A flexible and multi-functional organic Rankine cycle system: Preliminary experimental study and advanced exergy analysis

In the present study, a novel and flexible experimental facility of an organic Rankine cycle system is constructed. Four extra heat exchangers than traditional test bench are equipped for the system performance testing with different evaporator and condenser or heat transfer examinations of the evaporator and condenser. The combination of an expansion valve and a cooler is designed to simulate the expander with desired type and expansion characteristic. Meanwhile, a scroll expander is installed in parallel. Preliminary investigations are motivated to explore the operating characteristics of the novel experimental facility under different conditions and to quantitatively discover the system improvement potentials for further optimizations. After the steady-state operation evaluation, the system is investigated by varying the heat source temperature and heat sink temperature as well as the working fluid pump stroke. The constant expander isentropic efficiency scenario is simulated through the combination of the expansion valve and cooler, and it is also validated by the installed expander. Results show that the power output of the system and electricity consumption of the working fluid pump are in the ranges of 2.42-3.55 kW and 0.44-0.49 kW, respectively, and the system thermal efficiency varies from 5.2% to 7.3%. Moreover, the system is then deeply explored by using exergy analyses to reveal the potential for performance improvement. The conventional exergy analysis tells that the evaporator has the largest exergy destruction. However, the advanced exergy analysis gives a more realistic improvement potential and suggests that the expansion process should be firstly improved.