10 TRG-TRC003-EN
notes
period two
Refrigerants
Pure ice, however, does have an important disadvantage. It absorbs heat and
melts at 32°F [0°C]. Ice cream, for example, melts at a temperature lower than
32°F [0°C]. In the same frozen display case, ice cannot keep the ice cream frozen
because ice melts at a higher temperature than ice cream.
There is another type of ice known as dry ice, which is solid (frozen) carbon
dioxide (CO2). It evaporates directly from a solid phase to a vapor phase at
-109.4°F [-78.6°C]. Used in the same frozen display case, dry ice would keep the
ice cream frozen because it evaporates at a lower temperature than the
temperature at which ice cream melts, but would result in an unnecessarily low
temperature.
Additionally, both pure ice and dry ice would be consumed in the cooling
process, either melting away as a liquid or evaporating into a vapor. It would
have to be continually replaced.
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