2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 165 -
The result showed that a moisture ratio decreased with
time and increased with drying temperature. The
experimental data of the moisture ratio were fitted to
models there are shown in Fig. 5 and 6 for drying with air
impingement and infrared radiation of 1000 W,
respectively.
Fig. 5. Comparison of the experimental and
predicted moisture
ratio for air impingement dryer at drying temperatures of
60-100
q
C and constant air velocity of 7.3±0.2 m/s.
Fig. 6. Comparison of the experimental and
predicted moisture
ratio for infrared radiation of 1000 W at drying temperatures of
60-100
q
C.
F. The effective diffusion coefficient
From thin layer drying experiments, the effective
diffusion coefficient can be calculated employing
theoretical drying equation. The effective diffusion
coefficient value of GABA Sungyod rice which drying
with impingment dryer and infrared radiation 1000 W
showed that the effective diffusion coefficient depend on
the drying temperature are shown in Fig. 7. The diffusion
coefficient of GABA Sungyod rice increased from
1.369×10
-9
to 3.612×10
-9
and 1.273×10
-9
to 2.065×10
-9
m
2
/s for air impingement and infrared radiation of 1000
W, respectively, with increasing temperature from 60 to
100
q
C. The effective diffusion coefficient value when
using air impingement was slightly higher than infrared
radiation 1000 W.
Fig. 7. Comparison of the experimental and predicted diffusion
coefficient of air impingement and infrared radiation
of 1000 W.
The effective diffusion coefficient equations of air
impingement and infrared radiation of 1000 W are shown
in equations 12 and 13 as follows:
Impingment (IP)
D
eff
= 4.608×10
-5
exp(-3516.698/T) (12)
R
2
= 0.995 RMSE = 6.530×10
-11
Infrared Radiation (IR)
D
eff
= 1.177×10
-7
exp(-1502.288/T) (13)
R
2
= 0.992
RMSE = 2.998×10
-11
V. C
ONCLUSION
The result showed that equilibrium moisture content
decreased with temperature and increased with water
activity. The best fitted model representing equilibrium
moisture content of GABA Sungyod rice was the
Modified Oswin model. The apparent density increased
but the porosity and specific heat of GABA Sungyod rice
decreased linearly as the moisture content increased. The
moisture ratio decreased with time and increased with
drying temperature. The empirical thin-layer drying
equation using Page’s and Midlili’s model were the best
fitting model to describe the moisture ratio with drying
time of GABA Sungyod rice for drying with air
impingement dryer and infrared radiation of 1000 W,
respectively. The effective diffusion coefficient of the
materials depends on the drying temperature.
A
CKNOWLEDGMENT
The authors would like to thank the Department of
Chemical Engineering, in providing financial grant under
the program Discipline of Excellence in Chemical
Engineering (DOE), Faculty of Engineering, Department
of Physics, Faculty of Science and graduate school of
Prince of Songkla University for financial support.
0.0
0.2
0.4
0.6
0.8
1.0
0
10
20
30
Experiment 62.7
°
C
Experiment 80.7
°
C
Experiment 98.5
°
C
Page's model
Drying Time (min)
Moisture Ratio
0.0
0.2
0.4
0.6
0.8
1.0
0
20
40
60
Moisture ratio
Drying time (min)
Experiment 60.2
°
C
Experiment 79.8
°
C
Experiment 99.2
°
C
Midilli's model
0
1
2
3
4
50 60 70 80 90 100 110 120
Experimental,IP
Experimental,IR
Predict model
Diffusion coefficient
(D
eff
×
10
-9
m
2
/s)
Drying Temperature (
q
C)
