In Eq.2, represents the number of breakup events within time in unit volume for droplets within size interval from to . represents the duration of the measurement. The droplet diameter is determined by in the 2D images after measuring the long axis a and short axisb of the droplet. After and are counted from the video captured by the high speed camera, DBFF can be determined.
The DBFF obtained above is then applied to determine the value of DIFT by regression method based on Eq. 3, which was established in our previous work based on systematical experiments 37. The value of DIFT changes with the column height since the DBFF measured at every height is different, because the mass transfer condition varies along the column.