Abstract The liquid-film flow in a vertical, upward, two-phase annular flow of saturated R245fa is characterized experimentally under adiabatic conditions. The experiments are conducted inside a rectangular channel with a cross section of 11.6 × 36 mm2 for mass velocities ranging from 95 to 130 kg/m2s, vapor qualities from 0.63 to 0.9 and saturation temperature of 23 °C. Liquid-film thickness and disturbance-wave velocity and frequency are measured optically. Liquid-film thickness is recorded at a sampling frequency of 2000 Hz, while disturbance-wave velocity is recorded at a sampling frequency of 20 Hz. A parametric study as a function of quality and mass velocity is performed. Results show that the liquid-film thickness decreases linearly with increasing vapor quality. The liquid films investigated are very thin, and thinner than the critical liquid-film thickness below which momentum and mass transport are no longer driven by disturbance waves. Indeed, at high vapor quality, when the liquid film is very thin, the liquid-vapor interface becomes smoother and disturbance waves slow down and vanish. The frictional pressure gradient increases with quality until it reaches a peak. Results suggest that the subsequent decrease in pressure gradient is closely linked to the disappearance of disturbance waves. For the range of studied operating conditions, the frequency of disturbance waves remains constant within the uncertainty of the measurements. Experimental data is compared with prediction methods from the literature. Although reasonable predictions were obtained for the liquid film thickness, none of the tested methods could predict disturbance-wave velocity and frequency accurately.

中文翻译：

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矩形通道内饱和 R245fa 垂直向上两相环状流的液膜厚度和扰动波表征

摘要 在绝热条件下对饱和R245fa 的垂直向上两相环状流中的液膜流动进行了实验表征。实验在横截面为 11.6 × 36 mm2 的矩形通道内进行，质量速度范围为 95 至 130 kg/m2s，蒸汽质量为 0.63 至 0.9，饱和温度为 23 °C。液膜厚度和扰动波速度和频率是光学测量的。液膜厚度以 2000 Hz 的采样频率记录，而扰动波速度以 20 Hz 的采样频率记录。执行作为质量和质量速度函数的参数研究。结果表明，液膜厚度随着蒸汽质量的增加而线性降低。研究的液膜非常薄，并且比临界液膜厚度更薄，低于临界液膜厚度，动量和质量传输不再由扰动波驱动。事实上，在高蒸汽质量下，当液膜非常薄时，液-气界面变得更光滑，扰动波减慢并消失。摩擦压力梯度随着质量的增加而增加，直到达到峰值。结果表明，随后压力梯度的降低与扰动波的消失密切相关。对于研究的操作条件范围，干扰波的频率在测量的不确定性内保持恒定。将实验数据与文献中的预测方法进行比较。尽管对液膜厚度进行了合理的预测，