1,721,093 research outputs found
Theoretical and experimental analysys of the evaporative towers cooling system of a coal-fired power plant
No full textThe paper presents a theoretical and experimental analysis of the cooling system of a 150 MW coal-fed power plant
located in central Italy, where ten evaporative towers cool down the plant using water taken from a river. An updated
research on the state-of-the-art evaporative tower cooling system has been carried out to show the theoretical analysis
of the tower heat and mass balance, and taking into account sensible and latent heat exchanged during the processes
which occur inside these towers. A long-term statistical data analysis has been carried out concerning the operation of
the cooling towers; this information was correlated to the corresponding values of the environmental conditions of the
site, and used to evaluate heat exchanged by the towers in the various conditions. The whole analysis permitted to
evaluate the optimal conditions as far as the operation of the towers is concerned and to suggest an improvement of
the plant. Finally, since plant re-powering has become quite a common issue today, the evaluation of the cooling
system operation was conducted under the hypothesis of an increase in the plant nominal power of about 10%
Theoretical modelling and experimental evaluation of the optical properties of glazing systems with selective films
No full textTransparent spectrally selective coatings and films on glass or polymeric substrates have become
quite common in energy-efficient buildings, though their experimental and theoretical characterization
is still not complete. A simplified theoretical model was implemented to predict the optical
properties of multilayered glazing systems, including coating films, starting from the properties of
the single components. The results of the simulations were compared with the predictions of a
commercial simulation code which uses a ray tracing technique. Both models were validated
thanks to several measurements carried out with a spectrophotometer on single and double
sheet glazings with different films. Results show that both ray tracing simulations and the
theoretical model provide good estimations of optical properties of glazings with applied films,
especially in terms of spectral transmittance
Analisi termodinamica ed ottimizzazione dell’impianto di raffreddamento di una centrale termoelettrica
No full textE’ stato condotto uno studio dell’impianto di raffreddamento di una centrale termoelettrica a carbone, di potenza pari a 150 MW. L’analisi si è sviluppata sull’intero sistema: dal circuito del condensatore alle torri evaporative, comprendendo anche la condotta di sollevamento e di adduzione acqua di refrigerazione derivata da un vicino corso d’acqua. Dall’esame statistico dei dati relativi alle temperature in ingresso ed uscita dalle torri lato acqua ed alle portate complessivamente circolanti sul circuito di raffreddamento, si è proceduto ad una correlazione con i corrispondenti valori dei parametri meteoclimatici della zona. La variabilità delle condizioni atmosferiche (temperatura di bulbo umido e umidità relativa) influisce sul funzionamento delle torri ed in particolare sulle perdite percentuali per evaporazione e per trascinamento che sono suscettibili di miglioramento rispetto ai dati di targa in funzione delle effettive condizioni termoigrometriche che nel corso degli anni si riscontrano con maggiore frequenza. Si è poi indicata la possibilità di ottimizzare il circuito idraulico al variare delle condizioni di funzionamento. Il corretto esercizio dell’impianto di raffreddamento presenta infatti un duplice vantaggio: il miglioramento del ciclo di funzionamento della centrale di produzione di energia elettrica ed il risparmio della risorsa idrica
Evaluation of the acoustic properties of materials made from recycled tyre granules
No full textThe paper presents the results of a wide experimental campaign on the absorbing properties of new acoustic materials made from recycled tyre granules mixed with a proper binder. The influence of the various acoustic and non acoustic parameters is investigated. The methodology used to evaluate coefficient of absorption coefficient is indicated in EN ISO 10534-2 standard, thanks to an impedance tube. Also the acoustic damping properties of small size samples of various thicknesses have been investigated thanks to a dynamic stiffness test rig.
The results show that these new materials have satisfactory acoustic properties, comparable to the ones of commercially available materials, thus encouraging the prosecution of the research with the testing of larger size samples, both for absorption and damping properties
Thermo-acoustic properties of floors made of concrete and scraps from electric wires
No full textThe paper concerns the use of granulated polymeric materials obtained from sheaths of electric wires, mixed with concrete and water to produce under-floors with good sound and thermal insulating performance. This is a possible solution for the re-use of this typology of waste, so to avoid the disposal into landfills.
Several configurations of the product were tested in the reverberation rooms of the Laboratory of Acoustics according to ISO 140-6 and ISO 140-8 standards, in order to fully characterize the sound insulating properties; the thermal conductivity was measured through the hot box of the Laboratory of Thermotechnics, according to EN 1934. Also mechanical tests were executed in terms of dynamic stiffness according to ISO 9052-1 and compressibility according to EN 12431; a chemical analysis completes the investigation of the mixture.
The results show that the product presents satisfying thermal performance, together with good mechanical properties; the chemical analysis of the loose polymers underlined the presence of some chlorinated and polycyclic hydrocarbons. From the acoustic point view, the sound impact reduction index directly evaluated both with a direct test on the reverberation room and with the indirect estimations through the dynamic stiffness gave results comparable with common materials used for screeds. When the material was tested in conjunction with other typical components of floors, the sound impact reduction index show poorer performance, underlining that the optimization of the acoustic properties has to be done taking into account of the combination with other floor materials
Investigation on the Performances of High Sound Insulation Ventilating Windows
No full textAn extended measurement campaign was carried out in order to investigate the characteristics of High Sound Insulation Ventilating Windows (HSIVW), a proper solution in all the cases where the intervention on noise sources results unfeasible, such as buildings strictly close to motorways or railways, as well as to industrial plants. The first series of tests was implemented on different HSIVW prototypes equipped with aerators (with and without fans); afterwards, a filter was inserted in the aerator, to make the inlet airflow cleaner. Finally, an insulated rolling shutter box was added to four different prototypes: two with an aluminum frame and two with a PVC frame. For all the surveys the sound reduction index (R) and the single number sound reduction index (RW) were calculated, in compliance with the ISO 140/3 method, giving complete informations about the performances of the whole window. The global campaign shows that the windows designed with particular details care present high sound insulation properties, even those equipped with critical components, such as aerators or rolling shutter boxes. The PVC frames show better performances than the aluminum ones, even if all the different types of windows show significantly high values of RW
Experimental evaluation and ray-tracing modelling of the energy and optical properties of glazing systems with selective coatings
No full textTransparent materials play an important role on energy and comfort requirements of buildings; in the present work, a series of optical measurements has been carried out with a spectrophotometer on several kind of glazing, equipped with different coatings. A theoretical model was used to predict the optical properties of multilayered coated glazing systems, starting from characteristics of the single components. This model and a ray tracing approach (implemented with a commercial simulation code) were validated through experimental measurements, showing a satisfactory agreement and revealing that, for high thickness and diffusive glazing systems, the theoretical simulations are to be preferred, since the spectrophotometer analyses could bring to wrong results. The passage to simulation tools permits a wider investigation of all different panes combinations, with a little effort; it is therefore possible to change many variables such as glass thickness, type of coating, type of glass and coating position, at the aim of fulfilling to requirements of every single application
Life cycle assessment of buildings and electric lighting energy consumptions
No full textLife Cycle Assessment procedures are being used more and more by designers and consultants in the evaluation of the overall environmental impacts of a building throughout its entire life (“from cradle to grave”). Though many studies have demonstrated that the highest impacts of a building are due to its space heating and air-conditioning consumption, the impacts due to the construction phase and therefore the choice of materials, including glazing systems, are not negligible. The University of Perugia is carrying out a research, funded by the Italian Ministry for Environment, on the role of the building sector on greenhouse gas emissions; within this research, methodologies are being tested to help spread the knowledge of LCA procedures in Italy. The paper illustrates the aims and methodologies of LCA studies, and presents - thanks to two different case studies – the contribution of electrical lighting consumption and the influence of an increase (or decrease) of transparent surfaces to the impacts during the entire life cycle of the buildings.
Keywords: Life Cycle Assessment, daylighting, electrical lighting, residential buildings, office buildings
Analisi ed ottimizzazione energetico-ambientale di un edificio mediante la valutazione del ciclo di vita (LCA)
No full textIl presente lavoro si propone di individuare, attraverso lo studio di un caso-pilota, una metodologia specifica per la valutazione energetico-ambientale di un edificio, che consenta di scomporre il sistema edificio-impianti nelle sue fasi di vita e nelle sue componenti tecnologiche, individuando l’impatto ambientale attribuibile alle singole componenti e fasi, per andare ad intervenire laddove le criticità sono maggiori. Lo strumento più efficace per compiere la valutazione di impatto energetico-ambientale è la procedura standardizzata dalle norme ISO 14040 parti 1, 2 e 3 cioè l’analisi del ciclo di vita “LCA”. Questa procedura consente di studiare un prodotto o un processo seguendone passo per passo tutte le fasi che lo contraddistinguono.
Si è voluto in particolare verificare che la metodologia utilizzata consenta effettivamente di individuare le criticità e pensare alle possibili soluzioni alternative a vantaggio della sostenibilità ambientale [1]. Le fasi dello studio sono state suddivise in scelta dell’unità funzionale, definizione dei confini del sistema, analisi d’inventario e inserimento dei dati nel codice di calcolo SimaPro, valutazione dell’impatto e analisi dei risultati.
Al termine delle simulazioni sull’edificio pilota si sono proposte delle ottimizzazioni di carattere energetico e se ne sono valutate le ricadute in termini di ciclo di vita
I regolamenti edilizi comunali - Strumenti per la promozione delle fonti rinnovabili e del risparmio energetico in edilizia
No full textIl settore civile è responsabile nel nostro Paese, sommando i consumi energetici per la costruzione, l’esercizio, la ristrutturazione e la demolizione degli edifici, di circa il 30% del fabbisogno energetico nazionale. Il lavoro riporta i risultati relativi ad un’estesa indagine svolta su numerosi regolamenti edilizi di Comuni sparsi su tutto il territorio nazionale, discutendo, inoltre, alcuni aspetti riguardanti l’introduzione di concetti di certificazione energetica degli edifici nei regolamenti edilizi comunali ed al sistema di incentivazioni da implementare per promuovere interventi di risparmio energetico e di bioedilizia. Particolare attenzione è rivolta al recente Regolamento edilizio del Comune di Perugia, che contiene alcuni aspetti a carattere innovativ
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