Theoretical CHF predicted model for subcooled flow boiling

Abstract

To predict the critical heat flux (CHF) of flow boiling under subcooled conditions, this study comes up with a new model based on the Interfacial Lift-off CHF model. The new model makes up the shortcomings of the previous one used only under saturated conditions, and it also considers the effect of condensation on the interface between liquid and vapor phases. An all-new subcooled correctional coefficient is risen up based on the CHF value for the corresponding flow velocity under near-saturated conditions. By comparison between the predicted results of this model and the experimental ones at 6 subcoolings from 3 to 30 °C, and 18 flow velocities from 0.75 to 8 m/s, with the mean absolute error of 9.4%, the predicted trends are both intuitively reasonable and numerically accurate. It reflects the rule under which CHF changes with the outlet subcooling and flow velocity under both saturated and subcooled conditions, and the vapor amount within a vapor bulk decreases with the increase of subcooling. But as the flow velocity increases, it decreases first, and then tends to be a fixed value gradually.