Biomedical Engineering Reference
In-Depth Information
G
total
total Gibbs free energy (kJ)
acceleration due to gravity, 9.81 (m/s
2
)
g
Δ
H
k
heat of reaction of kth reaction at char surface (kJ/mol)
Δ
H
enthalpy change (kJ)
h
i
;
h
f
heat of formation at reference state (kJ/mol)
gas-wall convective heat transfer coefficient (kW/m
2
K)
h
conv
mass-transfer coefficient (kg carbon/m
2
bar
2
s)
h
m
first-order reaction rate constant (s
2
1
)
k
preexponential factor (s
2
1
)
k
0
rate constant for the liquid yield of pyrolysis (s
2
1
)
k
liq
k
BE
bubble
emulsion mass exchange coefficient (m/s)
rate constant for the char yield of pyrolysis (s
2
1
)
k
c
rate constant for the gas yield of pyrolysis (s
2
1
)
k
g
rate constant of three primary pyrolysis reactions taken together (s
2
1
)
k
1
K
number of element in
Eq. (7.77)
(7.72)
(bar
2
1
s
2
1
)
K
e1
,
k
e2
,
k
e3
rate constants in
Eq. (7.70)
surface reaction rate constant for kth reaction, mol/m
2
bar
n
K
s
k
K
e
,
K
equilibrium
equilibrium constant (
)
l
number of gaseous reactants (
)
L
r
length of the reactor (m)
L
Lagrangian function (
)
m
b
mass of the biomass in the primary pyrolysis process (kg)
m
0
initial mass of the biomass (kg)
m
c
mass of the biomass remaining after complete conversion (kg)
m
reaction order with respect to carbon conversion in
Eq. (7.42)
(
)
m, n, p, q
stoichiometric coefficients in
Eqs. (7.27)
(7.29)
n
reaction order with respect to the gas partial pressure,
Eq. (7.44)
(
)
N
number of species present (
)
N
c
number of char particles in unit gas volume (
)
N
or
number of orifices in a bed of area (A
r
)
P
g
partial pressure of gasifying agent outside the char particle (bar)
P
i
partial pressure of the species i (bar)
P
total pressure of the species (bar)
char gasification rate (kg Carbon/m
2
s)
Q
Q
gasification
,
Q
conv
,
Q
rad
, and
Q
mass
energy transfer due to gasification, convection, radiation, and mass trans-
fer, respectively (kW/m
3
of bed)
gas constant (8.314 J/mol K or 8.314
3
10
2
5
m
3
bar/mol K)
R
chemical kinetic reaction rate (kg carbon/m
2
bar
2
s)
R
c
rate of production or consumption of gas species j (kg/m
3
s)
R
m
,j
reaction rate of the ith reaction (s
2
1
)
r
i
r
c
char particle radius (m)
T
temperature (K)
T
s
surface temperature of char particles (K)
T
g
gas temperature (K)
T
w
wall temperature (K)
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