Design and Analysis of the Scroll Expander with Next Generation refrigerant in an ORC

Abstract

Organic Rankine Cycle (ORC) system is used to extract the waste heat from low to medium temperature heat source. The ORC system works as a reverse process of refrigeration. It has the four basic components of Condenser, Refrigerant pump, Evaporator and the Expander. The waste heat is absorbed in the Evaporator and the energy gained is used to rotate the expander which generate the power. The Expander used in the ORC are of different types like the scroll, Screw, Rotary, Turbo. Various refrigerants are used as the working fluid in the ORC system depending upon its physical and thermodynamic properties like R134a, R245fa etc. R245fa is currently used refrigerant in the ORC system. In recent research and development of the refrigerants, R1233zd(E) is also having suitable properties to be used in the ORC system. This refrigerant has zero ODP and very low GWP. This research work includes the analytical and the CFD analysis over the working fluid in the Scroll Expander of the ORC system. The working fluids considered for the analysis is R245fa which currently has a wide usage, and another is R1233zd(E) which has the suitable properties for ORC and is a green refrigerant. A specification for ORC system is considered and the p-h chart is plotted on the refrigerant charts for R245fa & R1233zd(E). The Scroll Fluid Geometry is drafted using ANSYS Design Modeller & Mesh. The Analytical & CFD analysis method is used to find the Force, Torque & Power output parameters for both the refrigerants under consideration at different operating angular positions. The results projected using the Analytical & the CFD method is almost similar with slight variation. The efficiency and the power output using the refrigerant R1233zd(E) is slightly less in comparison with the refrigerant R245fa. Considering the power output results from the scroll expander with both the working fluid under analysis, the refrigerant R1233zd(E) is a good alternate working fluid over the refrigerant R245fa in the ORC system with its Zero ODP and low GWP with a slight compromise over the power output from the ORC system.