102,169 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%
A methodology for impact assessment and acoustic monitoring of quarry activities
No full textThe work presents a methodology to assess the acoustic impact around extractive areas, the validation of which was made through the study of a quarry situated in Perugia (Italy). A preliminary analysis was conducted to locate sensitive areas, to characterize all the various noise sources in the quarry and to determine their contribution to the global acoustic climate. Afterwards, a simulation model for the noise sources in the quarry was implemented: through noise measurements, its reliability was verified. A detailed study on the quarry was therefore carried out, simulating different exercise conditions, corresponding to different noise sources at work in the quarry or to different morphologies during all the quarry life. The model allowed the individualisation of the specific contribution of each source to the global noise, to create different noise maps, to assess the effectiveness of the acoustic mitigation. The reliability of the model was also assessed by a one-year noise monitoring of the area of the quarry
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
The role of town energy planning in reducing urban transport emissions
No full textThe paper presents the main results obtained in the Energy Plan of the town of Perugia (Italy), which prominently features traffic aspects. For each possible action in this field, a very detailed technical analysis has been carried out. The actions have been divided into five groups:
- traffic planning (infrastructures, traffic restrictions, mobility management);
- alternative mobility (lifts, escalators, surface undergrounds and other kinds of public transport);
- alternative fuels (biodiesel, bioethanol, “white” gas oil);
- alternative vehicles (electric, hybrid, fuel cells);
- shared mobility (car pooling, car sharing and others).
For each group, technical, environmental, social and economic aspects have been taken into account; particular emphasis has been put on energy saving aspects and on the evaluation of greenhouse gases emissions reduction.
The paper gives useful indications to municipalities to choose the best solutions to reduce traffic consumptions and impact on a local scale, according to current technologies
Influence of cavities geometric and emissivity properties on the overall thermal performance of aluminum frames for windows
No full textThe increasing attention to energy saving in buildings has led to more accurate analysis of the thermal performance of windows. In particular, the use of aluminum frames has known a rapid development; thanks to the installation of thermal break systems, the performance of aluminum frames is nowadays comparable to the one wooden frames. The numerous air cavities inside aluminum frames suggest a deep investigation of the heat exchange process; the paper, therefore, analyzes the effect of the geometric and surface characteristics of the cavities on the overall performance of the profile. The attention was focused on the emissivity properties of the cavity inner surfaces, since they play a fundamental role on radiation heat transfer; furthermore, the frame thermal performance was evaluated when the geometries of some cavities are changed with the insertion of rubber gaskets.
All the analysis were conducted with two different approaches: numerical and experimental, obtaining a good match between the methods; the validation of the CFD model makes it a quick and user-friendly tool for the preliminary design and optimization of aluminum window frames with a high thermal resistance
Small size absorption refrigerators: a comparison among different solutions in solar feeding applications
No full textAbsorption refrigerating machines represent an interesting alternative to compression machines, especially when waste heat or heat produced by solar energy is available; the market is beginning to propose small-size absorption machines especially designed for air conditioning in residential buildings. A recognition of small size absorption refrigerators is reported, with particular emphasis on their performances in the case that the thermal source is constituted by solar energy. The examined machines cover different chilling powers (from 4 to 15 kW) and have different working principles. The study is conducted through the data supplied by manufacturers and collected in the experimental set-up available at the Labs of the University of Perugia; different refrigerators are compared taking into account the most significant parameters such as hot source and chilled water temperature, cooling circuit characteristics, coefficient of performance, weight and dimensions. Energy and environmental advantages deriving from the solar supply are also evaluated
Studio territoriale della risorsa eolica nel Comune di Perugia: aspetti metodologici, energetici ed ambientali
No full textNell’ambito del Piano Energetico e Ambientale del Comune di Perugia si è effettuato uno studio sulla disponibilità della risorsa eolica all’interno del territorio comunale. L’indagine si è sviluppata a partire dai dati anemometrici relativi a due stazioni di presenti nella zona, integrate con un codice di calcolo che, attraverso una serie di modelli numerici, ha reso possibile l’elaborazione della mappa del vento. Sono stati così individuati due siti potenzialmente idonei, per i quali si è condotta un’analisi di fattibilità tecnico-economica. Soltanto una delle due località è risultata valida per l’installazione di un campo eolico e per essa si è quindi proceduto alla valutazione delle prestazioni in termini di riduzione delle emissioni di gas serra; si è infine messa a punto una metodologia per la definizione dettagliata dell’impatto visivo della centrale eolica
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