1,720,973 research outputs found
Phase Change Materials (PCMs): an opportunity for energy saving in the cold chain
Get PDFMantenere la qualità e la sicurezza degli alimenti lungo tutta la catena del freddo, rappresenta una delle principali sfide per il settore della refrigerazione. Allo stesso tempo, garantire una temperatura costante lungo la filiera del freddo determina un elevato consumo energetico, comportando elevate emissioni di CO2 in atmosfera. A tale proposito l’attività di ricerca è stata finalizzata alla sperimentazione di diverse possibilità di utilizzo dei materiali in passaggio di fase (PCMs), per ottimizzare le prestazioni energetiche dei sistemi di trasporto e stoccaggio refrigerati. Inizialmente l’attività di ricerca si è focalizzata sull’applicazione del PCM nell’involucro di un container refrigerato, al fine di ridurre e sfasare temporalmente il carico di raffreddamento. Tale tecnologia è stata valutata mediante approccio numerico e sperimentale, consentendo pertanto di validare il modello numerico. In un secondo momento, sono stati valutati i benefici energetici legati ad uno scambiatore di calore contenete PCM posizionato in prossimità dell’evaporatore di una cella frigorifera. Gli obiettivi di tale attività sono stati quelli di ridurre il consumo di energia elettrica in condizioni di regime stazionario ed il tasso di incremento della temperatura all’interno del vano in caso di black-out. Inoltre, al fine di aiutare le compagnie di trasporto refrigerato ad implementare le giuste misure di efficienza per la produzione del freddo è stato prodotto un tool di calcolo. Infine, l’attività di ricerca è stata focalizzata sull’applicazione del PCM nelle pareti interne del vano refrigerato di una cella frigorifera, allo scopo di ridurre il picco di temperatura dell’aria ed il consumo di energia elettrica durante differenti aperture della porta. Complessivamente i risultati ottenuti hanno evidenziato come l’applicazione dei PCM nelle diverse tecnologie refrigerate, determina una interessante riduzione dei consumi di energia elettrica e delle emissioni di CO2 in atmosfera
A refrigerated container envelope with a PCM (Phase Change Material) layer: Experimental and theoretical investigation in a representative town in Central Italy
No full textIn this paper, a novel technology to improve the thermal performance of reefer container envelopes using a Phase Change Material (PCM) has been investigated. To that end, an external PCM layer was integrated with an insulated sandwich panel, in order to reduce and displace the heat flux phase caused by the external climatic conditions. The proposed technology was evaluated using an experimental and numerical design study. Specifically, during the experimental activities, a prototype panel was first tested inside a climatic test room and subsequently assembled on mini cold rooms and evaluated under real summer environmental conditions in Ancona (Italy). Finally, the numerical analysis was carried out using Finite Element Method (FEM) software in order to simulate a two-dimensional unsteady-state heat transfer with PCM. The calculation results were compared with the experimental values in order to validate the mathematical model, achieving a high reliability (correlation coefficient equal to 0.95)
Thermal performance analysis of PCM in refrigerated container envelopes in the Italian context - Numerical modeling and validation
No full textDue to external climatic conditions, radiation and temperature, refrigerated containers are subjected to high thermal stresses during storage in yards, warehouses, ships or during transport by rail or road. Moreover the consequent high thermal load has a great influence on both the electric and fuel energy consumption and on combined greenhouse gas emissions into the atmosphere. The aim of this research is the theoretical evaluation, using a previously validated Finite Element Method (FEM), of the related energy benefits deriving from the application of PCMs (Phase Change Materials) to a traditional refrigerated container envelope. Specifically the numerical analysis was performed for several kinds of PCMs, climatic conditions and exposures. The study also provides a numerical tool to be used in the prediction of the thermal performance of refrigerated container envelopes with PCM in the Italian context. An experimental analysis was carried out in order to test the accuracy of the numerical model and to validate it. Results show that PCM application to a 20' ISO container envelope can reduce and shift the daily heat load phases with respect to a traditional envelope fitted only with insulating material
Experimental analysis on a novel air heat exchanger containing PCM (Phase change material) in a cold room
No full textIn the present work the performance of a cold room with a novel air heat exchanger containing PCM (Phase Change Material) was experimentally investigated. Specifically, an air heat exchanger consisting of aluminium containers with finned surface filled with PCM (5 °C melting temperature), was located near the evaporator of a cold room. The aims are to reduce cooling energy consumption and improving the maintenance thermal conditions of stored products. For this purpose, an experimental campaign was carried out and a monitoring system was developed. The cold room thermal behaviour, with and without PCM, was studied under steady state operating conditions. As expected a reduced number of on/off compressor cycles (6 cycles instead 13 cycles) in the PCM added cold room was observed. Test results showed that by storing PCM in the air heat exchanger, up to 16% of energy saving can be achieved
Thermal analysis on a phase change material latent heat storage in a cold room in case of power outage
No full textLow perceived social support is associated with CD8+CD57+ lymphocyte expansion and increased TNF-α levels.
Get PDFSocial support has been supposed to have a positive impact on the function of the immune system. However, the relationship between perceived social support and immune function has not yet been fully investigated. In this cross-sectional study, we investigated the link between perceived social support and lymphocyte subpopulations and cytokines. 232 healthy subjects provided a blood sample and completed the Multidimensional Scale of Perceived Social Support (MSPSS) questionnaire. Lymphocyte immunophenotypes and cytokines were determined. Significantly increased CD8+CD57+ lymphocytes and TNF-α levels were found in group with low perceived social support. Multivariate linear regression corrected for possible confounders confirmed a significant role of perceived social support in predicting the number of CD8+CD57+ lymphocyte and TNF-α levels. This study supports the association between perceived social support and immune function. In particular, poor social support may be related to a state of chronic inflammation sustained by CD8+CD57+ lymphocyte expansion and increased TNF-α levels
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
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