2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 215 -
B. Conditions for the System Simulation
Table I. gives conditions of the solar collector for the
system simulation.
The collector supplied heat to a water
storage tank that had a capacity of 0.15 m
3
under no load
condition. The simulation was carried out during 7 a.m -
5 p.m. under Chiang Mai climate on October 18, 2009
which was a cloudy day and on February 8, 2009 which
was a clear sky day. All starting temperatures were at 30
o
C.
TABLE
I
T
HE CONDITIONS OF THE SOLAR COLLECTOR
.[7].
ܨ
ோ
ሺ߬
ߙ
ሻ
ܨ
ோ
ܷ
(W/m
2
-K)
Ac
(m
2
)
Di
(m)
L
(m)
W
(m)
Storage
Tank
(Liter)
0.8661
8.2902
2.16
0.00
5
2.16
1.0
150
IV. S
IMULATION RESULTS
Fig. 3. shows the weather data of Chiang Mai for the
system simulation. The selected days are October 18,
2009 and February 8, 2009 which are a cloudy day and a
clear sky day, respectively.
Fig. 3. The weather data for the simulation.
Fig. 4 shows the water mass flow rate, the useful heat
and the water
temperatures in the storage tank at various
positions on a cloudy day. For Fig. 4 (a), it could be seen
when the solar radiation level was low in some periods,
with the standard flow rate, the collector outlet water
temperature was lower than that at the top of the storage
tank then the pump was off. When the flow rate was
reduced the system could prolong the operation. From
Fig. 4 (b), it was found that the daily useful heat with
controlled mass flow rate was higher than that of the
standard mass flow rate. Moreover, the temperatures of
water in the storage tank for the previous condition were
also higher than that of the latter one. The results were
shown in Fig. 4 (c).
Fig. 4. The water mass flow rate, the useful heat and the storage
temperature on a cloudy day (The initial temperature
conditions were at 30
o
C).
For the standard mass flow rate, the daily useful heat
from the solar collector was 14.29 MJ and the daily
system efficiency was 45.88%. For the controlled mass
flow rate condition, the daily useful heat was 18.32 MJ
and the daily system efficiency was 58.82%. The final
storage temperatures at 5 p.m. were also calculated and
the results were shown in Table II.
(a)
I
T
and T
a
on October
18, 2009 (a cloudy day).
(
b
)
I
T
and T
a
on February
8, 2009 (a clear sky day).
(
a)
The mass flow rate.
(
b)
The useful heat
at the collector.
(
c) The water Temperature in various position of storage tank
0
5
10
15
20
25
30
35
40
0
200
400
600
800
1,000
T
a
(
o
C)
I
T
(W/m
2
)
LocalTime
IT
Ta
0
5
10
15
20
25
30
35
40
0
200
400
600
800
1,000
1,200
T
a
(
o
C)
I
T
(W/m
2
)
LocalTime
IT
Ta
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
Liter/min-m
2
Standardmass flow rate
Controlmass flow rate
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
Qu(W)
Qu,standardflowrate
Qu,controlflowrate
0
100
200
300
400
500
600
700
800
900
1,000
25
30
35
40
45
50
55
60
65
I
T
(W/m
2
)
Temperature (
o
C)
Ts3,standard
Ts2,standard
Ts1,standard
Ts3,control
Ts2,control
Ts1,control
IT
