Chemical and adsorption heat pumps: Comments on the second law efficiency

The thermodynamic analysis of an ideal cycle of chemical and adsorption heat pumps was performed in order to compare two definitions of the cycle efficiency used in literature and estimate the maximal efficiency that can be reached for particular non-regenerative cycle. It was shown that the efficiency equal to the Carnot efficiency can be, in principle, obtained for a chemical heat pump that results from a monovariant equilibrium of a gas–solid reaction. This was confirmed for various chemical reactions between salts and ammonia (or water). For a divariant equilibrium in adsorption heat pump there is inevitable degradation of the efficiency due to the thermal entropy production caused by the external thermal coupling. Simple estimation of the efficiency reduction is suggested.