Energy and exergy investigation of a hybrid refrigeration system activated by mid/low-temperature heat source

• Proposed an ammonia–water hybrid refrigeration system activated by flue gas.
• The flue gas heat is utilized in cascade to generate refrigerant vapor.
• The compressor is driven by the power generated by the turbine in the system.
• Energy and exergy analyses illustrate the energy utilization and exergy distribution of the system.
• Investigated the effects of key parameters on the system performance.

This study proposes a hybrid refrigeration system activated by mid/low-temperature sensible heat source with ammonia–water (NH3–H2O) binary mixture as working fluid. The heat source is utilized in cascade in the hybrid system. This heat source is used to generate a superheated NH3–H2O mixture vapor, which is used successively in the power generation and compression subsystem and in the absorption and rectification subsystem to produce refrigerant vapor. Energy and exergy analysis results show that the Coefficient Of Performance, System Coefficient Of Performance, and exergy efficiency of the proposed system in the base case are 0.722, 0.485, and 23.1%, respectively. Effects of turbine inlet pressure, turbine outlet pressure, and solution concentration in the power generation subsystem on system performance are examined. This study provides a new refrigeration method to effectively utilize mid/low-temperature sensible heat.