At least three sorption technologies (liquid absorption, solid adsorption, chemical reaction) compete for refrigeration and heat pumping. In contrast with expansion/compression heat engine cycles, which reach the Carnot efficiency, none of these technologies approaches the Carnot efficiency. To analyse why the efficiency differs so much from the Carnot efficiency and to analyse the differences between these technologies, it is interesting to describe each system through an equivalent Carnot cycle. This approach shows clearly that the sorption cycles cannot be described simply by the coupling between two two-temperature Carnot cycles but that more complicated structures must be used. The role and the importance of the mechanical energy in liquid absorption systems is clearly depicted by this approach. Moreover, the relative importance of external entropy production (due to temperature swings or heterogeneities) and of internal entropy productions (throttling or desuperheating, for example) is clearly depicted. The approach is possible for basic as well as for advanced cycles.

KEYWORDS: year 1997, Comparing, absorption refrigeration, cyclic, efficiency, Carnot cycle, entropy, coefficient of performance