Environmental Engineering Reference
In-Depth Information
Due to lack of data, the devaluation enthalpy
d
n
,C
6
H
12
O
6
≡
d
n
,
SU
=
2, 529, 590 kJ/
(kmol of sugar) is assumed as for the
-D-galactose, predicting that the devaluation
enthalpy of the real substance generated in the leaf differs insignificantly. Such an
assumption can be supported by the fact that the devaluation enthalpies tabulated
for the substances of the same chemical formula (
α
α
-D-galactose and L-sorbose), differ
insignificantly.
The physical
b
ph
and chemical
b
ch
exergy, are taken into account to calculate the
total exergy
b
b
ph
of any substance. The exergy of each gas (CO
2
,H
2
O and
O
2
) is zero because in the considered case their states are in full equilibrium with
environment.
The exergy of liquid water
b
w
, kJ/kmol, is the sum of the physical part
b
w
,
ph
and chemical part
b
w
,
ch
, where
b
w
,
ch
=
b
ch
+
=
·
·
ln(1/
ϕ
0
). Using the Szargut and Petela
(1965b) diagrams the interpolation formula for calculation of the physical exergy
b
w
,
ph
of liquid water is
b
w
,
ph
R
T
0
=
a
+
b
·
t
+
c
·
t
2
, where
a
=−
23
.
22
+
2
.
718
·
t
0
+
0
.
0675
·
t
0
,
t
0
, and
c
10
−
3
10
−
4
b
=
2
.
689
−
0
.
5787
·
t
0
+
0
.
00767
·
=
0
.
117
−
1
.
05
·
·
t
0
+
2
.
7
·
·
t
0
−
10
−
6
t
0
273.
The exergy of the generated biomass is the sum of the exergy of the components
(liquid water and sugar). The specific chemical exergy of sugar is determined based on
the standard tabulated value
b
n
,
SU
=
7
.
5
·
·
and where
t
0
=
T
0
−
2, 942, 570 kJ/kmol, to which the correction on
the difference of temperatures
T
n
and
T
0
is added according to formula (2.2.20). The
specific physical exergy
b
ph
,
SU
is determined from formula (2.2.21).
The radiation arriving at the leaf surface from the Sun is recognized as non-
polarized and uniformly propagating within the solid angle under which the Sun is
seen from the Earth. The radiosity
j
S
of such solar radiation of the real spectrum as
function of wavelength
λ
is:
⎛
⎞
⎝
⎠
j
S
=
2
cos
β
sin
β dβ dϕ
i
0,
λ
dλ
(2.4.97)
β
ϕ
λ
The double integral in the bracket of equation (2.4.97) was calculated in Example
2.4.1.1; formula (2.4.1), and if the single integral in equation (2.4.97) is presented in
a numerical form, then:
10
−
5
π
n
j
S
=
4
.
329
·
(
i
0,
λ
λ
)
n
(2.4.98)
where
i
0,
λ
is the measured monochromatic intensity of radiation depending on the
wave length
λ
, and
n
is the successive number of the wavelength interval within the
considered wavelength range. For the 0 to
1
.
3679 kW/m
2
,
as shown in Example 2.4.1.2. For the PAR arriving only within the wavelengths
range (400-700 nm) the radiosity of the PAR calculated from equation (2.4.98), is
j
V
=
∞
wavelength range
j
S
=
0
.
5446 kW/m
2
.
The energy emission of the leaf surface propagates in all directions of hemisphere
and it is assumed that the radiation of the environment arrives at the leaf surface
from all directions of the hemisphere. Therefore, the energy
e
L
exchanged between
the leaf and the environment is:
e
L
=
(
T
4
T
0
), where
α
L
,
a
is the average
α
L
,
a
·
σ
·
−
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