Nanofluid　in　a　mini/microchannel　heat　sink　is　an　effective　technique　that　combines　advantages　of　micro/　minichannels　and　nanofluids　to　obtain　high　single-phase　enhancement　of　heat　transfer.　Experiment　comparison　and　numerical　analysis　of　irreversibility　are　used　to　analyze　features　of　Al2O3-H2O　nanofluid　in　minichannels.　Results　showed　that　transition　point　of　the　nanofluid　from　laminar　flow　to　turbulent　flow　is　1300.　Nusselt　number　of　the　Al2O3-H2O　nanofluid　presents　the　maximum　increment　in　the　concentration　of　0.01%　when　Re　asymptotic　to　&　nbsp;5200,　with　a　maximum　increase　of　47.5%.　The　increase　of　friction　factor　of　the　nanofluid　is　15.1%.　Nu　and　f　value　indicated　the　efficient　heat　transfer　of　low-concentration　nanofluids　under　low　flow　resistance　compared　with　the　results　of　previous　studies.　Thermal　entropy　generation　rates　of　the　nanofluid　are　the　main　irreversible　loss　and　the　frictional　entropy　generation　rate　is　the　main　part　before　Re　=　5000.　(C)&　nbsp;2022　Elsevier　B.V.　All　rights　reserved.