Environmental Engineering Reference
In-Depth Information
In this equation,
h
−1
7000 g
W
cv
=
Þ
−1
=25
:
5kW
ð
produced
Þ
275 g
ð
kWh
h
−1
7kg
22 × 10
−5
kmol
s
−1
:
φ
n
,
fuel in
=
kmol
−1
=4
h
−1
×46
3600 s
:
07 kg
Substituting the tabulated values in the term between brackets gives
Q
cv
=25
22 × 10
−5
kmol
s
−1
×
kmol
−1
:
5kW+4
:
−
1, 004, 298 kJ
=
−
16
:
9 kW to be extracted
ð
Þ
:
Example 3.6 Adiabatic, stoichiometric flame temperature for DME
combustion
Dimethyl ether (DME) is considered as an alternative diesel fuel for trucks. Its
chemical formula is CH
3
OCH
3
. Consider an open-flow system in which DME is
combusted at a constant pressure of 1 atm. The inlet temperature of both air and fuel
is 25
C.
The
c
p
value of the generated flue gases is represented by the following
polynomial:
c
p
R
u
=
a
1
+
a
2
T+
a
3
T
2
+
a
4
T
3
+
a
5
T
4
K)
−1
R
u
= 8.3143 kJ
(kmol
The coefficients of the polynomial are given in the table below (Kee et al., 1991).
a
2
10
3
a
3
10
6
a
4
10
10
a
5
10
14
Compound
a
1
CO
2
4.453623
3.140168
−1.2784105
2.393996
−1.6690333
H
2
O
2.672145
3.056293
−0.873026
1.2009964
−0.6391618
N
2
2.926640
1.4879768
−0.568476
1.0097038
−0.6753351
The mole-specific enthalpies are given in the following table.
h
f
kmol
−1
)
(kJ
Compound
CH
3
OCH
3
−184,100
CO
2
−393,546
H
2
O (g)
−241,845
Calculate the final combustion temperature when the fuel is just completely
combusted with no oxygen excess under adiabatic conditions.
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