FRSF - INVESTIGACIÓN Y PRODUCCIÓN CIENTÍFICA
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Item Computational design of a massive solar-thermal collector enhanced with phase change materials(Energy and Buildings, 2022-11-01) Peralta, Ignacio; Fachinotti, Víctor D.; Koenders, Eduardus A. B.; Caggiano, AntonioA cement-based device that can meet, partially or completely, the heating loads of a building by absorbing the solar radiation and converting it into thermal energy can be defined as a Massive Solar-Thermal Collector. The absorbing material for the incoming radiation is made of a cementitious composite, generally concrete, and flowing water inside tubes acts as a heat transfer medium. For an optimized performance, during periods of solar radiation, the device has to efficiently conduct the heat flow from the absorbing surface of the collector and transfer this heat energy to the water. Then, when the radiation is reduced or became null, the device should retain as much as possible the heat energy, reducing the heat that is escaping the collector and consequently the losses to the surrounding environment. In this work, by performing a parametric analysis, different absorbing materials are tested with the objective of finding the best configuration that maximizes the energy efficiency of the collector. Cementitious materials, in combination with Phase Change Materials with distinct melting (and solidification) temperatures, are selected as candidate absorbing materials. The weather variables of an entire year and for two different locations are considered to evaluate the behavior of these devices in opposite climates. After numerical simulations, in where an enthalpy-based finite element formulation is used to solve the physical problem, the obtained results allow to conclude that the inclusion of Phase Change Materials within the absorber material of the collectors, if it is done in a correct way, can improve the energy performance of these devices. In this study, 34 ºC and 53 ºC are chosen as the most appropriated melting temperatures, which conduct to considerable improvements in the achieved performances, and in both warm and cold climates.Item Computational design of building envelopes as thermal metamaterials(SynerCrete 2023, 2023-06-11) Fachinotti, Víctor D.; Álvarez-Hostos, Juan C.; Peralta, Ignacio; Caggiano, AntonioA 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.Item 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.Item A shot in the dark : the current state of PCM hysteresis modelling in building energy simulation software(2025-02-16) Zhilyaev, Dmitry; Albanesi, Alejandro E.; Demarchi, María Cecilia; Fachinotti, Víctor D.; Bakker, Hans L. M.; Jonkers, Henk M.Phase change materials (PCM) are receiving an ever-growing attention as a promising construction material for improving building energy performance through thermal storage and peak load shifting. The analysis of PCM performance and decision-making related to PCM implementation in building envelope often rely on building energy simulation software such as EnergyPlus – a de-facto standard in the academic world and the industry. For a precise modelling of the dynamic PCM behaviour it is essential to correctly account for PCM hysteresis. This work provides an in-depth analysis of four publicly available EnergyPlus-based hysteresis models and identifies the existing limitations for each of them. Furthermore, it explores the effects of PCM model selection on decision-making using the example of novel PCM-embedded material development. The results of this study show that the current built-in hysteresis model in EnergyPlus is not implemented correctly, and none of the other analysed models is completely free of limitations. Moreover, this work draws attention to the existing contradictions between different PCM modelling approaches, highlighting the critical impact the selection of a PCM model has on PCM-related decision-making. We conclude that while the existing hysteresis models in EnergyPlus are operable – albeit with great caution – they are not yet at the stage where they could be used as a reliable decision-making support tool. Practical real-world integration of PCM in building envelopes is hardly possible without having dependable modelling tools to back it up, and the development of such tools requires far more attention than it is given at the moment.