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The most widely used refrigeration principle
is vapor compression, also referred to as
the reverse-Rankine cycle. It operates around
the refrigerant’s saturation curve (shown
in green):
The refrigerant starts
as a gas and is compressed and cooled to a
liquid. The liquid is throttled to a lower
pressure and evaporated to absorb heat, and
recycled to be compressed once again, completing
the cycle.
This cycle takes advantage of the universal
gas law:
PV=nRT,
where P
is pressure, V
is volume, R
is the universal gas constant, T
is temperature, and n is the number of moles
of gas (1 mole = 6.022x1023 molecules).
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William
John Macquorn Rankine (Scottish,
1820 - 1872) was an engineer and
physicist. He was a founding contributor
to the science of thermodynamics. |
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Sadi
Nicolas Léonard Carnot
(French, 1796 –
1832) discovered that the
efficiency of a heat engine depended
only on its input and output temperatures.
The Carnot cycle is thought of
as the most efficient heat engine
cycle allowed by physical laws..
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Jacob
Perkins (American,
1766-1849) built the first
practical refrigerating machine
in 1834. It used ether in a
vapor-compression cycle. |
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James
Harrison (Scottish,
1816-1893) created the first
commercial ice-making machine
in 1854. The machine employed
a 5 m flywheel and produced 3000
kg of ice per day. |
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