Micro Process Engineering

Micro Process Engineering

Edited by

Norbert Kockmann

Hessel, V., Renken, A., Schouten, J.C., Yoshida, J. (eds.)

Micro Process EngineeringA Comprehensive Handbook

2009

Print ISBN: 978-3-527-31550-5; also available in electronic formats

Saile, V., Wallrabe, U., Tabata, O., Korvink, J.G. (eds.)

LIGA and its Applications

2009


Hierold, C. (ed.)

Carbon Nanotube DevicesProperties, Modeling, Integration and Applications

2008


Bechtold, T., Schrag, G., Feng, L. (eds.)

System-level Modeling of MEMS

2013


Korvink, J.G., Smith, P.J., Shin, D. (eds.)

Inkjet-based Micromanufacturing

2012


Baltes, H., Brand, O., Fedder, G.K., Hierold, C., Korvink, J.G., Tabata, O. (eds.)

Enabling Technologies for MEMS and NanodevicesAdvanced Micro and Nanosystems

2004


Baltes, H., Brand, O., Fedder, G.K., Hierold, C., Korvink, J.G., Tabata, O. (eds.)

Enabling Technologies for MEMS and NanodevicesAdvanced Micro and Nanosystems

2004


Brand, O., Fedder, G.K. (eds.)

CMOS-MEMS

2013


Tabata, O., Tsuchiya, T. (eds.)

Reliability of MEMSTesting of Materials and Devices

2008


Iannacci, J.

Practical Guide to RF-MEMS

2013


Related Titles

Micro Process Engineering

Fundamentals, Devices, Fabrication, and Applications

Edited byNorbert Kockmann

Volume Editor

Dr.-Ing. Norbert KockmannUniversität Freiburg, IMTEKLS f. Konstr. v. MikrosystemenGeorges-Köhler-Allee 10279110 FreiburgGermany

Series Editors

Prof. Dr. Oliver BrandSchool of Electrical andComputer EngineeringGeorgia Institute of TechnologyAtlanta, GA 30332-0250USA

Prof. Dr. Gary K. FedderECE Department &The Robotics InstituteCarnegie Mellon UniversityPittsburgh,PA 15213-3890USA

Prof. Dr. ChristoferHieroldChair of Micro and NanosystemsETH ZürichETH-Zentrum, CLA H9Tannenstr. 38092 ZürichSwitzerland

Prof. Dr. Jan G. KorvinkIMTEK-Institut fürMikrosystemtechnikUniversität FreiburgGeorges-Köhler-Allee103/03.03379110 FreiburgGermany

Prof. Dr. Osamu TabataDepartment of MechanicalEngineeringFaculty of EngineeringKyoto UniversityYoshida Honmachi,Sakyo-kuKyoto 606-8501Japan

Cover:

Top left: mounting a chemical reactor with microstructured elements (Dr. Schirrmeister, Chapter 7; courtesy of Uhde GmbH and Degussa AG, Germany)Bottom right: mixing of aqueous solutions with Bromothymol Blue pH-indicator (Dr. Kockmann, Germany, Chapter 3)

First Edition 2006

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Besides the development of new devices the main goal of engineering activitiesis to achieve a high performance in technical systems with low effort for opti-mized processes and products. An incredible performance increase wasachieved in communication and information technology by the miniaturizationof electronic equipment down to the nanometer scale during the last decades.Moore’s law of doubling the number of circuits in electronic devices in 18months by miniaturization still holds since decades and is expected to last.

Process technology is a wide field where small processes down to the molecularscale happen in devices having a length of several meters. The scale-up of chemicalproduction or power plants has led to high energy efficiencies and affordable con-sumer products. Around 1920, cryogenic air separation units produced an amountof about 1.3 t/h oxygen with 98–99% purity. 30 years later, the largest air separationunits delivered about 5.2 t/h oxygen with 99% purity. Nowadays, the largest air sep-aration units are supplying large customers with about 65 t/h oxygen with 99.5%purity and higher. As the throughput increases, the specific energy consumptiondecreases from about 1.5 kW/kg oxygen to about 0.4 kW/kg oxygen. Besides thedevelopment of large units, the consumer specific supply was also addressed bysmall and adjusted plants for flexible production satisfying the costumer’s de-mand. Additionally, some branches of the chemical industry are not subjectedto the economy of scale like the pharmaceutical industry or fine chemicals; flexibil-ity as well as the product price and quality are the important factors.

The combination of process engineering and micro system engineering withthe design, fabrication, and integration of functional microstructures is one ofthe most promising research and development areas of the last two decades.This is reflected in the publishing of scientific journals like “Sensors and Actua-tors” (since 1981) as well as in the growing field of international conferenceslike �TAS (Micro Total Analysis Systems, since 1994), the IMRET (InternationalConference on Micro Reaction Technology by AIChE and DECHEMA, since1997), or the ICMM (International Conference on Micro and Mini Channels byASME, since 2003). This can also be seen in the growing industrial activitiesusing microstructured equipment in process development and production ofchemicals. Some activities can be summarized under the concept of process in-tensification, such as compact heat exchangers or structured packing in separa-tion columns for intensified heat and mass transfer. With characteristic lengthsof the devices in the size of boundary layers, the transfer processes can be en-

V

Preface

Micro Process Engineering. Edited by N. KockmannCopyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 978-3-527-33500-8

hanced and controlled in the desired way. Other activities include modular plat-forms and entire chemical plants consisting of several microstructure elementsand devices, mainly for laboratory and process development.

This book on micro process engineering is divided into four sections: funda-mentals (Chapter 1 to 6), the design and system integration (Chapter 7 to 9),fabrication technologies and materials (Chapter 10 to 12), and, finally, the appli-cations of microstructured devices and systems (Chapter 13 to 16). Each chapterhas review character and stands on its own, but is also integrated into the wholebook. A common nomenclature and index will help the orientation of the read-er. In Chapter 1 to 6 the fundamentals and tools of process engineering are pre-sented with single-phase and multiphase fluid flow, heat and mass transfer aswell as the treatment of chemical reactions following the concept of unit opera-tions. The equipment and process design is organized by project managementmethods and assisted by modeling and simulation as well as the integration ofsensors and analytical equipment, described in Chapter 7, 8, and 9. The broadfabrication variety of microstructured devices for micro process engineering isillustrated in Chapter 10, 11, and 12 grouped according the materials metal,polymers, silicon, glass, and ceramics. Some typical examples of microstruc-tured devices illustrate the various fabrication methods. Even more examplesare given in Chapter 13 to 15 with industrial applications in Europe, Japan andthe US. Last but not least Chapter 16 emphasizes the application of microstruc-tured devices in education and laboratory research work. This gives students adeeper insight into the complex behavior of chemical plants and will lead to amore sophisticated view of continuous flow processing in education, laboratoryexperiments, and chemical synthesis.

The aim of this book is the comprehensive description of actual knowledgeand competence for microfluidic and chemical process fundamentals, designrules, related fabrication technology, as well as an overview of actual and futureapplications. This work is located at the boundary of at least two different disci-plines, trying to collect and unify some of the special knowledge from differentareas, driven by the hope that innovation happens at the interfaces between thedisciplines. From this, the team of authors of various engineers, physicists andchemists, from universities, research institutes, and industry in different coun-tries contributes an embracing part of detailed know-how about processes inand applications of microstructures. I hope that this knowledge will help to lookout of the box to other related areas of chemical engineering, micro system en-gineering and to other engineering, physical, chemical, or biological areas.

Finally, I want to thank all the contributors for their enduring work, besidestheir actual work and activities. I hope that this enthusiasm can be readthroughout the book, will spread further on to the readers and will help to en-large the knowledge and activities on this new and gap-filling area of micro pro-cess engineering.

Norbert KockmannVolume EditorNovember 2005

PrefaceVI

We hereby present the fifth volume of Advanced Micro & Nanosystems (AMN),entitled Micro Process Engineering.

Usually, when engineering devices get smaller, we expect higher speeds, moreaccuracy, or less power consumption, but typically we do not associate smaller de-vices to successfully compete with larger ones when it comes to material through-put. Not so in micro process engineering. This research area has quietly grown inthe flanks, and promises to become one of the most profitable areas in microtech-nology. Why is this so? It turns out that micro process engineering targets themore efficient manufacture of chemical substances, no less than miniaturizedchemical factories that match the throughput of their macroscopic counterparts.

The volume editor, Dr. Norbert Kockmann, has assembled a notable interna-tional authors hip to bring to us the state of the art in this very exciting applica-tion area. At the microscale, many physical and chemical effects have to be re-evaluated as they apply to chemical engineering manufacturing processes, andin this volume six chapters guide us through the most important fundamentalconcepts. The revised theory implies the need for new design methods, and sothree chapters consider simulation, modelling, and system design. Device fabri-cation sets specific challenges, for all resulting production surfaces must bechemically and thermally resistant, and must target high throughput of liquidsand gases. Finally, because micro process engineering is driven by its excitingapplications, four chapters cover the most important topics from a completelyinternational perspective.

We are happy to report here that the decision to produce topical volumes such asCMOS-MEMS or Microengineering of Metals and Ceramics is finding tremendousacceptance with our readers and hence we will continue to plan further relevanttopics from either an application area or a specific manufacturing technology.

Looking ahead, we hope to welcome you back, dear reader, to the upcomingsixth member of the AMN series, in which we take a close look at the fascinat-ing field of LIGA and its application.

Oliver Brand, Gary K. Fedder, Christofer Hierold, Jan G. Korvink,and Osamu TabataSeries EditorsOctober 2005Atlanta, Pittsburgh, Zurich, Freiburg and Kyoto

VII

Foreword


Preface V

Foreword VII

List of Contributors XI

Nomenclature XV

1 Process Engineering Methods and Microsystem Technology 1Norbert Kockmann

2 Momentum and Heat Transfer in Microsized Devices 47Heinz Herwig

3 Transport Processes and Exchange Equipment 71Norbert Kockmann

4 Multiphase Flow, Evaporation, and Condensation at the Microscale 115Michael K. Jensen, Yoav Peles, Theodorian Borca-Tasciuc, andSatish G. Kandlikar

5 Generation and Multiphase Flow of Emulsions in Microchannels 149Isao Kobayashi and Mitsutoshi Nakajima

6 Chemical Reactions in Continuous-flow Microstructured Reactors 173Albert Renken and Lioubov Kiwi-Minsker

7 Design Process and Project Management 203Steffen Schirrmeister, Jürgen J. Brandner, and Norbert Kockmann

8 Simulation and Analytical Modeling for Microreactor Design 235Osamu Tonomura

IX

Contents


9 Integration of Sensors and Process-analytical Techniques 249Stefan Löbbecke

10 Microfabrication in Metals and Polymers 267Jürgen J. Brandner, Thomas Gietzelt, Torsten Henning, Manfred Kraut,Holger Mortiz, and Wilhelm Pfleging

11 Silicon Microfabrication for Microfluidics 321Frank Goldschmidtböing, Michael Engler, and Alexander Doll

12 Microfabrication in Ceramics and Glass 353Regina Knitter and Thomas R. Dietrich

13 Industrial Applications of Microchannel Process Technologyin the United States 387Daniel R. Palo, Victoria S. Stenkamp, Robert A. Dagle, andGoran N. Jovanovic

14 Industrial Applications in Europe 415Thomas Bayer and Markus Kinzl

15 Industrial Production Plants in Japan and Future Developments 439Jun-ichi Yoshida and Hideho Okamoto

16 Laboratory Applications of Microstructured Devicesin Student Education 463Walther Klemm, Bernd Ondruschka, Michael Köhler, and Mike Günther

Subject Index 497

ContentsX

XI

List of Contributors

Thomas BayerSiemens AGA&D SP Solutions Process IndustriesBusiness DevelopmentIndustriepark Höchst, Bldg. G 811D-65926 Frankfurt am MainGermany

Theodorian Borca-TasciucDepartment of Mechanical, Aerospaceand Nuclear EngineeringRensselaer Polytechnic Institute110 8th StreetTroy, NY 12180-3590USA

Jürgen J. BrandnerForschungszentrum KarlsruheInstitute for Micro Process Engineer-ing (IMVT)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany

Robert A. DaglePacific Northwest National Laboratory902 Battelle Blvd., K8-93Richland, WA 99354USA

Thomas R. DietrichMikroglas chemtech GmbHGalileo-Galilei-Str. 28D-55129 MainzGermany

Alexander DollLaboratory for Designof MicrosystemsDepartment of MicrosystemsEngineeringUniversity of Freiburg – IMTEKGeorges-Köhler-Allee 102D-79110 FreiburgGermany

Michael EnglerLaboratory for Designof MicrosystemsDepartment of MicrosystemsEngineeringUniversity of Freiburg – IMTEKGeorges-Köhler-Allee 102D-79110 FreiburgGermany

Thomas GietzeltForschungszentrum KarlsruheInstitute for Micro ProcessEngineering (IMVT)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany


List of ContributorsXII

Frank GoldschmidtböingLaboratory for Designof MicrosystemsDepartment of MicrosystemsEngineeringUniversity of Freiburg – IMTEKGeorges-Köhler-Allee 102D-79110 FreiburgGermany

Mike GüntherInstitute of PhysicsTechnical University IlmenauWeimarer Straße 32D-98684 IlmenauGermany

Torsten HenningForschungszentrum KarlsruheInstitute for Micro ProcessEngineering (IMVT)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany

Heinz HerwigTechnical ThermodynamicsTechnical UniversityHamburg-HarburgDenickestr. 17D-21073 HamburgGermany

Michael K. JensenDepartment of Mechanical, Aerospaceand Nuclear EngineeringRensselaer Polytechnic Institute110 8th StreetTroy, NY 12180-3590USA

Goran N. JovanovicDepartment of Chemical EngineeringOregon State University102 Gleeson HallCorvallis, OR 97331Microproducts Breakthrough InstituteCorvallis, OR 97330USA

Satish G. KandlikarDepartment of MechanicalEngineeringRochester Institute of TechnologyRochester, NY 14623-5604USA

Markus KinzlSiemens AGA&D SP Solutions Process IndustriesBusiness DevelopmentIndustriepark Höchst, Bldg. G 811D-65926 Frankfurt am MainGermany

Lioubov Kiwi-MinskerInstitute of Chemical Sciencesand EngineeringSwiss Federal Institute of Technology(EPFL)CH – LGRCCH-1015 LausanneSwitzerland

Walther KlemmInstitute of Technical Chemistryand Environmental ChemistryFriedrich Schiller University of JenaLessingstr. 12D-07743 JenaGermany

List of Contributors XIII

Regina KnitterForschungszentrum KarlsruheInstitute for MaterialScience III (IMF III)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany

Isao KobayashiFood Engineering DevisionNational Food Research InstituteKannondai 2-1-12, TsukubaIbaraki 305-8642Japan

Norbert KockmannLaboratory for Designof MicrosystemsDepartment of MicrosystemsEngineeringUniversity of Freiburg – IMTEKGeorges-Köhler-Allee 102D-79110 FreiburgGermany

Michael KöhlerInstitute of PhysicsTechnical University IlmenauWeimarer Straße 32D-98684 IlmenauGermany

Stefan LöbbeckeFraunhofer Institute for ChemicalTechnology (ICT)Joseph-von-Fraunhofer-Straße 7D-76327 PfinztalGermany

Manfred KrautForschungszentrum KarlsruheInstitute for Micro ProcessEngineering (IMVT)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany

Holger MoritzForschungszentrum KarlsruheInstitute for MicrostructureTechnology (IMT)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany

Mitsutoshi NakajimaFood Engineering DevisionNational Food Research InstituteKannondai 2-1-12, TsukubaIbaraki 305-8642Japan

Hideho OkamotoDepartment of Synthetic Chemistryand Biological EngineeringGraduate School of EngineeringKyoto UniversityKyoto 615-8510Japan

Bernd OndruschkaInstitute of Technical Chemistryand Environmental ChemistryFriedrich Schiller University of JenaLessingstr. 12D-07743 JenaGermany

List of ContributorsXIV

Daniel R. PaloPacific Northwest National Laboratory902 Battelle Blvd., K8-93Richland, WA 99354

Microproducts Breakthrough InstituteCorvallis, OR 97330USA

Yoav PelesDepartment of Mechanical, Aerospaceand Nuclear EngineeringRensselaer Polytechnic Institute110 8th StreetTroy, NY 12180-3590USA

Wilhelm PflegingForschungszentrum KarlsruheInstitute for MaterialScience I (IMF I)Hermann-von-Helmholtz-Platz 1D-76344 Eggenstein-LeopoldshafenGermany

Albert RenkenInstitute of Chemical Sciencesand EngineeringSwiss Federal Institute of Technology(EPFL)CH – LGRCCH-1015 LausanneSwitzerland

Steffen SchirrmeisterUhde GmbHFriedrich-Uhde-Str. 15D-44141 DortmundGermany

Victoria S. StenkampPacific Northwest National Laboratory902 Battelle Blvd., K6-28Richland, WA 99354USA

Osamu TonomuraDepartment of Chemical EngineeringKyoto UniversityKatsura Campus, Nishikyo-kuKyoto 615-8510Japan

Jun-ichi YoshidaDepartment of Synthetic Chemistryand Biological EngineeringGraduate School of EngineeringKyoto UniversityKyoto 615-8510Japan

List of main parameters

If not indicated in the text.

Name Unit Description

A m2 area or cross section

am2

stemperature conductivity a � �

�cp

b m geometrical factor, channel widthC – constantCi – ratio of heat capacity fluxes

cms

absolute velocity

ci – concentration of component i

cpkJ

kg Kisobaric specific heat capacity

cvkJ

kg Kisochoric specific heat capacity

Dm2

sdiffusion coefficient

D m diameter

dh m hydraulic diameter � 4AU

E J energy

eJ

kgspecific energy

F N forcef – probability distribution function

Gkg

m2smass velocity (US literature)

g m/s2 gravity constant

XV

Nomenclature


g m temperature jump coefficientH J enthalpyHi Pa Henry coefficient

hJ

kgspecific enthalpy

hLVJ

kglatent heat of vaporization

hW

m2Kheat transfer coefficient (US literature)

h m geometrical factor, heightI A electrical currentJ J/s general energy currentK – general coefficient

kW

m2Koverall heat transfer coefficient

kW

mKthermal conductivity (US literature)

k *) reaction rate constant, *) unit depends onreaction order

kMkgsPa

membrane conductivity

kJK

Boltzmann constant 1�380662� 10�23 JK

� �

L m lengthLij – general transport coefficientLp mol/s rate of productionl m length, characteristic

Mkg

kmolmolar mass

M� kg mass of an atom or moleculem kg massm – reaction order

�mkgs

mass flow

N – number

Ni – ratio of transferred heat to heat capacity,number of transfer units

n 1/s rotation speedn mol amount of substance�n mol/s molar flow rateP W power

p bar, Pa � Nm2

pressure

NomenclatureXVI

pi bar, Pa � Nm2

partial pressure

Q J � Nm � kg m2

s2 heat

�Q W � Js

heat flux

qJ

kgspecific heat

�qWm2 specific heat flux

R m radius

RJ

kg Kindividual gas constant � Rm

M

Rimolm3s

transformation rate

RmJ

kmol Kuniversal gas constant 8�314

kJkmol K

� �

RelVA

electrical resistance

r m location coordinate, radiusr 1/s reaction rate

SJK

entropy

S� – heat production potential

sJ

kg Kspecific entropy

T K temperature (Kelvin)t s timeU J inner energyU m circumference, perimeterU V electric voltage

uJ

kgspecific inner energy

ums

velocity in x-direction

V m3 volume�V m3/s volume flow rate

�ms

velocity in y-direction

�vms

vector of velocity

W J workWdiss J dissipation work

Nomenclature XVII

wms

velocity in z-direction

wJ

kgspecific work

X – general transport variableX – conversion�x m position vectorx m cartesian coordinatex – vapor quality or void fractionxi – liquid concentration of component iy m cartesian coordinateyi – vapor concentration of component iz m cartesian coordinate, main flow direction in a

channel

Greek letters

�W

m2Kheat transfer coefficient

� – mixing quality

�ms

mass transfer coefficient

� – Arrhenius number

�kg

m2smomentum transfer coefficient

�Nm

interfacial tension

�i – relative amount of substance, mole fraction

� m boundary layer thickness

�m2

s3 specific energy dissipation

� – porosity� – friction factor of channel fitting or installation� m slip length of rarefied gas flow

kgm s

� Nsm2

dynamic viscosity

– dimensionless temperature� deg contact angle� – heat exchanger efficiency� – isentropic exponent

m mean free path length

�W

mKheat conductivity

NomenclatureXVIII

�R – channel friction factor

� Pa s dynamic viscosity (US literature)

�m2

skinematic viscosity �

�

�i – stoichiometric coefficient�i Pa mole fraction acc. Raoult’s law

�kgm3

density � mV

� m diameter of an atom or molecule

�Nm

surface tension

��J

Ksdissipation function or local entropy production

� s space time

�N

m2shear stress

� – probability� – dispersion� 1/s angular velocity

Sub- and superscripts

�x vector description of x�x mean value of xx� dimensionless form of x

Dimensionless numbers of fluid mechanics, heat and mass transfer

Name Description

Bi � �l�

Biot number (�=�solid)

Bo � wlDax

Bodenstein number

Bo � q��

Ghfgboiling number (US literature)

Bo � WeFr� d2g�

�Bond number (US literature)

Ca � w�

capillary number

Nomenclature XIX

Co � 1� xx

� �0�8�V

�L

� �0�5

convection number

DaI � tr

�res1st Damköhler number

DaII � ks

kD� tr

tD2nd Damköhler number

Dn � ReDRc

� �1�2

Dean number

Ec � w2

cp�TEckert number

Eu � �p�w2

Euler number

Fo � atl2

Fourier number

Fr � w2

dgFroude number

Gr � gz�ps3�T

�2Grashoff number

Kn �

LKnudsen number

Le � aD

Lewis number

Ma � wc

Mach number

Ne � P�n3d5 Newton number

Nu � �l�

Nußelt number (�=�Fluid)

Pe � RePr � wla

Péclet number

Pr � �

aPrandtl number

Ra � GrPr Rayleigh number

Re � wl�

Reynolds number

Sc � LePr � �

DSchmidt number

NomenclatureXX

Sh � �lD

Sherwood number

We � w2d��

Weber number

� n2d3�

�

Mathematical operators

D substantial differential

d general differential

� partial differential

� delta, divergence, difference

� ��i

�

�x��

j�

�y��

k�

�zNabla operator

grad � � �� gradient of �

div �v � � �v divergence of �v

rot �v � �� v rotation of �v

�� 2�

�x2� �2�

�y2� �2�

�z2Laplace operator

Main conferences and their abbreviation

IMRET 1: W. Ehrfeld (Ed.), Microreaction Technology, Proc. of the 1st Int. Conf.on Microreaction Technology 1997, Springer, Berlin, 1998.

IMRET 2: Proc. of the 2nd Int. Conf. on Microreaction Technology, AIChE Na-tional Spring Meeting, New Orleans, 1998.

IMRET 3: W. Ehrfeld (Ed.), Microreaction Technology: Industrial Prospects, Proc.of the 3rd Int. Conf. on Microreaction Technology 1999, Frankfurt,Springer, Berlin, 2000.

IMRET 4: Microreaction Technology: Proc. of the 4th Int. Conf. on MicroreactionTechnology, AIChE National Spring Meeting, Atlanta, 2000.

IMRET 5: M. Matlosz, W. Ehrfeld, P. Baselt (Eds.), Microreaction Technology,Proc. of the 5th Int. Conf. on Microreaction Technology 2001, Straß-bourg, Springer, Berlin, 2002.

IMRET 6: P. Baselt, U. Eul, R. S. Wegeng, I. Rinard, B. Horch (Eds.), Proc. ofthe 6th Int. Conf. on Microreaction Technology, AIChE NationalSpring Meeting, New Orleans, 2002.

IMRET 7: A. Renken, M. Matlosz (Eds.), Proc. of the 7th Int. Conf. on Micro-reaction Technology 2003, Lausanne, 2003.

Nomenclature XXI

IMRET 8: Proc. of the 8th Int. Conf. on Microreaction Technology, AIChE Na-tional Spring Meeting, Atlanta, 2005.

ICMM2003: S.G. Kandlikar, ASME 1st Int. Conf. on Microchannels and Minichan-nels, Rochester NY, 2003.

ICMM2004: S.G. Kandlikar, ASME 2nd Int. Conf. on Microchannels and Mini-channels, Rochester NY, 2004.

ICMM2005: S.G. Kandlikar, M. Kawaji, ASME 3rd Int. Conf. on Microchannelsand Minichannels, Toronto, Canada, 2005.

NomenclatureXXII

Norbert Kockmann, Laboratory for Design of Microsystems, Department of MicrosystemEngineering (IMTEK), University of Freiburg, Germany

AbstractThe fundamentals of chemical engineering are presented with the aim of appli-cations in microsystem technology, microfluidics, and transport processes in mi-crostructures. After a general overview about both disciplines and commonareas the concept of unit operations is briefly introduced. The balance equationsare derived from statistical mechanics and applied to other relevant systems ofprocess engineering together with the kinetic description of main transfer pro-cesses. Engineering tools like dimensional analysis, order of magnitude estima-tions, or lumped element modeling are explained, which are very helpful fordealing with complex nonlinear systems. Concluding this chapter, the benefitsand limits of miniaturization of various unit operations and typical issues areexplained that might serve as a plentiful source for the future development.

KeywordsUnit operations, balance equations, transport equations, engineering modeling,scaling process

1.1 Introduction 21.2 Unit Operations and Beyond 51.3 Balances and Transport Equations 91.3.1 Statistical Mechanics and Boltzmann Equation 101.3.2 Macroscopic Balance Equations 131.3.3 The Mass Balance 141.3.4 The Species Equation 141.3.5 The Momentum Equation and Force Balance 151.3.6 The Energy Balance 161.3.7 The Entropy Equation and the Efficiency of a System 181.3.8 Elementary Transport Processes and their Description 19

1

1Process Engineering Methods and Microsystem Technology


1.3.9 Additional Remarks to Balance Equations 211.4 Calculation Methods and Simulation 211.4.1 Physical Variables and Dimensional Analysis 221.4.2 Similarity Laws and Scaling Laws 241.4.3 Order of Magnitude 241.4.4 Lumped Element Modeling 251.4.5 Numerical Simulation and Analytical Modeling 261.5 Miniaturization and its Application to Transport Processes 271.5.1 Length 271.5.2 Area 321.5.3 Volume 381.5.4 Other Topics 411.6 Conclusions and Outlook 42

References 42

1.1Introduction

Process technology and microsystem technology are both interdisciplinary engi-neering and natural science branches connecting physics, chemistry, biology, en-gineering arts, and management techniques to an enabling toolbox for variousapplications. Process engineering embraces orientating calculations for processand equipment design under general orientation, and system-orientated, cross-linked thinking. Process engineers are working in various areas ranging fromthe food industry through biotechnology to pharmaceutical products, from ana-lytical and laboratory equipment through energy conversion to industrial chem-istry for the production of millions of tons of chemicals [1, Chapter 1]. Chemicalprocess engineering covers not only the design and implementation of chemicalproduction and analytical processes but also deals with the equipment design,the appropriate materials, the fabrication, and operation of various chemicalproduction processes. The aims of process technology are the economical andsafe production of the desired products with the intended form and composi-tion.

Microsystem technology, coming from information technology and miniaturiza-tion of data-processing devices, has now entered many fields in our daily life. Sil-icon chips and sensors can be found in cars, washing machines or smart cardswith various functions. Besides the data-processing function, microsystems havetaken over other tasks like sensing and analyzing, actuating or controlling largersystems. Microsystem engineering comprises besides engineering skills like de-sign, simulation, or material knowledge also a deep physical and chemical knowl-edge for the fabrication and functional design issues. Also medical and biologicalskills are useful for the growing application fields for analysis, diagnostics, andtherapeutics. A good overview about the state-of-the-art in microsystem technology

1 Process Engineering Methods and Microsystem Technology2

is given in [2]. For the control and manipulation of still smaller systems, microsys-tem technology is a major link to nanotechnology [3, 4].

Figure 1.1 gives an impression of the wide field and complexity of both disci-plines, but also illustrates the multiple interfaces and common fields. The fruit-ful ideas from both sides may inspire the further development in both disci-plines and result in an enlargement of possibilities and applications for the in-novation across the borderlines.

Chemistry in miniaturized equipment is an emerging discipline coming to-gether from microsystem technology and from chemical engineering, but alsoan established discipline of chemical analytics. Starting at the end of the nine-teenth century a group of researchers at the University of Delft around Behrens[4a] and at the Technical University of Graz around Prof. Emich and Prof. Pregldeveloped the chemical analysis of very small amounts of reagents. In 1900Prof. Behrens wrote his book “Mikrochemische Technik” [4a] about micro chem-ical techniques. In 1911 Prof. Friedrich Emich published the textbook “Lehr-buch der Mikrochemie” [5] and Prof. Fritz Pregl was rewarded in 1923 by theNobel price for his fundamental work in microchemical analysis. In the middleof the last century in nuclear science small structures were developed for theseparation of isotopes, see [6]. From this work, among others, the LIGA technol-ogy emerges at German research institutes.

Dealing with very small geometrical structures is also a well-known area inprocess engineering. The adsorption technology and chemical reactions at cata-lytic surfaces are based on the flow and adhesion processes in nanoscale pores[7, Chapter 4]. Transformations and transfer processes on the molecular scaleare called “micro processes” in contrast to a “macro process” where convection

1.1 Introduction 3

Fig. 1.1 Disciplines of process engineering and microsystemtechnology, differing and common overlapping areas(middle column). The lists are not complete and the futurewill certainly bring new applications and new common fieldsand applications.

plays the major role. Some typical length scales for process technology, chemis-try and microtechnology are given in Fig. 1.2.

Figure 1.2 illustrates the different wording in process engineering, microsys-tem technology, and nanotechnology, especially the different meaning of “mi-cro”. The micropores in adsorption media are one characteristic example on thenanometer scale. Microstructured equipment has internal characteristic dimen-sions like channel diameter or gap height within the micrometer range. A cleardefinition of “micro” does not exist, but it is not necessarily required for all ap-plications and areas.

In the process industry, there are several applications of structures with typi-cal dimensions below 1 mm, like compact plate and fin heat exchangers orstructured packings in separation columns for enhanced heat and mass transfer.This is often summarized under the key word of process intensification. How-ever, the miniaturization of conventional technology is limited by two major re-strictions: the fabrication possibilities for the small structures at reasonablecosts and the increased fouling probability, the high danger of blocking, and to-tal failure of these structures. The first restriction has been widened with theenhanced fabrication possibilities, but the risk of fouling and blocking is stillthere and should not be underestimated.

The elementary setup of microstructured and conventional equipment is simi-lar and displayed in Fig. 1.3. Process plants consist of process units, whichthemselves are made of equipment like heat exchangers or vessels with internalstructures. The basic geometrical elements of the internal structures in conven-


Fig. 1.2 Characteristic length of important processes andequipment in chemical engineering and microsystemtechnology. The top and bottom line indicate also thedifferent wording of micro processes in the two disciplines,adopted from [8].

tional technology are the tube, the plate, and the film, on or in which the trans-port processes and transformations happen. The layout of process equipmentand process steps follow this scheme from small elementary active areas (“mi-cro process”) over the process space of the device (“macro process”) to the bal-ancing of the complete process.

The parallel arrangement of microstructured channels or elements is calledinternal numbering-up, which is the most frequent way to increase the through-put of an apparatus. The parallelization of microstructured devices is called ex-ternal numbering-up, applied to bypass the flow distribution problems withinthe equipment. A relatively new concept is the equal-up concept, the paralleliza-tion of similar effects [8]. The numbering-up and equal-up concepts facilitatethe scale-up process from laboratory equipment to production equipment, butstill have their own problems of flow distribution in manifolds, see Chapter 8.

1.2Unit Operations and Beyond

The consecutive groups or steps in a process plant can frankly be named formany cases as� pretreatment or conditioning of the incoming substances,� transformation of the reagents in chemical, physical, or biological processes,� separation of the received components, and� purification and conditioning of the products, see Fig. 1.4.

The physical and chemical processes in the various steps may be the same or sim-ilar, like heat transfer or extraction. They are called unit operations that are playing a

1.2 Unit Operations and Beyond 5

Fig. 1.3 Setup of microstructured andconventional equipment from single micro-structures through combined elements to anentire plant. The principle of the active area

can be applied in both cases(Sources: * from [9]; + courtesy of FhG-ICT,Pfinztal, Germany; o courtesy of Linde AG,Wiesbaden, Germany).

major role in the research and development of process engineering. The unit op-erations can be combined and connected in different forms. The concept of unitoperation combines a macro process with the apparatus to a process unit. It allowsus to treat all micro processes within the process space in the same manner and toderive scientifically based design rules and calculation instructions. For an entireprocess plant the unit operations are combined and switched in a proper way andintegrated for efficient material and energy use. Besides the energy and mass flowintegration the appropriate process control and automation determines the eco-nomical performance and safety of the plant. This gives a very complex pictureof a chemical or process technology plant, which is illustrated in Fig. 1.4. For a prop-er design and operation of a plant, many disciplines have to work closely together.

The unit operations can be categorized into three major groups according theemployed physical effects and major driving forces for combination or separa-tion of substances: the mechanical, the electromagnetic, and the thermal unitoperations (molecular driving forces) see Table 1.1. This list does not claim tobe complete, especially the separation processes from analytics are only shownschematically. Probably in the next years further operations will be developedenabled by enhanced fabrication and integration possibilities. In adsorption ofspecies or membrane separation, chemical processes may also be involved formass-transfer processes in microstructures, see [11, Chapter 3]. The consequenttreatment of unit operations allows the methodological design with help of thefollowing principles. The principle of continuity of substances, phases, energyand momentum includes the preference of continuous processes opposite tobatch processes. The principle of balancing of the relevant transport processesgives the energy, momentum, and mass fluxes in differential or black-box form.The principle of scaling and similarity of processes gives a calculation tool fortransferring experimental, analytical, and numerical results to processes on dif-ferent scales with the help of dimensionless numbers and groups.


Fig. 1.4 Main process steps in a chemical production plantwith pretreatment, conversion, separation, and purification ofthe products, adapted from [10]. The system integrationincludes the energy management, auxiliary media as well asinformation for the process control and automation.

Micro Process Engineering

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