Screening of waste-heat-driven ejector chillers using a state-based ejector model validated against industrial performance data.

A state-based thermodynamic ejector model is presented and validated against performance data from industrial-grade ejectors for both dry and wet refrigerants. Thermodynamic properties are calculated using the most accurate equation of state available for each fluid, accounting for possible partial condensation. Using the validated model, a screening analysis of ejector chiller architectures and natural refrigerants is performed. We consider cooling at both 0 ◦C and −10 ◦C for generator temperatures below 150 ◦C and condenser temperatures in the range 10–30 ◦C. Our work focuses on the natural refrigerants water, ammonia, methanol, cyclopentane, isobutane and propane. We find that water, ammonia and methanol generally have higher coefficients of performance (COPs) than the hydrocarbons, partly because the latter are superheated at the ejector outlet. The remaining performance variation indicates that COP generally increases with the critical temperature and pressure of the refrigerant, consistent with conclusions drawn previously for other refrigeration cycles. Volumetric refrigeration capacity is also considered, and we find that ammonia and propane exhibit roughly two orders of magnitude higher capacity than methanol and water. The single-stage ejector chiller and a cascade ejector chiller are the recommended cycle architectures for cooling at 0 ◦C and −10 ◦C, respectively. This work emphasizes the importance of calibrating ejector models to state-of-the-art industrial performance data for reliable screening of ejector cycles.