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Browsing Centros UC by browse.metadata.categoria "Ciencias"

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    Experimental and Numerical Analysis of a PCM-Integrated Roof for Higher Thermal Performance of Buildings
    (2024) Pierre Simon, François; Ruíz Valero, Letzai; Girard, Aymeric; Galleguillos, Héctor; CEDEUS (Chile)
    Phase change materials (PCMs) designate materials able to store latent heat. PCMs change state from solid to liquid over a defined temperature range. This process is reversible and can be used for thermo-technical purposes. The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management. The experiment is conducted in two test rooms in Antofagasta (Chile) during summer, fall, and winter. The PCM is integrated into the rooftop of the first test room, while the roof panel of the second room is a sealed air cavity. The work introduces a numerical model, which is built using the finite difference method and used to simulate the rooms’ thermal behavior. Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates. Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1°C±10.6°C, while the one of the air-panel room varies 28.3°C±18.5°C. Under the experiment’s conditions, the PCM room’s indoor temperature observes smoother diurnal fluctuations, with lower maximum and higher minimum indoor temperatures than that of the air-panel room. Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter, as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures. This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs, and improve indoor thermal comfort in different climates of Chile.
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    Multi-scale temporal analysis of evaporation on a saline lake in the Atacama Desert
    (2022) Lobos Roco, Felipe Andres; Hartogensis, Oscar; Suarez Poch, Francisco Ignacio; Huerta-Viso, Ariadna; Benedict, Imme; de la Fuente, Alberto; Vila-Guerau de Arellano, Jordi; CEDEUS (Chile)
    We investigate how evaporation changes depending on the scales in the Altiplano region of the Atacama Desert. More specifically, we focus on the temporal evolution from the climatological to the sub-diurnal scales on a high-altitude saline lake ecosystem. We analyze the evaporation trends over 70 years (1950–2020) at a high-spatial resolution. The method is based on the downscaling of 30 km ERA5 reanalysis data at hourly resolution to 0.1 km spatial resolution data, using artificial neural networks to analyze the main drivers of evaporation. To this end, we use the Penman open-water evaporation equation, modified to compensate for the energy balance non-closure and the ice cover formation on the lake during the night. Our estimation of the hourly climatology of evaporation shows a consistent agreement with eddy-covariance (EC) measurements and reveals that evaporation is controlled by different drivers depending on the time scale. At the sub-diurnal scale, mechanical turbulence is the primary driver of evaporation, and at this scale, it is not radiation-limited. At the seasonal scale, more than 70 % of the evaporation variability is explained by the radiative contribution term. At the same scale, and using a large-scale moisture tracking model, we identify the main sources of moisture to the Chilean Altiplano. In all cases, our regime of precipitation is controlled by large-scale weather patterns closely linked to climatological fluctuations. Moreover, seasonal evaporation significantly influences the saline lake surface spatial changes. From an interannual scale perspective, evaporation increased by 2.1 mm yr−1 during the entire study period, according to global temperature increases. Finally, we find that yearly evaporation depends on the El Niño–Southern Oscillation (ENSO), where warm and cool ENSO phases are associated with higher evaporation and precipitation rates, respectively. Our results show that warm ENSO phases increase evaporation rates by 15 %, whereas cold phases decrease it by 2 %.
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    The Quebrada Negra wetland study: An approach to understand plant diversity, hydrology, and hydrogeology of high-Andean wetlands
    (John Wiley and Sons Inc, 2023) Suarez Poch, Francisco; Sarabia A.; Sanzana P.; Latorre Hidalgo Claudio; Munoz J.F.; CEDEUS (Chile)
    High-Andean peatlands are high-altitude wetland ecosystems found throughout the arid central Andes of South America. They form through the establishment of specialized grasses and cushion sedges that are well-adapted to cold temperatures, in areas where groundwater emerges. The Silala River is a groundwater-fed high-Andean fluvial system, which emerges in various springs that generate wetlands, the Cajones and Orientales (Bolivia), the river's headwater sources, and the Quebrada Negra (Chile) being the most important. This article reviews detailed monitoring undertaken in the undisturbed Quebrada Negra wetland to provide insights into wetland processes, and to compare its functioning to that of the Bolivian wetlands, which were channelized a century ago. Vegetation composition was found to be similar among the three wetlands, and their spatiotemporal vegetation cover distribution showed strong seasonal and interannual variability. The channelized Bolivian wetlands have the highest annual actual evapotranspiration values (~700 mm, due to their higher vegetation vigor), as estimated using remote sensing, ~10% greater than that obtained in the undisturbed Quebrada Negra wetland. For the Quebrada Negra wetland, groundwater monitoring revealed that hydraulic head contours are consistent with the topography, although water sources to the wetland are complex to identify. While significant groundwater inflows arise at the wetland edges, upwelling and downwelling conditions are observed at various locations within the wetland, similar to other high-Andean wetlands. The observations suggest that while the underlying groundwater discharge sustains the saturated conditions of the wetland, the spatial variability of groundwater inputs results in a negligible impact of channelization on wetland evapotranspiration.