Working fluid selection for a high efficiency integrated power/cooling system combining an organic Rankine cycle and vapor compression-absorption cycles

This paper presents the performance evaluation of several combinations of working fluids for a new heat recovery cogeneration system which combines an Organic Rankine Cycle (ORC), a Vapor Absorption Cycle (VAC) and a Vapor Compression Cycle (VCC). NH3–NaSCN is chosen as the working fluid in the VAC. Seven different refrigerants in the ORC-VCC were studied to identify the fluid that would allow the overall system to achieve a high efficiency in the tropical region. These fluids were chosen because of their low Global Warming Potential and Ozone Depletion Potential. A thermodynamic simulation allowed to set the appropriate operating conditions of the VAC. Subsequently, energy and exergy analyses showed that R717 is the appropriate working fluid for system operation in the tropical region. For this fluid, the highest values of cooling capacity, net power output, thermal efficiency, exergy efficiency and exergy destruction of the system were respectively 1205 kW, 158.3 kW, 64.32%, 39.39% and 690.4 kW for VCC evaporation temperature of 15 °C, for ORC-VCC condensation temperature of 40 °C and for ORC steam generator outlet temperature of 219.7 °C. The most exergy-destroying components are the steam generator and the ORC/VCC condenser with 57.29% and 22.58%, respectively. •Vapor recovery at the turbine outlet improves overall system performance.•Electricity produced is not influenced by the operation of the VAC cycle.•For R717, cold production slightly increases with ORC/VCC condensation temperature.•Cold is produced by the VAC by recovering the waste heat at the turbine outlet.