94
Reference
Adiabatic Process
(ad-ee-uh-bat-ik)
Adiabatic compression and expansion are thermodynamic
processes in which the pressure of a gas is increased or
decreased without any exchange of heat energy with the
surroundings. Any process that occurs without heat transfer is
called an adiabatic process.
The adiabatic compression or expansion of a gas can occur if
the gas is insulated from its surroundings or if the process
takes place quickly enough to prevent any significant heat
transfer. This is essentially the case in a number of important
devices, including air compressors.
An adiabatic expansion is usually accompanied by a decrease
in the gas temperature. This can be observed in a common
aerosol can, which becomes cold after some compressed gas
is released. The reason for the temperature drop is that the gas
is released too quickly to absorb any significant heat energy
from its surroundings. Work performed in expanding the
released gas drains some internal energy of the gas still in the
can, making it colder. After the can metal becomes cold,
however, the process is no longer adiabatic.
In a similar fashion, adiabatic compression usually increases
the temperature of a gas, since work is done on the system by
the surroundings. For example, when air is pumped into an
automobile tire, the air temperature rises as a result of
adiabatic compression.
