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| Impact of tube expansion on fluid flow and condensation heat transfer for R22 and R1234ze(E) in micro-fin tubes |
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LIU Na1, LI Dekai2, LI Yuxing2, LI Junming3
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(1.School of Environmental and Municipal Engineering, Qingdao University of Technology, Qingdao 266033, China;2.College of Pipeline and Civil Engineering in China University of Petroleum (East China), Qingdao 266580, China;3.Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China)
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| Abstract: |
| The measured cross section variation, condensation heat transfer and friction pressure drop were studied during the condensation of R22 and R1234ze(E) in pristine (5.10 mm outer diameter(OD)) and expanded (5.26 mm OD) micro-fin tubes. The effects of mass flux, vapor quality and tube expansion on the condensation heat transfer coefficients and friction pressure gradients for R22 and R1234ze(E) were analyzed. Correlations were used to predict the experimental results and predicted performances were assessed. The results show that the micro-fin tube deformed after expansion. The condensation heat transfer coefficients and friction pressure gradients both increase with the mass flux and vapor quality. The tube expansion degraded the condensation heat transfer performance in the micro-fin tube with the mass flux being 100 kg/(m2·s). The effect of tube expansion on the heat transfer coefficient was not apparent with the mass fluxes being 200 kg/(m2·s) and 300 kg/(m2·s). However, for the mass fluxes being 100～300 kg/(m2·s), the effect of tube expansion on the friction pressure gradient was not significant. |
| Key words: micro-fin tube tube expansion two-phase flow condensation heat transfer friction pressure drop |
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