The　flow　and　heat　transfer　performance　of　mist/steam　coolant　in　a　straight　channel　with　45°/60°/75°V-shaped　ribs,　45°/60°/75°/90°paralleled　ribs　and　a　smooth　channel　under　different　working　conditions　are　studied.　Based　on　vortex　analysis,　for　mist/steam　coolant,　the　regions　where　the　Mainstream　Secondary　Flow　Vortexes　and　the　Longitudinal　Secondary　Flow　Vortexes　exist　simultaneously　can　achieve　better　cooling　performance.　Among　all　mentioned　rib　structures,　the　45°V-shaped　ribbed　passage　achieves　the　best　cooling　enhancement,　its　sidewall　average　Nu　number　ratio　is　33.8%-74.0%　higher　than　the　90°paralleled　ribbed　channel.　Although　the　heat　transfer　non-uniformity　of　the　channel　with　45°V-shaped　ribs　is　not　the　lowest,　it　has　lower　heat　transfer　non-uniformity　than　the　highest　45°paralleled　ribbed　channel.　For　mist/steam　coolant,　increasing　inlet　Re　number,　the　sidewalls　average　Nu　number　ratio　gradually　decreases,　but　their　heat　transfer　non-uniformity　increases.　As　wall　heat　flux　increases,　the　secondary　flow　vortexes　in　the　channel　does　not　change　but　both　average　Nu　number　ratio　and　the　heat　transfer　non-uniformity　clearly　decreases.　Raising　mist/steam　will　not　change　the　secondary　flow　vortexes　structure.　Instead,　it　will　obviously　increase　the　average　Nu　number　ratio　and　heat　transfer　unevenness.　Enlarging　the　mist　diameter　decreases　the　heat　transfer　performance　of　the　sidewall,　but　also　makes　the　sidewall　heat　transfer　become　less　even.　©　2022　The　Authors.