Chemical heat pumps beyond the Carnot limit

Based on the working mechanisms of heat pumps and chemical pumps, a model of the chemical heat pump operating between the two thermal material reservoirs with different temperatures and chemical potentials is established. The general expression of the coefficient of performance (i.e. generalized Carnot coefficient of performance) is derived, and a series of meaningful results are obtained. The different characteristics of the chemical heat pump operating under different conditions are revealed. It is found that the coefficient of performance of the chemical heat pump can be larger than that of the Carnot heat pump operating under the same temperature span or the reversible coefficient of performance of the chemical pump operating under the same chemical potential span. The reason is that the chemical heat pump operating between two thermal material reservoirs is driven by the temperature field and the chemical potential field at the same time. Moreover, it is expounded that these results accord with the second law of thermodynamics.