Performance Evaluation and Optimum Design of Ventilation Roofs with Different Positions of Shape-Stabilized PCM
Round 1
Reviewer 1 Report
Comments
In this paper, the thermal performances of ventilation roofs with different positions of shape stabilized PCM were numerically investigated. The topic of this research is interesting. I would suggest the publication of this article if the following issues were addressed.
- In the introduction more recent works should be added related to energy saving inside buildings. Authors may include the closely related works such as:
o Ben Khedher, N. 2018. “Numerical Study of the Thermal Behavior of a Composite Phase Change Material (PCM) Room”. Engineering, Technology & Applied Science Research 8 (2). Greece:2663-67. https://doi.org/10.48084/etasr.1824.
o Nidhal Ben Khedher, Rashad A. Bantan, Lioua Kolsi, Mohamed Omri, Performance investigation of a vertically configured LHTES via the combination of nano-enhanced PCM and fins: experimental and numerical approaches, International Communications in Heat and Mass Transfer,Volume 137, 2022, 106246, ISSN 0735-1933, https://doi.org/10.1016/j.icheatmasstransfer.2022.106246.
- The mathematical model is missing. The governing equations should be added.
- The boundary conditions should be written in equations (indoor and outdoor sides)
- The meshed domain should be depicted.
- The time step test should be performed and represented in a table or figure.
- The thermophysical properties of the chosen PCM should be represented clearly in a table, especially latent heat of melting and thermal capacity and thermal conductivity which are very important for the thermal behavior of PCM layer.
- In Fig8, the liquid fraction doesn’t start from 0 corresponding to solid state. Could you explain this behavior especially when temperature is lower than the melting temperature at that time
- Page 14, authors mentioned that “We also can conclude that when the melting temperature is low, it is difficult to reach the solidification temperature at night, which lead to a low UR;” from figure 8 for all cases PCM do not solidify completely. Only for figure 8-d for highest studied thickness (20-25mm) the small melted PCM during daytime was completely solidified at night.
- The overall liquid melting fraction should be computed and represented to ensure that the whole PCM melts and solidifies. Liquid fraction for every layer and for different thicknesses alone is not enough and sometimes it is difficult to judge the suitability of the PCM thickness. Since inner surface temperature can be reduced by the inertia of higher thicknesses or because of lower PCM conductivity and the PCM layer will play the role of insulator.
- For the case of VRSPO why different thicknesses and melting temperatures from VRSPM are taken? How they were defined and chosen
- In table8, the caption should be revised “Latent heat utilization rate of each PCM layer of VRSPM with different cavity sizes”. Since, VRSPO as well is there in the table.
- Why the cavity size for VRSPI was not studied
The text is well written. Few spelling mistakes should be checked in the whole text
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors presented a numerical study to optimize and design the ventilation roofs with different positions of shape-stabilized PCM.
The scientific soundness and English level are very low.
The main quantitative findings are to be mentioned in the abstract
The novelty of the paper is to be clearly stated.
The solved governing equations are to be presented.
The used turbulence model is to be justified.
A validation/verification of the numerical model is to be performed by comparing the results of your model with previously published results.
The boundary conditions are to be expressed mathematically.
The numerical method is to be detailed.
What is the convergence criterion?
The results of the grid sensitivity test are to be presented in a Table.
The authors considered a 3D configuration; thus, some 3D profiles are to be presented and discussed.
It will be interesting to present the streamlines for a better understanding of the flow structure.
What is the considered range for Reynolds number?
The paper is to be checked against misprints and grammatical mistakes.
Extensive editing of English language required
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
I reviewed the study titled "Performance evaluation and optimum design of ventilation roofs with different positions of shape-stabilized PCM" The study aims to introduce a novel ventilation roof with shape-stabilized PCM, which uses mechanical ventilation at night to remove the solidification heat of PCM. Overall the study is informative and well-conducted. However, the paper's novelty is limited, as a few recent papers used a similar approach. The manuscript may benefit from the following comments: Abstract: The abstract is well-written. Introduction: the literature review is limited and needs to be expanded and updated to include recent research. Results and discussion: dividing the results from the discussion is necessary. In the discussion, it is essential to compare the study results with recent articles with a similar approach and better identify how the current study contributes to the body of knowledge. Therefore, I recommend a major revision.
Minor editing of the English language is required.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
While selected research topic is actual and relevant to modern trends, the authors were not able to provide detailed description of methodology and research boundary conditions. Please provide information on indoor air parameters maintained during research? Does the 26 oC was maintained 24/7? So no day/night reduction? Have considered indoor heat gains? Also in would be very valuable to add information how PCM will affect heat loads during the winter.
Please explain how The sol-air temperature in summer typical day in Wuhan was obtained?
There are many similar studies are being published. What are your progress beyond the already MDPI published studies. As an example:
1. Heat Recovery Using PCM in Decentralised Façade Ventilation
2. Low-Temperature Applications of Phase Change Materials for Energy Storage: A Descriptive Review
3. Optimizing PCM Integrated Wall and Roof for Energy Saving in Building under Various Climatic Conditions of Mediterranean Region
4. Cooling Panel with Integrated PCM Layer: A Verified Simulation Study
5. And many other from MDPI database
Author Response
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Author Response File: Author Response.pdf
Reviewer 5 Report
From my point of view, this article presents a research project that deals with an interesting and important topic. However, this article has some important lacks in this present form. Therefore, this text is not acceptable to be published yet and this is mainly because of the following issues:
a) In general, there is a lack of presenting the limits of this research project. For example, is this a theoretical exclusively thermal behavior-based study? or Does it consider application and functional issues? Have the authors thought about the PCM product, format, application? Will this roof be walkable even for maintenance? Which are the mechanical properties of the roof components apart from the hollow core slab? Even hollow core slabs have different sizes and shapes of the hollows depending on the thickness which is related to the length, loads… These limits and its presentation and justification are essential in order to value the authors contribution.
b) The title and abstract lack presenting the context, application and also the limits of the research project.
c) The introduction lacks an explicit presentation and justification of the objectives and scope, boundaries, related to the context and former studies. It also lacks a proper ending and needs rewriting its final lines. The explanation of the last paragraph lines 14-19 should not be in the past, it should be present and referring to the following sections. The last 7 lines of the last paragraph of the introduction are a summary of the main results that could be in the abstract or in the conclusions but not in the introduction. Furthermore, this section lacks ending with a clearer explanation of the article main structure referring to the article sections, subsections, parts… that would help potential readers to understand the article.
d) Either in the introduction or a materials section is required to explain and justify the elements and materials chosen. For example, the manuscript lacks explaining explicitly why a hollow core slab is used and lacks explicitly relating it to the reviewed former experiences using hollow core slabs for ventilation. The same with the type of waterproofing layer, insulation, order of the layers apart from the PCM… Is this a commonly used roof?, Where? etc. The justification of the PCM and how it could be applied in the different locations of the roof is also unclear. Connecting this research project to the reality, to potential applications is also a lack of this article. Which type of buildings and where could be applied? Which is related to the case study and boundaries of the research project? Otherwise the authors could locate this study further previously to the application stage.
e) The methodology section needs to improve several weaknesses. In order that potential readers can understand it, Figure 1 steps’ names lack exactly matching with the description of the steps in the following subsections. Numbering is also required to refer to the steps. Moreover, the framework could improve by including the name of the step and the tools used in each step. For the same reason of understanding, the methodology needs to focus on clearly explaining the methods and tools and if needed explaining punctual connections to former studies, but reviewing literature (paragraph 1 and 2 of section 2.1) must be avoided to avoid creating confusion.
f) The discussion lacks commenting the results from other points of view. For example, it lacks weighting, screening the differences between this research project 3 options. In a real case, does it matter putting the PCM in each location? Which would be the contribution to the building performance in each case? Or is better to consider other issues? The rank between 75-58 days from 365 would it imply a big difference? Or it’s better to consider other issues? For example, put it where it easier to apply or depending on the PCM product format or in its mechanical properties? In this sense, the conclusions also lack quantifying the contribution of each alternative and this is crucial to evaluate this article contribution.
g- Other comments:
g1- This article lacks defining the acronyms in the manuscript the first time they are used. A section with all the acronyms used would also improve the article.
g2- Last spelling review, p.e. 2nd line, page 3, “high-reflctivity”
From my point of view, this article presents a research project that deals with an interesting and important topic. However, this article has some important lacks in this present form. Therefore, this text is not acceptable to be published yet and this is mainly because of the following issues:
a) In general, there is a lack of presenting the limits of this research project. For example, is this a theoretical exclusively thermal behavior-based study? or Does it consider application and functional issues? Have the authors thought about the PCM product, format, application? Will this roof be walkable even for maintenance? Which are the mechanical properties of the roof components apart from the hollow core slab? Even hollow core slabs have different sizes and shapes of the hollows depending on the thickness which is related to the length, loads… These limits and its presentation and justification are essential in order to value the authors contribution.
b) The title and abstract lack presenting the context, application and also the limits of the research project.
c) The introduction lacks an explicit presentation and justification of the objectives and scope, boundaries, related to the context and former studies. It also lacks a proper ending and needs rewriting its final lines. The explanation of the last paragraph lines 14-19 should not be in the past, it should be present and referring to the following sections. The last 7 lines of the last paragraph of the introduction are a summary of the main results that could be in the abstract or in the conclusions but not in the introduction. Furthermore, this section lacks ending with a clearer explanation of the article main structure referring to the article sections, subsections, parts… that would help potential readers to understand the article.
d) Either in the introduction or a materials section is required to explain and justify the elements and materials chosen. For example, the manuscript lacks explaining explicitly why a hollow core slab is used and lacks explicitly relating it to the reviewed former experiences using hollow core slabs for ventilation. The same with the type of waterproofing layer, insulation, order of the layers apart from the PCM… Is this a commonly used roof?, Where? etc. The justification of the PCM and how it could be applied in the different locations of the roof is also unclear. Connecting this research project to the reality, to potential applications is also a lack of this article. Which type of buildings and where could be applied? Which is related to the case study and boundaries of the research project? Otherwise the authors could locate this study further previously to the application stage.
e) The methodology section needs to improve several weaknesses. In order that potential readers can understand it, Figure 1 steps’ names lack exactly matching with the description of the steps in the following subsections. Numbering is also required to refer to the steps. Moreover, the framework could improve by including the name of the step and the tools used in each step. For the same reason of understanding, the methodology needs to focus on clearly explaining the methods and tools and if needed explaining punctual connections to former studies, but reviewing literature (paragraph 1 and 2 of section 2.1) must be avoided to avoid creating confusion.
f) The discussion lacks commenting the results from other points of view. For example, it lacks weighting, screening the differences between this research project 3 options. In a real case, does it matter putting the PCM in each location? Which would be the contribution to the building performance in each case? Or is better to consider other issues? The rank between 75-58 days from 365 would it imply a big difference? Or it’s better to consider other issues? For example, put it where it easier to apply or depending on the PCM product format or in its mechanical properties? In this sense, the conclusions also lack quantifying the contribution of each alternative and this is crucial to evaluate this article contribution.
g- Other comments:
g1- This article lacks defining the acronyms in the manuscript the first time they are used. A section with all the acronyms used would also improve the article.
g2- Last spelling review, p.e. 2nd line, page 3, “high-reflctivity”
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I think the revised version was not uploaded properly.
Authors mentioned that the modifications are highlighted in red :
Point 1: In the introduction more recent works should be added related to energy saving inside buildings.
Response 1: Thank you for your suggestion. Seven papers related to this research, including the two recommended articles, have been added to the manuscript. The introductory chapter has been expanded.
The corresponding supplementations were made in the section of Introduction, and marked in “red” color.
However, the new modifications were not highlighted in text. Please highlight the modifications in the revised text. Moreover, authors mentioned that they added the suggested papers but it is not the case.
Ben Khedher, N. 2018. “Numerical Study of the Thermal Behavior of a Composite Phase Change Material (PCM) Room”. Engineering, Technology & Applied Science Research 8 (2). Greece:2663-67. https://doi.org/10.48084/etasr.1824.
o Nidhal Ben Khedher, Rashad A. Bantan, Lioua Kolsi, Mohamed Omri, Performance investigation of a vertically configured LHTES via the combination of nano-enhanced PCM and fins: experimental and numerical approaches, International Communications in Heat and Mass Transfer,Volume 137, 2022, 106246, ISSN 0735-1933, https://doi.org/10.1016/j.icheatmasstransfer.2022.106246.
The mathematical model is still missing and authors mentioned in their report that it is detailed
Response 2: Thank you for your suggestion. The governing equations, including mass, momentum, and energy equations, have been added in Section 2. (Section 2.1 on page 6)
The text is well written and Minor editing of English language requiredAuthor Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
After revision, the paper can be accepted for publication
Author Response
Thank you very much for your careful review and helpful comments on the article. The revisions have made the article more readable and scholarly. Thank you very much for your support, it is very important for our research, thanks!
Reviewer 3 Report
The manuscript has improved and is ready for publication.
English is fine; just focus on the final presentation after accepting the modifications.
Author Response
Thank you very much for your careful review and helpful comments on the article. The revisions have made the article more readable and scholarly. Thank you very much for your support, it is very important for our research, thanks!
Reviewer 4 Report
Still validation of theoretical models is weak. Also, only one channel was simulated. How neighbor channels affect each other. All result present only 24 hours simulations. However, for PCM it is important to analysis longer time period. At least 3 to 5 days to see the charge and discharge.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 5 Report
From my point of view, the manuscript has improved significantly following the reviewers' comments and now is ready to be accepted for being published
Author Response
Thank you very much for your careful review and helpful comments on the article. The revisions have made the article more readable and scholarly. Thank you very much for your support, it is very important for our research, thanks!
Round 3
Reviewer 1 Report
The Authors have addressed all of my concerns with the original manuscript.
Dear Editor,
Thank you for inviting me to contribute to the review of this work.
Best Regards,
