二氧化碳微通道平行流气冷器流量分配特性研究

发布时间：2018-03-01 00:08

本文关键词： 二氧化碳气冷器数值模拟正交试验流量分配　出处：《郑州大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着节能减排、环境友好的呼声越来越高,寻找可替代破坏环境、造成温室效应的制冷工质已经成为一大研究热点,二氧化碳作为自然工质,特别是在超临界状态下,流动及传热性能优良,具有极其广阔的应用前景。国内外学者在超临界二氧化碳传热领域的研究很多,对于应用较多的超临界CO2平行流气冷器的流动研究较少,本文综合应用数值模拟、正交实验设计及实验研究的方法,对超临界二氧化碳平行流气冷器内部流量分配特性进行了分析研究,论文主要的研究内容及结果包括：(1)本文结合物性软件REFPROP得到二氧化碳超临界区域的物性,总结了几种不同参数随温度的变化曲线,发现基本的变化趋势一致,在临界点附近变化最为剧烈。温度一定时,压力越大对应的值越大；而在一定的压力下,随着温度的升高,曲线逐渐平缓。(2)数值模拟与正交实验设计法结合研究气冷器流量分配特性,首先列出影响内部流量分配的几个重要的因素：扁管与集流管组合深度、扁管长度、扁管排数、扁管间距、微通道孔径、微通道孔数,选取水平数和考察指标,查阅相关正交表,确定不同组合形式,共24组,在ANSYS软件中分别建立整体气冷器模型随后进行计算,结果表明：对于总的流量分配不均度而言,各因素的影响主次为扁管间距微通道孔数扁管排数组合深度扁管长度微通道孔径；对于进出口压降而言,各因素的主次为组合深度扁管长度扁管间距微通道孔数扁管排数微通道孔径。兼顾总的流量不均度和进出口压降两个指标,根据综合平衡法分析,在本文参数范围内,总的流量分配不均匀是主要考虑问题,最优组合为组合深度0.4,扁管长度200mmm,扁管排数8,扁管间距9.0mm,微通道孔径0.6mmm,微通道孔数9。(3)比较分析不同型式的集流管对微通道整体流量分配的影响,结果发现,集流管为D型结构的微通道气冷器流量分配最为均匀,比较了不同当量直径的D型集流管,当量直径为13.3mmm的D型管更适合用于提高流量分配性能。并将不同进口压力、进口温度、进口质量流量下的气冷器内部流量分配情况进行对比,分析表明,压力和温度对流量分配的均匀性影响很小,质量流量不同,曲线趋势基本一致,随着进口质量流量的增大,总的流量不均度也有上升的趋势。(4)根据实验的原理,制定了实验方案,设计了一套微通道气冷器冷模实验装置,测量进口流量分别为18L/h、28L/h、38L/h时各排微通道内的流量,与数值模拟结果吻合度较好,证明数值模拟结果的准确性和可靠性。
[Abstract]:With the energy saving and emission reduction, the demand of environmental friendliness is becoming higher and higher. To find alternative refrigerants to destroy the environment and to cause the Greenhouse Effect refrigerant has become a research hotspot. Carbon dioxide as a natural working medium, especially in the supercritical state, has become a hot topic. Because of its excellent flow and heat transfer performance, there are many researches on supercritical carbon dioxide heat transfer at home and abroad, and less on the flow of supercritical CO2 parallel flow cooler, which is widely used in the field of supercritical carbon dioxide heat transfer. In this paper, the internal flow distribution characteristics of supercritical carbon dioxide parallel flow cooler are analyzed and studied by means of numerical simulation, orthogonal experimental design and experimental study. The main contents and results of this paper include: (1) based on the physical property software REFPROP, the physical properties of the supercritical region of carbon dioxide are obtained, and the curves of several different parameters with temperature are summarized, and it is found that the basic change trend is the same. When the temperature is fixed, the larger the pressure is, the greater the corresponding value is, and at a certain pressure, with the increase of temperature, The numerical simulation and orthogonal experimental design method are combined to study the flow distribution characteristics of air cooler. Firstly, several important factors affecting the flow distribution are listed: the combination depth of flat tube and collector tube, the length of flat tube, the number of flat tube arrangement. The flat tube spacing, microchannel aperture, the number of microchannel holes, the horizontal number and the inspection index are selected, and the related orthogonal tables are consulted to determine the different combinations. In total 24 groups, the integral air cooler model is established in the ANSYS software, and then the overall air cooler model is calculated. The results show that, for the total flow distribution unevenness, the main and secondary factors are the number of flat tube spacing microchannel holes, the number of flat tube rows combined with the depth flat tube length microchannel aperture, and for the inlet and outlet pressure drop, The main and secondary factors of each factor are the number of pore holes in the combination depth flat tube length, the pore number of the flat tube row, the two indexes of the total flow unevenness and the inlet and outlet pressure drop, according to the comprehensive balance method, in the range of the parameters of this paper, Uneven overall flow distribution is the main consideration. The optimum combination is: combination depth 0.4, flat tube length 200mm, flat tube row 8, flat tube spacing 9.0 mm, microchannel aperture 0.6 mm, microchannel hole number 9.3). The effects of different types of collecting tubes on the overall flow distribution of microchannels are compared and analyzed. The flow distribution of the microchannel air cooler with D structure is the most uniform. Compared with the D type collector with different equivalent diameters, the D type tube with equivalent diameter of 13.3 mm is more suitable for improving the flow distribution performance, and different inlet pressures are applied. The internal flow distribution of air cooler under inlet temperature and inlet mass flow rate is compared. The analysis shows that pressure and temperature have little effect on the uniformity of flow distribution, and the flow rate is different and the curve trend is basically the same. With the increase of the inlet mass flow rate, the total flow unevenness also has an upward trend. (4) according to the principle of the experiment, the experimental scheme has been drawn up, and a set of experimental equipment for the cold model of the microchannel air cooler has been designed. When the inlet flow rate is 18 L / h / 28 L / h, the flow rate in each row of microchannels is in good agreement with the numerical simulation results, which proves the accuracy and reliability of the numerical simulation results.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.3;TQ021.3

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