172,403 research outputs found
Viaggio nell'India del Nord
No full textSi devono a C. Pieruccini le pp. V-XIV, 3-17, 41-50, 53-75, 98-140, 144-155, 161-166, 172-176, 188-216, 227-287
Effcient numerical simulation of dense gas flows past airfoils and wings
No full textDense gases are single-phase vapors whose properties deviate significantly from the ideal gas law, operating at temperatures and pressures of the order of magnitude of the critical ones. Bethe-Zel’dovich-Thompson (BZT) fluids, which can be commercially available heat transfer fluids, form a particular class of dense gases for which nonclassical gasdynamic behaviors are theoretically predicted: they display a Fundamental Derivative of Gasdynamics Γ=1+ρc∂c∂ρS , with ρ the fluid density, c the sound speed, and S the entropy, that becomes negative in a range of thermodynamic conditions above the liquid/vapor coexistence curve. In that case, the compression shocks of the perfect gas theory violate the entropy inequality and are therefore inadmissible. Such non-classical phenomena have several practical outcomes: prominent among them is an active research effort to reduce losses caused by wave drag and shock/boundary layer interactions in turbomachines and nozzles, with particular application to Organic Rankine Cycles (ORCs). The complexity of setting up experimental studies with such dense gases has motivated the development of numerical tools to analyze their performance, assess their interest and define their optimal conditions of use. This study deals with the extension to dense gas flow computations of a low-cost preconditioned implicit scheme previousy developed for perfect gas flows
Congedo parentale e diritto alle ferie nel quadro dell’ordinamento dell’Unione Europea
No full textL ́articolo analizza la sentenza della Corte di Giustizia Europea C-12/17 sul rapporto tra il congedo parentale e la maturazione delle ferie. Dopo una breve ricostruzione del caso commentato, tale rapporto é stato comparato con la legislazione italiana in materia di congedo parentale e quanto disposto dalla Contrattazione Colettiva di settore sulla maturazione delle ferie durante tale periodo
Climate change and building performance: pervasive role of climate change on residential building behavior in different climates
No full textOngoing climate change is posing new challenges in all fields. The building sector is strongly being affected. Comfort conditions inside buildings can be damaged, even in currently high-performing buildings. Temperatures are expected to rise globally. This study aims to provide an overview of building interior conditions under climate change in four very different climates. The locations under analysis are Miami, Damascus, Izmir, and Yakutsk, falling within the locations defined by the international Köppen-Geiger climate classification as tropical, arid, temperate, and continental. A small residential apartment was chosen as a case study and modeled in Termolog Epix 12. The results are plotted in terms of internal operative temperature in the free-floating regime, on an hourly and yearly basis, for the years 2020, 2050, and 2080. This application concentrates on the building envelope as it asserts that a building with an optimal envelope will need significantly less demand for air-conditioning systems. Moving from 2020 to 2080, maximum indoor operative temperatures increase by 5.8°C in Izmir, 3.7°C in Yakutsk, 3.2°C in Damascus, and 2.3°C in Miami; while minimum operative temperatures increase by 5.4°C in Yakutsk, and by 2.4°C in Miami, 2.2°C in Izmir, and 2.1°C in Damascus. From 2020 to 2080, annual indoor comfort hours decrease by 18% in Miami, increase by only 1.8% and 1.4% in Damascus and Izmir, and remain nearly unchanged in Yakutsk
Modeling of light pipes for the optimal disposition in buildings
No full textA light pipe is an excellent solution to transport and distribute daylight into environments without or with little lighting, guaranteeing comfort inside the rooms. As stated in the literature, the evaluation of the performances of light pipes presents numerous complexities, making the work very dicult for technicians and designers. This study is aimed to present a methodology that is able to identify the potential of light pipes using indices such as daylight autonomy (DA), continuous daylight autonomy (DAc), and useful daylight illuminance (UDI). This paper presents an analysis of daylight obtained by several configurations of simple models of light pipes installed into a 5 5 m plant area room. All simulations are carried out in a DAYSIM environment, which allows calculating the annual availability of daylight based on a RADIANCE raytracer backward. Several daylight conditions were analyzed for dierent light pipe configurations, considering dierent pipe lengths and a variable number of light pipes. The light pipes are tested also in the horizontal position, for dierent orientations. The results of all the combinations were compared with the performances of a window with dimensions equal to 1/8 of the internal surface, which was in accordance with the minimum value to be guaranteed by the Italian Regulation (D.M. 5 July 1975 n. 190) for dierent orientations. The results indicated a dierence in daylight distribution, showing a strong correlation between the percentage levels of DA and DAc with the length and number of pipes, during dierent periods of the year. The simulated model is strongly influenced by the aspect ratio (R = diameter/length). The results show that the illuminance levels decrease drastically, increasing the length
Scenarios for urban resilience—perspective on climate change resilience at the end of the 21st century of a photovoltaic-powered mixed-use energy community in two European capitals
No full textCities are particularly susceptible to extreme and sudden catastrophic events, such as climate change, pandemics, and wars, that change people's lives. No city is completely safe from unforeseen risks; resilience indicates the ability of cities to be prepared for disasters and sudden events, allowing people to adapt and live without being exposed to too much stress. Resilience shows that the threat is not entirely negative; it can be a great opportunity to generate change and open new possibilities related to development and innovation. In this perspective, cities can emerge as driving forces for adaptation to change in which resilience becomes a central and crucial factor for sustainable development. One of the recurring questions today is how to make cities energy independent. This work analyzes the change in electricity supply from photovoltaic (PV) systems as a consequence of climate change in a hypothetical mixed energy community located in two European cities characterized by different climates, Rome and Berlin. The analysis was extended to possible climate change scenarios by including possible future climate effects due to mitigation policies, scenarios selected from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Specifically, the Representative Concentration Pathways (RCP) 4.5 and RCP 8.5 scenarios were included, that is, the stabilization scenario and the high emissions scenario. The hourly electrical power values of the PV system are calculated in TRNSYS software, considering the years 2020 and 2100. A comparison of the different scenarios shows that Berlin RCP 8.5 suffers a greater impact than Rome RCP 8.5 in 2100. Even though the RCP 8.5 scenario is a worst-case scenario, comparing 2020 and 2100 shows that there are greater differences in Berlin than in Rome. Berlin shows a high level of excess energy, but this is not always a good thing because it does not always pay to overload the grid, especially during peak hours
Una nuova applicazione open source per il monitoraggio del consumo di suolo da telerilevamento
No full textIl consumo di suolo è un fenomeno antropico con notevoli conseguenze sull’ambiente e sul paesaggio, come ad esempio lo sprawl urbano, l’impatto sui servizi ecosistemici, l’influenza sul cambiamento climatico. In Italia il fenomeno del consumo di suolo si è sviluppato notevolmente fin dagli anni ’60, e continua tutt’oggi con ritmi considerevoli, motivo per cui in ambito scientifico è emersa la necessità del monitoraggio del consumo di suolo.
Il telerilevamento permette di acquisire informazioni (in particolare immagini satellitari multispettrali) indispensabili per il monitoraggio delle caratteristiche fisiche del paesaggio tra cui la copertura del suolo, definita come il materiale fisico che ricopre il suolo. In particolare, il telerilevamento e i GIS (Sistemi Informativi Geografici) sono strumenti fondamentali per la gestione del paesaggio e l’analisi della dinamicità tra spazi urbani, peri-urbani, rurali e naturali.
Obiettivo di questa tesi è lo sviluppo di una metodologia innovativa per aumentare la frequenza e diminuire i costi del monitoraggio del consumo di suolo (e di altre caratteristiche fisiche del paesaggio) tramite classificazioni semi-automatiche di immagini satellitari. Questo genere di classificazioni utilizza le firme spettrali ottenute dalle immagini per identificare i materiali, consentendo una rapida classificazione di territori anche molto vasti.
L'approccio di questa ricerca si colloca nella Land System Science (Scienza del Sistema Suolo), che è emersa negli ultimi anni come piattaforma di integrazione delle differenti dimensioni del cambiamento ambientale globale, e cerca di monitorare l'interazione tra sistema sociale ed il paesaggio. Assunto di questa tesi è che l’analisi del paesaggio necessiti di un approccio multidisciplinare e aperto, e pertanto si promuove un processo scientifico di analisi che sia accessibile alle varie professionalità che studiano il paesaggio, anche non esperte di telerilevamento.
In questa ricerca è stata sviluppata una metodologia innovativa di classificazione della copertura del suolo che utilizza immagini satellitari gratuite e software open source per l’elaborazione dei dati, al fine di rendere il monitoraggio economico ed efficiente. In particolare, la metodologia è stata implementata in un programma aperto per il software QGIS (tramite il linguaggio di programmazione Python), in modo da rendere la ricerca sostenibile e replicabile anche in altri contesti di monitoraggio del paesaggio.
L’applicazione al caso di studio si è concentrato sulla Regione Lazio, al fine di classificare la copertura del suolo con l’utilizzo di immagini gratuite Sentinel-2. Tale lavoro ha permesso la valutazione dell’evoluzione nel tempo della copertura del suolo, ed in particolare la stima del consumo di suolo avvenuto tra il 2016 e 2017 per effetto all’impermeabilizzazione delle superfici agricole e naturali.
Tra i risultati della ricerca, oltre allo sviluppo di una metodologia di classificazione e la mappatura del consumo di suolo nella Regione Lazio, vi è quindi il programma, reso disponibile apertamente e gratuitamente, che permette l’elaborazione dei dati satellitari e la classificazione della copertura del suolo. Tale programma è già stato utilizzato da vari ricercatori in ambito internazionale che lo hanno applicato al proprio caso di studio e in vari settori (urbano, agricolo, forestale, ecc.). Ciò è quindi in accordo con l’obiettivo di apertura e multidisciplinarità del monitoraggio ambientale, e in particolare con l’intento di questa tesi di promuovere l’avanzamento della conoscenza sulla dinamicità del paesaggio nei suoi vari ambiti tramite il telerilevamento
Hypothesis of thermal and mechanical energy storage with unconventional methods
No full textThere is not a real “storage market” and the range of technical solutions for electrical storage appears to be underdeveloped. The use of electrochemical batteries seems to be the easiest and cheapest way, but some problems related to disposal, average life span and storage capacity, still put a brake on their diffusion. The micro CAES-TES (Compressed Air Energy Storage – Thermal Energy Storage) systems with small renewable energy plants for cogeneration and trigeneration represent an important development perspective thank to the reuse of the heat generated at the stage of air compression (for heating) and air expansion (for cooling). This improves the complexity of the entire system because of the heat exchange and thermal storage units must match the capacities and performances of the air compression/expansion units. The paper presents a new mathematical model for micro CAES-TES systems, implemented in Matlab software environment. The novelty is the use of air compressed energy storage in small and residential applications, a trigeneration due to reuse of heat from air compression and expansion stage, only renewable energy used. By keeping the initial investment low, the analysis is extended to the optimal system configuration and identifies key parameters that have a dominant influence on improving system efficiency and provides useful guidance for CAES-TES system design. The results show that, for an air storage volume of 4 m3, the optimal configuration is with a compression ratio of 15 splitted in two stages, charging time 5 h, mechanical storage efficiency 48%, compression air flow rate 3.73 kg/hour. The proposed system has a possible future development overall if combined with new possible scenarios of direct use of compressed air in the residential sector
A new device hypothesis for water extraction from air and basic air condition system in developing countries
No full textThis work proposes a new device for air treatment with dehumidification and water recovery/storage, with possible mitigation of indoor environmental conditions. The system is based on Peltier cells coupled with a horizontal earth‐to‐air heat exchanger, it is proposed as an easy‐to-implement alternative to the heat pumps and air handling units currently used on the market, in terms of cost, ease of installation, and maintenance. The process provides the water collection from the cooling of warm‐humid air through a process that leads to condensation and water vapor separation. The airflow generated by a fan splits into two dual flows that lap the two surfaces of the Peltier cells, one flow laps the cold surfaces undergoing sensible, latent cooling with dehumidification; the other flow laps the hot surfaces and heats up. The airflow undergoes thermal pre‐treatment through the underground horizontal geothermal pipe that precedes the Peltier cells. In the water storage tank, which also works as a mixing chamber, the two air streams are mixed to regulate the outlet temperature. The system can be stand‐alone if equipped with a photovoltaic panel and a micro wind turbine, able to be used in places where electricity is absent. The system, with different configurations, is modeled in the African city Kigali, in Rwanda
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