Modelling and optimisation on scroll expander for waste heat recovery organic Rankine cycle

Scroll expander has demonstrated high efficiency at low power range. In this paper, a generic model of a scroll expander has been developed. It can calculate the ideal expander parameters to give the optimal efficiency and prevent under- or over-expansion at any given operating conditions or fluids. The dynamic model was validated by predicting the ideal volumetric expansion ratio with ideal expansion ratio of 4.03 at 0.7 MPa pressure, and showed agreement with experimental data. The results suggested that the rate of scroll increase K in the geometric model has little effect on volumetric expansion ratio or ideal scroll length of the expander, but when expansion ratio is kept constant, lower K value results in lower leakage losses