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Thermal permeability

The static thermal permeability is the low frequency limit of the dynamic thermal permeability. The thermal permeability problem is the thermal analogy of the viscous permeability problem.  When the frame of a porous medium has a sufficient thermal capacity for the compressibility to reach its isothermal value at low frequencies, the excess acoustical temperature can be considered to vanish at the pore walls (this replaces the no-slip condition for viscous flow) and a static « thermal permeability » exists [1].

Equipment: FOAM-X software with impedance tube or transmission tube
Standard: ASTM E1050-08, ISO 10534-2:1998, ASTM E2611-09
Method: Indirect acoustical method [2]
Property: ko′ – static thermal permeability (m²)

[1] D. Lafarge, P. Lemarinier, J.-F. Allard, and V. Tarnow, “Dynamic compressibility of air in porous structures at audible frequencies,” J. Acoust. Soc. Am. 102(4), 1994-2006 (1997).
[2] X. Olny and R. Panneton (2007), “Acoustical determination of the parameters governing thermal dissipation in porous media,” J. Acoust. Soc. Am. 123, 814-824 (2008).