Accidental　release　of　pressurized　CO2　pipeline　in　carbon　capture　and　storage　involves　the　interaction　of　phase　change　and　heavy-gas　dispersion.　However,　the　effect　of　the　phase　change　of　water　vapor　in　air　on　the　performance　of　cold　CO2　dispersion　is　usually　neglected.　In　this　study,　a　three-dimensional　two-phase　computational　fluid　dynamics　(CFD)　model　is　developed　to　evaluate　the　cold　CO2　dispersion　by　considering　the　phase　change　of　water.　A　phase-change　model　based　on　the　homogeneous　relaxation　model　is　used　to　describe　the　evaporation　and　condensation　of　water.　The　effects　of　terrain　roughness,　atmospheric　stability,　and　turbulence　models　on　the　dispersion　are　also　considered.　The　numerical　results　show　that　the　model　that　uses　the　k–ω　turbulent　equations　is　superior　to　the　other　models.　The　results　in　which　the　phase　change　of　water　is　considered　exhibit　a　better　agreement　with　the　data　from　the　experiments　than　those　that　do　not　consider　it.　The　model　is　subsequently　used　in　urban　areas,　which　results　in　over-predicted　CO2　concentration　in　the　near　field　and　under-predicted　CO2　concentration　in　the　far　field　when　the　phase　change　of　water　vapor　is　considered　than　that　when　it　is　neglected.　Therefore,　we　proposed　that　the　phase　change　of　water　vapor　in　the　atmosphere　should　not　be　overlooked　in　the　more　accurate　modeling　of　cold　CO2　dispersion.　©　2021　Institution　of　Chemical　Engineers