Investigating the effects of flow regime on hydrogen transport in salt rock
Bibliographic record
Abstract
• H 2 flow in salt rock is affected by nanoscale pores, where gas slippage enhances apparent permeability at low pressures. • First-order slip models underestimate permeability in the transitional regime, where higher-order slip models are required. • TMAC and slip corrections are essential for accurate hydrogen transport modeling in underground salt caverns. Underground hydrogen storage (UHS) in salt caverns is emerging as a promising solution for the transition to a sustainable energy future. However, a thorough understanding of hydrogen flow mechanisms through salt rock is essential to ensure safe and efficient storage operations. In this study, we conducted hydrogen flow experiments in salt rocks using the pressure pulse decay (PPD) method, covering a range of hydrogen pore pressures from 0.4 MPa to 7.5 MPa within the slip and transitional flow regimes (Knudsen numbers between 0.04 and 1.5). The Knudsen numbers were determined by measuring the pore size distribution (PSD) of the salt rock samples and assigning an average pore size to each sample based on the measured PSD. Our results indicate that the intrinsic permeability of the tested salt rock samples ranges from 5 × 10 −21 m 2 to 1.0 × 10 −20 m 2 . However, a significant enhancement in apparent permeability, up to 10 times the intrinsic permeability was observed, particularly at lower pressures. This permeability enhancement is attributed to the nanoscale pore structure of salt rocks, where the mean free path of hydrogen becomes comparable to the pore sizes, leading to a shift from slip flow to the transitional flow regime. The results further reveal that the first-order slip model underestimates the apparent permeability in the transitional flow regime, despite its satisfactory accuracy in the slip region. Moreover, the higher-order slip model demonstrates acceptable accuracy across both the slip and transitional flow regimes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".