You are currently viewing a new version of our website. To view the old version click .
MDPIMDPI
Search all articles
by
  • Hung-Tsung Tsai,
  • Bo-Jun Lu and
  • Yuh-Ming Ferng*
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous Reviewer 3: Rafał K. Wyczółkowski

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. Line 18: What data is being referred to here? Do you mean experimental data? Please clarify.

2. The first paragraph of the Introduction section should include relevant references to support the statements made.

3. After reading the Introduction, the research gap remains unclear. The necessity of this study should be articulated more clearly. Additionally, the specific objectives and contributions of the study should be presented in a more compelling manner.

4. All parameters used in the equations should be properly cited if the equations are not originally derived in this study. Furthermore, please explain the rationale behind the selection of these parameters.

5. The unmatched results in Fig. 12 should be explained and discussed more clearly. 

Author Response

Comments and Suggestions for Authors

  1. Line 18: What data is being referred to here? Do you mean experimental data? Please clarify.

Ans: Thanks for the reviewer’s comment.  The data in Abstract means the measured data that has been revised in the manuscript.

  1. The first paragraph of the Introduction section should include relevant references to support the statements made.

Ans: Thanks for the reviewer’s instruction. The relevant references supporting the statements in Introduction have been added.

  1. After reading the Introduction, the research gap remains unclear. The necessity of this study should be articulated more clearly. Additionally, the specific objectives and contributions of the study should be presented in a more compelling manner.

Ans: Thanks for the reviewer’s instruction.  The shortcomings of previous CFD works, and the specific objectives and contributions of present works have been revised and added in p. 8 of the revised manuscript.

  1. All parameters used in the equations should be properly cited if the equations are not originally derived in this study. Furthermore, please explain the rationale behind the selection of these parameters.

Ans: All of the parameter and the related empirical constants in the in the SSTKW turbulence model are based on the work of Menter (1994).  The missing reference has been added.

Menter, F.R. Two-equation eddy-viscosity turbulence models for engineering applications. AIAA J. 1994, 32, 1598-1605.

  1. The unmatched results in Fig. 12 should be explained and discussed more clearly. 

Ans: Thanks for the reviewer’s instruction. More discussion has been added in the last two paragraphs. (p. 19~21)

Reviewer 2 Report

Comments and Suggestions for Authors

This study presents the CFD results of heat transfer characteristics for a single-phase convection in a helical coil tube. The work presented is interesting but needs further clarity and modification before it can be considered for publication. Here are my comments:

  1. Please clearly list all assumptions considered in the model.
  2. I advise the authors to include Richardson Extrapolation for the grid sensitivity analysis.
  3. It is not clear what is the basis of the physical model, including the boundary conditions. It would be good to include a justification for these.
  4. It would be good to provide a schematic showing the boundary conditions.
  5. For the mesh sensitivity, I advise the authors to monitor other parameters, such as velocity.
  6. Please provide details of the mesh, such as element type, quality, skewness, and other important metrics.
  7. Please elaborate on the discussion regarding the discrepancy of peak temperature in Figures 8 and 9.
  8. It is not clear how shell-side modelling has been performed. Please clarify.

Author Response

Comments and Suggestions for Authors

This study presents the CFD results of heat transfer characteristics for a single-phase convection in a helical coil tube. The work presented is interesting but needs further clarity and modification before it can be considered for publication. Here are my comments:

  1. Please clearly list all assumptions considered in the model.

Ans: Per the reviewer’s suggestion, the assumptions have been listed before the presentation of all the governing equations.

  1. I advise the authors to include Richardson Extrapolation for the grid sensitivity analysis.

Ans: Thanks for the reviewer’s instruction.  Based on the BPGs [1] for CFD in the nuclear safety analysis, the mesh-independent calculations or the mesh uncertainty (i.e. Richardson Extrapolation) should be performed. For the CFD simulations with the simple structured grids, our research team prefers to perform the mesh-independent tests.  Consider the CFD with the hybrid structured /unstructured mesh model, the mesh uncertainty would be estimated.  The former simulations can appear in our works [2, 3] and the latter ones are shown in the works of our team[4, 5].  Therefore, in the present CFD simulation with the structured grids, the mesh-independent calculations are only adopted.

[1] NEA. Best practice guidelines for the use of CFD in nuclear reactor safety applications- revision. 2022, NEA/CSNI/R(2022).

[2] Y.H. Tsai, Y.M. Ferng*, Development of computational methodology in simulating thermal responses of spent fuel in deep geological disposal, Nuclear Engineering and Design, 415 (2023) 112671.

[3] Y.M. Ferng, W.C. Lin, C.C. Chieng, Numerically investigated effects of different Dean number and pitch size on flow and heat transfer characteristics in a helically coil-tube heat exchanger, Appl. Therm. Eng. 36 (2012) 378-385.

[4] B.J. Lu, Y.M. Ferng et al., Thermal management design for the Be target of an

 accelerator-based BNCT system using numerical simulations with boiling heat transfer models, Processes 2025 (13) 1929.

[5] Y. Wang, Y.M. Ferng, L.X. Sun, CFD assist in design of spacer-grid with mixing-vane for a rod bundle, Appl. Therm. Eng. 149 (2019) 565-577.

  1. It is not clear what is the basis of the physical model, including the boundary conditions. It would be good to include a justification for these.

Ans: Thanks for the reviewer’s instruction. The physical models for the single- phase thermal-hydraulic characteristics in a HCT include the conservation equations of mass, momentum, and energy, as well as the appropriate SSKW turbulence model. The boundary conditions are illustrated in Table 2 and are also schematically added in Fig. 1.

  1. It would be good to provide a schematic showing the boundary conditions.

Ans: Per the reviewer’s suggestion, the boundary conditions (BCs) have been schematically added in Fig. 1.

  1. For the mesh sensitivity, I advise the authors to monitor other parameters, such as velocity.

Ans: Thanks for the reviewer’s suggestion. The most important parameter for the present simulation work is the circumferential distributions of wall temperature. Therefore, this parameter is selected to confirm that the simulation results of wall temperature are mesh-independent.   

  1. Please provide details of the mesh, such as element type, quality, skewness, and other important metrics.

Ans: Thanks for the reviewer’s instruction.  The mesh skewness is the basic constraint for the CFD simulation, especially for the Fluent code.  The Fluent can prohibit the simulation with the higher values of skewness. Therefore, the authors just confirm if the mesh skewness meets the Fluent’ requirement, which is just suitable for the Technical report and would not present this result in the Journal paper. Based on the Best Practice Guidelines, the structured mesh is preferred to be accepted. All the mesh is set to be the structured one (Fig. 2) in which most of the mesh skewness is generally less than 0.3.  In addition, the concept of mesh element is adopted in some CFD codes and the mesh number is suitable for all the CFD codes. Therefore, the present paper just present the mesh number and distribution.

  1. Please elaborate on the discussion regarding the discrepancy of peak temperature in Figures 8 and 9.

Ans: Based on the data of Case 1, the peak wall temperature at x = -0.147 is measured to occur at f = 270o.  This result is obtained from the 8 discrete points measured on the peripheral tube wall, which provide the circumferential distribution of wall temperature.  However, as shown in Fig. 8 (c), the peak wall temperature is predicted to be located at f ~ 308o.  This result is observed in the line curve of circumferential wall temperature that consist of 64 predicted points (standard mesh in Fig. 2).

More discussion is added in p. 16 & 17 of the revised manuscript.

  1. It is not clear how shell-side modelling has been performed. Please clarify.

Ans: Thanks for the reviewer’s comment.  More detailed description about the shell-side modeling has been added in p. 20 & 21 of the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

I am sending my comments as an attachment

Comments for author File: Comments.pdf

Author Response

Please see the attached file

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I don't have any more comments. The authors have adequately addressed the comments raised by the reviewer.

Reviewer 3 Report

Comments and Suggestions for Authors The authors have responded comprehensively to my previous comments.
I have no further comments on the revised version of the article and request that it be submitted for publication in a journal.