Study On A New Refrigeration Method Based On Bernoulli’s Principle And Evaporative Refrigeration

With the development of modern refrigeration technology, serious environmental problems that brought from the use of traditional refrigerants have drawn more and more attention. It is important to study how to prevent ozone depletion and greenhouse gas emission through replacing traditional refrigerants with environmental-friendly ones. This master thesis focuses on the study of a liquid-gas ejector refrigeration system which is governed by Bernoulli’s principle and tries to validate the feasibility of using water and other environmental-friendly refrigerants to replace traditional ones.Firstly, through analyzing the ideal thermodynamic cycle of liquid-gas ejector refrigeration system, this article takes the applicable demand of refrigerants into consideration, to tell whether a refrigerant works well in the liquid-gas ejector refrigeration system. The article also studies the performance of three kinds of refrigerants, which are R601 a, R718 and R22, with application of the liquid-gas ejector refrigeration system, comparing to the three kinds refrigerants is used in vapor compression refrigeration cycle. Also the main factors which may have influence on the performance of real thermodynamic cycle of liquid-gas ejector refrigeration system is taken into attention of the paper. The study found that, liquid-gas ejector refrigeration cycle was more suitable for the refrigerating fluid with more gently saturated vapor line; when applying R718, the liquid-gas ejector refrigeration system can obtained higher refrigeration coefficient and thermodynamics consummating degree; the isothermal compression efficiency of liquid-gas ejector is the important effect factor of actual refrigeration effect of liquid-gas ejector refrigeration cycle.Secondly, there is an experimental study and a numerical simulation study on the performance of gas ejection. The study is on the effection due to characteristics of working liquid, the structure form of nozzle, changing back pressure, area ratio between throat and nozzle, and ratio between throat length and throat diameter. Through the theory and experiment study, it could be found that the applied working fluid should possess higher density, lower saturated vapor pressure, little surface tension and stable chemical property; under certain working condition, the inner ring type nozzle had obvious advantage compared with normal type nozzle, this showed that the improvement of ejector nozzle’s structure could significantly improve ejector ratio; similarly, it could be found that when the working condition was defined, more accurately defining the structure size’s parameters of ejector was the key to ensure that the available energy could be fully utilized by ejector.Lastly, there is an experimental study on the refrigerant performance of the liquid-gas ejector refrigeration system. Using R601 a as the refrigerant, the experimental studys different influence factors to the refrigerant performance containing of different nozzle form, changing distances between nozzle and throat and the characteristics of working liquid. Through the experiment study, it also found that the effect of reasonable structure and form of ejector was very great on liquid-gas ejector refrigeration system. Besides, there were difference between the ejector’s structure size with higher refrigeration performance and the designed structure size. Thus the design regular suitable for liquid-gas ejector device of ejector refrigeration should be kept deeply discussing and exploring. The features of GaInSn liquid metal with high density made it very suitable for liquid-gas ejector refrigeration system, but the feature that it was easy to affect with water, thus its flow properties was changed and non-condensable gas was generated, which made its proper role was severely limited. Therefore, how to change this feature also become the key of application of liquid-gas ejector refrigeration.