1,721,011 research outputs found
Control of Noise from a Fan in a Wall Gas Boiler
No full textMethods for reducing noise emissions from a fan in a wall gas boiler are investigated. Sound power and vibration measurements are conducted in order to identify the effect of noise reduction treatments. Numerical simulations and measurements of volume flow and temperature, before and after the installation of noise treatments, were conducted. A 3.5 dB reduction in the acoustic power and a 5.0 dB reduction in the vibration levels are achieved. The performance of the boiler was not affected by the noise control treatments
ODS alloys: A New Manufacturing Process
No full textOxide Dispersion Strengthened alloys (ODS alloys) typically consist of a metal matrix with nanoparticles of ceramic oxides dispersed within it. The microstructural stability of nanoparticles results in an improvement of the mechanical properties of alloys at high temperatures and in a high resistance to neutron irradiation. This makes the ODS alloys good candidates for applications in the nuclear environment. In the present work different components with metal matrix and dispersed ceramic oxides and carbon fibers have been produced in order to assess their applicability in containers for low and medium level Radioactive Wastes (RWs). An innovative technology has been adopted for the production of the ODS components which simplifies and reduces the costs of the manufacture process. The applied technology is the tape casting followed by thermal and mechanical processes that lead to the consolidation and the solid-state mixing of the alloys
A simplified approach for evaluating the effect of airgun blast underwater noise on marine wildlife
No full textAirguns are used for geological surveys of seabeds in order to detect and quantify the pres-ence and distribution of hydrocarbons. The approach is based on the emission of high pressure air bubbles from arrays of airguns. Acoustic waves are generated and the reflections from the seabed are picked up by hydrophone streamer systems. However, airgun blasts may induce behavioural problems in marine mammals and wild life due to their high power levels and the high noise propagation speed in water. The effect of the blast noise is often evaluated by advanced modelling packages such as range-dependent acoustic models or wavenumber integration methods. A new simplified approach is proposed for evaluating the effect of air gun blasts on marine mammals and wild life. Simple propagation equations are considered: they takes into account parameters such as the blast noise power, its spectrum, the distance from the single airgun, the bubble air volume, the water absorption coefficient, the distance from the seabed. The approach is based on simplifying hypotheses: seabeds are perfect lambertian reflectors with a 100% reflection coefficient. The frequency-dependent evaluation is introduced for determining the M-weighted levels at receptor points. The proposed procedure may be used for a preliminary evaluation of the noise effect on marine wild life because of the short estimation time and the easiness of use
Effects of injecting gaseous CO2 on natural gas hydrate reservoirs: comparison of differences in clathrate dissociation behaviour.
No full textThe present work deals with the investigation of effects produced by carbon dioxide hydrate presence around a natural gas hydrate deposit. A laboratory scale reactor was performed to reproduce conditions feasible for hydrate formation. Six experimental tests were made. Firstly methane hydrate were formed and, then, temperature was increased to describe its relation with hydrate dissociation. In the second group of tests, after methane hydrate formation, carbon dioxide was injected, to form a hydrate shell around the present methane nucleus; then temperature was increased for generating hydrate dissociation. Finally a complete CO2 replacement process was carried out in the third group of tests. In case of only methane hydrate presence, the temperature increase caused an abundant pressure increase (due to water cages dissociation). The same temperature increase did not provoke any dissociation in presence of CO2 hydrate. In the third group of tests, the gas-chromatographic analysis of gas mixture, present inside hydrate after the CO2 replacement process completion, revealed a consistent presence of methane. Results clearly show how the presence of CO2 hydrate hinder the methane hydrate dissociation, even if the thermodynamic conditions are not suitable for their stability
An Index for Motor Vehicle Passengers Acoustical Comfort
No full textUsually only noise equivalent levels are employed to individuate acoustical comfort for motor vehicle passengers. However, noise levels do not take into account many other phenomena which may contribute to acoustical comfort such as insulation, speech intelligibility, engine noise hearing expectance and so on. An original vehicle comfort index (VCI) is here proposed which is obtained by a peculiar procedure: physical parameters (PP) such as noise equivalent level, statistical levels, STI index and vehicle acoustic insulation have been measured for different vehicles at several velocities. An arbitrary VCI scale has been introduced. VCI values for different comfort conditions have been determined by a jury test. Jury test has been led by adopting a S.A.O. (Statistical Average Observer) which was asked to judge vehicle acoustical comfort in terms of the proposed VCI scale. A relation between jury test results (experimental VCI) and PP has been introduced; thus, VCI may be evaluated by means of a measurement campaign for any condition
Analisi dei fabbisogni energetici di un’azienda agroalimentare
No full textLo sviluppo di un’agricoltura sostenibile, in grado di mantenere una buona capacità di produzione a fronte di un ridotto inquinamento ambientale, congiuntamente alla liberalizzazione del mercato dell’energia, hanno focalizzato l’attenzione degli operatori del settore verso le celle a combustibile. Fra le varie tipologie in fase di studio e sperimentazione le celle a carbonati fusi, MCFC (Molten Carbonate Fuel Cells), sono quelle che presentano i requisiti più promettenti per applicazioni su larga scala.
Uno dei vantaggi offerti da questa tecnologia è la possibilità di realizzare impianti per la produzione contemporanea di energia elettrica e termica mediante l’integrazione con macchine ad assorbimento. Nel presente articolo viene presentato uno studio sull’analisi del fabbisogno energetico di una azienda agroalimentare, sia dal punto di vista elettrico che termico, al fine di individuare la taglia e le caratteristiche ottimali di un’impianto a celle a combustibile in grado di soddisfarne le esigenze
Soluzioni per il controllo del riscaldamento globale
No full textLa concentrazione di Gas Serra nell’atmosfera (in particolar modo di anidride carbonica) è velocemente
aumentata nell’ultimo secolo principalmente a causa dell’impiego di combustibili fossili per la produzione di
energia elettrica. Una conseguenza diretta di questo fenomeno è la crescita della temperatura media del pianeta. Il
quarto rapporto elaborato dall’IPCC (Intergovernmental Panel on Climate Change) presagisce che la continua
crescita di gas serra nell’atmosfera causerà, da qui alla fine del 21° secolo, un incremento medio della
temperatura della Terra tra 1,8 e 4°C.
L’unico tentativo significativo di ridurre l’immissione di gas serra nell’atmosfera è rappresentato dal Protocollo
di Kyoto. I limiti di emissione fissati dal Protocollo stesso non sono tuttavia sufficienti a risolvere il problema del
global warming. D’altra parte soluzioni più efficienti come la cattura dell’anidride carbonica per mezzo di
processi di assorbimento chimico o fisico sono molto costosi e tecnicamente complessi da realizzare.
Nel presente lavoro è stato affrontato lo studio teorico di un metodo semplice ed innovativo per il controllo del
global warming basato sulla modifica dell’albedo terrestre per mezzo di superfici bianco riflettenti. In
particolare il lavoro presenta una innovativa relazione (brevetto n. PG 2006 A 0086) tra la quantità di gas serra
(espressi in CO2 equivalente) emessi in atmosfera e l’estensione della superficie bianco riflettente in grado di
annullare l’incremento di temperatura da questi causato. Sono infine proposte alcune soluzioni per realizzare le
superfici bianco riflettenti: la pittura dei tetti, il trattamento sbiancante di strade e di aree a basso pregio, la
realizzazione di isole galleggianti bianche, la creazione di saline e di vasche di colmata, etc.. Anche le normali
abitudini delle persone e il loro atteggiamento possono contribuire a variare l’albedo della Terra: l’uso di
ombrelli e di vestiari di colore bianco, etc.
Use of Molten Carbonate Fuel Cell for CO2 Capture
No full textThe adoption of technologies for the separation, capture and subsequent storage of CO2 for geological time periods through injection into the subsoil (CCS, Carbon Dioxide Capture & Storage), has emerged as a key approach to reduce CO2 emissions from upstream emitting sources, to comply with EU-ETS directives on emissions control, which force polluting industries to reduce their CO2 emissions below given limits. However, the significant investments required, and the energy intensive nature of conventional capture processes, have fuelled the ongoing debate on the effectiveness of this means of reducing CO2 emissions. This thesis considers, as an alternative to conventional CCS, non-conventional systems to capture and concentrate emissions, through the use of both a Molten-carbonate fuel cell (MCFC) configured as an electrical power generator, and the same fuel cell configured as an electrolyser (MCEC), therefore absorbing a limited amount of electrical power. These systems will be set up in a cascade in settings which reproduce typical conditions of large scale high-CO2 emission environments, and compared through a technical-economic analysis
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
An experimental investigation to improve the hydrogen production by water photoelectrolysis when cyanin-chloride is used as sensibilizer
No full textThis paper deals with an experimental investigation to improve the hydrogen production by water photoelectrolysis. An experimental facility was built: it is mainly constituted by a solar simulator, the photoelectrolytic cell, the electric power supply system and a recirculating and gas sampling hydraulic circuit. Titanium dioxide was chosen as catalyst because of its good photocatalytic efficiency and its high stability to pH variations in watery solutions. Cyanin chloride was tested as sensibilizer: it is a flavonoid, an organic dye, which gives to the watery solution better solar radiation absorption performances. The catalyst and the sensibilizer were deposited on the cathode surface. A sacrificial reducing agent, Ethylenediaminetetraacetic acid (EDTA), was also introduced in the solution to reduce the sensibilizer and restore the original conditions. Different radiation power and electrolytic pH conditions were tested in order to verify the proposed arrangements. Results showed a growing in the hydrogen production by the proposed photoelectrolytic arrangements with respect to the performance of a simple electrolysis. Thus, the obtained results showed that this technology has good possibilities of improvement and interesting perspective of future development
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