Chemical Engineering & Technology最新文献

Graphene oxide (GO)-based humidity sensors are appealing because of their interesting physicochemical properties. This research focuses on developing a novel GO-based relative humidity (%RH) sensor for detecting moisture in transformer oil. GO is derived from the modified Hummers method using graphite as a precursor. The sensor fabrication includes depositing the GO layer on a substrate by drop-casting. The effects of vital parameters on sensor performance at different frequencies (100 Hz–100 kHz) for various %RH (10–90 %) are studied. The short-term stability of the capacitive response of the proposed sensor, showing a maximum deviation of 6.7 %, was found. An experimental setup simulated the environment of an oil-filled transformer to test the developed sensor inside the laboratory which can measure the moisture in transformer oil at different temperatures to prevent liquid insulation failure, ensuring longer life.

This study investigates electro-osmosis in an Oldroyd-B fluid with a nonlinear Arrhenius reaction to model temperature-dependent chemical kinetics, enhancing concentration predictions. Similarity transformations reduce the governing equations to ODEs, solved via a MATLAB-based shooting technique and RungeKutta method. The analysis highlights the combined effects of electro-osmosis, MHD flow, radiation, melting, and nonlinear reactions. Results reveal the interplay of these mechanisms, offering insights into thermal transport and microfluidic applications, with implications for engineering and industrial processes involving complex fluids.

This study presents an experimental investigation of a twin-fluid air-blast atomizer with tangential air entry, designed for fluid catalytic cracking (FCC) riser applications. An innovatively developed injector incorporating an impactor bolt is evaluated under varied operating conditions. Measurements reveal a nearly uniform mean droplet diameter across most of the spray field, distinguishing it from conventional designs, with noticeable deviations only at the periphery. The Sauter mean diameter (SMD) increases almost linearly toward the spray's outer zones, whereas the orientation of the impactor bolt exerts minimal influence on droplet velocity but induces slight variations in SMD. Based on the experimental data, separate empirical correlations are proposed for the non-dimensional supply pressure ratio and SMD, enabling precise prediction of spray characteristics.

Polymeric drag-reducing agents (DRAs) are known for their ability to reduce drag in turbulent flow, offering cost-effective alternative. However, DRAs face chain degradation under high shear forces. Blended polymeric DRAs shown greater resistance to shear forces in turbulent flow compared to single polymers. Research indicates that combining polymers enhance their properties. These findings suggest blended polymeric DRAs are practical and versatile drag reduction. Thus, this study summarizes research on polymer blends, including the synergistic effects and theirability to withstand high shear forces.

Taltirelin (TTL) polymorphism was controlled for the first time via isothermal antisolvent crystallization using water and acetone as the solvent and antisolvent, respectively. TTL crystallizes into two polymorphic forms: the metastable α-form and the stable β-form. The solubility of TTL in water/acetone mixtures from −10 °C to 30 °C was determined. Experiments were performed within a supersaturation ratio range of 9.2–18.0 and an antisolvent fraction of 0.78–0.85. The α-form was consistently obtained at supersaturation ratios above 10.8 and antisolvent fractions between 0.81 and 0.85, whereas the β-form was produced at supersaturation ratios below 10.8. The formation regions of each polymorph were mapped based on the supersaturation ratio and antisolvent fraction. The desired polymorph was selectively obtained by adjusting these parameters. Factors such as the nucleation rate, solubility ratio, and interfacial energy were also investigated to selectively crystallize TTL.

Depletion of fossil fuel sources, rising crude oil prices, and stringent emission regulations led to the development of a transesterification process to produce biodiesel as an alternative, sustainable fuel. The reaction conditions were carried out separately under magnetic stirring at 65 °C for 80 min. The results showed the high efficiency of the biodiesel produced by the addition of zinc oxide nanoparticles (ZnO NPs) with a viscosity of 0.9273 cSt and a density of 0.850 g mL⁻¹. The maximum efficiency of the biodiesel produced in terms of cloud point −14 °C, ˂−50 °C, 5 °C, and 5 °C, pour point ˂−50 °C, and surface tension (28.6, 24.8, 23.6, and 23.6 N m⁻¹) for biodiesel-KOH, biodiesel-ZnONPs, biodiesel-ZnONPs/3 % ethanol, and biodiesel-ZnONPs/5 % ethanol, respectively, was determined.

Thermal runaway not only happened in batch reactors but also was a big challenge for continuous flow reactor design. Continuous flow reactors are mainly used for high exothermic reactions due to their advantages of small volume and easy control of reaction conditions. In response to the current lack of thermal safety assessment for continuous flow reactors, this study used a coupled method of computational fluid dynamics (CFD) and HJ criterion to investigate the effects of different operating conditions on the thermal runaway. The results indicate that the diameter, jacket temperature, and the initial concentration of the reactants are critical parameters that contribute to the onset of thermal runaway. And this study presents a new method to help identify thermal runaway in continuous flow reactors, which can provide guidance for the safe design and optimization of the reactor.

Enameled steel chemical reactor equipment. © gen_A@AdobeStock

The study analyzes the fluid-dynamical and thermodynamical behavior of a viscous and incompressible third-grade fluid flowing upwards through a vertical microchannel. The flow is driven by a combination of three forces, namely an adverse pressure gradient, buoyancy forces, and electroosmosis. The fluid is subjected to exothermic reactions modeled under Arrhenius kinetics, and the fluid viscosity is assumed temperature dependent as modeled via a Nahme law. The vertical walls of the microchannel are subjected to convective cooling, modeled via Newton's law of cooling. The resultant system of nonlinear coupled partial differential equations is solved numerically using robust semi-implicit finite difference methods. The results primarily demonstrate, as expected, that both the flow velocity and fluid temperature increase with time, from the zero initial states, until steady states are reached—provided the exothermic reactions are kept low enough to avoid thermal runaway and hence allow for the attainment of steady states. Additionally, and as expected, both the flow velocity and fluid temperature are enhanced in response to increases in the buoyancy driving forces. The more pertinent results show that increased non-Newtonian character of the fluid as well as increased electroosmotic characteristic are both flow retarding. Furthermore, we observe that the presence of non-Newtonian character in the fluid also leads to better mitigation of the thermal runaway phenomena than corresponding Newtonian fluids.