The use of ejector cycles for increased performance and efficiency is becoming more prevalent in industry. Automotive refrigeration is a prime market for the use of this technology as it yields increased HVAC performance and reduces power draw to operate the system. In an ejector, a working fluid (liquid or gaseous) flows through a jet nozzle into a tube that first narrows and then expands in cross-sectional area. The fluid leaving the jet is flowing at a high velocity which &nbsp;results in it having low pressure, thus generating a low pressure region. The outer tube then narrows into a mixing section where the high velocity working fluid mixes with the fluid that is drawn in by the low pressure region, imparting enough velocity for it to be ejected, the tube then typically expands in order to decrease the velocity of the ejected stream, allowing the pressure to smoothly increase to the external pressure. The ejector device is used to enhance the performance standard vapor compression of the refrigeration cycle. Increases to the Coefficient of Performance can be on the order of 20% depending upon the working fluid. The design and analysis of such technologies has been limited by cost-prohibitive prototyping and testing. The use of Computational Fluid Dynamics (CFD) in the research and analysis of new technologies allows for rapid and reliable results paving the way for cost reduction and a decrease in first-time-engineering costs, along with subsequent optimization engineering. The goal of this study is to evaluate an HVAC system with an ejector cycle, using CFD to evaluate flow patterns, perform trade studies varying the type of refrigerant, and determine the entrainment ratio for each working fluid, over a range of boundary condition pressures, set at points along the ejector’s flow path. The 2012 Toyota Prius V is one of the first automobiles using an ejector cycle in their internal cabin refrigeration system. The Denso Corporation manufactured refrigeration system uses ejector technology to reduce overall power consumption. Denso hardware was used as the basis for the creation of geometry for the ejector. Herein, ANSYS FLUENT CFD is used to simulate the behavior in an ejector taken from a TOYOTA PRIUS hybrid vehicle refrigeration system. Working fluids examine are R134a, R245fa and R1234yf. The CFD model parametric trade study results shows the &nbsp;effects on press entrainment ratio with mass flow rate as ejector inlet &nbsp;pressure is varied , and mixing chamber inlet pressure is varied. The Ejector Inlet Pressure boundary condition was varied from 1.50E+05 Pa to 2.50E+05 Pa in 0.25E+05 Pa increments, with the Mixing Chamber and Outlet Pressures held constant at 1.00E+05 Pa. Each respective inlet pressure results in a unique mass flow rate. The Ejector Mixing Chamber Inlet Pressure boundary condition was varied from 9.00E+04 Pa to 1.10E+05 Pa, in a single 2.00E+04 Pa interval. The Injector Inlet Pressure was held constant at 2.00E+4 Pa, and the Injector Outlet Pressure was held constant at 1.00E+4 Pa. the Ejector Outlet Pressure boundary condition was varied from 1.10E+05 Pa to 1.20E+05 Pa, in a single 0.1E+05 Pa interval. The Injector Inlet Pressure was held constant at 2.00E+05 Pa and the Injector Mixing Chamber Inlet Pressure was held constant at 1.00E+05 Pa, showing a pressure drop internal to the mixing chamber, with a rise at the exit. Entrainment ratios varied from 1.5 to 3.0 depending upon the scenario. Details of the CFD methodology and results are provided in the paper.&nbsp;&nbsp;

CFD Analysis of Refrigeration Cycle Ejector

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.