One-dimensional modelling of the motive nozzle to be used in the two-phase ejector

Abstract Two-phase ejectors are used in the refrigeration cycles instead of the expansion valve to decrease the throttling losses and improve the cycle performance. A typical ejector consists of four sections in main, namely motive (primary) nozzle, suction (secondary) nozzle (chamber), mixing section, and diffuser. The motive nozzle which is of generally converging-diverging form is the critical section of the ejector since it creates the necessary pressure drop for the secondary fluid to be sucked into the ejector. Therefore, calculating the pressure distribution throughout the motive nozzle is important to the overall performance evaluation of the ejector expansion refrigeration cycle for a typical operating condition and nozzle geometry. In this study, the flow analyses are made for a converging-diverging nozzle to be used as the motive nozzle of an ejector. The motive flow is expected to be compressed liquid or saturated liquid at the nozzle inlet. One-dimensional model of the nozzle is established based on the conservation equations of mass, momentum, and energy and equation of state. Pressure, temperature, and Mach number distribution is validated experimentally and numerically with the help of the previous studies from the literature and the maximum difference for the pressure drop throughout the nozzle between the literature data and the calculated results is around 6%. R134a, R1234yf, and R1234ze(E) are selected as the working fluids. Subcooling temperature difference, mass flow rate, and motive nozzle outlet diameter is investigated parametrically.