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首页> 外文期刊>International Journal of Heat and Mass Transfer >Condensation heat transfer coefficients in an inclined smooth tube at low mass fluxes
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Condensation heat transfer coefficients in an inclined smooth tube at low mass fluxes

机译：低通量下倾斜光滑管中的冷凝传热系数

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The purpose of this study was to present the heat transfer coefficients and flow patterns during the condensation of R134a inside an inclined smooth tube at low mass fluxes and different temperature differences (the temperature differences were between the saturation temperature and wall temperature). Condensation experiments were conducted at different inclination angles ranging from -90 degrees (vertically downwards) to +90 degrees (vertically upwards), at low mass fluxes of 50, 75, and 100 kg/m(2).s, and temperature differences from 1 degrees C to 10 degrees C. Measurements were taken at different mean vapour qualities between 0.1 and 0.9 in a smooth tube test section with an internal diameter of 8.38 mm and length of 1.5 m. The average saturation temperature was kept constant at 40 degrees C. It was found that inclination significantly influenced the flow patterns and the heat transfer coefficients. Downwards flows accounted for an increase in heat transfer coefficient with the maximum heat transfer coefficient found at inclinations of -15 degrees and -30 degrees (downwards flow) at the corresponding minimum temperature difference was tested for in each case. The maximum inclination effect was approximately 60% and was obtained at the lowest mass flux of 50 kg/m(2).s. In general, it was concluded that the heat transfer coefficients were more sensitive to the temperature difference for downwards flows than for upwards flows. Furthermore, there was no significant effect of temperature difference on the heat transfer coefficients for upwards flows. It was also found that the downwards and upwards vertical orientations were almost independent of the temperature difference. With respect to the inclination effect, it was found that in general, it decreased with an increase in temperature difference but decreased with an increase in mass flux and vapour quality. (C) 2018 Elsevier Ltd. All rights reserved.
机译：这项研究的目的是提出在低通量和不同温度差（温度差在饱和温度和壁温之间）下，R134a在倾斜的光滑管内冷凝过程中的传热系数和流型。在质量倾角为50、75和100 kg / m（s）.s的低质量通量下，以-90度（垂直向下）至+90度（垂直向上）的不同倾角进行冷凝实验。从1摄氏度到10摄氏度。在光滑管测试段中以0.1到0.9的不同平均蒸汽质量进行测量，其内径为8.38 mm，长度为1.5 m。平均饱和温度保持恒定在40摄氏度。发现倾斜度显着影响流动模式和传热系数。在每种情况下，分别测试了在相应的最小温差下，在-15度和-30度倾斜处发现的最大传热系数（向下流动）时，向下流动引起的传热系数增加。最大倾角效应约为60％，是在最低质量通量50 kg / m（2）.s时获得的。总的来说，得出的结论是，对于向下流动的传热系数对温度差比对向上流动的传热系数更敏感。此外，温度差对向上流动的传热系数没有显着影响。还发现向下和向上的垂直方向几乎与温度差无关。关于倾斜效果，发现通常随着温度差的增加而减小，但是随着质量通量和蒸气质量的增加而减小。 （C）2018 Elsevier Ltd.保留所有权利。

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