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An absorption–compression refrigeration system driven by a mid-temperature heat source for low-temperature applications

Chen, Yi, Han, Wei, Jin, Hongguang
Energy 2015 v.91 pp. 215-225
absorption, energy conservation, exergy, flue gas, freezing, heat, power generation, process energy, refrigeration, temperature, wastes
An ammonia–water absorption refrigeration system is a promising way to make use of waste heat to generate cooling energy for freezing applications. When the refrigeration temperature is below −30 °C, the conventional absorption system cannot be adopted because its performance decreases dramatically. In this work, a totally heat-driven absorption–compression refrigeration system is proposed to produce cooling energy at temperatures of −40 °C to −55 °C. The proposed system comprises a heat-driven power generation subsystem using an ammonia–water mixture as the working fluid and an absorption–compression refrigeration subsystem. Simulation results showed that the coefficient of performance and the cooling capacity per unit mass of flue gas reach 0.357 and 84.18 kJ kg⁻¹, respectively. The results of a process energy analysis showed that the cycle coupling configuration of the proposed system enhances its energy cascade utilization. Furthermore, the energy saving mechanism of the proposed system was elucidated by means of an exergy analysis and a pinch point analysis. Finally, a more comprehensive comparison with a heat-driven double-stage compression refrigeration system was conducted to show the advantage of the proposed system. This work may provide a new way to produce low-temperature cooling energy by using a mid-temperature heat source.