Many researches had been carried out on the water jet pumps during the last few decades, and discussed the effect of changing the pump geometric parameters on its performance. Some other researches investigated pump performance with Two-phase (liquid-gas) and (liquid-solid) flow. In spite of the several researches, which investigated the case of liquid-liquid flow (almost as water-water), neither of them did have examined the case in which the secondary flow liquid differs from the power flow liquid in density and viscosity, which is the main objective of this paper. The subject is treated experimentally on a special test rig, with the primary fluid jet water and the secondary fluid of different types of oils. Performance of the jet pump and static wall pressure inside the mixing chamber, were measured as a function of the mixture Reynolds number. A one-dimensional analysis is also carried out, taking into account the difference of the viscosity and density of the two liquids (each primary and secondary fluids).
One-Dimensional Equations for the Jet Pump Performance
The one-dimensional flow assumptions are:-
1- Streams are one-dimensional at the entrance and exit of the mixing chamber.
2- Mixing is completed in the mixing chamber area.
3- Spacing between the nozzle exit and inlet of mixing chamber is zero, which is attainable due to the small nozzle diameter, relative to the large diameter of the mixing chamber. Momentum and continuity equations  were applied to different sections of the jet pump, namely the suction, inlet and outlet of the mixing chamber and the outlet of the diffuser. From this, the relationships between M, N & h and the performance of the jet pump were determined.