Numerical　investigations　were　conducted　to　examine　the　heat　transfer　and　friction　performance　of　a　U-shaped　coolant　channel　with　dimple　structure　on　one　surface　of　the　channel.　The　SST　k-ω　turbulence　model　and　the　large　eddy　simulation　(LES)　were　both　adopted　in　the　calculation　to　analyze　the　effect　of　dimple　structure　on　the　heat　transfer　performance　at　different　Reynolds　numbers.　The　results　indicate　that　the　heat　transfer　coefficient　for　the　second　row　line　in　the　U　channel　is　much　higher　than　that　for　the　first　row　line,　and　the　secondary　flow　exists　near　the　180°　bend　and　the　heat　transfer　rate　is　higher.　Dimple　structure　can　enhance　the　heat　transfer　process　on　the　channel　surface　considerably.　In　the　flow　direction,　the　average　Nu　of　the　dimple　surface　decreases　gradually,　and　it　increases　dramatically　after　the　bend.　Moreover,　the　pressure　loss　caused　by　dimple　structure　is　small,　almost　approaching　that　of　smooth　channels.　The　Nu　calculated　by　the　SST　model　is　slightly　higher　than　that　by　the　LES　method,　and　the　reattachment　position　obtained　by　the　RANS　method　occurs　earlier　than　that　by　the　LES　method.