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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated tube
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Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated tube

机译：R-134a在垂直波纹管中向下流动的蒸发传热和摩擦特性

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摘要

Differently from most previous studies, the heat transfer and friction characteristics of the pure refrigerant HFC-134a during evaporation inside a vertical corrugated tube are experimentally investigated. The double tube test sections are 0.5m long with refrigerant flowing in the inner tube and heating water flowing in the annulus. The inner tubes are one smooth tube and two corrugated tubes, which are constructed from smooth copper tube of 8.7mm inner diameter. The test runs are performed at evaporating temperatures of 10, 15, and 20°C, heat fluxes of 20, 25, and 30kW/m~2, and mass fluxes of 200, 300, and 400kg/m~2s. The quality of the refrigerant in the test section is calculated using the temperature and pressure obtained from the experiment. The pressure drop across the test section is measured directly by a differential pressure transducer. The effects of heat flux, mass flux, and evaporation temperature on the heat transfer coefficient and two-phase friction factor are also discussed. It is found that the percentage increases of the heat transfer coefficient and the two-phase friction factor of the corrugated tubes compared with those of the smooth tube are approximately 0-10% and 70-140%, respectively.
机译：与大多数以前的研究不同，对纯制冷剂HFC-134a在垂直波纹管内蒸发期间的传热和摩擦特性进行了实验研究。双管测试段的长度为0.5m，制冷剂在内管中流动，热水在环面中流动。内管是一根光滑管和两个波纹管，它们由内径为8.7mm的光滑铜管构成。测试运行在10、15和20°C的蒸发温度，20、25和30kW / m〜2的热通量以及200、300和400kg / m〜2s的质量通量下进行。使用从实验中获得的温度和压力来计算测试部分中制冷剂的质量。整个测试部分的压降直接由压差传感器测量。还讨论了热通量，质量通量和蒸发温度对传热系数和两相摩擦系数的影响。可以发现，与光滑管相比，波纹管的传热系数和两相摩擦系数的增加百分比分别约为0-10％和70-140％。

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