Study on the subcooled boiling pressure drop for downward flow in a narrow rectangular channel

Highlights: • Subcooled boiling pressure drop is obtained from an experiment under downward flow. • Some previous empirical correlations of subcooled boiling pressure drop are evaluated. • A new correlation was developed to predict subcooled boiling pressure drop. Subcooled boiling pressure drop is an issue worthy of attention for heat exchange systems, such as nuclear reactor core. Few related studies focused on the downward flow in narrow rectangular channel. In this study, the subcooled boiling pressure drop is obtained from an experiment in a narrow rectangular channel (2.3 mm$\times$67 mm) under downward flow with low heat flux, mass flux and pressure. To calculate the pressure drop multiplier ${\Phi }^2$, a correlation of single-phase adiabatic friction factor suitable for the present experiment is proposed and a new method is used to deal with the ${\Delta p}_{\mathrm{sc}}$. The experimental data are compared with previous empirical correlations of subcooled boiling pressure drop, and their predictive abilities for this experiment data are evaluated respectively. An empirical correlation for predicting subcooled boiling pressure drop is developed considering the effect of heat and mass flux, inlet subcooling and pressure. It shows good performance with the experimental data.