mol
volumeChangeUponSolidSolidPhaseTransition Volume change upon solid-solid phase transition m3/mol
volumeChangeUponSublimation Volume change for the solid on the sublimation line m3/mol
volumeChangeUponVaporization Volume change for the liquid on the saturation line m3/mol
volumeOfLiquid Volume of liquid on saturation line m3/mol
volumeOfSolid Volume of solid at 1 atm m3/mol

[edit] Single compound pressure-dependent properties

Identifier Meaning units
boilingPointTemperature Temperature at liquid-vapour transition K
glassTransitionTemperature Glass transition temperature K
meltingTemperature Temperature on melting line K
solidSolidPhaseTransitionTemperature Temperature at phase transition K

[edit] Non-constant single-phase mixture properties

Identifier Meaning units basis overall
activity Activity U
activityCoefficient Activity coefficient U
compressibility Isothermal compressibility 1/Pa U
compressibilityFactor Compressibility factor U Y
density Density mol/m3 mole/mass Y
diffusionCoefficient Binary diffusion coefficients for all species in mixture relative to all other species m2/s U
dissociationConstant Chemical equilibrium constant corresponding to a dissociation reaction. U
enthalpy Enthalpy J mole/mass Y
entropy Entropy J/K mole/mass Y
excessEnthalpy Excess enthalpy J mole/mass
excessEntropy Excess entropy J/K mole/mass
excessGibbsEnergy Excess Gibbs energy J mole/mass
excessHelmholtzEnergy Excess Helmholtz energy J mole/mass
excessInternalEnergy Excess internal energy J mole/mass
excessVolume Excess volume m3 mole/mass
flow Flows of each Compound in a given Phase (or the overall mixture) mol/s mole/mass Y
fraction Molar (or mass) fractions of each Compound in a given Phase (or the overall mixture) mole/mass Y
fugacity Fugacity Pa U
fugacityCoefficient Fugacity coefficient U
gibbsEnergy Gibbs energy J mole/mass Y
heatCapacityCp Heat capacity at constant pressure (Cp) J/K mole/mass Y
heatCapacityCv Heat capacity at constant volume (Cv) J/ K mole/mass Y
helmholtzEnergy Helmholtz energy J mole/mass Y
internalEnergy Internal energy J mole/mass Y
jouleThomsonCoefficient K/Pa U
logFugacity Natural logarithm of fugacity (expressed in Pa) U
logFugacityCoefficient Natural logarithm of fugacity coefficient U
meanActivityCoefficient The geometrical mean of the activity coefficients of the ions in an electrolyte solution. U
molecularWeight Mixture average molecular weight (relative molar mass) U
pH pH U
pOH pOH U
phaseFraction The molar (or mass) fraction of the fluid that is in the specified phase mole/mass
pressure Pressure Pa U Y
speedOfSound Thermodynamic speed of sound m/s U
temperature Temperature K U Y
thermalConductivity Thermal conductivity W/(m K) U
totalFlow Matter flow of a Phase or the overall mixture mol/s mole/mass Y
viscosity Viscosity Pa s U
volume Volume m3 mole/mass Y
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