Numerical Simulation of Boiling Flows Using an Eulerian Multi-Fluid Model

A mathematical model to simulate boiling flows in industrial applications is presented. Following the Eulerian multifluid framework, separate sets of mass, momentum, and energy conservation equations are solved for liquid and vapor phases, respectively. The interactions between the phases are accounted for by including relevant mass, momentum, heat exchanges and turbulent dispersion effects. Velocity-pressure coupling is achieved through a multiphase version of the SIMPLE method and the standard k-ε turbulence model is employed. In order to validate and assess the accuracy of the boiling model, subcooled nucleate boiling flows in a vertical annular pipe are simulated in the steady-state mode. The computed axial velocities, volume fractions, temperature profiles are compared with available experimental data (Roy et al., ASME J. of Heat Transfer, Vol. 119, 1997). The result obtained by assuming a constant value for the bubble diameter shows a reasonable agreement, but several limitations are observed in the details. A more advanced mathematical model incorporating separate transport equations for the bubble number density and the interfacial area is suggested.