2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 157 -
A
d
is dryer area, m
2
t is drying time, s
The output of the dryer in terms of energy required for
vaporization is:
fg w d
hm Q
(2)
Where Q
d
is energy required for vaporization, J
m
w
is moisture removed, kg
h
fg
is latent heat of vaporization of moisture, J/kg
The drying efficiency of the dryer is [5]:
100
u¸¸
¹
·
¨¨
©
§
c
s
d
d
QQ
Q
K
(3)
Where Q
c
is energy output from the solar cell module, J
C. Quality analysis
Hardness
: A texture analyzer model TA.XT plus was
used to measure the hardness of dried pork. The sample
was fixed on the platform having a hole with diameter of
0.5 cm at the center. The distance between platform and
base was 80 mm and 50 mm from probe to sample. The
needle probe with 0.2 mm diameter penetrated through
the sample. The program was returned to start and set
with speed of probe 2 mm/s moving forward and 5 mm/s
for moving back. The force in Newton (N) was required
to record as the peak load.
Shrinkage
: It was evaluated by displacement in n-
heptane according to the method of Yan et al. [11].
Shrinkage percentage was defined as the percentage
change in the volume of a sample. It was calculated as
follows:
100
1
u¸¸
¹
·
¨¨
©
§
o
V
V S
(4)
Where S is the shrinkage percentage
V and Vo are the volume of the dried and before
drying sample, respectively, cm
3
Color values
: The colorimetric data used to
characterize the surface color of dried pork were the L a b
values from hunter scale using Mini Scan XE Plus. L
represents the lightness, 0 is dark and 100 is bright. The
positive a is the red direction, negative a is the green
direction and positive b is the yellow direction, negative b
is the blue direction.
III. R
ESULT AND
D
ISCUSSION
During 30 days of experiments, the variations of the
solar radiation, ambient temperature and relative
humidity are shown in Fig. 3 for a typical day of October
2010 in Kalasin. During the drying experiment, the daily
mean values of ambient air temperature, relative humidity
and solar radiation were 34.7
q
C, 44% and 823.3 W/m
2
,
respectively. The ambient temperature and solar radiation
reached the highest figures between 11:30 and 13:30,
whereas relative humidity reached the lowest figures at
13:30.
Fig. 3. Variation of ambient temperature (Ta), relative humidity (RH)
and solar radiation (G) on 24/10/2010.
Fig. 4 indicates that the variations of the air flow rate
which was powered by the solar cell module for operating
the fans providing the required air flow rate inside the
dryer. The air flow rate increases as the solar radiation
increases, the maximum air flow rate was 0.18 kg/s at
solar radiation of 1180.7 W/m
2
, while the minimum air
flow rate was 0.063 kg/s at solar radiation of 355.2 W/m
2
.
The average air flow rate was 0.153 kg/s during the day
of experiment.
Fig. 4. Relation between the air flow rate and solar radiation.
Fig. 5. Variations of the drying temperature and relative humidity.
Fig. 5 shows the variations of average drying
temperature and relative humidity of the greenhouse
dryer. The drying temperature and relative humidity in
the greenhouse dryer changed continuously from morning
to evening. It was observed that the drying temperature in
the dryer was higher than the ambient temperature;
whereas, the relative humidity in the dryer was lower
than that the ambient humidity. Also, there was a
significant difference between the values of the
temperature and relative humidity. This difference for the
20
30
40
50
60
70
80
200
300
400
500
600
700
800
900
1000
1100
1200
9.00
10.00 12.00 14.00 16.00
Temperature (ºC)
Relative humidity,%
GT (W/m2)
Time (o' clock)
GT
RH
Ta
0
0.05
0.1
0.15
0.2
355 430 600 780 920 1000 1180
Solar radiation (W/m
2
)
Air flow rate (kg/s)
20.0
30.0
40.0
50.0
60.0
70.0
0 60 120 180 240 300 360 420
Temperature (ºC)
Relative humidity (%)
Elapsed drying time (h)
RHc
