A Modeling-Based Flammable Risk Treatment of Refrigerant Leakage from a Commercial R-290 Refrigeration Machine
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript detailed research into the effectiveness of ventilation systems in reducing the risk of R-290 leakage but has some potential shortcomings. Firstly, it could benefit from more detailed discussions on research limitations, such as assumptions in the CFD model and potential uncertainties in simulation results. Furthermore, there is no comprehensive comparison with the existing literature on similar research, which could provide more context and highlight the novelty of the research. Furthermore, since some sections seem repetitive and excessively detailed, the results and discussion may be more concise and focused. Finally, the conclusions can be strengthened by providing practical recommendations or future research directions based on the study's findings.
Author Response
Dear Reviewers and Editors,
Inventions
Thank you for allowing us to submit a revised draft of our manuscript titled A Modeling-Based Flammable Risk Treatment of Refrigerant Leakage from a Commercial R-290 Refrigeration Machine to Inventions. We appreciate the time and effort the editors and reviewers have dedicated to providing your valuable feedback on our manuscript. Following your guidance in the email, we have revised the manuscript to address each of the comments.
In this document, we have responded point-by-point to all the reviewers' and editor's comments. We have tracked all the changes in the revised manuscript and have used page and line numbers from the new revised manuscript to refer to the locations where the changes have been made. For your convenience, we have also included the revisions (in Italic) in our responses exactly as they occur in the revised manuscript.
In addition to the revised manuscript with all changes tracked.
We look forward to hearing from you in due time regarding our submission and to respond to any further questions and comments that you may have.
Best regards,
Mingkan Zhang, Ph.D.
Vishaldeep Sharma
Praveen Cheekatamarla, Ph.D.
Reviewer #1
- Firstly, it could benefit from more detailed discussions on research limitations, such as assumptions in the CFD model and potential uncertainties in simulation results.
Discussions about on the limitations of current have been added to the end of “Results and Discussion”, Line 341-349.
Although the model can successfully track the R-290 concentration and visualize the flammable zone of R-290, there are still some limitations of the research. In the CFD model, it is assumed that the leaking is from holes D = 1 mm. However, in real leaking scenarios, R-290 could leak from a small hole, or a crack. The size and shape of leaking source could influence the distribution of R-290, which does not include in present model. On the other hand, the model is lack of a control of ventilation system. In real applications, the ventilation fan needs to be controlled by a control strategy with a censor, i.e. when the sensor detects concentration of R-290 is higher than 100 ppm, the ventilation will be on. The control strategy will be added in future work.
- Furthermore, there is no comprehensive comparison with the existing literature on similar research, which could provide more context and highlight the novelty of the research.
We did a comprehensive literature in the “Introduction” already.
To highlight the novelty of our research, we added two sentences in the “Introduction” to summarize the shortcomings of the studies in the existing literature and, in lines 57-59, and lines 75-78, respectively. Moreover, “Thus, R-290 is becoming a popular choice among refrigeration systems, especially for commercial refrigeration device such as vending machines and ice cream machines.” was deleted. “Using postprocessing tools, one can also directly visualize the zones with flammable risk by plotting the zones that have refrigerant concentration between the LFL and UFL. More-over, evolution of the flammable zones can also be monitored by plotting them in different time frames.” was moved after “in present work” …
Although there are many studies dedicated to the leaking of flammable refrigerants, the visualization of flammable zones was rarely reported.
Although R-290 is becoming a popular choice for commercial refrigeration device such as vending machines and ice cream machines, there are not many studies focusing on commercial refrigeration devices.
- Furthermore, since some sections seem repetitive and excessively detailed, the results and discussion may be more concise and focused.
We deleted some too detailed contents in “Results and Discussion”, lines 203-204, lines 226-227, lines 255-259, lines 272-276, lines 298-299 , and lines 330-332.
- Finally, the conclusions can be strengthened by providing practical recommendations or future research directions based on the study's findings.
A paragraph about practical recommendations or future research directions was added to the “Conclusion”, lines 379-384
Based on the simulation results, it is recommended to install the ventilation system attaching to the commercial refrigeration device due to the flammability of R-290. It is also recommended to install a duct directly to the insulated chamber in the device to avoid accumulation of R-290 in the chamber. Future research will be focusing on improving the current ventilation design, e.g. adding a control strategy to the fan based on values from the gas sensor.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe submission presents interesting information on elimination of flammability risks associated with leakage of refrigerant (R290). I am having following points that if clarified would improve the quality of draft and improve its readability.
Literature review/findings are to be written in past tense (pg. 1 row 45, please double check whole manuscript)
What is meant by high thermal efficiency? (pg 2, row 60), thermal performance could be a better alternative.
Which commercial refrigeration system was considered
Methodology steps to be written in past tense (pg 2, row 92, see and correct at other places in the draft)
In the validation, it has been mentioned that the simulation model has been tested against experimental conditions where refrigerant leakage rate was 250 g/min. The size of leakage (diameter of leaking hole) for both experimental and simulated conditions should also be provided for clarity of readers. How about the size of refrigeration system for simulated and experimental cases? Do we know the total charge of refrigerant in the system (experimental) and the total time it took to leave the system??
Was only one ventilation rate (50 CFM) was simulated? Any rationale behind selection of this ventilation rate?
In my opinion it would be better to mention concentration of R290 in PPM instead of volume fractions for figure 3 and other such figures in the draft.
Comments on the Quality of English LanguageOverall sentence construction is quite good. In some sections however the tense needs to be corrected (see above comments in author's section).
Author Response
Dear Reviewers and Editors,
Inventions
Thank you for allowing us to submit a revised draft of our manuscript titled A Modeling-Based Flammable Risk Treatment of Refrigerant Leakage from a Commercial R-290 Refrigeration Machine to Inventions. We appreciate the time and effort the editors and reviewers have dedicated to providing your valuable feedback on our manuscript. Following your guidance in the email, we have revised the manuscript to address each of the comments.
In this document, we have responded point-by-point to all the reviewers' and editor's comments. We have tracked all the changes in the revised manuscript and have used page and line numbers from the new revised manuscript to refer to the locations where the changes have been made. For your convenience, we have also included the revisions (in Italic) in our responses exactly as they occur in the revised manuscript.
In addition to the revised manuscript with all changes tracked.
We look forward to hearing from you in due time regarding our submission and to respond to any further questions and comments that you may have.
Best regards,
Mingkan Zhang, Ph.D.
Vishaldeep Sharma
Praveen Cheekatamarla, Ph.D.
Reviewer #2
- Literature review/findings are to be written in past tense (pg. 1 row 45, please double check whole manuscript)
Literature review/findings are all changed to be in past tense, which are in line 44, 45, and 81.
- What is meant by high thermal efficiency? (pg 2, row 60), thermal performance could be a better alternative.
It has been revised to “performance” in line 62.
- Which commercial refrigeration system was considered.
The commercial refrigeration system could be vending machine, ice cream machine, fryer freezer, and so on. Commercial refrigeration device manufactures are switching to R-290 due to the low GWP refrigerant request. Therefore, the present work did not point to a specific commercial refrigeration system. The conclusions can be used in general commercial refrigeration systems.
- Methodology steps to be written in past tense (pg 2, row 92, see and correct at other places in the draft)
Methodology steps are all changed to be in past tense, which are in line 101, 102, 104, and 106.
- In the validation, it has been mentioned that the simulation model has been tested against experimental conditions where refrigerant leakage rate was 250 g/min. The size of leakage (diameter of leaking hole) for both experimental and simulated conditions should also be provided for clarity of readers. How about the size of refrigeration system for simulated and experimental cases? Do we know the total charge of refrigerant in the system (experimental) and the total time it took to leave the system??
The total charge was 1 kg, so it took 4 minutes to leak all R-32 from the RAC to the room. The leaking was from an indoor unit air outlet with dimensions of 0.6 m × 0.06 m in the experiment. The dimensions of the indoor unit were 0.6 m × 0.24 m × 0.3 m. The sentences have been added to lines 139 to 142.
- Was only one ventilation rate (50 CFM) was simulated? Any rationale behind selection of this ventilation rate?
A 50 CFM rating is recommended as a minimum for bathrooms 50 ft2 (4.6 m2).
Considering the room in present work is 6 m2, which is close to 4.6 m2, so the flow rate 50 CFM was chosen. Another consideration was that even if the relative low flow rate ventilation can help to reduce the flammable risk, a more powerful ventilation can do a better job. More flow rates will be considered in future work.
- In my opinion it would be better to mention concentration of R290 in PPM instead of volume fractions for figure 3 and other such figures in the draft.
The authors appreciate for the suggestion from the reviewer. However, we prefer to keep using volume faction because it is the key index to determine if the location is flammable or not. Therefore readers can directly using the contour to identify the flammable zone from the “volume fractions” figures.
Comments on the Quality of English Language
Overall sentence construction is quite good. In some sections however the tense needs to be corrected (see above comments in author's section).
All have been revised based on reviewer’s comments.
Author Response File: Author Response.pdf
