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Experimental research on flow mode transition of falling film flow on metal foam wrapped tubes
Experimental Thermal and Fluid Science ( IF 3.2 ) Pub Date : 2020-10-01 , DOI: 10.1016/j.expthermflusci.2020.110154
Faxian Zhou , Tianhong Lu , Guoliang Ding , Guocheng Yang

Abstract Flow mode transitions on metal foam wrapped tubes in shell and tube heat exchanger may affect the condensate characteristics obviously because the condensate inundation severely depends on the flow mode. In the present study, the flow mode transitions were experimentally investigated by observing the flow modes on metal foam wrapped tubes and determining the Reynolds numbers (Re) of flow mode transitions. The experimental conditions cover the metal foam pore density from 5 to 40 PPI (pore per inch), the tube spacing from 6 to 20 mm, working fluids of pure water and water/ethylene glycol mixture, and the flowing process of increasing flow rate and decreasing flow rate. The experiment results show that, as the PPI increases, the Reynolds numbers of droplet/droplet-column (D/DC) transition and droplet-column/column (DC/C) transition both increase, but the Reynolds numbers of column/column-sheet (C/CS) transition and column-sheet/sheet (CS/S) transition both decrease; as the Galileo number increases, the Reynolds numbers of flow mode transition increases. It is also found that, the Reynolds numbers of the D/DC and DC/C transition does not change obviously with the tube spacing, while the Reynolds numbers of the C/CS and CS/S transition increases sharply at first and then slightly with the increase of tube spacing. Correlations for flow mode transitions on metal foam wrapped tubes are developed, and the predicted results of the correlations agree with 94% of experimental data within a deviation of 20%.

中文翻译:

泡沫金属包裹管降膜流流动模式转变的实验研究

摘要 管壳式换热器中泡沫金属包裹管的流动模式转变可能对冷凝水特性产生明显影响,因为冷凝水淹没严重依赖于流动模式。在本研究中,通过观察金属泡沫包裹管上的流动模式并确定流动模式转变的雷诺数 (Re),对流动模式转变进行了实验研究。实验条件包括泡沫金属孔隙密度为5~40 PPI(每英寸孔隙),管间距为6~20 mm,工质为纯水和水/乙二醇混合液,增加流速和流量的流动过程。降低流速。实验结果表明,随着 PPI 的增加,液滴/液滴-柱(D/DC)跃迁和液滴-柱/柱(DC/C)跃迁的雷诺数均增加,但列/柱-片(C/CS)跃迁和柱-片的雷诺数增加/sheet (CS/S) 过渡都减少;随着伽利略数的增加,流动模式转变的雷诺数增加。还发现,D/DC和DC/C过渡的雷诺数不随管间距变化明显,而C/CS和CS/S过渡的雷诺数先急剧增加,然后随着管间距的增加而略有增加。管间距的增加。开发了金属泡沫包裹管上流动模式转换的相关性,相关性的预测结果与 94% 的实验数据一致,偏差为 20%。但柱/柱-片(C/CS)过渡和柱-片/片(CS/S)过渡的雷诺数均减小;随着伽利略数的增加,流动模式转变的雷诺数增加。还发现,D/DC和DC/C过渡的雷诺数不随管间距变化明显,而C/CS和CS/S过渡的雷诺数先急剧增加,然后随着管间距的增加而略有增加。管间距的增加。开发了金属泡沫包裹管上流动模式转换的相关性,相关性的预测结果与 94% 的实验数据一致,偏差为 20%。但柱/柱-片(C/CS)转变和柱-片/片(CS/S)转变的雷诺数均减小;随着伽利略数的增加,流动模式转变的雷诺数增加。还发现,D/DC和DC/C过渡的雷诺数不随管间距变化明显,而C/CS和CS/S过渡的雷诺数先急剧增加,然后随着管间距的增加而略有增加。管间距的增加。开发了金属泡沫包裹管上流动模式转换的相关性,相关性的预测结果与 94% 的实验数据一致,偏差为 20%。D/DC和DC/C过渡的雷诺数随管间距的变化不明显,而C/CS和CS/S过渡的雷诺数随着管间距的增加先急剧增加后小幅增加。开发了金属泡沫包裹管上流动模式转换的相关性,并且相关性的预测结果与 94% 的实验数据一致,偏差为 20%。D/DC和DC/C过渡的雷诺数随管间距的变化不明显,而C/CS和CS/S过渡的雷诺数随着管间距的增加先急剧增加后小幅增加。开发了金属泡沫包裹管上流动模式转换的相关性,相关性的预测结果与 94% 的实验数据一致,偏差为 20%。
更新日期:2020-10-01
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