Numerical and experimental investigation of pressure drop characteristics during upward boiling two-phase flow of nitrogen

The characteristics of overall pressure drop during upward boiling two-phase flow of nitrogen with constant mass flux and varying heat flux are experimentally investigated using a vertical tube with an inner diameter of 6.0 mm and numerically simulated using the two-fluid model with new closure correlations. Comparison of the numerical results against the experimental data shows that prior to the transition point in the curve of pressure drop evolution, the predicted pressure drop is in a satisfactory agreement with the experimental data. The present study demonstrates that both the wall lubrication force modeling and the bubble diameter modeling have significant effect on the pressure drop prediction. Both the theoretical analysis and the experimental evidence suggest that the transition point in the pressure drop evolution curve reflects the bubbly-to-slug flow regime transition.