A first step for validating CFD results.

Many cooling system designs may require CFD (Computations Fluid Dynamics) simulations to better understand the behavior of the involved physics phenomena. CFD software are basically able to simulate almost anything and they always give a result; that’s why CFD models should not be used as black boxes: the user should have a good understanding of the underlying numeric schemes to avoid generating results that are pretty pictures but not accurate.

The point is to understand the reliability and accuracy of CFD models/assumptions. A useful method when post-processing CFD results is to have the energy and mass balance verified.

Let us consider e.g. the control volume below (red circles are heat sources).

Mass balance:

Energy balance:

Applying the mass and energy balance to the control volume above, we found:

This equation need to be verified by the CFD results. If not, CFD simulations have not been set in the right way.