Chapter 6 Introduction to Refrigerants
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When this has happened, new driers and filters should
be placed in the system. These will keep the new lubri-
cant clean. Another indicator of contaminated lubri-
cant is odor. Dark-black, pungent oil is an indicator
of compressor failure. Metal shavings and chips are
another sure sign that the compressor is in need of
replacement.
Safety Note
Acidic Refrigeration Lubricant
Contaminated lubricant from a hermetic system is
very dirty and smells bad. It may also be acidic and can
burn skin. Avoid any contact.
Summary
✲ In order to protect the environment, the
Environmental Protection Agency (EPA)
enforces regulations outlined in the Clean Air
Act for working with refrigerants. All HVACR
technicians must be certifi ed by the EPA to
work with refrigerants.
✲ A refrigerant’s ozone depletion potential
(ODP) and global warming potential (GWP)
are number ratings used to determine the
refrigerant’s effect on the ozone layer and
climate change.
✲ CFCs, HCFCs, and HFCs are carbon-based,
halogenated refrigerants. They are the most
commonly used refrigerants in mechanical
refrigeration systems. HFCs have the lowest
ODP and are being used to replace CFCs or
HCFCs that have been phased out.
✲ Azeotropes respond to pressure and heat changes
like a single refrigerant, having fi xed boiling and
condensing points. Refrigerants in a zeotropic
blend respond individually to pressure
and heat, each having different boiling and
condensing points.
✲ Refrigerants are identifi ed by a standardized
numbering system. Each refrigerant is assigned
a number that follows the letter R. The third
number from the right indicates the series of
the refrigerant.
✲ ASHRAE Standard 34 categorizes refrigerants
according to their toxicity and fl ammability.
✲ Pressure-temperature curves and charts show
how a refrigerant’s temperature and pressure
both rise and fall in relation to each other. They
can be used to determine the proper operating
temperature or pressure of a system.
Acidic Refrigeration Lubrican t
C ontaminated lubricant from a hermetic system is
very dirty and smells bad. It may also be acidic and can
burn skin. Avoid any contact.
✲ A pressure-enthalpy table numerically shows
the thermodynamic properties of a refrigerant
under saturated conditions. It can be used to
calculate the latent heat of a refrigerant.
✲ A pressure-enthalpy diagram is a graph
version of a pressure-enthalpy table.
Pressure-enthalpy diagrams can be used to
calculate a refrigeration system’s coeffi cient of
performance.
✲ The type of refrigerant to be used in a given
system is determined by the manufacturer.
However, one type of refrigerant may be used in
a number of applications. Several items that are
considered when selecting a refrigerant include
the refrigerant’s boiling point, latent heat, and
operating temperatures and pressures.
✲ A popular inorganic refrigerant is R-717,
also called ammonia (NH3). Its low boiling
point makes it ideal for low-temperature
refrigeration. R-717 refrigeration systems are
constructed of iron or steel, as ammonia attacks
copper in the presence of moisture.
✲ An expendable refrigerant cools a substance
or absorbs heat from an evaporator and then is
released into the atmosphere, being used only
once. Systems often use cryogenic fl uids as
expendable refrigerants.
✲ Refrigeration lubricant is charged into a
refrigerant circuit with the system’s refrigerant
in order to lubricate the contact between moving
parts. Refrigeration lubricants must be compatible
with the refrigerant used in the system.
Review Questions
Answer the following questions using information in this
chapter.
1. Ozone _____ is a numeric value assigned to
refrigerants to compare how harmful they can
be to the ozone.
A. destructive power
B. depletion power
C. depletion potential
D. destruction potential
2. A refrigerant’s global warming potential (GWP)
is based on a ratio of the refrigerant’s warming
effect compared to the warming effect of _____.
A. argon
B. carbon dioxide
C. nitrogen
D. oxygen