https://repositorio.ufu.br/handle/123456789/19618 2026-08-07T01:47:39Z 2026-08-07T01:47:39Z https://repositorio.ufu.br/handle/123456789/49204 2026-07-31T06:23:43Z 2026-03-12T00:00:00Z

Title: Sedimentação de suspensões aquosas de carbonato de cálcio em condições não isotérmicas: uma investigação experimental por atenuação de raios Gama Abstract: This study investigated the sedimentation behavior of solid particles under lateral heating conditions, with emphasis on the coupling between particulate mass transport and heat transfer mechanisms. The experimental system consisted of an aqueous calcium carbonate suspension, and dyed silica oxide was employed as a tracer previously validated in terms of density and particle size distribution compatibility. Physical characterization was performed through pycnometry and laser diffraction analysis. The final structure of the sedimented bed was determined using the gamma-ray attenuation technique, enabling the determination of vertical profiles of local solid volume fraction. Thermal measurements revealed the development of a significant lateral temperature gradient near the oil reservoirs, establishing a non-isothermal condition along the width of the experimental cell. The solid volume fraction profiles indicated a consolidated bed with values ranging from approximately 0.52 to 0.55 in the lower region, accompanied by a systematic lateral displacement of the solid–liquid interface near the walls. The hypothesis of differential compaction was ruled out, as no significant variations in packing degree were observed across the cell width. Visual analysis using the tracer revealed inclined sedimented structures near the walls, consistent with transverse particle redistribution induced by natural convection arising from the imposed thermal gradient. The results demonstrate that sedimentation under lateral heating exhibits multi-dimensional behavior governed by the coupling between mass transport and heat transfer, and therefore cannot be adequately described by a simplified one-dimensional isothermal model.

2026-03-12T00:00:00Z https://repositorio.ufu.br/handle/123456789/49020 2026-07-24T06:19:03Z 2025-09-05T00:00:00Z

Title: Aplicação do radioisótopo Cs-137 na técnica de atenuação de raios gama para o monitoramento de suspensões aquosas de densidades variadas Abstract: This study aimed to establish the operating conditions of a gamma radiation detection system using a low-activity cesium-137 radioisotope, applied to the Gamma-Ray Attenuation (GRA) technique for monitoring high-density aqueous suspensions. Experimental parameters, including operating voltage, fine gain, lower and upper-level discriminators, counting time, minimum number of counts, and resolution time, were systematically adjusted to maximize the precision and reproducibility of the system. The initial calibration positioned the photoelectric peak at channel 238, whereas a second calibration centered the peak at channel 507, thereby focusing on the central region of the multichannel analyzer scale. During the experiments, the calibration constant β (1.3792) and the average resolution time τ′ (0.0180 s) were determined, and the Region of Interest (ROI) was defined based on the average full width at half maximum (FWHM). The system was validated through tests using a 30% (v/v) barite suspension, which was initially allowed to settle and subsequently resuspended by mechanical agitation. Measurements were conducted at different heights along the settled column, with an acquisition time of 1800 s per point, enabling the monitoring of volumetric solids concentration variations across the solid–liquid interface. The experimental results revealed a decreasing concentration profile with increasing height, consistent with the expected behavior of gravitational sedimentation. Overall, the system exhibited a stable and reproducible response in agreement with literature data, demonstrating the feasibility of the GRA technique as a non-invasive and reliable method for monitoring dense suspensions. It is concluded that the use of cesium-137 expanded the range of measurable concentrations and reinforced the applicability of the system to industrial solid–liquid separation processes.

2025-09-05T00:00:00Z https://repositorio.ufu.br/handle/123456789/48978 2026-07-23T06:22:43Z 2026-03-24T00:00:00Z

Title: Projeto de um trocador de calor casco tubo utilizando o algoritmo de busca cuco Abstract: Heat exchangers are widely used in industrial processes to enable the transfer of thermal energy between fluids. Among the various types available, shell-and-tube heat exchangers are particularly notable due to their robustness and versatility in industrial applications. However, the design of these systems involves the determination of several geometric and operational variables that simultaneously influence thermal performance, pressure drop, and both capital and operating costs. In this context, optimization techniques have been extensively employed to obtain economically efficient designs. In this study, the Cuckoo Search (CS) algorithm was applied to the design optimization of shell-and-tube heat exchangers with the objective of minimizing the total annual cost, taking into account both investment costs and operating costs associated with fluid pumping. The mathematical model employed is based on classical correlations available in the literature for the calculation of heat transfer coefficients, pressure drop, and heat transfer area. Two benchmark case studies commonly reported in the literature were evaluated, considering different geometric configurations for tube arrangements. The results indicate that the CS algorithm was able to obtain competitive solutions when compared with those reported in the literature, achieving a reduction of approximately 6.08% in the total annual cost. Furthermore, the analyzed geometric configurations resulted in very similar cost values, suggesting that the optimization procedure converges to economically equivalent designs. In addition, a sensitivity analysis of the main algorithm parameters was carried out in order to evaluate their influence on the final solution. The results demonstrated good stability and repeatability of the solutions, as well as the existence of parameter ranges that provide a suitable balance between solution quality and computational effort. Overall, the findings indicate that the CS algorithm represents an efficient and relatively simple alternative for solving engineering design optimization problems, showing good performance in the optimal design of shell-and-tube heat exchangers.

2026-03-24T00:00:00Z https://repositorio.ufu.br/handle/123456789/48840 2026-07-15T06:25:15Z 2025-05-08T00:00:00Z

Title: AAnálise da Aplicação de Processos de Filtração por Membranas para Separação de Dióxido de Carbono: Uma Revisão Bibliográfica

2025-05-08T00:00:00Z