Compounds

The chemical compounds used in the flowsheet are defined in the Compounds ... End Compounds section. There are more than 1700 compounds available in the thermodynamic database. If the chemical compound is not available, a text file named compounds.txt is generated when the problem solution is attempted. There are commonly used compounds that are available by default in the trial version of the software.

When only one compound is selected, the modeling system automatically creates a duplicate compound of the same type. This is used to simplify the management of modeling equations that are valid for 2 or greater number of compounds.

Compounds in the Object Library

The object library consists of chemical processing equipment such as feed streams, reactors, pumps, mixers, flash columns, vessels, and distillation stages. The compounds section is used to define the number, type, and order of chemical species in a stream or vessel.

Thermodynamic Properties Available in APMonitor

Thermo objects

Thermo objects access data from the underlying thermodynamic database. There are many compounds accessible in the database. To reduce the size of the APMonitor executable, only some of the more common compounds are currently incorporated. Additional compounds can be easily added but require a rebuild of the executable.

Temperature Independent Property Data

Temperature independent property data do not vary with temperature. They are defined as constants for each of the species declared in the Compounds ... End Compounds section of the model. If the Compounds ... End Compounds section is missing, all available compounds are included in the model.

thermo_mw Molecular Weight kg/kmol
thermo_tc Critical Temperature K
thermo_pc Critical Pressure Pa
thermo_vc Critical Volume m^3/kmol
thermo_ccf Crit Compress Factor unitless
thermo_mp Melting Point K
thermo_tpt Triple Pt Temperature K
thermo_tpp Triple Pt Pressure Pa
thermo_nbp Normal Boiling Point K
thermo_lmv Liq Molar Volume m^3/kmol
thermo_ighf IG Heat of Formation J/kmol
thermo_iggf IG Gibbs of Formation J/kmol
thermo_igae IG Absolute Entropy J/kmol*K
thermo_shf Std Heat of Formation J/kmol
thermo_sgf Std Gibbs of Formation J/kmol
thermo_sae Std Absolute Entropy J/kmol*K
thermo_hfmp Heat Fusion at Melt Pt J/kmol
thermo_snhc Std Net Heat of Comb J/kmol
thermo_af Acentric Factor unitless
thermo_rg Radius of Gyration m
thermo_sp Solubility Parameter (J/m^3)^0.5
thermo_dm Dipole Moment c*m
thermo_r van der Waals Volume m^3/kmol
thermo_q van der Waals Area m^2
thermo_ri Refractive Index unitless
thermo_fp Flash Point K
thermo_lfl Lower Flammability Limit K
thermo_ufl Upper Flammability Limit K
thermo_lflt Lower Flamm Limit Temp K
thermo_uflt Upper Flamm Limit Temp K
thermo_ait Auto Ignition Temp K

Temperature Dependent Property Data

The temperature dependent thermo objects produce values based on a specified temperature. When a temperature dependent property object is declared, a new temperature variable will be created. This variable can be adjusted or linked to an existing temperature of interest.

thermo_sd Solid Density kmol/m^3
thermo_ld Liquid Density kmol/m^3
thermo_svp Solid Vapor Pressure Pa
thermo_lvp Liquid Vapor Pressure Pa
thermo_hvap Heat of Vaporization J/kmol
thermo_scp Solid Heat Capacity J/kmol*K
thermo_lcp Liquid Heat Capacity J/kmol*K
thermo_igcp Ideal Gas Heat Capacity J/kmol*K
thermo_svc Second Virial Coefficient m^3/kmol
thermo_lv Liquid Viscosity Pa*s
thermo_vv Vapor Viscosity Pa*s
thermo_sk Solid Thermal Conductivity W/m*K
thermo_lk Liq Thermal Conductivity W/m*K
thermo_vk Vap Thermal Conductivity W/m*K
thermo_st Surface Tension N/m
thermo_sh Solid Enthalpy J/kmol
thermo_lh Liq Enthalpy J/kmol
thermo_vh Vap Enthalpy J/kmol

Example

 ! Example compounds section
 Model heat_exchanger
   Compounds
     water
     air
   End Compounds

   Objects
     exchanger As Vessel
   End Objects
 End Model
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