The latest release of Flownex, version 9.0.4, brings a compelling mix of major innovations and thoughtful refinements that elevate its 1D simulation capabilities to new heights. From the introduction of specialized Nuclear Reactor Components to the integration of the Henry-Fauske Critical Two-Phase Flow model, this update is packed with features that enhance both technical depth and user experience.
One standout addition is the Henry-Fauske model, now available in Flownex 2025 R3—a true game changer for simulating pressurized two-phase pipe break accident scenarios. Alongside this, users will appreciate a host of quality-of-life improvements, including a built-in Convergence Residual Plot for steady-state simulations, a versatile metadata editor, improved element iconography, and convenient solve hotkeys. Together, these enhancements make Flownex more powerful, intuitive, and efficient than ever before.
MAJOR ENHANCEMENT LIST
The complete Release Notes containing detailed descriptions of the enhancements in the Flownex SE Release 3 version 9.0.4 are available under the Help ribbon in the latest Flownex SE release:
Pebble Bed Reactor
A new Pebble Bed Reactor component has been added that allows a pebble bed reactor to be modelled more easily than using the reactor scripts from the previous Flownex version.
As part of this upgrade the old Pebble Bed Reactor component has been removed and the Nuclear Reactor component has been moved to a Legacy category. The geometry chart used for the new Pebble Bed Reactor has been streamlined and a point neutronics chart has been added to use in conjunction with the built-in component.
Figure 1: Nuclear library with Pebble Bed Reactor, Pressurized Water Reactor and Legacy categories.
Pressurized Water Reactor
A Pressurized Water Reactor (PWR) component has been added to the Nuclear library as shown in Figure 1. The PWR is set up in the same manner as the Pebble Bed Reactor and uses both a geometry chart and a point kinetics chart. The reactor component allows for specifying the fuel element and control rod geometry and generates a network that includes fuel elements and coolant flow paths. A representative fuel element consists of a central fuel region, a gas gap, and cladding, whereas a representative control rod consists of central rod material, a fluid gap and the control rod guide tube.
The PWR leverages the existing point kinetic neutronics model that is extended to allow for the use of the water density in the moderator reactivity feedback. The power calculated by the point kinetic model is distributed in the core based on a specified power distribution and assigned to the solid nodes in the representative fuel element in each zone.
Legacy Category for Nuclear Components
The previous generation of nuclear components have been moved to Legacy categories. This has been done for both the components and the charts, as shown in Figure 2.
Figure 2: Legacy categories for previous generation nuclear components.
There are a variety of critical two-phase flow applications where the flow does not adhere to equilibrium conditions such as pressurized water released through a valve or in pipe burst accidents involving the transport of pressurized water. Applying equilibrium modeling principles to these applications may result in a severe underprediction or overprediction of critical mass flow rates. The Henry-Fauske model is a well-known benchmark for the calculation of critical two-phase flow associated with short tube break cavitating flow as it accounts for the delay in mass and heat transfer in the choking plane.
An option has been added to the Restrictor with Discharge Coefficient, Restrictor with Loss Coefficient and Secondary Loss component to specifically apply the Henry-Fauske frozen model instead of the conventional homogenous equilibrium approach. The option is available for two-phase fluid types when selecting the “Specify advanced inputs” option as shown in Figure 3.
Figure 3: Henry-Fauske Frozen model.
The capability has been added to specify metadata for several different items. These items include components, charts, compounds, and component defaults. The capability to add metadata provides users with a place to store relevant data for an item, for example drawings, calculations, notes etc. The option to add metadata is available within the context menu of an item and can be accessed when right-clicking on the item:
Figure 4: Adding Metadata to a component.
Within the Metadata Editor window, metadata can be added in the form of Text files, Word documents, Excel files, PDF files or images as shown in Figure 5.
The “Add File” option can be used to add existing files and the “New” option can be used to add new blank files. The “Explore” option will open the location of the Metadata. Metadata is copied and exported with the items that they are associated with.
A Residuals plot has been added as a tab on the Flow Solver output window where the residuals are plotted as the network solves, as shown in Figure 6.
The Residuals plot is always active for steady state simulations and can optionally be enabled for transient simulations too. An option is also available to save the data to have the data available in a new session. It is however important to note that saving the data might take up a lot of disk space, especially in transient.
Flownex projects can now be saved as a “.projz” file. This is a zipped file containing the entire project folder.
Figure 7: Saving the network as a Single File Flownex Project files type (*.projz).
When opening a “.projz” file, the file will be extracted temporarily into the same directory as the location of the “.projz” file. Upon saving, the project will be saved to this extracted project folder and then zipped into the “.projz” file. When the project is closed the temporary folder will be deleted.
The user can at any stage switch between using the traditional “.proj” file type for a project or the new “.projz” by saving the project as the specific file type.
When creating a new project, the option to save the project as a “.projz” option is available, but the default type is “.proj”.
The capability has been implemented to copy scenarios and actions from a Flownex project to a different instance of Flownex.
If the target does not exist in the project in which the action or scenario has been pasted, the target field will appear red, as shown in Figure 8.
Figure 8: Copied scenario with red Target fields Indicating the target does not exist in the current project.
Figure 9: Critical Warning when running a transient simulation with an Action that contains a non-existing target.
A critical warning during a transient simulation will also be issued if an action with a non-existing target is started, as shown in Figure 9.
The Flow Solver component icons have been updated to enhance visual consistency and clarity across the interface. The previous icons varied in perspective and image quality, leading to a less cohesive user experience. The new icons feature a consistent isometric style, providing a more professional and modern look while remaining recognizable to long-time users.
Figure 10: Example of a network with previous icons.
Figure 11: Example of a network with updated icons.
These updates improve the overall visual language of Flownex SE, especially in complex models where quick identification of components is key.
Conduction Grading Factor Input
A Conduction Grading Factor input has been added to the Conduction component inputs, as seen in Figure 12.
Figure 12: Conduction Grading Factor input on Conduction component.
Convection Grading Factor Input
A Convection Grading Factor input has been added to the Convection component inputs, as seen in Figure 13.
Figure 13: Convection Grading Factor Input on Convection component.
The capability has been added to connect a Convection component between a solid Node and a Boundary Condition. This allows for the modelling of natural convection on the outside of solid structures.
The convection options are limited to natural convection correlations similar to the options available a Composite Heat Transfer component when using the ambient heat transfer option.
Figure 14: Convection coefficient correlation selection options to model external forced or natural convection.
Options have been added to the Push Button to turn solving on or off for all components on a specified page:
Figure 15: Turn solving on/off for page options.
An enhancement has been made to Lock or Unlock a shared or external database by setting a password. This will help to ensure that components within a shared database cannot be modified by any user that has access to the database without the password to modify the components within the shared database.
Figure 16: Entering a password to Lock or Unlock a Shared/External database.
With each release, Flownex continues to push the boundaries of what’s possible in system-level simulation, delivering tools that are not only technically powerful but also thoughtfully designed for engineers in the field. Whether you’re modeling complex nuclear systems or streamlining your workflow with intuitive UI enhancements, Version 9.0.4 offers something for everyone.
Check out the full release notes to explore everything that’s new in this latest Flownex release here:
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