Flow Boiling in Minigap in the Reversed Two-Phase Thermosiphon Loop

Round 1

Reviewer 1 Report

In the introduction section the literature review is very limited to few studies, for example in lines 27-28 the authors describes the issues of the system but they do not give any reference to previous article that exhist on this.

It is not clear what is the novelty of the study compared to what have been done before.

The experimental set-up is described very poorly, for example the model of the flow visualization camera is not mentioned in the text.

The authors do not describe the experimenta procedure. How the test were performed from the starting point to the end?

The data reduction procedure is not outlined. How the variables of interest have been evaluated?

In the Results part, many explanations are missing and the level of detail and description given is not adequate for a scientific article. The authors refer to the M-shape curve. This trend was obtained experimentally by some previous studies in the literature, and it is associated to the heat transfer coefficient versus the local vapor quality. In literature there are many different trends that show the heat  transfer coefficient versus the local vapor quality, and the M-shape trend is just one of the available explanations. Why the authors selected this one and not considered the others? This is not explained, but it is very important.

Moreover, the author try to compare the M-shape trend of heat transfer coefficient (from the literature) with a M-shape trend of the heat flux (from their experiments). Why the authors believe that the trend of the heat flux must be equal to the heat transfer coefficient one? This would mean that the temperature difference between the wall and the fluid remains constant, so how the authors justify this assumption?

In Table 1 it is not clear why the authors presented "Partial uncertaintes". The uncertaintes of variables such as heat flux and vapor quality must be indicated, since the majority of plots show heat flux and vapor quality. Thus, what is the accuracy on the experimental results?

In the Discussion section, point 1. The filling level is always crucial for the efficiency and the operation of thermosyphon systems. For example at very low or high filling ratio, the recirculation may stop. The authors claim that it is not a critical parameter, but it is not explained how he demonstrated that. Do the authors tested the limit conditions? 

Author Response

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Reviewer 2 Report

In this work, the authors demonstrated the experimental results of flow boiling of the minigap heat exchanger in a reversed two-phase thermosyphon loop. The behavior of flow inside evaporator was illustrated well and the work shows the interesting results to researchers in this field. But reviewer have a feeling that the paper was written in hurry. Some important parts of experimental research are lacked. The authors should consider the following comments to improve the quality of the manuscript.

The data reduction is an important part in this kind of work. Therefore, the authors need to implement how to calculate related parameters such as the heat flux, vapor quality, the percentage filling … Also, the authors should point out the percentage filling is based on what parameter (volume fraction or mass fraction) The heat balance process in evaporator should be described. The Weber number is defined by equation 1, but this state does not match with the content in the manuscript. Part 4 should be “Conclusion” instead of “discussions” as reviewer's understanding. Some typos should be also corrected in the paper. Some figures should be reproduced in better quality. The uncertainty analysis should also include the calculated parameters such as heat flux, vapor quality. Even the experimental results are significant, the range of testing condition (range of heat flux, mass flux, etc.) was not implemented. Also, Reviewer suggest that the effect of heat flux should be described more clearly.

 

Author Response

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Round 2

Reviewer 1 Report

Dear Authors,

 

I believe that with the new modifications implemented in the text, the article is now more complete and exhaustive. 

Your explanations and answers to my question were clear.

 

Best Regards

Author Response

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Reviewer 2 Report

The content of the paper has been improved. However, the data reduction should be described in the paper. Also, the data of heat balance process should be provided. 

Author Response

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