A Warning message in AFT Arrow

This warning alerts you to the fact that the converged results may be incorrect. Once a converged solution is obtained, AFT Arrow checks all junctions to ensure a concentration balance exists. It compares the imbalance to the flow tolerance you specified, and when it appears to exceed the tolerance, it gives you this warning.

If the magnitude of the concentration out of balance flow is close to the tolerance you specified, then it is generally safe to ignore this warning, although you may want to reduce your tolerances further and rerun the model.

If the magnitude of the concentration out of balance is large, then you have a converged solution that is incorrect. This can occur in rare circumstances. When this happens, then it is usually an indicator that your model is not realistic.

You should always review each of these warnings in detail, and perform hand calculations on the concentration balance at the affected junctions to verify whether an acceptable solution exists.