TRG-TRC003-EN 11
period two
Refrigerants
notes
Finally, Refrigerant-22 (R-22) is a chemical used in many refrigeration systems.
If, hypothetically, an open container of liquid R-22 were placed in the frozen
display case, when exposed to atmospheric pressure, it would absorb heat and
boil violently at -41.4°F [-40.8°C].
This is a hypothetical example because chemical refrigerants have
environmental regulations that legally require the refrigeration system to be
sealed. Any loss of refrigerant to the atmosphere is closely monitored and,
generally speaking, not allowed.
At atmospheric pressure, each of these three substances (pure ice, dry ice, and
R-22) absorbs heat and changes phase at its own fixed temperature. Pure ice
melts at 32°F [0°C], dry ice evaporates at -109.4 °F [-78.6°C], and R-22 boils at
-41.4°F [-40.8°C].
Why do we want a substance to change phase while producing refrigeration?
5HIULJHUDQW)
)
>&@
>&@
5ERLOVDW
5ERLOVDW
Figure 18