In this work, electrical capacitance tomography (ECT) was used to measure the changes in void fraction immediately after a sudden expansion for horizontally flowing refrigerant R-134a. The two-phase flow behavior occurring in the sudden expansion was also analyzed using a high-speed camera for two different area ratios of 0.145 and 0.44. Void fractions determined from correlations found in the literature were compared with experimental measurements made immediately after a sudden expansion. It was found that none of the correlations examined could represent the behavior of the void fraction immediately after the expansion. A modified correlation was proposed to model the void fraction behavior occurring right after the expansion. This new correlation was able to predict the void fraction within a ± 20% error band when compared with experimental data at mass velocities of 50 to 250 kg m⁻²s⁻¹ and area ratios of 0.145 and 0.44.

在这项工作中，使用电容层析成像（ECT）来测量水平流动的制冷剂R-134a突然膨胀后立即产生的空隙率变化。还使用高速摄像机针对两个不同的面积比0.145和0.44分析了突然膨胀中发生的两相流动行为。从文献中发现的相关性确定的空隙分数与突然膨胀后立即进行的实验测量结果进行了比较。结果发现，所检查的相关性均不能代表膨胀后立即产生的空隙率。提出了一种改进的相关性，以模拟膨胀后立即发生的空隙率行为。^-2 s ^-1，面积比为0.145和0.44。