Study on the Movement and Deposition of Particles in Supercritical Water Natural Circulation Based on Grey Correlation Theory
Round 1
Reviewer 1 Report
Minor points:
Fig. 2. in legend description
Destiny è Density
Fig. 11. in legend description
Frain size è Grain size
Comments
1. Lines 145 -149, this study also includes the model establishment and grid divisions. As for grid divisions more explanation on analysis procedure and used method for grids sensitivity analysis is needed.
2. In the model verification section (Lines 396-418), a large error of 300% emerges due to entrance factor. I think the model is only valid near the outlet of the pipe but fail when it is applied in the inlet part. The axial distance of 0% ~ 40% is almost half of the pipe length. The authors state that the whole simulation results are still reasonable.
3. In the conclusions section, authors do not state the results of verification analysis. Do you think the model you propose is still accurate?
Author Response
1.More explanations were added.
The influence of the number of grids on the results can be judged by calculating the models with different grid numbers. In addition, the appropriate grid number is selected under the comprehensive consideration of accuracy and calculation efficiency. As the number of grids continues to increase from 1.1 million, the parameters such as fluid temperature, flow rate and particle concentration in the loop by the calculation remain basically unchanged, which is totally different compared with 0.66 million.
2.There is no entrance section in the simulation section. The specific explanation is as follows:
In the experiment, shear force exists due to the presence of the inlet part, and particles are continuously carried to the inside of the pipeline under the action of the shear force. It was not until the axial distance was about 40% that the effect of shear force on the particle concentration completely disappeared. In the simulation, because of its closed loop, there is no shear force caused by the inlet. Therefore, the part of the experiment where shear force does not exist should be compared with the simulation.
3.The results of verification analysis was added.
Compared with the experimental results, the simulation results show the same trend without considering the entrance factor, which shows that the simulation results are reasonable.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper, the authors perform a numerical simulation study of the movement and deposition of particles in supercritical water in a natural circulation loop. Different factors that can influence the dynamics such as heating power, initial concentration of particles and their diameter have been analyzed. The results obtained are compared with experimental data. The paper is properly structured and is clear in the explanation of the results. The figures selected are adequate to show the results.
In consequence, I recommend that the paper be published. My only suggestion is related to section 4.2. Model Verification. When the results of the simulation are compared with the experimental data of Keigo Karakama, there does not seem to be a similar behavior in the 0 - 50% range of axial distance. The authors attribute this to the fact that "in the process of the experiment, the particles in the entrance are difficult to deposit as a result of the large shearing force." To test this hypothesis, it would be convenient to perform a simulation by introducing this factor to see if the experimental results are reproduced. I think this would greatly improve the quality of the study shown.
Author Response
The reviewers' comments are very meaningful. Thank you very much!
Therefore, the calculation of the situation including the influence of entrance factors has been added.
In order to ensure the accuracy of the simulation, the heating section is calculated separately to introduce the inlet effect, which compared with the experimental results to verify the accuracy of the model. As shown in Fig. 16.
As shown in Fig. 16, in this case, the change trend of experiment and calculation is consistent. This result verifies the accuracy of the analysis on the influence of entrance factors in the paper. Therefore, the simulation results are reasonable.
Author Response File: Author Response.pdf
Reviewer 3 Report
Please see attached
Comments for author File: Comments.pdf
Author Response
The reviewers' comments are very meaningful. Thank you very much! The following are my modifications.
1. ‘Four-Generation’ to be ‘Fourth Generation’
2. “This paper mainly studies and analyzes the natural circulation in supercritical water reactors.” This sentence has been added to the introduction of the article. (line 41)
3. All are as follows:
KW to Kw
Line 80, “in the three-dimensional rectangular heat transfer channel” changed
Line 90, “.”added
144 “the equivalent diameter of the pipeline is 8mm and the wall thickness is assumed to be 0mm.”
145 “four kinds of grids”
178 The terms in eq (4) were modified as a result of running it in CFX was stated.
195 ” If the shapes of curves are different, the correlation between sequences is smaller.”
211-213 Where M signifies that determine the maximum value among the N absolute differences of the class j influencing factors, and then ascertain the maximum value of all absolute differences corresponding to the M influencing factors based on j = 1, ..., N. Where m signifies that determine the maximum value among the N absolute differences of the class i influencing factors, and then ascertain the maximum value of all absolute differences corresponding to the N influencing factors based on i = 1, ..., N.
227 ” Fig. 4.”
Fig.4 “check”
Fig. 5 temperature distrubtion. This paper studies the movement and deposition of particulate matter. However, in order to help readers understand the article, the temperature distribution of the whole circuit is added.(Fig.5)
245-248 “elbow 1 and elbow 2”
268-269 4.7 have showed correlation analysis of varied particle volume fractions, particle diameter and changes.
269-270 It is reality that the calculation is carried out when the volume fraction reaches 0.5%, the micron-sized particle diameter is found to be 1μm, and heating section reaches 700kW.
285-288 “However, the density of particles is much higher than that of water, resulting in the fact that the ability of particles to flow with fluid is poor under the action of gravity. Therefore, the concentration of particle in the vertical section is relatively low.”
299 ” equidistantly around the pipe wall”
Fig. 9 During the simulation, the model was simplified. The heating power is set as a boundary condition and has no correlation with particle concentration and particle size. Therefore, it is difficult to analyze the influence of particle distribution and size on the change of heating power.
355-357 “The reason….following the fluid flow” is not statement correct and was deleted.
359-361‘Concentrating’
375-377 The diameter is set as a boundary condition, and its value is artificially set and will not change in each calculation. Different particle diameters are set for calculation to analyze the influence of diameter on particle deposition. Particulate materials have been described in section 2.2, using stainless steel materials. If the particle expands, its diameter increases, but its weight does not change, which has little influence on the calculation results.
377-379 “The increase of particle size leads to the increase of gravity, which is not conducive to the circulation of particles and aggravates the deposition phenomenon of particles.”
385-386 ‘degree of correlation’ is not same as the ‘correlation resolution coefficient’. ‘degree of correlation’ means degree of correlation between variables and results. The "correlation resolution coefficient" determines the accuracy of the grey correlation degree calculation method. In theory, the resolution of grey correlation degree can be selected within a reasonable range. The smaller the value, the higher the accuracy, but the more complex the calculation. Generally, the recommended resolution is 0.5. In order to ensure the accuracy of the results, higher resolution calculation results of 0.2 and 0.1 are added.
391-392 The sensitivity of each variable to the degree of influence has been marked on the diagram. The type of particulate matter does have an impact on the results. However, considering that most of the particles in the supercritical water reactor pipeline are stainless steel particles falling off the pipeline, this paper mainly studies the effects of particle concentration, particle size and heating power on particle deposition.
396-418 The experimental conditions are different from the simulated boundary conditions, so the comparison between the two is mainly used to refer to whether the general trends are the same, not whether the comparison results are the same. Considering that the existence of the inlet effect does cause a large gap between the experimental results and the simulation results, the heating section is specially calculated separately to introduce the inlet effect. The two results were compared again.
419-440
The article does not involve the selection of particulate matter materials, but mainly focuses on the influence of the concentration of particulate matter, particle size and heating power of pipelines on the calculation results.
The selection of power in the reactor is not only determined by the deposition of particulate matter. If the power is increased blindly in order to reduce the deposition of particulate matter, it is unfavorable to the operation of the whole reactor. The results of this paper show that under the same conditions, using higher heating power within a reasonable range is more conducive to inhibiting the deposition of pipelines and ensuring the normal and stable operation of equipment.
Higher power may indeed increase the degree of correlation. However, the grey correlation method itself is not to obtain the specific correlation value, because the value changes continuously with the change of sample size. This method is mainly used to compare the effects of several variables on the results.
There are some other energy and transport models, which have been assessed.
1. Spalatrt-Allmaras model: The model applies aerodynamic problems (transonic flow), such as transonic flow on the wing surface. It is not suitable for solving shear flow and separation flow.
2. k-w model: The model can predict the propagation rate of free shear flow, such as wake, mixed flow, plate flow, cylinder flow and radial jet. Therefore, it can be applied to wall bound flow and free shear flow, and is not suitable for smooth flow of fluid in pipelines.
Thermophoretic force, viscous force, friction force, shear force, virtual mass force and saffman lift force are also considered. They are caused by different reasons respectively. In order to ensure the reliability of the results, the influence of relevant forces should be considered as much as possible.
Author Response File: Author Response.pdf
