Experimental investigation of nozzle structure and heat source parameters on the performance of organic Rankine cycle used for geothermal power generation system

Geothermal energy is widely distributed worldwide, and organic Rankine cycle (ORC) power generation technology is a feasible technology for utilizing low/medium temperature renewable heat sources. Multi practical factors can affect ORC performance, including thermodynamic parameters and components structure. In this study, a simulated heat source is employed to simulate geothermal energy. Experiments are carried out to investigate the influence of several practical factors in ORC, including heat source parameters, turbine nozzle number and turbine nozzle shape. The results show that turbine inlet with 6-nozzles demonstrates 10% higher efficiency than 4-nozzles, and reduces pump work consumption, ultimately increasing the network and thermal efficiency of ORC by 18.8% and 19.0%, respectively. For circular nozzle and square nozzle with the same turbine inlet area, the relationship between system flow rate and turbine inlet pressure is almost identical. But turbine efficiency is slightly improved using a square nozzle. Finally, results show that increasing the heat source temperature leads to the increase of turbine inlet pressure, while decreasing heat source mass flow rate can increase temperature drop of heat source. The research presented in this paper will further advance the application of ORC in geothermal power generation applications.