Resolving warning 4410: Troubleshooting iterative heat flux convergence issues

Details

The thermal solver automatically uses ray-tracing to model specular reflections and transmissions. The ray-tracing operations are carried out after computing the solar view factors for all elements. Rays are launched from all elements with a non-zero solar view factor and a defined specular reflectivity or transmissivity component. Diffusely reflected fluxes are distributed through the model using the view factors.

The diffusely incident flux on each transparent and/or specular element is redistributed to all visible elements through reflection and/or transmission using an iterative method. The redistribution process continues iteratively until a maximum of 30 iterations, or until the absorbed energy is 99.99% of the total initial incident energy. If this convergence criterion is not reached, the remaining unabsorbed energy is evenly redistributed and the following warning 4410 is issued.

** WARNING 4410**
** Iterative heat flux calculation method did not converge,
** residual fraction of incident energy that was evenly
** redistributed was 2.579E-04.

This warning indicates that some energy couldn't be absorbed by elements within the enclosure and was instead redistributed to all elements. If this unabsorbed energy fraction is minor compared to the overall energy fluxes, it may be acceptable. However, to ensure accuracy, it's important to fix any issues in the model.

This issue may be caused by bad view factor sums or incomplete enclosures.

You can also increase the maximum number of iterations by adjusting the advanced parameter POWER MODULE ITERATIVE SOLVER PARAMETER (default set to 30) to improve convergence.

However, the most effective solution is to correct the underlying model issues to prevent these warnings from occurring.

Low view factor (VF) sums are indicated by Warning 4316.

** WARNING 4316**
** The view factor sum error of the following 430 element(s)
** exceeds 20%. The total number elements with non-zero
** view factor sum is 10279. Incomplete enclosures may
** exist in the model. A complete element list can be 
** found in file groups.unv under the group name:
** BAD_VIEW_FACTOR_SUM_ELEMENTS_000082
603290   603300   603303  603319  603325  603327  603328

These low sums often point to problematic elements affecting radiation calculations. Closely examine the elements flagged by Warning 4316 and correct any inaccuracies. To view these elements, import the group.unv file by choosing File → Import→ Simulation, and selecting Simcenter 3D Thermal/Flow. From the File Type list, select Solution Error/Warning Groups.