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УДК 536.4
Juergen J. Brandner, E. Anurjew, T. Henning, U. Schygulla, K. Schubert Forschungszentrum Karlsruhe institute for Micro Process Engineering IMVT, Germany
MICROSTRUCTURE DEVICES FOR APPLICATIONS IN THERMAL AND CHEMICAL PROCESS ENGINEERING (ИСПОЛЬЗОВАНИЕ МИКРОСТРУКТУРНЫХ УСТРОЙСТВ В ТЕПЛОВЫХ И ХИМИЧЕСКИХ ПРОЦЕССАХ)
Abstract
In this publication, an overview of the work dealing with thermal and chemical micro process engineering performed at the Institute for Micro Process Engineering (IMVT) of Forschungszentrum Karlsruhe will be given. The focus will be set on manufacturing of metallic microstructure devices and on microstructure heat exchangers. A brief outlook will describe possible future application fields.
Keywords
Microstructure, Micro Reaction Engineering, Heat exchanger, Multi-scale, Lab-scale, Application
Introduction
For a couple of years microstructure devices have been well-known as excellent tools for laboratory research in many application fields. The advantages of microstructure devices are well known and can be found in many references, we will not go into details here [1 - 5].
For lab scale type devices, mainly single microchannel systems either manufactured from silicon by semiconductor technologies or made from metals by mechanical micromachining or wet chemical etching (see [5]) are used for intense research activities in flow characterisation, heat transfer and experimental investigation of chemical reactions. By the use of single channels the mass flux is naturally limited to small values. To achieve higher mass fluxes several possibilities have been discussed, namely parallelization of single microchannel devices, scaling-up of the microchannel dimensions or generation of internally parallelized multi-channel systems, the so-called equaling-up [5]. All of these are possible and more or less feasible for lab-scale devices as well as for application devices. This led to a variety of microstructure devices suitable for lots of applications, namely heat exchange, evaporation, mixing, generation of emulsions, and running chemical reactions in the lab scale range. Unfortunately, the transfer to industrial applications is still underrepresented, since not many applications in industry have been published yet. This is not only a result of the lack of knowledge of the precise working mechanism of heat transfer and fluid flow in micro-scale (see, e.g., the discussion about the transition between laminar and turbulent flow in micro-scale) but also due to the difficulties in exact modelling and pre-calculation. Moreover, fouling and blocking problems have been widely discussed but are not yet solved. Also, prediction rules for the corrosion behaviour of microstructured materials are still under investigation. Thus, data on the long term stability of microstructure devices are not available yet.
Nomenclature
Latin symbols
A effective heat transfer area m2
C microchannel circumference m
F microchannel face area m2
Nu Nusselt number
P pressure Pa
Pr Prandtl number
Q thermal power W
Re Reynolds number
T temperature K, °C
cmean mean specific heat capacity J •kg-1 •K-1
CP specific heat capacity J •kg-1 •K-1
dh hydraulic diameter m, /im
k overall heat transfer coefficient -1 -2 -m
l microchannel length m
m mass flow kg • h1
nch number of microchannels per foil
nf number of microstructured foils per passage
o.r. of the range
o.v. of shown value
s path length, foil thickness m
Greek symbols
a heat transfer coefficient -1 -2 -m
A thermal conductivity -1 -1 -m
s efficiency of the heat transfer %
mean logarithmic temperature difference K
z form factor
Subscripts
cold cold water passage
hot hot water passage
in inlet position
lam laminar
out outlet position
turb turbulent
Basics
Basic calculations for heat transfer as well as pressure drop in microstructure devices can be performed using standard Nusselt theory equations [4, 5]. Some geometrical considerations have to be done, like, e.g., how to define the characteristic length for non-channel designs. We will consider microchannel designs here, therefore the characteristic length is set to be the hydraulic diameter of each microchannel. It can be calculated using the simple equation
4 • F
dh = — (1)
where dh is the hydraulic diameter, F is the face area of the channel and C is the circumference of the microchannels.
For further calculations with non-circular channels, a correction factor has to be applied to approximate a circular cross section. Those factors may be found, e.g., in VDI Warmeatlas [6]. For the pressure drop, equations like the Hagen-Poiseulle equation for laminar flow with a Reynolds number lower than approx. 2 300 or an equation developed by Petukhov and Gnielinski for turbulent flow with a Reynolds number Re between 3 000 and 105 may be applied (see VDI-Warmeatlas [6]).
For a microstructure heat exchanger having a defined geometry and known mass flows as well as inlet and outlet temperatures, the heat transfer therefore can be calculated by the energy balance equation (2).
m • cp • AT = k • A • A&m (2)
To calculate the effective heat transfer area A equation (3) may be used:
A = nf • nCh •C •l (3)
The mean logarithmic temperature difference A3m can be obtained from the formula given in VDI-Warmeatlas [6].
Assuming the same heat transfer area in each passage, the heat transfer coefficient is defined for both a cold and a hot passage in equation (4). Then, the overall heat transfer coefficient may be calculated using equation (5).
a = Nu •A Fluid dh
111 5
— =------1-------1------
k a hot a cold Asolid
For laminar flow (Re < 2 300), the Nusselt number is obtained using equations (6) to (9) [6].
Nuiam = 3(Nu,3 + 0.73 +(Nu2 _0.7)3 + Nu33) (6)
Nu1 = 3.66 (7)
(4)
(5)
Nu2 =1.615• 3 Re• Prdh 2 \ I
Nu,
v 1 + 22 • Pr J
du
Re • Pr -h-l
(9)
For turbulent flow (Re > 2 300), the Nusselt number is defined by equations (10) to (11).
Nutur
•(Re -1000). Pr
1+12.7 •
I ( 2/ ^
^ Pr/3-1
8 I
1+
✓ n2/^ ^ /3 l
(10)
^ = (1.82 • log (Re)-1.64)
-2
(11)
When fluids with similar specific heat capacity are applied to both passages, the heat transfer efficiency s can be used easily for comparison of differently designed (microstructure) devices. A definition is given in equation (12) [6 - 7].
Q
m • c
mean
hot,in Tcold
I,in )
(12)
In the specific case of symmetric fluid flow and using the same fluid for both passages, the capacity flow of both fluids is almost the same. Then, equation (12) can be rearranged to calculate the heat transfer efficiency s with equation (13) [6].
s =
mcold • cp,cold ' ' (Tcold,out Tcold,in )
mhot •cp,hot •{Thol. ~^n Tcold,in)
(13)
More details to the easy pre-calculation methods and other, more complex possibilities to calculate microstructure behaviour can be found in [5 - 9]
Beside these rather simple pre-calculations, CFD software like FLUENT or CFX can be used to simulate the flow behaviour, the pressure drop and the thermal behaviour of microstructure devices. In most cases a simulation of a complete microstructure device will result in the plenum outlet temperature at a certain mass flow. It is possible to perform calculations for complete microstructure devices to obtain temperature distributions, but the computational power needed is quite high due to the relatively high number of simulation cells needed to obtain a precise description. Examples for simulation results and more related references can be found in [8 - 11].
s
Manufacturing
Manufacturing of single microchannel or multi-channel devices out of polymers, metals, glass or ceramics is in many cases done with silicon technology
methods, i.e. dry etching or wet etching . Sometimes more complex methods like LIGA are used. For a lot of applications, wet chemical etching, mechanical micromachining or laser machining is the method of choice due to the low machining costs. Detailed description of manufacturing methods for microstructures can be found in [5, 12].
Process Parameter Restricrtions
The material of the devices as well as the design are mainly influenced by the process including the used fluids. This is specially true for industrial applications, where a certain lifetime has to be guaranteed. Laboratory equipment like single microchannel devices or single microstructure foil lab devices can easily and without major cost restrictions be designed in that way that the microstructures themselves are exchangeable. Here, thermal stress or corrosion may damage the microstructures, which will then be replaced.
For chemical reactions, the amount of heat needed by endothermic or generated by exothermic chemical reactions can be pre-calculated easily. For “simple” heat exchangers, the mass flux per passage as well as the fluid suitable to transfer the desired amount of heat can be pre-calculated using the equations given above, or using CFD methods, as it was mentioned before. In the following, we will focus on microstructure heat exchanger devices and their applications.
Material choice
Several factors influence the choice of materials for microstructure devices. The most important are temperature resistance, corrosion resistance and thermal properties. There are norms for temperature and pressure devices such as the European Pressure Equipment Directive (PED) 97/23/EG [13]. Microstructure devices are often exempted from these rules, since the active volume (the hold-up, respectively) is small. However, if technical relevant throughputs are to be obtained the active volume is in an order that the rules apply.
Another extremely important factor for the choice of materials for devices is the question of corrosion. This topic needs special attention. Standard literature on corrosion, e.g. the corrosion handbook by DECHEMA [14] takes a corrosion rate of 0.1 mm • y-1 as resistant, a corrosion rate of 1 mm • y-1 is taken as fairly resistant. These values are chosen with respect to standard, macroscopic reaction vessels, tubes and fittings, which normally provide wall thicknesses in the range of several mm or higher. When talking about microstructure devices, we often have wall thickness in the order of 0.1 mm (= 100 ^m) or even below. Consequently, the corrosion rate limitations given in the cited literature can not be applied to microstructure devices. Sadly enough corrosion has not been a topic in most publications dealing with microstructure devices, but it has normally been assumed that the material of choice is more or less completely resistant against corrosion by the given reaction system. In opposite, a material deemed resistant according to the corrosion handbook can prove unsuitable for the process running in the microstructure device.
Presently, no common design rules or regulations from any federal or private organization dealing with corrosion rates for microstructure devices are existing. Thus, for each process that should be handled with microstructure devices, the corrosivity of the fluids and the resistivity of the material has to be checked carefully to prevent damages and losses within short time. But measuring extremely small corrosion rates (by, e.g., gravimetric measurements) is time consuming and prone to errors, due to the small losses in weight. For some very corrosive fluids and processes, ceramic or glass microstructure devices are mandatory - or extremely corrosion resistant metals like tantalum.
To asses the suitability of a construction material for a given process, careful experiments under the expected conditions have to be undertaken. The choice of material in relation to corrosion should in first approximation be limited to ones which are expected to be completely resistant. However, if the use of the device is limited to comparatively short times, e.g. in a production or measurement campaign, the above mentioned limitation need not be strict. One should be sure that the complete destruction of the functionality is not to be feared during the time of the campaign. This is especially of importance in the industrial application.
Fluid Dynamics Restrictions
Aside of thermal stress and corrosion, fluiddynamics restrictions have a large influence on the design and the use of microstructure devices. Normally laminar flow is assumed to take place within microchannel devices. This may be correct for most lab scale and industrial applications, especially if the surface quality is very high, like it is the case for glass devices. Specially treated metallic microstructures like the one shown in Figure 1, where the roughness is in the range of some ten nanometers, can also be considered to act in laminar flow regime. This might not be the case anymore for wet chemically etched microstructures with very small dimensions, like the ones shown in Figure 2. The surface roughness of wet chemically etched microstructures is, depending on the material, in the range of some ^m. Assuming very small characteristic dimensions, the surface roughness might be in the same order of magnitude, which gives a certain probability of a distorted non-laminar flow. Anyway, in all cases laminar flow may not be expected anymore when fouling starts to occur.
Fouling is a general problem, not only for microstructure but also for conventional process equipment. Nevertheless, due to the small characteristic dimensions, the impact of fouling in microstructures is much higher than in macroscale devices. While the reduction of the hydraulic diameter caused by a 10 ^m thick fouling layer is beyond measurement possibilities in a multimillimeter channel, a microchannel hydraulic diameter of 133 ^m, assuming a typical rectangular channel of 200 ^m width and 100 ^m depth, is decreased by roughly 8%. This may lead to distortions of the flow, and a non-laminar behaviour may occur. Higher pressure drop and a decrease in heat transfer capacities are to expect.
Clockwise: Microchannel overview, sidewall upper edge and top of microchannel wall, sidewall lower edge and bottom of channel. The microchannels have been manufactured mechanically, followed by an electro-polishing process. The mean value of surface roughness was measured to about 30 nm.
Thus, strategies for the prevention of fouling and/or cleaning of microstructure devices have to be developed. One possibility is the application of protective layers, another might be the application of mechanical forces, e.g. ultrasound [15]. Like for the corrosion problem, the investigations on fouling in microstructure devices are just about to begin.
Laboratory Scale devices
Laboratory Scale Devices are normally either single microchannel devices or devices where a limited number of microstructures is integrated in a way that they are more or less easily exchangeable. The objective is either to perform initial tests on basic operations, to obtain data on fundamental process steps performed in microstructure devices or to obtain basic data sets to run, e.g., a chemical reaction in an application-scale microstructure device. There are lots of descriptions about such lab-scale devices [1-5].
An example for a single microchannel device is given in [16]. Here, within a single rectangular microchannel machined in stainless steel, the local heat transfer was measured for a regime up to a Reynolds number Re of roughly 4 000. Not only PT100 sensors but also optical methods using the induced fluorescence of
Rhodamin B was used to measure the local heat transfer. Another example is given in [17], where the critical heat flux in single microchannel tubes was measured using refrigerants as test fluids.
00011016 ------ 100 |jm JEOL
00011017 ------ 50 pm JEOL
Fig. 2: Wet Chemically Etched Microchannel Stainless Steel Foil
Top to bottom: Microchannel overview, sidewall top surface and bottom of channel quality. The microchannels have been wet chemically etched. The mean value of surface roughness is about some ^m.
Multichannel systems in lab-scale have been tested in many varieties. One example is a polymer device providing an enhanced, extremely high area-specific heat transfer combined with very low pressure drop [18 - 19]. In Figure 3, such a polymer microstructure heat exchanger is shown. Here, the microstructures are integrated into the polymer parts. These parts are manufactured by micro-stereolithography, which allows a wide variety of microstructures to be integrated [18] The metal (in the particular case: aluminum) foil is sealed between the two polymer parts with O-rings. The heat transfer between two fluids takes place on the
contact area of the fluids to this metal foil, which is not microstructured. As microstructures, a very large number of short microchannels have been combined with a smaller number of relatively large connection channels. This led to heat transfer capabilities combined with a low pressure drop. More details about this device can be found in [19]. Figure 4 shows the pressure drop of a reference microchannel device (blue line) compared to the new polymer microstructure heat exchanger (red line). In Figure 5, the specific thermal power transferred with a reference polymer device having straight microchannels (blue line) is compared to the specific thermal power transferred with the new polymer device (red line). With this device, a maximum of about 1 000 W • cm- specific thermal power is possible.
In Figure 6, a lab-scale electrically powered microstructure evaporator is shown. This device consists out of a stainless steel baseplate having holes to insert commercially available heater cartridges and a stainless steel cover frame. The microstructure foil is made exchangeable by clamping it, sealed with O-rings, between the baseplate and a (plexi-)glass cover pressed to the baseplate with the frame. The foil inserted while the photo for Fig. 6 was taken was made of brass, which results in a coloured surface by the use of deionized water as test fluid. A detailed description of the device, the test rig and first results obtained for the evaporation of water can be found in [20].
Fig. 3: Polymer Microchannel Heat Exchanger with Aluminum Separation Foil
Both half-shells of the polymer heat exchanger are made by micro-stereolithography. Heat transfer takes place on the non-contacted surface of the aluminum foil clamped between the polymer shells.
Aside of the lab-scale devices shown here, numerous manufacturers of microstructure devices provide different types of microstructure heat exchangers and modules for heat transfer experiments and lab-scale applications. Examples for a devices useful for lab or semi-industrial applications can be found in [21]. Here, within the framework of a public-funded project, a standardization of different microstructure devices from different manufacturers have been performed.
Beside this, numerous publications on lab-scale microstructure devices can be found. Resources for information on this topic are the topical conference proceedings [22, 23] as well as the meanwhile well-established books on microstructure technology and micro process / micro reaction engineering [5, 9, 11, 24].
For experiments and applications with certain corrosive fluids or at high temperatures, metallic devices may not be the first choice. Thus, devices made of glass or ceramics provide useful characteristics. As an example, a first test sample of an ceramic microstructure heat exchangers are shown in Figure 7. This counterflow device was tested and compared to metallic microstructure heat exchangers and showed promising results. More details can be found in [25].
0 100 200 300 400
cold water mass flow [kg/h]
Fig. 4: Comparison of Pressure Drop Measurements
The pressure drop of a straight microchannel reference design was measured and compared to the new micro heat exchanger.
cold water passage pressure drop [bar]
Fig. 5: Specific Thermal Power
In the plots, the specific thermal power transferred with a straight microchannel reference design (blue plot) and the new microstructure design (red plot) are compared.
Fig. 6: Electrically Powered Lab-scale Microchannel Evaporator
The microchannel foil is exchangeable and clamped to the baseplate by use of O-rings as sealings, a (plexi-)glass lid and a stainless steel frame.
Fig. 7: Ceramic Counterflow Microstructure Heat Exchanger
4 microstructured ceramic heat exchanger plates have been connected, sealed and tested.
Applications
In micro process engineering, the transition between lab-scale application and semi-industrial or industrial application is not strictly defined. A multi-channel lab-scale module may also be used for the production of fine chemicals in the industrial range - if this range is, e.g., some hundred kilograms per year only. On the other hand, the production of several thousand tons of any product might be difficult with a single microstructure foil device. Therefore, considerations on industrial scale devices have been done, resulting in the possibilities of scale-up, numbering-up and equaling-up, as it was mentioned before. Nevertheless, the advantages of microstructure devices allow to run processes in a way not accessible with conventional techniques [1, 2, 24]
In most cases, scale-up of the microstructure dimensions is only possible to a certain limit. If this limit is not respected, the specific advantages of the microstructures will be lost. Numbering-up might be an option if the overall throughput for the process is not to high, and therefore the expenditure on measurement and control hardware and software is not to high. A combination of both scale-up and numbering-up is named equaling-up (or, in other references, internal numbering-up). Here, a large number of microstructures with optimum dimensions is integrated into one more or less large device which then allows higher throughput. This multi-scale approach is described, e.g., in [26].
Moreover, there are two different types of microstructure devices available: Multi-objective microstructure modules (or devices) and devices which have been built to meet specific demands of one process (single objective devices). In the following, some examples for both types of devices / modules will be described briefly.
Micro heat exchangers used for semi-industrial or industrial applications are available from different providers. They are very good examples for multiobjective devices. In many cases, they are manufactured out of single microstructure foils which are stacked and bonded by, e.g., diffusion bonding, laser or electron beam welding, brazing or soldering. As materials, different metal alloys, glass, polymers and ceramics are used. The manufacturing for stainless steel crossflow microstructure heat exchanger devices is described in details in [4]. In Figure 8, a system of microchannel stainless steel foils made by mechanical micro-machining is shown. The foils are stacked in crossflow arrangement. Figure 9 shows wet chemically etched microchannel stainless steel foils used to build a conterflow microstructure heat exchanger. A crossflow microstructure device is shown in Figure 10, while Figure 11 shows a counterflow design.
With the microstructure devices shown in Fig. 10 and 11, mass fluxes of up to 2 000 kg • m- s- can be obtained, measured with water as test fluid at a pressure
drop of about 0.5 MPa per passage. Larger devices than the crossflow design
9 і
shown in Fig. 10 are able to handle a mass flux of up to 20 000 kg • m- s-, as it is
pointed out in [1, 4].
Fig. 8: Crossflow-arrangement of Mechanically Machined Microchannel Foils
The foils are made of stainless steel and connected by diffusion bonding to form a very stable stack.
Fig. 9: Microchannel Heat Exchanger Foils
The wet chemically etched microchannel design is used to build counterflow microstructure heat exchangers.
To increase the mass flux even further, either a parallelization of a small number of those devices can be used, or multi-scale systems can be manufactured. An example for a numbering - up with a limited number of devices is shown in Figure 12, where five stainless steel crossflow microstructure heat exchangers are taken in parallel. With this stack of devices, a mass flux of about 100 000 kg • m-
9 1
s- at a pressure drop of about 0.5 MPa is possible. A maximum thermal power of 1 MW is transferable. More details can be found in [1, 3, 4].
For some applications, even the extremely high overall heat transfer
9 1
coefficients of about 30 000 W • m- K- named in, e.g., [3], may be not sufficient. For these cases, a heat transfer enhancement is possible by changing the integrated microstructures of heat exchanger devices. Details on this topic are described in [27].
Heat exchanger devices like the above mentioned can easily be combined with other devices like micro mixers and microreactors to run reactions in lab-scale, pilot-scale or production scale plants.
Fig. 10: Stainless Steel Crossflow Microstructure Heat Exchanger
Within an active volume of 1 cm3, hundreds to thousands of microchannels have been integrated. At a mass flux of about 2 000 kg • m-2 s-1, a thermal power of up to 20 kW can be transferred using water as test fluid (95°C / 8°C). The pressure drop is in the range of 0.5 MPa.
Fig. 11: Stainless Steel Counterflow Microstructure Heat Exchanger
This device provides similar characteristic values than the crossflow design shown in Fig. 11.
Fig. 12: Microstructure Heat Exchanger Stack.
Five stainless steel crossflow microstructure heat exchangers in parallel. Each
-3
of the devices has an active volume of 27 cm . With this stack, a maximum mass
9 1
flux of about 100 000 kg • m- s- is possible at a pressure drop of around 0.5 MPa (test fluid: water). A thermal power of 1 MW can be transferred.
An example for a pilot scale plant for a chemical reaction is described in [28]. Here, the weight distribution of the macromolecules generated in a polymerization process could be improved significantly by the use of microstructure devices.
Another example for an industrial pilot-plant approach to run microstructure devices is described in [29]. Results from lab-scale devices [30] have been successfully transferred to a pilot-plant industrial application.
Nevertheless, publications on devices specially designed for industrial production applications are quite rare yet. This might be due to the previously mentioned problems with design rules and the lack of knowledge on the long term stability of microstructure devices.
One example for an industrial application is the heating of bio-diesel in a production facility. Here, an electrically powered microstructure device (see Figure 13) is used to heat up a mass flow of 1 000 kg • h-1 bio-diesel from 80°C to 105°C. The maximum electrical power of the device is 20 kW [31]. A description of the principal function and the design of the device can be found in [32]. Figure 14 shows an example for the temperature raise of the bio-diesel obtained by using the microstructure heat exchanger. Other microstructure devices may also be used with bio-fuels, as it is pointed out in [33].
Fig. 13: Electrically Powered Micro Heat Exchanger
With this device, the complete production mass flow of a bio-diesel production facility is heated.
An example for an objective-specific multi-scale microstructure reactor device is shown in Figure 15. This device results from a cooperative work between the Institute for Micro Process Engineering of Forschungszentrum Karlsruhe and DSM Fine Chemicals, Austria [34]. The device is 650 mm long and weights about 290 kg. A number of micro-mixers and several tenthousand microchannels for heat
transfer have been integrated to perform a highly exothermic chemical reaction for the production of fine chemicals. The applied mass flow was about 1 700 kg • h-1 of liquid reactants. the device was pre-calculated to handle a maximum thermal power of around 800 kW. With this microstructure device, the production costs of the fine chemical product per kg could be reduced significantly. At the same time, the purity of the product was increased. Thus, the reaction yield was increased, and less waste and by-products have been produced. In a first production campaign, abut 300 tons were successfully produced.
о -J---------------і--------------1---------------.--------------і--------------і---------------
О 200 400 600 800 1000 1200
bio-diesel mass flow [kg It1]
Fig. 14: Temperature Raise of Bio-Diesel
By use of the device shown in Fig. 13, the temperature of the complete production mass flow of the facility (1 000 kg • h-1) could be raised to the desired values.
Fig. 15: Multi-scale Production Reactor for Fine Chemicals
Within a cooperative work, a production reactor with integrated microstructures has been designed and manufactured. A highly exothermic chemical reaction was performed successfully.
Summary
Microstructure devices are clearly a valuable tool for laboratory research as well as for industrial applications. The heat transfer in microstructure devices is taken as one example to describe some aspects of the way of the devices from lab-scale up to industrial production range. Basic principles of heat transfer in Microscale have been described briefly. Examples for laboratory microstructure devices, microstructure devices suitable for all the range from lab to production and microstructure devices designed and manufactured for specific production problems have been presented. It was pointed out, that in the case of microstructure devices the transition between laboratory and production range is floating - there is no strictly defined border, where lab-scale ends and production scale starts due to the fact, that the advantages of microstructure devices may allow process parameters to be run which are not accessible with other techniques. Thus, production may take place with mass fluxes in the range of some kg per day up to some tons per day - depending on the product and the process.
Outlook
Micro reaction engineering is now in discussion for about a decade roughly. Since the first enthusiasm for a new and fascinating technology has faded, a more realistic view has been established in research and applications, supported by the experiences and research results of the last years. Now, the use of microstructure devices for process engineering is on the bedplate to become a well-known and evaluated technology not only for research labs but also for real production in chemical, pharmaceutical and biotech industry. Other applications in electronics, consumer goods, biomedicine, automotive, aircraft and space technology may follow up. The potential of microstructure devices has become quite clear in many cases, as well as the risks and limitations, in other cases researchers and industry are just starting to explore the potential benefits of microstructure devices. First lectures and courses dealing with microstructure technology only have been established at several universities worldwide, which will lead to a new generation of scientists and engineers being familiar with this technique. Thus, the technology has clearly achieved a promotion from a lab-style technique to an accessible and reasonable technology for industrial applications. This way will continue in near future.
Acknowledgments
Special thanks to mikroglas and IMM for providing photos and information of their devices.
References
1 Schubert, K., Brandner, J.J., Fichtner, M., Linder, G., Schygulla, U., Wenka, A., “Microstructure devices for applications in thermal and chemical process engineering”, Microscale Thermophysical Engineering, 5, 2001, 17-39
2 Hessel, V., Lowe, H., „Mikroverfahrenstechnik: Komponenten -
Anlagenkonzeptionen - Anwenderakzeptanz“, Chemie Ingenieur Technik (74) 2002, Vol. 1-2, 17-30, Vol. 3, 185-207, Vol. 4, 381-400
3 Brandner, J.J., Bohn, L., Schygulla, U., Wenka, A., Schubert, K., “Microstructure
devices for thermal and chemical process engineering”, Yoshida, J.I. [Ed.], Microreactors: Epoch-Making Technology for Synthesis; MCPT, 2001, Tokyo, J, CMC Publ. Co., 2003, 75-87, 213-223
4 Brandner, J.J., Schubert, K., “Fabrication and Testing of Microstructure Heat
Exchangers for Thermal Applications“, Proc., 3rd Int. Conf. on Microchannels and Minichannels, S.G. Kandlikar et al., eds., ASME, New York, N.Y. 10016, USA, paper
ICMM2005-750 71
4 Brandner, J.J., Schubert, K., “Fabrication and Testing of Microstructure Heat
Exchangers for Thermal Applications“, Proc., 3rd Int. Conf. on Microchannels and Minichannels, S.G. Kandlikar et al., eds., ASME, New York, N.Y. 10016, USA, paper
ICMM2005-750 71
5 Brandner, J.J., Gietzelt, T., Henning, T., Kraut, M., Moritz, H., Pfleging, W., “Microfabrication in Metals and Polymers“, in: Brand, Fedder, Hierold, Korvink, Tabata (Eds.): Advanced Micro- and Nano Systems AMN Vol 5, 2006, Wiley-VCH, Ch. 10, p. 267-319
6 VDI Warmeatlas, 7.ed., VDI-Verlag, Dusseldorf Germany, 1994
7 Wagner, W.,”Warmeaustauscher”, 2nd ed., Vogel-Verlag, Wurzburg, Germany, 1999
8 Herwig, H., ”Fluid Dynamics in Channels Below 1mm Hydraulic Diameters”, in: Brand, Fedder, Hierold, Korvink, Tabata (Eds.): Advanced Micro- and Nano Systems AMN Vol 5, 2006, Wiley-VCH, Ch. 2, p.47-70
9 Kockmann, N., “Transport Processes, Thermodynamics, Heat Exchange”, in: Brand, Fedder, Hierold, Korvink, Tabata (Eds.): Advanced Micro- and Nano Systems AMN Vol 5, 2006, Wiley-VCH, Ch. 3, p. 71-114
10 Hardt, S. Baier, T., ”A Computational Model for Heat Transfer in Multichannel Microreactors”, Proc., 3rd Int. Conf. on Microchannels and Minichannels, S.G. Kandlikar et al., eds., ASME, New York, N.Y. 10016, USA, paper ICMM2005-750 79
11 Tonomura, O., “Simulation and Analytical Modelling”, in: Brand, Fedder, Hierold, Korvink, Tabata (Eds.): Advanced Micro- and Nano Systems AMN Vol 5, 2006, Wiley-VCH, Ch. 8, p. 235-248
12 Madou, M.., “Fundamentals of Microfabrication”, CRCPress, 1997
13 AD 2000-Regelwerk (Ed.: Verband der Technischen Uberwachungs-Vereine e.V., Essen) Carl Heymanns Verlag KG, Koln, Germany, 2003
14 Dechema Corrosion Handbook (Ed.: D. Behrens) VCH, Weinheim, Germany, 1987
15 Benzinger, W., Schygulla, U., Schubert, K., Jaeger, M., "Anti-Fouling Investigations with Ultrasound in a Microstructured Heat Exchanger", Proceedings, Heat Exchanger Fouling and Cleaning - Challenges and Opportunities, Kloster Irsee, Germany, June 5-10, 2005
16 Klein, C., Ehrhard, P., “Development of a Measuring Technique for the Local Heat Transfer”,Proc. of the ECI Conference Heat Transfer and Fluid Flow in Microscale HTFFM 2005, Sep 25-30, 2005, Castelvecchio Pascoli, Italy, paper No. 56
17 Wojtan, L., Revellin, R., Thome, J.R., “Investigation of the Critical Heat Flux in single, uniformly heated Microchannels”, Proc. of the ECI Conference Heat Transfer and Fluid Flow in Microscale HTFFM 2005, Sep 25-30, 2005, Castelvecchio Pascoli, Italy, paper No. 6
18 Anurjew, E., Brandner, J.J., Hansjosten, E., Schygulla, U., Schubert, K., „Mikroverfahrenstechnik und stereolithographisch hergestellte Mikrostrukturapparate“, Proc. of the Int. Conf. Geo-Sirbiria-2005, April 25-29, 2005, Novosibirsk, Russia
19 Brandner, J.J., Anurjew, E., Hansjosten, E. Henning, T., Schygulla, U., Schubert, K., “A new Microstructure Heat Exchanger with Reduced Pressure Drop”, Proc. of the 4th Int. Workshop on Micro Chemical Process Technology, Jan. 26+27, 2006, Kyoto, Japan
20 Henning, T., Brandner, J.J., Schubert, K., “Comparison of Microchannel Array Water Evaporator Designs by High-Speed Videography”, ASME, Proc. of the 3rd Int. Conf. on Micro-andMinichannels ICMM2005, June 13-15, 2005, Toronto, Canada, paper ICMM2005-75097
21 Industrieplattform Mikroverfahrenstechnik, www.microchemtec.de
22 ASME Proceedings of the International Conferences on Micro and Minichannels
ICMM
23 AIChE Proceedings on the International Conferences on Micro Reaction Engineering IMRET
24 Hessel, V., Hardt, St., Lowe, H., „Chemical Micro Process Engineering Vol. 1+2”, Wiley-VCH, 200З
25 Alm, B., “Keramische Massen fur den Niederdruckspritzguss zur Herstellung von
Komponenten fur die Mikroverfahrenstechnik”, Tech. Rep. FZKA 7061, Forschungszentrum Karlsruhe,PhD thesis, Universitйt Karlsruhe, 2004,
http://bibliothek.fzk.de/zb/abstracts/7061.htm
26 EU Project “IMPULSE”: Integrated Multiscale Process Units with locally Structured Elements”, http://www.impulse-project.net/
21 Brandner, J.J., Anurjew, A., Bohn, L., Hansjosten, E., Henning, T., Schygulla, U., Wenka, A., Schubert, K., “Concepts and Realization of Microstructure Heat Exchangers for Enhanced Heat Transfer”, Experimental Thermal and Fluid Science, acc. for publication.
28 Iwasaki, T., Yoshida, J.-I., “Free Radicals Polymerization in Microreactors. Significant Improvement in Molecular Weight Distribution Control”, Macromolecules, 200З, 38, pp. 11З9-1163
29 Schirrmeister, St., et al., „DEMIS®: results from the development and operation of a pilot-scale micro-reactor on the basis of laboratory measurements”, Proc. of 8th Int. conf. on Micro reaction Eng. IMRET8, April 10-14, 200З, Atlanta, GA, USA
3G Klemm, E.J., Markowz, G., Mathivanan, G., Albrecht, J., Schirrmeister, St., „Evaporation of Hydrogen Peroxide in a Microstructured Falling Film”, Proc. of 8th Int. conf. on Micro reaction Eng. IMRET8, April 10-14, 200З, Atlanta, GA, USA
31 Rinke, G., Holpe, H., Wenka, A., „Einsatz eines elektrisch heizbaren Mikrowarmeubertragers an einer Biodieselproduktionsanlage“, Tech. Rep. FZKA 6990, 2004, pp.2^-216, http://bibliothek.fzk.de/zb/abstracts/6990.htm
32 Henning, T., Brandner, J.J., Schubert, K., “Characterisation of electrically powered micro heat exchangers”, Chem. Eng. J. Vol. 101/1-3 pp. 339-34З
33 Kerschbaum, S., Rinke, G., „Measurement of the temperature dependent viscosity of biodiesel fuels”, Fuel 83 (3), 2004, pp.287-291
34 Forschungszentrum Karlsruhe GmbH, “Mikro in Chemie ganz groB”, Press Release 13/200З, http://www.fzk.de/fzk/idcplg?IdcService=FZK&node=1298&lang=en
О Juergen J. Brandner, E. Anurjew, T. Henning, U. Schygulla, K. Schubert, 2006
