Mixing radial

Centrifugal, including radial, mixed flow, and axial flow designs... 

The effect of tube radius and coil aspect ratio on the onset of radial mixing in coiled tubes was investigated using the above equations. In Table 5, the dimensions of the coiled tubes examined are given and the curves relating (H) and (u) in Figure 8. 

In either laminar or turbulent flow, rotational eireulation of a proeessed material around its own hydraulie eenter in eaeh ehannel of the mixer eauses radial mixing of the material. All proeessed material is eontinuously and eompletely intermixed, virmally eliminating radial gradients in temperature, veloeity, and material eomposition. 

Statie mixers, as reviewed in Chapter 7, eontain mixing elements enelosed in a tubular housing through whieh radial mixing is aehieved. They redistribute fluid aeross the flow ehannel and eonsequently rearrange temperature and eomposition distributions. They are often used to promote mixing in laminar flow systems thus having a pro-nouneed effeet on the RTD. 

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. 

The Kenics STATIC MIXER unit is a series of fixed, helical elements enclosed within a tubular housing. The fixed geometric design of the unit produces the following unique patterns of flow division and radial mixing simultaneously. 

Hoek [86] proposed a radial spreading coefficient to characterize the liquid distribution. This coefficient is a measure of how quickly a packing can spread a vertical liquid stream radially as the liquid progresses down the column [86]. Radial mixing tends to reduce the effects of... 

Figure 7.27. Twisted-blade type of static mixer operating in the laminar flow regime (a) Distributive mixing mechanism showing, in principle, the reduction in striation thickness produced (f>) Radial mixing contribution...

Tubular reactors sometimes have side entrance points for downstream injection. Like the case of fed-batch reactors, this raises the question of how quickly the new ingredients are mixed. Mixing in the radial direction is the dominant concern. If radial mixing is fast, the assumption of piston flow may be reasonable and the addition of new ingredients merely reinitializes the problem. The equivalent phenomenon was discussed in Section 2.6.2 for fed-batch reactors. 

Shell-and-tube reactors may have dtldp = 3 or even smaller. A value of 3 is seen to decrease u dp/Dr by a factor of about 3. Reducing the tube diameter from Qdp to 3dp will increase Dr by a factor of about 10. Small tubes can thus have much better radial mixing than large tubes for two reasons R is lower and Dr is higher. 

In case I, the drug is highly soluble and the dissolution is not a limiting step. Assuming a complete radial mixing model, the drug concentration profile in the intestine is [23,53]... 

At high Reynolds numbers where molecular diffusion effects are negligible, experimental evidence confirms the general validity of equation 12.7.5. Figure 12.15 indicates how the Peclet number for radial mixing varies with the fluid Reynolds number. Above a Reynolds number of 40, the radial Peclet number is approximately 10. 

The solids mixing study by injection of tracer particles indicated that the axial mixing of solids in the bubble street is apparently very fast. Radial mixing flux depends primarily on the bubble size, bubble velocity, and bubble frequency, which in turn depend on the size of the jet nozzle employed and the operating jet velocity. 

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