Round 1

Reviewer 1 Report

The manuscript entitled “CFD simulation of dry pressure drop in a cross-flow rotating 2 packed bed” by Zhang et al. has been reviewed and it requires some revisions before it can be acceptable for publication.  Please consider the following comments.

• You must proofread for grammar/English
• The abstract needs to be modified, a general sentence(s) at the beginning to explain briefly about methodology and novelty of the work
• I'm not sure of the actual contribution of this paper, there seems no new knowledge produced. This needs to be clearly highlighted and discussed in the paper.
• Not enough details about the numerical model are provided. You need to provide more details. For example, did you conduct mesh (grid) independence test? The type of mesh used and how many cells were in the computation domain, etc. should be added. Line 94
• Figure 2 is not clear and needs to be in higher quality
• A better way of presenting Figure 2 would be very helpful
• There are many acronyms, abbreviations, and symbols in the manuscript. A nomenclature would be helpful.
• What does this paper contribute that is not already known? This needs to be clarified
• The conclusion needs to be modified, should provide the major findings of the present study, including the investigation methods and future work.
• The conclusion of the paper has high text similarity to “Jiao, W.Z., Y.Z. Liu, and G.S. Qi, Gas Pressure Drop and Mass Transfer Characteristics in a Cross-flow Rotating Packed Bed with Porous Plate Packing. Industrial & Engineering Chemistry Research, 2010. 49(8): pp. 3732-3740.” This needs to be revised.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

English must be slightly improved, e.g. in the lines 114, 169-171,182, 350, 364, etc. The model must be described more clearly including analysis of the boundary problem for the PDE array and the method for the solution. The case considered is very complex in numerical simulation but looks simple in the paper.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Re.:            Applied Sciences, manuscript applsci-1413742

Title:           CFD simulation of dry pressure drop in a cross-flow rotating packed bed

Authors:      Chao Zhang, Weizhou Jiao, Youzhi Liu, Guisheng Qi, Zhiguo Yuan and Qiaoling Zhang

General Statement

The paper deals with an up to date problem fully complying with the Applied Sciences journal profile. The study concerns a certain real assembly. To predict its behaviour advanced tools of numerical analysis were applied. In spite of the fact that the discussed issue is narrow in scope and that the idea of the research is copied from another works the outcomes are worth to be promoted in the scientific community if the results are correct. I would personally like to believe that it is so, but unfortunately I do not have that belief. It is because there is some important information missing and because the discussion of the results is limited mostly to the obtained data presentation. I have also objection to the contents of subsequent sections. Because of many minor faults, edition and grammar errors, rather incomprehensible English, the manuscript is also difficult in reading. For these reasons, it is difficult to be convinced that the publication could be recommended not only in its current state, but even after minor corrections. One of my major objections can be illustrated with the following comments concerning the Abstract section. The actual manuscript Abstract is limited to description of the results obtained. It resembles initial parts of a typical Conclusions section content. Details concerning the problem roots, methods or tools applied, goals etc. are missing. And a similar problem of improper contents and organisation applies to other parts.

Selected detailed suggestions are presented bellow. As for recommendations, I suggest resubmitting the article after major corrections.

Selected Major Comments and Suggestions

1. The goal of the research should be stated clearly.
2. The reference experimental research should be indentified and described or referred to.
3. Line 96: The arrows indicate points, not planes. I can guess that the authors wanted to indicate the appropriate control cross- sections.
4. Line 100: The illustration is illegible. I recommend replacing the screen shot with a proper schematic.
5. Line 125: Table 2 contains data accessible in another sources, even in the Fluent tutorial. Except of these commonly known equations the parameters taken for calculations should be listed or indicated if they were taken from the Fluent library.
6. Line 135, section 3.1 and the following sections: It is not clear which pressure the authors mean. Is it an average pressure form a cross-section area? Pressure taken from a certain point?
7. It is not clear which results are shown in Figure 3 and how they refer to the data shown in Figure 4.
8. Line 136: It is not clear at this point to which experiment the results were referred to.

Selected Minor Correction Suggestions

1. The whole text is difficult to assimilate – it needs to be reedited.
2. Line 64, an example of a grammar error: “the calculated results was lower” should read “the calculated results were lower”.
3. Lines 68-69, Re. “CFD can clarify the important hydrodynamic characteristics without disturbing the flow field in RPB”. Comment: It is obvious that numerical modelling does not disturb the flow.
4. Line 83, grammar: “shown” – “are shown”.
5. Line 85, edition (?), grammar (?): “to execute a comprehensively analysis”?
6. Line 100: The illustration is illegible. I recommend replacing the screen shot with a proper schematic.
7. Line 102, style (?), edition (?): In my opinion the word “which” should be replaced by the word “and”.
8. Line 108: “Turbulence model.” – this is not a statement. The problem reappears in the following parts.
9. Line 114: “is focus” –“ is focused”
10. Line 123, Table 1: What does it mean “Wire”?
11. Lines 142-142: The structure of the bed is not described.
12. Line 155: grammar error in the sentence “...with the rotating speed is increased...”.
13. Line 169: grammar error in the sentence “...depicts the pressure drop decreases gently...”.
14. Data on Ref. 11 is wrong. The issue number should read 2.
15. 18 – not found when applying the data provided by the authors.

Author Response

Response to Reviewer 3 Comments

 

Point 1: The goal of the research should be stated clearly.

 

Response 1: Following the reviewer’s comment, the abstract has been modified and the goal of the research is highlighted in the conclusion.

 

Point 2: The reference experimental research should be identified and described or referred to.

 

Response 2: Following the reviewer’s comment, the description of the experimental method has been added in section 3.

 

Point 3: Line 96: The arrows indicate points, not planes. I can guess that the authors wanted to indicate the appropriate control cross- sections.

 

Response 3: The arrows indicate the cross sections of each zone in the cross-flow RPB.

 

Point 4: Line 100: The illustration is illegible. I recommend replacing the screen shot with a proper schematic.

 

Response 4: Following the reviewer’s comment, Figure 2 has been deleted and the details of the computational grid are provided in section 2.3.

 

Point 5: Table 2 contains data accessible in another sources, even in the Fluent tutorial. Except of these commonly known equations the parameters taken for calculations should be listed or indicated if they were taken from the Fluent library.

 

Response 5: Following the reviewer’s comment, the parameters such as porosity, viscous resistance coefficient and inertial resistance coefficient are listed in Table 1.

 

Point 6: Line 135, section 3.1 and the following sections: It is not clear which pressure the authors mean. Is it an average pressure form a cross-section area? Pressure taken from a certain point?

 

Response 6: The pressure is the average value from a cross section area and following the reviewer’s comment, it has been highlighted in the revised manuscript.

 

Point 7: It is not clear which results are shown in Figure 3 and how they refer to the data shown in Figure 4.

 

Response 7: The comparison of experimental measured dry pressure drop with the simulation results calculated by the three turbulence models are shown in Figure 3, and it can be seen that both RNG k-ε model and RSM can well describe the turbulence behavior in cross-flow RPB. While, by analysing the total energy loss in the cavity zone A, the pressure drop in the cavity zone A should decrease with increasing rotating speed. So we can see that RNG k-ε model is more suitable to reveal the flow pattern in cross-flow RPB from Figure 4.

 

Point 8: Line 136: It is not clear at this point to which experiment the results were referred to.

 

Response 8: Following the reviewer’s comment, the description of the experimental method has been added in section 3.

 

Selected Minor Correction Suggestions

Point 1: The whole text is difficult to assimilate – it needs to be reedited.

 

Response 1: Following the reviewer’s comment, the whole text has been reedited.

 

Point 2: Lines 68-69, Re. “CFD can clarify the important hydrodynamic characteristics without disturbing the flow field in RPB”. Comment: It is obvious that numerical modelling does not disturb the flow.

 

Response 2: Although it is obvious that the CFD simulation does not disturb the flow field, we just want to emphasize that this is an advantage over the traditional experimental method.

 

Point 3: Line 100: The illustration is illegible. I recommend replacing the screen shot with a proper schematic.

 

Response 3: Following the reviewer’s comment, Figure 2 has been deleted and the details of the computational grid are provided in section 2.3.

 

Point 4: Line 123, Table 1: What does it mean “Wire”?

 

Response 4: It means the packing is constructed by metal wire.

 

Point 5: Lines 142-142: The structure of the bed is not described.

 

Response 5: Following the reviewer’s comment, the experimental method has been added in section 3 and the structure of the RPB is briefly described

 

Point 6: 18 – not found when applying the data provided by the authors.

 

Response 6: The data is provided by Figure 15(a).

 

Point 7:.

Line 64, an example of a grammar error: “the calculated results was lower” should read “the calculated results were lower”.

Line 83, grammar: “shown” – “are shown”.

Line 85, edition (?), grammar (?): “to execute a comprehensively analysis”?

Line 102, style (?), edition (?): In my opinion the word “which” should be replaced by the word “and”.

Line 108: “Turbulence model.” – this is not a statement. The problem reappears in the following parts.

Line 114: “is focus” –“ is focused”

Line 155: grammar error in the sentence “...with the rotating speed is increased...”.

Line 169: grammar error in the sentence “...depicts the pressure drop decreases gently...”.

Data on Ref. 11 is wrong. The issue number should read 2.

 

Response 7: Following the reviewer’s comment, these mistakes have been corrected in the revised manuscript.

 

 

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

Re.:              Applied Sciences, manuscript applsci-1413742_v2

Title:             CFD simulation of dry pressure drop in a cross-flow rotating packed bed

Authors:      Chao Zhang, Weizhou Jiao, Youzhi Liu, Guisheng Qi, Zhiguo Yuan and Qiaoling Zhang

General Statement

While reading the revised version I have impression that the authors misunderstood some of my comments. Let take the Abstract section as example. It still doesn’t provides a general information but not only presents the results without its physical background. Unacceptable is referring to details not presented yet like “cavity zone A”, “cavity zone B” etc. A proper abstract section should provide information on:

• objective of the research and the paper,
• materials, instrumentation and methods applied,
• results obtained,
• concluding remark.

It seems that focusing on the details obscured the authors of the need for the necessary generalization. The same concerns some parts of the revised text also. For example the information about the modelled medium can be inferred only from information provided within description of the experimental stand in line 114. Table 1 still does not contain information about the gas type and parameters/constitutive relation. Commenting on the Table 1 contents I would like to point out, that the “wire” is not a material but a material shape/form. If the whole section was modelled by a domain of a porous media it should be underlined within the text and the Table 1 should be limited to presentation of the significant features of the numerical model.

As the authors still do not mention the applied modules of the CFD software I recommend to comment on the information provided in line 91: Why the multiphase flow module was applied for a pure gaseous flow modelling? The model is limited to “dry pressure” drop evaluation.

On the other hand, the introduced corrections significantly improved the transparency of the work. I accept most of the changes introduced. The paper could be recommended for publication after some major corrections focused mostly on generalisation of the presentation in some parts.

Author Response

Response to Reviewer 3 Comments

 

 

Point 1: While reading the revised version I have impression that the authors misunderstood some of my comments. Let take the Abstract section as example. It still doesn’t provides a general information but not only presents the results without its physical background. Unacceptable is referring to details not presented yet like “cavity zone A”, “cavity zone B” etc. A proper abstract section should provide information on: objective of the research and the paper, materials, instrumentation and methods applied, results obtained，concluding remark.

 

Response 1: Following the reviewer’s comment, the abstract has been modified.

 

Point 2: For example the information about the modelled medium can be inferred only from information provided within description of the experimental stand in line 114. Table 1 still does not contain information about the gas type and parameters/constitutive relation. Commenting on the Table 1 contents I would like to point out, that the “wire” is not a material but a material shape/form. If the whole section was modelled by a domain of a porous media it should be underlined within the text and the Table 1 should be limited to presentation of the significant features of the numerical model.

 

Response 2: Following the reviewer’s comment, the information about gas type, gas flow rate and rotating speed have been added in Table 1. The packing zone is modelled by a domain of porous media, which has been underlined in abstract and section 2.2.

 

Point 3: As the authors still do not mention the applied modules of the CFD software I recommend to comment on the information provided in line 91: Why the multiphase flow module was applied for a pure gaseous flow modelling? The model is limited to “dry pressure” drop evaluation.

 

Response 3: Following the reviewer’s comment, the details of the applied modules have been introduced in section 2.2, and the single-phase flow model is used to simulate the gas flow, the mistake has been corrected in the revised manuscript.

 

 

 

 

Author Response File: Author Response.docx