Theoretical, CFD modelling and experimental investigation of a four-intersecting-vane rotary expander

Abstract

Expansion devices significantly impact the performance of the Vapor Compression Refrigeration system and Organic Rankine Cycles. Its improvement has been identified as one of the most crucial parts of future studies. The experiments were carried out using an improved experimental rig with direct coupling of the prototype and the dynamometer. This is done to correct any misalignments caused by external forces. The internal pressure in the working chambers was measured using six pressure transducers at various locations on the expander. A three-dimensional computational fluid dynamics and theoretical model was developed to investigate the effect of losses and inherent physical processes on the prototype. The actual geometry of the stator is taken in the computational fluid dynamics model. Conversely, employing the equation for an irregular stator shape in the theoretical model is difficult. Therefore, a circular stator is considered. The experimental results were used to validate the developed models. The prototype was tested up to 1550 rpm rotating speed, 5 bar (abs) suction pressure, and 1 bar discharge pressure (abs). The computational fluid dynamics and theoretical model results showed that though the volumetric and adiabatic efficiency was generally overpredicted, the trends were very closely predicted. The computational fluid dynamics and the theoretical model could predict the volumetric and adiabatic efficiency with a variance of <19.5% and 14.7%, respectively, for most of the experimental data points.