Eductors are simple devices with no moving parts that are used to convey solids, slurry and mix solids with liquids, and pump liquids.
The Venturi effect is a particular case of Bernoulli's principle. Fluid under high pressure is converted into a high-velocity jet at the throat of the convergent-divergent nozzle which creates a low pressure at the point between the two. The low pressure draws the suction fluid, gas or solid into the convergent-divergent nozzle where it mixes with the motive fluid and is ejected out the divergent end of the eductor.
Eductor sizes are dependent on the volumetric flow rate of the motive flow. The internals of an Eductor such as the jet nozzle size depends on the suction requirement and motive flow pressure and volume. Other factors also have to be considered when choosing an eductor, i.e. the requirement of downstream pressure that must be overcome.