Experimental investigation of a small-scale Organic Rankine Cycle under off-design conditions: From the perspective of data fluctuation

The Organic Rankine Cycle (ORC) technology is applicable for conversion of low-grade waste heat to electric power. Off-design performance of ORC system is one of the research hotspot. In the present paper, a small-scale ORC experimental bench was constructed with a scroll expander whose nominal output power was 3 kW. Experimental data including thermodynamic parameters at inlet and outlet of the main components from 15 steady-state operation conditions were collected. Special attention has been paid to analyzing the amplitude of data fluctuation. Standard deviation has been introduced to quantify the fluctuation amplitude. The comparison between the accuracy of measuring sensors and the amplitude of data fluctuation was conducted. Moreover, critical parameters affecting the expander output power calculation were investigated. Results indicated that the largest amplitude of the measured pressure and temperature fluctuation were at the pump outlet and evaporator outlet respectively. Besides, the fluctuation amplitude of measured volume flow rate in gas phase was greater than the liquid phase due to strong turbulence of gas phase. Furthermore, the measured volume flow rate of working fluid had a vital effect on the calculated expander output power compared to the measured tempera. tures and pressures.