1,721,018 research outputs found
Margherita Cannavacciuolo, El cuerpo cómplice: los cuentos de Julio Cortázar. Pról. de Rafael Olea Franco. Visor, Madrid, 2020; 256 pp
Full text linkOn the uncertainty of the measurements of friction factor in trapezoidal microchannels, a statistical analysis
No full textNon-Newtonian fluid flow in fractured media is of interest to hydrologists, geophysicists, and mining engineers. Since laboratory and field investigations evidence a strong degree of variability in fracture aperture, a large body of literature is specifically concerned with evaluation of an equivalent aperture (or permeability), adopting different constitutive equations and aperture variability models. The equivalent aperture for non-Newtonian fluid flow is defined as the parallel plate aperture which would permit a given volumetric flux under an assigned pressure gradient, thereby generalizing the concept of hydraulic aperture used for Newtonian flow. In this paper, the Bingham model with yield stress 0 has been adopted to describe the fluid rheology; the aperture is taken to vary as a spatially homogeneous and correlated random field with a lognormal aperture density distribution of assigned mean and variance 2. The equivalent fracture aperture is derived for a specific geometry where the flow is perpendicular to the aperture variation. Under ergodicity, results are obtained by discretizing the fracture into elements of equal aperture and assuming that the resistances due to each aperture element are in parallel. The equivalent fracture aperture is greater than the mean, and their ratio is found to depend on aperture variability, represented by log-aperture variance 2, and on a dimensionless parameter , equal to the wall shear stress in a fracture with aperture equal to divided by the Bingham yield stress. The ratio is weakly dependent on , and tends to increase as 2 increases. When tends to infinity, all our expressions reduce to those derived in the past for Newtonian flow and lognormal aperture distribution
On energy requirements and potential energy savings in Italian hospital buildings
No full textThe most of the Italian hospitals show a significant rise of their electricity demand during the summer. Such a growth represents a high penalizing aspect especially in structures characterized by considerable needs, being the contracts with the companies providing electricity normally set to the peak of consumption. An energy policy that would seek a requirement optimization through a cut of the summer peak of the electricity demand could therefore result in both energetic and economical savings. In this paper the electricity needs of twenty-three hospitals located in Emilia-Romagna, north Italy, are investigated. These electricity requirements have been broken down into main end-uses confirming that compression chillers, supporting the HVAC systems during the hot season, represent the major electricity end-use and are essentially to be considered as the responsible for the summer peak in electricity demand. Finally it has been detected the existence of a correlation between electricity requirements and cooling needs. Finally, a brief survey has been carried out to establish which technologies would best fit with the hospitals’ needs in sought of a rationalization of the energy demand. Among the different scenarios, solar technologies (e.g. solar collectors) in particular well suit with hospital facilities since these systems achieve their peak of production in correspondence of the peak of demand during the hottest sunny days of the summer
Greenhouse gas reductions and primary energy savings via adoption of hybrid plants in place of conventional ones
No full textWith the Kyoto agreement, there has been a greater emphasis on lowering energy waste and supporting low-emissions systems such as fuel cells (FC), photovoltaic (PV) systems or solar thermal systems (STS). These technologies produce environmental benefits since non-renewable energy can be preserved and environmental pollution can be drastically reduced. In addition to this, the decentralization of the electricity production plants mitigates the grid distribution losses. This paper developes a theoretical analysis focused on the environmental benefits achievable through a shift from the conventional systems, normally operating in hospitals, to different hybrid plants. The model site is a hospital located near Ferrara (Italy). At first, a numerical procedure has been adopted in order to calculate the energy requirements of the existing plant. Then several hybrid schemes have been investigated and compared: PAFCs (phosporic acid fuel cells), STS, PV systems. An energy analysis is developed for each option assuming the conventional systems, operating in the medical center, as the reference. At the same time, an economic study is developed for all the retrofit scenarios in terms of annual return, simple payback period and IRR. The results are presented with reference to the primary energy requirements and the pollutant emissions; it is demonstrated that in the case the existing conventional systems would be upgraded with these hybrid plants, overall greenhouse emissions could be abated with a significant reduction in primary fossil energy consumptions
Greenhouse Gas reduction and Primary Energy Saving via Adoption of a Fuel Cell Hybrid Plant in a Hospital
No full textThe Kyoto agreement, expressing great concern about global climate change, has stated emissions of greenhouse gases, especially CO2 from fossil fuel use, need to be reduced. According to this, existing plants have been required to cut emissions; moreover, there has been a greater emphasis on adopting efficient systems in order to reduce the energy losses. Among high efficiency technologies, fuel cells appear to be the most promising for their high efficiency and their very low environmental impact.
This paper first reviews the state-of-the-art of fuel cells systems, then simulates the operation of a hybrid fuel cells plant in a “typical hospital” analyzing how it could optimize the hospitals energetic requirements. Hospitals and sanitary structures are normally characterized by considerable energy demands not often suitable with resolute energy retrofit strategies.
Both the considerable primary energy savings and the pollutant emissions reduction, achieved upgrading conventional systems to a fuel cell hybrid plant, have the potential to prompt national boards to support their business development, as long as they achieve a consolidated market penetration
A Life Cycle Analysis of Building Integrated Photovoltaic Systems
No full textIn this paper a Life Cycle Analysis (LCA) methodology is used to
investigate the energetic and environmental impact of a Building Integrated
Photovoltaic installation (BIPV) with reference to a roof installation case study.
The results reveal that the roof integrated photovoltaic systems can bring
both energy and environmental benefits even in areas characterised by
medium values of insolation. It is demonstrated that the embodied energy
consumed during manufacturing phases is normally recovered after few years
of operation; the same can be said for pollutant emissions. On the contrary, the
economic payback time is always higher than the energy payback time and
sometimes exceeds the expected life of the systems
Energy efficient industrial parks cooperation: The case study of Fabbrico and Rolo in Reggio Emilia, Italy
No full textIn this paper we illustrate techniques and procedures for integrating common energy efficient services at Industrial Park level, in order to having larger equipment with higher performance, necessary to covering the required energy demand (by more effective services). Energy parks are responsible for big energy consumption: for this reason it is necessary to find smart solutions for managing energy outputs. We present a case of best-practice in Italy, in which the synergy between the SMEs (Small Medium Enterprises) leads to a sustainable development
Analisi Energetica LCA di un Collettore Solare Sotto-Vuoto
No full textNel panorama delle tecnologie alimentate da fonti rinnovabili, i sistemi che sfruttano la fonte solare rappresentano probabilmente le tecnologie oggi più affidabili. Gli stessi impianti sono peraltro soggetti ad una continua evoluzione tecnologica con rapidi tempi di recepimento da parte dell’industria.
Questo articolo rappresenta una analisi sul ciclo di vita (LCA, Life Cycle Assessment) di un impianto solare termico a collettore sottovuoto, a circolazione naturale, utilizzato per la produzione di acqua calda sanitaria e per il riscaldamento. L’analisi svolta ha permesso di valutare in termini energetici, ambientali ed economici la convenienza di un siffatto impianto solare termico con riferimento ad un edificio monofamiliare.
Le analisi energetiche sono state elaborate, simulando l’esercizio dell’impianto in tre diverse località italiane (Palermo, Roma e Bologna)
Pipe break data analysis in Emilia-Romagna, Italy: A first step towards effective management of water distribution networks
No full textThe management of water distribution networks in Emilia-Romagna (Italy) was discussed. The study focuses on pipe breaks during the years 1994-1997. Two main tasks were performed for this purpose, first was the development of standard format to collect and classify pipe break data and second was to determine the spatial and temporal distribution of breaks in space and time. The study showed weak positive correlation with precipitation, and no correlation with temperature, influenced the breaks. It is concluded that semiquantitative correlations were useful in scheduling timely substitution of the pipes in water distribution networks
- …
