Risk Assessment of Explosion Accidents in Hydrogen Fuel-Cell Rooms Using Experimental Investigations and Computational Fluid Dynamics Simulations

Round 1

Reviewer 1 Report

Dear Authors,

In your manuscript risk assessment of explosion accidents in Hydrogen Fuel-Cell rooms are presented through experimental investigations and computational fluid dynamics simulations. The topic is investigated from both experimental and computational sides. There are no major issues detected. In order to improve the quality of the manuscript you might consider providing some details of the measuring equipment used and some basics for error analysis. Also, there is a missing URL in reference 40.

Author Response

Reviewer 1

Thank you for taking your time and giving fruitful comments. We tried to give an answers for each comments as following. Thank you very much.

C1: In your manuscript risk assessment of explosion accidents in Hydrogen Fuel-Cell rooms are presented through experimental investigations and computational fluid dynamics simulations. The topic is investigated from both experimental and computational sides. There are no major issues detected. In order to improve the quality of the manuscript you might consider providing some details of the measuring equipment used and some basics for error analysis. Also, there is a missing URL in reference 40.

A1: Thank you for your comments. Manuscript is updated based on the comments(details of measuring equipment, URL of ref. 40).

Author Response File: Author Response.docx

Reviewer 2 Report

This paper reports an important study. The paper is well organized and the data has been presented systematically. It can be accepted for publication.

1.      Abstract: “Research quantifying blast loads resulting from such accidents is lacking”. This sentence must be rephrased.

2.      Line 28: “……..themselves to increasing their intended nationally……….” The “increasing” should be “increase”.

3.      Line 124: “A plastic sheet of thickness 2 mm was attached to the frame of the wooden door for this experiment”. Both plastic and wood catch fire, so how these substances can be used in blast experiments?

4.      Similarly, the other experimental set up like nozzles, pressure measuring device etc may also be damaged during experiment.

5.      Section 2.2: “the flame spreading from the ignition source was visually measured to be approximately 3 m in the horizontal direction” How can it be measured???

6.      Line 138: “During the explosion, a part of the plastic sheet caught on the pressure gauge (P1)……” What does it mean??

7.      In section 2.2, the pressure has been measured as a function of distance. However, Figure 5 shows the pressure as a function of time. There seems to be some contradictions.

8.      Several mathematical equations are given in the paper, but none of these has been applied to the experimental data.

It is acceptable.

Author Response

Thank you for taking your time and giving fruitful comments. We tried to give an answers for each comments as following. Thank you very much.

C1:  Abstract: “Research quantifying blast loads resulting from such accidents is lacking”. This sentence must be rephrased.

A1: This sentence is deleted because flow in abstract is better without this sentence.

C2: Line 28: “……..themselves to increasing their intended nationally……….” The “increasing” should be “increase”.

A2: Increasing is changed to increase, thank you very much.

C3:  Line 124: “A plastic sheet of thickness 2 mm was attached to the frame of the wooden door for this experiment”. Both plastic and wood catch fire, so how these substances can be used in blast experiments?

A3: Blast lasts for short time(e.g., 20~50 ms). So, wooden door can withstand during an explosion. But plastic sheet is not. It plays in holding hydrogen-air mixture before explosion. After explosion, plastic sheet is gone.

C4: Similarly, the other experimental set up like nozzles, pressure measuring device etc may also be damaged during experiment.

A4: All of devices in experiment are explosion proof device. So, it is presumed that explosion damage can be avoided during experiment.

C5: Section 2.2: “the flame spreading from the ignition source was visually measured to be approximately 3 m in the horizontal direction” How can it be measured???

A5:  This sentence should be changed as below. It is updated in manuscript. Thank you.

visually measured to be approximately 3 m in the horizontal direction

èvisualized

C6: Line 138: “During the explosion, a part of the plastic sheet caught on the pressure gauge (P1)……” What does it mean??

A6: Initially plastic sheet sticks to door opening. But once explosion happens, it is flying off. Since pressure gauge(P1) is just 1m apart from door opening, plastic sheet stuck on the pressure gauge(P1).

C7: In section 2.2, the pressure has been measured as a function of distance. However, Figure 5 shows the pressure as a function of time. There seems to be some contradictions..

A7: Figure 5 shows overpressure as a function of time at difference location such as 1m, 2m, 3m, 5m away from structure. Figure 9 is exactly shows overpressure as a function of distance.

C2: Several mathematical equations are given in the paper, but none of these has been applied to the experimental data.

A2: Numerical simulation was done after analyzing the experimental data. It is because experimental data couldn’t provide reason why form of pressure wave depending on time shows different peak and physics. To observe and find reason, simulation was done. So, it is not directly connected to experimental data. Rather, it supports physical evidence in explosion experiment.

Author Response File: Author Response.docx

Reviewer 3 Report

Currently, there is a strong development of hydrogen technologies. Issues related to the safety of work with hydrogen should have a special priority. The presented manuscript presents the modeling and experimental results of the impact of the shock wave and the heat wave on the destruction/damage of the human body depending on the concentration of hydrogen in the air. The presented results are very valuable, they are presented and discussed in a systematic and reliable manner. I recommend accepting it in its present form.

Author Response

Thank you for taking your time and giving fruitful comments. We tried to give an answers for each comments as following. Thank you very much.

C1:  Currently, there is a strong development of hydrogen technologies. Issues related to the safety of work with hydrogen should have a special priority. The presented manuscript presents the modeling and experimental results of the impact of the shock wave and the heat wave on the destruction/damage of the human body depending on the concentration of hydrogen in the air. The presented results are very valuable, they are presented and discussed in a systematic and reliable manner. I recommend accepting it in its present form.

A1: Thank you for your kind comment.

Author Response File: Author Response.docx