2022 年 55 巻 5 号 p. 201-216
New, reliable, and innovative methods (the new hybrid index (NHI) and the information index (II)) for flow regime (FR) identification in bubble columns (BCs) operated with air–deionized water or nitrogen–tap water systems (at ambient conditions), as well as nitrogen–ethanol systems (at pressures of 0.1 and 0.3 MPa) systems have been successfully developed. New parameters extract useful hidden information from time series measurements by division of various signals (gas holdup, differential pressure (DP) and gauge pressure fluctuations) into different equal parts. Salient advantage of the new parameters is that their definitions are not based on any assumption.
Based on the local minima in the NHI profile extracted from gas holdup time series, two transition gas velocities Utrans at 0.032 and 0.046 m/s have been identified in an air–deionized water BC (0.1 m in ID). The NHI profile based on DP fluctuations in a nitrogen–tap water BC (0.102 m in ID) distinguishes similar Utrans values at 0.029 m/s and 0.047 m/s. In a nitrogen–ethanol system at ambient pressure, the NHI identifies only the first Utrans value at Ug=0.028 m/s. At elevated pressure (0.3 MPa), it has been found that this first Utrans value shifts to a higher Ug value (0.045 m/s). In the annularly aerated BC (operated with an air-deionized water system), the main transition velocities have been identified at Ug=0.026 m/s and 0.073–0.079 m/s (depending on the clear liquid height), respectively, based on the newly defined II profile.
In summary, this work presents novel and reliable methods for FR identification in several BCs and reports new, useful experimental results about the FR boundaries based on them.
