Experimental investigation of lubricant oil on a 3 kW organic Rankine cycle (ORC) using R123

The lubricant oil can prevent the leakages and reduce the expander friction losses, but blend with the pure working fluid because of the absence of oil separator and affect eventually the organic Rankine cycle (ORC) operation characteristic. Based on a 3 kW ORC experimental prototype, the effect of lubricant oil ratio (1.2%, 3.1%, 5.0%, 6.7% and 9.0%) using R123 on the system behavior under three different degree of superheating (5, 10 and 15 °C) has been investigated. The heat source temperature is fixed at 130 °C, while the mass flow rate is controlled by adjusting the pump frequency. The heat input is first amended, and the detailed components’ behaviors are examined. The system overall performance, including thermal efficiency and system generating efficiency is explored. Results demonstrated that the deviation between the calculated heat input and modified heat input is no more than 5%. The lubricant oil enhances the pump behavior, whereas deteriorates the expander shaft power and electrical power. Meanwhile, the thermal efficiency is insensitive on the lubricant oil ratio for a degree of superheating higher than 10 °C. The system generating efficiencies for degree of superheating of 10 and 15 °C are in range of 5.44–5.61% (3.03%) and 5.34–5.69% (6.15%), respectively.