▎ 摘　　要

We present a method for substantially enhancing the rate of heat transfer into and out of the working fluid of a heat engine, using bidirectional thermal radiation exchange between the external environment and many individual graphene layers that are dispersed and suspended within an inert gas. This hybrid working fluid has the unique composite property of high optical absorption/emission yet low specific heat. Consequently, it can heat and cool rapidly, enabling a much greater cycle frequency and a commensurate increase in specific power, in comparison to conventional closed-cycle heat engines for which the cycle frequency is limited by the use of slower, non-radiative, thermal transfer. (C) 2019 Optical Society of America