where M is a mass of material, kg; C is sensible heat of material, kJ/kg·K; Δt is
temperature difference, K.
Adsorption value A, kg/kg is used when adsorption heat and heat input for
desorption
des
Q
and adsorbed water warming
h
w
s
Q
.
.
calculated:
w
ads
A
h
H
1000
=
(6)
des
ads
des
H
Ì
Q
=
(7)
)
(
.
.
.
env
reg
w
ads
h
w
s
t
t
C
A
M
Q
−
=
(8)
where h = 60 is heat adsorption of water vapor, kJ/mol; μ
w
is molar mass of water,
g/mole; ΔH
des
= 2850 kJ/kg is heat of desorption, M
ads
is mass of adsorbent, kg, C
w
is
specific heat of water, kJ/kg·K, t
reg
and t
env
. are temperatures of regeneration and
environment, ºC.
Adsorption value is computed by formula:
air
ads
V
M
C
C
A
−
=
0
(8)
where V
air
is air volume: V
air
= F
hs
·w·τ, m
3
; F
hs
is cross-section area of heat storage
device, m
2
, w is air-vapor flow rate, m/s, τ is sorption time, s, C
0
and С are inlet and
outlet concentration of air-vapor flow, kg/m
3
[9]:
1
]]
)
(
[
0
max
0
+
=
+
−
w
H
A
C
w
e
C
C
, (9)
where Н is height of adsorbent layer, m, A
max
is adsorption capacity of adsorbent,
kg/kg; β is mass transfer coefficient, s
-1
:
.
.
p
y
1
1
1
1
s
c
+
+
=
(10)
where β
y
, β
p
and β
c.s.
are mass transfer coefficients for gas phase, pores and
coplanar stirring, s
-1
[10]. According to results of calculations adsorption rate is limited
with rate of diffusion in pores, that being confirmed by kinetic study of water vapor
sorption [7, 11].
The calculation was carried out using the algorithm proposed.
As a result of simulation, the dependence of the adsorption value on the velocity
of the steam-air flow at a temperature of 45˚C with a relative humidity from 30 to 60%
was determined when composite adsorbent ‘silica gel – sodium sulphate’ used (Fig. 3).
Increasing of the vapor-air-flow rate and relative humidity is accompanied by raising
of the efficiency coefficient of heat energy storage device of closed-type η. The value
η is observed to be negligibly changed as vapor-air-flow temperature increased.
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