Notice bibliographique
Résumé
Abstract The use of natural gas has been on the increase for the past three decades and current consumption is expected to double by the year 2020. A rise in the number of transoceanic shipments will, logically, increase the risk of accidental spills, especially at terminal facilities. An LNG spill will generate a potentially dangerous cryogen vapour cloud. Consequently, the study of the rate of vapourization of this cryogen over water surfaces is of primary importance. Experimental measurements on confined LNG spills indicate the presence of high vapourization rates at early times after spillage. The present work introduces a vapourization model that has not been explored in previous studies. This model proposes the existence of a thin liquid layer at the cryogen-water interface that is not in thermodynamic equilibrium with the bulk of cryogen liquid. The implementation of the proposed model in a computer program allowed for the simulation of the boil-off process, and the estimation of the initial vapourization rates and heat transfer coefficients in confined and unconfined spills. The simulated cryogen spills offered a description of the vapourization rates that correlated well with experimental boil-off data. The simulations indicated the existence of early vapourization rates in the range of 0.03 to 0.06 gcm_2s_1P>, and an average initial heat transfer coefficient of 1576 Wm_2K_1 for a typical LNG mixture. Introduction Previous efforts to describe the rate of vapourization of LNG include a study to determine the effect of its chemical composition on the vapourization rate (1). The results of this study indicated that the vapourization rate of LNG differs from that of pure methane, especially in the late stages of a spill. The differences were attributed to the ethane-enrichment of the bulk liquid phase during vapourization, which dramatically decreased the rates during the last stages of film boiling, followed by increasing rates after the collapse of the vapour film layer. The vapourization rate, therefore, exhibited a minimum as a function of spill time. The alluded study, however, suggested a mechanism of vapourization that would not allow for the high vapourization rates measured experimentally. A major assumption of this previous work was that the bulk of liquid was in thermodynamic equilibrium with the vapour film throughout the vapourization process ("bulk model"). Some authors (2)(3)(4) have questioned the equilibrium hypothesis. The authors argue that the preferential vapourization of the more volatile component will cause the liquid layer of the cryogen in direct contact with the film of vapour to be richer in the heavier component than the bulk of liquid. Valencia-Chavez and Reid (3) have suggested the existence of a repetitive mechanism by which the thin layer of LNG is constantly being depleted of its light component (methane). The methane is preferentially vapourised and carried in the bubbles through the liquid layer.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».