A　novel　microchannel　heat　sink　with　triangular　cavities　and　rectangular　ribs　(TC-RR)　is　presented　and　the　characteristics　of　fluid　flow　and　heat　transfer　are　studied　numerically　for　Reynolds　number　(Re)　ranging　from　173　to　635.　The　effects　of　cavities　and　ribs　on　the　Nusselt　number　and　friction　factor　are　investigated.　The　method　of　entropy　generation　minimization　is　also　adopted　to　analysis　the　thermal　performance　of　the　micro　heat　sink　and　the　mechanism　of　heat　transfer　enhancement.　The　overall　performance　of　the　new　micro　heat　sink　is　assessed　based　on　thermal　enhancement　factor　and　augmentation　entropy　generation　number.　The　results　show　that　the　TC-RR　microchannel　obtains　significant　heat　transfer　enhancement　attributed　to　the　interruption　and　redevelopment　of　thermal　boundary　layer,　the　intensified　mainstream　disturbance　and　the　chaotic　mixing　between　the　cold　and　hot　water.　In　addition,　the　influence　of　relative　rib　width　(alpha)　and　relative　cavity　width　(beta)　on　the　flow　and　heat　transfer　performance　is　investigated.　The　thermal　enhancement　factor　for　TC-RR　microchannel　with　alpha　=　0.3　and　beta　=　2.24　achieves　1.619　at　Re　=　500.　Due　to　more　uniform　temperature　of　bottom　surface,　less　irreversibility　and　better　heat　transfer　performance,　the　novel　micro　heat　sink　is　more　promising　for　microelectronic　cooling　system.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.