气液分离器对两相流引射制冷系统性能影响的研究

发布时间：2018-02-10 06:53

本文关键词： 两相流引射制冷气液分离器引射器引射比 R134a　出处：《天津商业大学》2017年硕士论文　论文类型：学位论文

【摘要】：在两相流引射制冷系统中,气液分离器是其中一个重要部件,合适的气液分离器尺寸和结构,可以起到比较好的气液分离的效果,进而提高引射器的引射比及整个制冷系统的性能;引射器是另外一个重要的部件,用引射器来代替膨胀阀,可以回收高压工质的压力能,降低压缩机耗功,从而提高制冷系统的性能。本文对以R134a为制冷剂工质的两相流引射制冷系统实验台进行了改进,设计了新的气液分离器,并对其部件和系统性能进行了模拟和实验研究。首先利用FLUENT软件对原、新气液分离器内的流体流动分别进行了二维和三维的数值模拟,并对得到的液相分布云图、液相速度云图和气相速度云图作了对比分析。利用CFX软件对引射器的内部流体的流动进行了数值模拟,分析了引射器内部流体流动状况。其次,对R134a引射制冷系统进行了实验分析,比较了原、新气液分离器的分离效果,分析了在使用新气液分离器的制冷系统中,喷嘴第一喉部当量直径和第二喉部直径对引射器性能以及整个制冷系统性能的影响,并在相同引射器几何参数条件下,对实验和模拟结果进行了对比分析。得出如下结论:(1)实验结果表明,新设计的气液分离器的气液分离效果得到显著提高。在引射器几何尺寸和工况相同的条件下,使用新设计的气液分离器的两相流引射制冷系统的主蒸发器的制冷量远大于辅助蒸发器的制冷量,系统主蒸发器起主要作用。与原系统相比,新系统主蒸发器的制冷量占总制冷量的百分比大大提高,根据工况条件的不同,系统主蒸发器的制冷量占总制冷量的百分比由原来的21.1%~27.8%提高到82.2%~87.3%。(2)实验结果表明,使用新设计气液分离器的两相流引射制冷系统引射器的引射比得到了显著提高。在引射器几何尺寸和工况相同的条件下,新制冷系统中引射器的引射比远大于原系统中引射器的引射比。根据工况条件的不同,引射器的引射比由原来的0.2~0.46提高到0.56~0.64。(3)实验结果表明,使用新设计气液分离器的两相流引射制冷系统的总制冷量及COP与原系统的总制冷量和系统COP基本相同。但由于新制冷系统中主蒸发器制冷量占主导地位,而主蒸发器中蒸发温度稍低于辅助蒸发器,因此可以认为新系统的能量品质得到了改善。(4)将模拟结果与实验结果对比发现,随第一喉部当量直径的增大,模拟和实验的引射比均先减小后增大,而随第二喉部直径的增大,则先增大后减小,在两种情况下模拟引射比结果误差较大。通过多次实验证实,第一喉部当量直径不能小于1.8mm,第二喉部直径不能小于1.4mm,否则实验工况不能维持稳定。
[Abstract]:In the two-phase flow ejection refrigeration system, the gas-liquid separator is one of the important components. The appropriate size and structure of the gas-liquid separator can play a better effect of gas-liquid separation. The ejector is another important component. Using ejector instead of expansion valve can recover the pressure energy of high pressure working fluid and reduce the power consumption of compressor. In order to improve the performance of the refrigeration system, a new gas-liquid separator was designed for the two-phase flow ejector refrigeration system with R134a as refrigerant. The performance of its components and system is simulated and experimentally studied. Firstly, two and three dimensional numerical simulations of fluid flow in the original and new gas-liquid separators are carried out by using FLUENT software, and the liquid phase distribution cloud images are obtained. The liquid phase velocity cloud diagram and the vapor velocity cloud map are compared and analyzed. The flow inside the ejector is numerically simulated by using CFX software, and the fluid flow in the ejector is analyzed. The experimental analysis of R134a ejection refrigeration system is carried out, and the separation effect of the original and new gas-liquid separator is compared, and the refrigeration system using the new gas-liquid separator is analyzed. The influence of the equivalent diameter of the first throat of the nozzle and the diameter of the second throat on the performance of the ejector and the whole refrigeration system, and under the same geometric parameters of the ejector, The experimental results show that the gas-liquid separation efficiency of the newly designed gas-liquid separator has been greatly improved. Under the same geometry and working conditions, the ejector has the same geometric size and working conditions, and the experimental results are as follows: (1) the experimental results are as follows: (1) the experimental results show that the gas-liquid separation efficiency of the newly designed gas-liquid separator is significantly improved. The refrigerating capacity of the main evaporator of the two-phase ejection refrigeration system using the newly designed gas-liquid separator is much larger than that of the auxiliary evaporator, and the main evaporator of the system plays a major role. The refrigerating capacity of the main evaporator in the new system has greatly increased as a percentage of the total refrigerating capacity. According to the different operating conditions, the percentage of the refrigerating capacity of the main evaporator in the total refrigerating capacity has been increased from 21.1g / 27.8% to 82.2g / 87.30.2.) the experimental results show that, The ejector ratio of the ejector of the two-phase ejector refrigeration system using the newly designed gas-liquid separator has been greatly improved. The ejector's ejection ratio in the new refrigeration system is much higher than that in the original system. According to the different operating conditions, the ejector's ejection ratio is increased from 0.2g / 0.46 to 0.560.564.43). The total refrigerating capacity and COP of the two-phase flow ejector refrigeration system using the newly designed gas-liquid separator are basically the same as the total cooling capacity of the original system and the total cooling capacity of the system COP. However, the refrigeration capacity of the main evaporator occupies the dominant position in the new refrigeration system. However, the evaporation temperature in the main evaporator is slightly lower than that in the auxiliary evaporator, so the energy quality of the new system has been improved. (4) comparing the simulation results with the experimental results, it is found that with the increase of the equivalent diameter of the first larynx, The emitter ratio of the simulation and experiment decreases first and then increases, but increases first and then decreases with the increase of the diameter of the second larynx. In both cases, the error of the simulated ejection ratio is large. The equivalent diameter of the first throat should not be less than 1.8 mm, and the diameter of the second throat should not be less than 1.4 mm. Otherwise, the experimental conditions could not be maintained stable.
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB657

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