FLOWNEX SE 8.10.0 (2019)

Flownex® SE 2019 is pushing the boundaries of thermal fluid system simulation.

We’ve added a few new enhancements and additions, including improvements to our heat exchangers, a custom vortex as well as a whole new appearance and functionalities to our graphs. We’ve also updated a few of our components to allow liquid-gas mixture fluid types.
A NEW student version 2019 is also available to download. 

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LIST OF ENHANCEMENTS

MAJOR ENHANCEMENTS

Adaptive Timestep

Fig. 1 - Adaptive Time Step in Scheduler
An adaptive timestep functionality has been added to the Flownex® solver that automatically refines the timestep size through a transient simulation. This results in small timesteps when fast transients (such as pressure pulses during water hammer) are occurring to accurately predict the solution and larger timesteps when possible to effect shorter solving times. This feature monitors the pressure, energy, mass flow and density of all the components and will automatically reduce the timestep to ensure that the solution remains within the specified accuracy criteria. This allows the user to accurately predict fast transients such as pressure pulses without having to perform a temporal convergence study first. For more information about how the adaptive timestep algorithm is implemented, please refer to the Scheduling chapter of the General User Manual. A button has been added to the toolbar that gives the user quick access to the time step settings. It is located next to the Reset Time button in the Simulation Control section, as seen in Figure 2.
Fig. 2 - Time Step Settings

Cavity Editor

The inputs of the Rotor-Rotor and Rotor-Stator components have been significantly enhanced in order to allow a user to easily specify a complex geometry for the cavity.

The complex geometry can be specified by using the Cavity Editor, which opens when double clicking on a Rotor-Rotor or Rotor-Stator component. The Cavity Editor allows the user to import a background picture for the cavity. The geometry and dimensions can then be defined on the picture in the Cavity Editor, as seen in Figure 2.

Fig. 3 - Rotor-Stator Cavity Editor - Reference Measurements

After a picture has been imported, the user can define the dimensions of the cavity by specifying two points at any location on the drawing. Thereafter, the rotor and stator surface geometries are easily drawn on top of the picture.

Fig. 4 - Rotor-Stator Cavity Editor - Rotor Surface Geometry

Other geometric items like the position of bolts, gap and shroud width, as well as defining the discretization is also done easily using this Cavity Editor.

Fig. 5 - Rotor-Stator Cavity Editor - Discretisation

Custom Vortex

Fig. 6 - Customer Vortex Component
A Custom Vortex component has been added to the Rotating Components Library. The custom vortex is a vortex model commonly used in gas turbine cavity modelling. The tangential velocity is specified to produce a velocity profile between that of a forced vortex and free vortex. The radial velocity profile is specified in the following format Cθ= s⋅rn. A custom vortex is characterised by a swirl constant, s, and a vortex weighing factor, n. The custom vortex model provides a simplified cavity model that allows the user to adjust the swirl constant and vortex weighing factor to match the swirl pressure rise seen in empirical measurements.

Heat Exchanger Improvements

The Heat Exchanger components in Flownex® has been updated. These components are now easier to use and a few essential features have been added. The heat exchangers that has been updated is the Shell and Tube Heat Exchanger, Finned Tube Heat Exchanger and the Recuperator, which has been renamed to a Plate Heat Exchanger. The changes make using the heat exchangers for a general application like radiators etc. simpler. Furthermore, fouling factors and fin efficiencies have been added to the heat exchangers where relevant. These can be used to model degradation over time and changes in the condition of the heat exchangers.

Shell and Tube Heat Exchanger

Cosmetic Changes

New icons have been added for the Shell and Tube heat exchanger and the names now clearly indicate the shell side and the tube side.

Fig. 7 - Shell & Tube Heat Exchanger
Input Changes
Shell Side Primary Loss Calculations

The shell side supports specification of the friction factor through a constant value, using a script or using a Fanning friction chart. By default, the Fanning friction factor chart is used. The user can however easily use a correlation from another source in the script defined friction factor specification. These options can be seen in Figure 8.

Fig. 8 - Shell Side Primary Loss Options
Shell Side Heat Transfer Coefficient Calculation

The shell side now supports built in correlations for the heat transfer coefficient calculation, as well as script defined heat transfer coefficient calculation, constant value specification and Stanton Prandtl charts. By default, the Shell Side heat transfer coefficient calculation correlation is used. The user can however easily use a correlation from another source in the script defined heat transfer coefficient calculation, as seen in Figure 9.

Fig. 9 - Shell Side Convection Coefficient Options
Tube Side Primary Loss Calculation

The tube side supports specification of the friction factor through a constant value, Darcy Weisbach correlations, using a script or using a Fanning friction factor chart. By default, the Darcy Weisbach correlation is used, as seen in Figure 10.

Fig. 10 - Tube Side Primary Loss Options
Tube Side Heat Transfer Coefficient Calculation

The tube side supports built in correlations for the heat transfer coefficient calculation, as well as script defined heat transfer coefficient calculation, constant value specification and Stanton Prandtl charts, as seen in Figure 11. By default, the Gnielinski correlation is used for the tube side heat transfer coefficient calculation.

Fig. 11 - Tube Side Convection Coefficient Options
Finned Tube Heat Exchanger
Cosmetic Changes

New icons have been added for the Finned Tube heat exchanger and the names now clearly indicate the fin side and the tube side.

Fig. 12 - Finned Tube Heat Exchanger
Input Changes

Fin Side Geometry

A simplified set of inputs has been added to specify the geometry of a rectangular finned tube heat exchanger with round fins. This is the default option now, as seen in Figure 13.

Fig. 13 - Rectangle HX with Round Fins Inputs

The user now specifies more readily available geometric parameters like the heat exchanger width height and length as well as tube and fin diameters. The older more generic specification is still available.

Fin Side Primary Loss Calculation

The fin side supports specification of the friction factor through a constant value, using a script or using a Fanning friction factor chart. By default, the Fanning friction chart is used. The user can however easily use a correlation from another source in the script defined friction factor specification.

Fin Side Heat Transfer Coefficient Calculation

The shell side now supports script defined heat transfer coefficient calculation, constant value specification and Stanton Prandtl charts. By default, Stanton Prandtl chart is used. The user can however easily use a correlation from another source in the script defined heat transfer coefficient calculation.

Tube Side Primary Loss Calculation

The tube side supports specification of the friction factor through a constant value, Darcy Weisbach correlations, using a script or using a Fanning friction factor chart. By default, the Darcy Weisbach correlation is used.

Tube Side Heat Transfer Coefficient Calculation

The tube side supports built in correlations for the heat transfer coefficient calculation, as well as script defined heat transfer coefficient calculation, constant value specification and Stanton Prandtl charts. By default, the Gnielinski correlation is used for the tube side heat transfer coefficient calculation.

Plate Heat Exchanger
Cosmetic Changes

The Recuperator heat exchanger has been renamed to the Plate Heat Exchanger, which describes the functionality of the heat exchanger better. New icons have been added for this heat exchanger too.

Fig. 14 - Plate Heat Exchanger
Input Changes

Primary & Secondary Side Primary Loss Calculations

Both sides support specification of the friction factor through a constant value, Darcy Weisbach correlations, using a script or using a Fanning friction factor chart. By default, the Darcy Weisbach correlation is used with the addition of friction factor multipliers that can be used in the laminar and turbulent ranges to adjust the friction factor.

Primary & Secondary Side Heat Transfer Coefficient Calculation

Both sides support built in correlations for the heat transfer coefficient calculation, as well as script defined heat transfer coefficient calculation, constant value specification and Stanton Prandtl charts. By default, the Gnielinski correlation is used for the tube side heat transfer coefficient calculation.

Graph Improvements
The appearance of the graphs in Flownex® has been updated and the new graphs can be seen in Figure 14.
Fig. 15 - Comparison Between the Old and New Graphs in Flownex

The graphs inputs have been modified such that only basic graph properties are shown when creating a new graph to ease formatting/styling. Additional formatting properties are available when checking the Advanced Formatting properties, as seen in Figure 15.

Fig. 16 - Graph Properties

New graph functionalities include:

  • By default, the Y-Axis will zoom and pan automatically for easy navigation.
  • The X-Axis will auto scale.
  • Line types can be changed to Step, Spline, Scatter Line, Area, Step Area or Spline area.
  • Line graph plotting data can be saved to a CSV file by simply right clicking on the graph.
  • A Crosshair cursor showing all Y-Axis values for a specific X-Axis value has been added.
  • Graphs formatting can be changed without having to solve the network again.
Rotating Components

The Daily and Nece correlation for calculating moment coefficients on disk surfaces was added as an option for the Rotor-Stator and Rotor-Rotor cavities as seen in Figure 16.

Fig. 17 - Friction Coefficient Correlation Options

In the case of the Rotor-Stator cavity, the Daily and Nece correlation allows for four different regimes, including fully interfering boundary layers within very small gap widths. The possibility to modify the Haaser et. al. correlation to be dependent on the gap width to disk diameter ratio was also added.

The Rotor-Stator and Rotor-Rotor cavities were upgraded to allow specifying an inner radius and outer radius for each disk individually, this is specifically useful when modelling cavities with axial inflows/outflows.

The Rotor-Stator and Rotor-Rotor cavities were upgraded to allow a disk surface profile specification that is not strictly rising with radius.

An option was added to all elements connected to vortices and cavities to specify the radius at the connection rather than the radius fraction. This allows the user to easily link the connection radius input to a measurement on a scaled drawing.

An increment result for windage power was added to the Rotor-Stator and Rotor-Rotor cavities. The windage power calculation of the Rotating Channel, Rotating Nozzle, Labyrinth Seal and Rotating Annular Gap was modified to automatically account for windage addition/removal to the element on account of upstream node swirl speeds not equal to that inside the element. Previously the windage power added to these elements was solely attributed to that required to maintain the swirl speed inside the element. This modification may lead to modified results since windage affects gas density.

The windage power calculation on the Forced Vortex component was modified to account for changes in kinetic energy of incoming flow streams that must increase/decrease in order to be equal to the swirl speed of the vortex at the particular connection radius. This modification may lead to modified results since windage affects gas density.

Liquid Gas Mixtures

The following components were extended to allow liquid-gas mixture fluid types, thereby allowing coupling of the secondary air system with the lubrication system:

  • Rotating Channel
  • Rotating Nozzle
  • Nozzle
  • Rotor-Stator Cavity
  • Rotor-Rotor Cavity
  • Forced vortex
  • Free Vortex
Chemical Reactions

The combustion category has been renamed to Chemical Reactions. The existing Adiabatic Flame model is a chemical reaction where the end temperature and composition of the end product of the reaction is determined by the CEA calculations. Another component has been added to the Chemical Reactions library where the user can specify the end temperature of the chemical reaction, namely the Gibbs Free Energy Reactor.

Gibbs Free Energy Reactor
Fig. 18 - Gibbs Free Energy Reactor
The component uses the NASA CEA program to predict the reaction products at the specified end temperature. This component will then calculate the change in Gibbs free energy and enthalpy during the reaction. As part of this enhancement, a Gibbs free energy result has been added on all flow nodes. The first application of this reactor is to model fuel cells and use Flownex® to optimise the surrounding systems. There are however many other possible applications.

MINOR ENHANCEMENTS

Scale Drawings

The setup of measurements in scale drawings has been simplified. The user can now drag and drop properties from components onto measurement points and measurement lines.

If it is a measurement point, the user will be asked to which part of the coordinate (X,Y, or Z) it should be assigned.

Fig. 19 - Coordinates

If the user drags and drops on a line, the property will automatically be associated with the length of the line.

CFX Interface

Errors when using a comma as decimal separator were fixed. The interface is able to handle both a point or a comma as decimal separator.

The option was added to deactivate the simulation when the CFX Generic Interface encounters an error. A user can continue the simulation from the point where the error (can include CFX solver crash) occurred, saving the time it took to reach that point.

Fig. 20 - Deactivate Simulation when Error Occurs Option

FMI

The Flownex® Co-Simulation FMU capability has been enhanced. Flownex® now supports state serialization of the FMU. State serialization is however a slow process and therefore it is not recommended unless it is crucial. There is a new option in the FMU configuration to turn state serialization on and off. The option is false by default. An option has also been added to the FMU configuration to hide Flownex® during FMU execution.
Fig. 21 - FMU Configurations
An example of using a Flownex® FMU with CFX has been added as a tutorial (Tutorial 44).

AFT Importer

In the past, the AFT importer always searched for a scenario named Base Scenario or Base Case to import. This has been improved and the first scenario listed in the Scenario Manager section of the file will now be imported. This enhancement fixes issues were scenarios did not have the default Base names.

API

Functions were added to the network builder to set the page size for any page.

Ansys Mechanical Link

The Ansys mechanical link now allows a user to specify the name of boundary conditions to transfer load data. Specifying the same names for matching boundary conditions and named selections allows the user to use named selections in the link setup.

Fig. 22 - Use Boundary Condition Names

Units

The unit g/mol was added for molar mass.

The unit kN was added for force.

FlownexSEConsole

Errors and warnings were displayed in the console version of Flownex®, but were not recorded. The errors and warnings are now recorded to files named FlownexSEConsoleWarnings.txt and FlownexSEConsoleErrors.txt respectively. These files are located inside the project folder.

Convection Coefficient Correlations

Correlations for calculating convection heat transfer to ambient was added to the Composite Heat Transfer component, as well as the Insulated Pipe component.

Correlations for three different convection mechanisms were added, namely free convection over a horizontal cylinder, free convection over a vertical cylinder, or forced convection over a cylinder. The user can select the mechanism that should be used, as seen in Figure 22.

Fig. 23 - Convection Coefficient Correlation Selections

Pipe

Added Wall Shear Stress result for Pipe elements with Newtonian Fluids.

Material Warnings

Added warnings for low and high limits when interpolating from two-phase tables. Added warning when two-phase critical mass flux cannot be calculated due to low total pressure.

Nuclear Reactor

Improved the checking and issuing of errors for materials in the Advanced Reactor – materials that did not exist issued warnings even when options were active where they were not used.

Several improvements were made to the text based Nuclear results. This includes correcting the generated heat results for solid nodes and solid node volume results. Also, units were added and corrected for heat in several places.

Node Results

Added an energy source result on solid nodes, as well as transient energy source calculation on all node types. A Gibbs free energy result was also added to flow nodes.

Container Interface Components

The Container Interface Top and Container Interface Bottom components were enhanced to allow the specification of height or height fractions on adjacent elements. Previously, elements could only be connected at the bottom or top.

Fig. 24 - Connection Specification Options

BUG FIXES

Nuclear Reactor

Fixed a problem where the volume on flow nodes were too large when using Darcy Weisbach pressure drop in a nuclear reactor.

Scripts

Prevent snaps from loading new script code. This could cause the user to lose the current script and it would be reverted to the script that was used when the snap was saved.

Heat Transfer Component

When multiple Composite Heat Transfer elements were connected to a component, the downstream temperature exceeded the wall temperature. This has been fixed.

User Specified Pressure Drop

Fixed the problem with networks using multiple User Specified Pressure Drop Components that did not converge under some conditions.

Pipe

Fixed incremented pipes giving different results than non-incremented pipes when used with non-Newtonian fluid types.

Positive Displacement Compressor

Fixed the problem where the Polytropic coefficient value was limited between 0 and 1 for the Positive Displacement Compressor.

Charts & Data References

The full name and path of the chart were saved in the chart and then Chinese characters in the path caused a problem with the saving. This was removed and the charts are now better compatible with Chinese characters in file names and folders.

Fixed problems when turbo machinery charts have too many points. This caused losses of data and abnormal program termination. The errors that are issued when there are too many points are now handled gracefully.

Scale Drawings/GIS

Elevation retrieval for nodes on imported GIS networks did not work due to changes to the Google elevation API. The code has been updated to work with the new changes.

There was a problem on scale drawings where IO boxes displaying measurement positions or lengths did not update when measurement items were moved.

Fixed a problem where using groups on scale drawings caused duplicate views of components on the scale drawings.

Excel Input Sheet

Saving of snaps caused Excel Input Sheets to stop functioning. This has been fixed.

Excel Reports

There was a problem where the last time step during a run was not reported to the table with time steps. This has been fixed.

The cyclic option on reports did not always sample data at the correct time – it was sometimes off by a couple of timesteps.

Global Parameters

Fixed the problem where loading snaps created duplicate global parameters. This caused the global parameter list to become very large and caused serious slowdowns in the user interface. A script has been added to remove the duplicate items.

Licensing

Fixed a problem where checking licenses back in if the roam (borrowing) period is longer than the server license expiration date caused an exception.

Download full release notes here.

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