Theoretical calculation of the characteristics of annular flow in a rectangular narrow channel

Abstract A mathematical separated flow model has been developed that is applicable to the annular two-phase flow in the rectangular narrow channels with peripheral heating. The theoretical annular flow model is based on the fundamental conservation principles: the mass, momentum and energy conservation equations of liquid film, and the momentum conservation equation of the vapor core. Through numerically solving the closed equations, boiling heat transfer coefficient, axial pressure gradient, liquid film thickness and velocity profiles in the liquid film are obtained. A good agreement has been found through comparing the experimental data and theoretically predicted results. The liquid film thickness will decrease with the increase of heat flux and channel width, while increases with increasing flow rate and channel height. The velocity profile in the liquid film is not linear when the thickness of the liquid film is not very thin and it increases with increasing heat flux, while decreases with the increase of mass flow rate and channel size. The effects of heat flux and channel width on velocity in the liquid film are larger than that of mass flow rate. The velocity in liquid film tends towards linear, when the liquid film is mainly in the laminar boundary layer.