NLP model-based optimal design of LiBr–H2O absorption refrigeration systems

This paper addresses the optimization of a single effect absorption refrigeration system operating with lithium bromide-water solution. A non-linear programming mathematical model is developed to determine the operating conditions and the distribution of the total heat transfer area (sizes) along the involved process units to optimize the following two objective functions: (i) maximization of the coefficient of performance for a given amount of the total heat transfer area, and (ii) minimization of the total heat transfer area of the system for a given cooling capacity. The proposed model can either be used for simulation or optimization purposes. Simulated or optimized values of temperature, pressure, composition and flow rate of all streams and sizing of each process unit are predicted. In addition, because of the non linear nature of the resulting model, a systematic solution procedure is proposed in order to guarantee the model convergence. A detailed discussion of the optimization results are presented through different case studies.