1,720,960 research outputs found
Thermodynamic and economic seasonal analysis of a transcritical CO2 supermarket with HVAC supply through ice thermal energy storage (ITES)
Full text linkA real case of a supermarket where a CO2 refrigerating plant also supplies heating, air conditioning and hot water
is considered. Ice thermal energy storage (ITES) is used both as latent storage in summer and as sensible thermal
energy storage (TES) in winter to partially cover the space cooling/heating load of the supermarket. In particular,
it allows to reduce peaks in the electrical power use, when the refrigeration and HVAC systems are running at full
power together with ovens and heaters for meals. A thermodynamic analysis, including a detailed theoretical
model of the formation and melting of ice on the coils, is carried out to predict the behaviour of ITES during the
charging and the discharging phases. A daily energy analysis for both a winter and a summer typical day, and an
annual analysis are carried out for the whole system. In summer, two cases are evaluated, i.e. supplying the
whole AC demand in the morning or partially covering the AC demand to reduce the design capacity of the
reversible heat pump. In all cases, the use of ITES aimed at shaving electrical peaks leads to a higher electrical
energy use, also on an annual basis. However, the cost analysis reveals significant benefits, including a reduction
in the required capacity of the reversible heat pump, better exploitation of tariffs and the avoidance of installing
an electrical transformer in a dedicated room. This results in savings €58,699 over 10 years €47,888 over 15
years, making the choice of ITES more economically advantageous within the typical lifetime of these system
Experimental evaluation of zeotropic refrigerants in a dedicated mechanical subcooling system in a CO2 cycle
No full textUse of zeotropic blends in the dedicated mechanical subcooling system of a CO2 refrigeration system was suggested as a possible improvement due to matching of evaporating temperature with CO2 temperature profile during subcooling. This work has verified this possibility and has determined theoretically the best performing compositions of R-600, R-32 and CO2 with the base fluid R-152a. Then, the mixtures have been tested experimentally in a lab-test bench for constant heat load temperature for three heat rejection temperatures (25.1, 30.3 and 35.1°C). Optimum conditions are measured (subcooling degree and heat rejection) and a COP increase of 1.4% has been obtained. The work, for the optimum conditions, analyses the operating parameters of the cycles and focus specially on the thermal parameters of the subcooler. It has been verified that the use of zeotropic mixtures allows to reduce irreversibilities in the cycle, as pointed out theoretically by Dai et al. (2018)
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
Experimental comparison of cycle modifications and ejector control methods using variable geometry and CO2 pump in a multi-evaporator transcritical CO2 refrigeration system
Full text linkTo reduce the direct global warming impact of refrigerants in HVAC&R applications, low-global warming potential (GWP) refrigerants, including natural refrigerants, have been extensively investigated as alternatives to hydrofluorocarbon (HFC) refrigerants. Among the natural refrigerants, Carbon Dioxide (CO2) offers several advantages, such as excellent transport and thermo-physical properties, being neither toxic nor flammable, and having a low price and high availability around the world. However, the high critical pressure and low critical temperature of CO2 often lead to transcritical operation, resulting in lower efficiency due to the additional compressor power necessary to achieve transcritical operation relative to subcritical HFC cycles. Therefore, a number of cycle modifications are used to enhance the coefficient of performance (COP) of transcritical CO2 cycles to meet or surpass those of HFC cycles. This paper provides a systematic experimental investigation of four such cycle architectures by employing the same multi-stage, two-evaporator CO2 refrigeration cycle test stand, 3 of these configurations in transcritical and 1 in subcritical conditions. The four cycles architectures included intercooling, open economization, an internal heat exchanger and two different ejector control approaches. Specifically, a variable-diameter motive nozzle and a variable-speed liquid CO2 pump located directly upstream of the ejector motive nozzle inlet were analyzed. Based on the experimental data, the maximum COP improvements are 4.64 % and 9.47 % when the ejector and the internal heat exchanger are used, respectively. The CO2 pump, once successfully stabilized, can control the ejector, increase its efficiency by up to 15 % and increase the cooling capacity to a maximum of 6.2 %. Nevertheless, a reduction in COP is measured when the pump is in use; however, unlike the other three different configurations, it was only analyzed under subcritical conditions
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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