Molten　salt　is　one　of　the　most　commonly　used　heat　storage　working　fluids　in　solar　thermal　power.　However,　its　heat　transfer　coefficient　is　low.　Optimizing　the　heat　transfer　condition　could　improve　the　heat　transfer　performance　of　molten　salts,　thereby　facilitating　convection　that　enhances　heat　transfer.　In　trough　and　tower　solar　thermal　power　generation　systems,　the　heating　surface　of　the　molten　salt　collector　tube　differs　with　the　different　angles　of　sunlight　heating.　Numerical　simulations　on　the　characteristics　of　the　flow　and　mixed　convection　heat　transfer　of　Hitec　salt　in　one-,　two-,　and　three-sided　heating　conditions　in　pipes　were　carried　out　in　this　study.　The　results　of　mixed　convection　and　heat　transfer　of　molten　salt　on　different　multisided　heating　surfaces　showed　that　the　heat　accumulated　at　the　heating　surfaces　and　then　transferred　to　the　mainstream　core　region.　Under　nonuniform　heating　conditions,　the　buoyancy　effect　generated　a　vortex,　which　changed　the　shape　of　the　core　area　of　the　mainstream　and　resulted　in　the　enhancement　of　the　heat　transfer　ability.　Double　side　heating　showed　the　strongest　buoyancy　effect.　The　degree　of　heat　accumulation　under　three-sided　heating　was　the　lowest,　and　the　nonuniformity　of　the　heat　transfer　process　in　one-sided　heating　was　the　highest.