The latest Flownex® SE 2020 Release opens up new possibilities for modelling complete HVAC systems.

Exciting new features include an all new ducting components library based on ASHRAE standards, the psychrometric boundary condition and psychrometric chart, flow paths and property graphing, overall performance improvements and much more.  Be sure to have a look at the full list below.

Students can also benefit from the new features as the latest Flownex® SE 2020 Student Version is also available to download from our website.

Ducting Components

Many heating ventilation and air conditioning related components, including ducts, transitions, dampers, junctions, combiners, elbows, screens, entrances and exits have been added to the Flownex® component database, as seen in Figure 1.


Figure 1: Ducting Components.


These components allow for easy modelling of HVAC ducting systems in line with the ASHRAE standards.

Volume Flow Boundary Conditions

The boundary condition specification options have been expanded to include the specification of volume flow boundary conditions, as seen in Figure 3.  The volume flow specification will be used to calculate the equivalent mass flow boundary conditions commensurate with flow conditions.  The thermodynamic condition can be based on the current node conditions or user specified reference conditions.

Figure 3: Volume Flow Boundary Conditions.


Psychrometric Boundary Conditions

It is customary in HVAC applications to specify psychrometric boundary conditions for moist air.  A new Psychrometric Boundary Condition is available in the Nodes and Boundaries Library, as seen in Figure 4.

Figure 4: Psychrometric Boundary Condition in Nodes and Boundaries Library.

Flownex® now allows for the specification of wet bulb temperature, relative humidity and humidity ratio for moist air mixtures in addition to the psychrometric results that are available for two-phase non-condensable mixtures.  The calculation of wet-bulb temperature has been extended to include frost bulb temperatures. 

A new fluid named Humid Air has been added to the Mixed Fluids in the Master database for use with the Psychrometric Boundary Condition component.

Figure 5: Psychrometric Boundary Condition Inputs.

Psychometric Charts


A psychrometric chart can now be plotted for humid air. The psychrometric chart together with plotted component operating points can assist the user to graphically analyse the psychrometric processes of a system.

Figure 6: Psychrometric Chart.



Graphs Through Flow Paths

The ability to plot a property, for example, the total pressure through a network has been added.

Figure 7: Flow Paths in the Results Ribbon.

The property of components along a defined flow path is plotted.  Flow paths can be defined by selecting the start and end components of the flow path. The context menu can then be used to quickly define a new graph.


Figure 8: Flow Path Graph.


PH Diagram

Figure 8: Pressure vs. Enthalpy Diagram Option.

The option to plot a pressure and enthalpy diagram for two phase fluids has been added, as seen in Figure 8.

The pressure-enthalpy operating point of a component using the Fluid Property Graph can therefore be plotted.

Pressure Enthalpy Diagram.

FMI Master Capability

Further support for the FMI standard was added to Flownex. Flownex can now serve as an FMI master for version 2.0 compatible FMUs. It can import both model exchange and co-simulation FMUs.

Figure 11: FMI Master Capability.

FMUs are added as components in the project library and are used like any other simulation component. These FMUs can be used in both steady state and transient simulations.


Result Layer Improvements

The Result Layers has been updated to show density, energy source, mass source and an indication if choking is present, as seen in Figure 10.

Figure 10: Improved Result Layers.

The result layers were also improved to shade the area over the connecting fibres between nodes and elements, which makes it much easier to see the results graphically in large networks.



Performance Improvements

Working with large networks was optimised. Several improvements were made to decrease the time associated with opening large networks and selecting parts of the network. The initial time associated with opening Flownex® has been improved, as well as the time associated with opening networks. The time associated with assigning fluids in large networks has also been improved.

API Improvements

  • Added the ability to create data references through the API. This allows users to create charts such as pump charts, valve charts, etc. by using the API alone.
  • Added a Python example to demonstrate adding charts through the API.
  • Added a demo network example to demonstrate adding charts via C# scripts inside a project.
  • Added Visual Studio 2019 compatibility to the extendibility feature.
  • Made it possible to set the chart and other non-double properties on components using the MATLAB coupling.

Script Editor Improvements

One of the best ways to quickly generate a script is by using a Quick Script component. By using the Quick Script to add all the variables you need and then clicking the show entire script button, you can then copy and paste this code to an ordinary script to customise it further. To make this process easier, buttons and context menu items were added to the script dialog to select and copy script code in the Script Editor.

Figure 13: Copying and Pasting Code in the Script Editor.

Intellisense has been added to function scripts like the Pipe Friction Factor script and the Heat Transfer Coefficient calculation scripts.

Figure 14: Example of Intellisense added to Friction Factor Script.

Search and replace functionality were added to all the script editors. Press Ctrl+F to activate the search dialog or Ctrl+H to activate the Replace dialog.

Figure 15: Example of Find and Replace Functionality added to Scripts.

Quick Scripts

Several additional property types were added to the Quick Script – this include data references, component and property selectors. The primary reason for this was to make it possible to use fluid functions in the Quick Script as well as properties from other components.

Figure 16: Property Types added to Quick Script.

Example Scripts

An example script that interpolates on a 4D Generic Chart has been added – this is a good generic way to easily add lookup tables to simulations.

Figure 17: Interpolation Script added to Example Scripts.

The example scripts were changed so that they are not contained inside compounds anymore. This makes it easier to see the actual script code as well as to modify the scripts. The compound-based example scripts are still available in a category called “Legacy Compound Scripts”, as seen in Figure 17.


Iterative Scripts

  • The scripts will now only start executing once an initial flow field has been established. This is usually after five iterations depending on the solver settings.
  • A function has been added so that a user can specify whether data transfer should happen after the initialise method and before solving the Flow Solver components.

Parameters Tables

  • The user can now set Data Reference Properties, Integer, Boolean and Option Properties from Parameter Tables.
  • In order to distinguish between Result and Input parameters in a parameter table heading, the results parameters are shown with a darker grey colour.
  • The layout has been improved for Parameter Tables with different DPI screens and custom screen scaling.
  • The Parameter Table active conditions drop down now only shows the first thousand items. This was done to increase GUI performance when using very large Parameter Tables.


  • When saving details for a server license the Node Locked license details are now reset and vice versa. This makes it easier to switch between Server and Node Locked licenses.


  • Added the ability to change fluid property/characteristic graphs axes units.
  • Added the ability to plot the convection/radiation properties of a Composite Heat Transfer or a Distributed Heat Source along the length of one of the connected pipe components. Previously all points were plotted at the same length.
  • Added borders to graphs. White (hidden) by default.

GIS Importing

Added several new online map sources, as seen in Figure 18.

Figure 18: Example of Online Map Sources added.

FlownexSE Console

  • The console version of Flownex® can now be used to run parametric studies or sensitivity analysis. The user can specify the command line parameter -sensitivityandparametric to run the current active sensitivity analysis configuration in a project.

Nuclear Reactor

  • The Nuclear Reactor now allows the use of multiple Pebble Bed Fuel Zones in transient cases. Previously the chart based neutronics implementation only worked in transient cases for one fuel zone.
  • Added an error when the sum of fractions for heat input for all the zones in the nuclear reactor does not equal one. For cases when the sum is zero, this will be a warning only.
  • Added toggle buttons to ribbon menu to easily turn on and off result file generation settings, as seen in Figure 19.

Figure 19: Generate After Steady State and Generate After Transient Toggle Buttons.

Heat Exchangers

  • Added secondary loss inputs to the primary and secondary side of the Plate Heat Exchanger component.

Solver Properties

  • Added lower limits for the following inputs:
    • Number iteration Temp1
    • Number iteration Temp2
    • Number iteration Temp transient.
  • Changed name of "Use iterative temperature solver" input to "Use BiCG matrix solver for energy equation solution".
  • Add properties on the Scheduler to indicate if warnings and errors have occurred. These properties can be used in parametric studies etc. to monitor success of solving over all the runs. The warning and error count were also added as properties.

Distributed Heat Source

  • Added the ability to specify the heat input associated with the Distributed Heat Source component using a local specification option.
  • Added errors and warnings for the Distributed Heat Source when incorrectly connecting Distributed Heat Source components to each other or when the Distributed Heat Source is over specified.
  • Fixed problem with heat fractions not being applied during transient for distributed heat source.

Jet Pump Component

  • Added loss coefficient results to the Jet Pump component.


  • The Momentum addition inputs will now only be available on pipes and not on all components.
  • Implemented warning when small L/D values are used along with Dittus-Boelter and also for two phase flow.

Boundary Condition

  • Added the option to allow the specification of mass source conditions with fixed temperature/enthalpy, hereby allowing energy source calculations that are not based on ambient conditions.

Secondary Loss Component

  • Extended secondary loss component modelling capability to include Liquid-Gas mixtures, particularly for modelling oil-air mixtures in gas turbine lubrication systems.

Nozzle and Rotating Nozzle

  • Implemented input area option on Nozzle and Rotating Nozzle components, allowing for non-circular orifice shapes.

Labyrinth Seal

  • Added results for increments in discretized Labyrinth Seals.

Jet Impingement Convection

  • Removed upstream cross flow link in Jet Impingement component and instead use net inflow to fluid node. This enables modelling networks with jet impingement where the flow direction of the cross-flow stream is not pre-determined, but forms part of the solution.

Rotor-Stator and Rotor-Rotor

  • Added disk area results for increments in cavities. This allows more detailed heat transfer modelling and calculating thrust forces.


  • Added gauge pressure result.

All Element Types

  • Added humidity ratio result on all elements when used with the Humid Air fluid.

Validation Pack

  • The following items were added to the Validation Pack:

    Custom Losses
    • Flow Resistance
    • Secondary Loss
    • User Specified Pressure Drop
    • User Specified Pressure Ratio
    • Cross Junction
    • Damper
    • Duct
    • Elbow
    • Entrance
    • Exit
    • Obstruction
    • Transition
    Heat Exchangers
    • Finned-Tube Heat Exchanger
    • Plate Heat Exchanger
    • Shell & Tube Heat Exchanger
    Heat Transfer
    • Distributed Heat Source
    • External Pipe Heat Transfer
    • Slurry Networks
    Nodes and Boundaries
    • Psychrometric Boundary Condition
    • Volume Flow Boundary Condition
    • Nuclear Reactor
    • PBMM
    Rotating Components
    • Custom Vortex
    • Forced and Free Vortex
    • Labyrinth Seal
    • Rotating Annular Gap
    • Rotating Nozzle
    • Rotor-Rotor Cavity
    • Rotor-Stator Cavity
    Turbos and Pumps
    • Turbine and Compressor
    • Basic Valve
    • Check Valve
    • Control Valve with Loss Coefficient
    • Pressure Regulating Valve
    • Pressure Relief Valve

Bug Fixes


General Stability

  • When solving was disabled on components a crash happened after solving a second time and then saving the network. Several other actions also lead to a crash after disabling solving on components and then solving the network, which has been fixed.
  • Changed reactor fluid assignment from recursive to non-recursive to avoid a stack overflow for very large reactor sub-networks.


  • Fixed unit for kJ/mol where it appeared as kJ/kmol.

Parameter Tables

  • Fixed problem where the order of columns was not remembered when saving and reloading.
  • Fixed problem when reordering the inputs in a Parameter Table did not reorder the columns correctly.
  • Fixed problems when creating a copy of a parameter table, as the result parameters were changed to input parameters.

Data References

  • When a data reference was not found while loading compounds the way the error was reported made it difficult to pinpoint the source by double clicking on the error. This has been fixed.
  • Implemented a system where dynamic properties of charts gets saved to the project and to the snaps. This is done for charts in all databases. For instance, if scaling factors are changed from the chart property grid they will now be saved correctly.


  • Made CSV export for graphs work with different locales.
  • Fixed incorrect scaling on secondary Y-axes.
  • Added missing flow regime labels on the two-phase flow regime graphs.


  • Fixed the problem where the manual did not contain all the functions in the API.
  • Fixed the problem where constructing compounds using the displayed type name sometimes did not work.
  • Made properties such as Ck, Beta and Alpha of heat exchanger charts editable through API.

Compound Components

  • Add the ability to drop tooltip properties in the middle of the list when setting up tooltips – they were incorrectly added to the bottom previously.


  • Removed repeat option from actions – it was not used and did not function correctly. Repeating behaviour should rather be implemented using scripts.

GIS Importing

  • Fixed importing for some locales were the comma separator caused problems while retrieving elevations from google.
  • Fixed bug where identifier text etc. were sometimes displayed in reverse.


  • Fixed crash when running Designer etc. and a component that was used as part of the setup has been deleted.


  • Fixed the problem where increments in results did not update immediately on pipes when changing the number of increments.
  • Fixed “micro meter” spelling mistake in the Roughness Editor.
  • Fixed Transient and water hammer related results category wording on pipe.
  • Added convergence check for choking with unrealistic short pipe lengths in two-phase flow. In such cases the solution might have appeared to be converged, but actually required more iterations to accurately determine whether the choke point is reached or not.

Nuclear Reactor

  • Fixed the problem where an error was issued with the General Fuel Zone due to a material not being assigned when it should not be issued.
  • Fixed problem where reactors using the same neutronics chart gave the same results no matter what inputs were specified.
  • Fix problem where if you clicked in Top Height field for a row in the advanced reactor and it was negative, where the user needed to terminate Flownex to continue.
  • Several fields did not commit their data correctly in the editors for the Advanced Reactor.
  • Updated fractional heat assigned to subdivided zones.
  • The horizontal and vertical permeabilities are now correctly applied to the various zone types.
  • Convection heat transfer results were updated to include all flow convection flow paths for pebble bed and general fuel zones—this does not impact the solution.
  • Fixed error in the calculation of maximum moderator temperatures for general fuel zones.
  • Addressed code issue when a permeability value of zero was set to a solid with 1D vertical flow zone.
  • Fixed reactivity output units.
  • Added warning when user supplies a zero hydraulic diameter corresponding to a non-zero permeability.
  • A default value of 1 has been assigned to the heat fraction, and coefficient 0 of the axial and radial power profiles on the power distribution dialog.
  • Fixed sub-zone mass flow units.
  • Fixed an error in the height assignment of a single cavity that is in a sub-divided row.
  • Fixed Pebble Bed flow node volumes when DW friction losses are selected.
  • Added convection and conduction areas, length and height outputs in *.arr file.
  • Added porosity to the Reynolds number calculation to correctly use the local superficial velocity in the Kugeler-Schulten pressure drop correlation.
  • Changed friction factor result for packed bed flow elements so that it is based on the actual velocity and not the superficial velocity.
  • Changed static pressure calculation to use actual (not superficial) velocity for pebble bed elements with non-zero solid fractions.

Version Upgrading

  • Fixed upgrade of Cooling Orifice to Nozzle – fixed the transfer of area, number in parallel and Cd value.
  • Decreased the time of upgrading a Flownex project file to a newer version – some unnecessary files were checked during upgrading.
  • Fixed upgrade of compounds that contained some of the fields used in H calculation and Primary loss calculation.

Rotating Components

  • Disabled inputs on Rotor-Rotor and Rotor-Stator that are set from the Cavity Editor when using the Cavity Editor tool.
  • Fixed problem where the axial measurement of gap width and shroud used the radial measurement in the cavity editor.
  • Fixed static enthalpy calculation for reverse flow in Rotating Channel and Rotating Nozzle.
  • Changed Daily & Nece correlation in cavities to use outer radius for density and viscosity in Reynolds number definition.

Heat Exchangers

  • Fixed heat exchanger components that should not allow heat transfer to them from other components via generic heat transfer components.
  • Fixed elevation input for Cooling Tower and Bulk Air Cooler.
  • Fixed surface temperature result for Plate Heat Exchanger primary and secondary not showing correct results.


  • Fixed problem with enthalpy and viscosity being incorrectly reported in writing out data from material test dialog.
  • Report fluid type correctly in writing out of data from material test dialog.
  • The option was removed to specify the specific heat for fluids in a script.
  • If enthalpy is specified in a script and no inverse function is defined a Newton Raphson is done to determine temperature from enthalpy.
  • Fixed the calculation of enthalpy from the option where specific heat is specified as polynomial equation that resulted in unrealistic temperatures on account of the enthalpy being capped instead of extrapolated when used out of range.


  • Fixed problem where the direction of drawing influenced results on Butterfly Valves.

Turbo Machinery

  • Fixed showing of speed options with enabling and disabling of Shaft links on Basic Centrifugal Pump.
  • Fixed Simple Turbine tooltip not showing.
  • Plot head excluding elevation on operating point plots so that they are shown correctly on pump curve.
  • Improved speed line extrapolation in turbo machine charts to use an average gradient calculated between the two closest speed lines, instead of allowing this gradient to change over the reach of the mass flow axis. This leads to much more realistically shaped extrapolated speed curves, with corresponding improvement in solver convergence.

Steam Turbine Group Efficiency

  • Changed warning for Steam Turbine Group Efficiency calculation, in the event that the pressure is outside of the validity range, to be issued only for the governing stage where it is applicable.


  • Tooltip added to Friction Loss and Motor/Generator components.

Heat Transfer Coefficients

  • Fixed upper limit Rayleigh number warning for free convection coefficient correlation over a horizontal cylinder to be 1e12 instead of the previous incorrect value of 1e13.
  • Implemented non-zero lower limits for laminar and turbulent friction factors.
  • Rounded Gr and Ra numbers reported in warnings to reduce duplication of warnings.

Secondary Pressure Loss Component

  • Fixed Secondary Pressure Loss choked flow calculation when flow area is different from choking plane. The choking plane is now calculated (either upstream area, downstream area or element flow area), and not assumed to be coincident with the element flow area.

Boundary Conditions

  • Added warning when a mass source is specified without associated temperature specification.

Hydraulic Grade line and Energy Line Results

  • Changed hydraulic grade line and energy line results to use gauge pressures and not absolute pressures. This is more consistent with typical industry application where these results are used frequently, such as slurry flows.

British Standard Orifice

  • Removed choking result from British Standard Orifice since it is not applicable.

Composite Heat Transfer Elements

  • Added warnings when incremented Composite Heat Transfer components are connected to non-incremented heat transfer components resulting in a mismatch in the number of increments.
  • Changed solid node temperature result with multiple increments to reflect averaged temperature of the surface.

Flow and Solid Nodes

  • Fixed flow node Heat source result that incorrectly displayed twice the user specified heat input under some configurations.
  • Fixed Solid Nodes incorrectly displaying inputs for radial pressure boundary and trace elements.

Flow Resistance

  • Fixed Flow Resistance square root input option that did not converge for reverse flows.

Open Container and Vented Container

  • Changed steady-state behaviour for Open and Vented Container to issue an error after the solution is done and there is flow exiting from above the level in the container. Previously a check valve was activated during the solution process, but this gave rise to diverging solutions.

Incremented Elements

  • Fixed incremented elements not updating incremented node elevations correctly when connected to tanks and containers.
  • Fixed incremented elements not updating incremented nodes swirl properties correctly when these elements are specified to rotate at machine speed.

Manual Updates

The following sections in the Flownex® General User Manual have been updated:

  • Updated the Creating and Solving a Network chapter to include Solving using Flownex SE Console.
  • Updated the Scripting section of the Libraries chapter to reflect recent changes and include all functionalities such as repository scripts.
  • Updated the Visualisation chapter to include the Flow Path Graphs and Psychrometric Charts.
  • Updated the Charts and Lookup Tables chapter by adding the PH diagram drawn for two phase fluids.
  • Updated the Advanced Configuration chapter by moving the FMU Configuration to the Functional Mock-up Interface (FMI) chapter.
  • Updated the Excel Input and Parameter Tables chapter to reflect updates made to the Parameter Tables.
  • Updated the Importing chapter to reflect changes made to the GIS importer.
  • Added the Functional Mock-up Interface (FMI) chapter covering the import and export of FMUs.

The following sections in the Flownex® Library Manual have been updated:

  • Added a Ducting chapter.
  • Added the Psychrometric Boundary Condition to the Nodes and Boundaries chapter.
  • Added the Volume Flow Source input to the Boundary Condition.
  • Updated the Nuclear Chapter.

The following sections in the Flownex® Components Basics Manual have been updated:

  • The Nodes and Boundaries manual was updated to include the Psychrometric Boundary Condition.
  • A Ducting chapter has been added.

The following sections in the Flownex® Demo Manual have been updated:

  • The demos were updated and validated to ensure that the results provided in the PDFs agree with the results obtained in Flownex®.

The following Tutorials have been updated:

  • The tutorials have been updated using the latest version of Windows and Flownex®. They were also validated to ensure that the values expressed in the PDFs agrees with the values obtained in Flownex®.
  • Added Tutorial 46 – Duct Design.

The following video Tutorials have been updated:

  • Video Tutorial 08 - Graphs video tutorial updated to include the Flow Path Graphs and Psychrometric Charts.
  • Video Tutorial 07 - Result layer video to reflect recent result layer changes.

Manual Updates

The following sections in the Flownex® General User Manual have been updated:

  • Updated the Visualisation chapter to include the changes made to the graphs.
  • Updated the Dynamic Modelling chapter by removing the recorded, predefines and specific actions.
  • Updated the Scheduling chapter to include the adaptive timestep functionality.
  • Updated the Advanced Configuration chapter to include the functionalities updated on the FMU Configuration.
  • Updated the Importing chapter by removing the DWSim importer section.
  • Updated the Third-Party Software chapter to include the changes made to the CFX Generic Interface and the Mechanical Generic Interface. The operation and properties of the Mechanical Generic Interface are described in more detail.

The following sections in the Flownex® Library Manual have been updated:

  • Updated the Rotating Components chapter with the enhancements for the Rotor-Rotor and Rotor Stator Cavities.
  • Updated the Heat Exchangers chapter with the enhancements for the Finned Tube Heat Exchanger, Plate Heat Exchanger and Shell and Tube Heat Exchanger.
  • Updated the Heat Transfer chapter with the External Pipe Heat Transfer theory and necessary screenshots.
  • Updated the fluid capabilities of the components that can be used with liquid-gas mixtures.
  • Renamed the Combustion Chapter to Chemical Reactions and added the Gibbs Reactor component.

The following tutorials have been updated:

  • Tutorial 10 – Updated screenshots.
  • Tutorial 16 – Updated screenshots.
  • Tutorial 19 – Updated screenshots.
  • Added Tutorial 43 – Flownex Ansys Mechanical Integration.
  • Added Tutorial 44 – Flownex CFX Co-Simulation using FMI.
  • Added Tutorial 45 – Cavity Drawing Tool.

The following has been updated in the Components Basic Manual:

  • Updated the Finned Tube Heat Exchanger inputs.
  • Removed the Cooling Orifice from the Restrictors.
  • Added the CEA Gibbs Reactor and CEA Adiabatic Flame to Chemical Reactions.
  • Added the Swirl Boundary Condition to Nodes and Boundaries.
  • Added the Custom Vortex to the Rotating Components.

The following Video Tutorials have been updated:

  • Updated Video Tutorial 8 to show the new Graphs implemented in Flownex®.