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2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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Fig. 4. Influence of temperature on equilibrium moisture content (EMC)
of skim rubber at temperatures of 45-60°C and relative humidity of 10-
90%.
B. Verification of mathematical model
The experiment and simulated results of skim rubber
drying are shown in Table II and Fig. 5. The experiment
and simulated drying condition are fraction of air
recycled of 90 %, specific mass flow rate of 0.07 kg of
dry air/s-kg of dry rubber. The other conditions are also
shown in Table II. Specific energy consumption and
average drying rate are used for verification of the
mathematical model. Fig. 5 shown the experiment and
simulated moisture content, it is seemed that the
simulated moisture content is nearly the same as that
from experiment. Specific energy consumption of skim
rubber drying was shown in Table II. It can be observed
that the simulated results agree with the experiment. The
simulated results of specific energy consumption are
nearly the same as that from the experiment results. The
difference is less than 10%.
TABLE I
DIFFERECT MODEL FOR THE DETERMINATION OF THE SORPTION ISOTHERM OF SKIM RUBBER (ASABE Standards, 2007).
Model name Type R2 RMSE SEE
Modified Henderson ‡“ ൌ ሾെŽሺͳ െ ሻȀͳǤͶͶͺͲሺ െ ʹͺʹǤͲͻͳͳሻሿͳȀͲǤͺͶͺ͹ 0.969 0.0013 0.0079
Modified Halsey ‡“ ൌ ሾെŽሺ ሻȀ‡š’ሺെʹǤͷʹͺ͵ ൅ ͲǤͲͳͻͷሻሿͳǤʹ͹͸͵ 0.968 0.0013 0.0080
Modified Owsin ‡“ ൌ ሺͲǤͲ͸ʹͳ ൅ ͲǤͲͲͲʹ ሻሾሺ Ȁሺͳ െ ሻሿͲǤ͸͹͸ͺ 0.977 0.0011 0.0074
Iglesias and Chirife ‡“ ൌ ͲǤͲͲͳʹ ൅ ͲǤͲͲ͵͵ሾሺ Ȁሺͳ െ ሻሿ 0.881 0.0025 0.0091
where Meq is the equilibrium moisture content (% dry-basis), RH is the relative humidity and T is absolute temperature (K)
TABLE II
EXPERIMENT AND SIMULATED RESULTS OF SKIM RUBBER DRYING
Exp. No.
Drying
temperature
(°C)
T1/T2
Initial moisture
content
(%dry-basis)
Final moisture
content
(%dry-basis)
Drying time
(min)
t1/t2
Experiment Simulation
TDT SEC DR TDT SEC DR
1 110/105 47.5 0.50 110/110 220 25.84 0.033 215 23.37 0.034
2 130/110 49.1 0.43 40/140 180 19.90 0.042 185 18.97 0.041
3 130/110 49.1 0.69 40/120 160 15.73 0.047 160 14.88 0.047
4 130/105 50.6 0.67 40/140 180 18.48 0.043 185 20.10 0.042
5 130/110 48.7 0.78 50/90 140 13.55 0.053 145 11.93 0.051
6 100/100 50.1 0.56 240/-- 240 29.26 0.034 245 29.88 0.033
7 110/105 49.8 0.51 80/130 210 24.75 0.039 215 25.13 0.038
8 110/110 48.0 0.54 190/-- 190 25.42 0.042 200 26.23 0.040
9 120/120 49.6 0.53 185/-- 185 23.88 0.044 190 23.13 0.043
10 110/100 50.1 0.52 40/185 225 27.27 0.037 235 27.47 0.035
where TDT is the total drying time (min), SEC is the specific energy consumption (MJ/kg water evaporated) and DR is the drying rate
C. Prediction of the drying using the mathematical
model
As a result of inconclusive trial guidelines for proper
drying as well as. Therefore, the models mentioned above
to predict more drying. The simulated drying conditions
are specific mass flow rate varying from 0.03 to 0.13 kg
of dry air/s-kg of dry rubber, RC of 0-99%, initial skim
rubber weight of 16.74 kg, ambient temperature of 30 qC
, initial and final moisture content of 48 and 0.5% dry-
basis, respectively. The simulated were undertaken at 3
different strategies as follows;
x Strategy I, the skim rubber was dried at constant
temperature ranging from 100– 130°C and the air
flow was passed through the skim rubber from the
top to the bottom (one direction).
x Strategy II, the drying was carried out over 2 stages;
stage 1 the rubber was dried at 100-130°C with 40
min drying time; and followed by stage 2 dried at
0
1
2
3
4
0 20 40 60 80 100 Equilibrium moisture content
(%dry-basis)
Relative humidity (%)
40 °C
45 °C
50 °C
55 °C
60 °C
Modified Oswin model