A New Absorption–compression Refrigeration System Using a Mid-temperature Heat Source for Freezing Application

The use of an absorption refrigeration system is a promising way to utilize waste heat from industrial processes. Ammonia–water absorption refrigeration system is commonly used for freezing applications with temperatures lower than 0 °C. When the refrigeration temperature is lower than -30 °C, the performance dramatically decreases. We proposed a new absorption–compression refrigeration system to produce cooling energy at -30 °C to -55 °C. The proposed system comprised three subsystems, namely, a power generation subsystem using an ammonia–water mixture as the working fluid, an ammonia–water absorption refrigeration subsystem, and a CO2 compression refrigeration subsystem. The system utilized the heat source in a cascade manner. The power subsystem converted the high-temperature portion of heat into power to drive the CO2 compression refrigeration subsystem, thereby resulting in the generation of low-temperature cooling energy. The low-temperature portion of heat is converted into cooling energy to offer the heat sink of the CO2 compression refrigeration subsystem. A simulation study was conducted, and results showed that the coefficient of performance of the proposed system was 0.277, which was approximately 50% higher than that of a conventional two-stage absorption refrigeration system. This work may provide a new way to produce low-temperature cooling energy using mid-temperature heat source.