ALEX M. JUMPETER
This section contains extensive design and application experience for a variety of jet
pump configurations. Although this section concentrates on eductors (termed LJL jet
pumps in Section 4.1), experience with other motive (primary) and secondary fluids is
also included. The theoretical developments of Section 4.1 are the basis for what is pre-
sented here, the dimensional design ratios being generally within the ranges men-
tioned therein. Therefore, the only theory in this section is the empiricism that is
utilized in the examples and applications presented. Refer to Section 4.1 for further
DEFINITION OF TERMS________________________________________________
A definition of standard ejector terminology is as follows:
General name used to describe all types of jet pumps that
discharge at a pressure intermediate between motive and suction
A liquid jet pump using a liquid as motive fluid.
A particular type of jet pump that uses a condensable gas to
entrain a liquid and discharge against a pressure higher than
either motive or suction pressure; principally, a boiler injector.
A gas jet pump used to boost pressure of gases.
A liquid jet pump utilizing a condensable vapor, normally steam,
as the motive fluid.
FIGURE 1 Eductor elements and terminology
Design The elements of an eductor design are shown in Figure 1. Quantities involved
are defined as follows:
P1 static pressure upstream, lb/ft2 (N/m2)
Ps static pressure at suction (nozzle tip), lb/ft2 (N/m2)
V velocity, ft/s (m/s)
g1 specific weight (force) of motive fluid, lb/ft3 (N/m3)
Ps static pressure at suction, lb/ft2 (N/m2)
P2 static pressure at discharge, lb/ft2 (N/m2)
g2 specific weight (force) of mixed fluids, lb/ft3 (N/m3)
The head ratio RH is defined as the ratio of the operating head to the discharge head:
Because ratios are invol