In most applications, the key characteristics of porous media are pore size and permeability. In the case of Dynapore® diffusion-bonded wire mesh structures and other porous metals, these characteristics are augmented by the properties of the metal alloy, including mechanical strength, corrosion resistance, and/or high-temperature oxidation resistance. However, there is a class of applications for these materials that also depends on thermal properties of Dynapore® materials. These properties may in turn be affected by the surface area, mass, density, and void volume of the diffusion-bonded metal matrix.

By its nature, wire mesh has a fairly high surface area to mass ratio. Depending on the particular weave, a square inch of woven wire cloth may contain several square inches of wire surface area. A stack of many layers of wire mesh sintered together therefore creates a three-dimensional matrix with very high internal surface area.

As an example, consider a sintered stack of 250 layers of 200x200 mesh, plain square weave, .002" wire diameter. After diffusion-bonding, this stack may be processed to a thickness or height of 1". One cubic inch of this material contains approximately 636 square inches of wire surface area!! Its weight will be about .094 pounds, reflecting a volumetric density of about 32.3%. In other words, over 67% of the cubic inch is empty space, with the remaining volume being solid metal. There will be 250 x (200 + 200) = 100,000 individual one inch long wire strands in this cubic inch of material. If each aperture in each layer is counted as a pore, there will be 250 x 200 x 200 = 10,000,000 pores per cubic inch.

In addition, the sintering or diffusion-bonding of the wire mesh matrix bonds all points of contact within the weave, as well as between adjacent layers of a laminate. The fused contact points facilitate thermal transfer throughout the structure, reducing hot-spots and increasing efficiency.

The high surface area and high void volume of these structures, combined with the thermal capacity of metals, creates an engineering opportunity. Dynapore® structures may be remarkably efficient at removing heat from (or imparting heat to) gases that flow through the porous metal matrix. These properties have been used to good advantage in many applications, including:

• Regenerator Elements in Stirling Cycle Engines and Cryo-Coolers
• Sublimation Cooling in Manned Space Missions
• Transpiration Cooling in Rocket Engines
• Heat Pipe and Thermal Wicking Materials

Consult the factory today and find out how Dynapore® can help meet your thermal management needs.