The Study Of Characteristics And Optimization Of Small-scale Ejector For Solar Jet Refrigeration

With the unceasing energy consumption and increasing environment pollution, the world is facing a crisis of energy shortage and environment deterioration.The rational and efficient energy using and environment protection are getting more and more concern in each country.In our country's energy consumption structure,the proportion of refrigeration and air-conditioning is about 20%,and the refrigerant leak has led to the green house effect,ozone layer hole and other environmental problems. Therefore,it is very necessary to conserve the energy and protect the environment of refrigeration and air-conditioning.And solar jet refrigeration has that function.There are many advantages on ejector as the core component of the solar jet refrigeration, for example:simple,stable and reliable.However,the inside flow of the ejector is complex;most of the ejector theories are only a sum-up which are based on the performance disciplinarian of some certain ejectors;the design and evaluation of an ejector usually are based on 1-D analysis until now.And the study of small-scale ejector of solar jet refrigeration is rare at the same time.Therefore,it is the very significant for the study of performance disciplinarian and structure optimization of the small-scale ejector.In this paper,many relations between ejector performance and operating parameters or ejector structures are mastered,a new parameter is summarized to analyze the ejector performance simpler,and the ejector structure is optimized through analyzing the experiment and simulation results.The main work and results of this paper are given as follows:(1) set up an experiment system which is used to simulate the performance of ejector of solar jet refrigeration based on the ejector theory,and the performances of small-scale ejector of solar compression-enhanced jet refrigeration have been studied through changing the operating parameters and ejector structures.(2) Sum up the relationships between the ejector performances and operating parameters according to the analysis of a mass of experiment data,the operating parameters include motive fluid pressure,the suction fluid pressure,the discharging fluid pressure,expansion ratio and compression ratio.And analyze the coupling influence among the motive fluid pressure,the suction fluid pressure and the discharging fluid pressure through the two dimensionless parameters-expansion ratio and compression ratio.(3) Sum up a combination parameter B=[(P_c-P_e)P_e/P_p²]^k-1 (k=1.3,is the adiabatic index of vapor),thus the entrainment ratio of fixed structure ejector only rely on the motive fluid pressure and combination parameter,viz.u-u (P_p,B).At the same time,relationship between the ejector performance and combination parameter is also found through the analysis of experiment data.(4) Analyze the relationship between the ejector performance and structure-nozzle space, length of unchangeable mix-section-by the use of experiment method,which shows that the nozzle space and length of unchangeable mix-section have a great impact on ejector performance,and that the two structure parameters have optimization size.(5) Select a turbulence model which is suitable for ejector numerical simulation for further study of ejector performance,and analyze the ejector performance and internal supersonic flow by solving the 2-D axial symmetrical model of ejector.(6) Analyze the relations between the ejector performance and some structure parameters in detail. And find the optimization structure by tentative simulation of different shape and size of ejector taking advantages of the flexibility,easy repetition,and low cost of numerical simulation.In a word,both operating parameters and structure parameters of ejector have great impacts on ejector performance.In this paper,a detailed study of the relationship between operating parameters and ejector performance has been given based on the experiment,a new dimensionless parameter is summarized,the number of the operating parameters is reduced,and the analysis process is simplified.At the same time,the relationship between structure parameters and ejector performance and optimization structure of ejector has been gained through the study which is combined experiment and simulation.All these conclusions not only have some positive meanings on the development of ejector theory,but also should give some reference to the structure design of ejector.