1,721,549 research outputs found
A simple method for validating a simulation model of a radiant ceiling panel with thermal energy storage
No full textThis paper focuses on validating a simulation model of a radiant ceiling panel (RCP) incorporating phase change materials (PCM) for heating and cooling applications in buildings. The development of an RCP with thermal energy storage capacity aims to encourage high thermal mass radiant systems in existing buildings to replace the traditional all-air HVAC system. First, a heat flow meter (HFM) is used to perform enthalpy measurements at a product scale (macro-encapsulated PCM). Then, a small test chamber is constructed to measure the dynamic thermal performance of an RCP with PCM under well-known and realistic boundary conditions. A known thermal resistance is used to establish a realistic heat transfer coefficient between room air (represented by the temperature of a temperature-controlled metal plate) and ceiling. The results show that HFM enthalpy measurements of products incorporating PCM are within ± 2% of manufacturers' data. Additionally, results indicate that a test chamber can be used for validating a dynamic simulation model of the RCP with PCM installed in a room. The proposed method can be helpful during the system optimization phase, as many conditions and sample configurations can be tested without spending too much time or money on test rooms or real building monitoring
Analysis of the energy and thermal performance of a radiant cooling panel system with integrated phase change materials in very hot and humid conditions
No full textThis study evaluates the energy and thermal performance of a radiant cooling panel system with integrated phase change materials (PCMs) for application in building retrofit projects. The focus is on the energy saving potential of using two different strategies to avoid condensation in very hot and humid climate conditions. The cooling energy consumption of a DOE medium office prototype building model with a conventional all-air system is used as a baseline for comparing the proposed configurations. The results show that the radiant system yielded energy savings of around 48% compared to the all-air system for existing office buildings. Results also show that the proposed system is able to operate only during the night-time, which improves the plant efficiency. Thus, the energy savings are mainly due to a reduction in the energy consumption of the cold generation system and lower energy use for ventilation compared with conventional air systems
Experimental evaluation of the cooling performance of radiant ceiling panels with thermal energy storage
No full textDemand-side management (DSM) strategies in buildings generally rely on short-term heat storage in structural thermal mass. However, the thermal storage capacity is limited by the available thermal mass as buildings are increasingly built using lightweight technologies. In addition, the structural thermal mass generally has a low heat storage and release rate, limiting the ability to manage building thermal loads. To overcome these limitations, we propose an innovative, flexible cooling system that can be installed in office buildings to replace conventional all-air systems. The system utilizes the high thermal energy storage capacity of macro-encapsulated phase change materials (PCM) discreetly incorporated below the serpentine copper coil of standard radiant ceiling panels (RCP). A walk-in dual climate chamber was used to evaluate experimentally the ability of the RCP-PCM system to shift cooling loads to off-peak hours. In addition, the heat removal capacity rate and the resulting indoor thermal environment improvements are assessed. The measured passive cooling power ranged between 11 W/m2 and 31.4 W/m2, with an average of around 17.3 W/m2. Results indicate that the RCP-PCM system can shift the cooling loads to off-peak hours while maintaining acceptable thermal comfort conditions during work hours (8:00 to 18:00). During the testing period, the system was able to passively absorb heat gains between 180 and 230 Wh/m2 during the day and operate actively only at night during unoccupied periods. This load-shifting capability of the RCP-PCM system can be of great help in planning DSM strategies for increased penetration of renewable electricity in building cooling applications
Development and evaluation of a control strategy for water-based radiant systems with integrated phase change materials
No full textExperimental and numerical studies have demonstrated the great energy savings potential and CO2 emission reduction that can be achieved with thermally activated building systems (TABS). However, one downside of TABS is that the system has to be incorporated in the building from the design stage, which limits its application to new buildings. To encourage the application of high thermal mass radiant systems in refurbishment, the authors developed a radiant ceiling panel with incorporated phase change material (RCP-PCM). The focus of this study is on the control strategy to operate the system. Whole-building energy simulations have been used for evaluating the performance of the RCP-PCM system operating under the proposed control strategy. Results indicate that the control strategy can be regarded as effective since it can respond well to changes in cooling and heating demand, meet the thermal comfort requirements, is simple to implement, and can lead to an energy-efficient operation due to the capability to operate only at night-time. Results also show that for cooling-dominated climates, a phase change material (PCM) with a melting temperature of 21°C is desirable to increase the passive cooling power of the system. However, in climates where both cooling and heating are required, a PCM with a melting temperature of 24°C results in better thermal performance. The RCP-PCM system was able to maintain the indoor temperature within the specified range of thermal comfort for more than 96% of the total occupied hours in cooling-dominated climates and climates with both cooling and heating requirements
Design and control of radiant ceiling panels incorporating phase change materials for cooling applications
No full textExperimental and numerical studies have demonstrated that thermally activated building systems (TABS) may lead to significant energy savings. However, TABS are generally incorporated into the building during the construction phase, limiting their adoption to new buildings. To encourage the application of TABS during building refurbishments, the authors have developed a radiant ceiling panel (RCP) with macroencapsulated phase change materials (PCM). This study aims to provide the criteria to design, size, and control the newly proposed RCP-PCM system. A simplified method to size and design the RCP-PCM system for cooling applications is developed from a set of parametric dynamic simulations. At first, the thermal storage properties of the macro-encapsulated PCM were determined using the standard ASTM C1784-20. The obtained properties were then used in a whole-building simulation model validated using measurements in a small test chamber that replicates the conditions of an actual test room. The PCM panel thickness of 0.015 m and a supply water temperature of 15 °C showed the best results in terms of thermal comfort and effective thermal energy storage capacity. The implementation of the simplified method in a case study showed that the RCP-PCM system maintained room conditions within the specified thermal comfort range (−0.5 < PMV < 0.5) for more than 90% of the occupied periods in all of the evaluated cooling-dominated climates. Moreover, yearly-round, the PMV values never reached values higher than 0.8 or lower than −0.6, confirming the effectiveness of the proposed method for designing a RCP-PCM system. The results show that energy savings of 22% could be obtained in a very hot and humid climate using an RCP-PCM system instead of a conventional all-air system. In conclusions, this paper offers a new system to promote energy flexibility and Demand-Side Management (DSM) strategies to modulate the energy demands in retrofitted buildings
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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