Altair Flow Simulator 2024 Release Notes

• Flow Network Grouping in the GUI
• Turbulator Friction and Heat Transfer in Tube Elements
• Rotating Surfaces in Tube Elements

Flow Network Grouping in the GUI

Items in the flow network can now be grouped like thermal network grouping introduced in the last release, 2023.1. The groups can be named and colored. All entities displayed within the group can also be colored with the group’s color. Collapsing the groups into blocks can help model organization and visualization.

Turbulator Friction and Heat Transfer in Tube Elements

The advanced tube and incompressible tube elements now have turbulator friction and heat transfer coefficient (HTC) options. The options for the friction and HTC include:

1. Webb Turbulator – Circular duct, square rib profile, 45 to 90 degree rib angle. Ref.: Webb, R. L., Eckert, E. R. G., and Goldstein, R. J. "Heat Transfer and Friction in Tubes with Repeated-Rib Roughness", Int. Journal of Heat and Mass Transfer, 14 (1971).
2. TS Ravi Turbulator – Circular duct, multiple rib profile, 25 to 90 degree rib angle. Ref.: Ravigururajan, T.S., "General correlations for pressure drop and heat transfer for single-phase turbulent flows in ribbed tubes", Iowa State Univ, Thesis, 1986.
3. Han 90 deg Turbulator – Rectangular duct with ribs on two opposing walls, square rib profile, 90 degree rib angle. Ref.: Han J.C., "Heat Transfer and Friction Characteristics in Rectangular Channels with Rib Turbulators", Journal of Heat Transfer, ASME (1988)
4. Han Angled Turbulator – Rectangular duct with ribs on two opposing walls, square rib profile, 30 to 90 degree rib angle. Two references for low and high duct aspect ratio. Ref. for .25<W/H<1.0: Han, J. C., Ou, S., Park, J. S. and Lei, C. K. " Augmented Heat Transfer in Rectangular Channels of Narrow Aspect Ratios with Rib Turbulators" , International Journal of Heat Mass Transfer, 32, (1989) Ref. for 1.0<W/H<4.0: Han, J. C. and Park, J. S. "Developing Heat Transfer in Rectangular Channels with Rib Turbulators", International Journal of Heat Mass Transfer, 31, (1988).

Rotating Surfaces in Tube Elements

The advanced tube and incompressible tube elements can now calculate the fluid swirl and temperature change due to windage for an annulus or coaxial shaft with a rotating surface. Previous versions would assume the fluid swirl is the same as the tube rotation. If Rotating Annulus or Rotating Coaxial Shaft are selected, an angular momentum balance is calculated to get the change of swirl and temperature. For instance, if fluid with a low swirl (~0.1) enters a tube element with the inner surface of the annulus rotating, the fluid swirl increases as it moves through the element. The results file, *.res, has the details of the swirl change. The friction factor and heat transfer coefficient correlations use an effective velocity based on the relative tangential and axial velocity.

Parallel Rotating Tube Heat Transfer Coefficient Correlation

An additional HTC correlation is available to use with convection resistors in the thermal network and with tube elements. The new correlation is for a rotating tube that is parallel to and offset from the axis of rotation.

New Generic Heat Exchanger Options

The Generic Heat Exchanger (GHX) has one new pressure loss option and three new heat transfer options. The “No Loss” pressure drop option can be used when the fluid pressure drop is not important, but solution speed is critical. The “No Loss” option can significantly reduce solver solution time in models that have multiple GHX components. The Fixed Fluid Exit Temperature options determine the amount of heat transfer required between the hot and cold stream to achieve a target exit temperature set for the hot or cold stream. The Number of Transfer Units (NTU) can also be set to a constant value.

Generic Heat Exchanger Matrix Modeling

Generic Heat Exchanger components can be arranged in a matrix to capture more details of the heat exchanger. For example, a vehicle radiator can be modeled with a single GHX component using a single cold air inlet temperature to calculate the overall heat exchange between the air and coolant and a single air exit temperature. More detailed results can be obtained by modeling the vehicle radiator with a matrix of heat exchangers. Each heat exchanger in the matrix can have a unique air inlet temperature and will have a unique air exit temperature. One of the GHX components is declared the master and given inputs representing the performance of the entire heat exchanger. All the other GHX components in the matrix use the master GHX inputs. Thermal performance discretization methods are NTU scaling or even heat exchange Q distribution.

User Defined Material Property Improvements

The User Defined Material property window has the flexibility to use more properties, so the ideal gas assumptions are not needed. This allows for more accurate fluid properties for a “real” gas. For example, the gas density and gas constant can be specified, and the compressibility factor will be calculated.

Thermal Network Post-processing Improvements

The GUI has new color contour plotting options for Heat Flow and Nodal Heat on thermal networks. Thermal group post-processing includes minimum, maximum, and average temperatures for thermal nodes in the group. The Nodal Heat sum for the group is also available. Flow group post-processing will not be available until the 2024.1 release.

Mission Parameter Unit Options

The mission data table now has all the unit options available in Flow Simulator. This allows input of data like HTC in other unit sets.

The following known issues will be addressed in a future release as we continuously improve software performance:

• The FMU exported from Flow Simulator has not been tested with many different FMU importer programs. There may be issues when importing an Flow Simulator FMU into the other programs.

• Added a limit for the heat flow from the thermal network convector to a flow chamber. The heat flow is limited by the heat capacity of the fluid. The flow chamber is not allowed to rise above the wall temperature for heating or fall below the wall temperature for cooling.
• Changed the standard tube element that allows it to converge for lower Mach numbers (<.000001).
• The vortex element automatic flow flag option uses improved logic to try the various flow calculation options. If a model has worse convergence in the 2024 release, try changing the vortex flow flag to the automatic option.
• GUI problems with the multi-edit of controller and FMU variables.
• GUI problem with built-in heat transfer coefficient units’ conversion.
• GUI problems with rotating and scaling images.
• Accumulators now get proper fluid when clicking Apply in the Material Manager.