Thermal Conductivity and Rheology of Graphene Oxide Nanofluids and a Modified Predication Model

Round 1

Reviewer 1 Report

The paper proposes an experimental study of graphene oxide -water nanofluid properties, namely stability, viscosity, thermal conductivity for rather low five different concentrations, at six different temperatures, using ultrasonication. This type of experiment has been reported in several studies concerning GO-nanofluids, including the two parameters of influence, temperature and GO concentration. Based on thermal conductivity measurements and similar to other previous empirical models, another equation, containing a nondimensional temperature, is proposed.

 

The review comments are listed below:

1. The investigated range of parameter values should be clearly mentioned in the abstract.
2. Please include more updated references throughout the manuscript.
3. Twenty days is not a long period of time for a nanofluid stability assessment, usually one month up to several months are reported. Can you confirm its stability for longer periods of time (probably you still have the samples)?
4. The GO size and shape should be shown/mentioned, some STEM images could be included, if available.
5. The Newtonian behavior of the investigated GO nanofluid has been experimentally confirmed rather at low shear rates ≤100s^-1). How does your nanofluid behaves at higher shear rates?
6. Some studies found that an increase in sonication time can improve thermal conductivity values. On the other hand, excessive ultrasonication can induce structural defects. How did you choose the US time period? Have you investigated other values?
7. Please include comparisons to other GO nanofluid measured property data.
8. Other corrections:

• Please include explanations for acronyms (SDS etc.)
• There are two opposite statements:

“five kinds of graphene oxide nanofluids were prepared, with a mass fraction of 0.002% to 0.010% at the same concentration gradient.” (rows 49 -50)

and: “Four volumetric fractions from φ = 1 % to φ = 4 % will also be investigated.” (rows 64-65). Please clarify.

Also, for an easier grasp, please state clearly what mass or volume concentration are you referring at, throughout the entire manuscript (for ex. The GO mass concentration).

• Figure 3a seems to indicate a peak at about 32-33mV, rather than 45.3mV. Please correct in the text.
• Figures 4 a-f, 5 and 6 – please include units for temperature, wherever they are missing.
• “Kbf is the thermal conductivity of nanofluids”? or of base fluid? Please correct.

9. The title should be changed since the proposed equation (4) is very similar to previous literature models for nanofluid thermal conductivity.
10. The manuscript contains several English mistakes and needs revision.

Author Response

Please see the attachment.

Reviewer 2 Report

This novel study highlights the prediction model as well as the rheology and thermal conductivity of the graphene oxide nanofluids. However, before I can decide for the acceptance, the authors must revise the manuscript:

1) The introduction is too short for this topic of interest and contains old references. There are many recent review papers regarding the nanofluids (within this 5 years). The author must enhance the Introduction section with more references. 

2) In the Introduction section, the authors must highlight the significance of the graphene oxide nanofluids, the application of this kind of nanofluids. 

3) The experimental section can be discussed in detail. Please enhances this section for future reference. Please also include the thermophysical properties for the used graphene oxide nanofluids.

4) Is the proposed correlations can only be used for the graphene oxide nanofluids or all nanofluids?

5) There are many typing errors in the manuscript. For example the way you write Fig5 (line 158), Fig.6 (line 174). Please refers to the standard citation way for table/figure in this journal. 

6) What is the advantage of your proposed model as compared to the existing correlation of nanofluids?

7) It is good if you can provide one/two tables containing the detail data/value for the comparison result in Fig. 7. This also can be referred by other researchers. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The following major corrections should be incorporated carefully:

1- State the objective of the study clearly.

2- Describe more clearly  the experiment protocol. 

3- Improve the introduction by discussing all the following nanofluid applications:

https://doi.org/10.1016/j.icheatmasstransfer.2022.105937
https://doi.org/10.1007/s13369-020-04420-x
https://doi.org/10.1007/s13369-020-04757-3
https://doi.org/10.1016/j.csite.2020.100726
https://doi.org/10.1007/s10973-020-09865-8
https://doi.org/10.1016/j.icheatmasstransfer.2021.105395
https://doi.org/10.1088/1402-4896/ac2b4b
https://doi.org/10.1016/j.csite.2021.101428

4- Add a nomenclature table with SI units.

5- Reinforce your results by various pictures for the performed experiments.

6- Why you prefer studying the graphene oxide nanoparticles? Explain the reasons.

7- Validate your developed model.

8- Specify the validity game of these models in terms of volume fraction and temperature working. 

9- Improve the discussion statistically.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have revised the manuscript accordingly. Hence it can be accepted in current form.

Reviewer 3 Report

The paper becomes very good