Study On The Performance Of The Ejector In The Waste Heat Driving Jet Refrigeration System

An ejector refrigeration system mainly includes heater, ejector, condenser, evaporator, expansion valve and circulating water pump. People in favor of jet refrigeration system because of its simple structure, less expensive, reliable operation, convenient operation and save energy. However, the main shortcomings of the system is inefficient and often difficult to meet the demand of refrigeration. ejector is one of the most important factors affect the efficiency of an ejector refrigeration system. ejector is a kind of mixing device using high pressure fluid absorb low pressure fluid. It is widely used in industrial field. Although the ejector structure is simple, the current research on the performance of the ejector and the distribution regularity of flow field exploration is relatively lacking because its internal flow field is extremely complex. Existing ejector researches mostly adopt one-dimensional or two-dimensional analysis methods, these methods cannot reflect ejectors’ three-dimensional structure and its internal special physical phenomena very well.In this article, the ejector performance is numerically and experimentally investigated using R236 fa as working fluid to focus on the influence of the critical geometries of ejector. The ejector used in the simulation has simplified three-dimensional centrosymmetric structure. Three-dimensional research can more truly reflect the internal flow characteristics of ejector and get more mixed flow information. Ejector grids adopt full hexahedron structured grids and the adaptive grid technology is adopted to capture the shock wave. The technology improve the quality of the grids and calculation accuracy at the most extent. The Shear Stress Transport(SST)turbulence model provided by ANSYS-CFX has been used. Do the jet experiments with the same ejector structure using in the simulation through constructing double heat source bipolar jet refrigeration system test bench. The experiment data of ejector coefficient changing with the condenser pressure has been got. It is found that the simulation results are very reliable with the average relative error of 9.6% compared with the experiment results. The results show that the ejector structure do have a lot of important influence on its performance. when the operating parameters conditions are given, both of the length of nozzle outlet(D1) and the distance of nozzle exit to mixing chamber(D2) have an optimal value. At this point, the entrainment ratio reaches the maximum. While the nozzle throat diameter(d) and the angles of diffuser(α) increase, the performance of ejector decline. The research may lay the foundation of using jet refrigeration onto small fishing boats, as well as provide ideas of the three-dimensional simulation of ejector.