|James Prescott Joule, William Thomson, Lord Kelvin thermodynamics|
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.
To move heat from a cold place to a warm place for refrigeration heating and liquifying gases
The energy in a system equal to its internal energy plus the product of pressure and volume measured by the joule.
Throttle valve or porous plug irreversible aperture a passageway that gins up the cycle.