Review on Research Progress of Pulsating Heat Pipes
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors present a comprehensive review of pulsating heat pipes (PHPs). The manuscript is well-written and supported by a significant number of references. The first criticism is that the references are not cited in an orderly manner, which makes reading quite confusing. The authors must fix this issue in the revised manuscript.
Section 1 mentions that most reviews of PHPs focus on fluid selection, structure influence, mechanism study, and visualization under moving status. However, such related works are not cited clearly. In addition, it is not clear how the present survey differs from past research. Section 1 must be improved at this point.
Some questions remain unanswered:
1) What are the most recent advances and breakthroughs in research topics associated with PHPs? Although approximately 20% of the references in the manuscript are from the last two years, it seems that this recent research is not adequately highlighted or discussed.
2) Since working fluid and structural design impact the heat transfer efficiency directly, how could you optimize the design conditions? Please, elaborate.
3) What is the current status of PHP research in modern fields such as chip cooling and thermal management of batteries?
4) What advantages do PHPs offer over other conventional heat transfer methods regarding efficiency and applicability?
Minor non-technical issues include:
- Please, ensure the consistent usage of acronyms in the whole manuscript, especially PHPs.
- Most figures are of low quality and seem to be directly withdrawn from other works, which could raise copyright concerns.
There is a need for polishing the manuscript, starting from the abstract.
Author Response
The reply to comments are listed in the attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article reviews the latest research on pulsating heat pipes. My biggest remark goes to the excessively descriptive and passive tone of the text. A review article cannot simply recount what was said in the referenced articles. The literature should be reviewed more critically, by reading in between the lines. You should point out the limitations, the errors in the article but also suggest guidelines for future research. Also, it would be interesting to detect the disagreements and contradictions between different authors. Furthermore, if the authors of the referenced articles did not provide meaningful explanations for their results, then you should be able to do so on your own. The main findings from the literature should be generalized. From the literature you should be able to identify: 1) the major achievements, 2) the research problems and knowledge gaps, 3) the unsolved questions and debates, 4) the emerging lines of research; and 5) suggest guidelines for future research. The comments above go especially to section 2. Heat transfer performance of PHP. I also have the following comments:
1. Across the text both terms are used: pulsating heat pipes (PHPs) and oscillating heat pipes (OHPs). I suggest using only one term in the discussion but mentioning both at the start of the Introduction.
2. Line 99: "ethanol is easier to start because of the higher dynamic viscosity" but in line 113 "ethanol have faster start-up speed because of lower viscosity" - this is a contradiction?
3. Line 117: "it is necessary to choose the right working fluid according to the operating conditions" - how do we choose the right working fluid? Be specific.
4. Line 244: "They found that in the horizontal direction, no matter what the channel type, can’t start" - why the micro PHP cannot start? It is always like this for horizontal placement? In you opinion, what could be done to make it start in the horizontal position?
5. Line 249: "the pulsating heat pipes with non-uniform channels could start in the horizontal direction" - why is that?
6. Line 336: how much is the "critical number of turns"?
7. Search better terms for "still status" and "moving status". It could be "stationary" or "steady" and "moving" or "mobile" or "unsteady".
8. Line 399: "the bubble rise velocity is at its highest within 50° and 70° of inclination" - why it is higher that the velocity for 90°?
9. Line 406: "annual flow stage" - is it "annular flow"?
10. Line 506: how much is the "acceleration threshold"?
11. Section 3.1. discuss theoretical models for PHPs. What are the advantages and limitation of each model when compared to others? How can we know which model perform better? Which models have been compared against experimental data? Also, it is not necessary to write all the equations of these models since they can be easily found in the referenced articles.
12. Section 3.2. which numerical studies of PHPs have been compared against experiments? If no comparison is given in the referenced studies then how can we know that the results are reliable?
13. Lines 934-936 must be removed because they are from the instructions for authors.
14. Section 4. Application of PHPs is the most interesting. This section should be expanded with more details, limitations and possibilities for the use of PHPs in the industry. Also, you should be able to suggest how PHPs could be further implemented in various industrial sectors.
Comments on the Quality of English LanguageExtensive editing necessary for the writing style. The entire text should be checked for typos. Missing capital letters at the beginning of sentences.
Author Response
The reply to comments are listed in the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsCongratulations to the authors.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have addressed all my suggestions and have improved the article accordingly. I have no further comments.
Comments on the Quality of English LanguageMinor editing necessary.
