1,720,977 research outputs found
Dynamic Simulation of Solar Thermal Collectors for Domestic Hot Water Production
No full textAbstractIn this paper a system for the Domestic Hot Water (DHW) production based on solar collectors is analyzed by means of a dynamic approach based on a Simulink model and by using the F-chart method, able to evaluate system performances on a monthly basis. Following the dynamic approach, it is possible to evaluate hour by hour the energy collected by the solar panels and the temperature of the hot water produced by the system, by taking into account the impact of different daily DHW consumption profiles on the percentage of thermal energy produced by the solar collector (Solar Coverage Factor, SCF). The comparison between the prediction made both by using the Simulink model and the F-Chart method in terms of SCF is shown by taking into account the effect on SCF of the typology of solar collector (unglazed, glazed and evacuated collectors), of the storage tank volume connected to the solar panels and of the hourly DHW consumption profile. The results point out that SCF is strongly dependent on the daily DHW consumption profile, which cannot be taken into account in a quasi-static approach like the F-chart method
Dynamic simulation of outdoor swimming pool solar heating
Full text linkThis paper presents a dynamic model of a “passive” solar heating system composed by horizontal solar flat collectors coupled to
an outdoor swimming pool. The numerical model has been developed by using the Matlab/Simulink environment and it allows to
predict on a hourly basis the thermal energy collected by the solar panels, the inlet/outlet collector working fluid temperature, the
pool water temperature and the system efficiency. As a case study, three different pools characterized by different dimensions
and three different flat solar collectors (unglazed, glazed and evacuated collectors) have been considered. The Simulink model
allows to estimate the warm-up period of the swimming pool as a function of the characteristics of the pool and of the solar
collectors. It has been demonstrated that, by using the model, the designer can make the optimal sizing of the solar heating
system in order to obtain a water pool temperature ranging within a fixed interval. The results demonstrate that unglazed
collectors are appropriate for this kind of use and evacuated collectors can be useful just in case of very big swimming pools in
order to reduce the absorbing area of the solar panels
Caratterizzazione numerica di tubi capillari percorsi da fluidi HFC
No full textLo scopo di questo lavoro è quello di definire una procedura numerica che permetta di prevedere il valore di portata di refrigerante che attraversa un capillare di geometria e lunghezza nota e che risulti impiegabile all’interno di codici di calcolo per la simulazione del comportamento in regime dinamico di macchine frigorifere e/o pompe di calore. A tale scopo è stato messo a punto un modello matematico per la simulazione del funzionamento dei tubi capillari al fine di prevedere il comportamento del capillare in tutte quelle situazioni operative in cui le condizioni di funzionamento della macchina si differenziano notevolmente dalle condizioni “di regime”, come accade durante le fasi di accensione e spegnimento della macchina o durante l’inversione del ciclo nelle pompe di calore reversibili
Assessing energy efficiency at urban scale through the use of energy performance certificates: An application in the Emilia-Romagna region, Italy
Full text linkEnergy retrofitting of residential buildings is considered a challenge to be tackled not only at building level, but also at urban scale, to give a stronger impulse for a concrete transition towards climate neutrality. This paper presents an easy-to-use analysis method based on the elaboration and scaling-up of data collected through the energy performance certificates (EPCs) to identify different urban energy zones distinguished by their energy performance index. This method is therefore conceived for better informing urban planning decisions, thus boosting more effective energy-sensitive urban planning strategies and eventually to foresee dedicated financial instruments to act in the more energy demanding areas of the city, establishing priorities for integrated strategies. This analytical method has been applied and tested in one municipality in the Emilia-Romagna region, Italy, where the recent urban planning law is pushing municipalities towards the development of urban planning strategies oriented to drastically improve the energy efficiency of the existing building stock. Results show that only a small number of areas manage to reach a good performance with fairly low levels of energy performance index, with the most critical situation found in the most central areas of the capital and in the hamlets
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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