Pressure drop for highly subcooled water flow boiling under high heat and mass fluxes

Pressure drop is one of the most important thermal-hydraulic issues for the cooling system of high heat flux components, such as the plasma-facing divertors in fusion reactors. Experimental studies were carried out to investigate the pressure drop of highly subcooled water flow boiling in a vertical circular tube (d = 9 mm, LH = 400 mm) under high heat and mass fluxes. The operating parameters covered the range of heat fluxes (0-12.5 MW/m2), mass fluxes (6000-10,000 kg/m2 s), pressures (3-5 MPa), and liquid subcooling (6-224 °C). The parameter effects on subcooled boiling pressure drop were discussed. It was observed that subcooled boiling pressure drop increased with increasing heat and mass fluxes but decreased with increasing pressure. Available correlations for subcooled boiling pressure drop were compared with the experimental data. The results indicate that these correlations cannot well predict our data mainly due to the variations in operating parameters and working fluids. Therefore, a new correlation is proposed to calculate subcooled boiling pressure drop for high-heat-flux applications. The new correlation is presented as a function of boiling number, Jacob number, and density ratio. The new correlation predicts the experimental data within an accuracy of ±20%.