Performance analysis of a combined organic Rankine cycle and vapor compression cycle for power and refrigeration cogeneration

• Waste heat utilization can reduce emissions of carbon dioxide.
• The ORC/VCC cycle can deliver power and/or refrigeration using waste heat.
• Efficiencies and size parameters are used for cycle evaluation.
• The cycle performance is studied for eight suitable refrigerants. Isobutane is used for a sensitivity analysis.
• The work shows that the isobutene cycle is quite promising.

A thermodynamic analysis of cogeneration of power and refrigeration activated by low-grade sensible energy is presented in this work. An organic Rankine cycle (ORC) for power production and a vapor compression cycle (VCC) for refrigeration using the same working fluid are linked in the analysis, including the limiting case of cold production without net electricity production. We investigate the effects of key parameters on system performance such as net power production, refrigeration, and thermal and exergy efficiencies. Characteristic indexes proportional to the cost of heat exchangers or of turbines, such as total number of transfer units (NTUtot), size parameter (SP) and isentropic volumetric flow ratio (VFR) are also examined. Three important system parameters are selected, namely turbine inlet temperature, turbine inlet pressure, and the flow division ratio. The analysis is conducted for several different working fluids. For a few special cases, isobutane is used for a sensitivity analysis due to its relatively high efficiencies. Our results show that the system has the potential to effectively use low grade thermal sources. System performance depends both on the adopted parameters and working fluid.