Ejector (jet pump) is a very interesting type of pump without any rotating parts. It is using the energy of the gas flow to drive the suction of another fluid (liquid or gas) using the shear forces and reduced pressure due to its high velocity in the mixing chamber (see picture below). In certain conditions the flow may be supersonic! The ejector was initially invented by Henri Giffard in 1858 for use in steam locomotives. It was a brilliant idea to use the steam power to feed the boiler with water. In case of two-phase flow it may additionally condense mixed fluid which as important advantage used also in air conditioning systems. Although, the construction of such pump is very simple it needs careful design as each type of pump has its specific operation range. In 1858 there was no CFD and Mr Giffard used his outstanding mathematical skills do design the pump. Now it is a bit simpler, however, still requires some skills and experience. In CIM-mes we design such pumps for different applications including process installations (e.g., vacuum pumps).