Numerical Investigation on a Liquid–Gas Ejector for Carbon Dioxide Removal Using Amine Solution: Hydrodynamics and Mass Transfer Evaluation
Round 1
Reviewer 1 Report
The research presents a 3D CFD study of air-water mixing analysis of a gas-liquid ejector which is then coupled with a 2D CFD mixing analysis of CO2/air-mea solution. The purpose is to investigate certain parameters within an ejector system and to propose a CFD methodology for further investigation.
The manuscript is clear and follows a logical structure. The study is useful as it deals with an important topic.
The English language in the manuscript is decent, minor spell check is needed.
Comments:
Line 13 - Please write the meaning of the MEA abbreviation.
For a clear representation of Figure 1, the reviewer would suggest moving lines 60-68 of the introduction in Figure 1's caption.
Line 137 - Eulerian-Eulerian
Section 2.3. - For reproducibility purposes, please define the initial turbulence intensity used for the k-Epsilon model.
Line 302 - It is a bit unclear whether this geometry/setup was taken from previous study by Mandal or rather if it serves as a validation case for the numerical model. Perhaps this should have been mentioned in the introduction section, somewhere in the paragraph at lines 112-130.
Lines 348-359 - It would be extremely beneficial if the boundary conditions were added to Figure 3 for a clearer presentation.
Figure 7b should be improved, perhaps by adding velocity contours and enhancing the vector field.
The quality of most images (especially Figs 9-10) should be improved.
Author Response
Dear reviewer,
Thank you sincerely for profound review of our manuscript. Attempts have been made to satisfy all your suggestions and improve the manuscript from different stand of points. We would appreciate your helpful comments which improve the quality of the manuscript to be qualified to be published in Journal of Applied Sciences.
Action 1: Line 13 - Please write the meaning of the MEA abbreviation.
Response 1: done.
Action 2: For a clear representation of Figure 1, the reviewer would suggest moving lines 60-68 of the introduction in Figure 1's caption.
Response 2: Figure 1 is moved after the descriptions of lines 60 to 68.
Action 3: Line 137 - Eulerian-Eulerian
Response 3: Corrected.
Action 4: Section 2.3. - For reproducibility purposes, please define the initial turbulence intensity used for the k-Epsilon model.
Response 4: These initial values are added in lines 308-310.
Action 5: Line 302 - It is a bit unclear whether this geometry/setup was taken from previous study by Mandal or rather if it serves as a validation case for the numerical model. Perhaps this should have been mentioned in the introduction section, somewhere in the paragraph at lines 112-130.
Response 5: In this study, the experimental values such as water flow rate and separator pressure were taken from the experimental work by Mandal. Mandal has implemented a liquid-gas ejector in a down-flow jet loop reactor. Also, for mesh independence study, CFD simulation results (the gas flow rate) were compared with those obtained experimentally by Mandal. Finally, the validation of simulation performed against experimental values from Mandal. To implement your comment, we have added some of explanations in lines 124 to 126.
Action 6: Lines 348-359 - It would be extremely beneficial if the boundary conditions were added to Figure 3 for a clearer presentation.
Response 6: The boundary conditions are added to Figure 3.
Action 7: Figure 7b should be improved, perhaps by adding velocity contours and enhancing the vector field.
Response 7: Thnak you for your comment. We improved the Figure 7b and replaced the velocity contour with the pathlines of velocity (Figure 7a).
Action 8: The quality of most images (especially Figs 9-10) should be improved.
Response 8: Thank you for your comments. The quality of images are improved.
Reviewer 2 Report
The paper: Two-dimensional and three-dimensional CFD simulation of liquid-gas ejector for CO2 removal: hydrodynamics and mass transfer evaluation, by authors: Mohammad Mehdi Parivazh, Mohammad Rahmani and Mohammad Akrami presents numerical approach for modeling fluid flow in the liquid-gas ejector in order to analyze hydrodynamics and mass transfer.
This research could be interesting for the researcher involved in computational modeling, but also for the engineers involved in power industry.
The paper is interesting, but is not well written. Before publishing, the paper needs MAJOR revision.
Comments:
- You have to explain what CFD (UDF, MEA…) means, before you use it in the Abstract. Add at least CFD in the key words.
- Title is not good. Change it to Numerical simulations of…., or Computational fluid dynamics approach….., or Computational simulations….., or …. Numerical investigations of the hydrodynamics and mass transfer of……, or….
- Did you perform experiments? Or you used experimental results from [39] to validate your results? It is not clear from the manuscript. Are the same operating conditions in the experiment and your simulations?
- Add some new references in the Introduction section.
- Maybe, you can add Eulerian–Eulerian approach to key words.
- Why did not you use 3D model in both cases?
- Add all parameters of the numerical simulations, model, Turbulent intensity, Virtual mass coefficient, Turbulent dissipation rate, Turbulent kinetic energy, First order upwing or Second order….
Author Response
Dear reviewer,
Thank you sincerely for profound review of our manuscript. Attempts have been made to satisfy all your suggestions and improve the manuscript from different stand of points. We would appreciate your helpful comments which improve the quality of the manuscript to be qualified to be published in Journal of Applied Sciences.
Action 1: You have to explain what CFD (UDF, MEA…) means, before you use it in the Abstract. Add at least CFD in the key words.
Response 1: Thank you for your comment. The meaning of CFD, MEA, and UDF abbreviation are added to the abstract. Also some of them are added in the key words.
Action 2: Title is not good. Change it to Numerical simulations of…., or Computational fluid dynamics approach….., or Computational simulations….., or …. Numerical investigations of the hydrodynamics and mass transfer of……, or….
Response 2: The title has been changed to: Numerical investigation on gas-liquid ejector for carbon dioxide removal using amine solution: hydrodynamics and mass transfer evaluation
Action 3: Did you perform experiments? Or you used experimental results from [39] to validate your results? It is not clear from the manuscript. Are the same operating conditions in the experiment and your simulations?
Response 3: Yes. In this study, the experimental values such as water flow rate and separator pressure were used from the experimental work by Mandal. Mandal has implemented a liquid-gas ejector in a down-flow jet reactor. We used the same operating conditions as Mandal and compared our simulation results with experimental values (Mandal) for validation. To make this clear, some explanations were added to the manuscript in lines 124 to 126.
Action 4: Add some new references in the Introduction section.
Response 4: We added some new references (6,7,8, 11) in the Introduction section.
Action 5: Maybe, you can add Eulerian–Eulerian approach to key words.
Response 5: We added Eulerian–Eulerian approach to key words.
Action 6: Why did not you use 3D model in both cases?
Response 6: In the first step, a three-dimensional ejector was considered to study three-dimensional phenomena such as mixing shock. According to Table 2 in this study, for 3D mode it takes few days per run based on our computational resources (Core i5 laptop, 2.4GHz). Therefore, after ensuring the good performance of the ejector in three-dimensional mode, in two-dimensional mode due to the increase in the volume of calculations (because of mass transfer) the CO2 removal was studied in two dimensions.
Action 7: Add all parameters of the numerical simulations, model, turbulent intensity, Virtual mass coefficient, turbulent dissipation rate, Turbulent kinetic energy, First order upwing or Second order….
Response 7: In our CFD simulation, in the section of solution methods, the SIMPLE scheme was employed for the pressure–velocity coupling and also for discretization, volume fraction is discretized using the QUICK method. The First order upwind scheme was used for other equations. In Fluent software, these methods do not need to enter data and are selected from the First Order Upwind, Second Order Upwind, Power Law, QUICK methods. The initial values of turbulent kinetic energy (k) and turbulent dissipation rate (ε) are added in lines 308-310. Also, under-relaxation factors for pressure, density, momentum, volume fraction, turbulent kinetic energy, and turbulent dissipation rate are added in lines 410-414. Among different models for forces, Grace et al. Model, Tomiyama Lift Force Model, Burns et al. Model, and Antal et al. Model have been used to determine drag force coefficient, lift force coefficient, turbulent dispersion force, and Wall lubrication force, respectively. The equations of all these models and their constants are given in Section 2.1.1.
Round 2
Reviewer 2 Report
The authors improved the manuscript according to my remarks. The paper can be published in your journal.
