Visual Experiment Study On Bubble Characteristics From Single Submerged Orifice

The Filtered Containment Venting System(FCVS)is an important part of the nuclear power plant to prevent radioactive material inside containment leakageunder accident condition.The wet filter part includes the venture scrubber and the bubble filter.Consequently,further investigation of bubble formation and rising dynamic behavior can act as guidance for designing and optimizing bubble filtration program.In this paper,the characteristics of single-hole bubbling in distilled water,sodium thiosulfate solution,sodium hydroxide solution and aerosol particles were studied.The characteristic parameters of the bubble were extracted by image processing technique.And the bubble flow regime,departure bubble volume and terminal rising velocity were discussed.The main research work and results of this paper are as follows:1.A set of bubble visualization experimental device was built and the algorithm of bubble image was proposed based on Matlab image processing tool function,and the characteristic parameters of bubble were successfully extracted.2.At low flow rates,the departure volume of bubbles is mainly controlled by the surface tension and orifice size,and the effect of the viscous force is small.At high flow rates,the departure volume of the bubbles is mainly controlled by the inertial force,also the influence of the viscous force,but the effect of the surface tension and the orifice size is small.The aerosol particles were added to the distilled water,the volume of the bubbles was reduced.3.The terminal velocity of bubbles with diameter of 3 mm to 8 mm were a multi-valued relationship with its diameter.The instantaneous velocity of the bubble in the process of floating is inversely proportional to its aspect ratio.For the same diameter of the bubbles,adding sodium hydroxide,sodium thiosulfate and aerosol particles to the distilled water,the terminal velocity of the bubbles did not change significantly.The liquid temperature increased,and the terminal velocity of the bubbles increased.4.Finally,The drag coefficient of the bubble was analyzed.Based on the poor results predicted by the previous theoretical models,a new empirical relationship about the drag coefficient of the bubble was proposed,and the experimental data deviation was less than 30%.5.With the increase of the gas flow rate,the bubble generation flow regime will experiencethe follow flow regime,including single bubbling,double bubbling without collision,double bubbling collision without coalescence,double bubbling with coalescence,bubble chaining,jet with interruptions,continuous jet.The increase in orifice size leads to a decrease in the transition critical velocity of the bubble flow regime.Sodium hydroxide and sodium thiosulfate will reduce the transition critical gas flow rate from single bubbling to double bubbling.Sodium thiosulfate was added to the distilled water,the coalescence of the bubbles was inhibited,while the sodium hydroxide had no significant effect on the coalescence of the bubble.Finally we draw the corresponding bubble flow regime map based on the experimental results.