Turbine, disk

For tbe flat-blade disk turbines, at a spacing equal to 1.5d or greater, tbe combined power for both will approximate twice tbat for a single turbine. 

Power Consumption of Impellers Power consumption is related to fluid density, fluid viscosity, rotational speed, and impeller diameter by plots of power number (g P/pN Df) versus Reynolds number (DfNp/ l). Typical correlation lines for frequently used impellers operating in newtonian hquids contained in baffled cylindri-calvessels are presented in Fig. 18-17. These cui ves may be used also for operation of the respective impellers in unbaffled tanks when the Reynolds number is 300 or less. When Nr L greater than 300, however, the power consumption is lower in an unbaffled vessel than indicated in Fig. 18-17. For example, for a six-blade disk turbine with Df/D = 3 and D IWj = 5, = 1.2 when Nr = 10. This is only about... 

Mechanical agitation is needed to break up the gas bubbles but must avoid rupturing the cells. The disk turbine with radial action is most suitable. It can tolerate a superficial gas velocity up to 120 m/h. (394 ft/h) without flooding, whereas the propeller is limited to about 20 i7i/h (66 ft/h). When flooding occurs, the impeller is working in a gas phase and cannot assist the transfer of gas to the liquid phase. Power input by agitation and air sparger is 1 to 4 W/L (97 to 387 Btu/[fF-h]) of liquid. 

Paddle A paddle is similar to a turbine impeller but typically has only two large blades and operates at lower speeds than a turbine. They are primarily used in high viscosity mixing operations. In European and Japanese literature the term "paddle" also is used to describe the flat blade and pitched blade turbines discussed above. The term "turbine" generally is reserved for disk turbines. 

The most common type of agitator used is the four-bladed disk turbine. However, research on the hydrodynamics of the system has shown that other disk turbine agitators with 12, 18 or concave blades have advantages. 

For the standard disk turbine with h/d = 0,2 and H/D = 1, to which most of experimental data relate, the average value A = 0.4 can be derived from the publications mentioned. 

The comparison of the correlation functions of Fig. 6 and Fig. 9 for the disk turbines with analogues geometry produces an average approximately value of a = 4 for the constant in Eq. (20). 

CTSR 2, Interphase gas/liquid 3, Self-rotating floating baffle 4, Annulus for position limiting 5, Rushton disk turbine 6, Interphase liquid/liquid 7, Pitched blade turbine upward (mixer/stirrer) 8, Aqueous-... 

Multiannular nozzle design, 16 8, 9 MultiBatchDS software, 26 1040 Multibladed disk turbines, 15 692-693 Multiblock copolymers, applications of, 24 715-716 MULTICASE, 6 19... 

Double-impeller combinations Bouaifi et al. (2001) derived the following correlations for stirred gas-liquid reactors with various combinations of double impellers. The impellers used were the lightning axial flow impeller (A-310), the four 45° pitched blade turbine pumping down (PBTD) and the Rushton disk turbine (RDT). Furthermore, the tank was a dish-bottom cylindrical tank equipped with four baffles, while the gas was introduced by a ring sprager. The gas-flow rate ranged from 0.54 to 2.62 L/s, whereas the rotational speed was from 1.66 to 11.67 s. The gas holdup is... 

Suppose that a flat-blade disk turbine with six blades is used and the agitation rate is 800 rpm. For the other characteristics of the tank assume a typical design configuration. 

Case 2 Data on heat transfer between a liquid and the wall of vessel of diameter D, stirred by a varied-disk turbine, were correlated [5] by Equation 5.13. The values of a were 0.54 without baffles and 0.74 with baffles. 

Figure 10.11. Power consumption, (a) Ratio of power consumptions of aerated and unaerated liquids. Q is the volumetric rate of the gas (O) glycol ( X ) ethanol ( ) water. [After Calderbank, Trans. Inst. Chem. Eng. 36, 443 (1958)]. (b) Ratio of power consumptions of aerated and unaerated liquids at low values otQ/Nd3. Six-bladed disk turbine ( ) water ( ) methanol (10%) (A) ethylene glycol (8%) (A) glycerol (40%) Pg = gassed power input P = ungassed power input Q = gas flow rate IV = agitator speed d = agitator-impeller diameter. [Luong and Volesky, AIChE J. 25, 893 (1979)].

Estimate the mass-transfer coefficient for the oxygen dissolution in water 25°C in a mixing vessel equipped with flat-blade disk turbine and sparger bv using Calderbank and Moo-Young s correlations. 

Calderbank (1958) correlated the mterfacial areas for the gas-liquid dispersion agitated by a flat-blade disk turbine as follows ... 

The power required by an impeller in a gas sparged system Pm is usually less than the power required by the impeller operating at the same speed in a gas-free liquids Pmo. The Pm for the flat-blade disk turbine can be calculated from Pmo (Nagata, 1975), as follows ... 

A cylindrical tank (1.22 m diameter) is filled with water to an operating level equal to the tank diameter. The tank is equipped with four equally spaced baffles, the width of which is one tenth of the tank diameter. The tank is agitated with a 0.36 m diameter, flat-blade disk turbine. The impeller rotational speed is 4.43 rps. The air enters through an open-ended tube situated below the impeller and its volumetric flow rate is 0.0217 m3/s at 1.08 atm and 25°C. Calculate ... 

Flat blade disk turbine 4.6 Radial with high shear effect... 

Figure 3. Increase in stirrer speed necessary to keep the particles suspended if gas is fed to the stirred vessel for disk turbines of diameter 4/2 and clearance 4/4 A, 4 = 0.29 m B, 4 = 0.30m C. 4 = 0.91 m D, 4 = l-83m. Barred line ranges for 4 = 0.56 m at dilferent conditions [17].

Flow patterns in a mechanically agitated reactor with disk turbine, pitched-blade turbine, and propeller types of agitator are schematically illustrated by Joshi et al. (1982). The flow pattern in the presence of gas is described later in the section on slurry reactors. In each of these cases, the dimensionless velocity profile with respect to the impeller tip velocity has been found to be independent of the impeller speed and has shown slight dependence on the impeller diameter. 

Joshi (1980) proposed a relation on the basis of liquid circulation generated by an impeller (disk turbine) as... 

With the help of experimental data in three (12.2, 19.0, and 22.9 cm diameter) flat-bottom vessels with an eight-flat-blades disk turbine stirrer and four baffles, they obtained a relationship... 

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