| 摘要: |
| 对3根双侧强化管在饱和温度为8 ℃工况下进行了水平管外R417A沸腾换热特性研究。采用Wilson热阻分离法得到管外沸腾表面传热系数，并对实验结果进行了热阻分析。实验结果表明：管内轧制出0.32~0.34 mm的螺旋槽道，可以使管内对流传热系数提高到光管Gnielinski公式计算值的2.524~2.658倍。相同管型的强化换热表面，其沸腾传热系数随壁面温差变化的趋势相似，肋密度42fpi的E30管沸腾传热系数比50fpi的E32管大4.5%，表明沸腾传热系数的大小及变化趋势与肋密度（孔隙直径）及管型密切相关。双侧强化管外R417A沸腾换热，管外热阻约占总热阻的70%，管外仍需进一步强化，才能明显提高总体传热性能。R417A在强化管外沸腾传热系数仅为近似条件下其主要组分R134a的三分之一，表明混合工质沸腾换热与纯工质有较大差异。 |
| 关键词: 双侧强化管 R417A 沸腾换热 |
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| Study of Boiling Heat Transfer of R417A on Horizontal Doubly-enhanced Tubes |
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Zhang Dingcai1, Tian Songna1, Ji Wentao2, Zhao Anli1, Fan Xiaowei1, Tao Wenquan2
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| (1.School of Energy and Environment, Zhongyuan University of Technology;2.Key Laboratory of Thermo-Fluid Science and Engineering of MOE, School of Energy and Power Engineering, Xi’an Jiaotong University) |
| Abstract: |
| Experimental studies of boiling heat transfer of R417A on three single horizontal doubly-enhanced tubes have been conducted at the saturation temperature of 8 ℃. A modified Wilson plot technique was used to obtain the boiling heat transfer coefficients, and the thermal resistance analysis was conducted. The results indicate that the intube heat transfer coefficients of the three enhanced tubes are within 2.524-2.658 times as those of smooth tube, which were rolled 0.32-0.34 mm high spiral channel. For the same type of enhanced heat transfer surface, the trends of boiling heat transfer coefficient with the wall temperature difference are similar. Boiling heat transfer coefficients of tube E30 (42 fin per inch) are 4.5 percent higher than those of tube E32(50 fpi) at the same temperature difference. It is indicated that the boiling heat transfer coefficient and its trend were closely related with fin density (pore diameter) and tube type. Boiling heat transfer of R417A on doubly- enhanced tubes, the outer thermal resistance was about 70% of the total thermal resistance, further enhancement was useful for improving the overall heat transfer performance. Boiling heat transfer coefficient of R417A is only one third of R134a at approximate conditions, R134a is the main component of R417A, indicating that the boiling heat transfer of mixed refrigerants are quite different with pure refrigerants. |
| Key words: doubly-enhanced tubes refrigerant 417A boiling heat transfer |
