Optimal working conditions for an absorption heat transformer—analysis of the H2O/LiBr theoretical cycle

Abstract This article studies the optimal working conditions of an absorption heat transformer based on a theoretical cycle using the H 2 O/LiBr working pair. The efficiency parameters of the system are discussed and a new parameter, namely the exergetic index, directly related to the exergetic efficiency but more significant for evaluating the performance of the system, is introduced. Distinction is made between energetic optimisation—which involves maximal thermodynamic efficiency—and economic optimisation—for which the knowledge of both the energy and equipment costs are necessary. The existence of two kinds of decision variables related to each type of optimisation are discussed. Four criteria for energetic optimisation are defined from which simple prediction equations are obtained. These equations enable us to predict for a given pair, a range of energetically optimal working conditions, valid for a large number of cold and waste energy source temperatures. Finally, practical applications of the proposed predictions are given.