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Evaluation of the integration of an ammonia-water power cycle in an absorption refrigeration system of an industrial plant

Higa, Márcio, Yamamoto, Eduardo Y., Oliveira, Júlio César D. de, Conceição, Wagner André S.
Energy conversion and management 2018 v.178 pp. 265-276
absorption, case studies, energy efficiency, evaporators, exergy, generators (equipment), power generation, refrigeration, steam, temperature
Combination of binary components used for absorption refrigeration systems as ammonia-water can also be applied as working mixture for power generation in a Kalina Cycle, providing an interesting option in the use of energy sources at low temperatures. Using this possibility in a power-cooling cogeneration system, Kalina Cycle (KC) was proposed to be integrated in an ammonia-water absorption refrigeration system (AARS) of 1269 kW of cooling at 219 K, in order to take better advantage of the available energy from a steam generator in an industrial plant, used as a case study. The AARS uses water steam as hot utility, after the expansion in a pressure reducing valve from higher pressure. Applying exergy analysis, it was verified that the combined KC-AARS, besides the power generation, can decrease the exergy destruction in the AARS. For that, due to the very low working temperatures, the AARS involving double absorbers and evaporators, condenser and expansion valves in a complex system and its peculiarities were practically preserved at lower pressure levels, integrating the KC basically in the higher pressure levels, which is a very interesting proposal for existent systems. The results showed the possibility to reduce the exergy destruction in 43.3%, from 1614 to 915.8 kW, and to produce 493 kW of power generation. In addition, increases in the coefficient of performance from 0.256 to 0.376, energy efficiency of refrigeration from 0.297 to 0.360 and exergy efficiency from 0.185 to 0.468 were reached at 4.7 MPa of working pressure.