{"title":"氨水水平回流弯管中两相压力降的实验研究","authors":"","doi":"10.1016/j.ijrefrig.2024.09.021","DOIUrl":null,"url":null,"abstract":"<div><div>In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (<em>R/d<sub>o</sub></em> ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m<sup>−2</sup> s<sup>−1</sup>, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and <em>R/d<sub>o</sub></em> ratio of the bend.</div><div>Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.</div></div>","PeriodicalId":14274,"journal":{"name":"International Journal of Refrigeration-revue Internationale Du Froid","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Experimental study of two-phase pressure-drop in horizontal return bends with ammonia\",\"authors\":\"\",\"doi\":\"10.1016/j.ijrefrig.2024.09.021\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (<em>R/d<sub>o</sub></em> ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m<sup>−2</sup> s<sup>−1</sup>, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and <em>R/d<sub>o</sub></em> ratio of the bend.</div><div>Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. 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引用次数: 0
摘要
在制冷和空调系统的蒸发器和冷凝器中,各种直管通过 U 形弯管连接在一起。由于流动干扰和离心效应,这些 U 形弯管会产生较高的压降。准确预测这些弯管中的压降对于可靠的设计和运行至关重要。本研究调查了水平 U 形弯管中氨水在各种实验条件下的两相流压降。使用了三根公称外径在 22.2、15.9 和 9.5 毫米之间的管道,每根管道都有三个弯曲半径(R/do 比),水平配置的弯曲半径在 1.2 和 2.5 之间。试验在 +10 和 -15 °C 饱和温度下进行,质量通量在 10 和 50 kg m-2 s-1 之间变化,蒸汽质量在 0.1 和 0.9 之间变化。与小管子相比,大管子的压降随着质量通量的增加和弯曲率的减小而增大,而小管子的绝对值更高,在两个饱和温度下的整个蒸汽质量范围内的性能更稳定。在高饱和温度和高质量通量下,管子直径的影响较小,而弯曲曲率比则主要影响大直径管子的压降性能。只有当蒸汽质量低于 0.5 时,文献中的一种相关性才能很好地预测数据。对于更宽的质量范围,文献中的现有模型并不适合预测氨 U 形弯管的压降。
Experimental study of two-phase pressure-drop in horizontal return bends with ammonia
In evaporators and condensers of refrigeration and air conditioning systems, various straight tubes are joined via U-bends. These U-bends result in higher pressure drops due to flow disturbances and centrifugal effects. Accurate prediction of pressure drops in these bends is essential for reliable design and operation. This study investigates the two-phase flow pressure-drop in horizontal U-bends with ammonia under wide range of experimental conditions. Three pipes with nominal outer diameter between 22.2, 15.9, and 9.5 mm were used, each with three bend radii (R/do ratio) between 1.2 and 2.5 in horizontal configuration. Tests were conducted at saturation temperature of +10 and -15 °C, with mass flux varying between 10 and 50 kg m−2 s−1, and vapor quality between 0.1 and 0.9. The pressure-drop increased with mass flux and vapor quality while decreased with saturation temperature, pipe diameter and R/do ratio of the bend.
Large tubes exhibited a greater increase in pressure drop with rising mass flux and decreasing bend ratio compared to small tubes, which showed higher absolute values and more consistent performance across the vapor quality range at both saturation temperatures. The tube diameter had a less significant effect at high saturation temperature and high mass flux, while the bend curvature ratio predominantly influenced the pressure drop performance for large diameter tubes. One correlation from the literature predicted the data well only if the vapor quality was below 0.5. For wider range of quality, the existing models in the literature were not well-suited for predicting pressure drops in ammonia U-bends.
期刊介绍:
The International Journal of Refrigeration is published for the International Institute of Refrigeration (IIR) by Elsevier. It is essential reading for all those wishing to keep abreast of research and industrial news in refrigeration, air conditioning and associated fields. This is particularly important in these times of rapid introduction of alternative refrigerants and the emergence of new technology. The journal has published special issues on alternative refrigerants and novel topics in the field of boiling, condensation, heat pumps, food refrigeration, carbon dioxide, ammonia, hydrocarbons, magnetic refrigeration at room temperature, sorptive cooling, phase change materials and slurries, ejector technology, compressors, and solar cooling.
As well as original research papers the International Journal of Refrigeration also includes review articles, papers presented at IIR conferences, short reports and letters describing preliminary results and experimental details, and letters to the Editor on recent areas of discussion and controversy. Other features include forthcoming events, conference reports and book reviews.
Papers are published in either English or French with the IIR news section in both languages.