Explore the vast range of titles available.

Due to the heterogeneity of oils, the use of mixtures of lipases with different activity for a large number of glycerol-linked carboxylic acids that compose the substrate has been proposed as a better alternative than the use of one specific lipase preparation in the enzymatic synthesis of biodiesel. In this work, mixtures of lipases from different sources were evaluated in their soluble form in the ethanolysis of soybean oil. A mixture of lipases (50% of each lipase, in activity basis) from porcine pancreas (PPL) and Thermomyces lanuginosus lipase (TLL) gave the highest fatty acid ethyl ester (FAEE) yield (around 20 wt.%), while the individual lipases gave FAEE yields 100 and 5 times lower, respectively. These lipases were immobilized individually by the cross-linked enzyme aggregates (CLEAs) technique, yielding biocatalysts with 89 and 119% of expressed activity, respectively. A mixture of these CLEAs (also 50% of each lipase, in activity basis) gave 90.4 wt.% FAEE yield, while using separately CLEAs of PPL and TLL, the FAEE yields were 84.7 and 75.6 wt.%, respectively, under the same reaction conditions. The mixture of CLEAs could be reused (five cycles of 6 h) in the ethanolysis of soybean oil in a vortex flow-type reactor yielding an FAEE yield higher than 80% of that of the first batch.

Gravity settling is a widely employed technology that removes oil from produced water in oilfields. However, with the transition of reservoir development to low-permeability reservoirs, conventional produced water settling tanks face limitations in the treatment efficiency and coagulant dosage. This study presents an innovative approach that optimizes sedimentation tank structures and integrates micro-vortex flow technology to enhance coagulation and flocculation. Through chemical dosage experiments, comparative experiments, and long-term observation, the micro-vortex flow reactor demonstrates a 9.4% increase in oil removal efficiency while reducing the coagulant dosage by 30.0%. The MOR equipment achieved a 20.5% higher oil removal efficiency than conventional methods while maintaining effluent oil and suspended solids below 20 mg/L. The long-term observation experiment of MOR equipment further highlights oil removal efficiency of 94.2% and the micro-vortex reactor’s excellent anti-pollution performance. The MOR equipment significantly reduces the land occupancy area by over 50% compared to conventional methods, thanks to the implementation of micro-vortex flow technology that effectively addresses the limitations associated with traditional settling tanks. This study contributes to advancing efficient and sustainable practices in waterflooding reservoirs, particularly for meeting stringent standards of water injection in low-permeability oilfields.

A system that requires slurry handling such as reactive crystallization is not usually compatible with continuous flow synthesis due to the risk of clogging. Here we suggest the use of a Taylor vortex flow reactor to achieve the robust process for imination with reactive crystallization under continuous flow conditions. A Taylor vortex flow reactor realizes high shear stress and mixing efficiency, which accelerate the timing for nucleation of target imines and enable precise control of nucleation in reactive crystallization. A Taylor vortex flow reactor also mitigates the risk of adhesion to the flow reactor and clogging in reactive crystallization.

We describe the optimization and scale-up of two consecutive reaction steps in the synthesis of bio-derived alkoxybutenolide monomers that have been reported as potential replacements for acrylate-based coatings (Sci. Adv., 2020, 6, eabe0026). These monomers are synthesized by (i) oxidation of furfural with photo-generated singlet oxygen followed by (ii) thermal condensation of the desired 5-hydroxyfuranone intermediate product with an alcohol, a step which until now has involved a lengthy batch reaction. The two steps have been successfully telescoped into a single kilogram-scale process without any need to isolate the 5-hydroxyfuranone between the steps. Our process development involved FTIR reaction monitoring, FTIR data analysis via 2D-visualization and two different photo-reactors (i) a semi-continuous photo-reactor based on a modified rotary evaporator where FTIR and 2D-correlation spectroscopy (2D-COS) revealed the loss of the methyl formate co-product and (ii) our fully continuous Taylor Vortex photo-reactor which enhanced the mass transfer and permitted the use of near-stoichiometric equivalents of O2. The use of inline FTIR monitoring and modelling greatly accelerated process optimization in the Vortex reactor. This led to scale up of the photo-oxidation with an 85% yield and a projected productivity of 1.3 kg day-1, with a space time yield of 0.06 mol day-1 mL-1. Higher productivities could be achieved whilst sacrificing yield; e.g. 4 kg day-1 at 40% yield. The second step, the thermal condensation of 5-hydroxyfuranone, was transformed from a 20 h batch reflux reaction to a < 1 minute thermal flow reaction in a reactor only 3 mL in volume operating at 200 oC with projected productivities of >700 g day-1. Proof of concept for telescoping the two steps was established with an overall two-step yield of 67%, producing a process with projected productivity of 1.1 kg day-1 of the methoxybutenolide monomer without any purification of the 5-hydroxyfuranone intermediate.

We describe the optimization and scale-up of two consecutive reaction steps in the synthesis of bio-derived alkoxybutenolide monomers that have been reported as potential replacements for acrylate-based coatings (Sci. Adv., 2020, 6, eabe0026). These monomers are synthesized by (i) oxidation of furfural with photo-generated singlet oxygen followed by (ii) thermal condensation of the desired 5-hydroxyfuranone intermediate product with an alcohol, a step which until now has involved a lengthy batch reaction. The two steps have been successfully telescoped into a single kilogram-scale process without any need to isolate the 5-hydroxyfuranone between the steps. Our process development involved FTIR reaction monitoring, FTIR data analysis via 2D-visualization and two different photo-reactors (i) a semi-continuous photo-reactor based on a modified rotary evaporator where FTIR and 2D-correlation spectroscopy (2D-COS) revealed the loss of the methyl formate co-product and (ii) our fully continuous Taylor Vortex photo-reactor which enhanced the mass transfer and permitted the use of near-stoichiometric equivalents of O2. The use of inline FTIR monitoring and modelling greatly accelerated process optimization in the Vortex reactor. This led to scale up of the photo-oxidation with an 85% yield and a projected productivity of 1.3 kg day-1, with a space time yield of 0.06 mol day-1 mL-1. Higher productivities could be achieved whilst sacrificing yield; e.g. 5 kg day-1 at 65% yield. The second step, the thermal condensation of 5-hydroxyfuranone, was transformed from a 20 h batch reflux reaction to a < 1 minute thermal flow reaction in a reactor only 3 mL in volume operating at 200 oC with projected productivities of >700 g day-1. Proof of concept for telescoping the two steps was established with an overall two-step yield of 67%, producing a process with projected productivity of 1.1 kg day-1 of the methoxybutenolide monomer without any purification of the 5-hydroxyfuranone intermediate.

The design of new and more sustainable synthetic protocols to access new materials or valuable compounds will have a high impact on the broader chemistry community. In this sense, continuous‐flow photochemistry has emerged as a powerful technique which has been employed successfully in various areas such as biopharma, organic chemistry, as well as materials science. However, it is important to note that chemical processes must not only advance towards new or improved chemical transformations, but also implement new technologies that enable new process opportunities. For this reason, the design of novel photoreactors is key to advancing photochemical strategies. In this sense, the use of equipment and techniques embracing processes intensification is important in developing more sustainable protocols. Among the most recent applications, spinning continuous flow reactors, such as rotor reactors or vortex reactors, have shown promising performance as new synthetic tools. Nevertheless, there is currently no review in the literature that effectively summarizes and showcases the most recent applications of such type of photoreactors. Herein, we highlight fundamental aspects and applications of two categories of spinning reactors, the Spinning Disc Reactors (SDRs) and Thin Film Vortex reactors, critiquing the scope and limitations of these advanced processing technologies. Further, we take a view on the future of spinning reactors in flow as a synthetic toolbox to explore new photochemical transformations. Continuous‐flow technology has led to photochemistry and photocatalysis towards new horizons. Nowadays it is possible to perform a broad range of light‐induced reactions. Here we highlight the importance of combining appropriate technology such as photo‐spinning reactors with strategic light‐induced transformations,

This article presents an experimental study on the hydrodynamics of coolant flow within the pressure vessel of a small modular reactor (SMR) cooled with water, including areas such as the annular downcomer, bottom chamber, and core-simulating channels that are being developed for use in land-based nuclear power plants. This paper describes the experimental setup and test model, measurement techniques used, experimental conditions under which this research was conducted, and results obtained. This study was conducted at the Nizhny Novgorod State Technical University (NNSTU) using a high-pressure aerodynamic testing facility and a scale model that included structural components similar to those found in loop-type reactors. Experiments were performed with Reynolds numbers (Re) ranging from 20,000 to 50,000 in the annular downcomer space of the test model. Two independent techniques were used to simulate the non-uniform flow field in the pressure vessel: passive impurity injection (adding propane to the airflow) and hot tracer (heating one of the reactor circulation loops). The axial velocity field at the inlet to the reactor core was also investigated. This study provided information about the spatial distribution of a tracer within the coolant flow in the annular downcomer and bottom chamber of the pressure vessel. Data on the distribution of the contrasting admixture are presented in plots. The swirling nature of the coolant flow within the pressurized vessel was analyzed. It was shown that the intensity of mixing within the bottom chamber of the pressure vessel is influenced by the presence of a central vortex. Parameters associated with the mixing of admixtures within the model for the pressure vessel were estimated. Additionally, the possibility for simulating flow with different temperature mixing processes using isothermal models was observed.

Nuclear reactor coolant pumps (NRCP) are critical components in nuclear power plants (NPP), and their stable, efficient operation is essential. This study uses PIV measurements, flow structure analysis, and POD decomposition to investigate a model pump under the designed condition. PIV results reveal that the outlet pipe exhibits significant velocity differences: the right side shows lower, uneven speeds due to vortices and flow separation, while the left side maintains a uniform, smooth flow. Although the primary flow structure in the guide vane passage is the wake vortex shedding (γ region), POD analysis highlights that the main high-energy consumption occurs in the low-speed (α) region near the outlet pipe. These findings help identify high-energy structures and provide insights for further pump optimization.

This study is an effort to encapsulate the fundamentals and major findings in the area of fluid-solid interaction, particularly the flow-induced vibrations (FIV). Periodic flow separation and vortex shedding stretching downstream induce dynamic fluid forces on the bluff body and results in oscillatory motion of the body. The motion is generally referred to as flow-induced vibrations. FIV is a dynamic phenomenon as the motion, or the vibration of the body is subjected to the continuously changing fluid forces. Sometimes FIV is modeled as forced vibrations to mimic the vibration response due to the fluid forces. FIV is a deep concern of engineers for the design of modern heat exchangers, particularly the shell-and-tube type, as it is the major cause for the tube failures. Effect of important parameters such as Reynolds number, spacing ratio, damping coefficient, mass ratio and reduced velocity on the vibration characteristics (such as Strouhal number, vortex shedding, vibration frequency and amplitude, etc.) is summarized. Flow over a bluff body with wakes developed has been studied widely in the past decades. Several review articles are available in the literature on the area of vortex shedding and FIV. None of them, however, discusses the cases of FIV with heat transfer. In particular systems, FIV is often coupled to heat transfer, e.g., in nuclear power plants, FIV causes wear and tear to heat exchangers, which can eventually lead to catastrophic failure. As the circular shape is the most common shape for tubes and pipes encountered in practice, this review will only focus on the FIV of circular cylinders. In this attempt, FIV of single and multiple cylinders in staggered arrangement, including tandem and side-by-side arrangement is summarized for heated and unheated cylinder(s) in the one- and two-degree of freedom. The review also synthesizes the effect of fouling on heat transfer and flow characteristics. Finally, research prospects for heated circular cylinders are also stated.

Backward-facing step flow is a benchmark problem that has been studied in various fields, such as airfoils, diffusers, boilers, nuclear reactors, electronic devices, and air-conditioning ducts. In this study, a rigid rectangular flapping longitudinal vortex generator was mounted at the step of the channel to investigate the fluid flow and heat transfer characteristics at three flapping frequencies (0.167, 0.25, and 0.5 Hz) in the Reynolds number range of 3000 to 8000, while maintaining at a constant heat flux. When the fluid flowed over the backward-facing step with flapping longitudinal vortex generator, a train of longitudinal vortices developed simultaneously. At a flapping frequency of 0.167 Hz, the developed high-intensity longitudinal vortices were stable and augmented the heat transfer by 38.54 % more than the smooth channel. The friction factor at 0.167 Hz was found to be 19.47 % and 25.33 % greater than at the higher frequencies of 0.25 and 0.5 Hz, respectively.