Thank you for sharing your research in the International Journal of Hydrogen Energy. I would like to share my observations and highlight a few issues I noticed in your article:
– The first observation is that while the comparative analysis of energy and exergy efficiencies between ortho-para hydrogen conversion (OPHC) and non-OPHC systems is novel, the reported specific energy consumption (SEC) for Case A (8.45 kWh/kgLH) appears significantly lower than benchmarks in the literature, which typically range between 10–12 kWh/kgLH for similar configurations. This discrepancy is not discussed, and it raises questions about the validity of the simulation parameters and assumptions used.
– The second issue concerns the choice of the Peng-Robinson equation of state for modeling cryogenic hydrogen behavior. While standard, this method may not be the most accurate for such conditions. The article does not specify whether alternative equations of state were tested or compared to validate the robustness of the findings, which could affect the reliability of the results.
– Additionally, the absence of a detailed explanation for boil-off rate calculations in Case B, and missing supplementary data referenced in the text, limits the reproducibility and transparency of the study. For instance, how was the boil-off percentage (19.85%) calculated, and were experimental data or external validation used?
– Finally, while the article claims this is the first comparative analysis of its kind, some referenced studies (e.g., Teng et al., 2023) appear to address similar comparisons. Clarifying how this study uniquely contributes to the literature would strengthen the claim.
Could the authors please share their insights on these points? Thank you for considering these observations.