Initial Design of an Optical-Access Piston Expansion Chamber for Wet-Expansion

Abstract High efficiency expanders which can cope with fluid-vapour mixtures (i.e wet expansion) at the inlet and during expansion have the potential to increase the power output from thermodynamic power cycles. Volumetric expanders are considered suitable, yet experimental results are scarce and there is no model that can predict the performance of the expansion process. This is mainly due to the knowledge gap on the fundamental aspects off two-phase expansion and the non-equilibrium effects. Therefore, in this work, a variable volume piston expansion chamber is designed. The influence of the main design parameters are investigated by means of a simple deterministic model. Based on initial figures of merit, the component selection and technical layout is presented. The optical access in a later stage will be crucial to allow investigating the mechanistic process of the nucleation and the interfacial effects. This understanding is essential for generalization of the results to other working fluids and geometries.