Joule-Thomson effect Purpose Enthalpy Orifice Commentary

James Prescott Joule, William Thomson, Lord Kelvin thermodynamics

Joule-Thomson effect

• James Prescott Joule and his friend Lord Kelvin
• showed that passing gas through a throttled orifice
• letting it expand
• causes it to cool.
• Specifically, we are not accelerating the gas
• and we insulate the orifice to avoid exchanging heat.

Purpose

• To move heat
• from a cold place
• to a warm place
• for refrigeration
• heating
• and liquifying gases

Enthalpy

• The energy in a system
• equal to its internal energy plus
• the product of pressure and volume
• measured by the joule.

Orifice

• Throttle valve
• or porous plug
• irreversible
• aperture
• a passageway
• that gins up the cycle.