1,721,068 research outputs found
Thermal design and analysis of a nanosatellite in low earth orbit
No full textIn this paper, we present the process and the results of the thermal analysis applied to a nanosatellite developed at Politecnico di Torino. First, main mission parameters and the spacecraft design are presented, in order to fix the boundary conditions and the thermal environment used for the analysis. Then, the thermal model built to solve the thermal balance problem is described into details, and the numerical simulation code is presented. Finally, results are given and discussed in depth. The tool developed provides excellent modelling capabilities and temperature distributions have been validated through commercial software. The analysis has been used to refine the spacecraft configuration and to set the requirements applicable to the thermal control system of the satellite. The results showed that a basically passive control is sufficient to maintain most spacecraft's components within their temperature range when appropriate thermal coatings and/or tapes are provided. However, heaters to warm up batteries are recommended to survive coldest conditions. © 2015 IAA. Published by Elsevier Ltd. All rights reserved
Survey-based analysis of the electrical energy demand in Italian households
No full textAccording to Eurostat statistics, electrical energy covered 17.5% of the final energy consumptions in Italian households in 2015, and the electrical intensity increase of 8.9% from 2000 to 2015. ISTAT survey on energy consumption of households represents a valuable source of data for an extensive analysis of this topic. In order to evaluate these data, a model has been implemented in Matlab®, which calculates the electrical energy demand for lighting, electrical appliances, cooking appliances, DHW boilers, space heating and cooling. The present paper describes the methodology and the main results obtained with the above ISTAT dataset, consisting of 20,000 records. The numerical model allows allocating the electrical energy consumption for each end-use, in order to obtain a reliable estimation of the households' habits. Furthermore, it provides a useful tool applicable to the next surveys, in order to analyse the evolution of the electrical consumption of Italian households, to evaluate the potential energy savings of specific retrofit measures and to provide recommendations for policy actions supporting the improvement of the energy efficiency in the residential sector. © 2018, Mathematical Modelling of Engineering Problems
Titanium tetrachloride as novel working fluid for high temperature Rankine Cycles: Thermodynamic analysis and experimental assessment of the thermal stability
No full textIn this paper, Titanium tetrachloride (TiCl4) is analyzed/assessed and proposed as a new potential working fluid in Rankine Cycles. Besides its good thermodynamic properties, TiCl4 is in fact a fairly low cost, non-carcinogenic fluid, with zero Global Warming Potential (GWP) and Ozone Depleting Potential (ODP) and it is currently employed in high temperature industrial processes. It is however very reactive with humid air and water. A preliminary thermodynamic analysis confirms its possible application in power plants with maximum temperature up to 500 °C, considerably higher than the ORC state-of-the-art technology, performing electrical efficiencies as high as 35-40%. This suggests the potential use of TiCl4 as an alternative fluid in ORCs allowing the exploitation of high temperature sources (up to 500 °C), typically used in steam cycles. To assess the possibility of operating the cycle in such high temperature conditions, we carried out an experimental thermal stress analysis, showing that the fluid is remarkably stable at temperatures up to 500 °C, even in presence of P91 and Cupronickel, two materials typically employed in the high temperature section of power cycles. © 2016 Elsevier Ltd. All rights reserved
Catalytic wall flow filters for soot abatement from biomass boilers
No full textIn recent years rising costs of fossil fuels and, on the other hand, the availability of economic incentives and the development of advanced equipment solutions has made biomass combustion an attractive and efficient alternative for the production of heat and electricity at different scales of the plant. In fact, biomass is a renewable energy source widely used for energy production but, unfavourably, it is an important source of inhalable fine PM in ambient air as well. Among the different technologies for the abatement of these pollutants, wall flow catalytic filters may represent an efficient solution, since they combine physical filtration processes with catalytic oxidative reactions. The analysed filters, made of Silicon Carbide and loaded with 20%wt of Copper Ferrite (CuFe2O4), were properly shaped to be tested in the sampling line at the exhaust of a 30 kW pellet boiler located at ENEA research facilities. The paper presents the main experimental results related to the filter regeneration, the critical operative phase in order to provide adequate performance and service life of the filters. In the tests, regeneration, obtained by means of a high-temperature electrical heater wrapped around the filter housing, started when the pressure drop in the filter exceeded 600 Pa (the transition value from depth filtration to cake filtration) and the heater temperature was gradually increased from 180 °C to 500 °C. Tests showed high efficiency in PM reduction of wall-flow catalytic filters, moreover a relation between the beginning of the regeneration and the temperature of the flue gas at the filter outlet, in the range 220-280 °C, was found. The results provided useful information for the future researches, which will be focused on a microwave-based regeneration system, since both the matrix and the catalyst have good dielectric properties. Copyright © 2016, AIDIC Servizi S.r.l.
Soot abatement from biomass boilers by means of open-cell foams filters
No full textCurrently, fossil fuels such as oil, coal and natural gas represent the main energy sources in the world, but it is well known that these sources of energy will deplete within the next years. So, due to increasing environmental concerns especially related with the use of these fossil fuels, new solutions to limit the greenhouse gas effect are continuously sought. Among the available alternative energy sources, including hydro, solar, wind etc. to mitigate greenhouse emissions, biomass is the only carbon-based sustainable option. However despite an environmentally friendly use of renewable energies, incomplete combustion of biomass can lead to the emission of environmental pollutants as well as substances which are hazardous to health. In comparison to gaseous and liquid fossil fuels, the emissions of particulate matter (PM, or soot) are higher, leading to concerns about the availability of cost-effective techniques to reduce emissions in biomass combustion plants: so filtration devices are mandatory. Actually different filtration systems are available; some have reached a technological maturity and a consequent wide diffusion while others, though promising, have not yet demonstrated adequate features to be considered competitive. In the first class there are electrostatic precipitators, sleeve filters and wet scrubbers, which are standard solutions in medium to large plants. In the second class there are ceramic filters which in principle can be applied both in new equipment and in retrofit of existing boilers, and may be easily scaled according to the size of the boiler. In our previous works we studied the use of catalytic ceramic wall flow filters as soot emission control devices of biomass-fired boilers and stoves. Starting from those results, in this work we investigated the use of a different kind of filters, the open-cell ceramic foams, characterized by a different porosity if compared to wall flow filters. The prepared filters were tested in a customised sampling line at the exhaust of a 30 kW pellets boiler, and regeneration was specifically obtained by a high-temperature electrical heater. PM concentration in the flue gas was monitored by means of a real-time continuous detector and a cascade impactor. The tests evidenced that the higher average pores diameter of the foams, compared to ceramic wall-flow filters, resulted in two main consequences, (i) lower pressure drop, and (ii) a filtration efficiency higher than 50%. These results are very important, in particular because the pressure drop never reached a critical value for the normal biomass boiler functioning: in this way this solution could be a feasible device for soot emissions control. Further studies are still running to investigate the deposition of a catalyst on the foams. © 2018 Elsevier Lt
GENOVA CITTA' D'ARTE: LO SVILUPPO URBANISTICO (PP. 8-27); CHIESA E CONVENTO DI SANTA MARIA DI CASTELLO (PP. 66-77); COMMENDA DI SAN GIOVANNI DPRE' (PP. 78-83); CHIESA DI SAN DONATO (PP. 84-91); PALAZZO DUCALE (PP. 94-107); PIAZZA SAN MATTEO (PP. 108-119); LE ARCHITETTURE CIVILI (PP. 120-121); PALAZZO DEL PRINCIPE (PP. 122-135); STRADA NUOVA (PP. 136-149); GALEAZZO ALESSI A GENOVA (PP. 150-151); STRADA BALBI (PP. 152-165); VILLA DI LUCA GIUSTINIANI (PP. 166-171); L'INCANTESIMO DELLE GROTTE (PP. 172-173); LA CITTA' FORTIFICATA (PP. 174-183); TEATRO CARLO FELICE (PP. 184-191); PORTO ANTICO (PP. 202-207); LUCA CAMBIASO TRA MITO, PITTURA SACRA E PITTURA DI STORIA (PP. 270-277); QUATTRO CAPOLAVORI PER IL SECOLO D'ORO NELLA CHIESA DEL GESU' (PP. 278-285); COMMITTENZA E COLLEZIONISMO BRIGNOLE-SALE (PP. 322-335); IL CIMITERO MONUMENTALE DI STAGLIENO (PP. 338-347); FRANCO ALBINI E I MUSEI DI GENOVA (PP. 366-371).
No full textTests on catalytic wall flow filters for PM abatement from biomass boilers
No full textWall flow catalytic filters may represent an efficient solution for PM emission control of biomass-fired boilers and stoves, as they combine physical filtration processes with catalytic oxidative reactions. Moreover, such solution may be applied both in new equipment and in retrofit of existing appliances, and may be easily scaled according to the size of the boiler. The presented results were obtained from experimental tests carried out on filters with a silicon carbide matrix loaded with 20%wt of copper ferrite, and they aimed at evaluating the filter performance on fine PM abatement and the regeneration efficacy. The filters were tested in a customised sampling line at the exhaust of a 30 kW pellets boiler, and regeneration was specifically obtained by a high-temperature electrical heater. PM concentration in the flue gas was monitored by means of a real-time continuous detector and a cascade impactor. Tests showed high efficiency, over 90%, in PM reduction, and allowed to investigate in details the dynamics of regeneration and the effect of successive cycles, providing useful information in order to improve the service life and the performance of the catalytic filters. © 2016 ETA-Florence Renewable Energies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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