Effects of variable operating conditions of working fluid pumps on the performance of organic Rankine cycle system

Organic Rankine cycle (ORC) system has been widely used in industries due toits superior performance. The working fluid pump, providing the mass flow rate and the evaporation pressure of the ORC system, is one of important components in the system. In addition, the performance of working fluid pumps also has significant effects on the component and overall system performance. In this paper, the effects of different thermal parameters on the pump electric power input of unit mass flow and back work ratio (BWR) were analyzed. Furthermore, the experiment was conducted under simulative ORC conditions by using R245fa and condensing temperature of 303K. The experimental operating characteristics of two different types of working fluid pumps (multistage centrifugal pump and hydraulic diaphragm metering pump) were analyzed and its effects on the performance of ORC system were presented. Results showed that the mass flow rate delivered by the hydraulic diaphragm metering pump was low and was not significantly affected by the variation of outlet pressure. The maximum electric power input was only 360.34W, which was 16.29% of the multistage centrifugal pump. Their actual operation efficiency changes with operating conditions were up to 59.96% and 55.26%, respectively. By the theoretical calculation, the BWR for the ORC system using the two pumps varied between 0.03 and 0.48. And the maximum thermal efficiency could reach up to 11.66%, 10.35%, respectively. The hydraulic diaphragm metering pump is more suitable to the low mass flow ORC system. © 2019, Chemical Industry Press. All right reserved.