In thermodynamics , a change of state is referred to as isenthalpic where the enthalpy does not change:
An example of an isenthalpic process is the expansion of a gas through a throttle valve , see Joule-Thomson effect .
According to the equation of state of an ideal gas, the following applies
For ideal gases, the isenthalphic processes are precisely the isotherms .
An isothermal reversible process is always isenthalpic, but the reverse is not true.
The lines of equal enthalpy in the state diagram are also called isenthalps (or throttle curves).