Browsing by Author "Álvarez-Hostos, Juan C."

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    A regularized approach for derivative-based numerical solution of non-linearities in phase change static hysteresis modeling
    (International Communications in Heat and Mass Transfer, 2025-04) Dittler, Ramiro A.; Demarchi, María Cecilia; Álvarez-Hostos, Juan C.; Albanesi, Alejandro E.; Tourn, Benjamín A.
    Phase change materials (PCMs) represent a promising solution for thermal energy storage (TES) since they can store and release energy in the form of latent heat during solid↔liquid transitions. Nevertheless, accurately simulating the thermal behavior of PCMs remains challenging due to the non-linearities concerning latent heat effects and enthalpy hysteresis. This work introduces a stable and robust procedure based on the finite element method (FEM) under a mixed enthalpy–temperature formulation to address such non-linearities, which enables the numerical solutions using derivative-based algorithms such as the Newton–Raphson (NR) method. The static hysteresis model (SHM) is implemented in the FEM-based formulation via a regularization of the liquid fraction function in response to the sign of the temperature rate. This novel approach ensures a continuous and smooth heating↔cooling transition while retaining the SHM energy-conservative features to properly solve its non-linearities. The method is validated through a one-dimensional benchmark problem, demonstrating high performance and physical fidelity for both complete and partial phase changes. It achieves second-order convergence rates, ensures numerical stability even for large time steps, and maintains accuracy under diverse thermal boundary conditions. Finally, the method is extended to two-dimensional problems, highlighting its robustness and scalability for practical applications in TES systems.
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    Computational design of building envelopes as thermal metamaterials
    (SynerCrete 2023, 2023-06-11) Fachinotti, Víctor D.; Álvarez-Hostos, Juan C.; Peralta, Ignacio; Caggiano, Antonio
    A metamaterial is a composite with unprecedented properties, either in nature or in the market. Specifically designed, a metamaterial exhibits either extraordinary or “à la carte” macroscopic physical properties, or allows the device made of it (the “metadevice”) to have an optimal response. In the context of the thermal performance of a building, let the metadevice be the whole building envelope, say the “metaenvelope”. Then, the metamaterial in the metaenvelope is determined in order to maximize the building energy efficiency. To this end, we apply the optimization-based metamaterial design approach, which consists in solving a nonlinear constrained optimization problem where the objective function is the energy consumption for cooling and heating, and the design variables define the metamaterial in the envelope. Particular emphasis is given to the use of NRG-foams, which are foamed concretes with embedded microencapsulated phase change materials developed within the framework of the EU H2020 project NRG-STORAGE. Finally, metaenvelopes having NRG-foams as insulation materials will be compared with a standard envelope in terms of the energy consumed by the enclosed building to keep the indoor thermal comfort.
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    Modelo inverso iterativo acoplado a algoritmo genético para la calibración de modelos de simulación térmica de edificios
    (XL MECOM, 2024-11-08) Demarchi, María Cecilia; Albanesi, Alejandro E.; Favre, Federico; Álvarez-Hostos, Juan C.
    En este estudio se implementa un modelo inverso iterativo basado en optimización con algoritmo genético para la calibración y validación de modelos de simulación computacional del rendimiento térmico de edificios. Este modelo ajusta dinámicamente las resistencias térmicas del aire, la absortancia térmica y solar de los materiales exteriores, la infiltración de aire y el coeficiente convectivo para minimizar las discrepancias entre las temperaturas de aire medidas y simuladas. Este meticuloso enfoque garantiza una calibración precisa y una evaluación efectiva del rendimiento térmico y energético del modelo, proporcionando información valiosa para la optimización de las estrategias de diseño energético de edificios. Se considera como caso de estudio los edificios construidos en Bulgaria, Sofia, en el marco del proyecto NRG STORAGE (Integrated porous cementiciuos Nanocomposites in non-Residential building envelopes for Green active/pasive energy STORAGE).