Impeller three-blade marine

Figure 7.7 Typical impeller types (a) a six-flat blade turbine (b) a two-flat blade paddle and (c) a three-blade marine propeller. See the text for details of the abbreviations. 

In Figure 7.8, the curves a, b, and c correlate data for three types of impellers, namely, the six-flat blade turbine, two-flat blade paddle, and three-blade marine propeller, respectively. It should be noted that, for the range of (Re) >10, Afp is independent of (Re). For this turbulent regime it is clear from Equation 7.30 that... 

Power requirement data for three-bladed marine propellers were published by Stoops and Lovell (S8), who worked with axially-mounted propellers in an unbaffled tank. They found no effect of variations in liquid depth or impeller height, and did not report the extent of vortexing, which must have been present. They correlated their data in a dimensionless form similar to that discussed above, i.e.,... 

Examples of axial impellers are marine propeller and pitched blade turbine, shown in Fig 7.2. A three bladed marine t3rpe propeller is similar to the propeller blade used in driving boats. The propeller can be a side entering type in a tank or be clamped on the side of an open vessel in an off-center position. Axial flow impellers are used in blending and mixing of miscible liquids. 

Mixing impellers (a) three-blade marine propeller (b) open straight-blade turbine (c) bladed disk turbine (d) vertical curved-blade turbine (c) pitched-blade turbine. 

The lines e/e = const, are important parameters for the design and operation of stirred vessels applied as chemical reactors. In Fig. 3.7-4 such lines ate shown for a six-blade impeller and a three-blade marine-type propeller. 

Pumping the liquid volume pumped by the impeller = kp N where kp is a constant dependent upon the impeller Dj is the diameter of the impeller and N = rpm. For a three-bladed marine propeller whose pitch = Dj, kp = 0.5 many other types of impellers have smaller values, and therefore the marine propeller is one of the good axial flow impellers. In general, impellers giving axial flow are used in about 70 % of the mixing applications. 

Example 4-8 Calculate the power required for agitation for a three-blade marine impeller of 0.610-m pitch and 0.610-m diameter operating at 100 rpm in an unbaffled tank containing water at 21.1°C. The tank diameter is 1.83 m, the depth of... 

The value of K depends on the type of impeller/vessel arrangement, and whether the tank is fitted with baffles. For marine-type three-bladed propellers with pitch equal to diameter, K has been found to have a value of about 41. 

A large number of impeller types have been studied over the years, but interest has centered on three designs marine-type propellers, flat-or curve-bladed turbines, and flat paddles, with the first two of greater interest than the third. Propellers produce axial flow of the liquids and are turned in such fashion as to direct flow against the bottom of the tank. Turbines provide radial flow, but in any case the presence of baffles strongly influences the flow pattern in the tank. The effectiveness of these in liquid extraction has not been well established, but it appears that there... 

Naturally, the patterns of liquid movements will vary with the type of impeller used. When marine propeller-type impellers (which often have two or three blades see Figure 7.7c) are used, the liquid in the central part moves upwards along the tank axis and then downwards along the tank wall. Hence, this type of... 

Propellers. These are the most economical impellers for mixing low-viscosity liquids in small tanks (38). Marine types, with two, three, or four blades are usually used, three blades most commonly (Fig. 9.2o). 

Propeller A propeller is a three- or four-bladed flow impeller, having helically shaped blades. The flow is primarily axial (discharge flow parallel to the agitator shaft) and is most effective in low-viscosity fluids. The marine-type propeller (Figure 3.15) is characteristically operated at relatively high speed, particularly in low-viscosity liquids (Treybal, 1980). 

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