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Percorrer por autor "Silva, Paulo Bruno Rossi da"

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  • A case for including solar dehydrators in food processing
    Publication . Silva, Paulo Bruno Rossi da; Farrero, Bernardo; Ribeiro, Luís Frölén
    The access of small-scale food producers and big agro-industry players to equipment is abyssal. The latter have access to well-developed and appropriate technology. In this article, one proposes a novel design for food dehydration equipment to serve small-scale producers, reducing their technological gap regarding dehydration. Equipment that dries more than 1000 kg daily is costly and consumes much energy. Lower capacity machines, up to 100 kg per day, are often one-off handcrafted projects built with reused materials without dimensioning supporting the design. They are usually not easily transportable and underperform: the drying chamber tends to overheat; the solar collector's area is usually 50% inferior to the required product quantity. One proposes a mobile dehydrator with a solar collector area 7 times larger than average, promoting moisture removal by naturally convected airflow at lower temperatures, reaching up to 4,5 m/s and 44,3 °C inside the entrance of the drying chamber. Under these flow conditions, the food's organoleptic properties are preserved compared to the often high-temperature drying handspun machines continually adopted by small-scale producers. The internal layout of the drying chamber was also changed to promote the increase of turbulence and reduce the existence of recirculation areas, thus facilitating the transfer of moisture from the food to the airflow. The expected result from implementing this novel design is avoiding food losses due to natural degradation by increasing the product's shelf life before transport and transformation. Solar equipment has zero operational costs, and all these advantages are expected to encourage small-scale dehydration technology.
    2023Documento de conferência Acesso aberto Ver mais
  • Modeling the natural convection in a solar dehydrator
    Publication . Silva, Paulo Bruno Rossi da; Ribeiro, Luís Frölén; Olivio, Emillyn Ferreira Trevisani
    This study presents a computational model of natural convection in a solar food dehydrator, particularly acorns, by leveraging solar energy. Solar drying offers a sustainable, low-cost alternative to conventional drying methods, which rely on high-energy inputs. By simulating the dehydrator’s performance, this research aims to minimize experimental testing needs, which are constrained by seasonal and budgetary limitations. Using a three-part model (collector, chamber, and chimney), the dehydrator operates through a thermal siphon mechanism where air, heated by solar energy, flows naturally to remove moisture from the food. The model employs Computational Fluid Dynamics (CFD) using ANSYS Fluent to simulate temperature, velocity, and flow rate conditions, validated against experimental data from tests conducted in Carrascal, Portugal. Findings show that the natural convection mechanism alone generates limited internal air movement, insufficient for consistent drying across seasons. Thus, forced ventilation was introduced, resulting in significant performance improvements with up to 3.8 times increased air outflow in autumn and 2.4 times in summer. Simulation data, processed with MATLAB and cross-referenced with experimental measurements, underscore the need for forced ventilation in solar dryers to enhance air circulation and drying rates, especially under variable solar radiation conditions. The model offers insights for optimizing solar dryer design, potentially expanding their application in energy-limited, rural environments. Future work will explore enhanced data integration and alternative solar radiation databases to improve the predictive accuracy of the model.
    2024Dissertação de mestrado Acesso aberto Ver mais