Adiabatic Processes for Charged AdS Black Hole in the Extended Phase Space

TL;DR

This paper explores adiabatic processes in charged AdS black holes within extended phase space, identifying two types with distinct thermodynamic properties and comparing them to classical thermodynamic processes.

Contribution

It introduces a general method to derive all adiabatic processes for charged AdS black holes and classifies two distinct types with their thermodynamic characteristics.

Findings

Zero temperature adiabatic process is irreversible with entropy increasing.

Isochore adiabatic process is reversible with fixed entropy and internal energy.

The processes resemble classical thermodynamic processes like throttling and free expansion.

Abstract

In the extended phase space, a general method is used to derive all the possible adiabatic processes for charged AdS black hole. Two kinds are found, one is zero temperature adiabatic process which is irreversible, the other is isochore adiabatic process which is reversible. For the zero temperature adiabatic expansion process, entropy is increasing; pressure, enthalpy, Gibbs free energy and internal energy are decreasing; system's potential energy is transformed to the work done by the system to the outer system. For the isochore adiabatic process, entropy and internal energy are fixed; temperature, enthalpy and Gibbs free energy are proportional to pressure; during the pressure increasing process, temperature is increasing and system's potential energy is transformed to its kinetic energy. Comparing these two adiabatic processes with those in normal thermodynamic system, we find that the zero temperature adiabatic process is much like the adiabatic throttling process(both are irreversible and with work done), the isochore adiabatic process is much like a combination of the reversible adiabatic process (both with fixed entropy) and the adiabatic free expansion process (both with fixed internal energy).