Numerical Study Of Gas-Liquid Stratified Flow And Heat Transfer In Horizontal Self-Cleaning Single-Shaft Stirred Tank

The agitation of highly viscous fluid is a common unit operation in industry,widely used in chemical industry and so on.Horizontal self-cleaning single shaft is highly suitable to employ the agitation of highly viscous fluid.However,there is few theoretical studies about this tank.This paper focuses on this tank,and studies gas-liquid stratified flow and heat transfer by computational fluid dynamics.Effects of gravity on flow field of gas-liquid stratified flow with various liquid viscosities are investigated.Different VOF schemes are adopted to compute gas-liquid stratified flow under gravity.The results reveal that gravity has a distinct influence on flow field of gas-liquid stratified flow,no matter the liquid viscosity is low or high.The flow field of gas-liquid stratified flow are affected by both Froude number and Reynolds number.In addition,with regard to gas-liquid stratified flow under gravity,unusual diffusion of water or glycerin in the air is caused by explicit scheme and this is not in accord with the real situation.The results computed by implicit scheme correspond actually with the real situation.Heat transfer of highly viscous fluid with constant wall temperature is studied.The circumferential and axial distribution features of mean convective heat transfer coefficient?CHTC?are analyzed.The results indicate that as to part walls between two stirred blades in circumferential,the closer the part wall and stirred blade is,the relatively larger the mean CHTC of the part wall is.Difference of mean CHTC between each axial part wall and wall of stirred tank is slight.Besides,effects of various physical properties and operational parameters on circumferential distribution of CHTC are investigated.The results show that rotational speed has the greatest influence on mean CHTC in all the factors discussed.The mean CHTCs obtained via numerical simulations are correlated to a convection heat transfer correlation:Nu?28?837.Re^0.0605Pr^0.0409?DN/u_i?^-0.0127?102.4?Re?10.24,50000?Pr?5000,68?DN/u_i?11.33?The distribution of temperature filed are analyzed.The results show that high temperature area is located in the vicinity of wall and low and middle temperature area mostly occupy the sections.What's more,influences of different physical properties and operational parameters on temperature field contribution,outlet temperature increment and temperature rising rate are explored.The results reveal that increasing rotational speed can drop the area of low temperature region,but increasing viscosity,specific heat and inlet velocity can raise the area of low temperature region.In addition,inlet velocity is the the most marked factor effecting temperature increment and specific heat has the greatest impact on temperature rising rate.