  The throttling process of the Kerr-Newman-anti-de Sitter (KN-AdS) black holes
is systematically studied in the extended phase space. In this framework, the
cosmological constant is interpreted as a varying thermodynamic pressure, and
the black hole mass is identified with enthalpy. The throttling process is
essentially an isenthalpic (i.e., constant-mass) process for the KN-AdS black
holes. The Joule-Thomson coefficient, inversion temperature, inversion curve,
and isenthalpic curve are investigated in order, with both analytical and
numerical methods. It is found that there are no maximum inversion
temperatures, but only minimum ones that are around one half of the critical
temperatures of the KN-AdS black holes. Two characteristic masses are also
discussed to show the detailed features in the throttling behaviors of the
KN-AdS black holes.
