Matching and operating characteristics of working fluid pumps with organic Rankine cycle system

Highlights: • Comparison of operating characteristics of working fluid pumps for ORC is presented. • The impact of key parameters on each other and on the ORC performance is analyzed. • The optimum matching scheme between working fluid pumps and ORC is proposed. The present paper focuses on the comparative experimental operating characteristics of working fluid pumps used in the organic Rankine cycle (ORC) system with R245fa, including multistage centrifugal pump, hydraulic diaphragm metering pump, and roto-jet pump. Effects of mass flow rate and outlet pressure are investigated systemically on the performance of the three pumps. Further theoretical studies are conducted on the effects of various types of working fluid pumps on the system overall performance, such as exergy destruction rate, back work ratio (BWR), heat absorption rate, thermal and exergy efficiency, and net power output. Results show that the maximum actual efficiency of the three pumps can reach 58.76%, 55.26%, and 30.51%, respectively, when outlet pressure ranges from 0.4 to 1.1 MPa. A significant difference was observed between actual and theoretical BWR, which illustrates that the pump power cannot be ignored and lower pump efficiency has a negative impact on the increase in the net power output of the ORC system. Additionally, the selection of working fluid pumps has significant effects on the heat absorption rate. Consequently, the paper provides detailed and valuable insights into the selection of working fluid pumps for the ORC system with different heat capacities.