Navegando por Autor "Vanegas, Jaime Daniel Bustos"
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Item CFD modelling of diffusive-reactive transport of ozone gas in rice grains(Biosystems Engineering, 2019-03) Silva, Marcus Vinicius de Assis; Martins, Márcio Aredes; Faroni, Leda Rita D'Antonino; Vanegas, Jaime Daniel Bustos; Sousa, Adalberto Hipólito deThe search for alternatives to the use of chemical products to control insect pests in stored grains has stimulated the development of new techniques that allow the maintenance and preservation of grain quality without posing risks to people and the environment. One of these alternatives is the use of ozone gas (O3) as a fumigant, mainly due to its oxidising and biocidal characteristics. To investigate the transport mechanisms involved in the flow of the O3 gas through rice grains, the CFD (Computational Fluid Dynamics) analysis was used, and from this evaluation, it was possible to predict the decomposition reaction constant and the O3 effective diffusion coefficient. In the experiment, grains were submitted to fumigation process in a prototype adapted from a diaphragm cell. Data on the ozone gas concentration were collected from a monitoring point immediately above the grain layer every 10 min. Parallel to the experimental procedure, the modelling of the O3 gas flow using the CFD technique was performed. The adjustment parameters input to the CFD model were the effective diffusion and the decomposition reaction constant of the O3 gas in the rice grains. The estimated diffusivity value (1.0 × 10−6 m2 s−1), and decomposition reaction constant (0.00167 s−1) are of the same order of magnitude of several other gases for agricultural grains.Item Developing predictive models for determining physical properties of coffee beans during the roasting process(Industrial Crops and Products, 2018-02) Vanegas, Jaime Daniel Bustos; Corrêa, Paulo Cesar; Martins, Márcio Arêdes; Baptestini, Fernanda Machado; Campos, Renata Cássia; Oliveira, Gabriel Henrique Horta de; Nunes, Eduardo Henrique MartinsThis study aims to evaluate and model the variation in the physical properties of coffee beans in isothermal roasting conditions, providing mathematical expressions that can be used for heat and mass transfer models for coffee roasting. Arabica coffee beans were studied with an initial moisture content of 0.129 kgw kgdm−1 and roasted in a direct gas burning roaster. Five temperatures were set inside the cylinder (200, 220, 240, 260 and 280 °C). The beans were roasted uniformly by suspension in the center of the drum. A thermocouple recorded the temperature every 5 s. X-ray microtomography was used to analyze the evolution of the internal matrix during the roasting process. The moisture content and physical properties (volume, surface area, and density) of each coffee bean were evaluated every 20 s. Empirical models were fitted to represent the physical properties as a function of the moisture content. It was observed that the volumetric expansion is isotropic at roasting temperatures above 220 °C. The final bean volume can reach up to 1.8 times the initial volume. The bean density varied linearly with the moisture content, presenting a larger drop at a higher roasting temperature.