The condensation heat transfer characteristics of R290 (propane) in a horizontal smooth copper tube and a microfinned copper tube with an outside diameter of 5 mm were investigated experimentally to study the condensation heat transfer strengthening characteristics. The enhancement factor S_f was introduced to characterize the degree of strengthening condensation heat transfer of R290 in a microfinned copper tube, and the effects of mass flux (180-300 kg-m^-2·s^-1), saturation temperature (313.15-328.15 K), heat flux (5-10 kW·m^-2), and vapor quality (0.9-0.1) on the enhancement factor were analyzed. The results showed that the enhancement factor decreased with increasing mass flux or heat flux, but increased with a rising saturation temperature. Beside, the enhancement factor first increased but then decreased with a decreasing vapor quality accompanied by progressive liquefaction of R290. Finally, it was concluded that specific heat transfer conditions are essential to achieve the optimal heat transfer strengthening effect of R290 in tubes.

中文翻译：

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水平微细管中R290冷凝传热特性的实验研究

通过实验研究了R290（丙烷）在水平光滑铜管和外径为5 mm的微细铜管中的冷凝传热特性，以研究冷凝传热强化特性。引入增强因子S _f来表征R290在微翅片铜管中的强化冷凝传热程度，以及质量通量（180-300 kg-m ^-2 ·s ^-1），饱和温度（313.15- 328.15 K），热通量（5-10 kW·m ^-2），并分析了增强因子的蒸气质量（0.9-0.1）。结果表明，增强因子随质量通量或热通量的增加而减小，但随饱和温度的升高而增大。此外，增强因子首先增加，然后随着蒸汽质量的下降而下降，并伴随着R290的逐渐液化。最后，得出结论，特定的传热条件对于实现管中R290的最佳传热强化效果至关重要。