Radial impellers

The primary flow produced by radial impellers is directed radially outward towards the vessel wall, where it is then diverted upward and downward. Two ring vortices are therefore formed, thus giving an axial flow to the impeller from above and below. 

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Radial impeller Radial passenger tires Radial tires Radiance Radiant colors Radiation... 

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 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.)...

In this section, the rotational velocity is directly proportional to the rotational velocity n according to the equation u — irDn. The impeller blade angles remain the same regardless of the rotational velocity of the impeller. Hence, the inlet and exit velocity triangles have the same form. The axial velocity of an axial fan changes directly proportionally to the circumference velocity u. This is also valid for the radial velocity at the outer circumference of a radial impeller fan. These velocities are directly proportional to the fan flow volume hence. 

Figure 5-5H. A typical radial Impeller agitator. Operates as agitating turbine or a conventional propeller, wide range of applications. Courtesy of Struthers-Wells Corp., Warren, Pa.

Figure 12-46E. Radial impeller for single-stage compressor. (Used by permission A C Compressor Corporation.)...

For hydrodynamic turbomachines (Fig. 4.1-4), the speed of the fluid flow or the circumferential velocity of the radial impellers involved is of great importance for the pressure increase per stage (A p u2 p, where p is the density of the fluid, and u is the circumferential velocity). Obviously the high circumferential velocity required for effective pressure generation can be achieved by high angular speed and / or a suitable size of the impeller. 

Fig. 4.1-47. Labyrinth seals A, Radial impeller, B, Labyrinth piston.

In all these formulas axial inlet flow and radial impeller exit are assumed for all other cases uj/g should be replaced by the proper value for H. 

A stirred tank fermenter consists of a centrally mounted agitation system inside a cylindrical vessel. Typically, the agitation system is composed of either multiple radial flow impellers (see Fig. 4A) or a combination of radial and axial flow impellers as shown in Fig. 4B. A gas sparger is located below the radial gas dispersing impeller. The role of the bottom radial impeller... 

Fig. 4 Stirred tank fermenters (A) with multiple radial impellers and (B) with axial and radial impellers.

Values of the constant parameters a, b, d, and d, as shown in Table 2, depend on the radial impeller type. 

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