蒸发器面积对R404A重力供液制冷系统性能影响的研究

发布时间：2018-05-29 04:09

本文选题：重力供液 + 蒸发器面积　；参考：《天津商业大学》2014年硕士论文

【摘要】：重力供液制冷在制冷行业中占有重要的地位，重力供液制冷是以热虹吸为原理的。在重力供液制冷系统中，供液方式为超倍供液，该供液方式能够使蒸发器中制冷剂的供液量大于蒸发器自身的蒸发量。在蒸发器中由于制冷剂的供液量大于蒸发量，保证了蒸发器管内始终保持充分的润湿状态，提高了制冷剂在蒸发器管内的流速，从而强化了制冷剂侧的对流换热，提高了蒸发器的换热效率。蒸发器是制冷系统的重要组成部分，提高蒸发器的换热效率对制冷系统来说有着非常重要的作用。蒸发器的换热效率主要与传热系数和传热温差相关。因此，可以通过增大蒸发器的传热系数和传热温差来提高蒸发器的换热效率。增大蒸发器的传热系数主要从两个方面入手：一个是管内制冷剂侧，另一个是管外空气侧。提高蒸发器管内制冷剂的流速也能提高蒸发器的换热效率。对重力供液制冷系统中的蒸发器建立数学模型，并且对其进行仿真模拟计算。本课题是通过减小蒸发器的面积来达到增大蒸发器的传热系数和传热温差的目的，为了选择出与实验所用冷库所匹配的蒸发器，，因此在仿真模拟中对五种不同面积的蒸发器进行了模拟研究，这五种蒸发器面积是以原蒸发器面积为基础的，分别为原来的90%、85%、80%、75%、70%。通过仿真模拟选择出最适合实验所用冷库的蒸发器，并将该蒸发器加工出来，运用到重力供液制冷系统中，通过对其进行实验研究，并且将实验结果与仿真模拟出来的结果进行对比分析，通过分析得出选用的蒸发器面积为原蒸发器面积的75%的蒸发器与实验所用冷库最匹配。在本实验中，分别进行了原蒸发器与新蒸发器的实验对比，新蒸发器的仿真模拟与实验结果的对比，新蒸发器在不同供液高度情况下的实验对比和新蒸发器内部温度场的实验。通过对比实验得出减小面积后的蒸发器的传热系数和传热温差都相应增大；仿真模拟结果与实验结果相似，可以表明该仿真模拟能够对重力供液制冷系统的蒸发器进行预测和指导；最适合该重力供液制冷系统的供液高度为900mm；蒸发器内部温度场分布均匀性有待进一步提高。
[Abstract]:Gravity liquid cooling plays an important role in refrigeration industry. Gravity liquid supply refrigeration is based on thermosyphon. In the gravity liquid supply refrigeration system, the liquid supply mode is super multiple, which can make the refrigerant supply in the evaporator larger than that in the evaporator itself. In the evaporator, the refrigerant supply is larger than the evaporator, which ensures the full wetting state in the evaporator pipe, improves the flow rate of the refrigerant in the evaporator tube, and thus strengthens the convection heat transfer on the refrigerant side. The heat transfer efficiency of evaporator is improved. Evaporator is an important part of refrigeration system. Improving the heat transfer efficiency of evaporator plays a very important role in refrigeration system. The heat transfer efficiency of evaporator is mainly related to heat transfer coefficient and heat transfer temperature difference. Therefore, the heat transfer efficiency of evaporator can be improved by increasing the heat transfer coefficient and the difference of heat transfer temperature. Increasing the heat transfer coefficient of evaporator is mainly from two aspects: one is the refrigerant side inside the tube, the other is the air side outside the tube. The heat transfer efficiency of evaporator can also be improved by increasing the flow rate of refrigerant in the evaporator tube. The mathematical model of evaporator in gravity liquid supply refrigeration system is established and simulated. The purpose of this paper is to increase the heat transfer coefficient and heat transfer temperature difference of evaporator by reducing the area of evaporator. Therefore, five kinds of evaporators with different areas are simulated and studied in the simulation. These five evaporator areas are based on the original evaporator area, which are the original 90 pieces of the original evaporator area, and the original 90 pieces of the evaporator area. The evaporator, which is the most suitable for the experiment, is selected by simulation. The evaporator is processed and applied to the gravity liquid supply refrigeration system, and the experimental study is carried out on the evaporator. By comparing the experimental results with the simulated results, it is concluded that the evaporator with 75% of the original evaporator area is the most suitable for the cold storage used in the experiment. In this experiment, the experiments of the original evaporator and the new evaporator, the simulation of the new evaporator and the experimental results, the experimental comparison of the new evaporator under different liquid supply heights and the experiment of the internal temperature field of the new evaporator are carried out respectively. The results show that the heat transfer coefficient and the heat transfer temperature difference of the evaporator with reduced area increase correspondingly, and the simulation results are similar to the experimental results. It can be shown that the simulation can predict and guide the evaporator of the gravity liquid supply refrigeration system, the height of the liquid supply is 900mm, and the uniformity of the temperature field inside the evaporator needs to be further improved.
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB657

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