Experimental Results of A Novel Two-Phase Water Ejector Design for High-Temperature Heat Pump Applications

Abstract

High-temperature heat pumps (HTHPs) are a key technology for decarbonizing industrial process heat. Within such systems, two-phase water ejectors offer a promising opportunity to function as secondary steam compressors. By entraining hot steam with high-pressure water, they enable simultaneous cooling and pressure increase, thereby reducing power consumption and the number of mechanical compressor stages required. This integration can enhance the energy efficiency and economic viability of HTHPs.

However, the internal flow dynamics of two-phase ejectors remain insufficiently understood, particularly under high-pressure and high-temperature operating conditions relevant for heat pump applications. In the mixing region, where the two-phase flow approaches critical conditions, the speed of sound is affected, potentially giving rise to shock structures and variations in thermophysical properties. The lack of experimental insights into these phenomena limits reliable design and optimization of ejectors for industrial applications.

This paper investigates the experimental characterization of two-phase water ejectors to support their integration into HTHP systems. A novel closed-loop experimental facility has been developed, enabling continuous operation over representative water and steam conditions. The facility integrates designs for the nozzle and mixing chamber, a water separation and condensation system, and sensors and control strategies. The ejector is based on prior CFD simulations, enabling comparison with simulations. Initial tests provide pressure and entrainment ratios. The results deliver new ejector component designs, an experimental methodology, and initial data that deepen the understanding of two-phase ejector behavior and support their optimized application in advanced HTHP systems.