NUMERICAL INVESTIGATION OF TWO PHASE FLOW IN MICRO-SIZED CIRCULAR TUBE

摘要

Numerical simulations for the heat transfer characteristics in axisymetric air-water two phase flow have been carried out in microtubes of inner diameter 300 μm. The two-phase flow is achieved by injecting nitrogen gas coaxially through a centrally positioned tube to the continuous liquid phase flow. This measurement leads to a series of bubbles encapsulated by the continuous water phase. Uniform heat flux is applied on the outer surface of the outer tube. Comparison of numerical and experimental flow patterns show that the different is within 10%. The Nusselt number enhancement is about 200% and the two phase frictional pressure loss is about 20% for the bubbly flow. The simulation results shows that the thermal performance depends on the bubble size, frictional pressure drop and void fraction.