Fixed defects

General

4277539

This defect fix addresses an issue with importing simulations from versions earlier than AVEVA Process Simulation 2025 into the latest version of the software. Some simulations imported as properly specified (square) and solved but then crashed due to a "key not found" exception in some equations.

We have addressed this issue by ensuring that the software correctly generates the derivative equations for all system calculations and processes. You should no longer encounter a “key not found” exception in your imported simulations.

Process Library: Column

4108331

This defect fix addresses an issue with the Column model where if you change its reaction basis for stages, such as from Volume to Conversion, the Column model does not solve and becomes under-specified. This issue was present in AVEVA Process Simulation 2025 and 2024.2.

We have addressed this issue by updating the Column model to make it compatible with the ColStage submodel so that the simulation is always properly specified (square), even when you change its reaction basis.

Settings Library: OptimizationSettings and OptSetA

4086471

This defect fix addresses an issue where the optimization run shows an improved status but the simulation is not solved. A call to the flash initialization caused the failure. By default, an optimization run should not call the flash initialization.

We have addressed this issue by adding a new parameter named FlashInitializeOption into the OptimizationSettings and OptSetA models. By default, this parameter ensures that there are no flash initialization calls when AVEVA Process Simulation performs a flash during an optimization run. Prior to this addition, AVEVA Process Simulation would decide if an optimization run requires a flash initialization.

Thermodynamics

4228327

This defect fix addresses an issue where the thermodynamic calculation for the adiabatic compressibility factor (ks) of a single-phase fluid incorrectly used the equilibrium method in the corresponding Fluid Type instead of the selected enthalpy method.

We have addressed this issue by ensuring that the ks variable is registered as an enthalpy property so that it uses the enthalpy method for the calculation.

The equilibrium method is the thermodynamic method that you select in the System list in the System section of the Fluid Editor. The enthalpy method is the thermodynamic method that you select in the Vapor Enthalpy or Liquid Enthalpy list in the Property Options section of the Fluid Editor.

The ks variable appears in the stream only when one fluid phase is present (vapor only or liquid only). When both the vapor and liquid phase are present, the stream includes an adiabatic compressibility factor for each phase (ksv and ksl, respectively) instead of the ks variable.

Therefore, this defect fix applies only to simulations that use fluids where the following is true:

• Only one phase is present in the fluid (vapor only or liquid only).

• The equilibrium method and the enthalpy method (Vapor Enthalpy or Liquid Enthalpy, respectively) are different.

  You may see slightly different solution results in these simulations when you import them into AVEVA Process Simulation 2025.1.

Thermodynamics: GERG-2008

4023811

This defect fix addresses an issue where the GERG-2008 equation of state (EOS) has a slow performance.

We have addressed this GERG-2008 EOS issue by improving the thread safety and numeric derivatives.

Thermodynamics: Vapor-liquid-water equilibrium (VLWE)

3995855

This defect fix addresses an issue where the VLWE pilot flash equation could run into a singular matrix issue. This singularity was causing the pilot VLWE flash to fail to converge after 100 iterations.

We have addressed this issue by applying a fix to the pilot VLWE flash equation so that the singularity never occurs.