6

(152) 36.00

Source: Schutte and Koerting.

Source: Schutte and Koerting.

Referring to the bottom of Table 1, a 2-in (50.8-mm) eductor with a capacity ratio of 4.0 is obtained. The required motive flow is then in USCS units 4( 7.3) = 29.2 gpm in SI units 4(1.66) = 6.64 m3/h and the suction capacity is in USCS units 4(9.6) = 38.4 gpm in SI units 4( 2.18) = 8.72 m3/h

A 1^-in (38-mm) unit can handle 2.89 times the values in Table 1, or 27.7 gpm (6.3 m3/h) suction when using 21 gpm (4.8 m3/h) motive water at 40 lb/in2 (2.8 bar) gage. If suction flow rate is not critical, some capacity can be sacrificed in order to use a smaller and therefore lower-cost eductor. If optimum performance is desired, it is necessary to size a special eductor using Figures 3 and 4.

Figure 7 illustrates more streamlined versions for higher suction lifts or applications involving the handling of slurries. This type of eductor is often used to remove condensate from vessels under vacuum. The advantage is that eductors require only 2 ft (0.61 m) NPSH and, being smaller than mechanical pumps, save considerable space. Further, a partial vapor load is much less likely to vapor-lock a jet pump because the venturi tube

FIGURE 6 General purpose eductor (Schutte and Koerting)

FIGURE 7 Streamlined eductor (Schutte and Koerting)

FIGURE 6 General purpose eductor (Schutte and Koerting)

FIGURE 7 Streamlined eductor (Schutte and Koerting)

FIGURE 8 Sparger nozzle (Schutte and Koerting)

FIGURE 9 Motive flow rate of Sparger nozzles (gpm X 0.227 = m3/h; lb/in2 X 0.0689 = bar) (Schutte and Koerting)

FIGURE 8 Sparger nozzle (Schutte and Koerting)

FIGURE 9 Motive flow rate of Sparger nozzles (gpm X 0.227 = m3/h; lb/in2 X 0.0689 = bar) (Schutte and Koerting)

minimizes the expansion effect of flashing vapor. Sizing is done in the manner illustrated in Example 1, using Figures 3 and 4.

mixing eductors Although any eductor is inherently a mixing device, some are specifically designed as mixers. They are used to replace mechanical agitators and are located inside the tank containing the fluid to be agitated. Figure 8 illustrates the simplest type of eductor, the Sparger nozzle. These units entrain a volume of suction fluid that is approximately three times the volume of motive fluid. A 20-lb/in2 (1.4-bar) drop across the nozzle is recommended for proper mixing. Figure 9 shows the motive flow rates for this type

TABLE 2 Motive flow rates of tank mixing eductors, gpma

Pressure difference, inlet to tank, lb/in2 (bar) gage

Pressure difference, inlet to tank, lb/in2 (bar) gage

TABLE 2 Motive flow rates of tank mixing eductors, gpma

Size, in

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