Frigidaire LGUB2642LF2, Service Manual

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Sealed System
7-32
CFCs
Chlorofluorocarbons (CFCs) are compounds consisting of chlorine, fluorine, and carbon atoms which are very stable
in the troposphere. They are degraded only in the stratosphere by the sun’s radiation where released chlorine may
contribute to ozone depletion. They can persist in the troposphere for a hundred years or longer.
Fluorocarbons
These chemical compounds include CFCs, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). For
many years, CFCs have served vital functions in society. They are used in a variety of applications including refrig-
eration, air conditioning, energy efficient insulation, medical products, and cleaning of electronic and precision engi-
neering components. HCFCs and HFCs retain many of the desirable properties of CFCs but because they exist for
a shorter time in the atmosphere, ozone depletion and global warming concerns are significantly reduced.
Global Warming
Global warming, which is an increase in the natural greenhouse effect, refers to the physical phenomenon that may
lead to heating of the earth. Most of the sun’s energy reaches the earth as visible light. After passing through the
atmosphere, part of this energy is absorbed by the earth’s surface and in the process is converted into heat energy.
The earth, now warmed by the sun, radiates heat energy back into the atmosphere toward space.
Naturally occurring gases, such as carbon dioxide, water vapor, and ozone, absorb and thus retain some of the
outgoing heat energy. This process slows the heat loss, making the earth’s surface warmer than it would be if this
heat energy had passed unobstructed through the atmosphere into space. The warmer earth’s surface, in turn,
radiates more heat until a balance is established between incoming and outgoing energy. This warming process,
caused by the atmosphere’s absorption of the heat energy radiated from the earth’s surface, is called the green-
house effect.
Increasing concentrations of gases from man-made sources (e.g., carbon dioxide, methane, and CFCs) that absorb
the heat radiation could lead to a slow warming of the earth. This phenomenon is commonly referred to as global
warming.
Global Warming Potential (GYP)
An index developed to provide a simplified means of describing the relative ability of each greenhouse gas emission
to affect radiative forcing and thereby the global climate. GYPs are defined on amass basis, relative to either CFC-
11 (the Halocarbon GYP or HGWP) or carbon dioxide. Because CFC-11 has a finite lifetime in the atmosphere, the
HGWP can be calculated explicitly and is a single number. Because carbon dioxide does not have a finite lifetime
in the atmosphere, GYPs relative to it have to be calculated up to a particular time horizon, for example, 20, 100, or
500 years.
Greenhouse Gases
Gases present in relatively small quantities in the atmosphere that strongly absorb infrared radiation or “heat” emitted
by the earth. The primary greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, ozone, and
some of the chlorofluorocarbons. Concentrations of several greenhouse gases are increasing, primarily as a result of
human activities.