Answer :
the Joule–Thomson effect or Joule–Kelvin effect or Kelvin–Joule effect describes the temperature change of a gas or liquid when it is forced through a valve or porous plug while kept insulated so that no heat is exchanged with the environment
The change of a temperature of a gas when it is allowed to expand without doing any external work.The gas becomes cooler if it was initially below a certain temperature , or hotter if initially above it is known as Joule Thomson effect!