Investigation and numerical simulation of two-phase ejectors for use in the water desalination cycle

Abstract

This study investigates enhancing energy efficiency in desalination by introducing a novel combined ejector-solar vacuum tube collector cycle. The cycle utilizes a two-phase state and lower-temperature saturated steam generation to overcome the energy consumption hurdle, particularly by compressors. Water enters the ejector's primary nozzle in a liquid phase, while steam from the solar collector aids in separation, yielding desalinated water in a variable phase. Fluent software's computational fluid dynamics assesses the ejector's performance, considering primary and secondary inlet pressures' impact on hydrodynamic characteristics. TRNSYS software models the cycle transiently over a year in Tehran, exploring different pressures' effects on fluid behavior. Results indicate that increasing secondary nozzle pressure at constant primary pressure significantly boosts steam flow rate and inlet velocity. The investigation covers secondary inlet pressures ranging from 7000 Pa to 39,000 Pa and primary nozzle pressures between 200,000 Pa and 500,000 Pa, studying their impact on fluid behavior. Under Tehran's climatic conditions, the proposed cycle achieves a peak output rate of 1.35 kg/m2/h, a maximum daily yield of 8.47 kg/m2, and a total annual output of 767 kg/m2 for desalinated water. This innovative approach showcases promise for energy-efficient desalination, especially in regions with solar potential like Tehran.