Refrigerant
gases are the real workhorses of the refrigeration system. While many
people believe the compressor does all the work, its function is only to
re-circulate the refrigerant, as does a heart with blood.
In that the refrigerant is passed through the system repeatedly, in effect it
is re-used. The mechanical parts of the system allow it to vaporize and
condense in a constant cycle. Simply
passing a liquefied gas through a metering device and allowing it to pass to
atmosphere can accomplish Refrigeration. Since this is costly to the
consumer and to the environment, it is seldom done, the exception being
nitrogen in transport refrigeration. Nitrogen is an inert gas that
comprises approximately 80% of the air we breathe.
Modern day refrigerants are the result of 100 years of evolution. They
are chosen for their boiling points, inflammability, chemical stability and
lack of toxicity. While some modern refrigerants are still flammable and
toxic, they are rare and used only where no other substance can do the job for
which they are required, for example attaining temperatures of 100 degrees or
more below zero.
The
Montreal Protocol of 1994 (http://www.unep.org/ozone/Handbook2000.htm) was the result of world
scientists meeting over a decade, which dealt with the potential affects of
chlorofluorocarbons used in refrigerants on the earth’s ozone layer. This protocol created rules for the banning
of certain refrigerants, by industrialized nations, to protect the
environment. The most difficult task of today’s conscientious
refrigeration professional is to determine which of the replacement
refrigerants to use when converting systems from CFC’s (chlorofluorocarbons) to
HCFC’s (hydrochlorofluorocarbons… transition refrigerants) or HFC’s
(hydrofluorocarbons… permanent replacements).