IAM - Computational Materials Science

Microstructure – Diffusion

Diffusion is traditionally understood as the spread of one or more substances in a medium. Heat, however, can also diffuse through matter. Both phenomena are important for many types of energy storage.
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Research

The research activities of the research group “Microstructure - Diffusion” include the modelling of liquid and solid foams as well as the simulative investigation of heat transport in porous structures, which, among other things, is influenced by fluid flow.
The improvement of the efficiency of heat exchangers, heat collectors and heat storage systems, in dependence of the microstructure and the material properties, is the objective of the work. During the reproduction of the processes, the phase transformation processes of the fluid medium are considered. The work of the research group focuses on the development of an optimal structure of the participating porous materials, such as the structure of a metal foam.

Metal Foams

Metal foams are materials with excellent properties. They look like beer froth, but without the beer, and basically without partitions between the individual bubbles. Only where three or more bubbles meet is it that material still does exist. These so-called ligaments form an irregular solid mesh, which still possesses many properties of the base material – metal: thermal conductivity, stability, electrical conductivity and even more properties, such as the lightness, the reduced demand for base material and especially the large surface, compared to the volume. This surface, for example, enables the heat to be exchanged by the air surrounding the ligaments. Because of this property, in connection with the good thermal conductivity of metal, metal foams are extremely popular in our research within the KIT programme ''Energy Efficiency, Materials and Resources''.

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Computer model of a metal foam
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Simulation of a textile spacer fabric with paraffin storage

Solar Thermal Energy

Black objects can absorb solar energy extremely well. The skin of a polar bear is black, so that it is able to absorb as much energy as possible from the sunlight at the north pole. The white hairs of its fur, which allow the sunlight to pass through, are used to isolate the polar bear's own body heat. On the basis of this principle, heat collectors, consisting of textile spacer fabrics, were developed in the project “Solar Thermal Energy”, in cooperation with the Institute of Textile Technology and Process Engineering, Denkendorf, the project partner. Besides the generation of energy, the storage of energy does, of course, also play an important role. In the second part of the project, new storage systems were examined: small, thimble-sized buckets, filled with paraffin, which were positioned directly beneath the textile collector. During melting, paraffin stores the latent heat and releases it again during solidification. At the CMS, we examine the eligible systems by means of computer simulations and make suggestions for improvement, regarding their geometry.

Porous Water Pipes

Using energy resources in the most efficient manner is an important challenge of the future. In materials sciences, this results in a search for efficient, affordable and practical materials, for heat conduction and storage. Metal foams provide a promising solution for energy transmission and energy storage problems, as they possess both the capacity to allow fluids to permeate and a large surface. This enables fluids and other possible fillings to be heated more efficiently.
Hereby, the objective is to achieve a heat transfer, which is as high as possible, while, at the same time, the pressure drop is as low as possible. First, these foams are designed in computer simulations, in which the material is tested for different conditions, such as changes in temperature or pressure, as well as for the influence of different pore sizes. Subsequently, a 3D printer is used to produce a model for the investment casting of the optimal foam.
Metal foams are used, for example, in the design of water pipes that release their energy into the water more efficiently.

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Simulationof a flowed water pipe, filled with a metal foam
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Simulation of a liquid foam and process chain to solid metallic foams

InSeL

The InSeL research project  (innovative foam structures for an efficient lightweight design) is a research initiative in Baden-Wuerttemberg, concerned with research on lightweight design, which consists of an association of different universities, extramural institutions and companies, in which the IAM of the KIT is involved. It includes joint research, but also the communication of research results to companies, as well as the networking of the members of the InSeL project with other research projects.
At the CMS, we participate in the project by performing computer simulations in the field of liquid lather and solid polymer foams, which serve as preforms during the casting of particularly fine-pored and monodisperse metal foams.
The mechanical properties of the metallic lightweight tools, developed in this way, are examined by us, using computer simulations.

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Simulation of flowed granules

PoroSan

Even granules, such as soil materials, are porous media. They are contaminated and should be cleaned using flowing media. Therefore, understanding the flow and mass transfer properties of these media is of great importance. By simulating the flow of spheres, we try to get to the bottom of these phenomena.

Team
Name Function
 
Mitarbeiter
 
Research assistant
Research assistant
1 additional person visible within KIT only.

Publications


2020
Development of synthetic open porous structures for improved heat transfer.
August, A.; Jamshidi, F.; Kneer, A.; Wolf, R. H.; Wirtz, M.; Nestler, B.
2020. International journal of heat and mass transfer, 159, Article No.120071. doi:10.1016/j.ijheatmasstransfer.2020.120071
On counting cells in open pore foams.
August, A.; Nestler, B.
2020. Engineering Research Express, 2 (2), Art. Nr.: 025029. doi:10.1088/2631-8695/ab8c94
About the surface area to volume relations of open cell foams.
August, A.; Nestler, B.
2020. Engineering Research Express, 2 (1), Article No.015021. doi:10.1088/2631-8695/ab6ac6
2019
Modern Times need Enlightened Innovation and Sophisticated Materials.
Kneer, A.; Wirtz, M.; Yurtsever-Kneer, S.; Barbe, S.; August, A.
2019. Galvanotechnik, 2019 (4), 712–719
A bionic approach for heat generation and latent heat storage inspired by the polar bear.
August, A.; Kneer, A.; Reiter, A.; Wirtz, M.; Sarsour, J.; Stegmaier, T.; Barbe, S.; Gresser, G. T.; Nestler, B.
2019. Energy, 168, 1017–1030. doi:10.1016/j.energy.2018.11.143
2018
Effective Thermal Conductivity of Composite Materials Based on Open Cell Foams.
August, A.; Reiter, A.; Kneer, A.; Selzer, M.; Nestler, B.
2018. Heat and Mass Transfer Research Journal, 2 (1), 33–45
Computergestütztes Design gradierter Metallschäume.
August, A.; Kneer, A.; Nestler, B.
2018. Forschung aktuell, 2018 (März), 56–58
Perspectives on material modelling: Porous and particle-based microstructures.
Nestler, B.; August, A.; Selzer, M.; Hötzer, J.; Kellner, M.; Prajapati, N.; Rehn, V.; Seiz, M.
2018. Ceramic applications, 6 (1), 73–77
2017
Magische Schäume.
August, A.; Matz, A. M.; Mocker, B. S.; Heimann, J.; Nestler, B.; Jost, N.; Krug, P.
2017. Horizonte, 49, 3–5
2016
Heat propagation in computer designed and real metal foam structures.
August, A.; Matz, A. M.; Nestler, B.; Jost, N.
2016. Multidiscipline modeling in materials and structures, 12 (4). doi:10.1108/MMMS-03-2016-0012
2015
Simulation der Eigenspannungsentwicklung in metallischen Schäumen.
August, A.
2015. Nachwuchsakademie ’Analyse und Bewertung von Eigenspannungen auf unterschiedlichen Längenskalen’, Kassel, 24.-28.Mai 2010
Modellierung und Simulation der Starrkörperbewegung in Rückschlagventilen.
Jainta, M.; Reiter, A.; August, A.; Moik, F.; Nestler, B.
2015. Forschung aktuell, 2015, 13–15
Sonnenbäder am Nordpol: Das Eisbär-Prinzip für Gebäude.
August, A.; Nestler, B.; Kneer, A.
2015. Horizonte : Forschung an Fachhochschulen in Baden-Württemberg, (45), 68
Prediction of heat conduction in open-cell foams via the diffuse interface representation of the phase-field method.
August, A.; Ettrich, J.; Rölle, M.; Schmid, S.; Berghoff, M.; Selzer, M.; Nestler, B.
2015. International Journal of Heat and Mass Transfer, 84, 800–808. doi:10.1016/j.ijheatmasstransfer.2015.01.052
Phase-field simulations of large-scale microstructures by integrated parallel algorithms.
Hötzer, J.; Jainta, M.; Vondrous, A.; Ettrich, J.; August, A.; Stubenvoll, D.; Reichardt, M.; Selzer, M.; Nestler, B.
2015. High Performance Computing in Science and Engineering ’14 : Transactions of the High Performance Computing Center, Stuttgart (HLRS), 2014. Hrsg.: W. E. Nagel, 629–644, Springer, Cham. doi:10.1007/978-3-319-10810-0_41
2014
Digital representation of complex cellular structures for numerical simulations.
Ettrich, J.; August, A.; Roelle, M.; Nestler, B.
2014. Cellular Materials (CellMAT 2014), Dresden, October 22-24, 2014
Open cell metal foams: Measurement and numerical modelling of fluid flow and heat transfer.
Ettrich, J.; August, A.; Nestler, B.
2014. Cellular Materials (CellMAT 2014), Dresden, October 22-24, 2014
A numerical approach to derive analytical correlations for pressure drop and heat transfer for open cell porosities.
August, A.; Kneer, A.; Janßen-Tapken, K.; Nestler, B.
2014. Cellular Materials (CellMAT 2014), Dresden, October 22-24, 2014
Digital representation of complex cellular structures for numerical simulations.
Ettrich, J.; August, A.; Roelle, M.; Nestler, B.
2014. Cellular Materials (CellMAT 2014), Dresden, 22.-24. Oktober 2014, CD-ROM
Open cell metal foams: Measurement and numerical modelling of fluid flow and heat transfer.
Ettrich, J.; August, A.; Nestler, B.
2014. Cellular Materials (CellMAT 2014), Dresden, 22.-24. Oktober 2014, CD-ROM
Metallische Schneeflocken.
Wesner, E.; August, A.; Nestler, B.
2014. Horizonte : Forschung an Fachhochschulen in Baden-Württemberg, (43), 29–31
Modelling of transient heat conduction with diffuse interface methods.
Ettrich, J.; Choudhury, A.; Tschukin, O.; Schoof, E.; August, A.; Nestler, B.
2014. Modelling and simulation in materials science and engineering, 22 (8), Art.Nr. 085006/1–29. doi:10.1088/0965-0393/22/8/085006
2013
Advanced coupled simulation methods for heat transfer and stiffnessphenomena induced by fluid flow in metal foams.
Kneer, A.; Janssen-Tapken, K.; Reimann, K.; August, A.; Nestler, B.
2013. 5th International Conference on Computational Methods for Coupled Problems in Sciennce and Engineering, Santa Eulalia, Ibiza, E, June 17-19, 2013
Development and numerical investigation of metal foam based modular latent heat storage cell.
Kneer, A.; August, A.; Nestler, B.; Martens, E.
2013. 2nd International Conference on Materials for Energy (EnMat 2013), Karlsruhe, 12.-16. Mai 2013
Thermal conductivity of air filled open cell aluminum foams.
August, A.; Nestler, B.; Rölle, M.; Schmid, S.; Ettrich, J.
2013. 2nd International Conference on Materials for Energy (EnMat 2013), Karlsruhe, 12.-16. Mai 2013
2012
Eisbärbauten - Simulation der physikalischen Eigenschaften von textilen Wärmedämmstoffen.
Römmelt, M.; August, A.; Kneer, A.; Stegmaier, T.; Nestler, B.
2012. Forschung aktuell, 2012, 21–24
Metallische Schäume: Aktuelle Projekte am KIT-ZBS.
August, A.
2012. Nachwuchsakademie ’Analyse und Bewertung von Eigenspannungen auf unterschiedlichen Längenskalen’, Kassel, 23.-24.April 2012
Thermal conductivity of air filled open cell aluminum foams.
August, A.; Nestler, B.; Rölle, M.; Schmid, S.; Ettrich, J.
2012. Biannual Internat.Conf.on Materials Science Engineering (MSE 2012), Darmstadt, September 25-27, 2012
Computational analysis of bio inspired thermal absorber systems made of textile fabrics.
Schoof, E.; Römmelt, M.; Selzer, M.; August, A.; Nestler, B.; Kneer, A.; Stegmaier, T.
2012. International School and Conference on Biological Materials Science, Potsdam, March 20-23, 2012
A phase-field study of large-scale dendrite fragmentation in Al-Cu.
Wesner, E.; Choudhury, A.; August, A.; Berghoff, M.; Nestler, B.
2012. Journal of crystal growth, 359 (1), 107–121. doi:10.1016/j.jcrysgro.2012.08.036
Metallic foam structures, dendrites and implementation optimizations for phase-field modeling.
Vondrous, A.; Nestler, B.; August, A.; Wesner, E.; Choudhury, A.; Hötzer, J.
2012. High performance computing in science and engineering ’ 11 : transactions of the High Performance Computing Center, Stuttgart (HLRS) 2011. Ed.: W.E. Nagel, 595–606, Springer, Berlin. doi:10.1007/978-3-642-23869-7_43
Comparison of phase-field and cellular automaton models for dendritic solidification in Al-Cu alloy.
Choudhury, A.; Reuther, K.; Wesner, E.; August, A.; Nestler, B.; Rettenmayr, M.
2012. Computational materials science, 55, 263–268. doi:10.1016/j.commatsci.2011.12.019
2011
Metallic foam structures, dendrites and implementation optimizations for phase-field modeling.
Vondrous, A.; Nestler, B.; August, A.; Wesner, E.; Choudhury, A.; Hötzer, J.
2011. High Performance Computing in Science and Engineering, Stuttgart, October 4-5, 2011
Simulation of heat propagation in open cell metal foams.
August, A.
2011. Euromat 2011 : European Congress and Exhibition on Advanced Materials and Processes, Montpellier, F, September 12-15, 2011
Phase field simulations of heat propagation in open cell metal foam.
August, A.
2011. Materials Research Society Spring Meeting, San Francisco, Calif., April 25-29, 2011
Phase-field study of the fragmentation secondary arm in Al-Cu alloys.
Wesner, E.; Choudhury, A.; August, A.; Berghoff, M.; Nestler, B.
2011. Euromat 2011 : European Congress and Exhibition on Advanced Materials and Processes, Montpellier, F, September 12-15, 2011
Generierung offenporiger metallischer Schaumstrukturen zur Simulation der Wärmeübertragungseigenschaften.
Rölle, M.; August, A.; Selzer, M.; Nestler, B.
2011. Forschung aktuell, 2011, 21–23
Analysis of thermal evolution in textile fabrics using advanced microstructure simulation techniques.
Römmelt, M.; August, A.; Nestler, B.; Kneer, A.
2011. 5th Internat.Conf.on Textile Composites and Inflatable Structures (Structural Membranes 2011), Barcelona, E, October 5-7, 2011
Analysis of thermal evolution in textile fabrics using advanced microstructure simulation techniques.
Römmelt, M.; August, A.; Nestler, B.; Kneer, A.
2011. 5th Internat.Conf.on Textile Composites and Inflatable Structures (Structural Membranes 2011), Barcelona, E, October 5-7, 2011. Ed.: E. Onate, 614–626
Offenporige metallische Schäume.
August, A.; Nestler, B.; Kneer, A.; Wendler, F.; Rölle, M.; Selzer, M.
2011. Werkstoffe in der Fertigung, 2011 (6), 45–46
2010
Efficiency Study of Metal Foams for Heat Storage and Heat Exchange.
August, A.; Nestler, B.; Wendler, F.; Selzer, M.; Kneer, A.; Martens, E.
2010. CELLMAT 2010 : Proceedings of the International Conference on Cellular Materials, Dresden, Germany, October 27 - 29, 2010. Ed.: G. Stephan, 148–151, Fraunhofer Institute for Manufacturing Technology and Advanced Materials, Dresden
Efficiency study of metal foams for heat storage and heat exchange.
August, A.; Nestler, B.; Wendler, F.; Selzer, M.; Kneer, A.; Martens, E.
2010. Gumbsch, P. [Hrsg.] Proc.of the 5th Internat.Conf.on Multiscale Materials Modeling (MMM 2010), Freiburg, October 4-8, 2010 Stuttgart : Fraunhofer Verl., 2010, 355–358
Efficiency study of metal foams for heat storage and heat exchange.
August, A.
2010. International Conference on Cellular Materials (CellMat 2010), Dresden, October 27-29, 2010
Eigenspannungsentwicklung in metallischen Schäumen.
August, A.
2010. Nachwuchsakademie ’Analyse und Bewertung von Eigenspannungen auf unterschiedlichen Längenskalen’, Kassel, 15.Oktober 2010
Efficiency study of metal foams for heat storage and heat exchange.
August, A.; Nestler, B.; Wendler, F.; Selzer, M.; Kneer, A.; Martens, E.
2010. 5th Internat.Conf.on Multiscale Materials Modeling (MMM 2010), Freiburg, October 4-8, 2010
2007
Über die Dehn-Funktion von S-arithmetischen Gruppen. PhD dissertation.
August, A.
2007. Universität Karlsruhe, Karlsruhe. doi:10.5445/IR/1000007160