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4. Experimental set-up
Recommended accessories:
Halogen lamp with stem, 500 W
Support base
•
Position the metering panels inside the holders
and the insulating cases. 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.
If the experiment is conducted in direct sunlight,
the metering panel can be slanted in the holder to
match the angle of the sunbeams.
If the experiment cannot be conducted in direct
sunlight, a 500 W halogen lamp has to be used as a
substitute.
5. Experimental protocol
•
Position the halogen lamp at a distance of
approximately 65 cm from the metering pan-
els. The illumination is then as bright as sum-
mer sunshine.
1. white, 2. black, 3. black, insulated, 4. black, insulated, with acrylic plate
Elwe Didactic GmbH • Steinfelsstr. 6 • 08248 Klingenthal • Germany •
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany •
8476712
8614110
Fig. 1 Temperature increase in the solar meter panels
Subject to technical amendments
•
Read thermometer before the experiment, and
take a note of the reading.
•
Switch on lamp.
•
Read the temperature every minute, and enter
it into a table.
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 compen-
sates 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 me-
tering panel, furnished with thermal insulation and
a cover, has all the physical attributes of a solar
collector panel for a hot water heater.
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