Study On Bubble/non-Newtonian Fluid Two-phase Flow In Mini Channel With Open Cell Solid Foam

Non-Newtonian fluids are widely used in many process industries and often cause problems such as high energy consumption and pollution.The development of micro-chemical technology has intensified the mixing and transfer of fluids with low sample consumption,high efficiency of mass transfer and heat transfer,and no amplification effect,which is one of the important means to strengthen the chemical mass transfer process.At the same time,open cell solid foam(OCSF),as a kind of porous media with high void fraction,high specific surface area and low pressure drop,has become a research hotspot in the field of granular materials and chemical engineering in recent years.In this paper,the bubble characteristics of gas/non-Newtonian fluid two phase flow were studied in empty/ OCSF minichannel.The flow characteristics of air/polyacrylamide(PAM)solution two phase flows in minichannel were studied experimentally.The characteristic length of bubbles and liquid column,bubble velocity and formation frequency was investigated.And the influence of gas/liquid flow ratio,liquid concentration and surfactant concentration is analyzed in detail.The results show that the length of bubble increases and liquid column decreases with the gas/liquid flow ratio.As the concentration and surfactant concentration increase,the length of bubbles and liquid column decrease.Except that bubble velocity is not affected by surface tension,the bubble velocity and formation frequency increase with the increase of two phase flow,liquid concentration and surfactant concentration.Based on the dimensionless capillary number and the ratio of two-phase velocity,the prediction equation of bubble characteristic length was derived well.The movement behavior of bubble/sodium hydroxymethyl cellulose(CMC)solution two phase flow in a minichannel with OCSF was simulated by three-dimensional Volume-of-fluid(VOF)coupled Level-set(LS)method.The effects of liquid concentration,liquid velocity,void fraction,contact angle and bubble size were studied roundly.The results show that the process of bubbles passing through OCSF can be divided into four stages: proximity,intrusion,extrusion and separation process,among which the specific surface area of the intrusion and extrusion stages changes greatly with time.The average specific surface area of the two stages increased with the increase of concentration,but decreased with the increase of void fraction and bubble size.In addition,with the decrease of liquid flow velocity and increase of liquid concentration,OCSF voidage and bubble size,the residence time of bubbles increases and the permeability rate decreases,while the influence of contact angle on residence time and permeability is not obvious.