2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
- 216 -
T
ABLE
II
T
HE STORAGE TEMPERATURE
(
THE INITIAL VALUE WAS AT
30
O
C).
Fig. 5. The water mass flow rate, the useful heat and the storage
temperature on a clear sky day (The initial temperature
conditions were at 30
o
C).
Fig. 5 shows the results on a clear sky day. It could be
seen that results of both standard and the controlled mass
flow rate standard were similar.
V. A
CASE STUDY
A case study for a solar water heating system was
carried out at a nursery building in Chiang Mai, Thailand
of which the hot water requirement was given in Fig. 6.
The system had an external auxiliary heater to supply
heat when the required hot water was less than 45
o
C
Fig.
6.
The hot water consumption of a nursery building [8].
Fig. 7 shows the simulation results for three
consecutive cloudy days. It could be seen that for the
controlled mass flow rate condition, the water storage
temperatures were still higher than that of the standard
one which meant that more daily heat amount from the
solar collector and less amount of the auxiliary heat were
obtained. The results were shown in Figs. 8 and 9,
respectively.
Case
T
s1
(
o
C) T
s2
(
o
C) T
s3
(
o
C)
Q
u
(MJ)
System
efficiency
(%)
Standard
mass flow rate
53.98
52.84
51.42
14.29
45.88
Controlled
mass flow rate
60.50
59.12
57.86
18.32
58.82
(
a)
The mass flow rate.
(
b)
The useful heat
at the collector.
(
c) The water
temperature in various position of storage tank
0
10
20
30
40
50
60
70
Hotwaterconsumtion(Liter)
LocalTime
0
200
400
600
800
1,000
1,200
25
35
45
55
65
75
85
I
T
(W/m
2
)
Temperature (
o
C)
Ts3,standard
Ts1,standard
Ts3,control
Ts2,control
Ts2,standard
Ts1,control
IT
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
0.00
200.00
400.00
600.00
800.00
1,000.00
1,200.00
1,400.00
1,600.00
Qu(W)
Qu,standardflowrate
Qu,controlflowrate
0
200
400
600
800
1,000
1,200
1,400
0
10
20
30
40
50
60
Solar radiation (W/m
2
)
Temperature(
o
C)
Ts1,standard
Ts1,control
Solar radiation
(
a) The water
temperature at node1 of storage tank
0
200
400
600
800
1,000
1,200
1,400
0
10
20
30
40
50
60
Solar radiation (W/m
2
)
Temperature(
o
C)
Ts2,standard
Ts2,control
Solar radiation
(
b) The water
temperature at node2 of storage tank
