Analysis of the Influence of Convection Heat Transfer in Circular Tubes on Ships in a Polar Environment
Round 1
Reviewer 1 Report
This paper is focused on CFD simulation of crcular tubes on ships in a polar environment. I suggest the following revisions:
(1) Many format error like a blank or a comma should appear between cited author and year (e.g., Wan2020=>Wan 2020 or Wan, 2020)
(2) How did you explain the role of heat conduction in this study? What is the criteria to evaluate the dominant role of heat condution and heac convection?
(3) No validations appear in this work. How do you let audience convinced of your results?
(4) Please list key formulas for the modelling and simulation. I understandi you are using FLUENT. But please list formulas and boundary conditions.
(5) A detailed input is needed for the results and dicussions.
(6) Please highlight your key innovation point in the conclusion.
Author Response
Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses in below and my revisions/corrections in the re-submitted files.
(1)Many format error like a blank or a comma should appear between cited author and year (e.g., Wan2020=>Wan 2020 or Wan, 2020)
Response ：We have modified the sentence according to the previous comment (line 39 42 46 50 56 60 65).
(2) How did you explain the role of heat conduction in this study? What is the criteria to evaluate the dominant role of heat condution and heac convection?
Response ：We thank the reviewer for the comments. In fact, in this paper, we study the heat transfer through the internal heating of a circular tube, the heat conduction through the internal to its surface and the fluid in contact with it after reaching the surface. The heat transfer between the solid surface and the fluid in contact with it is mainly a process of convective heat transfer. Since the wall thickness of the metal tube tested in this paper is small and the thermal conductivity is large, the heat loss in the heat conduction process is negligible.
(3)No validations appear in this work. How do you let audience convinced of your results?
Response ：The temperature close to simulation was selected for analysis in the test; the result is shown in Figure 7. It can be seen from the figure that the simulation results are close to the test results. The mean error is 7.3%, and the correctness of the simulation model is verified.
(4) Please list key formulas for the modelling and simulation. I understandi you are using FLUENT. But please list formulas and boundary conditions.
Response ：We have modified the sentence according to the previous comment, Simulation of convection heat transfer in tubes is under the second boundary condition, the second boundary condition is the heat flux, that is boundary layer of normal component (line 130-135)
(5) A detailed input is needed for the results and dicussions.
Response ：A detailed analysis of the results as influenced by wind speed and temperature is presented in Table 2.
(6) Please highlight your key innovation point in the conclusion.
Response ：Thank you for underlining this deficiency. This section was revised and modified showed in the work suggested by the reviewer. In this paper, the influencing factors of environmental in the tube and polar regions are studied. The consideration given in the specification for heating lack of environment changes is supplemented. This was studied by numerical simulation under the second boundary condition, and the correctness of the simulation model is verified by test. (Line 266-271).
Reviewer 2 Report
The paper addresses the heating of a ship structure facing a polar environment to avoid by examples ice formation and snow accumulation. The heat transfer is studied between a circular tube and a cold airflow. The subject of the paper is very interesting. Nevertheless, the reading of the paper gives an insufficient number of details and a strong lack in the presentation of the research conducted. Moreover, the absence of links in term of arctic stations data and ice classification of ships let us give the recommendation to reject the paper or to ask for a very high reconfiguration of its contents. We give here after our comments from the scientific point of view and for the missing information.
Scientific
We understood that a steady state turbulent airflow is computed numerically, but it are not presented the initial, transient and steady regimes of the tube in the freezing experiment.
The temperature range could be justified by arctic stations measurements (idem for the wind speed), for example along the north route until the Kara Straight.
The ice classification of the polar ships studied is not given. The concept of heat tracing could be explicated. The tube material is not given (idem for its roughness).
The maximal wind speed is 15 m/s line 84, 40 m/s in the abstract and 13,7 m/s line 207.
The unit of h must be corrected in eq(1): W/(m²C) line 90, idem in Table 4
There are 7 thermocouples every 30° around the tube, but only one measure of the temperature (line 216 for example).
It could be mentioned that the numerical results are always greater than the experimental ones in fig 7.
How the tube is heated is a main point to clarify.
The computing mesh could be shown.
Missing information
Check sentence, lines 13-15.
Plural in “Reynolds numbers” is unclear, line 38.
Sometimes, the tube seams to rotate, but this fact is absent in the investigation (line 42 and ref 5). In the same manner sometimes the tubes are in tandem, not alone, but it is absent in the investigation (line 60).
“increase in tube” , “decrease in Re” must be edited, lines 52-53.
Is the subscript w in the notation t_w means wood, or not ? It is in reference to the wood device placed inside the tube during the experiment, fig 2.
Many information are missing in relation with fig 1, for examples:
Where is the heat source? Are upstream and downstream temperatures measured? Is there a grid after the fan to structure/smooth the air flow? Is the wall in bold along the channel bottom heated? Why the tube is outside the middle of the channel? What are the air properties (viscosity, moisture...)?
The paper address, Re, Pr and Nu numbers without explaining their respective usages, for example why only Re is addressed in fig 5.
-999-999 is unclear, table 1.
Ref(12) is absent, the reference list ends at 11, line 157.
% numbers are unclear, 3rd and 4th columns, table 2 (edit caption, table 2).
Thsu, line 248.
ABS to be declined, ref 10.
Author Response
Thanks very much for taking your time to review this manuscript. I really appreciate all your comments and suggestions! Please find my itemized responses in below and my revisions/corrections in the re-submitted files.
Scientific
We understood that a steady state turbulent airflow is computed numerically, but it are not presented the initial, transient and steady regimes of the tube in the freezing experiment.
Response ：Thank you for pointing this out. In this paper, we use the second boundary condition, which are measured when the surface temperature of the structure reaches a stable level during the test, the thermal conductivity process has been simplified so that initial and transient conditions are not analyzed during the simulation，The results of the steady-state calculations are not related to the initial values.
The temperature range could be justified by arctic stations measurements (idem for the wind speed), for example along the north route until the Kara Straight.
Response ：Thank you for underlining this deficiency. We have modified the sentence according to the previous comment (Line75 76). The Data from the guide to polar ship and references have been added.
The ice classification of the polar ships studied is not given. The concept of heat tracing could be explicated. The tube material is not given (idem for its roughness).
Response ：We are very sorry for our negligence. We have added the following explanations. The polar vessel is the PC3 class icebreaker and the test tube is the handrail on board, made of Q235 smooth steel, Already added at the manuscript.(lines 103 104)
The maximal wind speed is 15 m/s line 84, 40 m/s in the abstract and 13,7 m/s line 207.
Response ：Due to test conditions, 15m/s is the design maximum wind speed for the test, 13.7m/s is the measured maximum wind speed for the test and 40m/s in the abstract is the maximum wind speed set for the simulation. Already added at the manuscript.(lines 84 223 )
The unit of h must be corrected in eq(1): W/(m²C) line 90, idem in Table 4
Response ：We have modified the sentence according to the previous comment (Table4).
There are 7 thermocouples every 30° around the tube, but only one measure of the temperature (line 216 for example).
Response ：Thank you for underlining this deficiency. For data processing, we take the average of the convective heat transfer coefficients at all measurement point as the average heat transfer coefficient for the circular tube as a whole.
It could be mentioned that the numerical results are always greater than the experimental ones in fig 7.
Response ：Thank you for pointing this out. In fact, the experimentally measured temperature of the circular tube fluctuated periodically and was averaged three times for each set of experimental conditions. The calculated temperature is slightly lower than the actual temperature, so the overall convective heat transfer coefficient of the test is small.
How the tube is heated is a main point to clarify.
Response ：Thank you for the suggestion. We have added the information required as explained above. The heating tape is wrapped evenly around a stick wrapped in insulation, and add a note to the figure (Figure 2).
The computing mesh could be shown.
Response ：Figure 3 has been added to the manuscript to illustrate the mesh
Missing information
Check sentence, lines 13-15
Response ：We have modified the sentence, the modification is as follows, the effect of temperature on the convective heat transfer coefficient of the circular tube increases.
Plural in “Reynolds numbers” is unclear, line 38.
Response ：We have modified the number.
Sometimes, the tube seams to rotate, but this fact is absent in the investigation (line 42 and ref 5). In the same manner sometimes the tubes are in tandem, not alone, but it is absent in the investigation (line 60).
Response ：Ambiguity due to mis-ordering of expressions and references, We have modified the References.
“increase in tube” , “decrease in Re” must be edited, lines 52-53.
Response ：We have modified the sentence, the modification is as follows, The results show that the influence of natural convection is stronger with the increase in tube diameter; At low Reynolds number, the influence of diameter on natural convection is more obvious. （line 53）
Is the subscript w in the notation t_w means wood, or not ? It is in reference to the wood device placed inside the tube during the experiment, fig 2.
Response ：t_w indicates the temperature of the surface of the structure in contact with the air.
Many information are missing in relation with fig 1, for examples:
Where is the heat source? Are upstream and downstream temperatures measured? Is there a grid after the fan to structure/smooth the air flow? Is the wall in bold along the channel bottom heated? Why the tube is outside the middle of the channel? What are the air properties (viscosity, moisture...)?
Response ：Thank you for pointing this out. Please find my itemized responses in below:
(1) Electric tracing of carbon fibres as heat source (added in Fig. 2)
(2)The duct was calculated to be a laminar flow section at 0.8m and the circular duct was arranged in the laminar flow section. The convective heat transfer coefficients of the cross-swept tube are mainly measured, so there are no upstream and downstream temperatures measured.
(3) structure/smooth the air flow through the Air duct, we have added a footnote to Figure 1.
(4) The wall in bold along the channel bottom not heated.
(5)The air is circulated in the cryogenic chamber, so the gas characteristics are not considered.
The paper address, Re, Pr and Nu numbers without explaining their respective usages, for example why only Re is addressed in fig 5.
Response ：The variation in related parameters is less affected by temperature. Prandtl number and thermal conductivity are regarded as constants in the process of convective heat transfer. Only the Reynolds number is varied by environmental variables, so the analysis of the convective heat transfer coefficient at different Reynolds numbers is carried out on Figure 5.
-999-999 is unclear, table 1.
Response ：We have modified the −50 – 220(℃)
Ref(12) is absent, the reference list ends at 11, line 157.
Response ：We are very sorry for our negligence. there are two references with no. 1 in the list. We have modified the References.
% numbers are unclear, 3rd and 4th columns, table 2 (edit caption, table 2).
Response ：We have modified the caption, Influence of temperature on h increase, Influence of wind speed on h increase.
Thsu, line 248.
Response ：We have modified the “thus”.
ABS to be declined, ref 10.
Response ：We have modified the References, American Bureau of Shipping
Round 2
Reviewer 1 Report
Good to go now.
Author Response
Thank you for your affirmation
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.
