Abstract The condensing flow of R1234yf in a smooth horizontal helically coiled tube is studied experimentally to achieve the heat transfer coefficient and frictional pressure gradient. The helical coil diameter is 95.3 mm with a constant pitch of 16.7 mm and is made by coiling a flexible smooth tube with an internal diameter of 8.2 mm. The effect of vapor quality, mass velocity and saturation temperature on the two-phase heat transfer coefficient and frictional pressure gradient are investigated. The experiments are carried out at saturation temperatures of 20 °C and 30 °C for the mass velocity ranging from 95 kg m−2 s−1 to 285 kg m−2 s−1 and vapor quality from 0.1 to 0.8. In addition, the experimental results of the helically coiled tube are compared with those achieved for a straight smooth tube at the same operating conditions to evaluate the effect of coiling on the condensation heat transfer and frictional pressure gradient. The results suggest that the average heat transfer coefficients of the helically coiled tube are 60–120% higher than those of the straight tubes with the penalty of 46–108% for the frictional pressure gradient. Considering both thermal and hydraulic performances, the Performance Evaluation Criteria (PEC) is defined. The values of PEC are varied between 0.91 and 1.52 while the highest PECs are observed for the intermediate mass velocity of 190 kg m−2 s−1. New correlations to estimate the heat transfer coefficient and frictional pressure gradient are suggested based on the experimental results of the current study.

中文翻译：

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R1234yf在螺旋盘管内流动冷凝过程中传热系数和压降的实验研究

摘要 通过实验研究了R1234yf在光滑水平螺旋盘管中的冷凝流动，以获得传热系数和摩擦压力梯度。螺旋线圈直径为 95.3 毫米，恒定螺距为 16.7 毫米，由内径为 8.2 毫米的柔性光滑管盘绕制成。研究了蒸汽质量、质量速度和饱和温度对两相传热系数和摩擦压力梯度的影响。实验在 20 °C 和 30 °C 的饱和温度下进行，质量速度范围为 95 kg m-2 s-1 至 285 kg m-2 s-1，蒸汽质量为 0.1 至 0.8。此外，将螺旋盘管的实验结果与相同操作条件下的直线光滑管的实验结果进行比较，以评估盘管对冷凝传热和摩擦压力梯度的影响。结果表明螺旋盘管的平均传热系数比直管高 60-120%，摩擦压力梯度损失 46-108%。考虑到热性能和水力性能，定义了性能评估标准 (PEC)。PEC 的值在 0.91 和 1.52 之间变化，而对于 190 kg m-2 s-1 的中间质量速度观察到最高的 PEC。