In　order　to　comprehensively　assess　the　performance　of　microchannel　heat　sink　with　fan-shaped　ribs　on　sidewalls,　this　third　part　of　a　three-part　study　focuses　on　the　relationship　between　thermal　resistance　and　pumping　power,　and　further　the　entropy　generation　rate　and　performance　evaluation　criteria,　with　water　and　silicon　used　as　fluid　and　solid　for　the　computational　domain.　The　microchannel　has　the　width　of　0.1　mm　and　depth　of　0.2　mm　in　the　constant　cross-section　region.　The　geometric　parameters　include　the　width　(0.05-0.4　mm),　height　(0.005-0.025　mm)　and　spacing　(0.2-5　mm)　of　aligned　or　offset　fan　shaped　ribs.　For　deep　insight　into　the　basic　mechanisms　and　properties　of　such　heat　sinks,　the　entropy　generation　rate　due　to　heat　transfer　and　fluid　friction　are　separately　studied.　Results　show　that　the　fan-shaped　ribs　can　lead　to　better　comprehensive　performance　and　the　geometric　parameters　of　fan　shaped　ribs　have　a　significant　influence　on　the　performance　of　such　microchannel　heat　sinks.　With　the　increase　of　the　rib＇s　height,　the　microchannel　heat　sinks　with　offset　fan-shaped　ribs　gradually　perform　better　than　the　ones　with　aligned　fan-shaped　ribs.　With　the　decrease　of　the　rib＇s　spacing,　the　comprehensive　performance　firstly　becomes　better　and　then　gradually　deteriorates.　For　the　microchannel　heat　sink　with　large　rib＇s　height　and　small　rib＇s　spacing,　the　increase　of　Reynolds　number　can　lead　to　tremendously　increase　of　entropy　generation　rate　due　to　fluid　friction,　which　can　withdraw　the　decrease　of　entropy　generation　rate　due　to　heat　transfer　and　lead　to　the　increase　of　total　entropy　generation　rate,　making　the　comprehensive　performance　worse　than　the　smooth　one.　For　Reynolds　number　ranging　from　187　to　715　and　studied　geometric　parameters,　the　best　microchannel　heat　sink　shows　a　32%　decrease　in　entropy　generation　rate　and　1.33　in　performance　evaluation　criteria,　comparing　with　the　smooth　one.　Crown　Copyright　(C)　2016　Published　by　Elsevier　Ltd.　All　rights　reserved.