Investigation of Flow and Heat Transfer Characteristics in Microchannels with Fins

Round 1

Reviewer 1 Report

The authors have examined the flow and heat transfer characteristics in micro channels considering different aspect ratios, smoothness, and incident angles of fins, with the Reynolds number ranging from 0 to 500. The findings illustrate that the contribution of enhanced thermal performance by fins in the microchannel can be attributed to the redevelopment of the boundary layer, the induction of the fluid separation, the formation of vortices and the mixing between fluids. The paper seems to be interesting; however, the following comments should be addressed before the publication of the paper:

·       Authors need to improve the language of the paper. In addition, authors must highlight the scope of the study.

·       Abstract must provide precise information of the key findings of the present work. I suggest revising the abstract to highlight the novelty of the work.

·       Introduction: I suggest the authors expand the introduction, to include recent studies and to provide enough background and explanations to make the paper informative for a wider researcher. For instance, the authors are suggested to include the recently published articles related to heat transfer problem in the introduction section such as “Features and aspects of radioactive flow and slippage velocity on rotating two-phase Prandtl nanofluid with zero mass fluxing and convective constraints”, “Thermal-enhanced hybrid of copper–zirconium dioxide/ ethylene glycol nanofluid flowing in the solar collector of water-pump application”, “Dynamics of radiative Williamson hybrid nanofluid with entropy generation: significance in solar aircraft”, “Thermal analysis characterisation of solar-powered ship using Oldroyd hybrid nanofluids in parabolic trough solar collector: An optimal thermal application”, “Irreversibility analysis of time-dependent magnetically driven flow of Sutterby hybrid nanofluid: a thermal mathematical model”, “The flow, thermal and mass properties of Soret-Dufour model of magnetized Maxwell nanofluid flow over a shrinkage inclined surface”, etc. to make the paper informative for wider researchers.

·       The theoretical model of the problem should be explained in details and should be validated by the experimental findings or by the earlier published articles.

The governing equations (2) to (4) for the conservation of mass, momentum and energy should be cited properly.

·       From where the Equation 7 has been considered, there is no reference no calculations?

·       It is also suggested to include the physical description of all figures reported in the results and discussion section so that valid conclusions can be drawn from the present work.

·       The conclusion section also needs to be improved based on the revisions made in the results and discussions section.

Author Response

Dear reviewer:

 

On behalf of my co-authors, we would like to express our sincere appreciates for your constructive comments and suggestions on our manuscript entitled “Investigation of flow and heat transfer characteristics in microchannels with fins”. These comments are all valuable and helpful for improving our manuscript.

 

In this revised version, we have addressed the concerns of the reviewers, and an item-by item response to the reviewers’ comments is enclosed. Due to the large changes in the paper, it is almost rewritten, and now only the language problems are marked up using the “Track Changes” function. We hope that these revisions successfully addressed their concerns and that this manuscript will be accepted.

 

Please see the attachment.

 

Looking forward to your early reply.

 

Best wishes,

Murun Li

Author Response File: Author Response.pdf

Reviewer 2 Report

Review of the Machines-2100405

 AUTHORS:  Murun Li, Xuan Gao, Haiwang Li, Jichang Sang, Pengpeng Nie, Weidong Fang and Tiantong Xu

 TITLE: Investigation of Flow and Heat Transfer Characteristics in Micro-Channels with Fins

 The aim of the work was to check the influence of the shape of fins put inside of microchannel on heat transfer between fluid and solid matrix. Authors proposed a set of differential equations together with boundary conditions describing the problem. They solved the problem using CFD method.

Authors analyzed the influence of three geometrical parameters of fins: height, angle and smoothness on heat transfer. They showed that straight microchannel is the best in the low Reynolds number range. Channels with fins are better from the heat transfer point of view for flows with a higher Reynolds number.  .   

 

Generally speaking the article is interesting and worth publishing. However, Authors did not avoid some errors and should fill in some gaps.

 

Comments: All comments concern modelling

 Physical model:

 Figure 1 shows the geometry of the problem. Firstly, the drawing does not show the x,y,z coordinate system used. Secondly, the drawing suggests that the top surface is open.

Both of the above deficiencies are reflected in the boundary conditions of the mathematical model.

 

line 100 and equation (1):

The mean free path of water molecule is marked by “lambda”.

However, in the paper, the letter “lambda” stands for thermal conductivity (line 122) and a number of formulas. Therefore, I propose to denote the mean free path with a different letter, for example "l".

 

Equations (3), (4) and (13):

In all these equations there is fluid viscosity, described by the authors as kinematic viscosity (lines 115, 153). In fact, there is dynamic viscosity in these equations.

The question arises which value of this viscosity was used in the calculations.

 Under equation (4) add: C is the specific heat.

 One boundary condition is missing for heat transfer in the x direction - the second order differential equation requires two boundary conditions, and there is only one (equation (5)).

 

Interphase boundary conditions have been described twice: equations (7) and (10) are identical. Lines 121 should be replaced with lines 128-129 and lines 128-129 and equation (10) should be eliminated.

 There are no boundary conditions for the upper surface, both for liquids and solids (see comments concerning Figure 1).

 Under equation (14) add: f is the friction factor.

 The article should be supplemented with the numerical values of the constants used in the calculations, for example in the form of a table (density, viscosity, specific heat, thermal conductivities…)

 The abbreviation Po is usually used to mean the Power number, while the number Poiseuille should be denoted Poi.

 

Line 166:

Heat transfer is characterized by Nusselt number, not by Reynolds one.

 

Recapitulation

Article deserves to be published after corrections.

Author Response

Dear reviewer:

 

On behalf of my co-authors, we would like to express our sincere appreciates for your constructive comments and suggestions on our manuscript entitled “Investigation of flow and heat transfer characteristics in microchannels with fins”. These comments are all valuable and helpful for improving our manuscript.

 

In this revised version, we have addressed the concerns of the reviewers, and an item-by item response to the reviewers’ comments is enclosed. Due to the large changes in the paper, it is almost rewritten, and now only the language problems are marked up using the “Track Changes” function. We hope that these revisions successfully addressed their concerns and that this manuscript will be accepted.

 

Please see the attachment.

 

Looking forward to your early reply.

 

Best wishes,

Murun Li

Author Response File: Author Response.docx

Reviewer 3 Report

Although the presented work is interesting, however, it lack of some descriptions which are listed below:

1)      More discussion of geometry needed. Present more description on consideration of fins in microchannels with aspect ratios, incident angles 73 and smoothness.

2)      It is claimed that flow is laminar. How such assumptions are assumed.

3)      Proper commas after Eqs. (2-5) are not assigned.

4)      The boundary conditions are presented in Eq. (7). How such conditions are associated to the geometry. Express these conditions on geometry.

5)      Show novelty of work in built form in last paragraph of introduction section.

6)      No justification on dimensionless numbers defined in Eq. (13) (16) is presented.

7)      How formula (17) is defines. Justify it with proper reference please.

8)      More discussion of results needed. For instance, “with the large fin aspect ratio increases the fastest, and gradually overtakes the others…” How is such trend observed? How this observation is valid from physical point of view. ? Authors should observes the physical outcomes with more description.

9)      In figure 5, the observations for Reynolds numbers are presented. How are such outcomes associated to the laminar or turbulent flow? Moreover, how flow pattern is fluctuated for different numerical values of Reynolds number.

10)  If any experimental data is sed, mentioned clearly.

11)  Regarding the heat transfer, following studies are relevant and should be added in literature survey section:

a)      Photo-catalytic pretreatment of biomass for anaerobic digestion using visible light and Nickle oxide (NiO_x) Nanoparticles prepared by sol gel method, Renewable Energy, Volume 154, (2020), pp. 128-135

b)      Performance of second law in Carreau fluid flow by an inclined microchannel with radiative heated convective condition, International Communications in Heat and Mass Transfer, Volume 117, October 2020, 104761

Author Response

Dear reviewer:

 

On behalf of my co-authors, we would like to express our sincere appreciates for your constructive comments and suggestions on our manuscript entitled “Investigation of flow and heat transfer characteristics in microchannels with fins”. These comments are all valuable and helpful for improving our manuscript.

 

In this revised version, we have addressed the concerns of the reviewers, and an item-by item response to the reviewers’ comments is enclosed. Due to the large changes in the paper, it is almost rewritten, and now only the language problems are marked up using the “Track Changes” function. Important content changes are highlighted. We hope that these revisions successfully addressed their concerns and that this manuscript will be accepted.

 

Please see the attachment.

 

Looking forward to your reply.

 

Best wishes,

Murun Li

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have improved the manuscript as per the suggestions. Therefore, I recommend for the acceptance of manuscript in its present form.