Convective heat transfer within fibrous insulation slabs |
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Authors: | D K Joshi Prof Dr S P Sukhatme |
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Institution: | (1) Department of Mechanical Engineering, Indian Institute of Technology, Powai, Bombay 76, India |
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Abstract: | A numerical study of convective heat flow within a fibrous insulating slab is presented. The material is treated as an anisotropic porous medium and the variation of properties with temperature is taken into account. Good agreement is obtained with available experimental data for the same geometry.
Zusammenfassung Für den konvektiven Wärmestrom in einem faserförmigen Isolierstoff wird eine numerische Berechnung angegeben. Der Stoff wird als anisotropes poröses Medium mit temperaturabhängigen Stoffwerten angesehen. Die Übereinstimmung mit verfügbaren Versuchswerten ist gut. Nomenclature Cp
specific heat of the gas at the mean temperature
- Da
Darcy number=ky/H2
- Gr*
modified Grashof number=gTHky/2= (Grashof number) × (Darcy number)
- H
thickness of the specimen
- P
gas pressure
- Pr*
modified Prandtl number= Cp/x
- Ra*
modified Rayleigh number=Gr* Pr*
- Rp
ratio of permeabilities=ky/kx
- Rk
ratio of conductivities=
y/x
- T
absolute temperature of the gas
- t1
absolute temperature of the hot face
- T2
absolute temperature of the cold face
- Tm
mean temperature of the gas=(T1+T2)/2
- kx
specific permeability of the porous medium along the x-direction
- ky
specific permeability of the porous medium along the y-direction
- p
T/Tm
- q
exponent
- r
exponent
- u
gas velocity along the x-direction
- v
gas velocity along the y-direction
- X*
distance along the x-direction
- y*
distance along the y-direction
- T
temperature difference=t1–T2
-
thermal coefficient of expansion of the gas
-
m
thermal coefficient of expansion of the gas at the mean temperature
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*
T–Tm
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dimensionless temperature=
*/T
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a
apparent thermal conductivity of the porous medium along the x-direction
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al
local apparent thermal conductivity of the porous medium along the x-direction
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x
thermal conductivity of the porous medium along the x-direction in the absence of convection
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y
thermal conductivity of the porous medium along the y-direction in the absence of convection
-
dynamic viscosity of the gas
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m
dynamic viscosity of the gas at the mean temperature
-
kinematic viscosity of the gas
-
m
kinematic viscosity of the gas at the mean temperature
-
density of the gas
-
m
density of the gas at the mean temperature
-
*
stream function at any point
-
dimensionless stream function=
*/(
m/m) |
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Keywords: | |
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