http://hg272.persiangig.com/che/Most%20Populare%20Papers/Micromixers%E2%80%94a%20review%20on%20passive%20and%20active%20mixing%20principles.pdf

Micromixers—a review on passive and active mixing principles

Review on methanation – From fundamentals to current projects

Greener approaches to organic synthesis using microreactor technology.

Micro-structured reactors for gas phase reactions

This article presents a comprehensive review of numerical methods and models for interface resolving simulations of multiphase flows in microfluidics and micro process engineering. The focus of the paper is on continuum methods where it covers the three common approaches in the sharp interface limit, namely the volume-of-fluid method with interface reconstruction, the level set method and the front tracking method, as well as methods with finite interface thickness such as color-function based methods and the phase-field method. Variants of the mesoscopic lattice Boltzmann method for two-fluid flows are also discussed, as well as various hybrid approaches. The mathematical foundation of each method is given and its specific advantages and limitations are highlighted. For continuum methods, the coupling of the interface evolution equation with the single-field Navier–Stokes equations and related issues are discussed. Methods and models for surface tension forces, contact lines, heat and mass transfer and phase change are presented. In the second part of this article applications of the methods in microfluidics and micro process engineering are reviewed, including flow hydrodynamics (separated and segmented flow, bubble and drop formation, breakup and coalescence), heat and mass transfer (with and without chemical reactions), mixing and dispersion, Marangoni flows and surfactants, and boiling.

Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications

Metallic microstructure devices have been manufactured and tested for applications in technical applications in thermal and chemical process engineering and in the laboratory. Manufacturing has been performed by micromachining of metal foils and diffusion bonding of a laminated foil stack, followed by welding of the microstructured core into a housing. Crossflow and counterflow micro heat exchangers with microchannel or microcolumn structures have been developed for throughputs up to 7 t water/h with a heat transmission power up to 200 kW. Overall heat transfer coefficients up to 54,000 W/m2 K have been determined with water as test fluid. Electrically driven microstructured heaters have been developed for fast and precise heating of sensitive liquids or gases. The heater has been used as an evaporator as well. Static micromixers have been developed for fast and complete mixing of reactands. They can be utilized with parallel reactions, for example, to decrease the yield of undesired by-products. For hete...

Microstructure devices for applications in thermal and chemical process engineering

Concepts and realization of microstructure heat exchangers for enhanced heat transfer

At the Institute for Micro Process Engineering of the Forschungszentrum Karlsruhe, micro heat exchangers are manufactured out of single foils of base metal alloys. The characterisation of the thermohydraulic properties of microchannel heat exchangers is done using water as heat transfer medium on both passages at temperatures of 10°C and 95°C. The present publication will give an overview of the numerical simulation as well as experimental results for crossflow and counterflow microchannel heat exchangers. A comparison of three crossflow heat exchangers with different microchannel structures, and two different types of counterflow microchannel heat exchangers is shown. For comparison, the heat transfer rate, the overall heat transfer coefficients and efficiencies as well as pressure drop obtained from experiment and theory is shown. For numerical simulation, two models have been used. An easily accessibly method is to use classical engineering codes based on the Nusselt theory (VDI Warmeatlas, 1994). A more detailed model is to use computational fluid dynamics (CFD) with the commercially available tool FLUENT ®, where best estimation codes have been applied for numerical simulation. Both numerical calculations are a helpful complement to predict thermal and hydrodynamic behaviour of the microchannel heat exchangers.Copyright © 2004 by ASME

Comparison of Numerical Simulation and Experimental Results for Crossflow and Counterflow Microchannel Heat Exchangers

3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries

Abstract Aerosol jet printing is an alternative to inkjet printing, the currently most established fabrication technique for printed electronics, with the benefits of small feature sizes, more homogeneous thickness of the printed layers, and the possibility to print on 3D structures. Printers are available on the market, in which the aerosol is generated outside of the print heads, with the disadvantage that only continuous operation is possible due to the long distance between atomization unit and print head. We report on the development and validation of a new integrated principle, with the atomization of the ink directly inside the print head. This enables a compact design, printing in all spatial directions and jet-on-demand operation. Based on fluid dynamic simulations, an optimized integrated print head design was developed, and fabricated. First tests have been performed in a preliminary laboratory test setup. The successful focusing of the aerosol to approximately 1/7 of the spread of the non-focused aerosol spray was validated in experiments, thus confirming the operating principle of the new aerosol-on-demand print head.

A. Wenka

Papers

Microstructure devices for applications in thermal and chemical process engineering

Concepts and realization of microstructure heat exchangers for enhanced heat transfer

Comparison of Numerical Simulation and Experimental Results for Crossflow and Counterflow Microchannel Heat Exchangers

3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries

Design and experimental setup of a new concept of an aerosol-on-demand print head