Submerged　steam　jet　in　subcooled　water　flow　is　widely　used　in　many　industrial　processes.　When　non-condensable　gas　is　involved　in　the　steam　jet,　the　mechanisms　of　heat　and　mass　transfer　become　more　complicated　due　to　the　added　non-condensable　components　and　the　strong　effect　of　water　turbulence.　In　present　work,　a　three-dimensional　steady　numerical　simulation　is　conducted　to　study　the　steam　jet　condensation　in　subcooled　water　flow　in　a　vertical　pipe　with　the　presence　of　non-condensable　gas　based　on　inhomogeneous　multiphase　model.　The　effects　of　non-condensable　gas　on　steam　plume　shapes,　distributions　of　static　pressure,　velocity,　temperature　and　heat　transfer　characteristics　are　investigated.　As　air　contents　increases,　steam　plume　transforms　from　ellipsoidal　shape　to　divergent　shape　and　the　peak　value　of　static　pressure　decreases.　The　mechanism　of　the　peak　phenomenon　of　static　pressure　at　the　end　of　steam　plume　is　revealed　to　be　the　squeezing　effect　of　water　flow　towards　the　nozzle　axis.　Since　air　mass　fraction　rises　to　1%–9%,　the　average　heat　transfer　coefficient　declines　by　24.5%–54.9%.　The　local　heat　transfer　coefficient　is　evaluated　by　using　thermal　equilibrium　model　at　phase　interface.　Numerical　results　show　a　self-intensifying　effect　on　heat　transfer,　indicating　that　the　distribution　of　local　heat　transfer　coefficient　is　highly　similar　to　that　of　water　turbulent　kinetic　energy　near　phase　interface,　decreasing　first　and　then　rising　to　a　high　level　at　the　tail　of　steam　plume.　The　local　heat　transfer　coefficient　and　steam　condensation　rate　decrease　with　air　concentration　and　increase　with　water　mass　flow　rate.　©　2021　Elsevier　Masson　SAS