MASS BALANCE: WHY MASS FLOWS?

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MASS BALANCE WHY MASS FLOWS?
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MASS BALANCE EQ.CON. ALTERATION
Mass transport represents a possible way the
system has to get new equilibrium conditions
once the original ones have been altered.
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MASS FLOW (Kg/s) VSCi V velocity (m/s) S
cross section (m2) Ci i concentration (Kg/m3)
S
V
Ci
MASS FLUX (Kg/sm2) VCi V velocity (m/s) Ci
i concentration (Kg/m3)
S 1 m2
V
Ci
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Mass transport represents a possible way the
system has to get new equilibrium conditions
once the original ones have been altered.
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FICK LAW
MASS FLOW (Kg/s) -SDDCi/DX S cross section
(m2) D diffusion coefficient (m2/s) Ci i
concentration (Kg/m3) DCi/DX gradient
concentration (Kg/m2s)
DCi/DX (CiXDX-CiX)/DX
MASS FLUX (Kg/sm2) -DDCi/DX
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MASS BALANCE
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MASS BALANCE EXPRESSION
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DIVIDING FOR DV
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FLUXES EXPRESSIONS
Diffusion
Diffusion
Diffusion
Convection
Convection
Convection
Bi mobility of the diffusing components
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Remembering that
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MASS BALANCE CYLINDRICAL COORDINATES
TWO DIMENSIONS
r
z
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Remembering the derivative definition