Conclusions
This study measured the BSD of MBs generated with the recommended manual method using the microscopic shadow imaging technique. The MBs generated by the different operators were pushed through a transparent flow test section, and their images were taken by a microscope and a camera. After processing and analyzing the images, the BSD of the MBs was obtained. The data show that the diameter of MBs is mainly distributed between 10-100 µm, the mean bubble size is between 21-34 μm, the D32 is mainly between 50-300 μm, and the standard deviation is between 6-17 μm in 60 experiments. The data revealed the differences in the size distribution of manual operation bubbles for the different operators with different strengths. These findings are important for the future development of c-TCD. In our future work, the influence of different bubble sizes on the accuracy of c-TCD will be studied. A more suitable MBs generation procedure or device with high reliability will be developed to replace human manual operation in our future studies.