Glossary - Viessmann Vitosol
100 Technical Manual

5.2 Glossary

5.2 Glossary
Absorber
Device contained inside a solar panel for
absorbing radiation energy and
transferring this as heat to a liquid.
Absorption
Absorption of radiation.
Condenser
Device in which vapour is precipitated as
liquid.
Convection
Transfer of heat by a flowing medium.
Convection creates energy losses caused
by a temperature differential, e.g.
between the glass plate of the collector
and the hot absorber.
Dispersion
Interaction of radiation with matter by
which the radiation direction is altered;
total energy and wavelength remain
unchanged.
Efficiency
The efficiency of a solar panel is the ratio
between the input/output of the collector.
Relevant variables are, for example, the
ambient and absorber temperatures.
94
Emission
Radiation of beams, e.g. light or particles.
Evacuation
Evacuating air from a container. This
reduces the air pressure and creates a
vacuum.
Heat loss coefficients k and k
1
k is the constant component of a
1
collector heat loss, and is usually
(
designated as k value unit: W/(m
k is the quadratic component of the
2
temperature−dependent heat loss
( 2 2 )
unit: W/(m · K ) .
Any informative statement about the heat
losses of a collector requires both values
to be quoted.
Heat pipe
Closed, capillary container which contains
a small quantity of highly volatile liquid.
Photovoltaic effect
Gaining electrical energy from solar
energy.
Process medium
Fluid which picks up the useful heat in the
absorber of the collector and transfers it
to a consumer (heat exchanger).
Radiation energy
Quantity of energy transmitted by
radiation.
Radiation level (irradiation)
Radiation power, impacting per unit
surface, expressed in W/m
Selective surface
2
The absorber in the solar panel has been
given a highly selective coating to
2 )
· K) . improve its efficiency. This specially
applied coating enables the absorption to
be maintained at a very high level for the
incident sunlight spectrum (approx. 94 %).
The emission of the long−wave heat
radiation is largely avoided.
The highly selective black chromium
coating is very durable.
Stagnation
Condition of a collector when no heat is
being conducted away by the process
medium.
Vacuum
A space devoid of air.
2
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