Modeling and Experimental Activities on a Small-scale Sliding Vane Pump for ORC-based Waste heat Recovery Applications

Abstract

Pumping work in energy recovery units based on Organic Rankine Cycles (ORC) can severely affect the net power output recovered. Nevertheless, in recent years scientific and industrial communities mainly focused on expanders’ development. In order to address this lack of know-how and equipment, the current paper presents the development of a positive displacement ORC pump based on the sliding vane rotary technology. The machine was installed in a power unit for low-medium grade thermal energy recovery that operated with oil at 70-120°C as upper thermal source and tap water as lower one. Working fluid was R236fa while cycle pressure ratio ranged from 2.8 to 3.7. The ORC pump was also tested at different revolution speeds such that mass flow rate varied between 0.05 kg/s and 0.12 kg/s. These experimental data were further used to validate a comprehensive one-dimensional model that takes into account fluid dynamic filling and emptying processes, closed vane transformation and leakages at blade tip, rotor slots and end walls clearances. Viscous and dry friction phenomena occurring between components in relative motion were additionally considered. A full operating map of the sliding vane pump was eventually retrieved to explore multiple off-design operating conditions. The parametric and modular structure of the model will act as a design platform to outline enhanced ORC sliding vane pump prototypes.