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A novel coaxial mixer was proposed,which had an outer wall-scrapingframe and a combined inner impeller consisting of a four-pitched-bladeturbine paddle (PBT-4) and a Rushton turbine paddle (RT-6). Its heattransfer performance in Newtonian fluid under different operatingmodes (single rotation of inner impeller, corotation and counter-rotation)was experimentally investigated in a stainless steel agitated vesselwith semicircle spiral jacket and ellipsoidal head by measuring theaverage heat transfer coefficient of the inner wall. Meanwhile, thewall temperature, the heat flow rate and the local heat transfer coefficientin the coaxial agitated vessel were determined with the help of numericalsimulation. The results show that the heat transfer coefficient nearthe inner wall surface of the agitated vessel will increase with theincreasing speed of the inner or outer impeller whether under single-shaftagitation or under coaxial agitation mode, whereas the effect of speedof the inner impeller on heat transfer is more obvious and efficient.Under the same conditions, the heat transfer of coaxial agitationis more efficient than that of single-shaft agitation, especiallythe local heat transfer coefficient on the upper and lower part ofthe agitated vessel, which is increased greatly. In addition, thelocal heat transfer coefficient varies with the axial position ofthe agitated vessel, and the heat transfer coefficient in zones betweenthe upper and lower impeller is relatively high. The effect of thecorotation mode and counter-rotation mode on heat transfer is of littledifference, but the corotation mode is recommended owing to its advantageof low power consumption and good mixing performance. [ABSTRACT FROM AUTHOR]