Model for Cryogenic Flashing LNG Leak

Round 1

Reviewer 1 Report

This paper reads more like a company or consultant report. It does not try to discuss the finding in any academic meaningful way.  The discussion is basically a small paragraph. It does not discuss the finding in the context of the current  discourse on this subject.

There is described an easy and direct method of calculation which is always interesting to the practitioner but how it all fits into the overall context of such leaks (which is large and varied) I see very little commentary.

From a technical point of view I would have liked to hear more about what pressures were involved and very importantly the velocity immediately after exit (subsonic/transonic/supersonic).

In its present form I would not like to see this paper published.

 

 

Author Response

see attached file

Author Response File: Author Response.docx

Reviewer 2 Report

Hi,

Very interesting publication

The authors report the different grid sizes used and that the solution is grid independent within 5%. However,  it would be interesting to know the area (A3) of the leak used, to verify this against the  grid refinment guidelines for leaks as described in the FLACS documentation. . Also. was the grid of constant grid size or was it refined locally around the leak ?

Also, V3 is arbitrarily set as ¼ of V2. This is a valid assumption as long as the vaporization process is completed at that point. It would be interested to see if the results are sensitive to this choice, (This could be examined in future work) 

Author Response

see attached file

Author Response File: Author Response.docx

Reviewer 3 Report

Leakage of the cryogenic LNG fuel will lead to potential fatal fires. This work numerically investigated the process of leakage of cryogenic LNG using a commercially available software FLACS. The employed leak model which consists 9 equations is constructed by combining data from recently performed SPARCLING experiment and the Isenthalpic Homogeneous Equilibrium Model. Predicted results compared with TR56, Singapore safety guideline for LNG bunkering to verify the accuracy of the employed leak model.  Comparison shows that the dispersion result does not contradict the expected plume reach. However, as stated by the authors, further validation with risk analysis tools and actual experiments are needed to confirm the leak model. Some comments on this work are:

• The authors should state how they exactly determine the expansion zone. In my opinion, this zone should related to the mass flow rate, temperature and pressure in the tank etc.
• Both the liquid and gas phase temperatures are set to LNG ambient boiling temperature at the end of the expansion zone. The reason should be given.
• Plot of contour of temperature should be given.
• English editing should be improved, for example, on line 88, “given the vaporization occur rapidly…” should be “given the vaporization occurs rapidly…”.

On the whole, this manuscript is well organized, and adopted models, control equations and procedures for the simulation were well structured. 

Author Response

see attached file

Author Response File: Author Response.docx

Reviewer 4 Report

The article concerns the modeling of outflows and dispersion of LNG releases using FLACS software and presents the traditional leak model and calculations of hazard distances used in the LNG industry.

In my opinion, the scientific value of this article is negligible. Lack of literature review of the leak and dispersion models, very cursory analysis of the results obtained, and very poor summary of the work,  disqualify this manuscript for printing in Applied Sciences.

1. The title of the article does not fully correspond to the content of the work.
2. The introduction section should be reorganized to clearly point out the limitations of our current knowledge, and also the scientific goal and contribution of this study.
3. Literature review of the leak and dispersion models should be presented as well as LNG leaking experiments should be analyzed and summarized more accurately. Novelty and significance of work need to be highlighted.
4. In the abstract and introduction sections, 5 sentences are the same.
5. Results (velocity, mass flow rate…) obtained from the leak model for analyzed scenarios should be presented.
6. Why authors used 9 mm and 25 mm leak diameters?
7. What kind of dispersion model was used and why?
8. Why did the authors assume that LNG consists of 100% methane? It also contains small amounts of ethane, propane, butane, some heavier alkanes, and nitrogen. How this assumption influences the results of mass flow rate and LFL distance?
9. The conclusion should better reflect the content of the paper and the main results. Define better conclusions, it should vary vague and support better what the innovation is, the unique finding of this work as compared to similar works in international literature done through the years.
10. The titles of references have a different format, the title of the article is written in capital letters at the beginning of words, others only in lower case. Also, the standardized format of presentation in the journal's name. Because names have been written in a different format, one is not abbreviated, others are not.
11. Proofreading and linguistic style are recommended.

 

Author Response

see attached file

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Can now be published

Author Response

We would like to thank you reviewer # 1 for your guidance in making the manuscript better.

Reviewer 4 Report

1. Figure 7 in the manuscript is unreadable, which makes it difficult to read and analyze. Please improve it quality.
2. Some previous researchers studied the LNG  and are not acknowledged and discussed within the paper.  I suggest the authors include references like e.g. https://doi.org/10.1016/j.jlp.2012.07.020; 
3.  The Authors have effectively replayed all of the remarks, suggestions, comments and improved the manuscript after the first round. Congratulations. 

Author Response

We would like to thank reviewer # 4 for your guidance in making the manuscript better.

Author Response File: Author Response.docx