Finite-time thermodynamic optimization of an irreversible four-heat-source absorption refrigerator

To obtain a more useful upper bound for the performance of an absorption refrigerator from a thermodynamic angle, a four-heat-source cycle model for this system is presented. In the model, an absorption refrigerator is treated as a combined cycle system of an irreversible Carnot refrigerator driven by an irreversible Carnot heat engine. Using optimization theory, the fundamental optimal relation between the cooling rate and the coefficient of performance, the optimal distribution relations of the total heat conductance between the heat exchangers, and the general expressions of the maximum cooling rate and its corresponding coefficient of performance were derived. As compared with the refrigeration cycle model with three heat sources, the proposed refrigeration cycle model with four heat sources is closer to a real absorption refrigerator. Therefore, the results obtained here are more useful to guide optimal design and performance improvement of a real absorption refrigerator.