Axial impellers

Axeen Axerophthol Axial compressors Axial impeller Arad [76963-41-2]... 

AU tbe curves are for axial impeller shafts, witb liquid depth Z equal to tbe tank diameter d,. 

FIG. 23-30a A basic stirred tank design, not to scale, showing a lower radial impeller and an upper axial impeller boused in a draft tube. Four equally spaced baffles are standard. H = beigbt of liquid level, Dj = tank diameter, d = impeller diameter. For radial impellers, 0.3 < d/Dt < 0.6. 

Figure 3. High-efficiency aerofoil axial impeller.

As noted earlier, the impeller is a eentral part of any air eooled heat exehanger. To ensure that the best performance is achieved and power consumption and noise levels are as low as possible, it is important that the proper impeller is selected. Figure 3 shows a multi-wing high-efficiency aerofoil axial impeller. Multi-wing axial impellers can be used in almost any application. 

Figure 7-9. Agitator flow patterns, (a) Axial or radial impellers without baffles produoe vortex, (b) Off-oenter looation reduoes the vortex, (o) Axial impeller with baffles, (d) Radial impeller with baffles. (Source Wales, S. M., Chemioal Prooess Equipment—Seleotion and Design, Butterworths Series in Chemical Engineering, 1988.)...

The application of draft tubes as related to various mixing operations is showm in Figures 5-231 and 5-24A-5-241. The draft tubes are basically a tube or shell around the shaft of the mixer including the usual axial impeller, which allows a special or top-to-bottom fixed flow pattern to be set up in the fluid system. The size and location of the tube are related to both the mechanical and mixing performance characteristics as well as peculiar problems of the system. Usually they are used to ensure a mixing flow pattern that cannot or w ill not develop in the system. Weber gives the followdng points for draft tubes [23] ... 

With a draft tube inserted in a tank, no sidewall baffles are required, and, the flow into the axial impeller mounted inside the tube is flooded to give a uniform and high flow pattern into the inlet to the impeller. The upflow in the annulus around the tube has sufficient velocity to keep particles in suspension, if necessary. 

Fig. 7. Reference floe diameter dpv versus impeller power per impeller volume P/V, for radial and axial impellers 4 baffles w/D = 0.1 H/D = 1 D = 0.4 m...

The agitation was accomplished with the turbine-type mixer and the largest axial impeller was 40.64 cm. The pilot batch was mixed at 90rpm (1.5/sec). From the initially known data, the D/T ratio was determined. 

Now the appropriate shaft speed for scaled-up production equipment can be calculated. The tank used for production batches has a capacity of 3780 L. It is equipped with a turbine-type agitator that has a shaft speed range of 20 58 rpm. The diameter of this tank is 167 cm. The diameter of the largest axial impeller is 87 cm. Given the diameter of the production tank, the cross-sectional area can be determined as... 

Where Qa is the volumetric gas flow-rate under the reactor conditions. In the case where two co-axial impellers are used, the installed power should be doubled. 

Figure 17.8. Typical proportions of a stirred tank reactor with radial and axial impellers, four baffles, and a sparger feed inlet.

FIGURE 14 The velocity spectra in the axial direction for an axial impeller A200. 

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