Hybrid Multizonal gPROMS–CFD

High-precision multizonal gPROMS models with automated CFD coupling

PSE’s Hybrid Multizonal gPROMS-CFD (Hybrid Multizonal) software is a unique and powerful tool that allows you to connect gPROMS multizonal (multicompartment) models of processes such as crystallizers or stirred-tank reactors to FLUENT® computational fluid dynamics (CFD) models.

This provides a high degree of accuracy when modelling processes in which chemical phenomena are strongly dependent on local hydrodynamic (especially mixing) effects.

Hybrid Multizonal is applicable to both single-phase and multiphase (gas/liquid/solid) equipment.

Multizonal modelling

Multizonal (or multicompartment) models provide a way of modelling the effects of non-ideal mixing in industrial-scale process equipment, by representing equipment as a network of zones of similar characteristics – for example, concentrations of crystals or suspended catalyst.

The Hybrid Multizonal gPROMS-CFD interface links such zones with groups of cells – representing the equivalent physical volumes in a CFD model, as shown in the diagram. the CFD zones can be zones of similar characteristics; they do not have to have regular geometry.

The gPROMS zone model calculates the physical and chemical phenomena – for example, crystal nucleation and growth – based on information determined by the CFD model – for example, the flowrates into and out of the zone, and other local fluid properties such as turbulent dissipation energy.

The Hybrid Multizonal gPROMS-CFD interface

In the past, the wide application of such models has been limited by the difficulty of establishing the zone connectivity and calculating inter-zonal flowrates, a time-consuming and error-prone process.

However with the Hybrid Multizonal gPROMS-CFD interface, all the user has to do is provide a single gPROMS model (of any level of complexity) of a well-mixed zone, and specify the number of zones to be considered and the approximate (x,y,z) co-ordinates of their centres in the CFD model. Hybrid Multizonal does the rest automatically.

The benefits of the Hybrid Multizonal approach are:

  • unprecedented modelling accuracy for optimization of design and operations, by combining all relevant effects: complex physical and chemical phenomena with detailed hydrodynamics
  • allows accurate modelling of traditionally “difficult” processes, including crystallization, polymerisation, and large-scale gas-liquid reactors
  • provides a robust and reliable methos for accurate scale-up
  • allows solution of both steady-state and dynamic simulation and optimization problems within reasonable computational time, taking into account hydrodynamic effects
  • delivers new value from both CFD and process modelling investment via model re-use.

Using the Hybrid Multizonal gPROMS-CFD software – a simple step-by-step guide

The typical workflow for hybrid multizonal gPROMS-CFD modelling involves the following steps:

A. Prepare the CFD zone information

Step 1
Prepare a CFD model of the equipment of interest, incorporating total mass and momentum balances only.

Step 2
Perform a preliminary CFD calculation using nominal values of viscosity and density.

Step 3
Inspect the solution and identify approximately well-mixed zones.

Step 4
Specify the number of zones and the (x,y,z) co-ordinates of the centre of each zone in a simple text file

Hybrid Multizonal uses the specified (x,y,z) co-ordinates to group the cells in the CFD model into a number of zones of irregular geometry. The information is also used to automatically create a multizonal model in gPROMS, by connecting multiple instances of a gPROMS model for a single well-mixed zone.

Step 5
Run a utility that identifies the cells belonging to each zone, the volume of each zone, and the zone connectivity.

B. Prepare the gPROMS models

Step 6
Using gPROMS ModelBuildergCRYSTAL or any other gPROMS family product that supports multizonal applications, prepare a gPROMS model of a single well-mixed zone

C. Execute the combined simulation

Step 7
From your gPROMS enironment (e.g. gCRYSTAL), execute a simulation of the Multizonal model. gPROMS automatically creates the zone flowsheet

On execution, gPROMS reads initial inter-zone mass flowrates from the CFD model, performs the internal gPROMS calculations for each zone, and returns the zonal viscosities and densities to the CFD model, which then re-computes the mass flowrates.

Iteration between the two models (typically only 1 to 3 cycles) proceeds until the returned values are within tolerance.

Step 8
View the results of the calculation using gPROMS’ standard facilities

How Hybrid Multizonal gPROMS-CFD works

If necessary, the CFD model can also return zone volume-averaged hydrodynamic quantities (e.g. turbulent energy dissipation rate), which may affect some of the physical phenomena represented within the gPROMS zone model (e.g. the rate of nucleation in crystallization models).

Licensing, supported platforms and pre-requisites

The Hybrid Multizonal gPROMS-CFD software is licensed as an option under gPROMS ModelBuilder or gCRYSTAL. The licence includes the utility for the automatic construction of the zone network, a Foreign Object for gPROMS-CFD communication during execution, and a self-configuring gPROMS multizonal network model.

See supported platforms for the latest details on supported platforms.

More Information

Physical properties

gSAFT Physical properties

Hybrid Multizonal gPROMS-CFD interface – combining the best of gPROMS and CFD models

To iterate or not?

If necessary, the information calculated by the gPROMS model, such as crystal concentration, can be sent to the CFD model to update the hydrodynamic calculation.

Such iteration is only necessary in strongly-coupled systems, where the results of the gPROMS calculation strongly affect the CFD model.

Results of a multizonal model for a stirred-tank reactor