Thermohydraulic Performance of Chevron Pin-Fins
Round 1
Reviewer 1 Report
Dear Authors,
The term k* in Equation (15) should be the thermal conductivity of the aluminum and not the the ratio between the thermal conductivity of the aluminum and the thermal conductivity of the water. This equation refers to the heat conduction inside the Aluminum. Since this equation is equal to zero, k* can be removed.
The temperatures values appearing in the color scale in figure 13 looks very small. It should be explained. The units of the temperature should be shown in this figure.
Author Response
Reviewer#1
Question#1
The term k* in Equation (15) should be the thermal conductivity of the aluminum and not the the ratio between the thermal conductivity of the aluminum and the thermal conductivity of the water. This equation refers to the heat conduction inside the Aluminum. Since this equation is equal to zero, k* can be removed.
Answer#1
I was asked by a reviewer to add the conduction equation. In COMSOL the conducting equation is shown as in equation 15. Now within COMSOL, the model is always solved in transient mode even if we are solving it at steady state condition. Thus k* must be supplied to COMSOL code and if you convert the transient heat conduction to non-dimensional as is this case, k* will be obtained.
Question#2
The temperatures values appearing in the color scale in figure 13 looks very small. It should be explained. The units of the temperature should be shown in this figure.
Answer#2
In figure 13, the temperature had large font but the journal require reducing the size thus it is small but still readable. The temperature is shown in non-dimensional form. Thus no unit will be shown
Reviewer 2 Report
Authors have addressed all the comments.
Author Response
Reviewer#2
Authors have addressed all the comments.
Thank you so much
Reviewer 3 Report
Pin-fin made of solid and porous cylindrical shape forming chevron was investigated numerically using the finite element method. The design consisted of 3-chevron and 5-chevron configurations connected to a heated block with fluid circulating between the chevron and above them. Variable Reynolds number and pin-fins height ranging from 2mm to 8mm were investigated. The full Navier-Stokes equation combined with the energy equation was solved in the presence of the solid pin-fins. The Darcy Brinkman model with the effective energy equation was used in the presence of the porous pin-fins. The system was solved for Reynolds numbers ranging from 50 to 1000 thus remaining in the laminar regime. Results revealed that the best performance evaluation criterion was higher for the 8 mm porous pin-fins regardless of their permeability. However, some disadvantages are still not be addressed:
(1) Figs. 4-12 are vague. The authors have to modify them.
(2) The English writing of the paper is required to be improved. Please check the manuscript carefully for typos and grammatical errors. The reviewer found some typos and grammatical errors within this manuscript, which have been excluded from my review. In addition, the English structure of the article, including punctuation, semicolon, and other structures, must be carefully reviewed.
(3) The authors have to show their related computation equipment in the study.
(4) The reviewer concerns about the error analysis of the proposed method in the revision.
(5) The authors have to compare their results with the other literature and present the accuracy.
Author Response
Reviewer#3
Question#1
Figs. 4-12 are vague. The authors have to modify them.
Answer#1
You did not mentioned why they are vague. I completely disagree with you . We have explained each graph in details. Thus I reject your question.
Question#2
The English writing of the paper is required to be improved. Please check the manuscript carefully for typos and grammatical errors. The reviewer found some typos and grammatical errors within this manuscript, which have been excluded from my review. In addition, the English structure of the article,including punctuation, semicolon, and other structures, must be carefully reviewed.
Answer#2
We have run grammarly in the manuscript and no major English was detected. We have added few commas and shown in violet color. English writing can have different style. I leave it to the publisher to check via their expert
Question#3
The authors have to show their related computation equipment in the study.
Answer#3
No one these days talk about what computer has been used for computation. Nowadays any laptop can perform better than an old large computer
Question#4
The reviewer concerns about the error analysis of the proposed method in the revision.
Answer#4
I am not sure which error analysis is of your concern. We have in the manuscript equation 17 which highlight the convergence criteria. No experimental work is done to worry about errors of measurement.
Question#5
The authors have to compare their results with the other literature and present the accuracy.
Answer#5
We have compared our work with experimental data. This is the best accuracy one can do. We have also done some mesh sensitivity analysis and it is proven to be correct.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The paper presents numerical study of heat transfer performance of chevron pin-fins. The idea is of interest, however, there are several issues need to be addressed:
- Model is not validated against any experimental data.
- Thermophysical properties should be temperature dependent.
- Mesh independence test is missing
- How does porosity, permeability and inertial resistance be calculated/assumed?
Author Response
Dear Colleague
Thank you for taking the time to read our paper and thank you for teh constructive comments. Attached please find answers to your inquiries
Best regards
Ziad
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This work deals with optimum design effectiveness in heat removal for small surfaces. Pin-fin made of solid and porous cylindrical shape forming chevron is studied numerically by applying the finite element method. It is based on previous paper published in International Journal of Heat and Mass Transfer (reference [20]), which showed the results of experimental and numerical study of the use of aluminum foam as a heat sink for the Intel core i7 processor. In the framework of this research, COMSOL Multiphysics software has solved numerically three Steady-state transport equations: Continuity, Navier-Stokes and Energy equations. The heat conduction equation of the solid material hasn’t been solved. For the porous case, the Darcy-Brinkman model has been used. It is assumed that Reynolds numbers ranging from 50 to 1000. Thus the water flows in laminar regime. Two critical parameters have been studied in this analysis. The variable pin-fins height is implemented to investigate whether the higher the pin fins, the better heat performance. The second is the replacement of the solid pin-fins with porous pin-fins having three different permeabilities of 10 PPI, 20 PPI, and 40 PPI, respectively. The authors have carried out optimization of the mesh size of the model. There are several issues which haven’t been addressed in this work. It is recommended to reconsider this paper for publication, after performing the following major revisions.
Comments and Suggestions for Authors
1) The novelty of this study should be discussed.
2) (Line no. 225) the word “permeability” should be replaced with the word “permeabilities”
3) (Section 2 lines no. 230 - 246) the author should specify the numerical values of the thermo-physical properties of the water (i.e. density, thermal conductivities of the fluid and solid material, heat capacity, prandtl number, viscosity etc.).
4) (Section 3) There are abbreviations and variables used in this paper which haven’t been defined (For example Da number – probably it is Darcy number). They should be defined and explained before the introduction section or before the References section.
5) (Line no. 286) the heading of section number 3.1 should be renumbered.
6) (Section 3.1) what are the boundary conditions used to solve the Navier Stokes and Darcy-Brinkman equations? What is the value of inlet pressure?
7) (Section 3 Lines no. 248 - 270) the heat conduction equation of the solid material is missing (In COMSOL multi-physics software it is possible to couple the heat conduction with the other transport equations of the fluid). The author didn’t address the issue of water temperature. Is the water boils? If boiling occurs, then COMSOL should solve two phase flow equations. The author should elaborate the assumptions used in the computational algorithm.
8) (Line no. 254) the heading entitled “Momentum equation along X-direction” should be moved to the following page (page 7)
9) (Line no. 267 – Eq. (10)) the closing parenthesis is missing.
10) (Line no. 283 – Eq. (14)) the closing parenthesis is missing at right hand side of Eq. (14).
11) (Line no. 343 – Eq. (17)) this equation should be referenced.
12) (Line no. 364 – Eq. (19)) I have substituted the symbolic value of Pr number and the Renumber and theta. I have obtained the following equation:
Pr*Re*(theta_out-theta_in)=rho*Cp*V*L/(q”*De)*(Tout-Tin)=(Removed Heat flux)/(Supplied heat flux). In my opinion this term is the ratio between the heat flux removed and the supplied heat flux. Figure 11a clearly shows that for small values of Reynolds number this ratio decreases. For large number of Re number, the removed heat flux is larger than the supplied heat flux.
13) (Section 4 Results and Discussion section) the two dimensional temperature fields of the flow and the solid domains should be shown.
14) (Line no. 487 – Conclusion section) in my opinion the words “continuity equation” should be added to the sentence. COMSOL has solved three transport equations: continuity, flow equation and energy equation.
15) (References section) the year should be bold. The year should be placed after the title of the paper. The digital object identifier of the paper should appear (See the following reference example):
Author 1, A.B.; Author 2, C.D. Title of the article. Abbreviated Journal Name Year, Volume, page range, DOI.
Author Response
Dear Colleague
Thank you for taking the time to read our paper and thank you for teh constructive comments. Attached please find answers to your inquiries
Best regards
Ziad
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Dear Authors,
Thank you very much. (Lines no. 294 - 295) the authors should explain how did they couple the energy equation with the heat conduction equation. Have they solved separately these transport equations or they have coupled the numerical solutions of each equation. It is recommended to show the heat conduction equation in section 3. Figure 12 - It isn't clear from this figure what are the numerical temperature values. Typically, color scale is used to display a color palette and its numerical scale for color mapped or contour data plots. the numerical values of the temperature colors appearing in figure 12 should be shown. It is recommended to accept this manuscript for publication after performing major revisions.
Author Response
Reviewer#2
Round 2
Thank you very much. (Lines no. 294 - 295) the authors should explain how they coupled the energy equation with the heat conduction equation. Have they solved separately these transport equations, or they have coupled the numerical solutions of each equation?
Thank you for taking care of the manuscript. I have indicated that the set of equations, because are coupled, are solved simultaneously using the finite element technique
It is recommended to show the heat conduction equation in section 3.
I did show the conduction equation accordingly
Figure 12 - It isn't clear from this figure what are the numerical temperature values. Typically, color scale is used to display a color palette and its numerical scale for color mapped or contour data plots. the numerical values of the temperature colors appearing in figure 12 should be shown.
I did include a color palette as per your recommendation
It is recommended to accept this manuscript for publication after performing major revisions.
Thank you for your support
Best regards
Ziad
