Numerical simulation and optimal design of scroll expander applied in a small-scale organic rankine cycle

As an important component in the organic Rankine cycle (ORC), the operation characteristics of the scroll expander directly determine the ORC efficiency. In this study, numerical simulation and optimal design of scroll expander applied in a small-scale organic Rankine cycle are conducted. The expander unsteady flow characteristics using R245fa are examined. The dynamic mesh technology is applied to accurately achieve the eccentric motion of the orbiting scroll. The effects of four key parameters (inlet temperature, inlet pressure, outlet pressure and rotation speed) on the expander output power and isentropic efficiency are discussed. Considering maximum isentropic efficiency and maximum expander output power simultaneously, the optimal solution using response surface methodology (RSM) is yielded. Results indicate that the distribution of velocity and pressure in different working chambers are not completely symmetric, and the expander isentropic efficiency can be significantly improved by changing the boundary conditions. The maximum output power and isentropic efficiency are 2.458 kW and 72.98%, which deviates from the simulated value by 6.51% and 5.12%, respectively.