Joule-Thomson expansion of charged dilatonic black holes* *Supported by the National Natural Science Foundation of China (11465006, 11565009) and the Doctoral Foundation of Zunyi Normal University of China (BS [2022] 07, QJJ-[2022]-314)

Abstract

Based on the Einstein-Maxwell theory, the Joule-Thomson (J-T) expansion of charged dilatonic black holes (the solutions are neither flat nor AdS) in -dimensional spacetime is studied herein. To this end, we analyze the effects of the dimension n and dilaton field α on J-T expansion. An explicit expression for the J-T coefficient is derived, and consequently, a negative heat capacity is found to lead to a cooling process. In contrast to its effect on the dimension, the inversion curve decreases with charge Q at low pressures, whereas the opposite effect is observed at high pressures. We can observe that with an increase in the dimension n or parameter α, both the pressure cut-off point and the minimum inversion temperature change. Moreover, we analyze the ratio numerically and discover that the ratio is independent of charge; however, it depends on the dilaton field and dimension: for and , the ratio is 1/2. The dilaton field is found to enhance the ratio. In addition, we identify the cooling-heating regions by investigating the inversion and isenthalpic curves, and the behavior of the minimum inversion mass indicates that this cooling-heating transition may not occur under certain special conditions.