Microreactors eliminate batch‐to‐batch variability and allow better control over nanocrystal synthesis. A serpentine microreactor fabricated by femtosecond laser ablation is presented and characterized by computational fluid dynamics, since the micro channels show a trapezoidal cross‐section mainly due to the relatively high numerical aperture of the focusing lens. Mixing, macro and micro, throughout the device was investigated for inlet flow rates between 10–500 μL min−1 and the injection of an inert tracer with the same transport properties of water. The simulation of the whole microreactor enabled the analysis of the formation and destruction of structures. For instance, secondary flows played a major role in mixing behaviour: small flow rates did not promote mixing of the tracer and a stream of pure water even after 43 curved segments, while they were perfectly mixed after 9 segments for higher flow rates. According to the mixing index, the maximum effect of convective mixing was achieved for an inlet flow rate of 250 μL min−1. Tracer dispersion and the mixing index guided a scale‐up process of the microreactor, optimizing the number of curved segments while increasing total throughput. The upscaled design exhibited mixing saturation at 400 μL min−1 and promoted better control of residence time to allow nanocrystal growth.

Soybean peroxidase is an enzyme extracted from soybean seed hulls. In the presence of hydrogen peroxide, the enzyme has the potential to catalyze the biodegradation of toxic substances like chlorophenols. For this reason, its use in wastewater treatment processes is environmentally friendly since the enzyme can be obtained from a renewable and abundant raw material. In this work, enzymatic biodegradation of 2,4,6-trichlorophenol performed by soybean peroxidase in a microreactor was studied experimentally and theoretically. The experimental data set was obtained with a volume of 250 μL by using different soybean peroxidase concentrations and different reaction times. The fluid dynamics of the microreactor was modeled as well, using ANSYS CFX. The simulations exhibited secondary flows, which enhanced mixing. Although the laminar flow was developed, it can be assumed to be a well-mixed medium. The kinetic data were evaluated through a mechanistic model, the modified bi-bi ping-pong model, which is adequate to represent the enzymatic degradation using peroxidases. The model was composed of an initial value problem for ordinary differential equations that were solved using MATLAB. Some kinetic constants were estimated using the least square function. The results of the model fit well the experimental data.

Photochemical reactors tend to exhibit turbulent flow even with low Reynolds numbers. The k-e model is not always appropriate in this situation. An annular photoreactor was designed with tangential inlet and outlet tubes to investigate this. The fluid flow was characterized by residence time distribution (RTD) experiments, which were reproduced by computational fluid dynamics considering four relevant turbulence models: the k-e, the k-w, the shear stress transport, and the Reynolds stress models. Inlet effects induced helical flow throughout the reactor, switching to plug flow depending on the flow rate and the turbulence model. The k-w model properly deals with viscous effects and reproduces the experimental RTD curves with correlation coefficients greater than 0.9566, against 0.8705 from the k-e model.

The concentration profiles of species involved in the degradation of phenol by an advanced oxidation process (AOP) are modeled by a computational fluid dynamics tool in an annular reactor whose fluid dynamics was the object of a previous study. The reactive flow was fully described together with the radiation field and the kinetic model, which encompasses large kinetic constants such as 1010 L mol−1s−1. Phenol degradation can be simulated by using relaxation factors of at least 1012 kg m−3s−1. The hydroxyl radical concentration profile depends on the radiation field, assessed by the discrete ordinate and the discrete transfer methods. Phenol can be completely degraded along the reactor. A centrifugal effect was observed, with higher concentrations of degradation products along the inner wall at the reactor outlet.

Miniaturized reaction vessels are drawing attention of chemical industries because they promote better mass and heat transfer and also enhance process safety. To understand the relevance of each element of a microreactor on the velocity field of the equipment and the corresponding mixing processes, several microdevices were simulated using computational fluid dynamics: an assembly of two channels, a T-junction, 30 channels in a serpentine assembly and a full microreactor. The cross section of the devices is 100-300 µm wide and the length of the channels varies between 3000 and 25190 µm. Computational domains were discretized using hexahedral meshes and steady-state velocity fields were computed considering laminar flow for flow rates between 12,5 and 2000 µL min 1. Mixing was evaluated by injecting inert tracers and monitoring their distribution. Simulations were validated against experimental micro particle image velocimetry data. Velocities throughout the devices are relatively high despite the small dimensions of the cross sections and small flow rates. Experimental images of the flow elucidated the parabolic shape of the velocity profile and its distortion on curved segments caused by centrifugal forces, matching predictions of the computational model. Tracer maps indicated secondary flows play an important role in mixing stream perpendicular to the main flow direction. This study emphasizes the use of computational fluid dynamics as a tool for understating flow throughout microdevices and supporting their design.