Experimental Study on a New Small-Scale Absorption System: Response Surface and Inverse Analyses

In this paper, a new small-scale lithium bromide (LiBr)-water absorption system consisting water-cooled absorber and air-cooled condenser is experimentally studied. For compactness, the heat exchangers for evaporator, absorber, and generator are made helical-coiled type, whereas based on the water availability and load requirements, condenser is air-cooled. Accurate empirical correlations for thermal load and evaporator temperature against the concerning system driving factors have been reported. Response surface analyses of the performance parameters are studied with respect to LiBr concentration, temperature of generator, and mass flowrate of hot water. Using experimental data, the estimation of overall heat transfer coefficient (U) and its variation with system driving factors is quantified. The error margin between theoretical and actual pressure loss is limited within 5%. Next, a multi-objective inverse analysis of the developed system is done to simultaneously retrieve the required LiBr concentration, mass flowrate of hot water, and vapor generator temperature to derive a desired cooling performance demand from the system. The physics related to salt concentration and generator temperature in governing U values are reported. It can be established that the necessary operational parameters can be predicted by the present multi-objective inverse method to meet the necessary thermal load and temperature demands within an accuracy level of 6% and 5%, respectively.