PONE-D-24-50720Correction of natural ventilation pressure in mines based on heat–flow coupling characteristics of underground airflowPLOS ONE

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Reviewers' comments:

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Comments to the Author

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: N/A

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Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: No

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5. Review Comments to the Author

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Reviewer #1: Reviewer comments

The manuscript addresses an important issue related to deep mining ventilation, particularly the mismatch between the ventilation power parameters and the underground ventilation network due to neglecting unsteady heat transfer between the airflow and the thermal environment. This mismatch makes it difficult to maintain the balance of airflow supply and demand in the mine roadways. The authors, based on the unsteady-state heat transfer leading to the fundamental nature of heat flow in airflow, propose a thermally corrected natural ventilation pressure formula and use this corrected pressure as an environmental variable to build a mathematical model for airflow control. By applying this model to the Gucheng coal mine, management decisions regarding airflow control in terms of ventilation power and resistance are made based on the model results. The research contributes to the optimization of intelligent ventilation and supplements the basic theory of the ventilation network under the heat-flow coupling characteristic of airflow, which is a novel approach. However, there are several parts in the manuscript that need to be addressed:

1. In Section 2.2, a numerical model of unsteady heat transfer for airflow in the Gucheng Coal Mine is presented. It is recommended to incorporate field measurement data or experimental data to validate the accuracy of the simulation model.

2. In Section 2.3, The proposed airflow control model, which is based on the heat-flow coupling characteristic of airflow, should be compared with currently commonly used control models. It is suggested that the proposed model be compared with commonly used control models to clearly explain the advantages and disadvantages of the new model.

3. In Section 3.1, there are errors in the notation of Equations 14 and 15; please review and correct them. In Section 3.2, the ventilation resistance calculation for the central ventilation network and Taoyuan ventilation network in Scheme 2.1 are incorrectly written; please check and amend accordingly.

4. Figures 8 and 10 represent the fan characteristic curves. The working conditions and blade angles should be clearly labeled in the figures to help readers observe the fan's status before and after adjustment.

5. The units throughout the paper should be consistent, and variables in the equations should be defined. The figures and textual descriptions should be as clear and understandable as possible. Some figures are unclear; it is advised that the author revise them to improve clarity.

6. In the conclusion section, while the main findings and contributions of the study should be clearly stated, the practical significance of these findings for the design, operation, and decision-making of intelligent ventilation systems should also be highlighted. The paper currently lacks a detailed discussion on the practical implications of the work, which should be addressed in the conclusion.

I hope the authors consider these points to improve the clarity and overall quality of the paper.

Reviewer #2: Reviewer comments

To address the issue of inadequate matching between the mine ventilation operating condition and airflow demand in the control network, which arises from the heat-flow coupling characteristic of airflow, the authors propose that the primary factors causing the mismatch between the fan operating condition and underground airflow demand are the natural ventilation pressure and mine ventilation resistance, calculated solely based on aerodynamic forces. On this basis, they developed a mathematical model for airflow regulation that incorporates the heat-flow coupling characteristics of airflow under the combined effects of aerodynamic and thermodynamic forces. The model was solved using the particle swarm optimization algorithm and the simplex method. Based on the solution results, the authors propose adjustment strategies from both ventilation power and resistance perspectives to improve the compatibility between fan operating conditions and underground airflow demand. This research has significant potential for practical applications. However, before the manuscript can be formally accepted, some minor issues need to be addressed:

1) In Section 3.1, the authors perform transient solving of the non-steady-state heat transfer model for the coal mine. How were the continuous data for temperature, pressure, and time in Table 2 derived?

2) The grid has a significant impact on the results. In the grid independence verification for the heat transfer model, the grid evaluation parameters used in Figure 6 continue to rise as the number of grids increases. An additional analysis of the selected grid division scheme should be included. It is also suggested to adjust the content of Figure 6 to ensure that the curve remains complete.

3) How is the proposed airflow regulation model applied in conjunction with CFD numerical simulation software? Please provide more details.

4) The authors should consider the potential discrepancies between the simulation results and actual conditions, and evaluate the effectiveness of the simulation. More details should be provided, including the methods of data collection, as well as a thorough analysis of the experimental results, so that readers can assess the reliability and validity of the study.

5) The models and data results mentioned in the article should be presented clearly through figures and tables to aid reader comprehension. Each figure and table should include clear titles, legends, and annotations to facilitate interpretation.

6) The formatting of the article, such as line spacing and other elements, should be adjusted to ensure consistency throughout the manuscript. It is recommended to carefully review the entire document, including text, figures, and images, to ensure uniform formatting.

7) The conclusions do not fully summarize the research content and its innovations. It is suggested to refine and strengthen the conclusions to more effectively highlight the key contributions and novel aspects of the study.

Reviewer #3: The manuscript explores the density-pressure coupling rule's impact on airflow in a mechanically ventilated mine. The issue is interesting and should be published. However, the problem of the influence of natural ventilation pressure (NVP) on the airflow in a mine ventilation network and the characteristics of the fan's operation has been known and described in the literature since at least the first half of the last century.

Authors are reminded that in the introduction, they should refer to articles describing the influence of the compressibility of air NVP in mine ventilation networks. Many publications have been written on this subject. Many methods describe the determination of NVP in a mine ventilation network. Additionally, the work analyzes the influence of NVP on the operation of the main ventilation fan. Therefore, the article's title should indicate that this is a different way of approaching this issue. The title could sound similar to "Heat-airflow-coupled approach to correcting the influence of the natural ventilation pressure on the airflow in an underground mine's ventilation network."

Other major comments:

1) To avoid any confusion, it is recommended that the term' heat and airflow coupling' be used to clearly indicate the relationship between heat and airflow, rather than being associated with heat flow only.

2) The authors should remember that the resistance of a single branch and the total resistance of the ventilation network are functions of the variable air density. Therefore, it is recommended that the standardized resistance of branches and the standardized fan characteristics be considered. This understanding is crucial as it significantly impacts the results of the analysis at the Gucheng Coal Mine.

3) The particle swarm optimization algorithm for solving the ventilation network should be referred to the reference or described in more detail.

4) The term "frictional air resistance" should be changed to the total resistance of branches, equivalent to the resistance of branches in the real mine.

5) Mine ventilation power is a strictly defined term in the science of mine ventilation. The authors probably use this term for a different purpose. Ventilation power and the electric power of engines are different parameters. It is proposed to define the term "mine ventilation" in the article.

6) Similarly, "system power consumption" and "the flow power of the aerodynamic force" should be defined by appropriate formulas so that the reader can easily understand the article.

7) It is proposed that chapter 8 in McPherson's book in this manual be cited in the references.

8) In conclusion 1, the number of the developed formula should be given.

9) The first sentence of Conclusion 2 needs to be simplified and should be rewritten more clearly and comprehensively to ensure the reader's full understanding.

10) Conclusion 3 has not been proven to maintain a stable flow condition, and flow stability has yet to be defined.

Other minor comments

1) The term "stable airflow conditions: is used in the wrong context of the text.

2) What does "state equation" mean when giving an approximation equation of the fan characteristic curve?

3) The caption of Figure 7 needs to be corrected. The temperature color range is too extensive.

4) It is recommended that the symbols used in the manuscript be standardized.

5) English needs proofing.

It is recommended to study the publication (DOI):

https://hdl.handle.net/10520/AJA0038223X_5533 10.2478/amsc-2014-0036

10.1007/BF01560715

10.1134/S1062739147050145

10.19835/j.issn.1008-4495.2023.04.017

10.1016/j.ijmst.2017.09.004

10.1155/2022/8789955

10.1080/15567036.2019.1673512

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Decision on optimal airflow regulation solution set based on heat and airflow coupling characteristics of mine airflow in time series

PONE-D-24-50720R1

Dear Dr. Heng,

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Rajeev Singh

Academic Editor

PLOS ONE

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