Investigation of the Effects of Hydrogen-Enriched Natural Gas Blends and Pure Hydrogen on the Performance of a Domestic Condensing Boiler
Notice bibliographique
Résumé
Abstract Following increased awareness about the deleterious effects of climate change on the environment, many corporations and institutions are making concerted efforts to reduce their greenhouse gas emissions through policy reviews and technological changes. One area of promise is the replacement of natural gas (NG) with hydrogen (H2) for use in residential and industrial sectors. Hydrogen can play a significant role in reducing emissions in heating applications within the built environment. In a net-zero emissions future where distributed combustion emissions must be largely eliminated, zero-carbon fuels and hydrogen solutions for heating are some of the most cost-effective and flexible paths that will facilitate the sector’s energy transition. In the short term, hydrogen is currently being blended in small amounts into existing NG networks around the world. This has an impact on the performance of appliances designed for NG, as certain gas properties will change. In this study, the effects of hydrogen on a domestic condensing boiler designed for NG, was investigated. The combustion reaction as a function of hydrogen content and oxygen content was determined. Stoichiometric, lean, and incomplete combustion were considered. Incomplete combustion leads to the formation of polluting emissions, while lean combustion is used to mitigate this by using excess air. An analytical model was developed to determine the outputs, that are, theoretical condensable water mass, heating value ratio, saturation temperature, maximum saturation temperature, and condensation efficiency, which were the main outputs that were systematically analyzed. Results showed that water vapour in the exhaust gas had the most remarkable effect on properties, and in consequence, on the boiler’s operation. Optimum efficiency occurred when the molar fraction of water vapour was maximized. This corresponded to the combustion of pure hydrogen at stoichiometric conditions. It was further observed that pollutant emissions formation was minimized with greater amounts of excess air via lean combustion, which also resulted in a smaller water vapour fraction. The addition of hydrogen also reduced emissions since the only combustion product of pure hydrogen is water. Hydrogen should be used in lean combustion with minimal excess air to optimize economic and environmental benefits. This guarantees greater performance over pure natural gas dispensed in the same conditions, while mitigating the formation of polluting emissions.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| 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 source (Gemma direct ou Codex distillé), 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 ».