Study Of CO₂ Bubble Movement And Mass Transfer In Non-Newtonian Fluids

Bubble motion is widely existed in nature,industry and human life,and the law of bubble behaviors and mass transfer performance in the fluids has important guiding significance for the improvement of efficiency and the reduction of energy consumption in related processes.The rising behavior and mass transfer performance of CO₂ bubbles in power-law fluids is more complex due to the complex rheological properties of power-law fluids.Therefore,further research is needed on the rising behavior and mass transfer performance of CO₂ bubbles in shear thinning fluids.The main research contents of this paper are as follows.（1）The influence of bubble size and the rheological properties of the solutions on bubble rising behavior in tap water and CMC aqueous solutions with different weight percentages was investigated by high speed photography and digital image processing technology,It was found that the bubble’s shape,size and moving speed fluctuated violently in tap water,and the bubble showed a zigzag movement trend in the rising process.The bubble shape and velocity were relatively stable in CMC aqueous solution,and the bubble size decreased gradually during mass transfer process,and the bubbles in CMC aqueous solutions basically showed a linear upward movement trend owing to high apparent viscosity of CMC aqueous solutions.In addition,the dimensionless number relation of Re,Mo and We was introduced to describe the force on bubbles in CMC water solution.The fitting results showed that the relation could well describe the motion and deformation of CO₂ bubbles in power-law fluids.（2）The change rule of experimental mass transfer coefficient k_L value of single CO₂bubble in tap water and CMC aqueous solution was studied by combining with experimental k_L value and bubble rising behavior parameters,and the effects of bubble size and rheological properties on bubble mass transfer performance were also investigated.It was found that the theoretical k_L value obtained by Higbie formulation was closer to the experimental k_L value and the Fr?ssling formulation can be used to predict the k_L of CO₂ bubbles in CMC aqueous solutions by comparing experimental and theoretical k _L value.It was also found that the bubble interface in tap water was mobile,while the interface of bubbles in CMC aqueous solutions was immobile.However,the interface of larger bubble in CMC aqueous solutions with lower weight percentage was in a critical state from immobile to mobile.The study also found that the better the ability of bubble interface mobility was,the stronger the mass transfer ability of bubbles would be.（3）The effect of bubble residence time in solutions on bubble mass transfer performance was studied by calculating the amount of CO₂ diffusion into CMC aqueous solution.It was found that bubble residence time was an important factor affecting bubble mass transfer behavior in CMC aqueous solutions with different mass weight percentages,the gas diffusion amount of CO₂ bubbles generated by the needle with same size increased with increasing weight percentage of CMC aqueous solutions.