Numerical investigation of flow regimes in T‐shaped micromixers: Benchmark between finite volume and spectral element methods

Abstract

Computational fluid dynamics (CFD) is very appealing to investigate mixing and reaction in microdevices, as it allows easily investigating different operating conditions as well as mixer geometries. This latter aspect is very important as the flow in microdevices is laminar so the mixing between reactants should be promoted by a clever mixer design, aimed at breaking the flow symmetries. Recently time periodic motions that improve mixing have been observed to take place in a T‐junction at low Reynolds numbers. In this case the numerical modelling should be based on direct numerical simulations (DNS), thus involving high computational resources. In this work, two different CFD approaches, i.e., finite volume and spectral element methods, are applied and compared for the analysis of the mixing process in the well known T‐shaped micromixer. Spectral elements methods are particularly suited for DNS; however, they have been scarcely applied to study micromixers, while plenty of works can be found with finite volume methods. The analysis is carried out using both ideal and non‐ideal liquid binary mixtures, the latter presenting a negative fluidity of mixing (i.e., the viscosity of the mixture is higher than that of the pure components). Moreover the numerical results are validated with simple flow visualization experiments.

Steady flow regimes and mixing performance in arrow-shaped micro-mixers

“…Sc = O(100), as in [5]. However, as shown in [10], such low Sc number does not affect the results in the confluence region analyzed in the present work, due to the presence of strong transversal convection. The numerical data were postprocessed on purpose to average the concentration field over the mixer depth, thus allowing the proper comparison with the experimental flow visualizations.…”

“…and then passes to an unsteady periodic behavior (see e.g. [1,3,4,8,10]). Finally, it can be inferred from the dye field sections in Figure 13 that the new flow topology is less efficient in promoting mixing than the classical engulfment one (compare e.g.…”

“…Figure 17 shows δ m computed in numerical simulations at the Y = −8 section of the mixing channel as a function of the Reynolds number. The curve obtained for numerical simulations carried out with the same code for a T-mixer having the same geometry of the channels and operating in the same conditions [10] is also reported for comparison. Only…”

Microreactor technology for synthesis of ethyl methyl oxalate from diethyl oxalate with methanol and its kinectics

“…The emergence of microreactor technology made it possible to solve these problems by enhancing the mixing of materials and mass transfer of different phases in a continuous process. [ 20 ] With the strengthening and mixing of the microstructure of the microreactor, the reactants effectively increase the mass transfer efficiency and reaction efficiency between the substances; therefore, the two reactants can perform a high degree of contact reaction with extremely small volumes. Microreactors for organic synthesis could significantly improve the selectivity and the yield of the products, reduce the by‐products, improve the efficiency of synthesis, and significantly reduce the use of raw materials and solvents, which contribute to green sustainable chemistry.…”

CFD in Chemical Engineering: Process Design Symposium at the 10th World Congress of Chemical Engineering (WCCE10)

“…Multiphase flow was an important theme in this special section with applications for oil transport, liquid‐liquid dispersion, flashing spray jets, solid‐fluid systems in rotating drums, trickle bed, and fluidized bed reactors, and agglomeration in cyclone separators . Mixing phenomena were reported in variety of geometries and on diverse length scales: in an agitated tubular reactor, in T‐shaped micromixers, and in fluidic oscillators . Heat transfer was discussed in the context of almond drying, in unbaffled stirred tanks, and jacketed stirred tanks .…”