Experimental study and energy loss analysis of an R245fa organic Rankine cycle prototype system with a radial piston expander

In this paper, an R245fa organic Rankine cycle experimental prototype system with a 5-cylinders radial piston expander is presented to recovery waste heat from exhaust gas of diesel engine. In order to explore the system behavior and research the effective adjustment method, the performance was tested and analyzed with multiple operating parameters: pump speed, generator load, energy of waste heat source and working fluid filling quantity. Moreover, energy and exergy analysis were provided to evaluate the system energy loss. Combining simulation study of expander in GT-SUITE, the internal friction and leakage were calculated to illuminate the energy degradation processes of expansion. The experiments proved the feasibility of radial piston expander for organic Rankine cycle coupled to vehicle engine. The results demonstrate that expander power output can be optimized by adjusting pump speed under different heat sources and moderate filling quantity indicates the largest expander power output. The gross thermal efficiency and exergy efficiency of the organic Rankine cycle system can reach up to 2.02% and 10.5%, respectively. Overall system exergy losses are 4.24-4.63 kW and expander contributes about 1 kW. In the processes of expansion, entropy increment leads to larger energy degradation than working fluid flow loss and mechanical frictional loss. Under the influences of multiple energy losses, the maximum expander mechanical power output 279 W can be obtained.