The Scope of the Liquid & Gas Properties Module
The Liquid & Gas Properties Module provides tailor-made functionality for specifying properties of liquids and gases used in the modeling of fluid flow, energy transport, and mass transfer. The fluid properties provided are often dependent on temperature or temperature and pressure as well as on time and space. When modeling mixtures with multiple components, the impact of the chemical composition and changes therein can also be accounted for. The main components provided with module consist of a built-in properties database for chemical species, together with a thermodynamic properties calculator. When used together, these two make it possible to compute thermodynamic properties and transport properties for pure solutions and mixtures of chemical compounds in gas or liquid form. Examples of properties that can be computed are heat capacity, thermal conductivity, density, and diffusivity. The properties can furthermore often be computed using multiple models. Properties can be calculated for fluids consisting of a single gas phase or a single liquid phase and for liquid-liquid, gas-liquid, and gas-liquid-liquid systems. For multiphase systems, the equilibrium composition can also be calculated to, for example, to calculate the phase envelope for a liquid mixture at equilibrium with its gas phase (flash calculations).
All functionality provided with the Liquid & Gas Properties Module is available in the Thermodynamics node added to the Global Definitions branch of the Model Builder window. The natural way to start is to first define a Thermodynamic System including one or several compounds (chemical species) for which properties are to be defined. When the system is defined, a multitude of functions or constants describing physical properties can be created. This is accomplished using the thermodynamic features Species Property, Mixture Property or Equilibrium Calculation. You can, for example, create a Species Property function describing the density of a fluid, and use this function in a fluid-flow interface. With a Mixture Property you can define mixture functions — that is, functions that depend on the composition of a mixture, describing, for example, density, enthalpy, or heat capacity.
For a system with constant composition, the most convenient route to fluid properties is to create a material using the Generate Material Wizard. This automates the procedure of creating a Material node, which in turn uses functions or parameters from a thermodynamic system. The resulting material can contain common transport properties such as density, heat capacity, heat capacity ratio, thermal conductivity and viscosity.
For users of the Reaction Engineering, or Chemistry interface, it is straightforward to couple chemical species in these with corresponding species in an existing thermodynamic system. The property parameters and functions required in the interfaces are then automatically added under the corresponding thermodynamic system.
A more complete description of the options available for calculating physical properties is available the chapter Workflow for Thermodynamics Property Calculations.