Impact of major leakages on characteristics of a rotary vane expander for ORC

Volumetric expanders are used for low to medium power output ORC applications. For low power output ORCs ( This work describes a semi-empirical model with two different leakages – lumped leakage area between inlet and outlet and leakage between working chambers due to delayed contact of vane and stator. Primary purpose of the model is to demonstrate the effect of the delayed chamber closure. This is identified as a necessary parameter for modeling of the rotary vane expanders, compared to only single lumped leakage area for the other expander types. Results of the model for several case scenarios are presented, showing an impact of these leakages on an overall cycle performance, isentropic efficiency and filling factor. It is demonstrated that isentropic efficiency of the rotary vane expander might not be always sufficient to compare vane expanders or their modifications even within a same ORC. Lastly the model conclusions are preliminarily checked with our experimental data.