PPT - Mass Transfer Theories | Mass Transfer - Chemical Engineering PDF Download

 Page 1


¢ Turbulent flow is desired in most mass-
transfer operations:
1. to increase the rate of transfer per unit
area
2. to help disperse one fluid in another
3. to create more interfacial area
¢ Mass transfer to a fluid interface is often
unsteady-state type.
Mass Transfer Theories
Page 2


¢ Turbulent flow is desired in most mass-
transfer operations:
1. to increase the rate of transfer per unit
area
2. to help disperse one fluid in another
3. to create more interfacial area
¢ Mass transfer to a fluid interface is often
unsteady-state type.
Mass Transfer Theories
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢ Is defined as rate of mass transfer per unit area per
unit conc. difference.
¢k
c
is molar flux divided by conc. difference
¢k
c
has a unit of velocity in cm/s, m/s
¢ Concentration, c in moles/volume
Page 3


¢ Turbulent flow is desired in most mass-
transfer operations:
1. to increase the rate of transfer per unit
area
2. to help disperse one fluid in another
3. to create more interfacial area
¢ Mass transfer to a fluid interface is often
unsteady-state type.
Mass Transfer Theories
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢ Is defined as rate of mass transfer per unit area per
unit conc. difference.
¢k
c
is molar flux divided by conc. difference
¢k
c
has a unit of velocity in cm/s, m/s
¢ Concentration, c in moles/volume
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢k
y
in mol/area.time (mol/m
2
.s)
¢y or x are mole fractions in the vapor or liquid phase.
Page 4


¢ Turbulent flow is desired in most mass-
transfer operations:
1. to increase the rate of transfer per unit
area
2. to help disperse one fluid in another
3. to create more interfacial area
¢ Mass transfer to a fluid interface is often
unsteady-state type.
Mass Transfer Theories
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢ Is defined as rate of mass transfer per unit area per
unit conc. difference.
¢k
c
is molar flux divided by conc. difference
¢k
c
has a unit of velocity in cm/s, m/s
¢ Concentration, c in moles/volume
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢k
y
in mol/area.time (mol/m
2
.s)
¢y or x are mole fractions in the vapor or liquid phase.
Gas phase coefficient, k
g
Page 5


¢ Turbulent flow is desired in most mass-
transfer operations:
1. to increase the rate of transfer per unit
area
2. to help disperse one fluid in another
3. to create more interfacial area
¢ Mass transfer to a fluid interface is often
unsteady-state type.
Mass Transfer Theories
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢ Is defined as rate of mass transfer per unit area per
unit conc. difference.
¢k
c
is molar flux divided by conc. difference
¢k
c
has a unit of velocity in cm/s, m/s
¢ Concentration, c in moles/volume
MASSTRANSFERTHEORIES
Mass transfer coefficient, k
¢k
y
in mol/area.time (mol/m
2
.s)
¢y or x are mole fractions in the vapor or liquid phase.
Gas phase coefficient, k
g
MASS TRANSFER THEORIES MASS TRANSFER THEORIES
There are three types of theories in mass transfer
coefficients.
1) Film theories
2) Penetration theories
3) Surface –renewal theories