The pressure remains constant in the mixing chamber The expansion of the primary and secondary fluids in the inlet nozzle is assumed to be adiabatic, taking into account the irreversibilities by an isentropic efficiency The calculation of the ejector (one-dimensional model) is based on the following assumptions:
However, there are also cases where one of these fluids is liquid or two-phase, so that the mixture can be biphasic, and several hypotheses can be selected: either carry out calculations with the properties of a real fluid while using the hypothesis of a single-phase flow, or neglect the liquid phase when computing velocities, or consider an equivalent fluid.
Ejector modeling is mostly based on the assumption that primary and secondary fluids can be treated as ideal gases in the mixing chamber, which is roughly justified given the low pressure therein.
