Parametric optimization and performance analysis of a regenerative Organic Rankine Cycle using R-123 for waste heat recovery

This paper presents an analysis of regenerative Organic Rankine Cycle (ORC), based on parametric optimization using R-123 and R-134a during superheating at a constant pressure of 2.50 MPa under realistic conditions. The aim was to select a better working fluid on the basis of obtained system efficiency, turbine work output, irreversibility rate and second law efficiency under applied fixed and variable heat source temperature conditions. R-123 has been found a better working fluid than R-134 for converting low grade heat to power. A computer program has been developed to parametrically optimize and compare the system and second law efficiency, turbine work output, system mass flow rate, irreversibility rate and irreversibility ratio with increases in turbine inlet temperature (TIT) under different heat source temperature conditions to obtain the optimum operating conditions while using R-123 as the working fluid during superheating at various turbine inlet pressures for the utilization of the waste heat sources of temperatures above 150 °C. The calculated results reveal that an inlet pressure of 2.70 MPa gives the maximum system efficiency, turbine work output and second law efficiency with minimum irreversibility rate, irreversibility ratio and system mass flow rate up to a TIT in the range of 165 °C–250 °C.

► Analysis of regenerative ORC using R-123 during superheating at various TIP.
► Compared efficiencies, irreversibility ratio, work output etc. with increase in TIT under different heat source temperature.
► For variable heat source, the temperature of heat source is kept 15 °C above TIT.
► Obtained the optimum operating conditions for the utilization of waste heat sources above 150 °C.
► A TIP of 2.70 MPa at TIT in the range of 165 °C–250 °C is optimum for converting low grade waste heat to power.