Relation between entrainment performance and mixing efficiency in solar-desalination steam ejector with non-equilibrium phase transformation

Non-equilibrium phase transformation of condensable gas greatly affects the mixing efficiency and thus the entrainment performance of steam ejector in solar-driven desalination system, but their underlying relation remains unclear. In this study, a novel ejector model integrating non-equilibrium phase transformation with species transport is established. The transonic phase-changing mixing flow characteristics inside steam ejector are explored from multiple perspectives, with emphasis on how operating parameters affect the mixing layer development and mass transfer laws. Results revealed that phase transformation hinders the secondary fluid permeation into the primary jet flow, and the original exponential development of mixing layer disappears. The mixing layer growth and the entrainment performance of ejector largely governed by the mass transfer capacity, and a strong linear correlation exists among the entrainment ratio ε , non-mixing length λ l and mass transfer ratio λ ṁ . The three peak at a primary fluid pressure P p of 460 kPa before declining, increase distinctly with secondary fluid pressure P s , and remain constant until the back pressure P b exceeds its critical value. Across the tested ranges of P p , P s and P b , λ ṁ increases by up to 212.5% and 168.8%, and decreases by up to 95.6%, respectively. In the two-phase ejector, a mixing layer forms at the interface of two fluids, with its thickness increasing approximately linearly downstream. Concurrently, the entrainment ratio ε , non-mixing length λ l and mass transfer ratio λ ṁ exhibits similar variation trends, in contrast to the inverse behavior of the compressibility coefficient. Moreover, there exists a high linear correlation between ε / λ l and λ ṁ . The mixing layer growth and the entrainment performance of ejector largely depend on the mass transfer capacity. • A novel ejector model considering phase transformation and species transport. • Visualization of mass transfer accompanying non-equilibrium phase transformations. • Elucidating impact of non-equilibrium phase transformation on mixing layer growth. • Clarifying regular pattern of entrainment ratio, mixing layer and mass transfer. • Establishing relationship between mixing efficiency and ejector performance.