The　heat　transfer　of　supercritical　water　in　a　side-heated　square　channel　with　auxiliary　coolant　is　numerically　investigated,　and　the　mechanisms　of　heat　transfer　deterioration　and　recovery　are　explained　in　terms　of　boundary　layer　thickness　and　turbulent　kinetic　energy　in　the　near-wall　region.　The　heat　transfer　correlations　for　supercritical　water　heat　transfer　in　a　side-heated　square　channel　under　different　conditions　(pressure,　inlet　temperature,　heat　flux,　mass　flow,　flow　direction　and　pipe　diameter)　are　examined　and　the　Fan　correlation　achieves　the　highest　prediction　agreement.　The　PEC　factor　is　employed　to　evaluate　different　enhanced　heat　transfer　structures　(dual　channels　and　grooves).　It　is　found　that　the　PEC　factor　of　upper　and　lower　dual　channel　is　generally　less　than　1,　and　the　overall　heat　transfer　enhancement　is　low.　The　PEC　factor　of　the　downstream　asymmetric　chamfered　groove　is　in　the　range　of　1.13-1.51,　and　the　maximum　value　is　achieved　under　different　working　conditions.　The　field　synergy　analysis　also　proves　that　the　down　stream　asymmetric　chamfered　groove　structure　has　the　best　comprehensive　heat　transfer　performance.　©　2022,　Editorial　Board　of　CIESC　Journal.　All　right　reserved.