Research of Flow Boiling Bubble Dynamics in Vertical Rectangular Mini-channel

Abstract

Flow boiling in vertical rectangular mini-channel with width of 2mm and length of 390mm is studied in this paper. In single-side heating situation, the narrow channel is divided into three zones, bubbles generating zone, growth zone and annihilation zone. The motion characteristics of bubbles in various stages are accompanied by the changes of three zones. The courses of bubbles generation, growth and departure are numerically simulated. All the calculation conducted takes the gravity, surface tension and wall adhesion into account. Found that surface tension is much more important than gravity in the process of boiling heat transfer. As the overheating increases, the departure diameter D of bubbles increases significantly. When the bubble diameter D is larger than 1.5mm, it will be influenced by the incoming flow. The existence of bubble bottom micro-layer accelerates the flow convection on the wall and increases the coefficient of heat transfer. The results of simulation have a good coherence with experimental datum.