To　clarify　the　underlying　principle　of　heat　transfer　enhancement　in　a　steam-cooled　square　ribbed　channel,　the　flow　field　and　heat　transfer　characteristics　of　a　square　ribbed　channel　were　numerically　simulated　by　3-D　steady　RANS　equations　coupled　with　standard　k-ω　turbulence　model.　The　influences　of　Reynolds　number,　inlet　aspect　ratio　and　rib　pitch　on　the　flow　and　heat　transfer　characteristics　were　investigated,　the　heat　transfer　correlation　of　square　ribbed　channel　was　analyzed,　and　then　the　relationship　of　Nusselt　number　with　Reynolds　number,　inlet　aspect　ratio　and　rib　pitch　was　obtained.　The　result　indicates　that　heat　transfer　enhancement　is　caused　by　the　existence　of　ribs　which　destroy　the　thick　heat　transfer　boundary　layer.　As　Reynolds　number　grows　up,　the　average　Nusselt　number　and　thermal　enhancement　factor　increase　while　the　friction　factor　increases　slightly.　Larger　inlet　aspect　ratio　also　leads　to　greater　thermal　enhancement　factor　and　better　average　Nusselt　number,　and　the　friction　factor　also　increases　obviously.　The　increase　of　rib　pitch　results　in　a　growing　average　Nuusselt　number.　When　the　rib　pitch　increases,　the　friction　factor　increases　firstly　and　then　decreases,　while　thermal　enhancement　factor　decreases　firstly　and　then　increases.　©　2016,　Xi＇an　Jiaotong　University.　All　right　reserved.