3,829 research outputs found
Evaluation and control of thermal losses and solar fraction in a hot water solar system
No full textWater heating for domestic needs contributes significantly to energy demands in the residential sector. The paper reports an energetic analysis of a solar hot water system performed on a dwelling located in different European cities. The study is focused on a group of apartments, where the domestic hot water is provided by a solar system coupled with a storage tank. A recirculation loop, composed by a pump and a system of pipes from the tank to the more distant apartment is also considered in the study. The loop overcomes the problem of long waiting times for hot water for the user by keeping it flowing inside the system. Since the recirculation loop is compulsory in this kind of plants, a dynamic energetic analysis is performed in order to analyze the pipe heat loss influence on the solar fraction. Dynamic simulations are performed using TRNSYS by interrupting the flow in the recirculation loop during the night and monitoring the temperature in the circulation loop. The study shows the sizing process of the whole system, the variation of the solar fraction and heat loss fraction for all the analyzed cases
Analysis of the Influence of Thermal Losses of the Recirculation Flow Loop in a Residential Hot Water Solar System
No full textWater heating for domestic needs contributes significantly to energy demands in the residential sector. The paper reports an energetic analysis of a solar hot water system performed on a dwelling located in Rome, Italy. The study is focused on a group of apartments, where the domestic hot water is provided by a solar system coupled with a storage tank. A recirculation loop, composed by a pump and a system of pipes from the tank to the more distant apartment is also considered in the study. The loop overcomes the problem of long waiting times for hot water for the user, by keeping it flowing inside the system. Since the recirculation loop is compulsory in this kind of plants, a dynamic energetic analysis is performed in order to analyse the pipe heat loss influence on the solar fraction.
Dynamic simulations are performed using TRNSYS, by setting different parameters (insulation thickness, pipe length, mass flow rate) and by interrupting the flow in the recirculation loop during the night. The study shows the sizing process of the whole system, the variation of the solar fraction and heat loss fraction for all the analysed cases
convenzione di ricerca per lo studio teorico-sperimentale delle prestazioni energetiche, di comfort e di qualità dell’aria dei sistemi di climatizzazione Proter Imex a pannelli radianti e di sistemi tradizionali adottati nei reparti di Maternità (e similari) e ortopedia (e similari) dell’Ospedale Maggiore di Bologna - convenzione stipulata con Proter Imex srl - importo € 36.000,00
No full textLe attività si pongono l’obiettivo ultimo di definire sotto il profilo quantitativo e qualitativo le differenze di prestazioni, intese queste nel senso più ampio del termine, tra sistemi di climatizzazione per l’edilizia ospedaliera del tipo tradizionale (ad es. del tipo a fancoil o radiatori con o senza ricambio di aria primaria) e sistemi a pannelli radianti a soffitto con rinnovo di aria esterna, fermo restando che la validità dei risultati sarà estendibile anche ad ambienti a destinazione d’uso diversa, sia per applicazioni civili che industriali
Dynamic analysis of solar hot water systems: the case study of a dwelling located in Italy
No full textThe present paper is aimed at the energetic analysis of a solar hot water system performed on a dwelling located in different cities in Italy, precisely, from north to south: Bolzano, Turin, Bologna, Rome, Brindisi and Trapani. The study is focused on a group of apartments, where the domestic hot water is provided by a solar system coupled with a storage tank and a recirculation loop; it is worth to mention that the recirculation loop is obligatory on this kind of plants. Therefore, a dynamic energetic study is carried out, assigned the hot water load profiles and the set parameters of the solar collectors with reference to the configurations here tested (flat plane and evacuated tube). Thus, dynamic simulations have been performed by means of TRNSYS simulations tool, setting different parameters: collector configuration and mass flow rate. Several ideas and results emerged from this study, such as the sizing process of the whole system, according to the variation of the solar fraction for all the analyzed scenarios. A digression with simulation results regarding a specific case concludes the paper. More specifically, the study of water temperature oscillations in winter and summer time with reference to the climatic data of Bologna has been carried out under particular operating conditions: i) the pump of the recirculation loop is powered all time (24 hours a day) ii) the pump is switched off during the night, except when the water temperature in the loop falls below a certain threshold temperature
CONVENZIONE DI RICERCA PER LO STUDIO DELLE CONDIZIONI TERMICHE INVERNALI DI TUBAZIONI ANTINCENDIO NON COIBENTATE ENTRO GALLERIE STRADALI UBICATE IN ALTA MONTAGNA IN REGIME DI RIPOSO E DI FUNZIONAMENTO IDRAULICO - convenzione tipualat con CIAB scrl - importo € 13.200,00
No full textLe condizioni di funzionamento invernale di tubazioni antincendio non coibentate poste in gallerie stradali, sia in caso di riposo (tubazione piena non funzionante) che in regime di lavoro (tubazione erogante la portata di progetto della rete), possono diventare particolarmente critiche in caso di temperature esterne rigide (– 20 °C costanti per intervalli temporali di 1 mese continuativo).
In tal caso, per la sicurezza di funzionamento idraulico è indispensabile conoscere l’andamento delle temperature interne della galleria in funzione
- del suo sviluppo
- della temperatura esterna,
- dei venti predominanti
- di eventuali fenomeni di ricambio di aria imputabili sia a mezzi meccanici che a eventi di convezione naturale innescati da differenze di quota tra imbocco e sbocco del tunnel
- della temperatura dell’acqua di reintegro nella tubazione.
L’obiettivo della ricerca consiste nella determinazione delle condizioni termiche invernali di tubazioni antincendio non coibentate entro gallerie stradali ubicate in alta montagna in regime di riposo e di funzionamento idraulico e nella individuazione delle possibili soluzioni per evitarne il collass
Energy performance of an existing office building in the northern part of Italy: Retrofitting actions and economic assessment
No full textIn recent years, the interest of the scientific community towards building energy performance has become more evident in order to meet the National and European Directives. In this context, retrofits that result in improved building energy performance are widely investigated. The paper presents a comparative analysis of two different and complementary strategies to enhance the energy performance of an existing tertiary building located in Bologna, Italy. The first retrofit action is to reduce the heat transfer by transmission (i.e. use of low-emissivity glass) and the second one is to decrease the ventilation losses (i.e. installation of a heat recovery system). Then a third case has been investigated: it contemplates simultaneously both the solutions of windows replacement and installing a ventilation recovery system. Potential energy savings were calculated by means of dynamic simulation assisted by Trnsys energy simulation tool. Finally, an evaluation of the simple payback time and the net present value was performed in order to investigate global cost assessment. The window replacement option in the analyzed building office proved to be absolutely unprofitable, even if it would appear as the first and simplest action to be performed. On the contrary, the installation of a total energy recovery system resulted in sensible reduction of energy consumption and at the same time generated good values of NPV with reference to all the three different analyzed variation of the cost of energy
Motivi letterari nei libri per l’infanzia di Paolo Di Paolo
No full textThe article, organised in the form of a discussion, aims to analyse the themes and motifs of Paolo Di Paolo’s works that are addressed to young audiences. The author has recently published a large number of volumes directed just at younger readers. When beholding the titles that constitute the author’s bibliography, the reader is struck by Di Paolo’s predisposition to transform literary classics: as much in Giacomo il signor bambino as in the edition of the Divina Commedia, the author’s goal is to try to reach his new readers. Therefore, Di Paolo proves to be a prolific author of the genre; in fact, in his bibliography, volumes of fairy tales with a classic slant, such as La mucca volante, are listed as well.L’articolo contiene un’analisi di temi e di motivi delle opere di Paolo Di Paolo dirette al pubblico più piccolo. L’autore negli ultimi anni ha pubblicato un cospicuo numero di volumi indirizzati, infatti, proprio ai lettori più giovani. Ciò che stupisce scorgendo i titoli che costituiscono la bibliografia dell’autore, è la predisposizione a trasformare i classici della letteratura: tanto in Giacomo il signor bambino quanto nell’edizione della Divina Commedia l’obiettivo è cercare di raggiungere i lettori più giovani. Di Paolo si dimostra, quindi, un autore prolifico del genere, tant’è che nell’elenco non mancano volumi fiabeschi dal taglio classico come La mucca volante. Analizzare le opere giovanili dello scrittore costituisce un fatto inedito
Experimental parametric analysis of water-mist sprays: An investigation on coalescence and initial dispersion
No full textAn experimental approach and parametric analysis are here presented to investigate some dynamic aspects of water-mist sprays operating at high supply pressure. An already proposed methodology (P.E. Santangelo, 2010, Exp. Therm. Fluid Sci., 34, pp. 1353-1366) has been extended to a three-dimensional analysis, that emphasizes the characteristic drop-size evolution along the axial coordinate of the spray. Therefore, an evaluation of coalescence and secondary-atomization phenomena along the spray axis results as the ultimate scope of this study. With regard to dispersion, the initial-velocity field has been experimentally determined both as a contour/vector map and as magnitude profiles at different distances from the injector outlet. In addition, some evaluation of the spray-cone angle has been proposed, resulting from a simple geometric approach to the already mentioned maps. Advanced laser-based diagnostics has been employed to perform experimental measurements: a Malvern Spraytec device has been used to measure drop-size distribution and Particle Image Velocimetry has been chosen to evaluate both velocity and cone angle. Moreover, a mechanical patternator has been employed to introduce flux measurements as an averaging quantity. Two nozzles having different orifice diameter have been employed and operative pressure has been set at a value of interest for fire-protection applications. Copyright © 2011 by ASME
Le prestazioni termiche di facciata alla luce del Decreto Legislativo 19 Agosto 2005, n. 192
No full textIl presente studio ha per oggetto la valutazione del fabbisogno di energia primaria per la climatizzazione invernale alla luce del decreto legislativo 192/2005. L’analisi è stata condotta per tre differenti tipologie edilizie (torre, linea e schiera), situate a Bologna, per ottenere uno scenario esauriente al variare del rapporto tra la superficie disperdente e il volume riscaldato. Il calcolo è stato eseguito ponendo particolare attenzione alla composizione delle facciate in termini di alternanza tra elementi opachi e trasparenti, facendo variare il rapporto tra la superficie laterale finestrata e la superficie netta calpestabile. Lo studio ha rilevato l’importanza di costruire involucri a bassa trasmittanza, ma, allo stesso tempo, ha messo in evidenza come la variazione di alcuni parametri (percentuale delle forature, numero di ricambi orari, rendimento medio stagionale) sia rilevante per una corretta progettazione del sistema edificio impianto
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