Numerical Optimization of a Microchannel Geometry for Nanofluid Flow and Heat Dissipation Assessment
, César Rocha 2, Reinaldo R. Souza 2, Gonçalo Coutinho 1, Jose E. Pereira 1, Ana S. Moita 1,3,*, António L. N. Moreira 1, Rui Lima 2,4 and João M. Miranda 4Round 1
Reviewer 1 Report
The article is quite interesting as it concerns the influence of various solutions of supplying bundles of parallel microchannels on the uniformity of the flow. The authors also consider the influence of the shape of the supply manifold on single-phase flow and heat transfer in microchannels.
Comments:
- the formatting of the equations should be corrected,
- explain what is the standardized flow rate, and the symbols ql and q med,
- in line 291 there are 2 q,
- line 298 has a double bracket,
- in the description of the fig. 6 millilitres should be ml, not mL,
- in fig. 7 the description of the y-axis should be corrected, description should be vertical,
- it would be good to indicate the discrepancy between the results of simulation and experimental research,
- fig. 12-14, on the x-axis there should be "channel no.",
- why is the circular and triangular shape of the supply manifold not taken into account in Fig. 10?
- the influence of shape on heat transfer was not taken into account, which is emphasized in the abstract,
Author Response
Authors would like to acknowledge to the reviewer for the careful review and for the very relevant comments, that we addressed in the revised version of the manuscript. Minor corrections are shown in track changes and most relevant corrections are also highlighted in yellow. Here is a point-by-point answer to the comments addressed:
The article is quite interesting as it concerns the influence of various solutions of supplying bundles of parallel microchannels on the uniformity of the flow. The authors also consider the influence of the shape of the supply manifold on single-phase flow and heat transfer in microchannels.
Comments:
- the formatting of the equations should be corrected,
Reply: The formatting of the equations was corrected.
- explain what is the standardized flow rate, and the symbols ql and q med,
Reply: The standardized flow rate is the ratio between the flow rate of the channel I and the mean flow rate. This explanation was introduced in the point 2.5.
- in line 291 there are 2 q,
Reply: One of the qs in line 291 was deleted.
- line 298 has a double bracket,
Reply: The extra bracket was deleted.
- in the description of the fig. 6 millilitres should be ml, not mL,
Reply: The description of the figure 6 was corrected.
- in fig. 7 the description of the y-axis should be corrected, description should be vertical,
Reply: The description was corrected to vertical.
- it would be good to indicate the discrepancy between the results of simulation and experimental research,
Reply: The most marked discrepancy between the temperature difference was referred in the text.
- fig. 12-14, on the x-axis there should be "channel no.",
Reply: The X-axis legend of the Figures 12, 13 and 14 were corrected.
- why is the circular and triangular shape of the supply manifold not taken into account in Fig. 10?
Reply: Because the rectangular shape was the one that provided greater uniformity of the distribution of the heat transfer in the microchannels, as it was highlighted in the abstract and in the text now introduced in the point 3.2. Because of this, figure 10 and others present only the rectangular shape.
- the influence of shape on heat transfer was not taken into account, which is emphasized in the abstract,
Reply: The influence of the shape was taken into account as it was explained in the previous reply.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
Many thanks for your submission. You did an interesting work. However, you need to revise it according to below comments:
1- Please provide reference and the version for COMSOL. It is not acceptable to not mentioning the version of it and also the reference of it in the reference list!
2- Figure 2 shows the mesh of your work! Isnt it that coarse! Are you sure that this works!
3- For figure 3 you need the inflation layers for each junctions not only the main one! Moreover, what is the colorful legends relate to! Please put its title.
4- Why you used tetra mesh not quad! I can see that your geometry is very simple! Could be better to run with quad to see how fast you get the convergence!!
5- on Figure 4 or any figure that you like please show the inlet, outlet, etc.
6- All your figures are not prepared well! for Figure 6 on the legend of it please mention it is T and the dimension is []. All CFD papers have the same rules!!
7- Figures 8, 12, 13, 16, and 20 please mention the magnitude of the vectors. Please provide complete figures.
8- Please follow the comment 6 for figure 22 as well. Since they have the same legends remove the other 2 and keep one of them.
Author Response
Authors would like to acknowledge to the reviewer for the careful review and for the very relevant comments, that we addressed in the revised version of the manuscript. Minor corrections are shown in track changes and most relevant corrections are also highlighted in yellow. Here is a point-by-point answer to the comments addressed:
Many thanks for your submission. You did an interesting work. However, you need to revise it according to below comments:
1- Please provide reference and the version for COMSOL. It is not acceptable to not mentioning the version of it and also the reference of it in the reference list!
Reply: The version COMSOL Multiphysics 5.6® was identified in the text. The respective reference was added. Thank you for the comment.
2- Figure 2 shows the mesh of your work! Isnt it that coarse! Are you sure that this works!
Reply: This mesh is presented for illustrative purposes to explain that the mesh is constituted by a core and a layer near the walls. Mesh tests were performed to select the mesh density suitable for the computations, as it is now explained in the manuscript. The flow simulations were performed with a denser mesh (mesh A4, Table 1).
3- For figure 3 you need the inflation layers for each junctions not only the main one! Moreover, what is the colorful legends relate to! Please put its title.
Reply: The colorful legend is referred to temperature (°C). This was made clearer in the revised version of the manuscript. The temperature profile of the inflation layers of the rectangular manifold profile was presented in figure 22. The goal of the figure 3 is to show only the mesh in some details of the support manifold. While it is not completely perceptible in the figure, the mesh is denser in all junctions between mesh subregions.
4- Why you used tetra mesh not quad! I can see that your geometry is very simple! Could be better to run with quad to see how fast you get the convergence!!
Reply: The domain is a 3D geometry with a solid and a fluid domain. The fluid domain comprises different sub-domains with different shapes. The surfaces connecting the different sub-domaisn have also different shapes. The construction of a hexaedrical mesh using Clomsol was challenging and we opted for a tetrahedral mesh, which is easier to generate. Anyway, the meshes used can produce accurate results, as demonstrated by the mesh tests.
5- on Figure 4 or any figure that you like please show the inlet, outlet, etc.
Reply: Figure 4 was modified as requested.
6- All your figures are not prepared well! for Figure 6 on the legend of it please mention it is T and the dimension is []. All CFD papers have the same rules!!
Reply: T[°C] was added to the colorful legends of figure 6 and figure 22.
7- Figures 8, 12, 13, 16, and 20 please mention the magnitude of the vectors. Please provide complete figures.
Reply: Figures 8, 12, 13, 16 and 20 are now completed with the indication of the magnitude of the velocity vectors.
8- Please follow the comment 6 for figure 22 as well. Since they have the same legends remove the other 2 and keep one of them.
Reply: The colorful legends have the same magnitude. Only the value 60 °C was missing in two of them, but it was added in the revised version of the manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
This manuscript describes an original and interesting work. As such, it has the potential to be published in Applied Sciences. However, I have the following comments that the authors should implement in the revised manuscript before publication.
1) Introduction – Micro-devices are also used for power generation. In order to give a more complete picture, in the revised Introduction, the authors should highlight that the scaling down from macro to micro leads to several issues of thermal management also for micro-combustors, pushing the need for optimization of their geometry. In this regard, the following works should be cited: Catalysis Today, Volume 155, Issue 1-2, 2010, Pages 116-122; Catalysts, Volume 10, Issue 6, 2020, Article number 606.
2) Geometry, computational domain and mesh – It would be nice to see the results obtained with the different meshes tested to select the mesh to be used in the computations.
3) Results and Discussion – In order to give more strength to the work, in the discussion, the authors should link their results to the literature results, where appropriate.
4) Results and Discussion/Concluding Remarks - The practical impact of the results obtained in this work should be better highlighted.
I’m willing to review the revised manuscript.
Author Response
Authors would like to acknowledge to the reviewer for the careful review and for the very relevant comments, that we addressed in the revised version of the manuscript. Minor corrections are shown in track changes and most relevant corrections are also highlighted in yellow. Here is a point-by-point answer to the comments addressed:
This manuscript describes an original and interesting work. As such, it has the potential to be published in Applied Sciences. However, I have the following comments that the authors should implement in the revised manuscript before publication.
1) Introduction – Micro-devices are also used for power generation. In order to give a more complete picture, in the revised Introduction, the authors should highlight that the scaling down from macro to micro leads to several issues of thermal management also for micro-combustors, pushing the need for optimization of their geometry. In this regard, the following works should be cited: Catalysis Today, Volume 155, Issue 1-2, 2010, Pages 116-122; Catalysts, Volume 10, Issue 6, 2020, Article number 606.
Reply: The introduction was revised, and the suggested works were added and cited.
2) Geometry, computational domain and mesh – It would be nice to see the results obtained with the different meshes tested to select the mesh to be used in the computations.
Reply: A preliminary mesh independency study was indeed performed, which we chose not to introduce in the paper, as it would make it significantly longer. However, the revised manuscript now explains that such study was performed and details the choice of the type of meshes for the fluid flow and heat transfer simulations.
3) Results and Discussion – In order to give more strength to the work, in the discussion, the authors should link their results to the literature results, where appropriate.
Reply: The results and discussion section was revised and the comparison with the literature was stressed whenever it was possible. Hence, there were added more literature references, when the results found in those references are consistent with the ones obtained in this work.
4) Results and Discussion/Concluding Remarks - The practical impact of the results obtained in this work should be better highlighted.
Reply: The practical impact of the results obtained here was highlighted in the conclusions. Thank you for the comment.
I’m willing to review the revised manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Dear Authors,
Many thanks for the revised version. All my comments have been properly addressed and in the revised version, I can see huge improvement compare to their original draft.
Reviewer 3 Report
The authors have addressed my comments in a satisfactory manner. Overall, the manuscript has been improved after revisions. Therefore, it can be accepted for publication in Applied Sciences.
Minor - The name of the journal for Reference [7] is Catalysts (not Catalysis).
