Mixers Kenics

For creeping flow (Re 3), it was found that the relative mixing length Lm/D for a given degree of mixing T depended upon Pe = ReSc  

The Lra/D values increased strongly in the range Re 3. This could be put down to inertia effects, which unfavorably affected the partitioning mechanism. The blending action of Kenics elements is again satisfactory for Re 500. = 

The effects of injection location, flow ratio and geometry on Kenics mixer performance are described in [667]. This analysis was performed by the aid of CFD code FLUENT/UNS. See also [678]. 

---

Figure Bl.14.10. Flow tlirough an KENICS mixer, (a) A schematic drawing of the KENICS mixer in which the slices selected for the experiment are marked. The arrows indicate the flow direction. Maps of the z-component of the velocity at position 1 and position 2 are displayed in (b) and (c), respectively, (d) and (e) Maps of the v- and the y-velocity component at position 1. The FOV (field of view) is 10 nnn. (From [31].)...

Kendall structure Kenics mixer Ken-React KR TTS Kentucky bluegrass Kenyaite [12285-95-9]... 

Static mixing of immiscible Hquids can provide exceUent enhancement of the interphase area for increasing mass-transfer rate. The drop size distribution is relatively narrow compared to agitated tanks. Three forces are known to influence the formation of drops in a static mixer shear stress, surface tension, and viscous stress in the dispersed phase. Dimensional analysis shows that the drop size of the dispersed phase is controUed by the Weber number. The average drop size, in a Kenics mixer is a function of Weber number We = df /a, and the ratio of dispersed to continuous-phase viscosities (Eig. 32). 

Fig. 32. Dimensionless drop size vs Weber number A, empty pipe at pu j = 1 B through G, Kenics mixer at = 25, 10, 2, 1, 0.75, and 0.5,...

Heat transfer in static mixers is intensified by turbulence causing inserts. For the Kenics mixer, the heat-transfer coefficient b is two to three times greater, whereas for Sulzer mixers it is five times greater, and for polymer appHcations it is 15 times greater than the coefficient for low viscosity flow in an open pipe. The heat-transfer coefficient is expressed in the form of Nusselt number Nu = hD /k as a function of system properties and flow conditions. 

The pressure drop in the Kenics mixer of the same length and diameter as an empty pipe can be determined from... 

Add (T+1/8) inch per flange up to a maximum of 3/8 inch per flange when ordering with flanges (T= wall thickness of housing) (1/8 inch = 3.18 mm, 3/8 inch = 9.53 mm). Mod. Length is based on Model 6. (Source Chen, S.J. Pressure Drop in the Kenics Mixer, Kenics Technical data KTEK-2, 1978). 

Because there are no moving parts in the Kenics mixer, only the processed materials are in motion. Therefore, the only energy required for the mixer is the energy required to overcome the pressure drop (AP). The general equation for calculating the pressure drop in an empty pipe for isothermal incompressible fluids is given by... 

What Kenics Mixer model of 3-in. Schedule 40 is required to process a Newtonian fluid with a viscosity of 150,000 cP, a density of 60 Ib/ft, and a flowrate of 650 Ib/hr What is the pressure drop (AP) and theoretical horsepower ... 

A liquid-gas mixture is to flow in a 3-in. Schedule 40 Kenics mixer. Estimate the pressure drop of the unit. The system conditions and physical properties are ... 

The dispersed plug flow model has been successfully applied to describe the flow characteristics in the Kenics mixer. The complex flow behavior in the mixer is characterized by the one-parameter. The Peclet number, Np, is defined by ... 

The Kenics mixer has been shown to provide thorough radial mixing. This results in a reduction in radial gradients in velocity, composition, and temperature. Because the unit possesses nearly plug flow characteristics, both temperature and product quality controls are achieved. 

Figure 8-41 E-Function Exit residence time distrubtion for the Kenics Mixer and other fiow systems.

To improve the mixing quality in the tubular reactor, Kenics type in-line static mixer reactor was employed. The in-line static mixers were designed to mix two or more fluids efficiently since an improved treinsport process such as flow division, radial eddying, flow constriction, and shear reversal eliminated the gradients in concentration, velocity and temperature. However, only 70 % conversion was achieved with one Kenics mixer unit. As shown in Table 2, five mixer units were required to achieve the maximum conversion. 

Avalosse, Th., and Crochet, M. J., Finite element simulation of mixing 2. Three-dimensional flow through a Kenics mixer. AlChE J. 43, 588-597 (1997b). 

Figure 8.31 Modern Kenics mixers with alternating twist directions a) cutaway view, and b) schematic with mixing striations (courtesy of Kevin G. Walsh of Chemineer, Incorporated)...

Figure 8.32 Kenics mixer and mixing quality as a function of the helix angle [58] (courtesy of Han Meijer of Technische Universiteit Eindhoven)...

The Kenics mixer, Figure 10.14(a), for example, consists of a succession of helical elements twisted alternately in opposite directions. In laminar flow for instance, the flow is split in two at each element so that after n elements the number of striations becomes 2". The effect of this geometrical progression is illustrated in Figure 10.14(b) and points out how effective the mixing becomes after only a few elements. The Reynolds number in a corresponding empty pipe is the major discriminant for the size of mixer, one manufacturer s recommendations being... 

For transitional flow, precise correlations are not available but for both SMV and Chemineer Kenics mixers, extra elements are required to achieve a certain degree of mixing. The SMV does not achieve significant mixing downstream of the mixer as in turbulent flow, so elements are not spaced out. The HEV is not recommended for transitional flow. 

Despite the wide use of the striation thickness concept in the early commercial literature, the CoV is now the most widely used mixing index. The following correlations are valid for viscosity ratios 0.01 < nBlnA < 100, feeding into the center of the pipe and with CoV measured 2dp downstream for Sulzer mixers, 3dp downstream for Kenics mixer. 

Two very similar correlations have been developed for Kenics mixers (15,16) of the form... 

This barrier-embedded micro mixer was made with helical static elements, resembling the internals of a Kenics mixer, and barrier structures at the channel ceiling [3]. 

Fig. 7.41 Computation of the velocity pattern in the Kenics mixer, (a) the flow domain (b) the finite-element grid (c) the velocities at the cross section in the middle of an element (d) the same just after the transition. The contours in (c) and (d) are isolines of axial velocity, and the arrows show the lateral velocity. [Reprinted by permission from O. S. Galaktionov, P. D. Anderson, G. W. M. Peters, and H. E. H. Meijer, Analysis and Optimization of Kenics Mixers, Int. Polym. Process., 18,138-150, (2003).]...

Source Chen, S J. Pressure Drop in the Kenics Mixer, Kenics Technical data KTEK-2, 1978). 

---