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SECUENCIA DE CÁLCULOS.
Cantidad de agua evaporada.
W i=M i
θ0(60)
W i=9.850kg19.04min
(60 )=31.04kggravah
W s=M s
θ0(60)
W s=9.4 kg19.04min
(60 )=29.6218kggravah
W e=W i−W s
W e= (31.04−29.6218 )kggravah
=1.418kg A
h
Cantidad de aire necesario para el secado.
W 2=W 1=W a=W e
Y 2−Y 1
W 2=W 1=W a=1.418
kg A
h
(0.156−0.014 )kgAkgB
=0.2943kgBh
Nota: Y2 y Y1 obtenidas de grafica 1.
Masa velocidad del aire.
G=W 2
A=
W 2
2πrh
G=0.2943
kgBh
2π (0.126m)(1.877m)=0.1981
kgBh−m2
Tiempo de residencia.
F=W i
A=
W i
2 πrh
F=31.04
kggravah
2π (0.126m )(1.877m)=20.8885
kggravah−m2
β=5(Dp)−0.5
β=5(35,000μm)−0.5=0.0267
θ= 0.23 L
S N0.9D− βLG
F(1.97 )
θ=0.23(1.877m)
(0.085m /m )(1.5 r . p .m .)0.90.32m−
(0.0267 ) (1.877m)(0.1981 kgBh−m2 )
20.8885kggravah−m2
(1.97 )=11.0185min
%=θteo−θexpθ exp
100 = 19.04−11.0185
11.0185100=72.8%
Volumen de gas de secado.
V 2=( 129+Y 218 )( RT 2P )W 2
V 2=( 1
29kgBkmolB
+0.156
kg A
kgB
18kgAkmol A
)((0.08205atm−m3
kmolT−K )(164+273.15)K0.7697atm
) (0.2943 )kgBh
=0.5917 m3
h
Calor suministrado por el gas combustible.
ρg=ρC3 H 8(0.5686 )+ ρC4 H10 (0.4314 )
ρg=(1.83 gL )(0.5686 kmol AkmolT )+(2.52 gL )(0.4314 kmolBkmolT )=2.127 gL
W g=(Lg ) (17 )(60)(ρg )
1000
W g=(0.64 ) (17 )(60)(2.127 gL )
1000
W g=1.3885kggas LPh
P .C .=14,600C+62,000H
P .C .=14,600 (0.8235 )+62,000 (0.1764 )=22,959.9 btulbgas LP
=12,755.6 kcalkggas LP
Q g=(W g ) (P.C . )
Q g=(1.3885 kggas LPh )(12,755.6 kcalkggas LP )=17,711.15 kcalh
Calor absorbido por la grava.
Qs=W sCps (t f−ti )
Qs=(29.6218 kggravah )(0.17 kcalkggrava−°C ) (104−17 ) °C=438.1064 kcal
h
Calor absorbido por el gas de secado.
Qa=W aCpa ( t2−t a )
Qa=(0.2943 kgBh )(0.24 kcalkgB−° C ) (164−24 )° C=9.8884 kcal
h
Calor absorbido por el agua evaporada.
Qw=W e (H v−H a )
Qw=(1.418 kgAh ) (661.73−26.06 ) kcalkg
=901.3801 kcalh
Eficiencia térmica.
nt=Qs+Qa+Qw
Q g
(100 )
nt=(438.1064+9.8884+901.3801 ) kcal
h
17,711.15kcalh
(100 )=7.62%
Eficiencia de secado.
ns=Qw
Qs+Qa+Qw
(100 )
ns=901.3801
kcalh
(438.1064+9.8884+901.3801 ) kcalh
(100 )=66.8%
Costo de secado por kilogramo de producto.
C s=1W a
[ (W g ) (Cg )+(kW ) (C E ) ]
C s=1
0.2943kgproducto seco
h
[(1.3885 kggas LPh )(5.85 $kggas LP )+ (0.38kW )(0.7 $
kW−h )]CS=27.8661
$kg producto seco
ANEXOS
0 20 40 60 80 100
120
140
160
180
200
220
240
260
280
300
00.010.020.030.040.050.060.070.080.090.1
0.110.120.130.140.15
Ys vs. T
Temperatura
Ys
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