Experimental investigation on steady and dynamic performance of organic Rankine cycle with R245fa/R141b under different cooling and expander speed conditions

Highlights: • A kW-scaled ORC system using zeotropic mixture R245fa/R141b and R245fa is studied. • Steady performance and dynamic behavior of ORC are experimentally investigated. • The effects of coolant flow rate and expander speed on system performance are studied. • ORC system using R245fa and R245/R141b have the same response speed. A kW-scaled organic Rankine cycle (ORC) experimental apparatus with a modified scroll compressor as the expander was established to investigate its operation characteristics. The test rig uses steam with a temperature of about 110°Cfrom a 30 kW electric steam generator as the heat source. In this study, the steady-state performance and dynamic response of R245fa/R141b (mass ratio 0.5/0.5) and R245fa under variable cooling water flow rate and expander rotational speed are experimentally studied. In the steady-state experiments, system thermal efficiency decreases with the increase of expander rotational speed. The mechanical efficiency of scroll expander is in the range of 91%–99%. Additionally, the maximum shaft power and isentropic efficiency of the expander and thermal efficiency of ORC system with R245fa/R141b are 831 W, 58%, and 5.2%, respectively. Compared with R245fa, the maximum shaft power and thermal efficiency of R245fa/R141b are increased by 9.9% and 13.0%, respectively. In the dynamic experiment, the disturbance of rotational speed and cooling water flow rate has little influence on the inlet temperature of expander. Under the disturbance of the rotational speed, the response time of shaft power, torque and speed of expander is in the range of 1–5s. The dynamic response of the ORC system is mainly controlled by the condenser and pump. Under the disturbance of coolant flow rate, the response time of pump inlet temperature and outlet temperature is about 350s and 600s, respectively. The ORC system using R245fa and R245/R141b have the same response speed.