1,720,960 research outputs found
Transient Numerical Simulation of Regenerative Systems with Waste Gas Recirculation Strategies in Glass Production Plant
No full textThe glass production industry has one of the highest energy consumption rates and environmental emission impacts with respect to the existing industrial sectors. Glass furnaces nowadays are conceived with regenerative systems to take advantage of the residual heat from the combustion exhausts in order to increase the thermal efficiency of the system. The exhaust gases are also used in innovative systems to reduce the NOx emissions in specifically designed gas recirculation systems tailored to the glass furnace. In this paper, a numerical model for the simulation of the regenerative chambers in both steady and unsteady conditions is presented. The option of gas recirculation is also included. Special attention has been focused on the radiative heat transfer from the recirculated gases using a gas emissivity model previously developed by the authors
Numerical strategies for fluid-dynamic and heat transfer simulation for regenerative chambers in glass production plants
No full textModel for forecasting residential heat demand based on natural gas consumption and energy performance indicators
No full textThe forecasting of energy and natural gas consumption is a topic that spans different temporal and spatial scales and addresses scenarios that vary significantly in consistency and extension. Therefore, although forecasting models share common aims, the specific scale at which each model has been developed strongly impacts its features and the parameters that are to be considered or neglected. There are models designed to handle time scales, such as decades, years, and months, down to daily or hourly models of consumption. Similarly, there are patterns of forecasted consumption that range from continents or groups of nations down to the most limited targets of single individual users, passing through all intermediate levels. This paper describes a model that is able to provide a short-term profile of the hourly heat demand of end-users of a District Heating Network (DHN). The simulator uses the hourly natural gas consumptions of large groups of users and their correlation with the outside air temperature. Next, a procedure based on standards for estimating the energy performance of buildings is defined to scale results down to single-user consumption. The main objective of this work is to provide a simple and fast tool that can be used as a component of wider models of DHNs to improve the control strategies and the management of load variations. The novelty of this work lies in the development of a plain algebraic model for predicting hourly heat demand based only on average daily temperature and historical data of natural gas consumption. Whereas aggregated data of natural gas consumption for groups of end users are measured hourly or even more frequently, the thermal demand is typically evaluated over a significantly longer time horizon, such as a month or more. Therefore, the hourly profile of a single user's thermal demand is commonly unknown, and only long-term averaged values are available and predictable. With this model, used in conjunction with common weather forecasting services that reliably provide the average temperature of the following day, it is possible to predict the expected hourly heat demand one day in advance and day-by-day
Thermodynamic Transient Simulation of a Combined Heat & Power System
No full textAbstractIn this paper a numerical model aimed at studying dynamic behavior of CHP (Combined Heat and Power) plants is presented, paying particular attention to the components in which heat transfers take place. The analysis refers to a system powered by an internal combustion engine for a compression ignition type in cogeneration configuration, equipped with two heat extractors: the first one for coolant / water, the second one for exhaust gas / water. The numerical model has been implemented by using Matlab-Simulink software. After a description of the simplifying assumptions adopted for implementing the simulator, the model is exposed in detail with regards to each single element. Then simulation results are reported for two different operating conditions aiming to assess the effectiveness of the model in analyzing the dynamic behavior of CHP plants
A State-Space Analysis of a Single Zone Building Considering Solar Radiation, Internal Radiation, and PCM Effects
No full textThis paper deals with the dynamic modeling of a typical single-zone building. It describes the development of a dynamic model for thermal transient analysis and its application to a simplified test case considering solar irradiation and internal radiation. The dynamic behavior of the indoor air temperature has been investigated by means of a lumped approach using a state-space representation developed in MATLAB/Simulink. A set of daily temperature profiles, which are representative of the Mediterranean climatic condition, on a few different winter days, has been used as boundary conditions for the dynamic simulations. In addition, the model has been validated using two different sets of experimental data available in the literature, both statically and dynamically. Finally, a layer of insulation with a phase change material (PCM) is applied to the single zone building to quantify its effect on the building’s behavior. The results showed that the rate and amount of energy consumption in the building with PCM are moderately lower than the building without PCM. In addition, the variation of inlet air temperature, solar effects, and energy consumption have been evaluated for a case study example, as well as comfort in transient simulation to achieve a complete evaluation of the test building investigated. A satisfactory agreement was obtained between the experimental and the simulation results and shows that the model can be used for a wide range of materials, dimensions, thermal resistances, and boundary conditions
Simulation strategies for regenerative chambers in glass production plants with strategic exhaust gas recirculation system
No full textGlass production is an energy-intensive and a high-polluting industry. This study has the aim to describe the computational approaches developed and set up for the analysis of the innovative Strategic Waste Gas Recirculation (WGR) System applied to the glass industry to new or existing furnaces. The final goal is to reduce the production of NOx during combustion making a primary combustion zone poor of oxygen. In order to have a controlled combustion in the primary zone it is of utmost importance to properly design the recirculation system to get the desired distribution of the recirculated gases in a specific zone over the methane injection. Moreover, the WGR system can have a second positive effect: it enhances the thermal performance of the regeneration system due to the radiating capacity of the exhaust flow recirculated that contains CO2and H2O molecules. A CFD approach is presented and its applications to the design and optimization of WGR system are discussed. A numerical model for the evaluation of the emissive properties of radiant gases is developed and used for a parametric analysis on the thermal effects introduced by the WGR system
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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