Bubble Size and Group Influence for CFD Simulation in Vertical Tube Upward Flow

The near-wall bubble congregating in vertical tube upward flow exerts an influence on fluid heat transfer. A 0.5m test section is simulated using CFX10.0 to research the bubble influence on the heat transfer. The vapor-water two-phase CFD calculation is done. The bubbles are added at near wall area, taking no account of the mass transfer between water and vapor. The different bubble max diameter and the different MUSIG model size group get different calculation results, these results are compared, include the distribution of vapor void fraction, the wall temperature distribution and near-wall water temperature distribution, the bubble mean diameter. A guide setting is advised. The calculation result shows that the max bubble diameter and the MUSIG size group on the vapor void fraction distribution is large. The near-wall void fraction gets down to the least (nearly zero, while at the inlet, near wall vapor fraction is 0.95) at 0.1m∼0.14m axis height, then rises. The wall temperature gets highest at the same height, and then appears a flat, keeping this temperature about 0.1m long, after that the temperature gets down, then rises along the axis.