The Effect of a Teflon Insulation Layer Installed Inside the Pump on the Insulation of a Centrifugal Pump for Transporting Liquid Hydrogen

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper studies the influence of installing teflon insulation layer inside the liquid hydrogen transport centrifugal pump on the insulation effect of the pump.

This is a CFD model study and fits the scope of journal Energies.

Below are comments:

In introduction section, the study on heat transfer of the liquid hydrogen containers need to be summarized.

In addition, this study is focusing on the design of a centrifugal pump. The research status on this similar pump need to be summarized and critically reviewed.

Reference numbers should be expanded.

The full name of CHT should be given when they first appears.

Section 2, the computation models for example, fluid flow, turbulence and heat transfer models should be firstly introduced.

Detailed mesh should be presented.

And mesh independent test should be performed.

In line 85, the reference for the the analysis is missing.

The figure 3 is not clear, in a low resolution, a clear version need to be updated.

Besides, as described in line 91, the Y+ value less than 100, this is too wide. What is the detailed value? And how about the wall function?

The simulated heat transfer data are closely related to the Y+ and wall functions.

Is the temperature are set as constant value as indicated in line 83?

Is this a solid fluid interaction model? Since I found the solid and fluid mesh are given in table 1.

Most important, is this model validated with any experimental data? Without this, the results are not reliable.

The key findings should be highlighted in abstract, but not only the heat input values.

Author Response

Thank you for your helpful review.

I have revised the paper based on the reviewer's comments and attached the relevant responses.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

1. The paper only emphasizes the performance of the combined magnetic drive and internal Teflon insulation design, without clarifying its technical differences from traditional vacuum insulation or other insulation materials, nor identifying relevant academic gaps. It lacks quantitative comparisons with existing research. It is recommended to supplement comparative data between this design and traditional schemes in terms of thermal protection efficiency, cost, and weight to clearly demonstrate the research innovation.
2. The paper does not discuss the aging and shrinkage characteristics of the Teflon insulation layer under long-term low-temperature (20K) conditions, nor does it address the impact of installing a thick insulation layer inside the pump on impeller rotational resistance or manufacturing processes. It is recommended to supplement low-temperature stability test data of the material or analyze the manufacturing feasibility and engineering application limitations associated with laying the insulation layer.
3. The paper merely describes the phenomenon that temperature fluctuation-related entropy production (Spro,T') is concentrated at the pump inlet, without deeply explaining the intrinsic flow field mechanisms and it is recommended to supplement flow mechanism analysis of the entropy production-concentrated region by integrating the distribution of velocity and pressure fields inside the pump, thereby enhancing the depth of the result discussions.
4. The entropy production analysis only correlates heat loss with temperature distribution, without incorporating the core engineering requirement for liquid hydrogen transport—vaporization rate control. It is recommended to supplement discussions of the liquid hydrogen vaporization rate under different insulation thicknesses to clarify the impact of thermal protection performance on liquid hydrogen transport efficiency.
5. The thickness of the Teflon insulation layer only covers the range of 0–10 mm. The paper does not analyze the marginal benefits of thermal protection when the thickness exceeds 10 mm, nor does it discuss the optimal thickness by considering engineering constraints. It is recommended to supplement simulation data for thicknesses above 10 mm and determine the engineering-optimal insulation thickness through comprehensive cost-benefit analysis.
6. The paper does not analyze the impact of heat generated by the magnetic drive system itself on liquid hydrogen, only highlighting its advantage of blocking heat transfer from the motor shaft. It fails to quantify the heat generation from eddy current losses and their contribution to the temperature rise of the working fluid. It is recommended to supplement calculations of the magnetic drive's eddy current losses to evaluate their offsetting effect on the overall thermal protection performance.
7. The study does not address manufacturing feasibility or material limitations, nor does it discuss the interface treatment process or methods to avoid gaps between the insulation layer and the pump wall during manufacturing. It is recommended to clarify the laying process of the Teflon insulation layer and verify spatial compatibility (e.g., flow channel cross-sectional area retention rate, rationality of the magnetic drive gap) in conjunction with the internal structural dimensions of the pump.

Author Response

Thank you for your helpful review.

I have revised the paper based on the reviewer's comments and attached the relevant responses.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Comments on

 

 

The Effect of a Teflon Insulation Layer Installed Inside the Pump on the Insulation of a Centrifugal Pump for Transporting Liquid Hydrogen

 

The paper investigates the insulation performance of a centrifugal pump for liquid hydrogen when an internal Teflon layer of varying thickness is installed. The paper needs a major revision to be accepted in energies journal.

 

The following comments will help the authors improve the paper.

 

• Avoid using self-pronouns.
• The abstract should be improved by adding the range of parameters studied, and other essential outcomes should be added.
• The introduction is insufficient and must be improved.
• The novelty and positioning need clearer justification.
• There is no experimental or analytical validation of the CFD model. There should be a validation for the CFD results.
• The Figures resolutions should be enhanced.
• The outer-wall convection assumption (h=15 W/m²K) needs to be justified.
• Some typos and grammatical errors should be corrected.
• There must be a nomenclature part including all symbols and abbreviations. What is CHT? I can expect it but the reader will face difficulties in that.
• Define abbreviations for the first time it appears in the paper.
• Where is the Mesh independence study.
• The CFD mode must be improved, why do you use SST?
• Regarding the results and its discussion, LH₂ property variation with temperature was not discussed.
• Clarify whether operating conditions represent design point.
• - Link turbulence model coefficients to entropy equations.
• Review the presented equation again.

Author Response

Thank you for your helpful review.

I have revised the paper based on the reviewer's comments and attached the relevant responses.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Revision have been improved and can be accepted!

Reviewer 3 Report

Comments and Suggestions for Authors

Accepted