Development and Validation of Simulation Method for a Two-Phase Flow Ejector

Abstract

A two-phase ejector is a device to induce a suction flow without pump or electricity. The flow in the two-phase ejector consists of a drive flow and a suction flow. As the driving flow expands blowing out of a drive flow nozzle, the thermal energy potential is converted into momentum, and by giving it to the suction flow, it is possible to induce the flow without using external power. In a nuclear power plant, a two-phase ejector can be utilized as a device to drive coolant flow in the cases of power failure. Mixing of the drive flow and the suction flow accompanied with evaporation or condensation at the gas-liquid interface depends on thermal hydraulic parameters and flow rate, and it is necessary to control them to maintain the driving force, but it can easily come out of operation range with a slight change in balance. There is little knowledge about heat and mass transfer to find and design operating conditions and ejector configurations. In this study, a heat and mass transfer model of the gas-liquid interface in a critical two-phase flow was developed. To handle thermally non-equilibrium two-phase flow with phase changes occurring simultaneously at the interface, we implemented constitutive equations into CFD tool, such as a correlation for interfacial area concentrations, and we evaluated evaporation coefficient, which is an important parameter to determine the phase change rate, based on the physical property of the working fluid. The CFD simulation method was validated using the experimental data in the literature of a two-phase ejector. In the validation, the flow rates of the drive flow and the suction flow, and pressure distribution inside the ejector were compared. Then, the validity of the developed CFD simulation method have confirmed.