Abstract：To investigate the effects of non-condensable gas (NCG) content on direct contact condensation (DCC) characteristics in a water-driven steam ejector, a numerical model incorporating gas–liquid two-phase flow, species transport, and interphase heat and mass transfer was developed. The velocity, pressure, temperature, and steam volume fraction distributions within the ejector were comparatively analyzed under different NCG contents. The results indicate that increasing the NCG content suppresses interfacial heat and mass transfer, reduces the steam condensation rate, and significantly alters the pressure recovery process. Meanwhile, the accumulation of NCG weakens heat and mass exchange between the steam and liquid phases, thereby deteriorating the overall condensation performance of the ejector. It is concluded that NCG content is a key factor affecting the direct contact condensation characteristics of water-driven steam ejectors, and that maintaining an appropriate NCG content is beneficial for enhancing the condensation process and improving the overall operating performance of the ejector.

Steam ejector,Steam condensation,Entrainment ratio,Non-condensable gas