Abstract
During condensation of R134a the flow patterns inside two three-dimensional (3-D) micro-fin tubes with different fin geometries were investigated. The flow patterns and their transitions were visibly observed and recorded. The experimental findings revealed the following results: a comparison of the condensation flow patterns in the 3-D micro-fin tubes with those in smooth tubes revealed no qualitative differences. The mist flow and the mist-annular flow that appeared in the smooth tube entrance region were not observed in 3-D micro-fin tubes. In the maps of the Mandhane flow regime and the Soliman flow regime, the area of annular flow region of the 3-D micro-fin tube extends towards lower Fr number range in the Soliman map and smaller vapor velocity range in the Mandhane map when compared with that of a smooth tube. The criterion of the flow regime transition between the annular flow and the wavy flow decreases from Fr=7 to Fr=2 in the Soliman flow regime map. However, no significant effect on the criterion for the plug flow transition was observed. The experimental data points of plug flow in the 3-D micro-fin tubes were also obtained in the same regime of smooth tube in Mandhane flow regime map. The Soliman flow regime map indicates the criterion for plug flow transition to be Fr=0.4.
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Abbreviations
- D i :
-
diameter of inside surface of tube, mm
- D o :
-
diameter of outside surface of tube, mm
- J v :
-
the velocity of vapor phase, m/s
- J l :
-
the velocity of liquid phase, m/s
- x :
-
the vapor quality
- X tt :
-
Lockhart–Martinelli parameter. \(\eqalign{X_{\text{tt}}&=(\mu_{\text{l}}/\mu_{\text{v}})^{0.1} (\rho_{\text{v}}/\rho_{\text{l}})^{0.5} ((1 - x)/x)^{0.9}\cr \Phi &= [(\mu_{\text{v}}/\mu _{\text{l}})^{2} (\rho_{\text{l}}/\rho_{\text{v}})]^{0.084}}\)
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Acknowledgements
The authors acknowledge the support by the Development Plan of the State Key Fundamental Research of China (973 Project) Grant No G2000036305 for Qinghua Chen and Mingdao Xin. Thanks are also due to the financial support by NSF for Qinghua Chen under grant CMS-9821057.
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Chen, Q., Amano, R.S. & Xin, M. Experimental study of flow patterns and regimes of condensation in horizontal three-dimensional micro-fin tubes. Heat Mass Transfer 43, 201–206 (2006). https://doi.org/10.1007/s00231-006-0096-8
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DOI: https://doi.org/10.1007/s00231-006-0096-8