The comparison between the simulation results, results predicted by correlations and experimental results is plotted below:

Figure 16: Comparison between simulation results, experimental results [4] and correlations [10][11] for natural convection

As shown in the figure above (Figure 16) the results predicted by Neptune_CFD are very close to the experimental results, where the difference is estimated to be lower than 15% for a heat flux up to 2000 W/m2. Further from 2000 W/m2, the simulation results and even those obtained by the correlations are no longer comparable with experimental results. By referring to the boiling curve of propane (Figure 3 in ‘BIBLIOGRAPHY RESEARCH’ section), it is said that a transition regime exists between 2000 - 5000 W/m2 before the boiling takes place. Therefore, the incoherence between results is expected as the simulations and correlations are initially developed for natural convection regime.

Consequently, the simulation results by Neptune_CFD are proved to be reliable and the Boussinesq hypothesis is well-adapted to predict the natural convection for propane while for higher heat flux, the nucleate boiling model has to be taken into consideration.