Heat　transfer　capacity　of　compact　heat　exchanger　is　critical　for　applications　with　confined　space　and　with　large　heat　duty,　in　order　to　maintain　the　safety　and　efficiency　of　equipment.　As　a　high-efficient　and　energy-saving　compact　heat　exchanger,　microchannel　heat　sinks　have　attracted　extensive　attention　from　both　academics　and　industries.　However,　the　development　of　thermal　boundary　layer　in　microchannel　reduces　the　efficiency　of　heat　transfer.　Therefore,　extensive　efforts　have　been　paid　to　improve　the　heat　transfer　performance　in　microchannel,　for　example,　through　incorporation　of　periodic　rough　elements　of　pin-fin,　groove,　rib　and　protrusion,　which　could　disrupt　the　development　of　thermal　boundary　layer　and　induce　secondary　flow　for　thorough　mixing　between　near-wall　hot　fluid　and　main　fluid.　Despite　of　superiority　in　the　microchannel　heat　sink　with　protrusion,　further　structural　optimizations　are　necessary　to　reduce　resistance　and　enhance　the　heat　transfer　efficiency.　Investigations　on　the　flow　resistance　of　shark,　as　well　as　the　geometry　of　sharkskin,　show　that　the　discrete　gap　and　hump　of　sharkskin　reduce　the　flow　resistance.　Therefore,　the　split　protrusion　was　proposed　in　this　work,　which　was　based　on　the　common　protrusion　and　shark　skin　bionic　concept.　And,　the　detailed　flow　structure　and　heat　transfer　mechanisms　of　microchannel　heat　sinks　with　split　protrusion　were　studied.　Transitional　periodic　boundary　conditions　were　applied　at　the　inlet　and　outlet　with　water　as　the　working　fluid,　and　the　Reynolds　number　(Re)　at　the　inlet　were　varied　from　50　to　350.　Moreover,　a　uniform　constant　heat　flux　of　q＇＇=5×105　W　m-2　and　no-slip　boundary　condition　were　specified　at　other　surfaces　of　the　microchannel.　Furthermore,　to　avoid　local　hot　spot　of　microchannel　surfaces　due　to　the　existence　of　non-uniform　temperature　distribution,　the　temperature　uniformity　was　discussed　as　well.　The　results　show　that　thermal　performance　(TP)　increases　with　the　increase　of　Re　and　the　superior　heat　transfer　capacity　is　reached　when　the　split　width　is　10　μm.　In　this　study,　the　largest　TP　is　185.3%　at　the　case　of　Plan　A　with　Re=350　and　10　μm　split　width,　where　the　relative　friction　factor　(f/f0)　is　much　large.　As　the　width　of　split　increases　to　15　μm　in　Plan　A,　its　f/f0　significantly　decreases　but　the　thermal　performance　is　relative　large.　Moreover,　f/f0　is　also　smaller　than　others　at　the　case　of　Plan　B　with　15　μm　width　split.　For　Plan　B　with　large　split　width,　the　value　of　TP　increases　with　the　split　width　at　large　Re　(＞250),　while　there　is　an　opposite　trend　with　the　split　width　at　small　Re　(0　is　relatively　smaller　in　Plan　B　at　the　case　of　smaller　w/D,　especially　for　the　cases　with　wide　split　passage.　However,　the　f/f0　in　PlanC　with　the　smaller　w/D　is　much　larger　than　that　of　others,　especially　at　large　Re,　since　the　sideward-inclined　split　in　Plan　C　guides　the　part　of　main　flow　to　side　walls,　enhancing　the　secondary　passage　flow　of　whole　channel.　Therefore,　the　temperature　of　side　wall　corners　has　been　decreased　effectively　and　the　temperature　uniformity　of　all　walls　in　Plan　C　increases.　©　2019,　Science　Press.　All　right　reserved.