The parametric analysis on the system behaviors with scroll expanders employed in the ORC system: An experimental comparison

Organic Rankine cycle is a potential technology for the low-grade thermal energy utilization, which could assist the solution of electricity consumption. In this work, the experiments on the R245fa-ORC with a design capacity of 2 kW were presented, and different scroll expanders were considered in this experiment: a hermetic expander with the built-in volume ratio of 2.95, two open-drive expanders with the built-in volume ratio of 2.12 and 4.05. With the heat source temperature varying with 64.8 °C–98.2 °C, the parametric analysis of working fluid mass flowrate, the system pressure difference, and the superheat temperature on the isentropic efficiency, specific enthalpy difference, and output of the expanders are compared, and the overall system thermal efficiency are evaluated. The results show that the expander with larger built-in volume ratio is more adaptable in ORC with higher system pressure difference, and the medium Vr3 expander experts a favorable behavior with the system pressure difference of 0.3 MPã0.6 MPa. Besides, the thermal efficiency of the Vr4-ORC obtains 9.0% with the highest system pressure different of 0.7 MPa, which approach to the Carnot efficiency of 20.3%. This finding could support the scroll expander selection in the commercial ORC development.