Due to the increase in the number of people affected by chronic renal failure, the demand for hemodialysis treatment has increased considerably over the years. In this sense, theoretical and experimental studies to improve the equipment (hemodialyzer) are extremely important, due to their potential impact on the patient’s life quality undergoing treatment. To contribute to this research line, this work aims to study the fluid behavior inside a hollow fiber dialyzer using computational fluid dynamics. In that new approach, the blood is considered as multiphase fluid and the membrane as an extra flow resistance in the porous region (momentum sink). The numerical study of the hemodialysis process was based on the development of a mathematical model that allowed analyzing the performance of the system using Ansys® Fluent software. The predicted results were compared with results reported in the literature and a good concordance was obtained. The simulation results showed that the proposed model can predict the fluid behavior inside the hollow fiber membrane adequately. In addition, it was found that the clearance decreases with increasing radial viscous resistance, with greater permeations in the vicinity of the lumen inlet region, as well as the emergence of the retrofiltration phenomenon, characteristic of this type of process. Herein, velocity, pressure, and volumetric fraction fields are presented and analyzed.
In this work, recycled poly(ethylene terephthalate) (PETR) was blended with virgin high-density polyethylene (HDPE) in an internal mixer in an attempt to obtain a material with improved properties. A compatibilizer (PE-g-MA) and a chain extender (Joncryl) were added to the PETR/HDPE blend and the rheological and thermal properties of the modified and unmodified blends as well as those of virgin PET with virgin HDPE (PETV/HDPE). All the blends were characterized by torque rheometry, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The data obtained indicate that the incorporation of either the chain extender or the compatibilizer agent led to increases in torque (and hence in viscosity) of the blend compared to that of the neat polymers. The joint incorporation of the chain extender and compatibilizer further increased the viscosity of the systems. Their effect on the crystallinity parameters of HDPE was minimal, but they reduced the crystallinity and crystallization temperature of virgin and recycled PET in the blends. The thermal stability of the PETR/HDPE blend was similar to that of the PETV/HDPE blend, and it was not affected by the incorporation of the chain extender and/or compatibilizer.
The oil industry has sought to minimize the environmental impact from mining activities and oil transportation. The oil transportation by pipeline is subject to failures and leaks that cause financial losses and environmental damage, often irreparable. In this sense, the aim of this study is to evaluate the influence of the leak diameter in the behavior of the two-phase flow (oil and water) in a pipe. A transient and incompressible multiphase flow mathematical model based on the particle model was used here. Oil is the dispersed phase while water is the continuous phase. To model the turbulence effect it was used the standard k-ε model. All simulations were carried out using the Ansys CFX® commercial code. Results of the pressure, velocity and volumetric fraction of the phases are presented and discussed. The results confirm the difficulty to detect leakage with small diameters.
The onshore and offshore production of oil and natural gas is characterized by the multiphase flow in ducts and pipes, which are interconnected by various equipments such as wellhead, pumps, compressors, processing platforms, among others. The transport of oil and oil products is essential to the viability of the sector, but is susceptible to failures, that can cause great environmental damage. Considering this necessity of the transportation sector of oil and derivatives, leakage in pipelines with curved connections, are the object of study for various researchers. In this sense, this work contributes to the study of three-phase flow (oil-water-gas) in a curved pipe (90°) using Computational Fluid Dynamics. The physical domain is constituted by two tubes of 4 meters trenched by a 90° curve, with the poring whole in the curvated accessory. The mathematical model is based on a particle model, where the oil is considered as a continuous phase and the water and gas as a particulate phase. The SST (Shear Stress Transport) turbulence model was adopted. All simulations were carried out using the Ansys CFX® 12.1 commercial code. Results of the pressure, velocity and volumetric fraction of the phases are presented and discussed.
The objective of this work was the development of a processing methodology for embedding NiTi fibers into a polymer-based composite plate. A carbon fiber reinforced polymer (CFRP) prepreg and NiTi thin wires were used. A uniaxial hot press was prepared to be used in the composite processing. Two prototypes were fabricated to provide fiber alignment and fixation fixture. A CFRP composite plate without fiber and another with NiTi fibers were processed. Micrometers and a universal materials testing machine were used to measure the plate thickness and Young's modulus. It was possible to develop a processing methodology for embedding NiTi fibers into a polymer-based composite plate. The CFRP plate without fiber presented almost no variation in plate thickness and Young's modulus measurement thus enabling the CFRP manufacture by the hot uniaxial press. The fiber fixation fixture developed was able to produce CFRP-NiTi fiber hybrid composites with different number of fibers embedded, the spacing distance between fibers was at least 1 mm and the fiber alignment was achieved.
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