摘要
提出了粘弹性流体适于化工传递过程研究的流变模型和无量纲数,即Re~*=d^2Np/η_α,W_i=σ_1N/η_α,N_(VR)=σ_2/σ_1和r=W_i/Re~*。对比了牛顿流体、假塑性流体和粘弹性流体在数种搅拌器下的流型、流速分布、功耗和混合时间,并提出了适用于这三种流体的搅拌功率关联式: N_pRe~*f_s^(1-m)=K_p[1+(F_(1av)~*/k_s^2)f_s^((1-m-3)W_i]
This review of our laboratory 's work and with 14 references deals with four main areas of investigation : rheological model and dimensionless number ,flow pattern and velocity distribution , power consumption, and mixing . The apparent viscosity ηa and the first normal stress coefficient σ1, are used for characterizing the rheological behavior of viscoelastic fluids :where Kpsu K, and γ are consistency index , elastic coefficient and shear rate , respectively , m and / are rheological parameters .For researching the transport phenomena of viscoelastic fluid the following dimensionless numbers are usually used :where d, N and p are diameter of impeller , rotation speed and density of fluid , respectively .Sphere and most impellers (such as paddle and anchor impellers) rotating in a viscoelastic fluid may produce three types of flow pattern which depends on the value of r . For example , a sphere is rotated in a viscoelastic fluid , when r< 0.055 the flow pattern is controlled by inertial force .when r>0.3 the flow pattern is controlled by normal stress ,and when r=0.l - 0.3 an isolated vortex will be produced .However for screw propeller impeller the flow pattern is always axial .The velocity distribution of viscoelastic fluid was compared with that of Newtonian fluid for anchor and helical ribbon impellers ,it was found that the tangential velocityof viscoelastic fluid is greater than that of Newtonian fluid . and the radial and axial velocities of the viscoelastic fluid are lower .For shear rate distribution ,it can be divided into two regions , there is a high shear region in the vicinity of vessel wall , and there is a low shear region in the middle zone of vessel . In the high shear region the magnitude of shear rate of viscoelastic fluid is greater than that of Newtonian fluid at the same rotational speed of the impellers .A power consumption correlation was proposed by author and co - researchers for Newtonian , pseudoplastic and viscoelastic fluids (Re<100)for three types of impellers , the Kp , ks , C
出处
《合成橡胶工业》
CAS
CSCD
北大核心
1992年第1期55-59,共5页
China Synthetic Rubber Industry
基金
国家自然科学基金
关键词
槽式
反应器
粘弹性
流体
搅拌
viscoelastic fluid
stirring power
flow velocity distribution
mixing
review
