Abstract
A mathematical formulation of heat, mass and momentum transfers’ phenomena during drying of saturated deformable porous media was developed. The effect of the fluid pressure gradient on the fluid transfer is described by using the Darcy law. An elastic comportment has been used to close the mechanical problem. The model is solved numerically by using finite elements method based on Arbitrary Lagrangian–Eulerian description. The evolutions of moisture content, liquid pressure and stresses within a clay sample were discussed. A large tensional stress, which could induce a crack, was observed at the product surface exposed to the drying air.
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Abbreviations
- ρi :
-
Averaged density (kg m−3)
- ρi :
-
Intrinsic averaged density (kg m−3)
- Cp:
-
Heat capacity (J kg−1 K−1)
- g:
-
Gravity acceleration (m s−2)
- k:
-
Permeability (m2)
- Km:
-
Mass transfer coefficient (m s−1)
- Mv :
-
Molar weight of water vapor (kg mol−1)
- p:
-
Water pressure (Pa)
- Pv,sat :
-
Water vapor pressure (Pa)
- R:
-
Universal gas constant (Pa m3 K−1)
- RH:
-
Relative humidity of air (kg kg−1)
- T:
-
Temperature (K)
- u:
-
Displacement vector of the solid (m)
- v:
-
Averaged velocity (m s−1)
- vls :
-
Liquid velocity relative to the solid
- w:
-
Moisture (kg kg−1 dry basis)
- βT :
-
Coefficient of thermal expansion (−)
- βw :
-
Coefficient of humid expansion (−)
- Φ:
-
Porosity (−)
- ε:
-
Strain tensor (−)
- η:
-
Dynamic viscosity (kg m−1 s−1)
- κ:
-
Thermal conductivity (W m−1 K−1)
- μ and λ:
-
Coefficients of Lamé (Pa)
- ν:
-
Volume (m3)
- σ :
-
Stress tensor (Pa)
- t:
-
Time (s)
- KT:
-
Convective heat transfer coefficient (W m2 K−1)
- q:
-
Heat flux (W)
- \( \dot{m} \) :
-
Rate of moisture vaporization (kg m−2 s−1)
- aw:
-
Water activity (−)
- \( \Uplambda_{v} \) :
-
Heat of vaporization (J kg−1)
- s:
-
Solid
- l:
-
Liquid
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Mihoubi, D., Bellagi, A. Modeling of heat and moisture transfers with stress–strain formation during convective air drying of deformable media. Heat Mass Transfer 48, 1697–1705 (2012). https://doi.org/10.1007/s00231-012-1014-x
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DOI: https://doi.org/10.1007/s00231-012-1014-x