Operation and performance of a low temperature organic Rankine cycle

The test and analysis of an Organic Rankine Cycle (ORC) with R123 as the working fluid were presented in this paper. A scroll expander was integrated in the system to generate work. The expander was connected with an AC dynamometer unit, which was used to control and measure the expander shaft torque and rotating speed. The conductive oil simulated the low grade heat source. Operation characteristics were compared between the heat source temperatures of 140 °C and 160 °C. The experiments were conducted by adjusting two independent parameters: the pumping frequency of the R123 pump and the shaft torque of the expander. The former parameter was directly related to the R123 mass flow rate and the later to the external load. The optimum system performance can be determined by these two parameters. The maximum measured shaft power and thermal efficiency were 2.35 kW and 6.39% at the heat source temperature of 140 °C, but they were 3.25 kW and 5.12% at the heat source temperature of 160 °C. This study identified that the measured shaft power was about 15–20% lower than the enthalpy determined values, and the pumping power of the organic fluid was 2–4 times higher than the enthalpy determined values. The enthalpy determined values were based on the local pressure and temperature sensor measurements.