Theoretical And Experimental Investigation On Flow Distribution In Gas-Liquid Two-phase Flow Manifold

The two-phase flow distribution of parallel channels in the manifold under radial inlets has wide applications in conventional power plant, heat exchanger and steam generator, etc. Because of the complexity of two-phase flow fluid, there is severe phase separation during two-phase flow distribution in the manifold. Even phase distribution can't happen during operation at parallel channels of a manifold. The deterioration of the performance and safety for heat exchanger appears. There is practical and theoretical significances for the study of two-phase flow distribution in a manifold.An air-water two-phase experimental loop is designed and installed for the two-phase flow parallel channel distribution in the manifold. The experiments are performed on manifolds under single and two radial inlets. The inlet flow pattern belongs to stratify, wavy and slug. There is severe uneven two-phase flow distribution and the air and water flow ratios keep at 0.5-1.8 and 0.25～2.0 under the inlet mass quality,0.006～0.24 and mass flow flux,56-570kg/m2.s. The air and water flow ratios distribution have the converse trend.In order to analyze the two-phase flow distribution of parallel channels of manifold with one and two radical inlets, a calculating method is present. The method is based on two T-junction phase separating models, whose of the one is used for a horizontal impacting T-junction and the others is used for a vertical dividing T-junction with a horizontal inlet and a upward outlet and a horizontal outlet. The calculating method is applied to calculate respectively the flow distribution of two experimental test sections with a single and two radial inlets. The calculating and experimental results match well.The free surface model is applied to analyze the two-phase flow inside a manifold using computational flow dynamics (CFD) software. The simulating result is compared with that from a high-speed camera. The numerical simulation finds that there is severe recirculation in the end of manifold and the recirculation will change under different inlet conditions and it will have effects on the two-phase flow distribution of parallel channels. Based on the phenomena, new geometrical test section of manifold with flute is present to overcome the influence from the wavy interface between air and water inside manifold. The simulation shows that the new geometry can make an even two-phase distribution of parallel channels inside manifold.The experiments on a single and two radical inlets with a flute distributor are performed. The experimental results show that there are almost evenly distributed air and water flow ratios among the parallel channels compared with the ordinary manifolds. The air and water flow ratios are among 0.7 and 1.3 in varied inlet conditions. The experimental results are near to the single-phase flow distribution.A practical application is present to analysis a two-radial-inlet manifold. The experiment is performed on the pendant wall superheater in two utility boilers. The deformation in pendant wall superheater happened because of the uneven flow distribution at the downward manifolds in pendant wall superheater.