Review of Correlations of Flow Boiling Heat Transfer Coefficients for Nitrogen

As an excellent cryogenic cooling medium, Nitrogen (N₂) has been used in a variety of engineering fields, where the determination of N₂ two-phase flow boiling heat transfer is required. There were some studies evaluating the correlations of flow boiling heat transfer coefficient for N₂. However, either the number of correlations covered or the number of data used was limited. This work presents a comparative review of existing correlations of flow boiling heat transfer coefficients for N₂ applications. A database of N₂ flow boiling heat transfer containing 1043 experimental data points is compiled to evaluate 45 correlations of two-phase flow boiling heat transfer. The experimental parameters cover the ranges of mass flux from 28.0 to 1684.8 kg/m²s, heat flux from 0.2 to 135.6 kW/m², vapor quality from 0.002 to 0.994, saturation pressure from 0.1 to 3.16 MPa, and channel inner diameter from 0.351 to 14 mm. The results show that the best correlation has a mean absolute deviation of 31.8% against the whole database, suggesting that more efforts should be made to study N₂ flow boiling heat transfer to develop a more accurate correlation.