Description of numbering-up effects in heterogeneous

microchannels

Reporter : Lexiang Zhang

Supervisor : Feng Xin

2012.04.12

Tianjin University2

tasks and scheme

introduction

distributor fabrication and design

a network model

perspectives

Contents

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Multi-scale notion

catalyst particles

make the transitions from the microscale up to the macroscale progressive

The key scale-out consideration requires us to match the mean residence times or mean contact times in multiphase systems.

Scale out challenge is equivalent to the task of implementing the rational flow distribution and control.

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Flow patterns

standards for flow description and evaluation

other used coordinates: And Weber number

N. Shao, A. Gavriilidis, P. Angeli. Flow regimes for adiabatic gas–liquid flow in microchannels[J]. Chemical Engineering Science. 2009,64:2749-2761.

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General numbering-up methods

an integrated approach: internal numbering-up for distributing single phase fluids and external numbering-up for two-phase contacting

M.N. Kashid, A. Gupta, A. Renken et al. Numbering-up and mass transfer studies of liquid–liquid two-phase microstructured reactors[J]. Chemical Engineering Journal.2010, 158:233-240.

Václav Tesaˇ. Bifurcating channels supplying “numbered-up” microreactors[J]. Chemical Engineering Research and Design.2011,89:2507-2520.

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Most commonly used arrangementsmonolithic microreactors 、 tree-like networks 、 comb-like networks

Zhiwei Fan, Xinggui Zhou, Lingai Luo et al. Experimental investigation of the flow distribution of a 2-dimensional constructal distributor[J]. Experimental Thermal and Fluid Science.2008,33:77-83.

L. Luo, D. Tondeur, H. Le Gall et al. Constructal approach and multi-scale components[J]. Applied Thermal Engineering.2007,27:1708-1714.

M. Saber, J.-M. Commenge,L. Falk. Heat-transfer characteristics in multi-scale flow networks with parallel channels[J]. Chemical Engineering and Processing:Process Intensification.2010,49:732-739.

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Main tasks

Describe flow conditions at distributors

When flow fully develops , describe the contribution to mass transfer and flow stability made by each microchannel

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Rough scheme

devise 2-3 rational distirbutors

experimental research, utilizing micro sensors and optical methods

build models and process data

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Lithography and etching

Si-O-H…H-O-Si → Si-O-Si + H2O

thermal bonding: 500-1000℃

etching liquid: HF(HNO3,NH3F)

Daniel Haller, Peter Woias, Norbert Kockmann. Simulation and experimental investigation of pressure loss and heat transfer in microchannel networks containing bends and T-junctions[J]. International Journal of Heat and Mass Transfer.2009,52:2678-2689.

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Principles for distributors design

ensure every microchannel has the same inlet conditions , giving the channce for uniform flow distribution

universality , self-similarity , modularization

representativeness for characteristic scales

“If we were look at a picture of a portion of an ideal fractal boundary, we wouldn’t know the magnification of the photograph from the ruggedness of the boundary, since it always looks the same at every magnification. This “look-alike” feature of ideal fractal boundary at various magnification is describled by the mathematician as silf-similarity.”

Mandelbrot.A Random Walk Through Fractal Dimensions[M]. VCH Verlagsgesellschaft, Weinheim.1989

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Nascent design

Future “scale up” : ……

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An equivalent electrical resistance network model

Hagen–Poiseuille Equation:

adapted for single phaseor a pseudo-phase

This model should take into account inertial effects and fluid properties.

Minqiang Pan, Yong Tang, Liang Pan et al. Optimal design of complex manifold geometries for uniform flow distribution between microchannels[J]. Chemical Engineering Journal .2008,137:339-346.

J.-M. Commenge, M. Saber, L. Falk. Methodology for multi-scale design of isothermal laminar flow networks[J]. Chemical Engineering Journal.2011,173:541-551.

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An equivalent electrical resistance network model

RA,i=0

C. Amador, D. Wenn, J. Shaw et al. Design of a mesh microreactor for even flow distribution and narrow residence time distribution[J]. Chemical Engineering Journal.2008,135:259-269.

J.-M. Commenge, M. Saber, L. Falk. Methodology for multi-scale design of isothermal laminar flow networks[J]. Chemical Engineering Journal.2011.173:541-551.

Nuria de Mas, Axel Gunther, Tobias Kraus et al. Scaled-Out Multilayer Gas - Liquid Microreactor with Integrated Velocimetry Sensors[J]. Ind. Eng. Chem. Res.2005,44:8997-9013.

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Perspectives

Learn the micro sensor, AFM and μ-LIF experimental setups and corresponding data processing methods from references

Consult the descriptions for stochastic effects and stochastic models in conventional reactors

Expand the microreactor knowledge hierarchy