Assessment of the Force-Balance Model in Predicting the Bubble Departure Diameter in Inclined Channels

Abstract The flow boiling is widely encountered in various fields, ranging from the chemical and process industries to boiling water reactors and steam power plants etc. In order to gain a better understanding of this boiling process, one of the bubble dynamic parameters, the bubble departure diameter is studied in this paper. Firstly, the forces acting on a nucleation bubble were analyzed based on the force balance model, including the surface tension force, unsteady drag force, shear lift force, buoyancy force, hydrodynamic pressure force, quasi-steady drag force and contact pressure force. Then, a large number of experimental data for bubble departure diameter in flow boiling conditions under a wide range of orientation angle, mass flux, heat flux, and pressure were collected to quantify the predicting accuracy of existing force balance models. Considering that the influence of forces acting on a vapor bubbles would change with the channel inclination, these experimental data were divided into three parts based on the channel inclination. The verification results are of great importance for accurately determining the bubble departure diameter as well as analyzing the heat transfer process under various channel inclination angels.