Development Of Two-phase Flow Distributor In Air-conditioning System

The distributor is an important auxiliary components installed before the evaporator in the refrigeration system,whose purpose is to evenly distribute the two-phase refrigerant flow after the expansion valve to each path of the evaporator.With the development of refrigeration technology and the use of small diameter heat exchanger,the two-phase flow maldistribution is being paid more attention.The mal-distribution in refrigeration system evaporator will not only lead to a loss of heat exchanger capacity,but also lead to a malfunction of the expansion valve,uneven outlet air temperature and so on which cause a bad system coefficient of performance,enhance the difficulty of adjusting and spoil the comfort and user experience.Therefore,the development of high performance two-phase flow distributor has become an important research topic.For the importance of research and development of the distributor,by doing the literature research and previous studies,two new distributor structures have been proposed in full awareness of the advantages and limitations of the existing traditional distributors.By using the combination of experimental and numerical simulation methods,a systematic study has been done to new distributor structures.The main contents and results of this study are as below:1)A refrigerant distributor test rig have been built,which can control the quality and mass flow rate at the inlet of the distributor and measure the both mass flow and quality at the outlet of the distributor.By analyzing the distribute mechanism of the traditional distributors,Two new distributor structures have been proposed,which are double-barrel distributor and throat-barrel distributor.The contrast experiments have been done between the new type distributors and the traditional ones.The results shows that relative to the traditional ones,both new structures has an advantage in distribute performance,which prove the performance potential of new structures.The influence of inlet quality and mass flow rate on the distribution performance has also been analyzed by the experiments.2)Appropriate numerical simulation models have been selected by theoretical analysis and trials.CFD models of two new distributor structures have been built by Fluent.Compared with the experimental results,the on the average error deviations between CFD and experimental results in the mass flow rate are less than 10%,which proved the reliability of the established CFD models.Using the CFD models,the inner flow of the two new distributor structures are analyzed,the distribute mechanism and the influence of main parameters influence are studied.The performance advantages of the two new distributor structures are proved by from the distribute mechanisms.3)The structure parameters of the throat-barrel distributor are analyzed by Taguchi method.Six important structure parameters are selected and the influenced on distribution performance and pressure-drop performance are studied.The results show the influence degree on distribution performance of the six parameters and the most important parameters influencing pressure-drop performance.What is more,the reasons and the directions of the influences caused by the parameters and studied deeply.Optimum combination of parameters are obtained and the optimum sample are verified by experiment.4)Three non-structure parameters have been studied,including the capillary tubes length,the unevenness of the evaporator wind side and the connection order between evaporator and distributor.A possibility by changing the length of the capillary tubes to compensate the influence caused by the unevenness of the evaporator wind side and the connection order.Another test rig with the uniform evaporator has been built.The influence degrees of three non-structure parameters are reached and the feasibility of the compensation method are proved.