Mixer miscible fluids

A turbine type agitator is commonly used for liquid-solid systems. Mixing rates depend on the forces required to suspend all solid particles. Minimum levels can be determined for (1) lifting the particles, and (2) for suspending them in an homogeneous manner [200]. Similar requirements apply to liquid-liquid systems. For cases where two poorly miscible fluids of about equal volume are used in the reaction, the mixer is placed at the interface. For a bench-scale experimental system of about 2 liters capacity, the minimum rotational speed to obtain well-dispersed system is 300 to 400 rpm [201], depending on the type of mixer. This rotational value decreases as the vessel volume increases. 

The double-pipe mixer was designed and so far only used for contacting and reacting immiscible fluids [134], The respective flow-pattern maps were derived and annular and slug flows as well as complete spread of the inner-tube fluid were identified as distinct regimes. Since in this chapter only miscible liquids are concerned, no protocol and no results are given for the mixer below. H owever, the device is mentioned, since it could in principle be used also for mixing miscible fluids. 

A mixing unit consists of a twisted band, either left- or right-handed, which is similar to the so-called Mobius band, a ring-shaped structure with a one-sided surface Therefore this type of mixer is called Mobius mixer The principle is illustrated in figure 3 The layers of two non-miscible fluids are separated perpendicular to the boundary layers, subsequently twisted and reunited, thus doubling the exchange... 

Separation layer mixers use either a miscible or non-miscible layer between the reacting solutions, in the first case most often identical with the solvent used [48]. By this measure, mixing is postponed to a further stage of process equipment. Accordingly, reactants are only fed to the reaction device, but in a defined, e.g. multi-lamination-pattem like, fluid-compartment architecture. A separation layer technique inevitably demands micro mixers, as it is only feasible in a laminar flow regime, otherwise turbulent convective flow will result in plugging close to the entrance of the mixer chamber. 

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