1. The sola adia ion on a la pla e collec o o 2.1 m2 o ape u e is 800 W/m2. The collec o is
il ed 40º and sou h o ien ed. The angle o incidence o he adia ion is 20º. The ollowing da a
is also known:
• Ambien empe a u e 12 ºC
• O e all hea loss coe icien 4.32W/m2K
• Abso be pla e empe a u e 80ºC
• Collec o inle empe a u e 28ºC
• Mass low a e: 0.014kg/s m2
• Glass co e : e ac ion index n=1.526, ex inc ion coe icien by co e wid h (KL)=0.037
• Abso be abso p ance: 0.92
• Speci ic hea o he luid Cp=4180J/kgK
• Ai e ac ion index n=1
a) Which is he luid ou le empe a u e?
b) Which is he sola collec o e iciency o he gi e condi ions?
2. A la pla e collec o wi h dimensions 1.5x3 m il ed 40º has he ollowing speci ica ions:
• O e all hea loss coe icien : 5.6 W/m2K
• Con ec ion hea ans e coe icien be ween he ubes and he ci cula ing luid
200W/m2K
• Glass co e e ac ion index 1.526
• Glass co e ex inc ion coe icien by co e wid h (KL) 0.037
• Abso be abso p ance 0.92
• Abso be wid h 0.5mm
• Coppe ubes o 10/8 mm (ou e /inne diame e ) and 12 cm o dis ance be ween ubes
• Coppe hea conduc i i y 385 W/mK
• Hea capaci y o he luid: 4180 J/kgK
I a some ins an he no mal i adia ion on he collec o su ace is 850 W/m2, and he luid a he
inle is a 45ºC, es ima e he collec o e iciency.
Conside he mass low a e o 0.0135kg/s m2 and he ambien empe a u e o 15ºC
b) Which is he collec o ou le empe a u e?
3. Fo he sola collec o o exe cise 2, i a some ins an he adia ion on he collec o su ace is
o 850W/m2, bu he e is no luid ci cula ing h ough he collec o , which is he s agna ion
empe a u e? Wha does his mean?
4. Fo he same collec o o exe cise 2, de e mine he c i ical adia ion gi en an inle
empe a u e o 30ºC. Wha does his c i ical adia ion mean?
5. In he ollowing he able he ambien empe a u e, sola adia ion on he collec o su ace,
sola gains on he abso be pla e and sola ield inle empe a u e a e gi en. The sola ield is
made o 5 collec o s o 2m2 il ed 40º and sou h o ien ed. Fo he sola collec o , assume he
o e all hea loss coe icien o be UL=6.3 W/m2K and he pla e e iciency ac o (F’) o be
0.841. The mass low a e h ough a single sola collec o is 0.03kg/s. Assume ha he
con olle u ns o he pumps whene e he ou le empe a u e is less han he inle
empe a u e. Assume also ha he he mal capaci y o he luid is 3720 J/kgK. Calcula e he
daily use ul gains and he sola ield e iciency o ha pa icula day. Assume ha he da a
gi en in he able can be conside ed cons an o he whole hou .
Time
Ta[ºC]
I [W/m2]
S[W/m2]
T i
7-8
1
15
12.45
30
8-9
3
125
103.8
33
9-10
5
280
232.6
37
10-11
7
460
382.3
38
11-12
8
496
407
40
12-13
7
475
395
45
13-14
6
320
266
44
14-15
6
250
207.8
40
15-16
6
110
91.4
35
16-17
5
7
5.3
25
6. Two la pla e sola collec o s a e conside ed o be ins alled o a low- empe a u e sola
applica ion whe e he sola ield will be wo king be ween a empe a u e di e ences (T i- a) o
15ºC up o 35ºC and o sola i adia ion in he ange o 350W/m2and 800 W/m2. Conside ing
he wo king condi ions which collec o should be selec ed? Please, commen you answe .
The sola collec o s’ cha ac e is ics a e:
Ac[m2]
ηop
FRUL1[W/m2K2]
FRUL2 [W/m2K2]
TSTG[ºC]
Collec o 1
2.25
0.792
5.3
0.0182
148
Collec o 2
2.23
0.747
3.824
0.023
149.5
7. A la pla e collec o o 4 m2 is es ed indoo s in o de o de e mine i s o e all hea loss
coe icien . In he es , he mal oil is used as hea ans e luid (Cp=2035J/kgK) ci cula ing wi h
a mass low a e o 0.052kg/s. The luid en e s he collec o a 60ºC and a he ou le 49ºC is
measu ed. The ambien empe a u e du ing he whole expe imen was se o 15ºC. Which is
he o e all hea loss coe icien o he collec o ?
8. Fo a one-co e collec o o dimensions 2.5x1.3m il ed 45º, de e mine he o e all hea loss
coe icien . The ambien empe a u e is 10ºC and he wind is blowing a 3m/s. The abso be
pla e hick is 0.5 mm and i s emissi i y is 0.92. The glass co e is a 35 mm om he abso be
pla e and has an emissi i y o 0.88. The insula ion is ibe glass (k=0.038W/mK) o 45mm hick
a he back and 25 mm hick a he edges. The mean abso be pla e empe a u e is 90ºC.
Assume he con ec ion hea ans e coe icien o he back o he collec o o be 0.3W/m2K
and o he edge o he collec o o be o 2W/m2K. Fo he hea con ec ion coe icien om
he op o he collec o he ollowing co ela ion can be used:
hw=2.8+3.0 V, whe e V is he wind eloci y in m/s
Assume ha he sky empe a u e is he same as he ambien empe a u e.
9. A wa e hea ing collec o wi h a ape u e o 3.5 m2 is es ed ollowing he Eu opean s anda ds
wi h adia ion nea ly no mal o he collec o su ace. The ollowing able gi es some esul s o
he measu emen s
Qu[W]
I [W/m2]
Ta [ºC]
Ta[ºC]
2252
864
23.4
10
469
894
85.3
10
a.- Which is he collec o e iciency cu e?
b. As he es was ca ied ou ollowing EU s anda ds i migh be necessa y o con e he
da a o i s use in a compu e p og am which wo ks wi h F UL and F (τα). Please, e alua e
hem.
c. A Second es was pe o med so as o e alua e he incidence angle modi ie . To ha end
he collec o was se o ope a e a he same empe a u e as he ambien and o adia ion
incidence angle di e en han no mal. The ollowing in o ma ion comes om he es :
ϑ
I [W/m2]
Qu[W/m2]
0
850
747
30
750
639
45
630
526
60
530
396
