Performance improvements on energy and exergy basis for an ammonia-water absorption refrigeration system in a coffee industry

Abstract

Ammonia-water absorption refrigeration systems have broad applications in industrial and commercial facilities, easily driven by any available waste heat of low-medium temperatures. The objective is to evaluate, identify and propose improvements in the existing coffee industry using refrigeration system with a double absorption stage and single ammonia generator. A complete energy and exergy modeling and analysis are applied - components and overall efficiencies, including physical and chemical irreversibilities. Thermal system modeling uses Engineering Equation Solver containing 34 streams and 22 components. The main findings indicate that coupled energy-exergy analysis proves the ability to identify poor performance components and processes. Therefore, allowing to propose feasible modifications in the real facility by improving the systeḿs efficiency on 1st and 2nd Thermodynamics laws basis, respectively β and ε from 0.259 and 0.204 to reaching 0.388 and 0.304. As a result of the irreversibility analysis, the ammonia generator, regenerative heat exchanger and the pressure reducing valve had the most improvement in their performances when applying the proposed modifications. Altogether, about 33% lower fuel consumption at the steam generator, once the steam demand significantly reduced to 1.66 kg.s−1 in comparison to original demand of 2.49 kg.s−1.