Thermodynamic characteristics of a Brownian heat pump in a spatially periodic temperature field

This paper has studied the thermodynamic performance of a thermal Brownian heat pump, which consists of Brownian particles moving at a periodic sawtooth potential with external forces and contacting with the alternating hot and cold reservoirs along the space coordinate. The heat flows driven by both potential and kinetic energies are taken into account. The analytical expressions for the heating load, coefficient of performance (COP) and power input of the Brownian heat pump are derived and the performance characteristics are obtained by numerical calculations. It is shown that due to the heat flow via the change of kinetic energy of the particles, the Brownian heat pump is always irreversible and the COP can never attain the Carnot COP. The study has also investigated the influences of the operating parameters, i.e. the external force, barrier height of the potential, asymmetry of the sawtooth potential and temperature ratio of the heat reservoirs, on the performance of the Brownian heat pump. The effective regions of external force and barrier height of the potential in which the Brownian motor can operates as a heat pump are determined. The results show that the performance of the Brownian heat pump greatly depends on the parameters; if the parameters are properly chosen, the Brownian heat pump may be controlled to operate in the optimal regimes.