Heat Transfer Study of the Ferrofluid Flow in a Vertical Annular Cylindrical Duct under the Influence of a Transverse Magnetic Field
Round 1
Reviewer 1 Report
Dear Authors,
Many thanks for your work. It seems very interesting. However, there are several issues which are very important and must be improved in your paper. Pleased find below comments on your work.
1- The title is not that novel and specific! Very similar to the title that published by the authors in Physics of Fluids. Please change and make it more specific!
2- The Abstract is very general. It must consist of data and some values that we could compare and see their main outcomes!
3- The introduction is very week. It must be improved. First of all it is very short and secondly it didn't critically discussed the findings by other researchers in this field.
4- Please describe the novelty of your work! It is very similar to their previous data published and just geometry has been changed!!
5- You have many items and parameters. So, I suggest to add a nomenclature and mention if they have dimension or dimensionless!
6- The English of the paper must be revised and improved by and expert. As I can see there are many typos and usage of long sentences inside the texts. For example, I have been lost in their first sentence of Abstract in the middle of nowhere!
7- All of your contours are similar but the streamlines are different! the streamlines are started with = 0. How, I can compare them with the velocity contours!
8- Conclusions must be rewritten with bullets and make it more specific. All of those written are already known by the experts in this field!
9- The r vector in line 88 seems bad conversion in PDF and made it very messy.
Author Response
We would like to thank you for your valuable comments, bellow you can find our response.
Response to Reviewer 1 Comments
1- The title is not that novel and specific! Very similar to the title that published by the authors in Physics of Fluids. Please change and make it more specific!
The title has been revised to point out the novelty of the new work which is the heat transfer study of the magnetic fluid.
2- The Abstract is very general. It must consist of data and some values that we could compare and see their main outcomes!
Abstract has been revised. In all of our works we avoid adding results in the abstract and by a quick look, so do most of the authors of the special issue.
3- The introduction is very week. It must be improved. First of all it is very short and secondly it didn't critically discussed the findings by other researchers in this field.
The introduction has been enriched with six new references, one of which is a review paper on the subject, and the accompanying discussion.
The updated text is in the third paragraph of the introduction (please refer to the marked up manuscript) and the new references are
Bahiraei, M.; Hangi, M. Flow and Heat Transfer Characteristics of Magnetic Nanofluids: A Review. Journal of Magnetism and Magnetic Materials 2015, 374, 125–138, doi:10.1016/j.jmmm.2014.08.004.
Aminfar, H.; Mohammadpourfard, M.; Zonouzi, S.A. Numerical Study of the Ferrofluid Flow and Heat Transfer through a Rectangular Duct in the Presence of a Non-Uniform Transverse Magnetic Field. Journal of Magnetism and Magnetic Materials 2013, 327, 31–42, doi:10.1016/j.jmmm.2012.09.011.
Sun, B.; Guo, Y.; Yang, D.; Li, H. The Effect of Constant Magnetic Field on Convective Heat Transfer of Fe3O4/Water Magnetic Nanofluid in Horizontal Circular Tubes. Applied Thermal Engineering 2020, 171, doi:10.1016/j.applthermaleng.2020.114920.
Goharkhah, M.; Ashjaee, M. Effect of an Alternating Nonuniform Magnetic Field on Ferrofluid Flow and Heat Transfer in a Channel. Journal of Magnetism and Magnetic Materials 2014, 362, 80–89, doi:10.1016/j.jmmm.2014.03.025.
Tzirtzilakis, E.E.; Sakalis, V.D.; Kafoussias, N.G.; Hatzikonstantinou, P.M. Biomagnetic Cuid Dow in a 3D Rectangular Duct. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS Int. J. Numer. Meth. Fluids 2004, 44, 1279–1298, doi:10.1002//d.618.
Ferdows, M.; Murtaza, M.G.; Tzirtzilakis, E.E.; Alzahrani, F. Numerical Study of Blood Flow and Heat Transfer through Stretching Cylinder in the Presence of a Magnetic Dipole. ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik 2020, 100, doi:10.1002/zamm.201900278.
4- Please describe the novelty of your work! It is very similar to their previous data published and just geometry has been changed!!
The importance of the present work for engineering applications has been highlighted in the revised manuscript. It is clearly stated that this type flow is important for cooling units and heat exchangers, and it can be employed in various engineering applications. Moreover, the novelty has been presented more clearly, as to our knowledge, it is the first work that examines the effects of the magnetic field strength and the concentration of magnetic particles in a forced convection problem with the inclusion of buoyancy effects, in a toroidal pipe. To emphasize these facts, the following sentences have been added to the last paragraph of the Introduction section, in the revised manuscript.
… direction. This type flow is important for cooling units and heat exchangers, and it can be employed in various engineering applications. The numerical…
… of the flow. To our knowledge, it is the first work that examines the effects of these parameters in a forced convection problem with the inclusion of buoyancy effects. The results …
5- You have many items and parameters. So, I suggest to add a nomenclature and mention if they have dimension or dimensionless!
To our knowledge, MDPI Fluids style does not include nomenclature. Nomencalure is not mentioned at the instructions for authors and we have checked many publications and we only found one small nomenclature as an appendix.
6- The English of the paper must be revised and improved by and expert. As I can see there are many typos and usage of long sentences inside the texts. For example, I have been lost in their first sentence of Abstract in the middle of nowhere!
Abstract and text have been revised.
7- All of your contours are similar but the streamlines are different! the streamlines are started with = 0. How, I can compare them with the velocity contours!
For ξ=0 we do not have streamlines (ψ=0) as the magnetic field is the reason that secondary flow is induced. This is why Figure 3 begins at ξ=0.1.
8- Conclusions must be rewritten with bullets and make it more specific. All of those written are already known by the experts in this field!
Conclusions have been revised. We would like to avoid using bullets and we think that journal style does not include them.
9- The r vector in line 88 seems bad conversion in PDF and made it very messy.
On our submitted document it is well presented. If the conversion mess it again we will check it with the editorial office.
Reviewer 2 Report
TITLE: Effect of the magnetic field on the heat transfer of a forced ferrofluid flow in a vertical annular cylindrical duct
GENERAL COMMENTS
I found the paper to be interesting, well written and well organised. I think the authors have tried to put their findings into context and many of my suggestions are for minor comments/clarifications.
MINOR COMMENTS/CLARIFICATIONS
[line 19] Keywords. Add Continuity-Vorticity-Pressure before the acronym C.V.P.
[line 88] Please, revise the format of the equation of the vector r.
[line 168] Delete obviously. Of course, it is obvious, and, for this reason, it is an unnecessary word.
ENGLISH LANGUAGE AND STYLE
English language and style are fine/minor spell check required.
OVERALL RECOMMENDATION
Accept after minor revision.
Comments for author File: 
Comments.pdf
Author Response
We would like to thank you for your valuable comments, bellow you can find our response.
Response to Reviewer 2 Comments
[line 19] Keywords. Add Continuity-Vorticity-Pressure before the acronym C.V.P.
Revised
[line 88] Please, revise the format of the equation of the vector r.
In our submitted document r is well presented. If the pdf conversion mess it again we will check it with the editorial office.
[line 168] Delete obviously. Of course, it is obvious, and, for this reason, it is an unnecessary word.
Revised
Round 2
Reviewer 1 Report
Dear Authors,
Many thanks for the revised version. All of my comments have been properly addressed.
