Simulation of Two-phase Flow and Heat Transfer in a Channel and around a Tube by Lattice-Boltzmann Method

Determination of multiphase flow dynamics and thermal behavior of falling flow in a channel and around a cylinder are of importance due to its wide application in various industries. The small-scale surface tension effect plays a major role in multiphase flow behavior. So, based on simulation efficiency, precision, and stability, the mesoscopic Lattice Boltzmann method superiority has caused its broadening application. In the current study, the thermal-hydraulic behavior of subcooled falling flow in a vertical channel and around a single horizontal tube is simulated by using Lee method and Phase-Filed model, and thermal Passive Scalar model. The modified Boundary conditions for curved tube and two different boundary conditions for side boundaries are investigated. Simulations have been done for density ratio 20 and relevant viscosity and conductivity ratios of water. The film of liquid falls on a tube with a temperature of 110˚C and the outside diameter of 28.9mm. The results including contours and streamlines of the flow field, temperature, and pressure contours are presented and detailed understanding about the movement of the three-phase contact line, circulating flow and local and average Nusselt number are determined. The film thickness, thermal boundary layer variation by the film thickness, Reynold number effect on Nusselt number and mass conservation are investigated as verification. The results have shown good consistency and high effectiveness in the simulation of multiphase gas-liquid flows in the presence of a circular obstacle, and for viscosity and thermal diffusivity ratios of water.