The Modeling And Study Of The Flow Characteristics In Ejectors

Along with the increase of the demand, refrigeration technology is applied more and more widely and the refrigeration industry has become one of the high energy consumption industries. Therefore, energy saving of the refrigeration equipment is getting more and more attention. The biggest difference between the conventional refrigeration cycle and the compression-ejection hybrid refrigeration system is using the ejector to replace the throttle valve. Ejector enhances the entrance pressure of the compressor and recovers the throttling energy loss to improve the efficiency of the system. Firstly, the efficiency of the conventional refrigeration system and the compression-ejection hybrid refrigeration is compared and the change of the efficiency with the evaporating temperature and condensing temperature is studied by the thermodynamic calculation. Then the ejector model aimed at the flowing process in each part of the injector and the method of the specific design of the structure is given. The computational fluid dynamics software FLUENT is used to simulate the model. Then it is introduced that the structure and the process of the establishment of the computational model, including the model simplification, the discrete of the control equation, the meshing, boundary conditions setting, the choice of the solver, the choice of the turbulence model and the selection of the refrigerant, and finally the simulation of the model is set up. Maintaining the operating condition and other parameters unchanged, different models are established by changing the structure and position of nozzle, the diameter and length of the mixing chamber and the diameter and length of the diffusion chamber in succession, and then the pressure distribution, the velocity distribution, the axial velocity and pressure curve and the curve of the relation between the ejection coefficient and these parameters are obtained to analyze the effect of these parameters on the performance of the ejector. Keeping the structure and other operating parameters unchanged, the pressure of the working fluid, the pressure of the driving fluid and the outlet pressure are varied in succession to analyze the effect of these parameters on the performance of the ejector. Then the structure of the ejector is optimized and the operating condition is controlled in the normal range as far as possible in order to keep the ejector operate normally even efficiently.