Mixing operations in biological processes is of utmost importance due to its effect on scaling-up and heat and mass transfer. This paper presents the characterization of a bench-top bioreactor with different impeller configurations, agitation and oxygen transfer rates, using CFD simulations and experimental procedures. Here, it is demonstrated that factors such as the type of impeller and the flow regime can drastically vary the operation as in the preparation of cultures. It was observed that the bioreactor equipped with a Rushton generates a k L a of 0.0056 s−1 for an agitation velocity and airflow rate of 250 RPM and 5 L/min, respectively. It is suitable result for the dissolved oxygen (DO) but requires a considerable amount of power consumption. It is here where the importance of the agitator’s diameter can be observed, since, in the case of the two propeller types studied, lower energy consumption can be achieved with a smaller diameter, as well as a much smaller shear cup 2.376 against 0.723 s−1 by decreasing by 4 cm the standard diameter of an agitated tank (10 cm). Finally, the k L a values obtained for the different configurations are compared with the maximum shear rate values of different cell cultures to highlight the impact of this study and its applicability to different industries that use agitation processes for cell growth.
Excessive water production in mature heavy oil fields causes incremental costs, energy consumption, and inefficiency. Understanding multiphase flows near the wellbore is an alternative to improve production efficiency. Therefore, this study conducts a series of numerical experiments based on the full set of the Navier-Stokes equations in 3D to simulate multiphase flows in porous media for heavy oil production horizontal wells. The solution given by this advanced mathematical formulation led to the description of the movement of the fluids near the wellbore with unprecedented detail. A sensitivity analysis was conducted on different rock and fluid properties such as permeability and oil viscosity, assuming homogeneous porous media. The influence of these parameters on the prediction of the breakthrough time, aquifer movement, and the severity of water production was noticed. Finally, the numerical model was verified against field data using two approaches. The first one was conducting a history match assuming homogeneous rock properties. In contrast, the second one used heterogeneous rock properties measured from well logging, achieving a lower deviation than field data, about 20%. The homogeneous numerical experiments showed that the breakthrough occurs at the heel with a subsequent crestation along the horizontal well. Moreover, at adverse mobility ratios, excessive water production tends to happen in water connings at the heel with an inflow area less than 1% of the total inflow area of the completion liner. Different aquifer movement dynamics were found for the heterogeneous case, like the breakthrough through multiple locations along the horizontal well. Finally, critical hydraulic data in the well, such as the pressure and velocity profiles, were obtained, which could be used to improve production efficiency. The numerical model presented in this study is proposed as an alternative to conducting subsurface modeling and well designs.
Pteridium aquilinum (L.) Kuhn is a cosmopolitan plant with great competitive abilities, including allelopathy. The search for plants with negative allelopathic effects on other undesirable plants has led to the discovery of new useful substances for weed control. The objective of this research was to evaluate the allelopathic effect of P. aquilinum on seed germination and growth of four economically important weeds: Bidens pilosa L., Brachiaria decumbens Stapf, Emilia sonchifolia (L.) DC. ex DC and Rumex crispus L. Two experiments were conducted under laboratory and greenhouse conditions using extracts and dried plant residues of P. aquilinum, respectively. For the first experiment, extracts of bracken were obtained using four different solvents (hexane, dichloromethane, ethyl acetate, and methanol) and applied to the test seeds; germination rates were determined. For the second experiment, dry residues of bracken were applied to the soil at concentrations of 2, 5, and 10% and their effect on weed growth variables was determined; a control treatment (no appliacation) was also included. In addition, the presence of some chemical groups associated with each type of extract was qualitatively detected. The extracts inhibited seed germination by 52 -97% in all the studied species. Dichloromethane and methanol were the most efficient solvents, while E. sonchifolia was the most sensitive species. The dry residues of bracken reduced germination by 18 -44% of all the weeds, as well as root length of Bidens pilosa (-30%) and Brachiaria decumbens (-82%). The phytochemical analysis showed the presence of flavonoids, tannins, and polyphenols in the extracts. These results suggest that P. aquilinum can be a good alternative for the biocontrol of the weeds under study and provide knowledge for the development of bioherbicides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.