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4. Experimental set-up
If the experiment cannot be conducted in direct
sunlight, a 500 W halogen lamp has to be used as a
substitute.
Recommended accessories:
1 Halogen lamp, 500 W (230 V, 50/60 Hz)
or
1 Halogen lamp, 500 W (115 V, 50/60 Hz)
1 Tripod stand
•
Position one black and one white sample panel
in each of the holders and place the other two
black panels in an insulating case. The smooth,
coloured side should point towards the light
source.
•
Put the thermometer through the drill hole in
the holder or the insulating case, respectively,
and into the bottom hole at the rear of the me-
tering panel.
•
Mount the acrylic plate with the clamps to one
of the insulating cases.
•
Position the metering panels at the same dis-
tance and angle to the light source.
T
100
° C
Fig. 1 Temperature increase in the solar meter panels
Black ( ),black, insulated ( ),black, insulated, with acrylic plate ( ),white ( )
Elwe Didactic GmbH • Steinfelsstr. 5 • 08248 Klingenthal • Germany •
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany •
1000894
1000893
1002835
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60
40
20
0
0
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8
Subject to technical amendments
© Copyright 2012 3B Scientific GmbH
5. Experimental protocol
•
Position the halogen lamp at a distance of ap-
proximately 30 to 40 cm from the metering pan-
els.
•
Read thermometer before the experiment, and
take a note of the reading.
•
Switch on lamp.
•
Read the temperature every minute, enter it into
a table and plot a graph of the results.
The various metering panels reach their maximum
temperature within different periods of time.
The covered metering panel reaches its maximum
temperature after approximately 25 min.
The experiment can be halted once the maximum
temperature has been reached.
It can easily be seen (Fig. 1) that black surfaces lead
to a much higher rate of temperature increase than
white ones.
The thermal insulation of the insulating case pre-
vents energy losses from the rear of the metering
panel. Adding the acrylic plate improves utilisation
of the radiant power, since the "greenhouse effect"
prevents cooling of the meter panel by atmospheric
convection and by long-wave heat dissipation from
the front. This "greenhouse effect" even compensates
for the losses due to absorption by the acrylic plate,
which are reflected in the slightly shallower initial
slope of the measured curve. The black metering
panel, furnished with thermal insulation and a
cover, has all the physical attributes of a solar collec-
tor panel for a hot water heater.
10
12
14
16
18
t
min
20
22
24
26
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