Damp material conductivity
Damp material conductivity
(OP)
Before a material dries out I need to estimate the thermal conductivity. The conductivity of water is less than the conductivity of the materal itself when dry, but I have the feeling that the nett effect of the material being damp is to increase the thermal condcutivity. Would this be correct and is there any evidence for that? Can the overall conductivity of the damp material be estimated by the volume of water it contains?
corus





RE: Damp material conductivity
The beginnings of your answer can be found in the following empirical formula :
k_wet = k_dry + w * k_wet
where,
w (kg/m3): water content
k_wet (W.m2/kg/K): proportional factor
Some values are given below :
k_wet w
expanded polystyrene 0.00013 < 2
extruded polystyrene 0.00010 < 2
fiber of cellulose 0.0005 3
light Concrete : k_wet w
300 kg/m3 0.0009 7
600 kg/m3 0.0009 < 14
And there is the notion of apparent effective conductivity k_ap_wet :
k_ap_wet = k_wet + rho*L*D_T_v
where,
L (J/kg): Latent heat of vaporization
rho (kg/m3): density of water
D_T_v (m2/s/K): no isothermal specific diffusivity in vapor state due to the temperature T
Bibliography :
LANGLAIS (C.), SILBERSTEIN (A.), SANDBERG (P.I.).
Effects of moisture on the thermal performance of insulating materials,
in Moisture Control in Building. H.R. TRESCHEL, Editor,
ASTM Manual Series MNL 18.
ASTM Publication code Number (PCN) 28-078094-10 (1994).
Regards,
Torpen
RE: Damp material conductivity
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Damp material conductivity
corus