Comparison of New Entropy Profiles in Bubble Columns Operated with Air-Water and Air-Therminol Systems

In a bubble column (0.15 m in ID) operated with an air-water system, a new entropy was extracted from gas holdup fluctuations measured by conductivity wire-mesh sensor. It was capable of identifying three transition velocities Utrans at 0.045, 0.089 and 0.112 m/s. In a different bubble column (0.162 m in ID) operated with an air-therminol LT system at ambient conditions, the new entropy was extracted from photon count time series measured by computed tomography. Three Utrans values were also identified at 0.03, 0.08 and 0.1 m/s. The information entropies yielded similar results.
Based on the new entropy results it can be concluded that the type of fluid and gas sparger used do not affect significantly the second and third Utrans values. There is an effect on the first Utrans value which can be explained with the strong gas maldistribution in the case of the bubble column operated with an air-water system.