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Open-Pored Aluminum Foam for Vacuum Plates and Heat Exchangers

| Editor: Alexander Stark

The Swiss company Exxentis AG will present the advantages of porous aluminum at Hannover Messe 2019.

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Exxentis offers aluminum foam with different pore sizes.
Exxentis offers aluminum foam with different pore sizes.
( Source: Exxentis )

Porous aluminum is produced by casting with salt. This technology provides a unique structure of porous metal. The structure of porous aluminum and the structure of known sintered metals are complementary. The pores in the sintered metal correspond to those in the porous aluminum and vice versa. Theoretically, the minimum porosity of sintered metals is 26 % and the maximum porosity of porous aluminum is 74 %. In general, 50 - 55 % of porous aluminum consists of pores due to the imperfect stacking of salt particles. In the production of porous aluminum, each salt particle in in contact with other salt particles. The surface tension prevents molten aluminum from reaching the contact point between two salt particles. Therefore, first all salt particles and then all pores are connected with each other. All pores are open, so porous aluminum is permeable over its entire volume and in all directions. The shape and size of the material can be determined by the customer, whereby seven pore sizes are possible. Further advantages include:

  • high strength thanks to cast structure
  • homogeneous distribution of pores throughout the entire volume
  • high thermal conductivity and heat capacity

Components made of porous aluminum
Components made of porous aluminum
( Source: Exxentis )

Porous Aluminum Vacuum Plates

In porous aluminum plates for vacuum tables, pores occupy 50 - 55 % of the surface at any point of the vacuum plate and on any small area. This is achieved due to the small pore size and even distribution of pores on the surface of porous aluminum. These properties of porous aluminum provide maximum clamping force and allow to place the workpiece anywhere and in any position on the vacuum table.

Porous Aluminum Vacuum Plates

Porous aluminum is ideal for use as a heat exchanger. Water or other liquids, air or gas flow through the porous aluminum, which optimally absorbs the temperature on its large inner surface. This temperature can be transferred to a solid body or in the same way to a fluid. Porous aluminum is also excellently suited for cooling purposes. The object to be cooled is attached directly to the porous aluminum and the heat is optimally dissipated to the outside air by the large inner surface, if necessary by ventilation.

The heat exchange capacity of porous aluminum is higher than that of conventionally processed aluminum, as porous aluminum has a very large internal surface area in relation to its volume. However, other porous materials also have large surfaces, e.g. sintered metals. Today, however, it is not yet possible to manufacture products from aluminum with high volume porosity and sufficient strength using sintering technology.

This article was first published by Konstruktionspraxis.

Original: Dorothee Quitter / Translation: Alexander Stark

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