A simulation model of Organic Rankine Cycle (ORC) was developed with HYSYS software driven by R245fa, with NOVEC7000 and R141b as working fluids and Fluegas of boilers as a heat source of shell and tube Heat Exchanger to generate large scale electricity. The initial working condition was in subcooled liquid and steady state condition. R141b was found to generate the highest electricity power increment in specific mass flow rates and inlet pressures of Expander because of approaching its critical temperature to inlet Fluegas temperature. Howeever, in terms of economic considerations and cost of shell and tube Heat Exchanger that related to total heat transfer capacity, NOVEC7000 is the optimum selection. Furthermore, R245fa has the highest total effiiciency of ORC compared with other working fluids in this study.
A model of Subcritical Organic Rankine Cycle (SORC) driven by trans-1, 3, 3, 3-tetrafluoroprop-1-ene, R1234ze(E) as a new-typed environmental friendly refrigerant working fluid, was developed and analyzed in the view of the 180-220°C wet fluegas combustion and burning from natural gas, as a low to medium temperature heat source without the outlet temperature limit to generate optimum power by a turbine. The net power output, total efficiency, fluegas outlet temperature, and exergy efficiency of current SORC system were studied based on variation of vapor generator outlet temperature and turbine outlet pressure as optimized parameters in terms of per mass flow rates of working fluid, heat source, and heat sink. Results show that the maximum net power output is 5.2675 MW and with increasing of mass enthalpy change and temperature in expansion process causes to increase of net power output, steadily. And the maximum net power output was 53.1% increased. Furthermore, by decreasing the turbine outlet pressure, the total efficiency of the current SORC system is increased to 0.08107 because of the increase of net power output. Likewise, the exergy efficiency of the SORC system increasing significantly, and received to the 0.328, because of increasing the enthalpy change and decreasing the entropy change of fluegas in the evaporator system.
The simulation configuration and process analysis of the Subcritical Organic Rankine Cycle (SORC) system are carried out for the potential comparison between pure, binary, and ternary zeotropic mixtures of R1234ze(E), R1234yf, and R134a as refrigerant working fluids based on applying the flue gas as a heat source with medium temperature. The compression pressure was selected as an optimized variable input parameter of SORC with the lower limit of boundary condition (1.4 MPa); to mitigate air ingress and sub-atmospheric pressure that led to approach optimum net power output generated. Increasing the compression pressure has a positive relationship with the superheated temperature and the mass enthalpy change in the evaporation and, therefore, in the expansion process. In parallel, the enthalpy and entropy changes in the flue gas and cold water positively correlate with exergy efficiency. So, R1234ze(E)/ R1234yf/R134a with 68.35% and R1234yf/ R134a with 69.29% as the lowest and highest exergy efficiency in the highest compression pressure; furthermore, the SIC consequences of increasing the cost of each component of the SORC system that has a direct relationship with the PPC and the required exchanger area of evaporation and condensation process and generating a net power output of the turbine. As a result, the maximum to the minimum value of specific investment cost (SIC) achieves R134a with 5807402.18-22455670.61 $.kW-1 and R1234yf with 16.82-17.38% reduction, respectively. To sum up, the lowest payback period (PBP) was R1234yf with 302 days.
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