R290和R1234ze在水平微通道内流动凝结换热的实验研究

发布时间：2017-12-26 21:08

本文关键词：R290和R1234ze在水平微通道内流动凝结换热的实验研究　出处：《清华大学》2015年硕士论文　论文类型：学位论文

【摘要】：微通道换热器由于紧凑高效的特点,在空调制冷行业提高能效方面发挥着重要作用。随着HCFCs类制冷剂面临逐步淘汰,低GWP值的制冷剂成为了当下研究的热点。本文选取R290和R1234ze作为研究对象,实验研究了其在水平微通道中流动凝结的两相摩擦压降及换热特性,并与R22的实验结果进行比较。实验中选取了圆管与方管两种管型,圆管内径为1.085mm,方管当量直径为0.952mm。实验工质的饱和温度为40℃和50℃。R22的质量流率为200~1200kg/(m2·s),R290的质量流率为200~650kg/(m2·s),R1234ze的质量流率为200~800kg/(m2·s)。干度范围为0~1.0。基于实验结果分析了质量流率、干度、饱和温度及断面形状对摩擦压降和凝结对流换热系数的影响。对比了三种制冷剂在相同工况下摩擦压降与换热系数的大小,将压降与换热的实验数据与现有的关联式进行了比较。结果表明,摩擦压降及换热系数均随着质量流率及干度的增加而增加,随饱和温度的升高而降低;方管中的摩擦压降及换热系数大于圆管中的;R290的摩擦压降与换热系数均为最大,R1234ze的次之,R22的最小;Garimella、Kim关联式对压降的数据预测较好,Sun和Mishima、Lopez Belchi关联式的预测偏高。Kim、Koyama、Wang对换热的数据预测较好,Shah关联式只对R1234ze的实验数据预测较为准确,Bohdal关联式对实验中的三种制冷剂的预测都偏高。
[Abstract]:Because of its compact and efficient characteristics, microchannel heat exchanger plays an important role in improving energy efficiency in the air conditioning and refrigeration industry. With the gradual elimination of HCFCs refrigerants, low GWP refrigerants have become a hot spot in the present research. In this paper, R290 and R1234ze were chosen as the research object. The frictional pressure drop and heat transfer characteristics of flow and condensation in horizontal microchannel were experimentally studied, and compared with the experimental results of R22. In the experiment, two tubes with circular tube and square tube are selected. The inner diameter of the circular tube is 1.085mm, and the equivalent diameter of the square tube is 0.952mm. The saturated temperature of the experimental working fluid is 40 and 50. The mass flow rate of R22 is 200~1200kg/ (m2. S), and the mass flow rate of R290 is 200~650kg/ (m2. S), and the mass flow rate of R1234ze is 200~800kg/ (M2 s). The dry range is 0~1.0. Based on the experimental results, the effects of mass flow rate, dry degree, saturation temperature and section shape on the friction pressure drop and the convective heat transfer coefficient are analyzed. The friction pressure drop and heat transfer coefficient of three refrigerants under the same working conditions were compared, and the experimental data of pressure drop and heat transfer were compared with the existing correlations. The results show that the frictional pressure drop and heat transfer coefficient with the mass flow rate and dry degree increased with the rise of saturation temperature decreases; the tube frictional pressure drop and heat transfer coefficient is greater than the circular pipe; the frictional pressure drop and heat transfer coefficient of R290 were the largest, the second is R1234ze, the minimum of R22 Garimella, Kim; data correlation on the pressure drop prediction is good, high Sun, Lopez and Mishima predicted Belchi correlations. Kim, Koyama and Wang predict the heat transfer data better. Shah correlation is only more accurate for the experimental data of R1234ze, and Bohdal correlation is more predictive for the three refrigerants in the experiment.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK124

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