Most of the heat in industrial plants is supplied by steam. To minimize energy waste, measuring the steam flow rates in existing pipes is important. Clamp-on ultrasonic flowmeters are used for this purpose, for which the sensors are attached to the pipe wall. However, flow conditions that can be used are limited because the signal-to-noise ratio of the ultrasonic signal in a steam flow is low. Furthermore, the steam wetness increases with heat losses, which may affect measurement results. Therefore, flow rate measurements in wet steam flows using clamp-on ultrasonic flowmeters have not been fully established. In this study, steam flow rates with various wetness fractions and system pressures were measured using a laboratory-made clamp-on ultrasonic flowmeter. The results show that flow rates in wet steam could be determined within a 10% error under general conditions in a steam piping system, although the conversion factor from line-average to area-average velocities was calibrated in superheated conditions, and the speed of sound in saturated conditions at each pressure was used. However, the error of the flow rates tended to increase with the wetness fraction and was biased toward positive values. The speed of sound and liquid volume fraction were evaluated at different wetness fractions. The flow rate error due to the change in sound speed was less than 1%, and 1.2% of the flow rates were overestimated owing to the liquid volume fraction. The velocity distribution in wet steam was considered different from that in the superheated steam owing to the existence of the liquid phase, and the change in velocity profile may lead to an overestimation of the steam flow rates in the wet steam condition.

工业厂房中的大部分热量是由蒸汽提供的。为了最大限度地减少能源浪费，测量现有管道中的蒸汽流速很重要。夹式超声波流量计用于此目的，为此，传感器安装在管壁上。然而，可以使用的流动条件是有限的，因为蒸汽流中超声波信号的信噪比很低。此外，蒸汽湿度随着热损失的增加而增加，这可能会影响测量结果。因此，尚未完全建立使用夹式超声波流量计测量湿蒸汽流中的流速。在这项研究中，使用实验室制造的夹式超声波流量计测量了具有各种湿度分数和系统压力的蒸汽流速。结果表明，在蒸汽管道系统的一般条件下，湿蒸汽中的流速可以在 10% 的误差内确定，尽管在过热条件下校准了从线平均速度到面积平均速度的转换因子，并且声速在每个压力下的饱和条件下使用。然而，流速的误差往往随着湿度分数的增加而增加，并且偏向于正值。在不同的湿度分数下评估声速和液体体积分数。由于声速变化引起的流量误差小于1%，由于液体体积分数而高估了1.2%的流量。由于液相的存在，湿蒸汽中的速度分布被认为与过热蒸汽中的速度分布不同，