ISEL - Eng. Mecan. - Artigos
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- A systematic review of numerical modelling approaches for cryogenic energy storage systemsPublication . Semedo, Arian; Garcia, João Nuno Pinto Miranda; Brito, MoisésCryogenic Energy Storage (CES) has emerged as a promising solution for large-scale and long-duration energy storage, offering high energy density, zero local emissions, and compatibility with intermittent renewable energy sources. This systematic review critically examines recent advances in the numerical modeling of CES systems, with the objective of identifying prevailing methodologies, emerging trends, and existing research gaps. The studies analyzed are classified into three main categories: global thermodynamic modeling, simulation of specific components, and transient dynamic modeling. The findings highlight the continued use of thermodynamic models due to their simplicity and computational efficiency, alongside a growing reliance on high-fidelity CFD and transient models for more realistic operational analyses. A clear trend is also observed toward hybrid approaches, which integrate deterministic modeling with machine learning techniques and response surface methodologies to enhance predictive accuracy and computational performance. Nevertheless, significant challenges persist, including the absence of multiscale integrative models, the scarcity of high-resolution experimental data under transient conditions, and the limited consideration of operational uncertainties and material degradation. It is concluded that the development of integrated numerical frameworks will be critical to advancing the technological maturity of CES systems and ensuring their robust deployment in real-world energy transition scenarios. Additionally, the review also discusses local thermal non-equilibrium (LTNE) conditions, the influence of geometric and operational parameters, and the role of multidimensional and multi-region modeling in predicting thermal and exergy performance of packed-bed TES within LAES cycles.
- Sustainable energy management in the cheese industry: a simulation model integrated with renewable energy sourcesPublication . Teixeira, Tiago; Monteiro, Joaquim; Garcia, João Nuno Pinto Miranda; Dias, João MestreCheesemaking is an energy-intensive process that relies heavily on heating and cooling operations traditionally powered by fossil fuels and electricity from the national grid. Reducing this dependence and integrating renewable energy sources are essential to align the sector with European decarbonization targets. This study presents the development of a simulation tool for optimizing the energy management of a cheese production facility by integrating solar, wind, and biomass systems. The model evaluates techno-economic and environmental performance under different climatic conditions and operational scenarios. Experimental validation was carried out using a prototype installed at the Polytechnic Institute of Beja (Portugal), achieving a deviation of only 2.3% in renewable energy contribution between simulated and measured data. Results demonstrate that renewable integration can reduce non-renewable energy consumption, achieving weekly profits up to 0.019 €/kg of cheese and carbon emissions as low as 0.0109 kg CO2e/kg. The proposed approach provides a reliable decision-support tool for small- and medium-scale cheese producers, promoting both environmental sustainability and economic competitiveness in rural regions.
- Real-time rail electrification systems monitoring: a review of technologiesPublication . Sainz-Aja, Jose Adolfo; Pombo, João; Brant, Jordan; Antunes, Pedro; Rebelo, José M.; Santos, José; Ferreño, DiegoMost electrified railway networks are powered through a pantograph–overhead contact line (OCL) interface to ensure safe and reliable operation. The OCL is one of the most vulnerable components of the train traction power system as it is subjected to multiple impacts from the pantographs and to unpredictable environmental conditions. Wear, mounting imperfections, contact incidents, weather conditions, and inadequate maintenance lead to increased degradation of the pantograph–OCL current collection performance, causing degradation on contacting elements and assets failure. Incidents involving the pantograph–OCL system are significant sources of traffic disruption and train delays, e.g., Network Rail statistics show that, on average, delays due to OCL failures are 2500 h per year. In recent years, maintenance strategies have evolved significantly with improvements in technology and the increased interest in using real-time and historical data in decision support. This has led to an expansion in sensing systems for structures, vehicles, and machinery. The railway industry is currently investing in condition monitoring (CM) technologies in order to achieve lower failure rates and increase the availability, reliability, and safety of the railway service. This work presents a comprehensive review of the current CM systems for the pantograph–OCL, including their advantages and disadvantages, and outlines future trends in this area.
- Heat transfer mechanisms in refrigerated spaces: a comparative study of experiments, CFD predictions and heat load software accuracyPublication . Lança, Miguel; Garcia, João Nuno Pinto Miranda; Gomes, JoãoA correct cold room heat load calculation ensures that the refrigeration system operates efficiently, reducing operating costs while maintaining a constant temperature to prevent stored goods from spoiling. Refrigeration engineers typically use software to size equipment such as expansion devices and evaporators and to estimate heat loads in cold rooms. These tools are available for free from refrigeration manufacturers or can be purchased from software developers. Although practical and easy to use, most of these programs do not follow the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)-recommended approach for estimating heat loads. This article evaluates heat transfer mechanisms, especially natural convection in a refrigerator, through experimental and CFD simulations. Depending on the expression used, the estimated convection heat flux at the evaporator ranged from 5.3 W to 14.2 W in case 0-N, 7.7 W to 25.1 W in case −10-N, and 5.1 W to 22.4 W in case 0-Y. Compared to convective heat transfer, radiation heat flux estimations are often more consistent across different expressions. The results from validated simulations were used to assess the performance of cold room heat load estimation software. Differences of up to 236% in heat load estimates were reported between the results.
- Assessing the contribution of ERASMUS+ KA2 projects to the SDGs: an exploratory analysisPublication . Nogueira, João Robert; Dantas, Lucimar; Galego, Carla; Marques, PedroThis study examines the contribution of ERASMUS+ Key Action 2 (KA2) projects, funded between 2014 and 2020, to the dissemination and promotion of the United Nations Sustainable Development Goals (SDGs). A predominantly quantitative content analysis was conducted based on metadata extracted from the official European Commission database, focusing on the presence of SDG-related keywords within the titles, topics, and abstracts of the projects. In total, 24,838 KA2 projects were examined. The findings reveal a growing alignment between funded projects and certain SDGs, particularly SDG 3 (Good Health and Well-being), SDG 4 (Quality Education), SDG 13 (Climate Action), SDG 7 (Affordable and Clean Energy), and SDG 9 (Industry, Innovation, and Infrastructure). In contrast, goals such as SDG 2 (Zero Hunger), SDG 6 (Clean Water and Sanitation), and SDG 14 (Life Below Water) are scarcely represented. Overall, the results demonstrate an increasing commitment to sustainability themes over time and also highlight notable gaps in the promotion of several SDGs. This analysis offers valuable insights into the strategic alignment of ERASMUS+ funding with the 2030 Agenda and identifies opportunities for strengthening its future contributions to sustainable development.
- Limestone processing sludge: from waste to sustainable resourcePublication . Guedes, Mafalda; Carrasqueira, Joana; Seixas, Tomás; Afonso, Clélia; Gil, Maria Manuel; Bernardino, Raul; Gamboa, Roberto; Bernardino, SusanaThe limestone quarrying and processing industry generates huge amounts of waste, with limestone sludge being one of the most prevalent and challenging by-products. This study aims to evaluate the potential of limestone sludge as a sustainable secondary raw material for the mechanochemical synthesis of bioceramics, specifically hydroxyapatite (HA), for high-added-value applications in bone tissue engineering. High-energy milling is innovatively used as the processing route: dry sludge (functioning as the calcium source), a phosphate source, and water were milled with the aim of producing calcium phosphates (in particular, hydroxyapatite) via mechanosynthesis. The industrial sludge was thoroughly analyzed for chemical composition, heavy metals, and mineral phases to ensure suitability for biomedical applications. The mixture of reagents was tailored to comply with Ca/P = 1.67 molar ratio. Milling was carried out at room temperature; the milling velocity was 600 rpm, and milling time ranged from 5 to 650 min. Characterization by XRD, Raman spectroscopy, and SEM confirmed the progressive transformation of calcite into hydroxyapatite through a metastable DCPD intermediate, following logarithmic reaction kinetics. The resulting powders are fine, homogeneous, and phase-pure, demonstrating that mechanosynthesis provides a low-cost and environmentally friendly pathway to convert limestone waste into functional bioceramic materials. This suggests that Moleanos sludge is a viable and sustainable source to produce tailored calcium phosphates and confirms mechanosynthesis as a cost-effective and reliable technology to activate the low-kinetics chemical reactions in the CaCO3-H3PO4–H2O system. This work highlights a novel circular economy approach for the valorization of industrial limestone sludge, turning a difficult waste stream into a high-value, sustainable resource.
- Thermo-mechanical characterization of metal-polymer friction stir composite joints-a full factorial design of experimentsPublication . Correia, Arménio N.; Gaspar, Beatriz M.; Cipriano, Goncalo; Braga, Daniel F. O.; Miguel Gomes Simões Baptista, Ricardo; Infante, VirginiaWith the increasing demand for lighter, more environmentally friendly, and affordable solutions in the mobility sector, designers and engineers are actively promoting the use of innovative integral dissimilar structures. In this field, friction stir-based technologies offer unique advantages compared with conventional joining technologies, such as mechanical fastening and adhesive bonding, which recently demonstrated promising results. In this study, an aluminum alloy and a glass fiber-reinforced polymer were friction stir joined in an overlap configuration. To assess the main effects, interactions, and influence of processing parameters on the mechanical strength and processing temperature of the fabricated joints, a full factorial design study with three factors and two levels was carried out. The design of experiments resulted in statistical models with excellent fit to the experimental data, enabling a thorough understanding of the influence of rotational speed, travel speed, and tool tilt angle on dissimilar metal-to-polymer friction stir composite joints. The mechanical strength of the composite joints ranged from 1708.1 ± 45.5 N to 3414.2 ± 317.1, while the processing temperature was between 203.6 ± 10.7 °C and 251.5 ± 9.7.
- Energy efficiency and waste reduction through maintenance optimization: a case study in the pharmaceutical industryPublication . Soares Domingues, Nuno Alexandre; Patrício, JoãoThe global rise in population, increased life expectancy, and heightened international mobility have escalated disease prevalence and pharmaceutical demand. This growth intensifies energy consumption and chemical waste production within the pharmaceutical industry, challenging environmental sustainability and operational efficiency. Chromatography, a vital analytical technique for ensuring product quality and regulatory compliance, can also contribute to material waste and energy inefficiencies if not properly maintained and optimized. This study applies Failure Mode and Effects Analysis (FMEA) to chromatographic equipment maintenance within Hovione’s Engineering and Maintenance Department, aiming to identify and mitigate failure risks. By integrating environmental metrics derived from Life Cycle Assessment (LCA) into the FMEA framework, a hybrid risk evaluation tool was developed that prioritizes both equipment reliability and sustainability performance. The findings demonstrate how this integrated approach reduces unplanned downtime, lowers solvent waste, and improves energy efficiency. Additionally, the study proposes a conceptual dashboard to support proactive, sustainability-driven asset management in pharmaceutical laboratories. By bridging reliability engineering and environmental sustainability, this research offers a strategic model for optimizing resource use, minimizing chemical waste, and enhancing long-term operational resilience in regulated pharmaceutical environments.
- Retaining the specific capacitance under electrochemical stress: A pH-induced self-protection mechanism for manganese dioxide pseudocapacitive electrodesPublication . Alves, Aila Cossovan; Chiavassa, Luísa; Martins, Tiago D.; Taryba, Maryna; Baleizão, Carlos; Moura e Silva, Teresa; MONTEMOR, FATIMAIn this study, we report the enhanced electrochemical performance of a MnO2 electrode modified with a pH-sensitive co-polymer, activated at acidic pH, and designed to counteract MnO2 degradation in aqueous aqueous pseudocapacitors. The conformation of this polymer is controlled by the local pH changes that occur at the electrode/electrolyte interface during electrochemical stress associated to oxygen evolution. As a proof of concept, we demonstrate that the addition of the pH-sensitive polymer contributes to improved electrode integrity and lifetime under over-polarization with oxygen evolution. After undergoing 10 cycles of electrochemical stress, the MnO2/pH-sensitive polymer composite retains similar to 70 % of its capacitance. This remarkable result stands in stark contrast with the pristine MnO2 electrode which fails catastrophically under the same stress conditions. We believe that this pH-induced self-protection mechanism represents a significant advancement in the development of novel smarter self-healing electroactive materials for the next generation of energy storage devices.
- In situ ellipsometry and EIS study of potentiostatic synthesis of pseudocapacitive MnOxPublication . Sampaio, Rui F.V.; Moura e Silva, Teresa; MONTEMOR, FATIMAThis work discusses the one-step potentiostatic growth of manganese oxide on stainless steel for pseudocapacitor electrodes. The electrode material was studied through in situ ellipsometry and electrochemical impedance spectroscopy, in order to correlate its microstructure with the capacitive response. Ellipsometry results show the formation of three layers during the potentiostatic synthesis of manganese oxide on stainless steel: the thickening of the native oxide of the substrate, and the growth of two distinct layers of manganese oxide. The inner layer is slightly more compact (>n) and more resistive (