1,721,023 research outputs found
Investigation on a novel reactor for gas hydrate production
No full textGas hydrates have a large capacity for the storage of gases and are an attractive method for gas filtration and transportation. However, hydrate formation is usually controlled by the rate of crystallization and thus it can be a slow process. A technology that will rapidly and continuously form hydrate is necessary for scale-up. A novel reactor with an inner volume of 25 l has been designed, built and installed to form hydrates by injection of water through spray nozzles from the top of the methane-filled reactor. This method allows to maximize interfacial area between reactants and to minimize mass transfer barriers and thermal effects that negatively affect conversion of reactants into hydrate. A system was developed to remove heat released during hydrate formation, and to reach a good level of temperature control inside the reactor. A novel system for hydrate recovering and unloading was also designed. The objective of experimentation is to lower energetic costs of hydrate formation, also through surfactant promotion. Anionic surfactant sodium dodecyl sulfate, SDS, was tested. Results of a first set of experimental applications of the reactor for rapid methane hydrate formation are presented
Benefits and Challenges of Mechanical Spring Systems for Energy Storage Applications
No full textAbstractStoring the excess mechanical or electrical energy to use it at high demand time has great importance for applications at every scale because of irregularities of demand and supply. Energy storage in elastic deformations in the mechanical domain offers an alternative to the electrical, electrochemical, chemical, and thermal energy storage approaches studied in the recent years. The present paper aims at giving an overview of mechanical spring systems’ potential for energy storage applications. Part of the appeal of elastic energy storage is its ability to discharge quickly, enabling high power densities. This available amount of stored energy may be delivered not only to mechanical loads, but also to systems that convert it to drive an electrical load. Mechanical spring systems’ benefits and limits for storing macroscopic amounts of energy will be assessed and their integration with mechanical and electrical power devices will be discussed
Special Issue “Analysis and Experimental Study on Natural Gas Hydrate Exploitation Processes”
No full textGas hydrates are crystalline structures formed by water molecule cages hosting gas molecules [...
Optic-energy and visual comfort analysis of retro-reflective building plasters
No full textThis paper presents the results of the characterization of new retroreflective (RR) plasters for outdoor applications. The paint was obtained through deposition of four different types of RR microspheres on a traditional plaster for exterior applications. The plasters were characterized through a spectrophotometric, directional and colorimetric analysis. All the types of microspheres provide strong RR behavior for incident light directions from 0° to 60° with respect to the surface normal. However, the aluminum coating, with and without fluoropolymer coating, affects negatively the global reflectance and change completely the tiles’ original color, making the application of the aluminum RR tiles very limited. Glass and barium microspheres instead improve the optic properties of the original plaster, with negligible effects on the color. An analytic model was used to evaluate the amount of energy that is reflected beyond the canyon by the RR materials. It was found that at 42°N latitude, the best performing configurations are the combination of RR façade and RR pavement, for glass spheres. Two full-scale vertical surfaces, covered with RR plaster with glass microspheres and diffusive plaster respectively, were
developed to investigate the visual comfort of pedestrians, in particular glare. Results show that the Daily Glare Probability (DGP) and superficial temperature for the RR wall is always lower than those for the diffusive wall
Integrated improvement of occupants' comfort in urban areas during outdoor events
No full textOutdoor public spaces contribute to improve the quality of life in urban areas available for outdoor activities, leisure and social interactions. The vitality and the functionality of outdoor urban spaces depend significantly on comfort conditions of people in these places. For this reason, the analysis of comfort conditions in urban public environments is important also in relation to the intended use of the considered spaces.
Almost all the studies about outdoor comfort mainly focus on the thermal comfort; other surveys consider aspects, such as acoustic and visual quality. However, generally thermal, acoustic and visual comfort conditions are treated separately. There are cases in which it is appropriate to deal with the three aspects simultaneously (e.g. spaces for temporary urban events), in order to guarantee global comfort of the occupants. To enhance simultaneously acoustic, lighting and thermal comfort conditions of an outdoor public environment, an integrated approach is provided and a simple, innovative and low cost solution is studied. The suggested solution is a system of suspended modular and temporary white acoustic sails appropriately positioned during outdoor entertainment events on summer. The particular case study of Matteotti Square in Città di Castello, Italy is analyzed. The results showed that an improvement on global comfort conditions of the square may be obtained through the use of proper architectural solutions and materials, which additionally result easily applicable to similar (for issues, geometry and destination of use) outdoor environments
Sistema di accumulo di energia ad aria compressa (caes - compressed air energy storage) con recupero di calore integrato ad un impianto turbogas per la produzione di energia elettrica
No full textI sistemi di accumulo dell’energia possono essere opportunamente impiegati per garantire maggior flessibilità e stabilità alle reti elettriche. Infatti consentono una migliore gestione dei picchi di carico (peak shaving), il bilanciamento, la regolazione di frequenza e di tensione, compensano l’aleatorietà della produzione da fonti rinnovabili e consentono di evitare in molti casi interventi di potenziamento della rete stessa.
Tra le varie soluzioni esistenti per l’accumulo energetico i sistemi CAES presentano notevoli vantaggi:
- bassi costi;
- grande capacità di accumulo;
- elevata velocità di restituzione dell’energia;
- numero di cicli infinito.
Il presente modello di utilità propone l’integrazione di un sistema CAES ad un impianto turbogas per la produzione di energia elettrica.
Il sistema CAES permette lo stoccaggio dell’aria compressa prodotta dai compressori nelle ore di minore richiesta di energia elettrica e il suo successivo impiego per l’alimentazione delle turbine nei momenti in cui si presentano picchi di domanda.
In alcune centrali elettriche turbogas nazionali sono presenti serbatoi, originariamente adibiti allo stoccaggio di carburante per l’alimentazione di vecchi gruppi di produzione con motore diesel. Tali serbatoi, attualmente in disuso, opportunamente modificati, possono essere impiegati per l’accumulo dell’aria compressa
Reattore innovativo per la produzione di gas idrati: risultati delle prime prove sperimentali
No full textGas hydrates are crystalline compounds formed by the hydrogen-bonded water molecules in lattice structure that is stabilized by encapsulating a small guest gas molecule (CH4, C2H6, CO2, H2S, H2). Gas hydrates have a large capacity for the storage of gases and are an attractive method for gas filtration and transportation. However, hydrate formation is usually controlled by the rate of crystallization and thus it can be a slow process. A technology that will rapidly and continuously form hydrate is necessary for scale-up. A novel reactor has been designed, built and installed in the laboratories of Fisica Tecnica – Dept. of Industrial Engineering – university of Perugia to form hydrates by injection of water through spray nozzles from the top of the methane-filled reactor. This method allows to maximize interfacial area between reactants and to minimize mass transfer barriers and thermal effects that negatively affect conversion of reactants into hydrate. In addition to the description of the novel apparatus, results of a first set of experimental applications of the reactor for rapid methane hydrate formation are presented
SECOND GENERATION BIODIESEL VIA FISCHER-TROPSCH SYNTHESIS: BIODIE2 RESEARCH PROJECT AND PRELIMINARY TESTS
No full textHydrate-based removal of carbon dioxide and hydrogen sulphide from biogas mixtures: Experimental investigation and energy evaluations
No full textThis paper presents an experimental study on the application of gas hydrate technology to biogas upgrading. Since CH4, CO2 and H2S form hydrates at quite different thermodynamic conditions, the capture of CO2 and H2S by means of gas hydrate crystallization appears to be a viable technological alternative for their removal from biogas streams. Nevertheless, hydrate-based biogas upgrading has been poorly investigated. Works found in literature
are mainly at a laboratory scale and concern with thermodynamic and kinetic fundamental studies. The experimental campaign was carried out with an up-scaled apparatus, in which hydrates are produced in a rapid manner, with hydrate formation times of few minutes. Two types of mixtures were used: a CH4/CO2 mixture and a CH4/CO2/H2S mixture. The objective of the investigation is to evaluate the selectivity and the separation efficiency
of the process and the role of hydrogen sulphide in the hydrate equilibrium. Results show that H2S can be captured along with CO2 in the same process. The maximum value of the separation factor, defined as the ratio between the number of moles of CO2 and the number
of moles of CH4 removed from the gas phase, is 11. In the gas phase, a reduction of CO2 of 24.5% in volume is achievable in 30 min. Energy costs of a real 30-min separation process, carried out in the experimental campaign, are evaluated and compared with those obtained from theoretical calculations. Some aspects for technology improvement are discussed
Analisi e ottimizzazione della qualità acustica negli spazi aperti: il caso studio di piazza Matteotti di Città di Castello
No full textOggetto del presente lavoro è lo studio di soluzioni volte al miglioramento della qualità acustica di spazi aperti. A tal fine è stato analizzato il caso di piazza Matteotti di Città di Castello (PG), mediante la proposta e la validazione sperimentale di interventi di miglioramento delle condizioni di ascolto durante eventi sonori (concerti, rassegne teatrali), durante i quali sono state evidenziate problematiche di qualità di ascolto, dovu-te principalmente a fenomeni di riverbero ed eco. Il lavoro è articolato in due fasi: la prima ha riguardato l’effettuazione di una campagna di misure in sito, al fine di ottenere un quadro dettagliato della qualità acustica dello stato attuale; la seconda ha riguardato la realizzazione di un modello di calcolo rappresentativo della piazza, sulla base del quale sviluppare proposte di miglioramento acustico, soluzioni a carattere temporaneo e reversibile a contenuto impatto visivo e a basso costo
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