HEAT-TRANSFER TO VISCOUS NEWTONIAN AND NON-NEWTONIAN FLUIDS FOR HELICAL RIBBON MIXERS

Temperature distributions and heat transfer rates have been measured for helical ribbon impellers in vessels of diameter 0. 15 and 0. 4m. Viscous Newtonian and non-Newtonian liquids have been used covering a Reynolds number range of 10** minus **2 less than Re less than 10**3. The critical impeller speed required to eliminate gross temperature gradients within the bulk of the vessel has been established and has been shown to be influenced critically by agitator geometry and fluid properties. The measured rates of heat transfer from the wall of the vessel to the agitated liquid indicate that the film heat-transfer coefficient is dependent upon agitator speed in the creeping flow region. Further, the effect of impeller geometry upon rates of heat transfer has been shown to be significant in this region. General correlations have been provided for design purposes.