Influence of driving fluid properties on the performance of liquid-driving ejector

This study focuses on the influence of driving fluid properties on the mass transfer process of ejector apparatus. A liquid-actuated ejector system is firstly designed and three experimental cases working with different kinds of driving fluids, i.e., gallium-based liquid metal, aqueous NaI solution and water, are successively investigated. The results show that the ejector system working with liquid metal has high-vacuum ejecting capacity and good temperature stability. With a system power consumption of about 50 W, the liquid metal driving ejector obtains a no-entrainment vacuum pressure of 33 Pa which is three orders of magnitudes lower than that of the water driving case. When the gas-suction pressure exceeds 40 kPa, NaI solution driving case reveals the highest entrainment. The reasons for the differences in the ejector performance are later discussed. Based on the experimental results and theoretical analyses, the method of using high density, low viscosity and low vapor pressure working fluid to improve ejector performance is proposed. Other than conventional methods which focus on optimizing the geometrical design and operating parameters of ejectors, the method discussed here puts forward a new perspective to improve ejector performance. Moreover, the ejector system working with liquid metal demonstrates its advantages such as compact system design, oil-free vacuum pumping as well as high temperature operation.