Analysis of a Two Phase Flow Ejector For Transcritical CO2 Cycle

This paper presents the analysis of a two phase flow ejector for the transcritical CO2 cycle. A detailed simulation model of a two phase flow ejector was developed. A controllable ejector expansion device was designed, constructed, and installed in a transcritical CO2 experimental air conditioning system. System-level experimental results were obtained at different operation conditions and various ejector geometries. The ejector expansion model was then utilized to determine the efficiencies of the motive nozzle, suction nozzle, and mixing section using the system-level measured data. It was found that motive nozzle efficiency decreases as ejector throat area decreases and that the suction nozzle efficiency is affected by the outdoor temperature and ejector throat area. In addition, the distance from the motive nozzle exit to the mixing section constant area entry not only affects the suction nozzle efficiency, but also affects the mixing section efficiency.