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Effective thermal conductivity of metal foams


V. Skibina1, R. Wulf1, J. Meinert2 and U. Gross1

1TU Bergakademie Freiberg, Institute of Thermal Engineering, Germany
2Fraunhofer IFAM, Dresden, Germany

Keywords: metal foam
property: effective thermal conductivity
material: alloy, steel

Metal forms are widely used in different branches of industry, due to their specific properties like low density, energy and heat absorption, sound absorption, vibration damping and biocompatibility. Metal foams with closed porosity used in many cases of structural application. They will be used in machine construction, apparatus engineering, vehicle construction, railway construction and shipbuilding, in space hardware, building, for sporting equipment and for medical biological areas. On the other hand, the metal foams with open porosity are used in heat exchangers and heat storage devices, in refrigerating systems, for filtering and separation, as internal design in catalyst, for storage and transport of liquids, for control of liquids flow, for sound absorption, for electrode of electrical accumulator, for flame damper and for electrochemical applications.

Knowledge about heat transfer in metal foams plays an important role. It is basically determined by thermal conductivity and distribution of the two phases (solid material and gas). The effective thermal conductivity depends on porosity, structure of foams and physical properties of the phases. It is rather complicated to develop a method for effective thermal conductivity predictions from the base material properties alone. This is due to the complex structure of metal foams and big differences between thermal conductivity of gas and solid material [1].

In this paper transient hot disk (transient plane source) measurements will be presented for two kinds of metal foams, one with closed and one with open porosity. These measurements have been done at room temperature, and the results will be compared with selected data from own steady state measurements (panel test facility) in a wide temperature range. The technology for sample preparation will be among the interesting issues. The open celled metal foams have been produced from FeCrAl by powder metallurgy, the closed cell foams, e.g. hollow sphere samples, are from steel alloys. The presented results include structural characterization, and they are compared with experimental and physical models from the literature.

References
  1. R. Coquard, M. Loretz, D. Baillis, Adv. Engng Mat. 10 (2008) 4, 323-337

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