NUMERICAL-SIMULATION OF SUBCOOLED BOILING AND HEAT-TRANSFER IN VERTICAL DUCTS

A two-dimensional two-phase non-equilibrium model is presented to predict the void fraction distribution, flow and temperature fields for turbulent subcooled flow boiling at elevated pressures in heated vertical ducts (pipes and channels). The model is based on the conservation of mass, momentum, and energy equations for each of the two phases. Appropriate wall and interfacial conditions are formulated to close the problem. The non-equilibrium temperature and velocity distributions of the two phases and void fraction profiles show considerable variation along the radial and axial directions for the subcooled flow boiling cases considered. The effects of inlet subcooling, exit pressure and wall heat flux on the flow boiling behavior were predicted. The predicted radially averaged void fractions are compared with the experimental results available in the literature. The radial temperature distributions and void fraction profiles are also compared with available experimental measurements.