Numerical Simulation And Experimental Research Of Flow Field At The Ejector Nozzle Exit

With the high-speed development of economy, energy and environment problems have become the focus of worldwide attention. Ejector refrigeration can utilize thermal energy with a relatively low temperature ranging from100℃to200℃such as solar energy or industrial waste heat, to power the system and use the most environmentally friendly substance-water as the working fluid. The ejector refrigeration system has a number of other unique features such as simplicity in construction, high reliability and low cost. However, the ejector refrigeration system is labeled as low cooling capacity which restricts its applications. Supersonic nozzle plays a key role at transforming the pressure energy into kinetic energy in steam ejector refrigeration system, whose working performance determines the whole refrigerating capacity. Therefore, optimization of nozzle is an important method to improve the performance of ejector refrigeration system. The main works in this thesis are summarized as follows:First, the existing methods of nozzle design theory were summarized and two nozzles were designed by pneumatic function method. Second, the simulation calculations were carried on testing nozzle by Fluent to investigate the flow field at the nozzle exit under different conditions. At last, a particle image velocimetry (PIV) system was built up to study the flow field at the nozzle exit under different conditions, which is fit for the supersonic flow. Experimental results show that the effects of tracer particle, the dimension of nozzle, pressure ratio at the nozzle exit on the flow field at the nozzle exit could be readily obtained. The results in this thesis could be used as a reference to optimize the design of the nozzle in the ejector refrigeration system.