Energy Performance and Fluid Leakage in Rotary Volumetric Machines at Off-Design Operating Conditions

The main purpose of the present paper is to establish a thermodynamic model to examine the energy advantages of rotary machines when used as volumetric expanders. The screw expander is a particular volumetric machine which can exploit energy in working fluids of high temperature and pressure to produce mechanical power without high fluid velocities. In this research, to describe the real expansion process of the screw expander, a part-load numerical model is investigated also considering all the energy losses which affect thermodynamic performance at off-design working conditions (including fluid leakage losses). An energetic assessment of the part-load behavior is then performed to predict best working conditions of the screw expander.