New Methodology for Benchmarking Hydrodynamics in Bubble Columns with Intense Internals Using the Radioactive Particle Tracking (RPT) Technique

Round 1

Reviewer 1 Report

This manuscript shows an interesting alternative to study the hydrodynamic behavior of the two-phase exchange reactors. These studies represent a real challenge for the chemical industry because of the transport phenomenons involved in these kinds of reactors make very difficult the conventional CFD studies. I recommend accepting this manuscript, after the following comments:

1. The use of Co-60 isotopes is a very dangerous task. I recommend the authors to mention the radiological precautions and measures used in this work.

2. Although this is an interesting study and results, I am not still convinced about the benefits of the RPT studies, because of the complexity of its implementation and the current advances of the CFD techniques. The justification of this work requires a greater incentive to demonstrate the feasibility to continue with this line of work.

3. Since this work is an alternative to CFD study methods of chemical reactors, I recommend in the experimental development section to include the initial conditions of the fluids under study, that is, gas-liquid phases, types of interactions (such as surface tension). , viscosity and density of the solutions used.

4. The only major drawback I can see in this type of study is that in any reactor with fluids movements, it is essential to know the pressure drop inside this kind of reactor, especially considering the use of internals. Is it possible to obtain this information from this study?

Author Response

Please see the attached file. Thanks

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors used for the first time the RPT technique for the hydrodynamic study of bubble-liquid columns with and without dense internals. The technique has been previously used in literature to investigate the flow in liquid/solid and bubble/ slurry systems.

The study is complex, starting with an original experimental set-up, very well designed and drawing results in several directions: performing calibration by Monte Carlo simulation (with corrections explained in detail), estimating the axial and radial liquid movement and turbulent parameters, estimating the hydrodynamic parameters (normal stress, sher stresses, and turbulent kinetic energy), and observing the effect of internals on the liquid velocity field.

The authors obtained the following performances:

-have developed and validated this new technology based on RPT technique;

-obtained maximum relative errors of 4.2% when generating calibration points;

-obtained reliable results that can be used for CFD validation;

-needed less computation power during a shorter time to reconstruct the instant positions of the radioactive particle, comparing to previous studies in literature;

-explained the perspectives of this work's continuation.

The language is clear and descriptive as needed.

Author Response

The authors sincerely appreciate the reviewer for acknowledging the novelty of our work and recognizing its potential interest for publication in Processes journal. We value your positive feedback and are encouraged by your recognition of the unique contributions our research can make to the field. We remain committed to addressing any further comments or suggestions you may have to ensure the highest quality of our manuscript. Once again, we express our gratitude for your valuable feedback and consideration. 

Reviewer 3 Report

Please read comments in attached file

Comments for author File: Comments.pdf

Author Response

Please see the attached file. Thanks

Author Response File: Author Response.pdf

Reviewer 4 Report

Authors developed and tested a new methodology applying radioactive particle tracking. The results are promising in the field of CFD validation.

My comments to improve the manuscript are follows:

1.       CFD validation were mentioned many times, but it is not clear what type of CFD model could be verified by the data obtained (RANS, LES-SGS , multiphase model.)

2.       In the introduction section line 94-105 might suits better to the methodology section

3.       Please clarify your objective at the end of the Introduction section

4.         Between the results and Conclusion Sections a separate Discussion section could be beneficial.

Author Response

Please see the attached file. Thanks

Author Response File: Author Response.pdf

Reviewer 5 Report

Results from a carefully conducted set of experiments on multiphase flow in a vertical tube containing internals is conducted. These are used to illustrate the effectiveness of a method of observing flows using radioactive particle tracking as well as giving results for the particular arrangement of internals studied.  Overall this is very clear and there are just a few minor corrections needed, some listed by line number below.

21 synthesis. The [full stop]

67 internals occupying [delete "that"]

101 as is discussed [delete "it"]

111 Dimensional [and actually could just use 3-D]

check for minor errors only

Author Response

The authors sincerely appreciate the reviewer for acknowledging the novelty of our work and recognizing its potential interest for publication in Processes journal. We value your positive feedback and are encouraged by your recognition of the unique contributions our research can make to the field. We remain committed to addressing any further comments or suggestions you may have to ensure the highest quality of our manuscript. Once again, we express our gratitude for your valuable feedback and consideration. The corrections have been included in the manuscript.

Reviewer 6 Report

Manuscript: processes-2491434

Title: New Methodology for Benchmarking Hydrodynamics in Bubble Columns with Intense Internals Using Radioactive Particle Tracking (RPT) Technique

Authors: Omar J. Farid, Alexandre França Velo, Binbin Qi, Muthanna Al-Dahhan

The present research investigates hydrodynamics in a bubble column with intense internals using the radioactive particle tracking technique. The work is well-written and presented. I have a few minor comments:

Even though the authors compared their results with Al-Mesfer et al. [12] for a case study with and without internals, it will be great if the results can be verified with another few studies. These cases can be for cases without internals.

In Fig. 10, the axial velocity drops for h/D=11. What about for h/D>11? Do we get a fixed profile or does the velocity keep dropping till the outlet? This is crucial for the validation of the CFD results. For the case without internals, my understanding is that the gas holdup becomes fully developed after a certain h/D?!

Can you give more information about the type of sparger used? Have you conducted any measurements on the bubble size since this factor is crucial for the gas holdup distribution to be wall-peaked or core peaked!?

You mentioned the flow regime is churn. Can you elaborate on that maybe by mentioning the gas and liquid velocities on the map? Is the liquid stagnant at the initial?

Minor editing of English language required.

Author Response

Please see the attached file. Thanks

Author Response File: Author Response.pdf