Investigation of the Viscoelastic Effect on the Metzner and Otto Coefficient Through LDA Velocity Measurements  

作　　者：M.Jnhangiri M.R.Golkar-Narenji N.Montazerin S.Savarmand 

机构地区：[1]DepartmentofChemical [2]DepartmentofwMechanicalEngineering,AmirkabirUniversityofTechnology（Tehranpolytechnic）,No.424,HafezAve.,Tehran15914,I.R.Iran

出　　处：《Chinese Journal of Chemical Engineering》2001年第1期77-83,共7页中国化学工程学报（英文版）

摘　　要：The Metzner and Otto correlation is the single practical method for incorporating non-Newtonian effects in the mixing process. In this article, the Metzner and Otto' s idea, the role of viscoelasticity on the Metzner and Otto coefficient, ks, effects of flow regime on ks and the determination of fc3 for Rushton turbine impeller have been studied using the direct method of the laser Doppler anemometry (LDA) velocity measurement for the case of viscoelastic liquids. The normalized mean tangential velocity profiles are independent of Rushton turbine impeller speeds. Contrary to literature findings, it is shown that the variation of local shear rate against the impeller speed is better correlated by the power equation, i.e. y= k'a Nb' , in the transition region, i. e. - 30 < Re <- 2000. Also, a correlation between improved coefficient, ks', and the elasticity number of viscoelastic liquids is given which is very helpful in designing of the mixing of both viscoelastic and inelastic non-Newtonian fluids through relating rheological properties to kinematical and dynamical parameters of the mixing process.The Metzner and Otto correlation is the single practical method for incorporating non-Newtonian effects in the mixing process. In this article, the Metzner and Otto' s idea, the role of viscoelasticity on the Metzner and Otto coefficient, ks, effects of flow regime on ks and the determination of ks for Rushton turbine impeller have been studied using the direct method of the laser Doppler anemometry (LDA) velocity meusurement for the case of viscoelastic liquids. The normalized mean tangential velocity profiles are independent of Rushton turbine impeller speeds. Contrary to literature findings, it is shown that the variation of local shear rate against the impeller speed is better correlated by the power equation, i.e. γ = ks＇ * Nb＇, in the transition region, i.e. ～ 30 ＜ Re <～ 2000.Also, a correlation between improved coefficient, ks＇, and the elasticity number of viscoelastic liquids is given which is very helpful in designing of the mixing of both viscoelastic and inelastic non-Newtonian fluids through relating rheological properties to kinematical and dynamical parameters of the mixing process.

关 键 词：VISCOELASTIC MIXING Rushton turbine impeller laser Doppler anemometry (LDA) Metzner and Otto coefficient 

分 类 号：TQ021.1[化学工程]