矩形窄通道中气液混合物超声颗粒检测实验与分析

Experiment and Analysis for Utrasonic Particle Detection of Liquid-vapor Mixture in Narrow Rectangular Channel

本文以去离子水为工质,将超声颗粒检测系统应用于两相流传热过程,利用超声衰减谱法对垂直矩形窄通道中流动沸腾气液两相流进行了测量,通过理论模型和反演算法分别得到质量流量2.22 kg/(m^2·s)、2.86 kg/(m^2·s)和3.49 kg/(m^2·s)下的超声衰减谱及矩形窄通道出口处的气泡尺寸分布和含气率(干度)。实验结果表明:一定质量流量下,随着加热功率的增大,同一超声频率下的超声衰减系数增大,D50值增大,尺寸分布变宽;同一工况下,随着质量流量的增大,D50值减小,尺寸分布高度增大,带宽减小;超声检测系统测量的干度较理论值偏大,干度较小时,偏差较小,比较适用;干度增大,偏差增大,需要适当调整模型。

With deionized water as working fluid, ultrasonic particle detection system is applied to two-phase heat transfer process. The ultrasonic attenuation spectrum method is used to measure flow boiling in vertical narrow rectangular channel. The ultrasonic attenuation spectrum, the bubble size distribution and export rate of gas （dryness） under different mass flux of 2.22 kg/（m^2·s） ,2.86 kg/（ m^2·s） and 3.49 kg/（m^2·s） in the narrow rectangular are obtained by theoretical model and inversion algorithm, respectively. The experiment results show that when the mass flow rate is constant, with an increase of the heating power, ultrasonic attenuation coefficient will increase under the same ultrasonic frequency, the value of D50 will increase and the distribution of dimensions will broaden. Under the same operating conditions, with an increase of the mass flow rate, the value of D50 will decrease and the distribution of dimensions will heighten and narrow. The degree of dryness measured by ultrasonic testing system is higher than the theoretical value, and the measurement are closed to the theoretical values when the dryness is small. The error increases when the dryness increases and the theoretical model should be adjusted in this case.